Prolactin receptor expression in lymphocytes from patients with hyperprolactinemia or acromegaly

Hormones and B-cell development in health and autoimmunity

The development of B cells into antibody-secreting plasma cells is central to the adaptive immune system as they induce protective and specific antibody responses against invading pathogens. Various studies have shown that, during this process, hormones can play important roles in the lymphopoiesis, activation, proliferation, and differentiation of B cells, and depending on the signal given by the receptor of each hormone, they can have a positive or negative effect. In autoimmune diseases, hormonal deregulation has been reported to be related to the survival, activation and/or differentiation of autoreactive clones of B cells, thus promoting the development of autoimmunity. Clinical manifestations of autoimmune diseases have been associated with estrogens, prolactin (PRL), and growth hormone (GH) levels. However, androgens, such as testosterone and progesterone (P4), could have a protective effect. The objective of this review is to highlight the links between different hormones and the immune response mediated by B cells in the etiopathogenesis of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS). The data collected provide insights into the role of hormones in the cellular, molecular and/or epigenetic mechanisms that modulate the B-cell response in health and disease.

Minireview: prolactin regulation of adult stem cells

Adult stem/progenitor cells are found in many tissues, where their primary role is to maintain homeostasis. Recent studies have evaluated the regulation of adult stem/progenitor cells by prolactin in various target tissues or cell types, including the mammary gland, the prostate, the brain, the bone marrow, the hair follicle, and colon cancer cells. Depending on the tissue, prolactin can either maintain stem cell quiescence or, in contrast, promote stem/progenitor cell expansion and push their progeny towards differentiation. In many instances, whether these effects are direct or involve paracrine regulators remains debated. This minireview aims to overview the current knowledge in the field.

Transcriptional Profiling of Liver and Effect of Glucocorticoids in a Rat Adjuvant-Induced Arthritis Model

Glucocorticoids (GCs), despite having many undesirable side effects, remain effective for the treatment of many inflammatory diseases and are commonly used as benchmark drugs in animal models of disease. However, the molecular mechanisms underling systemic GC effects in these models are poorly characterized. In this study, prednisolone and dexamethasone were evaluated in the fully established Lewis rat adjuvant-induced arthritis (AIA) model. In AIA, adjuvant administration induced polyarticular and systemic inflammation, which included spleen and liver. In the liver, multifocal hepatic granulomas were observed. To characterize the systemic response and the pathways responsible for GC effects, histology, transcriptional profiling, and immunohistochemistry (IHC) were performed. There was a decrease in the incidence and histologic severity score for granulomas with GC treatment. There was no effect on cellular composition of granulomas as assessed by IHC for CD3+ lymphocytes, macrophages, and B cells, but there was a significant reduction in infiltrating lymphocytes in the hepatic parenchyma. By Affymetrix microarray analysis, 10% of hepatic transcripts were altered ( P < .01) in livers from AIA rats, with ~31% of them partially reversed with treatment with dexamethasone and ~13% with prednisolone. Many of these altered hepatic transcripts correspond to human genes that are dysregulated in the synovium in human rheumatoid arthritis (RA), indicating that the rat AIA model shares features with human RA. These data establish molecular changes in the liver and the effect of GCs in rat AIA, which can be used to aid in understanding the mechanism of action of novel anti-inflammatory compounds in this animal model.

Vasopressin in vasodilatory and septic shock

PURPOSE OF REVIEW

The aim of this article is to review mechanisms of action of vasopressin and clinical studies of vasopressin in septic shock.

RECENT FINDINGS

Arginine vasopressin is an important stress hormone that has both vasoactive and antidiuretic properties. The vasoactive properties of vasopressin have been more applicable clinically because of the discovery by Landry and colleagues that there is a deficiency of vasopressin in septic shock and that infusion of relatively low doses of vasopressin improves responsiveness to infused catecholamines (such as norepinephrine). There are at least 16 clinical studies of infusion of vasopressin in patients who have septic shock. The majority of studies found that vasopressin infusion increased blood pressure and urine output, and decreased the dose requirement of norepinephrine. Several studies showed that vasopressin infusion increased urine output. Both vasopressin and norepinephrine have important adverse effects including decreased cardiac output, decreased heart rate, arrhythmias, myocardial ischemia, mesenteric ischemia, and digital ischemia.

SUMMARY

It is still unclear whether there is net benefit from low dose vasopressin infusion in patients who have septic shock. There may be certain patients who benefit but there are few studies of a prolonged vasopressin infusion to determine which patients benefit.

Antitumor effects of recombinant human prolactin in human adenocarcinoma-bearing SCID mice with human NK cell xenograft

To survey the immune regulatory function of recombinant human prolactin (rhPRL) and its potential application in adoptive immunotherapy, CB17-SCID mice were loaded with human colon adenocarcinoma HT-29 cells (5 x 10(5) cells/mouse, i.p.) 24 h before adoptive transfer with the purified human NK cells followed by rhPRL injection (10 mug/mouse, every other day for a total of 10 injections). Upon analysis, rhPRL did not exert any direct inhibitory effects on HT-29 cells but slightly improved the tumor cell growth both in vitro and in vivo. After SCID mice were reconstituted with human NK cells, rhPRL improved the antitumor effects of human NK cells in HT-29-bearing SCID mice, showing a prolonged survival from 70.4 to 112.1 days, and the increased survival rate from all died to 40% survival for more than 160 days. rhPRL improved the proliferation of human NK cells with or without PHA stimulation. rhPRL also directly enhanced the cytotoxicity of human NK cells against HT-29 tumor cells in 4-h coculture. The supernatant of rhPRL-stimulating NK cells inhibited the proliferation of HT-29 cells through, at least partly, the interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in the supernatant. Thus, rhPRL administration in HT-29 tumor-bearing SCID mice promotes the antitumor effects of adoptively transferred NK cells.

Effects of prolactin level on burn-induced aberrations in myelopoiesis

In this study, we sought to determine if prolactin (PRL) had any influence on burn-induced alterations in myelopoiesis and serum IL-6, IL-10, IL-12, IFN-gamma, TNF-alpha, and MCP-1 levels. To do this, we used mice that were PRL normal, PRL deficient, or hyperprolactinemic and had received a 15% total body surface area burn, sham treatment, or no treatment. We performed clonogenic assays of bone marrow cells, and we found that sham treatment significantly decreased monocyte/macrophage (M) colony formation relative to the control group in the PRL-deficient and PRL-normal mice (P < 0.01). Hyperprolactinemia attenuated the sham-induced decrease in M colony formation. Burn injury significantly increased M colony formation relative to the sham group with an equal significance in the PRL-deficient and PRL-normal mice (P < 0.05). We also showed that burn led to a significant increase in GM colony formation relative to the sham group. This burn-induced increase was significant in the PRL-normal (P < 0.05) and the PRL-deficient (P < 0.01) mice. In the PRL-normal mice, burn injury caused a 2.1-fold increase in the GM colony number, whereas in the PRL-deficient mice burn led to a 2.6-fold increase in GM colony number. When comparing the effects of burn injury on colony formation to the control groups, there were no significant differences seen, irrespective of the PRL level. We observed that all of the cytokines studied, with the exception of IL-10, were influenced by either sham treatment, burn injury, or both forms of stress. This stress-induced response occurred most often in animals that were either hypo- or hyperprolactinemic. We conclude that the PRL level was able to influence the sham-induced and burn-induced alterations in GM and M colony formation. Under euprolactinemic conditions, mice exhibited less often with stress-induced serum cytokine level alterations. We did not find any significant correlations with any of the serum cytokine levels and the ability to form colonies. Importantly, the sham treatment led to immune alterations independent of, and sometimes opposite of burn-induced effects.

Exercise increases prolactin-receptor expression on human lymphocytes

Plasma prolactin has been shown to increase during stress; the immune system is responsive to prolactin and affected by stress. Therefore, this study was undertaken to investigate the effects of acute graded, maximal treadmill exercise on prolactin-receptor expression by lymphocytes. Eight healthy men underwent one exercise and one nonexercise session. Blood was sampled immediately before and after the exercise. On the day of the nonexercise session, two resting blood samples were obtained at the same times as the exercise session samples to act as baseline data. Plasma prolactin concentrations were significantly elevated in response to exercise and correlated positively with total prolactin-receptor expression per B lymphocyte. An increase in total prolactin-receptor expression per B lymphocyte in response to exercise also was observed. In addition, exercise significantly increased the total number of circulating B lymphocytes expressing prolactin receptor as well as the total number of circulating B lymphocytes. These data support the idea that exercise may enhance the interaction between immune target cells and prolactin, a stress hormone capable of enhancing immune function.

Prolactin induces calcium influx and release from intracellular pools in human T lymphocytes by activation of tyrosine kinases

