不同城市PM_(2.5)致小鼠肝脏纤维化的效应差异研究

Differential Effects of PM_(2.5) from different cities in the induction of hepaticfibrosis in mice

为阐明PM_(2.5)诱发肝脏纤维化的潜在机制以及导致这种不良效应的主要组分,本研究以采自我国太原、北京、杭州和广州市的PM_(2.5)暴露10月龄C57BL/6雌性小鼠4周后,利用组织切片染色,荧光定量PCR(qRT-PCR)以及Western blot技术检测小鼠肝脏纤维化的发生,并采用皮尔森相关系数法分析不同城市PM_(2.5)暴露组小鼠肝脏纤维化相关基因表达水平与各城市典型化学组分的线性相关关系.结果发现,与对照组相比,太原组和杭州组小鼠肝脏脏器系数显著降低;太原组小鼠肝脏胶原沉积面积显著增加,肝脏纤维化相关基因(Col1a1、Col3a1、TGF-β和MMP2)的转录水平显著升高,并且也仅有太原组PM_(2.5)暴露诱导了小鼠肝脏Col1a1蛋白的显著增高,而其他城市PM_(2.5)暴露组并未见上述纤维化相关因子的显著变化.相关性分析结果显示,Cr、Mn、Mo、Cs、Pb、Bi、U和Fe等金属组分与Col1a1和Col3a1的mRNA表达呈显著正相关,除NA、AC及BaP外其余15种多环芳烃均与Col1a1表达显著相关,18种PAHs之和与Col3a1表达显著相关.上述结果表明,PM_(2.5)暴露可导致小鼠肝脏纤维化的发生,其中太原市PM_(2.5)诱导肝脏纤维化发生最为显著,TGF-β及其通路中相关信号分子在介导PM_(2.5)诱发肝脏纤维化发生中发挥了重要作用,Cr、Mn、Mo、Cs、Pb、Bi、U、Fe及PAHs很可能是细颗粒物暴露导致小鼠肝脏纤维化的关键毒性组分.

To clarify the potential mechanism by which PM_(2.5)exposure causes liver fibrosis and the key components leading to this adverse effect,10-month-old C57BL/6 female mice were exposed to PM_(2.5)from different cities of China(Taiyuan,Beijing,Hangzhou and Guangzhou)for 4weeks.And tissue section staining,qRT-PCR and Western-blot technique were used to evaluate the features of liver fibrosis in mice.Pearson correlation coefficient was used to analyse the correlation between the expression level of liver fibrosis-related genes in mice and the typical chemical composition of PM_(2.5)from different cities.The results showed that a significant decrease in the organ coefficient of liver was found in Taiyuan and Hangzhou PM_(2.5)-exposed group.Taiyuan PM_(2.5)exposure significantly increased the area of collagen deposition and the relative expression level of fibrosis related genes(Col1a1,Col3a1,TGF-βand MMP2)in the mice liver,and only PM_(2.5)from Taiyuan induced the significant increase of Col1a1 protein in mice liver,while PM_(2.5)from other cities except Taiyuan exposure did not cause any of the above changes in fibrosis related factors.In addition,the results of correlation analysis showed that the metal components such as Cr,Mn,Mo,Cs,Pb,Bi,U and Fe were positively correlated with the mRNA expression of Col1a1 and Col3a1.Except for NA,AC and BaP,the other 15PAHs were significantly correlated with Col1a1 mRNA expression,and the sum of 18EPA PAHs was significantly correlated with Col3a1.The above results indicated that PM_(2.5)exposure induced hepatic fibrosis in mice,especially PM_(2.5)from Taiyuan.TGF-βand related signal molecules in its pathway has beenshownto play a vital role in mediating liver fibrosis induced by PM_(2.5).Cr,Mn,Mo,Cs,Pb,Bi,U,Fe and PAHs of PM_(2.5)were probably critical components to induce liver fibrosis.