Ethanolic Extract of Tridax procumbens Mitigates Pulmonary Inflammation via Inhibition of NF-κB/p65/ERK Mediated Signalling in an Allergic Asthma Model

Tridax procumbens is a traditionally used medicinal plant with high content of active phytoconstituents having anti-inflammatory activity. Accumulating evidences have shown that Tridax procumbens efficaciously diminished oxidative stress and inflammation. However the anti-inflammatory role of Tridax procumbens is not obscured in allergic asthma.Aim of this study was to decipher the anti-inflammatory role of Tridax procumbens in allergic asthma and its underlying mechanism.Ethanolic extract of Tridax procumbens (TP) was prepared and major phytoconstituents (flavonoids) were characterized by biochemical and UPLC/MS analysis. Rats were sensitized and challenged with environmental allergen ovalbumin (OVA) and lipopolysaccharide (LPS) to establish an allergic asthma model. Persuasive anti-inflammatory role of TP was demonstrated in vivo (100, 200 and 400 mg/kg) and in vitro (250, 125, 75 and 25 µg/ml) experiments.Characterization by UPLC/MS analysis showed the presence of various bioactive flavonoids. In in vitro study, significant reduction in ROS production, apoptosis and mitochondrial dysfunction were observed in alveolar type II cells upon pre-treatment with TP (250, 125, 75 and 25 µg/ml) in a concentration-dependant manner. In vivo, TP (200 mg/kg) oral administration showed robust anti-oxidative activity. TP treatment abrogated bronchial wall thickening, immune cell infiltration and bronchial wall fibre deposition. Immunohistochemical analysis showed the diminished expression of IL-1β, IL-6 in bronchial epithelium and vascular endothelium. TP abrogated inflammation by reducing the level of inflammatory cytokines including IL-2, IFN-γ, IL-6 and MCP-1, as well as inflammatory markers including TWEAK, TNF-α, TNF-R1 and its downstream transcription factor NF-ҡB/p65 activation and its nuclear translocation. Western blot analysis of TP treated lung tissue and alveolar type II cells showed reduced phosphorylation of ERK1/2 significantly.TP exhibited anti-inflammatory activity by inhibition of ROS production and down-regulation of NF-ҡB/ERK signalling in vitro and in vivo asthma model. Thus, TP can be envisaged as an effective anti-inflammatory agent for OVA-induced allergic asthma.