Trophoblastic mitochondrial DNA induces endothelial dysfunction and NLRP3 inflammasome activation: Implications for preeclampsia

Aims: Preeclampsia (PE) is characterised by systemic vascular endothelium dysfunction. Circulating trophoblastic secretions contribute to endothelial dysfunction, resulting in PE; however, the underlying mechanisms remain unclear. Herein, we aimed to determine the potential correlation between the release of trophoblastic mitochondrial deoxyribonucleic acid (DNA) (mtDNA) and endothelium damage in PE.

Materials and methods: Umbilical cord sera and tissues from patients with PE were investigated for inflammasome activation. Following this, trophoblastic mitochondria were isolated from HTR-8/SVneo trophoblasts under 21 % oxygen (O₂) or hypoxic conditions (1 % O₂ for 48 h) for subsequent treatments. Primary human umbilical veinendothelial cells (HUVECs) were isolated from the human umbilical cord and then exposed to a vehicle (phosphate-buffered saline [PBS]), mtDNA, hypo-mtDNA, or hypo-mtDNA with INF39 (nucleotide oligomerisation domain-like receptor family pyrin domain containing 3 [NLRP3]-specific inhibitor) for 12 h before flow cytometry and immunoblotting. The effects of trophoblastic mtDNA on the endothelium were further analysed in vivo using enzyme-linked immunosorbent assay (ELISA) and vascular reactivity assay. The effects of mtDNA on vascular phenotypes were also tested on NLRP3 knockout mice.

Results: Elevated interleukin (IL)-1β in PE sera was accompanied by NLRP3 inflammasome activation in cord tissues. In vitro and in vivo experiments revealed that the release of trophoblastic mtDNA could damage the endothelium via NLRP3 activation, resulting in the overexpression of NLRP3, Caspase-1 p20, IL-1β p17, and gasdermin D (GSDMD); reduced endothelial nitric oxide synthase (eNOS) levels; and impaired vascular relaxation. Flow cytometric analysis confirmed that extensive cell death was induced by mtDNA, and simultaneously, a more pronounced pro-apoptotic effect was caused by hypoxia-treated trophoblastic mtDNA. The NLRP3 knockout or pharmacologic NLRP3 inhibition partially reversed tumour necrosis factor-α (TNF-α) and IL-1β levels and endothelium-dependent vasodilation in mice.

Conclusion: These findings demonstrate that trophoblastic mtDNA induced NLRP3/Caspase-1/IL-1β signalling activation, eNOS-related endothelial injury, and vasodilation dysfunction in PE.

Endothelial dysfunction; Inflammation; Mitochondrial DNA; NLRP3 inflammasome; Preeclampsia.