Preconditioning of H 2 S inhalation protects against cerebral ischemia/reperfusion injury by induction of HSP70 through PI3K/Akt/Nrf2 pathway

A meta-analysis of animal studies evaluating the effect of hydrogen sulfide on ischemic stroke: is the preclinical evidence sufficient to move forward?

Hydrogen sulfide (H2S) is a gasotransmitter that has been studied for its potential therapeutic effects, including its role in the pathophysiology and treatment of stroke. This systematic review and meta-analysis aimed to determine the sufficiency of overall preclinical evidence to guide the initiation of clinical stroke trials with H2S and provide tailored recommendations for their design. PubMed, Web of Science, Scopus, EMBASE, and MEDLINE were searched for studies evaluating the effect of any H2S donor on in vivo animal models of regional ischemic stroke, and 34 publications were identified. Pooling of the effect sizes using the random-effect model revealed that H2S decreased the infarct area by 34.5% (95% confidence interval (CI) 28.2-40.8%, p < 0.0001), with substantial variability among the studies (I2 = 89.8%). H2S also caused a 37.9% reduction in the neurological deficit score (95% CI 29.0-46.8%, p < 0.0001, I2 = 63.8%) and in the brain water content (3.2%, 95% CI 1.4-4.9%, p = 0.0014, I2 = 94.6%). Overall, the studies had a high risk of bias and low quality of evidence (median quality score 5/15, interquartile range 4-9). The majority of the included studies had a "high" or "unclear" risk of bias, and none of the studies overall had a "low" risk. In conclusion, H2S significantly improves structural and functional outcomes in in vivo animal models of ischemic stroke. However, the level of evidence from preclinical studies is not sufficient to proceed to clinical trials due to the low external validity, high risk of bias, and variable design of existing animal studies.

Therapeutic Potential of Hydrogen Sulfide in Ischemia and Reperfusion Injury

Ischemia-reperfusion (I/R) injury, a prevalent pathological condition in medical practice, presents significant treatment challenges. Hydrogen sulfide (H2S), acknowledged as the third gas signaling molecule, profoundly impacts various physiological and pathophysiological processes. Extensive research has demonstrated that H2S can mitigate I/R damage across multiple organs and tissues. This review investigates the protective effects of H2S in preventing I/R damage in the heart, brain, liver, kidney, intestines, lungs, stomach, spinal cord, testes, eyes, and other tissues. H2S provides protection against I/R damage by alleviating inflammation and endoplasmic reticulum stress; inhibiting apoptosis, oxidative stress, and mitochondrial autophagy and dysfunction; and regulating microRNAs. Significant advancements in understanding the mechanisms by which H2S reduces I/R damage have led to the development and synthesis of H2S-releasing agents such as diallyl trisulfide-loaded mesoporous silica nanoparticles (DATS-MSN), AP39, zofenopril, and ATB-344, offering a new therapeutic avenue for I/R injury.

Research hotspots and frontiers of preconditioning in cerebral ischemia: A bibliometric analysis

Background

Preconditioning is a promising strategy against ischemic brain injury, and numerous studies in vitro and in vivo have demonstrated its neuroprotective effects. However, at present there is no bibliometric analysis of preconditioning in cerebral ischemia. Therefore, a comprehensive overview of the current status, hot spots, and emerging trends in this research field is necessary.

Materials and methods

Studies on preconditioning in cerebral ischemia from January 1999-December 2022 were retrieved from the Web of Science Core Collection (WOSCC) database. CiteSpace was used for data mining and visual analysis.

Results

A total of 1738 papers on preconditioning in cerebral ischemia were included in the study. The annual publications showed an upwards and then downwards trend but currently remain high in terms of annual publications. The US was the leading country, followed by China, the most active country in recent years. Capital Medical University published the largest number of articles. Perez-Pinzon, Miguel A contributed the most publications, while KITAGAWA K was the most cited author. The focus of the study covered three areas: (1) relevant diseases and experimental models, (2) types of preconditioning and stimuli, and (3) mechanisms of ischemic tolerance. Remote ischemic preconditioning, preconditioning of mesenchymal stem cells (MSCs), and inflammation are the frontiers of research in this field.

Conclusion

Our study provides a visual and scientific overview of research on preconditioning in cerebral ischemia, providing valuable information and new directions for researchers.

The hormesis principle of neuroplasticity and neuroprotection

Animals live in habitats fraught with a range of environmental challenges to their bodies and brains. Accordingly, cells and organ systems have evolved stress-responsive signaling pathways that enable them to not only withstand environmental challenges but also to prepare for future challenges and function more efficiently. These phylogenetically conserved processes are the foundation of the hormesis principle, in which single or repeated exposures to low levels of environmental challenges improve cellular and organismal fitness and raise the probability of survival. Hormetic principles have been most intensively studied in physical exercise but apply to numerous other challenges known to improve human health (e.g., intermittent fasting, cognitive stimulation, and dietary phytochemicals). Here we review the physiological mechanisms underlying hormesis-based neuroplasticity and neuroprotection. Approaching natural resilience from the lens of hormesis may reveal novel methods for optimizing brain function and lowering the burden of neurological disorders.

Mechanisms Underlying the Hydrogen Sulfide Actions: Target Molecules and Downstream Signaling Pathways

Significance: As a new important gas signaling molecule like nitric oxide (NO) and carbon dioxide (CO), hydrogen sulfide (H2S), which can be produced by endogenous H2S-producing enzymes through l-cysteine metabolism in mammalian cells, has attracted wide attention for long. H2S has been proved to play an important regulatory role in numerous physiological and pathophysiological processes. However, the deep mechanisms of those different functions of H2S still remain uncertain. A better understanding of the mechanisms can help us develop novel therapeutic strategies. Recent Advances: H2S can play a regulating role through various mechanisms, such as regulating epigenetic modification, protein expression levels, protein activity, protein localization, redox microenvironment, and interaction with other gas signaling molecules such as NO and CO. In addition to discussing the molecular mechanisms of H2S from the above perspectives, this article will review the regulation of H2S on common signaling pathways in the cells, including the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt), mitogen-activated protein kinase (MAPK), Janus kinase (JAK)/signal transducer, and activator of transcription (STAT) signaling pathway. Critical Issues: Although there are many studies on the mechanism of H2S, little is known about its direct target molecules. This article will also review the existing reports about them. Furthermore, the interaction between direct target molecules of H2S and the downstream signaling pathways involved also needs to be clarified. Future Directions: An in-depth discussion of the mechanism of H2S and the direct target molecules will help us achieving a deeper understanding of the physiological and pathophysiological processes regulated by H2S, and lay a foundation for developing new clinical therapeutic drugs in the future. Innovation: This review focuses on the regulation of H2S on signaling pathways and the direct target molecules of H2S. We also provide details on the underlying mechanisms of H2S functions from the following aspects: epigenetic modification, regulation of protein expression levels, protein activity, protein localization, redox microenvironment, and interaction with other gas signaling molecules such as NO and CO. Further study of the mechanisms underlying H2S will help us better understand the physiological and pathophysiological processes it regulates, and help develop new clinical therapeutic drugs in the future. Antioxid. Redox Signal. 40, 86-109.

Nrf2 for a key member of redox regulation: A novel insight against myocardial ischemia and reperfusion injuries

Nuclear factor erythroid-2 related factor 2 (Nrf2), a nuclear transcription factor, modulates genes responsible for antioxidant responses against toxic and oxidative stress to maintain redox homeostasis and participates in varieties of cellular processes such as metabolism and inflammation during myocardial ischemia and reperfusion injuries (MIRI). The accumulation of reactive oxygen species (ROS) from damaged mitochondria, xanthine oxidase, NADPH oxidases, and inflammation contributes to depraved myocardial ischemia and reperfusion injuries. Considering that Nrf2 played crucial roles in antagonizing oxidative stress, it is reasonable to delve into the up or down-regulated molecular mechanisms of Nrf2 in the progression of MIRI to provide the possibility of new therapeutic medicine targeting Nrf2 in cardiovascular diseases. This review systematically describes the generation of ROS, the regulatory metabolisms of Nrf2 as well as several natural or synthetic compounds activating Nrf2 during MIRI, which might provide novel insights for the anti-oxidative stress and original ideas targeting Nrf2 for the prevention and treatment in cardiovascular diseases.

