Induction of endothelin-1 expression by glucose: an effect of protein kinase C activation.

Abstract

Enhanced actions or levels of endothelin-1 (ET-1), a potent vasoconstrictor, have been associated with decreased blood flow in the retina and peripheral nerves of diabetic animals and may be related to the development of pathologies in these tissues. Hyperglycemia has been postulated to increase ET-1 secretion in endothelial cells. We have characterized the mechanism by which elevation of glucose is increasing ET-1 mRNA expression in capillary bovine retinal endothelial cells (BREC) and bovine retinal pericytes (BRPC). Elevation of glucose, but not mannitol, from 5.5 to 25 mmol/l for 3 days increased membranous protein kinase C (PKC) activities and ET-1 mRNA in parallel levels by 2-fold in BREC and BRPC. These effects were reversed by decreasing glucose levels to 5.5 mmol/l for an additional 2 days. Glucoseinduced ET-1 overexpression was inhibited by a general PKC inhibitor, GF109203X, and a mitogen-activated protein kinase kinase inhibitor, PD98059, but not by wortmannin, a phosphatidylinositol 3-kinase inhibitor. By immunoblot analysis, PKC-␤2 and -␦ isoforms in BREC were significantly increased relative to other isoforms in the membranous fractions when glucose level was increased. Overexpression of PKC-␤1 and -␦ isoforms but not PKC-isoform by adenovirus vectors containing the respective cDNA enhanced in parallel PKC activities, proteins, and basal and glucose-induced ET-1 mRNA expression by at least 2-fold. These results showed that enhanced ET-1 expression induced by hyperglycemia in diabetes is partly due to activation of PKC-␤ and -␦ isoforms, suggesting that inhibition of these PKC isoforms may prevent early changes in diabetic retinopathy and neuropathy.

The Hexosamine Pathway Regulates the Plasminogen Activator Inhibitor-1 Gene Promoter and Sp1 Transcriptional Activation through Protein Kinase C-βI and -δ

“…A 4.8 Ϯ 0.6-fold increase in PAI-1 promoter activity was observed in mesangial cells incubated with 2 mM glucosamine for 4 days. Pretreatment with the general PKC inhibitor, GF109203X (5 M) (9,12), diminished this to 1.5 Ϯ 0.3-fold (p Ͻ 0.01), but many chemical kinase inhibitors lack specificity (67). To confirm these results and address the roles of individual PKC isoforms, we cotransfected expression vectors for kinaseinactive, DN-PKC mutants with PAI-LUC.…”

“…High glucose results in de novo synthesis of diacylglycerol and membrane translocation of various PKC isoforms, including PKC-␣, -␤I, -␦, -⑀, and -in mesangial and other cells in vitro and in experimental animals (6 -13). In addition, there is good evidence that these activated PKC isoforms contribute to high glucose-induced increases in gene transcription and participate in the pathogenesis of diabetes complications (6,9,11,12,14,26,27,62).…”

Peripheral Effect of α-Melanocyte-stimulating Hormone on Fatty Acid Oxidation in Skeletal Muscle

“…of Molecular Biology, Kyung Hee University College of Medicine, Seoul, Korea). Adenoviruses containing either ␤-galactosidase (Ad-␤-gal) or a mixture of dominant-negative ␣1 AMPK and ␣2 AMPK (Ad-DN-AMPK) were added to subconfluent C2C12 cells at a concentration of 50 plaque-forming units per cell for 2 h at 37°C in Dulbecco's modified Eagle's medium without serum, as described previously (32).…”

Increased Expression of Endothelin-Converting Enzyme-1c Isoform in Response to High Glucose Levels in Endothelial Cells

“…receptor expression and nitric oxide (NO) production by activation of endothelial NO synthase (eNOS); however, the direction of these changes is unclear [3]. Recently, it has been shown that high glucose increases ET-1 mRNA and protein expression mediated partially by activation of protein kinase C (PKC) β and δ isoforms in bovine retinal endothelial cells [4]. …”