Objective To analyze the differential expression of nucleotide-binding oligomerization domain 1 (NOD1) in maternal-fetal interface cells during early and late pregnancy, and to investigate its molecular mechanisms in mediating inflammatory responses.

Methods Immunohistochemistry (IHC) and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect NOD1 mRNA and protein expression in normal first-trimester villi tissues (n = 30), normal early pregnancy decidua tissues (n = 30), and normal full-term placental tissues (n = 30). Human chorionic trophoblast HTR8/SVneo cells were stimulated with tumor necrosis factor-alpha (TNFα) at various concentrations (0, 0.01, 0.1, 1, 10, and 100 ng/mL) and exposure times (24, 48, and 72 h). Real-time quantitative PCR (qRT-PCR) and western blot analysis were performed to detect differential expression of NOD1, receptor-interacting protein (RIP)-like interacting CLARP kinase (RICK), and p65. ELISA was used to analyze the secretion levels of inflammatory cytokines IL-6 and IL-8. Electrophoretic mobility shift assay (EMSA) was conducted to assess the DNA-binding activity of nuclear factor-kappa B (NF-κB) and to investigate the regulatory mechanisms of NOD1 signaling pathways in trophoblasts.

Results NOD1 was expressed in normal first-trimester villi, decidua, and full-term placental tissues, primarily localized in the cytoplasm of trophoblasts, vascular endothelial cells, and decidual cells. The difference in NOD1 expression between full-term placental tissues and first-trimester villi and decidua was statistically significant (P < 0.05), with higher NOD1 expression observed in full-term placental tissues than in first-trimester villi and decidua. TNFα upregulated NOD1 expression in HTR8/SVneo cells in a dose- and time-dependent manner. IL-6 secretion levels positively correlated with TNFα concentration, while IL-6 and IL-8 release exhibited time-dependent responses to TNFα stimulation. Furthermore, TNFα stimulation enhanced RICK and p65 expression and increased NF-κB DNA-binding activity.

Conclusion  NOD1 is constitutively expressed in trophoblasts and decidual cells at the maternal-fetal interface during normal pregnancy, participating in the regulation of the gestational process. Changes in NOD1 expression correlate with TNFα-induced inflammatory responses. TNFα may trigger inflammatory cytokine release via the NOD1-RICK-NF-κB signaling axis, mediating inflammatory cascades in trophoblasts. These findings provide novel insights into immune regulatory mechanisms during pregnancy.