Modulation of the expression of murine lupus by gonadotropin-releasing hormone analogs

Systemic treatment with GnRH agonist produces antidepressant-like effects in LPS induced depression male mouse model

Gonadotropin-releasing hormone (GnRH) is at the head of the neuroendocrine reproductive axis. However, the non-reproductive functions of GnRH expressed in various tissues, including hippocampus, are still not known. Here, we unveil a previously unknown effect of GnRH, which mediates depression-like behaviors through the modulation of microglia function during immune challenge. Specifically, we found that either systemic treatment with GnRH agonist or over-expression of endogenous hippocampal GnRH via viral tool abolished the depression-like behavior after LPS challenges in mice. And the anti-depressant of GnRH was dependent on the hippocampal GnRHR signaling, since antagonizing GnRHR by drug treatment or by hippocampal GnRHR knockdown could block the antidepressant-effect of GnRH agonist. Interestingly, we found that the peripheral GnRH treatment prevented the microglia activation mediated inflammation in the hippocampus of mice. In light of the research findings presented here, we propose that, at least in the hippocampus, GnRH appears to act on GnRHR to regulate higher order non-reproductive functions associated with the microglia mediated neuroinflammation. These findings also provide insights into the function and cross-talk of GnRH, a known neuropeptide hormone, in neuro-immune response.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

Identification of key biomarkers and immune infiltration in sporadic vestibular schwannoma basing transcriptome-wide profiling

BACKGROUND

Vestibular schwannoma (VS) is a common intracranial tumor, with 95% of the cases being sporadic vestibular schwannoma (SVS). The purposed of this study was identifying genes responsible for inflammation in SVS and clarifying its underlying immune mechanisms.

METHODS

Transcriptional sequencing datasets (GSE141801 and GSE108237) from the Gene Expression Omnibus (GEO) database were used in this study. The candidate modules closely related to SVS and hub genes were screened out by weighted gene co-expression network analysis. Τhe sensitivity and specificity of the hub genes for SVS prediction were evaluated by ROC curve analysis. The CIBERSORT algorithm was subsequently applied to analyze the immune infiltration between SVS and controls. Finally, biological signaling pathways involved in the hub genes were identified via gene set enrichment analysis.

RESULTS

A total of 39 significantly enriched in myelination and collagen-containing extracellular matrix DEGs were identified at the screening step. Three hub genes (MAPK8IP1, SLC36A2, and OR2AT4) were identified, which mainly enriched in pathways of melanogenesis, GnRH, and calcium signaling pathways. Compared with normal nerves, SVS tissue contained a higher proportion of T cells, monocytes and activated dendritic cells, whereas proportions of M2 macrophages were lower.

CONCLUSIONS

The intergrated analysis revealed the pattern of immune cell infiltration in SVS and provided a crucial molecular foundation to enhance understanding of SVS. Hub genes MAPK8IP1, SLC36A2 and OR2AT4 are potential biomarkers and therapeutic targets to facilitate the accurate diagnosis, prognosis and therapy of SVS.

Thyroid Dysfunction after Gonadotropin-Releasing Hormone Agonist Administration in Women with Thyroid Autoimmunity

GnRH agonists (GnRHa) are a useful tool for pretreatment before artificial endometrial preparation for frozen-thawed embryo-transfer (FET). Their prolonged administration has been associated with thyroid dysfunction, both hyper and hypothyroidism. The aim of this study is to investigate the impact of GnRHa administration on thyroid function in women undergoing artificial endometrial preparation. Seventy-eight euthyroid women undergoing endometrial preparation with hormone replacement for FET were retrospectively reviewed. They were divided into two groups according to pretreatment with GnRHa (group A, 42 women) or with an oral contraceptive (group B, 36 women). Group A was subsequently divided into two subgroups according to thyroid autoimmunity presence. Thyroid function has been evaluated and compared among groups and subgroups. Our results did not show any statistically significant differences in age, body mass index, and basal thyroid stimulating hormone (TSH). Total estradiol dosage, duration of treatment, and endometrial thickness were comparable among groups. When TSH was measured 14 days after embryo transfer, no significant differences between the two groups were reported. Among women of group A, TSH was significantly higher only in women with thyroid autoimmunity. GnRHa seems to be associated with thyroid dysfunction in women with thyroid autoimmunity undergoing hormone replacement therapy for FET.

Gonadotropin-releasing hormone receptor pathway affects the function of human EBV-transformed B lymphocytes in an age-independent way

Immune system function changes during aging, but the molecular mechanisms of this phenomenon are not fully understood. The present study identified pathways that are associated with age-associated changes in human B lymphocytes. Initial in silico analysis of 1355 genes involved in aging revealed the strongest association (p = 4.36E-21) with the gonadotropin-releasing hormone receptor (GnRHR) pathway. Extended analysis of 2736 aging-related genes using updated databases confirmed such association (p = 2.41E-16). Genes involved in both aging and the GnRHR pathway were significantly involved in lymphocyte B and T activation and aging-related phenotypes, including hyperinsulinemia and diabetes, arthritis, cerebrovascular disease, and cancers. We, therefore, examined non-tumorigenic Epstein-Barr virus (EBV)-transformed B-lymphocyte cell lines that originated from 12 young subjects (20-31 years old) and 10 centenarians (100-102 years old). Gonadotropin-releasing hormone I (GnRH-I) and GnRHR levels did not depend on the age of the cell donors. Inhibition of the GnRHR pathway age-independently decreased cell proliferation (p < 0.001) and increased apoptosis (p < 0.001). However, the decrease in immunoglobulin G synthesis (p < 0.01) was twice as high in centenarian cells than in young cells. In conclusion, the GnRHR pathway regulated essential properties of B lymphocytes. However, upon EBV transformation, memory class-switched B cells became the dominant cell subpopulation. Therefore, the observed effects of GnRHR inhibition were attributable to this subpopulation.

Androgenic modulation of arterial baroreceptor dysfunction and neuroinflammation in endotoxic male rats

Autonomic neuropathy contributes to cardiovascular derangements induced by endotoxemia. In this communication, we tested the hypothesis that androgenic hormones improve arterial baroreflex dysfunction and predisposing neuroinflammatory response caused by endotoxemia in male rats. Baroreflex curves relating changes in heart rate to increases or decreases in blood pressure evoked by phenylephrine (PE) and sodium nitroprusside (SNP), respectively, were constructed in conscious sham-operated, castrated, and testosterone-replaced castrated rats treated with or without lipopolysaccharide (LPS, 10 mg/kg i.v.). Slopes of baroreflex curves were taken as measures of baroreflex sensitivity (BRS). In sham rats, LPS significantly reduced reflex bradycardia (BRSPE) and tachycardia (BRSSNP) and increased immunohistochemical expression of nuclear factor kappa B (NFκB) in heart and brainstem neurons of nucleus tractus solitarius (NTS) and rostral ventrolateral medulla (RVLM). The baroreflex depressant effect of LPS was maintained in castrated rats despite the remarkably attenuated inflammatory response. Testosterone replacement of castrated rats counteracted LPS-evoked BRSPE, but not BRSSNP, depression and increased cardiac, but not neuronal, NFκB expression. We also evaluated whether LPS responses could be affected following pharmacologic inhibition of androgenic biosynthetic pathways. Whereas none of LPS effects were altered in rats pretreated with formestane (aromatase inhibitor) or finasteride (5α-reductase inhibitor), the LPS-evoked BRSPE, but not BRSSNP, depression and cardiac and neuronal inflammation disappeared in rats pretreated with degarelix (gonadotropin-releasing hormone receptor blocker). Overall, despite the seemingly provocative role for the hypothalamic-pituitary-gonadal axis in the neuroinflammatory and baroreflex depressant effects of LPS, testosterone appears to distinctly modulate the two LPS effects.

Pregnancy in Women With Systemic Lupus and Lupus Nephritis

Pregnancy is an altered immunologic state in which hormonal changes impact the immune system to enable maternal tolerance of the fetus. These hormonal and immunologic changes may affect disease activity in systemic lupus erythematosus. Conversely, lupus nephritis and its complications may adversely impact pregnancy. Systemic lupus erythematosus increases the risk of pre-eclampsia and its complications, including preterm birth and intrauterine growth restriction. Comorbidities such as impaired kidney function and hypertension confer additional risk and complexity. Medications used to treat lupus nephritis may impact the fetus, so therapy needs to be tailored to balance maternal benefit and fetal risk. The diagnosis of lupus nephritis during pregnancy can be difficult, as it shares overlapping features with pre-eclampsia. Kidney biopsy is generally safe in pregnancy, and should be considered if the result will affect management. Here we review the clinical aspects of counseling, diagnosis, and management of lupus nephritis in pregnancy.

Updated advances of linking psychosocial factors and sex hormones with systemic lupus erythematosus susceptibility and development

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that primarily affects women, especially those of reproductive age. Genetics, environment, and gene-environment interactions play key roles in the development of SLE. Despite the numerous susceptibility genes of SLE identified to date, gene therapy is far from a clinical reality. Thus, more attention should be paid to the risk factors and underlying mechanisms of SLE. Currently, it is reported that psychosocial factors and sex hormones play vital roles in patients with SLE, which still need further investigated. The purpose of this review is to update the roles and mechanisms of psychosocial factors and sex hormones in the susceptibility and development of SLE. Based on review articles and reports in reputable peer-reviewed journals and government websites, this paper summarized psychosocial factors (e.g., alexithymia, depression, anxiety, negative emotions, and perceived stress) and sex hormones (e.g., estrogens, progesterone, androgens, and prolactin) involved in SLE. We further explore the mechanisms linking these factors with SLE susceptibility and development, which can guide the establishment of practical measures to benefit SLE patients and offer new ideas for therapeutic strategies.

Approach to Androgen Deprivation in the Prostate Cancer Patient with Pre-existing Cardiovascular Disease

PURPOSE OF REVIEW

Androgen deprivation therapy (ADT) is a mainstay of treatment for advanced prostate cancer. Several studies have reported an association between ADT and an increase in cardiovascular events, especially in those receiving gonadotropin-releasing hormone (GnRH) agonists compared to GnRH antagonists. We review the body of literature reporting the association of ADT and cardiovascular morbidity, and discuss the proposed mechanism of cardiovascular disease due to ADT including metabolic changes that may promote atherosclerosis and local hormonal effects that may increase plaque rupture and thrombosis.

RECENT FINDINGS

GnRH agonists appear to increase the risk of cardiovascular morbidity by 20-25% in men on these agents compared those who do not receive ADT. GnRH antagonists may appear to have halve this risk while improving PSA progression-free survival. GnRH antagonists may be superior to GnRH agonists for patients with significant cardiovascular disease, significant metastatic disease burden, or severe lower urinary tract symptoms.

The role of gonadotrophin-releasing hormone antagonists in the treatment of patients with advanced hormone-dependent prostate cancer in the UK

Purpose

Comparing gonadotrophin-releasing hormone (GnRH) antagonists and agonists as androgen deprivation therapy for advanced prostate cancer (PC).

Methods

This article stems from a round-table meeting in December 2014 to compare the properties of GnRH agonists and antagonists in the published literature in order to identify the patient groups most likely to benefit from GnRH antagonist therapy. A broad PubMed and congress abstract search was carried out in preparation for the meeting to ensure that the latest data and opinion were available for the discussions.

Results

In randomised, controlled trials, GnRH antagonist therapy provides more rapid suppression of luteinising hormone, follicle-stimulating hormone and testosterone than GnRH agonist treatment. Compared with the GnRH agonist, there is evidence of improved disease control by a GnRH antagonist, with longer interval to prostate-specific antigen progression and greater reduction of serum alkaline phosphatase. In a post hoc analysis of six randomised trials, the risk of cardiac events within 1 year of initiating therapy was significantly lower among men receiving GnRH antagonist than agonist. Pre-clinical laboratory data suggest a number of mechanisms whereby GnRH antagonist therapy may benefit men with pre-existing cardiovascular disease (CVD), the most plausible hypothesis being that, unlike GnRH agonists, GnRH antagonists do not activate T lymphocytes, which act to increase atherosclerotic plaque rupture.

Conclusion

When making treatment decisions, clinicians should consider comorbidities, particularly CVD, in addition to effects on PC. GnRH antagonists may be appropriate in patients with significant CV risk, existing osteopenia, lower urinary tract symptoms and significant metastatic disease.

Differences in Hypercholesterolemia and Atherogenesis Induced by Common Androgen Deprivation Therapies in Male Mice

BACKGROUND

Treatment of prostate cancer often involves androgen deprivation therapy (ADT) by gonadotropin-releasing hormone (GnRH) receptor agonists, GnRH receptor antagonists, or orchiectomy. ADT may increase the rate of cardiovascular disease events, but recent clinical studies suggested that not all means of ADT carry the same risk, raising the possibility of non-testosterone-mediated effects of different forms of ADT on atherosclerosis. Here we compared effects of ADT on atherosclerosis in intact and orchiectomized Apoe-deficient mice.

METHODS AND RESULTS

Chow-fed Apoe-deficient mice were allocated to orchiectomy and/or monthly injections with the GnRH receptor agonist leuprolide or the GnRH receptor antagonist degarelix. Atherosclerosis was quantified at 26 weeks of age in the aortic arch by en face examination and in the aortic root by histology. In intact Apoe-deficient mice, all types of ADT reduced testosterone production to castration levels. Although hypercholesterolemia was accentuated in leuprolide-treated mice, the amount and composition of atherosclerosis was not different between the different types of ADT. In orchiectomized Apoe-deficient mice, leuprolide, but not degarelix, augmented hypercholesterolemia, changed body, thymus, and spleen weights, and increased atherosclerosis in the aortic root. No direct effects of the drugs were detectable on cytokine secretion from murine bone marrow-derived macrophages or on splenocyte proliferation.

CONCLUSIONS

No differences in the development of atherosclerosis were detected among groups of intact Apoe-deficient mice treated with different types of ADT. A pro-atherogenic, possibly cholesterol-mediated, effect of leuprolide was seen in orchiectomized mice that might be relevant for understanding the potential cardiovascular risk associated with GnRH agonist-based ADT.

Risk and timing of cardiovascular disease after androgen-deprivation therapy in men with prostate cancer

PURPOSE

Findings on the association between risk of cardiovascular disease (CVD) and the duration and type of androgen-deprivation therapy (ADT) in men with prostate cancer (PCa) are inconsistent.

METHODS

By using data on filled drug prescriptions in Swedish national health care registers, we investigated the risk of CVD in a cohort of 41,362 men with PCa on ADT compared with an age-matched, PCa-free comparison cohort (n = 187,785) by use of multivariable Cox proportional hazards regression models.

RESULTS

From 2006 to 2012, 10,656 men were on antiandrogens (AA), 26,959 were on gonadotropin-releasing hormone (GnRH) agonists, and 3,747 underwent surgical orchiectomy. CVD risk was increased in men on GnRH agonists compared with the comparison cohort (hazard ratio [HR] of incident CVD, 1.21; 95% CI, 1.18 to 1.25; and orchiectomy: HR, 1.16; 95% CI, 1.08 to 1.25). Men with PCa on AA were at decreased risk (HR of incident CVD, 0.87; 95% CI, 0.82 to 0.91). CVD risk was highest during the first 6 months of ADT in men who experienced two or more cardiovascular events before therapy, with an HR of CVD during the first 6 months of GnRH agonist therapy of 1.91 (95% CI, 1.66 to 2.20), an HR of CVD with AA of 1.60 (95% CI, 1.24 to 2.06), and an HR of CVD with orchiectomy of 1.79 (95% CI, 1.16 to 2.76) versus the comparison cohort.

CONCLUSION

Our results support that there should be a solid indication for ADT in men with PCa so that benefit outweighs potential harm; this is of particular importance among men with a recent history of CVD.

Short-term treatment with a gonadotropin-releasing hormone antagonist, cetrorelix, in rheumatoid arthritis (AGRA): a randomized, double-blind, placebo-controlled study

Objectives

Gonadotropin-releasing hormone (GnRH) stimulates immune responses; therefore, antagonizing GnRH with cetrorelix may have anti-inflammatory effects. The aim of this study was to assess short-term cetrorelix therapy in rheumatoid arthritis (RA) patients.

Method

In this proof-of-concept, randomized, double-blind study involving 99 patients with active, long-standing RA, 48 patients received subcutaneous cetrorelix (5 mg/day on days 1 and 2; 3 mg/day on days 3–5) and 51 received placebo. The primary end-point was the change in the 28-joint Disease Activity Score based on C-reactive protein (DAS28-CRP) by day 5, when the greatest GnRH suppression was anticipated. Secondary end-points included the change in tumour necrosis factor (TNF)-α, and achievement of American College of Rheumatology (ACR) responses and DAS28-CRP < 2.6 by day 5. Patients were followed up on days 10 and 15.

Results

By day 5, DAS28-CRP was non-significantly reduced by 0.82 in the cetrorelix group compared to a 0.57 reduction in the placebo group (p = 0.091), TNF-α (log pg/mL) was significantly reduced in the cetrorelix group compared with the placebo group [0.55, 95% confidence interval (CI) 0.08–1.01, p = 0.023], and more patients on cetrorelix achieved ACR20 responses (40% vs. 18%, p = 0.015) and DAS28-CRP < 2.6 (13% vs. 0%, p = 0.009). Inflammatory markers increased towards baseline levels after withdrawal of treatment. Rates of adverse events were similar in both groups.

Conclusions

Although there was no significant difference in the primary end-point between groups, antagonizing GnRH led to significant improvements in key secondary end-points. Thus, GnRH antagonists may have rapid anti-inflammatory effects in RA, already occurring within 5 days. The data suggest a novel mode of action for TNF-α inhibition in RA, and potentially in other autoimmune diseases.

Hypothalamic neurohormones and immune responses

The aim of this review is to provide a comprehensive examination of the current literature describing the neural-immune interactions, with emphasis on the most recent findings of the effects of neurohormones on immune system. Particularly, the role of hypothalamic hormones such as Thyrotropin-releasing hormone (TRH), Corticotropin-releasing hormone (CRH) and Gonadotropin-releasing hormone (GnRH). In the past few years, interest has been raised in extrapituitary actions of these neurohormones due to their receptors have been found in many non-pituitary tissues. Also, the receptors are present in immune cells, suggesting an autocrine or paracrine role within the immune system. In general, these neurohormones have been reported to exert immunomodulatory effects on cell proliferation, immune mediators release and cell function. The implications of these findings in understanding the network of hypothalamic neuropeptides and immune system are discussed.

Pituitary-specific Gata2 knockout: effects on gonadotrope and thyrotrope function

GATA2 is expressed in the pituitary during development and in adult gonadotropes and thyrotropes. It is proposed to be important for gonadotrope and thyrotrope cell fate choice and for TSH production. To test this idea, we produced a pituitary-specific knockout of Gata2, designed so that the DNA-binding zinc-finger region is deleted in the presence of a pituitary-specific recombinase transgene. These mice have reduced secretion of gonadotropins basally and in response to castration challenge, although the mice are fertile. GATA2 deficiency also compromises thyrotrope function. Mutants have fewer thyrotrope cells at birth, male Gata2-deficient mice exhibit growth delay from 3-9 wk of age, and adult mutants produce less TSH in response to severe hypothyroidism after radiothyroidectomy. Therefore, Gata2 appears to be dispensable for gonadotrope and thyrotrope cell fate and maintenance, but important for optimal gonadotrope and thyrotrope function. Gata2-deficient mice exhibit elevated levels of Gata3 transcripts in the pituitary gland, suggesting that GATA3 can compensate for GATA2.

GnRH-I and GnRH-II have differential modulatory effects on human peripheral blood mononuclear cell proliferation and interleukin-2 receptor gamma-chain mRNA expression in healthy males

GnRH-I and its receptor (GnRHR-I) have previously been demonstrated and shown to be biologically active in the immune system, notably within peripheral lymphocytes. Recently however, a second form of GnRH (GnRH-II) has been described in the human. The functions of both these neuropeptides in PMBCs have not been understood yet. The present study was therefore designed to investigate the effects of GnRH-I and/or GnRH-II on human PMBC proliferation in males. Secondly, the effects of GnRH-I and GnRH-II on IL-2 dependent lymphocyte proliferation were examined. Finally, we analysed the role of GnRH-I and GnRH-II in IL-2R gamma-chain expression. Peripheral venous blood samples were obtained from six male healthy volunteers (Mean age 27.75 +/- 1.5). Non-radioactive cell proliferation assay was used for proliferation studies and we used quantitative real-time RT-PCR to examine the role of GnRH-I and GnRH-II on IL-2R gamma-chain expression in PMBCs. Treatment of PMBCs with GnRH-I (10(-9) M and 10(-5) M) and with interleukin-2 (IL-2) (50 U/ml) resulted in a significant increase in cell proliferation compared with the untreated control. PMBCs cotreated with IL-2 and GnRH-I demonstrated higher proliferative responses than IL-2 treatment alone, the enhancement of GnRH-I on IL-2 response being significant only at GnRH-I concentration of 10(-5) M. Co-incubation of IL-2+ GnRH 10(-5) M with a GnRH antagonist (Cetrorelix; 10(-6) M) significantly decreased the proliferation. GnRH-II did not affect the proliferation of PMBCs alone, and did not alter the proliferative response to IL-2. The proliferative responses to GnRH-I (alone and with IL-2) were significantly attenuated by GnRH-II coincubation (each in equal molar concentrations; 10(-9) M to 10(-5) M). It was found that GnRH-I increased the expression of IL-2Rgamma mRNA in a dose dependent manner, with a significant increase of percentage 162.3 +/- 14 of control at 10(-5) M. In contrast, IL-2Rgamma expression was significantly decreased in all concentrations of GnRH-II (10(-9) M to10(-5) M), and the maximum decrease was detected at 10(-5) M, with percentage 37.7 +/- 6.6 of control. All these findings strongly suggest that regulation of IL-2R expression may therefore be an important target for GnRH-I and GnRH-II in PMBCs in males. In summary, present study clearly demonstrates the differential effects of GnRH-I and GnRH-II on PMBC proliferation, IL-2 proliferative response, and IL-2Rgamma expression in PMBCs in males. To our knowledge, our observations provide the first evidence for the interactions of these local neuropeptides at lymphocyte level. Further experimental data in human are warranted to explore the clinical implications of these data.

Immunomodulatory actions of gonadal steroids may be mediated by gonadotropin-releasing hormone

Estrogens are considered to be immunostimulatory, whereas androgens are considered to be immunosuppressive. We hypothesized that the divergent actions of gonadal steroids on the immune system may be mediated indirectly, via their potent divergent feedback effects on the hypothalamic hormone GnRH, which is itself immunostimulatory. We used the GnRH-deficient HPG/Bm mouse in an effort to disentangle the effects of gonadal steroids from the effects of GnRH. We randomized GnRH-deficient mice and their GnRH-sufficient littermates to receive androgens, estrogens, or GnRH. We subsequently measured B and T cell proliferative responses to mitogen and serum IgG levels. We demonstrate that estrogens exert stimulatory effects on B cell proliferation and serum IgG levels in the presence of GnRH but not in the absence of GnRH. Testosterone exerts suppressive effects on B cell function in the presence of GnRH but not in its absence. Androgens and estrogens exerted divergent actions on T cell function irrespective of the presence and absence of GnRH, although responses were markedly attenuated in GnRH-deficient mice. Our data suggest that the immunostimulatory effects of estrogen and the immunosuppressive effects of androgens on B cell function may be mediated indirectly via GnRH.

Mast cells in the rat brain synthesize gonadotropin-releasing hormone

Mast cells occur in the brain and their number changes with reproductive status. While it has been suggested that brain mast cells contain the mammalian hypothalamic form of gonadotropin-releasing hormone (GnRH-I), it is not known whether mast cells synthesize GnRH-I de novo. In the present study, mast cells in the rat thalamus were immunoreactive to antisera generated against GnRH-I and the GnRH-I associated peptide (GAP); mast cell identity was confirmed by the presence of heparin, a molecule specific to mast cells, or serotonin. To test whether mast cells synthesize GnRH-I mRNA, in situ hybridization was performed using a GnRH-I cRNA probe, and the signal was identified as being within mast cells by the binding of avidin to heparin. GnRH-I mRNA was also found, using RT-PCR, in mast cells isolated from the peritoneal cavity. Given the function of GnRH-I in the regulation of reproduction, changes in the population of brain GnRH-I mast cells were investigated. While housing males with sexually receptive females for 2 h or 5 days resulted in a significant increase in the number of brain mast cells, the proportion of mast cells positive for GnRH-I was similar to that in males housed with a familiar male. These findings represent the first report showing that mast cells synthesize GnRH-I and that the mast cell increase seen in a reproductive context is the result of a parallel increase in GnRH-I positive and non-GnRH-I positive mast cells.

Pathogenesis of systemic lupus erythematosus

The exact patho-aetiology of systemic lupus erythematosus (SLE) remains elusive. An extremely complicated and multifactorial interaction among various genetic and environmental factors is probably involved. Multiple genes contribute to disease susceptibility. The interaction of sex, hormonal milieu, and the hypothalamo-pituitary-adrenal axis modifies this susceptibility and the clinical expression of the disease. Defective immune regulatory mechanisms, such as the clearance of apoptotic cells and immune complexes, are important contributors to the development of SLE. The loss of immune tolerance, increased antigenic load, excess T cell help, defective B cell suppression, and the shifting of T helper 1 (Th1) to Th2 immune responses leads to B cell hyperactivity and the production of pathogenic autoantibodies. Finally, certain environmental factors are probably required to trigger the disease.

Neuroendocrine-immune (NEI) circuitry from neuron-glial interactions to function: Focus on gender and HPA-HPG interactions on early programming of the NEI system

Bidirectional communication between the neuroendocrine and immune systems during ontogeny plays a pivotal role in programming the development of neuroendocrine and immune responses in adult life. Signals generated by the hypothalamic-pituitary-gonadal axis (i.e. luteinizing hormone-releasing hormone, LHRH, and sex steroids), and by the hypothalamic-pituitary-adrenocortical axis (glucocorticoids (GC)), are major players coordinating the development of immune system function. Conversely, products generated by immune system activation exert a powerful and long-lasting regulation on neuroendocrine axes activity. The neuroendocrine-immune system is very sensitive to preperinatal experiences, including hormonal manipulations and immune challenges, which may influence the future predisposition to several disease entities. We review our work on the ongoing mutual regulation of neuroendocrine and immune cell activities, both at a cellular and molecular level. In the central nervous system, one chief compartment is represented by the astroglial cell and its mediators. Hence, neuron-glial signalling cascades dictate major changes in response to hormonal manipulations and pro-inflammatory triggers. The interplay between LHRH, sex steroids, GC and pro-inflammatory mediators in some physiological and pathological states, together with the potential clinical implications of these findings, are summarized. The overall study highlights the plasticity of this intersystem cross-talk for pharmacological targeting with drugs acting at the neuroendocrine-immune interface.

Gender, neuroendocrine-immune interactions and neuron-glial plasticity. Role of luteinizing hormone-releasing hormone (LHRH)

Signals generated by the hypothalamic-pitutary-gonadal (HPG) axis powerfully modulate immune system function. This article summarizes some aspects of the impact of gender in neuroendocrine immunomodulation. Emphasis is given to the astroglial cell compartment, defined as a key actor in neuroendocrine immune communications. In the brain, the principal hormones of the HPG axis directly interact with astroglial cells. Thus, luteinizing hormone releasing hormone, LHRH, influences hypothalamic astrocyte development and growth, and hypothalamic astrocytes direct LHRH neuron differentiation. Hormonally induced changes in neuron-glial plasticity may dictate major changes in CNS output, and thus actively participate in sex dimorphic immune responses. The impact of gender in neuroimmunomodulation is further underlined by the sex dimorphism in the expression of genes encoding for neuroendocrine hormones and their receptors within the thymus, and by the potent modulation exerted by circulating sex steroids during development and immunization. The central role of glucocorticoids in the interactive communication between neuroendocrine and immune systems, and the impact of gender on hypothalamic-pituitary-adrenocortical (HPA) axis modulation is underscored in transgenic mice expressing a glucocorticoid receptor antisense RNA.

Gonadotropin-releasing hormone and G proteins: potential roles in autoimmunity

The hypothalamic homone gonadotropin-releasing hormone (GnRH) displays gender-specific actions. Pituitary responsiveness to GnRH is generally increased by estrogens and decreased by androgens. GnRH is now known to be produced by the immune system and to exert potent immunologic actions. Our central hypothesis is that gender differences in responsiveness to GnRH in the immune system play a pivotal role in the gender differences in immunity and autoimmunity. Studies in lupus-prone mice demonstrate that GnRH exacerbates murine lupus in a gender-specific fashion. Subsequent studies from our laboratory suggest that the gender differences in immunologic responsiveness to GnRH may relate to differences in the expression of the signal transducers through which GnRH acts, namely, the G proteins, Gs, and Gq/11. We have further demonstrated gender differences in second messengers for GnRH, IP3, and cAMF in immune cells. We have also demonstrated that GnRH agonist increases the quantities and/or activity of G proteins in immune cells in a gender-specific fashion. We speculate that gender differences in GnRH production and action, and in G protein expression play a role in a variety of autoimmune diseases that affect females predominantly.

Gender-specific exacerbation of murine lupus by gonadotropin-releasing hormone: potential role of G alpha(q/11)

We have previously demonstrated that GnRH and its analogues modulate the severity of murine systemic lupus erythematosus. In the present study, we demonstrate that GnRH alters disease severity in a sexually dimorphic fashion, even in gonadectomized mice. GnRH administration leads to an exacerbation of lupus in ovariectomized females, whereas it exerts no effect in castrated males. We initially hypothesized that gender differences in lymphocytic expression of GnRH receptor might explain these observations. Using competitive RT-PCR and binding studies to quantitate GnRH receptor expression in lymphoid organs, we found that GnRH administration led to decreased expression of GnRH receptor messenger RNA (mRNA) and GnRH binding, compared with vehicle, in spleens of ovariectomized females after 2 weeks of treatment. These decreases occurred concurrently with increased expression of interleukin-2 receptor mRNA and protein in females. GnRH administration did not alter GnRH receptor or interleukin-2 receptor mRNA or protein in castrated males. GnRH exerts actions on the pituitary through G protein signal transduction, specifically through G alpha(q/11). Competitive RT-PCR revealed that GnRH administration was associated with increases in the expression of G alpha(q/11) mRNA, compared with vehicle, in spleens in ovariectomized females but not in castrated males. Immunoblot analysis revealed a similar pattern. We conclude that gender differences in expression of G alpha(q/11) may contribute to gender differences in immunity and/or autoimmune disease.

