ABSTRACT
Homocysteine (Hcy) is an important and independent risk factor for arteriosclerosis, and apolipoprotein E (ApoE) is an important gene of anti atherosclerosis, but the characteristics and their key links that are involved in their pathogenic mechanisms are still poorly understood. The objective of the present study was to investigate the effects of Hcy and folate on ApoE as well as the underlying mechanism of ApoE expression induced by Hcy in monocytes. When clinically relevant concentrations of Hcy and folate were added to the cultured monocytes for 4 days, we found that clinically relevant Hcy (100 microM) may increase the levels of total cholesterol (TC), free cholesterol (FC), and cholesteryl ester (CE), and also decrease ApoE mRNA, protein expressions, leading to 34.28%, 45.00% in cultured primary human monocytes in comparison to the positive group. The effects of Hcy were primarily mediated by C-5 MTase, because Hcy could upregulate the activity of C-5 MTase and then accelerate DNA methylation of ApoE. However, folate decreased the levels of TC, FC, and CE (p < 0.001) and increased the ApoE expression; as to say, folate primarily repressed the effects of DNA methylation induced by Hcy and reduced anti atherosclerosis. In conclusion, these results suggested that ApoE DNA methylation that is induced by Hcy may play a potential role for ApoE expression in atherosclerosis. Folate has beneficial effects for anti atherosclerosis, and it may become a therapeutic target for preventing Hcy-induced atherosclerosis.
Subject(s)
Apolipoproteins E/metabolism , DNA Methylation/drug effects , Folic Acid/metabolism , Homocysteine/pharmacology , Monocytes/metabolism , Apolipoproteins E/genetics , Cells, Cultured , Cholesterol/metabolism , DNA (Cytosine-5-)-Methyltransferases/metabolism , Foam Cells/cytology , Folic Acid/genetics , Homocysteine/metabolism , Humans , Lipid Metabolism , Monocytes/cytology , Promoter Regions, GeneticABSTRACT
<p><b>OBJECTIVE</b>To study the effect of peroxisome proliferators activated receptors (PPAR) alpha, gamma ligand on ATP-binding cassette transporter A1 (ABCA1) and caveolin-1 expressions and cholesterol, ox-LDL contents in human monocyte derived foam cells.</p><p><b>METHOD</b>Malondialdehyde (MDA) was measured by TBARS method, ox-LDL detected by ELISA method, cholesterol measured by fluorescence spectrophotometric method, ABCA1, caveolin-1 mRNA and protein expressions determined by RT-PCR and Western blot, in human monocytes, foam cells [human monocyte-derived macrophage induced by myristate acetate (PMA) further treated with 50 mg/L ox-LDL for 24 h], foam cells plus 10 micromol/L pioglitazone for 48 h, foam cells plus 5 micromol/L clofibrate for 48 h.</p><p><b>RESULT</b>The intracellular total cholesterol (TC), free cholesterol (FC), cholesteryl ester (CE), ox-LDL and lipid peroxide were significantly increased and the membrane expressions of ABCA1, caveolin-1 were down-regulated in foam cells compared to monocytes (all P < 0.05) and these changes were significantly attenuated by cotreatment with PPARalpha, gamma ligand.</p><p><b>CONCLUSION</b>The anti-atherosclerosis effects of PPARalpha, gamma ligand are related to reducing cholesterol contents and up-regulating ABCA1, caveolin-1 expressions in foam cells.</p>
