Angiotensin-(1-7) increases neuronal potassium current via a nitric oxide-dependent mechanism.
Actions of angiotensin-(1-7) [Ang-(1-7)], a heptapeptide of the renin-angiotensin system, in the periphery are mediated, at least in part, by activation of nitric oxide (NO) synthase (NOS) and generation NO(·). Studies of the central nervous system have shown that NO(·) acts as a sympathoinhibitory molecule and thus may play a protective role in neurocardiovascular diseases associated with sympathoexcitation, such as hypertension and heart failure. However, the contribution of NO in the intraneuronal signaling pathway of Ang-(1-7) and the subsequent modulation of neuronal activity remains unclear. Here, we tested the hypothesis that neuronal NOS (nNOS)-derived NO(·) mediates changes in neuronal activity following Ang-(1-7) stimulation. For these studies, we used differentiated catecholaminergic (CATH.a) neurons, which we show express the Ang-(1-7) receptor (Mas R) and nNOS. Stimulation of CATH.a neurons with Ang-(1-7) (100 nM) increased intracellular NO levels, as measured by 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM) fluorescence and confocal microscopy. This response was significantly attenuated in neurons pretreated with the Mas R antagonist (A-779), a nonspecific NOS inhibitor (nitro-L-arginine methyl ester), or an nNOS inhibitor (S-methyl-L-thiocitrulline, SMTC), but not by endothelial NOS (eNOS) or inhibitory NOS (iNOS) inhibition {L-N-5-(1-iminoethyl)ornithine (L-NIO) and 1400W, respectively}. To examine the effect of Ang-(1-7)-NO(·) signaling on neuronal activity, we recorded voltage-gated outward K(+) current (I(Kv)) in CATH.a neurons using the whole cell configuration of the patch-clamp technique. Ang-(1-7) significantly increased I(Kv), and this response was inhibited by A-779 or S-methyl-L-thiocitrulline, but not L-NIO or 1400W. These findings indicate that Ang-(1-7) is capable of increasing nNOS-derived NO(·) levels, which in turn, activates hyperpolarizing I(Kv) in catecholaminergic neurons.
Yang
Rui-Fang
RF
University of Nebraska Medical Center, Omaha, 68198-5850, USA.
Yin
Jing-Xiang
JX
Li
Yu-Long
YL
Zimmerman
Matthew C
MC
Schultz
Harold D
HD
D000803:Angiotensin I / Q000378:metabolism*; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation; D008564:Membrane Potentials; D009474:Neurons / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism* / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D020033:Protein Isoforms; D011945:Receptors, Angiotensin / Q000378:metabolism; D015398:Signal Transduction
C092006:7-Ala-angiotensin (1-7); D057911:Angiotensin Receptor Antagonists; D010446:Peptide Fragments; D020033:Protein Isoforms; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D009569:Nitric Oxide; D000803:Angiotensin I; D052248:Nitric Oxide Synthase Type I; C118790:angiotensin I (1-7); D011188:Potassium