Potent Reversible Inhibition of Myeloperoxidase by Aromatic Hydroxamates (original) (raw)
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Myeloperoxidase: a target for new drug development?
British Journal of Pharmacology, 2007
Myeloperoxidase (MPO), a member of the haem peroxidase-cyclooxygenase superfamily, is abundantly expressed in neutrophils and to a lesser extent in monocytes and certain type of macrophages. MPO participates in innate immune defence mechanism through formation of microbicidal reactive oxidants and diffusible radical species. A unique activity of MPO is its ability to use chloride as a cosubstrate with hydrogen peroxide to generate chlorinating oxidants such as hypochlorous acid, a potent antimicrobial agent. However, evidence has emerged that MPO-derived oxidants contribute to tissue damage and the initiation and propagation of acute and chronic vascular inflammatory disease. The fact that circulating levels of MPO have been shown to predict risks for major adverse cardiac events and that levels of MPO-derived chlorinated compounds are specific biomarkers for disease progression, has attracted considerable interest in the development of therapeutically useful MPO inhibitors. Today, detailed information on the structure of ferric MPO and its complexes with low-and high-spin ligands is available. This, together with a thorough understanding of reaction mechanisms including redox properties of intermediates, enables a rationale attempt in developing specific MPO inhibitors that still maintain MPO activity during host defence and bacterial killing but interfere with pathophysiologically persistent activation of MPO. The various approaches to inhibit enzyme activity of MPO and to ameliorate adverse effects of MPO-derived oxidants will be discussed. Emphasis will be put on mechanism-based inhibitors and high-throughput screening of compounds as well as the discussion of physiologically useful HOCl scavengers.
Inhibition of Myeloperoxidase: A New Therapeutic Target
The oxidative modification of LDL is a key event in the process of atherosclerosis. Oxidized derivatives of lipoproteins accumulate in the vascular wall and promote local inflammatory lesions which trigger the progression of the atheromatous plaques.
Archives of biochemistry and biophysics, 2014
Myeloperoxidase (MPO) catalyzes the breakdown of hydrogen peroxide and the formation of the potent oxidant hypochlorous acid. We present the application of the fluorogenic peroxidase substrate 10-acetyl-3,7-dihydroxyphenoxazine (ADHP) in steady-state and transient kinetic studies of MPO function. Using initial kinetic parameters for the MPO system, we characterized under the same conditions a number of gold standards for MPO inhibition, namely 4-amino benzoic acid hydrazide (4-ABAH), isoniazid and NaN3 before expanding our focus to isomers of 4-ABAH and benzoic acid hydrazide analogs. We determined that in the presence of hydrogen peroxide that 4-ABAH and its isomer 2-ABAH are both slow-tight binding inhibitors of MPO requiring at least two steps, whereas NaN3 and isoniazid-based inhibition has a single observable step. We also determined that MPO inhibition by benzoic acid hydrazide and 4-(trifluoromethyl) benzoic acid hydrazide was due to hydrolysis of the ester bond between MPO h...
Regulation of the Nitric Oxide Oxidase Activity of Myeloperoxidase by Pharmacological Agents
Biochemical pharmacology, 2017
The leukocyte-derived heme enzyme myeloperoxidase (MPO) is released extracellularly during inflammation and impairs nitric oxide (NO) bioavailability by directly oxidizing NO or producing NO-consuming substrate radicals. Here, structurally diverse pharmacological agents with activities as MPO substrates/inhibitors or antioxidants were screened for their effects on MPO NO oxidase activity in human plasma and physiological model systems containing endogenous MPO substrates/antioxidants (tyrosine, urate, ascorbate). Hydrazide-based irreversible/reversible MPO inhibitors (4-ABAH, isoniazid) or the sickle cell anemia drug, hydroxyurea, all promoted MPO NO oxidase activity. This involved the capacity of NO to antagonize MPO inhibition by hydrazide-derived radicals and/or the ability of drug-derived radicals to stimulate MPO turnover thereby increasing NO consumption by MPO redox intermediates or NO-consuming radicals. In contrast, the mechanism-based irreversible MPO inhibitor 2-thioxanth...
Inhibition of myeloperoxidase: Evaluation of 2H-indazoles and 1H-indazolones
Bioorganic & Medicinal Chemistry, 2014
Myeloperoxidase (MPO) produces hypohalous acids as a key component of the innate immune response; however, release of these acids extracellularly results in inflammatory cell and tissue damage. The twostep, one-pot Davis-Beirut reaction was used to synthesize a library of 2H-indazoles and 1H-indazolones as putative inhibitors of MPO. A structure-activity relationship study was undertaken wherein compounds were evaluated utilizing taurine-chloramine and MPO-mediated H 2 O 2 consumption assays. Docking studies as well as toxicophore and Lipinski analyses were performed. Fourteen compounds were found to be potent inhibitors with IC 50 values <1 lM, suggesting these compounds could be considered as potential modulators of pro-oxidative tissue injury pertubated by the inflammatory MPO/H 2 O 2 /HOCl/ HOBr system.
Exploitation of the unusual thermodynamic properties of human myeloperoxidase in inhibitor design
Biochemical Pharmacology, 2005
Myeloperoxidase plays a fundamental role in oxidant production by neutrophils. It uses hydrogen peroxide and chloride to catalyze the production of hypochlorous acid (HOCl), which contributes to both bacterial killing and oxidative injury of host tissue. Thus, MPO is an interesting target for anti-inflammatory therapy. Here, based on the extraordinary and MPO-specific redox properties of its intermediates compound I and compound II, we present a rational approach in selection and design of reversible inhibitors of HOCl production mediated by MPO. In detail, indole and tryptamine derivatives were investigated for their ability to reduce compounds I and II and to affect the chlorinating activity of MPO. It is shown that these aromatic one-electron donors bound to the hydrophobic pocket at the distal heme cavity and were oxidized efficiently by compound I (k 3), which has a one-electron reduction potential of 1.35 V. By contrast, compound II (E8 0 of the compound II/ferric couple is 0.97 V) reduction (k 4) was extremely slow. As a consequence compound II, which does not participate in the halogenation cycle, accumulated. The extent of chlorinating activity inhibition (IC 50) was related to the k 3 /k 4 ratio. The most efficient inhibitors were 5-fluorotryptamine and 5-chlorotryptamine with IC 50 of 0.79 mM and 0.73 mM and k 3 /k 4 ratios of 386,000 and 224,000, respectively. The reversible mechanism of inhibition is discussed with respect to the enzymology of MPO and the development of drugs against HOCl-dependent tissue damage.
Journal of Biological …, 2009
The binding and structural studies of bovine lactoperoxidase with three aromatic ligands, acetylsalicylic acid (ASA), salicylhydoxamic acid (SHA), and benzylhydroxamic acid (BHA) show that all the three compounds bind to lactoperoxidase at the substrate binding site on the distal heme side. The binding of ASA occurs without perturbing the position of conserved heme water molecule W-1, whereas both SHA and BHA displace it by the hydroxyl group of their hydroxamic acid moieties. The acetyl group carbonyl oxygen atom of ASA forms a hydrogen bond with W-1, which in turn makes three other hydrogen-bonds, one each with heme iron, His-109 N ⑀2 , and Gln-105 N ⑀2. In contrast, in the complexes of SHA and BHA, the OH group of hydroxamic acid moiety in both complexes interacts with heme iron directly with Fe-OH distances of 3.0 and 3.2Å respectively. The OH is also hydrogen bonded to His-109 N ⑀2 and Gln-105N ⑀2. The plane of benzene ring of ASA is inclined at 70.7°from the plane of heme moiety, whereas the aromatic planes of SHA and BHA are nearly parallel to the heme plane with inclinations of 15.7 and 6.2°, respectively. The mode of ASA binding provides the information about the mechanism of action of aromatic substrates, whereas the binding characteristics of SHA and BHA indicate the mode of inhibitor binding.
ACS Medicinal Chemistry Letters, 2016
The implementation of dynamic combinatorial libraries allowed the determination of highly active reversible and irreversible inhibitors of myeloperoxidase (MPO) at the nanomolar level. Docking experiments highlighted the interaction between the most active ligands and MPO, and further kinetic studies defined the mode of inhibition of these compounds. Finally, in vivo evaluation showed that one dose of irreversible inhibitors is able to suppress the activity of MPO after inducing inflammation.
Journal of medicinal chemistry, 2015
Myeloperoxidase (MPO) is a heme peroxidase that catalyzes the production of hypochlorous acid. Clinical evidence suggests a causal role for MPO in various autoimmune and inflammatory disorders including vasculitis and cardiovascular and Parkinson's diseases, implying that MPO inhibitors may represent a therapeutic treatment option. Herein, we present the design, synthesis, and preclinical evaluation of N1-substituted-6-arylthiouracils as potent and selective inhibitors of MPO. Inhibition proceeded in a time-dependent manner by a covalent, irreversible mechanism, which was dependent upon MPO catalysis, consistent with mechanism-based inactivation. N1-Substituted-6-arylthiouracils exhibited low partition ratios and high selectivity for MPO over thyroid peroxidase and cytochrome P450 isoforms. N1-Substituted-6-arylthiouracils also demonstrated inhibition of MPO activity in lipopolysaccharide-stimulated human whole blood. Robust inhibition of plasma MPO activity was demonstrated wit...
Journal of medicinal chemistry, 2017
The heme enzyme myeloperoxidase (MPO) participates in innate immune defense mechanism through formation of microbicidal reactive oxidants. However, evidence has emerged that MPO-derived oxidants contribute to propagation of inflammatory diseases. Because of the deleterious effects of circulating MPO, there is a great interest in the development of new efficient and specific inhibitors. Here, we have performed a novel virtual screening procedure, depending on ligand-based pharmacophore modeling followed by structure-based virtual screening. Starting from a set of 727,842 compounds, 28 molecules were selected by this virtual method and tested on MPO in vitro. Twelve out of 28 compounds were found to have an IC50 less than 5 µM. The best inhibitors were 2-(7-methoxy-4-methylquinazolin-2-yl)guanidine (28) and (R)-2-(1-((2,3-dihydro-1H-imidazol-2-yl)methyl)pyrrolidin-3-yl)-5-fluoro-1H-benzo[d]imidazole (42) with IC50 values of 44 and 50 nM, respectively. Studies on the mechanism of inhib...