Apoptotic hepatocyte DNA inhibits hepatic stellate cell chemotaxis via toll-like receptor 9

Liver fibrosis

Liver fibrosis is a wound-healing response generated against an insult to the liver that causes liver injury. It has the potential to progress into cirrhosis, and if not prevented, it may lead to liver cancer and liver failure. The activation of hepatic stellate cells (HSCs) is the central event underlying liver fibrosis. In addition to HSCs, numerous studies have supported the potential contribution of bone marrow-derived cells and myofibroblasts to liver fibrosis. The liver is a heterogeneous organ; thus, molecular and cellular events that underlie liver fibrogenesis are complex. This review aims to focus on major events that occur during liver fibrogenesis. In addition, important antifibrotic therapeutic approaches and experimental liver fibrosis models will be discussed.

Triggering and resolution of inflammation in NASH

Nonalcoholic steatohepatitis (NASH) is considered the progressive form of nonalcoholic fatty liver disease (NAFLD) and is characterized by liver steatosis, inflammation, hepatocellular injury and different degrees of fibrosis. A central issue in this field relates to the identification of those factors that trigger inflammation, thus fuelling the transition from nonalcoholic fatty liver to NASH. These triggers of liver inflammation might have their origins outside the liver (such as in adipose tissue or the gut) as well as inside the organ (for instance, lipotoxicity, innate immune responses, cell death pathways, mitochondrial dysfunction and endoplasmic reticulum stress), both of which contribute to NASH development. In this Review, we summarize the currently available information on the key upstream triggers of inflammation in NASH. We further delineate the mechanisms by which liver inflammation is resolved and the implications of a defective pro-resolution process. A better knowledge of these mechanisms should help to design targeted therapies able to halt or reverse disease progression.

Distinctiveness in virological features and pathogenic potentials of subgenotypes D1, D2, D3 and D5 of Hepatitis B virus

Distinct clinical features of HBV infection have been associated with different viral genotype/subgenotype. HBV Genotype-D comprised of 10 subgenotypes, D1–D10, whose clinical implications still remain elusive. We investigated for the first-time, the virologic characteristics and cytopathic effects of four non-recombinant D-subgenotypes, D1/D2/D3/D5. Expressions of viral/host genes were evaluated in Huh7 cells transfected with full-length, linear-monomers of HBV/D-subgenotypes or pGL3-Basic vector carrying subgenotype-specific HBx. Intracellular HBV-DNA and pregenomic-RNA levels were high in D1/D2 than D3/D5. Expressions of PreC-mRNA and HBx were highest for D2 and D1 respectively, whereas PreS2/S-transcript was significantly reduced in D5. Increased apoptotic cell death and marked upregulation in caspase-3/Bax/TNF-R1/FasR/TRAIL-R1/ROS/MCP-1/IP-10/MIP-1β expression were noticed specifically in D2- and also in D3-transfected cells, while D5 resulted in over-expression of ER-stress-markers. D-subgenotype-transfected Huh7 cells were co-cultured with PBMC of healthy-donors or LX-2 cells and significant increase in pro-inflammatory cytokines in PBMC and fibrogenic-markers in LX-2 were noticed in presence of D2/D3. Further, Huh7 cells transfected with D1, in particular and also D5, displayed remarkable induction of EMT-markers and high proliferative/migratory abilities. Collectively, our results demonstrated that D2/D3 were more associated with hepatic apoptosis/inflammation/fibrosis and D1/D5 with increased risk of hepatocarcinogenesis and emphasize the need for determining HBV-subgenotype in clinical practice.

Food components with antifibrotic activity and implications in prevention of liver disease

Increasing prevalence of nonalcoholic fatty liver disease (NAFLD) in parallel with the obesity epidemic has been a major public health concern. NAFLD is the most common chronic liver disease in the United States, ranging from fatty liver to steatohepatitis, fibrosis and cirrhosis in the liver. In response to chronic liver injury, fibrogenesis in the liver occurs as a protective response; however, prolonged and dysregulated fibrogenesis can lead to liver fibrosis, which can further progress to cirrhosis and eventually hepatocellular carcinoma. Interplay of hepatocytes, macrophages and hepatic stellate cells (HSCs) in the hepatic inflammatory and oxidative milieu is critical for the development of NAFLD. In particular, HSCs play a major role in the production of extracellular matrix proteins. Studies have demonstrated that bioactive food components and natural products, including astaxanthin, curcumin, blueberry, silymarin, coffee, vitamin C, vitamin E, vitamin D, resveratrol, quercetin and epigallocatechin-3-gallate, have antifibrotic effects in the liver. This review summarizes current knowledge of the mechanistic insight into the antifibrotic actions of the aforementioned bioactive food components.

Hepatic stellate cells as key target in liver fibrosis

Progressive liver fibrosis, induced by chronic viral and metabolic disorders, leads to more than one million deaths annually via development of cirrhosis, although no antifibrotic therapy has been approved to date. Transdifferentiation (or "activation") of hepatic stellate cells is the major cellular source of matrix protein-secreting myofibroblasts, the major driver of liver fibrogenesis. Paracrine signals from injured epithelial cells, fibrotic tissue microenvironment, immune and systemic metabolic dysregulation, enteric dysbiosis, and hepatitis viral products can directly or indirectly induce stellate cell activation. Dysregulated intracellular signaling, epigenetic changes, and cellular stress response represent candidate targets to deactivate stellate cells by inducing reversion to inactivated state, cellular senescence, apoptosis, and/or clearance by immune cells. Cell type- and target-specific pharmacological intervention to therapeutically induce the deactivation will enable more effective and less toxic precision antifibrotic therapies.

SOCS1 and pattern recognition receptors: TLR9 and RIG-I; novel haplotype associations in Egyptian fibrotic/cirrhotic patients with HCV genotype 4

In this paper we explore the role of suppressor of cytokine signaling 1 (SOCS1) (rs243327), the regulator of toll-like receptor-9 (TLR9) (rs352140), retinoic acid inducible gene-I (RIG-I) (rs669260), and cluster of differentiation 152 (CD152) (rs231776) in fibrotic/cirrhotic patients. Single nucleotide polymorphisms (SNPs) within these genes as well as haplotype analyses were performed on a cohort of 120 Egyptian fibrotic patients. Fibrosis had progressed from HCV genotype 4 infections. Using RT-PCR, SNPs were evaluated in the DNA collected from each patient using TaqMan® genotyping assays. A regression model was used to evaluate allelic and haplotypic associations with a fibrosis/cirrhotic scale. The necroinflammatory A score was adjusted for non-genetic covariates. The genotype distributions for SOCS1 (rs243327) and TLR-9 (rs352140) differed significantly between the F1-F3 and F3-F4 groups. On the other hand, the genotype distributions for RIG-I (rs669260) and CD152 (rs231776) genes did not significantly differ. The allele frequency was calculated using Hardy-Weinberg Equilibrium (HWE) for the SOCS1 (rs243327), RIG-I (rs669260), and CD152 (rs231776) genes. These calculated frequency values indicated the need to compare them to another population for that locus. However, TLR9 (rs352140) did not show similar results. The A allele in SOCS1, TLR9, and RIG-I SNPs was an adverse prognostic factor for liver fibrosis and liver activity. Haplotype analysis revealed a significant association between SOCS1 and TLR9 in fibrotic/cirrhotic patients. This indicated the presence of the A allele in either gene, which is considered a risk factor for the progression of liver disease to cirrhosis. SOCS1 rs243327, TLR9 rs352140, and RIG-I rs669260 polymorphisms might affect liver pathophysiology and the cirrhotic outcome following genotype 4 HCV infection. Therefore, performing this specific SNP testing may be of value for the stratification of the population at risk.

The contribution of toll-like receptor signaling to the development of liver fibrosis and cancer in hepatocyte-specific TAK1-deleted mice

Hepatocyte death is associated with liver inflammation, fibrosis and hepatocellular carcinoma (HCC). Damaged cells trigger inflammation through activation of Toll-like receptors (TLRs). Although the role of TLR4 in HCC development has been reported, the role of TLR9 in the development of HCC remains elusive. To investigate the role of TLR4 and TLR9 signaling in liver inflammation-fibrosis-cancer axis, we took advantage of mice with hepatic deletion of transforming growth factor-β-activated kinase 1 (Tak1ΔHep) that develop spontaneous liver injury, inflammation, fibrosis, and HCC, recapitulating the pathology of human HCC. We generated double knockout mice lacking genes of our interest with hepatic Tak1. Tak1ΔHep mice and Tlr4-deficient Tak1ΔHep mice had similar serum ALT levels, but Tlr4-deficient Tak1ΔHep mice exhibited significantly reduced macrophage infiltration, myofibroblast activation and tumor formation. Ablation of TLR9 reduced spontaneous liver injury, inflammation, fibrosis, and cancer development in Tak1ΔHep mice. In addition, the common adaptor, myeloid differentiation factor 88 (MyD88)-deficient Tak1ΔHep mice also attenuated liver injury, macrophage recruitment, collagen deposition, and tumor growth compared with control Tak1ΔHep mice. Genetic ablation of TNF receptor type I (TNFR) in Tak1ΔHep mice remarkably reduced liver inflammation-fibrosis-cancer axis. Surprisingly, disruption of interleukin-1 receptor (IL-1R) had no effect on liver injury and tumor formation, although Il1r-deficient Tak1ΔHep showed attenuated macrophage infiltration and collagen deposition. In conclusion, TLR4- and TLR9-MyD88 are driving forces of progression to HCC accompanied by liver inflammation and fibrosis in Tak1ΔHep mice. Importantly, TLR4 and TLR9 downstream TNFR, but not IL-1R signaling is crucial for the development of HCC in Tak1ΔHep mice.

Fetal and Placental DNA Stimulation of TLR9: A Mechanism Possibly Contributing to the Pro-inflammatory Events During Parturition

INTRODUCTION

While there is evidence for a relationship between cell-free fetal DNA (cffDNA) and parturition, questions remain regarding whether cffDNA could trigger a pro-inflammatory response on the pathway to parturition. We hypothesized that placental and/or fetal DNA stimulates toll-like receptor 9 (TLR9) leading to secretion of pro-inflammatory cytokines by macrophage cells.

METHODS

Four in vitro DNA stimulation studies were performed using RAW 264.7 mouse peritoneal macrophage cells incubated in media containing the following DNA particles: an oligodeoxynucleotide (ODN2395), intact genomic DNA (from mouse placentas, fetuses and adult liver), mouse DNA complexed with DOTAP (a cationic liposome forming compound), and telomere-depleted mouse DNA. Interleukin 6 (IL6) secretion was measured in the media by enzyme-linked immunosorbent assay; and the cell pellet was homogenized for protein content (picograms IL6/mg protein).

RESULTS

Robust IL6 secretion was observed in response to ODN2395 (a CpG-rich TLR9 agonist), mouse DNA-DOTAP complexes, and telomere-depleted mouse DNA in concentrations of 5 to 15 μg/mL. In contrast, ODN A151 (containing telomere sequence motifs), intact genomic mouse DNA, and restriction enzyme-digested DNA had no effect on IL6 secretion. The IL6 response was significantly inhibited by chloroquine (10 μg/mL), thereby confirming the important role for TLR9 in the response by macrophage cells.

CONCLUSIONS

DNA derived from mouse placentas and fetuses, and depleted of telomeric sequences, stimulates a robust pro-inflammatory response by macrophage cells, thereby supporting the hypothesis that cffDNA is able to stimulate an innate immune response that could trigger the onset of parturition. These findings are of clinical importance, as we search for effective treatment/prevention of preterm parturition.

Protective effect of human serum amyloid P on CCl4-induced acute liver injury in mice

Human serum amyloid P (hSAP), a member of the pentraxin family, inhibits the activation of fibrocytes in culture and inhibits experimental renal, lung, skin and cardiac fibrosis. As hepatic inflammation is one of the causes of liver fibrosis, in the present study, we investigated the hepatoprotective effects of hSAP against carbon tetrachloride (CCl₄)-induced liver injury. Our data indicated that hSAP attenuated hepatic histopathological abnormalities and significantly decreased inflammatory cell infiltration and pro-inflammatory factor expression. Moreover, CCl₄-induced apoptosis in the mouse liver was inhibited by hSAP, as measured by terminal-deoxynucleotidyl transferase mediated nick-end labeling (TUNEL) assay and cleaved caspase-3 expression. hSAP significantly restored the expression of B cell lymphoma/leukemia (Bcl)-2 and suppressed the expression of Bcl-2-associated X protein (Bax) in vivo. The number of hepatocytes in early apoptosis stained with Annexin V was significantly reduced by 28–30% in the hSAP treatment group compared with the CCl₄ group, and the expression of Bcl-2 was increased, whereas the expression of Bax and cleaved caspase-3 were significantly inhibited in the hSAP pre-treatment group compared with the CCl₄ group. hSAP administration also inhibited the migration and activation of hepatic stellate cells (HSCs) in CCl₄-injured liver and suppressed the activation of isolated primary HSCs induced by transforming growth factor (TGF)-β1 in vitro. Collectively, these findings suggest that hSAP exerts a protective effect againts CCl₄-induced hepatic injury by suppressing the inflammatory response and hepatocyte apoptosis, potentially by inhibiting HSC activation.

Reversal of liver fibrosis: From fiction to reality

In chronic liver diseases, an ongoing hepatocellular injury together with inflammatory reaction results in activation of hepatic stellate cells (HSCs) and increased deposition of extracellular matrix (ECM) termed as liver fibrosis. It can progress to cirrhosis that is characterized by parenchymal and vascular architectural changes together with the presence of regenerative nodules. Even at late stage, liver fibrosis is reversible and the underlying mechanisms include a switch in the inflammatory environment, elimination or regression of activated HSCs and degradation of ECM. While animal models have been indispensable for our understanding of liver fibrosis, they possess several important limitations and need to be further refined. A better insight into the liver fibrogenesis resulted in a large number of clinical trials aiming at reversing liver fibrosis, particularly in patients with non-alcoholic steatohepatitis. Collectively, the current developments demonstrate that reversal of liver fibrosis is turning from fiction to reality.

The role of Kupffer cells in hepatic diseases

Kupffer cells (KCs) constitute 80-90% of the tissue macrophages present in the body. Essential to innate and adaptive immunity, KCs are responsible for the swift containment and clearance of exogenous particulates and immunoreactive materials which are perceived as foreign and harmful to the body. Similar to other macrophages, KCs also sense endogenous molecular signals that may result from perturbed homeostasis of the host. KCs have been implicated in host defense and the pathogenesis of various hepatic diseases, including endotoxin tolerance, liver transplantation, nonalcoholic fatty liver disease, and alcoholic liver disease. In this review, we summarized some novel findings associated with the role of KCs in hepatic diseases, such as the origin and mechanisms KCs polarization, molecular basis for caspase-1 activation called "non-canonical inflammasome pathway" involving the cleavage of Gsdmd by caspase-11, the important role of microRNA in liver transplantation, and so on. A better understanding of KCs biological characteristics and immunologic function in liver homeostasis and pathology may pave the way to investigate new diagnostic and therapeutic approaches for hepatic diseases.

Immune-Mediated Therapies for Liver Cancer

In recent years, immunotherapy has gained renewed interest as an alternative therapeutic approach for solid tumors. Its premise is based on harnessing the power of the host immune system to destroy tumor cells. Development of immune-mediated therapies, such as vaccines, adoptive transfer of autologous immune cells, and stimulation of host immunity by targeting tumor-evasive mechanisms have advanced cancer immunotherapy. In addition, studies on innate immunity and mechanisms of immune evasion have enhanced our understanding on the immunology of liver cancer. Preclinical and clinical studies with immune-mediated therapies have shown potential benefits in patients with liver cancer. In this review, we summarize current knowledge and recent developments in tumor immunology by focusing on two main primary liver cancers: hepatocellular carcinoma and cholangiocarcinoma.

Toll-like receptors in pathophysiology of liver diseases

Toll-like receptors (TLRs) are pattern recognition receptors that participate in host defense by recognizing pathogen-associated molecular patterns alongside inflammatory processes by recognizing damage associated molecular patterns. Given constant exposure to pathogens from gut, strict control of TLR-associated signaling pathways is essential in the liver, which otherwise may lead to inappropriate production of pro-inflammatory cytokines and interferons and may generate a predisposition to several autoimmune and chronic inflammatory diseases. The liver is considered to be a site of tolerance induction rather than immunity induction, with specificity in hepatic cell functions and distribution of TLR. Recent data emphasize significant contribution of TLR signaling in chronic liver diseases via complex immune responses mediating hepatocyte (i.e., hepatocellular injury and regeneration) or hepatic stellate cell (i.e., fibrosis and cirrhosis) inflammatory or immune pathologies. Herein, we review the available data on TLR signaling, hepatic expression of TLRs and associated ligands, as well as the contribution of TLRs to the pathophysiology of hepatic diseases.

Long-term effect of biochar application on yield-scaled greenhouse gas emissions in a rice paddy cropping system: A four-year case study in south China

To evaluate long-term effect of biochar application on yield-scaled greenhouse gas emissions (YSGE) in a paddy rice cropping system, a 4-year field experiment by static chamber - gas chromatograph method was conducted in South China. Principal component analysis and terminal restriction fragment length polymorphism (T-RFLP) and real-time qPCR was used to unravel the microbial mechanisms of biochar addition. Six treatments were included: control (CK), application of 5tha(-1) biochar (BC1), application of 10tha(-1) biochar (BC2), application of 10tha(-1) biochar (BC3), rice straw return at 2400kgha(-1)(RS) and inoculated rice straw return at 2400kgha(-1)(RI). The results indicated that biochar amendment significantly decreased methane (CH4) and gross greenhouse gas (GHG) emissions. This may primarily be ascribed to the stimulated biodiversity and abundance of methanotrophic microbes, increased soil pH and improved aeration by reducing bulk density after biochar incorporation. Compared with CK, RS and RI, 26.18%, 70.02%, 66.47% of CH4 flux and 26.14%, 70.16%, 66.46% of gross GHG emissions were reduced by biochar (mean of three biochar treatments), respectively. Furthermore, biochar significantly increased harvest index of double rice production (p<0.05). In comparison with CK, RS and RI, 29.14%, 68.04%, 62.28% of YSGE was reduced by biochar, respectively, and the highest biochar addition rate (20tha(-1)) contributed most to the mitigation of GHG emissions (36.24% decrease compared to CK) and improvement of rice yield (7.65% increase compared to CK). Results of our study suggested that long-term application of biochar should be the potential way to mitigate GHGs emissions and simultaneously improve rice productivity in the paddy rice system.

Targeting Hepatic Fibrosis in Autoimmune Hepatitis

Hepatic fibrosis develops or progresses in 25 % of patients with autoimmune hepatitis despite corticosteroid therapy. Current management regimens lack reliable noninvasive methods to assess changes in hepatic fibrosis and interventions that disrupt fibrotic pathways. The goals of this review are to indicate promising noninvasive methods to monitor hepatic fibrosis in autoimmune hepatitis and identify anti-fibrotic interventions that warrant evaluation. Laboratory methods can differentiate cirrhosis from non-cirrhosis, but their accuracy in distinguishing changes in histological stage is uncertain. Radiological methods include transient elastography, acoustic radiation force impulse imaging, and magnetic resonance elastography. Methods based on ultrasonography are comparable in detecting advanced fibrosis and cirrhosis, but their performances may be compromised by hepatic inflammation and obesity. Magnetic resonance elastography has excellent performance parameters for all histological stages in diverse liver diseases, is uninfluenced by inflammatory activity or body habitus, has been superior to other radiological methods in nonalcoholic fatty liver disease, and may emerge as the preferred instrument to evaluate fibrosis in autoimmune hepatitis. Promising anti-fibrotic interventions are site- and organelle-specific agents, especially inhibitors of nicotinamide adenine dinucleotide phosphate oxidases, transforming growth factor beta, inducible nitric oxide synthase, lysyl oxidases, and C-C chemokine receptors types 2 and 5. Autoimmune hepatitis has a pro-fibrotic propensity, and noninvasive radiological methods, especially magnetic resonance elastography, and site- and organelle-specific interventions, especially selective antioxidants and inhibitors of collagen cross-linkage, may emerge to strengthen current management strategies.

Promising therapies for treatment of nonalcoholic steatohepatitis

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) has become the most common etiology for abnormal aminotransferase levels and chronic liver disease. Its growing prevalence is largely linked to the presence of metabolic syndrome, particularly diabetes and insulin resistance. It is estimated that 60-80% of the type 2 diabetic population has NAFLD. NAFLD encompasses a range of conditions ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). A subset of patients with hepatic steatosis progress to NASH, while 15-20% of patients with NASH develop cirrhosis. This progression is thought to be multifactorial, and there are currently no FDA-approved medications for the treatment of NASH.

AREAS COVERED

We review drugs currently in Phase II and III clinical trials for treatment of NAFLD and NASH, including their mechanisms of action, relationship to the pathophysiology of NASH, and rationale for their development.

EXPERT OPINION

The treatment of NASH is complex and necessitates targeting a number of different pathways. Combination therapy, preferably tailored toward the disease stage and severity, will be needed to achieve maximum therapeutic effect. With multiple agents currently being developed, there may soon be an ability to effectively slow or even reverse the disease process in many NAFLD/NASH patients.

Toll-like Receptor 9 Signaling Is Augmented in Systemic Sclerosis and Elicits Transforming Growth Factor β-Dependent Fibroblast Activation

OBJECTIVE

Although transforming growth factor β (TGFβ) is recognized as being a key trigger of fibroblast activation in systemic sclerosis (SSc), prominent innate immunity suggests that additional pathways contribute to disease persistence. Toll-like receptor 9 (TLR9) is implicated in autoimmunity and fibrosis; however, the expression, mechanism of action, and pathogenic role of TLR9 signaling in SSc remain uncharacterized. The aim of this study was to explore the expression, activity, and potential pathogenic role of TLR9 in the context of skin fibrosis in SSc and in mouse models of experimental fibrosis.

METHODS

Expression and localization of TLR9 were evaluated in SSc skin biopsy specimens and explanted skin fibroblasts. Fibrotic responses elicited by type A CpG oligonucleotide and mitochondrial DNA (mtDNA) were examined in human skin fibroblasts by a combination of real-time quantitative polymerase chain reaction, Western blot analysis, transient transfection, immunofluorescence microscopy, and functional assays. Expression of TLR9 was examined in 2 distinct mouse models of experimental fibrosis.

RESULTS

Skin biopsy specimens obtained from 2 independent cohorts of SSc patients showed up-regulation of TLR9, and myofibroblasts were the major cellular source. Moreover, SSc skin biopsy specimens showed evidence of TLR9 pathway activation. CpG induced robust TLR9-dependent fibrotic responses in explanted normal fibroblasts that could be blocked by bortezomib and were mediated through the action of endogenous TGFβ. Mice with experimental fibrosis showed a time-dependent increase in TLR9 localized primarily to myofibroblasts in the dermis.

CONCLUSION

In isolated fibroblasts, TLR9 elicits fibrotic responses mediated via endogenous TGFβ. In patients with SSc, mtDNA and other damage-associated TLR9 ligands in the skin might trigger localized activation of TLR9 signaling, TGFβ production, and consequent fibroblast activation. Disrupting this fibrotic process with inhibitors targeting TLR9 or its downstream signaling pathways might therefore represent a novel approach to SSc therapy.

Exosome-mediated activation of toll-like receptor 3 in stellate cells stimulates interleukin-17 production by γδ T cells in liver fibrosis

During liver injury, hepatocytes secrete exosomes that include diverse types of self-RNAs. Recently, self-noncoding RNA has been recognized as an activator of Toll-like receptor 3 (TLR3). However, the roles of hepatic exosomes and TLR3 in liver fibrosis are not yet fully understood. Following acute liver injury and early-stage liver fibrosis induced by a single or 2-week injection of carbon tetrachloride (CCl4 ), increased interleukin (IL)-17A production was detected primarily in hepatic γδ T cells in wild-type (WT) mice. However, liver fibrosis and IL-17A production by γδ T cells were both significantly attenuated in TLR3 knockout (KO) mice compared with WT mice. More interestingly, IL-17A-producing γδ T cells were in close contact with activated hepatic stellate cells (HSCs), suggesting a role for HSCs in IL-17A production by γδ T cells. In vitro treatments with exosomes derived from CCl4 -treated hepatocytes significantly increased the expression of IL-17A, IL-1β, and IL-23 in WT HSCs but not in TLR3 KO HSCs. Furthermore, IL-17A production by γδ T cells was substantially increased upon coculturing with exosome-treated WT HSCs or conditioned medium from TLR3-activated WT HSCs. However, similar increases were not detected when γδ T cells were cocultured with exosome-treated HSCs from IL-17A KO or TLR3 KO mice. Using reciprocal bone marrow transplantation between WT and TLR3 KO mice, we found that TLR3 deficiency in HSCs contributed to decreased IL-17A production by γδ T cells, as well as liver fibrosis.

CONCLUSION

In liver injury, the exosome-mediated activation of TLR3 in HSCs exacerbates liver fibrosis by enhancing IL-17A production by γδ T cells, which might be associated with HSC stimulation by unknown self-TLR3 ligands from damaged hepatocytes. Therefore, TLR3 might be a novel therapeutic target for liver fibrosis. (Hepatology 2016;64:616-631).

New Concepts on Pathogenesis and Diagnosis of Liver Fibrosis; A Review Article

Liver fibrosis is a potentially reversible response to hepatic insults, triggered by different chronic diseases most importantly viral hepatitis, alcoholic, and nonalcoholic fatty liver disease. In the course of the chronic liver disease, hepatic fibrogenesis may develop, which is attributed to various types of cells, molecules, and pathways. Activated hepatic stellate cell (HSC), the primary source of extracellular matrix (ECM), is fundamental in pathophysiology of fibrogenesis, and thus is the most attractable target for reversing liver fibrosis. Although, liver biopsy has long been considered as the gold standard for diagnosis and staging of hepatic fibrosis, assessing progression and regression by biopsy is hampered by its limitations. We provide recent views on noninvasive approaches including serum biomarkers and radiologic techniques.

Review article: emerging anti-fibrotic therapies in the treatment of non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) can lead to non-alcoholic steatohepatitis (NASH) and cirrhosis. Fibrosis predicts worse outcomes and mortality. New treatments targeting fibrosis are being investigated to reverse disease progression.

AIM

To review the new pipeline therapeutic agents targeting fibrosis in NASH patients, with particular focus on clinical trials in which reversing fibrosis and portal hypertension are the primary outcomes.

METHODS

The literature was searched in PubMed between January 2000 and January 2016 using search terms non-alcoholic fatty liver disease and NASH, with filters of 'English language'. We focused on fibrosis improvement as the key outcome. We also searched the ClinicalTrials.gov for promising agents that target fibrosis in NASH patients.

RESULTS

Significant advances have been made on approaches targeting fibrosis in NASH patients. Many therapeutic agents are already in development, some of which have shown promising results in preclinical and phase I studies. Novel therapies have entered phase II and III studies targeting fibrosis reversal and/or improvement in portal hypertension. Innovative studies have also started looking into combining these agents, aiming at different mechanisms to maximise therapeutic outcomes. We found five clinical trials in phase II and one in phase III focusing on fibrosis in NASH patients as key outcomes. One of the phase II trials is using combination therapy to target fibrosis.

CONCLUSIONS

Ongoing research studies are already investigating new pathways aimed at reversing fibrosis in NASH patients. Novel therapeutic agents are in development and are expected to offer unique options to NASH patients with advanced fibrosis.

Hepatitis C may enhance key amplifiers of psoriasis

BACKGROUND

Multiple studies have noted an association between hepatitis C and psoriasis, but it is not known whether psoriasis is a result of treatment modalities for hepatitis C or a result of hepatitis C alone.

OBJECTIVE

To examine the relationship between psoriasis and hepatitis C by measuring the expression of cathelicidin, TLR9 and IFNγ in psoriatic lesional and non-lesional skin in HCV-positive and negative psoriatic patients.

METHODS

Two 2 mm punch biopsies of lesional and non-lesional skin in 10 patients who were HCV-negative psoriatics and seven HCV-positive psoriatics were used to measure cathelicidin, TLR9 and IFNγ mRNA expression by quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR).

RESULTS

The mRNA levels of cathelicidin, TLR9 and IFNγ were significantly higher in both non-lesional and lesional skin of HCV-positive patients with psoriasis as compared to HCV-negative psoriatic patients. Additionally, the IFNγ level in lesional skin of HCV-positive psoriatic patients was higher than the IFNγ level seen in non-lesional skin of those same patients.

CONCLUSION

These findings suggest that HCV infection upregulates these inflammatory cytokines, possibly increasing susceptibility to developing psoriasis.

Organ system view of the hepatic innate immunity in HCV infection

An orchestration of innate and adaptive immunity determines the infection outcome and whether the host achieves clearance or allows the pathogen to establish persistent infection. The robust activation of the innate immune response plays the most critical role in both limiting viral replication and halting the spread of the pathogen immediately after infection. The magnitude of innate immune activation is coupled with the efficient mounting of the adaptive immunity. Although immunity against HCV infection is known to be inadequate as most cases transitions to chronicity, approximately 25% of acute infection cases result in spontaneous clearance. The exact immune mechanisms that govern the infection outcome remain largely unknown; recent discoveries suggest that the innate immune system facilitates this event. Both infected hepatocytes and local innate immune cells trigger the front line defense program of the liver as well as the recruitment of diverse adaptive immune cells to the site of infection. Although hepatocyte is the target of HCV infection, nearly all cell types that exist in the liver are involved in the innate defense and contribute to the pathophysiology of hepatic inflammation. The main focus of this comprehensive review is to discuss the current knowledge on how each hepatic cell type contributes to the organ system level innate immunity against HCV infection as well as interplays with the viral evasion program. Furthermore, this review article also aims to synchronize the observations from both molecular biological studies and clinical studies with the ultimate goal of improving our understanding of HCV mediated hepatitis. J. Med. Virol. 88:2025-2037, 2016. © 2016 Wiley Periodicals, Inc.

