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IL4I1 augments CNS remyelination and axonal protection by modulating T cell driven inflammation

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ABSTRACT

See pluchino and peruzzotti-jametti (doi:10.1093/aww266) for a scientific commentary on this article: .

Macrophages have a critical role in remyelination. Psachoulia et al. show that IL4I1, a macrophage-secreted enzyme, promotes CNS remyelination by modulating T cell driven inflammation after focal demyelination in mice. Injection of recombinant IL4I1 protein reverses disease progression in a mouse model of multiple sclerosis, resulting in recovery from hindlimb paralysis.

No MeSH data available.


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IL4I1 modulates IFN-γ and IL-17 expression in CNS lesions and splenocytes. (A) Normalized expressions of Ifng, Il17 and Il4 in wild-type (WT, n = 4) and IL4I1-treated (n = 6) spinal cord lesions at 10 dpl by qRT-PCR. (B) Normalized expression of Ifng expression in splenocyte cultures treated with PMA+Ionomycin in the presence or absence of recombinant IL4I1 for 24 h (n = 3 per group) followed by qRT-PCR. (C) Cell death assay in splenocyte cultures treated with PMA+Ionomycin with or without recombinant IL4I1 for 24 h, and assessed by LIVE/DEAD® cell stain kit (n = 8 per group).
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aww254-F6: IL4I1 modulates IFN-γ and IL-17 expression in CNS lesions and splenocytes. (A) Normalized expressions of Ifng, Il17 and Il4 in wild-type (WT, n = 4) and IL4I1-treated (n = 6) spinal cord lesions at 10 dpl by qRT-PCR. (B) Normalized expression of Ifng expression in splenocyte cultures treated with PMA+Ionomycin in the presence or absence of recombinant IL4I1 for 24 h (n = 3 per group) followed by qRT-PCR. (C) Cell death assay in splenocyte cultures treated with PMA+Ionomycin with or without recombinant IL4I1 for 24 h, and assessed by LIVE/DEAD® cell stain kit (n = 8 per group).

Mentions: While our results indicated that IL4I1 modulates the inflammatory environment to promote CNS remyelination, its mechanism of action remained unclear. To determine if IL4I1 directly modulates the expression of the proinflammatory factor iNOS in innate immune cells, we treated purified astrocytes, microglia, and RAW264.7 cell cultures with recombinant IL4I1. qRT-PCR analysis showed that IL4I1 did not influence expression of Nos2, which encodes iNOS, in any of these cells in vitro (Supplementary Fig. 5). This observation suggests that IL4I1 regulates possibly other cell populations in CNS lesions in exerting its immunomodulatory effect. It has previously been demonstrated that IL4I1 regulates CD4+ T cell proliferation and interferon gamma (IFN-γ, encoded by IFNG) production in vitro (Lasoudris et al., 2011; Cousin et al., 2015). Because IFN-γ producing T cells are known to migrate to the CNS following blood–brain barrier breakdown and drive inflammation and oligodendrocyte destruction in the CNS (Ghasemlou et al., 2007; Ryu et al., 2015; Traka et al., 2016), we hypothesized that IL4I1 modulates CNS inflammation by regulating T cell activity. To determine if IL4I1 treatment affects T cell-associated cytokine production in CNS lesions, qRT-PCR analysis was performed on lysolecithin-demyelinated spinal cord tissues following recombinant IL4I1 or vehicle treatment. We found that IL4I1 treatment dramatically reduced Ifng and Il17 expression in CNS tissues at 10 dpl, and had no effect on Il4 expression (Fig. 6A), suggesting that IL4I1 injection modulates T-helper 1 (Th1) and Th17 cell activity in CNS lesions. To determine if IL4I1 directly regulates Ifng expression in CD4+ T cells, mouse splenocyte cultures were treated with ionomycin and phorbol myristate acetate (PMA) in the presence or absence of recombinant IL4I1 for 24 h. qRT-PCR analysis showed that IL4I1 addition significantly reduced Ifng expression in activated splenocytes (Fig. 6B). Moreover, IL4I1 treatment did not lead to apoptosis (Fig. 6C). This suggests that the reduction in Ifng resulted from the ability of IL4I1 to modulate T cell activity rather than an ability to decrease cell survival.Figure 6


