The severity of sepsis is attributed to excessive inflammatory responses leading to liver injury. Pregnane X receptor (PXR), a nuclear receptor that controls xenobiotic and endobiotic metabolism, has been implicated in regulating inflammation and liver regeneration. This study aimed to investigate the role of PXR in sepsis-induced liver injury and the underlying mechanisms. Sepsis models were established in mice, the mice were administered the typical mouse PXR agonist PCN (100 mg·kg-1·d-1, i.p.) for 3 consecutive days in advance, then subjected to CLP operation or LPS administration 1 h after the last administration of PCN. The results showed that PCN pretreatment significantly increased the survival rate of septic mice, while the survival rate was reduced after the knockout of Pxr. In addition, PCN pretreatment effectively alleviated sepsis-induced liver injury. In Pxr knockout mice, liver injury was more severe, whereas the protective effects of PCN pretreatment were abolished. Mechanistically, PCN pretreatment significantly upregulated the expression of yes-associated protein (YAP) and its downstream targets and decreased the level of phosphorylated nuclear factor-κB (NF-κB). Moreover, liver-specific knockdown of Yap blocked the protective effects of PCN pretreatment against sepsis-induced liver injury and downregulated the phosphorylation level of NF-κB. In summary, this study demonstrated that PXR activation protects against sepsis-induced liver injury through activation of the YAP signaling pathway, providing a new strategy for the diagnosis and treatment of sepsis-induced liver injury.

The Constitutive Androstane Receptor (CAR) (NR1I3), a pivotal member of the xenosensor family, plays a key role in the hepatic detoxification of xenobiotic and endobiotic chemicals through the induction of the expression of drug-metabolizing enzymes and transporters. CAR's involvement extends beyond detoxification, influencing gluconeogenesis, lipogenesis, bile acid regulation, and cellular processes such as proliferation, tissue regeneration, and carcinogenesis. This review explores CAR regulation by various factors, highlighting its role in mediating metabolic changes induced by environmental contaminants.

A literature search was conducted to identify all articles on the PubMed website in which the CAR-contaminant and CAR-hepatic steatosis relationship is analyzed in both in vitro and in vivo models.

Numerous contaminants, such as perfluorooctanoic acid (PFOA), Zearalenone mycotoxin, PCB, triazole fungicide propiconazole can activate hepatic nuclear receptors contributing to the development of steatosis through increased de novo lipogenesis, decreased fatty acid oxidation, increased hepatic lipid uptake, and decreased gluconeogenesis. Indirect CAR activation pathways, particularly involving PFOA, are discussed in the context of PPARα-independent mechanisms leading to hepatotoxicity, including hepatocellular hypertrophy and necrosis, and their implications in nonalcoholic steatohepatitis (NASH) and nonalcoholic fatty liver disease (NAFLD). The prevalence of NAFLD, a significant component of metabolic syndrome, underscores the importance of understanding CAR's role in its pathogenesis.

Experimental and epidemiological data suggest that endocrine disruptors, especially pesticides, play a significant role in NAFLD's development and progression via CAR-regulated pathways. This review advocates for the inclusion of modern toxicological risk assessment tools, such as New Approach Methodologies (NAMs), Adverse Outcome Pathways (AOPs), and Integrated Approaches to Testing and Assessment (IATA), to elucidate CAR-mediated effects and enhance regulatory frameworks.

The liver regenerative capacity is crucial for patients with end-stage liver disease following partial hepatectomy (PHx). The specific bacteria and mechanisms regulating liver regeneration post-PHx remain unclear. This study demonstrated dynamic changes in the abundance of Parabacteroides distasonis (P. distasonis) post-PHx, correlating with hepatocyte proliferation. Treatment with live P. distasonis significantly promoted hepatocyte proliferation and liver regeneration after PHx. Targeted metabolomics revealed a significant positive correlation between P. distasonis and β-hydroxybutyric acid (BHB), as well as hyodeoxycholic acid and 3-hydroxyphenylacetic acid in the gut after PHx. Notably, treatment with BHB, but not hyodeoxycholic acid or 3-hydroxyphenylacetic acid, significantly promoted hepatocyte proliferation and liver regeneration in mice after PHx. Moreover, STAT3 inhibitor Stattic attenuated the promotive effects of BHB on cell proliferation and liver regeneration both in vitro and in vivo. Mechanistically, P. distasonis upregulated the expression of fatty acid oxidation-related proteins, and increased BHB levels in the liver, and then BHB activated the STAT3 signaling pathway to promote liver regeneration. This study, for the first time, identifies the involvement of P. distasonis and its associated metabolite BHB in promoting liver regeneration after PHx, providing new insights for considering P. distasonis and BHB as potential strategies for promoting hepatic regeneration.

Liver repair and regeneration are crucial physiological responses to hepatic injury and are orchestrated through intricate cellular and molecular networks. This review systematically delineates advancements in the field, emphasizing the essential roles played by diverse liver cell types. Their coordinated actions, supported by complex crosstalk within the liver microenvironment, are pivotal to enhancing regenerative outcomes. Recent molecular investigations have elucidated key signaling pathways involved in liver injury and regeneration. Viewed through the lens of metabolic reprogramming, these pathways highlight how shifts in glucose, lipid, and amino acid metabolism support the cellular functions essential for liver repair and regeneration. An analysis of regenerative variability across pathological states reveals how disease conditions influence these dynamics, guiding the development of novel therapeutic strategies and advanced techniques to enhance liver repair and regeneration. Bridging laboratory findings with practical applications, recent clinical trials highlight the potential of optimizing liver regeneration strategies. These trials offer valuable insights into the effectiveness of novel therapies and underscore significant progress in translational research. In conclusion, this review intricately links molecular insights to therapeutic frontiers, systematically charting the trajectory from fundamental physiological mechanisms to innovative clinical applications in liver repair and regeneration.

The literature documenting the value of drug-like molecules found in natural products is vast. Although many dietary and herbal remedies have been found to be effective for treating intestinal inflammation, the identification of their active components has lagged behind. In this study, we find that a major ginger component, furanodienone (FDN), is a selective pregnane X receptor (PXR) ligand with agonistic transcriptional outcomes. We show that FDN binds within a sub-pocket of the PXR ligand binding domain (LBD), with subsequent alterations in LBD structure. Using male mice, we show that orally provided FDN has potent PXR-dependant anti-inflammatory outcomes that are colon-specific. Increased affinity and target gene activation in the presence of synergistically acting agonists indicates further opportunities for augmenting FDN activity, efficacy and safety. Collectively, these results support the translational potential of FDN as a therapeutic agent for the treatment and prevention of colonic diseases.

