Retinol binding protein-albumin domain III fusion protein deactivates hepatic stellate cells

Liver fibrosis is characterized by accumulation of extracellular matrix, and activated hepatic stellate cells (HSCs) are the primary source of the fibrotic neomatrix and considered as therapeutic target cells. We previously showed that albumin in pancreatic stellate cells (PSCs), the key cell type for pancreatic fibrogenesis, is directly involved in the formation of vitamin A-containing lipid droplets, inhibiting PSC activation. In this study, we evaluated the anti-fibrotic activity of both albumin and retinol binding protein-albumin domain III fusion protein (R-III), designed for stellate cell-targeted delivery of albumin III, in rat primary HSCs and investigated the underlying mechanism. Forced expression of albumin or R-III in HSCs after passage 2 (activated HSCs) induced lipid droplet formation and deactivated HSCs, whereas point mutations in high-affinity fatty acid binding sites of albumin domain III abolished their activities. Exogenous R-III, but not albumin, was successfully internalized into and deactivated HSC-P2. When HSCs at day 3 after plating (pre-activated HSCs) were cultured in the presence of purified R-III, spontaneous activation of HSCs was inhibited even after passage 2, suggestive of a potential for preventive effect. Furthermore, treatment of HSCs-P2 with R-III led to a significant reduction in both cytoplasmic levels of all-trans retinoic acid and the subsequent retinoic acid signaling. Therefore, our data suggest that albumin deactivates HSCs with reduced retinoic acid levels and that R-III may have therapeutic and preventive potentials on liver fibrosis.     

Activated hepatic stellate cells promote angiogenesis in hepatocellular carcinoma by secreting angiopoietin-1

Angiogenesis is the central pathological process in hepatocellular carcinoma (HCC), and its progression is affected by tumor cells and the microenvironment. Activated hepatic stellate cells (aHSCs) are the most significant stromal cells involved in HCC. This study was aimed to explore the effects and mechanisms of aHSCs on angiogenesis in HCC. We isolated primary hepatoma cells, aHSCs, and hepatic vascular endothelial cells from human HCC samples. Then, we performed a novel in vitro assay and in vivo experiment in a nude mouse HCC model to investigate the functions of aHSCs on angiogenesis in HCC. Our results demonstrated that aHSCs are the primary sources of angiopoietin-1 (Ang-1) in human HCC in vitro, and aHSCs could promote hepatic vascular endothelial cell (HVEC) growth by secreting Ang-1. Furthermore, aHSCs could induce HVEC microtubule formation, and this ability was reduced when Ang-1 expression was silenced in aHSCs. In addition, CD34 expression in a nude mouse HCC model was downregulated when Ang-1 messenger RNA was silenced in aHSCs. Our data also indicated that HSC Ang-1 expression could be inhibited by overexpressing Raf kinase inhibitor protein. Therefore, we suggest that aHSCs promote angiogenesis through secreting Ang-1, potentially providing an interesting target for antiangiogenic therapies for HCC.     

Stabilization of RNA strands in protein synthesis by type I procollagen C-proteinase enhancer protein, a potential RNA-binding protein, in hepatic stellate cells.

Type I procollagen C-proteinase enhancer (PCPE) exists in hepatic stellate cells (HSCs) which can produce collagen. The deduced amino acid sequence of PCPE contains motifs specific for RNA-binding proteins. The effect of PCPE on the syntheses of collagen and noncollagenous protein was studied using an HSC clone derived from cirrhotic rat liver. When the cells were cultured in the presence of an antisense oligonucleotide (AS) against PCPE mRNA, the synthesis of noncollagenous protein as well as collagen was reduced compared to the cells cultured with addition of a nonsense oligonucleotide (NS). The extent of the reduction was similar in both syntheses. The total RNA content of the AS-treated cells and NS-treated cells did not differ. In the presence of actinomycin D, however, such total RNA content was decreased more rapidly in the AS-treated cells than in the NS-treated cells. PCPE may be involved in stabilization of RNA strands in noncollagenous protein synthesis as well as collagen synthesis.     

Characterization of a cellular retinol-binding protein from lamprey, Lethenteron japonicum

Lampreys are ancestral representatives of vertebrates known as jawless fish. The Japanese lamprey, Lethenteron japonicum, is a parasitic member of the lampreys known to store large amounts of vitamin A within its body. How this storage is achieved, however, is wholly unknown. Within the body, the absorption, transfer and metabolism of vitamin A are regulated by a family of proteins called retinoid-binding proteins. Here we have cloned a cDNA for cellular retinol-binding protein (CRBP) from the Japanese lamprey, and phylogenetic analysis suggests that lamprey CRBP is an ancestor of both CRBP I and II. The lamprey CRBP protein was expressed in bacteria and purified. Binding of the lamprey CRBP to retinol (Kd of 13.2 nM) was identified by fluorimetric titration. However, results obtained with the protein fluorescence quenching technique indicated that lamprey CRBP does not bind to retinal. Northern blot analysis showed that lamprey CRBP mRNA was ubiquitously expressed, although expression was most abundant in the intestine. Together, these results suggest that lamprey CRBP has an important role in absorbing vitamin A from the blood of host animals.     

Soluble factors derived from human amniotic epithelial cells suppress collagen production in human hepatic stellate cells

BackgroundIntravenous infusion of human amniotic epithelial cells (hAECs) has been shown to ameliorate hepatic fibrosis in murine models. Hepatic stellate cells (HSCs) are the principal collagen-secreting cells in the liver. The aim of this study was to investigate whether factors secreted by hAECs and present in hAEC-conditioned medium (CM) have anti-fibrotic effects on activated human HSCs.MethodsHuman AECs were isolated from the placenta and cultured. Human hepatic stellate cells were exposed to hAEC CM to determine potential anti-fibrotic effects.ResultsHSCs treated for 48 h with hAEC CM displayed a significant reduction in the expression of the myofibroblast markers α-smooth muscle actin and platelet-derived growth factor. Expression of the pro-fibrotic cytokine transforming growth factor-β1 (TGF-β1) and intracellular collagen were reduced by 45% and 46%, respectively. Human AEC CM induced HSC apoptosis in 11.8% of treated cells and reduced HSC proliferation. Soluble human leukocyte antigen–G1, a hAEC-derived factor, significantly decreased TGF-β1 and collagen production in activated HSCs, although the effect on collagen production was less than that of hAEC CM. The reduction in collagen and TGF-B1 could not be attributed to PGE2, relaxin, IL-10, TGF-B3, FasL or TRAIL.ConclusionsHuman AEC CM treatment suppresses markers of activation, proliferation and fibrosis in human HSCs as well as inducing apoptosis and reducing proliferation. Human AEC CM treatment may be effective in ameliorating liver fibrosis and warrants further study.     

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。     

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。     

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.     

Human liver slices as an in vitro model to study toxicity-induced hepatic stellate cell activation in a multicellular milieu

INTRODUCTION: Hepatic stellate cell (HSC) activation is a key event in wound healing as well as in fibrosis development in the liver. Previously we developed a technique to induce HSC activation in slices from rat liver. Although this model provides a physiologic, multicellular milieu that is not present in current in vitro models it might still be of limited predictive value for the human situation due to species-differences. Therefore, we now aimed to evaluate the applicability of human liver slices for the study of HSC activation. METHOD: Liver slices (8 mm diameter, 250 microm thickness) were generated from human liver tissue and incubated for 3 or 16 h with 0-15 microl of carbon tetrachloride (CCl4) after which ATP-content and expression levels of HSC (activation) markers was determined. RESULTS: Human liver slices remained viable during incubation as shown by constant ATP levels. Incubation with CCl(4) caused a dose-dependent decrease in viability and an increase in mRNA expression of the early HSC activation markers HSP47 and alphaB-crystallin, but not the late markers for HSC activation, alphaSMA and pro-collagen 1a1. Synaptophysin mRNA expression remained constant during incubation with or without CCl4, indicating a constant number of HSC in the liver slices. CONCLUSION: We developed a technique to induce early toxicity-induced HSC activation in human liver slices. This in vitro model provides a multicellular, physiologic milieu to study mechanisms underlying toxicity-induced HSC activation in human liver tissue.     

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.     

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.     

GATA binding protein 3 is correlated with leptin regulation of PPARγ1 in hepatic stellate cells

Accumulating evidence reveals that hormone leptin, mainly produced by adipocyte, plays a unique role in promotion of liver fibrosis. Hepatic stellate cell (HSC) activation is a key step in liver fibrosis and peroxisome‐proliferator activated receptor γ (PPARγ) exerts a crucial role in inhibition of HSC activation. Our previous researches demonstrated that leptin reduced PPARγ1 (a major subtype of PPARγ in HSCs) expression through GATA binding protein 2 (GATA2) binding to a site around ?2323 in PPARγ1 promoter. The present researches aimed to examine the effect of GATA3 on leptin‐induced inhibition of PPARγ1 and elucidate the relationship between GATA3 and GATA2. Gene expressions were analysed by real‐time PCR, western blot, luciferase assay and immunostaining. C57BL/6J ob/ob mouse model of thioacetamide‐induced liver injury was used in vivo. Results demonstrate that leptin significantly induces GATA3 expression in HSCs by multiple signalling pathways including NADPH oxidase pathway. There exist crosstalks between NADPH oxidase pathway and the other pathways. GATA3 can bind to GATA2‐binding site in PPARγ1 promoter and interacts with GATA2, contributing to leptin inhibition of PPARγ1 expression in HSCs. These data demonstrated novel molecular events for leptin inhibition of PPARγ1 expression in HSCs and thus might have potential implications for clarifying the detailed mechanisms underlying liver fibrosis in diseases in which circulating leptin levels are elevated such as non‐alcoholic steatohepatitis in obese patients.     

PCR标记前胶原基因探针及其检测肝星状细胞前胶原基因表达

目的：建立一种新的前胶原基因探针制备方法,并用克勤克俭 检测HSC的前胶原mRNA表达。方法：从NCBIGeneBank查询Ⅰ、Ⅲ、Ⅳ型前胶原基因的序列,根据基因序列用OLIGO软件设计其引物：RT-PCR扩增基因,并用不对称PCR方法和DIG-dUTP标记前胶原基因探针,用其原位杂交检测HSC前胶原基因表达。结果：用所设计的引物和RT-PCR扩增得到目的基因,制备了DIG标记的前胶原基因探针,并用其检到HSC的前胶左面的基因表达。结论：建立了一种新的、较简易的前胶原基因探针标记方法,并对其它基因探针的标记有借鉴意义。     

Mouse retinol binding protein gene: Cloning,expression and regulation by retinoic acid

A full-length cDNA clone encoding the retinol binding protein (RBP) was isolated from a mouse liver cDNA library by hybridization screening. The nucleotide sequence of murine RBP is 85 and 95% homologous to that of human and rat RBP, respectively, with a deduced amino acid sequence 83% homologous to both species. Analysis of the tissue expression pattern of RBP mRNA in the female mouse indicated relatively abundant expression in the liver, with lesser amounts in extrahepatic tissues including adipose, kidney, spleen and uterus, suggesting that these tissues may have a significant role in retinol homeostasis. Mouse liver cell RBP regulation by retinoids was also investigated. Both all-trans retinoic acid (AT-RA) and 9-cis retinoic acid (9c-RA) induced RBP mRNA expression in a dose- and time-dependent manner. Maximal levels (up to 4-fold above controls) were observed at 48h following treatment of both mouse hepatoma cells in vitro and in vivo in mice receiving a single, oral dose of either retinoid. Interestingly, 9c-RA was more potent at RBP induction in both in vivo and in vitro systems. Given the extent and temporal pattern of RBP induction, we suggest that the RA-mediated increase in liver RBP is part of a cellular protection mechanism. Increased levels of RBP would facilitate sequestration and possibly cellular export of RA in cells receiving prolonged exposure to high levels of RA, thus minimizing toxicity.