Hydrogen sulfide inhibits homocysteine-induced endoplasmic reticulum stress and neuronal apoptosis in rat hippocampus via upregulation of the BDNF-TrkB pathway

Soy protein increases cognitive level in mice by modifying hippocampal nerve growth, oxidative stress, and intestinal microbiota

BACKGROUND

Three kinds of diet containing chicken protein isolate (CPI), bovine milk protein isolate (BMPI), and soy protein isolate (SPI), respectively, were designed to investigate the influences of proteins on cognitive levels and related mechanisms in mice.

RESULTS

A Morris water maze (MWM) test showed that the SPI group had a higher cognitive level than the BMPI group. Immunohistochemical staining and chemical analysis of the hippocampus showed that the SPI group had higher synaptophysin expression, doublecortin-positive cell proportion, superoxide dismutase activity, and lower malondialdehyde content compared with the BMPI group. The same parameters in the CPI group were between those of the BMPI and SPI groups. Microbiome sequencing indicated that the three groups differed significantly at the phylum, genus, and species levels, with higher microbial alpha diversity in the CPI and SPI groups. The association of intestinal microbiota with cognitive improvement was also assessed. The present study suggests that soy protein may increase cognitive function by the gut-brain axis.

CONCLUSION

In contrast with CPI and BMPI, SPI had a better effect on improving the cognitive level in mice, which was achieved through the regulation of hippocampal neural growth, oxidative stress, and intestinal microbiota. © 2022 Society of Chemical Industry.

Transcranial direct current stimulation alleviated ischemic stroke induced injury involving the BDNF-TrkB signaling axis in rats

Ischemic stroke causes a complicated sequence of apoptotic cascades leading to neuronal damage and functional impairments. Transcranial direct current stimulation (tDCS) is a non-invasive treatment technique that uses electrodes to deliver weak current to the head. It could influence brain activity and has a crucial role in neuronal survival and plasticity. The current study investigated the neuroprotective effects and potential mechanisms of tDCS by brain-derived neurotrophic factor (BDNF) and its related receptor tropomyosin-receptor kinase B (TrkB) against apoptosis following ischemic injury in vivo. The effect of consecutive treatment with tDCS for seven days on rats after Middle cerebral artery occlusion/reperfusion (MCAO/R) surgery was studied. Western blotting, immunofluorescent staining, TUNEL assay, and electron microscope were conducted seven days after tDCS treatment, and the motor function was assessed at 1, 3, and 7 days. Activities of BDNF-TrkB signaling axis and apoptosis-related proteins were determined in the cerebral cortex. At seven days after tDCS treatment, it increased BDNF levels and promoted the regeneration of axons compared with the MCAO/R group. There was also a reduction in neuronal apoptosis and improved functional deficits. Whereafter, a TrkB receptor inhibitor K252a was administrated to clarify whether the neuroprotection of tDCS is exerted via BDNF-TrkB signaling. The results depicted that K252a application significantly inhibited the neuroprotection impact of tDCS treatment. It was accompanied by a significant downregulation of phosphorylation of TrkB, PI3K, and Akt. Our study investigated the neuroprotective effects of tDCS against ischemic injury. The results indicate that upregulation of BDNF and its critical receptor TrkB, as well as its downstream PI3K/Akt pathway, were involved in the protective effects exerted by tDCS.

The Role of Gasotransmitter-Dependent Signaling Mechanisms in Apoptotic Cell Death in Cardiovascular, Rheumatic, Kidney, and Neurodegenerative Diseases and Mental Disorders

Cardiovascular, rheumatic, kidney, and neurodegenerative diseases and mental disorders are a common cause of deterioration in the quality of life up to severe disability and death worldwide. Many pathological conditions, including this group of diseases, are based on increased cell death through apoptosis. It is known that this process is associated with signaling pathways controlled by a group of gaseous signaling molecules called gasotransmitters. They are unique messengers that can control the process of apoptosis at different stages of its implementation. However, their role in the regulation of apoptotic signaling in these pathological conditions is often controversial and not completely clear. This review analyzes the role of nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and sulfur dioxide (SO₂) in apoptotic cell death in cardiovascular, rheumatic, kidney, and neurodegenerative diseases. The signaling processes involved in apoptosis in schizophrenia, bipolar, depressive, and anxiety disorders are also considered. The role of gasotransmitters in apoptosis in these diseases is largely determined by cell specificity and concentration. NO has the greatest dualism; scales are more prone to apoptosis. At the same time, CO, H₂S, and SO₂ are more involved in cytoprotective processes.

Effect of CaS Nanostructures in the Proliferation of Human Breast Cancer and Benign Cells In Vitro

We report on the effect of naked CaS nanostructures on the proliferation of carcinoma cancer cells and normal fibroblasts in vitro. The CaS nanostructures were prepared via the microwave-mediated decomposition of dimethyl sulfoxide (DMSO) in the presence of calcium acetate Ca ( CH 3 CO 2 ) 2 . Light scattering measurements revealed that dispersions contain CaS nanostructures in the size range of a few Å to about 1 nanometer, and are formed when DMSO is decomposed in the presence of Ca ( CH 3 CO 2 ) 2 . Theoretical calculations at the DFT/B3LYP/DGDZVP level of theory on ( C a S ) n clusters ( n = 1 , 2 , 3 , and 4) are consistent with clusters in this size range. The absorption spectra of the CaS nanostructures are dominated by strong bands in the UV, as well as weaker absorption bands in the visible. We found that a single dose of CaS nanoclusters smaller than 0.8 nm in diameter does not affect the survival and growth rate of normal fibroblasts and inhibits the proliferation rate of carcinoma cells in vitro. Larger CaS nanostructures, approximately (1.1 ± 0.2) nm in diameter, have a similar effect on carcinoma cell proliferation and survival rate. The CaS nanoclusters have little effect on the normal fibroblast cell cycle. Human carcinoma cells treated with CaS nanocluster dispersion exhibited a decreased ability to properly enter the cell cycle, marked by a decrease in cell concentration in the G0/G1 phase in the first 24 h and an increase in cells held in the SubG1 and G0/G1 phases up to 72 h post-treatment. Apoptosis and necrotic channels were found to play significant roles in the death of human carcinoma exposed to the CaS nanoclusters. In contrast, any effect on normal fibroblasts appeared to be short-lived and non-detrimental. The interaction of CaS with several functional groups was further investigated using theoretical calculations. CaS is predicted to interact with thiol ( R-SH ), hydroxide ( R - OH ), amino ( R - NH 2 ), carboxylic acid ( R - COOH ), ammonium ( R-NH 3 + ), and carboxylate ( R-COO - ) functional groups. None of these interactions are predicted to result in the dissociation of CaS. Thermodynamic considerations, on the other hand, are consistent with the dissociation of CaS into Ca 2 + ions and H 2 S in acidic media, both of which are known to cause apoptosis or cell death. Passive uptake and extracellular pH values of carcinoma cells are proposed to result in the observed selectivity of CaS to inhibit cancer cell proliferation with no significant effect on normal fibroblast cells. The results encourage further research with other cell lines in vitro as well as in vivo to translate this nanotechnology into clinical use.

