Postnatal inflammation in Apoe-/- mice is associated with immune training and atherosclerosis

Abstract

Background and aimsPreterm birth is associated with increased risk of cardiovascular disease (CVD). This may reflect a legacy of inflammatory exposures such as chorioamnionitis, that complicate pregnancies delivering preterm, or recurrent early-life infections, common in preterm infants. We previously reported that experimental chorioamnionitis followed by postnatal inflammation has additive and deleterious effects on atherosclerosis in Apoe-/- mice. Here, we aimed to investigate whether innate immune training is a contributory inflammatory mechanism in this murine model of atherosclerosis. MethodsBone marrow-derived macrophages and peritoneal macrophages were isolated from 13 week-old Apoe-/- mice, previously exposed to prenatal intra-amniotic (experimental choriomanionitis) and/or repeated postnatal (peritoneal) lipopolysaccharide (LPS). Innate immune responses were assessed by cytokine responses following 24-hour ex vivo stimulation with toll-like receptor (TLR) agonists (LPS, Pam3Cys), and RPMI for 24 hours. Bone marrow progenitor populations were studied using flow cytometric analysis. ResultsFollowing postnatal LPS exposure, bone marrow-derived macrophages and peritoneal macrophages produced more pro-inflammatory cytokines following TLR stimulation than those from LPS unexposed mice, characteristic of a trained phenotype. Cytokine production ex vivo correlated with atherosclerosis severity in vivo. Prenatal LPS did not affect cytokine production capacity. Combined prenatal and postnatal LPS exposure was associated with a reduction in common myeloid progenitor cells in the bone marrow. ConclusionsPostnatal inflammation results in a trained phenotype in atherosclerosis-prone mice that is not enhanced by prenatal inflammation. If analogous mechanisms occur in humans, then there may be novel early life opportunities to reduce CVD risk in infants with early life infections.