Browsing by Author "Sengelaub, Dale R."

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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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    Inhibition of cPLA2 has neuroprotective effects on motoneuron and muscle atrophy following spinal cord injury
    (Liebert, 2014) Liu, Nai-Kui; Byers, James S.; Lam, Tom; Lu, Qing-Bo; Sengelaub, Dale R.; Xu, Xiao-Ming; Department of Neurological Surgery, School of Medicine
    Surviving motoneurons undergo dendritic atrophy after spinal cord injury (SCI), suggesting an important therapeutic target for neuroprotective strategies to improve recovery of function after SCI. Our previous studies showed that phospholipase A2 (PLA2) may play an important role in the pathogenesis of SCI. In the present study, we investigated whether blocking cPLA2 pharmacologically with arachidonyl trifluoromethyl ketone (ATK) or genetically using cPLA2 knockout (KO) mice attenuates motoneuron atrophy following SCI. C57BL/6 mice received either sham or contusive SCI at the T10 level. At 30 min after SCI, mice were treated with ATK or vehicle. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. ATK administration reduced percent lesion volume and increased percent volume of spared white matter compared to the vehicle-treated control animals. SCI with or without ATK treatment had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with ATK. Similarly, the vastus lateralis muscle weights of untreated SCI animals were smaller than those of sham-surgery controls, and these reductions were prevented by ATK treatment. No effects on fiber cross-sectional areas, motor endplate area or density were observed across treatment groups. Remarkably, genetically deleting cPLA2 in cPLA2 KO mice attenuated dendritic atrophy after SCI. These findings suggest that after SCI, cord tissue damage and regressive changes in motoneuron and muscle morphology can be reduced by inhibition of cPLA2, further supporting a role for cPLA2 as a neurotherapeutic target for SCI treatment.
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    Protective Effects of Estradiol and Dihydrotestosterone following Spinal Cord Injury
    (Mary Ann Liebert, 2018-03-15) Sengelaub, Dale R.; Han, Qi; Liu, Nai-Kui; Maczuga, Melissa A.; Szalavari, Violetta; Valencia, Stephanie A.; Xu, Xiao-Ming; Neurological Surgery, School of Medicine
    Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. We previously demonstrated that motoneurons and the muscles they innervate show pronounced atrophy after SCI, and these changes are prevented by treatment with testosterone. Here, we assessed whether the testosterone active metabolites estradiol and dihydrotestosterone have similar protective effects after SCI. Young adult female rats received either sham or T9 spinal cord contusion injuries and were treated with estradiol, dihydrotestosterone, both, or nothing via Silastic capsules. Basso-Beattie-Bresnahan locomotor testing was performed weekly and voiding behavior was assessed at 3 weeks post-injury. Four weeks after SCI, lesion volume and tissue sparing, quadriceps muscle fiber cross-sectional area, and motoneuron dendritic morphology were assessed. Spontaneous locomotor behavior improved after SCI, but hormone treatments had no effect. Voiding behavior was disrupted after SCI, but was significantly improved by treatment with either estradiol or dihydrotestosterone; combined treatment was maximally effective. Treatment with estradiol reduced lesion volume, but dihydrotestosterone alone and estradiol combined with dihydrotestosterone were ineffective. SCI-induced decreases in motoneuron dendritic length were attenuated by all hormone treatments. SCI-induced reductions in muscle fiber cross-sectional areas were prevented by treatment with either dihydrotestosterone or estradiol combined with dihydrotestosterone, but estradiol treatment was ineffective. These findings suggest that deficits in micturition and regressive changes in motoneuron and muscle morphology seen after SCI are ameliorated by treatment with estradiol or dihydrotestosterone, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.
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    Protective effects of gonadal hormones on spinal motoneurons following spinal cord injury
    (Medknow Publications, 2018-06) Sengelaub, Dale R.; Xu, Xiao-Ming; Neurological Surgery, School of Medicine
    Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. The majority of treatment strategies after SCI have concentrated on the damaged spinal cord, for example working to reduce lesion size or spread, or encouraging regrowth of severed descending axonal projections through the lesion, hoping to re-establish synaptic connectivity with caudal targets. In our work, we have focused on a novel target for treatment after SCI, surviving spinal motoneurons and their target musculature, with the hope of developing effective treatments to preserve or restore lost function following SCI. We previously demonstrated that motoneurons, and the muscles they innervate, show pronounced atrophy after SCI. Importantly, SCI-induced atrophy of motoneuron dendrites can be attenuated by treatment with gonadal hormones, testosterone and its active metabolites, estradiol and dihydrotestosterone. Similarly, SCI-induced reductions in muscle fiber cross-sectional areas can be prevented by treatment with androgens. Together, these findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be ameliorated by treatment with gonadal hormones, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.
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    Regeneration and plasticity of descending propriospinal neurons after transplantation of Schwann cells overexpressing glial cell line-derived neurotrophic factor following thoracic spinal cord injury in adult rats
    (2015-07) Deng, Lingxiao; Xu, Xiao-Ming; Sengelaub, Dale R.; Jin, Xiao-Ming; Khanna, Rajesh; Chen, Jinhui
    After spinal cord injury (SCI), poor axonal regeneration of the central nervous system, which mainly attributed to glial scar and low intrinsic regenerating capacity of severely injured neurons, causes limited functional recovery. Combinatory strategy has been applied to target multiple mechanisms. Schwann cells (SCs) have been explored as promising donors for transplantation to promote axonal regeneration. Among the central neurons, descending propriospinal neurons (DPSN) displayed the impressive regeneration response to SCs graft. Glial cell line-derived neurotrophic factor (GDNF), which receptor is widely expressed in nervous system, possesses the ability to promote neuronal survival, axonal regeneration/sprouting, remyelination, synaptic formation and modulate the glial response. We constructed a novel axonal permissive pathway in rat model of thoracic complete transection injury by grafting SCs over-expressing GDNF (SCs-GDNF) both inside and caudal to the lesion gap. Behavior evaluation and histological analyses have been applied to this study. Our results indicated that tremendous DPSN axons as well as brain stem axons regenerated across the lesion gap back to the caudal spinal cord. In addition to direct promotion on axonal regeneration, GDNF also significantly improved the astroglial environment around the lesion. These regenerations caused motor functional recovery. The dendritic plasticity of axotomized DPSN also contributed to the functional recovery. We applied a G-mutated rabies virus (G-Rabies) co-expressing green fluorescence protein (GFP) to reveal Golgi-like dendritic morphology of DPSNs and its response to axotomy injury and GDNF treatment. We also investigated the neurotransmitters phenotype of FluoroGold (FG) labeled DPSNs. Our results indicated that over 90 percent of FG-labeled DPSNs were glutamatergic neurons. DPSNs in sham animals had a predominantly dorsal-ventral distribution of dendrites. Transection injury resulted in alterations in the dendritic distribution, with dorsal-ventral retraction and lateral-medial extension of dendrites. Treatment with GDNF significantly increased the terminal dendritic length of DPSNs. The density of spine-like structures was increased after injury and treatment with GDNF enhanced this effect.
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    The Role of Interleukin-10 in CD4+ T Cell-Mediated Neuroprotection after Facial Nerve Injury
    (2019-05) Runge, Elizabeth Marie; Jones, Kathryn J.; Block, Michelle L.; Sanders, Virginia M.; Sengelaub, Dale R.; Xu, Xiao-Ming
    The adaptive arm of the immune system is necessary for facial motoneuron (FMN) survival after facial nerve axotomy (FNA). CD4+ T cells mediate FMN survival after FNA in an interleukin-10 (IL-10) dependent manner, but are not themselves the cellular source of neuroprotective IL-10. The aims of this study are to elucidate the neuroprotective capacity of cell-specific IL-10 expression, and to investigate the manner in which CD4+ T cells participate in IL-10 signaling after FNA. Immunohistochemistry revealed that FMN themselves were constitutive producers of IL-10, and 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 is 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 was necessary for FMN survival. Gene expression analysis of wild-type, immunodeficient, and immune cell-reconstituted animals was performed to determine the role of the immune system in modulating the central IL-10 signaling cascade. This revealed that CD4+ T cells were necessary for full upregulation of central IL-10 receptor (IL-10R) expression after FNA, regardless of their own IL-10R beta (IL-10RB) expression or IL-10R signaling capability. Surprisingly, the ability of CD4+ T cells to respond to IL-10 was critical for their ability to mediate neuroprotection. Adoptive transfer of IL-10RB-deficient T cells resulted in increased central expression of genes associated with microglial activation, antigen presentation, T cell co-stimulation, and complement deposition in response to injury. These data suggest that IL-10RB functions on the T cell to prevent non-neuroprotective immune activation after axotomy. The conclusions drawn from this study support a revised hypothesis for the mechanisms of IL-10-mediated neuroprotection, in which IL-10 serves both trophic and immune-modulating roles after axotomy. This research has implications for the development of immune-modifying therapies for peripheral nerve injury and motoneuron diseases.