Nitric oxide inhibits IFN regulatory factor 1 and nuclear factor-κB pathways in rhinovirus-infected epithelial cells

Background Nitric oxide (NO) has previously been shown to inhibit human rhinovirus (HRV) replication in airway epithelial cells and to inhibit rhinovirus-induced epithelial cytokine and chemokine production independently of its effects on viral replication by modulating nuclear translocation and binding of transcription factors. Objective To define the molecular mechanisms by which NO inhibits HRV-16–induced epithelial production of CXCL10 by affecting nuclear translocation and binding of nuclear factor-κB (NF-κB) and IFN regulatory factor 1 (IRF-1). Methods Cultured human airway epithelial cells were infected with HRV-16 in the absence or presence of a NO donor, or were preincubated with 2 highly selective inhibitors of inhibitor of κB kinase (IKK)β and then infected with HRV-16. Effects on the NF-κB and IRF-1 pathways were examined by using electrophoretic mobility shift assays, Western blotting, and real-time RT-PCR. Results Nitric oxide directly inhibited the binding of both recombinant NF-κB p50 protein and recombinant IRF-1 to their recognition sequences from the CXCL10 promoter. NO also inhibited phosphorylation of the NF-κB inhibitor, IκBα, in HRV-16–infected cells. In addition, both NO and inhibitors of IKKβ inhibited viral induction of IRF-1 mRNA and protein. Conclusions Nitric oxide blocks rhinovirus-mediated activation and nuclear translocation of both NF-κB and IRF-1. NO also directly inhibits the binding of each of these transcription factors to their respective recognition sites in the CXCL10 promoter. In addition, the ability of HRV-16 to induce epithelial expression of IRF-1 is dependent, at least in part, on viral activation of NF-κB.