| Summary: | 碩士 === 國立清華大學 === 生醫工程與環境科學系 === 99 === Bisphenol A (BPA) is a common environmental estrogen as an endocrine disruptor to mimic endogenous estrogen 17??estradiol by binding to estrogen receptor. As lipophilicity and bioaccumulation, BPA has the potency to accumulate in adipose tissue and interfere with adipokin secretion and homeostasis of energy metabolism. BPA accumulates in adipose tissue might influence the gene expression of adiponectin and leptin leading to induce metabolic diseases. Due to common use for plastics products, human would expose low doses of BPA in daily life. Otherwise, BPA could cause abnormal DNA methylation affecting the stability of chromosome and gene expression to increase the risk of breast cancer and endometrial cancer. Thus, the purpose of this study was to investigate whether BPA caused cytotoxicity and gene expression in human breast cancer MCF-7 cells, and to explore the difference in DNA methylation and the BPA levels among pregnant women, women with endometrial hyperplasia (EH) and infertile women. The cell proliferation was increased in the 1 nM BPA treatment and attenuated at higher doses of BPA (104 and 105 nM). BPA changed the duration of S phase in cell cycle that prolonged at 10 and 105 nM BPA and shortened at 103 nM BPA. The results of real-time PCR showed that BPA treatment (10, 104 and 105 nM) attenuated the mRNA expression of ER? and increased the expression of ER?? With the treatment of 103 nM BPA, the gene expression of ER? was increased as well as ER?? Low-dose of BPA treatment (10 nM) increased the gene expression of adiponectin and decreased the expression of leptin. With the treatment of 105 nM BPA, MCF-7 cells had the increased expression of adiponectin and leptin. This study explored the distribution of DNA methylation and gene ontology to select candidate genes after BPA treatment using Illumina Infinium HumanMethylation27 BeadChip. Twenty-two genes selected from the difference of beta and M value were categorized into metabolic function, development and nervous process in analysis of GO term. LIPE (hormone-sensitive lipase) involved in the metabolic process was hypomethylated after BPA treatment (10 and 105 nM). MMP13 is a matrix metalloproteinase for tissue remodeling and its activity of promoter is regulated by ER. The results of this study showed that MMP13 had the hypomethylation level after BPA treatment in accompany with the low level of MMP13 mRNA expression.
Homeobox A10 (HOXA10) plays an important role in endometrium development. MSP (methyl specific PCR) was used in this study to determine the methylation level of HOXA10. This study found that a negative correlation between the methylation level of HOXA10 and its mRNA expression in pregnant women (r = -0.657), and a positive correlation in EH women (r = 0.8). In conclusion, these results indicated that BPA may influence the gene expression underlying DNA methylation and other epigenetic modulation.
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