Establishment of a sandwich ELISA using commercial antibody for plasma or serum 3-nitrotyrosine (3NT). Elevation in inflammatory diseases and complementary between 3NT and myeloperoxidase

The Effect of a Six-Week Nordic Walking Training Cycle on Oxidative Damage of Macromolecules and Iron Metabolism in Older Patients with Multiple Myeloma in Remission-Randomized Clinical Trial

Multiple myeloma (MM) is an incurable hematologic malignancy originating from clonal plasma cell proliferation within the bone marrow, predominantly affecting older individuals. While anemia serves as a diagnostic criterion for MM, it often ameliorates upon achieving disease remission. Iron metabolism parameters have emerged as potential prognostic indicators in MM. Notably, physical exercise has been established to influence iron metabolism. This study aimed to assess alterations in serum iron, ferritin, and transferrin concentrations, as well as leukocyte gene expression, in MM patients undergoing a six-week cycle of Nordic walking training. Thirty patients divided into an exercise group (NW, n = 15, mean age 63.1 ± 8.4 years) and a control group (CG, n = 15, mean age: 63.5 ± 3.6 years) completed the study protocol. Blood samples were collected at baseline, after three and six weeks of training, and after nine weeks. Serum ferritin, transferrin, and iron concentrations were measured, along with the leukocyte expression of genes. Additionally, serum oxidative damage marker levels were determined. Following the Nordic walking training cycle, a declining trend in serum ferritin concentrations was observed. Intracellular mRNA levels of genes associated with iron metabolism were positively influenced by the training regimen, indicating the potential impact of this physical activity on gene expression and ferritin concentrations. Although positive trends were noted, extended training periods might be requisite for significant changes. To conclude, moderate-intensity exercise induces favorable shifts in the analyzed parameters among MM patients, potentially influencing disease progression. Consequently, Nordic walking training is a safe recommendation for MM patients, though sustained training beyond six weeks could be necessary for notable effects on iron metabolism factors.

A Simplified Approach for the Aqueous Synthesis of Luminescent CdSe/ZnS Core/Shell Quantum Dots and Their Applications in Ultrasensitive Determination of the Biomarker 3-Nitro-l-tyrosine

In contrast to the hot-injection organometallic routes, synthesizing stable and highly luminescent core/shell nanocrystals with encapsulation of biocompatible groups through an aqueous route is a long-standing challenge. In recent years, relatively high quantum efficiency and unique properties of core/shell nanostructured materials (quantum dots) have contributed toward enhancement in sensing capability. The present work reports a facile aqueous synthesis process of core/shell CdSe/ZnS quantum dots (QDs) with encapsulation of glutathione (GSH). The optimal conditions for the synthesis of the most stable particles were ascertained, and the different experimental analyses suggest that the stable core/shell QDs in question have good crystallinity with a size around 4.7 nm with a shell thickness of 0.7 nm and a photoluminescence quantum yield of about 35%. Further, it is demonstrated that the as-synthesized material has great potential in detecting as low as 0.28 nM 3-nitro-l-tyrosine (3-NT), an important marker for oxidative stress, the level of which in our body signals several chronically diseased conditions. The enthalpy-driven interactions of CdSe/ZnS-GSH QDs with 3-NT were characterized through steady-state and time-resolved luminescence spectroscopy and isothermal microcalorimetry. The devised method of probing 3-NT was further validated with human serum samples. Thus, the proposed strategy may provide a protocol for selective determination of 3-NT under different pathological conditions.

In Situ Synthesis of a Bismuth Vanadate/Molybdenum Disulfide Composite: An Electrochemical Tool for 3-Nitro-l-Tyrosine Analysis

The quantification of 3-nitro-l-tyrosine (NO₂-Tyr), an in vivo biomarker of nitrosative stress, is indispensable for the clinical intervention of various inflammatory disorders caused by nitrosative stress. By integrating the unique features of BiVO₄ and MoS₂ with matching bandgap energies, electrode materials with amplified response signals can be developed. In this regard, we introduce a hydrothermally synthesized bismuth vanadate sheathed molybdenum disulfide (MoS₂@BiVO₄) heterojunction as a highly sensitive electrode material for the determination of NO₂-Tyr. Excellent electrochemical behavior perceived for the MoS₂@BiVO₄ augments the performance of the sensor and allows the measurement of NO₂-Tyr in biological media without any time-consuming pretreatments. The synergistic interactions between BiVO₄ and MoS₂ heterojunctions contribute to low resistance charge transfer (R_ct = 159.13 Ω·cm²), a reduction potential E_pc = -0.58 V (vs Ag/AgCl), and a good response range (0.001-526.3 μM) with a lower limit of detection (0.94 nM) toward the detection of NO₂-Tyr. An improved active surface area, reduced charge recombination, and high analyte adsorption contribute to the high loading of the biomarker for improved selectivity (in the presence of 10 interfering compounds), operational stability (1000 s), and reproducibility (six various modified electrodes). The proposed sensor was successfully utilized for the real-time determination of NO₂-Tyr in water, urine, and saliva samples with good recovery values (±98.94-99.98%), ascertaining the reliability of the method. It is noteworthy that the electrochemical activity remains unaffected by other redox interferons, thus leading to targeted sensing applications.

A new three-dimensional zinc(II) metal-organic framework as a fluorescence sensor for sensing the biomarker 3-nitrotyrosine

3-Nitrotyrosine (3-NT), an oxidative stress biomarker, is closely associated with various diseases. Thus, rapid and sensitive detection of 3-NT is of great significance for preventing and treating diseases. Herein, we reported a new 3D zinc-based metal-organic framework (Zn-MOF) [Zn(L)(HBTC)] (L = (E)-4,4'-(ethene-1,2-diyl)bis[(N-pyridin-3-yl)benzamide], H₃BTC = 1,3,5-benzenetricarboxylic acid), which was structurally characterized by single crystal X-ray diffraction, IR, PXRD and TG. The Zn-MOF can be used as a highly efficient fluorescence sensing material to provide a direct and low-cost method for the rapid detection of 3-NT and shows high sensitivity with a K_SV value of 6.596 × 10⁴ M^-1, a rapid luminescence response within 24 s, excellent selectivity, high anti-interference ability and good recyclability. It is the first example of a MOF being used to directly detect 3-NT as a luminescence sensor to our knowledge. The sensing mechanism of the Zn-MOF towards 3-NT is discussed in detail, which provides a basis for the rational design of MOF sensing materials and their application in biomarker detection.

A highly selective and sensitive spectrofluorimetric method for the assessment of 3-nitrotyrosine in serum using (Eu(TTA)3Phen) photo probe

A simple, accurate and fast method was developed for the assessment of 3-nitrotyrosine as a biomarker for the early diagnosis of liver cirrhosis with minimal hepatic encephalopathy (MHE) using a (Eu(TTA)₃Phen) photo probe. 3-Nitrotyrosine can remarkably quench the luminescence intensity of the (Eu(TTA)₃Phen) complex in DMSO at pH = 9 and λ_em = 617 nm. The quenching of the luminescence intensity of (Eu(TTA)₃Phen) complex particularly the electrical emission band at λ_em = 617 nm is used for the assessment of 3-nitrotyrosine in different serum samples of patients with liver cirrhosis.

A simple, accurate and fast method was developed for the assessment of 3-nitrotyrosine as a biomarker for the early diagnosis of liver cirrhosis with minimal hepatic encephalopathy (MHE) using a (Eu(TTA)₃Phen) photo probe.

Improvement of the fluorescent sensing biomarker 3-nitrotyrosine for a new luminescent coordination polymer by size regulation

A new 3D luminescent coordination polymer (LCP) 1 was synthesized for detecting biomarker 3-nitrotyrosine. By adjusting the reaction conditions, Nano-LCP 1 was synthesized, which has a more lower detection limit compared with LCP 1.

Simultaneous LC-MS/MS-Based Quantification of Free 3-Nitro-l-tyrosine, 3-Chloro-l-tyrosine, and 3-Bromo-l-tyrosine in Plasma of Colorectal Cancer Patients during Early Postoperative Period

Quantification with satisfactory specificity and sensitivity of free 3-Nitro-l-tyrosine (3-NT), 3-Chloro-l-tyrosine (3-CT), and 3-Bromo-l-tyrosine (3-BT) in biological samples as potential inflammation, oxidative stress, and cancer biomarkers is analytically challenging. We aimed at developing a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method for their simultaneous analysis without an extract purification step by solid-phase extraction. Validation of the developed method yielded the following limits of detection (LOD) and quantification (LOQ) for 3-NT, 3-BT, and 3-CT: 0.030, 0.026, 0.030 ng/mL (LODs) and 0.100, 0.096, 0.098 ng/mL (LOQs). Coefficients of variation for all metabolites and tested concentrations were <10% and accuracy was within 95-105%. Method applicability was tested on colorectal cancer patients during the perioperative period. All metabolites were significantly higher in cancer patients than healthy controls. The 3-NT was significantly lower in advanced cancer and 3-BT showed a similar tendency. Dynamics of 3-BT in the early postoperative period were affected by type of surgery and presence of surgical site infections. In conclusion, a sensitive and specific LC-MS/MS method for simultaneous quantification of free 3-NT, 3-BT, and 3-CT in human plasma has been developed.

Development of a surface plasmon resonance immunosensor and ELISA for 3-nitrotyrosine in human urine

3-Nitrotyrosine (3-NT) is thought to be a relevant biomarker of nitrosative stress which is associated with many inflammatory and chronic diseases. It is necessary to develop confidential method for specific and sensitive 3-NT detection. In this paper, on the basis of anti-3-NT specific antibody, we developed a label-free indirect competitive surface plasmon resonance (SPR) immunosensor and ELISA for the detection of 3-NT. Under the optimized conditions, the SPR immunosensor can obtain a linear range of 0.17-6.07 μg/mL and a limit of detection (LOD) of 0.12 μg/mL while the ELISA can reach 0.33-9.94 μg/mL and a LOD of 0.24 μg/mL.The selectivity of 3-NT was also testified by six kinds of amino acid analogues. Besides, the developed SPR immunosensor was compared thoroughly with a conventional ELISA in spiked analysis of urine samples. Good recoveries and correlation between these two methods were observed (R² = 0.964). Therefore, it is concluded that the automated SPR platform can be applied to quantify 3-NT in biological samples with its sensitivity, accuracy, and real-timing.

A high-sensitivity electrochemiluminescence-based ELISA for the measurement of the oxidative stress biomarker, 3-nitrotyrosine, in human blood serum and cells

The generation of 3-nitrotyrosine, within proteins, is a post-translational modification resulting from oxidative or nitrative stress. It has been suggested that this modification could be used as a biomarker for inflammatory diseases. Despite the superiority of mass spectrometry-based determinations of nitrotyrosine, in a high-throughput clinical setting the measurement of nitrotyrosine by an enzyme-linked immunosorbent assay (ELISA) is likely to be more cost-effective. ELISAs offer an alternative means to detect nitrotyrosine, but many commercially available ELISAs are insufficiently sensitive to detect nitrotyrosine in healthy human serum. Here, we report the development, validation and clinical application of a novel electrochemiluminescence-based ELISA for nitrotyrosine which provides superior sensitivity (e.g. a 50-fold increase in sensitivity compared with one of the tested commercial colorimetric ELISAs). This nitrotyrosine ELISA has the following characteristics: a lower limit of quantitation of 0.04 nM nitrated albumin equivalents; intra- and inter-assay coefficients of variation of 6.5% and 11.3%, respectively; a mean recovery of 106 ± 3% and a mean linearity of 0.998 ± 0.001. Far higher nitration levels were measured in normal human blood cell populations when compared to plasma. Mass spectrometry was used to validate the new ELISA method. The analysis of the same set of chemically modified albumin samples using the ELISA method and mass spectrometry showed good agreement for the relative levels of nitration present in each sample. The assay was applied to serum samples from patients undergoing elective surgery which induces the human inflammatory response. Matched samples were collected before and one day after surgery. An increase in nitration was detected following surgery (median (IQR): 0.59 (0.00-1.34) and 0.97 (0.00-1.70) nitrotyrosine (fmol of nitrated albumin equivalents/mg protein) for pre- and post-surgery respectively. The reported assay is suitable for nitrotyrosine determination in patient serum samples, and may also be applicable as a means to determine oxidative stress in primary and cultured cell populations.

