Abstract 494: Heat Shock Protein 27: Influence on Endothelial Cell Homeostasis and Correlation with Coronary Artery Disease
We recently identified heat shock protein 27 (HSP27) as an estrogen receptor beta associated protein and a biomarker for coronary atherosclerosis (ATVB 2005). Expression of HSP27 was markedly attenuated as the stage of atherosclerosis progressed in the coronary arteries of young individuals. To elucidate the possible roles of HSP27 in atherogenesis we hypothesized that the abundance of HSP27 may have an effect on endothelial cell homeostasis in the vessel wall. Moreover, we postulated that HSP27 activation, which involves phosphorylation by mitogen-activated protein kinases (MAPK) is necessary for the atheroprotective effects of HSP27. We began to test this hypothesis by assessing HSP27 serum levels in 9 individuals without clinical evidence of atherosclerosis (NORM) and 9 patients with angiographic evidence of coronary artery disease (CAD). HSP27 levels were more than 3-fold greater in NORM vs CAD individuals (919 ± 361 vs 202 ± 61; p=0.04). In vitro we found that SB203580 (SB), a P38-MAPK inhibitor could be used to inhibit HSP27 activation in human umbilical vein endothelial cells (HUVECs) grown in culture. For example, HUVEC DNA synthesis was 50% reduced by SB compared with control (8232 ± 1021 vs 16306 ± 1110 [3H]-thymidine incorporation (CPM), p< 0.001). Moreover, HUVECs migration was 61% reduced by SB compared with control (596 ± 175 vs 1497 ± 244 cell numbers/mm2, p< 0.001) as assessed by a monolayer scratch assay. HUVECs cultured within type-I collagen gel were altered from a monolayer appearance into tube-like/cord-like structures in a time-dependent manner. The tube structures were 2-fold greater in length in SB groups compared with control (8.89 ± 0.46 vs 4.69 ± 0.39 mm/mm2/HPF, p< 0.001), and apoptosis was reduced by 61% in SB compared with control (28 ± 4 vs. 11 ± 3%, p < 0.001) after 48hrs. In conclusion, these data suggest that HSP27 abundance and activation plays an important role in prevention of atherogenesis, likely by influencing EC homeostasis.