Mononuclear cells in liver fibrosis. Semin Immunopathol. 2009;31:345-358. [PMID: 19533130 DOI: 10.1007/s00281-009-0169-0]

The roles of Th cells in myocardial infarction

Myocardial infarction, commonly known as a heart attack, is a serious condition caused by the abrupt stoppage of blood flow to a part of the heart, leading to tissue damage. A significant aspect of this condition is reperfusion injury, which occurs when blood flow is restored but exacerbates the damage. This review first addresses the role of the innate immune system, including neutrophils and macrophages, in the cascade of events leading to myocardial infarction and reperfusion injury. It then shifts focus to the critical involvement of CD4+ T helper cells in these processes. These cells, pivotal in regulating the immune response and tissue recovery, include various subpopulations such as Th1, Th2, Th9, Th17, and Th22, each playing a unique role in the pathophysiology of myocardial infarction and reperfusion injury. These subpopulations contribute to the injury process through diverse mechanisms, with cytokines such as IFN-γ and IL-4 influencing the balance between tissue repair and injury exacerbation. Understanding the interplay between the innate immune system and CD4+ T helper cells, along with their cytokines, is crucial for developing targeted therapies to mitigate myocardial infarction and reperfusion injury, ultimately improving outcomes for cardiac patients.

Potential anti-tumor effects of regulatory T cells in the tumor microenvironment: a review

Regulatory T cells (Tregs) expressing the transcription factor FoxP3 are essential for maintaining immunological balance and are a significant component of the immunosuppressive tumor microenvironment (TME). Single-cell RNA sequencing (ScRNA-seq) technology has shown that Tregs exhibit significant plasticity and functional diversity in various tumors within the TME. This results in Tregs playing a dual role in the TME, which is not always centered around supporting tumor progression as typically believed. Abundant data confirms the anti-tumor activities of Tregs and their correlation with enhanced patient prognosis in specific types of malignancies. In this review, we summarize the potential anti-tumor actions of Tregs, including suppressing tumor-promoting inflammatory responses and boosting anti-tumor immunity. In addition, this study outlines the spatial and temporal variations in Tregs function to emphasize that their predictive significance in malignancies may change. It is essential to comprehend the functional diversity and potential anti-tumor effects of Tregs to improve tumor therapy strategies.

Serum ribonucleotide reductase M2 is a potential biomarker for diagnosing and monitoring liver fibrosis in chronic hepatitis B patients

It is known that ribonucleotide reductase M2 (RRM2) could be induced by hepatitis B virus (HBV) via DNA damage response. However, whether RRM2 is a potential biomarker for diagnosing and monitoring liver fibrosis in chronic hepatitis B (CHB) patients is still unclear. In this study, CHB patients from GSE84044 (a transcriptome data from GEO data set) were downloaded and RRM2 was selected as a hub gene. Interestingly, a positive correlation was found between serum RRM2 and liver fibrosis stage. The similar results were found in CHB patients with normal alanine aminotransferase (ALT). Notably, RRM2 could effectively differentiate preliminary fibrosis from advanced fibrosis in CHB patients with/without normal ALT. In addition, RRM2 had a better performance in diagnosing liver fibrosis than two commonly used noninvasive methods (aspartate aminotransferase-to-platelet ratio index and fibrosis index based on the four factors), two classic fibrotic biomarkers (hyaluronic acid and type IV collagen) as well as Mac-2 binding protein glycosylation isomer, a known serum fibrosis marker. Moreover, CHB patients with high RRM2, who were associated with advanced fibrosis, had higher expressions of immune checkpoints. Overall, serum RRM2 may be a promising biomarker for diagnosing and monitoring liver fibrosis in CHB patients.

The role of immune response in the pathogenesis of idiopathic pulmonary fibrosis: far beyond the Th1/Th2 imbalance

INTRODUCTION

. Idiopathic pulmonary fibrosis (IPF) is a chronic disease of unknown origin characterized by progressive scarring of the lung leading to irreversible loss of function. Despite the availability of two drugs that are able to slow down disease progression, IPF remains a deadly disease. The pathogenesis of IPF is poorly understood, but a dysregulated wound healing response following recurrent alveolar epithelial injury is thought to be crucial. Areas covered. In the last few years, the role of the immune system in IPF pathobiology has been reconsidered; indeed, recent data suggest that a dysfunctional immune system may promote and unfavorable interplay with pro-fibrotic pathways thus acting as a cofactor in disease development and progression. In this article, we review and critically discuss the role of T cells in the pathogenesis and progression of IPF in the attempt to highlight ways in which further research in this area may enable the development of targeted immunomodulatory therapies for this dreadful disease.

EXPERT OPINION

A better understanding of T cells interactions has the potential to facilitate the development of immune modulators targeting multiple T cell-mediated pathways thus halting disease initiation and progression.

Menstrual blood-derived mesenchymal stem cells attenuate inflammation and improve the mortality of acute liver failure combining with A2AR agonist in mice

BACKGROUND AND AIM

Acute liver failure (ALF) poses a serious public health issue. The menstrual blood-derived mesenchymal stem cells (MenSCs) have been applied to cure various liver-related diseases. However, the efficacy and mechanism are far from clear. This study aims to explore the efficacy and potential mechanism of MenSCs to cure ALF.

METHODS

We investigate the potential mechanism of MenSCs on the ALF in vitro and in vivo. A2A adenosine receptor (A2AR) activation was investigated as the potential reinforcer for MenSCs treatment. Lipid polysaccharide/d-galactosamine (d-GalN) was employed to induce ALF. Diverse techniques were used to measure the inflammatory cytokines and key signaling molecules. Hematoxylin-eosin stain and aminotransaminases were applied to evaluate the liver injury. Flow cytometry was employed to assess the T cells.

RESULTS

The MenSCs can decrease the lipid polysaccharide-induced inflammatory cytokine elevation and related signaling molecules in ALF, including TLR4, phosphorylated-NF-kBp65 (p-NF-kBp65), PI3K, and p-AKT, p-mTOR and p-IKK in vitro. Moreover, MenSCs also can significantly reverse the liver injury, inflammatory cytokines elevation and related signaling molecules increase, and Treg/Th17 ratio decrease in vivo. In addition, MenSCs plus A2AR agonist can enhance the above changes.

CONCLUSIONS

The MenSCs can attenuate the ALF-induced liver injury via inhibition of TLR4-mediated PI3K/Akt/mTOR/IKK signaling. Then, this inhibits the p-NF-κBp65 translocate into nuclear, which causes a decrease of inflammatory cytokines release. Moreover, A2AR agonist can play a synergic role with MenSCs and enhance the above-mentioned effects.

Cross-talk between hepatic stellate cells and T lymphocytes in liver fibrosis

BACKGROUND

Fibrosis results from inflammation and healing following injury. The imbalance between extracellular matrix (ECM) secretion and degradation leads to the ECM accumulation and liver fibrosis. This process is regulated by immune cells. T lymphocytes, including alpha beta (αβ) T cells, which have adaptive immune functions, and gamma delta (γδ) T cells, which have innate immune functions, are considered regulators of liver fibrosis. This review aimed to present the current understanding of the cross-talk between T lymphocytes and hepatic stellate cells (HSCs), which are the key cells in liver fibrosis.

DATA SOURCES

The keywords "liver fibrosis", "immune", and "T cells" were used to retrieve articles published in PubMed database before January 31, 2020.

