Preconditioning with sufentanil confers protective effects in transplantation by attenuating hepatic ischemia-reperfusion injury

Abstract

Hepatic ischemia-reperfusion injury (HIRI) is a significant contributor to liver dysfunction and failure following liver transplantation and hepatic surgical procedures. With the increasing global incidence of end-stage liver disease necessitating transplantation, strategies to mitigate HIRI have become important. Ferroptosis, a regulated form of cell death characterized by iron dependency and lipid peroxidation, has recently been recognized as a pivotal mechanism underlying hepatocellular injury during ischemia-reperfusion events. Emerging evidence suggests that in the context of HIRI, ferroptosis is facilitated by the convergence of iron overload, compromised antioxidant defenses, and excessive generation of lipid reactive oxygen species. Notably, EMP1/p38-mediated ferroptosis in liver sinusoidal endothelial cells directly contributes to hepatocyte damage via activation of the p38 mitogen-activated protein kinase pathway. Consequently, ferroptosis represents a promising therapeutic target for HIRI. Pharmacological inhibition of ferroptosis through modulation of the glutathione peroxidase 4 and cyclic guanosine monophosphate-adenosine monophosphate synthase pathways has been shown to ameliorate liver function. The organ-protective effects of sufentanil, a potent μ-opioid receptor agonist commonly employed for perioperative analgesia, extend beyond its anesthetic properties. Preconditioning with sufentanil appears to regulate ferroptosis by targeting activating transcription factor 3. Additionally, sufentanil downregulates the expression of hypoxia-inducible factor 1-alpha and the long noncoding RNA KCNQ1OT1 in HIRI, counteracting their pathological upregulation. These protective effects are closely associated with the attenuation of oxidative stress through the activation of nuclear factor erythroid 2-related factor 2, modulation of inflammatory responses, and preservation of mitochondrial integrity, all of which are mechanistically linked to the regulation of ferroptosis. This review synthesizes current insights into the role of ferroptosis in HIRI and explores the potential of sufentanil preconditioning in mitigating hepatic injury via ferroptosis-related pathways. The evidence to date suggests that sufentanil may attenuate ferroptosis and improve clinical outcomes in HIRI by modulating oxidative stress and associated signaling pathways. Further research on ferroptosis-targeted therapies, including pharmacological modulation of opioid receptor pathways, shows promise for developing novel interventions that protect the liver from ischemia-reperfusion injury.

Key Words: Hepatic ischemia-reperfusion injury; Liver transplantation; Ferroptosis; Iron metabolism; Lipid peroxidation; Oxidative stress; Hepatocellular injury; Sufentanil

Core Tip: Ferroptosis is critically involved in the pathogenesis of hepatic ischemia-reperfusion injury, primarily through the coordinated disruption of iron homeostasis, lipid peroxidation processes, and antioxidant defense mechanisms. Ferroptosis is characterized by morphological and biochemical features that differentiate it from apoptosis and necrosis; the inhibition of ferroptosis results in the reduction of injury markers, improving liver function in an experimental setting. Beyond its established analgesic properties, sufentanil may confer hepatoprotective effects by modulating pathways associated with ferroptosis. Investigating the interplay between sufentanil and ferroptotic mechanisms could yield valuable therapeutic strategies that enhance clinical outcomes in liver surgery and transplantation.

INTRODUCTION

Hepatic ischemia-reperfusion injury (HIRI) is an inevitable pathological event that occurs during liver transplantation, hepatic resection involving vascular occlusion, and hemorrhagic shock. While reperfusion is critical for the restoration of hepatic oxygenation and nutrient delivery, it paradoxically exacerbates hepatic injury through mechanisms involving excessive oxidative stress, activation of inflammatory pathways, and hepatocellular death[1,2]. Clinically, HIRI is strongly implicated in early allograft dysfunction, increased postoperative complications, and unfavorable long-term prognoses[1,3]. The incidence of end-stage liver disease and its associated mortality have increased substantially in recent years, with liver transplantation remaining the sole definitive therapeutic intervention for affected patients[4]. During transplantation, HIRI affects nearly all grafts to varying extents, with the severity of injury being correlated with elevated morbidity, primary graft dysfunction, and potential graft loss[5]. Furthermore, the increasing demand for liver grafts and the imperative to expand the donor pool have prompted the utilization of grafts obtained from donors meeting expanded criteria as well as from donors after cardiac death[6,7]. Due to inherent risk factors and prolonged warm ischemia times during procurement, these liver grafts exhibit heightened susceptibility to HIRI, resulting in an increased incidence of postoperative complications such as biliary stricture, primary nonfunction, and delayed graft function[8,9].

Recent advancements in the investigation of regulated cell death have improved the understanding of the pathogenesis of HIRI, extending beyond the traditional frameworks of apoptosis and necrosis. Ferroptosis, a unique form of regulated cell death characterized by iron-dependent lipid peroxidation, has garnered increasing recognition as a pivotal mechanism underlying HIRI[4-6]. Empirical studies have demonstrated that both pharmacological and genetic inhibition of ferroptosis markedly mitigate liver damage and enhance hepatic function following ischemia-reperfusion events[7-9]. The inhibition of ferroptosis interferes with cell death mechanisms mediated by the glutathione peroxidase 4 (GPX4) and guanosine monophosphate-adenosine monophosphate synthase pathways[10]. Notably, ferroptosis mediated by EMP1 and p38 in liver sinusoidal endothelial cells directly contributes to hepatocyte injury through the activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway. These findings demonstrate that EMP1/p38-mediated ferroptosis in liver sinusoidal endothelial cells directly contributes to hepatocyte injury[8]. Therefore, targeting ferroptosis has considerable potential as a therapeutic strategy for HIRI and renal dysfunction[8].

