Recruitment of dendritic cells to pathological niches in inflamed liver

Anti-inflammatory and antifibrotic effects of CBP/β-catenin inhibitor for hepatocytes: small molecular inhibitor, OP-724 possibly improves liver function

Wnt/β-catenin signals are associated with several functions, including organ fibrosis. A synthetic small molecule, OP-724 (prodrug of C-82), an inhibitor of cyclic AMP response element-binding protein (CREB)-binding protein (CBP)/β-catenin, has demonstrated antifibrotic activity in mouse models of hepatic fibrosis. OP-724 is mediated by profibrotic and antifibrotic cells, such as hepatic stellate cells, macrophages, and neutrophils. In this study, the direct effects of C-82 on hepatocytes in hepatic inflammation were investigated. Immortalized human hepatocytes were pretreated with inflammatory cytokines. Moreover, the alteration of mRNA and protein expressions of cytokines and chemokines associated with hepatic inflammation and fibrosis, and of mitochondria-related molecules after C-82 treatment were analyzed in this study. The mRNA expression of several proinflammatory and profibrotic chemokines was upregulated by the stimulation of these inflammatory cytokines. In addition, this increase was prevented by C-82. In particular, the protein secretion of CCL2, CCL5, CXCL1, CXCL9, and CXCL10 was noticeably upregulated by TNFα and prevented by additional C-82. Moreover, C-82 increased the VEGF-A and FGF-2 proteins, categorized as anti-inflammatory and antifibrotic molecules, respectively. It also increased the expression of mitochondrial components and mitochondrial membrane potential. In conclusion, C-82 inhibits hepatocyte-mediated proinflammation and fibrogenesis. It also directly activates the mitochondrial function, thus improving liver dysfunction.

Changing our view of the Schistosoma granuloma to an ecological standpoint

Schistosomiasis, a neglected parasitic tropical disease that has plagued humans for centuries, remains a major public health burden. A primary challenge to understanding schistosomiasis is deciphering the most remarkable pathological feature of this disease, the granuloma - a highly dynamic and self-organized structure formed by both host and parasite components. Granulomas are considered a remarkable example of how parasites evolved with their hosts to establish complex and intimate associations. However, much remains unclear regarding life within the granuloma, and strategies to restrain its development are still lacking. Here we explore current information on the hepatic Schistosoma mansoni granuloma in the light of Ecology and propose that this intricate structure acts as a real ecosystem. The schistosomal granuloma is formed by cells (biotic component), protein scaffolds, fibres, and chemical compounds (abiotic components) with inputs/outputs of energy and matter, as complex as in classical ecosystems. We review the distinct cell populations ('species') within the granuloma and examine how they integrate with each other and interact with their microenvironment to form a multifaceted cell community in different space-time frames. The colonization of the hepatic tissue to form granulomas is explained from the point of view of an ecological succession whereby a community is able to modify its physical environment, creating conditions and resources for ecosystem construction. Remarkably, the granuloma represents a dynamic evolutionary system that undergoes progressive changes in the 'species' that compose its community over time. In line with ecological concepts, we examine the granuloma not only as a place where a community of cells is settled (spatial niche or habitat) but also as a site in which the functional activities of these combined populations occur in an orchestrated way in response to microenvironmental gradients such as cytokines and egg antigens. Finally, we assert how the levels of organization of cellular components in a granuloma as conventionally defined by Cell Biology can fit perfectly into a hierarchical structure of biological systems as defined by Ecology. By rethinking the granuloma as an integrating and evolving ecosystem, we draw attention to the inner workings of this structure that are central to the understanding of schistosomiasis and could guide its future treatment.

Oral Preconditioning of Donors After Brain Death With Calcineurin Inhibitors vs. Inhibitors of Mammalian Target for Rapamycin in Pig Kidney Transplantation

Background: The systemic inflammatory cascade triggered in donors after brain death enhances the ischemia-reperfusion injury after organ transplantation. Intravenous steroids are routinely used in the intensive care units for the donor preconditioning. Immunosuppressive medications could be potentially used for this purpose as well. Data regarding donor preconditioning with calcineurin inhibitors or inhibitors of mammalian target for Rapamycin is limited. The aim of this project is to investigate the effects of (oral) donor preconditioning with a calcineurin inhibitor (Cyclosporine) vs. an inhibitor of mammalian target for Rapamycin (Everolimus) compared to the conventional administration of steroid in the setting of donation after brain death in porcine renal transplantation.

Methods: Six hours after the induction of brain death, German landrace donor pigs (33.2 ± 3.9 kg) were randomly preconditioned with either Cyclosporine (n = 9) or Everolimus (n = 9) administered via nasogastric tube with a repeated dose just before organ procurement. Control donors received intravenous Methylprednisolone (n = 8). Kidneys were procured, cold-stored in Histidine-Tryptophane-Ketoglutarate solution at 4°C and transplanted in nephrectomized recipients after a mean cold ischemia time of 18 h. No post-transplant immunosuppression was given to avoid confounding bias. Blood samples were obtained at 4 h post reperfusion and daily until postoperative day 5 for complete blood count, blood urea nitrogen, creatinine, and electrolytes. Graft protocol biopsies were performed 4 h after reperfusion to assess early histological and immunohistochemical changes.

Results: There was no difference in the hemodynamic parameters, hemoglobin/hematocrit and electrolytes between the groups. Serum blood urea nitrogen and creatinine peaked on postoperative day 1 in all groups and went back to the preoperative levels at the conclusion of the study on postoperative day 5. Histological assessment of the kidney grafts revealed no significant differences between the groups. TNF-α expression was significantly lower in the study groups compared with Methylprednisolone group (p = 0.01) Immunohistochemistry staining for cytochrome c showed no difference between the groups.

Conclusion: Oral preconditioning with Cyclosporine or Everolimus is feasible in donation after brain death pig kidney transplantation and reduces the expression of TNF-α. Future studies are needed to further delineate the role of oral donor preconditioning against ischemia-reperfusion injury.

Dendritic cells and Brucella spp. interaction: the sentinel host and the stealthy pathogen

As dendritic cells (DCs) are among the first cells to encounter antigens, these cells trigger both innate and T cell responses, and are the most potent antigen-presenting cells. Brucella spp., which is an intracellular facultative and stealthy pathogen, is able to evade the bactericidal activities of professional phagocytes. Several studies have demonstrated that Brucella can survive and replicate intracellularly, thereby provoking impaired maturation of DCs. Therefore, the interaction between DCs and Brucella becomes an interesting model to study the immune response. In this review, we first will describe the most common techniques for DCs differentiation in vitro as well as general features of brucellosis. Then, the interaction of DCs and Brucella, including pathogen recognition, molecular mechanisms of bacterial pathogenesis, and intracellular trafficking of Brucella to subvert innate response, will be reviewed. Finally, we will debate diversity in immunological DC response and the controversial role of DC activation against Brucella infection.

Macrophage Phenotype and Function in Liver Disorder

Hepatic macrophages are a remarkably heterogeneous population consisting of self-renewing tissue-resident phagocytes, termed Kupffer cells (KCs), and recruited macrophages derived from peritoneal cavity as well as the bone marrow. KCs are located in the liver sinusoid where they scavenge the microbe from the portal vein to maintain liver homeostasis. Liver injury may trigger hepatic recruitment of peritoneal macrophages and monocyte-derived macrophages. Studies describing macrophage accumulation have shown that hepatic macrophages are involved in the initiation and progression of various liver diseases. They act as tolerogenic antigen-presenting cells to inhibit T-cell activation by producing distinct sets of cytokines, chemokines, and mediators to maintain or resolve inflammation. Furthermore, by releasing regenerative growth factors, matrix metalloproteinase arginase, they promote tissue repair. Recent experiments found that KCs and recruited macrophages may play different roles in the development of liver disease. Given that hepatic macrophages are considerably plastic populations, their phenotypes and functions are likely switching along disease progression. In this review, we summarize current knowledge about the role of tissue-resident macrophages and recruited macrophages in pathogenesis of alcoholic liver disease (ALD), non-alcoholic steatohepatitis (NASH), viral hepatitis, and hepatocellular carcinoma (HCC).

Myeloid Cells and Chronic Liver Disease: a Comprehensive Review

Myeloid cells play a major role in the sensitization to liver injury, particularly in chronic inflammatory liver diseases with a biliary or hepatocellular origin, and the interplay between myeloid cells and the liver may explain the increased incidence of hepatic osteodystrophy. The myeloid cell-liver axis involves several mature myeloid cells as well as immature or progenitor cells with the complexity of the liver immune microenvironment aggravating the mist of cell differentiation. The unique positioning of the liver at the junction of the peripheral and portal circulation systems underlines the interaction of myeloid cells and hepatic cells and leads to immune tolerance breakdown. We herein discuss the scenarios of different chronic liver diseases closely modulated by myeloid cells and illustrate the numerous potential targets, the understanding of which will ultimately steer the development of solid immunotherapeutic regimens. Ultimately, we are convinced that an adequate modulation of the liver microenvironment to modify the functional and quantitative characteristics of myeloid cells will be a successful approach to treating chronic liver diseases of different etiologies.

Natural killer cells in liver diseases

The liver has been characterized as a frontline lymphoid organ with complex immunological features such as liver immunity and liver tolerance. Liver tolerance plays an important role in liver diseases including acute inflammation, chronic infection, autoimmune disease, and tumors. The liver contains a large proportion of natural killer (NK) cells, which exhibit heterogeneity in phenotypic and functional characteristics. NK cell activation, well known for its role in the immune surveillance against tumor and pathogen-infected cells, depends on the balance between numerous activating and inhibitory signals. In addition to the innate direct "killer" functions, NK cell activity contributes to regulate innate and adaptive immunity (helper or regulator). Under the setting of liver diseases, NK cells are of great importance for stimulating or inhibiting immune responses, leading to either immune activation or immune tolerance. Here, we focus on the relationship between NK cell biology, such as their phenotypic features and functional diversity, and liver diseases.

Plasmodium cellular effector mechanisms and the hepatic microenvironment

Plasmodium falciparum malaria remains one of the most serious health problems globally. Immunization with attenuated parasites elicits multiple cellular effector mechanisms capable of eliminating Plasmodium liver stages. However, malaria liver stage (LS) immunity is complex and the mechanisms effector T cells use to locate the few infected hepatocytes in the large liver in order to kill the intracellular LS parasites remain a mystery to date. Here, we review our current knowledge on the behavior of CD8 effector T cells in the hepatic microvasculature, in malaria and other hepatic infections. Taking into account the unique immunological and lymphogenic properties of the liver, we discuss whether classical granule-mediated cytotoxicity might eliminate infected hepatocytes via direct cell contact or whether cytokines might operate without cell–cell contact and kill Plasmodium LSs at a distance. A thorough understanding of the cellular effector mechanisms that lead to parasite death hence sterile protection is a prerequisite for the development of a successful malaria vaccine to protect the 40% of the world’s population currently at risk of Plasmodium infection.

Immunity and inflammatory signaling in alcoholic liver disease

The pathogenesis of alcoholic liver disease (ALD) is multifactorial and characterized by steatosis, steatohepatitis and cirrhosis. Several signaling pathways in different liver cell types that contribute to the development and progression of alcoholic liver injury have been identified. Among these, immune cells and signaling pathways are the most prominent and central to ALD. Both innate and adaptive immune responses contribute to ALD. The key features of inflammatory pathways in ALD including liver innate and adaptive immune cell types, signaling receptors/pathways, and pro- and antiinflammatory/protective responses are summarized here.

Linagliptin alleviates hepatic steatosis and inflammation in a mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a primary cause of cirrhosis and hepatocellular carcinoma. Dipeptidyl peptidase (DPP)-4 inhibitors are established therapies for type 2 diabetes and although DPP-4 inhibitors can reduce hepatic steatosis, their impact on local inflammation and fibrosis in NASH remains unknown. Using two different experimental treatment regimens (4- and 2-week treatments) in streptozotocin-treated neonatal mice on a high-fat diet, we show that the DPP-4 inhibitor linagliptin (10 and 30 mg/kg) significantly attenuated the NAS score from 4.9 ± 0.6 to 3.7 ± 0.4 and 3.6 ± 0.3, respectively, in the 4-week study. In the 2-week study, linagliptin 10 mg/kg significantly reduced NAS score from 4.1 ± 0.4 to 2.4 ± 0.4. Telmisartan was used as a positive control in both studies and lowered NAS score to 1.9 ± 0.7 and 1.4 ± 0.3, respectively. Due to streptozotocin treatment, elevated glucose levels were unchanged by either drug treatment. Further, linagliptin 10 mg/kg significantly reduced mRNA levels of SOCS-3 (from 1.68 ± 0.2 to 0.83 ± 0.08), IFN-γ (from 4.0 ± 0.5 to 2.3 ± 0.3), and TNF-α (from 5.7 ± 0.5 to 2.13 ± 0.3). The latter observation was confirmed by immunohistochemistry of TNF-α in liver specimens. In addition, using microautoradiography, we showed that the distribution of radiolabeled linagliptin was heterogeneous with the highest density associated with interlobular bile ducts and portal tracts (acini). In conclusion, these studies confirm that linagliptin has high exposure in hepatic tissue and has both anti-inflammatory and anti-steatotic activity in NASH.

Hepatic stellate cells undermine the allostimulatory function of liver myeloid dendritic cells via STAT3-dependent induction of IDO

Hepatic stellate cells (HSCs) are critical for hepatic wound repair and tissue remodeling. They also produce cytokines and chemokines that may contribute to the maintenance of hepatic immune homeostasis and the inherent tolerogenicity of the liver. The functional relationship between HSCs and the professional migratory APCs in the liver, that is, dendritic cells (DCs), has not been evaluated. In this article, we report that murine liver DCs colocalize with HSCs in vivo under normal, steady-state conditions, and cluster with HSCs in vitro. In vitro, HSCs secrete high levels of DC chemoattractants, such as MΙP-1α and MCP-1, as well as cytokines that modulate DC activation, including TNF-α, IL-6, and IL-1β. Culture of HSCs with conventional liver myeloid (m) DCs resulted in increased IL-6 and IL-10 secretion compared with that of either cell population alone. Coculture also resulted in enhanced expression of costimulatory (CD80, CD86) and coinhibitory (B7-H1) molecules on mDCs. HSC-induced mDC maturation required cell-cell contact and could be blocked, in part, by neutralizing MΙP-1α or MCP-1. HSC-induced mDC maturation was dependent on activation of STAT3 in mDCs and, in part, on HSC-secreted IL-6. Despite upregulation of costimulatory molecules, mDCs conditioned by HSCs demonstrated impaired ability to induce allogeneic T cell proliferation, which was independent of B7-H1, but dependent upon HSC-induced STAT3 activation and subsequent upregulation of IDO. In conclusion, by promoting IDO expression, HSCs may act as potent regulators of liver mDCs and function to maintain hepatic homeostasis and tolerogenicity.

The role of innate immunity in HBV infection

Hepatitis B virus (HBV) infection is one of the main causes of chronic liver diseases. Whether HBV infection is cleared or persists is determined by both viral factors and host immune responses. It becomes clear that innate immunity is of importance in protecting the host from HBV infection and persistence. However, HBV develops strategies to suppress the antiviral immune responses. A combined therapeutic strategy with both viral suppression and enhancement of antiviral immune responses is needed for effective long-term clearance and cure for chronic HBV infection. We and others confirmed that bifunctional siRNAs with both gene silencing and innate immune activation properties are beneficial for inhibition of HBV and represent a potential approach for treatment of viral infection. Understanding the nature of liver innate immunity and their roles in chronic HBV progression and HBV clearance may aid in the design of novel therapeutic strategies for chronic HBV infection.

What have we learned from brucellosis in the mouse model?

Brucellosis is a zoonosis caused by Brucella species. Brucellosis research in natural hosts is often precluded by practical, economical and ethical reasons and mice are widely used. However, mice are not natural Brucella hosts and the course of murine brucellosis depends on bacterial strain virulence, dose and inoculation route as well as breed, genetic background, age, sex and physiological statu of mice. Therefore, meaningful experiments require a definition of these variables. Brucella spleen replication profiles are highly reproducible and course in four phases: i), onset or spleen colonization (first 48 h); ii), acute phase, from the third day to the time when bacteria reach maximal numbers; iii), chronic steady phase, where bacterial numbers plateaus; and iv), chronic declining phase, during which brucellae are eliminated. This pattern displays clear physiopathological signs and is sensitive to small virulence variations, making possible to assess attenuation when fully virulent bacteria are used as controls. Similarly, immunity studies using mice with known defects are possible. Mutations affecting INF-γ, TLR9, Myd88, Tγδ and TNF-β favor Brucella replication; whereas IL-1β, IL-18, TLR4, TLR5, TLR2, NOD1, NOD2, GM-CSF, IL/17r, Rip2, TRIF, NK or Nramp1 deficiencies have no noticeable effects. Splenomegaly development is also useful: it correlates with IFN-γ and IL-12 levels and with Brucella strain virulence. The genetic background is also important: Brucella-resistant mice (C57BL) yield lower splenic bacterial replication and less splenomegaly than susceptible breeds. When inoculum is increased, a saturating dose above which bacterial numbers per organ do not augment, is reached. Unlike many gram-negative bacteria, lethal doses are large (≥ 108 bacteria/mouse) and normally higher than the saturating dose. Persistence is a useful virulence/attenuation index and is used in vaccine (Residual Virulence) quality control. Vaccine candidates are also often tested in mice by determining splenic Brucella numbers after challenging with appropriate virulent brucellae doses at precise post-vaccination times. Since most live or killed Brucella vaccines provide some protection in mice, controls immunized with reference vaccines (S19 or Rev1) are critical. Finally, mice have been successfully used to evaluate brucellosis therapies. It is concluded that, when used properly, the mouse is a valuable brucellosis model.

Identification of Cd101 as a susceptibility gene for Novosphingobium aromaticivorans-induced liver autoimmunity

Environmental and genetic factors define the susceptibility of an individual to autoimmune disease. Although common genetic pathways affect general immunological tolerance mechanisms in autoimmunity, the effects of such genes could vary under distinct immune challenges within different tissues. In this study, we demonstrate this by observing that autoimmune type 1 diabetes-protective haplotypes at the insulin-dependent diabetes susceptibility region 10 (Idd10) introgressed from chromosome 3 of C57BL/6 (B6) and A/J mice onto the NOD background increase the severity of autoimmune primary biliary cirrhosis induced by infection with Novosphingobium aromaticivorans, a ubiquitous alphaproteobacterium, when compared with mice having the NOD and NOD.CAST Idd10 type 1 diabetes-susceptible haplotypes. Substantially increased liver pathology in mice having the B6 and A/J Idd10 haplotypes correlates with reduced expression of CD101 on dendritic cells, macrophages, and granulocytes following infection, delayed clearance of N. aromaticivorans, and the promotion of overzealous IFN-γ- and IL-17-dominated T cell responses essential for the adoptive transfer of liver lesions. CD101-knockout mice generated on the B6 background also exhibit substantially more severe N. aromaticivorans-induced liver disease correlating with increased IFN-γ and IL-17 responses compared with wild-type mice. These data strongly support the hypothesis that allelic variation of the Cd101 gene, located in the Idd10 region, alters the severity of liver autoimmunity induced by N. aromaticivorans.

Distinct CCR2(+) Gr1(+) cells control growth of the Yersinia pestis ΔyopM mutant in liver and spleen during systemic plague

We are using a systemic plague model to identify the cells and pathways that are undermined by the virulence protein YopM of the plague bacterium Yersinia pestis. In this study, we pursued previous findings that Gr1(+) cells are required to selectively limit growth of ΔyopM Y. pestis and that CD11b(+) cells other than polymorphonuclear leukocytes (PMNs) are selectively lost in spleens infected with parent Y. pestis. When PMNs were ablated from mice, ΔyopM Y. pestis grew as well as the parent strain in liver but not in spleen, showing that these cells are critical for controlling growth of the mutant in liver but not spleen. In mice lacking expression of the chemokine receptor CCR2, wild-type growth was restored to ΔyopM Y. pestis in both organs. In spleen, the Gr1(+) cells differentially recruited by parent and ΔyopM Y. pestis infections were CCR2(+) Gr1(+) CD11b(+) CD11c(Lo-Int) MAC3(+) iNOS(+) (inducible nitric oxide synthase-positive) inflammatory dendritic cells (iDCs), and their recruitment to spleen from blood was blocked when YopM was present in the infecting strain. Consistent with influx of iDCs being affected by YopM in spleen, the growth defect of the ΔyopM mutant was relieved by the parent Y. pestis strain in a coinfection assay in which the parent strain could affect the fate of the mutant in trans. In a mouse model of bubonic plague, CCR2 also was shown to be required for ΔyopM Y. pestis to show wild-type growth in skin. The data imply that YopM's pathogenic effect indirectly undermines signaling through CCR2. We propose a model for how YopM exerts its different effects in liver and spleen.

The role of dendritic cells in mycobacterium-induced granulomas

The presence of dendritic cells (DCs) in mycobacterium-containing granulomas, as well as in other granuloma-inducing diseases, is beginning to be appreciated. This review will summarize what is known about DCs with regards to the granuloma and discuss the potential roles DCs may be playing during mycobacterial infection. Potential functions may include mycobacterial dissemination from lesions or sampling of granuloma-containing mycobacterial antigens and migration to the draining lymph nodes to maintain continuous T cell priming. Additionally, the review will discuss the potential outcomes of DC-T cell cross-talk within the granuloma and whether it results in boosting the effector functions of newly arrived T cells or anergizing systemic T cells locally. Understanding the DCs complex and changing role during this critical stage may help explain how latency is achieved and maintained. Such knowledge might also lead to improved vaccination strategies.

The liver as a lymphoid organ

The liver receives blood from both the systemic circulation and the intestine, and in distinctive, thin-walled sinusoids this mixture passes over a large macrophage population, termed Kupffer cells. The exposure of liver cells to antigens, and to microbial products derived from the intestinal bacteria, has resulted in a distinctive local immune environment. Innate lymphocytes, including both natural killer cells and natural killer T cells, are unusually abundant in the liver. Multiple populations of nonhematopoietic liver cells, including sinusoidal endothelial cells, stellate cells located in the subendothelial space, and liver parenchymal cells, take on the roles of antigen-presenting cells. These cells present antigen in the context of immunosuppressive cytokines and inhibitory cell surface ligands, and immune responses to liver antigens often result in tolerance. Important human pathogens, including hepatitis C virus and the malaria parasite, exploit the liver's environment, subvert immunity, and establish persistent infection.

Neutralization of CXCL10 accelerates liver regeneration in carbon tetrachloride-induced acute liver injury

Remodeling of hepatic tissue structure following injury requires the coordinated action of hepatocytes, hepatic stellate cells (HSCs), and endothelial cells. However, their in vivo properties are not fully understood. We report here that the chemokine CXCL10 regulates hepatic tissue remodeling in a carbon tetrachloride (CCl(4))-induced acute liver injury in mice. The production of CXCL10 was enhanced by hepatocytes after CCl(4) exposure. Neutralization of CXCL10 protected mice from acute liver dysfunction and diminished hepatocellular loss. The hepatoprotective effect was associated with increased numbers of 5'-bromo-2' deoxyuridine (BrdU)+ hepatocytes from day 1 and with accumulation of HSCs and endothelial cells within the injured zones from day 3. In vitro, recombinant CXCL10 directly inhibited the proliferation of hepatocytic cells, establishing a novel role of CXCL10 in modulating hepatocyte proliferation, in addition to a previously reported angiostatic role. In summary, neutralization of CXCL10 initially stimulates hepatocyte proliferation and, subsequently, HSC migration and angiogenesis to facilitate remodeling of hepatic cords. Thus, CXCL10 can be a novel therapeutic target for acute hepatocellular damage by regulating liver tissue remodeling.

Development of hepatic granulomas in patients receiving pegylated interferon therapy for recurrent hepatitis C virus post liver transplantation

Infrequently, hepatitis C (HCV) appears to be the cause of hepatic granulomas. Interferon therapy for HCV has been increasingly associated with the development of sarcoidosis.

