Melatonin modulates inflammation in human fetal membranes: an ex vivo approach

Choriodecidual infection is a major contributor to preterm birth, triggering inflammation in the human fetal membranes, through the release of pro-inflammatory cytokines and chemokines. Melatonin (Mel), a neurohormone produced by the pineal gland and placenta, has well-established anti-inflammatory properties; however, its immunomodulatory effects have not been previously investigated in fetal membranes. The aim of this study was to evaluate the ability of melatonin to exert an anti-inflammatory effect in tissues stimulated with lipopolysaccharide (LPS), as well as to assess the potential involvement of the TLR4/NF-κB pathway in this process. Whole fetal membrane explants from full-term cesarean deliveries (n = 12) were cultured in a two-chamber system. Both regions, choriodecidua (CHD) and Amnion (AMN) were pretreated with Mel (1nM) for 24 h, with re-stimulation every 6 h, followed by choriodecidual stimulation with LPS (500 ng/mL) for an additional 24 h. Melatonin treatment was maintained in both regions by re-stimulation every 6 h during LPS exposure. Cytokine (TNF-α, IL-1β, IL-6, IL-10) and chemokine (CCL5, CCL3, CCL2) secretion was quantified by ELISA, and mRNA expression was evaluated by qPCR. TLR4 and NF-κB protein levels were measured by ELISA and Western blot. LPS stimulation increased cytokine and chemokine secretion in both CHD and AMN, upregulated TNF‑α, IL‑1β, and CCL5 mRNA expression, and elevated protein levels of TLR4, MyD88, and NF‑κB. Mel treatment significantly suppressed the secretion of all assessed cytokines, as well as CCL5 and CCL3, in both CHD and AMN. In summary, Mel attenuates infection‑induced inflammation in fetal membranes, partly through modulation of the TLR4/NF‑κB pathway, supporting its potential role in mitigating inflammation‑associated preterm birth.