G protein-coupled receptor 30-dependent protein kinase A pathway is critical in nongenomic effects of estrogen in attenuating liver injury after trauma-hemorrhage

Protective effects of 17-β-estradiol on liver injury: The role of TLR4 signaling pathway and inflammatory response

Liver injury, a major global health issue, stems from various causes such as alcohol consumption, nonalcoholic steatohepatitis, obesity, diabetes, metabolic syndrome, hepatitis, and certain medications. The liver's unique susceptibility to ischemia and hypoxia, coupled with the critical role of the gut-liver axis in inflammation, underscores the need for effective therapeutic interventions. The study highlights E2's interaction with estrogen receptors (ERs) and its modulation of the Toll-like receptor 4 (TLR4) signaling pathway as key mechanisms in mitigating liver injury. Activation of TLR4 leads to the release of pro-inflammatory cytokines and chemokines, exacerbating liver inflammation and injury. E2 down-regulates TLR4 expression, reduces oxidative stress, and inhibits pro-inflammatory cytokines, thereby protecting the liver. Both classic (ERα and ERβ) and non-classic [G protein-coupled estrogen receptor (GPER)] receptors are influenced by E2. ERα is particularly crucial for liver regeneration, preventing liver failure by promoting hepatocyte proliferation. Furthermore, E2 exerts anti-inflammatory, antioxidant, and anti-apoptotic effects by inhibiting cytokines such as IL-6, IL-1β, TNF-α, and IL-17, and by reducing lipid peroxidation and free radical damage. The article calls for further clinical research to validate these findings and to develop estrogen-based treatments for liver injuries. Overall, the research emphasizes the significant potential of E2 as a therapeutic agent for liver injuries. It advocates for extensive clinical studies to validate E2 hepatoprotective properties and develop effective estrogen-based treatments.

G protein-coupled receptor 30 activation inhibits ferroptosis and protects chondrocytes against osteoarthritis

Background

Osteoarthritis (OA) is the most common joint disease worldwide, but its cause remains unclear. Oestrogen protects against OA, but its clinical use is limited. G protein-coupled receptor 30 (GPR30) is a receptor that binds oestrogen, and GPR30 treatment has benefitted patients with some degenerative diseases. However, its effects on OA prevention and treatment remain unclear. Moreover, several studies have found that activation of estrogen receptors exerting anti-ferroptosis effects, which plays an important role in chondrocyte survival. Therefore, this study explored the general and ferroptosis-related effects and mechanisms of GPR30 in OA.

Methods

Genome-wide RNA sequencing, western blotting, and immunohistochemistry were used to evaluate GPR30 expression and ferroptosis-related indicators in cartilage tissues from clinical patients. Next, we investigated the effects of G1 (a GPR30 receptor agonist) on the function and pathology of OA in an animal model. We also treated chondrocytes with erastin (ferroptosis agonist) plus G1, G15 (GPR30 receptor antagonist), GPR30 short hairpin RNA, or ferrostatin-1 (ferroptosis inhibitor), then measured cell viability and ferroptosis-related indices and performed proteomics analyses. Finally, western blotting and reverse transcription-polymerase chain reaction were used to assess the effects of G1 on yes-associated protein 1 (YAP1) and ferritin heavy chain 1 (FTH1) expression.

Results

GPR30 expression was lower in the OA cartilage tissues than in the normal tissues, and G1 treatment significantly improved the locomotor ability of mice. Moreover, chondrocyte cell viability significantly decreased after erastin treatment, but G1 treatment concentration-dependently mitigated this effect. Furthermore, G1 treatment decreased phosphorylated YAP1 expression, increased activated YAP1 expression, and increased FTH1 transcription and protein expression, protecting against ferroptosis.

Conclusion

GPR30 activation inhibited ferroptosis in chondrocytes by suppressing YAP1 phosphorylation, which regulates FTH1 expression.The Translational Potential of this Article: These results provide a novel potential target for therapeutic OA interventions.

GPER Acts Through the cAMP/Epac/JNK/AP-1 Pathway to Induce Transcription of Alpha 2C Adrenoceptor in Human Microvascular Smooth Muscle Cells

ABSTRACT

Raynaud's phenomenon, which results from exaggerated cold-induced vasoconstriction, is more prevalent in females than males. We previously showed that estrogen increases the expression of alpha 2C-adrenoceptors (α 2C -AR), the sole mediator of cold-induced vasoconstriction. This effect of estrogen is reproduced by the cell-impermeable form of the hormone (E 2 :bovine serum albumin [BSA]), suggesting a role of the membrane estrogen receptor, G-protein-coupled estrogen receptor [GPER], in E 2 -induced α 2C -AR expression. We also previously reported that E 2 upregulates α 2C -AR in microvascular smooth muscle cells (VSMCs) via the cAMP/Epac/Rap/JNK/AP-1 pathway, and that E 2 :BSA elevates cAMP levels. We, therefore, hypothesized that E 2 uses GPER to upregulate α 2C -AR through the cAMP/Epac/JNK/AP-1 pathway. Our results show that G15, a selective GPER antagonist, attenuates the E 2 -induced increase in α 2C -AR transcription. G-1, a selective GPER agonist, induced α 2C -AR transcription, which was concomitant with elevated cAMP levels and JNK activation. Pretreatment with ESI09, an Epac inhibitor, abolished G-1-induced α 2C -AR upregulation and JNK activation. Moreover, pretreatment with SP600125, a JNK-specific inhibitor, but not H89, a PKA-specific inhibitor, abolished G-1-induced α 2C -AR upregulation. In addition, transient transfection of an Epac dominant negative mutant (Epac-DN) attenuated G-1-induced activation of the α 2C -AR promoter. This inhibitory effect of Epac-DN on the α 2C -AR promoter was overridden by the cotransfection of constitutively active JNK mutant. Furthermore, mutation of AP-1 site in the α 2C -AR promoter abrogated G1-induced expression. Collectively, these results indicate that GPER upregulates α 2C -AR through the cAMP/EPAC/JNK/AP-1 pathway. These findings unravel GPER as a new mediator of cold-induced vasoconstriction, and present it as a potential target for treating Raynaud's phenomenon in estrogen-replete females.

The emerging role of estrogen's non-nuclear signaling in the cardiovascular disease

Sexual dimorphism exists in the epidemiology of cardiovascular disease (CVD), which indicates the involvement of sexual hormones in the pathophysiology of CVD. In particular, ample evidence has demonstrated estrogen's protective effect on the cardiovascular system. While estrogen receptors, bound to estrogen, act as a transcription factor which regulates gene expressions by binding to the specific DNA sequence, a subpopulation of estrogen receptors localized at the plasma membrane induces activation of intracellular signaling, called "non-nuclear signaling" or "membrane-initiated steroid signaling of estrogen". Although the precise molecular mechanism of non-nuclear signaling as well as its physiological impact was unclear for a long time, recent development of genetically modified animal models and pathway-selective estrogen receptor stimulant bring new insights into this pathway. We review the published experimental studies on non-nuclear signaling of estrogen, and summarize its role in cardiovascular system, especially focusing on: (1) the molecular mechanism of non-nuclear signaling; (2) the design of genetically modified animals and pathway-selective stimulant of estrogen receptor.

G protein estrogen receptor as a potential therapeutic target in Raynaud’s phenomenon

Exaggerated cold-induced vasoconstriction can precipitate a pathogenesis called Raynaud’s phenomenon (RP). Interestingly, RP is significantly more prevalent in females than age-matched men, highlighting the potential implication of 17β-estradiol (E2) in the etio-pathogenesis of this disease. Indeed, we have previously reported that E2 stimulates the expression of vascular alpha 2C-adrenoceptors (α2C-AR), the sole mediator of cold-induced constriction of cutaneous arterioles. This induced expression occurs through the cyclic adenosine monophosphate → exchange protein activated by cAMP→ Ras-related protein 1→ c-Jun N-terminal kinase→ activator protein-1 (cAMP/Epac/Rap/JNK/AP-1 pathway). On the basis that estrogen-induced rapid cAMP accumulation and JNK activation occurs so rapidly we hypothesized that a non-classic, plasma membrane estrogen receptor was the mediator. We then showed that an impermeable form of E2, namely E2:BSA, mimics E2 effects suggesting a role for the membranous G-protein coupled estrogen receptor (GPER) in E2-induced α2C-AR expression. Our current working hypothesis and unpublished observations further cement this finding, as G1, a GPER agonist, mimics while G15, a GPER antagonist, abrogates estrogen’s effect on the expression of vascular α2C-AR. These, and other observations, highlight the potential of GPER as a tractable target in the management of RP, particularly in pre-menopausal women.

