Administration Of Prolactin Research Articles

Synergistic neuroprotective action of prolactin and 17β-estradiol on kainic acid-induced hippocampal injury and long-term memory deficit in ovariectomized rats.

The neuroprotective actions of the ovarian hormone 17β-estradiol (E2) against different brain lesions have been constantly confirmed in a variety of models including kainic acid (KA) lesions. Similarly, the pituitary hormone prolactin (PRL), traditionally associated with lactogenesis, has recently been linked to a large diversity of functions, including neurogenesis, neuroprotection, and cognitive processes. While the mechanisms of actions of E2 as regards its neuroprotective and behavioral effects have been extensively explored, the molecular mechanisms of PRL related to these roles remain under investigation. The current study aimed to investigate whether the simultaneous administration of PRL and a low dose of E2 prevents the KA-induced cognitive deficit and if this action is associated with changes in hippocampal neuronal density. Ovariectomized (OVX) rats were treated with saline, PRL, and/or E2 in the presence or absence of KA. Neuroprotection was assessed by Nissl staining and neuron counting. Memory was evaluated with the novel object recognition test (NOR). On their own, both PRL and E2 prevented short- and long-term memory deficits in lesioned animals and exerted neuroprotection against KA-induced excitotoxicity in the hippocampus. Interestingly, the combined hormonal treatment was superior to either of the treatments administered alone as regards improving both memory and neuronal survival. Taken together, these results point to a synergic effect of E2 and PRL in the hippocampus to produce their behavioral, proliferative, and neuroprotective effects.

Prolactin promotes the recruitment of main olfactory bulb cells and enhances the behavioral exploration toward a socio-sexual stimulus in female mice

Olfactory communication is triggered by pheromones that profoundly influence neuroendocrine responses to drive social interactions. Two principal olfactory systems process pheromones: the main and the vomeronasal or accessory system. Prolactin receptors are expressed in both systems suggesting a participation in the processing of olfactory information. We previously reported that prolactin participates in the sexual and olfactory bulb maturation of females. Therefore, we explored the expression of prolactin receptors within the olfactory bulb during sexual maturation and the direct responses of prolactin upon pheromonal exposure. Additionally, we assessed the behavioral response of adult females exposed to male sawdust after prolactin administration and the consequent activation of main and accessory olfactory bulb and their first central relays, the piriform cortex and the medial amygdala. Last, we investigated the intracellular pathway activated by prolactin within the olfactory bulb. Here, prolactin receptor expression remained constant during all maturation stages within the main olfactory bulb but decreased in adulthood in the accessory olfactory bulb. Behaviorally, females that received prolactin actively explored the male stimulus. An increased cFos activation in the amygdala and in the glomerular cells of the whole olfactory bulb was observed, but an augmented response in the mitral cells was only found within the main olfactory bulb after prolactin administration and the exposure to male stimulus. Interestingly, the ERK pathway was upregulated in the main olfactory bulb after exposure to a male stimulus. Overall, our results suggest that, in female mice, prolactin participates in the processing of chemosignals and behavioral responses by activating the main olfactory system and diminishing the classical vomeronasal response to pheromones.

Prolactin Mediates Long-Term, Seasonal Rheostatic Regulation of Body Mass in Female Mammals.

A series of well-described anabolic and catabolic neuropeptides are known to provide short-term, homeostatic control of energy balance. The mechanisms that govern long-term, rheostatic control of regulated changes in energy balance are less well characterized. Using the robust and repeatable seasonal changes in body mass observed in Siberian hamsters, this report examined the role of prolactin in providing long-term rheostatic control of body mass and photoinduced changes in organ mass (ie, kidney, brown adipose tissue, uterine, and spleen). Endogenous circannual interval timing was observed after 4 months in a short photoperiod, indicated by a significant increase in body mass and prolactin mRNA expression in the pituitary gland. There was an inverse relationship between body mass and the expression of somatostatin (Sst) and cocaine- and amphetamine-regulated transcript (Cart). Pharmacological inhibition of prolactin release (via bromocriptine injection), reduced body mass of animals maintained in long photoperiods to winter-short photoperiod levels and was associated with a significant increase in hypothalamic Cart expression. Administration of ovine prolactin significantly increased body mass 24 hours after a single injection and the effect persisted after 3 consecutive daily injections. The data indicate that prolactin has pleiotropic effects on homeostatic sensors of energy balance (ie, Cart) and physiological effectors (ie, kidney, BAT). We propose that prolactin release from the pituitary gland acts as an output signal of the hypothalamic rheostat controller to regulate adaptive changes in body mass.

Effectiveness of post particular prolactin administration on follicle development the count in mice (Mouse muscle) female

This study aims to test the effectiveness of postpartum prolactin administration on follicle development in the count in mice (Mouse muscle). This type of research is a true experiment using a completely randomized design (RAL). The sample for this study was mice (Mouse muscle) female strain BALB/C, aged ± 4 months with a body weight between 25-30 gr in a healthy condition and not pregnant. The data obtained was analyzed using the One-way analysis of variance (F test) with a significance level of 0.05, followed by the Least Significant Difference test (BNT. The research results show that the sig. (p) = 0.001< α = 0.05, so it can be concluded that postpartum administration of prolactin has a significant effect on follicular development of the count in mice (Mouse muscle).

Mast Cell Dynamics in the Ovary Are Governed by GnRH and Prolactin.

Gonadotrophin releasing hormone (GnRH) facilitates the migration of mast cells (MCs) into the involuting mammary gland. As GnRH is also expressed in the ovary, we examined changes in ovarian MCs. MCs in the ovary were mainly in interstitial tissue and their number increased during the estrous cycle to produce 2 peaks, one at diestrus 2 (20:00 hours) and another at proestrus (17:00 hours). Laser microdissection demonstrated that GnRH mRNA is expressed throughout ovarian tissues (corpora lutea, follicles, and interstitial tissues). GnRH immunoreactivity was also ubiquitous, but MCs were the most strongly immunostained. Analysis of GnRH mRNA in the ovary showed it to fluctuate similarly to the variation in MC number during the estrous cycle, and MCs also expressed GnRH. Local administration of a GnRH agonist (GnRHa) into the hemilateral ovarian bursa increased MCs in the administered ovary. MC number and GnRH mRNA were significantly lowered in the pregnant ovary. Prolactin administration suppressed the normal peaks in MC number in the ovary at both diestrus and proestrus. By contrast, a dopamine agonist, administered when prolactin was elevated during pseudopregnancy, increased ovarian MC number. Furthermore, prolactin inhibited GnRHa-induced peritoneal MC migration in a Transwell assay. These data clearly demonstrate that ovarian MC number is regulated positively by local GnRH expression and negatively by prolactin. The suppressive effect of prolactin on GnRH and MCs would be part of its luteotrophic action.

Prolactin reduces the kainic acid-induced increase in intracellular Ca2+ concentration, leading to neuroprotection of hippocampal neurons

The aim of this study was to determine the effect of prolactin (PRL) on intracellular calcium (Ca2+) concentration and its neuroprotective role in a model of kainic acid (KA) excitotoxicity in primary cultures of hippocampal neurons. Cell viability and intracellular Ca2+ concentrations were determined by MTT and Fura-2 assays, respectively, either after induction by KA as an agonist or after treatment with NBQX antagonist alone or in combination with PRL administration. Expression of ionotropic glutamatergic receptors (iGluRs) subunits in neuronal cells was determined by RT-qPCR. Dose-response treatments with KA or glutamate (Glu), the latter used as endogenous agonist control, induced a significant increase in neuronal intracellular Ca2+ concentration followed by a significant decrease in hippocampal neuronal viability. Administration of PRL induced a significant increase in neuronal viability after treatment with KA. Furthermore, administration of PRL decreased intracellular Ca2+ concentrations induced by KA treatment. Independent administration of the AMPAR-KAR antagonist reversed cell death and reduced intracellular Ca2+ concentration in a similar manner as PRL. Additionally, mRNA expression of AMPAR, KAR and NMDAR subtypes were detected in hippocampal neurons; however, no significant changes in iGluRs subunit expression were observed due to excitotoxicity or PRL treatment. The results suggest that PRL inhibits the increase in intracellular Ca2+ concentration induced by KA, leading to neuroprotection.

Prolactin Action Is Necessary for Parental Behavior in Male Mice.

Parental care is critical for successful reproduction in mammals. Recent work has implicated the hormone prolactin in regulating male parental behavior, similar to its established role in females. Male laboratory mice show a mating-induced suppression of infanticide (normally observed in virgins) and onset of paternal behavior 2 weeks after mating. Using this model, we sought to investigate how prolactin acts in the forebrain to regulate paternal behavior. First, using c-fos immunoreactivity in prolactin receptor (Prlr) Prlr-IRES-Cre-tdtomato reporter mouse sires, we show that the circuitry activated during paternal interactions contains prolactin-responsive neurons in multiple sites, including the medial preoptic nucleus, bed nucleus of the stria terminalis, and medial amygdala. Next, we deleted Prlr from three prominent cell types found in these regions: glutamatergic, GABAergic, and CaMKIIα. Prlr deletion from CaMKIIα, but not glutamatergic or GABAergic cells, had a profound effect on paternal behavior as none of these KO males completed the pup-retrieval task. Prolactin was increased during mating, but not in response to pups, suggesting that the mating-induced secretion of prolactin is important for establishing the switch from infanticidal to paternal behavior. Pharmacological blockade of prolactin secretion at mating, however, had no effect on paternal behavior. In contrast, suppressing prolactin secretion at the time of pup exposure resulted in failure to retrieve pups, with exogenous prolactin administration rescuing this behavior. Together, our data show that paternal behavior in sires is dependent on basal levels of circulating prolactin acting at the time of interaction with pups, mediated through Prlr on CaMKIIα-expressing neurons.SIGNIFICANCE STATEMENT Parental care is critical for offspring survival. Compared with maternal care, however, the neurobiology of paternal care is less well understood. Here we show that the hormone prolactin, which is most well known for its female-specific role in lactation, has a role in the male brain to promote paternal behavior. In the absence of prolactin signaling specifically during interactions with pups, father mice fail to show normal retrieval behavior of pups. These data demonstrate that prolactin has a similar action in both males and females to promote parental care.

Expression of Opsin Genes in the Retina of Female and Male Three-Spined Sticklebacks Gasterosteus aculeatus L.: Effect of Freshwater Adaptation and Prolactin Administration.

Color vision sensitivity is crucial for fish adaptation during migration and reproduction. Prolactin and prolactin-like hormone are important regulators in both these processes. We hypothesized that prolactin influences the color vision sensitivity during freshwater migrations in fish. We studied the effects of prolactin and freshwater adaptation during the spawning period on the expression of opsin genes (SWS1, SWS2, RH2, LWS) in the retina of female and male three-spined sticklebacks Gasterosteus aculeatus L. Expression of the prolactin gene increased in the brain of females, but not males, while expression of the prolactin-like hormone decreased in the brain of both male and female sticklebacks during freshwater adaptation. Expression of the SWS2 gene decreased in the retina of females and males during freshwater adaptation and after prolactin administration. Expression of the SWS1 gene decreased in the retina of male sticklebacks after prolactin administration, but not during freshwater adaptation. Expression of the RH2 and LWS genes did not depend on prolactin administration in male and female sticklebacks. We conclude that expression of some opsin genes in the retina of sticklebacks is regulated by prolactin and depends on sex and freshwater adaptation. This expands our knowledge of the adaptive effects of prolactin on fish during freshwater migrations.

Prolactin signaling modulates stress-induced behavioral responses in a preclinical mouse model of migraine.

The aim of this study was to determine if prolactin signaling modulates stress-induced behavioral responses in a preclinical migraine model. Migraine is one of the most complex and prevalent disorders. The involvement of sex-selective hormones in migraine pathology is highly likely as migraine is more common in women and its frequency correlates with reproductive stages. Prolactin has been shown to be a worsening factor for migraine. Normally prolactin levels are low; however levels can surge during stress. Dopamine receptor agonists, which suppress pituitary prolactin release, are an effective migraine treatment in a subset of patients. Previously, we showed that administration of prolactin onto the dura mater induces female-specific behavioral responses, suggesting that prolactin may play a sex-specific role in migraine. The effects of prolactin signaling were assessed using a preclinical migraine model we published recently in which behavioral sensitization is induced by repeated stress. Plasma prolactin levels were assessed in naïve and stressed CD-1 mice (n=3-5/group) and transgenic mice with conditional deletion of the Prlr in Nav1.8-positive sensory neurons (Prlr conditional knock-out [CKO]; n=3/group). To assess the contribution of prolactin release during stress, naïve or stressed male and female CD-1 mice were treated with the prolactin release inhibitor bromocriptine (2mg/kg; n=7-12/group) or vehicle for 5days (8-12/group) and tested for facial hypersensitivity following stress. Additionally, the contribution of ovarian hormones in regulating the prolactin-induced responses was assessed in ovariectomized female CD-1 mice (n=6-10/group). Furthermore, the contribution of Prlr activation on Nav1.8-positive sensory neurons was assessed. Naïve or stressed male and female Prlr CKO mice and their control littermates were tested for facial hypersensitivity (n=8-9/group). Immunohistochemistry was used to confirm loss of Prlr in Nav1.8-positive neurons in Prlr CKO mice. The total sample size is n=245; the full analysis sample size is n=221. Stress significantly increased prolactin levels in vehicle-treated female mice (39.70±2.77; p<0.0001). Bromocriptine significantly reduced serum prolactin levels in stressed female mice compared to vehicle-treated mice (-44.85±3.1; p<0.0001). Additionally, no difference was detected between female stressed mice that received bromocriptine compared to naïve mice treated with bromocriptine (-0.70±2.9; p=0.995). Stress also significantly increased serum prolactin levels in male mice, although to a much smaller extent than in females (0.61±0.08; p<0.001). Bromocriptine significantly reduced serum prolactin levels in stressed males compared to those treated with vehicle (-0.49±0.08; p=0.002). Furthermore, bromocriptine attenuated stress-induced behavioral responses in female mice compared to those treated with vehicle (maximum effect observed on day 4 post stress [0.21±0.08; p=0.03]). Bromocriptine did not attenuate stress-induced behavior in males at any timepoint compared to those treated with vehicle. Moreover, loss of ovarian hormones did not affect the ability of bromocriptine to attenuate stress responses compared to vehicle-treated ovariectomy mice that were stressed (maximum effect observed on day 4 post stress [0.29±0.078; p=0.013]). Similar to CD-1 mice, stress increased serum prolactin levels in both Prlr CKO female mice (27.74±9.96; p=0.047) and control littermates (28.68±9.9; p=0.041) compared to their naïve counterparts. There was no significant increase in serum prolactin levels detected in male Prlr CKO mice or control littermates. Finally, conditional deletion of Prlr from Nav1.8-positive sensory neurons led to a female-specific attenuation of stress-induced behavioral responses (maximum effect observed on day 7 post stress [0.32±0.08; p=0.007]) compared to control littermates. These data demonstrate that prolactin plays a female-specific role in stress-induced behavioral responses in this preclinical migraine model through activation of Prlr on sensory neurons. They also support a role for prolactin in migraine mechanisms in females and suggest that modulation of prolactin signaling may be an effective therapeutic strategy in some cases.

Prolactin promotes a partial recovery from the atrophy of both male and female gerbil prostates caused by castration

BackgroundThe male and female prostates are controlled by steroid hormones, suffering important morphological and physiological changes after castration. Prolactin is involved in the regulation of the male prostate, having already been identified in the tissue, acting through its receptor PRLR. In the Mongolian gerbil, in addition to the male prostate, the female prostate is also well developed and active in its secretion processes. The aim of the present study was to evaluate the effects of exposure to exogenous prolactin in the prostate of both intact and castrated male and female gerbils in order to establish if prolactin administration can sustain prostate cell activity in conditions of sexual hormone deprivation.MethodsThe morphological analyses were performed by biometric analysis, lesion histological analysis and morphometric-stereological aspects. In addition, immune-cytochemical tests were performed for prolactin and its receptor, as well as for the receptors of androgen and oestrogen and serum prolactin dosage. All data were submitted to ANOVA or Kruskal-Wallis tests for comparison between groups. P < 0.05 was considered to be statistically significant.ResultsThe results showed a strong influence of prolactin on the morphology of the prostate, with the development of important epithelial alterations, after only 3 days of administration, and an expressive epithelial cell discard process after 30 days of administration. Prolactin acts in synergy with testosterone in males and mainly with oestrogens in females, establishing different steroid hormonal receptor immunoreactivity according to sex. It was also demonstrated that prolactin can assist in the recovery from some atrophic effects caused in the gland after castration, without causing additional tissue damage.ConclusionsThe prolactin and its receptor are involved in the maintenance of the homeostasis of male and female gerbils, and also cause distinct histological alterations after exogenous exposure for 3 and 30 days. The effects of prolactin are related to its joint action on androgens and oestrogens and it can also assist in the recovery from the atrophic effects of castration.

Prolactin induced cyto-architectural changes in the corpuscles of Stannius of stinging catfish, Heteropneustes fossilis acclimated to different calcium media

Adult fish Heteropneustes fossilis were divided into 4 groups –(i) Group A: kept in artificial freshwater and daily injected intraperitoneally with vehicle; (ii) Group B: kept in artificial freshwater and were daily injected intraperitoneally with 0.1 mg/100 g body wt of oProlactin; (iii) Group C: maintained in calcium-deficient freshwater and daily injected intraperitoneally with vehicle; (iv) Group D: kept in calcium-deficient freshwater and daily injected intraperitoneally with 0.1 mg/100 g body wt of oProlactin. Blood samples were taken 2 h after the last injection on 1, 3, 5, 10 and 15 days of the treatment. Plasma calcium levels were analyzed. The corpuscles of Stannius (CS) were fixed for histological studies. Artificial freshwater: The plasma calcium levels of vehicle-injected specimens (group A) remained unaltered throughout the experiment. Following prolactin treatment (group B) the plasma calcium levels progressively increased from day 3 to day 5. The values became normocalcemic at day 10 and day 15. After day 5 following prolactin administration (group B), the nuclear volume of AF-positive cells increased and the cells were seen degranulated. After day 10, there was an increased dilatation of sinusoids and the nuclear volume of AF-positive cells showed further increase. On day 15, these changes were exaggerated. The AFnegative cells of the corpuscles of Stannius of prolactin-treated fish (group B) showed no change in their histological structure and nuclear volume. Calcium-deficient freshwater: The plasma calcium level decreased in vehicle-injected fish (group C) from day 1 to day 3 (as compared to level of the fish kept in artificial freshwater). Thereafter, the level increased from day 5 resulting in hypercalcemia at day 10 and day 15. In prolactin treated fish (group D) the plasma calcium level indicated progressive increase from day 5 to day 15. In the vehicle-injected fish (group C) the AF-positive cells of corpuscles of Stannius showed accumulati

Sexually dimorphic effects of prolactin treatment on the onset of puberty and olfactory function in mice

The onset of puberty is associated with the psychophysiological maturation of the adolescent to an adult capable of reproduction when olfactory signals play an important role. This period begins with the secretion of the gonadotropin-releasing hormone (GnRH) from GnRH neurons within the hypothalamus. This is regulated by kisspeptin neurons that express high levels of transmembrane prolactin receptors (PRLR) that bind to and are activated by prolactin (PRL). The elevated levels of serum PRL found during lactation, or caused by chronic PRL infusion, decreases the secretion of gonadotropins and kisspeptin and compromised the estrous cyclicity and the ovulation. In the present work, we aimed to evaluate the effects of either increased or decreased PRL circulating levels within the peripubertal murine brain by administration of PRL or treatment with cabergoline (Cab) respectively. We showed that either treatment delayed the onset of puberty in females, but not in males. This was associated with the augmentation of the PRL receptor (Prlr) mRNA expression in the arcuate nucleus and decreased Kiss1 expression in the anteroventral periventricular zone. Then, during adulthood, we assessed the activation of the mitral and granular cells of the main (MOB) and accessory olfactory bulb (AOB) by cFos immunoreactivity (ir) after the exposure to soiled bedding of the opposite sex. In the MOB, the PRL treatment promoted an increased cFos-ir of the mitral cells of males and females. In the granular cells of male of either treatment an augmented activation was observed. In the AOB, an impaired cFos-ir was observed in PRL and Cab treated females after exposure to male soiled bedding. However, in males, only Cab impaired its activation. No effects were observed in the AOB-mitral cells. In conclusion, our results demonstrate that PRL contributes to pubertal development and maturation of the MOB-AOB during the murine juvenile period in a sex-dependent way.

Impaired prolactin transport into the brain and functional responses to prolactin in aged male mice.

Ageing is related to changes in a number of endocrine systems that impact on the central actions of hormones. The anterior pituitary hormone prolactin is present in the circulation in both males and females, with widespread expression of the prolactin receptor throughout the forebrain. We aimed to investigate prolactin transport into the brain, as well as circulating levels of prolactin and functional responses to prolactin, in aged male mice (23months). Transport of 125 I-labelled prolactin (125 I-prolactin) from the peripheral circulation into the brain was suppressed in aged compared to young adult (4months) male mice, with no significant transport into the brain occurring in aged males. We subsequently investigated changes in the negative-feedback regulation of prolactin secretion and prolactin-induced suppression of luteinising hormone (LH) pulsatile secretion in aged male mice. Feedback regulation of prolactin secretion appeared to be unaffected in aged males, with no change in levels of circulating prolactin, and normal prolactin-induced phosphorylated signal transducer and activator of transcription 5(pSTAT5) immunoreactivity in tuberoinfundibular dopaminergic (TIDA) neurones in the arcuate nucleus. There were, however, significant impairments in the ability of prolactin to suppress LH pulsatile secretion in aged males. In young adult males, acute prolactin administration significantly decreased LH pulses from 1.5±0.19 pulses of LH in 4hours to 0.5±0.27 pulses. In contrast, prolactin did not suppress LH pulse frequency in aged males, with prolactin leading to an increase in mean LH concentration. These data demonstrate the emergence of impairments in prolactin transport into the brain and deficits in specific functional responses to prolactin with ageing.

Abstract P1-12-02: Growth hormone and prolactin influences mammary epithelial and stromal interactions in early parity induced protection against breast cancer

Abstract Introduction: Early pregnancy has been shown to decrease the life-time risk of mammary cancer. Further, systemic alterations in circulating levels of growth hormone (GH) and prolactin (PRL) have been associated with the decreased risk. GH and PRL have been shown to affect the mammary stroma and epithelium. Carcinogenesis is a multistep process and there are several ways in which the host environment can affect progression of initiated cells to neoplasia. During normal and tumor development complex interactions occur between epithelial cells and stromal cells in the tissue microenvironment. These epithelial-stromal interactions in the microenvironment play a crucial role in the progression of mammary tumors. Determining the epithelial-stromal regulation by GH and PRL in the mammary gland of early parous rats is expected to improve our understanding of the dynamics of the epithelium and stromal interactions in mammary carcinogenesis. Materials and Methods: The inguinal mammary fat pad was cleared of the host mammary gland in 3-4-week-old female Lewis rats. One group (n=20) of rats were exposed to MNU at 7 weeks of age, and another group (n=20) of rats were not exposed to MNU. A subset (n=10) of rats from each of these experimental groups were mated at 9 weeks and allowed to go through a full-term pregnancy. The mothers were allowed to lactate for 3 weeks and weaned. All animals were terminated 6 weeks post-weaning. Mammary epithelial cells (MECs) were isolated using a standard collagenase cell dissociation procedure. The isolated MECs (5 × 105) were transplanted into the gland-free fat pads of respective hosts (n=30). MECs isolated from control and carcinogen treated age-matched nulliparous (AMNP) rats were transplanted into the gland-free fat pads of parous hosts and similarly MECs from control and carcinogen treated parous were transplanted into gland-free fats pads of AMNP hosts. In brief, we studied the following groups to understand the influence of early parity on epithelial-stromal interactions involved in mammary carcinogenesis: 1) carcinogen treated MECs from AMNP rats was transplanted into untreated parous rats; 2) carcinogen treated MECs from parous rats was transplanted into untreated AMNP rats; 3) untreated MECs from AMNP rats was transplanted into carcinogen treated parous rats and 4) untreated MECs from parous rats was transplanted into carcinogen treated AMNP rats. In another experiment, we treated a subset of the above mentioned groups with GH or PRL (n=10). Mammary carcinogenesis was monitored weekly for incidence, multiplicity, and latency. The cancerous nature of the palpable tumors was confirmed by histopathological analysis. Results: Our results demonstrate that when MECs from AMNP rats were transplanted to parous hosts they did not grow further to make palpable cancers. In contrast when MECs from parous rats were transplanted to AMNP they formed palpable cancers. Further, administration of GH or PRL increased carcinogenesis in parous rats. Conclusion: These findings indicate that the epithelial stromal interactions are important for mammary carcinogenesis and they are influenced significantly by GH and PRL. Citation Format: Ramadevi Subramani, Adriana Galvez, Diego Pedroza, Alejandro Bencomo, Madeline Dixon, Rajkumar Lakshmanaswamy. Growth hormone and prolactin influences mammary epithelial and stromal interactions in early parity induced protection against breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-12-02.

