High glucose stimulates GRO secretion from rat microglia via ROS, PKC, and NF-kappaB pathways.
Hyperglycemia causes direct neuronal damage in diabetic encephalopathy. Microglia have been found to be activated in diabetic encephalopathy, presumably mediating and amplifying neuron degeneration. Chemokine IL-8 plays an important role in the pathogenesis of encephalopathy. Therefore, we investigated whether high glucose could activate microglia and stimulate IL-8 secretion and if so, the possible mechanisms that were involved. ELISA results showed that treatment with high glucose (35 mM) compared with treatment with low glucose (10 mM) time-dependently elevated secretion of GRO (the rat ortholog of human IL-8) in primary cultured rat microglia. Real-time PCR results showed GRO mRNA expression also increased in response to high glucose in a time-dependent manner. These effects were specific to high glucose because the osmolality control had no such effect. High-glucose treatment stimulated the formation of ROS, as seen in the DCF fluorescence assay, increased phosphorylation of PKC, as seen in the Western blot analysis, and activated NF-kappaB, as seen in the luciferase reporter assay. In addition, treatment with the ROS scavenger NAC (2 mM) significantly reduced the high glucose-induced phosphorylation of PKC and GRO secretion. Treatment with the PKC activator PMA (10-50 nM) stimulated GRO secretion, and the PKC inhibitors calphostin C (300 nM) or chelerythrine (1 microM) attenuated the high glucose-induced GRO secretion. Furthermore, the NF-kappaB inhibitors MG132 (10 microM) or PDTC (5 microM) completely blocked the high glucose-induced GRO secretion. In conclusion, high glucose induces GRO secretion and mRNA expression in activated rat microglia, which is mediated by the ROS, PKC, and NF-kappaB pathways. High glucose-induced IL-8 production by microglia may contribute to diabetic encephalopathy.
Quan
Yi
Y
Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University, Beijing, People's Republic of China.
Du
Jianhai
J
Wang
Xian
X
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D054360:Chemokine CXCL1 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005947:Glucose / Q000494:pharmacology*; D017628:Microglia / Q000187:drug effects*; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013997:Time Factors; D000097782:NF-kappaB-Inducing Kinase
D054360:Chemokine CXCL1; D004791:Enzyme Inhibitors; D005947:Glucose; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D017382:Reactive Oxygen Species; D000097782:NF-kappaB-Inducing Kinase; C513297:Cxcl1 protein, rat