Impact Injury In Rats Research Articles

Research on skeletal muscle impact injury using a new rat model from a bioimpact machine.

Introduction: Skeletal muscle impact injury occurs frequently during sports, falls, and road traffic accidents. From the reported studies on skeletal muscle injury, it is difficult to determine the injury parameters. Therefore, we developed a new model of gastrocnemius impact injury in rats with a bioimpact machine, with which the experimental operation could be conducted in feasibility from the recorded parameters. Through this novel model, we study the skeletal muscle impact injury mechanisms by combining temporal and spatial variation. Methods: The gastrocnemius of anesthetized rats was injured by a small pneumatic-driven bioimpact machine; the moving speed and impact force were determined, and the whole impact process was captured by a high-speed camera. We observed the general condition of rats and measured the changes in injured calf circumference, evaluating calf injuries using MRI, gait analysis system, and pathology at different times after the injury. Results: The gastrocnemius was injured at an impact speed of 6.63m/s ± 0.25m/s and a peak force of 1,556.80 N ± 110.79 N. The gait analysis system showed that the footprint area of the RH limb decreased significantly on the first day and then increased. The calf circumference of the injured limb increased rapidly on the first day post-injury and then decreased in the next few days. MRI showed edema of subcutaneous and gastrocnemius on the first day, and the area of edema decreased over the following days. HE staining showed edema of cells, extensive hyperemia of blood vessels, and infiltration of inflammatory cells on the first day. Cell edema was alleviated day by day, but inflammatory cell infiltration was the most on the third day. TEM showed that the sarcoplasmic reticulum was dilated on the first day, the mitochondrial vacuolation was obvious on the second day, and the glycogen deposition was prominent on the fifth day. Conclusion: In our experiment, we developed a new and effective experimental animal model that was feasible to operate; the injured area of the gastrocnemius began to show "map-like" changes in the light microscope on the third day. Meanwhile, the gastrocnemius showed a trend of "edema-mitochondrial vacuolation-inflammatory cell aggregation" after impact injury.

Temporal changes in inflammatory mitochondria-enriched microRNAs following traumatic brain injury and effects of miR-146a nanoparticle delivery.

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate post-transcriptional gene expression and contribute to all aspects of cellular function. We previously reported that the activities of several mitochondria-enriched miRNAs regulating inflammation (i.e., miR-142-3p, miR-142-5p, and miR-146a) are altered in the hippocampus at 3–12 hours following a severe traumatic brain injury. In the present study, we investigated the temporal expression profile of these inflammatory miRNAs in mitochondria and cytosol fractions at more chronic post-injury times following severe controlled cortical impact injury in rats. In addition, several inflammatory genes were analyzed in the cytosol fractions. The analysis showed that while elevated levels were observed in cytoplasm, the mitochondria-enriched miRNAs, miR-142-3p and miR-142-5p continued to be significantly reduced in mitochondria from injured hippocampi for at least 3 days and returned to near normal levels at 7 days post-injury. Although not statistically significant, miR-146a also remained at reduced levels for up to 3 days following controlled cortical impact injury, and recovered by 7 days. In contrast, miRNAs that are not enriched in mitochondria, including miR-124a, miR-150, miR-19b, miR-155, and miR-223 were either increased or demonstrated no change in their levels in mitochondrial fractions for 7 days. The one exception was that miR-223 levels were reduced in mitochondria at 1 day following injury. No major alterations were observed in sham operated animals. This temporal pattern was unique to mitochondria-enriched miRNAs and correlated with injury-induced changes in mitochondrial bioenergetics as well as expression levels of several inflammatory markers. These observations suggested a potential compartmental re-distribution of the mitochondria-enriched inflammatory miRNAs and may reflect an intracellular mechanism by which specific miRNAs regulate injury-induced inflammatory signaling. To test this, we utilized a novel peptide-based nanoparticle strategy for in vitro and in vivo delivery of a miR-146a mimic as a potential therapeutic strategy for targeting nuclear factor-kappaB inflammatory modulators in the injured brain. Nanoparticle delivery of miR-146a to BV-2 or SH-SY5Y cells significantly reduced expression of TNF receptor-associated factor 6 (TRAF6) and interleukin-1 receptor-associated kinase 1 (IRAK1), two important modulators of the nuclear factor-kappaB (NF-κB) pro-inflammatory pathway. Moreover, injections of miR-146a containing nanoparticles into the brain immediately following controlled cortical impact injury significantly reduced hippocampal TNF receptor-associated factor 6 and interleukin-1 receptor-associated kinase 1 levels. Taken together, our studies demonstrate the subcellular alteration of inflammatory miRNAs after traumatic brain injury and establish proof of principle that nanoparticle delivery of miR-146a has therapeutic potential for modulating pro-inflammatory effectors in the injured brain. All of the studies performed were approved by the University of Kentucky Institutional Animal Care and Usage Committee (IACUC protocol # 2014-1300) on August 17, 2017.

Dynamics of blood brain barrier permeability and tissue microstructure following controlled cortical impact injury in rat: A dynamic contrast-enhanced magnetic resonance imaging and diffusion kurtosis imaging study

ObjectiveThe blood-brain barrier (BBB) and cerebral tissue microstructure can be impaired following traumatic brain injury (TBI). However, the spatiotemporal changes of BBB leakage and tissue microstructure are not completely understood. In this study, we evaluated the spatiotemporal changes of BBB leakage and tissue microstructure using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion kurtosis imaging (DKI) in controlled cortical impact (CCI) rats. Materials and methodsThe DCE-MRI parameters volume transfer coefficient (Ktrans) and DKI parameters were longitudinally measured in bilateral cortex, hippocampus, thalamus and corpus callosum (CC) at baseline (D0), acute stage (D1, D3), and subacute stage (D7, D14 and D28) post-injury. Immunohistochemistry analysis was performed at D28 after MRI scanning. Repeated-measures ANOVA was used to assess the temporal changes of MRI parameters. ResultsKtrans abnormality was only localized to ipsilateral perilesional cortex with a significant temporal change (F = 144.2, p < 0.0001). Compared to baseline, increased mean kurtosis (MK) was observed in ipsilateral regions of cortex and hippocampus and CC for all the time points (p < 0.05 for all). Increased MK was also observed in ipsilateral thalamus (p = 0.005) at subacute stage but not at acute stage while no change was observed with MD and FA (p > 0.05 for both). In ipsilateral cortex, the overall Ktrans value of D0, D1, D3, D7, D14, and D28 post-injury were significantly correlated with MK value (r = 0.84, p < 0.0001). The CCI group showed higher staining of glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (Iba-1) and lower staining of neuron-specific nuclear protein (NeuN) and myelin basic protein (MBP) in ipsilateral regions of cortex, hippocampus, thalamus and CC (p < 0.05 for all) as compared to control group. There were no significant differences in the contralateral regions by immunohistochemistry. ConclusionThe BBB disruption reflected by Ktrans correlated well with MK value in ipsilateral cortex. In addition, MK could detect the delayed microstructural changes in thalamus. DCE-MRI and DKI could be used to assess the BBB breakdown and cerebral microstructural changes of TBI.

Controlled cortical impact-induced neurodegeneration decreases after administration of the novel calpain-inhibitor Gabadur

One aspect of secondary injury in traumatic brain injury is the marked increase in intracellular calcium and resultant over-activation of the calcium-dependent neutral cysteine protease calpain. Gabadur is a novel protease inhibitor with calpain-inhibition properties formulated from the classic protease inhibitor leupeptin linked to a pregabalin carrier. This construction allows the entire compound to cross the blood-brain barrier after peripheral administration to better target the site of injury. In this study, a single intraperitoneal dose of Gabadur was administered immediately following controlled cortical impact injury in rats. Neocortical slices were examined at 48 h post-injury via Fluoro-Jade B staining, revealing an improvement in cortical neurodegeneration in Gabadur treated rats. Levels of detrimental active calpain-2 measured via western blot were also decreased in rats receiving Gabadur. This data supports the benefit of targeted protease inhibition in the treatment of traumatic brain injury.

Continuous Infusion of Phenelzine, Cyclosporine A, or Their Combination: Evaluation of Mitochondrial Bioenergetics, Oxidative Damage, and Cytoskeletal Degradation following Severe Controlled Cortical Impact Traumatic Brain Injury in Rats.