Membrane-Initiated Estrogen, Androgen, and Progesterone Receptor Signaling in Health and Disease

Rapid effects of steroid hormones were discovered in the early 1950s, but the subject was dominated in the 1970s by discoveries of estradiol and progesterone stimulating protein synthesis. This led to the paradigm that steroid hormones regulate growth, differentiation, and metabolism via binding a receptor in the nucleus. It took 30 years to appreciate not only that some cellular functions arise solely from membrane-localized steroid receptor (SR) actions, but that rapid sex steroid signaling from membrane-localized SRs is a prerequisite for the phosphorylation, nuclear import, and potentiation of the transcriptional activity of nuclear SR counterparts. Here, we provide a review and update on the current state of knowledge of membrane-initiated estrogen (ER), androgen (AR) and progesterone (PR) receptor signaling, the mechanisms of membrane-associated SR potentiation of their nuclear SR homologues, and the importance of this membrane-nuclear SR collaboration in physiology and disease. We also highlight potential clinical implications of pathway-selective modulation of membrane-associated SR.

State-of-the-Art Review: Sex Hormone Therapy in Trauma-Hemorrhage

ABSTRACT

Trauma-hemorrhage is the leading cause of prehospital and early in-hospital deaths, while also significantly contributing to the later development of multisystem organ dysfunction/failure and sepsis. Common and advanced resuscitative methods would potentially demonstrate benefits in the prehospital setting; however, they face a variety of barriers to application and implementation. Thus, a dialogue around a novel adjunct has arisen, sex hormone therapy. Proposed candidates include estradiol and its derivatives, metoclopramide hydrochloride/prolactin, dehydroepiandrosterone, and flutamide; with each having demonstrated a range of salutary effects in several animal model studies. Several retrospective analyses have observed a gender-based dimorphism in mortality following trauma-hemorrhage, thus suggesting that estrogens contribute to this pattern. Trauma-hemorrhage animal models have shown estrogens offer protective effects to the cardiovascular, pulmonary, hepatic, gastrointestinal, and immune systems. Additionally, a series of survival studies utilizing 17α-ethinylestradiol-3-sulfate, a potent, water-soluble synthetic estrogen, have demonstrated a significant survival benefit and beneficial effects on cardiovascular function. This review presents the findings of retrospective clinical studies, preclinical animal studies, and discusses how and why 17α-ethinylestradiol-3-sulfate should be considered for investigation within a prospective clinical trial.

Sex Differences, Estrogen Metabolism and Signaling in the Development of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex and devastating disease with a poor long-term prognosis. While women are at increased risk for developing PAH, they exhibit superior right heart function and higher survival rates than men. Susceptibility to disease risk in PAH has been attributed, in part, to estrogen signaling. In contrast to potential pathological influences of estrogen in patients, studies of animal models reveal estrogen demonstrates protective effects in PAH. Consistent with this latter observation, an ovariectomy in female rats appears to aggravate the condition. This discrepancy between observations from patients and animal models is often called the "estrogen paradox." Further, the tissue-specific interactions between estrogen, its metabolites and receptors in PAH and right heart function remain complex; nonetheless, these relationships are essential to characterize to better understand PAH pathophysiology and to potentially develop novel therapeutic and curative targets. In this review, we explore estrogen-mediated mechanisms that may further explain this paradox by summarizing published literature related to: (1) the synthesis and catabolism of estrogen; (2) activity and functions of the various estrogen receptors; (3) the multiple modalities of estrogen signaling in cells; and (4) the role of estrogen and its diverse metabolites on the susceptibility to, and progression of, PAH as well as their impact on right heart function.

The Hepatoprotective mechanisms of 17β-estradiol after traumatic brain injury in male rats: Classical and non-classical estrogen receptors

Protective effects of estrogen (E2) on traumatic brain injury (TBI) have been determined. In this study, the hepatoprotective effects of E2 after TBI through its receptors and oxidative stress regulation have been evaluated. Diffuse TBI induced by the Marmarou method in male rats. G15, PHTPP, MPP, and ICI182-780 as selective antagonists of E2 were injected before TBI. The results indicated that TBI induces a significant increase in liver enzymes [Alkaline phosphatase (ALP), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Glutamyl transferase (GGT)], and oxidants levels [Malondialdehyde (MDA), Nitric oxide (NO)] and decreases in antioxidant biomarkers [Glutathione peroxidase (GPx) and Superoxide dismutase (SOD)] in the brain and liver, and plasma. We also found that E2 significantly preserved levels of these biomarkers and enzymatic activity. All antagonists inhibited the effects of E2 on increasing SOD and GPx. Also, the effects of E2 on brain MDA levels were inhibited by all antagonists, but in the liver, only ICI + G15 + E2 + TBI group was affected. The impacts of E2 on brain and liver and plasma NO levels were inhibited by all antagonists. The current findings demonstrated that E2 probably improved liver injury after TBI by modulating oxidative stress. Also, both classic (ERβ, ERα) and non-classic [G protein-coupled estrogen receptor (GPER)] receptors are affected in the protective effects of E2.

GPER1 and microRNA: Two Players in Breast Cancer Progression

Breast cancer is the main cause of morbidity and mortality in women worldwide. However, the molecular pathogenesis of breast cancer remains poorly defined due to its heterogeneity. Several studies have reported that G Protein-Coupled Estrogen Receptor 1 (GPER1) plays a crucial role in breast cancer progression, by binding to estrogens or synthetic agonists, like G-1, thus modulating genes involved in diverse biological events, such as cell proliferation, migration, apoptosis, and metastasis. In addition, it has been established that the dysregulation of short sequences of non-coding RNA, named microRNAs (miRNAs), is involved in various pathophysiological conditions, including breast cancer. Recent evidence has indicated that estrogens may regulate miRNA expression and therefore modulate the levels of their target genes, not only through the classical estrogen receptors (ERs), but also activating GPER1 signalling, hence suggesting an alternative molecular pathway involved in breast tumor progression. Here, the current knowledge about GPER1 and miRNA action in breast cancer is recapitulated, reporting recent evidence on the liaison of these two players in triggering breast tumorogenic effects. Elucidating the role of GPER1 and miRNAs in breast cancer might provide new tools for innovative approaches in anti-cancer therapy.

G protein-coupled receptor 30 activation protects hepatic ischemia-reperfusion injury of liver tissue through inhibiting NLRP3 in the rat model

One of the most prominent characteristics of hepatic ischemia-reperfusion injury (HI/R) is an intense inflammatory reaction, which plays a key role in inflammatory injury induced by ischemia-reperfusion. Nucleotide-binding oligomerization domain-containing protein (NOD-), leucine-rich repeat (LRR), and pyrin domains-containing protein 3 (NLRP3) are involved in the inflammatory injury of ischemia-reperfusion as an important pattern recognition receptor for innate immunity. G protein-coupled receptor 30 (GPR30) is a newly identified as 7-transmembrane G protein-coupled receptor and can be activated by many stimulations including estrogen. The current study aims to explore whether GPR30 agonist (G1) can alleviate hepatic ischemia-reperfusion injury HI/R by inhibiting NLRP3. An induced HI/R rat model was generated, blood and liver samples were gathered and subjected to histological examination, biochemical assays, Western blot assays, and qRT-PCR. Our results indicated GPR30 agonist (G1) pretreatment or NLRP3 silencing significantly decreased the serum levels of Interleukin 1β (IL-1β), alanine aminotransferase (ALT) and aspartate aminotransferase, improved histological alterations and hepatocyte apoptosis. Moreover, G1 pretreatment or NLRP3 silencing downregulated the protein level of Caspase-1 and pro-Interleukin 1β (pro-IL-1β) while G1 pretreatment upregulated the expression of GPR30 (p < 0.05). In conclusion, the salutary effects of GPR30 agonists on HI/R are mediated at least in part through downregulating NLRP3 expression. GPR30 may be used as a therapy target of HI/R.

17β-estradiol protects sheep oviduct epithelial cells against lipopolysaccharide-induced inflammation in vitro

Estrogen has known anti-inflammatory effects, but the mechanism whereby 17β-estradiol (E2) protects oviduct sheep epithelial cells from inflammation remains unknown. In this study, we detected the E2 synthetase and E2 nuclear and membrane receptors in sheep oviducts, primarily in epithelial cells. Using lipopolysaccharide (LPS)-stimulated sheep oviduct epithelial cells as an in vitro inflammation model, we demonstrated that E2 attenuates the expression of inflammatory factors in a concentration-response manner. E2 also inhibited the LPS-stimulated phosphorylation of p38 MAPK and NF-κB p65 but did not reduce the phosphorylation of JNK and ERK 1/2. This attenuation was partially antagonized by an intracellular estrogen antagonist that was involved in genomic regulation and enhanced by a G protein-coupled estrogen receptor agonist that was involved in nongenomic cellular modulation. These results suggest that E2 has an inhibitory effect on LPS-induced oviduct epithelial cell inflammation in sheep, which is mediated by the downstream regulatory effects of estrogen receptors.

Neuroendocrine Modulation of the Immune Response after Trauma and Sepsis: Does It Influence Outcome?

Although the treatment of multiple-injured patients has been improved during the last decades, sepsis and multiple organ failure (MOF) still remain the major cause of death. Following trauma, profound alterations of a large number of physiological systems can be observed that may potentially contribute to the development of sepsis and MOF. This includes alterations of the neuroendocrine and the immune system. A large number of studies focused on posttraumatic changes of the immune system, but the cause of posttraumatic immune disturbance remains to be established. However, an increasing number of data indicate that the bidirectional interaction between the neuroendocrine and the immune system may be an important mechanism involved in the development of sepsis and MOF. The aim of this article is to highlight the current knowledge of the neuroendocrine modulation of the immune system during trauma and sepsis.

GPER-induced signaling is essential for the survival of breast cancer stem cells

G protein-coupled estrogen receptor-1 (GPER), a member of the G protein-coupled receptor (GPCR) superfamily, mediates estrogen-induced proliferation of normal and malignant breast epithelial cells. However, its role in breast cancer stem cells (BCSCs) remains unclear. Here we showed greater expression of GPER in BCSCs than non-BCSCs of three patient-derived xenografts of ER- /PR+ breast cancers. GPER silencing reduced stemness features of BCSCs as reflected by reduced mammosphere forming capacity in vitro, and tumor growth in vivo with decreased BCSC populations. Comparative phosphoproteomics revealed greater GPER-mediated PKA/BAD signaling in BCSCs. Activation of GPER by its ligands, including tamoxifen (TMX), induced phosphorylation of PKA and BAD-Ser118 to sustain BCSC characteristics. Transfection with a dominant-negative mutant BAD (Ser118Ala) led to reduced cell survival. Taken together, GPER and its downstream signaling play a key role in maintaining the stemness of BCSCs, suggesting that GPER is a potential therapeutic target for eradicating BCSCs.

Does GPER Really Function as a G Protein-Coupled Estrogen Receptor in vivo?

Estrogen can elicit pleiotropic cellular responses via a diversity of estrogen receptors (ERs)-mediated genomic and rapid non-genomic mechanisms. Unlike the genomic responses, where the classical nuclear ERα and ERβ act as transcriptional factors following estrogen binding to regulate gene transcription in estrogen target tissues, the non-genomic cellular responses to estrogen are believed to start at the plasma membrane, leading to rapid activation of second messengers-triggered cytoplasmic signal transduction cascades. The recently acknowledged ER, GPR30 or GPER, was discovered in human breast cancer cells two decades ago and subsequently in many other cells. Since its discovery, it has been claimed that estrogen, ER antagonist fulvestrant, as well as some estrogenic compounds can directly bind to GPER, and therefore initiate the non-genomic cellular responses. Various recently developed genetic tools as well as chemical ligands greatly facilitated research aimed at determining the physiological roles of GPER in different tissues. However, there is still lack of evidence that GPER plays a significant role in mediating endogenous estrogen action in vivo. This review summarizes current knowledge about GPER, including its tissue expression and cellular localization, with emphasis on the research findings elucidating its role in health and disease. Understanding the role of GPER in estrogen signaling will provide opportunities for the development of new therapeutic strategies to strengthen the benefits of estrogen while limiting the potential side effects.

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.

Individualized medicine: Sex, hormones, genetics, and adverse drug reactions

Clinically relevant adverse drug reactions differ between men and women. The underlying physiological and pharmacological processes contributing to these differences are infrequently studied or reported. As gene expression, cellular regulatory pathways, and integrated physiological functions differ between females and males, aggregating data from combined groups of men and women obscures the ability to detect these differences. This paper summarizes how genetic sex, that is, the presence of sex chromosomes XY for male or XX for female, and the influence of sex hormones affect transporters, receptors, and enzymes involved in drug metabolism. Changing levels of sex steroids throughout life, including increases at puberty, changes with pregnancy, and decreases with age, may directly and indirectly affect drug absorption, distribution, metabolism, and elimination. The direct and indirect effects of sex steroids in the form of exogenous hormones such as those used in hormonal contraceptives, menopausal hormone treatments, transgender therapy, and over-the-counter performance enhancing drugs may interfere with metabolism of other pharmaceuticals, and these interactions may vary by dose, formulation, and mode of delivery (oral, injection, or transdermal) of the steroid hormones. Few drugs have sex-specific labeling or dosing recommendations. Furthermore, there is limited literature evaluating how the circulating levels of sex steroids impact drug efficacy or adverse reactions. Such research is needed in order to improve the understanding of the impact of sex hormones on pharmacological therapies, particularly as medicine moves toward individualizing treatments.

Stabilization of MORC2 by estrogen and antiestrogens through GPER1- PRKACA-CMA pathway contributes to estrogen-induced proliferation and endocrine resistance of breast cancer cells

Aberrant activation of estrogen signaling through three ESR (estrogen receptor) subtypes, termed ESR1/ERα, ESR2/ERβ, and GPER1 (G protein-coupled estrogen receptor 1), is implicated in breast cancer pathogenesis and progression. Antiestrogens tamoxifen (TAM) and fulvestrant (FUL) are effective for treatment of ESR1-positive breast tumors, but development of resistance represents a major clinical challenge. However, the molecular mechanisms behind these events remain largely unknown. Here, we report that 17β-estradiol (E2), TAM, and FUL stabilize MORC2 (MORC family CW-type zinc finger 2), an emerging oncoprotein in human cancer, in a GPER1-dependent manner. Mechanistically, GPER1 activates PRKACA (protein kinase cAMP-activated catalytic subunit alpha), which in turn phosphorylates MORC2 at threonine 582 (T582). Phosphorylated MORC2 decreases its interaction with HSPA8 (heat shock protein family A [Hsp70] member 8) and LAMP2A (lysosomal associated membrane protein 2A), two core components of the chaperone-mediated autophagy (CMA) machinery, thus protecting MORC2 from lysosomal degradation by CMA. Functionally, knockdown of MORC2 attenuates E2-induced cell proliferation and enhances cellular sensitivity to TAM and FUL. Moreover, introduction of wild-type MORC2, but not its phosphorylation-lacking mutant (T582A), in MORC2-depleted cells restores resistance to antiestrogens. Clinically, the phosphorylation levels of MORC2 at T582 are elevated in breast tumors from patients undergoing recurrence after TAM treatment. Together, these findings delineate a phosphorylation-dependent mechanism for MORC2 stabilization in response to estrogen and antiestrogens via blocking CMA-mediated lysosomal degradation and uncover a dual role for MORC2 in both estrogen-induced proliferation and resistance to antiestrogen therapies of breast cancer cells.

ABBREVIATIONS

4-OHT: 4-hydroxytamoxifen; Baf A1: bafilomycin A₁; CMA: chaperone-mediated autophagy; E2: 17β-estradiol; ESR: estrogen receptor; FUL: fulvestrant; GPER1: G protein-coupled estrogen receptor 1; HSPA8: heat shock protein family A (Hsp70) member 8; LAMP2A: lysosomal associated membrane protein 2A; MORC2: MORC family CW-type zinc finger 2; PRKACA: protein kinase cAMP-activated catalytic subunit alpha; TAM: tamoxifen; VCL: vinculin.

