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An in vitro model yields ‘importin’ new insights into chronic traumatic encephalopathy: damaged astrocytes stop ‘thrombospondin’ to the injury An Editorial Highlight for ‘Defective synthesis and release of astrocytic thrombospondin‐1 mediates the neuronal TDP‐43 proteinopathy, resulting in defects in neuronal integrity associated with chronic traumatic encephalopathy: in vitro studies’This Editorial highlights a study by Jayakumar and colleagues (2016) in the current issue of Journal of Neurochemistry. The authors introduce an in vitro model of chronic traumatic encephalopathy (CTE) to explore the mechanistic underpinnings of CTE pathogenesis, including investigation of how traumatized astrocytes affect traumatized neurons through the release of secreted factors. The model recapitulates two key features of the human post-mortem CTE brain: neuronal tauopathy and TDP-43 proteinopathy—the respective accretion of hyperphosphorylated tau and cytoplasmic hyperphosphorylated and ubiquitinated TDP-43. Oxidative stress and casein kinase 1 episilon (CK1ε) are identified as key upstream regulators of cytoplasmic TDP-43 phosphorylation, and this phosphorylation is found to correlate with decreased importin-β protein level and a decline in synaptic integrity. RNA silencing of importin-β is sufficient to mimic both the phospho-TDP-43 accumulation and synaptic injury observed after mild in vitro trauma. Strikingly, Jayakumar et al. find that thrombospondin-1 (TSP-1), a protein secreted by traumatized astrocytes at elevated levels during the initial 5 days after damage, can attenuate CK1ε phosphorylation of TDP-43 and synaptic injury. However, TSP-1 secretion by astrocytes is lost at 10–15 days post-injury, and neurons succumb to unchecked TDP-43 pathogenesis.
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Chronic Sensory and Affective Craniofacial Pain After Blast-Induced Traumatic Brain Injury and Peripheral Nerve Injury in RatsThousands of military members suffer long-term consequences of blast-induced traumatic brain injury (Blast-TBI), including chronic head and face pain. Pain after blast-TBI usually manifests as post-traumatic headaches with a high degree of comorbid mood disorders, suggesting that the affective dimension of pain may burden survivors of blast-TBI. Here, we tested the hypothesis that an innovative model of the unique aspect of blast-TBI over blunt-force TBI, the primary blast injury, directed over the cranium sufficiently modeled long-term conditions of human blast exposure in rats. Rats exposed to cranium-directed primary blast-TBI demonstrated behavioral manifestations of ongoing pain, mechanical hyperalgesia, and cold allodynia three weeks after injury, recapitulating chronic facial pain in patients after blast-TBI. We predicted that maladaptive changes to pain-signaling and -processing nuclei in CNS would induce and maintain pain behavior after blast-TBI. We recorded single units in sensory pain-associated nuclei, the posterior nucleus of the thalamus (PO) and spinal trigeminal nucleus caudalis (SpVc), which have previously been causally associated with pain after spinal cord injury. We observed hyperexcitability at baseline of PO neurons after blast injury in absence of changes to evoked response to cutaneous noxious stimuli. Neuronal hyperexcitability in PO is not associated with persistent gliosis. Affective pain processing through the parabrachial complex (PB) occurs in parallel to information coding the sensory dimension of pain through PO. We assessed central changes to PB neuronal activity in a robust model of post-traumatic pain using the chronic constriction injury of the infraorbital nerve (CCI-ION). PB neurons, weeks to months after injury, are hyper-excitable in chronic pain, as shown by prolonged response after presentation of noxious cutaneous stimulation ("after-discharges"), previously observed to be causally-related to pain due to CCI-ION in SpVc. Further study of PB hyperexcitability in blast-TBI rodent models may elucidate the mechanism underlying blast-TBI-associated affective pain.
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Spinal cord injury in the setting of traumatic thoracolumbar fracture is not reliably associated with increased risk of associated intra-abdominal injury following blunt trauma: An analysis of a National Trauma Registry databasePurpose: There is a common opinion that spine fractures usually reflect the substantial impact of injuries and therefore may be used as a marker of significant associated injuries, specifically for intra-abdominal injury (IAI). The impact of concomitant spinal cord injury (SCI) with the risk of associated IAI has not been well clarified. The aim of this study was to evaluate the incidence and severity of IAIs in patients suffering from spine fractures with or without SCI. Methods: A retrospective cohort study using the Israeli National Trauma Registry was conducted. Patients with thoracic, lumbar and thoracolumbar fractures resulting from blunt mechanisms of injury from 1997 to 2018 were examined, comparing the incidence, severity and mortality of IAIs in patients with or without SCI. The collected variables included age, gender, mechanism of injury, incidence and severity of the concomitant IAIs and pelvic fractures, abbreviated injury scale, injury severity score, and mortality. Statistical analysis was performed using GraphPad InStat ® Version 3.10, with Chi-square test for independence and two sided Fisher's exact probability test. Results: Review of the Israeli National Trauma Database revealed a total of 16,878 patients with spinal fractures. Combined thoracic and lumbar fractures were observed in 7.5% of patients; isolated thoracic fractures in 29.4% and isolated lumbar fractures in 63.0%. The incidence of concomitant SCI was found in 4.95% (63/1272), 7.65% (380/4967) and 2.5% (266/10639) of these patients, respectively. The overall mortality was 2.5%, proving higher among isolated thoracic fractures patients than among isolated lumbar fractures counterparts (11.3% vs. 4.6%, p < 0.001). Isolated thoracic fractures with SCI were significantly more likely to die than non-SCI counterparts (8.2% vs. 3.1%, p < 0.001). There were no differences in the incidence of IAIs between patients with or without SCI following thoracolumbar fracture overall or in isolated thoracic fractures; although isolated lumbar fractures patients with SCI were more likely to have renal (3.4% vs. 1.6%, p = 0.02) or bowel injuries (2.3% vs. 1.0%, p = 0.04) than the non-SCI counterparts. Conclusion: SCI in the setting of thoracolumbar fracture does not appear to be a marker for associated IAI. However, in a subset of isolated lumbar fractures, SCI patient is associated with increased risks for renal and bowel injury.
