Blast Preconditioning Protects Retinal Ganglion Cells and Reveals Targets for Prevention of Neurodegeneration Following Blast-Mediated Traumatic Brian Injury

PURPOSE: The purpose of this study was to examine the effect of multiple blast exposures and blast preconditioning on the structure and function of retinal ganglion cells (RGCs), to identify molecular pathways that contribute to RGC loss, and to evaluate the role of kynurenine-3-monooxygenase (KMO) inhibition on RGC structure and function. METHODS: Mice were subjected to sham blast injury, one single blast injury, or three blast injuries separated by either 1 hour or 1 week, using a blast intensity of 20 PSI. To examine the effect of blast preconditioning, mice were subjected to sham blast injury, one single 20-PSI injury, or three blast injuries separated by 1 week (5 PSI, 5 PSI, 20 PSI and 5 PSI, 5 PSI, 5 PSI). RGC structure was analyzed by optical coherence tomography (OCT) and function was analyzed by the pattern electroretinogram (PERG). BRN3A-positive cells were quantified to determine RGC density. RNA-seq analysis was used to identify transcriptional changes between groups. RESULTS: Analysis of mice with multiple blast exposures of 20 PSI revealed no significant differences compared to one 20-pounds per square inch (PSI) exposure using OCT, PERG, or BRN3A cell counts. Analysis of mice exposed to two preconditioning 5-PSI blasts prior to one 20-PSI blast showed preservation of RGC structure and function. RNA-seq analysis of the retina identified multiple transcriptomic changes between conditions. Pharmacologic inhibition of KMO preserved RGC responses compared to vehicle-treated mice. CONCLUSIONS: Preconditioning protects RGC from blast injury. Protective effects appear to involve changes in KMO activity, whose inhibition is also protective.