Andrographolide prevents oxygen radical production by human neutrophils: possible mechanism(s) involved in its anti-inflammatory effect.
We have reported that andrographolide (ANDRO), an active component of Andrographis paniculata, inhibits inflammatory responses by rat neutrophils. To further elucidate the possible mechanism(s) underlying the ANDRO's effect, N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced adhesion and transmigration of isolated peripheral human neutrophils were studied. Pretreatment with ANDRO (0.1 - 10 microM) concentration-dependently prevented fMLP-induced neutrophil adhesion and transmigration. We further examined the up-expression of surface Mac-1 (CD11b/CD18), an essential integrin mediated in neutrophil adhesion and transmigration. ANDRO pretreatment significantly decreased fMLP-induced up-expression of both CD11b and CD18. Accumulation of reactive oxygen species (ROS) as well as quick intracellular calcium ([Ca(++)](i)) mobilization induced by fMLP displays two important signalling pathways in regulating the up-expression of Mac-1 by neutrophils. That ANDRO pretreatment diminished fMLP-induced production of H(2)O(2) and O(2)*(-), but failed to block that of [Ca(++)](i) mobilization suggested that the ROS but not [Ca(++)](i) signalling could be modulated by ANDRO. To clarify whether ROS production impeded by ANDRO could be an antagonism of fMLP binding, phorbol-12-myristate-13-acetate (PMA), a direct protein kinase C (PKC) activator, was introduced to activate ROS production. PMA triggered remarkable ROS production and adhesion, and were partially reversed by ANDRO. This indicated that a PKC-dependent mechanism might be interfered by ANDRO. We conclude that the prevention of ROS production through, at least in part, modulation of PKC-dependent pathway could confer ANDRO the ability to down-regulate Mac-1 up-expression that is essential for neutrophil adhesion and transmigration.
Shen
Yuh-Chiang
YC
National Research Institute of Chinese Medicine, 155-1, Li-Nung Street Section 2, Shih-Pai, Taipei 112, Taiwan.
Chen
Chieh-Fu
CF
Chiou
Wen-Fei
WF
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D004224:Diterpenes / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D016177:Macrophage-1 Antigen / Q000096:biosynthesis; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D004224:Diterpenes; D016177:Macrophage-1 Antigen; D017382:Reactive Oxygen Species; C030419:andrographolide; D002118:Calcium