PM2.5 Induces Epithelial-to-Mesenchymal Transition by Oxidative Stress in Normal Rat Kidney Tubular Epithelial Cells

Background: The incidence and prevalence of chronic kidney disease (CKD) are increasing worldwide. Recently, the exposure to air pollution, especially particulate matter2.5 (PM2.5) was newly identified to be a potential risk factor for CKD, however there are no studies on whether exposure to PM2.5 is a direct cause of CKD occurrence and exacerbation. Epithelial-to-mesenchymal transition (EMT) of tubular cells is one of the early mechanisms of progression of renal disease. Therefore, the identification of association between fine dust and EMT may allow to reveal the casualty toward CKD. Methods: Fine dust collected by PM2.5 filter (Ulaanbaatar, Mongolia) was dissolved in DMSO by sonication. Normal rat kidney (NRK) tubular epithelial cells were treated with dissolved PM2.5 (2 & 5 μL/mL). EMT was evaluated by morphological changes of NRK cells and the expressions of E-cadherin, α-SMA, and vimentin after the stimulation with PM2.5 and TGF-β (5 ng/mL) by WB and immunostaining. ROS generation was assessed by DCF-DA and MitoSox staining. RNA-seq analysis (Ebiogen, Korea) was performed to investigate which upregulated/downregulated-genes are associated with PM2.5-induced phenotype transition in NRK cells. Results: PM2.5 at the concentrations of 2 and 5 μL/mL did not alter LDH release and cell proliferation up to 48 hours of exposure. PM2.5 induced EMT of NRK cells assessed by morphologic changes associated with a decreased E-cadherin expression and de-novo expression of α-SMA and vimentin. PM2.5 also increased DCF-DA and Mito-Sox staining. RNA-seq analysis demonstrated the differences in gene expression related to EMT (16.7%), adipokine (15.9%), apoptotic process (13.7%), and oxidative stress (12.8%). Among them, lipocalin 2 (LCN2), Interleukin-11 (IL-11), and hyaluronan synthase 2 (HAS2) expression showed the highest fold difference (2.7-folds, 2.5-folds, and 2.0-folds, respectively) between control and PM2.5-treated NRK cells. Conclusion: This data suggest that exposure to PM2.5 induces EMT and oxidative stress in NRK cells, which may be one of the possible mechanisms for the association between fine dust exposure and the development of renal disease. Funding: Government Support – Non-U.S.