Suppression of interleukin-1 beta-induced nitric oxide production in RINm5F cells by inhibition of glucose-6-phosphate dehydrogenase.
In rat pancreatic islets and insulin-producing cell lines, IL-1beta induces expression of inducible nitric oxide synthase and NO production leading to impairment of glucose-stimulated insulin release and decreased cell survival. NADPH is an obligatory cosubstrate for iNOS synthesis of NO. We hypothesized that IL-1beta stimulates an increase in activity of NADPH-producing enzyme(s) prior to NO production and that this increase is necessary for NO production. Using rat insulin-secreting RINm5F cells, we found that (1) IL-1beta caused a biphasic change in the NADPH level (increased by 6 h and decreased after prolonged incubation in the presence of 2 ng/mL IL-1beta); (2) IL-1beta stimulated increased activity of glucose-6-phosphate dehydrogenase (G6PD) in a time- and dose-dependent manner, and G6PD expression was increased by about 80% after exposure to 2 ng/mL IL-1beta for 18 h: (3) IL-1beta-stimulated NO production was positively correlated with increased G6PD activity; (4) IL-1beta did not cause any significant change in enzyme activity of another NADPH-producing enzyme, malic enzyme; (5) IL-1beta-induced NO production was significantly reduced either by inhibiting G6PD activity using an inhibitor of G6PD (dehydroepiandrosterone) or by inhibiting G6PD expression using an antisense oligonucleotide to G6PD mRNA; and (6) IL-1beta stimulated a decrease in the cAMP level. 8-Bromo-cAMP caused decreased G6PD activity, and the protein kinase A inhibitor H89 led to a increase in G6PD activity in RINm5F cells. In conclusion, our data show that IL-1beta stimulated G6PD activity and expression level, providing NADPH that is required by iNOS for NO production in RINm5F cells. Also, inhibition of the cAMP-dependent PKA signal pathway is involved in an IL-1beta-stimulated increase in G6PD activity.
Guo
Li
L
Vascular Cell Biology, Joslin Diabetes Center and Harvard Medical School, One Joslin Place, Boston, Massachusetts 02215, USA.
Zhang
Zhiquan
Z
Green
Katherine
K
Stanton
Robert C
RC
D000818:Animals; D002478:Cells, Cultured; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D003687:Dehydroepiandrosterone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D009249:NADP / Q000037:antagonists & inhibitors / Q000378:metabolism; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D021381:Protein Transport / Q000502:physiology; D012333:RNA, Messenger / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007375:Interleukin-1; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D003687:Dehydroepiandrosterone; D009249:NADP; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+); D005954:Glucosephosphate Dehydrogenase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases