Mitochondrial estrogen receptor β inhibits cell apoptosis via interaction with Bad in a ligand-independent manner

Role of intrinsic apoptosis in environmental exposure health outcomes

Environmental exposures are linked to diseases of high public health concern, including cancer, neurodegenerative disorders, and autoimmunity. These diseases are caused by excessive or insufficient cell death, prompting investigation of mechanistic links between environmental toxicants and dysregulation of cell death pathways, including apoptosis. This review describes how legacy and emerging environmental exposures target the intrinsic apoptosis pathway to potentially drive pathogenesis. Recent discoveries reveal that dynamic regulation of apoptosis may heighten the vulnerability of healthy tissues to exposures in children, and that apoptotic signaling can guide immune responses, tissue repair, and tumorigenesis. Understanding how environmental toxicants dysregulate apoptosis will uncover opportunities to deploy apoptosis-modulating agents for the treatment or prevention of exposure-linked diseases.

Mitophagy involved the biological processes of hormones

Mitochondria fulfill vital functions in energy production, maintaining ion balance, and facilitating material metabolism. Mitochondria are sacrificed to protect cells or induce apoptosis when the body is under stress. The regulatory pathways of mitophagy include both ubiquitin-dependent and non-dependent pathways. The involvement of mitophagy has been demonstrated in the onset and progression of numerous diseases, highlighting its significant role. Endocrine hormones are chemical substances secreted by endocrine organs or endocrine cells, which participate in the regulation of physiological functions and internal environmental homeostasis of the body. Imbalances in endocrine hormones contribute to the development of various diseases. However, the precise impact of mitophagy on the physiological and pathological processes involving endocrine hormones remains unclear. This article aims to comprehensively overview recent advancements in understanding the mechanisms through which mitophagy regulates endocrine hormones.

The role of mitochondria and mitochondrial hormone receptors on the bioenergetic adaptations to lactation

The most recognized role of mitochondria is producing more than 90% of the total cellular energy in the form of ATP. In addition, mitochondrial function encompasses the maintenance of antioxidant balance, the regulation of intracellular calcium concentrations, the progression of cell death, and the biosynthesis of purines, hemes, lipids, amino acids and steroid hormones. Mitochondria are also important hormone targets. Estrogens, progestagens, and prolactin, are among the hormones that can impact mitochondrial function and modulate the underlying adaptations to changing bioenergetic and metabolic needs. Lactation represents a metabolic challenge with significant increases in energy requirements and fluctuating levels of hormones. To meet these bioenergetic demands, liver mitochondria increase their state 3 and 4 respiration, adjust superoxide dismutase activity, and elevate succinate dehydrogenase-related respiration. Skeletal muscle mitochondria respond by increasing their respiratory control ratio and adjusting catalase activity. In this review, these adaptations are described considering the lactation hormonal milieu.

Estrogens, Cancer and Immunity

Sex hormones are included in many physiological and pathological pathways. Estrogens belong to steroid hormones active in female sex. Estradiol (E2) is the strongest female sex hormone and, with its receptors, contributes to oncogenesis, cancer progression and response to treatment. In recent years, a role of immunosurveillance and suppression of immune response in malignancy has been well defined, forming the basis for cancer immunotherapy. The interplay of sex hormones with cancer immunity, as well as the response to immune checkpoint inhibitors, is of interest. In this review, we investigate the impact of sex hormones on natural immune response with respect to main active elements in anticancer immune surveillance: dendritic cells, macrophages, lymphocytes and checkpoint molecules. We describe the main sex-dependent tumors and the contribution of estrogen in their progression, response to treatment and especially modulation of anticancer immune response.

Identification of the estrogen receptor beta as a possible new tamoxifen-sensitive target in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype. Despite the proven efficacy of combined immunochemotherapy (R-CHOP) in the majority of patients, ~40% of DLBCL patients do not respond or will relapse and consequently have a very poor prognosis. The development of targeted therapies has not improved patient survival, underscoring the need for new treatment approaches. Using an unbiased genome-wide CD20 guilt-by-association approach in more than 1800 DLBCL patients, we previously identified the estrogen receptor beta (ERβ) as a new target in DLBCL. Here, we demonstrate that ERβ is expressed at significantly higher levels in DLBCL compared to normal B cells, and ERβ plays a role in the protection against apoptosis in DLBCL. Targeting of the ERβ with the selective estrogen receptor modulator tamoxifen reduces cell viability in all tested DLBCL cell lines. Tamoxifen-induced cell death was significantly decreased in an ERβ knock-out cell line. The activity of tamoxifen was confirmed in a xenograft human lymphoma model, as tumor growth decreased, and survival significantly improved. Finally, tamoxifen-treated breast cancer (BC) patients showed a significantly reduced risk of 38% for DLBCL compared to BC patients who did not receive tamoxifen. Our findings provide a rationale to investigate tamoxifen, a hormonal drug with a good safety profile, in DLBCL patients.

