Background

Evidence shows that individuals who are under long-term exposure to environmental PM_2.5 are at increased risk of chronic kidney disease. Various laboratory experiments also suggest several mechanistic links between PM_2.5 exposure and kidney injury. Polycyclic aromatic hydrocarbons (PAHs) are common organic chemicals existing in PM_2.5. However, whether benzo [b]fluoranthene (BbF), the most potent carcinogens and the highest content of PAHs, plays an important role in podocyte injury via reducing autophagy, have not been reported.

Methods

Podocytes were exposed to different concentrations and times of BbF. Cell viability was assessed by using CCK-8. Morphological phenotypes were detected by using optical microscopy. Cytoskeletons were detected by using immunofluorescence assay. Expression of podocyte injury markers were determined by Western blot. Podocytes were observed under TEM, autophagic activity was evaluated by Western blot analysis and immunofluorescence assay. A possible effect of an inhibitor (CQ, chloroquine) or an inducer (rapamycin) of autophagy on BbF-induced podocyte injury also was examined.

Results

BbF changed cellular morphology, decreased cell viability and rearranged cytoskeleton. The proteins' expression level of autophagy and the numbers of autophagosomes under TEM was decreased and the proteins’ expression level of slit diaphragm was increased in a dose- and time-dependent manner. In addition, BbF-induced podocyte injury was enhanced by inhibition of autophagy and inhibited by activation of autophagy in podocytes.

Conclusions

Taken together, our data suggest that BbF is toxic to podocytes, as well as reduce autophagy. Furthermore, inhibition of autophagy plays a regulatory role in BbF-induced podocyte injury.

中文翻译：

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大气细颗粒物中的苯并[b]荧蒽通过抑制自噬而引起小鼠肾小球足细胞损伤。

背景

有证据表明，长期暴露于环境PM _2.5中的个体患慢性肾脏疾病的风险增加。各种实验室实验还表明PM _2.5暴露与肾脏损伤之间存在多种机理联系。多环芳烃（PAHs）是PM _2.5中存在的常见有机化学物质。然而，尚未报道最有效的致癌物和最高的PAHs苯并[b]荧蒽（BbF）是否在通过减少自噬而导致足细胞损伤中发挥重要作用。

方法

足细胞暴露于不同浓度和时间的BbF。通过使用CCK-8评估细胞活力。使用光学显微镜检测形态表型。通过使用免疫荧光测定法检测细胞骨架。通过Western印迹确定足细胞损伤标志物的表达。在TEM下观察足细胞，通过Western印迹分析和免疫荧光分析评价自噬活性。还检查了自噬抑制剂（CQ，氯喹）或自噬诱导剂（雷帕霉素）对BbF诱导的足细胞损伤的可能作用。

结果

BbF改变了细胞形态，降低了细胞活力并重新排列了细胞骨架。透射电镜下蛋白质的自噬表达水平和自噬小体数目减少，缝膜的蛋白质表达水平呈剂量和时间依赖性。此外，BbF诱导的足细胞损伤可通过抑制自噬而增强，并被足细胞中的自噬激活所抑制。

结论

两者合计，我们的数据表明BbF对足细胞有毒性，并减少自噬。此外，自噬的抑制在BbF诱导的足细胞损伤中起调节作用。