Effect of valproic acid and injury on lesion size and endothelial glycocalyx shedding in a rodent model of isolated traumatic brain injury

Valproic Acid Treatment after Traumatic Brain Injury in Mice Alleviates Neuronal Death and Inflammation in Association with Increased Plasma Lysophosphatidylcholines

The histone deacetylase inhibitor (HDACi) valproic acid (VPA) has neuroprotective and anti-inflammatory effects in experimental traumatic brain injury (TBI), which have been partially attributed to the epigenetic disinhibition of the transcription repressor RE1-Silencing Transcription Factor/Neuron-Restrictive Silencer Factor (REST/NRSF). Additionally, VPA changes post-traumatic brain injury (TBI) brain metabolism to create a neuroprotective environment. To address the interconnection of neuroprotection, metabolism, inflammation and REST/NRSF after TBI, we subjected C57BL/6N mice to experimental TBI and intraperitoneal VPA administration or vehicle solution at 15 min, 1, 2, and 3 days post-injury (dpi). At 7 dpi, TBI-induced an up-regulation of REST/NRSF gene expression and HDACi function of VPA on histone H3 acetylation were confirmed. Neurological deficits, brain lesion size, blood-brain barrier permeability, or astrogliosis were not affected, and REST/NRSF target genes were only marginally influenced by VPA. However, VPA attenuated structural damage in the hippocampus, microgliosis and expression of the pro-inflammatory marker genes. Analyses of plasma lipidomic and polar metabolomic patterns revealed that VPA treatment increased lysophosphatidylcholines (LPCs), which were inversely associated with interleukin 1 beta (Il1b) and tumor necrosis factor (Tnf) gene expression in the brain. The results show that VPA has mild neuroprotective and anti-inflammatory effects likely originating from favorable systemic metabolic changes resulting in increased plasma LPCs that are known to be actively taken up by the brain and function as carriers for neuroprotective polyunsaturated fatty acids.

Effect of valproic acid upon skeletal muscle subjected to prolonged tourniquet application

Background

Valproic acid (VPA), a histone deacetylase inhibitor, has shown improved outcomes when used as a pharmaceutical intervention in animal studies of hemorrhage, septic shock, and combined injuries. This study was designed to investigate the ability of VPA to mitigate ischemia-reperfusion injury produced by prolonged tourniquet application to an extremity.

Methods

The ischemia-reperfusion model in anesthetized rats was established using hemorrhage and a 3-hour tourniquet application. VPA was administered intravenously prior to tourniquet wear and removal. Ischemia-reperfusion injury was evaluated by investigating pathway signaling, immune modulation of cytokine release, remote organ injury, and skeletal muscle function during convalescence.

Results

We found that VPA sustained Protein kinase B (Akt) phosphorylation and Insulin-like growth factor signaling and modulated the systemic release of interleukin (IL)-1β, tumor necrosis factor alpha, and IL-6 after 2 hours of limb reperfusion. Additionally, VPA attenuated a loss in glomerular filtration rate at 3 days after injury. Histological and functional evaluation of extremity skeletal muscle at 3, 7, and 21 days after injury, however, demonstrated no significant differences in myocytic degeneration, necrotic formation, and maximal isometric tetanic torque.

Conclusions

Our results demonstrate that VPA sustains early prosurvival cell signaling, reduces the inflammatory response, and improves renal function in a hemorrhage with prolonged ischemia and reperfusion model. However, these do not translate into meaningful preservation in limb function when applied as a pharmaceutical augmentation to tourniquet wear.

Level of evidence

IV.

Sustained Dysbiosis and Decreased Fecal Short-Chain Fatty Acids after Traumatic Brain Injury and Impact on Neurologic Outcome

Traumatic brain injury (TBI) alters microbial populations present in the gut, which may impact healing and tissue recovery. However, the duration and impact of these changes on outcome from TBI are unknown. Short-chain fatty acids (SCFAs), produced by bacterial fermentation of dietary fiber, are important signaling molecules in the microbiota gut-brain axis. We hypothesized that TBI would lead to a sustained reduction in SCFA producing bacteria, fecal SCFAs concentration, and administration of soluble SCFAs would improve functional outcome after TBI. Adult mice (n = 10) had the controlled cortical impact (CCI) model of TBI performed (6 m/sec, 2-mm depth, 50-msec dwell). Stool samples were collected serially until 28 days after CCI and analyzed for SCFA concentration by high-performance liquid chromatography-mass spectrometry/mass spectrometry and microbiome analyzed by 16S gene sequencing. In a separate experiment, mice (n = 10/group) were randomized 2 weeks before CCI to standard drinking water or water supplemented with the SCFAs acetate (67.5 mM), propionate (25.9 mM), and butyrate (40 mM). Morris water maze performance was assessed on post-injury Days 14-19. Alpha diversity remained stable until 72 h, at which point a decline in diversity was observed without recovery out to 28 days. The taxonomic composition of post-TBI fecal samples demonstrated depletion of bacteria from Lachnospiraceae, Ruminococcaceae, and Bacteroidaceae families, and enrichment of bacteria from the Verrucomicrobiaceae family. Analysis from paired fecal samples revealed a reduction in total SCFAs at 24 h and 28 days after TBI. Acetate, the most abundant SCFA detected in the fecal samples, was reduced at 7 days and 28 days after TBI. SCFA administration improved spatial learning after TBI versus standard drinking water. In conclusion, TBI is associated with reduced richness and diversity of commensal microbiota in the gut and a reduction in SCFAs detected in stool. Supplementation of soluble SCFAs improves spatial learning after TBI.

Valproic acid treatment rescues injured tissues after traumatic brain injury

BACKGROUND

No agents that are specifically neuroprotective are currently approved to emergently treat patients with traumatic brain injury (TBI). The histone deacetylase inhibitor, high-dose valproic acid (VPA) has been shown to have cytoprotective potential in models of combined TBI and hemorrhagic shock, but it has not been tested in an isolated TBI model. We hypothesized that VPA, administered after isolated TBI, will penetrate the injured brain, attenuate the lesion size, and activate prosurvival pathways.

METHODS

Yorkshire swine were subjected to severe TBI by cortical impact. One hour later, animals were randomized to VPA treatment (150 mg/kg delivered intravenously for 1 hour; n = 4) or control (saline vehicle; n = 4) groups. Seven hours after injury, animals were sacrificed, and brain lesion size was measured. Mass spectrometry imaging was used to visualize and quantitate brain tissue distribution of VPA. Sequential serum samples were assayed for key biomarkers and subjected to proteomic and pathway analysis.

RESULTS

Brain lesion size was 50% smaller (p = 0.01) in the VPA-treated animals (3,837 ± 948 mm) compared with the controls (1,900 ± 614 mm). Endothelial regions had eightfold higher VPA concentrations than perivascular regions by mass spectrometry imaging, and it readily penetrated the injured brain tissues. Serum glial fibrillary acid protein was significantly lower in the VPA-treated compared with the control animals (p < 0.05). More than 500 proteins were differentially expressed in the brain, and pathway analysis revealed that VPA affected critical modulators of TBI response including calcium signaling pathways, mitochondria metabolism, and biosynthetic machinery.

CONCLUSION

Valproic acid penetrates injured brain tissues and exerts neuroprotective and prosurvival effects that resulted in a significant reduction in brain lesion size after isolated TBI. Levels of serum biomarkers reflect these changes, which could be useful for monitoring the response of TBI patients during clinical studies.

Blood-Brain Barrier Damage in Ischemic Stroke and Its Regulation by Endothelial Mechanotransduction

Ischemic stroke, a major cause of mortality in the United States, often contributes to disruption of the blood-brain barrier (BBB). The BBB along with its supportive cells, collectively referred to as the “neurovascular unit,” is the brain’s multicellular microvasculature that bi-directionally regulates the transport of blood, ions, oxygen, and cells from the circulation into the brain. It is thus vital for the maintenance of central nervous system homeostasis. BBB disruption, which is associated with the altered expression of tight junction proteins and BBB transporters, is believed to exacerbate brain injury caused by ischemic stroke and limits the therapeutic potential of current clinical therapies, such as recombinant tissue plasminogen activator. Accumulating evidence suggests that endothelial mechanobiology, the conversion of mechanical forces into biochemical signals, helps regulate function of the peripheral vasculature and may similarly maintain BBB integrity. For example, the endothelial glycocalyx (GCX), a glycoprotein-proteoglycan layer extending into the lumen of bloods vessel, is abundantly expressed on endothelial cells of the BBB and has been shown to regulate BBB permeability. In this review, we will focus on our understanding of the mechanisms underlying BBB damage after ischemic stroke, highlighting current and potential future novel pharmacological strategies for BBB protection and recovery. Finally, we will address the current knowledge of endothelial mechanotransduction in BBB maintenance, specifically focusing on a potential role of the endothelial GCX.

Histone Deacetylase Inhibitors: A Novel Strategy in Trauma and Sepsis

Trauma remains a leading cause of morbidity and mortality among all age groups in the United States. Hemorrhagic shock and traumatic brain injury (TBI) are major causes of preventable death in trauma. Initial treatment involves fluid resuscitation to improve the intravascular volume. Although crystalloids may provide volume expansion, they do not have any pro-survival properties. Furthermore, aggressive fluid resuscitation can provoke a severe inflammatory response and worsen clinical outcomes. Due to logistical constraints, however, definitive resuscitation with blood products is often not feasible in the prehospital setting-highlighting the importance of adjunctive therapies. In recent years, histone deacetylase inhibitors (HDACis) have shown promise as pharmacologic agents for use in both trauma and sepsis. In this review, we discuss the role of histone deacetylases (HDACs) and pharmacologic agents that inhibit them (HDACis). We also highlight the therapeutic effects and mechanisms of action of HDACis in hemorrhagic shock, TBI, polytrauma, and sepsis. With further investigation and translation, HDACis have the potential to be a high-impact adjunctive therapy to traditional resuscitation.

Dose optimization of valproic acid in a lethal model of traumatic brain injury, hemorrhage, and multiple trauma in swine

BACKGROUND

Trauma is a leading cause of death, and traumatic brain injury is one of the hallmark injuries of current military conflicts. Valproic acid (VPA) administration in high doses (300-400 mg/kg) improves survival in lethal trauma models, but effectiveness of lower doses on survival is unknown. This information is essential for properly designing the upcoming clinical trials. We, therefore, performed the current study to determine the lowest dose at which VPA administration improves survival in a model of lethal injuries.

METHODS

Swine were subjected to traumatic brain injury (10-mm cortical impact), 40% blood volume hemorrhage, and multiple trauma (femur fracture, rectus crush, and Grade V liver laceration). After 1 hour of shock, animals were randomized (n = 6/group) to four groups: normal saline (NS) resuscitation; or NS with VPA doses of 150 mg/kg (VPA 150) or 100 mg/kg (VPA 100) administered over 3 hours or 100 mg/kg over 2 hours (VPA 100 over 2 hours). Three hours after shock, packed red blood cells were given, and animals were monitored for another 4 hours. Survival was assessed using Kaplan-Meier and log-rank test.

RESULTS

Without resuscitation, all of the injured animals died within 5 hours. Similar survival rates were observed in the NS (17%) and VPA 100 (0%) resuscitation groups. Survival rates in the 100-mg/kg VPA groups were significantly (p < 0.05) better when it was given over 2 hours (67%) compared to 3 hours (0%). 83% of the animals in the VPA 150 group survived, which was significantly higher than the NS and VPA 100 over 3 hours groups (p < 0.05).

CONCLUSION

A single dose of VPA (150 mg/kg) significantly improves survival in an otherwise lethal model of multiple injuries. This is a much lower dose than previously shown to have a survival benefit and matches the dose that is tolerated by healthy human subjects with minimal adverse effects.

LEVEL OF EVIDENCE

Therapeutic, level V.

Histone Deacetylase Inhibitors: A Novel Strategy for Neuroprotection and Cardioprotection Following Ischemia/Reperfusion Injury

Ischemia/reperfusion injury is a complex molecular cascade that causes deleterious cellular damage and organ dysfunction. Stroke, sudden cardiac arrest, and acute myocardial infarction are the most common causes of ischemia/reperfusion injury without effective pharmacologic therapies. Existing preclinical evidence suggests that histone deacetylase inhibitors may be an efficacious, affordable, and clinically feasible therapy that can improve neurologic and cardiac outcomes following ischemia/reperfusion injury. In this review, we discuss the pathophysiology and epigenetic modulations of ischemia/reperfusion injury and focus on the neuroprotective and cardioprotective effects of histone deacetylase inhibitors. We also summarize the protective effects of histone deacetylase inhibitors for other vital organs and highlight the key research priorities for their successful translation to the bedside.

Valproic acid improves survival and decreases resuscitation requirements in a swine model of prolonged damage control resuscitation

BACKGROUND

Although damage control resuscitation (DCR) is routinely performed for short durations, prolonged DCR may be required in military conflicts as a component of prolonged field care. Valproic acid (VPA) has been shown to have beneficial properties in lethal hemorrhage/trauma models. We sought to investigate whether the addition of a single dose of VPA to a 72-hour prolonged DCR protocol would improve clinical outcomes.

METHODS

Fifteen Yorkshire swine (40-45 kg) were subjected to lethal (50% estimated total blood volume) hemorrhagic shock (HS) and randomized to three groups: (1) HS, (2) HS-DCR, (3) HS-DCR-VPA (150 mg/kg over 3 hours) (n = 5/cohort). In groups assigned to receive DCR, Tactical Combat Casualty Care guidelines were applied (1 hour into the shock period), targeting a systolic blood pressure of 80 mm Hg. At 72 hours, surviving animals were given transfusion of packed red blood cells, simulating evacuation to higher echelons of care. Survival rates, physiologic parameters, resuscitative fluid requirements, and laboratory profiles were used to compare the clinical outcomes.

RESULTS

This model was 100% lethal in the untreated animals. DCR improved survival to 20%, although this was not statistically significant. The addition of VPA to DCR significantly improved survival to 80% (p < 0.01). The VPA-treated animals also had significantly (p < 0.05) higher systolic blood pressures, lower fluid resuscitation requirements, higher hemoglobin levels, and lower creatinine and potassium levels.

CONCLUSION

VPA administration improves survival, decreases resuscitation requirements, and improves hemodynamic and laboratory parameters when added to prolonged DCR in a lethal hemorrhage model.

Endothelial glycocalyx in acute care surgery - what anaesthesiologists need to know for clinical practice

The endothelial glycocalyx (EG) is the thin sugar-based lining on the apical surface of endothelial cells. It has been linked to the physiological functioning of the microcirculation and has been found to be damaged in critical illness and after acute care surgery. This review aims to describe the role of EG in severely injured patients undergoing surgery, discuss specific situations (e.G. major trauma, hemorrhagic shock, trauma induced coagulopathy) as well as specific interventions commonly applied in these patients (e.g. fluid therapy, transfusion) and specific drugs related to perioperative medicine with regard to their impact on EG.EG in acute care surgery is exposed to damage due to tissue trauma, inflammation, oxidative stress and inadequate fluid therapy. Even though some interventions (transfusion of plasma, human serum albumin, hydrocortisone, sevoflurane) are described as potentially EG protective there is still no specific treatment for EG protection and recovery in clinical medicine.The most important principle to be adopted in routine clinical practice at present is to acknowledge the fragile structure of the EG and avoid further damage which is potentially related to worsened clinical outcome.

The 'Omics' of Epigenetic Modulation by Valproic Acid Treatment in Traumatic Brain Injury-What We Know and What the Future Holds

Traumatic brain injury (TBI) is a heterogeneous injury that is a major cause of morbidity and mortality worldwide. Epigenetic modulation through the alteration of cellular acetylation by valproic acid (VPA) administration has shown promise as a novel pharmacological treatment for TBI. It improves clinical outcomes through multiple mechanisms, many of which are still poorly understood. In recent years, omics technologies have emerged as a promising strategy to detect molecular changes at the cellular level. This review highlights the use of these high throughput technologies in advancing the understanding of epigenetic modulation by VPA in TBI. It also describes the future role of omics techniques in developing a point of care test to guide patient selection for VPA administration.

Safety and Tolerability of Intravenous Valproic Acid in Healthy Subjects: A Phase I Dose-Escalation Trial

BACKGROUND

Valproic acid, a histone deacetylase inhibitor, has beneficial effects in the setting of cancer, neurologic diseases, and traumatic injuries. In animal models of traumatic injury, a single dose of valproic acid has been shown to reduce mortality. The purpose of this trial was to determine the maximum tolerated single dose of intravenous valproic acid in healthy humans.

METHODS

A double-blinded, placebo-controlled, dose-escalation trial design was used to identify dose-limiting toxicities in healthy subjects who received a single dose of intravenous valproic acid. Patients were monitored for adverse events and data were collected for pharmacokinetic, pharmacodynamic, and safety profiling of valproic acid.

RESULTS

Fifty-nine healthy subjects (mean 30 ± 12 years) were enrolled. Forty-four subjects received valproic acid in doses from 15 to 150 mg/kg. The most common adverse events were hypoacusis (n = 19), chills (n = 18), and headache (n = 16). The maximum tolerated dose was 140 mg/kg. Dose-limiting toxicities included headache and nausea lasting longer than 12 h. No drug-related abnormalities were seen in other safety measures including laboratory tests, hemodynamic parameters, cardiac rhythm monitoring, and cognitive testing. A two-compartment model was predictive of valproic acid concentration-time profiles, with a strong correlation (R ² = 0.56) observed between the number of reported adverse events and the dose level.

CONCLUSIONS

The maximum tolerated dose of intravenous valproic acid in healthy subjects is 140 mg/kg. This is significantly higher than the previously established maximum tolerated dose of 60-75 mg/kg. Next, the safety and tolerability of high-dose valproic acid will be tested in trauma patients in hemorrhagic shock. ClinicalTrials.gov Identifier: NCT01951560.

Detection of Glycan Shedding in the Blood: New Class of Multiple Sclerosis Biomarkers?

Introduction

Multiple sclerosis (MS) is a devastating autoimmune disease, afflicting people in the prime of their lives. Presently, after initial clinical presentation, there are no reliable markers for whether a patient will develop MS, or whether their prognosis will be aggressive or relapsing–remitting. Furthermore, many MS patients do not respond to treatment. Thus, markers for diagnosis, prognosis, and treatment-responsiveness are lacking for a disease, where a precision medicine approach would be valuable. The glycocalyx (GLX) is the carbohydrate-rich outer surface of the blood vessel wall and is the first interaction between the blood and the vessel. We hypothesized that cleavage of the GLX may be an early stage predictor of immune attack, blood–brain barrier (BBB) breakdown, and disease severity in MS.

Methods

Two experimental models of MS, experimental autoimmune encephalitis (EAE), were included in this study. EAE was induced in C57BL/6J mice and Lewis rats, which were monitored for weight loss and clinical presentation in comparison to healthy controls. Plasma samples were obtained longitudinally from mice until peak disease severity and at peak disease severity in rats. Soluble GLX-associated glycosaminoglycans (GAG) and proteoglycans (PG) were detected in plasma samples.

Results

All animals receiving EAE emulsion developed fulminant EAE (100% penetrance). Increased plasma levels of chondroitin sulfate were detected before the onset of clinical symptoms and remained elevated at peak disease severity. Hyaluronic acid was increased at the height of the disease, whereas heparan sulfate was transiently increased during early stages only. By contrast, syndecans 1, 3, and 4 were detected in EAE samples as well as healthy controls, with no significant differences between the two groups.

Discussion

In this study, we present data supporting the shedding of the GLX as a new class of biomarker for MS. In particular, soluble, sugar-based GLX components are associated with disease severity in two models of MS, molecules that would not be detected in proteomics-based screens of MS patient samples. Patient studies are presently underway.

Valproic acid induces prosurvival transcriptomic changes in swine subjected to traumatic injury and hemorrhagic shock

BACKGROUND

Valproic acid (VPA) is a histone deacetylase inhibitor that improves outcomes in large animal models of trauma. However, its protective mechanism of action is not completely understood. We sought to characterize the genetic changes induced by VPA treatment following traumatic injuries.

METHODS

Six female Yorkshire swine were subjected to traumatic brain injury (controlled cortical impact), polytrauma (liver and splenic laceration, rib fracture, rectus crush), and hemorrhagic shock (HS, 40% total blood volume). Following 2 hours of HS, animals were randomized to resuscitation with normal saline (NS) or NS + 150 mg/kg of intravenous VPA (n = 3/cohort, 18 samples total). Blood samples were collected for isolation of peripheral blood mononuclear cells at three distinct time points: baseline, 6 hours following injuries, and on postinjury day 1. RNA was extracted from peripheral blood mononuclear cells and sequenced. Differential expression analysis (false discovery rate < 0.001 and p value <0.001) and gene set enrichment (Panther Gene Ontology and Ingenuity Pathway Analysis) was used to compare VPA to non-VPA-treated animals.

RESULTS

A total of 628 differentially expressed RNA transcripts were identified, 412 of which were used for analysis. There was no difference between treatment groups at baseline. The VPA-induced genetic changes were similar at 6 hours and on postinjury day 1. Upregulated genes were associated with gene expression (p 2.13E-34), cellular development (1.19E-33), cellular growth and proliferation (1.25E-30), and glucocorticoid receptor signaling (8.6E-21). Downregulated genes were associated with cell cycle checkpoint regulation (3.64E-22), apoptosis signaling (6.54E-21), acute phase response signaling (5.84E-23), and the inflammasome pathway (1.7E-19).

CONCLUSION

In injured swine, VPA increases the expression of genes associated with cell survival, proliferation, and differentiation and decreases those associated with cell death and inflammation. These genetic changes could explain the superior clinical outcomes in VPA-treated animals, including smaller brain lesion size and improved neurologic recovery.

Different resuscitation strategies and novel pharmacologic treatment with valproic acid in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death in young adults, and effective treatment strategies have the potential to save many lives. TBI results in coagulopathy, endothelial dysfunction, inflammation, cell death, and impaired epigenetic homeostasis, ultimately leading to morbidity and/or mortality. Commonly used resuscitation fluids such as crystalloids or colloids have several disadvantages and might even be harmful when administered in large quantities. There is a need for next-generation treatment strategies (especially in the prehospital setting) that minimize cellular damage, improve survival, and enhance neurological recovery. Pharmacologic treatment with histone deacetylase inhibitors, such as valproic acid, has shown promising results in animal studies of TBI and may therefore be an excellent example of next-generation therapy. This review briefly describes traditional resuscitation strategies for TBI combined with hemorrhagic shock and describes preclinical studies on valproic acid as a new pharmacologic agent in the treatment of TBI. It finally discusses limitations and future directions on the use of histone deacetylase inhibitors for the treatment of TBI.

Effects of propranolol and clonidine on brain edema, blood-brain barrier permeability, and endothelial glycocalyx disruption after fluid percussion brain injury in the rat

BACKGROUND

Traumatic brain injury causes a disruption of the vascular endothelial glycocalyx layer that is associated with an overactivation of the sympathoadrenal system. We hypothesized that early and unselective beta-blockade with propranolol alone or in combination with the alfa2-agonist clonidine would decrease brain edema, blood-brain barrier permeability, and glycocalyx disruption at 24 hours after trauma.

METHODS

We subjected 53 adult male Sprague-Dawley rats to lateral fluid percussion brain injury and randomized infusion with propranolol (n = 16), propranolol + clonidine (n = 16), vehicle (n = 16), or sham (n = 5) for 24 hours. Primary outcome was brain water content at 24 hours. Secondary outcomes were blood-brain barrier permeability and plasma levels of syndecan-1 (glycocalyx disruption), cell damage (histone-complexed DNA fragments), epinephrine, norepinephrine, and animal motor function.

RESULTS

We found no difference in brain water content (mean ± SD) between propranolol (80.8 ± 0.3%; 95% confidence interval [CI], 80.7-81.0) and vehicle (81.1 ± 0.6%; 95% CI, 80.8-81.4) (p = 0.668) or between propranolol/clonidine (80.8 ± 0.3%; 95% CI, 80.7-81.0) and vehicle (p = 0.555). We found no effect of propranolol and propranolol/clonidine on blood-brain barrier permeability and animal motor scores. Unexpectedly, propranolol and propranolol/clonidine caused an increase in epinephrine and syndecan-1 levels.

CONCLUSION

This study does not provide any support for unselective beta-blockade with propranolol or the combination of propranolol and the alfa2-agonist clonidine on brain water content. The novel finding of an increase in plasma concentrations of epinephrine and syndecan-1 after propranolol treatment in traumatic brain injury is of unclear significance and should be investigated further.

Improvement of Blood-Brain Barrier Integrity in Traumatic Brain Injury and Hemorrhagic Shock Following Treatment With Valproic Acid and Fresh Frozen Plasma

OBJECTIVE

Combined traumatic brain injury and hemorrhagic shock are highly lethal. Following injuries, the integrity of the blood-brain barrier can be impaired, contributing to secondary brain insults. The status of the blood-brain barrier represents a potential factor impacting long-term neurologic outcomes in combined injuries. Treatment strategies involving plasma-based resuscitation and valproic acid therapy have shown efficacy in this setting. We hypothesize that a component of this beneficial effect is related to blood-brain barrier preservation.

DESIGN

Following controlled traumatic brain injury, hemorrhagic shock, various resuscitation and treatment strategies were evaluated for their association with blood-brain barrier integrity. Analysis of gene expression profiles was performed using Porcine Gene ST 1.1 microarray. Pathway analysis was completed using network analysis tools (Gene Ontology, Ingenuity Pathway Analysis, and Parametric Gene Set Enrichment Analysis).

SUBJECTS

Female Yorkshire swine were subjected to controlled traumatic brain injury and 2 hours of hemorrhagic shock (40% blood volume, mean arterial pressure 30-35 mmHg).

INTERVENTIONS

Subjects were resuscitated with 1) normal saline, 2) fresh frozen plasma, 3) hetastarch, 4) fresh frozen plasma + valproic acid, or 5) hetastarch + valproic acid (n = 5 per group). After 6 hours of observation, brains were harvested for evaluation.

MEASUREMENTS AND MAIN RESULTS

Immunofluoroscopic evaluation of the traumatic brain injury site revealed significantly increased expression of tight-junction associated proteins (zona occludin-1, claudin-5) following combination therapy (fresh frozen plasma + valproic acid and hetastarch + valproic acid). The extracellular matrix protein laminin was found to have significantly improved expression with combination therapies. Pathway analysis indicated that valproic acid significantly modulated pathways involved in endothelial barrier function and cell signaling.

CONCLUSIONS

Resuscitation with fresh frozen plasma results in improved expression of proteins essential for blood-brain barrier integrity. The addition of valproic acid provides significant improvement to these protein expression profiles. This is likely secondary to activation of key pathways related to endothelial functions.

Valproic acid decreases brain lesion size and improves neurologic recovery in swine subjected to traumatic brain injury, hemorrhagic shock, and polytrauma

BACKGROUND

We have previously shown that treatment with valproic acid (VPA) decreases brain lesion size in swine models of traumatic brain injury (TBI) and controlled hemorrhage. To translate this treatment into clinical practice, validation of drug efficacy and evaluation of pharmacologic properties in clinically realistic models of injury are necessary. In this study, we evaluate neurologic outcomes and perform pharmacokinetic analysis of a single dose of VPA in swine subjected to TBI, hemorrhagic shock, and visceral hemorrhage.

METHODS

Yorkshire swine (n = 5/cohort) were subjected to TBI, hemorrhagic shock, and polytrauma (liver and spleen injury, rib fracture, and rectus abdominis crush). Animals remained in hypovolemic shock for 2 hours before resuscitation with isotonic sodium chloride solution (ISCS; volume = 3× hemorrhage) or ISCS + VPA (150 mg/kg). Neurologic severity scores were assessed daily for 30 days, and brain lesion size was measured via magnetic resonance imaging on postinjury days (PID) 3 and 10. Serum samples were collected for pharmacokinetic analysis.

RESULTS

Shock severity and response to resuscitation were similar in both groups. Valproic acid-treated animals demonstrated significantly less neurologic impairment between PID 1 to 5 and smaller brain lesions on PID 3 (mean lesion size ± SEM, mm: ISCS = 4,956 ± 1,511 versus ISCS + VPA = 828 ± 279; p = 0.047). No significant difference in lesion size was identified between groups at PID 10 and all animals recovered to baseline neurologic function during the 30-day observation period. Animals treated with VPA had faster neurocognitive recovery (days to initiation of testing, mean ± SD: ISCS = 6.2 ± 1.6 vs ISCS + VPA = 3.6 ± 1.5; p = 0.002; days to task mastery: ISCS = 7.0 ± 1.0 vs ISCS + VPA = 4.8 ± 0.5; p = 0.03). The mean ± SD maximum VPA concentrations, area under the curve, and half-life were 145 ± 38.2 mg/L, 616 ± 150 hour·mg/L, and 1.70 ± 0.12 hours.

CONCLUSIONS

In swine subjected to TBI, hemorrhagic shock, and polytrauma, VPA treatment is safe, decreases brain lesion size, and reduces neurologic injury compared to resuscitation with ISCS alone. These benefits are achieved at clinically translatable serum concentrations of VPA.

LEVEL OF EVIDENCE

Therapeutic (preclinical study).

Trauma care: Finding a better way

In a Perspective, Hasan Alam discusses emerging treatment approaches in trauma care.

Repeated Low Intensity Blast Exposure Is Associated with Damaged Endothelial Glycocalyx and Downstream Behavioral Deficits

Current clinical research into mild traumatic brain injury (mTBI) has focused on white matter changes as identified by advanced MRI based imaging techniques. However, perivascular tau accumulation in the brains of individuals diagnosed with mTBI suggests that the vasculature plays a key role in the pathology. This study used a rat model to examine whether the endothelial glycocalyx, a layer of the vasculature responsible for sensing luminal shear forces, is damaged by exposure to repeated low intensity blast, and whether this layer is associated with observed behavioral deficits. The blast exposure used consisted of 12, 40 kPa blast exposures conducted with a minimum of 24 h between blasts. We found that repeated blast exposure reduced glycocalyx length and density in various brain regions indicating damage. This blast exposure paradigm was associated with a mild performance decrement in the Morris water maze (MWM) which assesses learning and memory. Administration of hyaluronidase, an enzyme that binds to and degrades hyaluronan (a major structural component of the glycocalyx) prior to blast exposure reduced the observed behavioral deficits and induced a thickening of the glycocalyx layer. Taken together these findings demonstrate that the endothelial glycocalyx degradation following repeated blast is associated with behavioral decrements which can be prevented by treatment with hyaluronidase.

Protocol for intraoperative assessment of the human cerebrovascular glycocalyx

INTRODUCTION

Adequate functioning of the blood-brain barrier (BBB) is important for brain homoeostasis and normal neuronal function. Disruption of the BBB has been described in several neurological diseases. Recent reports suggest that an increased permeability of the BBB also contributes to increased seizure susceptibility in patients with epilepsy. The endothelial glycocalyx is coating the luminal side of the endothelium and can be considered as the first barrier of the BBB. We hypothesise that an altered glycocalyx thickness plays a role in the aetiology of temporal lobe epilepsy (TLE), the most common type of epilepsy. Here, we propose a protocol that allows intraoperative assessment of the cerebrovascular glycocalyx thickness in patients with TLE and assess whether its thickness is decreased in patients with TLE when compared with controls.

METHODS AND ANALYSIS

This protocol is designed as a prospective observational case-control study in patients who undergo resective brain surgery as treatment for TLE. Control subjects are patients without a history of epileptic seizures, who undergo a craniotomy or burr hole surgery for other indications. Intraoperative glycocalyx thickness measurements of sublingual, cortical and hippocampal microcirculation are performed by video microscopy using sidestream dark-field imaging. Demographic details, seizure characteristics, epilepsy risk factors, intraoperative haemodynamic parameters and histopathological evaluation are additionally recorded.

ETHICS AND DISSEMINATION

This protocol has been ethically approved by the local medical ethical committee (ID: NL51594.068.14) and complies with the Declaration of Helsinki and principles of Good Clinical Practice. Informed consent is obtained before study enrolment and only coded data will be stored in a secured database, enabling an audit trail. Results will be submitted to international peer-reviewed journals and presented at international conferences.

TRIAL REGISTRATION NUMBER

NTR5568.

Cardiovascular Effects of Shock and Trauma in Experimental Models. A Review

Experimental models of human pathology are useful guides to new approaches towards improving clinical and surgical treatments. A systematic search through PubMed using the syntax (shock) AND (trauma) AND (animal model) AND (cardiovascular) AND ("2010/01/01"[PDat]: "2015/12/31"[PDat]) found 88 articles, which were reduced by manual inspection to 43 entries. These were divided into themes and each theme is subsequently narrated and discussed conjointly. Taken together, these articles indicate that valuable information has been developed over the past 5 years concerning endothelial stability, mesenteric lymph, vascular reactivity, traumatic injuries, burn and sepsis. A surviving interest in hypertonic saline resuscitation still exists.

Systemic complications of traumatic brain injury

PURPOSE OF REVIEW

Increased understanding of the pathophysiology in traumatic brain injury (TBI) has resulted in the development of core physiological targets and therapies to preserve cerebral oxygenation, and in doing so prevent secondary insult. This review addresses the many systemic complications of TBI that make achieving these targets challenging and can influence outcome.

RECENT FINDINGS

There are a wide range of systemic complications following TBI. Complications involve the cardiovascular, respiratory, immunological, haematological and endocrinological systems amongst others, and can influence early management and long-term outcomes.

SUMMARY

Effective management of TBI should go beyond formulaic-based pursuit of physiological targets and requires a detailed understanding of the multisystem response of the body.