Valsartan regulates the interaction of angiotensin II type 1 receptor and endothelial nitric oxide synthase via Src/PI3K/Akt signalling.
OBJECTIVE
Valsartan, a selective angiotensin II type 1 receptor (AT1R) blocker, has beneficial effects in the cardiovascular system in part by its increase of nitric oxide (NO) bioavailability, yet the mechanisms are unclear. We investigated the molecular mechanisms underlying this effect in endothelial cells (ECs).


RESULTS
NO production was examined by Griess reagent assay, DAF-2 DA fluorescence staining and cGMP ELISA kits. Protein interaction was determined by western blotting and immunoprecipitation. Treating bovine or human aortic ECs with valsartan increased NO production, as evidenced by elevated level of stable NO metabolites and intracellular cGMP. Valsartan increased the phosphorylation but not the protein level of endothelial NO synthase (eNOS). Inhibition of phosphoinositide-3 kinase (PI3K)/Akt and Src pathways by specific inhibitors suppressed valsartan-induced NO release. In addition, valsartan increased the tyrosine residue phosphorylation of AT1R, which was attenuated by inhibition of Src but not PI3K activities. Valsartan also suppressed the interaction of eNOS and AT1R, which was blocked by Src or PI3K inhibition.


CONCLUSIONS
Valsartan-induced NO production in ECs is mediated through Src/PI3K/Akt-dependent phosphorylation of eNOS. Valsartan-induced AT1R phosphorylation depends on Src but not PI3K, whereas valsartan-induced suppression of AT1R-eNOS interaction depends on Src/PI3K/Akt signalling. These results indicate a novel vasoprotective mechanism of valsartan in upregulating NO production in ECs.
Su
Kuo-Hui
KH
Department of Physiology, National Yang-Ming University, Taipei, Taiwan, ROC.
Tsai
Jin-Yi
JY
Kou
Yu Ru
YR
Chiang
An-Na
AN
Hsiao
Sheng-Huang
SH
Wu
Yuh-Lin
YL
Hou
Hsin-Han
HH
Pan
Ching-Chian
CC
Shyue
Song-Kun
SK
Lee
Tzong-Shyuan
TS
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001011:Aorta / Q000166:cytology; D002417:Cattle; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D015398:Signal Transduction; D013777:Tetrazoles / Q000494:pharmacology*; D014633:Valine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000068756:Valsartan; D019061:src-Family Kinases / Q000378:metabolism
D000959:Antihypertensive Agents; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D009569:Nitric Oxide; D000068756:Valsartan; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; D014633:Valine