High glucose increases the expression of G_q/11α and PLC-β proteins and associated signaling in vascular smooth muscle cells

Abstract

Descorbeth M, Anand-Srivastava MB. High glucose increases the expression of Gq/11␣ and PLC-␤ proteins and associated signaling in vascular smooth muscle cells. Am J Physiol Heart Circ Physiol 295: H2135-H2142, 2008. First published September 26, 2008 doi:10.1152/ajpheart.00704.2008.-The levels and activity of protein kinase C and diacylglycerol were shown to be upregulated in diabetes/ hyperglycemia; however, studies on the expression of upstream signaling molecules of phosphatidylinositol turnover were lacking. The present study was therefore undertaken to examine whether hyperglycemia/diabetes could also modulate the expression of G q␣ and phospholipase C-␤ (PLC-␤) proteins and associated phosphatidylinositol turnover signaling in aortic vascular smooth muscle cells (VSMCs) and A10 VSMCs exposed to high glucose. Aortic VSMCs from streptozotocin-diabetic rats exhibited an increased expression of G q␣ and PLC-␤ 1 proteins (60% and 30%, respectively) compared with control cells as determined by Western blot analysis. The pretreatment of A10 VSMCs with high glucose (26 mM) for 3 days also augmented the levels of G q␣, G11␣, PLC-␤1 and -␤2 proteins by about 50, 35, 30, and 30%, respectively, compared with control cells that were restored to control levels by endothelin-1 (ET-1), ET types A and B (ET A and ET B) receptors, and angiotensin II type 1 (AT1) receptor antagonists. In addition, ET-1-stimulated inositol triphosphate formation was also significantly higher in VSMCs exposed to high glucose, whereas the basal levels of inositol triphosphate were not different between the two groups. Furthermore, the treatment of A10 VSMCs with angiotensin II and ET-1 also significantly increased the levels of Gq/11␣ and PLC-␤ proteins that were restored toward control levels by ETA/ETB and AT1 receptor antagonists. These results suggest that high glucose augments the expression of Gq/11␣, PLC-␤, and mediated signaling in VSMCs, which may be attributed to AT1, ETA, and ETB receptors. Gq␣ protein; phospholipase C-␤; phosphatidylinositol turnover VASCULAR COMPLICATIONS including increased contractility and cell proliferation are most common complications in diabetes, and chronic hyperglycemia seems to be an important contributing factor in this process. Various signaling mechanisms such as adenylyl cyclase/cAMP, phosphatidylinositol (PI) turnover, and mitogen-activated protein kinase have been shown to be implicated in the regulation of vascular tone as well as proliferation, and the aberration of these mechanisms may contribute to vascular complications in hyperglycemia/diabetes. Guanine nucleotide regulatory proteins (G proteins) play an important role in the regulation of these signaling mechanisms. Adenylyl cyclase activity is regulated by inhibitory (G i ) and stimulatory (G s ) guanine nucleotide regulatory proteins, whereas the G q family of G proteins regulates PI turnover signaling. The G proteins are heterotrimeric proteins and are composed of ␣-, ␤-, and ␥-subunits. The activation of G q ␣ by a G protein-coupled rece...

Rho kinase and protein kinase C involvement in vascular smooth muscle myofilament calcium sensitization in arteries from diabetic rats

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Kinin B1receptor upregulation by angiotensin II and endothelin-1 in rat vascular smooth muscle cells: receptors and mechanisms

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Ca2+ handling alterations and vascular dysfunction in diabetes

“…Indeed, researchers have observed a significant increase in the expression levels of the heterotrimeric Gα q /11 proteins and phospholipase C-β (60% and 30%, respectively) in aortic VSMCs exposed to high glucose levels or isolated from STZ-induced diabetic rats. This effect was attributed to the activation of AngII type 1 and ET-1 receptors (AT 1 Rs and ET A /ET B Rs, respectively) [84]. AT 1 R was the first GPCR discovered to be involved in the vascular mechanosensitive response [85,86].…”