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-kappa B (NF-kappa B) 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 kappa B kinase (IKK)beta and then infected with HRV-16. Effects on the NF-kappa B 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-kappa B p50 protein and recombinant IRF-1 to their recognition sequences from the CXCL10 promoter. NO also inhibited phosphorylation of the NF-kappa B inhibitor, I kappa B alpha, in HRV-16-infected cells. In addition, both NO and inhibitors of IKK beta inhibited viral induction of IRF-1 mRNA and protein. Conclusions: Nitric oxide blocks rhinovirus-mediated activation and nuclear translocation of both NF-kappa B 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-kappa B. (J Allergy Clin Immunol 2009;124:551-7.)