GPER1 stimulation alters posttranslational modification of RGSz1 and induces desensitization of 5-HT1A receptor signaling in the rat hypothalamus

Exploring the promise of regulator of G Protein Signaling 20: insights into potential mechanisms and prospects across solid cancers and hematological malignancies

RGS (Regulator of G protein signaling) proteins have long captured the fascination of researchers due to their intricate involvement across a wide array of signaling pathways within cellular systems. Their diverse and nuanced functions have positioned them as continual subjects of scientific inquiry, especially given the implications of certain family members in various cancer types. Of particular note in this context is RGS20, whose clinical relevance and molecular significance in hepatocellular carcinoma we have recently investigated. These investigations have prompted questions into the prevalence of pathogenic mutations within the RGS20 gene and the intricate network of interacting proteins that could contribute to the complex landscape of cancer biology. In our study, we aim to unravel the mutations within the RGS20 gene and the multifaceted interplay between RGS20 and other proteins within the context of cancer. Expanding on this line of inquiry, our research is dedicated to uncovering the intricate mechanisms of RGS20 in various cancers. In particular, we have redirected our attention to examining the role of RGS20 within hematological malignancies, with a specific focus on multiple myeloma and follicular lymphoma. These hematological cancers hold significant promise for further investigation, as understanding the involvement of RGS20 in their pathogenesis could unveil novel therapeutic strategies and treatment avenues. Furthermore, our exploration has extended to encompass the latest discoveries concerning the potential involvement of RGS20 in diseases affecting the central nervous system, thereby broadening the scope of its implications beyond oncology to encompass neurobiology and related fields.

Does GPER1 Play a Role in Sexual Dimorphism?

Estrogens are critical in driving sex-typical social behaviours that are ethologically relevant in mammals. This is due to both production of local estrogens and signaling by these ligands, particularly in an interconnected set of nuclei called the social behavioural network (SBN). The SBN is a sexually dimorphic network studied predominantly in rodents that is thought to underlie the display of social behaviour in mammals. Signalling by the predominant endogenous estrogen, 17β-estradiol, can be either via the classical genomic or non-classical rapid pathway. In the classical genomic pathway, 17β-estradiol binds the intracellular estrogen receptors (ER) α and β which act as ligand-dependent transcription factors to regulate transcription. In the non-genomic pathway, 17β-estradiol binds a putative plasma membrane ER (mER) such as GPR30/GPER1 to rapidly signal via kinases or calcium flux. Though GPER1's role in sexual dimorphism has been explored to a greater extent in cardiovascular physiology, less is known about its role in the brain. In the last decade, activation of GPER1 has been shown to be important for lordosis and social cognition in females. In this review we will focus on several mechanisms that may contribute to sexually dimorphic behaviors including the colocalization of these estrogen receptors in the SBN, interplay between the signaling pathways activated by these different estrogen receptors, and the role of these receptors in development and the maintenance of the SBN, all of which remain underexplored.

Hypothalamic paraventricular nucleus neurons activated by estrogen GPER1 receptors promote anti-inflammation effects in the early stage of colitis

The hypothalamus-pituitary-adrenal (HPA) axis is known to mediate gut-brain interaction, and the pathological inflammatory process in the intestine can induce HPA axis involved 'fight or flight' response to suppress or facilitate intestinal inflammation. Hypothalamic paraventricular nucleus (PVN) neurons are responsible for controlling the HPA axis activity, but their exact role in modulating intestinal inflammation remains unclear. In this study, we used the dextran sulfate sodium (DSS)-induced mice colitis model, gene editing, and RNA interference to determine the effects of PVN neurons on intestinal inflammation. We found that at the early stage (third day) after DSS treatment, there was a mild inflammation in the colorectal area and an increased neuron activation in the PVN but not in the adjacent area. At the same time, ~80% of activated PVN neurons also expressed novel estrogen GPER1 receptor. The colitis noticeably worsened in GPER1-knockout mice and local PVN GPER1-knockdown mice. These results indicated that PVN GPER1 positive neurons potentially have a protective function during the early stages of DSS-induced colitis, and this may be a mechanism by which the central nervous system attempts to suppress intestinal inflammation to achieve self-protection.

