Understanding sex biases in immunity: effects of estrogen on the differentiation and function of antigen-presenting cells

The sex bias in systemic sclerosis: on the possible mechanisms underlying the female disease preponderance

Systemic sclerosis is a multifactorial and heterogeneous disease. Genetic and environmental factors are known to interplay in the onset and progression of systemic sclerosis. Sex plays an important and determinant role in the development of such a disorder. Systemic sclerosis shows a significant female preponderance. However, the reason for this female preponderance is incompletely understood. Hormonal status, genetic and epigenetic differences, and lifestyle have been considered in order to explain female preponderance in systemic sclerosis. Sex chromosomes play a determinant role in contributing to systemic sclerosis onset and progression, as well as in its sex-biased prevalence. It is known, in fact, that X chromosome contains many sex- and immuno-related genes, thus contributing to immuno tolerance and sex hormone status. This review focuses mainly on the recent progress on epigenetic mechanisms--exclusively linked to the X chromosome--which would contribute to the development of systemic sclerosis. Furthermore, we report also some hypotheses (dealing with skewed X chromosome inactivation, X gene reactivation, acquired monosomy) that have been proposed in order to justify the female preponderance in autoimmune diseases. However, despite the intensive efforts in elucidating the mechanisms involved in the pathogenesis of systemic sclerosis, many questions remain still unanswered.

Estrogen receptor agonists for attenuation of neuroinflammation and neurodegeneration

Recent results from laboratory investigations and clinical trials indicate important roles for estrogen receptor (ER) agonists in protecting the central nervous system (CNS) from noxious consequences of neuroinflammation and neurodegeneration. Neurodegenerative processes in several CNS disorders including spinal cord injury (SCI), multiple sclerosis (MS), Parkinson's disease (PD), and Alzheimer's disease (AD) are associated with activation of microglia and astrocytes, which drive the resident neuroinflammatory response. During neurodegenerative processes, activated microglia and astrocytes cause deleterious effects on surrounding neurons. The inhibitory activity of ER agonists on microglia activation might be a beneficial therapeutic option for delaying the onset or progression of neurodegenerative injuries and diseases. Recent studies suggest that ER agonists can provide neuroprotection by modulation of cell survival mechanisms, synaptic reorganization, regenerative responses to axonal injury, and neurogenesis process. The anti-inflammatory and neuroprotective actions of ER agonists are mediated mainly via two ERs known as ERα and ERβ. Although some studies have suggested that ER agonists may be deleterious to some neuronal populations, the potential clinical benefits of ER agonists for augmenting cognitive function may triumph over the associated side effects. Also, understanding the modulatory activities of ER agonists on inflammatory pathways will possibly lead to the development of selective anti-inflammatory molecules with neuroprotective roles in different CNS disorders such as SCI, MS, PD, and AD in humans. Future studies should be concentrated on finding the most plausible molecular pathways for enhancing protective functions of ER agonists in treating neuroinflammatory and neurodegenerative injuries and diseases in the CNS.

Chronic schizophrenia is associated with over-expression of the interleukin-2 receptor gamma gene

Altered immune response, including low-grade inflammatory processes, is involved in the pathogenesis of schizophrenia, a chronic psychiatric disorder with complex etiology. Distinct gene variants of a number of pro-inflammatory and chemotactic cytokines together with their receptors associate with this disorder. Interleukin-2 receptor gamma (IL-2RG) represents an important signaling component of many interleukin receptors and so far, no data on the functional state of this receptor in schizophrenia have been reported. The aim of this study was to investigate mRNA expression of the IL2RG gene (IL2RG) in schizophrenia patients in comparison with healthy subjects (controls). Total RNA was isolated from peripheral blood of 66 schizophrenia patients and 99 healthy subjects of Armenian population. The mRNA expression was determined by quantitative real-time polymerase chain reaction (RT-PCR) using PSMB2 as housekeeping gene. IL2RG mRNA expression was upregulated in peripheral blood of patients in comparison with controls (patients vs. controls, median [interquartile range]: 2.080 [3.428-1.046] vs. 0.324 [0.856-0.000], p<0.0001). In conclusion, our findings suggest that over-expression of the IL2RG gene may be implicated in altered immune response in schizophrenia and contribute to the pathomechanisms of this disorder.

Sequential episodes of dengue--Puerto Rico, 2005-2010

Of 53,633 suspected dengue cases reported to a passive dengue surveillance system in Puerto Rico during 2005-2010, 949 individuals were reported on more than one occasion and 21 had laboratory-confirmed dengue on two separate occasions. Median time between illness episodes was 2.9 years (range: 62 days-5.3 years). Seventeen (81%) individuals with sequential episodes of dengue were male, and seven (33%) were adults. All 21 individuals experienced one episode and seven (33%) individuals experienced both episodes during a large epidemic that occurred in 2010. These observations show that heterotypic dengue virus immunity that protects against illness may have considerable variability but typically does not last longer than 3 years.

The role of estrogen signaling in a mouse model of inflammatory bowel disease: a Helicobacter hepaticus model

The pathogenesis of inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis, is due in part to interactions between the immune system, genetics, the environment, and endogenous microbiota. Gonadal sex hormones (GSH), such as estrogen, are thought to be involved in the development of IBD as variations in disease severity occur during pregnancy, menopause, or oral contraceptives use. In certain strains of mice, infection with Helicobacter hepaticus triggers IBD-like mucosal inflammation that is more severe in female mice than in males, suggesting a role for GSH in this model. To determine the role of estrogen signaling in microbiota-induced intestinal inflammation, estrogen receptor (ER) α and β knock-out (KO) mice, ER agonists, and adoptive transfers were utilized. We demonstrate that, when signaling is limited to ERβ on a non-CD4⁺ cell subset, disease is less severe and this correlates with decreased expression of pro-inflammatory mediators.

Dendrogenin A arises from cholesterol and histamine metabolism and shows cell differentiation and anti-tumour properties

We previously synthesized dendrogenin A and hypothesized that it could be a natural metabolite occurring in mammals. Here we explore this hypothesis and report the discovery of dendrogenin A in mammalian tissues and normal cells as an enzymatic product of the conjugation of 5,6α-epoxy-cholesterol and histamine. Dendrogenin A was not detected in cancer cell lines and was fivefold lower in human breast tumours compared with normal tissues, suggesting a deregulation of dendrogenin A metabolism during carcinogenesis. We established that dendrogenin A is a selective inhibitor of cholesterol epoxide hydrolase and it triggered tumour re-differentiation and growth control in mice and improved animal survival. The properties of dendrogenin A and its decreased level in tumours suggest a physiological function in maintaining cell integrity and differentiation. The discovery of dendrogenin A reveals a new metabolic pathway at the crossroads of cholesterol and histamine metabolism and the existence of steroidal alkaloids in mammals.

It has been hypothesized that the steroidal alkaloid dendrogenin A (DDA) is a natural metabolite. de Medina et al. show that DDA is produced in mammalian tissues from 5,6α-epoxy-cholesterol and histamine metabolism, and that the compound displays cell differentiation and anti-tumour activities.

Estrogen signaling through the G protein-coupled estrogen receptor regulates granulocyte activation in fish

Neutrophils are major participants in innate host responses. It is well known that estrogens have an immune-modulatory role, and some evidence exists that neutrophil physiology can be altered by these molecules. Traditionally, estrogens act via classical nuclear estrogen receptors, but the identification of a G protein-coupled estrogen receptor (GPER), a membrane estrogen receptor that binds estradiol and other estrogens, has opened up the possibility of exploring additional estrogen-mediated effects. However, information on the importance of GPER for immunity, especially, in neutrophils is scant. In this study, we report that gilthead seabream (Sparus aurata L.) acidophilic granulocytes, which are the functional equivalent of mammalian neutrophils, express GPER at both mRNA and protein levels. By using a GPER selective agonist, G1, it was found that GPER activation in vitro slightly reduced the respiratory burst of acidophilic granulocytes and drastically altered the expression profile of several genes encoding major pro- and anti-inflammatory mediators. In addition, GPER signaling in vivo modulated adaptive immunity. Finally, a cAMP analog mimicked the effects of G1 in the induction of the gene coding for PG-endoperoxide synthase 2 and in the induction of CREB phosphorylation, whereas pharmacological inhibition of protein kinase A superinduced PG-endoperoxide synthase 2. Taken together, our results demonstrate for the first time, to our knowledge, that estrogens are able to modulate vertebrate granulocyte functions through a GPER/cAMP/protein kinase A/CREB signaling pathway and could establish therapeutic targets for several immune disorders in which estrogens play a prominent role.

Ovarian steroid hormones: effects on immune responses and Chlamydia trachomatis infections of the female genital tract

Female sex hormones are known to regulate the adaptive and innate immune functions of the female reproductive tract. This review aims to update our current knowledge of the effects of the sex hormones estradiol and progesterone in the female reproductive tract on innate immunity, antigen presentation, specific immune responses, antibody secretion, genital tract infections caused by Chlamydia trachomatis, and vaccine-induced immunity.

Age-matched dendritic cell subpopulations reference values in childhood

Dendritic cells (DCs) are the most potent antigen-presenting cells and are the key link between the innate and adaptive immune response. Only a few reports with study populations of up to 50 individuals have been published with age-based reference values for DC subpopulations in healthy children. Therefore, we aimed to establish reference ranges in a larger study population of 100 healthy children, which allowed age-matched subgroups. Most previous studies were performed using a dual-platform approach. In this study, a single-platform approach in a lyse no-wash procedure was used. DC subpopulations were defined as follows: CD45(+) CD85k(+) HLA-DR(+) CD14(-) CD16(-) CD33(+) cells as myeloid DCs (mDCs) and CD45(+) CD85k(+) HLA-DR(+) CD14(-) CD16(-) CD123(+) cells as plasmacytoid DCs (pDCs). Reference ranges were established using a semi-parametric regression of age-matched absolute and relative DC counts. We found a significant decline with increasing age in the medians of mDCs (P = 0.0003) and pDCs per μl peripheral blood (PB) (P = 0.004) and in the 50%, 90% and 95% reference ranges. We also identified significantly lower absolute cell counts of mDCs per μl PB in girls than in boys for all age groups (P = 0.0015). Due to the larger paediatric study population and single-platform approach, this study may give a more precise overview of the normal age-matched development of DC subpopulations and may provide a basis for analyzing abnormal DC counts in different illnesses or therapies such as post stem cell transplantation.

Impact of microbes on autoimmune diseases

Autoimmune and autoinflammatory diseases arise as a consequence of complex interactions of environmental factors with genetic traits. Although specific allelic variations cluster in predisposed individuals and promote the generation and/or expansion of autoreactive T and B lymphocytes, autoimmunity appears in various disease phenotypes and localizes to diverging tissues. Furthermore, the discovery that allelic variations within genes encoding components of the innate immune system drive self-reactive immune responses as well, led to the distinction of immune responses against host tissues into autoimmune and autoinflammatory diseases. In both categories of disorders, different pathogenic mechanisms and/or subsequent orders of tissue assaults may underlie the target cell specificity of the respective autoimmune attack. Furthermore, the transition from the initial tissue assault to the development of full-blown disease is likely driven by several factors. Thus, the development of specific forms of autoimmunity and autoinflammation reflects a multi-factorial process. The delineation of the specific factors involved in the pathogenic process is hampered by the fact that certain symptoms are assembled under the umbrella of a specific disease, although they might originate from diverging pathogenic pathways. These multi-factorial triggers and pathogenic pathways may also explain the inter-individual divergent courses and outcomes of diseases among humans. Here, we will discuss the impact of different environmental factors in general and microbial pathogens in particular on the regulation/expression of genes encoded within susceptibility alleles, and its consequences on subsequent autoimmune and/or autoinflammatory tissue damage utilizing primarily the chronic cholestatic liver disease primary biliary cirrhosis as model.

Regulation of the immune response by soybean isoflavones

Soybeans are rich in immuno-modulatory isoflavones such as genistein, daidzein, and glycitein. These isoflavones are well-known antioxidants, chemopreventive and anti-inflammatory agents. Several epidemiological studies suggest that consumption of traditional soy food containing isoflavones is associated with reduced prevalence of chronic health disorders. Isoflavones are considered to be phytoestrogens because of their ability to bind to estrogen receptors. The literature is extensive on the chemistry, bio-availability, and bio-activity of isoflavones. However, their effects on immune response are yet to be fully understood, but are beginning to be appreciated. We review the role of isoflavones in regulation of the immune response and their potential clinical applications in immune-dysfunction. Special emphasis will be made regarding in vivo studies including humans and animal model systems.

B cells as effectors and regulators of sex-biased arthritis

B cells have been implicated both with pathogenic as well as protective capabilities in induction and regulation of autoimmune diseases. Rheumatoid arthritis (RA) is an autoimmune disease that occurs more often in women than men. A significant role of B cells as antibody producing and antigen-presenting cells has been demonstrated in RA. Predisposition to RA is associated with the presence of certain HLA class II alleles that share sequences with DRB1*0401. To determine the role of HLA genes and B cells in vivo, we have generated transgenic mice carrying HLA genes, DRB1*0401 and DQ8, known to be associated with susceptibility to RA. Humanized mice can be induced to develop arthritis that mimics human disease in clinical, histopathological and sex bias. Effect of hormones on immune cells and their function has been described in humans and mice and has been suggested to be the major reason for female bias of autoimmune diseases. An immune response to an antigen requires presentation by HLA molecules thus suggesting a critical role of MHC in combination with sex hormones in susceptibility to develop rheumatoid arthritis. Based on our observations, we hypothesize that modulation of B cells by estrogen, presentation of modified antigens by DR4 and production of antigen-specific B cell modulating cytokines leads to autoreactivity in females. These data suggest that considering patient's sex may be crucial in selecting the optimal treatment strategy. Humanized mice expressing RA susceptible and resistant haplotype provide a means to investigate mechanism sex-bias of arthritis and future strategies for therapy.

Expression pattern and signalling pathways in neutrophil like HL-60 cells after treatment with estrogen receptor selective ligands

Estrogens play a role in the regulation of genes associated with inflammation and immunity in neutrophils. Estrogen signalling is mediated by estrogen receptor (ER)α, ERβ, and G-protein-coupled estrogen receptor-1 (GPER). The mechanisms by which estrogen regulate genes in neutrophils are poorly understood. Our aim was to identify the presence of ERs and to characterize estrogen responsive genes in terminally differentiated neutrophil like HL-60 (nHL-60) cells using estradiol and selective ER agonists. ERs were identified by Western blotting and immunocytochemistry. Microarray technique was used to screen for differentially expressed genes and the selected genes were verified by quantitative PCR. We show the presence of functional ERα, ERβ and GPER. Microarray analysis showed the presence of genes that are uniquely regulated by a single ligand and also genes that are regulated by multiple ligands. We conclude that ERs are functionally active in nHL-60 cells regulating genes involved in key physiological functions.

No evidence that estrogens affect the development of the immune system in the red-eared slider turtle, Trachemys scripta

Exposure to maternally derived substances during development can affect offspring phenotype. In ovo exposure to maternally derived steroids has been shown to influence traits such as growth and behavior in the offspring. The development of the immune system also can be altered by exposure to both androgens and glucocorticoids in a variety of species, but much less is known about the potential for estrogens to influence the development of this system. We examined the effect of estradiol on the development of both innate and adaptive immune components in the red-eared slider turtle (Trachemys scripta). A bacterial killing assay was used to assess innate immunity, a delayed-type hypersensitivity test for cellular immunity, and total immunoglobulin levels to measure the humoral immune response. We found no effect of in ovo estradiol treatment on any of our immune measures despite using doses that are known to influence other phenotypic parameters during development and varying the timing of dosing across development. Our results suggest that maternally derived estradiol does not affect the development of the immune system in T. scripta.

Effects of some endocrine disruptors on cell cycle progression and murine dendritic cell differentiation

Endocrine disruptor chemicals (EDCs), which are predominantly present in the environment, are able to mimic or antagonise the biological activity of hormones primarily through the interaction with specific receptors. The main consequences are adverse effects on the growth and development of reproductive organs, the induction of cancer and effects on neuronal differentiation. In this study, we investigated the ability of certain EDCs, Bisphenol A (BPA), Bisphenol B (BPB), Bisphenol F (BPF), 4-n Nonylphenol (NP) and Octylphenol (OP), belonging to a homogeneous group of phenol origin, to interfere with specific cellular processes, namely, proliferation, by using MCF-7 breast carcinoma cells, and differentiation, by using murine bone marrow dendritic cells. We correlated the data on cell growth with the stimulation of cell cycle progression, which could become a step in the development of cancer, and we established a proliferation ranking between the tested EDCs: NP>BPA>OP>BPB>BPF. In addition, we investigated the ability of NP, BPA and OP to induce the differentiation of dendritic cells, the powerful antigen-presenting cells of the immune system. The differentiation and activation of these cells could affect a well-regulated immune response and determine an allergic sensitisation. We found that BPA and NP were active in determining differentiation.

Influenza vaccination in patients with pulmonary sarcoidosis: efficacy and safety

BACKGROUND

Sarcoidosis is an inflammatory, granulomatous disorder of unknown etiology. The role of cellular and humoral immune systems in this disease is unclear, whereas dysregulation of the immune system is suggested. Patients with sarcoidosis show diverse responses while exposed to various antigens. Although influenza vaccination is recommended in pulmonary sarcoidosis, its efficacy and safety has not been investigated.

OBJECTIVES

  To evaluate safety and immunogenicity of influenza vaccine in patients with sarcoidosis.

PATIENTS/METHODS

Influenza vaccination was performed in 23 eligible patients with sarcoidosis (SP) and 26 healthy controls (HC). Antibody titers against H1N1, H3N2, and B influenza virus antigens were evaluated just before and 1 month after vaccination. Patients were followed for 6 months to assess vaccine safety.

RESULTS

Serological response and magnitude of changes in antibody titers against influenza vaccine antigens were comparable between SPs and HCs. Women showed a better serological response against B antigen (P = 0·034) than men. Twenty-four-hour urine calcium was associated with antibody response against H1N1 [correlation coefficient (CC) = 0·477, P = 0·003] and H3N2 (CC = 0·352, P = 0·028) antigens. Serum angiotensin-converting enzyme correlated negatively with antibody response against B antigen (CC = -0·331, P = 0·040). Higher residual volume was associated with fewer rises in antibody titer against H3N2 antigen (CC = -0·377, P = 0·035). No major adverse events or disease flare-up was observed during follow-up.

CONCLUSIONS

In this study, influenza vaccination did not cause any major adverse event in SPs, and their serological response was equal to HCs. Studies with larger sample size and a broader selection of subjects could help validate the results of this study.

The X chromosome and the sex ratio of autoimmunity

The number of human conditions that are currently considered to be autoimmune diseases (AID) has been steadily growing over the past decades and it is now estimated that over 10 million people are affected in the United States. One of the major shared features among AID is the predominance in the female sex which in some cases changes with the age at disease diagnosis. Numerous hypotheses have been formulated based on intuitive scientific backgrounds to justify this sex imbalance, i.e. sex hormones and reproductive factors, fetal microchimerism, other sex-related environmental factors, a skewing of the X-chromosome inactivation patterns, and major defects in sex chromosomes. Nevertheless, none of these hypotheses has thus far gathered enough convincing evidence and in most cases data are conflicting, as well illustrated by the reports on fetal microchimerism in systemic sclerosis or primary biliary cirrhosis. The present article will critically discuss the main hypotheses (loss of mosaicism, reactivation, and haploinsufficiency) that have been proposed based on findings in female patients with specific AID along with two additional mechanisms (X-chromosome vulnerability and X-linked polyamine genes) that have been observed in AID models. Further, recent data have significantly shifted the paradigm of X chromosome inactivation by demonstrating that a large number of genes can variably escape silencing on one or both chromosomes. As a result we may hypothesize that more than one mechanism may contribute to the female susceptibility to tolerance breakdown while the possibility that unknown factors may indeed protect men from AID should not be overlooked.

Geoepidemiology, gender and autoimmune disease

Autoimmune diseases include more than 70 different disorders affecting over 5% of the population of the Western countries. They are mainly characterized by female predominance and have great impact on the quality of life of affected subjects. It is generally accepted that ADs are the result of a complex interaction between genetic and environmental factors; however the mechanisms involved in the loss of tolerance remain unknown. Studying the distribution of these conditions across various global regions and ethnic groups by means of geoepidemiology might readily provide epidemiological data and also advance our understanding of their pathogenesis. Indeed, geoepidemiology demonstrates that genetic susceptibility interacts with lifestyle and environmental factors, which include socioeconomic status, infectious agents (triggering or protective agents), environmental pollutants, and vitamin D (dependent on sunlight exposure), in determining the risk of developing autoimmunity and in the understanding of their female prevalence. To properly understand the geoepidemiology of human autoimmunity, it is important to consider the many pleiotropic factors which lead to its initiation. In most studies the focus has been on genetics and environment. However, in this review the focus is primarily on gender. Overall, autoimmune diseases are well known to have female predominance, but there is significant variation in geographic area. Further, the mechanisms that influence female predominance are relatively unknown. Hence the attempt in this review is to focus on these critical issues.

Autoimmune disease and gender: plausible mechanisms for the female predominance of autoimmunity

A large number of autoimmune diseases (ADs) are more prevalent in women. The more frequent the AD and the later it appears, the more women are affected. Many ideas mainly based on hormonal and genetic factors that influence the autoimmune systems of females and males differently, have been proposed to explain this predominance. These hypotheses have gained credence mostly because many of these diseases appear or fluctuate when there are hormonal changes such as in late adolescence and pregnancy. Differences in X chromosome characteristics between men and women with an AD have led researchers to think that the genetic background of this group of diseases also relates to the genetic determinants of gender. These hormonal changes as well as the genetic factors that could explain why women are more prone to develop ADs are herein reviewed.

Estradiol impairs the Th17 immune response against Candida albicans

Candida albicans is a commensal opportunistic pathogen that is also a member of gastrointestinal and reproductive tract microbiota. Exogenous factors, such as oral contraceptives, hormone replacement therapy, and estradiol, may affect susceptibility to Candida infection, although the mechanisms involved in this process have not been elucidated. We used a systemic candidiasis model to investigate how estradiol confers susceptibility to infection. We report that estradiol increases mouse susceptibility to systemic candidiasis, as in vivo and ex vivo estradiol-treated DCs were less efficient at up-regulating antigen-presenting machinery, pathogen killing, migration, IL-23 production, and triggering of the Th17 immune response. Based on these results, we propose that estradiol impairs DC function, thus explaining the increased susceptibility to infection during estrus.

Estrogen-responsive genes in macrophages of the bony fish gilthead seabream: a transcriptomic approach

The role of sex steroids in the modulation of fish immune responses has received little attention. Previous studies have demonstrated that 17β-estradiol (E(2)) is able to alter the response of gilthead seabream leukocytes to infectious agents. We have used suppression subtractive hybridization to identify genes upregulated by E(2) (50 ng/ml) in macrophage cultures from gilthead seabream. We isolated 393 up-regulated cDNA fragments that led to the identification of 162 candidate estrogen-responsive genes. Functional analyses revealed the presence of several enriched immune processes and molecular pathways. The E(2) up-regulation of some immune-relevant genes was further confirmed by real time RT-PCR. Bioinformatics analysis revealed the ability of E(2) to orchestrate profound alterations in the macrophage expression profile, especially immune-related processes and pathways. This is the first report on E(2)-dependent modifications of fish macrophage transcriptome and lends weight to a suggested role for estrogen in the immune system, the possible significance of which is discussed.

Humoral immune response to ADAMTS13 in acquired thrombotic thrombocytopenic purpura

The apparently spontaneous development of autoantibodies to ADAMTS13 in previously healthy individuals is a major cause of thrombotic thrombocytopenic purpura (TTP). Epitope mapping studies have shown that in most patients antibodies directed towards the spacer domain of ADAMTS13 are present. A single antigenic surface comprising Arg(660) , Tyr(661) and Tyr(665) that contributes to the productive binding of ADAMTS13 to unfolded von Willebrand factor is targeted by anti-spacer domain antibodies. Antibodies directed to the carboxyl-terminal CUB1-2 and TSP2-8 domains have also been observed in the plasma of patients with acquired TTP. As yet it has not been established whether this class of antibodies modulates ADAMTS13 activity. Inspection of the primary sequence of human monoclonal anti-ADAMTS13 antibodies suggests that the variable heavy chain germline gene segment VH1-69 is frequently incorporated. We suggest a model in which 'shape complementarity' between the spacer domain and residues encoded by the VH1-69 gene segment explain the preferential use of this variable heavy chain gene segment. Finally, a model is presented for the development of anti-ADAMTS13 antibodies in previously healthy individuals that incorporates the recent identification of HLA DRB1*11 as a risk factor for acquired TTP.

17Beta-estradiol affects the response of complement components and survival of rainbow trout (Oncorhynchus mykiss) challenged by bacterial infection

Research on the endocrine role of estrogens has focused on the reproductive system, while other potential target systems have been less studied. Here, we investigated the possible immunomodulating role of 17β-estradiol (E2) using rainbow trout (Oncorhynchus mykiss) as a model. The aims of the study were to examine a) whether estrogens can modulate immune gene transcription levels, and b) whether this has functional implications for the resistance of trout towards pathogens. Trout were reared from fertilization until 6 months of age under (1) control conditions, (2) short-term E2-treatment (6-month-old juveniles were fed a diet containing 20 mg E2/kg for 2 weeks), or c) long-term E2-treatment (twice a 2-h-bath-exposure of trout embryos to 400 μg 17β-estradiol (E2)/L, followed by rearing on the E2-spiked diet from start-feeding until 6 months of age). Analysis of plasma estrogen levels indicated that the internal estrogen concentrations of E2-exposed fish were within the physiological range and analysis of hepatic vitellogenin mRNA levels indicated that the E2 administration was effective in activating the endogenous estrogen receptor pathway. However, expression levels of the hepatic complement components C3-1, C3-3, and Factor H were not affected by E2-treatment. In a next step, 6-month-old juveniles were challenged with pathogenic bacteria (Yersinia ruckeri). In control fish, this bacterial infection resulted in significant up-regulation of the mRNA levels of hepatic complement genes (C3-1, C3-3, Factor B, Factor H), while E2-treated fish showed no or significantly lower up-regulation of the complement gene transcription levels. Apparently, the E2-treated trout had a lower capacity to activate their immune system to defend against the bacterial infection. This interpretation is corroborated by the finding that survival of E2-treated fish under bacterial challenge was significantly lower than in the control group. In conclusion, the results from this study suggest that estrogens are able to modulate immune parameters of trout with functional consequences on their ability to cope with pathogens.

The multi-faceted influences of estrogen on lymphocytes: toward novel immuno-interventions strategies for autoimmunity management

Early studies of the immune system disclosed that, generally, females exhibit stronger responses to a variety of antigens than males. Perhaps as a result of this response, women are more prone to developing autoimmune diseases than men. Yet, the precise cellular and molecular mechanisms remain under investigation. Recently, interferon-gamma and the related pro-inflammatory interleukin-12 were found to be under effects of sex steroid hormones, with potential implications in regulating immune cells and autoimmune responses. In B lymphocytes, functional binding sites for estrogen receptors were identified in the promoter of the gene encoding activation-induced deaminase, an enzyme required for somatic hypermutation, and class-switch recombination. The observation that estrogen exerts direct impacts on antibody affinity-maturation provides a potential mechanism that could account for generating pathogenic high-affinity auto-antibodies. Further deciphering the multi-faceted influences of sex hormones on the responsiveness of immune cells could lead to novel therapeutic interventions for autoimmunity management.

Estrogen receptors in immunity and autoimmunity

Due to the female predominance of autoimmune diseases, the role of gender and sex hormones in the immune system is of long-term interest. Estrogen's primary effects are mediated via estrogen receptors alpha and beta (ER α/β) that are expressed on most immune cells. ERs are nuclear hormone receptors that can either directly bind to estrogen response elements in gene promoters or serve as cofactors with other transcription factors (i.e., NFkB/AP1). Cytoplasmic ER and membrane associated ER impact specific kinase signaling pathways. ERs have prominent effects on immune function in both the innate and adaptive immune responses. Genetic deficiency of ERα in murine models of lupus resulted in significantly decreased disease and prolonged survival, while ERβ deficiency had minimal to no effect in autoimmune models. The protective effect of ERα in lupus is multifactoral. In arthritis models, ERα agonists appears to mediate a protective effect. The modulation of ERα function appears to be a potential target for therapy in autoimmunity.

The unexplained female predominance of systemic lupus erythematosus: clues from genetic and cytokine studies

Despite recent progress in the understanding of systemic lupus erythematosus (SLE), the striking 9:1 female to male ratio of disease incidence remains largely unexplained. In addition, peak SLE incidence rates occur during the early reproductive years in women. Studies which illuminate potential causes underlying this sex difference and characteristic onset during the reproductive years have the potential to fundamentally advance our understanding of disease pathogenesis in SLE. Similarly, progress in this area will likely inform human reproductive immunology. Studies of sex hormone function in the immune system are of obvious importance; however, it seems likely that many other types of sex-related genetic and immunological differences will contribute to SLE. In this review, we will focus on recent work in sex-related differences in cytokine pathways and genetics of these pathways as they relate to SLE pathogenesis. It seems quite possible that many of these sex-related differences could be important to reproductive fitness, which may explain the conservation of these immune system features and the observed female predominance of SLE.

Sex differences in destructive periodontal disease: exploring the biologic basis

BACKGROUND

Epidemiologic studies provide broad-based evidence that men are at greater risk for developing destructive periodontal disease than women, even after adjusting for behavioral and environmental factors, such as oral hygiene practice and smoking. What requires clarification, however, is whether sex-specific differences in immune function provide a plausible biologic basis for a sexual dimorphism in susceptibility to destructive periodontal disease. This review examines evidence that might provide an underlying biologic basis for a sexual dimorphism in the prevalence and severity of destructive periodontal disease.

METHODS

A narrative review of the literature related to sexual dimorphism in pathogen-mediated inflammatory diseases and immune response was retrieved from searches of computerized databases (MEDLINE, PubMed, and SCOPUS).

RESULTS

Sex steroids exert profound effects on multiple immunologic parameters regulating both the amplification and resolution of inflammation. Strong evidence exists for sexual dimorphisms in immune function, involving both innate and acquired immunity. Injury and infection have been associated with higher levels of inflammatory cytokines, including interleukin-1β and tumor necrosis factor-α, in men than women, paralleling observed sex-specific differences in periodontitis.

CONCLUSION

Differential gene regulation, particularly in sex steroid-responsive genes, may contribute to a sexual dimorphism in susceptibility to destructive periodontal disease.

Genetic and hormonal factors in female-biased autoimmunity

Autoimmunity is controlled both by the environment and by genetic factors. One of the most well defined genetic factors is polymorphisms, with some alleles of particular genes promoting autoimmune diseases, whereas other alleles either not affecting susceptibility to disease or, in some cases actually inhibiting the appearance of such illnesses. Another genetically controlled factor, gender, also plays a profound role in the incidence of autoimmune diseases. For example, Systemic Lupus Erythematosus (SLE) occurs much more frequently in females than in males in both mice and man. The genetic differences that make some individuals susceptible to autoimmunity and protect others could act in many ways and affect many tissues. In this review we will discuss how gender may act on the cells of the immune system and thereby influence the predisposition of the host to autoimmune diseases.

Sustained hippocampal IL-1beta overexpression impairs contextual and spatial memory in transgenic mice

Neuroinflammatory conditions such as traumatic brain injury, aging, Alzheimer's disease, and Down syndrome are often associated with cognitive dysfunction. Much research has targeted inflammation as a causative mediator of these deficits, although the diverse cellular and molecular changes that accompany these disorders obscure the link between inflammation and impaired memory. Therefore, we used a transgenic mouse model with a dormant human IL-1beta excisional activation transgene to direct overexpression of IL-1beta with temporal and regional control. Two weeks of hippocampal IL-1beta overexpression impaired long-term contextual and spatial memory in both male and female mice, while hippocampal-independent and short-term memory remained intact. Human IL-1beta overexpression activated glia, elevated murine IL-1beta protein and PGE(2) levels, and increased pro-inflammatory cytokine and chemokine mRNAs specifically within the hippocampus, while having no detectable effect on inflammatory mRNAs in the liver. Sustained neuroinflammation also reduced basal and conditioning-induced levels of the plasticity-related gene Arc.

Rheumatoid arthritis: Disease or syndrome?

Rheumatoid arthritis (RA) has been described in the medical literature for over two hundred years, but its etiology remains unknown. RA displays phenotypic heterogeneity, and it is a relatively prevalent clinical entity: it affects approximately 1% of the population, resulting in enormous pathologic sequelae. Earlier studies targeting the cause(s) of RA suggested potential infectious involvement, whereas more recent reports have focused on a genetic origin of the disease. However, neither infection nor genetics, nor any other single factor is currently accepted as causative of RA. In this article we review studies relating to the etiology of RA, and those of several related matters, and we conclude that the literature indeed does provide insight into the causes underlying the initiation of RA pathogenesis. Briefly, given the remarkable phenotypic variation of RA, especially in its early stages, as well as a number of other characteristics of the condition, we contend that RA is not a discrete clinical entity with a single etiological source. Rather, we argue that it represents a common clinical endpoint for various starting points, each of which is largely guided by as yet poorly understood aspects of the genetic background of the affected individual. Adoption of this alternative view of the origin of RA will have significant consequences for future research and for development of new therapeutic interventions for this burdensome condition.

Impact of female sex hormones on the maturation and function of human dendritic cells

PROBLEM

During pregnancy, the immune and the endocrine system cooperate to ensure that the fetal allograft develops without eliciting a maternal immune response. This is presumably in part achieved by dendritic cells (DCs) that play a dominant role in maintaining peripheral tolerance. In this study, we investigated whether female sex hormones, such as human chorionic gonadotropin (hCG), progesterone (Prog), and estradiol (E2), which are highly elevated during pregnancy, induce the differentiation of DCs into a tolerance-inducing phenotype.

METHODS/RESULTS

Immature DCs were generated from blood-derived monocytes and differentiated in the presence of hCG, Prog, E2, or Dexamethasone (Dex) as a control. Unlike Dex, female sex hormones did not prevent the upregulation of surface markers characteristic for mature DCs, such as CD40, CD83, and CD86, except for hCG, which inhibited HLA-DR expression. Similarly, hCG, Prog, and E2 had any impact on neither the rearrangement of the F-actin cytoskeleton nor the enhanced chemokine secretion following DC maturation, both of which were strongly altered by Dex. Nevertheless, the T-cell stimulatory capacity of DCs was significantly reduced after hCG and E2 exposure.

CONCLUSION

Our findings suggest that the female sex hormones hCG and E2 inhibit the T-cell stimulatory capacity of DCs, which may help in preventing an allogenic T-cell response against the embryo.

Dendritic cell populations in the eutopic and ectopic endometrium of women with endometriosis

BACKGROUND

Immune alterations may be involved in the pathogenesis and progression of endometriosis. Dendritic cells (DCs) are potent antigen presenting cells that are highly involved in the initiation of the immune response. The aim of this study was to investigate DC populations in the eutopic and ectopic endometrium of women with endometriosis compared with controls.

METHODS

Hysterectomy samples were obtained from premenopausal women with (n = 33) and without (n = 28) endometriosis. In addition, paired peritoneal endometriotic lesions and uterine curettings were collected from 32 women with endometriosis. Specimen sections were stained immunohistochemically using antibodies for monoclonal mouse antibodies directed against human CD1a and CD83, which are specific for immature and mature DCs, respectively.

RESULTS

The mean density of endometrial CD1a+ DCs in the basal layer was significantly increased in women with endometriosis compared with controls during the proliferative phase only (P = 0.001). There was a highly significant decrease in the density of endometrial CD83+ DCs in women with endometriosis compared with controls in both layers of the endometrium across all phases of the menstrual cycle (P = 0.001). The density of CD1a+ DCs was significantly increased in peritoneal endometriotic lesions (P = 0.003) and in the surrounding peritoneum (P = 0.001) compared with paired uterine curettings and peritoneum distant from the lesion.

CONCLUSIONS

Both CD1a+ and CD83+ DC populations were altered in the eutopic and ectopic endometrium of women with endometriosis compared with controls. Alterations in these cells, which play a crucial role in the coordination of the immune response, may be involved in pain generation and the pathogenesis of endometriosis.

Progesterone inhibits activation-induced deaminase by binding to the promoter

Regulation of activation-induced deaminase (AID), an essential factor in Ig diversification, can alter not only somatic hypermutation and class switch recombination (CSR), but may also influence oncogenesis. AID deaminates cytosine to uracil in the Ig locus, thereby initiating Ig diversification. Unregulated AID can induce oncogenic DNA alterations in Ig and non-Ig loci, leading to mutations, recombination, and translocations. In this study, we demonstrate that AID mRNA production in activated mouse splenic B cells can be reduced by treatment with the sex hormone progesterone. This down-regulation is independent of translation or splicing and is predominantly achieved by inhibiting transcription. During cell treatment we could detect progesterone receptor bound to the AID promoter in proximity to NF-kappaB binding. Importantly, the progesterone-induced repression was also extended to the protein level of AID and its activity on somatic hypermutation and class switch recombination.

Current status and challenges of cytokine pharmacology

The major concern of pharmacology about cytokines has originated from plentiful data showing association between gross changes in their production and pathophysiological processes. Despite the enigmatic role of cytokines in diseases, a number of them have become a subject of cytokine and anti-cytokine immunotherapies. Production of cytokines can be influenced by many endogenous and exogenous stimuli including drugs. Cells of the immune system, such as macrophages and lymphocytes, are richly endowed with receptors for the mediators of physiological functions, such as biogenic amines, adenosine, prostanoids, steroids, etc. Drugs, agonists or antagonists of these receptors can directly or indirectly up- and down-regulate secretion of cytokines and expression of cytokine receptors. Vice versa, cytokines interfere with drug pharmacokinetics and pharmacodynamics through the interactions with cytochrome P450 and multiple drug resistance proteins. The aim of the review is to encourage more intensive studies in these fields of cytokine pharmacology. It also outlines major areas of searching promising candidates for immunotherapeutic interventions.

Role of plasmacytoid dendritic cells for aberrant class II expression in exocrine glands from estrogen-deficient mice of healthy background

Although it has been well documented that aberrant major histocompatibility complex class II molecules may contribute to the development of autoimmune disorders, the precise mechanisms responsible for their tissue-specific expression remain unknown. Here we show that estrogen deficiency induces aberrant class II major histocompatibility complex expression in exocrine glands via interactions between epithelial cells and plasmacytoid dendritic cells. Relatively modest but functionally significant expression levels of major histocompatibility complex class II and class II transactivator molecules were observed in the exocrine glands of ovariectomized (Ovx) C57BL/6 (B6) mice, but were not seen in the exocrine glands of control B6 mice. We observed that the salivary dendritic cells adjacent to the apoptotic epithelial cells positive for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, were activated in Ovx mice, but were not activated in control mice. We obtained evidence that the salivary gland cells express both interferon regulatory factor-1 and class II transactivator type IV molecules in Ovx mice. Salivary gland cells from Ovx mice were also capable of inducing the activation of antigen-specific T cells from OT-II transgenic mice. These findings indicate that estrogen deficiency initiates class II transactivator type IV mRNA expression in exocrine glands via interactions between epithelial cells and plasmacytoid dendritic cells, suggesting that plasmacytoid dendritic cells play a pivotal role in gender-based autoimmune disorders in postmenopausal women.

The X in sex: how autoimmune diseases revolve around sex chromosomes

Recent estimates suggest that autoimmune diseases cumulatively affect 5-10% of the general population worldwide. Although the etiology and pathogenesis remain poorly understood in most cases, similarities between diseases outnumber differences in the initiation and perpetuation of the autoimmune injury. One major example is the predominance of affected women, and perhaps its most intriguing putative mechanism is related to sex chromosomes, based on the recent observation that women with autoimmune diseases manifest a higher rate of circulating leukocytes with a single X chromosome. In a complementary fashion, there have been several reports on a role of X chromosome gene dosage through inactivation or duplication in autoimmunity. It is important not to overlook men with autoimmune diseases, who might manifest a more frequent loss of the Y chromosome in circulating leukocytes. Taken together, sex chromosome changes might constitute the common trait of autoimmunity.

Estrogen directly activates AID transcription and function

The immunological targets of estrogen at the molecular, humoral, and cellular level have been well documented, as has estrogen's role in establishing a gender bias in autoimmunity and cancer. During a healthy immune response, activation-induced deaminase (AID) deaminates cytosines at immunoglobulin (Ig) loci, initiating somatic hypermutation (SHM) and class switch recombination (CSR). Protein levels of nuclear AID are tightly controlled, as unregulated expression can lead to alterations in the immune response. Furthermore, hyperactivation of AID outside the immune system leads to oncogenesis. Here, we demonstrate that the estrogen-estrogen receptor complex binds to the AID promoter, enhancing AID messenger RNA expression, leading to a direct increase in AID protein production and alterations in SHM and CSR at the Ig locus. Enhanced translocations of the c-myc oncogene showed that the genotoxicity of estrogen via AID production was not limited to the Ig locus. Outside of the immune system (e.g., breast and ovaries), estrogen induced AID expression by >20-fold. The estrogen response was also partially conserved within the DNA deaminase family (APOBEC3B, -3F, and -3G), and could be inhibited by tamoxifen, an estrogen antagonist. We therefore suggest that estrogen-induced autoimmunity and oncogenesis may be derived through AID-dependent DNA instability.

Estrogen inhibits dendritic cell maturation to RNA viruses

Dendritic cells (DCs) play a central role in initiating and polarizing the immune response. Therefore, DC maturation represents a key control point in the shift from innate to adaptive immunity. It is suspected that during pregnancy, hormones are critical factors that modulate changes reported to occur in maternal immunity. Here we examined the effect of 17-beta-estradiol (E2) on the maturational response triggered by virus in human DCs and its influence on their ability to activate naive T cells. We developed an in vitro system to measure the response of DCs to virus infection with Newcastle disease virus (NDV) after a 24-hour E2 treatment. Using this system, we demonstrated that E2 pretreatment down-regulated the antiviral response to RNA viruses in DCs by profoundly suppressing type I interferon (IFN) synthesis and other important inflammatory products. In addition, the DCs capacity to stimulate naive CD4 T cells was also reduced. These results suggest an important role for E2 in suppressing the antiviral response and provide a mechanism for the reduced immunity to virus infection observed during pregnancy.

Cytokines and their relationship to the symptoms and outcome of cancer

Tumours contain immune cells and a network of pro- and anti-inflammatory cytokines, which collaborate in the development and progression of cancer. Cytokine profiles might prove to be prognostic. The systemic effects of pro-inflammatory cytokines are associated with fatigue, depression and cognitive impairment, and can affect quality of life before, during and after treatment. In people with advanced cancer, pro-inflammatory cytokines are additionally associated with anorexia and cachexia, pain, toxicity of treatment and resistance to treatment. However, physical activity might modify cytokine levels and decrease fatigue in patients with cancer, and might also improve their prognosis.

Dehydroepiandrosterone in systemic lupus erythematosus

Dehydroepiandrosterone (DHEA) is a weak androgen that exerts pleomorphic effects on the immune system. The hormone has no known receptor, and consequently, its mechanism of action on immunocompetent cells remains poorly understood. Interestingly, serum levels of DHEA are decreased in patients with inflammatory diseases including lupus, and these levels seem to correlate inversely with disease activity. Following encouraging studies demonstrating beneficial effects of DHEA supplementation in murine lupus models, several clinical studies have tested the effect of DHEA in lupus patients. DHEA treatment could improve overall quality-of-life assessment measures and glucocorticoid requirements in some lupus patients with mild to moderate disease; however, DHEA's effect on disease activity in lupus patients remains controversial. Long-term safety studies are required in light of the reported effect of DHEA supplementation in lowering high-density lipoprotein cholesterol in lupus patients.

Soy isoflavones and immunity

The amount of soy products consumed in Japan is much greater than that in Western countries. Recent evidence indicates that soy isoflavones play a beneficial role in obesity, cancer, osteoporosis, and cardiovascular disease. The soybean isoflavone genistein is present at high levels in soy products. Genistein is structurally similar to 17beta-estradiol (E2), and genistein has been suggested to be act as E2 or an antagonist against E2. Genistein suppresses antigen-specific immune response in vivo and lymphocyte proliferation response in vitro. However, genistein enhances the cytotoxic response mediated by NK and cytotoxic T cells and the cytokine production from T cells. Thus, the effect of genistein on immunity is immune cell-dependent. Due to its unique effect on immune function, genistein has been used for the treatment of the diseases in animal models and it has been found that genistein inhibits allergic inflammatory responses. In this review, we summarize current studies related to the effect of isoflavone genistein on the immune system.