MicroRNA-145 induces the senescence of activated hepatic stellate cells through the activation of p53 pathway by ZEB2

Activation of quiescent hepatic stellate cells (HSCs) is the major event in liver fibrosis, along with enhancement of cell proliferation and overproduction of extracellular matrix. Recent findings suggest that senescence of activated HSCs might limit the development of liver fibrosis. The p53, a guardian of the genome is associated with liver fibrosis, has been shown to regulate HSCs senescence. In this study, we report that microRNA-145 (miR-145) and p53 were downregulated in vivo and in vitro, concomitant with the enhanced expression of zinc finger E-box binding homeobox 2 (ZEB2). In addition, overexpression of miR-145 and p53 led to upregulation of the number of senescence-associated β-galactosidase-positive HSCs and the expression of senescence markers p16 and p21, along with the reduced abundance of HSC activation markers α-smooth muscle actin and type I collagen in activated HSCs. Furthermore, silencing of ZEB2 promoted senescence of activated HSCs. Moreover, we also demonstrated that miR-145 specifically targeted the 3′-untranslated regions of ZEB2. In vitro promoter regulation studies show that ZEB2 could bind to the E-box of the p53 promoter as well as inhibit its promoter activity and thus suppress the expression of p53, which in turn repressed activated HSCs senescence. Taken together, our results describe a novel miR-145-ZEB2-p53 regulatory line might participate in the senescence of activated HSCs and might carry potential therapeutic targets for restraining liver fibrosis.     

MiR-542-3p controls hepatic stellate cell activation and fibrosis via targeting BMP-7

There has been an increasing number of studies about microRNAs as key regulators in the development of hepatic fibrosis. Here, we demonstrate that miR-542-3p can promote hepatic fibrosis by downregulating the expression of bone morphogenetic protein 7 (BMP-7), which is known to antagonize transforming growth factor β1 (TGFβ1)-mediated fibrogenesis effect. The expression of miR-542-3p is increased in activated hepatic stellate cells (HSCs). Downregulation of MiR-542-3p by antisense inhibitors can inhibit HSCs activation markers, including α-smooth muscle actin (α-SMA) and collagen as well as TGFβ signaling pathways. MiR-542-3p was significantly upregulated in carbon tetrachloride (CCl₄)-induced hepatic fibrosis in mice, and downregulation of miR-542-3p by lentivirus could prevent the development of hepatic fibrosis. In addition, miR-542-3p can directly bind to the 3′-untranslated region of BMP-7 mRNA, indicating that its profibrotic effect appears to be caused by its inhibition of BMP-7. Our results suggest that downregulation of miR-542-3p prevents liver fibrosis both in vitro and in vivo, highlighting its potential as a novel biomarker or therapeutic target for hepatic fibrosis.     

Ribozymes against TGFbeta1 reverse character of activated hepatic stellate cells in vitro and inhibit liver fibrosis in rats

BACKGROUND/AIMS: Transforming growth factor beta (TGFbeta1) is considered the key mediator in the process of liver fibrosis. The purpose of this investigation was to evaluate the activity of ribozymes against TGFbeta1 in a cell-free system and activated hepatic stellate cells (HSCs), and antifibrotic effect in activated HSCs in vitro and in rats. METHODS: Three ribozymes targeting against TGFbeta1 mRNA were designed, and then cloned into the U1 snRNA expression cassette. The chimeric ribozymes were selected for the analysis of their performances in activated HSCs through the detection of their cleavage activities in a cell-free system. After ribozyme-encoding plasmids had been transfected into HSC-T6 cells, the effects of ribozymes on activated HSCs were evaluated through the analysis of proliferation, activation and collagen deposition of HSC-T6. The adenoviral vector expressing the ribozymes was constructed, and then delivered into rat models of hepatic fibrosis induced by carbon tetrachloride. RESULTS: TGFbeta1 expression was efficiently down-regulated in activated HSCs by U1 snRNA chimeric ribozymes which possessed perfect cleavage activity in a cell-free system. Further studies demonstrated that U1 snRNA chimeric ribozymes inhibited the synthesis of collagen I, reduced deposition of collagen I, suppressed BrdU incorporation, but had no effect on desmin and alpha-SMA expression in transfected HSC-T6 cells. Histological analysis demonstrated that the adenoviral vector expressing ribozyme (Rz803) could alleviate fibrotic pathology in rats treated with carbon tetrachloride. CONCLUSIONS: The anti-TGFbeta1 ribozymes could reverse the character of activated HSCs in vitro and improve fibrotic pathology in vivo. It indicated that TGFbeta1 could be considered as a novel candidate for a therapeutic agent against hepatic fibrosis.     

Serpine 1 induces alveolar type II cell senescence through activating p53‐p21‐Rb pathway in fibrotic lung disease

Senescence of alveolar type 2 (ATII) cells, progenitors of the alveolar epithelium, is implicated in the pathogeneses of idiopathic pulmonary fibrosis (IPF), an aging‐related progressive fatal lung disorder with unknown etiology. The mechanism underlying ATII cell senescence in fibrotic lung diseases, however, remains poorly understood. In this study, we report that ATII cells in IPF lungs express higher levels of serpine 1, also known as plasminogen activator inhibitor 1 (PAI‐1), and cell senescence markers p21 and p16, compared to ATII cells in control lungs. Silencing PAI‐1 or inhibition of PAI‐1 activity in cultured rat ATII (L2) cells leads to decreases in p53 serine 18 phosphorylation (p53^S18P), p53 and p21 protein expressions; an increase in retinoblastoma protein phosphorylation (ppRb); and a reduction in the sensitivity to bleomycin‐ and doxorubicin‐induced senescence. Silencing p53, on the other hand, abrogates PAI‐1 protein‐stimulated p21 expression and cell senescence. In vivo studies, using ATII cell‐specific PAI‐1 conditional knockout mouse model generated recently in this laboratory, further support the role of PAI‐1 in the activation of p53‐p21‐Rb cell cycle repression pathway, ATII cell senescence, and lung fibrosis induced by bleomycin. This study reveals a novel function of PAI‐1 in regulation of cell cycle and suggests that elevation of PAI‐1 contributes importantly to ATII cell senescence in fibrotic lung diseases.     

大鼠纤维化肝组织中SHP1表达与肝星状细胞活化及增殖的关系*

目的: 探讨大鼠肝纤维化病理过程中肝组织及在体肝星状细胞 (HSC)的含SH2结构域的蛋白酪氨酸磷酸酶1 (SHP1)表达变化与在体HSC活化及增殖的关系。方法: 随机将50只健康雄性SD大鼠分为对照组(10只)、模型组(40只),采用腹腔注射四氯化碳法建立大鼠肝纤维化模型,Masson三色染色及HE染色检测大鼠肝脏组织的病理组织学变化,SHP1与α-平滑肌肌动蛋白 (α-SMA)免疫荧光双标记检测大鼠肝组织中活化HSC的SHP1表达,免疫组织化学染色检测大鼠肝组织的α-SMA及SHP1表达,并分别对大鼠肝组织的SHP1表达及大鼠肝组织中活化HSC的SHP1表达与大鼠肝组织的α-SMA表达进行Pearson’s相关性分析。结果: 大鼠肝纤维化模型成功构建,随着造模时间延长,大鼠肝纤维化逐渐加重。与对照组大鼠肝组织的SHP1阳性表达平均光密度值 (MOD) (0.08±0.01)比较,造模不同时间(2周、4周、6周、8周)大鼠纤维化肝组织的SHP1阳性表达MOD (0.11±0.01、0.14±0.01、0.16±0.01、0.19±0.01)显著增加(P＜0.05),并逐渐升高(P＜0.05)。与对照组大鼠肝组织的α-SMA阳性表达MOD (0.04±0.01)比较,造模不同时间(2周、4周、6周、8周)大鼠纤维化肝组织的α-SMA阳性表达MOD (0.06±0.01、 0.09±0.01、0.12±0.01、0.16±0.02)明显增加(P＜0.05),并逐渐升高(P＜0.05),即在体HSC的活化及增殖逐渐加快(α-SMA是HSC的活化标志)。SHP1与α-SMA免疫荧光双标记检测显示,造模2周、4周、6周、8周大鼠纤维化肝组织中表达SHP1的活化HSC占总的活化HSC的百分比(26.49%±3.44%、37.14%±4.57%、44.90%±2.94%、58.09%±5.33%)逐渐升高(P＜0.05)。上述大鼠纤维化肝组织的SHP1表达及大鼠纤维化肝组织中表达SHP1的活化HSC占总的活化HSC的百分比均与大鼠纤维化肝组织的α-SMA表达呈显著正相关(r值为0.926, 0.984,P＜0.05)。结论: 在大鼠肝纤维病理过程中,肝组织及在体HSC 的SHP1表达与在体HSC的活化及增殖呈显著正相关。     

Circular RNA RSF1 promotes inflammatory and fibrotic phenotypes of irradiated hepatic stellate cell by modulating miR-146a-5p

The role of circular RNA (circRNA) in radiation-induced liver disease (RILD) remains largely unknown. In this study, Ras-related C3 botulinum toxin substrate 1 (RAC1) was elevated in irradiated human hepatic stellate cell (HSC) line LX2, the important effector cell mediating RILD. Overexpression of RAC1 promotes cell proliferation, proinflammatory cytokines production, and α-smooth muscle actin expression, which were blocked by microRNA (miR)-146a-5p mimics. CircRNA RSF1 (circRSF1) was upregulated in irradiated LX2 cells and predicted to harbor binding site for miR-146a-5p. Biotinylated-RNA pull down and dual-luciferase reporter detection confirmed the direct interaction of circRSF1 and miR-146a-5p. Enforced expression of circRSF1 increased RAC1 expression by acting as miR-146a-5p sponge to inhibit miR-146a-5p activity, and thus enhanced the cell viability, and promoted inflammatory and fibrotic phenotype of irradiated LX2 cells. These findings indicate a functional regulatory axis composing of circRSF1, miR-146a-5p, and RAC1 in irradiated HSC, which may provide attractive therapeutic targets for RILD.     

DHFR silence alleviated the development of liver fibrosis by affecting the crosstalk between hepatic stellate cells and macrophages

Liver fibrogenesis is a dynamic cellular and tissue process which has the potential to progress into cirrhosis of even liver cancer and liver failure. The activation of hepatic stellate cells (HSCs) is the central event underlying liver fibrosis. Besides, hepatic macrophages have been proposed as potential targets in combatting fibrosis. As for the relationship between HSCs and hepatic macrophages in liver fibrosis, it is generally considered that macrophages promoted liver fibrosis via activating HSCs. However, whether activated HSCs could in turn affect macrophage polarization has rarely been studied. In this study, mRNAs with significant differences were explored using exosomal RNA-sequencing of activated Lx-2 cells and normal RNA-sequencing of DHFR loss-of-function Lx-2 cell models. Cell functional experiments in both Lx-2 cells and macrophages animal model experiments were performed. The results basically confirmed exosomes secreted from activated HSCs could promote M1 polarization of macrophages further. Exosome harbouring DHFR played an important role in this process. DHFR silence in HSCs could decrease Lx-2 activation and M1 polarization of M0 macrophages and then alleviate the development of liver fibrosis both in vitro and vivo. Our work brought a new insight that exosomal DHFR derived from HSCs had a crucial role in crosstalk between HSCs activation and macrophage polarization, which may be a potential therapeutic target in liver fibrosis.     

细胞珠蛋白对肝星状细胞氧化损伤的保护作用

为揭示细胞珠蛋白对肝星状细胞氧化损伤的保护作用及相关机制,通过siRNA干扰内源性细胞珠蛋白基因,利用重组细胞珠蛋白作用于完全活化的人肝星状细胞系LX-2及大鼠原代肝星状细胞,并在LX-2细胞内过表达细胞珠蛋白,考察在过氧化氢及铁过载两种不同作用机制的氧化反应模型中细胞的增殖性及细胞内超氧化物水平。结果表明内源性细胞珠蛋白对于两种氧化反应导致的肝星状细胞损伤都具有显著性的保护作用,证明其在活化肝星状细胞内的表达上调是其应对氧化应激的保护性措施;重组细胞珠蛋白不仅能保护完全活化的LX-2细胞免受氧化应激损伤,并且能抑制未完全活化的原代肝星状细胞过度增殖以及保护其被过度损伤;重组细胞珠蛋白对细胞内的活性氧清除效果不理想,可能与其进出细胞缺乏相应的主动运输机制有关。进一步在LX-2细胞内过表达细胞珠蛋白对无论是铁过载或是过氧化氢引起的氧化反应均能发挥较好的保护性作用。为加速肝纤维化药物新靶点开发提供了理论依据。     

Exogenous expression of caveolin-1 is sufficient for hepatic stellate cell activation

Caveolin-1 (Cav-1) expression is increased in hepatic stellate cells (HSC) upon liver cirrhosis and it functions as an integral membrane protein of lipid rafts and caveolae that regulates and integrates multiple signals as a platform. This study aimed to evaluate the role of Cav-1 in HSC. Thus, the effects of exogenous expression of Cav-1 in GRX cells, a model of activated HSC, were determined. Here, we demonstrated through evaluating well-known HSC activation markers – such as α-smooth muscle actin, collagen I, and glial fibrillary acidic protein – that up regulation of Cav-1 induced GRX to a more activated phenotype. GRX^EGFP-Cav1 presented an increased migration, an altered adhesion pattern, a reorganization f-actin cytoskeleton, an arrested cell cycle, a modified cellular ultrastructure, and a raised endocytic flux. Based on this, GRX ^EGFP-Cav1 represents a new cellular model that can be an important tool for understanding of events related to HSC activation. Furthermore, our results reinforce the role of Cav-1 as a molecular marker of HSC activation.     

Acetyltransferase p300 regulates atrial fibroblast senescence and age-related atrial fibrosis through p53/Smad3 axis

Atrial fibrosis induced by aging is one of the main causes of atrial fibrillation (AF), but the potential molecular mechanism is not clear. Acetyltransferase p300 participates in the cellular senescence and fibrosis, which might be involved in the age-related atrial fibrosis. Four microarray datasets generated from atrial tissue of AF patients and sinus rhythm (SR) controls were analyzed to find the possible relationship of p300 (EP300) with senescence and fibrosis. And then, biochemical assays and in vivo electrophysiological examination were performed on older AF patients, aging mice, and senescent atrial fibroblasts. The results showed that (1) the left atrial tissues of older AF patients, aging mouse, and senescence human atrial fibroblasts had more severe atrial fibrosis and higher protein expression levels of p300, p53/acetylated p53 (ac-p53)/p21, Smad3/p-Smads, and fibrosis-related factors. (2) p300 inhibitor curcumin and p300 knockdown treated aging mouse and senescence human atrial fibroblasts reduced the senescence ratio of atrial fibroblasts, ameliorated the atrial fibrosis, and decreased the AF inducibility. In contrast, over-expression of p300 can lead to the senescence of atrial fibroblasts and atrial fibrosis. (3) p53 knockdown decreased the expression of aging and fibrosis-related proteins. (4) Co-immunoprecipitation and immunofluorescence showed that p53 forms a complex with smad3 and directly regulates the expression of smad3 in atrial fibroblasts. Our findings suggest that the mechanism of atrial fibrosis induced by aging is, at least, partially dependent on the regulation of p300, which provides new sights into the AF treatment, especially for the elderly.     

CX3CL1/fractalkine shedding by human hepatic stellate cells: contribution to chronic inflammation in the liver

Chemokines are the inflammatory mediators that modulate liver fibrosis, a common feature of chronic inflammatory liver diseases. CX3CL1/fractalkine is a membrane-associated chemokine that requires step processing for chemotactic activity and has been recently implicated in liver disease. Here, we investigated the potential shedding activities involved in the release of the soluble chemotactic peptides from CX3CL1 in the injured liver. We showed an increased expression of the sheddases ADAM10 and ADAM17 in patients with chronic liver diseases that was associated with the severity of liver fibrosis. We demonstrated that hepatic stellate cells (HSC) were an important source of ADAM10 and ADAM17 and that treatment with the inflammatory cytokine inter-feron-γ induced the expression of CX3CL1 and release of soluble peptides. This release was inhibited by the metalloproteinase inhibitor batimastat; however, ADAM10/ADAM17 inhibitor GW280264X only partially affected shedding activity. By using selective tissue metalloprotease inhibitors and overexpression analyses, we showed that CX3CL1 was mainly processed by matrix metalloproteinase (MMP)-2, a metalloprotease highly expressed by HSC. We further demonstrated that the CX3CL1 soluble peptides released from stimulated HSC induced the activation of the CX3CR1-dependent signalling pathway and promoted chemoattraction of monocytes in vitro . We conclude that ADAM10, ADAM17 and MMP-2 synthesized by activated HSC mediate CX3CL1 shedding and release of chemotactic peptides, thereby facilitating recruitment of inflammatory cells and paracrine stimulation of HSC in chronic liver diseases.     

Potential natural mTOR inhibitors screened by in silico approach and suppress hepatic stellate cells activation

The mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase, plays a central role in the regulation of cell proliferation, growth, differentiation, migration, and survival. In this study, the 3-D structure of the mTOR (PDB ID: 2FAP) was used for the docking of 47 natural compounds and compared with pharmacophore model of 14 known mTOR inhibitors to identify the novel and specific natural inhibitor. The top four compounds, rutin, curcumin, antroquinonol, and benzyl cinnamate, have been selected based on their PLP score and further validated with hepatic stellate cells NHSC and THSC. Curcumin and antroquinonol significantly inhibited NHSC and THSC cells proliferation in a dose-dependent manner, whereas rutin and benzyl cinnamate showed less alteration of cell viability. Rutin inhibited the phosphorylation of mTOR (p-mTOR) and p-p70 S6 K in NHSC and THSC cells by Western blotting. Additionally, p-p70 S6 K protein was significantly decreased by incubation with benzyl cinnamate and curcumin in THSC cells. Taken together, this result suggests that rutin is a potential mTOR inhibitor in screen hits of molecular docking to hamper the activation of HSC and further applications in the treatment of liver fibrosis.     

Acetyltransferase p300 regulates atrial fibroblast senescence and age‐related atrial fibrosis through p53/Smad3 axis

Atrial fibrosis induced by aging is one of the main causes of atrial fibrillation (AF), but the potential molecular mechanism is not clear. Acetyltransferase p300 participates in the cellular senescence and fibrosis, which might be involved in the age‐related atrial fibrosis. Four microarray datasets generated from atrial tissue of AF patients and sinus rhythm (SR) controls were analyzed to find the possible relationship of p300 (EP300) with senescence and fibrosis. And then, biochemical assays and in vivo electrophysiological examination were performed on older AF patients, aging mice, and senescent atrial fibroblasts. The results showed that (1) the left atrial tissues of older AF patients, aging mouse, and senescence human atrial fibroblasts had more severe atrial fibrosis and higher protein expression levels of p300, p53/acetylated p53 (ac‐p53)/p21, Smad3/p‐Smads, and fibrosis‐related factors. (2) p300 inhibitor curcumin and p300 knockdown treated aging mouse and senescence human atrial fibroblasts reduced the senescence ratio of atrial fibroblasts, ameliorated the atrial fibrosis, and decreased the AF inducibility. In contrast, over‐expression of p300 can lead to the senescence of atrial fibroblasts and atrial fibrosis. (3) p53 knockdown decreased the expression of aging and fibrosis‐related proteins. (4) Co‐immunoprecipitation and immunofluorescence showed that p53 forms a complex with smad3 and directly regulates the expression of smad3 in atrial fibroblasts. Our findings suggest that the mechanism of atrial fibrosis induced by aging is, at least, partially dependent on the regulation of p300, which provides new sights into the AF treatment, especially for the elderly.     

Methyl helicterate inhibits hepatic stellate cell activation through downregulating the ERK1/2 signaling pathway

The present study was to investigate the inhibitory effect of methyl helicterate (MH) on hepatic stellate cells (HSC-T6), primarily elucidating the underlying mechanism of MH against liver fibrosis. HSC-T6 cells were activated by platelet-derived growth factor (PDGF) stimulation, and then the effects of MH on cell viability, cytomembrane integrity, colony, migration, apoptosis, and cell cycle were detected. Moreover, the regulative mechanism of MH on HSCs was investigated by detecting the activation of the extracellular signal-regulated kinase (ERK1/2) signaling pathway. The results showed that MH significantly inhibited HSC-T6 cell viability and proliferation in a concentration-dependent manner. It notably promoted the release of lactate dehydrogenase, destroying cell membrane integrity. MH also markedly inhibited HSC-T6 cell clonogenicity and migration. Moreover, MH treatment significantly induced cell apoptosis and arrested cell cycle at the G2 phase. The further study showed that MH inhibited the expression of ERK1, ERK2, c-fos, c-myc, and Ets-1, blocking the ERK1/2 pathway. In conclusion, this study demonstrates that MH significantly inhibits HSC activation and promotes cell apoptosis via downregulation of the ERK1/2 signaling pathway.