Joonwoo Park

Estrogen receptor beta inhibits transcriptional activity of hypoxia inducible factor-1 through the downregulation of arylhydrocarbon receptor nuclear translocator

IntroductionEstrogen receptor (ER) β is predicted to play an important role in prevention of breast cancer development and metastasis. We have shown previously that ERβ inhibits hypoxia inducible factor (HIF)-1α mediated transcription, but the mechanism by which ERβ works to exert this effect is not understood.MethodsVascular endothelial growth factor (VEGF) was measured in conditioned medium by enzyme-linked immunosorbent assays. Reverse transcription polymerase chain reaction (RT-PCR), Western blotting, immunoprecipitation, luciferase assays and chromatin immunoprecipitation (ChIP) assays were used to ascertain the implication of ERβ on HIF-1 function.ResultsIn this study, we found that the inhibition of HIF-1 activity by ERβ expression was correlated with ERβs ability to degrade aryl hydrocarbon receptor nuclear translocator (ARNT) via ubiquitination processes leading to the reduction of active HIF-1α/ARNT complexes. HIF-1 repression by ERβ was rescued by overexpression of ARNT as examined by hypoxia-responsive element (HRE)-driven luciferase assays. We show further that ERβ attenuated the hypoxic induction of VEGF mRNA by directly decreasing HIF-1α binding to the VEGF gene promoter.ConclusionsThese results show that ERβ suppresses HIF-1α-mediated transcription via ARNT down-regulation, which may account for the tumour suppressive function of ERβ.

Activation of Estrogen Receptor by Bavachin from Psoralea corylifolia

In this study, we examined the estrogenic activity of bavachin, a component of Psoralea corylifolia that has been used as a traditional medicine in Asia. Bavachin was purified from ethanolic extract of Psoralea corylifolia and characterized its estrogenic activity by ligand binding, reporter gene activation, and endogenous estrogen receptor (ER) target gene regulation. Bavachin showed ER ligand binding activity in competitive displacement of [3H] E2 from recombinant ER. The estrogenic activity of bavachin was characterized in a transient transfection system using ERα or ERβ and estrogen-responsive luciferase plasmids in CV-1 cells with an EC50 of 320 nM and 680 nM, respectively. Bavachin increased the mRNA levels of estrogen-responsive genes such as pS2 and PR, and decreased the protein level of ERα by proteasomal pathway. However, bavachin failed to activate the androgen receptor in CV-1 cells transiently transfected with the corresponding receptor and hormone responsive reporter plasmid. These data indicate that bavachin acts as a weak phytoestrogen by binding and activating the ER.

Effects of ginseng on two main sex steroid hormone receptors: estrogen and androgen receptors

Ginseng has been used in China for at least two millennia and is now popular in over 35 countries. It is one of the worlds popular herbs for complementary and alternative medicine and has been shown to have helpful effects on cognition and blood circulation, as well as anti-aging, anti-cancer, and anti-diabetic effects, among many others. The pharmacological activities of ginseng are dependent mainly on ginsenosides. Ginsenosides have a cholesterol-like four trans-ring steroid skeleton with a variety of sugar moieties. Nuclear receptors are one of the most important molecular targets of ginseng, and reports have shown that members of the nuclear receptor superfamily are regulated by a variety of ginsenosides. Here, we review the published literature on the effects of ginseng and its constituents on two main sex steroid hormone receptors: estrogen and androgen receptors. Furthermore, we discuss applications for sex steroid hormone receptor modulation and their therapeutic efficacy.

Subglutinol A, an immunosuppressive α-pyrone diterpenoid from Fusarium subglutinans, acts as an estrogen receptor antagonist.

Subglutinol A is an immunosuppressive α-pyrone diterpenoid isolated from Fusarium subglutinans that exhibits osteogenic activity. Several non-steroid mycotoxins isolated from various strains of Fusarium fungi exhibit female steroid hormone activities. In this study, we characterized the estrogenic activity of subglutinol A (1). Subglutinol A blocked the 17β-estradiol-induced activation of reporter plasmids and endogenous estrogen-responsive target genes in a dose-dependent manner and efficiently destabilized ER proteins as shown using the estrogen receptor antagonist ICI 182,780. Subglutinol A also displaced the specific binding of [(3)H]17β-estradiol from ER in MCF-7 whole-cell ligand binding assays. These data demonstrate the potential of subglutinol A as an ER antagonist though its competition with 17β-estradiol for direct ER association.

