Testosterone affects type I/type II interferon response of neutrophils during hepatic amebiasis.

Differences in immune response between men and women may influence the outcome of infectious diseases. Intestinal infection with Entamoeba histolytica leads to hepatic amebiasis, which is more common in males. Previously, we reported that innate immune cells contribute to liver damage in males in the murine model for hepatic amebiasis. Here, we focused on the influences of sex and androgens on neutrophils in particular. Infection associated with neutrophil accumulation in the liver was higher in male than in female mice and further increased after testosterone treatment in both sexes. Compared with female neutrophils, male neutrophils exhibit a more immature and less activated status, as evidenced by a lower proinflammatory N1-like phenotype and deconvolution, decreased gene expression of type I and type II interferon stimulated genes (ISGs) as well as downregulation of signaling pathways related to neutrophil activation. Neutrophils from females showed higher protein expression of the type I ISG viperin/RSAD2 during infection, which decreased by testosterone substitution. Moreover, ex vivo stimulation of human neutrophils revealed lower production of RSAD2 in neutrophils from men compared with women. These findings indicate that sex-specific effects on neutrophil physiology associated with maturation and type I IFN responsiveness might be important in the outcome of hepatic amebiasis.

The Properties of Proinflammatory Ly6Chi Monocytes Are Differentially Shaped by Parasitic and Bacterial Liver Infections.

In the past, proinflammatory CD11b+Ly6Chi monocytes were predominantly considered as a uniform population. However, recent investigations suggests that this population is far more diverse than previously thought. For example, in mouse models of Entamoeba (E.) histolytica and Listeria (L.) monocytogenes liver infections, it was shown that their absence had opposite effects. In the former model, it ameliorated parasite-dependent liver injury, whereas in the listeria model it exacerbated liver pathology. Here, we analyzed Ly6Chi monocytes from the liver of both infection models at transcriptome, protein, and functional levels. Paralleled by E. histolytica- and L. monocytogenes-specific differences in recruitment-relevant chemokines, both infections induced accumulation of Ly6C+ monocytes at infection sites. Transcriptomic analysis revealed a high similarity between monocytes from naïve and parasite-infected mice and a clear proinflammatory phenotype of listeria-induced monocytes. This was further reflected by the upregulation of M2-related transcription factors (e.g., Mafb, Nr4a1, Fos) and higher CD14 expression by Ly6Chi monocytes in the E. histolytica infection model. In contrast, monocytes from the listeria infection model expressed M1-related transcription factors (e.g., Irf2, Mndal, Ifi204) and showed higher expression of CD38, CD74, and CD86, as well as higher ROS production. Taken together, proinflammatory Ly6Chi monocytes vary considerably depending on the causative pathogen. By using markers identified in the study, Ly6Chi monocytes can be further subdivided into different populations.

HIF-1α modulates sex-specific Th17/Treg responses during hepatic amoebiasis.

BACKGROUND & AIMS: An invasive form of intestinal Entamoeba (E.) histolytica infection, which causes amoebic liver abscess, is more common in men than in women. Immunopathological mechanisms are responsible for the more severe outcome in males. Here, we used a mouse model of hepatic amoebiasis to investigate the contribution of hepatic hypoxia-inducible factor (HIF)-1α to T helper 17 (Th17)/regulatory T cell (Treg) responses in the context of the sex-specific outcome of liver damage. METHODS: C57BL/6J mice were infected intrahepatically with E. histolytica trophozoites. HIF-1α expression was determined by qPCR, flow cytometry and immunohistochemistry. Tregs and Th17 cells were analysed by immunohistochemistry and flow cytometry. Finally, male and female hepatocyte-specific Hif1α knockout mice were generated, and the effect of HIF-1α on abscess development, the cytokine milieu, and Th17/Treg differentiation was examined. RESULTS: E. histolytica infection increased hepatic HIF-1α levels, along with the elevated frequencies of hepatic Th17 and Treg cells. While the Th17 cell population was larger in male mice, Tregs characterised by increased expression of Foxp3 in female mice. Male mice displayed increased IL-6 expression, contributing to immunopathology; this increase in IL-6 expression declined upon deletion of hepatic HIF-1α. In both sexes, hepatic deletion of HIF-1α reduced the Th17 cell frequency; however, the percentage of Tregs was reduced in female mice only. CONCLUSIONS: Hepatic HIF-1α modulates the sex-specific outcome of murine E. histolytica infection. Our results suggest that in male mice, Th17 cells can be modulated by hepatic HIF-1α via IL-6, indicating marked involvement in the immunopathology underlying abscess development. Strong expression of Foxp3 by hepatic Tregs from female mice suggests a potent immunosuppressive function, leading to initiation of liver regeneration. LAY SUMMARY: Infection with the parasite Entamoeba histolytica activates immunopathological mechanisms in male mice, which lead to liver abscesses that are larger than those in female mice. In the absence of the protein HIF-1α in hepatocytes, abscess formation is reduced; moreover, the sex difference in abscess size is abolished. These results suggest that HIF-1α modulates the immune response involved in the induction of immunopathology, resulting in differential disease susceptibility in males and females.

Monocyte dysregulation: consequences for hepatic infections.

Liver disorders due to infections are a substantial health concern in underdeveloped and industrialized countries. This includes not only hepatotropic viruses (e.g., hepatitis B, hepatitis C) but also bacterial and parasitic infections such as amebiasis, leishmaniasis, schistosomiasis, or echinococcosis. Recent studies of the immune mechanisms underlying liver disease show that monocytes play an essential role in determining patient outcomes. Monocytes are derived from the mononuclear phagocyte lineage in the bone marrow and are present in nearly all tissues of the body; these cells function as part of the early innate immune response that reacts to challenge by external pathogens. Due to their special ability to develop into tissue macrophages and dendritic cells and to change from an inflammatory to an anti-inflammatory phenotype, monocytes play a pivotal role in infectious and non-infectious liver diseases: they can maintain inflammation and support resolution of inflammation. Therefore, tight regulation of monocyte recruitment and termination of monocyte-driven immune responses in the liver is prerequisite to appropriate healing of organ damage. In this review, we discuss monocyte-dependent immune mechanisms underlying hepatic infectious disorders. Better understanding of these immune mechanisms may lead to development of new interventions to treat acute liver disease and prevent progression to organ failure.

Androgens predispose males to monocyte-mediated immunopathology by inducing the expression of leukocyte recruitment factor CXCL1.

Hepatic amebiasis, predominantly occurring in men, is a focal destruction of the liver due to the invading protozoan Entamoeba histolytica. Classical monocytes as well as testosterone are identified to have important functions for the development of hepatic amebiasis in mice, but a link between testosterone and monocytes has not been identified. Here we show that testosterone treatment induces proinflammatory responses in human and mouse classical monocytes. When treated with 5α-dihydrotestosterone, a strong androgen receptor ligand, human classical monocytes increase CXCL1 production in the presence of Entamoeba histolytica antigens. Moreover, plasma testosterone levels of individuals undergoing transgender procedure correlate positively with the TNF and CXCL1 secretion from their cultured peripheral blood mononuclear cells following lipopolysaccharide stimulation. Finally, testosterone substitution of castrated male mice increases the frequency of TNF/CXCL1-producing classical monocytes during hepatic amebiasis, supporting the hypothesis that the effects of androgens may contribute to an increased risk of developing monocyte-mediated pathologies.

Antileishmanial Effects of Synthetic EhPIb Analogs Derived from the Entamoeba histolytica Lipopeptidephosphoglycan.

With an estimated number of new cases annually of approximately 1.4 million, leishmaniasis belongs to the most important parasitic diseases in the world. Nevertheless, existing drugs against leishmaniasis in general have several drawbacks that urgently necessitate new drug development. A glycolipid molecule of the intestinal protozoan parasite Entamoeba histolytica and its synthetic analogs previously showed considerable immunotherapeutic effects against Leishmania major infection. Here, we designed and synthesized a series of new immunostimulatory compounds derived from the phosphatidylinositol b anchor of Entamoeba histolytica (EhPIb) subunit of the native compound and investigated their antileishmanial activity in vitro and in vivo in a murine model of cutaneous leishmaniasis. The new synthetic EhPIb analogs showed almost no toxicity in vitro Treatment with the analogs significantly decreased the parasite load in murine and human macrophages in vitro In addition, topical application of the EhPIb analog Eh-1 significantly reduced cutaneous lesions in the murine model, correlating with an increase in the production of selected Th1 cytokines. In addition, we could show in in vitro experiments that treatment with Eh-1 led to a decrease in mRNA expression of arginase-1 (Arg1) and interleukin 4 (IL-4), which are required by the parasites to circumvent their elimination by the immune response. The use of the host-targeting synthetic EhPIb compounds, either alone or in combination therapy with antiparasitic drugs, shows promise for treating cutaneous leishmaniasis and therefore might improve the current unsatisfactory status of chemotherapy against this infectious disease.

Androgen-dependent immune modulation in parasitic infection.

Parasitic infections modulate the immune system of the host, resulting in either immune tolerance or the induction of pro-inflammatory defense mechanisms against the pathogen. In both cases, sex hormones are involved in the regulation of the immune response, as they are present in the systemic circulation and can act on a wide variety of cell types, including immune cells. Men and women have a different milieu of sex hormones, and these hormones play a role in determining immune responses to parasitic infections. Men, who have higher plasma levels of androgens than women, are generally more susceptible to parasitic infections. Many immune cells express the androgen receptor (AR), and the immunologic functions of these cells can be modulated by androgens. In this review, we will highlight the immune cell types that are sensitive to male steroid hormones and describe their roles during three parasitic diseases, amebiasis, leishmaniasis, and helminthiasis.