Activin-A limits Th17 pathogenicity and autoimmune neuroinflammation via CD39 and CD73 ectonucleotidases and Hif1-a -dependent pathways

In multiple sclerosis (MS), Th17 cells are critical drivers of autoimmune central nervous system (CNS) inflammation and demyelination. Th17 cells exhibit functional heterogeneity fostering both pathogenic and non-pathogenic, tissue-protective functions. Still, the factors that control Th17 pathogenicity remain incompletely defined. Here, using experimental autoimmune encephalomyelitis (EAE), an established mouse MS model, we report that therapeutic administration of activin-A ameliorates disease severity and alleviates CNS immunopathology and demyelination, associated with decreased activation of Th17 cells. In fact, activin-A signaling through activin-like kinase (ALK)4 receptor represses pathogenic transcriptional programs in Th17-polarized cells, while it enhances anti-inflammatory gene modules. Whole genome profiling and in vivo functional studies revealed that activation of the ATP-depleting CD39 and CD73 ectonucleotidases is essential for activin-A-induced suppression of the pathogenic signature and the encephalitogenic functions of Th17 cells. Mechanistically, aryl hydrocarbon receptor, along with STAT3 and c-Maf, are recruited to promoter elements on Entpd1 and Nt5e (encoding CD39 and CD73, respectively) and other anti-inflammatory genes, and control their expression in Th17 cells in response to activin-A. Notably, we show that activin-A negatively regulates the metabolic sensor, hypoxia-inducible factor-1? and key inflammatory proteins linked to pathogenic Th17 cell states. Of translational relevance, we demonstrate that activin-A is induced in the CNS of individuals with MS and restrains human Th17 cell responses. These findings uncover activin-A as a novel critical controller of Th17 cell pathogenicity that can be targeted for the suppression of autoimmune CNS inflammation. Overall design: RNA-sequencing libraries were generated for Th17 or act-A-Th17 cells using the Illumina's TruSeq RNA Library Preparation Kit v2 and the sequencing was implemented with HiSeq 2000 by the European Molecular Biology Laboratory.