Abstract 4364790: Cyclohexanone Exposure in a Neonatal Rat Model Activates the Peripheral Immune System and Alters Neurological Function

Abstract

Introduction: Congenital heart disease repair is commonly associated with neuro-developmental abnormalities that affect quality of life. Cyclohexanone (CXO) is an industrial solvent used to soften medical plastics. Exposure to CXO during neonatal cardiac surgery is associated with poor neurodevelopmental outcomes. Hypothesis: Neonatal cyclohexanone exposure causes neurological damage and initiates peripheral inflammation, resulting in functional and behavioral deficits persisting to adulthood that mimic developmental abnormalities seen in human congenital heart disease. Methods: CXO Exposure: Neonatal rats from both sexes were given CXO (0.53 ul/g/day, i.p.) or saline from post-natal day 7 (P7) to P14. Peripheral Blood Mononuclear Cell (PBMC) and Serum: Whole blood was collected at P15, P28 and P70. Inflammatory markers in serum and the PBMC secretome were evaluated using a MesoScale Discovery platform. Open Field and Magnetic Resonance Imaging (MRI) : At P28, functional MRI (fMRI), diffusion tensor imaging (DTI), and open field behavior were assessed. Touchscreen : As adults, rats were trained on a touchscreen task of visual discrimination (VD) and reversal learning (RL). Statistics: Student’s T-test or Mann-Whitney U-test in n=8-16/group with p<0.05 considered significant. Results: One day after CXO exposure (P15), levels of IFN-γ, IL-10, IL-13, IL-4 (all p<0.05), and IL-6 (p<0.01) were high in serum compared to controls concomitant with sustained peripheral immune hyperreactivity (SPIHR). By P28 through P70, levels of CXCL1 remained elevated (p<0.05) and PBMCs were hyper-inflammatory. Inflammation coincides with diminished cerebral functional connectivity related to attention and reduced white matter microstructure in tracts responsible for cognition (p<0.05). CXO-exposed rats were hypermobile and hyperactive in an open field (p<0.05) with diminished performance on VD and RL tasks. Conclusion: CXO induces inflammation and SPIHR. Adult rats exposed to CXO as neonates have diminished executive function, functional and anatomical connectivity, and poor cognitive flexibility alongside hyperactivity and hypermobility. This supports that neonatal CXO exposure initiates SPIHR and neurological damage that results in altered function and behavior that completely recapitulates the human neuro-developmental delay phenotype after neonatal cardiac surgery. Future work will focus on the mechanism of CXO injury and reducing CXO exposure to improve neurodevelopment.