Homocysteine Triggers Inflammatory Responses in Macrophages through Inhibiting CSE-H2S Signaling via DNA Hypermethylation of CSE Promoter

The role of nonesterified fatty acids in cancer biology: Focus on tryptophan and related metabolism

Plasma nonesterified fatty acids (NEFA) are elevated in cancer, because of decreased albumin levels and of fatty acid oxidation, and increased fatty acid synthesis and lipolysis. Albumin depletion and NEFA elevation maximally release albumin-bound tryptophan (Trp) and increase its flux down the kynurenine pathway, leading to increased production of proinflammatory kynurenine metabolites, which tumors use to undermine T-cell function and achieve immune escape. Activation of the aryl hydrocarbon receptor by kynurenic acid promotes extrahepatic Trp degradation by indoleamine 2,3-dioxygenase and leads to upregulation of poly (ADP-ribose) polymerase, activation of which and also of SIRT1 (silent mating type information regulation 2 homolog 1) could lead to depletion of NAD+ and ATP, resulting in cell death. NEFA also modulate heme synthesis and degradation, changes in which impact homocysteine metabolism and production of reduced glutathione and hydrogen sulphide. The significance of the interactions between heme and homocysteine metabolism in cancer biology has received little attention. Targeting Trp disposition in cancer to prevent the NEFA effects is suggested.

Allicin in pregnancy diets modulates steroid metabolism in pregnant sows and placental sulphate metabolism promoting placental angiogenesis and foetal development

The low-birth-weight of piglets is an important factor affecting pig enterprises. The placenta, as a key organ for material exchange between mother and foetus, directly influences the growth and development of the foetus. Allicin exhibits various biological activities, including anti-inflammatory and antioxidant properties. It may also play a crucial role in enhancing sow reproductive performance and placental angiogenesis. In this study, we used 70 lactating Landrace × Yorkshire binary heterozygous sows to explore the effect of allicin on the reproductive performance of sows and placental development. The sows were randomly assigned into the Allicin group (Allicin), which was fed with a diet containing 0.25% allicin, and the negative control group, which was fed with basal feed. The experimental period lasted for 114 d from the date of mating to the end of farrowing. The results showed that the addition of allicin to the gestation diets increased the number of total born piglets, born alive piglets, and high-birth-weight piglets, reduced peripartum oxidative stress, alleviated dysregulation of glucose-lipid metabolism in sows, and increased the levels of antioxidant markers in the placenta. Differential analysis of metabolites in maternal plasma and placenta samples by non-targeted metabolomics revealed that allicin improved cholesterol metabolism, steroid biosynthesis, and increased plasma progesterone levels in sows. Allicin promoted sulphur metabolism, cysteine and methionine metabolism in placental samples and increased the hydrogen sulphide (H2S) content in the placenta. In addition, Quantitative Real-time PCR, Western blot and immunofluorescence results showed that allicin upregulated the expression of angiogenesis-related genes, VEGF-A, FLK 1 and Ang 1, in the placenta, implying that it promoted placental angiogenesis. These results indicate that supplementing the diet of pregnant sows with allicin reduces oxidative stress, alleviates dysregulation of glucose-lipid metabolism during the periparturient period, and promotes placental angiogenesis and foetal development by increasing plasma progesterone level and placental H2S content.

The Effects of 12 Weeks Colostrum Milk Supplementation on the Expression Levels of Pro-Inflammatory Mediators and Metabolic Changes among Older Adults: Findings from the Biomarkers and Untargeted Metabolomic Analysis

Senescence is a normal biological process that is accompanied with a series of deteriorations in physiological function. This study aimed to investigate the effects of bovine colostrum milk supplementation on metabolic changes and the expression of various biomarkers on inflammation, antioxidant and oxidative damage, nutrient metabolism, and genomic stability among older adults. Older adults (50-69 years old) who participated in the 12-week randomized, double-blinded, placebo-controlled trial were instructed to consume the IgCo bovine colostrum-enriched skim milk or regular skim milk (placebo) twice daily. Following 12 weeks of intervention, participants in the intervention group had lower expression levels in pro-inflammatory mediators (CRP, IL-6, and TNF-α), with significant (p < 0.05) interaction effects of the group and time observed. However, no significant interaction effect was observed in the vitamin D, telomerase, 8-OHdG, MDA, and SOD activities. UPLC-MS-based untargeted metabolomics analysis revealed that 22 metabolites were upregulated and 11 were downregulated in the intervention group compared to the placebo group. Glycerophospholipid metabolism, along with cysteine and methionine metabolism were identified as the potential metabolic pathways that are associated with bovine colostrum milk consumption. In conclusion, consuming bovine colostrum milk may induce metabolic changes and reduce the expression of various pro-inflammatory mediators, thus improving the immune function in older adults.

Hydrogen sulfide and epigenetics: Novel insights into the cardiovascular effects of this gasotransmitter

Epigenetics studies the heritable modifications of genome expression that do not affect the nucleotide sequence. Epigenetic modifications can be divided into: DNA methylation, histone modifications, and modulation of genome expression by non-coding RNAs. Alteration of these mechanisms can alter the phenotype, and can lead to disease onset. The endogenous gasotransmitter hydrogen sulfide (H2 S) plays pleiotropic roles in many systems, including the cardiovascular (CV) system, and its mechanism of action mainly includes S-persulfidation of cysteine residues. Recent evidence suggests that many H2 S-mediated biological activities are based on the epigenetic regulation of cellular function, with effects ranging from DNA methylation to modification of histones and regulation of non-coding RNAs. This review describes the role of H2 S-regulating epigenetic mechanisms, providing a panorama of the current literature, and offers a novel scenario for the development of H2 S-releasing 'epidrugs' with a potential clinical use in the prevention and treatment of many CV and non-CV disorders.

Influence of Coronary Artery Bypass Grafts on Blood Aminothiols in Patients with Coronary Artery Disease

Coronary artery disease (CAD) and the coronary artery bypass graft (CABG) are associated with a decreased blood glutathione (bGSH) level. Since GSH metabolism is closely related to other aminothiols (homocysteine and cysteine) and glucose, the aim of this study was to reveal the associations of bGSH with glucose and plasma aminothiols in CAD patients (N = 35) before CABG and in the early postoperative period. Forty-three volunteers with no history of cardiovascular disease formed the control group. bGSH and its redox status were significantly lower in CAD patients at admission. CABG had no significant effect on these parameters, with the exception of an increase in the bGSH/hemoglobin ratio. At admission, CAD patients were characterized by negative associations of homocysteine and cysteine with bGSH. All these associations disappeared after CABG. An association was found between an increase in oxidized GSH in the blood in the postoperative period and fasting glucose levels. Thus, CAD is associated with the depletion of the intracellular pool and the redox status of bGSH, in which hyperhomocysteinemia and a decrease in the bioavailability of the extracellular pool of cysteine play a role. The present study indicates that CABG causes disruptions in aminothiol metabolism and induces the synthesis of bGSH. Moreover, glucose becomes an important factor in the dysregulation of GSH metabolism in CABG.

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

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

The Roles of Aerobic Exercise and Folate Supplementation in Hyperhomocysteinemia-Accelerated Atherosclerosis

Background

Hyperhomocysteinemia (HHcy) is an independent risk factor for atherosclerosis. Effective interventions to reduce HHcy-accelerated atherosclerosis are required.

Objectives

This study aimed to investigate the effects of aerobic exercise (AE) and folate (FA) supplementation on plasma homocysteine (Hcy) level and atherosclerosis development in a mouse model.

