Effects of prolactin on hematopoiesis

Prolactin: The Third Hormone in Breast Cancer

Prolactin coordinates with the ovarian steroids to orchestrate mammary development and lactation, culminating in nourishment and an increasingly appreciated array of other benefits for neonates. Its central activities in mammary epithelial growth and differentiation suggest that it plays a role(s) in breast cancer, but it has been challenging to identify its contributions, essential for incorporation into prevention and treatment approaches. Large prospective epidemiologic studies have linked higher prolactin exposure to increased risk, particularly for ER+ breast cancer in postmenopausal women. However, it has been more difficult to determine its actions and clinical consequences in established tumors. Here we review experimental data implicating multiple mechanisms by which prolactin may increase the risk of breast cancer. We then consider the evidence for role(s) of prolactin and its downstream signaling cascades in disease progression and treatment responses, and discuss how new approaches are beginning to illuminate the biology behind the seemingly conflicting epidemiologic and experimental studies of prolactin actions across diverse breast cancers.

Pre-operative serum inflammation-based scores in patients with pituitary adenomas

OBJECTIVE

Full blood count (FBC) and serum inflammation-based scores reflect systemic inflammation and predict outcomes in cancer, but little is known in pituitary adenomas (PAs). We aimed to characterise FBC and inflammation-based scores in PA patients and investigate their usefulness in predicting challenging disease course.

METHODS

We studied 424 PA patients first operated at our centre with available pre-operative biochemical data. Patients with infection, malignancies, autoimmune or haematological conditions were excluded. Inflammation-based scores studied: Neutrophil-to-Lymphocyte Ratio (NLR), Platelet-to-Lymphocyte Ratio (PLR), Lymphocyte-to-Monocyte Ratio (LMR), Systemic Immune-Inflammation Index (SII), Neutrophil-Platelet Score (NPS), Prognostic Nutrition Index (PNI), and Glasgow Prognostic Score (GPS).

RESULTS

Cushing's disease patients had more platelets, leucocytes, neutrophils and monocytes, and higher NLR, NPS and SII. Serum inflammation-based scores didn't differ among non-Cushing PA subtypes. The glucocorticoid excess severity influenced leucocyte, eosinophil, basophil and platelet counts, and GPS in Cushing's disease. Patients with functioning non-Cushing PAs with suprasellar extension, cavernous sinus invasion and hypopituitarism had GPS ≥ 1, while NPS ≥ 1 was associated with suprasellar extension. More invasive and difficult to treat corticotrophinomas were associated with fewer platelets pre-operatively (< 299.5 × 10⁹/L predicting multimodal treatment). Non-functioning PA patients who suffered apoplexy had more leucocytes, neutrophils and monocytes, higher GPS ≥ 1 and fewer platelets; re-operated cases had fewer lymphocytes, higher NLR and PLR.

CONCLUSIONS

Serum inflammation-based scores may predict invasive/refractory PAs: GPS and PNI in non-functioning and functioning non-Cushing PAs; NPS in functioning non-Cushing PAs; NLR and PLR in non-functioning PAs. Platelets < 299.5 × 10⁹/L predict multimodal treatment in Cushing's disease. Further studies are needed to confirm these observations.

The tumour microenvironment of pituitary neuroendocrine tumours

The tumour microenvironment (TME) includes a variety of non-neoplastic cells and non-cellular elements such as cytokines, growth factors and enzymes surrounding tumour cells. The TME emerged as a key modulator of tumour initiation, progression and invasion, with extensive data available in many cancers, but little is known in pituitary tumours. However, the understanding of the TME of pituitary tumours has advanced thanks to active research in this field over the last decade. Different immune and stromal cell subpopulations, and several cytokines, growth factors and matrix remodelling enzymes, have been characterised in pituitary tumours. Studying the TME in pituitary tumours may lead to a better understanding of tumourigenic mechanisms, identification of biomarkers useful to predict aggressive disease, and development of novel therapies. This review summarises the current knowledge on the different TME cellular/non-cellular elements in pituitary tumours and provides an overview of their role in tumourigenesis, biological behaviour and clinical outcomes.

Prolactin Acts on Myeloid Progenitors to Modulate SMAD7 Expression and Enhance Hematopoietic Stem Cell Differentiation into the NK Cell Lineage

Numerous cell types modulate hematopoiesis through soluble and membrane bound molecules. Whether developing hematopoietic progenitors of a particular lineage modulate the differentiation of other hematopoietic lineages is largely unknown. Here we aimed to investigate the influence of myeloid progenitors on CD34+ cell differentiation into CD56+ innate lymphocytes. Sorted CD34+ cells cultured in the presence of stem cell factor (SCF) and FMS-like tyrosine kinase 3 ligand (FLT3L) give rise to numerous cell types, including progenitors that expressed the prolactin receptor (PRLR). These CD34+PRLR+ myeloid-lineage progenitors were derived from granulocyte monocyte precursors (GMPs) and could develop into granulocytes in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. Moreover, CD34+PRLR+ myeloid progenitors lacked lymphoid developmental potential, but when stimulated with prolactin (PRL) they increased the differentiation of other CD34+ cell populations into the NK lineage in a non-contact dependent manner. Both mRNA and protein analyses show that PRL increased mothers against decapentaplegic homolog 7 (SMAD7) in CD34+PRLR+ myeloid cells, which reduced the production of transforming growth factor beta 1 (TGF-β1), a cytokine known to inhibit CD56+ cell development. Thus, we uncover an axis whereby CD34+PRLR+ GMPs inhibit CD56+ lineage development through TGF-β1 production and PRL stimulation leads to SMAD7 activation, repression of TGF-β1, resulting in CD56+ cell development.

Attenuated allergic inflammatory response in the lungs during lactation

AIMS

To evaluate the influence of lactation on lung immune function during allergic inflammation.

MAIN METHODS

Female rats, 60-90days old, were divided into three groups: no lung allergy virgins (N group), ovalbumin (OVA)-immunized and sensitized virgins (V group), and OVA-immunized and sensitized lactating females (L group). On gestation day (GD) 10, all animals in L group received a subcutaneous injection of 0.1mg·kg(-1) OVA plus aluminum hydroxide. On GD17, the L group received a subcutaneous booster injection of 10μg OVA plus 10mg aluminum hydroxide. After 7days, an inhalatory challenge with 1% OVA was given in 15min sessions for 3 consecutive days. Animals from the V group received the same treatment, meaning both tests and time intervals between OVA treatment and inhalatory challenge were the same as in the L group. Twenty-four hours after the last inhalation session, the animals were euthanized, and the following tests were performed: total and differential bronchoalveolar lavage (BAL) and femoral marrow lavage (FML) leukocyte counts, quantification of tumor necrosis factor α (TNF-α) and interferon γ (IFN-γ) levels in BAL fluid, and quantification of plasma corticosterone and catecholamine levels.

KEY FINDINGS

The L group presented lower BAL total leukocyte counts and decreases in the number of eosinophils and macrophages compared with the V group. They also expressed higher BAL IFN-γ and lower plasma corticosterone levels. Plasma norepinephrine levels were higher in the L group than in the N and V groups.

SIGNIFICANCE

Lactating female rats presented less intense allergic lung inflammation. Our findings suggest that lactation may protect females from asthmatic crises.

Short-term hyperprolactinemia decreases allergic inflammatory response of the lungs

AIMS

Prolactin is a major immunomodulator. The present study evaluated the effects of short-term hyperprolactinemia induced by domperidone before ovalbumin antigenic challenge on the lung's allergic inflammatory response.

MAIN METHODS

To induce hyperprolactinemia, domperidone was injected in rats at a dose of 5.1mg·kg(-1) per day, i.p., for 5days from 10th to 14th day after OVA immunization. Total and differential leukocyte counts from bronchoalveolar lavage (BAL), femoral marrow lavage (FML), and blood were analyzed. The percentages of mucus and collagen production were evaluated. Levels of corticosterone and prolactin in serum, interleukin-4 (IL-4), IL-6, IL-10, tumor necrosis factor α (TNF-α) in lung explants supernatants were measured and interferon gamma (IFN-γ) in bronchiolar lavage cells suspensions (BAL) was measured.

KEY FINDINGS

The rats that were subjected to short-term hyperprolactinemia exhibited a decrease in leukocyte counts in bronchoalveolar lavage, cellularity decrease in femoral marrow lavage fluid, a lower percentage of mucus, and an increase in lung IL-4, IL-6, IL-10, TNF-α and IFN-γ expression.

SIGNIFICANCE

Hyperprolactinemia induced before antigenic challenge decreased allergic lung inflammation. These data suggest that prolactin may play a role in the pathophysiology of asthma. The present study demonstrates a prospective beneficial side effect of domperidone for asthmatic patients.

Panhypopituitarism secondary to a macroprolactinoma manifesting with pancytopenia: case report and literature review

OBJECTIVE

To present a case of pancytopenia associated with hypopituitarism secondary to a macroprolactinoma.

METHODS

We report the clinical features on presentation and results of laboratory investigation. Findings on magnetic resonance imaging are illustrated. The response to hormone replacement therapy is summarized.

RESULTS

A 46-year-old man was referred with pancytopenia and secondary hypothyroidism. Laboratory investigation revealed hypopituitarism and a substantially increased prolactin level. Magnetic resonance imaging of the head demonstrated a macroprolactinoma. Hematologic investigation disclosed no other cause for the pancytopenia. Hormone replacement therapy was initiated with hydrocortisone, levothyroxine, and testosterone. Cabergoline was used to induce regression of the prolactinoma. A rapid improvement was seen in the cytopenias, with normalization of the blood cell counts after 8 months of treatment. This result has been sustained during 29 months of follow-up.

CONCLUSION

Pancytopenia associated with hypopituitarism has been reported in the literature as a rare occurrence limited to isolated case reports, predominantly associated with Sheehan syndrome. To our knowledge, this is the first reported case of pancytopenia associated with a macroprolactinoma. This finding is noteworthy because prolactin alone has been reported to support hematopoiesis in animal studies.

Hematological changes associated with egg production: direct evidence for changes in erythropoiesis but a lack of resource dependence?

Reductions in hematological parameters among laying birds are well reported, but the cause of this anemia is not known. We tested specific predictions generated from several, non-mutually exclusive hypotheses for mechanisms underlying reproductive anemia associated with egg production(hemodilution, transient suppression of erythropoiesis, resource dependence)in relation to (1) the time-course of development and recovery from anemia,(2) changes in specific hematological traits, and (3) the effect of diet quality, in female zebra finches (Taeniopygia guttata). Female zebra finches showed marked decreases in hematocrit (∼6%), red blood cell counts(∼8%), and plasma hemoglobin concentration (∼9%) during egg production, even on a high-quality ad libitum diet, consistent with an effect of hemodilution associated with yolk precursor production. However,our results provide strong support for the hypothesis that erythropoiesis is transiently suppressed during egg-laying and that the recovery from anemia is relatively long-lasting, extending through incubation and hatching periods. Decreased hematocrit, red blood cell counts, and hemoglobin concentration did not recover at clutch completion, but showed evidence of recovery to baseline pre-breeding levels at hatching. More importantly, there was significant time-dependent variation in the proportion of reticulocytes, which increased at clutch completion but peaked at hatching 10–12 days after clutch completion, and in mean red blood cell volume, which showed a significant increase at clutch completion; consistent with enhanced production and release of larger immature cells into the circulation following suppression of erythropoiesis. Finally, we found no evidence for resource dependence of anemia associated with egg production in relation to diet quality, i.e. exogenous lipid and protein resources available to the laying female. This study demonstrates that transient suppression of erythropoiesis and,subsequently, increased reticulocytosis, are key components of reproductive anemia in egg-laying females.