The early events related to intracellular signals after prolactin (PRL) activation in T lymphocytes are not clearly established. The aim of this work was to study the effect of PRL in cytosolic calcium levels in human T lymphocytes. By using the dye FURA-2 AM, the variations in cytosolic Ca(2+) were studied in peripheral human T lymphocytes isolated from extracted blood from healthy donors. Fifty nanograms per milliliter PRL induces a small increase in cytosolic calcium. When the cells are preincubated overnight (16-20 h) in the presence of PRL, the increase in calcium is higher. This high increase is due to the release from intracellular pools and to the influx from the extracellular media. That is, after overnight incubation with PRL, calcium influx in T cells follows the capacitative model. Since PRL receptor (PRL-R) activation involves the tyrosine kinase pathway, we check calcium effect in the presence of genistein, a known inhibitor of tyrosine kinases. When cells are preincubated in the presence of 10 microM genistein, and PRL is immediately added, no increase in cytosolic calcium is observed. The presence of genistein also completely blocks the increase in cytosolic calcium stimulated by PRL after overnight incubation with PRL. In the presence of PRL and N,N-dimethyl-D-erythro-sphingosine (DMS), a stimulus that increases cytosolic calcium in T cells by tyrosine kinase stimulation, a high, even insignificant, calcium influx is induced. However, when the cells are incubated overnight in the presence of PRL, and then DMS is added, a significant increase in cytosolic calcium levels takes place. This increase is associated with an increase in calcium release from intracellular pools and an increase in calcium uptake. Genistein reduces the influx of external calcium induced by DMS after short incubation with PRL and significantly inhibits both, calcium pools empty, and calcium influx is induced by DMS after overnight incubation with PRL. In summary, PRL induces calcium influx in normal T lymphocytes. The influx is magnified after long PRL exposures, intracellular Ca(2+) pool-dependent, and activated through tyrosine kinases.

The uncoupled couple? Prolactin and CD4 lymphocytes in HIV infection

The possible role of prolactin (PRL) in human immunodeficiency virus (HIV) infection is unknown, despite the modulatory role of this hormone in humoral and cell-mediated immune responses. Recent studies have evidenced: (a) intralymphocyte synthesis of dopamine (DA) which down-regulates their own proliferation and differentiation; (b) decreased DA but increased PRL concentrations in cerebrospinal fluid of HIV-infected men; and (c) diminished hypothalamic DA tone in HIV-infected men. The present hypothesis proposes that, in HIV-infected men, a diminished generalized DA tone exists to stimulate human lymphocyte proliferation and differentiation at a maximum possible rate by: (1) decreasing the inhibitory influence of intralymphocyte DA; and (2) maintaining pituitary and extrapituitary (i.e. lymphocyte) PRL synthesis and release as high as possible. If this hypothesis is correct, it may have a potentially important therapeutic implication: the possibility to rebuild the battered immune system in HIV-infected patients from inside the body in a physiologic manner by the parenteral administration of recombinant human PRL.

Growth hormone (GH) and prolactin receptors in human peripheral blood mononuclear cells: relation with age and GH-binding protein

GH receptors (GHRs) and PRL receptors (PRLRs) were studied in human peripheral blood mononuclear cells (PBMC) using flow cytometry, biotinylated anti-GH receptor monoclonal antibody 10B8, and biotinylated human PRL. Variations of GHR and PRLR expression and the relationship of plasma GHBP and GH receptor in PBMC subsets were examined as a function of age and sex. By double immunofluorescence staining, we show that about 30% of total cells express GH receptors, with a low expression in T cells, whereas almost all B cells and monocytes are GH receptor positive. Four age groups were defined among the 64 normal volunteers, aged 12 to 85 yr, who were included in the study. The percentage of PBMC expressing GH receptors is significantly lower in group 2 (20-40 yr) than in group 1 (12-20 yr) and group 4 (>60 yr). In T cells, monocytes and B cells, no significant changes are detected in either the percentage of GH receptor positive cells or in the GH receptor level per cell. The level of PRLRs expressed in PBMC is significantly higher in age group 2 than in age group 4. A negative correlation is observed between plasma GHBP and the percentage of PBMC expressing GH receptors. These results suggest that regulation of GH receptors in lymphocytes and in other target cells could be different.

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 receptor messenger ribonucleic acid in normal and neoplastic human pituitary tissues

We examined the specific cell types in normal human pituitaries that expressed PRL receptor (PRL-R) messenger ribonucleic acid (mRNA) by combined in situ hybridization and immunohistochemistry. The distribution of PRL-R mRNA in 28 pituitary adenomas was examined by in situ hybridization and reverse transcription-PCR in 12 cases of adenomas. In another set of experiments, 34 PRL adenomas from men, women, and bromocriptine-treated patients were analyzed for PRL-R by in situ hybridization. In the normal pituitary, PRL- and LH-producing cells had significantly more mean grain counts per cell and higher percentages of cells positive for PRL-R than GH and TSH cells. PRL-R mRNA was present in all groups of adenomas by in situ hybridization and reverse transcription-PCR. PRL adenomas had a significantly higher density of labeling compared to other adenoma types. Although there was no difference in the levels of PRL-R mRNA in PRL adenomas from men and premenopausal and postmenopausal women, patients treated with bromocriptine before pituitary surgery had significantly lower levels of PRL-R compared to all other groups. These results indicate that in the normal pituitary, PRL and LH cells have the highest level of PRL-R mRNA, whereas PRL adenomas have significantly higher levels of PRL-R mRNA than other types of adenomas, and bromocriptine treatment decreases the levels of PRL-R mRNA in PRL adenomas.