Increased expression and activity of RhoA are associated with increased DNA synthesis and reduced p27(Kip1) expression in the vasculature of hypertensive rats.
We have previously shown that the function of the small G protein Rho is required for vascular smooth muscle cell proliferation and migration. We hypothesized that changes in Rho or Rho signaling might contribute to enhanced vascular proliferative responses associated with hypertension. Western blot analysis revealed that total RhoA expression was approximately 2-fold higher in aortas, tail arteries, and aortic smooth muscle cells (ASMCs) obtained from adult male spontaneously hypertensive rats (SHR) compared with those from Wistar Kyoto rats (WKY). An increase in active GTP-bound RhoA was detected in aortic homogenates by affinity precipitation with the RhoA effector rhotekin and by examining RhoA-[(35)S]GTPgammaS binding. RhoA protein and activity were also increased in vessels from rats treated with N-nitro-L-arginine methyl ester to increase blood pressure. Thrombin-stimulated RhoA activation was also significantly greater in ASMCs from SHR. As a functional correlate of these changes in Rho signaling, thrombin-stimulated DNA synthesis was enhanced in tail arteries and ASMCs from SHR. Expression of the cyclin-dependent kinase inhibitor p27(Kip1) was decreased by two thirds in SHR, and this decrease was mimicked in ASMCs by expression of a constitutively active (GTPase-deficient) mutant of RhoA. Wortmannin (10 nmol/L) fully inhibited the decrease in p27(Kip1) induced by RhoA, and a membrane-targeted catalytic subunit of phosphatidylinositol-3 kinase (PI3K [p110(CAAX)]) decreased p27(Kip1) expression, suggesting that RhoA signals through PI3K. These data provide evidence that RhoA brings about changes in DNA synthesis through reduced expression of p27(Kip1), mediated in part via PI3K, and suggest that increases in RhoA expression and activity contribute to the enhanced vascular responsiveness observed in hypertension.
Seasholtz
T M
TM
University of California, San Diego, Department of Pharmacology, La Jolla, USA.
Zhang
T
T
Morissette
M R
MR
Howes
A L
AL
Yang
A H
AH
Brown
J H
JH
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D001808:Blood Vessels / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000187:drug effects; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis* / Q000187:drug effects; D006973:Hypertension / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D013623:Tail / Q000098:blood supply; D013917:Thrombin / Q000494:pharmacology; D025521:Tumor Suppressor Proteins; D000077191:Wortmannin; D020742:rhoA GTP-Binding Protein / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*
D000730:Androstadienes; C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D013917:Thrombin; D020742:rhoA GTP-Binding Protein; D019331:NG-Nitroarginine Methyl Ester; D000077191:Wortmannin