IL-6, IFN-gamma and TNF-alpha production by liver-associated T cells and acute liver injury in rats administered concanavalin A

Protective role of resveratrol against VCM-induced hepatotoxicity in male wistar rats

Background: Vancomycin is a glycopeptide antibiotic with a high risk of acute liver injury. Resveratrol is believed to protect the liver against toxicity. Aim: To investigate the ability of resveratrol to attenuate vancomycin-induced liver toxicity in rats injected with vancomycin. Method: Twenty-four adult male Wistar rats were distributed into three groups. The control group received only a vehicle, while the treated group received either vancomycin 200 (mg/kg, i. p.) only or vancomycin (200 mg/kg, i. p.) with resveratrol (20 mg/kg, oral gavage). All groups received their dose once daily for 7 days. Hepatic damage was assessed by measuring biochemical parameter levels in serum, aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). Also, antioxidants and inflammation biomarkers such as Interleukin-6 (IL-6), malondialdehyde (MDA), nitric oxide (NO), and glutathione (GSH) were measured. Furthermore, the vancomycin-induced pathological changes in the liver were evaluated by histopathological studies. Results: In the vancomycin-treated group, hepatic serum biomarkers such as AST, ALT, ALP, IL-6, and MDA were elevated, while NO and GSH were depleted. However, resveratrol co-treatment with vancomycin prevented the elevation of AST, ALT, ALP, IL-6, and MDA and it protected the liver from NO and GSH depletion. Also, regarding vancomycin-induced degeneration of hepatocytes, resveratrol co-treatment with vancomycin prevented such degeneration and improved mononuclear cells in the liver. Conclusion: The results showed that oral administration of resveratrol has a significant hepatoprotective effect against vancomycin-induced hepatotoxicity.

Bioluminescence imaging of mouse monocyte chemoattractant protein-1 expression in inflammatory processes

Monocyte chemoattractant protein-1 (MCP-1) plays a crucial role in various inflammatory diseases. To reveal the impact of MCP-1 during diseases and to develop anti-inflammatory agents, we establish a transgenic mouse line. The firefly luciferase gene is incorporated into the mouse genome and driven by the endogenous MCP-1 promoter. A bioluminescence photographing system is applied to monitor luciferase levels in live mice during inflammation, including lipopolysaccharide-induced sepsis, concanavalin A-induced T cell-dependent liver injury, CCl ₄-induced acute hepatitis, and liver fibrosis. The results demonstrate that the luciferase signal induced in inflammatory processes is correlated with endogenous MCP-1 expression in mice. Furthermore, the expressions of MCP-1 and the luciferase gene are dramatically inhibited by administration of the anti-inflammatory drug dexamethasone in a septicemia model. Our results suggest that the transgenic MCP-1-Luc mouse is a useful model to study MCP-1 expression in inflammation and disease and to evaluate the efficiency of anti-inflammatory drugs in vivo.

Pattern recognition receptor CD14 gene polymorphisms in alcohol use disorder patients and its Influence on liver disease susceptibility

Background

Alcohol use disorders (AUDs) leading to liver disease is major concern over other spectrum of disorder. Excessive alcohol consumption resulting in leaky gut syndrome is attributed to alcohol-induced liver injury through portal translocation of bacterial endotoxin. Susceptibility to alcoholic liver disease (ALD) in AUD patients could be dependent upon genes responsible for inflammation and alcohol metabolism. The pattern recognition receptor CD14 gene is a major player in endotoxin-mediated inflammation and susceptibility to ALD. This study investigated the genetic association of CD14 polymorphisms and other mechanisms relevant to altered inflammatory responses leading to ALD.

Methods

Patients with alcohol use disorder with ALD (n = 128) and without liver disease (ALC, n = 184) and controls without alcohol use disorder (NALC, n = 152) from North India were enrolled. The CD4 gene polymorphisms in the North Indian population were evaluated by RFLP and sequencing. Secretory CD14 (sCD14), LBP, TLR4, MD2, TNFα, IL1b, IFNγ, IL6, IL10, and IL4 levels in serum were measured by ELISA among groups. The influence of polymorphisms on CD14 gene promoter activity and circulatory bacterial DNA level was determined.

Results

The CD14 gene promoter and exonic region SNPs were found to be monomorphic, except for SNP rs2569190 for the North Indian population. The genetic association of SNP rs2569190(C/T) with the risk of developing ALD was found significant for TT genotype [OR_TT, 95% CI = 2.19, 1.16–4.13 for ALD vs. ALC and OR, 2.09, 1.18–3.72 for ALD vs. NALC]. An increased sCD14 level was observed in AUD patients compared to NALC control. Increased levels of LBP, TLR4, TNFα, IL1β, IFNγ, and IL6 and reduced levels of MD2, IL10, and IL4 were observed among the ALD patients compared to the other two control groups. Elevated levels of pro-inflammatory and reduced levels of anti-inflammatory cytokines were observed in the risk genotype TT groups of ALD patients and the ALC group compared to NALC. Promoter activity was observed in the intronic region flanking SNPs and risk genotype can influence reporter activity, indicating CD14 gene expression.

Conclusion

Enhanced CD14 expression associated with inflammatory responses increases susceptibility to ALD in the TT genotype of AUD patients.

Pharmacokinetic/Pharmacodynamic Assessment of Selective Phosphodiesterase Inhibitors in a Mouse Model of Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a life-threatening disorder currently treated with nonspecific immunosuppressive drugs. It is postulated that phosphodiesterase (PDE) inhibitors, as agents exerting anti-inflammatory and immunomodulatory activities, may constitute a possible treatment of autoimmune disorders. This study develops a pharmacokinetic/pharmacodynamic (PK/PD) model to assess the effects of PDE-selective inhibitors, namely, cilostazol (PDE3), rolipram (PDE4), and BRL-50481 (PDE7), in a mouse model of AIH. The pharmacokinetics of the PDE inhibitors (PDEi) were assessed in male BALB/c mice after intraperitoneal administration. In pharmacodynamic studies, mice received PDEi and AIH was induced in these animals by intravenous injection of concanavalin A (ConA). Serum drug concentrations, tumor necrosis factor α (TNFα), interleukin 17 (IL-17), and aminotransferase activities were quantified. The PK/PD analysis was performed using ADAPT5 software. The PK/PD model assumes inhibition of cAMP hydrolysis in T cells by PDEi, ConA-triggered formation of TNFα and IL-17, suppression of TNFα and IL-17 production by cAMP, and stimulatory effects of TNFα and IL-17 on the hepatic release of aminotransferases. Selective blockage of PDE4 leads to the highest inhibition of cAMP degradation in T cells and amelioration of disease outcomes. However, inhibition of both PDE3 and PDE7 also contribute to this effect. The proposed PK/PD model may be used to assess and predict the activities of novel PDEi and their combinations in ConA-induced hepatitis. A balanced suppression of different types of PDE appears to be a promising treatment option for AIH; however, this hypothesis warrants testing in humans based on translation of the PK/PD model into clinical settings. SIGNIFICANCE STATEMENT: A novel PK/PD model of PDE inhibitor effects in mice with ConA-induced autoimmune hepatitis was developed involving a mechanistic component describing changes in cAMP concentrations in mouse T cells. According to model predictions, inhibition of PDE4 in T cells causes the highest cAMP elevation in T cells, but suppression of PDE3 and PDE7 also contribute to this effect. A balanced inhibition of PDE3, PDE4, and PDE7 appears to be a promising treatment strategy for AIH.

PK/PD Modeling of the PDE7 Inhibitor-GRMS-55 in a Mouse Model of Autoimmune Hepatitis

This study aimed to assess the efficacy and explore the mechanisms of action of a potent phosphodiesterase (PDE)7A and a moderate PDE4B inhibitor GRMS-55 in a mouse model of autoimmune hepatitis (AIH). The concentrations of GRMS-55 and relevant biomarkers were measured in the serum of BALB/c mice with concanavalin A (ConA)-induced hepatitis administered with GRMS-55 at two dose levels. A semi-mechanistic PK/PD/disease progression model describing the time courses of measured biomarkers was developed. The emetogenicity as a potential side effect of the studied compound was evaluated in the α₂-adrenoceptor agonist-induced anesthesia model. The results indicate that liver damage observed in mice challenged with ConA was mainly mediated by TNF-α and IFN-γ. GRMS-55 decreased the levels of pro-inflammatory mediators and the transaminase activities in the serum of mice with AIH. The anti-inflammatory properties of GRMS-55, resulting mainly from PDE7A inhibition, led to a high hepatoprotective activity in mice with AIH, which was mediated by an inhibition of pro-inflammatory signaling. GRMS-55 did not induce the emetic-like behavior. The developed PK/PD/disease progression model may be used in future studies to assess the potency and explore the mechanisms of action of new investigational compounds for the treatment of AIH.

Toxicity of Gold Nanoparticles in Mice due to Nanoparticle/Drug Interaction Induces Acute Kidney Damage

Nanomaterials are innovative materials with many useful properties, but there is concern regarding their many unknown effects on living organisms. Gold nanoparticles are widely used as industrial materials because of their excellent properties. The potential biological hazards of gold nanoparticles are unknown, and thus, here we examined the in vivo effects of gold nanoparticles 10, 50, and 100 nm in diameter (GnP10, GnP50, and GnP100, respectively) and their interactions with drugs in mice to clarify their safety in mammals. Cisplatin, paraquat, and 5-aminosalicylic acid cause side-effect damage to the liver and kidney in mice. No hepatotoxicity or nephrotoxicity was observed when any of the gold nanoparticles alone were administered via the tail vein. In contrast, co-administration of GnP-10 with cisplatin, paraquat, or 5-aminosalicylic acid caused side-effect damage to the kidney. This suggests that gold nanoparticles with a particle size of 10 nm are potentially nephrotoxic due to their interaction with drugs.

Hepatic ILC2 activity is regulated by liver inflammation-induced cytokines and effector CD4+ T cells

In immune-mediated hepatitis, type 2 innate lymphoid cells (ILC2) as well as effector CD4⁺ T cells have been shown to drive disease pathology. However, less is known about mechanisms involved in the regulation of ILC2 function during liver inflammation. We showed that in homeostasis, hepatic ILC2 constituted a very small population with a naive, inactive phenotype. During immune-mediated hepatitis, the cytokines IL-33 and IFNγ were expressed in liver tissue. IL-33 induced strong activation and expression of type 2 cytokines as well as IL-6 by hepatic ILC2 while IFNγ suppressed cytokine production. Interestingly, this inhibitory effect was overcome by IL-33. The phenotype of activated hepatic ILC2 were stable since they did not show functional plasticity in response to liver inflammation-induced cytokines. Moreover, hepatic ILC2 induced a Th2 phenotype in activated CD4⁺ T cells, which increased ILC2-derived cytokine expression via IL-2. In contrast, Th1 cells inhibited survival of ILC2 by production of IFNγ. Thus, hepatic ILC2 function is regulated by IL-33, IL-2, and IFNγ. While IL-33 and IL-2 support hepatic ILC2 activation, their inflammatory activity in immune-mediated hepatitis might be limited by infiltrating IFNγ-expressing Th1 cells.

Iron chelation by deferasirox confers protection against concanavalin A-induced liver fibrosis: A mechanistic approach

Hepatic iron overload is one of the causative factors for chronic liver injury and fibrosis. The present study aimed to investigate the potential antifibrotic effect of the iron chelator; deferasirox (DFX) in experimentally-induced liver fibrosis in rats. Male Sprague-Dawley rats were administered concanavalin A (Con A) and/or DFX for 6 consecutive weeks. Con A injection induced significant hepatotoxicity as was evident by the elevated transaminases activity, and decreased albumin level. Also, it disturbed the iron homeostasis through increasing C/EBP homologous protein (CHOP), decreasing phosphorylated cAMP responsive element binding protein(P-CREB) and hepcidin levels leading to significant serum and hepatic iron overload. In addition, it induced an imbalance in the oxidative status of the liver via upregulating NADPH oxidase 4 (NOX4), together with a marked decrease in anti-oxidant enzymes' activities. As a consequence, upregulation of nuclear factor-kappa b (NF-κB) and the downstream inflammatory mediators was observed. Those events all together precipitated in initiation of liver fibrosis as confirmed by the elevation of alpha-smooth muscle actin (α-SMA) and liver collagen content. Co-treatment with DFX protected against experimentally-induced liver fibrosis in rats via its iron chelating, anti-oxidant, and anti-inflammatory properties. These findings imply that DFX can attenuate the progression of liver fibrosis.

Crosstalk between leukocytes triggers differential immune responses against Salmonella enterica serovars Typhi and Paratyphi

Enteric fevers, caused by the Salmonella enterica serovars Typhi (ST), Paratyphi A (PA) and Paratyphi B (PB), are life-threatening illnesses exhibiting very similar clinical symptoms but with distinct epidemiologies, geographical distributions and susceptibilities to antimicrobial treatment. Nevertheless, the mechanisms by which the host recognizes pathogens with high levels of homology, such as these bacterial serovars, remain poorly understood. Using a three-dimensional organotypic model of the human intestinal mucosa and PA, PB, and ST, we observed significant differences in the secretion patterns of pro-inflammatory cytokines and chemokines elicited by these serovars. These cytokines/chemokines were likely to be co-regulated and influenced the function of epithelial cells, such as the production of IL-8. We also found differing levels of polymorphonuclear leukocyte (PMN) migration among various infection conditions that either included or excluded lymphocytes and macrophages (Mϕ), strongly suggesting feedback mechanisms among these cells. Blocking experiments showed that IL-1β, IL-6, IL-8, TNF-α and CCL3 cytokines were involved in the differential regulation of migration patterns. We conclude that the crosstalk among the lymphocytes, Mϕ, PMN and epithelial cells is cytokine/chemokine-dependent and bacterial-serotype specific, and plays a pivotal role in orchestrating the functional efficiency of the innate cells and migratory characteristics of the leukocytes.

Premobilization of CD133+ cells by granulocyte colony- stimulating factor attenuates ischemic acute kidney injury induced by cardiopulmonary bypass

Ischemic acute kidney injury (IAKI) is a common but severe complication after a cardiopulmonary bypass (CPB). Multiple studies have demonstrated that peripheral CD133+ or differentiated cells are able to home and repair the damaged tissues, but the number of available CD133+ cells is limited, and no efficient method published previously to mobilize them immediately. We analyzed the relationship between CD133+ cells and renal function in CPB patients, in addition, the efficacy of granulocyte colony-stimulating factor (G-CSF) pre-mobilized CD133+ cells in treating of mouse IAKI model have been investigated. In the clinical study, the prospective cohort study analyzed the correlation between BUN/Crea level and the peripheral CD133+ cell numbers. CPB was associated with postoperative renal dysfunction. The significant negative correlation was observed between patients' Crea and CD133+ cells (P < 0.05). The proposed mechanism studies were performed on the mouse IAKI model. The experimental mice were treated by G-CSF to mobilize CD133+ cells before implementing CPB. Data on cell count, inflammatory index, renal function/injury, and CD133+ cell mobilization were analyzed. The result demonstrated that pretreatment by G-CSF resulted in tremendous increase in the number of mouse peripheral blood and renal CD133+ cells, significantly reduces renal tissue inflammation and dramatically improves the renal function after CPB. In summary, we concluded that premobilization of CD133+ cells abated CPB induced IAKI, by promoting both repairing damaged epithelium and by its anti-inflammatory activity. Our findings stress the remarkable applications of CD133+ or differentiated cells-based therapies for potential preventing ischemic acute kidney injury.

Decreased Taurine and Creatine in the Thalamus May Relate to Behavioral Impairments in Ethanol-Fed Mice: A Pilot Study of Proton Magnetic Resonance Spectroscopy

Minimal hepatic encephalopathy (MHE) is highly prevalent, observed in up to 80% of patients with liver dysfunction. Minimal hepatic encephalopathy is defined as hepatic encephalopathy with cognitive deficits and no grossly evident neurologic abnormalities. Clinical management may be delayed due to the lack of in vivo quantitative methods needed to reveal changes in brain neurobiochemical biomarkers. To gain insight into the development of alcoholic liver disease–induced neurological dysfunction (NDF), a mouse model of late-stage alcoholic liver fibrosis (LALF) was used to investigate changes in neurochemical levels in the thalamus and hippocampus that relate to behavioral changes. Proton magnetic resonance spectroscopy of the brain and behavioral testing were performed to determine neurochemical alterations and their relationships to behavioral changes in LALF. Glutamine levels were higher in both the thalamus and hippocampus of alcohol-treated mice than in controls. Thalamic levels of taurine and creatine were significantly diminished and strongly correlated with alcohol-induced behavioral changes. Chronic long-term alcohol consumption gives rise to advanced liver fibrosis, neurochemical changes in the nuclei, and behavioral changes which may be linked to NDF. Magnetic resonance spectroscopy represents a sensitive and noninvasive measurement of pathological alterations in the brain, which may provide insight into the pathogenesis underlying the development of MHE.

DEVELOPMENT AND VALIDATION OF QUANTITATIVE PCR ASSAYS TO MEASURE CYTOKINE TRANSCRIPT LEVELS IN THE FLORIDA MANATEE ( TRICHECHUS MANATUS LATIROSTRIS)

Cytokines have important roles in the mammalian response to viral and bacterial infections, trauma, and wound healing. Because of early cytokine production after physiologic stresses, the regulation of messenger RNA (mRNA) transcripts can be used to assess immunologic responses before changes in protein production. To detect and assess early immune changes in endangered Florida manatees ( Trichechus manatus latirostris), we developed and validated a panel of quantitative PCR assays to measure mRNA transcription levels for the cytokines interferon (IFN)-γ; interleukin (IL)-2, -6, and -10; tumor necrosis factor-α; and the housekeeping genes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-actin (reference genes). Assays were successfully validated using blood samples from free-ranging, apparently healthy manatees from the east and west coasts of central Florida, US. No cytokine or housekeeping gene transcription levels were significantly different among age classes or sexes. However, the transcription levels for GAPDH, IL-2, IL-6, and IFN-γ were significantly higher ( P<0.05) in manatees from the east coast of Florida than they were from those from the west coast. We found IL-10 and β-actin to be consistent between sites and identified β-actin as a good candidate for use as a reference gene in future studies. Our assays can aid in the investigation of manatee immune response to physical trauma and novel or ongoing environmental stressors.

Endogenous IL-33 Deficiency Exacerbates Liver Injury and Increases Hepatic Influx of Neutrophils in Acute Murine Viral Hepatitis

The alarmin IL-33 has been described to be upregulated in human and murine viral hepatitis. However, the role of endogenous IL-33 in viral hepatitis remains obscure. We aimed to decipher its function by infecting IL-33-deficient mice (IL-33 KO) and their wild-type (WT) littermates with pathogenic mouse hepatitis virus (L2-MHV3). The IL-33 KO mice were more sensitive to L2-MHV3 infection exhibiting higher levels of AST/ALT, higher tissue damage, significant weight loss, and earlier death. An increased depletion of B and T lymphocytes, NKT cells, dendritic cells, and macrophages was observed 48 h postinfection (PI) in IL-33 KO mice than that in WT mice. In contrast, a massive influx of neutrophils was observed in IL-33 KO mice at 48 h PI. A transcriptomic study of inflammatory and cell-signaling genes revealed the overexpression of IL-6, TNFα, and several chemokines involved in recruitment/activation of neutrophils (CXCL2, CXCL5, CCL2, and CCL6) at 72 h PI in IL-33 KO mice. However, the IFNγ was strongly induced in WT mice with less profound expression in IL-33 KO mice demonstrating that endogenous IL-33 regulated IFNγ expression during L2-MHV3 hepatitis. In conclusion, we demonstrated that endogenous IL-33 had multifaceted immunoregulatory effect during viral hepatitis via induction of IFNγ, survival effect on immune cells, and infiltration of neutrophils in the liver.

Idiosyncratic Drug-Induced Liver Injury: Is Drug-Cytokine Interaction the Linchpin?

Idiosyncratic drug-induced liver injury continues to be a human health problem in part because drugs that cause these reactions are not identified in current preclinical testing and because progress in prevention is hampered by incomplete knowledge of mechanisms that underlie these adverse responses. Several hypotheses involving adaptive immune responses, inflammatory stress, inability to adapt to stress, and multiple, concurrent factors have been proposed. Yet much remains unknown about how drugs interact with the liver to effect death of hepatocytes. Evidence supporting hypotheses implicating adaptive or innate immune responses in afflicted patients has begun to emerge and is bolstered by results obtained in experimental animal models and in vitro systems. A commonality in adaptive and innate immunity is the production of cytokines, including interferon-γ (IFNγ). IFNγ initiates cell signaling pathways that culminate in cell death or inhibition of proliferative repair. Tumor necrosis factor-α, another cytokine prominent in immune responses, can also promote cell death. Furthermore, tumor necrosis factor-α interacts with IFNγ, leading to enhanced cellular responses to each cytokine. In this short review, we propose that the interaction of drugs with these cytokines contributes to idiosyncratic drug-induced liver injury, and mechanisms by which this could occur are discussed.

IL-38 alleviates concanavalin A-induced liver injury in mice

Interleukin (IL)-38 is a poorly characterized cytokine of the IL-1 family with anti-inflammatory activity. The role of IL-38 in liver injury remains unknown. We have investigated the potential effect of hydrodynamic-based gene delivery to express human IL-38 in mice with concanavalin A (Con A)-induced liver injury. Transfer of plasmid DNA encoding IL-38 significantly reduced hepatic toxicity and serum levels of aspartate aminotransferase and alanine aminotransferase compared with administration of a control plasmid. Moreover, IL-38 expression dramatically reduced serum levels of several pro-inflammatory cytokines, such as tumor necrosis factor-α, interferon-γ, IL-6, IL-17, and IL-22, but not levels of the anti-inflammatory cytokine IL-10. These results suggest that in vivo expression of human IL-38 in mice has hepatoprotective effects against Con A-induced liver injury by inhibition of inflammatory cytokine production.

Endogenous n-3 Polyunsaturated Fatty Acids Attenuate T Cell-Mediated Hepatitis via Autophagy Activation

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) exert anti-inflammatory effects in several liver disorders, including cirrhosis, acute liver failure, and fatty liver disease. To date, little is known about their role in immune-mediated liver diseases. In this study, we used fat-1 transgenic mice rich in endogenous n-3 PUFAs to examine the role of n-3 PUFAs in immune-mediated liver injury. Concanavalin A (Con A) was administered intravenously to wild-type (WT) and fat-1 transgenic mice to induce T cell-mediated hepatitis. Reduced liver damage was shown in Con A-administrated fat-1 transgenic mice, as evidenced by decreased mortality, attenuated hepatic necrosis, lessened serum alanine aminotransferase activity, and inhibited production of pro-inflammatory cytokines (e.g., TNF-α, IL-6, IL-17A, and IFN-γ). In vivo and in vitro studies demonstrated that n-3 PUFAs significantly inhibited the activation of hepatic T cells and the differentiation of Th1 cells after Con A challenge. Further studies showed that n-3 PUFAs markedly increased autophagy level in Con A-treated fat-1 T cells compared with the WT counterparts. Blocking hepatic autophagy activity with chloroquine diminished the differences in T cell activation and liver injury between Con A-injected WT and fat-1 transgenic mice. We conclude that n-3 PUFAs limit Con A-induced hepatitis via an autophagy-dependent mechanism and could be exploited as a new therapeutic approach for autoimmune hepatitis.

Stephanthraniline A suppressed CD4(+) T cell-mediated immunological hepatitis through impairing PKCθ function

Stephanthraniline A (STA), a C21 steroid isolated from Stephanotis mucronata (Blanco) Merr., was previously shown to inhibit T cells activation and proliferation in vitro and in vivo. The purpose of this study was to further evaluate the in vivo immunosuppressive activity of STA and to elucidate its potential mechanisms. The results showed that pretreatment with STA significantly attenuated concanavalin A (Con A)-induced hepatitis and reduced CD4(+) T cells activation and aggregation in hepatic tissue in mice. STA directly suppressed the activation and proliferation of Con A-induced CD4(+) T cells, and inhibited NFAT, NFκB and MAPK signaling cascades in activated CD4(+) T cells in vitro. Moreover, it was proved that STA inhibited T cells activation and proliferation through proximal T cell-receptor (TCR) signaling- and Ca(2+) signaling-independent way. The molecular docking studies predicted that STA could tight bind to PKCθ via five hydrogen. The further findings indicated STA directly inhibited PKCθ kinase activity, and its phosphorylation in activated CD4(+) T cells in vitro. Collectively, the present study indicated that STA could protect against CD4(+) T cell-mediated immunological hepatitis in mice through PKCθ and its downstream NFAT, NFκB and MAPK signaling cascades. These results highlight the potential of STA as an effective leading compound for use in the treatment of CD4(+) T cell-mediated inflammatory and autoimmune diseases.

Alpha-lipoic acid protects mice against concanavalin A-induced hepatitis by modulating cytokine secretion and reducing reactive oxygen species generation

BACKGROUND

Alpha-lipoic acid (α-LA), which exits in almost all types of prokaryotic and eukaryotic cells, is a key regulator of energy metabolism in mitochondria. This study was designed to explore the protective effect of α-LA against concanavalin A (Con A)-induced hepatitis in mice and explore the potential mechanism.

METHODS

Acute autoimmune hepatitis was induced by intravenous (IV) injection of Con A (15mg/kg) in C57BL/6 mice. α-LA (100mg/kg) was administered four days before Con A injection. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and histopathological change of the liver tissue were measured. Serum cytokine TNF-α, IL-6, IFN-γ and IL-10 were detected by ELISA. The mRNA levels of these inflammatory cytokines in the liver were detected by RT-PCR. Malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD) and reduced/oxidized glutathione (GSH/GSSG) in liver were determined using commercial kits. Phosphorylated NF-κB p65, IκBα and phosphorylated MAPK were measured by Western blot.

RESULTS

Con A injection induced severe immune responses and extensive hepatocellular apoptosis within 12h. Pretreatment of α-LA markedly reduced the serum ALT and AST activity and the increase of plasma TNF-α, IL-6, IFN-γ and IL-10. In addition, α-LA pretreatment decreased the tissue MPO activity and lipid peroxidation, but increased SOD and GSH levels. α-LA inhibited the phosphorylation of NF-κB p65, IκBα and JNK.

CONCLUSION

Pretreatment of α-LA markedly attenuated Con A-induced hepatitis by modulating cytokine secretion and reducing reactive oxygen species generation.

Experimental models of hepatotoxicity related to acute liver failure

Acute liver failure can be the consequence of various etiologies, with most cases arising from drug-induced hepatotoxicity in Western countries. Despite advances in this field, the management of acute liver failure continues to be one of the most challenging problems in clinical medicine. The availability of adequate experimental models is of crucial importance to provide a better understanding of this condition and to allow identification of novel drug targets, testing the efficacy of new therapeutic interventions and acting as models for assessing mechanisms of toxicity. Experimental models of hepatotoxicity related to acute liver failure rely on surgical procedures, chemical exposure or viral infection. Each of these models has a number of strengths and weaknesses. This paper specifically reviews commonly used chemical in vivo and in vitro models of hepatotoxicity associated with acute liver failure.

Metabolomic analysis of arginine metabolism in acute hepatic injury in rats

To clarify the relationship between arginine metabolism and hepatic injury, metabolomic analysis was performed in rats treated with 3 representative hepatotoxicants, monocrotaline (MCT), concanavalin A (ConA), and α-naphthyl isothiocyanate (ANIT); or a myotoxicant, tetramethyl-p-phenylenediamine (TMPD). A single dose of MCT, ConA, or ANIT dose-dependently induced hepatocellular necrosis accompanied by decreased blood arginine and increased blood alanine aminotransferase (ALT) and arginase. A close correlation was detected between arginine and ALT (r = -0.746, -0.795, -0.787 for MCT, ConA, ANIT, respectively) or between arginine and arginase (r = -0.605, -0.808, -0.672 for MCT, ConA, ANIT, respectively) in all three hepatic injury models. In contrast, neither hepatocellular necrosis nor alterations in arginine were found in the skeletal muscle injury model, although ALT was slightly increased. An in vitro assay revealed that blood samples obtained from ConA-treated rats transformed external arginine to ornithine, and the reaction was totally inhibited by an arginase inhibitor. These results suggest that blood arginase plays a crucial role in arginine metabolism associated with hepatic injury. In metabolomic analysis, nearly 450 endogenous metabolites were identified in blood obtained from all the models. Among the 13 metabolites involved in arginine metabolism, decreased arginine and increased ornithine occurred in common in the hepatic injury models, whereas citrulline and other metabolites were not altered. These results indicate that arginine metabolism, especially the arginine-to-ornithine pathway, is altered in association with acute hepatic injury. Furthermore, blood arginine and ornithine are possibly specific biomarkers for hepatic injury.

Coinhibitory receptor PD-1H preferentially suppresses CD4⁺ T cell-mediated immunity

T cell activation is regulated by the interactions of surface receptors with stimulatory and inhibitory ligands. Programmed death-1 homolog (PD-1H, also called VISTA) is a member of the CD28 family of proteins and has been shown to act as a coinhibitory ligand on APCs that suppress T cell responses. Here, we determined that PD-1H functions as a coinhibitory receptor for CD4⁺ T cells. CD4⁺ T cells in mice lacking PD-1H exhibited a dramatically increased response to antigen stimulation. Furthermore, delivery of a PD-1H-specific agonist mAb directly inhibited CD4⁺ T cell activation both in vitro and in vivo, validating a coinhibitory function of PD-1H. In a murine model of acute hepatitis, administration of a PD-1H agonist mAb suppressed CD4⁺ T cell-mediated acute inflammation. PD-1H-deficient animals were highly resistant to tumor induction in a murine brain glioma model, and depletion of CD4⁺ T cells, but not CD8⁺ T cells, promoted tumor formation. Together, our findings suggest that PD-1H has potential as a target of immune modulation in the treatment of human inflammation and malignancies.

IFN-γ deficiency attenuates hepatic inflammation and fibrosis in a steatohepatitis model induced by a methionine- and choline-deficient high-fat diet

Cytokines play important roles in all stages of steatohepatitis, including hepatocyte injury, the inflammatory response, and the altered function of sinusoidal cells. This study examined the involvement of a major inflammatory cytokine, interferon-γ (IFN-γ), in the progression of steatohepatitis. In a steatohepatitis model by feeding a methionine- and choline-deficient high-fat (MCDHF) diet to both wild-type and IFN-γ-deficient mice, the liver histology, expression of genes encoding inflammatory cytokines, and fibrosis-related markers were examined. To analyze the effects of IFN-γ on Kupffer cells in vitro, we examined the tumor necrosis factor-α (TNF-α) production by a mouse macrophage cell line. Forty two days of MCDHF diet resulted in weight loss, elevated aminotransferases, liver steatosis, and inflammation in wild-type mice. However, the IFN-γ-deficient mice exhibited less extensive changes. RT-PCR revealed that the expression of tumor necrosis factor-α (TNF-α), transforming growth factor-β, inducible nitric oxide synthase, interleukin-4 and osteopontin were increased in wild-type mice, although they were suppressed in IFN-γ-deficient mice. Seventy days of MCDHF diet induced much more liver fibrosis in wild-type mice than in IFN-γ-deficient mice. The expression levels of fibrosis-related genes, α-smooth muscle actin, type I collagen, tissue inhibitor of matrix metalloproteinase-1, and matrix metalloproteinase-2, were dramatically increased in wild-type mice, whereas they were significantly suppressed in IFN-γ-deficient mice. Moreover, in vitro experiments showed that, when RAW 264.7 macrophages were treated with IFN-γ, they produced TNF-α in a dose-dependent manner. The present study showed that IFN-γ deficiency might inhibit the inflammatory response of macrophages cells and subsequently suppress stellate cell activation and liver fibrosis. These findings highlight the critical role of IFN-γ in the progression of steatohepatitis.

Tupistra chinensis extract attenuates murine fulminant hepatitis with multiple targets against activated T lymphocytes

OBJECTIVES

The extract of Tupistra chinensis (TCE) is traditionally used for the treatment of inflammatory diseases in southwestern China for hundreds of years. The present study was designed to investigate the effects of the TCE against experimental hepatitis and to illustrate its potential mechanisms.

METHODS

Effects of TCE were investigated on Con A-induced hepatitis. Profiles of multiple cytokines were measured with biometric immuno-sandwich ELISA. Proliferation, activation and apoptosis of T lymphocytes were evaluated using Western blot, MTT analysis and flow cytometry.

KEY FINDINGS

TCE significantly inhibited levels of serum transaminases and lactic dehydrogenase in mice with Con A-induced hepatitis, accompanied with marked alleviation of the liver microscopic appearances. Moreover, it decreased levels of inflammatory cytokines in a concentration-dependent manner both in vivo and in vitro. It also suppressed mitogen-activated protein kinases and NF-κB-signalling in liver. These effects of TCE are attributed to its inhibition on activated T cells but not to hepatocytes protection. Flow cytometry and immunoblot assay data showed its effects on STAT1/NF-κB-signalling blockage and apoptosis induction in activated T cells.

CONCLUSION

Our findings illustrate the significant potential of TCE as a novel approach for treatment of T cell-mediated inflammatory diseases.

Pretreatment with lipopolysaccharide ameliorates Pseudomonas exotoxin A-induced hepatotoxicity in rats

CONTEXT

Liver injury can be induced by various hepatotoxicants, including Pseudomonas aeruginosa exotoxin A (PEA). Our previous study indicated that PEA-induced rat hepatotoxicity was T cells and Kupffer cells dependent. Several reports have demonstrated that non-toxic doses of bacterial lipopolysaccharide (LPS) can protect liver against the chemicals-induced toxicity such as acetaminophen and concanavalin-A.

OBJECTIVE

This study aimed to investigate the protecting mechanisms of LPS on PEA-induced hepatotoxicity.

RESULTS

Rats pretreated with LPS (40 μg/kg, 12 h before PEA admission) significantly decreased animal mortality, serum enzyme (ALT, AST and T-bil) activities, histopathological changes and hepatocytes apoptosis following challenge with PEA. The concentrations of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ) and interleukin-2 (IL-2) were reduced, but IL-6 and IL-10 were increased in the serum. In addition, prior treatment of these LPS-pretreated rats with gadolinium chloride (GdCl3), a selective Kupffer cell depletion agent, markedly enhanced liver injury after PEA administration. In contrast, the pretreatment of LPS to T-cell deficient athymic nude rats still display significant attenuation of PEA-induced liver injury. This observation further confirmed our hypothesis that LPS ameliorate PEA-hepatotoxicity was through Kupffer cells but not T cells. Moreover, LPS-induced hepatoprotection ability was neutralized by co-treatment with anti-TNF-α antibodies, but not with anti-IFN-γ antibodies. Finally, replacement of LPS with RS-LPS (Rhodobacter sphaeroides LPS), a Toll like receptor-4 (TLR-4) antagonist, resulted in severe hepatotoxicity.

CONCLUSION

These results suggested that Kupffer cells, TNF-α and TLR-4 play central mediator roles during the hepatoprotection against PEA-induced hepatotoxicity conferred by LPS.

Protective role of IL-33/ST2 axis in Con A-induced hepatitis

BACKGROUND & AIMS

We used Concanavalin A-induced liver injury to study the role of Interleukin 33 and its receptor ST2 in the induction of inflammatory pathology and hepatocellular damage.

METHODS

We tested susceptibility to Concanavalin A induced hepatitis in ST2 deficient and wild type BALB/c mice and analyzed the effects of single injection of Interleukin 33 as evaluated by liver enzyme test, quantitative histology, mononuclear cell infiltration, cytokine production, intracellular staining of immune cells, and markers of apoptosis in the liver.

RESULTS

ST2 deficient mice developed significantly more severe hepatitis and had significantly higher number of mononuclear cells in the liver, CD4+ and CD8+ T cells, NKp46+ and CD3+NKp46+ cells, and F4/80+ macrophages. The level of pro-inflammatory cytokines in the sera and number of TNF alpha, IFN gamma, and IL-17 producing cells was higher in ST2 deficient mice. In contrast, number of CD4+Foxp3+ cells was statistically higher in wild type mice. Additionally, treatment of wild type mice with single (1 μg) injection of Interleukin 33 led to attenuation of the liver injury and milder infiltration of mononuclear cells, increase in total number of liver CD4+Foxp3+ cells and IL-4 producing CD4+ T cells. Interleukin 33 also suppressed the activation of caspase 3, prevented the expression of BAX, and enhanced the expression of antiapoptotic Bcl-2 in the liver.

CONCLUSIONS

We concluded that Interleukin 33/ST2 axis downregulated Concanavalin A-induced liver injury and should be evaluated as potential target in fulminant hepatitis in humans.

Activation of farnesoid X receptor attenuates liver injury in systemic lupus erythematosus

To investigate the expression and effect of farnesoid X receptor (FXR) on systemic lupus erythematosus (SLE) liver dysfunction and indicate its hepatoprotective role and the immunomodulatory property. mRNA and protein levels of FXR were determined on the liver specimens of SLE patients with liver injury as well as MRL/lpr rodent models. The FXR agonist chenodeoxycholic acid (CDCA) was administrated to MRL/lpr mice and the control BALB/C with concanavalin A (ConA)-induced liver injury. Blood samples were taken 0, 4, 8, 12, 16, and 24 h after ConA injection for the detection of serum ALT, AST, IFN-γ, TNF-α, and IL-6. FXR was down-regulated at both mRNA and protein levels in the liver specimens of SLE patients with liver injury as well as MRL/lpr mice. MRL/lpr was more susceptible to ConA than BALB/C indicated by significantly higher levels of aminotransferase and inflammatory cytokines. Activation of FXR by CDCA significantly reduced aminotransferase and inflammatory cytokines IFN-γ, TNF-α, and IL-6 caused by ConA injection in MRL/lpr mice. FXR was down-regulated in SLE patients as well as MRL/lpr lupus models with liver dysfunction. FXR activation ameliorated liver injury and suppressed inflammatory cytokines, thereby showing its protective function in SLE. Our findings raised the promising potential target for the treatment of SLE liver injury.

Decreased IgA+ plasma cells and IgA expression in acute liver necrosis mice

AIM: To investigate the number of intestinal immunoglobulin A (IgA+) plasma cells and expression of intestinal IgA in mice with acute liver necrosis.

METHODS: A model of acute liver necrosis was established by intraperitoneal injection of galactosamine (GalN) and lipopolysaccharide (LPS). Sixty mice were randomly divided into one of 4 equal groups: normal control, acute liver necrosis, LPS, or GalN. Hematoxylin and eosin staining, immunohistochemistry, and an enzyme-linked immunosorbent assay were employed to assess liver and intestinal injury, count intestinal IgA+ plasma cells, and measure the expression level of IgA and interferon γ (IFN-γ) in the small intestinal mucosa of mice.

RESULTS: Injured intestinal mucosa was observed in the acute liver necrosis group but not in the normal, LPS or GalN groups. Compared with the normal group, intestinal IgA+ plasma cells were slightly decreased in the LPS and GalN groups [429 ± 20 per high power field (HPF), 406 ± 18/HPF, respectively], whereas they were markedly decreased in the acute liver necrosis group (282 ± 17/HPF vs 495 ± 26/HPF in normal group, P < 0.05). The expression of intestinal IgA was also slightly decreased in LPS and GalN groups, but was markedly reduced in the acute liver necrosis group as determined by enzyme-linked immunosorbent assay (P < 0.05). In contrast, the level of IFN-γ was slightly increased in LPS, GalN and acute liver necrosis groups, but with no statistical significance (P > 0.05).

CONCLUSION: Intestinal IgA+ plasma cells and IgA expression levels indicating that mucosal immune barrier dysfunction, does exist in acute liver necrosis.

Hepatoprotective effect of syringic acid and vanillic acid on concanavalin a-induced liver injury

The edible mushroom Lentinula edodes (shiitake) contains many bioactive compounds. In the present study, we cultivated L. edodes mycelia in solid medium and examined the hot-water extract (L.E.M.) for its suppressive effect on concanavalin A (ConA)-induced liver injury in mice. ConA injection into the tail vein caused a great increase in the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. The intraperitoneal administration of L.E.M. significantly decreased the levels of the transaminases. L.E.M. contains many bioactive substances, including polysaccharides and glucan, which could be immunomodulators. Since ConA-induced liver injury is caused by the activation of T cells, immunomodulating substances might be responsible for the suppressive effect of L.E.M. L.E.M. also contains phenolic compounds that are produced from lignocellulose by mycelia-derived enzymes. The major phenolics in L.E.M., syringic acid and vanillic acid, were intraperitoneally injected into mice shortly before the ConA treatment. Similar to L.E.M., the administration of syringic acid or vanillic acid significantly decreased the transaminase activity and suppressed the disorganization of the hepatic sinusoids. In addition, the inflammatory cytokines tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and interleukin (IL)-6 in the serum increased rapidly, within 3 h of the ConA administration, but the administration of syringic acid or vanillic acid significantly suppressed the cytokine levels. Together, these findings indicate that the phenolic compounds in L.E.M. are hepatoprotective through their suppression of immune-mediated liver inflammation.

Depletion of LAG-3 positive cells in cardiac allograft reveals their role in rejection and tolerance

BACKGROUND

Lymphocyte-activated gene-3 (LAG-3, CD223) is upregulated during the early stages of T-cell activation and could be the target of cytotoxic antibodies for induction therapy in transplantation.

METHODS

Fully vascularized heterotopic allogeneic heart transplantation was performed in rats across a full major histocompatibility complex-mismatch barrier (LEW.1W into LEW.1A). Recipients received two injections (day 0 and 3) of cytotoxic antibodies directed to the extra-loop of LAG-3 immunoglobulin (Ig)-like N-terminal domain or control antibodies.

RESULTS

LAG-3 mRNA transcripts accumulated in cardiac allografts undergoing rejection, but not in peripheral lymphoid organs. Administration of anti-LAG-3 antibodies on the day of transplantation did not modify alloreactivity of T lymphocytes from the spleen and did not change the alloantibody response. However, it inhibited graft infiltration by effector mononuclear cells, reduced intragraft levels of interferon-gamma mRNA and prolonged allograft survival from 6 days in controls to a median of 27 days. Anti-LAG-3 antibodies were also active in prolonging survival when administered in a delayed manner, after rejection onset. LAG-3 being also expressed by activated regulatory T (Treg) cells, we tested the effect of anti-LAG-3 antibodies on graft acceptance after donor blood transfusions, a Treg-dependent tolerance induction model. We found that tolerance induction was prevented by anti-LAG-3 antibodies.

CONCLUSIONS

Targeting LAG-3-positive cells with cytotoxic antibodies is immunosuppressive in transplantation by depleting effectors T cells and therefore may represent a treatment for rejection episodes focused only on pathogenic cells. However, it might not be compatible with tolerance-induction strategies.

c-Maf interacts with c-Myb to down-regulate Bcl-2 expression and increase apoptosis in peripheral CD4 cells

The transcription factor c-Maf is critical for IL-4 production and the development of Th2 cells, which promote humoral immunity and protect against extracellular parasites. Yet, little else is known of c-Maf function in CD4 cells. Here, we identify a novel role for c-Maf in regulating susceptibility to apoptosis. Overexpression of c-Maf results in increased susceptibility of CD4 cells to apoptosis induced by multiple stimuli, including growth factor withdrawal, dexamethasone, irradiation, and TCR engagement. This effect is independent of Fas or p53; however, Bcl-2 expression is reduced in c-Maf Tg CD4 cells. Immunoprecipitation and Western blot analyses demonstrate that c-Maf-c-Myb complex formation is enhanced among T cells from c-Maf Tg mice compared to non-Tg littermates following TCR engagement. Unlike non-Tg T cells, c-Myb binding to the Bcl-2 promoter is not detectable in c-Maf Tg T cells by chromatin immunoprecipitation. In reporter assays, Bcl-2 promoter activity is reduced by c-Maf in a dose-dependent manner. Furthermore, transgene-mediated Bcl-2 expression corrects the apoptosis defect observed among c-Maf Tg CD4 cells. These data suggest that c-Maf can interact with c-Myb to reduce Bcl-2 expression, thereby limiting CD4 cell survival following TCR engagement.

Baicalin protects mouse from Concanavalin A-induced liver injury through inhibition of cytokine production and hepatocyte apoptosis

BACKGROUND

Baicalin (BA) exhibits an anti-inflammatory effect in vivo and in vitro and is used to treat chronic hepatitis. However, the mechanism by which BA exerts the liver-protective effect remains largely unknown.

AIMS

The present study reports that BA inhibits cytokine production and hepatocyte apoptosis to protect mice from liver injury induced by concanavalin A (Con A), a T-cell-dependent liver injury model.

RESULTS

Con A injection of mice induced severe immune responses and extensive hepatocellular apoptosis within 24 h. Pretreatment of 200 or 100 mg/kg BA markedly reduced serum aminotransferase activities, protected hepatoycte apoptosis and reduced the increase of plasma cytokine levels, including tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and interleukin-6 (IL-6). Furthermore, BA pretreatment decreased tissue myeloperoxidase activity and lipid peroxidation, but increased the superoxide dismutase level. In vitro studies indicated that the beneficial effect of BA was associated with reduced cytokine production from lymphocytes and reduced TNF-alpha-induced hepatocyte apoptosis.

CONCLUSION

These results suggest that BA has therapeutic potential for T-cell-mediated liver injury.

IL-10, regulatory T cells, and Kupffer cells mediate tolerance in concanavalin A-induced liver injury in mice

The liver appears to play an important role in immunological tolerance, for example, during allo-transplantation. We investigated tolerance mechanisms in the model of concanavalin A (ConA)-induced immune-mediated liver injury in mice. We found that a single injection of a sublethal ConA dose to C57BL/6 mice induced tolerance toward ConA-induced liver damage within 8 days. This tolerogenic state was characterized by suppression of the typical Th1 response in this model and increased IL-10 production. Tolerance induction was fully reversible in IL-10 -/- mice and after blockade of IL-10 responses by anti-IL10R antibody. Co-cultures of CD4+CD25+ regulatory T cells (T(reg)s) and CD4+CD25- responder cells revealed T(reg) from ConA-tolerant mice being more effective in suppressing polyclonal T cell responses than T(reg) from control mice. Moreover, T(reg) from tolerant but not from control mice were able to augment in vitro IL-10 expression. Depletion by anti-CD25 monoclonal antibody (MAb) indicated a functional role of T(reg)s in ConA tolerance in vivo. Cell depletion studies revealed T(reg)S and Kupffer cells (KC) to be crucial for IL-10 expression in ConA tolerance. Studies with CD1d -/- mice lacking natural killer T (NKT) cells disclosed these cells as irrelevant for the tolerogenic effect. Finally, cellular immune therapy with CD4+CD25+ cells prevented ConA-induced liver injury, with higher protection by Treg from ConA-tolerized mice.

CONCLUSION

The immunosuppressive cytokine IL-10 is crucial for tolerance induction in ConA hepatitis and is mainly expressed by CD4+CD25+ T(reg) and KC. Moreover, T(reg)s exhibit therapeutic potential against immune-mediated liver injury.

A selective adenosine A2A receptor agonist, ATL-146e, prevents concanavalin A-induced acute liver injury in mice

BACKGROUND AND AIMS

Concanavalin A (Con A) activates T lymphocytes and induces CD4+ T cell-mediated hepatic injury in mice. Pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and interleukin-6 (IL-6), are critical mediators in this experimental model. Activation of adenosine A2A receptors reduces the production of various pro-inflammatory cytokines and suppresses T cell activation. A selective adenosine A2A receptor agonist (ATL-146e) has been shown to be a potent inhibitor of inflammation by increasing intracellular cyclic AMP (cAMP) in leukocytes. The aim of the present study was to determine whether ATL-146e could ameliorate Con A-induced hepatic injury, reduction of pro-inflammatory cytokine production.

METHODS

Balb/c mice were injected with 25mg/kg Con A with or without a single injection of ATL-146e (0.5-50 microg/kg), 5 min prior to Con A administration. Liver enzymes, histology, and serum levels of tumor necrosis factor-alpha, interferon-gamma, and interleukin-6 were examined. We also assessed the effects of ATL-146e on pro-inflammatory cytokine production with CD4+ T cell.

RESULTS

Pretreatment with ATL-146e significantly reduced serum levels of liver enzymes (P<0.001). The serum pro-inflammatory cytokines were all increased after Con A administration and reduced to near normal levels by ATL-146e. ATL-146e also inhibited CD4+ T cell pro-inflammatory cytokine production.

CONCLUSION

A selective adenosine A2A receptor agonist, ATL-146e, can prevent concanavalin A-induced hepatic injury that is presumably mediated by its anti-inflammatory properties.

A Regulatory Effect of the Balance between TNF-α and IL-6 in the Granulomatous and Inflammatory Response toRhodococcus aurantiacusInfection in Mice

After i.v. inoculation with Rhodococcus aurantiacus, wild-type (WT) mice develop nonnecrotic, epithelioid granulomas. Because a high level of TNF-alpha is observed during the initial phase postinfection, we examined the extent to which TNF-alpha contributes to granulomatous inflammation using TNF-alpha gene-deficient (TNF-alpha(-/-)) mice. Despite a lack of R. aurantiacus proliferation, TNF-alpha(-/-) mice displayed high mortality rates within 5 days postinfection, as well as a high level of IL-6 in their spleens. Histological examination showed an absence of granuloma formation in TNF-alpha(-/-) mice. Pretreatment of TNF-alpha(-/-) mice with rTNF-alpha failed to restore this granuloma formation but accelerated bacterial removal and cellular recruitment. This rTNF-alpha administration also attenuated IL-6 production, resulting in increased survival rates of TNF-alpha(-/-) mice. Heat-killed R. aurantiacus induced in vitro enhanced mRNA expression and production of IL-6 in macrophages and DCs from TNF-alpha(-/-) mice when compared with WT controls, and treatment of TNF-alpha(-/-) mouse cells with rTNF-alpha decreased the IL-6 secretion. Moreover, anti-TNF-alpha or anti-IL-6 treatment increased IL-6 or TNF-alpha production by WT mouse cells, respectively. These data suggest that the production of TNF-alpha and IL-6 can be negatively regulated by each other. Administration of rIFN-gamma to TNF-alpha(-/-) mice caused immature granulomas in livers, and treatment with both rTNF-alpha and rIFN-gamma led to the formation of mature granulomas. Overall, TNF-alpha appears crucial for bacterial clearance, cellular recruitment, and granuloma formation. The balance between TNF-alpha and IL-6 during the early phase of infection controls the development of the inflammatory response to R. aurantiacus infection.

Preventive effects of (5R)-5-hydroxytriptolide on concanavalin A-induced hepatitis

(5R)-5-hydroxytriptolide (LLDT-8) exhibits strong immunosuppressive activities in vitro and in vivo. Here, we investigated the effects of LLDT-8 on concanavalin A-induced hepatitis. Liver damage was evaluated by serum alanine transaminase (ALT) level and liver histology. The effects of LLDT-8 were determined by measurement of serum cytokines, lymphocyte proliferation assay, flow cytometry analysis of splenic T cell percentage and apoptosis, reverse-transcription polymerase chain reaction (RT-PCR) analysis for gene transcriptions. In LLDT-8-treated mice, serum ALT level and histological damage were markedly attenuated. The beneficial effect of LLDT-8 was closely associated with (i) reduction of serum tumor necrosis factor-alpha, interferon-gamma (IFN-gamma), interleukin-2, interleukin-12, and interleukin-6 levels; (ii) elimination of activated T cells by increasing proapoptotic genes signal transducer and activator of transcription 1 (STAT1) and interferon regulatory factor-1 (IRF-1) expression in spleens; (iii) blockade of mRNA expressions for chemokines (monokine induced by IFN-gamma, Mig; IFN-gamma-inducible protein-10, IP-10; IFN-inducible T cell-alpha chemoattractant, I-TAC), vascular adhesion molecule-1 (VCAM-1), and chemokine receptors (C-C chemokine receptor 1, CCR1; C-C chemokine receptor 5, CCR5; C-X-C chemokine receptor 3, CXCR3) in livers. These results suggested the therapeutic potential of LLDT-8 in IFN-gamma/STAT1/IRF-1 signaling- and inflammatory cytokines-mediated immune disorders.

Induction of thymocyte apoptosis by systemic administration of concanavalin A in mice: role of TNF-alpha, IFN-gamma and glucocorticoids

Administration of concanavalin A (Con A) is a well-established model of acute immune-mediated hepatitis. Here, we demonstrate that intravenous injection of Con A in mice induces profound thymic atrophy. Compared to liver damage, the kinetics of Con A-induced thymic atrophy is slower and more prolonged; the nadir in thymocyte number is reached 4 days after Con A injection, whereas peak transaminase levels are observed at 12-24 h. Marked alterations in the ratio of CD4+ and CD8+cells in the thymus and spleen and significantly increased rates of thymocyte and splenocyte apoptosis are observed. Neutralization of the cytokines TNF-alpha or IFN-gamma, which protects mice from Con A-induced hepatitis, prevents thymic atrophy as well as alterations in CD4+ and CD8+ cell numbers and apoptosis rates. However, neither TNF-alpha nor IFN-gamma are detectable in thymocyte lysates after Con A injection, whereas both cytokines are present in liver, spleen and serum. Administration of the glucocorticoid receptor antagonist mifepristone does not prevent thymic atrophy, thus ruling out a possible contribution of endogenous glucocorticoids. Con A-induced thymic atrophy is accompanied by down-regulation of Bcl-2 expression in the thymus, which is prevented by neutralization of TNF-alpha or IFN-gamma. These data demonstrate that the thymus is a critical target organ of Con A-induced inflammation; the effects of Con A on the thymus are mediated by extrathymic production of TNF-alpha and IFN-gamma, but not by glucocorticoids.

The IL-6–gp130–STAT3 pathway in hepatocytes triggers liver protection in T cell–mediated liver injury

Increasing evidence demonstrates that IL-6 has a protective role during liver injury. IL-6 activates intracellular pathways via the gp130 receptor. In order to identify IL-6-gp130 pathways involved in mediating liver protection, we analyzed hepatocyte-specific gp130 knockout mice in a concanavalin A-induced (Con A-induced) model of immune-mediated hepatitis. We demonstrated that IL-6-gp130-dependent pathways in hepatocytes alone are sufficient for triggering protection in Con A-induced hepatitis. gp130-STAT3 signaling in hepatocytes mediates the IL-6-triggered protective effect. This was demonstrated by analysis of IL-6-induced protection in mice selectively deficient for gp130-dependent STAT1/3 or gp130-SHP2-RAS signaling in hepatocytes. To identify IL-6-gp130-STAT1/3 dependently expressed liver-protective factors, we performed gene array analysis of hepatic gene expression in hepatocyte-specific gp130(-/-) mice as well as in gp130-STAT1/3- and gp130-SHP2-RAS-MAPK-deficient mice. The mouse IL-8 ortholog KC (also known as Gro-alpha) and serum amyloid A2 (SAA2) was identified as differentially IL-6-gp130-STAT3-regulated genes. Hepatic expression of KC and SAA2 mediate the liver-protective potential of IL-6, since treatment with recombinant KC or serum SAA2 effectively reduced liver injury during Con A-induced hepatitis. In summary, this study defines IL-6-gp130-STAT3-dependent gene expression in hepatocytes that mediates IL-6-triggered protection in immune-mediated Con A-induced hepatitis. Additionally, we identified the IL-6-gp130-STAT3-dependent proteins KC and SAA2 as new candidates for therapeutic targets in liver diseases.

The IL-6-gp130-STAT3 pathway in hepatocytes triggers liver protection in T cell-mediated liver injury

Increasing evidence demonstrates that IL-6 has a protective role during liver injury. IL-6 activates intracellular pathways via the gp130 receptor. In order to identify IL-6-gp130 pathways involved in mediating liver protection, we analyzed hepatocyte-specific gp130 knockout mice in a concanavalin A-induced (Con A-induced) model of immune-mediated hepatitis. We demonstrated that IL-6-gp130-dependent pathways in hepatocytes alone are sufficient for triggering protection in Con A-induced hepatitis. gp130-STAT3 signaling in hepatocytes mediates the IL-6-triggered protective effect. This was demonstrated by analysis of IL-6-induced protection in mice selectively deficient for gp130-dependent STAT1/3 or gp130-SHP2-RAS signaling in hepatocytes. To identify IL-6-gp130-STAT1/3 dependently expressed liver-protective factors, we performed gene array analysis of hepatic gene expression in hepatocyte-specific gp130(-/-) mice as well as in gp130-STAT1/3- and gp130-SHP2-RAS-MAPK-deficient mice. The mouse IL-8 ortholog KC (also known as Gro-alpha) and serum amyloid A2 (SAA2) was identified as differentially IL-6-gp130-STAT3-regulated genes. Hepatic expression of KC and SAA2 mediate the liver-protective potential of IL-6, since treatment with recombinant KC or serum SAA2 effectively reduced liver injury during Con A-induced hepatitis. In summary, this study defines IL-6-gp130-STAT3-dependent gene expression in hepatocytes that mediates IL-6-triggered protection in immune-mediated Con A-induced hepatitis. Additionally, we identified the IL-6-gp130-STAT3-dependent proteins KC and SAA2 as new candidates for therapeutic targets in liver diseases.

Effect of 2-amino-2-[2-(4-octylphenyl) ethyl] propane-1,3-diol hydrochloride (FTY 720) on immune liver injury in mice

AIM: To investigate the protective effect against two immune liver injury models in mice by 2-amino-2-[2-(4-octylphenyl) ethyl] propane-1,3-diol hydrochloride and its possible mechanisms in Con A-induced liver damage.

METHODS: Liver tissue or hepatocyte injury was monitored biochemically by measuring alanine aminotransferase (sALT) and aspartate aminotransferase (sAST) activity. Hematoxylin & eosin (HE) staining was used for histopathological examination. To evaluate the role of IFN-γ and IL-4 in the liver injury, serum levels of IFN-γ and IL-4 were determined using commercially available ELISA kit at 12 h after Con A challenge. We also determined FTY 720-induced spleen cell apoptosis by flow cytometry analysis or spleen cell proliferation test.

RESULTS: Different doses of FTY 720 treatment dramatically reduced circulating markers of hepatocyte injury in two kinds of immunological liver injury models. FTY 720 dramatically reduced the elevated serum IFN-γ and IL-4 levels after Con A injection. Effect of spleen cell supernatants treated with Con A or FTY 720 on hepatocytes showed that ALT activities in cultured hepatocyte supernatants in Con A treatment group increased markedly and FTY 720 could reduce this elevated ALT activities in FTY 720 treatment group. FTY 720 dose-dependently increased the percentage of apoptotic cells in T cells and inhibited splenocyte proliferation induced by Con A.

CONCLUSION: Pretreatment with FTY 720 was shown to produce protective effect on the immune liver injury in mice. The possible mechanism of FTY 720 on Con A-induced liver damage is that it could inhibit lymphocyte proliferation and induce lymphocyte apoptosis, resulting in the reduction of IL-4 or IFN-γ release, and subsequently protecting liver from being damaged by Con A.

Anti-inflammatory and antiviral effects of Glossogyne tenuifolia

Glossogyne tenuifolia (Hsiang-Ju) is a traditional antipyretic and hepatoprotective herb used in Chinese medicine. The aim of this research is to investigate the pharmacological activities and potent components of the ethanol extract of Glossogyne tenuifolia (GT) in human primary cells and cell line. We found that GT (0.1 approximately 0.25 mg/ml) exerted dose-dependent inhibitions on the release of TNF-alpha and IL-6 in LPS-activated human whole blood and peripheral blood mononuclear cells (PBMC), and IFN-gamma in PHA-stimulated human whole blood. The lack of cytotoxicity indicated that the inhibitory effects of GT on cytokine production were not due to cell death. Luteolin, the deglycosylated derivative of one of the major compositions, luteolin-7-glucoside, exerted inhibitory effects on TNF-alpha, IL-6 and IFN-gamma production in activated human whole blood with estimated IC(50)s of 42.73 microM, 44.86 microM and 3.34 microM, respectively. Furthermore, GT had potent anti-hepatitis B virus (HBV) effects on the human hepatocellular carcinoma cell line, PLC/PRF/5. GT exhibited a dose-dependent inhibition on the release of hepatitis B surface antigen (HBsAg) by repressing the expression of HBsAg with IC(50) of 0.093 mg/ml. We concluded that GT exerted combinatorial anti-inflammatory and antiviral effects, and the multiple actions may underlie its traditional hepatoprotective function.

Hyperproduction of Proinflammatory Cytokines by WSX-1-Deficient NKT Cells in Concanavalin A-Induced Hepatitis

Administration of Con A induces liver injury that is considered to be an experimental model for human autoimmune or viral hepatitis, where immunopathology plays roles mediated by activated lymphocytes, especially NK1.1+ CD3+ NKT cells, and inflammatory cytokines, including IFN-gamma and IL-4. In the present study we investigated the role of WSX-1, a component of IL-27R, in Con A-induced hepatitis by taking advantage of WSX-1 knockout mice. WSX-1-deficient mice were more susceptible to Con A treatment than wild-type mice, showing serum alanine aminotransferase elevation and massive necrosis in the liver. Although the development of NKT cells appeared normal in WSX-1 knockout mice, purified NKT cells from the knockout mice produced more IFN-gamma and IL-4 than those from wild-type mice in response to stimulation with Con A both in vitro and in vivo. In addition, hyperproduction of proinflammatory cytokines, including IL-1, IL-6, and TNF-alpha, was observed in the knockout mice after Con A administration. These data revealed a novel role for WSX-1 as an inhibitory regulator of cytokine production and inflammation in Con A-induced hepatitis.

Up-regulation of granulomatous inflammation in interleukin-6 knockout mice infected with Rhodococcus aurantiacus

After intravenous injection of Rhodococcus aurantiacus normal mice develop non-necrotic granulomas, the formation of which is dependent on endogenous interferon-gamma (IFN-gamma). In the early phase of R. aurantiacus infection a high level of endogenous interleukin-6 (IL-6) is detected in the spleen extracts, though its importance is unknown. Using IL-6 knockout (IL-6-/-) mice, we studied the role of IL-6 in granulomatous inflammation induced by R. aurantiacus. The size of granulomas generated in IL-6-/- mice was significantly larger than that of wild-type (IL-6+/+) mice at 2 weeks postinjection (p.i). Moreover, central necrosis of the granuloma was observed in IL-6-/- mice but not in IL-6+/+ controls. Titres of endogenous IFN-gamma and tumour necrosis factor-alpha (TNF-alpha) were markedly increased in the spleens and livers of IL-6-/- mice in comparison with IL-6+/+ mice at days 1 through 3 p.i. In vivo administration of either an anti-IFN-gamma monoclonal antibody (mAb) or anti-TNF-alpha mAb to IL-6-/- mice reduced the number and size of granulomas, and prevented formation of necrotic granulomas. In addition, the production of endogenous IFN-gamma and TNF-alpha in the early phase of R. aurantiacus infection by IL-6-/- mice was suppressed by treatment with recombinant IL-6 (rIL-6). This suppression of IFN-gamma and TNF-alpha production was followed by a reduction in the number and size of central necrotic granulomas at 2 weeks p.i. These findings suggest that overproduction of IFN-gamma and TNF-alpha induces central necrotic granuloma formation in IL-6-/- mice, and that IL-6 down-regulates granulomatous inflammation reaction in response to R. aurantiacus infection by modulating production of IFN-gamma and TNF-alpha.

WSX-1 Is Required for Resistance to Trypanosoma cruzi Infection by Regulation of Proinflammatory Cytokine Production

WSX-1 is a class I cytokine receptor with homology to the IL-12 receptors and is essential for resistance to Leishmania major infection. In the present study, we demonstrated that WSX-1 was also required for resistance to Trypanosoma cruzi. WSX-1-/- mice exhibited prolonged parasitemia, severe liver injury, and increased mortality over wild-type mice. WSX-1-/- splenocytes produced enhanced levels of Th2 cytokines, which were responsible for the prolonged parasitemia. Massive necroinflammatory lesions were observed in the liver of infected WSX-1-/- mice, and IFN-gamma that was overproduced in WSX-1-/- mice compared with wild-type mice was responsible for the lesions. In addition, vast amounts of various proinflammatory cytokines, including IL-6 and TNF-alpha, were produced by liver mononuclear cells in WSX-1-/- mice. Thus, during T. cruzi infection, WSX-1 suppresses liver injury by regulating production of proinflammatory cytokines, while controlling parasitemia by suppression of Th2 responses, demonstrating its novel role as an inhibitory regulator of cytokine production.

8-[3H]-hydroxy-2-(di-n-propylamino)tetralin binding sites in blood lymphocytes of rats and the modulation by mitogens and immobilization

Serotonin 5-HT(1A) receptors were characterized in rat resting lymphocytes obtained by cardiac puncture with the use of the ligand [3H]8-hydroxy-2-(di-n-propylamino)tetralin. Selectivity of the specific binding was demonstrated by inhibition experiments with various serotonergic and nonserotonergic drugs. The rank order of potency for inhibition was WAY-100478>pindobind>NAN-190>buspirone>imipramine>serotonin. While pimozide, desipramine, nomifensine, haloperidol and sulpiride did not inhibit the binding. Kinetic parameters calculated from saturation experiments indicated one site of interaction, with an equilibrium dissociation constant of 2.50 nM and maximum binding capacity of 487.21 nmol/10(6) cells. Complete dissociation was obtained with serotonin as the displacement agent, and equilibrium dissociation constant calculated by association and dissociation experiments was 2.03 nM. Thus, serotonin 5-HT(1A) receptors are present in resting lymphocytes. The in vivo administration of the mitogens lipopolysacharide (0.1 mg/kg, 18 h) or concanavalin A (0.2 mg/kg, 18 h) increased the number of sites. The elevation produced by the latter was of higher magnitude than that of lipopolysacharide, and two sites of the binding were determined by isotopic dilution. Immobilization stress (1 h daily for 7 days) also resulted in a significant increase of binding capacity, but was smaller than that produced by the mitogens. The affinity of binding was not affect by the treatments. The results indicate that serotonin 5-HT(1A) receptors are modulated by unspecific and specific immune system activation, as well as by a potent stress condition, which might result in relevant functional modifications in the response of rat lymphocytes.

Portal lymphocytic infiltrate in alcoholic liver disease

The aim of this study was to estimate the frequency of lymphocytic portal infiltrate in human alcoholic liver disease and to determine whether it was correlated with liver injury. This retrospective study included 200 consecutive patients referred between February 1996 and March 2001 to the Service Central d'Hépato-Gastroentérologie at Groupe Hospitalier Pitié-Salpêtrière Hospital, Paris, France. The inclusions criteria were as follows: (1) daily alcohol consumption greater than 40 g; (2) appropriate serological exclusion of B and C viral hepatitis; and (3) available liver biopsy specimen. Autoimmune hepatitis was excluded in all patients with the aid of a consensus scoring system. Forty percent of the patients had a predominantly lymphocytic portal infiltrate. On stepwise logistic regression of the predictive value of the 5 variables (gender, age, daily alcohol consumption, steatosis, and portal and septal fibrosis index), only 2 statistically independent predictors of predominant lymphocytic portal infiltrate were identified: portal and septal fibrosis index (P <.05) and age (P <.05). In conclusion, predominantly portal lymphocytic infiltrate occurs frequently in alcoholic liver disease, even in patients without serological markers of B and C viral hepatitis. Moreover, after adjustment for age, portal and septal fibrosis index remains significantly associated with the presence of a predominantly lymphocytic portal infiltrate. These results suggest that lymphocytes may play a role in the pathogenesis of alcohol-induced liver fibrosis.