Chronic exposure to aerosolized Arizona test dust reduces visual acuity in mice

Air pollution is associated with increased incidence of age-related macular degeneration (AMD), glaucoma and other retinal diseases. The time course of molecular and cellular changes induced by chronic air pollution exposure that lead to retinal pathology are unknown. In this study, we investigated the effects of moderate levels of air pollution on visual acuity and retinal phenotypes in mice using Arizona test dust (ATD) as a surrogate for ambient air pollution. Mice were exposed to aerosolized standardized test dust for three hours a day, four days a week, for up to four months in a custom-built chamber. Controls were exposed to room air. Visual function was assessed using an optomotor assay and demonstrated reduced visual acuity after one month of exposure that persisted throughout the study. Rod and cone photoreceptors also showed temporarily decreased light-evoked responses that returned to normal levels by four months. Furthermore, reduced cone photoreceptors and retinal ganglion cells were observed whereas markers of retinal stress, including Iba1-positive microglia/macrophage and GFAP expression in macroglia, were not significantly elevated. Molecular analyses indicated elevated expression of the genes in the Nrf2-ARE oxidative stress response pathway. Therefore, moderate levels of aerosolized ATD caused a persistent decline in visual acuity, mild retinal degeneration and transient functional changes. This study provides new information into the pathogenesis of pollution-induced retinal damage and establishes a new mouse model for investigating detrimental effects of moderate levels of air pollution in the retina.