Amyotrophic lateral sclerosis (ALS) is a progressive disease associated with neuronal cell death that is thought to involve aberrant immune responses. Here we investigated the role of innate immunity in a mouse model of ALS. We found that inflammatory monocytes were activated and that their progressive recruitment to the spinal cord, but not brain, correlated with neuronal loss. We also found a decrease in resident microglia in the spinal cord with disease progression. Prior to disease onset, splenic Ly6C hi monocytes expressed a polarized macrophage phenotype (M1 signature), which included increased levels of chemokine receptor CCR2. As disease onset neared, microglia expressed increased CCL2 and other chemotaxis-associated molecules, which led to the recruitment of monocytes to the CNS by spinal cord-derived microglia. Treatment with anti-Ly6C mAb modulated the Ly6C hi monocyte cytokine profile, reduced monocyte recruitment to the spinal cord, diminished neuronal loss, and extended survival. In humans with ALS, the analogous monocytes (CD14 + CD16 -) exhibited an ALS-specific microRNA inflammatory signature similar to that observed in the ALS mouse model, linking the animal model and the human disease. Thus, the profile of monocytes in ALS patients may serve as a biomarker for disease stage or progression. Our results suggest that recruitment of inflammatory monocytes plays an important role in disease progression and that modulation of these cells is a potential therapeutic approach.

The ligand-activated transcription factor aryl hydrocarbon receptor (AHR) participates in the differentiation of FoxP3 + T reg , Tr1 cells, and IL-17-producing T cells (Th17). Most of our understanding on the role of AHR on the FoxP3 + T reg compartment results from studies using the toxic synthetic chemical 2,3,7,8-tetrachlorodibenzo-p-dioxin. Thus, the physiological relevance of AHR signaling on FoxP3 + T reg in vivo is unclear. We studied mice that carry a GFP reporter in the endogenous foxp3 locus and a mutated AHR protein with reduced affinity for its ligands, and found that AHR signaling participates in the differentiation of FoxP3 + T reg in vivo. Moreover, we found that treatment with the endogenous AHR ligand 2-(1′H-indole-3′-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) given parenterally or orally induces FoxP3 + T reg that suppress experimental autoimmune encephalomyelitis. ITE acts not only on T cells, but also directly on dendritic cells to induce tolerogenic dendritic cells that support FoxP3 + T reg differentiation in a retinoic acid-dependent manner. Thus, our work demonstrates that the endogenous AHR ligand ITE promotes the induction of active immunologic tolerance by direct effects on dendritic and T cells, and identifies nontoxic endogenous AHR ligands as potential unique compounds for the treatment of autoimmune disorders. R egulatory T cells (T reg ) that express the transcription factor FoxP3 control immune autoreactivity in healthy individuals (1). FoxP3 + T reg are generated in the thymus (natural T reg , nT reg ) and also in the periphery (induced T reg , iT reg ). The importance of FoxP3 + T reg for immunoregulation is highlighted by the immune disorders that result from their depletion or loss of function in both mice and humans (1). Conversely, the induction of FoxP3 + T reg is viewed as a promising approach for the treatment of immunemediated disorders (2).We (3) and others (4-8) have found that the ligand-activated transcription factor aryl hydrocarbon receptor (AHR) controls the differentiation of T reg , Tr1 cells (9), and IL-17-producing T cells (Th17) in vitro and in vivo. AHR activation by its high-affinity ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vivo results in the expansion of the CD4+ T reg compartment (3). These CD4+ T reg are functional and suppress the development of experimental autoimmune encephalomyelitis (EAE) (3), experimental autoimmune uveoretinitis (7), and spontaneous autoimmune diabetes (10).TCDD is a valuable tool to study the immunological effects of AHR activation, but TCDD is not a natural AHR ligand and its toxicity rules out its therapeutic use. Thus, it is not yet known whether there is a physiological role for AHR in FoxP3 + T reg , and whether nontoxic AHR ligands exist which can expand FoxP3 + T reg in vivo to treat autoimmunity. To address these questions, we used mice carrying a GFP reporter in foxp3 and a mutant AHR protein with reduced affinity for its ligands. In addition, we investigated the effect and mechanisms of action...

OBJECTIVE To investigate miR-155 in the SOD1 mouse model and human sporadic and familial amyotrophic lateral sclerosis (ALS). METHODS Nanostring microRNA, microglia and immune gene profiles, protein mass spectrometry and RNA-seq analyses were measured in spinal cord microglia, splenic monocytes and spinal cord tissue from SOD1 mice and in spinal cord tissue of familial and sporadic ALS. miR-155 was targeted by genetic ablation or by peripheral or centrally administered anti-miR-155 inhibitor in SOD1 mice. RESULTS In SOD1 mice we found loss of the molecular signature that characterizes microglia and increased expression of miR-155. There was loss of the microglial molecules P2ry12, Tmem119, Olfml3, transcription factors Egr1, Atf3, Jun, Fos, Mafb and the upstream regulators Csf1r, Tgfb1 and Tgfbr1 which are essential for microglial survival. Microglia biological functions were suppressed including phagocytosis. Genetic ablation of miR-155 increased survival in SOD1 mice by 51d in females and 27d in males and restored the abnormal microglia and monocyte molecular signatures. Disease severity in SOD1 males was associated with early upregulation of inflammatory genes including Apoe in microglia. Treatment of adult microglia with APOE suppressed the M0-unique microglia signature and induced a M1-like phenotype. miR-155 expression was increased in the spinal cord of both familial and sporadic ALS. Dysregulated proteins that we identified in human ALS spinal cord were restored in SOD1G93A/miR-155−/− mice. Intraventricular anti-miR-155 treatment derepressed microglial miR-155 targeted genes and peripheral anti-miR-155 treatment prolonged survival. INERPRETATION We found overexpression of miR-155 in the SOD1 mouse and in both sporadic and familial human ALS. Targeting miR-155 in SOD1 mice restores dysfunctional microglia and ameliorates disease. These findings identify miR-155 as a therapeutic target for the treatment of ALS.

Inflammation appears to be a necessity for both metastasis and elimination of tumor cells. IL-17, a proinflammatory cytokine produced by Th17 cells, contributes to both the processes by playing a dual role in the antitumor immunity. On one hand, IL-17 promotes an antitumor cytotoxic T cell response leading to tumor regression. On the other hand, by facilitating angiogenesis and egress of tumor cells from the primary focus, IL-17 promotes tumor growth. Thus, the therapeutic application that uses IL-17 needs to be refined by minimizing its protumor functions.