Heat shock provides delayed protection against oxidative injury in cultured human umbilical vein endothelial cells

During both mild and severe ischemia, vascular endothelial cells lining lar ge and small vessels of the ischemic organ are exposed to oxygen-derived fr ee radicals resulting in oxidative damage to the organ. Heat shock has been shown to induce thermotolerance and also protect against ischemic injury, possibly via increased synthesis of heat shock proteins (HSPs), We hypothes ized that heat shock preconditioning may protect human endothelial cells ag ainst oxidative damage. Cultured human umbilical Vein endothelial cells (HU VEC) were subjected to heat shock (42 degrees C, Ih) and allowed to recover for 2 or 20 h, at which times the cells were oxidatively stressed for Ih b y exposing them to 100-200 mu mol/l of hydrogen peroxide (H2O2). Cellular d amage was assessed immediately and 18 h later by morphology and release of lactate dehydrogenase (LDH). No protection of HUVEC was seen using the 2-ho ur recovery interval, but a significant protection (P<0.05) was observed af ter the 20-hour delay, Northern blot analysis at 1 and 2 h after heating sh owed induction of HSP-70 mRNA. Western blot analysis demonstrated a signifi cant increase in HSP-72 protein after 2 as well as 20 h of recovery from he at shock, although the amounts of protein at the two times were not signifi cantly different. Furthermore, no differences in the activity of the antiox idant enzyme catalase were observed between heated and unheated HUVEC at 2 and 20h after heat preconditioning, Thus, heat shock preconditioning induce s delayed protection against oxidative injury in HUVEC, and the mechanism o f protection appears to involve more than the expression of HSP-72 or activ ity of catalase. (C) 1998 Academic Press.