Nitric oxide sets off an antioxidant response in adrenal cells: involvement of sGC and Nrf2 in HO-1 induction

Induction of microsomal heme oxygenase 1 (HO-1) activity is considered a cytoprotective mechanism in different cell types. In adrenal cells, HO-1 induction by ACTH exerts a modulatory effect on steroid production as well. As nitric oxide (NO) has been also regarded as an autocrine/paracrine modulator of adrenal steroidogenesis we sought to study the effects of NO on the induction of HO-1 and the mechanism involved. We hereby analyzed the time and dose-dependent effect of a NO-donor (DETA/NO) on HO-1 induction in a murine adrenocortical cell line. We showed that this effect is mainly exerted at a transcriptional level as it is inhibited by actinomycin D and HO-1 mRNA degradation rates were not affected by DETA/NO treatment. HO-1 induction by NO does not appear to involve the generation of oxidative stress as it was not affected by antioxidant treatment. We also demonstrated that NO-treatment results in the nuclear translocation of the nuclear factor-erythroid 2-related factor (Nrf2), an effect that is attenuated by transfecting the cells with a dominant negative isoform of Nrf2. We finally show that the effects of the NO-donor are reproduced by a permeable analog of cGMP and that a soluble guanylate cyclase specific inhibitor blocked both the induction of HO-1 by NO and the nuclear translocation of Nrf2.