Sex steroid hormones modulate the activation of murine peritoneal macrophages: receptor mediated modulation

The best of both worlds: no apparent trade-off between immunity and reproduction in two group-living African mole-rat species

Co-operatively breeding mammals often exhibit a female reproductive skew and suppression of the subordinate non-breeding group members. According to evolutionary theory and the immunity-fertility axis, an inverse relationship between reproductive investment and survival (through immunocompetence) is expected. As such, this study investigated if a trade-off between immunocompetence and reproduction arises in two co-operatively breeding African mole-rat species, namely the Damaraland mole-rat (Fukomys damarensis) and common mole-rat (Cryptomys hottentotus hottentotus), which possess female reproductive division of labour. This study also attempted to investigate the relationship between the immune and endocrine systems in Damaraland mole-rats. There was no trade-off between reproduction and immunocompetence in co-operatively breeding African mole-rat species, and in the case of the Damaraland mole-rats, breeding females (BFs) possessed increased immunocompetence compared with non-breeding females (NBFs). Furthermore, the increased levels of progesterone possessed by Damaraland mole-rat BFs compared with NBFs appear to be correlated to increased immunocompetence. In comparison, BF and NBF common mole-rats possess similar immunocompetence. The species-specific differences in the immunity-fertility axis may be due to variations in the strengths of reproductive suppression in each species. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Evaluation of the sex steroids mediated modulation of leucocyte immune responses in an ophidian Natrix piscator

The immune-suppressive role of sex steroids in mammals is well documented, but information on other vertebrates is limited. The present study was planned to analyze the effect of testosterone and progesterone in the modulation of immune functions of leucocytes in a reptile, Natrix piscator. Reptiles are unique organisms and this study is novel in that it provides an insight into immune-reproductive cross-talk in a reptile. Leucocytes were isolated from peripheral blood, cultured with different concentrations of testosterone and progesterone and different immune parameters like phagocytosis, superoxide production, and nitrite release were assessed. Lymphocytes were isolated and cell-mediated immunity was assessed through proliferation responses utilizing tetrazolium salt. Concentration-dependent suppressive effects of both the steroids on immune responses were observed. A differential suppressive effect of testosterone was also observed when a lymphocyte proliferation assay was studied. Using receptor antagonists such as cyproterone acetate and mifepristone restored the immune responses of cultured cells. It was summarized that gonadal steroids mediate a direct suppressive effect on innate and cell-mediated immune responses of blood immune cells. It was concluded that when gonadal steroids are high in reproductive seasons, the immune functions are suppressed to gain optimum reproductive success.

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Reptilian immune responses are differentially affected by sex steroids.

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Testosterone interacts with nuclear receptors and suppress proliferative responses of lymphocytes.

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Superoxide anion production by blood immune cells are inhibited by gonadal steroids.

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Use of receptor antagonists resulted in amelioration of immune responses indicating the direct action of steroids.

Sex-Steroid Signaling in Lung Diseases and Inflammation

Sex/gender difference exists in the physiology of multiple organs. Recent epidemiological reports suggest the influence of sex-steroids in modulating a wide variety of disease conditions. Sex-based discrepancies have been reported in pulmonary physiology and various chronic inflammatory responses associated with lung diseases like asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and rare lung diseases. Notably, emerging clinical evidence suggests that several respiratory diseases affect women to a greater degree, with increased severity and prevalence than men. Although sex-specific differences in various lung diseases are evident, such differences are inherent to sex-steroids, which are major biological variables in men and women who play a central role to control these differences. The focus of this chapter is to comprehend the sex-steroid biology in inflammatory lung diseases and to understand the mechanistic role of sex-steroids signaling in regulating these diseases. Exploring the roles of sex-steroid signaling in the regulation of lung diseases and inflammation is crucial for the development of novel and effective therapy. Overall, we will illustrate the importance of differential sex-steroid signaling in lung diseases and their possible clinical implications for the development of complementary and alternative medicine to treat lung diseases.

The role of 5-reduction in physiology and metabolic disease: evidence from cellular, pre-clinical and human studies

The 5-reductases (5α-reductase types 1, 2 and 3 [5αR1-3], 5β-reductase [5βR]) are steroid hormone metabolising enzymes that hold fundamental roles in human physiology and pathology. They possess broad substrate specificity converting many steroid hormones to their 5α- and 5β-reduced metabolites, as well as catalysing crucial steps in bile acid synthesis. 5αRs are fundamentally important in urogenital development by converting testosterone to the more potent androgen 5α-dihydrotestosterone (5αDHT); inactivating mutations in 5αR2 lead to disorders of sexual development. Due to the ability of the 5αRs to generate 5αDHT, they are an established drug target, and 5αR inhibitors are widely used for the treatment of androgen-dependent benign or malignant prostatic diseases. There is an emerging body of evidence to suggest that the 5-reductases can impact upon aspects of health and disease (other than urogenital development); alterations in their expression and activity have been associated with metabolic disease, polycystic ovarian syndrome, inflammation and bone metabolism. This review will outline the evidence base for the extra-urogenital role of 5-reductases from in vitro cell systems, pre-clinical models and human studies, and highlight the potential adverse effects of 5αR inhibition in human health and disease.

Do Androgens Modulate the Pathophysiological Pathways of Inflammation? Appraising the Contemporary Evidence

The role of testosterone in the pathophysiology of inflammation is of critical clinical importance; however, no universal mechanism(s) has been advanced to explain the complex and interwoven pathways of androgens in the attenuation of the inflammatory processes. PubMed and EMBASE searches were performed, including the following key words: "testosterone", "androgens", "inflammatory cytokines", "inflammatory biomarkers" with focus on clinical studies as well as basic scientific studies in human and animal models. Significant benefits of testosterone therapy in ameliorating or attenuating the symptoms of several chronic inflammatory diseases were reported. Because anti⁻tumor necrosis factor therapy is the mainstay for the treatment of moderate-to-severe inflammatory bowel disease; including Crohn's disease and ulcerative colitis, and because testosterone therapy in hypogonadal men with chronic inflammatory conditions reduce tumor necrosis factor-alpha (TNF-α), IL-1β, and IL-6, we suggest that testosterone therapy attenuates the inflammatory process and reduces the burden of disease by mechanisms inhibiting inflammatory cytokine expression and function. Mechanistically, androgens regulate the expression and function of inflammatory cytokines, including TNF-α, IL-1β, IL-6, and CRP (C-reactive protein). Here, we suggest that testosterone regulates multiple and overlapping cellular and molecular pathways involving a host of immune cells and biochemical factors that converge to contribute to attenuation of the inflammatory process.

Endocrine regulation of lung disease and inflammation

IMPACT STATEMENT

Sex-differences in the incidence and severity of inflammatory lung diseases have been recognized for years. Women of reproductive age are more likely to suffer from chronic lung disease, with higher mortality rates than men. Physiological changes in hormone levels such as those occurring during the menstrual cycle, pregnancy, and menopause have been associated with lung function changes and asthma symptoms. Despite this, the roles of sex hormones in the mechanisms associated with lung diseases have not been fully elucidated. This review summarizes basic and clinical studies of sex hormones as potential modulators of lung function and inflammation. The information obtained from sex-specific research on lung physiology and pathology will potentially help in the development of sex-specific therapeutics for inflammatory lung disease that may account for the hormonal status of the patient.

Assessment of leukocyte activity in mice devoid of the glucocorticoid receptor in the noradrenergic system (GRDBHCre)

Disturbances in brain monoamines, overactivity of the hypothalamo-pituitary adrenal (HPA) axis and pro-inflammatory tendency in the immune system are the key features of depressive disorders. Recently, several murine lines with mutations in glucocorticoid receptors (GRs) have been generated and these animals may be utilized for study depressive-like disorders. In the present study, we have investigated whether selective ablation of GRs in noradrenergic neurons affects functional properties of leukocytes and redirects them towards pro-inflammatory activity. Transgenic mice selectively devoid of GRs on noradrenergic cells were constructed using the Cre/loxP approach. Peritoneal leukocytes were collected from mutant and wild type (WT) animals of both sexes and were cultured in vitro for 24h both in basal conditions and after application of selected pro- or anti-inflammatory stimuli. Metabolic activity and adherence were measured in basal conditions. Nitric oxide (NO) synthesis and arginase (ARG) activity were assessed as the markers of functional status of the cells. Because adult mutant mice lack adrenal medulla and thereby peripheral adrenaline, we modulated pro- and anti-inflammatory culture conditions by addition of noradrenaline (10-6M). Finally, effects of in vivo pro-inflammatory challenge (with intraperitoneal administration of lipopolysaccharide) on properties of leukocytes were assessed 24h (in both sexes) and 48h later (in males only). The experiments indicated that selective ablation of GR in noradrenergic neurons did not affect fundamental properties of peritoneal leukocytes and exerted effects only under conditions of selected pro- or anti-inflammatory stimuli in vitro. Stronger response to pro-inflammatory stimulation in terms of NO synthesis and ARG activity may suggest pro-inflammatory tendency in mutant mice. In vivo inflammatory challenge failed to show any effect of GR ablation on selected parameters of leukocyte activity. Both in vitro studies and in vivo challenge revealed mainly sex-related differences in leukocyte activity.

