Optimized Protocol for the In Situ Derivatization of Glutathione with N-Ethylmaleimide in Cultured Cells and the Simultaneous Determination of Glutathione/Glutathione Disulfide Ratio by HPLC-UV-QTOF-MS

Generation, characterization, and toxicological assessment of reference ultrafine soot particles with different organic content for inhalation toxicological studies

Ultrafine particles (UFP) are the smallest atmospheric particulate matter linked to air pollution-related diseases. The extent to which UFP's physical and chemical properties contribute to its toxicity remains unclear. It is hypothesized that UFP act as carriers for chemicals that drive biological responses. This study explores robust methods for generating reference UFP to understand these mechanisms and perform toxicological tests. Two types of combustion-related UFP with similar elemental carbon cores and physical properties but different organic loads were generated and characterized. Human alveolar epithelial cells were exposed to these UFP at the air-liquid interface, and several toxicological endpoints were measured. UFP were generated using a miniCAST under fuel-rich conditions and immediately diluted to minimize agglomeration. A catalytic stripper and charcoal denuder removed volatile gases and semi-volatile particles from the surface. By adjusting the temperature of the catalytic stripper, UFP with high and low organic content was produced. These reference particles exhibited fractal structures with high reproducibility and stability over a year, maintaining similar mass and number concentrations (100 μg/m3, 2.0·105 #/cm3) and a mean particle diameter of about 40 nm. High organic content UFP had significant PAH levels, with benzo[a]pyrene at 0.2 % (m/m). Toxicological evaluations revealed that both UFP types similarly affected cytotoxicity and cell viability, regardless of organic load. Higher xenobiotic metabolism was noted for PAH-rich UFP, while reactive oxidation markers increased when semi-volatiles were stripped off. Both UFP types caused DNA strand breaks, but only the high organic content UFP induced DNA oxidation. This methodology allows modification of UFP's chemical properties while maintaining comparable physical properties, linking these variations to biological responses.

A bimodal time-gated luminescence-magnetic resonance imaging nanoprobe based on a europium(III) complex anchored on BSA-coated MnO2 nanosheets for highly selective detection of H2O2

A novel nanocomposite, [Eu(BTD)3(DPBT)]-BSA@MnO2, is reported to serve as an effective nanoprobe for bimodal time-gated luminescence (TGL) and magnetic resonance (MR) imaging of H2O2in vitro and in vivo. The nanoprobe was fabricated by immobilizing visible-light-excitable Eu3+ complexes in bovine serum albumin (BSA)-coated lamellar MnO2 nanosheets. The TGL of the Eu3+ complex was effectively quenched by the MnO2 nanosheets. Upon exposure to H2O2, the MnO2 nanosheets underwent reduction to Mn2+, which simultaneously triggered rapid, selective and sensitive "turn-on" responses toward H2O2 in both TGL and MR detection modes. The presence of a protective "corona" formed by BSA enables the nanoprobe to withstand high concentrations of glutathione (GSH), a strong reducing agent of MnO2 nanosheets. This capability allows the nanoprobe to be utilized for detecting H2O2 in living biosamples. The combined utilization of TGL and MR detection modes enables the nanoprobe to image H2O2 across a wide range of resolutions, from the subcellular level to the whole body, without any depth limitations. The results obtained from these modes can be cross-validated, enhancing the accuracy of the detection. The capability of the nanoprobe was validated by TGL imaging of endogenous and exogenous H2O2 in live HeLa cells, as well as bimodal TGL-MR imaging of H2O2 in tumor-bearing mice. The research achievements suggest that the integration of luminescent lanthanide complexes with protein-coated MnO2 nanosheets offers a promising bimodal TGL-MR sensing platform for H2O2in vitro and in vivo.

Amino acid supplementation confers protection to red blood cells before Plasmodium falciparum bystander stress

ABSTRACT

Malaria is a highly oxidative parasitic disease in which anemia is the most common clinical symptom. A major contributor to the malarial anemia pathogenesis is the destruction of bystander, uninfected red blood cells (RBCs). Metabolic fluctuations are known to occur in the plasma of individuals with acute malaria, emphasizing the role of metabolic changes in disease progression and severity. Here, we report conditioned medium from Plasmodium falciparum culture induces oxidative stress in uninfected, catalase-depleted RBCs. As cell-permeable precursors to glutathione, we demonstrate the benefit of pre-exposure to exogenous glutamine, cysteine, and glycine amino acids for RBCs. Importantly, this pretreatment intrinsically prepares RBCs to mitigate oxidative stress.

Accurate redox state indication by in situ derivatization with N-ethylmaleimide - Profiling of transsulfuration and glutathione pathway metabolites by UPLC-MS/MS

BACKGROUND

Reduced and oxidized glutathione play an important role for the intracellular detoxification of reactive oxygen species. The iron-dependent formation of such reactive oxygen species in conjunction with the inhibition of the redox-balancing enzyme glutathione peroxidase 4 underlie an imbalance in the cellular redox state, thereby resulting in a non-apoptotic form of cell death, defined as ferroptosis, which is relevant in several pathologies.

METHODS

Here we present a rapid ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) based method providing the accurate quantification of 12 glutathione pathway metabolites after in situ derivatization with N-Ethylmaleimide (NEM). The method was validated regards linearity, recovery and accuracy as well as precision. The assay includes glutathione and its oxidized form glutathione disulfide. Furthermore, the related precursors cysteine, cystine, glutamic acid, γ-glutamylcysteine and cysteinylglycine, biomarkers of protein crosslinking such as cystathionine and lanthionine, as well as metabolites of the transsulfuration pathway, methionine, homocysteine and serine are simultaneously determined.

RESULTS

Twelve glutathione pathway metabolites were simultaneously analyzed in four different human cell line extracts within a total LC run time of 5.5 min. Interday coefficients of variation (1.7 % to 12.0 %), the mean observed accuracy (100.0 % ± 5.2 %), linear quantification ranges over three orders of magnitude for all analytes and sufficient metabolite stability after NEM-derivatization demonstrate method reliability. Immediate derivatization with NEM at cell harvesting prevents autooxidation of glutathione, ensures accurate results for the GSH/GSSG redox ratio and thereby allows interpretation of cellular redox state.

CONCLUSION

The described UPLC-MS/MS method provides a sensitive and selective tool for a fast and simultaneous analysis of glutathione pathway metabolites, its direct precursors and related compounds. Assay performance characteristics demonstrate the suitability of the method for applications in different cell cultures. Therefore, by providing glutathione related functional metabolic readouts, the method enables investigations in mechanisms of ferroptosis and alterations in oxidative stress levels in several pathophysiologies.

Amino acid supplementation confers protection to red blood cells prior to Plasmodium falciparum bystander stress

Malaria is a highly oxidative parasitic disease in which anemia is the most common clinical symptom. A major contributor to malarial anemia pathogenesis is the destruction of bystander, uninfected red blood cells. Metabolic fluctuations are known to occur in the plasma of individuals with acute malaria, emphasizing the role of metabolic changes in disease progression and severity. Here, we report that conditioned media from Plasmodium falciparum culture induces oxidative stress in healthy uninfected RBCs. Additionally, we show the benefit of amino acid pre-exposure for RBCs and how this pre-treatment intrinsically prepares RBCs to mitigate oxidative stress.

Key points

Intracellular ROS is acquired in red blood cells incubated with Plasmodium falciparum conditioned media Glutamine, cysteine, and glycine amino acid supplementation increased glutathione biosynthesis and reduced ROS levels in stressed RBCs.

An activatable nanoprobe based on nanocomposites of visible-light-excitable europium(III) complex-anchored MnO2 nanosheets for bimodal time-gated luminescence and magnetic resonance imaging of tumor cells

Bimodal imaging probes that combine magnetic resonance imaging (MRI) and photoluminescence imaging are quite appealing since they can supply both anatomical and molecular information to effectively ameliorate the accuracy of detection. In this study, an activatable nanoprobe, [Eu(BTD)₃(DPBT)]@MnO₂, for bimodal time-gated luminescence imaging (TGLI) and MRI has been constructed by anchoring visible-light-excitable Eu³⁺ complexes on lamellar MnO₂ nanosheets. Due to the luminescence quenching effect and non-magnetic resonance (MR) activity of MnO₂ nanosheets, the developed nanoprobe presents quite weak TGL and MR signals. After exposure to H₂O₂ or GSH, accompanied by the transformation from MnO₂ to Mn²⁺, the nanoprobe exhibits rapid, sensitive, and selective "turn-on" responses towards GSH and H₂O₂ in TGL and MR detection modes. Furthermore, the nanoprobe displays high stability, low cytotoxicity, good biocompatibility and water dispersion. Given the high contents of GSH and H₂O₂ in cancer cells, the nanoprobe was used for the identification of cancer cells by TGLI of intracellular GSH and H₂O₂, as well as for the tracing of tumor cells in tumor-bearing mice by tumor-targeting in vivo MRI and TGLI of tumor tissues. The research outcomes proved the potential of [Eu(BTD)₃(DPBT)]@MnO₂ as a useful nanoprobe for the tracing and accurate detection of cancer cells in vitro and in vivo via bimodal TGLI and MRI.

