Acute exposure to cell-free mitochondrial DNA induces pregnancy-specific aortic endothelial dysfunction and organ-selective inflammation in rats.

Abstract

Pregnancy complications such as preeclampsia are associated with circulating cell-free mitochondrial DNA (mtDNA), a damage-associated molecular pattern capable of activating Toll-like receptor 9 (TLR9). We hypothesized that acute mtDNA exposure induces maternal inflammation and endothelial dysfunction during pregnancy via TLR9 activation. Nonpregnant and pregnant rats (gestational days 14 and 15) were treated intravenously with saline or purified mtDNA and euthanized 4 h after treatment. mtDNA increased cytokine mRNA expression in the lungs and liver of nonpregnant and pregnant rats, with magnitude varying by pregnancy status and organ. Aortas from pregnant, but not nonpregnant, rats exhibited reduced acetylcholine (ACh)-induced relaxation following mtDNA treatment (Emax, saline: 90.1 ± 3.9% vs. mtDNA: 62.1 ± 20.7% KClmax, P < 0.05), whereas uterine artery function was preserved, indicating vascular bed-specific effects. Ex vivo incubation of aortic rings with mtDNA ± white blood cells did not replicate in vivo findings, implicating systemic rather than direct vascular mechanisms. Nuclear DNA did not affect ACh-induced relaxation (P > 0.05), confirming that the vascular effects were mtDNA-specific. Pharmacological antagonism of TLR9 with ODN2088 partially attenuated mtDNA-induced maternal endothelial dysfunction. Although overt increases in vascular reactive oxygen species (ROS) were not detected, aortas from pregnant rats had reduced sod-1 expression (P < 0.05) and increased endothelial nitric oxide synthase (eNOS) protein abundance (P < 0.05). In conclusion, acute mtDNA exposure during pregnancy induces maternal organ inflammation and impairs endothelium-dependent vasodilation, with partial TLR9 involvement. Aortic transcriptional changes in antioxidant pathways and increased eNOS abundance were also observed, though their functional significance remains to be determined.NEW & NOTEWORTHY To our knowledge, this is the first study to demonstrate that acute exposure to circulating mtDNA induces pregnancy-specific maternal endothelial dysfunction and organ-selective inflammatory responses. Our findings reveal pregnancy- and vascular-bed-specific responses of the maternal vasculature to mitochondrial danger signals, with partial TLR9 involvement. Aortic transcriptional changes in antioxidant pathways and increased nitric oxide synthase abundance were identified as molecular correlates of this dysfunction.