Fenofibrate is a clinically prescribed drug for treating hypertriglyceridemia, which is also a classic peroxisome proliferator-activated receptor α (PPARα) agonist. We previously reported that fenofibrate induced liver enlargement in adult mice partially through activation of the yes-associated protein (YAP) signaling pathway. However, the effects of fenofibrate on liver enlargement and the YAP signaling pathway in aging mice remain unclear. In this study, D-galactose-induced aging mice, naturally aging mice, and senescence-accelerated mice P8 (SAMP8) were used to investigate the effects of aging on fenofibrate-induced liver enlargement and YAP signaling activation. The results showed that fenofibrate-induced liver enlargement in aging mice was consistent with that of adult mice. The effects of fenofibrate on hepatocyte enlargement around the central vein (CV) area and hepatocyte proliferation around the portal vein (PV) area were comparable between adult and aging mice. There was no significant difference in the upregulation of PPARα downstream proteins between the two groups following fenofibrate treatment. Fenofibrate treatment also increased the expression of proliferation-related proteins and activated the YAP signaling pathway to a similar degree in both groups. In summary, these results demonstrate that the fenofibrate-induced liver enlargement and activation of the YAP pathway are consistent between adult and aging mice, indicating that the effects of fenofibrate on promoting liver enlargement and its activation of the PPARα and YAP pathway were independent of aging. These findings offer a new perspective for the clinical use of fenofibrate in elderly patients and provide a new insight for the role of PPARα in liver enlargement.

Liver regeneration is a complex process that involves the recruitment of bone marrow (BM)-derived hematopoietic stem and progenitor cells (HSPCs). Pregnane X receptor (PXR), also known as NR1I2, is an important regulator for liver enlargement and regeneration. However, the role of PXR activation in hematopoiesis during liver regeneration remains unclear. This study investigates the effects of PXR activation on HSPCs and hematopoiesis during liver regeneration, as well as the underlying mechanisms involved. Using a 70 % partial hepatectomy (PHx) on C57BL/6 wild-type (WT) and Pxr-null mice, we observed a significant correlation between the changes in HSPCs numbers in BM and the process of liver regeneration. PXR activation significantly increased the population of Lineage- Sca-1+ c-Kit+ (LSK) cells in the BM, which are key HSPCs involved in hematopoiesis. Additionally, PXR activation increased serum levels of thrombopoietin (TPO) and erythropoietin (EPO), factors known to support HSPCs proliferation and hematopoiesis in the process of liver regeneration. PXR activation does not affect the hematopoietic function of normal mice. Furthermore, mice subjected to irradiation or busulfan-induced hematopoietic dysfunction exhibited impaired liver regeneration, which was alleviated by PXR activation. Importantly, in Pxr-null mice, the promotive effects of PXR activation on liver regeneration and increase of HSPCs were markedly diminished. Moreover, liver-specific Pxr silencing using AAV-Pxr shRNA attenuated the PXR activation-mediated liver regeneration and increase in BM LSK cells, confirming the critical role of hepatic PXR in hematopoiesis during liver regeneration. Collectively, these findings reveal that PXR activation promotes HSPCs proliferation and hematopoiesis during liver regeneration, providing new insights into the molecular mechanisms underlying the role of PXR in liver regeneration and hematopoiesis.

Background: Sepsis-induced liver injury (SILI) is an independent risk factor for organ dysfunction and mortality in critical care units. Methods: In this study, the roles of lipocalin 2 (LCN2) in SILI were investigated because LCN2 expression was increased in liver tissues of the septic mice induced by caecal ligation and puncture (CLP), as well as in hepatocytes treated with lipopolysaccharide (LPS). To evaluate liver injury in mice, the levels of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) were measured in both serum and liver tissues. Oxidative stress was evaluated by measuring the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) in serum and liver samples. Additionally, ferroptosis was assessed by examining the expression of prostaglandin endoperoxide synthase 2 (PTGS2), solute carrier family 7 member 11 (SLC7A11), and glutathione peroxidase 4 (GPX4) in liver tissue. Results: The results demonstrated that LCN2 depletion significantly exacerbated SILI, oxidative stress, and ferroptosis. Moreover, in in vitro sepsis model, LCN2 overexpression notably ameliorated LPS-induced cell injury, oxidative stress, and ferroptosis by inhibiting PTGS2 expression. Conclusion: In conclusion, our study provides evidence that LCN2 depletion aggravates SILI by regulating PTGS2-mediated ferroptosis.

Pregnane X receptor (PXR) belongs to the nuclear receptor superfamily that plays a crucial role in hepatic physiologic and pathologic conditions. Phase separation is a process in which biomacromolecules aggregate and condense into a dense phase as liquid condensates and coexist with a dilute phase, contributing to various cellular and biologic functions. Until now, whether PXR could undergo phase separation remains unclear. This study aimed to investigate whether PXR undergoes phase separation. Analysis of the intrinsically disordered regions (IDRs) using algorithm tools indicated a low propensity of PXR to undergo phase separation. Experimental assays such as hyperosmotic stress, agonist treatment, and optoDroplets assay demonstrated the absence of phase separation for PXR. OptoDroplets assay revealed the inability of the fusion protein of Cry2 with PXR to form condensates upon blue light stimulation. Moreover, phase separation of PXR did not occur even though the mRNA and protein expression levels of PXR target, cytochrome P450 3A4, changed after sorbitol treatment. In conclusion, for the first time, these findings suggested that exogenous PXR does not undergo phase separation following activation or under hyperosmotic stress in nucleus of cells. SIGNIFICANCE STATEMENT: PXR plays a critical role in hepatic physiological and pathological processes. The present study clearly demonstrated that exogenous PXR does not undergo phase separation after activation by agonist or under hyperosmotic stress in nucleus. These findings may help understand PXR biology.

The aryl hydrocarbon receptor (AHR) is a transcription factor activated by ligands that participates in many important physiological processes. Although AHR activation is associated with hepatomegaly, the underlying mechanism remains unclear. This study evaluated the effects of AHR activation on liver enlargement and regeneration in various transgenic mice and animal models. Activation of AHR by the non-toxic ligand YH439 significantly induced liver/body weight ratio in wild-type mice (1.37-fold) and AHRfl/fl.ALB-CreERT2 mice (1.54-fold). However, these effects not present in AHRΔHep mice. Additionally, the activation of AHR promotes hepatocyte enlargement (1.43-fold or 1.41-fold) around the central vein (CV) and increases number of Ki67+ cells (42.5-fold or 48.8-fold) around the portal vein (PV) in wild-type mice and AHRfl/fl.ALB-CreERT2 mice. In the 70 % partial hepatectomy (PHx) model, YH439 significantly induced hepatocyte enlargement (1.40-fold) and increased number of Ki67+ cells (3.97-fold) in AHRfl/fl.ALB-CreERT2 mice. However, these effects were not observed in AHRΔHep mice. Co-immunoprecipitation results suggested a potential protein-protein interaction between AHR and Yes-associated protein (YAP). Disruption of the association between YAP and transcription enhancer domain family member (TEAD) significantly inhibited AHR-induced liver enlargement and regeneration. Furthermore, AHR failed to induce liver enlargement and regeneration in YAPΔHep mice. Blocking the YAP signaling pathway effectively eliminated AHR-induced liver enlargement and regeneration. This study revealed the molecular mechanism of AHR regulation of liver size and regeneration through the activation of AHR-TEAD signaling pathway, thereby offering novel insights into the physiological role of AHR. These findings provide a theoretical foundation for the prevention and treatment of disorders associated with liver regeneration.

