Reduced expression of IL-12 p35 by SJL/J macrophages responding to Theiler's virus infection is associated with constitutive activation of IRF-3

Abstract

Macrophages responding to viral infections may contribute to autoimmune demyelinating diseases (ADD). Macrophages from ADD-susceptible SJL/J mice responding to Theiler's Virus (TMEV) infection, the TLR7 agonist loxoribine, or the TLR4 agonist-LPS expressed less IL-12 p35 but more IL-12/23 p40 and IFN-beta than macrophages from ADD-resistant B10.S mice. While expression of IRF-1 and -7 was similar between B10.S and SJL/J TMEV-infected macrophages, SJL/J but not B10.S macrophages exhibited constitutively active IRF-3. In contrast to overexpressed IRF-1, IRF-5, and IRF-7, which stimulated p35 promoter reporter activity, overexpressed IRF-3 repressed p35 promoter activity in response to TMEV infection, loxoribine, IFN-gamma/LPS, but not IFN-gamma alone. IRF-3 lessened but did not eliminate IRF-1-stimulated p35 promoter activity. Repression by IRF-3 required bp -172 to -122 of the p35 promoter. The data suggest that pre-activated IRF-3 is a major factor in the differences in IL-12 production between B10.S and SJL/J macrophages responding to TMEV.

Promoter Analysis Reveals Critical Roles for SMAD-3 and ATF-2 in Expression of IL-23 p19 in Macrophages

“…6B). Previously, we showed that IRF-3 is constitutively active and localized in the nucleus in SJL/J macrophages (36). Interestingly, in agreement with that finding, we show in this study that IRF-3 is strongly associated with the p19 promoter in unchallenged SJL/J macrophage (Fig.…”

“…However, additional phosphorylations through the PI3K/Akt pathway are required for complete activation, binding to the CBP protein, and association with promoter regions (55). We have shown previously that IRF-3 is constitutively active and localized to the nucleus in SJL/J macrophages, which are susceptible to TMEV-induced demyelinating disease, but not in macrophages from B10.S mice, which are resistant to TMEV-induced demyelinating disease (36). ChIP assays presented in this study agree with that observation, in that IRF-3 exhibits strong constitutive association with the endogenous p19 promoter in SJL/J macrophages and to some extent RAW264.7 cells.…”

“…ATF-2 is activated by phosphorylation through either the JNK, ERK, or p38 MAPK pathways (38), all of which are activated following TMEV infection of RAW264.7 cells or SJL/J macrophages (36,39,40). To determine which of the MAPKs are responsible for the ATF-2 activation that is required for p19 expression, RAW264.7 cells were pretreated with SB203580 (10 M), which inhibits activation of components downstream of the p38 pathway; U0126 (20 M), which inhibits activation of ERK; SP 600125 (10 M), which inhibits JNK MAPKs; or 1 l of DMSO, which was used to dissolve the inhibitors.…”

Differential Modulation of TLR3- and TLR4-Mediated Dendritic Cell Maturation and Function by Progesterone

“…Numerous studies have described that elevated IRF-3 activation leads to enhanced antiviral responses, including gross expression of IFNs (53). Therefore, sustained phosphorylation may imply an expected elevation of cytokine production.…”

“…Therefore, sustained phosphorylation may imply an expected elevation of cytokine production. More recently, however, experiments in macrophages (54) have detailed reduced expression of IL-12 p35 in response to viral infection due to constitutive activation of IRF-3 and its function as a repressor of transcription via binding to bp 2172 to 2122 of the p35 promoter (53). Whether this regulatory function is apparent in BMDCs and can be correlated with IRF-3 protein phosphorylation status remains to be determined.…”