Amygdalar nuclei vulnerability to protein aggregates in Lewy body diseases.

The amygdala is highly vulnerable to protein aggregation and heavily affected in Lewy body diseases (LBDs). However, vulnerability might vary per amygdalar nucleus and it is unclear if the pattern of vulnerability across the nuclei differs between types of protein aggregation and between LBDs. In this study, we aimed to assess the vulnerability of amygdalar nuclei to multiple types of protein aggregation across LBDs. Post-mortem amygdala tissue of donors with incidental LBD (iLBD, n = 6), Parkinson's disease (PD; n = 18), dementia with Lewy bodies (DLB; n = 9) and Alzheimer's disease with Lewy bodies (AD + LB; n = 15) was immunostained with antibodies against alpha-synuclein (aSyn; EP1536Y and 5G4), amyloid beta (Aβ; 4G8), phosphorylated tau (p-tau; AT8) and phosphorylated TDP-43 (p-TDP-43; 11-9), and quantitatively analyzed using QuPath. Neuronal and astrocytic aSyn pathology were most pronounced in the parahippocampal-amygdaloid transition area (PHA) and the basal nucleus, a pattern shared by all disease groups. Vulnerability to Aβ pathology varied per group but was highest in the PHA in AD + LB, whereas diffuse plaques were most common in the accessory basal nucleus. The PHA of DLB and both the basal and accessory basal nucleus of AD + LB cases were most susceptible to p-tau pathology, with fine granular cytoplasmic neuronal tau inclusions being mostly observed in the basal nucleus and neurofibrillary tangles in the accessory basal nucleus. The nuclei in the ventromedial part of the amygdala (PHA, ventral part of the basal nucleus, and cortical nucleus) were found to be hotspots for protein aggregation across LBDs. aSyn pathology in these nuclei predominantly correlated with dementia, hallucinations and anxiety. Our results show that amygdalar nuclei vulnerability differs per protein aggregate and disease entity, although the PHA, basal nucleus and cortical nucleus are generally more vulnerable. Together, our study provides a deeper insight into the selective vulnerability of amygdalar nuclei to protein aggregates and their relation to clinical characteristics in LBDs.