Free Radical Chain Reactions and Polyunsaturated Fatty Acids in Brain Lipids.

Polyunsaturated fatty acyl chains (PUFAs) concentrate in the brain and give rise to numerous oxidative chemical degradation products. It is widely assumed that these products are the result of free radical chain reactions, and reactions of this type have been demonstrated in preparations where a single PUFA substrate species predominates. However, it is unclear whether such reactions can occur in the biologically complex milieu of lipid membranes where PUFA substrates are a minority species, and where diverse free radical scavengers or other quenching mechanisms are present. It is of particular interest to know whether they occur in brain, where PUFAs are concentrated and where PUFA oxidation products have been implicated in the pathogenesis of neurodegenerative disorders. To ascertain whether free radical chain reactions can occur in a complex brain lipid mixture, mouse brain lipids were extracted, formed into vesicles, and treated with a fixed number of hydroxyl radicals under conditions wherein the concentrations and types of PUFA-containing phospholipids were varied. Specific phospholipid species in the mixture were assayed by tandem mass spectrometry to quantify the oxidative losses of endogenous PUFA-containing phospholipids. Results reveal crosstalk between the oxidative degradation of ω3 and ω6 PUFAs that can only be explained by the occurrence of free radical chain reactions. These results demonstrate that PUFAs in a complex brain lipid mixture can participate in free radical chain reactions wherein the extent of oxidative degradation is not limited by the number of reactive oxygen species available to initiate such reactions. These reactions may help explain otherwise puzzling in vivo interactions between ω3 and ω6 PUFAs in mouse brain.

Quantitative Mass Spectrometric Assay of Whole and CNBr-Cleaved Amyloid-ß Peptides in Human Brain.

Various amyloid-ß (Aß) peptides accumulate in brain in Alzheimer's disease, and the amounts of specific peptide variants may have pathological significance. The quantitative determination of these variants is challenging because losses inevitably occur during tissue processing and analysis. This report describes the use of stable-isotope-labeled Aß peptides as internal standards for quantitative mass spectrometric assays, and the use of cyanogen bromide (CNBr) to remove C-terminal residues beyond Met35. The removal of residues beyond Met35 reduces losses due to aggregation, and facilitates the detection of post-translationally modified Aß peptides. Results from 8 human brain samples suggest that the tissue concentrations of the 42-residue Aß peptide tend to be similar in different patients. Concentrations of the 40-residue Aß peptide are more variable, and may be greater or lesser than the 42-residue peptide. The concentration of the CNBr cleavage product closely matches the sum of the 40-residue and 42-residue peptide concentrations, indicating that these two Aß peptides account for most of the C-terminal variants in these patients. CNBr treatment facilitated the detection of post-translational modifications such as pyroglutamyl and hexose-modified Aß peptides.

The presence of Aspergillus fumigatus is associated with worse respiratory quality of life in cystic fibrosis.

BACKGROUND: The clinical effects of Aspergillus fumigatus in the cystic fibrosis (CF) airway, with the exception of allergic bronchopulmonary aspergillosis, is unclear. METHODS: CF adolescents and adults (age 14 years and older) underwent bacterial and semi-selective fungal culture testing to determine the prevalence of fungi in the CF respiratory tract and the independent association between the presence of Aspergillus fumigatus and clinical characteristics. RESULTS: Aspergillus fumigatus (10.3%) and Candida species (57.8%) were the most common filamentous fungi and yeast seen respectively in the sputa of 206 individuals with CF. Inhaled corticosteroid (ICS) use was more common in Aspergillus fumigatus-positive than Aspergillus fumigatusnegative (100% versus 75.8%, p = .01). Aspergillus fumigatus was significantly associated with lower respiratory domain score (ß -8.74, 95% CI -16.6, -0.88, p = .03), representing worse respiratory-related quality of life, accounting for demographics, disease characteristics, and the presence of a pulmonary exacerbation. CONCLUSION: The presence of Aspergillus fumigatus in CF sputum was associated with worse respiratory quality of life in CF in a crosssectional, single center study. Longitudinal analysis examining the clinical implications of Aspergillus fumigatus on respiratory health over time is needed.