Molecular mechanisms of liver fibrogenesis--a homage to the role of activated fat-storing cells

Liver fibrosis: pathological features, clinical treatment and application of therapeutic nanoagents

Liver fibrosis is a reversible damage-repair response, the pathological features of which mainly include damage to hepatocytes, sinusoid capillarization, hepatic stellate cells activation, excessive accumulation of extracellular matrix and inflammatory response. Although some treatments (including drugs and stem cell therapy) for these pathological features have been shown to be effective, more clinical trials are needed to confirm their effectiveness. In recent years, nanomaterials-based therapies have emerged as an innovative and promising alternative to traditional drugs, being explored for the treatment of liver fibrosis diseases. Natural nanomaterials (including extracellular vesicles) and synthetic nanomaterials (including inorganic nanomaterials and organic nanomaterials) are developed to facilitate drug targeting delivery and combination therapy. In this review, the pathological features of liver fibrosis and the current anti-fibrosis drugs in clinical trials are briefly introduced, followed by a detailed introduction of the therapeutic nanoagents for the precise delivery of anti-fibrosis drugs. Finally, the future development trend in this field is discussed.

Molecular Mechanisms of Colorectal Liver Metastases

The liver is the most frequently target for metastasis among patients with colorectal cancer mainly because of the portal vein circulation that directly connects the colon and rectum with the liver. The liver tumor microenvironment consists of different cell types each with unique characteristics and functions that modulate the antigen recognition and immune system activation. Primary tumors from other sites "prime" the liver prior to the seeding of cancer cells, creating a pre-metastatic niche. Following invasion into the liver, four different phases are key to the development of liver metastases: a microvascular phase in which cancer cells infiltrate and become trapped in sinusoidal vessels; an extravascular, pre-angiogenic phase; an angiogenic phase that supplies oxygen and nutrients to cancer cells; and a growth phase in which metastatic cells multiply and enlarge to form detectable tumors. Exosomes carry proteins, lipids, as well as genetic information that can create a pre-metastatic niche in distant sites, including the liver. The complexity of angiogenic mechanisms and the exploitation of the vasculature in situ by cancer cells have limited the efficacy of currently available anti-angiogenic therapies. Delineating the molecular mechanisms implicated in colorectal liver metastases is crucial to understand and predict tumor progression; the development of distant metastases; and resistance to chemotherapy, immunotherapy, and targeted treatment.

Polyherbal mixture ameliorates hyperglycemia, hyperlipidemia and histopathological changes of pancreas, kidney and liver in a rat model of type 1 diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

One of the commonly prescribed 'anti-diabetic' polyherbal mixtures by European herbalists is made of Rubus fruticosus and Vaccinium myrtillus leaves, Potentilla erecta roots, Geum urbanum aerial parts and Phaseolus vulgaris pods.

AIM OF THE STUDY

This study aimed to evaluate the phytochemical composition, antioxidant capacity, potential toxicity, hypoglycemic, hypolipidemic, nephroprotective and hepatoprotective activities of this polyherbal mixture decoction.

MATERIALS AND METHODS

The phytochemical composition was evaluated using HPLC-UV. The antioxidant activity was assessed using the DPPH test. Potential toxicity was evaluated using the acute and sub-chronic oral toxicity method. Diabetes was induced in Wistar female rats with a single intraperitoneal injection of alloxan monohydrate (150 mg/kg). The animals whose blood glucose was >20 mmol/L for 14 consecutive days were considered diabetic. For the next 14 days, D-10 and D-20 groups were treated with the polyherbal mixture (10 and 20 g of dry plant material/kg, respectively). I and M were control groups treated with insulin glargine (13 IU/kg) and metformin (150 mg/kg), respectively. Healthy control (HC) and diabetic control (DC) groups were treated with water. The blood glucose level was measured on days 14, 21 and 28. Lipid profile analysis was done on day 28. Pancreas, kidney and liver histopathology was evaluated using the H&E and Masson's trichrome staining. The liver tissue was additionally tested for PAS-positive cells.

RESULTS

The HPLC-UV analysis revealed the presence of quinic, gallic and caftaric acid, arbutin, rutin, trifolin, astragalin, hyperoside, isoquercetin and quercitrin. The antioxidant activity of the extract was higher than the reference's one (p < 0.01). Treatment with the polyherbal mixture (10 and 20 g/kg) has shown no toxic effects. No major decline in blood sugar was recorded in I and M groups compared to the DC one (22.86 ± 2.58, 28.5 ± 0.42 and 27.82 ± 0.9 mmol/L, respectively). The polyherbal mixture lowered the blood glucose level to the normal value (8.64 ± 4.09, 5.26 ± 1.3 and 6.76 ± 1.54 mmol/L in D-10, D-20 and HC groups, respectively). Furthermore, it decreased the levels of total cholesterol, triglycerides, VLDL, LDL, atherogenic and cardiovascular risk indices (p < 0.001) compared to the DC group. In addition, the extract restored histopathological changes of the pancreas, kidneys and liver to the healthy animal level.

CONCLUSION

Treatment with the polyherbal mixture extract was more effective than the standard drugs (insulin and metformin) in the amelioration of hyperglycemia, hyperlipidemia, and histopathological changes of the pancreas, kidney and liver tissue.

Activation of Hepatic Stellate Cells Requires Dissociation of E-Cadherin-Containing Adherens Junctions with Hepatocytes

Hepatic stellate cells (HSCs) are resident mesenchymal cells in the space of Disse interposed between liver sinusoidal endothelial cells and hepatocytes. Thorn-like microprojections, or spines, project out from the cell surface of HSCs, crossing the space of Disse, to establish adherens junctions with neighboring hepatocytes. Although HSC activation is initiated largely from stimulation by adjacent cells, isolated HSCs also activate spontaneously in primary culture on plastic. Therefore, other unknown HSC-initiating factors apart from paracrine stimuli may promote activation. The dissociation of adherens junctions between HSCs and hepatocytes as an activating signal for HSCs was explored, establishing epithelial cadherin (E-cadherin) as an adhesion molecule linking hepatocytes and HSCs. In vivo, following carbon tetrachloride-induced liver injury, HSCs lost their spines and dissociated from adherens junctions in the early stages of injury, and were subsequently activated along with an increase in YAP/TAZ expression. After abrogation of liver injury, HSCs reconstructed their spines and adherens junctions. In vitro, reconstitution of E-cadherin-containing adherens junctions by forced E-cadherin expression quiesced HSCs and suppressed TAZ expression. Additionally, increase of TAZ expression leading to the activation of HSCs by autocrine stimulation of transforming growth factor-β, was revealed as a mechanism of spontaneous activation. Thus, we have uncovered a critical event required for HSC activation through enhanced TAZ-mediated mechanotransduction after the loss of adherens junctions between HSCs and hepatocytes.

CAT1 silencing inhibits TGF-β1-induced mouse hepatic stellate cell activation in vitro and hepatic fibrosis in vivo

Hepatic fibrosis is characterized by abnormal accumulation of extracellular matrix (ECM). Hepatic stellate cells (HSCs) are the primary cells that produce ECM in response to hepatic injury, and transforming growth factor-beta (TGF-β) has been regarded as the central stimulus responsible for HSC-mediated ECM production. In the present study, we attempted to identify a critical factor in HSC activation and the underlying mechanism. By analyzing online microarray expression profiles, we found that the expression of high-affinity cationic amino acid transporter 1 (CAT1) was upregulated in hepatic fibrosis models and activated HSCs. We isolated and identified mouse HSCs (MHSCs) and found that in these cells, CAT1 was most highly upregulated by TGF-β1 stimulation in both time- and dose-dependent manners. In vitro, CAT1 overexpression further enhanced, while CAT1 silencing inhibited, the effect of TGF-β1 in promoting MHSC activation. In vivo, CAT1 silencing significantly improved the hepatic fibrosis induced by both CCl4 and non-alcoholic fatty liver disease (NAFLD). In summary, CAT1 was significantly upregulated in TGF-β1-activated MHSCs and mice with hepatic fibrosis. CAT1 silencing inhibited TGF-β1-induced MHSC activation in vitro and fibrogenic changes in vivo. CAT1 is a promising target for hepatic fibrosis treatment that requites further investigation in human cells and clinical practice.