RESULTS

The ratio of CD8+ (suppressor) T cells to CD4+ (helper) T cells is significantly higher in the liver than in the peripheral blood. T cells secrete a series of cytokines and chemokines to regulate the inflammation in the liver and the activation of HSCs to influence the course of liver fibrosis. In addition, HSCs also regulate the differentiation and proliferation of T cells.

CONCLUSIONS

The cross-talk between T cells and HSCs regulates liver fibrosis progression. The elucidation of this communication process will help us to understand the pathological process of liver fibrosis.

A double-edged sword of immuno-microenvironment in cardiac homeostasis and injury repair

The response of immune cells in cardiac injury is divided into three continuous phases: inflammation, proliferation and maturation. The kinetics of the inflammatory and proliferation phases directly influence the tissue repair. In cardiac homeostasis, cardiac tissue resident macrophages (cTMs) phagocytose bacteria and apoptotic cells. Meanwhile, NK cells prevent the maturation and transport of inflammatory cells. After cardiac injury, cTMs phagocytose the dead cardiomyocytes (CMs), regulate the proliferation and angiogenesis of cardiac progenitor cells. NK cells prevent the cardiac fibrosis, and promote vascularization and angiogenesis. Type 1 macrophages trigger the cardioprotective responses and promote tissue fibrosis in the early stage. Reversely, type 2 macrophages promote cardiac remodeling and angiogenesis in the late stage. Circulating macrophages and neutrophils firstly lead to chronic inflammation by secreting proinflammatory cytokines, and then release anti-inflammatory cytokines and growth factors, which regulate cardiac remodeling. In this process, dendritic cells (DCs) mediate the regulation of monocyte and macrophage recruitment. Recruited eosinophils and Mast cells (MCs) release some mediators which contribute to coronary vasoconstriction, leukocyte recruitment, formation of new blood vessels, scar formation. In adaptive immunity, effector T cells, especially Th17 cells, lead to the pathogenesis of cardiac fibrosis, including the distal fibrosis and scar formation. CMs protectors, Treg cells, inhibit reduce the inflammatory response, then directly trigger the regeneration of local progenitor cell via IL-10. B cells reduce myocardial injury by preserving cardiac function during the resolution of inflammation.

KIR2DL2/S2 and KIR2DS5 in alcoholic cirrhotic patients undergoing liver transplantation

INTRODUCTION

The molecular mechanisms underlying alcoholic liver fibrosis and cirrhosis are not completely understood. Hepatic fibrosis involves the interplay of diverse cells and factors, including hepatic stellate cells (HSCs), Kupffer, NK cells, and T-lymphocyte subsets. Killer-cell immunoglobulin-like receptors (KIR) are membrane receptors involved in mediation between NK and activated HSCs, regulating NK cell function through their interaction with HLA-I molecules. The aim of this study was to analyse the genetic association between KIR genes and the susceptibility to or protection from alcoholic cirrhosis (AC) in a cohort of male AC patients undergoing liver transplantation (LT) with and without concomitant viral infections.

MATERIAL AND METHODS

KIR genotyping was performed in nuclear DNA extracted from 281 AC patients and compared with 319 male controls.

RESULTS

Significant differences between total AC patients and healthy controls were only found in the case of KIR2DL2 and KIR2DS5. KIR2DL2 was significantly underrepresented in non-viral AC patients (52.6% vs. 63.3%; p = 0.015), while patients heterozygous for KIR2DL2 were also underrepresented in the non-viral AC group compared with controls (p = 0.034). KIR2DS5 was overrepresented in this group compared with healthy controls (p = 0.002). All these observations were only evident in AC patients older than 54 years old.

CONCLUSIONS

Our data suggest a contrary effect of KIR2DL2 and KIR2DS5 in AC patients older than 54 years, in whom the presence of KIR2DL2 appears to be protective against AC, whereas the presence of KIR2DS5 seems to promote the fibrotic process, particularly in patients with no associated viral infection.

Sphingosine 1-Phosphate Receptor Blockade Affects Pro-Inflammatory Bone Marrow-Derived Macrophages and Relieves Mouse Fatty Liver Injury

Fatty liver injury is characterized by liver fat accumulation and results in serious health problems worldwide. There is no effective treatment that reverses fatty liver injury besides etiological therapy. Inflammation is an important macrophage-involving pathological process of liver injury. Here, we investigated the role of sphingosine 1-phosphate receptors (S1PRs) in fatty liver injury and explored whether S1PR_2/3 blockade could cure fatty liver injury. A methionine-choline-deficient and a high-fat (MCDHF) diet was used to induce fatty liver injury, and the number of macrophages was evaluated by flow cytometry. Gene expressions were detected using RT-qPCR and cytometric bead array. In MCDHF-diet-fed mice, pro-inflammatory factor expressions were upregulated by fatty liver injury. The S1P level and S1PR_2/3 expressions were significantly elevated. Moreover, increased S1P level and S1PR_2/3 mRNA expressions were positively correlated with pro-inflammatory factor expressions in the liver. Furthermore, the number of pro-inflammatory macrophages (iMφ) increased in injured liver, and they were mainly bone-marrow-derived macrophages. In vivo, S1PR_2/3 blockade decreased the amount of iMφ and inflammation and attenuated liver injury and fibrosis, although liver fat accumulation was unchanged. These data strongly suggest that anti-inflammatory treatment by blocking the S1P/S1PR_2/3 axis attenuates fatty liver injury, which might serve as a potential target for fatty liver injury.

Immune suppression in chronic hepatitis B infection associated liver disease: A review

Hepatitis B virus (HBV) infection is one the leading risk factors for chronic hepatitis, liver fibrosis, cirrhosis and hepatocellular cancer (HCC), which are a major global health problem. A large number of clinical studies have shown that chronic HBV persistent infection causes the dysfunction of innate and adaptive immune response involving monocytes/macrophages, dendritic cells, natural killer (NK) cells, T cells. Among these immune cells, cell subsets with suppressive features have been recognized such as myeloid derived suppressive cells(MDSC), NK-reg, T-reg, which represent a critical regulatory system during liver fibrogenesis or tumourigenesis. However, the mechanisms that link HBV-induced immune dysfunction and HBV-related liver diseases are not understood. In this review we summarize the recent studies on innate and adaptive immune cell dysfunction in chronic HBV infection, liver fibrosis, cirrhosis, and HCC, and further discuss the potential mechanism of HBV-induced immunosuppressive cascade in HBV infection and consequences. It is hoped that this article will help ongoing research about the pathogenesis of HBV-related hepatic fibrosis and HBV-related HCC.

LOXL2-A New Target in Antifibrogenic Therapy?

The concept of liver fibrosis and cirrhosis being static and therefore irreversible is outdated. Indeed, both human and animal studies have shown that fibrogenesis is a dynamic and potentially reversible process that can be modulated either by stopping its progression and/or by promoting its resolution. Therefore, the study of the molecular mechanisms involved in the pathogenesis of liver fibrosis is critical for the development of future antifibrotic therapies. The fibrogenesis process, common to all forms of liver injury, is characterized by the increased deposition of extracellular matrix components (EMCs), including collagen, proteoglycans, and glycoproteins (laminin and fibronectin 2). These changes in the composition of the extracellular matrix components alter their interaction with cell adhesion molecules, influencing the modulation of cell functions (growth, migration, and gene expression). Hepatic stellate cells and Kupffer cells (liver macrophages) are the key fibrogenic effectors. The antifibrogenic mechanism starts with the activation of Ly6C^high macrophages, which can differentiate into macrophages with antifibrogenic action. The research of biochemical changes affecting fibrosis irreversibility has identified lysyl oxidase-like 2 (LOXL2), an enzyme that promotes the network of collagen fibers of the extracellular matrix. LOXL2 inhibition can decrease cell numbers, proliferation, colony formations, and cell growth, and it can induce cell cycle arrest and increase apoptosis. The development of a new humanized IgG4 monoclonal antibody against LOXL2 could open the window of a new antifibrogenic treatment. The current therapeutic target in patients with liver cirrhosis should focus (after the eradication of the causal agent) on the development of new antifibrogenic drugs. The development of these drugs must meet three premises: Patient safety, in non-cirrhotic phases, down-staging or at least stabilization and slowing the progression to cirrhosis must be achieved; whereas in the cirrhotic stage, the objective should be to reduce fibrosis and portal pressure.

