Protein phosphorylation involved in the gene expression of the hydrogen sulphide producing enzyme cystathionine γ-lyase in the pancreatic β-cell

Endothelium as a Source and Target of H2S to Improve Its Trophism and Function

The vascular endothelium consists of a single layer of squamous endothelial cells (ECs) lining the inner surface of blood vessels. Nowadays, it is no longer considered as a simple barrier between the blood and vessel wall, but a central hub to control blood flow homeostasis and fulfill tissue metabolic demands by furnishing oxygen and nutrients. The endothelium regulates the proper functioning of vessels and microcirculation, in terms of tone control, blood fluidity, and fine tuning of inflammatory and redox reactions within the vessel wall and in surrounding tissues. This multiplicity of effects is due to the ability of ECs to produce, process, and release key modulators. Among these, gasotransmitters such as nitric oxide (NO) and hydrogen sulfide (H₂S) are very active molecules constitutively produced by endotheliocytes for the maintenance and control of vascular physiological functions, while their impairment is responsible for endothelial dysfunction and cardiovascular disorders such as hypertension, atherosclerosis, and impaired wound healing and vascularization due to diabetes, infections, and ischemia. Upregulation of H₂S producing enzymes and administration of H₂S donors can be considered as innovative therapeutic approaches to improve EC biology and function, to revert endothelial dysfunction or to prevent cardiovascular disease progression. This review will focus on the beneficial autocrine/paracrine properties of H₂S on ECs and the state of the art on H₂S potentiating drugs and tools.

Transcriptional Induction of Cystathionine γ-Lyase, a Reactive Sulfur-Producing Enzyme, by Copper Diethyldithiocarbamate in Cultured Vascular Endothelial Cells

As toxic substances can enter the circulating blood and cross endothelial monolayers to reach parenchymal cells in organs, vascular endothelial cells are an important target compartment for such substances. Reactive sulfur species protect cells against oxidative stress and toxic substances, including heavy metals. Reactive sulfur species are produced by enzymes, such as cystathionine γ-lyase (CSE), cystathionine β-synthase, 3-mercaptopyruvate sulfurtransferase, and cysteinyl-tRNA synthetase. However, little is known about the regulatory mechanisms underlying the expression of these enzymes in vascular endothelial cells. Bio-organometallics is a research field that analyzes biological systems using organic-inorganic hybrid molecules (organometallic compounds and metal coordinating compounds) as molecular probes. In the present study, we analyzed intracellular signaling pathways that mediate the expression of reactive sulfur species-producing enzymes in cultured bovine aortic endothelial cells, using copper diethyldithiocarbamate (Cu10). Cu10 selectively upregulated CSE gene expression in vascular endothelial cells independent of cell density. This transcriptional induction of endothelial CSE required both the diethyldithiocarbamate scaffold and the coordinated copper ion. Additionally, the present study revealed that ERK1/2, p38 MAPK, and hypoxia-inducible factor (HIF)-1α/HIF-1β pathways mediate transcriptional induction of endothelial CSE by Cu10. The transcription factors NF-κB, Sp1, and ATF4 were suggested to act in constitutive CSE expression, although the possibility that they are involved in the CSE induction by Cu10 cannot be excluded. The present study used a copper complex as a molecular probe to reveal that the transcription of CSE is regulated by multiple pathways in vascular endothelial cells, including ERK1/2, p38 MAPK, and HIF-1α/HIF-1β. Bio-organometallics appears to be an effective strategy for analyzing the functions of intracellular signaling pathways in vascular endothelial cells.

Hydrogen Sulfide Promotes Bone Homeostasis by Balancing Inflammatory Cytokine Signaling in CBS-Deficient Mice through an Epigenetic Mechanism

Previously, we have shown hyperhomocysteinemia (HHcy) to have a detrimental effect on bone remodeling, which is associated with osteoporosis. During transsulfuration, Hcy is metabolized into hydrogen sulfide (H₂S), a gasotransmitter molecule known to regulate bone formation. Therefore, in the present study, we examined whether H₂S ameliorates HHcy induced epigenetic and molecular alterations leading to osteoporotic bone loss. To test this mechanism, we employed cystathionine-beta-synthase heterozygote knockout mice, fed with a methionine rich diet (CBS^+/− +Met), supplemented with H₂S-donor NaHS for 8 weeks. Treatment with NaHS, normalizes plasma H₂S, and completely prevents trabecular bone loss in CBS^+/− mice. Our data showed that HHcy caused inhibition of HDAC3 activity and subsequent inflammation by imbalancing redox homeostasis. The mechanistic study revealed that inflammatory cytokines (IL-6, TNF-α) are transcriptionally activated by an acetylated lysine residue in histone (H3K27ac) of chromatin by binding to its promoter and subsequently regulating gene expression. A blockade of HDAC3 inhibition in CBS^+/− mice by HDAC activator ITSA-1, led to the remodeling of histone landscapes in the genome and thereby attenuated histone acetylation-dependent inflammatory signaling. We also confirmed that RUNX2 was sulfhydrated by administration of NaHS. Collectively, restoration of H₂S may provide a novel treatment for CBS-deficiency induced metabolic osteoporosis.

