Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release

Steven A. Everett, Elizabeth Swann, Matthew A. Naylor, Michael R. L. Stratford, Kantilal B. Patel, Natasha Tian, Robert G. Newman, Borivoj Vojnovic, Christopher J. Moody, Peter Wardman

    Research output: Contribution to journalArticle

    26 Citations (Scopus)

    Abstract

    3-(4-Methylcoumarin-7-yloxy)methylindole-4,7-diones were synthesised as model prodrugs in order to investigate the correlation between rates of reductive elimination from the (indolyl-3-yl)methyl position with reductive metabolism by hypoxic tumor cells and NADPH: cytochrome P450. Rates of elimination of the chromophore/fluorophore (7-hydroxy-4-methylcoumarin) following one-electron reduction of indolequinones to their semiquinone radicals (Q·-) was measured by pulse radiolysis utilising spectrophotometric and fluorometric detection. Incorporation of a thienyl or methyl substituent at the (indol-3-yl)CHR-position (where R=thienyl or methyl adjacent to the phenolic ether linking bond) significantly shortened the half-life of reductive elimination from 87 to 6 and 2 ms, respectively. Elimination from the methyl substituted analogue can thus compete effectively with the reaction of the semiquinone radical with oxygen at levels typically present in tumours (half-life ~1.8 ms at 0.5% O2). Chemical kinetic predictions were confirmed by metabolism in breast tumour MCF-7 cells between 0–2.1% O2. Rates of reductive release of the fluorophore from the non-fluorescent parent indolequinones (R=H, Me, thienyl) were similar under anoxia (~1.7 nmol coumarin min?¹mg protein?¹) reflecting the similarity in one-electron reduction potential. Whereas coumarin release from the indolequinone (R=H) was completely inhibited above 0.5% O2, the enhanced rate of reductive elimination when R=thienyl or Me increased the metabolic rate of release to ~0.35 and 0.7 nmol coumarin min?¹ mg protein?¹, respectively at 0.5% O2; complete inhibition occurring by 2.1% O2. Similar ‘oxygen profiles’ of release were observed with NADPH: cytochrome P450 reductase. In conclusion, it is possible to modify rates of reductive elimination from indolequinones to control the release of drugs over a range of tumour hypoxia.
    Original languageEnglish
    Pages (from-to)1629-1639
    Number of pages11
    JournalBiochemical Pharmacology
    Volume63
    Issue number9
    DOIs
    Publication statusPublished - May 2002

    Fingerprint

    Indolequinones
    Prodrugs
    Tumors
    Fluorophores
    Metabolism
    Pharmaceutical Preparations
    Half-Life
    Pulse Radiolysis
    Electrons
    Oxygen
    NADPH-Ferrihemoprotein Reductase
    Radiolysis
    Drug and Narcotic Control
    MCF-7 Cells
    Chromophores
    NADP
    Reaction kinetics
    Ether
    Cytochrome P-450 Enzyme System
    Neoplasms

    Keywords

    • Indolequinone
    • 7-Hydroxy-4-methylcoumarin
    • Reduction
    • Chemical kinetics
    • Semiquinone radical
    • Pulse radiolysis
    • MCF-7 breast tumour cells
    • NADPH
    • Cytochrome P450 reductase
    • Hypoxia

    Cite this

    Everett, Steven A. ; Swann, Elizabeth ; Naylor, Matthew A. ; Stratford, Michael R. L. ; Patel, Kantilal B. ; Tian, Natasha ; Newman, Robert G. ; Vojnovic, Borivoj ; Moody, Christopher J. ; Wardman, Peter. / Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release. In: Biochemical Pharmacology. 2002 ; Vol. 63, No. 9. pp. 1629-1639.
    @article{6202cf050c5f4fd99d88bc7f459e2ff8,
    title = "Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release",
    abstract = "3-(4-Methylcoumarin-7-yloxy)methylindole-4,7-diones were synthesised as model prodrugs in order to investigate the correlation between rates of reductive elimination from the (indolyl-3-yl)methyl position with reductive metabolism by hypoxic tumor cells and NADPH: cytochrome P450. Rates of elimination of the chromophore/fluorophore (7-hydroxy-4-methylcoumarin) following one-electron reduction of indolequinones to their semiquinone radicals (Q·-) was measured by pulse radiolysis utilising spectrophotometric and fluorometric detection. Incorporation of a thienyl or methyl substituent at the (indol-3-yl)CHR-position (where R=thienyl or methyl adjacent to the phenolic ether linking bond) significantly shortened the half-life of reductive elimination from 87 to 6 and 2 ms, respectively. Elimination from the methyl substituted analogue can thus compete effectively with the reaction of the semiquinone radical with oxygen at levels typically present in tumours (half-life ~1.8 ms at 0.5{\%} O2). Chemical kinetic predictions were confirmed by metabolism in breast tumour MCF-7 cells between 0–2.1{\%} O2. Rates of reductive release of the fluorophore from the non-fluorescent parent indolequinones (R=H, Me, thienyl) were similar under anoxia (~1.7 nmol coumarin min?¹mg protein?¹) reflecting the similarity in one-electron reduction potential. Whereas coumarin release from the indolequinone (R=H) was completely inhibited above 0.5{\%} O2, the enhanced rate of reductive elimination when R=thienyl or Me increased the metabolic rate of release to ~0.35 and 0.7 nmol coumarin min?¹ mg protein?¹, respectively at 0.5{\%} O2; complete inhibition occurring by 2.1{\%} O2. Similar ‘oxygen profiles’ of release were observed with NADPH: cytochrome P450 reductase. In conclusion, it is possible to modify rates of reductive elimination from indolequinones to control the release of drugs over a range of tumour hypoxia.",
    keywords = "Indolequinone, 7-Hydroxy-4-methylcoumarin, Reduction, Chemical kinetics, Semiquinone radical, Pulse radiolysis, MCF-7 breast tumour cells, NADPH, Cytochrome P450 reductase, Hypoxia",
    author = "Everett, {Steven A.} and Elizabeth Swann and Naylor, {Matthew A.} and Stratford, {Michael R. L.} and Patel, {Kantilal B.} and Natasha Tian and Newman, {Robert G.} and Borivoj Vojnovic and Moody, {Christopher J.} and Peter Wardman",
    note = "dc.publisher: Elsevier dc.description.sponsorship: Gray Cancer Institute (GCI) Cancer Research UK",
    year = "2002",
    month = "5",
    doi = "10.1016/S0006-2952(02)00885-7",
    language = "English",
    volume = "63",
    pages = "1629--1639",
    journal = "Biochemical Pharmacology",
    issn = "0006-2952",
    publisher = "Elsevier",
    number = "9",

    }

    Everett, SA, Swann, E, Naylor, MA, Stratford, MRL, Patel, KB, Tian, N, Newman, RG, Vojnovic, B, Moody, CJ & Wardman, P 2002, 'Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release', Biochemical Pharmacology, vol. 63, no. 9, pp. 1629-1639. https://doi.org/10.1016/S0006-2952(02)00885-7

    Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release. / Everett, Steven A.; Swann, Elizabeth; Naylor, Matthew A.; Stratford, Michael R. L.; Patel, Kantilal B.; Tian, Natasha; Newman, Robert G.; Vojnovic, Borivoj; Moody, Christopher J.; Wardman, Peter.

    In: Biochemical Pharmacology, Vol. 63, No. 9, 05.2002, p. 1629-1639.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Modifying rates of reductive elimination of leaving groups from indolequinone prodrugs: a key factor in controlling hypoxia-selective drug release

    AU - Everett, Steven A.

    AU - Swann, Elizabeth

    AU - Naylor, Matthew A.

    AU - Stratford, Michael R. L.

    AU - Patel, Kantilal B.

    AU - Tian, Natasha

    AU - Newman, Robert G.

    AU - Vojnovic, Borivoj

    AU - Moody, Christopher J.

    AU - Wardman, Peter

    N1 - dc.publisher: Elsevier dc.description.sponsorship: Gray Cancer Institute (GCI) Cancer Research UK

    PY - 2002/5

    Y1 - 2002/5

    N2 - 3-(4-Methylcoumarin-7-yloxy)methylindole-4,7-diones were synthesised as model prodrugs in order to investigate the correlation between rates of reductive elimination from the (indolyl-3-yl)methyl position with reductive metabolism by hypoxic tumor cells and NADPH: cytochrome P450. Rates of elimination of the chromophore/fluorophore (7-hydroxy-4-methylcoumarin) following one-electron reduction of indolequinones to their semiquinone radicals (Q·-) was measured by pulse radiolysis utilising spectrophotometric and fluorometric detection. Incorporation of a thienyl or methyl substituent at the (indol-3-yl)CHR-position (where R=thienyl or methyl adjacent to the phenolic ether linking bond) significantly shortened the half-life of reductive elimination from 87 to 6 and 2 ms, respectively. Elimination from the methyl substituted analogue can thus compete effectively with the reaction of the semiquinone radical with oxygen at levels typically present in tumours (half-life ~1.8 ms at 0.5% O2). Chemical kinetic predictions were confirmed by metabolism in breast tumour MCF-7 cells between 0–2.1% O2. Rates of reductive release of the fluorophore from the non-fluorescent parent indolequinones (R=H, Me, thienyl) were similar under anoxia (~1.7 nmol coumarin min?¹mg protein?¹) reflecting the similarity in one-electron reduction potential. Whereas coumarin release from the indolequinone (R=H) was completely inhibited above 0.5% O2, the enhanced rate of reductive elimination when R=thienyl or Me increased the metabolic rate of release to ~0.35 and 0.7 nmol coumarin min?¹ mg protein?¹, respectively at 0.5% O2; complete inhibition occurring by 2.1% O2. Similar ‘oxygen profiles’ of release were observed with NADPH: cytochrome P450 reductase. In conclusion, it is possible to modify rates of reductive elimination from indolequinones to control the release of drugs over a range of tumour hypoxia.

    AB - 3-(4-Methylcoumarin-7-yloxy)methylindole-4,7-diones were synthesised as model prodrugs in order to investigate the correlation between rates of reductive elimination from the (indolyl-3-yl)methyl position with reductive metabolism by hypoxic tumor cells and NADPH: cytochrome P450. Rates of elimination of the chromophore/fluorophore (7-hydroxy-4-methylcoumarin) following one-electron reduction of indolequinones to their semiquinone radicals (Q·-) was measured by pulse radiolysis utilising spectrophotometric and fluorometric detection. Incorporation of a thienyl or methyl substituent at the (indol-3-yl)CHR-position (where R=thienyl or methyl adjacent to the phenolic ether linking bond) significantly shortened the half-life of reductive elimination from 87 to 6 and 2 ms, respectively. Elimination from the methyl substituted analogue can thus compete effectively with the reaction of the semiquinone radical with oxygen at levels typically present in tumours (half-life ~1.8 ms at 0.5% O2). Chemical kinetic predictions were confirmed by metabolism in breast tumour MCF-7 cells between 0–2.1% O2. Rates of reductive release of the fluorophore from the non-fluorescent parent indolequinones (R=H, Me, thienyl) were similar under anoxia (~1.7 nmol coumarin min?¹mg protein?¹) reflecting the similarity in one-electron reduction potential. Whereas coumarin release from the indolequinone (R=H) was completely inhibited above 0.5% O2, the enhanced rate of reductive elimination when R=thienyl or Me increased the metabolic rate of release to ~0.35 and 0.7 nmol coumarin min?¹ mg protein?¹, respectively at 0.5% O2; complete inhibition occurring by 2.1% O2. Similar ‘oxygen profiles’ of release were observed with NADPH: cytochrome P450 reductase. In conclusion, it is possible to modify rates of reductive elimination from indolequinones to control the release of drugs over a range of tumour hypoxia.

    KW - Indolequinone

    KW - 7-Hydroxy-4-methylcoumarin

    KW - Reduction

    KW - Chemical kinetics

    KW - Semiquinone radical

    KW - Pulse radiolysis

    KW - MCF-7 breast tumour cells

    KW - NADPH

    KW - Cytochrome P450 reductase

    KW - Hypoxia

    U2 - 10.1016/S0006-2952(02)00885-7

    DO - 10.1016/S0006-2952(02)00885-7

    M3 - Article

    VL - 63

    SP - 1629

    EP - 1639

    JO - Biochemical Pharmacology

    JF - Biochemical Pharmacology

    SN - 0006-2952

    IS - 9

    ER -