Sulfur signaling pathway in cardiovascular disease

Hydrogen sulfide (H2S) and sulfur dioxide (SO2), recognized as endogenous sulfur-containing gas signaling molecules, were the third and fourth molecules to be identified subsequent to nitric oxide and carbon monoxide (CO), and exerted diverse biological effects on the cardiovascular system. However, the exact mechanisms underlying the actions of H2S and SO2 have remained elusive until now. Recently, novel post-translational modifications known as S-sulfhydration and S-sulfenylation, induced by H2S and SO2 respectively, have been proposed. These modifications involve the chemical alteration of specific cysteine residues in target proteins through S-sulfhydration and S-sulfenylation, respectively. H2S induced S-sulfhydrylation can have a significant impact on various cellular processes such as cell survival, apoptosis, cell proliferation, metabolism, mitochondrial function, endoplasmic reticulum stress, vasodilation, anti-inflammatory response and oxidative stress in the cardiovascular system. Alternatively, S-sulfenylation caused by SO2 serves primarily to maintain vascular homeostasis. Additional research is warranted to explore the physiological function of proteins with specific cysteine sites, despite the considerable advancements in comprehending the role of H2S-induced S-sulfhydration and SO2-induced S-sulfenylation in the cardiovascular system. The primary objective of this review is to present a comprehensive examination of the function and potential mechanism of S-sulfhydration and S-sulfenylation in the cardiovascular system. Proteins that undergo S-sulfhydration and S-sulfenylation may serve as promising targets for therapeutic intervention and drug development in the cardiovascular system. This could potentially expedite the future development and utilization of drugs related to H2S and SO2.

Scutellarin attenuates oxidative stress and neuroinflammation in cerebral ischemia/reperfusion injury through PI3K/Akt-mediated Nrf2 signaling pathways

Cerebral ischemia/reperfusion injury (CIRI) seriously threatens human life and health. Scutellarin (Scu) exhibits neuroprotective effects, but little is known about its underlying mechanism. Therefore, we explored its protective effect on CIRI and the underlying mechanism. Our results demonstrated that Scu rescued HT22 cells from cytotoxicity induced by oxygen and glucose deprivation/reoxygenation (OGD/R). Scu also showed antioxidant activity by promoting nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation, upregulating heme oxygenase-1 (HO-1) expression, increasing superoxide dismutase (SOD) activity, and inhibiting reactive oxygen species (ROS) generation in vitro. Additionally, Scu reduced nuclear factor-kappa B (NF-κB) activity and the levels of pro-inflammatory factors. Interestingly, these effects were abolished by Nrf2 inhibition. Furthermore, Scu reduced infarct volume and blood-brain barrier (BBB) permeability, improved sensorimotor functions and depressive behaviors, and alleviated oxidative stress and neuroinflammation in rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). Mechanistically, Scu-induced Nrf2 nuclear accumulation and inactivation of NF-κB were accompanied by an enhanced level of phosphorylated protein kinase B (p-AKT) both in vitro and in vivo. Pharmacologically inhibiting the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathway blocked Scu-induced Nrf2 nuclear translocation and inactivation of NF-κB, as well as its antioxidant and anti-inflammatory activities. In summary, these results suggest that Scu exhibits antioxidant, anti-inflammatory, and neuroprotective effects in CIRI through Nrf2 activation mediated by the PI3K/Akt pathway.

Hydrogen sulfide and its donors for the treatment of cerebral ischaemia-reperfusion injury: A comprehensive review

As an endogenous gas signalling molecule, hydrogen sulfide (H₂S) is frequently present in a variety of mammals and plays a significant role in the cardiovascular and nervous systems. Reactive oxygen species (ROS) are produced in large quantities as a result of cerebral ischaemia-reperfusion, which is a very serious class of cerebrovascular diseases. ROS cause oxidative stress and induce specific gene expression that results in apoptosis. H₂S reduces cerebral ischaemia-reperfusion-induced secondary injury via anti-oxidative stress injury, suppression of the inflammatory response, inhibition of apoptosis, attenuation of cerebrovascular endothelial cell injury, modulation of autophagy, and antagonism of P2X7 receptors, and it plays an important biological role in other cerebral ischaemic injury events. Despite the many limitations of the hydrogen sulfide therapy delivery strategy and the difficulty in controlling the ideal concentration, relevant experimental evidence demonstrating that H₂S plays an excellent neuroprotective role in cerebral ischaemia-reperfusion injury (CIRI). This paper examines the synthesis and metabolism of the gas molecule H₂S in the brain as well as the molecular mechanisms of H₂S donors in cerebral ischaemia-reperfusion injury and possibly other unknown biological functions. With the active development in this field, it is expected that this review will assist researchers in their search for the potential value of hydrogen sulfide and provide new ideas for preclinical trials of exogenous H₂S.

Protective Effect of Hydrogen Sulfide on Cerebral Ischemia-Reperfusion Injury

The brain is the most sensitive organ to hypoxia in the human body. Hypoxia in the brain will lead to damage to local brain tissue. When the blood supply of ischemic brain tissue is restored, the damage will worsen, that is, cerebral ischemia-reperfusion injury. Hydrogen sulfide (H₂S) is a gaseous signal molecule and a novel endogenous neuroregulator. Indeed, different concentrations of H₂S have different effects on neurons. Low concentration of H₂S can play an important protective role in cerebral ischemia-reperfusion injury by inducing anti-oxidative stress injury, inhibition of inflammatory response, inhibition of cell apoptosis, reduction of cerebrovascular endothelial cell injury, regulation of autophagy, and other ways, which provides a new idea for clinical diagnosis and treatment of related diseases. This review aims to report the recent research progress on the dual effect of H₂S on brain tissue during cerebral ischemia/reperfusion injury.

Anserine and Carnosine Induce HSP70-Dependent H2S Formation in Endothelial Cells and Murine Kidney

Anserine and carnosine have nephroprotective actions; hydrogen sulfide (H₂S) protects from ischemic tissue damage, and the underlying mechanisms are debated. In view of their common interaction with HSP70, we studied possible interactions of both dipeptides with H₂S. H₂S formation was measured in human proximal tubular epithelial cells (HK-2); three endothelial cell lines (HUVEC, HUAEC, MCEC); and in renal murine tissue of wild-type (WT), carnosinase-1 knockout (Cndp1-KO) and Hsp70-KO mice. Diabetes was induced by streptozocin. Incubation with carnosine increased H₂S synthesis capacity in tubular cells, as well as with anserine in all three endothelial cell lines. H₂S dose-dependently reduced anserine/carnosine degradation rate by serum and recombinant carnosinase-1 (CN1). Endothelial Hsp70-KO reduced H₂S formation and abolished the stimulation by anserine and could be restored by Hsp70 transfection. In female Hsp70-KO mice, kidney H₂S formation was halved. In Cndp1-KO mice, kidney anserine concentrations were several-fold and sex-specifically increased. Kidney H₂S formation capacity was increased 2-3-fold in female mice and correlated with anserine and carnosine concentrations. In diabetic Cndp1-KO mice, renal anserine and carnosine concentrations as well as H₂S formation capacity were markedly reduced compared to non-diabetic Cndp1-KO littermates. Anserine and carnosine induce H₂S formation in a cell-type and Hsp70-specific manner within a positive feedback loop with CN1.

