Extrapituitary prolactin promotes generation of Eomes-positive helper T cells mediating neuroinflammation.

Induction of eomesodermin-positive CD4+ T cells (Eomes+ T helper [Th] cells) has recently been correlated with the transition from an acute stage to a later stage of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. Moreover, these cells' pathogenic role has been experimentally proven in EAE. While exploring how the pathogenic Eomes+ Th cells are generated during the course of EAE, we unexpectedly found that B cells and MHC class II+ myeloid cells isolated from the late EAE lesions strikingly up-regulated the expression of prolactin (PRL). We demonstrate that such PRL-producing cells have a unique potential to induce Eomes+ Th cells from naïve T cells ex vivo, and that anti-MHC class II antibody could block this process. Furthermore, PRL levels in the cerebrospinal fluid were significantly increased in the late phase of EAE, and blocking the production of PRL by bromocriptine or Zbtb20-specific siRNA significantly reduced the numbers of Eomes+ Th cells in the central nervous system (CNS) and ameliorated clinical signs in the later phase of EAE. The PRL dependency of Eomes+ Th cells was confirmed in a series of in vitro and ex vivo experiments. Collectively, these results indicate that extrapituitary PRL plays a crucial role in the CNS inflammation mediated by pathogenic Eomes+ Th cells. Cellular interactions involving PRL-producing immune cells could be considered as a therapeutic target for the prevention of chronic neuroinflammation.

Evaluation of autoantibodies and immunoglobulin G subclasses in women with suspected macroprolactinemia.

BACKGROUND: Macroprolactin mostly composed of an immunoglobulin G (IgG) and a monomeric prolactin (PRL) represents the major circulating PRL form in the patients with macroprolactinemia that are usually asymptomatic and may not require treatment. In this study, we aimed to evaluate the prevalence of antithyroid and antinuclear antibodies, as well as the IgG subclass distributions in the patients suspected for macroprolactinemia. METHODS: From January to July in 2018, totally 317 patients with elevated PRL were subjected to the polyethylene glycol (PEG) precipitation assay. The patients with recovery rates of ≤60% were subjected for IgG subclass determination and autoantibody testing including thyroid peroxidase antibody (aTPO), antithyroglobulin antibody (aTG), and antinuclear antibodies (ANA). RESULTS: The higher the post-PEG PRL recovery rates, the less typical hyperprolactinemia symptoms and the higher prevalence of autoantibodies were observed. The IgG1 and IgG3 were the predominant subclasses in the PRL-IgG complexes according to the immunoprecipitation experiments. CONCLUSION: The patients with post-PEG PRL recovery rates of <40% and 40%-60% were likely to represent two distinct populations of different clinical presentations. The prevalence of autoantibodies and IgG subclasses distribution suggested their pathogenic significance in the development of macroprolactinemia.

Serum prolactin revisited: parametric reference intervals and cross platform evaluation of polyethylene glycol precipitation-based methods for discrimination between hyperprolactinemia and macroprolactinemia.

BACKGROUND: Hyperprolactinemia diagnosis and treatment is often compromised by the presence of biologically inactive and clinically irrelevant higher-molecular-weight complexes of prolactin, macroprolactin. The objective of this study was to evaluate the performance of two macroprolactin screening regimes across commonly used automated immunoassay platforms. METHODS: Parametric total and monomeric gender-specific reference intervals were determined for six immunoassay methods using female (n=96) and male sera (n=127) from healthy donors. The reference intervals were validated using 27 hyperprolactinemic and macroprolactinemic sera, whose presence of monomeric and macroforms of prolactin were determined using gel filtration chromatography (GFC). RESULTS: Normative data for six prolactin assays included the range of values (2.5th-97.5th percentiles). Validation sera (hyperprolactinemic and macroprolactinemic; n=27) showed higher discordant classification [mean=2.8; 95% confidence interval (CI) 1.2-4.4] for the monomer reference interval method compared to the post-polyethylene glycol (PEG) recovery cutoff method (mean=1.8; 95% CI 0.8-2.8). The two monomer/macroprolactin discrimination methods did not differ significantly (p=0.089). Among macroprolactinemic sera evaluated by both discrimination methods, the Cobas and Architect/Kryptor prolactin assays showed the lowest and the highest number of misclassifications, respectively. CONCLUSIONS: Current automated immunoassays for prolactin testing require macroprolactin screening methods based on PEG precipitation in order to discriminate truly from falsely elevated serum prolactin. While the recovery cutoff and monomeric reference interval macroprolactin screening methods demonstrate similar discriminative ability, the latter method also provides the clinician with an easy interpretable monomeric prolactin concentration along with a monomeric reference interval.

