[Effects of autophagy modulator on autophagy and uridine 5'-diphospho-glucuronosyltransferase 1A1 induced by sulforaphane].

Objective: To explore the effects of 3-methyladenine (3-MA) and rapamycin (Rapa) on autophagy and uridine 5'-diphospho-glucuronosyltransferase 1A1 (UGT1A1) induced by sulforaphane (SFN) in human colon cancer Caco-2 cells.

Methods: Western blot was used to detect the expression of microtubule-associated protein 1 light chain 3 (LC3) and UGT1A1 proteins. And immunocytochemistry was employed to observe the intracellular distribution of LC3 and nuclear localization of NF-E2-related factor 2 (Nrf2). Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was employed to examine the mRNA expression of UGT1A1 and human pregnane X receptor (hPXR).

Results: After the treatment of SFN, the LC3-II protein was induced in a dose and time-dependent manner. SFN-induced LC3-II protein could be attenuated and enhanced by 3-MA and Rapa respectively. In comparison with the control group, UGT1A1 mRNA levels increased significantly after the treatment of Rapa, SFN or their combination (2.4, 4.12 and 2.41 folds respectively, all P < 0.01). And the combination of SFN and Rapa possessed the highest level. UGT1A1 protein band intensity was also enhanced in three groups. There was no obvious nuclear staining of Nrf2 in control group while intense nuclear fluorescent labeling of Nrf2 could be observed in the SFN-treated groups, especially the combination group of SFN and Rapa. The hPXR mRNA levels increased significantly in the Rapa and combination groups (1.82 and 1.4 folds respectively, both P < 0.01).

Conclusion: The treatment of 3-MA or Rapa may attenuate or enhance SFN-induced autophagy respectively. And Rapa also potentiates SFN-induced UGT1A1 expression. The mechanism for the synergic effect of Rapa and SFN on UGT1A1 induction may be a simultaneous activation of Nrf2 and hPXR signaling pathway.