Selective Susceptibility of Human Dopaminergic Neural Stem Cells to Dopamine-Induced Apoptosis

Dysfunctions of ubiquitin-proteasome system and toxicity of dopamine have been known as the key mechanisms in the pathogenesis of Parkinson's disease (PD) and proteasome inhibitors are widely used in experimental models of PD to reproduce cell death of dopaminergic neurons. In the present study, immortalized human neural stem cells (HB1.F3, F3) and those transfected with human aromatic acid decarboxylase gene (F3.AADC), were used to investigate the mechanism of selective dopaminergic neuronal cell death mediated by dopamine or proteasome inhibitors. Flow cytometric analysis revealed that F3.AADC was more susceptible to dopamine than parental F3 cell which does not carry dopaminergic phenotype. The dopamine-induced apoptosis was mediated by activation of caspases 3 and 9 and cleavage of PARP. Proteasome inhibitors also induced apoptosis in dose-dependent manner but there was no difference between cell types. Prolonged exposure to subtoxic dose of proteasome inhibitors further enhanced dopamine-induced apoptosis in the F3.AADC, and increased presence of alpha-synuclein and ubiquitin-positive inclusions was noted in the cytoplasm of apoptotic cells by immunocytochemistry. These findings indicate that dopaminergic cells are selectively susceptible to dopamine toxicity and prolonged suppression of proteasome system further enhances selective sensitivity to dopamine toxicity. Chronic subtoxic proteasomal dysfunction of dopaminergic cells might contribute to selective cell death of dopaminergic neurons during the pathogenesis of Parkinson's disease.

Clopidogrel Resistance in Acute Ischemic Stroke

BACKGROUND: Clopidogrel has been widely used in the treatment of acute atherothrombosis. However, until now, there has been little information about its resistance during the acute stage of ischemic stroke. In this study, we investigated platelet responsiveness after using clopidogrel in acute ischemic stroke. METHODS: ADP (10 uM) induced platelet aggregation was serially measured in 81 acute ischemic stroke patients at initial, after 24 hrs and 5 days since using clopidogrel. We defined Clopidogrel resistance as less than 30% decrease in platelet aggregation by clopidogrel and investigated the differences of clinical and laboratory findings between the Clopidogrel response and resistance groups. RESULTS: The baseline ADP induced platelet aggregation was 10.2+/-5.5 ohm and was significantly (p<0.05) reduced to 4.0+/-4.5 ohm after the use of Clopidogrel. After 5 days of treatment, the clopidogrel resistance was observed in 18.5% of patients. Of the 15 patients with clopidogrel resistance, 12 patients (80%) had large artery atherosclerotic infarctions, 2 others had an unknown type of stroke, and 1 patient had small vessel disease. The patients with clopidogrel resistance showed significantly higher initial clinical severity (p=0.015), C-reactive protein levels (p=0.001) and WBC counts (p<0.001) than those with good responsiveness. In multiple logistic regression analysis, the WBC count was significantly correlated with the clopidogrel resistance (p=0.01). CONCLUSIONS: Our results indicate that the clopidogrel resistance was observed in up to 18.5% of patients with acute ischemic stroke and might be affected by enhanced inflammatory reactions.

Three Cases of Chronic Cerebral Paragonimiasis

Although CNS involvement of paragonimiasis is not frequently encountered, it has been reported in 10-25% of clinical cases of all paragonimiasis. It causes various symptoms and signs including epilepsy, headache, hemiparesis, visual field defect or other neurologic deficits. Infestation usually occurs by ingestion of freshwater crabs or crayfish infected with Paragonimus metacercariae. We report three patients with chronic cerebral paragonimiasis, which were diagnosed by history, neurologic examination, radiological and serological evaluations, Two of them had history of ingestion of freshwater crabs or crayfish in childhood. Only one patient showed a positive enzyme-linked immunosorbent assay reaction for Paragonimus specific antibody in serum and CSF. Their clinical manifestations were seizure, headache, and visual field defect. In their plain skull X-rays, congregated round oval calcifications were recognized. Brain computed tomography of patients revealed pathognomonic findings of multiple, variable sized, round, calcified lesions surrounded by low density areas together with cortical atrophy in occipital, parietal, and temporal lobes.