Objective: To investigate the cellular mechanism of renal proximal tubular epithelial cell(PTEC) injury induced by aristolochic acid I (AA-I) and aristololactam I (AL-I).
Methods: Human PTEC cell line HK-2 was used as the subject. Cell apoptosis was evaluated by using FACS. Fibronectin (FN) and TGF-beta1 levels were assayed in the supernatant from cultured HK-2 cells by ELISA. In the blocking study, anti-TGF-beta1 neutralizing antibody was used as an antagonist. The changes of FN level and apoptosis were compared.
Results: After stimulation by 2.5 mg/L AA-I, HK-2 cells secreted TGF-beta1 at hour 12 and FN at hour 36. HK-2 cell apoptosis was detected at hour 48. Anti-TGF-beta1 neutralizing antibody (5 mg/L) could suppress AA-I induced apoptosis by 63.7%(P<0.001), and it blocked AA-I induced FN secretion by 50.2%(P<0.001). In contrast, Anti-TGF-beta1 neutralizing antibody had no effect on AL-I-induced apoptosis and FN secretion, even though AL-I (5 mg/L) had similar effect on these events compared to AA-I.
Conclusion: The effects of AA-I on stimulating cell apoptosis and FN secretion are mediated by TGF-beta1. As the metabolite of that of AA-I, the cellular injury mechanism of AL-I is different from that of AA-I, although it has similar effects like AA-I. The effects of AL-I may be mediated by different mechanisms except TGF-beta1 pathway.