Progesterone receptor-mediated actions and the treatment of central nervous system disorders: An up-date of the known and the challenge of the unknown

Association between duration of birth control pill use and risk of depression among US women: A cross-sectional NHANES study

ObjectiveTo explore the association between the duration of birth control pill use (DBCPU) and the risk for depressive symptoms among women in the United States.MethodData from 4996 American women obtained from the National Health and Nutrition Examination Survey, 2005-2012, were analyzed to evaluate the association between DBCPU and depressive symptoms using multivariate logistic regression models, fitted smooth curves, and subgroup and threshold analyses.ResultsStatistically significant differences (P < 0.05) were found between the 2 groups in DBCPU, age at menarche, age stratification, race, and marital status. The adjusted weighted logistic regression model revealed a negative correlation between DBCPU and depressive symptoms. Subgroup analysis revealed that this association was stronger among women without diabetes. The restricted cubic splines plot indicated that the risk for depressive symptoms decreased as DBCPU increased. Threshold effect analysis identified an inflection point at 9.3, with a more significant risk reduction below this value (odds ratio 0.94 [95% confidence interval 0.90-0.98]; P = 0.006).ConclusionLong-term oral contraceptive use may be an effective intervention strategy for the prevention and treatment of depression in women; however, further prospective studies are needed to confirm this hypothesis.

Progestagens and progesterone receptor modulation: Effects on the brain, mood, stress, and cognition in females

Progesterone is a highly lipophilic gonadal hormone that can influence behavior and mental health through its receptors in the brain. Fluctuations in progesterone levels across critical periods of a females life are associated with increased susceptibility to mental conditions. This review highlights the effects of progestagens, including progesterone and synthetic progestins, on the brain, mood, stress, and cognition in females. The primary focus is on experimental pharmacological research that teases out the distinct effects of progestagens from those of estrogens. Additionally, the key literature on puberty, the menstrual cycle, pregnancy, perimenopause, hormonal contraceptives, and menopausal hormone therapy is reviewed, although conclusions are limited by the nested effects of progestagens and estrogens. Single study-findings suggest an influence of progesterone on amygdala reactivity related to processing of emotional stimuli and memory. In patients with premenstrual dysphoric disorder, progesterone receptor modulation improves premenstrual mood symptoms and potentially enhances fronto-cingulate control over emotion processing. The interaction between progestagens and the systems involved in the regulation of stress seems to influence subjective experiences of mood and stress. Sparse studies investigating the effects of progestin-only contraceptives suggest effects of progestagens on the brain, mood, and stress. Progesterone and progestins used for contraception can influence neural processes as myelination and neuroprotection, exerting protective effects against stroke. Concerning menopausal hormonal therapy, the effects of progestins are largely unknown. Levels of progesterone as well as type, administration route, timing, dose regimen, metabolism, and intracellular activity of progestins in hormonal contraceptives and menopausal hormonal therapy are factors whose effects remain to be elucidated. Altogether, current knowledge highlights the potential role of progestagens in females health but also calls for well-designed pharmaco-behavioral studies disentangling the effects of progestagens from those of estrogens.

Neuroactive steroids in the neuroendocrine control of food intake, metabolism, and reproduction

Neuroactive steroids are a type of steroid hormones produced within the nervous system or in peripheral glands and then transported to the brain to exert their neuromodulatory effects. Neuroactive steroids have pleiotropic effects, that include promoting myelination, neuroplasticity, and brain development. They also regulate important physiological functions, such as metabolism, feeding, reproduction, and stress response. The homoeostatic processes of metabolism and reproduction are closely linked and mutually dependent. Reproductive events, such as pregnancy, bring about significant changes in metabolism, and metabolic status may affect reproductive function in mammals. In females, the regulation of reproduction and energy balance is controlled by the fluctuations of oestradiol and progesterone throughout the menstrual cycle. Neurosteroids play a key role in the neuroendocrine control of reproduction. The synthesis of neuroestradiol and neuroprogesterone within the brain is a crucial process that facilitates the release of GnRH and LH, which in turn, regulate the transition from oestrogen-negative to oestrogen-positive feedback. In addition to their function in the reproductive system, oestrogen has a key role in the regulation of energy homoeostasis by acting at central and peripheral levels. The oestrogenic effects on body weight homoeostasis are primarily mediated by oestrogen receptors-α (ERα), which are abundantly expressed in multiple brain regions that are implicated in the regulation of food intake, basal metabolism, thermogenesis, and brown tissue distribution. The tight interplay between energy balance and reproductive physiology is facilitated by shared regulatory pathways, namely POMC, NPY and kisspeptin neurons, which are targets of oestrogen regulation and likely participate in different aspects of the joint control of energy balance and reproductive function. The aim of this review is to present a summary of the progress made in uncovering shared regulatory pathways that facilitate the tight coupling between energy balance and reproductive physiology, as well as their reciprocal interactions and the modulation induced by neurosteroids.

Progesterone Receptor Agonist, Nestorone, Exerts Long-Term Neuroprotective Effects Against Permanent Focal Cerebral Ischemia in Adult and Aged Male Rats

Stroke is a leading cause of death and disability worldwide. Tissue plasminogen activator (tPA) is currently the most effective medicine for stroke; however, it has a narrow therapeutic time window (4.5 h after symptom onset). We demonstrated that nestorone, a progesterone (P4) receptor agonist, exerted neuroprotective effects against transient focal cerebral ischemia 6 h post-ischemic administration in adult male rats. This study examines its effects on permanent focal cerebral ischemia in adult and aged male rats, which are better models for evaluating treatment outcomes in typical stroke patients. Adult (6-month-old) or aged (18-month-old) male rats subjected to permanent middle cerebral artery occlusion (pMCAO) were continuously administered nestorone (10µg/day) or its vehicle (30% hydroxypropyl-β-cyclodextrin) for 7 days via an osmotic pump subcutaneously implanted, starting at 18 h post-pMCAO. Nestorone-treated adult male rats showed marked improvements in behavioral outcomes in the adhesive removal and rotarod tests and a significant reduction in infarct size compared to vehicle-treated rats 9 and 30 days post-pMCAO. The same administration of nestorone resulted in apparently comparable neuroprotective effects in aged male rats. The inflammatory mediator NF-κB/p65 was increased in Iba-1 positive cells 24 h post-pMCAO, but was significantly suppressed by subcutaneous injection of nestorone. These results suggested that nestorone exerts long-term neuroprotective effects against permanent focal cerebral ischemia in adult and aged male rats. Nestorone is thus a promising agent for post-stroke treatment owing to its wide age-independent therapeutic time window (18 h after symptom onset), which is longer than that of tPA therapy.

Understanding the Biological Relationship between Migraine and Depression

Migraine is a highly prevalent neurological disorder. Among the risk factors identified, psychiatric comorbidities, such as depression, seem to play an important role in its onset and clinical course. Patients with migraine are 2.5 times more likely to develop a depressive disorder; this risk becomes even higher in patients suffering from chronic migraine or migraine with aura. This relationship is bidirectional, since depression also predicts an earlier/worse onset of migraine, increasing the risk of migraine chronicity and, consequently, requiring a higher healthcare expenditure compared to migraine alone. All these data suggest that migraine and depression may share overlapping biological mechanisms. Herein, this review explores this topic in further detail: firstly, by introducing the common epidemiological and risk factors for this comorbidity; secondly, by focusing on providing the cumulative evidence of common biological aspects, with a particular emphasis on the serotoninergic system, neuropeptides such as calcitonin-gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP), substance P, neuropeptide Y and orexins, sexual hormones, and the immune system; lastly, by remarking on the future challenges required to elucidate the etiopathological mechanisms of migraine and depression and providing updated information regarding new key targets for the pharmacological treatment of these clinical entities.

Progesterone distribution in the trigeminal system and its role to modulate sensory neurotransmission: influence of sex

BACKGROUND

Women are disproportionately affected by migraine, representing up to 75% of all migraine cases. This discrepancy has been proposed to be influenced by differences in hormone levels between the sexes. One such hormone is progesterone. Calcitonin gene-related peptide (CGRP) system is an important factor in migraine pathophysiology and could be influenced by circulating hormones. The purpose of this study was to investigate the distribution of progesterone and its receptor (PR) in the trigeminovascular system, and to examine the role of progesterone to modulate sensory neurotransmission.

METHODS

Trigeminal ganglion (TG), hypothalamus, dura mater, and the basilar artery from male and female rats were carefully dissected. Expression of progesterone and PR proteins, and mRNA levels from TG and hypothalamus were analyzed by immunohistochemistry and real-time quantitative PCR. CGRP release from TG and dura mater were measured using an enzyme-linked immunosorbent assay. In addition, the vasomotor effect of progesterone on male and female basilar artery segments was investigated with myography.

RESULTS

Progesterone and progesterone receptor -A (PR-A) immunoreactivity were found in TG. Progesterone was located predominantly in cell membranes and in Aδ-fibers, and PR-A was found in neuronal cytoplasm and nucleus, and in satellite glial cells. The number of positive progesterone immunoreactive cells in the TG was higher in female compared to male rats. The PR mRNA was expressed in both hypothalamus and TG; however, the PR expression level was significantly higher in the hypothalamus. Progesterone did not induce a significant change neither in basal level nor upon stimulated release of CGRP from dura mater or TG in male or female rats when compared to the vehicle control. However, pre-treated with 10 µM progesterone weakly enhanced capsaicin induced CGRP release observed in the dura mater of male rats. Similarly, in male basilar arteries, progesterone significantly amplified the dilation in response to capsaicin.

CONCLUSIONS

In conclusion, these results highlight the potential for progesterone to modulate sensory neurotransmission and vascular responses in a complex manner, with effects varying by sex, tissue type, and the nature of the stimulus. Further investigations are needed to elucidate the underlying mechanisms and physiological implications of these findings.

Network pharmacology and topological analysis on tibolone metabolites and their molecular mechanisms in traumatic brain injury

Traumatic brain injury (TBI) is a pathology of great social impact, affecting millions of people worldwide. Despite the scientific advances to improve the management of TBI in recent years, we still do not have a specific treatment that controls the inflammatory process after mechanical trauma. The discovery and implementation of new treatments is a long and expensive process, making the repurpose of approved drugs for other pathologies a clinical interest. Tibolone is a drug in use for the treatment of symptoms associated with menopause and has been shown to have a broad spectrum of actions by regulating estrogen, androgen and progesterone receptors, whose activation exerts potent anti-inflammatory and antioxidant effects. In the present study, we aimed to investigate the therapeutic potential of the tibolone metabolites 3α-Hydroxytibolone, 3β-Hydroxytibolone, and Δ4-Tibolone as a possible therapy in TBI using network pharmacology and network topology analysis. Our results demonstrate that the estrogenic component mediated by the α and β metabolites can regulate synaptic transmission and cell metabolism, while the Δ metabolite may be involved in modulating the post-TBI inflammatory process. We identified several molecular targets, including KDR, ESR2, AR, NR3C1, PPARD, and PPARA, which are known to play critical roles in the pathogenesis of TBI. Tibolone metabolites were predicted to regulate the expression of key genes involved in oxidative stress, inflammation, and apoptosis. Overall, the repurposing of tibolone as a neuroprotective treatment for TBI holds promise for future clinical trials. However, further studies are needed to confirm its efficacy and safety in TBI patients.

Neurosteroid enantiomers as potentially novel neurotherapeutics

Endogenous neurosteroids and synthetic neuroactive steroids (NAS) are important targets for therapeutic development in neuropsychiatric disorders. These steroids modulate major signaling systems in the brain and intracellular processes including inflammation, cellular stress and autophagy. In this review, we describe studies performed using unnatural enantiomers of key neurosteroids, which are physiochemically identical to their natural counterparts except for rotation of polarized light. These studies led to insights in how NAS interact with receptors, ion channels and intracellular sites of action. Certain effects of NAS show high enantioselectivity, consistent with actions in chiral environments and likely direct interactions with signaling proteins. Other effects show no enantioselectivity and even reverse enantioselectivity. The spectrum of effects of NAS enantiomers raises the possibility that these agents, once considered only as tools for preclinical studies, have therapeutic potential that complements and in some cases may exceed their natural counterparts. Here we review studies of NAS enantiomers from the perspective of their potential development as novel neurotherapeutics.

Sex and Brain: The Role of Sex Chromosomes and Hormones in Brain Development and Parkinson's Disease

Sex hormones and genes on the sex chromosomes are not only key factors in the regulation of sexual differentiation and reproduction but they are also deeply involved in brain homeostasis. Their action is crucial for the development of the brain, which presents different characteristics depending on the sex of individuals. The role of these players in the brain is fundamental in the maintenance of brain function during adulthood as well, thus being important also with respect to age-related neurodegenerative diseases. In this review, we explore the role of biological sex in the development of the brain and analyze its impact on the predisposition toward and the progression of neurodegenerative diseases. In particular, we focus on Parkinson's disease, a neurodegenerative disorder that has a higher incidence in the male population. We report how sex hormones and genes encoded by the sex chromosomes could protect from the disease or alternatively predispose toward its development. We finally underline the importance of considering sex when studying brain physiology and pathology in cellular and animal models in order to better understand disease etiology and develop novel tailored therapeutic strategies.

Therapeutic potential of progesterone in spinal cord injury-induced neuropathic pain: At the crossroads between neuroinflammation and N-methyl-D-aspartate receptor

In recent decades, an area of active research has supported the notion that progesterone promotes a wide range of remarkable protective actions in experimental models of nervous system trauma or disease, and has also provided a strong basis for considering this steroid as a promising molecule for modulating the complex maladaptive changes that lead to neuropathic pain, especially after spinal cord injury. In this review, we intend to give the readers a brief appraisal of the main mechanisms underlying the increased excitability of the spinal circuit in the pain pathway after trauma, with particular emphasis on those mediated by the activation of resident glial cells, the subsequent release of proinflammatory cytokines and their impact on N-methyl-D-aspartate receptor function. We then summarize the available preclinical data pointing to progesterone as a valuable repurposing molecule for blocking critical cellular and molecular events that occur in the dorsal horn of the injured spinal cord and are related to the development of chronic pain. Since the treatment and management of neuropathic pain after spinal injury remains challenging, the potential therapeutic value of progesterone opens new traslational perspectives to prevent central pain.

Role of allopregnanolone-mediated γ-aminobutyric acid A receptor sensitivity in the pathogenesis of premenstrual dysphoric disorder: Toward precise targets for translational medicine and drug development

Premenstrual dysphoric disorder (PMDD) can be conceptualized as a disorder of suboptimal sensitivity to neuroactive steroid hormones. Its core symptoms (emotional instability, irritability, depression, and anxiety) are related to the increase of stress sensitivity due to the fluctuation of hormone level in luteal phase of the menstrual cycle. In this review, we describe the emotional regulatory effect of allopregnanolone (ALLO), and summarize the relationship between ALLO and γ-aminobutyric acid A (GABA_A) receptor subunits based on rodent experiments and clinical observations. A rapid decrease in ALLO reduces the sensitivity of GABA_A receptor, and reduces the chloride influx, hindered the inhibitory effect of GABAergic neurons on pyramidal neurons, and then increased the excitability of pyramidal neurons, resulting in PMDD-like behavior. Finally, we discuss in depth the treatment of PMDD with targeted GABA_A receptors, hoping to find a precise target for drug development and subsequent clinical application. In conclusion, PMDD pathophysiology is rooted in GABA_A receptor sensitivity changes caused by rapid changes in ALLO levels. Targeting GABA_A receptors may alleviate the occurrence of PMDD.

Progestogens exhibit progestogen-, promoter- and isoform-specific effects via the progesterone receptor

Hormonal contraceptives (HCs) and hormone replacement therapy (HRT) are therapies designed to target the progesterone receptor (PR) to prevent unwanted pregnancy and to alleviate the symptoms of menopause, respectively, in women. Although these therapies are widely used globally, few studies have investigated in parallel how the transcriptional responses of the progestogens used in these therapies compare to each other via the PR isoforms (PR-A and PR-B). Using dose-response promoter-reporter and endogenous gene expression assays, we compared the transcriptional responses of six widely-used progestogens via each PR isoform. The present study shows that progestogens exhibit progestogen-specific potencies and efficacies via both PR isoforms. In addition, the endogenous gene expression data reveals that progestogens exhibit promoter-specific effects. Furthermore, this study reveals that progestogen responses via PR-A are significantly more potent and less efficacious than those observed via PR-B, and that this is unlikely due to differences in PR protein levels. Correlation analysis revealed that there is no detectable correlation between potency or efficacy of progestogens for PR-B or PR-A versus reported relative binding affinity (RBA) of progestogens for the PR, consistent with complex mechanisms of PR regulation. Taken together, our data show that it cannot be assumed that all progestogens have similar transcriptional responses on all genes. Since the PR plays a role in cognition, regulation of inflammation, mitochondrial function, neurogenesis, female reproduction and disease, the data suggest that these important physiological functions could be differentially affected depending on progestogen, promoter, and ratios of PR isoforms.

Hormonal contraceptives, stress, and the brain: The critical need for animal models

Hormonal contraceptives are among the most important health and economic developments in the 20thCentury, providing unprecedented reproductive control and a range of health benefits including decreased premenstrual symptoms and protections against various cancers. Hormonal contraceptives modulate neural function and stress responsivity. These changes are usually innocuous or even beneficial, including their effects onmood. However, in approximately 4-10% of users, or up to 30 million people at any given time, hormonal contraceptives trigger depression or anxiety symptoms. How hormonal contraceptives contribute to these responses and who is at risk for adverse outcomes remain unknown. In this paper, we discussstudies of hormonal contraceptive use in humans and describe the ways in which laboratory animal models of contraceptive hormone exposure will be an essential tool for expanding findings to understand the precise mechanisms by which hormonal contraceptives influence the brain, stress responses, and depression risk.

Reduced Hippocampal and Anterior Cingulate Expression of Antioxidant Enzymes and Membrane Progesterone Receptors in Alzheimer's Disease with Depression

BACKGROUND

Major depressive disorder (MDD) is a risk factor for dementia including that caused by Alzheimer's disease (AD). Both MDD and AD have a higher prevalence in women than men, and estrogen-related processes have been implicated in this sex difference.

OBJECTIVE

To identify if enhanced oxidative stress and decreased expression of the memory enhancer insulin-like growth factor 2 (IGF2), each implicated separately in MDD and AD, are exaggerated in individuals with both AD and MDD compared to those with AD.

METHODS

Expression of target genes are determined by qPCR in postmortem hippocampus (Hip) and anterior cingulate cortex (ACC) of individuals with dementia and autopsy confirmed AD and those of AD+MDD.

RESULTS

Transcript levels of the antioxidant enzymes catalase (CAT) and superoxide dismutase 1 (SOD1), as well as IGF2 and its receptor (IGF2R) were significantly lower in the Hip and ACC of individuals with both AD and MDD compared to those with AD and no MDD. Expressions of Progestin and AdipoQ Receptor Family Member 7 (PAQR7, alias progesterone receptor alpha, mPRa) and PAQR8 (mPRβ), receptors that bind neurosteroids, were also lower in the Hip and ACC of AD+MDD samples compared to those of AD without MDD. Correlations among these transcripts revealed that estrogen receptor 2 (ESR2) and mPR β are direct or indirect regulators of the expression of the antioxidant enzymes and IGF2R.

CONCLUSION

Reduced levels of antioxidant enzymes, decreased IGF2 expression, and diminished estrogen or membrane progesterone receptor-dependent processes might be more pronounced in the subpopulation of individuals with AD and MDD than without MDD.

Network pharmacology and in vitro studies reveal the pharmacological effects and molecular mechanisms of Shenzhi Jiannao prescription against vascular dementia

Background

Shenzhi Jiannao (SZJN) prescription is a type of herbal formula adopted in the management of cognitive impairment and related disorders. However, its effects and related regulatory mechanisms on vascular dementia (VD) are elusive. Herein, network pharmacology prediction was employed to explore the pharmacological effects and molecular mechanisms of SZJN prescription on VD using network pharmacology prediction, and validated the results through in vitro experiments.

Methods

Through a search in the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) database, chemical composition and targets for SZJN prescription were retrieved. The potential targets for VD were then obtained from the GeneCards and DisGeNET databases. The network was constructed that depicted the interactions between putative SZJN prescription and known therapeutic targets for VD using Cytoscape 3.7.1. Analysis of protein-protein interaction was achieved via STRING 11.0 software, followed by Gene Ontology (GO) functional enrichment and Kyoto Gene and Genome Encyclopedia (KEGG) pathway analyses. To validate the computer-predicted results, in vitro experiments based on an excitotoxic injury model were designed using glutamate-exposed PC12 cells, and treated with varying concentrations (low, 0.05; medium, 0.1 and high, 0.2 mg/mL) of SZJN prescription. Cell viability and cell death were detected using the IncuCyte imaging system. Moreover, the expression profiles of Caspase-3 were analyzed through qRT-PCR.

Results

Twenty-eight potentially active ingredients for SZJN prescription, including stigmasterol, beta-sitosterol, and kaempferol, plus 21 therapeutic targets for VD, including PTGS2, PTGS1, and PGR were revealed. The protein-protein interaction network was employed for the analysis of 20 target proteins, including CASP3, JUN, and AChE. The enrichment analysis demonstrated candidate targets of SZJN prescription were more frequently involved in neuroactive ligand-receptor interaction, calcium, apoptosis, and cholinergic synaptic signaling pathways. In vitro experiments revealed that SZJN prescription could significantly reverse glutamate-induced cell viability loss and cell death, and lower the levels of Caspase-3 mRNA in glutamate-induced PC12 cells.

Conclusions

Collectively, this study demonstrated that SZJN prescription exerted the effect of treating VD by regulating multi-targets and multi-channels with multi-components through the method of network pharmacology. Furthermore, in vitro results confirmed that SZJN prescription attenuated glutamate-induced neurotoxicity.

Does inflammation mediate behavioural alterations in anaesthesia-induced developmental neurotoxicity?

Anaesthesia exposure early in life potentially impairs neurobehavioural development. A recent study in the Journal investigated the possibility that progesterone mitigates anaesthesia-induced developmental neurotoxicity in neonatal rats exposed to sevoflurane. The novel findings show that the steroid hormone progesterone protects against development of behavioural alterations caused by sevoflurane. The protective mechanism is proposed to relate to anti-inflammatory properties of progesterone, which brings up important questions regarding the role of inflammation in mediating the neurobehavioural alterations in anaesthesia-induced developmental neurotoxicity. We discuss this mechanism and encourage new research that may clarify the underlying mechanisms of progesterone-induced protection and extend these findings into a translational model.

Risk Factors for Retinal Ganglion Cell Distress in Glaucoma and Neuroprotective Potential Intervention

Retinal ganglion cells (RGCs) are a population of neurons of the central nervous system (CNS) extending with their soma to the inner retina and with their axons to the optic nerve. Glaucoma represents a group of neurodegenerative diseases where the slow progressive death of RGCs results in a permanent loss of vision. To date, although Intra Ocular Pressure (IOP) is considered the main therapeutic target, the precise mechanisms by which RGCs die in glaucoma have not yet been clarified. In fact, Primary Open Angle Glaucoma (POAG), which is the most common glaucoma form, also occurs without elevated IOP. This present review provides a summary of some pathological conditions, i.e., axonal transport blockade, glutamate excitotoxicity and changes in pro-inflammatory cytokines along the RGC projection, all involved in the glaucoma cascade. Moreover, neuro-protective therapeutic approaches, which aim to improve RGC degeneration, have also been taken into consideration.

Selective ligands of membrane progesterone receptors as a key to studying their biological functions in vitro and in vivo

Progesterone modulates many processes in the body, acting through nuclear receptors (nPR) in various organs and tissues. However, a number of effects are mediated by membrane progesterone receptors (mPRs), which are members of the progestin and adipoQ (PAQR) receptor family. These receptors are found in most tissues and immune cells. They are expressed in various cancer cells and appear to play an important role in the development of tumors. The role of mPRs in the development of insulin resistance and metabolic syndrome has also attracted attention. Since progesterone efficiently binds to both nPRs and mPRs, investigation of the functions of the mPRs both at the level of the whole body and at the cell level requires ligands that selectively interact with mPRs, but not with nPRs, with an affinity comparable with that of the natural hormone. The development of such ligands faces difficulties primarily due to the lack of data on the three-dimensional structure of the ligand-binding site of mPR. This review is the first attempt to summarize available data on the structures of compounds interacting with mPRs and analyze them in terms of the differences in binding to membrane and nuclear receptors. Based on the identified main structural fragments of molecules, which affect the efficiency of binding to mPRs and are responsible for the selectivity of interactions, we propose directions of modification of the steroid scaffold to create new selective mPRs ligands.

Exposure of Adult Female Mice to Low Doses of di(2-ethylhexyl) Phthalate Alone or in an Environmental Phthalate Mixture: Evaluation of Reproductive Behavior and Underlying Neural Mechanisms

BACKGROUND

We have previously shown that adult male mice exposure to low doses of an ubiquitous endocrine disruptor, di(2-ethylhexyl) phthalate (DEHP), alters courtship behavior.

OBJECTIVE

The effects of adult exposure to low doses of DEHP alone or in an environmental phthalate mixture on estrous cyclicity, reproductive behavior, and underlying neural structures were analyzed in female mice.

METHODS

Two-month-old C57BL/6J females were exposed orally for 6 wk to DEHP alone (0, 5 or 50μg/kg/d) or to DEHP (5μg/kg/d) in a phthalate mixture. Estrous cyclicity was analyzed in intact mice, and behavior [lordosis, olfactory preference, partner preference, ability to stimulate male ultrasonic vocalizations (USVs)] was measured in ovariectomized mice primed with estradiol and progesterone. Immunohistochemical studies were conducted in the neural structures involved in behavior for estrogen receptor (ER) α and progesterone receptor (PR).

RESULTS

Exposure to DEHP alone or in mixture lengthened the estrous cycle duration, with a shorter proestrus and longer estrus and metestrus stages. Under normalized hormonal levels, females exposed to DEHP alone or in mixture exhibited altered olfactory preference. A lower lordosis behavior and ability to attract and stimulate male emission of courtship USVs was observed, probably due to modifications of pheromonal emission in exposed females. The behavioral alterations were associated with a lower number of PR-expressing neurons, without changes in ERα, in the neural circuitry underlying sexual behavior. The majority of effects observed was comparable between the two DEHP doses and were driven by DEHP in the mixture.

CONCLUSIONS

Exposure to environmental doses of DEHP alone or in mixture altered several components of female sexual behavior in mice, probably through selective disruption of neural PR signaling. Together with the previously reported vulnerability of male mice, this finding suggests a major impact of exposure to phthalates on sexual reproduction, including in other species with similar neural regulatory processes. https://doi.org/10.1289/EHP7662.

Botanical Drug Puerarin Promotes Neuronal Survival and Neurite Outgrowth against MPTP/MPP+-Induced Toxicity via Progesterone Receptor Signaling

Background

Progesterone receptor (PR) modulates neuroprotective and regenerative responses in Parkinson's disease and related neurological diseases.

Objectives

The present study was designed to determine whether botanical drug puerarin could exhibit neuroprotective and neurorestorative activities via PR signaling.

Methods

The neuroprotective and neurotrophic activities of puerarin were investigated in MPTP-lesioned mice and MPP⁺-challenged primary rat midbrain neurons. Rotarod performance test and tail suspension test were used to assess motor functions. Tyrosine hydroxylase (TH) and PR were determined by immunostaining, Western blotting, and luciferase reporter assays. Neurite outgrowth was assessed by fluorescence staining and immunostaining.

Results

Puerarin effectively ameliorated the MPTP-induced motor abnormalities in MPTP-lesioned mice and protected primary rat midbrain neurons against MPP⁺-induced toxicity via PR signaling although progesterone exhibited the neuroprotection. PR antagonist mifepristone (RU486) diminished the neuroprotection of puerarin in MPTP-lesioned mice and MPP⁺-induced primary rat midbrain neurons. Moreover, puerarin promoted the differentiation of primary rat midbrain neurons and potentiated NGF to induce neuritogenesis in PC12 cells. RU486 and PR-siRNA could inhibit the effect of puerarin. Puerarin and progesterone could enhance the PR promoter.

Conclusion

Puerarin attenuated MPTP- and MPP⁺-induced toxicity and potentiated neurite outgrowth via PR. These results suggested that puerarin may become an alternative hormone for suppressing MPTP- and MPP⁺-induced toxicity in neurodegenerative diseases.

A critical evaluation of some of the recent so-called 'evidence' for the involvement of vertebrate-type sex steroids in the reproduction of mollusks

Many studies on the control of reproduction in mollusks have focused on hormones (and proteins associated with the production and signaling of those hormones) which were originally discovered in humans, in the belief that if they are also present in mollusks, they must have the same role. However, although human sex steroids can be found in mollusks, they are so readily absorbed that their presence is not necessarily evidence of endogenous synthesis. A homolog of the vertebrate nuclear estrogen receptor has been found in mollusks, but it does not bind to estrogens or indeed to any steroid at all. Antibodies against human aromatase show positive immunostaining in mollusks, yet the aromatase gene has not been found in the genome of any invertebrates (let alone mollusks). This review will deal with these and other examples of contradictory evidence for a role of human hormones in invertebrate reproduction.

Progesterone in the Brain: Hormone, Neurosteroid and Neuroprotectant

Progesterone has a broad spectrum of actions in the brain. Among these, the neuroprotective effects are well documented. Progesterone neural effects are mediated by multiple signaling pathways involving binding to specific receptors (intracellular progesterone receptors (PR); membrane-associated progesterone receptor membrane component 1 (PGRMC1); and membrane progesterone receptors (mPRs)) and local bioconversion to 3α,5α-tetrahydroprogesterone (3α,5α-THPROG), which modulates GABA_A receptors. This brief review aims to give an overview of the synthesis, metabolism, neuroprotective effects, and mechanism of action of progesterone in the rodent and human brain. First, we succinctly describe the biosynthetic pathways and the expression of enzymes and receptors of progesterone; as well as the changes observed after brain injuries and in neurological diseases. Then, we summarize current data on the differential fluctuations in brain levels of progesterone and its neuroactive metabolites according to sex, age, and neuropathological conditions. The third part is devoted to the neuroprotective effects of progesterone and 3α,5α-THPROG in different experimental models, with a focus on traumatic brain injury and stroke. Finally, we highlight the key role of the classical progesterone receptors (PR) in mediating the neuroprotective effects of progesterone after stroke.

Anti-apoptotic Actions of Allopregnanolone and Ganaxolone Mediated Through Membrane Progesterone Receptors (PAQRs) in Neuronal Cells

The neurosteroids progesterone and allopregnanolone regulate numerous neuroprotective functions in neural tissues including inhibition of epileptic seizures and cell death. Many of progesterone's actions are mediated through the nuclear progesterone receptor (PR), while allopregnanolone is widely considered to be devoid of hormonal activity and instead acts through modulation of GABA-_A receptor activity. However, allopregnanolone can also exert hormonal actions in neuronal cells through binding and activating membrane progesterone receptors (mPRs) belonging to the progestin and adipoQ receptor (PAQR) family. The distribution and functions of the five mPR subtypes (α, β, γ, δ, ε) in neural tissues are briefly reviewed. mPRδ has the highest binding affinity for allopregnanolone and is highly expressed throughout the human brain. Low concentrations (20 nM) of allopregnanolone act through mPRδ to stimulate G protein (G_s)-dependent signaling pathways resulting in reduced cell death and apoptosis in mPRδ-transfected cells. The 3-methylated synthetic analog of allopregnanolone, ganaxolone, is currently undergoing clinical trials as a promising GABA-_A receptor-selective antiepileptic drug (AED). New data show that low concentrations (20 nM) of ganaxolone also activate mPRδ signaling and exert anti-apoptotic actions through this receptor. Preliminary evidence suggests that ganaxolone can also exert neuroprotective effects by activating inhibitory G protein (G_i)-dependent signaling through mPRα and/or mPRβ in neuronal cells. The results indicate that mPRs are likely intermediaries in multiple actions of natural and synthetic neurosteroids in the brain. Potential off-target effects of ganaxolone through activation of mPRs in patients receiving long-term treatment for epilepsy and other disorders should be considered and warrant further investigation.