Estrogen receptor beta increases clear cell renal cell carcinoma stem cell phenotype via altering the circPHACTR4/miR-34b-5p/c-Myc signaling

Early clinical studies indicated that estrogen receptor beta (ERβ) might play key roles to impact the progression of clear cell renal cell carcinoma (ccRCC). The detailed molecular mechanisms, however, remain unclear. Here, we found ERβ could increase the cancer stem cell (CSC) population via altering the circPHACTR4/miR-34b-5p/c-Myc signaling. Mechanism dissection revealed that ERβ could suppress circular RNA PHACTR4 (circPHACTR4) expression via direct binding to the estrogen response elements (EREs) on the 5' promoter region of its host gene, phosphatase and actin regulator 4 (PHACTR4) to decrease miR-34b-5p expression. The decreased miRNA-34b-5p could then increase c-Myc mRNA translation via targeting its 3' untranslated region (3' UTR). The in vivo mouse model with subcutaneous xenografts of ccRCC cells also validated the in vitro data. Importantly, analysis results from ccRCC TCGA database and our clinical data further confirmed the above in vitro/in vivo data. Together, these results suggest that ERβ may increase CSC population in ccRCC via altering ERβ/circPHACTR4/miR-34b-5p/c-Myc signaling and that targeting this newly identified signal pathway may help physicians to better suppress ccRCC progression.

Role of sex hormones in lung cancer

Lung cancer represents the world's leading cause of cancer deaths. Sex differences in the incidence and mortality rates for various types of lung cancers have been identified, but the biological and endocrine mechanisms implicated in these disparities have not yet been determined. While some cancers such as lung adenocarcinoma are more commonly found among women than men, others like squamous cell carcinoma display the opposite pattern or show no sex differences. Associations of tobacco product use rates, susceptibility to carcinogens, occupational exposures, and indoor and outdoor air pollution have also been linked to differential rates of lung cancer occurrence and mortality between sexes. While roles for sex hormones in other types of cancers affecting women or men have been identified and described, little is known about the influence of sex hormones in lung cancer. One potential mechanism identified to date is the synergism between estrogen and some tobacco compounds, and oncogene mutations, in inducing the expression of metabolic enzymes, leading to enhanced formation of reactive oxygen species and DNA adducts, and subsequent lung carcinogenesis. In this review, we present the literature available regarding sex differences in cancer rates, associations of male and female sex hormones with lung cancer, the influence of exogenous hormone therapy in women, and potential mechanisms mediated by male and female sex hormone receptors in lung carcinogenesis. The influence of biological sex on lung disease has recently been established, thus new research incorporating this variable will shed light on the mechanisms behind the observed disparities in lung cancer rates, and potentially lead to the development of new therapeutics to treat this devastating disease.

Anti-Apoptotic and Antioxidant Activities of the Mitochondrial Estrogen Receptor Beta in N2A Neuroblastoma Cells

Estrogens are steroid hormones that play a crucial role in the regulation of the reproductive and non-reproductive system physiology. Among non-reproductive systems, the nervous system is mainly affected by estrogens due to their antioxidant, anti-apoptotic, and anti-inflammatory activities, which are mediated by membranous and nuclear estrogen receptors, and also by non-estrogen receptor-associated estrogen actions. Neuronal viability and functionality are also associated with the maintenance of mitochondrial functions. Recently, the localization of estrogen receptors, especially estrogen receptor beta, in the mitochondria of many types of neuronal cells is documented, indicating the direct involvement of the mitochondrial estrogen receptor beta (mtERβ) in the maintenance of neuronal physiology. In this study, cell lines of N2A cells stably overexpressing a mitochondrial-targeted estrogen receptor beta were generated and further analyzed to study the direct involvement of mtERβ in estrogen neuroprotective antioxidant and anti-apoptotic actions. Results from this study revealed that the presence of estrogen receptor beta in mitochondria render N2A cells more resistant to staurosporine- and H₂O₂-induced apoptotic stimuli, as indicated by the reduced activation of caspase-9 and -3, the increased cell viability, the increased ATP production, and the increased resistance to mitochondrial impairment in the presence or absence of 17-β estradiol (E2). Thus, the direct involvement of mtERβ in antioxidant and anti-apoptotic activities is documented, rendering mtERβ a promising therapeutic target for mitochondrial dysfunction-associated degenerative diseases.

