Anti-Inflammatory Effect of Different Solvent Extracts from the Rhizome of Imperata Cylindrica on Lipopolysaccharide-Stimulated RAW264.7 Cells

Abstract

Background: Imperata cylindrica Beauv. var. major C. E. Hubb., a plant of Poaceae, is abundant in nature, and its rhizome has anti-inflammatory and anticancer activities. Aim: This study investigated the anti-inflammatory properties and signaling pathways of different solvent extracts from the rhizome of Imperata cylindrica (IMP) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Methods: Extracts with water, n-butanol, petroleum ether (PE), and ethyl acetate (EA) from the rhizome of IMP were incubated with LPS-stimulated RAW264.7 cells. CCK-8 (Cell Counting Kit-8) was used to perform in vitro cytotoxicity test to validate the concentration and reaction time of extracts. The experiment of scavenging superoxide anion free radical and DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical was applied to detect the antioxidant capacity and reducibility of different solvent extracts. RT-qPCR (real-time quantitative polymerase chain reaction) and ELISA (enzyme-linked immunosorbent assay) were applied to examine the impact of the drugs on LPS-induced IL-6 (Interleukin 6), IL-1β (Interleukin-1β), TNF-α (Tumour Necrosis Factor alpha), and iNOS (inducible nitric oxide synthase). The effectiveness of the extracts on the NF-κB (nuclear transcription factor-kappa B) and Nrf2 (Nuclear factor erythroid 2-related factor 2) signaling pathways induced by LPS was measured using western blot. Results: The appropriate action time and concentration of different solvent extracts were determined by cytotoxicity test for subsequent experiments. The various extracts effectively scavenged DPPH free radicals and had good antioxidant capacity, while their performance in scavenging superoxide anion was non-specific. Different IMP rhizome constituents significantly diminished the synthesis of IL-6, IL-1β, TNF-α, and iNOS in RAW264.7 cells, dramatically impeded the phosphorylation of the LPS-induced NF-κB signaling pathway and notably increased Nrf2 expression. Conclusions: This study found that various solvent extracts from the rhizome of IMP possessed antioxidant capacity and antiinflammatory activity on LPS-induced RAW264.7 cells, which may be provoked by suppressing the NF-κB and activating the Nrf2. Therefore, the rhizome of IMP has the potential to develop new therapeutic agents for treating inflammatory diseases.