4-Hydroxyestradiol induces mammary epithelial cell transformation through Nrf2-mediated heme oxygenase-1 overexpression

Mammary hydroxylated oestrogen activates the NLRP3 inflammasome in tumor-associated macrophages to promote breast cancer progression and metastasis

Breast cancer remains one of the primary causes of cancer-related death. An imbalance of oestrogen homeostasis and an inflammatory tumor microenvironment (TME) are vital risk factors for the progression and metastasis of breast cancer. Here, we showed that oestrogen homeostasis was disrupted both in breast cancer patients and in a transgenic MMTV-PyMT mouse model of breast cancer, and significant levels of hydroxylated oestrogen accumulated in the mammary tissues of these patients and mice. We also observed that tumor-associated macrophages (TAMs) were the main population of immune cells present in the breast TME. TAM-dependent tumor metastasis could be triggered by hydroxylated oestrogen via NLRP3 inflammasome activation and IL-1β production. Mechanistically, TAM-derived inflammatory cytokines induced the expression of matrix metalloproteinases (MMPs) in breast tumor cells, leading to breast tumor invasion and metastasis. Conceptually, our study reveals a previously unknown role of hydroxylated oestrogen in the reprogramming of the TME via NLRP3 inflammasome activation in TAMs, which ultimately facilitates breast cancer cells proliferation, migration, and invasion.

Interplay between Estrogen, Kynurenine, and AHR Pathways: An immunosuppressive axis with therapeutic potential for breast cancer treatment

Breast cancer is one of the most common malignancies among women worldwide. Estrogen exposure via endogenous and exogenous sources during a lifetime, together with environmental exposure to estrogenic compounds, represent the most significant risk factor for breast cancer development. As breast tumors establish, multiple pathways are deregulated. Among them is the aryl hydrocarbon receptor (AHR) signaling pathway. AHR, a ligand-activated transcription factor associated with the metabolism of polycyclic aromatic hydrocarbons and estrogens, is overexpressed in breast cancer. Furthermore, AHR and estrogen receptor (ER) cross-talk pathways have been observed. Additionally, the Tryptophan (Trp) catabolizing enzymes indolamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO) are overexpressed in breast cancer. IDO/TDO catalyzes the formation of Kynurenine (KYN) and other tryptophan-derived metabolites, which are ligands of AHR. Once KYN activates AHR, it stimulates the expression of the IDO enzyme, increases the level of KYN, and activates non-canonical pathways to control inflammation and immunosuppression in breast tumors. The interplay between E2, AHR, and IDO/TDO/KYN pathways and their impact on the immune system represents an immunosuppressive axis on breast cancer. The potential modulation of the immunosuppressive E2-AHR-IDO/TDO/KYN axis has aroused great expectations in oncotherapy. The present article will review the mechanisms implicated in generating the immunosuppressive axis E2-AHR-IDO/TDO/KYN in breast cancer and the current state of knowledge as a potential therapeutic target.

Reproductive toxicity of combined effects of endocrine disruptors on human reproduction

Confluence of environmental, genetic, and lifestyle variables is responsible for deterioration of human fecundity. Endocrine disruptors or endocrine disrupting chemicals (EDCs) may be found in a variety of foods, water, air, beverages, and tobacco smoke. It has been demonstrated in experimental investigations that a wide range of endocrine disrupting chemicals have negative effects on human reproductive function. However, evidence on the reproductive consequences of human exposure to endocrine disrupting chemicals is sparse and/or conflicting in the scientific literature. The combined toxicological assessment is a practical method for assessing the hazards of cocktails of chemicals, co-existing in the environment. The current review provides a comprehensive overview of studies emphasizing the combined toxicity of endocrine disrupting chemicals on human reproduction. Endocrine disrupting chemicals interact with each other to disrupt the different endocrine axes, resulting in severe gonadal dysfunctions. Transgenerational epigenetic effects have also been induced in germ cells, mostly through DNA methylation and epimutations. Similarly, after acute or chronic exposure to endocrine disrupting chemicals combinations, increased oxidative stress (OS), elevated antioxidant enzymatic activity, disrupted reproductive cycle, and reduced steroidogenesis are often reported consequences. The article also discusses the concentration addition (CA) and independent action (IA) prediction models, which reveal the importance of various synergistic actions of endocrine disrupting chemicals mixtures. More crucially, this evidence-based study addresses the research limitations and information gaps, as well as particularly presents the future research views on combined endocrine disrupting chemicals toxicity on human reproduction.

