Function and its significance of Rac1 in aristolochic acid-induced renal tubular epithelial cellular injury

Objective: To investigate the molecular mechanisms of aristolochic acid(AA)-induced renal tubular epithelial cellullar(NRK-52E) injury, and to evaluate the possible role of small G protein Rac1 in this process. Methods: The proliferation inhibition rate was measured by WST-1 assay in NRK-52E cells treated with AA for 24 h. Hoechst 33258 staining was used to determine cell apoptosis. Cell immunofluorescent assay was applied to detect the levels of Rac1 and type III collagen. TGF-β1 mRNA was detected by real-time RT-PCR. ELISA assay was used to test the levels of Rac1 and TGF-β1, and the correlation between them was analyzed. Results: AA significantly inhibited the proliferation of NRK-52E cells, and induced cell apoptosis. The expres- sion of TGF-β1 mRNA was markedly increased in NRK-52E cells with the treatment of AA(10 μg/mL). Also, the expression of type III collagen was significantly increased in AA-treated cells. In addition, enhanced expression of Rac1 protein, an important molecular of GTPase Rho, induced by AA was observed. Moreover, there was positive correlation between Rac1 and TGF-β1 in AA-induced collagen deposition(r=0.967, P0.01). Conclusion: AA can significantly inhibit the proliferation and induce the apoptosis of NRK-52E cells. In this process, Rac1 and Rac1-related signaling pathways may be activated and followed by high expression of TGF-β1, and then promote collagen deposition in renal tubular epithelial cells after AA injury.