Sufentanil, a synthetic μ-opioid receptor (MOR) agonist, is extensively utilized in clinical anesthesia because of its potent analgesic effects and stable hemodynamic profile. In addition to its anesthetic properties, sufentanil has been reported to confer protective effects against ischemia-reperfusion injury across various organs by attenuating oxidative stress, inflammation, and mitochondrial dysfunction[8]. Considering the significant mechanistic intersections between these pathological processes and ferroptosis, it is plausible that sufentanil may alleviate HIRI by modulating ferroptosis-associated signaling pathways.

The administration of sufentanil has been demonstrated to reduce lipid peroxidation, restore GPX4 expression, and mitigate liver injury through the modulation of hypoxia-associated noncoding RNA signaling pathways[10-12]. Furthermore, sufentanil inhibits ferroptosis in cerebral ischemia-reperfusion injury by activating the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant pathway, which is intimately linked to resistance against ferroptosis[13-16]. These observations support the hypothesis that the hepatoprotective effects of sufentanil may be mediated, at least in part, by the suppression of ferroptosis-related oxidative damage. Additionally, inhibition of ferroptosis by liproxstatin-1 has been shown to alleviate ischemia/reperfusion (I/R)-induced intestinal injury. Acyl-CoA synthetase long-chain family member 4 (ACSL4), a critical enzyme involved in regulating lipid composition, has been implicated in the execution of ferroptosis; however, its specific role in I/R injury remains to be elucidated[17,18].

Ferroptosis represents a promising therapeutic target for the treatment of HIRI. The MOR has been implicated in the regulation of ferroptosis in HIRI. Additionally, the administration of sufentanil has been shown to reduce the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and the long noncoding RNA KCNQ1OT1 in HIRI models[19]. Sufentanil preconditioning has been reported to mitigate HIRI in a rat model by regulating ferroptosis via the activation of activating transcription factor 3 (ATF3)[20].

The current narrative review consolidates the contemporary understanding of the involvement of ferroptosis in HIRI and investigates the potential of sufentanil preconditioning to attenuate liver damage through ferroptosis-associated mechanisms, while assessing the feasibility of its application in clinical settings. The available literature was identified through structured searches of PubMed and Scopus using terms related to HIRI, ferroptosis, and sufentanil. Priority was given to recent, mechanistic, and clinically relevant transplantation studies, however, no formal systematic review methodology was used.

HIRI

HIRI is a complex, multifactorial process that occurs when the temporary interruption of hepatic blood flow is followed by the restoration of oxygen delivery. HIRI is primarily associated with surgical procedures such as major hepatectomies and liver transplantation but it also occurs in other clinical conditions, including hypovolemic shock, various forms of hepatotoxicity, hepatic veno-occlusive disease, and Budd-Chiari syndrome. Additionally, cold HIRI results in cellular damage mainly during graft preservation prior to transplantation[1,21]. The pathophysiology of HIRI has a biphasic evolution, with an early phase occurring within hours of reperfusion and characterized by oxidative stress and Kupffer cell activation and a late phase marked by neutrophil infiltration and sustained inflammatory injury[22]. During the ischemic phase, oxygen deprivation suppresses mitochondrial oxidative phosphorylation, leading to rapid depletion of intracellular adenosine triphosphate (ATP) and cellular energy deficiency. To maintain the necessary energy balance, the hepatocytes shift toward anaerobic glycolysis, resulting in the accumulation of lactate and the development of metabolic acidosis. Concurrent failure of ATP-dependent ion pumps, particularly sodium-potassium-ATPase, disrupts ionic homeostasis, causing intracellular sodium and calcium accumulation, cellular edema, and early impairment of sinusoidal microcirculation[23,24].

The reperfusion phase exacerbates hepatocellular injury through excessive generation of reactive oxygen species (ROS). Mitochondria, Kupffer cells, activated neutrophils, and enzymes such as xanthine oxidase contribute to a burst of ROS that overwhelms endogenous antioxidant mechanisms. Oxidative stress induces lipid peroxidation, protein oxidation, DNA damage, and mitochondrial dysfunction, ultimately triggering multiple forms of hepatocellular death, including apoptosis, pyroptosis, and ferroptosis[24,25].

A wide range of cytokines and chemokines contribute to HIRI. Key mediators include tumor necrosis factor-α (TNF-α), platelet-activating factor, and interleukins (ILs) such as IL-1β, IL-6, and IL-10, which act through autocrine, paracrine, and endocrine mechanisms to induce the inflammatory response. TNF-α, which is primarily released by Kupffer cells, plays a central role in HIRI by promoting leukocyte activation, endothelial adhesion molecule expression, and downstream signaling pathways that exacerbate hepatocellular dysfunction and cell death. Additional cytokines, including interferon-γ, IL-12, and IL-17-related pathways, and chemokines of the ELR⁺ CXC family, further amplify neutrophil recruitment and inflammatory injury. By contrast, selected cytokines such as IL-6, IL-10, and IL-13 and hepatocyte growth factor exert hepatoprotective effects by limiting oxidative stress, suppressing excessive inflammation, and supporting tissue repair and regeneration[26,27]. Complement activation and nuclear factor kappa-B (NF-κB)-dependent transcription further amplify inflammatory signaling and microvascular dysfunction[28,29]. The mechanisms of HIRI are shown in Figure 1.

