Interleukin (IL)-6 and IL-8 production by human amnion: Regulation by cytokines, growth factors, glucocorticoids, phorbol esters, and bacterial lipopolysaccharide

Amniotic fluid at term contains high concentrations of interleukin (IL)-6 and IL-8. The source of these cytokines has not been identified, although the fetal membranes (amnion and chorion) are likely contributors. Amnion cytokine production was investigated by using amnion cells isolated by enzymatic digestion (from placentas delivered at term before labor) and cultured in vitro. IL-6 and IL-8 were measured in conditioned media by ELISA. Amnion cells produced detectable amounts of both IL-6 and IL-8 throughout the 7-day culture period. The ratio of IL-8 to IL-6 was approximately 5:1, similar to the ratio found in amniotic fluid. Production of both IL-6 and IL-8 was stimulated in a concentration-dependent fashion by interleukin-1 beta (0.1-10 ng/ml), tumor necrosis factor-alpha (1-100 ng/ml), and bacterial lipopolysaccharide (0.1-10 mu g/ml), and also by 100 nM phorbol 12-myristate 13-acetate. Epidermal growth factor (1-25 ng/ml) had only minimal effects on amnion cytokine production. Dexamethasone (10 nM) inhibited IL-6/-8 production by approximately 50% throughout the culture period. Production of IL-6/-8 by cultured amniotic fibroblasts, which under basal conditions was much lower than that by epithelial cells, was regulated by all the agents tested in a fashion similar to that of the epithelial cells. These findings suggest that the amnion contributes to the pool of IL-6 and IL-8 in amniotic fluid. We speculate that amnion-derived cytokines might have functions during normal human parturition that are distinct from their conventional roles as inflammatory mediators.