Mitochondria-produced superoxide mediates angiotensin II-induced inhibition of neuronal potassium current.
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.
Yin
Jing-Xiang
JX
Dept. of Cellular and Integrative Physiology, Univ. of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, NE 68198-5850, USA.
Yang
Rui-Fang
RF
Li
Shumin
S
Renshaw
Alex O
AO
Li
Yu-Long
YL
Schultz
Harold D
HD
Zimmerman
Matthew C
MC
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
D005456:Fluorescent Dyes; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013481:Superoxides; D000804:Angiotensin II; D013482:Superoxide Dismutase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2