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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.


Related in: MedlinePlus

LRP1 deficient myeloid cells have a pro-inflammatory signature. Microglia (MG) and BMDM (MΦ) isolated from Cx3cr1cre-Lrp1fl/fl and Lrp1fl/fl mice were treated with LPS (1 μg/mL) for 3 h (qPCR) or 24 h (ELISA). TNF-α expression in microglia was determined by qPCR (a) and ELISA (b). TNF-α expression in macrophages was determined by qPCR (c) and ELISA (d). Expression of IL-1β (e) and IL-6 (f) in macrophages was determined by qPCR. g Transcript expression of IL-1β, IL-6, and TNF-α from the CNS of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice at the peak of EAE. 5, **p < 0.01, ***p < 0.001; Student’s t-test
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Fig6: LRP1 deficient myeloid cells have a pro-inflammatory signature. Microglia (MG) and BMDM (MΦ) isolated from Cx3cr1cre-Lrp1fl/fl and Lrp1fl/fl mice were treated with LPS (1 μg/mL) for 3 h (qPCR) or 24 h (ELISA). TNF-α expression in microglia was determined by qPCR (a) and ELISA (b). TNF-α expression in macrophages was determined by qPCR (c) and ELISA (d). Expression of IL-1β (e) and IL-6 (f) in macrophages was determined by qPCR. g Transcript expression of IL-1β, IL-6, and TNF-α from the CNS of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice at the peak of EAE. 5, **p < 0.01, ***p < 0.001; Student’s t-test

Mentions: One potential mechanism by which microglia lacking LRP1 could affect EAE pathology is through increased production of inflammatory mediators, as LRP1 functions as an inhibitor of the inflammatory response [15]. To test the inflammatory response in LRP1 deficient microglia, we isolated primary microglia from Lrp1fl/fl and Cx3cr1cre-Lrp1fl/fl mice and analyzed their production of TNF-α, a key cytokine involved in EAE pathology [38]. LPS stimulation of LRP1 deficient microglia results in increased production of TNF-α at both the transcript (Fig. 6a) and the protein level (Fig. 6b). This increase in TNF-α is comparable to the one observed in primary cultures of BMDM (Fig. 6c-d), as we have previously reported [15]. In BMDM, the pro-inflammatory signature generated by the lack of LRP1 also extends to IL-1β and IL-6 production (Fig. 6e-f). More importantly, this pro-inflammatory signature was also observed in the CNS of Cx3cr1creER-Lrp1fl/fl mice at the disease onset, as detected by qPCR (Fig. 6g). Taken together, our results demonstrate that, in the absence of LRP1, microglia adopt a pro-inflammatory phenotype that could contribute to increased pathology in EAE.Fig. 6


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)

LRP1 deficient myeloid cells have a pro-inflammatory signature. Microglia (MG) and BMDM (MΦ) isolated from Cx3cr1cre-Lrp1fl/fl and Lrp1fl/fl mice were treated with LPS (1 μg/mL) for 3 h (qPCR) or 24 h (ELISA). TNF-α expression in microglia was determined by qPCR (a) and ELISA (b). TNF-α expression in macrophages was determined by qPCR (c) and ELISA (d). Expression of IL-1β (e) and IL-6 (f) in macrophages was determined by qPCR. g Transcript expression of IL-1β, IL-6, and TNF-α from the CNS of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice at the peak of EAE. 5, **p < 0.01, ***p < 0.001; Student’s t-test
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4940960&req=5

Fig6: LRP1 deficient myeloid cells have a pro-inflammatory signature. Microglia (MG) and BMDM (MΦ) isolated from Cx3cr1cre-Lrp1fl/fl and Lrp1fl/fl mice were treated with LPS (1 μg/mL) for 3 h (qPCR) or 24 h (ELISA). TNF-α expression in microglia was determined by qPCR (a) and ELISA (b). TNF-α expression in macrophages was determined by qPCR (c) and ELISA (d). Expression of IL-1β (e) and IL-6 (f) in macrophages was determined by qPCR. g Transcript expression of IL-1β, IL-6, and TNF-α from the CNS of Cx3cr1creER-Lrp1fl/fl and Lrp1fl/fl mice at the peak of EAE. 5, **p < 0.01, ***p < 0.001; Student’s t-test
Mentions: One potential mechanism by which microglia lacking LRP1 could affect EAE pathology is through increased production of inflammatory mediators, as LRP1 functions as an inhibitor of the inflammatory response [15]. To test the inflammatory response in LRP1 deficient microglia, we isolated primary microglia from Lrp1fl/fl and Cx3cr1cre-Lrp1fl/fl mice and analyzed their production of TNF-α, a key cytokine involved in EAE pathology [38]. LPS stimulation of LRP1 deficient microglia results in increased production of TNF-α at both the transcript (Fig. 6a) and the protein level (Fig. 6b). This increase in TNF-α is comparable to the one observed in primary cultures of BMDM (Fig. 6c-d), as we have previously reported [15]. In BMDM, the pro-inflammatory signature generated by the lack of LRP1 also extends to IL-1β and IL-6 production (Fig. 6e-f). More importantly, this pro-inflammatory signature was also observed in the CNS of Cx3cr1creER-Lrp1fl/fl mice at the disease onset, as detected by qPCR (Fig. 6g). Taken together, our results demonstrate that, in the absence of LRP1, microglia adopt a pro-inflammatory phenotype that could contribute to increased pathology in EAE.Fig. 6

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