title: Anti-inflammatory effects of Melaleuca alternifolia essential oil on human polymorphonuclear neutrophils and monocytes.
abstract: OBJECTIVE
  The fungicidal and bactericidal actions of the essential oil (EO) of Melaleuca alternifolia seem well established, but their anti-inflammatory and anti-oxidative effects remain unclear. In this study, we investigated in vitro the possible role of whole M. alternifolia EO as a modulator of the oxidative response, i.e. reactive oxygen species (ROS) production, of leukocytes (monocytes and polymorphonuclear neutrophils (PMNs)) in humans.
  
  
  METHODS
  Whole blood leukocytes from healthy human volunteers (n = 7), isolated from erythrocytes by haemolytic shock, were incubated for 30 min with M. alternifolia EO (0-0.1%) to determine their ROS production by flow cytometry with or without stimulation of cells. We compared the effects of 3 different stimulating agents acting differently on transductional pathways to stimulate the ROS production: a phorbol ester (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonised zymosan (OZ).
  
  
  RESULTS
  As attested by the Krüskall-Wallis test, M. alternifolia EO at 0.1% directly stimulated ROS production by PMNs (x 8.7 vs. 0% EO, p < 0.05) and increased the intracellular ROS produced by monocytes. Whichever the stimulating agent used (PMA, fMLP or OZ), M. alternifolia EO decreased the intracellular ROS production at the dilution of 0.1% by PMNs and monocytes, more so with PMNs.
  
  
  CONCLUSIONS
  M. alternifolia EO may be both a direct active mediator of the bactericidal action of the circulating leukocytes and may be efficient in protecting the organism from an excess of ROS, through an anti-oxidant and radical scavenging activity.
authors.affiliation: Laboratoire de Botanique, Cryptogamie et Microbiologie, Faculté des Sciences, Clermont-Ferrand, France. florence.caldefie-chezet@u-clermont1.fr
authors.forename: F
authors.initials: F
authors.lastname: Caldefie-Chézet
authors.forename: M
authors.initials: M
authors.lastname: Guerry
authors.forename: J C
authors.initials: JC
authors.lastname: Chalchat
authors.forename: C
authors.initials: C
authors.lastname: Fusillier
authors.forename: M P
authors.initials: MP
authors.lastname: Vasson
authors.forename: J
authors.initials: J
authors.lastname: Guillot
mesh_terms: D000893:Anti-Inflammatory Agents / Q000737:chemistry / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D031650:Melaleuca / Q000737:chemistry; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020947:Tea Tree Oil / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000893:Anti-Inflammatory Agents; D017382:Reactive Oxygen Species; D020947:Tea Tree Oil; D006861:Hydrogen Peroxide