Journal Article

Interleukin-9 regulates macrophage activation in the progressive multiple sclerosis brain

Donninelli, Gloria, Grasso, Maria Grazia, Magliozzi, Roberta, Saraf-Sinik, Inbar, Capone, Alessia, Reynolds, Richard, Mazziotti, Valentina, Volpe, Elisabetta, Battistini, Luca

2020

Overview

Background Multiple sclerosis (MS) is an immune-mediated, chronic inflammatory, and demyelinating disease of the central nervous system (CNS). Several cytokines are thought to be involved in the regulation of MS pathogenesis. We recently identified interleukin (IL)-9 as a cytokine reducing inflammation and protecting from neurodegeneration in relapsing–remitting MS patients. However, the expression of IL-9 in CNS, and the mechanisms underlying the effect of IL-9 on CNS infiltrating immune cells have never been investigated. Methods To address this question, we first analyzed the expression levels of IL-9 in post-mortem cerebrospinal fluid of MS patients and the in situ expression of IL-9 in post-mortem MS brain samples by immunohistochemistry. A complementary investigation focused on identifying which immune cells express IL-9 receptor (IL-9R) by flow cytometry, western blot, and immunohistochemistry. Finally, we explored the effect of IL-9 on IL-9-responsive cells, analyzing the induced signaling pathways and functional properties. Results We found that macrophages, microglia, and CD4 T lymphocytes were the cells expressing the highest levels of IL-9 in the MS brain. Of the immune cells circulating in the blood, monocytes/macrophages were the most responsive to IL-9. We validated the expression of IL-9R by macrophages/microglia in post-mortem brain sections of MS patients. IL-9 induced activation of signal transducer and activator of transcription (STAT)1, STAT3, and STAT5 and reduced the expression of activation markers, such as CD45, CD14, CD68, and CD11b in inflammatory macrophages stimulated in vitro with lipopolysaccharide and interferon (IFN)-γ. Similarly, in situ the number of activated CD68 + macrophages was significantly reduced in areas with high levels of IL-9. Moreover, in the same conditions, IL-9 increased the secretion of the anti-inflammatory cytokine, transforming growth factor (TGF)-β. Conclusions These results reveal a new cytokine expressed in the CNS, with a role in the context of MS. We have demonstrated that IL-9 and its receptor are both expressed in CNS. Moreover, we found that IL-9 decreases the activation state and promotes the anti-inflammatory properties of human macrophages. This mechanism may contribute to the beneficial effects of IL-9 that are observed in MS, and may be therapeutically potentiated by modulating IL-9 expression in MS.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Adult / Age / Aged / Anti-inflammatory agents / Antibodies / Biomedical and Life Sciences / Biomedicine / Blood & organ donations / CD11b antigen / CD14 antigen / CD4 antigen / CD45 antigen / Cell activation / Central nervous system / Cerebrospinal fluid / Cytokines / Demyelinating diseases / Demyelination / Female / Flow cytometry / Health aspects / Humans / Immunohistochemistry / Immunology / Inflammation / Interferon / Interleukin 9 / Interleukin-9 - immunology / Interleukin-9 - metabolism / Interleukin-9 receptor / Laboratories / Lipopolysaccharides / Lymphocytes T / Macrophage Activation - immunology / Macrophages / Macrophages - immunology / Macrophages - metabolism / Male / Microglia / Middle Aged / Monocytes / Multiple sclerosis / Multiple Sclerosis, Chronic Progressive - immunology / Multiple Sclerosis, Chronic Progressive - metabolism / Nervous system / Neurobiology / Neurodegeneration / Neurology / Neurosciences / Pathogenesis / Physiological aspects / Progressive multiple sclerosis / Receptors, Interleukin-9 - immunology / Receptors, Interleukin-9 - metabolism / Stat3 protein / Stat5 protein / Transcription / Variance analysis