Identification of 3',4',5'-trihydroxyflavone as an mammalian target of rapamycin inhibitor and its suppressive effects on dextran sulfate sodium-induced ulcerative colitis.

Flavone derivatives have been shown to possess anti-inflammatory properties in various inflammation model systems; however, their underlying molecular mechanisms remain elusive. In this study, a flavone derivative 3',4',5'-trihydroxyflavone (THF; NJK16003) was synthesized, and its anti-inflammatory effects and molecular targets were investigated using in vitro systems and an in vivo colitis model. NJK16003 showed potent anti-inflammatory activities in cell-based assays using macrophages. In vitro enzyme activity assays using various inflammation-related kinases revealed the mammalian target of rapamycin (mTOR) as a possible molecular target. Treatment of RAW264.7 cells with NJK16003 resulted in an increase in light chain 3B protein lipidation and a decrease in p62 protein levels and ribosomal S6 kinase phosphorylation, indicating that NJK16003 induces autophagy through mTOR inhibition. NJK16003 treatment resulted in significant induction of autophagy and suppression of inflammatory responses in intestinal epithelial cells. Autophagy induction has been shown to alleviate colitis by suppressing inflammatory responses and apoptotic cell death of intestinal epithelial cells. Indeed, inflammatory responses and intestinal epithelial cell death in our DSS-induced colitis mouse model were significantly suppressed by NJK16003 treatment. Our results indicate that NJK16003 could suppress inflammation by inducing autophagy through its mTOR inhibitory activity. These results suggest that NJK16003 could be a possible therapeutic agent for the treatment of inflammatory bowel diseases including colitis.

Bardoxolone Methyl Suppresses Hepatitis B Virus Large Surface Protein Variant W4P-Related Carcinogenesis and Hepatocellular Carcinoma Cell Proliferation Via the Inhibition of Signal Transducer and Activator of Transcription 3 Signaling.

Bardoxolone methyl (CDDO-me) is a synthetic triterpenoid that has been shown to suppress various cancers and inflammation. It has been implicated for the suppression of signal transducer and activator of transcription 3 (STAT3)-mediated signaling, which plays crucial roles in the development and progression of hepatocellular carcinoma (HCC). Previously, we showed that hepatitis B virus (HBV) large surface protein (LHB) variant W4P promotes carcinogenesis and tumor progression through STAT3 activation. Thus, we examined the anti-cancer activity of CDDO-me against HCC using W4P-LHB-expressing NIH3T3 cells and HepG2 and Huh7 HCC cell lines. CDDO-me exerted cytotoxic activity against W4P-LHB-expressing NIH3T3 cells, HepG2 cells, and Huh7 cells, and induced apoptotic cell death in a dose-dependent manner, demonstrating its anti-cancer activity against HCC. Sublethal concentrations of CDDO-me suppressed STAT3 activation by W4P-LHB ectopic expression and interleukin-6 treatment in W4P-LHB-NIH3T3 and Huh7 cells respectively. The suppression of STAT3 activation by CDDO-me in W4P-LHB-NIH3T3 cells was further confirmed by decreased cyclin D1 protein levels and increased p21 and p53 mRNA synthesis. In addition, CDDO-me treatment resulted in decreased cell migration and colony formation in in vitro assays using W4P-LHB-NIH3T3, HepG2, or Huh7 cell lines, supporting its anti-cancer activity through STAT3 inhibition. Furthermore, -CDDO-me administration significantly suppressed tumor growth induced by W4P-LHB-expressing NIH3T3 cells in nude mice, confirming its anti-cancer activity. Collectively, our findings demonstrated that CDDO-me is capable of suppressing STAT3 activation in HCC cells and cells transformed by the natural variant of HBV protein. The results suggest that CDDO-me can be a potential therapeutic agent against HCC, especially tumors related to HBV mutations.