Poly I:C enhances production of nitric oxide in response to interferon-γ via upregulation of interferon regulatory factor 7 in vascular endothelial cells

• Poly I:C enhances IFN-gamma-induced NO production in vascular endothelial cells.
• Poly I:C enhances the expression of an inducible NO synthase protein.
• Poly I:C enhances the activation of interferon-regulatory factor 7.
• Poly I:C enhances IFN-gamma-induced NO production via IRF7 activation.

The effect of poly I:C on interferon (IFN)-γ-induced nitric oxide (NO) production in vascular endothelial cells was examined using murine aortic endothelial END-D cells. Poly I:C augmented IFN-γ-induced NO production although it alone did not induce the NO production. Poly I:C augmented the NO production via enhanced expression of an inducible NO synthase protein. Poly I:C did not affect the activation of Janus kinase (JAK) 1/2, and signal transducer and activator of transcription (STAT) 1 in IFN-γ signaling. Moreover, there was no significant difference in the IFN-γ-induced interferon regulatory factor (IRF) 1 expression between the presence and absence of poly I:C. Poly I:C led to the activation of IRF7 in END-D cells. Inhibition of poly I:C signaling by amlexanox, an inhibitor of TANK-binding kinase (TBK) 1 and IκB kinase (IKK) ε, abolished the augmentation of IFN-γ-induced NO production. Therefore, poly I:C was suggested to augment IFN-γ-induced NO production at the transcriptional level via enhanced IRF7 activation.