The Steroidogenesis Inhibitor Finasteride Reduces the Response to Both Stressful and Rewarding Stimuli

Finasteride (FIN) is the prototypical inhibitor of steroid 5α-reductase (5αR), the enzyme that catalyzes the rate-limiting step of the conversion of progesterone and testosterone into their main neuroactive metabolites. FIN is clinically approved for the treatment of benign prostatic hyperplasia and male baldness; while often well-tolerated, FIN has also been shown to cause or exacerbate psychological problems in vulnerable subjects. Evidence on the psychological effects of FIN, however, remains controversial, in view of inconsistent clinical reports. Here, we tested the effects of FIN in a battery of tests aimed at capturing complementary aspects of mood regulation and stress reactivity in rats. FIN reduced exploratory, incentive, prosocial, and risk-taking behavior; furthermore, it decreased stress coping, as revealed by increased immobility in the forced-swim test (FST). This last effect was also observed in female and orchiectomized male rats, suggesting that the mechanism of action of FIN does not primarily reflect changes in gonadal steroids. The effects of FIN on FST responses were associated with a dramatic decrease in corticotropin release hormone (CRH) mRNA and adrenocorticotropic hormone (ACTH) levels. These results suggest that FIN impairs stress reactivity and reduces behavioral activation and impulsive behavior by altering the function of the hypothalamus-pituitary-adrenal (HPA) axis.

Serotonin-estrogen interactions: What can we learn from pregnancy?

We have reviewed the scientific literature related to four diseases in which to serotonin (5-HT) is involved in the etiology, herein named 5-HT-linked diseases, and whose prevalence is influenced by estrogenic status: depression, migraine, irritable bowel syndrome and eating disorders. These diseases all have in common a sex-dimorphic prevalence, with women more frequently affected than men. The co-occurrence between these 5-HT-linked diseases suggests that they have common physiopathological mechanisms. In most 5-HT-linked diseases (except for anorexia nervosa and irritable bowel syndrome), a decrease in the serotonergic tone is observed and estrogens are thought to contribute to the improvement of symptoms by stimulating the serotonergic system. Human pregnancy is characterized by a unique 5-HT and estrogen synthesis by the placenta. Pregnancy-specific disorders, such as hyperemesis gravidarum, gestational diabetes mellitus and pre-eclampsia, are associated with a hyperserotonergic state and decreased estrogen levels. Fetal programming of 5-HT-linked diseases is a complex phenomenon that involves notably fetal-sex differences, which suggest the implication of sex steroids. From a mechanistic point of view, we hypothesize that estrogens regulate the serotonergic system, resulting in a protective effect against 5-HT-linked diseases, but that, in turn, 5-HT affects estrogen synthesis in an attempt to retrieve homeostasis. These two processes (5-HT and estrogen biosynthesis) are crucial for successful pregnancy outcomes, and thus, a disruption of this 5-HT-estrogen relationship may explain pregnancy-specific pathologies or pregnancy complications associated with 5-HT-linked diseases.

The Role of G-proteins and G-protein Regulating Proteins in Depressive Disorders

Progress toward new antidepressant therapies has been relatively slow over the past few decades, with the result that individuals suffering from depression often struggle to find an effective treatment – a process often requiring months. Furthermore, the neural factors that contribute to depression remain poorly understood, and there are many open questions regarding the mechanism of action of existing antidepressants. A better understanding of the molecular processes that underlie depression and contribute to antidepressant efficacy is therefore badly needed. In this review we highlight research investigating the role of G-proteins and the regulators of G-protein signaling (RGS) proteins, two protein families that are intimately involved in both the genesis of depressive states and the action of antidepressant drugs. Many antidepressants are known to indirectly affect the function of these proteins. Conversely, dysfunction of the G-protein and RGS systems can affect antidepressant efficacy. However, a great deal remains unknown about how these proteins interact with antidepressants. Findings pertinent to each individual G-protein and RGS protein are summarized from in vitro, in vivo, and clinical studies.

