ALDH1/2 deficiency modulates dieldrin-induced dopaminergic neurodegeneration and reactive glial morphometry in male mice

The etiology of Parkinson’s disease (PD) is associated with exposure to environmental contaminants, including the organochlorine pesticide dieldrin. This is thought to occur through induction of oxidative damage and dysregulation of dopamine homeostasis via impairment of aldehyde dehydrogenase (ALDH) enzymes, resulting in neuronal stress that may contribute to glial-mediated neurotoxicity. We postulated that sub-chronic murine dieldrin exposure would induce PD-relevant histopathologic changes in the substantia nigra (SN) which would be exacerbated in ALDH-deficient mice. To test this hypothesis, six-month-old wildtype and Aldh1a1 −/− X Aldh2 −/− (Aldh1/2 KO) mice were fed dieldrin in chow at doses of 0, 0.2, or 0.6ppm for 6 weeks. Slide scanning microscopy and deep learning-based image analysis were then applied to quantify neuronal injury and glial morphometry. Dieldrin exposure resulted in male-specific dopaminergic neurodegeneration, a dose-dependent increase in astrocytic density, and disease-associated alterations in microglial morphology in the substantia nigra. Interestingly, Aldh1/2 KO attenuated neuronal loss and distinctly modulated reactive astrocytosis and microglial morphometric changes. These results highlight a sex-dependent susceptibility to dieldrin-induced neurotoxicity and suggest a role of ALDH in modulating glial reactivity in the context of PD-like neurodegeneration.