Activated NK cells kill hepatic stellate cells via p38/PI3K signaling in a TRAIL-involved degranulation manner

NK cells are important in regulating hepatic fibrosis via their cytotoxic killing of hepatic stellate cells (HSCs). NK cells are activated by both cytokines such as IL-12 and IL-18, and innate immune stimuli such as ligation of TLRs. The secretion of IL-18 depends upon activation of the inflammasome, whereas TLRs are stimulated by microbial products. In the case of NK cells, IL-18 acts synergistically with stimulation of TLR3 to cause cell activation and cytotoxic function. In the present study, we activated NK cells to kill HSCs via IL-18 and TLR3 ligand stimulation, and dissected the signaling pathways or molecules critical for such activation or killing. We find that such activation depends on signaling via the p38/PI3K/AKT pathway, and that the activated NK cells mediate HSC death in a TRAIL-involved mechanism. As liver fibrosis is a major global health problem with no good solution, these results emphasize that the p38/PI3K/AKT pathway in NK cells may be a novel drug target to promote fibrosis regression.

The innate immune receptor TREM-1 promotes liver injury and fibrosis

Inflammation occurs in all tissues in response to injury or stress and is the key process underlying hepatic fibrogenesis. Targeting chronic and uncontrolled inflammation is one strategy to prevent liver injury and fibrosis progression. Here, we demonstrate that triggering receptor expressed on myeloid cells 1 (TREM-1), an amplifier of inflammation, promotes liver disease by intensifying hepatic inflammation and fibrosis. In the liver, TREM-1 expression was limited to liver macrophages and monocytes and was highly upregulated on Kupffer cells, circulating monocytes, and monocyte-derived macrophages in a mouse model of chronic liver injury and fibrosis induced by carbon tetrachloride (CCl4) administration. TREM-1 signaling promoted proinflammatory cytokine production and mobilization of inflammatory cells to the site of injury. Deletion of Trem1 reduced liver injury, inflammatory cell infiltration, and fibrogenesis. Reconstitution of Trem1-deficient mice with Trem1-sufficient Kupffer cells restored the recruitment of inflammatory monocytes and the severity of liver injury. Markedly increased infiltration of liver fibrotic areas with TREM-1-positive Kupffer cells and monocytes/macrophages was found in patients with hepatic fibrosis. Our data support a role of TREM-1 in liver injury and hepatic fibrogenesis and suggest that TREM-1 is a master regulator of Kupffer cell activation, which escalates chronic liver inflammatory responses, activates hepatic stellate cells, and reveals a mechanism of promotion of liver fibrosis.

T cell responses to tumor: how dominant assumptions on immune activity led to a neglect of pathological functions, and how evolutionary considerations can help identify testable hypotheses for improving immunotherapy

Cancer immunotherapy is based on the premise that activated, pro-inflammatory T cell responses to tumor will mostly combat tumor growth. Nowadays accepted as largely valid, this hypothesis has been formed as a result of extensive theoretical and experimental argumentation on the inherent function of the immune system and the nature of the immunological self, dating back to the foundations of immunology. These arguments have also been affected by how current working hypotheses were set by researchers, an issue that has been the focus of study by medical anthropologists. As a result of these processes, cancer immunotherapy has developed into a truly promising anti-cancer strategy, with very substantial benefits in clinical outcomes. However, as immunotherapy still has large margins for improvement, a more thorough examination of both the historical background and evolutionary context of current assumptions for how the immune system responds to cancer can help reveal novel, testable questions. We describe how attempting to answer some of these questions experimentally, such as identifying the contributors of tumor-associated fibrosis, has led to potentially useful insights on how to improve immunotherapy.

Tailored chemokine receptor modification improves homing of adoptive therapy T cells in a spontaneous tumor model

In recent years, tumor Adoptive Cell Therapy (ACT), using administration of ex vivo-enhanced T cells from the cancer patient, has become a promising therapeutic strategy. However, efficient homing of the anti-tumoral T cells to the tumor or metastatic site still remains a substantial hurdle. Yet the tumor site itself attracts both tumor-promoting and anti-tumoral immune cell populations through the secretion of chemokines. We attempted to identify these chemokines in a model of spontaneous metastasis, in order to “hijack” their function by expressing matching chemokine receptors on the cytotoxic T cells used in ACT, thus allowing us to enhance the recruitment of these therapeutic cells. Here we show that this enabled the modified T cells to preferentially home into spontaneous lymph node metastases in the TRAMP model, as well as in an inducible tumor model, E.G7-OVA. Due to the improved homing, the modified CD8⁺ T cells displayed an enhanced in vivo protective effect, as seen by a significant delay in E.G7-OVA tumor growth. These results offer a proof of principle for the tailored application of chemokine receptor modification as a means of improving T cell homing to the target tumor, thus enhancing ACT efficacy. Surprisingly, we also uncover that the formation of the peri-tumoral fibrotic capsule, which has been shown to impede T cell access to tumor, is partially dependent on host T cell presence. This finding, which would be impossible to observe in immunodeficient model studies, highlights possible conflicting roles that T cells may play in a therapeutic context.

The Superficial Dermis May Initiate Keloid Formation: Histological Analysis of the Keloid Dermis at Different Depths

Several studies have reported on certain aspects of the characteristics of different sites within a keloid lesion, but detailed studies on the keloid dermis at different depths within a keloid lesion are scarce. The aim of this study was to investigate the histology of the keloid dermis at different depths. This study included 19 keloid tissue samples that were collected from 19 patients and 19 normal skin samples, which were harvested from subjects without keloids or hypertrophic scar. Samples were studied by light microscopy using routine hematoxylin and eosin histochemical staining, and immunohistochemistry to detect CD20-positive B-lymphocytes and CD3-positive T-lymphocytes. Sirius Red histochemical staining was used to determine the type of collagen in keloid tissue and normal skin samples. The migratory properties of fibroblasts within the keloid dermis at different depths was compared, using an in vitro migration assay. The findings of this study showed that although the papillary and reticular dermis could be clearly distinguished in normal skin, three tissue layers were identified in the keloid dermis. The superficial dermis of keloid was characterized by active fibroblasts and lymphocytes; the middle dermis contained dense extracellular matrix (ECM) with large numbers fibroblasts, and the deep dermis was poorly cellular and characterized by hyalinized collagen bundles. In the keloid samples, from the superficial to the deep dermis, type I collagen increased and type III collagen decreased, and fibroblasts from the superficial dermis of the keloid were found to migrate more rapidly. In conclusion, the findings of this study showed that different depths within the keloid dermis displayed different biological features. The superficial dermis may initiate keloid formation, in which layer intralesional injection of pharmaceuticals and other treatments should be performed for keloid.

The Processes and Mechanisms of Cardiac and Pulmonary Fibrosis

Fibrosis is the formation of fibrous connective tissue in response to injury. It is characterized by the accumulation of extracellular matrix components, particularly collagen, at the site of injury. Fibrosis is an adaptive response that is a vital component of wound healing and tissue repair. However, its continued activation is highly detrimental and a common final pathway of numerous disease states including cardiovascular and respiratory disease. Worldwide, fibrotic diseases cause over 800,000 deaths per year, accounting for ~45% of total deaths. With an aging population, the incidence of fibrotic disease and subsequently the number of fibrosis-related deaths will rise further. Although, fibrosis is a well-recognized cause of morbidity and mortality in a range of disease states, there are currently no viable therapies to reverse the effects of chronic fibrosis. Numerous predisposing factors contribute to the development of fibrosis. Biological aging in particular, interferes with repair of damaged tissue, accelerating the transition to pathological remodeling, rather than a process of resolution and regeneration. When fibrosis progresses in an uncontrolled manner, it results in the irreversible stiffening of the affected tissue, which can lead to organ malfunction and death. Further investigation into the mechanisms of fibrosis is necessary to elucidate novel, much needed, therapeutic targets. Fibrosis of the heart and lung make up a significant proportion of fibrosis-related deaths. It has long been established that the heart and lung are functionally and geographically linked when it comes to health and disease, and thus exploring the processes and mechanisms that contribute to fibrosis of each organ, the focus of this review, may help to highlight potential avenues of therapeutic investigation.

Cytoplasmic domain of tissue factor promotes liver fibrosis in mice

AIM

To evaluate the role of tissue factor (TF) and protease activated receptor (PAR)-2 in liver fibrosis.

METHODS

Using CCl₄ administration for eight weeks, we induced hepatic fibrosis in wild-type C57BL/6 mice and in mice with deletion of the cytoplasmic signalling domain of TF (TF^§CT/§CT), deletion of PAR-2 (PAR-2^-/-) and combined deletion of TF signalling domain and PAR-2 (TF^§CT/§CT/PAR-2^-/-). Hepatic fibrosis area was assessed by quantitative imaging of picrosirius red staining. Hepatic collagen content was assessed by hydroxyproline levels. Hepatic stellate cells (αSMA positive) and hepatic macrophages (CD68 positive) were identified by immunohistochemistry. Hepatic gene expression was determined by PCR and liver TGFβ1 content by ELISA.

RESULTS

CCl₄ treated mice with deletion of the PAR-2 gene (PAR-2^-/-) and the cytoplasmic domain of TF (TF^§CT/§CT) developed significantly less hepatic fibrosis, characterised by reduced liver fibrosis area and hydroxyproline content, compared to control wildtype mice treated with CCl₄. The observed reduction in histological fibrosis was accompanied by a significant decrease in the hepatic content of TGFβ, the prototypic fibrogenic cytokine, as well as fewer activated hepatic stellate cells and hepatic macrophages. Deletion of the TF cytoplasmic signalling domain reduced hepatic fibrosis to levels similar to those observed in mice lacking PAR-2 signalling but combined deletion provided no added protection against fibrosis indicating a lack of mutual modulating effects that have been observed in other contexts such as angiogenic responses.

CONCLUSION

Tissue factor cytoplasmic domain is involved in TF-PAR-2 signalling initiating hepatic fibrosis and is a potential therapeutic target, as its deletion would not impact coagulation.

Spleen-derived lipocalin-2 in the portal vein regulates Kupffer cells activation and attenuates the development of liver fibrosis in mice

The liver has an immune tolerance against gut-derived products from the portal vein (PV). A disruption of the gut-liver axis leads to liver injury and fibrosis. The spleen is connected to the PV and regulates immune functions. However, possible splenic effects on liver fibrosis development are unclear. Lipocalin-2 (Lcn2) is an antimicrobial protein that regulates macrophage activation. To clarify the role of the spleen in liver fibrosis development, we induced liver fibrosis in mice after splenectomy, and investigated liver fibrosis development. Liver fibrosis resulted in significantly increased splenic Lcn2 levels, but all other measured cytokine levels were unchanged. Splenectomized mice showed enhanced liver fibrosis and inflammation accompanied by significantly decreased Lcn2 levels in PV. Lipopolysaccharide-stimulated primary Kupffer cells, resident liver macrophages, which were treated with recombinant Lcn2 (rLcn2) produced less tumor necrosis factor-α and Ccl2 and the activation of hepatic stellate cells, the effector cells for collagen production in the liver, was suppressed by co-culture with rLcn2-treated Kupffer cells. In addition, the involvement of gut-derived products in splenectomized mice was evaluated by gut sterilization. Interestingly, gut sterilization blocked the effect of splenectomy on liver fibrosis development. In conclusion, spleen deficiency accelerated liver fibrosis development and decreased PV Lcn2 levels. The mechanism of splenic protection against liver fibrosis development may involve the splenic Lcn2, triggered by gut-derived products that enter the liver through the PV, regulates Kupffer cells activated by the gut-liver axis. Thus, the splenic Lcn2 may have an important role in regulating the immune tolerance of the liver in liver fibrosis development.

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.

Key role of liver sinusoidal endothelial cells in liver fibrosis

Because of the prevalence of viral hepatitis and nonalcoholic fatty liver disease (NAFLD), liver fibrosis has become a very common disease in Asia and elsewhere in the world, constantly increasing the burden of care borne by society. Hepatic sinusoidal capillarization, characterized by gradually shrinking fenestrae on the surface of liver sinusoidal endothelial cells (LSECs) and the formation of an organized basement membrane, is an initial pathologic change associated with liver fibrosis. Basic and clinical studies have indicated that LSECs play a key role in hepatic sinusoidal capillarization by affecting various aspects of the development and progression of liver fibrosis. Reviewing studies on the effect of LSECs on liver fibrosis is essential to better understanding the pathogenesis of liver fibrosis and its mechanism of progression. Moreover, such a review will provide a theoretical basis for identifying new methods to promote the regression or even inhibition of fibrosis. This review will focus on structural and functional changes in LSECs during hepatic sinusoidal capillarization and the interaction between the micro-environment of the liver and the body's immune system.

A deleterious role for Th9/IL-9 in hepatic fibrogenesis

T helper 9 (Th9) cells, a recently recognized Th cell subset, are involved in autoimmune diseases. We aimed to investigate the role of Th9/interleukin-9 (IL-9) in the pathogenesis of hepatic fibrosis. Th9 and Th17 cells were quantified in chronic hepatitis B (CHB) patients with hepatic fibrosis, HBV-associated liver cirrhosis (LC) patients and healthy controls (HC). The percentages of Th9 and Th17 cells, concentrations of IL-9 and IL-17, as well as expression of IL-17, TNF-α, IL-6, IL-4, IL-21, TGF-β1 and IFN-γ were significantly increased in plasma of CHB and LC patients compared with those in HC. Splenic Th9 and Th17 cells, plasma concentrations and liver expression of IL-9 and IL-17A were significantly elevated in mice with hepatic fibrosis compared with controls. Neutralization of IL-9 in mice ameliorated hepatic fibrosis, attenuated the activation of hepatic stellate cells, reduced frequencies of Th9, Th17 and Th1 cells in spleen, and suppressed expression of IL-9, IL-17A, IFN-γ, TGF-β1, IL-6, IL-4 and TNF-α in plasma and liver respectively. Our data suggest a deleterious role of Th9/IL-9 in increasing hepatic fibrosis and exacerbating disease endpoints, indicating that Th9/IL9 based immunotherapy may be a promising approach for treating hepatic fibrosis.

