title: Modulation of the peroxiredoxin system by cytokines in insulin-producing RINm5F cells: down-regulation of PRDX6 increases susceptibility of beta cells to oxidative stress.
abstract: Peroxiredoxins are a family of six antioxidant enzymes (PRDX1-6), and may be an alternative system for the pancreatic beta cells to cope with oxidative stress. This study investigated whether the main diabetogenic pro-inflammatory cytokines or the anti-inflammatory cytokine IL-4 modulate PRDXs levels and putative intracellular pathways important for this process in the insulin-producing RINm5F cells. RINm5F cells expressed significant amounts of PRDX1, PRDX3 and PRDX6 enzymes. Only PRDX6 was modulated by cytokines, showing both mRNA and protein down-regulation following incubation of RINm5F cells with TNF-alpha and IFN-gamma but not with IL-1beta. Separately IFN-gamma or TNF-alpha decreased PRDX6 protein but not mRNA levels. The blockage of the JNK signalling and of the calpains and proteasome proteolysis systems restored PRDX6 protein levels. IL-4 alone did not modulate PRDXs levels. However, pre/co-incubation with IL-4 substantially prevented the decrease in PRDX6 induced by pro-inflammatory cytokines. Knockdown of PRDX6 increased susceptibility of RINm5F cells to the deleterious effects of pro-inflammatory cytokines and to oxidative stress. These results show that, from the PRDXs significantly expressed in RINm5F cells, only PRDX6 is modulated by the diabetogenic cytokines IFN-gamma and TNF-alpha. This PRDX6 down-regulation depends on the calpain and proteasome systems and JNK signalling. PRDX6 is an important enzyme for protection against oxidative stress and the interaction between pro- and anti-inflammatory cytokines might be important to determine the antioxidant capacity of the cells.
authors.affiliation: Department of Anatomy, Cellular Biology and Physiology and Biophysics, Institute of Biology, State University of Campinas, UNICAMP, Campinas, Brazil.
authors.forename: Flavia M M
authors.initials: FM
authors.lastname: Paula
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Ferreira
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Boschero
authors.forename: Kleber L A
authors.initials: KL
authors.lastname: Souza
mesh_terms: D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D005786:Gene Expression Regulation; D007328:Insulin / Q000096:biosynthesis*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology*; D053583:Interleukin-1beta / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D054465:Peroxiredoxin VI / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D007328:Insulin; D053583:Interleukin-1beta; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D015847:Interleukin-4; D007371:Interferon-gamma; D054465:Peroxiredoxin VI; C515984:Prdx6 protein, rat; D048670:MAP Kinase Kinase 4; D002154:Calpain; D046988:Proteasome Endopeptidase Complex