Immunomodulatory mechanism of the aqueous extract of sword brake fern (Pteris ensiformis Burm.)

Sword brake fern (Pteris ensiformis Burm.) is an ingredient in most of the traditional herbal beverage formulas in Taiwan; however, no information is available to explain its bioactivity. The aim of this study is to elucidate the molecular pharmacological activity in the aqueous extract of sword brake fern (SBF). We found that SBF (0.05-0.25 mg/ml) slightly induced TNF-α, IL-6, NO (nitric oxide) and PGE2 (prostaglandin E2) production in unstimualted murine macrophages, RAW264.7 cells. Furthermore, SBF (0.05-0.25 mg/ml) dose-dependently suppressed LPS-induced TNF-α, IL-1β, IL-6, NO and PGE2 in activated RAW264.7 cells without exerting cytotoxicity. Further analysis of molecular mechanisms revealed that SBF prominently repressed LPS-induced iNOS (inducible nitric oxide synthase) and COX-2 (cyclooxygenase-2) promoter activities. Activation of the transcription factor NF-κB, which is one of the important pathways for transduction of LPS-stimulated inflammatory mediator producing signals, was suppressed by SBF in a dose-dependent manner, as demonstrated by both electrophoretic mobility shift assay (EMSA) and transfection with pNF-κB-Luc plasmid. These results suggest that SBF attenuates inflammatory mediator synthesis of activated macrophages partially through a NF-κB-dependent pathway. The immunomodulatory activity of SBF supports its traditional health promotion effect.