To date, all monotherapy clinical traumatic brain injury (TBI) trials have failed, and there are currently no Food and Drug Administration (FDA)-approved pharmacotherapies for the acute treatment of severe TBI. Due to the complex secondary injury cascade following injury, there is a need to develop multi-mechanistic combinational neuroprotective approaches for the treatment of acute TBI. As central mediators of the TBI secondary injury cascade, both mitochondria and lipid peroxidation-derived aldehydes make promising therapeutic targets. Cyclosporine A (CsA), an FDA-approved immunosuppressant capable of inhibiting the mitochondrial permeability transition pore, and phenelzine (PZ), an FDA-approved monoamine oxidase inhibitor capable of scavenging neurotoxic lipid peroxidation-derived aldehydes, have both been shown to be partially neuroprotective following experimental TBI. Therefore, it follows that the combination of PZ and CsA may enhance neuroprotection over either agent alone through the combining of distinct but complementary mechanisms of action. Additionally, as the first 72 h represents a critical time period following injury, it follows that continuous drug infusion over the first 72 h following injury may also lead to optimal neuroprotective effects. This is the first study to examine the effects of a 72 h subcutaneous continuous infusion of PZ, CsA, and the combination of these two agents on mitochondrial respiration, mitochondrial bound 4-hydroxynonenal (4-HNE), and acrolein, and α-spectrin degradation 72 h following a severe controlled cortical impact injury in rats. Our results indicate that individually, both CsA and PZ are able to attenuate mitochondrial 4-HNE and acrolein, PZ is able to maintain mitochondrial respiratory control ratio and cytoskeletal integrity but together, PZ and CsA are unable to maintain neuroprotective effects.

MiR-124-3p and miR-140-3p.2 act as negative regulators of Beclin1 and LC3 expression in the liver of rat model with hepatic impact injury

Objective: To investigate the effect of autophagy on hepatic impact injury in rats and its molecular mechanism inovlved. Methods: Sixty healthy male Sprague-Dawley (SD) rats (clean grade) were randomly divided into two groups, the normal group and the model group (n=30 in each group). An impact injury model of rat liver was established by impacting rat liver with 200 kPa impact using BIM-V biological impactor. The enzyme activity of ALT and AST in blood serum was measured by rate method; the changes of TNF-α, IL-8 and IL-2 levels were detected by ELISA; morphological changes were observed by microscope after routine HE staining; the formation of autophagosomes was observed by laser scanning confocal microscopy; protein expression levels were detected by Western blotting and immunohistochemical methods, and the relative expression levels of genes were determined by RT-PCR; Bioinformatics software was used to analysis the regulate miRNAs of microtubule-associated protein l light chain 3 (LC3) and Beclin1; a double-fluorescent reporter gene vector was constructed to detect the interactions between genes. Results: The serum levels of ALT, AST, TNF, IL-8 and IL-2 in the model group were markedly higher than those in the normal group, and the difference was statistically significant (p<0.01). The morphology of the liver tissue in the normal group was normal, versus that in the model group was damaged to different degrees, for example, the sheet necrosis occurred in the surrounding area of the central veins of hepatic lobules where a large number of necrotic cells were observed. The expression of LC3 and Beclin1 proteins of liver tissues in the model group was significantly increased (p<0.05). MiR-124-3p negatively regulated the Beclin1 expression and miR-140-3p.2 negatively regulated the LC3 expression. Conclusion: Autophagy plays an important role in the hepatic impact injury in rats, and miR-124-3p and miR-140-3p.2 may act as negative regulators of Beclin1 and LC3 expressions, respectively.

Neuroprotective efficacy of decompressive craniectomy after controlled cortical impact injury in rats: An MRI study

Decompressive craniectomy (DC) is one of the therapeutic options for severe traumatic brain injury (TBI), and it has long been used for the treatment of patients with malignant post-traumatic brain edema. However, a lack of definitive evidence prevents physicians from drawing any conclusions about the efficacy of DC for the treatment of TBI. Magnetic resonance imaging (MRI) is widely used to evaluate the effects of TBI in both experimental and clinical studies. Therefore, the aim of the present study was to investigate the MRI assessment of DC post-TBI in rats to provide experimental animal data and radiological evidence to support the clinical application of DC. We used both in vivo MRI and proton magnetic resonance spectroscopy (1H-MRS) to evaluate the therapeutic effect of DC on lateral controlled cortical impact (CCI) rat models at 3h, 1 d, 2 d, 3d and 7d after TBI. Our data suggest that DC can reduce brain edema; decrease the apparent diffusion coefficient value, contusion volume and lactate (Lac)/creatine (Cr) ratio; and increase the N-acetylaspartate (NAA)/Cr and choline (Cho)/Cr ratios after TBI. The present results suggest that DC can indeed reduce brain edema formation and exhibits good neuroprotective efficacy after CCI injury in rats.

Multiparametric and longitudinal MRI characterization of mild traumatic brain injury in rats.

This study reports T2 and diffusion-tensor magnetic resonance imaging (MRI) studies of a mild open-skull, controlled cortical impact injury in rats (n=6) from 3 h to up to 14 d after traumatic brain injury (TBI). Comparison was made with longitudinal behavioral measurements and end-point histology. The impact was applied over the left primary forelimb somatosensory cortex (S1FL). The major findings were: 1) In the S1FL, T2 increased and fractional anisotropy (FA) decreased at 3 h after TBI and gradually returned toward normal by Day 14; 2) in the S1FL, the apparent diffusion coefficient (ADC) increased at 3 h, peaked on Day 2, and gradually returned toward normal at Day 14; 3) in the corpus callosum underneath the S1FL, FA decreased at 3 h to Day 2 but returned to normal at Day 7 and 14, whereas T2 and ADC were normal throughout; 4) heterogeneous hyperintense and hypointense T2 map intensities likely indicated the presence of hemorrhage but were not independently verified; 5) lesion volumes defined by abnormal T2, ADC, and FA showed similar temporal patterns, peaking around Day 2 and returning toward normal on Day 14; 6) the temporal profiles of lesion volumes were consistent with behavioral scores assessed by forelimb placement and forelimb foot fault tests; and 7) at 14 d post-TBI, there was substantial tissue recovery by MRI, which could either reflect true tissue recovery or reabsorption of edema. Histology performed 14 d post-TBI, however, showed a small cavitation and significant neuronal degeneration surrounding the cavitation in S1FL. Thus, the observed improvement of behavioral scores likely involves both functional recovery and functional compensation.

Characterization of Closed Head Impact Injury in Rat.

The closed head impact (CHI) rat models are commonly used for studying the traumatic brain injury. The impact parameters vary considerably among different laboratories, making the comparison of research findings difficult. In this work, numerical CHI experiments were conducted to investigate the sensitivities of intracranial responses to various impact parameters (e.g., impact depth, velocity, and position; impactor diameter, material, and shape). A three-dimensional finite element rat head model with anatomical details was subjected to impact loadings. Results revealed that impact depth and impactor shape were the two leading factors affecting intracranial responses. The influence of impactor diameter was region-specific and an increase in impactor diameter could substantially increase tissue strains in the region which located directly beneath the impactor. The lateral impact could induce higher strains in the brain than the central impact. An indentation depth instead of impact depth would be appropriate to characterize the influence of a large deformed rubber impactor. The experimentally observed velocity-dependent injury severity could be attributed to the “overshoot” phenomenon. This work could be used to better design or compare CHI experiments.

Chondroitinase Enhances Cortical Map Plasticity and Increases Functionally Active Sprouting Axons after Brain Injury

The beneficial effect of interventions with chondroitinase ABC enzyme to reduce axon growth-inhibitory chondroitin sulphate side chains after central nervous system injuries has been mainly attributed to enhanced axonal sprouting. After traumatic brain injury (TBI), it is unknown whether newly sprouting axons that occur as a result of interventional strategies are able to functionally contribute to existing circuitry, and it is uncertain whether maladaptive sprouting occurs to increase the well-known risk for seizure activity after TBI. Here, we show that after a controlled cortical impact injury in rats, chondroitinase infusion into injured cortex at 30 min and 3 days reduced c-Fos⁺ cell staining resulting from the injury alone at 1 week postinjury, indicating that at baseline, abnormal spontaneous activity is likely to be reduced, not increased, with this type of intervention. c-Fos⁺ cell staining elicited by neural activity from stimulation of the affected forelimb 1 week after injury was significantly enhanced by chondroitinase, indicating a widespread effect on cortical map plasticity. Underlying this map plasticity was a larger contribution of neuronal, rather than glial cells and an absence of c-Fos⁺ cells surrounded by perineuronal nets that were normally present in stimulated naïve rats. After injury, chondroitin sulfate proteoglycan digestion produced the expected increase in growth-associated protein 43-positive axons and perikarya, of which a significantly greater number were double labeled for c-Fos after intervention with chondroitinase, compared to vehicle. These data indicate that chondroitinase produces significant gains in cortical map plasticity after TBI, and that either axonal sprouting and/or changes in perineuronal nets may underlie this effect. Chondroitinase dampens, rather than increases nonspecific c-Fos activity after brain injury, and induction of axonal sprouting is not maladaptive because greater numbers are functionally active and provide a significant contribution to forelimb circuitry after brain injury.

Acetylcholinesterase Inhibition Interacts with Training To Reverse Spatial Learning Deficits after Cortical Impact Injury

Cholinergic mechanisms are known to play a key role in cognitive functions that are profoundly altered in traumatic brain injury (TBI). The present investigation was designed to test the ability of continuous administration, starting at the time of injury, of physostigmine (PHY), an acetylcholinesterase (AChE) inhibitor that crosses the blood-brain barrier (BBB), to ameliorate the alterations of learning and memory induced by cerebral cortex impact injury in rats under isoflurane anesthesia. Learning and memory were assessed with the Morris water maze implemented during days 7-11 (WM1), and days 21-25 post-TBI (WM2), with four trials per day for 3 days, followed by target reversal and 2 additional days of training. These groups of Sprague-Dawley male rats were used: TBI treated with PHY at 3.2 μmol/kg/day (TBI-PHY3.2), or 6.4 μmol/kg/day (TBI-PHY6.4), by subcutaneous osmotic pumps, or TBI and no injury (Sham) treated with saline. AChE activity was measured in brain tissue samples of non-traumatized animals that received PHY at the doses used in the TBI animals. In WM1 tests, PHY3.2 improved learning within sessions, but not between sessions, in the recall of the target position, while PHY6.4 had no significant effects. In WM2 tests, PHY improved within- and between-sessions performance at both dose levels. We found that continuous AChE inhibition interacted with repeated training on the water maze task to completely reverse the deficits seen in learning and memory induced by TBI. The PHY treatment also reduced the amount of brain tissue loss as measured using cresyl violet staining.

Cerebral metabolism after early decompression craniotomy following controlled cortical impact injury in rats

<title/>After traumatic brain injury, a cascade of metabolic changes promotes the development of secondary brain damage. In this study, we examined metabolic changes in rats in the acute stage after trauma. Furthermore, we investigated the effect of a very early decompression craniotomy on intracranial pressure (ICP) and on metabolic parameters. For this study, a moderate controlled cortical impact injury (CCII) on rats was performed. The observation time was 180 minutes after trauma. ICP was measured continuously and microdialysate samples were collected every 30 minutes from the peri-contusional region. As representative metabolic parameters, glutamate, lactate, lactate/pyruvate ratio (L/P ratio), and glucose concentrations were measured. Compared to sham-operated animals, a significant, sustained decrease in glucose concentration and increase in L/P ratio occurred immediately after CCII. Additionally, delayed increase in lactate and glutamate concentrations occurred 60 minutes after trauma. After this initial peak, glutamate concentrations declined continuously via the observation time and reached levels comparable to sham-operated animals. In our model, thus we could detect a very early deterioration of glucose utilization and energy supply after trauma that recovered, due to the moderate intensity of the trauma, within 60 minutes without leading to ischemia in the peri-contusional region. Following decompression craniotomy, the increase of intracranial pressure could be reduced significantly. Any significant beneficial effects on metabolic changes, however, could not be proven in this very early stage after moderate CCII.

Early Microstructural and Metabolic Changes following Controlled Cortical Impact Injury in Rat: A Magnetic Resonance Imaging and Spectroscopy Study

Understanding tissue alterations at an early stage following traumatic brain injury (TBI) is critical for injury management and limiting severe consequences from secondary injury. We investigated the early microstructural and metabolic profiles using in vivo diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy ((1)H MRS) at 2 and 4 h following a controlled cortical impact injury in the rat brain using a 7.0 Tesla animal MRI system and compared profiles to baseline. Significant decrease in mean diffusivity (MD) and increased fractional anisotropy (FA) was found near the impact site (hippocampus and bilateral thalamus; p<0.05) immediately following TBI, suggesting cytotoxic edema. Although the DTI parameters largely normalized on the contralateral side by 4 h, a large inter-individual variation was observed with a trend towards recovery of MD and FA in the ipsilateral hippocampus and a sustained elevation of FA in the ipsilateral thalamus (p<0.05). Significant reduction in metabolite to total creatine ratios of N-acetylaspartate (NAA, p=0.0002), glutamate (p=0.0006), myo-inositol (Ins, p=0.04), phosphocholine and glycerophosphocholine (PCh+GPC, p=0.03), and taurine (Tau, p=0.009) were observed ipsilateral to the injury as early as 2 h, while glutamine concentration increased marginally (p=0.07). These metabolic alterations remained sustained over 4 h after TBI. Significant reductions of Ins (p=0.024) and Tau (p=0.013) and marginal reduction of NAA (p=0.06) were also observed on the contralateral side at 4 h after TBI. Overall our findings suggest significant microstructural and metabolic alterations as early as 2 h following injury. The tendency towards normalization at 4 h from the DTI data and no further metabolic changes at 4 h from MRS suggest an optimal temporal window of about 3 h for interventions that might limit secondary damage to the brain. Results indicate that early assessment of TBI patients using DTI and MRS may provide valuable information on the available treatment window to limit secondary brain damage.

The dopamine and cAMP regulated phosphoprotein, 32 kDa (DARPP-32) signaling pathway: A novel therapeutic target in traumatic brain injury

Traumatic brain injury (TBI) causes persistent neurologic deficits. Current therapies, predominantly focused upon cortical and hippocampal cellular survival, have limited benefit on cognitive outcomes. Striatal damage is associated with deficits in executive function, learning, and memory. Dopamine and cAMP regulated phosphoprotein 32 (DARPP-32) is expressed within striatal medium spiny neurons and regulates striatal function. We found that controlled cortical impact injury in rats produces a chronic decrease in DARPP-32 phosphorylation at threonine-34 and an increase in protein phosphatase-1 activity. There is no effect of injury on threonine-75 phosphorylation or on DARPP-32 protein. Amantadine, shown to be efficacious in treating post-TBI cognitive deficits, given daily for two weeks is able to restore the loss of DARPP-32 phosphorylation and reduce protein phosphatase-1 activity. Amantadine also decreases the phosphorylation of threonine-75 consistent with activity as a partial N-methyl-D-aspartate (NMDA) receptor antagonist and partial dopamine agonist. These data demonstrate that targeting the DARPP-32 signaling cascade represents a promising novel therapeutic approach in the treatment of persistent deficits following a TBI.

Improved Cerebrovascular Function and Reduced Histological Damage with Darbepoietin Alfa Administration after Cortical Impact Injury in Rats

Darbepoetin alfa (darbEpo) is an erythropoietic glycoprotein that activates the erythropoietin receptor. The aim of our study was to determine whether darbEpo is neuroprotective in a cortical impact injury (CII) model and to determine the characteristics of dose response and time window. To better understand the vascular mechanism of darbEpo neuroprotection, the reactivity of cerebral blood flow (CBF) to l-arginine administration was also studied. Rats were given saline or darbEpo from 2.5 to 50 μg/kg at 5 min after CII or a dose of 25 μg/kg darbEpo at times ranging from 5 min to 24 h after CII. Histological assessment was determined 2 weeks after a severe CII. Other rats were given either darbEpo (25 μg/kg) or saline daily for 3 days before injury. Five minutes after severe CII, they were given either l-arginine or d-arginine. Hemodynamic variables were monitored for 2 h after injury. In the dose-response study, darbEpo in doses of 25 and 50 μg/kg significantly reduced contusion volume from 39.1 ± 6.7 to 8.1 ± 3.1 and 11.2 ± 6.0 mm(3), respectively. In the time window study, darbEpo reduced contusion volume when given in a dose of 25 μg/kg at 5 min to 6 h after the impact injury. In animals pretreated with darbEpo, the CBF response to l-arginine was significantly greater than in the animals pretreated with saline. These data demonstrate that darbEpo has neuroprotective effects in traumatic brain injury in a dose- and time-dependent manner and that vascular effects of darbEpo may have a role in neuroprotection.

The Effects of Age and Ketogenic Diet on Local Cerebral Metabolic Rates of Glucose after Controlled Cortical Impact Injury in Rats

Previous studies from our laboratory have shown the neuroprotective potential of ketones after TBI in the juvenile brain. It is our premise that acutely after TBI, glucose may not be the optimum fuel and decreasing metabolism of glucose in the presence of an alternative substrate will improve cellular metabolism and recovery. The current study addresses whether TBI will induce age-related differences in the cerebral metabolic rates for glucose (CMRglc) after cortical controlled impact (CCI) and whether ketone metabolism will further decrease CMRglc after injury. Postnatal day 35 (PND35; n = 48) and PND70 (n = 42) rats were given either sham or CCI injury and placed on either a standard or a ketogenic (KG) diet. CMRglc studies using (14)C-2 deoxy-D-glucose autoradiography were conducted on days 1, 3, or 7 post-injury. PND35 and PND70 standard-fed CCI-injured rats exhibited no significant neocortical differences in CMRglc magnitude or time course compared to controls. Measurement of contusion volume also indicated no age differences in response to TBI. However, PND35 subcortical structures showed earlier metabolic recovery compared to controls than PND70. Ketosis induced by the KG diet was shown to affect CMRglc in an age-dependent manner after TBI. The presence of ketones after injury further reduced CMRglc in PND35 and normalized CMRglc in PND70 rats at 7 days bilaterally after injury. The changes in CMRglc seen in PND35 TBI rats on the KG diet were associated with decreased contusion volume. These results suggest that conditions of reduced glucose utilization and increased alternative substrate metabolism may be preferable acutely after TBI in the younger rat.

Changes in autophagy proteins in a rat model of controlled cortical impact induced brain injury

Autophagy has been implicated in several neurodegenerative diseases and recently its role in acute brain injury has received increased interest. In our study, we investigated the profiles of autophagy-linked proteins (MAP-LC3 (Atg8), beclin-1 (Atg6) and the beclin-1-binding protein, bcl-2, following controlled cortical impact injury in rats—a model for moderate-to-severe traumatic brain injury. We observed significant increases in the levels of the processed form of LC3 (LC3-II) in the ipsilateral cortex 2h to 2 days after injury when compared to sham. Furthermore, the beclin-1/bcl-2 ratio in the ipsilateral cortex was found to have increased from 1 and 2 days after injury. Since both of these changes are established autophagy-enabling events, and, based on these data, we propose that autophagy, plays a role in the manifestation of cell injury following brain trauma.

Ubiquitin Reduces Contusion Volume after Controlled Cortical Impact Injury in Rats

