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This Article Full Text Full Text (PDF) All Versions of this Article: 296/1/H106    most recent 00239.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lavrentyev, E. N. Articles by Malik, K. U. Search for Related Content PubMed PubMed Citation Articles by Lavrentyev, E. N. Articles by Malik, K. U.

High glucose-induced Nox1-derived superoxides downregulate PKC-βII, which subsequently decreases ACE2 expression and ANG(1-7) formation in rat VSMCs

Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee

Submitted 6 March 2008 ; accepted in final form 28 October 2008

In rat diabetic animal models, ANG(1-7) treatment prevents the development of cardiovascular complications. Angiotensin-converting enzyme (ACE)2 is a major ANG(1-7)-generating enzyme in vascular smooth muscle cells (VSMCs), and its expression is decreased by a prolonged exposure to high glucose (HG), which is reflected by lower ANG(1-7) levels. However, the underlying mechanism of its downregulation is unknown and was the subject of this study. Rat aortic VSMCs were maintained in normal glucose (NG) or HG (4.1 and 23.1 mmol/l, respectively) for up to 72 h. Several PKC and NADPH oxidase inhibitors and short interfering (si)RNAs were used to determine the mechanism of HG-induced ACE2 downregulation. Cell lysates were subjected to Western blot analysis, real-time quantitative PCR, and ANG(1-7) radioimmunodetection. At 72 h of HG exposure, ACE2 mRNA, protein, and ANG(1-7) levels were decreased (0.17 ± 0.01-, 0.47 ± 0.03-, and 0.16 ± 0.01-fold, respectively), and the expression of NADPH oxidase subunit Nox1 was increased (1.70 ± 0.2-fold). The HG-induced ACE2 decrease was reversed by antioxidants and Nox1 siRNA as well as by inhibitors of glycotoxin formation. ACE2 expression was PKC-βII dependent, and PKC-βII protein levels were reduced in the presence of HG (0.32 ± 0.03-fold); however, the PKC-βII inhibitor CG-53353 prevented the HG-induced ACE2 loss and Nox1 induction, suggesting a nonspecific effect of the inhibitor. Our data suggest that glycotoxin-induced Nox1 expression is regulated by conventional PKCs. ACE2 expression is PKC-βII dependent. Nox1-derived superoxides reduce PKC-βII expression, which lowers ACE2 mRNA and protein levels and consequently decreases ANG(1-7) formation.

angiotensin-coverting enzyme 2/angiotensin-(1-7); NADPH oxidase; smooth muscle; vascular smooth muscle cells; glycotoxins; protein kinase C-βII