FLIP(L) protects neurons against in vivo ischemia and in vitro glucose deprivation-induced cell death.
Knowledge of the molecular mechanisms that underlie neuron death after stroke is important to allow the development of effective neuroprotective strategies. In this study, we investigated the contribution of death receptor signaling pathways to neuronal death after ischemia using in vitro and in vivo models of ischemic injury and transgenic mice that are deficient in tumor necrosis factor receptor I (TNFRI KO) or show neuron-specific overexpression of the long isoform of cellular Fas-associated death domain-like interleukin-1-beta-converting enzyme-inhibitory protein (FLIP(L)). Caspase 8 was activated in brain lesions after permanent middle cerebral artery occlusion (pMCAO) and in cortical neurons subjected to glucose deprivation (GD) and was necessary for GD-induced neuron death. Thus, neurons treated with zIETD-FMK peptide or overexpressing a dominant-negative caspase 8 mutant were fully protected against GD-induced death. The presence of the neuroprotective TNFRI was necessary for selectively sustaining p50/p65NF-kappaB activity and the expression of the p43 cleavage form of FLIP(L), FLIP(p43), an endogenous inhibitor of caspase 8, in pMCAO lesions and GD-treated neurons. Moreover, TNF pretreatment further upregulated p50/p65NF-kappaB activity and FLIP(p43) expression in neurons after GD. The knock-down of FLIP in wild-type (WT) neurons using a short hairpin RNA revealed that FLIP(L) is essential for TNF/TNFRI-mediated neuroprotection after GD. Furthermore, the overexpression of FLIP(L) was sufficient to rescue TNFRI KO neurons from GD-induced death and to enhance TNF neuroprotection in WT neurons, and neuron-specific expression of FLIP(L) in transgenic mice significantly reduced lesion volume after pMCAO. Our results identify a novel role for the TNFRI-NF-kappaB-FLIP(L) pathway in neuroprotection after ischemia and identify potential new targets for stroke therapy.
Taoufik
Era
E
Laboratory of Molecular Genetics, Hellenic Pasteur Institute, 11521 Athens, Greece.
Valable
Samuel
S
Müller
Georg J
GJ
Roberts
Michael L
ML
Divoux
Didier
D
Tinel
Antoine
A
Voulgari-Kokota
Anda
A
Tseveleki
Vivian
V
Altruda
Fiorella
F
Lassmann
Hans
H
Petit
Edwige
E
Probert
Lesley
L
D000818:Animals; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000502:physiology*; D016923:Cell Death / Q000235:genetics; D015687:Cell Hypoxia / Q000235:genetics; D002478:Cells, Cultured; D005947:Glucose / Q000172:deficiency* / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism* / Q000473:pathology*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000502:physiology
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D005947:Glucose