[Effect of herba schizonepetae volatile oil (STO) on activity of 5-lipoxygenase in rat thoracic cavity leukocytes].
OBJECTIVE
To investigate the effect of herba schizonepetae volatile oil (STO) on the activity of 5-lipoxygenase (5-LO), so as to elucidate its mechanisms of anti-inflammatory action which is related to the arachidonic acid (AA) metabolism.


METHODS
Thoracic cavity leukocytes from the pleurisy model rat induced by injecting 1%-carrageenan into the pleural cavity were collected. Then 0. 4 mL cell suspension including 2 x 10(7) cells per millilitre were used as the reaction system in vitro. STO in different concentrations (final concentration 0.011, 0.022, 0.043, 0.087, 0.179, 0.255, 0.364 g x L(-1)), zileuton (final concentration 0.625 x 10(-3) g x L(-1)), and DMSO in the same volume were added into the reaction tube respectively. The reaction tubes were incubated at 37 degrees C for 20 min and CaCl2 (final concentration 2 mmol x L(-1)), MgCl2 (final concentration 0.5 mmol x L(-1)), exogenous AA (final concentration 200 micromol x L(-1)) and A23187 (final concentration 5 micromol x L(-1)) were added in turns during this period. The reaction tubes were mixed and continuously incubated at 37 degrees C for 30 min. After terminating reaction by adding methanol, the metabolites of 5-LO, leukotriene B4 (LTB4) and 5-hydroxy-6, 8, 11, 14-eicosatetraenoic acid (5-HETE), were extracted, separated and detected by means of RP-HPLC.


RESULTS
Compared with control group, STO significantly inhibited the biosynthesis of LTB4 and 5-HETE at final concentration between 0. 022 g x L(-1) and 0.364 g x L(-1) (P < 0.05 or 0.001) in dose dependence manner, and its IC50 value was 0.124 g x L(-1) and 0.142 g x L(-1) for LTB4 and 5-HETE, respectively.


CONCLUSIONS
STO can inhibited the activity of 5-LO, which is an important enzyme of AA metabolism, in rat thoracic cavity leukocytes in a dose-dependent manner in vitro. It is suggested that the mechanism of anti-inflammatory action of STO is related to its inhibiting the activity of 5-LO and decreasing the level of major inflammatory mediators LTB4.
Zhao
Lu
L
Department of Pharmacology, Chengdu Urtiversity of Traditional Chinese Medicine, Chengdu 611137, China.
Zeng
Nan
N
Tang
Yong-xin
YX
Liu
Xiao-shuai
XS
Yang
Xuan
X
Qu
Li-ping
LP
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D002478:Cells, Cultured; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D007962:Leukocytes / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D009822:Oils, Volatile / Q000494:pharmacology*; D010938:Plant Oils / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D035423:Thoracic Cavity / Q000187:drug effects / Q000201:enzymology / Q000276:immunology*
D000893:Anti-Inflammatory Agents; D004365:Drugs, Chinese Herbal; D009822:Oils, Volatile; D010938:Plant Oils; D001094:Arachidonate 5-Lipoxygenase