Anti-Inflammatory Activity of Populus deltoides Leaf Extract via Modulating NF-kappa B and p38/JNK Pathways

Abstract

Populus deltoides, known as eastern cottonwood, has been commonly used as a medicinal plant. The aim of the present study was to investigate the mechanism underlying the anti-inflammatory activity of P. deltoides leaf extract (PLE). PLE effectively inhibited the expression of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, but not that of cyclooxygenase-2 (COX-2) and prostaglandin E2. Proinflammatory tumor necrosis factor alpha (TNF-alpha) levels were also reduced by the extract. PLE inhibited the phosphorylation of nuclear factor-kappa B (NF-kappa B) and inhibitor of Kappa B alpha (I kappa B alpha), and blunted LPS-triggered enhanced nuclear translocation of NF-kappa B p65. In mitogen-activated protein kinase (MAPK) signaling, PLE effectively decreased the phosphorylation of p38 and c-Jun N-terminal protein kinase (JNK), but not of extracellular signal-regulated kinase 1/2 (ERK1/2). Taken together, these results suggest that anti-inflammatory activity of P. deltoides leaf extract might be driven by iNOS and NO inhibition mediated by modulation of the NF-kappa B and p38/JNK signaling pathways.