Anti-inflammatory effects of Placenta-derived exosomal miR-24-1-5p through targeting TNFAIP8 and its implication in enhancing placental endotoxin tolerance in a model of lipopolysaccharide (LPS)-induced placental inflammation

Abstract Objective and design: Intra-amniotic infection (IAI) represents a potentially catastrophic complication during parturition, with potential for significant maternal and neonatal consequences. As a crucial immunological organ at the maternal-fetal interface, the immunoregulatory capacities of the placenta and the underlying molecular dynamics at play in the pathogenesis of IAI continue to be unclear. Recent studies have found that placenta-derived exosomes (Pd-Exos) and their contained microRNAs (miRNAs) may be involved in immune regulation during pregnancy. This study aimed to investigate the immunoregulatory function of the placenta in connection with the progression of IAI, as well as to elucidate its potential molecular mechanisms. Material or subjects: An IAI model was developed by co-culturing full-term placental explants obtained from elective cesarean sections with lipopolysaccharide (LPS). Using RT-qPCR and ELISA, the dynamic expression patterns of inflammatory factors within the placental explants were identified at varying time points post-LPS exposure. Pd-Exos were then isolated from the culture supernatant of placental explants and subjected to miRNA sequencing to pinpoint exosomal miRNAs integral to the immunoregulatory functions of the placenta. Subsequently, the role of a differentially expressed exosomal miRNA was validated. Results In the early phase of LPS stimulation, extensive pro-inflammatory responses were observed in placental explants, evidenced by the augmented expression of TNF-α and IL-1β. However, as the LPS stimulation progressed to the latter stages, a decrease in the pro-inflammatory response was noted, alongside a gradually surging anti-inflammatory response, signified by a diminishing ratio between pro-inflammatory and anti-inflammatory indicators (TNF-α/IL-10 and IL-1β/IL-1Ra). Following prolonged LPS stimulation of placental explants, the expression of miR-24-1-5p was upregulated in Pd-Exos. Upon internalization by receptor cells (THP-1 cells and Swan 71 cells), miR-24-1-5p can inhibit the expression of its target gene Tumor necrosis factor alpha-induced protein 8 (TNFAIP8), thereby suppressing the expression of downstream inflammatory factors TNF-α and IL-1β. Conclusion Prolonged exposure to the LPS in human term placental tissues induced endotoxin tolerance. Additionally, the placenta-derived exosomal miR-24-1-5p down-regulated the expression of the inflammatory markers TNF-α and IL-1β by inhibiting the functionality of TNFAIP8, thereby contributing to the placental endotoxin tolerance.