Figure 1 Schematic mechanisms of hepatic ischemia-reperfusion injury. NO: Nitric oxide; ATP: Adenosine triphosphate; Ca: Calcium; ROS: Reactive oxygen species; pH: Potential of hydrogen; TNF: Tumor necrosis factor; IL: Interleukin; NF-κB: Nuclear factor kappa-B.

The combination of metabolic failure, mitochondrial dysfunction, oxidative stress, and inflammatory activation ultimately leads to hepatocellular death through the regulation of cell death pathways, disruption of hepatic microcirculation, and progressive impairment of liver function. Although necrosis appears to be the predominant mode of cell death during HIRI, additional forms of programmed cell death contribute to the complexity of hepatocellular injury. Apoptosis is mediated through both extrinsic death receptor–dependent and intrinsic mitochondria-dependent pathways, involving signaling cascades such as transforming growth factor-beta activated kinase 1, c-Jun N-terminal kinase (JNK), p38 MAPK, apoptosis signal-regulating kinase 1, and phosphoinositide-3 kinase (PI3K)/activation of protein kinase B (Akt)[30]. Pyroptosis is a proinflammatory form of cell death driven by NLRP3 inflammasome activation, caspase-1/4/11, and gasdermin D, which amplifies hepatic inflammation, while ferroptosis is characterized by iron-dependent lipid peroxidation and membrane damage, adding an additional layer to HIRI[8,31,32].

Cellular and molecular events during HIRI are closely associated with clinical risk factors in liver transplantation, including donor organ steatosis, ischemic duration, donor age, and donor-recipient coagulopathy. These events may vary according to the type of ischemic insult (warm or cold); graft characteristics, such as donation after circulatory death; or the use of machine perfusion. Warm HIRI is driven mainly by hepatocytes, whereas cold HIRI primarily involves injury to hepatic sinusoidal endothelial cells, resulting in microvascular dysfunction. Liver steatosis, advanced donor age and prolonged ischemic time are recognized risk factors for increased HIRI, whereas the use of ex vivo perfusion has been associated with reduced liver injury. This approach is based on the principle that sustained sinusoidal flow during hypothermic perfusion alleviates injury to liver sinusoidal endothelial cells[33,34]. Clinically, HIRI is characterized by altered biochemical markers of hepatocellular injury, including transaminase levels and impaired synthetic function. In liver transplant patients, HIRI is associated with early allograft dysfunction and increased rates of acute and chronic rejection. In severe cases, it may result in a systemic inflammatory response and multiorgan dysfunction syndrome, contributing to significant morbidity and mortality. These clinical manifestations of HIRI underscore the importance of understanding the underlying molecular mechanisms as potential therapeutic targets to improve graft function and patient outcomes[34].

FERROPTOSIS

Ferroptosis was first described by Dixon et al[4] in 2012 as a regulated, iron-dependent form of cell death distinct from apoptosis, marked by excessive lipid ROS accumulation. Ferroptosis was initially uncovered through studies of erastin, a compound that selectively induces nonapoptotic cell death in RAS-expressing cancer cells. This form of cell death was characterized by the absence of caspase activation, DNA fragmentation, and nuclear morphological changes and was later shown to be iron dependent and suppressible by iron chelators. Ferroptosis is distinguished by characteristic mitochondrial alterations, depletion of glutathione (GSH), inactivation of GPX4, and excessive iron-driven lipid peroxidation, culminating in oxidative damage. Ferroptosis-inducing agents can be broadly classified into four categories on the basis of their mechanisms of action. The first category includes erastin, the prototypical ferroptosis inducer, which triggers ferroptosis by inhibiting the cystine/glutamate antiporter system Xc^-, leading to GSH depletion. Notably, GSH synthesis depends on the uptake of cystine via system Xc^-, a cystine-glutamate antiporter composed of the light chain SLC7A11 (xCT) and the heavy chain SLC3A2 (CD98hc)[35]. The second category comprises compounds such as RSL3 and DPI7, which directly inactivate GPX4. Accumulating evidence indicates that ATF3 plays a crucial role in the ferroptotic process, primarily through modulation of the cystine/glutamate antiporter system Xc^- and GPX4. Conversely, ATF3 may exert anti-ferroptotic effects in specific contexts, including ischemia-reperfusion injury, by upregulating GPX4 expression and regulating FANCD2 promoter activity[36-38]. The third category includes FIN56, which induces ferroptosis by promoting GPX4 degradation and depleting the antioxidant coenzyme Q10 (CoQ10) through inhibition of squalene synthase, while the fourth category involves FINO2, an organic peroxide that induces ferroptosis via the combination of unstable iron oxidation and GPX4 inactivation[39-41]. Simplified mechanisms of ferroptosis are shown in Figure 2.