Rutin Attenuates Hepatotoxicity in High-Cholesterol-Diet-Fed Rats

Background and Objective. High-cholesterol diet (HCD) intends to increase the oxidative stress in liver tissues inducing hepatotoxicity. Rutin is a natural flavonoid (vitamin p) which is known to have antioxidative properties. The aim of the present study was to investigate the potential effects of Rutin on hypercholesterolemia-induced hepatotoxicity in rats. Materials and Methods. Male Wistar rats were divided into four groups: G-I control, G-II Rutin, G-III HCD, and G-IV Rutin + HCD. The liver functions and lipid profile were used to evaluate the HCD-induced hepatotoxicity. Quantitative real time-PCR was carried out to evaluate the expression levels of genes in TGF-β/Smad signaling pathway. Results. Rutin in combination with HCD showed a significant protective effect against hepatotoxicity. HCD caused significant increase in the mRNA expression of transforming growth factor beta (TGF-β), Mothers Against Decapentaplegic Homolog 2 (Smad-2), Mothers Against Decapentaplegic Homolog 4 (Smad-4), Bcl-2-binding component 3 (Bbc3), caspase-3, P53 and Interleukin-6 (IL-6) and decrease in the expression levels of Cyclin depended kinase inhibitor (P21) and Interleukin-3 (IL-3) in hepatic cells. Conclusion. TGF-β/Smad signaling pathway is involved in HCD-induced hepatotoxicity and Rutin inhibits the hepatotoxicity via suppressing this pathway. Therefore, Rutin might be considered as a protective agent for hepatotoxicity.

Hepatocyte mitochondrial DNA drives nonalcoholic steatohepatitis by activation of TLR9

Nonalcoholic steatohepatitis (NASH) is the most common liver disease in industrialized countries. NASH is a progressive disease that can lead to cirrhosis, cancer, and death, and there are currently no approved therapies. The development of NASH in animal models requires intact TLR9, but how the TLR9 pathway is activated in NASH is not clear. Our objectives in this study were to identify NASH-associated ligands for TLR9, establish the cellular requirement for TLR9, and evaluate the role of obesity-induced changes in TLR9 pathway activation. We demonstrated that plasma from mice and patients with NASH contains high levels of mitochondrial DNA (mtDNA) and intact mitochondria and has the ability to activate TLR9. Most of the plasma mtDNA was contained in microparticles (MPs) of hepatocyte origin, and removal of these MPs from plasma resulted in a substantial decrease in TLR9 activation capacity. In mice, NASH development in response to a high-fat diet required TLR9 on lysozyme-expressing cells, and a clinically applicable TLR9 antagonist blocked the development of NASH when given prophylactically and therapeutically. These data demonstrate that activation of the TLR9 pathway provides a link between the key metabolic and inflammatory phenotypes in NASH.

Cytokeratin 18-Aspartate396 apoptotic fragment for fibrosis detection in patients with non-alcoholic fatty liver disease and chronic viral hepatitis

BACKGROUND

The combination of non-invasive markers for the detection of fibrosis in patients with chronic liver diseases is still a matter of debate.

AIMS

To test the performance of cytokeratin18-Aspartate396 alone or in combination with transient elastography as a marker of fibrosis, compared to liver biopsy as gold standard.

METHODS

In 259 prospectively enrolled patients with chronic liver diseases, clinical, biochemical, and histological features were assessed. Serum cytokeratin18-Aspartate396 and Fibroscan were performed within 6 months prior to liver biopsy.

RESULTS

Cytokeratin18-Aspartate396 levels predicted both significant and advanced fibrosis in non-alcoholic fatty liver disease group, correctly identifying 83.7% and 80.8% of cases, respectively. Liver stiffness performed best in predicting severe fibrosis in patients with chronic viral infection, correctly identifying 78.7% of chronic hepatitis B and 88.6% of chronic hepatitis C subjects. The combination of cytokeratin18-Aspartate396 and liver stiffness improved their diagnostic performance for the detection of significant and advanced fibrosis in non-alcoholic fatty liver disease group, only (sensitivity=78.3%, specificity=90.7%; sensitivity=91.7%, specificity=71.6%, respectively).

CONCLUSION

Cytokeratin18-Aspartate396 and liver stiffness can improve the non-invasive prediction of significant and advanced fibrosis in patients with non-alcoholic fatty liver disease, while in hepatitis B and C virus infected patients their combined use had no advantage over the diagnostic accuracy of transient elastography alone.

Imaging the dynamic platelet-neutrophil response in sterile liver injury and repair in mice

Although platelets have been extensively studied in hemostasis and inflammation, their role is not well understood in sterile liver injury and repair. Using a thermally induced focal liver injury and repair model and multichannel spinning disk confocal microscopy allowed visualization of the dynamic behavior of platelets and neutrophils in this insult. Platelets instantaneously adhered to molecularly altered sinusoidal endothelium adjacent to the afflicted area, paving approximately 200 µm abutting the injury. Platelets remained adherent for at least 4 hours, but dissipated by 8 hours. The early recruitment occurred by GPIIbIIIa (CD41) and the later recruitment was dependent upon both GPIIbIIIa and GPIb (CD42B). Platelets did not occlude the vessels, but rather paved the altered endothelium. Endothelin-induced vasoconstriction by hepatic stellate cells, and not platelet accumulation or coagulation, was responsible for temporarily restricted perfusion around the injury. Neutrophils crawled into the injury from significant distances through the sinusoids. The crawling neutrophils required the platelet-paved endothelium given that very little neutrophil recruitment was noted in thrombocytopenic or CD41-deficient mice. As platelets slowly dissipated, neutrophil recruitment was also halted. Previous work suggested that platelets binding to immobilized neutrophils induced neutrophil extracellular trap (NET) formation in response to infection as well as during thrombosis and other forms of sterile injury. In this model of neutrophils crawling on immobilized platelets, very few NETs were observed and no additional injury was noted. In fact, GPIIbIIIa-deficient mice had delayed repair.

CONCLUSION

In a liver model of sterile injury and repair, platelets play a critical role in forming a substratum and pave the way for neutrophils to enter the injured site for subsequent repair.

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

BACKGROUND&AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Cell-Free Fetal DNA, Telomeres, and the Spontaneous Onset of Parturition

Multiple previous reports have provided compelling support for the premise that spontaneous parturition is mediated by activation of inflammation-related signaling pathways leading to increased secretion of cytokines and chemokines, the influx of neutrophils and macrophages into the pregnant uterus, increased production of uterine activation proteins (eg, connexin-43, cyclo-oxygenase-2, oxytocin receptors, etc), activation of matrix metalloproteinases, and the release of uterotonins leading to cervical ripening, membrane rupture, and myometrial contractions. The missing link has been the fetal/placental signal that triggers these proinflammatory events in the absence of microbial invasion and intrauterine infection. This article reviews the biomedical literature regarding the increase in cell-free fetal DNA (cffDNA), which is released during apoptosis in the placenta and fetal membranes at term, the ability of apoptosis modified vertebrate DNA to stimulate toll-like receptor-9 (TLR9) leading to increased release of cytokines and chemokines, and the potential "fail-safe" role for the anti-inflammatory cytokine IL-10. This article also reviews the literature supporting the key role that telomere loss plays in regard to increasing the ability of vertebrate (including placental) DNA to stimulate TLR9, and in regard to signaling the onset of apoptosis in the placenta and fetal membranes, thereby providing a biologic clock that determines the length of gestation and the timing for the onset of parturition. In summary, this literature review provides a strong rationale for future research to test the hypothesis that telomere loss and increased cffDNA levels trigger the proinflammatory events leading to the spontaneous onset of parturition in mammals: the "cffDNA/telomere hypothesis."

