Overexpressed heat shock protein 70 attenuates hypoxic injury in coronary endothelial cells

Previous studies indicate that heat shock protein 70 (hsp70) improves the myocardial tolerance to ischemia-reperfusion injury by a mechanism that is not well understood. To better define this protective function, it is important to distinguish a role of hsp70 on coronary endothelial cells (cEC) from that on cardiac myocytes. Thus, we transfected rat cEC with a human hsp70 cDNA by using hemagglutinating virus of Japan-liposome method (group H). Control cells (group C) were transfected with a vector containing no gene. Immunohistochemical staining demonstrated overexpression of hsp70 in the cytosol of the cells in group H. Western blotting also showed large amounts of hsp70 expression in these cells. After 18 h of hypoxia followed by 2 h of reoxygenation, the adenosine triphosphate content was higher in group H (H v C; 1.05 +/- 0.08 v 0.68 +/- 0.04 microgram/dish, P = 0.0007). In addition, lactate dehydrogenase leakage after hypoxic insult was lower in group H than that in group C (61.3 +/- 4.5 v 85.4 +/- 6.1 10(-3) IU/dish/37 degrees C, P = 0.004). Conversely, the leakage of FITC-albumin through a confluent monolayer of cEC after hypoxia-reoxygenation was less in group H than that in group C (11.1 +/- 1.8 v 27.4 +/- 3.1%, P = 0.0003). Thus, the high level expression of hsp70 caused by gene transfection enhanced the hypoxic tolerance of coronary endothelial cell. Therefore, coronary endothelial cell is an important targets of hsp70-mediated cardioprotection as well as cardiac myocytes.