Bone Marrow Stroma-Derived Prolactin Is Involved in Basal and Platelet-Activating Factor–Stimulated In Vitro Erythropoiesis

Abstract

Cooperation between in vitro exogenous prolactin (PRL), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-3 (IL-3) at an early step of in vitro erythroid differentiation has been shown in a previous study. To gain more insight into the role of PRL in in vivo hematopoiesis, we have now addressed the involvement of endogenous PRL in the growth of hematopoietic progenitors in a bone marrow (BM) stroma environment. The possible modulation of local PRL production by the inflammatory mediator platelet-activating factor (PAF), which is known to be produced by BM cells and to regulate pituitary PRL release, has also been evaluated. Development of burst-forming unit-erythroid (BFU-E) colonies from CD34+ hematopoietic progenitors cultured on a BM stroma cells (BMSC) layer was slightly, but significantly, reduced in the presence of an antihuman PRL antibody. Pretreatment of BMSC with PAF increased the BFU-E colony efficiency of cocultured CD34+ cells, and this effect was completely abrogated by the antiserum. PAF-modulated release of PRL by BMSC was confirmed by an enzyme-linked-immunospot (Elispot) technique. In addition, immunoprecipitation and Western blotting experiments showed two immunoreactive products in the BMSC culture medium. These corresponded to the nonglycosylated (23 kD) and glycosylated (25.5 kD) forms of pituitary PRL that are also expressed by the B-lymphoblastoid cell line IM9-P3. Specific increase of the nonglycosylated form and decrease of the glycosylated form was observed after PAF treatment. Polymerase chain reaction (PCR) amplification of reverse transcribed RNA using PRL-specific primers showed the presence of PRL message in BMSC and IM9-P3 cells. In situ hybridization experiments with a rat PRL cDNA probe cross-reacting with human PRL mRNA confirmed its presence in a small fraction of unstimulated BMSC and in the majority of PAF-stimulated BMSC. The enhancing effect of PAF on PRL-mediated colony formation, PRL release, and mRNA activation was counteracted by pretreating BMSC with the PAF-receptor (R) antagonist WEB 2170. Lastly, responsiveness of BMSC to PAF was substantiated by the presence of the PAF-R mRNA on these cells.

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

“…Prolactin (PRL) has been implicated as a regulator of haematopoiesis Lowenstein 1964, 1965;Bellone et al 1997;Abkowitz et al 2002;Akiyama et al 2005). Early studies demonstrated that PRL stimulates erythropoiesis in nonpregnant, pregnant and lactating mice Lowenstein 1964, 1965).…”

“…Early studies demonstrated that PRL stimulates erythropoiesis in nonpregnant, pregnant and lactating mice Lowenstein 1964, 1965). In addition, in vivo and in vitro studies have shown that PRL can increase the number of erythroid progenitors in haematopoietic tissue (Bellone et al 1997;Woody et al 1999;Richards and Murphy 2000;Welniak et al 2001). In the rat and mouse, mating activates twice-daily PRL surges for the first half of pregnancy; in addition, suckling during lactation is a wellestablished stimulus for PRL secretion (Erskine 1995;Soares 2004;Andrews 2005).…”

Individual and combined effect of granulocyte–macrophage colony‐stimulating factor and prolactin on maturation of dendritic cells from blood monocytes under serum‐free conditions

“…PRL has been shown to either interact with lymphohaemopoietic cytokines or mimic their action. Its co-operation with IL-2 in development of lymphokine-activated killer (LAK) cells 19±21 and with GM-CSF in maturation of CD34 + stem cells to erythropoietin (EPO)-responsive erythroid progenitors 16,17 has been documented by our group. Here we show that physiological concentrations of PRL (10±20 ng/ml) co-operate with GM-CSF in inducing monocytes to differentiate into DC, as judged by their morphological changes, expression of antigen-presenting and costimulatory molecules MHC II, CD80 and CD86, and ability to present alloantigens to CD4 T lymphocytes.…”

“…They thus become active T-cell stimulators. Because PRL has been shown by our group to interact with GM-CSF, 16,17 we have here addressed its possible involvement, alone or in combination with GM-CSF, in the process of DC maturation and antigen presentation.…”

Acute myeloid leukaemia presenting as galactorrhoea

“…Both at presentation and in remission the majority of prolactin immuno-reactive cells in the marrow were interstitial mononuclear cells. Lymphoid cells produce prolactin (Montgomery, 2001), and stromal cells have a basal level of prolactin synthesis, which can be increased in response to cytokines (Bellone et al, 1997). It is possible that prolactin secretion might be upregulated as a result of interaction between the AML blasts and other bone marrow cells.…”