Role and application of chemokine CXCL13 in central nervous system lymphoma

Chemokine ligand 13 (CXCL13) and its chemokine receptor 5 (CXCR5) both play significant roles in the tumor microenvironment (TME). CXCL13 in cerebrospinal fluid (CSF) has recently been found to have significant diagnostic and prognostic value in primary and secondary central nervous system (CNS) diffuse large B-cell lymphoma (DLBCL), and the CXCL13-CXCR5 axis has been shown to play an important chemotactic role in the TME of CNS-DLBCL. In this review, we first describe the clinical value of CXCL13 in CSF as a prognostic and diagnostic biomarker for CNS-DLBCL. In addition, this review also discusses the specific mechanisms associated with the CXCL13-CXCR5 axis in tumor immunity of primary diffuse large B cell lymphoma of the central nervous system (PCNS-DLBCL) by reviewing the specific mechanisms of this axis in the immune microenvironment of DLBCL and CNS inflammation, as well as the prospects for the use of CXCL13-CXCR5 axis in immunotherapy in PCNS-DLBCL.

Suppression of neuroinflammation by an allosteric agonist and positive allosteric modulator of the α7 nicotinic acetylcholine receptor GAT107

Background

The α7 nicotinic acetylcholine receptor (α7 nAChR) negatively regulates the synthesis and release of pro-inflammatory cytokines by immune cells. Our previous studies showed that in encephalitogenic T cells, α7 nAChR expression is upregulated and that activation of the cholinergic system can attenuate experimental autoimmune encephalomyelitis (EAE). GAT107 is an allosteric agonist and positive allosteric modulator (ago-PAM) of α7 nAChR that can produce persistent activation of this receptor. Therefore, in the present study, we investigated the effect of GAT107 on neuroinflammation in EAE, the animal model used for the study of multiple sclerosis (MS) via α7 nAChR, and the inflammatory pathways involved.

Methods

EAE was induced by administration of myelin oligodendrocyte glycoprotein (MOG_35–55) in C57BL/6 mice. EAE mice were treated with the ago-PAM GAT107 or a placebo for 9 days, starting from the day of EAE induction. Clinical assessment and immunological evaluation of immune cells and cytokine production was performed.

Results

Following activation of the α7 nAChR by GAT107 during EAE, disease severity was significantly reduced by 70% and was correlated with a reduction in the extent of neuroinflammation in the CNS. The treatment reduced encephalitogenic T cell proliferation and the production of pro-inflammatory cytokines, as well as increased the production of the anti-inflammatory cytokine IL-10. Furthermore, the expression of immune cell markers was altered by GAT107 treatment, which induced a significant reduction in macrophages, dendritic cells, and B cells, as well as a reduction in anti-MOG_35–55 antibodies. Additionally, GAT107 was found to directly activate α7 nAChR in murine macrophage RAW264.7 cells and in human PBMCs derived from MS patients and healthy donors.

Conclusions

Our results show that GAT107 can be a useful molecule for harnessing the cholinergic anti-inflammatory pathway for long-lasting and wide-ranging modulation and downregulation of neuroinflammation in EAE.

CD8+ T cells in the central nervous system of mice with herpes simplex infection are highly activated and express high levels of CCR5 and CXCR3

Herpes simplex virus type 2 (HSV-2) is a neurotropic virus that can cause meningitis, an inflammation of the meninges in the central nervous system. T cells are key players in viral clearance, and these cells migrate from peripheral blood into the central nervous system upon infection. Several factors contribute to T cell migration, including the expression of chemokines in the inflamed tissue that attract T cells through their expression of chemokine receptors. Here we investigated CD8⁺ T cell profile in the spinal cord in a mouse model of herpes simplex virus type 2 neuroinflammation. Mice were infected with HSV-2 and sacrificed when showing signs of neuroinflammation. Cells and/or tissue from spinal cord, spleen, and blood were analyzed for expression of activation markers, chemokine receptors, and chemokines. High numbers of CD8⁺ T cells were present in the spinal cord following genital HSV-2-infection. CD8⁺ T cells were highly activated and HSV-2 glycoprotein B -specific effector cells, some of which showed signs of recent degranulation. They also expressed high levels of many chemokine receptors, in particular CCR2, CCR4, CCR5, and CXCR3. Investigating corresponding receptor ligands in spinal cord tissue revealed markedly increased expression of the cognate ligands CCL2, CCL5, CCL8, CCL12, and CXCL10. This study shows that during herpesvirus neuroinflammation anti-viral CD8⁺ T cells accumulate in the CNS. CD8⁺ T cells in the CNS also express chemotactic receptors cognate to the chemotactic gradients in the spinal cord. This indicates that anti-viral CD8⁺ T cells may migrate to infected areas in the spinal cord during herpesvirus neuroinflammation in response to chemotactic gradients.

