Suppressing FXR promotes antiviral effects of bile acids via enhancing the interferon transcription

Bile acids(BAs)are natural metabolites in mammals and have the potential to function as drugs against viral infection.However,the limited understanding of chenodeoxycholic acid(CDCA)receptors and downstream signaling,along with its lower suppression efficiency in inhibiting virus infection limits its clinical application.In this study,we demonstrate that farnesoid X receptor(FXR),the receptor of CDCA,negatively regulates interferon signaling,thereby contributing to the reduced effectiveness of CDCA against virus replication.FXR deficiency or pharmacological inhibition enhances interferon signaling activation to suppress virus infection.Mechanistically,FXR impairs the DNA binding and transcriptional abilities of activated interferon regulatory factor 3(IRF3)through interaction.Reduced IRF3 transcriptional activity by FXReIRF3 interaction significantly undermines the expression of Interferon Beta 1(IFNB1)and the antiviral response of cells,especially upon the CDCA treatment.In FXR-deficient cells,or when combined with Z-guggulsterone(GUGG)treatment,CDCA exhibits a more potent ability to restrict virus infection.Thus,these findings suggest that FXR serves as a limiting factor for CDCA in inhibiting virus replication,which can be attributed to the“signaling-brake”roles of FXR in interferon signaling.Targeting FXR inhibition represents a promising pharmaceutical strategy for the clinical application of BAs metabolites as antiviral drugs.

Carrimycin inhibits coronavirus replication by decreasing the efficiency of programmed–1 ribosomal frameshifting through directly binding to the RNA pseudoknot of viral frameshift-stimulatory element

The pandemic of SARS-CoV-2 worldwide with successive emerging variants urgently calls for small-molecule oral drugs with broad-spectrum antiviral activity.Here,we show that carrimycin,a new macrolide antibiotic in the clinic and an antiviral candidate for SARS-CoV-2 in phase III trials,decreases the efficiency of programmed–1 ribosomal frameshifting of coronaviruses and thus impedes viral replication in a broad-spectrum fashion.Carrimycin binds directly to the coronaviral frameshift-stimulatory element(FSE)RNA pseudoknot,interrupting the viral protein translation switch from ORF1a to ORF1b and thereby reducing the level of the core components of the viral replication and transcription complexes.Combined carrimycin with known viral replicase inhibitors yielded a synergistic inhibitory effect on coronaviruses.Because the FSE mechanism is essential in all coronaviruses,carrimycin could be a new broad-spectrum antiviral drug for human coronaviruses by directly targeting the conserved coronaviral FSE RNA.This finding may open a new direction in antiviral drug discovery for coronavirus variants.