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Hameed MQ, Hodgson N, Lee HHC, Pascual-Leone A, MacMullin PC, Jannati A, Dhamne SC, Hensch TK, Rotenberg A. N-acetylcysteine treatment mitigates loss of cortical parvalbumin-positive interneuron and perineuronal net integrity resulting from persistent oxidative stress in a rat TBI model. Cereb Cortex 2023; 33:4070-4084. [PMID: 36130098 PMCID: PMC10068300 DOI: 10.1093/cercor/bhac327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 11/12/2022] Open
Abstract
Traumatic brain injury (TBI) increases cerebral reactive oxygen species production, which leads to continuing secondary neuronal injury after the initial insult. Cortical parvalbumin-positive interneurons (PVIs; neurons responsible for maintaining cortical inhibitory tone) are particularly vulnerable to oxidative stress and are thus disproportionately affected by TBI. Systemic N-acetylcysteine (NAC) treatment may restore cerebral glutathione equilibrium, thus preventing post-traumatic cortical PVI loss. We therefore tested whether weeks-long post-traumatic NAC treatment mitigates cortical oxidative stress, and whether such treatment preserves PVI counts and related markers of PVI integrity and prevents pathologic electroencephalographic (EEG) changes, 3 and 6 weeks after fluid percussion injury in rats. We find that moderate TBI results in persistent oxidative stress for at least 6 weeks after injury and leads to the loss of PVIs and the perineuronal net (PNN) that surrounds them as well as of per-cell parvalbumin expression. Prolonged post-TBI NAC treatment normalizes the cortical redox state, mitigates PVI and PNN loss, and - in surviving PVIs - increases per-cell parvalbumin expression. NAC treatment also preserves normal spectral EEG measures after TBI. We cautiously conclude that weeks-long NAC treatment after TBI may be a practical and well-tolerated treatment strategy to preserve cortical inhibitory tone post-TBI.
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Affiliation(s)
- Mustafa Q Hameed
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Department of Neurosurgery, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Nathaniel Hodgson
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Henry H C Lee
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children’s Hospital, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Andres Pascual-Leone
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Paul C MacMullin
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Ali Jannati
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Sameer C Dhamne
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
| | - Takao K Hensch
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Department of Molecular & Cellular Biology, Center for Brain Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, United States
| | - Alexander Rotenberg
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, United States
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children’s Hospital, 300 Longwood Avenue, Boston, MA 02115, United States
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Golub VM, Reddy DS. Post-Traumatic Epilepsy and Comorbidities: Advanced Models, Molecular Mechanisms, Biomarkers, and Novel Therapeutic Interventions. Pharmacol Rev 2022; 74:387-438. [PMID: 35302046 PMCID: PMC8973512 DOI: 10.1124/pharmrev.121.000375] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Post-traumatic epilepsy (PTE) is one of the most devastating long-term, network consequences of traumatic brain injury (TBI). There is currently no approved treatment that can prevent onset of spontaneous seizures associated with brain injury, and many cases of PTE are refractory to antiseizure medications. Post-traumatic epileptogenesis is an enduring process by which a normal brain exhibits hypersynchronous excitability after a head injury incident. Understanding the neural networks and molecular pathologies involved in epileptogenesis are key to preventing its development or modifying disease progression. In this article, we describe a critical appraisal of the current state of PTE research with an emphasis on experimental models, molecular mechanisms of post-traumatic epileptogenesis, potential biomarkers, and the burden of PTE-associated comorbidities. The goal of epilepsy research is to identify new therapeutic strategies that can prevent PTE development or interrupt the epileptogenic process and relieve associated neuropsychiatric comorbidities. Therefore, we also describe current preclinical and clinical data on the treatment of PTE sequelae. Differences in injury patterns, latency period, and biomarkers are outlined in the context of animal model validation, pathophysiology, seizure frequency, and behavior. Improving TBI recovery and preventing seizure onset are complex and challenging tasks; however, much progress has been made within this decade demonstrating disease modifying, anti-inflammatory, and neuroprotective strategies, suggesting this goal is pragmatic. Our understanding of PTE is continuously evolving, and improved preclinical models allow for accelerated testing of critically needed novel therapeutic interventions in military and civilian persons at high risk for PTE and its devastating comorbidities.
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Affiliation(s)
- Victoria M Golub
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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Mountney A, Blaze J, Wang Z, Umali M, Flerlage WJ, Dougherty J, Ge Y, Shear D, Haghighi F. Penetrating Ballistic Brain Injury Produces Acute Alterations in Sleep and Circadian-Related Genes in the Rodent Cortex: A Preliminary Study. Front Neurol 2021; 12:745330. [PMID: 34777213 PMCID: PMC8580116 DOI: 10.3389/fneur.2021.745330] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/22/2021] [Indexed: 11/23/2022] Open
Abstract
Traumatic brain injury (TBI) affects millions of Americans each year, with extremely high prevalence in the Veteran community, and sleep disturbance is one of the most commonly reported symptoms. Reduction in the quality and amount of sleep can negatively impact recovery and result in a wide range of behavioral and physiological symptoms, such as impaired cognition, mood and anxiety disorders, and cardiovascular effects. Thus, to improve long-term patient outcomes and develop novel treatments, it is essential to understand the molecular mechanisms involved in sleep disturbance following TBI. In this effort, we performed transcriptional profiling in an established rodent model of penetrating ballistic brain injury (PBBI) in conjunction with continuous sleep/wake EEG/EMG recording of the first 24 h after injury. Rats subjected to PBBI showed profound differences in sleep architecture. Injured animals spent significantly more time in slow wave sleep and less time in REM sleep compared to sham control animals. To identify PBBI-related transcriptional differences, we then performed transcriptome-wide gene expression profiling at 24 h post-injury, which identified a vast array of immune- related genes differentially expressed in the injured cortex as well as sleep-related genes. Further, transcriptional changes associated with total time spent in various sleep stages were identified. Such molecular changes may underlie the pathology and symptoms that emerge following TBI, including neurodegeneration, sleep disturbance, and mood disorders.
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Affiliation(s)
- Andrea Mountney
- Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Jennifer Blaze
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Zhaoyu Wang
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Michelle Umali
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | | | - Jacqueline Dougherty
- Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Yongchao Ge
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Deborah Shear
- Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Fatemeh Haghighi
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Research and Development Service, James J. Peters Veterans Affairs Medical Center, Bronx, NY, United States
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Smith DH, Kochanek PM, Rosi S, Meyer R, Ferland-Beckham C, Prager EM, Ahlers ST, Crawford F. Roadmap for Advancing Pre-Clinical Science in Traumatic Brain Injury. J Neurotrauma 2021; 38:3204-3221. [PMID: 34210174 PMCID: PMC8820284 DOI: 10.1089/neu.2021.0094] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pre-clinical models of disease have long played important roles in the advancement of new treatments. However, in traumatic brain injury (TBI), despite the availability of numerous model systems, translation from bench to bedside remains elusive. Integrating clinical relevance into pre-clinical model development is a critical step toward advancing therapies for TBI patients across the spectrum of injury severity. Pre-clinical models include in vivo and ex vivo animal work-both small and large-and in vitro modeling. The wide range of pre-clinical models reflect substantial attempts to replicate multiple aspects of TBI sequelae in humans. Although these models reveal multiple putative mechanisms underlying TBI pathophysiology, failures to translate these findings into successful clinical trials call into question the clinical relevance and applicability of the models. Here, we address the promises and pitfalls of pre-clinical models with the goal of evolving frameworks that will advance translational TBI research across models, injury types, and the heterogenous etiology of pathology.
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Affiliation(s)
- Douglas H Smith
- Center for Brain Injury and Repair, Department of Neurosurgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Patrick M Kochanek
- Department of Critical Care Medicine; Safar Center for Resuscitation Research, University of Pittsburgh School of Medicine and Children's Hospital of Pittsburgh of UPMC, Rangos Research Center, Pittsburgh, Pennsylvania, USA
| | - Susanna Rosi
- Departments of Physical Therapy Rehabilitation Science, Neurological Surgery, Weill Institute for Neuroscience, University of California San Francisco, Zuckerberg San Francisco General Hospital, San Francisco, California, USA
| | - Retsina Meyer
- Cohen Veterans Bioscience, New York, New York, USA.,Delix Therapeutics, Inc, Boston, Massachusetts, USA
| | | | | | - Stephen T Ahlers
- Department of Neurotrauma, Operational and Undersea Medicine Directorate Naval Medical Research Center, Silver Spring, Maryland, USA
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Santana-Gomez CE, Medel-Matus JS, Rundle BK. Animal models of post-traumatic epilepsy and their neurobehavioral comorbidities. Seizure 2021; 90:9-16. [DOI: 10.1016/j.seizure.2021.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 05/07/2021] [Accepted: 05/09/2021] [Indexed: 12/30/2022] Open
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Andrade P, Banuelos-Cabrera I, Lapinlampi N, Paananen T, Ciszek R, Ndode-Ekane XE, Pitkänen A. Acute Non-Convulsive Status Epilepticus after Experimental Traumatic Brain Injury in Rats. J Neurotrauma 2019; 36:1890-1907. [PMID: 30543155 DOI: 10.1089/neu.2018.6107] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Severe traumatic brain injury (TBI) induces seizures or status epilepticus (SE) in 20-30% of patients during the acute phase. We hypothesized that severe TBI induced with lateral fluid-percussion injury (FPI) triggers post-impact SE. Adult Sprague-Dawley male rats were anesthetized with isoflurane and randomized into the sham-operated experimental control or lateral FPI-induced severe TBI groups. Electrodes were implanted right after impact or sham-operation, then video-electroencephalogram (EEG) monitoring was started. In addition, video-EEG was recorded from naïve rats. During the first 72 h post-TBI, injured rats had seizures that were intermingled with other epileptiform EEG patterns typical to non-convulsive SE, including occipital intermittent rhythmic delta activity, lateralized or generalized periodic discharges, spike-and-wave complexes, poly-spikes, poly-spike-and-wave complexes, generalized continuous spiking, burst suppression, or suppression. Almost all (98%) of the electrographic seizures were recorded during 0-72 h post-TBI (23.2 ± 17.4 seizures/rat). Mean latency from the impact to the first electrographic seizure was 18.4 ± 15.1 h. Mean seizure duration was 86 ± 57 sec. Analysis of high-resolution videos indicated that only 41% of electrographic seizures associated with behavioral abnormalities, which were typically subtle (Racine scale 1-2). Fifty-nine percent of electrographic seizures did not show any behavioral manifestations. In most of the rats, epileptiform EEG patterns began to decay spontaneously on Days 5-6 after TBI. Interestingly, also a few sham-operated and naïve rats had post-operation seizures, which were not associated with EEG background patterns typical to non-convulsive SE seen in TBI rats. To summarize, our data show that lateral FPI-induced TBI results in non-convulsive SE with subtle behavioral manifestations; this explains why it has remained undiagnosed until now. The lateral FPI model provides a novel platform for assessing the mechanisms of acute symptomatic non-convulsive SE and for testing treatments to prevent post-injury SE in a clinically relevant context.
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Affiliation(s)
- Pedro Andrade
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Ivette Banuelos-Cabrera
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Niina Lapinlampi
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Tomi Paananen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Robert Ciszek
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | | | - Asla Pitkänen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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Brady RD, Casillas-Espinosa PM, Agoston DV, Bertram EH, Kamnaksh A, Semple BD, Shultz SR. Modelling traumatic brain injury and posttraumatic epilepsy in rodents. Neurobiol Dis 2018; 123:8-19. [PMID: 30121231 DOI: 10.1016/j.nbd.2018.08.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 07/25/2018] [Accepted: 08/13/2018] [Indexed: 12/14/2022] Open
Abstract
Posttraumatic epilepsy (PTE) is one of the most debilitating and understudied consequences of traumatic brain injury (TBI). It is challenging to study the effects, underlying pathophysiology, biomarkers, and treatment of TBI and PTE purely in human patients for a number of reasons. Rodent models can complement human PTE studies as they allow for the rigorous investigation into the causal relationship between TBI and PTE, the pathophysiological mechanisms of PTE, the validation and implementation of PTE biomarkers, and the assessment of PTE treatments, in a tightly controlled, time- and cost-efficient manner in experimental subjects known to be experiencing epileptogenic processes. This article will review several common rodent models of TBI and/or PTE, including their use in previous studies and discuss their relative strengths, limitations, and avenues for future research to advance our understanding and treatment of PTE.
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Affiliation(s)
- Rhys D Brady
- Departments of Neuroscience and Medicine, Central Clinical School, Monash University, VIC 3004, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, VIC 3052, Australia.
| | - Pablo M Casillas-Espinosa
- Departments of Neuroscience and Medicine, Central Clinical School, Monash University, VIC 3004, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, VIC 3052, Australia.
