Nigral injection of a proteasomal inhibitor, lactacystin, induces widespread glial cell activation and shows various phenotypes of Parkinson’s disease in young and adult mouse

Abstract

Proteinaceous inclusions, called Lewy bodies, are used as a pathological hallmark for Parkinson's disease (PD). Lewy bodies contain insoluble α-synuclein (aSyn) and many other ubiquitinated proteins, suggesting a role for protein degradation system failure in the PD pathogenesis. Indeed, proteasomal dysfunction has been linked to PD but commonly used in vivo toxin models, such as 6-OHDA or MPTP, do not have a significant effect on the proteasomal system or protein aggregation. Therefore, we wanted to study the characteristics of a proteasomal inhibitor, lactacystin, as a PD model on young and adult mice. To study this, we performed stereotactic microinjection of lactacystin above the substantia nigra pars compacta in young (2 month old) and adult (12-14 month old) C57Bl/6 mice. Motor behavior was measured by locomotor activity and cylinder tests, and the markers of neuroinflammation, aSyn, and dopaminergic system were assessed by immunohistochemistry and HPLC. We found that lactacystin induced a Parkinson's disease-like motor phenotype 5-7 days after injection in young and adult mice, and this was associated with widespread neuroinflammation based on glial cell markers, aSyn accumulation in substantia nigra, striatal dopamine decrease, and loss of dopaminergic cell bodies in the substantia nigra and terminals in the striatum. When comparing young and adult mice, adult mice were more sensitive for dopaminergic degeneration after lactacystin injection that further supports the use of adult mice instead of young when modeling neurodegeneration. Our data showed that lactacystin is useful in modeling various aspects of Parkinson's disease, and taken together, our findings emphasize the role of a protein degradation deficit in Parkinson's disease pathology, and support the use of proteasomal inhibitors as Parkinson's disease models.

Nigrostriatal proteasome inhibition impairs dopamine neurotransmission and motor function in minipigs

“…Previous reports have shown an increased ipsilateral SNr α-syn immunoreactivity to lactacystintreatment in both mice and rats compared to control animals accompanied by neuroinflammation and oxidative stress (Miwa et al, 2005;Savolainen et al, 2017). We observed immunopositive α-syn granules in both the ipsilateral and contralateral SNr that were slightly more pronounced in the lactacystin-than the saline-injected animals (Figure 7), presumably caused by the minor inflammatory response seen in these animals.…”

Back and to the Future: From Neurotoxin‐Induced to Human Parkinson's Disease Models

“…Loss of dopaminergic neurons has been reported with impaired motor behavior and filamental proteinaceous inclusions in brain regions affected by PD. However, later studies could not reproduce most of these findings, although some aspects of the model, such as the loss of nigral dopaminergic neurons and accumulation of proteinaceous inclusions, have been replicated (Savolainen, Albert, Airavaara, & Myohanen, ). In addition, the observed motor deficits were not as prominent as in the original studies (Kordower et al., ; Manning‐Bog et al., ).…”

“…The model produces α-synuclein protein expression in the dopaminergic neurons of the nigrostriatal tract which can cause loss of TH expression and unilateral motor deficits (Decressac et al, 2013;. While loss of TH in the SNpc is common in this model, the outcome of other measures often used in the field of animal models of PD such as loss of TH expression in the striatum, dopamine content levels, and certain motor phenotypes are less clearly observed or not shown at all (Albert et al, 2017).…”

“…As discussed above, several studies using different viral vectors were reported to result in neuronal cell death in the SNpc, decreased dopamine release in striatum and motor deficits (Albert et al, 2017;Visanji et al, 2016). However, overexpression of α-synuclein relies on very high nonphysiological levels of protein, which cause cell death due to protein buildup, and, therefore, might not mimic sporadic PD pathology.…”

Ketamine Does Not Exert Protective Properties on Dopaminergic Neurons in the Lactacystin Mouse Model of Parkinson’s Disease

“…Proteasomal dysfunction, leading to aberrant protein turnover and build-up of misfolded or damaged proteins, has emerged as a potential contributor to cell death in PD (Poewe et al, 2017 ) and might be linked to the accumulation of both non-ubiquitinated and ubiquitinated proteins in the SNpc and in Lewy bodies of PD patients (McNaught et al, 2001 ). Accordingly, administration of lactacystin (LAC), a selective proteasome inhibitor, leads to dopaminergic cell death when applied to the nigrostriatal pathway of rodents (Mackey et al, 2013 ; Savolainen et al, 2017 ). We recently reported that intranigral administration of LAC—reflecting PD pathology where proteasome dysfunction is limited to the SN (McNaught et al, 2003 )—leads to acute and non-progressive dopaminergic cell loss in mice (Bentea et al, 2015 ).…”