Manganese-Induced Oxidative Stress Contributes to Intestinal Lipid Deposition via the Deacetylation of PPARγ at K339 by SIRT1

Aims: Excessive manganese (Mn) exposure is toxic, and induces lipid deposition, but the underlying mechanisms remain elusive. Herein, we explored how dietary Mn supplementation affects lipid deposition and metabolism in the intestine of vertebrates using the yellow catfish Pelteobagrus fulvidraco as the model. Results: High-Mn (H-Mn) diet increased intestinal Mn content, promoted lipid accumulation and lipogenesis, and inhibited lipolysis. In addition, it induced oxidative stress, upregulated metal-response element-binding transcription factor-1 (MTF-1), and peroxisome proliferator-activated receptor gamma (PPARγ) protein expression in the nucleus, induced PPARγ acetylation, and the interaction between PPARγ and retinoid X receptor alpha (RXRα), while it downregulated sirtuin 1 (SIRT1) expression and activity. Mechanistically, Mn activated the MTF-1/divalent metal transporter 1 (DMT1) pathway, increased Mn accumulation in the mitochondria, and induced oxidative stress. This in turn promoted lipid deposition via deacetylation of PPARγ at K339 by SIRT1. Subsequently, PPARγ mediated Mn-induced lipid accumulation through transcriptionally activating fatty acid translocase, stearoyl-CoA desaturase 1, and perilipin 2 promoters. Innovation: These studies uncover a previously unknown mechanism by which Mn induces lipid deposition in the intestine via the oxidative stress-SIRT1-PPARγ pathway. Conclusion: High dietary Mn intake activates MTF-1/DMT1 and oxidative stress pathways. Oxidative stress-mediated PPARγ deacetylation at K339 site contributes to increased lipid accumulation. Our results provided a direct link between Mn and lipid metabolism via the oxidative stress-SIRT1-PPARγ axis. Antioxid. Redox Signal. 37, 417-436.

Hydrogen-Deuterium Addition and Exchange in N-Ethylmaleimide Reaction with Glutathione Detected by NMR Spectroscopy

Glutathione (GSH) is an important and ubiquitous thiol compound abundantly present in virtually every living cell. It is a powerful antioxidant critically required to protect cells from oxidative damage and free radical injury. Its quantification in ex vivo analysis remains a major challenge because it spontaneously oxidizes to form glutathione disulfide. N-Ethylmaleimide (NEM) is a well-known Michael acceptor, which reacts rapidly and irreversibly with thiol and prevents disulfide bond formation. Based on thiol conjugation to NEM, recently, the concentration of GSH was determined in human blood using NMR spectroscopy [Anal. Chem, 2021, 93(44): 14844-14850]. It was found that hydrogen-deuterium addition and exchange occur during the thiol-maleimide reaction as well as NMR analysis, generating a series of poorly explored diastereomers/isotopomers. Here, we establish a general NMR approach to identify the thiosuccinimide diastereomers/isotopomers derived from the thiol-maleimide reaction. The thiol-Michael addition reaction was conducted for GSH and another thiol compound, cysteine, separately, using D2O and H2O. The conjugates were characterized by 1H/13C 1D/2D NMR under different solvent, buffer, and pH conditions. The Michael addition combined with the H/D exchange formed twelve unique diastereomers/isotopomers. NMR measurements allowed the distinct assignment of all structures in solutions and quantification of H/D addition and exchange. Interestingly, the deuterium exchange rate was dependent on structure, pH, and buffer. The elucidation of the thiol-maleimide reaction and H/D exchange mechanism can potentially impact areas including metabolomics, small molecule synthesis, and bioconjugation chemistry.

Exposure of human cerebral microvascular endothelial cells hCMEC/D3 to laminar shear stress induces vascular protective responses

Endothelial cells (ECs) are constantly submitted in vivo to hemodynamical forces derived from the blood circulation, including shear stress (SS). ECs are able to detect SS and consequently adapt their phenotype, thus affecting many endothelial functions. If a plethora of shear stress-regulated molecular networks have been described in peripheral ECs, less is known about the molecular responses of microvascular brain ECs which constitute the blood-brain barrier (BBB). In this work, we investigated the response of human cerebral microvascular ECs to laminar physiological shear stress using the well characterized hCMEC/D3 cell line. Interestingly, we showed that hCMEC/D3 cells responded to shear stress by aligning perpendicularly to the flow direction, contrary to peripheral endothelial cells which aligned in the flow direction. Whole proteomic profiles were compared between hCMEC/D3 cells cultured either in static condition or under 5 or 10 dyn.cm-2 SS for 3 days. 3592 proteins were identified and expression levels were significantly affected for 3% of them upon both SS conditions. Pathway analyses were performed which revealed that most proteins overexpressed by SS refer to the antioxidant defense, probably mediated by activation of the NRF2 transcriptional factor. Regarding down-regulated proteins, most of them participate to the pro-inflammatory response, cell motility and proliferation. These findings confirm the induction of EC quiescence by laminar physiological SS and reveal a strong protective effect of SS on hCMEC/D3 cells, suggesting a similar effect on the BBB. Our results also showed that SS did not significantly increase expression levels nor did it affect the localization of junctional proteins and did not afect either the functional activity of several ABC transporters (P-glycoprotein and MRPs). This work provides new insights on the response of microvascular brain ECs to SS and on the importance of SS for optimizing in vitro BBB models.

