The lung-brain axis represents a complex bidirectional communication network that is pivotal in the crosstalk between respiratory and neurological functions. This review summarizes the current understanding of the mechanisms and protein markers that mediate the effects of lung diseases on brain health.

In this review, we explore the mechanisms linking lung injury to neurocognitive impairments, focusing on neural pathways, immune regulation and inflammatory responses, microorganism pathways, and hypoxemia. Specifically, we highlight the role of the vagus nerve in modulating the central nervous system response to pulmonary stimuli; Additionally, the regulatory function of the immune system is underscored, with evidence suggesting that lung-derived immune mediators can traverse the blood-brain barrier, induce neuroinflammation and cognitive decline; Furthermore, we discuss the potential of lung microbiota to influence brain diseases through microbial translocation and immune activation; Finally, the impact of hypoxemia is examined, with findings indicating that it can exacerbate cerebral injury via oxidative stress and impaired perfusion. Moreover, we analyze how pulmonary conditions, such as pneumonia, ALI/ARDS, and asthma, contribute to neurological dysfunction. Prolonged mechanical ventilation can also contribute to cognitive impairment. Conversely, brain diseases (e.g., stroke, traumatic brain injury) can lead to acute respiratory complications. In addition, protein markers such as TLR4, ACE2, A-SAA, HMGB1, and TREM2 are crucial to the lung-brain axis and correlate with disease severity. We also discuss emerging therapeutic strategies targeting this axis, including immunomodulation and microbiome engineering. Overall, understanding the lung-brain interplay is crucial for developing integrated treatment strategies and improving patient outcomes. Further research is needed to elucidate the molecular mechanisms and foster interdisciplinary collaboration.

Traditional Chinese medicine has been recognized for its significant role in treating acute lung injury (ALI) due to its distinct therapeutic advantages. Liang-Ge-San (LGS), a formulation from the ancient "Taiping Huimin Hejiju Fang", is believed to possess beneficial effects for treating ALI. However, LGS's precise mechanisms and efficacy in addressing viral ALI remain inadequately explored.

To evaluate LGS's therapeutic effects and underlying mechanisms in treating viral-induced ALI.

The protective effects of LGS were examined in a Polyinosinic-polycytidylic acid [Poly(I:C)]-induced ALI model using real-time quantitative PCR, enzyme-linked immunosorbent assay, and histopathological analysis. A bioinformatics approach combined with network pharmacology was utilized to ascertain the key targets of LGS in viral pneumonia. The pharmacodynamic mechanisms of LGS in viral ALI were further validated through immunofluorescence, overexpression, short hairpin RNA, chromatin immunoprecipitation, and target agonist assays.

LGS administration resulted in a reduction of IL-1β, IL-6, and TNF-α levels, along with a decrease in macrophage infiltration, pulmonary damage, and pneumonedema following the Poly(I:C) challenge. Bioinformatics and network pharmacology analyses suggested that Farnesyl X receptor (FXR) and angiotensin converting enzyme 2 (ACE2) are potential therapeutic targets for LGS in viral pneumonia. Further experiments revealed that LGS suppressed the expression of FXR, ACE2, and NF-κB-p65 in Poly(I:C)-infected cells. Notably, overexpression of FXR counteracted the repressive effects of LGS, while ACE2 expression remained unchanged in FXR-knockdown RAW264.7 cells upon treatment with Poly(I:C) or LGS. Additionally, LGS inhibited the interaction between FXR and ACE2 transcriptional promoters. In vivo, LGS attenuated the Poly(I:C)-induced upregulation of FXR, ACE2, IL-1β, IL-6, and TNF-α in ALI zebrafish and mice models, effects that could be reversed by chenodeoxycholic acid (CDCA), an FXR agonist. Moreover, LGS markedly alleviated weight loss, improved survival rates, reduced lung index, diminished viral load, and inhibited lung pathological changes in H1N1-PR8-induced ALI mice. IL-1β, IL-6, TNF-α, INF-γ, FXR, ACE2, small heterodimer partner, and NF-κB-p65 levels were markedly reduced by LGS, with these effects being reversed by CDCA.

This investigation provides the first evidence that FXR/ACE2 signaling is pivotal in acute respiratory viral infections, while LGS demonstrates antiviral activity against viral-induced ALI. LGS inhibits ACE2 expression induced by viral infection via FXR inhibition and modulates the cytokine storm, thus alleviating viral ALI. These findings suggest that LGS may be a promising treatment strategy for treating viral ALI.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a virus of the coronaviridae family. The virus enters the cell through binding to the corresponding receptor angiotensin-converting enzyme 2 (ACE2) on host cell membrane with the spike protein (S protein) on its envelope; thus, we can design inhibitors that bind the S protein to block the entry of the virus into cells. Aptamers are single stranded DNA or RNA molecules that can form specific three-dimensional structures and bind their target molecules with high affinity and specificity and thus are promising candidates for S protein inhibitors. This paper reviews the replication cycle and cell entry mechanisms of SARS-CoV-2 as well as the preparation principle and characteristics of aptamers, features a discussion of the advantages of using aptamers to target the S protein to prevent SARS-CoV-2 from infecting cells, and finally summarizes the research progress in S protein-blocking aptamers.

Particulate matter 2.5 (PM2.5) pollution and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic are the greatest environmental health issues worldwide. Several statistics revealed the significant positive correlation between the morbidity of coronavirus disease-19 (COVID-19) and the levels of air pollution. Nevertheless, there is no direct experimental evidence to indicate the effect of PM2.5 exposure on SARS-CoV-2 infection. The objective of this study was to evaluate whether the infection of SARS-CoV-2 affected by PM2.5 through angiotensin-converting enzyme II (ACE2) expression enhances and investigate the function of ACE2 in lung injury induced by PM2.5. An animal model of PM2.5-induced lung injury was established using wild-type (WT, C57BL/6), human ACE2 transgenic (K18-hACE2 TG), and murine ACE2 gene knockout (mACE2 KO) mice. The results indicate that PM2.5 exposure facilitates SARS-CoV-2 infection through inducing ACE2 expression in vitro (10 μg/mL) and in vivo (6.25 mg/kg/day in 50 μL saline). The levels of ACE, inflammatory cytokines, and mitogen-activated protein kinase (MAPK) proteins in WT, K18-hACE TG and mACE2 KO mice were significantly increased after PM2.5 instillation. The severest PM2.5-induced lung damage was observed in mACE2 KO mice. In summary, ACE2 plays a double-edged sword role in lung injury, PM2.5 exposure contributed to SARS-CoV-2 infection through inducing ACE2 expression, but ACE2 also protected pulmonary inflammation from PM2.5 challenge.

Patient-specific premorbidity, age, and sex are significant heterogeneous factors that influence the severe manifestation of lung diseases, including COVID-19 fibrosis. The renin-angiotensin system (RAS) plays a prominent role in regulating the effects of these factors. Recent evidence shows patient-specific alterations of RAS peptide homeostasis concentrations with premorbidity and the expression level of angiotensin-converting enzyme 2 (ACE2) during COVID-19. However, conflicting evidence suggests decreases, increases, or no changes in RAS peptides after SARS-CoV-2 infection. A multiscale computational model was developed to quantify the systemic contribution of heterogeneous factors of RAS during COVID-19. Three submodels were connected-an agent-based model for in-host COVID-19 response in the lung tissue, a RAS dynamics model, and a fibrosis dynamics model to investigate the effects of patient-group-specific factors in the systemic alteration of RAS and collagen deposition in the lung. The model results indicated cell death due to inflammatory response as a major contributor to the reduction of ACE and ACE2. The model explained possible mechanisms for conflicting evidence of patient-group-specific changes in RAS peptides in previously published studies. RAS peptides decreased for all virtual patient groups with aging in both sexes. In contrast, large variations in the magnitude of reduction were observed between male and female virtual patients in the older and middle-aged groups. The patient-specific variations in homeostasis RAS peptide concentrations of SARS-CoV-2-negative patients affected the dynamics of RAS during infection. This model may find further applications in patient-specific calibrations of tissue models for acute and chronic lung diseases to develop personalized treatments.

SARS-CoV-2 targets angiotensin-converting enzyme-2 (ACE2), a key peptidase of the renin-angiotensin system (RAS), which regulates the balance of the vasoconstrictor/inflammatory peptide Ang II and the vasodilator/anti-inflammatory peptide Ang-(1-7). Few studies have quantified the circulating elements of the RAS longitudinally in SARS-CoV-2 infection and their association with COVID-19 outcomes. Thus, we evaluated the association of circulating RAS enzymes and peptides with mortality among patients with COVID-19. Blood samples were collected from 111 patients with COVID-19 and new-onset hypoxemia during the delta and omicron waves at 19 hospitals in the United States. Circulating RAS components were quantified via radioimmunoassay or ELISA at 0 (baseline), 1, 3, and 5 days after randomization. We used multivariable Cox regression to estimate the association of baseline and longitudinal RAS concentrations with 90-day mortality. Participants were aged 18-90 (means [SD]: 55 [14]) yr and 62% were male. There were 22 (20%) deaths over 90 days of follow-up. ACE2 levels above the sample median (≥4.9 pM; adjusted HR [95% CI]: 0.10 [0.02, 0.43]) and ACE2/ACE ratio (≥6.0 × 10-3; adjusted HR: 0.08 [0.02, 0.39]) were associated with significantly lower mortality. Similarly, when analyzed as continuous, log2-normalized, time-varying predictors from day 0 to day 5, twofold increments of ACE2 and ACE2/ACE ratio over this period were associated with lower mortality (adjusted HR: 0.79 [0.65, 0.97] and 0.78 [0.63, 0.97], respectively). Circulating Ang II, Ang-(1-7), and ACE levels were not associated with mortality. These results suggest higher circulating ACE2 protein in hospitalized patients with COVID-19 is associated with reduced mortality.NEW & NOTEWORTHY We measured circulating components of the renin-angiotensin system (RAS) longitudinally over 5 days among patients hospitalized with COVID-19 and new-onset hypoxemia. We found that higher serum angiotensin-converting enzyme (ACE)-2 protein and ACE2/ACE ratio, both at baseline and when analyzed as time-varying, repeated measures, were associated with lower 90-day mortality. Results suggest a role for circulating ACE2 as a biomarker of adverse outcomes and could inform treatment strategies targeting the RAS in severe COVID-19 illness.

The primary objective of this study is to explore the potential link between the utilization of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) and its impact on mortality, disease severity, and healthcare resource utilization in individuals diagnosed with COVID-19. We aim to establish a solid theoretical foundation for safe and effective clinical medications.

We conducted a comprehensive search of various databases, including CNKI, PubMed, Science, Cell, Springer, Nature, Web of Science, and Embase. We also traced the literature of the included studies to ensure a thorough analysis of the available evidence. After applying a set of inclusion and exclusion criteria, we ultimately included a total of 41 articles in our analysis. To determine the overall effect size for dichotomous variables, we used the Mantel-Haenszel odds ratio in random effect models. For continuous variables, we calculated the inverse variance SMD using random effect models. To assess the outcomes and heterogeneity, we considered p-values (p < 0.05) and I2 values for all outcomes. We performed multivariate and univariate meta-regression analyses using the maximum likelihood approach with the CMA 3.0 software.

The results of our analysis indicated that the use of ACEIs or ARBs did not significantly influence mortality (OR = 1.10, 95% CI 0.83-1.46, p = 0.43, I2 = 84%), severity (OR = 0.99, 95% CI 0.68-1.45, p = 0.98, I2 = 84%), or healthcare resource utilization (SMD = 0.03, 95% CI 0.06-0.12, p = 0.54, I2 = 37%) in patients with COVID-19 compared to those not taking ACEIs or ARBs. The multivariate meta-regression analysis model explained 63%, 31%, and 100% of the sources of heterogeneity for the three outcome indicators.

