Novel liquid chromatography method based on linear weighted regression for the fast determination of isoprostane isomers in plasma samples using sensitive tandem mass spectrometry detection

Cellular senescence mediates hexavalent chromium-associated lung function decline: Insights from a structural equation Model

There is sufficient evidence suggesting that exposure to hexavalent chromium [Cr(VI)] can cause a decline in lung function and the onset of lung diseases. However, no studies have yet explored the underlying mechanisms of these effects from various perspectives such as systemic inflammation, oxidative stress, and cellular senescence, simultaneously. This cross-sectional study was conducted among 304 workers engaged in chromate production and processing in China. Urine was used for detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-iso-prostaglandin F2α (8-iso-PGF2α), while RNA and DNA extraction from peripheral blood cells was used for detection of mRNA, telomere length, and ribosomal DNA copy numbers (rDNA CNs). A 2.7-fold elevation in blood chromate (Cr) corresponded to a 7.86% (95% CI: 2.57%, 13.42%) rise in urinary 8-OHdG and a 4.14% (0.02%, 8.42%) increase in urinary 8-iso-PGF2α, indicating that exposure to chromates can cause oxidative stress. Furthermore, strong correlations emerged between blood Cr concentration and mRNA levels of P16, P21, TP53, and P15 in the cellular senescence pathway. Simultaneously, a 2.7-fold elevation in blood Cr associated with a -5.47% (-8.72%, -2.1%) change in telomere length, while rDNA CNs (5S, 5.8S, 18S, and 28S) changed by -3.91% (-7.99%, 0.34%), -9.4% (-15.73%, -2.6%), -8.06% (-14.01%, -1.69%), and -5.86% (-10.67%, -0.78%), respectively. Structural equation model highlighted that cellular senescence exerted significant indirect effects on Cr(VI)-associated lung function decline, with a mediation proportion of 23.3%. This study provided data supporting for 8-iso-PGF2α, telomere length, and rDNA CNs as novel biomarkers of chromate exposure, emphasizing the significant role of cellular senescence in the mechanism underlying chromate-induced lung function decline.

Analysis of 19 urinary biomarkers of oxidative stress, nitrative stress, metabolic disorders, and inflammation using liquid chromatography–tandem mass spectrometry

Environmental chemical exposures have been associated with cancer, diabetes, hormonal and immunological disorders, and cardiovascular diseases. Some direct effects of chemical exposure that are precursors to adverse health outcomes, including oxidative stress, nitrative stress, hormonal imbalance, neutrophilia, and eosinophilia, can be assessed through the analysis of biomarkers in urine. In this study, we describe a novel methodology for the determination of 19 biomarkers of health effects: malondialdehyde (MDA), 8-isoprostaglandin-F_2α (8-PGF_2α), 11-β-prostaglandin-F_2α (11-PGF_2α), 15-prostaglandin-F_2α (15-PGF_2α), 8-iso-15-prostaglandin-F_2α (8,15-PGF_2α), 8-hydroxy-2′-deoxyguanosine (8-OHdG), 8-hydroxyguanosine (8-HdG), 8-hydroxyguanine (8-HG), dityrosine (diY), allantoin (Alla), and two metabolic products of 4-hydroxynonenal (HNE), namely 4-hydroxy-2-nonenal glutathione (HNE-GSH) and 4-hydroxy-2-nonenal mercapturic acid (HNE-MA) (in total, 12 oxidative stress biomarkers, OSBs); 8-nitroguanosine (8-NdG), 8-nitroguanine (8-NG), and 3-nitrotyrosine (NY) (3 nitrative stress biomarkers, NSBs); chlorotyrosine (CY) and bromotyrosine (BY) (2 inflammatory biomarkers); and the advanced glycation end-products (AGEs) N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) (2 metabolic disorder biomarkers). Since these biomarkers are trigged by a variety of environmental insults and produced by different biomolecular pathways, their selective and sensitive determination in urine would help broadly elucidate the pathogenesis of diseases mediated by environmental factors.

Single-Drop Analysis of Epinephrine and Uric Acid on a Screen-Printed Carbon Electrode

This work demonstrates the analysis of epinephrine (EP) and uric acid (UA) in a single drop (the volume of the test solution was only 50 µL) using a screen-printed carbon electrode (SPCE) sensor and square-wave voltammetry (SWV). The limit of detection, limit of quantification, linearity, accuracy, precision, and robustness were validated. The normality of the experimental data was tested and confirmed for both methods. Heteroscedasticity was checked by residual analysis followed by a statistical F-test. The latter was confirmed for both analytes. The low relative standard deviations (RSD) at all calibration points and repetitive slopes justified the use of a calibration curve; therefore, the standard addition methodology was avoided (the latter is common in electroanalysis, but time-consuming). Since the conditions for using an ordinary least squares (OLS) regression were not met, weighted linear regression (WLR) was used to improve the accuracy of the analytical results at low concentrations of the analytes. In this manner, the best weighted model was determined and used for the quantification. A comparison was made between the OLS and WLR methods to show the necessity of using the WLR method for EP and UA analysis. The newly developed and validated methods were also shown to be effective in the analysis of real samples. The content of EP in an EP auto-injector and UA in human urine was tested by employing the best weighted model. For EP and UA, the accuracy in terms of the average recovery value was 101.01% and 94.35%, and precision in terms of RSD was 5.65% and 2.75%, respectively. A new analytical methodology is presented that uses a low volume (a single drop), and it offers the advantage of electroanalysis for on-site analysis, where conventional chromatographic techniques cannot be easily employed. Furthermore, the developed technique has additional advantages in terms of speed, cost, and miniaturization.

Isoprostanes in Veterinary Medicine: Beyond a Biomarker

Oxidative stress has been associated with many pathologies, in both human and animal medicine. Damage to tissue components such as lipids is a defining feature of oxidative stress and can lead to the generation of many oxidized products, including isoprostanes (IsoP). First recognized in the early 1990s, IsoP are formed in numerous biological fluids and tissues, chemically stable, and easily measured by noninvasive means. Additionally, IsoP are highly specific indicators of lipid peroxidation and thereby are regarded as excellent biomarkers of oxidative stress. Although there have been many advancements in the detection and use of IsoP as a biomarker, there is still a paucity of knowledge regarding the biological activity of these molecules and their potential roles in pathology of oxidative stress. Furthermore, the use of IsoP has been limited in veterinary species thus far and represents an avenue of opportunity for clinical applications in veterinary practice. Examples of clinical applications of IsoP in veterinary medicine include use as a novel biomarker to guide treatment recommendations or as a target to mitigate inflammatory processes. This review will discuss the history, biosynthesis, measurement, use as a biomarker, and biological action of IsoP, particularly in the context of veterinary medicine.

Recent progress in the LC-MS/MS analysis of oxidative stress biomarkers

The presence of a dynamic and balanced equilibrium between the production of reactive oxygen (ROS) and nitrogen (RNS) species and the in-house antioxidant defense mechanisms is characteristic for a healthy body. During oxidative stress (OS), this balance is switched to increased production of ROS and RNS, exceeding the capacity of physiological antioxidant systems. This can cause damage to biological molecules, leading to loss of function and even cell death. Nowadays, there is increasing scientific and clinical interest in OS and the associated parameters to measure the degree of OS in biofluids. An increasing number of reports using LC-MS/MS methods for the analysis of OS biomarkers can be found. Since bioanalysis is usually complicated by matrix effects, various types of cleanup procedures are used to effectively separate the biomarkers from the matrix. This is an essential part of the analysis to prepare a reproducible and homogenous solution suitable for injection onto the column. The present review gives a summary of the chromatographic methods used for the determination of OS biomarkers in both urine and plasma, serum, and whole blood samples. The first part mainly describes the biological background of the different OS biomarkers, while the second part reports examples of chromatographic methods for the analysis of different metabolites connected with OS in biofluids, covering a period from 2015 till early 2020. The selected examples mainly include LC-MS/MS methods for isoprostanes, oxidized proteins, oxidized lipoproteins, and DNA/RNA biomarkers. The last part explains the clinical relevance of this review.

Toxicological analyses: analytical method validation for prevention or diagnosis

The need for reliable results in Toxicological Analysis is recognized and required worldwide. The analytical validation ensures that a method will provide trustworthy information about a particular sample when applied in accordance with a predefined protocol, being able to determine a specific analyte at a distinct concentration range for a well-defined purpose. The driving force for developing method validation for bioanalytical projects comes from the regulatory agencies. Thus, the approach of this work is to present theoretical and practical aspects of method validation based on the analysis objective, whether for prevention or diagnosis. Although various legislative bodies accept differing interpretations of requirements for validation, the process for applying validation criteria should be adaptable for each scientific intent or analytical purpose.

Influence of Diosmin Treatment on the Level of Oxidative Stress Markers in Patients with Chronic Venous Insufficiency

Oxidative stress plays an important role in the pathophysiology of many human disorders, while antioxidants prevent the development of various adverse symptoms. Diosmin is a natural flavonoid applied in vascular system disorders, especially in chronic venous insufficiency (CVI), and it plays a significant part in the alleviation of CVI symptoms. Due to antioxidant activity, it also has the ability to scavenge the oxygen free radicals and hence decreases the level of oxidative stress biomarkers, such as prostaglandins and their precursors—isoprostanes. In the study, the influence of diosmin treatment on the level of isoprostanes in plasma samples of patients suffering from CVI was examined. The qualitative analysis was performed using high-performance liquid chromatography with spectrometry detection (LC-MS). The statistically significant decrease of isoprostane content after 3 months of treatment was observed within the studied group; however, the most significant changes were observed in patients who smoke.

Simultaneous Analysis of Seven Biomarkers of Oxidative Damage to Lipids, Proteins, and DNA in Urine

The determination of oxidative stress biomarkers (OSBs) is useful for the assessment of health status and progress of diseases in humans. Whereas previous methods for the determination of OSBs in urine were focused on a single marker, in this study, we present a method for simultaneous determination of biomarkers of oxidative damage to lipids, proteins, and DNA. 2,4-Dinitrophenylhydrazine (DNPH) derivatization followed by solid phase extraction (SPE) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) allowed the determination of 8-hydroxy-2'-deoxyguanosine (8-OHdG), o- o'-dityrosine (diY), malondialdehyde (MDA), and four F₂-isoprostane isomers: 8-iso-prostaglandinF_2α (8-PGF_2α), 11β-prostaglandinF_2α (11-PGF_2α), 15( R)-prostaglandinF_2α (15-PGF_2α), and 8-iso,15( R)-prostaglandinF_2α (8,15-PGF_2α) in urine. Derivatization with DNPH and SPE was optimized to yield greater sensitivity and selectivity for the analysis of target chemicals. The limits of detection of target analytes in urine were below 30 pg mL^-1. The assay intra- and interday variability was below 16% of the relative standard deviation, and the recoveries of target chemicals spiked into synthetic urine were near 100%. The method was applied to the analysis of 21 real urine samples, and the analytes were found at a detection frequency of 85% for 8-PGF_2α and 15-PGF_2α, 71% for 11-PGF_2α, 81% for 8,15-PGF_2α, and 100% for diY, 8-OHdG, and MDA. This method offers simultaneous determination of multiple OSBs of different molecular origin in urine samples selectively with high accuracy and precision.

Development of an LC-ESI(-)-MS/MS method for the simultaneous quantification of 35 isoprostanes and isofurans derived from the major n3- and n6-PUFAs

Misregulation of oxidative and antioxidative processes in the organism - oxidative stress - contributes to the pathogenesis of different diseases, e.g. inflammatory or neurodegenerative diseases. Oxidative stress leads to autoxidation of polyunsaturated fatty acids giving rise to prostaglandin-like isoprostanes (IsoP) and isofurans (IsoF). On the one hand they could serve as biomarker of oxidative stress and on the other hand may act as lipid mediators, similarly as the enzymatically formed oxylipins. In the present paper we describe the development of an LC-ESI(-)-MS/MS method allowing the parallel quantification of 27 IsoP and 8 IsoF derived from 6 different PUFA (ALA, ARA, EPA, AdA, n6-DPA, DHA) within 12 min. The chromatographic separation was carried out on an RP-C18 column (2.1 × 150 mm, 1.8 μm) yielding narrow peaks with an average width at half maximum of 3.3-4.2 s. Detection was carried out on a triple quadrupole mass spectrometer operating in selected reaction monitoring mode allowing the selective detection of regioisomers. The limit of detection ranged between 0.1 and 1 nM allowing in combination with solid phase extraction the detection of IsoP and IsoF at subnanomolar concentrations in biological samples. The method was validated for human plasma showing high accuracy and precision. Application of the approach on the investigation of oxidative stress in cultured cells indicated a distinct pattern of IsoP and IsoF in response to reactive oxygen species which warrants further investigation. The described method is not only the most comprehensive approach for the simultaneous quantification of IsoP and IsoF, but it was also integrated in a targeted metabolomics method (Ostermann et al. (2015) Anal Bioanal Chem) allowing the quantification of in total 164 oxylipins formed enzymatically and non-enzymatically within 30.5 min.

Application of gas chromatography-tandem mass spectrometry for the determination of amphetamine-type stimulants in blood and urine

Amphetamine, methamphetamine, phentermine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxy-N-ethylamphetamine (MDEA) are the most popular amphetamine-type stimulants. The use of these substances is a serious societal problem worldwide. In this study, a method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) with simple and rapid liquid-liquid extraction (LLE) and derivatization was developed and validated for the simultaneous determination of the six aforementioned amphetamine derivatives in blood and urine. The detection of all compounds was based on multiple reaction monitoring (MRM) transitions. The most important advantage of the method is the minimal sample volume (as low as 200μL) required for the extraction procedure. The validation parameters, i.e., the recovery (90.5-104%), inter-day accuracy (94.2-109.1%) and precision (0.5-5.8%), showed the repeatability and sensitivity of the method for both matrices and indicated that the proposed procedure fulfils internationally established acceptance criteria for bioanalytical methods The procedure was successfully applied to the analysis of real blood and urine samples examined in 22 forensic toxicological cases. To the best of our knowledge, this is the first work presenting the use of GC-MS/MS for the determination of amphetamine-type stimulants in blood and urine. In view of the low limits of detection (0.09-0.81ng/mL), limits of quantification (0.26-2.4ng/mL), and high selectivity, the procedure can be applied for drug monitoring in both fatal and non-fatal intoxication cases in routine toxicology analysis.