Macrophages are exquisite sensors of tissue homeostasis that can rapidly switch between pro- and anti-inflammatory or regulatory modes to respond to perturbations in their microenvironment. This functional plasticity involves a precise orchestration of gene expression patterns whose transcriptional regulators have not been fully characterized. We had previously identified the transcription factor NFAT5 as an activator of TLR-induced responses, and in this study we explore its contribution to macrophage functions in different polarization settings. We found that both in classically and alternatively polarized macrophages, NFAT5 enhanced functions associated with a proinflammatory profile such as bactericidal capacity and the ability to promote Th1 polarization over Th2 responses. In this regard, NFAT5 upregulated the Th1-stimulatory cytokine IL-12 in classically activated macrophages, whereas in alternatively polarized ones it enhanced the expression of the pro-Th1 mediators Fizz-1 and arginase 1, indicating that it could promote proinflammatory readiness by regulating independent genes in differently polarized macrophages. Finally, adoptive transfer assays in vivo revealed a reduced antitumor capacity in NFAT5-deficient macrophages against syngeneic Lewis lung carcinoma and ID8 ovarian carcinoma cells, a defect that in the ID8 model was associated with a reduced accumulation of effector CD8 T cells at the tumor site. Altogether, detailed analysis of the effect of NFAT5 in pro- and anti-inflammatory macrophages uncovered its ability to regulate distinct genes under both polarization modes and revealed its predominant role in promoting proinflammatory macrophage functions.

This work was supported by grants from the Spanish Ministry of Economy and Competitiveness and Fondo Europeo de Desarrollo Regional/European Fund for Regional Development (SAF2012-36535, and SAF2015-71363-R) and Fundació la Marató TV3 (1225-30 and 201619-30). We also acknowledge funding support from Generalitat de Catalunya (Grant 2014SGR1153) and the Spanish Ministry of Economy and Competitiveness through the María de Maeztu Program for Units of Excellence in Research and Development (Grant MDM-2014-0370). M.T. was supported by fellowships from Fundació Catalunya-La Pedrera (2011) and Generalitat de Catalunya (Formació Investigadors-Direcció General de Recerca program 2013). S.T. was supported by a predoctoral fellowship of the Spanish Ministry of Economy and Competitiveness (Grant BES-2013-062670). C.L.-R. is a recipient of an Institució Catalana de Recerca i Estudis Avançats (Generalitat de Catalunya) Acadèmia Award.