Serum levels of GPER-1 in euthymic bipolar patients

INTRODUCTION

Estrogen and its receptors have been suggested as playing a role in the pathogenesis of bipolar disorder (BD). Estrogen functions through the estrogen receptors alpha and beta and the recently discovered G-protein-coupled estrogen receptor-1 (GPER-1). The aim of this study was to evaluate serum GPER-1 levels in euthymic BD patients.

PATIENTS AND METHODS

The study population consisted of 38 euthymic outpatients meeting the criteria for BD in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition and 35 age- and gender-matched healthy controls. Medical histories were obtained and physical examinations and laboratory tests conducted.

RESULTS

Serum GPER-1 levels were measured in both patients and controls and found to be significantly higher in the BD patients than in controls. These results were not influenced by the medications in use.

CONCLUSION

The results of this study demonstrated that GPER-1 may play a role in BD pathophysiology.

Increased Serum G Protein-coupled Estrogen Receptor 1 Levels and Its Diagnostic Value in Drug Naïve Patients with Major Depressive Disorder

Objective

The facts that depression is more prevalent in females than in males and females are exposed to depression more commonly during certain hormonal fluctuating periods indicate the role of sex hormones in physiopathology. Estrogen acts over estrogen receptors alpha and beta and recently identified G protein-coupled estrogen receptor 1 (GPER1). The present study aimed, for the first time, to evaluate serum GPER1 levels in drug-naïve major depressive disorder (MDD) patients.

Methods

The study included 56 newly diagnosed drug-naïve MDD patients aged between 18 and 50 years and 42 age- and gender-matched healthy volunteers. Medical history was obtained and physical examinations, laboratory tests, and the Hamilton Depression Rating Scale (HAM-D), Hamilton Anxiety Rating Scale (HAM-A) were performed. The serum GPER1 levels were measured.

Results

The HAM-D score was significantly higher in the MDD patients than in the controls. The GPER1 level was significantly higher in the MDD patients than in the controls. A positive correlation was found with GPER1 levels and depression scores. The receiver operating characteristic analysis revealed sensitivity, specificity, positive predictive value, and negative predictive value as 82.1%, 90.5%, 92.0%, and 79.2%, respectively, for the presence of depression, when the serum GPER1 value was ≥0.16.

Conclusion

This study demonstrated significantly higher serum GPER1 levels in the MDD patients than in the controls, a positive correlation was found between GPER1 levels and depression scores and serum GPER1 level was valuable in predicting the presence of depression.

Depressive-like effect of prenatal exposure to DDT involves global DNA hypomethylation and impairment of GPER1/ESR1 protein levels but not ESR2 and AHR/ARNT signaling

Several lines of evidence suggest that exposures to Endocrine Disrupting Chemicals (EDCs) such as pesticides increase the risks of neuropsychiatric disorders. Despite extended residual persistence of dichlorodiphenyltrichloroethane (DDT) in the environment, the mechanisms of perinatal actions of DDT that could account for adult-onset of depression are largely unknown. This study demonstrated the isomer-specific induction of depressive-like behavior and impairment of Htr1a/serotonin signaling in one-month-old mice that were prenatally exposed to DDT. The effects were reversed by the antidepressant citalopram as evidenced in the forced swimming (FST) and tail suspension (TST) tests in the male and female mice. Prenatally administered DDT accumulated in mouse brain as determined with gas chromatography and tandem mass spectrometry, led to global DNA hypomethylation, and altered the levels of methylated DNA in specific genes. The induction of depressive-like behavior and impairment of Htr1a/serotonin signaling were accompanied by p,p'-DDT-specific decrease in the levels of estrogen receptors i.e. ESR1 and/or GPER1 depending on sex. In contrast, o,p'-DDT did not induce depressive-like effects and exhibited quite distinct pattern of biochemical alterations that was related to aryl hydrocarbon receptor (AHR), its nuclear translocator ARNT, and ESR2. Exposure to o,p'-DDT increased AHR expression in male and female brains, and reduced expression levels of ARNT and ESR2 in the female brains. The evolution of p,p'-DDT-induced depressive-like behavior was preceded by attenuation of Htr1a and Gper1/GPER1 expression as observed in the 7-day-old mouse pups. Because p,p'-DDT caused sex- and age-independent attenuation of GPER1, we suggest that impairment of GPER1 signaling plays a key role in the propagation of DDT-induced depressive-like symptoms.

