Soy isoflavones improves endometrial barrier through tight junction gene expression

Contamination with bacterial endotoxin causes the disruption of the tight junction (TJ) barrier. We investigated the ameliorative effect of dietary flavonoids genistein (Ge) and daidzein (Di) in normal or lipopolysaccharide (LPS)-induced disruption of epithelial barrier function of the endometrium. Using the immortalized porcine glandular endometrial epithelial cells (PEG), transepithelial electrical resistance (TER) and FITC-dextran flux (FD-4) across the monolayer were measured. The mRNA expression of TJ proteins, zona occludens-1 (ZO1), and claudin-1, -3, -4, -7 and -8 was evaluated by real-time RT-PCR for coinciding effect of Ge or Di occurred at the gene transcription level. The results revealed that Ge and Di altered the TER, depending on times and concentrations. Low concentration (10(-10) M) of both compounds decreased the TER, whereas higher concentrations (10(-8) and 10(-6) M) increased the TER which was not related to the FD-4 flux. The increased TER by Ge or Di was parallel to the induction of claudin-3 and -4 or -8 mRNA expression respectively. With LPS inoculation, all isoflavone treatments inhibited the decreased TER induced by LPS, but only Ge (10(-8) or 10(-6) M) or Di (10(-10) or 10(-6) M) was coincidence with the decreased FD-4 flux. Under this LPS-stimulated condition, some or all examined TJ gene expressions appeared to be promoted by specific concentration of Ge or Di respectively. Our findings suggest that the soy isoflavones treatment could promote and restore the impaired endometrial barrier function caused by LPS contamination.