Effectiveness of absorption and passage through the small intestine, as a model of oral prolactin administration

The process of absorption and permeation of PRL through the small intestine of 1-day-old piglet from the different compositions of solutions prepared for oral administration was investigated. This was achieved by determining the effect of hormone concentration (0.25 mg / ml or 0.5 mg / ml or 0.75 mg / ml), the concentration of stabilizing substances - trehalose (6 mg / ml or 12 mg / ml or 18 mg / ml) and mannitol (6 mg / ml or 12 mg / ml or 18 mg / ml) and the pH of the solution (2.5 or 3.0 or 3.5) on the degree of absorption and permeation of the PRL. The conditions for the absorption and penetration of PRL from solutions of various compositions for oral administration through the natural membrane (small intestine of the 1-day-old sucking piglet) in the in vivo conditions were simulated. The studies used an in vivo model in which the enzymatic profile in the body is not yet fully developed (no pepsin).It was found that in the studied range the absorption of PRL in the small intestine of the 1-day-old sucking piglet is significantly related to the concentration of the hormone and trehalose in the solution from which it is absorbed. In contrast, all factors studied (hormone concentration, trehalose and mannitol concentration, pH value of the solution) influence the process of penetration of the PRL in the studied range. It was also found that the hormone concentration significantly influences the rate of its absorption and permeation (the fastest occurs at a concentration of 0.5 mg/mL). The results suggest possibility of oral prolactin administration in order to ensure proper growth, development and increase the resistance and survival of sucking piglets.

Transcription factor E2F4 is a positive regulator of milk biosynthesis and proliferation of bovine mammary epithelial cells.

The transcription factor E2F4 is a key determinant of cell differentiation and cell-cycle progression, but its function and regulatory mechanism are not completely understood. Here, we report that E2F4 acts as a positive regulator of the biosynthesis of milk components and proliferation of bovine mammary epithelial cells (BMECs). Overexpression of E2F4 in BMECs resulted in the upregulation of β-casein, triglyceride, and lactose levels and increased cell proliferation, whereas E2F4 knockdown by small interfering RNA had the opposite effects. We further detected that overexpression of E2F4 significantly increased the messenger RNA expression of mTOR, SREBP-1c, and Cyclin D1, and increased protein levels of SREBP-1c, and Cyclin D1, and the ratio of p-mTOR/mTOR, whereas E2F4 knockdown had the opposite effects. E2F4 was almost entirely located in the nucleus, and we further identified, via ChIP-qPCR analysis, that mTOR, SREBP-1c, and Cyclin D1 were E2F4 target genes, and exogenous administration of methionine, leucine, β-estradiol, and prolactin markedly increased the protein levels of E2F4 and its binding to the promoters of these three genes. In summary, our data reveal that E2F4 responds to extracellular stimuli and regulates the expression of mTOR, SREBP-1c, and Cyclin D1 for milk biosynthesis and proliferation of BMECs.

Does Prolactin treatment trigger imunoendocrine alterations during experimental T. cruzi infection?

Prolactin (PRL) is a pleiotropic polypeptide hormone produced by the anterior pituitary gland and negatively controlled by dopamine. Some researchers have associated the immune regulatory functions of PRL with some infectious diseases like Toxoplasma gondii and T. cruzi. This work aimed to analyze the possible immuno-modulatory effects of this hormone through the subcutaneous administration of PRL during the experimental Chagas disease. On the 14th day post-infection (dpi), PRL triggered increased percentages of NK cells in treated infected animals as compared to the infected and untreated ones. For early and late apoptosis, our results showed that in chronically infected groups, PRL counteracted splenocyte apoptosis as revealed by the reduced percentages of both, early and late apoptosis. Reduced percentages of spleen CD4+ and CD8+ T cells were detected in infected PRL treated rats (60 days post-infection). Concerning to B cells, a significant increased percentage of these cells was found for all PRL treated infected animals (14th dpi), but no statistically significant alteration was observed on the 60th days post-infection. Furthermore, PRL treatment triggered a significant increase in the percentage of CD4+ T lymphocytes IFN-γ producers, while on the 60th dpi, a reduced percentage of IFN-γ in these cells was observed in prolactin-treated rats compared to infected and untreated ones. Enhanced serum IL-12 levels were detected in infected and PRL treated subjects (60th dpi). Only on 7th day post-infection, the flow cytometric analysis of CFSE-stained CD3+ T cells showed an enhanced proliferation of polyclonal stimulated T cells in PRL-treated and infected animals. In this study, we demonstrated that PRL can influence many aspects of the immune response during the experimental Chagas' disease, and this substance could be used as a supporting trial along with the conventional drug treatment.

The median eminence detects and responds to circulating prolactin in the male mouse.