Figure 2 Simplified mechanisms of ferroptosis. ROS: Reactive oxygen species; GSH: Glutathione; GPX4: Glutathione peroxidase 4; CoQ10: Coenzyme Q10.

On the basis of the cellular mechanism of action, several protective pathways against ferroptosis have been identified. The system Xc^--GSH-GPX4 axis constitutes the core intracellular defense against ferroptosis. The inhibition of this axis, either at the level of cystine transport or GPX4 activity, sensitizes cells to ferroptosis[42]. Antioxidant pathways, including the transsulfuration pathway and GPX4-independent systems such as ferroptosis suppressor protein 1 (FSP1)-CoQ10 and guanosine triphosphate cyclohydrolase 1-regulated tetrahydro-biopterin synthesis, further modulate ferroptosis sensitivity in a cell type-dependent manner[43,44]. Specifically, the antiferroptotic activity of FSP1 is mediated by ubiquinone (CoQ10), while FSP1 catalyzes the reduction of nicotinamide adenine dinucleotide phosphate hydrogen-dependent CoQ10 to ubiquinol, which neutralizes lipid peroxyl radicals[43,45]. In an experimental setting, the transcriptional inhibition of GPX4 mediated by the interferon regulatory factor-1/Zinc finger protein 350 complex resulted in the initiation of ferroptosis[46]. The NFE2 L2 (NRF2) transcriptional program constitutes another protective pathway that orchestrates a broad range of antioxidant and cytoprotective responses during HIRI. Upon oxidative stress, NRF2 induces the expression of genes involved in GSH synthesis, iron sequestration, lipid detoxification, and redox homeostasis, thereby conferring resistance to ferroptosis. Dysregulation of this pathway can profoundly influence ferroptotic vulnerability, particularly in the cases of cancer and ischemia-reperfusion[47-50]. The activation of NRF2 through the carbon monoxide-protein kinase RNA-like endoplasmic reticulum kinase-NRF2-immune-responsive gene 1 axis suppresses inflammation in Kupffer cells and inhibits ferroptosis in hepatocytes[51]. The specificity protein 1 (SP1)/DNA-dependent protein kinase catalytic subunit (DNA-PKcs) axis exerts anti-ferroptotic effects by reducing iron-dependent lipid peroxidation. Specifically, SP1-mediated transcriptional activation of PRKDC (DNA-PKcs) enhances resistance to ferroptotic stress and limits lipid peroxidation-induced cell death[52]. Additionally, ESCRT-III acts as a late-stage membrane repair system that preserves membrane integrity and limits inflammatory cell death, including ferroptosis, necroptosis, and pyroptosis[49,53,54]. Together, these pathways underscore that ferroptosis is not a passive oxidative breakdown but a regulated process consisting of coordinated antioxidant, transcriptional, and membrane repair defences.

FERROPTOSIS IN HIRI

Ferroptosis has been implicated in ischemia-reperfusion injury in multiple organs, including the brain, heart, kidney, intestine, and liver. In the pathophysiology of liver diseases, ferroptosis is increasingly recognized as a critical mechanism contributing to hepatocellular injury during HIRI, and it is characterized by iron overload, excessive ROS accumulation, mitochondrial swelling, and the subsequent release of damage-associated molecular patterns (DAMPs)[35,55,56]. In clinical settings, iron overload has emerged as an independent risk factor for liver transplantation; however, the pathways linking ferroptosis to HIRI pathogenesis remain to be clarified[57,58]. In addition, ferroptosis plays a critical role in fatty liver HIRI, which is driven by enhanced lipid peroxidation in the presence of stored iron in hepatic tissue[59]. Recent data suggest that ferroptosis may also act as a triggering mechanism in nonalcoholic steatohepatitis, acute liver injury, and drug-induced liver injury, contributing to hepatocellular injury, immune cell infiltration, and inflammatory responses[60,61].

During HIRI, ferroptosis is triggered by a complex interaction of metabolic, oxidative, and inflammatory events, leading to iron-dependent lipid peroxidation and oxidative stress. Iron overload enhances ROS generation, activates intracellular signaling pathways, and promotes IL-1β-mediated cytokine release, exacerbating hepatocellular injury[57,62]. Mitochondria are a major source of ROS during the respiratory chain reactions, whereas iron-dependent lipid ROS drive phospholipid peroxidation, leading to the accumulation of lipid peroxides. These peroxides disrupt membrane integrity, inactivate membrane-bound proteins and impair receptor signaling pathways, thereby promoting the inflammatory response. Excessive mitochondrial ROS damage the electron transport chain, reduce ATP production, and induce mitochondrial DNA mutations, creating a vicious cycle of oxidative stress and mitochondrial dysfunction[8,63]. Transient receptor potential melastatin 2 (TRPM2) plays a critical role in HIRI by promoting ferroptosis. Specifically, TRPM2-mediated calcium influx leads to mitochondrial calcium overload and arachidonate 12-lipoxygenase-dependent lipid peroxidation, leading to hepatocellular injury[56]. Ma et al[64] highlighted the crucial role of indoleamine 2,3-dioxygenase 1 activation in macrophages in triggering hepatocellular ferroptosis in hepatocytes during HIRI.

Recent evidence implicates signal transducer and activator of transcription 1 (STAT1) as a key regulator in HIRI. STAT1, a transcription factor involved in immune and inflammatory signaling, is significantly upregulated during HIRI and interacts with pathways related to ferroptosis and inflammation. Mechanistically, STAT1 suppresses miR-497-5p transcription, resulting in histone deacetylase 7 activation, which collectively enhances ferroptosis and inflammatory responses during HIRI[65]. Overall, growing evidence suggests that microRNAs play a central role as mediators of the pathophysiological effects of HIRI. Among the identified microRNAs, miR-1275 exerts protective effects in aged hepatocytes, especially when enriched in mesenchymal stem cell-derived extracellular vesicles. SLC39A14, a key iron importer, was identified as a validated target of miR-1275, suggesting that miR-1275 may represent a novel therapeutic target for protecting aged liver grafts during transplantation by limiting iron accumulation and ferroptosis[66-68]. HIRI-induced ferroptosis was further investigated using bioinformatics analysis, which identified 11 ferroptosis-related genes associated with HIRI, underscoring the strong link between ferroptosis and HIRI and supporting ferroptosis inhibition as a potential therapeutic strategy[69].

Ferroptosis induction in liver tissue appears to be associated with elevated hepatic malondialdehyde levels and upregulation of the expression of the ferroptosis markers cyclooxygenase-2 (COX-2) (gene Ptgs2) and heme oxygenase 1 (HO-1) (gene Hmox1), along with increased levels of inflammatory mediators, such as serum myeloperoxidase, IL-6 and IL-1β, and TNF-α[70]. The upregulation of pro-ferroptotic genes (Hmox1, Tfrc, and Slc11a2) and the downregulation of anti-ferroptotic genes (Slc40a1 and Gpx4) are connected with the signal transducer and activator of transcription 3 (STAT3) signaling pathway. During HIRI, STAT3 regulates mitochondrial function through multiple signaling pathways and is involved in apoptosis and other forms of programmed cell death. Moreover, STAT3 interacts with key pathways, including Janus kinase (JAK), PI3K, and HO-1 signaling[70,71]. Collectively, these findings indicate that the STAT3-HO-1/COX-2 pathway contributes to iron-induced ferroptosis during HIRI. Inhibiting the activation of the JAK2/STAT3 signaling pathway using pharmacological agents has been reported to significantly alleviate HIRI and associated inflammation by reducing the release of proinflammatory cytokines[72,73]. However, the activation of the PI3K/Akt signaling pathway protects against HIRI-induced ferroptosis by reducing lipid peroxidation, iron overload, and oxidative stress and by upregulating GPX4 expression[10,74,75]. In parallel, the activation of NRF2, a critical cytoprotective regulator, enhances antioxidant defenses by upregulating molecules such as GPX4 and SLC7A11, thereby limiting ROS accumulation, inhibiting ferroptosis, and protecting hepatocytes from oxidative injury[76-79].

Several studies have highlighted the role of the mitogen extracellular kinase-extracellular signal-regulated kinase (MEK/ERK) signaling pathway in mediating HIRI through the regulation of the inflammatory response, autophagy, and apoptosis, although its role in ferroptosis remains to be elucidated. Recent evidence has indicated that HIRI reduces the phosphorylation of MEK1/2 and ERK1/2, whereas the restoration of MEK/ERK activity attenuates ferroptosis-related changes and increases cellular viability. Conversely, inhibition of ERK signaling exacerbates ferroptotic cell death[80,81]. The key molecular pathways involved in ferroptosis during HIRI are shown in Table 1.

Table 1 Key molecular pathways of ferroptosis on hepatic ischemia-reperfusion injury.

Regulatory pathway/factor	Mechanism in HIRI
TRPM2	Calcium-calcium overload (increase); ALOX12-dependent lipid peroxidation
IDO-1 (macrophage)	Immune activation
STAT1	miR-497-5p transcription (decrease)-HDAC7 activation
Pro-ferroptotic genes (Hmox1, Tfrc, Slc11a2)	Upregulation
Anti-ferroptotic genes (Slc40a1, Gpx4)	Downregulation
STAT3-HO-1/COX-2 axis	Regulation of iron metabolism and inflammation
JAK2/STAT3 pathway	Release of pro-inflammatory cytokines
MEK/ERK signaling pathway	Regulation of inflammatory response

HIRI: Hepatic ischemia-reperfusion injury; TRPM2: Transient receptor potential melastatin 2; IDO-1: Indoleamine 2, 3-dioxygenase 1; STAT1: Signal transducer and activator of transcription 1; STAT3: Signal transducer and activator of transcription 3; HO-1: Heme oxygenase 1; ALOX12: Arachidonate 12-lipoxygenase; HDAC7: Histone deacetylase 7; COX-2: Cyclooxygenase-2; JAK2: Janus kinase 2; MEK: Mitogen extracellular kinase; ERK: Extracellular signal-regulated kinase.

In the context of HIRI, ferroptosis plays a central role in promoting hepatocyte death and amplifying tissue damage during the reperfusion phase. Ferroptosis is characterized by mitochondrial dysregulation, increased membrane density, and iron-dependent accumulation of lipid peroxides within cellular membranes, ultimately leading to membrane rupture. Ferroptotic hepatocytes release DAMPs, triggering neutrophil and macrophage infiltration in hepatic tissue and promoting the production of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. Concurrently, intracellular iron overload further accelerates injury through ROS generation. In chronic or repetitive injury settings, sustained ferroptosis may contribute to fibrosis progression by activating hepatic stellate cells[82,83].

SUFENTANIL

Various strategies have been investigated to mitigate HIRI, by targeting oxidative stress, inflammation, and cell death pathways. Pharmacological agents, including melatonin, N-acetylcysteine, caspase inhibitors, prostacyclin analogs, anesthetic agents (such as remifentanil), P-selectin antagonists and other interventions, have been shown to have protective effects in experimental models, although clinical evidence remains lacking[21,34,84,85]. Emerging targets, such as Akt and peroxisome proliferator-activated receptor gamma signaling pathways and microRNA-based and stem cell therapies, further highlight the importance of HIRI modulation[23,34]. Parallel surgical techniques, including ischemic preconditioning, postconditioning, and machine perfusion approaches, have shown encouraging preclinical and clinical benefits (Table 2)[34,86]. In this context, sufentanil has emerged as a potential modulator of HIRI.

Table 2 Available data on strategies targeting hepatic ischemia-reperfusion injury.

Strategy/drug	Animal evidence	Human evidence	Reported effect
Melatonin	Extensive	Limited	Positive
N-acetylcysteine	Extensive	Moderate	Mixed
Nobel gases	Limited	Limited	Insufficient
Caspase inhibitors	Extensive	Limited	Positive
P-selectin antagonists	Moderate	Limited	Mixed
Prostaglandins	Extensive	Moderate	Positive
Remifentanil	Moderate	Limited	Positive
Noble gases	Limited	Limited	insufficient
Akt activators	Moderate	None	Positive
PPARγ agonists	Moderate	None	Positive
miRNA based therapies	Moderate	None	Positive
Stem cell therapies	Extensive	Limited	Positive
Ischemic preconditioning	Expensive	Moderate	Positive
Ischemic postconditioning	Moderate	Limited	Mixed
Machine perfusion techniques	Extensive	Extensive	Positive

Akt: Activation of protein kinase B; PPARγ: Peroxisome proliferator-activated receptor gamma; miRNA: MicroRNA.

Sufentanil is a highly lipophilic opioid agonist with strong selectivity for MORs, exhibiting potent analgesic and sedative effects and hemodynamic stability. It was developed in the 1970s and received approval from the United States Food and Drug Administration (FDA) in 1984. Sufentanil has a methoxymethyl group (-CH₂OCH₃) added to the 4-position of the piperidine ring (Figure 3). This addition is believed to increase the drug’s lipophilicity, potency, and binding affinity to the MOR, as compared with those of fentanyl[87-89]. Originally used in cardiac anesthesia, it has also proven effective in spine, obstetric, and orthopedic surgery because of its potent analgesic effects, rapid onset, and limited interference with neuromonitoring. Compared with short-acting opioids, when sufentanil is administered as a continuous infusion, epidural, intrathecal, or sublingual formulation, it provides reliable intraoperative stability and enhanced postoperative pain control. The sublingual administration of sufentanil, approved by the FDA in 2018, further expanded its clinical utility, particularly in the context of postoperative pain management, where intravenous access is limited[90-93].

Figure 3 Structural comparison of sufentanil, fentanyl, and morphine.

In addition to its anesthetic properties, growing experimental and clinical evidence has demonstrated that sufentanil may exert cytoprotective effects during ischemia-reperfusion in different organs, such as the myocardium, kidney, brain, and liver (Table 3)[16,94-97]. The protective effects observed may not be specific to sufentanil but could reflect a broader class effect of opioid or anesthetic agents. This is suggested by similar findings with remifentanil, where proposed mechanisms include attenuation of oxidative stress, preservation of mitochondrial function, suppression of proinflammatory signaling cascades, and modulation of cell death regulatory pathways[88,96,97]. Emerging evidence indicates that sufentanil may modulate oxidative stress and iron-dependent lipid peroxidation pathways, attracting increasing attention because of its potential role in regulating ferroptosis.

Table 3 Cytoprotective effects of sufentanil in ischemia-reperfusion injury across different organs.

Organ	Main protective mechanisms	Biological outcomes
Myocardium	miR-125a/DRAM2 axis; activation of ERK1/2 pathway; activation of PI3K/Akt-GSK-3β pathway; modulation of Bax and Bcl-2 expression	Regulation of cardiomyocyte autophagy and oxidative injury; reduction of apoptosis
Kidney	Upregulation of miR-145-mediated autophagy; inhibition of KCNQ1OT1 and HMGB1 expression, promotion of miR-211-5p expression; activation of the PI3K/Akt/FOXO1	Regulation of autophagy; alleviation of inflammatory infiltration; suppress of cell apoptosis and oxidative stress
Brain	Activation of the Akt/GSK-3β pathway	Suppression of oxidative stress-related inflammation and ferroptosis
Liver	Suppression of the p38/ERK/JNK/NF-κB-p65/COX-2 pathways; upregulation of ATF3 expression; HIF-1α/KCNQ1OT1 axis; inhibition of ATF4-Induced TP53BP2 expression	Regulation of inflammatory response; mitigation of ferroptosis; reduction of apoptosis

DRAM2: Damage-regulated autophagy modulator protein 2; ERK: Extracellular signal-regulated kinase; PI3K: Phosphoinositide-3 kinase; Akt: Activation of protein kinase B; GSK-3β: Glycogen synthase kinase-3 beta; JNK: C-Jun N-terminal kinase; NF-κB-p65: Nuclear factor kappa-light-chain-enhancer of activated B cells p65 subunit; COX-2: Cyclooxygenase-2; ATF3: Activating transcription factor 3; HIF-1α: Hypoxia-inducible factor 1-alpha; ATF4: Activating transcription factor 4.

