Distinct Pathways for NF-κB Regulation Are Associated with Aberrant Macrophage IL-12 Production in Lupus- and Diabetes-Prone Mouse Strains

Abstract

One characteristic of mice prone to a variety of autoimmune diseases is the aberrant regulation of cytokine production by macrophages (Mφ), noted in cells isolated well before the onset of disease. Strikingly, the pattern of IL-12 dysregulation, in particular, is consistent with the nature of the autoimmune disease that will develop in each strain, i.e., elevated in mice prone to Th1-mediated organ-specific disease (nonobese diabetic (NOD) and SJL mice) and reduced in lupus-prone strains (MRL/+ and NZB/W). Mechanistically, the abnormal regulation of IL-12 in these strains was found to be strictly associated with novel patterns of Rel binding in vitro to the unique NF-κB site in the IL-12 p40 promoter. In this study, we report several new findings related to these Rel-κB interactions. Evaluation of the p40 NF-κB site in vivo, assessed by chromatin immunoprecipitation, revealed Rel usage patterns similar to those found in vitro using EMSA, with preferential association of the p40 κB site with c-Rel in NOD Mφ but with p50 in NZB/W Mφ. Moreover, blocking c-Rel in primary Mφ, using short interfering RNA, selectively blocked IL-12 production and normalized the minimal, residual IL-12 levels. Nuclear extracts from NOD Mφ were characterized by c-Rel hyperphosphorylation, and dephosphorylation of nuclear proteins completely blocked binding to the κB site. In contrast, elevated IκB appears to be a likely mechanism accounting for the reduced nuclear c-Rel levels noted in NZB/W Mφ. Alterations in NF-κB metabolism thus appear to define a pathway regulating intrinsic IL-12 defects in both diabetes- and lupus-prone strains.

Immunology of β-Cell Destruction

“…Most alterations described in mice are consistent with the hypothesis of an increased DC capacity to activate CD4+ and CD8+ T cells [302], such as upregulation of costimulatory molecules, enhanced secretion of cytokines IL-12p70 and TNF-a [303], and downregulation of IDO [304]. An abnormal cytokine response by DC from T1D patients upon antigenic [305] or nonantigenic stimulation was proposed [306] but has not been confirmed by other studies [307].…”

“…DC may therefore indirectly participate to T1D autoimmunity through a reduced efficacy in stimulating Treg, as is also reported in mice [309] and BB rats [310]. This immature phenotype of T1D human DC may result from abnormal activation of the NF-kB pathway [311], consistently with the strong involvement of this transcription factor in the induction of self-tolerance in mice [157,303].…”

Inhibition of Interleukin-12 p40 Transcription and NF-κB Activation by Nitric Oxide in Murine Macrophages and Dendritic Cells

“…There is a selective requirement for the NF-B family member c-Rel in IL-12 p40 gene expression. Alterations in the ratios of NF-B family members (27) may explain a phenomena observed in this study; NO profoundly inhibited IL-12 p40 expression, but other cytokines that are regulated through NF-B, such as IL-1 receptor antagonist (28), were induced normally (data not shown). Activation of NF-B has been well described through MyD88-independent signal transduction pathways (29), which may also explain why all NF-B-regulated genes are not inhibited by NO to the same extent or with the same kinetics as IL-12 p40.…”

Heat shock protein 90 inhibition by 17-DMAG lessens disease in the MRL/lpr mouse model of systemic lupus erythematosus

“…68 It has been shown that the severity of SLE can be diminished in mice and humans through downregulation of many of these HSP90-dependent inflammatory pathways. [69][70][71][72] Our current studies were undertaken to determine if modulation of HSP90 would decrease mesangial cell inflammatory mediator production and lessen renal disease in MRL/lpr lupus mice.…”