Pressor effect of apelin-13 in the rostral ventrolateral medulla: role of NAD(P)H oxidase-derived superoxide.
Microinjection of apelin-13 into the rostral ventrolateral medulla (RVLM) in the brainstem increases blood pressure in rats. In the present study, we tested the hypotheses that apelin-13 directly stimulates neuronal activity in neurons cultured from the brainstem and that NAD(P)H oxidase-derived reactive oxygen species are involved in this action of apelin-13. Microinjection of apelin-13 into the RVLM resulted in increases in arterial pressure and in renal sympathetic nerve activity in Sprague-Dawley rats. The pressor effect of apelin-13 was attenuated by the specific NAD(P)H-oxidase inhibitor gp91ds-tat. In neurons cultured from the ventral brainstem, spontaneous action potentials were recorded using current-clamp recording. Superfusion of neurons with apelin-13 (100 nM) increased the neuronal firing rate from 0.79 ± 0.14 to 1.45 ± 0.26 Hz (n = 7, P < 0.01) in angiotensin II receptor-like 1-positive neurons, identified with single-cell reverse transcriptase-polymerase chain reaction. Neither the angiotensin II type 1 receptor antagonist losartan nor the angiotensin II type 2 receptor antagonist 1-[[4-(dimethylamino)-3-methylphenyl[methyl]-5-(diphenylacetyl)-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid ditrifluoroacetate (PD123319) altered the positive chronotropic effect of apelin-13. Pretreatment of cells with either the reactive oxygen species scavenger superoxide dismutase [polyethylene glycol-superoxide dismutase (PEG-SOD), 25 U/ml] or with gp91ds-tat significantly attenuated the chronotropic action of apelin-13. PEG-SOD and gp91ds-tat alone had no effect on basal neuronal firing. In addition, apelin-13 significantly increased NAD(P)H oxidase activity and elevated intracellular superoxide levels in neuronal cultures. The superoxide generator xanthine-xanthine oxidase also increased neuronal activity in neurons, mimicking the neuronal response to apelin-13. These observations provide the first evidence that apelin-13 directly increases neuronal activity via stimulation of NAD(P)H oxidase-derived superoxide, a cellular signaling mechanism that may be involved in the pressor effect of apelin-13 in the RVLM.
Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58108-6050, USA.
Fanrong
F
Yao
Amit
A
Modgil
Qi
Q
Zhang
Ajeeth
A
Pingili
Neha
N
Singh
Stephen T
ST
O'Rourke
Chengwen
C
Sun
D000818:Animals; D000075244:Apelin Receptors; D001794:Blood Pressure / Q000187:drug effects*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D006023:Glycoproteins / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects* / Q000502:physiology; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D013481:Superoxides / Q000378:metabolism*
C104575:APLNR protein, human; D000075244:Apelin Receptors; D015220:Calcium Channels; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D017382:Reactive Oxygen Species; D044140:Receptor, Angiotensin, Type 1; D043562:Receptors, G-Protein-Coupled; C495199:apelin-13 peptide; C473031:gp91ds-tat protein, chimeric; D013481:Superoxides; D019255:NADPH Oxidases