CD4^＋CD25^＋调节性T细胞对巨噬细胞泡沫化的影响

CD4^＋CD25^＋ regulatory T cells inhibit macrophage-derived foam ceils formation by down-regulating scavenger receptor expression

目的研究CD4^＋CD25^＋调节性T细胞（Tr）对巨噬细胞泡沫化过程的影响及机制。方法磁性细胞分离器（MACS）分离CD4^＋CD25^＋T细胞及CD4^＋CD25^-T细胞，在氧化型低密度脂蛋白（oxLDL）作用下，将巨噬细胞分别与CD4^＋CD25^＋T细胞、CD4^＋CD25^-T细胞共培养48h。采用油红O染色和细胞内脂质测定的方法观察CD4^＋CD25^＋T细胞对巨噬细胞泡沫化的影响；采用RT—PCR、real-timePCR、Western blot的方法测定泡沫细胞清道夫受体（CD36和SRA）的表达。结果与对照组比较，CD4^＋CD25^＋T细胞可显著抑制巨噬细胞脂质聚集及清道夫受体的表达。结论CD4^＋CD25^＋T细胞可显著抑制巨噬细胞泡沫化，其作用机制可能为下调清道夫受体的表达。

Objective To investigate whether and how regulatory T cells（Tr） affect macrophages foam-cell formation, and thereby investigate the mechanism of Tr in the development of atherosclerosis. Methods Tr were isolated from lymphocyte suspensions by magnetic cell sorting-column and analyzed by flow cytometry. Macrophages were cultured alone, with CD4^＋CD25^＋ T, or CD4^＋CD25^ - T ceils in the pres- ence of oxLDL for 48 h to transform macrophages into foam cells. Oil red O staining and cellular lipid measurement were used to identify macrophage foam cell formation. Semi-quantitative PCR, quantitative real-time PCR and Western blot analysis were carried out to explore the mechanism of Tr-mediated suppression on macrophages foam cell formation. Results Foam cell formation, as identified by oil red O staining, was readily apparent in cells treated with CD4^＋CD25^- T cells and without T cells. After treatment with Tr, a marked decrease（ 13.9% ± 5.6% ） in foam cell count was observed, compared with untreated cells（ 13.9% ±5.6% vs 52.9% ±10.4%, P〈0.001） or CD4^＋ CD25^- T-treated cells（13.9% ±5.6% vs 53.1% ±17.2%, P〈0.001）, 52.9% ±10.4% and 53. 1% ±17.2%, respectively （P〈0.001）. The similar effect of Tr was obtained when extracted oil red O and measured by a spectrophotometer. Cholesteryl ester accumulation also used to quantify foam cell formation. Compared with untreated （ no T） and CD4^＋CD25^- Tr- treated macrophage cells （ CD25 ^- ） , the lipids accumulation in CD4^＋CD25^＋ Tr-treated macrophage foam cells （ CD25^ ＋ ） was significantly reduced. Total cellular cholesterol and cellular cholesteryl ester was siginificantly reduced in CD25 ^＋ cultures relative to no T [ TC （ total cholesterol） ： 57.46 ±17.92 vs 159.48 ±16.38, P 〈0.01 ; CE（ esterified cholesterol） ： 26.68 ±8.88 vs 102.54 ±16.67, P 〈 0. 001 ] or CD25 - （TC ： 58.50 ±7.00 vs 150.55 ±25.11, P 〈 0.01 ; CE ： 26.68 ±8.88 vs 96.90 ±11.95, P 〈 0. 001 ） cultures. Moreover, PCR and Western blot analysis showed that the expression of both CD36 and SRA in Trtreated macrophage foam cells was significantly down-regulated. Conclusion Results collectively suggest that CD4^＋CD25^＋ Tr cells may inhibit macrophage foam-cell formation, which is largely attributed to a downregulated expression in scavenger receptor in Tr-treated macrophage foam cells.