Abstract 454: Endoplasmic Reticulum Stress Response in Pressure-Overloaded Ischemic-Reperfused Hearts

Abstract

An integral component of endoplasmic reticulum (ER) stress-induced apoptosis is expression of growth arrest- and DNA damage inducible protein 153 (GADD153); this protein is normally expressed in low levels but its expression markedly increases following sustained stress to the ER. GADD153 regulates both apoptosis and inflammatory response. We previously showed that pressure overload exacerbates myocardial ischemia reperfusion (IR) injury. In this study, we tested the hypothesis that pressure overload regulates ER stress response manifested as increased GADD153 expression thereby upregulating inflammatory cytokine production and contributing to worsening of myocardial IR injury. Accordingly, Langendorff-perfused rat hearts were subjected to global IR protocol with perfusion pressure set at 80 or 160 cmH 2 O; normoxic hearts served as controls. Compared to normoxia, an IR insult increased expressions of pro-inflammatory cytokine (interleukin (IL)-17) and GADD153 in association with increased cell death. In the ischemic-reperfused hearts, pressure overload a) increased expression of GADD153, b) reduced interleukin (IL)-10 but increased IL-17 and c) increased annexin V immunostaining as well as apoptotic and necrotic cell death. Collectively, the results suggest that pressure overload exacerbates cell death in the isolated ischemic-reperfused heart involving regulation of ER stress response and inflammation.