title: Inhibition of human neutrophil protein kinase C activity by the antimalarial drug mefloquine.
abstract: Mefloquine (alpha-(2-piperidyl)-2,8-bis(trifluoromethyl)-4-quinolinemethanol) , an antimalarial drug, has been shown to inhibit human neutrophil functions, particularly oxygen-dependent bactericidal activity. Since calcium- and phospholipid-dependent protein kinase C (PKC) has a central role in the regulation of this function, we hypothesized that its activity might be altered by mefloquine. We found that mefloquine directly inhibited PKC in a dose-dependent manner, with an IC50 of 45 microM. This inhibition appeared to be non-competitive with respect to ATP, histone and phosphatidylserine. In addition, mefloquine inhibited the binding of [3H]phorbol 12,13 dibutyrate to PKC, indicating that it interacts with the regulatory domain of PKC. By contrast, mefloquine had little or no effect on neutrophil cAMP-dependent protein kinase or its catalytic subunit. Phorbol myristate acetate-induced protein phosphorylation in intact neutrophils was also inhibited by preincubation with mefloquine at concentrations similar to those inhibiting superoxide anion production. These data suggest that inhibition of neutrophil functions by mefloquine may be due to the inhibition of cellular PKC and that mefloquine could have further biological effects in situations in which PKC is involved.
authors.affiliation: Laboratoire d'Immunologie et d'Hématologie, INSERM U 294, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: el Benna
authors.forename: J
authors.initials: J
authors.lastname: Hakim
authors.forename: M T
authors.initials: MT
authors.lastname: Labro
mesh_terms: D004305:Dose-Response Relationship, Drug; D006801:Humans; D007700:Kinetics; D015767:Mefloquine / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D016897:Respiratory Burst / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D013481:Superoxides; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D015767:Mefloquine