ML-7 inhibits exocytosis of superoxide-producing intracellular compartments in human neutrophils stimulated with phorbol myristate acetate in a myosin light chain kinase-independent manner.
ML-7, (5-iodonaphthalene-1-sulfonyl) homopiperazine, is commonly employed as a myosin light chain kinase (MLCK) inhibitor. In the present study, we demonstrated that ML-7 affects the superoxide (O(2)(-))-producing system of human neutrophils in an MLCK-independent manner. Human neutrophils were stimulated with phorbol myristate acetate (PMA), which does not activate MLCK. ML-7 inhibited extracellular release, but not intracellular production of O(2)(-) in the stimulated cells. Fluorescence microscopy revealed the generation of O(2)(-) at intracellular compartments in the stimulated cells exposed to ML-7. At the electron microscopic level, the reaction product of NADPH oxidase activity was found in intracellular compartments. ML-7 strongly inhibited the association of the oxidant-producing intracellular compartments with the plasma membrane. Furthermore, the upregulation of alkaline phosphatase activity, a marker enzyme of the oxidant-producing intracellular compartments, was also inhibited by ML-7. These findings indicate that ML-7 inhibits the fusion of the oxidant-producing intracellular compartments to the plasma membrane resulting in the inhibition of the extracellular release of O(2)(-) in PMA-stimulated human neutrophils in an MLCK-independent manner.
Department of Radiology, Kochi Medical School, Nankoku, 783-5305 Kochi, Japan.
Keita
K
Odani
Toshihiro
T
Kobayashi
Yasuhiro
Y
Ogawa
Shoji
S
Yoshida
Harumichi
H
Seguchi
D000469:Alkaline Phosphatase / Q000378:metabolism; D001381:Azepines / Q000494:pharmacology*; D015415:Biomarkers / Q000032:analysis; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects*; D006651:Histocytochemistry; D006801:Humans; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D019255:NADPH Oxidases / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology*; D018375:Neutrophil Activation / Q000187:drug effects / Q000502:physiology; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation
D001381:Azepines; D015415:Biomarkers; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D009281:Naphthalenes; C070571:ML 7; D013481:Superoxides; D019255:NADPH Oxidases; D009219:Myosin-Light-Chain Kinase; D000469:Alkaline Phosphatase; D013755:Tetradecanoylphorbol Acetate