Abstracts

The role of tumor necrosis factor receptor 1 (TNFR1) signaling in temporal lobe epilepsy (TLE) is incompletely understood. Experimental modeling suggests seizures activate TNFR1 and downstream pro- and anti-apoptotic signaling cascades, although little is known about whether these pathways function in human TLE brain., We examined TNFR1 signaling in hippocampus surgically obtained from refractory TLE patients (n=10), and compared results to matched autopsy controls (n = 6). TNFR1 signaling was also examined in hippocampus obtained from mice following focally-evoked limbic seizures. Samples were processed for detection of protein in whole cell lysates or subcellular fractions, immunoprecipitation studies and immunohistochemistry., Western blotting established total protein levels of the TNFR1 proximal signaling adaptor TNFR-associated protein with death domain (TRADD) and cleaved caspase-8 were higher in TLE samples than matched autopsy controls. Intracellular distribution analyses determined cytoplasmic levels of TNFR1, TRADD and the caspase-8 recruitment adaptor Fas-associated protein with death domain (FADD), and microsomal levels of TRADD, FADD and cleaved caspase-8, were raised in TLE samples. Immunoprecipitation studies, supported by fluorescence microscopy revealed increased TNFR1-TRADD and TRADD-FADD association in TLE samples. Expression and localization of these proteins was similar in mouse hippocampus. Seizures evoked by intraamygdala kainic acid increased microsomal levels of TNFR1 signaling components and triggered TNFR1-TRADD and TRADD-FADD complex formation and caspase-8 processing., These data show seizures in mice activate hippocampal TNFR1 signaling and reveal this pathway to be engaged in patients with temporal lobe epilepsy. Accordingly, the TNFR1 pathway may be a potential target for adjunctive neuroprotective therapy following status epilepticus or in the setting of recurrent epileptic seizures., (Supported by NIH/NINDS grants NS39016 and NS41935, Science Foundation Ireland, Health Research Board, Marie Curie Foundation and the Program for Human Genomics, PRTLI [amp] Higher Education Authority, Ireland.)