Hydrogen Sulfide Attenuated Sepsis-Induced Myocardial Dysfunction Through TLR4 Pathway and Endoplasmic Reticulum Stress

Molecular mechanisms of endoplasmic reticulum stress-mediated acute kidney injury in juvenile rats and the protective role of mesencephalic astrocyte-derived neurotrophic factor

OBJECTIVES

This study examined the role of endoplasmic reticulum stress in pediatric acute kidney injury and the therapeutic effect of midbrain astrocyte-derived neurotrophic factor.

METHODS

Two-week-old Sprague-Dawley rats were divided into: Sham, ischemia-reperfusion injury-induced acute kidney injury (AKI), mesencephalic astrocyte-derived neurotrophic factor (MANF)-treated, tauroursodeoxycholic acid (TUDCA)-treated. Analyses were conducted 24 h post-treatment. Serum creatinine, cystatin C, Albumin, MANF levels were measured, cytokine concentrations in serum and renal tissues were determined using a Luminex assay. Histopathology was assessed via light and electron microscopy. Western blotting and RT-qPCR analyzed markers for oxidative stress, apoptosis, endoplasmic reticulum (ER) stress, and autophagy. HK-2 cells underwent hypoxia/reoxygenation (H/R) to simulate AKI and were treated with MANF or TUDCA.

RESULTS

AKI rats had increased serum creatinine, cystatin C, and inflammatory cytokines, along with significant renal damage, and showed loose and swollen ER structures, reduced cell proliferation, and elevated levels of IRE1, PERK, ATF6, CHOP, LC3-II/I, KIM-1, TLR4, JNK, and NF-κB. MANF treatment reduced these biomarkers and protein levels, improved ER structure and cell proliferation, alleviated oxidative stress, apoptosis, ER stress, and inhibited JNK/TLR4/NF-κB signaling. In HK-2 cells, MANF reduced ER stress and inflammation post-H/R exposure.

CONCLUSIONS

MANF treatment alleviates ER stress, oxidative stress, apoptosis, and inflammation in pediatric AKI, improving renal function and morphology.

Clinical implications of septic cardiomyopathy: A narrative review

Sepsis is caused by the body's dysregulated response to infection, which can lead to multiorgan injury and death. Patients with sepsis may develop acute cardiac dysfunction, termed septic cardiomyopathy, which is a global but reversible dysfunction of both sides of the heart. This narrative review discusses the mechanistic changes in the heart during septic cardiomyopathy, its diagnosis, existing treatment options regarding severity and course, and emerging treatment approaches. Although no standardized definition for septic cardiomyopathy exists, it is described as a reversible myocardial dysfunction that typically resolves within 7 to 10 days. Septic cardiomyopathy is often diagnosed based on electrocardiography, cardiac magnetic resonance imaging, biomarkers, and direct invasive and noninvasive measures of cardiac output. Presently, the treatment of septic cardiomyopathy is similar to that of sepsis, primarily focusing on acute interventions. Treatments for cardiomyopathy often include angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and diuretics. However, because of profound hypotension in sepsis, many cardiomyopathy treatments are contraindicated in patients with septic cardiomyopathy. Substantial efforts have been made to study the pathophysiological mechanisms and diagnostic options; however, the lack of a uniform definition for septic cardiomyopathy is challenging for physicians when considering treatments. Another challenge for physicians is that the treatment for septic cardiomyopathy has only focused on acute intervention, whereas the treatment for other cardiomyopathies has been provided on a long-term basis. A better understanding of the underlying mechanisms of septic cardiomyopathy may contribute to the development of a unified definition of the condition and novel treatment options.

Weakening of M1 macrophage and bone resorption in periodontitis cystathionine γ-lyase-deficient mice

OBJECTIVES

Cystathionine-γ-lyase (CTH) has been proved to involve in inflammation and bone remolding, implying its potential role in the progression of periodontitis. This study was aimed to investigate the function of CTH and its relation to the macrophage polarization in periodontitis.