The use of ACEIs and ARBs is not significantly correlated with mortality, severity, or healthcare resource utilization in patients with COVID-19, indicating safe clinical use of the medications.

Background/Objectives: The SARS-CoV-2's high mutations and replication rates contribute to its high infectivity and resistance to current vaccinations and treatments. The primary cause of resistance to most current treatments aligns within the coding regions for the spike S protein of SARS-CoV-2 that has mutated. As a potential novel immunotherapy, we generated a novel fusion protein composed of a soluble ACE2 (sACE2) linked to llama-derived anti-CD16 that targets different variants of spike proteins and enhances natural killer cells to target infected cells. Methods: Here, we generated a novel sACE2-AntiCD16VHH fusion protein using a Gly4Ser linker, synthesized and cloned into the pLVX-EF1alpha-IRES-Puro vector, and further expressed in ExpiCHO-S cells and purified using Ni+NTA chromatography. Results: The fusion protein significantly blocked SARS-CoV-2 alpha, beta, delta, gamma, and omicron S-proteins binding and activating angiotensin-converting enzyme receptor-2 (ACE2) on ACE2-expressing RAW-Blue macrophage cells and the secretion of several key inflammatory cytokines, G-CSF, MIP-1A, and MCP-1, implicated in the cytokine release storm (CRS). The sACE2-Anti-CD16VHH fusion protein also bridged NK cells to ACE2-expressing human lung carcinoma A549 cells and significantly activated NK-dependent cytotoxicity. Conclusions: The findings show that a VHH directed against CD16 could be an excellent candidate to be linked to soluble ACE2 to generate a bi-specific molecule (sACE2-AntiCD16VHH) suitable for bridging effector cells and infected target cells to inhibit SARS-CoV-2 variant spike proteins binding to the ACE2 receptor in the RAW-Blue cell line and pro-inflammatory cytokines and to activate natural killer cell cytotoxicity.

Dysregulated renin-angiotensin system (RAS) signaling contributes to elevated blood pressure (BP), inflammation, and organ damage in systemic arterial hypertension (HTN). We have demonstrated that hypertensive humans and rats exhibit higher expression of classic RAS components and lower expression of counterregulatory RAS components in the lungs compared with normotensive counterparts. Here, we investigated whether BP control could restore the balance between classic [angiotensin I-converting enzyme 2 (ACE)/angiotensin II (Ang II)] and counterregulatory [angiotensin I-converting enzyme 2 (ACE2)/Ang (1-7)] RAS, thereby mitigating lung inflammation. Male spontaneously hypertensive rats (SHRs) were treated with either losartan or amlodipine, both of which effectively reduced BP. These interventions up-regulated lung Ace2 and down-regulated Ace gene expression. Pulmonary membrane ACE2 abundance and activity were higher in losartan- and amlodipine-treated SHRs than in vehicle-treated SHRs, whereas ACE protein and function remained unchanged. Drug-treated SHRs exhibited lower levels of lung Ang II and higher levels of Ang (1-7) than vehicle-treated SHRs. Rebalancing the pulmonary RAS remarkably reduced macrophage number and down-regulated pro-inflammatory genes in SHR lungs, with lower expression of lung pro-inflammatory genes correlating with lower circulating levels of ACE2. Serum analysis in healthy and hypertensive individuals supported these findings, showing higher ACE2 levels in uncontrolled compared with controlled hypertension and normotension. Collectively, these findings suggest that high blood pressure may induce lung inflammation via an ACE/ACE2 imbalance. BP control with either an RAS inhibitor or a calcium channel blocker rebalances RAS in SHR lungs and alleviates inflammation. Furthermore, this study provides a mechanistic link between inflammatory lung diseases (such as COVID-19) and hypertension as a major risk factor.

The COVID-19 pandemic has become a serious global public health problem. Although the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor type 1 blockers (ARBs) has been recommended in patients with COVID-19 and cardiovascular diseases (CVDs), according to the results of some small-sample retrospective analyses, there remains a lack of sufficient evidence to validate their efficacy. This multicenter retrospective study investigated whether ACEI/ARB administration was beneficial in patients with COVID-19 and CVDs.

A total of 11,231 patients with confirmed COVID-19 and CVDs, from 138 hospitals in Hubei Province, were included in this multicenter retrospective study. We compared the clinical characteristics and outcomes between the ARB and non-ARB groups and analyzed the risk factors for in-hospital death using univariate and multivariate Cox regression analyses and Kaplan-Meier curves.

In the multivariate Cox regression model, after adjusting for age, gender, comorbidities, and in-hospital medications, ARB use was associated with lower all-cause mortality (adjusted HR, 0.53; 95% CI, 0.38-0.73; P < 0.001). After propensity score-matched analysis, the adjusted HR for the use of ARB associated with all-cause mortality was 0.62 (95% CI, 0.40-0.88; P = 0.02). Further subgroup analyses found that the adjusted HRs for the use of ARB associated with all-cause mortality were 0.52 (95% CI, 0.30-0.89; P = 0.016), 0.37 (95% CI, 0.21-0.64; P < 0.001), 0.42 (95% CI, 0.28-0.64; P < 0.001), and 0.55 (95% CI, 0.37-0.84; P = 0.005) in patients with heart failure, diabetes, and hypercholesterolemia, and severe COVID-19, respectively.

ARB administration was significantly associated with a lower risk of all-cause mortality in patients with COVID-19 and CVDs.

ClinicalTrials.gov NCT05615792. https://www.

gov/ct2/show/NCT05615792.

