The
mineralocorticoid receptor (MR) plays an important role in
salt and water homeostasis and pathological tissue modifications, such as cardiovascular and renal
fibrosis. Importantly, MR activation by
aldosterone per se is not sufficient for the deleterious effects but requires the additional presence of a certain pathological milieu. Phenomenologically, this milieu could be generated by enhanced nitrosative stress. However, little is known regarding the modulation of MR transcriptional activity in a pathological milieu. The
glucocorticoid receptor (GR), the closest relative of the MR, binds to the same
hormone-response element but elicits protective effects on the cardiovascular system. To investigate the possible modulation of MR and GR by nitrosative stress under controlled conditions we used human embryonic kidney (HEK) cells and measured MR and GR transactivation after stimulation with the
nitric oxide (NO)-donor SNAP and the
peroxynitrite-donor Sin-1. In the presence of
corticosteroids NO led to a general reduced
corticosteroid receptor activity by repression of
corticosteroid receptor-
DNA interaction. The NO-induced diminished transcriptional MR activity was most pronounced during stimulation with physiological
aldosterone concentrations, suggesting that NO treatment prevented its pathophysiological overactivation. In contrast, single
peroxynitrite administration specifically induced the MR transactivation activity whereas genomic GR activity remained unchanged. Mechanistically,
peroxynitrite permitted nuclear MR translocation whereas the cytosolic GR distribution was unaffected. Consequently,
peroxynitrite represents a MR-specific
aldosterone mimetic. In summary, our data indicate that the genomic function of
corticosteroid receptors can be modulated by nitrosative stress which may induce the shift from physiological toward pathophysiological MR effects.