Growth hormone and prolactin expression in the immune system

The molecular basis of hypoprolactinaemia

Hypoprolactinaemia is an endocrinopathy which is typically encountered as part of a combined pituitary hormone deficiency picture. The vast majority of genetic causes identified to date have been in the context of congenital hypopituitarism with multiple co-existent endocrinopathies. This is primarily with its closest hormonal relation, namely growth hormone. Acquired hypoprolactinaemia is generally rare in paediatric patients, and usually occurs together with other hormonal deficiencies. Congenital hypopituitarism occurs with an incidence of 1:4,000-10,000 cases and mutations in the following transcription factors account for the majority of documented genetic causes: PROP-1, POU1F1, LHX3/4 as well as documented case reports for a smaller subset of transcription factors and other molecules implicated in lactotroph development and prolactin secretion. Isolated prolactin deficiency has been described in a number of sporadic case reports in the literature, but no cases of mutations in the gene have been described to date. A range of genetic polymorphisms affecting multiple components of the prolactin signalling pathway have been identified in the literature, ranging from RNA spliceosome mutations (RNPC3) to loss of function mutations in IGSF-1. As paediatricians gain a greater understanding of the long-term ramifications of hypoprolactinaemia in terms of metabolic syndrome, type 2 diabetes mellitus and impaired fertility, the expectation is that clinicians will measure prolactin more frequently over time. Ultimately, we will encounter further reports of hypoprolactinaemia-related clinical presentations with further genetic mutations, in turn leading to a greater insight into the molecular basis of hypoprolactinaemia in terms of signalling pathways and downstream mediators. In the interim, the greatest untapped reserve of genetic causes remains within the phenotypic spectrum of congenital hypopituitarism.

Growth hormone proteoformics atlas created to promote predictive, preventive, and personalized approach in overall management of pituitary neuroendocrine tumors

Human growth hormone (GH) is the indispensable hormone for the maintenance of normal physiological functions of the human body, including the growth, development, metabolism, and even immunoregulation. The GH is synthesized, secreted, and stored by somatotroph cells in adenohypophysis. Abnormal GH is associated with various GH-related diseases, such as acromegaly, dwarfism, diabetes, and cancer. Currently, some studies found there are dozens or even hundreds of GH proteoforms in tissue and serum as well as a series of GH-binding protein (GHBP) proteoforms and GH receptor (GHR) proteoforms were also identified. The structure-function relationship of protein hormone proteoforms is significantly important to reveal their overall physiological and pathophysiological mechanisms. We propose the use of proteoformics to study the relationship between every GH proteoform and different physiological/pathophysiological states to clarify the pathogenic mechanism of GH-related disease such as pituitary neuroendocrine tumor and conduct precise molecular classification to promote predictive preventive personalized medicine (PPPM / 3P medicine). This article reviews GH proteoformics in GH-related disease such as pituitary neuroendocrine tumor, which has the potential role to provide novel insight into pathogenic mechanism, discover novel therapeutic targets, identify effective GH proteoform biomarker for patient stratification, predictive diagnosis, and prognostic assessment, improve therapy method, and further accelerate the development of 3P medicine.

Modulation of the somatotropic axis, adiponectin and cytokine secretion during highly pathogenic porcine reproductive and respiratory syndrome virus type 1 (HP-PRRSV-1) infection

