Hydrogen Sulfide (H2S) as a regulator of myocardial redox state and the redox-sensitive regulation of cystathionine γ-lyase (CSE)

In advanced stages, cardiac disease causes millions of deaths each year. Superoxide anions (O2.-) and their derivative peroxynitrite (ONOO-) contribute to cardiac disease pathogenesis, yet strategies to reduces these reactive oxygen species through antioxidants in large scale clinical trials have largely been unsuccessful. Better understanding of pathways regulating enzymatic sources of O2.- like NADPH oxidases, uncoupled nitric oxide synthases (NOSs) and mitochondrial oxidases are required to regulate myocardial oxidative stress in patients with advanced stages of cardiac disease. Hydrogen sulfide (H2S) is a gaseous signalling molecule generated by transsulfuration pathway enzymes cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (MST). H2S regulates oxidative stress in animal models and shows promise for cardiovascular therapeutic strategy. This thesis investigates whether H2S/CSE biology is related to human myocardial redox state in a cohort of individuals with advanced cardiac disease (Oxford Heart, Fat, Vessels Cohort; Ox-HVF). Individuals with varying levels of myocardial oxidative stress and function were extensively phenotyped for H2S biology. Individuals with high myocardial oxidative stress from NADPH oxidases and NOSs were found to have high expression of myocardial CSE. To examine first the positive association with NADPH oxidase activity, CSE expression was examined after myocardial oxidative injury and CSE was found to be redox-sensitive. Furthermore, direct effects of two exogenous H2S donors (NaHS and GYY4137) demonstrated a direct regulation of O2.- from NOSs in myocardium from individuals with advanced cardiac disease, further supporting H2Sâs direct role in the regulation of NOS biology. Finally, identification of a SNP in CSE further demonstrated CSEâs causal role in the regulation of O2.- generation from mitochondrial oxidases. Taken together, we demonstrate for the first time that H2S and CSE biology are linked to human myocardial redox state and have a causal role in redox regulation in the human heart. These findings suggest H2S/CSE biology are important endogenous regulators of myocardial redox state in humans and continued exploration of these pathways may develop novel therapeutic strategies against myocardial oxidative stress in cardiac disease.</p

Hydrogen Sulfide (H2S) as a regulator of myocardial redox state and the redox-sensitive regulation of cystathionine γ-lyase (CSE)

In advanced stages, cardiac disease causes millions of deaths each year. Superoxide anions (O2.-) and their derivative peroxynitrite (ONOO-) contribute to cardiac disease pathogenesis, yet strategies to reduces these reactive oxygen species through antioxidants in large scale clinical trials have largely been unsuccessful. Better understanding of pathways regulating enzymatic sources of O2.- like NADPH oxidases, uncoupled nitric oxide synthases (NOSs) and mitochondrial oxidases are required to regulate myocardial oxidative stress in patients with advanced stages of cardiac disease. Hydrogen sulfide (H2S) is a gaseous signalling molecule generated by transsulfuration pathway enzymes cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (MST). H2S regulates oxidative stress in animal models and shows promise for cardiovascular therapeutic strategy. This thesis investigates whether H2S/CSE biology is related to human myocardial redox state in a cohort of individuals with advanced cardiac disease (Oxford Heart, Fat, Vessels Cohort; Ox-HVF). Individuals with varying levels of myocardial oxidative stress and function were extensively phenotyped for H2S biology. Individuals with high myocardial oxidative stress from NADPH oxidases and NOSs were found to have high expression of myocardial CSE. To examine first the positive association with NADPH oxidase activity, CSE expression was examined after myocardial oxidative injury and CSE was found to be redox-sensitive. Furthermore, direct effects of two exogenous H2S donors (NaHS and GYY4137) demonstrated a direct regulation of O2.- from NOSs in myocardium from individuals with advanced cardiac disease, further supporting H2S’s direct role in the regulation of NOS biology. Finally, identification of a SNP in CSE further demonstrated CSE’s causal role in the regulation of O2.- generation from mitochondrial oxidases. Taken together, we demonstrate for the first time that H2S and CSE biology are linked to human myocardial redox state and have a causal role in redox regulation in the human heart. These findings suggest H2S/CSE biology are important endogenous regulators of myocardial redox state in humans and continued exploration of these pathways may develop novel therapeutic strategies against myocardial oxidative stress in cardiac disease.</p

ZBTB33 is mutated in clonal hematopoiesis and myelodysplastic syndromes and impacts RNA splicing

Clonal hematopoiesis results from somatic mutations in cancer driver genes in hematopoietic stem cells. We sought to identify novel drivers of clonal expansion using an unbiased analysis of sequencing data from 84,683 persons and identified common mutations in the 5-methylcytosine reader ZBTB33 as well as in YLPM1, SRCAP, and ZNF318. We also identified these mutations at low frequency in patients with myelodysplastic syndrome. Zbtb33-edited mouse hematopoietic stem and progenitor cells exhibited a competitive advantage in vivo and increased genome-wide intron retention. ZBTB33 mutations potentially link DNA methylation and RNA splicing, the two most commonly mutated pathways in clonal hematopoiesis and myelodysplastic syndromes.SIGNIFICANCE: Mutations in known driver genes can be found in only about half of individuals with clonal hematopoiesis. Here, we performed a somatic mutation discovery effort in nonmalignant blood samples, which identified novel candidate genes that may play biological roles in hematopoietic stem cell expansion and hematologic malignancies