Abstract T P233: Diabetes Potentiates Ischemia-reperfusion (I/R) Brain Injury: Role for Methylglyoxal, Glutathione, and Cerebral Microvascular Thrombosis

Abstract

Introduction: Diabetes is a risk factor for stroke. We previously showed that hyperglycemic and low glutathione (GSH) conditions (as is found in diabetes), enhanced methylglyoxal (MG)-induced occludin-MG glycation and disrupted barrier integrity in brain microvascular endothelial cells. In vitro , MG activated platelets and promoted platelet-leukocyte aggregation. These results suggest that MG-mediated carbonyl stress could promote thrombotic events and brain microvascular dysfunction. Hypothesis: GSH, MG and/or a pro-thrombotic phenotype play important roles in brain I/R injury. Methods: The streptozotocin mouse model of type 1 diabetes was used as an in vivo model of carbonyl stress. Untreated mice (NT) and citrate buffer vehicle (Veh) served as controls. Brain infarct area, edema, and tissue or plasma GSH and MG were examined after ischemia (45min) and reperfusion (24h) at 4-wks diabetes, and MG-adduct formation in brain microvessels at 8-wks. Blood platelet-leukocyte aggregation and thrombus formation in venules and arterioles were examined at 4-wks diabetes, and intravital videomicroscopy at 20-wks diabetes, respectively. Results: As compared to NT and Veh, cerebral infarct area and edema were significantly increased in diabetic mice that paralleled elevated plasma glucose levels. Diabetic brain injury was associated with high brain MG and low GSH contents. Infarct areas were positively correlated with MG, and MG-to-GSH ratio. Immunohistochemistry revealed increases in MG-positive microvessels in diabetic brain, suggesting a susceptibility of the cerebral microvasculature to MG-protein glycation. Dramatic hepatic GSH depletion occurred at 4-wk diabetes that correlated with elevated plasma MG at 8-wks. At diabetes onset (4-wk), aggregation of platelets with neutrophils and lymphocytes was enhanced. Onset of thrombus formation in brain venules and arterioles was accelerated, and time to complete occlusion of arterioles was shortened in 20-wk diabetic mice. Conclusion: These results show that the diabetic brain is susceptible to I/R injury in association with elevated MG, decreased GSH, and heightened pro-thrombotic events, factors that could contribute to enhanced stroke risk and worse outcome in diabetes.