The contribution of cyclophilin A to immune-mediated central nervous system inflammation

Cyclophilin A has multiple known functions in inflammation. Intracellular cyclophilin A modulates T helper 2 response (Th2) and extracellular cyclophilin A functions as a leukocyte chemotactic factor. The contribution of cyclophilin A to central nervous system (CNS) inflammation has not been reported. To test the hypothesis that inhibition of cyclophilin A would ameliorate immune-mediated CNS inflammation, we compared the course and neuroimmunology of experimental allergic encephalomyelitis (EAE) in cyclophilin A knockout mice and wild type littermates. There was a trend towards lower incidence of EAE in cyclophilin A knockout mice, but the clinical course of EAE among animals that manifested clinical signs of EAE was similar in cyclophilin A knockout and wild type littermates. Antigen recall response to myelin oligodendrocyte glycoprotein (MOG) peptide showed that interferon-γ release was lower in cyclophilin A knockout mice. Analysis of CNS inflammatory cells showed that CD3+ T cell infiltration into the CNS was lower in cyclophilin A knockout mice. These results showed that the loss of cyclophilin A results in altered peripheral immune activation and CNS leukocyte infiltration, but these changes did not result in a substantial change in the clinical course of EAE.

Role of tissue plasminogen activator in clinical aggravation of experimental autoimmune encephalomyelitis and its therapeutic potential

Tissue plasminogen activator (tPA), a component of the plasminogen activator (PA) system, is elevated in inflammatory neurological disorders. In the present study, we explored the immunomodulatory activity of tPA in experimental autoimmune encephalomyelitis (EAE). The EAE was treated with two catalytic inactive tPA variant proteins: S(481)A and S(481)A + KHRR(296-299)AAAA. EAE-induced tPA^-/- mice presented with markedly more severe disease than wt EAE mice. Further, treatment with tPA variants, demonstrated a significant suppression of disease severity in tPA^-/- and wt mice. Immunological evaluation showed that specific T-cell reactivity was markedly reduced in the tPA^-/- animals, as indicated by decreased T-cell reactivity and reduction in T-regulatory cells. The current findings indicate that tPA plays a role in the pathogenesis of EAE. Moreover, successful amelioration of EAE was achieved by administration of tPA variant proteins. This might mean that these proteins have potential for the immunomodulation of neuroinflammation.

The Role of the Mineralocorticoid Receptor in Inflammation: Focus on Kidney and Vasculature

BACKGROUND

The remarkable success of clinical trials in mineralocorticoid receptor (MR) inhibition in heart failure has driven research on the physiological and pathological role(s) of nonepithelial MR expression. MR is widely expressed in the cardiovascular system and is a major determinant of endothelial function, smooth muscle tone, vascular remodeling, fibrosis, and blood pressure. An important new dimension is the appreciation of the role MR plays in immune cells and target organ damage in the heart, kidney and vasculature, and in the development of insulin resistance.

SUMMARY

The mechanism for MR activation in tissue injury continues to evolve with the evidence to date suggesting that activation of MR results in a complex repertoire of effects involving both macrophages and T cells. MR is an important transcriptional regulator of macrophage phenotype and function. Another important feature of MR activation is that it can occur even with normal or low aldosterone levels in pathological conditions. Tissue-specific conditional models of MR expression in myeloid cells, endothelial cells, smooth muscle cells and cardiomyocytes have been very informative and have firmly demonstrated a critical role of MR as a key pathophysiologic variable in cardiac hypertrophy, transition to heart failure, adipose inflammation, and atherosclerosis. Finally, the central nervous system activation of MR in permeable regions of the blood-brain barrier may play a role in peripheral inflammation. Key Message: Ongoing clinical trials will help clarify the role of MR blockade in conditions, such as atherosclerosis and chronic kidney disease.

Phospholipase D1 mediates lymphocyte adhesion and migration in experimental autoimmune encephalomyelitis

Lymphocyte adhesion and subsequent trafficking across endothelial barriers are essential steps in various immune-mediated disorders of the CNS, including MS. The molecular mechanisms underlying these processes, however, are still unknown. Phospholipase D1 (PLD1), an enzyme that generates phosphatidic acid through hydrolysis of phosphatidylcholine and additionally yields choline as a product, has been described as regulator of the cell mobility. By using PLD1-deficient mice, we investigated the functional significance of PLD1 for lymphocyte adhesion and migration in vitro and after myelin oligodendrocyte glycoprotein (MOG)35-55 -induced EAE, a model of human MS. The lack of PLD1 reduced chemokine-mediated static adhesion of lymphocytes to the endothelial adhesion molecules vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) in vitro, and was accompanied by a decreased migratory capacity in both blood brain barrier and cell migration models. Importantly, PLD1 is also relevant for the recruitment of immune cells into the CNS in vivo since disease severity after EAE was significantly attenuated in PLD1-deficient mice. Furthermore, PLD1 expression could be detected on lymphocytes in MS patients. Our findings suggest a critical function of PLD1-dependent intracellular signaling cascades in regulating lymphocyte trafficking during autoimmune CNS inflammation.