ROLE OF SUFENTANIL PRECONDITIONING IN PROTECTION AGAINST HIRI AND MODULATING FERROPTOSIS

Anesthetic preconditioning of the liver is a protective strategy in which anesthetics, mainly volatile agents, are administered prior to hepatic ischemia to attenuate HIRI, thereby reducing postischemic cellular damage[98]. Experimental studies have indicated that sufentanil has the potential to attenuate oxidative stress, to reduce proinflammatory cytokine production, and to suppress the activation of key stress-related signaling pathways. Recent data have demonstrated that sufentanil may attenuate HIRI by inhibiting the activation of the p38/ERK/JNK/NF-κB-p65/COX-2 signaling pathways in a dose-dependent manner[96]. Moreover, the inhibition of the expression of activating transcription factor 4 (ATF4) by sufentanil and the subsequent downregulation of the expression of the TP53BP2 attenuated TP53-dependent apoptosis of hepatic cells, providing hepatoprotection and highlighting the potential of sufenatnil as a therapeutic agent in HIRI[97,99].

Administration of sufentanil in patients with cerebral ischemia reperfusion injury alleviated cellular damage by activating the Akt/glycogen synthase kinase-3 beta (GSK-3β)/NRF2 axis, thereby suppressing oxidative stress-induced inflammation and ferroptosis[16]. Given the demonstrated protective effects of sufentanil, its potential application in HIRI and in modulating HIRI-induced ferroptosis warrants continued investigation. Recent studies have indicated that sufentanil pretreatment alleviates HIRI-induced ferroptosis through several pathways. ATF3 expression was evaluated in rat liver tissues after sufentanil administration through western blot and reverse transcription quantitative polymerase chain reaction. Compared with HIRI alone, sufentanil pretreatment significantly restored ATF3 expression, which was accompanied by a corresponding increase in GPX4 expression and a reduction in iron content. These findings indicated that sufentanil may attenuate ferroptosis in HIRI through an ATF3-associated mechanism[20].

HIF-1α overexpression represents an adaptive response to hypoxia, regulating genes involved in energy metabolism and oxygen transfer[100]. However, sustained HIF-1α activation during HIRI contributes to mitochondrial dysfunction, oxidative stress, inflammation and cell death[101-103]. A recent study demonstrated the significance of a HIF-1α and long noncoding RNA gene KCNQ1OT1 axis in which HIF-1α transcriptionally upregulates KCNQ1OT1, promoting ferroptosis in hepatocytes[19]. Mechanistically, KCNQ1OT1 interacts with the RNA-binding protein serine/arginine splicing factor 1 (SRSF1) to stabilize ACSL4 messenger RNA, enhancing lipid peroxidation and ferroptosis during HIRI progression[104,105]. Sufentanil administration has been reported to reduce HIF-1α and KCNQ1OT1 expression, thereby decreasing ACSL4 levels and limiting polyunsaturated fatty acid oxidation. These findings indicated that sufentanil has been shown to attenuate HIRI by inhibiting ferroptosis through modulation of the HIF-1α/KCNQ1OT1/SRSF1/ACSL4 signaling axis, highlighting its potential therapeutic value in HIRI[19]. The molecular mechanisms underlying the protective effects of sufentanil against HIRI are shown in Table 4.

Table 4 Molecular mechanisms underlying the protective effects of sufentanil in hepatic ischemia-reperfusion injury.

Signaling pathway	Sufentanil effect	Downstream mechanism	Consequences
p38/ERK/JNK/NF-κB-p65/COX-2	Inhibition	Suppression of inflammatory signaling	Cytokines production (decrease)
ATF4/TP53BP2 axis	Downregulation	Reduction of apoptosis	Hepatoprotection
ATF3 pathway	Restoration of ATF3 expression	GPX4 (increase), iron accumulation (decrease)	Attenuation of ferroptosis
HIF-1α/KCNQ1OT1 axis	Reduction of HIF-1α transcriptional activity	KCNQ1OT1 expression (decrease)	Inhibition of ferroptosis
KCNQ1OT1/SRSF1/ACSL4 pathway	ACSL4 levels stabilization	Limitation of PUFA oxidation	Inhibition of ferroptosis

ERK: Extracellular signal-regulated kinase; JNK: C-Jun N-terminal kinase; NF-κB-p65: Nuclear factor kappa-light-chain-enhancer of activated B cells p65 subunit; COX-2: Cyclooxygenase-2; ATF3: Activating transcription factor 3; HIF-1α: Hypoxia-inducible factor 1-alpha; ATF4: Activating transcription factor 4; SRSF1: Serine/arginine splicing factor 1; ACSL4: Acyl-CoA synthetase long-chain family member 4; GPX4: Glutathione peroxidase 4; PUFA: Polyunsaturated fatty acids.

