title: High glucose, glucose fluctuation and carbonyl stress enhance brain microvascular endothelial barrier dysfunction: Implications for diabetic cerebral microvasculature.
abstract: We previously demonstrated that in normal glucose (5mM), methylglyoxal (MG, a model of carbonyl stress) induced brain microvascular endothelial cell (IHEC) dysfunction that was associated with occludin glycation and prevented by N-acetylcysteine (NAC). Herein, we investigated the impact of high glucose and low GSH, conditions that mimicked the diabetic state, on MG-induced IHEC dysfunction. MG-induced loss of transendothelial electrical resistance (TEER) was potentiated in IHECs cultured for 7 or 12 days in 25 mM glucose (hyperglycemia); moreover, barrier function remained disrupted 6h after cell transfer to normal glucose media (acute glycemic fluctuation). Notably, basal occludin glycation was elevated under these glycemic states. TEER loss was exaggerated by inhibition of glutathione (GSH) synthesis and abrogated by NAC, which corresponded to GSH decreases and increases, respectively. Significantly, glyoxalase II activity was attenuated in hyperglycemic cells. Moreover, hyperglycemia and GSH inhibition increased MG accumulation, consistent with a compromised capacity for MG elimination. α-Oxoaldehydes (MG plus glyoxal) levels were elevated in streptozotocin-induced diabetic rat plasma. Immunohistochemistry revealed a prevalence of MG-positive, but fewer occludin-positive microvessels in the diabetic brain in vivo, and Western analysis confirmed an increase in MG-occludin adducts. These results provide the first evidence that hyperglycemia and acute glucose fluctuation promote MG-occludin formation and exacerbate brain microvascular endothelial dysfunction. Low occludin expression and high glycated-occludin contents in diabetic brain in vivo are factors that would contribute to the dysfunction of the cerebral microvasculature during diabetes.
authors: Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
authors: Wei
authors: W
authors: Li
authors: Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
authors: Ronald E
authors: RE
authors: Maloney
authors: Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA; Center for Cardiovascular Disease and Sciences, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA. Electronic address: taw@lsuhsc.edu.
authors: Tak Yee
authors: TY
authors: Aw
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D005978:Glutathione / Q000037:antagonists & inhibitors / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D007791:Lactoylglutathione Lyase / Q000378:metabolism; D008297:Male; D055806:Microvessels / Q000378:metabolism*; D062793:Occludin / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D011765:Pyruvaldehyde / Q000032:analysis / Q000097:blood / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D013869:Thiolester Hydrolases / Q000378:metabolism; D000099301:Hydroxyacylglutathione Hydrolase
chemical_list: D000111:Acetylcysteine; D019328:Buthionine Sulfoximine; D016166:Free Radical Scavengers; D005947:Glucose; D005978:Glutathione; D007791:Lactoylglutathione Lyase; D062793:Occludin; D011765:Pyruvaldehyde; D013869:Thiolester Hydrolases; D000099301:Hydroxyacylglutathione Hydrolase
keywords: Carbonyl stress & endothelial GSH; Diabetic brain microvascular dysfunction; Hyperglycemia & methylglyoxal; N-acetylcysteine & endothelial barrier function; Occludin glycation & brain endothelial barrier function; Streptozotocin & diabetes