oxLDL通过TLR4诱导脂质累积和炎症反应促进动脉粥样硬化的分子机制

Molecular mechanism of oxLDL inducing lipid accumulation and inflammation in macrophages to promot atherosclerosis via TLR4 signaling pathway

目的·探究TLR4诱导脂质累积和炎症反应从而调控动脉粥样硬化的分子机制。方法·采用TLR4特异性siRNA敲除巨噬细胞,通过油红O染色法比较对照组和实验组中细胞内脂质含量;通过Western blotting检测CD36和血凝素样氧化低密度脂蛋白受体1(LOX-1)表达;通过ELISA检测白介素-6(IL-6)、IL-8、单核细胞趋化蛋白-1(MCP-1)和基质金属蛋白酶-9(MMP-9)等炎症因子的表达。结果·动脉粥样硬化斑块中巨噬细胞(CD68^+)大量聚集,且TLR4表达明显上调。ox LDL刺激巨噬细胞,可促进细胞中脂质累积(P<0.01)并导致ox LDL相关受体CD36和LOX-1的表达上调以及炎症因子表达(P<0.01)。特异性si RNA敲除TLR4可抑制ox LDL诱导的巨噬细胞内脂质累积(P<0.01)和炎症因子分泌(P<0.01),并影响ox LDL诱导的CD36表达,但对LOX-1表达没有影响。结论·ox LDL/TLR4可能通过上调CD36介导巨噬细胞中脂质累积和炎症反应,从而促进动脉粥样硬化发生和发展。

Objective·To investigate the possible role of TLR4signaling pathway in the mediation of atherosclerosis.Methods·TLR4were knocked down via transfection with TLR4-specific siRNA,and the lipid accumulation was further detected in control and TLR4-knockdown groups by oil red O staining.The expression of CD36and Lectin-like oxLDL receptor1(LOX-1)in macrophages were detected by Western blotting to investigate the role of TLR4in the expression of oxLDL-related receptors.Cytokines such as interleukin-6(IL-6),IL-8,monocyte chemoattractant protein1(MCP-1),and matrix metalloproteinase-9(MMP-9)were tested by ELISA to confirm the possible role of TLR4in the secretion of inflammatory factors.Results·Macrophages(namely CD68+cells)were found to accumulate within atherosclerosis plaques with TLR4highly expressed on the surface of macrophages;the stimulation with oxLDL promoted the lipid accumulation(P<0.01),the secretion of inflammatory factors(P<0.01),and the expression of CD36and LOX-1.The oxLDL-associated expression of CD36was decreased but the expression of LOX-1was not affected.The knockdown of TLR4inhibits oxLDL-induced lipid accumulation(P<0.01)and inflammatory cytokines(IL-6,IL-8,MCP-1and MMP-9)secretion(P<0.01).Conclusion·TLR4signaling pathway possibly promotes the lipid accumulation and the secretion of inflammatory factors via up-regulating the expression of CD36to affect the formation and development of atherosclerosis.