Hydrogen Sulfide (H2S) Signaling as a Protective Mechanism against Endogenous and Exogenous Neurotoxicants

In view of the significant role of H₂S in brain functioning, it is proposed that H₂S may also possess protective effects against adverse effects of neurotoxicants. Therefore, the objective of the present review is to discuss the neuroprotective effects of H₂S against toxicity of a wide spectrum of endogenous and exogenous agents involved in the pathogenesis of neurological diseases as etiological factors or key players in disease pathogenesis. Generally, the existing data demonstrate that H₂S possesses neuroprotective effects upon exposure to endogenous (amyloid β, glucose, and advanced-glycation end-products, homocysteine, lipopolysaccharide, and ammonia) and exogenous (alcohol, formaldehyde, acrylonitrile, metals, 6-hydroxydopamine, as well as 1-methyl-4-phenyl- 1,2,3,6- tetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenyl pyridine ion (MPP)) neurotoxicants. On the one hand, neuroprotective effects are mediated by S-sulfhydration of key regulators of antioxidant (Sirt1, Nrf2) and inflammatory response (NF-κB), resulting in the modulation of the downstream signaling, such as SIRT1/TORC1/CREB/BDNF-TrkB, Nrf2/ARE/HO-1, or other pathways. On the other hand, H₂S appears to possess a direct detoxicative effect by binding endogenous (ROS, AGEs, Aβ) and exogenous (MeHg) neurotoxicants, thus reducing their toxicity. Moreover, the alteration of H₂S metabolism through the inhibition of H₂S-synthetizing enzymes in the brain (CBS, 3-MST) may be considered a significant mechanism of neurotoxicity. Taken together, the existing data indicate that the modulation of cerebral H₂S metabolism may be used as a neuroprotective strategy to counteract neurotoxicity of a wide spectrum of endogenous and exogenous neurotoxicants associated with neurodegeneration (Alzheimer's and Parkinson's disease), fetal alcohol syndrome, hepatic encephalopathy, environmental neurotoxicant exposure, etc. In this particular case, modulation of H₂S-synthetizing enzymes or the use of H₂S-releasing drugs should be considered as the potential tools, although the particular efficiency and safety of such interventions are to be addressed in further studies.

Hydrogen sulfide prevents arecoline-induced neurotoxicity via promoting leptin/leptin receptor signaling pathway

Arecoline, a major alkaloid of the areca nut, has potential toxicity to the nervous system. Our previous study reveals that the neurotoxicity of arecoline involves in inhibited endogenous hydrogen sulfide (H₂ S) generation. Therefore, the present study investigated whether exogenous H₂ S protects against arecoline-induced neurotoxicity and further explore the underlying mechanisms focusing on leptin/leptin receptor signaling pathway. The cell viability was measured by CCK-8 kit. The apoptosis were detected by Hoechst 33258 and Annexin V/PI (propidium iodide) staining. The protein expressions were determined by Western blot analysis. Our results demonstrated that NaHS, an exogenous H₂ S donor, significantly increases the cell viability, decreases apoptosis ratio, and reduces caspase-3 activity as well as Bax/Bcl-2 ratio in PC12 cells exposed to arecoline, indicating the protection of H₂ S against arecoline-induced cytotoxicity and apoptosis. Also, NaHS attenuated arecoline-induced endoplasmic reticulum (ER) stress, as evidenced by the decreases in the expressions of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and Cleaved caspase-12. Meanwhile, NaHS promoted leptin/leptin receptor signaling pathway in arecoline-exposed PC12 cells, as illustrated by upregulations of leptin and leptin receptor expressions. Furthermore, leptin tA, an antagonist of leptin receptor, obviously abolished the inhibitory effects of NaHS on arecoline-induced cytotoxicity, apoptosis, and ER stress in arecoline-exposed PC12 cells. Taken together, these results suggested that H₂ S prevents arecoline-induced neurotoxicity via enhancing the leptin/leptin receptor signaling pathway.

Improvement of autophagic flux mediates the protection of hydrogen sulfide against arecoline-elicited neurotoxicity in PC12 cells

Arecoline, the most abundant alkaloid of the areca nut, induces toxicity to neurons. Hydrogen sulfide (H₂S) is an endogenous gas with neuroprotective effects. We recently found that arecoline reduced endogenous H₂S content in PC12 cells. In addition, exogenously administration of H₂S alleviated the neurotoxicity of arecoline on PC12 cells. Increasing evidence has demonstrated the neuroprotective role of improvement of autophagic flux. Therefore, the aim of the present work is to explore whether improvement of autophagic flux mediates the protection of H₂S against arecoline-caused neurotoxicity. Transmission electron microscope (TEM) for observation of ultrastructural morphology. Western blotting was used to detect protein expression of the related markers. Functional analysis contained LDH release assay, Hoechst 33,258 nuclear staining and flow cytometry were used to detect cytotoxicity and apoptosis. In the present work, we found that arecoline disrupted autophagy flux in PC12 cells as evidenced by accumulation of autophagic vacuoles, increase in LC3II/LC3I, and upregulation of p62 expression in PC12 cells. Notably, we found that sodium hydrosulfide (NaHS), the donor of H₂S improved arecoline-blocked autophagy flux in PC12 cells. Furthermore, we found that blocking autophagic flux by chloroquine (CQ), the inhibitor of autophagy flux, antagonized the inhibitory role of NaHS in arecoline-induced cytotoxicity apoptosis and endoplasmic reticulum (ER) stress. In conclusion, H₂S improves arecoline-caused disruption of autophagic flux to exert its protection against the neurotoxicity of arecoline.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Hydrogen Sulfide Inhibits Bronchial Epithelial Cell Epithelial Mesenchymal Transition Through Regulating Endoplasm Reticulum Stress

Epithelial mesenchymal transition (EMT) is a contributing factor in remodeling events of chronic obstructive pulmonary disease (COPD). Hydrogen sulfide (H₂S) has been implicated in the pathogenesis of COPD, but the effect of H₂S in regulating EMT and the underlying mechanisms is not clear. In this study, we assessed endoplasmic reticulum (ER) stress markers, EMT markers and associated signal molecules in rat lungs, bronchial epithelial cells, and human peripheral lung tissues to investigate the effect of H₂S in regulating EMT and the underlying mechanisms. We found that EMT and ER stress occurred in lung epithelial cells, especially in the bronchial epithelial cells of smokers and COPD patients. In cigarette smoke (CS)-exposed rats, intraperitoneal injection of NaHS significantly alleviated CS-induced lung tissue damage, small airway fibrosis, ER stress, and EMT, while intraperitoneal injection of propargylglycine (cystathionine-gamma-lyase inhibitor) aggravated these effects induced by CS. In the nicotine-exposed 16HBE cells, an appropriate concentration of H₂S donor not only inhibited nicotine-induced ER stress, but also inhibited nicotine-induced enhancement of cell migration ability and EMT. ER stress nonspecific inhibitors taurine and 4-phenyl butyric acid also inhibited nicotine-induced enhancement of cell migration ability and EMT. Both H2S and inositol-requiring enzyme 1 (IRE1) activation inhibitor 4μ8C inhibited nicotine-induced activation of IRE1, Smad2/3 and EMT. These results suggest that H₂S inhibits CS- or nicotine-induced ER stress and EMT in bronchial epithelial cells and alleviates CS-induced lung tissue damage and small airway fibrosis. The IRE1 signal pathway and Smad2/3 may be responsible for the inhibitory effect of H₂S.

Protein S-sulfhydration: Unraveling the prospective of hydrogen sulfide in the brain, vasculature and neurological manifestations

Hydrogen sulfide (H₂S) and hydrogen polysulfides (H₂S_n) are essential regulatory signaling molecules generated by the entire body, including the central nervous system. Researchers have focused on the classical H₂S signaling from the past several decades, whereas the last decade has shown the emergence of H₂S-induced protein S-sulfhydration signaling as a potential therapeutic approach. Cysteine S-persulfidation is a critical paradigm of post-translational modification in the process of H₂S signaling. Additionally, studies have shown the cross-relationship between S-sulfhydration and other cysteine-induced post-translational modifications, namely nitrosylation and carbonylation. In the central nervous system, S-sulfhydration is involved in the cytoprotection through various signaling pathways, viz. inflammatory response, oxidative stress, endoplasmic reticulum stress, atherosclerosis, thrombosis, and angiogenesis. Further, studies have demonstrated H₂S-induced S-sulfhydration in regulating different biological processes, such as mitochondrial integrity, calcium homeostasis, blood-brain permeability, cerebral blood flow, and long-term potentiation. Thus, protein S-sulfhydration becomes a crucial regulatory molecule in cerebrovascular and neurodegenerative diseases. Herein, we first described the generation of intracellular H₂S followed by the application of H₂S in the regulation of cerebral blood flow and blood-brain permeability. Further, we described the involvement of S-sulfhydration in different biological and cellular functions, such as inflammatory response, mitochondrial integrity, calcium imbalance, and oxidative stress. Moreover, we highlighted the importance of S-sulfhydration in cerebrovascular and neurodegenerative diseases.

