title: Differential efficacy of caspase inhibitors on apoptosis markers during sepsis in rats and implication for fractional inhibition requirements for therapeutics.
abstract: 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.
authors.affiliation: Merck Frosst Centre for Therapeutic Research, Merck Research Laboratories, Montreal, Quebec, Canada H9H 3L1. nathalie_methot@merck.com
authors.forename: Nathalie
authors.initials: N
authors.lastname: Méthot
authors.forename: JingQi
authors.initials: J
authors.lastname: Huang
authors.forename: Nathalie
authors.initials: N
authors.lastname: Coulombe
authors.forename: John P
authors.initials: JP
authors.lastname: Vaillancourt
authors.forename: Dita
authors.initials: D
authors.lastname: Rasper
authors.forename: John
authors.initials: J
authors.lastname: Tam
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Han
authors.forename: John
authors.initials: J
authors.lastname: Colucci
authors.forename: Robert
authors.initials: R
authors.lastname: Zamboni
authors.forename: Steven
authors.initials: S
authors.lastname: Xanthoudakis
authors.forename: Sylvie
authors.initials: S
authors.lastname: Toulmond
authors.forename: Donald W
authors.initials: DW
authors.lastname: Nicholson
authors.forename: Sophie
authors.initials: S
authors.lastname: Roy
mesh_terms: 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
chemical_list: 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