9:40-10:00 Effects of F0 maternal diesel engine exhaust exposure during gestation on F1 and F2 offspring phenotype

Airborne pollution is a rising concern in urban areas, particularly diesel engine exhaust (DE), known to have major health effects on directly exposed subjects. The intergenerational consequences of indirect exposure to DE, however, are poorly characterized. The study aimed at exploring intergenerational effects of maternal exposure to DE in a rabbit model. Pregnant females were exposed to diluted (1 mg/m3), filtered DE (Nanoparticle diameter ≈ 69 nm) or clean air (controls) for 2 h/day, 5 days/week by nose-only exposure (total exposure: 20 days). They were allocated to one of two groups, respectively to evaluate the effects of in utero exposure on feto-placental development and to explore offspring phenotype at adulthood. Feto-placental development and growth were monitored by ultrasound. At 28 days post-coitum (dpc), dams were euthanized and feto-placental units were measured and collected. The second group of females gave birth to pups that were raised to adulthood. Their cardio-metabolic phenotype was explored, including body weight, food intake, fasting biochemistry, body composition, cardiovascular parameters and glucose tolerance. At 6.5 months of age, females were mated to control males. Second generation feto-placental units were collected at 28 dpc to analyze placental structure and gene expression. At mid gestation, DE exposure induced early signs of fetal growth retardation with decreased head length and umbilical pulse. Near term, fetal head length, plasma insulin and IGF1 concentrations were reduced. Placental function was also affected, with reduced placental efficiency, decreased placental blood flow and fetal vessel volume. Non-aggregated and "fingerprint-like" nanoparticles were observed in maternal blood space, in both trophoblastic cells and fetal blood, demonstrating transplacental transfer. In adult offspring, in utero exposure to DE led to blood pressure increase, hyperglycaemia, and increased perirenal fat mass, together with reduced plasma HDL-cholesterol and peripheral fat-to-body weight ratio in males, altogether suggesting a metabolic syndrome. Only trends were observed in adult exposed females with higher plasma triglyceride concentrations and decreased bone density compared to controls. Once pregnant, however, these F1 females developed fatty liver. Although second generation 28dpc fetoplacental biometry was not affected, fetal lipid metabolism was altered with decreased fetal plasma cholesterol and increased triglyceride concentrations. Placental function (explored using gene set enrichment analyses of placental transcriptomic data) was altered in the “exposed” group with over-representation of proteasome complex and ubiquitin pathway gene sets together with under-representation of genes sets involved in ion channel function and inflammation pathways. Using this rabbit model, repeated daily gestational exposure to DE at levels close to urban pollution can affect feto-placental development in both first and second generation and predispose offspring to cardiometabolic disorders in a sex-specific manner. These results demonstrate that DE exposure and in utero indirect exposure in particular should be considered as a programming factor within the context of the Developmental Origins of Health and Disease leading to intergenerational transmission.