Theaflavin Attenuates TBHP-Induced Endothelial Cells Oxidative Stress by Activating PI3K/AKT/Nrf2 and Accelerates Wound Healing in Rats

The treatment of wounds remains a clinical challenge because of poor angiogenesis under the wound bed, and increasingly, the patients’ need for functional and aesthetically pleasing scars. Previous reports have shown that Theaflavin can induce angiogenesis and terminate the progression of ischemic cardiovascular disease, but limited therapy is available for the management of cutaneous wounds. In this study, our in vitro work discovered that human umbilical vein endothelial cells (HUVECs) exposed to Theaflavin can alleviate apoptosis and cell dysfunction induced by tert-butyl hydroperoxide (TBHP). The cellular activity of HUVECs were assessed by cell tube formation, migration and adhesion. Mechanistically, Theaflavin protected HUVECs from TBHP-stimulated cell apoptosis through the activation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor (erythroid-derived 2)-like 2 (Nrf2) axis, so Nrf2 silencing can partly eliminate the cytoprotective effect of Theaflavin treatment. In in vivo experiments, administering Theaflavin orally can enhance vascularization in regenerated tissues and accelerate wound healing. In summary, our data served as a novel evidence for the wound healing treatment with Theaflavin, and certified the potential mechanism of Theaflavin, which can be used as a potential agent for cutaneous wound therapy.

Endocrine Disruptors as a New Etiologic Factor of Bone Tissue Diseases (Review)

At present, diseases of bones and joints stand third after cardiovascular and oncological pathologies which demands the necessity of searching for new etiological factors and pathogenetical mechanisms of these illnesses. The accumulating data show the association between the impairment of bone tissue development and regeneration and endocrine disruptor impact. Endocrine disruptors are chemical substances, mainly of anthropogenic origin, capable of affecting endocrine system functioning and interfering with organ morphogenesis and physiological functions. The development and regeneration of bone tissues have a complex hormonal regulation and therefore bone tissue cells, osteoblasts, and osteoclasts can be considered as potential targets for endocrine disruptors. Endocrine disruptors have been established to be able to impair calcium metabolism which also contributes to the development of musculoskeletal system pathology. Data on histogenesis of bone tissue and regeneration, calcium metabolism as well as on hormonal regulation of bone growth and remodeling processes are presented in this work. Recent information on the effect of the main endocrine disruptor classes (diethylstilbestrol, organochlorine pesticides, alkylphenols, bisphenol A, dioxins, polychlorinated biphenyls, and phthalic acid esters) on the development and remodeling of bone tissues and calcium metabolism has been summarized. The established physiological and molecular mechanisms of their action have been also considered.

Effect of estrogens and their metabolites genotoxicity on the pathogenesis and progression of estrogen-dependent breast cancer

Oncological diseases, due to the still increasing morbidity and mortality, are one of the main problems of modern medicine. Cancer of the mammary gland is the most common cancer among women around the world, and is the second cause of cancer deaths in this group, immediately after lung cancer. This kind of cancer belongs to an estrogen-dependent cancer, with proven associations with hormonal disorders in the body, occurring especially in the perimenopausal period and among women using hormone replacement therapy, as well as a result of the action of various xenobiotics that may interact with the estrogen receptor. Hormone steroids are widely used in medicine and their side effects are constantly discussed. The role of these compounds and their metabolites in maintaining hormonal balance is well understood, while many studies indicate the possible contribution of these steroids in the progression of the cancer process, especially in mammary gland tissue. Therefore, the genotoxic action of this group of compounds is still studied. Due to the limited number of scientific reports, the aim of this paper was to review and critically analyze data from the literature regarding the participation of estrogens (17β-estradiol) and their metabolites (2-methoxy estradiol, 4-hydroxy estradiol, 16α-hydroxyestrone) in the induction of carcinogenesis in mammary gland, in particular concerning the genotoxic activity of 17β-estradiol metabolites.

