Inhibitory Effect Of RXRα Ligand K-80003 On Liver Fibrosis And Identify Novel Modulators Of RXRα

In eukaryotic organisms,nuclear receptor is a very important class of proteins,regulating a variety of biological functions.In this study,we focused on the nuclear receptor RXRa as the research object,divided into two parts.RXRa is a member of the nuclear receptor family and can mediate a variety of biological functions including homeostasis,metabolic balance,cell differentiation,cell apoptosis and other functions,RXRa in the liver is highly expressed,and in the process of liver fibrosis,expression of RXRa is downregulation.Based on this,I found that RXRa ligand K-80003 can inhibit liver fibrosis,hoping to explain RXRa is how to participate in the regulation of liver fibrosis through K-80003.In this study,K-80003 can inhibit the activation of hepatic stellate cells and reduce the production of extracellular matrix at the cellular level.At the animal level,K-80003 can improve CCl4-induced liver injury and hepatic fibrosis induced by liver injury.In addition,K-80003 inhibits the transcriptional activation of Smad but does not affect the phosphorylation of Smad2/3 in the process of inhibiting the activation of hepatic stellate cells,further,I found that K-80003 decreased ATP levels by inhibiting RXRa,which led to AMPKa phosphorylation to inhibit the transcriptional activation of Smad and liver fibrosis.In addition,we discuss virtual screening and experimental validation identify novel modulators of nuclear receptor RXRa from Drugbank database.Retinoid X receptor alpha(RXRa),an important ligand-dependent transcription factor,is associated with various cancers and metabolic and neurodegenerative diseases.Therefore,it has been a crucial target in modern drug discovery.In this study,Drugbank 2.0 with 1280 old drugs were virtually screened by Glide according to the crystal structure of ligand-binding domain(LBP)of RXRa.15 compounds selected were tested for their binding and transcriptional activity toward RXRa by Biacore or reporter gene assay.The identified new scafford ligand of RXRa,Pitavastatin,was chemically optimized.Our results demonstrated that statin compounds Pitavastatin and Fluvastatin could bind to the LBP of RXRa(KD=13.30 μM and 11.04 μM,respectively)and serve as transcriptional antagonists of RXRa.On the contrary,Domperidone and Rosiglitazone maleate could bind to the LBP of RXRa(KD=8.80μM and 15.01μM,respectively)but serve as transcriptional agonists of RXRa.