Potential role of an endothelium-specific growth factor, hepatocyte growth factor, on endothelial damage in diabetes

Endothelial cells are known to secrete various antiproliferative and vasodilating factors. Although injury of endothelial cells has been postulated as an initial trigger of the progression of atherosclerosis in patients with diabetes, the mechanisms of endothelial injury in diabetes are not yet clarified. Therefore, it is important to know the effects of high glucose on the factors that may influence endothelial cell growth. A novel member of endothelium-specific growth factors, hepatocyte growth factor (HGF), is produced in vascular cells. To investigate the effects of high glucose on vascular cells, we examined 1) the effects of high glucose on endothelial cell and vascular smooth muscle cell (VSMC) growth and 2) the effects of high glucose on local HGF production in endothelial cell and VSMC. Treatment of human aortic endothelial cell with a high concentration of D-glucose, but not mannitol and L-glucose, resulted in a significant decrease in cell number. Interestingly, addition of recombinant HGF attenuated high D-glucose-induced endothelial cell death. Therefore, we measured local HGF secretion of endothelial cell. Importantly, local HGF production was significantly decreased by high D-glucose treatment. In contrast, high D-glucose treatment resulted in a significant increase in the number of human aortic VSMCs, whereas local HGF production was significantly decreased in accordance with increase in D-glucose concentration. No significant changes in numbers were observed in VSMC treated with high mannitol and L-glucose. We also studied the mechanisms of local HGF suppression by high D-glucose. High D-glucose treatment stimulated transforming growth factor-beta (TGF-beta) concentration in endothelial cell and VSMC. Decreased local vascular HGF production was abolished by addition of anti-TGF-beta antibody. As TGF-beta inhibited local HGF production in endothelial cell and VSMC, increased TGF-beta induced by high D-glucose may suppress local HGF production. This study demonstrated that high D-glucose induced endothelial cell death, stimulated VSMC growth, and decreased local HGF production through the stimulation of TGF-beta production both in endothelial cell and VSMC. Overall, decrease in a local endothelial stimulant, HGF, by high D-glucose may be a trigger of endothelial injury in diabetes, potentially resulting in the progression of atherosclerosis.