Hypochlorous acid stimulates heme oxygenase-1 gene expression in human endothelial cells

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] In the present study, we tested the hypothesis that Hypochlorous acid (HOCl) regulates the expression of the cytoprotective protein heme oxygenase-1 (HO-1) in human umbilical vein and human aortic ECs. Treatment of human endothelial cells (Ecs) with pathophysiologically relevant concentrations of HOCl (3-300 [micrometer]) stimulated a concentration- and time-dependent increase in HO-1 protein. A significant rise in HO-1 protein was first detected after 4 hours and levels progressively increased over 24 hours of HOCl exposure. HOCl-mediated increases in HO-1 protein were preceded by significant elevations in HO-1 mRNA that peaked 4 to 8 hours after HOCl treatment. The induction of HO-1 by HOCl was dependent on de novo RNA and protein synthesis since it was blocked by the transcriptional inhibitor, actinomycin D, and by the protein synthesis inhibitor, cycloheximide. In addition, the induction of HO-1 mRNA and protein by HOCl was inhibited by the glutathione donor, N-acetyl-L-cysteine. Interestingly, treatment of human ECs with HOCl (300 [micrometer]) caused significant cell death that was enhanced by the HO inhibitor, tin protoporphyrin-IX, indicating a potential cytoprotective role for HO-1. In conclusion, this study demonstrates that HOCl stimulates HO-1 gene expression in human ECs via a transcriptional- and redox-sensitive pathway. The ability of HOCl to induce HO-1 in ECs may represent a critical adaptive response to preserve cell function and viability at sites of atherosclerosis.