Estrogen and progesterone receptors in murine models of systemic lupus erythematosus

Pristane cadmium chloride nanoemulsion accelerates the onset of systemic lupus erythematosus in a C57BL/6 mouse model

OBJECTIVE

To accelerate the onset of systemic lupus erythematosus in C57BL/6 mice by injecting cadmium chloride nanoemulsion and shorten the traditional modeling time.

METHODS

Pristane cadmium chloride nanoemulsion was prepared, and 66 C57BL/6 mice were randomly divided into four groups. The pristane group was intraperitoneally injected with 0.6 mL of pristane blank nanoemulsion, the model group was injected with 0.6 mL of pristane cadmium chloride nanoemulsion, the Cadmium chloride control group was injected with 0.6 mL of cadmium chloride nanoemulsion, and the control group was injected with the same amount of 0.9% sodium chloride solution. Urine protein content, anti-dsDNA antibody content, Th1 cell/Th2 cell ratio, and kidney staining were detected in each group.

RESULTS

The model group began to develop disease in the 4th week, the anti-dsDNA antibody level reached 566.71 ± 1.44 ng/L, and the proteinuria reached 245.38 ± 30.54 ng/mL. The model group showed an onset at least 5 weeks earlier than that in the pristane group. There was no significant difference in anti-dsDNA antibody content between Cadmium chloride control group and blank group. At the 12th week, the Th1/Th2 cell ratio in the model group significantly decreased, and the pathological changes in the kidneys were consistent with the typical manifestations of lupus in mouse models.

CONCLUSION

These results suggest that cadmium chloride promotes earlier onset of pristane-induced systemic lupus erythematosus in a C57BL/6 mouse model.

Progesterone Receptor Signaling in the Breast Tumor Microenvironment

The tumor microenvironment (TME) is a complex infrastructure composed of stromal, epithelial, and immune cells embedded in a vasculature ECM. The microenvironment surrounding mammary epithelium plays a critical role during the development and differentiation of the mammary gland, enabling the coordination of the complex multihormones and growth factor signaling processes. Progesterone/progesterone receptor paracrine signaling interactions in the microenvironment play vital roles in stem/progenitor cell function during normal breast development. In breast cancer, the female sex hormones, estrogen and progesterone, and growth factor signals are altered in the TME. Progesterone signaling modulates not only breast tumors but also the breast TME, leading to the activation of a series of cross-communications that are implicated in the genesis of breast cancers. This chapter reviews the evidence that progesterone and PR signaling modulates not only breast epitheliums but also the breast TME. Furthermore, crosstalk between estrogen and progesterone signaling affecting different cell types within the TME is discussed. A better understanding of how PR and progesterone affect the TME of breast cancer may lead to novel drugs or a therapeutic approach for the treatment of breast cancer shortly.

Sex Hormones in Acquired Immunity and Autoimmune Disease

Women have stronger immune responses to infections and vaccination than men. Paradoxically, the stronger immune response comes at a steep price, which is the high incidence of autoimmune diseases in women. The reasons why women have stronger immunity and higher incidence of autoimmunity are not clear. Besides gender, sex hormones contribute to the development and activity of the immune system, accounting for differences in gender-related immune responses. Both innate and adaptive immune systems bear receptors for sex hormones and respond to hormonal cues. This review focuses on the role of sex hormones particularly estrogen, in the adaptive immune response, in health, and autoimmune disease with an emphasis on systemic lupus erythematosus.

The Immune System Is a Natural Target for Estrogen Action: Opposing Effects of Estrogen in Two Prototypical Autoimmune Diseases

Analogous to other physiological systems, the immune system also demonstrates remarkable sex differences. Although the reasons for sex differences in immune responses are not precisely understood, it potentially involves differences in sex hormones (estrogens, androgens, and differential sex hormone receptor-mediated events), X-chromosomes, microbiome, epigenetics among others. Overall, females tend to have more responsive and robust immune system compared to their male counterparts. It is therefore not surprising that females respond more aggressively to self-antigens and are more susceptible to autoimmune diseases. Female hormone (estrogen or 17β-estradiol) can potentially act on all cellular subsets of the immune system through estrogen receptor-dependent and -independent mechanisms. This minireview highlights differential expression of estrogen receptors on immune cells, major estrogen-mediated signaling pathways, and their effect on immune cells. Since estrogen has varied effects in female-predominant autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus, we will mechanistically postulate the potential differential role of estrogen in these chronic debilitating diseases.

AID dysregulation in lupus-prone MRL/Fas(lpr/lpr) mice increases class switch DNA recombination and promotes interchromosomal c-Myc/IgH loci translocations: modulation by HoxC4

Immunoglobulin gene somatic hypermutation (SHM) and class switch DNA recombination (CSR) play important roles in the generation of autoantibodies in systemic lupus erythematosus. Systemic lupus is characterized by the production of an array of pathogenic high-affinity mutated and class-switched, mainly IgG, antibodies to a variety of self-antigens, including nuclear components, such as dsDNA, histones, and chromatin. We previously found that MRL/Fas(lpr/lpr) mice, which develop a systemic autoimmune syndrome sharing many features with human lupus, display greatly upregulated CSR, particularly to IgG2a, in B cells of the spleen, lymph nodes, and Peyer's patches. In MRL/Fas(lpr/lpr) mice, the significant upregulation of CSR is associated with increased expression of activation-induced cytidine deaminase (AID), which is critical for CSR and SHM. We also found that HoxC4 directly activates the promoter of the AID gene to induce AID expression, CSR and SHM. Here, we show that in both lupus patients and lupus-prone MRL/Fas(lpr/lpr) mice, the expression of HoxC4 and AID is significantly upregulated. To further analyze the role of HoxC4 in lupus, we generated HoxC4(-/-) MRL/Fas(lpr/lpr) mice. In these mice, HoxC4-deficiency resulted in reduced AID expression, impaired CSR, and decreased serum anti-dsDNA IgG, particularly IgG2a, autoantibodies, which were associated with a reduction in IgG deposition in kidney glomeruli. In addition, consistent with our previous findings in MRL/Fas(lpr/lpr) mice that upregulated AID expression is associated with extensive DNA lesions, comprising deletions and insertions in the IgH locus, we found that c-Myc to IgH (c-Myc/IgH) translocations occur frequently in B cells of MRL/Fas(lpr/lpr) mice. The frequency of such translocations was significantly reduced in HoxC4(-/-) MRL/Fas(lpr/lpr) mice. These findings suggest that in lupus B cells, upregulation of HoxC4 plays a major role in dysregulation of AID expression, thereby increasing CSR and autoantibody production and promoting c-Myc/IgH translocations.

Estrogen receptors bind to and activate the HOXC4/HoxC4 promoter to potentiate HoxC4-mediated activation-induced cytosine deaminase induction, immunoglobulin class switch DNA recombination, and somatic hypermutation

Estrogen enhances antibody and autoantibody responses through yet to be defined mechanisms. It has been suggested that estrogen up-regulates the expression of activation-induced cytosine deaminase (AID), which is critical for antibody class switch DNA recombination (CSR) and somatic hypermutation (SHM), through direct activation of this gene. AID, as we have shown, is induced by the HoxC4 homeodomain transcription factor, which binds to a conserved HoxC4/Oct site in the AICDA/Aicda promoter. Here we show that estrogen-estrogen receptor (ER) complexes do not directly activate the AID gene promoter in B cells undergoing CSR. Rather, they bind to three evolutionarily conserved and cooperative estrogen response elements (EREs) we identified in the HOXC4/HoxC4 promoter. By binding to these EREs, ERs synergized with CD154 or LPS and IL-4 signaling to up-regulate HoxC4 expression, thereby inducing AID and CSR without affecting B cell proliferation or plasmacytoid differentiation. Estrogen administration in vivo significantly potentiated CSR and SHM in the specific antibody response to the 4-hydroxy-3-nitrophenylacetyl hapten conjugated with chicken γ-globulin. Ablation of HoxC4 (HoxC4(-/-)) abrogated the estrogen-mediated enhancement of AID gene expression and decreased CSR and SHM. Thus, estrogen enhances AID expression by activating the HOXC4/HoxC4 promoter and inducing the critical AID gene activator, HoxC4.

