Poster Sessions

Imm-35

Ariel Bulua

A. Bulua, A. Simon, R. Maddipati, H. Park, H. Komarow, D. Kastner, R. Siegel

Reactive Oxygen Species Are Involved in the Inflammation and Altered Signaling Of TNF Receptor-Associated Periodic Syndrome (TRAPS)

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autosomal dominantly inherited autoinflammatory disorder characterized by recurrent fevers with abdominal pain, migratory rash, and inflammation. The disorder, which often occurs without an obvious trigger, is caused by mutations in the type 1 TNF receptor (TNFR1). We have previously shown that TRAPS associated mutant receptors do not traffic to the cell surface and do not bind TNF, suggesting that they may have a TNF independent component. Quantitation of TNFR1 by western blotting has shown that mutant TNF receptors accumulate to high levels in cells of TRAPS patients and mice with mutations homologous to two TRAPS associated mutants (TRAPS “knock-in” mice). Intracellular accumulation of TNFR1 may lead to abnormal TNF-independent receptor signaling and sustained inflammation. Analysis of signaling events downstream of TNFR1 revealed elevated activation of p38 and JNK MAP kinases. Reactive Oxygen Species have previously been shown to lead to sustained MAPK activation through inactivation of MAPK phosphatases. To determine whether elevated levels of ROS may play a role in abnormal signaling and inflammation in cells harboring TNFR1 mutations, we measured ROS levels in mouse embryonic fibroblasts (MEFs), mouse bone marrow-derived macrophages and neutrophils, and human blood samples. The results show elevated ROS at baseline and after activating stimuli. The production of ROS is inhibited by a number of antioxidants including N-Acetyl Cysteine and DPI, as well as in GP91phox knock-out mice, implicating NADPH Oxidase as the ROS-generating mechanism. Using IL-6 as an inflammatory marker, we studied the secretion of cytokines in response to both an LPS trigger alone and with the addition of antioxidant. Importantly, antioxidant treatment reduced hyperproduction of inflammatory cytokines by MEFs from TRAPS “knock-in” mice and TRAPS patient samples. This suggests that signaling from mutant TNFR1 potentiates TLR signaling through ROS. ROS may be a novel therapeutic target in TRAPS.