Effect of post-traumatic mild hypothermia on hippocampal cell death after traumatic brain injury in rats

Impact of hyper- and hypothermia on cellular and whole-body physiology

The incidence of heat-related illnesses and heatstroke continues to rise amidst global warming. Hyperthermia triggers inflammation, coagulation, and progressive multiorgan dysfunction, and, at levels above 40 °C, can even lead to cell death. Blood cells, particularly granulocytes and platelets, are highly sensitive to heat, which promotes proinflammatory and procoagulant changes. Key factors in heatstroke pathophysiology involve mitochondrial thermal damage and excessive oxidative stress, which drive apoptosis and necrosis. While the kinetics of cellular damage from heat have been extensively studied, the mechanisms driving heat-induced organ damage and death are not yet fully understood. Converse to hyperthermia, hypothermia is generally protective, as seen in therapeutic hypothermia. However, accidental hypothermia presents another environmental threat due to arrhythmias, cardiac arrest, and coagulopathy. From a cellular physiology perspective, hypothermia generally supports mitochondrial homeostasis and enhances cell preservation, aiding whole-body recovery following resuscitation. This review summarizes recent findings on temperature-related cellular damage and preservation and suggests future research directions for understanding the tempo-physiologic axis.

The combination treatment of hypothermia and intranasal insulin ameliorates the structural and functional changes in a rat model of traumatic brain injury

The present study aimed to investigate the combination effects of hypothermia (HT) and intranasal insulin (INS) on structural changes of the hippocampus and cognitive impairments in the traumatic brain injury (TBI) rat model. The rats were divided randomly into the following five groups (n = 10): Sham, TBI, TBI with HT treatment for 3 h (TBI + HT), TBI with INS (ten microliters of insulin) treatment daily for 7 days (TBI + INS), and TBI with combining HT and INS (TBI + HT + INS). At the end of the 7th day, the open field and the Morris water maze tests were done for evaluation of anxiety-like behavior and memory performance. Then, after sacrificing, the brain was removed for stereological study. TBI led to an increase in the total volume of hippocampal subfields CA1 and DG and a decrease in the total number of neurons and non-neuronal cells in both sub-regions, which was associated with anxiety-like behavior and memory impairment. Although, the combination of HT and INS prevented the increased hippocampal volume and cell loss and improved behavioral performances in the TBI group. Our study suggests that the combined treatment of HT and INS could prevent increased hippocampal volume and cell loss in CA1 and DG sub-regions and consequently improve anxiety-like behaviors and memory impairment following TBI.

Ginkgolide A attenuated apoptosis via inhibition of oxidative stress in mice with traumatic brain injury

Traumatic brain injury (TBI) is the main cause of death among young adults and the main cause of mortality and disability for all ages groups worldwide. Ginkgolides terpenoid compounds unique to Ginkgo biloba, which have protective effects on cardiovascular and cerebrovascular diseases. The aim of this study is to investigate whether ginkgolide A (GA) can improve TBI in mice and whether it can alleviate cell apoptosis in the brain of TBI mice by reducing oxidative stress. Mice received TBI and GA administration for 7 days. Neurological deficits were monitored and brain tissues were examined for molecular pathological markers. TBI mice had more severer neurobehavioral deficits compared with sham group, which could be improved by administration of GA. GA administration improveed Modified Neurological Severity Scale (mNSS) scores, Grid-Walking test and Rotarod test of TBI mice. The apoptosis increased in TBI mice, and reduced after GA treatment. The biomarkers of oxidative stress 8-OHdG and malondialdehyde (MDA) in the brain of TBI mice increased, while SOD reduced. These changes were reversed after GA administration. These outcomes showed that GA could raise neurobehavioral deficiency of TBI mice. GA treatment could attenuate apoptosis in TBI mice by reducing oxidative stress.

Ferristatin II, an Iron Uptake Inhibitor, Exerts Neuroprotection against Traumatic Brain Injury via Suppressing Ferroptosis

As a specific ferroptosis marker, transferrin receptor 1 (TfR1) expression is increased following traumatic brain injury (TBI), but the precise role of TfR1 in TBI-induced ferroptosis and neurodegeneration remains to be determined. To further identify more potent ferroptosis inhibitors and effective targets for treating TBI, our study aims at investigating the effects of TfR1 on ferroptosis in a mouse TBI model using ferristatin II (an iron uptake and TfR1 inhibitor). The effect of ferristatin II was first verified in the HT-22 cell line in vitro and showed antiferroptotic action when exposed to ferric citrate (FAC), which is in parallel with the results obtained from the positive controls, including deferoxamine (DFO) and liproxstatin-1 (Lip-1). In vivo, ferristatin II administration reduced the expression of TfR1 at 12 h after TBI, and immunofluorescence experiments further confirmed that this decreased TfR1-positive cells were neurons. Importantly, ferristatin II suppressed TBI-induced iron homeostatic imbalance by decreasing the content of Fe (III) and iron-positive deposits and reversed the expression of iron homeostasis-related proteins. Moreover, ferristatin II attenuated TBI-induced lipid peroxidation by reversing the expression of lipid peroxidative genes and proteins, as well as the increase in malondialdehyde (MDA) level following TBI. Finally, ferristatin II alleviated TBI-induced neuronal injury and neurodegeneration, as detected by staining with Nissl and Fluoro-Jade B, thereby exerting a neuroprotective effect. In summary, these data indicated that ferristatin II might be a potential strategy to restrain ferroptosis and develop novel therapeutic agents against TBI.