MATERIALS AND METHODS

Bone marrow-derived macrophages (BMDMs) from wild-type (WT) and Cth knockout (Cth-/- ) mice were stimulated with lipopolysaccharide (LPS) in vitro and pro-inflammatory cytokines were analyzed by qRT-PCR. Ligature-induced periodontitis was established on WT and Cth-/- mice. Histological analysis, tartrate-resistant acid phosphatase staining, immunostaining, and Western blot were performed to analyze the periodontium destruction and M1 macrophage polarization.

RESULTS

Cth expression in BMDMs was upregulated upon increasing LPS stimulation. Deletion of Cth suppressed BMDMs inflammatory response with decreased Il1b, Il6, and Tnf mRNA. Cth-/- mice with periodontitis showed attenuated bone loss and impaired osteoclast differentiation compared with WT. Moreover, Cth knockout hindered M1 macrophage polarization, reduced the expression of IL-1β, IL-6, and TNF-α in periodontally diseased tissue.

CONCLUSION

This study demonstrated that CTH played an important role in regulating the inflammatory responses and periodontitis tissue destruction. Importantly, Cth knockout suppressed M1 macrophages polarization in periodontitis.

Apelin ameliorates sepsis-induced myocardial dysfunction via inhibition of NLRP3-mediated pyroptosis of cardiomyocytes

Sepsis-induced myocardial dysfunction (SMD) is the major cause of death in sepsis. Nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3)-mediated pyroptosis contributes to the occurrence and development of SMD. Although Apelin confers direct protection against SMD, the potential mechanisms remain unclear. This study aimed to determine whether Apelin protects against SMD via regulation of NLRP3-mediated pyroptosis of cardiomyocytes. Experimental SMD was induced in wild-type (WT) control mice and Apelin knockout (Apelin-/-) mice by cecal ligation and puncture (CLP). Neonatal mouse cardiomyocytes (NMCs) were treated with lipopolysaccharide (LPS) to simulate the physiological environment of SMD in vitro. The expression of Apelin was greatly decreased in the plasma from septic patients and septic mouse heart. Knockout of Apelin aggravated SMD, evidenced by decreased cardiac function, and increased cardiac fibrosis and NLRP3 inflammasome and pyroptosis levels in CLP-treated Apelin-/- mice compared with WT mice. Overexpression of Apelin activated the AMPK pathway and thereby inhibited NLRP3 inflammasome-mediated pyroptosis of NMCs induced by LPS in vitro These protective effects were partially abrogated by AMPK inhibitor. In conclusion, Apelin attenuated SMD by inhibiting NLRP3-mediated pyroptosis via activation of the AMPK pathway. Apelin may serve as a promising therapeutic target for SMD.

Novel tripeptide RKH derived from Akkermansia muciniphila protects against lethal sepsis

OBJECTIVE

The pathogenesis of sepsis is complex, and the sepsis-induced systemic proinflammatory phase is one of the key drivers of organ failure and consequent mortality. Akkermansia muciniphila (AKK) is recognised as a functional probiotic strain that exerts beneficial effects on the progression of many diseases; however, whether AKK participates in sepsis pathogenesis is still unclear. Here, we evaluated the potential contribution of AKK to lethal sepsis development.

DESIGN

Relative abundance of gut microbial AKK in septic patients was evaluated. Cecal ligation and puncture (CLP) surgery and lipopolysaccharide (LPS) injection were employed to establish sepsis in mice. Non-targeted and targeted metabolomics analysis were used for metabolites analysis.

RESULTS

We first found that the relative abundance of gut microbial AKK in septic patients was significantly reduced compared with that in non-septic controls. Live AKK supplementation, as well as supplementation with its culture supernatant, remarkably reduced sepsis-induced mortality in sepsis models. Metabolomics analysis and germ-free mouse validation experiments revealed that live AKK was able to generate a novel tripeptide Arg-Lys-His (RKH). RKH exerted protective effects against sepsis-induced death and organ damage. Furthermore, RKH markedly reduced sepsis-induced inflammatory cell activation and proinflammatory factor overproduction. A mechanistic study revealed that RKH could directly bind to Toll-like receptor 4 (TLR4) and block TLR4 signal transduction in immune cells. Finally, we validated the preventive effects of RKH against sepsis-induced systemic inflammation and organ damage in a piglet model.