IL4I1 augments CNS remyelination and axonal protection by modulating T cell driven inflammation
IL4I1 modulates IFN-γ and IL-17 expression in CNS lesions and splenocytes. (A) Normalized expressions of Ifng, Il17 and Il4 in wild-type (WT, n = 4) and IL4I1-treated (n = 6) spinal cord lesions at 10 dpl by qRT-PCR. (B) Normalized expression of Ifng expression in splenocyte cultures treated with PMA+Ionomycin in the presence or absence of recombinant IL4I1 for 24 h (n = 3 per group) followed by qRT-PCR. (C) Cell death assay in splenocyte cultures treated with PMA+Ionomycin with or without recombinant IL4I1 for 24 h, and assessed by LIVE/DEAD® cell stain kit (n = 8 per group).
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aww254-F6: IL4I1 modulates IFN-γ and IL-17 expression in CNS lesions and splenocytes. (A) Normalized expressions of Ifng, Il17 and Il4 in wild-type (WT, n = 4) and IL4I1-treated (n = 6) spinal cord lesions at 10 dpl by qRT-PCR. (B) Normalized expression of Ifng expression in splenocyte cultures treated with PMA+Ionomycin in the presence or absence of recombinant IL4I1 for 24 h (n = 3 per group) followed by qRT-PCR. (C) Cell death assay in splenocyte cultures treated with PMA+Ionomycin with or without recombinant IL4I1 for 24 h, and assessed by LIVE/DEAD® cell stain kit (n = 8 per group).
Mentions: While our results indicated that IL4I1 modulates the inflammatory environment to promote CNS remyelination, its mechanism of action remained unclear. To determine if IL4I1 directly modulates the expression of the proinflammatory factor iNOS in innate immune cells, we treated purified astrocytes, microglia, and RAW264.7 cell cultures with recombinant IL4I1. qRT-PCR analysis showed that IL4I1 did not influence expression of Nos2, which encodes iNOS, in any of these cells in vitro (Supplementary Fig. 5). This observation suggests that IL4I1 regulates possibly other cell populations in CNS lesions in exerting its immunomodulatory effect. It has previously been demonstrated that IL4I1 regulates CD4+ T cell proliferation and interferon gamma (IFN-γ, encoded by IFNG) production in vitro (Lasoudris et al., 2011; Cousin et al., 2015). Because IFN-γ producing T cells are known to migrate to the CNS following blood–brain barrier breakdown and drive inflammation and oligodendrocyte destruction in the CNS (Ghasemlou et al., 2007; Ryu et al., 2015; Traka et al., 2016), we hypothesized that IL4I1 modulates CNS inflammation by regulating T cell activity. To determine if IL4I1 treatment affects T cell-associated cytokine production in CNS lesions, qRT-PCR analysis was performed on lysolecithin-demyelinated spinal cord tissues following recombinant IL4I1 or vehicle treatment. We found that IL4I1 treatment dramatically reduced Ifng and Il17 expression in CNS tissues at 10 dpl, and had no effect on Il4 expression (Fig. 6A), suggesting that IL4I1 injection modulates T-helper 1 (Th1) and Th17 cell activity in CNS lesions. To determine if IL4I1 directly regulates Ifng expression in CD4+ T cells, mouse splenocyte cultures were treated with ionomycin and phorbol myristate acetate (PMA) in the presence or absence of recombinant IL4I1 for 24 h. qRT-PCR analysis showed that IL4I1 addition significantly reduced Ifng expression in activated splenocytes (Fig. 6B). Moreover, IL4I1 treatment did not lead to apoptosis (Fig. 6C). This suggests that the reduction in Ifng resulted from the ability of IL4I1 to modulate T cell activity rather than an ability to decrease cell survival.Figure 6

View Article: PubMed Central - PubMed

ABSTRACT

See pluchino and peruzzotti-jametti (doi:10.1093/aww266) for a scientific commentary on this article: .

Macrophages have a critical role in remyelination. Psachoulia et al. show that IL4I1, a macrophage-secreted enzyme, promotes CNS remyelination by modulating T cell driven inflammation after focal demyelination in mice. Injection of recombinant IL4I1 protein reverses disease progression in a mouse model of multiple sclerosis, resulting in recovery from hindlimb paralysis.

No MeSH data available.


Related in: MedlinePlus