Restoring homeostasis of CD4+ T cells in hepatitis-B-virus-related liver fibrosis

Immune-mediated liver injury is widely seen during hepatitis B virus (HBV) infection. Unsuccessful immune clearance of HBV results in chronic hepatitis and increases the risk of liver cirrhosis and hepatocellular carcinoma. HBV-related liver fibrosis (HBVLF), occurring as a result of HBV-induced chronic hepatitis, is a reversible, intermediate stage of chronic hepatitis B (CHB) and liver cirrhosis. Therefore, defining the pathogenesis of HBVLF is of practical significance for achieving better clinical outcomes. Recently, the homeostasis of CD4⁺ T cells was considered to be pivotal in the process of HBVLF. To better uncover the underlying mechanisms, in this review, we systematically retrospect the impacts of different CD4⁺ T-cell subsets on CHB and HBVLF. We emphasize CD4⁺ T-cell homeostasis and the important balance between regulatory T (Treg) and T helper 17 (Th17) cells. We discuss some cytokines associated with Treg and Th17 cells such as interleukin (IL)-17, IL-22, IL-21, IL-23, IL-10, IL-35 and IL-33, as well as surface molecules such as programmed cell death protein 1, cytotoxic T lymphocyte-associated antigen 4, T cell immunoglobulin domain and mucin domain-containing molecule 3 and cannabinoid receptor 2 that have potential therapeutic implications for the homeostasis of CD4⁺ T cells in CHB and HBVLF.

Sphingosine 1-Phosphate Receptor 2 and 3 Mediate Bone Marrow-Derived Monocyte/Macrophage Motility in Cholestatic Liver Injury in Mice

Sphingosine 1-phosphate (S1P)/S1P receptor (S1PR) system has been implicated in the pathological process of liver injury. This study was designed to evaluate the effects of S1P/S1PR on bone marrow-derived monocyte/macrophage (BMM) migration in mouse models of cholestatic liver injury, and identify the signaling pathway underlying this process. S1PR_1–3 expression in BMM was characterized by immunofluorescence, RT-PCR and Western blot. Cell migration was determined in Boyden chambers. In vivo, the chimera mice, which received BM transplants from EGFP-transgenic mice, received an operation of bile duct ligation (BDL) to induce liver injury with the administration of S1PR_2/3 antagonists. The results showed that S1PR_1–3 were all expressed in BMMs. S1P exerted a powerful migratory action on BMMs via S1PR₂ and S1PR₃. Furthermore, PTX and LY-294002 (PI3K inhibitor) prevented S1PR_2/3-mediated BMM migration, and Rac1 activation by S1P was inhibited by JTE-013, CAY-10444 or LY294002. Administration of S1PR_2/3 antagonists in vivo significantly reduced BMM recruitment in BDL-treated mice, and attenuated hepatic inflammation and fibrosis. In conclusion, S1P/S1PR_2/3 system mediates BMM motility by PTX-PI3K-Rac1 signaling pathway, which provides new compelling information on the role of S1P/S1PR in liver injury and opens new perspectives for the pharmacological treatment of hepatic fibrosis.

Activated rat hepatic stellate cells influence Th1/Th2 profile in vitro

AIM: To investigate the effects of activated rat hepatic stellate cells (HSCs) on rat Th1/Th2 profile in vitro.

METHODS: Growth and survival of activated HSCs and CD4⁺ T lymphocytes cultured alone or together was assessed after 24 or 48 h. CD4⁺ T lymphocytes were then cultured with or without activated HSCs for 24 or 48 h and the proportion of Th1 [interferon (IFN)-γ⁺] and Th2 [interleukin (IL)-4⁺] cells was assessed by flow cytometry. Th1 and Th2 cell apoptosis was assessed after 24 h of co-culture using a caspase-3 staining procedure. Differentiation rates of Th1 and Th2 cells from CD4⁺ T lymphocytes that were positive for CD25 but did not express IFN-γ or IL-4 were also assessed after 48 h of co-culture with activated HSCs. Galectin-9 expression in HSCs was determined by immunofluorescence and Western blotting. ELISA was performed to assess galectin-9 secretion from activated HSCs.

RESULTS: Co-culture of CD4⁺ T lymphocytes with activated rat HSCs for 48 h significantly reduced the proportion of Th1 cells compared to culture-alone conditions (-1.73% ± 0.71%; P < 0.05), whereas the proportion of Th2 cells was not altered; the Th1/Th2 ratio was significantly decreased (-0.44 ± 0.13; P < 0.05). In addition, the level of IFN-γ in Th1 cells was decreased (-65.71 ± 9.67; P < 0.01), whereas the level of IL-4 in Th2 cells was increased (82.79 ± 25.12; P < 0.05) by co-culturing, as measured by mean fluorescence intensity by flow cytometry. Apoptosis rates in Th1 (12.27% ± 0.99%; P < 0.01) and Th2 (1.71% ± 0.185%; P < 0.01) cells were increased 24 h after co-culturing with activated HSCs; the Th1 cell apoptosis rate was significantly higher than in Th2 cells (P < 0.01). Galectin-9 protein expression was significantly decreased in HSCs only 24 h after co-culturing (P < 0.05) but not after 48 h. Co-culture for 48 h significantly increased the differentiation of Th1 and Th2 cells; however, the increase in the proportion of Th2 cells was significantly higher than that of Th1 cells (1.85% ± 0.48%; P < 0.05).

CONCLUSION: Activated rat HSCs lower the Th1/Th2 profile, inhibiting the Th1 response and enhancing the Th2 response, and this may be a novel pathway for liver fibrogenesis.

Risk of hepatitis B virus reactivation in rheumatoid arthritis patients undergoing biologic treatment: Extending perspective from old to newer drugs

Hepatitis B virus (HBV) reactivation in rheumatoid arthritis (RA) patients undergoing biological therapy is not infrequent. This condition can occur in patients with chronic hepatitis B as well as in patients with resolved HBV infection. Current recommendations are mainly focused on prevention and management strategies of viral reactivation under tumor necrosis factor-α inhibitors or chimeric monoclonal antibody rituximab. In recent years, growing data concerning HBV reactivation in RA patients treated with newer biological drugs like tocilizumab and abatacept have cumulated. In this review, epidemiology, pathogenesis and natural history of HBV infection have been revised first, mainly focusing on the role that specific therapeutic targets of current biotechnological drugs play in HBV pathobiology; finally we have summarized current evidences from scientific literature, including either observational studies and case reports as well, concerning HBV reactivation under different classes of biological drugs in RA patients. Taking all these evidences into account, some practical guidelines for screening, vaccination, prophylaxis and treatment of HBV reactivation have been proposed.

Telbivudine therapy may shape CD4(+) T-cell response to prevent liver fibrosis in patients with chronic hepatitis B

BACKGROUND & AIMS

Nucleos(t)ide analogues (NAs) can indirectly restore host immunity against hepatitis B virus (HBV) by inhibiting virus replication. We aimed to investigate whether telbivudine could prevent HBV-related fibrosis progression by their influence on CD4(+) T-cell response.

METHODS

Thirty-six HBeAg-positive patients with chronic hepatitis B (CHB) were enrolled for 52-week telbivudine monotherapy and were followed at treatment week (TW)-0, 4, 12, 24 and 52. By TW-52, the patients were classified into a complete-response group (CR, n = 10) with both negative HBV-DNA and HBeAg, or a part-response group (PR, n = 11) only with negative DNA, or a non-response group (NR, n = 15) still with positive DNA. The peripheral blood mononuclear cells (PBMCs) were prepared for further flow cytometric and real-time PCR analyses, and also for the in vitro experiments with primary hepatic stellate cells (HSCs).

RESULTS

Peripherally, all chronic HBV-infected subjects showed the involvement of CD4(+) T-cell responses, among whom the inactive carriers (IC) had Th1 (CD4(+) IFNγ(+) ) dominated, CHB had Th17 (CD4(+) IL-17(+) ) dominated, while the immune tolerant (IT) subjects had Treg (CD4(+) CD25(high) Foxp3(+) ) dominated. Besides, we found the therapeutic responses to telbivudine were especially associated with up-regulation of Th1 and Th17, and down-regulation of Treg. Furthermore, compared to CD4(+) cells from CR, those from NR could in vitro significantly exacerbate cell activation, proliferation and cytokine production of HSCs, which were partly mediated by IL-4 and TGF-β1.

CONCLUSIONS

Telbivudine might slow down HBV-related liver fibrosis progression by restoring CD4(+) T-cell responses against HBV.

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.

Immuno-pathomechanism of liver fibrosis: targeting chemokine CCL2-mediated HIV:HCV nexus

Even in the era of successful combination antiretroviral therapy (cART), co-infection of Hepatitis C virus (HCV) remains one of the leading causes of non-AIDS-related mortality and morbidity among HIV-positive individuals as a consequence of accelerated liver fibrosis and end-stage liver disease (ESLD). The perturbed liver microenvironment and induction of host pro-inflammatory mediators in response to HIV and HCV infections, play a pivotal role in orchestrating the disease pathogenesis and clinical outcomes. How these viruses communicate each other via chemokine CCL2 and exploit the liver specific cellular environment to exacerbate liver fibrosis in HIV/HCV co-infection setting is a topic of intense discussion. Herein, we provide recent views and insights on potential mechanisms of CCL2 mediated immuno-pathogenesis, and HIV-HCV cross-talk in driving liver inflammation. We believe CCL2 may potentially serve an attractive target of anti-fibrotic intervention against HIV/HCV co-infection associated co-morbidities.

Paricalcitol reduces peritoneal fibrosis in mice through the activation of regulatory T cells and reduction in IL-17 production

Fibrosis is a significant health problem associated with a chronic inflammatory reaction. The precise mechanisms involved in the fibrotic process are still poorly understood. However, given that inflammation is a major causative factor, immunomodulation is a possible therapeutic approach to reduce fibrosis. The vitamin D receptor (VDR) that is present in all hematopoietic cells has been associated with immunomodulation. We investigated whether the intraperitoneal administration of paricalcitol, a specific activator of the VDR, modulates peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis. We characterized the inflammatory process in the peritoneal cavity of mice treated or not treated with paricalcitol and analyzed the ensuing fibrosis. The treatment reduced peritoneal IL-17 levels, which strongly correlated with a significantly lower peritoneal fibrotic response. In vitro studies demonstrate that both CD4⁺ and CD8⁺ regulatory T cells appear to impact the regulation of IL-17. Paricalcitol treatment resulted in a significantly increased frequency of CD8⁺ T cells showing a regulatory phenotype. The frequency of CD4⁺ Tregs tends to be increased, but it did not achieve statistical significance. However, paricalcitol treatment increased the number of CD4⁺ and CD8⁺ Treg cells in vivo. In conclusion, the activation of immunological regulatory mechanisms by VDR signaling could prevent or reduce fibrosis, as shown in peritoneal fibrosis induced by PDF exposure in mice.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Monocyte subsets in schistosomiasis patients with periportal fibrosis

A major issue with Schistosoma mansoni infection is the development of periportal fibrosis, which is predominantly caused by the host immune response to egg antigens. Experimental studies have pointed to the participation of monocytes in the pathogenesis of liver fibrosis. The aim of this study was to characterize the subsets of monocytes in individuals with different degrees of periportal fibrosis secondary to schistosomiasis. Monocytes were classified into classical (CD14⁺⁺CD16⁻), intermediate (CD14⁺⁺CD16⁺), and nonclassical (CD14⁺CD16⁺⁺). The expressions of monocyte markers and cytokines were assessed using flow cytometry. The frequency of classical monocytes was higher than the other subsets. The expression of HLA-DR, IL-6, TNF-α, and TGF-β was higher in monocytes from individuals with moderate to severe fibrosis as compared to other groups. Although no differences were observed in receptors expression (IL-4R and IL-10R) between groups of patients, the expression of IL-12 was lower in monocytes from individuals with moderate to severe fibrosis, suggesting a protective role of this cytokine in the development of fibrosis. Our data support the hypothesis that the three different monocyte populations participate in the immunopathogenesis of periportal fibrosis, since they express high levels of proinflammatory and profibrotic cytokines and low levels of regulatory markers.

Clinical feature of intrahepatic B-lymphocytes in chronic hepatitis B

Humoral immunity constitutes major defense mechanism against viral infections. However, the association of hepatic injury and B-cells population in chronic hepatitis B virus (HBV) carriers has not been studied well. In this study, fifty seven hepatitis B surface antigen (HBsAg) positive and HBeAg negative patients were studied to determine the expression of CD20, a cell surface marker expressed on B-cells, in liver biopsy sections using immunohistochemistry. The patients' clinical data at the time of liver biopsy were acquired from their medical records. There was a significant association between log HBV DNA and both ALT (r = 0.36, P = 0.006) and histologic activity index (HAI) total score (r = 0.3, P = 0.02), respectively. The CD20 was expressed in all 57 liver biopsy samples with a submembranous and membranous staining pattern and its expression was significantly associated with HAI total score (r = 0.32, P = 0.01) and stage of fibrosis (r = 0.31, P = 0.02). The susceptible B lymphocytes to hepatitis B virus might be implicated in the development of immune mediated inflammation of HBV-induced hepatic injury. The present data also support that the liver is potentially one of the secondary lymphoid organs.

Inflammatory regulation of iron metabolism during thioacetamide-induced acute liver injury in rats

Systemic iron homeostasis is tightly regulated by the interaction between iron regulatory molecules, mainly produced by the liver. However, the molecular mechanisms of iron regulation in liver diseases remain to be elucidated. Here we analyzed the expression profiles of iron regulatory molecules during transient iron overload in a rat model of thioacetamide (TAA)-induced acute liver injury. After TAA treatment, mild hepatocellular degeneration and extensive necrosis were observed in the centrilobular region at hour 10 and on day 1, respectively. Serum iron increased transiently at hour 10 and on day 1, in contrast to hypoferremia in other rodent models of acute inflammation reported previously. Thereafter, up-regulation of hepcidin, a central regulator of systemic iron homeostasis, was observed in hepatocytes on day 2. Expression of transferrin receptor 1 and ferritin subunits increased to a peak on day 3, followed by increases in liver iron content and stainable iron on day 5, in parallel with regeneration of hepatocytes. Histopathological lesions and hepatocellular iron accumulation disappeared until day 10. The hepcidin induction was preceded by activation of IL6/STAT3 pathway, whereas other pathways known to induce hepcidin were down-regulated. IL6 was expressed by MHC class II-positive macrophages in the portal area, suggestive of dendritic cells. Our results suggest that IL6 released by portal macrophages may regulate hepatocyte hepcidin expression via STAT3 activation during transient iron overload in TAA-induced acute liver injury.