CONCLUSION

We revealed that a novel tripeptide, RKH, derived from live AKK, may act as a novel endogenous antagonist for TLR4. RKH may serve as a novel potential therapeutic approach to combat lethal sepsis after successfully translating its efficacy into clinical practice.

Determination of sulfide in complex biofilm matrices using silver-coated, 4-mercaptobenzonitrile-modified gold nanoparticles, encapsulated in ZIF-8 as surface-enhanced Raman scattering nanoprobe

A surface-enhanced Raman scattering nanoprobe has been developed for sulfide detection and applied to  complex bacterial biofilms. The nanoprobe, Au@4-MBN@Ag@ZIF-8, comprised a gold core modified with 4-mercaptobenzonitrile (4-MBN) as signaling source, a layer of silver shell as the sulfide sensitization material, and a zeolitic imidazolate framework-8 (ZIF-8) as surface barrier. ZIF-8, with its high surface area and mesoporous structure, was applied to preconcentrate sulfide around the nanoprobe with its excellent adsorption capacity. Besides, the external wrapping of ZIF-8 can not only prevent the interference of biomolecules, such as proteins, with the Au@4-MBN@Ag assay but also enhance the detection specificity through the sulfide cleavage function towards ZIF-8. These properties are critical for the application of this nanoprobe to complex environmental scenarios. In the presence of sulfide, it was first enriched through adsorption by the outer ZIF-8 layer, then destroyed the barrier layer, and subsequently reacted with the Ag shell, leading to changes in the Raman signal. Through this rational design, the Au@4-MBN@Ag@ZIF-8 nanoprobe exhibited excellent detection sensitivity, with a sulfide detection limit in the nanomolar range and strong linearity in the concentration range  50 nM to 500 μM. Furthermore, the proposed Au@4-MBN@Ag@ZIF-8 nanoprobe was effectively utilized for sulfide detection in intricate biofilm matrices, demonstrating its robust selectivity and reproducibility.

Comprehensive analysis of endoplasmic reticulum stress-associated genes signature of ulcerative colitis

Background

Endoplasmic reticulum stress (ERS) is a critical factor in the development of ulcerative colitis (UC); however, the underlying molecular mechanisms remain unclear. This study aims to identify pivotal molecular mechanisms related to ERS in UC pathogenesis and provide novel therapeutic targets for UC.

Methods

Colon tissue gene expression profiles and clinical information of UC patients and healthy controls were obtained from the Gene Expression Omnibus (GEO) database, and the ERS-related gene set was downloaded from GeneCards for analysis. Weighted gene co-expression network analysis (WGCNA) and differential expression analysis were utilized to identify pivotal modules and genes associated with UC. A consensus clustering algorithm was used to classify UC patients. The CIBERSORT algorithm was employed to evaluate the immune cell infiltration. Gene Set Variation Analysis (GSVA), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to explore potential biological mechanisms. The external sets were used to validate and identify the relationship of ERS-related genes with biologics. Small molecule compounds were predicted using the Connectivity Map (CMap) database. Molecular docking was performed to simulate the binding conformation of small molecule compounds and key targets.

Results

The study identified 915 differentially expressed genes (DEGs) and 11 ERS-related genes (ERSRGs) from the colonic mucosa of UC patients and healthy controls, and these genes had good diagnostic value and were highly correlated. Five potential small-molecule drugs sharing tubulin inhibitors were identified, including albendazole, fenbendazole, flubendazole, griseofulvin, and noscapine, among which noscapine exhibited the highest correlation with a high binding affinity to the targets. Active UC and 10 ERSRGs were associated with a large number of immune cells, and ERS was also associated with colon mucosal invasion of active UC. Significant differences in gene expression patterns and immune cell infiltration abundance were observed among ERS-related subtypes.

Conclusion

The results suggest that ERS plays a vital role in UC pathogenesis, and noscapine may be a promising therapeutic agent for UC by affecting ERS.

