| Objective Hyperhomocysteinemia is considered to be an important risk factor and playsan important role in atherosclerosis. Atherosclerosis has been established as a complexinflammatory disease characterized by the accumulation of lipids, fibrous materials and celldebris in the arteries. A most significant and best-characterized chemokine is monocytechemoattractant protein-1（MCP-1/CCL2）, which is increased in atherosclerotic lesion but notin normal arteries, suggesting its potential value in stimulating the migration of monocytesinto the intima of the arterial wall and taking part in most processes during atherosclerosis.Aberrant DNA methylation is associated with advanced stages of disease such asatherosclerosis and may represent signs of predisposition. The present study was to explorethe pathogenesis that blood MCP-1DNA hypomethylation might promote formation ofatherosclerosis under hyperhomocysteinemia as well as the effect of NF-κB/DNMT1in thepathogenesis.Methods The atherosclerotic effect of MCP-1in apolipoprotein E-deficient (ApoE-/-)and wild-type C57BL/6J mice was evaluated using atherosclerotic lesion area, serum NF-κB,MCP-1and DNMT1levels and MCP-1DNA methylation expression. Serum Hcyconcentrations were measured by automatic biochemistry analyzer. Serum SAM and SAHconcentrations were measured by high-performance liquid chromatography （HPLC）. In vitro,THP-1monocytes were cultured in25cm2flasks with4×106, when were observed undermicroscope, the cells were adherent, irregular in shape and had extended pseudopodia, whichconfirmed that THP-1cells were differentiated into macrophages. The mechanism responsible for the effect of NF-κB/DNMT1on foam cells was investigated whether NF-κB/DNMT1hadan effect on gene expression by measuring NF-κB and DNMT1levels.Results1. Analysis of Aortic Pathological Section with HE Staining and Levels of SerumHcy, SAM, SAH in MiceWe found that atherosclerotic lesion areas of ApoE-/-control group, HM group andHM+FA+VB group were increased respectively than those of blank control group. Insummary, atherosclerosis model of mice was established successfully.After15weeks, serum Hcy concentrations were confirmed in mice fed with differentdiets. Serum Hcy concentrations were elevated about38.9%,2.5-fold,96.0%in ApoE-/-control, HM and HM+FA+VB groups and a remarkable increase was observed in HM groupcompared with blank control group （P<0.01）. Taken together, our data suggested that Hcymight induce the formation of atherosclerosis in ApoE-/-mice and folate and vitamin B12could reduce the effect of Hcy-induced atherosclerosis.After15-week experimental diets, serum SAM concentrations were increasedrespectively to3,3.6,2.45-fold in ApoE-/-control, HM and HM+FA+VB groups comparedwith the blank control group, and serum SAH concentrations of HM group were obviouslyincreased in comparison with blank control group.2. Analysis of MCP-1DNA Methylation and Serum MCP-1Concentrations in MiceOur data suggested that in HM group the change of MCP-1DNA hypomethylation wasthe most obvious and that its levels were higher about6.2%than those in blank control group（P<0.05）. In HM+FA+VB group, antagonistic effects could been observed on thehypomethylation change. As a result, serum MCP-1levels were the highest in HM group（P<0.05）. The atherosclerotic lesion in HM group was the most severe and widespread,MCP-1DNA hypomethylation and atherosclerosis area were positive correlation （γ=0.5175,P<0.05）. 3. Serum NF-κB and DNMT1Levels by ELISA Analysis in Mice and Foam CellsIn this study serum NF-κB levels were the highest in HM group （P<0.05）, and serumNF-κB levels were lower by2.9-fold in HM+FA+VB group than those in HM group （P<0.01）.To compare with blank group serum DNMT1concentrations were decreased by20.8%in HMgroup （P<0.01） and slightly higher in HM+FA+VB group than those in HM group （P<0.05）.Serum NF-κB and DNMT1concentrations were negative correlation （γ=0.3394, P<0.05）.Our results might confirm that NF-κB concentrations were decreased by PDTCintervention （P<0.01, Fig.7A） and DNMT1levels were increased in foam cell+100μmol/LHcy+50μmol/L PDTC group to cmpare with100μmol/L Hcy group （P<0.05, Fig.7B）. Takentogether, these findings showed that NF-κB might suppress the activity of DNMT1andinvolve MCP-1DNA hypomethylation.ConclusionsTherefore accumulating evidence suggests MCP-1DNA hypomethylation may promotethe formation of atherosclerotic plaque under hyperhomocysteinemia through NF-κB/DNMT1.This fact may be significant for therapy of atherosclerosis that is associated with geneexpression due to hypomethylation of gene’s regulatory regions. The induction of MCP-1DNA hypomethylation by hyperhomocysteinemia is a new element of their mechanisms. Inall, our findings reveal a novel role of Hcy in the pathogenesis of atherosclerosis. |
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