Introduction: The liver is the only organ capable of full regeneration in mammals. However, the exact mechanism of gut microbiota and metabolites derived from them relating to liver regeneration has not been fully elucidated. Methods: To demonstrate how the gut-liver axis contributes to liver regeneration, using an LC-QTOF/MS-based metabolomics technique, we examine the gut microbiota-derived metabolites in the gut content of C57BL/6J mice at various points after 2/3 partial hepatectomy (PHx). Compound identification, multivariate/univariate data analysis and pathway analysis were performed subsequently. The diversity of the bacterial communities in the gastrointestinal content was measured using 16S rRNA gene sequencing. Then, the integration analysis of gut microbiota and metabolome was performed. Results: After 2/3 PHx, the residual liver proliferated quickly in the first 3 days and had about 90% of its initial weight by the seventh day. The results of PLS-DA showed that a significant metabolic shift occurred at 6 h and 36 h after 2/3 PHx that was reversed at the late phase of liver regeneration. The α and β-diversity of the gut microbiota significantly changed at the early stage of liver regeneration. Specifically, Escherichia Shigella, Lactobacillus, Akkermansia, and Muribaculaceae were the bacteria that changed the most considerably during liver regeneration. Further pathway analysis found the most influenced co-metabolized pathways between the host and gut bacteria including glycolysis, the TCA cycle, arginine metabolism, glutathione metabolism, tryptophan metabolism, and purine and pyrimidine metabolism. Specifically, steroid hormone biosynthesis is the most significant pathway of the host during liver regeneration. Discussion: These findings revealed that during liver regeneration, there was a broad modification of gut microbiota and systemic metabolism and they were strongly correlated. Targeting specific gut bacterial strains, especially increasing the abundance of Akkermansia and decreasing the abundance of Enterobacteriaceae, may be a promising beneficial strategy to modulate systemic metabolism such as amino acid and nucleotide metabolism and promote liver regeneration.

Nuclear receptors such as constitutive androstane receptor (CAR), pregnane X receptor (PXR), and peroxisome proliferator-activated receptor-alpha (PPARα), and transcription factors with nuclear receptor type activity such as aryl hydrocarbon receptor (AhR) function as xenobiotic sensors. Hepatocyte nuclear factor 4alpha (HNF4α) is a highly conserved orphan nuclear receptor essential for liver function. We tested the hypothesis that HNF4α is essential for the function of these 4 major xenosensors. Wild-type (WT) and hepatocyte-specific Hnf4a null (HNF4α-KO) mice were treated with the mouse-specific activators of AhR (TCDD, 30 µg/kg), CAR (TCPOBOP, 2.5 µg/g), PXR, (PCN, 100 µg/g), and PPARα (WY-14643, 1 mg/kg). Blood and liver tissue samples were collected to study receptor activation. TCDD (AhR agonist) treatment did not affect the liver-to-body weight ratio (LW/BW) in either WT or HNF4α-KO mice. Further, TCDD activated AhR in both WT and HNF4α-KO mice, confirmed by increase in expression of AhR target genes. TCPOBOP (CAR agonist) significantly increased the LW/BW ratio and CAR target gene expression in WT mice, but not in HNF4α-KO mice. PCN (a mouse PXR agonist) significantly increased LW/BW ratio in both WT and HNF4α-KO mice however, failed to induce PXR target genes in HNF4α-KO mice. The treatment of WY-14643 (PPARα agonist) increased LW/BW ratio and PPARα target gene expression in WT mice but not in HNF4α-KO mice. Together, these data indicate that the function of CAR, PXR, and PPARα but not of AhR was disrupted in HNF4α-KO mice. These results demonstrate that HNF4α function is critical for the activation of hepatic xenosensors, which are critical for toxicological responses.

Human pregnane X receptor (PXR) is critical for regulating the expression of key drug-metabolizing enzymes such as CYP3A and CYP2C. Our recent study revealed that treatment with rodent-specific PXR agonist pregnenolone-16α-carbonitrile (PCN) significantly induced hepatomegaly and promoted liver regeneration after two-thirds partial hepatectomy (PHx) in mice. However, it remains unclear whether PXR activation induces hepatomegaly and liver regeneration and simultaneously promotes metabolic function of the liver. Here, we investigated the metabolism activity of CYP1A2, CYP3A1/2 and CYP2C6/11 during PXR activation-induced liver enlargement and regeneration in rats after cocktail dosing of CYP probe drugs. For PCN-induced hepatomegaly, a notable increase in the metabolic activity of CYP3A1/2 and CYP2C6/11, as evidenced by the plasma exposure of probe substrates and the AUC ratios of the characteristic metabolites to its corresponding probe substrates. The metabolic activity of CYP1A2, CYP3A1/2 and CYP2C6/11 decreased significantly after PHx. However, PCN treatment obviously enhanced the metabolic activity of CYP2C6/11 and CYP3A1/2 in PHx rats. Furthermore, the protein expression levels of CYP3A1/2 and CYP2C6/11 in liver were up-regulated. Taken together, this study demonstrates that PXR activation not only induces hepatomegaly and liver regeneration in rats, but also promotes the protein expression and metabolic activity of the PXR downstream metabolizing enzymes such as CYP3A1/2 and CYP2C6/11 in the body.

Hepatocyte nuclear factor 4 alpha (HNF4α) and the pregnane X receptor (PXR) are involved in hepatocyte regeneration. It is not clear whether HNF4α is involved in hepatocyte regeneration through the regulation of PXR. This study aims to explore the regulatory relationship between HNF4a and PXR, and whether it affects hepatocyte regeneration. A mouse PXR gene reporter and an HNF4α overexpression plasmid were constructed and transfected into mouse hepatoma cells (Hepa1-6). Overexpression of HNF4α, detection of the PXR gene reporter fluorescence value, PXR gene, and protein expression analysis were conducted to explore the regulatory relationship between HNF4α and PXR. Apoptosis and cell cycle data were measured to verify whether HNF4α is involved in hepatocyte regeneration through PXR. The luciferase gene reporter assay results indicated when HNF4α was overexpressed, the fluorescence value of the PXR gene reporter was higher than that in the control at 24 h. With increasing HNF4α expression, the PXR gene and protein expression increased, indicating that HNF4α binds to the PXR promoter and upregulates PXR expression. Apoptosis and cell cycle analysis results demonstrated that when the expression of HNF4α increased, the expression of PXR increased, the apoptosis rate decreased, and the proliferation rate increased. Meanwhile, when the upward trend of PXR gene expression was inhibited by ketoconazole, the proliferation rate decreased. By inhibiting HNF4α and creating a partial hepatectomy (PHx), we demonstrated that HNF4α can upregulate PXR to promote liver regeneration in vivo. Therefore, HNF4α is shown to improve hepatocyte regeneration by upregulating PXR, which provides a reference for future research on the combined application of drugs for the treatment of liver injury.

Fenofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist, is widely prescribed for hyperlipidemia management. Recent studies also showed that it has therapeutic potential in various liver diseases. However, its effects on hepatomegaly and liver regeneration and the involved mechanisms remain unclear. Here, the study showed that fenofibrate significantly promoted liver enlargement and regeneration post-partial hepatectomy in mice, which was dependent on hepatocyte-expressed PPARα. Yes-associated protein (YAP) is pivotal in manipulating liver growth and regeneration. We further identified that fenofibrate activated YAP signaling by suppressing its K48-linked ubiquitination, promoting its K63-linked ubiquitination, and enhancing the interaction and transcriptional activity of the YAP-TEAD complex. Pharmacological inhibition of YAP-TEAD interaction using verteporfin or suppression of YAP using AAV Yap shRNA in mice significantly attenuated fenofibrate-induced hepatomegaly. Other factors, such as MYC, KRT23, RAS, and RHOA, might also participate in fenofibrate-promoted hepatomegaly and liver regeneration. These studies demonstrate that fenofibrate-promoted liver enlargement and regeneration are PPARα-dependent and partially through activating the YAP signaling, with clinical implications of fenofibrate as a novel therapeutic agent for promoting liver regeneration.

Pregnane X receptor (PXR) is essential in the regulation of liver homeostasis, and the gut microbiota is closely linked to liver physiologic and pathologic status. We previously found that activation of PXR significantly promotes liver enlargement through interaction with yes-associated protein (YAP). However, whether gut microbiota contributes to PXR-induced hepatomegaly and the involved mechanisms remain unclear. In this study, C57BL/6 mice were administered the mouse-specific agonist pregnenolone 16α-carbonitrile (PCN) for 5 days. Depletion of gut microbiota was achieved using broad-spectrum antibiotics (ABX) and fecal microbiota transplantation (FMT) was performed to restore the gut microbia. The composition of gut microbiota was analyzed by 16S rRNA sequencing, while the expression of PXR, YAP, and their downstream target genes and proteins were assessed. The results indicated that PCN treatment altered the composition and abundance of specific bacterial taxa. Furthermore, depletion of gut microbiota using ABX significantly attenuated PCN-induced hepatomegaly. FMT experiments further demonstrated that the fecal microbiota from PCN-treated mice could induce liver enlargement. Mechanistic studies revealed that ABX treatment impeded the PXR and YAP activation induced by PCN, as evidenced by decreased expression of PXR, YAP, and their downstream targets. Moreover, alterations in PXR and YAP activation were likely contributing to hepatomegaly in recipient mice following FMT from PCN-treated mice. Collectively, the current study demonstrated that gut microbiota is involved in PCN-induced hepatomegaly via regulating PXR and YAP activation, providing potential novel insights into the involvement of gut microbiota in PXR-mediated hepatomegaly. SIGNIFICANCE STATEMENT: This work describes that the composition of gut microbiota is altered in mouse pregnane X receptor (PXR) agonist pregnenolone 16α-carbonitrile (PCN)-induced hepatomegaly. Treatment with an antibiotic cocktail depletes the intestinal microbiota, leading to the impairment of liver enlargement caused by PCN. Additionally, fecal microbiota transplantation from PCN-treated mice induces liver enlargement. Further study revealed that gut microbiota is involved in hepatomegaly via regulating PXR and yes-associated protein activation.

The activation of pregnane X receptor (PXR) or peroxisome proliferator-activated receptor α (PPARα) can induce liver enlargement. Recently, we reported that PXR or PPARα activation-induced hepatomegaly depends on yes-associated protein (YAP) signaling and is characterized by hepatocyte hypertrophy around the central vein area and hepatocyte proliferation around the portal vein area. However, it remains unclear whether PXR or PPARα activation-induced hepatomegaly can be reversed after the withdrawal of their agonists. In this study, we investigated the regression of enlarged liver to normal size following the withdrawal of PCN or WY-14643 (typical agonists of mouse PXR or PPARα) in C57BL/6 mice. The immunohistochemistry analysis of CTNNB1 and KI67 showed a reversal of hepatocyte size and a decrease in hepatocyte proliferation after the withdrawal of agonists. In details, the expression of PXR or PPARα downstream proteins (CYP3A11, CYP2B10, ACOX1, and CYP4A) and the expression of proliferation-related proteins (CCNA1, CCND1, and PCNA) returned to the normal levels. Furthermore, YAP and its downstream proteins (CTGF, CYR61, and ANKRD1) also restored to the normal states, which was consistent with the change in liver size. These findings demonstrate the reversibility of PXR or PPARα activation-induced hepatomegaly and provide new data for the safety of PXR and PPARα as drug targets.

Endotoxemia-related acute liver injury has a poor prognosis and high mortality, and macrophage polarization plays a central role in the pathological process. Pregnane X receptor (PXR) serves as a nuclear receptor and xenosensor, safeguarding the liver from toxic stimuli. However, the effect and underlying mechanism of PXR activation on endotoxemic liver injury remain largely unknown. Here, the expression of PXR is reported in human and murine macrophages, and PXR activation modified immunotypes of macrophages. Moreover, PXR activation significantly attenuated endotoxemic liver injury and promoted macrophage M2 polarization. Macrophage depletion by GdCl3 confirmed the essential of macrophages in the beneficial effects observed with PXR activation. The role of PXR in macrophages is further validated using AAV8-F4/80-Pxr shRNA-treated mice; the PXR-mediated hepatoprotection is impaired, and M2 polarization enhancement is blunted. Additionally, treatment with PXR agonists inhibited lipopolysaccharide (LPS)-induced M1 polarization and favored M2 polarization in BMDM, Raw264.7, and THP-1 cells. Further analyses revealed an interaction between PXR and p-STAT6 in vivo and in vitro. Moreover, blocking Pxr or Stat6 abolished the PXR-induced polarization shift. Collectively, macrophage PXR activation attenuated endotoxin-induced liver injury and regulated macrophage polarization through the STAT6 signaling pathway, which provided a potential therapeutic target for managing endotoxemic liver injury.

Liver regeneration after liver tumor resection or liver transplantation is crucial, the remaining liver frequently fails to regenerate in some patients. Oleanolic acid (OA), a pentacyclic triterpenoid compound which has been shown to protect against various liver diseases. However, the effect of OA on liver regeneration after partial hepatectomy (PHx) is still unclear. In this study, the results showed that OA (50 mg/kg, twice daily) treatment induced liver mass restoration and increased the liver-to-body weight ratio of mice following PHx. Meanwhile, OA promoted hepatocyte proliferation and increased the number of BrdU-, Ki67-and PCNA-positive cells. Furthermore, OA increased the nuclear accumulation of PXR and induced the expression of PXR downstream proteins such as CYP3A11, UGT1A1 and GSTM2 in mice, as well as in AML12 and HepRG cells. Luciferase reporter assay and nuclear localization of PXR further demonstrated the effect of OA on PXR activation in vitro. Molecular docking simulation showed that OA could interact with the PXR active sites. Moreover, OA inhibited the expression of FOXO1, RBL2 and CDKN1B, and increased the expression of PCNA, CCND1 and CCNE1 in vivo and in vitro. Silencing of Pxr further confirmed that OA-mediated upregulation of proliferation-related proteins depended on PXR. The current study illustrated that OA exhibited a significant promoting effect on liver regeneration following PHx, potentially through regulation of the PXR signaling pathway to accelerate liver recovery.

Environmental exposure to endocrine-disrupting chemicals (EDCs) can lead to metabolic disruption, resulting in metabolic complications including adiposity, dyslipidemia, hepatic lipid accumulation, and glucose intolerance. Hepatic nuclear receptor activation is one of the mechanisms mediating metabolic effects of EDCs. Here, we investigated the potential to use a repeated dose 28-day oral toxicity test for identification of EDCs with metabolic endpoints. Bisphenol A (BPA), pregnenolone-16α-carbonitrile (PCN), and perfluorooctanoic acid (PFOA) were used as reference compounds. Male and female wild-type C57BL/6 mice were orally exposed to 5, 50, and 500 μg/kg of BPA, 1000, 10 000, and 100 000 µg/kg of PCN and 50 and 300 μg/kg of PFOA for 28 days next to normal chow diet. Primary endpoints were glucose tolerance, hepatic lipid accumulation, and plasma lipids. After 28-day exposure, no changes in body weight and glucose tolerance were observed in BPA-, PCN-, or PFOA-treated males or females. PCN and PFOA at the highest dose in both sexes and BPA at the middle and high dose in males increased relative liver weight. PFOA reduced plasma triglycerides in males and females, and increased hepatic triglyceride content in males. PCN and PFOA induced hepatic expression of typical pregnane X receptor (PXR) and peroxisome proliferator-activated receptor (PPAR)α target genes, respectively. Exposure to BPA resulted in limited gene expression changes. In conclusion, the observed changes on metabolic health parameters were modest, suggesting that a standard repeated dose 28-day oral toxicity test is not a sensitive method for the detection of the metabolic effect of EDCs.

As a devastating neurological disease, spinal cord injury (SCI) results in severe tissue loss and neurological dysfunction. Pregnane X receptor (PXR) is a ligand-activated nuclear receptor with a major regulatory role in xenobiotic and endobiotic metabolism and recently has been implicated in the central nervous system. In the present study, we aimed to investigate the role and mechanism of PXR in SCI.

The clip-compressive SCI model was performed in male wild-type C57BL/6 (PXR+/+ ) and PXR-knockout (PXR-/- ) mice. The N2a H2 O2 -induced injury model mimicked the pathological process of SCI in vitro. Pregnenolone 16α-carbonitrile (PCN), a mouse-specific PXR agonist, was used to activate PXR in vivo and in vitro. The siRNA was applied to knock down the PXR expression in vitro. Transcriptome sequencing analysis was performed to discover the relevant mechanism, and the NRF2 inhibitor ML385 was used to validate the involvement of PXR in influencing the NRF2/HO-1 pathway in the SCI process.

The expression of PXR decreased after SCI and reached a minimum on the third day. In vivo, PXR knockout significantly improved the motor function of mice after SCI, meanwhile, inhibited apoptosis, inflammation, and oxidative stress induced by SCI. On the contrary, activation of PXR by PCN negatively influenced the recovery of SCI. Mechanistically, transcriptome sequencing analysis revealed that PXR activation downregulated the mRNA level of heme oxygenase-1 (HO-1) after SCI. We further verified that PXR deficiency activated the NRF2/HO-1 pathway and PXR activation inhibited this pathway in vitro.

PXR is involved in the recovery of motor function after SCI by regulating NRF2/HO-1 pathway.

Nuclear receptors including Aryl hydrocarbon Receptor (AhR), Constitutive Androstane Receptor (CAR), Pregnane X Receptor (PXR), and Peroxisome Proliferator-Activated Receptor-alpha (PPARα) function as xenobiotic sensors. Hepatocyte nuclear factor 4alpha (HNF4α) is a highly conserved orphan nuclear receptor essential for liver function. We tested the hypothesis that HNF4α is essential for function of these four major xenosensors. Wild-type (WT) and hepatocyte-specific HNF4α knockout (HNF4α-KO) mice were treated with the mouse-specific activators of AhR (TCDD, 30 µg/kg), CAR (TCPOBOP, 2.5 µg/g), PXR, (PCN, 100 µg/g), and PPARα (WY-14643, 1 mg/kg). Blood and liver tissue samples were collected to study nuclear receptor activation. TCDD (AhR agonist) treatment did not affect the liver-to-body weight ratio (LW/BW) in either WT or HNF4α-KO mice. Further, TCDD activated AhR in both WT and HNF4-KO mice, confirmed by increase in expression of its target genes. TCPOBOP (CAR agonist) significantly increased the LW/BW ratio and CAR target gene expression in WT mice, but not in HNF4α-KO mice. PCN (a mouse PXR agonist) significantly increased LW/BW ratio in both WT and HNF4α-KO mice however, it failed to induce PXR target genes in HNF4 KO mice. The treatment of WY-14643 (PPARα agonist) increased LW/BW ratio and PPARα target gene expression in WT mice but not in HNF4α-KO mice. Together, these data indicate that the function of CAR, PXR, and PPARα but not of AhR was disrupted in HNF4α-KO mice. These results demonstrate that HNF4α function is critical for the activation of hepatic xenosensors, which are critical for toxicological responses.

Peroxisome proliferator-activated receptor alpha (PPARα) activation-induced hepatomegaly is accompanied by hepatocyte hypertrophy around the central vein (CV) area and hepatocyte proliferation around the portal vein (PV) area. However, the molecular mechanisms underlying this spatial change of hepatocytes remains unclear. In this study, we examined the characteristics and possible reasons for the zonation distinction of hypertrophy and proliferation during PPARα activation-induced mouse liver enlargement. Mice were injected with corn oil or a typical mouse PPARα agonist WY-14643 (100 mg·kg-1·d-1, i.p.) for 1, 2, 3, 5 or 10 days. At each time point, the mice were sacrificed after the final dose, and liver tissues and serum were harvested for analysis. We showed that PPARα activation induced zonal changes in hepatocyte hypertrophy and proliferation in the mice. In order to determine the zonal expression of proteins related to hepatocyte hypertrophy and proliferation in PPARα-induced liver enlargement, we performed digitonin liver perfusion to separately destroy the hepatocytes around the CV or PV areas, and found that PPARα activation-induced increase magnitude of its downstream targets such as cytochrome P450 (CYP) 4 A and acyl-coenzyme A oxidase 1 (ACOX1) levels around the CV area were higher compared with those around the PV area. Upregulation of proliferation-related proteins such as cell nuclear antigen (PCNA) and cyclin A1 (CCNA1) after WY-14643-induced PPARα activation mainly occurred around the PV area. This study reveals that the zonal expression of PPARα targets and proliferation-related proteins is responsible for the spatial change of hepatocyte hypertrophy and proliferation after PPARα activation. These findings provide a new insight into the understanding of PPARα activation-induced liver enlargement and regeneration.

Chronic infection with Clonorchis sinensis can cause hepatobiliary fibrosis and even lead to hepatobiliary carcinoma. Epstein-Barr virus-induced gene 3 protein (EBI3) is a subunit of interleukin 35, which can regulate inflammatory response and the occurrence of fibrotic diseases. Previous studies have reported that the expression of EBI3 in the serum of patients with liver cirrhosis is reduced. The present study aims to investigate the biological effects of EBI3 on liver fibrosis caused by C. sinensis and the underlying molecular mechanisms.

We first established a mouse model of liver fibrosis induced by C. sinensis infection and then measured the serum expression of EBI3 during the inflammatory and fibrotic phase. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analyses were performed to investigate the potential role of EBI3 in liver fibrosis by regulating the extracellular matrix structural constituent and collagen catabolic process. Recombinant protein EBI3 (rEBI3) was added to hepatic stellate cells (HSCs) in vitro with C. sinensis antigen to explore its function. Finally, the therapeutic effect of rEBI3 was verified by intravenous injection into C. sinensis-infected mice.

The results showed that the serum expression of EBI3 increased in the inflammatory response phase but decreased in the fibrotic phase. The excretory-secretory products of C. sinensis (Cs.ESP) were able to stimulate HSC activation, while rEBI3 reduced the activation of HSCs induced by Cs.ESP. Also, the protein expression of gp130 and downstream protein expressions of JAK1, p-JAK1, STAT3 and p-STAT3 in HSCs were increased after rEBI3 incubation. Finally, intravenously injected rEBI3 inhibited hepatic epithelial-mesenchymal transition in C. sinensis-infected mice by inhibiting HSC activation and reducing liver injury.

This study confirms that rEBI3 can attenuate C. sinensis-induced liver fibrosis by inhibiting HSC activation and may be one of the potential treatments for liver fibrosis.

Tripterygium wilfordii tablets (TWT) is widely used to treat autoimmune diseases such as rheumatoid arthritis. Celastrol, one main active ingredient in TWT, has been shown to produce a variety of beneficial effects, including anti-inflammatory, anti-obesity, anti-cancer, and immunomodulatory. However, whether TWT could protect against Concanavalin A (Con A)-induced hepatitis remains unclear.

This study aims to investigate the protective effect of TWT against Con A-induced hepatitis and elucidate the underlying mechanism.

Metabolomic analysis, pathological analysis, biochemical analysis, qPCR and Western blot analysis and the Pxr-null mice were used in this study.

The results indicated that TWT and its active ingredient celastrol could protect against Con A-induced acute hepatitis. Plasma metabolomics analysis revealed that metabolic perturbations related to bile acid and fatty acid metabolism induced by Con A were reversed by celastrol. The level of itaconate in the liver was increased by celastrol and speculated as an active endogenous compound mediating the protective effect of celastrol. Administration of 4-octanyl itaconate (4-OI) as a cell-permeable itaconate mimicker was found to attenuate Con A-induced liver injury through activation of the pregnane X receptor (PXR) and enhancement of the transcription factor EB (TFEB)-mediated autophagy.

Celastrol increased itaconate and 4-OI promoted activation of TFEB-mediated lysosomal autophagy to protect against Con A-induced liver injury in a PXR-dependent manner. Our study reported a protective effect of celastrol against Con A-induced AIH via an increased production of itaconate and upregulation of TFEB. The results highlighted that PXR and TFEB-mediated lysosomal autophagic pathway may offer promising therapeutic target for the treatment of autoimmune hepatitis.

The morbidity and mortality of sepsis are extremely high, which is a major problem plaguing human health. However, current drugs and measures for the prevention and treatment of sepsis have little effect. Sepsis-associated acute liver injury (SALI) is an independent risk factor for sepsis, which seriously affects the prognosis of sepsis. Studies have found that gut microbiota is closely related to SALI, and indole-3-propionic Acid (IPA) can activate Pregnane X receptor (PXR). However, the role of IPA and PXR in SALI has not been reported.

This study aimed to explore the association between IPA and SALI. The clinical data of SALI patients were collected and IPA level in feces was detected. The sepsis model was established in wild-type mice and PXR knockout mice to investigate the role of IPA and PXR signaling in SALI.

We showed that the level of IPA in patients' feces is closely related to SALI, and the level of IPA in feces has a good ability to identify and diagnose SALI. IPA pretreatment significantly attenuated septic injury and SALI in wild-type mice, but not found in knockout PXR gene mice.

IPA alleviates SALI by activating PXR, which reveals a new mechanism of SALI, and provides potentially effective drugs and targets for the prevention of SALI.

Liver fibrosis can be characterized by the over-deposition of extracellular matrix (ECM). It has been reported that β-catenin/TCF4 interaction was enhanced in bile duct ligation (BDL) model, which implicated the critical role of β-catenin/TCF4 interaction during the progression of fibrosis. However, whether inhibiting β-catenin/TCF4 signaling attenuates liver fibrosis remains unknown. In the current study, we used ICG-001, an inhibitor that disrupts the interaction between CREB binding protein (CBP) and β-catenin, to inhibit β-catenin/TCF4 transcriptional activity. We also used LF3, a small molecule antagonist, to inhibit β-catenin/TCF4 interaction. The antifibrotic effect of ICG-001 and LF3 was assessed on BDL-induced liver fibrosis model. The results indicated both ICG-001 and LF3 significantly reduced the positive staining area of Sirius Red and α-SMA. The protein expression levels of α-SMA, Collagen Ⅰ and CD31 were also significantly downregulated in BDL + ICG-001 and BDL + LF3 groups. Besides, ICG-001 and LF3 promoted portal angiogenesis and inhibited sinusoids capillarization in fibrotic livers. For mechanistic study, we measured the level of leukocyte cell-derived chemotaxin 2 (LECT2), a direct target of β-catenin/TCF4, which was recently reported to participate in hepatic fibrosis by regulating angiogenesis. The results showed that both ICG-001 and LF3 reduced LECT2 expression in BDL mice. LF3 also downregulated pSer 675 β-catenin and nuclear β-catenin. In conclusion, this study demonstrated that inhibiting β-catenin/TCF4 signaling by ICG-001 or LF3 mitigated liver fibrosis by downregulating LECT2, promoting portal angiogenesis and inhibiting sinusoids capillarization, which provided new evidence that β-catenin/TCF4 signaling might be a target for the treatment of liver fibrosis.

Pregnane X receptor (PXR) plays an important role in the regulation of metabolic homeostasis. Yes-associated protein (YAP) is a critical regulator of liver size and liver regeneration. Recently, we reported that PXR-induced liver enlargement and regeneration depend on YAP signalling, but the underlying mechanisms remain unclear. This study aimed to reveal how PXR regulates or interacts with YAP signalling during PXR-induced hepatomegaly and liver regeneration. Immunoprecipitation (IP), Co-IP and GST pull-down assays were performed in vitro to reveal the regulatory mechanisms involved in the PXR-YAP interaction. The roles of YAP-TEAD binding and Sirt2-driven deacetylation and polyubiquitination of YAP were further investigated in vitro and in vivo. The results showed that the ligand-binding domain (LBD) of PXR and the WW domain of YAP were critical for the PXR-YAP interaction. Furthermore, disruption of the YAP-TEAD interaction using the binding inhibitor verteporfin significantly decreased PXR-induced liver enlargement and regeneration after 70 % partial hepatectomy (PHx). Mechanistically, PXR activation significantly decreased YAP acetylation, which was interrupted by the sirtuin inhibitor nicotinamide (NAM). In addition, p300-induced YAP acetylation contributed to K48-linked YAP ubiquitination. Interestingly, PXR activation remarkably inhibited K48-linked YAP ubiquitination while inducing K63-linked YAP polyubiquitination. Sirt2 interference abolished the deacetylation and K63-linked polyubiquitination of YAP, suggesting that the PXR-induced deacetylation and polyubiquitination of YAP are Sirt2 dependent. Taken together, this study demonstrates that PXR induce liver enlargement and regeneration via the regulation of YAP acetylation and ubiquitination and YAP-TEAD binding, providing evidences for using PXR as potential target to promote hepatic development and liver repair.

Pregnane X receptor (PXR) is highly expressed in the liver and plays a pivotal role in xenobiotic and endobiotic metabolism. We previously reported that PXR activation by its specific mouse agonist pregnenolone 16α-carbonitrile (PCN) significantly induces liver enlargement and lipid accumulation. However, the effect of long-term PCN treatment on PXR and mouse liver is still unknown. This study aimed to explore the influence of long-term administration of PCN on mouse liver and hepatic lipid homeostasis. Male C57BL/6 mice were injected intraperitoneally with PCN (100 mg/kg once a week) for 42 weeks. Serum and liver samples were collected for biochemical and histological analysis. PXR activation was investigated by Western blot. Ultra-high-performance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (UHPLC-ESI-HRMS)-based lipidomics analysis was performed to explore the change in different lipid categories. The results showed that long-term treatment with PCN significantly promoted hepatomegaly without hepatocyte proliferation and enlargement. Long-term treatment with PCN did not upregulate PXR target proteins in mice, and there was no significant upregulation of CYP3A11, CYP2B10, UGT1A1, MRP2, or MRP4. Lipidomics analysis showed obvious hepatic lipid accumulation in the PCN-treated mice, and the most significant change was found in triglycerides (TGs). Additionally, long-term treatment with PCN had no risk for carcinogenesis. These findings demonstrated that long-term PCN treatment induces hepatomegaly and lipid accumulation without hepatocyte proliferation or enlargement.

During liver development, hepatocytes, and cholangiocytes are concurrently differentiated from common liver progenitor cells and are assembled into hepatobiliary architecture to perform proper hepatic function. However, the generation of functional hepatobiliary architecture from hepatocytes in vitro is still challenging, and the exact molecular drivers of hepatobiliary cell lineage determination is largely unknown. In this study, functional hepatobiliary organoids (HBOs) are generated from hepatocytes. These HBOs contain a bile duct network surrounded by mature hepatocytes and stably maintain hepatic characteristics and function in vitro and upon transplantation in vivo. Morphological transition and expression profile of hepatocyte-derived organoids recapitulate the process of liver development. Gene regulation landscape of hepatocyte-derived organoids reveal that Tead4 and Ddit3 promote the cell fate commitment of liver progenitors to functional cholangiocytes and hepatocytes, respectively. Liver cell fate determination is reversed by inhibiting Tead4 or increasing Ddit3 expression both in vitro and upon transplantation in vivo. Collectively, hepatocyte-derived HBOs reveal the essential transcription drivers of liver hepatobiliary cell lineage determination and represent powerful models for liver development and regeneration.

Liver is the central hub regulating energy metabolism during feeding-fasting transition. Evidence suggests that fasting and refeeding induce dynamic changes in liver size, but the underlying mechanisms remain unclear. Yes-associated protein (YAP) is a key regulator of organ size. This study aims to explore the role of YAP in fasting- and refeeding-induced changes in liver size. Here, fasting significantly reduced liver size, which was recovered to the normal level after refeeding. Moreover, hepatocyte size was decreased and hepatocyte proliferation was inhibited after fasting. Conversely, refeeding promoted hepatocyte enlargement and proliferation compared to fasted state. Mechanistically, fasting or refeeding regulated the expression of YAP and its downstream targets, as well as the proliferation-related protein cyclin D1 (CCND1). Furthermore, fasting significantly reduced the liver size in AAV-control mice, which was mitigated in AAV Yap (5SA) mice. Yap overexpression also prevented the effect of fasting on hepatocyte size and proliferation. Besides, the recovery of liver size after refeeding was delayed in AAV Yap shRNA mice. Yap knockdown attenuated refeeding-induced hepatocyte enlargement and proliferation. In summary, this study demonstrated that YAP plays an important role in dynamic changes of liver size during fasting-refeeding transition, which provides new evidence for YAP in regulating liver size under energy stress.

Peroxisome proliferator-activated receptor α (PPARα) is closely related to lipid metabolism and various liver diseases. Previous study has shown that chronic treatment with PPARα agonist WY-14643 can induce liver tumors in rodents, but the implications of this process on lipid metabolism in the liver remain unclear. Thus, this study aimed to explore the influences of chronic treatment with WY-14643 on the liver and hepatic lipid metabolism. Wild-type C57BL/6 mice were treated with WY-14643 (100 mg/kg/week, i.p.) or corn oil, and liver and serum samples were collected for testing after 42 weeks of WY-14643 treatment. The results showed that hepatomegaly, liver tumors with mild liver injury, and hepatocyte proliferation were induced in mice treated with WY-14643. The mRNA and protein expression levels of PPARα downstream targets acyl-CoA oxidase 1 and cytochrome P450 4A were significantly upregulated in the WY-14643-treated group. Lipidomic analysis revealed that chronic treatment with WY-14643 disturbed lipid homeostasis, especially triglycerides (TGs), which were significantly elevated after WY-14643 treatment. Moreover, TG homeostasis-related genes were significantly increased in the WY-14643-treated group. In conclusion, these findings demonstrated that hepatomegaly and liver tumors induced by chronic treatment with WY-14643 in mice are accompanied by hepatocyte proliferation and TG accumulation. SIGNIFICANCE STATEMENT: The present study clearly demonstrated that sustained peroxisome proliferator-activated receptor α (PPARα) activation by chronic treatment with WY-14643 induces hepatomegaly and liver tumors with triglyceride accumulation by regulating lipid homeostasis-related genes in mice. These findings may help to clarify the influences of sustained PPARα activation on liver lipid homeostasis and provide data for the clinically rational use of drugs that can activate PPARα.