Nrf2 Regulates Oxidative Stress and Its Role in Cerebral Ischemic Stroke

Cerebral ischemic stroke is characterized by acute ischemia in a certain part of the brain, which leads to brain cells necrosis, apoptosis, ferroptosis, pyroptosis, etc. At present, there are limited effective clinical treatments for cerebral ischemic stroke, and the recovery of cerebral blood circulation will lead to cerebral ischemia-reperfusion injury (CIRI). Cerebral ischemic stroke involves many pathological processes such as oxidative stress, inflammation, and mitochondrial dysfunction. Nuclear factor erythroid 2-related factor 2 (Nrf2), as one of the most critical antioxidant transcription factors in cells, can coordinate various cytoprotective factors to inhibit oxidative stress. Targeting Nrf2 is considered as a potential strategy to prevent and treat cerebral ischemia injury. During cerebral ischemia, Nrf2 participates in signaling pathways such as Keap1, PI3K/AKT, MAPK, NF-κB, and HO-1, and then alleviates cerebral ischemia injury or CIRI by inhibiting oxidative stress, anti-inflammation, maintaining mitochondrial homeostasis, protecting the blood-brain barrier, and inhibiting ferroptosis. In this review, we have discussed the structure of Nrf2, the mechanisms of Nrf2 in cerebral ischemic stroke, the related research on the treatment of cerebral ischemia through the Nrf2 signaling pathway in recent years, and expounded the important role and future potential of the Nrf2 pathway in cerebral ischemic stroke.

The Effects of H2S and Recombinant Human Hsp70 on Inflammation Induced by SARS and Other Agents In Vitro and In Vivo

The ongoing epidemic caused by SARS-CoV-2 infection led to the search for fundamentally new ways and means to combat inflammation and other pathologies caused by this virus. Using a cellular model of lipopolysaccharide (LPS)-induced sepsis (human promonocytes), we showed that both a hydrogen sulfide donor (sodium thiosulfate, STS) and a recombinant Heat shock protein 70 (rHsp70) effectively block all major inflammatory mediators when administrated before and after LPS challenge. The protective anti-inflammatory effect of rHsp70 and H2S was also confirmed in vivo using various animal models of pneumonia. Specifically, it was found that rHsp70 injections prevented the development of the acute respiratory distress syndrome in highly pathogenic pneumonia in mice, increased animal survival, and reduced the number of Programmed death-1 (PD-1)-positive T-lymphocytes in peripheral blood. Based on our model experiments we developed a combined two-phase therapeutic approach for the treatment of COVID-19 patients. This procedure includes the inhalation of hot helium–oxygen mixtures for induction of endogenous Hsp70 in the first phase and STS inhalation in the second phase. The use of this approach has yielded positive results in COVID-19 patients, reducing the area of lung lesions, restoring parameters of innate immunity and T-cell immune response against coronavirus infection, and preventing the development of pulmonary fibrosis and immune exhaustion syndrome.

NO, CO and H2S: A Trinacrium of Bioactive Gases in the Brain

Oxygen and carbon dioxide are time honored gases that have direct bearing on almost all life forms, but over the past thirty years, and in large part due to the Nobel Prize Award in Medicine for the elucidation of nitric oxide (NO) as a bioactive gas, the research and medical communities now recognize other gases as critical for survival. In addition to NO, hydrogen sulfide (H₂S) and carbon monoxide (CO) have emerged as a triumvirate or Trinacrium of gases with analogous importance and that serve important homeostatic functions. Perhaps, one of the most intriguing aspects of these gases is the functional interaction between them, which is intimately linked by the enzyme systems that produce them. Despite the need to better understand NO, H₂S and CO biology, the notion that these are environmental pollutants remains ever present. For this reason, incorporating the concept of hormesis becomes imperative and must be included in discussions when considering developing new therapeutics that involve these gases. While there is now an enormous literature base for each of these gasotransmitters, we provide here an overview of their respective physiologic roles in the brain.

Recent Advances in Chinese Herbal Medicine for Cerebral Ischemic Reperfusion Injury

Cerebral ischemic reperfusion injury (CI/RI) is a critical factor that leads to a poor prognosis in patients with ischemic stroke. It is an extremely complicated pathological process that is clinically characterized by high rates of disability and mortality. Current available treatments for CI/RI, including mechanical and drug therapies, are often accompanied by significant side effects. Therefore, it is necessary to discovery new strategies for treating CI/RI. Many studies confirm that Chinese herbal medicine (CHM) was used as a potential drug for treatment of CI/RI with the advantages of abundant resources, good efficacy, and few side effects. In this paper, we investigate the latest drug discoveries and advancements on CI/RI, make an overview of relevant CHM, and systematically summarize the pathophysiology of CI/RI. In addition, the protective effect and mechanism of related CHM, which includes extraction of single CHM and CHM formulation and preparation, are discussed. Moreover, an outline of the limitations of CHM and the challenges we faced are also presented. This review will be helpful for researchers further propelling the advancement of drugs and supplying more knowledge to support the application of previous discoveries in clinical drug applications against CI/RI.

Sulfur Dioxide: Endogenous Generation, Biological Effects, Detection, and Therapeutic Potential

Significance: Previously, sulfur dioxide (SO₂) was recognized as an air pollutant. However, it is found to be endogenously produced in mammalian tissues. As a new gasotransmitter, SO₂ is involved in regulating the structure and function of blood vessels, heart, lung, gastrointestinal tract, nervous system, etc.Recent Advances: Increasing evidence showed that endogenous SO₂ regulates cardiovascular physiological processes, such as blood pressure control, vasodilation, maintenance of the normal vascular structure, and cardiac negative inotropy. Under pathological conditions including hypertension, atherosclerosis, vascular calcification, aging endothelial dysfunction, myocardial injury, myocardial hypertrophy, diabetic myocardial fibrosis, sepsis-induced cardiac dysfunction, pulmonary hypertension, acute lung injury, colitis, epilepsy-related brain injury, depression and anxiety, and addictive drug reward memory consolidation, endogenous SO₂ protects against the pathological changes via different molecular mechanisms and the disturbed SO₂/aspartate aminotransferase pathway is likely involved in the mechanisms for the earlier mentioned pathologic processes. Critical Issues: A comprehensive understanding of the biological effects of endogenous SO₂ is extremely important for the development of novel SO₂ therapy. In this review, we summarized the biological effects, mechanism of action, SO₂ detection methods, and its related prodrugs. Future Directions: Further studies should be conducted to understand the effects of endogenous SO₂ in various physiological and pathophysiological processes and clarify its underlying mechanisms. More efficient and accurate SO₂ detection methods, as well as specific and effective SO₂-releasing systems should be designed for the treatment and prevention of clinical related diseases. The translation from SO₂ basic medical research to its clinical application is also worthy of further study. Antioxid. Redox Signal. 36, 256-274.

Isoginkgetin attenuates endoplasmic reticulum stress-induced autophagy of brain after ischemic reperfusion injury

Isoginkgetin is characterized by properties of potent anticancer and anti-inflammation. To explore its effect on ischemic stroke, a rat model of ischemia/reperfusion (I/R) injury was established and induced by transient middle cerebral artery occlusion/reperfusion (MCAO/R). Different doses of isoginkgetin were intraperitoneally injected into each rat. Expressions of ER stress activation-related makers including phosphorylated inositol-requiring enzyme 1 (IRE1), phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), activating transcription factor-6 (ATF6), and two autophagy markers (ratio of LC3II/I and Beclin-1) were detected by western blot. Infarct volume, neurological deficits, and brain water content were detected. The results showed that ER stress and autophagy were activated by cerebral (I/R) injury, which could be effectively attenuated following pre-ischemia isoginkgetin administration. Moreover, autophagy induced by ER stress was triggered by the activation of PERK and IRE1 pathways. ER stress inhibitor (4-PBA) and ER related signaling inhibitors including PERK, GSK, IRE1, and DBSA markedly inhibited ER stress and autophagy induced by I/R. In addition, isoginkgetin markedly mitigated cerebral infarction, edema, neuronal apoptosis as well as neurological impairment induced by I/R injury, while tunicamycin (ER stress activator TM) and rapamycin (autophagy activator RAPA) could eliminate these lesions. This research identified a novel therapeutic agent isoginkgetin, which could effectively attenuate I/R injury by blocking autophagy induced by ER stress.

The Antioxidant Transcription Factor Nrf2 in Cardiac Ischemia-Reperfusion Injury

Nuclear factor erythroid-2 related factor 2 (Nrf2) is a transcription factor that controls cellular defense responses against toxic and oxidative stress by modulating the expression of genes involved in antioxidant response and drug detoxification. In addition to maintaining redox homeostasis, Nrf2 is also involved in various cellular processes including metabolism and inflammation. Nrf2 activity is tightly regulated at the transcriptional, post-transcriptional and post-translational levels, which allows cells to quickly respond to pathological stress. In the present review, we describe the molecular mechanisms underlying the transcriptional regulation of Nrf2. We also focus on the impact of Nrf2 in cardiac ischemia-reperfusion injury, a condition that stimulates the overproduction of reactive oxygen species. Finally, we analyze the protective effect of several natural and synthetic compounds that induce Nrf2 activation and protect against ischemia-reperfusion injury in the heart and other organs, and their potential clinical application.

Cardioprotective effects of hydrogen sulfide in attenuating myocardial ischemia‑reperfusion injury (Review)

Ischemic heart disease is one of the major causes of cardiovascular‑related mortality worldwide. Myocardial ischemia can be attenuated by reperfusion that restores the blood supply. However, injuries occur during blood flow restoration that induce cardiac dysfunction, which is known as myocardial ischemia‑reperfusion injury (MIRI). Hydrogen sulfide (H₂S), the third discovered endogenous gasotransmitter in mammals (after NO and CO), participates in various pathophysiological processes. Previous in vitro and in vivo research have revealed the protective role of H₂S in the cardiovascular system that render it useful in the protection of the myocardium against MIRI. The cardioprotective effects of H₂S in attenuating MIRI are summarized in the present review.

O-GlcNAc Transferase (OGT) Protects Cerebral Neurons from Death During Ischemia/Reperfusion (I/R) Injury by Modulating Drp1 in Mice

Previous studies have demonstrated that increased O-linked N-acetylglucosamine (O-GlcNAc) level could promote cell survival following environmental stresses. This study aimed to explore the role of O-GlcNAc transferase (OGT) during cerebral ischemia/reperfusion (I/R) injury. The mouse model with cerebral I/R injury was induced by middle cerebral artery occlusion/reperfusion (MCAO/R). The expression of ogt in brain tissues was detected by qRT-PCR, Western blot, and immunohistochemistry (IHC) staining assay. Neurological deficit was evaluated using a modified scoring system. The infarct volume was assessed by TTC staining assay. Neuronal apoptosis in brain tissues was evaluated by TUNEL staining assay. The level of cleaved caspase-3 in brain tissues was detected by Western blot and IHC staining assay. The expression of critical proteins involved in mitochondrial fission, including OPA1, Mfn1, and Mfn2, as well as Mff and Drp1 was detected by Western blot and IHC, respectively. The expression of ogt during cerebral I/R injury was significantly upregulated. Ogt knockdown significantly increased neurological score and infarct volume in I/R-induced mice. Meanwhile, ogt knockdown significantly enhanced neuronal apoptosis and cleaved caspase-3 level in brain tissues of I/R-induced mice. In addition, ogt knockdown markedly decreased serine 637 phosphorylation level of mitochondrial fission protein dynamin-related protein 1 (Drp1) and promoted Drp1 translocation from the cytosol to the mitochondria. Moreover, the specific Drp1 inhibitor mdivi-1 effectively attenuated ogt knockdown-induced brain injury of I/R-stimulated mice in vivo. Our study revealed that OGT protects against cerebral I/R injury by inhibiting the function of Drp1 in mice, suggesting that ogt may be a potential therapeutic target for cerebral I/R injury.

DL-3-n-butylphthalide protects H9c2 cardiomyoblasts from ischemia/reperfusion injury by regulating HSP70 expression via PI3K/AKT pathway activation

DL-3-n-butylphthalide (NBP) is commonly used to treat ischemic strokes due to its antioxidative and anti-inflammatory effects. The present study aimed to examine the protective effects of NBP on myocardial ischemia-reperfusion injury (MIRI) by establishing a MIRI model in H9c2 cells. Cell viability assay using Cell Counting Kit-8, lactate dehydrogenase (LDH) cytotoxicity and lipid peroxidation malondialdehyde (MDA) content were assessed to detect cell activity, degree of cell injury and oxidative stress reaction. Reverse transcription-quantitative PCR was used to quantify the expression of inflammatory factors in H9c2 cells. Western blotting and immunofluorescence staining were used to detect the protein expression of PI3K/AKT and heat shock protein 70 (HSP70). The present results indicated that NBP significantly increased cell viability during ischemia-reperfusion. Moreover, NBP inhibited the release of LDH and the production of MDA. NBP treatment also significantly decreased the expression of inflammatory factors at the mRNA level. Additionally, NBP activated the PI3K/AKT pathway and upregulated the expression of HSP70 compared with cells in the MIRI model. LY294002, a PI3K inhibitor, reversed the protective effects of NBP and suppressed the expression of HSP70. The present study demonstrated that NBP protected H9c2 cells from MIRI by regulating HSP70 expression via PI3K/AKT pathway activation.

An evolutionary perspective on the interplays between hydrogen sulfide and oxygen in cellular functions

The physiological effects of the endogenously generated hydrogen sulfide (H2S) have been extensively studied in recent years. This review summarized the role of H2S in the origin of life and H2S metabolism in organisms from bacteria to vertebrates, examined the relationship between H2S and oxygen from an evolutionary perspective and emphasized the oxygen-dependent manner of H2S signaling in various physiological and pathological processes. H2S and oxygen are inextricably linked in various cellular functions. H2S is involved in aerobic respiration and stimulates oxidative phosphorylation and ATP production within the cell. Besides, H2S has protective effects on ischemia and reperfusion injury in several organs by acting as an oxygen sensor. Also, emerging evidence suggests the role of H2S is in an oxygen-dependent manner. All these findings indicate the subtle relationship between H2S and oxygen and further explain why H2S, a toxic molecule thriving in an anoxia environment several billion years ago, still affects homeostasis today despite the very low content in the body.

The Slow-Releasing and Mitochondria-Targeted Hydrogen Sulfide (H2S) Delivery Molecule AP39 Induces Brain Tolerance to Ischemia

Ischemic stroke is the third leading cause of death in the world, which accounts for almost 12% of the total deaths worldwide. Despite decades of research, the available and effective pharmacotherapy is limited. Some evidence underlines the beneficial properties of hydrogen sulfide (H₂S) donors, such as NaSH, in an animal model of brain ischemia and in in vitro research; however, these data are ambiguous. This study was undertaken to verify the neuroprotective activity of AP39, a slow-releasing mitochondria-targeted H₂S delivery molecule. We administered AP39 for 7 days prior to ischemia onset, and the potential to induce brain tolerance to ischemia was verified. To do this, we used the rat model of 90-min middle cerebral artery occlusion (MCAO) and used LC-MS/MS, RT-PCR, Luminex^TM assays, Western blot and immunofluorescent double-staining to determine the absolute H₂S levels, inflammatory markers, neurotrophic factor signaling pathways and apoptosis marker in the ipsilateral frontal cortex, hippocampus and in the dorsal striatum 24 h after ischemia onset. AP39 (50 nmol/kg) reduced the infarct volume, neurological deficit and reduced the microglia marker (Iba1) expression. AP39 also exerted prominent anti-inflammatory activity in reducing the release of Il-1β, Il-6 and TNFα in brain areas particularly affected by ischemia. Furthermore, AP39 enhanced the pro-survival pathways of neurotrophic factors BDNF-TrkB and NGF-TrkA and reduced the proapoptotic proNGF-p75^NTR-sortilin pathway activity. These changes corresponded with reduced levels of cleaved caspase 3. Altogether, AP39 treatment induced adaptative changes within the brain and, by that, developed brain tolerance to ischemia.

Hydrogen sulfide restores cardioprotective effects of remote ischemic preconditioning in aged rats via HIF-1α/Nrf2 signaling pathway

The present study explored the therapeutic potential of hydrogen sulfide (H₂S) in restoring aging-induced loss of cardioprotective effect of remote ischemic preconditioning (RIPC) along with the involvement of signaling pathways. The left hind limb was subjected to four short cycles of ischemia and reperfusion (IR) in young and aged male rats to induce RIPC. The hearts were subjected to IR injury on the Langendorff apparatus after 24 h of RIPC. The measurement of lactate dehydrogenase, creatine kinase and cardiac troponin served to assess the myocardial injury. The levels of H₂S, cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), nuclear factor erythroid 2-related factor 2 (Nrf2), and hypoxia-inducible factor (HIF-1α) were also measured. There was a decrease in cardioprotection in RIPC-subjected old rats in comparison to young rats along with a reduction in the myocardial levels of H₂S, CBS, CSE, HIF-1α, and nuclear: cytoplasmic Nrf2 ratio. Supplementation with sodium hydrogen sulfide (NaHS, an H₂S donor) and l-cysteine (H₂S precursor) restored the cardioprotective actions of RIPC in old hearts. It increased the levels of H₂S, HIF-1α, and Nrf2 ratio without affecting CBS and CSE. YC-1 (HIF-1α antagonist) abolished the effects of NaHS and l-cysteine in RIPC-subjected old rats by decreasing the Nrf2 ratio and HIF-1α levels, without altering H₂S.The late phase of cardioprotection of RIPC involves an increase in the activity of H₂S biosynthetic enzymes, which increases the levels of H₂S to upregulate HIF-1α and Nrf2. H₂S has the potential to restore aging-induced loss of cardioprotective effects of RIPC by upregulating HIF-1α/Nrf2 signaling.

Therapeutic modulation of the phosphatidylinositol 3-kinases (PI3K) pathway in cerebral ischemic injury

The cerebral ischemic reperfusion injury may leads to morbidity and mortality in patients. phosphatidylinositol 3-kinase (PI3K) signaling pathway has been believed to work in association with its downstream targets, other receptors, and pathways that may offer antioxidant, anti-inflammatory, anti-apoptotic effects, neuroprotective role in neuronal excitotoxicity. This review elaborates the mechanistic interventions of the PI3K pathway in cerebral ischemic injury in context to nuclear factor erythroid 2-related factor 2 (Nrf2) regulation, Hypoxia-inducible factor 1 signaling (HIF-1), growth factors, Endothelial NOS (eNOS) proinflammatory cytokines, Erythropoietin (EPO), Phosphatase and tensin homologous protein of chromosome 10 gene (PTEN) signaling, NF-κB/Notch signaling, c-Jun N-terminal kinase (JNK) and Glycogen synthase kinase-3β (GSK-3β) signaling pathway. Evidences showing the activation of PI3K inhibits apoptotic pathway, which results in its neuroprotective effect in ischemic injury. Despite discussing the therapeutic role of the PI3K pathway in treating cerebral ischemic injury, the review also enlighten the selective modulation of PI3K pathway with activators and inhibitors which may provide promising results in clinical and preclinical settings.

L-Cysteine Provides Neuroprotection of Hypoxia-Ischemia Injury in Neonatal Mice via a PI3K/Akt-Dependent Mechanism

Background

Previous work within our laboratory has revealed that hydrogen sulfide (H₂S) can serve as neuroprotectant against brain damage caused by hypoxia-ischemia (HI) exposure in neonatal mice. After HI insult, activation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway has been shown to be implicated in neuro-restoration processes. The goal of the current study was to determine whether the neuroprotective effects of H₂S were mediated by the PI3K/Akt signaling pathway.

Methods

The mouse HI model was built at postnatal day 7 (P7), and the effects of L-Cysteine treatment on acute brain damage (72 h post-HI) and long-term neurological responses (28 days post-HI) were evaluated. Nissl staining and Transmission electron microscopy were used to evaluate the neuronal loss and apoptosis. Immunofluorescence imaging and dihydroethidium staining were utilized to determine glial cell activation and ROS content, respectively.

Results

Quantitative results revealed that L-Cysteine treatment significantly prevented the acute effects of HI on apoptosis, glial cell activation and oxidative injury as well as the long-term effects upon memory impairment in neonatal mice. This protective effect of L-Cysteine was found to be associated with the phosphorylation of Akt and phosphatase and a tensin homolog deletion on chromosome 10 (PTEN). Following treatment with the PI3K inhibitor, LY294002, the neuroprotective effects of L-Cysteine were attenuated.

Conclusion

PTEN/PI3K/Akt signaling was involved in mediating the neuroprotective effects of exogenous H₂S against HI exposure in neonatal mice.

Biologic Effect of Hydrogen Sulfide and Its Role in Traumatic Brain Injury

Ever since endogenous hydrogen sulfide (H₂S) was found in mammals in 1989, accumulated evidence has demonstrated that H₂S functions as a novel neurological gasotransmitter in brain tissues and may play a key role in traumatic brain injury. It has been proved that H₂S has an antioxidant, anti-inflammatory, and antiapoptosis function in the neuron system and functions as a neuroprotective factor against secondary brain injury. In addition, H₂S has other biologic effects such as regulating the intracellular concentration of Ca²⁺, facilitating hippocampal long-term potentiation (LTP), and activating ATP-sensitive K channels. Due to the toxic nature of H₂S when exceeding the physiological dose in the human body, only a small amount of H₂S-related therapies was applied to clinical treatment. Therefore, it has huge therapeutic potential and has great hope for recovering patients with traumatic brain injury.

Hydrogen Sulfide and Carnosine: Modulation of Oxidative Stress and Inflammation in Kidney and Brain Axis

Emerging evidence indicates that the dysregulation of cellular redox homeostasis and chronic inflammatory processes are implicated in the pathogenesis of kidney and brain disorders. In this light, endogenous dipeptide carnosine (β-alanyl-L-histidine) and hydrogen sulfide (H₂S) exert cytoprotective actions through the modulation of redox-dependent resilience pathways during oxidative stress and inflammation. Several recent studies have elucidated a functional crosstalk occurring between kidney and the brain. The pathophysiological link of this crosstalk is represented by oxidative stress and inflammatory processes which contribute to the high prevalence of neuropsychiatric disorders, cognitive impairment, and dementia during the natural history of chronic kidney disease. Herein, we provide an overview of the main pathophysiological mechanisms related to high levels of pro-inflammatory cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and neurotoxins, which play a critical role in the kidney–brain crosstalk. The present paper also explores the respective role of H₂S and carnosine in the modulation of oxidative stress and inflammation in the kidney–brain axis. It suggests that these activities are likely mediated, at least in part, via hormetic processes, involving Nrf2 (Nuclear factor-like 2), Hsp 70 (heat shock protein 70), SIRT-1 (Sirtuin-1), Trx (Thioredoxin), and the glutathione system. Metabolic interactions at the kidney and brain axis level operate in controlling and reducing oxidant-induced inflammatory damage and therefore, can be a promising potential therapeutic target to reduce the severity of renal and brain injuries in humans.

