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LRP1 expression in microglia is protective during CNS autoimmunity.

Chuang TY, Guo Y, Seki SM, Rosen AM, Johanson DM, Mandell JW, Lucchinetti CF, Gaultier A - Acta Neuropathol Commun (2016)

Bottom Line: While T cells are known orchestrators of the immune response leading to MS pathology, the precise contribution of CNS resident and peripheral infiltrating myeloid cells is less well described.We further show that the increased disease severity in experimental autoimmune encephalomyelitis is not due to haplodeficiency of the Cx3cr1 locus.At the cellular level, microglia lacking LRP1 adopt a pro-inflammatory phenotype characterized by amoeboid morphology and increased production of the inflammatory mediator TNF-α.

View Article: PubMed Central - PubMed

Affiliation: Center for Brain Immunology and Glia, Department of Neuroscience, University of Virginia, Charlottesville, VA, USA.

ABSTRACT
Multiple sclerosis is a devastating neurological disorder characterized by the autoimmune destruction of the central nervous system myelin. While T cells are known orchestrators of the immune response leading to MS pathology, the precise contribution of CNS resident and peripheral infiltrating myeloid cells is less well described. Here, we explore the myeloid cell function of Low-density lipoprotein receptor-related protein-1 (LRP1), a scavenger receptor involved in myelin clearance and the inflammatory response, in the context of Multiple sclerosis. Supporting its central role in Multiple sclerosis pathology, we find that LRP1 expression is increased in Multiple sclerosis lesions in comparison to the surrounding healthy tissue. Using two genetic mouse models, we show that deletion of LRP1 in microglia, but not in peripheral macrophages, negatively impacts the progression of experimental autoimmune encephalomyelitis, an animal model of Multiple sclerosis. We further show that the increased disease severity in experimental autoimmune encephalomyelitis is not due to haplodeficiency of the Cx3cr1 locus. At the cellular level, microglia lacking LRP1 adopt a pro-inflammatory phenotype characterized by amoeboid morphology and increased production of the inflammatory mediator TNF-α. We also show that LRP1 functions as a robust inhibitor of NF-kB activation in myeloid cells via a MyD88 dependent pathway, potentially explaining the increase in disease severity observed in mice lacking LRP1 expression in microglia. Taken together, our data suggest that the function of LRP1 in microglia is to keep these cells in an anti-inflammatory and neuroprotective status during inflammatory insult, including experimental autoimmune encephalomyelitis and potentially in Multiple sclerosis.

No MeSH data available.


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Microglial LRP1 deficient mice have increased demyelination and numbers of immune cells in the CNS during EAE. Spinal cord sections of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice were stained with Luxol Fast Blue a at day 30 (n = 4 for each group), and CD3 b (n = 4 for each group) and Iba1 c (n = 4 for each group) at day 15. Cells were manually quantified. For LFB, 2 sections per spinal cord level are plotted from each animal. For CD3 and Iba1, each point represents one animal. Immune cells were isolated by percoll gradient from spinal cords of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice. Number of d peripheral myeloid cells (CD11bhiCD45hi), e T cells (TCRβ+) cells, f microglia (CD11bhiCD45mid), and g B cells (CD19+) were determined by flow cytometry analysis (n = 3 for each group). *p < 0.05, **p < 0.01; Student’s t-test, mean ± s.e.m
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Fig3: Microglial LRP1 deficient mice have increased demyelination and numbers of immune cells in the CNS during EAE. Spinal cord sections of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice were stained with Luxol Fast Blue a at day 30 (n = 4 for each group), and CD3 b (n = 4 for each group) and Iba1 c (n = 4 for each group) at day 15. Cells were manually quantified. For LFB, 2 sections per spinal cord level are plotted from each animal. For CD3 and Iba1, each point represents one animal. Immune cells were isolated by percoll gradient from spinal cords of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice. Number of d peripheral myeloid cells (CD11bhiCD45hi), e T cells (TCRβ+) cells, f microglia (CD11bhiCD45mid), and g B cells (CD19+) were determined by flow cytometry analysis (n = 3 for each group). *p < 0.05, **p < 0.01; Student’s t-test, mean ± s.e.m

Mentions: To explore the pathological conditions leading to an exacerbated disease course in EAE mice lacking LRP1 expression in microglia, we performed histological analysis of the spinal cord during the chronic phase of the disease (day 30). Myelin staining of the spinal cord sections with Luxol Fast Blue revealed that Cx3cr1creER-Lrp1fl/fl mice have significantly more white matter demyelination than the control group (Fig. 3a). This difference was statistically significant at all of the spinal cord levels that were examined: Lumbar, thoracic and cervical levels. Immune cells are responsible for driving demyelination during EAE. To explore if LRP1 deficiency in microglia could alter immune cell numbers, we performed flow cytometry and immunohistochemical analysis of the spinal cords at the onset of disease (day 15). Histologically, we find increased numbers of CD3+ T cells and Iba1+ cells in the Cx3cr1creER-Lrp1fl/fl mice at disease onset (Fig. 3b-c), especially evident in the dense infiltrates in the white matter of the spinal cord. By flow cytometry (Additional file 1: Figure S3), our results reveal that the number of T cells and peripheral myeloid (CD11bhiCD45hi) cells was significantly increased in animals lacking LRP1 (Fig. 3d-e). Finally, there was a trend towards increased numbers of microglia (CD11bmidCD45hi) and B cells (CD19+) (Fig. 3f-g). Taken together, our results show that mice lacking LRP1 in microglia had increased EAE susceptibility that is associated with robust demyelination and increased infiltration of immune cells from the innate and adaptive arms of the immune system.Fig. 3


LRP1 expression in microglia is protective during CNS autoimmunity.

