Background: Delayed central conduction times in the auditory brainstem have been observed in Mexico City (MC) healthy children breathing fine particulate matter (PM2.5) and ozone (O3) above the current United States Environmental Protection Agency (US-EPA) standards. MC children have α synuclein brainstem accumulation and medial superior olivary complex (MSO) dysmorphology. The present study used a dog model to further investigate the potential effects of air pollution on the function and morphology of the auditory brainstem.
Methodology: Twenty-four dogs living in clean air v MC, average age 37.1± 26.3 months, underwent brainstem auditory evoked potential (BAEP) measurements. Eight dogs (4 MC, 4 Controls) were analysed for auditory brainstem morphology and histopathology.
Results: MC dogs showed ventral cochlear nuclei hypotrophy and MSO dysmorphology with a significant decrease in cell body size, with many cell bodies < 100 μm2, a significant decrease in neuronal packing density with many regions in the nucleus devoid of neurons and marked gliosis. MC dogs showed significant delayed BAEP absolute wave I, III and V latencies compared to controls.
Conclusions: Auditory nuclei dysmorphology and BAEPs consistent with an alteration of the generator sites of the auditory brainstem response waveform are a common denominator for dogs and children in highly polluted MC. This study puts forward the usefulness of BAEPs to study auditory brainstem neurodegenerative changes associated with air pollution in dogs and its potential use in young urbanites as a proxy for an evolving neurodegenerative process towards Alzheimer Disease. Recognition of the role of non-invasive BAEPs in urban dogs is warranted to elucidate novel neurodegenerative pathways link to air pollution and may be a promising early diagnostic strategy for AD.
This is an author-produced, peer-reviewed version of this article. © 2017, Elsevier. Licensed under the Creative Commons Attribution Non-Commercial No Derivatives 4.0 license. http://creativecommons.org/licenses/by-nc-nd/4.0/ . The final, definitive version of this document can be found online at Environmental Research, doi: 10.1016/j.envres.2017.06.026
Mukherjee, Partha S. (2017). "Exposures to Fine Particulate Matter and Ozone Above USA Standards are Associated with Auditory Brainstem Dysmorphology and Delayed Auditory Brainstem Evoked Potentials in Healthy Dogs". Environmental Research, 158,324-332. https://doi.org/10.1016/j.envres.2017.06.026