Prolactin receptor gene expression in lymphoid cells

Primary Pituitary Lymphoma As Rare Cause Of A Pituitary Mass And Hypopituitarism In Adulthood

OBJECTIVE

Differential diagnosis of nonadenomatous sellar masses causing hypopituitarism is still a challenge. Among these masses, growing evidence has demonstrated that primary pituitary lymphoma is a specific and emerging entity. The aim of our study was to describe our experience with a case of primary pituitary lymphoma and to perform a review of the available literature.

METHODS

We searched relevant databases up to March 2020, identifying 36 suitable articles basing on inclusion criteria (primary pituitary lymphoma in adult immunocompetent subjects). Overall, 43 cases were included in the review, adding a new case diagnosed and treated in our hospital. Epidemiologic data, clinical presentation, hormonal status, radiologic findings, pathology, treatment, and outcome were extracted.

RESULTS

Mean age at diagnosis was 58.9 years, without gender difference. Symptoms related to mass were common (52.3%), in particular cranial nerve palsy (70.5%), headache (56.8%), and alteration in visual field (40.9%). Impaired hormonal status was detected in 89.7% of patients; of them, 58.9% presented with anterior pituitary failure (partial or total), while 25.6% presented with panhypopituitarism. Overall, diabetes insipidus was present in 30.8% and hyperprolactinemia in 41.0% of patients. The majority of patients presented a radiologically invasive mass in the suprasellar region and cavernous sinus (65.9% and 40.9%, respectively) and histologic diagnosis of diffuse B-cell lymphoma (54.5%).

CONCLUSION

The differential diagnosis of sellar and parasellar masses causing hypopituitarism should include primary pituitary lymphoma, even in absence of systemic symptoms or posterior pituitary dysfunction. The disease has a heterogeneous pattern, so a collaboration between endocrinologists, neuroradiologists, neurosurgeons, and hematologists is desirable.

Concomitant Primary CNS Lymphoma and FSH-Pituitary Adenoma Arising Within the Sella. Entirely Coincidental?

BACKGROUND AND IMPORTANCE: Collision tumors are the simultaneous occurrence of more than one type of neoplasm within an anatomic space. In the pituitary sella, collision tumors are exceedingly rare, and not much is known about their etiology and prognosis.

CLINICAL PRESENTATION: A 74-year-old man presented with a concomitant primary pituitary lymphoma (diffuse large B-cell non-Hodgkin's lymphoma; DLBCL) and follicle-stimulating hormone (FSH)-adenoma diagnosed histologically after clinical features of apoplexy prompted urgent surgical decompression and resection. Strong immunoreactivity for FSH by the lymphoma was evident. Full-body workup demonstrated no other source for the lymphoma. He subsequently underwent 4 cycles of chemotherapy and has been in remission for over 32 months. His ophthalmoplegia at presentation persisted with no further deficits.

CONCLUSIONS: Four cases of collision tumors of primary pituitary lymphoma and adenoma have previously been reported. This case represents the first combination of an FSH-adenoma and a DLBCL in the literature. Prompt involvement of the hematology-oncology team contributed to the good outcome seen in this case. The putative role played by pituitary hormones in tumorigenesis is reviewed in this case report. The association is either a chance occurrence or due to the induction of lymphoma cell proliferation by the binding of FSH produced by the adenoma to the FSH receptors on the lymphoma cells.

Primary pituitary lymphoma: an update of the literature

Primary intracranial lymphomas (Weller et al. in Neuro Oncol 14(12):1481-1484, 2012) are an emerging disease and an isolated localization in the pituitary gland i.e. primary pituitary lymphoma (PPL) represents a rare condition. We present an update of the most recent evidence for PPL through a systematic review of the literature. A systematic literature review was conducted using PubMed database up to October 2015. The population was defined as immunocompetent patients with a pathologically confirmed diagnosis of PPL. Patients' characteristics, clinical presentation, radiological features, pathology reports, adjuvant treatment and follow-up data were analyzed. We reported one case of PPL and included our data in this analysis. A total of 33 cases of PPL were identified, including ours. A slight not significant female prevalence was evident, with a mean age of 59 years at diagnosis. Visual troubles and headaches were the most common presenting symptoms. About 80 % of patients presented a cranial nerve (CN) deficit. The most frequently involved were the II and III CN. Anterior hypopituitarism was present in 70 % of cases and a diabetes insipidus in 36 % of cases. PPL was rarely limited to the sella and most often extended to the suprasellar and parasellar space. 70 % of cases underwent resection, 21 % a biopsy. A B-cell lymphoma was isolated in 82 % of cases, a T-cell lymphoma in 15 % and a NK/T cell lymphoma in one case. Overall mean survival rate was 14.4 months (95 % confidence interval 9.0-19.8 months) and there was no difference in terms of survival rates when patients were stratified according to the treatment they received. PPL is an emerging clinical entity. Literature data are too scarce to allow the definition of specific protocols of treatment and the management is based on the guidelines present for PCNSL. The role of surgery aiming at a complete resection of PPL should be reevaluated in wider studies including only this category of patients, to establish the real role of each therapeutic strategy.

Primary pituitary diffuse large B-cell lymphoma with somatotroph hyperplasia and acromegaly: case report

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma and comprises approximately 30% of all lymphomas. Patients typically present with a nonpainful mass in the neck, groin, or abdomen associated with constitutional symptoms. In this report, however, the authors describe a rare case of a 61-year-old woman with hyperprolactinemia, hypothyroidism, and acromegaly (elevation of insulin-like growth factor-1 [IGF-1]) with elevated growth hormone-releasing hormone (GHRH) in whom an MRI demonstrated diffuse enlargement of the pituitary gland. Despite medical treatment, the patient had persistent elevation of IGF-1. She underwent a transsphenoidal biopsy, which yielded a diagnosis of DLBCL with an activated B-cell immunophenotype with somatotroph hyperplasia. After stereo-tactic radiation therapy in combination with chemotherapy, she is currently in remission from her lymphoma and has normalized IGF-1 levels without medical therapy, 8 months after her histopathological diagnosis. This is the only reported case of its kind and displays the importance of a broad differential diagnosis, multidisciplinary evaluation, and critical intraoperative decision-making when treating atypical sellar lesions.

High prevalence of autoimmune thyroid diseases in patients with prolactinomas: A cross-sectional retrospective study in a single tertiary referral centre

BACKGROUND

Prolactin has been shown to exert potent immunomodulatory activities.

DESIGN

Retrospective cross-sectional study examining the prevalence of autoimmune thyroid diseases (AITD) in patients with prolactinomas. The medical files of 462 patients (367 women and 95 men) followed up at a single tertiary referral centre were analyzed.

RESULTS

The prevalence of AITD among prolactinoma patients was estimated at 21.0% (23.2% in females and 12.6% in males). In 51.5% of the patients, diagnosis of prolactinoma preceded the development of AITD; in 37.2%, both diseases were simultaneously diagnosed and 11.3% of patients were diagnosed first with AITD. Hyperthyroidism was observed in 1.24% of the investigated subjects. Primary hypothyroidism was detected in 15.6% of all patients (16.4% in women; 10.7% in men) with a mean incidence of 24 cases/1000/year.

CONCLUSIONS

Our results demonstrate the high frequency of AITD in patients with prolactinomas. The prevalence rate of hyperthyroidism is comparable with the literature data from community-based studies. In contrast, the prevalence of the spontaneous hypothyroidism due to autoimmune thyroiditis is significantly higher in female and male subgroups of patients with prolactinomas in comparison with the general population. A possible role of supraphysiologically increased prolactin levels in the pathogenesis and the clinical course of AITD in patients with prolactinomas can be suggested. Based on these findings we recommend routine screening for AITD with simple thyroid tests (TSH, TPO-Abs and ultrasound examination) in all patients diagnosed with prolactinoma.

Precursor T-lymphoblastic lymphoma within a recurrent pituitary adenoma

Only single examples of lymphoma associated with pituitary adenoma have been reported. In our patient, a precursor T-lymphoblastic lymphoma developed within a recurrent pituitary adenoma 17 years after the first resection. Histomorphologically, lymphoma and adenoma components were tightly admixed. The features harbour remarkable similarity to the previous report by Kuhn et al.. In both patients the lymphomas were composed of T-cells, there was no evidence of further sites involved, and both adenomas expressed follicle-stimulating hormone. The hormone may have posed a proliferative and transforming effect on lymphatic cells and could have played a crucial role in "lymphomagenesis" as an exceptional phenomenon.

Expression patterns of the prolactin receptor gene in chicken lymphoid tissues during embryogenesis and posthatch period

Prolactin (PRL) is a pituitary hormone with multiple homeostatic roles among vertebrates. Although it has mainly been studied in relation to its role during the initiation and maintenance of incubation behavior in avian species, it has also been shown to act on the immune system. In this study, levels of PRL receptor (PRLR) mRNA were quantified by real-time PCR, and tissue expression was localized by in situ hybridization in primary and secondary lymphoid organs. Prolactin receptor was shown to be expressed in the bursa follicles, thymus lobules, and splenic pulp at all stages of development examined. Levels of PRLR expression were consistently higher in the bursa of Fabricius when compared with other lymphoid organs, suggesting that PRL acts primarily on bursal development. Furthermore, levels of PRLR mRNA appeared to fluctuate during embryogenesis, with a significant increase observed at embryonic day 19 in the bursa, at 7 d of age in the thymus, and on hatching day in the spleen. Thus, PRL might play an important role during the development of the immune system in chickens.

Prolactin induces chitotriosidase gene expression in human monocyte-derived macrophages

Human chitotriosidase (Chit), a chitinolytic enzyme, is a member of the chitinase family. In human's plasma Chit activity have been proposed as a biochemical marker of macrophage activation in several lysosomal diseases. Recently we found that Chit activity is higher in patients affected by Plasmodium falciparum malaria infection suggesting that chitotriosidase may induce an immunological response. The pituitary hormone prolactin (PRL) is a multifunctional polypeptide also produced by immune cells and represents a key component of the neuroendocrine-immune loop. The presence of PRL receptors in macrophage suggests that PRL is involved in regulating functions in these cells. Our objective in this study was to investigate the effect of PRL in human monocyte-derived macrophages (HMMs) on Chit production. Administration of PRL in HMMs was found to increase both expression and activity of Chit in a time and dose dependent manner as quantified, respectively, by real time PCR and Chit activity assay. PRL-treated monocyte-derived macrophages showed also an enhanced release of superoxide anion (O2-) release. Our observations confirm that PRL regulates HMMs activation and suggest, for the first time, that it influences immune function also through the induction of Chit activity.

