title: The effect of phenotype on mechanical stretch-induced vascular smooth muscle cell apoptosis.
abstract: The present study evaluated mechanical stretch-induced apoptosis in swine vascular smooth muscle cells (VSMC) of different phenotypes. We demonstrated that differentiated VSMC express a greater level of Bcl-2-associated death factor (BAD) and have a significant cell loss when exposed to mechanical stretch (10% elongation, 1 Hz) for 24 h. We further demonstrated that apoptosis was significantly increased only in differentiated VSMC exposed to mechanical stretch. To test the hypothesis that the intracellular level of BAD in VSMC determines its response to mechanical stretch-induced apoptosis, we examined whether BAD expression was upregulated by mechanical stretch-induced apoptosis and was associated with the increase in the apoptosis level of differentiated VSMC. When exposed to mechanical stretch, the expression of BAD in differentiated VSMC was elevated at 1 h and remained at higher levels during the application of stretch (24 h). In contrast, Bcl-2 expression was suppressed during the application of stretch. Moreover, the proapoptotic function of BAD was inhibited by overexpression of Bcl-2 through transient transfection of VSMC with pCEP4-Bcl-2 or incubation of VSMC with vascular epithelial growth factor. These results suggest that mechanical stretch-induced VSMC apoptosis is phenotype dependent. The higher levels of apoptosis of differentiated VSMC upon mechanical stretch were, at least in part, dependent on their intrinsic level of BAD.
authors.affiliation: Columbus Children's Research Institute, Children's Hospital, Columbus, Ohio 43205, USA. sub@ccri.net
authors.forename: Baogen Y
authors.initials: BY
authors.lastname: Su
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Shontz
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Flavahan
authors.forename: Philip T
authors.initials: PT
authors.lastname: Nowicki
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation; D049109:Cell Proliferation; D048430:Cell Shape; D002478:Cells, Cultured; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D010641:Phenotype; D011169:Portal Vein; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D013314:Stress, Mechanical; D013552:Swine; D013997:Time Factors; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D051025:bcl-Associated Death Protein / Q000378:metabolism
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D042461:Vascular Endothelial Growth Factor A; D051025:bcl-Associated Death Protein