Oestrogen treatment reduces duration of experimental allergic neuritis in rats and suppresses T cell responses to myelin

Estrogen receptor β ligand therapy activates PI3K/Akt/mTOR signaling in oligodendrocytes and promotes remyelination in a mouse model of multiple sclerosis

The identification of a drug that stimulates endogenous myelination and spares axon degeneration during multiple sclerosis (MS) could potentially reduce the rate of disease progression. Using experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, we have previously shown that prophylactic administration of the estrogen receptor (ER) β ligand 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) decreases clinical disease, is neuroprotective, stimulates endogenous myelination, and improves axon conduction without altering peripheral cytokine production or reducing central nervous system (CNS) inflammation. Here, we assessed the effects of therapeutic DPN treatment during peak EAE disease, which represents a more clinically relevant treatment paradigm. In addition, we investigated the mechanism of action of DPN treatment-induced recovery during EAE. Given that prophylactic and therapeutic treatments with DPN during EAE improved remyelination-induced axon conduction, and that ER (α and β) and membrane (m)ERs are present on oligodendrocyte lineage cells, a direct effect of treatment on oligodendrocytes is likely. DPN treatment of EAE animals resulted in phosphorylated ERβ and activated the phosphatidylinositol 3-kinase (PI3K)/serine-threonine-specific protein kinase (Akt)/mammalian target of rapamycin (mTOR) signaling pathway, a pathway required for oligodendrocyte survival and axon myelination. These results, along with our previous studies of prophylactic DPN treatment, make DPN and similar ERβ ligands immediate and favorable therapeutic candidates for demyelinating disease.

17beta-estradiol affords protection against 4-vinylcyclohexene diepoxide-induced ovarian follicle loss in Fischer-344 rats

Repeated dosing with 4-vinylcyclohexene diepoxide (VCD) accelerates atresia via apoptosis in primordial and primary follicles in ovaries of rats. The mechanisms that control atresia and VCD-induced toxicity are unknown; however, they could involve 17beta-E2. Atresia slows as animals enter puberty, whereas circulating E2 levels increase with the the onset of cyclicity. This inverse relationship suggests that E2 may be involved in the control of atresia. Therefore, this study was designed to determine whether treatment of immature rats with E2 could protect follicles normally destroyed by VCD-induced apoptosis. Female F344 rats were treated daily with E2, ER analogs, and/or VCD for 15 d. VCD alone caused a 50% reduction in primordial and primary follicles. Coinjection of E2 (0.1 mg/kg) and VCD (80 mg/kg) selectively protected primary follicles from VCD-induced follicle loss. This protection was mimicked by an ER agonist, genistein (0.1 mg/kg), and prevented by an ER antagonist, 4-hydroxytamoxifen (2 mg/kg). VCD treatment increased caspase-3-like activity, whereas concurrent treatment with genistein and VCD restored caspase-3-like activity to control levels. VCD treatment had no effect on circulating E2 levels, uterine weight, or E2 binding to the ER, nor could it directly displace E2 from ERbeta. These observations support the idea that ER-mediated protection against VCD-induced follicle toxicity is obtained by reducing apoptosis in small preantral follicles, although VCD does not appear to directly interact with ER.

Therapeutic effects of estradiol benzoate on development of collagen-induced arthritis (CIA) in the Lewis rat are mediated via suppression of the humoral response against denatured collagen type II (CII)

The effects of estradiol benzoate (EB) on the development of anti-CII antibodies and their pathogenic potential were studied during the progress of established CIA in the rat. CIA was induced in mature female Lewis rats by two subcutaneous inoculations containing bovine native CII (BCIIn), emulsified in Freund's incomplete adjuvant. Clinical arthritis fully developed by day 18 and then EB (1 mg/kg body wt per day, diluted in corn oil (CO)) was administered intramuscularly every second day thereafter. Antibodies binding four different CIIs (bovine or rat, either native or heat-denatured) were detected in sera and joint tissue extracts by means of solid-phase ELISA. Pharmacological doses of EB (>0.2 mg/kg body wt per day) caused significant remission of established CIA 5-7 days after treatment, and selectively suppressed the production of antibodies specific for denatured CII. To evaluate the arthritogenic potential of circulating anti-CIId IgG, transfer experiments were performed. IgG anti-CIIn, purified from EB-treated CIA rats, was not arthritogenic, whereas IgG anti-denatured (CIId), purified from CO-treated CIA rats, caused severe passive arthritis. Furthermore, pretreatment with rat CIId protected against subsequent induction of CIA, and this protection was associated with suppressed antibody production against CIId. Collectively, our results indicate that antibodies specific for CIId are involved in the pathogenesis of CIA, and that oestrogen-related remission of clinical arthritis may by caused by a selective suppression of antibodies produced against degraded/denatured CII.

Additive effects of suboptimal doses of estrogen and cortisone on the suppression of T lymphocyte dependent inflammatory responses in mice

Many immune-mediated inflammatory diseases are treated with corticosteroids. This type of treatment is, however, often afflicted with side-effects such as osteoporosis and atherosclerosis. During the last decades also sex steroids, such as estrogens, have been shown to have immunoregulatory properties. In this report we studied the effect of combined treatment with suboptimal doses of dexamethasone and estradiol on T lymphocyte mediated delayed type hypersensitivity (DTH), granulocyte-mediated inflammatory responses, immunoglobulin production and antigen specific antibody responses in mice. The results show that the two hormones display additive effects on suppression of DTH. In contrast, such additive effects were not observed in granulocyte-mediated inflammation. B lymphocyte activity, measured by immunoglobulin production and antigen-specific antibody responses, were increased after exposure to estradiol and suppressed by dexamethasone. In mice treated with both hormones the up regulation of B lymphocytes was still evident. The results could indicate the potential to use combinations of corticosteroids and estrogen in the treatment of T lymphocyte dependent rheumatic diseases such as rheumatoid arthritis (RA). In addition, the B lymphocyte stimulation by estrogen in cortisone exposed mice stimulate to future studies in humans if estrogen containing contraceptives or post menopausal hormone treatment could have triggering effects in patients with immune complex mediated diseases also when they are on corticosteroid treatment.

Histocompatibility complex gene products and exposure to oestrogen: two independent disease accelerating factors in murine lupus

A number of studies have demonstrated that oestrogen exerts a significant impact on the course of experimental autoimmune diseases. Exposure to oestrogen aggravates SLE glomerulonephritis whereas the opposite outcome has been demonstrated in experimental arthritis, vasculitis, thyroiditis, and sialadenitis. In this report we have analysed the respective impact of H-2z linked gene products and long-term treatment with physiological doses of oestradiol on clinical and immunological variables in castrated backcrosses of lupus prone NZB/W and NZB mice. Our results demonstrate that H-2z linked gene products accelerate B-cell activation and stimulate autoantibody production resulting in aggravation of glomerulonephritis and precocious death in renal failure. These H-2z linked gene products do not influence T-cell mediated sialadenitis. Irrespectively of the H-2 haplotype of the mice, administration of oestrogen resulted in intense polyclonal B cell activation and aggravation of glomerulonephritis. However, exposure to oestrogen resulted in amelioration of sialadenitis. Notably, our result indicates that B-cell activation achieved by oestrogen and H-2z gene linked products, respectively is mediated by independent mechanisms. In addition, we have developed a predictive in vivo test that permits forecasts regarding efficiency of oestrogen treatment for suppression of T-cell mediated lesions. Using this test procedure in young, clinically healthy SLE mice we have been able to prove that animals displaying suppressed delayed type hypersensitivity (DTH) after short-term oestrogen exposure showed significantly lower long-term morbidity regarding development of sialadenitis upon continuous treatment with physiological doses of oestradiol.

Estrogen accelerates immune complex glomerulonephritis but ameliorates T cell-mediated vasculitis and sialadenitis in autoimmune MRL lpr/lpr mice

Estrogen is known to influence immune responses in healthy subjects in a dichotomous fashion. Thus, in number of previous studies we and others have demonstrated that B cell activities are augmented after exposure to estrogen whereas T cell reactivity is suppressed. Furthermore, it has been shown that this hormone has significant impact on the course of certain human and experimental autoimmune diseases. In this study we report that treatment with physiological doses of estradiol exerts dichotomous effects on different manifestations of the lupus disease in MRL/l mice. On one hand immune complex-mediated glomerulonephritis was significantly accelerated. This outcome was due to polyclonal B cell activation with increased production of antibodies to double-stranded DNA and formation of circulating immune complexes. In contrast, T cell-mediated lesions such as focal sialadenitis, renal vasculitis, and periarticular inflammation were all significantly ameliorated in MRL/l mice exposed to estrogen. Thus, we were able to demonstrate that, within one subject and even within one organ, administration of estrogen leads to differential outcome of SLE morbidity. We propose that the differential effect of estrogen on the manifestations of the autoimmune disease of MRL/l mice is due to its dichotomous effects on B and T cell-mediated immune responses.

Maintained pregnancy levels of oestrogen afford complete protection from post-partum exacerbation of collagen-induced arthritis

Pregnancy is known to influence the course of rheumatoid arthritis (RA) in women, as well as type II collagen-induced arthritis (CIA) in DBA/1 mice. A characteristic feature is the remission during gestation and the exacerbation of the diseases during the post-partum period. In the case of CIA in DBA 1 mice, two hormonal changes have been assumed to be critical for the induction of the post-partum flare: (i) the fall in steroid hormone levels from those present during pregnancy; and (ii) surges of prolactin (PRL) release at and after delivery. Our results show that treatment with oestradiol during a short period immediately after parturition protects the mouse from a post-partum flare of the disease, and that treatment with bromocriptine, a drug known to inhibit the endogenous PRL release, has a significant though less marked effect. Studies of lactating (i.e. animals with physiological stimulation of endogenous PRL release) and non-lactating arthritic mice revealed no clear-cut differences, indicating that PRL is of minor importance for the induction of the post-partum flare. Some steroids other than oestradiol, which may be implicated in the exacerbation of arthritis, namely progesterone and hydrocortisone, had no clinical effect. Analyses of agalactosyl IgG levels in mice with CIA, and anti-collagen II antibodies in sera collected at the end of the experiments revealed no significant differences between the oestradiol and the control groups. The successful oestradiol treatment of the mice indicates that the drop in endogenous oestradiol levels prior to delivery ends the oestrogen-mediated protection against arthritis during pregnancy.