Study On Expression Of TNF-α And IL-6 In Human Endometrial Cells Induced By TCDD In Vitro

BackgroundAlthough endometriosis is a common gynecological problem, the etiology is still unknown. Recently environmental contaminants have been suggested to play a role in the pathogenesis of endometriosis. Epidemiological findings and animal experiments have shown that dioxins are associated with an increased prevalence and severity of endometriosis, however, the underlying mechanism of dioxin is not clear.Endometriosis is a multifactorial disease. Researches have suggested that dioxins might exert multi-effects on the pathophysiology of endometriosis through a number of pathways. At present, there are accumulating studies showing that the effects of dioxin on the immune systems are one of the most important mechanisms. As the key mediators of intercellular communication within the immune system, cytokines are believed to be crucial in the pathogenesis of endometriosis. It is notable that the level of IL-6 and TNF-α , which are believed to be implicated in the pathogenesis of endometriosis, can be regulated by dioxins in animal or in vitro experiments. Therefore, we postulated that dioxins may play a role in the pathogenesis of endometriosis by modulating the secretion of IL-6 and TNF-α fromendometrial cells.In present study, we determined the expression of messenger RNA and protein of IL-6 and TNF-α induced by TCDD in endometrial cells in vitro, and analyzed the difference of the levels about the expression of messenger RNA and protein of IL-6 and TNF- a in eutopic endometrial cells from the patients with and without endometriosis in order to get insight into the possible involvement of TCDD in the pathogenesis of endometriosis.Materials and MethodsSubjects undergoing elective surgery for leiomyoma uteri were recruited for non-endometriosis biopsies (n=15), women with surgery and pathology confirmed ovary endometriosis were recruited for endometriosis (n=13). Firstly, immunocytochemistry was performed to identify endometrial cells, and secondly MTT was used to determine the viability of endometrial cells exposed to different doses TCDD for 24 hours(0,0.1nM,lnM,10nM,100nMTCDD). Thirdly, the dose response(0,0.01nM,0.1nM,lnM,10nM,100nMTCDD) of human endometrial cells to 24 hours exposure was examined for the mRNA and protein expression of IL-6 and TNF-α by real-time PCR and ELISA, respectively. Lastly, the mRNA and protein expression of IL-6 and TNF-α by different endometrial cells exposed to 10nM TCDD were measured by real-time PCR and ELISA.One-way ANOVA, Kruskal-Wallis H, T test, Mann-Whitney U and Wilcoxon non-parametric tests were used for statistical analysis, two-tailed test with p<0.05 were considered significant. All data were managed with SPSS 10.0 for windows.Results1. The TNF-α protein secreted by endometrial cells from women with or without endometriosis was both significantly increased after exposing to 10nM TCDD for 24 hours (P<0.05), and the induced expression was more strikingly higher in theeutopic endometrial cells from endometriosis patients (P<0.05).2. The IL-6 protein secreted by endometrial cells from endometriosis patients was significantly inhibited after exposing to 10nM TCDD for 24 hours (P<0.05), but not in endometrial cells from women without endometriosis (P>0.05).3. The mRNA expression of IL-6 and TNF-α were not affected by endometrial cells from women with or without endometriosis exposed to 10nM TCDD for 24 hours (P>0.05).Conclusions1. Human endometrial tissues may be one of the targets of dioxin. The proposed link between dioxin exposure and endometriosis may be explained in part by the up-regulation of TNF-α and down-regulation of IL-6 expression in endometrial cells.2. The regulatory effect of TCDD on endometrial cells was different in women with or without endometriosis.3. The main mechanism that TCDD regulates the expression of TNF-α and IL-6 in endometrial cells may not act on the transcription level.