BACKGROUND: Gender is a significant risk factor for late-onset Alzheimer\'s disease (AD), often attributed to the decline of estrogen. The plant estrogen secoisolariciresinol diglucoside (SDG) has demonstrated anti-inflammatory and neuroprotective effects. However, the protective effects and mechanisms of SDG in female AD remain unclear.
METHODS: Ten-month-old female APPswe/PSEN1dE9 (APP/PS1) transgenic mice were treated with SDG to assess its potential ameliorative effects on cognitive impairments in a female AD model through a series of behavioral and biochemical experiments. Serum levels of gut microbial metabolites enterodiol (END) and enterolactone (ENL) were quantified using HPLC-MS. Correlation analysis and broad-spectrum antibiotic cocktail (ABx) treatment were employed to demonstrate the involvement of END and ENL in SDG\'s cognitive improvement effects in female APP/PS1 mice. Additionally, an acute neuroinflammation model was constructed in three-month-old C57BL/6J mice treated with lipopolysaccharide (LPS) and subjected to i.c.v. injection of G15, an inhibitor of G protein-coupled estrogen receptor (GPER), to investigate the mediating role of the estrogen receptor GPER in the cognitive benefits conferred by SDG.
RESULTS: SDG administration resulted in significant improvements in spatial, recognition, and working memory in female APP/PS1 mice. Neuroprotective effects were observed, including enhanced expression of CREB/BDNF and PSD-95, reduced β-amyloid (Aβ) deposition, and decreased levels of TNF-α, IL-6, and IL-10. SDG also altered gut microbiota composition, increasing serum levels of END and ENL. Correlation analysis indicated significant associations between END, ENL, cognitive performance, hippocampal Aβ-related protein mRNA expression, and cortical neuroinflammatory cytokine levels. The removal of gut microbiota inhibited END and ENL production and eliminated the neuroprotective effects of SDG. Furthermore, GPER was found to mediate the inhibitory effects of SDG on neuroinflammatory responses.
CONCLUSIONS: These findings suggest that SDG promotes the production of gut microbial metabolites END and ENL, which inhibit cerebral β-amyloid deposition, activate GPER to enhance CREB/BDNF signaling pathways, and suppress neuroinflammatory responses. Consequently, SDG exerts neuroprotective effects and ameliorates cognitive impairments associated with AD in female mice.

In this work, we performed anti-proliferative assays for the compound N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) on breast cancer (BC) cells (MCF-7, SKBR3, and triple-negative BC (TNBC) MDA-MB-231 cells) to explore its pharmacological mechanism regarding the type of cell death associated with G protein-coupled estrogen receptor (GPER) expression. The results show that HO-AAVPA induces cell apoptosis at 5 h or 48 h in either estrogen-dependent (MCF-7) or -independent BC cells (SKBR3 and MDA-MB-231). At 5 h, the apoptosis rate for MCF-7 cells was 68.4% and that for MDA-MB-231 cells was 56.1%; at 48 h, that for SKBR3 was 61.6%, that for MCF-7 cells was 54.9%, and that for MDA-MB-231 (TNBC) was 43.1%. HO-AAVPA increased the S phase in MCF-7 cells and reduced the G2/M phase in MCF-7 and MDA-MB-231 cells. GPER expression decreased more than VPA in the presence of HO-AAVPA. In conclusion, the effects of HO-AAVPA on cell apoptosis could be modulated by epigenetic effects through a decrease in GPER expression.

The G protein-coupled estrogen receptor, also known as GPER1 or originally GPR30, is found in various tissues, indicating its diverse functions. It is typically present in immune cells, suggesting its role in regulating immune responses to infectious diseases. Our previous studies have shown that G-1, a selective GPER agonist, can limit the pathogenesis mediated by Staphylococcus aureus alpha-hemolysin (Hla). It aids in clearing bacteria in a mouse skin infection model and restricts the surface display of the Hla receptor, ADAM10 (a disintegrin and metalloprotease 10) in HaCaT keratinocytes. In this report, we delve into the modulation of GPER in human immune cells in relation to the NLRP3 inflammasome. We used macrophage-like differentiated THP-1 cells for our study. We found that treating these cells with G-1 reduces ATP release, decreases the activity of the caspase-1 enzyme, and lessens cell death following Hla intoxication. This is likely due to the reduced levels of ADAM10 and NLRP3 proteins, as well as the decreased display of the ADAM10 receptor in the G-1-treated THP-1 cells. Our studies, along with our previous work, suggest the potential therapeutic use of G-1 in reducing Hla susceptibility in humans. This highlights the importance of GPER in immune regulation and its potential as a therapeutic target.