Moderate intensity continuous training reverses the detrimental effects of ovariectomy on RyR1 phosphorylation in rat skeletal muscle

High 17β-Estradiol (E2) concentrations in isolated ventricular myocytes as well as a lack of ovarian hormones in cardiac muscle of ovariectomized (OVX) rodents has been shown to lead to arrhythmogenic effects by inducing post-translational modifications, including phosphorylation of the sarcoplasmic reticulum (SR) Ca²⁺ release channel ryanodine receptor-2 (RyR2). The effects of estrogens on the phosphorylation status of the RyR1 in skeletal muscle have not been investigated before. Furthermore, while high intensity exercise has been shown to increase RyR phosphorylation, there is no data on the effects of moderate intensity continuous training (MICT). The aims of the study were to investigate the effects of a 3-day treatment with low (1 nM, moderate (5 nM) and high (10 nM, 100 nM) E2 concentrations on RyR1 mRNA and protein expression and phosphorylation status (pRyRSer²⁸⁴⁴) in cultured C2C12 myotubes and to study the effects of OVX on RyR1 expression and phosphorylation in rat skeletal muscle in combination with 3 weeks of MICT. Treatment with low, physiological E2 concentrations reduced dihydropyridine receptor (DHPR) and RyR1 mRNA content in C2C12 myotubes compared to untreated control cells, whereas RyR1 protein phosphorylation (pRyRSer²⁸⁴⁴) was significantly increased after treatment with high, non-physiological E2 concentrations (p ≤ 0.05). RyR1 protein content (p ≤ 0.05) and pRyRSer²⁸⁴⁴ (p ≤ 0.05) were significantly elevated in skeletal muscle of OVX vs. sham-operated rats. Importantly, pRyRSer²⁸⁴⁴ levels were similar to sham-operated controls in OVX rats after MICT (OVX vs. OVX + MICT, p ≤ 0.05). Our results indicate, that one of the actions of estrogens is to alter skeletal muscle Ca²⁺ homeostasis by modulating the expression and phosphorylation of the RyR1 in skeletal muscle. Notably, regular MICT was able to counteract RyR1 phosphorylation in skeletal muscle of OVX rats.

Equilin displays similar endothelium-independent vasodilator potential to 17β-estradiol regardless of lower potential to inhibit calcium entry

Conjugated equine estrogens (CEE) have been widely used by women who seek to relieve symptoms of menopause. Despite evidence describing protective effects against risk factors for cardiovascular diseases by naturally occurring estrogens, little is known about the vascular effects of equilin, one of the main components of CEE and not physiologically present in women. In this regard, the present study aims to compare the vascular effects of equilin in an experimental model of hypertension with those induced by 17β-estradiol. Resistance mesenteric arteries from female spontaneously hypertensive rats (SHR) were used for recording isometric tension in a small vessel myograph. As effectively as 17β-estradiol, equilin evoked a concentration-dependent relaxation in mesenteric arteries from female SHRs contracted with KCl, U46619, PDBu or ET-1. Equilin-induced vasodilation does not involve classical estrogen receptor activation, since the estrogen receptor antagonist (ICI 182,780) failed to inhibit relaxation in U46619-precontracted mesenteric arteries. Vasorelaxation was not affected by either endothelium removal or by inhibiting the release or action of endothelium-derived factors. Incubation with L-NAME (NOS inhibitor), ODQ (guanylyl cyclase inhibitor) or KT5823 (inhibitor of protein kinase G) did not affect equilin-induced relaxation. Similarly, indomethacin (COX inhibitor) or blockage of potassium channels with tetraethylammonium, glibenclamide, 4-aminopyridine, or ouabain did not affect equilin-induced relaxation. Inhibitors of adenylyl cyclase SQ22536 or protein kinase A (KT5720) also had no effects on equilin-induced relaxation. While 17β-estradiol inhibited calcium (Ca²⁺) -induced contractions in high-K⁺ depolarization medium in a concentration-dependent manner, equilin induced a slight rightward-shift in the contractile responses to Ca²⁺. Comparable pattern of responses were observed in the concentration-response curves to (S)-(-)-Bay K 8644, a L-type Ca²⁺ channel activator. Equilin was unable to block the transitory contraction produced by caffeine-induced Ca²⁺ release from intracellular stores. In conclusion, equilin blocks L-type Ca²⁺ channels less effectively than 17β-estradiol. Despite its lower effectiveness, equilin equally relaxes resistance mesenteric arteries by blocking Ca²⁺ entry on smooth muscle.

Gender differences in trauma, shock and sepsis

Despite efforts in prevention and intensive care, trauma and subsequent sepsis are still associated with a high mortality rate. Traumatic injury remains the main cause of death in people younger than 45 years and is thus a source of immense social and economic burden. In recent years, the knowledge concerning gender medicine has continuously increased. A number of studies have reported gender dimorphism in terms of response to trauma, shock and sepsis. However, the advantageous outcome following trauma-hemorrhage in females is not due only to sex. Rather, it is due to the prevailing hormonal milieu of the victim. In this respect, various experimental and clinical studies have demonstrated beneficial effects of estrogen for the central nervous system, the cardiopulmonary system, the liver, the kidneys, the immune system, and for the overall survival of the host. Nonetheless, there remains a gap between the bench and the bedside. This is most likely because clinical studies have not accounted for the estrus cycle. This review attempts to provide an overview of the current level of knowledge and highlights the most important organ systems responding to trauma, shock and sepsis. There continues to be a need for clinical studies on the prevailing hormonal milieu following trauma, shock and sepsis.

S-Equol, a Major Isoflavone from Soybean, Inhibits Nitric Oxide Production in Lipopolysaccharide-Stimulated Rat Astrocytes Partially via the GPR30-Mediated Pathway

Cumulative evidence indicates that estrogen receptor (ER) agonists attenuate neuroinflammation. Equol, a major isoflavone from soybean, exhibits estrogen-like biological activity, but their effect on inflammatory response has not been well established. Here, we investigated the effect of S-equol on nitric oxide (NO) production, well-known inflammatory change in astrocytes stimulated by LPS. S-Equol attenuated LPS-induced NO production with a concomitant decrease in expression of inducible NO synthase (iNOS). S-Equol did not affect LPS-induced increase in intracellular ROS production. Intracellular ER blocker ICI 182.780 had no effect on S-equol-induced decrease in NO production. Addition of G-15, antagonist of G protein-coupled receptor 30 which is nongenomic ER and located on cell surface, partially recovered S-equol-induced attenuation of NO production. These findings suggest that attenuation of NO production by S-equol may mitigate LPS-induced neuroinflammation in astrocytes. S-Equol may exert a glioprotective effect, at least in part, via a nongenomic effect.

Effects of Intracordal Estradiol and Dexamethasone Injection on Wound Healing in Vocal Fold Injuries

OBJECTIVE

The aim of this study was to investigate the effects of intracordal estradiol and dexamethasone injection on wound healing in vocal fold injuries.

STUDY DESIGN

A prospective controlled animal study was carried out.

SETTING

This study was conducted at a tertiary center.

SUBJECTS-METHODS

Ten rabbits were randomly divided into two groups. As surgical procedure, cordotomy technique was performed in the middle third of the vocal folds bilaterally. In the first group, 0.1 mL of dexamethasone was injected into the right side, and 0.1 mL of saline was injected into the left side. In the second group, 0.1 mL of estradiol was injected into the right side, and 0.1 mL of saline was injected into the left side. Animals were sacrificed after 1 month and laryngeal specimens were evaluated histopathologically.

RESULTS

No statistically significant difference was observed in terms of inflammatory response, epithelial thickness, type I and III collagen, and hyaluronic acid parameters in dexamethasone and estradiol injections compared to the saline injection. In terms of elastin level, estradiol injection demonstrated statistically higher values compared to the saline injection. Elastin level of dexamethasone injected vocal folds was not statistically different compared to the saline injection. No significant differences were observed in terms of inflammatory response, epithelial thickness, type I and III collagen, and hyaluronic acid parameters between the estradiol and dexamethasone injected vocal folds.

CONCLUSION

It is thought that the effects of estradiol or dexamethasone injections may have similar effects on wound healing in vocal fold injuries. Intracordal estradiol injection has positive effects on tissue elastin levels.

The Role and Use of Estrogens Following Trauma

Several lines of evidence indicate that female sex is a protective factor in trauma and hemorrhage. In both clinical and experimental studies, proestrus females have been shown to have better chances of survival and reduced rates of posttraumatic sepsis. Estrogen receptors are expressed in a variety of tissues and exert genomic, as well as nongenomic effects. By improving cardiac, pulmonary, hepatic, and immune function, estrogens have been shown to prolong survival in animal models of hemorrhagic shock. Despite encouraging results from experimental studies, retrospective clinical studies have not clearly pointed to advantages of estrogens following trauma-hemorrhage, which may be due to insufficient study design. Therefore, this review aims to give an overview on the current evidence and emphasizes on the importance of further clinical investigation on estrogens following trauma.

The influence of sex steroid hormones on the response to trauma and burn injury

Trauma and related sequelae result in disturbance of homeostatic mechanisms frequently leading to cellular dysfunction and ultimately organ and system failure. Regardless of the type and severity of injury, gender dimorphism in outcomes following trauma have been reported, with females having lower mortality than males, suggesting that sex steroid hormones (SSH) play an important role in the response of body systems to trauma. In addition, several clinical and experimental studies have demonstrated the effects of SSH on the clinical course and outcomes following injury. Animal studies have reported the ability of SSH to modulate immune, inflammatory, metabolic and organ responses following traumatic injury. This indicates that homeostatic mechanisms, via direct and indirect pathways, can be maintained by SSH at local and systemic levels and hence result in more favourable prognosis. Here, we discuss the role and mechanisms by which SSH modulates the response of the body to injury by maintaining various processes and organ functions. Such properties of sex hormones represent potential novel therapeutic strategies and further our understanding of current therapies used following injury such as oxandrolone in burn-injured patients.