Astragalin alleviates ischemia/reperfusion‑induced brain injury via suppression of endoplasmic reticulum stress

Excessive apoptosis and neuronal dysfunction are pathological features of ischemic stroke. Previous studies have demonstrated that astragalin (AST) exerted both anti‑​apoptotic and anti‑inflammatory effects in several types of disease, although its potential effect in ischemic stroke remains unclear. The purpose of the present study was to investigate the effects of AST on cerebral ischemia/reperfusion (I/R)‑induced brain injury and the underlying mechanisms. Brain injury was assessed in an experimental rat model using measurement of neurological scores and inflammatory factors. To assess the role of AST in I/R‑induced brain injury and the potential mechanism of action, SH5Y were treated with thapsigargin and AST. Apoptotic rate and ER stress levels were measured by western blotting, reverse transcription‑quantitative PCR and immunofluorescence staining. It was discovered that AST significantly improved long‑term neurological outcomes in rats following cerebral I/R injury, through the attenuation of the expression levels of apoptotic proteins (Bax and cleaved‑caspase‑3) and the release of inflammatory cytokines, as well as upregulating the expression levels of the anti‑apoptotic protein Bcl‑2. Furthermore, AST attenuated the expression levels of the endoplasmic reticulum (ER) stress‑related protein, glucose‑regulated protein, 78 kDa, as well as its downstream apoptotic mediators (CHOP and caspase‑12). Thapsigargin‑induced ER stress activation and apoptosis were also attenuated by AST in an in vitro neuronal cell culture model. In conclusion, these results suggested that AST may protect against I/R‑induced brain injury, thus, highlighting its therapeutic potential in patients with ischemic stroke.

Genome-wide transcriptional effects of deletions of sulphur metabolism genes in Drosophila melanogaster

In recent years, the gasotransmitter hydrogen sulphide (H₂S), produced by the transsulphuration pathway, has been recognized as a biological mediator playing an important role under normal conditions and in various pathologies in both eukaryotes and prokaryotes. The transsulphuration pathway (TSP) includes the conversion of homocysteine to cysteine following the breakdown of methionine. In Drosophila melanogaster and other eukaryotes, H₂S is produced by cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulphurtransferase (MST). In the experiments performed in this study, we were able to explore the CRISPR/Cas9 technique to obtain single and double deletions in homozygotes of these three major genes responsible for H₂S production in Drosophila melanogaster. In most cases, the deletion of one studied gene does not result in the compensatory induction of two other genes responsible for H₂S production. Transcriptomic studies demonstrated that the deletions of the above CBS and CSE genes alter genome expression to different degrees, with a more pronounced effect being exerted by deletion of the CBS gene. Furthermore, the double deletion of both CBS and CSE resulted in a cumulative effect on transcription in the resulting strains. Overall, we found that the obtained deletions affect numerous genes involved in various biological pathways. Specifically, genes involved in the oxidative reduction process, stress-response genes, housekeeping genes, and genes participating in olfactory and reproduction are among the most strongly affected. Furthermore, characteristic differences in the response to the deletions of the studied genes are apparently organ-specific and have clear-cut sex-specific characteristics. Single and double deletions of the three genes responsible for the production of H₂S helped to elucidate new aspects of the biological significance of this vital physiological mediator.

Protective role of NRF2 in macrovascular complications of diabetes

Macrovascular complications develop in over a half of the diabetic individuals, resulting in high morbidity and mortality. This poses a severe threat to public health and a heavy burden to social economy. It is therefore important to develop effective approaches to prevent or slow down the pathogenesis and progression of macrovascular complications of diabetes (MCD). Oxidative stress is a major contributor to MCD. Nuclear factor (erythroid‐derived 2)‐like 2 (NRF2) governs cellular antioxidant defence system by activating the transcription of various antioxidant genes, combating diabetes‐induced oxidative stress. Accumulating experimental evidence has demonstrated that NRF2 activation protects against MCD. Structural inhibition of Kelch‐like ECH‐associated protein 1 (KEAP1) is a canonical way to activate NRF2. More recently, novel approaches, such as activation of the Nfe2l2 gene transcription, decreasing KEAP1 protein level by microRNA‐induced degradation of Keap1 mRNA, prevention of proteasomal degradation of NRF2 protein and modulation of other upstream regulators of NRF2, have emerged in prevention of MCD. This review provides a brief introduction of the pathophysiology of MCD and the role of oxidative stress in the pathogenesis of MCD. By reviewing previous work on the activation of NRF2 in MCD, we summarize strategies to activate NRF2, providing clues for future intervention of MCD. Controversies over NRF2 activation and future perspectives are also provided in this review.

The role of medical gas in stroke: an updated review

Medical gas is a large class of bioactive gases used in clinical medicine and basic scientific research. At present, the role of medical gas in neuroprotection has received growing attention. Stroke is a leading cause of death and disability in adults worldwide, but current treatment is still very limited. The common pathological changes of these two types of stroke may include excitotoxicity, free radical release, inflammation, cell death, mitochondrial disorder, and blood-brain barrier disruption. In this review, we will discuss the pathological mechanisms of stroke and the role of two medical gases (hydrogen and hydrogen sulfide) in stroke, which may potentially provide a new insight into the treatment of stroke.

Mistimed H2S upregulation, Nrf2 activation and antioxidant proteins levels in renal tubular epithelial cells subjected to anoxia and reoxygenation

Ischemia-reperfusion (I-R) injury is involved in the pathogenesis of several human diseases. In the present study, the kinetics of the H₂S producing enzymes-nuclear factor erythroid 2-like 2 (Nrf2)-antioxidant proteins axis under anoxia or reoxygenation was evaluated, as well as its effects on survival of mouse renal proximal tubular epithelial cells (RPTECs). In RPTECs subjected to anoxia and subsequent reoxygenation, reactive oxygen species (ROS) production, lipid peroxidation, ferroptotic cell death, the levels of the H₂S producing enzymes and H₂S, the expression of Nrf2 and its transcriptional targets superoxide dismutase-3, glutathione reductase, ferritin H and cystine-glutamate antiporter, as well as apoptosis, and the levels of p53, Bax and phosphorylated p53 were assessed. When needed, the H₂S producing enzyme inhibitor aminooxyacetate, or the ferroptosis inhibitor α-tocopherol, were used. Reoxygenation induced ferroptosis, whereas anoxia activated the p53-Bax pathway and induced apoptosis. The H₂S producing enzymes-Nrf2-antioxidant proteins axis was activated only during anoxia and not during reoxygenation, when cellular viability is threatened by ROS overproduction and the ensuing ferroptosis. The activation of the above axis during anoxia ameliorated the effects of the apoptotic p53-Bax pathway, but did not adequately protect against apoptosis. In conclusion, the H₂S-Nrf2 axis is activated by anoxia, and although it reduces apoptosis, it does not completely prevent apoptotic cell death. Additionally, following reoxygenation, the above axis was not activated. This mistimed activation of the H₂S producing enzymes-Nrf2-antioxidant proteins axis contributes to reoxygenation-induced cell death. Determining the exact molecular mechanisms involved in reoxygenation-induced cell death may assist in the development of clinically relevant interventions for preventing I-R injury.

H2S counteracts proinflammatory effects of LPS through modulation of multiple pathways in human cells

BACKGROUND

Hydrogen sulfide donors reduce inflammatory signaling in vitro and in vivo. The biological effect mediated by H₂S donors depends on the kinetics of the gas release from the donor molecule. However, the molecular mechanisms of H₂S-induced immunomodulation were poorly addressed. Here, we studied the effect of two different hydrogen sulfide (H₂S)-producing agents on the generation of the LPS-induced inflammatory mediators. Importantly, we investigated the transcriptomic changes that take place in human cells after the LPS challenge, combined with the pretreatment with a slow-releasing H₂S donor-GYY4137.

