Interferon regulatory factor-1 is a key transcription factor in murine beta cells under immune attack.
OBJECTIVE
IFN-gamma, together with other inflammatory cytokines such as IL-1beta and TNF-alpha, contributes to beta cell death in type 1 diabetes. We analysed the role of the transcription factor interferon regulatory factor (IRF)-1, a downstream target of IFN-gamma/signal transducer and activator of transcription (STAT)-1, in immune-mediated beta cell destruction.


METHODS
Islets from mice lacking Irf-1 (Irf-1 (-/-)) and control C57BL/6 mice were transplanted in overtly diabetic NOD mice. Viability and functionality of islets were evaluated in vitro. Chemokine expression by Irf-1 (-/-) islets and INS-1E cells transfected with Irf-1 short interfering RNA (siRNA) was measured by real-time PCR as well as in functional assays in vitro.


RESULTS
IRF-1 deletion in islets was associated with higher prevalence of primary non-function (63% vs 25%, p <or= 0.05) and shorter functioning graft survival (6.0 +/- 2.6 vs 10.4 +/- 4.8 days, p <or= 0.05) in contrast to similar skin graft survival. Although Irf-1 (-/-) islets were resistant to cytokine-induced cell death, insulin secretion by them was lower than that of control C57BL/6 islets under medium and cytokine conditions. IL-1 receptor antagonist partly restored the cytokine-induced secretory defect in vitro and completely prevented primary non-function in vivo. Cytokine-exposed Irf-1 (-/-) islets and INS-1E cells transfected with Irf-1 siRNA showed increased expression of Mcp-1 (also known as Ccl2), Ip-10 (also known as Cxcl10), Mip-3alpha (also known as Ccl20) and Inos (also known as Nos2) mRNA and elevated production of monocyte chemoattractant protein-1 (MCP-1) and nitrite compared with controls. In vivo, Irf-1 (-/-) islets displayed a higher potential to attract immune cells, reflected by more aggressive immune infiltration in the grafted islets.


CONCLUSIONS
These data indicate a key regulatory role for IRF-1 in insulin and chemokine secretion by pancreatic islets under inflammatory attack.
Gysemans
C
C
LEGENDO, Campus Gasthuisberg O&N1, Herestraat 49, bus 902, 3000, Leuven, Belgium.
Callewaert
H
H
LEGENDO, Campus Gasthuisberg O&N1, Herestraat 49, bus 902, 3000, Leuven, Belgium.
Moore
F
F
Laboratory of Experimental Medicine, Université Libre de Bruxelles (ULB), Brussels, Belgium.
Nelson-Holte
M
M
LEGENDO, Campus Gasthuisberg O&N1, Herestraat 49, bus 902, 3000, Leuven, Belgium.
Overbergh
L
L
LEGENDO, Campus Gasthuisberg O&N1, Herestraat 49, bus 902, 3000, Leuven, Belgium.
Eizirik
D L
DL
Laboratory of Experimental Medicine, Université Libre de Bruxelles (ULB), Brussels, Belgium.
Mathieu
C
C
LEGENDO, Campus Gasthuisberg O&N1, Herestraat 49, bus 902, 3000, Leuven, Belgium. chantal.mathieu@med.kuleuven.be.
D000818:Animals; D016923:Cell Death; D002470:Cell Survival; D017931:DNA Primers; D005947:Glucose / Q000494:pharmacology; D006085:Graft Survival / Q000276:immunology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D050856:Interferon Regulatory Factor-1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016381:Islets of Langerhans Transplantation / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD / Q000601:surgery; D018345:Mice, Knockout; D016133:Polymerase Chain Reaction / Q000379:methods; D034741:RNA, Small Interfering / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014184:Transplantation, Homologous / Q000276:immunology / Q000502:physiology
D017931:DNA Primers; D007328:Insulin; D050856:Interferon Regulatory Factor-1; D034741:RNA, Small Interfering; D014157:Transcription Factors; D005947:Glucose