Adiponectin inhibits hepatic stellate cell activation by targeting the PTEN/AKT pathway.

Adiponectin inhibits hepatic stellate cell (HSC) activation and subsequent development of liver fibrosis via multiple mechanisms. Phosphatase and tensin homolog deletion 10 (PTEN) plays a crucial role in suppression of HSC activation, but its regulation by adiponectin is not fully understood. Here, we investigated the effect of adiponectin on PTEN in LX-2 cells, a human cell line and examined the underlying molecular mechanisms involved in adiponectin-mediated upregulation of PTEN activity during fibrosis. PTEN expression was found to be significantly reduced in the livers of mice treated with CCl4, whereas its expression was rescued by adiponectin treatment. The DNA methylation proteins DNMT1, DNMT3A, and DNMT3B are all highly expressed in activated primary HSCs compared to quiescent HSCs, and thus represent additional regulatory targets during liver fibrogenesis. Expression of DNMT proteins was significantly induced in the presence of fibrotic stimuli; however, only DNMT3B expression was reduced in the presence of adiponectin. Adiponectin-induced suppression of DNMT3B was found to be mediated by enhanced miR-29b expression. Furthermore, PTEN expression was significantly increased by overexpression of miR-29b, whereas its expression was markedly reduced by a miR-29b inhibitor in LX-2 cells. These findings suggest that adiponectin-induced upregulation of miR-29b can suppress DNMT3B transcription in LX-2 cells, thus resulting in reduced methylation of PTEN CpG islands and ultimately suppressing the PI3K/AKT pathway. Together, these data suggest a possible new explanation for the inhibitory effect of adiponectin on HSC activation and liver fibrogenesis.

Kumar P ，Raeman R ，Chopyk DM ，Smith T ，Verma K ，Liu Y ，Anania FA ... -  《-》

Curcumin up-regulates phosphatase and tensin homologue deleted on chromosome 10 through microRNA-mediated control of DNA methylation--a novel mechanism suppressing liver fibrosis.

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.

Zheng J ，Wu C ，Lin Z ，Guo Y ，Shi L ，Dong P ，Lu Z ，Gao S ，Liao Y ，Chen B ，Yu F ... -  《-》

HOTAIR Epigenetically Modulates PTEN Expression via MicroRNA-29b: A Novel Mechanism in Regulation of Liver Fibrosis.

Homeobox transcript antisense RNA (HOTAIR), as a long intergenic non-coding RNA (lincRNA), is upregulated in various cancers and involved in diverse cellular functions. However, its role in liver fibrosis is unclear. In this study, HOTAIR expression was upregulated in hepatic stellate cells (HSCs) in vivo and in vitro during liver fibrosis. HOTAIR knockdown suppressed HSC activation including α-smooth muscle actin (α-SMA) and typeIcollagen in vitro and in vivo. Both HSC proliferation and cell cycle were inhibited by HOTAIR knockdown. Notably, inhibition of HOTAIR led to an increase in PTEN, associated with the loss of DNA methylation. miR-29b-mediated control of PTEN methylation was involved in the effects of HOTAIR knockdown. HOTAIR was confirmed a target of miR-29b and lack of the miR-29b binding site in HOTAIR prevented the suppression of miR-29b, suggesting HOTAIR contributes to PTEN expression downregulation via sponging miR-29b. Interestingly, increased HOTAIR was also observed in hepatocytes during liver fibrosis. Loss of HOTAIR additionally led to the increase in PTEN and the reduction in typeIcollagen in hepatocytes. Collectively, we demonstrate that HOTAIR downregulates miR-29b expression and attenuates its control on epigenetic regulation, leading to enhanced PTEN methylation, which contributes to the progression of liver fibrosis.

Yu F ，Chen B ，Dong P ，Zheng J ... -  《-》

Inhibition of miR-188-5p alleviates hepatic fibrosis by significantly reducing the activation and proliferation of HSCs through PTEN/PI3K/AKT pathway.

Persistent hepatic damage and chronic inflammation in liver activate the quiescent hepatic stellate cells (HSCs) and cause hepatic fibrosis (HF). Several microRNAs regulate the activation and proliferation of HSCs, thereby playing a critical role in HF progression. Previous studies have reported that miR-188-5p is dysregulated during the process of HF. However, the role of miR-188-5p in HF remains unclear. This study investigated the potential role of miR-188-5p in HSCs and HF. Firstly, we validated the miR-188-5p expression in primary cells isolated from liver of carbon tetrachloride (CCl4 )-induced mice, TGF-β1-induced LX-2 cells, livers from 6-month high-fat diet (HFD)-induced rat and 4-month HFD-induced mice NASH models, and human non-alcoholic fatty liver disease (NAFLD) patients. Furthermore, we used miR-188-5p inhibitors to investigate the therapeutic effects of miR-188-5p inhibition in the HFD + CCl4 induced in vivo model and the potential role of miR-188-5p in the activation and proliferation of HSCs. This present study reported that miR-188-5p expression is significantly increased in the human NAFLD, HSCs isolated from liver of CCl4 induced mice, and in vitro and in vivo models of HF. Mimicking the miR-188-5p resulted in the up-regulation of HSC activation and proliferation by directly targeting the phosphatase and tensin homolog (PTEN). Moreover, inhibition of miR-188-5p reduced the activation and proliferation markers of HSCs through PTEN/AKT pathway. Additionally, in vivo inhibition of miR-188-5p suppressed the HF parameters, pro-fibrotic and pro-inflammatory genes, and fibrosis. Collectively, our results uncover the pro-fibrotic role of miR-188-5p. Furthermore, we demonstrated that miR-188-5p inhibition decreases the severity of HF by reducing the activation and proliferation of HSCs through PTEN/AKT pathway.

Riaz F ，Chen Q ，Lu K ，Osoro EK ，Wu L ，Feng L ，Zhao R ，Yang L ，Zhou Y ，He Y ，Zhu L ，Du X ，Sadiq M ，Yang X ，Li D ... -  《-》

Hepatic stellate cell is activated by microRNA-181b via PTEN/Akt pathway.

Zheng J ，Wu C ，Xu Z ，Xia P ，Dong P ，Chen B ，Yu F ... -  《-》