Interferon regulatory factor-1 down-regulates cytokine-induced IP-10 expression in pancreatic islets.
BACKGROUND
Interferon (IFN)-gamma acts synergistically with interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha to activate isoform of nitric oxide synthetase (iNOS) gene expression, induce apoptosis, and impair glucose-stimulated insulin release (GSIR) in pancreatic islets. This effect is an important mechanism of islet dysfunction in models of pancreatitis, type I diabetes, and islet allograft rejection. We tested the hypothesis that transcription factor interferon regulatory factor (IRF)-1 plays a regulatory role in both this cytokine-induced islet injury and cytokine-induced gene expression for chemotactic chemokines.


METHODS
Isolated islets from wild-type (WT) or IRF-1(-/-) C57BL/6 mice were cultured in a mixture of IL-1beta, TNF-alpha, and IFN-gamma +/- the iNOS inhibitor L-NMMA. The following end points were assessed: i) GSIR; ii) rates of apoptosis; and iii) gene expression for iNOS, IRF-1 and inducible protein (IP)-10, monocyte chemoattractive protein (MCP)-1, macrophage inflammatory protein-1alpha, and macrophage inflammatory protein-1beta.


RESULTS
Cytokine-treated WT islets demonstrated an increase in IRF-1 and iNOS gene expression, inhibition of GSIR, increased rates of apoptosis, and increased gene transcription and protein release for IP-10 and MCP-1. Cytokine-treated IRF-1(-/-) islets demonstrated relatively less iNOS gene expression, preserved GSIR, reduced rates of apoptosis, and a more marked increase in transcription for IP-10 and MCP-1 and in IP-10 protein release. L-NMMA-cotreated WT islets were completely resistant to cytokine-induced dysfunction and apoptosis but demonstrated the same degree of cytokine-induced chemokine gene expression as cytokine-treated WT without L-NMMA.


CONCLUSIONS
IFN-gamma, IL-1beta, and TNF-alpha in combination induce chemokine gene expression in pancreatic islets. Transcription factor IRF-1 mediates cytokine-induced islet dysfunction, apoptosis, and iNOS gene expression but down-regulates IP-10 gene expression.
Baker
Marshall S
MS
Department of Surgery, Division of Organ Transplantation, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
Chen
Xiaojuan
X
Rotramel
Alizah R
AR
Nelson
Jeffrey J
JJ
Kaufman
Dixon B
DB
D000818:Animals; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D054357:Chemokine CXCL10; D018925:Chemokines / Q000235:genetics; D019743:Chemokines, CXC / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D005821:Genetic Techniques; D066298:In Vitro Techniques; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D007515:Islets of Langerhans / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010750:Phosphoproteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D018932:Chemokine CCL2; D054357:Chemokine CXCL10; D018925:Chemokines; D019743:Chemokines, CXC; D016207:Cytokines; D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D007375:Interleukin-1; C494258:Irf1 protein, mouse; D010750:Phosphoproteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D012260:Ribonucleases