The role of the prolactin/vasoinhibin axis in rheumatoid arthritis: an integrative overview.

Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease destroying articular cartilage and bone. The female preponderance and the influence of reproductive states in RA have long linked this disease to sexually dimorphic, reproductive hormones such as prolactin (PRL). PRL has immune-enhancing properties and increases in the circulation of some patients with RA. However, PRL also suppresses the immune system, stimulates the formation and survival of joint tissues, acquires antiangiogenic properties upon its cleavage to vasoinhibins, and protects against joint destruction and inflammation in the adjuvant-induced model of RA. This review addresses risk factors for RA linked to PRL, the effects of PRL and vasoinhibins on joint tissues, blood vessels, and immune cells, and the clinical and experimental data associating PRL with RA. This information provides important insights into the pathophysiology of RA and highlights protective actions of the PRL/vasoinhibin axis that could lead to therapeutic benefits.

Sensitivity of T-Lymphocytes to Hormones of the Anterior Pituitary Gland.

The review provides information about the features of the sensitivity of thymocytes, lymphoid organs' cells and T-lymphocytes of peripheral blood to the hormones secreted by anterior pituitary gland's cells: growth hormone, thyrotropin, adrenocorticotropic hormone, prolactin and ß-endorphin. Some aspects of the T-lymphocytes's response to humoral signals from the hypophysis are shown in the article. Also the pituitary hormones' role in the regulation of proliferation, differentiation, and cytokine production of T-lymphocytes in normal and pathological conditions of the organism being discussed.

A possible cause of the variable detectability of macroprolactin by different immunoassay systems.

BACKGROUND: Macroprolactinaemia is a major cause of hyperprolactinaemia. The detectability of macroprolactin varies widely among different immunoassay systems, but the causes are not fully known. This study aimed to identify the factors influencing the detectability of macroprolactin by immunoassay systems. METHODS: The study included 1544 patients who visited an obstetric and gynaecological hospital. Macroprolactinaemia was screened using the polyethylene glycol (PEG) method and confirmed using gel filtration chromatography and the protein G method. The prolactin (PRL) values determined by enzyme immunoassay (EIA) were compared with those of a chemiluminescence immunoassay system (Centaur) that is known to cross-react the least with macroprolactin. RESULTS: Macroprolactinaemia was found in 62 of 1544 patients (4.02%) who visited an obstetric and gynaecological hospital. The ratio of EIA-determined total PRL to free PRL in the supernatant after PEG precipitation was significantly elevated in all 62 serum samples with macroprolactin compared to those in 1482 serum samples without macroprolactin. In contrast, the ratio of Centaur-determined total PRL to free PRL was significantly elevated in 32 serum samples (group 1) and was within the normal range in 30 (group 2) of 62 serum samples with macroprolactin. The prevalence of non-IgG-type macroprolactin was significantly higher in group 1 than in group 2. Centaur diagnosed hyperprolactinaemia less frequently than EIA (n=2 vs. 16) in 62 patients with macroprolactinaemia. Those two hyperprolactinaemic patients diagnosed by Centaur had non-IgG-type macroprolactin. CONCLUSIONS: Macroprolactinaemia was present in 4% of patients visiting an obstetric and gynaecological hospital. The nature of macroprolactin (IgG-type or non-IgG-type) may partly explain why macroprolactin detectability varies among different immunoassay systems.

Ames hypopituitary dwarf mice demonstrate imbalanced myelopoiesis between bone marrow and spleen.

Ames hypopituitary dwarf mice are deficient in growth hormone, thyroid-stimulating hormone, and prolactin. The phenotype of these mice demonstrates irregularities in the immune system with skewing of the normal cytokine milieu towards a more anti-inflammatory environment. However, the hematopoietic stem and progenitor cell composition of the bone marrow (BM) and spleen in Ames dwarf mice has not been well characterized. We found that there was a significant decrease in overall cell count when comparing the BM and spleen of 4-5 month old dwarf mice to their littermate controls. Upon adjusting counts to differences in body weight between the dwarf and control mice, the number of granulocyte-macrophage progenitors, confirmed by immunophenotyping and colony-formation assay was increased in the BM. In contrast, the numbers of all myeloid progenitor populations in the spleen were greatly reduced, as confirmed by colony-formation assays. This suggests that there is a shift of myelopoiesis from the spleen to the BM of Ames dwarf mice; however, this shift does not appear to involve erythropoiesis. The reasons for this unusual shift in spleen to marrow hematopoiesis in Ames dwarf mice are yet to be determined but may relate to the decreased hormone levels in these mice.

