The p17 cleaved form of caspase-3 is present within viable macrophages in vitro and in atherosclerotic plaque.
OBJECTIVE
In vitro studies of macrophage death in response to oxidized LDL (oxLDL) were undertaken as a model for the formation of the necrotic core of atherosclerotic plaque.


RESULTS
Thioglycollate-elicited mouse peritoneal macrophages avidly incorporated both oxLDL and acetylated LDL (acLDL) to become foam cells. oxLDL-treated macrophages, but not acLDL-treated macrophages, showed nearly 100% death, with characteristics consistent with apoptosis, including cell surface phosphatidylserine exposure, intracellular caspase-3 activity, cleavage of caspase-3 substrates, and DNA fragmentation, as shown by TUNEL assay. The activated form of caspase-3 (p17 cleaved form) was present in attached, viable macrophages before exposure to oxLDL. This p17 form was also found in apparently viable as well as in TUNEL-positive cells within atherosclerotic lesions of chow-fed apolipoprotein E-deficient (ApoE-/-) mice. The amount of p17 caspase-3 was reduced by in vitro blockade of FasL with an FasL-blocking antibody and was absent in macrophages from lpr/lpr mice, which lack functional Fas. Moreover, lpr/lpr macrophages resisted oxLDL cytotoxicity.


CONCLUSIONS
The naturally occurring Fas-FasL induction of caspase-3 cleavage after macrophage attachment may represent an important physiologic mechanism that primes for cytotoxicity by oxLDL and possibly, other death-inducing molecules.
Nhan
Thomas Q
TQ
Department of Pathology, School of Medicine, University of Washington, Seattle, WA 98195, USA.
Liles
W Conrad
WC
Chait
Alan
A
Fallon
John T
JT
Schwartz
Stephen M
SM
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001161:Arteriosclerosis / Q000201:enzymology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D005487:Foam Cells / Q000166:cytology; D020287:In Situ Nick-End Labeling; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000494:pharmacology; D019014:fas Receptor / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008077:Lipoproteins, LDL; D008562:Membrane Glycoproteins; D009842:Oligopeptides; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases