Regulation of the Endothelin/Endothelin Receptor System by Interleukin-1β in Human Myometrial Cells

Abstract

Proinflammatory cytokines produced at the fetomaternal interface, such as IL-1β, have been implicated in preterm and term labor. The present study was performed to evaluate the influence of IL-1β on the endothelin (ET)/ET receptor system in human myometrial cells. We report that myometrial cells under basal conditions not only respond to but also secrete ET-1, one of the main regulators of uterine contractions. Prolonged exposure of the cells to IL-1β led to a decrease in prepro-ET-1 and ET-3 mRNA correlated with a decrease in immunoreactive ET-1 and ET-3 levels in the culture medium. Whereas ETA receptor expression at both protein and mRNA levels was not affected by IL-1β treatment, we demonstrated an unexpected predominance of the ETB receptor subtype under this inflammatory condition. Whereas the physiological function of ETB remains unclear, we confirmed that only ETA receptors mediate ET-1-induced myometrial cell contractions under basal conditions. By contrast, prolonged exposure of the cells to IL-1β abolished the contractile effect induced by ET-1. Such a regulation of IL-1β on the ET release and the balance of ETA to ETB receptors leading to a loss of ET-1-induced myometrial cell contractions suggest that complex regulatory mechanisms take place to constraint the onset of infection-induced premature contractions.