AIMS

We sought to determine the incidence of hepatic granulomas in patients with recurrent HCV post liver transplantation (LT).

METHODS

Between 1994 and 2005, 820 patients were transplanted for HCV at our institution. The pathology database was searched for patients having recurrent HCV and granulomas. At Mount Sinai Medical Center, protocol biopsies have been performed for the last 2 years in patients receiving pegylated interferon-alpha2b and ribavirin (PEG) for recurrent HCV. Review of slides from explanted livers, pre- and post-perfusion biopsies, and all allograft biopsies were evaluated. Lipogranulomas were excluded because of their frequent association with steatosis.

RESULTS

A total of 10,225 liver biopsies were performed on HCV patients, and 25 (0.24%) showed non-caseating epithelioid granulomas. Hepatic granulomas were detected in 14 post-LT HCV patients; 9 patients received PEG. Typically, only 1 lobular granuloma was found. None of these patients had granulomas in the native liver or in any biopsy before interferon therapy; 6/9 patients had undetectable HCV-RNA levels, and 4 had sustained viral response. No other cause for granuloma formation was identified in the 6 patients.

CONCLUSIONS

Hepatic granulomas are infrequently found in HCV liver biopsies and rarely found in post-LT biopsies with recurrent HCV. When present, they occur more commonly in patients receiving and virologically responding to PEG therapy. The presence of granulomas in patients with HCV being treated with PEG may not warrant an extensive etiologic work-up for granulomatous hepatitis unless otherwise clinically indicated.

Critical role of toll-like receptors and the common TLR adaptor, MyD88, in induction of granulomas and liver injury

BACKGROUND/AIMS

Toll-like receptors (TLR) recognize pathogens and regulate innate immune activation. Here, we investigated the roles of TLR9 and the common TLR adaptor, MyD88, in liver injury.

METHODS

C57BL6, TLR9(-/-), IFNgamma(-/-) or MyD88(-/-) mice were primed with Propionibacterium acnes, TLR9 (CpG) or TLR2 (lipoteichoic acid) ligands followed by LPS challenge. ALT, cytokines and liver histology were assessed.

RESULTS

Selective priming through TLR9 but not TLR2 induced granulomas, elevated serum ALT, and sensitized C57BL6 mice to increased LPS-induced serum IL-6, IL-12 and IFNgamma levels. Further, TLR2 and TLR9 ligands synergized in induction of granulomas and sensitization to LPS-induced inflammation. IFNgamma induction by P. acnes, TLR2 and TLR9 ligands required MyD88. In MyD88(-/-) mice P. acnes failed to induce granulomas and both MyD88 and TLR9 deficiency prevented P. acnes-induced sensitization to LPS. Increased mRNA expression of genes of the TLR4 signaling complex (TLR4, CD14, MD-2, and MyD88) and the NADPH complexes (p47phox, p67phox, gp91phox, and p22phox) was induced by priming with P. acnes or TLR9 plus TLR2 suggesting mechanisms for LPS sensitization and liver injury.

CONCLUSIONS

TLR9+/-TLR2 activation via MyD88-dependent pathways plays a pivotal role in liver sensitization and granuloma formation.

Avian hepatic granuloma. A review

Hepatic granuloma is a chronic inflammatory disease characterized by a granulomatous reaction with accumulation of macrophages and/or epithelioid cells, which may fuse to form multinucleated giant cells. The hepatic granulomas typically have a surrounding rim of lymphocytes and fibrous tissues. The etiology of some hepatic granulomas in birds is well known. It could be due to viral, bacterial, fungal, protozoal, or helminthic infection. The presence of these pathogens in the liver is usually through systemic infections that might preferentially colonize the liver or be opportunistic invaders. Persistence of these pathogens infecting the liver can lead to granulomatous inflammation with different gross lesions and histopathologic patterns depending on the causative agent. This review describes the etiology, clinical signs, pathological changes, and diagnosis in a wide variety of diseases associated with hepatic granulomas in birds in which the detection of granulomatous inflammation is an aid in the differential diagnosis.