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

Role of cystathionine-β-synthase and hydrogen sulfide in down syndrome

Down syndrome (DS) is a genetic condition where the person affected by it is born with an additional - full or partial - copy of chromosome 21. DS presents with characteristic morphological features and is associated with a wide range of biochemical alterations and maladaptations. Cystathionine-β-synthase (CBS) - one of the key mammalian enzymes responsible for the biogenesis of the gaseous transmitter hydrogen sulfide (H2S) - is located on chromosome 21, and people with DS exhibit a significant upregulation of this enzyme in their brain and other organs. Even though 3-mercaptopyruvate sulfurtransferase - another key mammalian enzyme responsible for the biogenesis of H2S and of reactive polysulfides - is not located on chromosome 21, there is also evidence for the upregulation of this enzyme in DS cells. The hypothesis that excess H2S in DS impairs mitochondrial function and cellular bioenergetics was first proposed in the 1990s and has been substantiated and expanded upon over the past 25 years. DS cells are in a state of metabolic suppression due to H2S-induced, reversible inhibition of mitochondrial Complex IV activity. The impairment of aerobic ATP generation in DS cells is partially compensated by an upregulation of glycolysis. The DS-associated metabolic impairment can be reversed by pharmacological CBS inhibition or CBS silencing. In rodent models of DS, CBS upregulation and H2S overproduction contribute to the development of cognitive dysfunction, alter brain electrical activity, and promote reactive gliosis: pharmacological inhibition or genetic correction of CBS overactivation reverses these alterations. CBS can be considered a preclinically validated drug target for the experimental therapy of DS.

Interplay of Endoplasmic Reticulum Stress, Inflammation, Apoptosis, and Oxidative Stress in Corticosteroid-Induced Anxiety and Depression: Exploring Therapeutic Potential of Hydrogen Sulfide and Sertraline

Prolonged exposure to corticosteroids (CORTs) triggers depression and anxiety symptoms either endogenously or exogenously via stimulating endoplasmic reticulum stress (ERS). The study assessed the therapeutic implications of hydrogen sulfide (H2S) versus sertraline (SERT) in alleviating anxiety and depression induced by CORTs through the modulation of ERS and its inflammatory, oxidative, and apoptotic consequences. Rats were subdivided into four groups: control, CORT (20 mg/kg), NaHS (100 μmol/kg), and SERT (10 mg/kg) for 21 days. Behavioral and histological examinations of the cerebral cortex were performed. The levels of CHOP, GADD34, EIF2AK3, GRP78, caspase 3, and miR-146a were analyzed using qRT-PCR. The levels of CORTs, serotonin, BDNF, TNF-α, BCL2, NRF2, and ATF4 were measured using ELISA, whereas those of IL-1β and BAX were measured using immunohistochemical techniques. Total and phosphorylated PERK were assessed via western blotting, whereas GSH and MDA were assessed via a colorimetric assay. In the present study, CORTs upregulated the gene expression of CHOP, GADD34, EIF2AK3, GRP78, and Caspase 3, whereas it downregulated that of miR-146a. The levels of serotonin, BDNF, BCL2, GSH, and NRF2 were decreased, whereas those of ATF4, TNF-α, IL-1β, BAX, and MDA were elevated. On the contrary, NaHS and SERT reversed all the above-mentioned changes. H2S shows promise in counteracting anxiety and depression symptoms induced by CORTs by targeting ERS cascades, mitigating inflammation, oxidative insults, and apoptosis in the cerebral cortex. H2S elicits neuroprotective effects by targeting the miR-146a-3p/GRP78/CHOP/PERK/ATF4/GADD34 signaling pathway and regulating apoptotic markers BAX/BCL2 and inflammatory markers TNF-α and/IL-1β. Compared with SERT, H2S exhibited superior anxiolytic and antidepressive effects.

Diallyl Trisulfide Attenuates Ischemia-Reperfusion-Induced ER Stress and Kidney Dysfunction in Aged Female Mice

Ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI) in the aging population. Gender studies show that aging is associated with loss of protection from AKI in the female population. While ER stress contributes to IRI-induced AKI in the young, ER regulation during IR in the aged kidney is unclear. Because current evidence suggests hydrogen sulfide (H2S) modulates ER stress, we investigated whether exogenous supplementation of diallyl trisulfide (DATS), an H2S donor, mitigates AKI in aged female kidneys. Wild-type (WT, C57BL/6J) mice aged 75-78 weeks were treated with or without DATS before and after renal IRI. IRI increased ER stress proteins, inflammation, and fibrosis markers in the IRI kidney compared to the control. DATS mitigated ER stress, and reduced inflammation and fibrosis markers in the IRI kidney. Further, IRI kidneys demonstrated reduced blood flow, vascularity, angiogenesis, increased resistive index (RI), and reduced function. DATS treatment upregulated PI3K, AKT, p-mTOR, and pMAPK signaling to stimulate angiogenesis, which improved vascular density, blood flow, and renal function. Together, our results suggest that DATS rescues the aged female kidney IRI by modulating ER stress and upregulation of angiogenesis.

Protective effects of anthocyanins on the nervous system injury caused by fluoride-induced endoplasmic reticulum stress in rats

Long-term fluoride exposure can produce neurotoxicity. Anthocyanins, as antioxidants, have a certain protective effect in nerve damage. This study aimed to investigate the protective role of anthocyanins in fluoride-induced neurological damage due to endoplasmic reticulum stress (ERS). Using a fluoride-exposed Wistar rat model, we assessed learning memory capacity and pathologic and ultrastructural injury. The level of oxidative stress (OS) in vivo was detected by colorimetric method, the level of ERS was analyzed by immunohistochemistry, and the apoptosis of neuronal cells was observed by TUNEL staining. The results showed that fluoride exposure could decrease the learning and memory ability in rats, and led to histopathological and ultrastructural damage in the hippocampal CA1, CA3 and cortical regions. Fluoride exposure-induced OS in vivo, which further activates ERS, which was manifested by increased levels of ERS-related proteins GRP78, Caspase 12, and Caspase 3 in hippocampal CA1, CA3, and cortical regions, and eventually led to a significant increase in neuronal apoptosis rate. Notably, after anthocyanins treatment, pathological and ultrastructural damage was restored, the level of OS and ERS were significantly restored, and the apoptosis rate of neuronal cells was significantly reduced. In summary, as nutritional interventions, anthocyanins exert a protective role in fluoride-induced neurological injury.

In Situ Slow-Release Hydrogen Sulfide Therapeutics for Advanced Disease Treatments

Hydrogen sulfide (H2S) gas therapygarners significant attention for its potential to improve outcomes in various disease treatments. The quantitative control of H2S release is crucial for effective the rapeutic interventions; however, traditional researchon H2S therapy frequently utilizes static release models and neglects the dynamic nature of blood flow. In this study, we propose a novel slow-release in-situ H2S release model that leverages the dynamic hydrolysis of H2S donorswithin the bloodstream. Calcium sulfide nanoparticles (CaS NPs) withmicrosolubility characteristics exhibit continuous H2S release, surpassing 24 h at normal blood flow velocities. The extended-release profile demonstrates superior potential in aligning with the bell-shapedpharmacological effect of H2S, compared to NaHS. Moreover, we synthesisedrare earth-doped CaS NPs (CaS: Eu2+, Sm3+ NPs) tha texhibit persistent luminescence, enabling visualisation of the continuous H2S release in trials. Our results demonstrate that lowdose CaS: Eu2+, Sm3+ NPs significantly reduces seizureduration to 1.2 ± 0.7 minutes, while high dose effectively suppresses colontumor growth with a tumor inhibition rate of 54%. Remarkably, these findings closely resemble endogenous H2S levels in treating epilepsy and tumors. This innovative slow-release, in-situ H2S the rapeutic approach via hydrolysis rejuvenates the development of H2S-basedtherapeutics.

Hydrogen Sulfide Sustained Release Donor Alleviates Spinal Cord Ischemia-Reperfusion-Induced Neuron Death by Inhibiting Ferritinophagy-Mediated Ferroptosis

AIMS

Spinal cord ischemia-reperfusion injury (SCIRI) is a disastrous complication that cannot be completely prevented in thoracoabdominal aneurysm surgery, leading to sensory and motor dysfunction and even paraparesis, causing tremendous socioeconomic burden. Ferritinophagy is a form of autophagic ferroptosis, which is a contributor to SCIRI. Hydrogen sulfide (H2S) has been reported to be neuroprotective in various diseases. However, it remains unclear whether H2S alleviates SCIRI-induced neural death via regulating ferritinophagy-mediated ferroptosis. The aim of this study was to explore their relationship and interaction in SCIRI.

RESULTS

The results demonstrate that Nissl bodies and motor function were obviously lost in SCIRI rats. Meanwhile, SCIRI led to a significant increase in DHE-positive neurons, TUNEL-positive neurons, LC3-positive neurons, and ferritin-positive neurons, downregulation of GPx4, Slc7a11, p62, and ferritin expression, and upregulation of LC3 II/I and NCOA4 expression. Additionally, there was upregulation of the level of MDA, GSH, and Fe2+. Finally, we found that H2S could significantly relieve neuronal death and loss of motor function in SCIRI rats by inhibiting ferritinophagy and ferroptosis.