Role of neurotoxicants in the pathogenesis of Alzheimer's disease: a mechanistic insight

Alzheimer's disease (AD) is the most conspicuous chronic neurodegenerative syndrome, which has become a significant challenge for the global healthcare system. Multiple studies have corroborated a clear association of neurotoxicants with AD pathogenicity, such as Amyloid beta (Aβ) proteins and neurofibrillary tangles (NFTs), signalling pathway modifications, cellular stress, cognitive dysfunctions, neuronal apoptosis, neuroinflammation, epigenetic modification, and so on. This review, therefore, aimed to address several essential mechanisms and signalling cascades, including Wnt (wingless and int.) signalling pathway, autophagy, mammalian target of rapamycin (mTOR), protein kinase C (PKC) signalling cascades, cellular redox status, energy metabolism, glutamatergic neurotransmissions, immune cell stimulations (e.g. microglia, astrocytes) as well as an amyloid precursor protein (APP), presenilin-1 (PSEN1), presenilin-2 (PSEN2) and other AD-related gene expressions that have been pretentious and modulated by the various neurotoxicants. This review concluded that neurotoxicants play a momentous role in developing AD through modulating various signalling cascades. Nevertheless, comprehension of this risk agent-induced neurotoxicity is far too little. More in-depth epidemiological and systematic investigations are needed to understand the potential mechanisms better to address these neurotoxicants and improve approaches to their risk exposure that aid in AD pathogenesis.Key messagesInevitable cascade mechanisms of how Alzheimer's Disease-related (AD-related) gene expressions are modulated by neurotoxicants have been discussed.Involvement of the neurotoxicants-induced pathways caused an extended risk of AD is explicited.Integration of cell culture, animals and population-based analysis on the clinical severity of AD is addressed.

Adipocyte factor CTRP6 inhibits homocysteine-induced proliferation, migration, and dedifferentiation of vascular smooth muscle cells through PPARγ/NLRP3

NLRP3 and PPARγ play important roles in the development of atherosclerosis (AS). Studies have shown that PPARγ regulates the expression of NLRP3 in vascular diseases. In addition, the adipocyte factor CTRP6 can improve the activation of PPARγ in vascular diseases. However, the regulatory relationship between CTRP6, PPARγ, and NLRP3 in AS and its underlying mechanism have not been reported. Since proliferation, migration, and dedifferentiation of vascular smooth muscle cells (VSMCs) are key events in AS, in this study, we induced proliferation, migration, and dedifferentiation of VSCMs through homocysteine (HCY) to detect the specific effects of CTRP6, PPARγ, and NLRP3. Subsequently, CTRP6 was overexpressed and the PPARγ inhibitor GW9662 and agonist rosiglitazone were administered to HCY-induced VSCMs to investigate the mechanisms. The results show that the expression of CTRP6 decreased in HCY-induced VSMCs. In addition, CTRP6 overexpression inhibited the proliferation and migration of HCY-induced VSMCs, as well as cell cycle acceleration and dedifferentiation. Overexpression of CTRP6 increased HCY-induced PPARγ expression and inhibited NLRP3 expression. The addition of GW9662 and rosiglitazone further demonstrated that overexpression of CTRP6 inhibited HCY-induced VSMC proliferation, migration, and dedifferentiation through PPARγ/NLRP3 signaling. In conclusion, CTRP6 inhibited HCY-induced proliferation, migration, and dedifferentiation of VSMCs through PPARγ/NLRP3.

Research progress of hydrogen sulfide in Alzheimer's disease from laboratory to hospital: a narrative review

Alzheimer's disease is a neurodegenerative disease that mainly occurs in old age and early stages. Its main manifestations are memory impairment, aphasia, apraxia, loss of identity, abstract thinking and impairment of computing power, personality and behavior changes, etc. At present, the treatment of Alzheimer's disease only stays on reducing the disease and delaying the development, which is also a difficult problem to overcome in clinical practice. Hydrogen sulfide, as a third gaseous signal molecule after carbon monoxide and nitrogen monoxide, has become very popular in recent years. It shows very promising prospects in the Alzheimer's disease model. It can protect the nerve function and prevent the progress of the disease by affecting the amyloid precursor protein metabolism, anti-apoptosis, anti-inflammatory, and antioxidant pathways. Therefore, this article summarizes the relevant basic and clinical research of hydrogen sulfide in Alzheimer's disease, and discusses its progress and findings and mechanism characteristics.

The baroreflex afferent pathway plays a critical role in H2S-mediated autonomic control of blood pressure regulation under physiological and hypertensive conditions

Hydrogen sulfide (H2S), which is closely related to various cardiovascular disorders, lowers blood pressure (BP), but whether this action is mediated via the modification of baroreflex afferent function has not been elucidated. Therefore, the current study aimed to investigate the role of the baroreflex afferent pathway in H2S-mediated autonomic control of BP regulation. The results showed that baroreflex sensitivity (BRS) was increased by acute intravenous NaHS (a H2S donor) administration to renovascular hypertensive (RVH) and control rats. Molecular expression data also showed that the expression levels of critical enzymes related to H2S were aberrantly downregulated in the nodose ganglion (NG) and nucleus tractus solitarius (NTS) in RVH rats. A clear reduction in BP by the microinjection of NaHS or L-cysteine into the NG was confirmed in both RVH and control rats, and a less dramatic effect was observed in model rats. Furthermore, the beneficial effects of NaHS administered by chronic intraperitoneal infusion on dysregulated systolic blood pressure (SBP), cardiac parameters, and BRS were verified in RVH rats. Moreover, the increase in BRS was attributed to activation and upregulation of the ATP-sensitive potassium (KATP) channels Kir6.2 and SUR1, which are functionally expressed in the NG and NTS. In summary, H2S plays a crucial role in the autonomic control of BP regulation by improving baroreflex afferent function due at least in part to increased KATP channel expression in the baroreflex afferent pathway under physiological and hypertensive conditions.

The Role of the Signaling Pathways Involved in the Effects of Hydrogen Sulfide on Endoplasmic Reticulum Stress

Endoplasmic reticulum (ER) is a kind of organelle with multiple functions including protein synthesis, modification and folding, calcium storage, and lipid synthesis. Under stress conditions, ER homeostasis is disrupted, which is defined as ER stress (ERS). The accumulation of unfolded proteins in the ER triggers a stable signaling network named unfolded protein response (UPR). Hydrogen sulfide is an important signal molecule regulating various physiological and pathological processes. Recent studies have shown that H₂S plays an important role in many diseases by affecting ERS, but its mechanism, especially the signaling pathways, is not fully understood. Therefore, in this review, we summarize the recent studies about the signaling pathways involved in the effects of H₂S on ERS in diseases to provide theoretical reference for the related in-depth researches.

