The Cytoprotective Effects of Tumor Necrosis Factor Are Conveyed Through Tumor Necrosis Factor Receptor–Associated Factor 2 in the Heart

Abstract

Background— Activation of both type 1 and type 2 tumor necrosis factor (TNF) receptors (TNFR1 and TNFR2) confers cytoprotection in cardiac myocytes. Noting that the scaffolding protein TNF receptor–associated factor 2 (TRAF2) is common to both TNF receptors, we hypothesized that the cytoprotective responses of TNF were mediated through TRAF2. Methods and Results— Mice with cardiac-restricted overexpression of low levels of TNF (MHCsTNF ₃ ) and TRAF2 (MHC-TRAF2 _LC ) and mice lacking TNFR1, TNFR2, and TNFR1/TNFR2 were subjected to ischemia (30 minutes) reperfusion (30 minutes) injury ex vivo using a Langendorff apparatus. MHCsTNF ₃ mice were protected against ischemia-reperfusion injury as shown by a significant ≈30% greater left ventricular developed pressure, ≈80% lower creatine kinase release, and Evans blue dye uptake compared with littermates. The extent of ischemia-reperfusion induced injury was similar in wild-type, TNFR1, and TNFR2 deficient mice; however, mice lacking TNFR1/TNFR2 had a significant ≈40% lower left ventricular developed pressure, a ≈65% greater creatine kinase release, and ≈40% greater Evans blue dye uptake compared with littermates. Interestingly, MHC-TRAF2 _LC mice had a significant ≈50% lower left ventricular developed pressure, a ≈70% lower creatine kinase release, and ≈80% lower Evans blue dye uptake compared with littermate controls after ischemia-reperfusion injury. Biochemical analysis of the MHC-TRAF2 _LC hearts showed that there was activation of nuclear factor-kappaB but not c-Jun N-terminal kinase activation. Conclusion— Taken together, these results suggest that TNF confers cytoprotection in the heart through TRAF2-mediated activation of nuclear factor-κB.