| Respiratory syncytial virus(RSV)infection is a major cause of hospitalization for infants,immunocompromised individuals,and the elderly due to acute lower respiratory tract inflammation.RSV primarily infects airway epithelial cells,triggering respiratory infections.To counter viral infections,the host innate immune system is activated,inducing pulmonary immune or inflammatory mediators such as cytokines,chemokines,and interferons(IFNs).Among these,interferons play a crucial role in antiviral immunity,with IFN-λ plays a pivotal role in the suppression of respiratory viruses.However,RSV can suppress IFN-λ production in lung epithelial cells,making it imperative to investigate the mechanisms by which RSV inhibits its expression to fully harness the antiviral and immunoregulatory capabilities of interferons.Increasingly,studies have indicated that interferons are regulated by the combined action of various receptors and Reactive Oxygen Species(ROS)signaling.RSV infection rapidly induces the production of ROS in respiratory epithelial cells,utilizing ROS for immune evasion.This suggests that RSV may inhibit interferon expression through ROS,and the specific mechanism requires further investigation.ROS can attack DNA,producing 8-oxo-7,8-dihydroguanine(8-oxo G),which not only serves as a primary marker of oxidative stress but also functions as an epigenetic marker involved in the transcriptional regulation of many genes under the control of the repair enzyme 8-oxoguanine DNA glycosylase 1(OGG1).Studies have shown that mice lacking OGG1 protein exhibit increased interferon expression.Therefore,it remains to be explored whether ROS and OGG1 are involved in the regulation of interferon expression after RSV infection and the specific mechanisms involved.This study found that:(1)Functional loss of OGG1,achieved through CRISPR Cas9 gene knockout,si RNA-mediated OGG1 m RNA interference,the use of the small molecule inhibitor TH5487 to inhibit OGG1 binding to 8-oxo G,significantly increased expression of IFN-λ2/3 in RSV-infected epithelial cells.And under Poly(I:C)stimulation conditions,loss of OGG1 function also promoted IFN-λ2/3 expression.(2)Chromatin immunoprecipitation(ChIP)and Immunoprecipitation(IP)experiments revealed that,OGG1 cysteine residues are oxidized and OGG1 binds to 8-oxo G near the Interferon-stimulated response element(ISRE)following RSV infection in the early stages,promoting the binding of the transcriptional repressor p50-p50 homodimer to the IFN-λ2/3 promoter,thereby inhibiting the binding of the transcription factor IRF3 and IRF7 to DNA and suppressing IFN-λ transcription.After RSV infection in the late stages,OGG1 was induced to undergo O-Glc NAc modification that inhibiting OGG1 binding to 8-oxo G and facilitating the binding of transcription factors IRF3 and IRF7,promoting expression of IFN-λ2/3.(3)Electrophoretic mobility shift assay(EMSA)further demonstrated that OGG1 promotes the binding of the transcriptional repressor p50-p50 homodimer binding to the IFN-λ2/3 promoter while inhibiting transcription factor IRF3 DNA occupancy.(4)Using a RSV-infected mouse model of bronchiolitis,we found that functional ablation of OGG1 by a small molecule inhibitor(TH5487)enhances IFN-λ production in lung,promotes the expression of interferon stimulated genes(ISGs),inhibits virus replication,decreases immunopathology,neutrophilia,and confers antiviral protection,with similar therapeutic effects to recombinant IFN-λ2(r IFN-λ2).These findings indicate that ROS-generated epigenetic mark 8-oxo Gua via its reader OGG1 serves as a homeostatic thresholding factor in IFN-λ expression.This unveils the mechanism by which RSV utilizes ROS to inhibit IFN-λ expression and evade immunity.Moreover,the OGG1 inhibitor TH5487 holds clinical application value in the field of combating RSV infections,laying the foundation for exploring molecular mechanisms of immune evasion by other viruses. |
