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.

No seroconversion among healthcare workers exposed to SARS-CoV-2 during the early phase of the pandemic.

BACKGROUND: The SARS-CoV-2 pandemic is associated with morbidity, hospitalizations, absenteeism, and mortality among healthcare workers (HCW). AIM: To evaluate the seroconversion rate in HCW exposed to SARS-CoV-2 in the early pandemic phase in 2020 at a regional reference hospital. MATERIAL AND METHODS: One hundred seventy-nine HCW working at a regional hospital were invited to a longitudinal study performed between April-July 2020. A serological analysis by ELISA IgG for viral nucleoprotein and protein S with a secondary analysis by ELISA IgG protein S1/S2 for samples with positive or doubtful result was carried out together with a complementary online survey to inquire about occupational or community exposures to SARS-CoV-2. RESULTS: Two cases with baseline infection were detected (1.1%, one symptomatic and one asymptomatic) and no cases of seroconversion were detected. During the study period, there were 136 patients hospitalized with COVID-19, and regional weekly COVID-19 incidence ranged from 2.7 to 24.4 per 100,000 inhabitants. No SARS-CoV-2 cases were detected by PCR among 27 HCW who consulted for respiratory symptoms in the period. Online surveys confirmed direct care of COVID-19 patients and also detected a high degree of unprotected social interaction at work. CONCLUSIONS: There was no evidence of seroconversion in this group of HCW exposed to the risk of infection by SARS-CoV-2 during the onset of the COVID-19 pandemic. Personal protective equipment and other measures used by the HCW were extremely useful for their protection in the initial phase of the pandemic.

Prolactin Attenuates Neuroinflammation in LPS-Activated SIM-A9 Microglial Cells by Inhibiting NF-κB Pathways Via ERK1/2.

Prolactin (PRL) is a pleiotropic hormone with multiple functions in several tissues and organs, including the brain. PRL decreases lesion-induced microgliosis and modifies gene expression related to microglial functions in the hippocampus, thereby providing a possible mechanism through which it might participate in neuroimmune modulatory responses and prevent neuronal cell damage. However, the direct contribution of microglial cells to PRL-mediated neuroprotection is still unclear and no studies have yet documented whether PRL can directly activate cellular pathways in microglial cells. The aim of this study is to elucidate in vitro actions of PRL on the immortalized SIM-A9 microglia cell line in basal and LPS-stimulated conditions. PRL alone induced a time-dependent extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Pretreatment with PRL attenuated LPS (200 ng/ml) stimulated pro-inflammatory markers: nitric oxide (NO) levels, inducible nitric oxide synthase (iNOS), interleukins (IL)-6, -1ß and tumor necrosis factor (TNF-α) expression at 20 nM dosage. PRL suppressed LPS-induced nuclear factor (NF)-κappaB (NF-κB) p65 subunit phosphorylation and its upstream p-ERK1/2 activity. In conclusion, PRL exhibits anti-inflammatory effects in LPS-stimulated SIM-A9 microglia by downregulating pro-inflammatory mediators corresponding to suppression of LPS-activated ERK1/2 and NF-κB phosphorylation.

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.

Glial cells as mediators of protective actions of prolactin (PRL) in the CNS.

Prolactin (PRL) is a hormone with multiple actions in the central nervous system (CNS) spanning from physiology to pathology. PRL exerts different actions through its receptors that can be found in both neurons and glial cells (astrocytes, microglia and oligodendrocytes) of the brain. Even though its effects during pregnancy and lactation, stress, anxiety, and depression are well studied, recent work on this hormone has brought to light a new role of PRL: that of a protective agent against brain damage and, consequently, against neurodegeneration. The mechanisms through which this protection takes place have not been fully elucidated; however, neurogenesis and anti-apoptosis are some of the plausible mechanisms that could mediate this effect. There is substantial information that implies the involvement of glial activation in this PRL effect, as shown in various models of brain damage. Taking into account glial cell dynamics and actions in various pathological conditions, combined with the neuroprotective effect of PRL, we consider of importance the revision of all the information about the interaction between these two cell types, as it will provide comprehensive knowledge about this new target of PRL against neuropathology.

Microglia modulate respiratory rhythm generation and autoresuscitation.

Inflammation has been linked to the induction of apneas and Sudden Infant Death Syndrome, whereas proinflammatory mediators inhibit breathing when applied peripherally or directly into the CNS. Considering that peripheral inflammation can activate microglia in the CNS and that this cell type can directly release all proinflammatory mediators that modulate breathing, it is likely that microglia can modulate breathing generation. It might do so also in hypoxia, since microglia are sensitive to hypoxia, and peripheral proinflammatory conditions affect gasping generation and autoresuscitation. Here, we tested whether microglial activation or inhibition affected respiratory rhythm generation. By measuring breathing as well as the activity of the respiratory rhythm generator (the preBötzinger complex), we found that several microglial activators or inhibitors, applied intracisternally in vivo or in the recording bath in vitro, affect the generation of the respiratory rhythms both in normoxia and hypoxia. Furthermore, microglial activation with lipopolysaccharide affected the ability of the animals to autoresuscitate after hypoxic conditions, an effect that is blocked when lipopolysaccharide is co-applied with the microglial inhibitor minocycline. Moreover, we found that the modulation of respiratory rhythm generation induced in vitro by microglial inhibitors was reproduced by microglial depletion. In conclusion, our data show that microglia can modulate respiratory rhythm generation and autoresuscitation.

Anorexia Reduces GFAP+ Cell Density in the Rat Hippocampus.

Anorexia nervosa is an eating disorder observed primarily in young women. The neurobiology of the disorder is unknown but recently magnetic resonance imaging showed a volume reduction of the hippocampus in anorexic patients. Dehydration-induced anorexia (DIA) is a murine model that mimics core features of this disorder, including severe weight loss due to voluntary reduction in food intake. The energy supply to the brain is mediated by astrocytes, but whether their density is compromised by anorexia is unknown. Thus, the aim of this study was to estimate GFAP+ cell density in the main regions of the hippocampus (CA1, CA2, CA3, and dentate gyrus) in the DIA model. Our results showed that GFAP+ cell density was significantly reduced (~20%) in all regions of the hippocampus, except in CA1. Interestingly, DIA significantly reduced the GFAP+ cells/nuclei ratio in CA2 (-23%) and dentate gyrus (-48%). The reduction of GFAP+ cell density was in agreement with a lower expression of GFAP protein. Additionally, anorexia increased the expression of the intermediate filaments vimentin and nestin. Accordingly, anorexia increased the number of reactive astrocytes in CA2 and dentate gyrus more than twofold. We conclude that anorexia reduces the hippocampal GFAP+ cell density and increases vimentin and nestin expression.

Lactation attenuates pro-oxidant reactions in the maternal brain.

Reactive oxygen species (ROS) are intimately linked to bioenergetics and redox biology, contributing to cellular functioning and physiological signaling, but also acting as toxic agents during oxidative stress. Hence, the balance between pro-oxidant reactions and the activity of antioxidant defenses sustains a basal oxidative status, controls the increase of redox signaling, and mediates potential pathological events during oxidative stress. Maternal experience, especially during nursing, requires high energetic demands and expenditure to ensure the well-being of the offspring. The mother must adapt from satisfying her own needs to additionally fulfilling those of her descendants. Oxidative stress has been proposed as one of the reproductive trade-off hallmarks. However, the oxidative shielding hypothesis has also been proposed in the context of reproduction. The reproductive experience induces a wide range of well-documented changes in the female brain, which potentially lead to protection against the enhanced oxidative activity. To date, the metabolic and cellular mechanisms that underlie lactation-induced neuroprotection against oxidants are unknown. The neuroendocrine changes in the brain of the lactating dam promote diminished propensity to excitotoxic brain injury and stress, as well as enhanced neuroprotection and plasticity. In addition to review studies on the oxidant balance due to motherhood, we included new data from our laboratory, addressing the importance of measuring pro-oxidant reactions in separated brain regions. The hippocampus of lactating rats exhibits lower levels of pro-oxidant reactions than that of virgin rats, supporting the oxidative shielding hypothesis in lactation.

Activation of the central but not the medial and cortical amygdala during anticipation for daily nursing in the rabbit.

Rabbits have remarkable nursing behavior: after parturition, does visit daily their pups for nursing only once with circadian periodicity. Before the nursing events, they present increased activity and arousal, which shift according to the timing of scheduled nursing, either during the day or night. Brain areas related to maternal behavior and neuroendocrine cells for milk secretion are also entrained. The daily return of the doe for nursing at approximately the same hour suggests a motivational drive with circadian periodicity. Previously, we reported the activation of the mesolimbic system at the time of nursing, but not 12 h before that. Aiming at a better understanding of the mechanism of this anticipatory behavior, we explored the participation of the limbic regions of the amygdala and the bed nucleus of the stria terminalis, as well as the possible activation of the hypothalamic-pituitaryadrenal axis, specifically the corticotropin-releasing factor cells in the hypothalamic paraventricular nucleus of does at different times before and after nursing. The medial and cortical amygdala, the bed nucleus of the stria terminalis, and corticotropin cells showed activation only after nursing. However, the central amygdala was also activated before nursing. We conclude that the medial and the cortical amygdala form part of the afferent olfactory pathway for entrainment, and the central amygdala participates in the anticipatory motivational circuit of the control of periodic nursing. The lack of activation of corticotropin cells before nursing is consistent with the possible harmful effects of the doe's high glucocorticoid levels on the developing pups.

Extremely missing numerical data in Electronic Health Records for machine learning can be managed through simple imputation methods considering informative missingness: A comparative of solutions in a COVID-19 mortality case study.

BACKGROUND AND OBJECTIVE: Reusing Electronic Health Records (EHRs) for Machine Learning (ML) leads on many occasions to extremely incomplete and sparse tabular datasets, which can hinder the model development processes and limit their performance and generalization. In this study, we aimed to characterize the most effective data imputation techniques and ML models for dealing with highly missing numerical data in EHRs, in the case where only a very limited number of data are complete, as opposed to the usual case of having a reduced number of missing values. METHODS: We used a case study including full blood count laboratory data, demographic and survival data in the context of COVID-19 hospital admissions and evaluated 30 processing pipelines combining imputation methods with ML classifiers. The imputation methods included missing mask, translation and encoding, mean imputation, k-nearest neighbors' imputation, Bayesian ridge regression imputation and generative adversarial imputation networks. The classifiers included k-nearest neighbors, logistic regression, random forest, gradient boosting and deep multilayer perceptron. RESULTS: Our results suggest that in the presence of highly missing data, combining translation and encoding imputation-which considers informative missingness-with tree ensemble classifiers-random forest and gradient boosting-is a sensible choice when aiming to maximize performance, in terms of area under curve. CONCLUSIONS: Based on our findings, we recommend the consideration of this imputer-classifier configuration when constructing models in the presence of extremely incomplete numerical data in EHR.

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.

Rabbits can be conditioned in a food-induced place preference paradigm.

The conditioned place preference (CPP) paradigm has been employed in behavioral studies to investigate the responses to an environment where a reinforcing event occurs. It is applied to reveal incentive motivational responses to reward-related stimuli. It is standardized and widely applied in mice and rats, two of the most common species of laboratory animals. However, no studies using the CPP protocol have been performed in rabbits, even though this animal model is commonly used in pharmacological and behavioral research. There are important physiological and behavioral differences between rodents and rabbits. For example, rodents are spontaneous ovulators while rabbits are induced ovulators. In addition, lactation in the rabbit is circadian, which is unique among mammals. The present investigation aims to establish whether rabbits can be conditioned by using a food-induced CPP protocol in subjects with caloric restriction. Adult female rabbits were subjected to a three-compartment CPP protocol. The food produced place preference, demonstrating for the first time that rabbits can be conditioned using the CPP paradigm opening a new field of opportunities for behavioral studies of positive affective states in a species with important behavioral and physiological differences from rodents.

Prolactin neuroprotective action against excitotoxic insult in the hippocampus of male mice.

Prolactin (PRL) is known to exert neuroprotective effects against excitotoxic damage in the hippocampus of female rats, both in vitro and in vivo. It is still unknown whether this effect can be seen in the male hippocampus and intracellular signaling mediating such action. To assess this, adult male CD-1 mice were subjected to excitotoxic damage with kainic acid (KA; i.c.v.), after a) no manipulation (control group), b) treatment with saline, and c) treatment with PRL (8 µg of PRL/100 µl of saline s.c.). Treatments consisted of one daily injection of the mentioned dosage for seven consecutive days until the day of the excitotoxic lesion. Neurodegeneration (Fluoro-Jade C), neuronal survival (NeuN) and astrogliosis (GFAP) markers were identified with immunohistochemistry in the CA1, CA3 and CA4 areas of the dorsal hippocampus, as well as PRL-related protein levels by Western blot in the whole hippocampus 48 h after excitotoxicity. Anatomical measurements revealed a preferential protective effect of PRL against excitotoxic damage in the CA3 hippocampal subfield, with lower levels of cell death and neurodegeneration, compared to controls. In CA4, the results were not conclusive, and no damage was observed in CA1 after KA administration. PRL treatment provoked an upregulation of active Akt, a well-known cell survival pathway, after KA administration. PRL also caused downregulation of active MAPK, independently of the excitotoxic damage. The present results indicate a neuroprotective role for PRL preferentially located in the CA3 area of the hippocampus of male mice, possibly mediated by Akt-related survival mechanisms.

Prolactin released in vitro from the pituitary of lactating, pregnant, and steroid-treated female or male rats stimulates prolactin secretion from pituitary lactotropes of male rats.

We have previously shown that soluble factor(s) in conditioned media (CM) from the central and peripheral regions of the anterior pituitary (AP) gland of lactating rats promoted the in vitro dose-related release of prolactin (PRL) from pituitary glands of male rats. In the present experiments we sought to determine whether CM from rats in different physiological states provoked similar effects (like those of lactating rats), and the nature of the factors, whether 23K PRL or other variants of the hormone, were responsible for these effects. Stimulatory effects were induced by CM from pregnant females and steroid-treated castrated males or females, but not from untreated castrated rats, intact males, or by a PRL standard. More potent effects occurred with CM from APs of early- than from mid- or late-lactating rats, and from rats unsuckled for 8 or 16 h than from those unsuckled for 32 h. With respect to the nature of factor(s) responsible for these effects, immunoprecipitation of PRL from the CM of lactating females and of steroid-treated, castrated males eliminated, whereas dephosphorylation or deglycosylation of CM of lactating rats greatly increased its effects upon PRL release. Also, electrophoretic analysis and Western blotting of the CM proteins under native and denaturing conditions revealed a variety of PRL variants, ranging from 14 to <90 kDa, in CM from lactating rats, and the main effects on PRL release were provoked by the 23- to 46-kDa PRL variants. These results indicate that specific effects upon male rat lactotropes may be exerted by PRL variants released from APs of lactating and non-lactating rats.

Prolactin treatment reduces kainic acid-induced gliosis in the hippocampus of ovariectomized female rats.

Neuroinflammation involves a set of responses occurring as a result of brain damage including astro- and microgliosis. In previous studies, we showed that treatment with prolactin (PRL) decreased neuronal loss induced by kainic acid (KA) in the hippocampus of female rats. This effect correlated with a decrease in astrogliosis. Here, we investigate whether treatment with PRL decreases astro- and microgliosis in the dorsal hippocampus, and how it modulates the expression of some important inflammatory factors such as TNFα, iNOS, IL-6, IL-10 and IL-4 after an excitotoxic lesion. For this, ovariectomized female rats were treated chronically with PRL (0.1 mg / day for 4 days, SC). On the third day of treatment, they received a KA injection (7.5 mg / kg, IP) and were sacrificed 24 or 48 h later. Chronic treatment with PRL reduced the astro- and micro-gliosis in CA4, CA3, and CA1 hippocampal subfields induced by KA. Morphometric analysis in CA4 showed that PRL reduced microglial activation. The analysis for anti- and pro-inflammatory cytokines revealed an increase of IL-10 and IL-4 in neurons due to treatment with PRL, accompanied by a decrease in the expression of TNFα and iNOS in lesioned rats. These results indicate that PRL has anti-inflammatory actions in the hippocampus, both by decreasing the astrogliosis and microglial activation and by reducing the level of pro-inflammatory cytokines probably through the upregulation of neuronal IL-10 and IL-4.

