The prolactin gene is expressed in the mouse kidney

A cautionary tale: Alien prolactins may induce lesser, no, or opposite effects to homologous hormone!

Cost and availability have often dictated the use of heterologous/alien prolactins in experiments, particularly in vivo. The assumption has been that what is initiated in the target cell is representative of the homologous hormone since many heterologous mammalian prolactins bind to and activate rodent receptors. Here, we examined gene expression in mouse liver in response to a 7-day treatment with recombinant mouse prolactin (mRecPRL), recombinant ovine prolactin (oRecPRL) and pituitary extract ovine prolactin (oPitPRL). Having established mouse ribosomal protein S9 as the most stable reference gene in the liver in the absence and presence of prolactin treatment, we examined expression of the two most highly expressed prolactin receptors (PRLRs) and three members of the Cyp3a group of cytochrome P450 isoenzymes by qRTPCR. For short form (SF) 3 PRLR, mRecPRL doubled expression while for oRecPRL and oPitPRL expression was only 1.3-fold control. For the long form (LF) PRLR, changes were similar to those seen for SF 3 PRLR, such that the SF3:LF PRLR ratio remained the same. Expression of the Cyp3as was also dependent on the prolactin origin and, although mRecPRL always stimulated, the other PRLs caused varying results. Compared to control, Cyp3a16 was stimulated 12-fold by mRecPRL, 3-fold by oRecPRL, and 6-fold by oPitPRL. For Cyp3a41, mRecPRL was 3.7-fold control, oRecPRL was without effect, and oPitPRL was 2-fold control. Importantly, for Cyp3a44, mRecPRL stimulated 2-fold, whereas both oRecPRL and oPitPRL had an opposite, inhibitory effect, with expression at 0.5-fold control. We conclude that homologous hormone had the largest stimulatory effect on expression of all measured genes and that by contrast heterologous hormone showed reduced activity, no activity, or opposite activity, depending on the gene being analyzed. Thus, experimentation using alien heterologous PRL may lead to inaccurate conclusions.

Significance of Duodenal Prolactin Receptor Modulation by Calcium and Vitamin D in Sulpiride-Induced Hyperprolactinemia

Background and Objectives: Hyperprolactinemia, as a potential side-effect of some antipsychotic medications, is associated with decreased bone density and an increased risk of fractures. This study investigates whether calcium and vitamin D supplementation affects prolactin receptor (Prlr) gene expression in the duodenum, vertebrae, and kidneys of female rats with sulpiride-induced hyperprolactinemia. Materials and Methods: Twenty-one-week-old female Wistar rats were assigned to three groups: Group S consisted of ten rats who received sulpiride injections (10 mg/kg) twice daily for 6 weeks; Group D (10 rats) received daily supplementation of 50 mg calcium and 500 IU vitamin D along with sulpiride for the last 3 weeks; and Group C consisting of seven age-matched nulliparous rats serving as a control group. Real-time PCR was used to assess Prlr gene expression in the duodenum, vertebrae, and kidneys. Results: In Group S, Prlr gene expression was notably decreased in the duodenum (p < 0.01) but elevated in the vertebrae and kidneys compared to Group C. Conversely, Group D exhibited significantly increased Prlr expression in the duodenum (p < 0.01) alongside elevated expression in the vertebrae and kidneys. Conclusions: In sulpiride-induced hyperprolactinemia, decreased Prlr gene expression in the duodenum may lead to reduced intestinal calcium absorption. Consequently, prolactin may draw calcium from the skeletal system to maintain calcium balance, facilitated by increased Prlr gene expression in the vertebrae. However, vitamin D supplementation in sulpiride-induced hyperprolactinemia notably enhances Prlr gene expression in the duodenum, potentially ameliorating intestinal calcium absorption and mitigating adverse effects on bone health.

Neuroimmunoendocrine Link Between Chronic Kidney Disease and Olfactory Deficits

Chronic kidney disease (CKD) is a multifactorial pathology that progressively leads to the deterioration of metabolic functions and results from deficient glomerular filtration and electrolyte imbalance. Its economic impact on public health is challenging. Mexico has a high prevalence of CKD that is strongly associated with some of the most common metabolic disorders like diabetes and hypertension. The gradual loss of kidney functions provokes an inflammatory state and endocrine alterations affecting several systems. High serum levels of prolactin have been associated with CKD progression, inflammation, and olfactory function. Also, the nutritional status is altered due to impaired renal function. The decrease in calorie and protein intake is often accompanied by malnutrition, which can be severe at advanced stages of the disease. Nutrition and olfactory functioning are closely interconnected, and CKD patients often complain of olfactory deficits, which ultimately can lead to deficient food intake. CKD patients present a wide range of deficits in olfaction like odor discrimination, identification, and detection threshold. The chronic inflammatory status in CKD damages the olfactory epithelium leading to deficiencies in the chemical detection of odor molecules. Additionally, the decline in cognitive functioning impairs the capacity of odor differentiation. It is not clear whether peritoneal dialysis and hemodialysis improve the olfactory deficits, but renal transplants have a strong positive effect. In the present review, we discuss whether the olfactory deficiencies caused by CKD are the result of the induced inflammatory state, the hyperprolactinemia, or a combination of both.

Sex Differences in Renal Function: Participation of Gonadal Hormones and Prolactin

Kidney pathophysiology is influenced by gender. Evidence suggests that kidney damage is more severe in males than in females and that sexual hormones contribute to this. Elevated prolactin concentration is common in renal impairment patients and is associated with an unfavorable prognosis. However, PRL is involved in the osmoregulatory process and promotes endothelial proliferation, dilatation, and permeability in blood vessels. Several proteinases cleavage its structure, forming vasoinhibins. These fragments have antagonistic PRL effects on endothelium and might be associated with renal endothelial dysfunction, but its role in the kidneys has not been enough investigated. Therefore, the purpose of this review is to describe the influence of sexual dimorphism and gonadal hormones on kidney damage, emphasizing the role of the hormone prolactin and its cleavage products, the vasoinhibins.

Therapeutic Potential of Selenium as a Component of Preservation Solutions for Kidney Transplantation

Selenium has strong antioxidant properties and diverse effects on the immune system. The aim of the study was to analyse the protective effect of selenium as a component of a kidney preservation solution on the prevention of ischemia-reperfusion injury of nephrons. The solution was modified by the addition of Se (1 µg/L), prolactin (0.1 µg/L) and Se with prolactin (1 µg/L Se + 0.1 µg/L PRL). The study used a model for storing isolated porcine kidneys in Biolasol^® (modified Biolasol^®), which minimizes ischemia-reperfusion injury of grafts. The introduction of Se⁴⁺ ions at a dose of 1 µg/L into the Biolasol^® preservation solution in the form of Na₂SeO₃ caused an increase in the activity/concentration of the analysed biochemical parameters: aspartate transaminase, alanine transaminase, urea and protein. This suggests an adverse effect of Se⁴⁺ on nephron function during ischemia-reperfusion. The best graft protection was obtained by using Biolasol^® modified with the addition of selenium (IV) at a dose of 1 µg/L and prolactin at a concentration of 0.1 µg/L. We proposed the mechanism of prolactin action in the metabolic reduction of selenite (SO₃²⁻) during ischemia/reperfusion.

Expression of prolactin receptors in the duodenum, kidneys and skeletal system during physiological and sulpiride-induced hyperprolactinaemia

INTRODUCTION AND AIM

Hyperprolactinaemia in pregnancy leads to mild and reversible changes in the maternal skeletal system, and medicamentous hyperprolactinemia causes more detrimental effects. We conducted an experimental study to evaluate differences between Prlr gene expression in the duodenum, vertebrae and kidneys during physiological and medicamentous hyperprolactinaemia, which could influence calcium homeostasis.

METHODS

Experimental animals (18 weeks old, Wistar female rats) were divided as follows: group P (nine rats that were 3 weeks pregnant), group M (ten rats that were intramuscularly administrated sulpiride (10 mg/kg) twice daily for 3 weeks), and the control group (C, ten age-matched nulliparous rats, 18-week-old). Laboratory investigations included measurements of serum ionized calcium, phosphorus, urinary calcium and phosphorus excretion, osteocalcin (OC), serum procollagen type 1 N-terminal propeptide (P1NP), vitamin D, parathyroid hormone (PTH) and prolactin (PRL). Relative quantification of gene expression for prolactin receptors in the duodenum, vertebrae and kidneys was determined using real-time PCR.

