Heat-induced increases in endothelial NO synthase expression and activity and endothelial NO release

Abstract
Endothelial nitric oxide (NO) synthase (eNOS) is regulated by heat shock protein 90 (HSP90), a heat-inducible protein; however, the effect of heat shock on eNOS expression and eNO release is unknown. Bovine aortic endothelial cells were incubated for 1 h at 37°C, 42°C, or 45°C and cell lysates were evaluated with the use of Western blotting. We observed a 2.1 ± 0.1-fold increase in eNOS protein content, but no change in HSP90 content, HSP70 content, or HSP90/eNOS association, 24 h after heat shock at 42°C. We also observed a 7.7 ± 1.5-fold increase in HSP70 protein content, but did not observe a change in eNOS or HSP90 24 h after heat shock at 45°C. eNOS activity and maximal bradykinin-stimulated NO release was significantly increased 24 h after heat shock at 42°C. Heat shock in rats (core temperature: 42°C, 15 min) resulted in a significant increase in aortic eNOS, HSP90, and HSP70 protein content. The aorta from heat-shocked rats exhibited a decreased maximal contractile response to phenylephrine, which was abolished by preincubation with N G-nitro-l-arginine. We conclude that prior heat shock is a physical stimulus of increased eNOS expression and is associated with an increase in eNOS activity, agonist-stimulated NO release, and a decreased vasoconstrictor response.