SIRT1 Mediates H2S-Ameliorated Diabetes-Associated Cognitive Dysfunction in Rats: Possible Involvement of Inhibiting Hippocampal Endoplasmic Reticulum Stress and Synaptic Dysfunction

Diabetes-associated cognitive dysfunction (DACD) characterized by hippocampal injury increases the risk of major cerebrovascular events and death. Endoplasmic reticulum (ER) stress and synaptic dysfunction play vital roles in the pathological process. At present, no specific treatment exists for the prevention and/or the therapy of DACD. We have recently reported that hydrogen sulfide (H2S) exhibits therapeutic potential for DACD, but the underlying mechanism has not been fully elucidated. Silent information regulator 1 (SIRT1) has been shown to play a role in regulating the progression of diabetes and is also indispensable for memory formation and cognitive performance. Hence, the present study was performed to explore whether SIRT1 mediates the protective effect of H2S on streptozotocin (STZ)-induced cognitive deficits, an in vivo rat model of DACD, via inhibiting hippocampal ER stress and synaptic dysfunction. The results showed that administration of NaHS (an exogenous H2S donor) increased the expression of SIRT1 in the hippocampus of STZ-induced diabetic rats. Then, results proved that sirtinol, a special blocker of SIRT1, abrogated the inhibition of NaHS on STZ-induced cognitive deficits, as appraised by Morris water maze test, Y-maze test, and Novel object recognition behavioral test. In addition, administration of NaHS eliminated STZ-induced ER stress as evidenced by the decreases in the expressions of ER stress-related proteins including glucose-regulated protein 78, C/EBP homologous protein, and cleaved caspase-12 in the hippocampus, while these effects of NaHS were also reverted by sirtinol. Furthermore, the NaHS-induced up-regulation of hippocampal synapse-related protein (synapsin-1, SYN1) expression in STZ-induced diabetic rats was also abolished by sirtinol. Taken together, these results demonstrated that SIRT1 mediates the protection of H2S against cognitive dysfunction in STZ-diabetic rats partly via inhibiting hippocampal ER stress and synaptic dysfunction.

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.

Involvement of H2 S, NO and BDNF-TrkB signalling pathway in the protective effects of simvastatin against pentylenetetrazole-induced kindling and cognitive impairments in mice

Cognitive dysfunction was observed in pentylenetetrazole (PTZ)-kindled mice. The potential effectiveness of simvastatin (SIM) on PTZ-induced kindling and cognitive impairments in mice was evaluated. The influence of SIM on hydrogen sulphide (H2 S), nitric oxide (NO), reactive aldehydes and brain-derived neurotrophic factor/tyrosine receptor kinase B (BDNF-TrkB) signalling was also investigated. Kindling and cognitive impairments in mice were induced by 12 ip injections of PTZ (35 mg/kg) once every alternate day. The levels of reactive aldehydes and nitrite were increased while H2 S was decreased in PTZ-treated mice. These results were accompanied by a reduction in the gene expression of aldehyde dehydrogenase 2, cystathionine β-synthase, BDNF and TrkB. In PTZ-kindled mice, a rise in brain inducible nitric oxide synthase protein expression associated with histopathological changes was observed. SIM administration (1, 5 and 10 mg/kg, daily orally) along with alternate day of PTZ (35 mg/kg) resulted in a decrease in PTZ-induced kindling with a dose-dependent improvement in cognitive function. SIM (10 mg/kg) prevented, to variable extent, the disturbances associated with PTZ-kindled mice with cortical, cerebellar and hippocampal structural improvement. These results suggested that SIM triggers multiple mechanisms that improve cognitive function in PTZ-kindled mice through modulation of oxidative stress, H2 S, NO and BDNF-TrkB signalling pathway.

Hydrogen Sulfide Ameliorates Cognitive Dysfunction in Formaldehyde-Exposed Rats: Involvement in the Upregulation of Brain-Derived Neurotrophic Factor

OBJECTIVE

To investigate whether hydrogen sulfide (H2S) counteracts formaldehyde (FA)-induced cognitive defects and whether the underlying mechanism is involved in the upregulation of hippocampal brain-derived neurotrophic factor (BDNF) expression.

METHODS

The cognitive function of rats was evaluated by the Morris water maze (MWM) test and the novel object recognition test. The content of superoxide dismutase (SOD) and malondialdehyde (MDA) in the hippocampus were detected by enzyme-linked immunosorbent assay (ELISA). The neuronal apoptosis in the hippocampal CA1 region was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end (TUNEL) staining. The expression of the BDNF protein was detected by Western blot and immunohistochemistry.

RESULTS

We found that sodium hydrosulfide (NaHS, a donor of H2S) significantly reversed the impairment in the function of learning and memory in the MWM test and the novel objective recognition task induced by intracerebroventricular injection of FA. We also showed that NaHS significantly reduced the level of MDA, elevated the level of SOD, and decreased the amount of TUNEL-positive neurons in the hippocampus of FA-exposed rats. Moreover, NaHS markedly increased the expression of hippocampal BDNF in FA-exposed rats.

CONCLUSIONS

H2S attenuates FA-induced dysfunction of cognition and the underlying mechanism is involved in the reduction of hippocampal oxidative damage and apoptosis as well as upregulation of hippocampal BDNF.

Dietary methionine restriction attenuates renal ischaemia/reperfusion-induced myocardial injury by activating the CSE/H2S/ERS pathway in diabetic mice

Methionine restrictive diet may alleviate ischaemia/reperfusion (I/R)‐induced myocardial injury, but its underlying mechanism remains unclear. HE staining was performed to evaluate the myocardial injury caused by I/R and the effect of methionine‐restricted diet (MRD) in I/R mice. IHC and Western blot were carried out to analyse the expression of CSE, CHOP and active caspase3 in I/R mice and hypoxia/reoxygenation (H/R) cells. TUNEL assay and flow cytometry were used to assess the apoptotic status of I/R mice and H/R cells. MTT was performed to analyse the proliferation of H/R cells. H2S assay was used to evaluate the concentration of H2S in the myocardial tissues and peripheral blood of I/R mice. I/R‐induced mediated myocardial injury and apoptosis were partially reversed by methionine‐restricted diet (MRD) via the down‐regulation of CSE expression and up‐regulation of CHOP and active caspase3 expression. The decreased H2S concentration in myocardial tissues and peripheral blood of I/R mice was increased by MRD. Accordingly, in a cellular model of I/R injury established with H9C2 cells, cell proliferation was inhibited, cell apoptosis was increased, and the expressions of CSE, CHOP and active caspase3 were dysregulated, whereas NaHS treatment alleviated the effect of I/R injury in H9C2 cells in a dose‐dependent manner. This study provided a deep insight into the mechanism underlying the role of MRD in I/R‐induced myocardial injury.

The role of CREB and BDNF in neurobiology and treatment of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia worldwide. β-amyloid peptide (Aβ) is currently assumed to be the main cause of synaptic dysfunction and cognitive impairments in AD, but the molecular signaling pathways underlying its neurotoxic consequences have not yet been completely explored. Additional investigations regarding these pathways will contribute to development of new therapeutic targets. In context, developing evidence suggest that Aβ decreases brain-derived neurotrophic factor (BDNF) mostly by lowering phosphorylated cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) protein. In fact, it has been observed that brain or serum levels of BDNF appear to be beneficial markers for cognitive condition. In addition, the participation of transcription mediated by CREB has been widely analyzed in the memory process and AD development. Designing pharmacologic or genetic therapeutic approaches based on the targeting of CREB-BDNF signaling could be a promising treatment potential for AD. In this review, we summarize data demonstrating the role of CREB-BDNF signaling pathway in cognitive status and mediation of Aβ toxicity in AD. Finally, we also focus on the developing intervention methods for improvement of cognitive decline in AD based on targeting of CREB-BDNF pathway.

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.

Hydrogen Sulfide and Endoplasmic Reticulum Stress: A Potential Therapeutic Target for Central Nervous System Degeneration Diseases

There are three members of the endogenous gas transmitter family. The first two are nitric oxide and carbon monoxide, and the third newly added member is hydrogen sulfide (H₂S). They all have similar functions: relaxing blood vessels, smoothing muscles, and getting involved in the regulation of neuronal excitation, learning, and memory. The cystathionine β-synthase (CBS), 3-mercaptopyruvate sulfur transferase acts together with cysteine aminotransferase (3-MST/CAT), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfur transferase with D-amino acid oxidase (3-MST/DAO) pathways are involved in the enzymatic production of H₂S. More and more researches focus on the role of H₂S in the central nervous system (CNS), and H₂S plays a significant function in neuroprotection processes, regulating the function of the nervous system as a signaling molecule in the CNS. Endoplasmic reticulum stress (ERS) and protein misfolding in its mechanism are related to neurodegenerative diseases. H₂S exhibits a wide variety of cytoprotective and physiological functions in the CNS degenerative diseases by regulating ERS. This review summarized on the neuroprotective effect of H₂S for ERS played in several CNS diseases including Alzheimer’s disease, Parkinson’s disease, and depression disorder, and discussed the corresponding possible signaling pathways or mechanisms as well.

