Simultaneous determination of indole metabolites of tryptophan in rat feces by chemical labeling assisted liquid chromatography-tandem mass spectrometry

Glycosylase Pretreatment with Chemical Labeling-Assisted HPLC-MS/MS: An Ultrasensitive and Reliable Strategy for Quantification of 8-Oxo-7,8-dihydro-2'-deoxyguanosine in Genomic DNA

8-Oxo-7,8-dihydro-2'-deoxyguanosine (dOG), the dominant oxidative product of 2'-deoxyguanosine (dG) under high levels of reactive oxygen species, usually serves as a biomarker for oxidative stress and a risk assessment factor for various diseases. Due to the extremely low abundance of dOG and the susceptibility of dOG detection to the interference of spurious oxidation, research on related biological processes is limited by insufficient sensitivity and specificity. In this work, an ultrasensitive and reliable approach for genome-wide dOG quantification was developed through chemical labeling-assisted high-performance liquid chromatography-tandem mass spectrometry with the introduction of glycosylase pretreatment. Upon derivatization by a novel labeling reagent rhodamine B ethylenediamine, the detection sensitivity of dOG was enhanced by 100-fold, and the detection limit was as low as 25 amol, which was superior to those of reported mass spectrometry-based methods. Potassium ferricyanide, as a single-electron oxidant, was shown to possess strong selectivity for dOG versus dG, improving the labeling specificity and reducing the interference from dG. The spurious oxidation during sample pretreatment was systematically explored and minimized, and a control assay of glycosylase pretreatment was proposed to further improve the quantitative accuracy of dOG. Precise quantification of endogenous dOG in different cells was achieved with less than 500 ng of genomic DNA. This method was successfully applied to the assessment of the overall level of oxidative damage under the treatment of glycosylase inhibitors, potentially contributing to the exploration of the complex role of dOG in physiological status and disease phenotype.

Bromine signature coded derivatization LC-MS for specific profiling of carboxyl or carbonyl-containing metabolites in Mycoplasma pneumoniae infection

Carboxyl or carbonyl-containing metabolites (CoCCMs) are widely distributed in biological samples. Global profiling of CoCCMs is essential for ascertaining specific functions of metabolites and their potential physiological roles in biogenic activities. However, simultaneous determination of these compounds is hampered by poor ionization efficiency, vast polarity differences, wide discrepancy of concentration ranges. Herein, a novel bromine isotope derivatization reagent 5-bromo-2- hydrazinopyridine was employed for CoCCMs profiling by liquid chromatography-mass spectrometry (LC-MS). This method enabled rapid derivatization of 44 CoCCMs under mild conditions. Enhanced separation efficiencies, detection sensitivities, and distinctive MS fragmentation characteristics were observed. Furthermore, this method was demonstrated to be efficient in revealing metabolic alternations, and abnormal serum levels of 6-keto-PGF1α, 12(S)-HHTrE, 15(S)-HEPE and N-acetyl tryptophan were disclosed for the first time in Mycoplasma pneumoniae (MP) infectious patients. Finally, based on the distinctive 2 Da differences of molecular ion peak pairs with almost 1:1 intensity ratio originated from 79Br and 81Br isotopes, an MS-DIAL and Python assisted MS1 isotope screening-MS2 fragments characterization combination strategy was developed for rapid screening, classification, and identification of detected CoCCMs. A total of 1069 CoCCMs were detected, of which 198 CoCCMs were identified in untargeted analysis. Statistical analysis revealed altered metabolic pathways, while glutamic acid, oxoglutaric acid, succinic acid, pyruvic acid, glyceric acid, and glycine were selected as potential biomarkers of MP infection. This bromine signature coded derivatization-LC-MS approach was proved to be a valuable tool for global probing of CoCCMs in biological samples with high sensitivity and broad coverage.

Chemical Isotope Labeling and Dual-Filtering Strategy for Comprehensive Profiling of Urinary Glucuronide Conjugates