Hepatic metastasis from colorectal cancer

Colorectal cancer (CRC) is one of the most common cancers in the world. About two third of patients with CRC will develop distant recurrence at some point in time. Liver is the most common site where distant metastasis takes place. While the overall survival (OS) of patients with metastatic CRC was poor about 3 decades ago, there has been tremendous improvement in this area in the recent years. With the advent of effective systemic chemotherapy and biologic agents and better understanding of the biological behaviour of the tumour, aggressive treatment strategies such as metastatectomy of the liver metastases (or lung metastases) are now acceptable. More importantly, it has transformed the way how stage IV CRCs are being managed. From predominantly palliative as the primary aim, a comprehensive multidisciplinary approach is now the mainstay of treatment with very successful outcomes. Combination of systemic therapies with liver resection has been shown to be effective in providing promising survival benefits. In addition, other adjunctive modalities in targeting the liver metastases such as ablation, combining resection and ablation, transarterial chemoembolization, stereotactic body radiotherapy (SBRT), hepatic artery perfusion, etc. have also been demonstrated variable outcome in treating colorectal liver metastasis (CRLM). Very recently, transplant oncologists have also explored using liver transplantation as a treatment modality for unresectable CRLM, which has demonstrated very good long-term survival in well selected cases. The new paradigm in the treatment of metastatic CRC has dawned.

Roles of exosomes in liver metastases: Novel diagnosis and treatment choices

Tumors tend to metastasize to the liver. Premetastatic niche formation is a vital step in liver metastasis. Tumor-derived exosomes can influence premetastatic niche formation from three aspects: vascular leakiness and angiogenesis, recruitment of nonresident cells, and changes in local resident cells. Exosomes from other tissues, such as mesenchymal stem cell-derived exosomes and engineered exosomes, also have therapeutic potential, but further research on these exosomes is required. Based on the mechanism of premetastatic niche formation, we summarize the therapeutic and diagnostic potential of exosomes in inhibiting liver metastases in this review in an attempt to provide new avenues for the prevention and treatment of liver metastases.

Stromal heterogeneity in pancreatic cancer and chronic pancreatitis

BACKGROUND/OBJECTIVES

An abundant stromal reaction is a hallmark of pancreatic ductal adenocarcinoma (PDAC) and chronic pancreatitis (CP). The cells mainly responsible for the stromal reaction are activated pancreatic stellate cells (PSCs). Despite their crucial role, PSCs are not well characterized. PSCs share characteristics with the better-known hepatic stellate cells (HSCs). The aim of this study was a detailed analysis of PSCs in PDAC and CP.

METHODS

Whole-slide specimens of CP (n = 12) and PDAC (n = 10) were studied by histochemistry and immunohistochemistry. The stroma was evaluated using Movat's pentachrome stain. PSCs were tested by immunohistochemistry for PSC markers (α-SMA, CD34, desmin, NGFR, SPARC and tenascin C) and HSC markers (α-crystallin B, CD56, NGF, NT-3, synaptophysin and TrkC). Alpha-SMA, tenascin C, SPARC and NT-3 staining were verified on tissue micro arrays (TMAs) from a well-characterized cohort of 223 PDAC patients. PSCs isolated from human PDAC and CP tissue samples as well as HSCs were evaluated by immunofluorescence.

RESULTS

While the stroma of CP cases was characterized by a collagen-rich fibrosis, PDAC stroma displayed higher mucin content (p = 0.0002). PSCs showed variable expression of tested markers. In PDAC samples, staining of most markers was found around tumor complexes, while CP samples showed a greater variety of localizations. Alpha-SMA staining correlated with collagen-rich fibrosis (p = 0.012), while NT-3 staining correlated with mucin-rich stroma (p = 0.008). A peritumoral staining was confirmed for α-SMA, tenascin C, SPARC and NT-3 in the PDAC TMA cohort (n = 223). In a subgroup of patients with pancreatic head tumors and UICC 2009 IIB (n = 144), α-SMA staining intensity was a prognostic factor for overall survival at uni- and multivariate analysis (p = 0.036 and p = 0.002).

CONCLUSIONS

The close similarities between PSCs and HSCs were confirmed. Heterogeneous expression patterns of the tested markers might reflect different levels of activation or differentiation, or even multiple subpopulations of PSCs. Survival analysis suggests an impact of stromal composition on survival.

Geraniin Protects High-Fat Diet-Induced Oxidative Stress in Sprague Dawley Rats

Geraniin, a hydrolysable polyphenol derived from Nephelium lappaceum L. fruit rind, has been shown to possess significant antioxidant activity in vitro and recently been recognized for its therapeutic potential in metabolic syndrome. This study investigated its antioxidative strength and protective effects on organs in high-fat diet (HFD)-induced rodents. Rats were fed HFD for 6 weeks to induce obesity, followed by 10 and 50 mg/kg of geraniin supplementation for 4 weeks to assess its protective potential. The control groups were maintained on standard rat chows and HFD for the same period. At the 10th week, oxidative status was assessed and the pancreas, liver, heart and aorta, kidney, and brain of the Sprague Dawley rats were harvested and subjected to pathological studies. HFD rats demonstrated changes in redox balance; increased protein carbonyl content, decreased levels of superoxide dismutase, glutathione peroxidase, and glutathione reductase with a reduction in the non-enzymatic antioxidant mechanisms and total antioxidant capacity, indicating a higher oxidative stress (OS) index. In addition, HFD rats demonstrated significant diet-induced changes particularly in the pancreas. Four-week oral geraniin supplementation, restored the OS observed in the HFD rats. It was able to restore OS biomarkers, serum antioxidants, and the glutathione redox balance (reduced glutathione/oxidized glutathione ratio) to levels comparable with that of the control group, particularly at dosage of 50 mg geraniin. Geraniin was not toxic to the HFD rats but exhibited protection against glucotoxicity and lipotoxicity particularly in the pancreas of the obese rodents. It is suggested that geraniin has the pharmaceutical potential to be developed as a supplement to primary drugs in the treatment of obesity and its pathophysiological sequels.

Molecular Pathways: Targeting the Microenvironment of Liver Metastases

Curative treatment for metastatic solid cancers remains elusive. The liver, which is nourished by a rich blood supply from both the arterial and portal venous systems, is the most common site of visceral metastases, particularly from cancers arising in the gastrointestinal tract, with colorectal cancer being the predominant primary site in Western countries. A mounting body of evidence suggests that the liver microenvironment (LME) provides autocrine and paracrine signals originating from both parenchymal and nonparenchymal cells that collectively create both pre- and prometastatic niches for the development of hepatic metastases. These resident cells and their molecular mediators represent potential therapeutic targets for the prevention and/or treatment of liver metastases (LM). This review summarizes: (i) the current therapeutic options for treating LM, with a particular focus on colorectal cancer LM; (ii) the role of the LME in LM at each of its phases; (iii) potential targets in the LME identified through preclinical and clinical investigations; and (iv) potential therapeutic approaches for targeting elements of the LME before and/or after the onset of LM as the basis for future clinical trials. Clin Cancer Res; 23(21); 6390-9. ©2017 AACR.

Pathophysiology of liver fibrosis and the methodological barriers to the development of anti-fibrogenic agents

Liver fibrosis and cirrhosis resulting from long-standing liver damage represents a major health care burden worldwide. To date, there is no anti-fibrogenic agent available, making liver transplantation the only curative treatment for decompensated cirrhotic liver disease. Liver fibrosis can result from different underlying chronic liver disease, such as chronic viral infection, excessive alcohol consumption, fatty liver disease or autoimmune liver diseases. It is becoming increasingly recognised that as a result from different pathogenic mechanisms liver fibrosis must be considered as many different diseases for which individual treatment strategies need to be developed. Moreover, the pathogenic changes of both liver architecture and vascularisation in cirrhotic livers, as well as the lack of "true-to-life" in vitro models have impeded the development of an effective anti-fibrogenic drug. Thus, in order to identify an efficient anti-fibrogenic compound, novel in-vitro models mimicking the interplay between pro-fibrogenic cell populations, immune cells and, importantly, the extracellular matrix need to be developed.

Pancreatic cancer-derived exosomes promote tumor metastasis and liver pre-metastatic niche formation

Exosomes play important roles in cell-cell communication, and are likely mediators of the metastatic cascade in cancer. This study examined the role of exosomes in pancreatic cancer cell adhesion, migration, and invasion. We isolated and purified exosomes from two isogenic pancreatic cancer cell lines with different metastatic potentials. Uptake of exosomes from highly metastatic Panc02-H7 cells decreased adhesion and increased migration and invasion capacity in weakly metastatic Panc02 cells in vitro. Exosomes from highly metastatic pancreatic cancer cells induced liver pre-metastatic niche formation in naïve mice and promoted primary tumor growth and liver metastasis in vivo. We identified 4,517 proteins in exosomes from Panc02 and Panc02-H7 cells via iTRAQ quantitative proteomic analyses, 79 of which were differentially expressed between the two cell lines. Bioinformatics analyses showed that most of the differentially expressed proteins were involved in pancreatic cancer growth, invasion, and metastasis, and that metabolism-related signaling pathways were involved in exosome-mediated intracellular communication. Further studies will be needed to determine whether these proteins are potential pancreatic cancer diagnostic/prognostic markers or novel therapeutic targets.

The stellate cell system (vitamin A-storing cell system). Anat Sci Int. 2017;92:387-455. [PMID: 28299597 DOI: 10.1007/s12565-017-0395-9]

Past, present, and future research into hepatic stellate cells (HSCs, also called vitamin A-storing cells, lipocytes, interstitial cells, fat-storing cells, or Ito cells) are summarized and discussed in this review. Kupffer discovered black-stained cells in the liver using the gold chloride method and named them stellate cells (Sternzellen in German) in 1876. Wake rediscovered the cells in 1971 using the same gold chloride method and various modern histological techniques including electron microscopy. Between their discovery and rediscovery, HSCs disappeared from the research history. Their identification, the establishment of cell isolation and culture methods, and the development of cellular and molecular biological techniques promoted HSC research after their rediscovery. In mammals, HSCs exist in the space between liver parenchymal cells (PCs) or hepatocytes and liver sinusoidal endothelial cells (LSECs) of the hepatic lobule, and store 50-80% of all vitamin A in the body as retinyl ester in lipid droplets in the cytoplasm. SCs also exist in extrahepatic organs such as pancreas, lung, and kidney. Hepatic (HSCs) and extrahepatic stellate cells (EHSCs) form the stellate cell (SC) system or SC family; the main storage site of vitamin A in the body is HSCs in the liver. In pathological conditions such as liver fibrosis, HSCs lose vitamin A, and synthesize a large amount of extracellular matrix (ECM) components including collagen, proteoglycan, glycosaminoglycan, and adhesive glycoproteins. The morphology of these cells also changes from the star-shaped HSCs to that of fibroblasts or myofibroblasts.

Reversal of liver cirrhosis: current evidence and expectations

In the past, liver cirrhosis was considered an irreversible phenomenon. However, many experimental data have provided evidence of the reversibility of liver fibrosis. Moreover, multiple clinical studies have also shown regression of fibrosis and reversal of cirrhosis on repeated biopsy samples. As various etiologies are associated with liver fibrosis via integrated signaling pathways, a comprehensive understanding of the pathobiology of hepatic fibrogenesis is critical for improving clinical outcomes. Hepatic stellate cells play a central role in hepatic fibrogenesis upon their activation from a quiescent state. Collagen and other extracellular material components from activated hepatic stellate cells are deposited on, and damage, the liver parenchyma and vascular structures. Hence, inactivation of hepatic stellate cells can lead to enhancement of fibrolytic activity and could be a potential target of antifibrotic therapy. In this regard, continued efforts have been made to develop better treatments for underlying liver diseases and antifibrotic agents in multiple clinical and therapeutic trials; the best results may be expected with the integration of such evidence. In this article, we present the underlying mechanisms of fibrosis, current experimental and clinical evidence of the reversibility of liver fibrosis/cirrhosis, and new agents with therapeutic potential for liver fibrosis.

SECs (Sinusoidal Endothelial Cells), Liver Microenvironment, and Fibrosis

Liver fibrosis is a wound-healing response to chronic liver injury such as alcoholic/nonalcoholic fatty liver disease and viral hepatitis with no FDA-approved treatments. Liver fibrosis results in a continual accumulation of extracellular matrix (ECM) proteins and paves the way for replacement of parenchyma with nonfunctional scar tissue. The fibrotic condition results in drastic changes in the local mechanical, chemical, and biological microenvironment of the tissue. Liver parenchyma is supported by an efficient network of vasculature lined by liver sinusoidal endothelial cells (LSECs). These nonparenchymal cells are highly specialized resident endothelial cell type with characteristic morphological and functional features. Alterations in LSECs phenotype including lack of LSEC fenestration, capillarization, and formation of an organized basement membrane have been shown to precede fibrosis and promote hepatic stellate cell activation. Here, we review the interplay of LSECs with the dynamic changes in the fibrotic liver microenvironment such as matrix rigidity, altered ECM protein profile, and cell-cell interactions to provide insight into the pivotal changes in LSEC physiology and the extent to which it mediates the progression of liver fibrosis. Establishing the molecular aspects of LSECs in the light of fibrotic microenvironment is valuable towards development of novel therapeutic and diagnostic targets of liver fibrosis.

Role of the Microenvironment in Liver Metastasis: From Pre- to Prometastatic Niches

Liver metastases remain a major barrier to successful management of malignant disease, particularly for cancers of the gastrointestinal tract but also for other malignancies, such as breast carcinoma and melanoma. The ability of metastatic cells to survive and proliferate in the liver is determined by the outcome of complex, reciprocal interactions between tumor cells and different local resident subpopulations, including the sinusoidal endothelium, stellate, Kupffer, and inflammatory cells that are mediated through cell-cell and cell-extracellular matrix adhesion and the release of soluble factors. Cross-communication between different hepatic resident cells in response to local tissue damage and inflammation and the recruitment of bone marrow cells further enhance this intercellular communication network. Both resident and recruited cells can play opposing roles in the progression of metastasis, and the balance of these divergent effects determines whether the tumor cells will die, proliferate, and colonize the new site or enter a state of dormancy. Moreover, this delicate balance can be tilted in favor of metastasis, if factors produced by the primary tumor precondition the microenvironment to form niches of activated resident cells that promote tumor expansion. This review aims to summarize current knowledge on these diverse interactions and the impact they can have on the clinical management of hepatic metastases. Clin Cancer Res; 22(24); 5971-82. ©2016 AACR.

Distinct Hepatic Macrophage Populations in Lean and Obese Mice

Obesity is a complex metabolic disorder associated with the development of non-communicable diseases such as cirrhosis, non-alcoholic fatty liver disease, and type 2 diabetes. In humans and rodents, obesity promotes hepatic steatosis and inflammation, which leads to increased production of pro-inflammatory cytokines and acute-phase proteins. Liver macrophages (resident as well as recruited) play a significant role in hepatic inflammation and insulin resistance (IR). Interestingly, depletion of hepatic macrophages protects against the development of high-fat-induced steatosis, inflammation, and IR. Kupffer cells (KCs), liver-resident macrophages, are the first-line defense against invading pathogens, clear toxic or immunogenic molecules, and help to maintain the liver in a tolerogenic immune environment. During high fat diet feeding and steatosis, there is an increased number of recruited hepatic macrophages (RHMs) in the liver and activation of KCs to a more inflammatory or M1 state. In this review, we will focus on the role of liver macrophages (KCs and RHMs) during obesity.

Kinetin inhibits proliferation of hepatic stellate cells by interrupting cell cycle and induces apoptosis by down-regulating ratio of Bcl-2/Bax

Liver fibrosis is an important health problem that can further progress into cirrhosis or liver cancer, and result in significant morbidity and mortality. Inhibiting proliferation and inducing apoptosis of hepatic stellate cells (HSCs) may be the key point to reverse liver fibrosis. At present, anti-fibrosis drugs are rare. Kinetin is a type of plant-derived cytokinin which has been reported to control differentiation and induce apoptosis of human cells. In this study, the HSCs were incubated with different concentrations of kinetin. The proliferation of rat HSCs was measured by MTT assay, cell cycle and apoptosis were analyzed by flow cytometry, and the apoptosis was examined by TUNEL method. The expression of Bcl-2 and Bax proteins was detected by immunocytochemistry staining. It was found that kinetin could markedly inhibit proliferation of HSCs. In a concentration range of 2 to 8 μg/mL, the inhibitory effects of kinetin on proliferation of HSCs were increased with the increased concentration and the extension of time (P < 0.01). Flow cytometry indicated that kinetin could inhibit the DNA synthesis from G0/G1 to S phase in a dose-dependent manner (P < 0.01). The apoptosis rates of the HSCs treated with 8, 4 and 2 μg/mL kinetin (25.62% ± 2.21%, 15.31% ± 1.9% and 6.18% ± 1.23%, respectively) were increased significantly compared with the control group (3.81% ± 0.93%) (P < 0.01). All the DNA frequency histogram in kinetin-treated groups showed obvious hypodiploid peak (sub-G1 peak), and with the increase of kinetin concentrations, the apoptosis rate of HSCs also showed a trend of increase. It was also found that kinetin could down-regulate the expression of Bcl-2, and up-regulate the expression of Bax, leading to the decreased ratio of Bcl-2/Bax significantly. The kinetin-induced apoptosis of HSCs was positively correlated with the expression of Bax, and negatively with the expression of Bcl-2. It was concluded that kinetin can inhibit activation and proliferation of HSCs by interrupting the cell cycle at G1/S restriction point and inducing apoptosis of HSCs via reducing the ratio of Bcl-2/Bax.

Human liver myofibroblasts during development and diseases with a focus on portal (myo)fibroblasts

Myofibroblasts are stromal cells mainly involved in tissue repair. These cells present contractile properties and play a major role in extracellular matrix deposition and remodeling. In liver, myofibroblasts are found in two critical situations. First, during fetal liver development, especially in portal tracts, myofibroblasts surround vessels and bile ducts during their maturation. After complete development of the liver, myofibroblasts disappear and are replaced in portal tracts by portal fibroblasts. Second, during liver injury, myofibroblasts re-appear principally deriving from the activation of local stromal cells such as portal fibroblasts and hepatic stellate cells or can sometimes emerge by an epithelial-mesenchymal transition process. After acute injury, myofibroblasts play also a major role during liver regeneration. While myofibroblastic precursor cells are well known, the spectrum of activation and the fate of myofibroblasts during disease evolution are not fully understood. Some data are in accordance with a possible deactivation, at least partial, or a disappearance by apoptosis. Despite these shadows, liver is definitively a pertinent model showing that myofibroblasts are pivotal cells for extracellular matrix control during morphogenesis, repair and fibrous scarring.

PDGF-D signaling in portal myofibroblasts and hepatic stellate cells proves identical to PDGF-B via both PDGF receptor type α and β

Platelet-derived growth factor-D (PDGF-D) is one member of PDGF growth factors and known to signal by binding to and activating its cognate receptor type β (PDGFR-β). Beside PDGF-B, PDGF-D is a potent growth factor for stellate cell growth and proliferation and therefore potentiates the extracellular matrix deposition in liver fibrogenesis. We aimed to explore the signaling and molecular mechanisms of PDGF-D in liver fibrogenesis using the primary liver portal myofibroblasts and hepatic stellate cells. Unexpectedly we found PDGF-D to bind to PDGFR-α, thus inducing receptor endocytosis and decreasing the amount of PDGFR-α significantly. PDGF-D activates PDGFR-α specific tyrosine 754 and -1018 phosphorylation and CrkII, the adaptor protein that is specifically recruited by activated PDGFR-α. As a novel finding we could also demonstrate that recombinant PDGFR-α-Fc chimera homodimer is able to bind PDGF-D and thus prevent PDGF-D signaling. PDGF-D does induce individual PDGFR-β specific tyrosine phosphorylation similar to the PDGF-B. Additionally, PDGF-D enhances extracellular matrix accumulation comparable to the PDGF-B isoform.

CONCLUSION

PDGF-D signaling in pMF and HSC is identical to that of PDGF-B by binding to both PDGFR-α and -β.

RNA-seq analysis of broiler liver transcriptome reveals novel responses to high ambient temperature

BACKGROUND

In broilers, high ambient temperature can result in reduced feed consumption, digestive inefficiency, impaired metabolism, and even death. The broiler sector of the U.S. poultry industry incurs approximately $52 million in heat-related losses annually. The objective of this study is to characterize the effects of cyclic high ambient temperature on the transcriptome of a metabolically active organ, the liver. This study provides novel insight into the effects of high ambient temperature on metabolism in broilers, because it is the first reported RNA-seq study to characterize the effect of heat on the transcriptome of a metabolic-related tissue. This information provides a platform for future investigations to further elucidate physiologic responses to high ambient temperature and seek methods to ameliorate the negative impacts of heat.

RESULTS

Transcriptome sequencing of the livers of 8 broiler males using Illumina HiSeq 2000 technology resulted in 138 million, 100-base pair single end reads, yielding a total of 13.8 gigabases of sequence. Forty genes were differentially expressed at a significance level of P-value < 0.05 and a fold-change ≥ 2 in response to a week of cyclic high ambient temperature with 27 down-regulated and 13 up-regulated genes. Two gene networks were created from the function-based Ingenuity Pathway Analysis (IPA) of the differentially expressed genes: "Cell Signaling" and "Endocrine System Development and Function". The gene expression differences in the liver transcriptome of the heat-exposed broilers reflected physiological responses to decrease internal temperature, reduce hyperthermia-induced apoptosis, and promote tissue repair. Additionally, the differential gene expression revealed a physiological response to regulate the perturbed cellular calcium levels that can result from high ambient temperature exposure.

CONCLUSIONS

Exposure to cyclic high ambient temperature results in changes at the metabolic, physiologic, and cellular level that can be characterized through RNA-seq analysis of the liver transcriptome of broilers. The findings highlight specific physiologic mechanisms by which broilers reduce the effects of exposure to high ambient temperature. This information provides a foundation for future investigations into the gene networks involved in the broiler stress response and for development of strategies to ameliorate the negative impacts of heat on animal production and welfare.

Effects of oral intake of hydrogen water on liver fibrogenesis in mice

AIM

Liver fibrosis is the universal consequence of chronic liver diseases. Sustained hepatocyte injury initiates an inflammatory response, thereby activating hepatic stellate cells, the principal fibrogenic cells in the liver. Reactive oxygen species are involved in liver injury and are a promising target for treating liver fibrosis. Hydrogen water is reported to have potential as a therapeutic tool for reactive oxygen species-associated disorders. This study aimed to investigate the effects of hydrogen water on liver fibrogenesis and the mechanisms underlying these effects.

METHODS

C57BL/6 mice were fed with hydrogen water or control water, and subjected to carbon tetrachloride, thioacetamide and bile duct ligation treatments to induce liver fibrosis. Hepatocytes and hepatic stellate cells were isolated from mice and cultured with or without hydrogen to test the effects of hydrogen on reactive oxygen species-induced hepatocyte injuries or hepatic stellate cell activation.

RESULTS

Oral intake of hydrogen water significantly suppressed liver fibrogenesis in the carbon tetrachloride and thioacetamide models, but these effects were not seen in the bile duct ligation model. Treatment of isolated hepatocyte with 1 μg/mL antimycin A generated hydroxyl radicals. Culturing in the hydrogen-rich medium selectively suppressed the generation of hydroxyl radicals in hepatocytes and significantly suppressed hepatocyte death induced by antimycin A; however, it did not suppress hepatic stellate cell activation.

CONCLUSION

We conclude that hydrogen water protects hepatocytes from injury by scavenging hydroxyl radicals and thereby suppresses liver fibrogenesis in mice.

Kupffer cells in the liver

Kupffer cells are a critical component of the mononuclear phagocytic system and are central to both the hepatic and systemic response to pathogens. Kupffer cells are reemerging as critical mediators of both liver injury and repair. Kupffer cells exhibit a tremendous plasticity; depending on the local metabolic and immune environment, then can express a range of polarized phenotypes, from the proinflammatory M1 phenotype to the alternative/M2 phenotype. Multiple M2 phenotypes can be distinguished, each involved in the resolution of inflammation and wound healing. Here, we have provided an update on recent research that has contributed to the developing delineation of the contribution of Kupffer cells to different types of liver injury, with an emphasis on alcoholic and nonalcoholic liver diseases. These recent advances in our understanding of Kupffer cell function and regulation will likely provide new insights into the potential for therapeutic manipulation of Kupffer cells to promote the resolution of inflammation and enhance wound healing in liver disease.

Semaphorin 7A Contributes to TGF-β–Mediated Liver Fibrogenesis

Semaphorin7A (SEMA7A) is a membrane-anchored protein involved in immune and inflammatory responses, exerting an effect on pulmonary fibrosis. Thus, we aimed to investigate the role of SEMA7A in hepatic fibrosis. Liver injury was induced in vivo by carbon tetrachloride i.p. injection or bile duct ligation in wild-type and SEMA7A knockout (KO) mice. Human and mouse liver samples and primary mouse hepatic cell populations were used for Western blot analysis, quantitative real-time RT-PCR, and immunohistochemistry. SEMA7A is highly expressed in hepatic stellate cells (HSCs). The expression of SEMA7A and its receptor β1-integrin subunit increase during liver injury and in activated HSCs. Transforming growth factor β-stimulated HSCs showed increased expression of SEMA7A in a SMAD2/3-independent manner, leading to increased expression of fibrogenic and inflammation markers. This pattern was significantly blunted in SEMA7A KO HSCs. Overexpression of SEMA7A in HSCs showed increased fibrogenic and inflammation markers expression. In vivo, SEMA7A KO mice treated with carbon tetrachloride and bile duct ligation developed reduced fibrosis versus wild-type mice. Moreover, SEMA7A expression increased in liver samples of patients with fibrosis versus healthy controls. SEMA7A was expressed in the liver and was increased in the course of liver fibrosis, both in mice and in humans. SEMA7A was mainly expressed in HSCs with respect to other cell types in the liver and plays a critical role in regulating fibrosis.

The effects of bile duct obstruction on liver volume: an experimental study

Objectives. This study is aimed at investigating alterations in liver volume during obstructive jaundice in rat liver. Materials and Methods. Thirty-six rats were divided into four groups. Abdominal tomography was performed for baseline volumetric analyses. The main bile ducts were ligated (BDL). Volumetric analyses were repeated 3 days after BDL in group 1, 7 days after BDL in group 2, 15 days after BDL in group 3, and 25 days after BDL in group 4, and total hepatectomy was performed in all animals. Control group (n = 4) was created with the rats that died before bile duct ligation. Results. There was no difference found in liver volume in group 1 compared to control animals. The liver volume was increased 7 days after BDL (P = 0.01). It was increased up to 60% of baseline values 25 days after BDL (P = 0.002). Wet liver weights of animals were also increased compared to control group. Liver weights were increased up to 40% percent of baseline values in group 4 (P = 0.002). Conclusions. Liver volume and weight were increased after BDL. Liver surgery in patients with huge liver mass is generally associated with significant difficulty. The surgeon should be aware of the time-dependent alteration in liver volume after obstructive jaundice.

Effect of sinapic acid against dimethylnitrosamine-induced hepatic fibrosis in rats

Sinapic acid is a member of the phenylpropanoid family and is abundant in cereals, nuts, oil seeds, and berries. It exhibits a wide range of pharmacological properties. In this study, we investigated the hepatoprotective and antifibrotic effects of sinapic acid on dimethylnitrosamine (DMN)-induced chronic liver injury in rats. Sinapic acid remarkably prevented DMN-induced loss of body weight. This was accompanied by a significant increase in levels of serum alanine transaminase, aspartate transaminase, and liver malondialdehyde content. Furthermore, sinapic acid reduced hepatic hydroxyproline content, which correlated with a reduction in the expression of type I collagen mRNA and histological analysis of collagen in liver tissue. Additionally, the expression of hepatic fibrosis-related factors such as α-smooth muscle actin and transforming growth factor-β1 (TGF-β1), were reduced in rats treated with sinapic acid. Sinapic acid exhibited strong scavenging activity. In conclusion, we find that sinapic acid exhibits hepatoprotective and antifibrotic effects against DMN-induced liver injury, most likely due to its antioxidant activities of scavenging radicals, its capacity to suppress TGF-β1 and its ability to attenuate activation of hepatic stellate cells. This suggests that sinapic acid is a potentially useful agent for the protection against liver fibrosis and cirrhosis.

Functional complexity of the Leishmania granuloma and the potential of in silico modeling

In human and canine visceral leishmaniasis and in various experimental models of this disease, host resistance is strongly linked to efficient granuloma development. However, it is unknown exactly how the granuloma microenvironment executes an effective antileishmanial response. Recent studies, including using advanced imaging techniques, have improved our understanding of granuloma biology at the cellular level, highlighting heterogeneity in granuloma development and function, and hinting at complex cellular, temporal, and spatial dynamics. In this mini-review, we discuss the factors involved in the formation and function of Leishmania donovani-induced hepatic granulomas, as well as their importance in protecting against inflammation-associated tissue damage and the generation of immunity to rechallenge. Finally, we discuss the role that computational, agent-based models may play in answering outstanding questions within the field.

Aqueous extract of Artemisia iwayomogi Kitamura attenuates cholestatic liver fibrosis in a rat model of bile duct ligation

Cholestatic liver fibrosis, characterized by excessive accumulation of extracellular matrix (ECM) proteins, is associated with bile acid-induced oxidative stress and lipid peroxidation. We evaluated the therapeutic or protective effect of an aqueous extract of Artemisia iwayomogi Kitamura (WAI) in a rat bile duct ligation (BDL)-induced hepatic fibrogenesis model. After BDL, rats were treated once daily with 25 or 50 mg/kg of WAI for 2weeks. The serum bilirubin, aspartate transaminase, alanine transaminase, malondialdehyde, and liver hydroxyproline levels were drastically increased in the BDL group. WAI administration significantly reduced these markers and restored BDL-induced depletion of glutathione content and glutathione peroxidase activity. Cholestatic liver injury and collagen deposition were markedly attenuated by WAI treatment, and these changes were paralleled by significantly suppressed gene and protein expression of fibrogenic factors, including hepatic alphasmooth muscle actin, platelet-derived growth factor, and transforming growth factor β. Our data suggest that WAI may have antifibrotic properties via both improvement of antioxidant activities and inhibition of ECM protein production in the rat model of BDL.

Ascorbic acid supplementation down-regulates the alcohol induced oxidative stress, hepatic stellate cell activation, cytotoxicity and mRNA levels of selected fibrotic genes in guinea pigs

Both oxidative stress and endotoxins mediated immunological reactions play a major role in the progression of alcoholic hepatic fibrosis. Ascorbic acid has been reported to reduce alcohol-induced toxicity and ascorbic acid levels are reduced in alcoholics. Hence, we investigated the hepatoprotective action of ascorbic acid in the reversal of alcohol-induced hepatic fibrosis in male guinea pigs (n = 36), and it was compared with the animals abstenting from alcohol treatment. In comparison with the alcohol abstention group, there was a reduction in the activities of toxicity markers and levels of lipid and protein peroxidation products, expression of α-SMA, caspase-3 activity and mRNA levels of CYP2E1, TGF-β(1), TNF-α and α(1)(I) collagen in liver of the ascorbic acid-supplemented group. The ascorbic acid content in liver was significantly reduced in the alcohol-treated guinea pigs. But it was reversed to normal level in the ascorbic acid-supplemented group. The anti-fibrotic action of ascorbic acid in the rapid regression of alcoholic liver fibrosis may be attributed to decrease in the oxidative stress, hepatic stellate cells activation, cytotoxicity and mRNA expression of fibrotic genes CYP2E1, TGF-β(1), TNF-α and α(1) (I) collagen in hepatic tissues.

In vivo imaging of bile accumulation and biliary infarction after common bile duct ligation in rats

Obstructive cholestasis is caused by mechanical constriction or occlusion leading to reduced bile flow. Serious complications such as jaundice and even death may follow. Little is known about the initial phase of cholestasis and its consequences for the hepatic microarchitecture. This in vivo study aimed to characterize the nature and kinetics of developing obstructive cholestasis and focused on areas with biliary stasis and infarction by visualizing the autofluorescence of bile acids using intravital microscopy of the liver over a period of 30 h after bile duct ligation in rats. The innovation resided in performing fluorescence microscopy without applying fluorescent dyes. In animals subjected to obstructive cholestasis, the most significant changes observed in vivo were the concomitant appearance of (1) areas with bile accumulation increasing in size (6 h: 0.163 ± 0.043, 18 h: 0.180 ± 0.086, 30 h: 0.483 ± 0.176 mm(2)/field) and (2) areas with biliary infarction (6 h: 0.011 ± 0.006, 18 h: 0.010 ± 0.004, 30 h: 0.010 ± 0.050 mm(2)/field) as well as (3) a relation between the formation of hepatic lesions and enzyme activity in serum. The sequential in vivo analysis presented herein is a new method for the in vivo visualization of the very early changes in the hepatic parenchyma caused by obstructive cholestasis.

Protective effects of allopurinol against acute liver damage and cirrhosis induced by carbon tetrachloride: modulation of NF-κB, cytokine production and oxidative stress

BACKGROUND

The aim of this work was to evaluate the hepatoprotective ability of allopurinol to prevent the liver injury induced by carbon tetrachloride (CCl(4)).

METHODS

Acute liver damage was induced with CCl(4) (4g/kg, by gavage); allopurinol (50mg/kg, by gavage) was given 1h before and 1h after CCl(4) intoxication and two daily doses for the previous three days. Cirrhosis was established by CCl(4) administration (0.4g/kg, i. p. three times a week, eight weeks); allopurinol was administered (100mg/kg, by gavage, daily) during the long-term of CCl(4) treatment. Alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GTP), xanthine oxidase (XO), lipid peroxidation, reduced and oxidized glutathione (GSH, GSSG, respectively), hydroxyproline and histopathologycal analysis were performed. Nuclear factor-κB (NF-κB), pro-inflammatory and anti-inflammatory cytokines, transforming growth factor-β (TGF-β) and metalloproteinase-13 (MMP-13) were analyzed by Western blots.

RESULTS

Acute injury increased ALT and γ-GTP activities, additionally enhanced NF-κB nuclear translocation and cytokines production such as tumor necrosis factor-α, interleukine-1β, and interleukine-6. Allopurinol partially prevented these effects, while increased interleukine-10. Acute and chronic CCl(4) treatments altered the levels of XO activity, lipid peroxidation, and GSH/GSSG ratio, while these remained within normal range with allopurinol administration. Necrosis, fibrosis and TGF-β production induced in chronic injury were partially prevented by allopurinol, interestingly, this drug induced MMP-13 activity.

CONCLUSIONS

Allopurinol possesses antioxidant, anti-inflammatory and antifibrotic properties, probably by its capacity to reduce NF-κB nuclear translocation and TGF-β expression, as well as to induce MMP-13. General significance Allopurinol might be effective treatment of liver diseases.

Ginsenoside Rb1 inhibits cell activation and liver fibrosis in rat hepatic stellate cells

Chronic hepatitis/cirrhosis is the eighth leading cause of death in Taiwan. Excess accumulated extracellular matrix produced by activated hepatic stellate cells (HSCs) is the major cause of liver fibrosis. Ginsenoside Rb1, the most active compound purified from ginseng, has been considered to be hepatoprotective. This study investigated the effects of ginsenoside Rb1 (98.8% purity) on activation, proliferation, and profibrotic factors in rat HSC-T6 cells under H₂O₂ oxidative stress. Rat HSC-T6 cells were activated by 10 nM H₂O₂ and then incubated with different concentrations of ginsenoside Rb1 (5, 10, 20, 40, and 80 μg/mL) for 24 hours. Medium containing 0.08% dimethyl sulfoxide or 5 mM N-acetyl-l-cysteine was used as a negative or positive control, respectively. The results showed that ginsenoside Rb1 at 5-40 μg/mL significantly reduced α-smooth muscle actin levels and at 5-80 μg/mL inhibited cell proliferation in HSC-T6 cells after induction with H₂O₂ (P<.05). Collagen secreted by HSC-T6 cells was decreased by ginsenoside Rb1 at 5-80 μg/mL (P<.05). Protein expression of transforming growth factor-β1 (TGF-β1), matrix metalloproteinase (MMP)-2, and tissue inhibitor of metalloproteinase (TIMP)-1 was suppressed by ginsenoside Rb1 at 10-80 μg/mL (P<.05). In addition, mRNA expression of type I and III collagen, TGF-β1, and TIMP-1 was inhibited by ginsenoside Rb1 (10 and 80 μg/mL) (P<.05). Therefore, ginsenoside Rb1 exerted an antifibrotic effect on HSCs by inhibiting activation, proliferation, and expression of collagen, TGF-β1, MMP-2, and TIMP-1.

Redox signaling and the innate immune system in alcoholic liver disease

The development of alcoholic liver disease (ALD) is a complex process involving both parenchymal and nonparenchymal cells resident in the liver. Although the mechanisms for ALD are not completely understood, it is clear that increased oxidative stress, and activation of the innate immune system are essential elements in the pathophysiology of ALD. Oxidative stress from ethanol exposure results from increased generation of reactive oxygen species and decreased hepatocellular antioxidant activity, including changes in the thioredoxin/peroxiredoxin family of proteins. Both cellular and circulating components of the innate immune system are activated by exposure to ethanol. For example, ethanol exposure enhances toll-like receptor-4 (TLR-4)-dependent cytokine expression by Kupffer cells, likely due, at least in part, to dysregulation of redox signaling. Similarly, complement activation in response to ethanol leads to increased production of the anaphylatoxins, C3a and C5a, and activation C3a receptor and C5a receptor. Complement activation thus contributes to increased inflammatory cytokine production and can influence redox signaling. Here we will review recent progress in understanding the interactions between oxidative stress and innate immunity in ALD. These data illustrate that ethanol-induced oxidative stress and activation of the innate immune system interact dynamically during ethanol exposure, exacerbating ethanol-induced liver injury.

Transcriptome analysis of the effects of gomisin a on the recovery of carbon tetrachloride-induced damage in rat liver

Gomisin A possesses a hepatic function-facilitating property in liver-injured rats. Its preventive action on carbon tetrachloride-induced cholestasis is due to maintenance of the function of the bile acids-independent fraction. To investigate alterations in gene expression after gomisin A treatment on injured rat liver, DNA microarray analyses were performed on a Rat 44K 4-Plex Gene Expression platform with duplicated reactions after gomisin A treatment. We identified 255 up-regulated and 230 down-regulated genes due to the effects of gomisin A on recovery of carbon tetrachloride-induced rat liver damage. For functional characterization of these genes, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes biochemical pathways analyses were performed. Many up-regulated or down-regulated genes were related to cell cycle or focal adhesion and cell death genes, respectively. Our microarray experiment indicated that the liver repair mechanism induced by gomisin A was strongly associated with increased gene expressions related to cell cycle and suppression of the gene expression related in cell death.

The effect of anti-hypertensive drugs on the obstructive pancreatitis in rats

PURPOSE

To investigate the effect of ACE inhibitor, lisinopril and AT1 blocker, losartan, on the obstructive pancreatitis in rat.

METHODS

Acute pancreatitis in rats (n=21) was induced for a common hepatic duct were ligated proximal to its entry into the pancreas and the common bile - pancreatic duct were also ligated near its junction with the duodenum, under ether anesthesia, after which the abdomen were closed. The animals was divided in tree groups, being two treated and control group. The animals was treated with Losartan and Lisinopril at the dose of 10µg/Kg body weight per day, i.p., in a proportional volume, for five days, before and after treatment.

RESULTS

The inflammation, collagen deposition in the pancreas of treated animals were smaller, suggesting that the use of antihypertensive agents interfered positively in the depletion of the injury of the pancreas. Scythe showed a correlation between activity of pancreatic stellate cells (PSCs) lower in treated animals when compared to control.

CONCLUSION

The pancreatic stellate cells strength are involved in collagen production during acute pancreatitis and why antihypertensive drugs such as lisinopril and losartan may possibly have beneficial effects in reducing pancreatic fibrosis in models of experimental obstructive pancreatitis.

Interaction of stellate cells with pancreatic carcinoma cells. Cancers (Basel). 2010;2:1661-1682. [PMID: 24281180 PMCID: PMC3837330 DOI: 10.3390/cancers2031661]

Pancreatic cancer is characterized by its late detection, aggressive growth, intense infiltration into adjacent tissue, early metastasis, resistance to chemo- and radiotherapy and a strong “desmoplastic reaction”. The dense stroma surrounding carcinoma cells is composed of fibroblasts, activated stellate cells (myofibroblast-like cells), various inflammatory cells, proliferating vascular structures, collagens and fibronectin. In particular the cellular components of the stroma produce the tumor microenvironment, which plays a critical role in tumor growth, invasion, spreading, metastasis, angiogenesis, inhibition of anoikis, and chemoresistance. Fibroblasts, myofibroblasts and activated stellate cells produce the extracellular matrix components and are thought to interact actively with tumor cells, thereby promoting cancer progression. In this review, we discuss our current understanding of the role of pancreatic stellate cells (PSC) in the desmoplastic response of pancreas cancer and the effects of PSC on tumor progression, metastasis and drug resistance. Finally we present some novel ideas for tumor therapy by interfering with the cancer cell-host interaction.

Adiponectin deficiency enhanced the severity of cerulein-induced chronic pancreatitis in mice

BACKGROUND

Adiponectin is recognized as an antiinflammatory and antifibrotic protein derived from adipocytes, and low serum adiponectin levels are present in obesity. Recent studies have highlighted the relationship between obesity and pancreatic diseases. However, the role of adiponectin in chronic pancreatitis remains uncertain. The aim of this study was to determine the effects of adiponectin in chronic pancreatitis.

METHODS

We investigated the effects of adiponectin in experimental chronic pancreatitis by using adiponectin-knockout (APN-KO) mice. Chronic pancreatitis was induced by repeated hourly (6 times) intraperitoneal injections of 50 microg/kg cerulein three times per week for 4 weeks in wild-type (WT) and APN-KO mice. We evaluated the severity of chronic pancreatitis biochemically and morphologically.

RESULTS

In cerulein-treated mice, macroscopically and histologically, severe pancreatic damage was observed in APN-KO mice compared with findings in WT mice. The histological scores for chronic pancreatitis, including glandular atrophy, pseudotubular complex, fibrosis, and total scores, were significantly higher in APN-KO mice than in WT mice. Activated pancreatic stellate cells and F4/80-positive pancreatic macrophages accumulated in the pancreas of APN-KO mice but not in WT mice. Overexpression of the mRNAs of transforming growth factor-beta1, CD68, and monocyte chemoattractant protein-1 was noted in APN-KO mice but not in WT mice. The gene expression level of collagen1 (alpha1) tended to be higher in APN-KO mice than in WT mice, albeit insignificantly.

CONCLUSIONS

Adiponectin deficiency enhanced the severity of cerulein-induced chronic pancreatitis in mice. Hypoadiponectinemia could enhance the severity of chronic pancreatitis.

Bee Venom Inhibits Hepatic Fibrosis Through Suppression of Pro-Fibrogenic Cytokine Expression

Bee venom (BV) has a long tradition of use for the control of pain and inflammation in various chronic diseases. Carbon tetrachloride ( CCl4) is known to induce hepatotoxicity after being metabolized to the highly reactive trichloromethyl free radical and its peroxy radical. The purpose of the current study was to examine whether BV regulates the pro-inflammation and fibrosis related genes against a mouse model of hepatic fibrosis induced by CCl4and ethanol-treated hepatocytes (ETH). Test mice were administered with CCl4(2 ml/mg) and hepatocytes were treated with 25 mM ethanol. BV was added to the final concentration of 0.05–0.5 mg/kg and 1–100 ng/ml for in vivo and in vitro testing, respectively. Fibrotic livers and ETH were used for the measurement of hepatocyte necrosis, pro-inflammatory cytokines and fibrogenic genes. BV suppressed CCl4-induced hepatocyte necrosis markers of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT). It also inhibited the secretion of interleukin (IL)-1β and tumor necrosis factor (TNF)-α. Moreover, BV inhibited CCl4-induced expression of transforming growth factor (TGF)-β1, α-smooth muscle actin (SMA) and fibronectin. Similarly, ETH exhibited significant suppression of IL-1β, TNF-α, TGF-β1 and fibronectin when cultured with BV. These results suggest that BV possesses anti-fibrogenic properties that are mediated by the suppression of pro-inflammatory cytokines and fibrogenic gene expression. BV has substantial therapeutic potential for the treatment of fibrotic diseases.

Expression of ECM proteins fibulin-1 and -2 in acute and chronic liver disease and in cultured rat liver cells

Fibulin-2 has previously been considered as a marker to distinguish rat liver myofibroblasts from hepatic stellate cells. The function of other fibulins in acute or chronic liver damage has not yet been investigated. The aim of this study has been to evaluate the expression of fibulin-1 and -2 in models of rat liver injury and in human liver cirrhosis. Their cellular sources have also been investigated. In normal rat liver, fibulin-1 and -2 were both mainly present in the portal field. Fibulin-1-coding transcripts were detected in total RNA of normal rat liver, whereas fibulin-2 mRNA was only detected by sensitive, real-time quantitative polymerase chain reaction. In acute liver injury, the expression of fibulin-1 was significantly increased (17.23-fold after 48 h), whereas that of fibulin-2 was not modified. The expression of both fibulin-1 and -2 was increased in experimental rat liver cirrhosis (19.16- and 26.47-fold, respectively). At the cellular level, fibulin-1 was detectable in hepatocytes, "activated" hepatic stellate cells, and liver myofibroblasts (2.71-, 122.65-, and 469.48-fold over the expression in normal rat liver), whereas fibulin-2 was restricted to liver myofibroblasts and was regulated by transforming growth factor beta-1 (TGF-beta1) in 2-day-old hepatocyte cultures and in liver myofibroblasts. Thus, fibulin-1 and -2 respond differentially to single and repeated damaging noxae, and their expression is differently present in liver cells. Expression of the fibulin-2 gene is regulated by TGF-beta1 in liver myofibroblasts.

Comparative atomic force and scanning electron microscopy: an investigation of structural differentiation of hepatic stellate cells

The molecular mechanism leading to the transdifferentiation of hepatic stellate cells (HSC) into myofibroblast-like cells following liver injury is not well understood. The state of cultured rat HSCs was determined using primarily fluorescence microscopy (UV), immunofluorescence (IF) (Glial fibrillary acidic protein (GFAP), Desmin, alpha-smooth muscle actin (alpha-SMA), F-actin) and immunocytochemistry (ICC) (GFAP, Desmin, alpha-SMA, Fibulin-2). Additionally, tapping-mode atomic force microscopy (TM-AFM) and field-emission scanning electron microscopy (FE-SEM) with low-resistivity indium-tin-oxide (ITO) thin-film were performed to observe the micro-morphological character of cells during HSC differentiation. Quiescent HSCs changed to the activated state were identified via UV, IF, and ICC observations. Normal rat HSCs (NHSCs) and thioacetamide-induced rat HSCs (THSCs) were demonstrated to be UV(-), GFAP(+), Desmin(+), alpha-SMA(+) and Fibulin-2(-). After F-actin staining, lamellipodia and filopodia were found in both NHSCs and THSCs, but membrane ruffles were only seen in THSCs. The micro-structures of lamellipodia and filopodia in both NHSCs and THSCs were confirmed using FE-SEM and TM-AFM with ITO; in contrast, the micro-projection was not found. Moreover, "aerial root" structures were observed for the first time in the filopodia of THSCs using TM-AFM. These results reveal that HSC transdifferentiation to a myofibroblastic-like cell (activated HSC) from thioacetamide-induced rat HSC induces extensive changes in the cytoskeleton.

Up-regulation of uPARAP/Endo180 during culture activation of rat hepatic stellate cells and its presence in hepatic stellate cell lines from different species

Background

The urokinase plasminogen activator receptor associated protein (uPARAP)/Endo180 is a novel endocytic receptor that mediates collagen uptake and is implicated to play a role in physiological and pathological tissue-remodelling processes by mediating intracellular collagen degradation.

Result

This study investigates the expression of uPARAP/Endo180 protein and messenger RNA in primary rat hepatic stellate cell (HSC) cultures. The results show that uPARAP/Endo180 protein is not expressed in freshly isolated HSCs or during the first few days of culture while the cells still display quiescent features. In contrast, uPARAP/Endo180 protein is expressed early during HSC activation when cells are transdifferentiated into myofibroblast-like cells. Very low levels of uPARAP/Endo180 mRNA are detectable during the first days of culture but uPARAP/Endo180 mRNA is strongly up-regulated with increasing time in culture. Moreover, endocytic uptake of denatured collagen increases as transdifferentiation proceeds over time and correlates with increased expression of uPARAP/Endo180. Finally, analysis of uPARAP/Endo180 expression in four hepatic stellate cell lines from three different species showed that all these cell lines express uPARAP/Endo180 and are able to take up denatured collagen efficiently.

Conclusion

These results demonstrate that uPARAP/Endo180 expression by rat HSCs is strongly up-regulated during culture activation and identify this receptor as a feature common to culture-activated HSCs.

The therapeutic potential of human umbilical mesenchymal stem cells from Wharton's jelly in the treatment of rat liver fibrosis

We investigated the effect of human umbilical mesenchymal stem cells (HUMSCs) from Wharton's jelly on carbon tetrachloride (CCl4)-induced liver fibrosis in rats. Rats were treated with CCl4 for 4 weeks, and this was followed by a direct injection of HUMSCs into their livers. After 4 more weeks of CCl4 treatment (8 weeks in all), rats with HUMSC transplants [CCl4 (8W)+HUMSC liver] exhibited a significant reduction in liver fibrosis, as evidenced by Sirius red staining and a collagen content assay, in comparison with rats treated with CCl4 for 8 weeks without HUMSC transplants [CCl4 (8W)]. Moreover, rats in the CCl4 (8W)+HUMSC (liver) group had significantly lower levels of serum glutamic oxaloacetic transaminase, glutamic pyruvate transaminase, alpha-smooth muscle actin, and transforming growth factor-beta1 in the liver, whereas the expression of hepatic mesenchymal epithelial transition factor-phosphorylated type (Met-P) and hepatocyte growth factor was up-regulated, in comparison with the CCl4 (8W) group. Notably, engrafted HUMSCs scattered mostly in the hepatic connective tissue but did not differentiate into hepatocytes expressing human albumin or alpha-fetoprotein. Instead, these engrafted, undifferentiated HUMSCs secreted a variety of bioactive cytokines that may restore liver function and promote regeneration. Human cytokine assay revealed that the amounts of human cutaneous T cell-attracting chemokine, leukemia inhibitory factor, and prolactin were substantially greater in the livers of the CCl4 (8W)+HUMSC (liver) group, with considerably reduced hepatic inflammation manifested by a micro positron emission tomography scan. Our findings suggest that xenogeneic transplantation of HUMSCs is a novel approach for treating liver fibrosis and may be a promising therapeutic intervention in the future.

An early complement-dependent and TLR-4-independent phase in the pathogenesis of ethanol-induced liver injury in mice

The innate immune system has been implicated in the pathogenesis of alcoholic liver disease. Although innate immunity is usually considered an early response to injury, previous work implicating innate immunity in ethanol-induced liver injury focuses primarily on long-term ethanol exposure. We investigated the early period of ethanol exposure to determine whether there were temporal associations between activation of innate immune responses and known correlates of liver injury. Female C57BL/6 mice were allowed free access to an ethanol-containing Lieber-DeCarli diet or were pair-fed a control diet. Within 4 days of ethanol exposure, we observed a striking spike in expression of hepatic proinflammatory cytokines-including tumor necrosis factor alpha (TNF-alpha), interleukin-6, and interferon-gamma-prior to hepatic triglyceride accumulation or increased plasma alanine aminotransferase activities, as well as before the induction of cytochrome P450 2E1 or oxidative stress. This early spike in inflammatory cytokines coincided with deposition of C3b-iC3b/C3c (C3b) in the liver. This deposition, resulting from the cleavage of the third component of the complement system (C3), is evidence for activation of complement in response to ethanol. C3(-/-) mice were protected from the early, ethanol-induced increase in hepatic TNF-alpha expression. Ethanol increased C3b deposition in mice deficient in C3a receptor or C5a receptor, as well as in wild-type mice depleted of hepatic macrophages; however, there was no increase in hepatic TNF-alpha in the absence of C3a receptor, C5a receptor, or hepatic macrophages. In contrast, the absence of Toll-like receptor 4 (TLR-4) had no effect on the early, ethanol-induced increase in either C3b or TNF-alpha.

CONCLUSION

We have identified a complement- and macrophage-dependent, but TLR-4 independent, phase in the pathogenesis of ethanol-induced liver injury.

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.

An intravital microscopic study of the hepatic microcirculation in cirrhotic mice models: relationship between fibrosis and angiogenesis

This intravital fluorescence microscopy (IVFM) study validates cirrhotic mice models and describes the different intrahepatic alterations and the role of angiogenesis in the liver during genesis of cirrhosis. Cirrhosis was induced by subcutaneous injection of carbon tetrachloride (CCl(4)) and by common bile duct ligation (CBDL) in mice. Diameters of sinusoids, portal venules (PV), central venules (CV) and shunts were measured at different time points by IVFM. Thereafter, liver samples were taken for sirius red, CD31, Ki67, vascular endothelial growth factor (VEGF) and alpha-smooth muscle actin (alpha-SMA) evaluation by immunohistochemistry (IHC). In parallel with fibrogenesis, hepatic microcirculation was markedly disturbed in CCl(4) and CBDL mice with a significant decrease in sinusoidal diameter compared to control mice. In CCl(4) mice, CV were enlarged, with marked sinusoidal-free spaces around CV. In contrast, PV were enlarged in CBDL mice and bile lakes were observed. In both mice models, intrahepatic shunts developed gradually after induction. During genesis of cirrhosis using CD31 IHC we observed a progressive increase in the number of blood vessels within the fibrotic septa area and a progressively increase in staining by Ki67, VEGF and alpha-SMA of endothelial cells, hepatocytes and hepatic stellate cells respectively. In vivo study of the hepatic microcirculation demonstrated a totally disturbed intrahepatic architecture, with narrowing of sinusoids in both cirrhotic mice models. The diameters of CV and PV increased and large shunts, bypassing the sinusoids, were seen after both CCl(4) and CBDL induction. Thus present study shows that there is angiogenesis in the liver during cirrhogenesis, and this is probably due partially to an increased production of VEGF.

Synergistic growth inhibitory effects of the dual endothelin-1 receptor antagonist bosentan on pancreatic stellate and cancer cells

Pancreatic stellate cells (PSC) play a key role in pancreatic fibrosis. Activation of PSC occurs in response to pro-fibrogenic stimuli and is maintained by autocrine loops of mediators, such as endothelin (ET)-1. Here, we have evaluated effects of the dual ET receptor antagonist bosentan in models of pancreatic fibrogenesis and cancer. Cell culture studies revealed that PSC and DSL6A pancreatic cancer cells expressed both ET-1 and ET receptors. Bosentan efficiently inhibited proliferation of both cell types and collagen synthesis in PSC. Expression of the myofibroblastic marker alpha-smooth muscle actin, connective tissue growth factor, and ET-1 itself in PSC was reduced, while expression of matrix metalloproteinase-9 was enhanced. Like PSC, DSL6A cells secrete less ET-1 when cultured with bosentan. In a rat model of pancreatic fibrosis, chronic pancreatitis induced by dibutyltin dichloride, a tendency towards a diminished disease progression was observed in a subgroup of rats with less severe disease. Together, our results indicate that bosentan exerts antifibrotic and antitumor effects in vitro. Its efficiency in vivo warrants further investigation.

Cell survival, activation and apoptosis of hepatic stellate cells: modulation by extracellular matrix proteins

AIM

Cytokines and growth factors released by various hepatic cells exert both paracrine and autocrine effects on hepatic stellate cell (HSC) activation during liver injury. The aim of the present study was to examine whether the surrounding extracellular matrix (ECM) influences the activation, transdifferentiation and survival of HSCs.

METHODS

An in vitro model system of isolated HSCs maintained in culture on different matrix protein substrata was employed.

RESULTS

The rate of loss of HSC-specific retinol uptake activity and gain of myofibroblast-like activity such as (35)[S] proteoglycan synthesis varied in cells maintained on different matrix proteins and was in the order collagen I > collagen IV >/= laminin. (3)[H]-thymidine incorporation by HSCs maintained on different matrix proteins varied and was in the order collagen I > collagen IV > laminin. MTT assay revealed that the growth inhibition in response to curcumin was significantly low in cells maintained on collagen I. Apoptotic marker activities such as DNA fragmentation, 4',6'-diamidino-2-phenylindole dihydrochloride (DAPI) staining, annexin staining and caspase-3 activities showed that cells maintained on collagen I showed minimal apoptosis than those maintained on collagen IV, laminin and polylysine, showing the influence of ECM on HSC apoptosis. Experiments using blocking antibodies showed that the collagen I effect was mediated through alpha(2)beta(1) integrin.

CONCLUSIONS

These results indicate that ECM influences activation, transdifferentiation and survival of HSCs, and suggest that apart from diffusible factors, the surrounding ECM also influences HSC behavior critical in both the progression of the fibrosis and the restitution of the liver during recovery after hepatic injury.

Oxidative and nitrosative stress and fibrogenic response

Uncontrolled production of collagen I is the main feature of liver fibrosis. Following a fibrogenic stimulus such as alcohol, hepatic stellate cells (HSC) transform into an activated collagen-producing cell. In alcoholic liver disease, numerous changes in gene expression are associated with HSC activation, including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses for understanding the molecular basis of the collagen I gene regulation have revealed a complex process involving reactive oxygen species (ROS) as key mediators. Less is known, however, about the contribution of reactive nitrogen species (RNS). In addition, a series of cytokines, growth factors, and chemokines, which activate extracellular matrix (ECM)-producing cells through paracrine and autocrine loops, contribute to the fibrogenic response.