METHODS

We investigated the effects of GYY4137 and sodium hydrosulfide on the release of proinflammatory molecules such as ROS, NO and TNF-α from LPS-treated human SH-SY5Y neuroblastoma and the THP-1 promonocytic cell lines. Transcriptomic and RT-qPCR studies using THP-1 cells were performed to monitor the effects of the GYY4137 on multiple signaling pathways, including various immune-related and proinflammatory genes after combined action of LPS and GYY4137.

RESULTS

The GYY4137 and sodium hydrosulfide differed in the ability to reduce the production of the LPS-evoked proinflammatory mediators. The pre-treatment with GYY4137 resulted in a drastic down-regulation of many TNF-α effectors that are induced by LPS treatment in THP-1 cells. Furthermore, GYY4137 pretreatment of LPS-exposed cells ameliorates the LPS-mediated induction of multiple pro-inflammatory genes and decreases expression of immunoproteasome genes. Besides, in these experiments we detected the up-regulation of several important pathways that are inhibited by LPS.

CONCLUSION

Based on the obtained results we believe that our transcriptomic analysis significantly contributes to the understanding of the molecular mechanisms of anti-inflammatory and cytoprotective activity of hydrogen sulfide donors, and highlights their potential against LPS challenges and other forms of inflammation.

Hydrogen sulfide alleviates cigarette smoke-induced COPD through inhibition of the TGF-1/smad pathway

Smoking has become a major cause of chronic obstructive pulmonary disease through weakening of the respiratory mucus-ciliary transport system, impairing cough reflex sensitivity, and inducing inflammation. Recent researches have indicated that hydrogen sulfide is essential in the development of various lung diseases. However, the effect and mechanism of hydrogen sulfide on cigarette smoke-induced chronic obstructive pulmonary disease have not been reported. In this study, rats were treated with cigarette smoke to create a chronic obstructive pulmonary disease model followed by treatment with a low concentration of hydrogen sulfide. Pulmonary function, histopathological appearance, lung edema, permeability, airway remodeling indicators, oxidative products/antioxidases levels, inflammatory factors in lung, cell classification in bronchoalveolar lavage fluid were measured to examine the effect of hydrogen sulfide on chronic obstructive pulmonary disease model. The results showed that hydrogen sulfide effectively improved pulmonary function and reduced histopathological changes, lung edema, and permeability. Airway remodeling, oxidative stress, and inflammation were also reduced by hydrogen sulfide treatment. To understand the mechanisms, we measured the expression of TGF-β1, TGF-βIand TGF-βII receptors and Smad7 and phosphorylation of Smad2/Smad3. The results indicated that the TGF-β1 and Smad were activated in cigarette smoke-induced chronic obstructive pulmonary disease model, but inhibited by hydrogen sulfide. In conclusion, this study showed that hydrogen sulfide treatment alleviated cigarette smoke-induced chronic obstructive pulmonary disease through inhibition of the TGF-β1/Smad pathway.

Impact statement

COPD has become a severe public health issue in the world and smoking has become a major cause of COPD. As a result, it is a demandingly needed to explore new potential therapy for cigarette smoke-associated COPD. The present study suggested that H2S treatment improved pulmonary function and reduced histopathological changes, lung edema, permeability, inflammation, airway remodeling and oxidative injury in a COPD model induced by cigarette smoke. Although additional studies are required to elucidate the pharmacodynamics, pharmacokinetics, and pharmacology of H2S in the cigarette smoke-associated COPD, our findings provide an experimental basis for the potential clinical application of H2S in COPD treatment.

Theaflavin attenuates cerebral ischemia/reperfusion injury by abolishing miRNA‑128‑3p‑mediated Nrf2 inhibition and reducing oxidative stress

Theaflavin has been proven to own strong antioxidative capacity; however, the molecular mechanism underlying its protective effect against cerebral ischemia-reperfusion (I/R) injury remains unclear. Therefore, the present study was designed to elucidate the neuroprotective effects of theaflavin on cerebral I/R injury and its underlying molecular mechanisms. To investigate the effects of theaflavin on neurological function, neurogenesis, and oxidative stress, experiments were performed using a cerebral I/R injury rat model, and neural stem cells (NSCs) were subjected to oxygen-glucose deprivation and reoxygenation (OGD/R). Further, the expression profiles of miRNA-128-3p and the regulatory function of nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) were evaluated in these models. We found that theaflavin treatment significantly reduced infarct volume and neuronal injury, and thus improved the impaired memory and learning ability. Furthermore, theaflavin treatment significantly enhanced the increase in NSC proliferation, reduction in the apoptotic rate and inhibition of oxidative stress. Mechanistically, theaflavin targeted miRNA-128-3p and further activated the Nrf2 pathway to reduce oxidative stress. In summary, theaflavin has a strong ability to attenuate cerebral I/R injury through miRNA-128-3p-mediated recovery of the impaired antioxidant defense system, which suggests that it could be a potential drug candidate for ischemic stroke.

The H2S-Nrf2-Antioxidant Proteins Axis Protects Renal Tubular Epithelial Cells of the Native Hibernator Syrian Hamster from Reoxygenation-Induced Cell Death

During hibernation, repeated cycles of ischemia-reperfusion (I-R) leave vital organs without injury. Studying this phenomenon may reveal pathways applicable to improving outcomes in I-R injury-induced human diseases. We evaluated whether the H₂S–nuclear factor erythroid 2-like 2 (Nrf2)–antioxidant proteins axis protects renal proximal tubular epithelial cells (RPTECs) of the native hibernator, the Syrian hamster, from reperfusion-induced cell death. To imitate I-R, the hamsters’, and control mice’s RPTECs were subjected to warm anoxia, washed, and then subjected to reoxygenation in fresh culture medium. Whenever required, the H₂S-producing enzymes inhibitor aminooxyacetate or the lipid peroxidation inhibitor α-tocopherol were used. A handmade H₂S detection methylene blue assay, a reactive oxygen species (ROS) detection kit, a LDH release cytotoxicity assay kit, and western blotting were used. Reoxygenation upregulated the H₂S-producing enzymes cystathionine beta-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase in the hamster, but not in mouse RPTECs. As a result, H₂S production increased only in the hamster RPTECs under reoxygenation conditions. Nrf2 expression followed the alterations of H₂S production leading to an enhanced level of the antioxidant enzymes superoxide dismutase 3 and glutathione reductase, and anti-ferroptotic proteins ferritin H and cystine-glutamate antiporter. The upregulated antioxidant enzymes and anti-ferroptotic proteins controlled ROS production and rescued hamster RPTECs from reoxygenation-induced, lipid peroxidation-mediated cell death. In conclusion, in RPTECs of the native hibernator Syrian hamster, reoxygenation activates the H2S–Nrf2–antioxidant proteins axis, which rescues cells from reoxygenation-induced cell death. Further studies may reveal that the therapeutic activation of this axis in non-hibernating species, including humans, may be beneficial in I-R injury-induced diseases.

H2S-based therapies for ischaemic stroke: opportunities and challenges

Stroke is a cerebrovascular disease displaying high mortality and morbidity. Despite extensive efforts, only very few therapies are available for stroke patients as yet. Hydrogen sulfide (H₂S) is thought to be a signalling molecule that is endogenously produced and plays functional roles in the central nervous system. Currently, numerous studies show that H₂S impacts stroke outcomes in animal and cellular models. Here, we review the recent research regarding the effects of endogenously produced H₂S as well as exogenous H₂S donors on stroke pathology, focusing on the potential of H₂S-based therapies in treating ischaemic stroke. We also discuss the several issues that hinder the clinical translation of H₂S-based therapies from the bench. Taken together, we think that H₂S-based therapies are promising strategies for treating cerebral ischaemia if we successfully address these issues.

