Abstract
BackgroundProlactin from pituitary gland helps maintain homeostasis but it is also released in immune cells where its function is not completely understood. Pleiotropic functions of prolactin (PRL) might be mediated by different isoforms of its receptor (PRLr).MethodsThe aim of this study was to investigate the relationship between the eventual synthesis of PRL and PRLr isoforms with the inflammatory response in monocytes. We used THP-1 and monocytes isolated from healthy subjects stimulated with lipopolysaccharide (LPS). Western blot, real time PCR and immunocytochemistry were performed to identify both molecules. The bioactivity of the PRL was assessed using a bioassay and ELISA to detect pro inflammatory cytokines.ResultsPRLr mRNA and PRL mRNA were synthesized in THP-1 monocytes activated with LPS with peaks of 300-fold and 130-fold, respectively. The long (100 kDa) and the intermediate (50 kDa) isoforms of PRLr and big PRL (60 kDa) were time-dependent upregulated for monocytes stimulated with LPS. This expression was confirmed in monocytes from healthy subjects. The PRLr intermediate isoform and the big PRL were found soluble in the culture media and later in the nucleus in THP-1 monocytes stimulated with LPS. Big PRL released by monocytes showed bioactivity in Nb2 Cells, and both PRL and PRLr, synthesized by monocytes were related with levels of nitrites and proinflammatory citokines.ConclusionsOur results suggest the expression of a full-autocrine loop of PRL enhances the inflammatory response in activated monocytes. This response mediated by big PRL may contribute to the eradication of potential pathogens during innate immune response in monocytes but may also contribute to inflammatory disorders.
Highlights
Prolactin from pituitary gland helps maintain homeostasis but it is released in immune cells where its function is not completely understood
Nitrates released indicated that THP-1 monocytes stimulated with 1 μg of LPS of S. enterica showed significant difference in comparison with lower and higher doses (p
Cytometry analyses of THP-1 cells stimulated showed significant differences in size versus granularity when LPS of E. coli was used in comparison with LPS of S. entrerica (Additional file 1: Figure S1E)
Summary
Prolactin from pituitary gland helps maintain homeostasis but it is released in immune cells where its function is not completely understood. Pleiotropic functions of prolactin (PRL) might be mediated by different isoforms of its receptor (PRLr). PRL is a hormone produced primarily by the anterior pituitary gland and acts on different cell types [1]. PRLr shares structures and signal transduction pathways with the type 1 cytokines and their receptors. In fibroblast treated with proinflammatory cytokines, the expression of the long isoform of the PRLr (of 100 kDa) has been associated with the phosphorylation of signal transducer and activator of transcription 5B (STAT5B), and with the inhibition of the interferon regulatory factor 1 (IRF-1) and inducible nitric oxide synthase (iNOS) expression [15]. The role of PRL during inflammation has been investigated in Mφ and fibroblast, the results might be considered controversial due to masked effects of other molecules released by differentiated inflammatory cells into the culture medium
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