Recent data suggest that ubiquitin has anti-inflammatory properties and therapeutic potential after severe trauma and brain injuries. However, direct evidence for its neuroprotective effects has not yet been provided. We hypothesized that ubiquitin treatment is neuroprotective, and thus reduces brain edema formation and cortical contusion volume after closed traumatic brain injuries. To test this hypothesis, a focal cortical contusion was induced using a controlled cortical impact (CCI) model in Sprague-Dawley rats. Animals (n = 27) were randomized to either 1.5 mg/kg ubiquitin or vehicle (placebo) intravenously within 5 min after CCI. Blood pressure, arterial blood gases (ABG) and intracranial pressure (ICP) were monitored. Ubiquitin serum and cerebrospinal fluid levels were measured by ELISA. Brain water content was quantified gravimetrically after 24 h and cerebral contusion volume was determined in triphenyltetrazolium-chloride stained brains after 7 days. All animals recovered to normal activity. ICP and cerebral perfusion pressures were normal at the end of the observation period. Ubiquitin serum and CSF levels at 24 h and 7 days after CCI were similar in both groups. With ubiquitin brain water content of the injured hemisphere was slightly lower (n = 6/group; 79.97 +/- 0.29% vs. 81.11 +/- 0.52%; p = 0.08). Cortical contusion volume was significantly lower with ubiquitin (n = 7-8/group; 32.88 +/- 2.1 mm(3) vs. 43.96 +/- 4.56 mm(3); p = 0.025). This study shows that ubiquitin treatment after brain injury has direct neuroprotective effects, as demonstrated by improved brain morphology 7 days after brain injury. In connection with its beneficial effects in our previous studies, these data suggest ubiquitin as a promising candidate protein therapeutic for the treatment of brain injuries.

Heterogeneous regional and temporal energetic impairment following controlled cortical impact injury in rats

Objectives: Following traumatic brain injury metabolic stability is impaired. Duration and reversibility of these changes might be important to guide specific interventions.Methods: To characterize temporal and regional changes in cerebral metabolism, 68 male Sprague–Dawley rats were subjected to a focal cortical contusion. Lesion progression and mitochondrial impairment were determined by magnetic resonance imaging (MRI) and triphenyl tetrazolium chloride (TTC) staining, respectively. Metabolic alterations were determined at hours 6 and 24 and day 7 by measuring extracellular glucose, lactate and hypoxanthine levels with microdialysis catheters placed adjacent and distant to the contusion and by quantifying changes in tissue ATP, lactate and glucose using bioluminescence imaging.Results: The cortical lesion reached its maximal extent at hour 24 and remained confined to the ipsilateral hemisphere. In microdialysate, at hour 6, extracellular hypoxanthine and lactate reached maximal values, thereafter hypoxanthine normalized while lactate remained increased. Extracellular glucose reached the highest values at hour 24 and remained elevated. Bioluminescence imaging revealed heterogeneous changes in areas distant to the contusion. No significant changes were found in ATP content. Slightly elevated tissue glucose until 24 hours in the ipsilateral hemisphere was observed. Following a continuous increase, lactate levels were the highest by 6 hours in the ipsilateral cortex and hippocampus.Discussion: CCI is associated with disturbances in energetic metabolism. Metabolic perturbation is not restricted to the early phase and the contusional region following focal cortical contusion, but also involves hippocampus and primarily uninjured parts of the hemisphere.

Neuroprotection with Erythropoietin Administration Following Controlled Cortical Impact Injury in Rats

This study was designed to determine the effect of erythropoietin (Epo) on cerebral blood flow (CBF), nitric oxide (NO) concentration, and neurological outcome after traumatic brain injury. In one experiment, the hemodynamic effects of Epo were determined after controlled cortical impact injury (CCII) by measuring mean arterial pressure, intracranial pressure, CBF using laser Doppler flowmetry, and brain tissue NO concentrations using an NO electrode. In total, 41 rats were given either Epo (5000 U/kg) or saline s.c. 3 days before injury. In animals pretreated with saline, L-arginine but not D-arginine administration resulted in a significant increase in tissue NO concentrations and an improvement in CBF at the impact site. Likewise, in animals pretreated with Epo, L-arginine but not D-arginine given postinjury increased brain tissue NO concentrations and increased CBF. In another experiment, 74 rats underwent CCII (3-mm deformation, velocity 5 m/s), and they were given saline or Epo 5000 U/kg s.c. at 5 min, 1 h, 3 h, 6 h, 9 h, or 12 h postinjury. The contusion volume and cell counts of viable neurons in the CA1 and CA3 regions of the hippocampus were assessed at 2 weeks postinjury. The contusion volume was significantly reduced at 5 min, 1 h, 3 h, and 6 h postinjury Epo administration. The neuron density in the CA1 and CA3 region of the hippocampus was increased at 1, 3, and 6 h after injury. These data demonstrate the neuroprotective effects of Epo in traumatic injury, and the effects are optimal when Epo is given within 6 h of injury.