From Gasotransmitter to Immunomodulator: The Emerging Role of Hydrogen Sulfide in Macrophage Biology

Hydrogen sulfide (H₂S) has been increasingly recognized as a crucial inflammatory mediator in immune cells, particularly macrophages, due to its direct and indirect effects on cellular signaling, redox homeostasis, and energy metabolism. The intricate regulation of endogenous H₂S production and metabolism involves the coordination of transsulfuration pathway (TSP) enzymes and sulfide oxidizing enzymes, with TSP's role at the intersection of the methionine pathway and glutathione synthesis reactions. Additionally, H₂S oxidation mediated by sulfide quinone oxidoreductase (SQR) in mammalian cells may partially control cellular concentrations of this gasotransmitter to induce signaling. H₂S is hypothesized to signal through the posttranslational modification known as persulfidation, with recent research highlighting the significance of reactive polysulfides, a derivative of sulfide metabolism. Overall, sulfides have been identified as having promising therapeutic potential to alleviate proinflammatory macrophage phenotypes, which are linked to the exacerbation of disease outcomes in various inflammatory conditions. H₂S is now acknowledged to have a significant influence on cellular energy metabolism by affecting the redox environment, gene expression, and transcription factor activity, resulting in changes to both mitochondrial and cytosolic energy metabolism processes. This review covers recent discoveries pertaining to the involvement of H₂S in macrophage cellular energy metabolism and redox regulation, and the potential implications for the inflammatory response of these cells in the broader framework of inflammatory diseases.

Hydrogen sulfide alleviates lipopolysaccharide-induced myocardial injury through TLR4-NLRP3 pathway

To investigate the effect of hydrogen sulfide (H2S) on myocardial injury in sepsis-induced myocardial dysfunction (SIMD), male C57BL/6 mice were intraperitoneally injected with lipopolysaccharide (LPS) (10 mg/kg, i.p.) to induce cardiac dysfunction without or with the H2S donor sodium hydrosulfide (NaHS) (50 µmol/kg, i.p.) administration 3 h after LPS injection. Six hours after the LPS injection, echocardiography, cardiac hematoxylin and eosin (HE) staining, myocardial damage and inflammatory biomarkers and Western blot results were analyzed. In mice, the administration of LPS decreased left ventricular ejection fraction (LVEF) by 30 % along with lowered H2S levels (35 % reduction). It was observed that cardiac troponin I (cTnI), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta) levels were all increased (by 0.22-fold, 2000-fold and 0.66-fold respectively). HE staining revealed structural damage and inflammatory cell infiltration in the myocardial tissue after LPS administration. Moreover, after 6 h of LPS treatment, toll-like receptor 4 (TLR4) and nod-like receptor protein 3 (NLRP3) expressions were up-regulated 2.7-fold and 1.6-fold respectively. When compared to the septic mice, NaHS enhanced ventricular function (by 0.19-fold), decreased cTnI, TNF-alpha, and IL-1beta levels (by 11 %, 33 %, and 16 % respectively) and downregulated TLR4 and NLRP3 expressions (by 64 % and 31 % respectively). Furthermore, NaHS did not further improve cardiac function and inflammation in TLR4-/- mice or mice in which NLRP3 activation was inhibited by MCC950, after LPS injection. In conclusion, these findings imply that decreased endogenous H2S promotes the progression of SIMD, whereas exogenous H2S alleviates SIMD by inhibiting inflammation via the TLR4-NLRP3 pathway suppression.

Hydrogen sulfide plays an important role by regulating endoplasmic reticulum stress in myocardial diseases

Endoplasmic reticulum (ER) is an important organelle for protein translation, folding and translocation, as well as the post-translational modification and assembly of newly synthesized secreted proteins. When the excessive accumulation of misfolded and/or unfolded proteins exceeds the processing capacity of ER, ER stress is triggered. The integrated intracellular signal cascade, namely the unfolded protein response, is induced to avoid ER stress. ER stress is involved in many pathological and physiological processes including myocardial diseases. For a long time, hydrogen sulfide (H₂S) has been considered as a toxic gas with the smell of rotten eggs. However, more and more evidences indicate that H₂S is an important gas signal molecule after nitric oxide and carbon monoxide, and regulates a variety of physiological and pathological processes in mammals. In recent years, increasing studies have focused on the regulatory effects of H₂S on ER stress in myocardial diseases, however, the mechanism is not very clear. Therefore, this review focuses on the role of H₂S regulation of ER stress in myocardial diseases, and deeply analyzes the relevant mechanisms so as to lay the foundation for the future researches.

