GLUCOSE-INDUCED OXIDATIVE STRESS IN VASCULAR CONTRACTILE CELLS - COMPARISON OF AORTIC SMOOTH-MUSCLE CELLS AND RETINAL PERICYTES

Free radical-mediated damage to vascular cells may be involved in the pathogenesis of diabetic vasculopathy. The aim of this study was to co mpare the extent of glucose-induced oxidative stress in both vascular smooth muscle cells (VSMCs) and pericytes and the effect on antioxidan t enzyme gene expression and activities. Porcine aortic VSMC and retin al pericytes were cultured in either 5 or 25 mmol/l glucose for 10 day s. Intracellular malondialdehyde (MDA) was measured as a marker of per oxidative damage, and mRNA expression of CuZn-SOD, MnSOD, catalase, an d glutathione peroxidase (GPX) were measured by Northern analysis. Glu tathione (GSH) was also measured. There was a significant increase in MDA in VSMCs in 25 mmol/l glucose (1.34 +/- 0.11 vs. 1.88 +/- 0.24 nmo l/mg protein, 5 vs. 25 mmol/l D-glucose, mean +/- SE, n = 15, P < 0.01 ), but not in pericytes (0.38 +/- 0.05 vs. 0.37 +/- 0.05 nmol/mg prote in, n = II). There was a significant decrease in GSH in both cell type s (VSMC, 1.40 +/- 0.13 vs. 0.69 +/- 0.12 nmol/mg protein, n = 15, P < 0.001; pericytes, 1.97 +/- 0.17 vs. 0.94 +/- 0.16 nmol/mg protein, n = 11, P < 0.001). mRNA expression of CuZnSOD and MnSOD was increased on ly in VSMCs (by 58.5 +/- 8.1 and 41.0 +/- 6.9%, respectively, n 8, P < 0.01). CuZnSOD protein was increased by similar to 120% (P < 0.00001) . None of the antioxidant enzyme activities was altered between 5 and 25 mmol/l glucose in either cell type. Both MnSOD activities and GSH c oncentrations were higher in pericytes compared with VSMC under basal (5 mmol/l) conditions (P < 0.05 and P < 0.02, respectively). These res ults demonstrate glucose-induced reduction of GSH in both cells, but o nly in VSMC is there evidence of oxidant damage in the form of lipid p eroxidation, implying significant differences in intracellular respons es to glucose between contractile cells in the macro-and microvasculat ure.