Minocycline attenuates neuronal apoptosis and improves motor function after traumatic brain injury in rats

Minocycline is a type of tetracycline antibiotic with broad-spectrum antibacterial activity that has been demonstrated to protect the brain against a series of central nervous system diseases. However, the precise mechanisms of these neuroprotective actions remain unknown. In the present study, we found that minocycline treatment significantly reduced HT22 cell apoptosis in a mechanical cell injury model. In addition, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining confirmed the neuroprotective effects of minocycline in vivo through the inhibition of apoptosis in a rat model of controlled cortical impact (CCI) brain injury. The western blotting analysis revealed that minocycline treatment significantly downregulated the pro-apoptotic proteins BAX and cleaved caspase-3 and upregulated the anti-apoptotic protein BCL-2. Furthermore, the beam-walking test showed that the administration of minocycline ameliorated traumatic brain injury (TBI)-induced deficits in motor function. Taken together, these findings suggested that minocycline attenuated neuronal apoptosis and improved motor function following TBI.

Fourier Transform Infrared Imaging-A Novel Approach to Monitor Bio Molecular Changes in Subacute Mild Traumatic Brain Injury

Traumatic brain injury (TBI) can be defined as a disorder in the function of the brain after a bump, blow, or jolt to the head, or penetrating head injury. Mild traumatic brain injury (mTBI) can cause devastating effects, such as the initiation of long-term neurodegeneration in brain tissue. In the current study, the effects of mTBI were investigated on rat brain regions; cortex (Co) and corpus callosum (CC) after 24 h (subacute trauma) by Fourier transform infrared (FTIR) imaging and immunohistochemistry (IHC). IHC studies showed the formation of amyloid-β (Aβ) plaques in the cortex brain region of mTBI rats. Moreover, staining of myelin basic protein presented the shearing of axons in CC region in the same group of animals. According to FTIR imaging results, total protein and lipid content significantly decreased in both Co and CC regions in mTBI group compared to the control. Due to this significant decrease in both lipid and protein content, remarkable consistency in lipid/protein band ratio in mTBI and control group, was observed. Significant decrease in methyl content and a significant increase in olefinic content were observed in Co and CC regions of mTBI rat brain tissues. Classification amongst distinguishable groups was performed using principal component analysis (PCA) and hierarchical clustering (HCA). This study established the prospective of FTIR imaging for assessing biochemical changes due to mTBI with high sensitivity, precision and high-resolution.

Targeting NRF2 to suppress ferroptosis in brain injury

Brain injury is accompanied by serious iron metabolism disorder and oxidative stress. As a novel form of regulated cell death (RCD) depending on lipid peroxidation caused by iron overload, ferroptosis (FPT) further aggravates brain injury, which is different from apoptosis, autophagy and other traditional cell death in terms of biochemistry, morphology and genetics. Noteworthy, transcriptional regulator NRF2 plays a key role in the cell antioxidant system, and many genes related to FPT are under the control of NRF2, including genes for iron regulation, thiol-dependent antioxidant system, enzymatic detoxification of RCS and carbonyls, NADPH regeneration and ROS sources from mitochondria or extra-mitochondria, which place NRF2 in the key position of regulating the ferroptotic death. Importantly, NRF2 can reduce iron load and resist FPT. In the future, it is expected to open up a new way to treat brain injury by targeting NRF2 to alleviate FPT in brain.

Serum caspase-3 levels during the first week of traumatic brain injury

OBJECTIVE

Confluence between the intrinsic and extrinsic apoptosis pathways is reached at the point of caspase-3 activation, which induces death cell. Higher serum caspase-3 levels have been recorded on day 1 of traumatic brain injury (TBI) in 30-day non-survivors compared to survivors. The objectives of this study therefore were to determine whether serum caspase-3 levels are persistently higher in non-survivors than in survivors, and whether these levels may be used to predict 30-day mortality.

DESIGN

A prospective observational study was carried out.

SETTING

Six Spanish Intensive Care Units.

PATIENTS

Patients with severe isolated TBI (defined as Glasgow Coma Scale <9 points and non-cranial Injury Severity Score <10 points).

INTERVENTIONS

Serum caspase-3 concentrations were measured on days 1, 4 and 8 of TBI.

MAIN VARIABLES OF INTEREST

Thirty-day mortality was considered as the study endpoint.

RESULTS

In comparison with non-survivors (n=34), 30-day survivors (n=90) showed lower serum caspase-3 levels on days 1 (p=0.001), 4 (p<0.001) and 8 (p<0.001) of TBI. Analysis of the ROC curves showed serum caspase-3 concentrations on days 1, 4 and 8 of TBI to have an AUC (95% CI) in predicting 30-day mortality of 0.70 (0.61-0.78; p=0.001), 0.83 (0.74-0.89; p<0.001) and 0.87 (0.79-0.93; p<0.001), respectively.

CONCLUSIONS

The novel findings of our study were that serum caspase-3 levels during the first week of TBI were lower in survivors and could predict 30-day mortality.

Inhibition of ferroptosis attenuates tissue damage and improves long-term outcomes after traumatic brain injury in mice

AIMS

Ferroptosis, a new form of iron-dependent programmed cell death, has been shown to be involved in a range of diseases. However, the role of ferroptosis in traumatic brain injury (TBI) has yet to be elucidated. We aimed to investigate whether ferroptosis is induced after TBI and whether the inhibition of ferroptosis would protect against traumatic brain injury in a controlled cortical impact injury (CCI) mouse model.

METHODS

After establishing the TBI model in mice, we determined the biochemical and morphological changes associated with ferroptosis, including iron accumulation with Perl's staining, neuronal cell death with Fluoro-Jade B (FJB) staining, iron metabolism dysfunction with Western blotting, reactive oxygen species (ROS) accumulation with malondialdehyde (MDA) assays, and shrunken mitochondria with transmission electron microscopy. Furthermore, a specific inhibitor of ferroptosis, ferrostatin-1(fer-1), was administrated by cerebral ventricular injection after CCI. We used cresyl violet (CV) staining to assess lesion volume, along with the Morris water maze and beam walk test to evaluate long-term outcomes.

RESULTS

TBI was followed by iron accumulation, dysfunctional iron metabolism, the upregulation of ferroptosis-related genes, reduced glutathione peroxidase (GPx) activity, and the accumulation of lipid-reactive oxygen species (ROS). Three days (d) after TBI, transmission electron microscopy (TEM) confirmed that the mitochondria had shrunk a typical characteristic of ferroptosis. Importantly, the administration of Fer-1 by cerebral ventricular injection significantly reduced iron deposition and neuronal degeneration while attenuating injury lesions and improving long-term motor and cognitive function.

CONCLUSION

This study demonstrated an effective method with which to treat TBI by targeting ferroptosis.

Therapeutic hypothermia and targeted temperature management for traumatic brain injury: Experimental and clinical experience

Traumatic brain injury (TBI) is a worldwide medical problem, and currently, there are few therapeutic interventions that can protect the brain and improve functional outcomes in patients. Over the last several decades, experimental studies have investigated the pathophysiology of TBI and tested various pharmacological treatment interventions targeting specific mechanisms of secondary damage. Although many preclinical treatment studies have been encouraging, there remains a lack of successful translation to the clinic and no therapeutic treatments have shown benefit in phase 3 multicenter trials. Therapeutic hypothermia and targeted temperature management protocols over the last several decades have demonstrated successful reduction of secondary injury mechanisms and, in some selective cases, improved outcomes in specific TBI patient populations. However, the benefits of therapeutic hypothermia have not been demonstrated in multicenter randomized trials to significantly improve neurological outcomes. Although the exact reasons underlying the inability to translate therapeutic hypothermia into a larger clinical population are unknown, this failure may reflect the suboptimal use of this potentially powerful therapeutic in potentially treatable severe trauma patients. It is known that multiple factors including patient recruitment, clinical treatment variables, and cooling methodologies are all important in yielding beneficial effects. High-quality multicenter randomized controlled trials that incorporate these factors are required to maximize the benefits of this experimental therapy. This article therefore summarizes several factors that are important in enhancing the beneficial effects of therapeutic hypothermia in TBI. The current failures of hypothermic TBI clinical trials in terms of clinical protocol design, patient section, and other considerations are discussed and future directions are emphasized.

Biomarkers Associated with the Outcome of Traumatic Brain Injury Patients

This review focuses on biomarkers associated with the outcome of traumatic brain injury (TBI) patients, such as caspase-3; total antioxidant capacity; melatonin; S100B protein; glial fibrillary acidic protein (GFAP); glutamate; lactate; brain-derived neurotrophic factor (BDNF); substance P; neuron-specific enolase (NSE); ubiquitin carboxy-terminal hydrolase L-1 (UCH-L1); tau; decanoic acid; and octanoic acid.

Establishment of an ideal time window model in hypothermic-targeted temperature management after traumatic brain injury in rats

Although hypothermic-targeted temperature management (HTTM) holds great potential for the treatment of traumatic brain injury (TBI), translation of the efficacy of hypothermia from animal models to TBI patientshas no entire consistency. This study aimed to find an ideal time window model in experimental rats which was more in accordance with clinical practice through the delayed HTTM intervention. Sprague-Dawley rats were subjected to unilateral cortical contusion injury and received therapeutic hypothermia at 15mins, 2 h, 4 h respectively after TBI. The neurological function was evaluated with the modified neurological severity score and Morris water maze test. The brain edema and morphological changes were measured with the water content and H&E staining. Brain sections were immunostained with antibodies against DCX (a neuroblast marker) and GFAP (an astrocyte marker). The apoptosis levels in the ipsilateral hippocampi and cortex were examined with antibodies against the apoptotic proteins Bcl-2, Bax, and cleaved caspase-3 by the immunofluorescence and western blotting. The results indicated that each hypothermia therapy group could improve neurobehavioral and cognitive function, alleviate brain edema and reduce inflammation. Furthermore, we observed that therapeutic hypothermia increased DCX expression, decreased GFAP expression, upregulated Bcl-2 expression and downregulated Bax and cleaved Caspase-3 expression. The above results suggested that HTTM at 2h or even at 4h post-injury revealed beneficial brain protection similarly, despite the best effect at 15min post-injury. These findings may provide relatively ideal time window models, further making the following experimental results more credible and persuasive.

Selective Brain Hypothermia Mitigates Brain Damage and Improves Neurological Outcome after Post-Traumatic Decompressive Craniectomy in Mice

Hypothermia and decompressive craniectomy (DC) have been considered as treatment for traumatic brain injury. The present study investigates whether selective brain hypothermia added to craniectomy could improve neurological outcome after brain trauma. Male CD-1 mice were assigned into the following groups: sham; DC; closed head injury (CHI); CHI followed by craniectomy (CHI+DC); and CHI+DC followed by focal hypothermia (CHI+DC+H). At 24 h post-trauma, animals were subjected to Neurological Severity Score (NSS) test and Beam Balance Score test. At the same time point, magnetic resonance imaging using a 9.4 Tesla scanner and subsequent volumetric evaluation of edema and contusion were performed. Thereafter, the animals were sacrificed and subjected to histopathological analysis. According to NSS, there was a significant impairment among all the groups subjected to trauma. Animals with both trauma and craniectomy performed significantly worse than animals with craniectomy alone. This deleterious effect disappeared when additional hypothermia was applied. BBS was significantly worse in the CHI and CHI+DC groups, but not in the CHI+DC+H group, compared to the sham animals. Edema and contusion volumes were significantly increased in CHI+DC animals, but not in the CHI+DC+H group, compared to the DC group. Histopathological analysis showed that neuronal loss and contusional blossoming could be attenuated by application of selective brain hypothermia. Selective brain cooling applied post-trauma and craniectomy improved neurological function and reduced structural damage and may be therefore an alternative to complication-burdened systemic hypothermia. Clinical studies are recommended in order to explore the potential of this treatment.

Neuroprotective effects of bloodletting at Jing points combined with mild induced hypothermia in acute severe traumatic brain injury

Bloodletting at Jing points has been used to treat coma in traditional Chinese medicine. Mild induced hypothermia has also been shown to have neuroprotective effects. However, the therapeutic effects of bloodletting at Jing points and mild induced hypothermia alone are limited. Therefore, we investigated whether combined treatment might have clinical effectiveness for the treatment of acute severe traumatic brain injury. Using a rat model of traumatic brain injury, combined treatment substantially alleviated cerebral edema and blood-brain barrier dysfunction. Furthermore, neurological function was ameliorated, and cellular necrosis and the inflammatory response were lessened. These findings suggest that the combined effects of bloodletting at Jing points (20 μL, twice a day, for 2 days) and mild induced hypothermia (6 hours) are better than their individual effects alone. Their combined application may have marked neuroprotective effects in the clinical treatment of acute severe traumatic brain injury.

High Ca2+ Influx During Traumatic Brain Injury Leads to Caspase-1-Dependent Neuroinflammation and Cell Death

We investigated the hypothesis that high Ca²⁺ influx during traumatic brain injury induces the activation of the caspase-1 enzyme, which triggers neuroinflammation and cell apoptosis in a cell culture model of neuronal stretch injury and an in vivo model of fluid percussion injury (FPI). We first established that stretch injury causes a rapid increase in the intracellular Ca²⁺ level, which activates interleukin-converting enzyme caspase-1. The increase in the intracellular Ca²⁺ level and subsequent caspase-1 activation culminates into neuroinflammation via the maturation of IL-1β. Further, we analyzed caspase-1-mediated apoptosis by TUNEL staining and PARP western blotting. The voltage-gated sodium channel blocker, tetrodotoxin, mitigated the stretch injury-induced neuroinflammation and subsequent apoptosis by blocking Ca²⁺ influx during the injury. The effect of tetrodotoxin was similar to the caspase-1 inhibitor, zYVAD-fmk, in neuronal culture. To validate the in vitro results, we demonstrated an increase in caspase-1 activity, neuroinflammation and neurodegeneration in fluid percussion-injured animals. Our data suggest that neuronal injury/traumatic brain injury (TBI) can induce a high influx of Ca²⁺ to the cells that cause neuroinflammation and cell death by activating caspase-1, IL-1β, and intrinsic apoptotic pathways. We conclude that excess IL-1β production and cell death may contribute to neuronal dysfunction and cognitive impairment associated with TBI.

Subdural hematoma decompression model: A model of traumatic brain injury with ischemic-reperfusional pathophysiology: A review of the literature

The prognosis for patients with traumatic brain injury (TBI) with subdural hematoma (SDH) remains poor. In accordance with an increasing elderly population, the incidence of geriatric TBI with SDH is rising. An important contributor to the neurological injury associated with SDH is the ischemic damage which is caused by raised intracranial pressure (ICP) producing impaired cerebral perfusion. To control intracranial hypertension, the current management consists of hematoma evacuation with or without decompressive craniotomy. This removal of the SDH results in the immediate reversal of global ischemia accompanied by an abrupt reduction of mass lesion and an ensuing reperfusion injury. Experimental models can play a critical role in improving our understanding of the underlying pathophysiology and in exploring potential treatments for patients with SDH. In this review, we describe the epidemiology, pathophysiology and clinical background of SDH.

Therapeutic hypothermia attenuates tissue damage and cytokine expression after traumatic brain injury by inhibiting necroptosis in the rat

Necroptosis has been shown as an alternative form of cell death in many diseases, but the detailed mechanisms of the neuron loss after traumatic brain injury (TBI) in rodents remain unclear. To investigate whether necroptosis is induced after TBI and gets involved in the neuroprotecton of therapeutic hypothermia on the TBI, we observed the pathological and biochemical change of the necroptosis in the fluid percussion brain injury (FPI) model of the rats. We found that receptor-interacting protein (RIP) 1 and 3, and mixed lineage kinase domain-like protein (MLKL), the critical downstream mediators of necroptosis recently identified in vivo, as well as HMGB1 and the pro-inflammation cytokines TNF-α, IL-6 and IL-18, were increased at an early phase (6 h) in cortex after TBI. Posttraumatic hypothermia (33 °C) led to the decreases in the necroptosis regulators, inflammatory factors and brain tissue damage in rats compared with normothermia-treated TBI animals. Immunohistochemistry studies showed that posttraumatic hypothermia also decreased the necroptosis-associated proteins staining in injured cortex and hippocampal CA1. Therefore, we conclude that the RIP1/RIP3-MLKL-mediated necroptosis occurs after experimental TBI and therapeutic hypothermia may protect the injured central nervous system from tissue damage and the inflammatory responses by targeting the necroptosis signaling after TBI.

Microdialysis as Clinical Evaluation of Therapeutic Hypothermia in Rat Subdural Hematoma Model

Cerebral microdialysis (MD) is a fine laboratory technique which has been established for studying physiological, pharmacological, and pathological changes in the experimental studies of traumatic brain injury (TBI). This technique has also been well translated and widely applied to clinical bedside monitoring to provide pathophysiological analysis in severe TBI patients. The MD technique is thus well suited for straightforward translation from basic science to clinical application.In this chapter, we describe our evaluation of MD method in acute subdural hematoma (ASDH) rat model. With 100 kDa cut-off microdialysis membrane, we could measure several biomarkers such as ubiquitin carboxy hydrolase L1 (UCH-L1), a neuronal marker and glial fibrillary acidic protein (GFAP), and a glial marker in extracellular fluid. In this experiment, we could detect that the peak of extracellular UCH-L1 in the early hypothermia group was significantly lower than in the normothermia group. Also, in the late phase of reperfusion (>2.5 h after decompression), extracellular GFAP in the early hypothermia group was lower than in the normothermia. These data thus suggested that early, preoperatively induced hypothermia could mediate the reduction of neuronal and glial damage in the reperfusion phase of ischemia/reperfusion brain injury.Microdialysis allows for the direct measurement of extracellular molecules in an attempt to characterize metabolic derangements before they become clinically relevant. Advancements in technology have allowed for the bedside assay of multiple markers of ischemia and metabolic dysfunction, and the applications for traumatic brain injury have been well established. As clinicians become more comfortable with these tools their widespread use and potential for clinical impact with continue to rise.

Serum caspase-3 levels and mortality are associated in patients with severe traumatic brain injury

Background

Different apoptosis pathways activate caspase-3. In a study involving 27 patients with traumatic brain injury (TBI), higher caspase-3 levels were found in contusion brain tissue resected from non-survivors than from survivors. The objective of this study was to determine whether there is an association in TBI patients between serum caspase-3 levels (thus using an easier, quicker, less expensive and less invasive procedure) and mortality, in a larger series of patients.

Methods

We carried out a prospective, observational and multicenter study in six Spanish Hospital Intensive Care Units including 112 patients with severe TBI. All had Glasgow Coma Scale (GCS) scores lower than 9. Patients with an Injury Severity Score (ISS) in non-cranial aspects higher than 9 were excluded. Blood samples were collected on day 1 of TBI to measure serum caspas-3 levels. The endpoint was 30-day mortality.

Results

We found that non-surviving patients (n = 31) showed higher (p = 0.003) serum caspase-3 levels compared to survivors (n = 81). Kaplan-Meier survival analysis showed a higher risk of death in TBI patients with serum caspase-3 levels >0.20 ng/mL than in patients with lower concentrations (Hazard Ratio = 3.15; 95 % CI = 1.40 to 7.08; P < 0.001). Multiple logistic regression analysis showed that serum caspase-3 levels > 0.20 ng/mL were associated with mortality at 30 days in TBI patients controlling for Marshall CT classification, age and GCS (Odds ratio = 7.99; 95 % CI = 2.116 to 36.744; P = 0.001).

Conclusions

The association between serum caspase-3 levels and mortality in TBI patients was the major novel finding of our study.

Autophagy Inhibitor 3-MA Weakens Neuroprotective Effects of Posttraumatic Brain Injury Moderate Hypothermia

OBJECTIVE

The role of autophagy in moderate hypothermia in posttraumatic brain injury (post-TBI) remains elusive. In this study, we evaluated the protective role of autophagy in post-TBI moderate hypothermia.

METHODS

Adult male Sprague-Dawley rats were randomly divided into 3 groups (n = 36/group): TBI with hypothermia group (sham), TBI with hypothermia and a single intracerebroventricular injection of saline (saline, 5 μL), and TBI with hypothermia and a single intracerebroventricular injection of 3-methyladenine (600 nmol, diluted in 0.9% saline to a final volume of 5 μL). All rats, except those in the behavioral tests, were killed at 24 hours after fluid percussion TBI. Immunohistochemistry staining, western blot, and transmission electron microscopy were performed to assess changes in apoptosis and autophagy after injection of 3-methyladenine. Motor function (beam-walk test) and spatial learning/memory (Morris water maze) were assessed on postoperative days 1-5 and 11-15, respectively.

RESULTS

Our results showed downregulation of the expression level of microtubule-associated protein 1 light chain 3 and Beclin-1, aggravation of behavioral outcome, and increase of apoptosis.

CONCLUSION

Our results suggest that the autophagy pathway is involved in the neuroprotective effect of post-TBI hypothermia and negative modulation of apoptosis may be 1 possible mechanism.

[The effect of gene therapy with the APOE3 Gene on structural and functional manifestations of secondary hippocampal damages in experimental traumatic brain injury]

AIM OF THE STUDY

to study the efficiency of gene therapy following traumatic brain injury (TBI) by evaluating the influences of liposomal transfection of the brain tissue by APOE3-containing plasmid vector on the structural and functional manifestations of development of secondary brain injuries after acute experimental TBI in the rats of different age.

MATERIAL AND METHODS

Severe diffuse TBI in rats was inflicted under overall anesthesia by free load weighing 450 g, falling from a 1.5 m elevation. The mixture of DOTAP liposome and 25 μg of plasmid vector pCMV·SPORT6 with cDNA of APOE3 gene was infused intraventricularly using ALZET osmotic pumps. Combined morphological, electron microscopic, immunohistochemical and morphometric studies of СА1 hippocampal region were conducted in rats at days 5 and 10 following TBI and gene therapy after investigation of motor functions (using composite neurological motor score) and cognitive functions in Morris water maze.

RESULTS

Significant changes in the morphofunctional state of hippocampus, as well as in the neurological and cognitive functions were shown on the model of severe TBI in the adult and old Wistar rats. Gene therapy, specifically cationic-liposome mediated APOE3 gene transfer to the CNS cells by plasmid vector, decreased a TBI-induced death of neurons and improved qualitative composition of neuronal population, normalized neuron-glial relations, decreased gliosis and microglial activation, axonal damage, myelin destruction and lipofuscin accumulation, all these having age-related peculiarities. After gene therapy observed in the animal brain was a lower intensity of the processes of apoptosis and a decrease of its rate in old animals. The above changes were accompanied with a more fast and expressed regress of neurological and cognitive disturbances typical for TBI. Administration of plasmid vector after TBI resulted in an increase of survival rate of old animals vs. old animals which got no gene therapy.

CONCLUSION

APOE3 gene therapy has therapeutic potential in the treatment of severe TBI.

Moderate Hypothermia Significantly Decreases Hippocampal Cell Death Involving Autophagy Pathway after Moderate Traumatic Brain Injury

Here, we evaluated changes in autophagy after post-traumatic brain injury (TBI) followed by moderate hypothermia in rats. Adult male Sprague-Dawley rats were randomly divided into four groups: sham injury with normothermia group (37 °C); sham injury with hypothermia group (32 °C); TBI with normothermia group (TNG; 37 °C); and TBI with hypothermia group (THG; 32 °C). Injury was induced by a fluid percussion TBI device. Moderate hypothermia (32 °C) was achieved by partial immersion in a water bath (0 °C) under general anesthesia for 4 h. All rats were killed at 24 h after fluid percussion TBI. The ipsilateral hippocampus in all rats was analyzed with hematoxylin and eosin staining; terminal deoxynucleoitidyl transferase-mediated nick end labeling staining was used to determine cell death in ipsilateral hippocampus. Immunohistochemistry and western blotting of microtubule-associated protein light chain 3 (LC3), Beclin-1, as well as transmission electron microscopy performed to assess changes in autophagy. At 24 h after TBI, the cell death index was 27.90 ± 2.36% in TNG and 14.90 ± 1.52% in THG. Expression level of LC3 and Beclin-1 were significantly increased after TBI and were further up-regulated after post-TBI hypothermia. Further, ultrastructural observations showed that there was a marked increase of autophagosomes and autolysosomes in ipsilateral hippocampus after post-TBI hypothermia. Our data demonstrated that moderate hypothermia significantly attenuated cell death and increased autophagy in ipsilateral hippocampus after fluid percussion TBI. In conclusion, autophagy pathway may participate in the neuroprotective effect of post-TBI hypothermia.

Effects of mild induced hypothermia on hippocampal connexin 43 and glutamate transporter 1 expression following traumatic brain injury in rats

Traumatic brain injury (TBI) is a common cause of worldwide disability and mortality. Currently, the incidence and prevalence of TBI is markedly increasing and an effective therapy is lacking. Therapeutic hypothermia (32‑35˚C) has been reported to reduce intracranial pressure and induce putative neuroprotective effects. However, the underlying molecular mechanisms remain to be elucidated. The aim of the present study was to investigate the effects of mild induced hypothermia (MIH) on the expression of connexin 43 (Cx43) and glutamate transporter 1 (GLT‑1) in the hippocampus following TBI in rats. A rat model of TBI was created using a modified weight‑drop device, followed by 4 h of hypothermia (33˚C) or normothermia (37˚C). A wet‑dry weight method was used to assess brain edema and spatial learning ability was evaluated using a Morris water maze. The levels of Cx43 and GLT‑1 were detected by immunohistochemical and western blot analysis, respectively. The results demonstrated that MIH treatment improved TBI‑induced brain edema and neurological function deficits. In addition, therapeutic MIH significantly downregulated Cx43 expression and upregulated the levels of GLT‑1 in the hippocampus post‑TBI. These findings suggested that treatment with MIH may provide a novel neuroprotective therapeutic strategy for TBI through reversing the increase in Cx43 protein and the decrease in GLT‑1.

MMP-9 inhibitor SB-3CT attenuates behavioral impairments and hippocampal loss after traumatic brain injury in rat

The aim of this study was to evaluate the potential efficacy of SB-3CT, a matrix metallopeptidase 9 inhibitor, on behavioral and histological outcomes after traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were randomly divided into three groups (n=15/group): TBI with SB-3CT treatment, TBI with saline, and sham injury. The TBI model was induced by a fluid percussion TBI device. SB-3CT (50 mg/kg in 10% dimethyl sulfoxide) was administered intraperitoneally at 30 min, 6 h, and 12 h after the TBI. Motor function (beam-balance/beam-walk tests) and spatial learning/memory (Morris water maze) were assessed on post-operative Days 1-5 and 11-15, respectively. Fluoro-Jade staining, immunofluorescence, and cresyl violet-staining were carried out for histopathological evaluation at 24 h, 72 h, and 15 days after TBI, respectively. It was shown that TBI can result in significant behavioral deficit induced by acute neurodegeneration, increased expression of cleaved caspase-3, and long-term neuronal loss. SB-3CT intervention via the current regime provides robust behavioral protection and hippocampal neurons preservation from the deleterious effects of TBI. Hence, the efficacy of SB-3CT on TBI prognosis could be ascertained. It is believed that the current study adds to the growing literature in identifying SB-3CT as a potential therapy for human brain injury.

A pilot study evaluating presurgery neuroanatomical biomarkers for postoperative cognitive decline after total knee arthroplasty in older adults

BACKGROUND

Total knee arthroplasty improves quality of life but is associated with postoperative cognitive dysfunction in older adults. This prospective longitudinal pilot study with a parallel control group tested the hypotheses that (1) nondemented adults would exhibit primary memory and executive difficulties after total knee arthroplasty, and (2) reduced preoperative hippocampus/entorhinal volume would predict postoperative memory change, whereas preoperative leukoaraiosis and lacunae volumes would predict postoperative executive dysfunction.

METHODS

Surgery (n = 40) and age-education-matched controls with osteoarthritis (n = 15) completed pre- and postoperative (3 weeks, 3 months, and 1 yr) memory and cognitive testing. Hypothesized brain regions of interest were measured in patients completing preoperative magnetic resonance scans (surgery, n = 31; control, n = 12). Analyses used reliable change methods to identify the frequency of cognitive change at each time point.

RESULTS

The incidence of postoperative memory difficulties was shown with delay test indices (i.e., story memory test: 3 weeks = 17%, 3 months = 25%, 1 yr = 9%). Postoperative executive difficulty with measures of inhibitory function (i.e., Stroop Color Word: 3 weeks = 21%, 3 months = 22%, 1 yr = 9%). Hierarchical regression analysis assessing the predictive interaction of group (surgery, control) and preoperative neuroanatomical structures on decline showed that greater preoperative volumes of leukoaraiosis/lacunae were significantly contributed to postoperative executive (inhibitory) declines.

CONCLUSIONS

This pilot study suggests that executive and memory declines occur in nondemented adults undergoing orthopedic surgery. Severity of preoperative cerebrovascular disease may be relevant for understanding executive decline, in particular.

Preconditioning for traumatic brain injury

Traumatic brain injury (TBI) treatment is now focused on the prevention of primary injury and reduction of secondary injury. However, no single effective treatment is available as yet for the mitigation of traumatic brain damage in humans. Both chemical and environmental stresses applied before injury have been shown to induce consequent protection against post-TBI neuronal death. This concept termed "preconditioning" is achieved by exposure to different pre-injury stressors to achieve the induction of "tolerance" to the effect of the TBI. However, the precise mechanisms underlying this "tolerance" phenomenon are not fully understood in TBI, and therefore even less information is available about possible indications in clinical TBI patients. In this review, we will summarize TBI pathophysiology, and discuss existing animal studies demonstrating the efficacy of preconditioning in diffuse and focal type of TBI. We will also review other non-TBI preconditioning studies, including ischemic, environmental, and chemical preconditioning, which maybe relevant to TBI. To date, no clinical studies exist in this field, and we speculate on possible future clinical situations, in which pre-TBI preconditioning could be considered.

Neuroprotective effect of preoperatively induced mild hypothermia as determined by biomarkers and histopathological estimation in a rat subdural hematoma decompression model

OBJECT

In patients who have sustained a traumatic brain injury (TBI), hypothermia therapy has not shown efficacy in multicenter clinical trials. Armed with the post hoc data from the latest clinical trial (National Acute Brain Injury Study: Hypothermia II), the authors hypothesized that hypothermia may be beneficial in an acute subdural hematoma (SDH) rat model by blunting the effects of ischemia/reperfusion injury. The major aim of this study was to test the efficacy of temperature management in reducing brain damage after acute SDH.

METHODS

The rats were induced with acute SDH and placed into 1 of 4 groups: 1) normothermia group (37°C); 2) early hypothermia group, head and body temperature reduced to 33°C 30 minutes prior to craniotomy; 3) late hypothermia group, temperature lowered to 33°C 30 minutes after decompression; and 4) sham group, no acute SDH (only craniotomy with normothermia). To assess for neuronal and glial cell damage, the authors analyzed microdialysate concentrations of GFAP and ubiquitin carboxyl-terminal hydrolase-L1 (UCH-L1) by using a 100-kD probe. Fluoro-Jade B-positive neurons and injury volume with 2,3,5-triphenyltetrazolium chloride staining were also measured.

RESULTS

In the early phase of reperfusion (30 minutes, 2.5 hours after decompression), extracellular UCH-L1 in the early hypothermia group was significantly lower than in the normothermia group (early, 4.9 ± 1.0 ng/dl; late, 35.2 ± 12.1 ng/dl; normothermia, 50.20 ± 28.3 ng/dl; sham, 3.1 ± 1.3 ng/dl; early vs normothermia, p < 0.01; sham vs normothermia, p < 0.01, analyzed using ANOVA followed by a post hoc Bonferroni test). In the late phase of reperfusion (> 2.5 hours after decompression), extracellular GFAP in the early hypothermia group was also lower than in the normothermia and late hypothermia groups (early, 5.5 ± 2.9 ng/dl; late, 7.4 ± 3.4 ng/dl; normothermia, 15.3 ± 8.4 ng/dl; sham, 3.3 ± 1.0 ng/dl; normothermia vs sham; p < 0.01). The number of Fluoro-Jade B-positive cells in the early hypothermia group was significantly smaller than that in the normothermia group (normothermia vs early: 774,588 ± 162,173 vs 180,903 ± 42,212, p < 0.05). Also, the injury area and volume were smaller in the early hypothermia group in which hypothermia was induced before craniotomy and cerebral reperfusion (early, 115.2 ± 15.4 mm(3); late, 344.7 ± 29.1 mm(3); normothermia, 311.2 ± 79.2 mm(3); p < 0.05).

CONCLUSIONS

The data suggest that early, preoperatively induced hypothermia could mediate the reduction of neuronal and glial damage in the reperfusion phase of ischemia/reperfusion brain injury.

Effects of Lactobacillus plantarum on gut barrier function in experimental obstructive jaundice

AIM: To investigate the mechanisms of Lactobacillus plantarum (L. plantarum) action on gut barrier in preoperative and postoperative experimental obstructive jaundice in rats.

METHODS: Forty rats were randomly divided into groups of sham-operation, bile duct ligation (BDL), BDL + L. plantarum, BDL + internal biliary drainage (IBD), and BDL + IBD + L. plantarum. Ten days after L. plantarum administration, blood and ileal samples were collected from the rats for morphological examination, and intestinal barrier function, liver function, intestinal oxidative stress and protein kinase C (PKC) activity measurement. The distribution and expression of the PKC and tight junction (TJ) proteins, such as occludin, zonula occludens-1, claudin-1, claudin-4, junction adhesion molecule-A and F-actin, were examined by confocal laser scanning microscopy, immunohistochemistry, Western blotting, real-time fluorescent quantitative polymerase chain reaction assay.

RESULTS: L. plantarum administration substantially restored gut barrier, decreased enterocyte apoptosis, improved intestinal oxidative stress, promoted the activity and expression of protein kinase (BDL vs BDL + L. plantarum, 0.295 ± 0.007 vs 0.349 ± 0.003, P < 0.05; BDL + IBD vs BDL + IBD + L. plantarum, 0.407 ± 0.046 vs 0.465 ± 0.135, P < 0.05), and particularly enhanced the expression and phosphorylation of TJ proteins in the experimental obstructive jaundice (BDL vs BDL + L. plantarum, 0.266 ± 0.118 vs 0.326 ± 0.009, P < 0.05). The protective effect of L. plantarum was more prominent after internal biliary drainage ( BDL + IBD vs BDL + IBD + L. plantarum, 0.415 ± 0.105 vs 0.494 ± 0.145, P < 0.05).

CONCLUSION: L. plantarum can decrease intestinal epithelial cell apoptosis, reduce oxidative stress, and prevent TJ disruption in biliary obstruction by activating the PKC pathway.

Hypothermia in Traumatic Brain Injury – A Literature Review

Traumatic brain injury is the leading cause of death in young people. Induced hypothermia has been used as a therapeutic intervention to improve outcome, based on results of animal studies. This article reviews the mechanisms of brain injury, the results of animal and human studies and the reasons that human studies do not always reflect the success seen in animal studies and why results may be ‘lost in translation’ to treatment of patients. It concludes by suggesting further areas of work to investigate the clinical use of therapeutic hypothermia.

Effect of therapeutic mild hypothermia on the genomics of the hippocampus after moderate traumatic brain injury in rats

BACKGROUND

Traumatic brain injury (TBI), a major cause of morbidity and mortality, is a serious public health concern.

OBJECTIVE

To evaluate the effect of mild hypothermia on gene expression in the hippocampus and to try to elucidate molecular mechanisms of hypothermic neuroprotection after TBI.

METHODS

Rats were subjected to mild hypothermia (group 1: n = 3, 33 degrees C, 3H) or normothermia (group 2: n = 3; 37 degrees C, 3H) after TBI. Six genome arrays were applied to detect the gene expression profiles of ipsilateral hippocampus. Functional clustering and gene ontology analysis were then carried out. Another 20 rats were randomly assigned to 4 groups (n = 5 per group): group 3, sham-normothermia; group 4, sham-hypothermia; group 5, TBI-normothermia; and group 6, TBI-hypothermia. Real-time fluorescent quantitative reverse-transcription polymerase chain reaction was used to detect specific selected genes.

RESULTS

We found that 133 transcripts in the hypothermia group were statistically different from those in the normothermia group, including 57 transcripts that were upregulated and 76 that were downregulated after TBI (P < .01). Most of these genes were involved in various pathophysiological processes, and some were critical to cell survival. Analysis showed that 9 gene ontology categories were significantly affected by hypothermia, including the most affected categories: synapse organization and biogenesis (upregulated) and regulation of inflammatory response (downregulated). The mRNA expression of Ank3, Cmbp, Nrxn3, Tgm2, and Fcgr3 was regulated by hypothermia, TBI, or a combination of TBI and hypothermia compared with the sham-normothermia group. Their mRNA expression was significantly regulated by hypothermia in TBI groups.

CONCLUSION

Posttraumatic mild hypothermia has a significant effect on the gene expression profiles of the hippocampus, especially those genes belonging to the 9 gene ontology categories. Differential expression of those genes may be involved in the most fundamental molecular mechanisms of cerebral protection by mild hypothermia after TBI.

Pharyngeal selective brain cooling is associated with reduced CNS cortical lesion after experimental traumatic brain injury in rats

Therapeutic hypothermia (TH) is still being explored as a therapeutic option after traumatic brain injury (TBI) but clinical data has not supported its efficacy. Experimental approaches were promising, but clinical data did not support its efficacy in the treatment of TBI. A novel approach of pharyngeal selective brain cooling (pSBC), recently introduced by our group, has been accompanied by superior neurofunctional, sensorimotor, and cognitive outcomes. This work is now extended by data on histomorphological and physical outcomes after pSBC in a model of experimental TBI. Male Sprague-Dawley rats were subjected to lateral fluid-percussion (LFP) brain injury, and randomized to the following experimental groups: (1) TBI with pSBC, (2) TBI without pSBC, and (3) sham animals. On day post-injury (DPI) 14, the animals were sacrificed and their brains were harvested for immunohistochemistry using the following antibodies: (1) glial fibrillary acidic protein (GFAP), (2) neurofilament (NF), and (3) synaptophysin (SY). In pSBC animals brain temperature was selectively lowered to 33 ± 0.5°C within 15 min post-injury, and maintained for 180 min after induction, while keeping rectal temperatures at physiological levels. Animals that had undergone pSBC showed a significantly faster recovery of body weight starting on DPI 3, and had gained substantially more weight than TBI-only animals on DPI 14 (p < 0.001), indicating superior physical recovery. Areas of cortical damage were significantly smaller in pSBC animals compared to TBI-only animals (p < 0.01). pSBC was associated with preservation of cortical tissue ipsilateral to the lesion, and superior physical recovery after experimental TBI. These results complement earlier reports in which pSBC was associated with superior neurofunctional and cognitive outcomes using the same experimental model.

The evidence for hypothermia as a neuroprotectant in traumatic brain injury

This article reviews published experimental and clinical evidence for the benefits of modest hypothermia in the treatment of traumatic brain injury (TBI). Therapeutic hypothermia has been reported to improve outcome in several animal models of CNS injury and has been successfully translated to specific patient populations. A PubMed search for hypothermia and TBI was conducted, and important papers were selected for review. The research summarized was conducted at major academic institutions throughout the world. Experimental studies have emphasized that hypothermia can affect multiple pathophysiological mechanisms thought to participate in the detrimental consequences of TBI. Published data from several relevant clinical trials on the use of hypothermia in severely injured TBI patients are also reviewed. The consequences of mild to moderate levels of hypothermia introduced by different strategies to the head-injured patient for variable periods of time are discussed. Both experimental and clinical data support the beneficial effects of modest hypothermia following TBI in specific patient populations. Following on such single-institution studies, positive findings from multicenter TBI trials will be required before this experimental treatment can be considered standard of care.