Downregulated lncRNA UCA1 accelerates proliferation and migration of vascular smooth muscle cells by epigenetic regulation of MMP9

Function of long non-coding RNA urothelial carcinoma antigen 1 (lncRNA UCA1) in regulating the proliferative and migratory abilities of vascular smooth muscle cells (VSMCs) by mediating matrix metalloproteinase-9 (MMP9) level were elucidated. After treatment with different concentrations of ox-LDL for different time points, lncRNA UCA1 level in VSMCs was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Subcellular distribution of UCA1 was analyzed. Proliferative and migratory abilities of VSMCs transfected with pcDNA-UCA1 were assessed. Protein level of MMP9 in HA-VSMCs treated with different concentrations of ox-LDL for different time points was also determined. The potential interaction between UCA1 and enhancer of zeste homolog 2 (EZH2) was identified by RNA immunoprecipitation (RIP) assay. Recruitment ability of EZH2 to MMP9 promoter region influenced by UCA1 was determined by Chromatin immunoprecipitation (ChIP) assay. Finally, the potential function of MMP9 in UCA1-mediated cellular behavior of VSMCs was explored. UCA1 was time-dependently and dose-dependently upregulated in VSMCs by ox-LDL treatment. Proliferative and migratory abilities of VSMCs were enhanced by treatment of 100 mg/l ox-LDL for 48 h, which were further reduced after transfection of pcDNA-UCA1. Subcellular distribution analysis showed that UCA1 was mainly distributed in the nucleus. Protein level of MMP9 was gradually elevated with the treatment of increased concentrations of ox-LDL in VSMCs. Its level was downregulated by transfection of pcDNA-UCA1 in VSMCs. The interaction between UCA1 and EZH2 was confirmed by RIP assay. Transfection of pcDNA-UCA1 stimulated the binding of EZH2 on MMP9 promoter region. Finally, overexpression of MMP9 reversed the decreased proliferative and migratory abilities in ox-LDL-treated VSMCs overexpressing UCA1. Downregulated UCA1 accelerates VSMCs to proliferate and migrate through negatively regulating MMP9 level.

Vitamin B12 is neuroprotective in experimental pneumococcal meningitis through modulation of hippocampal DNA methylation

Background

Bacterial meningitis (BM) causes apoptotic damage to the hippocampus and homocysteine (Hcy) accumulation to neurotoxic levels in the cerebrospinal fluid of children. The Hcy pathway controls bioavailability of methyl, and its homeostasis can be modulated by vitamin B₁₂, a cofactor of the methionine synthase enzyme. Herein, the neuroprotective potential and the underlying mode of action of vitamin B₁₂ adjuvant therapy were assessed in an infant rat model of BM.

Methods

Eleven-day old rats were intracysternally infected with Streptococcus pneumoniae serotype 3, or saline, treated with B₁₂ or placebo, and, 24 h after infection, their hippocampi were analyzed for apoptosis in the dentate gyrus, sulfur amino acids content, global DNA methylation, transcription, and proximal promoter methylation of candidate genes. Differences between groups were compared using 2-way ANOVA followed by Bonferroni post hoc test. Correlations were tested with Spearman’s test.

Results

B₁₂ attenuated BM-induced hippocampal apoptosis in a Hcy-dependent manner (r = 0.80, P < 0.05). BM caused global DNA hypomethylation; however, B₁₂ restored this parameter. Accordingly, B₁₂ increased the methylation capacity of hippocampal cells from infected animals, as inferred from the ratio S-adenosylmethionine (SAM):S-adenosylhomocysteine (SAH) in infected animals. BM upregulated selected pro-inflammatory genes, and this effect was counteracted by B₁₂, which also increased methylation of CpGs at the promoter of Ccl3 of infected animals.

Conclusion

Hcy is likely to play a central role in hippocampal damage in the infant rat model of BM, and B₁₂ shows an anti-inflammatory and neuroprotective action through methyl-dependent epigenetic mechanisms.

Hydrogen Sulfide Prevents Sleep Deprivation-Induced Hippocampal Damage by Upregulation of Sirt1 in the Hippocampus

Sleep deprivation (SD) induces hippocampal damage. Hydrogen sulfide (H₂S) is a neuronal protective factor. Silence information regulating factor 1 (Sirt1) plays an important role in neuroprotection. Therefore, this study was aimed at exploring whether H₂S meliorates SD-induced hippocampal damage and whether Sirt1 mediates this protective role of H₂S. We found that sodium hydrosulfide (NaHS, a donor of H₂S) alleviated SD-generated hippocampal oxidative stress, including increases in the activation of SOD and the level of GSH as well as a decrease in the level of MDA. Meanwhile, we found that NaHS reduced SD-exerted hippocampal endoplasmic reticulum (ER) Stress, including downregulations of GRP78, CHOP, and cleaved-caspase-12 expression. Moreover, NaHS reduced the apoptosis in the SD-exposed hippocampus, and this included decreases in the number of apoptotic cells and the activation of caspase-3, downregulation of Bax expression, and upregulation of Bcl-2 expression. NaHS upregulated the expression of Sirt1 in the hippocampus of SD-exposed rats. Furthermore, Sirtinol, the inhibitor of Sirt1, abrogated the protection of NaHS against SD-exerted hippocampal oxidative stress, ER stress, and apoptosis. These results suggested that H₂S alleviates SD-induced hippocampal damage by upregulation of hippocampal Sirt1.

Hydrogen Sulfide Plays an Important Protective Role through Influencing Endoplasmic Reticulum Stress in Diseases

The endoplasmic reticulum is an important organelle responsible for protein synthesis, modification, folding, assembly and transport of new peptide chains. When the endoplasmic reticulum protein folding ability is impaired, the unfolded or misfolded proteins accumulate to lead to endoplasmic reticulum stress. Hydrogen sulfide is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicate that H₂S plays an important protective role in many diseases through influencing endoplasmic reticulum stress, but its mechanism is not fully understood. This article reviewed the progress about the effect of H₂S on endoplasmic reticulum stress and its mechanisms involved in diseases in recent years to provide theoretical basis for in-depth study.

Hydrogen Sulfide Inhibits Homocysteine-Induced Neuronal Senescence by Up-Regulation of SIRT1

Homocysteine (Hcy) accelerates neuronal senescence and induces age-related neurodegenerative diseases. Silence signal regulating factor 1 (SIRT1) prolongs lifespan and takes neuroprotective effects. We have previously demonstrated that hydrogen sulfide (H₂S) prevents Hcy-induced apoptosis of neuronal cells and has neuroprotective effect. In the present work, we aimed to investigate whether H₂S protects HT22 cells against Hcy-induced neuronal senescence and whether SIRT1 mediates this role of H₂S. We found that Hcy induced cellular senescence in HT22 cells, as determined by β-galactosidase staining, expressions of P16^INK4a, P21^CIPL, and trypan blue Staining, which are the markers of cellular senescence. However, sodium hydrosulfide (NaHS, the donor of H₂S) significantly reversed Hcy-induced cellular senescence. Interestingly, NaHS not only up-regulated the expression of SIRT1 in HT22 cells but also reversed Hcy-downregulated the expression of SIRT1 in HT22 cells. Furthermore, we found that pretreatment with Sirtinol (an inhibitor of SIRT1) markedly reversed the protection of NaHS against Hcy-induced HT22 cells senescence and apoptosis. Our findings illustrated that H₂S protects HT22 cells against Hcy-induced senescence by up-regulating SIRT1.

