Ethnopharmacological relevance: There is growing inclination towards developing bioactive molecule-based strategies for the management of allergic airway inflammation associated respiratory diseases. Vitex negundo Linn., also known as Nirgundi, is one such medicinal plant enriched with phytochemicals and used for inflammatory and respiratory disorders including asthma in traditional system of medicine. Preliminary studies have claimed anti-tussive and bronchodilator potential of V. negundo Linn. However, its attributes as well as molecular mechanism (s) in modulation of asthma mediated by allergic inflammation are yet to be delineated scientifically.
Aim of the study: Present study attempted to assess the effectiveness of Vitex negundo leaf extract (VNLE) in mitigation of allergen induced inflammation associated asthmatic lung damage with emphasis to delineate its molecular mechanism (s).
Materials and methods: Allergic lung inflammation was established in Balb/c mice using Ovalbumin-lipopolysaccharide (OVA-LPS). Several allergic inflammatory parameters, histopathological changes, alveolar macrophage activation and signalling pathways were assessed to examine protective effects of VNLE. UHPLC-DAD-QTOF-ESI-IMS was used to characterize VLNE.
Results: VNLE administration effectively attenuated LPS-induced oxi-inflammatory stress in macrophages suggesting its anti-inflammatory potential. Further, VNLE showed protective effect in mitigating asthmatic lung damage as evident by reversal of pathological changes including inflammatory cell influx, congestion, fibrosis, bronchial thickness and alveolar collapse observed in allergen group. VNLE suppressed expressions of inflammatory Th1/Th2 cytokines, chemokines, endopeptidases (MMPs), oxidative effector enzyme (iNOS), adhesion molecules, IL-4/IFN-γ release with simultaneous enhancement in levels of IL-10, IFN-γ, MUC3 and tight junction proteins. Subsequent mechanistic investigation revealed that OVA-LPS concomitantly enhanced phosphorylation of NF-κB, PI3K, Akt and p38MAPKs and downregulated AMPK which was categorically counteracted by VNLE treatment. VNLE also suppressed OVA-LPS induced fibrosis, apoptosis, autophagy and gap junction proteins which were affirmed by reduction in TGF-β, Smad2/3/4, Caspase9/3, Bax, LC3A/B, connexin 50, connexin 43 and enhancement in Bcl2 expression. Additionally, suppression of alveolar macrophage activation, inflammatory cells in blood and elevation of splenic CD8+T cells was demonstrated. UHPLC-DAD-QTOF-ESI-IMS revealed presence of iridoids glycoside and phenolics which might contribute these findings.
Conclusion: These findings confer protective effect of VNLE in attenuation of allergic lung inflammation and suggest that it could be considered as valuable medicinal source for developing safe natural therapeutics for mitigation of allergic inflammation during asthma.
Keywords: Alveolar macrophages; Cytokine homeostasis; Gap junction proteins; OVA-LPS; Signalling cascade; UHPLC–DAD-QTOF–ESI-IMS; V. negundo.
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