Methods

Six-week-old female apoE-/- mice were grouped into five groups (N = 6-8): HHcy (1.8 g/L DL-homocysteine (DL-Hcy) in drinking water), HHcy + AE (1.8 g/L DL-Hcy and aerobic exercise training on a treadmill), HHcy + FA (1.8 g/L DL-Hcy and 0.006% folate in diet), HHcy + AE + FA (1.8 g/L DL-Hcy, 0.006% folate, and aerobic exercise training on a treadmill), and a control group (regular water and diet). All treatment was sustained for 8 weeks. Triglyceride, cholesterol, lipoprotein, and Hcy levels were determined enzymatically. Plaque and monocyte chemoattractant protein-1 (MCP-1) expression levels in mouse aortic roots were evaluated by immunohistochemistry.

Results

Compared to the HHcy group (18.88 ± 6.13 μmol/L), plasma Hcy concentration was significantly reduced in the HHcy + AE (14.79 ± 3.05 μmol/L, p = 0.04), HHcy + FA (9.4 ± 3.85 μmol/L, p < 0.001), and HHcy + AE + FA (9.33 ± 2.21 μmol/L, p < 0.001) groups. Significantly decreased aortic root plaque area and plaque burden were found in the HHcy + AE and HHcy + AE + FA groups compared to those in the HHcy group (both p < 0.05). Plasma MCP-1 level and MCP-1 expression in atherosclerotic lesions were significantly decreased in the HHcy + AE and HHcy + AE + FA groups compared to the HHcy group (all p < 0.05).

Conclusions

AE reduced atherosclerosis development in HHcy apoE-/- mice independently of reducing Hcy levels. FA supplementation decreased plasma Hcy levels without attenuating HHcy-accelerated atherosclerosis. AE and FA supplementation have distinct mechanisms in benefiting atherosclerosis.

Epigenetic Regulation of Macrophage Polarization in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of hospitalization and death worldwide, especially in developing countries. The increased prevalence rate and mortality due to CVDs, despite the development of several approaches for prevention and treatment, are alarming trends in global health. Chronic inflammation and macrophage infiltration are key regulators of the initiation and progression of CVDs. Recent data suggest that epigenetic modifications, such as DNA methylation, posttranslational histone modifications, and RNA modifications, regulate cell development, DNA damage repair, apoptosis, immunity, calcium signaling, and aging in cardiomyocytes; and are involved in macrophage polarization and contribute significantly to cardiac disease development. Cardiac macrophages not only trigger damaging inflammatory responses during atherosclerotic plaque formation, myocardial injury, and heart failure but are also involved in tissue repair, remodeling, and regeneration. In this review, we summarize the key epigenetic modifications that influence macrophage polarization and contribute to the pathophysiology of CVDs, and highlight their potential for the development of advanced epigenetic therapies.

Hydrogen Sulfide Regulates Macrophage Function in Cardiovascular Diseases

Significance: Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that plays a vital role in immune system regulation. Recently, the regulation of macrophage function by H₂S has been extensively and actively recognized. Recent Advances: The mechanisms by which endogenous H₂S controls macrophage function have attracted increasing attention. The generation of endogenous H₂S from macrophages is mainly catalyzed by cystathionine-γ-lyase. H₂S is involved in the macrophage activation and inflammasome formation, which contributes to macrophage apoptosis, adhesion, chemotaxis, and polarization. In addition, H₂S has redox ability and interacts with reactive oxygen species to prevent oxidative stress. Moreover, H₂S epigenetically regulates gene expression. Critical Issues: In this article, the generation of endogenous H₂S in macrophages and its regulatory effect on macrophage function are reviewed. In addition, the signal transduction targeting macrophages by H₂S is also addressed. Finally, the potential therapeutic effect of H₂S on macrophages is discussed. Future Directions: Further experiments are required to explore the involvement of endogenous H₂S in the regulation of macrophage function in various physiological and pathophysiological processes and elucidate the mechanisms involved. Regarding the clinical translation of H₂S, further exploration of the application of H₂S in inflammation-related diseases is needed. Antioxid. Redox Signal. 38, 45-56.

The Role of Hydrogen Sulfide in Plaque Stability

Atherosclerosis is the greatest contributor to cardiovascular events and is involved in the majority of deaths worldwide. Plaque rapture or erosion precipitates life-threatening thrombi, resulting in the obstruction blood flow to the heart (acute coronary syndrome), brain (ischemic stroke) or low extremities (peripheral vascular diseases). Among these events, major causation dues to the plaque rupture. Although the initiation, procession, and precise time of controlling plaque rupture are unclear, foam cell formation and apoptosis, cell death, extracellular matrix components, protease expression and activity, local inflammation, intraplaque hemorrhage, and calcification contribute to the plaque instability. These alterations tightly associate with the function regulation of intraplaque various cell populations. Hydrogen sulfide (H₂S) is gasotransmitter derived from methionine metabolism and exerts a protective role in the genesis of atherosclerosis. Recent progress also showed H₂S mediated the plaque stability. In this review, we discuss the progress of endogenous H₂S modulation on functions of vascular smooth muscle cells, monocytes/macrophages, and T cells, and the molecular mechanism in plaque stability.

Serum Homocysteine and Vascular Calcification: Advances in Mechanisms, Related Diseases, and Nutrition

Identifying and preventing modifiable risk factors for cardiovascular disease is very important. Vascular calcification has been studied clinically as an asymptomatic preclinical marker of atherosclerosis and a risk factor for cardio-cerebrovascular disease. It is known that higher homocysteine levels are associated with calcified plaques and the higher the homocysteine level, the higher the prevalence and progression of vascular calcification. Homocysteine is a byproduct of methionine metabolism and is generally maintained at a physiological level. Moreover, it may increase if the patient has a genetic deficiency of metabolic enzymes, nutritional deficiencies of related cofactors (vitamins), chronic diseases, or a poor lifestyle. Homocysteine is an oxidative stress factor that can lead to calcified plaques and trigger vascular inflammation. Hyperhomocysteinemia causes endothelial dysfunction, transdifferentiation of vascular smooth muscle cells, and the induction of apoptosis. As a result of transdifferentiation and cell apoptosis, hydroxyapatite accumulates in the walls of blood vessels. Several studies have reported on the mechanisms of multiple cellular signaling pathways that cause inflammation and calcification in blood vessels. Therefore, in this review, we take a closer look at understanding the clinical consequences of hyperhomocysteinemia and apply clinical approaches to reduce its prevalence.

Endogenous H2S targets mitochondria to promote continual phagocytosis of erythrocytes by microglia after intracerebral hemorrhage

Hematoma clearance, which is achieved largely by phagocytosis of erythrocytes in the hemorrhagic brain, limits injury and facilitates recovery following intracerebral hemorrhage (ICH). Efficient phagocytosis critically depends on the capacity of a single phagocyte to phagocytize dead cells continually. However, the mechanism underlying continual phagocytosis following ICH remains unclear. We aimed to investigate the mechanism in this study. By using ICH models, we found that the gasotransmitter hydrogen sulfide (H₂S) is an endogenous modulator of continual phagocytosis following ICH. The expression of the H₂S synthase cystathionine β-synthase (CBS) and CBS-derived H₂S were elevated in brain-resident phagocytic microglia following ICH, which consequently promoted continual phagocytosis of erythrocytes by microglia. Microglia-specific deletion of CBS delayed spontaneous hematoma clearance via an H₂S-mediated mechanism following ICH. Mechanistically, oxidation of CBS-derived endogenous H₂S by sulfide-quinone oxidoreductase initiated reverse electron transfer at mitochondrial complex I, leading to superoxide production. Complex I-derived superoxide, in turn, activated uncoupling protein 2 (UCP2) to promote microglial phagocytosis of erythrocytes. Functionally, complex I and UCP2 were required for spontaneous hematoma clearance following ICH. Moreover, hyperhomocysteinemia, an established risk factor for stroke, impaired ICH-enhanced CBS expression and delayed hematoma resolution, while supplementing exogenous H₂S accelerated hematoma clearance in mice with hyperhomocysteinemia. The results suggest that the microglial CBS-H₂S-complex I axis is critical to continual phagocytosis following ICH and can be targeted to treat ICH.

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CBS-derived H₂S is elevated in brain-resident phagocytic microglia following ICH.

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CBS-derived H₂S promotes continual erythrophagocytosis and hematoma clearance.

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CBS-derived H₂S promotes microglial phagocytosis via complex I-derived ROS.

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Hyperhomocysteinemia inhibits CBS expression to delay hematoma resolution.

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The CBS-H₂S-complex I axis can be targeted to treat ICH.

Elevated Homocysteine Levels Predict Hospital-Acquired Pneumonia and Poor Functional Outcomes in Primary Intracerebral Hemorrhage

Background

Homocysteine (Hcy) has been extensively acknowledged to be correlated with inflammation. In this study, the relationship between Hcy and hospital-acquired pneumonia (HAP) in primary intracerebral hemorrhage (pICH) was explored.

Methods

We conducted a hospital-based study on screened eligible patients with primary intracerebral hemorrhage admitted within 24 h after symptom onset from January 2019 to June 2021. The associations between Hcy and HAP and poor outcomes in pICH were investigated using univariate and multivariate logistic regression analyses. The predictive accuracy of Hcy was assessed by the receiver operating characteristic curve and the optimal cutoff value of Hcy was determined by Youden Index. The patterns and magnitudes of associations between Hcy and HAP and poor outcomes were evaluated using a restricted cubic spline (RCS).

Results

A total of 579 patients with pICH were included in the study. Hcy level was significantly higher in patients with HAP and poor outcomes (p &lt; 0.001). The univariate and multivariate logistic regression analyses demonstrated that elevated Hcy was independently associated with both HAP and poor outcomes (p &lt; 0.001). Furthermore, receiver operating characteristic analysis indicated that Hcy exhibited a moderate predictive accuracy for both HAP and poor outcomes after pICH. The RCS model showed that there were linear relationships between Hcy and HAP and poor outcomes.

Conclusions

Higher Hcy level was independently associated with HAP and poor outcomes in patients with pICH.

Diallyl Trisulfide Promotes Placental Angiogenesis by Regulating Lipid Metabolism and Alleviating Inflammatory Responses in Obese Pregnant Mice

The placental tissue serves as an exchanger between the mother and the fetus during pregnancy in mammals. Proper placental angiogenesis is central to the health of both the mother and the growth and development of the fetus. Maternal obesity is associated with impaired placental function, resulting in restricted placental blood vessel development and fetal developmental disorders. Hydrogen sulfide (H₂S) is a ubiquitous second messenger in cells that has many biological effects such as promoting angiogenesis, anti-inflammation, anti-oxidation and promoting lipid metabolism. However, in the case of maternal obesity, whether H₂S can be used as an important signaling molecule to regulate body metabolism, alleviate placental inflammation levels and promote placental angiogenesis is still unclear. In this study, diallyl trisulfide (DATS), which is a well-known H₂S donor, was derived from garlic and used to treat obese pregnant mice induced by a high-fat diet, to determine its effects on lipid metabolism and inflammation, as well as placental morphology and placental angiogenesis. Here, we show that DATS treatment increased litter size and alive litter size. DATS improved the H₂S level in the serum and placenta of the mice. In addition, DATS treatment improved insulin resistance and lipid metabolism, reduced the inflammatory response and alleviated placental vascular dysplasia caused by obesity in obese mice. In summary, our research revealed that H₂S is an important signaling molecule in vivo, which can regulate placental angiogenesis and improve the reproductive performance in maternal obesity. The addition of H₂S donor DATS during pregnancy promoted placental angiogenesis by regulating lipid metabolism and alleviating inflammatory responses in obese pregnant mice.

IFC-305 attenuates renal ischemia-reperfusion injury by promoting the production of hydrogen sulfide (H2S) via suppressing the promoter methylation of cystathionine γ-lyase (CSE)

Renal ischemia-reperfusion (I/R) injury is characterized by elevated expression of homocysteine and decreased production of hydrogen sulfide (H₂S). Cystathionine γ-lyase (CSE) is a key factor in the onset of renal I/R injury, while IFC-305 can regulate the expression of CSE via epigenetic modification. Animal and cellular models of I/R were established in this work, followed by H&E staining to evaluate the extent of renal tissue injury under distinct conditions. Several methods, including ELISA, qPCR and Western blot, were used to analyze the levels of creatinine, CSE and H₂S in various I/R models. Bisulfite sequencing PCR was used to evaluate the level of DNA methylation. The severity of the renal injury was significantly elevated in I/R rats and alleviated by the IFC-305 treatment. The level of Hcy was increased in the renal tissue and peripheral blood of I/R rats, while the IFC-305 treatment inhibited the expression of homocysteine (Hcy). Mechanistically, the DNA methylation in the CSE promoter was dramatically enhanced in I/R rats and cells, while the IFC-305 treatment reduced the level of DNA methylation in the CSE promoter. Moreover, the IFC-305 increased the concentration of H₂S, which was reduced in I/R rats and cells. Finally, I/R rats and cells showed aberrantly high levels of MDA and superoxide, while the IFC-305 treatment reduced the levels of malondialdehyde (MDA) and superoxide. IFC-305, an adenosine derivative, promoted the production of H₂S and attenuated renal injury in cellular and animal models of renal I/R by modifying the methylation status of the CSE promoter.

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

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

Homocysteine, Vitamins B6 and Folic Acid in Experimental Models of Myocardial Infarction and Heart Failure—How Strong Is That Link?

Cardiovascular diseases are the leading cause of death and the main cause of disability. In the last decade, homocysteine has been found to be a risk factor or a marker for cardiovascular diseases, including myocardial infarction (MI) and heart failure (HF). There are indications that vitamin B6 plays a significant role in the process of transsulfuration in homocysteine metabolism, specifically, in a part of the reaction in which homocysteine transfers a sulfhydryl group to serine to form α-ketobutyrate and cysteine. Therefore, an elevated homocysteine concentration (hyperhomocysteinemia) could be a consequence of vitamin B6 and/or folate deficiency. Hyperhomocysteinemia in turn could damage the endothelium and the blood vessel wall and induce worsening of atherosclerotic process, having a negative impact on the mechanisms underlying MI and HF, such as oxidative stress, inflammation, and altered function of gasotransmitters. Given the importance of the vitamin B6 in homocysteine metabolism, in this paper, we review its role in reducing oxidative stress and inflammation, influencing the functions of gasotransmitters, and improving vasodilatation and coronary flow in animal models of MI and HF.

Oxidative Stress and Redox Signaling in the Pathophysiology of Liver Diseases

The increased production of derivatives of molecular oxygen and nitrogen in the form of reactive oxygen species (ROS) and reactive nitrogen species (RNS) lead to molecular damage called oxidative stress. Under normal physiological conditions, the ROS generation is tightly regulated in different cells and cellular compartments. Any disturbance in the balance between the cellular generation of ROS and antioxidant balance leads to oxidative stress. In this article, we discuss the sources of ROS (endogenous and exogenous) and antioxidant mechanisms. We also focus on the pathophysiological significance of oxidative stress in various cell types of the liver. Oxidative stress is implicated in the development and progression of various liver diseases. We narrate the master regulators of ROS-mediated signaling and their contribution to liver diseases. Nonalcoholic fatty liver diseases (NAFLD) are influenced by a "multiple parallel-hit model" in which oxidative stress plays a central role. We highlight the recent findings on the role of oxidative stress in the spectrum of NAFLD, including fibrosis and liver cancer. Finally, we provide a brief overview of oxidative stress biomarkers and their therapeutic applications in various liver-related disorders. Overall, the article sheds light on the significance of oxidative stress in the pathophysiology of the liver. © 2022 American Physiological Society. Compr Physiol 12:3167-3192, 2022.

The Controversial Role of HCY and Vitamin B Deficiency in Cardiovascular Diseases

Plasma homocysteine (HCY) is an established risk factor for cardiovascular disease CVD and stroke. However, more than two decades of intensive research activities has failed to demonstrate that Hcy lowering through B-vitamin supplementation results in a reduction in CVD risk. Therefore, doubts about a causal involvement of hyperhomocysteinemia (HHcy) and B-vitamin deficiencies in atherosclerosis persist. Existing evidence indicates that HHcy increases oxidative stress, causes endoplasmatic reticulum (ER) stress, alters DNA methylation and, thus, modulates the expression of numerous pathogenic and protective genes. Moreover, Hcy can bind directly to proteins, which can change protein function and impact the intracellular redox state. As most mechanistic evidence is derived from experimental studies with rather artificial settings, the relevance of these results in humans remains a matter of debate. Recently, it has also been proposed that HHcy and B-vitamin deficiencies may promote CVD through accelerated telomere shortening and telomere dysfunction. This review provides a critical overview of the existing literature regarding the role of HHcy and B-vitamin deficiencies in CVD. At present, the CVD risk associated with HHcy and B vitamins is not effectively actionable. Therefore, routine screening for HHcy in CVD patients is of limited value. However, B-vitamin depletion is rather common among the elderly, and in such cases existing deficiencies should be corrected. While Hcy-lowering with high doses of B vitamins has no beneficial effects in secondary CVD prevention, the role of Hcy in primary disease prevention is insufficiently studied. Therefore, more intervention and experimental studies are needed to address existing gaps in knowledge.

Small Vessel Disease: Ancient Description, Novel Biomarkers

Small vessel disease (SVD) is one of the most frequent pathological conditions which lead to dementia. Biochemical and neuroimaging might help correctly identify the clinical diagnosis of this relevant brain disease. The microvascular alterations which underlie SVD have common origins, similar cognitive outcomes, and common vascular risk factors. Nevertheless, the arteriolosclerosis process, which underlines SVD development, is based on different mechanisms, not all completely understood, which start from a chronic hypoperfusion state and pass through a chronic brain inflammatory condition, inducing a significant endothelium activation and a consequent tissue remodeling action. In a recent review, we focused on the pathophysiology of SVD, which is complex, involving genetic conditions and different co-morbidities (i.e., diabetes, chronic hypoxia condition, and obesity). Currently, many points still remain unclear and discordant. In this paper, we wanted to focus on new biomarkers, which can be the expression of the endothelial dysfunction, or of the oxidative damage, which could be employed as markers of disease progression or for future targets of therapies. Therefore, we described the altered response to the endothelium-derived nitric oxide-vasodilators (ENOV), prostacyclin, C-reactive proteins, and endothelium-derived hyperpolarizing factors (EDHF). At the same time, due to the concomitant endothelial activation and chronic neuroinflammatory status, we described hypoxia-endothelial-related markers, such as HIF 1 alpha, VEGFR2, and neuroglobin, and MMPs. We also described blood–brain barrier disruption biomarkers and imaging techniques, which can also describe perivascular spaces enlargement and dysfunction. More studies should be necessary, in order to implement these results and give them a clinical benefit.

Treatment-resistant schizophrenia: focus on the transsulfuration pathway

Treatment-resistant schizophrenia (TRS) is a severe form of schizophrenia. The severity of illness is positively related to homocysteine levels, with high homocysteine levels due to the low activity of the transsulfuration pathway, which metabolizes homocysteine in synthesizing L-cysteine. Glutathione levels are low in schizophrenia, which indicates shortages of L-cysteine and low activity of the transsulfuration pathway. Hydrogen sulfide (H2S) levels are low in schizophrenia. H2S is synthesized by cystathionine β-synthase and cystathionine γ-lyase, which are the two enzymes in the transsulfuration pathway. Iron-sulfur proteins obtain sulfur from L-cysteine. The oxidative phosphorylation (OXPHOS) pathway has various iron-sulfur proteins. With low levels of L-cysteine, iron-sulfur cluster formation will be dysregulated leading to deficits in OXPHOS in schizophrenia. Molybdenum cofactor (MoCo) synthesis requires sulfur, which is obtained from L-cysteine. With low levels of MoCo synthesis, molybdenum-dependent sulfite oxidase (SUOX) will not be synthesized at appropriate levels. SUOX detoxifies sulfite from sulfur-containing amino acids. If sulfites are not detoxified, there can be sulfite toxicity. The transsulfuration pathway metabolizes selenomethionine, whereby selenium from selenomethionine can be used for selenoprotein synthesis. The low activity of the transsulfuration pathway decreases selenoprotein synthesis. Glutathione peroxidase (GPX), with various GPXs being selenoprotein, is low in schizophrenia. The dysregulations of selenoproteins would lead to oxidant stress, which would increase the methylation of genes and histones leading to epigenetic changes in TRS. An add-on treatment to mainline antipsychotics is proposed for TRS that targets the dysregulations of the transsulfuration pathway and the dysregulations of other pathways stemming from the transsulfuration pathway being dysregulated.

Estradiol-17β inhibits homocysteine mediated damage by promoting H2 S production via upregulating CBS and CSE expression in human umbilical vein endothelial cells

Associated with reduced hydrogen sulfide (H₂ S) production in Hcy metabolic disorders, Plasma Hcy accumulation can bring about vascular dysfunction. Nevertheless, recently proposed therapies for vascular damage by estrogen could contribute to promoting endogenous hydrogen sulfide production. This study explores whether estrogen can come into play in protection in hyperhomocysteinemia and hypertensive patients at a population level, and then analyses the specific mechanism of estrogen protection in homocysteine (Hcy)-treated human umbilical vein endothelial cells (HUVECs) at the foundational level. A case-control study, conducted on 1277 female hypertension and non-hypertensive patients from Hunan Provincial People's Hospital, showed that the Hcy concentration of hypertensive patients emerged higher than that of healthy controls (P < .001), and that of estrogen was the reverse (P < .001). Estrogen had a negative correlation with systolic blood pressure and plasma Hcy concentration. HUVECs were treated with estrogen and Hcy in the basic experimental part, and 17β-estradiol (E2β) stimulated proliferation and inhibited damage in Hcy-treated umbilical vein endothelial cells. Treatment with Hcy dampens the expression of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) then cuts down H₂ S production in cultured HUVECs, however, E2β reverses this process. To sum up, we have demonstrated a significant correlation between estrogen, Hcy concentration and systolic blood pressure reduction, which is bound up with Hcy metabolism and endogenous hydrogen sulfide production. The role of E2β was further strengthened by CBS and the CSE inhibitor through overthrowing the change in hydrogen sulfide of Hcy-treated HUVECs.

Urine S-Adenosylmethionine are Related to Degree of Renal Insufficiency in Patients with Chronic Kidney Disease

OBJECTIVE

To determine whether urine S-adenosylmethionine (SAM) might be an indicator of chronic kidney disease (CKD).

METHODS

We investigated urine levels of SAM and related metabolites (S-adenosylhomocysteine and homocysteine cysteine) in 62 patients (average age, 65.9 years) with CKD (stages II-V).

RESULTS

Patients with stages III-V CKD stages have significantly decreased urine levels and SAM/S-adenosylhomocysteine ratio and also cysteine/homocysteine ratio in blood plasma (P <.05), compared with patients with stage II CKD. Urine SAM levels allowed us to distinguish patients with mildly decreased kidney function from those with moderate to severe renal impairment (AUC, 0.791; sensitivity, 85%; specificity, 78.6%).

