IRF5 regulates airway macrophage metabolic responses.

Interferon regulatory factor 5 (IRF5) is a master regulator of macrophage phenotype and a key transcription factor involved in expression of proinflammatory cytokine responses to microbial and viral infection. Here, we show that IRF5 controls cellular and metabolic responses. By integrating ChIP sequencing (ChIP-Seq) and assay for transposase-accessible chromatin using sequencing (ATAC)-seq data sets, we found that IRF5 directly regulates metabolic genes such as hexokinase-2 (Hk2). The interaction of IRF5 and metabolic genes had a functional consequence, as Irf5-/- airway macrophages but not bone marrow-derived macrophages (BMDMs) were characterized by a quiescent metabolic phenotype at baseline and had reduced ability to utilize oxidative phosphorylation after Toll-like receptor (TLR)-3 activation, in comparison to controls, ex vivo. In a murine model of influenza infection, IRF5 deficiency had no effect on viral load in comparison to wild-type controls but controlled metabolic responses to viral infection, as IRF5 deficiency led to reduced expression of Sirt6 and Hk2. Together, our data indicate that IRF5 is a key component of AM metabolic responses following influenza infection and TLR-3 activation.