Porcine reproductive and respiratory syndrome virus (PRRSV) is known to be clinically responsible for reproductive failure in sows and post-weaning respiratory disease in growing piglets. During the last years, highly pathogenic PRRSV isolates have been discovered. In Italy, a PRRSV-1 subtype 1 strain (namely PR40/2014) characterized by high pathogenicity was isolated and experimental infection was characterized in terms of virological/clinical features and immune modulation (Canelli et al., 2017; Ferrari et al., 2018). The present study was performed in 4-week-old pigs experimentally infected with the highly pathogenic PRRSV1_PR40/2014 (HP-PR40) or with the conventional PRRSV1_PR11/2014 (PR11). The aim was to evaluate the interrelation between plasmatic hormones and cytokines in infected pigs compared to uninfected controls in order to address potential effects on the course of an experimental infection. The time-related changes of growth hormone (GH), insulin-like growth factor-1 (IGF-1), adiponectin, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels appear to be modulated by the infection depending on the PRRSV isolate (HP-PR40 vs. PR11). In particular, in HP-PR40 infected animals, the association between high GH levels and viremia may testify the need to block the anabolic action of GH in order to shift available energy towards the immune response. This need appeared to be delayed in PR11 animals, given the lower pathogenicity of the isolate. Adiponectin, IL-6 and TNF-α course supports the hypothesis of GH resistance mechanisms to guarantee homeostasis in HP-PR40 animals and underlines the key role of energy availability in events leading to an effective response to the virus.

Minireview: Extrapituitary prolactin: an update on the distribution, regulation, and functions

Prolactin (PRL) is an important hormone with many diverse functions. Although it is predominantly produced by lactrotrophs of the pituitary there are a number of other organs, cells, and tissues in which PRL is expressed and secreted. The impact of this extrapituitary PRL (ePRL) on localized metabolism and cellular functions is gaining widespread attention. In 1996, a comprehensive review on ePRL was published. However, since this time, there have been a number of advancements in ePRL research. This includes a greater understanding of the components of the control elements located within the superdistal promoter of the ePRL gene. Furthermore, several new sites of ePRL have been discovered, each under unique control by a range of transcription factors and elements. The functional role of ePRL at each of the expression sites also varies widely leading to gender and site bias. This review aims to provide an update to the research conducted on ePRL since the 1996 review. The focus is on new data concerning the sites of ePRL expression, its regulation, and its function within the organs in which it is expressed.

Serum prolactin levels in psoriasis vulgaris

Background. Psoriasis is a chronic inflammatory skin disease affecting approximately 1–3% of Caucasians. Prolactin has proliferative effects on human keratinocytes, a dominant feature of psoriasis, and it is thought that this hormone may play a role in the pathogenesis of the disease. This study was conducted to confirm or refute these findings in order to better understand the disease pathogenesis. Methods. The subjects were 90 individuals aged between 15 and 47 years. They were divided into three groups of 30 individuals each: psoriatic patients, atopic dermatitis patients, and control group. A questionnaire was filled regarding their demographic and medical history. All of the study subjects underwent venous blood sampling (5 mL), and serum TSH and prolactin levels were checked. Subjects with abnormal TSH were omitted. Results. None of the patients in the study had raised prolactin, and there was no significant difference in the serum prolactin level between patients with psoriasis and atopic dermatitis and the control group. There was no relationship between the severity of psoriasis and serum levels of prolactin. Conclusion. Prolactin does not seem to play a role in the pathogenesis of psoriasis as its serum levels are comparable with atopic dermatitis patients and that of the normal population.

Lymphocyte GH-axis hormones in immunity

The production and utilization 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. The sharing of ligands and receptors allows the immune system to serve as the sixth sense notifying the nervous system of the presence of foreign entities. Within this framework, it is also clear that immune cell functions can be altered by neuroendocrine hormones and that cells of the immune system have the ability to produce neuroendocrine hormones. This review summarizes a part of this knowledge with particular emphasis on growth hormone (GH). The past two decades have uncovered a lot of detail about the actions of GH, acting through its receptor, at the molecular and cellular level and its influence on the immune system. The production and action of immune cell-derived GH is less well developed although its important role in immunity is also slowly emerging. Here we discuss the production of GH, GH-releasing hormone (GHRH) and insulin-like growth factor-1 (IGF-1) and their cognate receptors on cells of the immune system and their influence via endocrine/autocrine/paracrine and intracrine pathways on immune function. The intracellular mechanisms of action of immune cell-derived GH are still largely unexplored, and it is anticipated that further work in this particular area will establish an important role for this source of GH in normal physiology and in pathologic situations.

