Proteasome Inhibitor Lactacystin Induces Cholinergic Degeneration

Abstract

The failure of ubiquitin proteasome (UP) function is widely believed to participate in the development of Parkinson's disease (PD) [1][2][3] . Recent studies have shown that most causative genes of familial PD are associated with ubiquitin proteasome system, including α-synuclein 4 , parkin 5 , ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) 6 and DJ-1 7 . Above all, evidence shows that proteasome inhibition has been found in the substantia nigra pars compacta (SNpc) of sporadic PD [8][9][10] , which accounts for 95 percent of all PD cases. All of these have triggered big interest in exploring the role of UP dysfunction in the pathogenesis of PD. Recently several studies have revealed that proteasome inhibitors could produce excellent PD animal models [11][12][13] , ABSTRACT: Objective: Ubiquitin proteasome system dysfunction is believed to play an important role in the development of Parkinson's disease (PD), and almost all studies till now have mainly focused on the susceptibility of dopaminergic neurons to proteasome inhibition. However, in fact, there are many other types of neurons such as cholinergic ones involved in PD. In our present study, we attempt to figure out what effect the failure of ubiquitin proteasome function would execute on cholinergic cells in culture. Methods:We treated cholinergic cells in culture with various doses of lactacystin. Then MTT assay was used to evaluate the cellular viability and the AnnexinV-PI method was used to detect apoptosis. Both cellular soluble and insoluble polyubiquitinated proteins were detected by western blot. Furthermore, the mitochondrial membrane potential was analyzed using JC-1 and the intracellular production of reactive oxygen species (ROS) was determined using the fluorescent probe CM-H2DCFDA. Results: We found that low doses of lactacystin were enough to induce significant apoptotic cell death, disturb the mitochondrial membrane potential, and cause oxidative stress. We also found that the amounts of polyubiquitinated proteins dramatically increased with high doses, although the loss of cells did not increase accordingly. Conclusions: Our results suggest that cholinergic cells are sensitive to ubiquitin proteasome system dysfunction, which exerts its toxic effect by causing mitochondrial dysfunction and subsequent oxidative stress, not through polyubiquitinated proteins accumulation.RÉSUMÉ: La lactacystine, un inhibiteur du protéasome, induit une dégénérescence cholinergique. Objectif : La dysfonction du système protéasome-ubiquitine jouerait un rôle important dans la genèse de la maladie de Parkinson (MP) et presque toutes les études ont ciblé la susceptibilité des neurones dopaminergiques à l'inhibition du protéasome. Cependant, il y a plusieurs autres types de neurones tels les neurones cholinergiques qui son impliqués dans la MP. Dans cette étude nous avons cherché à comprendre quelles sont les conséquences d'une dysfonction du système protéasome-ubiquitine sur des cellules cholinergiques en culture. Méthodes : Nous avons traité des cellules chol...

Temporal-Spatial Profiling of Pedunculopontine Galanin-Cholinergic Neurons in the Lactacystin Rat Model of Parkinson’s Disease

“…4A), galanin retained upregulation within PPN cholinergic neurons, but at significantly lower levels than was seen at the acute time-point. The finding of this transient upregulation of galanin within toxin-challenged PPN cholinergic neurons, with this change in expression levels being restricted to segments nearest to the direct insult, indicates that galanin fulfils a neuroregulatory role in PPN cholinergic neurons' response to an irreversible ubiquitin proteasome system inhibitor, with a disturbance to the mitochondrial membrane potential and excessive oxidative stress that eventuates to apoptotic cell death (Zhou et al 2010).…”