Puromycin aminonucleoside-induced podocyte injury is ameliorated by the Smad3 inhibitor SIS3

Smad3 signaling and transgelin expression are often activated during puromycin aminonucleoside (PAN)-induced podocyte injury. Here, we investigated whether the Smad3 inhibitor SIS3 can ameliorate damage to injured podocytes. A model of PAN-induced podocyte injury was constructed using the MPC5 cell line. The effects of SIS3 on the expression of the podocyte cytoskeletal proteins transgelin, p15(INK4B), phosphor-smad3, phosphor-JAK/stat3, the apoptotic marker cleaved caspase 3, and c-myc were investigated using western blot. The distribution of F-actin in PAN-induced podocyte injury was observed under an immunofluorescence microscope. PAN-induced podocyte injury altered the distribution of F-actin and transgelin, and colocalization of these two proteins was observed. Transgelin expression and Smad3 phosphorylation were increased in the MPC5 cell line with prolonged PAN treatment. In addition, c-myc expression, p15(INK4B), and JAK phosphorylation were all increased after treatment with PAN. Treatment with the Smad3 inhibitor SIS3 reversed these phenomena and protected against PAN-induced podocyte injury. Moreover, stimulating podocytes directly with TGF beta-1 also led to enhanced expression of transgelin or phosphor-JAK/stat3, and this could be inhibited by SIS3. In conclusion, transgelin expression was induced through the Smad3 signaling pathway during PAN-induced podocyte injury, and the resulting abnormal distribution of F-actin and the enhanced expression of transgelin could be reversed by blockade of this pathway.