AnIn VitroModel of Parkinson's Disease: Linking Mitochondrial Impairment to Altered α-Synuclein Metabolism and Oxidative Damage

Abstract

Chronic systemic complex I inhibition caused by rotenone exposure induces features of Parkinson's disease (PD) in rats, including selective nigrostriatal dopaminergic degeneration and formation of ubiquitin- and alpha-synuclein-positive inclusions (Betarbet et al., 2000). To determine underlying mechanisms of rotenone-induced cell death, we developed a chronic in vitro model based on treating human neuroblastoma cells with 5 nm rotenone for 1-4 weeks. For up to 4 weeks, cells grown in the presence of rotenone had normal morphology and growth kinetics, but at this time point, approximately 5% of cells began to undergo apoptosis. Short-term rotenone treatment (1 week) elevated soluble alpha-synuclein protein levels without changing message levels, suggesting that alpha-synuclein degradation was retarded. Chronic rotenone exposure (4 weeks) increased levels of SDS-insoluble alpha-synuclein and ubiquitin. After a latency of >2 weeks, rotenone-treated cells showed evidence of oxidative stress, including loss of glutathione and increased oxidative DNA and protein damage. Chronic rotenone treatment (4 weeks) caused a slight elevation in basal apoptosis and markedly sensitized cells to further oxidative challenge. In response to H2O2, there was cytochrome c release from mitochondria, caspase-3 activation, and apoptosis, all of which occurred earlier and to a much greater extent in rotenone-treated cells; caspase inhibition provided substantial protection. These studies indicate that chronic low-grade complex I inhibition caused by rotenone exposure induces accumulation and aggregation of alpha-synuclein and ubiquitin, progressive oxidative damage, and caspase-dependent death, mechanisms that may be central to PD pathogenesis.

Mitochondrial pathology and muscle and dopaminergic neuron degeneration caused by inactivation of Drosophila Pink1 is rescued by Parkin

“…Of these five genes, ␣-Syn, parkin, and DJ-1 have been most intensively studied. Studies using in vivo animal models and in vitro cell culture have linked mutations of these genes to impairments of mitochondrial structure and function and oxidative stress response, reinforcing the general involvement of mitochondrial dysfunction and oxidative stress in PD pathogenesis (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Consistent with this notion, these proteins have been shown to be present in mitochondria or interact with mitochondrial proteins (8,(22)(23)(24), suggesting that they may directly regulate mitochondria function.…”

Parkinson's disease and pesticides: a toxicological perspective

“…The damage reported in these studies was seen in the striatum first, followed by the SNpc (this is similar to the 'dying-back' phenomenon in PD); however, these changes were seen only in a subset of exposed animals. Additionally, increased oxidative stress, ubiquitin accumulation, proteasomal inhibition and inflammation all have been observed in response to rotenone exposure [19,[48][49][50]. Despite this evidence of a role for rotenone in PD pathogenesis, it is unlikely the rotenone is a major contributor because of its limited commercial use, short half-life in the environment and low bioavailability.…”

Near-infrared light via light-emitting diode treatment is therapeutic against rotenone- and 1-methyl-4-phenylpyridinium ion-induced neurotoxicity

“…Dopamine deficiency and defects in mitochondrial complex I activity play important roles in the manifestation of PD (Javitch et al 1985;Parker et al 1989). Previous studies in humans and experimental animals have shown that 1-methyl-4-phenylpyridinium ion (MPP + ), the ultimate metabolic product of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), can induce PD-like symptoms (Lagnston et al 1983;Schmidt and Ferger, 2001;Sherer et al 2002). MPP + is taken into dopaminergic neurons and presumably other neurons and accumulates in the mitochondria, where it inhibits complex I activity.…”