Hydrogen Sulfide Plays an Important Role by Regulating Endoplasmic Reticulum Stress in Diabetes-Related Diseases

Endoplasmic reticulum (ER) plays important roles in protein synthesis, protein folding and modification, lipid biosynthesis, calcium storage, and detoxification. ER homeostasis is destroyed by physiological and pharmacological stressors, resulting in the accumulation of misfolded proteins, which causes ER stress. More and more studies have shown that ER stress contributes to the pathogenesis of many diseases, such as diabetes, inflammation, neurodegenerative diseases, cancer, and autoimmune diseases. As a toxic gas, H₂S has, in recent years, been considered the third most important gas signal molecule after NO and CO. H₂S has been found to have many important physiological functions and to play an important role in many pathological and physiological processes. Recent evidence shows that H₂S improves the body’s defenses to many diseases, including diabetes, by regulating ER stress, but its mechanism has not yet been fully understood. We therefore reviewed recent studies of the role of H₂S in improving diabetes-related diseases by regulating ER stress and carefully analyzed its mechanism in order to provide a theoretical reference for future research.

mTOR pathway mediates endoplasmic reticulum stress-induced CD4+ T cell apoptosis in septic mice

Endoplasmic reticulum stress (ERS) has been well documented to participate in the pathophysiological processes of apoptosis in many diseases. Inhibition of ERS ameliorates pathological organ injury. However, the upstream signaling pathways and molecular regulatory mechanisms of which are still unknown. mTOR, an evolutionarily conserved protein kinase, is a key regulator of apoptosis. Hence, in this study, a classical cecal ligation and puncture (CLP) sepsis model was constructed by using the T cell-specific knockout mTOR and TSC1 (Tuberous Sclerosis Complex, the inhibitor of mTOR signaling pathway) mice to explore the underlying signaling pathway and molecular mechanism of host immune imbalance caused by apoptosis in sepsis. We found that mTOR may modulate septic T cell apoptosis by regulating Akt-IRE1-JNK pathway. To further clarify the possible mechanism, the specific inhibitors of PI3K-Akt and IRE1-JNK were used to intervene in mice before/after CLP, respectively. By analyzing the proteins of mTOR-ERS signaling pathway and the expression of apoptosis-related proteins and genes, we found that mTOR mediated the ER stress induced CD4⁺ T cell apoptosis in Septic mice by negatively regulating the Akt-IRE1-JNK-Caspase 3 signaling cascades. These results indicate that mTOR-Akt-IRE1α-JNK signaling pathway mediated the Endoplasmic reticulum stress induced CD4⁺ T cell apoptosis in Septic mice.

Mineralocorticoid Receptor Antagonism Prevents the Synergistic Effect of Metabolic Challenge and Chronic Kidney Disease on Renal Fibrosis and Inflammation in Mice

Obesity and/or metabolic diseases are frequently associated with chronic kidney disease and several factors associated with obesity may contribute to proteinuria and extracellular matrix production. Mineralocorticoid receptor antagonists have proven their clinical efficacy in diabetic kidney disease with preclinical data suggesting that they may also be efficient in non-diabetic chronic kidney disease associated to metabolic diseases. In the present study we developed a novel mouse model combining severe nephron reduction and High Fat Diet challenge that led to chronic kidney disease with metabolic alterations. We showed that the Mineralocorticoid Receptor antagonist canrenoate improved metabolic function, reduced albuminuria and prevented the synergistic effect of high fat diet on renal fibrosis and inflammation in chronic kidney disease mice.