KLF2 protects BV2 microglial cells against oxygen and glucose deprivation injury by modulating BDNF/TrkB pathway

Cerebral ischemia injury is common in cerebral ischemic disease, and treatment options remain limited. Krueppel-like factor 2 (KLF2) is reported to negatively regulate inflammation in several ischemic diseases. Our study aimed to investigate the effects and underlying mechanism of KLF2 in BV2 microglial cells exposed to oxygen and glucose deprivation (OGD). We first found decreased KLF2 and toll-like receptor 2 (TLR2)/TLR4 in these cells. OGD also led to decrease in cell viability and increase in LDH release, apoptosis, the Bax/Bcl-2 ratio, and caspase3/9 expression, as well as production of inflammatory cytokines (e.g., TNFα, IL-1β and IL-6), reactive oxygen species (ROS), and TLR2/TLR4. To examine KLF2's effects on these OGD effects, we infected BV2 microglial cells with an ad-KLF2 or negative control vector, and we found that KLF2 reversed all of the effects of OGD exposure. Furthermore, KLF2 significantly increased levels of BDNF and TrkB in these cells, but these effects were blocked by K252a, a BDNF/TrkB inhibitor. K252a also decreased cell viability and increased apoptosis, inflammatory factors, ROS production, and TLR2/TLR4 expression in OGD-exposed BV2 cells that were treated with KLF2, were implying that K252a could reverse the effects of KLF2 on these cells. Taken together, our study results indicate that KLF2 may protect BV2 microglial cells against OGD injury by activating the BDNF/TrkB pathway.

Imbalance of Homocysteine and H2S: Significance, Mechanisms, and Therapeutic Promise in Vascular Injury

While the role of hyperhomocysteinemia in cardiovascular pathogenesis continuously draws attention, deficiency of hydrogen sulfide (H₂S) has been growingly implicated in cardiovascular diseases. Generation of H₂S is closely associated with the metabolism of homocysteine via key enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). The level of homocysteine and H₂S is regulated by each other. Metabolic switch in the activity of CBS and CSE may occur with a resultant operating preference change of these enzymes in homocysteine and H₂S metabolism. This paper presented an overview regarding (1) linkage between the metabolism of homocysteine and H₂S, (2) mutual regulation of homocysteine and H₂S, (3) imbalance of homocysteine and H₂S in cardiovascular disorders, (4) mechanisms underlying the protective effect of H₂S against homocysteine-induced vascular injury, and (5) the current status of homocysteine-lowering and H₂S-based therapies for cardiovascular disease. The metabolic imbalance of homocysteine and H₂S renders H₂S/homocysteine ratio a potentially reliable biomarker for cardiovascular disease and development of drugs or interventions targeting the interplay between homocysteine and H₂S to maintain the endogenous balance of these two molecules may hold an even bigger promise for management of vascular disorders than targeting homocysteine or H₂S alone.

Hydrogen Sulfide Attenuates β2-Microglobulin-Induced Cognitive Dysfunction: Involving Recovery of Hippocampal Autophagic Flux

Background and Aim

Accumulation of β₂-microglobulin (B2M), a systemic pro-aging factor, regulates negatively cognitive function. Hydrogen sulfide (H₂S), a novel gas signaling molecule, exerts protection against cognitive dysfunction. Therefore, the present work was designed to explore whether H₂S attenuates cognitive dysfunction induced by B2M and the underlying mechanism.

Materials and Methods

The cognitive function of rats was assessed by Y-maze, Novel object recognition (NOR), and Morris water maze (MWM) tests. The levels of autophagosome and autolysosome in hippocampus were observed by transmission electron microscopy. The expression of p62 protein in hippocampus was detected by western blot analysis.

Results

NaHS (a donor of H₂S) significantly alleviated cognitive impairments in the B2M-exposed rats tested by Y-maze test, NOR test and MWM test. Furthermore, NaHS recovered autophagic flux in the hippocampus of B2M-exposed rats, as evidenced by decreases in the ratio of autophagosome to autolysosome and the expression of p62 protein in the hippocampus.

Conclusion

In summary, these data indicated that H₂S attenuates B2M-induced cognitive dysfunction, involving in recovery of the blocked autophagic flux in the hippocampus, and suggested that H₂S may be a novel approach to prevent B2M-induced cognitive dysfunction.

Homocysteine induces human mesangial cell apoptosis via the involvement of autophagy and endoplasmic reticulum stress

Homocysteine (Hcy) level characterizes a progressive increase in chronic kidney disease (CKD). In fact, Hcy accumulation is considered to be a crucial biochemical culprit in CKD progression, but the mechanism underlying this remains poorly understood. This study investigated the role of Hcy in glomerular mesangial cell (MC) apoptosis and the potential involvement of autophagy and endoplasmic reticulum (ER) stress in this process, shedding light on Hcy toxicity in kidney disease. Human mesangial cells (HMCs) were incubated with different concentrations of Hcy for different times. Flow cytometry was used to determine the proportion of apoptotic cells and western blotting was used to analyze protein levels after the administration of Hcy, endoplasmic reticulum inhibitor 4-phenylbutyric acid (4-PBA), and Atg5 siRNA. The results demonstrated that the cell viability gradually decreased and the proportion of HMCs undergoing apoptosis increased with increasing Hcy concentration and prolonged incubation time. Meanwhile, levels of the apoptosis-related proteins Bax and cleaved caspase-3 were significantly increased, while ER stress-related proteins such as ATF4, CHOP, GRP78, and phospho-eIF2α significantly increased. Levels of cleaved LC3, and beclin1 and Atg5 proteins also increased, accompanied by p62 degradation, indicating autophagy activation. 4-PBA effectively inhibited ER stress and reversed Hcy-induced apoptosis and autophagy. Moreover, Atg5 siRNA alleviated Hcy-induced apoptosis. Taken together, these results suggest that Hcy induces HMC apoptosis in a dose- and time-dependent manner via the activation of Atg5-dependent autophagy triggered by ER stress. This study suggests a novel strategy against Hcy toxicity in kidney injury and should help in clarifying the pathogenesis of CKD.

Hydrogen sulphide mitigates homocysteine-induced apoptosis and matrix remodelling in mesangial cells through Akt/FOXO1 signalling cascade

Cellular damage and accumulation of extracellular matrix (ECM) protein in the glomerulo-interstitial space are the signatures of chronic kidney disease (CKD). Hyperhomocysteinemia (HHcy), a high level of homocysteine (Hcy) is associated with CKD and further contributes to kidney damage. Despite a large number of studies, the signalling mechanism of Hcy-mediated cellular damage and ECM remodelling in kidney remains inconclusive. Hcy metabolizes to produce hydrogen sulphide (H2S), and a number of studies have shown that H2S mitigates the adverse effect of HHcy in a variety of diseases involving several signalling molecules, including forkhead box O (FOXO) protein. FOXO is a group of transcription factor that includes FOXO1, which plays important roles in cell growth and proliferation. On the other hand, a cell survival factor, Akt regulates FOXO under normal condition. However, the involvement of Akt/FOXO1 pathway in Hcy-induced mesangial cell damage remains elusive, and whether H2S plays any protective roles has yet to be clearly defined. We treated mouse mesangial cells with or without H2S donor, GYY4137 and FOXO1 inhibitor, AS1842856 in HHcy condition and determined the involvement of Akt/FOXO1 signalling cascades. Our results indicated that Hcy inactivated Akt and activated FOXO1 by dephosphorylating both the signalling molecules and induced FOXO1 nuclear translocation followed by activation of the FOXO1 transcription factor. These led to the induction of cellular apoptosis and synthesis of excessive ECM protein, in part, due to increased ROS production, loss of mitochondrial membrane potential (ΔΨm), reduction in intracellular ATP concentration, increased MMP-2, -9, -14 mRNA and protein expression, and Col I, IV and fibronectin protein expression. Interestingly, GYY4137 or AS1842856 treatment prevented these changes by modulating Akt/FOXO1 axis in HHcy. We conclude that GYY4137 and/or AS1842856 mitigates HHcy induced mesangial cell damage and ECM remodelling by regulating Akt/FOXO1 pathway.