Lack of association between hyperprolactinemia and soluble IL-2 receptor levels in systemic lupus erythematosus

The aim of the study was to evaluate the association between hyperprolactinemia and T lymphocyte activation through the soluble IL-2 receptor (sIL-2R) in systemic lupus erythematosus (SLE) patients. Seventy SLE patients, 18 of them with hyperprolactinemia (HPRL), were compared with 18 normoprolactinemic (NPRL) patients and 10 age-matched healthy blood-bank donor women. Patients were evaluated by means of the SLE activity index (SLEDAI). Total serum IgG and sIL-2R levels were determined by an ELISA assay. Differences between sIL-2R and IgG serum levels in patients and controls were examined by Kruskal-Wallis analysis and a Spearman r correlation to determine the association between sIL-2R, IgG and prolactin (PRL) levels. IgG and sIL-2R serum levels did not differ significantly between HPRL and NPRL patients: 1827.3 (1428-2226) vs 2028.8 (1586-2467) mg/dl and 882.2 (511-1254) vs 740.1 (534-946.4) U/ml, respectively (confidence interval 95%). In the total SLE group, sIL-2R and IgG serum levels were positively associated (P = 0.0009), however, this was not the case for sIL-2R and PRL (P > 0.49). We did not demonstrate an association between HPRL and lymphocyte activation measured through serum sIL-2R in female patients with SLE.

Role of prolactin receptor and CD25 in protection of circulating T lymphocytes from apoptosis in patients with breast cancer

Prolactin (PRL) has been reported to inhibit apoptosis in various cell types and to serve as a cofactor in the upregulation of CD25 on T cells during activation. We investigated a possible relation between prolactin receptor (PRL-R) or IL-2 receptor alpha (IL-2Ralpha, CD25) expression on circulating T lymphocytes and their apoptosis in patients with breast cancer. Peripheral blood mononuclear cells obtained from 25 patients, 25 normal controls (NC) and three cord blood samples were evaluated for Annexin V binding and expression of CD95, CD25, and PRL-R on CD3(+) T cells by multicolour flow cytometry. Plasma levels of PRL, sCD95L, and sIL-2R were determined in patients and controls and related to T-cell apoptosis. The ability of PRL to protect T cells from apoptosis induced by various agents was also studied. Expression of PRL-R on the surface of T cells was comparable in patients with breast cancer and NC, but PRL plasma levels in patients were significantly lower (P<0.05). In patients, 18+/-11% (mean+/-s.d.) of CD3(+) cells bound Annexin V, compared to 9+/-6% in NC (P<0.0004). Percentages of CD3(+)Fas(+) and CD3(+)CD25(+) cells were higher in the peripheral circulation of patients than NC (P<0.0001 and <0.04, respectively). Levels of sFasL were lowest in plasma of the patients with the highest proportions of CD3(+)Fas(+) T cells. Most T cells undergoing apoptosis were CD3(+)CD25(-) in patients, and the proportion of CD3(+)CD25(-) Annexin V(+) cells was significantly increased in patients compared to NC (P<0.006). Ex vivo PRL protected T cells from starvation-induced or anti-CD3Ab-induced but not from Fas/FasL-dependent apoptosis. These results indicate that expression of CD25 but not of PRL-R on the surface of activated T lymphocytes appears to be involved in modulating Fas/Fas - ligand interactions, which are, in part, responsible for apoptosis of T lymphocytes and excessive turnover of immune cells in the circulation of patients with breast cancer.

Effect of prolactin on the antigen presenting function of monocyte-derived dendritic cells

Monocyte derived macrophages (Mphi) and dendritic cells (DC) play critical roles at the interface between innate and adaptive immunity. Both types of cells can effectively phagocytose exogenous antigens, whereas only DC can process and present them efficiently to antigen-specific T lymphocytes. The hormone PRL is also produced by immune cells and is regarded as a key component of the neuroendocrine--immune loop and a local regulator of lymphocyte response. Its main feature is cooperation with cytokines and hemopoietins. Triggering of monocyte PRL receptors with physiological-to-supraphysiological concentrations of PRL up-regulates the GM-CSF receptors, resulting in synergistic PRL-GM-CSF induced maturation of immature (i)DC. Further incubation induces increased antigen-presenting activity at the highest PRL concentrations studied (200 ng/ml). IFN-gamma, release by allogeneic lymphocytes is dependent on T cell-triggered IL-12 release by PRL-preincubated iDC. This, in turn, may be secondary to increased DC expression of CD40 or IFN-gamma. The permissive action of high PRL concentrations in the antigen presenting process may be of significance in initiation of the response against major histocompatibility complex (MHC)-presented self-antigens and may explain the association of hyperprolactinemia with autoimmune diseases.

Prolactin regulates antitumor immune response through induction of tumoricidal macrophages and release of IL-12

The involvement of PRL in regulating monocyte/macrophage functions is suggested by the presence of PRL-Rs in these cells. Here, we show that PRL, though it failed to activate mouse peritoneal resident macrophages (RMs), acted as a second signal and activated mouse peritoneal inflammatory macrophages (EMs) to a tumoricidal state. The cytotoxicity of mouse tumor-associated macrophages (TAMs) isolated at day 1 of tumor (Ehrlich ascites carcinoma, EAC) growth was enhanced by PRL. However, with progression of tumor growth, TAMs became nonresponsive to the hormone. PRL-induced killing of P815 target cells by EMs and TAMs was independent of TNF but correlated with the hormone-induced augmentation of NO2(-) and O2(-) release in these macrophages. Administration of PRL in vivo inhibited EAC growth and augmented NO2(-) release by TAMs. PRL synergized with the TH1 cytokine IFN-gamma, a known activator of macrophages, in inducing tumor killing and release of NO2(-) from EMs and TAMs. The hormone might activate macrophages at least partially, through the release of IFN-gamma as anti-IFN-gamma blocked IFN-gamma- as well as PRL-induced cytotoxicity in EMs. The TH2 cytokine IL-4 suppressed PRL-induced activation of macrophages. PRL induced release of IL-12 from EMs also, which suggested that the hormone might drive the TH1 response through IL-12. Our observations further suggest that PRL alone and in synergy with IFN-gamma, released through induction of IL-12, may generate tumoricidal macrophages and thus regulate the antitumor immune response of tumor hosts.