Berberine attenuates sepsis‑induced cardiac dysfunction by upregulating the Akt/eNOS pathway in mice

The present study aimed to investigate the cardioprotective role of berberine in sepsis-induced cardiac dysfunction and consider the underlying mechanisms. C57BL/6J mice were randomized into four groups, namely, Control, lipopolysaccharide (LPS), LPS + berberine and LPS + N^ω-nitro-L-arginine methyl ester (L-NAME) + berberine. A single dose (10 mg/kg body weight) of LPS was intraperitoneally administered to mice to induce cardiac dysfunction, whereas the Control group was administered with an equivalent volume of saline. In the LPS + berberine and LPS + L-NAME + berberine group, berberine (10 mg/kg body weight) dissolved in hot water was intraperitoneally administered 30 min after the LPS treatment. In the LPS + L-NAME + berberine group, L-NAME (100 mg/kg body weight) dissolved in saline was intraperitoneally administered 30 min before the LPS treatment. Then, ~6 h after the LPS treatment, a significant decrease was observed in the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS). Meanwhile, the plasma myocardial injury markers, inflammatory factors and oxidative stress levels were significantly increased in the LPS group compared with the Control group. The administration of berberine improved the ventricular function and decreased the plasma myocardial injury markers, inflammatory factors and oxidative stress levels. In addition, it increased the heart total nitric oxide synthase (NOS) activity and upregulated the protein expressions of p-Akt and phosphorylated endothelial (e)NOS, which indicated that the Akt/eNOS pathway was activated by berberine. However, the cardioprotective effects of berberine were counteracted by L-NAME, an NOS inhibitor, which inhibited the eNOS activity. In conclusion, berberine attenuated sepsis-induced cardiac dysfunction by upregulating the Akt/eNOS pathway in mice.

Gases in Sepsis: Novel Mediators and Therapeutic Targets

Sepsis, a potentially lethal condition resulting from failure to control the initial infection, is associated with a dysregulated host defense response to pathogens and their toxins. Sepsis remains a leading cause of morbidity, mortality and disability worldwide. The pathophysiology of sepsis is very complicated and is not yet fully understood. Worse still, the development of effective therapeutic agents is still an unmet need and a great challenge. Gases, including nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), are small-molecule biological mediators that are endogenously produced, mainly by enzyme-catalyzed reactions. Accumulating evidence suggests that these gaseous mediators are widely involved in the pathophysiology of sepsis. Many sepsis-associated alterations, such as the elimination of invasive pathogens, the resolution of disorganized inflammation and the preservation of the function of multiple organs and systems, are shaped by them. Increasing attention has been paid to developing therapeutic approaches targeting these molecules for sepsis/septic shock, taking advantage of the multiple actions played by NO, CO and H2S. Several preliminary studies have identified promising therapeutic strategies for gaseous-mediator-based treatments for sepsis. In this review article, we summarize the state-of-the-art knowledge on the pathophysiology of sepsis; the metabolism and physiological function of NO, CO and H2S; the crosstalk among these gaseous mediators; and their crucial effects on the development and progression of sepsis. In addition, we also briefly discuss the prospect of developing therapeutic interventions targeting these gaseous mediators for sepsis.

Protective effect of H2S on LPS‑induced AKI by promoting autophagy

The present study explored the protective effect of exogenous hydrogen sulfide (H2S) on lipopolysaccharide (LPS)‑induced acute kidney injury (AKI) and the underlying mechanisms. To establish an AKI injury mouse model, LPS (10 mg/kg) was intraperitoneally injected into mice pretreated with 0.8 mg/kg sodium hydrosulfide hydrate (NaHS), an H2S donor. The mouse survival rate and the degree of kidney injury were examined. To construct a cell damage model, HK‑2 cells were pretreated with different concentrations (0.1, 0.3 and 0.5 mM) of NaHS, and then the cells were stimulated with LPS (1 µg/ml). The cell viability, autophagy, apoptosis levels and the release of inflammatory factors were examined in mouse kidney tissue and HK‑2 renal tubular epithelial cells. It was found that pretreatment with NaHS significantly improved the survival rate of septic AKI mice, and reduced the renal damage, release of inflammatory factors and apoptosis. In HK‑2 cells, NaHS protected cells from LPS caused damage via promoting autophagy and inhibiting apoptosis and the release of inflammatory factors. In order to clarify the relationship between autophagy and apoptosis and inflammatory factors, this study used 3‑methyladenine (3‑MA) to inhibit autophagy. The results revealed that 3‑MA eliminated the protective effect of NaHS in HK‑2 cells and AKI mice. Overall, NaHS can protect from LPS‑induced AKI by promoting autophagy and inhibiting apoptosis and the release of inflammatory factors.

