The antifolate pemetrexed induces innate tolerance in human macrophages

Macrophage phenotypic and functional heterogeneity derives from tissue-specific transcriptional signatures shaped by the local microenvironment. GM-CSF drives the generation of human monocyte-derived macrophages with a potent pro-inflammatory activity upon stimulation. One-carbon metabolism (OCM) is a complex network of biosynthetic pathways that includes de novo biosynthesis of purines and thymidylate, amino acid metabolism, and methylation reactions. We explored the molecular impact of blocking OCM with the anti-folate pemetrexed (PMX) on the gene expression profile in LPS-activated GM-CSF-primed human monocyte derived macrophages. The specificity of blocking OCM with the anti-folate PMX was demonstrated with folinic acid. Overall design: mRNA profiles of human monocyte-derived macrophages exposed to 10 ng/ml LPS for 3h. Monocytes were cultured for 7 days containing GM-CSF (1000 U/ml) to generate GM-CSF-polarized macrophages (GM-MØ). GM-CSF was added every two days. Pemetrexed (PMX, 50 nM), folinic acid (FA, 5 µM) or both (PMX+FA) were added once on monocytes together with GM-CSF.