Nitration of tyrosine and its effect on DNA hybridization

One major marker of nitrosative stress is the formation of 3-Nitrotyrosine (3-NT) from Tyrosine (Tyr) by adding a nitro group (-NO₂) with nitrating agents. Nitration of Tyr often causes loss of protein activity and is linked with many diseases. In this article, we detect 3-NT and discriminate it from Tyr with Differential Pulse Voltammetry (DPV) as it is a very important biomarker. We first examined redox (oxidation/reduction) properties and stability of 3-NT in detail. Second, we provided the Tyr and 3-NT discrimination with DPV and compared with the chromatography. We then explored the interaction of 3-NT and DNA oligonucleotides. Our findings demonstrate that 3-NT can be used as a new electrochemical indicator, which is able to detect hybridization of probe (single stranded DNA-ssDNA) and hybrid (double stranded DNA-dsDNA) both via 3-NT reduction and guanine oxidation signal changes at the same time. The signal differences enabled us to distinguish ssDNA and dsDNA without using a label or a tag. Moreover, we achieved to detect hybridization of DNA by using the reduction signal of 3-NT obtained at -0.4V vs. Ag/AgCl. More importantly, we observed the changes of the reduction signals of 3-NT after the interaction of probe and hybrid sequences. We showed that 3-NT signal decreases more with hybrid than the probe. Our platform, for the first time, demonstrates the detection of hybridization both guanine oxidation and indicator reduction signal changes at the same time. Moreover, we, for the first time, demonstrated the interaction between 3-NT and DNA.

3-Nitrotyrosine quantification methods: Current concepts and future challenges

BACKGROUND

Measurement of 3-nitrotyrosine (3-NT) in biological samples can be used as a biomarker of nitrosative stress, since it is very stable and suitable for analysis. Increased 3-NT levels in biological samples have been associated with several physiological and pathological conditions. Different methods have been described for the detection and quantification of this molecule, such as (i) immunological methods; (ii) liquid chromatography, namely high-pressure liquid chromatography (HPLC)-based methods that use ultraviolet-visible (UV/VIS) absorption, electrochemical (ECD) and diode array (DAD) detection, liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS); (iii) gas chromatography, such as gas chromatography-mass spectrometry (GC-MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS).

METHODS

A literature review on nitrosative stress, protein nitration, as well as 3-NT quantification methods was carried out.

RESULTS

This review covers the different methods for analysis of 3-NT that have been developed during the last years as well as the latest advances in this field. Overall, all methods present positive and negative aspects, although it is clear that chromatography-based methods present good sensitivity and specificity. Regarding this, GC-based methods exhibit the highest sensibility in the quantification of 3-NT, although it requires a prior time consuming derivatization step. Conversely, HPLC does not require such derivatization step, despite being not as accurate as GC.

CONCLUSION

It becomes clear that all the methods described during this literature review, although accurate for 3-NT quantification, need to be improved regarding both sensitivity and specificity. Moreover, optimization of the protocols that have been described is clearly needed.

Astragaloside IV improves the isoproterenol-induced vascular dysfunction via attenuating eNOS uncoupling-mediated oxidative stress and inhibiting ROS-NF-κB pathways

OBJECTIVE

Oxidative stress and inflammation are regarded as two important triggers of endothelial dysfunction and play pivotal role in progression of vascular damage associated with cardiac hypertrophy. Our previous studies demonstrated that astragaloside IV (AsIV) could protect against cardiac hypertrophy in rats induced by isoproterenol (Iso), but its effects on the aorta are not known. In present study, we aimed to assess the effects of AsIV on Isoinduced vascular dysfunction.

METHODS

Sprague-Dawley (SD) rats were treated with Iso (10mg/kg/d) alone or in combination with AsIV (50mg/kg/d).

RESULTS

Compared with Isotreated alone, AsIV significantly reduced the ratios of heart weight/body weight and left ventricular weight/body weight. AsIV ameliorated the increased vasoconstriction response to phenylephrine induced by Iso and suppressed superoxide anion generation in rat aorta, increased endothelial nitric oxide synthase (eNOS) dimer/monomer ratio and its critical cofactor tetrahydrobiopterin (BH4) content in aorta as well as the NO production in the serum, reduced the plasmatic peroxynitrite (ONOO-). Moreover, in contrast with Isotreatment alone, AsIV decreased the ratio of nuclear-to-cytosolic protein expression of the NF-κB p65 subunit while enhanced its inhibited protein expression of IκB-α, down-regulated mRNA expression of IL-1β, IL-6 and TNF-α of the aorta.

CONCLUSIONS

The present study suggested that AsIV protects against Isoinduced vascular dysfunction probably via attenuating eNOS uncoupling-mediated oxidative stress and inhibiting ROS-NF-κB pathways.

