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The benefits of neuroinflammation for the repair of the injured central nervous system.

ABSTRACT: Inflammation of the nervous system (neuroinflammation) is now recognized as a hallmark of virtually all neurological disorders. In neuroinflammatory conditions such as multiple sclerosis, there is prominent infiltration and a long-lasting representation of various leukocyte subsets in the central nervous system (CNS) parenchyma. Even in classic neurodegenerative disorders, where such immense inflammatory infiltrates are absent, there is still evidence of activated CNS-intrinsic microglia. The consequences of excessive and uncontrolled neuroinflammation are injury and death to neural elements, which manifest as a heterogeneous set of neurological symptoms. However, it is now readily acknowledged, due to instructive studies from the peripheral nervous system and a large body of CNS literature, that aspects of the neuroinflammatory response can be beneficial for CNS outcomes. The recognized benefits of inflammation to the CNS include the preservation of CNS constituents (neuroprotection), the proliferation and maturation of various neural precursor populations, axonal regeneration, and the reformation of myelin on denuded axons. Herein, we highlight the benefits of neuroinflammation in fostering CNS recovery after neural injury using examples from multiple sclerosis, traumatic spinal cord injury, stroke, and Alzheimer's disease. We focus on CNS regenerative responses, such as neurogenesis, axonal regeneration, and remyelination, and discuss the mechanisms by which neuroinflammation is pro-regenerative for the CNS. Finally, we highlight treatment strategies that harness the benefits of neuroinflammation for CNS regenerative responses.

SUBMITTER: Yong HYF

PROVIDER: S-EPMC6804643 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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The benefits of neuroinflammation for the repair of the injured central nervous system.

Yong Heather Y F HYF Rawji Khalil S KS Ghorbani Samira S Xue Mengzhou M Yong V Wee VW

Cellular & molecular immunology 20190315 6

Inflammation of the nervous system (neuroinflammation) is now recognized as a hallmark of virtually all neurological disorders. In neuroinflammatory conditions such as multiple sclerosis, there is prominent infiltration and a long-lasting representation of various leukocyte subsets in the central nervous system (CNS) parenchyma. Even in classic neurodegenerative disorders, where such immense inflammatory infiltrates are absent, there is still evidence of activated CNS-intrinsic microglia. The co ...[more]

PMID: 30874626

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Project description:BackgroundMultiple sclerosis (MS) is a chronic autoimmune disease driven by sustained inflammation in the central nervous system. One of the pathological hallmarks of MS is extensive free radical production. However, the subsequent generation, potential pathological role, and detoxification of different lipid peroxidation-derived reactive carbonyl species during neuroinflammation are unclear, as are the therapeutic benefits of carbonyl quenchers. Here, we investigated the reactive carbonyl acrolein and (the therapeutic effect of) acrolein quenching by carnosine during neuroinflammation.MethodsThe abundance and localization of acrolein was investigated in inflammatory lesions of MS patients and experimental autoimmune encephalomyelitis (EAE) mice. In addition, we analysed carnosine levels and acrolein quenching by endogenous and exogenous carnosine in EAE. Finally, the therapeutic effect of exogenous carnosine was assessed in vivo (EAE) and in vitro (primary mouse microglia, macrophages, astrocytes).ResultsAcrolein was substantially increased in inflammatory lesions of MS patients and EAE mice. Levels of the dipeptide carnosine (β-alanyl-L-histidine), an endogenous carbonyl quencher particularly reactive towards acrolein, and the carnosine-acrolein adduct (carnosine-propanal) were ~ twofold lower within EAE spinal cord tissue. Oral carnosine treatment augmented spinal cord carnosine levels (up to > tenfold), increased carnosine-acrolein quenching, reduced acrolein-protein adduct formation, suppressed inflammatory activity, and alleviated clinical disease severity in EAE. In vivo and in vitro studies indicate that pro-inflammatory microglia/macrophages generate acrolein, which can be efficiently quenched by increasing carnosine availability, resulting in suppressed inflammatory activity. Other properties of carnosine (antioxidant, nitric oxide scavenging) may also contribute to the therapeutic effects.ConclusionsOur results identify carbonyl (particularly acrolein) quenching by carnosine as a therapeutic strategy to counter inflammation and macromolecular damage in MS.

Project description:Background: Cystatin F is a secreted lysosomal cysteine protease inhibitor that has been implicated in affecting the severity of demyelination and enhancing remyelination in pre-clinical models of immune-mediated demyelination. How cystatin F impacts neurologic disease severity following viral infection of the central nervous system (CNS) has not been well characterized and was the focus of this study. We used cystatin F null-mutant mice (Cst7-/-) with a well-established model of murine coronavirus-induced neurologic disease to evaluate the contributions of cystatin F in host defense, demyelination and remyelination. Methods: Wildtype controls and Cst7-/- mice were intracranially (i.c.) infected with a sublethal dose of the neurotropic JHM strain of mouse hepatitis virus (JHMV), with disease progression and survival monitored daily. Immune cell infiltration into the brain and spinal cord was determined by flow cytometry. Spinal cord demyelination was determined by luxol fast blue (LFB) and Hematoxylin/Eosin (H&E) staining and remyelination evaluated by electron microscopy (EM) and calculation of g-ratios. Immune cell infiltration into the CNS and microglia activation were determined by flow cytometry and 10X genomics chromium 3’ single cell RNA sequencing (scRNAseq). Results: JHMV-infected Cst7-/- mice were able to control viral replication within the CNS, indicating that cystatin F is not essential for an effective Th1 anti-viral immune response. Infiltration of T cells and monocytes/macrophages into the spinal cords of JHMV-infected Cst7-/- mice was increased compared to infected controls, and this correlated with amplified demyelination and impaired remyelination. Single-cell RNA-seq of CD45+ cells enriched from spinal cords of infected Cst7-/- and control mice at day 21 post-infection (p.i.) revealed enhanced expression of transcripts encoding macrophage chemoattractant, Ccl2, and T cell chemoattractants, Cxcl9 and Cxcl10, combined with elevated expression of interferon-g (Ifng) transcripts and activation markers in CD8+ T cells from Cst7-/- mice compared to controls. Conclusions: Cystatin F is not required for immune-mediated control of JHMV replication within the CNS. However, JHMV-infected Cst7-/- mice exhibited more severe clinical disease associated with increased demyelination and impaired remyelination. The increase in disease severity was associated with elevated expression of macrophage and T cell chemoattractant chemokines, concurrent with increased neuroinflammation. These findings support the theory that one mechanism by which cystatin F affects chronic disease in mice persistently infected with JHMV is through regulating expression of pro-inflammatory molecules that impact neuroinflammation and neurologic disease.

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The benefits of neuroinflammation for the repair of the injured central nervous system.

Publications

The benefits of neuroinflammation for the repair of the injured central nervous system.

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