The dual role of glucocorticoid regeneration in inflammation at parturition.

Introduction: Fetal membrane inflammation is an integral event of parturition. However, excessive pro-inflammatory cytokines can impose threats to the fetus. Coincidentally, the fetal membranes express abundant 11b-hydroxysteroid dehydrogenase 1 (11b-HSD1), which generates biologically active cortisol to promote labor through induction of prostaglandin synthesis. Given the wellrecognized anti-inflammatory actions of glucocorticoids, we hypothesized that cortisol regenerated in the fetal membranes might be engaged in restraining fetus-hazardous pro-inflammatory cytokine production for the safety of the fetus, while reserving pro-labor effect on prostaglandin synthesis to ensure safe delivery of the fetus. Methods: The hypothesis was examined in human amnion tissue and cultured primary human amnion fibroblasts as well as a mouse model. Results: 11b-HSD1 was significantly increased in the human amnion in infectioninduced preterm birth. Studies in human amnion fibroblasts showed that lipopolysaccharide (LPS) induced 11b-HSD1 expression synergistically with cortisol. Cortisol completely blocked NF-kB-mediated pro-inflammatory cytokine expression by LPS, but STAT3-mediated cyclooxygenase 2 expression, a crucial prostaglandin synthetic enzyme, remained. Further studies in pregnant mice showed that corticosterone did not delay LPS-induced preterm birth, but alleviated LPS-induced fetal organ damages, along with increased 11b-HSD1, cyclooxygenase 2, and decreased pro-inflammatory cytokine in the fetal membranes. Discussion: There is a feed-forward cortisol regeneration in the fetal membranes in infection, and cortisol regenerated restrains pro-inflammatory cytokine expression, while reserves pro-labor effect on prostaglandin synthesis. This dual role of cortisol regeneration can prevent excessive pro-inflammatory cytokine production, while ensure in-time delivery for the safety of the fetus. [ABSTRACT FROM AUTHOR]