INHIBITING JNK, A NEW ANTI-INFLAMMATORY STRATEGY

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DESCRIPTION (Adapted from Investigator's Abstract): The primary goal of this proposal is to characterize proinflammatory cytokines TNF and IL-1 activated signal transduction in vascular endothelial cells (EC) to identify unique TNF-mediated pathways in inflammation. Inflammation is a process essential for host defense and tissue repair. However, defense may cause pathogenic changes leading to vascular diseases such as atherosclerosis. TNF triggers survival signal via activation of NF-kappaB, inflammation (and apoptosis) via activation of JFK. The major hypothesis of this proposal is that inhibition of JNK without disruption of NF-kappaB activation would provide a valid approach for anti-inflammatory therapy. We have elucidated that different proinflammatory cytokines activate unique as well as common intracellular signaling pathways as demonstrated by homologous desensitization (HMD) and heterologous desensitization (HTD). EC pre-treated with TNF become refractory to TNF restimulation but can be restimualted by IL-1 to active JNK and express E-selectin and vice versa (i.e. JNK activation and E-selectin expression show homologous desensitization - HMD). In contrast, atheroprotective laminar flow inhibits both TNF and IL-1-induced JNK and adhesion molecules (heterologous desensitization-HTD). We believe that HMD modulates a cytokine-specific inflammation, whereas HTD modulates all-cytokine-induced inflammation. We will use HMD and HTD as models to dissect TNF-activated JNK activation from NF-kappaB and from IL-1 signaling pathway. The specific hypothesis to be investigated is that: 1). HMD is via TNF receptor-associated factor 2 (TRAF2), an adaptor protein in TNF signaling as a bifurcation point for JNK and NF-kappaB. 2). HTD is via the MAP kinase kinase kinase ASK1, a convergent point of TNF and IL-1 signaling in EC. Exciting preliminary data indicate that overexpression of TRAF2 in EC desensitizes TNF-induced JNK and E-selectin, and that the specific domains and the natural cleavage products of TRAF2 play roles in JNK activation. Three specific aims are proposed. 1). HMD is via TRAF2 focusing on characterizing TRAF2 unique residues, binding proteins and cleavage products in JNK activation. 2) HTD is via ASK1 focusing on characterizing flow effect on TNF and IL-1-induced ASK lactivation. 3) Characterizing roles of TRAF2 and ASK1 in TNF-induced inflammation in murine models by gene delivery of TRAF2 or ASK1 into cornea endothelium. This proposal should provide candidate proteins that are specific or unique targets for TNF-mediated inflammatory events and facilitate development of new therapeutic approaches to control inflammation in various disease settings.