Meningioma and systemic lupus erythematosus: a matter of pure coincidence?

To describe three cases of meningioma observed in a large cohort of 546 patients with systemic lupus erythematosus (SLE) followed at our Department in the last 15 years. We identified three cases of meningioma among 181 patients with SLE who underwent a brain magnetic resonance imaging (MRI) during their disease course (prevalence 1.65%). All three SLE cases were women with a disease onset at 47-, 18- and 42 -years-old, respectively. All patients presented neuropsychiatric (NP) symptoms and had an incidental finding of a meningioma at brain MRI. One patient presented simultaneously a breast cancer. Only one patient had the surgical removal of the mass without improvement of her symptoms while in the other two patients, the removal was not indicated. The association between meningioma and SLE may be a pure coincidence. However, it draws our attention because its detection may represent a confounding factor in the setting of a NPSLE patient.

Do Genetic Alterations in Sex Steroid Receptors Contribute to Lacrimal Gland Disease in Sjögren's Syndrome?

BACKGROUND: Defects in sex steroid receptors have been linked to the onset, progression and severity, as well as the sex-related prevalence, of a variety of autoimmune disorders, including lupus, rheumatoid arthritis, multiple sclerosis and diabetes. We hypothesize that defects in estrogen receptor alpha (ESR1), estrogen receptor beta (ESR2) and/or the androgen receptor (AR) may also contribute to the development of lacrimal gland autoimmune sequelae in Sjögren's syndrome. To begin to test this hypothesis, we examined whether mutations exist in the coding regions of ESR1, ESR2 and AR transcripts in lacrimal tissues of mouse models of Sjögren's syndrome. METHODS: Lacrimal and submandibular glands were collected from adult MRL/MpJ-Tnfrsf6(lpr), nonobese diabetic and/or BALB/c mice. Tissues were pooled according to sex and experiment and processed for cDNA generation. PCR primers were designed to amplify 566-875 base pair segments of the entire open reading frame of each receptor. Segments were amplified, purified and then sequenced. Receptor sequences were assembled and compared to each other and to known NCBI sequences. RESULTS: Our results show that almost all ESR1, ESR2 and AR sequences in exocrine tissues of male and female autoimmune and non-autoimmune mice were identical to those of NCBI standards. There was a G-->A shift at position 998 of the ESR2 complete coding sequence in all tissue samples when compared to NCBI reference sequence U81451.1, but this polymorphism was not found in other ESR2 reference sequences. CONCLUSIONS: Our findings indicate that defects in the coding region of sex steroid receptors do not contribute to the pathogenesis of lacrimal gland disease in mouse models of Sjögren's syndrome.

Hormonal influence on expression and functionality of alpha1-adrenoceptor in rat submandibular gland

In this work, we characterized alpha(1)-adrenoceptor expression and functionality in rat submandibular gland. Cumulative dose-response curve of methoxamine was constructed to determine the peroxidase secretion by glands from proestrous, estrous, metestrous and diestrous rats. They were compared to those from animals untreated or treated with sex hormones, estradiol and progesterone. The sensitivity of glands to an alpha(1)-adrenoceptor agonist varied depending on hormonal state, i.e. glands from proestrous and estrous were more sensitive to the stimulatory action of methoxamine than those from metestrous, diestrous and ovariectomised animals. The efficacy of the alpha(1) agonist was enhanced in glands from ovariectomised estrogen-treated rats but it was ineffective in glands from ovariectomised progesterone-treated rats. The functional studies correlated with 3H-prazosin binding assays in which estrogen increased alpha(1)-adrenoceptor density while progesterone decreased it. The results demonstrated that alpha(1)-adrenoceptor expression and functionality in rat submandibular glands are apparently under hormonal control and probably represent other examples of bidirectional interactions between neuronal and exocrine systems.