Signals involved in the effects of bisphenol A (BPA) on proliferation and motility of Leydig cells: a comparative proteomic analysis.

Recent studies indicated that bisphenol A (BPA) can disrupt spermatogenesis and then cause male infertility. The present study revealed that BPA greater than 10-6 M inhibited the proliferation of Leydig TM3 cells via a concentration dependent manner. The proteomic study revealed that 50 proteins were modulated in TM3 cells following exposure to BPA, which was relevant to structure, motility, cell metabolism, protein and nucleotide processing, and cell proliferation. Furthermore, BPA increased the in vitro migration and invasion of Leydig TM3 cells, which might be due to the BPA's modulation of proteins related to cell structure and motility such as actin and heat shock protein (HSP). Silencing of galectin-1, which was up regulated by BPA, significantly abolished the BPA-induced migration of TM3 cells. BPA treatment obviously increased the phosphorylation of ERK1/2 and Akt, while only PD98509 (ERK1/2 inhibitor) significantly attenuated BPA induced up regulation of galectin-1. Furthermore, PD98509 also reversed BPA induced migration of TM3 cells. Our study demonstrated that xenoestrogen BPA at micromolar or greater concentrations can modulate protein profiles, inhibit cell proliferation, and promote the in vitro migration and invasion of Leydig TM3 cells. It provided new insight into the mechanisms responsible for BPA induced male infertility.

Bisphenol A stimulates the epithelial mesenchymal transition of estrogen negative breast cancer cells via FOXA1 signals.

Estrogen receptor negative (ER-) breast cancer are associated with increased risks for metastasis and high rates of recurrence. Our present study revealed that nanomolar bisphenol A (BPA), a typical endocrine disrupting chemical, promoted the in vitro migration and induced mesenchymal transition (EMT) of ER-breast cancer cells. PCR array revealed that BPA can down regulate 12 and up regulate 2 genes involved in regulation of signal transduction and biological pathways of breast cancer. The down regulated genes included FOXA1, which is a key determinant of endocrine response and down regulated by BPA via a time dependent manner. Silencing of FOXA1 by siRNA triggered the EMT of SkBr3 cells. While over expression of FOXA1 abolished BPA induced EMT. Further, 10(-8) M BPA significantly increased the phosphorylation of ERK1/2, p38-MAPK, and Akt in SkBr3 cells, while only PI3K/Akt inhibitor LY294002 attenuated the BPA induced down regulation of FOXA1 and E-Cadherin (E-Cad). Over expression of Akt also suppressed FOXA1 expression in SkBr3 cells. It suggested that PI3K/Akt mediated, at least partially, BPA induced EMT of ER-breast cancer cells. In summary, our data provided the first evidence that BPA can promote the EMT of ER-breast cancer cells through down regulation of FOXA1.

Signaling related with biphasic effects of bisphenol A (BPA) on Sertoli cell proliferation: a comparative proteomic analysis.

BACKGROUND: Biphasic effects on cell proliferation of bisphenol A (BPA) can occur at lesser or greater exposures. Sertoli cells play a pivotal role in supporting proliferation and differentiation of germ cells. The mechanisms responsible for inverse effects of great and low concentrations of BPA on Sertoli cell proliferation need further study. METHODS: We utilized proteomic study to identify the protein expression changes of Sertoli TM4 cells treated with 10(-8)M and 10(-5)M BPA. The further mechanisms related to mitochondria, energy metabolism and oxidative stress were investigated by qRT-PCR and Western-blotting analysis. RESULTS: Proteomic studies identified 36 proteins and two major clusters of proteins including energy metabolism and oxidative stress expressed with opposite changes in Sertoli cells treated with 10(-8)M and 10(-5)M BPA, respectively, for 24h. Exposure to 10(-5)M BPA resulted in greater oxidative stress and then inhibited cell proliferation, while ROS scavenger NAC effectively blocked these effects. Exposure to 10(-8)M BPA caused higher intercellular ATP, greater activities of mitochondria, and resulted in significant proliferation of TM4 cells, while oligomycin A, an inhibitor of ATP synthase, abolished these growth advantages. CONCLUSIONS: Our study demonstrated that micromolar BPA inhibits proliferation of Sertoli cells by elevating oxidative stress while nanomolar BPA stimulates proliferation by promoting energy metabolism. GENERAL SIGNIFICANCE: Micromolar BPA inhibits cell proliferation by elevating oxidative stress while nanomolar BPA stimulates cell proliferation by promoting energy metabolism.

Involvement of activating ERK1/2 through G protein coupled receptor 30 and estrogen receptor α/ß in low doses of bisphenol A promoting growth of Sertoli TM4 cells.

Sertoli cells play a pivotal role in supporting proliferation of germ cells and differentiation during spermatogenesis in mammals. Nanomolar concentrations of Bisphenol A (BPA) can significantly stimulate the proliferation of mouse immature Sertoli (TM4) cells. However, mechanisms by which BPA caused these effects were still unclear. In the present study, an inverse U-shaped curve was observed when treating TM4 cells with increasing doses of BPA: 1 to 10nM BPA significantly stimulated the proliferation of TM4 cells and increased the proportion of cells in S phase; >1 µM BPA caused lesser proliferation of cells. Exposure of TM4 cells to G15 or ICI 182,780, which are specific antagonists of GPR30 and estrogen receptor α/ß (ERα/ß), respectively, abolished BPA-induced proliferation of cells, which suggests that both GPR30 and ERα/ß were involved in the observed effects of BPA. Furthermore, exposure to BPA caused rapid (5 min) activation of ERK1/2 via both GPR30 and ERα/ß. Blocking the GPR30/EGFR signal transduction pathway by antagonists suppressed both phosphorylation of ERK and BPA-induced cell proliferation. BPA up-regulated mRNA and protein expression of GPR30 in a concentration-dependent manner. In summary, the results reported here indicated that activating ERK1/2 through GPR30 and ERα/ß is involved in low doses of BPA that promoted growth of Sertoli TM4 cells. The GPR30/EGFR/ERK signal is the downstream transduction pathway in BPA-induced proliferation of TM4 Sertoli cells.

In vitro estimation of exposure of Hong Kong residents to mercury and methylmercury via consumption of market fishes.

In order to evaluate effects of exposure to mercury (tHg) and methylmercury (MeHg) of Hong Kong residents via consumption of fish, total and bioaccessible concentrations of tHg and MeHg were measured in 10 freshwater and 10 marine fishes collected from markets in Hong Kong. Concentrations of tHg and MeHg in fishes ranged from 27.2 to 311ngg(-1) (median 88.9ngg(-1)) and ND to 116ngg(-1) (median 45.0ngg(-1)), respectively. Concentrations of MeHg in marine fishes (64.4±28.5ngg(-1)) were significantly greater than those in freshwater fishes (40.3±26.0ngg(-1)). Bioaccessibility tHg and MeHg was predicted for edible flesh of twenty fishes by use of an in vitro gastrointestinal assay. Bioaccessibilities of tHg and MeHg ranged from 21.4 to 51.7% (mean 37.4%) and 19.5 to 59.2% (mean 43.7%), respectively. Based on total concentrations, diets of 36% of adults and 51% of children exceeded the reference dose (RfD, 100ngkg(-1)bodymass(bm)d(-1)) for MeHg, but when bioaccessibility was considered, consumption of local market fish would not result in an EDIbio exceeded the RfD of MeHg for Hong Kong adults. These contradictory results suggested that risk assessments based on total concentrations would overestimate exposure because not all of contaminants consumed are bioaccessible. Furthermore, 9% of children had EDIbio for MeHg that exceeded the RfD, which suggests that more attention should be paid to consumption of local fish on health and development of children in Hong Kong.

Hydroxylated and methoxylated polybrominated diphenyl ethers in blood plasma of humans in Hong Kong.

Hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDE) are suspected endocrine disruptors. Little is known about the accumulation or sources of these chemicals in tissues of humans, particularly those residing in Hong Kong, which is one of the most densely populated cities in the world. Seven MeO-BDEs, fifteen OH-BDEs and three bromophenols (BRPs) were analyzed in blood plasma of 116 humans that had been collected by the Hong Kong Red Cross. Total concentrations of MeO-BDEs, OH-BDEs and BRPs ranged from 3.8×10² to 52×10³ pg g⁻¹ lipid (median 4.5×10³ pg g⁻¹), 5.3 to 4.9×10² pg g⁻¹ lipid (81 pg g⁻¹) and ND to 1.1×10² pg g⁻¹ lipid (3.7 pg g⁻¹), respectively. 3-MeO-BDE-47, 6-OH-BDE-47 and 2, 4, 5-TBP were the predominant MeO-BDEs, OH-BDEs and BRPs, respectively. These results are consistent with accumulation of MeO-BDEs, OH-BDEs and BRPs in human plasma being primarily from natural products and inter-conversion of natural products. Coefficients of determination for some pairs of congeners such as 3-OH-BDE-100 and 6-OH-BDE-47, 6-OH-BDE-85 and 5'-OH-BDE-99, and 2, 4-DBP and 6-OH-BDE-85, were near 1.0, which is consistent with them having common sources. Patterns of relative concentrations of the target analytes were similar in the diet, particularly fish, as in blood plasma of humans, which suggests that the diet and particularly seafood might be a source of these compounds and PBDEs. Furthermore, biotransformation of natural chemicals such as OH-BDEs to BRPs might be the primary route of their elimination from humans.