Abstract 5571: Induction of Macrophage Activation and Foam Cell Formation by High Glucose is Mediated by Rho-associated Coiled-coil Forming Kinase
Background: Vascular complications are major causes of morbidity and mortality in patients with diabetes mellitus. Although the precise mechanism by which diabetes leads to vascular disease remains unknown, hyperglycemia has been shown to accelerate atherogenesis, a process involving the uptake of modified low-density lipoproteins (LDL) by macrophages and formation of macrophage-derived foam cells. We have recently shown that deletion of Rho-associated coiled-coil forming kinase (ROCK)-1 in macrophages leads to decreased LDL uptake, foam cell formation, and atherosclerosis. Therefore, we hypothesize that high glucose may enhance atherogenesis by inducing uptake of LDL by macrophages and increasing foam cell formation through activation of ROCK.
Methods & Results: To investigate the effects of high glucose on ROCK and macrophage function, we isolated bone marrow-derived macrophage (BMDM). Treatment with high glucose but not mannitol increased ROCK activity in BMDM in a dose-dependent manner, with initial increase observed after 8 hrs. Downstream metabolites of glucose such as sorbitol and L-glutamine, as well as intracellular oxidative stress and protein kinase C all induced ROCK activation in BMDM. Indeed, co-treatment with the ROCK inhibitor, fasudil (30 uM), decreased glucose-induced oxidative stress. High glucose increased BMDM adhesion and migration, which was inhibited by co-treatment with fasudil. Proliferation and phagocytic activity of BMDM as determined by [3H]-tritium incorporation and zymosan uptake, respectively, were increased in high glucose culture medium, but these effects of high glucose were not affected by fasudil. High glucose (4.5 g/L) increased the size of BMDM compared to low glucose (1.0 g/L), and led to more foam cell formation in the presence of 50 ug/ml of cholesterol. In addition, the expression of TNFalpha in BMDM was increased by 2.7-fold in high glucose medium, which was suppressed by treatment with fasudil.
Conclusion: These findings indicate that high glucose induces macrophage activation and foam cell formation is mediated by increased ROCK activity. These results suggest that targeting ROCK may have therapeutic benefits in ameliorating atherosclerosis in diabetic patients.