Binding partners of NRF2: Functions and regulatory mechanisms

NRF2 is a redox-sensitive transcription factor that plays an important role in protecting organisms against diverse types of electrophiles or oxidants. The level of NRF2 is maintained low in normal cells, but highly elevated in cancer provoking chemoresistance or radioresistance. It is now recognized that NRF2 does not merely maintain the redox balance, but also plays significant roles in autophagy, apoptosis, cell cycle progression, and stem cell differentiation, all of which could be possibly attributable to the existence of multiple binding proteins. In the present manuscript, we summarize direct binding partners of NRF2 and illustrate how they bind to NRF2 and regulate its stability or activity.

Long-term exposure of 4-hydroxyestradiol induces the cancer cell characteristics via upregulating CYP1B1 in MCF-10A cells

Life-long estrogen exposure is one of the major risk factors in the development and progression of breast cancer. However, little is known about the molecular mechanisms, by which chronic exposure to estrogen contributes to breast carcinogenesis. The aim of the present study was to investigate the effects of long-term exposure with 4-hydroxyestradiol (4-OHE₂) on acquired cancer characteristics of human mammary epithelial MCF-10A cells. The possible regulators were further studied in chronic 4-OHE₂-treated MCF-10A cells. We observed that MCF-10A cells long-term exposed to 4-OHE₂ acquire the characteristics of cancer cells, such as enhanced cell growth, EMT properties, and increased migration and invasiveness. Moreover, the expression of CYP1B1 was significantly elevated in long-term 4-OHE₂-treated MCF-10A cells. Block of CYP1B1 significantly reduced the cancer cell characteristics in long-term 4-OHE₂-treated MCF-10A cells. Our results indicated that 4-OHE₂ mediated enhanced cancer cell characteristics in mammary epithelial cells are an important key event for breast carcinogenesis process. CYP1B1 partially contributes to the 4-OHE₂ induced cancer cell characteristics in MCF-10A cells. Targeting CYP1B1 might offer a new strategy for the treatment of estrogen-induced breast cancer.

Heme Oxygenase-1 Has an Antitumor Role in Breast Cancer

Aims: Heme oxygenase-1 (HO-1) is an enzyme involved in cellular responses to oxidative stress and has also been shown to regulate processes related to cancer progression. In this regard, HO-1 has been shown to display a dual effect with either antitumor or protumor activity, which is also true for breast cancer (BC). In this work, we address this discrepancy regarding the role of HO-1 in BC. Results: HO-1 was detected in human BC tissues, and its protein levels correlated with reduced tumor size and longer overall survival time of patients, thus suggesting the clinical importance of HO-1 in this type of cancer. Contrariwise, nuclear localization of HO-1 correlated with higher tumor grade suggesting that the effect of HO-1 is dependent on its cellular localization. In vivo experiments showed that both pharmacological activation and genetic overexpression of HO-1 reduce the tumor burden in two different animal models of BC. Furthermore, the pharmacological and genetic activation of HO-1 in several BC cell lines reduce the cellular viability by inducing apoptosis and cell cycle arrest and decrease the cellular migration and invasion rates by modulating pathways involved in the epithelial-mesenchymal transition. Furthermore, HO-1 activation impaired in vivo the metastatic dissemination. Innovation and Conclusion: By using various BC cell lines and animal models as well as human tumor samples, we demonstrated that total HO-1 displays antitumor activities in BC. Furthermore, our study suggests that HO-1 subcellular localization may explain the differential effects observed for the protein in different tumor types.

