Endothelin-1-induced oxidative stress in DOCA-salt hypertension involves NADPH-oxidase-independent mechanisms.
We have demonstrated recently [Callera, Touyz, Teixeira, Muscara, Carvalho, Fortes, Schiffrin and Tostes (2003) Hypertension 42, 811-817] that increased vascular oxidative stress in DOCA (deoxycorticosterone acetate)-salt rats is associated with activation of the ET (endothelin) system via ETA receptors. The exact source of ET-1-mediated oxidative stress remains unclear. The aim of the present study was to investigate whether ET-1 increases generation of ROS (reactive oxygen species) in DOCA-salt hypertension through NADPH-oxidase-dependent mechanisms. Xanthine oxidase, eNOS (endothelial nitric oxide synthase) and COX-2 (cyclo-oxygenase-2) were also examined as potential ET-1 sources of ROS as well as mitochondrial respiration. DOCA-salt and control UniNX (uninephrectomized) rats were treated with the ETA antagonist BMS182874 (40 mg.day(-1).kg(-1) of body weight) or vehicle. Plasma TBARS (thiobarbituric acid-reacting substances) were increased in DOCA-salt compared with UniNX rats. Activity of NADPH and xanthine oxidases in aorta, mesenteric arteries and heart was increased in DOCA-salt rats. BMS182874 decreased plasma TBARS levels without influencing NADPH and xanthine oxidase activities in DOCA-salt rats. Increased p22(phox) protein expression and increased p47(phox) membrane translocation in arteries from DOCA-salt by rats were not affected by BMS182874 treatment. Increased eNOS and COX-2 expression, also observed in aortas from DOCA-salt rats, was unaltered by BMS182874. Increased mitochondrial generation of ROS in DOCA-salt rats was normalized by BMS182874. ETA antagonism also increased the expression of mitochondrial MnSOD (manganese superoxide dismutase) in DOCA-salt rats. In conclusion, activation of NADPH oxidase does not seem to be the major source of oxidative stress induced by ET-1/ETA in DOCA-salt hypertension, which also appears to be independent of increased activation of xanthine oxidase or eNOS/COX-2 overexpression. Mitochondria may play a role in ET-1-driven oxidative stress, as evidenced by increased mitochondrial-derived ROS in this model of hypertension.
Callera
Glaucia E
GE
Kidney Research Centre, Ottawa Health Research Institute, University of Ottawa, Ottawa, Canada. gcallera@uottawa.ca
Tostes
Rita C
RC
Yogi
Alvaro
A
Montezano
Augusto C I
AC
Touyz
Rhian M
RM
D000818:Animals; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001011:Aorta; D003619:Dansyl Compounds / Q000627:therapeutic use*; D003900:Desoxycorticosterone; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D006973:Hypertension / Q000378:metabolism*; D008297:Male; D008638:Mesenteric Arteries; D008928:Mitochondria / Q000378:metabolism; D023421:Models, Animal; D009206:Myocardium; D019255:NADPH Oxidases; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A / Q000378:metabolism; D017673:Sodium Chloride, Dietary; D013482:Superoxide Dismutase / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism; D000099156:Superoxide Dismutase 2
D000959:Antihypertensive Agents; D003619:Dansyl Compounds; D003900:Desoxycorticosterone; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1; D019255:NADPH Oxidases; D052250:Nitric Oxide Synthase Type III; D044022:Receptor, Endothelin A; D017673:Sodium Chloride, Dietary; D013482:Superoxide Dismutase; D017392:Thiobarbituric Acid Reactive Substances; D014969:Xanthine Oxidase; D000099156:Superoxide Dismutase 2; C085754:5-(dimethylamino)-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesulfonamide