Th17 cells and their associated cytokines in liver diseases

Ursodeoxycholyl Lysophosphatidylethanolamide Protects Against CD95/FAS-Induced Fulminant Hepatitis

Increased activation of CD95/Fas by Fas ligand in viral hepatitis and autoimmunity is involved in pathogenesis of fulminant hepatitis and liver failure. We designed a bile-acid phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE with LPE containing oleate at the sn-1) as a hepatoprotectant that was shown to protect against fulminant hepatitis induced by endotoxin. We herein further assessed the ability of UDCA-LPE to prevent death receptor CD95/Fas-induced fulminant hepatitis. C57BL/6 mice were intravenously administered with CD95/Fas agonistic monoclonal antibody (Jo-2) with or without 1 h pretreatment with 50 mg/kg UDCA-LPE. Jo-2 administration caused massive hepatocyte damage as seen by histology, and this was associated with a significant decrease in hepatic phosphatidylcholine (PC), lysoPC, and lysophosphatidylethanolamine levels. By histology, UDCA-LPE pretreatment improved hepatocyte damage and restored the loss of these phospholipids in part by a mechanism involving an inhibition of cytosolic phospholipaseA2 expression. Accordingly, Jo-2 treatment increased hepatic expression of cleaved caspase 8, caspase 3, and poly (ADP-Ribose) polymerase-1, and on the other hand decreased that of anti-apoptotic cellular FLICE-inhibitory protein. UDCA-LPE pretreatment was able to reverse all these changes. Moreover, UDCA-LPE attenuated inflammatory response by lowering the levels of Jo-2-induced proinflammatory cytokines TNF-α, IL-6, and IL-1β in liver and serum. UDCA-LPE was also able to decrease the levels of stimulated Th1/Th17 cytokines in Jo-2-primed isolated splenocytes. Taken together, UDCA-LPE exhibited potent anti-inflammatory effects against CD95/Fas-induced fulminant hepatitis.

Role of altered immune cells in liver diseases: a review

Immune cells play an important role in controlling liver tumorigenesis, viral hepatitis, liver fibrosis and contribute to pathogenesis of liver inflammation and injury. Accumulating evidence suggests the effectiveness of natural killer (NK) cells and Kupffer cells (KCs) against viral hepatitis, hepatocellular damage, liver fibrosis, and carcinogenesis. Activation of natural killer cells provides a novel therapeutic strategy to cure liver related diseases. This review discusses the emerging roles of immune cells in liver disorders and it will provide baseline data to scientists to design better therapies for treatment.

Immune response of Th17-associated cytokines by peripheral blood mononuclear cells from patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) chronic infection causes severe cellular immune dysfunction. Here, we investigated the production of Th17-associated cytokines by peripheral blood mononuclear cells (PBMCs) of untreated patients with HCV, patients presenting an early virologic response (EVR) after 12weeks of treatment with interferon-α plus ribavirin with or without HCV protease inhibitors, and patients who were nonresponders to HCV therapy. PBMCs were stimulated with HCV core and nonstructural antigens, and the production of Th17-associated cytokines was measured with a Milliplex MAP immunoassay. Core-stimulated PBMCs from both untreated and nonresponder patients produced interleukin (IL)-17A, and vigorous production of IL-17A in response to NS3 antigen was only verified in the untreated group. Nonresponder patients also produced IL-17F after core antigen stimulation. IL-21 production was unaltered in the three groups of patients, whereas IL-17E and IL-22 were not detected. The production of Th17 cytokines by cells from patients showing an EVR was insignificant. IL-17A and IL-17F levels were not correlated with alanine aminotransferase levels or viremia. However, advanced fibrosis was associated with higher IL-17A production in T0 cells stimulated with core antigen. Untreated patients with HCV and patients who were nonresponders to antiviral treatment differed in their PBMC immune responses of Th17-associated cytokines. The early virological response to antiviral treatment dramatically decreased Th17 immune responses to HCV antigens.

Interleukins-17 and 27 promote liver regeneration by sequentially inducing progenitor cell expansion and differentiation

Liver progenitor cells (LPCs)/ductular reactions (DRs) are associated with inflammation and implicated in the pathogenesis of chronic liver diseases. However, how inflammation regulates LPCs/DRs remains largely unknown. Identification of inflammatory processes that involve LPC activation and expansion represent a key step in understanding the pathogenesis of liver diseases. In the current study, we found that diverse types of chronic liver diseases are associated with elevation of infiltrated interleukin (IL)-17-positive (+) cells and cytokeratin 19 (CK19)⁺ LPCs, and both cell types colocalized and their numbers positively correlated with each other. The role of IL-17 in the induction of LPCs was examined in a mouse model fed a choline-deficient and ethionine-supplemented (CDE) diet. Feeding of wild-type mice with the CDE diet markedly elevated CK19⁺Ki67⁺ proliferating LPCs and hepatic inflammation. Disruption of the IL-17 gene or IL-27 receptor, alpha subunit (WSX-1) gene abolished CDE diet-induced LPC expansion and inflammation. In vitro treatment with IL-17 promoted proliferation of bipotential murine oval liver cells (a liver progenitor cell line) and markedly up-regulated IL-27 expression in macrophages. Treatment with IL-27 favored the differentiation of bipotential murine oval liver cells and freshly isolated LPCs into hepatocytes. Conclusion: The current data provide evidence for a collaborative role between IL-17 and IL-27 in promoting LPC expansion and differentiation, respectively, thereby contributing to liver regeneration. (Hepatology Communications 2018;2:329-343).

Interleukin-17 alters the biology of many cell types involved in the genesis of psoriasis, systemic inflammation and associated comorbidities

Psoriasis is a chronic, immune-mediated, systemic inflammatory disease that is defined by a characteristic skin reaction produced when elevated levels of inflammatory cytokines such as interleukin (IL)-17 alter the growth and differentiation of skin cells. The pathogenesis of comorbid conditions associated with psoriasis, including psoriatic arthritis, cardiovascular disease, obesity, metabolic syndrome, liver disorders, renal disease and depression, is also largely affected by inflammation. In this review, we examine the effect of IL-17 on the inflammatory pathways in a variety of different cell types, including keratinocytes, as well as epithelial cells of the colon, kidney, gut and liver. Additionally, we investigate the role of IL-17 in mediating the psoriasis-associated comorbidities detailed above.

TLR2 Expression in Peripheral CD4+ T Cells Promotes Th17 Response and Is Associated with Disease Aggravation of Hepatitis B Virus-Related Acute-On-Chronic Liver Failure

Th17 responses have been shown to play crucial roles in the pathogenesis of hepatitis B virus (HBV)-associated acute-on-chronic liver failure (ACLF). The mechanism underlying the enhanced Th17 responses in these patients remains largely unclear. Here we investigated toll-like receptors (TLRs) expression in peripheral T cells and their roles in Th17 cell differentiation and disease aggravation in ACLF patients. 18 healthy subjects (HS), 20 chronic HBV-infected (CHB) patients, and 26 ACLF patients were enrolled and examined for TLRs expression in peripheral blood mononuclear cells (PBMCs). The correlations of T cell TLR2 expression with the antigen non-specific Th17 responses and disease aggravation, as well as the Th17 response to TLR2 ligand stimulation were evaluated in ACLF patients. Compared to HS and CHB patients, ACLF patients showed a distinct TLRs expression pattern in PBMCs. Significantly increased TLR2 expression in T cells was observed in ACLF patients. The TLR2 expression in CD4+ T cells was correlated with the Th17 responses and the clinical markers for disease aggravation in ACLF patients. Moreover, TLR2 ligands stimulation promoted Th17 cell differentiation and response in PBMCs of ACLF patients. These findings implicate that TLR2 signaling plays critical roles in Th17 cell differentiation and disease aggravation of HBV-related ACLF.

Immune checkpoint inhibition: prospects for prevention and therapy of hepatocellular carcinoma

The global prevalence of liver cancer is rapidly rising, mostly as a result of the amplified incidence rates of viral hepatitis, alcohol abuse and obesity in recent decades. Treatment options for liver cancer are remarkably limited with sorafenib being the gold standard for advanced, unresectable hepatocellular carcinoma but offering extremely limited improvement of survival time. The immune system is now recognised as a key regulator of cancer development through its ability to protect against infection and chronic inflammation, which promote cancer development, and eliminate tumour cells when present. However, the tolerogenic nature of the liver means that the immune response to infection, chronic inflammation and tumour cells within the hepatic environment is usually ineffective. Here we review the roles that immune cells and cytokines have in the development of the most common primary liver cancer, hepatocellular carcinoma (HCC). We then examine how the immune system may be subverted throughout the stages of HCC development, particularly with respect to immune inhibitory molecules, also known as immune checkpoints, such as programmed cell death protein-1, programmed cell death 1 ligand 1 and cytotoxic T lymphocyte antigen 4, which have become therapeutic targets. Finally, we assess preclinical and clinical studies where immune checkpoint inhibitors have been used to modify disease during the carcinogenic process. In conclusion, inhibitory molecule-based immunotherapy for HCC is in its infancy and further detailed research in relevant in vivo models is required before its full potential can be realised.

Mesenchymal stem cells attenuate acute liver injury by altering ratio between interleukin 17 producing and regulatory natural killer T cells

Mesenchymal stem cells (MSCs) are, due to immunomodulatory characteristics, considered as novel agents in the treatment of immune-mediated acute liver failure. Although it is known that MSCs can regulate activation of T lymphocytes, their capacity to modulate function of neutrophils and natural killer T (NKT) cells, major interleukin (IL) 17-producing cells in acute liver injury, is still unknown. By using 2 well-established murine models of neutrophil and NKT cell-mediated acute liver failure (induced by carbon tetrachloride and α-galactoceramide), we investigated molecular and cellular mechanisms involved in MSC-mediated modulation of IL17 signaling during acute liver injury. Single intravenous injection of MSCs attenuate acute hepatitis and hepatotoxicity of NKT cells in a paracrine, indoleamine 2,3-dioxygenase (IDO)-dependent manner. Decreased levels of inflammatory IL17 and increased levels of immunosuppressive IL10 in serum, reduced number of interleukin 17-producing natural killer T (NKT17) cells, and increased presence of forkhead box P3 + IL10-producing natural killer T regulatory cells (NKTregs) were noticed in the injured livers of MSC-treated mice. MSCs did not significantly alter the total number of IL17-producing neutrophils, CD4+, and CD8 + T lymphocytes in the injured livers. Injection of mesenchymal stem cell-conditioned medium (MSC-CM) resulted with an increased NKTreg/NKT17 ratio in the liver and attenuated hepatitis in vivo and significantly reduced hepatotoxicity of NKT cells in vitro. This phenomenon was completely abrogated in the presence of IDO inhibitor, 1-methyltryptophan. In conclusion, the capacity of MSCs to alter NKT17/NKTreg ratio and suppress hepatotoxicity of NKT cells in an IDO-dependent manner may be used as a new therapeutic approach in IL17-driven liver inflammation. Liver Transplantation 23 1040-1050 2017 AASLD.

Therapeutic strategies for alcoholic liver disease: Focusing on inflammation and fibrosis (Review)

Excessive alcohol consumption is the most common cause of liver disease in the world. Chronic alcohol abuse leads to liver damage, liver inflammation, fibrosis and hepatocellular carcinoma. Inflammatory cytokines, such as tumor necrosis factor-α and interferon-γ, induce liver injury, which leads to the develo-pment of alcoholic liver disease (ALD). Hepatoprotective cytokines, such as interleukin (IL)-6 and IL-10, are also associated with ALD. IL-6 improves ALD via the activation of STAT3 and the subsequent induction of a variety of hepatoprotective genes in hepatocytes. Alcohol consumption promotes liver inflammation by incre-asing the translocation of gut-derived endotoxins to the portal circulation and by activating Kupffer cells through the lipopolysaccharide/Toll-like receptor 4 pathways. Oxidative stress and microflora products are also associated with ALD. Hepatic stellate cells play an important role in angiogenesis and liver fibrosis. Anti-angiogenic therapy has been found to be effective in the prevention of fibrosis. This suggests that blocking angiogenesis could be a promising therapeutic option for patients with advanced fibrosis. This review discusses the main pathways associated with liver inflammation and liver fibrosis as well as new therapeutic strategies.

Hepatic overexpression of cAMP-responsive element modulator α induces a regulatory T-cell response in a murine model of chronic liver disease

OBJECTIVE

Th17 cells are a subset of CD4⁺ T-helper cells characterised by interleukin 17 (IL-17) production, a cytokine that plays a crucial role in inflammation-associated diseases. The cyclic AMP-responsive element modulator-α (CREMα) is a central mediator of T-cell pathogenesis, which contributes to increased IL-17 expression in patients with autoimmune disorders. Since an increased Th17 response is associated with a poor prognosis in patients with chronic liver injury, we investigated the relevance of Th17 cells for chronic liver disease (CLD) and hepatocarcinogenesis.

DESIGN

Transgenic mice overexpressing CREMα were crossed with hepatocyte-specific Nemo knockout mice (Nemo^Δhepa) to generate Nemo^Δhepa/CREMα^Tg mice. The impact of CREMα^Tg on CLD progression was examined. Additionally, soft agar colony formation assays, in vitro studies, adoptive transfer of bone marrow-derived cells (BMDCs) and T cells, and gene arrays in T cells were performed.

RESULTS

8-week-old Nemo^Δhepa/CREMα^Tg mice presented significantly decreased transaminase levels, concomitant with reduced numbers of CD11b⁺ dendritic cells and CD8⁺ T cells. CREMα^Tg overexpression in Nemo^Δhepa mice was associated with significantly reduced hepatic fibrogenesis and carcinogenesis at 52 weeks. Interestingly, hepatic stellate cell-derived retinoic acid induced a regulatory T-cell (Treg) phenotype in CREMα^Tg hepatic T cells. Moreover, simultaneous adoptive transfer of BMDCs and T cells from CREMα^Tg into Nemo^Δhepa mice ameliorated markers of liver injury and hepatitis.

CONCLUSIONS

Our results demonstrate that overexpression of CREMα in T cells changes the inflammatory milieu, attenuating initiation and progression of CLD. Unexpectedly, our study indicates that CREMα transgenic T cells shift chronic inflammation in Nemo^Δhepa livers towards a protective Treg response.

Interleukin-17A exacerbates high-fat diet-induced hepatic steatosis by inhibiting fatty acid β-oxidation

There is a growing body of evidence that the interleukin-17A (IL-17A) signaling pathway contributes to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). However, the mechanism by which IL-17A signaling induces hepatocyte injury is unclear. The aim of the present study was to investigate the significance of the IL-17A axis in NAFLD and to explore the role of IL-17A in high-fat diet (HFD)-induced NAFLD in C57BL/6 mice and oleic acid (OA)-induced lipid accumulation in hepatocytes. Firstly, Consistent upregulation of IL-17A was observed in the HFD-induced steatosis mice but not the normal chow-fed control mice. Administration of IL-17A impaired liver function, aggravated hepatic lipid accumulation by inhibiting fatty acid oxidation in the HFD mice. Conversely, inhibition of IL-17A using an anti-IL-17A monoclonal antibody (mAb) significantly attenuated HFD-induced liver injury. Furthermore, IL-17A accelerated hepatic steatosis through activation of the JNK-PPARα pathway in the HFD mice and OA-preloaded hepatocytes.

CONCLUSION

The present study demonstrated that a high fat diet induces IL-17A expression, which exacerbates the progression of NAFLD by inhibiting fatty acid β-oxidation and promoting the accumulation of triglycerides (TG).

How Does Interleukin-22 Mediate Liver Regeneration and Prevent Injury and Fibrosis?

Interleukin-22 (IL-22) is a pluripotent T cell-derived cytokine which is a member of IL-10 cytokine family. It is the only interleukin produced by immune cells but does not target immune system components. IL-22 is mainly produced by dendritic cells (DCs) and TH17, TH22, NK, and NKT cells and targets a number of body tissues including liver, pancreas, and other epithelial tissues. It provokes a series of downstream signaling pathways upon binding with IL-22R complex which protects liver damage through STAT3 activation. IL-22BP is an inhibitor of IL-22 which has 20-1000x more affinity to bind with IL-22 compared to IL-22R1 that inhibits IL-22 activity. Its level was found to be positively correlated with the severity of liver damage and fibrosis. So, the present review is an effort to reveal the exact mechanism lying in the hepatoprotective activity of IL-22 and some of its future therapeutic implications.

Baicalin Attenuates IL-17-Mediated Acetaminophen-Induced Liver Injury in a Mouse Model

BACKGROUND

IL-17 has been shown to be involved in liver inflammatory disorders in both mice and humans. Baicalin (BA), a major compound extracted from traditional herb medicine (Scutellariae radix), has potent hepatoprotective properties. Previous study showed that BA inhibits IL-17-mediated lymphocyte adhesion and downregulates joint inflammation. The aim of this study is to investigate the role of IL-17 in the hepatoprotective effects of BA in an acetaminophen (APAP)-induced liver injury mouse model.

METHODS

Eight weeks male C57BL/6 (B6) mice were used for this study. Mice received intraperitoneal hepatotoxic injection of APAP (300 mg/kg) and after 30 min of injection, the mice were treated with BA at a concentration of 30 mg/kg. After 16 h of treatment, mice were killed. Blood samples and liver tissues were harvested for analysis of liver injury parameters.

RESULTS

APAP overdose significantly increased the serum alanine transferase (ALT) levels, hepatic activities of myeloperoxidase (MPO), expression of cytokines (TNF-α, IL-6, and IL-17), and malondialdehyde (MDA) activity when compared with the control animals. BA treatment after APAP administration significantly attenuated the elevation of these parameters in APAP-induced liver injury mice. Furthermore, BA treatment could also decrease hepatic IL-17-producing γδT cells recruitment, which was induced after APAP overdose.

CONCLUSION

Our data suggested that baicalin treatment could effectively decrease APAP-induced liver injury in part through attenuation of hepatic IL-17 expression. These results indicate that baicalin is a potential hepatoprotective agent.

MicroRNA-26a-interleukin (IL)-6-IL-17 axis regulates the development of non-alcoholic fatty liver disease in a murine model

Non-alcoholic fatty liver disease (NAFLD) is a hepatic presentation of obesity and metabolic syndrome. MicroRNA 26a (Mir-26a) has been reported to play functions in cellular differentiation, cell growth, cell apoptosis and metastasis. A recent paper indicated that Mir-26a regulated insulin sensitivity and metabolism of glucose and lipids. However, the role of Mir-26a in NAFLD still needs to be investigated further. In our current study, vectors encoding pre-Mir-26a (LV-26a) and an empty lentiviral vector (LV-Con) delivered approximately 2 × 10⁷ transforming units of recombinant lentivirus were injected into mice through the tail vein. LV-26a-infected mice were protected from glucose dysmetabolism and showed markedly decreased total liver weight, hepatic triglyceride deposition and serum alanine transaminase (ALT) concentration when compared with LV-Con-treated mice. LV-26a-treated mice also exhibited decreased infiltration of immune cells in the liver - something attributed to reduce infiltration of T cell receptor (TCR)-γδ⁺ , granulocyte-differentiation antigen-1 (Gr-1)⁺ cells and CD11b⁺ cells. Next, we found that Mir-26a inhibited the expression of interleukin (IL)-17 and IL-6 in vivo and in vitro. Furthermore, the decreased expression of IL-17 in the liver tissue induced by Mir-26a was abrogated completely by IL-6 overexpression. The decreased total liver weight, hepatic triglyceride deposition and serum ALT concentration induced by Mir-26a was also abrogated completely by IL-6 over-expression. In conclusion, the Mir-26a-IL-6-IL-17 axis regulates the development of NAFLD in a murine model.

Inhibition of the JAK/STAT pathway by ruxolitinib ameliorates thioacetamide-induced hepatotoxicity

In an attempt to explore the role of the JAK/STAT pathway in liver inflammation, we investigated the effect of intervening this pathway by ruxolitinib in thioacetamide (TAA)-induced hepatotoxicity. Ruxolitinib treatments were administered to male mice either before or after intoxication with TAA. The hepatic histopathological and serum biochemical assessment revealed that ruxolitinib pre-treatments dose-dependently reduced TAA-induced liver injury, caspase 3 cleavage and increase in number of hepatocytes positive for the pro-apoptotic Bax, as well as inflammatory cells positive for F4/80 and myeloperoxidase activity in the liver. Ruxolitinib pre-treatments also curbed TAA-induced rise in NF-κB nuclear expression and STAT3 phosphorylation. Ruxolitinib pre-treatments also lowered TAA-induced elevation of hepatic oxidative stress parameters (total nitrate/nitrite and 4-hydroxynonenal), but did not restore the hepatic antioxidant reduced glutathione. Interestingly, ruxolitinib, especially at a dose of 200 mg/kg, dampened the overproduction of pro-inflammatory cytokines (TNF-α, IL-1β, IFN-γ, IL-23 and IL-17A), which coincided with boosting the release of the anti-inflammatory cytokine IL-10. Ruxolitinib when used as a post-treatment (1 and 3 h after TAA-insult) could still spare the liver from injury and might be clinically applicable. In conclusion, the multimechanistic-hepatoprotective activity of ruxolitinib can be linked to its ameliorative properties on cellular death, oxidative stress and inflammation machinery.

Progression of fibrosis in patients with chronic viral hepatitis is associated with IL-17(+) neutrophils

BACKGROUND & AIMS

The pro-inflammatory cytokine IL-17 plays a crucial role in liver diseases associated with hepatic fibrosis and increased risk of cancer development. Nevertheless, the cellular source of this cytokine has never been characterized in patients with liver fibrosis.

METHODS

In this study, we investigated liver biopsies from 49 patients with chronic viral hepatitis at different stages of liver fibrosis. We monitored IL-17 production by intracellular flow cytometry, immunofluorescence and immunohistochemical in situ stainings, allowing a precise quantification, characterization and localization of IL-17(+) cells.

RESULTS

Density of IL-17(+) cells increased with the stage of liver fibrosis specifically in fibrotic septa and portal areas (correlation coefficient r = 0.7373; P < 0.0001). Data clearly show that the frequency of intrahepatic IL-17(+) lymphocytes (including T, NKT and NK cells) was independent on stage of liver fibrosis, and we observed no statistical differences in number of IL-17(+) macrophages during progression of fibrosis. On the other hand, the number of IL-17(+) neutrophils in fibrotic septa and portal areas strongly correlated with the stages of fibrosis (correlation coefficient r = 0.6986; P < 0.0001), contributing significantly to total IL-17 production in liver tissue.

CONCLUSIONS

Our data indicate that neutrophils represent an important source of IL-17 in the human liver, especially in late fibrosis stages. Inhibition of this specific harmful subset of neutrophils may offer therapeutic opportunities in fibrotic liver.

Metabolic Inflammation-Associated IL-17A Causes Non-alcoholic Steatohepatitis and Hepatocellular Carcinoma

Obesity increases hepatocellular carcinoma (HCC) risks via unknown mediators. We report that hepatic unconventional prefoldin RPB5 interactor (URI) couples nutrient surpluses to inflammation and non-alcoholic steatohepatitis (NASH), a common cause of HCC. URI-induced DNA damage in hepatocytes triggers inflammation via T helper 17 (Th17) lymphocytes and interleukin 17A (IL-17A). This induces white adipose tissue neutrophil infiltration mediating insulin resistance (IR) and fatty acid release, stored in liver as triglycerides, causing NASH. NASH and subsequently HCC are prevented by pharmacological suppression of Th17 cell differentiation, IL-17A blocking antibodies, and genetic ablation of the IL-17A receptor in myeloid cells. Human hepatitis, fatty liver, and viral hepatitis-associated HCC exhibit increased IL-17A correlating positively with steatosis. IL-17A blockers may prevent IR, NASH, and HCC in high-risk patients.

Neutralization of Interleukin-17 Attenuates Cholestatic Liver Fibrosis in Mice

Anti-inflammation strategy is one of the proposed therapeutic approaches to hepatic fibrosis. IL-17 is critical in inflammation, but the role of IL-17 in liver fibrosis has not yet been elucidated. In this study, we investigate the role of IL-17 on bile duct ligation-induced liver injury and fibrosis in C57BL/6 mice. Animals were sacrificed at designated times, and serum and liver tissues were collected for analysis of liver function and serum IL-6, IL-1β, tumour necrosis factor-alpha (TNF-α) and transforming growth factor-β (TGF-β) levels. IL-17 blockade with anti-IL-17A mAb significantly improved liver function and decreased hepatocellular necrosis, pro-inflammatory cytokines, neutrophils and macrophages influx. Furthermore, CD3 + and CD8 + lymphocytes, neutrophils and macrophages were found to express IL-17, and neutrophils are the principal IL-17-producing cells after BDL-induced liver injury. These data indicated that IL-17 signal contributes to the pathogenesis of cholestatic liver injury and blocked of IL-17 could potentially benefit patients with cholestatic liver disease.

NKT cell subsets as key participants in liver physiology and pathology

Natural killer T (NKT) cells are innate-like lymphocytes that generally recognize lipid antigens and are enriched in microvascular compartments of the liver. NKT cells can be activated by self- or microbial-lipid antigens and by signaling through toll-like receptors. Following activation, NKT cells rapidly secrete pro-inflammatory or anti-inflammatory cytokines and chemokines, and thereby determine the milieu for subsequent immunity or tolerance. It is becoming clear that two different subsets of NKT cells-type I and type II-have different modes of antigen recognition and have opposing roles in inflammatory liver diseases. Here we focus mainly on the roles of both NKT cell subsets in the maintenance of immune tolerance and inflammatory diseases in liver. Furthermore, how the differential activation of type I and type II NKT cells influences other innate cells and adaptive immune cells to result in important consequences for tissue integrity is discussed. It is crucial that better reagents, including CD1d tetramers, be used in clinical studies to define the roles of NKT cells in liver diseases in patients.

Update on Alcoholic Hepatitis

Alcoholic liver disease is one of the most prevalent liver diseases worldwide, and a major cause of morbidity and mortality. Alcoholic hepatitis is a severe form of liver injury in patients with alcohol abuse, can present as an acute on chronic liver failure associated with a rapid decline in liver synthetic function, and consequent increase in mortality. Despite therapy, about 30%-50% of patients with severe alcoholic hepatitis eventually die. The pathogenic pathways that lead to the development of alcoholic hepatitis are complex and involve oxidative stress, gut dysbiosis, and dysregulation of the innate and adaptive immune system with injury to the parenchymal cells and activation of hepatic stellate cells. As accepted treatment approaches are currently limited, a better understanding of the pathophysiology would be required to generate new approaches that improve outcomes. This review focuses on recent advances in the diagnosis, pathogenesis of alcoholic hepatitis and novel treatment strategies.

C57BL/6 and A/J Mice Have Different Inflammatory Response and Liver Lipid Profile in Experimental Alcoholic Liver Disease

Alcoholic liver disease (ALD) is an important worldwide public health issue characterized by liver steatosis, inflammation, necrosis, and apoptosis of hepatocytes with eventual development of fibrosis and cirrhosis. Comparison of murine models with different inflammatory responses for ALD is important for an evaluation of the importance of genetic background in the interpretation of ethanol-induced phenotypes. Here, we investigated the role of inflammation and genetic background for the establishment of ALD using two different mouse strains: C57BL/6 (B6) and A/J. B6 and A/J mice were treated with a high fat diet containing ethanol (HFDE) and compared to the controls for 10 weeks. Hepatomegaly and steatohepatitis were similar in B6 and A/J mice, but only A/J mice were resistant to weight gain. On the other hand, HFDE-fed B6 accumulated more triglycerides (TG) and cholesterol and presented more intense cellular infiltrate in the liver when compared to HFDM-fed mice. Liver inflammatory environment was distinct in these two mouse strains. While HFDE-fed B6 produced more liver IL-12, A/J mice increased the TNF-α production. We concluded that mouse genetic background could dictate the intensity of the HFDE-induced liver injury.

Th2-biased GATA-3 transgenic mice developed severe experimental peritoneal fibrosis compared with Th1-biased T-bet and Th17-biased RORγt transgenic mice

Encapsulating peritoneal sclerosis is one of the most serious complications of long-term peritoneal dialysis. The pathogenesis of encapsulating peritoneal sclerosis has not been elucidated, but several putative factors necessary for the development of peritoneum fibrosis (PF) have been reported. However, the roles of T helper (Th) cells in the progression of PF are unknown. The purpose of this study was to clarify the roles of Th1, Th2, and Th17 cells in the progression of PF. T-bet, GATA-3, and RORγt are Th1, Th2, and Th17 lineage commitment transcription factors, respectively. We previously generated Th1-biased (T-bet transgenic (Tg)) mice, Th2-biased (GATA-3 Tg) mice, and Th17-biased (RORγt Tg) mice. In this study, Th1, Th2, Th17-biased, and wild-type mice were administered chlorhexidine gluconate (CG) intraperitoneally and analyzed on day 21. CG-injected GATA-3 Tg mice showed a distended intestinal tract and developed marked thickening of the submesothelial space compared with the other groups. CG-injected GATA-3 Tg mice also showed significant expression of α-SMA positive cells, macrophages, and collagen III in the submesothelium. In contrast, CG-injected T-bet Tg mice only developed mild peritoneal fibrosis. Cytokines analysis in peritoneal fluid showed that IFN-γ was significantly increased in CG-injected T-bet Tg mice and that IL-13 was significantly increased in CG-injected GATA-3 Tg mice. Moreover, intraperitoneal administration of IFN-γ improved PF in GC-injected wild-type mice. Our results suggest that Th2 cells may play roles in the development of experimental PF and that Th1 cells may alleviate the severity of experimental PF.

Human Cytokinome Analysis for Interferon Response

Cytokines are a group of small secreted proteins that mediate a diverse range of immune and nonimmune responses to inflammatory and microbial stimuli. Only a few of these cytokines mount an antiviral response, including type I, II, and III interferons (IFNs). During viral infections and under inflammatory conditions, a number of cytokines and chemokines are coproduced with IFN; however, no systematic study exists on the interactions of the cytokine repertoire with the IFN response. Here, we performed the largest cytokine and chemokine screen (the human cytokinome, with >240 members) to investigate their modulation of type I and type II IFN responses in a cell line model. We evaluated the cytokine activities in both IFN-stimulated response element (ISRE) and IFN-γ activation sequence (GAS) reporter systems. Several cytokine clusters that augment either or both ISRE- and GAS-mediated responses to IFNs were derived from the screen. We identified novel modulators of IFN response-betacellulin (BTC), interleukin 11 (IL-11), and IL-17F-that caused time-dependent induction of the IFN response. The ability to induce endogenous IFN-β and IFN-stimulated genes varies among these cytokines and was largely dependent on Stat1, as assessed by Stat1 mutant fibroblasts. Certain cytokines appear to augment the IFN-β response through the NF-κB pathway. The novel IFN-like cytokines augmented the antiviral activity of IFN-α against several RNA viruses, including encephalomyocarditis virus, vesicular stomatitis virus, and influenza virus, in susceptible cell lines. Overall, the study represents a large-scale analysis of cytokines for enhancing the IFN response and identified cytokines capable of enhancing Stat1, IFN-induced gene expression, and antiviral activities.

IMPORTANCE

Innate immunity to viruses is an early defense system to ward off viruses. One mediator is interferon (IFN), which activates a cascade of biochemical events that aim to control the virus life cycle. In our work, we examined more than 200 cytokines, soluble mediators produced within the body as a result of infection, for the ability to enhance IFN action. We identified enhanced interactions with specific IFNs and cytokines. We also revealed that betacellulin, IL-17, and IL-11 cytokines have the novel property of enhancing the antiviral action of IFN against several viruses. These results demonstrate that the human genome codes for previously unknown proteins with unrelated functions that can augment the innate immunity to viruses. Knowing these interactions not only helps our understanding of immunity to viruses and emerging diseases, but can also lead to devising possible new therapeutics by enhancing the mediator of antiviral action itself, IFN.

Role of interleukin-22 in liver diseases

Interleukin (IL)-22, which is discovered by the Dumoutier team during the stimulation of murine BW5147 T lymphoma cells with IL-9, is a member of the IL-10 cytokine family because of the similarity of structure and encoding genes. IL-22 is involved in many inflammatory diseases and autoimmune diseases, such as psoriasis, ulcerative colitis, and systemic lupus erythematosus. Recently it has been found that IL-22 can protect against liver injury and promote hepatocytes proliferation. This paper will make a brief introduction of the role of IL-22 in liver diseases.

Lack of IL-17 signaling decreases liver fibrosis in murine schistosomiasis japonica

Accumulating evidence has identified the profibrogenic properties of IL-17A in organ fibrosis. However, the role of IL-17A signal in liver fibrosis induced by Schistosoma japonicum infection remains unclear. In this study, we investigated liver fibrosis in wild-type (WT) and IL-17RA(-/-) mice upon S. japonicum infection. Hepatic IL-17A, IL-17C, IL-17E (IL-25), IL-17F, IL-17RA, IL-17RB and IL-17RC transcript levels were determined by RT-PCR. IL-17A(+) cells were analyzed by flow cytometry and confocal microscopy among granuloma cells. Immunostaining of IL-17R was performed on liver sections. Collagen deposition was assessed by Van Gieson's staining. IL-17A, IL-17C, IL-17E, IL-17F, IL-17RA and IL-17RC mRNA levels were dramatically increased in fibrotic livers. Among granuloma cells, CD3(+) and CD3(-) lymphocytes, neutrophils and macrophages were found to express IL-17A. Compared to WT, IL-17RA(-/-) mice displayed attenuated granulomatous inflammation, liver fibrosis, improved liver function and high survival. Meanwhile, α-smooth muscle actin staining and the expression of fibrogenic genes (transforming growth factor β, IL-13 and collagen-I) as well as IL-17A-induced proinflammatory mediators (IL-1β, IL-6, tumor necrosis factor α, CXCL1 and CXCL2) and proteinases (MMP3 and TIMP1) involved in fibrosis were markedly reduced in IL-17RA(-/-) mice. In addition, Th2 cytokines IL-4 and IL-17E (IL-25) were also decreased in IL-17RA(-/-) mice. These results indicated that IL-17A signal contributes to the pathogenesis of liver fibrosis in murine schistosomiasis. This effect was induced possibly by activating hepatic stellate cells and stimulating the release of proinflammatory cytokines and chemokines. Furthermore, the Th2 response was also enhanced by IL-17A signals. Our data demonstrate that IL-17A may serve as a promising target for antifibrotic therapy.

T-helper 17-related cytokines and IgE antibodies during hepatitis A virus infection in children

We determined the serum IgE levels and T-helper (Th)17-related cytokines during distinct hepatitis A virus (HAV)-induced clinical courses in children. A significantly higher concentration of macrophage inflammatory protein 3α, interleukin (IL)-17E and IL-17F in HAV-infected children with intermediate liver injury compared with those with minor liver damage was found. A reduction in the IgE levels in those patients who showed the highest levels of IL-17F in the group of intermediate liver injury was found. The data suggested that the Th17-related profile is associated with the severity of HAV infection and might play a role on the modulation achieved by HAV during allergies.

Alcohol's Effect on Host Defense

Alcohol affects many organs, including the immune system, with even moderate amounts of alcohol influencing immune responses. Although alcohol can alter the actions of all cell populations involved in the innate and adaptive immune responses, the effect in many cases is a subclinical immunosuppression that becomes clinically relevant only after a secondary insult (e.g., bacterial or viral infection or other tissue damage). Alcohol's specific effects on the innate immune system depend on the pattern of alcohol exposure, with acute alcohol inhibiting and chronic alcohol accelerating inflammatory responses. The proinflammatory effects of chronic alcohol play a major role in the pathogenesis of alcoholic liver disease and pancreatitis, but also affect numerous other organs and tissues. In addition to promoting proinflammatory immune responses, alcohol also impairs anti-inflammatory cytokines. Chronic alcohol exposure also interferes with the normal functioning of all aspects of the adaptive immune response, including both cell-mediated and humoral responses. All of these effects enhance the susceptibility of chronic alcoholics to viral and bacterial infections and to sterile inflammation.

Osteopontin deficiency does not prevent but promotes alcoholic neutrophilic hepatitis in mice

Alcoholic hepatitis (AH) is a distinct spectrum of alcoholic liver disease (ALD) with intense neutrophilic (polymorphonuclear; PMN) inflammation and high mortality. Although a recent study implicates osteopontin (SPP1) in AH, SPP1 is also shown to have protective effects on experimental ALD. To address this unsettled question, we examined the effects of SPP1 deficiency in male mice given 40% calories derived from ad libitum consumption of the Western diet high in cholesterol and saturated fat and the rest from intragastric feeding of alcohol diet without or with weekly alcohol binge. Weekly binge in this new hybrid feeding model shifts chronic ASH with macrophage inflammation and perisinusoidal and pericellular fibrosis to AH in 57% (15 of 26) of mice, accompanied by inductions of chemokines (Spp1, Cxcl1, and interleukin [Il]-17a), progenitor genes (Cd133, Cd24, Nanog, and epithelial cell adhesion molecule), PMN infiltration, and clinical features of AH, such as hypoalbuminemia, bilirubinemia, and splenomegaly. SPP1 deficiency does not reduce AH incidence and inductions of progenitor and fibrogenic genes, but rather enhances the Il-17a induction and PMN infiltration in some mice. Furthermore, in the absence of SPP1, chronic ASH mice without weekly binge begin to develop AH.

CONCLUSION

These results suggest that SPP1 has a protective, rather than causal, role for experimental AH reproduced in our model.

New Approaches for Studying Alcoholic Liver Disease

Alcoholic liver disease (ALD) is major cause of chronic liver injury which results in liver fibrosis and cirrhosis. According to the surveillance report published by the National Institute on Alcohol Abuse and Alcoholism, liver cirrhosis is the 12th leading cause of death in the United States with 48 % of these deaths being attributed to excessive alcohol consumption. ALD includes a spectrum of disorders from simple steatosis to steatohepatitis, fibrosis, and hepatocellular carcinoma. Several mechanisms play a critical role in the pathogenesis of ALD. These include ethanol-induced oxidative stress and depletion of glutathione, pathological methionine metabolism, increased gut permeability and release of endotoxins into the portal blood, recruitment and activation of inflammatory cells including bone marrow-derived and liver resident macrophages (Kupffer cells). Chronic alcohol consumption results in liver damage and activation of hepatic stellate cells (HSCs) and myofibroblasts, leading to liver fibrosis. Here we discuss the current view on factors that are specific for different stages of ALD and those that regulate its progression, including cytokines and chemokines, alcohol-responsive intracellular signaling pathways, and transcriptional factors. We also review recent studies demonstrating that alcohol-mediated changes can be regulated on an epigenetic level, including microRNAs. Finally, we discuss the reversibility of liver fibrosis and inactivation of HSCs as a potential strategy for treating alcohol-induced liver damage.

Differential modulation by IL-17A of Cholangitis versus Colitis in IL-2Rα deleted mice

IFN-γ is a signature Th1 cell associated cytokine critical for the inflammatory response in autoimmunity with both pro-inflammatory and potentially protective functions. IL-17A is the hallmark of T helper 17 (Th17) cell subsets, produced by γδT, CD8+ T, NK and NKT cells. We have taken advantage of our colony of IL-2Rα-/- mice that spontaneously develop both autoimmune cholangitis and inflammatory bowel disease. In this model CD8+ T cells mediate biliary ductular damage, whereas CD4+ T cells mediate induction of colon-specific autoimmunity. Importantly, IL-2Rα-/- mice have high levels of interferon γ (IFN-γ), and interleukin-17A (IL-17A). We produced unique double deletions of mice that were either IL-17A-/-IL-2Rα-/- or IFN-γ-/-IL-2Rα-/- to specifically address the precise role of these two cytokines in the natural history of autoimmune cholangitis and colitis. Of note, deletion of IL-17A in IL-2Rα-/- mice led to more severe liver inflammation, but ameliorated colitis. In contrast, there were no significant changes in the immunopathology of double knock-out IFN-γ-/- IL-2Rα-/- mice, compared to single knock-out IL-2Rα-/- mice with respect to cholangitis or colitis. Furthermore, there was a significant increase in pathogenetic CD8+ T cells in the liver of IL-17A-/-IL-2Rα-/- mice. Our data suggest that while IL-17A plays a protective role in autoimmune cholangitis, it has a pro-inflammatory role in inflammatory bowel disease. These data take on particular significance in the potential use of anti-IL-17A therapy in humans with primary biliary cirrhosis.

Regulatory role of CD4(+)CD25 (+)Foxp3 (+) regulatory T cells on IL-17-secreting T cells in chronic hepatitis B patients

BACKGROUND

Both interleukin (IL)-17-secreting CD4(+) T (Th17) and CD4(+)CD25(+)Foxp3(+) T regulatory (Treg) cells have been shown to be associated with disease progression or liver damage in chronic hepatitis B (CHB) patients. However, the relationship between Treg cells and IL-17-secreting T cells in hepatitis B virus (HBV) infections is unclear.

METHODS

The frequencies of Treg cells and IL-17-secreting T cells in hepatitis B e antigen (HBeAg)-positive CHB patients and healthy subjects were measured by flow cytometric analysis. The role of Treg cells on the differentiation of Ag-specific IL-17-secreting T cells was determined by removing the Treg cells from peripheral blood mononuclear cells (PBMCs) in HBeAg-positive CHB patients.

RESULTS

The frequencies of both Th17 (1.71 ± 0.58 vs. 1.08 ± 0.36 %; P < 0.01) and Treg cells (8.92 ± 4.11 vs. 6.45 ± 1.56 %; P < 0.01) were increased in the peripheral blood of HBeAg-positive CHB patients compared with healthy controls, but in not the IL-17-secreting CD8(+) T (Tc17) cells. The frequency of Treg cells was significantly associated with that of Th17 cells (r = 0.625, P = 0.001) in CHB patients. Spearman analysis showed a positive correlation between the frequency of Treg cells and HBV DNA load (r = 0.508, P = 0.008), as well as between the frequency of Th17 cells and serum alanine aminotransferase level (r = 0.516, P = 0.007). The deletion of Treg cells significantly enhanced both Th17 and Tc17 cell development in PBMCs following recombinant HBV core antigen stimulation.

CONCLUSIONS

Our data indicate a clear inverse relationship between Th17 cells and Treg cells and that Treg cells can inhibit Th17 cell development in CHB patients.

The effect of antifibrotic drug halofugine on Th17 cells in concanavalin A-induced liver fibrosis

Anti-inflammation strategy is one of the proposed therapeutic approaches to hepatic fibrosis. T helper (Th) 17 cells, which play a detrimental role in experimental murine models of inflammatory diseases, have been demonstrated to participate in the pathogenesis of liver damage. The inhibitory effect of halofuginone (HF), an active component of extracts derived from the plant alkaloid febrifugine, on collagen synthesis has been shown in animal models of the fibrotic disease. The aim of this study was to clarify the in vivo effect of HF on Th17 cells in concanavalin A-induced fibrosis rats. Haematoxylin-eosin (HE) staining and Masson staining were performed to observe collagen deposition. The presence of INF-gamma, TNF-alpha, IL-6, IL-17, IL-1beta, IL-33 and IL-10 in serum and the presence of ROR-γt, IL-17, TGF-β1 and α-SMA in liver tissue were detected. Flow cytometry was performed to analyse the percentage of Th17 cells. We observed significantly lower levels of INF-gamma, TNF-alpha, IL-6, IL-17, IL-1beta, TGF-β1 and α-SMA in HF-treated group of rats, and the percentage of Th17 cells in splenic lymphocyte was decreased well. Histological examination demonstrated that HF significantly reduced the severity of liver fibrosis in HF-treated rats. We concluded that HF (10 mg/kg) exerts an antifibrotic impact on Th17 cells and its relative cytokines in rats with ConA-induced fibrosis.

IL-17 signaling accelerates the progression of nonalcoholic fatty liver disease in mice

Inflammation plays a central pathogenic role in the pernicious metabolic and end-organ sequelae of obesity. Among these sequelae, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in the developed world. The twinned observations that obesity is associated with increased activation of the interleukin (IL)-17 axis and that this axis can regulate liver damage in diverse contexts prompted us to address the role of IL-17RA signaling in the progression of NAFLD. We further examined whether microbe-driven IL-17A regulated NAFLD development and progression. We show here that IL-17RA(-/-) mice respond to high-fat diet stress with significantly greater weight gain, visceral adiposity, and hepatic steatosis than wild-type controls. However, obesity-driven lipid accumulation was uncoupled from its end-organ consequences in IL-17RA(-/-) mice, which exhibited decreased steatohepatitis, nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase enzyme expression, and hepatocellular damage. Neutralization of IL-17A significantly reduced obesity-driven hepatocellular damage in wild-type mice. Further, colonization of mice with segmented filamentous bacteria (SFB), a commensal that induces IL-17A production, exacerbated obesity-induced hepatocellular damage. In contrast, SFB depletion protected from obesity-induced hepatocellular damage.

CONCLUSION

These data indicate that obesity-driven activation of the IL-17 axis is central to the development and progression of NAFLD to steatohepatitis and identify the IL-17 pathway as a novel therapeutic target in this condition.

Intrahepatic innate lymphoid cells secrete IL-17A and IL-17F that are crucial for T cell priming in viral infection

Intrahepatic cell-derived, early IL-17 is important for activating APCs in viral infection; however, the source and regulation of this IL-17 surge in the liver microenvironment are not well defined. In this article, we present evidence for a significant expansion of IL-17A/F-producing cells in mouse liver within 24 h of adenovirus infection. In addition to γδ T cells, a subset of IL-17A/F(+) cells expressed no myeloid or lymphoid lineage markers. Instead, they expressed high levels of stem cell markers, IL-7R and RORγt, consistent with the newly described innate lymphoid cells (ILCs). Based on their unique surface markers and cytokine profiles, these cells were confirmed as group 3 ILCs. In addition to adenovirus infection, group 3 ILCs were also found in mouse liver within 24 h of lymphocytic choriomeningitis virus infection. They contributed significantly to the establishment of the early cytokine milieu in virus-infected liver. Functional studies with mice deficient of IL-17R, IL-17A, and IL-17F further revealed that IL-17 signaling was critical for priming T cell responses in viral hepatitis. IL-17A repressed IL-17F secretion in vitro and in vivo; IL-17F(+) intrahepatic cells expanded more vigorously in IL-17A knockout animals, permitting efficient Ag presentation and T cell function. However, IL-17F neither inhibited IL-17A in vitro nor regulated its secretion in vivo. Together, this study has demonstrated the importance of a unique intrahepatic subpopulation and subsequent IL-17A/F regulation at initial stages of viral infection in the liver. These results have important implications for anticytokine biologic therapy and vaccine development.

Cannabinoid receptor 2 counteracts interleukin-17-induced immune and fibrogenic responses in mouse liver

Interleukin (IL)-17 is a proinflammatory and fibrogenic cytokine mainly produced by T-helper (Th)17 lymphocytes, together with the hepatoprotective and antifibrogenic cytokine, IL-22. Cannabinoid receptor 2 (CB2) is predominantly expressed in immune cells and displays anti-inflammatory and antifibrogenic effects. In the present study, we further investigated the mechanism underlying antifibrogenic properties of CB2 receptor and explored its effect on the profibrogenic properties of IL-17. After bile duct ligation (BDL), the hepatic expression of Th17 markers and IL-17 production were enhanced in CB2(-/-) mice, as compared to wild-type (WT) counterparts, and correlated with increased fibrosis in these animals. In contrast, IL-22-induced expression was similar in both animal groups. Inhibition of Th17 differentiation by digoxin lowered Th17 marker gene expression and IL-17 production and strongly reduced liver fibrosis in CB2(-/-) BDL mice. In vitro, differentiation of CD4(+) naïve T cells into Th17 lymphocytes was decreased by the CB2 agonist, JWH-133, and was associated with reduced Th17 marker messenger RNA expression and IL-17 production, without modification of IL-22 release. The inhibitory effect of JWH-133 on IL-17 production relied on signal transducer and activator of transcription (STAT)5 phosphorylation. Indeed, STAT5 phosphorylation and translocation into the nucleus was enhanced in JWH133-treated Th17 lymphocytes, and the addition of a STAT5 inhibitor reversed the inhibitory effect of the CB2 agonist on IL-17 production, without affecting IL-22 levels. Finally, in vitro studies also demonstrated that CB2 receptor activation in macrophages and hepatic myofibroblasts blunts IL-17-induced proinflammatory gene expression.

CONCLUSION

These data demonstrate that CB2 receptor activation decreases liver fibrosis by selectively reducing IL-17 production by Th17 lymphocytes via a STAT5-dependent pathway, and by blunting the proinflammatory effects of IL-17 on its target cells, while preserving IL-22 production.

The effect of inflammatory cytokines in alcoholic liver disease

Alcohol is the most common cause of liver disease in the world. Chronic alcohol consumption leads to hepatocellular injury and liver inflammation. Inflammatory cytokines, such as TNF-α and IFN-γ, induce liver injury in the rat model of alcoholic liver disease (ALD). Hepatoprotective cytokines, such as IL-6, and anti-inflammatory cytokines, such as IL-10, are also associated with ALD. IL-6 improves ALD via activation of the signal transducer and activator of transcription 3 (STAT3) and the subsequent induction of a variety of hepatoprotective genes in hepatocytes. IL-10 inhibits alcoholic liver inflammation via activation of STAT3 in Kupffer cells and the subsequent inhibition of liver inflammation. Alcohol consumption promotes liver inflammation by increasing translocation of gut-derived endotoxins to the portal circulation and activating Kupffer cells through the LPS/Toll-like receptor (TLR) 4 pathways. Oxidative stress and microflora products are also associated with ALD. Interactions between pro- and anti-inflammatory cytokines and other cytokines and chemokines are likely to play important roles in the development of ALD. The present study aims to conduct a systemic review of ALD from the aspect of inflammation.

T helper 17 cells in autoimmune liver diseases

Many autoimmune diseases are driven by self-reactive T helper (Th) cells. A new population of effector CD4⁺ T cells characterized by the secretion of interleukin (IL)-17, referred to as Th17 cells, has been demonstrated to be phenotypically, functionally, and developmentally distinct from Th1 and Th2 cells. Because the liver is known to be an important source of transforming growth factor-β and IL-6, which are cytokines that are crucial for Th17 differentiation, it is very likely that Th17 cells contribute to liver inflammation and autoimmunity. In contrast, another distinct subset of T cells, regulatory T cells (Treg), downregulate immune responses and play an important role in maintaining self-tolerance. In addition, there is a reciprocal relationship between Th17 cells and Tregs, in development and effector functions, and the balance between Th17 and Treg cells can affect the outcome of immune responses, particularly in autoimmune diseases. In this review, we will focus on the latest investigative findings related to Th17 cells in autoimmune liver disease.

Effects of N-acetylcysteine on cytokines in non-acetaminophen acute liver failure: potential mechanism of improvement in transplant-free survival

BACKGROUND

N-Acetylcysteine (NAC) improves transplant-free survival in patients with non-acetaminophen acute liver failure (ALF) when administered in early stages of hepatic encephalopathy. The mechanisms of this benefit are unknown.

AIM

To determine whether NAC improves transplant-free survival in ALF by ameliorating the surge of pro-inflammatory cytokines.

METHODS

Serum samples were obtained from 78 participants of the randomized, ALF Study Group NAC Trial with grade 1 or 2 hepatic encephalopathy on randomization. Concentrations of ten cytokines, chosen to represent a wide array of inflammatory responses, were determined by multiplex enzyme-linked immunosorbent assay ELISA.

RESULTS

In univariate analysis, predictors of transplant-free survival included NAC administration (P = 0.012), admission bilirubin (P = 0.003), international normalized ratio INR (P = 0.0002), grade 1 vs. grade 2 encephalopathy (P = 0.006) and lower admission interleukin (IL)-17 concentrations (P = 0.011). IL-17 levels were higher in patients with grade 2 vs. grade 1 encephalopathy on randomization (P = 0.007) and in those who progressed to grade 3 or grade 4 encephalopathy over the following 7 days (P ≤ 0.01). Stepwise multivariate logistic regression analysis identified only NAC administration and lower IL-17 concentrations as independent predictors of transplant-free survival. In patients with detectable IL-17 concentrations on admission, 78% of those who received NAC vs. 44% of those who received placebo had undetectable levels by day 3-5 (P = 0.042), and the mean decrease in IL-17 concentrations between admission and late samples was significantly greater in patients who received NAC vs. placebo (P = 0.045).

CONCLUSIONS

N-acetylcysteine (NAC) may improve transplant-free survival in patients with non-acetaminophen ALF by ameliorating the production of IL-17, which is associated with progression of hepatic encephalopathy and poor outcome.

IL-17A plays a critical role in the pathogenesis of liver fibrosis through hepatic stellate cell activation

Liver fibrosis is a severe, life-threatening clinical condition resulting from nonresolving hepatitis of different origins. IL-17A is critical in inflammation, but its relation to liver fibrosis remains elusive. We find increased IL-17A expression in fibrotic livers from HBV-infected patients undergoing partial hepatectomy because of cirrhosis-related early-stage hepatocellular carcinoma in comparison with control nonfibrotic livers from uninfected patients with hepatic hemangioma. In fibrotic livers, IL-17A immunoreactivity localizes to the inflammatory infiltrate. In experimental carbon tetrachloride-induced liver fibrosis of IL-17RA-deficient mice, we observe reduced neutrophil influx, proinflammatory cytokines, hepatocellular necrosis, inflammation, and fibrosis as compared with control C57BL/6 mice. IL-17A is produced by neutrophils and T lymphocytes expressing the Th17 lineage-specific transcription factor Retinoic acid receptor-related orphan receptor γt. Furthermore, hepatic stellate cells (HSCs) isolated from naive C57BL/6 mice respond to IL-17A with increased IL-6, α-smooth muscle actin, collagen, and TGF-β mRNA expression, suggesting an IL-17A-driven fibrotic process. Pharmacologic ERK1/2 or p38 inhibition significantly attenuated IL-17A-induced HSC activation and collagen expression. In conclusion, IL-17A(+) Retinoic acid receptor-related orphan receptor γt(+) neutrophils and T cells are recruited into the injured liver driving a chronic, fibrotic hepatitis. IL-17A-dependent HSC activation may be critical for liver fibrosis. Thus, blockade of IL-17A could potentially benefit patients with chronic hepatitis and liver fibrosis.

Association of IL-17, IL-21, and IL-23R gene polymorphisms with HBV infection in kidney transplant patients

Inflammatory cytokine gene polymorphisms may influence the hepatic and extrahepatic HBV-related disease in transplant patients. In this study, the association between IL-17, IL-23R, and IL-21 gene polymorphisms with hepatitis B virus (HBV) infection was evaluated in kidney transplant patients. In total, 220 kidney transplant patients were enrolled in this cross-sectional study between years 2007 and 2011. The genomic HBV DNA was identified using an HBV PCR detection Kit according to the manufacturer's instruction. The cytokine gene polymorphisms, including IL-17 197 A/G (rs2275913), IL-21 +1472 G/T (rs2055979), IL-21 5250 C/T (rs4833837), and IL-23R C/A (rs10889677) were evaluated by PCR-RFLP and ARMS-PCR protocols. The serum levels of IL-17 and IL-21 were analyzed in HBV infected and noninfected transplant patients by ELISA methods according to manufacturer's instructions. 70 of 220 (35%) transplant patients experienced acute rejection. HBV DNA was detected in 52 of 220 (23.64%) transplant patients. 16 of 52 (30.8%) HBV-infected kidney transplant patients experienced acute rejection. A significant higher frequency of C allele of IL-23R (rs10889677) polymorphism, a higher frequency of AG heterozygote genotype and A allele of IL-17-G197A (rs2275913) polymorphism, a higher frequency of TT homozygote genotype and T allele of IL-21-G1472T (rs2055979) polymorphism, and a higher frequency of CC homozygote genotype and C allele of IL-21-C5250T (rs4833837) polymorphism were found in HBV-infected kidney transplant patients with acute rejection. Diagnosis of the higher frequency of the IL-17, IL-21, and IL-23R cytokine genotypes and allele polymorphisms in HBV-infected kidney transplant patients who experienced acute rejection, illustrates the importance of Th17-related cytokine genetic patterns. A better evaluation of HBV infection in kidney transplant patients is needed.

Th17 cells and liver diseases

In recent years, it has been demonstrated that T helper cells 17 (Th17) are closely related to the occurrence and development of many kinds of liver diseases such as viral hepatitis, autoimmune liver diseases and fatty liver diseases. Th17 cells are a new CD4⁺ T cell subset, which can interact with Th1, Th2 and Treg cells. There exists complex antagonistic or collaborative relationship among these cells. Understanding the role of Th17 cells in liver diseases will help explore the pathogenesis and treatment of these diseases.

Deletion of interleukin (IL)-12p35 induces liver fibrosis in dominant-negative TGFβ receptor type II mice

Mice with a dominant-negative transforming growth factor β receptor restricted to T cells (dnTGFβRII mice) develop an inflammatory biliary ductular disease that strongly resembles human primary biliary cirrhosis (PBC). Furthermore, deletion of the gene encoding interleukin (IL)-12p40 resulted in a strain (IL-12p40(-/-) dnTGFβRII) with dramatically reduced autoimmune cholangitis. To further investigate the role of the IL-12 cytokine family in dnTGFβRII autoimmune biliary disease, we deleted the gene encoding the IL-12p35 subunit from dnTGFβRII mice, resulting in an IL-12p35(-/-) dnTGFβRII strain which is deficient in two members of the IL-12 family, IL-12 and IL-35. In contrast to IL-12p40(-/-) mice, the IL-12p35(-/-) mice developed liver inflammation and bile duct damage with similar severity but delayed onset as the parental dnTGFβRII mice. The p35(-/-) mice also demonstrated a distinct cytokine profile characterized by a shift from a T-helper 1 (Th1) to a Th17 response. Strikingly, liver fibrosis was frequently observed in IL-12p35(-/-) mice. In conclusion, IL-12p35(-/-) dnTGFβRII mice, histologically and immunologically, reflect key features of PBC, providing a useful generic model to understand the immunopathology of human PBC.

High expression of IL-17 and IL-17RE associate with poor prognosis of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a typical malignancy in a background of chronic inflammation. Th17 cells (a major source of IL-17) constitute crucial components of infiltrating inflammatory/immune cells in HCC and can amplify inflammatory response via binding to interleukin-17 receptor (IL-17R). Thus, we investigated the expression and clinical significance of IL-17 and IL-17 receptor family cytokines in HCC.

METHODS

The expression and prognostic value of IL-17 and IL-17R (A-E) were examined in 300 HCC patients after resection. Six Th17 associated cytokines in serum (n = 111) were quantified using enzyme-linked immunosorbent assays. Phenotypic features of IL-17+ CD4+ T cells were determined by flow cytometry analysis.

RESULTS

High expression of intratumoral IL-17 and IL1-7RE were significantly associated with poorer survival (p = 0.016 and <0.001, respectively) and increased recurrence (both P < 0.001) of HCC patients. Moreover, intratumoral IL-17, individually or synergistically with IL-17RE, could predict HCC early recurrence and late recurrence. Also, peritumoral IL-17RE showed the prognostic ability in HCC (P < 0.001 for OS/TTR). Furthermore, expression levels of Th17 associated cytokines including IL-6, -22, -17R and TNF-α were increased in serum of HCC patients compared to haemangioma patients. Importantly, activated human hepatic stellate cells induced in vitro expansion of IL-17+ CD4+ T cells.

CONCLUSIONS

High expression of IL-17 and IL-17RE were promising predictors for poor outcome of HCC patients. The protumor power of IL-17 producing CD4+ T cells was probably involved in the crosstalk with different types of inflammatory/immune cells in HCC.

Inhibition of inflammatory CD4 T cell activity by murine liver sinusoidal endothelial cells

BACKGROUND & AIMS

The liver can mitigate the inflammatory activity of infiltrating T cells by mechanisms that are not entirely clear. Here we investigated the role of liver sinusoidal endothelial cells (LSECs) in regulating the activity of inflammatory CD4 T cells.

METHODS

Interactions between T helper (Th) 1 or Th17 cells and LSEC were studied by intravital microscopy and by in vitro stimulation assays.

RESULTS

Circulating CD4 T cells established lasting and repeated interactions with liver endothelium in vivo. Stimulation of Th1 and Th17 cells by LSEC greatly inhibited their capacity to secrete interferon-γ or interleukin-17 in vitro; in contrast, stimulation by dendritic cells (DCs) resulted in considerable secretion of both cytokines. Cytokine release by Th1 or Th17 cells seemed to be actively suppressed by LSEC, as indicated by the inhibition of cytokine secretion even in the presence of Th1- and Th17-promoting DC. This inhibition of CD4 T cell effector function seemed to depend on the dominance of inhibitory over activating co-stimulatory signals on LSEC, since (1) cytokine secretion could be restored by increased CD28 co-activation; (2) LSEC from interleukin-10(-/-) mice, which manifest increased activating signals, such as MHC II, and decreased inhibitory signals, such as PD-L1, failed to suppress cytokine secretion; and (3) cytokine secretion by Th1 or Th17 cells that lacked PD-1, the ligand for inhibitory PD-L1, could not be suppressed by LSEC.

CONCLUSIONS

LSEC inhibit inflammatory cytokine secretion of Th1 and Th17 effector CD4 T cells in dependence of interleukin-10 and PD-1.

Increased Th17 cells and interleukin-17 contribute to immune activation and disease aggravation in patients with chronic hepatitis B virus infection

T helper17 (Th17) cells have been demonstrated to participate in the pathogenesis of hepatitis B virus (HBV) associated liver damage. However, the contribution of Th17 cells to immune activation and disease aggravation in patients with HBV infection is not fully clear. In this study, we investigated the Th17 cells frequencies and interleukin-17 (IL-17) mRNA expressions in peripheral blood mononuclear cells (PBMCs), intrahepatic IL-17-positive cells accumulation, as well as serum IL-17 levels in asymptomatic chronic HBV carriers (AsC), and patients with chronic hepatitis B (CHB) and HBV related acute-on-chronic liver failure (ACLF). Furthermore, the dynamic changes of Th17 cells frequencies and IL-17 concentration in different prognostic ACLF patients were observed. As result, the intrahepatic and peripheral Th17 cells and serum IL-17 concentration were both significantly higher in CHB and HBV related ACLF patients than that in AsC and normal control groups, and increased gradually with immune inflammation aggravation from AsC, CHB to ACLF. Moreover, in ACLF patients, peripheral Th17 cells frequencies were positively correlated with international normalized ratio (INR) and model of end-stage liver disease (MELD) score. Especially the survival patients had an initially lower Th17 cells frequencies and IL-17 levels which gradually decreased following condition improvement as compared with higher baseline level followed by gradually increasing trend in the non-survivals. In conclusion, Th17 cells can be contributed to the immune activation and disease aggravation in patients with chronic HBV infection. This may places Th17 cells as a potential blocking target for controlling CHB and ACLF.

Immunology in alcoholic liver disease

Hepatic fibrosis is a known consequence of long-term use of alcohol and is regarded as a turning point in alcohol-induced liver disease because it can lead to cirrhosis. The mechanisms of injury are not well understood, but recent studies have helped advance the understanding of the earliest events in the process that eventually leads to hepatic injury and, in some cases, fibrosis. It is hoped that increasing understanding of the role played by the immune system in the process will lead to the development of new therapies for these patients.

Interleukin-22 predicts severity and death in advanced liver cirrhosis: a prospective cohort study

BACKGROUND

Interleukin-22 (IL-22), recently identified as a crucial parameter of pathology in experimental liver damage, may determine survival in clinical end-stage liver disease. Systematic analysis of serum IL-22 in relation to morbidity and mortality of patients with advanced liver cirrhosis has not been performed so far.

METHODS

This is a prospective cohort study including 120 liver cirrhosis patients and 40 healthy donors to analyze systemic levels of IL-22 in relation to survival and hepatic complications.

RESULTS

A total of 71% of patients displayed liver cirrhosis-related complications at study inclusion. A total of 23% of the patients died during a mean follow-up of 196 ± 165 days. Systemic IL-22 was detectable in 74% of patients but only in 10% of healthy donors (P < 0.001). Elevated levels of IL-22 were associated with ascites (P = 0.006), hepatorenal syndrome (P < 0.0001), and spontaneous bacterial peritonitis (P = 0.001). Patients with elevated IL-22 (>18 pg/ml, n = 57) showed significantly reduced survival compared to patients with regular (≤18 pg/ml) levels of IL-22 (321 days versus 526 days, P = 0.003). Other factors associated with reduced overall survival were high CRP (≥2.9 mg/dl, P = 0.005, hazard ratio (HR) 0.314, confidence interval (CI) (0.141 to 0.702)), elevated serum creatinine (P = 0.05, HR 0.453, CI (0.203 to 1.012)), presence of liver-related complications (P = 0.028, HR 0.258, CI (0.077 to 0.862)), model of end stage liver disease (MELD) score ≥20 (P = 0.017, HR 0.364, CI (0.159 to 0.835)) and age (P = 0.011, HR 0.955, CI (0.922 to 0.989)). Adjusted multivariate Cox proportional-hazards analysis identified elevated systemic IL-22 levels as independent predictors of reduced survival (P = 0.007, HR 0.218, CI (0.072 to 0.662)).

CONCLUSIONS

In patients with liver cirrhosis, elevated systemic IL-22 levels are predictive for reduced survival independently from age, liver-related complications, CRP, creatinine and the MELD score. Thus, processes that lead to a rise in systemic interleukin-22 may be relevant for prognosis of advanced liver cirrhosis.