Differential expression of genes identified by suppression subtractive hybridization in liver and adipose tissue of gerbils with diabetes

Objectives

We aimed at identifying genes related to hereditary type 2 diabetes expressed in the liver and the adipose tissue of spontaneous diabetic gerbils using suppression subtractive hybridization (SSH) screening.

Methods

Two gerbil littermates, one with high and the other with normal blood glucose level, from our previously bred spontaneous diabetic gerbil strain were used in this study. To identify differentially expressed genes in the liver and the adipose tissue, mRNA from these tissues was extracted and SSH libraries were constructed for screening. After sequencing and BLAST analyzing, up or down-regulated genes possibly involved in metabolism and diabetes were selected, and their expression levels in diabetic gerbils and normal controls were analyzed using quantitative RT-PCR and Western blotting.

Results

A total of 4 SSH libraries were prepared from the liver and the adipose tissue of gerbils. There are 95 up or down-regulated genes were identified to be involved in metabolism, oxidoreduction, RNA binding, cell proliferation, and differentiation or other function. Expression of 17 genes most possibly associated with diabetes was analyzed and seven genes (Sardh, Slc39a7, Pfn1, Arg1, Cth, Sod1 and P4hb) in the liver and one gene (Fabp4) in the adipose tissue were identified that were significantly differentially expressed between diabetic gerbils and control animals.

Conclusions

We identified eight genes associated with type 2 diabetes from the liver and the adipose tissue of gerbils via SSH screening. These findings provide further insights into the molecular mechanisms of diabetes and imply the value of our spontaneous diabetic gerbil strain as a diabetes model.

Gaseous Signaling Molecules in Cardiovascular Function: From Mechanisms to Clinical Translation

Carbon monoxide (CO), hydrogen sulfide (H₂S), and nitric oxide (NO) constitute endogenous gaseous molecules produced by specific enzymes. These gases are chemically simple, but exert multiple effects and act through shared molecular targets to control both physiology and pathophysiology in the cardiovascular system (CVS). The gases act via direct and/or indirect interactions with each other in proteins such as heme-containing enzymes, the mitochondrial respiratory complex, and ion channels, among others. Studies of the major impacts of CO, H₂S, and NO on the CVS have revealed their involvement in controlling blood pressure and in reducing cardiac reperfusion injuries, although their functional roles are not limited to these conditions. In this review, the basic aspects of CO, H₂S, and NO, including their production and effects on enzymes, mitochondrial respiration and biogenesis, and ion channels are briefly addressed to provide insight into their biology with respect to the CVS. Finally, potential therapeutic applications of CO, H₂S, and NO with the CVS are addressed, based on the use of exogenous donors and different types of delivery systems.

The metabolism and significance of homocysteine in nutrition and health

An association between arteriosclerosis and homocysteine (Hcy) was first demonstrated in 1969. Hcy is a sulfur containing amino acid derived from the essential amino acid methionine (Met). Hyperhomocysteinemia (HHcy) was subsequently shown in several age-related pathologies such as osteoporosis, Alzheimer's disease, Parkinson's disease, stroke, and cardiovascular disease (CVD). Also, Hcy is associated with (but not limited to) cancer, aortic aneurysm, hypothyroidism and end renal stage disease to mention some. The circulating levels of Hcy can be increased by defects in enzymes of the metabolism of Met, deficiencies of vitamins B6, B12 and folate or by feeding Met enriched diets. Additionally, some of the pharmaceuticals currently in clinical practice such as lipid lowering, and anti-Parkinsonian drugs are known to elevate Hcy levels. Studies on supplementation with folate, vitamins B6 and B12 have shown reduction in Hcy levels but concomitant reduction in certain associated pathologies have not been definitive. The enormous importance of Hcy in health and disease is illustrated by its prevalence in the medical literature (e.g. > 22,000 publications). Although there are compelling data in favor of Hcy as a modifiable risk factor, the debate regarding the significance of Hcy mediated health effects is still ongoing. Despite associations between increased levels of Hcy with several pathologies being well documented, whether it is a causative factor, or an effect remains inconclusive. The present review though not exhaustive, is focused on several important aspects of Hcy metabolism and their relevance to health.

The expression of cystathionine gamma-lyase is regulated by estrogen receptor alpha in human osteoblasts

Hydrogen sulfide (H2S), generated in the osteoblasts predominantly via cystathionine-γ-lyase (CSE), is bone protective. Previous studies suggested that the onset of bone loss due to estrogen deficiency is associated to decreased levels of H2S and blunted gene expression of CSE. However, there are still a lot of unknowns on how H2S levels influence bone cells function. The present study aims to explore the mechanisms by which estrogen may regulate CSE expression, in particular the role of estrogen receptor alpha (ERα) in human osteoblasts (hOBs). Vertebral lamina derived hOBs were characterized and then assessed for CSE expression by western blot analysis in the presence or absence of ERα overexpression. Bioinformatic analysis, luciferase reporter assay and ChIP assay were performed to investigate ERα recruitment and activity on hCSE gene promoter. Three putative half Estrogen Responsive Elements (EREs) were identified in the hCSE core promoter and were found to participate in the ERα - mediated positive regulation of CSE expression. All osteoblast samples responded to ERα over-expression increasing the levels of CSE protein in a comparable manner. Notably, the ERα recruitment on the regulatory regions of the CSE promoter occurred predominantly in female hOBs than in male hOBs. The obtained results suggest that CSE/H2S system is in relation with estrogen signaling in bone in a gender specific manner.

