Transgenic mice neuronally expressing baculoviral p35 are resistant to diverse types of induced apoptosis, including seizure-associated neurodegeneration

Abstract

Apoptosis is a cell-suicide process that appears to play a central role not only during normal neuronal development but also in several neuropathological disease states. An important component of this process is a proteolytic cascade involving a family of cysteine proteases called caspases. Caspase inhibitors have been demonstrated to be effective in inhibiting neuronal cell death in various apoptotic paradigms. We have created transgenic mice that neuronally express the baculoviral caspase inhibitor p35. Neuronal expression of the p35 protein was found to confer functional caspase inhibitory activity and prevent apoptosis in isolated cerebellar granular cultures induced to undergo apoptosis either via staurosporine treatment or through withdrawal of extracellular potassium. Neuronal expression of p35 was also found to attenuate neurodegeneration associated with the excitotoxic glutamate analogue kainic acid (KA) in vitro and in vivo. Organotypic hippocampal cultures isolated from p35 transgenics demonstrated lowered caspase activity and decreased apoptosis compared with wild type when exposed to KA. In vivo injection of KA also produced decreased caspase activity and cell death in p35 transgenics vs. wild type. These results suggest that the presence of p35 in neurons in vivo is protective against various types of apoptosis, including seizure-related neurodegeneration, and that caspases may be attractive potential targets for preventing neuronal injury associated with diseases such as epilepsy. These mice also provide a valuable tool for exploring the role of caspases in other neuropathological conditions in which apoptosis has been implicated. A poptosis is a highly ordered, morphologically distinct process of cell death involving the activation of a family of cysteine proteases called caspases (1). Caspases were first implicated in apoptosis by the discovery of the Caenorhabditis elegans ced-3 gene (2). Since then, a large family of these caspases has been described in a wide variety of organisms. Caspases are expressed as proenzymes and are activated during apoptosis either by autocatalytic cleavage or via other caspases (3).Much interest in the process of neuronal apoptosis has been generated recently because of a growing body of evidence suggesting that inappropriate apoptosis may contribute to the pathology associated with several neurological disorders (4-6). In several instances, inhibition of caspases has been shown to functionally rescue neurons from death. After permanent focal ischemia, for example, transgenic mice expressing a dominantnegative form of caspase-1 display significantly reduced brain injury and behavioral deficits (7). The presence of this transgene also delays the appearance of symptoms and increases survival rates in mouse models of both amyotrophic lateral sclerosis and Huntington's disease (8, 9).To further explore the role of caspases in various neuropathological processes, we have created transgenic mice that neuronally express the baculoviral caspase inhibitor protein, p35.Expre...

HSV-mediated delivery of virally derived anti-apoptotic genes protects the rat hippocampus from damage following excitotoxicity, but not metabolic disruption

“…6,7,27 However, there is some evidence for an apoptotic pathway of neuron death, as demonstrated by the appearance of certain morphological and biochemical features characteristic of apoptosis. [28][29][30][31][32][33] Emerging data support the idea that apoptosis and necrosis in vivo are not distinct, clear-cut pathways, but rather represent a morphological continuum of neuronal death processes.…”

“…Studies have demonstrated that inhibition of caspase 3-like activation prevents neuronal death following excitotoxicity 38,39 and that a transgenic mouse expressing p35 is resistant to seizure-induced cell loss. 30 Though crmA rescued neurons from excitotoxic death in vitro, 20 such a dissociation of protective efficacy in culture versus whole animal has been observed previously in our hands with the examination of Hsp72's protective potential. 21,27 KsBcl-2's lack of protection following the administration of KA, though in agreement with previous in vitro results, 20 was nonetheless surprising since human Bcl-2 has been shown to robustly protect area CA3 from seizure damage.…”

Baculovirus apoptotic suppressor P49 is a substrate inhibitor of initiator caspases resistant to P35 in vivo

“…Indeed, P49 blocked virus-induced apoptosis in cultured cells from Drosophila (Figure 8). Apoptosis of DL-1 cells was also suppressed by P35, which has been shown to prevent programmed cell death in invertebrates and vertebrates (Hay et al, 1994;Sugimoto et al, 1994;Grether et al, 1995;Izquierdo et al, 1999;Hisahara et al, 2000;Viswanath et al, 2000). Since P49 and P35 were proteolytically cleaved in Drosophila cells (Figure 8), a substrate inhibitor mechanism for both apoptotic suppressors is likely.…”

Nigrostriatal Dopaminergic Neurodegeneration in theWeaverMouse Is Mediated via Neuroinflammation and Alleviated by Minocycline Administration

“…All mice were maintained on B6CBACa-A w-J / A-Kcnj6 wv hybrid background and were offspring of breeding pairs obtained from The Jackson Laboratory (Bar Harbor, ME). A transgene consisting of the neuron-specific enolase promoter and the p35 coding sequence was microinjected into fertilized B6C3F1 oocytes to generate p35 transgenic mice as described previously (Viswanath et al, 2000). Mice used for this study were offspring of breeding pairs between female ϩ/wv, p35 ϩ/Ϫ, or wv/wv, p35 ϩ/Ϫ mice, and male ϩ/wv, p35 ϩ/Ϫ mice.…”