Peritonitis activates transcription of the human prolactin locus in myeloid cells in a humanized transgenic rat model

Prolactin (PRL) is mainly expressed in the pituitary in rodents, whereas in humans, expression is observed in many extrapituitary sites, including lymphocytes. Due to the lack of adequate experimental models, the function of locally produced PRL in the immune system is largely unknown. Using transgenic rats that express luciferase under the control of extensive human PRL regulatory regions, we characterized immune cell responses to thioglycollate (TG)-induced peritonitis. Resident populations of myeloid cells in the peritoneal cavity of untreated rats expressed barely detectable levels of luciferase. In contrast, during TG-induced peritonitis, cell-specific expression in both neutrophils and monocytes/macrophages in peritoneal exudates increased dramatically. Elevated luciferase expression was also detectable in peripheral blood and bone marrow CD11b(+) cells. Ex vivo stimulation of primary myeloid cells showed activation of the human extrapituitary promoter by TNF-α, lipopolysaccharide, or TG. These findings were confirmed in human peripheral blood monocytes, showing that the transgenic rat provided a faithful model for the human gene. Thus, the resolution of an inflammatory response is associated with dramatic activation of the PRL gene promoter in the myeloid lineage.

High molecular weight isoforms of growth hormone in cells of the immune system

A substantial body of research exists to support the idea that cells of the immune system produce growth hormone (GH). However, the structure and mechanism of action of lymphocyte-derived GH continues to remain largely unknown. Here we present the results of Western analysis of whole cell extracts showing that different molecular weight isoforms of GH of approximately 100, 65, and 48 kDa can be detected in primary mouse cells of the immune system and in the mouse EL4 cell line. The identity of the 65 and 48 kDa isoforms of GH were confirmed by mass spectrometry. The various isoforms were detected in both enriched T and B spleen cell populations. The large molecular weight isoform appears to reside primarily in the cytoplasm, whereas the lower molecular weight 65 and 48 kDa isoforms were detected primarily in the nucleus. These results also suggest that GH isoforms are induced by oxidative stress. In EL4 cells overexpressing GH, the expression of luciferase controlled by a promoter containing the antioxidant response element is increased almost threefold above control. The data suggest that the induction of isoforms of the GH molecule in cells of the immune system may be an important mechanism of adaptation and/or protection of lymphoid cells under conditions of oxidative stress.

Extrapituitary growth hormone

Pituitary somatotrophs secrete growth hormone (GH) into the bloodstream, to act as a hormone at receptor sites in most, if not all, tissues. These endocrine actions of circulating GH are abolished after pituitary ablation or hypophysectomy, indicating its pituitary source. GH gene expression is, however, not confined to the pituitary gland, as it occurs in neural, immune, reproductive, alimentary, and respiratory tissues and in the integumentary, muscular, skeletal, and cardiovascular systems, in which GH may act locally rather than as an endocrine. These actions are likely to be involved in the proliferation and differentiation of cells and tissues prior to the ontogeny of the pituitary gland. They are also likely to complement the endocrine actions of GH and are likely to maintain them after pituitary senescence and the somatopause. Autocrine or paracrine actions of GH are, however, sometimes mediated through different signaling mechanisms to those mediating its endocrine actions and these may promote oncogenesis. Extrapituitary GH may thus be of physiological and pathophysiological significance.

Growth hormone and fish immune system

This paper reviews the immunomodulatory effects, extra-pituitary expression and paracrine action of growth hormone (GH), and a possible role of GH/insulin-like growth factor-I (IGF-I) axis in the immune system of teleost fish. In some euryhaline fish, the activation of immune functions observed during seawater acclimation appears to be associated with the osmoregulatory action of GH. Administration of GH enhances many aspects of immune functions including non-specific defences; cytotoxic, phagocytic, haemolytic and lysozyme activities. GH also activates immunoglobulin production as a specific defense and increases ceruloplasmin levels as an acute-phase protein. The GH gene is also expressed in many extra-pituitary tissues of fish, especially in lymphoid organs and cells. Several endocrine factors appear to act on immune function through modification of GH secretion from fish leucocytes. Exposure of phagocytic leucocytes of tilapia to IGF-I in vitro stimulated proliferation and superoxide production associated with phagocytosis. Exposure to GH had no significant effect on IGF-I secretion from tilapia leucocytes, despite of the fact that they secreted significant amounts of IGF-I. GH and IGF-I appear to act in a paracrine manner in the regulation of the teleostean immune system. Further studies are necessary to characterize the interactions of GH with other endocrine and paracrine factors.