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.

Hepatic estrogen receptor α is critical for regulation of gluconeogenesis and lipid metabolism in males

Impaired estrogens action is associated with features of the metabolic syndrome in animal models and humans. We sought to determine whether disruption of hepatic estrogens action in adult male mice could recapitulate aspects of the metabolic syndrome to understand the mechanistic basis for the phenotype. We found 17β-estradiol (E2) inhibited hepatic gluconeogenic genes such as phosphoenolpyruvate carboxykinase 1 (Pck-1) and glucose 6-phosphatase (G6Pase) and this effect was absent in mice lacking liver estrogen receptor α (Esr1) (LERKO mice). Male LERKO mice displayed elevated hepatic gluconeogenic activity and fasting hyperglycemia. We also observed increased liver lipid deposits and triglyceride levels in male LERKO mice, resulting from increased hepatic lipogenesis as reflected by increased mRNA levels of fatty acid synthase (Fas) and acetyl-CoA carboxylase (Acc1). ChIP assay demonstrated estradiol (E2) induced ESR1 binding to Pck-1, G6Pase, Fas and Acc1 promoters. Metabolic phenotyping demonstrated both basal metabolic rate and feeding were lower for the LERKO mice as compared to Controls. Furthermore, the respiratory exchange rate was significantly lower in LERKO mice than in Controls, suggesting an increase in lipid oxidation. Our data indicate that hepatic E2/ESR1 signaling plays a key role in the maintenance of gluconeogenesis and lipid metabolism in males.

The presence of the ovary prevents hepatic mitochondrial oxidative stress in young and aged female mice through glutathione peroxidase 1

BACKGROUND

For unknown reasons a woman's risk for developing Metabolic Syndrome (MetS) increases dramatically with age and/or loss of ovarian function. The MetS is characterized by hepatic insulin resistance (IR), which is strongly associated with intrahepatic lipid (IHL) accumulation, mitochondrial dysfunction, and oxidative stress. Although circumstantial evidence suggests that the endocrine function of the ovary can directly impact hepatic mitochondrial function, this hypothesis remains untested. Thus, the purpose of this study was to assess the influence of age and secretory function of the ovary on mechanisms that regulate hepatic mitochondrial function.

METHODS

Adult (10 week-old) and aged (88 week-old) female C57BL/6 mice were separated into two groups to undergo bilateral ovariectomy (OVX) or control surgery (SHAM). Eight weeks after surgery hepatic tissue was removed for measurements of total IHL and fatty acid species within hepatic triglycerides, mitochondrial function, and reactive oxygen species (ROS) production.

RESULTS

Hepatic IHL content was not affected by OVX, but was increased by age. OVX had no effect on mitochondrial respiration, however, hepatic mitochondria from aged mice had lower O2 consumption, lower complex IV and higher complex I content. Mitochondrial H2O2 production was highest in OVX groups and exacerbated by age, while mitochondrial lipid peroxidation was highest in the aged mice and exacerbated by OVX. Regardless of age, OVX resulted in lower mitochondrial content of antioxidant glutathione peroxidase 1 (Gpx1). Isolated liver tissue from a sub-set of animals were acutely treated with conditioned ovarian media which increased Gpx1 mRNA expression compared to vehicle treated liver tissue.

CONCLUSION

Ovarian secretory function is necessary for the maintenance of hepatic ROS buffering capacity in the mitochondria, while age significantly influences mitochondrial respiration. These data suggest that when age is coupled with loss of ovarian function there is an increased risk for developing hepatic mitochondrial dysfunction, which may influence the onset of metabolic disease. Thus, in females there is critical organ cross-talk occurring between hepatic tissue and the ovary that impacts hepatic mitochondrial function.

A novel form of synaptic plasticity in field CA3 of hippocampus requires GPER1 activation and BDNF release

Estrogen gates metabotropic glutamate receptor–dependent long-term depression at mossy fiber–CA3 synapses through a mechanism involving GPER1-mediated BDNF release, mTOR-dependent protein synthesis, and proteasome activity.

Estrogen is an important modulator of hippocampal synaptic plasticity and memory consolidation through its rapid action on membrane-associated receptors. Here, we found that both estradiol and the G-protein–coupled estrogen receptor 1 (GPER1) specific agonist G1 rapidly induce brain-derived neurotrophic factor (BDNF) release, leading to transient stimulation of activity-regulated cytoskeleton-associated (Arc) protein translation and GluA1-containing AMPA receptor internalization in field CA3 of hippocampus. We also show that type-I metabotropic glutamate receptor (mGluR) activation does not induce Arc translation nor long-term depression (LTD) at the mossy fiber pathway, as opposed to its effects in CA1, and it only triggers LTD after GPER1 stimulation. Furthermore, this form of mGluR-dependent LTD is associated with ubiquitination and proteasome-mediated degradation of GluA1, and is prevented by proteasome inhibition. Overall, our study identifies a novel mechanism by which estrogen and BDNF regulate hippocampal synaptic plasticity in the adult brain.

G Protein-Coupled Estrogen Receptor 1 Mediates Acute Estrogen-Induced Cardioprotection via MEK/ERK/GSK-3β Pathway after Ischemia/Reperfusion

Three types of estrogen receptors (ER) exist in the heart, Esr1, Esr2 and the G protein-coupled estrogen receptor 1, Gper1. However, their relative importance in mediating estrogen protective action is unknown. We found that, in the male mouse ventricle, Gper1 transcripts are three- and seventeen-fold more abundant than Esr1 and Esr2 mRNAs, respectively. Analysis of the three ER knockouts (Esr1^-/-, Esr2^-/- and Gper1^-/-) showed that only the Gper1^-/- hearts lost their ability to be protected by 40 nM estrogen as measured by heart function, infarct size and mitochondrial Ca²⁺ overload, an index of mitochondrial permeability transition pore (mPTP) activity. Analysis of Akt, ERK_1/2 and GSK-3β salvage kinases uncovered Akt and ERK_1/2 transient activation by estrogen whose phosphorylation increased during the first 5 min of non-ischemic perfusion. All these increase in phosphorylation effects were abrogated in Gper1^-/-. Inhibition of MEK_1/2/ERK_1/2 (1 μM U0126) and PI-3K/Akt (10 μM LY294002) signaling showed that the MEK_1/2/ERK_1/2 pathway via GSK-3β exclusively was responsible for cardioprotection as an addition of U0126 prevented estrogen-induced GSK-3β increased phosphorylation, resistance to mitochondrial Ca²⁺-overload, functional recovery and protection against infarction. Further, inhibiting PKC translocation (1 μM chelerythrin-chloride) abolished estrogen-induced cardioprotection. These data indicate that estrogen-Gper1 acute coupling plays a key role in cardioprotection against ischemia/reperfusion injury in male mouse via a cascade involving PKC translocation, ERK_1/2/GSK-3β phosphorylation leading to the inhibition of the mPTP opening.

International Union of Basic and Clinical Pharmacology. XCVII. G Protein-Coupled Estrogen Receptor and Its Pharmacologic Modulators

Estrogens are critical mediators of multiple and diverse physiologic effects throughout the body in both sexes, including the reproductive, cardiovascular, endocrine, nervous, and immune systems. As such, alterations in estrogen function play important roles in many diseases and pathophysiological conditions (including cancer), exemplified by the lower prevalence of many diseases in premenopausal women. Estrogens mediate their effects through multiple cellular receptors, including the nuclear receptor family (ERα and ERβ) and the G protein-coupled receptor (GPCR) family (GPR30/G protein-coupled estrogen receptor [GPER]). Although both receptor families can initiate rapid cell signaling and transcriptional regulation, the nuclear receptors are traditionally associated with regulating gene expression, whereas GPCRs are recognized as mediating rapid cellular signaling. Estrogen-activated pathways are not only the target of multiple therapeutic agents (e.g., tamoxifen, fulvestrant, raloxifene, and aromatase inhibitors) but are also affected by a plethora of phyto- and xeno-estrogens (e.g., genistein, coumestrol, bisphenol A, dichlorodiphenyltrichloroethane). Because of the existence of multiple estrogen receptors with overlapping ligand specificities, expression patterns, and signaling pathways, the roles of the individual receptors with respect to the diverse array of endogenous and exogenous ligands have been challenging to ascertain. The identification of GPER-selective ligands however has led to a much greater understanding of the roles of this receptor in normal physiology and disease as well as its interactions with the classic estrogen receptors ERα and ERβ and their signaling pathways. In this review, we describe the history and characterization of GPER over the past 15 years focusing on the pharmacology of steroidal and nonsteroidal compounds that have been employed to unravel the biology of this most recently recognized estrogen receptor.