Bisphenol A induces COX-2 through the mitogen-activated protein kinase pathway and is associated with levels of inflammation-related markers in elderly populations

Abstract Bisphenol A (BPA) is a well‐known endocrine‐disrupting chemical, and it is one of the highest volume chemicals produced worldwide. Even though several in vivo and in vitro studies showed positive associations of BPA exposure with pro‐inflammatory cytokines such as tumor necrosis factor‐&agr; and interleukin (IL)‐6, the mechanism by which BPA induces inflammation is unclear. We investigated the mechanism by which BPA induces inflammation (expression of inflammation‐related genes, changes in oxidative stress, and cell proliferation and migration) and evaluated the effect of BPA exposure on inflammation‐related markers in epidemiologic studies using repeat urine and serum samples from elderly subjects. BPA induced COX‐2 expression via nuclear translocation of NF‐&kgr;B and activation of mitogen‐activated protein kinase (MAPK) by phosphorylation of ERK1/2 and enhanced the migration of lung cancer A549 and breast cancer MDAMB‐231 cells. In two epidemiologic studies, we detected associations of BPA with six inflammation‐related markers (WBC, CRP, IL‐10, ALT, AST, and &ggr;‐GTP levels). Our findings probably suggest that BPA exposure induces inflammation and exacerbates tumorigenesis. HighlightsBPA induces COX‐2 expression in lung cancer A549 and breast cancer MDAMB‐231 cells.Induction of COX‐2 is through nuclear translocation of NF‐&kgr;B and activation of MAPK.BPA enhances the migration of A549 and MDAMB‐231 cells.Relations between BPA and inflammation‐related markers were evaluated in elderly.BPA exposure was associated with WBC, CRP, IL‐10, ALT, AST, and &ggr;‐GTP levels.

Mammalian MST2 kinase and human Salvador activate and reduce estrogen receptor alpha in the absence of ligand

Mammalian MST2 kinase plays an important role in cell proliferation, survival, and apoptosis. In search of interacting proteins of MST2, we found that estrogen receptor α (ERα) co-immunoprecipitates with MST2 and its adaptor protein human Salvador (hSAV). Using reporter assays, we observed that overexpression of MST2 and hSAV leads to ligand-independent activation of ERα in human breast cancer MCF-7 cells, which was attenuated by the knockdown of hSAV. Furthermore, using truncated mutants of hSAV, we observed that the C terminus of hSAV is necessary and sufficient for the induction of ERα transactivation. The expression of hSAV and MST2 results in the phosphorylation of ERα at serine residues 118 and 167 and represses ERα expression. We then investigated the incidence of MST2 and ERα expression with other tumor biomarkers using commercially available tissue microarrays. Among 40 breast cancer samples analyzed, 60% (24 out of 40) expressed MST2. Nineteen among the 40 cases were MST2-positive and ERα-negative, implying a correlation between expressions of MST2 with loss of ERα in breast tumor samples. This study suggests that MST and hSAV act as novel co-regulators of ERα and may play an important role in breast cancer pathogenesis.

Methyl syringate, a TRPA1 agonist represses hypoxia-induced cyclooxygenase-2 in lung cancer cells.

BACKGROUND We have previously found that methyl syringate is a specific and selective agonist of the human transient receptor potential channel ankyrin 1 (TRPA1) and suppresses food intake and gastric emptying in imprinting control region mice. Because TRPA1 has been implicated in inflammatory responses, and inflammation and tumorigenesis are stimulated by the cyclooxygenase-2 (COX-2)/prostaglandin E2 pathway in hypoxic cancer cells. PURPOSE This study examined the effects of methyl syringate on hypoxia-induced COX-2 in human distal lung epithelial A549 cells. STUDY DESIGN The effect of the methyl syringate on suppression of hypoxia-induced COX-2 in A549 cells were determined by Western blot and/or quantitative real-time polymerase chain reaction. The anti-invasive effect of methyl syringate was evaluated on A549 cells using matrigel invasion assay. RESULTS Methyl syringate suppressed hypoxia-induced COX-2 protein and mRNA expression and promoter activity and reduced hypoxia-induced cell migration and invasion and secretion of vascular endothelial growth factor. These effects were antagonized by a TRPA1 antagonist, implying their mediation by the TRPA1 pathway. CONCLUSION Together, these results indicate that methyl syringate inhibits the hypoxic induction of COX-2 expression and cell invasion through TRPA1 activation. These findings suggest that methyl syringate could be effective to suppress hypoxia-induced inflammation and indicate an additional functional effect of methyl syringate.

