Apolipoprotein C-I induces apoptosis in human aortic smooth muscle cells via recruiting neutral sphingomyelinase.
OBJECTIVE
Apolipoprotein C-I (apoC-I) influences lipoprotein metabolism, but little is known about its cellular effects in aortic smooth muscle cells (ASMC).


RESULTS
In cultured human ASMC, apoC-I and immunoaffinity purified apoC-I-enriched high-density lipoproteins (HDL) markedly induced apoptosis (5- to 25-fold), compared with control cells, apoC-I-poor HDL, and apolipoprotein C-III (apoC-III) as determined by 4', 6-diamidino-2-phenylindole dihydrochloride staining and DNA ladder assay. Preincubation of cells with GW4869, an inhibitor of neutral sphingomyelinase (N-SMase), blocked apoC-I-induced apoptosis, an effect that was bypassed by C-2 ceramide. The activity of N-SMase was increased 2- to 3-fold in ASMC by apoC-I, apoC-I-enriched HDL, and tumor necrosis factor alpha (TNF-alpha) (positive control) after 10 minutes and then decreased over 60 minutes, which is a kinetic pattern not seen with controls, apoC-III, and apoC-I-poor HDL. ApoC-I and apoC-I-enriched HDL stimulated the generation of ceramide, the release of cytochrome c from mitochondria, and activation of caspase-3 greater than that found in controls, apoC-III, and apoC-I-poor HDL. GW4869 inhibited apoC-I-induced production of ceramide and cytochrome c release.


CONCLUSIONS
ApoC-I and apoC-I-enriched HDL activate the N-SMase-ceramide signaling pathway, leading to apoptosis in human ASMC, which is an effect that may promote plaque rupture in vivo.
Kolmakova
Antonina
A
Lipid Research Atherosclerosis Division, Johns Hopkins University, Baltimore, MD, USA.
Kwiterovich
Peter
P
Virgil
Donna
D
Alaupovic
Petar
P
Knight-Gibson
Carolyn
C
Martin
Sergio F
SF
Chatterjee
Subroto
S
D000814:Aniline Compounds / Q000494:pharmacology; D001011:Aorta / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D053302:Apolipoprotein C-I; D001056:Apolipoproteins C / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001597:Benzylidene Compounds / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002518:Ceramides / Q000096:biosynthesis; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*
D000814:Aniline Compounds; D053302:Apolipoprotein C-I; D001056:Apolipoproteins C; D001597:Benzylidene Compounds; D002518:Ceramides; D004791:Enzyme Inhibitors; C468773:GW 4869; D008075:Lipoproteins, HDL; D045304:Cytochromes c; C491484:SMPD3 protein, human; D013108:Sphingomyelin Phosphodiesterase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases