Molecular regulation of hepatic fibrogenesis

Nanoparticle-Mediated RNA Therapy Attenuates Nonalcoholic Steatohepatitis and Related Fibrosis by Targeting Activated Hepatic Stellate Cells

Chronic liver injury and inflammation triggered by metabolic abnormalities initiate the activation of hepatic stellate cells (HSCs), driving fibrosis and parenchymal dysfunction, culminating in disorders such as nonalcoholic steatohepatitis (NASH). Unfortunately, there are currently no approved drugs capable of effectively treating NASH due to the challenges in addressing fibrosis and restoring extracellular matrix (ECM) homeostasis. We discovered a significant up-regulation of interleukin-11 (IL-11) in fibrotic livers using two well-established murine models of NASH. To leverage this signaling pathway, we developed a nanoparticle (NP)-assisted RNA interfering approach that specifically targets activated HSCs (aHSCs), blocking IL-11/ERK signaling to regulate HSC transdifferentiation along with fibrotic remodeling. The most potent NP, designated NP-AEAA, showed enhanced accumulation in fibrotic livers with NASH and was primarily enriched in aHSCs. We further investigated the therapeutic efficacy of aHSC-targeting NP-AEAA encapsulating small interfering RNA (siRNA) against IL11 or its cognate receptor IL11ra1 (termed siIL11@NP-AEAA or siIL11ra1@NP-AEAA, respectively) for resolving fibrosis and NASH. Our results demonstrate that both siIL11@NP-AEAA and siIL11ra1@NP-AEAA effectively inhibit HSC activation and resolve fibrosis and inflammation in two well-established murine models of NASH. Notably, siIL11ra1@NP-AEAA exhibits a superior therapeutic effect over siIL11@NP-AEAA, in terms of reducing liver steatosis and fibrosis as well as recovering liver function. These results constitute a targeted nanoparticulate siRNA therapeutic approach against the IL-11 signaling pathway of aHSCs in the fibrotic liver, offering a promising therapeutic intervention for NASH and other diseases.

Cell-to-Cell Communications in Alcohol-Associated Liver Disease

This review covers some important new aspects of the alcohol-induced communications between liver parenchymal and non-parenchymal cells leading to liver injury development. The information exchange between various cell types may promote end-stage liver disease progression and involves multiple mechanisms, such as direct cell-to-cell interactions, extracellular vesicles (EVs) or chemokines, cytokines, and growth factors contained in extracellular fluids/cell culture supernatants. Here, we highlighted the role of EVs derived from alcohol-exposed hepatocytes (HCs) in activation of non-parenchymal cells, liver macrophages (LM), and hepatic stellate cells (HSC). The review also concentrates on EV-mediated crosstalk between liver parenchymal and non-parenchymal cells in the settings of HIV- and alcohol co-exposure. In addition, we overviewed the literature on the crosstalk between cell death pathways and inflammasome activation in alcohol-activated HCs and macrophages. Furthermore, we covered highly clinically relevant studies on the role of non-inflammatory factors, sinusoidal pressure (SP), and hepatic arterialization in alcohol-induced hepatic fibrogenesis. We strongly believe that the review will disclose major mechanisms of cell-to-cell communications pertained to alcohol-induced liver injury progression and will identify therapeutically important targets, which can be used for alcohol-associated liver disease (ALD) prevention.

Ingestion of mannose ameliorates thioacetamide-induced intrahepatic oxidative stress, inflammation and fibrosis in rats

BACKGROUND AND AIMS

The monosaccharide mannose has gained recent interest for its beneficial effect against certain inflammatory disorders. Nevertheless, the influence of mannose on experimentally-induced liver fibrosis and the ensued inflammation is still not fully clear to date.

MAIN METHODS

The current study investigated the outcomes of treating rats with mannose (0.2 ml of 20% w/v, oral gavage) 30 min before the twice weekly intoxication with thioacetamide (TAA) (200 mg/kg, intraperitoneal) for a total period of 8 weeks.

KEY FINDINGS

The data indicated that mannose markedly dampened TAA-induced liver fibrosis, as indicated by lowering the fibrotic bridges shown by Masson's trichrome staining. This effect was consistent with reducing TAA-induced hepatocellular injury, as evidenced biochemically (serum ALT and AST activities) and pathologically (necroinflammation score). These hepatoprotective effects mediated by mannose were attributed to i) reversing TAA-induced rise in malondialdehyde (MDA) and decrease in reduced glutathione (GSH) expressions in the liver, ii) limiting TAA-induced release of the proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), iii) impairing TAA-induced activation of hepatic stellate cells by downregulating α-smooth muscle actin expression (α-SMA), and more importantly, iv) dampening TAA-induced fibrogenesis driven by transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF).

SIGNIFICANCE

Mannose may be a valuable candidate for preventing oxidative stress, inflammation and fibrogenesis in the liver.

An ultrasound image-based deep multi-scale texture network for liver fibrosis grading in patients with chronic HBV infection

BACKGROUND & AIMS

The evaluation of the stage of liver fibrosis is essential in patients with chronic liver disease. However, due to the low quality of ultrasound images, the non-invasive diagnosis of liver fibrosis based on ultrasound images is still an outstanding question. This study aimed to investigate the diagnostic accuracy of a deep learning-based method in ultrasound images for liver fibrosis staging in multicentre patients.

METHODS

In this study, we proposed a novel deep learning-based approach, named multi-scale texture network (MSTNet), to assess liver fibrosis, which extracted multi-scale texture features from constructed image pyramid patches. Its diagnostic accuracy was investigated by comparing it with APRI, FIB-4, Forns and sonographers. Data of 508 patients who underwent liver biopsy were included from 4 hospitals. The area-under-the ROC curve (AUC) was determined by receiver operating characteristics (ROC) curves for significant fibrosis (≥F2) and cirrhosis (F4).

RESULTS

The AUCs (95% confidence interval) of MSTNet were 0.92 (0.87-0.96) for ≥F2 and 0.89 (0.83-0.95) for F4 on the validation group, which significantly outperformed APRI, FIB-4 and Forns. The sensitivity and specificity of MSTNet (85.1% (74.5%-92.0%) and 87.6% (78.0%-93.6%)) were better than those of three sonographers in assessing ≥F2.

CONCLUSIONS

The proposed MSTNet is a promising ultrasound image-based method for the non-invasive grading of liver fibrosis in patients with chronic HBV infection.

Taurine ameliorates thioacetamide induced liver fibrosis in rats via modulation of toll like receptor 4/nuclear factor kappa B signaling pathway

Liver fibrosis is a significant health problem that can cause serious illness and death. Unfortunately, a standard treatment for liver fibrosis has not been approved yet due to its complicated pathogenesis. The current study aimed at assessing the anti-fibrotic effect of taurine against thioacetamide induced liver fibrosis in rats through the modulation of toll like receptor 4/nuclear factor kappa B signaling pathway. Both concomitant and late taurine treatment (100 mg/kg, IP, daily) significantly reduced the rise in serum ALT and AST activities and significantly reversed the decrease in serum albumin and total protein. These results were confirmed by histopathological examinations and immunehistochemical inspection of α-SMA, caspase-3 and NF-κB. The antioxidant potential of taurine was verified by a marked increase of GSH content and a reduction of MDA level in liver tissue. The anti-fibrotic effects of taurine were evaluated by investigating the expression of TLR4, NF-κB. The protein levels of IL-6, LPS, MyD88, MD2, CD14, TGF-β1 and TNF-α were determined. Docking studies were carried out to understand how taurine interacts inside TLR4-MD2 complex and it showed good binding with the hydrophobic binding site of MD2. We concluded that the anti-fibrotic effect of taurine was attributable to the modulation of the TLR4/NF-κB signaling.