Ginseng on Nuclear Hormone Receptors

The first record of ginseng use dates back over two millennia, and ginseng is now popular in more than 35 countries. Ginsenosides are the pharmacological constituents responsible for the beneficial effects of ginseng. There is increasing evidence that ginseng and its bioactive ingredients are involved in the regulation of nuclear receptors, molecules that act in response to the specific binding of hormones, which link to a diverse array of signaling pathways, such as the ERK and PI3K/Akt pathways. Knowledge of the mechanism of how ginseng mediates these complexes is essential for the development of multi-target phytomedicine as possible therapy for different diseases. Here, we discuss the literature on the effects of ginseng and its constituents on estrogen, glucocorticoid, peroxisome proliferator-activated, and androgen nuclear hormone receptors, as well as how ginseng and its constituents exert their biological function in the treatment of cancer, obesity, and cardiovascular and neurological disorders. The accumulated results definitely show that the nuclear receptors are cellular targets of ginsenosides, but more rigorous data are required to establish and provide a scientific basis to confirm the suggested efficacy of ginseng or products with ginsenosides.

Hypoxia induced phosphorylation of estrogen receptor at serine 118 in the absence of ligand

The estrogen receptor (ER) plays an important role in breast cancer development and progression. Hypoxia modulates the level of ERα expression and induces ligand-independent transcriptional activation of ERα, which is closely related with the biology of breast carcinomas. Since phosphorylation itself affects the transcriptional activity and stabilization of ERα, we examined changes in ERα phosphorylation under hypoxic conditions. Hypoxia induced phosphorylation of ERα at serine residue 118 (S118) in the absence of estrogen through the mitogen-activated protein kinase (MAPK)/ERK1/2 pathway. Cell proliferation was significantly decreased under normoxia or hypoxia when ERα harboring the S118A mutation was overexpressed. Our previous studies showed that ER degradation is the most prominent phenomenon under hypoxia. E2-induced ER protein downregulation is dependent on phosphorylation of S118. However, hypoxia-induced ERα degradation did not involve S118 phosphorylation. Our study implies the existence of a differential mechanism between E2 and hypoxia-mediated ERα protein degradation. Understanding the mechanistic behavior of ER under hypoxia will likely facilitate understanding of endocrine therapy resistance and development of treatment strategies for breast cancer.

4,5-Di-O-Caffeoylquinic Acid from Ligularia fischeri Suppresses Inflammatory Responses Through TRPV1 Activation

Ligularia fischeri (Ledeb.) Turcz., a perennial plant native to northeastern Asia, has long been used as folk remedies for the alleviation of inflammatory symptoms. We investigated whether the extract of L. fischeri (LFEx) and caffeoylquinic acid (CQA) derivatives, the pharmacologically active ingredients identified from L. fischeri, regulate inflammation via a transient receptor potential vanilloid 1 (TRPV1)‐mediated pathway. Changes in intracellular Ca2+ levels to the LFEx and trans‐5‐O‐CQA, 3,4‐di‐O‐CQA, 3,5‐di‐O‐CQA, and 4,5‐di‐O‐CQA were monitored in TRPV1‐expressing human embryonic kidney cell HEK 293T. LFEx and 4,5‐di‐O‐CQA (EC50 = 69.34 ± 1.12 μM) activated TRPV1, and these activations were significantly inhibited by ruthenium red, a general blocker of TRP channels, and capsazepine, a specific antagonist of TRPV1. 4,5‐Di‐O‐CQA has been determined having antiinflammatory effect under hypoxic conditions by detecting the expression of cyclooxygenase‐2 (COX‐2), a representative inflammatory marker, and cellular migration in human pulmonary epithelial A549 cells. 4,5‐Di‐O‐CQA suppressed COX‐2 expression and cell migration, and this inhibition was countered by co‐treatment with capsazepine. This study provides evidence that L. fischeri is selective to inflammatory responses via a TRPV1‐mediated pathway, and 4,5‐di‐O‐CQA might play a key role to create these effects. Copyright