Background: Infections during pregnancy are associated with adverse maternal and fetal outcomes. We previously showed that exposure to immunostimulatory CpG oligonucleotides (ODN2395, synthetic Toll-like receptor 9 agonist) during pregnancy induces maternal vascular inflammation and enhances vascular tone in pregnant rats. These outcomes were mediated in part by activation of the cyclooxygenase/thromboxane A2 (COX/TxA2) pathway. The objective of this study was to investigate the impact of ODN2395-induced immune system stimulation on maternal hearts during pregnancy.
Hypotheses: Exposure to TLR9-mediated immune system activation during pregnancy upregulates the COX/TxA2signaling pathway in maternal cardiac tissues.
Methods: Rats were treated with a synthetic CpG DNA (ODN2395, 1 mg/kg, intraperitoneal injection) or vehicle (saline) in late pregnancy (gestational day (GD) 14, 16, and 18) and euthanized on GD 20 (term 22-23). Fetoplacental biometrics were recorded after euthanasia and maternal hearts were collected to assess COX-1 and COX-2 expression via western blotting and 6-keto PGF1α (PGI2 metabolic byproduct) and TxB2 (TxA2 metabolic byproduct) production use ELISA.
Results: Maternal heart weights did not differ between groups (ODN2395: 0.26 g/100 g BW vs. Vehicle: 0.23 g/100 g BW, n≥7, p=0.11). Left ventricular tissues from dams treated with ODN2395 released higher concentrations of TxB2compared to cardiac tissues from vehicle-treated dams (ODN2395: 0.56 ± 0.06 ng/mg total protein vs. Vehicle: 0.31 ± 0.04 ng/mg total protein, n≥5, p=0.0041) but there were no differences in cardiac 6-keto PGF1α release between groups (p=0.16). COX-2 expression was lower in left ventricles from ODN2395-treated rats compared to vehicle-treated rats (p=0.009). There were no differences in cardiac COX-1 expression between groups (p=0.27). Exposure to ODN2395 during pregnancy did not affect fetal weights (ODN2395: 2.28 ± 0.03 g vs. Vehicle: 2.25 ± 0.06 g, n≥7, p=0.9) or placenta weights (ODN2395: 0.44 ± 0.02 g vs. Vehicle 0.49 ± 0.01 g, n≥7, p=0.06), but increased fetal-placental weight ratio (ODN2395: 5.3 ± 0.22 vs. Vehicle: 4.7 ± 0.15, p = 0.04). COX-2 expression was greater in placental tissues from ODN2395-treated rats (p=0.004) but there were no differences in placental 6-keto PGF1α(p=0.51) and TxB2 production (p=0.32).
Conclusion: Exposure to immunostimulatory CpG ODN during pregnancy induces upregulation of TxB2 synthesis in maternal cardiac tissues coupled with a reduction in COX-2 expression. We suggest that cardiac inflammation during pregnancy may increase maternal risk for future cardiovascular events.
National Institutes of Health R01HL0146562, T32AG020494, R25GM125587