Inhibitory Effect of Hydroxysafflor Yellow B on the Proliferation of Human Breast Cancer MCF-7 Cells

BACKGROUND

A recent patent has been issued for hydroxysafflor yellow A (HSYA) as a drug to prevent blood circulation disorders. Hydroxysafflor yellow B (HSYB), an isomer of HSYA with antioxidative effects, has been isolated from the florets of Carthamus tinctorius. The effects of HSYB on the proliferation of cancer cells and its mechanism of action have not been investigated.

OBJECTIVE

The aims of this study were to investigate the anti-cancer effects and the molecular mechanism of HSYB for breast cancer MCF-7 cells.

METHODS

MTT assays and colony formation assays were used to assess the survival and proliferation of MCF-7 cells, respectively. Hoechst 33258 and flow cytometry were used to measure cell apoptosis and flow cytometry to determine effects on the cell cycle. Western blots were used to measure protein levels.

RESULTS

Treatment with HSYB reduced survival and proliferation of human breast cancer MCF-7 cells in a dose-dependent manner. Furthermore, HSYB arrested the MCF-7 cell cycle at the S phase and downregulated cyclin D1, cyclin E, and CDK2. Compared with a control group, HSYB suppressed the protein levels of p-PI3K, PI3K, AKT, and p-AKT in MCF-7 cells. In addition, HSYB decreased the levels of Bcl- 2, increased the levels of Bax, cleaved caspase-3 and caspase-9, and subsequently induced MCF-7 cell apoptosis.

CONCLUSION

These data demonstrate that HSYB arrests the MCF-7 cell cycle at the S phase and induces cell apoptosis. Patent US20170246228 indicates that HSYB can be potentially used for the prevention and treatment of human breast cancer.

Role of estrogen and its receptors mediated-autophagy in cell fate and human diseases

Studies have shown that morbidity of several diseases varies between males and females. This difference likely arises due to sex-related hormones. Estrogen, a primary female sex steroid hormone, plays a critical role in mediating many of the physiological functions like growth, differentiation, metabolism, and cell death. Recently, it has been demonstrated that estrogen mediates autophagy through its receptors (ERs) namely ERα, ERβ, and G-protein coupled estrogen receptor (GPER). However, the specific role of estrogen and its receptors mediated-autophagy in cell fate and human diseases such as cancers, cardiovascular disease and nervous system disease remains unclear. In this review, we comprehensively summarize the complex role of estrogen and its receptors-mediated autophagy in different cell lines and human diseases. In addition, we further discuss the key signaling molecules governing the role of ERs in autophagy. This review will serve as the basis for a proposed model of autophagy constituting a new frontier in estrogen-related human diseases. Here, we discuss the dual role of ERα in classical and non-classical autophagy through B-cell lymphoma 2 (BCL2)-associated athanogene 3 (BAG3). Next, we review the role of ERβ in pro-survival pathways through the promotion of autophagy under stress conditions. We further discuss activation of GPER via estrogen often mediates autophagy or mitophagy suppression, respectively. In summary, we believe that understanding the relationship between estrogen and its receptors mediated-autophagy on cell fate and human diseases will provide insightful knowledge for future therapeutic implications.

Roles of ERK1/2 and PI3K/AKT signaling pathways in mitochondria-mediated apoptosis in testes of hypothyroid rats