| | - Denes V Agoston
- Anatomy, Physiology & Genetics, Uniformed Services University, Bethesda, MD 20814, USA
| | - Edward H Bertram
- Department of Neurology, University of Virginia, P.O. Box 800394, Charlottesville, VA 22908-0394, USA
| | - Alaa Kamnaksh
- Anatomy, Physiology & Genetics, Uniformed Services University, Bethesda, MD 20814, USA
| | - Bridgette D Semple
- Departments of Neuroscience and Medicine, Central Clinical School, Monash University, VIC 3004, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, VIC 3052, Australia
| | - Sandy R Shultz
- Departments of Neuroscience and Medicine, Central Clinical School, Monash University, VIC 3004, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, VIC 3052, Australia
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Combination therapy of levetiracetam and gabapentin against nonconvulsive seizures induced by penetrating traumatic brain injury. J Trauma Acute Care Surg 2017; 83:S25-S34. [PMID: 28452872 DOI: 10.1097/ta.0000000000001470] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Posttraumatic seizures are a medical problem affecting patients with traumatic brain injury. Yet effective treatment is lacking owing to the limitations of antiepileptic drugs (AEDs) applicable to these patients. METHODS In this study, we evaluated the dose-response efficacy of levetiracetam (12.5-100.0 mg/kg) and gabapentin (1.25-25.0 mg/kg) administered either individually or in pairs at fixed-dose ratios as a combination in mitigating posttraumatic nonconvulsive seizures induced by severe penetrating ballistic-like brain injury (PBBI) in rats. Seizures were detected by continuous electroencephalogram (EEG) monitoring for 72 hours postinjury. Animals were treated twice per day for 3 days by intravenous injections. RESULTS Both levetiracetam (25-100 mg/kg) and gabapentin (6.25-25 mg/kg) significantly reduced PBBI-induced seizure frequency by 44% to 73% and 61% to 69%, and seizure duration by 45% to 64% and 70% to 78%, respectively. However, the two drugs manifested different dose-response profiles. Levetiracetam attenuated seizure activity in a dose-dependent fashion, whereas the beneficial effects of gabapentin plateaued across the three highest doses tested. Combined administration of levetiracetam and gabapentin mirrored the more classic dose-response profile of levetiracetam monotherapy. However, no additional benefit was derived from the addition of gabapentin. Furthermore, isobolographic analysis of the combination dose-response profile of levetiracetam and gabapentin failed to reach the expected level of additivity, suggesting an unlikelihood of favorable interactions between these two drugs against spontaneously occurring posttraumatic seizure activities at the particular set of dose ratios tested. CONCLUSION This study was the first attempt to apply isobolographic approach to studying AED combination therapy in the context of spontaneously occurring posttraumatic seizures. Despite the failure to achieve additivity from levetiracetam and gabapentin combination, it is important to recognize the objectivity of the isobolographic approach in the evaluation of AED combination therapy against seizures directly associated with brain injuries.
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Acute and subacute microRNA dysregulation is associated with cytokine responses in the rodent model of penetrating ballistic-like brain injury. J Trauma Acute Care Surg 2017; 83:S145-S149. [DOI: 10.1097/ta.0000000000001475] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Mountney A, Boutté AM, Cartagena CM, Flerlage WF, Johnson WD, Rho C, Lu XC, Yarnell A, Marcsisin S, Sousa J, Vuong C, Zottig V, Leung LY, Deng-Bryant Y, Gilsdorf J, Tortella FC, Shear DA. Functional and Molecular Correlates after Single and Repeated Rat Closed-Head Concussion: Indices of Vulnerability after Brain Injury. J Neurotrauma 2017; 34:2768-2789. [PMID: 28326890 DOI: 10.1089/neu.2016.4679] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Closed-head concussive injury is one of the most common causes of traumatic brain injury (TBI). Isolated concussions frequently produce acute neurological impairments, and individuals typically recover spontaneously within a short time frame. In contrast, brain injuries resulting from multiple concussions can result in cumulative damage and elevated risk of developing chronic brain pathologies. Increased attention has focused on identification of diagnostic markers that can prognostically serve as indices of brain health after injury, revealing the temporal profile of vulnerability to a second insult. Such markers may demarcate adequate recovery periods before concussed patients can return to required activities. We developed a noninvasive closed-head impact model that captures the hallmark symptoms of concussion in the absence of gross tissue damage. Animals were subjected to single or repeated concussive impact and examined using a battery of neurological, vestibular, sensorimotor, and molecular metrics. A single concussion induced transient, but marked, acute neurological impairment, gait alterations, neuronal death, and increased glial fibrillary acidic protein (GFAP) expression in brain tissue. As expected, repeated concussions exacerbated sensorimotor dysfunction, prolonged gait abnormalities, induced neuroinflammation, and upregulated GFAP and tau. These animals also exhibited chronic functional neurological impairments with sustained astrogliosis and white matter thinning. Acute changes in molecular signatures correlated with behavioral impairments, whereas increased times to regaining consciousness and balance impairments were associated with higher GFAP and neuroinflammation. Overall, behavioral consequences of either single or repeated concussive impact injuries appeared to resolve more quickly than the underlying molecular, metabolic, and neuropathological abnormalities. This observation, which is supported by similar studies in other mTBI models, underscores the critical need to develop more objective prognostic measures for guiding return-to-play decisions.
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Affiliation(s)
- Andrea Mountney
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Angela M Boutté
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Casandra M Cartagena
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - William F Flerlage
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Wyane D Johnson
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Chanyang Rho
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Xi-Chu Lu
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Angela Yarnell
- 2 Behavioral Biology Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Sean Marcsisin
- 3 Division of Experimental Therapeutics, Military Malaria Research, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Jason Sousa
- 3 Division of Experimental Therapeutics, Military Malaria Research, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Chau Vuong
- 3 Division of Experimental Therapeutics, Military Malaria Research, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Victor Zottig
- 3 Division of Experimental Therapeutics, Military Malaria Research, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Lai-Yee Leung
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Ying Deng-Bryant
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Janice Gilsdorf
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Frank C Tortella
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Deborah A Shear
- 1 Brain Trauma Neuroprotection and Neurorestoration Branch, Walter Reed Army Institute of Research , Silver Spring, Maryland
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Caudle KL, Lu XCM, Mountney A, Shear DA, Tortella FC. Neuroprotection and anti-seizure effects of levetiracetam in a rat model of penetrating ballistic-like brain injury. Restor Neurol Neurosci 2016; 34:257-70. [PMID: 26890099 DOI: 10.3233/rnn-150580] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE We assessed the therapeutic efficacy of FDA-approved anti-epileptic drug Levetiracetam (LEV) to reduce post-traumatic nonconvulsive seizure (NCS) activity and promote neurobehavioral recovery following 10% frontal penetrating ballistic-like brain injury (PBBI) in male Sprague-Dawley rats. METHODS Experiment 1 anti-seizure study: 50 mg/kg LEV (25 mg/kg maintenance doses) was given twice daily for 3 days (LEV3D) following PBBI; outcome measures included seizures incidence, frequency, duration, and onset. Experiment 2 neuroprotection studies: 50 mg/kg LEV was given twice daily for either 3 (LEV3D) or 10 days (LEV10D) post-injury; outcome measures include motor (rotarod) and cognitive (water maze) functions. RESULTS LEV3D treatment attenuated seizure activity with significant reductions in NCS incidence (54%), frequency, duration, and delayed latency to seizure onset compared to vehicle treatment. LEV3D treatment failed to improve cognitive or motor performance; however extending the dosing regimen through 10 days post-injury afforded significant neuroprotective benefit. Animals treated with the extended LEV10D dosing regimen showed a twofold improvement in rotarod task latency to fall as well as significantly improved spatial learning performance (24%) in the MWM task. CONCLUSIONS These findings support the dual anti- seizure and neuroprotective role of LEV, but more importantly identify the importance of an extended dosing protocol which was specific to the therapeutic targets studied.
