[Pathogenesis of sporadic Parkinson's disease: contribution of genetic and environmental risk factors]

Effects of in vitro and in vivo avermectin exposure on alpha synuclein expression and proteasomal activity in pigeons

Avermectins (AVMs) are used worldwide in agriculture and veterinary medicine. Residues of avermectin drugs, causing toxicological effects on non-target organisms, have raised great concern. The aim of this study was to investigate the effects of AVM on the expression levels of alpha synuclein (α-Syn) and proteasomal activity in pigeon (Columba livia) neurons both in vivo and in vitro. The results showed that, the mRNA and protein levels of α-Syn increased in AVM treated groups relative to control groups in the cerebrum, cerebellum and optic lobe in vivo. Dose-dependent decreases in the proteasomal activity (i.e., chymotrypsin-like, trypsin-like and peptidylglutamyl peptidehydrolase) were observed both in vivo and in vitro. The results suggested that AVM could induce the expression levels of α-Syn and inhibit the normal physiological function of proteasome in brain tissues and neurons. The information presented in this study is helpful to understand the mechanism of AVM-induced neurotoxicology in birds.

Oxidative stress: A major pathogenesis and potential therapeutic target of antioxidative agents in Parkinson's disease and Alzheimer's disease

Oxidative stress reflects an imbalance between the overproduction and incorporation of free radicals and the dynamic ability of a biosystem to detoxify reactive intermediates. Free radicals produced by oxidative stress are one of the common features in several experimental models of diseases. Free radicals affect both the structure and function of neural cells, and contribute to a wide range of neurodegenerative diseases, including Parkinson's disease and Alzheimer's disease. Although the precise mechanisms that result in the degeneration of neurons and the relevant pathological changes remain unclear, the crucial role of oxidative stress in the pathogenesis of neurodegenerative diseases is associated with several proteins (such as α-synuclein, DJ-1, Amyloid β and tau protein) and some signaling pathways (such as extracellular regulated protein kinases, phosphoinositide 3-kinase/Protein Kinase B pathway and extracellular signal-regulated kinases 1/2) that are tightly associated with the neural damage. In this review, we present evidence, gathered over the last decade, concerning a variety of pathogenic proteins, their important signaling pathways and pathogenic mechanisms associated with oxidative stress in Parkinson's disease and Alzheimer's disease. Proper control and regulation of these proteins' functions and the related signaling pathways may be a promising therapeutic approach to the patients. We also emphasizes antioxidative options, including some new neuroprotective agents that eliminate excess reactive oxygen species efficiently and have a certain therapeutic effect; however, controversy surrounds some of them in terms of the dose and length of therapy. These agents require further investigation by clinical application in patients suffering Parkinson's disease and Alzheimer's disease.

Analysis of genome-wide association study-linked loci in Parkinson's disease of Mainland China

BACKGROUND

Genome-wide association studies (GWAS) have identified numerous single-nucleotide polymorphisms (SNPs) that can modulate the risk of developing Parkinson's disease (PD).

METHODS

We investigated the association of previously identified loci in a Mainland Chinese population to identify a possible ethnic-specific effect with GWAS analysis. Seventeen SNPs were genotyped from those loci using case-control methodology to analyze a total of 1,737 individuals.

RESULTS

Strong evidence of an association for reference SNP 894278 (rs894278) and rs11931074 on 4q22 throughout the α synuclein (SNCA) region was observed in our study. The SNP rs894278 confers risk via a dominant model and an additive model, whereas the minor allele G of rs11931074 reduces the risk of PD progression. The minor allele frequency of rs11724635 produced weaker signals for PD, but this was not replicated in the genotype after adjusting for age and sex.

CONCLUSIONS

This study yields new clues about GWAS-linked data in patients with PD from Mainland China.

Membrane bound α-synuclein is fully embedded in the lipid bilayer while segments with higher flexibility remain

Cellular pathways involving α-synuclein (αS) seem to be causative for development of Parkinson's disease. Interactions between αS and lipid membranes appear to be important for the physiological function of the protein and influence the pathological aggregation of αS leading to the formation of amyloid plaques. Upon membrane binding the unstructured αS folds into amphipathic helices. In our work we characterized the penetration depth and probed the local environment of Trp-residues introduced along the αS sequence. We could show that while the entire helix is well embedded in the lipid bilayer, segments with a shallower penetration and supposable higher flexibility exist.

Polypharmacy increases the risk of Parkinson's disease in older people in Taiwan: a population-based study

BACKGROUND

Little is known about the relationship between polypharmacy and Parkinson's disease (PD). In the present study, we tested the hypothesis that polypharmacy increases the risk of PD in older people in Taiwan.

METHODS

From a randomly sampled cohort of one million health insurance enrollees, we identified 2827 new cases of PD over the period 2000-2008 aged ≥ 65 years and selected 11 308 age-matched controls without PD. Medication history and baseline comorbidities were compared between the two groups. We defined 'polypharmacy' as an average daily use of five or more prescribed drugs.

RESULTS

Compared with patients using between none and one drug, the odds ratios (ORs) for PD increased to 1.53, 2.08, 2.64, and 2.95 for patients using two to four, five to seven, eight to nine, and ≥ 10 drugs, respectively. The other conditions associated with PD were dementia (OR 3.43), stroke (OR 2.30), depression (OR 2.15), and alcoholism (OR 2.11). Hyperlipidemia (OR 0.90) was inversely associated with PD.

CONCLUSIONS

Polypharmacy was shown to increase the risk of PD in older people in Taiwan, with risk increasing with the number of medications taken daily. Dementia, stroke, depression, and alcoholism were also associated with an increased risk of PD, whereas there was an inverse correlation between PD and hyperlipidemia.