Down-regulation of NF-κB signalling by methanolic extract of Viola odorata (L.) attenuated in vivo inflammatory and angiogenic responses.

Abstract

Intractable inflammation plays a key role in the progression of autoimmune diseases such as rheumatoid arthritis. Oedema and angiogenesis are the hall marks of chronic inflammation. The current study was aimed to investigate the pharmacological effects of the methanolic extract of Viola odorata (Vo.Me)on inflammation induced oedema and angiogenesis, and to identify the active principles and explore the molecular mechanisms thereof. Various models of inflammation were utilized in rats, including carrageenan- and histamine-induced acute oedema, as well as chronic models of Complete Freund's Adjuvant (CFA)-induced arthritis and cotton pellet-induced granuloma. Anti-angiogenic activity was evaluated by CAM assay followed by quantification of phytoconstituents through HPLC.Effect ofVo.Me treatment on the expression of various mediators (PGE-2 andNO) and genes (IL-1β, TNF-α,NF-κB, and COX-2) were explored byqPCR and ELISA assays.HPLCanalysis showed the presence of quercetin, chlorogenic acid, gallic acid, benzoic acid, m-coumaric acid, p-coumaric acid, synergic acid, caffeic acid, vanillic acid, sinapic acid, and cinnamic acid in Vo.Me. Significant dose-dependent inhibition of rats' paw oedema was observed in the Vo.Me administered groups (p < 0.05)in both acute and chronic inflammatory models. Moreover, at a dosage of 500mg/kg, Vo.Me exhibited a comparable anti-inflammatory effect to indomethacin (p > 0.05). Additionally, Vo.Me demonstrated a remarkable anti-granulomatous activity. Histopathological findings demonstrated amelioration of inflammation in animal paws which were treated with Vo.Meand indomethacin. CAM assay also displayed significant inhibitory effect of Vo.Me on the blood vasculature growth. Vo.Me treatment also causedrelatively less gastric irritation and hepatic damage as compared toindomethacin.At amolecular level, thedown-regulation of NF-κB signalling leading tothedecreased activation of pro-inflammatory mediators (such as IL-1β, TNF-α, and COX-2) and their downstream molecules including prostaglandin E-2 (PGE-2) and nitric oxide (NO), is suggested to be responsible for these diverse anti-inflammatory effects. These findings confirmed the promising anti-inflammatory and anti-angiogenic activities of Vo.Me, which warrant bench-to-bedside translational studies to assess its safety and suitability for clinical usage.