CONCLUSIONS

Our study results demonstrate that urine SAM is a potent biomarker for monitoring renal function decline at early CKD stages. Urine SAM testing confers an additional advantage to healthcare professionals in that it is noninvasive.

Multiple roles of haem in cystathionine β-synthase activity: implications for hemin and other therapies of acute hepatic porphyria

The role of haem in the activity of cystathionine β-synthase (CBS) is reviewed and a hypothesis postulating multiple effects of haem on enzyme activity under conditions of haem excess or deficiency is proposed, with implications for some therapies of acute hepatic porphyrias. CBS utilises both haem and pyridoxal 5′-phosphate (PLP) as cofactors. Although haem does not participate directly in the catalytic process, it is vital for PLP binding to the enzyme and potentially also for CBS stability. Haem deficiency can therefore undermine CBS activity by impairing PLP binding and facilitating CBS degradation. Excess haem can also impair CBS activity by inhibiting it via CO resulting from haem induction of haem oxygenase 1 (HO 1), and by induction of a functional vitamin B₆ deficiency following activation of hepatic tryptophan 2,3-dioxygenase (TDO) and subsequent utilisation of PLP by enhanced kynurenine aminotransferase (KAT) and kynureninase (Kynase) activities. CBS inhibition results in accumulation of the cardiovascular risk factor homocysteine (Hcy) and evidence is emerging for plasma Hcy elevation in patients with acute hepatic porphyrias. Decreased CBS activity may also induce a proinflammatory state, inhibit expression of haem oxygenase and activate the extrahepatic kynurenine pathway (KP) thereby further contributing to the Hcy elevation. The hypothesis predicts likely changes in CBS activity and plasma Hcy levels in untreated hepatic porphyria patients and in those receiving hemin or certain gene-based therapies. In the present review, these aspects are discussed, means of testing the hypothesis in preclinical experimental settings and porphyric patients are suggested and potential nutritional and other therapies are proposed.

Nitric oxide and hydrogen sulfide: Sibling rivalry in the family of epigenetic regulators

Nitric oxide (NO) and hydrogen sulfide (H₂S) were previously only known for their toxic properties. Now they are regarded as potent gaseous messenger molecules (gasotransmitters) that rapidly transverse cell membranes and transduce cellular signals through their chemical reactions and modifications to protein targets. Both are known to regulate numerous physiological functions including angiogenesis, vascular tone, and immune response, to name a few. NO and H₂S often work synergistically and in competition to regulate each other's synthesis, target protein activity via posttranslational modifications (PTMs), and chemical interactions. In addition to their canonical modes of action, increasing evidence has demonstrated that NO and H₂S share another signaling mechanism: epigenetic regulation. This review will compare and contrast biosynthesis and metabolism of NO and H₂S, their individual and shared interactions, and the growing body of evidence for their roles as endogenous epigenetic regulatory molecules.

Homocysteine and Age-Related Central Nervous System Diseases: Role of Inflammation

Hyperhomocysteinemia (HHcy) is remarkably common among the aging population. The relation between HHcy and the development of neurodegenerative diseases, such as Alzheimer's disease (AD) and eye diseases, and age-related macular degeneration (AMD) and diabetic retinopathy (DR) in elderly people, has been established. Disruption of the blood barrier function of the brain and retina is one of the most important underlying mechanisms associated with HHcy-induced neurodegenerative and retinal disorders. Impairment of the barrier function triggers inflammatory events that worsen disease pathology. Studies have shown that AD patients also suffer from visual impairments. As an extension of the central nervous system, the retina has been suggested as a prominent site of AD pathology. This review highlights inflammation as a possible underlying mechanism of HHcy-induced barrier dysfunction and neurovascular injury in aging diseases accompanied by HHcy, focusing on AD.

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.

Association of homocysteine with ankylosing spondylitis: a systematic review and meta-analysis

Background

Hyperhomocysteinemia is associated with autoimmune diseases such as ankylosing spondylitis (AS), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). Current findings regarding plasma/serum homocysteine (HCY) levels in AS patients are inconsistent. This study aims to systematically evaluate the association between circulating HCY levels and AS.

Methods

Online electronic databases (PubMed, Web of Science, Embase, ScienceDirect, China National Knowledge Infrastructure (CNKI), and Wanfang data) were used to retrieve all relevant articles published up to May 7, 2020. The pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated using the random-effect model, Stata16 software.

Results

Nine articles containing 778 AS patients and 522 controls were included in this meta-analysis. No significant differences in HCY levels were found between AS and control groups (pooled SMD = 0.46, 95% CI = − 0.30 to 1.23, P = 0.23). However, subgroup analysis suggested that HCY levels were significantly higher (P < 0.05) in the AS group treated with methotrexate (MTX) compared with the control group. In contrast, HCY levels were significantly (P < 0.05) lower in the AS group receiving anti-TNF-α treatment compared with the control group. No significant differences were detected between HCY levels and disease activity scores (Bath AS disease activity index, BASDAI), and methylenetetrahydrofolate reductase (MTHFR) C677T genotype.

Conclusion

This meta-analysis indicates that HCY levels are similar between AS and controls, and do not correlate with disease activity. However, different medical treatments cause fluctuations of circulating HCY levels in AS patients. Further and larger-scale studies are needed to confirm these findings.

Trial registration

This study was registered at international prospective register of systematic reviews (PROSPERO), registration number: CRD42020184426.

Homocysteine in Neurology: A Possible Contributing Factor to Small Vessel Disease

Homocysteine (Hcy) is a sulfur-containing amino acid generated during methionine metabolism, accumulation of which may be caused by genetic defects or the deficit of vitamin B12 and folate. A serum level greater than 15 micro-mols/L is defined as hyperhomocysteinemia (HHcy). Hcy has many roles, the most important being the active participation in the transmethylation reactions, fundamental for the brain. Many studies focused on the role of homocysteine accumulation in vascular or degenerative neurological diseases, but the results are still undefined. More is known in cardiovascular disease. HHcy is a determinant for the development and progression of inflammation, atherosclerotic plaque formation, endothelium, arteriolar damage, smooth muscle cell proliferation, and altered-oxidative stress response. Conversely, few studies focused on the relationship between HHcy and small vessel disease (SVD), despite the evidence that mice with HHcy showed a significant end-feet disruption of astrocytes with a diffuse SVD. A severe reduction of vascular aquaporin-4-water channels, lower levels of high-functioning potassium channels, and higher metalloproteinases are also observed. HHcy modulates the N-homocysteinylation process, promoting a pro-coagulative state and damage of the cellular protein integrity. This altered process could be directly involved in the altered endothelium activation, typical of SVD and protein quality, inhibiting the ubiquitin-proteasome system control. HHcy also promotes a constant enhancement of microglia activation, inducing the sustained pro-inflammatory status observed in SVD. This review article addresses the possible role of HHcy in small-vessel disease and understands its pathogenic impact.

Hyperhomocysteinemia and Cardiovascular Disease: Is the Adenosinergic System the Missing Link?

The influence of hyperhomocysteinemia (HHCy) on cardiovascular disease (CVD) remains unclear. HHCy is associated with inflammation and atherosclerosis, and it is an independent risk factor for CVD, stroke and myocardial infarction. However, homocysteine (HCy)-lowering therapy does not affect the inflammatory state of CVD patients, and it has little influence on cardiovascular risk. The HCy degradation product hydrogen sulfide (H2S) is a cardioprotector. Previous research proposed a positive role of H2S in the cardiovascular system, and we discuss some recent data suggesting that HHCy worsens CVD by increasing the production of H2S, which decreases the expression of adenosine A2A receptors on the surface of immune and cardiovascular cells to cause inflammation and ischemia, respectively.