Hepatic inflammation and fibrosis: functional links and key pathways

Inflammation is one of the most characteristic features of chronic liver disease of viral, alcoholic, fatty, and autoimmune origin. Inflammation is typically present in all disease stages and associated with the development of fibrosis, cirrhosis, and hepatocellular carcinoma. In the past decade, numerous studies have contributed to improved understanding of the links between hepatic inflammation and fibrosis. Here, we review mechanisms that link inflammation with the development of liver fibrosis, focusing on the role of inflammatory mediators in hepatic stellate cell (HSC) activation and HSC survival during fibrogenesis and fibrosis regression. We will summarize the contributions of different inflammatory cells, including hepatic macrophages, T and B lymphocytes, natural killer cells and platelets, as well as key effectors, such as cytokines, chemokines, and damage-associated molecular patterns. Furthermore, we will discuss the relevance of inflammatory signaling pathways for clinical liver disease and for the development of antifibrogenic strategies.

TRAIL-producing NK cells contribute to liver injury and related fibrogenesis in the context of GNMT deficiency

Glycine-N-methyltransferase (GNMT) is essential to preserve liver homeostasis. Cirrhotic patients show low expression of GNMT that is absent in hepatocellular carcinoma (HCC) samples. Accordingly, GNMT deficiency in mice leads to steatohepatitis, fibrosis, cirrhosis, and HCC. Lack of GNMT triggers NK cell activation in GNMT(-/-) mice and depletion of TRAIL significantly attenuates acute liver injury and inflammation in these animals. Chronic inflammation leads to fibrogenesis, further contributing to the progression of chronic liver injury regardless of the etiology. The aim of our study is to elucidate the implication of TRAIL-producing NK cells in the progression of chronic liver injury and fibrogenesis. For this we generated double TRAIL(-/-)/GNMT(-/-) mice in which we found that TRAIL deficiency efficiently protected the liver against chronic liver injury and fibrogenesis in the context of GNMT deficiency. Next, to better delineate the implication of TRAIL-producing NK cells during fibrogenesis we performed bile duct ligation (BDL) to GNMT(-/-) and TRAIL(-/-)/GNMT(-/-) mice. In GNMT(-/-) mice, exacerbated fibrogenic response after BDL concurred with NK1.1(+) cell activation. Importantly, specific inhibition of TRAIL-producing NK cells efficiently protected GNMT(-/-) mice from BDL-induced liver injury and fibrogenesis. Finally, TRAIL(-/-)/GNMT(-/-) mice showed significantly less fibrosis after BDL than GNMT(-/-) mice further underlining the relevance of the TRAIL/DR5 axis in mediating liver injury and fibrogenesis in GNMT(-/-) mice. Finally, in vivo silencing of DR5 efficiently protected GNMT(-/-) mice from BDL-liver injury and fibrogenesis, overall underscoring the key role of the TRAIL/DR5 axis in promoting fibrogenesis in the context of absence of GNMT. Overall, our work demonstrates that TRAIL-producing NK cells actively contribute to liver injury and further fibrogenesis in the pathological context of GNMT deficiency, a molecular scenario characteristic of chronic human liver disease.

Use of mesenchymal stem cells to treat liver fibrosis: Current situation and future prospects

Progressive liver fibrosis is a major health issue for which no effective treatment is available, leading to cirrhosis and orthotopic liver transplantation. However, organ shortage is a reality. Hence, there is an urgent need to find alternative therapeutic strategies. Cell-based therapy using mesenchymal stem cells (MSCs) may represent an attractive therapeutic option, based on their immunomodulatory properties, their potential to differentiate into hepatocytes, allowing the replacement of damaged hepatocytes, their potential to promote residual hepatocytes regeneration and their capacity to inhibit hepatic stellate cell activation or induce their apoptosis, particularly via paracrine mechanisms. The current review will highlight recent findings regarding the input of MSC-based therapy for the treatment of liver fibrosis, from in vitro studies to pre-clinical and clinical trials. Several studies have shown the ability of MSCs to reduce liver fibrosis and improve liver function. However, despite these promising results, some limitations need to be considered. Future prospects will also be discussed in this review.

Cellular and molecular functions of hepatic stellate cells in inflammatory responses and liver immunology

The liver is a central immunological organ. Liver resident macrophages, Kupffer cells (KC), but also sinusoidal endothelial cells, dendritic cells (DC) and other immune cells are involved in balancing immunity and tolerance against pathogens, commensals or food antigens. Hepatic stellate cells (HSCs) have been primarily characterized as the main effector cells in liver fibrosis, due to their capacity to transdifferentiate into collagen-producing myofibroblasts (MFB). More recent studies elucidated the fundamental role of HSC in liver immunology. HSC are not only the major storage site for dietary vitamin A (Vit A) (retinol, retinoic acid), which is essential for proper function of the immune system. This pericyte further represents a versatile source of many soluble immunological active factors including cytokines [e.g., interleukin 17 (IL-17)] and chemokines [C-C motif chemokine (ligand) 2 (CCL2)], may act as an antigen presenting cell (APC), and has autophagy activity. Additionally, it responds to many immunological triggers via toll-like receptors (TLR) (e.g., TLR4, TLR9) and transduces signals through pathways and mediators traditionally found in immune cells, including the Hedgehog (Hh) pathway or inflammasome activation. Overall, HSC promote rather immune-suppressive responses in homeostasis, like induction of regulatory T cells (Treg), T cell apoptosis (via B7-H1, PDL-1) or inhibition of cytotoxic CD8 T cells. In conditions of liver injury, HSC are important sensors of altered tissue integrity and initiators of innate immune cell activation. Vice versa, several immune cell subtypes interact directly or via soluble mediators with HSC. Such interactions include the mutual activation of HSC (towards MFB) and macrophages or pro-apoptotic signals from natural killer (NK), natural killer T (NKT) and gamma-delta T cells (γδ T-cells) on activated HSC. Current directions of research investigate the immune-modulating functions of HSC in the environment of liver tumors, cellular heterogeneity or interactions promoting HSC deactivation during resolution of liver fibrosis. Understanding the role of HSC as central regulators of liver immunology may lead to novel therapeutic strategies for chronic liver diseases.

The nucleic acid scavenger polyamidoamine third-generation dendrimer inhibits fibroblast activation and granulation tissue contraction

BACKGROUND

Pathologic cutaneous scarring affects over 40 million people worldwide and costs billions of dollars annually. Understanding mechanisms of fibroblast activation and granulation tissue contraction is the first step toward preventing pathologic scarring. The authors hypothesize that nucleic acids increase fibroblast activation and cause granulation tissue contraction and that sequestration of nucleic acids by application of a nucleic acid scavenger dendrimer, polyamidoamine third-generation dendrimer, will decrease pathologic scarring.

METHODS

In vitro experiments were performed to assess the effect of nucleic acids on pathologic scar-associated fibroblast activity. The effect of nucleic acids on cytokine production and migration on mouse fibroblasts was evaluated. Immunofluorescence microscopy was used to determine the effect of nucleic acids on the differentiation of human primary fibroblasts into myofibroblasts. Using a murine model, the effect of polyamidoamine third-generation dendrimer on granulation tissue contraction was evaluated by gross and histologic parameters.

