Treatment of bone marrow-derived macrophages with hFc-FNDC4 recombinant protein

FNDC4 is a novel secreted factor sharing high homology with the exercise-associated myokine irisin (FNDC5). Here we report that Fndc4 is robustly upregulated in various mouse models of inflammation as well as in human inflammatory conditions. Specifically, subjects with inflammatory bowel disease show increased FNDC4 levels locally at inflamed sites of the intestine. Interestingly, administration of recombinant FNDC4 during colitis development in mice resulted in markedly reduced disease severity compared to mice injected with a control protein. Conversely, mice that lacked Fndc4 showed increased colitis severity. Analysis of binding of FNDC4 to different immune cell types revealed strong and specific binding to macrophages and monocytes. FNDC4 treatment of bone marrow-derived macrophages in vitro resulted in reduced phagocytosis, improved survival and reduced pro-inflammatory chemokine expression. Hence, treatment with FNDC4 resulted in a state of dampened macrophage activity, while enhancing their survival. Thus, we have characterized a novel factor with direct therapeutic potential in inflammatory bowel disease and possibly other inflammatory diseases. Bone marrow-derived macrophages were grown in growth media (DMEM, 10% FCS, 1% PenStrep and 20% L9209-media), starved for 24h in 1% FCS-DMEM and then treated for 24h in 1%FCS-DMEM with 100nM hFc-FNDC4 or hFc control protein.