Cutting Edge: Serpine1 Negatively Regulates Th1 Cell Responses in Experimental Autoimmune Encephalomyelitis.

Th1 cells are critical in experimental autoimmune encephalomyelitis (EAE). Serine protease inhibitor clade E1 (Serpine1) has been posited as an inhibitor of IFN-γ from T cells, although its role in autoimmunity remains unclear. In this study, we show that Serpine1 knockout (KO) mice develop EAE of enhanced severity relative to wild-type (WT) controls. Serpine1 overexpression represses Th1 cell cytokine production and pathogenicity, whereas Serpine1-KO:2D2 Th1 cells transfer EAE of increased severity in comparison with WT 2D2 Th1 cells. Notably, polarized Serpine1-KO Th1 cells display delayed expression of the Th1-specific inhibitory receptor, Tim-3 (T cell Ig and mucin-domain containing-3). Serpine1-KO:Tim-3-Tg Th1 cells, which transgenically overexpress Tim-3, showed increased expression of IFN-γ and reduced expression of the checkpoint molecules Lag-3 and PD-1 relative to WT Tim-3-Tg counterparts. Furthermore, Serpine1 deficiency restored the EAE phenotype of Tim-3-Tg mice that normally develop mild disease. Taken together, we identify Serpine1 as a negative regulator of Th1 cells.

Protein translocation and retro-translocation across the endoplasmic reticulum are crucial to inflammatory effector CD4+ T cell function.

Effector CD4+ T cells can be classified by the cytokines they secrete, with T helper 1 (Th1) cells generating interferon (IFN)γ and Th17 cells secreting interleukin (IL)-17. Both Th1 and Th17 cells are strongly implicated in the initiation and chronicity of autoimmune diseases such as multiple sclerosis. The endoplasmic reticulum (ER) has been implicated as a potentially crucial site in regulating CD4+ T cell function. Secretory and transmembrane proteins are shuttled into the ER via the Sec61 translocon, where they undergo appropriate folding; misfolded proteins are retro-translocated from the ER in a p97-dependent manner. Here, we provide evidence that both processes are crucial to the secretion of inflammatory cytokines from effector CD4+ T cells. The pan-ER inhibitor eeeyarestatin-1 (ESI), which interferes with both Sec61 translocation and p97 retro-translocation, inhibited secretion of interferon (IFN)γ, interleukin (IL)-2 and tumor necrosis factor (TNF)α from Th1 cells in a dose-dependent manner. Selective inhibition of Sec61 by Apratoxin A (ApraA) revealed that ER translocation is crucial for Th1 cytokine secretion, while inhibition of p97 by NMS-873 also inhibited Th1 function, albeit to a lesser degree. By contrast, none of ESI, ApraA or NMS-873 could significantly reduce IL-17 secretion from Th17 cells. ApraA, but not NMS-873, reduced phosphorylation of Stat1 in Th1 cells, indicating the involvement of ER translocation in Th1 differentiation pathways. ApraA had modest effects on activation of the Th17 transcription factor Stat3, while NMS-873 had no effect. Interestingly, NMS-873 was able to reduce disease severity in CD4+ T cell-driven experimental autoimmune encephalomyelitis (EAE). Together, our data indicate that CD4+ T cell function, and Th1 cell function in particular, is dependent on protein translocation and dislocation across the ER.

Myelin-reactive B cells exacerbate CD4+ T cell-driven CNS autoimmunity in an IL-23-dependent manner.

B cells and T cells collaborate in multiple sclerosis (MS) pathogenesis. IgH[MOG] mice possess a B cell repertoire skewed to recognize myelin oligodendrocyte glycoprotein (MOG). Here, we show that upon immunization with the T cell-obligate autoantigen, MOG[35-55], IgH[MOG] mice develop rapid and exacerbated experimental autoimmune encephalomyelitis (EAE) relative to wildtype (WT) counterparts, characterized by aggregation of T and B cells in the IgH[MOG] meninges and by CD4+ T helper 17 (Th17) cells in the CNS. Production of the Th17 maintenance factor IL-23 is observed from IgH[MOG] CNS-infiltrating and meningeal B cells, and in vivo blockade of IL-23p19 attenuates disease severity in IgH[MOG] mice. In the CNS parenchyma and dura mater of IgH[MOG] mice, we observe an increased frequency of CD4+PD-1+CXCR5- T cells that share numerous characteristics with the recently described T peripheral helper (Tph) cell subset. Further, CNS-infiltrating B and Tph cells from IgH[MOG] mice show increased reactive oxygen species (ROS) production. Meningeal inflammation, Tph-like cell accumulation in the CNS and B/Tph cell production of ROS were all reduced upon p19 blockade. Altogether, MOG-specific B cells promote autoimmune inflammation of the CNS parenchyma and meninges in an IL-23-dependent manner.