RESULTS

Expression of the Prlr gene was significantly higher in the duodenum (p < 0.001) and lower in vertebrae (p < 0.001) and kidneys (p < 0.01) in rats with physiological hyperprolactinaemia (PHP) than in the control group. Significantly lower Prlr expression in the duodenum was verified (p < 0.001), along with increased Prlr gene expression in vertebrae (p < 0.001) and kidneys (p < 0.01), in rats with medicamentous hyperprolactinaemia (MHP) than in the C group.

CONCLUSIONS

Downregulation of Prlr gene expression in the duodenum may explain the diminished intestinal calcium absorption in medicamentous hyperprolactinaemia. Prolactin takes calcium from the skeletal system following increased Prlr gene expression in the vertebrae to maintain calcium homeostasis, which increases the harmful effect on bone metabolism compared to that of physiological hyperprolactinaemia.

Autocrine/paracrine roles of extrapituitary growth hormone and prolactin in health and disease: An overview

Growth hormone (GH) and prolactin (PRL) are both endocrines that are synthesized and released from the pituitary gland into systemic circulation. Both are therefore hormones and both have numerous physiological roles mediated through a myriad of target sites and both have pathophysiological consequences when present in excess or deficiency. GH or PRL gene expression is not, however, confined to the anterior pituitary gland and it occurs widely in many of their central and peripheral sites of action. This may reflect "leaky gene" phenomena and the fact that all cells have the potential to express every gene that is present in their genome. However, the presence of GH or PRL receptors in these extrapituitary sites of GH and PRL production suggests that they are autocrine or paracrine sites of GH and PRL action. These local actions often occur prior to the ontogeny of pituitary somatotrophs and lactotrophs and they may complement or differ from the roles of their pituitary counterparts. Many of these local actions are also of physiological significance, since they are impaired by a blockade of local GH or PRL production or by an antagonism of local GH or PRL action. These local actions may also be of pathophysiological significance, since autocrine or paracrine actions of GH and PRL are thought to be causally involved in a number of disease states, particularly in cancer. Autocrine GH for instance, is thought to be more oncogenic than pituitary GH and selective targeting of the autocrine moiety may provide a therapeutic approach to prevent tumor progression. In summary, GH and PRL are not just endocrine hormones, as they have autocrine and/or paracrine roles in health and disease.

Prolactine receptor expression in kidney tissue of female rats with cholestasis: the effect of hyperprolactinemia

Immunohistochemistry with semiquantitative image analysis showed that prolactin receptor in distal renal tubules of female rats is most sensitive to the negative effects of both cholestasis and hyperprolactinemia. The responses of medullary tubules to cholestasis and hyperprolactinemia were less pronounced: decrease and increase in prolactin receptor expression, respectively. Proximal tubules were characterized by stable levels of prolactin receptor expression insensitive to the effects of obstructive cholestasis and hyperprolactinemia. The cholestasis-induced changes in the intensity of prolactin receptor expression were opposite in kidney and liver cells. It is concluded that different parts of the nephron differ by the presence, type, and direction of regulation of prolactin receptor expression in obstructive cholestasis and hyperprolactinemia.

Regulation of epithelial calcium transport by prolactin: from fish to mammals

Among the reported ∼300 biological actions, the established role of prolactin (PRL) is to act as a vertebrate hypercalcemic hormone that regulates epithelial calcium transport in several organs, such as the gills, intestine, and kidney. In fish, PRL stimulates the branchial calcium transport by increasing the activity of Ca(2+)-ATPase. Although this calciotropic hormone also induces hypercalcemia in amphibians, reptiles and birds, little has been known regarding the underlying mechanism. In contrast, the effects of PRL on the epithelial calcium transport in mammals are well documented. In rodents, PRL has been shown to stimulate the renal tubular calcium reabsorption and intestinal calcium absorption, the latter of which is mediated by the PRL-induced upregulation of calcium transporter gene expression and activities. Recently, we demonstrated that the duodenal calcium absorption in lactating rats was markedly enhanced by the suckling-induced PRL surge, presumably to provide calcium for milk production. The cellular and molecular mechanisms of the PRL-stimulated calcium transport in mammals have been elaborated in this review.

Is prolactin the cardinal calciotropic maternal hormone?

