The involvement of glucose metabolism in the regulation of inducible nitric oxide synthase gene expression in glial cells: possible role of glucose-6-phosphate dehydrogenase and CCAAT/enhancing binding protein.
In rat glial cells the lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) gene expression was enhanced by extracellular glucose concentration in a dose-dependent manner. On the other hand, 2-deoxy-d-glucose decreased the LPS-induced iNOS gene expression even in the presence of glucose (6 gm/l), suggesting that glucose metabolism is linked to the regulation of iNOS gene expression. The intracellular NADPH/NADP+ directly correlated with the extracellular glucose concentration, and the reduction of NADPH generation via a block of glucose-6-phosphate dehydrogenase (G6PD) by treatment with dehydroepiandrosterone or the antisense DNA oligomer of G6PD mRNA resulted in the inhibition of iNOS gene expression. Gel shift assays showed that CAAT/enhancing binding protein (C/EBP), rather than AP-1 or NF-kappaB, correlated better with a glucose-dependent increase in iNOS gene expression. The induction of C/EBP DNA binding activity by LPS and glucose was attributable mainly to the increase in C/EBP-delta protein. The cotransfection with wild-type C/EBP-delta increased the iNOS promoter activity to the level achieved with a higher glucose concentration in the presence of LPS. Therefore, our results suggest that C/EBP-delta may be a critical mediator in glucose-mediated regulation of iNOS gene expression.
Won
Je-Seong
JS
Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Im
Yeong-Bin
YB
Key
Lyndon
L
Singh
Inderjit
I
Singh
Avtar K
AK
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology*; D002478:Cells, Cultured; D003687:Dehydroepiandrosterone / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D005954:Glucosephosphate Dehydrogenase / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009457:Neuroglia / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D020218:Response Elements; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; C497254:Cebpd protein, rat; D008070:Lipopolysaccharides; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D051743:CCAAT-Enhancer-Binding Protein-delta; D009569:Nitric Oxide; D003687:Dehydroepiandrosterone; D009249:NADP; D000255:Adenosine Triphosphate; D005954:Glucosephosphate Dehydrogenase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D020559:Monomeric GTP-Binding Proteins; D005947:Glucose