Parkinson's disease: Mechanisms and models

The cause of Parkinson's disease (PD) is unknown, but epidemiological studies suggest an association with pesticides and other environmental toxins, and biochemical studies implicate a systemic defect in mitochondrial complex I. We report that chronic, systemic inhibition of complex I by the lipophilic pesticide, rotenone, causes highly selective nigrostriatal dopaminergic degeneration that is associated behaviorally with hypokinesia and rigidity. Nigral neurons in rotenone-treated rats accumulate fibrillar cytoplasmic inclusions that contain ubiquitin and alpha-synuclein. These results indicate that chronic exposure to a common pesticide can reproduce the anatomical, neurochemical, behavioral and neuropathological features of PD.

/pdf/chronic-systemic-pesticide-exposure-reproduces-features-of-11pdan5pm0.pdf

Chronic systemic pesticide exposure reproduces features of Parkinson's disease

Lewy bodies and Lewy neurites are the defining neuropathological characteristics of Parkinson’s disease and dementia with Lewy bodies. They are made of abnormal filamentous assemblies of unknown composition. We show here that Lewy bodies and Lewy neurites from Parkinson’s disease and dementia with Lewy bodies are stained strongly by antibodies directed against amino-terminal and carboxyl-terminal sequences of α-synuclein, showing the presence of full-length or close to full-length α-synuclein. The number of α-synuclein-stained structures exceeded that immunoreactive for ubiquitin, which is currently the most sensitive marker of Lewy bodies and Lewy neurites. Staining for α-synuclein thus will replace staining for ubiquitin as the preferred method for detecting Lewy bodies and Lewy neurites. We have isolated Lewy body filaments by a method used for the extraction of paired helical filaments from Alzheimer’s disease brain. By immunoelectron microscopy, extracted filaments were labeled strongly by anti-α-synuclein antibodies. The morphologies of the 5- to 10-nm filaments and their staining characteristics suggest that extended α-synuclein molecules run parallel to the filament axis and that the filaments are polar structures. These findings indicate that α-synuclein forms the major filamentous component of Lewy bodies and Lewy neurites.

https://www.pnas.org/content/pnas/95/11/6469.full.pdf

α-Synuclein in filamentous inclusions of Lewy bodies from Parkinson’s disease and dementia with Lewy bodies

Familial parkinsonism and dementia with cortical and subcortical Lewy bodies is uncommon, and no genetic defect has been reported in the previously described sibships We present a Spanish family with autosomal dominant parkinsonism, dementia, and visual hallucinations of variable severity The postmortem examination showed atrophy of the substantia nigra, lack of Alzheimer pathology, and numerous Lewy bodies which were immunoreactive to alpha-synuclein and ubiquitin in cortical and subcortical areas Sequencing of the alpha-synuclein gene showed a novel, nonconservative E46K mutation in heterozygosis The E46K mutation was present in all affected family members and in three young asymptomatic subjects, but it was absent in healthy and pathological controls The novel mutation, that substitutes a dicarboxylic amino acid, glutamic acid, with a basic amino acid such as lysine in a much conserved area of the protein, is likely to produce severe disturbance of protein function Our data show that, in addition to the previously described hereditary alpha-synucleinopathies, dementia with Lewy bodies is related to mutation of alpha-synuclein

The new mutation, E46K, of alpha-synuclein causes Parkinson and Lewy body dementia.

Helicobacter pylori infection is associated with a variety of clinical outcomes including gastric cancer and duodenal ulcer disease. The reasons for this variation are not clear, but the gastric physiological response is influenced by the severity and anatomical distribution of gastritis induced by H. pylori. Thus, individuals with gastritis predominantly localized to the antrum retain normal (or even high) acid secretion, whereas individuals with extensive corpus gastritis develop hypochlorhydria and gastric atrophy, which are presumptive precursors of gastric cancer. Here we report that interleukin-1 gene cluster polymorphisms suspected of enhancing production of interleukin-1-beta are associated with an increased risk of both hypochlorhydria induced by H. pylori and gastric cancer. Two of these polymorphism are in near-complete linkage disequilibrium and one is a TATA-box polymorphism that markedly affects DNA-protein interactions in vitro. The association with disease may be explained by the biological properties of interleukin-1-beta, which is an important pro-inflammatory cytokine and a powerful inhibitor of gastric acid secretion. Host genetic factors that affect interleukin-1-beta may determine why some individuals infected with H. pylori develop gastric cancer while others do not.

/pdf/interleukin-1-polymorphisms-associated-with-increased-risk-42608maro7.pdf

Sigfried Kösel

Papers

Ala30Pro mutation in the gene encoding alpha-synuclein in Parkinson's disease.