CONCLUSION

Ferroptosis and ferritinophagy play a crucial role in the etiopathogenesis of SCIRI, and H2S exerts neuroprotection by inhibiting ferritinophagy-mediated ferroptosis.

Polysulfide and persulfide-mediated activation of the PERK-eIF2α-ATF4 pathway increases Sestrin2 expression and reduces methylglyoxal toxicity

Unfolded protein response (UPR) is activated in cells under endoplasmic reticulum (ER) stress. One sensor protein involved in this response is PERK, which is activated through its redox-dependent oligomerization. Prolonged UPR activation is associated with the development and progression of various diseases, making it essential to understanding the redox regulation of PERK. Sulfane sulfur, such as polysulfides and persulfides, can modify the cysteine residues and regulate the function of various proteins. However, the regulatory mechanism and physiological effects of sulfane sulfur on the PERK-eIF2α-ATF4 pathway remain poorly understood. This study focuses on the persulfidation of PERK to elucidate the effects of polysulfides on the PERK-eIF2α-ATF4 pathway and investigate its cytoprotective mechanism. Here, we demonstrated that polysulfide treatment promoted the oligomerization of PERK and PTP1B in neuronal cells using western blotting under nonreducing conditions. We also observed that l-cysteine, a biological source of sulfane sulfur, promoted the oligomerization of PERK and the knockdown of CBS and 3-MST, two sulfane sulfur-producing enzymes, and reduced PERK oligomerization induced by l-cysteine treatment. Furthermore, the band shift assay and LC-MS/MS studies revealed that polysulfides and persulfides induce PTP1B and PERK persulfidation. Additionally, polysulfides promoted eIF2α phosphorylation and ATF4 accumulation in the nucleus, suggesting that polysulfides activate the PERK-eIF2α-ATF4 pathway in neuronal cells. Moreover, polysulfides protected neuronal cells from methylglyoxal-induced toxicity, and this protective effect was reduced when the expression of Sestrin2, regulated by ATF4 activity, was suppressed. This study identified a novel mechanism for the activation of the PERK-eIF2α-ATF4 pathway through persulfidation by polysulfides and persulfides. Interestingly, activation of this pathway overcame the toxicity of methylglyoxal in dependence on Sestrin2 expression. These findings deepen our understanding of neuronal diseases involving ER stress and UPR disturbance and may inspire new therapeutic strategies.

Unearthing the Potential Therapeutic Effects of Oxyresveratrol Based on Intrinsic Links between Pharmacological Effects: Implications for the Gut-Liver-Brain Axis

Oxyresveratrol is a stilbene compound with a simple chemical structure and various therapeutic potentials. This study summarized and analyzed the multiple pharmacological effects and mechanisms of oxyresveratrol, identifying its prominent performance in neuroprotection, hepatoprotection, and anti-inflammatory activities in the intestines. By integrating the pharmacological effects of oxyresveratrol with insights from the network pharmacology and molecular docking of its interactions with targets linked to gut-liver-brain axis disorders, it has been shown that oxyresveratrol may hold promise for the treatment of gut-liver-brain axis-related disorders. The synergistic effect between various mechanisms has inspired further research and the development of oxyresveratrol's application value.

Astrocyte modulation in cerebral ischemia-reperfusion injury: A promising therapeutic strategy

Cerebral ischemia-reperfusion injury (CIRI) poses significant challenges for drug development due to its complex pathogenesis. Astrocyte involvement in CIRI pathogenesis has led to the development of novel astrocyte-targeting drug strategies. To comprehensively review the current literature, we conducted a thorough analysis from January 2012 to December 2023, identifying 82 drugs aimed at preventing and treating CIRI. These drugs target astrocytes to exert potential benefits in CIRI, and their primary actions include modulation of relevant signaling pathways to inhibit neuroinflammation and oxidative stress, reduce cerebral edema, restore blood-brain barrier integrity, suppress excitotoxicity, and regulate autophagy. Notably, active components from traditional Chinese medicines (TCM) such as Salvia miltiorrhiza, Ginkgo, and Ginseng exhibit these important pharmacological properties and show promise in the treatment of CIRI. This review highlights the potential of astrocyte-targeted drugs to ameliorate CIRI and categorizes them based on their mechanisms of action, underscoring their therapeutic potential in targeting astrocytes.

Theranostic Fluorescent Probes

The ability to gain spatiotemporal information, and in some cases achieve spatiotemporal control, in the context of drug delivery makes theranostic fluorescent probes an attractive and intensely investigated research topic. This interest is reflected in the steep rise in publications on the topic that have appeared over the past decade. Theranostic fluorescent probes, in their various incarnations, generally comprise a fluorophore linked to a masked drug, in which the drug is released as the result of certain stimuli, with both intrinsic and extrinsic stimuli being reported. This release is then signaled by the emergence of a fluorescent signal. Importantly, the use of appropriate fluorophores has enabled not only this emerging fluorescence as a spatiotemporal marker for drug delivery but also has provided modalities useful in photodynamic, photothermal, and sonodynamic therapeutic applications. In this review we highlight recent work on theranostic fluorescent probes with a particular focus on probes that are activated in tumor microenvironments. We also summarize efforts to develop probes for other applications, such as neurodegenerative diseases and antibacterials. This review celebrates the diversity of designs reported to date, from discrete small-molecule systems to nanomaterials. Our aim is to provide insights into the potential clinical impact of this still-emerging research direction.

Exploring the complexities of 1C metabolism: implications in aging and neurodegenerative diseases

The intricate interplay of one-carbon metabolism (OCM) with various cellular processes has garnered substantial attention due to its fundamental implications in several biological processes. OCM serves as a pivotal hub for methyl group donation in vital biochemical reactions, influencing DNA methylation, protein synthesis, and redox balance. In the context of aging, OCM dysregulation can contribute to epigenetic modifications and aberrant redox states, accentuating cellular senescence and age-associated pathologies. Furthermore, OCM's intricate involvement in cancer progression is evident through its capacity to provide essential one-carbon units crucial for nucleotide synthesis and DNA methylation, thereby fueling uncontrolled cell proliferation and tumor development. In neurodegenerative disorders like Alzheimer's and Parkinson's, perturbations in OCM pathways are implicated in the dysregulation of neurotransmitter synthesis and mitochondrial dysfunction, contributing to disease pathophysiology. This review underscores the profound impact of OCM in diverse disease contexts, reinforcing the need for a comprehensive understanding of its molecular complexities to pave the way for targeted therapeutic interventions across inflammation, aging and neurodegenerative disorders.

Pharmacological interventions targeting the microcirculation following traumatic spinal cord injury

Traumatic spinal cord injury is a devastating disorder characterized by sensory, motor, and autonomic dysfunction that severely compromises an individual's ability to perform activities of daily living. These adverse outcomes are closely related to the complex mechanism of spinal cord injury, the limited regenerative capacity of central neurons, and the inhibitory environment formed by traumatic injury. Disruption to the microcirculation is an important pathophysiological mechanism of spinal cord injury. A number of therapeutic agents have been shown to improve the injury environment, mitigate secondary damage, and/or promote regeneration and repair. Among them, the spinal cord microcirculation has become an important target for the treatment of spinal cord injury. Drug interventions targeting the microcirculation can improve the microenvironment and promote recovery following spinal cord injury. These drugs target the structure and function of the spinal cord microcirculation and are essential for maintaining the normal function of spinal neurons, axons, and glial cells. This review discusses the pathophysiological role of spinal cord microcirculation in spinal cord injury, including its structure and histopathological changes. Further, it summarizes the progress of drug therapies targeting the spinal cord microcirculation after spinal cord injury.

Transsulfuration pathway: a targeting neuromodulator in Parkinson's disease

The transsulfuration pathway (TSP) is a metabolic pathway involving sulfur transfer from homocysteine to cysteine. Transsulfuration pathway leads to many sulfur metabolites, principally glutathione, H2S, taurine, and cysteine. Key enzymes of the TSP, such as cystathionine β-synthase and cystathionine γ-lyase, are essential regulators at multiple levels in this pathway. TSP metabolites are implicated in many physiological processes in the central nervous system and other tissues. TSP is important in controlling sulfur balance and optimal cellular functions such as glutathione synthesis. Alterations in the TSP and related pathways (transmethylation and remethylation) are altered in several neurodegenerative diseases, including Parkinson's disease, suggesting their participation in the pathophysiology and progression of these diseases. In Parkinson's disease many cellular processes are comprised mainly those that regulate redox homeostasis, inflammation, reticulum endoplasmic stress, mitochondrial function, oxidative stress, and sulfur content metabolites of TSP are involved in these damage processes. Current research on the transsulfuration pathway in Parkinson's disease has primarily focused on the synthesis and function of certain metabolites, particularly glutathione. However, our understanding of the regulation of other metabolites of the transsulfuration pathway, as well as their relationships with other metabolites, and their synthesis regulation in Parkinson´s disease remain limited. Thus, this paper highlights the importance of studying the molecular dynamics in different metabolites and enzymes that affect the transsulfuration in Parkinson's disease.

Effects of Nutraceuticals on Cisplatin-Induced Cytotoxicity in HEI-OC1 Cells

Cisplatin is a chemotherapeutic drug for the treatment of several solid tumors, whose use is limited by its nephrotoxicity, neurotoxicity, ototoxicity, and development of resistance. The toxicity is caused by DNA cross-linking, increase in reactive oxygen species and/or depletion of cell antioxidant defenses. The aim of the work was to study the effect of antioxidant compounds (Lisosan G, Taurisolo®) or hydrogen sulfide (H2S)-releasing compounds (erucin) in the auditory HEI-OC1 cell line treated with cisplatin. Cell viability was determined using the MTT assay. Caspase and sphingomyelinase activities were measured by fluorometric and colorimetric methods, respectively. Expression of transcription factors, apoptosis hallmarks and genes codifying for antioxidant response proteins were measured by Western blot and/or RT-qPCR. Lisosan G, Taurisolo® and erucin did not show protective effects. Sodium hydrosulfide (NaHS), a donor of H2S, increased the viability of cisplatin-treated cells and the transcription of heme oxygenase 1, superoxide dismutase 2, NAD(P)H quinone dehydrogenase type 1 and the catalytic subunit of glutamate-cysteine ligase and decreased reactive oxygen species (ROS), the Bax/Bcl2 ratio, caspase-3, caspase-8 and acid sphingomyelinase activity. Therefore, NaHS might counteract the cytotoxic effect of cisplatin by increasing the antioxidant response and by reducing ROS levels and caspase and acid sphingomyelinase activity.

Why Is Iron Deficiency/Anemia Linked to Alzheimer's Disease and Its Comorbidities, and How Is It Prevented?

Impaired iron metabolism has been increasingly observed in many diseases, but a deeper, mechanistic understanding of the cellular impact of altered iron metabolism is still lacking. In addition, deficits in neuronal energy metabolism due to reduced glucose import were described for Alzheimer's disease (AD) and its comorbidities like obesity, depression, cardiovascular disease, and type 2 diabetes mellitus. The aim of this review is to present the molecular link between both observations. Insufficient cellular glucose uptake triggers increased ferritin expression, leading to depletion of the cellular free iron pool and stabilization of the hypoxia-induced factor (HIF) 1α. This transcription factor induces the expression of the glucose transporters (Glut) 1 and 3 and shifts the cellular metabolism towards glycolysis. If this first line of defense is not adequate for sufficient glucose supply, further reduction of the intracellular iron pool affects the enzymes of the mitochondrial electron transport chain and activates the AMP-activated kinase (AMPK). This enzyme triggers the translocation of Glut4 to the plasma membrane as well as the autophagic recycling of cell components in order to mobilize energy resources. Moreover, AMPK activates the autophagic process of ferritinophagy, which provides free iron urgently needed as a cofactor for the synthesis of heme- and iron-sulfur proteins. Excessive activation of this pathway ends in ferroptosis, a special iron-dependent form of cell death, while hampered AMPK activation steadily reduces the iron pools, leading to hypoferremia with iron sequestration in the spleen and liver. Long-lasting iron depletion affects erythropoiesis and results in anemia of chronic disease, a common condition in patients with AD and its comorbidities. Instead of iron supplementation, drugs, diet, or phytochemicals that improve energy supply and cellular glucose uptake should be administered to counteract hypoferremia and anemia of chronic disease.

Organelle-Targeted Fluorescent Probes for Sulfane Sulfur Species

Sulfane sulfurs, which include hydropersulfides (RSSH), hydrogen polysulfides (H2Sn, n > 1), and polysulfides (RSnR, n > 2), play important roles in cellular redox biology and are closely linked to hydrogen sulfide (H2S) signaling. While most studies on sulfane sulfur detection have focused on sulfane sulfurs in the whole cell, increasing the recognition of the effects of reactive sulfur species on the functions of various subcellular organelles has emerged. This has driven a need for organelle-targeted detection methods. However, the detection of sulfane sulfurs, particularly of RSSH and H2Sn, in biological systems is still a challenge due to their low endogenous concentrations and instabilities. In this review, we summarize the development and design of organelle-targeted fluorescent sulfane sulfur probes, examine their organelle-targeting strategies and choices of fluorophores (e.g., ratiometric, near-infrared, etc.), and discuss their mechanisms and ability to detect endogenous and exogenous sulfane sulfur species. We also present the advantages and limitations of the probes and propose directions for future work on this topic.