FOXC1 promotes HCC proliferation and metastasis by Upregulating DNMT3B to induce DNA Hypermethylation of CTH promoter

BACKGROUND

Forkhead box C1 (FOXC1), as a member of the FOX family, is important for promote HCC invasion and metastasis. FOX family protein lays a pivotal role in metabolism. ROS is involved in tumor progression and is associated with the expression of lots of transcription factors. We next explored the mechanism underlying FOXC1 modulating the metabolism and ROS hemostasis in HCC.

METHODS

We used amino acids arrays to verify which metabolism is involved in FOXC1-induced HCC. The kits were used to detect the ROS levels in HCC cells with over-expression or down-expression of FOXC1. After identified the downstream target genes and candidate pathway which regulated by FOXC1 during HCC progression in vitro and in vivo, we used western blot, immunohistochemistry, bisulfite genomic sequencing, methylation-specific PCR, chromatin immunoprecipitation analysis and luciferase reporter assays to explore the relationship of FOXC1 and downstream genes. Moreover, the correlation between FOXC1 and target genes and the correlation between target genes and the recurrence and overall survival were analyzed in two independent human HCC cohorts.

RESULTS

Here, we reported that FOXC1 could inhibit the cysteine metabolism and increase reactive oxygen species (ROS) levels by regulating cysteine metabolism-related genes, cystathionine γ-lyase (CTH). Overexpression of CTH significantly suppressed FOXC1-induced HCC proliferation, invasion and metastasis, while the reduction in cell proliferation, invasion and metastasis caused by the inhibition of FOXC1 could be reversed by knockdown of CTH. Meanwhile, FOXC1 upregulated de novo DNA methylase 3B (DNMT3B) expression to induce DNA hypermethylation of CTH promoter, which resulted in low expression of CTH in HCC cells. Moreover, low levels of ROS induced by N-acetylcysteine (NAC) which is an antioxidant inhibited the cell proliferation, migration, and invasion abilities mediated by FOXC1 overexpression, whereas high levels of ROS induced by L-Buthionine-sulfoximine (BSO) rescued the suppression results mediated by FOXC1 knockdown. Our study demonstrated that the overexpression of FOXC1 that was induced by the ROS dependent on the extracellular regulated protein kinases 1 and 2 (ERK1/2)- phospho-ETS Transcription Factor 1 (p-ELK1) pathway. In human HCC tissues, FOXC1 expression was positively correlated with oxidative damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG), p-ELK1 and DNMT3B expression, but negatively correlated with CTH expression. HCC patients with positive co-expression of 8-OHdG/FOXC1 or p-ELK1/FOXC1 or FOXC1/DNMT3B had the worst prognosis, whereas HCC patients who had positive FOXC1 and negative CTH expression exhibited the worst prognosis.

CONCLUSION

In a word, we clarify that the positive feedback loop of ROS-FOXC1-cysteine metabolism-ROS is important for promoting liver cancer proliferation and metastasis, and this pathway may provide a prospective clinical treatment approach for HCC.

Role of hydrogen sulfide in endothelial dysfunction: Pathophysiology and therapeutic approaches

BACKGROUND

The vascular endothelium represents a fundamental mechanical and biological barrier for the maintenance of vascular homeostasis along the entire vascular tree. Changes in its integrity are associated to several cardiovascular diseases, including hypertension, atherosclerosis, hyperhomocysteinemia, diabetes, all linked to the peculiar condition named endothelial dysfunction, which is referred to the loss of endothelial physiological functions, comprehending the regulation of vascular relaxation and/or cell redox balance, the inhibition of leukocyte infiltration and the production of NO. Among the endothelium-released vasoactive factors, in the last years hydrogen sulfide has been viewed as one of the main characters involved in the regulation of endothelium functionality, and many studies demonstrated that H2S behaves as a vasoprotective gasotransmitter in those cardiovascular diseases where endothelial dysfunction seems to be the central issue.

AIM

The role of hydrogen sulfide in endothelial dysfunction-related cardiovascular diseases is discussed in this review.

KEY SCIENTIFIC CONCEPTS

Possible therapeutic approaches using molecules able to release H2S.

Activation of the CaR-CSE/H2S pathway confers cardioprotection against ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a multifactorial process triggered when an organ is subjected to transiently reduced blood supply. The result is a cascade of pathological complications and organ damage due to the production of reactive oxygen species following reperfusion. The present study aims to evaluate the role of activated calcium-sensing receptor (CaR)-cystathionine γ-lyase (CSE)/hydrogen sulfide (H2S) pathway in I/R injury. Firstly, an I/R rat model with CSE knockout was constructed. Transthoracic echocardiography, TTC and HE staining were performed to determine the cardiac function of rats following I/R Injury, followed by TUNEL staining observation on apoptosis. Besides, with the attempt to better elucidate how CaR-CSE/H2S affects I/R, in-vitro culture of human coronary artery endothelial cells (HCAECs) was conducted with gadolinium chloride (GdCl3, a CaR agonist), H₂O₂, siRNA against CSE (siCSE), or W7 (a CaM inhibitor). The interaction between CSE and CaM was subsequently detected. Plasma oxidative stress indexes, H2S and CSE, and apoptosis-related proteins were all analyzed following cell apoptosis. We found that H2S elevation led to the improvement whereas CSE knockdown decreased cardiac function in rats with I/R injury. Moreover, oxidative stress injury in I/R rats with CSE knockout was aggravated, while the increased expression of H2S and CSE in the aortic tissues resulted in alleviated the oxidative stress injury. Moreover, increased H2S and CSE levels were found to inhibit cell apoptotic ability in the aortic tissues after I/R injury, thus attenuating oxidative stress injury, accompanied by inhibited expression of apoptosis-related proteins. In HCAECs following oxidative stress treatment, siCSE and CaM inhibitor were observed to reverse the protection of CaR agonist. Coimmunoprecipitation assay revealed the interaction between CSE and CaM. Taken together, all above-mentioned data provides evidence that activation of the CaR-CSE/H2S pathway may confer a potent protective effect in cardiac I/R injury.

Identification of Potential Biomarkers for CAD Using Integrated Expression and Methylation Data

DNA methylation plays an essential role in the pathogenesis of coronary artery disease (CAD) through regulating mRNA expressions. This study aimed to identify hub genes regulated by DNA methylation as biomarkers of CAD. Gene expression and methylation datasets of peripheral blood leukocytes (PBLs) of CAD were downloaded from the Gene Expression Omnibus (GEO) database. Subsequently, multiple computational approaches were performed to analyze the regulatory networks and to recognize hub genes. Finally, top hub genes were verified in a case-control study, based on their differential expressions and methylation levels between CAD cases and controls. In total, 535 differentially expressed-methylated genes (DEMGs) were identified and partitioned into 4 subgroups. TSS200 and 5′UTR were confirmed as high enrichment areas of differentially methylated CpGs sites (DMCs). The function of DEMGs is enriched in processes of histone H3-K27 methylation, regulation of post-transcription and DNA-directed RNA polymerase activity. Pathway enrichment showed DEMGs participated in the VEGF signaling pathway, adipocytokine signaling pathway, and PI3K-Akt signaling pathway. Besides, expressions of hub genes fibronectin 1 (FN1), phosphatase (PTEN), and tensin homolog and RNA polymerase III subunit A (POLR3A) were discordantly expressed between CAD patients and controls and related with DNA methylation levels. In conclusion, our study identified the potential biomarkers of PBLs for CAD, in which FN1, PTEN, and POLR3A were confirmed.