The absence of the thyroid hormone (TH) could impair testicular function, but its mechanism is still rudimentary. This study aims to explore the roles of estrogen receptor (ER α, β) and G protein-coupled receptor 30 (GPR30), extracellular signal regulated kinase (ERK1/2) and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways in apoptosis in testes of hypothyroidism rats. Male Wistar rats were randomly divided into control (C), low-(L) and high-hypothyroidism (H) groups [1 mL per 100 g BW per day normal saline, 0.001% and 0.1% propylthiouracil (PTU), respectively] by intragastrical gavage for 60 days. The levels of triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) in serum were measured. Expressions of ERα, ERβ and GPR30, pathway related protein expressions of ERK1/2 and PI3 K/AKT and apoptosis were detected in testicular homogenates. The results showed that T3 and T4 levels were decreased, and the TSH level was increased significantly in the H group. Protein expressions of ERα, ERβ and GPR30 decreased significantly in the H group. Significantly decreased protein expressions of p-ERK1/2, p-PI3K p85, p-AKT Ser473, Ras, p-Raf-1 Ser259, p-Raf-1 Ser338 and cyclin D1 in L and H groups as well PI3K p85, p-AKT and Thr308 in the H group were observed. Moreover, there was a significant increase in the Bad protein expression in L and H groups. In addition, there was a significant increase in the expression of Bax/Bcl-2, caspase 9 and cleaved caspase 3 and a significant decrease in the total caspase 3 protein expression in the H group. These results suggested that ERK1/2 and PI3K/AKT signaling pathways could be suppressed by hypothyroidism via inhibiting the expressions of ERs and could finally induce apoptosis in testes.

Estrogens regulate life and death in mitochondria

Estrogens coordinate and integrate cellular metabolism and mitochondrial activities by direct and indirect mechanisms mediated by differential expression and localization of estrogen receptors (ER) in a cell-specific manner. Estrogens regulate transcription and cell signaling pathways that converge to stimulate mitochondrial function- including mitochondrial bioenergetics, mitochondrial fusion and fission, calcium homeostasis, and antioxidant defense against free radicals. Estrogens regulate nuclear gene transcription by binding and activating the classical genomic estrogen receptors α and β (ERα and ERβ) and by activating plasma membrane-associated mERα, mERβ, and G-protein coupled ER (GPER, GPER1). Localization of ERα and ERβ within mitochondria and in the mitochondrial membrane provides additional mechanisms of regulation. Here we review the mechanisms of rapid and longer-term effects of estrogens and selective ER modulators (SERMs, e.g., tamoxifen (TAM)) on mitochondrial biogenesis, morphology, and function including regulation of Nuclear Respiratory Factor-1 (NRF-1, NRF1) transcription. NRF-1 is a nuclear transcription factor that promotes transcription of mitochondrial transcription factor TFAM (mtDNA maintenance factorFA) which then regulates mtDNA-encoded genes. The nuclear effects of estrogens on gene expression directly controlling mitochondrial biogenesis, oxygen consumption, mtDNA transcription, and apoptosis are reviewed.

Nuclear Transcription Factors in the Mitochondria: A New Paradigm in Fine-Tuning Mitochondrial Metabolism

Noncanonical functions of several nuclear transcription factors in the mitochondria have been gaining exceptional traction over the years. These transcription factors include nuclear hormone receptors like estrogen, glucocorticoid, and thyroid hormone receptors: p53, IRF3, STAT3, STAT5, CREB, NF-kB, and MEF-2D. Mitochondria-localized nuclear transcription factors regulate mitochondrial processes like apoptosis, respiration and mitochondrial transcription albeit being nuclear in origin and having nuclear functions. Hence, the cell permits these multi-stationed transcription factors to orchestrate and fine-tune cellular metabolism at various levels of operation. Despite their ubiquitous distribution in different subcompartments of mitochondria, their targeting mechanism is poorly understood. Here, we review the current status of mitochondria-localized transcription factors and discuss the possible targeting mechanism besides the functional interplay between these factors.

Estrogen receptor-β in mitochondria: implications for mitochondrial bioenergetics and tumorigenesis

Estrogen enhances mitochondrial function by enhancing mitochondrial biogenesis and sustaining mitochondrial energy-transducing capacity. Shifts in mitochondrial bioenergetic pathways from oxidative phosphorylation to glycolysis have been hypothesized to be involved in estrogen-induced tumorigenesis. Studies have shown that mitochondria are an important target of estrogen. Estrogen receptor-β (ERβ) has been shown to localize to mitochondria in a ligand-dependent or -independent manner and can affect mitochondrial bioenergetics and anti-apoptotic signaling. However, the functional role of mitochondrial ERβ in tumorigenesis remains unclear. Clinical studies of ERβ-related tumorigenesis have shown that ERβ stimulates mitochondrial metabolism to meet the high energy demands of processes such as cell proliferation, cell survival, and transformation. Thus, in elucidating the precise role of mitochondrial ERβ in cell transformation and tumorigenesis, it will be particularly valuable to explore new approaches for the development of medical treatments targeting mitochondrial ERβ-mediated mitochondrial function and preventing apoptosis.