Cyclophosphamide plus somatostatin, bromocriptin, retinoids, melatonin and ACTH in the treatment of low-grade non-Hodgkin's lymphomas at advanced stage: results of a phase II trial

PURPOSE

Somatostatin, prolactin, retinoids, melatonin and ACTH have been shown to influence the lymphatic growth, and the action of the cyclophosphamide in lymphoproliferative disorders is well known. This provided the rationale to conduct, in patients with low-grade non-Hodgkin's lymphomas (NHL), a phase II trial of a combined association of cyclophosphamide, somatostatin, bromocriptin, retinoids, melatonin and ACTH.

PATIENTS AND METHODS

Twenty patients with a diagnosis of low-grade NHL, stage III or IV, were included in this study. Patients received for one month the following treatment: cyclophosphamide, somatostatin, bromocriptin, retinoids, melatonin, and ACTH. The therapy was continued for two additional months in patients with stable or responding disease. After three months, the responding patients continued the therapy for three months and more.

RESULTS

Twenty patients were assessable for toxicity and response; 70% (14 of 20 patients; 95% confidence interval [CI], 50% to 90%) had a partial response; 20% (4 of 20) had stable disease, and 10% (2 of 20) progressed on therapy. Going on with the treatment, none of the 14 patients with partial response had a disease progression (average follow-up time of 21 months, range, 7 to 25), and 50% of these patients had a complete response; among 4 patients with stable disease, 25% (1 of 4) had a partial response and 75% (3 of 4) progressed on therapy (mean time to progression [TTP] 14.3 months, range, 7 to 21). The toxicity was very mild, the most common side effects being drowsiness, diarrhea and hyperglycemia.

CONCLUSIONS

The association of cyclophosphamide, somatostatin, bromocriptin, retinoids, melatonin, and ACTH is well tolerated and effective in treatment of low-grade NHL at advanced stage.

The roles of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormones in lymphocyte development and function: insights from genetic models of hormone and hormone receptor deficiency

An extensive literature suggesting that PRL, GH, IGF-I, and thyroid hormones play an important role in immunity has evolved. Because the use of one or more of these hormones as immunostimulants in humans is being considered, it is of critical importance to resolve their precise role in immunity. This review addresses new experimental evidence from analysis of lymphocyte development and function in mice with genetic defects in expression of these hormones or their receptors that calls into question the presumed role played by some of these hormones and reveals unexpected effects of others. These recent findings from the mutant mouse models are integrated and placed in context of the wider literature on endocrine-immune system interactions. The hypothesis that will be developed is that, with the exception of a role for thyroid hormones in B cell development, PRL, GH, and IGF-I are not obligate immunoregulators. Instead, they apparently act as anabolic and stress-modulating hormones in most cells, including those of the immune system.

Association of 2',5'-oligoadenylate synthetase with the prolactin (PRL) receptor: alteration in PRL-inducible stat1 (signal transducer and activator of transcription 1) signaling to the IRF-1 (interferon-regulatory factor 1) promoter

The PRL receptor (PRL-R) signals through the Janus tyrosine kinases (JAK) and other non-JAK tyrosine kinases, some of which are preassociated with the PRL-R. To clone PRL-R interacting proteins, the intracellular domain (ICD) of the long form of the PRL-R was used in a yeast two-hybrid screen of a human B cell cDNA library. One PRL-R interacting protein was identified as the 42-kDa form of the enzyme 2',5'-oligoadenylate synthetase (OAS). The in vivo interactions in yeast were further confirmed by an in vitro interaction assay and by coimmunoprecipitation in transfected mammalian cells. Functionally, OAS reduced the basal activity of two types of promoters in transiently transfected COS-1 cells. In the presence of PRL, OAS inhibited PRL induction of the immediate early IRF-1 (interferon-regulatory factor 1) promoter, but not PRL induction of the differentiation-specific beta-casein promoter, suggesting that OAS exerts specific effects on immediate early gene promoters. The inhibitory effects of OAS were accompanied by a reduction in PRL-inducible Stat1 (signal transducer and activator of transcription 1) DNA binding activity at the IRF-1 GAS (interferon-gamma-activated sequence) element. These results demonstrate a novel interaction of OAS with the PRL-R and suggest a role for OAS in modulating Stat1-mediated signaling to an immediate early gene promoter. Although previously characterized as a regulator of ribonuclease (RNase) L antiviral responses, OAS may have additional effects on cytokine receptor signal transduction pathways.

Analysis of prolactin-modulated gene expression profiles during the Nb2 cell cycle using differential screening techniques

BACKGROUND

Rat Nb2-11C lymphoma cells are dependent on prolactin for proliferation and are widely used to study prolactin signaling pathways. To investigate the role of this hormone in the transcriptional mechanisms that underlie prolactin-stimulated mitogenesis, five different techniques were used to isolate differentially expressed transcripts: mRNA differential display, representational difference analysis (RDA), subtractive suppressive hybridization (SSH), analysis of weakly expressed candidate genes, and differential screening of an organized library.

RESULTS

About 70 transcripts were found to be modulated in Nb2 cells following prolactin treatment. Of these, approximately 20 represent unknown genes. All cDNAs were characterized by northern blot analysis and categorized on the basis of their expression profiles and the functions of the known genes. We compared our data with other cell-cycle-regulated transcripts and found several new potential signaling molecules that may be involved in Nb2 cell growth. In addition, abnormalities in the expression patterns of several transcripts were detected in Nb2 cells, including the constitutive expression of the immediate-early gene EGR-1. Finally, we compared the differential screening techniques in terms of sensitivity, efficiency and occurrence of false positives.