Selective Immunomodulatory and Neuroprotective Effects of a NOD2 Receptor Agonist on Mouse Models of Multiple Sclerosis.

The significance of monocytes has been demonstrated in multiple sclerosis (MS). One of the therapeutic challenges is developing medications that induce mild immunomodulation that is solely targeting specific monocyte subsets without affecting microglia. Muramyl dipeptide (MDP) activates the NOD2 receptor, and systemic MDP administrations convert Ly6Chigh into Ly6Clow monocytes. Here, we report selective immunomodulatory and therapeutic effects of MDP on cuprizone and experimental autoimmune encephalomyelitis (EAE) mouse models of MS. MDP treatment exerted various therapeutic effects in EAE, including delaying EAE onset and reducing infiltration of leukocytes into the CNS before EAE onset. Of great interest is the robust beneficial effect of the MDP treatment in mice already developing the disease several days after EAE onset. Finally, we found that the NOD2 receptor plays a critical role in MDP-mediated EAE resistance. Our results demonstrate that MDP is beneficial in both early and progressive phases of EAE. Based on these results, and upon comprehensive basic and clinical research, we anticipate developing NOD2 agonist-based medications for MS in the future.

Male sex chromosomal complement exacerbates the pathogenicity of Th17 cells in a chronic model of central nervous system autoimmunity.

Sex differences in multiple sclerosis (MS) incidence and severity have long been recognized. However, the underlying cellular and molecular mechanisms for why male sex is associated with more aggressive disease remain poorly defined. Using a T cell adoptive transfer model of chronic experimental autoimmune encephalomyelitis (EAE), we find that male Th17 cells induce disease of increased severity relative to female Th17 cells, irrespective of whether transferred to male or female recipients. Throughout the disease course, a greater frequency of male Th17 cells produce IFNγ, a hallmark of pathogenic Th17 responses. Intriguingly, XY chromosomal complement increases the pathogenicity of male Th17 cells. An X-linked immune regulator, Jarid1c, is downregulated in pathogenic male murine Th17 cells, and functional experiments reveal that it represses the severity of Th17-mediated EAE. Furthermore, Jarid1c expression is downregulated in CD4+ T cells from MS-affected individuals. Our data indicate that male sex chromosomal complement critically regulates Th17 cell pathogenicity.

Endogenous T Cell Receptor Rearrangement Represses Aggressive Central Nervous System Autoimmunity in a TcR-Transgenic Model on the Non-Obese Diabetic Background.

The T cell response to central nervous system (CNS) antigen in experimental autoimmune encephalomyelitis (EAE) permits one to model the immune aspects of multiple sclerosis. 1C6 transgenic mice on the non-obese diabetic (NOD) background possess a class II-restricted T cell receptor (TcR; Vα5-Vß7) specific for the encephalitogenic peptide myelin oligodendrocyte glycoprotein (MOG)[35-55]. It remains to be determined what role is played by allelic inclusion in shaping the TcR repertoire of these mice. Here, we show that 1C6 T cells display substantial promiscuity in their expression of non-transgenically derived Vα chains. Further, enforced expression of the transgenic TcR in 1C6 × Rag1-/- mice profoundly disrupted thymic negative selection and led to a sharp decrease in the number of mature peripheral T cells. 1C6 × Rag1-/- mice developed spontaneous EAE at a significant frequency and rapidly developed fatal EAE upon immunization with myelin oligodendrocyte glycoprotein (MOG)[35-55]. Passive transfer of 1C6 × Rag1+/+ CD4+ T cells, but not CD8+ T cells or B cells, partially rescued 1C6 × Rag1-/- mice from severe EAE. FoxP3+ CD4+ Treg cells were present in the CNS of immunized 1C6 mice, as well as immunized 1C6 × Rag1-/- that had been supplemented with 1C6 CD4+ T cells. However, they were not observed in 1C6 × Rag1-/- that did not receive Rag1-sufficient 1C6 CD4+. Further, in vivo blockade of Treg accelerated the onset of symptoms in 1C6 mice immunized with MOG[35-55], indicating the pertinence of Treg-mediated control of autoimmune inflammation in this model. Thus, TcR allelic inclusion is crucial to the generation of FoxP3+ CD4+ T cells necessary for the suppression of severe CNS autoimmunity.

