Macrophages and their monocyte precursors mediate innate immune responses and can promote a spectrum of phenotypes from pro-inflammatory to pro-resolving. Currently, there are few markers that allow for robust dissection of macrophage phenotype. We recently identified CD38 as a marker of inflammatory macrophages in murine in vitro and in vivo models. However, it is unknown whether CD38 plays a similar marker and/or functional role in human macrophages and inflammatory diseases. Here, we establish that CD38 transcript and protein are robustly induced in human macrophages exposed to LPS (±IFN-γ) inflammatory stimuli, but not with the alternative stimulus, IL-4. Pharmacologic and/or genetic CD38 loss-of-function significantly reduced the secretion of inflammatory cytokines IL-6 and IL-12p40 and glycolytic activity in human primary macrophages. Finally, monocyte analyses in systemic lupus erythematosus patients revealed that, while all monocytes express CD38, high CD38 expression in the non-classical monocyte subpopulation is associated with disease. These data are consistent with an inflammatory marker role for CD38 in human macrophages and monocytes.

No abstract

Multiple sclerosis is an autoimmune disease of the central nervous system (CNS) mediated by CD4+ T cells and modeled via experimental autoimmune encephalomyelitis (EAE). Inhibition of PRMT5, the major Type II arginine methyltransferase, suppresses pathogenic T cell responses and EAE. PRMT5 is transiently induced in proliferating memory inflammatory Th1 cells and during EAE. However, the mechanisms driving PRMT5 protein induction and repression as T cells expand and return to resting is currently unknown. Here, we used naive mouse and memory mouse and human Th1/Th2 cells as models to identify mechanisms controlling PRMT5 protein expression in initial and recall T cell activation. Initial activation of naive mouse T cells resulted in NF-κB-dependent transient Prmt5 transcription and NF-κB, mTOR and MYC-dependent PRMT5 protein induction. In murine memory Th cells, transcription and miRNA loss supported PRMT5 induction to a lesser extent than in naive T cells. In contrast, NF-κB/MYC/mTOR-dependent non-transcriptional PRMT5 induction played a major role. These results highlight the importance of the NF-κB/mTOR/MYC axis in PRMT5-driven pathogenic T cell expansion and may guide targeted therapeutic strategies for MS.

Multiple sclerosis (MS) is a debilitating autoimmune disease of the central nervous system (CNS) mediated by CD4+ T cells. Clinical data has provided evidence that MS patient T cells display an activated or memory phenotype and genome-wide association studies (GWAS) have identified single nucleotide polymorphisms linked to NF-kB complex and MYC genes in MS patients. These data imply a role for TcR (T cell receptor) signaling pathways in MS. PRMT5 is the major type II arginine methyltransferase catalyzing the symmetric dimethylation of histones and other proteins. Our lab has recently reported PRMT5 plays a crucial role in inflammatory T cell expansion and EAE disease. From cancer studies, we are aware of links between NF-kB/MYC signaling and PRMT5 induction. Here, we unravel the impact of NF-kB/MYC pathways in T cell PRMT5 expression and pathogenic T cell responses. We used naïve and memory mouse Th1/Th2 CD4+T cells as models to identify mechanisms controlling PRMT5 protein expression in initial and recall T cell activation. Naïve (initial) mouse T cell activation resulted in NF-kB-dependent transient Prmt5 transcription and NF-kB, mTOR and Myc-dependent PRMT5 protein induction. Recall activation in memory T cells showed rapid induction of PRMT5 protein expression, supported by both transcription and loss of Prmt5-targeting miRNAs. These results highlight the importance of the NF-kB/mTOR/MYC axis in PRMT5-driven pathogenic T cell expansion and may guide targeted therapeutic strategies for MS.

18 Protein Arginine Methyltransferase (PRMT) 5 catalyzes symmetric dimethylation of arginine, a 19 post-translational modification involved in cancer and embryonic development. However, the 20 role of PRMT5 in T helper (Th) cell polarization and Th cell-mediated disease has not yet been 21 elucidated. Here we report that PRMT5 is necessary for Th17 differentiation and EAE, via 22 enhancement of cholesterol biosynthesis and activation of ROR-γt. PRMT5 additionally controls 23 thymic and peripheral homeostasis in the CD4 Th cell life cycle, as well as iNK T and CD8 T cell 24 development or maintenance, respectively. Overall, our two conditional PRMT5 KO models that 25 selectively delete PRMT5 in all T cells (T-PRMT5 ∆/∆ ) or Th cells (iCD4-PRMT5 ∆/∆ ) unveil a crucial 26 role for PRMT5 in T cell proliferation, Th17 responses and disease. These results point to Th 27 PRMT5 and its downstream cholesterol biosynthesis pathway as promising therapeutic targets 28 in Th17-mediated diseases. 29 30