Preventive effect of icariin on transition from acute kidney injury to chronic kidney disease in mouse model.

Objective * To investigate the effect of icariin on the transition from acute kidney disease (AKI) to chronic kidney disease (CKD) in mice and the possible mechanism. Methods * C57BL/6 mice were intraperitoneally injected with aristolochic acid for 2 weeks to mimic AKI to CKD transition. Icariin was intragastrically administered for 2 or 5 weeks at the end of 2 weeks of aristolochic acid injection or 1 week before modeling. The renal function and pathological injury of the mice were monitored. The mitochondrial structure of renal tubular epithelial cells was observed by transmission electron microscopy. The indexes related to fatty acid oxidative metabolic pathway, fibrosis, and inflammation were detected by quantitative PCR (qPCR) and immunohistochemical staining. The rat renal fibroblast cell line and the rat renal tubular epithelial cell lines were co-cultured in Transwell cell chambers to simulate the interaction between the two types of cells. The renal tubular epithelial cells were pretreated with icariin for 1 h, and then treated with aristolochic acid for 24 h. After removing the two drugs, the renal tubular epithelial cells and the fibroblasts were co-cultured for 24 h. The mRNA or protein expression levels of peroxisome proliferator-activated receptor a (Ppara), pro-fibrotic factors, inflammatory factors, activated caspase-3 (cleaved caspase-3), and extracellular matrix-associated genes in renal fibroblasts were detected by qPCR or Western blotting. The renal tubular epithelial cells were transfected with Ppara-siRNA to observe the expression changes of cleaved caspase-3 and the related indicators of mitochondrial fatty acid oxidative metabolism in the downstream of PPARa after icariin intervention prior to aristolochic acid. Results * Compared with the control group, the serum creatinine and urea nitrogen levels of the mice injected with aristolochic acid only were significantly higher, with a large number of inflammatory cells infiltrating into the kidney and serious renal tubular injury at the end of 2 weeks of aristolochic acid injection and 2 weeks after the last injection (4 weeks). The renal function was significantly improved, and the pathological damage was attenuated in the mice pretreated with icariin. After 4 weeks of modeling, the mitochondrial structure of renal tubular epithelial cells was seriously damaged in the aristolochic acid group, and the mRNA levels of fatty acid oxidative metabolic pathway- related genes were significantly downregulated, compared to the control group, accompanied by macrophage infiltration and renal fibrosis. Icariin pretreatment attenuated these damages generated by aristolochic acid. The serum creatinine and urea nitrogen levels, renal pathological injury, and fibrotic markers of the mice treated with icariin at the end of 2 weeks of aristolochic acid injection showed no difference from the aristolochic acid group. In the in vitro experiments, aristolochic acid treatment suppressed Ppara mRNA expression and elevated cleaved caspase-3, inflammatory factors, and pro-fibrotic factors in renal tubular epithelial cells. It also upregulated the expression of extracellular matrix-related genes in co-cultured renal fibroblasts. In contrast, icariin pretreatment abrogated the changes caused by aristolochic acid. The knockdown of Ppara by siRNA in renal tubular epithelial cells removed the preventive effects of icariin on aristolochic acid inhibiting fatty acid oxidative metabolism and promoting cell apoptosis. Conclusion Icariin prevents AKI to CKD transition induced by aristolochic acid in mice. It may play its protective role by improving the mitochondrial fatty acid oxidative metabolic pathway, especially through PPARa, in renal tubular epithelial cells. [ABSTRACT FROM AUTHOR]