Lack of Parkinsonian Pathology and Neurodegeneration in Mice After Long-Term Injections of a Proteasome Inhibitor in Olfactory Bulb and Amygdala

Abstract

Proteinaceous inclusions, called Lewy bodies (LBs), are used as a pathological hallmark for Parkinson’s disease (PD). Recent studies suggested a prion-like spreading mechanism for α-synucleinopathy where early neuropathological deposits occur, among others, in the olfactory bulb (OB) and amygdala. LBs contain insoluble α-synuclein and many other ubiquitinated proteins, suggesting a role of protein degradation system failure in PD pathogenesis. Therefore, we wanted to study the effects of a proteasomal inhibitor, lactacystin, on the aggregability and transmissibility of α-synuclein in the OB and amygdala. We performed injections of lactacystin in the OB and amygdala of wild-type mice. Motor behavior, markers of neuroinflammation, α-synuclein, and dopaminergic integrity were assessed by immunohistochemistry. Overall, there were no differences in the number of neurons and α-synuclein expression in these regions following injection of lactacystin into either the OB or amygdala. Microglial and astroglial labeling appeared to be correlated with surgery-induced inflammation or local effects of lactacystin. Consistent with the behavior and pathological findings, there was no loss of dopaminergic cell bodies in the substantia nigra and terminals in the striatum. Our data showed that long-term lactacystin injections in extra nigrostriatal regions may not mimic spreading aspects of PD and reinforce the special vulnerability of dopaminergic neurons of the substantia nigra pars compacta (SNc).

Specific proteolysis mediated by a p97-directed proteolysis-targeting chimera (PROTAC)

“…Mouse (C57BL6 / C mice), rat (sprague dawley), and monkey (Macaca fascicularis) brain sections were obtained from the brain bank of HM CINAC. All procedures with animals were carried out in accordance with the Directive of the Council of the European Communities (2010/63 / EU) and Spanish legislation (RD53 / 2013) on animal experimentation 88 . Animal perfusion, fixation, and tissue processing was carried out as previously described 88,89 .…”