Functions of Liver Natural Killer Cells Are Dependent on the Severity of Liver Inflammation and Fibrosis in Chronic Hepatitis C

During chronic hepatitis C virus (HCV) infection, the role of intra-hepatic (IH) natural killer (NK) cells is still controversial. To clarify their functions, we investigated anti-viral and cytotoxic activity of NK cells in human fresh liver biopsies. We compared the functions of IH-NK cells in HCV-infected and NASH patients in physiological conditions as well as after stimulation using flow cytometric and immunohistochemical analyses. Interestingly, few IH-NK cells produced anti-viral cytokine IFN-γ in HCV-infected patients similarly as in non-infected individuals. Spontaneous degranulation activity was extremely low in peripheral NK cells compared to IH-NK cells, and was significantly higher in IH-NK cells from HCV-infected patients compared to non-infected individuals. Immunohistochemical analysis revealed that perforin granules were polarized at the apical pole of IH-NK cells. The presence of CD107a and perforin in IH-NK cells demonstrated that NK cells exerted a cytolytic activity at the site of infection. Importantly, IH-NK cell functions from HCV-infected patients were inducible by specific exogenous stimulations. Upon ex vivo K562 target cell stimulations, the number of degranulating NK cells was significantly increased in the pool of IH-NK cells compared to circulating NK cells. Interestingly, after stimulation, the frequency of IFN-γ-producing IH-NK cells in HCV-infected patients was significantly higher at early stage of inflammation whereas the spontaneous IH-NK cell degranulation activity was significantly impaired in patients with highest inflammation and fibrosis Metavir scores. Our study highlights that some IH-NK cells in HCV-infected patients are able to produce INF-γ and degranulate and that those two activities depend on liver environment including the severity of liver injury. Thus, we conclude that critical roles of IH-NK cells have to be taken into account in the course of the liver pathogenesis associated to chronic HCV infection.     

Myeloid Derived Suppressor Cells (MDSCs) Are Increased and Exert Immunosuppressive Activity Together with Polymorphonuclear Leukocytes (PMNs) in Chronic Myeloid Leukemia Patients

Tumor immune tolerance can derive from the recruitment of suppressor cell population, including myeloid derived suppressor cells (MDSCs), able to inhibit T cells activity. We identified a significantly expanded MDSCs population in chronic myeloid leukemia (CML) patients at diagnosis that decreased to normal levels after imatinib therapy. In addition, expression of arginase 1 (Arg1) that depletes microenvironment of arginine, an essential aminoacid for T cell function, resulted in an increase in patients at diagnosis. Purified CML CD11b+CD33+CD14-HLADR- cells markedly suppressed normal donor T cell proliferation in vitro. Comparing CML Gr-MDSCs to autologous polymorphonuclear leukocytes (PMNs) we observed a higher Arg1 expression and activity in PMNs, together with an inhibitory effect on T cells in vitro. Our data indicate that CML cells create an immuno-tolerant environment associated to MDSCs expansion with immunosuppressive capacity mediated by Arg1. In addition, we demonstrated for the first time also an immunosuppressive activity of CML PMNs, suggesting a strong potential immune escape mechanism created by CML cells, which control the anti-tumor reactive T cells. MDSCs should be monitored in imatinib discontinuation trials to understand their importance in relapsing patients.     

Progression of Chronic Liver Inflammation and Fibrosis Driven by Activation of c-JUN Signaling in Sirt6 Mutant Mice

The human body has a remarkable ability to regulate inflammation, a biophysical response triggered by virus infection and tissue damage. Sirt6 is critical for metabolism and lifespan; however, its role in inflammation is unknown. Here we show that Sirt6-null (Sirt6^−/−) mice developed chronic liver inflammation starting at ∼2 months of age, and all animals were affected by 7–8 months of age. Deletion of Sirt6 in T cells or myeloid-derived cells was sufficient to induce liver inflammation and fibrosis, albeit to a lesser degree than that in the global Sirt6^−/− mice, suggesting that Sirt6 deficiency in the immune cells is the cause. Consistently, macrophages derived from the bone marrow of Sirt6^−/− mice showed increased MCP-1, IL-6, and TNFα expression levels and were hypersensitive to LPS stimulation. Mechanistically, SIRT6 interacts with c-JUN and deacetylates histone H3 lysine 9 (H3K9) at the promoter of proinflammatory genes whose expression involves the c-JUN signaling pathway. Sirt6-deficient macrophages displayed hyperacetylation of H3K9 and increased occupancy of c-JUN in the promoter of these genes, leading to their elevated expression. These data suggest that Sirt6 plays an anti-inflammatory role in mice by inhibiting c-JUN-dependent expression of proinflammatory genes.     

Myeloid Derived Suppressor Cells Are Present at High Frequency in Neonates and Suppress In Vitro T Cell Responses

Over 4 million infants die each year from infections, many of which are vaccine-preventable. Young infants respond relatively poorly to many infections and vaccines, but the basis of reduced immunity in infants is ill defined. We sought to investigate whether myeloid-derived suppressor cells (MDSC) represent one potential impediment to protective immunity in early life, which may help inform strategies for effective vaccination prior to pathogen exposure. We enrolled healthy neonates and children in the first 2 years of life along with healthy adult controls to examine the frequency and function of MDSC, a cell population able to potently suppress T cell responses. We found that MDSC, which are rarely seen in healthy adults, are present in high numbers in neonates and their frequency rapidly decreases during the first months of life. We determined that these neonatal MDSC are of granulocytic origin (G-MDSC), and suppress both CD4+ and CD8+ T cell proliferative responses in a contact-dependent manner and gamma interferon production. Understanding the role G-MDSC play in infant immunity could improve vaccine responsiveness in newborns and reduce mortality due to early-life infections.     

Treatment of Tumors with Vitamin E Suppresses Myeloid Derived Suppressor Cells and Enhances CD8+ T Cell-Mediated Antitumor Effects

Vitamin E has been shown to have strong anticarcinogenic properties, including antioxidant characteristics, making it an ideal candidate for use in combination with immunotherapies that modify the tumor microenvironment. The tumor microenvironment contains immunosuppressive components, which can be diminished, and immunogenic components, which can be augmented by immunotherapies in order to generate a productive immune response. In the current study, we employ the α-tocopherol succinate isomer of vitamin E to reduce immunosuppression by myeloid derived suppressor cells (MDSCs) as well as adoptive transfer of antigen-specific CD8+ T cells to generate potent antitumor effects against the HPV16 E7-expressing TC-1 tumor model. We show that vitamin E alone induces necrosis of TC-1 cells and elicits antitumor effects in TC-1 tumor-bearing mice. We further demonstrate that vitamin E reverses the suppression of T cell activation by MDSCs and that this effect is mediated in part by a nitric oxide-dependent mechanism. Additionally, treatment with vitamin E reduces the percentage of MDSCs in tumor loci, and induces a higher percentage of T cells, following T cell adoptive transfer. Finally, we demonstrate that treatment with vitamin E followed by E7-specific T cell adoptive transfer experience elicits potent antitumor effects in tumor-bearing mice. Our data provide additional evidence that vitamin E has anticancer properties and that it has promise for use as an adjuvant in combination with a variety of cancer therapies.     

Chemokine Receptor Ccr6 Deficiency Alters Hepatic Inflammatory Cell Recruitment and Promotes Liver Inflammation and Fibrosis

Chronic liver diseases are characterized by a sustained inflammatory response in which chemokines and chemokine-receptors orchestrate inflammatory cell recruitment. In this study we investigated the role of the chemokine receptor CCR6 in acute and chronic liver injury. In the absence of liver injury Ccr6 ^-/- mice presented a higher number of hepatic macrophages and increased expression of pro-inflammatory cytokines and M1 markers Tnf-α, Il6 and Mcp1. Inflammation and cell recruitment were increased after carbon tetrachloride-induced acute liver injury in Ccr6 ^-/- mice. Moreover, chronic liver injury by carbon tetrachloride in Ccr6 ^-/- mice was associated with enhanced inflammation and fibrosis, altered macrophage recruitment, enhanced CD4⁺ cells and a reduction in Th17 (CD4⁺IL17⁺) and mature dendritic (MHCII⁺CD11c⁺) cells recruitment. Clodronate depletion of macrophages in Ccr6 ^-/- mice resulted in a reduction of hepatic pro-inflammatory and pro-fibrogenic markers in the absence and after liver injury. Finally, increased CCR6 hepatic expression in patients with alcoholic hepatitis was found to correlate with liver expression of CCL20 and severity of liver disease. In conclusion, CCR6 deficiency affects hepatic inflammatory cell recruitment resulting in the promotion of hepatic inflammation and fibrosis.     

Continuous AMD3100 Treatment Worsens Renal Fibrosis through Regulation of Bone Marrow Derived Pro-Angiogenic Cells Homing and T-Cell-Related Inflammation

AMD3100 is a small molecule inhibitor of chemokine receptor type 4 (CXCR4), which is located in the cell membranes of CD34+ cells and a variety of inflammatory cells and has been reported to reduce organ fibrosis in the lung, liver and myocardium. However, the effect of AMD3100 on renal fibrosis is unknown. This study investigated the impact of AMD3100 on renal fibrosis. C57bl/6 mice were subjected to unilateral ureteral obstruction (UUO) surgery with or without AMD3100 administration. Tubular injury, collagen deposition and fibrosis were detected and analyzed by histological staining, immunocytochemistry and Western Blot. Bone marrow derived pro-angiogenic cells (CD45+, CD34+ and CD309+ cells) and capillary density (CD31+) were measured by flow cytometry (FACS) and immunofluorescence (IF). Inflammatory cells, chemotactic factors and T cell proliferation were characterized. We found that AMD3100 treatment did not alleviate renal fibrosis but, rather, increased tissue damage and renal fibrosis. Continuous AMD3100 administration did not improve bone marrow derived pro-angiogenic cells mobilization but, rather, inhibited the migration of bone marrow derived pro-angiogenic cells into the fibrotic kidney. Additionally, T cell infiltration was significantly increased in AMD3100-treated kidneys compared to un-treated kidneys. Thus, treatment of UUO mice with AMD3100 led to an increase in T cell infiltration, suggesting that AMD3100 aggravated renal fibrosis.     

Macrophages and Dendritic Cells Emerge in the Liver during Intestinal Inflammation and Predispose the Liver to Inflammation

The liver is a physiological site of immune tolerance, the breakdown of which induces immunity. Liver antigen-presenting cells may be involved in both immune tolerance and activation. Although inflammatory diseases of the liver are frequently associated with inflammatory bowel diseases, the underlying immunological mechanisms remain to be elucidated. Here we report two murine models of inflammatory bowel disease: RAG-2^−/− mice adoptively transferred with CD4⁺CD45RB^high T cells; and IL-10^−/− mice, accompanied by the infiltration of mononuclear cells in the liver. Notably, CD11b⁻CD11c^lowPDCA-1⁺ plasmacytoid dendritic cells (DCs) abundantly residing in the liver of normal wild-type mice disappeared in colitic CD4⁺CD45RB^high T cell-transferred RAG-2^−/− mice and IL-10^−/− mice in parallel with the emergence of macrophages (Mφs) and conventional DCs (cDCs). Furthermore, liver Mφ/cDCs emerging during intestinal inflammation not only promote the proliferation of naïve CD4⁺ T cells, but also instruct them to differentiate into IFN-γ-producing Th1 cells in vitro. The emergence of pathological Mφ/cDCs in the liver also occurred in a model of acute dextran sulfate sodium (DSS)-induced colitis under specific pathogen-free conditions, but was canceled in germ-free conditions. Last, the Mφ/cDCs that emerged in acute DSS colitis significantly exacerbated Fas-mediated hepatitis. Collectively, intestinal inflammation skews the composition of antigen-presenting cells in the liver through signaling from commensal bacteria and predisposes the liver to inflammation.     

Ly6Chi Monocyte Recruitment Is Responsible for Th2 Associated Host-Protective Macrophage Accumulation in Liver Inflammation due to Schistosomiasis

Accumulation of M2 macrophages in the liver, within the context of a strong Th2 response, is a hallmark of infection with the parasitic helminth, Schistosoma mansoni, but the origin of these cells is unclear. To explore this, we examined the relatedness of macrophages to monocytes in this setting. Our data show that both monocyte-derived and resident macrophages are engaged in the response to infection. Infection caused CCR2-dependent increases in numbers of Ly6C^hi monocytes in blood and liver and of CX₃CR1⁺ macrophages in diseased liver. Ly6C^hi monocytes recovered from liver had the potential to differentiate into macrophages when cultured with M-CSF. Using pulse chase BrdU labeling, we found that most hepatic macrophages in infected mice arose from monocytes. Consistent with this, deletion of monocytes led to the loss of a subpopulation of hepatic CD11c^hi macrophages that was present in infected but not naïve mice. This was accompanied by a reduction in the size of egg-associated granulomas and significantly exacerbated disease. In addition to the involvement of monocytes and monocyte-derived macrophages in hepatic inflammation due to infection, we observed increased incorporation of BrdU and expression of Ki67 and MHC II in resident macrophages, indicating that these cells are participating in the response. Expression of both M2 and M1 marker genes was increased in liver from infected vs. naive mice. The M2 fingerprint in the liver was not accounted for by a single cell type, but rather reflected expression of M2 genes by various cells including macrophages, neutrophils, eosinophils and monocytes. Our data point to monocyte recruitment as the dominant process for increasing macrophage cell numbers in the liver during schistosomiasis.     

Prevention of Liver Fibrosis by Intrasplenic Injection of High-Density Cultured Bone Marrow Cells in a Rat Chronic Liver Injury Model

Endothelial progenitor cells (EPCs) from bone marrow have proven to be functional for the prevention of liver fibrosis in chronic liver injury. However, expansion of EPCs in culture is complicated and expansive. Previously, we have established a simple method that could enrich and expand EPCs by simple seeding bone marrow cells in high density dots. The purpose of this study is to evaluate whether cells derived from high-density (HD) culture of rat bone marrow cells could prevent the liver fibrosis in a chronic liver injury rat model, induced by carbon tetrachloride (CCl₄). Flow cytometric analysis showed that cells from HD culture were enriched for EPCs, expressing high levels of EPC markers. Intrasplenic injection of HD cultured bone marrow cells in the CCl₄-induced liver injury rat showed an enhanced antifibrogenic effect compared with animals treated with cells from regular-density culture. The antifibrogenic effect was demonstrated by biochemical and histological analysis 4 weeks post-transplantation. Furthermore, cells from HD culture likely worked through increasing neovascularization, stimulating liver cell proliferation, and suppressing pro-fibrogenic factor expression. HD culture, which is a simple and cost-effective procedure, could potentially be used to expand bone marrow cells for the treatment of liver fibrosis.     

Induction of Nitric Oxide Synthase in Rat C6 Glioma Cells

Abstract: We have examined the induction of nitric oxide syhthase (NOS) activity in the rat astrocyte-derived C6 glioma cell line. In contrast to the previous results with primary astrocyte cultures, incubation of C6 cells with bacterial endotoxin lipopolysaccharide (LPS; 1 μg/ml for 24 h) did not stimulate NO₂ production. However, addition of either tumor necrosis factor-a (TNF-α) or interferon-γ (IFN-γ), cytokines that by themselves had no effect on NOS activity, imparted LPS responsiveness onto these cells in a dose-dependent manner (EC₅₀ values of 39 ng/ml of TNF-α and 9.4 U/ml of IFN-γ), and the effect of TNF-α could be further potentiated (twofold) by the presence of interleukin-1β. The simultaneous presence of TNF-α and IFN-γ yielded a greater response than either cytokine alone; however, the respective EC₅₀ values were not affected. A cytoplasmic extract from induced C6 cells catalyzed the Ca²⁺-independent conversion of l -arginine to l - citrulline, with an apparent K _m of 51.2 n M , and this activity could be blocked by l -arginine analogues in the potency order amino > methyl > nitroarginine. Immunoblot analysis revealed an apparent molecular mass of 125 kDa for the NOS protein induced in C6 cells. These results indicate that the combination of LPS plus cytokines can induce NOS activity in C6 glioma cells with properties similar to those of the enzyme expressed in primary astrocyte cultures.     

Induction of Type C Virions from Normal Rat Kidney Cells by 2-Deoxy-d-Glucose

The sugar 2-deoxy-d-glucose (2-DG) induced the release of type C virions from an established line of normal rat kidney (NRK) cells. Within 20 h after the addition of 5 mg of 2-DG per ml to exponentially growing NRK cultures, more than 80% of the cells expressed the mammalian type C virus interspecies-specific antigen (p30) as determined by indirect cytoplasmic immunofluorescence. Maximal virion release occurred 1 to 2 days after 2-DG was added for 24 h to the growth medium, although a low level of virion production was detected as early as 2.5 h after 2-DG treatment. Studies with inhibitors of RNA synthesis indicated a requirement for de novo RNA synthesis after the addition of 2-DG. Sensitivity of NRK cells to type C virion induction was limited to a relatively short period of in vitro growth and preceded spontaneous virion release by 8 to 10 subculture generations. A model is presented for the sequential derepression of latent type C virus information in serially propagated NRK cells.     

Discordance between Liver Biopsy and FibroTest in Assessing Liver Fibrosis in Chronic Hepatitis B

Background and Aims

The FibroTest (FT) demonstrated excellent diagnostic performance in the prediction of liver fibrosis in patients with chronic hepatitis B (CHB). Here, we aimed to identify predictors of discordance between FT and liver biopsy (LB) in Asian patients with CHB.

Methods

Consecutive patients with CHB who underwent both LB and FT on the same day between 2007 and 2010 were recruited from three medical institutes. Laboratory evaluations including specific parameters for calculating FT score, such as α2-macroglobulin, apolipoprotein A1, haptoglobin, γ-glutamyl transpeptidase, and total bilirubin levels, were obtained. The Batts and Ludwig scoring system was used for histological analysis.

Results

A total of 330 patients (200 male and 130 female) were analyzed. Discordances of at least two fibrosis stages between FT and LB were observed in 30 (9.1%) patients; using FT, fibrosis was underestimated in 25 patients and overestimated in 5 patients with reference to LB. Patients with discordance had a higher proportion of F3–4 (P<0.001) and F4 (P = 0.012) compared with those with nondiscordance. The discordance rate was significantly higher in those with F3–4 than those with F1–2 (15.4% vs. 3.0%, P<0.001). Multivariate analysis demonstrated F3–4 at LB as the only independent factor for discordance (P<0.001; odds ratio 5.95). After adjusting fibrosis stages, neither necroinflammatory activity on histology nor serum ALT level influenced FT values independently.

Conclusion

Advanced fibrosis stage (F3–4) is the sole factor of discordance between FT and LB in Asian patients with CHB.     

Hepatitis C Virus Nonstructural 3/4A Protein Dampens Inflammation and Contributes to Slow Fibrosis Progression during Chronic Fibrosis In Vivo

HCV infection typically induces liver injury and inflammation, which appears to be responsible for the associated fibrogenesis. To date, the mechanism underlying the different rates of disease progression remains unclear. The aim of the study is to understand the possible role of the HCV non-structural (NS) 3/4A protein in the fibrosis progression. We used NS3/4A-expressing transgenic mice (NS3/4A-Tg) to accomplish the goals of the study. Different stages of liver fibrosis were induced in wild-type and NS3/4A-Tg mice by single carbon tetrachloride (acute) or multiple injections for 4 (intermediate) or 8 (chronic) weeks. Fibrotic parameters, inflammatory responses and hepatocyte turnover were extensively examined. Hepatic expression of HCV NS3/4A did not induce spontaneous liver damage. However, NS3/4A expression exerted contrasting effects during acute and chronic liver damage. During early fibrogenesis and intermediate fibrosis (4 weeks), NS3/4A-Tg mice exhibited enhanced liver damage whereas reduced fibrosis was observed in NS3/4A-Tg during chronic liver fibrosis (8 weeks). Furthermore, attenuated inflammation was observed in NS3/4A-Tg during chronic fibrosis with increase in M2 macrophages, hepatocyte proliferation, decreased hepatocyte apoptosis and decreased ductular reaction. In conclusion, during early fibrogenesis, HCV NS3/4A contributes to liver damage. While, during chronic liver fibrosis, NS3/4A dampens inflammation and induces hepatocyte regeneration thereby contributing to slow fibrosis progression to promote its survival or persistence.     

干扰素联合利巴韦林治疗慢性丙型肝炎的疗效及对肝功能和肝纤维化指标的影响

目的:探讨干扰素联合利巴韦林治疗慢性丙型肝炎(Chronic Hepatitis C,CHC)的临床疗效以及对肝功能和肝纤维化指标的影响。方法:收集我院2011年3月至2012年3月收治的88例CHC患者,随机平均分为两组,对照组单用干扰素,观察组采用干扰素联合利巴韦林治疗,比较两组治疗后的临床疗效以及治疗前后肝功能和肝纤维化指标变化情况。结果:观察组治疗总有效率为90.91%,明显高于对照组的68.18%,两组比较差异具有统计学意义(P0.05);观察组治疗后ALT和AST分别为(70.24±7.94)和(79.45±9.72),HA、PCⅢ、CⅣ和LN分别为(76.87±10.32)、(79.45±9.72)、(79.76±8.00)和(118.41±16.97),均明显高于治疗前和对照组,差异具有统计学意义(P0.05)。结论:干扰素联合利巴韦林治疗慢性丙型肝炎疗效显著,可明显改善患者肝功能,具有较好的抗纤维化作用,值得临床推广和应用。     

Role of Arginase 1 from Myeloid Cells in Th2-Dominated Lung Inflammation

Th2-driven lung inflammation increases Arginase 1 (Arg1) expression in alternatively-activated macrophages (AAMs). AAMs modulate T cell and wound healing responses and Arg1 might contribute to asthma pathogenesis by inhibiting nitric oxide production, regulating fibrosis, modulating arginine metabolism and restricting T cell proliferation. We used mice lacking Arg1 in myeloid cells to investigate the contribution of Arg1 to lung inflammation and pathophysiology. In six model systems encompassing acute and chronic Th2-mediated lung inflammation we observed neither a pathogenic nor protective role for myeloid-expressed Arg1. The number and composition of inflammatory cells in the airways and lungs, mucus secretion, collagen deposition, airway hyper-responsiveness, and T cell cytokine production were not altered if AAMs were deficient in Arg1 or simultaneously in both Arg1 and NOS2. Our results argue that Arg1 is a general feature of alternative activation but only selectively regulates Th2 responses. Therefore, attempts to experimentally or therapeutically inhibit arginase activity in the lung should be examined with caution.