Browsing by Subject "Axotomy"

Now showing 1 - 4 of 4
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    CD4+ T cell expression of the IL-10 receptor is necessary for facial motoneuron survival after axotomy
    (BMC, 2020) Runge, Elizabeth M.; Iyer, Abhirami K.; Setter, Deborah O.; Kennedy, Felicia M.; Sanders, Virginia M.; Jones, Kathryn J.; Anatomy and Cell Biology, School of Medicine
    Background: After peripheral nerve transection, facial motoneuron (FMN) survival depends on an intact CD4+ T cell population and a central source of interleukin-10 (IL-10). However, it has not been determined previously whether CD4+ T cells participate in the central neuroprotective IL-10 cascade after facial nerve axotomy (FNA). Methods: Immunohistochemical labeling of CD4+ T cells, pontine vasculature, and central microglia was used to determine whether CD4+ T cells cross the blood-brain barrier and enter the facial motor nucleus (FMNuc) after FNA. The importance of IL-10 signaling in CD4+ T cells was assessed by performing adoptive transfer of IL-10 receptor beta (IL-10RB)-deficient CD4+ T cells into immunodeficient mice prior to injury. Histology and qPCR were utilized to determine the impact of IL-10RB-deficient T cells on FMN survival and central gene expression after FNA. Flow cytometry was used to determine whether IL-10 signaling in T cells was necessary for their differentiation into neuroprotective subsets. Results: CD4+ T cells were capable of crossing the blood-brain barrier and associating with reactive microglial nodules in the axotomized FMNuc. Full induction of central IL-10R gene expression after FNA was dependent on CD4+ T cells, regardless of their own IL-10R signaling capability. Surprisingly, CD4+ T cells lacking IL-10RB were incapable of mediating neuroprotection after axotomy and promoted increased central expression of genes associated with microglial activation, antigen presentation, T cell co-stimulation, and complement deposition. There was reduced differentiation of IL-10RB-deficient CD4+ T cells into regulatory CD4+ T cells in vitro. Conclusions: These findings support the interdependence of IL-10- and CD4+ T cell-mediated mechanisms of neuroprotection after axotomy. CD4+ T cells may potentiate central responsiveness to IL-10, while IL-10 signaling within CD4+ T cells is necessary for their ability to rescue axotomized motoneuron survival. We propose that loss of IL-10 signaling in CD4+ T cells promotes non-neuroprotective autoimmunity after FNA.
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    Cellular Sources and Neuroprotective Roles of Interleukin-10 in the Facial Motor Nucleus after Axotomy
    (MDPI, 2022-10-09) Runge, Elizabeth M.; Setter, Deborah O.; Iyer, Abhirami K.; Regele, Eric J.; Kennedy, Felicia M.; Sanders, Virginia M.; Jones, Kathryn J.; Anatomy, Cell Biology and Physiology, School of Medicine
    Facial motoneuron (FMN) survival is mediated by CD4+ T cells in an interleukin-10 (IL-10)-dependent manner after facial nerve axotomy (FNA), but CD4+ T cells themselves are not the source of this neuroprotective IL-10. The aims of this study were to (1) identify the temporal and cell-specific induction of IL-10 expression in the facial motor nucleus and (2) elucidate the neuroprotective capacity of this expression after axotomy. Immunohistochemistry revealed that FMN constitutively produced IL-10, whereas astrocytes were induced to make IL-10 after FNA. Il10 mRNA co-localized with microglia before and after axotomy, but microglial production of IL-10 protein was not detected. To determine whether any single source of IL-10 was critical for FMN survival, Cre/Lox mouse strains were utilized to selectively knock out IL-10 in neurons, astrocytes, and microglia. In agreement with the localization data reflecting concerted IL-10 production by multiple cell types, no single cellular source of IL-10 alone could provide neuroprotection after FNA. These findings suggest that coordinated neuronal and astrocytic IL-10 production is necessary for FMN survival and has roles in neuronal homeostasis, as well as neuroprotective trophism after axotomy.
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    Immunoregulation of the central response to peripheral nerve injury: motoneuron survival and relevance to ALS
    (2017-04) Setter, Deborah Olmstead; Jones, Kathryn J.; Block, Michelle L.; Sanders, Virginia M.; Sengelaub, Dale R.; Xu, Xiao-Ming
    Facial nerve axotomy (FNA) in immunodeficient mice causes significantly more facial motoneuron (FMN) loss relative to wild type (WT), indicating that the immune system is neuroprotective. Further studies reveal that both CD4+ T cells and interleukin 10 (IL-10) act centrally to promote neuronal survival after injury. This study first investigated the roles of IL-10 and CD4+ T cells in neuroprotection after axotomy. CD4+ T cell-mediated neuroprotection requires centrally-produced IL-10, but the source of IL-10 is unknown. Using FNA on IL-10 reporter mice, immunohistochemistry was employed to identify the IL-10 source. Unexpectedly, axotomy induced astrocyte production of IL-10. To test if microglia- or astrocyte-specific IL-10 is needed for neuroprotection, cell-specific conditional knockout mice were generated. Neither knockout scenario affected FMN survival after FNA, suggesting that coordinated IL-10 production by both glia contributes to neuroprotection. The effect of immune status on the post-FNA molecular response was studied to characterize CD4+ T cell-mediated neuroprotection. In the recombinase-activating gene2 knockout (RAG-2-/-) mouse model of immunodeficiency, glial microenvironment responses were significantly impaired. Reconstitution with CD4+ T cells restored glial activation to normal levels. Motoneuron regeneration responses remained unaffected by immune status. These findings indicate that CD4+ T cell-mediated neuroprotection after injury occurs indirectly via microenvironment regulation. Immunodysregulation is evident in amyotrophic lateral sclerosis (ALS), and FMN survival after FNA is worse in the mutant superoxide dismutase (mSOD1) mouse model of ALS. Further experiments reveal that mSOD1 CD4+ T cells are neuroprotective in RAG-2-/- mice, whereas mSOD1 whole splenocytes (WS) are not. The third aim examined if the mSOD1 WS environment inhibits mSOD1 CD4+ T cell glial regulation after axotomy. Unexpectedly, both treatments were equally effective in promoting glial activation. Instead, mSOD1 WS treatment induced a motoneuron-specific death mechanism prevalent in ALS. In conclusion, the peripheral immune system regulates the central glial microenvironment utilizing IL-10 to promote neuronal survival after axotomy. Astrocytes, specifically, may be responsible for transducing peripheral immune signals into microenvironment regulation. Additionally, the immune system in ALS may directly participate in disease pathology.
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    Impact of peripheral immune status on central molecular responses to facial nerve axotomy
    (Elsevier, 2018-02) Setter, Deborah O.; Runge, Elizabeth M.; Schartz, Nicole D.; Kennedy, Felicia M.; Brown, Brandon L.; McMillan, Kathryn P.; Miller, Whitney M.; Shah, Kishan M.; Haulcomb, Melissa M.; Sanders, Virginia M.; Jones, Karthryn J.; Anatomy and Cell Biology, IU School of Medicine
    When facial nerve axotomy (FNA) is performed on immunodeficient recombinase activating gene-2 knockout (RAG-2-/-) mice, there is greater facial motoneuron (FMN) death relative to wild type (WT) mice. Reconstituting RAG-2-/- mice with whole splenocytes rescues FMN survival after FNA, and CD4+ T cells specifically drive immune-mediated neuroprotection. Evidence suggests that immunodysregulation may contribute to motoneuron death in amyotrophic lateral sclerosis (ALS). Immunoreconstitution of RAG-2-/- mice with lymphocytes from the mutant superoxide dismutase (mSOD1) mouse model of ALS revealed that the mSOD1 whole splenocyte environment suppresses mSOD1 CD4+ T cell-mediated neuroprotection after FNA. The objective of the current study was to characterize the effect of CD4+ T cells on the central molecular response to FNA and then identify if mSOD1 whole splenocytes blocked these regulatory pathways. Gene expression profiles of the axotomized facial motor nucleus were assessed from RAG-2-/- mice immunoreconstituted with either CD4+ T cells or whole splenocytes from WT or mSOD1 donors. The findings indicate that immunodeficient mice have suppressed glial activation after axotomy, and cell transfer of WT CD4+ T cells rescues microenvironment responses. Additionally, mSOD1 whole splenocyte recipients exhibit an increased astrocyte activation response to FNA. In RAG-2-/- + mSOD1 whole splenocyte mice, an elevation of motoneuron-specific Fas cell death pathways is also observed. Altogether, these findings suggest that mSOD1 whole splenocytes do not suppress mSOD1 CD4+ T cell regulation of the microenvironment, and instead, mSOD1 whole splenocytes may promote motoneuron death by either promoting a neurotoxic astrocyte phenotype or inducing Fas-mediated cell death pathways. This study demonstrates that peripheral immune status significantly affects central responses to nerve injury. Future studies will elucidate the mechanisms by which mSOD1 whole splenocytes promote cell death and if inhibiting this mechanism can preserve motoneuron survival in injury and disease.