Expression of a dominant negative mutant of interleukin-1 beta converting enzyme in transgenic mice prevents neuronal cell death induced by trophic factor withdrawal and ischemic brain injury

To explore the role of the interleukin (IL)-1 beta converting enzyme (ICE) in neuronal apoptosis, we designed a mutant ICE gene (C285G) that acts as a dominant negative ICE inhibitor. Microinjection of the mutant ICE gene into embryonal chicken dorsal root ganglial neurons inhibits trophic factor withdrawal-induced apoptosis. Transgenic mice expressing the fused mutant ICE-lacZ gene under the control of the neuron specific enolase promoter appeared neurologically normal. These mice are deficient in processing pro-IL-1 beta, indicating that mutant ICE(C285G) blocks ICE function. Dorsal root ganglial neurons isolated from transgenic mice were resistant to trophic factor withdrawal-induced apoptosis. In addition, the neurons isolated from newborn ICE knockout mice are similarly resistant to trophic factor withdrawal-induced apoptosis. After permanent focal ischemia by middle cerebral artery occlusion, the mutant ICE(C285G) transgenic mice show significantly reduced brain injury as well as less behavioral deficits when compared to the wild-type controls. Since ICE is the only enzyme with IL-1 beta convertase activity in mice, our data indicates that the mutant ICE(C285G) inhibits ICE, and hence mature IL-1 beta production, and through this mechanism, at least in part, inhibits apoptosis. Our data suggest that genetic manipulation using ICE family dominant negative inhibitors can ameliorate the extent of ischemia-induced brain injury and preserve neurological function.