The SARS-CoV-2 outbreak in late 2019 triggered a major increase in activities related to immunobiology and immunotherapy to cope with and find solutions to end the COVID-19 pandemic. The unprecedented approach to research and development of drugs and vaccines against SARS-CoV-2 has substantially improved the understanding of immunobiology for COVID-19, which can also be applied to other infectious diseases. Major efforts were dedicated to the repurposing of existing antiviral drugs and the development of novel ones. For this reason, numerous approaches to evaluating interferons, immunoglobulins, and cytokine inhibitors have been conducted. Antibody-based therapies, especially employing monoclonal antibodies have also been on the agenda. Cell-based therapies involving dendritic cells, macrophages, and CAR T-cell approaches have been evaluated. Many existing antiviral drugs have been repurposed for COVID-19 and novel formulations have been tested. The extraordinarily rapid development of efficient vaccines led to the breakthrough of novel vaccine approaches such as mRNA-based vaccines saving millions of lives. Waning immunity of existing vaccines and emerging SARS-CoV-2 variants have required additional booster vaccinations and re-engineering of new versions of COVID-19 vaccines.

Angiotensin II (Ang II) is associated with macrophage polarization and apoptosis, but the role of the angiotensin type 2 receptor (AT2R) in these processes remains controversial. However, the effect of AT2Rs on alveolar macrophages and mechanical ventilation-induced lung injury has not been determined. Mechanical ventilation-induced lung injury in Sprague‒Dawley (SD) rats and LPS-stimulated rat alveolar macrophages (NR8383) were used to determine the effects of AT2Rs, selective AT2R agonists and selective AT1Rs or AT2R antagonists. Macrophage polarization, apoptosis, and related signaling pathways were assessed via western blotting, QPCR and flow cytometry. AT2R expression was decreased in LPS-stimulated rat alveolar macrophages (NR8383). Administration of the AT2R agonist CGP-42112 was associated with an increase in AT2R expression and M2 polarization, but no effect was observed upon administration of the AT2R antagonist PD123319 or the AT1R antagonist valsartan. In mechanical ventilation-induced lung injury in Sprague‒Dawley (SD) rats, the administration of the AT2R agonist C21 was associated with attenuation of the pathological damage score, lung wet/dry weight, cell count and protein content in BALF. C21 can significantly reduce proinflammatory factor TNF-α, IL-1β levels, increase anti-inflammatory factor IL-4, IL-10 levels in BALF, compared with the model group (p < 0.01). Similarly, compared with those at the same time points, the M1/M2 ratios in alveolar macrophages and apoptosis in peritoneal macrophages at 4 h, 6 h and 8 h in the mechanical ventilation models were lower after C21 administration. These findings indicated that the expression of AT2Rs in alveolar macrophages mediates M1 macrophage polarization and apoptosis and that AT2Rs play a protective role in mediating mechanical ventilation-induced lung injury.

Angiotensin-converting enzyme 2 (ACE2) has been reported to exert a protective effect in acute lung injury (ALI), though its underlying mechanism remains incompletely understood. In this study, ACE2 expression was found to be upregulated in a mouse model of ALI induced by lipopolysaccharide (LPS) injection. ACE2 knockdown modulated the severity of ALI, the extent of autophagy, and the mTOR pathway in this model. ACE2 regulated liver kinase B1 (LKB1) gene expression by sequestering miR-326, thereby alleviating ALI severity through enhanced autophagy. In cell-based experiments, miR-326 was shown to regulate ACE2 and LKB1 expression and autophagy. Overexpression of ACE2 disrupted miR-326's regulatory effect on LKB1, suggesting that LKB1 may function as an endogenous sponge for miR-326. These findings imply that elevated ACE2 expression in lung could play enhance the autophagy via the consumption of miR-326.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the result of an exaggerated inflammatory response triggered by a variety of pulmonary and systemic insults. The lung tissues are comprised of a variety of cell types, including alveolar epithelial cells, pulmonary vascular endothelial cells, macrophages, neutrophils, and others. There is mounting evidence that these diverse cell populations within the lung interact to regulate lung inflammation in response to both direct and indirect stimuli. The aim of this review is to provide a summary and discussion of recent advances in the understanding of the importance of cell-cell crosstalk in the pathogenesis of ALI/ARDS, with a specific focus on the cell-cell interactions that may offer prospective therapeutic avenues for ALI/ARDS.

Acute respiratory distress syndrome (ARDS) is a life-threatening and heterogeneous disorder leading to lung injury. To date, effective therapies for ARDS remain limited. Sepsis is a frequent inducer of ARDS. However, the precise mechanisms underlying sepsis-induced ARDS remain unclear.

Here RNA methylation was detected by methylated RNA immunoprecipitation (MeRIP), RNA stability was determined by RNA decay assay while RNA antisense purification (RAP) was used to identify RNA-protein interaction. Besides, co-immunoprecipitation (Co-IP) was utilized to detect protein-protein interaction. Moreover, mice were injected with lipopolysaccharide (LPS) to establish sepsis-induced ARDS model in vivo.

This study revealed that long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) aggravated lung injury through suppressing angiotensin-converting enzyme 2 (ACE2) in sepsis-induced ARDS models in vitro and in vivo. Mechanistically, NEAT1 declined ACE2 mRNA stability through heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1) in lipopolysaccharide (LPS)-treated alveolar type II epithelial cells (AT-II cells). Besides, NEAT1 destabilized ACE2 mRNA depending on RNA methylation by forming methylated NEAT1/hnRNPA2B1/ACE2 mRNA complex in LPS-treated AT-II cells. Moreover, lin-28 homolog A (LIN28A) improved NEAT1 stability whereas insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) augmented NEAT1 destabilization by associating with LIN28A to disrupt the combination of LIN28A and NEAT1 in LPS-treated AT-II cells. Nevertheless, hnRNPA2B1 increased NEAT1 stability by blocking the interaction between LIN28A and IGF2BP3 in LPS-treated AT-II cells.

These findings uncover mechanisms of sepsis-triggering ARDS and provide promising therapeutic targets for sepsis-induced ARDS.

