No abstract

No abstract

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) has been reported to play a role in the suppression of activated hepatic stellate cells (HSCs). Moreover, it has been demonstrated that hypermethylation of the PTEN promoter is responsible for the loss of PTEN expression during HSC activation. Methylation is now established as a fundamental regulator of gene transcription. MicroRNAs (miRNAs), which can control gene expression by binding to their target genes for degradation and/or translational repression, were found to be involved in liver fibrosis. However, the mechanism responsible for miRNA‐mediated epigenetic regulation in liver fibrosis still remained unclear. In the present study, curcumin treatment significantly resulted in the inhibition of cell proliferation and an increase in the apoptosis rate through the up‐regulation of PTEN associated with a decreased DNA methylation level. Only DNA methyltransferase 3b (DNMT3b) was reduced in vivo and in vitro after curcumin treatment. Further studies were performed aiming to confirm that the knockdown of DNMT3b enhanced the loss of PTEN methylation by curcumin. In addition, miR‐29b was involved in the hypomethylation of PTEN by curcumin. MiR‐29b not only was increased by curcumin in activated HSCs, but also was confirmed to target DNMT3b by luciferase activity assays. Curcumin‐mediated PTEN up‐regulation, DNMT3b down‐regulation and PTEN hypomethylation were all attenuated by miR‐29b inhibitor. Collectively, it is demonstrated that curcumin can up‐regulate miR‐29b expression, resulting in DNMT3b down‐regulation in HSCs and epigenetically‐regulated PTEN involved in the suppression of activated HSCs. These results indicate that miRNA‐mediated epigenetic regulation may be a novel mechanism suppressing liver fibrosis.

Abbreviations: a-SMA, smooth muscle a-actin; Ad-shCtrl, adenoviral vectors expressing the scrambled shRNA; Ad-shMALAT1, adenoviral vectors expressing shRNA against MALAT1. EdU, 5-Ethyny-2 0 -deoxyuridine; Ago2, Argonaute-2; BDL, bile duct ligation; CCl 4 , carbon tetrachloride; ceRNAs, competing endogenous RNAs; Col1a1, collagen type I, a 1; DMEM, Dulbecco's modified Eagle's medium; HSCs, hepatic stellate cells; IgG, immunoglobulin G; IHC, immunohistochemical; lncRNAs, long noncoding RNAs; MALAT1, Metastasis-associated lung adenocarcinoma transcript 1; miR-101, microRNA-101; miR-NC, miR-101b negative control; miRNAs, microRNAs; ncRNAs, non-coding RNAs; qRT-PCR, quantitative real-time PCR; Rac1, RAS-related C3 botulinum substrate 1; siCtrl, scrambled siRNA; siRNAs, small interfering RNAs.Emerging evidence shows that Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays a pivotal role in cell proliferation, migration, and invasion in tumors. However, the biological role and underlying mechanism of MALAT1 in liver fibrosis remains undefined. In this study, up-regulation of MALAT1 was observed in fibrotic liver tissues and in activated hepatic stellate cells (HSCs). In addition, depletion of MALAT1 inhibited the activation of HSCs in vitro and attenuated collagen deposits in vivo. Our results demonstrated that MALAT1 expression is negatively correlated with microRNA-101b (miR-101b) expression. Furthermore, there was a negative feedback loop between the levels of MALAT1 and miR-101b. Luciferase reporter assay indicated that MALAT1 and RAS-related C3 botulinum substrate 1 (Rac1) are targets of miR-101b. We uncovered that MALAT1 regulates Rac1 expression through miR-101b as a competing endogenous RNA (ceRNA), thereby influencing the proliferation, cell cycle and activation of primary HSCs. Collectively, The ceRNA regulatory network may prompt a better understanding of liver fibrogenesis and contribute to a novel therapeutic strategy for liver fibrosis.

NEAT1 was significantly increased in CCl-induced mice and activated HSCs. Loss of NEAT1 suppressed liver fibrosis in vivo and in vitro. KLF6 and miR-122 were required for the effects of NEAT1 on HSC activation. NEAT1 contributes to HSC activation via competitively binding miR-122. We disclose a novel NEAT1-miR-122-KLF6 signaling cascade.