The Antidepressant Mirtazapine Inhibits Hepatic Innate Immune Networks to Attenuate Immune-Mediated Liver Injury in Mice

Activation of the innate immune system, including tissue macrophages and associated neutrophil infiltration, is an important driver of subsequent adaptive immune responses in many autoimmune diseases, including autoimmune hepatitis (AIH). The antidepressant mirtazapine has a unique complex pharmacology, altering signaling through a number of serotonin and histamine receptors that can impact macrophage function; an effect potentially influencing AIH outcome. In the mouse model of concanavalin A (Con A) induced liver injury (mimics many aspects of human AIH), in which early innate immune activation (i.e., stimulated hepatic macrophages/monocytes recruit neutrophils and additional monocytes to the liver) critically drives immune-mediated hepatitis induction, mirtazapine strikingly and dose-dependently inhibited Con A-induced liver injury. This inflammation-suppressing effect of mirtazapine was linked to an attenuation of Con A-stimulated early innate immune responses within the liver, including inhibition of hepatic macrophage/monocyte activation, decreased hepatic macrophage/monocyte-derived pro-inflammatory cytokine (e.g., TNFα) and chemokine (e.g., CXCL1 and CXCL2) production, suppression of Con A-induced increases in the hepatic expression of the neutrophil relevant endothelial cell adhesion molecule ICAM-1, with the resultant significant reduction in neutrophil recruitment into the liver. Consistent with our findings in the Con A model, mirtazapine also significantly reduced activation-induced release of cytokine/chemokine mediators from human CD14+ monocytes in vitro.Conclusion: Our data suggest that mirtazapine can attenuate hepatic innate immune responses that critically regulate the subsequent development of autoimmune liver injury. Therefore, given that it is a safe and widely used medication, mirtazapine may represent a novel therapeutic approach to autoimmune liver disease

Regulatory Immune-Responses Occurring within the Liver Downstream of Hepatic iNKTcell activation

Despite its` high prevalence, the pathogenesis of immune-mediated liver injury is poorly understood. Invariant Natural killer T (iNKT) cells are a distinct innate immune T cell believed to orchestrate a balance between pro-and-anti-inflammatory responses within the liver during immune mediated liver injury. However, the regulatory roles of iNKT cells in the modulation of the hepatic immune response are still poorly defined. In this work we utilized the alpha-galactosylceramide-induced hepatitis model, a model of specific iNKT cell activation, to help us dissect basic immune regulatory mechanisms occurring in the liver during hepatic innate immune activation. We have now documented the rapid recruitment and activation of innate-like regulatory B cells in the liver subsequent to iNKT cell activation. These regulatory B cells were recruited from the spleen and peritoneum. Moreover, depletion of B cells exacerbated iNKT cell-driven liver injury, in association with a profound alteration in the hepatic cytokine milieu and enhanced neutrophil recruitment. This suppression of hepatic inflammation was IL-10 and TGFβ1 independent, and involved activity of ecto-5'-nucleotidase/CD73. IL-22 is an innate cytokine which has been broadly implicated in the regulation of hepatic immunity, and IL-22BP is a secreted specific IL-22 antagonist. In our second paper, we found that activation of hepatic iNKT cells led to the striking, parallel early recruitment of both IL-22 and IL-22BP producing immune cells. Additionally, we found a marked increase in the hepatic expression of both IL-22BP and IL-22R1 in liver biopsies obtained from patients with viral and autoimmune liver diseases compared to normal livers. We also found that the inflammasome plays an important role in regulating IL-22BP expression within liver recruited immune cells and hepatocytes. In this dissertation we have uncovered previously unrecognized regulatory mechanisms induced by activated iNKT cells within the liver. These findings give insight into pathological changes occurring in various human liver diseases in which iNKT cells have been implicated, and in which liver injury is immune-mediated. These findings could potentially be used to develop new regulatory B-cell-based and/or cytokine-based therapies to beneficially alter hepatic innate immune responses in patients suffering with immune-mediated liver diseases

Effects of prostaglandin D₂ and the DP₁ and DP₂ receptors in eosinophil recruitment into the Brown Norway rat lungs

The accumulation of eosinophils at sites of inflammation is one of the hallmarks of asthma. The aim of the present study was to investigate the involvement of PGD2 and the DP1 and DP2 receptors in eosinophil recruitment in vivo. In this project, a group of Brown Norway rats were administered intratracheally with PGD2, which activates both DP1 and DP2 receptors, as well as selective agonists of DP1 (BW245C) and DP2 (15R-methyl-PGD 2 and 13,14-dihydro-15-oxo-PGD2) receptors. In addition, we have also tested the effect of 15-deoxy-Delta12,14-PGJ 2 which known to activate PPARgamma and NF-kappaB, and DP2 receptors. Negative control animals received saline alone while positive control animals received 5-oxo-ETE. In this work, we have shown for the first time that PGD2 and selective DP2 receptor agonists induce pulmonary eosinophilia in vivo in the following order of potency; (15R-methyl-PGD 2 > PGD2 ≈ 15-deoxy-Delta12,14-PGJ 2 > dhk-PGD2). This effect was time dependent with the maximal response being observed after 24 h. Interestingly; this response was somehow diminished when higher dose was tested (10mug). This effect is most likely to be mediated solely through the DP2 receptor since this effect was not shared by the DP1 specific agonist BW245C. These results are consistent with an important role for PGD2 and the DP 2 receptor/CRTH2 in allergic diseases such as asthma and suggest that this receptor may be an important therapeutic target for these conditions

The impact of depression and antidepressant usage on primary biliary cholangitis clinical outcomes.

