Hypoxia induces heat shock protein expression in human coronary artery bypass grafts

Objective: Heat shock proteins (HSPs) are molecular chaperones which are es sential for cell survival. Heat shock and hypoxia markedly increase the exp ression of several HSPs in various tissues, i.e. heart. In our in vitro stu dy, we investigated whether HSPs are inducible in human vessels which are u sed as coronary artery bypass grafts. Methods: We used remnants of the saph enous vein and the internal mammary artery from 34 patients undergoing coro nary artery bypass surgery. Each vessel was divided into segments, one for control conditions at 37 degreesC (5% CO2-95% air), the remaining ones for thermal (30 min at 42 degreesC) or hypoxic treatment (6 h oxygen deprivatio n with nitrogen). The expression of Hsp60, Hsp72 and Hsp73 was investigated by immunohistochemistry and Western-blot analysis. Results: Compared to co ntrols, segments of the saphenous vein undergoing heat treatment showed sig nificantly increased expression of Hsp72 in the intima (P=0.035) and Hsp73 in the media (P=0.003). In the internal mammary artery, Hsp72 and Hsp73 wer e expressed in the intima at significantly higher levels (P=0.042 each). A 6 h oxygen deprivation with nitrogen resulted in elevated levels of Hsp60 ( media: P=0.048), of Hsp72 (intima: P<0.001 and media: P=0.003) and of Hsp73 (intima: P=0.029) in the saphenous vein. In the internal mammary artery, H sp73 expression was significantly enhanced (intima: P=0.048 and media: P=0. 017). The results were confirmed by Western-blot analysis in representative veins. Conclusions: These findings demonstrate the common cellular defense mechanism of HSP expression in response to stress in coronary artery bypas s grafts. Hypoxia and heat treatment strongly induce Hsp72 and Hsp73 expres sion in human coronary artery bypass grafts. (C) 2001 Published by Elsevier Science B.V.