Spontaneous in contrast to CD95-induced neutrophil apoptosis is independent of caspase activity.
BACKGROUND
The influence of caspase inhibitors on spontaneous and on CD95-triggered apoptosis was investigated in neutrophils from healthy volunteers and compared with neutrophils from patients with severe sepsis.


METHODS
To further elucidate the mechanisms of neutrophil apoptosis, isolated neutrophils from healthy volunteers (n = 9) were either stimulated with the agonistic anti-CD95 antibody (100 ng/mL) or left unstimulated in the presence or absence of the caspase inhibitors zIETD-fmk (10 micromol/L), zDEVD-fmk (10 micromol/L), or zVAD-fmk (20 micromol/L). Apoptosis was determined by measuring DNA fragmentation and Annexin-V binding in FACS, and caspase-3-like activity by DEVD-afc cleavage assay. Results were compared with those from patients with severe sepsis (n = 15).


RESULTS
Reduced spontaneous neutrophil apoptosis in patients with sepsis (-48.7%) was completely restored by incubation with agonistic anti-CD95 antibody (p < 0.05). Inhibition of caspases did not influence spontaneous neutrophil apoptosis in both groups. However, zVAD-fmk reduced anti-CD95 antibody-induced apoptosis in neutrophils from controls by -22.6% (p < 0.05) and in patients with sepsis by -43.1% (p < 0.05).


CONCLUSIONS
These results indicate that spontaneous in contrast to CD95-induced neutrophil apoptosis is independent of caspase activity.
Härter
L
L
Division of Trauma Surgery, University Hospital Zürich, Raemistrasse 100, CH-8091 Zürich, Switzerland.
Keel
M
M
Hentze
H
H
Steckholzer
U
U
Ungethüm
U
U
Trentz
O
O
Ertel
W
W
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis; D016022:Case-Control Studies; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D009504:Neutrophils / Q000378:metabolism / Q000473:pathology*; D018805:Sepsis / Q000276:immunology / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D020169:Caspases