Fenamates as TRP channel blockers: mefenamic acid selectively blocks TRPM3

Authors

  • Chihab Klose,

    1. Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Interfaculty Center of Pharmacogenomics and Pharmaceutical Research (ICePhA), Eberhard-Karls-University, Tübingen, Germany
    2. Molecular Pharmacology and Cell Biology, Charité, Berlin, Germany
    3. Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin, Berlin, Germany
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    • The first two authors contributed equally to the work.

  • Isabelle Straub,

    1. Molecular Pharmacology and Cell Biology, Charité, Berlin, Germany
    2. Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Leipzig, Germany
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    • The first two authors contributed equally to the work.

  • Marc Riehle,

    1. Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Interfaculty Center of Pharmacogenomics and Pharmaceutical Research (ICePhA), Eberhard-Karls-University, Tübingen, Germany
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  • Felicia Ranta,

    1. Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Medicine, Nephrology, and Clinical Chemistry, Eberhard-Karls-University, Tübingen, Germany
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  • Dietmar Krautwurst,

    1. Deutsche Forschungsanstalt für Lebensmittelchemie, Molekulare Zellphysiologie und Chemorezeption, Freising, Germany
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  • Susanne Ullrich,

    1. Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Medicine, Nephrology, and Clinical Chemistry, Eberhard-Karls-University, Tübingen, Germany
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  • Wolfgang Meyerhof,

    1. Abteilung Molekulare Genetik, Deutsches Institut für Ernährungsforschung Potsdam-Rehbrücke, Nuthetal, Germany
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  • Christian Harteneck

    Corresponding author
    1. Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Interfaculty Center of Pharmacogenomics and Pharmaceutical Research (ICePhA), Eberhard-Karls-University, Tübingen, Germany
    2. Molecular Pharmacology and Cell Biology, Charité, Berlin, Germany
      Dr Christian Harteneck, Institute of Pharmacology and Toxicology, Eberhard-Karls-Universität, Wilhelmstr. 56, 72074 Tübingen, Germany. E-mail: christian.harteneck@uni-tuebingen.de
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Dr Christian Harteneck, Institute of Pharmacology and Toxicology, Eberhard-Karls-Universität, Wilhelmstr. 56, 72074 Tübingen, Germany. E-mail: christian.harteneck@uni-tuebingen.de

Abstract

BACKGROUND AND PURPOSE Fenamates are N-phenyl-substituted anthranilic acid derivatives clinically used as non-steroid anti-inflammatory drugs in pain treatment. Reports describing fenamates as tools to interfere with cellular volume regulation attracted our attention based on our interest in the role of the volume-modulated transient receptor potential (TRP) channels TRPM3 and TRPV4.

EXPERIMENTAL APPROACH Firstly, we measured the blocking potencies and selectivities of fenamates on TRPM3 and TRPV4 as well as TRPC6 and TRPM2 by Ca2+ imaging in the heterologous HEK293 cell system. Secondly, we further investigated the effects of mefenamic acid on cytosolic Ca2+ and on the membrane voltage in single HEK293 cells that exogenously express TRPM3. Thirdly, in insulin-secreting INS-1E cells, which endogenously express TRPM3, we validated the effect of mefenamic acid on cytosolic Ca2+ and insulin secretion.

KEY RESULTS We identified and characterized mefenamic acid as a selective and potent TRPM3 blocker, whereas other fenamate structures non-selectively blocked TRPM3, TRPV4, TRPC6 and TRPM2.

CONCLUSIONS AND IMPLICATIONS This study reveals that mefenamic acid selectively inhibits TRPM3-mediated calcium entry. This selectivity was further confirmed using insulin-secreting cells. KATP channel-dependent increases in cytosolic Ca2+ and insulin secretion were not blocked by mefenamic acid, but the selective stimulation of TRPM3-dependent Ca2+ entry and insulin secretion induced by pregnenolone sulphate were inhibited. However, the physiological regulator of TRPM3 in insulin-secreting cells remains to be elucidated, as well as the conditions under which the inhibition of TRPM3 can impair pancreatic β-cell function. Our results strongly suggest mefenamic acid is the most selective fenamate to interfere with TRPM3 function.

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