Cytoplasmic and mitochondrial-produced superoxide mediates angiotensin II (AngII)-induced inhibition of K+ current in CATH.a neurons.

Reactive oxygen species, such as superoxide (O2•-) and hydrogen peroxide, have been identified as key signaling intermediates in AngII-induced neuronal activation and sympathoexcitation associated with heart failure and hypertension. Here, we hypothesized that AngII-induced inhibition of the delayed rectifier K+ current (IKv) is mediated specifically by intracellular O2•-. Differentiated CATH.a neurons were infected with adenoviral vectors (50 MOI) encoding the primarily cytoplasmic-localized O2•- dismutase (CuZnSOD), or the mitochondrial-targeted isoform (MnSOD). Four days later, IKv was recorded using the whole cell configuration of the patch-clamp technique. In non-infected and control vector (AdEmpty)-infected neurons, AngII (100 nM) decreased the density of IKv by 45 ± 4% and 37 ± 6%, respectively (IKv elicited by 400 ms pulse from -80 to +80 mV, P<0.05 vs vehicle). This AngII effect was significantly blunted in neurons overexpressing active MnSOD or CuZnSOD as AngII inhibited IKv by merely 18 ± 8% and 11 ± 3%, respectively (P<0.05 vs AdEmpty-treated and non-infected cells). In contrast, extracellular SOD protein (400 U/ml)-treated cells exhibited the characteristic AngII-induced inhibition of IKv (34 ± 7%). These data suggest that intracellular O2•- produced from both cytoplasmic and mitochondrial sources attenuates AngII-induced inhibition of IKv in neurons. NIH P20RR017675; P01HL062222 [ABSTRACT FROM AUTHOR]