Abstract
BackgroundWe have previously reported on the use of the phosphorescence oxygen analyzer for measuring spinal cord cellular respiration. This analytical tool is used here to investigate the effects of two inhibitors of NADH:ubiquinone oxidoreductase, rotenone and 1-methyl-4-phenylpyridinium, on cellular respiration in striatal tissue. Both neurotoxins can induce Parkinson's disease-like symptoms, and have been used to study this disease in animals. Our hypothesis is that striatal cellular respiration is a sensitive biomarker for the adverse effects of toxins, and the phosphorescence oxygen analyzer can be used as a screening tool for this purpose. MethodsStriatal fragments were collected from C57BL6 mice and immersed in Pd phosphor solution [phosphate-buffered saline, 3.0 μM ‘Pd(II)-meso-tetra (sulfophenyl) tetrabenzoporphyrin’ and 0.5% fat-free albumin, with and without 5.0 mM glucose]. The sample was transferred to a glass vial containing 2-mL Pd phosphor solution. The vial was sealed from air and placed in the instrument that measures dissolved oxygen as function of time. Immunoblots of the studied tissue were positive for the dopamine neuronal cell biomarker tyrosine hydroxylase. ResultsStriatal oxygen consumption was linear with time, exhibiting zero-order kinetics of oxygen reduction by cytochrome oxidase. Cyanide sensitive respiration was ≥90%, confirming oxygen was reduced by cytochrome oxidase. The rate of respiration increased by ~2-fold in the presence of glucose. Striatal oxygen consumption in the presence of rotenone or 1-methyl-4-phenylpyridinium was exponential, demonstrating impaired respiration. ConclusionStriatal cellular mitochondrial oxygen consumption was impaired by the studied inhibitors of complex I of the respiratory chain. This effect is expected to deplete NAD+ (oxidized nicotinamide adenine dinucleotide), a principle driver of glycolysis. In vivo studies are required to determine if these toxin-induced metabolic derangements contribute to the development of sporadic Parkinson's disease. This analytic tool can be used to screen environmental toxins for their in vitro effects on the striatum.
Highlights
Parkinson's disease is a progressive neurodegenerative disorder of the central nervous system, which mainly affects our voluntary movements
Striatal cellular respiration was studied in the Pd phosphor solution with and without 5.0 mM glucose
The potential link between Parkinson's disease and mitochondrial poisons, such as rotenone and MPTP has been extensively studied [5, 6]. These mitochondrial toxins can alter the cellular bioenergetics of the midbrain, causing substantial changes in the dopaminergic neurons [7]
Summary
Parkinson's disease is a progressive neurodegenerative disorder of the central nervous system, which mainly affects our voluntary movements. There are no analytic tools that screen for the adverse outcomes (e.g., mitochondrial dysfunction) of environmental substances on the striatum (i.e., identifying a ‘potential initiating event’ or ‘key event relationship’) [3] This preliminary study investigates the use of the phosphorescence oxygen analyzer that measures ‘striatal cellular respiration’ status for this purpose. We have previously reported on the use of the phosphorescence oxygen analyzer for measuring spinal cord cellular respiration This analytical tool is used here to investigate the effects of two inhibitors of NADH:ubiquinone oxidoreductase, rotenone and 1-methyl-4-phenylpyridinium, on cellular respiration in striatal tissue. Both neurotoxins can induce Parkinson's disease-like symptoms, and have been used to study this disease in animals. This analytic tool can be used to screen environmental toxins for their in vitro effects on the striatum
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