Activation of GPR30 attenuates chronic pain-related anxiety in ovariectomized mice

Estrogen regulates neuroendocrine and inflammatory processes that play critical roles in neuroinflammation, anxiety, and chronic pain. Patients suffering from chronic pain often complain of anxiety. However, limited information is available regarding the neural circuitry of chronic pain-related anxiety and the related function of estrogen. Hindpaw injection of complete Freund's adjuvant (CFA) and chronic constriction injury (CCI) of the sciatic nerve induced notable pain sensitization and anxiety-like behavior in ovariectomized (OVX) mice. We found that the level of G-protein-coupled receptor 30 (GPR30), a membrane estrogen receptor, was significantly increased in the basolateral amygdala (BLA) of ovariectomized (OVX) mice suffering from chronic inflammatory and neuropathic pain. Subcutaneous injection or BLA local infusion of the GPR30 agonist G1 significantly reduced anxiety-like behavior in CFA-injected and CCI-OVX mice; however, this treatment did not alter the nociceptive threshold. GPR30 knock down by shRNA in the BLA of OVX mice inhibited the anxiolytic effects of GPR30 activation. G1 administration reversed the upregulation of GluR1 subunit in AMPA and NR2A-containing NMDA receptors and the downregulation of GABAA receptors in the BLA of CFA-injected and CCI-OVX mice. Electrophysiological recording revealed that GPR30 activation could prevent imbalance between excitatory and inhibitory transmissions in the BLA synapses of CFA-injected OVX mice. In conclusion, GPR30 activation induced anxiolytic effects but did not affect the nociceptive threshold of mice under chronic pain. The anxiolytic effects of GPR30 were partially due to maintaining the balance between excitatory and inhibitory transmissions in the BLA.

G-protein coupled estrogen receptor (GPER) inhibits final oocyte maturation in common carp, Cyprinus carpio

GPR-30, now named as GPER (G protein-coupled estrogen receptor) was first identified as an orphan receptor and subsequently shown to be required for estrogen-mediated signaling in certain cancer cells. Later studies demonstrated that GPER has the characteristics of a high affinity estrogen membrane receptor on Atlantic croaker and zebra fish oocytes and mediates estrogen inhibition of oocyte maturation in these two distantly related teleost. To determine the broad application of these findings to other teleost, expression of GPER mRNA and its involvement in 17β-estradiol mediated inhibition of oocyte maturation in other cyprinid, Cyprinus carpio was investigated. Carp oocytes at pre-vitellogenic, late-vitellogenic and post-vitellogenic stages of development contained GPER mRNA and its transcribed protein with a maximum at late-vitellogenic oocytes. Ovarian follicular cells did not express GPER mRNA. Carp oocytes GPER mRNA was essentially identical to that found in other perciformes and cyprinid fish oocytes. Both spontaneous and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P)-induced oocyte maturation in carp was significantly decreased when they were incubated with either E2, or GPER agonist G-1. On the other hand spontaneous oocyte maturation was significantly increased when carp ovarian follicles were incubated with an aromatase inhibitor, fadrozole, GPER antagonist, G-15 and enzymatic removal of the ovarian follicle cell layers. This increase in oocyte maturation was partially reversed by co-treatment with E2. Consistent with previous findings with human and fish GPR30, E2 treatment in carp oocytes caused increase in cAMP production and simultaneously decrease in oocyte maturation, which was inhibited by the addition of 17,20β-P. The results suggest that E2 and GPER play a critical role in regulating re-entry in to meiotic cell cycle in carp oocytes.

Inhibition of de novo NAD(+) synthesis by oncogenic URI causes liver tumorigenesis through DNA damage

Molecular mechanisms responsible for hepatocellular carcinoma (HCC) remain largely unknown. Using genetically engineered mouse models, we show that hepatocyte-specific expression of unconventional prefoldin RPB5 interactor (URI) leads to a multistep process of HCC development, whereas its genetic reduction in hepatocytes protects against diethylnitrosamine (DEN)-induced HCC. URI inhibits aryl hydrocarbon (AhR)- and estrogen receptor (ER)-mediated transcription of enzymes implicated in L-tryptophan/kynurenine/nicotinamide adenine dinucleotide (NAD(+)) metabolism, thereby causing DNA damage at early stages of tumorigenesis. Restoring NAD(+) pools with nicotinamide riboside (NR) prevents DNA damage and tumor formation. Consistently, URI expression in human HCC is associated with poor survival and correlates negatively with L-tryptophan catabolism pathway. Our results suggest that boosting NAD(+) can be prophylactic or therapeutic in HCC.

G-protein estrogen receptor as a regulator of low-density lipoprotein cholesterol metabolism: cellular and population genetic studies

OBJECTIVE

Estrogen deficiency is linked with increased low-density lipoprotein (LDL) cholesterol. The hormone receptor mediating this effect is unknown. G-protein estrogen receptor (GPER) is a recently recognized G-protein-coupled receptor that is activated by estrogens. We recently identified a common hypofunctional missense variant of GPER, namely P16L. However, the role of GPER in LDL metabolism is unknown. Therefore, we examined the association of the P16L genotype with plasma LDL cholesterol level. Furthermore, we studied the role of GPER in regulating expression of the LDL receptor and proprotein convertase subtilisin kexin type 9.

APPROACH AND RESULTS

Our discovery cohort was a genetically isolated population of Northern European descent, and our validation cohort consisted of normal, healthy women aged 18 to 56 years from London, Ontario. In addition, we examined the effect of GPER on the regulation of proprotein convertase subtilisin kexin type 9 and LDL receptor expression by the treatment with the GPER agonist, G1. In the discovery cohort, GPER P16L genotype was associated with a significant increase in LDL cholesterol (mean±SEM): 3.18±0.05, 3.25±0.08, and 4.25±0.33 mmol/L, respectively, in subjects with CC (homozygous for P16), CT (heterozygotes), and TT (homozygous for L16) genotypes (P<0.05). In the validation cohort (n=339), the GPER P16L genotype was associated with a similar increase in LDL cholesterol: 2.17±0.05, 2.34±0.06, and 2.42±0.16 mmol/L, respectively, in subjects with CC, CT, and TT genotypes (P<0.05). In the human hepatic carcinoma cell line, the GPER agonist, G1, mediated a concentration-dependent increase in LDL receptor expression, blocked by either pretreatment with the GPER antagonist G15 or by shRNA-mediated GPER downregulation. G1 also mediated a GPER- and concentration-dependent decrease in proprotein convertase subtilisin kexin type 9 expression.

CONCLUSIONS

GPER activation upregulates LDL receptor expression, probably at least, in part, via proprotein convertase subtilisin kexin type 9 downregulation. Furthermore, humans carrying the hypofunctional P16L genetic variant of GPER have increased plasma LDL cholesterol. In aggregate, these data suggest an important role of GPER in the regulation of LDL receptor expression and consequently LDL metabolism.

Progress in solving the sex hormone paradox in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a devastating and progressive disease with marked morbidity and mortality. Even though being female represents one of the most powerful risk factors for PAH, multiple questions about the underlying mechanisms remain, and two "estrogen paradoxes" in PAH exist. First, it is puzzling why estrogens have been found to be protective in various animal models of PAH, whereas PAH registries uniformly demonstrate a female susceptibility to the disease. Second, despite the pronounced tendency for the disease to develop in women, female PAH patients exhibit better survival than men. Recent mechanistic studies in classical and in novel animal models of PAH, as well as recent studies in PAH patients, have significantly advanced the field. In particular, it is now accepted that estrogen metabolism and receptor signaling, as well as estrogen interactions with key pathways in PAH development, appear to be potent disease modifiers. A better understanding of these interactions may lead to novel PAH therapies. It is the purpose of this review to 1) review sex hormone synthesis, metabolism, and receptor physiology; 2) assess the context in which sex hormones affect PAH pathogenesis; 3) provide a potential explanation for the observed estrogen paradoxes and gender differences in PAH; and 4) identify knowledge gaps and future research opportunities. Because the majority of published studies investigated 17β-estradiol and/or its metabolites, this review will primarily focus on pulmonary vascular and right ventricular effects of estrogens. Data for other sex hormones will be discussed very briefly.

