Caspase inhibition after neonatal ischemia in the rat brain.

Caspase-3 has been identified as a key protease in the execution of apoptosis and appears to be an important downstream event after hypoxia-ischemia in the immature brain. The efficacy of a pan-caspase inhibitor, boc-aspartyl-(Ome)-fluoromethyl-ketone (BAF), was tested in a model of unilateral focal ischemia with reperfusion in 7-day-old rats. The BAF inhibitor was given intraperitoneally 5 minutes before reperfusion via the carotid artery. This procedure reduced the activity of caspase-3 by 79% but did not induce a significant reduction in infarct volume (23.8 +/- 7.5% versus 30.1 +/- 6.4%). Animals were distributed in two populations. One population exhibited an infarct, whereas the other appeared to be fully protected. BAF-treated animals exhibiting an infarct mostly displayed necrotic cell death, whereas apoptotic nuclei were observed in untreated or vehicle-treated animals. Repeated dose of BAF (5 minutes before and 9 hours after reperfusion) did not also provide benefit after neonatal ischemia, although a general trend to reduce lesion was observed (20.5 +/- 3.7% versus 34.4 +/- 5.9%). These findings raise critical questions about the use of peptide ketone apoptotic inhibitors in improving histopathologic outcomes after neonatal stroke.