Reproductive status impact on tau phosphorylation induced by chronic stress.

Sex and exposure to chronic stress have been identified as risk factors for developing Alzheimer's disease (AD). Although AD has been demonstrated to be more prevalent in females, sex is often overlooked in research studies, likely due to the complexity of the hormonal status. In female rats, the reproductive status can modulate the well-known increase in tau phosphorylation (pTau) caused by the exposure to acute physical and psychological stressors. To test the hypothesis that reproductive status can impact hippocampal pTau induced by chronic stress, cohorts of virgin, lactating (4-5 days pp), and post-maternal (1-month post-weaned) rats were subjected to a daily 30-min episode of restraint stress for 14 days and were sacrificed either 20 min or 24 h after their last stress/handling episode. Western blot analysis of two well-characterized AD-relevant pTau epitopes (AT8 and PHF-1) and upstream pTau mechanisms (e.g. GSK3ß) analysis, showed that stressed post-maternal rats have increased pTau in comparison to stressed lactating rats 20 min after their last stress episode. Furthermore, an increase in pTau was also seen 24 h after the last stress episode in stressed post-maternal rats in comparison to their non-stressed controls in the detergent-soluble fraction. GSK3 analysis showed an increase in total levels of GSK3ß in virgin rats and an increase of inactive levels of GSK3ß in post-maternal rats, which suggests a different stress response in pTau after the rat has gone through the maternal experience. Interestingly, post-maternal rats also presented the more variability in their estrous cycles in response to stress. Besides no differences in pTau, non-stressed lactating rats showed an increase in inactive GSK3ß 24 h after the last handling episode. Immunohistochemical detection of the PHF-1 epitope revealed increased pTau in the CA4/hilar subfield of the hippocampus of virgin and post-maternal rats exposed to chronic stress shortly after their last stress episode. Overall, lactating rats remained unresponsive to chronic restraint stress. These results suggest increased sensitivity of the virgin and post-maternal rats to hippocampal stress-induced pTau with chronic restraint stress compared to lactating rats. Because no differences were detected in response to stress by lactating rats and an exaggerated response was observed in post-maternal rats, current results support the hypothesis that lactation affects tau processing in the brain of the female.

Chronic kidney disease and the olfactory system. / Enfermedad renal crónica y olfato.

Alterations in the sense of smell (dysosmia, anosmia, hyposmia) are frequently experienced by patients with chronic kidney disease. However, currently, the aetiology and consequences are poorly understood, with no effective treatments available to address such impairment. In general, the capacity of olfactory perception is affected in patients with chronic kidney disease (even in those who have not undergone dialysis therapy), and whether these alterations improve after dialysis is disputed. Patients in peritoneal dialysis and haemodialysis have the same olfactory perception defects. Kidney transplantation improves olfactory perception, and one important consequence of such impairment is the potential impact on the patient's nutritional status.

[Clinical guideline for the diagnosis and treatment of subclinical thyroid dysfunction in pregnancy. Working Group on Subclinical Thyroid Dysfunction of the Spanish Endocrinology Society]. / Guía clínica para el diagnóstico y el tratamiento de la disfunción tiroidea subclínica en la gestación. Grupo de Trabajo sobre la Disfunción Tiroidea Subclínica de la Sociedad Española de Endocrinología.

Subclinical thyroid disease is a biochemical diagnosis and is common during pregnancy. Because of the physiological hormonal changes that take place during pregnancy and the absence of normal ranges for thyroid hormones during this period, subclinical thyroid disease is difficult to interpret during pregnancy. Subclinical hyperthyroidism during pregnancy has few clinical consequences and no treatment is required. In contrast, subclinical hypothyroidism seems to improve with thyroxine treatment. Iodine supplements during pregnancy and lactation, even in iodine-sufficient areas, are also indicated.