To produce offspring, mothers require a large amount of calcium for fetal growth and milk production. Increased calcium demand leads to enhanced intestinal calcium absorption and stockpiling of bone calcium in pregnancy prior to demineralization in lactation. These coordinated events must be carefully organized by calciotropic hormone(s), but the classical hormones, namely 1,25-dihydroxyvitamin D(3), parathyroid hormone and calcitonin, do not appear to be responsible. Plasma prolactin (PRL) levels are elevated during pregnancy and, in view of the presence of PRL receptors in gut, bone and mammary glands, as well as recent evidence of the stimulatory effects of PRL on intestinal calcium transport, bone resorption and mammary calcium secretion, we postulate that PRL is the cardinal calciotropic hormone during pregnancy and lactation.

Characterization of a novel and functional human prolactin receptor isoform (deltaS1PRLr) containing only one extracellular fibronectin-like domain

Prolactin (PRL)-dependent signaling occurs as the result of ligand-induced homodimerization of the PRL receptor (PRLr). To date, short, intermediate, and long human PRLr isoforms have been characterized. To investigate the expression of other possible human PRLr isoforms, RT-PCR was performed on mRNA isolated from the breast carcinoma cell line T47D. A 1.5-kb PCR fragment was isolated, subcloned, and sequenced. The PCR product exhibited a nucleotide sequence 100% homologous to the human long isoform except bp 71-373 were deleted, which code for the S1 motif of the extracellular domain. Therefore, this isoform was designated the deltaS1 PRLr. Northern analysis revealed variable deltaS1 PRLr mRNA expression in a variety of tissues. Transfection of Chinese hamster ovary cells with deltaS1 cDNA showed the isoform is expressed at the protein level on the cell surface with a molecular mass of approximately 70 kDa. Kinetic studies indicated the deltaS1 isoform bound ligand at a lower affinity than wild-type receptor. The deltaS1 PRLr was also shown to activate the proximal signaling molecule Jak2 upon addition of ligand to transfected cells, and, unlike the long PRLr, high concentrations of ligand did not function as a self-antagonist to signaling during intervals of PRL serum elevation, i.e. stress and pregnancy. Given its apparent widespread expression, this PRLr isoform may contribute to PRL action. Furthermore, the functionality of this receptor raises interesting questions regarding the minimal extracellular domain necessary for ligand-induced receptor signaling.

Pituitary and extrapituitary growth hormone: Pit-1 dependence?

Growth hormone (GH) is primarily produced in pituitary somatotrophs. The synthesis of this hormone is thought to be dependent upon a pituitary-specific transcription factor (Pit-1). However, many extrapituitary tissues are now known to express GH genes. The extrapituitary production of GH may therefore indicate an extrapituitary distribution of the Pit-1 gene. The extrapituitary production of GH may, alternatively, indicate that GH expression occurs independently of Pit-1 in extrapituitary tissues. These possibilities are considered in this brief review.Key words: growth hormone, pituitary, pituitary transcription factor 1.

Functional characterization of the intermediate isoform of the human prolactin receptor

Prolactin-dependent signaling occurs as the result of ligand-induced dimerization of the prolactin receptor (PRLr). While three PRLr isoforms have been characterized in the rat, studies have suggested the existence of several human isoforms in breast carcinoma species and normal tissues. Reverse transcription polymerase chain reaction was performed on mRNA isolated from the breast carcinoma cell line T47D, revealing two predominant receptor isoforms: the previously described long PRLr and a novel human intermediate PRLr. The nucleotide sequence of the intermediate isoform was found to be identical to the long isoform except for a 573-base pair deletion occurring at a consensus splice site, resulting in a frameshift and truncated intracytoplasmic domain. Scatchard analysis of the intermediate PRLr revealed an affinity for PRL comparable with the long PRLr. While Ba/F3 transfectants expressing the long PRLr proliferated in response to PRL, intermediate PRLr transfectants exhibited modest incorporation of [(3)H]thymidine. Significantly, however, both the long and intermediate PRLr were equivalent in their inhibition of apoptosis of the Ba/F3 transfectants after PRL treatment. The activation of proximal signaling molecules also differed between isoforms. Upon ligand binding, Jak2 and Fyn were activated in CHO-K1 cells transiently transfected with the long PRLr. In contrast, the intermediate PRLr transfectants showed equivalent levels of Jak2 activation but only minimal activation of Fyn. Last, Northern analysis revealed variable tissue expression of intermediate PRLr transcript that differed from that of the long PRLr. Taken together, differences in signaling and tissue expression suggest that the human intermediate PRLr differs from the long PRLr in physiological function.