The influence of sex steroid hormones on the response to trauma and burn injury

Trauma and related sequelae result in disturbance of homeostatic mechanisms frequently leading to cellular dysfunction and ultimately organ and system failure. Regardless of the type and severity of injury, gender dimorphism in outcomes following trauma have been reported, with females having lower mortality than males, suggesting that sex steroid hormones (SSH) play an important role in the response of body systems to trauma. In addition, several clinical and experimental studies have demonstrated the effects of SSH on the clinical course and outcomes following injury. Animal studies have reported the ability of SSH to modulate immune, inflammatory, metabolic and organ responses following traumatic injury. This indicates that homeostatic mechanisms, via direct and indirect pathways, can be maintained by SSH at local and systemic levels and hence result in more favourable prognosis. Here, we discuss the role and mechanisms by which SSH modulates the response of the body to injury by maintaining various processes and organ functions. Such properties of sex hormones represent potential novel therapeutic strategies and further our understanding of current therapies used following injury such as oxandrolone in burn-injured patients.

Neuroendocrine control of photoperiodic changes in immune function

Seasonal variation in immune function putatively maximizes survival and reproductive success. Day length (photoperiod) is the most potent signal for time of year. Animals typically organize breeding, growth, and behavior to adapt to spatial and temporal niches. Outside the tropics individuals monitor photoperiod to support adaptations favoring survival and reproductive success. Changes in day length allow anticipation of seasonal changes in temperature and food availability that are critical for reproductive success. Immune function is typically bolstered during winter, whereas reproduction and growth are favored during summer. We provide an overview of how photoperiod influences neuronal function and melatonin secretion, how melatonin acts directly and indirectly to govern seasonal changes in immune function, and the manner by which other neuroendocrine effectors such as glucocorticoids, prolactin, thyroid, and sex steroid hormones modulate seasonal variations in immune function. Potential future research avenues include commensal gut microbiota and light pollution influences on photoperiodic responses.

Differential suppressive effects of testosterone on immune function in fresh water snake, Natrix piscator: an in vitro study

Reptiles represent the crucial phylogenetic group as they were the ancestors of both birds and mammals hence very important to study. The objectives of the present study were to investigate the potential roles of testosterone in the innate immune responses and splenic lymphocyte proliferation in fresh water snake, Natrix piscator. Animals were mildly anesthetized and spleens were taken out to study the splenic macrophage phagocytosis, super oxide production and nitrite release using in vitro testosterone. Splenic lymphocytes were isolated by density gradient centrifugation and were studied for mitogen induced proliferation in presence of in vitro testosterone. Testosterone suppressed the phagocytosis and nitrite release in a concentration dependent manner. Biphasic suppressive effect of testosterone was observed in superoxide production as judged by reduction of nitroblue tetrazolium salt where salt reduction was suppressed at lower and higher concentrations of testosterone. Mitogen induced splenic lymphocyte proliferation was also suppressed by testosterone. By suppressing immune responses, testosterone may, therefore, act as a physiological mechanism regulating the relative amount of energy invested into either reproductive effort or immunocompetence.

Non-Hodgkin lymphomas in pregnancy: tackling therapeutic quandaries

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) often present with systemic symptoms such as fatigue, shortness of breath and night sweats, mimicking pregnancy-related features which may result in delayed disease diagnosis. Furthermore, the wish to avoid investigational imaging, aiming to protect the fetus from radiation exposure, may lead to a further delay, which does not often result in significant changes in HL clinical nature and patient outcome. In contrast, a more aggressive behavior (i.e., advanced disease stage and reproductive organ involvement) of most NHL types diagnosed in pregnancy may require urgent therapeutic intervention to prevent disease progression. Current management of pregnancy-associated NHL depends on histological subtype of the disease, gestational stage at diagnosis and the urgency of treatment for a specific patient. Patients diagnosed with indolent lymphoma may often be just followed, whereas those presenting with aggressive or highly aggressive disease need to be urgently treated with chemoimmunotherapy, either after undergoing an elective pregnancy termination if diagnosed at an early gestational stage, or with pregnancy preservation, if diagnosed later. Supportive care of NHL is also important; however, granulocyte colony stimulating factor (G-CSF) which is commonly used outside of pregnancy, should be cautiously employed, considering its established teratogenicity in animals, though this is less proven in humans. In conclusion, given the paucity of studies prospectively evaluating the outcome of pregnant women with NHL, international efforts are warranted to elucidate critical issues and develop guidelines for the management of such patients.

Role of sex steroid hormones in bacterial-host interactions

Sex steroid hormones play important physiological roles in reproductive and nonreproductive tissues, including immune cells. These hormones exert their functions by binding to either specific intracellular receptors that act as ligand-dependent transcription factors or membrane receptors that stimulate several signal transduction pathways. The elevated susceptibility of males to bacterial infections can be related to the usually lower immune responses presented in males as compared to females. This dimorphic sex difference is mainly due to the differential modulation of the immune system by sex steroid hormones through the control of proinflammatory and anti-inflammatory cytokines expression, as well as Toll-like receptors (TLRs) expression and antibody production. Besides, sex hormones can also affect the metabolism, growth, or virulence of pathogenic bacteria. In turn, pathogenic, microbiota, and environmental bacteria are able to metabolize and degrade steroid hormones and their related compounds. All these data suggest that sex steroid hormones play a key role in the modulation of bacterial-host interactions.

Pregnancy and pregnancy-associated hormones alter immune responses and disease pathogenesis

During pregnancy, it is evolutionarily advantageous for inflammatory immune responses that might lead to fetal rejection to be reduced and anti-inflammatory responses that promote transfer of maternal antibodies to the fetus to be increased. Hormones modulate the immunological shift that occurs during pregnancy. Estrogens, including estradiol and estriol, progesterone, and glucocorticoids increase over the course of pregnancy and affect transcriptional signaling of inflammatory immune responses at the maternal-fetal interface and systemically. During pregnancy, the reduced activity of natural killer cells, inflammatory macrophages, and helper T cell type 1 (Th1) cells and production of inflammatory cytokines, combined with the higher activity of regulatory T cells and production of anti-inflammatory cytokines, affects disease pathogenesis. The severity of diseases caused by inflammatory responses (e.g., multiple sclerosis) is reduced and the severity of diseases that are mitigated by inflammatory responses (e.g., influenza and malaria) is increased during pregnancy. For some infectious diseases, elevated inflammatory responses that are necessary to control and clear a pathogen have a negative consequence on the outcome of pregnancy. The bidirectional interactions between hormones and the immune system contribute to both the outcome of pregnancy and female susceptibility to disease.

Immune cells have sex and so should journal articles

Males and females have the same immunological cells, proteins, and pathways in place to protect against the development of disease. The kinetics, magnitude, and skewing of the responses mounted against pathogens, allergens, toxins, or self-antigens, however, can differ dramatically between the sexes. Generally, females mount higher innate and adaptive immune responses than males, which can result in faster clearance of pathogens but also contributes to increased susceptibility to inflammatory and autoimmune diseases in females compared with males. Hormonal and genetic factors contribute significantly to sex differences in immune function and disease pathogenesis. In particular, the expression of X-linked genes and microRNA as well as sex steroid hormones signaling through hormone receptors in immune cells can affect responses to immunological stimuli differently in males and females. Despite data illustrating profound differences between the sexes in immune function, sex differences in the pathogenesis of disease are often overlooked in biomedical research. Establishing journal policies that require authors to report the sex of their cells, animals, and subjects will improve our understanding of the pathogenesis of diseases, with the long-term goal of personalizing treatments for immune-mediated diseases differently for males and females in an effort to protect us equally.

Membrane progesterone receptor expression in mammalian tissues: a review of regulation and physiological implications

The recent discovery of a novel, membrane localized progestin receptor (mPR) unrelated to the classical progesterone receptor (PR) in fishes and its subsequent identification in mammals suggests a potential mediator of non-traditional progestin actions, particularly in tissues where PR is absent. While early studies on mPR focused on final oocyte maturation in fishes, more current studies have examined mPRs in multiple mammalian systems in both reproductive and non-reproductive tissues as well as in diseased tissues. Here we review the current data on mPR in mammalian systems including male and female reproductive tracts, liver, neuroendocrine tissues, the immune system and breast and ovarian cancer. We also provide new data demonstrating mPR expression in the RAW 264.7 immune cell line and bone marrow-derived macrophages as well as mPR expression and downstream gene regulation in ovarian cancer cells.

Effects of gender on serum biomarkers of systemic inflammation coincident to experimentally-induced periapical lesions

OBJECTIVE

The literature suggests that females have less adverse effects to infection than males, due to the protective effects of oestrogen. The purpose of our study is to compare the systemic effects of induced periapical lesions between groups of animals with various serum concentrations of oestrogen.

METHODS

To induce periapical inflammation, two molar tooth pulps were exposed in ovariectomized (OVX) and normal female (F) and castrated (Cast-M) and normal male (M) Sprague-Dawley rats (Experimental group, E). Sham-operated control animals from each group were also studied (Control group, C). Twenty-eight days later, serum and maxillas were collected. Serum 17β-oestradiol, testosterone, MMP-9, IL-18, IL-6, TNF-α, and IL-1β concentrations were measured by ELISA. Maxillas were cleaned of residual tissue and digital radiographs were made to verify the presence of periapical lesions. Data were compared by factorial ANOVA, post hoc Tukey, and Pearson correlation tests. Groups were considered to be significantly different when p<0.05.

RESULTS

The serum concentration of IL-18, TNF-α, IL-1-β, IL-6 and MMP-9 was greatest in OVX-E animals, compared to all other groups (p<0.001). F-E rats had significantly higher serum concentrations of these cytokines, compared to F-C. The fold difference in serum concentration of the biomarkers (between E and C groups) was significantly greater in females than males, even though males had higher baseline concentrations of all these biomarkers.

CONCLUSION

When females are oestrogen-deficient, their systemic response to periapical lesions is significantly greater than males, suggesting that oestrogen is essential in protecting females from the effects of this type of inflammation.

The Xs and Y of immune responses to viral vaccines

The biological differences associated with the sex of an individual are a major source of variation, affecting immune responses to vaccination. Compelling clinical data illustrate that men and women differ in their innate, humoral, and cell-mediated responses to viral vaccines. Sex affects the frequency and severity of adverse effects of vaccination, including fever, pain, and inflammation. Pregnancy can also substantially alter immune responses to vaccines. Data from clinical trials and animal models of vaccine efficacy lay the groundwork for future studies aimed at identifying the biological mechanisms that underlie sex-specific responses to vaccines, including genetic and hormonal factors. An understanding and appreciation of the effect of sex and pregnancy on immune responses might change the strategies used by public health officials to start efficient vaccination programmes (optimising the timing and dose of the vaccine so that the maximum number of people are immunised), ensure sufficient levels of immune responses, minimise adverse effects, and allow for more efficient protection of populations that are high priority (eg, pregnant women and individuals with comorbid conditions).

Sex hormones and mucosal wound healing

Wound healing studies, which have chiefly examined dermal tissues, have reported a female advantage in healing rates. In contrast, our laboratory recently demonstrated women heal mucosal wounds more slowly than men. We hypothesized sex hormones influence wound healing rates, possibly through their modulating effects on inflammation. This study involved 329 younger subjects aged 18-43 (165 women, 164 men) and 93 older subjects aged 50-88 (60 women, 33 men). A 3.5mm diameter wound was created on the hard oral palate and videographed daily to assess wound closure. Blood collected at the time of wounding was used to assess circulating testosterone, progesterone and estradiol levels, and in vitro cytokine production in response to LPS. No strong associations were observed between healing times and estradiol or progesterone levels. However, in younger subjects, lower testosterone levels related to faster wound closure. Conversely, in older women higher testosterone levels related to (1) lower inflammatory responses; and (2) faster healing times. No such relationships were seen in older men, or in women taking oral contraceptives or hormone replacement therapy [HRT]. Older women (50-54 years) not yet experiencing menopause healed similarly to younger women and dissimilarly from age-matched post-menopausal women. This suggests that the deleterious effects of aging on wound healing occur secondary to the effects of menopause. Supporting this, there was evidence in post-menopausal women that HRT augmented wound closure. Overall, this study suggests that human mucosal healing rates are modulated by testosterone levels. Based upon when between-group differences were observed, testosterone may impact upon the proliferative phase of healing which involves immune processes such as re-epithelialization and angiogenesis.

The APOE4 genotype alters the response of microglia and macrophages to 17beta-estradiol

The apolipoprotein E4 (APOE4) gene is a well-known risk factor for Alzheimer's disease (AD) and other neurological disorders. Post-menopausal women with AD who express at least one APOE4 gene have more severe neuropathology and worsened cognitive scores than their non-expressing counterparts. Since 17beta-estradiol down-regulates inflammation as part of its neuroprotective role, we examined the effect of 17beta-estradiol on the response of microglia to immune activation as a function of APOE genotype. Our data show that the anti-inflammatory activity of 17beta-estradiol is significantly reduced in APOE4 targeted replacement mice compared to APOE3 mice. A significant interaction between APOE genotype and the response to 17beta-estradiol was observed for NO and cytokine production by immune activated microglia. The genotype specific effect was not restricted to brain macrophages since peritoneal macrophages from APOE4 ovariectomized mice also demonstrated a significant difference in 17beta-estradiol responsiveness. ERbeta protein levels in APOE4 microglia were higher than APOE3 microglia, suggesting a difference in post-translational protein regulation in the presence of the APOE4 gene. Overall, our data indicate that the APOE genotype may be a critical component in assessing the effectiveness of 17beta-estradiol's action and may impact the neuroprotective role of 17beta-estradiol and of hormone replacement therapy on brain function when the APOE4 gene is expressed.

Androgens modulate the inflammatory response during acute wound healing

Impaired wound healing states in the elderly lead to substantial morbidity and mortality, and a cost to the health services of over 9 billion dollars per annum. In addition to intrinsic ageing processes that per se cause delayed healing, studies have suggested marked differences in wound repair between the sexes. We have previously reported that, castration of male mice results in a striking acceleration of local cutaneous wound healing and dampens the associated inflammatory response. In this study, we report that systemic 5alpha-reductase inhibition, which blocks the conversion of testosterone to its more active metabolite 5alpha-dihydrotestosterone, mimics the effects of castration in a rat model of cutaneous wound healing. The mechanisms underlying the observed effects involve a direct, cell-specific upregulation of pro-inflammatory cytokine expression by macrophages, but not fibroblasts, in response to androgens. Androgens require the transforming growth factor beta signalling intermediate Smad3 to be present in order to influence repair and local pro-inflammatory cytokine levels. That reducing 5alpha-dihydrotestosterone levels through 5alpha-reductase antagonism markedly accelerates healing suggests a specific target for future therapeutic intervention in impaired wound healing states in elderly males.

Hormonal and immunological mechanisms mediating sex differences in parasite infection

The prevalence and intensity of infections caused by protozoa, nematodes, trematodes, cestodes, and arthropods is higher in males than females. The primary thesis of this review is that immunological differences exist between the sexes that may underlie increased parasitism in males compared to females. Several field and laboratory studies link sex differences in immune function with circulating steroid hormones; thus, the roles of sex steroids, including testosterone, oestradiol, and progesterone, as well as glucocorticoids will be discussed. Not only can host hormones affect responses to infection, but parasites can both produce and alter hormone concentrations in their hosts. The extent to which changes in endocrine-immune interactions following infection are mediated by the host or the parasite will be considered. Although males are more susceptible than females to many parasites, there are parasites for which males are more resistant than females and endocrine-immune interactions may underlie this sex reversal. Finally, although immunological differences exist between the sexes, genetic and behavioural differences may explain some variability in response to infection and will be explored as alternative hypotheses for how differences between the sexes contribute to dimorphic responses to parasites.

Sex differences in the effects of muramyl dipeptide and lipopolysaccharide on locomotor activity and the development of behavioral tolerance in rats

Administration of bacterial agents, such as muramyl dipeptide (MDP) or lipopolysaccharide (LPS), induces a number of illness symptoms including decreased locomotor activity and weight loss. This study provides a detailed multivariate assessment of the effects of repeated exposures of various doses of MDP and LPS, alone and in combination, on various aspects of locomotion in male and female rats. Animals were given a single intraperitoneal injection of either MDP (0.8 or 1.6 mg/kg), LPS (100 or 200 microg/kg), a combination of MDP and LPS (0.8 mg/kg and 100 microg/kg, respectively), or vehicle on Days 1, 4, and 7. Two hours after each injection, locomotor activity was recorded for 30 min in an automated open-field. Both doses of LPS and the high dose of MDP produced significant decrements in locomotor activity in male and female rats, with tolerance becoming evident over repeated administrations, although LPS decreased activity more robustly than MDP. Sex differences were evident in the combined effects of MDP and LPS. Together, MDP and LPS reduced male activity levels in an additive manner but significantly potentiated both horizontal and vertical activity decrements in females. In addition, the rate of behavioral tolerance development to repeated bacterial injections was significantly higher in females than in males. These findings provide evidence for sex differences in the actions of MDP and LPS on various aspects of locomotor activity and in the development of behavioral tolerance to infection.

Modulatory effects of estrogen in two murine models of experimental colitis

The association between oral contraceptives or pregnancy and inflammatory bowel disease is unclear. We investigated whether 17beta-estradiol modulates intestinal inflammation in two models of colitis. Female mice were treated with 17beta-estradiol alone or with tamoxifen, tamoxifen alone, 17 alpha-estradiol, or placebo. Dinitrobenzene sulfonic acid (DNB)- or dextran sodium sulfate (DSS)-induced colitis were assessed macroscopically, histologically, and by myeloperoxidase (MPO) activity. Malondialdehyde and mRNA levels of intercellular adhesion molecule-1 (ICAM-1), interferon-gamma (IFN-gamma), and interleukin-13 (IL-13) were determined. In DNB colitis, 17beta-estradiol alone, but not 17beta-estradiol plus tamoxifen, or 17 alpha-estradiol reduced macroscopic and histological scores, MPO activity and malondialdehyde levels. 17beta-Estradiol also decreased the expression of ICAM-1, IFN-gamma, and IL-13 mRNA levels compared with placebo. In contrast, 17beta-Estradiol increased the macroscopic and histological scores compared with placebo in mice with DSS colitis. These results demonstrate anti-inflammatory and proinflammatory effects of 17beta-estradiol in two different models of experimental colitis. The net modulatory effect most likely reflects a combination of estrogen receptor-mediated effects and antioxidant activity and may explain, in part, conflicting results from clinical trials.

Apolipoprotein E isoform mediated regulation of nitric oxide release

Progressive dysfunction and death of neurons in Alzheimer's dementia is enhanced in patients carrying one or more APOE4 alleles who also display increased presence of oxidative stress markers. Modulation of oxidative stress is a nontraditional and physiologically relevant immunomodulatory function of apolipoprotein E (apoE). Stimulated peritoneal macrophages from APOE-transgenic replacement (APOE-TR) mice expressing only human apoE3 or human apoE4 protein isoforms were utilized as mouse models to investigate the role of apoE protein isoforms and gender in the regulation of oxidative stress. Macrophages from male APOE4/4-TR mice produced significantly higher levels of nitric oxide than from male APOE3/3-TR mice, while macrophages from female APOE3/3-TR and female APOE4/4-TR mice produced the similar levels of nitric oxide. Primary cultures of microglial cells of APOE4 transgenic mice also produced significantly more nitric oxide than microglia from APOE3 transgenic mice. These data suggest a potentially novel mechanism for gender-dependent and apoE isoform-dependent immune responses that parallel the genetic susceptibility of APOE4 carriers for the development of Alzheimer's disease.

Progesterone fails to modulate Toxoplasma gondii replication in the RAW 264.7 murine macrophage cell line

Cell mediated immunity is very important for host defence against intracellular pathogens and many studies have shown the role of the production of nitric oxide (NO) by interferon (IFN)-gamma/lipopolysaccharide (LPS)-activated macrophages. As the progesterone level increases during pregnancy in mammals, and as previous studies have shown that progesterone inhibits inducible nitric oxide synthase (iNOS) expression and NO production, we aimed to investigate whether progesterone might modulate intracellular replication of Toxoplasma gondii in macrophages. Our results showed that progesterone does not influence T. gondii replication in non-activated RAW 264.7 cells, and although progesterone inhibits NO production induced by IFN-gamma/LPS, we observed that it fails to restore the growth of T. gondii blocked by IFN-gamma/LPS. After discussing the reasons for this apparent discrepancy, we concluded that progesterone has no direct effect on the macrophage response. The real effect of the sex steroids in T. gondii infection and their implication in clinical toxoplasmosis therefore need to be investigated further to involve wider mechanisms of the immune system.

