Hypertension is the most prevalent cardiovascular disorder worldwide. Deregulation of vascular smooth muscle cell (VSMC) contraction is a final common pathway in hypertension. Intracellular calcium (Ca2+) is a trigger and key determinant of VSMC contraction. Vascular smooth muscle cytosolic Ca2+ concentration is tightly regulated by Ca2+ influx and efflux from the extracellular space and from intracellular stores, most notably the sarcoplasmic reticulum. Inositol 1,4,5- trisphosphate (IP3) through its receptors (IP3R) controls Ca2+ release form the sarcoplasmic reticulum into the cytoplasm. Hypertension is a multi-system disease. Disruption of homeostatic mechanisms in distant organs can affect vascular tone. As one example, bacteria that inhabit the gut (gut microbiome) can modulate blood pressure. Normotensive animals become hypertensive when transplanted with gut microbiota from hypertensive animals, and vice versa. Furthermore, hypertension in humans is associated with specific alterations in gut microbial diversity, lending credence to the premise that a change in gut microbial load and diversity (dysbiosis) contributes to the pathogenesis of hypertension. Our preliminary data shows that dysbiosis in mice caused by broad-spectrum antibiotics leads to hypercontractility of blood vessels and associated upregulation of IP3R1. In addition, we have evidence that broad-spectrum antibiotics downregulate expression of miR-204, a microbiome-sensitive microRNA, in vascular smooth muscle cells. Moreover, miR-204 targets IP3R1, and mice with global deletion of miR-204 are susceptible to developing hypertension. We therefore hypothesize that miR-204 is a key regulator of VSMC contractility, and its downregulation due to gut microbial dysbiosis promotes hypertension. This application will examine the role of miR-204 in regulating VSMC Ca2+ and explore the mechanisms by which it does so. It will use mice with deletion of miR-204 and IP3R1 in VSMC, and state-of-the-art methodologies to assess Ca2+ flux in cells and in vessels of live animals. Using these unique tools, and with the assembled expertise, it will determine if miR-204 controls blood pressure, VSMC Ca2+ homeostasis and VSMC contraction via IP3R1. In addition, it will blaze a trail connecting the gut microbiome and regulation of vascular tone, by determining if gut microbial dysbiosis disrupts VSMC Ca2+ homeostasis, and promotes hypertension through downregulation of miR-204. Information gained from this work will be a vertical advancement in the field of hypertension research.
The significance of this proposal is driven by the potential impact of identifying novel therapies to enhance the cardiovascular function during hypertension. We will explore gut microbiota and miR-204 as potential cardiovascular- therapeutic agents, evaluating their effect on vascular calcium and vascular smooth muscle cells (VSMC) function. Understanding the mechanism by which microbiota and miR-204 mediates vascular caclium disruption and VSMC dysfunction may lead to novel treatment strategies conferring the benefits of calcium control while circumventing the potential risks of delivering live biologics.