G-protein-coupled receptor 30/adenylyl cyclase/protein kinase A pathway is involved in estradiol 17ß-D-glucuronide-induced cholestasis

Estradiol-17ß-D-glucuronide (E17G) activates different signaling pathways (e.g., Ca(2+) -dependent protein kinase C, phosphoinositide 3-kinase/protein kinase B, mitogen-activated protein kinases [MAPKs] p38 and extracellular signal-related kinase 1/2, and estrogen receptor alpha) that lead to acute cholestasis in rat liver with retrieval of the canalicular transporters, bile salt export pump (Abcb11) and multidrug resistance-associated protein 2 (Abcc2). E17G shares with nonconjugated estradiol the capacity to activate these pathways. G-protein-coupled receptor 30 (GPR30) is a receptor implicated in nongenomic effects of estradiol, and the aim of this study was to analyze the potential role of this receptor and its downstream effectors in E17G-induced cholestasis. In vitro, GPR30 inhibition by G15 or its knockdown with small interfering RNA strongly prevented E17G-induced impairment of canalicular transporter function and localization. E17G increased cyclic adenosine monophosphate (cAMP) levels, and this increase was blocked by G15, linking GPR30 to adenylyl cyclase (AC). Moreover, AC inhibition totally prevented E17G insult. E17G also increased protein kinase A (PKA) activity, which was blocked by G15 and AC inhibitors, connecting the links of the pathway, GPR30-AC-PKA. PKA inhibition prevented E17G-induced cholestasis, whereas exchange protein activated directly by cyclic nucleotide/MAPK kinase, another cAMP downstream effector, was not implicated in cAMP cholestatic action. In the perfused rat liver model, inhibition of the GPR30-AC-PKA pathway totally prevented E17G-induced alteration in Abcb11 and Abcc2 function and localization.

CONCLUSION

Activation of GPR30-AC-PKA is a key factor in the alteration of canalicular transporter function and localization induced by E17G. Interaction of E17G with GPR30 may be the first event in the cascade of signaling activation.

Sex- and age-dependent effects of Gpr30 genetic deletion on the metabolic and cardiovascular profiles of diet-induced obese mice

The G protein-coupled receptor 30 (GPR30) has been claimed as an estrogen receptor. However, the literature reports controversial findings and the physiological function of GPR30 is not fully understood yet. Consistent with studies assigning a role of GPR30 in the cardiovascular and metabolic systems, GPR30 expression has been reported in small arterial vessels, pancreas and chief gastric cells of the stomach. Therefore, we hypothesized a role of GPR30 in the onset and progression of cardiovascular and metabolic diseases. In order to test our hypothesis, we investigated the effects of a high-fat diet on the metabolic and cardiovascular profiles of Gpr30-deficient mice (GPR30-lacZ mice). We found that GPR30-lacZ female, rather than male, mice had significant lower levels of HDL along with an increase in fat liver accumulation as compared to control mice. However, two indicators of cardiac performance assessed by echocardiography, ejection fraction and fractional shortening were both decreased in an age-dependent manner only in Gpr30-lacZ male mice. Collectively our results point to a potential role of Gpr30 in preserving lipid metabolism and cardiac function in a sex- and age-dependent fashion.

Anatomical location and redistribution of G protein-coupled estrogen receptor-1 during the estrus cycle in mouse kidney and specific binding to estrogens but not aldosterone

Prior studies have linked renoprotective effects of estrogens to G-protein-coupled estrogen receptor-1 (GPER-1) and suggest that aldosterone may also activate GPER-1. Here, the role of GPER-1 in murine renal tissue was further evaluated by examining its anatomical distribution, subcellular distribution and steroid binding specificity. Dual immunofluorescent staining using position-specific markers showed that GPER-1 immunoreactivity primarily resides in distal convoluted tubules and the Loop of Henle (stained with Tamm-Horsfall Protein-1). Lower GPER-1 expression was observed in proximal convoluted tubules marked with megalin, and GPER-1 was not detected in collecting ducts. Plasma membrane fractions prepared from whole kidney tissue or HEK293 cells expressing recombinant human GPER-1 (HEK-GPER-1) displayed high-affinity, specific [(3)H]-17β-estradiol ([(3)H]-E2) binding, but no specific [(3)H]-aldosterone binding. In contrast, cytosolic preparations exhibited specific binding to [(3)H]-aldosterone but not to [(3)H]-E2, consistent with the subcellular distribution of GPER-1 and mineralocorticoid receptor (MR) in these preparations. Aldosterone and MR antagonists, spironolactone and eplerenone, failed to compete for specific [(3)H]-E2 binding to membranes of HEK-GPER-1 cells. Furthermore, aldosterone did not increase [(35)S]-GTP-γS binding to membranes of HEK-GPER-1 cells, indicating that it is not involved in G protein signaling mediated through GPER-1. During the secretory phases of the estrus cycle, GPER-1 is upregulated on cortical epithelia and localized to the basolateral surface during proestrus and redistributed intracellularly during estrus. GPER-1 is down-modulated during luteal phases of the estrus cycle with significantly less receptor on the surface of renal epithelia. Our results demonstrate that GPER-1 is associated with specific estrogen binding and not aldosterone binding and that GPER-1 expression is modulated during the estrus cycle which may suggest a physiological role for GPER-1 in the kidney during reproduction.

Estrogen-induced nongenomic calcium signaling inhibits lipopolysaccharide-stimulated tumor necrosis factor α production in macrophages

Estrogen is traditionally thought to exert genomic actions through members of the nuclear receptor family. Here, we investigated the rapid nongenomic effects of 17β-estradiol (E₂) on tumor necrosis factor α (TNF-α) production following lipopolysaccharide (LPS) stimulation in mouse bone marrow-derived macrophages (BMMs). We found that LPS induced TNF-α production in BMMs via phosphorylation of p38 mitogen-activated protein kinase (MAPK). E₂ itself did not affect the MAPK pathway, although it attenuated LPS-induced TNF-α production through suppression of p38 MAPK activation. Recently, G protein-coupled receptor 30 (GPR30) was suggested to be a membrane estrogen receptor (mER) that can mediate nongenomic estradiol signaling. We found that BMMs expressed both intracellular estrogen receptors (iER) and mER GPR30. The specific GPR30 antagonist G-15 significantly blocked effects of estradiol on LPS-induced TNF-α production, whereas an iER antagonist did not. Moreover, E₂ induced a rapid rise in intracellular free Ca²⁺ that was due to the influx of extracellular Ca²⁺ and was not inhibited by an iER antagonist or silencing of iER. Ca²⁺ influx was also induced by an impermeable E₂ conjugated to BSA (E₂-BSA), which has been used to investigate the nongenomic effects of estrogen. Consequently, Ca²⁺, a pivotal factor in E₂-stimulated nongenomic action, was identified as the key mediator. The inhibitory effects of E₂ on LPS-induced TNF-α production and p38 MAPK phosphorylation were dependent on E₂-triggered Ca²⁺ influx because BAPTA, an intracellular Ca²⁺ chelator, prevented these effects. Taken together, these data indicate that E₂ can down-regulate LPS-induced TNF-α production via blockade of p38 MAPK phosphorylation through the mER-mediated nongenomic Ca²⁺ signaling pathway in BMMs.

Estrogen attenuates lipopolysaccharide-induced nitric oxide production in macrophages partially via the nongenomic pathway

Steroid hormones exert genotropic effects through members of the nuclear hormone receptor family. In the present study, we examined the effects of 17β-estradiol (E2) on nitric oxide (NO) production following lipopolysaccharide (LPS) stimulation and investigated the mechanisms in mouse bone marrow-derived macrophages (BMMs). E2 alone did not affect NO production. In contrast, E2 inhibited LPS-induced production of NO in BMMs. Using a cell-impermeable E2 conjugated to BSA (E2-BSA), which has been used to investigate the nongenomic effects of estrogen, we found that the increase in NO production induced by LPS was also attenuated. In addition, the intracellular estrogen receptor blocker, ICI 182780, only partially antagonized the total effects of E2 on LPS-stimulated NO production capacity. E2 also attenuated the LPS activation of p38 mitogen-activated protein kinase (MAPK) but not that of extracellular-regulated protein kinase 1/2 (ERK1/2) and c-Jun NH2-terminal kinase (JNK). This attenuation was not abrogated by ICI 182780. Moreover, the p38 inhibitor, SB 203580, greatly reduced the LPS-induced NO production, and the remaining NO levels were no longer regulated by E2. Additionally, E2-BSA inhibited LPS-mediated changes in p38 MAPK activation to the same extent as E2. Moreover, E2 and E2-BSA inhibited LPS-induced activation of nuclear factor-kappa B (NF-κB) and activator protein 1 (AP-1). This inhibitory effect of E2 was only partially antagonized by ICI 182780. Taken together, these results suggest that E2 has an inhibitory effect on LPS-induced NO production in BMMs through inhibition of p38 MAPK phosphorylation, and blockade of NF-κB and AP-1 activation. These effects are mediated at least in part via a nongenomic pathway.