Prolactin modulates cytokine production induced by culture filtrate proteins of M. bovis through different signaling mechanisms in THP1 cells.

The immunomodulatory functions of prolactin (PRL) are well recognized. Augmented PRL plasma levels were observed in patients with advanced tuberculosis (TB). Recently, we have reported that LPS and Mycobacterium bovis (M. bovis) induced differential expression of PRL receptor (PRLR) isoforms in THP-1 cells and bovine macrophages, respectively. The aim of this work was to determine whether PRL should be considered as a potential modulator of the signaling pathways and cytokine synthesis, induced by culture filtrate protein (CFP) from M. bovis in THP-1 monocytes. The THP-1 cells were stimulated with PRL (20ng/mL), M. bovis CFP (50µg/mL). PRLR as well as phosphorylated STAT3, STAT5, Akt1/2/3, ERK1/2 and p38 expression were evaluated by Western blot. IL1-ß, TNF-α, IL-6, IL-12, IL-8, and IL-10 concentrations were measured by ELISA. Our results demonstrated that the expression pattern of PRLR short isoforms is induced by M. bovis CFP. M bovis CFP induced phosphorylation of Akt2, ERK1/2, p38, STAT3, and STAT5 pathways. In turn, PRL only activated the JAK2/STAT3-5 signaling pathway. However, when combined both stimuli, PRL significantly increased STAT3-5 phosphorylation and downregulated Akt2, ERK1/2, and p38 phosphorylation. As expected, M. bovis CFP induced substantial amounts of IL1-ß, IL-6, TNF-α, IL-8, IL-12, and IL-10. However, the PRL costimulation considerably decreased IL1-ß, TNF-α, and IL-12 secretion, and increased IL-10 production. This results suggest that up-regulation of IL-10 by PRL might be modulating the pro-inflammatory response against mycobacterial antigens through the MAPK pathway.

Prolactin is not required for the development of severe chronic experimental autoimmune encephalomyelitis.

Predominance of multiple sclerosis (MS) in women, reductions of disease flares during pregnancy, and their increase in the postpartum period have suggested a hormonal influence on MS activity. The hormone prolactin (PRL) has long been debated as a potential immune-stimulating factor in several autoimmune disorders, including MS and its animal model experimental autoimmune encephalomyelitis (EAE). However, to date, no data clearly ascribe a pathogenic role to PRL in these diseases. Using PRL receptor-deficient (Prlr(-/-)) and PRL-deficient (Prl(-/-)) mice, we show that PRL plays a redundant role in the development of chronic EAE. In Prlr(-/-) and Prl(-/-) mice, EAE developed with a delayed onset compared with littermate control mice, but with full clinical severity. In line with the clinical outcome, T cell proliferation and production of IFN-γ, IL-17A, and IL-6 induced by myelin Ag were delayed in Prlr(-/-) and Prl(-/-) mice. Ag-specific IgG Ab responses were not affected by PRLR or PRL deficiency. We also show that mouse lymph node cells and purified CD4(+) T cells express transcript for Prlr, but not for Prl. These results reveal that PRL does not play a central role in the development of chronic EAE and optimal Th1 and Th17 responses against myelin. Moreover, they also rule out a possible contribution of PRL secreted by immune cells to the modulation of autoreactive T cell response in this model.

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.

Arthritis and prolactin: a phylogenetic viewpoint.

Arthritic disorders are family of diseases that have existed since vertebrate life began. Their etiology is multifactorial with genetic, environmental, and gender factors driving chronic joint inflammation. Prolactin is a sexually dimorphic hormone in mammals that can act to both promote and ameliorate rheumatic diseases. It is found in all vertebrate groups where it exerts a wide diversity of actions. This review briefly addresses the presence and features of arthritic diseases in vertebrates, the effects of PRL on joint tissues and immune cells, and whether PRL actions could have contributed to the ubiquity of arthritis in nature. This comparative approach highlights the value of PRL as a biologically conserved factor influencing the development and progression of arthritis.

[Prolactin as an immunomodulatory factor in psoriatic arthritis]. / Prolaktyna jako czynnik immunomodulujacy w luszczycowym zapaleniu stawów.

Prolactin (PRL) is a hormone synthesized and secreted by lactotroph cells in the anterior pituitary gland. There is also extrapituitary hormone secretion by many cells, including cells of the immune system. In physiological conditions PRL is responsible for lactogenesis and other processes associated with it. PRL plays a significant role during the immune response as a cytokine, affecting proliferation and differentiation of many immune system cells. The biological effect of the hormone depends on binding with the specific prolactin receptor PRL-R, and activation of the transcription factors of targeted genes. For T lymphocyte stimulated PRL, that factor is mainly the interferon regulatory factor (IRF-1), which gives the possibility of adjusting the prolactin immune response. Literature data indicate that hyperprolactinemia (HPRL) is one of the important factors in the pathogenesis and course of autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis and Sjogren's syndrome. HPRL is diagnosed in nearly one-third of these patients. However, only a few data indicate the role of prolactin in psoriatic arthritis (PsA), whose etiology and disease progression are not fully elucidated, and the diagnosis is very difficult. Currently there is indicated a pronounced connection between the course of HPRL and activity of PsA. It seems also to be interesting that, regardless of the PRL levels in serum of patients with PsA, administration of bromocriptine--drug-lowering hormone--improves joint and skin symptoms, which indicates a decrease in disease activity, and is a promising way of alternative therapy for psoriatic arthritis. However, the effect of PRL on the pathogenesis and the severity of psoriatic arthritis has not yet been fully understood and further research will provide a possibility to assess the prognostic and diagnostic significance of prolactin in patients with PsA.

Immunomodulatory effect of prolactin on Atlantic salmon (Salmo salar) macrophage function.

The in vitro and in vivo effect of prolactin (PRL) on kidney macrophages from Atlantic salmon (Salmo salar) was investigated under the assumption that PRL stimulates immune innate response in mammals. Kidney macrophages were treated two ways: first, cultured in RPMI 1640 medium containing 10, 25, 50 and 100 ng/mL of PRL and second, isolated from a fish with a PRL-injected dose of 100 ng/Kg. Reduced nitro blue tetrazolium (formazan) was used to produce intracellular superoxide anion. Phagocytic activity of PRL was determined in treated cells by optical microscopy observation of phagocytized Congo red-stained yeast. Kidney lysozyme activity was measured in PRL-injected fish. In vitro and in vivo macrophages treated with PRL presented an enhanced superoxide anion production, elevated phagocytic index and increased phagocytic activity. Treated fish showed higher levels of lysozyme activity in the head kidney compared to the control. These results indicate that PRL-stimulated innate immune response in Atlantic salmon and future studies will allow us to assess the possibility of using PRL as an immunostimulant in the Chilean salmon industry.

Functional -1149 g/t polymorphism of the prolactin gene in schizophrenia.

BACKGROUND: Prolactin in schizophrenia is considered in the context of antipsychotic drug-induced hyperprolactinemia. However, the European First Episode Schizophrenia Trial showed that hyperprolacti nemia occurred in a significant proportion of drug-naïve first-episode schizophrenia patients, which shows that it may also be caused by other factors, including genetic predisposition. Therefore, we investigated the functional polymorphism of the prolactin gene in schizophrenic patients compared with control subjects. METHOD: The experimental group consisted of 403 patients with schizophrenia: 202 females and 201 males. The control group consisted of 653 subjects: 377 females and 276 males. The functional polymorphism -1149 G/T (rs1341239) of the prolactin gene was genotyped using the TaqMan single-nucleotide polymorphism allelic discrimination method. RESULTS: The distribution of genotypes in schizophrenic patients was significantly different from those of the control subjects (p=0.031). After breaking down by gender, for male patients, the difference versus control males was significant for both genotypes and alleles (p=0.031 and p=0.002, respectively), with allele G being observed more frequently in schizophrenic patients. CONCLUSION: The results may suggest a possible abnormality of the functional -1149 G/T polymorphism of the prolactin gene in schizophrenia, especially in male patients, similar to that found in autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. This could also correspond with an autoimmune pathogenesis of schizophrenia.

Unfavorable effects of hyperprolactinemia in autoimmune endocrine disorders.

Prolactin is a hormone with a multidirectional proinflammatory action. It has an anti-apoptotic effect, enhances proliferative response to antigens and mitogens, as well as enhances the production of immunoglobulins and autoantibodies. Increased prolactin levels are commonly observed in various organ and multi-organ specific autoimmune diseases. In our article, we report a case of a woman who developed progression of autoimmune thyroid disorder and developed insufficiency of the zona glomerulosa when her prolactin levels were increased. A normalization of plasma prolactin levels by quinagolide and replacement of risperidone with aripiprazole improved her clinical condition. Our study suggests that, in some patients, hyperprolactinemia may predispose to the development and progression of autoimmune disorders of endocrine glands.

Prolactin is involved in the systemic inflammatory response in myocardial infarction.

Prolactin may contribute to an atherogenic phenotype. Furthermore, previous studies have shown that prolactin levels increase in situations of acute stress and inflammation. We therefore aimed to investigate the relationship between prolactin, acute stress and inflammation in patients with myocardial infarction. We performed a case-control study in 40 patients with myocardial infarction and 39 controls, aged 41-84 years. Blood for assessment of prolactin and high sensitive C-reactive protein (hsCRP) was drawn at inclusion, that is, during the acute phase of the event, and 2-3 weeks later. Unexpectedly, prolactin levels at inclusion did not differ between cases and controls (7.0 ng/ml and 6.0 ng/ml, respectively, p=0.28). 2-3 weeks later prolactin levels in cases had not decreased. However, univariate regression analysis indicated that hsCRP is associated with prolactin levels (regression coefficient ß 0.11; [95% CI 0.01; 0.21]; p=0.03) in cases during the acute phase of myocardial infarction. Our findings may suggest that prolactin is involved in the systemic inflammatory response, which takes place during myocardial infarction; however, this association may not be strong enough to induce higher prolactin levels in patients with myocardial infarction.

Prolactin may not play a role in primary antiphospholipid (Hughes') syndrome.

The relationship between prolactin (PRL) and the immune system has been demonstrated in the last two decades and has opened new windows in the field of immunoendocrinology. However, there are scarce reports about PRL in primary antiphospholipid syndrome (pAPS). The objective of this study was to evaluate PRL levels in patients with pAPS compared to healthy controls and to investigate their possible clinical associations. Fifty-five pAPS patients according to Sapporo criteria were age- and sex-matched with 41 healthy subjects. Individuals with secondary causes of hyperprolactinemia (HPRL) were excluded; demographic, biometric, and clinical data, PRL levels, antiphospholipid antibodies, inflammatory markers, and other routine laboratory findings were analyzed. PRL levels were similar between pAPS and healthy controls (8.94 ± 7.02 versus 8.71 ± 6.73 ng/mL, P = .876). Nine percent of the pAPS patients and 12.1% of the control subjects presented HPRL (P = .740). Comparison between the pAPS patients with hyper- and normoprolactinemia revealed no significant differences related to anthropometrics, clinical manifestations, medications, smoking, and antiphospholipid antibodies (P > .05). This study showed that HPRL does not seem to play a role in clinical manifestations of the pAPS, differently from other autoimmune rheumatic diseases.

Prolactin, metabolic and immune parameters in naïve subjects with a first episode of psychosis.

BACKGROUND: Prolactin (Prl) is a pleiotropic hormone initially described for its regulation of lactation in mammals but later associated with metabolic and immune homeostasis, stress, inflammatory response and human behavior. Its regulation through dopamine receptors highlights its importance in psychiatry mostly because hyperprolactinemia is a common secondary side effect of dopamine antagonists. Despite its undeciphered patho-physiological mechanisms, hyperprolactinemia in naïve psychosis patients has been widely described. Its consequences might underlie the increased morbidity and early mortality found in naïve subjects as described in the general population where prolactin values have been correlated with inflammatory, immune and metabolic parameters. METHODS: We aimed to evaluate the correlation between prolactin values and other biochemical parameters (C-reactive Protein-CrP, blood cell count, lipid and hepatic profile, fasting glucose) in a cohort of first episode psychosis naïve subjects (N = 491) stratified by sex. Regression analyses with confounders were performed to evaluate the association. FINDINGS: Prl displayed significant correlations with C-Reactive Protein (CrP), Low-Density Lipoprotein (LDL), Aspartate Transaminase (AST) for females and High-Density Lipoprotein (HDL) and eosinophil count for males. However, and despite previous specific sex correlations, significant associations were described for CrP, HDL, LDL, AST and ALT without sex interaction and despite confounders such as age, Body Mass Index or smoking status. CONCLUSIONS: Our results show a specific relation of Prl with immune and metabolic parameters describing a heterogeneous pattern. Our results suggest that prolactin might underlie the excess of morbidity and early mortality in naïve patients through a specific pathway.

CGRP-Mediated Prolactin Upregulation: a Possible Pathomechanism in IgG4-Related Disease.

Similar to other immune-mediated diseases, IgG4-related disease (IgG4-RD) is the disease that develops in genetically susceptible individuals exposed to external or endogenous antigens. In the present study, it was confirmed that MAG (myelin-associated glycoprotein) antibodies (IgG, IgG4, and IgM) were detected by immunofluorescence (IFA) in serum of the patients with IgG4-RD. In vivo, the levels of prolactin and Th2 cytokines in CGRP+/- rats were higher than those in wild-type. Our findings indicate that the presence of CGRP-deficiency-mediated MAG antibodies is a probable molecular basis for the initial events which were triggered in IgG4-RD immune responses via prolactin upregulation.