The Ca2+ activated SK3 channel is expressed in microglia in the rat striatum and contributes to microglia-mediated neurotoxicity in vitro

<p>Abstract</p> <p>Background</p> <p>Small-conductance Ca²⁺activated K⁺channels are expressed in the CNS, where <it>KCNN2</it>/SK2/KCa2.2 and <it>KCNN3</it>/SK3/KCa2.3 help shape the electrical activity of some neurons. The SK3 channel is considered a potential therapeutic target for diseases and disorders involving neuron hyper-excitability but little is known about its expression and roles in non-neuronal cells in either the healthy or damaged CNS. The purpose of this study was to examine expression of <it>KCNN3</it>/SK3 in CNS microglia <it>in vivo </it>and <it>in vitro</it>, and to use an established <it>in vitro </it>model to determine if this channel contributes to the neurotoxic capacity of activated microglia.</p> <p>Methods</p> <p><it>KCNN3 </it>mRNA (real-time RT-PCR) and SK3 immunoreactivity were examined in rat microglia. Lipopolysaccharide was then used to activate microglia (monitored by iNOS, nitric oxide, activation of NF-κB and p38 MAPK) and transform them to a neurotoxic state. Microglia-mediated neuron damage (TUNEL, activated caspase 3) and nitrotyrosine levels were quantified using a two-chamber system that allowed microglia to be treated with channel blockers, washed and then added to neuron/astrocyte cultures. Contributions of SK3 to these processes were discriminated using a subtractive pharmacological approach with apamin and tamapin. ANOVA and post-hoc tests were used to assess the statistical significance of differences between treatment groups. SK3 immunoreactivity was then compared in the normal and damaged adult rat striatum, by injecting collagenase (a hemorrhagic stroke) or endothelin-1 (a transient ischemic stroke).</p> <p>Results</p> <p><it>KCNN3 </it>mRNA was prevalent in cultured microglia and increased after lipopolysaccharide-induced activation; SK3 channel blockade inhibited microglial activation and reduced their ability to kill neurons. SK3 immunoreactivity was prevalent in cultured microglia and throughout the adult rat striatum (except white matter tracts). After strokes, SK3 was highly expressed in activated microglia/macrophages within the lesions, but reduced in other cells.</p> <p>Conclusions</p> <p>SK3 is expressed in microglia in both the healthy and damaged adult striatum, and mechanistic <it>in vitro </it>studies show it contributes to transformation of microglia to an activated neurotoxic phenotype. Thus, SK3 might be a therapeutic target for reducing inflammation-mediated acute CNS damage. Moreover, its roles in microglia must be considered when targeting this channel for CNS diseases, disorders and reducing neuron hyper-excitability.</p

Medulloblastoma has a global impact on health related quality of life: Findings from an international cohort.

BackgroundUnderstanding the global impact of medulloblastoma on health related quality of life (HRQL) is critical to characterizing the broad impact of this disease and realizing the benefits of modern treatments. We evaluated HRQL in an international cohort of pediatric medulloblastoma patients.MethodsSeventy-six patients were selected from 10 sites across North America, Europe, and Asia, who participated in the Medulloblastoma Advanced Genomics International Consortium (MAGIC). The Health Utilities Index (HUI) was administered to patients and/or parents at each site. Responses were used to determine overall HRQL and attributes (ie specific subdomains). The impact of various demographic and medical variables on HRQL was considered-including molecular subgroup.ResultsThe majority of patients reported having moderate or severe overall burden of morbidity for both the HUI2 and HUI3 (HUI2&nbsp;=&nbsp;60%; HUI3&nbsp;=&nbsp;72.1%) when proxy-assessed. Self-care in the HUI2 was rated as higher (ie better outcome) for patients from Western versus Eastern sites, P&nbsp;=&nbsp;.02. Patients with nonmetastatic status had higher values (ie better outcomes) for the HUI3 hearing, HUI3 pain, and HUI2 pain, all P&nbsp;&lt;&nbsp;.05. Patients treated with a gross total resection also&nbsp;had better outcomes for the HUI3 hearing (P&nbsp;=&nbsp;.04). However, those who underwent a gross total resection reported&nbsp;having worse outcomes on the HUI3 vision (P&nbsp;=&nbsp;.02). No differences in HRQL were evident as a function of subgroup.ConclusionsBy examining an international sample of survivors, we characterized the worldwide impact of medulloblastoma. This is a critical first step in developing global standards for evaluating long-term outcomes

Medulloblastoma has a global impact on health related quality of life: Findings from an international cohort

Background: Understanding the global impact of medulloblastoma on health related quality of life (HRQL) is critical to characterizing the broad impact of this disease and realizing the benefits of modern treatments. We evaluated HRQL in an international cohort of pediatric medulloblastoma patients. Methods: Seventy-six patients were selected from 10 sites across North America, Europe, and Asia, who participated in the Medulloblastoma Advanced Genomics International Consortium (MAGIC). The Health Utilities Index (HUI) was administered to patients and/or parents at each site. Responses were used to determine overall HRQL and attributes (ie specific subdomains). The impact of various demographic and medical variables on HRQL was considered—including molecular subgroup. Results: The majority of patients reported having moderate or severe overall burden of morbidity for both the HUI2 and HUI3 (HUI2 = 60%; HUI3 = 72.1%) when proxy-assessed. Self-care in the HUI2 was rated as higher (ie better outcome) for patients from Western versus Eastern sites, P =.02. Patients with nonmetastatic status had higher values (ie better outcomes) for the HUI3 hearing, HUI3 pain, and HUI2 pain, all P <.05. Patients treated with a gross total resection also had better outcomes for the HUI3 hearin

White Matter Damage and Inflammation in Rat Models of Ischemic and Hemorrhagic Stroke

Cerebral ischemia and intracerebral hemorrhage (ICH) are both characterized by a prolonged inflammatory response and secondary injury phase, yet the spatial/temporal relationships between inflammation and white matter (WM) damage were largely unknown. Thus, I quantified the development of WM damage and inflammation over 7 days after ischemia, and 14 days after ICH. Following ischemia, myelin and axons were progressively damaged, and myelin damage coincided with neutrophil infiltration. Activated microglia/macrophages increased dramatically in the lesion core and edge, and selectively infiltrated damaged WM tracts while surrounding undamaged ones. To investigate the involvement of neutrophils in WM damage and inflammation after ICH, rats were rendered neutropenic before performing ICH. Neutrophil depletion reduced peri-hematomal axonal damage, BBB breakdown, and MMP-9 production at early times, and lessened microglia/macrophage and astrocyte responses at later times. Activated microglia/macrophages infiltrated peri-hematomal WM tracts, correlating with myelin fragmentation and axonal loss, and this was reduced with neutrophil depletion.MAS

White Matter Microstructure and Emotional Functioning in Children Treated for Posterior Fossa Tumours

Children treated for brain tumours that arise in the posterior fossa (PF) experience lifelong cognitive and emotional difficulties, and exhibit white matter (WM) damage. This thesis combined diffusion tensor imaging (DTI), eye-tracking and standardized measures of cognitive and emotional functioning in children treated for PF tumours and typically developing children, to: 1) characterize outcomes related to decreases in treatment intensity, 2) objectively evaluate emotional functioning, and 3) examine the associations between WM microstructure and emotional functioning. It was found that treatment with the lowest intensity craniospinal irradiation protocol spared WM in the temporal lobe of children treated for malignant PF tumours. In addition, patients treated on lower intensity protocols had largely preserved cognitive, social and affective functioning. However, novel eye-tracking tasks designed to evaluate emotional functioning uncovered some remaining deficits; children treated for PF tumours had difficulty recognizing facial emotions despite attending to the faces, and difficulty regulating their initial attention away from emotional faces. Notably, this eye-tracking measure of emotion regulation was associated with emotional control in daily life. The current work also revealed that relations between WM microstructure and emotional functioning can diverge in the injured and uninjured brain; WM predicted facial emotion recognition in typically developing children only, whereas WM was associated with emotion regulation in patients only. In a field dominated by findings that characterize negative sequelae, this work highlights the possibility of favourable outcomes for PF tumour patients who are eligible for treatment with lower intensity protocols. Despite these positive outcomes, subtle emotional functioning deficits not captured by standardized questionnaires persist. To better understand how emotional processes are altered in children treated for PF tumours, novel objective measures are required. This thesis detailed one such behavioural marker to evaluate emotion regulation, using eye-tracking technology, and characterized an oculomotor response that may warrant interventional follow-up.Ph.D

Neuropsychological Outcome following Cranio-spinal Radiation in Medulloblastoma Patients: A Longitudinal Analysis of Predictors

Medulloblastoma is the most common malignant central nervous system (CNS) tumor in childhood. The cranio-spinal radiation (CSR) required to treat this disease results in long-term cognitive and neurologic impairments. Medulloblastoma was recently categorized into four genetic subgroups (WNT, SHH, Group 3, and Group 4). This study examined neuropsychological and intellectual functioning in 91 medulloblastoma patients (41 Group 4; 20 Group 3; 18 SHH; 12 WNT) following treatment, and examined the impact of several medical, treatment and demographic factors on functioning over time. Longitudinal growth curve analyses revealed hydrocephalus most clearly predisposes to poor neuropsychological functioning. Results also indicate medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. All subgroups experience intellectual declines following treatment; however, comparing between subgroups revealed Group 4 performs most poorly, and Group 3 has the best overall intellectual outcome. Lastly, qualitative analyses suggest treatment with a larger CSR dose may contribute to poor intellectual functioning.MAS

Modulation of Dorsolateral Prefrontal Cortex Glutamate/Glutamine Levels Following Repetitive Transcranial Magnetic Stimulation in Young Adults With Autism

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