Hydrogen Sulfide Inhibits High Glucose-Induced Neuronal Senescence by Improving Autophagic Flux via Up-regulation of SIRT1

Hyperglycemia, a key characteristic and risk factor for diabetes mellitus (DM), causes neuronal senescence. Hydrogen sulfide (H₂S) is a novel neuroprotectant. The present work was to investigate the potential effect of H₂S on hyperglycemia-induced neuronal senescence and the underlying mechanisms. We found that NaHS, a donor of H₂S, inhibited high glucose (HG)-induced cellular senescence in HT22 cells (an immortalized mouse hippocampal cell line), as evidenced by a decrease in the number of senescence associated-β-galactosidase (SA-β-gal) positive cells, increase in the growth of cells, and down-regulations of senescence mark proteins, p16^INK4a and p21^CIP1. NaHS improved the autophagic flux, which is judged by a decrease in the amount of intracellular autophagosome as well as up-regulations of LC3II/I and P62 in HG-exposed HT22 cells. Furthermore, blocked autophagic flux by chloroquine (CQ) significantly abolished NaHS-exerted improvement in the autophagic flux and suppression in the cellular senescence of GH-exposed HT22 cells, which indicated that H₂S antagonizes HG-induced neuronal senescence by promoting autophagic flux. We also found that NaHS up-regulated the expression of silent mating type information regulation 2 homolog 1 (SIRT1), an important anti-aging protein, in HG-exposed HT22 cells. Furthermore, inhibition of SIRT1 by sirtinol reversed the protection of H₂S against HG-induced autophagic flux blockade and cellular senescence in HT22 cells. These data indicated that H₂S protects HT22 cells against HG-induced neuronal senescence by improving autophagic flux via up-regulation of SIRT1, suggesting H₂S as a potential treatment strategy for hyperglycemia-induced neuronal senescence and neurotoxicity.

Role of hydrogen sulfide in the musculoskeletal system

Hydrogen sulfide (H₂S) has been known as a gasotransmitter, and it contributes to various physiological and pathological processes. Multiple enzymes such as cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-Mercaptopyruvate sulfurtransferase (MST) produce endogenous H₂S, and these are differentially expressed in the various tissue systems including the skeletal system. However, abnormal H₂S production is associated with deregulation of the signaling cascade and imbalanced tissue homeostasis. Several studies have previously provided evidence showing the essential regulatory action of H₂S in skeletal homeostasis. In this review, we have emphasized the novel function of H₂S in both bone and skeletal muscle anabolism, in particular. Additionally, we also reviewed the molecular and epigenetic basis of H₂S signaling in bone development and skeletal muscle function.

Implication of homocysteine in protein quality control processes

Homocysteine (Hcy) is a key metabolite generated during methionine metabolism. The elevated levels of Hcy in the blood are reffered to as hyperhomocystenimeia (HHcy). The HHcy is caused by impaired metabolism/deficiency of either folate or B12 or defects in Hcy metabolism. Accumulating evidence suggests that HHcy is associated with cardiovascular and brain diseases including atherosclerosis, endothelial injury, and stroke etc. Vitamin B12 (cobalamin; B12) is a water-soluble vitamin essential for two metabolic reactions. It acts as a co-factor for methionine synthase and L-methylmalonyl-CoA mutase. Besides, it is also vital for DNA synthesis and maturation of RBC. Deficiency of B12 is associated with haematological and neurological disorders. Hyperhomocysteinemia (HHcy)-induced toxicity is thought to be mediated by the accumulation of Hcy and its metabolites, homocysteinylated proteins. Cellular protein quality control (PQC) is essential for the maintenance of proteome integrity, and cell viability and its failure contributes to the development of multiple diseases. Chaperones, unfolded protein response (UPR), ubiquitin-proteasome system (UPS), and autophagy are analogous strategies of PQC that maintain cellular proteome integrity. Recently, multiple studies reported that HHcy responsible for perturbation of PQC by reducing chaperone levels, activating UPR, and impairing autophagy. Besides, HHcy also induce cytotoxicity, inflammation, protein aggregation and apoptosis. It has been shown that some of the factors including altered SIRT1-HSF1 axis and irreversible homocysteinylation of proteins are responsible for folate and/or B12 deficiency or HHcy-induced impairment of PQC. Therefore, this review highlights the current understanding of HHcy in the context of cellular PQC and their pathophysiological and clinical consequences, epigenomic changes, therapeutic implications of B12, and chemical chaperones based on cell culture and experimental animal models.

Restoration of skeletal muscle homeostasis by hydrogen sulfide during hyperhomocysteinemia-mediated oxidative/ER stress condition 1

Elevated homocysteine (Hcy), i.e., hyperhomocysteinemia (HHcy), causes skeletal muscle myopathy. Among many cellular and metabolic alterations caused by HHcy, oxidative and endoplasmic reticulum (ER) stress are considered the major ones; however, the precise molecular mechanism(s) in this process is unclear. Nevertheless, there is no treatment option available to treat HHcy-mediated muscle injury. Hydrogen sulfide (H₂S) is increasingly recognized as a potent anti-oxidant, anti-apoptotic/necrotic/pyroptotic, and anti-inflammatory compound and also has been shown to improve angiogenesis during ischemic injury. Patients with CBS mutation produce less H₂S, making them vulnerable to Hcy-mediated cellular damage. Many studies have reported bidirectional regulation of ER stress in apoptosis through JNK activation and concomitant attenuation of cell proliferation and protein synthesis via PI3K/AKT axis. Whether H₂S mitigates these detrimental effects of HHcy on muscle remains unexplored. In this review, we discuss molecular mechanisms of HHcy-mediated oxidative/ER stress responses, apoptosis, angiogenesis, and atrophic changes in skeletal muscle and how H₂S can restore skeletal muscle homeostasis during HHcy condition. This review also highlights the molecular mechanisms on how H₂S could be developed as a clinically relevant therapeutic option for chronic conditions that are aggravated by HHcy.

Fucosterol from an Edible Brown Alga Ecklonia stolonifera Prevents Soluble Amyloid Beta-Induced Cognitive Dysfunction in Aging Rats

Fucosterol from edible brown seaweeds has various biological activities, including anti-inflammatory, anti-adipogenic, antiphotoaging, anti-acetylcholinesterase, and anti-beta-secretase 1 activities. However, little is known about its effects on soluble amyloid beta peptide (sAβ)-induced endoplasmic reticulum (ER) stress and cognitive impairment. Fucosterol was isolated from the edible brown seaweed Ecklonia stolonifera, and its neuroprotective effects were analyzed in primary hippocampal neurons and in aging rats. Fucosterol attenuated sAβ1-42-induced decrease in the viability of hippocampal neurons and downregulated sAβ1-42-induced increase in glucose-regulated protein 78 (GRP78) expression in hippocampal neurons via activation of tyrosine receptor kinase B-mediated ERK1/2 signaling. Fucosterol co-infusion attenuated sAβ1-42-induced cognitive impairment in aging rats via downregulation of GRP78 expression and upregulation of mature brain-derived neurotrophic factor expression in the dentate gyrus. Fucosterol might be beneficial for the management of cognitive dysfunction via suppression of aging-induced ER stress.

The Effect of Trimebutine on the Overlap Syndrome Model of Guinea Pigs

Background/Aims

Functional dyspepsia (FD) and irritable bowel syndrome (IBS) are common gastrointestinal (GI) disorders and these patients frequently overlap. Trimebutine has been known to be effective in controlling FD co-existing diarrhea-dominant IBS, however its effect on overlap syndrome (OS) patients has not been reported. Therefore, we investigated the effect of trimebutine on the model of OS in guinea pigs.

Methods

Male guinea pigs were used to evaluate the effects of trimebutine in corticotropin-releasing factor (CRF) induced OS model. Different doses (3, 10, and 30 mg/kg) of trimebutine were administered orally and incubated for 1 hour. The next treatment of 10 μg/kg of CRF was intraperitoneally injected and stabilized for 30 minutes. Subsequently, intragastric 3 mL charcoal mix was administered, incubated for 10 minutes and the upper GI transit analyzed. Colonic transits were assessed after the same order and concentrations of trimebutine and CRF treatment by fecal pellet output assay.

