Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan.
Eur J Pharmacol. 2011 Jan 15;650(2-3):519-25. doi: 10.1016/j.ejphar.2010.10.051. Epub 2010 Oct 31.
Human serum paraoxonase 1 (PON1), an arylesterase, is associated with high-density lipoprotein (HDL) and can inhibit the oxidative modification of low-density lipoprotein (LDL), implying that PON1 may prevent atherosclerosis. Berberine, a botanical alkaloid, lowers the cholesterol level in serum and is thought to display cardioprotective properties. However, the effect of berberine on PON1 gene expression remains unclear. Thus, we evaluated how berberine regulates PON1 gene expression. In human hepatoma HepG2 and Huh7 cells, the PON1 protein levels were increased by berberine in a dose- and time-dependent manner. Data from real time PCR analysis indicated that berberine could up-regulate PON1 expression at the transcriptional level. Additionally, treating HepG2 cells with berberine increased the levels of phosphorylated JNK and its downstream target c-Jun. The PON1 upstream region contained a consensus binding site for AP1, and the electrophoretic mobility shift assay and chromatin immunoprecipitation analysis indicated that the AP1 factors, especially c-Jun, bind to the upstream sequence of the PON1 promoter upon berberine treatment. Moreover, pretreatment with SP600125 (JNK inhibitor) or curcumin (AP-1 inhibitor) markedly attenuated the berberine-induced PON1 promoter activity and protein expression. This is the first study to suggest that JNK/c-Jun signalling pathway plays a crucial role in berberine-regulated PON1 transcription in human hepatoma cells. The induction of PON1 by berberine elucidates a potential mechanism through which berberine may protect against atherosclerosis.
人血清对氧磷酶 1（PON1），一种芳酯酶，与高密度脂蛋白（HDL）相关，可以抑制低密度脂蛋白（LDL）的氧化修饰，这意味着 PON1 可能预防动脉粥样硬化。小檗碱，一种植物生物碱，可以降低血清中的胆固醇水平，被认为具有心脏保护作用。然而，小檗碱对 PON1 基因表达的影响尚不清楚。因此，我们评估了小檗碱如何调节 PON1 基因表达。在人肝癌 HepG2 和 Huh7 细胞中，小檗碱以剂量和时间依赖的方式增加 PON1 蛋白水平。实时 PCR 分析数据表明，小檗碱可以在转录水平上上调 PON1 表达。此外，用小檗碱处理 HepG2 细胞增加了磷酸化 JNK 及其下游靶标 c-Jun 的水平。PON1 上游区域包含一个 AP1 结合位点的共识序列，电泳迁移率变动分析和染色质免疫沉淀分析表明，AP1 因子，特别是 c-Jun，在小檗碱处理时结合到 PON1 启动子的上游序列。此外，用 SP600125（JNK 抑制剂）或姜黄素（AP-1 抑制剂）预处理可显著减弱小檗碱诱导的 PON1 启动子活性和蛋白表达。这是第一项研究表明 JNK/c-Jun 信号通路在人肝癌细胞中小檗碱调节 PON1 转录中起关键作用。小檗碱诱导 PON1 阐明了小檗碱可能预防动脉粥样硬化的潜在机制。
