Dysregulated TLR3-dependent signaling and innate immune activation in superoxide-deficient macrophages from nonobese diabetic mice

• Published in: Free radical biology & medicine 2012-05, Vol.52 (9), p.2047-2056
• Main Authors: Seleme, Maria C., Lei, Weiqi, Burg, Ashley R., Goh, Kah Yong, Metz, Allison, Steele, Chad, Tse, Hubert M.
• Format: Article
• Language: English
• Subjects: adaptor proteins; alpha -Interferon; Animals; beta -Interferon; Beta cells; Bone marrow; CD4 antigen; CD4-positive T-lymphocytes; Cell activation; Cytokines; Diabetes mellitus; Diabetes Mellitus, Experimental - immunology; Diabetes Mellitus, Experimental - metabolism; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Free radicals; Immunity, Innate; Inflammation; Innate immunity; insulin-dependent diabetes mellitus; interferon-beta; Lymphocytes T; Macrophage; Macrophages; Macrophages - metabolism; Major histocompatibility complex; Mice; Mice, Inbred NOD; NF- Kappa B protein; NOD mouse; Pancreas; Poly(I:C); Reactive oxygen species; Reactive Oxygen Species - metabolism; Receptor mechanisms; Reverse Transcriptase Polymerase Chain Reaction; Signal transduction; Signal Transduction - physiology; Superoxide; Superoxides - metabolism; TLR3 protein; TLR3 signaling; Toll-like receptor 3; Toll-Like Receptor 3 - physiology; Toll-like receptors; transcription factor NF-kappa B; Tumor necrosis factor- alpha; Type 1 diabetes
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2012.01.027

In type 1 diabetes (T1D), reactive oxygen species (ROS) and proinflammatory cytokines produced by macrophages and other innate immune cells destroy pancreatic β cells while promoting autoreactive T cell maturation. Superoxide-deficient nonobese diabetic mice (NOD.Ncf1m1J) are resistant to spontaneous diabetes, revealing the integral role of ROS signaling in T1D. Here, we evaluate the innate immune activation state of bone marrow-derived macrophages (BM-Mϕ) from NOD and NOD.Ncf1m1J mice after poly(I:C)-induced Toll-like receptor 3 (TLR3) signaling. We show that ROS synthesis is required for efficient activation of the NF-κB signaling pathway and concomitant expression of TLR3 and the cognate adaptor molecule, TRIF. Poly(I:C)-stimulated NOD.Ncf1m1J BM-Mϕ exhibited a 2- and 10-fold decrease in TNF-α and IFN-β proinflammatory cytokine synthesis, respectively, in contrast to NOD BM-Mϕ. Optimal expression of IFN-α/β is not solely dependent on superoxide synthesis, but requires p47phox to function in a NOX-independent manner to mediate type I interferon synthesis. Interestingly, MHC-II I-Ag7 expression necessary for CD4 T cell activation is increased 2-fold relative to NOD, implicating a role for superoxide in I-Ag7 downregulation. These findings suggest that defective innate immune-pattern-recognition receptor activation and subsequent decrease in TNF-α and IFN-β proinflammatory cytokine synthesis necessary for autoreactive T cell maturation may contribute to the T1D protection observed in NOD.Ncf1m1J mice. ► Loss of superoxide decreases TLR3 and TRIF expression and TNF-α and IFN-α/β synthesis in poly(I:C)-stimulated NOD.Ncf1m1J macrophages. ► Defects in NF-κB signaling may account for dysregulated TLR3 expression. ► Exogenous superoxide can rescue TNF-α, but not IFN-α/β production; thus, type I interferon synthesis may be mediated in part by a NOX-independent mechanism. ► Compromised antiviral and innate immune responses in NOX-deficient NOD mice may partially explain resistance to type 1 diabetes.