Wilson disease (WD) is a metabolic disorder caused by inactivation of the copper-transporting ATPase 2 (ATP7B) and copper (Cu) overload in tissues. Excess Cu causes oxidative stress and pathologic changes with poorly understood mechanistic connections. In Atp7b^-/- mice with established liver disease, Cu overload activates the stress-sensitive transcription factor Nrf2 (nuclear factor erythroid-derived 2-like 2). Nrf2 targets, especially sulfotransferase 1e1 (Sult1e1), are strongly induced and cause elevation of sulfated sterols, whereas oxysterols are decreased. This sterol misbalance results in inhibition of the liver X receptor (LXR) and up-regulation of LXR targets associated with inflammatory responses. Pharmacological inhibition of Sult1e1 partially reverses oxysterol misbalance and LXR inhibition. Contribution of this pathway to advanced hepatic WD was demonstrated by treating mice with an LXR agonist. Treatment decreased inflammation by reducing expression of proinflammatory molecules, diminished fibrosis by down-regulating the noncanonical transforming growth factor-β signaling pathway, and improved liver morphology and function. Thus, the identified pathway is an important driver of WD.

St. John's wort (SJW) is a medicinal herb remedy for mild depression. However, long-term use of SJW has raised safety concerns in clinical practice because of drug-drug interactions. Excessive use of acetaminophen (APAP) causes severe hepatotoxicity, but whether SJW modulates APAP-induced liver injury remains unclear. In this study, the effect of long-term SJW administration on APAP-induced acute hepatotoxicity and the involved mechanisms were investigated. Morphological and biochemical assessments clearly demonstrated that SJW exacerbates APAP-induced toxicity in vivo and in vitro. Moreover, SJW markedly promoted glutathione depletion and increased the levels of the APAP-cysteine and APAP-N-acetylcysteinyl adducts in mice, which enhanced APAP metabolic activation and aggravated APAP-induced liver injury. To further elucidate APAP metabolic activation in liver injury induced by SJW, the activities and expression levels of CYP2E1 and CYP3A were measured. The results showed that the activities and expression levels of CYP2E1 and CYP3A were increased after SJW treatment. Furthermore, the PXR-CYP signaling pathway was activated by SJW, and its downstream target genes were upregulated. Collectively, this study demonstrated that the long-term administration of SJW extract led to the metabolic activation of APAP and significantly exacerbated APAP-induced liver injury, which may suggest caution for the clinical use of SJW and APAP.

Nuclear receptor pregnane X receptor (PXR) can induce significant liver enlargement through hepatocyte hypertrophy and proliferation. A previous report showed that during the process of PXR-induced liver enlargement, hepatocyte hypertrophy occurs around the central vein (CV) area while hepatocyte proliferation occurs around the portal vein (PV) area. However, the features of this spatial change remain unclear. Therefore, this study aims to explore the features of the spatial changes in hepatocytes in PXR-induced liver enlargement. PXR-induced spatial changes in hepatocyte hypertrophy and proliferation were confirmed in C57BL/6 mice. The liver was perfused with digitonin to destroy the hepatocytes around the CV or PV areas, and then the regional expression of proteins related to hepatocyte hypertrophy and proliferation was further measured. The results showed that the expression of PXR downstream proteins, such as cytochrome P450 (CYP) 3A11, CYP2B10, P-glycoprotein (P-gp) and organ anion transporting polypeptide 2 (OATP2) was upregulated around the CV area, while the expression of proliferation-related proteins such as cyclin B1 (CCNB1), cyclin D1 (CCND1) and serine/threonine NIMA-related kinase 2 (NEK2) was upregulated around the PV area. At the same time, the expression of cyclin-dependent kinase inhibitors such as retinoblastoma-like protein 2 (RBL2), cyclin-dependent kinase inhibitor 1B (CDKN1B) and CDKN1A was downregulated around the PV area. This study demonstrated that the spatial change in PXR-induced hepatocyte hypertrophy and proliferation is associated with the regional expression of PXR downstream targets and proliferation-related proteins and the regional distribution of triglycerides (TGs). These findings provide new insight into the understanding of PXR-induced hepatomegaly.

The prevalence of liver disease has been increasing worldwide. Moreover, the burden of end-stage liver disease, including cirrhosis and liver cancer, is high because of high mortality and suboptimal treatment. The pathological process of liver disease includes steatosis, hepatocyte death, and fibrosis, which ultimately lead to cirrhosis and liver cancer. Clinical and preclinical evidence indicates that non-neoplastic liver diseases, particularly cirrhosis, are major risk factors for liver cancer, although the mechanism underlying this association remains unclear. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional activators that regulate organ size and cancer development. YAP and TAZ play important roles in liver development, regeneration, and homeostasis. Abnormal YAP and TAZ levels have also been implicated in non-neoplastic liver diseases (e.g., non-alcoholic fatty liver disease, alcoholic liver disease, liver injury, and liver fibrosis). Here, we review recent findings on the roles of YAP and TAZ in non-neoplastic liver diseases and discuss directions for future research. This review provides a basis for the study of non-neoplastic liver diseases.

Pregnane X receptor (PXR) and constitutively active receptor/constitutive androstane receptor (CAR) are xenobiotic-responsible transcription factors belonging to the same nuclear receptor gene subfamily and highly expressed in the liver. These receptors are activated by a variety of chemicals and play pivotal roles in many liver functions, including xenobiotic metabolism and disposition. Phenobarbital, an enzyme inducer and liver tumor promoter, activates both rodent and human CAR but causes liver tumors only in rodents. Although the precise mechanism for phenobarbital/CAR-mediated liver tumor formation remains to be established, intracellular pathways, including the Hippo pathway/Yes-associated protein-TEA-domain family members system and β-catenin signaling, seem to be involved. In contrast to CAR, previous findings by our group suggest that PXR activation does not promote hepatocyte proliferation but it enhances the proliferation induced by various stimuli. Moreover, and surprisingly, PXR may have antitumor effects in both rodents and humans by targeting inflammatory cytokine signals, angiogenesis and epithelial-mesenchymal transition. In this review, we summarize the current knowledge on the associations of PXR and CAR with hepatocyte proliferation and liver tumorigenesis and their molecular mechanisms and species differences. SIGNIFICANCE STATEMENT: Pregnane X receptor and constitutively active receptor/constitutive androstane receptor have very similar functions in the gene regulation associated with xenobiotic disposition, as suggested by their identification as xenosensors for enzyme induction. In contrast, recent reports clearly suggest that these receptors play distinct roles in the control of hepatocyte proliferation and liver cancer development. Understanding these differences at the molecular level may help us evaluate the human safety of chemical compounds and develop novel drugs targeting liver cancers.