Interleukin-1beta swiftly down-regulates UCP-2 mRNA in beta-cells by mechanisms not directly coupled to toxicity.
Regulation of uncoupling protein-2 (UCP-2) in beta-cells is presently unclear but may involve oxidative stress. We tested for regulation by beta-cell toxic cytokines. Exposure to interleukin-1beta (IL-1beta, 10 ng/ml) for 6 h down-regulated UCP-2 mRNA in clonal INS-1 cells, by 37 +/- 7%, and in rat pancreatic islets, by 55 +/- 8%. In contrast, a 6 h exposure to IL-1beta did not affect viability as assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, or mitochondrial membrane potential, or ATP cellular contents. Continued exposure to IL-1beta was accompanied by decreased viability and persisting down-regulation of UCP-2 mRNA. Exposure to a combination of IL-1beta and tumor necrosis factor (TNF)-alpha for 48 h additively decreased cell viability and UCP-2 mRNA. The constitutive nitric oxide (NO) synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME, 1 mM) partially protected against toxicity but failed to significantly affect UCP-2 mRNA expression. The inducible NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA, 1 mM) protected completely against cytokine-induced toxicity. L-NMMA per se down-regulated UCP-2 mRNA (by 64 +/- 7%). Transfection with a UCP-2-antisense nucleotide failed to affect IL-1beta induced toxicity. In conclusion, down-regulation of UCP-2 mRNA by IL-1beta is an early event of cytokine interaction with beta-cells which is not directly coupled to toxicity.
Li
Li-Xin
LX
Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489 Trondheim, Norway.
Yoshikawa
Hiroyasu
H
Egeberg
Kjartan Wollo
KW
Grill
Valdemar
V
D000704:Analysis of Variance; D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation; D005786:Gene Expression Regulation / Q000187:drug effects; D007375:Interleukin-1 / Q000494:pharmacology*; D007473:Ion Channels; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000502:physiology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D000071246:Uncoupling Protein 2; D019323:omega-N-Methylarginine / Q000494:pharmacology
D007375:Interleukin-1; D007473:Ion Channels; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester