Oestrogen is a potent disease accelerator in SLE-prone MRL lpr/lpr mice

Xist Deletion in B Cells Results in Systemic Lupus Erythematosus Phenotypes

Systemic lupus erythematosus (SLE) is an autoimmune disease preferentially observed in females. X-linked gene expression in XX females is normalized to that of XY males by X-Chromosome Inactivation (XCI). However, B cells from female SLE patients and mouse models of SLE exhibit mislocalization of Xist RNA, a critical regulator of XCI, and aberrant expression of X-linked genes, suggesting that impairment of XCI may contribute to disease. Here, we find that a subset of female mice harboring a conditional deletion of Xis t in B cells ("Xist cKO") spontaneously develop SLE phenotypes, including expanded activated B cell subsets, disease-specific autoantibodies, and glomerulonephritis. Moreover, pristane-induced SLE-like disease is more severe in Xist cKO mice. Activated B cells from Xist cKO mice with SLE phenotypes have increased expression of proinflammatory X-linked genes implicated in SLE. Together, this work indicates that impaired XCI maintenance in B cells directly contributes to the female-bias of SLE.

Increased development of T-bet+CD11c+ B cells predisposes to lupus in females: Analysis in BXD2 mouse and genetic crosses

Cardinal features of lupus include elevated B cell activation and autoantibody production with a female sex preponderance. We quantified interactions of sex and genetic variation on the development of autoimmune B-cell phenotypes and autoantibodies in the BXD2 murine model of lupus using a cohort of backcrossed progeny (BXD2 x C57BL/6J) x BXD2. Sex was the key factor leading to increased total IgG, IgG2b, and autoantibodies. The percentage of T-bet+CD11c+ IgD+ activated naive B cells (aNAV) was higher in females and was associated with increased T-bet+CD11c+ IgD- age-related B cells, Fas+GL7+ germinal center B cells, Cxcr5-Icos+ peripheral T-helper cells, and Cxcr5+Icos+ follicular T-helper cells. IFN-β was elevated in females. Variation in aNAV cells was mapped to Chr 7 in a locus that shows significant interactions between the female sex and heterozygous B/D variant. Our results suggest that activation of naive B cells forms the basis for the female-predominant development of autoantibodies in lupus-susceptible BXD2 mice.

A tissue-selective estrogen complex as treatment of osteoporosis in experimental lupus

Osteoporosis is a common secondary complication in patients with systemic lupus erythematosus (SLE). Current osteoporosis treatment with bisphosphonates has some negative side effects and there is a lack of data regarding newer treatments options for SLE associated osteoporosis. The tissue-selective estrogen complex (TSEC) containing conjugated estrogens and the selective estrogen receptor modulator bazedoxifene (Bza) is approved for treatment of postmenopausal vasomotor symptoms and prevention of osteoporosis. However, it has not been evaluated for treatment of osteoporosis in postmenopausal SLE patients. Ovariectomized MRL/lpr mice constitute a model for postmenopausal lupus that can be used for osteoporosis studies. We used this model in a set of experiments where the mice were treated with different doses of 17β-estradiol-3-benzoate (E2), Bza, or TSEC (E2 plus Bza), administered in the early or late phases of disease development. The skeleton was analyzed by dual-energy X-ray absorptiometry, peripheral quantitative computed tomography, and high-resolution microcomputed tomography. The lupus disease was assessed by determination of proteinuria, hematuria, and lupus disease markers in serum. Treatment with medium dose TSEC administered in early disease protected ovariectomized MRL/lpr mice from trabecular bone loss, while there were no differences in lupus disease parameters between treatments. This is the first experimental study to investigate TSEC as a potential new therapy for osteoporosis in postmenopausal SLE.

Osteoporosis in a murine model of postmenopausal lupus

BACKGROUND/OBJECTIVE

Postmenopausal women with systemic lupus erythematosus have an increased risk of osteoporosis and associated fractures. Their increased osteoporosis risk is probably caused by a high level of inflammation, use of glucocorticoids, impaired kidney function, and early menopause as these are known risk factors for osteoporosis. Due to these risk factors and the lack of safe and effective treatments, new therapies for the treatment of osteoporosis in this group of patients are needed. Ovariectomized MRL/lpr mice constitute a well-established model for studies of postmenopausal systemic lupus erythematosus; however, it is not clear to what extent this experimental model is associated with the development of osteoporosis. Thus, the aim of this study was to characterize the skeleton of ovariectomized MRL/lpr mice to determine the suitability of this model in studies of prospective new therapies for osteoporosis in postmenopausal systemic lupus erythematosus patients.

METHODS

Skeletal parameters were measured in MRL/lpr mice and MRL/++ control mice, using peripheral quantitative computed tomography, high-resolution micro-computed tomography and biomechanical analyses. mRNA expression of bone-remodeling markers was measured by quantitative polymerase chain reaction and serological markers of lupus disease were evaluated using ELISA.

RESULTS

Total bone mineral density was reduced in MRL/lpr mice compared with MRL/++ mice and MRL/lpr mice had reduced cortical and trabecular bone thickness compared with MRL/++ mice. In line with the low bone mass of MRL/lpr mice, gene expression analysis of cortical bone from these mice indicated an increased osteoclast activity as well as a decreased osteoblastogenesis and osteoblast activity, compared with MRL/++ mice.

CONCLUSION

Ovariectomized MRL/lpr mice constitute a valuable experimental model for studies of osteoporosis development in postmenopausal systemic lupus erythematosus and this model is thus suitable for future studies of osteoporosis treatment in systemic lupus erythematosus.

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.

Sex Differences in Older Adults' Immune Responses to Seasonal Influenza Vaccination

Background: Sex differences in immune responses to influenza vaccine may impact efficacy across populations. Methods: In a cohort of 138 older adults (50-74 years old), we measured influenza A/H1N1 antibody titers, B-cell ELISPOT response, PBMC transcriptomics, and PBMC cell compositions at 0, 3, and 28 days post-immunization with the 2010/11 seasonal inactivated influenza vaccine. Results: We identified higher B-cell ELISPOT responses in females than males. Potential mechanisms for sex effects were identified in four gene clusters related to T, NK, and B cells. Mediation analysis indicated that sex-dependent expression in T and NK cell genes can be partially attributed to higher CD4+ T cell and lower NK cell fractions in females. We identified strong sex effects in 135 B cell genes whose expression correlates with ELISPOT measures, and found that cell subset differences did not explain the effect of sex on these genes' expression. Post-vaccination expression of these genes, however, mediated 41% of the sex effect on ELISPOT responses. Conclusions: These results improve our understanding of sexual dimorphism in immunity and influenza vaccine response.

Complete knockout of estrogen receptor alpha is not directly protective in murine lupus

Systemic lupus erythematosus (SLE) is a chronic and potentially severe autoimmune disease that disproportionately affects women. Despite a known role for hormonal factors impacting autoimmunity and disease pathogenesis, the specific mechanisms of action remain poorly understood. Our laboratory previously backcrossed "estrogen receptor alpha knockout (ERαKO)" mice onto the NZM2410 lupus prone background to generate NZM/ERαKO mice. This original ERαKO mouse, developed in the mid-1990s and utilized in hundreds of published studies, is not in fact ERα null. They express an N-terminally truncated ERα, and are considered a functional KO. They have physiologic deficiencies including infertility due to disruption of a critical activation domain (AF-1) at the N terminus of ERα, required for most classic estrogen (E2) actions. We demonstrated that female NZM/ERαKO mice had significantly less renal disease and significantly prolonged survival compared to WT littermates despite similar serum levels of autoantibodies and glomerular immune complex deposition. Herein, we present results of experiments using a lupus prone true ERα-/- mice (deletional KO mice on the NZM2410 background), surprisingly finding that these animals were not protected if they were ovariectomized, suggesting that another hormonal component confers protection, possibly testosterone, rather than the absence of the full-length ERα.

Estrogen-induced expression of tumor necrosis factor-like weak inducer of apoptosis through ERα accelerates the progression of lupus nephritis

OBJECTIVES

Oestrogens have been shown to play key roles in the pathogenesis of SLE. The aim of this study was to investigate the roles and mechanisms of 17β-estradiol (E2) in TNF-like weak inducer of apoptosis (TWEAK) expression in LN.

METHODS

Peripheral blood mononuclear cells (PBMCs) obtained from LN patients were used for in vitro experiments, while female MRL/lpr and MRL/MpJ mice were used for in vivo studies. E2, ICI 182 780 [estrogen receptor (ER)-selective antagonist], methyl-piperidino-pyrazole (MPP, ERα-selective modulator), lentivirus (LV)-TWEAK-short hairpin RNA (shRNA) and LV-control-shRNA treatments were used in this study.

RESULTS

TWEAK mRNA expression in PBMCs was significantly increased following E2 treatment and downregulated after incubation with ICI 182 780 or MPP. Compared with sham-operated MRL/lpr mice, ovariectomized mice, treated with dimethyl sulphoxide vehicle alone, showed lower expression levels of renal TWEAK mRNA and protein. The expression of both mRNA and protein in ovariectomized mice was upregulated after E2 treatment and downregulated after ICI 182 780 or MPP co-treatment. Severe renal damage was observed in E2-treated ovariectomized mice, as were higher serum levels of IL-6, compared with dimethyl sulphoxide vehicle-treated ovariectomized mice. Co-treatment with LV-TWEAK-shRNA reversed these changes, and LV-control-shRNA treatment had no effect on them.

CONCLUSION

Our results demonstrated that E2 plays an important role in the upregulation of TWEAK expression in LN, most likely through an ERα-dependent pathway, causing kidney damage. This provides a novel insight into the mechanisms of the E2-TWEAK signalling pathway in LN.

Early Ovariectomy Results in Reduced Numbers of CD11c+/CD11b+ Spleen Cells and Impacts Disease Expression in Murine Lupus

Ninety percent of those diagnosed with systemic lupus erythematosus are female, with peak incidence between the ages of 15 and 45, when women are most hormonally active. Despite significant research effort, the mechanisms underlying this sex bias remain unclear. We previously showed that a functional knockout of estrogen receptor alpha (ERα) resulted in significantly reduced renal disease and increased survival in murine lupus. Dendritic cell (DC) development, which requires both estrogen and ERα, is impacted, as is activation status and cytokine production. Since both estrogen and testosterone levels have immunomodulating effects, we presently studied the phenotype of NZM2410 lupus-prone mice following post- and prepubertal ovariectomy (OVX) ± estradiol (E2) replacement to determine the impact of hormonal status on disease expression and DC development in these mice. We observed a trend toward survival benefit in addition to decreased proteinuria and improved renal histology in the early OVX, but not late OVX- or E2-repleted WT mice. Interestingly, there was also a significant difference in splenic DC subsets by flow cytometry. Spleens from NZM mice OVX'd early had a significant decrease in proinflammatory CD11c+CD11b+ DCs (vs. unmanipulated WTs, late OVX- and E2-repleted mice). These early OVX'd animals also had a significant increase in tolerogenic CD11c+CD8a+ DCs vs. WT. These data join a growing body of evidence that supports a role for hormone modulation of DCs that likely impacts the penetrance and severity of autoimmune diseases, such as lupus.

17β-Estradiol enhances the activation of IFN-α signaling in B cells by down-regulating the expression of let-7e-5p, miR-98-5p and miR-145a-5p that target IKKε

The activation of IFN-α signaling in B cells contributes to the pathogenesis of systemic lupus erythematosus (SLE). Many studies suggest that estrogens are closely related to the gender difference in the prevalence of SLE. However, the underlying mechanism of the interaction between estrogens and the activation of IFN-α signaling in SLE B cells remains incompletely understood. In the present study, we first found that healthy female mice showed an up-regulated type I IFN-induced gene signature in B cells compared with age-matched male mice, and an in vivo study revealed that the gender difference was related to 17β-estradiol. Moreover, we found that 17β-estradiol could enhance the activation of IFN-α signaling in an ERα-dependent manner by down-regulating the expression of three microRNAs, including let-7e-5p, miR-98-5p and miR-145a-5p. These microRNAs could target the 3'UTR of the IKKε-encoding gene IKBKE directly and regulate the expression of IKKε, which can promote the activation of IFN-α signaling. In addition, compared with age-matched male mice, female mice showed a higher level of IKKε and lower levels of let-7e-5p, miR-98-5p and miR-145a-5p in B cells. Moreover, peripheral blood mononuclear cells from women showed a higher level of IKKε and lower levels of let-7e-5p, miR-98-5p and miR-145a-5p compared with those from age-matched men. These data suggest that 17β-estradiol amplifies the activation of IFN-α signaling in B cells via IKKε by down-regulating the expression of let-7e-5p, miR-98-5p and miR-145a-5p. Our findings may provide a new perspective for understanding the mechanism underlying the gender difference in the prevalence of SLE.

Treatment for insomnia in combat-exposed OEF/OIF/OND military veterans: preliminary randomized controlled trial

Chronic insomnia is highly prevalent among military personnel returning from Iraq and Afghanistan. We evaluated the effects of a military version of a brief behavioral treatment of insomnia (BBTI-MV) compared to an information only control (IC) condition in combat-exposed Veterans of Operations Enduring/Iraqi Freedom or Operation New Dawn (OEF/OIF/OND) on insomnia, sleep quality, and daytime symptoms of anxiety and depression. Forty OEF/OIF/OND Veterans (Mean age = 38.4 years old, s.d. = 11.69; 85% men; 77.5% white) were randomized to one of two conditions. BBTI-MV consisted of two in-person sessions and two telephone contacts delivered over four weeks, and included personalized recommendations to reduce insomnia. The IC condition also consisted of 2 in-person sessions two telephone contacts delivered over four weeks, and Veterans were encouraged to read written information about sleep-promoting behaviors. The Insomnia Severity Index, Pittsburgh Sleep Quality Index, PTSD Checklist, and Beck Depression and Anxiety Inventories were completed at baseline, post-treatment, and at the six-month follow-up. Both interventions were associated with clinically significant improvements in insomnia, although the magnitude of improvements in sleep and rates of treatment response and remission were greater for BBTI-MV compared to IC from pre- to post-treatment. Both BBTI-MV and the provision of information were associated with clinically significant improvements in insomnia among Veterans. Despite the preliminary nature of the findings and limitations inherent to small controlled trials, the findings suggest that both approaches may provide viable options in a stepped-care approach to the treatment of insomnia in retuning combat-exposed Veterans. Larger, confirmatory effectiveness trials are required.

CLINICALTRIALSGOV IDENTIFIER

NCT00840255.

Does estrogen deficiency cause lacrimal gland inflammation and aqueous-deficient dry eye in mice?

Researchers have proposed that estrogen deficiency will lead to a Sjögren's syndrome (SjS)-like lacrimal gland inflammation, aqueous tear deficiency and dry eye. The purpose of this study was to determine whether this proposal is correct. Lacrimal glands were obtained from adult, age-matched wild type (WT) and aromatase knockout (ArKO) mice, in which estrogen synthesis is completely eliminated. Tissues were also obtained from autoimmune MRL/Mp-lpr/lpr (MRL/lpr) mice as inflammation controls. Tear volumes in WT and ArKO mice were measured and glands were processed for molecular biological and histological evaluation. Our results demonstrate that estrogen absence does not lead to a SjS-like inflammation in lacrimal tissue or to an aqueous-deficient dry eye. There was no upregulation of genes associated with inflammatory pathways in lacrimal glands of male or female ArKO mice. Such inflammatory activity was prominent in autoimmune MRL/lpr tissues. We also found no evidence of inflammation in lacrimal gland tissue sections of estrogen-deficient mice, and tear volumes of ArKO males were actually increased as compared to those WT controls. Interestingly, our study did show that estrogen absence influences the expression of thousands of lacrimal gland genes, and that this impact is sex- and genotype-specific. Our findings demonstrate that estrogen absence is not a risk factor for the development of SjS-like lacrimal gland inflammation or for aqueous-deficient dry eye in mice.

Estrogen receptor α regulates tripartite motif-containing protein 21 expression, contributing to dysregulated cytokine production in systemic lupus erythematosus

OBJECTIVE

To examine the role of 17β-estradiol in the regulation of the autoantigen tripartite motif-containing protein 21 (TRIM-21) in patients with systemic lupus erythematosus (SLE).

METHODS

Monocytes isolated from healthy control subjects and patients with SLE were stimulated with 17β-estradiol and/or the estrogen receptor α (ERα) antagonist methyl-piperidino-pyrazole dihydrochloride. TRIM-21, ERα, and CREMα expression was determined by real-time polymerase chain reaction (PCR) analysis. MatInspector software was used to identify putative binding sites within the TRIM-21 promoter. ERα binding to the TRIM-21 gene promoter region in monocytes was analyzed by chromatin immunoprecipitation (ChIP) assay. TRIM-21 and interferon regulatory factor 3 protein levels were analyzed by Western blotting.

RESULTS

Real-time PCR analysis demonstrated a role of estrogen in the regulation of TRIM-21 expression in monocytes, which correlated positively with ERα gene expression in patients with SLE. Investigations into the human TRIM-21 promoter revealed the presence of an estrogen response element, with ChIP assays confirming ERα binding to this site. Studies into estrogen-induced TRIM-21 expression revealed a hyperresponsiveness of SLE patients to 17β-estradiol, which led to the enhanced levels of TRIM-21 observed in these individuals.

CONCLUSION

Our results demonstrate a role of estrogen in the regulation of TRIM-21 expression through an ERα-dependent mechanism, a pathway that we observed to be overactive in SLE patients. Treatment of monocytes with an ERα antagonist abrogated estrogen-induced TRIM-21 expression and, as a consequence, decreased the expression of interleukin-23. These findings identify TRIM-21 as a novel ERα-regulated gene and provide novel insights into the link between estrogen and the molecular pathogenesis of SLE.

17β-Estradiol protects against the progression of hypertension during adulthood in a mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disorder with a high prevalence of hypertension and cardiovascular disease. Because SLE predominantly affects women, estrogen is commonly implicated as a contributor to SLE disease progression. Using an established mouse model of SLE (female NZBWF1), we tested whether estrogen has a causal role in the development of hypertension in adulthood. Thirty-week-old SLE and control mice (NZW/LacJ) underwent either a sham or ovariectomy (OVX) procedure. 17β-Estradiol (E2; 5 μg/mouse, twice/week, subcutaneously) was administered to a subset of OVX mice. Mean arterial pressure (in mm Hg) was increased in SLE mice (134±4 versus 119±3 in controls). Contrary to our hypothesis, OVX exacerbated the hypertension in female SLE mice (153±3; P<0.05 versus SLE sham), and repletion of E2 prevented the OVX-induced increase in blood pressure (132±2). The prevalence of albuminuria was increased in SLE mice compared with controls (37% versus 0%). OVX increased the prevalence in SLE mice (70% versus 37% in SLE shams). Repletion of E2 completely prevented albuminuria in OVX SLE mice. Renal cortical tumor necrosis factor α was increased in SLE mice compared with controls and was further increased in OVX SLE. The OVX-induced increase in renal tumor necrosis factor α expression was prevented by repletion of E2. Treatment of OVX SLE mice with the tumor necrosis factor α inhibitor, etanercept, blunted the OVX-induced increase in blood pressure (140±2) and prevalence of albuminuria (22%). These data suggest that 17β-estradiol protects against the progression of hypertension during adulthood in SLE, in part, by reducing tumor necrosis factor α.

17-β Estradiol reduces atherosclerosis without exacerbating lupus in ovariectomized systemic lupus erythematosus-susceptible LDLr(-/-) mice

OBJECTIVE

To test the hypothesis that estrogen treatment in a radiation chimera mouse model of systemic lupus erythematosus (SLE) and atherosclerosis will increase SLE-associated atherosclerosis by increasing autoantibody production and inflammation.

METHODS

We used a radiation chimera mouse model in which bone marrow from the polygenic B6.Sle1.2.3 model of SLE was transferred to the low density lipoprotein receptor knock out (LDLr(-/-)) model of atherosclerosis on a C57BL/6 background (Sle/LDLr(-/-)). Ovariectomized chimeric mice were treated for 10 weeks with either 5.6 μg/day of 17β-estradiol or placebo; outcomes included atherosclerosis plaque size, anti-dsDNA autoantibody production and renal pathology.

RESULTS

Mean atherosclerosis plaque size was 67.4 ± 7.6% smaller in the estrogen treated group (p < 0.0001). Estrogen treated Sle/LDLr(-/-) mice had no significant difference in serum cholesterol concentration, lipoprotein distribution, anti-dsDNA autoantibody concentration, antibody isotype concentration and renal histopathology score compared to placebo. However, they had significantly lower mean urine protein to urine creatinine ratio (UP:UC). There was no correlation between atherosclerosis lesion size and either the renal histology score or UP:UC ratio in Sle/LDLr(-/-) mice.

CONCLUSION

These results indicate that 17β-estradiol is atheroprotective within the context of murine SLE independent of changes in serum cholesterol concentration, autoantibody concentration, or renal pathology. The SLE phenotype in Sle/LDLr(-/-) mice is not exacerbated by exogenous 17β-estradiol administration, and the reduced UP:UC ratio suggests a protective effect against lupus nephritis.

17β-Estradiol enhances response of mice spleen B cells elicited by TLR9 agonist

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies against nucleic acid-associated antigens. B cells play cardinal roles in SLE. Many evidences have proved estrogen contribute to the gender bias in SLE and 17β-estradiol (E2) could accelerate the disease by regulating B cells. On the other hand, B cells express TLR9 which recognized dsDNA and played a critical role in SLE. However, the crosstalk between estrogen and TLR9 in B cells remains unknown. So we investigated the E2 effect in the presence of the TLR9 ligand CpG on mice spleen B cells. We found that the up-regulation of cell viability, life-span, co-stimulation molecules (CD40, CD86) expression, IgM secretion, TLR9 and MCM6 expression were more significant than CpG ODN or E2 stimulated alone. It may provide a new way to investigate the mechanism of how E2 modulate the B cells function in lupus.

Autoantibodies to estrogen receptor α interfere with T lymphocyte homeostasis and are associated with disease activity in systemic lupus erythematosus

OBJECTIVE

Estrogens influence many physiologic processes and are also implicated in the development or progression of numerous diseases, including autoimmune disorders. Aberrations of lymphocyte homeostasis that lead to the production of multiple pathogenic autoantibodies, including autoantibodies specific to estrogen receptor (ER), have been detected in the peripheral blood of patients with systemic lupus erythematosus (SLE). This study was undertaken to assess the presence of both anti-ERα and anti-ERβ antibodies in sera from patients with SLE, to analyze the effect of these antibodies on peripheral blood T lymphocyte homeostasis, and to evaluate their role as determinants of disease pathogenesis and progression.

METHODS

Anti-ER antibody serum immunoreactivity was analyzed by enzyme-linked immunosorbent assay in samples from 86 patients with SLE and 95 healthy donors. Phenotypic and functional analyses were performed by flow cytometry and Western blotting.

RESULTS

Anti-ERα antibodies were present in 45% of the patients with SLE, whereas anti-ERβ antibodies were undetectable. In healthy donors, anti-ERα antibodies induced cell activation and consequent apoptotic cell death in resting lymphocytes as well as proliferation of anti-CD3-stimulated T lymphocytes. A significant association between anti-ERα antibody values and clinical parameters, i.e., the SLE Disease Activity Index and arthritis, was found.

CONCLUSION

Our data suggest that anti-ERα autoantibodies interfere with T lymphocyte homeostasis and are significantly associated with lupus disease activity.

The XX sex chromosome complement in mice is associated with increased spontaneous lupus compared with XY

OBJECTIVES

Many autoimmune diseases are characterised by a female predominance. This may be caused by sex hormones, sex chromosomes or both. This report uses a transgenic mouse model to investigate how sex chromosome complement, not confounded by differences in gonadal type, might contribute to lupus pathogenesis.

METHODS

Transgenic NZM2328 mice were created by deletion of the Sry gene from the Y chromosome, thereby separating genetic from gonadal sex. Survival, renal histopathology and markers of immune activation were compared in mice carrying the XX versus the XY(-) sex chromosome complement, with each genotype being ovary bearing.

RESULTS

Mice with XX sex chromosome complement compared with XY(-) exhibited poorer survival rates and increased kidney pathology. Splenic T lymphocytes from XX mice demonstrated upregulated X-linked CD40 ligand expression and higher levels of activation markers ex vivo. Increased MMP, TGF and IL-13 production was found, while IL-2 was lower in XX mice. An accumulation of splenic follicular B cells and peritoneal marginal zone B cells was observed, coupled with upregulated costimulatory marker expression on B cells in XX mice.

CONCLUSION

These data show that the XX sex chromosome complement, compared with XY(-), is associated with accelerated spontaneous lupus.

IL-6 contributes to an immune tolerance checkpoint in post germinal center B cells

The generation of a B cell repertoire involves producing and subsequently purging autoreactive B cells. Receptor editing, clonal deletion and anergy are key mechanisms of central B cell tolerance. Somatic mutation of antigen-activated B cells within the germinal center produces a second wave of autoreactivity; but the regulatory mechanisms that operate at this phase of B cell activation are poorly understood. We recently identified a post germinal center tolerance checkpoint, where receptor editing is re-induced to extinguish autoreactivity that is generated by somatic hypermutation. Re-induction of the recombinase genes RAG1 and RAG2 in antigen-activated B cells requires antigen to engage the B cell receptor and IL-7 to signal through the IL-7 receptor. We demonstrate that this process requires IL-6 to upregulate IL-7 receptor expression on post germinal center B cells. Diminishing IL-6 by blocking antibody or haplo-insufficiency leads to reduced expression of the IL-7 receptor and RAG and increased titers of anti-DNA antibodies following immunization with a peptide mimetope of DNA. The dependence on IL-6 to initiate receptor editing is B cell intrinsic. Interestingly, estradiol decreases IL-6 expression thereby increasing the anti-DNA response. Our data reveal a novel regulatory cascade to control post germinal center B cell autoreactivity.

17β-Estradiol (E-2) administration to male (NZB × SWR)F1 mice results in increased IdLNF1-reactive memory T-lymphocytes and accelerated glomerulonephritis

While it has been shown that estradiol treatment accelerates the onset of lupus nephritis with autoantibody production and kidney damage in both male and female lupus-prone mice, the specific mechanism(s) involved are unknown. Our previous work has shown that alterations in IdLNF1-reactive T cells and IdLNF1+ antibodies correlated closely with the onset of autoimmune nephritis in female F1 progeny of SWR and NZB (SNF1) mice, supporting a critical role for the IdLNF1 idiotype in the development of disease. Since male SNF1 mice normally do not develop nephritis, we tested whether administration of 17β-estradiol (E-2) to male SNF1 mice would increase IdLNF1 IgG levels and autoreactive T cells, and further, induce nephritis. We found that E-2-treated male SNF1 mice developed nephritis with the same time course and mean survival as normal female SNF1 mice. Moreover, it appeared that the mechanism involved increased serum IdLNF1+IgG and its deposition in kidney glomeruli, preceded by astriking twofold increase in T-lymphocytes expressing the memory phenotype (CD44+CD45RBlo) predominantly in the IdLNF1-reactive T-cell population. In addition, we noted that cells with this phenotype were increased in the nephritic kidneys of treated mice, suggesting a direct involvement of those cells in the renal pathology. E-2 treatment also induced increased numbers of pathogenic IdLNF1+ antibody-producing B cells and elevated presentation of pathogenic IdLNF1+ peptide. Taken together, these results suggest a mechanism of E-2-induced acceleration of autoimmune disease in lupus-prone mice may involve expansion of autoreactive idiotypic T and B-cell populations.

Estrogens in rheumatoid arthritis; the immune system and bone

Rheumatoid arthritis (RA) is an autoimmune disease that is more common in women than in men. The peak incidence in females coincides with menopause when the ovarian production of sex hormones drops markedly. RA is characterized by skeletal manifestations where production of pro-inflammatory mediators, connected to the inflammation in the joint, leads to bone loss. Animal studies have revealed distinct beneficial effects of estrogens on arthritis, and a positive effect of hormone replacement therapy has been reported in women with postmenopausal RA. This review will focus on the influence of female sex hormones in the pathogenesis and progression of RA.

The MRL/lpr mouse strain as a model for neuropsychiatric systemic lupus erythematosus

To date, CNS disease and neuropsychiatric symptoms of systemic lupus erythematosus (NP-SLE) have been understudied compared to end-organ failure and peripheral pathology. In this review, we focus on a specific mouse model of lupus and the ways in which this model reflects some of the most common manifestations and potential mechanisms of human NP-SLE. The mouse MRL lymphoproliferation strain (a.k.a. MRL/lpr) spontaneously develops the hallmark serological markers and peripheral pathologies typifying lupus in addition to displaying the cognitive and affective dysfunction characteristic of NP-SLE, which may be among the earliest symptoms of lupus. We suggest that although NP-SLE may share common mechanisms with peripheral organ pathology in lupus, especially in the latter stages of the disease, the immunologically privileged nature of the CNS indicates that early manifestations of particularly mood disorders maybe derived from some unique mechanisms. These include altered cytokine profiles that can activate astrocytes, microglia, and alter neuronal function before dysregulation of the blood-brain barrier and development of clinical autoantibody titres.

Sex hormones and autoimmunity

Autoimmune diseases occur more in women than in men, and this may be attributable to the role of estrogens. Androgens promote autoimmune diseases with a profile of type 1 cytokines, such as rheumatoid arthritis, whereas estrogens promote autoimmune diseases with a type 2 cytokine profile, like systemic lupus erythematosus. Both androgens and estrogens regulate the Th1/Th2 balance. Type 1 autoimmune diseases are improved when decrease type 1 cytokines (i.e. during fasting), or when there is a rise in type 2 cytokines (increased estrogens, as in pregnancy). Type 2 autoimmune diseases improve when type 2 cytokines are diminished (decreased estrogen, as in post-partum period) or when type 1 response is stimulated.

The role of estrogen receptor beta (ERbeta) in malignant diseases--a new potential target for antiproliferative drugs in prevention and treatment of cancer

The discovery of ERbeta in the middle of the 1990s represents a paradigm shift in our understanding of estrogen signaling. It has turned out that estrogen action is not mediated by one receptor, ERalpha, but by two balancing factors, ERalpha and ERbeta, which are often antagonistic to one another. Excitingly, ERbeta has been shown to be widespread in the body and to be involved in a multitude of physiological and pathophysiological events. This has led to a strong interest of the pharmaceutical industry to target ERbeta by drugs against various diseases. In this review, focus is on the role of ERbeta in malignant diseases where the anti proliferative activity of ERbeta gives hope of new therapeutic approaches.

Suppression of the inflammatory response in experimental arthritis is mediated via estrogen receptor alpha but not estrogen receptor beta

Introduction

The immune modulatory role of estrogens in inflammation is complex. Both pro- and anti-inflammatory effects of estrogens have been described. Estrogens bind both estrogen receptor (ER)α and β. The contribution of ERα and ERβ to ER-mediated immune modulation was studied in delayed type hypersensitivity (DTH) and in experimental arthritis

Methods

ER-mediated suppression of rat adjuvant arthritis (AA) was studied using ethinyl-estradiol (EE) and a selective ERβ agonist (ERB-79). Arthritis was followed for 2 weeks. Next, effects of ER agonists (ethinyl-estradiol, an ERα selective agonist (ERA-63) and a selective ERβ agonist (ERB-79) on the development of a tetanus toxoid (TT)-specific delayed type hypersensitivity response in wild type (WT) and in ERα - or ERβ-deficient mice were investigated. Finally, EE and ERA-63 were tested for their immune modulating potential in established collagen induced arthritis in DBA/1J mice. Arthritis was followed for three weeks. Joint pathology was examined by histology and radiology. Local synovial cytokine production was analyzed using Luminex technology. Sera were assessed for COMP as a biomarker of cartilage destruction.

Results

EE was found to suppress clinical signs and symptoms in rat AA. The selective ERβ agonist ERB-79 had no effect on arthritis symptoms in this model. In the TT-specific DTH model, EE and the selective ERα agonist ERA-63 suppressed the TT-specific swelling response in WT and ERβKO mice but not in ERαKO mice. As seen in the AA model, the selective ERβ agonist ERB-79 did not suppress inflammation. Treatment with EE or ERA-63 suppressed clinical signs in collagen induced arthritis (CIA) in WT mice. This was associated with reduced inflammatory infiltrates and decreased levels of proinflammatory cytokines in CIA joints.

Conclusions

ERα, but not ERβ, is key in ER-mediated suppression of experimental arthritis. It remains to be investigated how these findings translate to human autoimmune disease.

Association of estrogen and aromatase gene polymorphisms with systemic lupus erythematosus

Experimental and animal studies suggested that estrogens play an important role in the development of systemic lupus erythematosus (SLE) through a variety of mechanisms involved in the regulation of the immune system. The objective of this study was to investigate the association between genetic variations in estrogen metabolic pathway genes, including estrogen receptor alpha (ESR1), estrogen receptor beta (ESR2), and aromatase (CYP19A1), and risk of SLE. We performed a genetic study of SLE among 46 medical record-confirmed female SLE cases and 102 female controls participating in an Internet-based case-control study of SLE. Polymorphisms analysed included: ESR1 PvuII, XbaI, and GT repeat; ESR2 RsaI, AluI, and CA repeat; and CYP19A1 RsaI, SfaN1, and TTTA repeat. We found significant association of the ESR1 PvuII (PP vs. pp, odds ratio (OR): 3.1, 95% confidence interval (CI): 1.1-9.3) and XbaI (XX vs. xx, adjusted OR: 3.4, 95% CI: 1.1-10.5) with SLE. Carrying the PPXX genotype conferred the highest risk (PPXX vs. ppxx, OR: 4.6, 95% CI: 1.3-15.9). We also found an association of SLE with the ESR2 CA repeat (SS vs. LL, OR: 2.8, 95% CI: 1.0-8.0). Our results support a role of estrogen in pathogenesis of SLE and suggested that genetic variants in the estrogen receptor genes might influence susceptibility.

The role of B cells in lupus pathogenesis

Autoantibodies clearly contribute to tissue inflammation in systemic lupus erythematosus. In order to therapeutically target B cells making pathogenic autoantibodies, it is necessary to identify their phenotype. It is also important to understand the defects in B cell repertoire selection that permit pathogenic autoreactive B cells to enter the immunocompetent B cell repertoire. We present the data that both marginal zone and follicular B cells can produce pathogenic autoantibodies. Moreover, we discuss how B cell survival and maturation are regulated centrally prior to antigen activation and in the periphery after antigen activation to form the repertoire that generates the spectrum of circulating antibodies.

Clinical mini-review: systemic lupus erythematosus and the eye

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease, the exact etiology of which is unknown. It is characterized by the production of pathological autoantibodies which adhere to cellular surfaces or form immune complexes which deposit in tissue, leading to end-organ damage via inflammatory mechanisms including complement activation. SLE may manifest itself in any organ system. In the eye, keratoconjunctivitis sicca is the most common finding. Other ophthalmic sites of involvement include the cornea, conjunctiva, episclera, sclera, uveal tract, retina, vasculature, optic nerve, and orbit. Therapy varies based on the disease manifestation and severity.

Regulation of dendritic cells by female sex steroids: Relevance to immunity and autoimmunity

Dendritic cells (DCs) are critical mediators of adaptive immunity, tolerance and autoimmunity. The human immune system exhibits sexual dimorphism, which is most evident in the female predominance of autoimmune diseases such as systemic lupus erythematosus (SLE). Female sex steroids are strongly implicated in mediating immune sexual dimorphism, in part because estrogen accentuates disease in several models of lupus autoimmunity. In contrast, progesterone may prevent disease development. While much investigation has focused on the effects of estrogen and progesterone on lymphocyte functions, far less attention has been paid to the effects of these hormones on DCs. Current evidence now indicates estrogen can activate DCs, while in contrast, progesterone inhibits DC functions. Thus, we hypothesize that the opposite effects these two hormones have on lupus autoimmunity reflect opposing effects on DC functions. Thus, through direct actions on DCs, female sex steroids may influence autoimmunity, immunity and tolerance.

The ethyl acetate extract of alfalfa sprout ameliorates disease severity of autoimmune-prone MRL-lpr/lpr mice

Previous study showed that soy isoflavone supplement alleviates disease severity in autoimmune-prone mice. As the ethyl acetate extract of alfalfa sprout (AS) has selective oestrogenic and anti-inflammatory activity, this study evaluated the effects of alfalfa sprout ethyl acetate extract (ASEA) on disease severity of systemic lupus erythematosus, using autoimmune-prone female MRL- lpr/lpr mice. In Experiment 1, five groups of 12-week-old female mice were per oral treated with vehicle (control), lyophilized AS (550 mg wt/kg BW), ASEA (ASEA, 25 mg/kg BW), coumestrol (CUM, 0.075 mg/kg BW) and tamoxifen (TAM, 0.375 mg/kg BW) as the positive control. The onset of proteinuria was delayed, and the life span was significantly longer in the ASEA and TAM groups but neither in the AS nor in the CUM groups, compared to the control. To examine the changes in the immunological parameters related to disease process, three more groups of MRL- lpr/lpr female mice (control, ASEA and TAM) were fed in a similar manner for 6 weeks in the Experiment 2. Flow cytometric analysis of splenocytes showed a significantly lower percentage of activated T cells in the ASEA and TAM groups. The ex-vivo interferon-γ and interleukin (IL)-4 production from splenocytes and tumour necrosis factor-α and IL-1β production from peritoneal exudate cells were also significantly lower in the ASEA group compared with the control. The ASEA group also had less severe glomerulonephritis. Thus, ASEA attenuated cytokine and inflammatory responses of self-reactive lymphocytes, decreased the disease severity, increased survival and life span of the autoimmune-prone MRL- lpr/lpr mice, suggesting a potential of ASEA in the treatment of autoimmune diseases.

Hormonal regulation of B-cell function and systemic lupus erythematosus

The prevalence of systemic lupus erythematosus (SLE) is far higher in females than in males and numerous investigations to understand this gender bias have been performed, which propose as casual actors genetic predispositions and sex hormones effects. We will describe in this review how the sex hormones estrogen and prolactin influence B cell maturation and selection, permitting B cells to mature to immunocompetence in a mouse model of lupus. Finally, we will discuss the relevance and implications of these results for human disease.

Soy isoflavones supplementation alleviates disease severity in autoimmune-prone MRL-lpr/lpr mice

Soy isoflavones supplements, which are phyto-oestrogens widely used as alternatives to alleviate menopausal syndromes or prevent chronic diseases, may exert oestrogenic and anti-oestrogenic activities. This study aimed to investigate the effects of soy isoflavones supplement on oestrogen-related autoimmune disease, such as systemic lupus erythematosus, using autoimmune-prone female MRL- lpr/lpr mice. Eighty mice of 8 weeks were divided into five groups: 0 (Control), 2 (Isf 2), 10 (Isf 10) and 20 (Isf 20) mg/kg BW/day Phyto SoyaTM isoflavones or 0.375 mg/kg BW/day tamoxifen (TAM) as the positive control, by tube-feeding. Some mice were killed at age 15 weeks for cellular cytokine secretion. The data suggested that the Isf 20 and TAM groups had higher weight gain and survival compared with the control group. At age 22 weeks, the Isf 20 group still had 75% survival comparable to mice treated with TAM. At age 14 weeks, the TAM group showed significantly lower serum anti-double-stranded (ds) DNA IgG and anti-cardiolipin IgG. The mice in the Isf 10 and Isf 20 groups also had lower anti-dsDNA IgG and anti-cardiolipin IgG. The interferon (IFN)-γ secretion from mitogen-stimulated T cells in the Isf 20 and TAM groups were significantly lower than those of control mice. Furthermore, the oestrogenic activity of the methanol extracts of soy isoflavones for oestrogen receptor (ER)β, but not ERα, significantly increased, suggesting that soy isoflavones have a selective modulation of ER activation. Thus, soy isoflavone supplementation did not aggravate murine lupus, but apparently ameliorated the disease.

Impact of estrogen receptor deficiency on disease expression in the NZM2410 lupus prone mouse

Systemic lupus erythematosus (SLE) occurs nine times more often in females than males. The purpose of this study was to determine the impact of estrogen receptor (ER) null genotypes on disease in lupus prone NZM2410 (NZM) and MRL/lpr mice, as a method to define the role of estrogen receptor signaling in lupus. ER alpha deficient NZM females, but not males, had significantly prolonged survival, reduced proteinuria, renal pathology scores and serum urea nitrogen levels compared to wildtype mice, despite higher serum anti-dsDNA levels. ER alpha deficient MRL/lpr female, but not male, mice also had significantly less proteinuria and renal pathology scores with no effect on autoantibody levels. Deficiency of ER beta had no effect on disease in either strain or sex. Taken together, these data demonstrate a key role for ER alpha, but not ER beta, in the development of lupus like disease, but not autoimmunity, in female NZM and MRL/lpr mice.

Skin disease is prevented but nephritis is accelerated by multiple pregnancies in autoimmune MRL/LPR mice

The role of pregnancy in the progression of systemic lupus erythematosus (SLE) is still poorly understood. We analysed the effect of repeated pregnancies in MRL/lpr mice, a murine model of SLE. Seven-week old female mice were used: multiparous mice underwent three consecutive pregnancies (M); age-matched virgin mice served as controls (V). Animals were harvested at 20 weeks of age. Skin lesions were characterized by hair loss and scabs in the dorsum of the neck. Virgin skins showed thickened dermis, fibrosis and mononuclear cell infiltrates, which were practically absent in M. This was accompanied by higher IFN-gamma and lower IL-10 mRNA expression levels in V compared to M skin. Plasma IFN-gamma protein levels were also upregulated in V versus M. However, survival and kidney function were dramatically reduced and accompanied by hypertension after multiple pregnancies. Kidney histology also showed markedly increased renal lesions in M. In contrast to plasma and skin levels, both IL-10 and IFN-gamma mRNA were lower in the kidneys of V versus M mice. Concluding our findings, the pathomechanisms of lupus kidney and skin disease may be regulated differently at the organ level during pregnancy. Both IFN-gamma and IL-10 may be important regulatory cytokines at the local level.

Tearful relationships? Sex, hormones, the lacrimal gland, and aqueous-deficient dry eye

Sex and the endocrine system exert a significant influence on the physiology and pathophysiology of the lacrimal gland. The purpose of this article is to briefly review the nature and magnitude of these interactions between sex, hormones and lacrimal tissue, and to address how they may relate to the pathogenesis of aqueous-deficient dry eye. Towards this end, this article has a 3-fold approach: first, to summarize the influence of androgens, estrogens, glucocorticoids, mineralocorticoids, retinoic acid, prolactin, alpha-melanocyte stimulating hormone, adrenocorticotropic hormone, luteinizing hormone, follicle-stimulating hormone, growth hormone, thyroid-stimulating hormone, arginine vasopressin, oxytocin, thyroxine, parathyroid hormone, insulin, glucagon, melatonin, human chorionic gonadotropin and cholecystokinin on the structure and function of the lacrimal gland; second, to discuss the mechanism of action of each hormone on lacrimal tissue; and third, to discuss the clinical relevance of the endocrine-lacrimal gland interrelationship, with a particular focus on each hormone's role (i.e. if relevant) in the development of aqueous-tear deficiency.

Effects of estrogen receptor subtype-selective agonists on autoimmune disease in lupus-prone NZB/NZW F1 mouse model

The specific roles of estrogen receptor (ER) subtypes alpha and beta in mediating estrogen's influences on lupus autoimmunity are unknown. Herein we found that ovariectomized NZB/NZW F1 mice treated with propyl pyrazole triol (ERalpha-selective agonist) had significantly shorter survival, earlier development of albuminuria, higher serum concentrations of total IgG and prolactin, increased serum levels of anti-DNA IgG3, IgG2a and IgG2b and decreased anti-DNA IgG1 level compared to vehicle controls. In contrast, diarylpropionitrile (ERbeta-selective agonist) administration significantly decreased serum anti-DNA IgG2b level but did not significantly affect serum levels of other anti-DNA IgG subclasses, serum total IgG or prolactin concentration, mortality or the occurrence of albuminuria. These findings suggest that ERalpha activation plays the predominant and immunostimulatory role in estrogen-mediated modulation of lupus while ERbeta activation appears to have a slightly immunosuppressive effect on this disease. ERalpha activation coincidentally increased serum prolactin concentrations and may accelerate lupus disease activity also through this mechanism.

Physiologically high concentrations of 17β-estradiol enhance NF-κB activity in human T cells

Estrogen has diverse effects on inflammation and immune responses. That pregnancy is associated with remission of some autoimmune diseases and exacerbation of others suggests that physiological fluctuation in estrogen levels could affect the immune responses in humans. However, the molecular basis for these phenomena is poorly understood. We hypothesized that fluctuations of estrogen levels modulate intracellular signaling for immune responses via estrogen receptors (ERs). In reporter assays, 17β-estradiol (E2) at a physiologically high concentration increased the activity of NF-κB in Jurkat cells stimulated by PMA/ionomycin or TNF-α. Overexpression and RNA interference experiments suggested that the effects were mediated through ERβ. Immunoprecipitation assay showed that both ERα and ERβ are directly associated with NF-κB in the cell nucleus. Using chromatin immunoprecipitation assay, we confirmed that ERα and ERβ associated with NF-κB and steroid hormone coactivators at the promoter region of NF-κB regulated gene. Considering that NF-κB regulates the expression of various genes essential for cell growth and death, estrogen could regulate the fate of T cells by affecting the activity of NF-κB. To determine whether E2 alters the fate of T cells, we investigated E2 actions on T cell apoptosis, a well-known NF-κB-mediated phenomenon. E2 increased apoptosis of Jurkat cells and decreased that of human peripheral blood T cells. Our results indicate that E2 at a physiologically high concentration modulates NF-κB signaling in human T cells via ERβ and affects T cell survival, suggesting that these actions may underlie the gender differences in autoimmune diseases.

Sex and systemic lupus erythematosus: the role of the sex hormones estrogen and prolactin on the regulation of autoreactive B cells

PURPOSE OF REVIEW

For many decades, it has been speculated that sex hormones play a role in systemic lupus erythematosus. Recent data accumulated during the past few years provide striking evidence that hormonal modulation of B cells can have a profound impact on the survival, maturation and repertoire selection of autoreactive B cells and begin to explain the sex bias associated with the condition.

RECENT FINDINGS

While there are still insufficient clinical data to define a role for estrogen or prolactin in human systemic lupus erythematosus, recent studies of anti-DNA antibody transgenic mice clearly demonstrate that an elevation in either estrogen or prolactin breaks tolerance of high affinity DNA-reactive B cells and induces a lupus phenotype. B cells with the same antigenic specificities are rescued by either estrogen or prolactin, but estrogen promotes the survival and activation of the T independent marginal zone B cell subset, while prolactin promotes the survival and activation of the T dependent follicular B cell subset.

SUMMARY

Elevations in the levels of estrogen or prolactin can promote the survival and activation of high affinity autoreactive B cells. These hormones engage different B cell pathways to interfere with B cell tolerance. The identification of systemic lupus erythematosus patients with either an estrogen-responsive or prolactin-responsive disease will further the development of therapeutics that can specifically modulate hormonal responses.

