Differential efficacy of caspase inhibitors on apoptosis markers during sepsis in rats and implication for fractional inhibition requirements for therapeutics.
A rodent model of sepsis was used to establish the relationship between caspase inhibition and inhibition of apoptotic cell death in vivo. In this model, thymocyte cell death was blocked by Bcl-2 transgene, indicating that apoptosis was predominantly dependent on the mitochondrial pathway that culminates in caspase-3 activation. Caspase inhibitors, including the selective caspase-3 inhibitor M867, were able to block apoptotic manifestations both in vitro and in vivo but with strikingly different efficacy for different cell death markers. Inhibition of DNA fragmentation required substantially higher levels of caspase-3 attenuation than that required for blockade of other apoptotic events such as spectrin proteolysis and phosphatidylserine externalization. These data indicate a direct relationship between caspase inhibition and some apoptotic manifestations but that small quantities of uninhibited caspase-3 suffice to initiate genomic DNA breakdown, presumably through the escape of catalytic quantities of caspase-activated DNase. These findings suggest that putative caspase-independent apoptosis may be overestimated in some systems since blockade of spectrin proteolysis and other cell death markers does not accurately reflect the high degrees of caspase-3 inhibition needed to prevent DNA fragmentation. Furthermore, this requirement presents substantial therapeutic challenges owing to the need for persistent and complete caspase blockade.
Méthot
Nathalie
N
Merck Frosst Centre for Therapeutic Research, Merck Research Laboratories, Montreal, Quebec, Canada H9H 3L1. nathalie_methot@merck.com
Huang
JingQi
J
Coulombe
Nathalie
N
Vaillancourt
John P
JP
Rasper
Dita
D
Tam
John
J
Han
Yongxin
Y
Colucci
John
J
Zamboni
Robert
R
Xanthoudakis
Steven
S
Toulmond
Sylvie
S
Nicholson
Donald W
DW
Roy
Sophie
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers; D053148:Caspase 3; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects; D005260:Female; D019254:Genes, bcl-2; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010069:Oxadiazoles / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018805:Sepsis / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D013049:Spectrin / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000473:pathology
D015415:Biomarkers; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C489028:M867 compound; D010069:Oxadiazoles; D011719:Pyrazines; D013049:Spectrin; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3