Estradiol and progesterone exhibit similar patterns of hepatic gene expression regulation in the bovine model

Female sex steroid hormones, estradiol-17β (E2-17β) and progesterone (P4) regulate reproductive function and gene expression in a broad range of tissues. Given the central role of the liver in regulating homeostasis including steroid hormone metabolism, we sought to understand how E2-17β and P4 interact to affect global gene expression in liver. Ovariectomized cows (n = 8) were randomly assigned to 4 treatment groups applied in a replicated Latin Square design: 1) No hormone supplementation, 2) E2-17β treatment (ear implant), 3) P4 treatment (intravaginal inserts), and 4) E2-17β combined with P4. After 14 d of treatment, liver biopsies were collected, allowing 28 d intervals between periods. Changes in gene expression in the liver biopsies were monitored using bovine-specific arrays. Treatment with E2-17β altered expression of 479 genes, P4 472 genes, and combined treatment significantly altered expression of 468 genes. In total, 578 genes exhibited altered expression including a remarkable number (346 genes) that responded similarly to E2-17β, P4, or combined treatment. Additional evidence for similar gene expression actions of E2-17ß and/or P4 were: principal component analysis placed almost every treatment array at a substantial distance from controls; Venn diagrams indicated overall treatment effects for most regulated genes; clustering analysis indicated the two major clusters had all treatments up-regulating (172 genes) or down-regulating (173 genes) expression. Thus, unexpectedly, common biological pathways were regulated by E2-17β and/or P4 in liver. This indicates that the mechanism of action of these steroid hormones in the liver might be either indirect or might occur through non-genomic pathways. This unusual pattern of gene expression in response to steroid hormones is consistent with the idea that there are classical and non-classical tissue-specific responses to steroid hormone actions. Future studies are needed to elucidate putative mechanism(s) responsible for overlapping actions of E2-17β and P4 on the liver transcriptome.

17β-estradiol confers protection after traumatic brain injury in the rat and involves activation of G protein-coupled estrogen receptor 1

Abstract Traumatic brain injury (TBI) is a significant public health problem in the United States. Despite preclinical success of various drugs, to date all clinical trials investigating potential therapeutics have failed. Recently, sex steroid hormones have sparked interest as possible neuroprotective agents after traumatic injury. One of these is 17β-estradiol (E2), the most abundant and potent endogenous vertebrate estrogen. The goal of our study was to investigate the acute potential protective effects of E2 or the specific G protein-coupled estrogen receptor 1 (GPER) agonist G-1 when administered in an intravenous bolus dose 1 hour post-injury in the lateral fluid percussion (LFP) rodent model of TBI. The results of this study show that, when assessed at 24 hours post-injury, E2 or G-1 confers protection in adult male rats subjected to LFP brain injury. Specifically, we found that an acute bolus dose of E2 or G-1 administered intravenously 1 hour post-TBI significantly increases neuronal survival in the ipsilateral CA 2/3 region of the hippocampus and decreases neuronal degeneration and apoptotic cell death in both the ipsilateral cortex and CA 2/3 region of the hippocampus. We also report a significant reduction in astrogliosis in the ipsilateral cortex, hilus, and CA 2/3 region of the hippocampus. Finally, these effects were observed to be chiefly dose-dependent for E2, with the 5 mg/kg dose generating a more robust level of protection. Our findings further elucidate estrogenic compounds as a clinically relevant pharmacotherapeutic strategy for treatment of secondary injury following TBI, and intriguingly, reveal a novel potential therapeutic target in GPER.

Gender, sex hormones and pulmonary hypertension

Most subtypes of pulmonary arterial hypertension (PAH) are characterized by a greater susceptibility to disease among females, although females with PAH appear to live longer after diagnosis. While this "estrogen paradoxȍ of enhanced female survival despite increased female susceptibility remains a mystery, recent progress has begun to shed light upon the interplay of sex hormones, the pathogenesis of pulmonary hypertension, and the right ventricular response to stress. For example, emerging data in humans and experimental models suggest that estrogens or differential sex hormone metabolism may modify disease risk among susceptible subjects, and that estrogens may interact with additional local factors such as serotonin to enhance the potentially damaging chronic effects of estrogens on the pulmonary vasculature. Regardless, it remains unclear why not all estrogenic compounds behave equally, nor why estrogens appear to be protective in certain settings but detrimental in others. The contribution of androgens and other compounds, such as dehydroepiandrosterone, to pathogenesis and possibly treatment must be considered as well. In this review, we will discuss the recent understandings on how estrogens, estrogen metabolism, dehydroepiandrosterone, and additional susceptibility factors may all contribute to the pathogenesis or potentially to the treatment of pulmonary hypertension, by evaluating current human, cell-based, and experimental model data.

Interplay of estrogen receptors and GPR30 for the regulation of early membrane initiated transcriptional effects: A pharmacological approach

Estrogens exert their effect through ERα and ERβ intracellular transcription factors and rapid, usually membrane-initiated receptors, influencing cytosolic signaling and transcription. The nature of extranuclear estrogen elements has not been elucidated so far; classical or alternatively transcribed ER isoforms (ERα36, ERα46) anchored to the plasma membrane and GPR30 (GPER1) have been reported to exert early estrogen actions. Here, we used E2-BSA, an impermeable estradiol analog for a transcriptome analysis in four GREP1 positive breast cancer cell lines with different estrogen receptor profiles (T47D, MCF-7, MDA-MB-231 and SKBR3) in order to evaluate GPER1 transcriptional effects. Early effects of E2-BSA were assayed after 3h of incubation, in the absence/presence of ICI182,780 (ER-inhibitor) or G15 (GREP1-specific inhibitor). E2-BSA specifically modified 277-549 transcripts in the different cell lines. Two different clusters of transcripts could be identified: (1) the majority of transcripts were inhibited by both ICI182,780 and G15, suggesting an interaction of E2-BSA with a common ER-related element, or a direct ER-GPER1 interaction; (2) a small number of G15-only modified transcripts, in two cell lines (T47D and SKBR3 cells), indicative of specific GPER1-related effects. The latter transcripts were significantly related to pathways including FOXA2/FOXA3 transcription factor networks, RNA-Polymerases Transcription Regulation and lipid metabolism, while ICI/G15 inhibited transcripts affected pathways related to apoptosis, erythropoietin signaling, metabolic effects through the citric acid cycle, IL-4 and IL-5 mediated events and homologous DNA recombination. Finally, we review the current literature of GPER1 actions, in view of our results of ER-dependent and independent GPER1-modified pathways.

G-protein-coupled receptor 30 mediates rapid neuroprotective effects of estrogen via depression of NR2B-containing NMDA receptors

17-β-estradiol (E2) is a steroid hormone involved in neuroprotection against excitotoxicity and other forms of brain injury. Through genomic and nongenomic mechanisms, E2 modulates neuronal excitability and signal transmission by regulating NMDA and non-NMDA receptors. However, the mechanisms and identity of the receptors involved remain unclear, even though studies have suggested that estrogen G-protein-coupled receptor 30 (GPR30) is linked to protection against ischemic injury. In the culture cortical neurons, treatment with E2 and the GPR30 agonist G1 for 45 min attenuated the excitotoxicity induced by NMDA exposure. The acute neuroprotection mediated by GPR30 is dependent on G-protein-coupled signals and ERK1/2 activation, but independent on transcription or translation. Knockdown of GPR30 using short hairpin RNAs (shRNAs) significantly reduced the E2-induced rapid neuroprotection. Patch-clamp recordings revealed that GPR30 activation depressed exogenous NMDA-elicited currents. Short-term GPR30 activation did not affect the expression of either NR2A- or NR2B-containing NMDARs; however, it depressed NR2B subunit phosphorylation at Ser-1303 by inhibiting the dephosphorylation of death-associated protein kinase 1 (DAPK1). DAPK1 knockdown using shRNAs significantly blocked NR2B subunit phosphorylation at Ser-1303 and abolished the GPR30-mediated depression of exogenous NMDA-elicited currents. Lateral ventricle injection of the GPR30 agonist G1 (0.2 μg) provided significant neuroprotection in the ovariectomized female mice subjected to middle cerebral artery occlusion. These findings provide direct evidence that fast neuroprotection by estradiol is partially mediated by GPR30 and the subsequent downregulation of NR2B-containing NMDARs. The modulation of DAPK1 activity by GPR30 may be an important mediator of estradiol-dependent neuroprotection.