HSP70 silencing aggravates apoptosis induced by hypoxia/reoxygenation in vitro

Lung ischemia-reperfusion can cause acute lung injury, which is closely associated with apoptosis. Heat shock protein 70 (HSP70) is an anti-apoptotic protein that promotes cell survival under a variety of different stress conditions. However, the role and mechanism of HSP70 in lung ischemia-reperfusion injury is yet to be fully elucidated. In the present study, an in vitro hypoxia/reoxygenation model of A549 cells was established to simulate lung ischemia-reperfusion and HSP70 was silenced by transfecting A549 cells with an shRNA sequence targeting HSP70. Western blotting, reverse transcription-quantitative polymerase chain reaction, Cell Counting kit-8 and flow cytometry were used to detect protein levels, RNA expression, cell activity and apoptosis. The results revealed that silencing HSP70 reduced cell viability, aggravated apoptosis, increased lactate dehydrogenase levels and induced a G2/M blockade in a hypoxia-reoxygenation A549 cell model. Furthermore, silencing HSP70 decreased the phosphorylation levels of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK); however, the total AKT and ERK levels did not change significantly. Pretreating A549 cells with the AKT pathway inhibitor, LY294002 and the ERK pathway inhibitor, U0216 led to a decrease in HSP70 expression. These results indicate that silencing HSP70 may aggravate apoptosis in hypoxia-reoxygenation cell models, potentially via the mitogen-activated protein kinase/ERK and phosphoinositide 3-kinase/AKT signaling pathways.

Critical Role of Nrf2 in Experimental Ischemic Stroke

Ischemic stroke is one of the leading causes of death and long-term disability worldwide; however, effective clinical approaches are still limited. The transcriptional factor Nrf2 is a master regulator in cellular and organismal defense against endogenous and exogenous stressors by coordinating basal and stress-inducible activation of multiple cytoprotective genes. The Nrf2 network not only tightly controls redox homeostasis but also regulates multiple intermediary metabolic processes. Therefore, targeting Nrf2 has emerged as an attractive therapeutic strategy for the prevention and treatment of CNS diseases including stroke. Here, the current understanding of the Nrf2 regulatory network is critically examined to present evidence for the contribution of Nrf2 pathway in rodent ischemic stroke models. This review outlines the literature for Nrf2 studies in preclinical stroke and focuses on the in vivo evidence for the role of Nrf2 in primary and secondary brain injuries. The dynamic change and functional importance of Nrf2 signaling, as well as Nrf2 targeted intervention, are revealed in permanent, transient, and global cerebral ischemia models. In addition, key considerations, pitfalls, and future potentials for Nrf2 studies in preclinical stroke investigation are discussed.

Inhibition of endogenous hydrogen sulfide production improves viral elimination in CVB3-infected myocardium in mice

BACKGROUND

To find whether administration of hydrogen sulfide has interaction with coxsackie virus B3 (CVB3) replication and spread.

METHODS

Six-week-old inbred male Balb/c mice were injected intraperitoneally with CVB3. Mice were randomized to four groups (n = 10 for each group): group N (sham infection + vehicle), group C (virus + vehicle), group P (virus + DL-proparglygylcine (PAG)), and group S (virus + sodium hydrogen sulfide (NaHS)). PAG and NaHS were administered intraperitoneally daily and mice were killed on day 4 after viral inoculation. Serum specimens were obtained to assay tumor necrosis factor-α (TNFα) level, and heart specimens were harvested for histological examination, 50% tissue culture infection dose (TCID50) assay, reverse transcription-polymerase chain reaction and Western blot analysis.

RESULTS

The ratio of heart-weight to body-weight and inflammatory scores showed no significant difference between infected groups. The circulatory and local concentrations of TNFα, nitric oxide synthase 2 messenger RNA, and protein were higher in group P, and were lower in group S compared to those in group C. Mice treated with PAG and NaHS had significantly lower and higher viral stocks than those inoculated with CVB3 only, respectively.

CONCLUSION

Inhibition of endogenous hydrogen sulfide production contributed to viral clearance in acute viremia of CVB3-induced myocarditis.

Mechanisms by which hydrogen sulfide attenuates muscle function following ischemia-reperfusion injury: effects on Akt signaling, mitochondrial function, and apoptosis

Ischemia–reperfusion injury is caused by a period of ischemia followed by massive blood flow into a tissue that had experienced restricted blood flow. The severity of the injury is dependent on the time the tissue was restricted from blood flow, becoming more severe after longer ischemia times. This can lead to many complications such as tissue necrosis, cellular apoptosis, inflammation, metabolic and mitochondrial dysfunction, and even organ failure. One of the emerging therapies to combat ischemic reperfusion injury complications is hydrogen sulfide, which is a gasotransmitter that diffuses across cell membranes to exert effects on various signaling pathways regulating cell survival such as Akt, mitochondrial activity, and apoptosis. Although commonly thought of as a toxic gas, low concentrations of hydrogen sulfide have been shown to be beneficial in promoting tissue survival post-ischemia, and modulate a wide variety of cellular responses. This review will detail the mechanisms of hydrogen sulfide in affecting the Akt signaling pathway, mitochondrial function, and apoptosis, particularly in regards to ischemic reperfusion injury in muscle tissue. It will conclude with potential clinical applications of hydrogen sulfide, combinations with other therapies, and perspectives for future studies.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

UHPLC-Q-TOF MS-Based Metabolic Analysis for the Therapeutic Efficacy of "Xuebijing Injection" against Sepsis-Induced Acute Lung Injury

“Xuebijing Injection” (XBJ) is a traditional Chinese medicine and has been wildly used in the treatment of sepsis in China. However, few studies have reported the use of XBJ in sepsis with acute lung injury (ALI). This study aimed to investigate the therapeutic efficacy of XBJ against sepsis-induced ALI. Generally a total of 27 mice were equally randomized into three groups: a sham group was given saline before sham operation. A sepsis group received the cecal ligation and puncture (CLP) operation only. A sepsis+XBJ group, XBJ, was injected at 72, 48, and 24 h before CLP operation. The lung tissue was collected for UHPLC-Q-TOF/MS profiling analysis, biomarker identification, and pathway analysis. With the analysis of principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), forty-five purine, amino acid, and sphingolipid metabolites in lung tissues were identified as potential biomarkers of sepsis-induced ALI, among which 22 were reversed in the sepsis+XBJ group significantly. Conclusively, our results suggest that purine metabolic pathway, glutathione metabolic pathway, sphingomyelin metabolic pathway, arachidonic acid metabolic pathway, and phospholipid metabolic pathway may be the potential therapeutic pathways to overcome sepsis-induced acute lung injury and we provided the potential mechanisms of protective effects of XBJ against ALI.

MicroRNA‑634 alters nerve apoptosis via the PI3K/Akt pathway in cerebral infarction

In the present study, the role and mechanism of microRNA‑634 (miRNA‑634) in the adjustment of nerve inflammation and apoptosis in cerebral infarction were investigated. In a cerebral infarction rat model, the expression of miRNA‑634 was increased, compared with that in the normal control group. The upregulated expression of miRNA‑634 in an in vitro model of cerebral infarction increased cell apoptosis and the protein expression of capsase‑3/B‑cell lymphoma 2‑associated X protein (Bax) via inactivation of the phosphoinositide 3‑kinase (PI3K)/Akt pathway. The downregulation of miRNA‑634 enhanced cell growth and inhibited cell apoptosis in the in vitro model of cerebral infarction through induction of the PI3K/Akt pathway. Subsequently, a PI3K inhibitor was used to inhibit the expression of PI3K in the in vitro model of cerebral infarction via the downregulation of miRNA‑634, which showed that cell apoptosis and the protein expression of capsase‑3/Bax were also increased. A PI3K agonist reduced the effects of the upregulation of miRNA‑634 in the in vitro model of cerebral infarction. In conclusion, the data obtained demonstrated the possible future use of miRNA‑634 as a therapeutic target in cerebral infarction through the PI3K/Akt pathway.