Edlaine Linares, Divinomar Severino, Daniela R. Truzzi, Natalia Rios, Rafael Radi and Ohara Augusto*,
{"title":"Production of Peroxymonocarbonate by Steady-State Micromolar H2O2 and Activated Macrophages in the Presence of CO2/HCO3– Evidenced by Boronate Probes","authors":"Edlaine Linares, Divinomar Severino, Daniela R. Truzzi, Natalia Rios, Rafael Radi and Ohara Augusto*, ","doi":"10.1021/acs.chemrestox.4c00059","DOIUrl":null,"url":null,"abstract":"<p >Peroxymonocarbonate (HCO<sub>4</sub><sup>–</sup>/HOOCO<sub>2</sub><sup>–</sup>) is produced by the reversible reaction of CO<sub>2</sub>/HCO<sub>3</sub><sup>–</sup> with H<sub>2</sub>O<sub>2</sub> (<i>K</i> = 0.33 M<sup>–1</sup>, pH 7.0). Although produced in low yields at physiological pHs and H<sub>2</sub>O<sub>2</sub> and CO<sub>2</sub>/HCO<sub>3</sub><sup>–</sup> concentrations, HCO<sub>4</sub><sup>–</sup> oxidizes most nucleophiles with rate constants 10 to 100 times higher than those of H<sub>2</sub>O<sub>2</sub>. Boronate probes are known examples because HCO<sub>4</sub><sup>–</sup> reacts with coumarin-7-boronic acid pinacolate ester (CBE) with a rate constant that is approximately 100 times higher than that of H<sub>2</sub>O<sub>2</sub> and the same holds for fluorescein-boronate (Fl-B) as reported here. Therefore, we tested whether boronate probes could provide evidence for HCO<sub>4</sub><sup>–</sup> formation under biologically relevant conditions. Glucose/glucose oxidase/catalase were adjusted to produce low steady-state H<sub>2</sub>O<sub>2</sub> concentrations (2–18 μM) in Pi buffer at pH 7.4 and 37 °C. Then, CBE (100 μM) was added and fluorescence increase was monitored with time. The results showed that each steady-state H<sub>2</sub>O<sub>2</sub> concentration reacted more rapidly (∼30%) in the presence of CO<sub>2</sub>/HCO<sub>3</sub><sup>–</sup> (25 mM) than in its absence, and the data permitted the calculation of consistent rate constants. Also, RAW 264.7 macrophages were activated with phorbol 12-myristate 13-acetate (PMA) (1 μg/mL) at pH 7.4 and 37 °C to produce a time-dependent H<sub>2</sub>O<sub>2</sub> concentration (8.0 ± 2.5 μM after 60 min). The media contained 0, 21.6, or 42.2 mM HCO<sub>3</sub><sup>–</sup> equilibrated with 0, 5, or 10% CO<sub>2</sub>, respectively. In the presence of CBE or Fl-B (30 μM), a time-dependent increase in the fluorescence of the bulk solution was observed, which was higher in the presence of CO<sub>2</sub>/HCO<sub>3</sub><sup>–</sup> in a concentration-dependent manner. The Fl-B samples were also examined by fluorescence microscopy. Our results demonstrated that mammalian cells produce HCO<sub>4</sub><sup>–</sup> and boronate probes can evidence and distinguish it from H<sub>2</sub>O<sub>2</sub> under biologically relevant concentrations of H<sub>2</sub>O<sub>2</sub> and CO<sub>2</sub>/HCO<sub>3</sub><sup>–</sup>.</p>","PeriodicalId":31,"journal":{"name":"Chemical Research in Toxicology","volume":null,"pages":null},"PeriodicalIF":3.7000,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.chemrestox.4c00059","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Chemical Research in Toxicology","FirstCategoryId":"3","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.chemrestox.4c00059","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MEDICINAL","Score":null,"Total":0}
引用次数: 0
Abstract
Peroxymonocarbonate (HCO4–/HOOCO2–) is produced by the reversible reaction of CO2/HCO3– with H2O2 (K = 0.33 M–1, pH 7.0). Although produced in low yields at physiological pHs and H2O2 and CO2/HCO3– concentrations, HCO4– oxidizes most nucleophiles with rate constants 10 to 100 times higher than those of H2O2. Boronate probes are known examples because HCO4– reacts with coumarin-7-boronic acid pinacolate ester (CBE) with a rate constant that is approximately 100 times higher than that of H2O2 and the same holds for fluorescein-boronate (Fl-B) as reported here. Therefore, we tested whether boronate probes could provide evidence for HCO4– formation under biologically relevant conditions. Glucose/glucose oxidase/catalase were adjusted to produce low steady-state H2O2 concentrations (2–18 μM) in Pi buffer at pH 7.4 and 37 °C. Then, CBE (100 μM) was added and fluorescence increase was monitored with time. The results showed that each steady-state H2O2 concentration reacted more rapidly (∼30%) in the presence of CO2/HCO3– (25 mM) than in its absence, and the data permitted the calculation of consistent rate constants. Also, RAW 264.7 macrophages were activated with phorbol 12-myristate 13-acetate (PMA) (1 μg/mL) at pH 7.4 and 37 °C to produce a time-dependent H2O2 concentration (8.0 ± 2.5 μM after 60 min). The media contained 0, 21.6, or 42.2 mM HCO3– equilibrated with 0, 5, or 10% CO2, respectively. In the presence of CBE or Fl-B (30 μM), a time-dependent increase in the fluorescence of the bulk solution was observed, which was higher in the presence of CO2/HCO3– in a concentration-dependent manner. The Fl-B samples were also examined by fluorescence microscopy. Our results demonstrated that mammalian cells produce HCO4– and boronate probes can evidence and distinguish it from H2O2 under biologically relevant concentrations of H2O2 and CO2/HCO3–.
期刊介绍:
Chemical Research in Toxicology publishes Articles, Rapid Reports, Chemical Profiles, Reviews, Perspectives, Letters to the Editor, and ToxWatch on a wide range of topics in Toxicology that inform a chemical and molecular understanding and capacity to predict biological outcomes on the basis of structures and processes. The overarching goal of activities reported in the Journal are to provide knowledge and innovative approaches needed to promote intelligent solutions for human safety and ecosystem preservation. The journal emphasizes insight concerning mechanisms of toxicity over phenomenological observations. It upholds rigorous chemical, physical and mathematical standards for characterization and application of modern techniques.