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Reduced levels of cyclic AMP contribute to the enhanced oxidative stress in vascular smooth muscle cells from spontaneously hypertensive rats.

Authors: Saha, S  Li, Y  Anand-Srivastava, MB 
Citation: Saha S, etal., Can J Physiol Pharmacol. 2008 Apr;86(4):190-8.
Pubmed: (View Article at PubMed) PMID:18418428
DOI: Full-text: DOI:10.1139/Y08-012

We have earlier shown that aortic vascular smooth muscle cells (VSMC) from 12-week-old spontaneously hypertensive rats (SHR) exhibited enhanced production of superoxide anion (O(2)(-)) compared with Wistar-Kyoto (WKY) rats. This production was attenuated to control levels by losartan, an angiotensin II (Ang II) AT(1)-receptor antagonist, suggesting that the AT(1) receptor is implicated in enhanced oxidative stress in SHR. Since AT(1) receptor activation signals via adenylyl cyclase inhibition and decreases cAMP levels, it is possible that AT(1) receptor-mediated decreased levels of cAMP contribute to the enhanced production of O(2)(-) in SHR. The present study was undertaken to investigate this possibility. The basal adenylyl cyclase activity as well as isoproterenol and forskolin-mediated stimulation of adenylyl cyclase was significantly attenuated in VSMC from 12-week-old SHR compared with those from WKY rats, whereas Ang II-mediated inhibition of adenylyl cyclase was significantly enhanced by about 70%, resulting in decreased levels of cAMP in SHR. NADPH oxidase activity and the levels of O2- were significantly higher (about 120% and 200%, respectively) in VSMC from SHR than from WKY rats. In addition, the levels of p47(phox) and Nox4 proteins, subunits of NADPH oxidase, were significantly augmented about 35%-40% in VSMC from SHR compared with those from WKY rats. Treatment of VSMC from SHR with 8Br-cAMP, as well as with cAMP-elevating agents such as isoproterenol and forskolin, restored to control WKY levels the enhanced activity of NADPH oxidase and the enhanced levels of O(2)(-), p47(phox), and Nox4. Furthermore, in the VSMC A10 cell line, 8Br-cAMP also restored the Ang II-evoked enhanced production of O(2)(-), NADPH oxidase activity, and enhanced levels of p47(phox) and Nox4 proteins to control levels. These data suggest that decreased levels of cAMP in SHR may contribute to the enhanced oxidative stress in SHR and that increasing the levels of cAMP may have a protective effect in reducing oxidative stress and thereby improve vascular function.

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CRRD Object Information
CRRD ID: 2324669
Created: 2010-05-10
Species: All species
Last Modified: 2010-05-10
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.