Fluorene-9-bisphenol (BHPF) is an emerging contaminant. Presently, there is no report on its interaction with G protein-coupled estrogen receptor 1 (GPER). By using an integrated toxicity research scenario that combined theoretical study with experimental methods, BHPF was found to inhibit the GPER-mediated effect via direct receptor binding. Molecular dynamics simulations found that Trp2726.48 and Glu2756.51 be the key amino acids of BHPF binding with GPER. Moreover, the calculation indicated that BHPF was a suspected GPER inhibitor, which neither can activate GPER nor is able to form water channels of GPER. The role of two residues was successfully verified by following gene knockout and site-directed mutagenesis assays. Further in vitro assays showed that BHPF could attenuate the increase in intracellular concentration of free Ca2+ induced by G1-activated GPER. Besides, BHPF showed an enhanced cytotoxicity compared with G15, indicating that BHPF might be a more potent GPER inhibitor than G15. In addition, a statistically significant effect on the mRNA level of GPER was observed for BHPF. In brief, the present study proposes that BHPF be a GPER inhibitor, and its GPER molecular recognition mechanism has been revealed, which is of great significance for the health risk and assessment of BHPF.

Estrogen and related receptors have been shown to have a significant impact on human development, reproduction, metabolism and immune regulation and to play a critical role in tumor development and treatment. Traditionally, the nuclear estrogen receptors (nERs) ERα and ERβ have been thought to be involved in mediating the estrogenic effects. However, our group and others have previously demonstrated that the G protein-coupled estrogen receptor (GPER) is the third independent ER, and estrogen signaling mediated by GPER is known to play an important role in normal physiology and a variety of abnormal diseases. Interestingly, recent studies have progressively revealed GPER involvement in the maintenance of the normal immune system, abnormal immune diseases, and inflammatory lesions, which may be of significant clinical value primarily in the immunotherapy of tumors. In this article, we review current advances in GPER-related immunomodulators and provide a theoretical basis and potential clinical targets to ameliorate immune-related diseases and immunotherapy for tumors.

Type 1 diabetes (T1D) affects gastrointestinal (GI) motility, favoring gastroparesis, constipation, and fecal incontinence, which are more prevalent in women. The mechanisms are unknown. Given the G-protein-coupled estrogen receptor\'s (GPER) role in GI motility, we investigated sex-related diabetes-induced epigenetic changes in GPER. We assessed GPER mRNA and protein expression levels using qPCR and Western blot analyses, and quantified the changes in nuclear DNA methyltransferases and histone modifications (H3K4me3, H3Ac, and H3K27Ac) by ELISA kits. Targeted bisulfite and chromatin immunoprecipitation assays were used to evaluate DNA methylation and histone modifications around the GPER promoter by chromatin immunoprecipitation assays in gastric and colonic smooth muscle tissues of male and female control (CTR) and non-obese diabetic (NOD) mice. GPER expression was downregulated in NOD, with sex-dependent variations. In the gastric smooth muscle, not in colonic smooth muscle, downregulation coincided with differences in methylation ratios between regions 1 and 2 of the GPER promoter of NOD. DNA methylation was higher in NOD male colonic smooth muscle than in NOD females. H3K4me3 and H3ac enrichment decreased in NOD gastric smooth muscle. H3K4me3 levels diminished in the colonic smooth muscle of NOD. H3K27ac levels were unaffected, but enrichment decreased in NOD male gastric smooth muscle; however, it increased in the NOD male colonic smooth muscle and decreased in the female NOD colonic smooth muscle. Male NOD colonic smooth muscle exhibited decreased H3K27ac levels, not female, whereas female NOD colonic smooth muscle demonstrated diminished enrichment of H3ac at the GPER promoter, contrary to male NOD. Sex-specific epigenetic mechanisms contribute to T1D-mediated suppression of GPER expression in the GI tract. These insights advance our understanding of T1D complications and suggest promising avenues for targeted therapeutic interventions.