CYP2E1-dependent and leptin-mediated hepatic CD57 expression on CD8+ T cells aid progression of environment-linked nonalcoholic steatohepatitis

Environmental toxins induce a novel CYP2E1/leptin signaling axis in liver. This in turn activates a poorly characterized innate immune response that contributes to nonalcoholic steatohepatitis (NASH) progression. To identify the relevant subsets of T-lymphocytes in CYP2E1-dependent, environment-linked NASH, we utilized a model of diet induced obese (DIO) mice that are chronically exposed to bromodichloromethane. Mice deficient in CYP2E1, leptin (ob/ob mice), or both T and B cells (Pfp/Rag2 double knockout (KO) mice) were used to delineate the role of each of these factors in metabolic oxidative stress-induced T cell activation. Results revealed that elevated levels of lipid peroxidation, tyrosyl radical formation, mitochondrial tyrosine nitration and hepatic leptin as a consequence of metabolic oxidative stress caused increased levels of hepatic CD57, a marker of peripheral blood lymphocytes including NKT cells. CD8+CD57+ cytotoxic T cells but not CD4+CD57+ cells were significantly decreased in mice lacking CYP2E1 and leptin. There was a significant increase in the levels of T cell cytokines IL-2, IL-1β, and IFN-γ in bromodichloromethane exposed DIO mice but not in mice that lacked CYP2E1, leptin or T and B cells. Apoptosis as evidenced by TUNEL assay and levels of cleaved caspase-3 was significantly lower in leptin and Pfp/Rag2 KO mice and highly correlated with protection from NASH. The results described above suggest that higher levels of oxidative stress-induced leptin mediated CD8+CD57+ T cells play an important role in the development of NASH. It also provides a novel insight of immune dysregulation and may be a key biomarker in NASH.

Adoptive transfer of regulatory T cells protects against Coxsackievirus B3-induced cardiac fibrosis

Background

Cardiac fibrogenesis in the late stage of viral myocarditis causing contractile dysfunction and ventricular dilatation, is a major pathogenic factor for the progression of myocarditis to serious cardiovascular diseases including dilated cardiomyopathy (DCM) and congestive heart failure (HF). Recent studies indicate that regulatory T cells (Tregs) are involved in the fibrotic process of liver and lung fibosis. However, the role of Tregs in the development of viral myocarditis-caused cardiac fibrosis and their therapeutic potential remains unclear.

Methodology/Principal Findings

Myocardial fibrosis was induced in BALB/c mice by intraperitoneal injection of Coxsackievirus B3 (CVB3) assessed by picrosirius red staining and detection of expression levels of collagen I, matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinase-1 (TIMP-1). Myocardial Treg frequency was down-regulated during the course of viral myocarditis and a negative correlation with the severity of cardiac fibrosis was found. To explore the role of Tregs in CVB-induced cardiac fibrosis, Treg was in vivo depleted by injecting anti-CD25 mAb which resulted in aggravation of cardiac fibrosis. In consistent with that, after adoptive transfer of isolated Tregs into mice, significant amelioration of CVB3-induced cardiac fibrosis was confirmed. Interleukin-10 (IL-10) neutralizing antibodies were used in vivo and in vitro to explore the molecular mechanism of the therapeutic effect of Treg. It was found that administration of anti-IL-10 mAb after Treg transfer abrogated Treg’s treating effect and the inhibition of Treg on collagen production by cardiac fibroblasts was mediated mainly through IL-10.

Conclusion/Significance

Our data suggested that Tregs have a protective role in the fibrotic process of CVB3-induced cardiac fibrosis via secreting IL-10 and might provide an alternative option for the future treatment of cardiac fibrosis.

Natural killer and natural killer T cells in liver fibrosis

The liver lymphocyte population is enriched with natural killer (NK) cells, which play a key role in host defense against viral infection and tumor transformation. Recent evidence from animal models suggests that NK cells also play an important role in inhibiting liver fibrosis by selectively killing early or senescence activated hepatic stellate cells (HSCs) and by producing the anti-fibrotic cytokine IFN-γ. Furthermore, clinical studies have revealed that human NK cells can kill primary human HSCs and that the ability of NK cells from HCV patients to kill HSCs is enhanced and correlates inversely with the stages of liver fibrosis. IFN-α treatment enhances, while other factors (e.g., alcohol, TGF-β) attenuate, the cytotoxicity of NK cells against HSCs, thereby differentially regulating liver fibrogenesis. In addition, the mouse liver lymphocyte population is also enriched for natural killer T (NKT) cells, whereas human liver lymphocytes have a much lower percentage of NKT cells. Many studies suggest that NKT cells promote liver fibrogenesis by producing pro-fibrotic cytokines such as IL-4, IL-13, hedgehog ligands, and osteopontin; however, NKT cells may also attenuate liver fibrosis under certain conditions by killing HSCs and by producing IFN-γ. Finally, the potential for NK and NKT cells to be used as therapeutic targets for anti-fibrotic therapy is discussed. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

The chemokine CCL3 promotes experimental liver fibrosis in mice

Liver fibrosis is associated with infiltrating immune cells and activation of hepatic stellate cells. We here aimed to investigate the effects of the CC chemokine CCL3, also known as macrophage inflammatory protein-1α, in two different fibrosis models. To this end, we treated mice either with carbon tetrachloride or with a methionine- and choline-deficient diet to induce fibrosis in CCL3 deficient and wild-type mice. The results show that the protein expression of CCL3 is increased in wild-type mice after chronic liver injury. Deletion of CCL3 exhibited reduced liver fibrosis compared to their wild-type counterparts. We could validate these results by treating the two mouse groups with either carbon tetrachloride or by feeding a methionine- and choline-deficient diet. In these models, lack of CCL3 is functionally associated with reduced stellate cell activation and liver immune cell infiltration. In vitro, we show that CCL3 leads to increased proliferation and migration of hepatic stellate cells. In conclusion, our results define the chemokine CCL3 as a mediator of experimental liver fibrosis. Thus, therapeutic modulation of CCL3 might be a promising target for chronic liver diseases.

Evolving therapies for liver fibrosis

Fibrosis is an intrinsic response to chronic injury, maintaining organ integrity when extensive necrosis or apoptosis occurs. With protracted damage, fibrosis can progress toward excessive scarring and organ failure, as in liver cirrhosis. To date, antifibrotic treatment of fibrosis represents an unconquered area for drug development, with enormous potential but also high risks. Preclinical research has yielded numerous targets for antifibrotic agents, some of which have entered early-phase clinical studies, but progress has been hampered due to the relative lack of sensitive and specific biomarkers to measure fibrosis progression or reversal. Here we focus on antifibrotic approaches for liver that address specific cell types and functional units that orchestrate fibrotic wound healing responses and have a sound preclinical database or antifibrotic activity in early clinical trials. We also touch upon relevant clinical study endpoints, optimal study design, and developments in fibrosis imaging and biomarkers.

