The prolyl hydroxylase PHD3 identifies proinflammatory macrophages and its expression is regulated by activin A.
Modulation of macrophage polarization underlies the onset and resolution of inflammatory processes, with polarization-specific molecules being actively sought as potential diagnostic and therapeutic tools. Based on their cytokine profile upon exposure to pathogenic stimuli, human monocyte-derived macrophages generated in the presence of GM-CSF or M-CSF are considered as proinflammatory (M1) or anti-inflammatory (M2) macrophages, respectively. We report in this study that the prolyl hydroxylase PHD3-encoding EGLN3 gene is specifically expressed by in vitro-generated proinflammatory M1(GM-CSF) human macrophages at the mRNA and protein level. Immunohistochemical analysis revealed the expression of PHD3 in CD163(+) lung macrophages under basal homeostatic conditions, whereas PHD3(+) macrophages were abundantly found in tissues undergoing inflammatory responses (e.g., Crohn's disease and ulcerative colitis) and in tumors. In the case of melanoma, PHD3 expression marked a subset of tumor-associated macrophages that exhibit a weak (e.g., CD163) or absent (e.g., FOLR2) expression of typical M2-polarization markers. EGLN3 gene expression in proinflammatory M1(GM-CSF) macrophages was found to be activin A dependent and could be prevented in the presence of an anti-activin A-blocking Ab or inhibitors of activin receptor-like kinase receptors. Moreover, EGLN3 gene expression was upregulated in response to hypoxia only in M2(M-CSF) macrophages, and the hypoxia-mediated upregulation of EGLN3 expression was significantly impaired by activin A neutralization. These results indicate that EGLN3 gene expression in macrophages is dependent on activin A both under basal and hypoxic conditions and that the expression of the EGLN3-encoded PHD3 prolyl hydroxylase identifies proinflammatory macrophages in vivo and in vitro.
Laboratorio de Células Mieloides, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid 28040, Spain. mescribese@cib.csic.es
María M
MM
Escribese
Elena
E
Sierra-Filardi
Concha
C
Nieto
Rafael
R
Samaniego
Carmen
C
Sánchez-Torres
Takami
T
Matsuyama
Elisabeth
E
Calderon-Gómez
Miguel A
MA
Vega
Azucena
A
Salas
Paloma
P
Sánchez-Mateos
Angel L
AL
Corbí
D028341:Activins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015153:Blotting, Western; D049308:Dioxygenases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D007150:Immunohistochemistry; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology; D018613:Microscopy, Confocal; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
C422405:activin A; D028341:Activins; D049308:Dioxygenases; C488894:EGLN3 protein, human; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases