Matrix metalloproteinase inhibition attenuates brain edema in an in vivo model of surgically-induced brain injury

Matrix metalloproteinase 9 (MMP-9) activity, hippocampal extracellular free water, and cognitive deficits are associated with each other in early phase psychosis

Increasing evidence points toward the role of the extracellular matrix, specifically matrix metalloproteinase 9 (MMP-9), in the pathophysiology of psychosis. MMP-9 is a critical regulator of the crosstalk between peripheral and central inflammation, extracellular matrix remodeling, hippocampal development, synaptic pruning, and neuroplasticity. Here, we aim to characterize the relationship between plasma MMP-9 activity, hippocampal microstructure, and cognition in healthy individuals and individuals with early phase psychosis. We collected clinical, blood, and structural and diffusion-weighted magnetic resonance imaging data from 39 individuals with early phase psychosis and 44 age and sex-matched healthy individuals. We measured MMP-9 plasma activity, hippocampal extracellular free water (FW) levels, and hippocampal volumes. We used regression analyses to compare MMP-9 activity, hippocampal FW, and volumes between groups. We then examined associations between MMP-9 activity, FW levels, hippocampal volumes, and cognitive performance assessed with the MATRICS battery. All analyses were controlled for age, sex, body mass index, cigarette smoking, and years of education. Individuals with early phase psychosis demonstrated higher MMP-9 activity (p < 0.0002), higher left (p < 0.05) and right (p < 0.05) hippocampal FW levels, and lower left (p < 0.05) and right (p < 0.05) hippocampal volume than healthy individuals. MMP-9 activity correlated positively with hippocampal FW levels (all participants and individuals with early phase psychosis) and negatively with hippocampal volumes (all participants and healthy individuals). Higher MMP-9 activity and higher hippocampal FW levels were associated with slower processing speed and worse working memory performance in all participants. Our findings show an association between MMP-9 activity and hippocampal microstructural alterations in psychosis and an association between MMP-9 activity and cognitive performance. Further, more extensive longitudinal studies should examine the therapeutic potential of MMP-9 modulators in psychosis.

Immediate neural impact and incomplete compensation after semantic hub disconnection

The human brain extracts meaning using an extensive neural system for semantic knowledge. Whether broadly distributed systems depend on or can compensate after losing a highly interconnected hub is controversial. We report intracranial recordings from two patients during a speech prediction task, obtained minutes before and after neurosurgical treatment requiring disconnection of the left anterior temporal lobe (ATL), a candidate semantic knowledge hub. Informed by modern diaschisis and predictive coding frameworks, we tested hypotheses ranging from solely neural network disruption to complete compensation by the indirectly affected language-related and speech-processing sites. Immediately after ATL disconnection, we observed neurophysiological alterations in the recorded frontal and auditory sites, providing direct evidence for the importance of the ATL as a semantic hub. We also obtained evidence for rapid, albeit incomplete, attempts at neural network compensation, with neural impact largely in the forms stipulated by the predictive coding framework, in specificity, and the modern diaschisis framework, more generally. The overall results validate these frameworks and reveal an immediate impact and capability of the human brain to adjust after losing a brain hub.

Case studies in neuroscience: reversible signatures of edema following electric and piezoelectric craniotomy drilling in macaques

In vivo electrophysiology requires direct access to brain tissue, necessitating the development and refinement of surgical procedures and techniques that promote the health and well-being of animal subjects. Here, we report a series of findings noted on structural magnetic resonance imaging (MRI) scans in monkeys with MRI-compatible implants following small craniotomies that provide access for intracranial electrophysiology. We found distinct brain regions exhibiting hyperintensities in T2-weighted scans that were prominent underneath the sites at which craniotomies had been performed. We interpreted these hyperintensities as edema of the neural tissue and found that they were predominantly present following electric and piezoelectric drilling, but not when manual, hand-operated drills were used. Furthermore, the anomalies subsided within 2-3 wk following surgery. Our report highlights the utility of MRI-compatible implants that promote clinical examination of the animal's brain, sometimes revealing findings that may go unnoticed when incompatible implants are used. We show replicable differences in outcome when using electric versus mechanical devices, both ubiquitous in the field. If electric drills are used, our report cautions against electrophysiological recordings from tissue directly underneath the craniotomy for the first 2-3 wk following the procedure due to putative edema.NEW & NOTEWORTHY Close examination of structural MRI in eight nonhuman primates following craniotomy surgeries for intracranial electrophysiology highlights a prevalence of hyperintensities on T2-weighted scans following surgeries conducted using electric and piezoelectric drills, but not when using mechanical, hand-operated drills. We interpret these anomalies as edema of neural tissue that resolved 2-3 wk postsurgery. This finding is especially of interest as electrophysiological recordings from compromised tissue may directly influence the integrity of collected data immediately following surgery.

Effects of antifibrinolytics on systemic and cerebral inflammation after traumatic brain injury

BACKGROUND

Administration of antifibrinolytic medications, including tranexamic acid (TXA), may reduce head injury-related mortality. The effect of these medications on post-traumatic brain injury (TBI) inflammatory response is unknown. The goal of this study was to investigate the role of available antifibrinolytic medications on both systemic and cerebral inflammation after TBI.

METHODS

An established murine weight drop model was used to induce a moderate TBI. Mice were administered 1, 10, or 100 mg/kg of TXA, 400 mg/kg of aminocaproic acid (Amicar, Hospira, Lake Forest, IL), 100 kIU/kg of aprotonin, or equivalent volume of normal saline (NS) 10 minutes after recovery. Mice were euthanized at 1, 6, or 24 hours. Serum and cerebral tissue were analyzed for neuron-specific enolase and inflammatory cytokines. Hippocampal histology was evaluated at 30 days for phosphorylated tau accumulation.

RESULTS

One hour after TBI, mice given TXA displayed decreased cerebral cytokine concentrations of tumor necrosis factor α (TNF-α) and, by 24 hours, displayed decreased concentrations of cerebral TNF-α, interleukin (IL)-6, and monocyte chemoattractant protein 1 compared with TBI-NS. However, serum concentrations of TNF-α and macrophage inflammatory protein 1α (MIP-1α) were significantly elevated from 1 to 24 hours in TBI-TXA groups compared with TBI-NS. The concentration of phosphorylated tau was significantly decreased in a dose-dependent manner in TBI-TXA groups compared with TBI-NS. By contrast, Amicar administration increased cerebral cytokine levels of IL-6 1 hour after TBI, with serum elevations noted in TNF-α, MIP-1α, and monocyte chemoattractant protein 1 at 24 hours compared with TBI-NS. Aprotonin administration increased serum TNF-α, IL-6, and MIP-1α from 1 to 24 hours without differences in cerebral cytokines compared with TBI-NS.

CONCLUSION

Tranexamic acid administration may provide acute neuroinflammatory protection in a dose-dependent manner. Amicar administration may be detrimental after TBI with increased cerebral and systemic inflammatory effects. Aprotonin administration may increase systemic inflammation without significant contributions to neuroinflammation. While no antifibrinolytic medication improved systemic inflammation, these data suggest that TXA may provide the most beneficial inflammatory modulation after TBI.

Holmes T, Obenaus A, Xu X. Longitudinal dynamics of microvascular recovery after acquired cortical injury

Acquired brain injuries due to trauma damage the cortical vasculature, which in turn impairs blood flow to injured tissues. There are reports of vascular morphological recovery following traumatic brain injury, but the remodeling process has not been examined longitudinally in detail after injury in vivo. Understanding the dynamic processes that influence recovery is thus critically important. We evaluated the longitudinal and dynamic microvascular recovery and remodeling up to 2 months post injury using live brain miniscope and 2-photon microscopic imaging. The new imaging approaches captured dynamic morphological and functional recovery processes at high spatial and temporal resolution in vivo. Vessel painting documented the initial loss and subsequent temporal morphological vascular recovery at the injury site. Miniscopes were used to longitudinally image the temporal dynamics of vascular repair in vivo after brain injury in individual mice across each cohort. We observe near-immediate nascent growth of new vessels in and adjacent to the injury site that peaks between 14 and 21 days post injury. 2-photon microscopy confirms new vascular growth and further demonstrates differences between cortical layers after cortical injury: large vessels persist in deeper cortical layers (> 200 μm), while superficial layers exhibit a dense plexus of fine (and often non-perfused) vessels displaying regrowth. Functionally, blood flow increases mirror increasing vascular density. Filopodia development and endothelial sprouting is measurable within 3 days post injury that rapidly transforms regions devoid of vessels to dense vascular plexus in which new vessels become increasingly perfused. Within 7 days post injury, blood flow is observed in these nascent vessels. Behavioral analysis reveals improved vascular modulation after 9 days post injury, consistent with vascular regrowth. We conclude that morphological recovery events are closely linked to functional recovery of blood flow to the compromised tissues, which subsequently leads to improved behavioral outcomes.

Blood-Brain Barrier Breakdown and Astrocyte Reactivity Evident in the Absence of Behavioral Changes after Repeated Traumatic Brain Injury

Repeated traumatic brain injuries (TBIs) cause debilitating effects. Without understanding the acute effects of repeated TBIs, treatment options to halt further degeneration and damage cannot be developed. This study sought to examine the acute effects of blood-brain barrier (BBB) dysfunction, edema, inflammation and behavioral changes after either a single or double TBI using a C57BL/6 mouse model. We examined the effects of one or two TBIs, of either a mild or moderate severity. Double injuries were spaced 7 days apart, and all analysis was performed 24 h post-injury. To examine edema and inflammation, protein levels of glial fibrillary acidic protein (GFAP), S100 calcium-binding protein B, interleukin-6, and matrix metallopeptidase 9 (MMP9) were analyzed. Aquaporin-4 (AQP4) and zonula occludens-1 (ZO-1) were analyzed to observe BBB dysfunction. Ionized calcium-binding adapter molecule 1 (IBA1) was analyzed to observe microglial activation. Rotarod, beam walking, and grip strength tests were used to measure changes in physical behavior post-injury. A sample size of ≥5 was used for all analysis. Double injuries led to an increase in BBB breakdown, as indicated by altered MMP-9, AQP4, and ZO-1 protein expression. Single injuries showed an increase in microglial activation, astrocyte activation, and BBB breakdown. Behavioral tasks showed no significant differences between injured and control groups. Based on our findings, we suggest that behavioral studies should not be used as the sole clinical indicator on brain tissue recovery. Analysis of markers such as IBA1, GFAP, MMP-9, AQP4, and ZO-1 provide valuable insight on pathophysiological response to injury.

Real-Time Intraoperative Pressure Monitoring to Avoid Surgically Induced Localized Brain Injury Using a Miniaturized Piezoresistive Pressure Sensor

Neurosurgical procedures often cause damage to the brain tissue at the periphery from surgical manipulations. Especially during retraction, a large amount of pressure could be applied on the brain surface, which can damage it, leading to brain herniation, which can be fatal for patients. To resolve this issue, we have developed a pressure sensor that can be used to monitor the applied pressure during surgery for intraoperative care. This device was tested on a rodent model to create a superficial surgically induced damage profile for three different applied pressures (30, 50, and 70 mmHg) and compared to a standard intracranial pressure monitoring system. Magnetic resonance imaging has been performed after surgical procedures to detect the herniation caused by applied pressure. To evaluate the damage to brain cells and tissue rupture, histological analysis was performed using hematoxylin and eosin staining. A scoring system was developed to understand the severity of the surgically induced brain injury, which will help neurosurgeons to limit the pressure to an optimum point without causing damage.

The Activation of Phosphatidylserine/CD36/TGF-β1 Pathway prior to Surgical Brain Injury Attenuates Neuroinflammation in Rats

Neuroinflammation plays an important pathological role in experimental surgical brain injury (SBI). Apoptotic associated with phosphatidylserine (PS) externalization promotes anti-inflammatory mediator TGF-β1 release. In the present study, we investigated the anti-neuroinflammation effect of PS liposome or isoflurane pretreatment via PS/CD36/TGF-β1 signaling in a rat model of SBI. A total of 120 male Sprague-Dawley rats (weighing 280-330 gms) were used. SBI was induced by partial right frontal lobe corticotomy. Intranasal PS liposome or isoflurane inhalation was administered prior to SBI induction. CD36 small interfering RNA (siRNA) was administered intracerebroventricularly. Recombinant Annexin V protein (rAnnexin V) was delivered intranasally. Post-SBI assessments included neurological tests, brain water content, Western blot, and immunohistochemistry. Endogenous CD36 protein levels but not TGF-β1 was significantly increased within peri-resection brain tissues over 72 h after SBI. SBI rats were associated with increased brain water content surrounding corticotomy and neurological deficits. PS liposome pretreatment significantly reduced brain water content and improved some neurological deficits at 24 hours and 72 hours after SBI. PS liposome increased CD36 and TGF-β1 protein levels, but decreased IL-1β and TNFα protein levels in peri-resection brain tissues at 24 hours after SBI. CD36 siRNA or rAnnexin V partially countered the protective effect of PS liposome. Isoflurane pretreatment produced similar antineuroinflammation and neurological benefits in SBI rats partially by upregulating CD36/Lyn/TGF-β1 signaling. Collectively, our findings suggest that the activation of PS/CD36/TGF-β1 pathway by PS liposome or isoflurane prior to SBI could attenuate neuroinflammation and improve neurological outcomes in rats. PS liposome or isoflurane pretreatment may serve as an effective preventive strategy to minimize the brain injury caused by neurosurgical procedures in patients.

Blocking matrix metalloproteinase-mediated syndecan-4 shedding restores the endothelial glycocalyx and glomerular filtration barrier function in early diabetic kidney disease

The endothelial glycocalyx is a key component of the glomerular filtration barrier. We have shown that matrix metalloproteinase (MMP)-mediated syndecan 4 shedding is a mechanism of glomerular endothelial glycocalyx damage in vitro, resulting in increased albumin permeability. Here we sought to determine whether this mechanism is important in early diabetic kidney disease, by studying streptozotocin-induced type 1 diabetes in DBA2/J mice. Diabetic mice were albuminuric, had increased glomerular albumin permeability and endothelial glycocalyx damage. Syndecan 4 mRNA expression was found to be upregulated in isolated glomeruli and in flow cytometry-sorted glomerular endothelial cells. In contrast, glomerular endothelial luminal surface syndecan 4 and Marasmium oreades agglutinin lectin labelling measurements were reduced in the diabetic mice. Similarly, syndecan 4 protein expression was significantly decreased in isolated glomeruli but increased in plasma and urine, suggesting syndecan 4 shedding. Mmp-2, 9 and 14 mRNA expression were upregulated in isolated glomeruli, suggesting a possible mechanism of glycocalyx damage and albuminuria. We therefore characterised in detail the activity of MMP-2 and 9 and found significant increases in kidney cortex, plasma and urine. Treatment with MMP-2/9 inhibitor I for 21 days, started six weeks after diabetes induction, restored endothelial glycocalyx depth and coverage and attenuated diabetes-induced albuminuria and reduced glomerular albumin permeability. MMP inhibitor treatment significantly attenuated glomerular endothelial and plasma syndecan 4 shedding and inhibited plasma MMP activity. Thus, our studies confirm the importance of MMPs in endothelial glycocalyx damage and albuminuria in early diabetes and demonstrate that this pathway is amenable to therapeutic intervention. Hence, treatments targeted at glycocalyx protection by MMP inhibition may be of benefit in diabetic kidney disease.

Surgically-induced brain injury: where are we now?

Neurosurgical procedures cause inevitable brain damage from the multitude of surgical manipulations utilized. Incisions, retraction, thermal damage from electrocautery, and intraoperative hemorrhage cause immediate and long-term brain injuries that are directly linked to neurosurgical operations, and these types of injuries, collectively, have been termed surgical brain injury (SBI). For the past decade, a model developed to study the underlying brain pathologies resulting from SBI has provided insight on cellular mechanisms and potential therapeutic targets. This model, as seen in a rat, mouse, and rabbit, mimics a neurosurgical operation and causes commonly encountered post-operative complications such as brain edema, neuroinflammation, and hemorrhage. In this review, we elaborate on SBI and its clinical impact, the SBI animal models and their clinical relevance, the importance of applying therapeutics before neurosurgical procedures (i.e., preconditioning), and the new direction of applying venom-derived proteins to attenuate SBI.

Matrix metalloproteinase signals following neurotrauma are right on cue

Neurotrauma, a term referencing both traumatic brain and spinal cord injuries, is unique to neurodegeneration in that onset is clearly defined. From the perspective of matrix metalloproteinases (MMPs), there is opportunity to define their temporal participation in injury and recovery beginning at the level of the synapse. Here we examine the diverse roles of MMPs in the context of targeted insults (optic nerve lesion and hippocampal and olfactory bulb deafferentation), and clinically relevant focal models of traumatic brain and spinal cord injuries. Time-specific MMP postinjury signaling is critical to synaptic recovery after focal axonal injuries; members of the MMP family exhibit a signature temporal profile corresponding to axonal degeneration and regrowth, where they direct postinjury reorganization and synaptic stabilization. In both traumatic brain and spinal cord injuries, MMPs mediate early secondary pathogenesis including disruption of the blood-brain barrier, creating an environment that may be hostile to recovery. They are also critical players in wound healing including angiogenesis and the formation of an inhibitory glial scar. Experimental strategies to reduce their activity in the acute phase result in long-term neurological recovery after neurotrauma and have led to the first clinical trial in spinal cord injured pet dogs.

Persistently high circulating tissue inhibitor of matrix metalloproteinase-1 levels in non-survivor brain trauma injury patients

PURPOSE

Previously, higher circulating levels of matrix metalloproteinase (MMP)-9 and tissue inhibitor matrix metalloproteinases (TIMP)-1 were reported in the first hours after TBI in blood samples from patients with poor prognosis. Thus, the objectives of this study were to determine whether MMP-9 and TIMP-1 levels during the first week of a severe TBI could be used as biomarker predictive of mortality.

METHODS

We included patients with severe TBI (defined as Glasgow Coma Scale lower than 9), and with Injury Severity Score in non-cranial aspects lower than 9. We determined serum concentrations of MMP-9 and TIMP-1 at days 1, 4 and 8 of TBI.

RESULTS

TIMP-1 concentrations at days 1 (p < .001), 4 (p = .001), and 8 (p = .01) of TBI were higher in non-surviving (n = 34) than in surviving (n = 90) patients. ROC curve analyses showed an area under curve of TIMP-1 concentrations at days 1, 4, and 8 of TBI to predict 30-day mortality of 78% (p < .001), 76% (p < .001) and 71% (p = .02) respectively.

CONCLUSIONS

The most relevant new findings of our study were that TIMP-1 levels during the first week of a severe TBI were higher in non-surviving than in surviving patients and that could be used as biomarker predictive of mortality.

Endothelial colony-forming cell-derived exosomes restore blood-brain barrier continuity in mice subjected to traumatic brain injury

Traumatic brain injury (TBI) tends to cause disruption of the blood-brain barrier (BBB). Previous studies have shown that intravenously or intracerebroventricularly infused human umbilical cord blood-derived endothelial colony-forming cells (ECFCs) can home to injury sites and improve outcomes in mice subjected to experimental TBI. Several reports have demonstrated that these cells did not incorporate directly into newly formed vasculature but instead stimulated the proliferation and migration of tissue-resident endothelial cells (ECs) via paracrine mechanisms. In the present study, exosomes, which range from 30 to 150 nm in diameter, were isolated from ECFC-conditioned medium. The exosomes were labeled with PKH67 ex vivo, and we observed that they were taken up by ECs with high efficiency after 12 h of incubation. Pretreatment with ECFC-derived exosomes promoted the migration of ECs subjected to scratch injury, and incubating ECs exposed to hypoxia with ECFC-derived exosomes decreased PTEN expression, stimulated AKT phosphorylation and increased tight junction (TJ) protein expression in the cells. Furthermore, in vivo delivery of ECFC-derived exosomes into TBI mice also inhibited PTEN expression and increased AKT expression, changes accompanied by reductions in Evans blue (EB) dye extravasation, brain edema and TJ degradation. These data demonstrated that ECFC-derived exosomes have beneficial effects on BBB integrity in mice with TBI.

Neurotrophin-3 provides neuroprotection via TrkC receptor dependent pErk5 activation in a rat surgical brain injury model

BACKGROUND

Surgical brain injury (SBI) which occurs due to the inadvertent injury inflicted to surrounding brain tissue during neurosurgical procedures can potentiate blood brain barrier (BBB) permeability, brain edema and neurological deficits. This study investigated the role of neurotrophin 3 (NT-3) and tropomyosin related kinase receptor C (TrkC) against brain edema and neurological deficits in a rat SBI model.

METHODS

SBI was induced in male Sprague Dawley rats by partial right frontal lobe resection. Temporal expression of endogenous NT-3 and TrkC was evaluated at 6, 12, 24 and 72 h after SBI. SBI rats received recombinant NT-3 which was directly applied to the brain surgical injury site using gelfoam. Brain edema and neurological function was evaluated at 24 and 72 h after SBI. Small interfering RNA (siRNA) for TrkC and Rap1 was administered via intracerebroventricular injection 24 h before SBI. BBB permeability assay and western blot was performed at 24 h after SBI.

RESULTS

Endogenous NT-3 was decreased and TrkC expression increased after SBI. Topical administration of recombinant NT-3 reduced brain edema, BBB permeability and improved neurological function after SBI. Recombinant NT-3 administration increased the expression of phosphorylated Rap1 and Erk5. The protective effect of NT-3 was reversed with TrkC siRNA but not Rap1 siRNA.

CONCLUSIONS

Topical application of NT-3 reduced brain edema, BBB permeability and improved neurological function after SBI. The protective effect of NT-3 was possibly mediated via TrkC dependent activation of Erk5.

A composite neurobehavioral test to evaluate acute functional deficits after cerebellar haemorrhage in rats

Cerebellar haemorrhage accounts for 5-10% of all intracerebral haemorrhages and leads to severe, long-lasting functional deficits. Currently, there is limited research on this stroke subtype, which may be due to the lack of a suitable composite neuroscoring system specific for cerebellar injury in rodents. The purpose of this study is to develop a comprehensive composite neuroscore test for cerebellar injury using a rat model of cerebellar haemorrhage. Sixty male Sprague-Dawley rats were subjected to either sham surgery or cerebellar haemorrhage. Twenty-four hours post-injury, neurological behaviour was evaluated using 17 cost-effective and easy-to-perform tests, and a composite neuroscore was developed. The composite neuroscore was then used to assess functional recovery over seven days after cerebellar haemorrhage. Differences in the composite neuroscore deficits for the mild and moderate cerebellar haemorrhage models were observed for up to five days post-ictus. Until now, a composite neuroscore for cerebellar injury was not available for rodent studies. Herein, using mild and moderate cerebellar haemorrhage rat models a composite neuroscore for cerebellar injury was developed and used to assess functional deficits after cerebellar haemorrhage. This composite neuroscore may also be useful for other cerebellar injury models.

Multiple mechanisms underlying neuroprotection by secretory phospholipase A2 preconditioning in a surgically induced brain injury rat model

BACKGROUND

Intra-operative bleeding, post-operative brain edema and neuroinflammation are major complications in patients with surgical brain injury (SBI). Phospholipase A2 (PLA2) is the upstream enzyme which initiates the PLA2, 5-lipoxygenase (5-LOX) and leukotriene B4 (LTB4) inflammatory pathway. We hypothesized PLA2preconditioning (PPC) prior to SBI can activate endogenous anti-inflammatory responses to protect against SBI. This study evaluated if PPC can ameliorate neurosurgical complications and elucidated PPC-mediated possible protective mechanisms in a rat SBI model.

METHODS

Total 105 adult male Sprague Dawley rats were used for this study. SBI was induced by partial resection of the right frontal lobe. PLA2 or 0.9% NaCl was injected via rats' tail vein for 3 consecutive days prior to SBI. For mechanism study, a selective PLA2 inhibitor, Manoalide and 5-LOX inhibitor, Zileuton were injected intravenously with PPC to elucidate the role of PLA2 and 5-LOX in PPC-mediated anti-inflammatory effects. Brain water content (BWC) and lung water content, neurological tests, ELISA, western blot, immunohistochemistry, white blood cells (WBC) count, and spectrophotometric assay for intra-operative hemorrhage volume were evaluated.

RESULTS

First, PPC reduced brain water content, intra-operative bleeding, and improved neurological function after SBI. Second, PPC decreased 5-LOX expression and brain leukocyte infiltration, while increasing glial fibrillary acidic protein (GFAP) expression in the peri-resection brain tissue after SBI. Third, PPC induced peripheral inflammation represented by mild pulmonary inflammation and increased peripheral blood WBC count and LTB4 level. Lastly, PPC increased blood glucose concentration and glucocorticoid levels after SBI. In addition, PPC mediated above-mentioned changes were partially reversed by administration of PLA2 inhibitor, Manoalide and 5-LOX inhibitor, Zileuton.

CONCLUSIONS

PPC conferred neuroprotection against SBI via multi-target involvement induced anti-inflammatory mechanisms.

Naja sputatrix Venom Preconditioning Attenuates Neuroinflammation in a Rat Model of Surgical Brain Injury via PLA2/5-LOX/LTB4 Cascade Activation

Inflammatory preconditioning is a mechanism in which exposure to small doses of inflammatory stimuli prepares the body against future massive insult by activating endogenous protective responses. Phospholipase A2/5-lipoxygenase/leukotriene-B4 (PLA2/5-LOX/LTB4) axis is an important inflammatory signaling pathway. Naja sputatrix (Malayan spitting cobra) venom contains 15% secretory PLA2 of its dry weight. We investigated if Naja sputatrix venom preconditioning (VPC) reduces surgical brain injury (SBI)-induced neuroinflammation via activating PLA2/5-LOX/LTB4 cascade using a partial frontal lobe resection SBI rat model. Naja sputatrix venom sublethal dose was injected subcutaneously for 3 consecutive days prior to SBI. We observed that VPC reduced brain edema and improved neurological function 24 h and 72 h after SBI. The expression of pro-inflammatory mediators in peri-resection brain tissue was reduced with VPC. Administration of Manoalide, a PLA2 inhibitor or Zileuton, a 5-LOX inhibitor with VPC reversed the protective effects of VPC against neuroinflammation. The current VPC regime induced local skin inflammatory reaction limited to subcutaneous injection site and elicited no other toxic effects. Our findings suggest that VPC reduces neuroinflammation and improves outcomes after SBI by activating PLA2/5-LOX/LTB4 cascade. VPC may be beneficial to reduce post-operative neuroinflammatory complications after brain surgeries.

Recombinant Slit2 Reduces Surgical Brain Injury Induced Blood Brain Barrier Disruption via Robo4 Dependent Rac1 Activation in a Rodent Model

Brain tissue surrounding surgical resection site can be injured inadvertently due to procedures such as incision, retractor stretch, and electrocauterization when performing neurosurgical procedures, which is termed as surgical brain injury (SBI). Blood brain barrier (BBB) disruption due to SBI can exacerbate brain edema in the post-operative period. Previous studies showed that Slit2 exhibited vascular anti-permeability effects outside the brain. However, BBB protective effects of Slit2 following SBI has not been evaluated. The objective of this study was to evaluate whether recombinant Slit2 via its receptor roundabout4 (Robo4) and the adaptor protein, Paxillin were involved in reducing BBB permeability in SBI rat model. Our results showed that endogenous Slit2 increased in the surrounding peri-resection brain tissue post-SBI, Robo4 remained unchanged and Paxillin showed a decreasing trend. Recombinant Slit2 administered 1 h before injury increased BBB junction proteins, reduced BBB permeability, and decreased neurodeficits 24 h post-SBI. Furthermore, recombinant Slit2 administration increased Rac1 activity which was reversed by Robo4 and Paxillin siRNA. Our findings suggest that recombinant Slit2 reduced SBI-induced BBB permeability, possibly by stabilizing BBB tight junction via Robo4 mediated Rac1 activation. Slit2 may be beneficial for BBB protection during elective neurosurgeries.

Crotalus helleri venom preconditioning reduces postoperative cerebral edema and improves neurological outcomes after surgical brain injury

INTRODUCTION

Postoperative cerebral edema is a devastating complication in neurosurgical patients. Loss of blood-brain barrier integrity has been shown to lead to the development of brain edema following neurosurgical procedures. The aim of this study was to evaluate preconditioning with Crotalus helleri venom (Cv-PC) as a potential preventive therapy for reducing postoperative brain edema in the rodent SBI model. C. helleri venom is known to contain phospholipase A2 (PLA2), an enzyme upstream to cyclooxygenase-2 (COX-2) in the inflammatory cascade, acts to increase the production of inflammatory mediators, such as prostaglandins. We hypothesize that Cv-PC will downregulate the response of the COX-2 pathway to injury, thereby reducing the inflammatory response and the development of brain edema after SBI.

MATERIALS AND METHODS

75 male Sprague Dawley rats (280-330g) were divided to the following groups-naïve+vehicle, naïve+Cv-PC, sham, vehicle, Cv-PC, Cv-PC+NS398 (COX-2 inhibitor). Vehicle preconditioned and Cv-PC animals received either three daily subcutaneous doses of saline or C. helleri venom at 72h, 48h, and 24h prior to surgery. In Cv-PC+NS398 animals, NS398 was administered intraperitoneally 1h prior to each Cv-PC injection. Sham-operated animals received craniotomy only, whereas SBI animals received a partial right frontal lobectomy. Neurological testing and brain water content were assessed at 24h and 72h after SBI; COX-2 and PGE₂ expression was assessed at 24h postoperatively by Western blot and immunohistochemistry, respectively.

RESULTS

At 24h after SBI, the vehicle-treated animals were observed to have increased brain water content (83.1±0.2%) compared to that of sham animals (80.2±0.1%). The brain water content of vehicle-treated animals at 72h post-SBI was elevated at 83.3±0.2%. Cv-PC-treated animals with doses of 10% LD₅₀ had significantly reduced brain water content of 81.92±0.7% and 81.82±0.3% at 24h and 72h, respectively, after SBI compared to that of vehicle-treated animals, while Cv-PC with 5% LD₅₀ doses showed brain water content that trended lower but did not reach statistical significance. At 24h and 72h post-SBI, Cv-PC-treated animals had significantly higher neurological score than vehicle-treated animals. The COX-2 over-expression characterized in SBI was attenuated in Cv-PC-treated animals; NS398 reversed the protective effect of Cv-PC on COX-2 expression. Cv-PC tempered the over-expression of the inflammatory marker PGE₂.

CONCLUSION

Our findings indicate that Cv-PC may provide a promising therapy for reducing postoperative edema and improving neurological function after neurosurgical procedures.

Surgical management of skull base tumors

AIM

To present a review of the contemporary surgical management of skull base tumors.

BACKGROUND

Over the last two decades, the treatment of skull base tumors has evolved from observation, to partial resection combined with other therapy modalities, to gross total resection and no adjuvant treatment with good surgical results and excellent clinical outcomes.

MATERIALS AND METHODS

The literature review of current surgical strategies and management of skull base tumors was performed and complemented with the experience of Barrow Neurological Institute.

RESULTS

Skull base tumors include meningiomas, pituitary tumors, sellar/parasellar tumors, vestibular and trigeminal schwannomas, esthesioneuroblastomas, chordomas, chondrosarcomas, and metastases. Surgical approaches include the modified orbitozygomatic, pterional, middle fossa, retrosigmoid, far lateral craniotomy, midline suboccipital craniotomy, and a combination of these approaches. The selection of an appropriate surgical approach depends on the characteristics of the patient and the tumor, as well as the experience of the neurosurgeon.

CONCLUSION

Modern microsurgical techniques, diagnostic imaging, intraoperative neuronavigation, and endoscopic technology have remarkably changed the concept of skull base surgery. These refinements have extended the boundaries of tumor resection with minimal morbidity.

The brain tissue response to surgical injury and its possible contribution to glioma recurrence

Surgery is the first line therapy for glioma. However, glioma recurs in 90 % of the patients in the resection margin. The impact of surgical brain injury (SBI) on glioma recurrence is largely overlooked. Herein, we review some of the mechanisms involved in tissue repair that may impact glioma recurrence at the resection margin. Many processes or molecules involved in tissue repair after brain injury are also critical for glioma growth. They include a wide array of secreted growth factors, cytokines and transcription factors including NFКB and STAT3 which in turn activate proliferative and anti-apoptotic genes and processes such as angiogenesis and inflammation. Because some residual glioma cells always remain in the tumor resection margin, there are now compelling arguments to suggest that some aspects of the brain tissue response to SBI can also participate to glioma recurrence at the resection margin. Brain tissue response to SBI recruits angiogenesis and inflammation that precede and then follow tumor recurrence at the resection margin. The healing response to SBI is double edged, as inflammation is involved in regeneration and healing, and has both pro- and anti-tumorigenic functions. A promising therapeutic approach is to normalize and re-educate the molecular and cellular responses at the resection margin to promote anti-tumorigenic processes involved in healing while inhibiting pro-tumorigenic activities. Manipulation of the inflammatory response to SBI to prevent local recurrence could also enhance the efficacy of other therapies such as immunotherapy. However, our current knowledge is far from sufficient to achieve this goal. Acknowledging, understanding and manipulating the double-edged role played by SBI in glioma recurrence is surely challenging, but it cannot be longer delayed.

Epsilon Aminocaproic Acid Pretreatment Provides Neuroprotection Following Surgically Induced Brain Injury in a Rat Model

Neurosurgical procedures can damage viable brain tissue unintentionally by a wide range of mechanisms. This surgically induced brain injury (SBI) can be a result of direct incision, electrocauterization, or tissue retraction. Plasmin, a serine protease that dissolves fibrin blood clots, has been shown to enhance cerebral edema and hemorrhage accumulation in the brain through disruption of the blood brain barrier. Epsilon aminocaproic acid (EAA), a recognized antifibrinolytic lysine analogue, can reduce the levels of active plasmin and, in doing so, potentially can preserve the neurovascular unit of the brain. We investigated the role of EAA as a pretreatment neuroprotective modality in a SBI rat model, hypothesizing that EAA therapy would protect brain tissue integrity, translating into preserved neurobehavioral function. Male Sprague-Dawley rats were randomly assigned to one of four groups: sham (n = 7), SBI (n = 7), SBI with low-dose EAA, 150 mg/kg (n = 7), and SBI with high-dose EAA, 450 mg/kg (n = 7). SBI was induced by partial right frontal lobe resection through a frontal craniotomy. Postoperative assessment at 24 h included neurobehavioral testing and measurement of brain water content. Results at 24 h showed both low- and high-dose EAA reduced brain water content and improved neurobehavioral function compared with the SBI groups. This suggests that EAA may be a useful pretherapeutic modality for SBI. Further studies are needed to clarify optimal therapeutic dosing and to identify mechanisms of neuroprotection in rat SBI models.

Propofol Pretreatment Fails to Provide Neuroprotection Following a Surgically Induced Brain Injury Rat Model

Neurosurgical procedures are associated with unintentional damage to the brain during surgery, known as surgically induced brain injuries (SBI), which have been implicated in orchestrating structural and neurobehavioral deterioration. Propofol, an established hypnotic anesthetic agent, has been shown to ameliorate neuronal injury when given after injury in a number of experimental brain studies. We tested the hypothesis that propofol pretreatment confers neuroprotection against SBI and will reduce cerebral edema formation and neurobehavioral deficits in our rat population. Sprague-Dawley rats were treated with low- and high-dose propofol 30 min before SBI. At 24 h post injury, brain water content and neurobehavioral assessment was conducted based on previously established models. In vehicle-treated rats, SBI resulted in significant cerebral edema and higher neurological deficit scores compared with sham-operated rats. Low- or high-dose propofol therapy neither reduced cerebral edema nor improved neurologic function. The results suggest that propofol pretreatment fails to provide neuroprotection in SBI rats. However, it is possible that a SBI model with less magnitude of injury or that propofol re-dosing, given the short-acting pharmacokinetic property of propofol, may be needed to provide definitive conclusions.

Valproic Acid Pretreatment Reduces Brain Edema in a Rat Model of Surgical Brain Injury

Surgically induced brain injury (SBI) results in brain edema and neurological decline. Valproic acid (VA) has been shown to be neuroprotective in several experimental brain diseases. In this study, we investigated the pretreatment effect of VA in a rat model of SBI. A total of 57 male Sprague-Dawley rats were use in four groups: sham, SBI + vehicle, SBI + low dose (100 mg/kg) VA, and SBI + high dose (300 mg/kg) VA. SBI was induced by partially resecting right frontal lobes. Shams underwent identical surgical procedures without brain resection. VA or vehicle was administered subcutaneously 30 min prior to SBI. At 24 and 72 h post SBI, neurobehavior and brain water content were assessed as well as matrix metalloproteinases (MMPs) activities. There was significantly higher brain water content within the right frontal lobe in SBI rats than in shams. Without neurobehavioral improvements, the low-dose but not high-dose VA significantly reduced brain edema at 24 h post SBI. The protection tends to persist to 72 h post SBI. At 24 h post SBI, low-dose VA did not significantly reduce the elevated MMP-9 activity associated with SBI. In conclusion, VA pretreatment attenuated brain edema at 24 h after SBI but lacked MMP inhibition. The single dose VA was not associated with neurobehavioral benefits.

Recombinant Slit2 attenuates neuroinflammation after surgical brain injury by inhibiting peripheral immune cell infiltration via Robo1-srGAP1 pathway in a rat model

BACKGROUND AND PURPOSE

Peripheral immune cell infiltration to the brain tissue at the perisurgical site can promote neuroinflammation after surgical brain injury (SBI). Slit2, an extracellular matrix protein, has been reported to reduce leukocyte migration. This study evaluated the effect of recombinant Slit2 and the role of its receptor roundabout1 (Robo1) and its downstream mediator Slit-Robo GTPase activating protein 1 (srGAP1)-Cdc42 on peripheral immune cell infiltration after SBI in a rat model.

METHODS

One hundred and fifty-three adult male Sprague-Dawley rats (280-350 g) were used. Partial resection of right frontal lobe was performed to induce SBI. Slit2 siRNA was administered by intracerebroventricular injection 24h before SBI. Recombinant Slit2 was injected intraperitoneally 1h before SBI. Recombinant Robo1 used as a decoy receptor was co-administered with recombinant Slit2. srGAP1 siRNA was administered by intracerebroventricular injection 24h before SBI. Post-assessments included brain water content measurement, neurological tests, ELISA, Western blot, immunohistochemistry, and Cdc42 activity assay.

RESULTS

Endogenous Slit2 was increased after SBI. Robo1 was expressed by peripheral immune cells. Endogenous Slit2 knockdown worsened brain edema after SBI. Recombinant Slit2 administration reduced brain edema, neurological deficits, and pro-inflammatory cytokines after SBI. Recombinant Slit2 reduced peripheral immune cell markers cluster of differentiation 45 (CD45) and myeloperoxidase (MPO), as well as Cdc42 activity in the perisurgical brain tissue which was reversed by recombinant Robo1 co-administration and srGAP1 siRNA.

CONCLUSIONS

Recombinant Slit2 improved outcomes by reducing neuroinflammation after SBI, possibly by decreasing peripheral immune cell infiltration to the perisurgical site through Robo1-srGAP1 mediated inhibition of Cdc42 activity. These results suggest that Slit2 may be beneficial to reduce SBI-induced neuroinflammation.

New Prognostic Biomarkers in Patients With Traumatic Brain Injury

CONTEXT

Traumatic brain injury (TBI) is a leading cause of death, disability, and resource consumption per year. There are two kinds of brain injury in TBI, primary and secondary injuries. Primary injury refers to the initial physical forces applied to the brain at the moment of impact. Secondary injury occurs over a period of hours or days following the initial trauma and results from the activation of different pathways such as inflammation, coagulation, oxidation, and apoptosis.

EVIDENCE ACQUISITION

This review focuses on new prognostic biomarkers of mortality in TBI patients related to inflammation, coagulation, oxidation, and apoptosis.

RESULTS

Recently circulating levels of substance P (SP), soluble CD40 ligand (sCD40L), tissue inhibitor of matrix metalloproteinases (TIMP)-1, malondialdehyde (MDA), and cytokeratin (CK)-18 fragmented have been found to be associated with mortality in TBI patients. Substance P is a neuropeptide of the tachykinin family, mainly synthesized in the central and peripheral nervous system, with proinflammatory effects when binding to their neurokinin-1 receptor (NK1R). Soluble CD40 ligand, a member of the tumor necrosis factor (TNF) family that is released into circulation from activated platelets, exhibit proinflamatory, and procoagulant properties on binding to their cell surface receptor CD40. Matrix metalloproteinases (MMPs) are a family of zinc-containing endoproteinases involved neuroinflammation and TIMP-1 is the inhibitor of some of them. Malondialdehyde is an end-product formed during lipid peroxidation due to degradation of cellular membrane phospholipids, that is released into extracellular space and finally into the blood. Cytokeratin -18 is cleaved by the action of caspases during apoptosis, and CK-18 fragmented is released into the blood.

CONCLUSIONS

Circulating levels of some biomarkers, such as SP, sCD40L, TIMP-1, MDA, and CK-18 fragmented, related to inflammation, coagulation, oxidation, and apoptosis have been recently associated with mortality in patients with TBI. These biomarkers could help in the prognostic classification of the patients and open new research lines in the treatment of patients with TBI.

Role of Matrix Metalloproteinases in the Pathogenesis of Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Studies revealed that the pathogenesis of TBI involves upregulation of MMPs. MMPs form a large family of closely related zinc-dependent endopeptidases, which are primarily responsible for the dynamic remodulation of the extracellular matrix (ECM). Thus, they are involved in several normal physiological processes like growth, development, and wound healing. During pathophysiological conditions, MMPs proteolytically degrade various components of ECM and tight junction (TJ) proteins of BBB and cause BBB disruption. Impairment of BBB causes leakiness of the blood from circulation to brain parenchyma that leads to microhemorrhage and edema. Further, MMPs dysregulate various normal physiological processes like angiogenesis and neurogenesis, and also they participate in the inflammatory and apoptotic cascades by inducing or regulating the specific mediators and their receptors. In this review, we explore the roles of MMPs in various physiological/pathophysiological processes associated with neurological complications, with special emphasis on TBI.

Correlation between subacute sensorimotor deficits and brain water content after surgical brain injury in rats

Brain edema is a major contributor to poor outcome and reduced quality of life after surgical brain injury (SBI). Although SBI pathophysiology is well-known, the correlation between cerebral edema and neurological deficits has not been thoroughly examined in the rat model of SBI. Thus, the purpose of this study was to determine the correlation between brain edema and deficits in standard sensorimotor neurobehavior tests for rats subjected to SBI. Sixty male Sprague-Dawley rats were subjected to either sham surgery or surgical brain injury via partial frontal lobectomy. All animals were tested for neurological deficits 24 post-SBI and fourteen were also tested 72 h after surgery using seven common behavior tests: modified Garcia neuroscore (Neuroscore), beam walking, corner turn test, forelimb placement test, adhesive removal test, beam balance test, and foot fault test. After assessing the functional outcome, animals were euthanized for brain water content measurement. Surgical brain injury resulted in significantly elevated frontal lobe brain water content 24 and 72 h after surgery compared to that of sham animals. In all behavior tests, significance was observed between sham and SBI animals. However, a correlation between brain water content and functional outcome was observed for all tests except Neuroscore. The selection of behavior tests is critical to determine the effectiveness of therapeutics. Based on this study's results, we recommend using beam walking, the corner turn test, the beam balance test, and the foot fault test since correlations with brain water content were observed at both 24 and 72 h post-SBI.

Phosphoinositide 3-Kinase Gamma Contributes to Neuroinflammation in a Rat Model of Surgical Brain Injury

Neuroinflammation plays an important role in the pathophysiology of surgical brain injury (SBI). Phosphoinositide 3-kinase gamma (PI3Kγ), predominately expressed in immune and endothelial cells, activates multiple inflammatory responses. In the present study, we investigated the role of PI3Kγ and PI3Kγ-activated phosphodiesterase 3B (PDE3B) in neuroinflammation in a rat model of SBI. One hundred and fifty-two male Sprague Dawley rats (weight 280-350 g) were subjected to a partial right frontal lobe corticotomy model of SBI. A PI3Kγ pharmacological inhibitor (AS252424 or AS605240) was administered intraperitoneally. PI3Kγ siRNA, human recombinant active-PI3Kγ protein, or human recombinant active-PDE3B protein were administered intracerebroventricularly. Post-SBI assessments included neurobehavioral tests, brain water content, Western blot, and immunohistochemistry. Endogenous PI3Kγ levels were increased within peri-resection brain tissues after SBI, accompanied by increased brain water content and neurological functional deficits. There was a trend toward increased endogenous PDE3B phosphorylation after SBI. The selective PI3Kγ inhibitors AS252424 and AS605240 reduced brain water content surrounding corticotomy and improved neurological function after SBI. SBI increased and PI3Kγ inhibitor decreased levels of myeloperoxidase, cluster of differentiation 3, mast cell degranulation, E-selectin, and IL-1 in peri-resection brain tissues. Direct administration of human recombinant active-PI3Kγ protein and active-PDE3B protein countered the protective effect of AS252424. PI3Kγ siRNA reduced PI3Kγ levels, decreased brain water content within peri-resection brain tissues, and improved neurological function after SBI. Collectively, our findings suggest that PI3Kγ contributed to neuroinflammation after SBI. The use of selective PI3Kγ inhibitors may be a novel approach to ameliorating SBI via their anti-inflammation effects. Significance statement: Life-saving or elective neurosurgeries often involve unavoidable damages to neighboring, nondiseased brain tissues. Such surgical brain injury (SBI) is attributable exclusively to the neurosurgical procedure itself and may cause postoperative complications that exacerbate neurological function. Although the importance of this medical problem is fully acknowledged, intraoperative administration of adjunctive treatment such as steroids and mannitol to patients undergoing neurosurgery appear not to be efficient remedies for SBI. To date, the issue of perioperative neuroprotection specifically against SBI has not been well studied. Using a clinically relevant rat model of SBI, we are exploring a new neuroprotective strategy targeting phosphoinositide 3-kinase gamma (PI3Kγ). PI3Kγ activates multiple inflammatory responses. By attenuating neuroinflammation, selective PI3Kγ inhibition would limit postoperative complications and benefit neurological outcomes.

Matrix Metalloproteinase Expression in Contusional Traumatic Brain Injury: A Paired Microdialysis Study

Matrix metalloproteinases (MMPs) are extracellular enzymes that have been implicated in the pathophysiology of blood–brain barrier (BBB) breakdown, contusion expansion, and vasogenic edema after traumatic brain injury (TBI). Specifically, in focal injury models, increased MMP-9 expression has been observed in pericontusional brain, and MMP-9 inhibitors reduce brain swelling and final lesion volume. The aim of this study was to examine whether there is a similarly localized increase of MMP concentrations in patients with contusional TBI. Paired microdialysis catheters were inserted into 12 patients with contusional TBI (with or without associated mass lesion) targeting pericontusional and radiologically normal brain defined on admission computed tomography scan. Microdialysate was pooled every 8 h and analyzed for MMP-1, -2, -7, -9, and -10 using a multiplex immunoassay. Concentrations of MMP-1, -2, and -10 were similar at both monitoring sites and did not show discernible temporal trends. Overall, there was a gradual increase in MMP-7 concentrations in both normal and injured brain over the monitoring period, although this was not consistent in every patient. MMP-9 concentrations were elevated in pericontusional, compared to normal, brain, with the maximal difference at the earliest monitoring times (i.e., <24 h postinjury). Repeated-measures analysis of variance showed that MMP-9 concentrations were significantly higher in pericontusional brain (p=0.03) and within the first 72 h of injury, compared with later in the monitoring period (p=0.04). No significant differences were found for the other MMPs assayed. MMP-9 concentrations are increased in pericontusional brain early post-TBI and may represent a potential therapeutic target to reduce hemorrhagic progression and vasogenic edema.

Ablation of matrix metalloproteinase-9 gene decreases cerebrovascular permeability and fibrinogen deposition post traumatic brain injury in mice

Traumatic brain injury (TBI) is accompanied with enhanced matrix metalloproteinase-9 (MMP-9) activity and elevated levels of plasma fibrinogen (Fg), which is a known inflammatory agent. Activation of MMP-9 and increase in blood content of Fg (i.e. hyperfibrinogenemia, HFg) both contribute to cerebrovascular disorders leading to blood brain barrier disruption. It is well-known that activation of MMP-9 contributes to vascular permeability. It has been shown that at an elevated level (i.e. HFg) Fg disrupts blood brain barrier. However, mechanisms of their actions during TBI are not known. Mild TBI was induced in wild type (WT, C57BL/6 J) and MMP-9 gene knockout (Mmp9(-/-)) homozygous, mice. Pial venular permeability to fluorescein isothiocyanate-conjugated bovine serum albumin in pericontusional area was observed 14 days after injury. Mice memory was tested with a novel object recognition test. Increased expression of Fg endothelial receptor intercellular adhesion protein-1 and formation of caveolae were associated with enhanced activity of MMP-9 causing an increase in pial venular permeability. As a result, an enhanced deposition of Fg and cellular prion protein (PrP(C)) were found in pericontusional area. These changes were attenuated in Mmp9(-/-) mice and were associated with lesser loss of short-term memory in these mice than in WT mice. Our data suggest that mild TBI-induced increased cerebrovascular permeability enhances deposition of Fg-PrP(C) and loss of memory, which is ameliorated in the absence of MMP-9 activity. Thus, targeting MMP-9 activity and blood level of Fg can be a possible therapeutic remedy to diminish vasculo-neuronal damage after TBI.

Propofol inhibits inflammation and lipid peroxidation following cerebral ischemia/reperfusion in rabbits

The present study established a rabbit model of global cerebral ischemia using the ‘six-vessel’ method, which was reperfused after 30 minutes of ischemia. Rabbits received intravenous injection of propofol at 5 mg/kg prior to ischemia and 20 mg/kg per hour after ischemia until samples were prepared. Results revealed that propofol inhibited serum interleukin-8, endothelin-1 and malondialdehyde increases and promoted plasma superoxide dismutase activity after cerebral ischemia/reperfusion. In addition, cerebral cortex edema was attenuated with little neuronal nuclear degeneration and pyknosis with propofol treatment. The cross-sectional area of neuronal nuclei was, however, increased following propofol treatment. These findings suggested that propofol could improve anti-oxidant activity and inhibit synthesis of inflammatory factors to exert a protective effect on cerebral ischemia/reperfusion injury.

Melanocortin MC4 receptor agonists alleviate brain damage in abdominal compartment syndrome in the rat

Intra-abdominal hypertension (IAH) is accompanied by high morbidity and mortality in surgical departments and ICUs. However, its specific pathophysiology is unclear. IAH not only leads to intra-abdominal tissue damage but also causes dysfunction in distal organs, such as the brain. In this study, we explore the protective effects of melanocortin 4 receptor agonists in IAH-induced brain injury. The IAH rat models were induced by hemorrhagic shock/resuscitation (with the mean arterial pressure (MAP) maintained at 30 mm Hg for 90 min followed by the reinfusion of the withdrawn blood with lactated Ringer's solution). Then, air was injected into the peritoneal cavity of the rats to maintain an intra-abdominal pressure of 20 mm Hg for 4 h. The effects of the melanocortin 4 receptor agonist RO27-3225 in alleviating the rats' IAH brain injuries were observed, which indicated that RO27-3225 could reduce brain edema, the expressions of the IL-1β and TNF-α inflammatory cytokines, the blood-brain barrier's permeability and the aquaporin4 (AQP4) and matrix metalloproteinase 9 (MMP9) levels. Moreover, the nicotinic acetylcholine receptor antagonist chlorisondamine and the selective melanocortin 4 receptor antagonist HS024 can negate the protective effects of the RO27-3225. The MC4R agonist can effectively reduce the intracerebral proinflammatory cytokine gene expression and alleviate the brain injury caused by blood-brain barrier damage following IAH.

Novel targets for Spinal Cord Injury related neuropathic pain

Millions of people suffer from spinal cord injury (SCI) with little known effective clinical therapy. Neuropathic pain (NP) is often accompanied with SCI, making clinical treatment challenging. Even though the key mediators in the development of NP have been discovered, the pathogenesis is still unclear. Some of the key mediators in the sustenance of NP include the inflammatory processes, cannabinoid receptors, matrix metalloproteases, and their tissue inhibitors. Animal models have shown promising results with modulation of these mediators, yet the clinical models have been unsuccessful. One such study with matrix metalloproteases (MMPs) has yielded encouraging results. The relationship between MMPs and their tissue inhibitors (TIMPs) plays a significant role in the pathogenesis and recovery of SCI and the CNS. Key factors that lead to the functional consequences of MMP activity are cellular localization, tissue distribution, and temporal pattern of MMP expression. Studies concluding that MMPs can be seen as contributors of tissue damage and as contributors in the repair mechanisms have provided a need to reexamine their roles after acute and chronic neuropathic pain

Baicalin attenuates brain edema in a rat model of intracerebral hemorrhage

Baicalin is a flavonoid compound purified from the roots of Scutellaria baicalensis, which possesses multiple biological activities. Previous studies have shown that baicalin is protective in ischemic cerebral diseases. The aim of the present study was to examine the effects of baicalin on brain injury in a rat model of intracerebral hemorrhage (ICH) and to explore the possible mechanisms. Intracerebral hemorrhage was induced in male Wistar rats by injection of 0.5 U collagenaseVII to the caudate nucleus. Sham operation rats were injected with equal volume of saline. After the induction of ICH, the rats were randomly divided into four groups and administered with different dose of baicalin (0, 25, 50, or 100 mg/kg in saline) through peritoneal injection. The brain tissues around the hemorrhage areas were collected on days 1, 3, and 5 after treatment. Brain edema was analyzed by desiccation method; the metalloproteinase-9 (MMP-9) protein and mRNA expression were determined by western blotting and real time RT-PCR, respectively. Nuclear factor-κB (NF-κB) protein expression was analyzed by western blotting. IL-1β and IL-6 levels were determined by enzyme-linked immunosorbent assay. Blood-brain barrier permeability was determined by Evans blue leakage method. The results showed that baicalin reduced brain edema following ICH in a dose-dependent manner, with concomitant inhibition of NF-κB activation and suppression of MMP-9 expression. In addition, baicalin also reduced IL-1β and IL-6 production, as well as blood-brain barrier permeability. The above results indicated that baicalin prevents against perihematomal edema development after intracerebral hemorrhage possibly through an anti-inflammatory mechanism.

Antihyperalgesic and anti-inflammatory effects of atorvastatin in chronic constriction injury-induced neuropathic pain in rats

Atorvastatin is a 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitor used in treatment of hypercholesterolemia and prevention of coronary heart disease. The aim of this study is to investigate the antihyperalgesic and anti-inflammatory effects of atorvastatin (3, 10, and 30 mg/kg by oral gavages for 14 days) in chronic constriction injury (CCI) model of neuropathic pain in rats. CCI caused significant increase in tumor necrosis factor-α, interleukin 1 beta, prostaglandin E2, along with matrix metalloproteases (MMP-2) and nerve growth factor (NGF) levels in sciatic nerve and spinal cord concomitant with mechanical and thermal hyperalgesia, which were significantly reduced by oral administration of atorvastatin for 14 days as compared to CCI rats. Our study demonstrated that atorvastatin attenuates neuropathic pain through inhibition of cytokines, MMP-2, and NGF in sciatic nerve and spinal cord suggesting that atorvastatin could be an additional therapeutic strategy in management of neuropathic pain.

Association between serum tissue inhibitor of matrix metalloproteinase-1 levels and mortality in patients with severe brain trauma injury

OBJECTIVE

Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) play a role in neuroinflammation after brain trauma injury (TBI). Previous studies with small sample size have reported higher circulating MMP-2 and MMP-9 levels in patients with TBI, but no association between those levels and mortality. Thus, the aim of this study was to determine whether serum TIMP-1 and MMP-9 levels are associated with mortality in patients with severe TBI.

METHODS

This was a multicenter, observational and prospective study carried out in six Spanish Intensive Care Units. Patients with severe TBI defined as Glasgow Coma Scale (GCS) lower than 9 were included, while those with Injury Severity Score (ISS) in non-cranial aspects higher than 9 were excluded. Serum levels of TIMP-1, MMP-9 and tumor necrosis factor (TNF)-alpha, and plasma levels of tissue factor (TF) and plasminogen activator inhibitor (PAI)-1 plasma were measured in 100 patients with severe TBI at admission. Endpoint was 30-day mortality.

RESULTS

Non-surviving TBI patients (n = 27) showed higher serum TIMP-1 levels than survivor ones (n = 73). We did not find differences in MMP-9 serum levels. Logistic regression analysis showed that serum TIMP-1 levels were associated 30-day mortality (OR = 1.01; 95% CI = 1.001-1.013; P = 0.03). Survival analysis showed that patients with serum TIMP-1 higher than 220 ng/mL presented increased 30-day mortality than patients with lower levels (Chi-square = 5.50; P = 0.02). The area under the curve (AUC) for TIMP-1 as predictor of 30-day mortality was 0.73 (95% CI = 0.624-0.844; P<0.001). An association between TIMP-1 levels and APACHE-II score, TNF- alpha and TF was found.

CONCLUSIONS

The most relevant and new findings of our study, the largest series reporting data on TIMP-1 and MMP-9 levels in patients with severe TBI, were that serum TIMP-1 levels were associated with TBI mortality and could be used as a prognostic biomarker of mortality in TBI patients.

Effects of atorvastatin on plasma matrix metalloproteinase-9 concentration after glial tumor resection; a randomized, double blind, placebo controlled trial

Background

Neurosurgical procedures such as craniotomy and brain tumor resection could potentially lead to unavoidable cerebral injuries. Matrix metalloproteinase-9 (MMP-9) is up-regulated in neurological injuries. Statins have been suggested to reduce MMP- 9 level and lead to neuroprotection. Atorvastatin preoperatively administered to evaluate its neuroprotective effects and outcome assessment in neurosurgical-induced brain injuries after glial tumor resection. In this prospective, randomized, double-blind, placebo-controlled trial, 42 patients undergoing glial tumor surgery randomly received 40 mg atorvastatin or placebo twice daily from seven days prior to operation and continued for a 3 weeks period. Plasma MMP-9 concentration measured 4 times, immediately before starting atorvastatin or placebo, immediately before surgery, 24 hours and two weeks after the surgery. Karnofsky performance score was assessed before first dose of atorvastatin as a baseline and 2 months after the surgery.

Results

Karnofsky performance scale after surgery raised significantly more in Atorvastatin group (11.43 +/- 10.62 vs. 4.00 +/- 8.21) (p = 0.03). Atorvastatin did not significantly reduce MMP-9 plasma concentration 24 hours after surgery in comparison to placebo. No statistical significance detected regarding length of hospital stay among the groups. Significant reduction in MMP-9 plasma concentration was recorded in atorvastatin group two weeks after surgery (p = 0.048).

Conclusions

Significant statistical differences detected with atorvastatin group regarding MMP-9 plasma concentration, clinical outcome and Karnofsky performance score. Consequently, atorvastatin use may lead to better outcome after neurosurgical procedures.

Surgical brain injury and edema prevention

Neurosurgical procedures, carried out routinely in health institutions, present postoperative complications that result from unavoidable brain injury inflicted by surgical maneuvers. These maneuvers, which include incisions, electrocauterization, and retraction, place brain tissue at the margins of the operative site at risk of injury. Brain edema is a major complication that develops subsequent to this surgically induced brain injury. In the present review, we will discuss type of injury as well as the animal model available to study it. In addition, we will discuss potential mediators, including vascular endothelial growth factor, metalloproteinases, and cyclooxygenases, which have been tested in in vivo experimental studies and have been shown to be potential targets for the development of clinical therapies for neuroprotection against brain edema.

Blood-brain barrier permeability is positively correlated with cerebral microvascular perfusion in the early fluid percussion-injured brain of the rat

The blood-brain barrier (BBB) opening following traumatic brain injury (TBI) provides a chance for therapeutic agents to cross the barrier, yet the reduction of the cerebral microvascular perfusion after TBI may limit the intervention. Meanwhile, optimizing the cerebral capillary perfusion by the strategies such as fluid administration may cause brain edema due to the BBB opening post trauma. To guide the TBI therapy, we characterized the relationship between the changes in the cerebral capillary perfusion and BBB permeability after TBI. First, we observed the changes of the cerebral capillary perfusion by the intracardiac perfusion of Evans Blue and the BBB disruption with magnetic resonance imaging (MRI) in the rat subjected to lateral fluid percussion (FP) brain injury. The correlation between two variables was next evaluated with the correlation analysis. Since related to BBB breakdown, matrix metalloproteinase-9 (MMP-9) activity was finally detected by gelatin zymography. We found that the ratios of the perfused microvessel numbers in the lesioned cortices were significantly reduced at 0 and 1 h post trauma compared with that in the normal cortex, which then dramatically recovered at 4 and 24 h after injury, and that the BBB permeability was greatly augmented in the ipsilateral parts at 4, 12, and 24 h, and in the contralateral area at 24 h after injury compared with that in the uninjured brain. The correlation analysis showed that the BBB permeability increase was related to the restoration of the cerebral capillary perfusion over a 24-h period post trauma. Moreover, the gelatin zymography analysis indicated that the MMP-9 activity in the injured brain increased at 4 h and significantly elevated at 12 and 24 h as compared to that at 0 or 1 h after TBI. Our findings demonstrate that the 4 h post trauma is a critical turning point during the development of TBI, and, importantly, the correlation analysis may guide us how to treat TBI.

PAR-1 antagonist SCH79797 ameliorates apoptosis following surgical brain injury through inhibition of ASK1-JNK in rats

Neurosurgical procedures inevitably produce intraoperative hemorrhage. The subsequent entry of blood into the brain parenchyma results in the release of large amounts of thrombin, a known contributor to perihematomal edema formation and apoptosis after brain injury. The present study seeks to test 1) the effect of surgically induced brain injury (SBI) on thrombin activity, expression of thrombin's receptor PAR-1, and PAR-1 mediated apoptosis; 2) the effect of thrombin inhibition by argatroban and PAR-1 inhibition by SCH79797 on the development of secondary brain injury in the SBI model on rats. A total of 88 Sprague-Dawley male rats were randomly divided into sham, vehicle-, argatroban-, or SCH79797-treated groups. SBI involved partial resection of the right frontal lobe under inhalation isoflurane anesthesia. Sham-operated animals received only craniotomy. Thrombin activity, brain water content, and neurological deficits were measured at 24 h following SBI. Involvement of the Ask1/JNK pathway in PAR-1-induced post-SBI apoptosis was characterized by using Ask1 or JNK inhibitors. We observed that SBI increased thrombin activity, yet failed to demonstrate any effect on PAR-1 expression. Argatroban and SCH79797 reduced SBI-induced brain edema and neurological deficits in a dose-dependent manner. SBI-induced apoptosis seemed mediated by the PAR-1/Ask1/JNK pathways. Administration of SCH79797 ameliorated the apoptosis following SBI. Our findings indicate that PAR-1 antagonist protects against secondary brain injury after SBI by decreasing both brain edema and apoptosis by inactivating PAR-1/Ask1/JNK pathway. The anti-apoptotic effect of PAR-1 antagonists may provide a promising path for therapy following SBI.

Effect of dexmedetomidine on brain edema and neurological outcomes in surgical brain injury in rats

BACKGROUND

Surgical brain injury (SBI) is damage to functional brain tissue resulting from neurosurgical manipulations such as sharp dissection, electrocautery, retraction, and direct applied pressure. Brain edema is the major contributor to morbidity with inflammation, necrosis, oxidative stress, and apoptosis likely playing smaller roles. Effective therapies for SBI may improve neurological outcomes and postoperative morbidities associated with brain surgery. Previous studies show an adrenergic correlation to blood-brain barrier control. The α-2 receptor agonist dexmedetomidine (DEX) has been shown to improve neurological outcomes in stroke models. We hypothesized that DEX may reduce brain edema and improve neurological outcomes in a rat model of SBI.

METHODS

Male Sprague-Dawley rats (n = 63) weighing 280 to 350 g were randomly assigned to 1 of 4 IP treatment groups: sham IP, vehicle IP, DEX 10 mg/kg, and DEX 30 mg/kg. Treatments were given 30 min before SBI. These treatment groups were repeated to observe the physiologic impact of DEX on mean arterial blood pressure (MAP), heart rate (HR), and blood glucose on SBI naïve animals. Rats were also assigned to 4 postinjury IV treatment groups: sham IV, vehicle IV, DEX 10/5, and DEX 30/15 (DEX group doses were 10 and 30 mg/kg/hr, with 5 and 15 mg/kg initial loading doses, respectively). Initial loading doses began 20 min after SBI, followed by 2 h of infusion. SBI animals were subjected to neurological testing 24 h after brain injury by a blinded observer, promptly killed, and brain water content measured via the dry/wet weight method.

RESULTS

All treatment groups showed a significant difference in ipsilateral frontal brain water content and neurological scores when compared with sham animals. However, there was no difference between DEX-treated and vehicle animals. Physiologic monitoring showed treatment with low or high doses of DEX significantly decreased MAP and HR, and briefly increased blood glucose compared with naïve or vehicle-treated animals.

CONCLUSIONS

DEX administration did not reduce brain edema or improve neurological function after SBI in this study. The statistical difference in brain water content and neurological scores when comparing sham treatment to vehicle and DEX treatments shows consistent reproduction of this model. Significant changes in MAP, HR, and blood glucose after DEX as compared to vehicle and sham treatments suggest appropriate delivery of drug.

The quiet revolution: retractorless surgery for complex vascular and skull base lesions

Object

Smaller operative exposures, endoscopic approaches, and minimally invasive neurosurgery have emerged as a dominant trend in the modern era. In keeping with this evolution, the authors have recently eliminated the use of fixed retractors, instead employing dynamic retraction, with the use of handheld instruments. In the present study, the authors report the results of applying this strategy to challenging vascular and skull base lesions.

Methods

This 6-month study prospectively analyzed the use of retractorless surgery in a consecutive series of 223 patients with intracranial vascular or skull base lesions undergoing craniotomy. A single surgeon performed all operations.

Results

The microsurgical approaches (in descending order of frequency) included an orbitozygomatic craniotomy (77 patients [35%]), frontal (36 patients [16%]), retrosigmoid (27 patients [12%]), interhemispheric (16 patients [7%]), and lateral supracerebellar (15 patients [7%]). The most common lesions were aneurysms (83 lesions overall [37%]), 18 of which required a bypass. Of 159 vascular lesions, there were also 46 cavernous malformations (29%). Meningiomas were the most common skull base tumors (37 cases [58%]). Of the 223 patients, 7 cases of various vascular and skull base lesions required fixed retraction. Therefore, 97% of the cases were successfully treated without a self-retaining retractor system.

Conclusions

Fixed retraction can be supplanted by dynamic retraction with surgical instruments, limiting the risk of retractor-induced tissue edema and injury. This quiet revolution has precipitated a major change in surgical techniques. Extensive dissection of arachnoidal planes, careful placement of the handheld suction device, patient positioning that enhances gravity retraction, the refinement of microsurgical instrumentation, and appropriate selection of the operative corridor all serve to obviate the need for fixed retraction in most intracranial procedures. Retractorless neurosurgery is an achievable goal, even when complex lesions of the vasculature and skull base are being treated.

Dexamethasone inhibits ICAM-1 and MMP-9 expression and reduces brain edema in intracerebral hemorrhagic rats

BACKGROUND

The molecular mechanism of hemorrhagic stroke is unclear, and the identification of therapeutic agents for attenuating post-stroke brain damage remains an unresolved challenge. Dexamethasone (DEX) is used clinically to treat spinal cord injury and brain tumor patients by reducing edema formation, but has produced conflicting results in stroke management.

METHODS

In this study, intracerebral hemorrhage (ICH) was induced in rats by intracranial stereotactic injection of collagenase into the caudate nucleus. DEX was given immediately and 3 days after ICH. The expression of intercellular adhesion molecule-1 (ICAM-1), matrix metalloproteinase-9 (MMP-9), nuclear factor (NF)-κB, and IκB were analyzed by Western blotting, and perihematomal edema formation was evaluated by magnetic resonance imaging.

RESULTS

The results showed that ICH caused an increase of ICAM-1 and MMP-9 expression from 4 h to 7 days, which was inhibited following the administration of DEX. The perihematomal edema volume in ICH rats was high, with two peak periods at 12 h and 3 days, which was also reduced in DEX-treated groups. Furthermore, the administration of DEX not only maintained IκB in cytoplasm, but also decreased NF-κB elevation in the nucleus at 3 and 5 days in ICH rats.

CONCLUSIONS

In conclusion, these data show that DEX successfully reduced post-stroke brain edema by decreasing MMP-9 and ICAM-1 levels, partially through the IκB/NF-κB signaling pathway. The timing of DEX administration in relation to the onset of brain injury may be critical.

Hydrogen is neuroprotective against surgically induced brain injury

Background

Neurosurgical operations cause unavoidable damage to healthy brain tissues. Direct surgical injury as well as surgically induced oxidative stress contributes to the subsequent formation of brain edema. Therefore, we tested the neuroprotective effects of hydrogen (H₂) in an established surgical brain injury (SBI) model in rats.

Materials and methods

Adult male Sprague - Dawley rats (weight 300-350g) were divided into three groups to serve as sham operated, SBI without treatment, and SBI treated with H₂ (2.9%). Brain water content, myeloperoxidase (MPO) assay, lipid peroxidation (LPO), and neurological function were measured at 24 hrs after SBI.

Results

SBI resulted in localized brain edema (p = < 0.001). Hydrogen (2.9%) administered concurrently with surgery significantly decreased the formation of cerebral edema (p = 0.028) and improved neurobehavioral score (p = 0.022). However, hydrogen treatment failed to reduce oxidative stress (LPO assay) or inflammation (MPO assay) in brain tissues.

Conclusions

Hydrogen appears to be promising as an effective, yet inexpensive way to reduce cerebral edema caused by surgical procedures. Hydrogen has the potential to improve clinical outcome, decrease hospital stay, and reduce overall cost to patients and the health care system.