Reduced beta2-glycoprotein I protects macrophages from ox-LDL-induced foam cell formation and cell apoptosis.
BACKGROUND
Reduced beta2-glycoprotein I (beta2-GPI) is a free thiol-containing form of beta2-GPI that displays a powerful effect in protecting endothelial cells from oxidative stress-induced cell death. The present study aims to investigate the effect of beta2-GPI or reduced beta2-GPI on ox-LDL-induced foam cell formation and on cell apoptosis and to determine the possible mechanisms.


METHODS
The RAW264.7 macrophage cell line was selected as the experimental material. Oil red O staining and cholesterol measurement were used to detect cholesterol accumulation qualitatively and quantitatively, respectively. Flow cytometry was used to detect cell apoptosis. Real-time quantitative PCR was used to detect the mRNA expression of the main proteins that are associated with the transport of cholesterol, such as CD36, SRB1, ABCA1 and ABCG1. Western blot analysis was used to detect the protein expression of certain apoptosis-related proteins, such as caspase-9, caspase-3, p38 MAPK/p-p38 MAPK and JNK/p-JNK.


RESULTS
Beta2-GPI or reduced beta2-GPI decreased ox-LDL-induced cholesterol accumulation (96.45 ± 8.51 μg/mg protein vs. 114.35 ± 10.38 μg/mg protein, p < 0.05;74.44 ± 5.27 μg/mg protein vs. 114.35 ± 10.38 μg/mg protein, p < 0.01) and cell apoptosis (30.00 ± 5.10% vs. 38.70 ± 7.76%, p < 0.05; 20.66 ± 2.50% vs. 38.70 ± 7.76%, p < 0.01), and there are significant differences between beta2-GPI and reduced beta2-GPI (p < 0.05). Reduced beta2-GPI decreased the ox-LDL-induced expression of CD36 mRNA and ABCA1 mRNA (p < 0.05), as well as CD36, cleaved caspase-9, cleaved caspase-3, p-p38 MAPK and p-JNK proteins (p < 0.05 or p < 0.01). Beta2-GPI did not significantly decrease the expression of ABCA1 mRNA and the p-p38 MAPK protein.


CONCLUSIONS
Both beta2-GPI and reduced beta2-GPI inhibit ox-LDL-induced foam cell formation and cell apoptosis, and the latter exhibits a stronger inhibition effect. Both of these glycoproteins reduce the lipid intake of macrophages by downregulating CD36 as well as protein expression. Reduced beta2-GPI inhibits cell apoptosis by reducing the ox-LDL-induced phosphorylation of p38 MAPK and JNK, and the amount of cleaved caspase-3 and caspase-9. Beta2-GPI does not inhibit the ox-LDL-induced phosphorylation of p38 MAPK.
Wei-Lin
WL
Wang
Zhen-Xing
ZX
Meng
Sai-Jun
SJ
Zhou
Chun-Jun
CJ
Li
Rui
R
Chen
Lin
L
Lv
Ze-Jun
ZJ
Ma
2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, the Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, 300070, Tianjin, China. yudemintij@126.com.
De-Min
DM
Yu
Pei
P
Yu
D064286:ATP Binding Cassette Transporter 1 / Q000235:genetics / Q000378:metabolism; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D018955:CD36 Antigens / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D005487:Foam Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D010084:Oxidation-Reduction; D010766:Phosphorylation / Q000187:drug effects; D051122:Scavenger Receptors, Class B / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D053482:beta 2-Glycoprotein I / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D018955:CD36 Antigens; D020169:Caspases; D002784:Cholesterol; D008074:Lipoproteins; D008077:Lipoproteins, LDL; D048670:MAP Kinase Kinase 4; D051122:Scavenger Receptors, Class B; D053482:beta 2-Glycoprotein I; D048051:p38 Mitogen-Activated Protein Kinases; C577833:Abca1 protein, mouse; C487540:ABCG1 protein, mouse; C454739:Scarb1 protein, mouse; C099252:oxidized low density lipoprotein