ERK1- and TBK1-targeted anti-inflammatory activity of an ethanol extract of Dryopteris crassirhizoma

Ethnopharmacological relevance: Dryopteris crassirhizoma Nakai (Aspiadaceae) has been traditionally used as an herbal medicine for treating various inflammatory and infectious diseases such as tapeworm infestation, colds, and viral diseases. However, no systematic studies on the anti-inflammatory actions of Dryopteris crassirhizoma and its inhibitory mechanisms have been reported. We therefore aimed at exploring the anti-inflammatory effects of 95% ethanol extracts (Dc-EE) of this plant. Materials and methods: The anti-inflammatory effect of Dc-EE on the production of inflammatory mediators in RAW264.7 cells and HCl/EtOH-induced gastritis was examined. Inhibitory mechanisms were also evaluated by exploring activation of transcription factors, their upstream signalling, and target enzyme activities. Finally, the active components from this extract were also identified using HPLC system. Results: Dc-EE diminished the production of nitric oxide (NO) and prostaglandin (PG)E₂ in lipopolysaccharide (LPS)-stimulated RAW264.7 cells in a dose-dependent manner. Dc-EE also downregulated the levels of mRNA expression of pro-inflammatory genes such as inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and TNF-α by inhibiting the activation of activator protein (AP-1) and IRF3. Indeed, the extract strongly blocked the activities of their upstream kinases ERK1 and TBK1. This extract also strongly ameliorated gastritis symptoms stimulated by HCl/EtOH in mice. According to HPLC fingerprinting, resveratrol, quercetin, and kampferol were identified from Dc-EE. Conclusion: Dc-EE displays strong anti-inflammatory activity by suppressing ERK/AP-1 and TBK1/IRF3 pathways, which contribute to its major ethno-pharmacological role as an anti-inflammatory and anti-infectious disease remedy.