Structure-function relationship of estrogen receptor alpha and beta: impact on human health

17Beta-estradiol (E2) controls many aspects of human physiology, including development, reproduction and homeostasis, through regulation of the transcriptional activity of its cognate receptors (ERs). The crystal structures of ERs with agonists and antagonists and the use of transgenic animals have revealed much about how hormone binding influences ER conformation(s) and how this conformation(s), in turn, influences the interaction of ERs with co-activators or co-repressors and hence determines ER binding to DNA and cellular outcomes. This information has helped to shed light on the connection between E2 and the development or progression of numerous diseases. Current therapeutic strategy in the treatment of E2-related pathologies relies on the modulation of ER trancriptional activity by anti-estrogens; however, data accumulated during the last five years reveal that ER activities are not only restricted to the nucleus. ERs are very mobile proteins continuously shuttling between protein targets located within various cellular compartments (e.g., membrane, nucleus). This allows E2 to generate different and synergic signal transduction pathways (i.e., non-genomic and genomic) which provide plasticity for cell response to E2. Understanding the structural basis and the molecular mechanisms by which ER transduce E2 signals in target cells will allow to create new pharmacologic therapies aimed at the treatment of a variety of human diseases affecting the cardiovascular system, the reproductive system, the skeletal system, the nervous system, the mammary gland, and many others.

The immune system as a target for environmental chemicals: Xenoestrogens and other compounds

The immune system in higher organisms is under integrated control and has the capacity to rapidly respond to the environment. Recently, there has been a significant increase in the prevalence of allergic diseases. Environmental factors likely play a major role in the explosion of allergy. Although the "hygiene hypothesis" may explain the increase in allergic diseases which are prone to T helper 2 (Th2) immune responses, recent findings highlight the possible involvement of environmental xenobiotic chemicals which can modulate normal immune function. Interestingly, several reports suggest that the prevalence of systemic lupus erythematosus, a Th2-type autoimmune disease, is also increasing, although the development of high-sensitivity immunological tests may be a possible cause. The increased prevalence of autoimmune disease in women, the sexual dimorphism of the immune response, and the immunomodulatory effects of sex steroids, have focused attention on the role of chemicals which influence sex steroids in the development of immune diseases. Moreover, recent reports indicate that some environmental chemicals can work on nuclear hormone receptors, other than sex hormone receptors, and modulate immune reactions. This review focuses on the impact of environmental chemicals on immune system function and pathogenesis of immune diseases, including allergy and autoimmune diseases.

Differential expression of oestrogen receptors in human secondary lymphoid tissues

Many autoimmune diseases including rheumatoid arthritis (RA), Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE) occur much more frequently in women than in men. There is much evidence that oestrogen is the major cause of this gender difference. Interestingly, oestrogen relieves the symptoms of RA and SS but it exacerbates SLE. This contradictory effect of oestrogen on autoimmune diseases is not well understood. Most of the effects of oestrogen are mediated by two receptors: oestrogen receptor alpha and beta (ERalpha and ERbeta). To determine whether these contradictory effects of oestrogen relate to the involvement of distinct effects of the two ERs, we investigated expression of ERalpha and ERbeta in human secondary lymphoid tissues. We observed that, in tonsils, ERbeta is expressed in lymphocytes of germinal centres (GC) and the follicular mantle zone as well as in granulocytes, while ERalpha is expressed only in activated germinal centres but not in the follicular zone. ERbeta is the predominant ER in human leucocytes from peripheral blood, spleen and in leucocytes infiltrating cancers in both males and females. In addition, in different human lymphoma cell lines including Hodgkin lymphoma, Burkitt lymphoma, and multiple myeloma, ERbeta is abundant while ERalpha is not detectable. Our results indicate that ERbeta is the predominant type of ER in mature lymphocytes. We suggest that ERalpha and ERbeta have distinct roles in secondary lymphoid tissues and that further studies with ERbeta-specific agonists will help to elucidate the role of ERbeta in these tissues.

Sex hormones and SLE: influencing the fate of autoreactive B cells

The prevalence of systemic lupus erythematosus (SLE) is far higher in females than in males and numerous investigations to understand this gender bias have been conducted. While it is plausible that some sex-linked genes may contribute to the genetic predisposition for the disease, other likely culprits are the sex hormones estrogen and prolactin. In this chapter we review studies that have addressed the influence of sex hormones in SLE activity and discuss the recent data established in a BALB/c mouse transgenic for the heavy chain of an anti-DNA antibody. These mice are prone to develop lupus following exposure to exogenous sex hormones. We describe how estrogen and prolactin influence B cell maturation and selection, permitting B cells to mature to immunocompetence. Finally, we discuss the relevance and implications of these data for human disease.

A soy diet accelerates renal damage in autoimmune MRL/Mp-lpr/lpr mice

Isoflavones, which are phytoestrogens present in large quantities in soy and soy-derived products, have estrogenic activity, inhibit protein tyrosine kinase, and exert other effects in the human body. Thus, the recent spread of soy consumption in Western populations emphasizes the need to more fully understand the potential effects in the body, especially in abnormal immune conditions. In the present study, the influence of a soy diet on lupus disease in MRL/Mp-lpr/lpr (MRL/lpr) mice was investigated. Weanling female MRL/lpr mice (4 weeks) were fed a soy diet (20% soybean protein and 5% soybean oil). The soy diet exacerbated renal damage; findings in this mouse strain included accelerated proteinuria, elevated serum creatinine concentrations, and reduced creatinine clearance. No effects were detected, however, in C3H/HeN mice, which have the same H-2(k) genetic background as MRL/lpr mice do. A tendency toward an increase in thymus weight and proliferation of T cells in spleen and B cells in lymph nodes were found at the age of 16 weeks. These findings indicate that a soy diet, in comparison with a casein diet, significantly exacerbates the clinical course of this autoimmune disease. Further research on the mechanism of this effect of soy-rich diets is needed, and isoflavone supplementation for systemic lupus erythematosus patients should be carefully reevaluated.

Hormonal modulation of B cell development and repertoire selection

Systemic lupus erythematosus is an autoimmune disorder characterized by the production of pathogenic autoantibodies, primarily to nuclear antigens. The etiology of SLE is not entirely understood, but it is well-appreciated that multiple factors such as genetics and environment contribute to disease progression and pathogenesis. There is also convincing evidence that gender plays an import role in SLE since the incidence of disease occurs with a female to male ratio of 9:1. While it is plausible that some sex-linked genes may contribute to the genetic predisposition for the disease, other likely culprits for this gender bias are the sex hormones estrogen and prolactin. The data implicating estrogen and prolactin in SLE, until recently, were largely circumstantial. However, within the last few years, data collected from both human and mouse studies have provided compelling evidence that alterations in sex hormone levels can alter tolerance of autoreactive B cells and exacerbate disease. In this review, we will discuss recent data demonstrating a role for estrogen and prolactin in SLE and the effect of these hormones on B cell maturation, selection and activation.