Results

Different concentrations (1, 3, and 10 μg/kg) of rat/human CRF peptides was tested to establish the OS model in guinea pigs. CRF 10 μg/kg was the most effective dose in the experimental OS model of guinea pigs. Trimebutine (3, 10, and 30 mg/kg) treatment significantly reversed the upper and lower GI transit of CRF induced OS model. Trimebutine significantly increased upper GI transit while it reduced fecal pellet output in the CRF induced OS model.

Conclusions

Trimebutine has been demonstrated to be effective on both upper and lower GI motor function in peripheral CRF induced OS model. Therefore, trimebutine might be an effective drug for the treatment of OS between FD and IBS patients.

Remote ischemic conditioning as a cytoprotective strategy in vasculopathies during hyperhomocysteinemia: An emerging research perspective

Higher levels of nonprotein amino acid homocysteine (Hcy), that is, hyperhomocysteinemia (HHcy) (~5% of general population) has been associated with severe vasculopathies in different organs; however, precise molecular mechanism(s) as to how HHcy plays havoc with body's vascular networks are largely unknown. Interventional modalities have not proven beneficial to counter multifactorial HHcy's effects on the vascular system. An ancient Indian form of exercise called 'yoga' causes transient ischemia as a result of various body postures however the cellular mechanisms are not clear. We discuss a novel perspective wherein we argue that application of remote ischemic conditioning (RIC) could, in fact, deliver anticipated results to patients who are suffering from chronic vascular dysfunction due to HHcy. RIC is the mechanistic phenomenon whereby brief episodes of ischemia-reperfusion events are applied to distant tissues/organs; that could potentially offer a powerful tool in mitigating chronic lethal ischemia in target organs during HHcy condition via simultaneous reduction of inflammation, oxidative and endoplasmic reticulum stress, extracellular matrix remodeling, fibrosis, and angiogenesis. We opine that during ischemic conditioning our organs cross talk by releasing cellular messengers in the form of exosomes containing messenger RNAs, circular RNAs, anti-pyroptotic factors, protective cytokines like musclin, transcription factors, small molecules, anti-inflammatory, antiapoptotic factors, antioxidants, and vasoactive gases. All these could help mobilize the bone marrow-derived stem cells (having tissue healing properties) to target organs. In that context, we argue that RIC could certainly play a savior's role in an unfortunate ischemic or adverse event in people who have higher levels of the circulating Hcy in their systems.

RETRACTED: Protective effect of exogenous hydrogen sulfide on pulmonary artery endothelial cells by suppressing endoplasmic reticulum stress in a rat model of chronic obstructive pulmonary disease

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concern was raised about the reliability of the Western blot data in Figure 4A, which appear to represent a distinct phenotype as found in many other publications, as detailed here: https://pubpeer.com/publications/029A84E50BD071A2088140723E3CF0; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Independent analysis confirmed the presence of suspected image duplications between the Western blots in Figure 4A and those contained in Yan et al (2017). The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Neurotoxic Agent-Induced Injury in Neurodegenerative Disease Model: Focus on Involvement of Glutamate Receptors

Glutamate receptors play a crucial role in the central nervous system and are implicated in different brain disorders. They play a significant role in the pathogenesis of neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Although many studies on NDDs have been conducted, their exact pathophysiological characteristics are still not fully understood. In in vivo and in vitro models of neurotoxic-induced NDDs, neurotoxic agents are used to induce several neuronal injuries for the purpose of correlating them with the pathological characteristics of NDDs. Moreover, therapeutic drugs might be discovered based on the studies employing these models. In NDD models, different neurotoxic agents, namely, kainic acid, domoic acid, glutamate, β-N-Methylamino-L-alanine, amyloid beta, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 1-methyl-4-phenylpyridinium, rotenone, 3-Nitropropionic acid and methamphetamine can potently impair both ionotropic and metabotropic glutamate receptors, leading to the progression of toxicity. Many other neurotoxic agents mainly affect the functions of ionotropic glutamate receptors. We discuss particular neurotoxic agents that can act upon glutamate receptors so as to effectively mimic NDDs. The correlation of neurotoxic agent-induced disease characteristics with glutamate receptors would aid the discovery and development of therapeutic drugs for NDDs.

Neuroprotective Effect of Hydrogen Sulfide in Hyperhomocysteinemia Is Mediated Through Antioxidant Action Involving Nrf2

Homocysteine (Hcy) is a sulfur-containing amino acid derived from methionine metabolism. Elevated plasma Hcy levels (> 15 µM) result in a condition called hyperhomocysteinemia (HHcy), which is an independent risk factor in the development of various neurodegenerative disorders. Reactive oxygen species (ROS) produced by auto-oxidation of Hcy have been implicated in HHcy-associated neurological conditions. Hydrogen sulfide (H₂S) is emerging as a potent neuroprotective and neuromodulator molecule. The present study was aimed to evaluate the ability of NaHS (a source of H₂S) to attenuate Hcy-induced oxidative stress and altered antioxidant status in animals subjected to HHcy. Impaired cognitive functions assessed by Y-maze and elevated plus maze in Hcy-treated animals were reversed on NaHS administration. Increased levels of ROS, lipid peroxidation, protein carbonyls, and 4-hydroxynonenal (4-HNE)-modified proteins were observed in the cortex and hippocampus of Hcy-treated animals suggesting accentuated oxidative stress. This increase in Hcy-induced oxidative stress was reversed following NaHS supplementation. GSH/GSSG ratio, activity of antioxidant enzymes viz; superoxide dismutase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase were decreased in Hcy-treated animals. NaHS supplementation, on the otherhand, restored redox ratio and activity of antioxidant enzymes in the brains of animals with HHcy. Further, NaHS administration normalized nuclear factor erythroid 2-related factor 2 expression and acetylcholinesterase (AChE) activity in the brain of Hcy-treated animals. Histopathological studies using cresyl violet indicated higher number of pyknotic neurons in the cortex and hippocampus of HHcy animals, which were reversed by NaHS administration. The results clearly demonstrate that NaHS treatment significantly ameliorates Hcy-induced cognitive impairment by attenuating oxidative stress, improving antioxidant status, and modulating AChE activity thereby suggesting potential of H₂S as a therapeutic molecule.

BDNF/TrkB Pathway Mediates the Antidepressant-Like Role of H2S in CUMS-Exposed Rats by Inhibition of Hippocampal ER Stress

Our previous works have shown that hydrogen sulfide (H₂S) significantly attenuates chronic unpredictable mild stress (CUMS)-induced depressive-like behaviors and hippocampal endoplasmic reticulum (ER) stress. Brain-derived neurotrophic factor (BDNF) generates an antidepressant-like effect by its receptor tyrosine protein kinase B (TrkB). We have previously found that H₂S upregulates the expressions of BDNF and p-TrkB in the hippocampus of CUMS-exposed rats. Therefore, the present work was to explore whether BDNF/TrkB pathway mediates the antidepressant-like role of H₂S by blocking hippocampal ER stress. We found that treatment with K252a (an inhibitor of BDNF/TrkB pathway) significantly increased the immobility time in the forced swim test and tail suspension test and increased the latency to feed in the novelty-suppressed feeding test in the rats cotreated with sodium hydrosulfide (NaHS, a donor of H₂S) and CUMS. Similarly, K252a reversed the protective effect of NaHS against CUMS-induced hippocampal ER stress, as evidenced by increases in the levels of ER stress-related proteins, glucose-regulated protein 78, CCAAT/enhancer binding protein homologous protein and cleaved caspase-12. Taken together, our results suggest that BDNF/TrkB pathway plays an important mediatory role in the antidepressant-like action of H₂S in CUMS-exposed rats, which is by suppression of hippocampal ER stress. These data provide a novel mechanism underlying the protection of H₂S against CUMS-induced depressive-like behaviors.