Hepatic stellate cells and alcoholic liver disease

From Inflammation to Fibrosis: Novel Insights into the Roles of High Mobility Group Protein Box 1 in Schistosome-Induced Liver Damage

Schistosomiasis is a chronic helminthic disease of both humans and animals and the second most prevalent parasitic disease after malaria. Through a complex migration process, schistosome eggs trapped in the liver can lead to the formation of granulomas and subsequent schistosome-induced liver damage, which results in high mortality and morbidity. Although praziquantel can eliminate mature worms and prevent egg deposition, effective drugs to reverse schistosome-induced liver damage are scarce. High mobility group box 1 (HMGB1) is a multifunctional cytokine contributing to liver injury, inflammation, and immune responses in schistosomiasis by binding to cell-surface Toll-like receptors and receptors for advanced glycation end products. HMGB1 is increased in the serum of patients with schistosomiasis and enables hepatic stellate cells to adopt a proliferative myofibroblast-like phenotype, which is crucial to schistosome-induced granuloma formation. Inhibition of HMGB1 was found to generate protective responses against fibrotic diseases in animal models. Clinically, HMGB1 presents a potential target for treatment of the chronic sequelae of schistosomiasis. Here, the pivotal role of HMGB1 in granuloma formation and schistosome-induced liver damage, as well the potential of HMGB1 as a therapeutic target, are discussed.

Beneficial Effects of Betaine: A Comprehensive Review

Medicinal herbs and many food ingredients possess favorable biological properties that contribute to their therapeutic activities. One such natural product is betaine, a stable, nontoxic natural substance that is present in animals, plants, and microorganisms. Betaine is also endogenously synthesized through the metabolism of choline or exogenously consumed through dietary intake. Betaine mainly functions as (i) an osmolyte and (ii) a methyl-group donor. This review describes the major physiological effects of betaine in whole-body health and its ability to protect against both liver- as well as non-liver-related diseases and conditions. Betaine's role in preventing/attenuating both alcohol-induced and metabolic-associated liver diseases has been well studied and is extensively reviewed here. Several studies show that betaine protects against the development of alcohol-induced hepatic steatosis, apoptosis, and accumulation of damaged proteins. Additionally, it can significantly prevent/attenuate progressive liver injury by preserving gut integrity and adipose function. The protective effects are primarily associated with the regulation of methionine metabolism through removing homocysteine and maintaining cellular SAM:SAH ratios. Similarly, betaine prevents metabolic-associated fatty liver disease and its progression. In addition, betaine has a neuroprotective role, preserves myocardial function, and prevents pancreatic steatosis. Betaine also attenuates oxidant stress, endoplasmic reticulum stress, inflammation, and cancer development. To conclude, betaine exerts significant therapeutic and biological effects that are potentially beneficial for alleviating a diverse number of human diseases and conditions.

Hepatic Stellate Cells Play a Functional Role in Exacerbating Ischemia-Reperfusion Injury in Rat Liver

PURPOSE

The involvement of hepatic stellate cells (HSCs) with ischemia-reperfusion (I/R) injury in rat liver was examined using gliotoxin, which is known to induce HSC apoptosis.

METHODS

Male Sprague-Dawley rats were used. HSC was represented by a glial fibrillary acidic protein (GFAP)-positive cell. Liver ischemia was produced by cross-clamping the hepatoduodenal ligament. The degree of I/R injury was evaluated by a release of aminotransferases. Sinusoidal diameter and sinusoidal perfusion rates were examined using intravital fluorescence microscopy.

RESULTS

Gliotoxin significantly decreased the number of GFAP-positive cells 48 h after dosing (2.50 ± 0.19% [mean ± SD] in the nontreated group vs. 1.91 ± 0.46% in the gliotoxin-treated group). Liver damage was significantly suppressed by the pretreatment with gliotoxin. Sinusoidal diameters in zone 3 were wider in the gliotoxin group (10.25 ± 0.35 µm) than in the nontreated group (8.21 ± 0.50 µm). The sinusoidal perfusion rate was maintained as well in the gliotoxin group as in normal livers, even after I/R.

CONCLUSIONS

Pretreatment with gliotoxin significantly reduced the number of HSCs in the liver and further suppressed liver injury following I/R. It is strongly suggested that HSCs play a functional role in exacerbating the degree of I/R injury of the liver.

