Alcohol Regulation of Resident Vascular Stem Cells.

University Of Rochester, Rochester NY

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Abstract

? DESCRIPTION (provided by applicant): Vascular smooth muscle cells (vSMC) play a key role in the pathophysiology of cardiovascular disease (CVD). Emerging evidence suggests that stem cells present within the vessel wall differentiate to vSMC and are the active contributors to the remodeling and repair of the artery wall. This information highlights a new cell target to investigate for agents known to affect CVD, as well as a novel potential therapeutic target for treatment of vascular disease. While alcohol (EtOH) consumption is a well-established factor affecting the incidence and severity of CVD, its effects on the regenerative capacity of resident vascular stem cells have yet to be ascertained. A stem cell population implicated in vascular disease progression includes Sca1+ adventitial progenitor cells (APC) that reside at the medial adventitial boundary. APC proliferate and differentiate into vSMC that invade the intima in vascular injury models. Several factors have been described as regulators of stem cell self-renewal, differentiation and growth, most notably the morphogen sonic hedgehog (Shh). We have shown that a-actin negative, Hh-positive cells that co- localize with the APC population are located at the medial-adventitial boundary of normal vessels and later appear within the a-actin positive medial and intimal layer following injury. Hedgehog signaling is triggered by binding of the secreted Shh ligand with the transmembrane receptor Patched (Ptch) and is subsequently mediated by transcriptional effectors belonging to the Gli family. Components of the Hedgehog pathway are induced after vascular injury in vivo and a Hedgehog - Notch signaling axis controls vSMC growth and phenotype in vitro. Crucially, we have recently shown that local inhibition of hedgehog signaling in situ within the vessel wall attenuates intimal-medial thickening following injury. Our preliminary data now indicate that alcohol regulates the expression of hedgehog signaling components in vSMC, and that Shh controls stem cell transition to vSMC in vitro. Therefore, our overall hypothesis is that alcohol interferes with the renewal and/or differentiatio of resident vascular stem cells, and thus affects vessel remodeling and CVD, by affecting hedgehog signaling. We will test the validity of this hypothesis in vitro (APC) and in vivo (caroti ligation mouse model of atherosclerosis) and investigate the mechanism(s) whereby alcohol may modulate Hedgehog signaling, focusing on Ptch1 receptor-Caveolin-1 co-localization in lipid rafts and degradation by E3 ubiquitin ligases. Deciphering the mechanisms whereby alcohol affects cardiovascular disease is of major clinical importance and significance.