A New and Fast-Response Fluorescent Probe for Monitoring Hypochlorous Acid Derived from Myeloperoxidase

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Abstract

Hypochlorous acid (HOCl) has been implicated in numerous pathologies associated with an inflammatory component, but its selective and sensitive detection in biological settings remains a challenge. In this report, imaging of HOCl was realized with a thiomorpholine-based probe as derivative of nitrobenzothiadiazole (NBD-S-TM). The fluorescence is based on photoinduced electron transfer by using nitrobenzothiadiazole core as a donor and thiomorpholine substituent as an acceptor. NBD-S-TM showed high sensitivity and a fast response to HOCl k = (2.6 ± 0.2) × 107 M−1s−1 with a 1:1 stoichiometry. The detection limit for HOCl was determined to be 60 nM. Furthermore, the desirable features of NBD-S-TM for the detection of HOCl in aqueous solutions, such as its reliability at physiological pH, rapid fluorescence response, and biocompatibility, enabled its application in the detection of HOCl in myeloperoxidase enzymatic system. Moreover, NBD-S-TM exhibited excellent selectivity and sensitivity for HOCl over other biologically relevant species, such as hydrogen peroxide and peroxynitrite. The fluorescent S-oxidized product (NBD-S-TSO) is only formed in the presence of HOCl. Probing with NBD-S-TM may be helpful to further the development of high throughput screening assays to monitor the activity of myeloperoxidase.

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Reconciling the chemistry and biology of reactive oxygen species.

Christine Winterbourn (2008)

There is a vast literature on the generation and effects of reactive oxygen species in biological systems, both in relation to damage they cause and their involvement in cell regulatory and signaling pathways. The biological chemistry of different oxidants is becoming well understood, but it is often unclear how this translates into cellular mechanisms where redox changes have been demonstrated. This review addresses this gap. It examines how target selectivity and antioxidant effectiveness vary for different oxidants. Kinetic considerations of reactivity are used to assess likely targets in cells and how reactions might be influenced by restricted diffusion and compartmentalization. It also highlights areas where greater understanding is required on the fate of oxidants generated by cellular NADPH oxidases and on the identification of oxidant sensors in cell signaling.

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Oxygen radicals, nitric oxide, and peroxynitrite: Redox pathways in molecular medicine

Rafael Radi (2018)

Aerobic life in humans imposes the hazard of excess oxidation in cell and tissue components that may compromise cell function and viability. The formation and accumulation of oxidized products in biomolecules such as proteins and lipids are observed in various pathologies and during the normal aging process. This review article aims to integrate some early and remarkable discoveries in the field, with more recent developments that helped to define a causative role of oxygen radicals, nitric oxide, and peroxynitrite in human physiology and pathology. These aspects of human redox biochemistry contribute to the understanding of the molecular basis of diseases and aging and open avenues for the development of preventive and therapeutic strategies in molecular medicine. Oxygen-derived free radicals and related oxidants are ubiquitous and short-lived intermediates formed in aerobic organisms throughout life. These reactive species participate in redox reactions leading to oxidative modifications in biomolecules, among which proteins and lipids are preferential targets. Despite a broad array of enzymatic and nonenzymatic antioxidant systems in mammalian cells and microbes, excess oxidant formation causes accumulation of new products that may compromise cell function and structure leading to cell degeneration and death. Oxidative events are associated with pathological conditions and the process of normal aging. Notably, physiological levels of oxidants also modulate cellular functions via homeostatic redox-sensitive cell signaling cascades. On the other hand, nitric oxide ( • NO), a free radical and weak oxidant, represents a master physiological regulator via reversible interactions with heme proteins. The bioavailability and actions of • NO are modulated by its fast reaction with superoxide radical ( O 2 • − ), which yields an unusual and reactive peroxide, peroxynitrite, representing the merging of the oxygen radicals and • NO pathways. In this Inaugural Article, I summarize early and remarkable developments in free radical biochemistry and the later evolution of the field toward molecular medicine; this transition includes our contributions disclosing the relationship of • NO with redox intermediates and metabolism. The biochemical characterization, identification, and quantitation of peroxynitrite and its role in disease processes have concentrated much of our attention. Being a mediator of protein oxidation and nitration, lipid peroxidation, mitochondrial dysfunction, and cell death, peroxynitrite represents both a pathophysiologically relevant endogenous cytotoxin and a cytotoxic effector against invading pathogens.