The role of hydrogen sulphide signalling in macrophage activation

Hydrogen sulphide (H₂S) is the latest identified small gaseous mediator enabled by its lipophilic nature to freely permeate the biological membranes. Initially, H₂S was recognized by its roles in neuronal activity and vascular relaxation, which makes it an important molecule involved in paracrine signalling pathways. Recently, the immune regulatory function of gasotransmitters, H₂S in particular, is increasingly being appreciated. Endogenous H₂S level has been linked to macrophage activation, polarization and inflammasome formation. Mechanistically, H₂S‐induced protein S‐sulphydration suppresses several inflammatory pathways including NF‐κB and JNK signalling. Moreover, H₂S serves as a potent cellular redox regulator to modulate epigenetic alterations and to promote mitochondrial biogenesis in macrophages. Here in this review, we intend to summarize the recent advancements of H₂S studies in macrophages, and to discuss with focus on the therapeutic potential of H₂S donors by targeting macrophages. The feasibility of H₂S signalling component as a macrophage biomarker under disease conditions would be also discussed.

Microglial memory of early life stress and inflammation: Susceptibility to neurodegeneration in adulthood

We review evidence supporting the role of early life programming in the susceptibility for adult neurodegenerative diseases while highlighting questions and proposing avenues for future research to advance our understanding of this fundamental process. The key elements of this phenomenon are chronic stress, neuroinflammation triggering microglial polarization, microglial memory and their connection to neurodegeneration. We review the mediating mechanisms which may function as early biomarkers of increased susceptibility for neurodegeneration. Can we devise novel early life modifying interventions to steer developmental trajectories to their optimum?

Hyperhomocysteinemia and Endothelial Dysfunction in Multiple Sclerosis

Endothelial dysfunction is recognized as one of the leading factors in the pathogenesis of diseases of the central nervous system of various etiologies. Numerous studies have shown the role of hyperhomocysteinemia in the development of endothelial dysfunction and the prothrombogenic state. The most important condition in the development of multiple sclerosis (MS) is a dysregulation of the blood-brain barrier (BBB) and transendothelial leukocyte migration. It has been proven that homocysteine also contributes to the damage of neurons by the mechanism of excitotoxicity and the induction of the apoptosis of neurons. These processes can be one of the factors of neurodegenerative brain damage, which plays a leading role in the progression of MS. This review describes the pleiotropic effect of homocysteine on these processes and its role in MS pathogenesis.

CD4+ T-Cell Endogenous Cystathionine γ Lyase-Hydrogen Sulfide Attenuates Hypertension by Sulfhydrating Liver Kinase B1 to Promote T Regulatory Cell Differentiation and Proliferation

BACKGROUND

Hydrogen sulfide (H₂S) has antihypertension and anti-inflammatory effects, and its endogenous-generation key enzyme cystathionine γ lyase (CSE) is expressed in CD4⁺ T cells. However, the role of CD4⁺ T-cell endogenous CSE/H₂S in the development of hypertension is unclear.

METHODS

Peripheral blood lymphocytes were isolated from hypertensive patients or spontaneously hypertensive rats, then H₂S production and expression of its generation enzymes, cystathionine β synthase and CSE, were measured to determine the major H₂S generation system changes in hypertension. Mice with CSE-specific knockout in T cells (conditional knockout, by CD4^cre mice hybridization) and CD4 null mice were generated for investigating the pathophysiological relevance of the CSE/H₂S system.

RESULTS

In lymphocytes, H₂S from CSE, but not cystathionine β synthase, responded to blood pressure changes, supported by lymphocyte CSE protein changes and a negative correlation between H₂S production with systolic blood pressure and diastolic blood pressure, but positive correlation with the serum level of interleukin 10 (an anti-inflammatory cytokine). Deletion of CSE in T cells elevated BP (5-8 mm Hg) under the physiological condition and exacerbated angiotensin II-induced hypertension. In keeping with hypertension, mesenteric artery dilation impaired association with arterial inflammation, an effect attributed to reduced immunoinhibitory T regulatory cell (Treg) numbers in the blood and kidney, thus causing excess CD4⁺ and CD8⁺ T cell infiltration in perivascular adipose tissues and kidney. CSE knockout CD4⁺ T cell transfer into CD4 null mice, also showed the similar phenotypes' confirming the role of endogenous CSE/H₂S action. Adoptive transfer of Tregs (to conditional knockout mice) reversed hypertension, vascular relaxation impairment, and immunocyte infiltration, which confirmed that conditional knockout-induced hypertension was attributable, in part, to the reduced Treg numbers. Mechanistically, endogenous CSE/H₂S promoted Treg differentiation and proliferation by activating AMP-activated protein kinase. In part, it depended on activation of its upstream kinase, liver kinase B1, by sulfhydration to facilitate its substrate binding and phosphorylation.

CONCLUSION

The constitutive sulfhydration of liver kinase B1 by CSE-derived H₂S activates its target kinase, AMP-activated protein kinase, and promotes Treg differentiation and proliferation, which attenuates the vascular and renal immune-inflammation, thereby preventing hypertension.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

The Importance of Telomere Shortening for Atherosclerosis and Mortality

Telomeres are the protective end caps of chromosomes and shorten with every cell division. Short telomeres are associated with older age and adverse lifestyle factors. Leucocyte telomere length (LTL) has been proposed as a biomarker of biological age. The shortening of LTL with age is the result of the end-replication problem, environmental, and lifestyle-related factors. Epidemiologic studies have shown that LTL predicts cardiovascular disease, all-cause mortality, and death from vascular causes. Age appears to be an important co-variate that explains a substantial fraction of this effect. Although it has been proposed that short telomeres promote atherosclerosis and impair the repair of vascular lesions, existing results are inconsistent. Oxidative stress and chronic inflammation can both accelerate telomere shortening. Multiple factors, including homocysteine (HCY), vitamin B6, and vitamin B12 modulate oxidative stress and inflammation through direct and indirect mechanisms. This review provides a compact overview of telomere physiology and the utility of LTL measurements in atherosclerosis and cardiovascular disease. In addition, it summarizes existing knowledge regarding the impact of oxidative stress, inflammation, HCY, and B-vitamins on telomere function.

Hydrogen sulfide signaling in regulation of cell behaviors

Recent advances in the biomedical importance of H₂S have help us understand various cellular functions and pathophysiological processes from a new aspect. Specially, H₂S has been demonstrated to play multiple roles in regulating cell behaviors, including cell survival, cell differentiation, cell senescence, cell hypertrophy, cell atrophy, cell metaplasia, and cell death, etc. H₂S contributes to cell behavior changes via various mechanisms, such as histone modification, DNA methylation, non-coding RNA changes, DNA damage repair, transcription factor activity, and post-translational modification of proteins by S-sulfhydration, etc. In this review, we summarized the recent research progress on H₂S signaling in control of cell behaviors and discussed the ways of H₂S regulation of gene expressions. Given the key roles of H₂S in both health and diseases, a better understanding of the regulation of H₂S on cell behavior change and the underlying molecular mechanisms will help us to develop novel and more effective strategies for clinical therapy.

Hydrogen Sulfide Alleviates Anxiety, Motor, and Cognitive Dysfunctions in Rats with Maternal Hyperhomocysteinemia via Mitigation of Oxidative Stress

Hydrogen sulfide (H₂S) is endogenously produced from sulfur containing amino acids, including homocysteine and exerts neuroprotective effects. An increase of homocysteine during pregnancy impairs fetal growth and development of the offspring due to severe oxidative stress. We analyzed the effects of the H₂S donor—sodium hydrosulfide (NaHS) administered to female rats with hyperhomocysteinemia (hHcy) on behavioral impairments and levels of oxidative stress of their offspring. Rats born from females fed with control or high methionine diet, with or without H₂S donor injections were investigated. Rats with maternal hHcy exhibit increased levels of total locomotor activity and anxiety, decreased muscle endurance and motor coordination, abnormalities of fine motor control, as well as reduced spatial memory and learning. Oxidative stress in brain tissues measured by activity of glutathione peroxidases and the level of malondialdehyde was higher in rats with maternal hHcy. Concentrations of H₂S and the activity and expression of the H₂S generating enzyme—cystathionine-beta synthase—were lower compared to the control group. Administration of the H₂S donor to females with hHcy during pregnancy prevented behavioral alterations and oxidative stress of their offspring. The acquisition of behavioral together with biochemical studies will add to our knowledge about homocysteine neurotoxicity and proposes H₂S as a potential agent for therapy of hHcy associated disorders.

