Scutellarin ameliorates hepatic lipid accumulation by enhancing autophagy and suppressing IRE1α/XBP1 pathway.

Nonalcoholic fatty liver disease is the most prevalent liver disease characterized by excessive lipid accumulation in hepatocytes. Endoplasmic reticulum (ER) stress and autophagy play an important role in lipid accumulation. In this study, scutellarin (Scu) was examined in palmitic acid-treated HepG2 cells and C57/BL6 mice fed a high-fat diet (HFD). Scu reduced intracellular lipid content and inhibited sterol regulatory element binding protein-1c (SREBP-1c)-mediated lipid synthesis and fatty acid translocase-mediated lipid uptake in HepG2 cells. Additionally, Scu restored impaired autophagy and inhibited excessive activation of ER stress in vivo and in vitro. Moreover, Scu upregulated forkhead box O transcription factor 1-mediated autophagy by inhibiting inositol-requiring enzyme 1α (IRE1α)/X-box-binding protein 1 (XBP1) branch activation, while XBP1s overexpression exacerbated the lipid accumulation and impaired autophagy in HepG2 cells and also weakened the positive effects of Scu. Furthermore, Scu attenuated ER stress by activating autophagy, ultimately downregulating SREBP-1c-mediated lipid synthesis, and autophagy inhibitors offset these beneficial effects. Scu inhibited the crosstalk between autophagy and ER stress and downregulated saturated fatty acid-induced lipid accumulation in hepatocytes. These findings demonstrate that Scu ameliorates hepatic lipid accumulation by enhancing autophagy and suppressing ER stress via the IRE1α/XBP1 pathway.

Peperomin E Induces Promoter Hypomethylation of Metastatic-Suppressor Genes and Attenuates Metastasis in Poorly Differentiated Gastric Cancer.

BACKGROUND/AIMS: Peperomin E (PepE), a natural secolignan isolated from the whole plant of Peperomia dindygulensis, has been reported by ourselves and others to display potent anti-cancer effects in many types cancer cells, especially gastric cancer. However, the effects of PepE on the metastasis of poorly-differentiated gastric cancer cells and the underlying molecular mechanisms have not been well elucidated. METHODS: We evaluated PepE effects on gastric cancer cell invasion and migration in vitro via wound healing and transwell assays and those on growth and metastasis in vivo using an orthotopic xenograft NOD-SCID mouse model. DNA methyltransferase (DNMT) activity was determined using a colorimetric DNMT activity/inhibition assay kit. PepE binding kinetics to DNMTs were determined using the bio-layer interferometry binding assay. Gene and protein levels of DNMTs, AMPKα-Sp1 signaling molecules, and metastatic-suppressor genes in PepE-treated gastric cancer cells were determined using quantitative reverse transcription-PCR arrays and western blotting. The effect of PepE on Sp1 binding to the DNMT promoter was determined by electrophoretic mobility-shift assay. Global DNA methylation levels were determined using liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The methylation status of silenced metastatic-suppressor genes (MSGs) in gastric cancer cells was investigated by methylation-specific PCR. RESULTS: PepE can dose-dependently suppress invasion and migration of poorly-differentiated gastric cancer cells in vitro and in vivo with low toxicity against normal cells. Mechanistically, PepE not only covalently binds to the catalytic domain of DNMT1 and inhibits its activity (IC50 value 3.61 µM) but also down-regulates DNMT1, 3a, and 3b mRNA and protein expression in in gastric cancer cells, by disruption of the physical interaction of Sp1 with the DNMT1, 3a, and 3b promoter and mediation of the AMPKα-Sp1 signaling pathway. The dual inhibition activity of PepE toward DNMTs renders a relative global DNA hypomethylation, which induces MSG promoter hypomethylation (e.g., E-cadherin and TIMP3) and enhances their expression in gastric cancer cells. CONCLUSION: Collectively, our data indicated that PepE may represent a promising therapeutic lead compound for intervention in gastric cancer metastasis and may also exhibit potential as a DNA methylation inhibitor for use in epigenetic cancer therapy.