CONCLUSIONS

Using these techniques to determine which genes are differentially expressed in Nb2 lymphoma cells, we have obtained valuable insight into the potential functions of some of these genes in the cell cycle. Although this information is preliminary, comparison with other eukaryotic models of cell-cycle progression enables identification of expression abnormalities and proteins potentially involved in signal transduction, which could indicate new directions for research.

Lactation increases prolactin receptor expression in spleen and thymus of rats

Prolactin receptors (PRL-R) are widely expressed on cells of the immune system. During lactation, the increase in serum PRL levels may modify the gene expression of these receptors. Specific PRL binding sites and the expressions of both PRL-R-L and PRL-R-S forms in thymus and spleen of nulliparous control, 10-day postpartum lactating, and 10-day postpartum nonlactating rats were studied. A semi-quantitative RT-PCR technique was used to detect the PRL-R gene transcript in the tissues. Our results showed that specific PRL binding sites and PRL-R-L mRNA and PRL-R-S mRNA were present in the lymphoid tissues with the PRL-R-L mRNA predominant. Lactation markedly increased specific binding sites and PRL-R-L mRNA in both spleen and thymus and only PRL-R-S in spleen. No differences between nulliparous control and postpartum nonlactating rats were observed in any of the parameters measured. The parallel increase in specific PRL binding sites and PRL-R-L mRNA suggests that lactation up-regulates PRL-R expression in lymphoid tissues and may be beneficial to the maternal immune system.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

The lissencephaly gene product Lis1, a protein involved in neuronal migration, interacts with a nuclear movement protein, NudC

Important clues to how the mammalian cerebral cortex develops are provided by the analysis of genetic diseases that cause cortical malformations [1-5]. People with Miller-Dieker syndrome (MDS) or isolated lissencephaly sequence (ILS) have a hemizygous deletion or mutation in the LIS1 gene [3,6]; both conditions are characterized by a smooth cerebral surface, a thickened cortex with four abnormal layers, and misplaced neurons [7,8]. LIS1 is highly expressed in the ventricular zone and the cortical plate [9,10], and its product, Lis1, has seven WD repeats [3]; several proteins with such repeats have been shown to interact with other polypeptides, giving rise to multiprotein complexes [11]. Lis1 copurifies with platelet-activating factor acetylhydrolase subunits alpha 1 and alpha 2 [12], and with tubulin; it also reduces microtubule catastrophe events in vitro [13]. We used a yeast two-hybrid screen to isolate new Lis1-interacting proteins and found a mammalian ortholog of NudC, a protein required for nuclear movement in Aspergillus nidulans [14]. The specificity of the mammalian NudC-Lis1 interaction was demonstrated by protein-protein interaction assays in vitro and by co-immunoprecipitation from mouse brain extracts. In addition, the murine mNudC and mLis1 genes are coexpressed in the ventricular zone of the forebrain and in the cortical plate. The interaction of Lis1 with NudC, in conjunction with the MDS and ILS phenotypes, raises the possibility that nuclear movement in the ventricular zone is tied to the specification of neuronal fates and thus to cortical architecture.

Defective mammopoiesis, but normal hematopoiesis, in mice with a targeted disruption of the prolactin gene

Prolactin (PRL) has been implicated in numerous physiological and developmental processes. The mouse PRL gene was disrupted by homologous recombination. The mutation caused infertility in female mice, but did not prevent female mice from manifesting spontaneous maternal behaviors. PRL-deficient males were fertile and produced offspring with normal Mendelian gender and genotype ratios when they were mated with heterozygous females. Mammary glands of mutant female mice developed a normal ductal tree, but the ducts failed to develop lobular decorations, which is a characteristic of the normal virgin adult mammary gland. The potential effect of PRL gene disruption on antigen-independent primary hematopoiesis was assessed. The results of this analysis indicated that myelopoiesis and primary lymphopoiesis were unaltered in the mutant mice. Consistent with these observations in PRL mutant mice, PRL failed to correct the bone marrow B cell deficiency of Snell dwarf mice. These results argue that PRL does not play any indispensable role in primary lymphocyte development and homeostasis, or in myeloid differentiation. The PRL-/- mouse model provides a new research tool with which to resolve a variety of questions regarding the involvement of both endocrine and paracrine sources of PRL in reproduction, lactogenesis, tumorigenesis and immunoregulation.

A bioactive 60-kilodalton prolactin species is preferentially secreted in cultures of mitogen-stimulated and nonstimulated peripheral blood mononuclear cells from subjects with systemic lupus erythematosus

We have evaluated the production of PRL by human peripheral mononuclear cells (PBMNC) from normal subjects and patients with systemic lupus erythematosus (SLE). Conditioned medium prepared from basal and Con-A-stimulated PBMNC was assessed for the presence of PRL-like by its ability to stimulate growth of PRL-responsive Nb2 rat lymphoma cells. In the presence or absence of Con-A, SLE PBMNC secrete significantly higher (P < 0.001) amounts of bioactive PRL-like species than normal cells. Growth of Nb2 cells by conditioned medium was inhibited with specific antiserum to human PRL. Western blotting using a polyclonal antibody to human PRL revealed a single 60-kDa PRL-like species in both normal and SLE PBMNC extracts, the immunoreactivity of which was preferentially found in SLE subjects. With the use of reverse transcription-PCR an expected 633-bp band was observed, and its similarity to pituitary PRL was further confirmed by Southern blot analysis with human PRL complementary DNA as a probe. We conclude that a high molecular mass PRL-like species is synthesized and secreted by PBMNC, and patients with SLE have an increased secretion of lymphocyte-derived PRL-like material.

