The benzo[b] fluoranthene in the atmospheric fine particulate matter induces mouse glomerular podocytes injury via inhibition of autophagy

Background: Evidence shows that individuals who are under long-term exposure to environmental PM2.5 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 PM2.5. 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.