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Browning M, Shear DA, Bramlett HM, Dixon CE, Mondello S, Schmid KE, Poloyac SM, Dietrich WD, Hayes RL, Wang KKW, Povlishock JT, Tortella FC, Kochanek PM. Levetiracetam Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy. J Neurotrauma 2016; 33:581-94. [PMID: 26671550 DOI: 10.1089/neu.2015.4131] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Levetiracetam (LEV) is an antiepileptic agent targeting novel pathways. Coupled with a favorable safety profile and increasing empirical clinical use, it was the fifth drug tested by Operation Brain Trauma Therapy (OBTT). We assessed the efficacy of a single 15 min post-injury intravenous (IV) dose (54 or 170 mg/kg) on behavioral, histopathological, and biomarker outcomes after parasagittal fluid percussion brain injury (FPI), controlled cortical impact (CCI), and penetrating ballistic-like brain injury (PBBI) in rats. In FPI, there was no benefit on motor function, but on Morris water maze (MWM), both doses improved latencies and path lengths versus vehicle (p < 0.05). On probe trial, the vehicle group was impaired versus sham, but both LEV treated groups did not differ versus sham, and the 54 mg/kg group was improved versus vehicle (p < 0.05). No histological benefit was seen. In CCI, there was a benefit on beam balance at 170 mg/kg (p < 0.05 vs. vehicle). On MWM, the 54 mg/kg dose was improved and not different from sham. Probe trial did not differ between groups for either dose. There was a reduction in hemispheric tissue loss (p < 0.05 vs. vehicle) with 170 mg/kg. In PBBI, there was no motor, cognitive, or histological benefit from either dose. Regarding biomarkers, in CCI, 24 h glial fibrillary acidic protein (GFAP) blood levels were lower in the 170 mg/kg group versus vehicle (p < 0.05). In PBBI, GFAP blood levels were increased in vehicle and 170 mg/kg groups versus sham (p < 0.05) but not in the 54 mg/kg group. No treatment effects were seen for ubiquitin C-terminal hydrolase-L1 across models. Early single IV LEV produced multiple benefits in CCI and FPI and reduced GFAP levels in PBBI. LEV achieved 10 points at each dose, is the most promising drug tested thus far by OBTT, and the only drug to improve cognitive outcome in any model. LEV has been advanced to testing in the micropig model in OBTT.
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Affiliation(s)
- Megan Browning
- 1 Department of Critical Care Medicine, Safar Center for Resuscitation Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Deborah A Shear
- 2 Brain Trauma Neuroprotection/Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Helen M Bramlett
- 3 Department of Neurological Surgery, The Miami Project to Cure Paralysis, Miller School of Medicine, University of Miami , Miami, Florida.,4 Bruce W. Carter Department of Veterans Affairs Medical Center , Miami, Florida
| | - C Edward Dixon
- 5 Department of Neurological Surgery, Brain Trauma Research Center, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
| | - Stefania Mondello
- 6 Department of Neurosciences, University of Messina , Messina, Italy
| | - Kara E Schmid
- 2 Brain Trauma Neuroprotection/Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Samuel M Poloyac
- 7 Center for Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy , Pittsburgh, Pennsylvania
| | - W Dalton Dietrich
- 3 Department of Neurological Surgery, The Miami Project to Cure Paralysis, Miller School of Medicine, University of Miami , Miami, Florida
| | - Ronald L Hayes
- 8 Center for Innovative Research, Center for Neuroproteomics and Biomarkers Research , Banyan Biomarkers, Inc., Alachua, Florida
| | - Kevin K W Wang
- 9 Center of Neuroproteomics and Biomarkers Research, Department of Psychiatry and Neuroscience, University of Florida. Gainesville, Florida
| | - John T Povlishock
- 10 Department of Anatomy and Neurobiology, Virginia Commonwealth University , Richmond, Virginia
| | - Frank C Tortella
- 2 Brain Trauma Neuroprotection/Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Patrick M Kochanek
- 1 Department of Critical Care Medicine, Safar Center for Resuscitation Research, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania
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Abstract
Traumatic brain injury (TBI) greatly increases the risk of medically intractable epilepsy. Several models of TBI have been developed to investigate the relationship between TBI and posttraumatic epileptogenesis. Because the incident that precipitates development of epilepsy is known, studying mechanisms of epileptogenesis, identifying biomarkers to predict PTE, and developing treatments to prevent epilepsy after TBI are attainable research goals.
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Cui J, Ng LJ, Volman V. Callosal dysfunction explains injury sequelae in a computational network model of axonal injury. J Neurophysiol 2016; 116:2892-2908. [PMID: 27683891 DOI: 10.1152/jn.00603.2016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 09/22/2016] [Indexed: 12/28/2022] Open
Abstract
Mild traumatic brain injury (mTBI) often results in neurobehavioral aberrations such as impaired attention and increased reaction time. Diffusion imaging and postmortem analysis studies suggest that mTBI primarily affects myelinated axons in white matter tracts. In particular, corpus callosum, mediating interhemispheric information exchange, has been shown to be affected in mTBI. Yet little is known about the mechanisms linking the injury of myelinated callosal axons to the neurobehavioral sequelae of mTBI. To address this issue, we devised and studied a large, biologically plausible neuronal network model of cortical tissue. Importantly, the model architecture incorporated intra- and interhemispheric organization, including myelinated callosal axons and distance-dependent axonal conduction delays. In the resting state, the intact model network exhibited several salient features, including alpha-band (8-12 Hz) collective activity with low-frequency irregular spiking of individual neurons. The network model of callosal injury captured several clinical observations, including 1) "slowing down" of the network rhythms, manifested as an increased resting-state theta-to-alpha power ratio, 2) reduced response to attention-like network stimulation, manifested as a reduced spectral power of collective activity, and 3) increased population response time in response to stimulation. Importantly, these changes were positively correlated with injury severity, supporting proposals to use neurobehavioral indices as biomarkers for determining the severity of injury. Our modeling effort helps to understand the role played by the injury of callosal myelinated axons in defining the neurobehavioral sequelae of mTBI.
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Affiliation(s)
- Jianxia Cui
- L-3 Applied Technologies, Inc., San Diego, California
| | - Laurel J Ng
- L-3 Applied Technologies, Inc., San Diego, California
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15
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Ping X, Jin X. Chronic Posttraumatic Epilepsy following Neocortical Undercut Lesion in Mice. PLoS One 2016; 11:e0158231. [PMID: 27348225 PMCID: PMC4922553 DOI: 10.1371/journal.pone.0158231] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 06/13/2016] [Indexed: 12/01/2022] Open
Abstract
Posttraumatic epilepsy (PTE) usually develops in a small percentage of patients of traumatic brain injury after a varying latent period. Modeling this chronic neurological condition in rodents is time consuming and inefficient, which constitutes a significant obstacle in studying its mechanism and discovering novel therapeutics for its prevention and treatment. Partially isolated neocortex, or undercut, is known to induce cortical hyperexcitability and epileptiform activity in vitro, and has been used extensively for studying the neurophysiological mechanism of posttraumatic epileptogenesis. However, whether the undercut lesion in rodents causes chronic epileptic seizures has not been systematically characterized. Here we used a miniature telemetry system to continuously monitor electroencephalography (EEG) in adult C57BL mice for up to 3 months after undercut surgery. We found that 50% of animals developed spontaneous seizures between 16–50 days after injury. The mean seizure duration was 8.9±3.6 seconds, and the average seizure frequency was 0.17±0.17 times per day. There was no progression in seizure frequency and duration over the recording period. Video monitoring revealed behavioral arrests and clonic limb movement during seizure attacks. A pentylenetetrazol (PTZ) test further showed increased seizure susceptibility in the undercut mice. We conclude that undercut lesion in mice is a model of chronic PTE that involves spontaneous epileptic seizures.
