Microvascular mechanisms of growth restriction after environmental toxicant exposure

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ABSTRACT The uterine circulation and placenta are specifically designed to regulate the flow of blood and transport of es- sential nutrients to the fetus. Disruption of maternal hemodynamic regulation during pregnancy can adversely impact fetal health, resulting in miscarriage and intrauterine growth restriction (IUGR). Current treatment op- tions for IUGR patients are extremely limited, focusing primarily on early delivery; thus, putting the mother and child at risk for complications associated with preterm birth. Epidemiological studies indicate that pregnant women exposed to fine particulate matter (PM) have a heightened risk of fetal loss and development of IUGR. We have reproduced this phenomenon in laboratory rodent models, wherein animals exposed to nanosized titanium dioxide (nano-TiO2) aerosols develop IUGR and suffer a greater number of ‘miscarriages’ (fetal reabsorptions). We have demonstrated that acute and chronic exposures significantly impair uterine vascular endothelium-dependent dilation, severely limiting maternal-to-fetal blood flow and impacting fetal growth. An understanding of the mechanisms underlying dysregulation in uterine and placental blood flow is critical for developing treatments and reducing IUGR. Based on previous findings, we hypothesize that maternal inhalation of nano-TiO2 aerosols during pregnancy promotes the development of IUGR by disrupting endothelium-dependent NO and AA signaling cascades, resulting in reduced uterine vasodilation and blood flow. Moreover, folic acid (FA) supplementation will rescue this utero-placental hemodynamic imbalance and prevent IUGR through its action in NO signaling. Using novel approaches and methodolo- gies, these studies will: (1) evaluate uterine nitric oxide-driven vasodilation, (2) determine whether alterations in arachidonic acid metabolism impair uterine vascular reactivity and impact placental perfusion, and (3) assess the therapeutic benefit of dietary folic acid supplementation to improve utero-placental blood flow and attenuate the development of IUGR after maternal exposure to nano-TiO2 aerosols. These studies are conceptually innovative as we will utilize our unique resources to identify mechanistic targets within the utero-placental mi- crocirculation and test directed nutritional interventions for IUGR. This work is technically innovative as we will use novel methodologies developed for the evaluation of environmental toxicity in maternal-fetal medicine. Overall, the successful completion of these studies will: (1) create the conceptual framework to identify environmental exposure as a risk factor for the development of IUGR; (2) reveal new mechanistic insight into the vascular pathogenesis resulting from nanomaterial exposure; (3) provide a molecular basis to identify how nanomaterial exposure manifests as vascular disruptions; and (4) identify mechanistic targets for therapeutic strategies to ameliorate microvascular dysfunction and improve utero-placental blood flow. These intervention- al strategies are not only limited to PM, but are widely applicable to understanding the role of a spectrum of environmental toxicants in the pathophysiological development of IUGR.