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Icariin, a flavonoid glycoside, is extracted from Epimedium. This study aimed to investigate the vascular protective effects of icariin in type 1 diabetic rats by inhibiting high-mobility group box 1 (HMGB1)-related inflammation and exploring its potential mechanisms. The impact of icariin on vascular dysfunction was assessed in streptozotocin (STZ)-induced diabetic rats through vascular reactivity studies. Western blotting and immunofluorescence assays were performed to measure the expressions of target proteins. The release of HMGB1 and pro-inflammation cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The results revealed that icariin administration enhanced acetylcholine-induced vasodilation in the aortas of diabetic rats. It also notably reduced the release of pro-inflammatory cytokines, including interleukin-8 (IL-8), IL-6, IL-1β, and tumor necrosis factor-alpha (TNF-α) in diabetic rats and high glucose (HG)-induced human umbilical vein endothelial cells (HUVECs). The results also unveiled that the pro-inflammatory cytokines in the culture medium of HUVECs could be increased by rHMGB1. The increased release of HMGB1 and upregulated expressions of HMGB1-related inflammatory factors, including advanced glycation end products (RAGE), Toll-like receptor 4 (TLR4), and phosphorylated p65 (p-p65) in diabetic rats and HG-induced HUVECs, were remarkably suppressed by icariin. Notably, HMGB1 translocation from the nucleus to the cytoplasm in HUVECs under HG was inhibited by icariin. Meanwhile, icariin could activate G protein-coupled estrogen receptor (GPER) and sirt1. To explore the role of GPER and Sirt1 in the inhibitory effect of icariin on HMGB1 release and HMGB-induced inflammation, GPER inhibitor and Sirt1 inhibitor were used in this study. These inhibitors diminished the effects of icariin on HMGB1 release and HMGB1-induced inflammation. Specifically, the GPER inhibitor also negated the activation of Sirt1 by icariin. These findings suggest that icariin activates GPER and increases the expression of Sirt1, which in turn reduces HMGB1 translocation and release, thereby improving vascular endothelial function in type 1 diabetic rats by inhibiting inflammation.

G protein-coupled estrogen receptor (GPER) plays a prominent role in facilitating the rapid, non-genomic signaling of estrogens in breast cancer cells. Herein, a comprehensive overview of the role of GPER in ER-ɑ-negative breast cancer is provided. Activation of GPER affected proliferation, metastasis and epithelial mesenchymal transition in ER-ɑ negative breast cancer cells. Clinical studies have demonstrated that GPER positivity was strongly correlated with larger tumor size and advanced clinical stage, suggesting that GPER/ERK signaling may play a role in promoting tumor progression. Strong evidence existed that environmental contaminants like bisphenol A have a carcinogenic potential mediated by GPER activation. The complexity of the cross talk between GPER and other receptors including ER-β, ER-α36, Estrogen-related receptor α (ERRα) and androgen receptor has been discussed. The potential utility of small molecules and phytoestrogens targeting GPER, adds valuable insights into its therapeutic potential. This review holds promises in advancing our understanding of GPER role in ER-ɑ-negative breast cancer. Overall, the consequences of GPER activation are still an area of active research and the implication are not entirely clear.

The porcine bulbourethral glands produce a gel-type secretion. Although the role of these contributions to reproductive success remains murky, the bulbourethral glands are major accessory sex glands in this species. Isometric growth in the early neonatal interval is followed by allometric growth in the late juvenile interval (6 to 11 weeks of age), while circulating endogenous steroids are low. The rate of allometric growth increases during the peripuberal interval (16 to 20 weeks of age) when systemic testosterone is relatively high. Gene expression for androgen receptor (AR) and for the steroid 5 alpha-reductase 2 (SRD5A2) enzyme that synthesizes the more potent androgen dihydrotestosterone from its precursor was evaluated by qPCR analyses of bulbourethral gland tissue. Tissues were collected from control boars (2 weeks to 40 weeks of age) and from littermates of these boars treated with letrozole to suppress endogenous estrogen synthesis. Gene expression for these two key proteins in androgen signaling was quite low during the initial allometric growth in the late juvenile and prepuberal intervals, suggesting that this initial growth was not primarily stimulated by androgens. These observations are consistent with a more direct estrogen-mediated inhibition of growth via GPER previously proposed, with the sensitivity extending into the late juvenile interval when estrogens as well as androgens are normally relatively low.