GLUCOSE-INDUCED PROTEIN-KINASE-C ACTIVATION REGULATES VASCULAR-PERMEABILITY FACTOR MESSENGER-RNA EXPRESSION AND PEPTIDE PRODUCTION BY HUMANVASCULAR SMOOTH-MUSCLE CELLS IN-VITRO

Hyperglycemia is an independent risk factor for the development of dia betic microvascular disease. Vascular permeability factor (VPF)/vascul ar endothelial growth factor (VEGF) is a potent cytokine family that i nduces angiogenesis and markedly increases endothelial permeability. V PF is produced by many cell types, including vascular smooth muscle (V SM) cells, and has been implicated in the pathogenesis of neovasculari zation and endothelial dysfunction in diabetes. This study used cultur ed human VSM cells to study the regulation of VPF production and deter mine whether elevated glucose concentrations, per se, are a sufficient stimulus for increased VPF production by human cells. In human VSM ce lls, high extracellular glucose concentrations (20 mmol/l) increased V PF mRNA expression within 3 h (3-fold vs. glucose 5 mmol/l) and signif icantly increased VPF peptide production within 24 h (1.5-fold) in a t ime-and glucose concentration-dependent manner. The high glucose-induc ed increase in VPF mRNA expression was rapidly reversed after normaliz ing the extracellular glucose concentration and was specific for a hig h D-glucose concentration, as these effects were not reproduced by osm otic control media containing elevated concentrations of mannitol or L -glucose. High glucose concentrations activate protein kinase C (PKC) in human VSM cells, and PKC inhibitors (H-7 or chelerythrine chloride) or PKC downregulation each prevented the glucose-induced increases in VPF mRNA expression by human VSM cells. In conclusion, high glucose c oncentrations directly increase VPF mRNA expression and peptide produc tion by human VSM cells via a PKC-dependent mechanism. These results d emonstrate a cellular mechanism, whereby hyperglycemia could directly contribute to the development of endothelial dysfunction and neovascul arization in diabetes.