Gender is a major factor in determining the severity of mycoplasma respiratory disease in mice

Gender is a significant factor in determining the susceptibility to and severity of pulmonary diseases in both humans and animals. Murine respiratory mycoplasmosis (MRM), due to Mycoplasma pulmonis infection, is an excellent animal model for evaluation of the role of various host factors on the development of acute or chronic inflammatory lung diseases. MRM has many similarities to mycoplasma respiratory disease in humans. The purpose of the present study was to determine whether gender has a significant impact on lung disease due to M. pulmonis infection in mice. It was demonstrated that male mice consistently developed more severe disease in the lung parenchyma than did female mice. There was no gender difference in disease severity along the airways or any difference in mycoplasma numbers in lungs of male and female mice. Furthermore, surgical removal of reproductive organs reduced the severity of mycoplasma disease and the numbers of mycoplasma organisms recovered from lungs. Thus, gender plays a significant role in determining the severity of M. pulmonis disease. In fact, the gender of the host was a major factor in determining whether an acute or chronic inflammatory lung disease developed after infection with M. pulmonis.

Sex steroid hormones enhance immune function in male and female Siberian hamsters

Immune function is better in females than in males of many vertebrate species, and this dimorphism has been attributed to the presence of immunosuppressive androgens in males. We investigated the influence of sex steroid hormones on immune function in male and female Siberian hamsters. Previous studies indicated that immune function was impaired in male and female hamsters housed under short-day photoperiods when androgen and estrogen concentrations were virtually undetectable. In experiment 1, animals were gonadally intact, gonadectomized (gx), or gx with hormone replacement. Females exhibited the expected increase in antibody production over males, independent of hormone treatment condition, whereas male and female gx animals exhibited decreased lymphocyte proliferation to the T cell mitogen, phytohemagglutinin (PHA) compared with intact animals, and this effect was reversed in gx hamsters following testosterone and estradiol treatment, respectively. In experiment 2, testosterone, dihydrotestosterone, and estradiol all enhanced cell-mediated immunity in vitro, suggesting that sex steroid hormones may be enhancing immune function through direct actions on immune cells. In experiment 3, an acute mitogen challenge of lipopolysaccharide significantly suppressed lymphocyte proliferation to PHA in intact males but not females, suggesting that males may be less reactive to a subsequent mitogenic challenge than females. Contrary to evidence in many species such as rats, mice, and humans, these data suggest that sex steroid hormones enhance immunity in both male and female Siberian hamsters.

Interleukin-1beta deficiency results in reduced NF-kappaB levels in pregnant mice

Interleukin (IL)-1beta-deficient (IL-1beta(-/-)) mice were assessed for cytokine production during pregnancy. A significant reduction in nuclear factor (NF)-kappaB p65 protein content was observed in the uteri and spleens of pregnant IL-1beta(-/-) mice, as demonstrated by immunohistochemistry and Western immunoblot analysis. In addition, electromobility gel shift assay revealed less DNA binding activity of NF-kappaB p65-containing complex in pregnant IL-1beta(-/-) mice. To investigate differences in cytokine production regulated by NF-kappaB, the levels of tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, and interferon-gamma were measured in the uterine wall, spleen homogenates, and spleen cell cultures obtained from pregnant mice. Endocervical administration of lipopolysaccharide (LPS) increased cytokine levels in both wild-type (IL-1beta(+/+)) and IL-1beta(-/-) animals, but in IL-1beta(-/-) mice this response was 50-75% lower. Splenocytes from nonpregnant mice exhibited decreased LPS-induced cytokine production when primed in vitro with progesterone. This suppression was 25% greater in IL-1beta(-/-) than in IL-1beta(+/+) mice. These data suggest that constitutive NF-kappaB p65 protein synthesis is regulated by IL-1beta, particularly during pregnancy.