Nox2, Ca2+, and protein kinase C play a role in angiotensin II-induced free radical production in nucleus tractus solitarius.
The dorsomedial portion of the nucleus tractus solitarius (dmNTS) is the site of termination of baroreceptor and cardiorespiratory vagal afferents and plays a critical role in cardiovascular regulation. Angiotensin II (Ang II) is a powerful signaling molecule in dmNTS neurons and exerts some of its biological effects by modulating Ca(2+) currents via reactive oxygen species (ROS) derived from reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase. We investigated whether a Nox2-containing NADPH oxidase is the source of the Ang II-induced ROS production and whether the signaling mechanisms of its activation require intracellular Ca(2+) or protein kinase C (PKC). Second-order dmNTS neurons were anterogradely labeled with 4-(4-[didecylamino]styryl)-N-methylpyridinium iodide transported from the vagus and isolated from the brain stem. ROS production was assessed in 4-(4-[didecylamino]styryl)-N-methylpyridinium iodide-positive dmNTS neurons using the fluorescent dye 6-carboxy-2',7'-dichlorodihydro-fluorescein di(acetoxymethyl ester). Ang II (3 to 2000 nmol/L) increased ROS production in dmNTS neurons (EC(50)=38.3 nmol/L). The effect was abolished by the ROS scavenger Mn (III) porphyrin 5,10,20-tetrakis (benzoic acid) porphyrin manganese (III), the Ang II type 1 receptor antagonist losartan, or the NADPH oxidase inhibitors apocynin or gp91ds-tat. Ang II failed to increase ROS production or to potentiate L-type Ca(2+) currents in dmNTS neurons of mice lacking Nox2. The PKC inhibitor GF109203X or depletion of intracellular Ca(2+) attenuated Ang II-elicited ROS production. We conclude that the powerful effects of Ang II on Ca(2+) currents in dmNTS neurons are mediated by PKC activation leading to ROS production via Nox2. Thus, a Nox2-containing NADPH oxidase is the critical link between Ang II and the enhancement of Ca(2+) currents that underlie the actions of Ang II on central autonomic regulation.
Wang
Gang
G
Division of Neurobiology, Weill Medical College of Cornell University, 411 East 69th St, New York, NY 10021, USA. gaw2001@med.cornell.edu
Anrather
Josef
J
Glass
Michael J
MJ
Tarsitano
M Jacqueline
MJ
Zhou
Ping
P
Frys
Kelly A
KA
Pickel
Virginia M
VM
Iadecola
Costantino
C
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D004553:Electric Conductivity; D005456:Fluorescent Dyes; D005609:Free Radicals / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D011726:Pyridinium Compounds; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D015220:Calcium Channels; D005456:Fluorescent Dyes; D005609:Free Radicals; D008562:Membrane Glycoproteins; D011726:Pyridinium Compounds; D017382:Reactive Oxygen Species; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; C076868:4-(4-dihexadecylaminostyryl)-N-methylpyridium; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D011493:Protein Kinase C; D002118:Calcium