Iron–Immune Crosstalk at the Maternal–Fetal Interface: Emerging Mechanisms in the Pathogenesis of Preeclampsia

Preeclampsia (PE) is a pregnancy-specific hypertensive disorder characterized by systemic inflammation, endothelial dysfunction, and placental insufficiency. While inadequate trophoblast invasion and impaired spiral artery remodeling have long been recognized as central to its pathogenesis, emerging evidence underscores the critical roles of dysregulated iron metabolism and its crosstalk with immune responses, particularly macrophage-mediated inflammation, in driving PE development. This review systematically explores the dynamic changes in iron metabolism during pregnancy, including increased maternal iron demand, placental iron transport mechanisms, and the molecular regulation of placental iron homeostasis. We further explore the contribution of ferroptosis, an iron-dependent form of regulated cell death driven by lipid peroxidation, to trophoblast dysfunction and pregnancy-related diseases, including PE. Macrophages, pivotal immune regulators at the maternal–fetal interface, exhibit distinct polarization states that shape tissue remodeling and immune tolerance. We outline their origin, distribution, and polarization in pregnancy, and emphasize their aberrant phenotype and function in PE. The bidirectional crosstalk between iron and macrophages is also dissected: iron shapes macrophage polarization and function, while macrophages reciprocally modulate iron homeostasis. Notably, excessive reactive oxygen species (ROS) and pro-inflammatory cytokines secreted by M1-polarized macrophages may exacerbate trophoblast ferroptosis, amplifying placental injury. Within the context of PE, we delineate how iron overload and macrophage dysfunction synergize to potentiate placental inflammation and oxidative stress. Key iron-responsive immune pathways, such as the HO-1/hepcidin axis and IL-6/TNF-α signaling, are discussed in relation to disease severity. Finally, we highlight promising therapeutic strategies targeting the iron–immune axis, encompassing three key modalities—iron chelation therapy, precision immunomodulation, and metabolic reprogramming interventions—which may offer novel avenues for PE prevention and treatment.