ABSTRACT
ObjectiveTo explore the protective mechanism of paeoniflorin on mice with ulcerative colitis （UC） through the adenosine monophosphate-activated protein kinase （AMPK）/mammalian target of rapamycin （mTOR） autophagy pathway. MethodUC mouse model was established by allowing mice freely drink 4% DSS， and 56 BALB/c male mice were randomly divided into model group， AMPK inhibitor group （20 mg·kg-1）， paeoniflorin （50 mg·kg-1） + inhibitor （20 mg·kg-1） group， and high dose （50 mg·kg-1）， medium dose （25 mg·kg-1）， and low dose （12.5 mg·kg-1） paeoniflorin groups. After seven days of drug intervention， the protective effect of paeoniflorin on mice with UC was determined by comparing the body weight， disease activity index （DAI） changes， and Hematoxylin-eosin （HE） staining results. Enzyme linked immunosorbent assay （ELISA） was used to detect the levels of tumor necrosis factor-α （TNF-α） and interleukin-6 （IL-6） in the serum of mice in each group， and immunofluorescence was utilized to detect microtubule-associated protein 1 light chain 3 （LC3） content in the colon， AMPK， mTOR proteins， and their phosphorylated proteins including p-AMPK and p-mTOR in the colon tissue were detected by Western blot， and the mRNA expression levels of AMPK， mTOR， Beclin1， LC3， and p62 were detected by Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR）. ResultCompared with the blank group， the model group showed a decrease in body mass， an increase in DAI score， and severe pathological damage to the colon. The levels of inflammatory factors including TNF-α and IL-6 increased in serum （P<0.01）， while the protein levels of LC3 and p-AMPK/AMPK were down-regulated in colon tissue， and those of p-mTOR/mTOR were up-regulated （P<0.01）. The mRNA expression levels of AMPK and LC3 were down-regulated， while the mRNA expression levels of mTOR and p62 were up-regulated （P<0.01）. Compared with the model group and the paeoniflorin + inhibitor group， the mice treated with paeoniflorin showed an increase in body mass， a decrease in DAI score， a reduction in pathological damage to colon tissue， and a reduction in the levels of inflammatory factors of TNF-α and IL-6 in serum （P<0.05）. The protein levels of LC3 and p-AMPK/AMPK in colon tissue were up-regulated， while the protein levels of p-mTOR/mTOR were down-regulated （P<0.01）. The mRNA expression levels of AMPK， Beclin1， and LC3 were up-regulated， while the mRNA expression of mTOR and p62 were down-regulated （P<0.01）. The colon tissue of the inhibitor group was severely damaged， and the trend of various indicators was completely opposite to that of the high dose paeoniflorin group. ConclusionPaeoniflorin can enhance autophagy and reduce inflammatory damage in mice with UC by activating the AMPK/mTOR signaling pathway and thus play a protective role.