Water and soil pollution as determinant of water and food quality/contamination and its impact on male fertility

Over the past two decades, public health has focused on the identification of environmental chemical factors that are able to adversely affect hormonal function, known as endocrine disruptors (EDs). EDs mimic naturally occurring hormones like estrogens and androgens which can in turn interfere with the endocrine system. As a consequence, EDs affect human reproduction as well as post and pre-natal development. In fact, infants can be affected already at prenatal level due to maternal exposure to EDs. In particular, great attention has been given to those chemicals, or their metabolites, that have estrogenic properties or antagonistic effects on the activity of androgen or even inhibiting their production. These compounds have therefore the potential of interfering with important physiological processes, such as masculinization, morphological development of the urogenital system and secondary sexual traits. Animal and in vitro studies have supported the conclusion that endocrine-disrupting chemicals affect the hormone-dependent pathways responsible for male gonadal development, either through direct interaction with hormone receptors or via epigenetic and cell-cycle regulatory modes of action. In human populations, epidemiological studies have reported an overall decline of male fertility and an increased incidence of diseases or congenital malformations of the male reproductive system. The majority of studies point towards an association between exposure to EDs and male and/or female reproductive system disorders, such as infertility, endometriosis, breast cancer, testicular cancer, poor sperm quality and/or function. Despite promising discoveries, a causal relationship between the reproductive disorders and exposure to specific toxicants has yet to be established, due to the complexity of the clinical protocols used, the degree of occupational or environmental exposure, the determination of the variables measured and the sample size of the subjects examined. Despite the lack of consistency in the results of so many studies investigating endocrine-disrupting properties of many different classes of chemicals, the overall conclusion points toward a positive association between exposure to EDs and reproductive system. Future studies should focus on a uniform systems to examine human populations with regard to the exposure to specific EDs and the direct effect on the reproductive system.

Redox Signaling by Reactive Electrophiles and Oxidants

The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.

Ferulic acid protects against heat stress-induced intestinal epithelial barrier dysfunction in IEC-6 cells via the PI3K/Akt-mediated Nrf2/HO-1 signaling pathway

PURPOSE

Intestinal epithelial barrier dysfunction is crucial in the pathogenesis of intestinal and systemic diseases. Ferulic acid (FA) possesses promising antioxidant activities. In a previous study, we demonstrated potentially protective effects of FA against heat stress-induced intestinal epithelial barrier dysfunction in IEC-6 cells. However, the underlying mechanisms are unclear. The present study aimed to elucidate whether FA protects IEC-6 cells from heat stress-induced intestinal epithelial barrier dysfunction via antioxidative mechanisms.

MATERIALS AND METHODS

IEC-6 cells were pretreated with FA prior to hyperthermia exposure at 42 °C for 6 h, and the levels of intracellular reactive oxygen species (ROS), malondialdehyde (MDA), nitrogen oxide (NO), and superoxide dismutase (SOD) activity were analyzed. The intestinal epithelial barrier function was determined by transepithelial electrical resistance (TER) values and 4-kDa fluorescein isothiocyanate-dextran (FD4) flux in IEC-6 cell monolayers. Expression of related proteins was detected by Western blotting.

RESULTS

FA suppressed heat stress-induced intestinal oxidative stress damage by reducing ROS, MDA and NO production, while enhancing SOD activity. Furthermore, FA treatment strengthened intestinal barrier function via increasing the phosphorylation levels of Akt, nuclear factor-erythroid 2-related factor 2 (Nrf2) and hemeoxygenase-1 (HO-1) protein expression, which was reversed by zinc protoporphyrin (an HO-1 inhibitor). Additionally, LY294002, a specific PI3K/Akt inhibitor, significantly suppressed FA-induced Nrf2 nuclear translocation and HO-1 protein expression and inhibited FA-induced occludin and ZO-1 protein expression.

CONCLUSIONS

FA protected against heat stress-induced intestinal epithelial barrier dysfunction via activating the PI3K/Akt-mediated Nrf2/HO-1 signaling pathway in IEC-6 cells.