Sitagliptin attenuates neuronal apoptosis via inhibiting the endoplasmic reticulum stress after acute spinal cord injury

Regulation of endoplasmic reticulum stress (ER) stress-induced apoptosis and nerve regeneration is a hopeful way for acute spinal cord injury (SCI). Sitagliptin (Sita) is one of dipeptidyl peptidase-4 (DPP-4) inhibitor, which is beneficial neurons damaged diseases. However, its protective mechanisms of avoiding nerve injury remain unclear. In this study, we further investigated the mechanism of the anti-apoptotic and neuroprotective effects of Sita in promoting locomotor recovery from SCI. In vivo results showed that Sita treatment reduced neural apoptosis caused by SCI. Moreover, Sita effectively attenuated the ER tress and associated apoptosis in rats with SCI. A striking feature was the occurrence of nerve fiber regeneration at the lesion site, which eventually led to significant locomotion recovery. In vitro results showed that the PC12 cell injury model induced by Thapsigargin (TG) also showed similar neuroprotective effects. Overall, sitagliptin showed potent neuroprotective effects by targeting the ER stress-induced apoptosis both in vivo and vitro, thus facilitating the regeneration of the injured spinal cord.

Feedback Interaction Between Apelin and Endoplasmic Reticulum Stress in the Rat Myocardium

ABSTRACT

Apelin is an endogenous active peptide, playing a crucial role in regulating cardiovascular homeostasis. This study aimed to investigate the interaction between apelin and endoplasmic reticulum stress (ERS). Tunicamycin (Tm) and dithiothreitol (DTT) were used to induce ERS in the ex vivo cultured myocardium of rats. Myocardial injury was determined by the activities of lactate dehydrogenase and creatine kinase-MB in the culture medium. The protein levels of an ERS-associated molecule, apelin, and its receptor angiotensin domain type 1 receptor-associated proteins (APJ) in the myocardium were determined by western blot analysis. The level of apelin in the culture medium was determined by enzyme immunoassay. Administration of Tm and DTT triggered ERS activation and myocardial injury, and led to a decrease in protein levels of apelin and APJ, in a dose-dependent manner. Integrated stress response inhibitor, an inhibitor of eukaryotic initiation factor 2α phosphorylation that is commonly used to prevent activation of protein kinase R-like ER kinase cascades, blocked ERS-induced myocardial injury and reduction of apelin and APJ levels. The ameliorative effect of integrated stress response inhibitor was partially inhibited by [Ala]-apelin-13, an antagonist of APJ. Furthermore, apelin treatment inhibited activation of the 3 branches of ERS induced by Tm and DTT in a dose-dependent manner, thereby preventing Tm-induced or DTT-induced myocardial injury. The negative feedback regulation between ERS activation and apelin/APJ suppression might play a critical role in myocardial injury. Restoration of apelin/APJ signaling provides a potential target for the treatment and prevention of ERS-associated tissue injury and diseases.

Protective effect of Huangpu Tongqiao capsule against Alzheimer's disease through inhibiting the apoptosis pathway mediated by endoplasmic reticulum stress in vitro and in vivo

Objectives

Huangpu Tongqiao Capsule (HPTQC) is a traditional Chinese medicine (TCM) that has been used to treat Alzheimer's disease (AD). This study was to explore the pharmacological action and molecular mechanism of HPTQC in the treatment of AD.

Methods

The possible targets of HTPQC were predicted by the molecular docking technique. Intraperitoneal injection of D-galactose and bilateral injection of Aβ25-35 in hippocampus induced AD rat model. Morris water maze was used to observe learning and memory function. The primary hippocampal neurons were induced by Aβ25-35. Moreover, the apoptosis rate of hippocampal nerve cells was detected through AnnexinV/PI double standard staining. The mRNA and protein levels of GRP78, CHOP, Caspase 12, Caspase 9, and Caspase 3 were detected by PCR and western blot.

Results

The prediction results suggest that HPTQC may act on GRP78. HPTQC significantly improved the learning and memory function, and decreased neuronal apoptosis in vivo and in vitro. In addition, HPTQC could decrease the mRNA and protein expression levels of GRP78, CHOP, Caspase12, Caspase9, and Caspase3, and the effect trend was consistent with the specific inhibitor of GRP78.

Conclusions

HPTQC has a neuroprotective effect against AD by inhibiting the apoptosis pathway mediated by endoplasmic reticulum stress.

