Homocysteine activates autophagy by inhibition of CFTR expression via interaction between DNA methylation and H3K27me3 in mouse liver

[H3K27me3 Expression Level and Its Epigenetic Regulation Mechanisms in Th17 Cell Differentiation in Patients With Ankylosing Spondylitis]

Objective

To investigate the roles of histone H3K27me3 methylation and its regulatory enzymes JMJD3 and EZH2 in the differentiation of Th17 cells in ankylosing spondylitis (AS), to unveil their potential involvement in the pathogenesis of AS, and to provide new strategies and targets for the clinical treatment of AS by analyzing the methylation state of H3K27me3 and its interactions with Th17-related factors.

Methods

A total of 84 AS patients (42 active AS patiens and 42 patients in the stable phase of AS) were enrolled for the study, while 84 healthy volunteers were enrolled as the controls. Blood samples were collected. Peripheral blood mononuclear cells were isolated. ELISA assay was performed to examine Th17 cells and the relevant cytokines IL-21, IL-22, and IL-17. The mRNA expressions of RORc, JAK2, and STAT3 were analyzed by RT-PCR, the protein expressions of RORc, JAK2/STAT3 pathway protein, H3K27me3 and the relevant protease (EZH2 and JMJD3) were determined by Western blot. Correlation between H3K27me3, EZH2 and JMJD3 and the key signaling pathway molecules of Th cell differentiation was analyzed by Pearson correlation analysis.

Results

The mRNA expressions of RORc, JAK2, and STAT3 were significantly higher in the active phase group than those in the stable phase group ( P<0.05). The relative grayscale values of H3K27me3 and EZH2 in the active phase group were lower than those of the stable phase group, which were lower than those of the control group, with the differences being statistically significant ( P<0.05). The relative grayscale values of JMJD3, RORc, JAK2, pJAK2, STAT3, and pSTAT3 proteins were significantly higher in the active phase group than those in the stable phase group, which were higher than those in the control group (all P<0.05). The proportion of Th17 and the expression level of inflammatory factors in the active period group were higher than those in the other two groups (P<0.05). H3K27me3 was negatively correlated with RORc, JAK2, STAT3, and IL-17, JMJD3 was positvely correlated with JAK2, STAT3, and IL-17, and EZH2 was negatively correlated with JAK2, STAT3, and IL-17 (all P<0.05).

Conclusion

The low expression of H3K27me3 in AS is influenced by the gene loci JMJD3 and EZH2, which can regulate the differentiation of Th17 cells and thus play a role in the pathogenesis and progression of AS.

Epigenetic regulation of H3K27me3 in laying hens with fatty liver hemorrhagic syndrome induced by high-energy and low-protein diets

BACKGROUND

Fatty liver hemorrhagic syndrome (FLHS) in the modern poultry industry is primarily caused by nutrition. Despite encouraging progress on FLHS, the mechanism through which nutrition influences susceptibility to FLHS is still lacking in terms of epigenetics.

RESULTS

In this study, we analyzed the genome-wide patterns of trimethylated lysine residue 27 of histone H3 (H3K27me3) enrichment by chromatin immunoprecipitation-sequencing (ChIP-seq), and examined its association with transcriptomes in healthy and FLHS hens. The study results indicated that H3K27me3 levels were increased in the FLHS hens on a genome-wide scale. Additionally, H3K27me3 was found to occupy the entire gene and the distant intergenic region, which may function as silencer-like regulatory elements. The analysis of transcription factor (TF) motifs in hypermethylated peaks has demonstrated that 23 TFs are involved in the regulation of liver metabolism and development. Transcriptomic analysis indicated that differentially expressed genes (DEGs) were enriched in fatty acid metabolism, amino acid, and carbohydrate metabolism. The hub gene identified from PPI network is fatty acid synthase (FASN). Combined ChIP-seq and transcriptome analysis revealed that the increased H3K27me3 and down-regulated genes have significant enrichment in the ECM-receptor interaction, tight junction, cell adhesion molecules, adherens junction, and TGF-beta signaling pathways.

CONCLUSIONS

Overall, the trimethylation modification of H3K27 has been shown to have significant regulatory function in FLHS, mediating the expression of crucial genes associated with the ECM-receptor interaction pathway. This highlights the epigenetic mechanisms of H3K27me3 and provides insights into exploring core regulatory targets and nutritional regulation strategies in FLHS.

Insights into DNMT1 and programmed cell death in diseases

DNMT1 (DNA methyltransferase 1) is the predominant member of the DNMT family and the most abundant DNMT in various cell types. It functions as a maintenance DNMT and is involved in various diseases, including cancer and nervous system diseases. Programmed cell death (PCD) is a fundamental mechanism that regulates cell proliferation and maintains the development and homeostasis of multicellular organisms. DNMT1 plays a regulatory role in various types of PCD, including apoptosis, autophagy, necroptosis, ferroptosis, and others. DNMT1 is closely associated with the development of various diseases by regulating key genes and pathways involved in PCD, including caspase 3/7 activities in apoptosis, Beclin 1, LC3, and some autophagy-related proteins in autophagy, glutathione peroxidase 4 (GPX4) and nuclear receptor coactivator 4 (NCOA4) in ferroptosis, and receptor-interacting protein kinase 1-receptor-interacting protein kinase 3-mixed lineage kinase domain-like protein (RIPK1-RIPK3-MLKL) in necroptosis. Our study summarizes the regulatory relationship between DNMT1 and different types of PCD in various diseases and discusses the potential of DNMT1 as a common regulatory hub in multiple types of PCD, offering a perspective for therapeutic approaches in disease.

Increased DNMT1 Involvement in the Activation of LO2 Cell Death Induced by Silver Nanoparticles via Promoting TFEB-Dependent Autophagy

The accumulation of exogenous silver nanoparticles (AgNPs) will terminally bring about liver injury, including cell death, where DNA methylation tends to be a crucial epigenetic modulator. The change in the cell autophagy level verified to be closely associated with hepatocyte death has been followed with wide interest. But the molecular toxicological mechanisms of AgNPs in relation to DNA methylation, autophagy, and cell death remain inconclusive. To address the issue above, in LO2 cells treated with increasing concentrations of AgNPs (0, 5, 10, and 20 μg/mL), a cell cytotoxicity assay was performed to analyze the level of cell death, which also helped to choose an optimal concentration for next experiments. An immunofluorescence assay was used to determine the autophagic flux as well as TFEB translocation, with qRT-PCR and western blot being used to analyze the expression level of autophagy-related genes and proteins. According to our findings, in the determination of cell viability, 20 μg/mL (AgNPs) was adopted as the best working concentration. LO2 cell death, autophagy, and TFEB nuclear translocation were induced by AgNPs, which could be inhibited by lysosome inhibitor chloroquine (CQ) or siRNA specific for TFEB. Moreover, AgNP exposure led to DNA hypermethylation, with DNMT1 taking part mainly, which could be obviously prevented by 5-Aza-2'-deoxycytidine (5-AzaC) or trichostatin A (TSA) treatment or DNMT1 knockout in LO2 cells. Our studies suggest that through TFEB-dependent cell autophagy, increased DNMT1 may facilitate cell death induced by AgNPs.

Advances in the role of epigenetics in homocysteine-related diseases

Homocysteine has a wide range of biological effects. However, the specific molecular mechanism of its pathogenicity is still unclear. The diseases induced by hyperhomocysteinemia (HHcy) are called homocysteine-related diseases. Clinical treatment of HHcy is mainly through folic acid and B-complex vitamins, which are not effective in reducing the associated end point events. Epigenetics is the alteration of heritable genes caused by DNA methylation, histone modification, noncoding RNAs and chromatin remodeling without altering the DNA sequence. In recent years the role of epigenetics in homocysteine-associated diseases has been gradually discovered. This article summarizes the latest evidence on the role of epigenetics in HHcy, providing new directions for its prevention and treatment.

Hyperhomocysteinemia and Accelerated Aging: The Pathogenic Role of Increased Homocysteine in Atherosclerosis, Osteoporosis, and Neurodegeneration

Cardiovascular diseases and osteoporosis, seemingly unrelated disorders that occur with advanced age, share major pathogenetic mechanisms contributing to accelerated atherosclerosis and bone loss. Hyperhomocysteinemia (hHcy) is among these mechanisms that can cause both vascular and bone disease. In its more severe form, hHcy can present early in life as homocystinuria, an inborn error of metabolic pathways of the sulfur-containing amino acid methionine. In its milder forms, hHcy may go undiagnosed and untreated into adulthood. As such, hHcy may serve as a potential therapeutic target for cardiovascular disease, osteoporosis, thrombophilia, and neurodegeneration, collectively representing accelerated aging. Multiple trials to lower cardiovascular risk and improve bone density with homocysteine-lowering agents, yet none has proven to be clinically meaningful. To understand this unmet clinical need, this review will provide mechanistic insight into the pathogenesis of vascular and bone disease in hHcy, using homocystinuria as a model for accelerated atherosclerosis and bone density loss, a model for accelerated aging.

Regulation of autophagy gene expression and its implications in cancer

Autophagy is a catabolic cellular process that targets and eliminates superfluous cytoplasmic components via lysosomal degradation. This evolutionarily conserved process is tightly regulated at multiple levels as it is critical for the maintenance of homeostasis. Research in the past decade has established that dysregulation of autophagy plays a major role in various diseases, such as cancer and neurodegeneration. However, modulation of autophagy as a therapeutic strategy requires identification of key players that can fine tune the induction of autophagy without complete abrogation. In this Review, we summarize the recent discoveries on the mechanism of regulation of ATG (autophagy related) gene expression at the level of transcription, post transcription and translation. Furthermore, we briefly discuss the role of aberrant expression of ATG genes in the context of cancer.

Homocysteine accelerates hepatocyte autophagy by upregulating TFEB via DNMT3b-mediated DNA hypomethylation

Autophagy plays a critical role in the physiology and pathophysiology of hepatocytes. High level of homocysteine (Hcy) promotes autophagy in hepatocytes, but the underlying mechanism is still unknown. Here, we investigate the relationship between Hcy-induced autophagy level and the expression of nuclear transcription factor EB (TFEB). The results show that Hcy-induced autophagy level is mediated by upregulation of TFEB. Silencing of TFEB decreases the level of autophagy-related protein LC3BII/I and increases p62 expression level in hepatocytes after exposure to Hcy. Moreover, the effect of Hcy on the expression of TFEB is regulated by hypomethylation of the TFEB promoter catalyzed by DNA methyltransferase 3b (DNMT3b). In summary, this study shows that Hcy can activate autophagy by inhibiting DNMT3b-mediated DNA methylation and upregulating TFEB expression. These findings provide another new mechanism for Hcy-induced autophagy in hepatocytes.

Pharmacological inhibition of CFTR attenuates nonalcoholic steatohepatitis (NASH) progression in mice

Nonalcoholic steatohepatitis (NASH) is considered a pivotal stage in nonalcoholic fatty liver disease (NAFLD) progression and increases the risk of end-stage liver diseases such as fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). The etiology of NASH is multifactorial and identifying reliable molecular players has proven difficult. Presently, there are no approved drugs for NASH treatment, which has become a leading cause of liver transplants worldwide. Here, using public human transcriptomic NAFLD dataset, we uncover Cystic fibrosis transmembrane conductance receptor (CFTR) as a differentially expressed gene in the livers of human NASH patients. Similarly, murine Cftr expression was also found to be upregulated in two mouse models of diet-induced NASH. Furthermore, the pharmacological inhibition of CFTR significantly reduced NASH progression in mice and its overexpression aggravated lipotoxicity in human hepatic cells. These results, thus, underscore the involvement of murine Cftr in the pathogenesis of NASH and raise the intriguing possibility of its pharmacological inhibition in human NASH.

Antagonizing EZH2 combined with vitamin D3 exerts a synergistic role in anti-fibrosis through bidirectional effects on hepatocytes and hepatic stellate cells

BACKGROUND AND AIM

Whether vitamin D3 (VD3) supplementation is associated with improved liver fibrosis is controversial.

METHODS

Liver fibrosis models were treated with VD3, active VD (1,25-OH2 Vitamin D3), or collaboration with GSK126 (Ezh2 inhibitor), respectively. Hepatic stellate cells (HSCs) were co-cultured with hepatocytes and then stimulated with TGF-β. Autophagy of hepatocytes was determined after the intervention of 1,25-OH2 Vitamin D3 and GSK126. Also, the active status of HSCs and the mechanism with 1,25-OH2 Vitamin D3 and GSK126 intervention were detected.

RESULTS

1,25-OH2 Vitamin D3, but not VD3, is involved in anti-fibrosis and partially improves liver function, which might be associated with related enzymes and receptors (especially CYP2R1), leading to decreased of its biotransformation. GSK126 plays a synergistic role in anti-fibrosis. The co-culture system showed increased hepatocyte autophagy after HSCs activation. Supplementation with 1,25-OH2 Vitamin D3 or combined GSK126 reduced these effects. Further studies showed that 1,25-OH2 Vitamin D3 promoted H3K27 methylation of DKK1 promoter through VDR/Ezh2 due to the weakening for HSCs inhibitory signal.

CONCLUSIONS

VD3 bioactive form 1,25-OH2 Vitamin D3 is responsible for the anti-fibrosis, which might have bidirectional effects on HSCs by regulating histone modification. The inhibitor of Ezh2 plays a synergistic role in this process.

Epigenetic and post-translational modifications in autophagy: biological functions and therapeutic targets

Autophagy is a conserved lysosomal degradation pathway where cellular components are dynamically degraded and re-processed to maintain physical homeostasis. However, the physiological effect of autophagy appears to be multifaced. On the one hand, autophagy functions as a cytoprotective mechanism, protecting against multiple diseases, especially tumor, cardiovascular disorders, and neurodegenerative and infectious disease. Conversely, autophagy may also play a detrimental role via pro-survival effects on cancer cells or cell-killing effects on normal body cells. During disorder onset and progression, the expression levels of autophagy-related regulators and proteins encoded by autophagy-related genes (ATGs) are abnormally regulated, giving rise to imbalanced autophagy flux. However, the detailed mechanisms and molecular events of this process are quite complex. Epigenetic, including DNA methylation, histone modifications and miRNAs, and post-translational modifications, including ubiquitination, phosphorylation and acetylation, precisely manipulate gene expression and protein function, and are strongly correlated with the occurrence and development of multiple diseases. There is substantial evidence that autophagy-relevant regulators and machineries are subjected to epigenetic and post-translational modulation, resulting in alterations in autophagy levels, which subsequently induces disease or affects the therapeutic effectiveness to agents. In this review, we focus on the regulatory mechanisms mediated by epigenetic and post-translational modifications in disease-related autophagy to unveil potential therapeutic targets. In addition, the effect of autophagy on the therapeutic effectiveness of epigenetic drugs or drugs targeting post-translational modification have also been discussed, providing insights into the combination with autophagy activators or inhibitors in the treatment of clinical diseases.

One-Carbon and Polyamine Metabolism as Cancer Therapy Targets

Cancer metabolic reprogramming is essential for maintaining cancer cell survival and rapid replication. A common target of this metabolic reprogramming is one-carbon metabolism which is notable for its function in DNA synthesis, protein and DNA methylation, and antioxidant production. Polyamines are a key output of one-carbon metabolism with widespread effects on gene expression and signaling. As a result of these functions, one-carbon and polyamine metabolism have recently drawn a lot of interest for their part in cancer malignancy. Therapeutic inhibitors that target one-carbon and polyamine metabolism have thus been trialed as anticancer medications. The significance and future possibilities of one-carbon and polyamine metabolism as a target in cancer therapy are discussed in this review.

DNA methyltransferase 1 (DNMT1) suppresses mitophagy and aggravates heart failure via the microRNA-152-3p/ETS1/RhoH axis

DNA methyltransferase 1 (DNMT1) shows close link with heart disease. This study aimed to define the role DNMT1 plays in heart failure and determine the underlying mechanism. Expression of microRNA (miR)-152-3p, DNMT1, E26 transformation specific-1 (ETS1) and ras homolog gene family member H (RhoH) was determined by RT-qPCR and/or western blot analysis. The interaction between miR-152-3p and ETS1 was predicted and verified. Methylation of the miR-152-3p promoter region was assessed using methylation-specific PCR. H9c2 cells were chosen for in vitro assays to examine the regulatory role of DNMT1 in autophagy and mitophagy with respect to miR-152-3p/ETS1/RhoH. Doxorubicin (DOX)-induced rat models of heart failure were employed for in vivo validation. DNMT1 expression was upregulated in the heart tissues of DOX-induced rats, where it showed an inverse correlation with miR-152-3p expression. Moreover, DNMT1 was shown to enhance methylation of the miR-152-3p promoter region and suppress its expression, leading to inhibition of mitophagy in H9c2 cells. In addition, DNMT1 enhanced expression of ETS1, which further elevated RhoH expression. Moreover, ETS1-elevated RhoH reduced cell viability and promoted autophagy and mitophagy in H9c2 cells upon treatment with DOX. Next, in vivo results demonstrated that depletion of DNMT1 protected rats from heart failure in a miR-152-3p/ETS1/RhoH-dependent manner. Overall, these findings indicate that DNMT1 may inhibit expression of miR-152-3p by promoting the methylation of miR-152-3p and enhancing the expression of ETS1, thereby inducing RHOH transcriptional activation and inhibiting mitochondrial autophagy, ultimately promoting the development of heart failure.

Folate ameliorates homocysteine-induced osteoblast dysfunction by reducing endoplasmic reticulum stress-activated PERK/ATF-4/CHOP pathway in MC3T3-E1 cells

INTRODUCTION

Homocysteine (Hcy) is considered a newly identified risk factor for osteoporosis. Nevertheless, the underlying mechanism of folate (FA), a key factor in the metabolism of Hcy, in protection against osteoblast dysfunction remains unclear. The purpose of this study was to investigate the mechanism by which FA attenuates Hcy-induced osteoblast damage.

MATERIALS AND METHODS

The Hcy-induced MC3T3-E1 cells were treated with different concentrations of FA. Cell morphology, cell density, cell proliferation ability, alkaline phosphatase (ALP) activity and mineralization capacity were observed and determined; the gene expression of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (BAX) and ERS-associated factors, including glucose-regulated protein 78 (GRP-78), activating transcription factor 4 (ATF-4) and growth arrest and DNA damage inducible gene 153 (CHOP/GADD153), were assessed by RT-PCR; and protein levels of GRP-78 and ATF-4 were analyzed by western blotting.

RESULTS

Hcy suppressed the proliferation, differentiation and mineralization ability of MC3T3-E1 cells in a concentration-dependent manner and activated the ERS signaling pathway. After intervention with different concentrations of FA, the cell viability and density, ALP activity, number of mineralized nodules, calcium content and Bcl-2 gene expression were all significantly increased, whereas the gene expression of GRP-78, CHOP/GADD153, ATF-4 and Bax was markedly downregulated, and protein levels of GRP-78 and ATF-4 were also markedly decreased.

CONCLUSION

The adverse effects of Hcy on osteoblast differentiation are dose dependent. FA not only protects against osteoblasts apoptosis but also has a direct osteogenic effect on Hcy-induced osteoblasts, which could be partially mediated by inhibition of the PERK-activated ERS pathway.

Increased homocysteine regulated by androgen activates autophagy by suppressing the mammalian target of rapamycin pathway in the granulosa cells of polycystic ovary syndrome mice

The purpose of this study was to explore the potential molecular mechanisms of excess homocysteine in relation to autophagic activity in the ovarian tissue of polycystic ovarian syndrome (PCOS) with hyperandrogenism.A PCOS model was constructed using ICR mice. ELISA was used to detect the Hcy levels in the serum and ovarian tissues of PCOS model. The expression level of key enzymes (Methionine synthase and Betaine-homocysteine methyltransferase, MTR and BHMT) in homocysteine metabolism and autophagy-related proteins were detected in ovarian tissues and mouse granulosa cells (mGCs) that were treated with homocysteine, androgen, autophagy inhibitors or BHMT-expressing plasmid by western blot and immunohistochemistry. Electron microscope experiments were used to evaluate autophagosomes in Hcy-treated mGCs. The prenatally androgenized (PNA) PCOS mouse model showed hyperhomocysteinemia and hyperandrogenism. Homocysteine levels displayed a significant increase, while its metabolic enzymes levels were significantly decreased in ovarian tissues of PCOS mice and dihydrotestosterone (DHT)-stimulated mGCs. The LC3II and Beclin1 expression levels were increased and the P62 and p-mTOR levels were decreased in vivo in ovarian tissue from the PCOS mice. The in vitro data were similarly with the in vivo by stimulation of mGCs with DHT or homocysteine. These effects could be diminished by the autophagy inhibitor (MHY1485), androgen receptor antagonists (ARN509) or BHMT-expressing plasmid. Androgen increases homocysteine concentration by downregulating the key enzymes in homocysteine metabolism. And then Hcy promotes GCs autophagy via the mTOR signal pathway.

Autophagy in Cancer: A Metabolic Perspective

Autophagy is an intracellular catabolic degradative process in which damaged cellular organelles, unwanted proteins and different cytoplasmic components get recycled to maintain cellular homeostasis or metabolic balance. During autophagy, a double membrane vesicle is formed to engulf these cytosolic materials and fuse to lysosomes wherein the entire cargo degrades to be used again. Because of this unique recycling ability of cells, autophagy is a universal stress response mechanism. Dysregulation of autophagy leads to several diseases, including cancer, neurodegeneration and microbial infection. Thus, autophagy machineries have become targets for therapeutics. This chapter provides an overview of the paradoxical role of autophagy in tumorigenesis in the perspective of metabolism.

miR-30a-5p promotes glomerular podocyte apoptosis via DNMT1-mediated hypermethylation under hyperhomocysteinemia

Abnormal elevation of homocysteine (Hcy) level is closely related to the development and progression of chronic kidney disease (CKD), with the molecular mechanisms that are not fully elucidated. Given the demonstration that miR-30a-5p is specifically expressed in glomerular podocytes, in the present study we aimed to investigate the role and potential underlying mechanism of miR-30a-5p in glomerular podocyte apoptosis induced by Hcy. We found that elevated Hcy downregulates miR-30a-5p expression in the mice and Hcy-treated podocytes, and miR-30a-5p directly targets the 3'-untranslated region (3'-UTR) of the forkhead box A1 (FOXA1) and overexpression of miR-30a-5p inhibits FOXA1 expression. By nMS-PCR and MassARRAY quantitative methylation analysis, we showed the increased DNA methylation level of miR-30a-5p promoter both and . Meanwhile, dual-luciferase reporter assay showed that the region between --1400 and --921 bp of miR-30a-5p promoter is a possible regulatory element for its transcription. Mechanistic studies indicated that DNA methyltransferase enzyme 1 (DNMT1) is the key regulator of miR-30a-5p, which in turn enhances miR-30a-5p promoter methylation level and thereby inhibits its expression. Taken together, our results revealed that epigenetic modification of miR-30a-5p is involved in glomerular podocyte injury induced by Hcy, providing a diagnostic marker candidate and novel therapeutic target in CKD induced by Hcy.

Mechanism and Therapeutic Opportunities of Histone Modifications in Chronic Liver Disease

Chronic liver disease (CLD) represents a global health problem, accounting for the heavy burden of disability and increased health care utilization. Epigenome alterations play an important role in the occurrence and progression of CLD. Histone modifications, which include acetylation, methylation, and phosphorylation, represent an essential part of epigenetic modifications that affect the transcriptional activity of genes. Different from genetic mutations, histone modifications are plastic and reversible. They can be modulated pharmacologically without changing the DNA sequence. Thus, there might be chances to establish interventional solutions by targeting histone modifications to reverse CLD. Here we summarized the roles of histone modifications in the context of alcoholic liver disease (ALD), metabolic associated fatty liver disease (MAFLD), viral hepatitis, autoimmune liver disease, drug-induced liver injury (DILI), and liver fibrosis or cirrhosis. The potential targets of histone modifications for translation into therapeutics were also investigated. In prospect, high efficacy and low toxicity drugs that are selectively targeting histone modifications are required to completely reverse CLD and prevent the development of liver cirrhosis and malignancy.

Interaction between PSMD10 and GRP78 accelerates endoplasmic reticulum stress-mediated hepatic apoptosis induced by homocysteine

Background

The liver plays an important role in production and metabolism of homocysteine (Hcy), which has been reported to be involved in liver injury. In our previous work, we confirm that Hcy can induce liver injury by activating endoplasmic reticulum (ER) stress. However, the underlying mechanisms remain largely unknown.

Results

In present study, we established the Hcy-induced liver injury model by feeding cbs^+/− mice with high methionine diet, and found that a considerable mass of disordered arrangement of hepatocytes and enlarged space between hepatocytes were frequently occurred in the liver of cbs^+/− mice, accompanied with elevated expression levels of apoptosis-related proteins. In addition, Hcy could activate ER stress both in cbs^+/− mice and hepatocytes. Mechanistically, Hcy promoted the expression levels of proteasome 26S subunit non-ATPase 10 (PSMD10) in hepatocytes; and the expression of ER stress indicators and apoptosis-associated proteins were significantly suppressed when PSMD10 was silenced in hepatocytes under Hcy treatment. Moreover, bioinformatics analysis and luciferase reporter assay demonstrated that PSMD10 was a target gene of miR-212-5p. Consistently, miR-212-5p overexpression could inhibit ER stress-mediated apoptosis of hepatocytes under Hcy treatment. With the help of co-immunoprecipitation assay, we identified that the interaction between PSMD10 and GRP78 accelerated ER stress-mediated hepatic apoptosis induced by Hcy.

