Pre-incubation with interleukin-4 mediates a direct protective effect against the loss of pancreatic beta-cell viability induced by proinflammatory cytokines.
Loss of pancreatic beta-cells in type I diabetes is associated with an increase in T helper 1 (Th1) proinflammatory cytokines in the islet milieu, with a concomitant reduction in Th2 anti-inflammatory cytokines. In animal models, manoeuvres designed to polarize Th1 responses towards Th2, particularly involving interleukin (IL)-4, have been shown to protect against insulitis and diabetes. The aim of this study was to determine whether IL-4 can exert a direct effect on beta-cell viability. The rat pancreatic beta-cell line, BRIN-BD11, was used. IL-4R mRNA expression was assayed by reverse transcription-polymerase chain reaction and DNA sequencing and protein expression measured using anti-IL-4R antibodies and confocal microscopy. Cells were pretreated in vitro with IL-4, incubated with IL-1beta and interferon (IFN)-gamma and DNA fragmentation and nitrite production analysed by flow cytometry and Griess assay, respectively. Expression of type I (IL-4R alpha and common gamma-chain) and type II (IL-4R alpha, IL-13R alpha-1) IL-4R mRNA transcripts, together with cell surface expression of IL-4R, was demonstrated. Pre-incubation with IL-4 reduced significantly cell death induced by IL-1beta alone or by a combination of IL-1beta and IFN-gamma, although this was not accompanied by a reduced production of nitrite. The protective effect of IL-4 was not seen when all three cytokines were added simultaneously. These results demonstrate, for the first time, expression of IL-4 receptor components on rat pancreatic beta-cells and reveal a direct protective effect on the loss of viability mediated by proinflammatory cytokines when beta-cells are pre-incubated with IL-4.
Kaminski
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Institute of Biomedical and Clinical Science, Peninsula Medical School, Plymouth, UK.
Kaminski
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Morgan
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D000818:Animals; D017209:Apoptosis / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D018836:Inflammation Mediators / Q000276:immunology*; D050417:Insulin-Secreting Cells / Q000276:immunology*; D015847:Interleukin-4 / Q000276:immunology*; D018613:Microscopy, Confocal; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D016207:Cytokines; D018836:Inflammation Mediators; D015847:Interleukin-4