Canine visceral leishmaniasis as a systemic fibrotic disease

We propose that canine visceral leishmaniasis (CVL) is a systemic fibrotic disease, as evidenced by the wide distribution of fibrosis that we have found in the dogs suffering from chronic condition. The inflammatory cells apparently direct fibrosis formation. Twenty-four cases (symptomatic dogs) were identified from a total of one hundred and five cases that had been naturally infected with Leishmania chagasi and had been documented during an epidemiological survey of CVL carried out by the metropolitan area of the municipality of Belo Horizonte, MG, Brazil. The histological criterion was intralobular liver fibrosis, as has been described previously in dogs with visceral leishmaniasis. In addition to the findings in the liver, here we describe and quantify conspicuous and systemic deposition of collagen in other organs, including spleen, cervical lymph nodes, lung and kidney of all the infected symptomatic dogs. Thus we report that there is a systematic fibrotic picture in these animals, where inflammatory cells appear to direct fibrosis in all organs that have been studied. Therefore we propose that CVL is a systemic fibrotic disease.

Toll-like receptors in liver disease

Activation of inflammatory signaling pathways is of central importance in the pathogenesis of alcoholic liver disease (ALD) and nonalcoholic steatohepatitis (NASH). Recent studies demonstrated that Toll-like receptors, the sensors of microbial and endogenous danger signals, are expressed and activated in innate immune cells as well as in parenchymal cells in the liver and thereby contribute to ALD and NASH. In this review, we emphasize the importance of gut-derived endotoxin and its recognition by TLR4 in the liver. The significance of TLR-induced intracellular signaling pathways and cytokine production as well as the contribution of individual cell types to the inflammation is evaluated. The contribution of TLR signaling to the induction of liver fibrosis and to the progression of liver pathology mediated by viral pathogens is reviewed in the context of ALD and NASH.

Chemokines in tissue fibrosis

Fibrosis or scarring of diverse organs and tissues is considered as a pathologic consequence of a chronically altered wound healing response which is tightly linked to inflammation and angiogenesis. The recruitment of immune cells, local proliferation of fibroblasts and the consecutive accumulation of extracellular matrix proteins are common pathophysiological hallmarks of tissue fibrosis, irrespective of the organ involved. Chemokines, a family of chemotactic cytokines, appear to be central mediators of the initiation as well as progression of these biological processes. Traditionally chemokines have only been considered to play a critical role in orchestrating the influx of immune cells to sites of tissue injury. However, within the last years, further aspects of chemokine biology including fibroblast activation and angiogenesis have been deciphered in tissue fibrosis of many different organs. Interestingly, certain chemokines appear to mediate common effects in liver, kidney, lung, and skin of various animal models, while others mediate tissue specific effects. These aspects have to be kept in mind when extrapolating data of animal studies to early human trials. Nevertheless, the further understanding of chemokine effects in tissue fibrosis might be an attractive approach for identifying novel therapeutic targets in chronic organ damage associated with high morbidity and mortality. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Glycyrrhizin regulates CD4+T cell response during liver fibrogenesis via JNK, ERK and PI3K/AKT pathway

The aims of this study were to elucidate the immunomodulatory effects of glycyrrhizin (GL) on CD4(+)T cell responses during liver fibrogenesis. To obtain in vivo evidence about the effects of GL on CD4(+)T cells in livers and spleens of concanavalin A (ConA)-induced mouse model, mice were administrated with ConA together with or without GL for 8 weeks. Mice treated with GL dramatically prevented liver inflammation and fibrosis. Besides, GL inhibited the infiltration of T helper (Th) cell type 1, Th2, Th17 and regulatory T cells (Treg) in livers and spleens of mouse fibrosis models, and regulated the Th1/Th2 and Treg/Th17 balances respectively to a relative dominance of Th1 and Treg lineages in livers. Moreover, GL dramatically enhanced the antifibrotic cytokine interferon (IFN)-γ and interleukin (IL)-10. GL at a concentration of 10 or 100 μg/mL was respectively incubated with ConA-stimulated splenic CD4(+)T cells in vitro, and JNK inhibitor (SP600125), ERK inhibitor (U0126), p38 inhibitor (SB203580) or PI3K/AKT inhibitor (LY29400225) was added during the incubation. Notably, GL not only inhibited ConA-induced proliferation of splenic CD4(+)T cells but also enhanced the mRNAs of IFN-γ and IL-10 in these cells. Be similar to the effects of GL, SP600125, U0126 and LY29400225, however not SB203580, also inhibited ConA-induced CD4(+)T cell proliferation, indicating the involvement of JNK, ERK and PI3K/AKT in this process. Moreover, GL significantly inhibited ConA-induced phosphorylation of JNK, ERK and PI3K/AKT in vitro. Collectively, GL might alleviate liver injury and fibrosis progression via regulation of CD4(+)T cell response in JNK, ERK and PI3K/AKT-dependent pathways.

Lack of CC chemokine ligand 2 differentially affects inflammation and fibrosis according to the genetic background in a murine model of steatohepatitis

Expression of CCL2 (CC chemokine ligand 2) (or monocyte chemoattractant protein-1) regulates inflammatory cell infiltration in the liver and adipose tissue, favouring steatosis. However, its role in the pathogenesis of steatohepatitis is still uncertain. In the present study, we investigated the development of non-alcoholic steatohepatitis induced by an MCD diet (methionine/choline-deficient diet) in mice lacking the CCL2 gene on two different genetic backgrounds, namely Balb/C and C57/Bl6J. WT (wild-type) and CCL2-KO (knockout) mice were fed on a lipid-enriched MCD diet or a control diet for 8 weeks. In Balb/C mice fed on the MCD diet, a lack of CCL2 was associated with lower ALT (alanine transaminase) levels and reduced infiltration of inflammatory cells, together with a lower generation of oxidative-stress-related products. Sirius Red staining demonstrated pericellular fibrosis in zone 3, and image analysis showed a significantly lower matrix accumulation in CCL2-KO mice. This was associated with reduced hepatic expression of TGF-β (transforming growth factor-β), type I procollagen, TIMP-1 (tissue inhibitor of metalloproteinases-1) and α-smooth muscle actin. In contrast, in mice on a C57Bl/6 background, neither ALT levels nor inflammation or fibrosis were significantly different comparing WT and CCL2-KO animals fed on an MCD diet. In agreement, genes related to fibrogenesis were expressed to comparable levels in the two groups of animals. Comparison of the expression of several genes involved in inflammation and repair demonstrated that IL (interleukin)-4 and the M2 marker MGL-1 (macrophage galactose-type C-type lectin 1) were differentially expressed in Balb/C and C57Bl/6 mice. No significant differences in the degree of steatosis were observed in all groups of mice fed on the MCD diet. We conclude that, in experimental murine steatohepatitis, the effects of CCL2 deficiency are markedly dependent on the genetic background.

Profibrogenic chemokines and viral evolution predict rapid progression of hepatitis C to cirrhosis

Chronic hepatitis C may follow a mild and stable disease course or progress rapidly to cirrhosis and liver-related death. The mechanisms underlying the different rates of disease progression are unknown. Using serial, prospectively collected samples from cases of transfusion-associated hepatitis C, we identified outcome-specific features that predict long-term disease severity. Slowly progressing disease correlated with an early alanine aminotransferase peak and antibody seroconversion, transient control of viremia, and significant induction of IFN-γ and MIP-1β, all indicative of an effective, albeit insufficient, adaptive immune response. By contrast, rapidly progressive disease correlated with persistent and significant elevations of alanine aminotransferase and the profibrogenic chemokine MCP-1 (CCL-2), greater viral diversity and divergence, and a higher rate of synonymous substitution. This study suggests that the long-term course of chronic hepatitis C is determined early in infection and that disease severity is predicted by the evolutionary dynamics of hepatitis C virus and the level of MCP-1, a chemokine that appears critical to the induction of progressive fibrogenesis and, ultimately, the ominous complications of cirrhosis.