Mechanistic investigation of PPARg-facilitated anti-asthmatic effects of Galangin (Norizalpinin): Insights from in silico and in vivo analyses Linda Jeeva Kumari Henry a, b , Mohan Kumar Ramar a, b , Selvamani Palanisamy a, b , Subramanian Natesan a, b , Ruckmani Kandasamy a, b, * a Laboratory of Pulmonary Research, National Facility for Drug Development (NFDD) for Academia, Pharmaceutical and Allied Industries, Bharathidasan Institute of Technology, Anna University, Tiruchirappalli, 620024, Tamil Nadu, India b Department of Pharmaceutical Technology, Centre for Excellence in NanobioTranslational Research (CENTRE), Bharathidasan Institute of Technology, Anna University, Tiruchirappalli, 620024, Tamil Nadu, India article info Article history: Received 7 March 2020 Accepted 27 March 2020 Available online xxx Keywords: PPARg Galangin Molecular docking Asthma GW9662 abstract Peroxisome proliferator-activated receptor gamma (PPARg) is a multifaceted ligand-activated tran- scription factor that regulates inflammatory responses in asthma pathophysiology. The present study corroborates PPARg-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 p- sigma bond (Arg288) with PPARg, contributing to the binding affinity and stability of the complex. In vivo studies explore the role of galangin as a propitious PPARg agonist in mitigating airway inflammation, thereby excluding ligand-independent action of PPARg. Accordingly, oral administration of galangin significantly ameliorated airway hyperresponsiveness, inflammation and goblet cell hyperplasia by the suppression of IL-4, 5, 13, 17, TNF-a, NO, ROS, EPO, IgE and increase of IFN-g in ovalbumin-induced allergic asthma model. PPARg expression (mRNA and protein) studies were performed to elucidate a possible mechanism by which galangin modulates. Furthermore, to eliminate PPARg-independent effects of galangin, a specific PPARg antagonist (GW9662) was administered, which dramatically reversed the effects of galangin on PPARg up-regulation, confirming the pleiotropic role of galangin as a PPARg agonist in asthma therapeutics. Taken together, our findings communicate that PPARg plays as a master regulator in the anti-asthmatic action of galangin. © 2020 Elsevier Inc. All rights reserved. 1. Introduction Asthma is a chronic inflammatory disease of the airways, affecting globally about 300 million people [1]. It is characterized by bronchoconstriction, caused by intermittent airflow obstruction, airway hyperresponsiveness and remodeling. Inflammatory re- sponses to triggers like inhaled allergens and non-specific stimuli are orchestrated by infiltration of inflammatory cells, activation of T-helper-2 (Th2) cytokines and production of several pro- inflammatory mediators [2]. Regulation of such inflammatory re- sponses relies on various potential mechanisms, one being the pleiotropic effects of peroxisome proliferator-activated receptor gamma (PPARg)[3]. PPARg is a nuclear hormone receptor which upon activation by natural/synthetic ligands acts as a transcription factor. Functionally, PPARg is a promising target for antidiabetic drugs that regulates glucose and lipid metabolism [3]. Neverthe- less, numerous reports reveal that activation of PPARg negatively regulates signaling pathways like nuclear factor-kB (NF-kB) and suppresses the expression of pro-inflammatory genes in inflam- matory cells, which may contribute to its anti-asthmatic potential [4,5]. Therefore, PPARg is a multifaceted therapeutic target for in- flammatory lung diseases like asthma. Exploring potent ligands of PPARg for clinical implications of asthma forms the rationale of the study. Several PPARg-targeting drugs such as thiazolidinediones (TZDs) are reported to have anti- asthmatic potential [6,7]. Rosiglitazone, a well known TZD is one of the specific PPARg agonists that can effectively attenuate airway inflammation in asthmatic mice model by activating PPARg/heme oxygenase-1(HO-1) [6], NF-kB and hypoxia-inducible factor (HIF)- * Corresponding author. Department of Pharmaceutical Technology, Centre for Excellence in Nanobio Translational Research (CENTRE), Bharathidasan Institute of Technology, Anna University, Tiruchirappalli, 620024, Tamil Nadu, India. E-mail addresses: ruckmani@aubit.edu.in, hodpharma@gmail.com (R. Kandasamy). Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc https://doi.org/10.1016/j.bbrc.2020.03.158 0006-291X/© 2020 Elsevier Inc. All rights reserved. Biochemical and Biophysical Research Communications xxx (xxxx) xxx Please cite this article as: L.J.K. Henry et al., Mechanistic investigation of PPARg-facilitated anti-asthmatic effects of Galangin (Norizalpinin): Insights from in silico and in vivo analyses, Biochemical and Biophysical Research Communications, https://doi.org/10.1016/j.bbrc.2020.03.158