Silymarin Ameliorates Diabetes-Induced Proangiogenic Response in Brain Endothelial Cells through a GSK-3β Inhibition-Induced Reduction of VEGF Release

Diabetes mellitus (DM) is a major risk factor for cardiovascular disease. Additionally, it was found to induce a dysfunctional angiogenic response in the brain that was attributed to oxidative stress. Milk thistle seed extract (silymarin) has potent antioxidant properties, though its potential use in ameliorating diabetes-induced aberrant brain angiogenesis is unknown. Glycogen synthase kinase-3 beta is a regulator of angiogenesis that is upregulated by diabetes. Its involvement in diabetes-induced angiogenesis is unknown. To evaluate the potential of silymarin to ameliorate diabetes-induced aberrant angiogenesis, human brain endothelial cells (HBEC-5i) were treated with 50 mu g/mL advanced glycation end (AGE) products in the presence or absence of silymarin (50, 100 mu M). The angiogenic potential of HBEC-5i was evaluated in terms of migration and in vitro tube formation capacities. The involvement of GSK-3 beta was also evaluated. AGE significantly increased the migration and tube formation rates of HBEC-5i by about onefold (p = 0 0001). Silymarin reduced AGE-induced migration in a dose-dependent manner where 50 mu M reduced migration by about 50%, whereas the 100 mu M completely inhibited AGE-induced migration. Similarly, silymarin 50 mu g/mL blunted AGE-induced tube formation (p = 0 001). This effect was mediated through a GSK-3 beta-dependent inhibition of VEGF release. In conclusion, silymarin inhibits AGE-induced aberrant angiogenesis in a GSK-3 beta-mediated inhibition of VEGF release.