Relevant variations and neuroprotecive effect of hydrogen sulfide in a rat glaucoma model

Glaucoma is an irreversible and blinding neurodegenerative disease of the eye, and is characterized by progressive loss of retinal ganglion cells (RGCs). Since endogenous hydrogen sulfide (H₂S) was reported to be involved in neurodegeneration in the central nervous system, the authors aimed to develop a chronic ocular hypertension (COH) rat model simulating glaucoma and therein test the H₂S level together with the retinal protein expressions of related synthases, and further investigated the effect of exogenous H₂S supplement on RGC survival. COH rat model was induced by cross-linking hydrogel injection into anterior chamber, and the performance of the model was assessed by intraocular pressure (IOP) measurement, RGC counting and retinal morphological analysis. Endogenous H₂S level was detected along with the retinal protein expressions of H₂S-related synthases cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) in the COH rats. Retinal H₂S level and RGC survival were evaluated again after NaHS (a H₂S donor) treatment in the COH rats. The results showed that the COH model succeeded in simulating glaucoma features, and retinal H₂S level decreased significantly when the retinal protein expressions of CBS, CSE and 3-MST were downregulated generally in the COH rats. Furthermore, the decrease of retinal H₂S level and loss of RGCs were both improved by NaHS treatment in experimental glaucoma, without obvious variation of IOP. Our study revealed that the intracameral injection of cross-linking hydrogel worked efficiently in modeling glaucoma, and H₂S had protective effect on RGCs and might be involved in the pathological mechanism of glaucomatous neuropathy.

Urotensin II Protects Cardiomyocytes from Apoptosis Induced by Oxidative Stress through the CSE/H2S Pathway

Plasma urotensin II (UII) has been observed to be raised in patients with acute myocardial infarction; suggesting a possible cardiac protective role for this peptide. However, the molecular mechanism is unclear. Here, we treated cultured cardiomyocytes with H₂O₂ to induce oxidative stress; observed the effect of UII on H₂O₂-induced apoptosis and explored potential mechanisms. UII pretreatment significantly reduced the number of apoptotic cardiomyocytes induced by H₂O₂; and it partly abolished the increase of pro-apoptotic protein Bax and the decrease of anti-apoptotic protein Bcl-2 in cardiomyocytes induced by H₂O₂. SiRNA targeted to the urotensin II receptor (UT) greatly inhibited these effects. Further analysis revealed that UII increased the production of hydrogen sulfide (H₂S) and the level of cystathionine-γ-lyase (CSE) by activating the ERK signaling in H₂O₂-treated-cardiomyocytes. Si-CSE or ERK inhibitor not only greatly inhibited the increase in CSE level or the phosphorylation of ERK induced by UII but also reversed anti-apoptosis of UII in H₂O₂-treated-cadiomyocytes. In conclusion, UII rapidly promoted the phosphorylation of ERK and upregulated CSE level and H₂S production, which in turn activated ERK signaling to protect cardiomyocytes from apoptosis under oxidative stress. These results suggest that increased plasma UII level may protect cardiomyocytes at the early-phase of acute myocardial infarction in patients.

Hydrogen sulfide preconditions the db/db diabetic mouse heart against ischemia-reperfusion injury by activating Nrf2 signaling in an Erk-dependent manner

Hydrogen sulfide (H2S) therapy protects nondiabetic animals in various models of myocardial injury, including acute myocardial infarction and heart failure. Here, we sought to examine whether H2S therapy provides cardioprotection in the setting of type 2 diabetes. H2S therapy in the form of sodium sulfide (Na2S) beginning 24 h or 7 days before myocardial ischemia significantly decreased myocardial injury in db/db diabetic mice (12 wk of age). In an effort to evaluate the signaling mechanism responsible for the observed cardioprotection, we focused on the role of nuclear factor E2-related factor (Nrf2) signaling. Our results indicate that diabetes does not alter the ability of H2S to increase the nuclear localization of Nrf2, but does impair aspects of Nrf2 signaling. Specifically, the expression of NADPH quinine oxidoreductase 1 was increased after the acute treatment, whereas the expression of heme-oxygenase-1 (HO-1) was only increased after 7 days of treatment. This discrepancy was found to be the result of an increased nuclear expression of Bach1, a known repressor of HO-1 transcription, which blocked the binding of Nrf2 to the HO-1 promoter. Further analysis revealed that 7 days of Na2S treatment overcame this impairment by removing Bach1 from the nucleus in an Erk1/2-dependent manner. Our findings demonstrate for the first time that exogenous administration of Na2S attenuates myocardial ischemia-reperfusion injury in db/db mice, suggesting the potential therapeutic effects of H2S in treating a heart attack in the setting of type 2 diabetes.