Red Clover Aryl Hydrocarbon Receptor (AhR) and Estrogen Receptor (ER) Agonists Enhance Genotoxic Estrogen Metabolism

Many women consider botanical dietary supplements (BDSs) as safe alternatives to hormone therapy for menopausal symptoms. However, the effect of BDSs on breast cancer risk is largely unknown. In the estrogen chemical carcinogenesis pathway, P450 1B1 metabolizes estrogens to 4-hydroxylated catechols, which are oxidized to genotoxic quinones that initiate and promote breast cancer. In contrast, P450 1A1 catalyzed 2-hydroxylation represents a detoxification pathway. The current study evaluated the effects of red clover, a popular BDS used for women’s health, and its isoflavones, biochanin A (BA), formononetin (FN), genistein (GN), and daidzein (DZ), on estrogen metabolism. The methoxy estrogen metabolites (2-MeOE₁, 4-MeOE₁) were measured by LC-MS/MS, and CYP1A1 and CYP1B1 gene expression was analyzed by qPCR. Nonmalignant ER-negative breast epithelial cells (MCF-10A) and ER-positive breast cancer cells (MCF-7) were derived from normal breast epithelial tissue and ER+ breast cancer tissue. Red clover extract (RCE, 10 μg/mL) and isoflavones had no effect on estrogen metabolism in MCF-10A cells. However, in MCF-7 cells, RCE treatments downregulated CYP1A1 expression and enhanced genotoxic metabolism (4-MeOE₁/CYP1B1 > 2-MeOE₁/CYP1A1). Experiments with the isoflavones showed that the AhR agonists (BA, FN) preferentially induced CYP1B1 expression as well as 4-MeOE₁. In contrast, the ER agonists (GN, DZ) downregulated CYP1A1 expression likely through an epigenetic mechanism. Finally, the ER antagonist ICI 182,780 potentiated isoflavone-induced XRE-luciferase reporter activity and reversed GN and DZ induced downregulation of CYP1A1 expression. Overall, these studies show that red clover and its isoflavones have differential effects on estrogen metabolism in “normal” vs breast cancer cells. In breast cancer cells, the AhR agonists stimulate genotoxic metabolism, and the ER agonists downregulate the detoxification pathway. These data may suggest that especially breast cancer patients should avoid red clover and isoflavone based BDSs when making choices for menopausal symptom relief.

Docosahexaenoic Acid Induces Expression of Heme Oxygenase-1 and NAD(P)H:quinone Oxidoreductase through Activation of Nrf2 in Human Mammary Epithelial Cells

Docosahexaenoic acid (DHA), an ω-3 fatty acid abundant in fish oils, has diverse health beneficial effects, such as anti-oxidative, anti-inflammatory, neuroprotective, and chemopreventive activities. In this study, we found that DHA induced expression of two representative antioxidant/cytoprotective enzymes, heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase (NQO1), in human mammary epithealial (MCF-10A) cells. DHA-induced upregulation of these enzymes was accompanied by enhanced translocation of the redox-sensitive transcription factor Nrf2 into the nucleus and its binding to antioxidant response element. Nrf2 gene silencing by siRNA abolished the DHA-induced expression of HO-1 and NQO1 proteins. When MCF-10A cells were transfected with mutant constructs in which the cysteine 151 or 288 residue of Keap1 was replaced by serine, DHA-induced expression of HO-1 and NQO1 was markedly reduced. Moreover, DHA activated protein kinase C (PKC)δ and induced Nrf2 phosphorylation. DHA-induced phosphorylation of Nrf2 was abrogated by the pharmacological PKCδ inhibitor rottlerin or siRNA knockdown of its gene expression. The antioxidants N-acetyl-l-cysteine and Trolox attenuated DHA-induced activation of PKCδ, phosphorylation of Nrf2, and and its target protein expression. In conclusion, DHA activates Nrf2, possibly through modification of critical Keap1 cysteine 288 residue and PKCδ-mediated phosphorylation of Nrf2, leading to upregulation of HO-1 and NQO1 expression.