Depression is prevalent in primary biliary cholangitis (PBC) patients. Our aims were to examine the effects of depression and antidepressants on hepatic outcomes of PBC patients.We used the UK Health Improvement Network database to identify PBC patients between 1974 and 2007. Our primary outcome was one of three clinical events: decompensated cirrhosis, liver transplantation and death. We assessed depression and each class of antidepressant medication in adjusted multivariate Cox proportional hazards models to identify independent predictors of outcomes. In a sensitivity analysis, the study population was restricted to PBC patients using ursodeoxycholic acid (UDCA).We identified 1,177 PBC patients during our study period. In our cohort, 86 patients (7.3%) had a depression diagnosis prior to PBC diagnosis, while 79 patients (6.7%) had a depression diagnosis after PBC diagnosis. Ten-year incidence of mortality, decompensated cirrhosis, and liver transplantation were 13.4%, 6.6%, and 2.0%, respectively. In our adjusted models, depression status was not a predictor of poor outcomes. After studying all classes of antidepressants, using the atypical antidepressant mirtazapine after PBC diagnosis was significantly protective (Adjusted HR 0.23: 95% CI 0.07-0.72) against poor liver outcomes (decompensation, liver transplant, mortality), which remained statistically significant in patients using UCDA (HR 0.21: 95% CI 0.05-0.83).In our study, depression was not associated with poor clinical outcomes. However, using the antidepressant mirtazapine was associated with decreased mortality, decompensated cirrhosis and liver transplantation in PBC patients. These findings support further assessment of mirtazapine as a potential treatment for PBC patients

Supplementary Material for: TNFα Augments Cytokine-Induced NK Cell IFNγ Production through TNFR2

<p>NK cells play a central role in innate immunity, acting directly through cell-mediated cytotoxicity and by secreting cytokines. TNFα activation of TNFR2 enhances NK cell cytotoxicity, but its effects on the other essential function of NK cells - cytokine production, for which IFNγ is paramount - are poorly defined. We identify the expression of both TNFα receptors on human peripheral blood NK cells (TNFR2 > TNFR1) and show that TNFα significantly augments IFNγ production from IL-2-/IL-12-treated NK cells in vitro, an effect mimicked by a TNFR2 agonistic antibody. TNFα also enhanced murine NK cell IFNγ production via TNFR2 in vitro. In a mouse model characterized by the hepatic recruitment and activation of NK cells, TNFR2 also regulated NK cell IFNγ production in vivo. Specifically, in this model, after activation of an innate immune response, hepatic numbers of TNFR2-expressing and IFNγ-producing NK cells were both significantly increased; however, the frequency of IFNγ-producing hepatic NK cells was significantly reduced in TNFR2-deficient mice. We delineate an important role for TNFα, acting through TNFR2, in augmenting cytokine-induced NK cell IFNγ production in vivo and in vitro, an effect with significant potential implications for the regulation of innate and adaptive immune responses.</p

Recruitment of α4β7 monocytes and neutrophils to the brain in experimental colitis is associated with elevated cytokines and anxiety-like behavior

Abstract Background Behavioral comorbidities, such as anxiety and depression, are a prominent feature of IBD. The signals from the inflamed gut that cause changes in the brain leading to these behavioral comorbidities remain to be fully elucidated. We tested the hypothesis that enhanced leukocyte–cerebral endothelial cell interactions occur in the brain in experimental colitis, mediated by α4β7 integrin, to initiate neuroimmune activation and anxiety-like behavior. Methods Female mice treated with dextran sodium sulfate were studied at the peak of acute colitis. Circulating leukocyte populations were determined using flow cytometry. Leukocyte–cerebral endothelial cell interactions were examined using intravital microscopy in mice treated with anti-integrin antibodies. Brain cytokine and chemokines were assessed using a multiplex assay in animals treated with anti-α4β7 integrin. Anxiety-like behavior was assessed using an elevated plus maze in animals after treatment with an intracerebroventricular injection of interleukin 1 receptor antagonist. Results The proportion of classical monocytes expressing α4β7 integrin was increased in peripheral blood of mice with colitis. An increase in the number of rolling and adherent leukocytes on cerebral endothelial cells was observed, the majority of which were neutrophils. Treatment with anti-α4β7 integrin significantly reduced the number of rolling leukocytes. After anti-Ly6C treatment to deplete monocytes, the number of rolling and adhering neutrophils was significantly reduced in mice with colitis. Interleukin-1β and CCL2 levels were elevated in the brain and treatment with anti-α4β7 significantly reduced them. Enhanced anxiety-like behavior in mice with colitis was reversed by treatment with interleukin 1 receptor antagonist. Conclusions In experimental colitis, α4β7 integrin-expressing monocytes direct the recruitment of neutrophils to the cerebral vasculature, leading to elevated cytokine levels. Increased interleukin-1β mediates anxiety-like behavior

Flow diagram of identified PBC patients in The Health Improvement Network between April 1974 and May 2007.

<p>Flow diagram of identified PBC patients in The Health Improvement Network between April 1974 and May 2007.</p

Kaplan-meier curves indicating 10-year decompensation, liver transplant and mortality free survival among PBC patients according to mirtazapine usage.

<p>Kaplan-meier curves indicating 10-year decompensation, liver transplant and mortality free survival among PBC patients according to mirtazapine usage.</p