A new in vitro study reveals how melatonin can quell inflammation of fetal membranes caused by infection, providing new clues for future strategies against inflammation-related preterm birth.
Study: Melatonin modulates inflammation in human fetal membranes: an ex vivo approach. Image credit: Pikovit / Shutterstock
In a recent study published in the journal scientific reportA group of researchers evaluated whether melatonin reduces lipopolysaccharide-induced inflammation in human fetal membranes in an in vitro model and determined whether the TLR4/MyD88/NF-κB signaling pathway is involved in this effect.
background
Preterm birth is one of the leading causes of infant mortality and morbidity. Inflammation of the fetal membranes due to infection is a major trigger for premature birth, as it stimulates the release of inflammatory molecules that weaken these protective tissues. The pineal gland and placenta produce melatonin. Melatonin regulates circadian rhythms, including the timing of sleep and wakefulness, and suppresses inflammatory responses. During pregnancy, melatonin production increases significantly and can affect the environment in which the fetus develops. Further studies are needed to clarify how melatonin influences inflammation regulation in human fetal membranes.
About research
In this study, 12 healthy women who had uncomplicated term cesarean deliveries without prior labor were selected and fetal membranes were collected from each. The women did not have diabetes, hypertension, obesity, or other metabolic diseases during pregnancy, and did not have any urinary tract or vaginal infections during the third trimester. Fetal tissue samples were cultured in a two-chamber culture system that maintains the natural separation of the maternally facing choriodecidual region and the fetally facing amniotic cavity. Each side of the fetal membranes was processed independently. Assays were performed on independent experimental subsets of these samples.
Before exposure to LPS, the researchers treated the compartments with melatonin at physiological amniotic fluid concentrations (1 nM) for 24 hours and then administered fresh melatonin every 6 hours due to its short half-life. To mimic the inflammation associated with bacterial infection, we exposed the choriodecidual side to the bacterial endotoxin lipopolysaccharide (LPS; 500 ng/mL) while continuing melatonin treatment. In addition to LPS treatment, some samples were co-treated with luzindole, a non-selective melatonin receptor antagonist, to investigate whether melatonin receptors were responsible for the observed effects.
After treatment, the researchers used ELISA to analyze the levels of cytokines and chemokines, including TNF-α, IL-1β, IL-6, IL-10, CCL2, CCL3, and CCL5. Additionally, the researchers measured gene expression using quantitative polymerase chain reaction (qPCR) and analyzed TLR4, MyD88, and NF-κB proteins using ELISA and Western blotting.
Research results
Exposure to LPS caused a strong inflammatory response in both the choriodecidual and amniotic regions of the fetal membranes. This increased the secretion of the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6, as well as the anti-inflammatory cytokine IL-10. Melatonin significantly reduced the secretion of all four cytokines, with significant reductions in TNF-α and IL-1β. This indicates that melatonin attenuates important early inflammatory signals in this ex vivo model. Treatment of tissues with luzindole reduced many of the anti-inflammatory effects of melatonin, suggesting that these protective effects are mediated, at least in part, through melatonin receptors. Regulation of IL-6 differs between the choriodecidual and amniotic compartments, suggesting that IL-6 may also be regulated by mechanisms independent of melatonin receptors.
Messenger ribonucleic acid (mRNA) expression of TNF-α and IL-1β genes was significantly increased when tissues were treated with LPS, but was suppressed by melatonin and restored by luzindole. IL-6 was also increased in response to LPS, but melatonin had no significant effect on IL-6 mRNA and IL-10 gene expression was not measured.
LPS stimulation increased the levels of CCL5, CCL2, and CCL3, chemokines involved in immune cell recruitment during infection-related inflammation. Melatonin decreased the production of CCL5 and CCL3 in the fetal membrane compartment, but the effect varied by compartment. In contrast, there was no statistically significant effect of melatonin on CCL2 chemokine production. After LPS addition, CCL5 mRNA expression increased, and both CCL2 and CCL3 showed an increased expression trend. Melatonin did not alter the expression of any of these three chemokines at the transcriptional level, suggesting that the observed changes in secretion levels may involve post-transcriptional mechanisms, preformed chemokine release, or indirect effects through changes in cytokine signaling rather than direct changes in chemokine mRNA expression.
Further analysis showed that LPS increases TLR4, MyD88, and NF-κB, which are important components of the inflammatory signaling pathway. Melatonin significantly reduced the levels of these proteins, but luzindole nearly reversed these changes. Taken together, these findings indicate that melatonin suppresses infection-induced inflammation in human fetal membranes by limiting the production of inflammatory cytokines, reducing selected chemokines, and modulating the TLR4/MyD88/NF-κB signaling pathway.
conclusion
The results of this study demonstrate that melatonin exerts significant anti-inflammatory effects in human fetal membranes exposed to LPS-induced inflammation. This decreased inflammation-related readouts by decreasing cytokine secretion, selected cytokine mRNA expression, and proteins involved in the TLR4/MyD88/NF-κB signaling pathway. Although these effects are partially mediated through melatonin receptors, additional mechanisms appear to be involved in some responses.
Overall, the results support a potential role for melatonin-related pathways in limiting infection-associated membrane inflammation and provide the basis for future studies to test whether these pathways can be safely and effectively targeted in inflammation-related preterm birth. Because this is an in vitro study using undelivered fetal membranes from term births, the results of this study do not yet demonstrate that melatonin supplementation can prevent preterm birth in pregnant patients.
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Reference magazines:
- Hernández-Bones, K., Torres-Ramos, Y.D., Mancilla-Herrera, I., Najera, N., Díaz, L., Cisneros, J., Olmos-Ortiz, A., Rodríguez-Flores, S., Velázquez-Sánchez, P., Helguera-Repetto, C., Zaga-Claverina, V., & Flores-Espinosa, P. (2026). Melatonin modulates inflammation in human fetal membranes: an ex vivo approach. Scientific report. Doi: https://doi.org/10.1038/s41598-026-59528-1