Evaluation of anticoagulants for serologic assays of cholera vaccination

Blood collected with an anticoagulant is beneficial for simultaneous evaluation of immune cells and humoral components such as antibodies. However, it is critical that the anticoagulant does not affect quantitative and qualitative analyses of antibodies. In the present study, we examined the potential interference of the widely used anticoagulants heparin, EDTA, and acid citrate dextrose (ACD) on vibriocidal antibody activities and Vibrio cholerae lipopolysaccharide (LPS)-specific IgG, IgM, and IgA levels in the plasma and sera obtained from cholera patients or vaccinees. Serum vibriocidal antibody titer was inhibited in the presence of EDTA or ACD but not in the presence of heparin. Moreover, 100% (8/8) of the vibriocidal antibody titers of plasma samples obtained from the vaccinees in tubes containing heparin were identical to the titers of matched sera when compared with 37.5% (3/8) and 50% (4/8) of the plasma samples prepared with EDTA and ACD, respectively. Among LPS-specific Igs, the Pearson correlation coefficient (r) for IgA in serum and plasma was low (r = 0.716), and the coefficients for IgG and IgM were relatively high (r = 0.997 and r = 0.945, respectively) in heparinized plasma samples compared with the coefficient for IgG and IgM of EDTA- and ACD-treated plasma. Our results suggest that heparin is an appropriate anticoagulant for the collection of blood when measuring vibriocidal activities and antibody levels in plasma samples.

Rapid and sensitive determination of protein-nitrotyrosine by ELISA: Application to human plasma

3-Nitrotyrosine (3NT) is known as an important indicator of nitrosative stress and has been linked to various diseases. Our aim was to develop an indirect ELISA (enzyme-linked immunosorbent assay) method suitable for the detection of protein-bound 3NT in clinical plasma and serum samples. Nitrated protein standards and reduced protein standards were prepared. Limit of detection was determined for standards; recovery and reproducibility were determined for human plasma samples. The limit of detection for this method is 1.82±0.56 pmol/mg protein. Mean recovery of standards was 95%. 3NT concentration in plasma samples of obese and normal weight subjects was determined to be between 2 pmol/mg and 19 pmol/mg. No time-consuming sample preparation or expensive laboratory equipment is required, and applied antibodies are commercially available. Sensitivity, rapid analysis time, possibilities of high throughput applications and small sample volumes make this ELISA attractive for use in clinical laboratories.

Quantification of protein modification by oxidants

Proteins are major targets for oxidative damage due to their abundance and rapid rates of reaction with a wide range of radicals and excited state species, such as singlet oxygen. Exposure of proteins to these oxidants results in loss of the parent amino acid residue, formation of unstable intermediates, and the generation of stable products. Each of these events can be used, to a greater or lesser extent, to quantify damage to proteins. In this review the advantages and disadvantages of a number of these approaches are discussed, with an emphasis on methods that yield absolute quantitative data on the extent of protein modification. Detailed methods sheets are provided for many of these techniques.

Link between obstructive sleep apnea and increased bone resorption in men

The bone metabolic abnormalities in patients with obstructive sleep apnea (OSA) were examined. Severity-dependent increases in the serum/urinary levels of bone resorption markers and their attenuation following continuous positive airway pressure therapy in subjects with OSA provide the first evidence of a link between OSA and abnormal bone metabolism.

INTRODUCTION

Hypoxia, microinflammation and oxidative stress, well-known pathophysiological features of obstructive sleep apnea (OSA), are also known to affect bone metabolism. We examined the bone metabolic abnormalities in patients with OSA and also the effects of continuous positive airway pressure (CPAP) therapy on these abnormalities.

METHODS

A cross-sectional and prospective study was conducted in 50 consecutive male subjects visiting a sleep clinic and 15 age-matched control subjects without OSA. Plasma concentrations of IL-1beta, IL-6, TNF-alfa, 3-nitrotyrosine, osteocalcin, bone-specific alkaline phosphatase (BAP), and urinary concentrations of cross-linked C-terminal telopeptide of type I collagen (CTX) were examined before and after 3 months' CPAP in subjects with OSA.

RESULTS

The plasma levels of the cytokines as well as the urinary CTX levels were higher in subjects with severe OSA than in those with mild OSA or control subjects. Significant decrease of the urinary excretion of CTX (before: 211+/-107 vs. after: 128+/-59 microg/mmol/creatinine; p<0.01) as well as of the plasma levels of the cytokines was observed following 3 months' CPAP.

CONCLUSIONS

Severity-dependent increases in the serum/urinary levels of bone resorption markers and their reversal following CPAP in subjects with OSA provide the first evidence of a link between OSA and abnormal bone metabolism.

A panel of multiple markers associated with chronic systemic inflammation and the risk of atherogenesis is detectable in asthma and chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease (COPD) are both lung diseases involving chronic inflammation of the airway. The injury is reversible in asthma whereas it is mostly irreversible in COPD. Both patients of asthma and COPD are known at risk for cardiovascular disease (CVD) and type 2 diabetes (T2DM), nephropathy, and cancer. We measured multiple risk markers for atherogenesis in 55 patients with asthma and 62 patients with COPD. We wanted to know whether risk markers for atherogenesis corresponding to sequence of events of chronic inflammation were also detectable in the airway inflammatory diseases. Elevation of almost all markers involving inflammation of the endothelial cells in the coronary artery were detectable in asthma and COPD involving the inflammation of the epithelial cell lining of the airway. Both the level and % elevation of all markers were found mostly higher in COPD, the more severe form of the lung disease. We believe that these markers are useful for predicting risk of developing clinical complications such as CVD.

Cosmetic liposuction causes only transient elevation of acute inflammatory response and does not advance to oxidative and nitrosative stress

Cosmetic liposuction is a surgical procedure performed on normal nonobese subjects to remove unwanted fat. We are interested to know whether the impact of acute inflammatory response induced by liposuction differs from that of chronic inflammation and whether acute inflammatory response will also advance further and cause oxidative and nitrosative stress leading to various clinical complications. In our investigation we monitored 15 nonobese women prior to liposuction, and one day and one month after the surgery with multiple markers associated with chronic inflammation and oxidative stress. Our results indicate that liposuction causes only a transient elevation of acute inflammatory markers such as interleukin-6 (IL-6), high sensitive C-reactive protein (hCRP), and serum amyloid A (SAA), and a transient decrease of nitric oxide (NO). Apparently the impact of liposuction for normal subjects did not advance beyond acute inflammatory response; there was little change in the levels of markers corresponding to downstream events of chronic systemic inflammation such as adhesion molecules, urinary microalbumin (uMA), homocysteine (Hcy), uric acid (UA), and markers of oxidative stress, including urinary 8-hydroxydeoxyguanosine (8-OhdG) and 3-nitrotyrosine (3NT). It appears that the acute inflammatory response of cosmetic liposuction does not lead to impaired renal function and oxidative and nitrosative damage, which are frequently associated with chronic inflammation.

Multiple risk markers for atherogenesis associated with chronic inflammation are detectable in patients with renal stones

Patients with renal stones are known to be at risk of clinical complications such as cardiovascular disease (CVD), nephropathy, and cancer. Recently, it has been realized that almost all risk markers for CVD, nephropathy, etc. are all markers associated with the sequence of reactions of chronic inflammation. It has been reported that chronic inflammation is involved not only in the pathogenesis of nephrolithiasis but also contributes to the development of clinical complications in this condition; therefore, we decided to find out whether these multiple markers are detectable in patients with renal stones so that they can be used to predict the risk of clinical complications in these patients. There were 33 patients with nephrolithiasis included in this study. We found that almost all major markers of chronic inflammation were elevated in patients with renal stones, including proinflammatory cytokine, acute inflammation markers, adhesion molecules, urinary microalbumin (uMA), myeloperoxidase (MPO), 8-hydroxydeoxyguanosine (8-OHdG), 3-nitrotyrosine (3NT), and monocyte chemoattractant protein. It appears that it is possible to assess the risk of clinical complications by monitoring these markers in patients with renal stones.

Assay of 3-nitrotyrosine in tissues and body fluids by liquid chromatography with tandem mass spectrometric detection

3-Nitrotyrosine (3-NT) is a marker of protein nitration in physiological systems. It is present as 3-nitrotyrosine residues in proteins of tissue, extracellular matrix, plasma, and other body fluids and food. It is also present in body fluids and some beverages as free nitrotyrosine and is excreted in urine with the major urinary metabolite 3-nitro-4-hydroxyphenylacetic acid. Quantitation of 3-nitrotyrosine requires tandem mass spectrometry for specific detection. The method developed to determine 3-nitrotyrosine (along with protein glycation and oxidation adducts in a quantitative screening assay) by liquid chromatography with tandem mass spectrometric detection is described. The 3-NT residue contents of plasma protein, hemoglobin, lipoproteins, and cerebrospinal fluid protein and the concentrations of free 3-nitrotyrosine in plasma, urine, and cerebrospinal fluid are given. Changes of 3-nitrotyrosine residue and free 3-nitrotyrosine in diabetes, cirrhosis, acute and chronic renal failure, and neurological disorders, including Alzheimer's disease, are presented and compared with independent estimates.