Abstract
F2-isoprostanes (F2-IsoPs) are a gold marker of lipid peroxidation in vivo, whereas F4-neuroprostanes (F4-NPs) measured in cerebrospinal fluid (CSF) or brain tissue selectively indicate neuronal oxidative damage. Gas chromatography/negative-ion chemical-ionization mass spectrometry (GC/NICI-MS) is the most sensitive and robust method for quantifying these compounds, which is essential for CSF samples because abundance of these compounds in CSF is very low. The present study revealed potential interferences on the analysis of F2-IsoPs and F4-NPs in CSF by GC/NICI-MS due to the use of improper analytical methods that have been employed in the literature. First, simultaneous quantification of F2-IsoPs and F4-NPs in CSF samples processed for F4-NPs analysis could cause poor chromatographic separation and falsely higher F2-IsoPs values for CSF samples with high levels of F2-IsoPs and F4-NPs. Second, retention of unknown substances in GC columns from CSF samples during F4-NPs analysis and from plasma samples during F2-IsoPs analysis might interfere with F4-NPs analysis of subsequent runs, which could be solved by holding columns at a high temperature for a period of time after data acquisition. Therefore, these special issues should be taken into consideration when performing analysis of F2-IsoPs and F4-NPs in CSF to avoid misleading results.
Highlights
Reliable assessment of oxidative stress in vivo has been important for investigating the roles of oxidative stress in the pathogenesis or progression of diseases [1]
These cerebrospinal fluid (CSF) samples were pooled from specimen collected during our previous study on aneurysmal subarachnoid hemorrhage (aSAH) that have been published [13, 17], in which we showed that CSF samples from aSAH had much higher levels of F4-NPs than that from non-aSAH controls including those with normal pressure hydrocephalus [13]
To address the question that whether simultaneous analysis of F2-IsoPs and F4-NPs for the same CSF sample processed for F4-NPs analysis was appropriate, we first analyzed F2-IsoPs and F4NPs simultaneously for L-CSF, M-CSF, and H-CSF samples processed for F4-NPs analysis from three independent replicates of each sample
Summary
Reliable assessment of oxidative stress in vivo has been important for investigating the roles of oxidative stress in the pathogenesis or progression of diseases [1]. F2-isoprostanes (F2-IsoPs) are prostaglandin (PG)-like compounds derived from lipid peroxidation of arachidonic acid (AA, C20:4 ω6), which is abundant in all kinds of cells, initiated by free radicals independent of the cyclooxygenase pathway. They are initially formed as esterified form on phospholipids and can be released into surrounding body fluids to become free form via the action of enzymes with the phospholipaselike activities [2,3,4,5]. Measurement of F4NPs in CSF or brain tissue has been considered as a more selective marker for neuronal oxidative damage because DHA is enriched in neurons [10]
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