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Am J Physiol Cell Physiol. 2010 Apr;298(4):C857-65. doi: 10.1152/ajpcell.00313.2009. Epub 2010 Jan 20.

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

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  • 1Dept. of Cellular and Integrative Physiology, Univ. of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, NE 68198-5850, USA.


Reactive oxygen species (ROS), particularly superoxide (O(2)(.-)), 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)(.-) in ANG II-stimulated neurons; however, additional sources of O(2)(.-), including mitochondria, have been mostly overlooked. Here, we tested the hypothesis that ANG II increases mitochondria-produced O(2)(.-) in neurons and that increased scavenging of mitochondria-produced O(2)(.-) attenuates ANG II-dependent intraneuronal signaling. Stimulation of catecholaminergic (CATH.a) neurons with ANG II (100 nM) increased mitochondria-localized O(2)(.-) levels, as measured by MitoSOX Red fluorescence. This response was significantly attenuated in neurons overexpressing the mitochondria-targeted O(2)(.-)-scavenging enzyme Mn-SOD. To examine the biological significance of the ANG II-mediated increase in mitochondria-produced O(2)(.-), we used the whole cell configuration of the patch-clamp technique to record the well-characterized ANG II-induced inhibition of voltage-gated K(+) current (I(Kv)) in neurons. Adenovirus-mediated Mn-SOD overexpression or pretreatment with the cell-permeable 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 Ca(2+)/calmodulin kinase II, a redox-sensitive protein known to modulate I(Kv). These data indicate that ANG II increases mitochondrial O(2)(.-), which mediates, at least in part, ANG II-induced activation of Ca(2+)/calmodulin kinase II and inhibition of I(Kv) in neurons.

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