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Affiliation(s)
- Xingjie Ping
- Department of Anatomy and Cell Biology, Stark Neurosciences Research Institute, Indiana Spinal Cord and Brain Injury Research Group, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, Indiana, 46202, United States of America
| | - Xiaoming Jin
- Department of Anatomy and Cell Biology, Stark Neurosciences Research Institute, Indiana Spinal Cord and Brain Injury Research Group, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, Indiana, 46202, United States of America
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16
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Lu XCM, Shear DA, Deng-Bryant Y, Leung LY, Wei G, Chen Z, Tortella FC. Comprehensive Evaluation of Neuroprotection Achieved by Extended Selective Brain Cooling Therapy in a Rat Model of Penetrating Ballistic-Like Brain Injury. Ther Hypothermia Temp Manag 2015; 6:30-9. [PMID: 26684246 DOI: 10.1089/ther.2015.0017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Brain hypothermia has been considered as a promising alternative to whole-body hypothermia in treating acute neurological disease, for example, traumatic brain injury. Previously, we demonstrated that 2-hours selective brain cooling (SBC) effectively mitigated acute (≤24 hours postinjury) neurophysiological dysfunction induced by a penetrating ballistic-like brain injury (PBBI) in rats. This study evaluated neuroprotective effects of extended SBC (4 or 8 hours in duration) on sub-acute secondary injuries between 3 and 21 days postinjury (DPI). SBC (34°C) was achieved via extraluminal cooling of rats' bilateral common carotid arteries (CCA). Depending on the experimental design, SBC was introduced either immediately or with a 2- or 4-hour delay after PBBI and maintained for 4 or 8 hours. Neuroprotective effects of SBC were evaluated by measuring brain lesion volume, axonal injury, neuroinflammation, motor and cognitive functions, and post-traumatic seizures. Compared to untreated PBBI animals, 4 or 8 hours SBC treatment initiated immediately following PBBI produced comparable neuroprotective benefits against PBBI-induced early histopathology at 3 DPI as evidenced by significant reductions in brain lesion volume, axonal pathology (beta-amyloid precursor protein staining), neuroinflammation (glial fibrillary acetic protein stained-activated astrocytes and rat major histocompatibility complex class I stained activated microglial cell), and post-traumatic nonconvulsive seizures. In the later phase of the injury (7-21 DPI), significant improvement on motor function (rotarod test) was observed under most SBC protocols, including the 2-hour delay in SBC initiation. However, SBC treatment failed to improve cognitive performance (Morris water maze test) measured 13-17 DPI. The protective effects of SBC on delayed axonal injury (silver staining) were evident out to 14 DPI. In conclusion, the CCA cooling method of SBC produced neuroprotection measured across multiple domains that were evident days/weeks beyond the cooling duration and in the absence of overt adverse effects. These "proof-of-concept" results suggest that SBC may provide an attractive neuroprotective approach for clinical considerations.
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Affiliation(s)
- Xi-Chun May Lu
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Deborah A Shear
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Ying Deng-Bryant
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Lai Yee Leung
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Guo Wei
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Zhiyong Chen
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
| | - Frank C Tortella
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
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McGinn MJ, Povlishock JT. Cellular and molecular mechanisms of injury and spontaneous recovery. HANDBOOK OF CLINICAL NEUROLOGY 2015; 127:67-87. [PMID: 25702210 DOI: 10.1016/b978-0-444-52892-6.00005-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Until recently, most have assumed that traumatic brain injury (TBI) was singularly associated with the overt destruction of brain tissue resulting in subsequent morbidity or death. More recently, experimental and clinical studies have shown that the pathobiology of TBI is more complex, involving a host of cellular and subcellular changes that impact on neuronal function and viability while also affecting vascular reactivity and the activation of multiple biological response pathways. Here we review the brain's response to injury, examining both focal and diffuse changes and their implications for post-traumatic brain dysfunction and recovery. TBI-induced neuronal dysfunction and death as well as the diffuse involvement of multiple fiber projections are discussed together with considerations of how local axonal membrane changes or channelopathy translate into local ionic dysregulation and axonal disconnection. Concomitant changes in the cerebral microcirculation are also discussed and their relationship with the parallel changes in the brain's metabolism is considered. These cellular and subcellular events occurring within neurons and their blood supply are correlated with multiple biological response modifiers evoked by generalized post-traumatic inflammation and the parallel activation of oxidative stress processes. The chapter closes with considerations of recovery following focal or diffuse injury. Evidence for dynamic brain reorganization/repair is presented, with considerations of traumatically induced circuit disruption and their progression to either adaptive or in some cases, maladaptive reorganization.
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Affiliation(s)
- Melissa J McGinn
- Department of Anatomy and Neurobiology, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, VA, USA
| | - John T Povlishock
- Department of Anatomy and Neurobiology, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, VA, USA.
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18
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Cunningham TL, Cartagena CM, Lu XCM, Konopko M, Dave JR, Tortella FC, Shear DA. Correlations between blood-brain barrier disruption and neuroinflammation in an experimental model of penetrating ballistic-like brain injury. J Neurotrauma 2014; 31:505-14. [PMID: 24138024 DOI: 10.1089/neu.2013.2965] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract Blood-brain barrier (BBB) disruption is a pathological hallmark of severe traumatic brain injury (TBI) and is associated with neuroinflammatory events contributing to brain edema and cell death. The goal of this study was to elucidate the profile of BBB disruption after penetrating ballistic-like brain injury (PBBI) in conjunction with changes in neuroinflammatory markers. Brain uptake of biotin-dextran amine (BDA; 3 kDa) and horseradish peroxidase (HRP; 44 kDa) was evaluated in rats at 4 h, 24 h, 48 h, 72 h, and 7 days post-PBBI and compared with the histopathologic and molecular profiles for inflammatory markers. BDA and HRP both displayed a uniphasic profile of extravasation, greatest at 24 h post-injury and which remained evident out to 48 h for HRP and 7 days for BDA. This profile was most closely associated with markers for adhesion (mRNA for intercellular adhesion molecule-1) and infiltration of peripheral granulocytes (mRNA for matrix metalloproteinase-9 [MMP-9] and myeloperoxidase staining). Improvement of BBB dysfunction coincided with increased expression of markers implicated in tissue remodeling and repair. The results of this study reveal a uniphasic and gradient opening of the BBB after PBBI and suggest MMP-9 and resident inflammatory cell activation as candidates for future neurotherapeutic intervention after PBBI.
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Affiliation(s)
- Tracy L Cunningham
- Walter Reed Army Institute of Research, Center for Military Psychiatry and Neuroscience , Branch of Brain Trauma Neuroprotection and Neurorestoration, Silver Spring, Maryland
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19
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Kovacs SK, Leonessa F, Ling GSF. Blast TBI Models, Neuropathology, and Implications for Seizure Risk. Front Neurol 2014; 5:47. [PMID: 24782820 PMCID: PMC3988378 DOI: 10.3389/fneur.2014.00047] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/26/2014] [Indexed: 12/31/2022] Open
Abstract
Traumatic brain injury (TBI) due to explosive blast exposure is a leading combat casualty. It is also implicated as a key contributor to war related mental health diseases. A clinically important consequence of all types of TBI is a high risk for development of seizures and epilepsy. Seizures have been reported in patients who have suffered blast injuries in the Global War on Terror but the exact prevalence is unknown. The occurrence of seizures supports the contention that explosive blast leads to both cellular and structural brain pathology. Unfortunately, the exact mechanism by which explosions cause brain injury is unclear, which complicates development of meaningful therapies and mitigation strategies. To help improve understanding, detailed neuropathological analysis is needed. For this, histopathological techniques are extremely valuable and indispensable. In the following we will review the pathological results, including those from immunohistochemical and special staining approaches, from recent preclinical explosive blast studies.
