Mechanistic investigation of PPARγ-facilitated anti-asthmatic effects of Galangin (Norizalpinin): Insights from in silico and in vivo analyses

Abstract

Peroxisome proliferator-activated receptor gamma (PPARγ) is a multifaceted ligand-activated transcription factor that regulates inflammatory responses in asthma pathophysiology. The present study corroborates PPARγ-mediated anti-asthmatic action of the flavonoid, galangin (norizalpinin). In silico molecular interactions reveal that galangin formed three H-bonds (Glu291, Leu340 and Ser342) and a π-sigma bond (Arg288) with PPARγ, contributing to the binding affinity and stability of the complex. In vivo studies explore the role of galangin as a propitious PPARγ agonist in mitigating airway inflammation, thereby excluding ligand-independent action of PPARγ. Accordingly, oral administration of galangin significantly ameliorated airway hyperresponsiveness, inflammation and goblet cell hyperplasia by the suppression of IL-4, 5, 13, 17, TNF-α, NO, ROS, EPO, IgE and increase of IFN-γ in ovalbumin-induced allergic asthma model. PPARγ expression (mRNA and protein) studies were performed to elucidate a possible mechanism by which galangin modulates. Furthermore, to eliminate PPARγ-independent effects of galangin, a specific PPARγ antagonist (GW9662) was administered, which dramatically reversed the effects of galangin on PPARγ up-regulation, confirming the pleiotropic role of galangin as a PPARγ agonist in asthma therapeutics. Taken together, our findings communicate that PPARγ plays as a master regulator in the anti-asthmatic action of galangin.

Keywords: Asthma; GW9662; Galangin; Molecular docking; PPARγ.