title: Alpha2-adrenoceptors enhance angiotensin II-induced renal vasoconstriction: role for NADPH oxidase and RhoA.
abstract: Alpha(2)-adrenoceptors potentiate renal vascular responses to angiotensin II via coincident signaling at phospholipase C. This leads to increased activation of the phospholipase C/protein kinase C/c-src pathway. Studies suggest that c-src activates the reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase/superoxide system, and reactive oxygen species stimulate the RhoA/Rho kinase pathway. Therefore, we hypothesized that NADPH oxidase/superoxide and RhoA/Rho kinase are downstream components of the signal transduction pathway that mediate the interaction between alpha(2)-adrenoceptors and angiotensin II on renal vascular resistance. In rat kidneys, both in vivo and in vitro, intrarenal infusions of angiotensin II increased renal vascular resistance, and UK14,304 (alpha(2)-adrenoceptor agonist) enhanced this response. Intrarenal Tempol (superoxide dismutase mimetic) or Y27632 (Rho kinase inhibitor) abolished the interaction between UK14,304 and angiotensin II both in vivo and in vitro. The interaction was also blocked by inhibitors of NADPH oxidase (in vivo using chronic gp91ds-tat administration and in vitro with diphenyleneiodonium). In cultured preglomerular vascular smooth muscle cells, UK14,304 enhanced angiotensin II-induced intracellular superoxide (2-hydroxyethidium production) and potentiated activation of RhoA (Western blot of activated RhoA bound to the binding domain of rhotekin). The interaction between angiotensin II and UK14,304 on superoxide generation and RhoA activation was blocked by inhibitors of phospholipase C (U73312), protein kinase C (GF109203X), c-src (PP1), NADPH oxidase (diphenyleneiodonium), or superoxide (Tempol). We conclude that NADPH oxidase/superoxide and RhoA/Rho kinase are involved in the interaction between alpha(2)-adrenoceptors and angiotensin II on renal vascular resistance by mediating signaling events downstream of the phospholipase C/protein kinase C/c-src pathway.
authors.affiliation: Center for Clinical Pharmacology, Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA. edj+@pitt.edu
authors.forename: Edwin K
authors.initials: EK
authors.lastname: Jackson
authors.forename: Delbert G
authors.initials: DG
authors.lastname: Gillespie
authors.forename: Chongxue
authors.initials: C
authors.lastname: Zhu
authors.forename: Jin
authors.initials: J
authors.lastname: Ren
authors.forename: Lefteris C
authors.initials: LC
authors.lastname: Zacharia
authors.forename: Zaichuan
authors.initials: Z
authors.lastname: Mi
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology; D007668:Kidney / Q000098:blood supply* / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D019255:NADPH Oxidases / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013481:Superoxides / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*; D019061:src-Family Kinases
chemical_list: C547770:Adra2a protein, rat; D000316:Adrenergic alpha-Agonists; D004791:Enzyme Inhibitors; D018341:Receptors, Adrenergic, alpha-2; D013481:Superoxides; D000804:Angiotensin II; D019255:NADPH Oxidases; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D020742:rhoA GTP-Binding Protein