title: Angiotensin II AT(2) receptor decreases AT(1) receptor expression and function via nitric oxide/cGMP/Sp1 in renal proximal tubule cells from Wistar-Kyoto rats.
abstract: BACKGROUND
  The renin-angiotensin (Ang) system controls blood pressure, in part, by regulating renal tubular sodium transport. In the kidney, activation of the angiotensin II type 1 (AT(1)) receptor increases renal sodium reabsorption, whereas the angiotensin II type 2 (AT(2)) receptor produces the opposite effect. We hypothesized that the AT(2) receptor regulates AT(1) receptor expression and function in the kidney.
  
  
  RESULTS
  In immortalized renal proximal tubule (RPT) cells from Wistar-Kyoto rats, CGP42112, an AT(2) receptor agonist, decreased AT(1) receptor mRNA and protein expression (P < 0.05), as assessed by reverse transcriptase-polymerase chain reaction and immunoblotting. The inhibitory effect of the AT(2) receptor on AT(1) receptor expression was blocked by the AT(2) receptor antagonist, PD123319 (10 (-6)mol/l), the nitric oxide synthase inhibitor N(w)-nitro-L-arginine methyl ester (10(-4) mol/l), or the nitric oxide-dependent soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo-[4,3-a] quinoxalin-1-one (10(-5) mol/l), indicating that both nitric oxide and cyclic guanosine monophosphate (cGMP) were involved in the signaling pathway. Furthermore, CGP42112 decreased Sp1 serine phosphorylation and reduced the binding of Sp1 to AT(1) receptor DNA. Stimulation with Ang II (10(-11) mol/l per 30 min) enhanced Na(+)-K(+)-ATPase activity in RPT cells, which was prevented by pretreatment with CGP42112 (10(-7) mol/l per 24 h) (P < 0.05). The above-mentioned results were confirmed in RPT cells from AT(2) receptor knockout mice; AT(1) receptor expression and Ang II-stimulated Na-K-ATPase activity were greater in these cells than in RPT cells from wild-type mice (P < 0.05). AT(1)/AT(2) receptors co-localized and co-immunoprecipitated in RPT cells; short-term CGP42112 (10 mol/l per 30 min) treatment increased AT(1)/AT(2) receptor co-immunoprecipitation (P < 0.05).
  
  
  CONCLUSIONS
  These results indicate that the renal AT(2) receptor, via nitric oxide/cGMP/Sp1 pathway, regulates AT(1 )receptor expression and function, which may be important in the regulation of sodium excretion and blood pressure.
authors.affiliation: Department of Cardiology, Daping Hospital, The Third Military Medical University, Chongqing, PR China.
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.forename: Caiyu
authors.initials: C
authors.lastname: Chen
authors.forename: Hongmei
authors.initials: H
authors.lastname: Ren
authors.forename: Yu
authors.initials: Y
authors.lastname: Han
authors.forename: Duofen
authors.initials: D
authors.lastname: He
authors.forename: Lin
authors.initials: L
authors.lastname: Zhou
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hopfer
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Jose
authors.forename: Chunyu
authors.initials: C
authors.lastname: Zeng
mesh_terms: D000818:Animals; D001483:Base Sequence; D002461:Cell Line, Transformed; D006152:Cyclic GMP / Q000378:metabolism*; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D007687:Kidney Tubules, Proximal / Q000201:enzymology / Q000378:metabolism*; D018613:Microscopy, Confocal; D009569:Nitric Oxide / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism* / Q000502:physiology; D044139:Receptor, Angiotensin, Type 2 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D009842:Oligopeptides; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D016329:Sp1 Transcription Factor; C060894:CGP 42112A; D009569:Nitric Oxide; D000254:Sodium-Potassium-Exchanging ATPase; D006152:Cyclic GMP