Selective, reversible caspase-3 inhibitor is neuroprotective and reveals distinct pathways of cell death after neonatal hypoxic-ischemic brain injury.
Hypoxia-ischemia (H-I) in the developing brain results in brain injury with prominent features of both apoptosis and necrosis. A peptide-based pan-caspase inhibitor is neuroprotective against neonatal H-I brain injury, suggesting a central role of caspases in brain injury. Because previously studied peptide-based caspase inhibitors are not potent and are only partially selective, the exact contribution of specific caspases and other proteases to injury after H-I is not clear. In this study, we explored the neuroprotective effects of a small, reversible caspase-3 inhibitor M826. M826 selectively and potently inhibited both caspase-3 enzymatic activity and apoptosis in cultured cells in vitro. In a rat model of neonatal H-I, M826 blocked caspase-3 activation and cleavage of its substrates, which begins 6 h and peaks 24 h after H-I. Although M826 significantly reduced DNA fragmentation and brain tissue loss, it did not prevent calpain activation in the cortex. This activation, which is associated with excitotoxic/necrotic cell injury, occurred within 30 min to 2 h after H-I even in the presence of M826. Similar to calpain activation, we found evidence of caspase-2 processing within 30 min to 2 h after H-I that was not affected by M826. Caspase-2 processing appeared to be secondary to calpain-mediated cleavage and was not associated with caspase-2 activation. These data suggest that caspase-3 specifically contributes to delayed cell death and brain injury after neonatal H-I and that calpain activation is associated with and likely a marker for the early component of excitotoxic/necrotic brain injury previously demonstrated in this model.
Han
Byung Hee
BH
Department of Neurology, Washington University, St. Louis, Missouri 63110, USA.
Xu
Daigen
D
Choi
Junjeong
J
Han
Yongxin
Y
Xanthoudakis
Steven
S
Roy
Sophie
S
Tam
John
J
Vaillancourt
John
J
Colucci
John
J
Siman
Robert
R
Giroux
Andre
A
Robertson
George S
GS
Zamboni
Robert
R
Nicholson
Donald W
DW
Holtzman
David M
DM
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D053148:Caspase 3; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D006868:Hydrolysis; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology / Q000517:prevention & control*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010069:Oxadiazoles / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C465343:M 826 compound; D018696:Neuroprotective Agents; D010069:Oxadiazoles; D011719:Pyrazines; C505410:Casp3 protein, rat; D053148:Caspase 3