SARS-CoV-2 has continued spreading around the world in recent years since the initial outbreak in 2019, frequently developing into new variants with greater human infectious capacity. SARS-CoV-2 and its mutants use the angiotensin-converting enzyme 2 (ACE2) as a cellular entry receptor, which has triggered several therapeutic strategies against COVID-19 relying on the use of ACE2 recombinant proteins as decoy receptors. In this work, we propose an ACE2 silent Fc fusion protein (ACE2-hFcLALA) as a candidate therapy against COVID-19. This fusion protein was able to block the binding of SARS-CoV-2 RBD to ACE2 receptor as measured by ELISA and flow cytometry inhibition assays. Moreover, we used classical neutralization assays and a progeny neutralization assay to show that the ACE2-hFcLALA fusion protein is capable of neutralizing the authentic virus. Additionally, we found that this fusion protein was more effective in preventing in vitro infection with different variants of interest (alpha, beta, delta, and omicron) compared to the D614G strain. Our results suggest the potential of this molecule to be used in both therapeutic and preventive settings against current and emerging mutants that use ACE2 as a gateway to human cells.

Toll-like receptors (TLRs) of human are considered as the most critical immunological mediators of inflammatory pathogenesis of COVID-19. These immunoregulatory glycoproteins are located on the surface and/or intracellular compartment act as innate immune sensors. Upon binding with distinct SARS-CoV-2 ligand(s), TLRs signal activation of different transcription factors that induce expression of the proinflammatory mediators that collectively induce 'cytokine storm'. Similarly, TLR activation is also pivotal in conferring protection to infection and invasion as well as upregulating the tissue repair pathways. This dual role of the human TLRs in deciding the fate of SARS-CoV-2 has made these receptor proteins as the critical mediators of immunoprotective and immunopathogenic consequences associated with COVID-19. Herein, pathbreaking discoveries exploring the immunobiological importance of the TLRs in COVID-19 and developing TLR-directed therapeutic intervention have been reviewed by accessing the up-to-date literatures available in the public domain/databases. In accordance with our knowledge in association with the importance of TLRs' role against viruses and identification of viral particles, they have been recognized as suitable candidates with high potential as vaccine adjuvants. In this regard, the agonists of TLR4 and TLR9 have effective potential in vaccine technology while the others need further investigations. This comprehensive review suggests that basal level expression of TLRs can act as friends to keep our body safe from strangers but act as a foe via overexpression. Therefore, selective inhibition of the overexpressed TLRs appears to be a solution to counteract the cytokine storm while TLR-agonists as vaccine adjuvants could lessen the risk of infection in the naïve population.

Recently, angiotensin-converting enzyme 2 (ACE2) gene has emerged as a potential candidate gene for susceptibility to SARS-CoV-2 infection. We investigated whether ACE2 G8790A (rs2285666) polymorphism could be a genetic marker for susceptibility to COVID-19 and disease severity in Egyptian children and adolescents.

This was a prospective case-control study included 580 cases diagnosed with COVID-19, and 580 matched control children and adolescents. The ACE2 G8790A (rs2285666) polymorphism was genotyped using polymerase chain reaction (PCR) and ACE2 serum level was measured by ELISA.

The ACE2 A/A genotype and A-allele were significantly more represented in cases with COVID-19 as compared to control group (44% vs. 30%; OR = 2.83; [95% CI: 1.27-2.63]; p = 0.006; for the A/A genotype) and (65% vs. 51%; OR = 1.9; [95% CI: 1.06-1.72]; p = 0.01; for the A-allele). The presence of ACE2 G/G genotype was an independent risk factor for severe disease (adjusted OR: 2.08; [95% CI: 1.57-6.78]; p = 0.003).

The ACE2 G8790A (rs2285666) polymorphism may confer susceptibility to COVID-19 in Egyptian children and adolescents. The ACE2 G/G genotype and G-allele was associated with lower ACE2 serum levels and may constitute independent risk factors for disease severity.

The potential impact of cigarette and cannabis smoking on COVID-19 infection outcomes is not well understood. We investigated the association between combustible tobacco use and dried cannabis use with COVID-19 infection in a longitudinal cohort of community adults.

The sample comprised 1,343 participants, originally enrolled in 2018, who reported their cigarette and cannabis use in 11 assessments over 44 months, until 2022. COVID-19 infection history were self-reported after the onset of the pandemic. Univariate and multivariate logistic regression analyses were performed. The potentially confounding factor of vaccination status was also considered by stratifying data by booster vaccination self-reporting.

Among 1,343 participants, 820 (61.1%) reported any COVID-19 infection. Dried cannabis use (46.3% of participants, n = 721) was associated with higher self-reporting of 2+ COVID-19 infections (13.3% vs. 7.3% in non-users, p = .0004), while tobacco use (18.5% of participants, n = 248) had no significant effect (13.3% vs. 10.0% in no use group, p = .116). When stratified into single or dual substance use groups, dried cannabis-only use was associated with increased reporting of 1 or 2+ COVID-19 infections compared to substance non-users, while tobacco-only use and dual use groups were not significantly different from non-users. To account for differences in vaccination rates between substance use groups, we found that, among individuals with a COVID-19 booster vaccine, dried cannabis use was still associated with increased reporting of 2+ COVID-19 infections (p = .008).

Our study suggests that dried cannabis use is associated with a higher likelihood of reporting 2+ COVID-19 infections. Although the study was observational and relied on self-report infection status, our findings support the need for further investigation into the impact of cannabis use on COVID-19 infection, particularly studies employing controlled experimental designs.