The effect of metformin on ameliorating neurological function deficits and tissue damage in rats following spinal cord injury: A systematic review and network meta-analysis

Spinal cord injury (SCI) is a devastating condition with few treatment options. Metformin, a classical antidiabetic and antioxidant, has extended its application to experimental SCI treatment. Here, we performed a systematic review to evaluate the neurobiological roles of metformin for treating SCI in rats, and to assess the potential for clinical translation. PubMed, Embase, China National Knowledge Infrastructure, WanFang data, SinoMed, and Vip Journal Integration Platform databases were searched from their inception dates to October 2021. Two reviewers independently selected controlled studies evaluating the neurobiological roles of metformin in rats following SCI, extracted data, and assessed the quality of methodology and evidence. Pairwise meta-analyses, subgroup analyses and network analysis were performed to assess the roles of metformin in neurological function and tissue damage in SCI rats. Twelve articles were included in this systematic review. Most of them were of moderate-to-high methodological quality, while the quality of evidence from those studies was not high. Generally, Basso, Beattie, and Bresnahan scores were increased in rats treated with metformin compared with controls, and the weighted mean differences (WMDs) between metformin and control groups exhibited a gradual upward trend from the 3rd (nine studies, n = 164, WMD = 0.42, 95% CI = −0.01 to 0.85, P = 0.06) to the 28th day after treatment (nine studies, n = 136, WMD = 3.48, 95% CI = 2.04 to 4.92, P < 0.00001). Metformin intervention was associated with improved inclined plane scores, tissue preservation ratio and number of anterior horn motor neurons. Subgroup analyses indicated an association between neuroprotection and metformin dose. Network meta-analysis showed that 50 mg/kg metformin exhibited greater protection than 10 and 100 mg/kg metformin. The action mechanisms behind metformin were associated with activating adenosine monophosphate-activated protein kinase signaling, regulating mitochondrial function and relieving endoplasmic reticulum stress. Collectively, this review indicates that metformin has a protective effect on SCI with satisfactory safety and we demonstrate a rational mechanism of action; therefore, metformin is a promising candidate for future clinical trials. However, given the limitations of animal experimental methodological and evidence quality, the findings of this pre-clinical review should be interpreted with caution.

The Role of Hydrogen Sulfide Targeting Autophagy in the Pathological Processes of the Nervous System

Autophagy is an important cellular process, involving the transportation of cytoplasmic contents in the double membrane vesicles to lysosomes for degradation. Autophagy disorder contributes to many diseases, such as immune dysfunction, cancers and nervous system diseases. Hydrogen sulfide (H₂S) is a volatile and toxic gas with a rotten egg odor. For a long time, it was considered as an environmental pollution gas. In recent years, H₂S is regarded as the third most important gas signal molecule after NO and CO. H₂S has a variety of biological functions and can play an important role in a variety of physiological and pathological processes. Increasingly more evidences show that H₂S can regulate autophagy to play a protective role in the nervous system, but the mechanism is not fully understood. In this review, we summarize the recent literatures on the role of H₂S in the pathological process of the nervous system by regulating autophagy, and analyze the mechanism in detail, hoping to provide the reference for future related research.

The role of adipose tissue-derived hydrogen sulfide in inhibiting atherosclerosis

Hydrogen sulfide (H₂S) is the third gaseous signaling molecule discovered in the body after NO and CO and plays an important organismal protective role in various diseases. Within adipose tissue, related catalytic enzymes (cystathionine-β-synthetase, cystathionine-γ-lyase, and 3-mercaptopyruvate transsulfuration enzyme) can produce and release endogenous H₂S. Atherosclerosis (As) is a pathological change in arterial vessels that is closely related to abnormal glucose and lipid metabolism and a chronic inflammatory response. Previous studies have shown that H₂S can act on the cardiovascular system, exerting effects such as improving disorders of glycolipid metabolism, alleviating insulin resistance, protecting the function of vascular endothelial cells, inhibiting vascular smooth muscle cell proliferation and migration, regulating vascular tone, inhibiting the inflammatory response, and antagonizing the occurrence and development of As.

Hydrogen sulfide action in the regulation of plant autophagy

Hydrogen sulfide is a signaling molecule with a well-established impact on both plant and animal physiology. Intense investigation into the regulation of autophagy by sulfide in Arabidopsis thaliana has revealed that the post-translational modification of persulfidation/S-sulfhydration plays a key role. In this review focused on plants, we discuss the nature of the sulfide molecule involved in the regulation of autophagy, the final outcome of this modification, and the persulfidated autophagy proteins identified so far. A detailed outline of the actual knowledge of the regulation mechanism of the autophagy-related proteins ATG4a and ATG18a from Arabidopsis by sulfide is also included. This information will be instrumental for furthering research on the regulation of autophagy by sulfide.

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.