Schistosome-Induced Fibrotic Disease: The Role of Hepatic Stellate Cells

Hepatic fibrosis is a common pathology in various liver diseases. Hepatic stellate cells (HSCs) are the main cell type responsible for collagen deposition and fibrosis formation in the liver. Schistosomiasis is characterised by granulomatous fibrosis around parasite eggs trapped within the liver and other host tissues. This response is facilitated by the recruitment of immune cells and the activation of HSCs. The interactions between HSCs and schistosome eggs are complex and diverse, and a better understanding of these interactions could lead to improved resolution of fibrotic liver disease, including that associated with schistosomiasis. Here, we discuss recent advances in HSC biology and the role of HSCs in hepatic schistosomiasis.

Ion Channels and Oxidative Stress as a Potential Link for the Diagnosis or Treatment of Liver Diseases

Oxidative stress results from a disturbed balance between oxidation and antioxidant systems. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) may be either harmful or beneficial to the cells. Ion channels are transmembrane proteins that participate in a large variety of cellular functions and have been implicated in the development of a variety of diseases. A significant amount of the available drugs in the market targets ion channels. These proteins have sulfhydryl groups of cysteine and methionine residues in their structure that can be targeted by ROS and RNS altering channel function including gating and conducting properties, as well as the corresponding signaling pathways associated. The regulation of ion channels by ROS has been suggested to be associated with some pathological conditions including liver diseases. This review focuses on understanding the role and the potential association of ion channels and oxidative stress in liver diseases including fibrosis, alcoholic liver disease, and cancer. The potential association between ion channels and oxidative stress conditions could be used to develop new treatments for major liver diseases.

Ischemia reperfusion-facilitated sinusoidal endothelial cell injury in liver transplantation and the resulting impact of extravasated platelet aggregation

Background

The exact sequence of events leading to ultimate hepatocellular damage following ischemia/reperfusion (I/R) is incompletely understood. In this article, we review a mechanism of organ dysfunction after hepatic I/R or immunosuppressive treatment, in addition to the potential of liver sinusoidal endothelial cell (LSEC) protection and antiplatelet treatment for the suppression of hepatocellular damage.

Methods

A review of the literature, utilizing PubMed-NCBI, was used to provide information on the components necessary for the development of hepatocellular damage following I/R.

Results

It is well-established that LSECs damage following hepatic I/R or immunosuppressive treatment followed by extravasated platelet aggregation (EPA) is the root cause of organ dysfunction in liver transplantation. We have classified three phases, from LSECs damage to organ dysfunction, utilizing the predicted pathogenic mechanism of sinusoidal obstruction syndrome. The first phase is detachment of LSECs and sinusoidal wall destruction after LSECs injury by hepatic I/R or immunosuppressive treatment. The second phase is EPA, accomplished by sinusoidal wall destruction. The various growth factors, including thromboxane A2, serotonin, transforming growth factor-beta and plasminogen activator inhibitor-1, released by EPA in the Disse’s space of zone three, induce portal hypertension and the progression of hepatic fibrosis. The third phase is organ dysfunction following portal hypertension, hepatic fibrosis, and suppressed liver regeneration through various growth factors secreted by EPA.

Conclusion

We suggest that EPA in the space of Disse, initiated by LSECs damage due to hepatic I/R or immunosuppressive treatment, and activated platelets may primarily contribute to liver damage in liver transplantation. Endothelial protective therapy or antiplatelet treatment may be useful in the treatment of hepatic I/R following EPA.

Liver Failure Impairs the Intrahepatic Elimination of Interleukin-6, Tumor Necrosis Factor-Alpha, Hepatocyte Growth Factor, and Transforming Growth Factor-Beta

The strategic location of the liver and its metabolic activity make it a key organ regulating homeostasis. Our purpose was to examine its participation in removal of cytokines: interleukin-6 (Il-6), tumor necrosis factor-alpha (TNF-α), hepatocyte growth factor (HGF), and transforming growth factor-beta (TGF-β) from the portal circulation in human. 20 liver donors and 20 patients with end-stage liver failure were included in the study. Their blood was collected during liver transplantation from the portal, hepatic, and peripheral vein, and the hepatic artery and cytokines' concentrations were determined. Using the results the mathematical model of cytokine elimination by the liver was developed. In donors significantly lower levels of IL-6, TNF-α, HGF, and TGF-β were detected in portal blood compared to hepatic vein. In patients with cirrhosis there were no significant differences of IL-6, TNF-α, and TGF-β levels between portal and hepatic veins. Significantly higher level of HGF in hepatic compared to portal vein was observed. In healthy liver elimination of the cytokines prevailed over their synthesis, as reflected by the positive values of the elimination ratios. In the cirrhotic liver elimination ratios of Il-6, HGF, and TGF-β were negative indicating the prevalence of intrahepatic synthesis of cytokines over their removal.

Pathology of Alcoholic Liver Disease

Alcohol-attributable burden on global health is increasing, and the relationship between population alcohol consumption and liver-related deaths is strong. Longstanding scientific and clinical work has led to a relatively thorough, if not complete, understanding of the effects of alcohol consumption on the liver. Pathologic features of alcoholic liver disease (ALD) are recognized by pathologists and used to assist clinicians in diagnosing and determining severity of disease in patients suspected of ALD. In this review, we discuss the pathologic manifestations of ALD and provide salient points on their pathophysiology. In addition, the benefits and indications of liver biopsy and important differential diagnoses, including features distinguishing these entities, are reviewed.

Carvedilol improves ethanol-induced liver injury via modifying the interaction between oxidative stress and sympathetic hyperactivity in rats

AIM

Oxidative stress is a major pathway mediating ethanol hepatotoxicity and liver injury. We previously found that carvedilol, which can block the sympathetic nervous system via β1-, β2- and α1-adrenoreceptors, modifies ethanol-induced production of lipogenesis- and fibrogenesis-related mediators from hepatic stellate cells (HSC). In the present study, we assessed the effects of carvedilol on ethanol-induced liver injury, hepatic insulin resistance, and the interaction between oxidative stress and sympathetic hyperactivity in rats with alcoholic fatty liver disease (AFLD).

METHODS

Male Wistar rats were pair-fed for 49 days and divided into four groups: control and ethanol liquid-diet-fed rats with and without 7-day carvedilol treatment. Rats' sympathetic activity, hepatic oxidative stress, hepatic insulin resistance and liver injury were evaluated based on biochemical analysis, enzyme-linked immunosorbent assay, fluorescence immunohistochemistry, western blot and reverse transcriptase polymerase chain reaction.

RESULTS

Forty-nine days of ethanol consumption induced the increases in circulating noradrenaline metabolite (3-methoxy-4-hydroxyphenylglycol), hepatic noradrenaline and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, the downregulation of hepatic insulin receptor substrate-1 gene expression, and the accumulation of fatty droplets within hepatocytes with the increased hepatic triglyceride and blood alanine aminotransferase levels. All of these changes were modified by carvedilol treatment. 8-OHdG was detected in activated HSC and suppressed by carvedilol treatment based on fluorescence immunohistochemical double-staining analysis.

CONCLUSION

Carvedilol may modify the interaction between the oxidative stress and the sympathetic hyperactivity, and then contribute to attenuating the development of AFLD in rats. Additionally, oxidative stress may be responsible for the activation of HSC during the early stage of alcoholic liver disease.

Liver fibrogenesis in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is emerging as one of the most common chronic liver diseases in developed western countries. Non-alcoholic steatohepatitis (NASH) is the most severe form of NAFLD, and can progress to more severe forms of liver disease, including fibrosis, cirrhosis, and even hepatocellular carcinoma. The activation of hepatic stellate cells plays a critical role in NASH-related fibrogenesis. Multiple factors, such as insulin resistance, oxidative stress, pro-inflammatory cytokines and adipokines, and innate immune responses, are known to contribute to the development of NASH-related fibrogenesis. Furthermore, these factors may share synergistic interactions, which could contribute to the process of liver fibrosis. Given the complex etiology of NASH, combined treatment regimes that target these different factors provide potential treatment strategies for NASH-related liver fibrosis.

Soy isoflavone delays the progression of thioacetamide-induced liver fibrosis in rats

OBJECTIVE

Our aim was to investigate the effect of soy isoflavone (SI) on liver fibrosis in a thioacetamide (TAA)-induced rat model.

MATERIALS AND METHODS

Twenty-eight rats were assigned to four groups: sham group, fibrosis group, low-dose treatment group (LDg) and high-dose treatment group (HDg). SI (90 or 270 mg/kg) was administered daily during the model development by TAA. Standard liver tests, platelet derived growth factor-BB (PDGF-BB) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were measured. The expression of collagen, α-smooth muscle actin (α-SMA) and transforming growth factor-β1 (TGF-β1) in liver tissue was determined. Electron microscopy was used to perform ultrastructural analysis of the livers.

RESULTS

Hepatic fibrosis was induced by 8 weeks of TAA administration. However, following the administration of SI, collagen staining significantly declined as compared with the fibrosis group (p < 0.01). Less collagen fibers around the hepatic stellate cells (HSCs) were observed in HDg as compared to the fibrosis group and LDg. There was no significant difference in standard liver tests between the fibrosis group and the two treatment groups. The levels of PDGF-BB and TIMP-1 in the two SI-treated groups were significantly lower than in the fibrosis group (p < 0.01). The expression of α-SMA and TGF-β1 in HDg was less than that in the fibrosis group and LDg (p < 0.01).

CONCLUSION

Administration of a high dose of SI resulted in an obvious inhibitory effect on liver fibrosis induced by TAA in rats. One hypothesis is that the effect may be related to the inhibition of HSC activation and proliferation.

Inhibition of nitric oxide synthesis during induced cholestasis ameliorates hepatocellular injury by facilitating S-nitrosothiol homeostasis

Cholestatic liver injury following extra- or intrahepatic bile duct obstruction causes nonparenchymal cell proliferation and matrix deposition leading to end-stage liver disease and cirrhosis. In cholestatic conditions, nitric oxide (NO) is mainly produced by a hepatocyte-inducible NO synthase (iNOS) as a result of enhanced inflow of endotoxins to the liver and also by accumulation of bile salts in hepatocytes and subsequent hepatocellular injury. This study was aimed to investigate the role of NO and S-nitrosothiol (SNO) homeostasis in the development of hepatocellular injury during cholestasis induced by bile duct ligation (BDL) in rats. Male Wistar rats (200-250 g) were divided into four groups (n=10 each), including sham-operated (SO), bile duct-ligated (BDL), tauroursodeoxycholic acid (TUDCA, 50 mg/kg) and S-methylisothiourea (SMT, 25 mg/kg) treated. After 7 days, BDL rats showed elevated serum levels of gamma-glutamiltranspeptidase, aspartate aminotransferase, alanine aminotransferase, LDH, and bilirubin, bile duct proliferation and fibrosis, compared with the SO group. TUDCA treatment did not significantly alter these parameters, but the iNOS inhibitor SMT ameliorated hepatocellular injury, as shown by lower levels of circulating hepatic enzymes and bilirubin, and a decreased grade of bile duct proliferation and fibrosis. Both TUDCA and SMT treatments reversed Mrp2 canalicular pump expression to control levels. However, only SMT treatment significantly lowered the increased levels of plasma NO and S-nitrosation (S-nitrosylation) of liver proteins in BDL rats. Moreover, BDL resulted in a reduction of the S-nitrosoglutathione reductase (GSNOR/Adh5) enzymatic activity and a downregulation of the GSNOR/Adh5 mRNA expression that was reverted by SMT, but not TUDCA, treatment. A total of 25 liver proteins, including S-adenosyl methionine synthetase, betaine-homocysteine S-methyltransferase, Hsp90 and protein disulfide isomerase, were found to be S-nitrosated in BDL rats. In conclusion, the inhibition of NO production during induced cholestasis ameliorates hepatocellular injury. This effect is in part mediated by the improvement of cell proficiency in maintaining SNO homeostasis.

Trans-resveratrol alone and hydroxystilbenes of rhubarb (Rheum rhaponticum L.) root reduce liver damage induced by chronic ethanol administration: a comparative study in mice

The hepatoprotective effects and pharmacokinetics of trans-resveratrol and hydroxystilbenes of the garden rhubarb (Rheum rhaponticum L., R. rhaponticum) root ethanol extract were studied. Ethanol was administered to male BALB/c mice for 35 days in an inhalation chamber. During this time vehicle, trans-resveratrol (20 mg/kg per day) or R. rhaponticum extract was intraperitoneally (i.p.) administered and mice were sacrificed for the collection of liver and blood. In an additional experiment, the level of parent compounds and metabolites was estimated in the blood after acute i.p. administration of trans-resveratrol or R. rhaponticum extract. The levels of hydroxystilbenes, their metabolites and fatty acid oxy-metabolites (oxylipins) were studied by LC-tandem DAD-MS/MS. Ethanol induced hepatotoxicity, as evidenced by histological changes and accumulation of oxylipins in the blood. Both trans-resveratrol and R. rhaponticum extract reduced the extent of these changes. The pharmacokinetics of trans-resveratrol was characterized by a rapid removal from the blood and metabolism to sulfates and glucuronides. After the administration of R. rhaponticum extract, in addition to trans-resveratrol glucoside and its metabolites, several other hydroxystilbenes were found. Inhibition of oxidation of polyunsaturated fatty acids is proposed as a basis of the hepatoprotective effect of both trans-resveratrol and R. rhaponticum extract.