Glucuronidation, a crucial process in phase II metabolism, plays a vital role in the detoxification and elimination of endogenous substances and xenobiotics. A comprehensive and confident profiling of glucuronate-conjugated metabolites is imperative to understanding their roles in physiological and pathological processes. In this study, a chemical isotope labeling and dual-filtering strategy was developed for global profiling of glucuronide metabolites in biological samples. N,N-Dimethyl ethylenediamine (DMED-d0) and its deuterated counterpart DMED-d6 were used to label carboxylic acids through an amidation reaction. First, carboxyl-containing compounds were extracted based on a characteristic mass difference (Δm/z, 6.037 Da) observed in MS between light- and heavy-labeled metabolites (filter I). Subsequently, within the pool of carboxyl-containing compounds, glucuronides were identified using two pairs of diagnostic ions (m/z 247.1294/253.1665 and 229.1188/235.1559 for DMED-d0/DMED-d6-labeled glucuronides) originating from the fragmentation of the derivatized glucuronic acid group in MS/MS (filter II). Compared with non-derivatization, DEMD labeling significantly enhanced the detection sensitivity of glucuronides, as evidenced by a 3- to 55-fold decrease in limits of detection for representative standards. The strategy was applied to profiling glucuronide metabolites in urine samples from colorectal cancer (CRC) patients. A total of 685 features were screened as potential glucuronides, among which 181 were annotated, mainly including glucuronides derived from lipids, organic oxygen, and phenylpropanoids. Enzymatic biosynthesis was employed to accurately identify unknown glucuronides without standards, demonstrating the reliability of the dual-filtering strategy. Our strategy exhibits great potential for profiling the glucuronide metabolome with high coverage and confidence to reveal changes in CRC and other diseases.

A Novel RP-UHPLC-MS/MS Approach for the Determination of Tryptophan Metabolites Derivatized with 2-Bromo-4'-Nitroacetophenone

Many biologically active metabolites of the essential amino acid L-tryptophan (Trp) are associated with different neurodegenerative diseases and neurological disorders. Precise and reliable methods for their determination are needed. Variability in their physicochemical properties makes the analytical process challenging. In this case, chemical modification of analyte derivatization could come into play. Here, we introduce a novel fast reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled with tandem mass spectrometry (MS/MS) method for the determination of Trp and its ten metabolites in human plasma samples after derivatization with 2-bromo-4'-nitroacetophenone (BNAP). The derivatization procedure was optimized in terms of incubation time, temperature, concentration, and volume of the derivatization reagent. Method development comprises a choice of a suitable stationary phase, mobile phase composition, and gradient elution optimization. The developed method was validated according to the ICH guidelines. Results of all validation parameters were within the acceptance criteria of the guideline, i.e., intra- and inter-day precision (expressed as relative standard deviation; RSD) were in the range of 0.5-8.2% and 2.3-7.4%, accuracy was in the range of 93.3-109.7% and 94.7-110.1%, limits of detection (LODs) were in the range of 0.15-9.43 ng/mL, coefficients of determination (R2) were higher than 0.9906, and carryovers were, in all cases, less than 8.8%. The practicability of the method was evaluated using the blue applicability grade index (BAGI) with a score of 65. Finally, the developed method was used for the analysis of Alzheimer's disease and healthy control plasma to prove its applicability. Statistical analysis revealed significant changes in picolinic acid (PA), anthranilic acid (AA), 5 hydroxyindole-3-acetic acid (5-OH IAA), and quinolinic acid (QA) concentration levels. This could serve as the basis for future studies that will be conducted with a large cohort of patients.

Development of a label-free impedimetric aptasensor based on Zr-MOF and titaniom carbide nanosheets for detection of L-tryptophan

This study primarily focuses on the L-Tryptophan (Trp) biomarker assay, with particular attention given to its objectives. The investigation centers on the potential implications of imbalanced Trp levels and its associated metabolites, which have been attributed to the spectrum of both psychological and physiological disorders, encompassing conditions such as cancer. Therefore, the swift and accurate detection of this amino acid is of paramount importance in cancer monitoring, as it plays a crucial role in preventing the metastasis and spread of cancer cells. Thus, an electrochemical aptasensor was designed based on nanocomposite of AgNPs@UiO-66/Ti3C2 (MXene) as immobilization strategy for the ultrasensitive detection of Trp. Zirconium metal-organic frameworks (Zr-MOFs) were employed as carriers for silver nanoparticles to facilitate subsequent binding with aptamers. Markedly, the obtained results show that the constructed aptasensor can specifically detect Trp in the two concentration range from 1fM to 1 nM and 1 nM to 200 nM and with a low detection limit of 0.35 fM. When applied to real samples, the experimental results demonstrated positive recovery rates. Consequently, a discerning and sensitive electrochemical aptasensor devoid of labeling agents was successfully fabricated for the explicit purpose of Trp detection.

