Mitochondria-produced superoxide mediates angiotensin II-induced inhibition of neuronal potassium current

Yin JX, Yang RF, Li S, Renshaw AO, Li Y, Schultz HD, Zimmerman MC. Mitochondria-produced superoxide mediates angiotensin II-induced inhibition of neuronal potassium current. Am J Physiol Cell Physiol 298: C857-C865, 2010. First published January 20, 2010; doi:10.1152/ajpcell.00313.2009.-Reactive oxygen species (ROS), particularly superoxide (O-2(center dot-)), have been identified as key signaling intermediates in ANG II-induced neuronal activation and sympathoexcitation associated with cardiovascular diseases, such as hypertension and heart failure. Studies of the central nervous system have identified NADPH oxidase as a primary source of O-2(center dot-) in ANG II-stimulated neurons; however, additional sources of O-2(center dot-), including mitochondria, have been mostly overlooked. Here, we tested the hypothesis that ANG II increases mitochondria-produced O-2(center dot-) in neurons and that increased scavenging of mitochondria-produced O-2(center dot-) attenuates ANG II-dependent intraneuronal signaling. Stimulation of catecholaminergic (CATH.a) neurons with ANG II (100 nM) increased mitochondria-localized O-2(center dot-) levels, as measured by MitoSOX Red fluorescence. This response was significantly attenuated in neurons overexpressing the mitochondria-targeted O-2(center dot-)-scavenging enzyme Mn-SOD. To examine the biological significance of the ANG II-mediated increase in mitochondria-produced O-2(center dot-) , we used the whole cell configuration of the patch-clamp technique to record the well-characterized ANG IIinduced inhibition of voltage-gated K+ current (I-Kv) in neurons. Adenovirus- mediated Mn-SOD overexpression or pretreatment with the cellpermeable antioxidant tempol (1 mM) significantly attenuated ANG II-induced inhibition of I-Kv. In contrast, pretreatment with extracellular SOD protein (400 U/ml) had no effect. Mn-SOD overexpression also inhibited ANG II-induced activation of Ca2+/calmodulin kinase II, a redox-sensitive protein known to modulate I-Kv. These data indicate that ANG II increases mitochondrial O-2(center dot-), which mediates, at least in part, ANG II-induced activation of Ca2+/calmodulin kinase II and inhibition of I-Kv in neurons.