Inefficient secretion of human H27A-prolactin, a mutant that does not bind Zn2+

Human PRL binds Zn2+, but the function of the binding is not known. We investigated the effect on PRL production in pituitary cells by obtaining clones of GH4C1 cells stably transfected with human H27A-PRL, a mutant that does not bind Zn2+. Unexpectedly, clones transfected with the mutant human PRL made little rat PRL. Untransfected GH4C1 cells made between 0.5 to 10 microg rat PRL/10(5) cells in 24 h. Clones transfected with vector alone (four of four), wild type human PRL (six of six), or with human K69A-PRL (two of two) made amounts of rat PRL in the same range. Clones transfected with human H27A-PRL (five of five) made 0.003-0.1 microg rat PRL/10(5) cells in 24 h, and the production of rat PRL mRNA was reduced. Human H27A-PRL was not efficiently secreted; 20-40% newly synthesized H27A-PRL was degraded by 60 min, and there was usually a delay in release of newly synthesized H27A-PRL. Reduction of rat PRL production is not mediated through the PRL receptor, because no sequences for the receptor in GH4C1 cells were detected by RT-PCR. Proteins involved in folding, such as BiP, were not specifically elevated in the H27A-PRL clones. In transient transfections, in which cells have not undergone selection, we found no evidence for disulfide-bonded aggregates of the mutant protein. The results indicate that Zn2+ binding stabilizes PRL in the secretory pathway; the instablility of the mutant protein may trigger effects that suppress rat PRL production directly or that indirectly result in selection of clones with low rat PRL production.

Up-regulation of the human prolactin receptor in the endometrium

In humans, uterine endometrial stromal cells differentiate (decidualize) into decidual cells that express prolactin (PRL). Decidual PRL expression continues throughout pregnancy, thus decidual cells lining fetal membranes of term placenta synthesize and secrete PRL. To examine the hypothesis that PRL may play an autocrine role in the decidual cells, we examined the expression of the PRL receptor (PRL-R) during in vitro decidualization of stromal cells and in term decidua. In endometrial stromal cells decidualized by treatment with 1 μM medroxyprogesterone and 10 nM estradiol for 3, 6, and 9 d, respectively, a 12.7 kb PRL-R transcript increased 3-3.5-fold, 16.5-17-fold, and 23.5-24-fold, respectively, compared with untreated controls, in duplicate experiments. Progesterone-dependent PRL-R and PRL expression were stimulated by 1 μ/M prostaglandin E(2). Term decidua expressed the long form of the PRL-R and five major PRL-R transcripts (12.7, 9.7, 7.0, 3.6, and 2.8 kb). In contrast, human liver expressed two major transcripts (12.7 and 9.7 kb) while hepG2 cells expressed a single 7.0-kb-sized transcript. These studies demonstrate that PRL-R expression is stimulated upon progesterone-induced PRL gene expression in endometrial stromal cells supporting the hypothesis that PRL may have an autocrine effect in the endometrium and decidua.

Multiple stat complexes interact at the interferon regulatory factor-1 interferon-gamma activation sequence in prolactin-stimulated Nb2 T cells

Interferon regulatory factor-1 (IRF-1) is a major immediate early gene induced by prolactin (PRL) in a biphasic, cell cycle-dependent manner in Nb2 T cells. This biphasic expression (30 min and 10 h) is mediated in part by an interferon-gamma activation sequence (GAS) in the IRF-1 promoter which binds factors belonging to the Signal Transducers and Activators of Transcription (Stat) family. By electrophoretic mobility shift assays (EMSA), Stat1 alpha was found to be the major and Stat5a a minor component of the 30 min complex. At 10 h, Stat-like factors were again found at the IRF-1 GAS. Western blot analyses show that Stat5a was rapidly induced by PRL to enter the nucleus, but unexpectedly, Stat1 alpha and the alternatively-spliced Stat1 beta were already present in the uninduced nucleus. Further, Stat1 alpha but not Stat1 beta is preferentially tyrosine phosphorylated in response to PRL stimulation. Our studies suggest that multiple Stat complexes may contribute to the biphasic transcription of the IRF-1 gene in PRL-stimulated T cells.

Immunoregulatory properties of growth hormone and prolactin

Reciprocal communication between the neuroendocrine and immune systems is critical to the establishment of host homeostatic and defence mechanisms. The production and utilisation of common ligands and their receptors by cells of the immune and neuroendocrine systems constitutes a biochemical information circuit between and within the immune and neuroendocrine systems. Although the structures of the various signalling components appear to be similar in both systems, the regulation of their synthesis may be different. Growth hormone and prolactin have similar and marked influences on the function/activity of each of the major immune cell types, both in vitro and in vivo. The underlying molecular mechanisms are just beginning to be unravelled, and it is anticipated that further work in this rapidly developing field will establish abnormal pituitary and/or lymphocyte growth hormone and prolactin synthesis and function as a contributory factor to a number of pathologic situations, including leukaemia and autoimmunity.

Immunoendocrine mechanisms in mammary tumor progression: direct prolactin modulation of peripheral and preneoplastic hyperplastic-alveolar-nodule- infiltrating lymphocytes

We have previously shown that the immunoregulatory function of prolactin may play a role in the progression of the mouse mammary preneoplastic hyperplastic alveolar nodule (HAN) line C4 to carcinoma. In this study we investigated the direct effect of prolactin on lymphocytes isolated from normal and C4-HAN-bearing mice. In addition, we tested the effect of ovariectomy on prolactin/lymphocyte interaction to see whether, as has been reported in rats [Mukherjee P., Hymer W. C. (1992) Prog Neuroendocrinol Immunol 5: 108; Viselli S. M. et al. (1991) Endocrinology 129: 983], removal of estrogen would enhance the response to prolactin in mice. Proliferation of splenocytes, lymph node cells and HAN-infiltrating lymphocytes was stimulated by prolactin in a dose-responsive fashion. Ovariectomy did not alter this effect consistently. Cell-cycle analysis based on simultaneous staining of DNA and RNA revealed that prolactin-stimulated lymphocytes progress through all phases of the cell cycle whereas anti-prolactin antiserum inhibits this stimulation. Two-color flow-cytometric analysis revealed the time-dependent induction of interleukin-2 (IL-2) receptor expression on both CD4+ and CD8+ cells by prolactin. Prolactin-treated lymphocytes also produced low yet detectable levels of bioactive IL-2 in a dose- and time-dependent fashion. Prolactin enhanced lymphocyte responsiveness to mitogens and showed a marked synergism at suboptimal concentrations. Pretreatment of splenocytes from HAN bearers with a high concentration of prolactin slightly enhanced natural killer (NK) activity; anti-prolactin antiserum reduced the NK lytic activity of poly(I).poly(C)-activated splenocytes from HAN-bearing mice. Our results provide direct experimental evidence for the stimulatory effect of prolactin on lymphocyte function and IL-2-mediated lymphocyte proliferation and suggest a mechanism linking the endocrine system to immunomediated enhancement of HAN progression.

Expression of short and long forms of prolactin receptor in murine lymphoid tissues

Two different forms of the prolactin receptor, differing in the length of their cytoplasmic domains, have been characterized in many tissues of rodents. To better understand whether short and long forms of PRLR are involved in the immune effects of PRL, we evaluated the distribution of these different forms in the thymus, spleen, lymph nodes and bone marrow from rats and mice. Total RNA was used for cDNA synthesis which was amplified by PCR, using oligonucleotides specific to the different forms of the prolactin receptor. We detected transcripts encoding both forms of prolactin receptor in all lymphoid tissues examined in mouse and rat. Finally we studied the transcript encoding prolactin itself in these rodent tissues; a clear signal was only found in rat thymus. The ubiquitous presence of both forms of receptor transcripts in different lymphoid tissues points to an important role of the PRLR and suggests that such forms of the receptor may be involved in differential functions in lymphocytes.

Prolactin heterogeneity: a limitation on the evaluation of results from prolactin assays due to differences in immunoassays and the different bioactivities of prolactin forms

Prolactin exists in biological fluids in several molecular forms. This raises two questions: (1) whether the assay of prolactin by immunotechniques is valid and reliable and (2) whether the different forms have different physiological roles, which might be exploited to improve diagnostic accuracy and data interpretation by the use of appropriate methods. To investigate these questions, prolactin from human amniotic fluid was separated, by concanavalin A-Sepharose affinity chromatography, into bound, retarded and unbound fractions (bound prolactin fraction, retarded prolactin fraction, unbound prolactin fraction), which were characterized by electrophoresis, immunoblotting and glycan detection blot. Virtually no contamination was found in the bound prolactin fraction, and the unbound prolactin fraction and retarded prolactin fraction were 74-83% pure according to densitometry of the electrophoretic and immunoblot patterns. High variability was found among the individual patterns. Glycan detection in the blotted fractions revealed that the bound prolactin fraction bands corresponding to M(r)25,000-29,000 were weakly glycolysated, whereas the bands of M(r)60,000-64,000 were significantly glycan-positive. Immunoreactive bands of unbound prolactin fraction and retarded prolactin fraction also stained positively for glycans. Using two commercial prolactin kits, the bound prolactin fraction forms were virtually undetectable. To demonstrate that the prolactin forms may depend on the hypothalamic state, two behaviourly different breeds of cattle were used as an animal model for studying hypothalamic activities. The number of immunoreactive bands, representing the prolactin forms, and the change of the forms in response to thyroliberin differed strikingly among the groups. The bioactivity of the forms was examined in bovine granulosa, oviductal, endometrial and spleen cells, and in murine splenocytes, the latter being activated by concanavalin A or allogeneically to create in vitro conditions that may have relevance for situations in vivo. The rate of incorporation of [3H]thymidine in murine splenocytes was dose-dependently enhanced only by bound prolactin fraction. The increase was abolished by purified anti-prolactin antiserum. However, the standard prolactin from the kits inhibited the proliferation even in low dose (1.25 microgram/l) and the inhibition was abolished in part by bound prolactin fraction. Thymidine incorporation into the bovine cells was significantly increased by low concentrations (2 micrograms/l) of unbound prolactin fraction and retarded prolactin fraction. Oviduct epithelial cells and splenocytes were stimulated by unbound prolactin fraction but not by retarded prolactin fraction in a dose of 16 micrograms/l. Thymidine incorporation into granulosa cells was inhibited by retarded prolactin fraction (16 micrograms/l) but not by unbound prolactin fraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatolactogens, somatomedins, and immunity

The neuroendocrine and immune systems participate as active partners in host homeostatic and defense mechanisms. This partnership involves a complex intercommunication system employing an array of shared ligands and receptors. Hormones of the somatolactogen family have marked influences on immune events in vivo, including the maintenance of lymphoid tissue cellularity, the promotion of DNA synthesis in these tissues, and the stimulation of a number of immune effector mechanisms. Both growth hormone and prolactin function to promote erythropoiesis and DNA synthesis in bone marrow precursors. Our results have shown that the somatolactogens and a member of the somatomedin family, IGF-I, are particularly effective in modulating the effector functions in phagocytic cells, including the production of reactive oxygen intermediates and tumor necrosis factor-alpha and the oxygen-dependent killing of bacteria. Evidence indicating a role of IGF-I in modulating immune functions is more recent but nonetheless compelling. Accumulated data suggest that somatolactogenic hormones, as well as one member of the somatomedins, are produced by cells of the immune system and can regulate local immune events. Although the molecular mechanisms by which the somatolactogens and somatomedins exert their effects on immune tissues are only now being explored, the pleiotropic nature of these effects suggests that these hormones participate at endocrine, paracrine, and perhaps autocrine sites of action.

Prolactin receptor expression by lymphoid tissues in normal and immunized rats

Prolactin receptor (PRLr) expression and distribution in thymus, spleen, bone marrow, lymph nodes, and peripheral blood lymphocytes from young adult Lewis rats are analyzed using single-color flow cytometry and a well-characterized monoclonal antibody directed against the rat liver PRLr. The in vivo effects of regional immunization on PRLr expression are also examined. PRLr is found to be widely distributed among cells of the immune system and demonstrates lymphoid tissue-specific patterns of expression. Footpad immunization caused the rapid, but transient, induction of PRLr expression in the draining lymph node, with only modest effects on PRLr expression in other distant lymphoid tissues. These studies indicate that PRL may be capable of direct interaction with the immune system through differential expression of the PRL cell surface receptor on select lymphoid target cell populations.

Interferon-gamma modulates retinoblastoma gene mRNA in monocytoid cells

To study the effect of interferon gamma (IFN-gamma) on the expression of the retinoblastoma (RB) susceptibility gene, we performed Northern-blot analysis on RNA extracted from Wish, HEL and monocytoid cell lines U-937 and THP-1 treated with 1,000 IU/ml of recombinant IFN-gamma. In U-937 and THP-1 cells, IFN-gamma increased the abundance of RB mRNA. In Wish and HEL cells, co-treatment with cycloheximide was required for IFN-gamma to increase the level of RB mRNA. Pre-treatment of THP-1 cells with cycloheximide prior to IFN-gamma treatment augmented the effects of IFN-gamma on RB gene expression. The effect of IFN-gamma in THP-1 cells was observed after 3 hr of treatment, being more pronounced after 6 hr and persisting until at least 18 hr, although at a lower level. These results suggest that IFN-gamma regulates the level of RB mRNA by different mechanisms in the different cell types. This cytokine increases the abundance of RB mRNA in monocytoid cell lines, reinforced by prior treatment with cycloheximide. Inhibition of protein synthesis is required in Wish and HEL cell lines before IFN-gamma has an effect on RB gene expression.

Prolactin and prolactin secretagogues reverse immunosuppression in mice treated with cysteamine, glucocorticoids, or cyclosporin-A

Suppression of prolactin (PRL) secretion with the dopamine agonist, bromocriptine, has been shown in rodents to diminish a variety of immunologic responses, including delayed type hypersensitivity, primary antibody response, T-cell dependent macrophage activation, and ex vivo T- and B-lymphocyte proliferation in response to mitogens. These same responses can be suppressed by endogenous or exogenous glucocorticosteroids and, in large measure, the immunosuppressant peptide cyclosporin A. The sulfhydryl reducing agent cysteamine (2-aminoethanethiol) is known to reduce pituitary and plasma prolactin levels. Treatment of mice with cysteamine at doses which suppressed circulating PRL levels resulted in suppression of ex vivo blastogenic responses of lymphocytes from treated mice. The T-cell-dependent primary IgM response to immunization with sheep red blood cells was also suppressed by cysteamine treatment. Treatment of mice with drugs stimulating the release of endogenous PRL, or with exogenous ovine PRL, was found to antagonize the suppression of lymphocyte proliferative responses to mitogens induced in mice by glucocorticoid or cyclosporin treatment. These data suggest that many drugs in common clinical use could have potential immunomodulatory actions due to suppression or stimulation of pituitary PRL secretion. Furthermore, lactogenic hormones appear to exert counterregulatory actions which may modify glucocorticosteroid actions on immune and other target issues.

Prolactin gene expression in human thymocytes

Recent evidence suggests that lymphocytes produce prolactin (PRL). Here, we report the cDNA cloning and expression of PRL from normal human thymocytes. Sequence analysis showed that the thymocyte cDNA encodes a 23 kDa protein which is identical to pituitary PRL. RNA blot analysis showed that the thymocyte PRL mRNA is approximately 170 nucleotides larger than the pituitary PRL message. PRL message was also detected in several non-pituitary human cell lines including Jurkat T, HeLa, and JEG cells. Furthermore, PRL gene expression in JEG cells was inhibited by glucocorticoid treatment. Our data support the hypothesis that PRL is a T cell-derived cytokine.

Interferon regulatory factor-1 is inducible by prolactin, interleukin-2 and concanavalin A in T cells

Interferon regulatory factor-1 (IRF-1) gene expression is rapidly upregulated in the prolactin (PRL)-activated Nb2 rat T lymphoma cell line. To further elucidate its role as a T cell activation molecule, IRF-1 gene expression in response to various T cell stimuli was examined. In Nb2 T cells, PRL induced two peaks of IRF-1 gene expression: a rapid, transient peak at 1 h and a sustained peak at 12 h. PRL subsequently induced interferon-gamma (IFN-gamma) gene expression at 3-6 h. However, the early induction of IRF-1 and IFN-gamma does not appear to be interdependent. Interleukin-2 (IL-2) also induced IRF-1 gene expression in Nb2 T cells but only one broad peak at 10 h was observed. In primary mouse splenocytes, concanavalin A induced rapid and transient expression of the IRF-1 gene; maximal expression occurred by 6 h, and then returned to basal levels by 12-15 h. These results provide additional evidence for the importance of IRF-1 in T cell activation.