The mitochondrial secret(ase) of Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized clinically by progressive decline in memory and cognition and pathologically by extracellular amyloid-beta (Abeta) deposits and intraneuronal aggregates of hyperphosphorylated tau. Since its proposal in 1992, the amyloid cascade hypothesis implicates Abeta overproduction as a causative event in disease pathogenesis, and this thinking has predominated the field's understanding of AD pathogenesis and the development of potential therapeutics (i.e., Abeta-reducing agents). Though Abeta has been shown to induce AD pathology, unanswered questions for sporadic AD development suggests this hypothesis is best applied to familial disease only. The more recent mitochondrial cascade hypothesis is supported by data showing that early impairments of mitochondrial dysfunction and oxidative stress may precede Abeta overproduction and deposition. However, the development of Abeta-reducing agents continues. Unfortunately, these agents have not been efficiently tested for their effect on one of the earliest AD pathologies, i.e., mitochondrial dysfunction. This paper will review supporting data for the amyloid and mitochondrial cascade hypotheses, reports of the effects of secretase inhibitors on AD-phenotypic cells and animals, and begin to look at a potential role for gamma-secretase, which is localized to mitochondria, in AD-related mitochondrial dysfunction.

Automated solid-phase extraction method for measuring urinary polycyclic aromatic hydrocarbon metabolites in human biomonitoring using isotope-dilution gas chromatography high-resolution mass spectrometry.

In order to perform comprehensive epidemiological studies where multiple metabolites of several PAHs are measured and compared in low-dose urine samples, fast and robust methods are needed to measure many analytes in the same sample. We have modified a previous method used for measuring polycyclic aromatic hydrocarbon (PAH) metabolites by automating the solid-phase extraction (SPE) and including an additional eight metabolites. We also added seven new carbon-13 labeled standards, which improves the use of isotope-dilution calibration. Our method included enzyme hydrolysis, automated SPE and derivatization with a silylating reagent followed by gas chromatography (GC), coupled with high-resolution mass spectrometry (HRMS). Using this method, we measured 23 metabolites, representing 9 parent PAHs, with detection limits in the low pg/mL range. All steps in the clean-up procedure were optimized individually, resulting in a method that gives good recoveries (69-93%), reproducibility (coefficient of variation for two quality control pools ranged between 4.6 and 17.1%, N>156), and the necessary specificity. We used the method to analyze nearly 3000 urine samples in the fifth National Health and Nutrition Examination Survey (NHANES 2001-2002).