Prolactin and gonadal hormones: a key relationship that may have clinical, monitoring and therapeutic implications in systemic lupus erythematosus

Hormonal milieu at time of B cell activation controls duration of autoantibody response

A strong gender bias is seen in many autoimmune diseases including systemic lupus erythematosus (SLE). To investigate the basis for the female preponderance in SLE, we have been studying BALB/c mice in which B cells express the R4A heavy chain of an anti-DNA antibody in association with an endogenous light chain repertoire (R4Atg mice). In unmanipulated mice, approximately 5% of B cells express the R4A transgene. R4Atg mice do not spontaneously develop elevated serum titers of anti-DNA antibodies. Administration of either estradiol (E2) or prolactin (Pr) results in escape from tolerance of autoreactive B cells, expressed as an increase in transgene-expressing B cells and elevated serum titers of anti-DNA antibodies. We previously demonstrated that autoreactive B cells maturing in an estrogenic milieu develop as marginal zone (MZ) B cells; when these same B cells mature in the presence of increased prolactin, they develop as follicular (Fo) B cells. To determine the long term consequence of this differential maturation of DNA-reactive B cells, we treated R4Atg BALB/c mice with E2 or Pr for 6 weeks until serum titers of anti-DNA antibody were high, at which time hormonal exposure was discontinued. In E2-treated mice, the anti-DNA titers remained high even 3 months after discontinuation of hormone exposure. Nascent B cells underwent normal tolerance induction, but existing autoreactive MZ B cells persisted and continued to secrete autoantibody. In contrast, Pr caused only a short-term increase in anti-DNA antibody titers. By 3 months after cessation of hormone treatment, serum anti-DNA antibody titers and B cell subsets were indistinguishable from those in placebo (P) treated mice. These findings suggest that autoantibody responses are sustained for variable lengths of time depending on the B cell subset producing the autoantibodies. This observation may be relevant to understanding the heterogeneous presentation of patients with SLE and to the design of therapies targeting specific B-cell populations in autoimmune disease.

Human prolactin promotes human secondary immunoglobulin response in human/SCID mouse chimeras

Recombinant human prolactin (rhPRL) was administered to huPBL-SCID mice to determine its effects on production of human immunoglobulin (Ig). The huPBL-SCID mice were injected intraperitoneally (i.p.) with 10 mug rhPRL every other day for a total of 10 injections. The results reconfirmed that rhPRL significantly increased the numbers of human CD3+ T cells and human CD19+ B cells in spleens, lymph nodes, and thymuses of huPBL-SCID mice. The huPBL-SCID mice were then concurrently given various doses of diphtheria-tetanus (DT) vaccine and 10-mug i.p. injections of rhPRL and were examined for the presence of human DT-specific proliferation of lymph node cells in vitro and antibody production in vivo. rhPRL greatly improved the engraftment of functional human lymphocytes (CD3+ T cells and CD19+ B cells) in DT-immunized huPBL-SCID mice. The rhPRL-treated, DT-immunized huPBL-SCID mice produced significantly larger amounts of DT-specific antibodies in response to the vaccine. The predominant Ig isotype induced after immunization was IgG. Thus, rhPRL stimulation promotes human secondary IgG responses in huPBL-SCID mice.

Prolactin modulates the naive B cell repertoire

Prolactin is a peptide hormone produced by the anterior pituitary gland that is critical in lactation. Prolactin can also be produced by lymphocytes, and both B and T cells express prolactin receptors. These findings have suggested that prolactin has immunomodulatory functions. Studies in spontaneously autoimmune hosts have demonstrated a role for prolactin in augmenting autoreactivity. We chose to analyze prolactin effects on anti-DNA B cells in nonspontaneously autoimmune female BALB/c mice transgenic for the heavy chain of an anti-DNA antibody. Treatment with prolactin for 4 weeks induced a lupus-like phenotype with an increased number of transgene-expressing B cells, elevated serum anti-DNA antibody titers, and glomerular immunoglobulin deposits. Prolactin caused a decrease in the population of transitional B cells and an increase in mature follicular and marginal zone B cells. The DNA-reactive B cells had a follicular cell phenotype. Anti-DNA hybridomas demonstrated that prolactin alters selection of the naive B cell repertoire. The expansion and activation of anti-DNA B cells in prolactin-treated R4A-gamma2b BALB/c mice was dependent on the presence of CD4(+) T cells. Finally, treatment with prolactin was unable to break tolerance in R4A-gamma2b transgenic C57Bl/6 mice, suggesting that responsiveness of the immune system to prolactin is genetically determined.

Bromocriptine in rheumatic and autoimmune diseases

BACKGROUND AND OBJECTIVES

Multiple lines of evidence support the concept that the anterior pituitary hormone prolactin has a pathogenic role in rheumatic and autoimmune diseases including, but not limited to, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Reiter's syndrome, psoriatic arthritis, and uveitis. Conversely, the dopaminergic agonist bromocriptine appears to have therapeutic effects through suppression of pituitary prolactin secretion and, perhaps, through actions on peripheral dopamine receptors. This article reviews the experimental and clinical data supporting the therapeutic use of bromocriptine as a nonstandard or adjunctive therapy in rheumatic and autoimmune diseases.

METHODS

Data addressing the potential therapeutic role of bromocriptine in rheumatic and autoimmune diseases, as well as frequently associated comorbidities, was accumulated from the author's work, online literature search of the National Library of Medicine, and references from these identified publications.

RESULTS

There have been a number of clinical therapeutic trials using 2.5 to 30 mg of bromocriptine per day in a single or divided dose, which have shown efficacy with minimal side effects in the treatment of rheumatic and autoimmune diseases. In RA, bromocriptine administration has induced immunosuppression of several immune parameters and has been associated with improvements in morning stiffness, grip strength, numbers of swollen/painful joints, and the Health Assessment Questionnaire disability index. In two blinded studies, bromocriptine reduced the number of SLE flares and was as effective as hydroxychloroquine in reducing lupus disease activity indices, respectively. In case reports, bromocriptine has been used successfully in the treatment of Reiter's syndrome enthesopathy and psoriatic arthritis. The potential efficacy of bromocriptine in the treatment of uveitis and multiple sclerosis is suggested but remains to be verified.

CONCLUSIONS

Double-blind, placebo-controlled studies are limited, but clinical observations and trials support the use of bromocriptine as a nonstandard primary or adjunctive therapy in the treatment of recalcitrant RA, SLE, Reiter's syndrome, and psoriatic arthritis and associated conditions unresponsive to traditional approaches. Additional investigation is needed to verify this conclusion and extend preliminary results.

RELEVANCE

In patients with rheumatic and autoimmune diseases, bromocriptine may be a relatively safe and efficacious alternative therapy. Semin Arthritis Rheum 31:21-32.

Bromocriptine restores tolerance in estrogen-treated mice

Estrogen can modulate autoimmunity in certain models of systemic lupus erythematosus. Recently, we have shown that it can mediate survival and activation of anti-DNA B cells in a mouse transgenic for the heavy chain of a pathogenic anti-DNA antibody. To identify whether estrogen effects reflect increased prolactin secretion, we characterized B-cell autoreactivity in transgenic mice given both bromocriptine (an inhibitor of prolactin secretion) and estradiol. Treatment of mice with estradiol plus bromocriptine led to reduced titers of anti-DNA antibodies and diminished IgG deposition in kidneys compared with treatment with estradiol alone. However, mice treated with estradiol plus bromocriptine showed an expansion of transgene-expressing B cells and enhanced Bcl-2 expression, similar to those of estradiol-treated mice. We identified anergic high-affinity anti-DNA B cells in mice treated with estradiol plus bromocriptine, and we showed by molecular analysis of anti-DNA hybridomas that their B cells derive from a naive repertoire. Thus, the estradiol-induced breakdown in B-cell tolerance can be abrogated by bromocriptine, which induces anergy in the high-affinity DNA-reactive B cells. These studies demonstrate that some of the effects of estrogen on naive autoreactive B cells require the presence of prolactin and, thus, suggest potential therapeutic interventions in lupus.

Sex hormones and pregnancy in rheumatoid arthritis and systemic lupus erythematosus

Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are autoimmune disorders with a preponderance in females. RA and SLE differ in their response to sex hormones. Disease development of RA is mitigated by estrogen and pregnancy whereas SLE tends to flare during pregnancy and in response to estrogen. Pregnancy improves the symptoms of RA in about 75% of pregnant patients, but relapses within six months postpartum in 90% of cases. RA is regarded as a T cell-mediated and TH1 immune response-driven disease. Pregnancy induces a shift from TH1 to TH2 immune response, increasing the anti-inflammatory cytokines IL-4 and IL-10, which may contribute to gestational amelioration of RA. Prospective studies of SLE pregnancies indicate that about 50% of patients experience a flare, however, with no permanent aggravation of the disease. Lupus nephritis, presence of antiphospholipid antibodies, and a previous history of pregnancy loss increase the risk of complications during pregnancy and fetal loss. The marked increase of estrogen and progesterone during pregnancy seems to enhance some of the manifestations of SLE. The shift to a TH2 immune response may trigger SLE manifestations that are dependent on humoral immune responses such as lupus nephritis. Another factor stimulating immune responses is the pituitary hormone prolactin, which has been found elevated in SLE patients of both sexes and correlated to disease activity in several studies. The hyperprolactinemia of lactation seems to influence postpartum behavior of SLE as well as RA.

Systemic lupus erythematosus flares during pregnancy

Lupus activity during pregnancy has been the subject of much research and debate recently. Data point to increased SLE activity during pregnancy. SLE may flare during any trimester of pregnancy, as well as in the puerperium; however, flares are usually mild, affecting skin and joints, and, unless affecting the kidney, do not confer any adverse prognosis on pregnancy outcome. Diagnosis of SLE flares can be difficult during pregnancy and must rely on a thorough clinical and laboratory assessment. Recent data link sex hormones, particularly prolactin, to SLE activity, which may be one explanation for the high frequency of SLE flares during pregnancy. No data support the thesis that corticosteroids prevent SLE flares during pregnancy, and therefore, prophylactic prednisone should not be given routinely. HCQ does seem to be safe for the fetus, however. SLE flares can be treated, depending on severity, with NSAIDs or with HCQ, prednisone, or azathioprine.

Systemic lupus erythematosus: sex hormones in male patients

Systemic lupus erythematosus (SLE) is a rare disease in males. There is evidence that a functional state of hypoandrogenism is important in the pathogenesis of the disease. We analysed the levels of several hormones (follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), estradiol (E2), free estradiol (FE2) and prolactin (PRL)) in 17 male SLE patients and 17 male healthy controls with similar age distribution. Three lupus patients were excluded from the analysis due to previous cyclophosphamide therapy or pre-puberty. Thus 14 male lupus patients were eligible for the study. Six of the 14 SLE patients (43%) showed at least one abnormal level of FSH, LH or T. There were no abnormalities in these hormones in the 17 controls. This difference was significant (P < 0.01). In five of these 6 male patients (36% of all lupus patients) the hormonal profile was compatible with a functional state of hypoandrogenism (high LH and/or low T). The ratio E2/T (estradiol/testosterone:pmol/nmol) was also significantly higher in the SLE group (average = 6.5; SD 4.3) when compared with that of the control group (average 4.2; SD 1.2; Mann-Whitney rank sum test: P < 0.03). There were no significant differences in E2, FE2 or PRL between lupus patients and controls. We did not confirm the notion that left-handedness is frequent in male lupus as all our patients were right-handed. We found a significantly higher prevalence of sex hormone abnormalities in male lupus patients when compared with healthy controls with a similar age distribution.(ABSTRACT TRUNCATED AT 250 WORDS)