Systemic inflammation accelerates neurodegeneration in a rat model of Parkinson's disease overexpressing human alpha-synuclein

Increasing efforts have been made to elucidate how genetic and environmental factors interact in Parkinsons disease (PD). In the present study, we assessed the development of symptoms on a genetic PD rat model that overexpresses human -synuclein (Snca+/+) at a presymptomatic age, exposed to a pro-inflammatory insult by intraperitoneal injection of lipopolysaccharide (LPS), using immunohistology, high-dimensional flow cytometry, constant potential amperometry, and behavioral analyses. A single injection of LPS into WT and Snca+/+ rats triggered long-lasting increase in the activation of pro-inflammatory microglial markers, monocytes, and T lymphocytes. However, only LPS Snca+/+ rats showed dopaminergic neuronal loss in the substantia nigra pars compacta (SNpc), associated with a reduction in the release of evoked dopamine in the striatum. No significant changes were observed in the behavioral domain. We propose our double-hit animal as a reliable model to investigate the mechanisms whereby -synuclein and inflammation interact to promote neurodegeneration in PD.