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Lewy body disorders are associated with hallmark inclusions containing aggregated forms of alpha‐synuclein. When alpha‐synuclein aggregates in the synapse, it may be transported along axonal microtubular tracks to the soma for degradation or deposition into insoluble inclusions. However, during this transportation, alpha‐synuclein aggregates may also adhere to the microtubules and impede the axonal transport of other cellular constituents. Axonal transport is known to depend upon the stability of the microtubule tracks, but the specific impact of alpha‐synucleinopathy on microtubular dynamicity is unclear. Here, we assessed markers of microtubule stabilization in olfactory bulb and amygdala samples harvested postmortem from men and women with Lewy body disorders and age‐matched control subjects. Unexpectedly, we observed that women showed higher levels of detyrosinated alpha‐tubulin (marker of microtubule stability) as well as higher levels of tyrosinated alpha‐tubulin (marker of non‐stabilized microtubules) compared to men. Second, the impact of microtubule stability on inclusion body formation is also poorly understood. Thus, we measured inclusion counts in primary hippocampal cultures treated with novel heterocyclic microtubule stabilizers and challenged with preformed alpha‐synuclein fibrils. As expected, the microtubule stabilizers reduced pathologically phosphorylated (pSer129) alpha‐synuclein+ inclusion counts, and the microtubule destabilizer nocodazole prevented this reduction in pathological inclusions. These collective data suggest that microtubule stability may influence the emergence of alpha‐synucleinopathy in experimental Lewy body disease.

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Lewy body disorders are characterized by proteostatic and redox disequilibrium, leading to deposition of α‐synuclein in hallmark inclusions and oxidative damage to DNA. One common pathway for repair of oxidative DNA damage is base excision repair (BER), which involves the coordinated activity of several enzymes, including apurinic/apyrimidinic endonuclease 1 (APE1). The main goal of this study was to assess APE1 in rodents and humans with α‐synucleinopathy, and to test the functional impact of APE1 in the preformed α‐synuclein fibril model. First, we report that knockdown of APE1 with two independent shRNA sequences or inhibition of APE1 DNA repair activity increased inclusions bearing pathologically‐phosphorylated α‐synuclein (pSer129) in preformed fibril‐treated primary hippocampal cultures. Second, we examined APE1 expression in a mouse model of limbic‐centered α‐synucleinopathy, in which α‐synuclein fibrils are infused into the olfactory bulb/anterior olfactory nucleus (OB/AON). Six months later, we observed a fibril‐induced decrease in APE1 expression in the brains of male mice and an increase in females. Similar sex‐opposing patterns were noted for APE1 mRNA expression. Third, we demonstrated that the loss of APE1 in fibril‐infused male mice in vivo is mediated by oxidative stress, as APE1 loss was abolished by dietary administration of the antioxidant N‐acetylcysteine. Fourth, OB/AON tissues harvested from fibril‐infused male mice displayed higher cleavage of synthetic DNA lesions on a biochip than tissues collected in parallel from fibril‐infused female mice. However, OB/AON tissues harvested from fibril‐infused female mice had higher DNA repair activity compared to males. Assessments of open field activity measures and sucrose preference revealed a negative behavioral impact of α‐synuclein fibril infusions in male but not female mice. Fifth, men with Lewy body disorders displayed lower APE1 expression in the OB and amygdala compared to women with Lewy body disorders, similar to fibril‐infused mice. Finally, we infused α‐synuclein fibrils into the OB/AON of transgenic APE1 overexpressing rats and observed a reduction in pSer129 levels in male and female brains compared to fibril‐infused wildtype rats. Preliminary data suggest that APE1 overexpression in fibril‐infused rats improved olfaction and anxiety measures, especially in males. These findings reveal a sex‐biased impact of limbic α‐synucleinopathy on APE1 expression and function but also suggest that APE1 overexpression attenuates α‐synucleinopathy in both sexes.