All trans retinoic acid modulates TNF-α and CYP2E1 pathways and enhances regression of ethanol-induced fibrosis markers in hepatocytes and HSCs in abstaining rodent model

Context: Our previous studies showed that all trans retinoic acid (ATRA) ameliorates alcohol-induced toxicity. Hence, we evaluated the efficacy of ATRA and abstention in the regression of alcohol-induced hepatotoxicity. Materials and methods: After ethanol administration to rats for 90 days, the regression of alcohol-induced toxicity was studied by supplementing ATRA at a dose of 100 μg/kg body weight for 30 days. It was also compared with animals in abstention. Results and discussion: Ethanol administration enhanced oxidative stress, activated HSCs and increased collagen deposition. All these alterations were reversed to a certain extent by ATRA supplementation. Conclusions: ATRA had better efficacy than just abstention in reducing ethanol-induced toxicity. The mechanism might be downregulation of CYP2E1, leading to reduced oxidative stress in the hepatocytes and thus impeding NFκB activation, cytokine production, activation of HSC and resulting in the reduction of inflammation and remodelling of fibrosis by modulating MMP and TIMP.

Liver sinusoidal endothelial cell ICAM-1 mediated tumor/endothelial crosstalk drives the development of liver metastasis by initiating inflammatory and angiogenic responses

The prometastatic stroma generated through tumor cells/host cells interaction is critical for metastatic growth. To elucidate the role of ICAM-1 on the crosstalk between tumor and primary liver sinusoidal endothelial cells (LSECs) and hepatic stellate cells (HSCs), implicated in tumor adhesion and angiogenesis, we performed in vitro cocultures and an in vivo model of liver metastasis of colorectal cancer (CRC). ICAM-1 blockade in the LSECs decreased the adhesion and transmigration of tumor cells through an LSEC in vitro and vivo. Cocultures of C26 cells and LSECs contained higher amounts of IL-1β, IL-6, PGE-2, TNF-α and ICAM-1 than monocultures. C26 cells incubated with sICAM-1 secreted higher amounts of PGE-2, IL-6, VEGF, and MMPs, while enhanced the migration of LSECs and HSCs. HSCs cultures activated by media from C26 cells pretreated with sICAM-1 contained the largest amounts of VEGF and MMPs. C26 cell activation with sICAM-1 enhanced their metastasizing potential in vivo, while tumor LFA-1 blockade reduced tumor burden and LSECs and HSC-derived myofibroblasts recruitment. In vivo ICAM-1 silencing produced similar results. These findings uncover LSEC ICAM-1 as a mediator of the CRC metastatic cascade in the liver and identifies it as target for the inhibition of liver colonization and metastatic progression.

Multi-cellular transitional organotypic models to investigate liver fibrosis

Hepatic fibrosis is the result of wound healing and inflammation resulting in organ dysfunction. Hepatocytes, liver sinusoidal endothelial cells (LSECs), Kupffer cells (KCs), and hepatic stellate cells (HSCs) play critical roles in fibrogenesis. As the liver undergoes fibrosis, there are populations of cells that are healthy, fibrotic as well as those undergoing fibrosis. We investigated how a varying mechanical environment could induce changes in hepatic cells. In this study, a gradient in the mechanical properties of the microenvironment resulted in transitioning phenotypes in hepatic cells. We have designed detachable polyelectrolyte multilayers (PEMs) whose elastic moduli ranged from 21 to 43 kPa to serve as Space of Disse mimics. We assembled novel 3D organotypic liver models comprised of hepatocytes, LSECs, HSCs, KCs, and the Space of Disse mimic. We demonstrate how cells in contact with a mechanical gradient exhibit different properties compared to cells cultured using non-gradient PEMs. Significant differences were observed in HSC and KC proliferation between 3D cultures assembled with gradient and non-gradient PEMs. While HSCs on the stiffer regions of the gradient PEMs expressed both GFAP and α-SMA, cells in cultures assembled with homogeneous 43 kPa multilayers primarily expressed α-SMA. Over an 8-day culture, the elastic modulus in the 21 and 43 kPa regions of the gradient PEMs increased by 1.6 and 3.7-fold, respectively. This was accompanied by a 4-fold increase in hydroxyproline. Such in vitro tissues can be used to investigate the effects of liver fibrosis. STATEMENT OF SIGNIFICANCE: We have assembled a liver model assembled with four major primary hepatic cell types to investigate how a varying mechanical environment induces changes in hepatic cells. In this study, a gradient in the mechanical properties of the microenvironment results in transitioning phenotypes in hepatic cells. Our goal was to investigate the interplay between mechanical properties and a multi-cellular engineered liver tissue. In these models, Kupffer cell proliferation and hepatic stellate cell activation occurred due to mechanical cues and inter-cellular signaling across a distance of 2000 μm. These models are unique, in that, fibrosis was initiated purely through changes to the microenvironment. These models were not exposed to fibrogenic factors nor were the models assembled with cells from fibrotic rats. To the best of our knowledge, these are the first liver models that capture how a gradient microenvironment can result in transitioning cellular phenotypes.

Osteopontin promotes collagen I synthesis in hepatic stellate cells by miRNA-129-5p inhibition

Activation of hepatic stellate cells (HSCs) is an essential event in the initiation and progression of liver fibrosis. HSCs are believed to be the major source of collagen-producing myofibroblasts in fibrotic livers. A key feature in the pathogenesis of liver fibrosis is fibrillar Collagen I (Col 1) deposition. Osteopontin (OPN), an extracellular matrix (ECM) cytokine expressed in HSCs, could drive fibrogenesis by modulating the HSC pro-fibrogenic phenotype and Col 1 expression. Here, we aimed to investigate the molecular mechanism of OPN regulating the activation of HSCs. Our results showed that hepatic expression of OPN was increased in patients with liver fibrosis. In addition, hepatic OPN was positively correlated with Col 1 and α-SMA. Recombinant OPN (rOPN) upregulated Col 1 and α-SMA expression in LX-2 cells. However, OPN knockdown downregulated Col 1 expression. The 3'-UTR of the collagen 1 (Col 1) was identified to bind miR-129-5p. Transfection of miR-129-5p mimic in HSC resulted in a marked reduction of Col 1 expression. Conversely, a decrease in miR-129-5p in HSCs transfected by anti-sense miR-129-5p (AS-miR-129-5p) caused Col 1 upregulation. Furthermore, luciferase reporter assay showed that miR-129-5p directly target the 3'-UTR of Col1α1 mRNA via repressing its post-transcriptional activities. Finally, miR-129-5p level was decreased in fibrotic liver of human, and reduced by rOPN treatment. In contrast, miR-129-5p was induced in HSCs transfected by OPN siRNA. These data suggested that OPN induces Col 1 expression via suppression of miR-129-5p in HSCs.

Hepatoprotective activities of rosmarinic acid against extrahepatic cholestasis in rats

Though rosmarinic acid possesses nutritional, pharmaceutical, and toxic properties and shows therapeutic potential on liver diseases, its therapeutic effects against cholestatic liver diseases have not been proven. Using an extrahepatic cholestasis rat model by bile-duct ligation (BDL), daily oral administration of rosmarinic acid showed improvement effects on liver histology, serum biochemicals, ductular reaction, oxidative stress, inflammation, and fibrosis. Rosmarinic acid alleviated BDL-induced transforming growth factor beta-1 (TGF-β1) production and hepatic collagen deposition, and the anti-fibrotic effects were accompanied by reductions in matrix-producing cells and Smad2/3. BDL rats showed increased hepatic NF-κB/AP-1 activities, inflammatory cell infiltration/accumulation, and cytokine production, and these signs of hepatic inflammation were ameliorated by rosmarinic acid. Mechanistic study revealed an inhibitory effect of rosmarinic acid on the axis of the high mobility group box-1 (HMGB1)/toll-like receptor-4 (TLR4) in BDL rats. Results of cultured hepatic stellate cells further showed the impacts of rosmarinic acid which attenuated TGF-β1-induced stellate cell mitogenic and fibrogenic activation. Our findings support the concept that rosmarinic acid could serve as a hepatoprotective agent, and dietary rosmarinic acid supplementation may be beneficial in terms of improving cholestasis-related liver injury via mechanisms involving resolution of oxidative burden and down-regulation of HMGB1/TLR4, NF-κB, AP-1, and TGF-β1/Smad signaling.

DNA Oncogenic Virus-Induced Oxidative Stress, Genomic Damage, and Aberrant Epigenetic Alterations

Approximately 20% of human cancers is attributable to DNA oncogenic viruses such as human papillomavirus (HPV), hepatitis B virus (HBV), and Epstein-Barr virus (EBV). Unrepaired DNA damage is the most common and overlapping feature of these DNA oncogenic viruses and a source of genomic instability and tumour development. Sustained DNA damage results from unceasing production of reactive oxygen species and activation of inflammasome cascades that trigger genomic changes and increased propensity of epigenetic alterations. Accumulation of epigenetic alterations may interfere with genome-wide cellular signalling machineries and promote malignant transformation leading to cancer development. Untangling and understanding the underlying mechanisms that promote these detrimental effects remain the major objectives for ongoing research and hope for effective virus-induced cancer therapy. Here, we review current literature with an emphasis on how DNA damage influences HPV, HVB, and EBV replication and epigenetic alterations that are associated with carcinogenesis.

Higher Anti-Liver Fibrosis Effect of Cordyceps militaris-Fermented Product Cultured with Deep Ocean Water via Inhibiting Proinflammatory Factors and Fibrosis-Related Factors Expressions

Deep ocean water (DOW) has been shown to enhance the functional components of fungi, resulting in increased health benefits. Therefore, using DOW for culturing fungi can enhance the cordycepin and adenosine of Cordyceps militaris (CM) and its protective effects on the liver. In this study, the antiliver fibrosis effects and mechanisms of ultrapure water-cultured CM (UCM), DOW-cultured CM (DCM), synthetic water-cultured CM, DOW, cordycepin, and adenosine were compared in the liver fibrosis mice induced by intraperitoneal injections of thioacetamide (TAA). The results indicated that DCM exhibited superior performance in reducing liver collagen accumulation, mitigating liver injuries, inhibiting proinflammatory factors and fibrosis-related factor (TGF-β1, Smad2/3, α-SMA, COL1A1) expression compared with UCM. DOW, cordycepin, and adenosine also performed antiliver fibrosis effect. Therefore, because DCM is rich in DOW and functional components, it can achieve anti-liver fibrosis effects through multiple pathways. These ameliorative effects are considerably superior to those of UCM.

DNA methylation of angiotensin II receptor gene in nonalcoholic steatohepatitis-related liver fibrosis

AIM

To clarify whether Agtr1a methylation is involved in the development of nonalcoholic steatohepatitis (NASH)-related liver fibrosis in adult rats.

METHODS

A choline-deficient amino acid (CDAA) diet model was employed for methylation analysis of NASH-related liver fibrosis. Agtr1a methylation levels were measured in the livers of CDAA- and control choline-sufficient amino acid (CSAA)-fed rats for 8 and 12 wk using quantitative methylation-specific PCR. Hepatic stellate cells (HSCs) were isolated by collagenase digestion of the liver, followed by centrifugation of the crude cell suspension through a density gradient. Agtr1a methylation and its gene expression were also analyzed during the activation of HSCs.

RESULTS

The mean levels of Agtr1a methylation in the livers of CDAA-fed rats (11.5% and 18.6% at 8 and 12 wk, respectively) tended to be higher (P = 0.06 and 0.09, respectively) than those in the livers of CSAA-fed rats (2.1% and 5.3% at 8 and 12 wk, respectively). Agtr1a was not methylated at all in quiescent HSCs, but was clearly methylated in activated HSCs (13.8%, P < 0.01). Interestingly, although Agtr1a was hypermethylated, the Agtr1a mRNA level increased up to 2.2-fold (P < 0.05) in activated HSCs compared with that in quiescent HSCs, suggesting that Agtr1a methylation did not silence its expression but instead had the potential to upregulate its expression. These findings indicate that Agtr1a methylation and its upregulation of gene expression are associated with the development of NASH-related liver fibrosis.

CONCLUSION

This is the first study to show that DNA methylation is potentially involved in the regulation of a renin-angiotensin system-related gene expression during liver fibrosis.

Pioglitazone attenuates hepatic inflammation and fibrosis in phosphatidylethanolamine N-methyltransferase-deficient mice

Phosphatidylethanolamine N-methyltransferase (PEMT) is an important enzyme in hepatic phosphatidylcholine (PC) biosynthesis. Pemt(-/-) mice are protected against high-fat diet (HFD)-induced obesity and insulin resistance; however, these mice develop nonalcoholic fatty liver disease (NAFLD). We hypothesized that peroxisomal proliferator-activated receptor-γ (PPARγ) activation by pioglitazone might stimulate adipocyte proliferation, thereby directing lipids from the liver toward white adipose tissue. Pioglitazone might also act directly on PPARγ in the liver to improve NAFLD. Pemt(+/+) and Pemt(-/-) mice were fed a HFD with or without pioglitazone (20 mg·kg(-1)·day(-1)) for 10 wk. Pemt(-/-) mice were protected from HFD-induced obesity but developed NAFLD. Treatment with pioglitazone caused an increase in body weight gain in Pemt(-/-) mice that was mainly due to increased adiposity. Moreover, pioglitazone improved NAFLD in Pemt(-/-) mice, as indicated by a 35% reduction in liver weight and a 57% decrease in plasma alanine transaminase levels. Livers from HFD-fed Pemt(-/-) mice were steatotic, inflamed, and fibrotic. Hepatic steatosis was still evident in pioglitazone-treated Pemt(-/-) mice; however, treatment with pioglitazone reduced hepatic fibrosis, as evidenced by reduced Sirius red staining and lowered mRNA levels of collagen type Iα1 (Col1a1), tissue inhibitor of metalloproteinases 1 (Timp1), α-smooth muscle actin (Acta2), and transforming growth factor-β (Tgf-β). Similarly, oxidative stress and inflammation were reduced in livers from Pemt(-/-) mice upon treatment with pioglitazone. Together, these data show that activation of PPARγ in HFD-fed Pemt(-/-) mice improved liver function, while these mice were still protected against diet-induced obesity and insulin resistance.

Pentoxifylline Inhibits Epidural Fibrosis in Post-Laminectomy Rats

BACKGROUND

The aim of this experimental study was to investigate the effectiveness of intramuscular pentoxifylline in the prevention of postoperative fibrosis.

MATERIAL/METHODS

We divided 16 adult Wistar albino rats into 2 equal groups: treatment and control. Both groups underwent L1 vertebral total laminectomy to expose the dura. The intramuscular treatment group received pentoxifylline. Four weeks later, epidural fibrosis was studied in both groups using electron microscopy, light microscopy, histology, biochemistry, and macroscopy.

RESULTS

The evaluation of epidural fibrosis in the 2 groups according to macroscopic (p<0.01) assessment and light microscopy revealed that epidural scar tissue formation was lower in the treatment group compared to the control group (p<0.001) and the number of fibroblasts was also decreased significantly in the pentoxifylline-treated group (p<0.05). More immature fibers were demonstrated in the treatment group by electron microscopy in comparison with the control group. In biochemical analysis, a statistically significant decrease was detected in hydroxyproline, which indicates fibrosis and myeloperoxidase activity, and shows an inflammatory response (P<0.001).

CONCLUSIONS

Systemic pentoxifylline application prevents postoperative epidural fibrosis and adhesions with various mechanisms. Our study is the first to present evidence of experimental epidural fibrosis prevention with pentoxifylline.

Lipid-induced hepatocyte-derived extracellular vesicles regulate hepatic stellate cell via microRNAs targeting PPAR-γ

BACKGROUND&AIMS

Hepatic stellate cells (HSCs) play a key role in liver fibrosis in various chronic liver disorders including nonalcoholic fatty liver disease (NAFLD). The development of liver fibrosis requires a phenotypic switch from quiescent to activated HSCs. The triggers for HSCs activation in NAFLD remain poorly understood. We investigated the role and molecular mechanism of extracellular vesicles (EVs) released by hepatocytes during lipotoxicity in modulation of HSC phenotype.

METHODS

EVs were isolated from fat-laden hepatocytes by differential centrifugation and incubated with HSCs. EV internalization and HSCs activation, migration and proliferation were assessed. Loss- and gain-of-functions studies were performed to explore the potential role of PPAR-γ-targeting miRNAs carried by EVs into HSC.

RESULTS

Hepatocyte-derived EVs released during lipotoxicity are efficiently internalized by HSCs resulting in their activation, as shown by marked up-regulation of pro-fibrogenic genes (Collagen-I, α-SMA and TIMP-2), proliferation, chemotaxis and wound healing responses. These changes were associated with miRNAs shuttled by EVs and suppression of PPAR-γ expression in HSC. Hepatocyte-derived EVs miRNA content included various miRNAs that are known inhibitors of PPAR-γ expression with miR-128-3p being the most effectively transferred. Furthermore loss- and gain-of-function studies identified miR-128-3p as a central modulator of the effects of EVs on PPAR-γ inhibition and HSC activation.

CONCLUSION

Our findings demonstrate a link between fat-laden hepatocyte-derived EVs and liver fibrosis and have potential implications for the development of novel anti-fibrotic targets for NAFLD and other fibrotic diseases.

The mechanisms of HSC activation and epigenetic regulation of HSCs phenotypes

Epigenetics is a dynamically expanding field of science entailing numerous regulatory mechanisms controlling changes of gene expression in response to environmental factors. Over the recent years there has been a great interest in epigenetic marks as a potential diagnostic and prognostic tool or future target for treatment of various human diseases. There is an increasing body of published research to suggest that epigenetic events regulate progression of chronic liver disease. Experimental manipulation of epigenetic signatures such as DNA methylation, histone acetylation / methylation and the activities of proteins that either annotate or interpret these epigenetic marks can have profound effects on the activation and phenotype of HSC, key cells responsible for onset and progression of liver fibrosis. This review presents recent advances in epigenetic alterations, which could provide mechanistic insight into the pathogenesis of chronic liver disease and provide novel clinical applications.

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

Activation of hepatic stellate cells (HSCs) is an essential event in the initiation and progression of liver fibrosis. MicroRNAs have been shown to play a pivotal role in regulating HSC functions such as cell proliferation, differentiation, and apoptosis. Recently, miR-181b has been reported to promote HSCs proliferation by targeting p27. But whether alpha-smooth muscle actin (α-SMA) or collagens could be promoted by miR-181b in activated HSCs is still not clear. Therefore, the understanding of the role of miR-181b in liver fibrosis remains limited. Our results showed that miR-181b expression was increased much higher than miR-181a expression in vitro in transforming growth factor-β1-induced HSC activation as well as in vivo in carbon tetrachloride-induced rat liver fibrosis. Of note, overexpression of miR-181b significantly increased the expressions level of α-SMA and type I collagen, and further promoted HSCs proliferation. Furthermore, phosphatase and tensin homologs deleted on chromosome 10 (PTEN), a negative regulator of PI3K/Akt pathway, were confirmed as a direct target of miR-181b. We demonstrated that miR-181b could suppress PTEN expression and increase Akt phosphorylation in HSCs. Interestingly, the effects of miR-181b on the activation of HSCs were blocked down by Akt inhibitor LY294002. Our results revealed a profibrotic role of miR-181b in HSC activation and demonstrated that miR-181b could activate HSCs, at least in part, via PTEN/Akt pathway.

Protective effects of rutin on liver injury induced by biliary obstruction in rats

Rutin has been shown to possess beneficial health effects, including hepatoprotection. However, to date, it has not been demonstrated to have a hepatoprotective effect against cholestatic liver injury. This is the first report to show a protective effect of rutin on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily oral administration of rutin was started 1 week before injury and was maintained for 4 weeks. In comparison with the control group, the BDL group showed liver injury as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation, and oxidative stress. These pathophysiological changes were attenuated by rutin supplementation. Rutin alleviated BDL-induced transforming growth factor β1 (TGF-β1), interleukin-1β, connective tissue growth factor, and collagen expression. The antifibrotic effect of rutin was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad2/3 activity critical to the fibrogenic potential of TGF-β1. Rutin attenuated BDL-induced oxidative stress, leukocyte accumulation, NF-κB activation, and proinflammatory cytokine production. Further studies demonstrated an inhibitory effect of rutin on the redox-sensitive intracellular signaling molecule extracellular signal-regulated kinase (ERK). Rutin also attenuated BDL-induced reduction in NF-E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and AMP-activated protein kinase (AMPK). Taken together, the beneficial effects of rutin were shown to be associated with antioxidative and anti-inflammatory effects as well as the downregulation of NF-κB and TGF-β/Smad signaling, probably via interference of ERK activation and/or enhancement of Nrf2, HO-1, and AMPK activity.

Beneficial effect of quercetin on cholestatic liver injury

Bile duct obstruction and subsequent cholestasis are associated with hepatocellular injury, cholangiocyte proliferation, stellate cell activation, Kupffer cell activation, oxidative stress, inflammation and fibrosis. Flavonoids have been shown to confer beneficial health effects, including hepatoprotection. However, the molecular mechanism of flavonoid-mediated hepatoprotection is incompletely understood. In this study, we report the protective effect of quercetin on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily oral administration of quercetin was started 1 week before injury and lasted for 4 weeks. In comparison with the control group, the BDL group showed liver injury, as evidenced by histological changes, and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation and oxidative stress. These pathophysiological changes were attenuated by daily quercetin supplementation. Quercetin alleviated BDL-induced transforming growth factor beta-1 (TGF-β1), interleukin-1 beta, connective tissue growth factor and collagen expression. The antifibrotic effect of quercetin was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad 2/3 activity critical to the fibrogenic potential of TGF-β1. Quercetin also attenuated BDL-induced oxidative stress, leukocyte accumulation, nuclear factor (NF)-κB activation and proinflammatory cytokine production. Further studies demonstrated an inhibitory effect of quercetin on MyD88 and TGF-β-activated kinase-1 critical for linking toll-like receptor (TLR) and NF-κB. Taken together, the hepatoprotective, anti-inflammatory and antifibrotic effects of quercetin seem to be multifactorial. The beneficial effects of daily quercetin supplementation are associated with antioxidative and anti-inflammatory potential as well as down-regulation of NF-κB and TGF-β/Smad signaling, probably via interference with TLR signaling.

Effects of silymarin and pentoxifylline on matrix metalloproteinase-1 and -2 expression and apoptosis in experimental hepatic fibrosis

BACKGROUND

Many therapeutic strategies have been proposed to treat liver fibrosis, but no drugs have been proved effective. Matrix metalloproteinases (MMPs) have been reported to play a role in some cellular cascades of hepatic inflammation and fibrosis.

OBJECTIVE

The purpose of this study was to investigate whether silymarin and pentoxifylline (PTX) have hepatoprotective and antifibrotic effects in experimental hepatic fibrosis.

METHODS

Sprague-Dawley rats were divided into 4 groups: silymarin group (silymarin 4 mg/kg · d(-1) orally, common bile duct ligation [CBDL]); PTX group (PTX 2 mg/kg · d(-1) intraperitoneally, CBDL); sham group (common bile duct [CBD] exploration only); and control group (saline 1 mL/d orally, CBDL). The CBD was explored and dissected sufficiently to allow passage of a 3/0 silk suture via midline laparotomy. On day 10, all animals were euthanized via cervical dislocation. Then, 5-cm(3) liver samples from the right lobe were removed for histomorphologic evaluation and 3-mL blood samples were taken via cardiac puncture for biochemical analyses. Apoptosis was determined using the terminal deoxynucleotidyltransferase-biotin nick end-label (TUNEL) staining method. Plasma levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyltransferase; total and indirect bilirubin concentration; hepatic MMP-1 and -2 and tissue inhibitor of MMP (TIMP)-l and -2 activity; and transforming-growth factor (TGF)-β1 concentration were measured. Collagen content was determined by measuring hydroxyproline in liver samples. Malondialdehyde (MDA) was used to estimate lipid peroxidation.

RESULTS

Thirty-two adult male Sprague-Dawley rats were divided into 4 groups: silymarin group (n = 7), PTX group (n = 7), sham group (n = 9), and control group (n = 9). Compared with the control group (14.6 [2.44]), mean (SD) hepatocyte apoptosis (as measured by the ratio of TUNEL-positive cells) was significantly suppressed in the silymarin group (1.2 [0.13]; P = 0.001) and the PTX group (3.8 [0.34]; P = 0.001). Mean (SD) MMP-2 activity in the silymarin group (57.35 [9.89] μg/mL; P = 0.04) and the PTX group (46.88 [9.56] μg/mL; P = 0.04) was significantly lower than that observed in the control group (232.32 [79.76] μg/mL). Compared with the control group (1.37 [0.38] μg/mL), TIMP-2 activity was significantly lower in the silymarin group (0.55 [0.13] μg/mL; P = 0.04) and the PTX group (0.42 [0.09] μg/mL; P = 0.01). Compared with the control group (909.17 [117.35] μg/mL), TGF-β1 was significantly lower in the silymarin group (518.24 [30.34] μg/mL; P = 0.01) and the PTX group (519.57 [47.27] μg/mL; P = 0.01). Histomorphologic changes were significantly greater in the sham group than in the silymarin and PTX groups: hemorrhage (2.44 [0.29] vs 1.29 [0.18] and 1.57 [0.20], respectively; both, P = 0.04); sinusoidal dilatation (2.22 [0.22] vs 1.57 [0.20] and 1.71 [0.18]; both, P = 0.04); presinusoidal polymorphonuclear cell infiltration (3-44 [0.24] vs 2.57 [0.20] and 2.14 [0.26]; P = 0.03 and P = 0.008, respectively); and inflammation (3.44 [0.24] vs 2.57 [0.20] and 2.14 [0.26]; P = 0.03 and P = 0.008, respectively). In the control group, all biochemical markers were elevated, supporting the presence of liver injury. Compared with the control group (630.00 [46.80] U/L), plasma AST activity was significantly lower in the silymarin group (443.11 [78.73]; P = 0.04) and the PTX group (349.42 [34.00]; P = 0.03). Compared with the control group (191.12 [32.93] U/L), plasma ALT activity was significantly lower in the silymarin group (86.14 [4.97]; P = 0.04) and the PTX group (84.14 [11.21]; P = 0.04). MDA concentration was significantly lower in the silymarin group compared with the control group (0.08 [0.01] vs 0.22 [0.03] nmol/mL; P = 0.004); MDA was also significantly lower in the silymarin group than in the PTX group (0.11 [0.02]; P = 0.03).

CONCLUSIONS

Silymarin and PTX were associated with lower histopathologic liver damage, hepatocyte apoptosis, and regulation of extracellular matrix proteins. Lipid peroxidation in hepatocytes was significantly lower in the silymarin group compared with the PTX group. Silymarin and PTX appeared to have hepatoprotective effects in this experimental liver fibrosis model, but further clinical and experimental studies are needed.

MiR-29b inhibits collagen maturation in hepatic stellate cells through down-regulating the expression of HSP47 and lysyl oxidase

Altered expression of miR-29b is implicated in the pathogenesis and progression of liver fibrosis. We and others previously demonstrated that miR-29b down-regulates the expression of several extracellular-matrix (ECM) genes including Col 1A1, Col 3A1 and Elastin via directly targeting their 3'-UTRs. However, whether or not miR-29b plays a role in the post-translational regulation of ECM biosynthesis has not been reported. Heat shock protein 47 (HSP47) and lysyl oxidase (LOX) are known to be essential for ECM maturation. In this study we have demonstrated that expression of HSP47 and LOX was significantly up-regulated in culture-activated primary rat hepatic stellate cells (HSCs), TGF-β stimulated LX-2 cells and liver tissue of CCl4-treated mice, which was accompanied by a decrease of miR-29b level. In addition, over-expression of miR-29b in LX-2 cells resulted in significant inhibition on HSP47 and LOX expression. Mechanistically, miR-29b inhibited the expression of a reporter gene that contains the respective full-length 3'-UTR from HSP47 and LOX gene, and this inhibitory effect was abolished by the deletion of a putative miR-29b targeting sequence from the 3'-UTRs. Transfection of LX-2 cells with miR-29b led to abnormal collagen structure as shown by electron-microscopy, presumably through down-regulation of the expression of molecules involved in ECM maturation including HSP47 and LOX. These results demonstrated that miR-29b is involved in regulating the post-translational processing of ECM and fibril formation.

The antihepatic fibrotic effects of fluorofenidone via MAPK signalling pathways

BACKGROUND

Fluorofenidone (AKF-PD) is a novel pyridone agent. The purpose of this study is to investigate the inhibitory effects of AKF-PD on dimethylnitrosamine (DMN)-induced liver fibrosis in rats and the involved molecular mechanism related to hepatic stellate cells (HSCs).

MATERIALS AND METHODS

Wistar rats were randomly divided into normal control, DMN, DMN/AKF-PD treatment and DMN/pirfenidone (PFD) treatment groups. AKF-PD and PFD treatments were, respectively, performed for two activated HSCs lines, rat CFSC-2G and human LX2. The cell proliferation was analysed by MTT. The expression of collagen I was determined by immunohistochemical staining and real-time RT-PCR. The expression of α-smooth muscle actin (α-SMA), tissue inhibitor of metalloproteinases-1 (TIMP-1), extracellular signal regulated kinase (ERK1/2), p38 MAPK (p38), and c-Jun N-terminal kinase/stress-activated protein kinase (JNK) were also detected by real-time RT-PCR and/or Western blot.

RESULTS

AKF-PD significantly reduced PDGF-BB-induced proliferation and activation of HSCs, as determined by reducing protein expression of α-SMA and TIMP-1. AKF-PD treatment attenuated PDGF-BB-induced upregulation of phosphorylation of ERK1/2, p38 and JNK. In fibrotic rat liver, AKF-PD reduced the degree of liver injury and hepatic fibrosis, which was associated with reduced the expression of collagen I, α-SMA, TIMP-1 at both mRNA and protein levels.

CONCLUSION

AKF-PD treatment inhibits the progression of hepatic fibrosis by suppressing HSCs proliferation and activation via MAPK signalling pathway.

miR-122 regulates collagen production via targeting hepatic stellate cells and suppressing P4HA1 expression

BACKGROUND & AIMS

MicroRNAs (miRNAs) have been shown to be involved in many biological processes by affecting their target gene expression. miR-122 has been extensively studied in hepatocarcinogenesis. However, the role of miR-122 in liver fibrosis remains unknown.

METHODS

The mRNA expression levels of miR-122, prolyl 4-hydroxylase subunit alpha-1 (P4HA1), and CCAAT/enhancer binding protein alpha (C/EBPα) were assessed by real-time PCR. The protein expression levels of P4HA1, C/EBPα and collagen, type I, alpha 1 (COL1A1) were analyzed by Western blot and immunofluorescence. MTT assay was used to assess cell proliferation. Chromatin immunoprecipitation (ChIP) assay was used to examine the binding activity of C/EBPα to miR-122 promoter.

RESULTS

miR-122 expression was significantly reduced in transactivated HSCs and in the livers of mice treated with CCl(4). Overexpression of miR-122 inhibited the proliferation of LX2 cells. We also demonstrated that P4HA1 was a target gene of miR-122. The mRNA expression level of PAHA1 inversely correlated with that of miR-122 in HSCs and in the mouse liver. Overexpression of miR-122 markedly attenuated the expression of P4HA1 via targeting a binding site located at 3'-UTR of P4HA1 mRNA. We further showed that miR-122 overexpression led to decreased collagen maturation and ECM production. Finally, the binding activity of C/EBPα to miR-122 promoter was significantly decreased in activated HSCs.

CONCLUSIONS

Our study suggests that miR-122 may play an important role in negatively regulating collagen production in HSCs and that targeted expression of miR-122 in HSCs may represent a new strategy for the treatment of liver fibrosis.

DNA methylation: new therapeutic implications for hepatic fibrosis

DNA methylation refers to a heritable alteration in the pattern of gene expression that is regulated by a mechanism specifically not owing to changes in the primary nucleotide sequence. The transcriptional silencing caused by DNA methylation affects genes involved in the main cellular pathways: cell cycle control, Ras signaling, apoptosis, and detoxification. Recent studies have shown that methylation modifications orchestrate the activation of hepatic stellate cells (HSCs) characterized by excessive accumulation of extracellular matrices (ECMs). The activation of HSCs is mediated by multiple signal transduction pathways and is generally regarded as the major ECM producer responsible for liver fibrosis. In addition, aberrant methylation of specific gene involved in the activation of multiple signal transduction pathways in liver fibrosis. The aim of this review is to compile recent information on aberrant DNA methylation in hepatic fibrosis and to highlight key genes and molecular pathways in hepatic fibrosis formation.

DNMT1-mediated PTEN hypermethylation confers hepatic stellate cell activation and liver fibrogenesis in rats

Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is a negative regulator of this process. PTEN promoter hypermethylation is a major epigenetic silencing mechanism in tumors. The present study aimed to investigate whether PTEN promoter methylation was involved in HSC activation and liver fibrosis. Treatment of activated HSCs with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-azadC) decreased aberrant hypermethylation of the PTEN gene promoter and prevented the loss of PTEN expression that occurred during HSC activation. Silencing DNA methyltransferase 1 (DNMT1) gene also decreased the PTEN gene promoter methylation and upregulated the PTEN gene expression in activated HSC-T6 cells. In addition, knockdown of DNMT1 inhibited the activation of both ERK and AKT pathways in HSC-T6 cells. These results suggest that DNMT1-mediated PTEN hypermethylation caused the loss of PTEN expression, followed by the activation of the PI3K/AKT and ERK pathways, resulting in HSC activation.

The anti-fibrotic effect of betulinic acid is mediated through the inhibition of NF-κB nuclear protein translocation

The purpose of the study was to investigate the anti-fibrotic effect and the potential mechanisms of action of betulinic acid (BA) against hepatic fibrosis in vivo and in vitro. BA is an active compound isolated from the bark of the birch tree Betula spp. (Betulaceae). Liver fibrosis was induced by intraperitoneal injections of thioacetamide (TAA, 200mg/kg) twice weekly for 6weeks in Wistar rats. The administration of BA (20 or 50mg/kg) was started following TAA injections and was continued for 6 or 8weeks to evaluate both the preventive and the protective effects. BA demonstrated great efficacy in preventing and curing hepatic fibrosis via attenuating the TAA-mediated increases in liver tissue hydroxyproline and α-smooth muscle actin (α-SMA). In vitro, BA effectively decreased the HSC-T6 cell viability induced by TNF-α and showed low toxicity in normal human chang liver cells. Moreover, BA significantly attenuated the expression of α-SMA and tissue inhibitor of metalloproteinase-1 (TIMP-1) and increased the levels of matrix metalloprotease (MMP)-13. BA also inhibited the expression of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and the activation of nuclear factor-κB (NF-κB) in a time-dependent manner. This study provides evidence that BA exerts a significant anti-fibrosis effect by modulating the TLR4/MyD88/NF-κB signaling pathway.

Non-alcoholic fatty liver disease: is iron relevant?

Non-alcoholic fatty liver disease (NAFLD) is a common and ubiquitous disorder (Bedogni et al. in Hepatology 42:44-52, 2005; Bellentani et al. in Ann Intern Med 132:112-117, 2000) which in a proportion of subjects leads to non-alcoholic steatohepatitis (NASH), advanced liver disease and hepatocellular carcinoma. Although the factors responsible for progression of disease are still uncertain, there is evidence that insulin resistance (IR) is a key operative mechanism (Angulo et al. in Hepatology 30:1356-1362, 1999) and that two stages are involved. The first is the accumulation of triglycerides in hepatocytes followed by a "second hit" which promotes cellular oxidative stress. Several factors may be responsible for the induction of oxidative stress but hepatic iron has been implicated in various studies. The topic is controversial, however, with early studies showing an association between hepatic iron (with or without hemochromatosis gene mutations) and the progression to hepatic fibrosis. Subsequent studies, however, could not confirm an association between the presence of hepatic iron and any of the histological determinants of NAFLD or NASH. Recent studies have reactivated interest in this subject firstly, with the demonstration that hepatic iron loading increases liver cholesterol synthesis with increased lipid deposition in the liver increasing the cellular lipid burden and secondly, a large clinical study has concluded that hepatocellular iron deposition is associated with an increased risk of hepatic fibrosis, thus, strongly supporting the original observation made over a decade ago. An improvement in insulin sensitivity has been demonstrated following phlebotomy therapy but a suitably powered controlled clinical trial is required before this treatment can be implemented.

Beneficial effect of docosahexaenoic acid on cholestatic liver injury in rats

Bile duct obstruction and subsequent cholestasis are associated with hepatocellular injury, cholangiocyte proliferation, stellate cell activation, Kupffer cell activation, oxidative stress, inflammation and fibrosis. Docosahexaenoic acid (DHA) is an essential polyunsaturated fatty acid that has been shown to possess health beneficial effects, including hepatoprotection. However, the molecular mechanism of DHA-mediated hepatoprotection is not fully understood. In the present study, we report the protective effect of DHA on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily administration of DHA was started 2 weeks before injury and lasted for 5 weeks. In comparison with the control group, the BDL group showed hepatic damage as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation and oxidative stress. These pathophysiological changes were attenuated by chronic DHA supplementation. DHA alleviated BDL-induced transforming growth factor beta-1 (TGF-β1), intereukin-1beta, connective tissue growth factor and collagen expression. The anti-fibrotic effect of DHA was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad 2/3 activity critical to the fibrogenic potential of TGF-β1. DHA also attenuated BDL-induced leukocyte accumulation and nuclear factor-κB (NF-κB) activation. Further studies demonstrated an inhibitory effect of DHA on redox-sensitive intracellular signaling molecule extracellular signal-regulated kinase (ERK). Taken together, the hepatoprotective, anti-inflammatory and anti-fibrotic effects of DHA seem to be multifactorial. The beneficial effects of chronic DHA supplementation are associated with anti-oxidative and anti-inflammatory potential as well as down-regulation of NF-κB and transforming growth factor beta/Smad signaling probably via interference with ERK activation.

Preventive effects of a fractioned polysaccharide from a traditional Chinese herbal medical formula (Yu Ping Feng San) on carbon tetrachloride-induced hepatic fibrosis

OBJECTIVES

The study was to investigate the prevention effects and possible mechanism of Yu Ping Feng San fractioned polysaccharide (YPF-P) on CCl(4)-induced liver fibrosis in rats.

METHODS

YPF-P was prepared from root of Astragalus membranaceus, rhizome of Atractylodes macrocephaia and root of Raidix saposhnikoviae, and compared with polysaccharide from root of Astragalus membranaceus (AP). Hepatic fibrosis was induced by subcutaneous injection with carbon tetrachloride twice weekly for 12 weeks in Sprague-Dawley rats. YPF-P, AP and colchicine were administered intragastrically daily to carbon tetrachloride-treated rats. Histopathological changes of the liver and hepatic stellate cells were evaluated by Masson staining and transmission electron microscopy, respectively. Markers of fibrosis were determined by radioimmunoassay, biochemistry assay and ELISA. The mRNA expressions of tissue inhibitor of metalloproteinase-1 (TIMP-1), matrix metalloproteinase-13 (MMP-13), procollagen I and collagen III were detected by RT-PCR.

KEY FINDINGS

YPF-P dose-dependently alleviated the degree of liver fibrosis and inhibited hepatic stellate cell transformation into myofibroblast-like cells, markedly reduced the elevated levels of hyaluronic acid, laminin, type IV collagen, type III procollagen, hydroxyproline and transforming growth factor beta-1, suppressed procollagen I, collagen III and TIMP-1 expression, and improved the TIMP-1/MMP-13 ratio. MMP-13 expression was only promoted moderately by YPF-P. Compared with AP, YPF-P showed more potency on most markers except laminin, type IV collagen and MMP-13 mRNA.

CONCLUSIONS

YPF-P prevented the progress of rat liver fibrosis induced by carbon tetrachloride and had a more potent preventative effect. The preventative effect may be associated with the ability of YPF-P to inhibit the synthesis of matrix collagen and balance the TIMP/MMP system.

Protective effects of Phyllanthus amarus on fibrotic markers during alcohol and polyunsaturated fatty acid-induced toxicity

Alcoholic liver disease (ALD) remains a major problem, with significant morbidity and mortality worldwide. One of the serious consequences of ALD is hepatic fibrosis. This happens when the matrix synthesis rate exceeds that of matrix degradation. Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) play a key role in matrix remodeling. Disruption of MMP/TIMP balance can lead to excessive accumulation of extracellular matrix components resulting in severe liver injury. The focus of the present study is to analyze the effect of Phyllanthus amarus on MMP and TIMPs activity in alcohol and thermally oxidized polyunsaturated fatty acid (PUFA)-induced hepatic fibrosis. Male albino Wistar rats were used for the study. The matrix metalloproteinase expression was found to be significantly decreased and the levels of TIMPs and the collagen were significantly increased in alcohol + thermally oxidized PUFA-treated rats. Administration of Phyllanthus amarus extract significantly decreased the levels of collagen and TIMPs; and positively modulated the expression of MMPs. From this study, we conclude that Phyllanthus amarus effectively modifies alcohol + thermally oxidized PUFA-induced fibrosis.

Liver immunolocalization and plasma levels of MMP-9 in non-alcoholic steatohepatitis (NASH) and hepatitis C infection

Non-alcoholic steatohepatitis (NASH) is a progressive fibrotic disease. Many issues related to the pathogenesis of this disease remain unresolved. Because of NASH association with the activation of liver fibrogenesis, we examined the plasma levels and liver immunolocalization of matrix metalloprotease-9 (MMP-9), a molecule involved in the remodelling processes of fibrogenesis. In addition, patients with chronic hepatitis C (HCV) were analyzed. Plasma concentrations of MMP-9 were determined by ELISA from peripheral blood and immunohistochemistry of the same protein was carried out in formalin-fixed and paraffin wax-embedded liver specimens. The mean value of circulating concentrations of MMP-9 in healthy controls was 39.7 ng/ml (SD: +/-4.6). In NASH and HCV-infected patients, MMP-9 concentrations were higher: 69.0 ng/ml (SD: +/-14.5) and 61.7 ng/ml (SD: +/-11.0), respectively. In NASH livers, MMP-9 was mainly immunolocalized on neutrophils, whereas in HVC-infected livers it was mainly localized over biliary canaliculi, bile ducts and hepatocyte cytoplasm. The different MMP-9 immunolocalization patterns in the examined diseases suggest the presence of a different pathophysiological involvement of this protease in the fibrogenesis underlying these diseases.

Mechanisms underlying the therapeutic effect of Huangqi Decoction against dimethylnitrosamine-induced liver fibrosis in rats

AIM: To investigate the mechanisms underlying the therapeutic effect of Huangqi Decoction against dimethylnitrosamine (DMN)-induced liver fibrosis in rats.

METHODS: Liver fibrosis was induced in rats by intraperitoneal injection of DMN for 4 wk. Rats were randomly divided into two groups: normal group and model group. Fibrotic rats in the model group were further randomly divided into two subgroups: model control subgroup and Huangqi Decoction subgroup. The Huangqi Decoction subgroup was intragastrically administered Huangqi Decoction for 2 wk, while the model control subgroup was administered equal volume of saline. At the end of 2, 4 and 6 wk, hepatic tissue samples were collected to detect the protein expression of Fas, caspase-8, caspase-3, matrix metallopeptidase-9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1) and TIMP-2 by Western blot, mRNA expression of α-SMA by real time-PCR, and MMP-2 and MMP-9 activity by gelatin enzymography.

RESULTS: Compared with the normal group, the expression levels of Fas, caspase-8, caspase-3, TIMP-1 and TIMP-2 proteins and α-SMA mRNA as well as MMP-2 and MMP-9 activity in liver tissue increased gradually in the model group and peaked at 4 wk. Compared with the model control subgroup, the expression levels of Fas, caspase-8, caspase-3, TIMP-1 and TIMP-2 proteins and α-SMA mRNA as well as MMP-2 activity at 6 wk were significantly reduced (1.05 ± 0.02 vs 1.17 ± 0.04, 1.41 ± 0.04 vs 1.98 ± 0.06, 0.86 ± 0.01 vs 1.19±0.04, 1.03 ± 0.03 vs 1.58 ± 0.06, 1.16 ± 0.04 vs 1.53 ± 0.01, 3.12 ± 0.47 vs 8.48 ± 0.45 and 2.15 ± 0.03 vs 2.33 ± 0.05, respectively; all P < 0.05 or 0.01), and MMP-9 protein expression and activity were significantly increased (1.21 ± 0.00 vs 1.12 ± 0.01 and 1.25 ± 0.07 vs 1.10 ± 0.04, respectively; both P < 0.05 or 0.01) in liver tissue in the Huangqi Decoction subgroup.

CONCLUSION: Huangqi Decoction exerts significant anti-fibrotic effects perhaps by inhibiting hepatic cell apoptosis and hepatic stellate cell (HSC) activation, modulating the MMPs/TIMPs system, and promoting extracellular matrix (ECM) degradation.

Hepatoprotective role of bis-demethoxy curcumin analog on the expression of matrix metalloproteinase induced by alcohol and polyunsaturated fatty acid in rats

Liver fibrosis is one of the major health problems worldwide. Chronic alcohol abuse is one of the main causes of fibrosis. Ingestion of polyunsaturated fatty acids (PUFA) along with alcohol further aggravates the toxicity of alcohol. Fibrosis results due to increased deposition of extra cellular matrix (ECM). The degree of abnormal ECM degradation depends on the ratio of active matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). The present work studied the influence of bis-desmethoxy curcumin analog (BDMC-A) on the expression of MMPs and TIMPs during alcohol and DeltaPUFA induced liver toxicity. Male albino Wistar rats were used for the study. The MMP expression was found to be increased in alcohol as well as DeltaPUFA treated rats and decreased in alcohol + DeltaPUFA treated rats. The levels of TIMPs and the collagen were increased in alcohol, DeltaPUFA, and alcohol + DeltaPUFA groups. Administration of BDMC-A significantly decreased the levels of collagen and TIMPs; and positively modulated the expression of MMPs. From this study, it is concluded that BDMC-A influences MMPs, TIMPs expression, and acts as an efficient anti-fibrotic agent.

The impact of Schistosoma japonicum infection and treatment on ultrasound-detectable morbidity: a five-year cohort study in Southwest China

BACKGROUND

Ultrasonography allows for non-invasive examination of the liver and spleen and can further our understanding of schistosomiasis morbidity.

METHODOLOGY/PRINCIPAL FINDINGS

We followed 578 people in Southwest China for up to five years. Participants were tested for Schistosoma japonicum infection in stool and seven standard measures of the liver and spleen were obtained using ultrasound to evaluate the relationship between schistosomiasis infection and ultrasound-detectable pathology, and the impact of targeted treatment on morbidity. Parenchymal fibrosis, a network pattern of the liver unique to S. japonicum, was associated with infection at the time of ultrasound (OR 1.40, 95% CI: 1.03-1.90) and infection intensity (test for trend, p = 0.002), adjusting for age, sex and year, and more strongly associated with prior infection status and intensity (adjusted OR 1.84, 95% CI: 1.30-2.60; test for trend: p<0.001 respectively), despite prompt treatment of infections. While declines in parenchymal fibrosis over time were statistically significant, only 28% of individuals with severe parenchymal fibrosis (grades 2 or 3) at enrollment reversed to normal or grade 1 within five years. Other liver abnormalities were less consistently associated with S. japonicum infection.

CONCLUSIONS/SIGNIFICANCE

Parenchymal fibrosis is an appropriate measure of S. japonicum morbidity and can document reductions in disease following control efforts. Other ultrasound measures may have limited epidemiological value in regions with similar infection levels. Because severe fibrosis may not reverse quickly following treatment, efforts to reduce exposure to S. japonicum should be considered in combination with treatment to prevent schistosomiasis morbidity.

Hepatic stellate cell activation and hepatic fibrosis in children with type 1 autoimmune hepatitis: an immunohistochemical study of paired liver biopsies before treatment and after clinical remission

OBJECTIVES

The activation of hepatic stellate cells (HSC) is considered the most important event in hepatic fibrogenesis. The precise mechanism of this process is unknown in autoimmune hepatitis (AIH), and more evidence is needed on the evolution of fibrosis. The aim of this study was to assess these aspects in children with type 1 AIH.

METHODS

We analyzed 16 liver biopsy samples from eight patients, paired before treatment and after clinical remission, performed an immunohistochemical study with anti-alpha actin smooth muscle antibody and graded fibrosis and inflammation on a scale of 0-4 (Batts and Ludwig scoring system).

RESULTS

There was no significant reduction in fibrosis scores after 24+/-18 months (2.5+/-0.93 vs. 2.0+/-0.53, P=0.2012). There was an important decrease in inflammation: portal (2.6+/-0.74 vs. 1.3+/-0.89, P=0.0277), periportal/periseptal (3.0+/-0.76 vs. 1.4+/-1.06, P=0.0277), and lobular (2.8+/-1.04 vs. 0.9+/-0.99, P=0.0179). Anti-alpha actin smooth muscle antibodies were expressed in the HSC of the initial biopsies (3491.93+/-2051.48 mum), showing a significant reduction after remission (377.91+/-439.47 microm) (P=0.0117).

CONCLUSION

HSC activation was demonstrated in the AIH of children. The reduction of this activation after clinical remission, which may precede a decrease in fibrosis, opens important perspectives in the follow-up of AIH.

Effects of chelerythine on hepatic TGF-β1 and α-SMA expression in rats with hepatic fibrosis

AIM: To study the effects of chelerythine on TGF-β1 and α-SMA expression of CCl₄ -induced hepatic fibrosis in rats.

METHODS: Models of hepatic fibrosis were established by hypodermic injection of tetrachloride, in combination with the control of nutrition and the drinking of 100 mL/L alcohol to rats. According to histological sections, hepatic fibrosis in rats emerged at the end of the fourth week. Subsequently different doses of chelerythine were used of hepatic fibrosis in rats. In addition, normal control group, fibrotic model group, γ-interform group in experiment was arranged. At the end of the eighth week, all the rats were executed. Transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) in liver were examined with the immunohistochemistrical technique.

RESULTS: The expression of TGF-β1 and α-SMA in liver of rats in fibrotic model group induced by CCl₄ were ameliorated significantly compared with the model group (TGF-β1: 6.08 ± 2.35, 4.31 ± 2.10, 4.7 ± 1.70 vs 9.33 ± 3.08; α-SMA: 3.75 ± 1.76, 3.23 ± 1.42, 3.20 ± 1.17 vs 6.67 ± 2.29, all P < 0.01). The expression of TGF-β1 and α-SMA in liver was not obviously different between all chelerythine groups and γ-INF group (4.23 ± 2.24, 3.38 ± 1.39, both P > 0.05).

CONCLUSION: Chelerythine can decrease the expression of TGF-β1 as well as α-SMA CCl4 -induced hepatic fibrosis in rats.

A novel function of thrombin-activatable fibrinolysis inhibitor during rat liver regeneration and in growth-promoted hepatocytes in primary culture

Thrombin-activatable fibrinolysis inhibitor (TAFI) exhibits anti-fibrinolytic activity by removing C-terminal lysine residues from fibrin or plasminogen receptor proteins on the cellular surface, and plays an important role in the regulation of fibrinolysis. In this study, we examined the regulation of TAFI in hepatocytes during liver regeneration, and revealed its pivotal role in hepatocyte proliferation. In rat models, partial hepatectomy or carbon tetrachloride (CCl4)-induced acute liver injury suppressed the levels of plasma TAFI activity and hepatic TAFI mRNA, whereas this operation markedly increased both the hepatic plasmin activity and the level of proliferating cell nuclear antigen. In primary cultures of rat hepatocytes, the TAFI mRNA level was decreased under growth-promoting culture conditions. Treatment of the hepatocytes with TAFI siRNA increased the amount of plasmin on the hepatocytes and promoted hepatocyte proliferation. We concluded that TAFI regulates plasmin activity through its enzymatic activity whereby it reduces the plasminogen-binding capacity of the hepatocytes. The TAFI gene expression is down-regulated in hepatocyte proliferation for producing a fibrinolytic microenvironment suitable for cell growth. This is the first report on the role of TAFI in the pericellular fibrinolysis necessary for cellular proliferation.

Regression of fibrosis in paediatric autoimmune hepatitis: morphometric assessment of fibrosis versus semiquantiatative methods

Background

Regression of hepatic fibrosis in patients with autoimmune hepatitis (AIH) has been described in response to immunosuppressive therapy. These studies, however, besides being few in number, were conducted on adult populations. Our aim was to assess the regression of hepatic fibrosis, using morphometric assessment of fibrosis versus semi-quantitative methods, in children with AIH who achieved clinical and biochemical remission. Thirteen patients who achieved clinical and biochemical remission were included in the study, out of 62 children with AIH. Repeat biopsy was performed after 6 to 12 months of clinical and biochemical remission. Morphometric assessment of fibrosis was performed and correlated with METAVIR and Ishak semi-quantitative scores.

Results

The study group included eight male and five female patients. The median age at presentation was 4 years (range 2 to 12 years). The mean duration of treatment was 22 ± 7.3 months, and the mean interval between biopsies was 26.2 ± 6.5 months. Following therapy, there was significant reduction in aspartate aminotransferase, ALT and IgG levels as well as improvement of necroinflammation. The mean fibrosis scores were significantly decreased from 4.5 ± 1.19 and 2.9 ± 0.7 before therapy to 2.7 ± 1.16 and 2 ± 0.8 after treatment as assessed by Ishak and METAVIR scores, respectively (P = 0.001 and 0.004). The mean morphometric assessment of fibrosis before treatment was 20% ± 9.7 and following therapy it decreased to 5.6% ± 3.9 (P = 0.000).

Conclusion

Significant regression of fibrosis in paediatric AIH could occur with current therapeutic regimens. Morphometric assessment of fibrosis is more sensitive than semi-quantitative methods to identify changes in fibrosis.

Hepatic sinusoidal cells in health and disease: update from the 14th International Symposium

This review aims to give an update of the field of the hepatic sinusoid, supported by references to presentations given at the 14th International Symposium on Cells of the Hepatic Sinusoid (ISCHS2008), which was held in Tromsø, Norway, August 31-September 4, 2008. The subtitle of the symposium, 'Integrating basic and clinical hepatology', signified the inclusion of both basal and applied clinical results of importance in the field of liver sinusoidal physiology and pathophysiology. Of nearly 50 oral presentations, nine were invited tutorial lectures. The authors of the review have avoided writing a 'flat summary' of the presentations given at ISCHS2008, and instead focused on important novel information. The tutorial presentations have served as a particularly important basis in the preparation of this update. In this review, we have also included references to recent literature that may not have been covered by the ISCHS2008 programme. The sections of this review reflect the scientific programme of the symposium (http://www.ub.uit.no/munin/bitstream/10037/1654/1/book.pdf): 1. Liver sinusoidal endothelial cells. 2. Kupffer cells. 3. Hepatic stellate cells. 4. Immunology. 5. Tumor/metastasis. Symposium abstracts are referred to by a number preceded by the letter A.

Detection of novel biomarkers of liver cirrhosis by proteomic analysis

Hepatic cirrhosis is a life-threatening disease arising from different chronic liver disorders. One major cause for hepatic cirrhosis is chronic hepatitis C. Chronic hepatitis C is characterized by a highly variable clinical course, with at least 20% developing liver cirrhosis within 40 years. Only liver biopsy allows a reliable evaluation of the course of hepatitis C by grading inflammation and staging fibrosis, and thus serum biomarkers for hepatic fibrosis with high sensitivity and specificity are needed. To identify new candidate biomarkers for hepatic fibrosis, we performed a proteomic approach of microdissected cirrhotic septa and liver parenchyma cells. In cirrhotic septa, we detected an increasing expression of cell structure associated proteins, including actin, prolyl 4-hydroxylase, tropomyosin, calponin, transgelin, and human microfibril-associated protein 4 (MFAP-4). Tropomyosin, calponin, and transgelin reflect a contribution of activated stellate cells/myofibroblasts to chronic liver injury. The expression of tropomyosin, transgelin, and MFAP-4, an extracellular matrix associated protein, were further evaluated by immunohistochemistry. Tropomyosin and MFAP-4 demonstrated high serum levels in patients with hepatic cirrhosis of different causes.

CONCLUSION

A quantitative analysis of MFAP-4 serum levels in a large number of patients showed MFAP-4 as novel candidate biomarker with high diagnostic accuracy for prediction of nondiseased liver versus cirrhosis [area under receiver operating characteristic curve (AUC) = 0.97, P < 0.0001] as well as stage 0 versus stage 4 fibrosis (AUC = 0.84, P < 0.0001), and stages 0 to 3 versus stage 4 fibrosis (AUC = 0.76, P < 0.0001).