Synthetic secoisolariciresinol diglucoside (LGM2605) inhibits myeloperoxidase activity in inflammatory cells

• Published in: Biochimica et biophysica acta Vol. 1862; no. 6; pp. 1364 - 1375
• Main Authors: Mishra, Om P., Popov, Anatoliy V., Pietrofesa, Ralph A., Nakamaru-Ogiso, Eiko, Andrake, Mark, Christofidou-Solomidou, Melpo
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2018
• Subjects: Animals; Butylene Glycols - pharmacology; Catalysis; Cells, Cultured; chlorination; electron paramagnetic resonance spectroscopy; fluorescein; Gene Expression Regulation, Enzymologic - drug effects; Glucosides - pharmacology; Humans; Hypochlorite ion; Hypochlorous acid; inflammation; Leukocytes - drug effects; Leukocytes - enzymology; LGM2605; Macrophages; Macrophages - drug effects; Macrophages - enzymology; Mice; Mice, Inbred C57BL; Myeloperoxidase; Neutrophils - drug effects; Neutrophils - enzymology; Oxidation-Reduction; peroxidase; Peroxidase - antagonists & inhibitors; porphyrins; SDG; taurine; PBS; RFU; Hypochlorous acid; PMA; EPR; ClO; H2O2; Macrophages; MPO; LGM2605; LPS; ACS; HOCl; Hypochlorite ion; APF; ROS; SDG; OH; Myeloperoxidase; SEM; ELISA
• ISSN: 0304-4165; 0006-3002; 1872-8006; 1878-2434
• DOI: 10.1016/j.bbagen.2018.03.003

Myeloperoxidase (MPO) generates hypochlorous acid (HOCl) during inflammation and infection. We showed that secoisolariciresinol diglucoside (SDG) scavenges radiation-induced HOCl in physiological solutions. However, the action of SDG and its synthetic version, LGM2605, on MPO-catalyzed generation of HOCl is unknown. The present study evaluated the effect of LGM2605 on human MPO, and murine MPO from macrophages and neutrophils. MPO activity was determined fluorometrically using hypochlorite-specific 3′-(p-aminophenyl) fluorescein (APF). The effect of LGM2605 on (a) the peroxidase cycle of MPO was determined using Amplex Red while the effect on (b) the chlorination cycle was determined using a taurine chloramine assay. Using electron paramagnetic resonance (EPR) spectroscopy we determined the effect of LGM2605 on the EPR signals of MPO. Finally, computational docking of SDG was used to identify energetically favorable docking poses to enzyme's active site. LGM2605 inhibited human and murine MPO activity. MPO inhibition was observed in the absence and presence of Cl−. EPR confirmed that LGM2605 suppressed the formation of Compound I, an oxoiron (IV) intermediate [Fe(IV)O] containing a porphyrin π-radical of MPO's catalytic cycle. Computational docking revealed that SDG can act as an inhibitor by binding to the enzyme's active site. We conclude that LGM2605 inhibits MPO activity by suppressing both the peroxidase and chlorination cycles. EPR analysis demonstrated that LGM2605 inhibits MPO by decreasing the formation of the highly oxidative Compound I. This study identifies a novel mechanism of LGM2605 action as an inhibitor of MPO and indicates that LGM2605 may be a promising attenuator of oxidant-dependent inflammatory tissue damage. •Synthetic SDG (LGM2605) inhibits myeloperoxidase (MPO) activity in murine inflammatory cells and human MPO.•LGM2605 directly interferes with Compound I an oxoiron (IV) intermediate [Fe(IV) = O], on the catalytic cycle of MPO•SDG inhibits MPO by interacting at the active site of MPO decreasing damaging HOCl formation.•This study identified MPO inhibition as a novel mechanism of LGM2605 action.•LGM2605 is a promising potential attenuator of oxidant-dependent inflammatory tissue damage.