Homocysteine impairs porcine oocyte quality via deregulation of one-carbon metabolism and hypermethylation of mitochondrial DNA†

Homocysteine (Hcy) is an intermediate in the one-carbon metabolism that donates methyl groups for methylation processes involved in epigenetic gene regulation. Although poor oocyte quality in polycystic ovarian syndrome (PCOS) patients is associated with elevated Hcy concentration in serum and follicular fluid, whether Hcy directly affects oocyte quality and its mechanisms are poorly understood. Here we show that Hcy treatment impaired oocyte quality and developmental competence, indicated by significantly reduced survival rate, polar body extrusion rate, and cleavage rate. Hcy treatment resulted in mitochondrial dysfunction, with increased production of mitochondrial ROS, reduced mtDNA copy number, and the expression of 7 out of 13 mtDNA-encoded genes and 2 ribosome RNA genes, 12S rRNA and 16S rRNA. Upon Hcy treatment, the expression of one-carbon metabolic enzymes and DNMT1 was enhanced. Interestingly, DNA methyltransferase inhibitor 5'AZA rescued Hcy-induced mitochondrial dysfunction, impaired oocyte quality and developmental competence. Concurrently, expression of one-carbon metabolic enzymes and methylation status of mtDNA coding sequences were also normalized, at least partially, by 5'AZA treatment. Our findings not only extend the understanding about how Hcy induces poor oocyte quality, but also contribute to a novel angle of identifying targets for enhancing the quality of oocyte from PCOS patients.

Reactive Sulfur Species: A New Redox Player in Cardiovascular Pathophysiology

Hydrogen sulfide has emerged as an important gaseous signaling molecule and a regulator of critical biological processes. However, the physiological significance of hydrogen sulfide metabolites such as persulfides, polysulfides, and other reactive sulfur species (RSS) has only recently been appreciated. Emerging evidence suggests that these RSS molecules may have similar or divergent regulatory roles compared with hydrogen sulfide in various biological activities. However, the chemical nature of persulfides and polysulfides is complex and remains poorly understood within cardiovascular and other pathophysiological conditions. Recent reports suggest that RSS can be produced endogenously, with different forms having unique chemical properties and biological implications involving diverse cellular responses such as protein biosynthesis, cell-cell barrier functions, and mitochondrial bioenergetics. Enzymes of the transsulfuration pathway, CBS (cystathionine beta-synthase) and CSE (cystathionine gamma-lyase), may also produce RSS metabolites besides hydrogen sulfide. Moreover, CARSs (cysteinyl-tRNA synthetase) are also able to generate protein persulfides via cysteine persulfide (CysSSH) incorporation into nascently formed polypeptides suggesting a new biologically relevant amino acid. This brief review discusses the biochemical nature and potential roles of RSS, associated oxidative stress redox signaling, and future research opportunities in cardiovascular disease.

Effect of Sows Gestational Methionine/Lysine Ratio on Maternal and Placental Hydrogen Sulfide Production

Simple Summary

Hydrogen sulfide (H₂S) is an important second messenger, which has been implicated in regulating placental angiogenesis. Our findings revealed that gestational dietary methionine could affect maternal and placental H₂S concentrations. With the increase of dietary methionine, maternal plasma and placental H₂S concentrations changed quadratically, which was consistent with placental vascular density and reproductive performance. The decrease in H₂S production caused by an increase in dietary methionine was likely to be the cause for the increase in the rate of low birth weight piglets and needs further study.

Abstract

The placenta is a unique bond between the mother and the fetus during pregnancy, and a proper placental angiogenesis is vital for fetal development. H₂S is an endogenous stimulator of angiogenesis that is mainly produced by the methionine transsulfurationpathway. The goal of this study was to evaluate the effect of gestational dietary methionine on maternal and placental H₂S production in sows. Multiparous sows (Large×White; third parity; n = 65) were randomly allocated into five groups, with feed diets comprisingstandardized ileal digestible methionine/lysine (Met/Lys) ratios of 0.27 (nutrient requirements of swine (NRC); 2012 level), 0.32, 0.37, 0.42, and 0.47, respectively. The litter size and weight at birth were measured and recorded. Maternal blood samples were obtained at embryonic day (E) E40 d, E90 d, and E114 d of gestation. The placental samples were collected at parturition. The results showed that maternal plasma H₂S concentration was not affected at E40 d. However, the maternal plasma H₂S concentration changed quadratically with the dietary Met/Lys ratio at E90 d (p < 0.01) and E114 d (p = 0.03). The maximum maternal plasma H₂S concentration was at the dietary Met/Lys ratio of 0.37. Meanwhile, maternal plasma H₂S concentration was positively correlated with piglets born alive (p < 0.01) and litter weight (p < 0.01). Consistent with the maternal plasma, the placental H₂S concentration also changed quadratically with the dietary Met/Lys ratio (p = 0.03); the Met/Lys ratio of 0.37 showed the maximum H₂S concentration. In conclusion, our findings revealed that the gestational dietary Met/Lys ratio could affect maternal and placental H₂S concentrations, which may be an important molecular mechanism affecting placental angiogenesis and piglet development.

[Hyperhomocysteinemia and endothelial dysfunction in patients with cerebral vascular and autoimmune diseases]

Endothelial dysfunction today is recognized as one of the leading factors in the pathogenesis of diseases of the central nervous system of various etiologies. Numerous studies have shown the role of hyperhomocysteinemia in the development of endothelial dysfunction and prothrombogenic state. The most important condition in the development of multiple sclerosis (MS) is dysregulation of the blood-brain barrier (BBB) and transendothelial leukocyte migration. It has been proven that homocysteine also contributes to the damage of neurons by the mechanism of excitotoxicity and induction of apoptosis of neurons. These processes can be one of the factors of neurodegenerative brain damage, which plays a leading role in the progression of MS. This review describes the pleiotropic effect of homocysteine on these processes and its role in the pathogenesis of MS.

Hydrogen sulfide protects against particle-induced inflammatory response and osteolysis via SIRT1 pathway in prosthesis loosening

Wear debris-induced osteolysis and ensuing aseptic loosening is the main cause of implant failure and revision surgery. Wear debris-induced inflammatory response plays key roles in peri-implant osteolysis. Recently, substantial of evidence suggests that hydrogen sulfide (H₂ S), the third gasotransmitter, is a critical player regulating inflammation. However, the role and therapeutic potential of H₂ S in wear debris-induced inflammation and osteolysis remains to be defined. In the present study, we investigated the effect of H₂ S on wear debris-induced pro-inflammatory cytokines expression and osteolysis in vitro and in vivo. With a slow-releasing H₂ S donor GYY4137, our study demonstrated that H₂ S attenuated wear debris-induced osteolysis and osteoclastogenesis in murine calvaria resorption models. The expression of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) that stimulated by wear particles were significantly reduced by GYY4137. Further, the level of sirtuin 1 (SIRT1), which possesses anti-inflammation property, was examined in vivo and in macrophages. And we found that wear debris decreased the expression of SIRT1. Cotreated macrophages with GYY4137 in part reversed the decline of SIRT1. More importantly, with the SIRT1 recombinant lentivirus and small interfering RNAs (siRNA) against SIRT1, our data indicated that SIRT1 mediated the inhibitory effects of GYY4137 on wear debris-induced inflammation. Collectively, these results suggested that exogenous H₂ S production (via H₂ S donors) may represent a potential approach for the treatment of wear particle-induced osteolysis.