Absence of major accumulation of mitochondrial ND5 mutations in Parkinson patient muscle.

UNLABELLED: The pathogenesis of the selective loss of dopaminergic neurons in idiopathic Parkinson's disease (PD) has not been understood up to now. Respiratory chain dysfunction and accumulation of mitochondrial DNA deletions to biochemically relevant levels have been observed in the dopaminergic neurons. However, respiratory chain defects have also been reported in other tissues, pointing to a generalized component of oxidative stress in PD. Recently, somatic point mutations in a narrow region of the complex I polypeptide ND5 (codons 120 - 150) were suggested to separate PD patients from age-matched controls, using frontal cortex homogenates. OBJECTIVE: The present study intended to analyze whether those recently described ND5 mutations may also generally occur in skeletal muscle tissue of PD patients, in which complex I dysfunction had been measured earlier with biochemical approaches. MATERIAL: Skeletal muscle biopsy samples of 5 PD individuals with a previously characterized biochemical complex I defect and of 5 age-matched controls were used. METHOD: DNA was extracted from the muscle samples. The relevant ND5 region was PCR-cloned using a high fidelity Pfu polymerase and a low number of PCR cycles (15). Amean number of 96 clones were randomly selected from the ampicillin plates and sequenced by the dye terminator method to allow the detection of low abundance mutations with a sensitivity around 1%. RESULTS: Mutations between codons 120 and 150 were only slightly more frequent in PD versus controls (60 versus 40% of samples affected), while this ratio had been 100 versus 12.5% in frontal cortex. CONCLUSIONS: In contrast to results reported for PD frontal cortex, low-level ND5 mutations between codons 120 and 150 do not accumulate severely in biochemically affected skeletal muscle samples of PD patients.

Reduced urocortin 1 immunoreactivity in the non-preganglionic Edinger-Westphal nucleus during late pregnancy in rats.

Pregnancy is accompanied by an array of adaptive changes that play an important role in pre- and postnatal events. In rats, urocortin 1, a corticotropin-releasing factor-like peptide, is expressed mainly in the non-preganglionic Edinger-Westphal nucleus. We investigated the number of neurons immunoreactive for urocortin 1 at three different levels of the Edinger-Westphal nucleus in female rats by immunohistochemistry. The number of urocortin 1 immunoreactive cells was found to be decreased in pregnant rats compared to virgin rats. These results indicate that the hormonal status of the female rat affects urocortin 1 immunoreactive neurons in the non-preganglionic Edinger-Westphal nucleus and its signaling to target brain areas.

Glutathione depletion in antioxidant defense of differentiated NT2-LHON cybrids.

The mechanism of retinal ganglion cell loss in Leber's hereditary optic neuropathy (LHON) is still uncertain, and a role of enhanced superoxide production by the mutant mitochondrial complex I has been hypothesized. In the present study, it was shown that LHON cybrids, carrying the np11778 mutation, became selectively more H(2)O(2) sensitive compared with the parental cell line only following short-term retinoic acid differentiation. They contained a decreased cellular glutathione pool (49%, p< or =0.05), despite 1.5-fold enhanced expression of the regulatory subunit of gamma-glutamylcysteine synthetase (p< or =0.05). This points to a reduction of the capacity to detoxify H(2)O(2) and to changes in thiol redox potential. The activity of the H(2)O(2) degrading enzyme glutathione peroxidase (GPx) and the activities of glutathione reductase (GR) and superoxide dismutase (SOD) were unaffected.