Conclusions

Our findings indicate that miR-212-5p directly targets PSMD10 and subsequently activates ER stress to promote Hcy-induced apoptosis of hepatocytes. We propose that endogenous PSMD10 physically interacts with GRP78 to regulate ER stress. Our study may provide the therapeutic target for the liver injury induced by Hcy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00455-z.

miR-195-3p alleviates homocysteine-mediated atherosclerosis by targeting IL-31 through its epigenetics modifications

Atherosclerosis is a serious age-related disease, which has a tremendous impact on health care globally. Macrophage inflammation is crucial for the initiation and progression of atherosclerosis, and microRNAs (miRNAs) recently have emerged as potent modulators of inflammation, while the underlying mechanisms of its involvement in homocysteine (Hcy)-mediated macrophage inflammation of atherosclerosis remain largely unknown. Here, we demonstrated that elevated Hcy inhibits the expression of miR-195-3p, which in turn enhances IL-31 expression and thereby causes the secretion of macrophages pro-inflammatory factors IL-1β, IL-6 and TNF-α and accelerate atherosclerosis. Furthermore, we identified that Hcy can induce DNA hypermethylation and H3K9 deacetylation of miR-195-3p promoter due to the increased the binding of DNMT3a and HDAC11 at its promoter. More importantly, Sp1 interacts with DNMT3a suppressed the binding of HDAC11 at miR-195-3p promoter and promoted its transcription. In summary, our results revealed a novel mechanism that transcriptional and epigenetic regulation of miR-195-3p inhibits macrophage inflammation through targeting IL-31, which provides a candidate diagnostic marker and novel therapeutic target in cardiovascular diseases induced by Hcy.

DNA Methylation-Mediated Low Expression of CFTR Stimulates the Progression of Lung Adenocarcinoma

In recent years, the mortality rate of lung adenocarcinoma (LUAD) is persistently increasing, which has already caused a huge impact on human living standards. Hence, there is an urgent need to probe the molecular mechanism of LUAD progression, so as to disclose prognostic and diagnostic markers for patients with LUAD. Methylation 450 K data and mRNA expression data of LUAD were obtained via bioinformatics analysis to screen methylation-driven genes. The expression of the target gene was detected through qRT-PCR, while the methylation level was evaluated via methylation-specific PCR (MSP). The impact of the gene on cell proliferation, migration, invasion, apoptosis and cell cycle was measured through CCK-8, wound healing, Transwell invasion assay, and flow cytometry. CFTR was defined by bioinformatics analysis as the target gene for this study. qRT-PCR revealed that CFTR was lowly expressed in LUAD cells. MSP displayed that the CFTR promoter region in LUAD cells was hypermethylated, and demethylation could pronouncedly increase the level of CFTR mRNA in LUAD cells. Cell biological functional experiments exhibited that CFTR hindered cell proliferation, migration, and invasion, fostered cell apoptosis of LUAD, and blocked the cell cycle in G2-M phase. CFTR was hypermethylated in LUAD, which mediated the low expression of CFTR in LUAD to stimulate the progression of LUAD.

Early Life Nutrition and Mental Health: The Role of DNA Methylation

Does the quality of our diet during early life impact our long-term mental health? Accumulating evidence suggests that nutrition interacts with our genes and that there is a strong association between the quality of diet and mental health throughout life. Environmental influences such as maternal diet during pregnancy or offspring diet have been shown to cause epigenetic changes during critical periods of development, such as chemical modifications of DNA or histones by methylation for the regulation of gene expression. One-carbon metabolism, which consists of the folate and methionine cycles, is influenced by the diet and generates S-Adenosylmethinoine (SAM), the main methyl donor for methylation reactions such as DNA and histone methylation. This review provides current knowledge on how the levels of one-carbon metabolism associated micronutrients such as choline, betaine, folate, methionine and B vitamins that play a role in brain function can impact our well-being and mental health across the lifespan. Micronutrients that act as methyl donors for SAM formation could affect global or gene methylation, altering gene expression and phenotype. Strategies should then be adopted to better understand how these nutrients work and their impact at different stages of development to provide individualized dietary recommendations for better mental health outcomes.

Epigenetic Regulation of Autophagy Beyond the Cytoplasm: A Review

Autophagy is a highly conserved catabolic process induced under various stress conditions to protect the cell from harm and allow survival in the face of nutrient- or energy-deficient states. Regulation of autophagy is complex, as cells need to adapt to a continuously changing microenvironment. It is well recognized that the AMPK and mTOR signaling pathways are the main regulators of autophagy. However, various other signaling pathways have also been described to regulate the autophagic process. A better understanding of these complex autophagy regulatory mechanisms will allow the discovery of new potential therapeutic targets. Here, we present a brief overview of autophagy and its regulatory pathways with emphasis on the epigenetic control mechanisms.

Homocysteine induces podocyte apoptosis by regulating miR-1929-5p expression through c-Myc, DNMT1 and EZH2

Chronic kidney disease (CKD) is a common and complex disease in kidneys which has been associated with an increased risk of renal cell carcinoma. Elevated homocysteine (Hcy) levels are known to influence the development and progression of CKD by regulating podocyte injury and apoptosis. To investigate the molecular mechanisms triggered in podocytes by Hcy, we used cbs^+/− mice and observed that higher Hcy levels increased the apoptosis rate of podocytes with accompanying glomerular damage. Hcy‐induced podocyte injury and apoptosis in cbs^+/− mice was regulated by inhibition of microRNA (miR)‐1929‐5p expression. Overexpression of miR‐1929‐5p in podocytes inhibited apoptosis by upregulating Bcl‐2. Furthermore, the expression of miR‐1929‐5p was regulated by epigenetic modifications of its promoter. Hcy upregulated DNA methyltransferase 1 (DNMT1) and enhancer of zeste homolog 2 (EZH2) levels, resulting in increased DNA methylation and H3K27me3 levels on the miR‐1929‐5p promoter. Additionally, we observed that c‐Myc recruited DNMT1 and EZH2 to the miR‐1929‐5p promoter and suppressed the expression of miR‐1929‐5p. In summary, we demonstrated that Hcy promotes podocyte apoptosis through the regulation of the epigenetic modifiers DNMT1 and EZH2, which are recruited by c‐Myc to the promoter of miR‐1929‐5p to silence miR‐1929‐5p expression.

Decreased autophagy of vascular smooth muscle cells was involved in hyperhomocysteinemia-induced vascular ageing

Ageing and hyperhomocysteinemia (HHcy) are important risk factors for cardiovascular diseases (CVDs). HHcy affects the occurrence of vascular diseases in the elderly. So far, the mechanism of HHcy-induced vascular ageing remains largely unknown. Autophagy level is significantly reduced in the ageing process, and restoring impaired autophagy to a normal state may be one of the possible ways to extend the expected longevity and lifespan in the future. In this study, we established the HHcy rat model by feeding a 2.5% methionine diet. Small animal ultrasound and the tail-cuff method indicated that the vascular pulse wave velocity (PWV) and pulse pressure (PP) of HHcy rats were increased significantly compared with the control group. Vascular morphology and structure have been changed in HHcy rats, including lumen dilation, increased collagen fibre deposition and increased p53/p21/p16 expression. In vitro, under the stimulation of homocysteine (500 μmol/L, 24 hours), the rat vascular smooth muscle cells (VSMCs) presented senescence, which was characterized by the increased expression of ageing-related markers, such as p16, p21 and p53 as well as increased senescence-associated beta-galactosidase (SA-β-gal) activity. Meanwhile, the autophagy level was decreased both in vivo and in vitro, shown as the increased level of autophagy substrate p62 and the reduced level of autophagy marker LC3 II/I in the thoracic aorta of HHcy rats and in Hcy-treated VSMCs, respectively. The senescence phenotype of VSMCs was reversed by increased autophagy levels induced by rapamycin. Our findings indicate that decreased autophagy of VSMCs is involved in hyperhomocysteinemia-induced vascular ageing.