Cooperation of Genomic and Rapid Nongenomic Actions of Estrogens in Synaptic Plasticity

Neuroplasticity refers to the changes in the molecular and cellular processes of neural circuits that occur in response to environmental experiences. Clinical and experimental studies have increasingly shown that estrogens participate in the neuroplasticity involved in cognition, behavior, and memory. It is generally accepted that estrogens exert their effects through genomic actions that occur over a period of hours to days. However, emerging evidence indicates that estrogens also rapidly influence the neural circuitry through nongenomic actions. In this review, we provide an overview of the genomic and nongenomic actions of estrogens and discuss how these actions may cooperate in synaptic plasticity. We then summarize the role of epigenetic modifications, synaptic protein synthesis, and posttranslational modifications, and the splice variants of estrogen receptors in the complicated network of estrogens. The combination of genomic and nongenomic mechanisms endows estrogens with considerable diversity in modulating neural functions including synaptic plasticity.

Epileptogenic effects of G protein-coupled estrogen receptor 1 in the rat pentylenetetrazole kindling model of epilepsy

BACKGROUND

G protein-coupled estrogen receptor 1 (GPER-1) has been demonstrated in several parts of the brain and may play an important role in estrogen downstream signaling pathway. However, the effects of this receptor on epileptic seizure are not clearly known. Therefore, the effects of GPER-1 agonist, G-1, GPER-1 antagonist, G-15 and the main estrogenic hormone, 17β-estradiol were investigated on seizures and brain tissue oxidative damages induced by pentylenetetrazole (PTZ) in rats.

METHODS

In this study, 30 adult male Wistar albino rats were used. Due to intraperitoneal (ip) injections of a subconvulsant dose of PTZ (35mg/kg) which was repeated 12 times every 48h, chemical kindling occurred and kindling seizure was recorded for 30min. The rats were injected with 17β-estradiol (5μg/kg, ip) or G-1 (5μg/kg, ip), G-15 (5μg/kg, ip), Saline, Ethanol and Dimethyl sulfoxide (DMSO) 30min before each dose of PTZ. Observed seizures were classified between the phase 0-5. Thirty minutes later when the last 12. PTZ administration, all rats were sacrificed and the brain cortex, hippocampus sections were removed and the tissue superoxide dismutase (SOD), malondialdehyde (MDA) and nitric oxide (NO) levels on these tissues were studied.

RESULTS

GPER1 agonist, G-1 and estrogenic hormone, 17β-estradiol significantly increased the development of PTZ kindling the seizures. However, GPER1 antagonist, G-15 did not change the development of PTZ kindling the seizures. In the cortex and hippocampus homogenates, the NO levels after G-1 administration had significantly increased (p<0.05) compared to the PTZ groups but SOD activities and MDA levels demonstrated no difference between the groups.

CONCLUSIONS

This is the first study that explores that GPER-1 receptors have epileptogenic effect on PTZ-induced kindling rat. GPER1 may mediate the epileptogenic effect of estrogens by changing the oxidative or anti-oxidative parameters in the brain.