Extrachromosomal circular DNA drives ferroptosis and immunity in trophoblasts via the STING pathway in preeclampsia

Preeclampsia (PE) is a pregnancy-specific disorder characterized by placental dysfunction, immune activation, and oxidative stress. Extrachromosomal circular DNA (eccDNA), a class of circular DNA fragments that exist outside the chromosomes, has been implicated in cancer, aging, and inflammation, but its role in PE remains poorly understood.

EccDNA abundance was quantified in placental tissues from PE and control pregnancies and correlated with clinical parameters. Synthetic eccDNA was used to treat trophoblast cells in vitro. Functional assays, ferroptosis biomarkers, RNA sequencing, and STING pathway activation were assessed. STING knockdown and pharmacological inhibition were employed for validation.

We confirmed abundant eccDNA in trophoblasts, enriched in nuclear heterochromatin, with significantly elevated levels in PE. Mechanistically, eccDNA acts as a potent activator of the STING signaling pathway, inducing downstream pro-inflammatory cytokines including IFN-β, IL-6, and TNF-α.RNA sequencing and biochemical assays further demonstrated that eccDNA also triggered ferroptosis. STING activation promoted lipid peroxide accumulation and impaired antioxidant defenses, exacerbating ferroptotic cell death. Inflammatory signaling synergized with ferroptosis to exacerbate oxidative stress and cell damage, ultimately leading to trophoblast dysfunction. Genetic silencing or pharmacological inhibition of STING effectively reversed both inflammatory and ferroptotic damage. Analysis of clinical samples revealed an upregulation of STING in trophoblasts derived from preeclamptic placentas, accompanied by enhanced ferroptosis.

Our study identifies eccDNA as a key activator of the STING pathway, driving inflammation and ferroptosis in PE, contributing to trophoblast dysfunction. This dual pathological mechanism represents a potential etiological pathway in the onset of PE.