Prolactin action is necessary for parental behavior in male mice

Parental care is critical for successful reproduction in mammals. In comparison to maternal care, the neuroendocrine mechanisms supporting paternal care are less well-studied. Laboratory mice show a mating-induced suppression of infanticide (normally observed in virgins) and onset of paternal behavior. Using this model, we sought to investigate whether the hormone prolactin plays a role in paternal behavior, as it does for maternal behavior. First, using c-fos immunoreactivity in Prlr-IRES-Cre-tdtomato reporter mouse sires, we show that the circuitry activated during paternal interactions contains prolactin-responsive neurons, including the medial preoptic area, bed nucleus of the stria terminalis, and medial amygdala. To evaluate whether prolactin action is required for the establishment and display of paternal behavior, we conditionally deleted the prolactin receptor (Prlr) from 3 distinct cell types: glutamatergic, GABAergic, and CaMKIIα-expressing forebrain neurons. Prlr-deletion from CaMKIIα-expressing forebrain neurons, but not from glutamatergic or GABAergic cells, resulted in a profound effect on paternal behavior, as none of these males completed the pup retrieval task. Finally, although sires do not show an acute increase in circulating prolactin levels in response to pups, pharmacological blockade of prolactin-release at the time of pup exposure resulted in failure to retrieve pups, similar to when the Prlr was deleted from CaMKIIα neurons, with prolactin administration rescuing this behavior. Taken together, our data show that paternal behavior in sires is dependent on basal levels of circulating prolactin acting at the Prlr on CaMKIIα-expressing neurons. These new data in male mice demonstrate that prolactin has a similar action in both sexes to promote parental care.

4SC-202 Exerts An Anti-tumor Effect in Cervical Cancer By Targeting PRLR Signaling Pathway

The aim of the present study is to investigate whether 4SC-202, a selective class I histone deacetylase inhibitor (HDACi), plays an anti-tumor role in cervical cancer (CC) by targeting prolactin receptor (PRLR). CCK-8 and colony formation assays were used to evaluate the effects of 4SC-202 on the proliferation of CC cells in vitro. Effects of 4SC-202 on the cell cycle distribution and apoptosis in SiHa cells were determined by flow cytometry and western blotting, respectively. Immunofluorescence and western blotting were performed to detect the activities of PRLR-related pathways and PRLR expression in CC cells. A xenograft tumor model in nude mice was established to examine effects of 4SC-202 on the tumor growth, apoptosis and PRLR-related pathways in vivo. The biochemical analyzer and H&E staining were used to detect the serum biochemical indexes and organ toxicity. 4SC-202 inhibited the proliferation of CC cells (SiHa, HeLa, and CaSki) in vitro in a time- and dose-dependent manner. SiHa cells were treated with 1 or 5 μM 4SC-202 for 72 h and then subjected to various functional assays. The assays showed that 4SC-202 significantly induced G2/M phase arrest and apoptosis, while inhibiting the activities of PRLR-related pathways and PRLR expression. In addition, 4SC-202 reduced tumor growth and induced apoptosis in vivo. 4SC-202 down-regulated the expression of PRLR and activities of PRLR-related pathways in the mouse model, displayed no effects on serum biochemical indicators and caused no toxicity to mouse organs. This finding suggests that 4SC-202 may serve as a novel therapeutic agent for CC.

Prolactin-Induced Adaptation in Glucose Homeostasis in Mouse Pregnancy Is Mediated by the Pancreas and Not in the Forebrain

Adaptive changes in glucose homeostasis during pregnancy require proliferation of insulin-secreting beta-cells in the pancreas, together with increased sensitivity for glucose-stimulated insulin secretion. Increased concentrations of maternal prolactin/placental lactogen contribute to these changes, but the site of action remains uncertain. Use of Cre-lox technology has generated pancreas-specific prolactin receptor (Prlr) knockouts that demonstrate the development of a gestational diabetic like state. However, many Cre-lines for the pancreas also express Cre in the hypothalamus and prolactin could act centrally to modulate glucose homeostasis. The aim of the current study was to examine the relative contribution of prolactin action in the pancreas and brain to these pregnancy-induced adaptations in glucose regulation. Deletion of prolactin receptor (Prlr) from the pancreas using Pdx-cre or Rip-cre led to impaired glucose tolerance and increased non-fasting blood glucose levels during pregnancy. Prlrlox/lox/Pdx-Cre mice also had impaired glucose-stimulated insulin secretion and attenuated pregnancy-induced increase in beta-cell fraction. Varying degrees of Prlr recombination in the hypothalamus with these Cre lines left open the possibility that central actions of prolactin could contribute to the pregnancy-induced changes in glucose homeostasis. Targeted deletion of Prlr specifically from the forebrain, including areas of expression induced by Pdx-Cre and Rip-cre, had no effect on pregnancy-induced adaptations in glucose homeostasis. These data emphasize the pancreas as the direct target of prolactin/placental lactogen action in driving adaptive changes in glucose homeostasis during pregnancy.

Prolactin-regulated Pbk is involved in pregnancy-induced β cell proliferation in mice

Gestational diabetes mellitus(GDM) is a condition of glucose intolerance of glucose intolerance with onset or first recognition in pregnancy. Its incidence is increasing and GDM deleteriously affects both mother and fetus during and even after pregnancy. Previous studies in mice have shown that during pregnancy, β cell proliferation increases during pregnancy and return to normal levels after delivery. Hormones as well as protein kinases, play important roles in regulating gestation-mediated β cell proliferation, however the regulatory relationship between them are uncertain. We previously found that protein kinase Pbk was crucial for basal proliferation of mouse islet cells. Herein we show that Pbk is upregulated during pregnancy in mice and Pbk kinase activity is required for enhanced β cell proliferation during pregnancy. Notably, knock-in (KI) of a kinase-inactivating Pbk mutation leads to impaired glucose tolerance, and reduction of β cell proliferation and islet mass in mice during pregnancy. Prolactin upregulates the expression of Pbk, but the upregulation is diminished by knockdown of the prolactin receptor and by the inhibitors of JAK and STAT5, which mediate prolactin receptor signaling, in β cells. Treatment of β cells with prolactin increases STAT5 binding to the Pbk locus, as well as the recruitment of RNA polymerase II, resulting in increased Pbk transcription. These results demonstrate that Pbk is upregulated during pregnancy, at least partly by prolactin induced and STAT5-mediated enhancement of gene transcription, and Pbk is essential for pregnancy-induced β cell proliferation in preclinical models. These findings provide new insights into the interplay between hormones and protein kinases that ultimately prevent the development of GDM.

Phosphatases are predicted to govern prolactin-mediated JAK-STAT signaling in pancreatic beta cells

Patients with diabetes are unable to produce a sufficient amount of insulin to properly regulate their blood-glucose levels. One potential method of treating diabetes is to increase the number of insulin-secreting beta cells in the pancreas to enhance insulin secretion. It is known that during pregnancy, pancreatic beta cells proliferate in response to the pregnancy hormone, prolactin. Leveraging this proliferative response to prolactin may be a strategy to restore endogenous insulin production for patients with diabetes. To investigate this potential treatment, we previously developed a computational model to represent the prolactin-mediated JAK-STAT signaling pathway in pancreatic beta cells. However, this model does not account for variability in protein expression that naturally occurs between cells. Here, we applied the model to understand how heterogeneity affects the dynamics of JAK-STAT signaling. We simulated a sample of 10,000 heterogeneous cells with varying initial protein concentrations responding to prolactin stimulation. We used partial least squares regression to analyze the significance and role of each of the varied protein concentrations in producing the response of the cell. Our regression models predict that the concentrations of the cytosolic and nuclear phosphatases strongly influence the response of the cell. The model also predicts that increasing prolactin receptor strengthens negative feedback mediated by the inhibitor SOCS. These findings reveal biological targets that can potentially be used to modulate the proliferation of pancreatic beta cells to enhance insulin secretion and beta cell regeneration in the context of diabetes.

PSVI-19 Evaluation of birth weight, weaning weight and average daily weight gain of Holstein female calves carrying the SLICK1 allele of the Prolactin Receptor (PRLR) gene

Objectives of this study were to evaluate birth weight (BW), weaning weight (WW), and average daily weight gain (ADG) of female calves carrying the SLICK1 allele, i.e., the slick gene. Holstein cows in four dairy farms located in central California were inseminated with semen from two heterozygous slick Holstein sires to produce slick and non-slick calves. Calves were born during the cool season (November 2019-March 2020). BW was recorded for 125 calves in four farms within 24 h of birth; WW was recorded for 92 calves in three farms within one week of weaning. Weaning age was recorded at day of weighing. ADG was calculated as the weight difference between birth and weaning divided by days of age at weaning. Only female calves were used in the analysis. Statistical analyses were performed using the GLIMMIX procedure of SAS version 9.4. The model for BW included the effects of genotype, farm, sire, and the interaction between genotype and farm. The model for WW and ADG included the effects of BW, genotype, farm, weaning age, sire, and interaction between genotype and farm. Significant effects were considered as those with P < 0.05. There was no difference in BW or WW between genotypes (BW: slick=40.1 ± 0.7 vs non-slick=39.7 ± 0.6 kg; P = 0.7 and WW: slick=82.5 ± 2.8 vs non-slick=80.9 ± 2.8 kg; P = 0.6). The mean age at weaning was 64.8 ± 0.4 and was similar for both genotype groups (P = 0.8). As a result, ADG was similar between genotypes (P = 0.7). There was a main effect of farm on BW, WW and ADG. Results indicate that slick heifer calves born in the cool season perform similarly to non-slick calves in regards to birth weight, average daily weight gain, and weaning weight. Funding provided by the Holstein Association USA Research Program and L.E. “Red” Larson Endowment.