Renal consequences of the novel coronavirus disease 2019 (COVID-19) and hydrogen sulfide as a potential therapy

The novel coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, is a global pandemic which is primarily considered a respiratory illness. However, emerging reports show that the virus exhibits both pulmonary and extra-pulmonary manifestations in humans, with the kidney as a major extra-pulmonary target due to its abundant expression of angiotensin-converting enzyme 2 and transmembrane protease serine 2, which facilitate entry of the virus into cells. Acute kidney injury has become prevalent in COVID-19 patients without prior any history of kidney dysfunction. In addition, the virus also worsens kidney conditions and increases mortality of COVID-19 patients with pre-existing chronic kidney disease, renal cancer, diabetic nephropathy, end-stage kidney disease as well as dialysis and kidney transplant patients. In the search for antiviral agents for the treatment of COVID-19, hydrogen sulfide (H₂S), the third established member of gasotransmitter family, is emerging as a potential candidate, possessing important therapeutic properties including antiviral, anti-inflammatory, anti-thrombotic and antioxidant properties. A recent clinical study revealed higher serum H₂S levels in survivors of COVID-19 pneumonia with reduced interleukin-6 levels compared to fatal cases. In this review, we summarize the global impact of COVID-19 on kidney conditions and discuss the emerging role of H₂S as a potential COVID-19 therapy.

Hydrogen sulfide as a therapeutic option for the treatment of Duchenne muscular dystrophy and other muscle-related diseases

Hydrogen sulfide (H₂S) has been known for years as a poisoning gas and until recently evoked mostly negative associations. However, the discovery of its gasotransmitter functions suggested its contribution to various physiological and pathological processes. Although H₂S has been found to exert cytoprotective effects through modulation of antioxidant, anti-inflammatory, anti-apoptotic, and pro-angiogenic responses in a variety of conditions, its role in the pathophysiology of skeletal muscles has not been broadly elucidated so far. The classical example of muscle-related disorders is Duchenne muscular dystrophy (DMD), the most common and severe type of muscular dystrophy. Mutations in the DMD gene that encodes dystrophin, a cytoskeletal protein that protects muscle fibers from contraction-induced damage, lead to prominent dysfunctions in the structure and functions of the skeletal muscle. However, the main cause of death is associated with cardiorespiratory failure, and DMD remains an incurable disease. Taking into account a wide range of physiological functions of H₂S and recent literature data on its possible protective role in DMD, we focused on the description of the 'old' and 'new' functions of H₂S, especially in muscle pathophysiology. Although the number of studies showing its essential regulatory action in dystrophic muscles is still limited, we propose that H₂S-based therapy has the potential to attenuate the progression of DMD and other muscle-related disorders.

Novel Insights Into the Potential Mechanisms of N6-Methyladenosine RNA Modification on Sepsis-Induced Cardiovascular Dysfunction: An Update Summary on Direct and Indirect Evidences

