Inhibition of tight junction protein ZO-1 expression by estrogen in human gut mucosa

Abstract

Abstract Background Females have stronger cellular and humoral immunities compared to males. Sex hormones are playing roles in these differences; however, the role of sex hormones in human gut permeability is essentially unknown. Methods The expression of tight junction ZO-1, estrogen receptor (ER)-α and β in male and female primary gut tissues were analyzed using immunohistochemistry. The inhibition of estrogen on ZO-1 was evaluated in primary gut tissues by qPCR. ZO-1 expression and NF-κB activation in Caco-2 cells was evaluated by western blot, immunofluorescent staining and reporter activity assays. Data are presented as median (interquartile range [IQR]). Results The expression of ZO-1 and ER-β but not ER-α were present in both male and female gut tissues, the median immunofluorescence intensities (MFI) of ZO-1 expression were 2.48 (2.40–3.11) and 3.59 (3.11–4.23) for females and males respectively (P = 0.02, non-parametric Mann-whitney test). No sex difference in MFI expression of ER-β was found (P = 0.79). After 24 h incubating with physiologic dose of estrogen (200 pg/mL) in primary gut tissues in vitro, the median ZO-1 mRNA relative expression to GADPH by qPCR was 1.002 (1.000–1.003) and 0.80 (0.21–0.84) for treatment with medium alone and estrogen respectively. The median MFI expression of ZO-1 in Caco-2 cells assessed by microscopy was 0.97 (0.77–1.14) and 1.16 (0.76–1.37) for treatment with estrogen and medium alone respectively (P = 0.01). The median luciferase activity of NK-κB in Caco-2 cells assessed by NK-κB reporter activity assay was 0.58 (0.53–0.60) and 0.98 (0.87–1.05) for treatment with estrogen and medium alone respectively (P = 0.002). Conclusion Estrogen inhibits the ZO-1 expression and NF-κB activity in human gut mucosa.