Dietary Plant Polyphenols as the Potential Drugs in Neurodegenerative Diseases: Current Evidence, Advances, and Opportunities

Neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), are characterized by the progressive degeneration of neurons. Although the etiology and pathogenesis of neurodegenerative diseases have been studied intensively, the mechanism is still in its infancy. In general, most neurodegenerative diseases share common molecular mechanisms, and multiple risks interact and promote the pathologic process of neurogenerative diseases. At present, most of the approved drugs only alleviate the clinical symptoms but fail to cure neurodegenerative diseases. Numerous studies indicate that dietary plant polyphenols are safe and exhibit potent neuroprotective effects in various neurodegenerative diseases. However, low bioavailability is the biggest obstacle for polyphenol that largely limits its adoption from evidence into clinical practice. In this review, we summarized the widely recognized mechanisms associated with neurodegenerative diseases, such as misfolded proteins, mitochondrial dysfunction, oxidative damage, and neuroinflammatory responses. In addition, we summarized the research advances about the neuroprotective effect of the most widely reported dietary plant polyphenols. Moreover, we discussed the current clinical study and application of polyphenols and the factors that result in low bioavailability, such as poor stability and low permeability across the blood-brain barrier (BBB). In the future, the improvement of absorption and stability, modification of structure and formulation, and the combination therapy will provide more opportunities from the laboratory into the clinic for polyphenols. Lastly, we hope that the present review will encourage further researches on natural dietary polyphenols in the treatment of neurodegenerative diseases.

H2S Donors and Their Use in Medicinal Chemistry

Hydrogen sulfide (H2S) is a ubiquitous gaseous signaling molecule that has an important role in many physiological and pathological processes in mammalian tissues, with the same importance as two others endogenous gasotransmitters such as NO (nitric oxide) and CO (carbon monoxide). Endogenous H2S is involved in a broad gamut of processes in mammalian tissues including inflammation, vascular tone, hypertension, gastric mucosal integrity, neuromodulation, and defense mechanisms against viral infections as well as SARS-CoV-2 infection. These results suggest that the modulation of H2S levels has a potential therapeutic value. Consequently, synthetic H2S-releasing agents represent not only important research tools, but also potent therapeutic agents. This review has been designed in order to summarize the currently available H2S donors; furthermore, herein we discuss their preparation, the H2S-releasing mechanisms, and their -biological applications.

The Mitochondrial Carnitine Acyl-carnitine Carrier (SLC25A20): Molecular Mechanisms of Transport, Role in Redox Sensing and Interaction with Drugs

The SLC25A20 transporter, also known as carnitine acyl-carnitine carrier (CAC), catalyzes the transport of short, medium and long carbon chain acyl-carnitines across the mitochondrial inner membrane in exchange for carnitine. The 30-year story of the protein responsible for this function started with its purification from rat liver mitochondria. Even though its 3D structure is not yet available, CAC is one of the most deeply characterized transport proteins of the inner mitochondrial membrane. Other than functional, kinetic and mechanistic data, post-translational modifications regulating the transport activity of CAC have been revealed. CAC interactions with drugs or xenobiotics relevant to human health and toxicology and the response of the carrier function to dietary compounds have been discovered. Exploiting combined approaches of site-directed mutagenesis with chemical targeting and bioinformatics, a large set of data on structure/function relationships have been obtained, giving novel information on the molecular mechanism of the transport catalyzed by this protein.

Metformin alleviates high glucose-induced ER stress and inflammation by inhibiting the interaction between caveolin1 and AMPKα in rat astrocytes

Hyperglycemia-induced endoplasmic reticulum (ER) stress and inflammatory response afflict neuropathological diseases (such as epilepsy and Alzheimer's disease). Astrocytes are the critical cells that mediate brain inflammation in this process. Metformin is a kind of hypoglycemic drugs widely used in clinical practice, which has anti-inflammatory and antioxidant effects. However, the biological mechanism of metformin in regulating inflammation and ER stress induced by hyperglycemia remains unclear. Therefore, in this study, rat primary astrocytes were preincubated with metformin and AMPK agonist AICAR for 1 h prior to administration of high glucose (33 mM glucose). Our findings indicated that metformin treatment inhibited the elevated ER stress and inflammation in high glucose-treated astrocytes. Moreover, metformin inhibited the formation of caveolin1/AMPKα complex. Additionally, the effects of AICAR on astrocytes were similar to metformin. In conclusion, metformin reduced high glucose-induced ER stress and inflammation by inhibiting the interaction between caveolin1 and AMPKα, suggesting that the caveolin1/AMPKα complex may be a potential therapeutic target for metformin.