Hyperthermia-induced Hsp90·eNOS preserves mitochondrial respiration in hyperglycemic endothelial cells by down-regulating Glut-1 and up-regulating G6PD activity.
Uncoupling of NO production from NADPH oxidation by endothelial nitric-oxide synthase (eNOS) is enhanced in hyperglycemic endothelium, potentially due to dissociation of heat shock proteins 90 (Hsp90), and cellular glucose homeostasis is enhanced by a ROS-induced positive feed back mechanism. In this study we investigated how such an uncoupling impacts oxygen metabolism and how the oxidative phosphorylation can be preserved by heat shock (42 °C for 2 h, hyperthermia) in bovine aortic endothelial cells. Normal and heat-shocked bovine aortic endothelial cells were exposed to normoglycemia (NG, 5.0 mM) or hyperglycemia (30 mM). With hyperglycemia treatment, O(2) consumption rate was reduced (from V(O(2)max) = 7.51 ± 0.54 to 2.35 ± 0.27 mm Hg/min/10(6) cells), whereas in heat-shocked cells, O(2) consumption rate remained unaltered (8.19 ± 1.01 mm Hg/min/10 × 10(6) cells). Heat shock was found to enhance Hsp90/endothelial NOS interactions and produce higher NO. Moreover, ROS generation in the hyperglycemic condition was also reduced in heat-shocked cells. Interestingly, glucose uptake was reduced in heat-shocked cells as a result of decrease in Glut-1 protein level. Glucose phosphate dehydrogenase activity that gives rise to NADPH generation was increased by hyperthermia, and mitochondrial oxidative metabolism was preserved. In conclusion, the present study provides a novel mechanism wherein the reduced oxidative stress in heat-shocked hyperglycemic cells down-regulates Glut-1 and glucose uptake, and fine-tuning of this pathway may be a potential approach to use for therapeutic benefit of diabetes mellitus.
Presley
Tennille
T
Biophysics Program, Ohio State University, Columbus, Ohio 43210, USA.
Vedam
Kaushik
K
Druhan
Lawrence J
LJ
Ilangovan
Govindasamy
G
D000818:Animals; D001011:Aorta / Q000378:metabolism; D002417:Cattle; D015536:Down-Regulation / Q000502:physiology*; D042783:Endothelial Cells / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000378:metabolism*; D005954:Glucosephosphate Dehydrogenase / Q000096:biosynthesis*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology*; D006358:Hot Temperature; D006943:Hyperglycemia / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology
D051272:Glucose Transporter Type 1; D018841:HSP90 Heat-Shock Proteins; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D009249:NADP; D005954:Glucosephosphate Dehydrogenase; D052250:Nitric Oxide Synthase Type III; D005947:Glucose