Synergistic stimulation of MHC class I and IRF-1 gene expression by IFN-gamma and TNF-alpha in oligodendrocytes.
In order to understand the molecular basis of the synergistic action of interferon gamma (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha) on rat oligodendrocyte development, we studied some aspects of the signalling pathways involved in the regulation of the major histocompatibility complex (MHC) class I and the interferon regulatory factor 1 (IRF-1) gene expression. Two well-defined inducible enhancers of the MHC class I gene promoter, the MHC class I regulatory element (MHC-CRE) and the interferon consensus sequence (ICS), were analysed. Neither IFN-gamma nor TNF-alpha was capable of inducing MHC-CRE binding activity when administrated alone. Following the exposure of oligodendrocytes to IFN-gamma, TNF-R1 expression was transcriptionally induced by the binding of signal transducer and activator of transcription (STAT-1) homodimers to the IFN-gamma activated site (GAS) present in the gene promoter. The upregulation of TNF-R1 allowed TNF-alpha to induce the binding of nuclear factor-kappaB (NF-kappaB) to the MHC-CRE site. With respect to ICS element, IFN-gamma induced IRF-1 binding, that was further enhanced upon co-treatment with TNF-alpha. The existence of a synergism between IFN-gamma and TNF-alpha in stimulating IRF-1 expression at the transcriptional level was supported by IRF-1 promoter analysis: IFN-gamma directly induced the binding of STAT-1 homodimers to the GAS element, while NF-kappaB binding to the kappaB sequence was activated by TNF-alpha only after IFN-gamma treatment. This transcriptional regulation of IRF-1 gene by IFN-gamma and TNF-alpha was confirmed at the mRNA level. The synergism demonstrated in the present study highlights the importance of cytokine interactions in magnifying their biological effects during brain injury and inflammation.
Laboratory of Organ and System Pathophysiology, Istituto Superiore di Sanità, Rome, Italy. neurobio@iss.it
C
C
Agresti
A
A
Bernardo
N
N
Del Russo
G
G
Marziali
A
A
Battistini
F
F
Aloisi
G
G
Levi
E M
EM
Coccia
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D001483:Base Sequence; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects*; D005805:Genes, MHC Class I / Q000187:drug effects* / Q000235:genetics; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009836:Oligodendroglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010750:Phosphoproteins / Q000187:drug effects* / Q000235:genetics*; D051381:Rats; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis; D047888:Receptors, Tumor Necrosis Factor, Type I; D050794:STAT1 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D015703:Antigens, CD; D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; C494259:Irf1 protein, rat; D010750:Phosphoproteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D050794:STAT1 Transcription Factor; C494081:Stat1 protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma