NITRIC OXIDE INDUCES HO-1 IN ADRENOCORTICAL CELLS

FRANCISCO ASTORT; MARÍA MERCAU; CAMILA MARTINEZ CALEJMAN; MARTÍN REPETTO; PABLO ARIAS; CORA B. CYMERYNG.

Simposio; The First South American Spring Symposium in Signal Transduction and Molecular Medicine; 2010

Previous results from our laboratory demonstrated the reciprocal regulation of two local modulatory systems of adrenal steroidogenesis, e.g. nitric oxide (NO) synthase and heme oxygenase (HO). We then showed that adrenal HO-1 expression levels were positively regulated by endogenously generated NO. Present experiments were designed to analyze the mechanisms involved in the induction of HO-1 by NO in adrenal cells. Both HO-1 mRNA and protein levels were upregulated in Y1 cells incubated for 8 hours in the presence of a NO donor (DETA-NO, 1 mM). The signalling pathways involved were then analyzed. In regard to the NFB pathway, DETA-NO treatment resulted in a significant inhibition of the activity of the reporter plasmid KB-LUC, while overexpression of p65 decreased HO-1 protein levels. At the same time, DETA-NO had no significant effect on the activity of a Nrf2 reporter plasmid although Nrf2 overexpression significantly increased HO-1 protein levels. PKC inhibition blocked the increase in HO-1 protein levels triggered by the NO-donor. We hypothesize that in Y1 adrenal cells the NO-induced increase in HO-1 expression levels is negatively regulated by NFB-dependent mechanisms, is independent of the activation of the redox dependent transcription factor Nrf2, and is mediated by a PKC-dependent mechanism. The possible involvement of a NO-dependent HO-1 mRNA stabilization mechanism is currently under investigation.