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Affiliation(s)
- S Krisztian Kovacs
- Laboratory of Neurotrauma, Department of Neurology, Uniformed Services University of the Health Sciences , Bethesda, MD , USA
| | - Fabio Leonessa
- Laboratory of Neurotrauma, Department of Neurology, Uniformed Services University of the Health Sciences , Bethesda, MD , USA
| | - Geoffrey S F Ling
- Laboratory of Neurotrauma, Department of Neurology, Uniformed Services University of the Health Sciences , Bethesda, MD , USA
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20
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Abstract
Post-traumatic epilepsy accounts for 10-20% of symptomatic epilepsy in the general population and 5% of all epilepsy. During the last decade, an increasing number of laboratories have investigated the molecular and cellular mechanisms of post-traumatic epileptogenesis in experimental models. However, identification of critical molecular, cellular, and network mechanisms that would be specific for post-traumatic epileptogenesis remains a challenge. Despite of that, 7 of 9 proof-of-concept antiepileptogenesis studies have demonstrated some effect on seizure susceptibility after experimental traumatic brain injury, even though none of them has progressed to clinic. Moreover, there has been some promise that new clinically translatable imaging approaches can identify biomarkers for post-traumatic epileptogenesis. Even though the progress in combating post-traumatic epileptogenesis happens in small steps, recent discoveries kindle hope for identification of treatment strategies to prevent post-traumatic epilepsy in at-risk patients.
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Affiliation(s)
- Asla Pitkänen
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211, Kuopio, Finland,
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21
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Mountney A, Shear DA, Potter B, Marcsisin SR, Sousa J, Melendez V, Tortella FC, Lu XCM. Ethosuximide and phenytoin dose-dependently attenuate acute nonconvulsive seizures after traumatic brain injury in rats. J Neurotrauma 2013; 30:1973-82. [PMID: 23822888 DOI: 10.1089/neu.2013.3001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acute seizures frequently occur following severe traumatic brain injury (TBI) and have been associated with poor patient prognosis. Silent or nonconvulsive seizures (NCS) manifest in the absence of motor convulsion, can only be detected via continuous electroencephalographic (EEG) recordings, and are often unidentified and untreated. Identification of effective anti-epileptic drugs (AED) against post-traumatic NCS remains crucial to improve neurological outcome. Here, we assessed the anti-seizure profile of ethosuximide (ETX, 12.5-187.5 mg/kg) and phenytoin (PHT, 5-30 mg/kg) in a spontaneously occurring NCS model associated with penetrating ballistic-like brain injury (PBBI). Rats were divided between two drug cohorts, PHT or ETX, and randomly assigned to one of four doses or vehicle within each cohort. Following PBBI, NCS were detected by continuous EEG monitoring for 72 h post-injury. Drug efficacy was evaluated on NCS parameters of incidence, frequency, episode duration, total duration, and onset latency. Both PHT and ETX attenuated NCS in a dose-dependent manner. In vehicle-treated animals, 69-73% experienced NCS (averaging 9-10 episodes/rat) with average onset of NCS occurring at 30 h post-injury. Compared with control treatment, the two highest PHT and ETX doses significantly reduced NCS incidence to 13-40%, reduced NCS frequency (1.8-6.2 episodes/rat), and delayed seizure onset: <20% of treated animals exhibited NCS within the first 48 h. NCS durations were also dose-dependently mitigated. For the first time, we demonstrate that ETX and PHT are effective against spontaneously occurring NCS following PBBI, and suggest that these AEDs may be effective at treating post-traumatic NCS.
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Affiliation(s)
- Andrea Mountney
- 1 Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research , Silver Spring, Maryland
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22
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Hunt RF, Boychuk JA, Smith BN. Neural circuit mechanisms of post-traumatic epilepsy. Front Cell Neurosci 2013; 7:89. [PMID: 23785313 PMCID: PMC3684786 DOI: 10.3389/fncel.2013.00089] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 05/22/2013] [Indexed: 01/13/2023] Open
Abstract
Traumatic brain injury (TBI) greatly increases the risk for a number of mental health problems and is one of the most common causes of medically intractable epilepsy in humans. Several models of TBI have been developed to investigate the relationship between trauma, seizures, and epilepsy-related changes in neural circuit function. These studies have shown that the brain initiates immediate neuronal and glial responses following an injury, usually leading to significant cell loss in areas of the injured brain. Over time, long-term changes in the organization of neural circuits, particularly in neocortex and hippocampus, lead to an imbalance between excitatory and inhibitory neurotransmission and increased risk for spontaneous seizures. These include alterations to inhibitory interneurons and formation of new, excessive recurrent excitatory synaptic connectivity. Here, we review in vivo models of TBI as well as key cellular mechanisms of synaptic reorganization associated with post-traumatic epilepsy (PTE). The potential role of inflammation and increased blood-brain barrier permeability in the pathophysiology of PTE is also discussed. A better understanding of mechanisms that promote the generation of epileptic activity versus those that promote compensatory brain repair and functional recovery should aid development of successful new therapies for PTE.
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Affiliation(s)
- Robert F Hunt
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California San Francisco, CA, USA
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Mechanism of action for NNZ-2566 anti-inflammatory effects following PBBI involves upregulation of immunomodulator ATF3. Neuromolecular Med 2013; 15:504-14. [PMID: 23765588 DOI: 10.1007/s12017-013-8236-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 05/24/2013] [Indexed: 12/20/2022]
Abstract
The tripeptide glycine-proline-glutamate analogue NNZ-2566 (Neuren Pharmaceuticals) demonstrates neuroprotective efficacy in models of traumatic brain injury. In penetrating ballistic-like brain injury (PBBI), it significantly decreases injury-induced upregulation of inflammatory cytokines including TNF-α, IFN-γ, and IL-6. However, the mechanism by which NNZ-2566 acts has yet to be determined. The activating transcription factor-3 (ATF3) is known to repress expression of these inflammatory cytokines and was increased at the mRNA and protein level 24-h post-PBBI. This study investigated whether 12 h of NNZ-2566 treatment following PBBI alters atf3 expression. PBBI alone significantly increased atf3 mRNA levels by 13-fold at 12 h and these levels were increased by an additional fourfold with NNZ-2566 treatment. To confirm that changes in mRNA translated to changes in protein expression, ATF3 expression levels were determined in vivo in microglia/macrophages, T cells, natural killer cells (NKCs), astrocytes, and neurons. PBBI alone significantly increased ATF3 in microglia/macrophages (820%), NKCs (58%), and astrocytes (51%), but decreased levels in T cells (48%). NNZ-2566 treatment further increased ATF3 protein expression in microglia/macrophages (102%), NKCs (308%), and astrocytes (13%), while reversing ATF3 decreases in T cells. Finally, PBBI increased ATF3 levels by 55% in neurons and NNZ-2566 treatment further increased these levels an additional 33%. Since increased ATF3 may be an innate protective mechanism to limit inflammation following injury, these results demonstrating that the anti-inflammatory and neuroprotective drug NNZ-2566 increase both mRNA and protein levels of ATF3 in multiple cell types provide a cellular mechanism for NNZ-2566 modulation of neuroinflammation following PBBI.
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Shear DA, Tortella FC. A military-centered approach to neuroprotection for traumatic brain injury. Front Neurol 2013; 4:73. [PMID: 23781213 PMCID: PMC3679469 DOI: 10.3389/fneur.2013.00073] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 05/31/2013] [Indexed: 12/14/2022] Open
Abstract
Studies in animals show that many compounds and therapeutics have the potential to greatly reduce the morbidity and post-injury clinical sequela for soldiers experiencing TBI. However, to date there are no FDA approved drugs for the treatment of TBI. In fact, expert opinion suggests that combination therapies will be necessary to treat any stage of TBI recovery. Our approach to this research effort is to conduct comprehensive pre-clinical neuroprotection studies in military-relevant animal models of TBI using the most promising neuroprotective agents. In addition, emerging efforts incorporating novel treatment strategies such as stem cell based therapies and alternative therapeutic approaches will be discussed. The development of a non-surgical, non-invasive brain injury therapeutic clearly addresses a major, unresolved medical problem for the Combat Casualty Care Research Program. Since drug discovery is too expensive to be pursued by DOD in the TBI arena, this effort capitalizes on partnerships with the Private Sector (Pharmaceutical Companies) and academic collaborations (Operation Brain Trauma Therapy Consortium) to study therapies already under advanced development. Candidate therapies selected for research include drugs that are aimed at reducing the acute and delayed effects of the traumatic incident, stem cell therapies aimed at brain repair, and selective brain cooling to stabilize cerebral metabolism. Each of these efforts can also focus on combination therapies targeting multiple mechanisms of neuronal injury.
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Affiliation(s)
- Deborah A. Shear
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Frank C. Tortella
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, USA
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25
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Lu XCM, Dave JR, Chen Z, Cao Y, Liao Z, Tortella FC. Nefiracetam attenuates post-ischemic nonconvulsive seizures in rats and protects neuronal cell death induced by veratridine and glutamate. Life Sci 2013; 92:1055-63. [PMID: 23603142 DOI: 10.1016/j.lfs.2013.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 02/21/2013] [Accepted: 04/01/2013] [Indexed: 11/15/2022]
Abstract
AIMS Stroke patients are at a high risk of developing post-ischemic seizures and cognitive impairment. Nefiracetam (NEF), a pyrrolidone derivative, has been shown to possess both anti-epileptic and cognitive-enhancing properties. In this study the anti-seizure effects of NEF were evaluated in a rat model of post-ischemic nonconvulsive seizures (NCSs). Its potential mechanisms were investigated in neuronal cell culture assays of neurotoxicity associated with ischemic brain injury and epileptogenesis. MAIN METHODS In the in vivo study, rats received 24h permanent middle cerebral artery occlusion. NEF was administered intravenously either at 15 min post-injury but prior to the first NCS event (30 mg/kg, pre-NCS treatment) or immediately after the first NCS occurred (30 or 60 mg/kg, post-NCS treatment). In the in vitro study, neuronal cell cultures were exposed to veratridine or glutamate and treated with NEF (1-500 nM). KEY FINDINGS The NEF pre-NCS treatment significantly reduced the NCS frequency and duration, whereas the higher NEF dose (60 mg/kg) was required to achieve similar effects when given after NCS occurred. The NEF treatment also dose-dependently (5-500 nM) protected against neuronal cell death induced by veratridine as measured by MTT cell viability assay, but higher doses (250-500 nM) were required against glutamate toxicity. SIGNIFICANCE The anti-seizure property of NEF was demonstrated in a clinically relevant rat model of post-ischemic NCS. The preferential effects of NEF against in vitro veratridine toxicity suggest the involvement of its modulation of sodium channel malfunction. Future studies are warranted to study the mechanisms of NEF against ischemic brain injury and post-ischemic seizures.
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Affiliation(s)
- Xi-Chun May Lu
- Branch of Brain Trauma and Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
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Lu XCM, Mountney A, Chen Z, Wei G, Cao Y, Leung LY, Khatri V, Cunningham T, Tortella FC. Similarities and differences of acute nonconvulsive seizures and other epileptic activities following penetrating and ischemic brain injuries in rats. J Neurotrauma 2013; 30:580-90. [PMID: 23234254 DOI: 10.1089/neu.2012.2641] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The similarities and differences between acute nonconvulsive seizures (NCS) and other epileptic events, for example, periodic epileptiform discharges (PED) and intermittent rhythmic delta activities (IRDA), were characterized in rat models of penetrating and ischemic brain injuries. The NCS were spontaneously induced by either unilateral frontal penetrating ballistic-like brain injury (PBBI) or permanent middle cerebral artery occlusion (pMCAO), and were detected by continuous electroencephalogram (EEG) monitoring begun immediately after the injury and continued for 72 h or 24 h, respectively. Analysis of NCS profiles (incidence, frequency, duration, and time distribution) revealed a high NCS incidence in both injury models. The EEG waveform expressions of NCS and PED exhibited intrinsic variations that resembled human electrographic manifestations of post-traumatic and post-ischemic ictal and inter-ictal events, but these waveform variations were not distinguishable between the two types of brain injury. However, the NCS after pMCAO occurred more acutely and intensely (latency=0.6 h, frequency=25 episodes/rat) compared with the PBBI-induced NCS (latency=24 h, frequency=10 episodes/rat), such that the most salient features differentiating post-traumatic and post-ischemic NCS were the intensity and time distribution of the NCS profiles. After pMCAO, nearly 50% of the seizures occurred within the first 2 h of injury, whereas after PBBI, NCS occurred sporadically (0-5%/h) throughout the 72 h recording period. The PED were episodically associated with NCS. By contrast, the IRDA appeared to be independent of other epileptic events. This study provided comprehensive comparisons of post-traumatic and post-ischemic epileptic profiles. The identification of the similarities and differences across a broad spectrum of epileptic events may lead to differential strategies for post-traumatic and post-stroke seizure interventions.
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Affiliation(s)
- Xi-Chun May Lu
- Branch of Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, USA
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Longitudinal assessment of gait abnormalities following penetrating ballistic-like brain injury in rats. J Neurosci Methods 2013; 212:1-16. [DOI: 10.1016/j.jneumeth.2012.08.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 08/24/2012] [Accepted: 08/28/2012] [Indexed: 01/19/2023]
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Elias PZ, Spector M. Treatment of penetrating brain injury in a rat model using collagen scaffolds incorporating soluble Nogo receptor. J Tissue Eng Regen Med 2012; 9:137-50. [PMID: 23038669 DOI: 10.1002/term.1621] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 05/18/2012] [Accepted: 08/25/2012] [Indexed: 02/06/2023]
Abstract
Injuries and diseases of the central nervous system (CNS) have the potential to cause permanent loss of brain parenchyma, with severe neurological consequences. Cavitary defects in the brain may afford the possibility of treatment with biomaterials that fill the lesion site while delivering therapeutic agents. This study examined the treatment of penetrating brain injury (PBI) in a rat model with collagen biomaterials and a soluble Nogo receptor (sNgR) molecule. sNgR was aimed at neutralizing myelin proteins that hinder axon regeneration by inducing growth cone collapse. Scaffolds containing sNgR were implanted in the brains of adult rats 1 week after injury and analysed 4 weeks or 8 weeks later. Histological analysis revealed that the scaffolds filled the lesion sites, remained intact with open pores and were infiltrated with cells and extracellular matrix. Immunohistochemical staining demonstrated the composition of the cellular infiltrate to include macrophages, astrocytes and vascular endothelial cells. Isolated regions of the scaffold borders showed integration with surrounding viable brain tissue that included neurons and oligodendrocytes. While axon regeneration was not detected in the scaffolds, the cellular infiltration and vascularization of the lesion site demonstrated a modification of the injury environment with implications for regenerative strategies.
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Affiliation(s)
- Paul Z Elias
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA; Tissue Engineering Laboratories, VA Boston Healthcare System, Boston, MA, USA
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Elias PZ, Spector M. Characterization of a Bilateral Penetrating Brain Injury in Rats and Evaluation of a Collagen Biomaterial for Potential Treatment. J Neurotrauma 2012; 29:2086-102. [DOI: 10.1089/neu.2011.2181] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Paul Z. Elias
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Tissue Engineering Laboratories, VA Boston Healthcare System, Boston, Massachusetts
| | - Myron Spector
- Tissue Engineering Laboratories, VA Boston Healthcare System, Boston, Massachusetts
- Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
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Changes in apoptotic mechanisms following penetrating ballistic-like brain injury. J Mol Neurosci 2012; 49:301-11. [PMID: 22684621 DOI: 10.1007/s12031-012-9828-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 05/30/2012] [Indexed: 10/28/2022]
Abstract
We investigated apoptotic pathways in a model of severe traumatic brain injury, penetrating ballistic-like brain injury (PBBI). TUNEL staining identified increasing apoptosis within 24 h. From targeted arrays, 11 genes were identified for temporal mRNA evaluation. In addition, mRNA levels and enzyme activity for caspases 3, 8, and 9 were examined. In the death receptor-mediated apoptosis pathway, the relative quantities (RQs) of mRNA for tnfr1, fas, and tnf were upregulated while trail mRNA was downregulated. In the anti-apoptotic TNF-R2 pathway, tnfr2 and flip were upregulated while xiap was downregulated. These findings indicate that increases in tnf levels following injury are not only pro-apoptotic but may also signal competing anti-apoptotic mechanisms. For the mitochondria-mediated apoptosis pathway, RQs of anti-apoptotic factors bcl2a1d and birc3 were upregulated while both bcl2 and bax were downregulated. RQs for casp 3 and casp 8 increased while casp9 decreased. Enzymatic activity increased for caspases 3, 8, and 9. While multiple mechanisms promoting and inhibiting apoptosis are at play during the first week after a PBBI, the cumulative result remains increased apoptosis. The ability to understand and dissect these events will assist in the development and evaluation of treatments targeting apoptosis following severe brain injury.
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Brain oxygen tension monitoring following penetrating ballistic-like brain injury in rats. J Neurosci Methods 2011; 203:115-21. [PMID: 21983109 DOI: 10.1016/j.jneumeth.2011.09.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 09/22/2011] [Accepted: 09/23/2011] [Indexed: 11/22/2022]
Abstract
While brain oxygen tension (PbtO(2)) monitoring is an important parameter for evaluating injury severity and therapeutic efficiency in severe traumatic brain injury (TBI) patients, many factors affect the monitoring. The goal of this study was to identify the effects of FiO(2) (fraction of inspired oxygen) on PbtO(2) in uninjured anesthetized rats and measure the changes in PbtO(2) following penetrating ballistic-like brain injury (PBBI). Continuous PbtO(2) monitoring in uninjured anesthetized rats showed that PbtO(2) response was positively correlated with FiO(2) (0.21-0.35) but PbtO(2) remained stable when FiO(2) was maintained at ∼0.26. Importantly, although increasing FiO(2) from 0.21 to 0.35 improved P(a)O(2), it concomitantly reduced pH levels and elevated P(a)CO(2) values out of the normal range. However, when the FiO(2) was maintained between 0.26 and 0.30, the pH and P(a)O(2) levels remained within the normal or clinically acceptable range. In PBBI rats, PbtO(2) was significantly reduced by ∼40% (16.9 ± 1.2 mm Hg) in the peri-lesional region immediately following unilateral, frontal 10% PBBI compared to sham rats (28.6 ± 1.7 mm Hg; mean ± SEM, p<0.05) and the PBBI-induced reductions in PbtO(2) were sustained for at least 150 min post-PBBI. Collectively, these results demonstrate that FiO(2) affects PbtO(2) and that PBBI produces acute and sustained hypoxia in the peri-lesional region of the brain injury. This study provides important information for the management of PbtO(2) monitoring in this brain injury model and may offer insight for therapeutic strategies targeted to improve the hypoxia/ischemia state in the penetrating-type brain injury.
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Shear DA, Lu XCM, Pedersen R, Wei G, Chen Z, Davis A, Yao C, Dave J, Tortella FC. Severity profile of penetrating ballistic-like brain injury on neurofunctional outcome, blood-brain barrier permeability, and brain edema formation. J Neurotrauma 2011; 28:2185-95. [PMID: 21644814 DOI: 10.1089/neu.2011.1916] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This study evaluated the injury severity profile of unilateral, frontal penetrating ballistic-like brain injury (PBBI) on neurofunctional outcome, blood-brain barrier (BBB) permeability, and brain edema formation. The degree of injury severity was determined by the delivery of a water-pressure pulse designed to produce a temporary cavity by rapid (<40 ms) expansion of the probe's elastic balloon calibrated to equal 5%, 10%, 12.5%, or 15% of total rat brain volume (control groups consisted of sham surgery or insertion of the probe only). Neurofunctional assessments revealed motor and cognitive deficits related to the degree of injury severity, with the most clear-cut profile of PBBI injury severity depicted by the Morris water maze (MWM) results. A biphasic pattern of BBB leakage was detected in the injured hemisphere at all injury severity levels at 4 h post-injury, and again at 48-72 h post-injury, which remained evident out to 7 days post-PBBI in the 10% and 12.5% PBBI groups. Likewise, significant brain edema was detected in the injured hemisphere by 4 h post-injury and remained elevated out to 7 days post-injury in the 10% and 12.5% PBBI groups. However, following 5% PBBI, significant levels of edema were only detected from 24 h to 48h post-injury. These results identify an injury severity profile of BBB permeability, brain edema, and neurofunctional impairment that provides sensitive and clinically relevant outcome metrics for studying potential therapeutics.
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Affiliation(s)
- Deborah A Shear
- Brain Trauma Neuroprotection and Neurorestoration, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, USA.
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