Glutathione production by Saccharomyces cerevisiae: current state and perspectives

Glutathione (L-γ-glutamyl-cysteinyl-glycine, GSH) is a tripeptide synthesized through consecutive enzymatic reactions. Among its several metabolic functions in cells, the main one is the potential to act as an endogenous antioxidant agent. GSH has been the focus of numerous studies not only due to its role in the redox status of biological systems but also due to its biotechnological characteristics. GSH is usually obtained by fermentation and shows a variety of applications by the pharmaceutical and food industry. Therefore, the search for new strategies to improve the production of GSH during fermentation is crucial. This mini review brings together recent papers regarding the principal parameters of the biotechnological production of GSH by Saccharomyces cerevisiae. In this context, aspects, such as the medium composition (amino acids, alternative raw materials) and the use of technological approaches (control of osmotic and pressure conditions, magnetic field (MF) application, fed-batch process) were considered, along with genetic engineering knowledge, trends, and challenges in viable GSH production. KEY POINTS: • Saccharomyces cerevisiae has shown potential for glutathione production. • Improved technological approaches increases glutathione production. • Genetic engineering in Saccharomyces cerevisiae improves glutathione production.

In situ synthesis of chiral AuNCs with aggregation-induced emission using glutathione and ceria precursor nanosheets for glutathione biosensing

Au(i)–SG/Ce(CO3)2 NS conjugated nanoprobe was developed for selective GSH detection. The redox reaction between GSH and the NS could release Ce3+ ions to initiate the intense AIE of Au(i)–SG oligomers.

Extensive Thiol Profiling for Assessment of Intracellular Redox Status in Cultured Cells by HPLC-MS/MS

Oxidative stress may contribute to the pathology of many diseases, and endogenous thiols, especially glutathione (GSH) and its metabolites, play essential roles in the maintenance of normal redox status. Understanding how these metabolites change in response to oxidative insult can provide key insights into potential methods of prevention and treatment. Most existing methodologies focus only on the GSH/GSH disulfide (GSSG) redox couple, but GSH regulation is highly complex and depends on several pathways with multiple redox-active sulfur-containing species. In order to more fully characterize thiol redox status in response to oxidative insult, a high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) method was developed to simultaneously determine seven sulfur-containing metabolites, generating a panel that systematically examines several pathways involved in thiol metabolism and oxidative stress responses. The sensitivity (LOQ as low as 0.01 ng/mL), accuracy (88–126% spike recovery), and precision (≤12% RSD) were comparable or superior to those of existing methods. Additionally, the method was used to compare the baseline thiol profiles and oxidative stress responses of cell lines derived from different tissues. The results revealed a previously unreported response to oxidative stress in lens epithelial (B3) cells, which may be exploited as a new therapeutic target for oxidative-stress-related ocular diseases. Further application of this method may uncover new pathways involved in oxidative-stress-related diseases and endogenous defense mechanisms.

Development of a HPLC-MS/MS method for assessment of thiol redox status in human tear fluids

Oxidative stress is reported to be part of the pathology of many ocular diseases. For the diagnosis of ocular diseases, tear fluid has unique advantages. Although numerous analytical methods exist for the measurement of different types of biomolecules in tear fluid, few have been reported for comprehensive understanding of oxidative stress-related thiol redox signaling. In this study, a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to determine a panel of twelve metabolites that systematically covered several thiol metabolic pathways. With optimization of MS/MS parameters and HPLC mobile phases, this method was sensitive (LOQ as low as 0.01 ng/ml), accurate (80-125% spike recovery) and precise (<10% RSD). This LC-MS/MS method combined with a simple tear fluid collection with Schirmer test strip followed by ultrafiltration allowed the high-throughput analysis for efficient determination of metabolites associated with thiol redox signaling in human tear fluids. The method was then applied to a small cohort of tear fluids obtained from healthy individuals. The method presented here provides a new technique to facilitate future work aiming to determine the complex thiol redox signaling in tear fluids for accurate assessment and diagnosis of ocular diseases.