Pregnancy and lactation modulate maternal splenic growth and development of the erythroid lineage in the rat and mouse

Maternal physiology changes dramatically during the course of gestation and lactation to meet the needs of the developing fetus and newborn. In the present study, we examined the influence of pregnancy and lactation on growth and erythroid gene expression patterns of the maternal spleen. Holtzman Sprague-Dawley rats and CD-1 mice were killed at various stages of gestation and post partum. We observed pregnancy dependent increases in spleen weight and spleen DNA content in both the rat and mouse. In the rat, spleen size was greatest at the end of pregnancy and regressed post partum. In contrast, mouse spleen size peaked by gestational Day 13 and regressed to its non-pregnant weight before parturition. Pregnancy dependent changes in the size of the spleen were primarily due to an increase in red pulp. Maternal spleen expression of erythroid-associated genes (erythroid Krüppel-like factor, erythroid 5-aminolevulinate synthase-2, β-major globin) was influenced by pregnancy and lactation. A pregnancy dependent increase in erythroid progenitors was also observed. In summary, the demands of pregnancy and lactation cause marked adaptations in the maternal spleen. The maternal spleen increases in size and exhibits an expansion of the erythroid lineage.

Stress and prolactin effects on bone marrow myeloid cells, serum chemokine and serum glucocorticoid levels in mice

OBJECTIVE

Current evidence supports the conclusion that prolactin (PRL) is not an obligate immunoregulatory hormone and influences the immune system predominantly during stress conditions. In this study, we examined the impact of PRL on the psychogenic stress-induced responses of myeloid cells.

METHODS

Seven-week-old PRL+/- (normal) and PRL-/- (deficient) mice were exposed to a predator for 1 h/day on 3 consecutive days. Another group of PRL-deficient mice received either 1 pituitary graft (hyperprolactinemic) or sham surgery at 5 weeks of age, while PRL-normal mice only received sham surgery. Two weeks later, these mice were also subjected to predator exposure. One day after the last predator exposure session, all mice were killed and the bone marrow and blood harvested.

RESULTS

Significant differences in the myeloid cells between PRL-normal and PRL-deficient mice only occurred in stressed conditions. The median serum corticosterone levels were consistently higher in PRL-deficient mice. The implantation of a pituitary graft lowered the corticosterone levels to those observed in PRL-normal mice. The absolute number of immature neutrophils as well as the numbers of granulocyte macrophage, monocyte/macrophage and granulocyte colonies were significantly higher in the stressed PRL-deficient mice; however, only the increased number of immature neutrophils was reversed by pituitary grafting.

CONCLUSIONS

Our findings support previous observations that PRL influences myeloid cells of the bone marrow most profoundly in stressed conditions. However, the mechanism by which PRL influences bone marrow myeloid cells during stress cannot be explained solely by its effect on serum corticosterone.

Altered Functional Status of the Hypothalamic Dopaminergic Tone in Patients with Chronic Graft-versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation: A Pilot Study

We compared the functional status of the hypothalamic dopaminergic tone in patients given an allogeneic hematopoietic stem cell transplantation (allo-HSCT) with chronic graft-versus-host disease (GVHD) with that observed in patients with allo-HSCT without chronic GVHD and in healthy controls. The effect of acute dopaminergic blockade with intravenous metoclopramide on serum prolactin (PRL) concentrations was evaluated. Twenty volunteers, 20 to 52 years of age, seronegative for both hepatitis C virus and the human immunodeficiency virus, were studied: (1) 10 clinically healthy men (group 1), and (2) 9 patients with leukemia, and 1 patient with refractory aplastic anemia who underwent allo-HSCT, 5 of whom (3 men and 2 women) developed chronic GVHD (group 2), and 5 (3 men and 2 women) who did not develop chronic GVHD (group 3). Serum PRL concentrations were measured both fasting and after intravenous administration of metoclopramide (10-mg bolus). The area under the PRL curve was calculated. Patients in group 2 were older than those in groups 1 and 3 (P<.018), but their body mass index was similar. Fasting serum PRL concentrations were similar among the 3 groups; however, group 2 had higher PRL concentrations throughout the test (P<.001) and a greater area under the PRL curve than groups 1 and 3 (P<.001), without differences between the last 2 groups. The differences remained significant after adjustment for age (P<.01). Our results in a small group of patients with chronic GVHD after allo-HSCT suggest the existence of an increased functional level of their hypothalamic dopamine tone, which would favor a tendency toward a diminished endogenous production, release of pituitary PRL, or both. This could represent an adaptive mechanism aiming to maintain circulating PRL concentrations within a physiological range.

Transgenic prolactin−/− mice: effect of trauma-hemorrhage on splenocyte functions

Prolactin (PRL) is involved in the regulation of immune functions under normal and pathological conditions. Trauma-hemorrhage (T-H) produces profound immunosuppression in male mice but not in proestrus female mice. Administration of PRL in males after T-H, however, restores immune functions. In this study, PRL+/+ and transgenic (PRL−/−) male and female mice were used to assess immune suppression after T-H and to determine the reasons for the hormone's beneficial effect. In vitro lymphoproliferation assay with Nb2 cells showed complete absence of PRL in the circulation of the transgenic PRL−/− mice of both sexes, whereas very high levels of the hormone were detected in the wild-type PRL+/+ mice of both sexes. Moreover, T-H resulted in the appearance of significant levels of the hormone in circulation, but only in PRL+/+ mice. Splenocyte proliferation in male PRL−/− mice was significantly lower than in PRL+/+ mice after T-H. Marginal differences between PRL+/+ and PRL−/− mice were observed in the release of IL-2 and IFN-γ by splenocytes, while the release of IL-10 was significantly higher in PRL−/− than in PRL+/+ mice. A significant observation of our study is the release of a ∼25-kDa protein in the concanavalin A-stimulated splenocytes of male PRL+/+ and PRL−/− mice that was active in the in vitro lymphoproliferation assay with Nb2 cells. It is unlikely that this protein is PRL because it is also present in the splenocyte extracts of PRL−/− transgenic mice. Nonetheless, because control of lymphoid cell proliferation is considered one of the characteristics of the immune system, the local release of this protein may be significant in the differences observed in splenocyte cytokine release after T-H in wild-type as well as transgenic mice.

Synthesis and chromatographic purification of recombinant human pituitary hormones

Recombinant DNA-derived proteins and, in particular, human pituitary hormones, are increasingly used for research, diagnostic and therapeutic purposes. This trend has demanded new synthetic approaches and improved purification techniques. The type and sequence of the purification steps have to be selected in accordance with the cloning and protein expression strategy, the host organism and cellular localization of the protein of interest, with a view to producing the desired product at a required purity, biological activity and acceptable cost. This review article describes and analyzes the main synthetic and purification strategies that have been used for the production of recombinant human growth hormone, prolactin, thyrotropin, luteinizing hormone and follicle-stimulating hormone, giving special consideration to the few published downstream processes utilized by the biotechnology industry. Practically all types of prokaryotic and eukaryotic organisms utilized for this purpose are also reviewed.

Stimulation of interferon regulatory factor-1 by prolactin

Prolactin (PRL), a pituitary peptide hormone, is known to regulate diverse cellular functions including proliferation, differentiation, angiogenesis and protection against apoptosis and inflammation. To understand the mechanism of PRL signaling in T cells, we have cloned both PRL and its receptor (PRL-R), one potent mediator of PRL signaling, Stat5b, and a panel of PRL-inducible immediate early genes from T cells. We are employing these genes as tools with which to understand how PRL regulates the expression of one target gene, the transcription factor interferon regulatory factor-1 (IRF-1), which is a multifunctional immune regulator gene. In investigating regulatory events along the PRL-R/JAK/Stat/IRF-1 signaling pathway, we show that Stat factors can activate as well as inhibit IRF-1 promoter activity and that cross-talk between Stat and NFkappaB signaling pathways also regulates IRF-1 promoter activity. These findings have much broader implications not only for T lymphocytes but also for other PRL responsive target cells and tissues.