Angiotensin-converting enzyme 2 (ACE2) receptors facilitate the entry of the causative virus severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) into target cells. Some ACE gene variants have been suggested to be involved in COVID-19 pathogenesis. So, the aim was to assess the association between ACE1 rs4646994 and ACE2 rs2285666 genes polymorphisms and the susceptibility and severity of COVID-19. This case-control study was conducted on 197 patients with COVID-19 and 197 healthy controls. ACE-1 insertion/deletion (I/D) (rs4646994) and ACE2 rs2285666 genes polymorphisms were determined by the amplification refractory mutation system- polymerase chain reaction (ARMS-PCR) technique. The DD genotype of ACE1 I/D polymorphism was associated with increased susceptibility to COVID-19 infection (p = 0.012), whereas the ID genotype of this polymorphism was associated with decreased susceptibility (p = 0.003) (significance level = 0.017). There was no significant association in allele and genotype distribution of ACE2 rs2285666 polymorphism between cases and controls. The ACE1 I/D polymorphism may be considered as a risk factor for COVID-19 susceptibility.

The pivotal role of the cell entry receptor ACE2 for SARS-CoV-2 infection is well-established. When ACE2 is shed from cell surface into plasma as soluble ACE2 (sACE2), it can effectively neutralize SARS-CoV-2. This longitudinal prospective cohort study analyzed sACE2 activity in 1192 participants, aged 4 months to 81 years, 3 and 12 months after SARS-CoV-2 household exposure. Following SARS-CoV-2 exposure, participants exhibited significantly elevated sACE2 activity, irrespective of confirmed infection, with the highest levels observed in exposed children. Longitudinal analysis revealed a decline in sACE2 levels over time, reaching levels comparable to age- and sex-matched pre-pandemic controls. An increase in sACE2 activity was also confirmed in vitro in Calu-3 (human lung) cells within hours of SARS-CoV-2 exposure, providing a direct link between SARS-CoV-2 exposure and elevated sACE2. This study, therefore, challenges the dichotomy of categorizing SARS-CoV-2 exposed participants as infected or not infected solely on currently established diagnostic assays. It demonstrates lasting host responses independent of B- and T-cell memory and may help to keep SARS-CoV-2 infections in balance and contribute to successful virus clearance in children and adults lacking humoral and cellular immune responses following SARS-CoV-2 exposure. Trial Registration: German Registry for Clinical Studies; Identifier: D 00021521.

Continued phenotyping and ongoing molecular epidemiology are important in current and future monitoring of emerging SARS-CoV-2 lineages. Herein we developed pragmatic strategies to track the emergence, spread and phenotype of SARS-CoV-2 variants in Australia in an era of decreasing diagnostic PCR testing and focused cohort-based studies. This was aligned to longitudinal studies that span 4 years of the COVID-19 pandemic.

Throughout 2023, we partnered with diagnostic pathology providers and pathogen genomics teams to identify relevant emerging or circulating variants in the New South Wales (NSW) community. We monitored emerging variants through viral culture, growth algorithms, neutralisation responses and changing entry requirements defined by ACE2 and TMPRSS2 receptor use. To frame this in the context of the pandemic stage, we continued to longitudinally track neutralisation responses at the population level using pooled Intravenous Immunoglobulins (IVIG) derived from in excess of 700,000 donations.

In antibodies derived from recent individual donations and thousands of donations pooled in IVIGs, we observed continued neutralisation across prior and emerging variants with EG.5.1, HV.1, XCT and JN.1 ranked as the most evasive SARS-CoV-2 variants. Changes in the type I antibody site at Spike positions 452, 455 and 456 were associated with lowered neutralisation responses in XBB lineages. In longitudinal tracking of population immunity spanning three years, we observed continued maturation of neutralisation breadth to all SARS-CoV-2 variants over time. Whilst neutralisation responses initially displayed high levels of imprinting towards Ancestral and early pre-Omicron lineages, this was slowly countered by increased cross reactive breadth to all variants. We predicted JN.1 to have a marked transmission advantage in late 2023 and this eventuated globally at the start of 2024. We could not attribute this advantage to neutralisation resistance but rather propose that this growth advantage arises from the preferential utilisation of ACE2 pools that cannot engage TMPRSS2 at its Collectrin-Like Domain (CLD).

The emergence of many SARS-CoV-2 lineages documented at the end of 2023 was found to be initially associated with lowered neutralisation responses. This continued to be countered by the gradual maturation of cross-reactive neutralisation responses over time. The later appearance and dominance of the divergent JN.1 lineage cannot be attributed to a lack of neutralisation responses alone, and our data supports that its dominance is a culmination of both lowered neutralisation and changes in ACE2/TMPRSS2 entry preferences.

This work was primarily supported by Australian Medical Foundation research grants MRF2005760 (ST, GM & WDR), MRF2001684 (ADK and ST) and Medical Research Future Fund Antiviral Development Call grant (WDR), Medical Research Future Fund COVID-19 grant (MRFF2001684, ADK & SGT) and the New South Wales Health COVID-19 Research Grants Round 2 (SGT).

Dysregulation of the renin-angiotensin-aldosterone-system (RAAS) in sepsis is a complex and early phenomenon with a likely significant contribution to organ failure and patient outcomes. A better understanding of the pathophysiology and intricacies of the RAAS in septic shock has led to the use of exogenous angiotensin II as a new therapeutic agent. In this review, we report a multinational and multi-disciplinary expert panel discussion on the role and implications of RAAS modulation in sepsis and the use of exogenous angiotensin II. The panel proposed guidance regarding patient selection and treatment options with exogenous angiotensin II which should trigger further research.

