A novel role for FOXO3 in human labor: increased expression in laboring myometrium, and regulation of proinflammatory and prolabor mediators in pregnant human myometrial cells.

Preterm birth is the leading factor causing neonatal mortality and morbidity. Inflammation plays a central role in stimulating uterine contractility, which is responsible for approximately one-third of all preterm births. Recent studies have shown that the transcription factor Forkhead box O3 (FOXO3) regulates inflammation in nongestational tissues such as adipocytes and hepatocytes. Thus, in this study, we sought to determine the effect of 1) human term labor on myometrial FOXO3 expression and 2) FOXO3 inhibition and FOXO3 overexpression on proinflammatory and prolabor mediators in human myometrial cells. Higher FOXO3 gene and protein expression were detected in myometrium obtained from women in labor when compared to samples taken from nonlaboring women. Myometrial cells were isolated from pregnant human myometrium, and FOXO3 silencing was achieved using siRNA and overexpression using a cDNA clone. We found that the loss of FOXO3 in myometrial cells was associated with a significant decrease in IL1B-induced IL6 and IL8 expression and production, cyclooxygenase ([COX]-2, official symbol PTGS2) expression and subsequent prostaglandin (PGE2 and PGF2alpha) release, and matrix metalloproteinase 9 (MMP9) and mRNA expression and activity. Conversely, FOXO3 overexpression increased cytokine expression and secretion, prostaglandin production, and MMP9 expression in myometrial cells treated with IL1B. In summary, we have identified FOXO3 as an upstream mediator of inflammation in human myometrium. Thus, FOXO3 may present an alternative therapeutic target for preventing preterm birth and its associated morbidity and mortality.