RESULTS

Mouse fibroblasts stimulated with nucleic acids had increased cytokine production (i.e., transforming growth factor-β, monocyte chemotactic protein 1, interleukin-10, tumor necrosis factor-α, and interferon-γ), migration, and differentiation into myofibroblasts. Polyamidoamine third-generation dendrimer blocked cytokine production, migration, and differentiation into myofibroblasts. Using a murine model of granulation tissue contraction, polyamidoamine third-generation dendrimer decreased wound contraction and angiogenesis. Collagen deposition in polyamidoamine third-generation dendrimer-treated tissues was aligned more randomly and whorl-like compared with control tissue.

CONCLUSIONS

The data demonstrate that nucleic acid-stimulated fibroblast activation and granulation tissue contraction are blocked by polyamidoamine third-generation dendrimer. Sequestration of pathogen-associated molecular patterns may be an approach for preventing pathologic scarring.

4Ps medicine of the fatty liver: the research model of predictive, preventive, personalized and participatory medicine-recommendations for facing obesity, fatty liver and fibrosis epidemics

Relationship between adipose tissue and fatty liver, and its possible evolution in fibrosis, is supported by clinical and research experience. Given the multifactorial pathogenesis of non-alcoholic fatty liver disease (NAFLD), treatments for various contributory risk factors have been proposed; however, there is no single validated therapy or drug association recommended for all cases which can stand alone. Mechanisms, diagnostics, prevention and treatment of obesity, fatty liver and insulin resistance are displayed along with recommendations and position points. Evidences and practice can get sustainable and cost-benefit valuable outcomes by participatory interventions. These recommendations can be enhanced by comprehensive research projects, addressed to societal issues and innovation, market appeal and industry development, cultural acceptance and sustainability. The basis of participatory medicine is a greater widespread awareness of a condition which is both a disease and an easy documented and inclusive clue for associated diseases and unhealthy lifestyle. This model is suitable for addressing prevention and useful for monitoring improvement, worsening and adherence with non-invasive imaging tools which allow targeted approaches. The latter include health psychology and nutritional and physical exercise prescription expertise disseminated by continuous medical education but, more important, by concrete curricula for training undergraduate and postgraduate students. It is possible and recommended to do it by early formal teaching of ultrasound imaging procedures and of practical lifestyle intervention strategies, including approaches aimed to healthier fashion suggestions. Guidelines and requirements of research project funding calls should be addressed also to NAFLD and allied conditions and should encompass the goal of training by research and the inclusion of participatory medicine topics. A deeper awareness of ethics of competences in health professionals and the articulation of knowledge, expertise and skills of medical doctors, dieticians, health psychologists and sport and physical exercise graduates are the necessary strategy for detectin a suboptimal health status and achieving realistically beneficial lifestyle changes. “The devil has put a penalty on all things we enjoy in life. Either we suffer in health or we suffer in soul or we get fat” (Albert Einstein); the task of medical research and intervention is to make possible to enjoy life also without things that make sufferance in health and souls and which excessively increase body fat.

Liver fibrosis and protection mechanisms action of medicinal plants targeting apoptosis of hepatocytes and hepatic stellate cells

Following chronic liver injury, hepatocytes undergo apoptosis leading to activation of hepatic stellate cells (HSC). Consequently, activated HSC proliferate and produce excessive extracellular matrix, responsible for the scar formation. The pandemic trend of obesity, combined with the high incidence of alcohol intake and viral hepatitis infections, highlights the urgent need to find accessible antifibrotic therapies. Treatment strategies should take into account the versatility of its pathogenesis and act on all the cell lines involved to reduce liver fibrosis. Medicinal plants are achieving popularity as antifibrotic agents, supported by their safety, cost-effectiveness, and versatility. This review will describe the role of hepatocytes and HSC in the pathogenesis of liver fibrosis and detail the mechanisms of modulation of apoptosis of both cell lines by twelve known hepatoprotective plants in order to reduce liver fibrosis.

Fuzheng Huayu recipe alleviates hepatic fibrosis via inhibiting TNF-α induced hepatocyte apoptosis

Background

What was the relationship of Fuzheng Huayu recipe (FZHY) inhibiting hepatocyte apoptosis and HSC activation at different stage of liver fibrosis? In order to answer this question, the study was carried out to dynamically observe FZHY’s effect on hepatocyte apoptosis and HSC activation and further explored underling mechanism of FZHY against hepatocyte apoptosis.

Methods

Mice were randomly divided into four groups: normal, model, FZHY, and N-acetylcystein (NAC) groups. Acute hepatic injury and liver fibrosis in mice were induced by CCl₄. Three days before the first CCl₄ injection, treatment with FZHY powder or NAC respectively was started. In vitro, primary hepatocytes were pretreated with FZHY medicated serum or Z-VAD-FMK and then incubated with ActD and TNF-α. Primary HSCs were treated with DNA from apoptotic hepatocytes incubated by Act D/TNF-α or FZHY medicated. Liver sections were analyzed for HE staining and immunohistochemical evaluation of apoptosis. Serum ALT and AST, Alb content and TNF-α expression in liver tissue were detected. Hyp content was assayed and collagen deposition was visualized. Expressions of α-SMA and type I collagen were analyzed by immunofluorescence and immunoblotting. Flow cytometry, immunofluorescence, and DNA ladder for hepatocyte apoptosis and immunoblotting for TNF-R1, Bcl-2 and Bax were also analyzed.

Results

Mice showed characteristic features of massive hepatocytes apoptosis in early stage of liver injury and developed severe hepatic fibrosis in later phase. FZHY treatment significantly alleviated acute liver injury and hepatocyte apoptosis, and inhibited liver fibrosis by decreasing α-SMA expression and hepatic Hyp content. In vitro, primary hepatocytes were induced by TNF-α and Act D. The anti-apoptotic effect of FZHY was generated by reducing TNFR1 expression and balancing the expressions of Bcl-2 and Bax. Meanwhile, the nuclear DNA from apoptotic hepatocytes stimulated HSC activation in a dose dependent manner, and the DNA from apoptotic hepatocytes treated with FZHY or Z-VAD-FMK reduced HSC activation and type I collagen expression.

Conclusion

These findings suggested that FZHY suppressed hepatocyte apoptosis through regulating mediators in death receptor and mitochondrial pathways, and the effect of FZHY on hepatocyte apoptosis might play an important role in inhibiting liver fibrosis.

Acute organ failure following the loss of anti-apoptotic cellular FLICE-inhibitory protein involves activation of innate immune receptors

Apoptosis signaling is involved in both physiological tissue homeostasis and acute and chronic diseases. The role of regulatory apoptosis signaling molecules and their organ-specific functions are less defined. Therefore, we investigated the loss of the anti-apoptotic cellular FLICE-inhibitory protein (cFLIP) and the mechanisms of the resulting lethal organ failure in vivo using inducible knockout mice. These were generated by crossing floxed cFLIP mice to a tamoxifen inducible Rosa26-creERT2 mouse strain. Death following global loss of cFLIP resulted from liver failure, accumulation of M1-polarized macrophages and accompanying hepatic cell death and inflammation. Apoptosis was also prominent in immune cells, the kidney and intestinal epithelial cells (IECs) but not in cardiomyocytes. Cellular injury led to the release of damage-associated molecular patterns (DAMPs) and the induction of innate immune receptors including toll-like receptors (TLRs) 4 and 9, and stimulator of interferon genes (STING). Transplantation of bone marrow with intact cFLIP or depletion of macrophages prevented the phenotype of acute liver failure. Interestingly, compound deletion of cFLIP in bone marrow-derived cells and hepatocytes did not promote organ failure. Thus, cFLIP exerts a critical role in tissue homeostasis by preventing the activation of monocytic cells and innate immunity, which causes cell death and inflammation in susceptible tissues. These results encourage the development of organ-specific anti-apoptotic and anti-inflammatory therapies in acute organ failure.