Patient-specific premorbidity, age, and sex are significant heterogeneous factors that influence the severe manifestation of lung diseases, including COVID-19 fibrosis. The renin-angiotensin system (RAS) plays a prominent role in regulating the effects of these factors. Recent evidence shows patient-specific alterations of RAS homeostasis concentrations with premorbidity and the expression level of angiotensin-converting enzyme 2 (ACE2) during COVID-19. However, conflicting evidence suggests decreases, increases, or no changes in RAS peptides after SARS-CoV-2 infection. In addition, detailed mechanisms connecting the patient-specific conditions before infection to infection-induced RAS alterations are still unknown. Here, a multiscale computational model was developed to quantify the systemic contribution of heterogeneous factors of RAS during COVID-19. Three submodels were connected-an agent-based model for in-host COVID-19 response in the lung tissue, a RAS dynamics model, and a fibrosis dynamics model to investigate the effects of patient-group-specific factors in the systemic alteration of RAS and collagen deposition in the lung. The model results indicated cell death due to inflammatory response as a major contributor to the reduction of ACE and ACE2. In contrast, there were no significant changes in ACE2 dynamics due to viral-bound internalization of ACE2. The model explained possible mechanisms for conflicting evidence of patient-group-specific changes in RAS peptides in previously published studies. Simulated results were consistent with reported RAS peptide values for SARS-CoV-2-negative and SARS-CoV-2-positive patients. RAS peptides decreased for all virtual patient groups with aging in both sexes. In contrast, large variations in the magnitude of reduction were observed between male and female virtual patients in the older and middle-aged groups. The patient-specific variations in homeostasis RAS peptide concentrations of SARS-CoV-2-negative patients also affected the dynamics of RAS during infection. The model results also showed that feedback between RAS signaling and renin dynamics could restore ANGI homeostasis concentration but failed to restore homeostasis values of RAS peptides downstream of ANGI. In addition, the results showed that ACE2 variations with age and sex significantly altered the concentrations of RAS peptides and led to collagen deposition with slight variations depending on age and sex. This model may find further applications in patient-specific calibrations of tissue models for acute and chronic lung diseases to develop personalized treatments.

Pro-resolving molecules, including the peptide Angiotensin-(1-7) [Ang-(1-7)], have potential adjunctive therapy for infections. Here we evaluate the actions of Ang-(1-7) in betacoronavirus infection in mice.

C57BL/6J mice were infected intranasally with the murine betacoronavirus MHV-3 and K18-hACE2 mice were infected with SARS-CoV-2. Mice were treated with Ang-(1-7) (30 µg/mouse, i.p.) at 24-, 36-, and 48-hours post-infection (hpi) or at 24, 36, 48, 72, and 96 h. For lethality evaluation, one additional dose of Ang-(1-7) was given at 120 hpi. At 3- and 5-days post- infection (dpi) blood cells, inflammatory mediators, viral loads, and lung histopathology were evaluated.

Ang-(1-7) rescued lymphopenia in MHV-infected mice, and decreased airways leukocyte infiltration and lung damage at 3- and 5-dpi. The levels of pro-inflammatory cytokines and virus titers in lung and plasma were decreased by Ang-(1-7) during MHV infection. Ang-(1-7) improved lung function and increased survival rates in MHV-infected mice. Notably, Ang-(1-7) treatment during SARS-CoV-2 infection restored blood lymphocytes to baseline, decreased weight loss, virus titters and levels of inflammatory cytokines, resulting in improvement of pulmonary damage, clinical scores and lethality rates.

Ang-(1-7) protected mice from lung damage and death during betacoronavirus infections by modulating inflammation, hematological parameters and enhancing viral clearance.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are accompanied by high mortality rates and few effective treatments. Transplantation of human placental mesenchymal stem cells (hPMSCs) may attenuate ALI and the mechanism is still unclear. Our study aimed to elucidate the potential protective effect and therapeutic mechanism of hPMSCs against lipopolysaccharide (LPS)-induced ALI, An ALI model was induced by tracheal instillation of LPS into wild-type (WT) and angiotensin-converting enzyme 2 (ACE2) knockout (KO) male mice, followed by injection of hPMSCs by tail vein. Treatment with hPMSCs improved pulmonary histopathological injury, reduced pulmonary injury scores, decreased leukocyte count and protein levels in bronchoalveolar lavage fluid(BALF), protected the damaged alveolar epithelial barrier, and reversed LPS-induced upregulation of pro-inflammatory factors Interleukin-6 (IL-6) and Tumor necrosis factor-α(TNF-α) and downregulation of anti-inflammatory factor Interleukin-6(IL-10) in BALF. Moreover, administration of hPMSCs inhibited Angiotensin (Ang)II activation and promoted the expression levels of ACE2 and Ang (1-7) in ALI mice. Pathological damage, inflammation levels, and disruption of alveolar epithelial barrier in ALI mice were elevated after the deletion of ACE2 gene, and the Renin angiotensin system (RAS) imbalance was exacerbated. The therapeutic effect of hPMSCs was significantly reduced in ACE2 KO mice. Our findings suggest that ACE2 plays a key role in hPMSCs repairing the alveolar epithelial barrier to protect against ALI, laying a new foundation for the clinical treatment of ALI.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to angiotensin-converting enzyme 2 (ACE2) on host cells, via its spike protein, and transmembrane protease, serine 2 (TMPRSS2) cleaves the spike-ACE2 complex to facilitate virus entry. As rate-limiting steps for virus entry, modulation of ACE2 and/or TMPRSS2 may decrease SARS-CoV-2 infectivity and COVID-19 severity. In silico modeling suggested the natural bioactive flavonoid quercetin can bind to ACE2 and a recent randomized clinical trial demonstrated that oral supplementation with quercetin increased COVID-19 recovery. A range of cultured human cells were assessed for co-expression of ACE2 and TMPRSS2. Immortalized Calu-3 lung cells, cultured and matured at an air-liquid interface (Calu-3-ALIs), were established as the most appropriate. Primary bronchial epithelial cells (PBECs) were obtained from healthy adult males (N = 6) and cultured under submerged conditions to corroborate the outcomes. Upon maturation or reaching 80% confluence, respectively, the Calu-3-ALIs and PBECs were treated with quercetin, and mRNA and protein expression were assessed by droplet digital PCR and ELISA, respectively. SARS-CoV-2 infectivity, and the effects of pre- and co-treatment with quercetin, was assessed by median tissue culture infectious dose assay. Quercetin dose-dependently decreased ACE2 and TMPRSS2 mRNA and protein in both Calu-3-ALIs and PBECs after 4 h, while TMPRSS2 remained suppressed in response to prolonged treatment with lower doses (twice daily for 3 days). Quercetin also acutely decreased ADAM17 mRNA, but not ACE, in Calu-3-ALIs, and this warrants further investigation. Calu-3-ALIs, but not PBECs, were successfully infected with SARS-CoV-2; however, quercetin had no antiviral effect, neither directly nor indirectly through downregulation of ACE2 and TMPRSS2. Calu-3-ALIs were reaffirmed to be an optimal cell model for research into the regulation of ACE2 and TMPRSS2, without the need for prior genetic modification, and will prove valuable in future coronavirus and respiratory infectious disease work. However, our data demonstrate that a significant decrease in the expression of ACE2 and TMPRSS2 by a promising prophylactic candidate may not translate to infection prevention.

Estrogen receptor-positive (ER+) breast cancer commonly disseminates to bone marrow, where interactions with mesenchymal stromal cells (MSCs) shape disease trajectory. We modeled these interactions with tumor-MSC co-cultures and used an integrated transcriptome-proteome-network-analyses workflow to identify a comprehensive catalog of contact-induced changes. Conditioned media from MSCs failed to recapitulate genes and proteins, some borrowed and others tumor-intrinsic, induced in cancer cells by direct contact. Protein-protein interaction networks revealed the rich connectome between "borrowed" and "intrinsic" components. Bioinformatics prioritized one of the borrowed components, CCDC88A/GIV, a multi-modular metastasis-related protein that has recently been implicated in driving a hallmark of cancer, growth signaling autonomy. MSCs transferred GIV protein to ER+ breast cancer cells (that lack GIV) through tunnelling nanotubes via connexin (Cx)43-facilitated intercellular transport. Reinstating GIV alone in GIV-negative breast cancer cells reproduced approximately 20% of both the borrowed and the intrinsic gene induction patterns from contact co-cultures; conferred resistance to anti-estrogen drugs; and enhanced tumor dissemination. Findings provide a multiomic insight into MSC→tumor cell intercellular transport and validate how transport of one such candidate, GIV, from the haves (MSCs) to have-nots (ER+ breast cancer) orchestrates aggressive disease states.

Given the sparse data on the renin-angiotensin system (RAS) and its biological effector molecules ACE1 and ACE2 in pediatric COVID-19 cases, we investigated whether the ACE1 insertion/deletion (I/D) polymorphism could be a genetic marker for susceptibility to COVID-19 in Egyptian children and adolescents.

This was a case-control study included four hundred sixty patients diagnosed with COVID-19, and 460 well-matched healthy control children and adolescents. The I/D polymorphism (rs1799752) in the ACE1 gene was genotyped by polymerase chain reaction (PCR), meanwhile the ACE serum concentrations were assessed by ELISA.

The ACE1 D/D genotype and Deletion allele were significantly more represented in patients with COVID-19 compared to the control group (55% vs. 28%; OR = 2.4; [95% CI: 1.46-3.95]; for the DD genotype; P = 0.002) and (68% vs. 52.5%; OR: 1.93; [95% CI: 1.49-2.5] for the D allele; P = 0.032). The presence of ACE1 D/D genotype was an independent risk factor for severe COVID-19 among studied patients (adjusted OR: 2.6; [95% CI: 1.6-9.7]; P < 0.001.

The ACE1 insertion/deletion polymorphism may confer susceptibility to SARS-CoV-2 infection in Egyptian children and adolescents.

Recent studies suggested a crucial role of renin-angiotensin system and its biological effector molecules ACE1 and ACE2 in the pathogenesis and progression of COVID-19. To our knowledge, ours is the first study to investigate the association of ACE1 I/D polymorphism and susceptibility to COVID-19 in Caucasian children and adolescents. The presence of the ACE1 D/D genotype or ACE1 Deletion allele may confer susceptibility to SARS-CoV-2 infection and being associated with higher ACE serum levels; may constitute independent risk factors for severe COVID-19. The ACE1 I/D genotyping help design further clinical trials reconsidering RAS-pathway antagonists to achieve more efficient targeted therapies.

Renin-angiotensin-aldosterone system plays a crucial role in the regulation of blood pressure and fluid homeostasis. It is reported to be involved in mediating osteoclastogenesis and bone loss in diseases of inflammatory bone resorption such as osteoporosis. Angiotensin-(1-7), a product of Angiotensin I and II (Ang I, II), is cleaved by Angiotensin-converting enzyme 2 and then binds to Mas receptor to counteract inflammatory effects produced by Ang II. However, the mechanism by which Ang-(1-7) reduces bone resorption remains unclear. Therefore, we aim to elucidate the effects of Ang-(1-7) on lipopolysaccharide (LPS)-induced osteoclastogenesis. In vivo, mice were supracalvarial injected with Ang-(1-7) or LPS ± Ang-(1-7) subcutaneously. Bone resorption and osteoclast formation were compared using micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) stain, and real-time PCR. We found that Ang-(1-7) attenuated tumor necrosis factor (TNF)-α, TRAP, and Cathepsin K expression from calvaria and decreased osteoclast number along with bone resorption at the suture mesenchyme. In vitro, RANKL/TNF-α ± Ang-(1-7) was added to cultures of bone marrow-derived macrophages (BMMs) and osteoclast formation was measured via TRAP staining. The effect of Ang-(1-7) on LPS-induced osteoblasts RANKL expression and peritoneal macrophages TNF-α expression was also investigated. The effect of Ang-(1-7) on the MAPK and NF-κB pathway was studied by Western blotting. As a result, Ang-(1-7) reduced LPS-stimulated macrophages TNF-α expression and inhibited the MAPK and NF-κB pathway activation. However, Ang-(1-7) did not affect osteoclastogenesis induced by RANKL/TNF-α nor reduce osteoblasts RANKL expression in vitro. In conclusion, Ang-(1-7) alleviated LPS-induced osteoclastogenesis and bone resorption in vivo via inhibiting TNF-α expression in macrophages.