Chuang TY, Guo Y, Seki SM, Rosen AM, Johanson DM, Mandell JW, Lucchinetti CF, Gaultier A - Acta Neuropathol Commun (2016)

Microglial LRP1 deficient mice have increased demyelination and numbers of immune cells in the CNS during EAE. Spinal cord sections of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice were stained with Luxol Fast Blue a at day 30 (n = 4 for each group), and CD3 b (n = 4 for each group) and Iba1 c (n = 4 for each group) at day 15. Cells were manually quantified. For LFB, 2 sections per spinal cord level are plotted from each animal. For CD3 and Iba1, each point represents one animal. Immune cells were isolated by percoll gradient from spinal cords of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice. Number of d peripheral myeloid cells (CD11bhiCD45hi), e T cells (TCRβ+) cells, f microglia (CD11bhiCD45mid), and g B cells (CD19+) were determined by flow cytometry analysis (n = 3 for each group). *p < 0.05, **p < 0.01; Student’s t-test, mean ± s.e.m
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Fig3: Microglial LRP1 deficient mice have increased demyelination and numbers of immune cells in the CNS during EAE. Spinal cord sections of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice were stained with Luxol Fast Blue a at day 30 (n = 4 for each group), and CD3 b (n = 4 for each group) and Iba1 c (n = 4 for each group) at day 15. Cells were manually quantified. For LFB, 2 sections per spinal cord level are plotted from each animal. For CD3 and Iba1, each point represents one animal. Immune cells were isolated by percoll gradient from spinal cords of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice. Number of d peripheral myeloid cells (CD11bhiCD45hi), e T cells (TCRβ+) cells, f microglia (CD11bhiCD45mid), and g B cells (CD19+) were determined by flow cytometry analysis (n = 3 for each group). *p < 0.05, **p < 0.01; Student’s t-test, mean ± s.e.m
Mentions: To explore the pathological conditions leading to an exacerbated disease course in EAE mice lacking LRP1 expression in microglia, we performed histological analysis of the spinal cord during the chronic phase of the disease (day 30). Myelin staining of the spinal cord sections with Luxol Fast Blue revealed that Cx3cr1creER-Lrp1fl/fl mice have significantly more white matter demyelination than the control group (Fig. 3a). This difference was statistically significant at all of the spinal cord levels that were examined: Lumbar, thoracic and cervical levels. Immune cells are responsible for driving demyelination during EAE. To explore if LRP1 deficiency in microglia could alter immune cell numbers, we performed flow cytometry and immunohistochemical analysis of the spinal cords at the onset of disease (day 15). Histologically, we find increased numbers of CD3+ T cells and Iba1+ cells in the Cx3cr1creER-Lrp1fl/fl mice at disease onset (Fig. 3b-c), especially evident in the dense infiltrates in the white matter of the spinal cord. By flow cytometry (Additional file 1: Figure S3), our results reveal that the number of T cells and peripheral myeloid (CD11bhiCD45hi) cells was significantly increased in animals lacking LRP1 (Fig. 3d-e). Finally, there was a trend towards increased numbers of microglia (CD11bmidCD45hi) and B cells (CD19+) (Fig. 3f-g). Taken together, our results show that mice lacking LRP1 in microglia had increased EAE susceptibility that is associated with robust demyelination and increased infiltration of immune cells from the innate and adaptive arms of the immune system.Fig. 3

Bottom Line: While T cells are known orchestrators of the immune response leading to MS pathology, the precise contribution of CNS resident and peripheral infiltrating myeloid cells is less well described.We further show that the increased disease severity in experimental autoimmune encephalomyelitis is not due to haplodeficiency of the Cx3cr1 locus.At the cellular level, microglia lacking LRP1 adopt a pro-inflammatory phenotype characterized by amoeboid morphology and increased production of the inflammatory mediator TNF-α.

View Article: PubMed Central - PubMed

Affiliation: Center for Brain Immunology and Glia, Department of Neuroscience, University of Virginia, Charlottesville, VA, USA.

ABSTRACT
Multiple sclerosis is a devastating neurological disorder characterized by the autoimmune destruction of the central nervous system myelin. While T cells are known orchestrators of the immune response leading to MS pathology, the precise contribution of CNS resident and peripheral infiltrating myeloid cells is less well described. Here, we explore the myeloid cell function of Low-density lipoprotein receptor-related protein-1 (LRP1), a scavenger receptor involved in myelin clearance and the inflammatory response, in the context of Multiple sclerosis. Supporting its central role in Multiple sclerosis pathology, we find that LRP1 expression is increased in Multiple sclerosis lesions in comparison to the surrounding healthy tissue. Using two genetic mouse models, we show that deletion of LRP1 in microglia, but not in peripheral macrophages, negatively impacts the progression of experimental autoimmune encephalomyelitis, an animal model of Multiple sclerosis. We further show that the increased disease severity in experimental autoimmune encephalomyelitis is not due to haplodeficiency of the Cx3cr1 locus. At the cellular level, microglia lacking LRP1 adopt a pro-inflammatory phenotype characterized by amoeboid morphology and increased production of the inflammatory mediator TNF-α. We also show that LRP1 functions as a robust inhibitor of NF-kB activation in myeloid cells via a MyD88 dependent pathway, potentially explaining the increase in disease severity observed in mice lacking LRP1 expression in microglia. Taken together, our data suggest that the function of LRP1 in microglia is to keep these cells in an anti-inflammatory and neuroprotective status during inflammatory insult, including experimental autoimmune encephalomyelitis and potentially in Multiple sclerosis.

No MeSH data available.


Related in: MedlinePlus