In addition to its established lactational roles, prolactin acts on multiple target tissues and its circulating levels are responsive to a range of physiological stimuli. The present study used immunohistochemistry to demonstrate that systemic administration of prolactin activates target cells in the arcuate nucleus and median eminence of the male mouse. Prolactin receptor stimulation results in the phosphorylation and thus activation of thesignal transducer and activator of transcription (STAT)5pathway. Interestingly, although, in the arcuate nucleus, this response was localised to cell nuclei, the median eminence displayed both nuclear and diffuse, non-nuclear, phospho-STAT5 (pSTAT5) staining. Dual-label immunostaining demonstrated that, although the majority of nuclear pSTAT5 within the median eminence was located within vimentin-positive tanycytes, the non-nuclear staining occurred primarily in neuronal (βIII tubulin immunoreactive) elements. This conclusion was supported by the marked reduction of this signal in prolactin-treated mice lacking neuronal prolactin receptors. A smaller reduction was also seen in animals lacking prolactin receptors on GABAergic but not glutamatergic neurones. These findings identify a new prolactin target tissue and, in doing so, support the proposal that the median eminence has a sensory role in addition to its established secretory function. The physiological significance of this prolactin response is unknown, although its rapidity (maximum within 2minutes of i.p. injection) suggests that it may enable the early detection of an increase in circulating prolactin. It is also possibile that non-nuclear prolactin-generated pSTAT5 in the median eminence may have a local, non-transcriptional, action. To this end, we used Evans Blue dye to demonstrate that elevated prolactin appears to reduce median eminence permeability and also that this effect is lost in animals lacking neuronal prolactin receptors.

Acute Suppression of LH Secretion by Prolactin in Female Mice Is Mediated by Kisspeptin Neurons in the Arcuate Nucleus.

Hyperprolactinemia causes infertility, but the specific mechanism is unknown. It is clear that elevated prolactin levels suppress pulsatile release of GnRH from the hypothalamus, with a consequent reduction in pulsatile LH secretion from the pituitary. Only a few GnRH neurons express prolactin receptors (Prlrs), however, and thus prolactin must act indirectly in the underlying neural circuitry. Here, we have tested the hypothesis that prolactin-induced inhibition of LH secretion is mediated by kisspeptin neurons, which provide major excitatory inputs to GnRH neurons. To evaluate pulsatile LH secretion, we collected serial blood samples from diestrous mice and measured LH levels by ultrasensitive ELISA. Acute prolactin administration decreased LH pulses in wild-type mice. Kisspeptin neurons in the arcuate nucleus and in the rostral periventricular area of the third ventricle (RP3V) acutely responded to prolactin, but prolactin-induced signaling in kisspeptin neurons was up to fourfold higher in the arcuate nucleus when compared with the RP3V. Consistent with this, conditional knockout of Prlr specifically in arcuate nucleus kisspeptin neurons prevented prolactin-induced suppression of LH secretion. Our data establish that during hyperprolactinemia, suppression of pulsatile LH secretion is mediated by Prlr on arcuate kisspeptin neurons.

The maternal hormone in the male brain: Sexually dimorphic distribution of prolactin signalling in the mouse brain.

Research of the central actions of prolactin is highly focused on females, but this hormone has also documented roles in male physiology and behaviour. Here, we provide the first description of the pattern of prolactin-derived signalling in the male mouse brain, employing the immunostaining of phosphorylated signal transducer and activator of transcription 5 (pSTAT5) after exogenous prolactin administration. Next, we explore possible sexually dimorphic differences by comparing pSTAT5 immunoreactivity in prolactin-supplemented males and females. We also assess the role of testosterone in the regulation of central prolactin signalling in males by comparing intact with castrated prolactin-supplemented males. Prolactin-supplemented males displayed a widespread pattern of pSTAT5 immunoreactivity, restricted to brain centres showing expression of the prolactin receptor. Immunoreactivity for pSTAT5 was present in several nuclei of the preoptic, anterior and tuberal hypothalamus, as well as in the septofimbrial nucleus or posterodorsal medial amygdala of the telencephalon. Conversely, non-supplemented control males were virtually devoid of pSTAT5-immunoreactivity, suggesting that central prolactin actions in males are limited to situations concurrent with substantial hypophyseal prolactin release (e.g. stress or mating). Furthermore, comparison of prolactin-supplemented males and females revealed a significant, female-biased sexual dimorphism, supporting the view that prolactin has a preeminent role in female physiology and behaviour. Finally, in males, castration significantly reduced pSTAT5 immunoreactivity in some structures, including the paraventricular and ventromedial hypothalamic nuclei and the septofimbrial region, thus indicating a region-specific regulatory role of testosterone over central prolactin signalling.