Prolactin and Growth Hormone Responses to Hypoglycemia in Patients with Systemic Sclerosis and Psoriatic Arthritis

This study compared prolactin (PRL) and growth hormone (GH) responses to hypoglycemia in premenopausal females with systemic sclerosis (SSc) and psoriatic arthritis (PsA) with those in matched healthy controls. No differences were found in glucose and GH responses to hypoglycemia in both groups of patients compared to controls. SSc patients had lower PRL response (P < 0.05) to hypoglycemia compared to controls. PRL response tended to be lower also in PsA patients, however the difference did not reach level of statistical significance (P = 0.11). The present study showed decreased PRL response to hypoglycemia in premenopausal females with SSc.

Sex differences in immune responses and immune reactivity to stress in adolescents

The immune system is the body's major defense mechanism against disease. However, psychosocial factors, such as stress, can modulate various immune responses. Although they have been examined in adult humans and other animals, sex differences in immune responses and immune reactivity to stress have rarely been examined in adolescents, particularly comparing healthy and asthmatic adolescents. In 151 healthy and asthmatic high school adolescents (91 females and 60 males), natural killer cell (NK) cytotoxicity, polymorphonuclear leukocyte (PMN) superoxide release, lymphocyte proliferative responses, and CD subsets were measured twice: once during mid-semester and again during final examinations. There was little difference in these measures between healthy and asthmatic adolescents. Similarly, only sex difference was noted in NK cytotoxicity at a 25:1 effector-to-target cell ratio, with males showing significantly higher responses than females. For PMN superoxide release, females significantly increased their responses during final examinations, whereas males demonstrated no changes. For lymphocyte proliferative responses, both females and males increased their responses during final examinations, but the magnitude of increase was much greater in males. Furthermore, racial comparisons indicated that African American adolescents (n = 16), as compared with Caucasian adolescents (n = 128), had significantly higher responses in PMN superoxide release to N-Formyl-Met-Leu-Phe (FMLP) activation during mid-semester and lymphocyte proliferative responses at both time points. Nevertheless, the overall findings indicate limited differences in immune responses and immune reactivity to stress in adolescents between males and females, healthy and asthmatic adolescents, and Caucasians and African Americans. However, further investigations with larger samples are warranted.

Immunologic and hematopoietic effects of recombinant human prolactin after syngeneic bone marrow transplantation in mice

The period of immune deficiency following bone marrow transplantation (BMT) results in a susceptibility to opportunistic infections and remains a growing obstacle in improving the efficacy of BMT. Neuroendocrine hormones have been shown to affect numerous immunologic and hematologic responses after in vivo administration. We investigated whether neuroendocrine hormones, notably prolactin (PRL), could be administered after BMT and result in improved immunologic recovery. Mice were given lethal total body irradiation followed with a congeneic or a syngeneic BMT. Some groups then received recombinant human PRL (rhPRL) daily for 3 weeks. Effects on immune reconstitution and function were then monitored. The results show that PRL could increase thymic cellularity and donor T-cell reconstitution after congeneic BMT. Increases in B cells and myeloid progenitors were also observed. Mitogenic responses by both T and B cells were observed after PRL treatment. These results suggest that PRL may be of use to promote immune and myeloid reconstitution after BMT.