Sepsis is a life-threatening organ dysfunction caused by a host’s dysfunctional response to infection. As is known to all, septic heart disease occurs because pathogens invading the blood stimulate the activation of endothelial cells, causing a large number of white blood cells to accumulate and trigger an immune response. However, in severe sepsis, the hematopoietic system is inhibited, and there will also be a decline in white blood cells, at which time the autoimmune system will also be suppressed. During the immune response, a large number of inflammatory factors are released into cells to participate in the inflammatory process, which ultimately damages cardiac myocytes and leads to impaired cardiac function. N6-methyladenosine (m6A) is a common RNA modification in mRNA and non-coding RNA that affects RNA splicing, translation, stability, and epigenetic effects of some non-coding RNAs. A large number of emerging evidences demonstrated m6A modification had been involved in multiple biological processes, especially for sepsis and immune disorders. Unfortunately, there are limited results provided to analyze the association between m6A modification and sepsis-induced cardiovascular dysfunction (SICD). In this review, we firstly summarized current evidences on how m6A mediates the pathophysiological process in cardiac development and cardiomyopathy to emphasize the importance of RNA methylation in maintaining heart biogenesis and homeostasis. Then, we clarified the participants of m6A modification in extended inflammatory responses and immune system activation, which are the dominant and initial changes secondary to sepsis attack. After that, we deeply analyzed the top causes of SICD and identified the activation of inflammatory cytokines, endothelial cell dysfunction, and mitochondrial failure. Thus, the highlight of this review is that we systematically collected all the related potential mechanisms between m6A modification and SICD causes. Although there is lack of direct evidences on SICD, indirect evidences had been demonstrated case by case on every particular molecular mechanism and signal transduction, which require further explorations into the potential links among the listed mechanisms. This provides novel insights into the understanding of SICD.

The Antiviral Roles of Hydrogen Sulfide by Blocking the Interaction between SARS-CoV-2 and Its Potential Cell Surface Receptors

The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is posing a great threat to the global economy and public health security. Together with the acknowledged angiotensin-converting enzyme 2, glucose-regulated protein 78, transferrin receptor, AXL, kidney injury molecule-1, and neuropilin 1 are also identified as potential receptors to mediate SARS-CoV-2 infection. Therefore, how to inhibit or delay the binding of SARS-CoV-2 with the abovementioned receptors is a key step for the prevention and treatment of COVID-19. As the third gasotransmitter, hydrogen sulfide (H2S) plays an important role in many physiological and pathophysiological processes. Recently, survivors were reported to have significantly higher H2S levels in COVID-19 patients, and mortality was significantly greater among patients with decreased H2S levels. Considering that the beneficial role of H2S against COVID-19 and COVID-19-induced comorbidities and multiorgan damage has been well-examined and reported in some excellent reviews, this review will discuss the recent findings on the potential receptors of SARS-CoV-2 and how H2S modulates the above receptors, in turn blocking SARS-CoV-2 entry into host cells.

ROCK1 regulates sepsis-induced acute kidney injury via TLR2-mediated endoplasmic reticulum stress/pyroptosis axis

BACKGROUND

It has been reported that ROCK1 participates in the progression of multiple diseases, including septic intestinal barrier, cardiac dysfunction and acute lung injury. However, its regulatory role and specific mechanism in sepsis-induced acute kidney injury (AKI) remain unclear.

METHODS

Cecal ligation puncture (CLP) was conducted to establish sepsis mouse model, and in vitro model was achieved by lipopolysaccharide (LPS) stimulation. Genes expression was evaluated by qRT-PCR, western blot or ELISA was conducted to assess the levels of proteins. Hoechst staining was performed to evaluate cell pyroptosis. LDH activity assay was detected to assess cytotoxicity. Immunohistochemistry was conducted to detect Ly-6G expression and neutrophils distribution in kidney tissues of mice. H&E and TUNEL staining were carried to evaluate kidney injury of mice.

RESULTS

Our findings illuminated that ROCK1 was highly expressed in sepsis-induced AKI, and ROCK1 knockdown inhibited NLRP3-mediated cell pyroptosis in LPS-induced HK-2 cells. Moreover, ROCK1 modulated HK-2 cell pyroptosis by regulating endoplasmic reticulum stress (ERS). TLR2 inhibitor could suppress ERS mediated cell pyroptosis under LPS treatment. Further, TLR2 activator partially reversed the effects of ROCK1 inhibition on ERS mediated pyroptosis in LPS-treated HK-2 cells and CLP mice.

CONCLUSION

In conclusion, ROCK1 may regulate sepsis-induced AKI via TLR2-mediated ERS/pyroptosis axis. Our data demonstrated the role and underlying mechanism of ROCK1 in septic AKI, providing theoretical basis for sepsis-induced AKI treatment.