Chronic hepatitis C and liver fibrosis

Chronic infection with hepatitis C virus (HCV) is a leading cause of liver-related morbidity and mortality worldwide and predisposes to liver fibrosis and end-stage liver complications. Liver fibrosis is the excessive accumulation of extracellular matrix proteins, including collagen, and is considered as a wound healing response to chronic liver injury. Its staging is critical for the management and prognosis of chronic hepatitis C (CHC) patients, whose number is expected to rise over the next decades, posing a major health care challenge. This review provides a brief update on HCV epidemiology, summarizes basic mechanistic concepts of HCV-dependent liver fibrogenesis, and discusses methods for assessment of liver fibrosis that are routinely used in clinical practice. Liver biopsy was until recently considered as the gold standard to diagnose and stage liver fibrosis. However, its invasiveness and drawbacks led to the development of non-invasive methods, which include serum biomarkers, transient elastography and combination algorithms. Clinical studies with CHC patients demonstrated that non-invasive methods are in most cases accurate for diagnosis and for monitoring liver disease complications. Moreover, they have a high prognostic value and are cost-effective. Non-invasive methods for assessment of liver fibrosis are gradually being incorporated into new guidelines and are becoming standard of care, which significantly reduces the need for liver biopsy.

The inflammasome in liver injury and non-alcoholic fatty liver disease

The liver possesses a strong inflammatory response, as seen experimentally and clinically with liver inflammation due to toxic and metabolic stress, sepsis and ischemia. Initiation of this inflammatory response requires the interaction of two types of extracellular signals which collectively upregulate and activate a cytosolic molecular complex termed the inflammasome. Signal 1 is via activation of pattern recognition receptors, and signal 2 is delivered by diverse stimuli including particulates and adenosine triphosphate. The common end result of inflammasome activation is the activation of the protease caspase-1 with release of active interleukin-1β. The inflammasome is important in a wide range of conditions including alcoholic and non-alcoholic steatohepatitis. Kupffer cells are known to be important, but the consequences of inflammasome activation in other hepatic immune cells have not been well characterized. The inflammasome pathway is also known to be required for a full fibrotic response, as demonstrated by reduced lung, skin and liver fibrosis in inflammasome-deficient mice. Identification of the inflammasome machinery has opened up novel therapeutic avenues by the use of antagonists for Toll-like receptors as well as the adenosine triphosphate receptor P2X7, and the interleukin-1 receptor. There is now great interest in how inflammasome pathways are regulated. The initial challenge is to understand how an acute inflammatory response is sustained. This is a significant issue as the known stimuli result in an acute response that is self-limited to under 24 h. This suggests that there are significant regulators which allow sustained inflammasome activation in conditions such as non-alcoholic steatohepatitis and alcoholic hepatitis.

Adenosine is required for sustained inflammasome activation via the A₂A receptor and the HIF-1α pathway

Inflammasome pathways are important in chronic diseases, but it is not known how the signalling is sustained after initiation. Inflammasome activation is dependent on stimuli such as LPS and ATP that provide two distinct signals resulting in rapid production of IL-1β, with lack of response to repeat stimulation. Here we report that adenosine is a key regulator of inflammasome activity, increasing the duration of the inflammatory response via the A_2A receptor. Adenosine does not replace signals provided by stimuli such as LPS or ATP, but sustains inflammasome activity via a cAMP/PKA/CREB/HIF-1α pathway. In the setting of lack of IL-1β responses after previous exposure to LPS, adenosine can supersede this tolerogenic state and drive IL-1β production. These data reveal that inflammasome activity is sustained, after initial activation, by A_2A receptor-mediated signalling.

Innate immune cell networking in hepatitis C virus infection

Persistent viral infection, such as HCV infection, is the result of the inability of the host immune system to mount a successful antiviral response, as well as the escape strategies devised by the virus. Although each individual component of the host immune system plays important roles in antiviral immunity, the interactive network of immune cells as a whole acts against the virus. The innate immune system forms the first line of host defense against viral infection, and thus, virus elimination or chronic HCV infection is linked to the direct outcome of the interactions between the various innate immune cells and HCV. By understanding how the distinct components of the innate immune system function both individually and collectively during HCV infection, potential therapeutic targets can be identified to overcome immune dysfunction and control chronic viral infection.

Toll-like receptor 7-mediated type I interferon signaling prevents cholestasis- and hepatotoxin-induced liver fibrosis

Toll-like receptor 7 (TLR7) signaling predominantly regulates production of type I interferons (IFNs), which has been suggested in clinical studies to be antifibrotic. However, the mechanistic role of the TLR7-type I IFN axis in liver fibrosis has not been elucidated. In the present study, liver fibrosis was induced in wild-type (WT), TLR7-deficient, and IFN-α/β receptor-1 (IFNAR1)-deficient mice and TLR7-mediated signaling was assessed in liver cells isolated from these mice. TLR7-deficient and IFNAR1-deficient mice were more susceptible to liver fibrosis than WT mice, indicating that TLR7-type I IFN signaling exerts a protective effect against liver fibrosis. Notably, the hepatic expression of interleukin-1 receptor antagonist (IL-1ra) was suppressed in TLR7- or IFNAR1-deficient mice compared with respective WT mice, and treatment with recombinant IL-1ra reduced liver fibrosis. In vivo activation of TLR7 significantly increased IFNa4 and IL-1ra expression in the liver. Interestingly, each cytokine had a different cellular source, showing that dendritic cells (DCs) are the responsible cell type for production of type I IFN, while Kupffer cells (KCs) mainly produce IL-1ra in response to type I IFN. Furthermore, TLR7 activation by R848 injection suppressed liver fibrosis and production of proinflammatory cytokines, and these effects were dependent on type I IFN signaling. Consistent with in vivo data, IFN-α significantly induced IL-1ra production in primary KCs.

CONCLUSION

TLR7 signaling activates DCs to produce type I IFN, which in turn induces antifibrogenic IL-1ra production in KCs. Thus, manipulation of the TLR7-type I IFN-IL-1ra axis may be a new therapeutic strategy for the treatment of liver fibrosis.

Inhibition of acid-sensing ion channel 1a in hepatic stellate cells attenuates PDGF-induced activation of HSCs through MAPK pathway

Acid-sensing ion channels (ASICs), a group of Na(+)-selective and Ca(2+)-permeant ligand-gated cation channels, can be transiently activated by extracellular acid. Among seven subunits of ASICs, acid-sensing ion channel 1a (ASIC1a), which is responsible for Ca(2+) transportation, is elevated in response to inflammation, tumor, and ischemic injury in central nervous system and non-neuronal tissues. In this study, we demonstrated for the first time the presence of ASIC1a in rat liver and hepatic stellate cells (HSCs). Furthermore, the expression of ASIC1a was increased in primary HSCs and liver tissues of CCl4-treated rats, suggesting that ASIC1a may play certain role in liver fibrosis. Interestingly, we identified that the level of ASIC1a was significantly elevated in response to platelet-derived growth factor (PDGF) induction in a time- and dose-dependent manner. It was also established that Ca(2+)-transporting ASIC1a was involved in acid-induced injury of different cell types. Moreover, inhibition or silencing of ASIC1a was able to inhibit PDGF-induced pro-fibrogenic effects of activated rat HSCs, including cell activation, de novo synthesis of extracellular matrix components through mitogen-activated protein kinase signaling pathway. Collectively, our studies identified that ASIC1a was expressed in rat liver and HSCs and provided a strong evidence for the involvement of the ASIC1a in the progression of hepatic fibrosis.