Prostate hyperplasia in a transgenic mouse with prostate-specific expression of prolactin

Prolactin (PRL) is one of several polypeptide factors known to exert trophic effects on the prostate. We have previously reported a dramatic prostate enlargement with concurrent chronic hyperprolactinemia and elevated serum androgen levels in a PRL transgenic mouse (Mt-PRL) with ubiquitous expression of the transgene. To address the role of local PRL action in the prostate, a new transgenic mouse model (Pb-PRL) was generated using the prostate-specific rat probasin (Pb) minimal promoter to drive expression of the rat PRL gene. Pb-PRL transgenic males developed a significant enlargement of both the dorsolateral and ventral prostate lobes evident from 10 wk of age and increasing with age. Expression of the transgene was restricted to the prostate and detected from 4 wk of age. Low levels of transgenic rat PRL were detectable in the serum of adult Pb-PRL animals. Serum androgen levels were normal. The Pb-PRL prostate displayed significant stromal hyperplasia, ductal dilation, and focal areas of epithelial dysplasia. Quantitative analysis of prostatic tissue cellularity demonstrated a marked increase in the stromal to epithelial ratio in all lobes of Mt-PRL and Pb-PRL transgenic prostates compared with controls. Microdissections demonstrated an increased ductal morphogenesis in dorsolateral and ventral prostate lobes of Mt-PRL prostate vs. Pb-PRL and controls. In conclusion, this study indicates the ability of PRL to promote, directly or indirectly, ductal morphogenesis in the developing prostate and further to induce abnormal growth primarily of the stroma in the adult gland in a setting of normal androgen levels.

Interaction between endocrine and immune systems in fish

Diseases in fish are serious problems for the development of aquaculture. The outbreak of fish disease is largely dependent on environmental and endogenous factors resulting in opportunistic infection. Recent studies, particularly on stress response, have revealed that bidirectional communication between the endocrine and immune systems via hormones and cytokines exists at the level of teleost fish. Recently information on such messengers and receptors has accumulated in fish research particularly at the molecular level. Furthermore, it has become apparent in fish that cells of the immune system produce or express hormones and their receptors and vice versa to exchange information between the two systems. This review summarizes and updates the knowledge on endocrine-immune interactions in fish with special emphasis on the roles of such mediators or receptors for their interactions.

Regulation of prolactin expression in leukemic cell lines and peripheral blood mononuclear cells

To address the role of different intracellular signals in prolactin (PRL) expression in leukocytes, we have investigated the effects of chlorophenylthio-cAMP (cptcAMP), phorbol myristate acetate (PMA) and ionomycin on the activation of the upstream PRL promoter in several leukemic cell lines. All three stimulators, alone or in synergism with each other, were able to modulate promoter activity, but their actions were cell-type dependent. In freshly isolated peripheral blood mononuclear cells (PBMC), PRL expression could only be stimulated by cptcAMP. The physiological importance of cAMP in the regulation of PRL expression in leukocytes is suggested by the finding that in PBMC, PRL expression is enhanced by prostaglandin-E(2) and the beta(2)-adrenergic agonist terbutaline, which both signal through cAMP.

Prolactin: the new biology of an old hormone

Prolactin (PRL) is a paradoxical hormone. Historically known as the pituitary hormone of lactation, it has had attributed to it more than 300 separate actions, which can be correlated to the quasi-ubiquitous distribution of its receptor. Meanwhile, PRL-related knockout models have mainly highlighted its irreplaceable role in functions of lactation and reproduction, which suggests that most of its other reported target tissues are presumably modulated by, rather than strictly dependent on, PRL. The multiplicity of PRL actions in animals is in direct opposition to the paucity of arguments that suggest its involvement in human pathophysiology other than effects on reproduction. Although many experimental data argue for a role of PRL in the progression of some tumors, such as breast and prostate cancers, drugs lowering circulating PRL levels are ineffective. This observation opens new avenues for research into the understanding of whether local production of PRL is involved in tumor growth and, if so, how extrapituitary PRL synthesis is regulated. Finally, the physiological relevance of PRL variants, such as the antiangiogenic 16K-like PRL fragments, needs to be elucidated. This review is aimed at critically discussing how these recent findings have renewed the manner in which PRL should be considered as a multifunctional hormone.