Aldose reductase inhibitor, fidarestat regulates mitochondrial biogenesis via Nrf2/HO-1/AMPK pathway in colon cancer cells

Although we have shown earlier that aldose reductase (AR) inhibitors prevent colorectal cancer cell (CRC) growth in culture as well as in nude mice xenografts, the mechanism(s) is not well understood. In this study, we have investigated how AR inhibition prevents CRC growth by regulating the mitochondrial biogenesis via Nrf2/HO-1 pathway. Incubation of CRC cells such as SW-480, HT29, and HCT116 with AR inhibitor, fidarestat that non-covalently binds to the enzyme, increases the expression of Nrf2. Further, fidarestat augmented the EGF-induced expression of Nrf2 in CRC cells. Fidarestat also increased the Nrf2 -DNA binding activity as well as expression of HO-1 and NQO1 and activation of SOD and catalase in SW480 cells. Similarly, in nude mice xenograft tumor tissues, Nrf2 and HO-1 levels were significantly higher in fidarestat-treated mice compared to controls. Further, stimulation of CRC cells with EGF in the presence of fidarestat increased the mRNA levels of PGC-1α, Nrf1 and TFAM and protein levels of PGC-1α, TFAM and COX-IV and decreased the mitochondrial DNA damage as measured by 8-hydroxy-2′-deoxyguanosine levels. AR inhibitor also modulated the phosphorylations of AMPK and mTOR and expression of p53 in EGF-treated cells. Collectively, our results indicate that AR inhibitor prevents CRC growth by increasing mitochondrial biogenesis via increasing the expression of Nrf2/HO-1/AMPK/p53 and decreasing the mitochondrial DNA damage.