Human exposure to endocrine disrupting chemicals: effects on the male and female reproductive systems

Endocrine disrupting chemicals (EDCs) comprise a group of chemical compounds that have been examined extensively due to the potential harmful effects in the health of human populations. During the past decades, particular focus has been given to the harmful effects of EDCs to the reproductive system. The estimation of human exposure to EDCs can be broadly categorized into occupational and environmental exposure, and has been a major challenge due to the structural diversity of the chemicals that are derived by many different sources at doses below the limit of detection used by conventional methodologies. Animal and in vitro studies have supported the conclusion that endocrine disrupting chemicals affect the hormone dependent pathways responsible for male and female gonadal development, either through direct interaction with hormone receptors or via epigenetic and cell-cycle regulatory modes of action. In human populations, the majority of the studies point towards an association between exposure to EDCs and male and/or female reproduction system disorders, such as infertility, endometriosis, breast cancer, testicular cancer, poor sperm quality and/or function. Despite promising discoveries, a causal relationship between the reproductive disorders and exposure to specific toxicants is yet to be established, due to the complexity of the clinical protocols used, the degree of occupational or environmental exposure, the determination of the variables measured and the sample size of the subjects examined. Future studies should focus on a uniform system of examining human populations with regard to the exposure to specific EDCs and the direct effect on the reproductive system.

Cytoprotective effects of mild plasma-activated medium against oxidative stress in human skin fibroblasts

Non-thermal atmospheric pressure plasma (NTAPP) has recently been applied to living cells and tissues and has emerged as a novel technology for medical applications. NTAPP affects cells not only directly, but also indirectly with previously prepared plasma-activated medium (PAM). The objective of this study was to demonstrate the preconditioning effects of “mild PAM” which was prepared under relatively mild conditions, on fibroblasts against cellular injury generated by a high dose of hydrogen peroxide (H₂O₂). We observed the preconditioning effects of mild PAM containing approximately 50 μM H₂O₂. Hydrogen peroxide needs to be the main active species in mild PAM for it to exert preconditioning effects because the addition of catalase to mild PAM eliminated these effects. The nuclear translocation and recruitment of nuclear factor erythroid 2-related factor 2 (Nrf2) to antioxidant response elements (ARE) in heme oxygenase 1 (HO-1) promoters and the up-regulation of HO-1 were detected in fibroblasts treated with mild PAM. The addition of ZnPP, a HO-1-specific inhibitor, or the knockdown of Nrf2 completely abrogated the preconditioning effects. Our results demonstrate that mild PAM protects fibroblasts from oxidative stress by up-regulating HO-1, and the H₂O₂-induced activation of the Nrf2-ARE pathway needs to be involved in this reaction.

What has passed is prolog: new cellular and physiological roles of G6PD

G6PD deficiency has been the most pervasive inherited disorder in the world since having been discovered. G6PD has an antioxidant role by functioning as a major nicotinamide adenine dinucleotide phosphate (NADPH) provider to reduce excessive oxidative stress. NADPH can produce reactive oxygen species (ROS) and reactive nitrogen species (RNS) mediated by NADPH oxidase (NOX) and nitric oxide synthase (NOS), respectively. Hence, G6PD also has a pro-oxidant role. Research in the past has focused on the enhanced susceptibility of G6PD-deficient cells or individuals to oxidative challenge. The cytoregulatory role of G6PD has largely been overlooked. By using a metabolomic approach, it is noted that upon oxidant challenge, G6PD-deficient cells will reprogram the GSH metabolism from regeneration to synthesis with exhaustive energy consumption. Recently, new cellular/physiologic roles of G6PD have been discovered. By using a proteomic approach, it has been found that G6PD plays a regulatory role in xenobiotic metabolism possibly via NOX and the redox-sensitive Nrf2-signaling pathway to modulate the expression of xenobiotic-metabolizing enzymes. Since G6PD is a key regulator responsible for intracellular redox homeostasis, G6PD deficiency can alter redox balance leading to many abnormal cellular effects such as the cellular inflammatory and immune response against viral infection. G6PD may play an important role in embryogenesis as G6PD-knockdown mouse cannot produce offspring and G6PD-deficient C. elegans with defective egg production and hatching. This array of findings indicates that the cellular and physiologic roles of G6PD, other than the classical role as an antioxidant enzyme, deserve further attention.