Nitric oxide induces thymocyte apoptosis via a caspase-1-dependent mechanism.
We previously showed that NO induces apoptosis in thymocytes via a p53-dependent pathway. In the present study, we investigated the role of caspases in this process. The pan-caspase inhibitor, ZVAD-fmk, and the caspase-1 inhibitor, Ac-YVAD-cho, both inhibited NO-induced thymocyte apoptosis in a dose-dependent manner, whereas the caspase-3 inhibitor, Ac-DEVD-cho, had little effect even at concentrations up to 500 microM. ZVAD-fmk and Ac-YVAD-cho were able to inhibit apoptosis when added up to 12 h, but not 16 h, after treatment with the NO donor S-nitroso-N-acetyl penicillamine (SNAP). Caspase-1 activity was up-regulated at 4 h and 8 h and returned to baseline by 24 h; caspase-3 activity was not detected. Cytosolic fractions from SNAP-treated thymocytes cleaved the inhibitor of caspase-activated deoxyribonuclease. Such cleavage was completely blocked by Ac-YVAD-cho, but not by Ac-DEVD-cho or DEVD-fmk. Poly(ADP-ribose) polymerase (PARP) was also cleaved in thymocytes 8 h and 12 h after SNAP treatment; addition of Ac-YVAD-cho to the cultures blocked PARP cleavage. Furthermore, SNAP induced apoptosis in 44% of thymocytes from wild-type mice; thymocytes from caspase-1 knockout mice were more resistant to NO-induced apoptosis. These data suggest that NO induces apoptosis in thymocytes via a caspase-1-dependent but not caspase-3-dependent pathway. Caspase-1 alone can cleave inhibitor of caspase-activated deoxyribonuclease and lead to DNA fragmentation, thus providing a novel pathway for NO-induced thymocyte apoptosis.
Zhou
X
X
Department of Surgery, University of Pittsburgh School of Medicine, and Children's Hospital of Pittsburgh, Pittsburgh, PA 15213, USA.
Gordon
S A
SA
Kim
Y M
YM
Hoffman
R A
RA
Chen
Y
Y
Zhang
X R
XR
Simmons
R L
RL
Ford
H R
HR
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins; D020170:Caspase 1 / Q000378:metabolism / Q000502:physiology*; D061945:Caspase Inhibitors; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003851:Deoxyribonucleases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000187:drug effects; D006868:Hydrolysis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000502:physiology*; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D026423:S-Nitroso-N-Acetylpenicillamine; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D011506:Proteins; C109664:caspase-activated DNase inhibitor; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D011065:Poly(ADP-ribose) Polymerases; D003851:Deoxyribonucleases; D020170:Caspase 1; D010396:Penicillamine