S-adenosylmethionine: A metabolite critical to the regulation of autophagy

Autophagy is a mechanism that enables cells to maintain cellular homeostasis by removing damaged materials and mobilizing energy reserves in conditions of starvation. Although nutrient availability strongly impacts the process of autophagy, the specific metabolites that regulate autophagic responses have not yet been determined. Recent results indicate that S-adenosylmethionine (SAM) represents a critical inhibitor of methionine starvation-induced autophagy. SAM is primarily involved in four key metabolic pathways: transmethylation, transsulphuration, polyamine synthesis and 5'-deoxyadenosyl 5'-radical-mediated biochemical transformations. SAM is the sole methyl group donor involved in the methylation of DNA, RNA and histones, modulating the autophagic process by mediating epigenetic effects. Moreover, the metabolites of SAM, such as homocysteine, glutathione, decarboxylated SAM and spermidine, also exert important influences on the regulation of autophagy. From our perspective, nuclear-cytosolic SAM is a conserved metabolic inhibitor that connects cellular metabolic status and the regulation of autophagy. In the future, SAM might be a new target of autophagy regulators and be widely used in the treatment of various diseases.

Complex interplay between autophagy and oxidative stress in the development of pulmonary disease

The autophagic pathway involves the encapsulation of substrates in double-membraned vesicles, which are subsequently delivered to the lysosome for enzymatic degradation and recycling of metabolic precursors. Autophagy is a major cellular defense against oxidative stress, or related conditions that cause accumulation of damaged proteins or organelles. Selective forms of autophagy can maintain organelle populations or remove aggregated proteins. Dysregulation of redox homeostasis under pathological conditions results in excessive generation of reactive oxygen species (ROS), leading to oxidative stress and the associated oxidative damage of cellular components. Accumulating evidence indicates that autophagy is necessary to maintain redox homeostasis. ROS activates autophagy, which facilitates cellular adaptation and diminishes oxidative damage by degrading and recycling intracellular damaged macromolecules and dysfunctional organelles. The cellular responses triggered by oxidative stress include the altered regulation of signaling pathways that culminate in the regulation of autophagy. Current research suggests a central role for autophagy as a mammalian oxidative stress response and its interrelationship to other stress defense systems. Altered autophagy phenotypes have been observed in lung diseases such as chronic obstructive lung disease, acute lung injury, cystic fibrosis, idiopathic pulmonary fibrosis, and pulmonary arterial hypertension, and asthma. Understanding the mechanisms by which ROS regulate autophagy will provide novel therapeutic targets for lung diseases. This review highlights our current understanding on the interplay between ROS and autophagy in the development of pulmonary disease.

Self-eating: friend or foe? The emerging role of autophagy in fibrotic diseases

Fibrosis occurs in most human organs including the liver, lung, heart and kidney, and is crucial for the progression of most chronic diseases. As an indispensable catabolic process for intracellular quality control and homeostasis, autophagy occurs in most mammalian cells and is implicated in many biological processes including fibrogenesis. Although advances have been made in understanding autophagy process, the potential role of autophagy in fibrotic diseases remains controversial and has recently attracted a great deal of attention. In the current review, we summarize the commonalities of autophagy affecting different types of fibrosis in different organs, including the liver, lung, heart, and kidney as well as in cystic fibrosis, systematically outline the contradictory results and highlight the distinct role of autophagy during the various stages of fibrosis. In summary, the exact role autophagy plays in fibrogenesis depends on specific cell types and different stimuli, and identifying and evaluating the pathogenic contribution of autophagy in fibrogenesis will promote the discovery of novel therapeutic strategies for the clinical management of these fibrotic diseases.

DNA Hypomethylation of miR-30a Mediated the Protection of Hypoxia Postconditioning Against Aged Cardiomyocytes Hypoxia/Reoxygenation Injury Through Inhibiting Autophagy

BACKGROUND

Ischemic postconditioning (IPostC) is an endogenous protective mechanism to reduce ischemia-reperfusion (I/R) injury. However, whether IPostC protects aged cardiomyocytes against I/R injury is not fully understood. Considering the protective function of microRNA 30a (miR-30a) against ischemia-induced injury in H9C2 cells, its role in the protective effects of IPostC on I/R injury of aged cardiomyocytes was investigated further.Methods and Results:To mimic I/R and IPostC in vitro, the aged cardiomyocyte model for hypoxia postconditioning (HPostC) treatment was established by 9 days of incubation with 8 mg/mL D-galactose and then followed by exposure to hypoxic environment. HPostC significantly alleviated hypoxia/reoxygenation (H/R) injury and reduced autophagy of aged cardiomyocytes, as evidenced by decreased LC3B-II expression and increased p62 by Western blot. Quantified by quantitative real-time polymerase chain reaction (qRT-PCR), miR-30a was increased in aged cardiomyocytes treated with HPostC compared with I/R injury group. Overexpression of miR-30a by LV3-rno-miR-30a mimic promoted cardioprotective effect of HPostC in aged cardiomyocytes by suppressing BECN1-mediated autophagy, all of which was abrogated by knockdown of miR-30a expression. Epigenetic analyses demonstrated that HPostC reduced DNA methyltransferase 3b-mediated DNA hypomethylation levels at miR-30a promoter, leading to upregulation of miR-30a.

CONCLUSIONS

HPostC protected aged cardiomyocytes survival against H/R injury via DNMT3b-dependent activation of miR-30a. miR-30a could be a potential therapeutic target for ischemic myocardial infarction.

The complex interplay between DNA methylation and miRNAs in gene expression regulation

The short, non-coding RNAs, also called microRNAs (miRNAs) can bind complementary sequences on cellular mRNAs. The consequence of this binding is generally the degradation of mRNA and the inhibition of its translation. For this reason, miRNAs are included among the epigenetic factors acting as a modulator of gene expression. How miRNAs expression is, in turn, regulated is still the object of active investigation, but DNA methylation, another epigenetic modification, seems to play a central role in this sense. The "one-carbon" metabolism is responsible for the metabolic regulation of trans-methylation reactions and, therefore, DNA methylation. For this reason, to investigate the possible correlations between alterations of the one-carbon metabolism and differential DNA methylation sounds interesting. Moreover, recent evidence indicates that, vice-versa, miRNAs are associated with DNA methylation modulation, in a mutual cross-talk. The present review will discuss the interplay between miRNAs and DNA methylation and its fall-out on gene expression regulation.

Autophagy activation is required for homocysteine-induced apoptosis in bovine aorta endothelial cells

An elevated level of homocysteine (Hcy) in plasma is an independent risk factor for cardiovascular disease and central nervous system disease. Endothelial dysfunction as a result of apoptosis in endothelial cells is involved in the development and progression of these diseases. In this study, we aimed to investigate the effect of autophagy activation by amino acid starvation on Hcy-induced cytotoxicity in bovine aorta endothelial cells (BAECs). Hcy-induced lactate dehydrogenase (LDH) release was promoted by amino acid starvation. In addition, Hcy increased cleaved caspase-3 level, an indicator of apoptosis, by amino acid starvation. We revealed that oxidative stress is not involved in the Hcy-induced cytotoxicity promoted by amino acid starvation. Salazosulfapyridine (SASP), an SLC7A11 inhibitor, protected against the Hcy-induced LDH release promoted by amino acid starvation. SASP decreased the Hcy-induced cleaved caspase-3 level by amino acid starvation. We demonstrate for the first time that autophagy activation by amino acid starvation promotes Hcy-induced apoptosis in BAECs. Moreover, SLC7A11 inhibitor SASP, which is an amino acid transporter, protects against Hcy-induced apoptosis due to autophagy.

The cellular responses of autophagy, apoptosis, and 5-methylcytosine level in zebrafish cells upon nutrient deprivation stress

Here we reported the stress responses of nutrient deprivation and extended observation of autophagy, apoptosis, and DNA methylation in zebrafish embryonic fibroblast (ZF4) cells. Our results showed that serum deprivation resulted in the changes of cell shape and adherent ability, the suppressed cell growth and viability, and the inhibited proliferation and cell cycle. Besides, the appearance of lysosome and autophagosome/autolysosome with significantly increased expression of mRNAs (ulk1a, becn1, atg12, sqstm1, maplc3, and lamp1) and proteins (Atg12, Becn1, Sqstm1, and Lamp1) indicate the autophagic activity was boosted at initial stage but relatively weakened at 48 h of serum starvation. When autophagy no longer mitigate for the stress, cell apoptosis detected by the mRNA expression of caspases, Bcl-2/Bax expression, and Annexin V/PI was gradually enhanced to execute the death plan upon prolonged starvation process. Furthermore, the methyl group metabolism was increased in accordance with autophagic activity and was suppressed by enhanced apoptotic activity. These data suggested that the recycle activity induced by autophagy could compensate the substrates and reactions of DNA transmethylation, which obviously increased 5-methylcytosine (5 mC) level in ZF4 cells. In summary, our results discovered the cellular responses under prolonged serum starvation stress and elaborated the switch from autophagy to apoptosis and corresponding correlation with 5 mC level changes in teleost fish in vitro.

The Impact of One Carbon Metabolism on Histone Methylation

The effect of one carbon metabolism on DNA methylation has been well described, bridging nutrition, metabolism, and epigenetics. This modification is mediated by the metabolite S-adenosyl methionine (SAM), which is also the methyl-donating substrate of histone methyltransferases. Therefore, SAM levels that are influenced by several nutrients, enzymes, and metabolic cofactors also have a potential impact on histone methylation. Although this modification plays a major role in chromatin accessibility and subsequently in gene expression in healthy or diseased states, its role in translating nutritional changes in chromatin structure has not been extensively studied. Here, we aim to review the literature of known mechanistic links between histone methylation and the central one carbon metabolism.

Homocysteine enhances neural stem cell autophagy in in vivo and in vitro model of ischemic stroke

The elevated level of the amino acid metabolite homocysteine (Hcy) is known as a risk factor for ischemic stroke. The molecular mechanisms responsible for neurotoxicity of Hcy remain largely unknown in ischemic brains. The previous studies have shown that Hcy decreases the proliferation and viability of neural stem cells (NSCs) in vivo and in vitro. Autophagy is required for the maintenance of NSCs homeostasis. In the current study, we hypothesized that the toxic effect of Hcy on NSCs may involve the changes in autophagy level following cerebral ischemia/reperfusion injury. The results showed that Hcy reduced cell viability, increased LDH release, and induced nonapoptotic cell death in primary NSCs exposed to oxygen–glucose deprivation)/reoxygenation (OGD/R). Treatment with autophagy inhibitor 3-methyladenine (3MA) partly reversed the decrease in the viability and prevented LDH release triggered by Hcy combined with OGD/R. Increased punctate LC3 dots co-localizing with Nestin-stained NSCs were also observed in the subventricular zone of Hcy-treated MCAO animals, which were partially blocked by 3MA. In vitro studies further revealed that Hcy induced the formation of autophagosomes, markedly increased the expression of the autophagic markers and decreased p-ERK, p-PI3K, p-AKT, and p-mTOR levels. In addition, MHY1485, an activator of mTOR, reduced Hcy-induced increase in LC3 and Beclin 1 protein levels, meanwhile ERK and PI3K activators (TPA, curcumin for ERK and IGF-1 for PI3K, respectively) enhanced Hcy-triggered mTOR inhibition in OGD/R NSCs. Our findings suggest that Hcy may cause excessive autophagy by downregulation of both PI3K-AKT- and ERK- dependent mTOR signaling, thereby facilitates the toxicity of Hcy on NSCs in ischemic brains.

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.

Dysregulation of Epigenetic Mechanisms of Gene Expression in the Pathologies of Hyperhomocysteinemia

Hyperhomocysteinemia (HHcy) exerts a wide range of biological effects and is associated with a number of diseases, including cardiovascular disease, dementia, neural tube defects, and cancer. Although mechanisms of HHcy toxicity are not fully uncovered, there has been a significant progress in their understanding. The picture emerging from the studies of homocysteine (Hcy) metabolism and pathophysiology is a complex one, as Hcy and its metabolites affect biomolecules and processes in a tissue- and sex-specific manner. Because of their connection to one carbon metabolism and editing mechanisms in protein biosynthesis, Hcy and its metabolites impair epigenetic control of gene expression mediated by DNA methylation, histone modifications, and non-coding RNA, which underlies the pathology of human disease. In this review we summarize the recent evidence showing that epigenetic dysregulation of gene expression, mediated by changes in DNA methylation and histone N-homocysteinylation, is a pathogenic consequence of HHcy in many human diseases. These findings provide new insights into the mechanisms of human disease induced by Hcy and its metabolites, and suggest therapeutic targets for the prevention and/or treatment.

