Abstract: NMB/NMBR had been involved in anti-influenza A virus (IAV/H1N1/PR8) infection by regulating the expression of cytokines. To explore the signaling pathway of NMB/NMBR against IAV/H1N1 infection, the MLE-12 cells and mice were infected with IAV/H1N1 subtype PR8 or WSN strain respectively, and the cells were treated with NF-κB inhibitor BAY11-7028 alone or in combination with NMB, meanwhile, the mice were injected with NMB or NMBRA. The expression profiles of NMB, NMBR, IL-6, IFN-α and NP genes in transcript levels were analyzed by the methods of RT-PCR and qRT-PCR, and the expression profiles of NMB, NMBR, P65/p-P65, IκBα and NP in protein levels were analyzed by Western blot. The results showed that the decreased expression levels of NMB, NMBR, IL-6 and IFN-α, and increased NP levels in MLE-12 cells after PR8 or WSN infection were induced by BAY11-7028 treatment. Meanwhile, the significantly decreased expression levels of NMB, NMBR and p-P65 proteins, and increased expression levels of IκBα and NP proteins were also induced by BAY11-7028. However, NMB combined with BAY11-7028 could induce a significant decrease in IL-6 and NP, and a significant increase in IFN-α in MLE-12 cells after PR8 or WSN infection. NMB could inhibit the expression of p-P65 and NP proteins, and promoted the expression level of IκBα protein in lung tissues of PR8 and WSN infected mice. NMBR inhibitor NMBRA combined with NMB could counteract the regulatory effects of NMB on the expression of these proteins after PR8 or WSN infection. These results suggest that NMB could regulate the phosphorylation of P65 protein and the expression of IκBα involved in NF-κB signaling pathway in PR8 or WSN infected MLE-12 cells and mice, and affect the expressions of downstream cytokines, IL-6 and IFN-α, thereby play the innate immune response against IAV/H1N1 infection.

Key words: neuromedin B(NMB), neuromedin B receptor(NMBR), influenza A virus H1N1, NF-κB