Anti-inflammatory effects of the ethyl acetate extract of Aquilaria crassna inhibits LPS-induced tumour necrosis factor-alpha production by attenuating P38 MAPK activation

Abstract

To study the inhibitory effect of the ethyl acetate extract of Aquilaria crassna on lipopolysaccharide (LPS)-induced tumour necrosis factor-alpha (TNF-α) secretion from isolated human peripheral blood mononuclear cells and its mechanisms of antiinflammation so as to provide some evidence for its traditional use. Human peripheral blood mononuclear cells (hPBMCs) were isolated from healthy volunteers. Cells, at a concentration of 1×106 cell/ml, were induced to secrete TNF-α by exposure to 10 ng/ml LPS in the presence and absence of the ethyl acetate extract of Aquilaria crassna. The TNF-α secretion in the collection medium was measured by enzyme-linked immunosorbent assay and the TNF-α gene expression was measured by reverse transcriptase-polymerase chain reaction. Determination of ERK1/2 MAPK and p38 MAPK activation were performedby Western blot analysis using a specific phosphorylated form of ERK1/2, p38 MAPK antibody. LPS at a concentration of 10 ng/ ml significantly increased in TNF-α secretion and was significantly inhibited when treated with 1.5 mg/ml ethyl acetate extract of Aquilaria crassna (P<0.05). Moreover, on treatment with 1.5 mg/ml, the extracts showed TNF-α gene expression inhibition. Co-treatment of the extract with LPS could not block p38 MAPK activation, but pre-treatment of the extracts significantly reduced the p38 MAPK phosphorylation without affecting the ERK1/2 MAPK activation (P<0.05). The ethyl acetate extract of Aquilaria crassna inhibits TNF-α gene expression and secretion in LPS-induced hPBMCs. This inhibitory effect apparently resulted from selectively attenuating the p38 MAPK activation. Key words: Anti-inflammatory, Aquilaria crassna, p38 MAPK, PBMCs, TNF-α