Is there a role for autophagy in ascending aortopathy associated with tricuspid or bicuspid aortic valve?

Autophagy is a conserved process by which cytoplasmatic elements are sequestered in vesicles and degraded after their fusion with lysosomes, thus recycling the precursor molecules. The autophagy-mediated removal of redundant/harmful/damaged organelles and biomolecules plays not only a replenishing function, but protects against stressful conditions through an adaptive mechanism. Autophagy, known to play a role in several pathological conditions, is now gaining increasing attention also in the perspective of the identification of the pathogenetic mechanisms at the basis of ascending thoracic aortic aneurysm (TAA), a localized or diffused dilatation of the aorta with an abnormal widening greater than 50 percent of the vessel's normal diameter. TAA is less frequent than abdominal aortic aneurysm (AAA), but is encountered with a higher percentage in patients with congenital heart disease or known genetic syndromes. Several biological aspects of TAA pathophysiology remain to be elucitated and therapeutic needs are still widely unmet. One of the most controversial and epidemiologically important forms of TAA is that associated with the congenital bicuspid malformation of the aortic valve (BAV). Dysregulated autophagy in response, for example, to wall shear stress alterations, has been demonstrated to affect the phenotype of vascular cells relevant to aortopathy, with potential consequences on signaling, remodeling, and angiogenesis. The most recent findings and hypotheses concerning the multiple aspects of autophagy and of its dysregulation are summarized, both in general and in the context of the different vascular cell types and of TAA progression, with particular reference to BAV-related aortopathy.

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.

Astragaloside IV reversed the autophagy and oxidative stress induced by the intestinal microbiota of AIS in mice

Acute ischaemic stroke (AIS) seriously affects patient quality of life. We explored the role of the intestinal microbiota on oxidative stress and autophagy in stroke, and Astragaloside IV (AS-IV) reversed the changes induced by intestinal microbiota. We determined the characteristics of the intestinal microbiota of AIS and transient ischaemic attack (TIA) patients by 16S sequencing and found that the structure and diversity of the intestinal microbiota in patients with AIS and TIA were significantly different from those in healthy subjects. Specifically, the abundance of genus Bifidobacterium, Megamonas, Blautia, Holdemanella, and Clostridium, content of homocysteine and triglyceride was increased significantly, thus it may be as a potential mechanism of AIS and TIA. Furthermore, germ-free mice were infused intracolonically with fecal supernatants of TIA and AIS with/without feed AS-IV for 12 weeks, and we found that the feces of AIS up-regulated the autophagy markers Beclin-1, light chain 3 (LC3)-II and autophagy-related gene (Atg)12, and the expression of reactive oxygen species (ROS) and NADPH oxidase 2/4 (NOX2/4), malondialdehyde (MDA), however, the expression of total antioxidant capacity (T-AOC) and activity of superoxide dismutase (SOD) and glutathione (GSH) was down-regulated in brain tissue, the content of homocysteine and free fatty acids (FFA) in serum of the mice. Meanwhile, AS-IV could reverse the above phenomenon, however, it does not affect the motor function of mice. AS-IV reversed these changes and it may be a potential drug for AIS therapeutics.

Polyamine Metabolism and Gene Methylation in Conjunction with One-Carbon Metabolism

Recent investigations have revealed that changes in DNA methylation status play an important role in aging-associated pathologies and lifespan. The methylation of DNA is regulated by DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) in the presence of S-adenosylmethionine (SAM), which serves as a methyl group donor. Increased availability of SAM enhances DNMT activity, while its metabolites, S-adenosyl-l-homocysteine (SAH) and decarboxylated S-adenosylmethionine (dcSAM), act to inhibit DNMT activity. SAH, which is converted from SAM by adding a methyl group to cytosine residues in DNA, is an intermediate precursor of homocysteine. dcSAM, converted from SAM by the enzymatic activity of adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize the polyamines spermine and spermidine. Increased homocysteine levels are a significant risk factor for the development of a wide range of conditions, including cardiovascular diseases. However, successful homocysteine-lowering treatment by vitamins (B6, B12, and folate) failed to improve these conditions. Long-term increased polyamine intake elevated blood spermine levels and inhibited aging-associated pathologies in mice and humans. Spermine reversed changes (increased dcSAM, decreased DNMT activity, aberrant DNA methylation, and proinflammatory status) induced by the inhibition of ornithine decarboxylase. The relation between polyamine metabolism, one-carbon metabolism, DNA methylation, and the biological mechanism of spermine-induced lifespan extension is discussed.

Hydrogen sulfide improves postischemic neoangiogenesis in the hind limb of cystathionine-β-synthase mutant mice via PPAR-γ/VEGF axis

Neoangiogenesis is a fundamental process which helps to meet energy requirements, tissue growth, and wound healing. Although previous studies showed that Peroxisome proliferator-activated receptor (PPAR-γ) regulates neoangiogenesis via upregulation of vascular endothelial growth factor (VEGF), and both VEGF and PPAR-γ expressions were inhibited during hyperhomocysteinemic (HHcy), whether these two processes could trigger pathological effects in skeletal muscle via compromising neoangiogenesis has not been studied yet. Unfortunately, there are no treatment options available to date for ameliorating HHcy-mediated neoangiogenic defects. Hydrogen sulfide (H2 S) is a novel gasotransmitter that can induce PPAR-γ levels. However, patients with cystathionine-β-synthase (CBS) mutation(s) cannot produce a sufficient amount of H2 S. We hypothesized that exogenous supplementation of H2 S might improve HHcy-mediated poor neoangiogenesis via the PPAR-γ/VEGF axis. To examine this, we created a hind limb femoral artery ligation (FAL) in CBS+/- mouse model and treated them with GYY4137 (a long-acting H2 S donor compound) for 21 days. To evaluate neoangiogenesis, we used barium sulfate angiography and laser Doppler blood flow measurements in the ischemic hind limbs of experimental mice post-FAL to assess blood flow. Proteins and mRNAs levels were studied by Western blots and qPCR analyses. HIF1-α, VEGF, PPAR-γ and p-eNOS expressions were attenuated in skeletal muscle of CBS+/- mice after 21 days of FAL in comparison to wild-type (WT) mice, that were improved via GYY4137 treatment. We also found that the collateral vessel density and blood flow were significantly reduced in post-FAL CBS+/- mice compared to WT mice and these effects were ameliorated by GYY4137. Moreover, we found that plasma nitrite levels were decreased in post-FAL CBS+/- mice compared to WT mice, which were mitigated by GYY4137 supplementation. These results suggest that HHcy can inhibit neoangiogenesis via antagonizing the angiogenic signal pathways encompassing PPAR-γ/VEGF axis and that GYY4137 could serve as a potential therapeutic to alleviate the harmful metabolic effects of HHcy conditions.