Cytokine Induced Phenotypic and Epigenetic Signatures Are Key to Establishing Specific Macrophage Phenotypes |
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| Authors: | Nicolai A Kittan Ronald M Allen Abhay Dhaliwal Karen A Cavassani Matthew Schaller Katherine A Gallagher William F Carson IV Sumanta Mukherjee Jolanta Grembecka Tomasz Cierpicki Gabor Jarai John Westwick Steven L Kunkel Cory M Hogaboam |
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| Institution: | 1. Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America.; 2. Division of Vascular Surgery, University of Michigan Hospital, Ann Arbor, Michigan, United States of America.; 3. Novartis Institutes of Biomedical Research, Respiratory Disease Area, Horsham, West Sussex, United Kingdom .; University Medical Center Freiburg, Germany, |
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| Abstract: | Macrophages (MΦ) play an essential role in innate immune responses and can either display a pro-inflammatory, classically activated phenotype (M1) or undergo an alternative activation program (M2) promoting immune regulation. M-CSF is used to differentiate monocytes into MΦ and IFN-γ or IL-4+IL-13 to further polarize these cells towards M1 or M2, respectively. Recently, differentiation using only GM-CSF or M-CSF has been described to induce a M1- or M2-like phenotype, respectively. In this study, we combined both approaches by differentiating human MΦ in GM-CSF or M-CSF followed by polarization with either IFN-γ or IL-4+IL-13. We describe the phenotypic differences between CD14hi CD163hi CD206int FOLR2-expressing M-CSF MΦ and CD14lo CD163lo CD206hi GM-CSF MΦ but show that both macrophage populations reacted similarly to further polarization with IFN-γ or IL-4+IL-13 with up- and down-regulation of common M1 and M2 marker genes. We also show that high expression of the mannose receptor (CD206), a marker of alternative activation, is a distinct feature of GM-CSF MΦ. Changes of the chromatin structure carried out by chromatin modification enzymes (CME) have been shown to regulate myeloid differentiation. We analyzed the expression patterns of CME during MΦ polarization and show that M1 up-regulate the histone methyltransferase MLL and demethylase KDM6B, while resting and M2 MΦ were characterized by DNA methyltransferases and histone deacetylases. We demonstrate that MLL regulates CXCL10 expression and that this effect could be abrogated using a MLL-Menin inhibitor. Taken together we describe the distinct phenotypic differences of GM-CSF or M-CSF MΦ and demonstrate that MΦ polarization is regulated by specific epigenetic mechanisms. In addition, we describe a novel role for MLL as marker for classical activation. Our findings provide new insights into MΦ polarization that could be helpful to distinguish MΦ activation states. |
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