Notably, the precise mechanistic link between sufentanil and ferroptosis remains undefined. While experimental studies suggest that sufentanil may influence processes closely associated with ferroptosis, direct evidence demonstrating a causal anti-ferroptotic effect in hepatic models remains limited. Preclinical data suggest the involvement of pathways such as the ATF3, ATF4 and HIF-1α-related signaling pathways in sufentanil preconditioning, whereas other proposed mechanisms, including NRF2 activation, are primarily inferred from studies of other organ systems. Therefore, these pathways should be considered hypothesis-generating rather than definitive.

FUTURE PROSPECTS

A number of reports have investigated the use of sufentanil in HIRI beyond its approved labeling, but clinical evidence remains limited. Sufentanil is a synthetic, highly selective MOR agonist with 7-10-fold higher potency than fentanyl and 500-1000-fold higher potency than morphine. Sufentanil has a known opioid-related side effect profile, consisting of nausea, vomiting, and headache, but it may also induce respiratory depression and neuropsychiatric effects, including dizziness, sedation, somnolence, and confusion, particularly in postoperative patients receiving concomitant central nervous system depressants[106-108].

While the available preclinical data suggest that sufentanil may attenuate HIRI through the modulation of ferroptosis-related pathways, several limitations must be considered when these findings are translated into clinical practice. Most evidence is derived from in vitro and animal models, which differ from humans in terms of hepatic anatomy and physiology, metabolic rate, and susceptibility to ischemic injury. Moreover, experimental models often involve controlled study conditions and homogeneous populations, in contrast to the variability encountered in clinical settings, including differences in donor characteristics, comorbidities, and perioperative management. While these studies provide important biological insights, their translational applicability should be interpreted with caution. A clearer distinction between experimental observations and clinical evidence is essential to avoid overstating the readiness of these findings for clinical implementation. The absence of standardized protocols for the use of sufentanil may present challenges, as inappropriate dosing or timing and route of administration could compromise its potential protective effects. Differences in dosing regimens, pharmacokinetics, and administration routes significantly influence drug efficacy. Although sufentanil is widely used in anesthesia practice, its application as a modulatory agent against HIRI remains investigational. In practice, sufentanil administration is driven by anesthetic requirements and may not coincide optimally with the ischemia–reperfusion window. Additionally, the complexity of human surgical procedures, including variable ischemia duration, comorbidities, and perioperative management, may further modulate the observed effects. Determining the optimal dosing strategies, timing of administration (preconditioning or postconditioning) and duration of treatment requires systematic evaluation. Expanding its use beyond established anesthetic indications necessitates comprehensive research in both experimental and clinical settings.

Despite the promising evidence suggesting antioxidative, anti-inflammatory, antiapoptotic, and antiferroptotic properties, further mechanistic and clinical studies are essential to confirm both the safety and therapeutic efficacy of sufentanil in the context of liver transplantation. Preclinical studies employing experimental HIRI models should clarify the effects of sufentanil on oxidative stress pathways, ferroptosis regulation, mitochondrial function, and inflammatory signaling cascades, as well as define dose-response relationships and toxicity thresholds. Particular attention should be given to its interaction with key signaling pathways, such as the Akt/GSK-3β/NRF2, HIF-1α-dependent mechanisms, and the MAPK/NF-κB cascades, as well as other molecular axes.

From a translational perspective, a first step toward clinical validation would be the design of randomized controlled trials comparing sufentanil-based anesthetic regimens with alternative opioid or anesthetic strategies in patients undergoing liver transplantation or major hepatic resection. Such studies could randomize patients to receive either sufentanil or a comparator agent, with standardized perioperative protocols to minimize confounding factors. Clearly defined primary and secondary endpoints, such as biochemical markers of liver injury, inflammatory and ferroptotic biomarkers, post-transplant liver function, and long-term graft survival, will be crucial. Although challenging, such trials would provide critical evidence regarding the clinical relevance of ferroptosis modulation and help determine whether sufentanil confers meaningful hepatoprotection in humans. Given its established perioperative use and favorable hemodynamic profile, sufentanil holds promise as a translational therapeutic strategy to mitigate HIRI, especially in patients undergoing liver resection and transplantation. However, its application beyond conventional analgesic use should be individualized and evidence-based.

CONCLUSION

Hepatic ischemia-reperfusion injury continues to be a pivotal factor influencing postoperative liver dysfunction. Accumulating evidence suggests that ferroptosis plays a central role in mediating hepatocellular damage under these conditions. Ferroptosis contributes to injury by disrupting iron homeostasis, enhancing lipid peroxidation, and compromising antioxidant defense mechanisms, thereby integrating multiple pathological processes initiated during ischemia and reperfusion. Recent experimental studies have indicated that in addition to its established role in perioperative analgesia, sufentanil may mitigate HIRI by reducing ferroptosis-associated oxidative damage and inflammatory responses. Elucidating the molecular mechanisms underlying the interaction between sufentanil and ferroptosis-related signaling pathways could inform the development of innovative and clinically applicable interventions aimed at improving outcomes in liver transplantation.