Abstract 4848: Angintensin II Stimulates Microtubule Reorganization Mediated by SIRT2 in Endothelial Cells
Angiotensin II has been implicated in the pathophysiology of vascular remodeling. Microtubule composed of tubulins regulates cell shape, migration and survival. Tubulin acetylation plays an important role in the control of microtubule structure and microtubule-based cellular functions. We studied angiotensin II-induced changes in microtubules in endothelial cells. Immunofluorescence microscopy showed that acetylated tubulin was decreased in PECAM-1-positive cells in the intima of the aortic walls in mice loaded with angiotensin II, compared to mice loaded with control vehicle. In cultured human endothelial cells in quiescence, α-tubulin-positive microtubules were acetylated and showed radial layout from microtubule-organizing center to peripheral edge of cells. Angiotensin II induced disassembly and deacetylation of α-tubulin, which were blocked by pretreatment with losartan that is an angiotensin II type 1 receptor blocker, sirtinol that is an inhibitor for sirtuin class deacetylases, and depletion of a deacetylase SIRT2 by RNA interference. We investigated the involvement of SIRT2 in angiotensin II-induced endothelial cell migration using Boyden chamber method. Angiotensin II caused a significant increase in cell migration, which was blocked by pretreatment with sirtinol and SIRT2 depletion. It has been reported that angiotensin II is involeved in cytoskeletal reorganization stimulated by mechanical stretch in endothelial cells. To investigate the effects of mechanical stretch on microtubule reorganization, cultured endothelial cells were subjected to 10% uniaxial stretch and examnied by immunofluorescence. Mechanically stretched cells showed vertical alignment to tension direction and tubulin deacetylation in peripheral side of cells, compared to control static cells. Mechanical stretch-induced changes of microtubules were blocked by pretreatment with sirtinol and SIRT2 depletion. These data suggest that angiotensin II and mechanical stretch stimulate microtubule redistribution and deacetylation via SIRT2 in endothelial cells. Further studies are necessary to elucidate the roles of SIRT2-mediated microtubule reorganization in vascular remodeling.