RESUMO
BACKGROUND: Oxidative stress contributes to vascular diseases in patients with diabetes. As the mechanism of development and progression of diabetic vascular complications is poorly understood, this study was aimed to assess the potential role of hyperglycemia-induced oxidative stress and to determine whether the oxidative stress is a major factor in hyperglycemia-induced migration of vascular smooth muscle cells (VSMCs). METHODS: We treated primary cultured rat aortic smooth muscle cells for 72 hours with medium containing 5.5 mM D-glucose (normal glucose), 30 mM D-glucose (high glucose) or 5.5 mM D-glucose plus 24.5 mM mannitol (osmotic control). We measured the migration of VSMCs and superoxide production. Immunoblotting of PKC isozymes using phoshospecific antibodies was performed, and PKC activity was also measured. RESULTS: Migration of VSMCs incubated under high glucose condition were markedly increased compared to normal glucose condition. Treatment with diphenyleneiodonium (DPI, 10 micromol/L) and superoxide dismutase (SOD, 500 U/mL) significantly suppressed high glucose-induced migration of VSMCs. Superoxide production was significantly increased in high glucose condition and was markedly decreased after treatment with DPI and SOD. High glucose also markedly increased activity of PKC-delta isozyme. When VSMCs were treated with rottlerin or transfected with PKC-delta siRNA, nitro blue tetrazolium (NBT) staining and NAD(P)H oxidase activity were significantly attenuated in the high glucose-treated VSMCs. Furthermore, inhibition of PKC-delta markedly decreased VSMC migration by high glucose. CONCLUSION: These results suggest that high glucose-induced VSMC migration is dependent upon activation of PKC-delta, which may responsible for elevated intracellular ROS production in VSMCs, and this is mediated by NAD(P)H oxidase.