Genetic disruption of the nuclear receptor Nur77 (Nr4a1) in rat reduces dopamine cell loss and l-Dopa-induced dyskinesia in experimental Parkinson's disease.

Parkinson's disease (PD) is an idiopathic progressive neurodegenerative disorder characterized by the loss of midbrain dopamine neurons. Levodopa (l-dopa) is the main pharmacological approach to relieve PD motor symptoms. However, chronic treatment with l-Dopa is inevitably associated with the generation of abnormal involuntary movements (l-Dopa-induced dyskinesia). We have previously shown that Nr4a1 (Nur77), a transcription factor of the nuclear receptor family, is closely associated with dopamine neurotransmission in the mature brain. However, the role of Nr4a1 in the etiology of PD and its treatment remain elusive. We report here that the neurotoxin 6-hydroxydopamine in rat lead to a rapid up-regulation of Nr4a1 in the substantia nigra. Genetic disruption of Nr4a1 in rat reduced neurotoxin-induced dopamine cell loss and l-Dopa-induced dyskinesia, whereas virally-driven striatal overexpression of Nr4a1 enhanced or partially restored involuntary movements induced by chronic l-Dopa in wild type and Nr4a1-deficient rats, respectively. Collectively, these results suggest that Nr4a1 is involved in dopamine cell loss and l-Dopa-induced dyskinesia in experimental PD.

Interferon-ß suppresses murine Th1 cell function in the absence of antigen-presenting cells.

Interferon (IFN)-ß is a front-line therapy for the treatment of the relapsing-remitting form of multiple sclerosis. However, its immunosuppressive mechanism of function remains incompletely understood. While it has been proposed that IFN-ß suppresses the function of inflammatory myelin antigen-reactive T cells by promoting the release of immunomodulatory cytokines such as IL-27 from antigen-presenting cells (APCs), its direct effects on inflammatory CD4+ Th1 cells are less clear. Here, we establish that IFN-ß inhibits mouse IFN-γ+ Th1 cell function in the absence of APCs. CD4+ T cells express the type I interferon receptor, and IFN-ß can suppress Th1 cell proliferation under APC-free stimulation conditions. IFN-ß-treated myelin antigen-specific Th1 cells are impaired in their ability to induce severe experimental autoimmune encephalomyelitis (EAE) upon transfer to lymphocyte-deficient Rag1-/- mice. Polarized Th1 cells downregulate IFN-γ and IL-2, and upregulate the negative regulatory receptor Tim-3, when treated with IFN-ß in the absence of APCs. Further, IFN-ß treatment of Th1 cells upregulates phosphorylation of Stat1, and downregulates phosphorylation of Stat4. Our data indicate that IFN-γ-producing Th1 cells are directly responsive to IFN-ß and point to a novel mechanism of IFN-ß-mediated T cell suppression that is independent of APC-derived signals.

Dimethyl sulfoxide induces both direct and indirect tau hyperphosphorylation.

Dimethyl sulfoxide (DMSO) is widely used as a solvent or vehicle for biological studies, and for treatment of specific disorders, including traumatic brain injury and several forms of amyloidosis. As Alzheimer's disease (AD) brains are characterized by deposits of ß-amyloid peptides, it has been suggested that DMSO could be used as a treatment for this devastating disease. AD brains are also characterized by aggregates of hyperphosphorylated tau protein, but the effect of DMSO on tau phosphorylation is unknown. We thus investigated the impact of DMSO on tau phosphorylation in vitro and in vivo. One hour following intraperitoneal administration of 1 or 2 ml/kg DMSO in mice, no change was observed in tau phosphorylation. However, at 4 ml/kg, tau was hyperphosphorylated at AT8 (Ser(202)/Thr(205)), PHF-1 (Ser(396)/Ser(404)) and AT180 (Thr(231)) epitopes. At this dose, we also noticed that the animals were hypothermic. When the mice were maintained normothermic, the effect of 4 ml/kg DMSO on tau hyperphosphorylation was prevented. On the other hand, in SH-SY5Y cells, 0.1% DMSO induced tau hyperphosphorylation at AT8 and AT180 phosphoepitopes in normothermic conditions. Globally, these findings demonstrate that DMSO can induce tau hyperphosphorylation indirectly via hypothermia in vivo, and directly in vitro. These data should caution researchers working with DMSO as it can induce artifactual results both in vivo and in vitro.