Differential effects of estrogen and prolactin on autoimmune disease in the NZB/NZW F1 mouse model of systemic lupus erythematosus

Estrogen and prolactin have been shown to modulate autoimmunity in the NZB/NZW F1 (B/W) mouse model of systemic lupus erythematosus (SLE). However, estrogen stimulates prolactin secretion. The goal of this study was to examine differential effects of estrogen and prolactin in the female B/W mouse model of SLE. B/W females were manipulated to create combinations of low and high concentrations of serum estrogen and prolactin. Hyperprolactinemic mice with either low or high serum estrogen levels had accelerated development of albuminuria at 24 and 32 weeks of age compared to normal and hypoprolatinemic mice. High estrogen/high prolactin mice also had a higher percentage of anti-DNA antibodies compared to mice in the low estrogen/low prolactin and the high estrogen/low prolactin groups. IgG levels were not significantly different between groups. Mean survival was shortest in the high estrogen/high prolactin group (34+/-1.0 weeks) and longest in the high estrogen/low prolactin group (42+/-1.2 weeks; P < 0.05). High levels of serum estrogen were associated with depressed in vitro lymphoproliferation and IL-2 production. This study suggests that high prolactin levels in either high or low serum estrogen states are associated with accelerated autoimmunity in the B/W mouse. This study further demonstrates that high estrogen levels do not accelerate murine SLE when the prolactin-stimulating property of estrogen is suppressed by bromocriptine. Further investigation of hormonal interactions in autoimmunity will provide a better understanding of hormonal immunoregulation and, perhaps, lead to improved clinical application of hormonal immunomodulation.

Gonadotropin-releasing hormone agonist influences absolute levels of lymphocyte subsets in vivo in male mice

Our earlier studies have demonstrated that gonadotropin-releasing hormone (GnRH) agonists suppress immune system function in female mice. No systematic studies regarding the effect of gender on immune system function following GnRH agonist treatment, however, have been reported. This study, therefore, investigated sequential changes in lymphocyte subsets in 3- and 10-week-old male mice following agonist or placebo administration. Changes in immunophenotypic expression of lymphocytes from thymus, bone marrow, spleen, and blood were analysed at periodic intervals. Upon agonist administration, plasma testosterone levels were significantly increased in pre-pubertal mice, but were significantly decreased in post-pubertal males. Absolute thymic weights, thymocytes and T subsets were significantly increased from the third week regardless of gonadal status. Blood lymphocyte subsets showed a decreasing trend after agonist administration in pre-pubertal males, whereas no differences were observed in post-pubertal males. No significant differences were observed in spleen cells after agonist administration. These studies, together with earlier observations in female mice indicate that GnRH agonist effects on the immune system, are independent of steroid hormone levels. In contrast to suppressive effects in females, GnRH agonist induce no change or ultimately enhanced lymphocyte counts in males, indicating differential effects on the immune system between males and females. This may have important implications for the treatment of various diseases.

Neuroendocrineimmunology (NEI) at the turn of the century: towards a molecular understanding of basic mechanisms and implications for reproductive physiopathology

The interactions between the nervous, endocrine and immune systems require a complex communication network. The central nervous system (CNS) affects the immune system through endocrine, paracrine and neuronal mechanisms. Evidence that this bidirectional communication plays a vital role in the regulation of physiological homeostatic mechanisms while a disfunction of the neuroendocrineimmune balance favors the susceptibility to a number of diseases is derived largely by animal models but also by an increasing number of clinical studies in different fields, including endocrinology, reproductive physiology, pediatrics, oncology, neurology and psychiatry. An increasing number of endocrine hormones, neurotransmitters and neuropeptides are expressed in immune tissues and cells and are actively involved in the physiological regulation of immunity. Conversely, the endocrine and nervous systems harbor receptors for a wide variety of immunologically-derived substances, suggesting potential regulatory feedback loops between the three major integrative bodily systems. Major implications for the reproductive endocrinology field are that psychoneuroendocrine processes may alter fertility via immunomodulation, and that events that occur as part of immune responses influence the neuroendocrine axes, which in turn counter-regulate immune function. In the present article, some features of reproductive-immune interactions will be described, and the neuroendocrineimmune dialogue via the chief reproductive hormone, luteinizing hormone-releasing hormone (LHRH), will be summarized as prototype of intersystem crosstalk. A particular emphasis will be given to the cytokine-LHRH interrelationships both at central (i.e. especially with the astroglial compartment) and peripheral levels. The surprisingly similar communication network systems used by the gonads and the thymus will be summarized, and the sexually-driven dimorphisms dictating female versus male reproductive and immunological capacities reviewed. Evidence that neural, endocrine and immune systems work together as a single unit are emphasized in animal models and human pathologies where interruption of NEI feedback loops results in long lasting pathological consequences for the nervous, endocrine and immune functions.