Determination of dimethylated nucleosides in serum from colorectal cancer patients by hydrophilic interaction liquid chromatography-tandem mass spectrometry

RNA modifications play a crucial regulatory role in a variety of biological processes and are closely related to numerous diseases, including cancer. The diversity of metabolites in serum makes it a favored biofluid for biomarkers discovery. In this work, a robust and accurate hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) approach was established for simultaneous determination of dimethylated nucleosides in human serum. Using the established method, we were able to accurately quantify the concentrations of N6-2'-O-dimethyladenosine (m6Am), N2,N2-dimethylguanosine (m2,2G), and 5,2'-O-dimethyluridine (m5Um) in serum samples from 53 healthy controls, 57 advanced colorectal adenoma patients, and 39 colorectal cancer (CRC) patients. The results showed that, compared with healthy controls and advanced colorectal adenoma patients, the concentrations of m6Am and m2,2G were increased in CRC patients, while the concentration of m5Um was decreased in CRC patients. These results indicate that these three dimethylated nucleosides could be potential biomarkers for early detection of colorectal cancer. Interestingly, the level of m5Um was gradually decreased from healthy controls to advanced colorectal adenoma patients to CRC patients, indicating m5Um could also be used to evaluate the level of malignancy of colorectal tumor. In addition, this study will contribute to the investigation on the regulatory mechanisms of RNA dimethylation in the onset and development of colorectal cancer.

Simultaneous and dynamic measurement of Schisandrol A changes in rat blood and brain and its comparative pharmacokinetic study in control and Parkinson's disease rats by dual-probe in vivo microdialysis

Schisandrol A (SchA) is the main active ingredient of Schisandra chinensis (Turcz.) Baill., which is a famous traditional Chinese herbal medicine. SchA can penetrate the blood-brain barrier and has a significant neuroprotective effect. A group of multiplexed stable isotope mass tags (MSIMTs, m/z 332, 338, 346, 349, 351, 354, 360, 363, 374 and 377) were synthesized to perform multiplexed stable isotope labeling derivatization (MSILD) of SchA in rat microdialysates and standards. A new magnetic molecularly imprinted polymer was prepared using MSIMT-375-SchA as dummy template. All the 10-plexed derivatives of MSIMTs-SchA can be efficiently and selectively enriched and purified using this adsorbent by magnetic dispersive solid phase extraction (MDSPE) before ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis. It should be pointed out that the MSIMT-346-SchA standard derivative was used as internal standard in the process of MDSPE and UHPLC-MS/MS. On these bases, 9 different rat microdialysate samples can be determined by UHPLC-MS/MS in a single run. The utilization of MSIMTs significantly increased the sensitivity, accuracy, selectivity and analysis throughput. Under the optimized conditions, satisfactory linearity (R²> 0.987), limit of detection (LODs, 0.15-0.26 pg/mL) and lower limit of quantitative (LLOQ, 0.8-2.0 pg/mL) were obtained. Intra- and inter-day precisions were in the range of 2.2% -12.5%, and recoveries 94.2% -106.2%. The matrix effects were very low, and the average derivatization efficiency of 10-plex MSIMTs to SchA was as high as 97.8%. Using the developed dual-probe in vivo microdialysis sampling technique, the proposed analytical method has been applied for comparative pharmacokinetics of SchA in the brain and blood of control and Parkinson's disease (PD) rats.

Effect of Tryptophan Metabolites on Cell Damage Revealed by Bacteria-Cell Interactions in Hydrogel Microspheres

This work presented an alternative approach for studying bacteria-cell interactions in three-dimensional (3D) hydrogel microspheres formed by the cross-linking reaction of alginate and calcium-ethylenediaminetetraacetic acid (EDTA-Ca) produced in a microfluidic chip. During the co-culture process of hepatocytes (HepG2) and Escherichia coli (E. coli) 25922, we concluded that the content change of tryptophan metabolites detected via ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was related to the cell damage level and the change of interleukin (IL-22) detected by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) was related to the ways of co-cultivation. Compared to the two-dimensional (2D) adherent cell culture process in a Petri dish (2D), the co-culture process of HepG2 and E. coli 25922 in hydrogel microspheres indicated more information about metabolism such as the appearance of indole-3-propionic acid (IPA) and possibly IL-22. The method provides a new perspective to investigate the bacteria-cell interaction and it could be a promising tool in the study of gut microbiota and human health.

Acupuncture treatment for post-stroke depression: Intestinal microbiota and its role

Stroke-induced depression is a common complication and an important risk factor for disability. Besides psychiatric symptoms, depressed patients may also exhibit a variety of gastrointestinal symptoms, and even take gastrointestinal symptoms as the primary reason for medical treatment. It is well documented that stress may disrupt the balance of the gut microbiome in patients suffering from post-stroke depression (PSD), and that disruption of the gut microbiome is closely related to the severity of the condition in depressed patients. Therefore, maintaining the balance of intestinal microbiota can be the focus of research on the mechanism of acupuncture in the treatment of PSD. Furthermore, stroke can be effectively treated with acupuncture at all stages and it may act as a special microecological regulator by regulating intestinal microbiota as well. In this article, we reviewed the studies on changing intestinal microbiota after acupuncture treatment and examined the existing problems and development prospects of acupuncture, microbiome, and poststroke depression, in order to provide new ideas for future acupuncture research.