The Effects of Fisetin on Gene Expression Profile and Cellular Metabolism in IFN-γ-Stimulated Macrophage Inflammation

Although interferon-gamma (IFN-γ) is known as a critical factor in polarizing macrophages into the pro-inflammatory state for immune response, how dietary flavonoids regulate IFN-γ response for anti-inflammation is incompletely elucidated. This study aims to investigate the effect of fisetin, a typical flavonol, on the inhibition of IFN-γ-induced inflammation by RNA sequencing (RNA-Seq) and cellular metabolism analysis. RAW264 macrophages pretreated with fisetin following IFN-γ stimulation were subjected to RNA-Seq to analyze alterations in gene expression. Cellular signaling and transcription were investigated using enrichment analysis, motif analysis, and transcription factor prediction. Cellular metabolic state was assessed by measuring the oxygen consumption rate (OCR) and lactate level to reflect mitochondrial respiration and glycolysis. Alterations in signaling proteins were confirmed by Western blot. The results revealed that fisetin downregulated the IFN-γ-induced expression of pro-inflammatory genes and M1 marker genes such as <i>Cxcl9</i>, <i>Il6</i>, <i>Cd80</i>, <i>Cd86</i>, and <i>Nos2</i>. In cellular metabolism, fisetin upregulated the oxidative phosphorylation (OXPHOS) pathway, restored impaired OCR, and reduced lactate production induced by IFN-γ. Motif analysis suggested that fisetin suppressed the activation of IFN-regulatory factor 1 (IRF1). Western blot data further confirmed that fisetin inhibited the phosphorylation of Jak1, Jak2, and STAT1, and decreased the nuclear accumulation of phosphorylated STAT1 and IRF1 induced by IFN-γ. Taken together, our data revealed that fisetin is a potent flavonoid that attenuates IFN-γ-stimulated murine macrophage inflammation and ameliorates disrupted cellular metabolism with a possible Jak1/2-STAT1-IRF1 pathway.