Prolonged Therapeutic Window for Ischemic Brain Damage Caused by Delayed Caspase Activation

Abstract

Apoptotic cell death is prominent in neurodegenerative disorders, such as Alzheimer's disease and Huntington's disease, and is found in cerebral ischemia. Using a murine model of delayed cell death, we determined that cleavage of zDEVD-amino-4-trifluoromethyl coumarin (zDEVD-afc) in brain homogenate, a measure of caspase activation, increased initially 9 hours after brief (30 minutes) middle cerebral artery occlusion along with caspase-3p20 immunoreactive cleavage product as determined by immunoblotting. zDEVD-afc cleavage activity was blocked by pretreatment or posttreatment with the caspase-inhibitor N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl-ketone (zDEVD-fmk), and ischemic damage was reduced when the drug was injected up to 9 hours after reperfusion. The protection was long lasting (21 days). Hence, the period before caspase activation defined the therapeutic opportunity for this neuroprotective agent after mild ischemic brain injury. Prolonged protection after caspase inhibition plus the extended treatment window may be especially relevant to the treatment of neurodegenerative disorders.

Caspase activation and neuroprotection in caspase-3- deficient mice after in vivo cerebral ischemia and in vitro oxygen glucose deprivation

“…Caspase-3 is also the most abundant cysteine aspartase expressed in adult rodent brain and caspase-3-like enzyme activity and activated caspase-3 subunits are detected in ischemic tissues by immunoblotting and immunohistochemistry (6,7). Treatment with peptide-based caspase inhibitors protects brain from mild ischemic injury and improves neurological deficits (8)(9)(10). We extend the findings above by studying ischemic mechanisms in caspase-3 Ϫ/Ϫ brain in vivo and in vitro.…”

The kinder side of killer proteases: Caspase activation contributes to neuroprotection and CNS remodeling

“…31 Moreover, caspase inhibitors are neuroprotective in in vivo and in vitro models of ischemia. [32][33][34][35][36] We have, however, recently found that caspase activation also contributes to endogenous pathway which can protect against ischemic and excitotoxic injury.…”

Mice overexpressing human caspase 3 appear phenotypically normal but exhibit increased apoptosis and larger lesion volumes in response to transient focal cerebral ischaemia

“…Caspase 3 activation has been detected following focal (and global) ischaemic insults to the brain [14][15][16][17][18][19] where it coincides with areas of enhanced apoptotic cell death 14 and treatment with caspase 3 inhibitors has been reported to reduce infarct size following MCA occlusion. 14,[56][57][58] Moreover, studies in caspase 3-deficient mice indicate that these animals are relatively resistant to ischaemic insults with smaller lesions than their WT littermates.…”

“…10 The decreased apoptosis observed in the brain suggested a critical role for caspase 3 in the development of the central nervous system. Caspase 3 has also been implicated in cell death following a number of neurodegenerative insults including global ischaemia, 12,13 focal ischaemia, [14][15][16][17][18][19] transient ischaemia of the spinal cord, 20 neonatal cerebral hypoxia-ischaemia, [21][22][23] traumatic brain injury, [24][25][26] Alzheimer's disease, [27][28][29] Huntington's disease, [30][31][32] and Parkinson's disease. [33][34][35][36][37] It was therefore hypothesized that overexpression of caspase 3 may sensitize the animal to normal (physiological) apoptotic processes that occur during development and natural ageing and confer particular susceptibility to neurodegenerative insults.…”