Preclinical Model of Military Burn Pit Exposure Reveals Altered Inflammatory and Metabolic Pathways in the Rat Lung-Brain Axis
Military personnel deployed to combat zones in Iraq and Afghanistan were exposed to toxic emissions from open-air burn pits, raising concerns about long-term health effects. Burn pit exposures are linked to a wide range of pulmonary and extra-pulmonary morbidities. This study aimed to model military burn pit exposure and investigate its impact on lung-brain axis signaling. Rats were exposed to carbon black nanoparticles and naphthalene (CBN) via whole body inhalation chamber for six hours to simulate burn pit exposure. Gene expression and inflammatory protein changes in lung and brain tissue were examined 24 hours post-exposure using next-generation RNA sequencing, Meso Scale Discovery biomarker assays, and western blot. Multiple inflammatory pathway proteins were significantly altered in plasma, lung and brain. Gene Set Enrichment Analysis (GSEA) in lung and brain revealed significant alterations in molecular processes in lung tissue, including increased cell cycle activity, lipid balance disruption, and enhanced inflammatory responses. Conversely, processes such as adipogenesis, oxidative phosphorylation, and epithelial to mesenchymal transition were suppressed. An elastic net penalized regression model identified a set of 104 genes in lung tissue that could indicate CBN exposure in lung. We focus on the nine genes with the greatest contribution to this model. These genes, including Tiam1, Cpsf3, and Tgfrb1, are involved in various cellular processes such as inflammation, cell signaling, and tissue remodeling. We observed significant increases in lung, brain and peripheral inflammation as well as signaling changes in lung and brain that demonstrate disruption of tissue homeostasis. Our findings demonstrate notable gene expression changes that may represent similarities to Veterans suffering from Deployment-Related Respiratory Disease (DRRD). This study provides insights into the molecular mechanisms underlying lung and brain response to burn pit-like exposures and identifies potential biomarkers for further investigation of the lung-brain axis. These results contribute to our understanding of the health impacts of military burn pit exposures and may inform future diagnostic and therapeutic strategies. Overall design: Lung and brain tissues were harvested from male Sprague Dawley rats 24 hours after whole body inhalation of carbon black nanoparticles and naphthalene (CBN) or sham air for six hours a day for 3 consecutive days. Libraries were prepared using a TruSeq Stranded Total RNA Library Prep Kit (Illumina, San Diego, CA), and next-generation sequencing was performed using a Novaseq 6000 (Illumina) to generate 150 bp read pairs.