Bench-to-bedside review: Apoptosis/programmed cell death triggered by traumatic brain injury

Small interfering RNA directed against CTMP reduces acute traumatic brain injury in a mouse model by activating Akt

OBJECTIVE

Protein kinase B (PKB/Akt), which is phosphorylated and activated by upstream activators, exerts critical neuroprotective effects by phosphorylating downstream targets after traumatic brain injury (TBI). Studies on the regulation of Akt will be crucial for our understanding of neuronal survival. The goal of this study is to investigate the effects of carboxyl-terminal modulator protein (CTMP) on phosphorylation of Akt and neurological function in a mouse model of TBI.

METHODS

Traumatic brain injury in mice was performed by a controlled cortical impact device. The expression of Akt, phospho-Akt, and CTMP was examined in the injured cortices by immunohistochemistry and Western blot analysis. To determine the effects of CTMP, small interfering RNAs (siRNAs) directed against CTMP were injected in mice with TBI, and the expression of phosphorylated Akt and neurological function were evaluated.

RESULTS

Phospho-Akt significantly increased at 4 hours post-TBI in the nucleus (P < 0.01) and remained at high levels until 72 hours after TBI, as shown by Western blot analysis. In the cytosol, the expression of phospho-Akt reached its peak at 4 hours post-TBI, but decreased markedly at 24 hours and maintained below pre-TBI levels until 72 hours post-TBI. Interestingly, the expression of CTMP significantly increased 4 hours after TBI (P < 0.01) and sustained those levels until 72 hours without dramatic changes. Treatment with CTMP siRNA effectively augmented the phosphorylation of Akt and significantly improved the neurological functional recovery up to 28 days post-TBI.

CONCLUSION

We conclude that Akt is phosphorylated and translocated to nucleus after TBI to exert neuroprotective effects. However, CTMP is simultaneously triggered to inhibit the phosphorylation of Akt. Inhibition of CTMP by siRNA improves the recovery of neurological functions after TBI.

Angiotensin II protects cortical neurons against oxygen-glucose deprivation-induced injury in vitro

Ischemic cerebrovascular disease is a common type of cerebrovascular disease and the leading cause of disability and mortality worldwide. Therefore, it is crucial to elucidate its pathogenesis and develop novel therapeutic strategies. This study was performed to investigate whether angiotensin (Ang) II exerts a protective effect against cerebral ischemia/reperfusion (I/R) injury in vitro. The primary cultured neurons were prepared and an I/R model was established by incubation of cortical neurons with Na₂S₂O₄, followed by culture in fresh medium. The protective effect of Ang II and its underlying mechanisms were investigated by morphology observation, MTT assay, flow cytometry analysis and reverse transcription-polymerase chain reaction (RT-PCR). The data demonstrated that Ang II significantly ameliorated the neuronal injury caused by oxygen-glucose deprivation. Furthermore, Ang II increased cell viability through inhibiting cell apoptosis. The RT-PCR results revealed that Ang II was able to reverse the increased bax mRNA and the decreased bcl2 mRNA expression. Of note, the protective activity of Ang II may be attenuated by co-treatment with Ang II type 2 (AT2) receptor blockade (PD123319), but not Ang II type 1 (AT1) receptor blockade (valsartan). These findings suggested that Ang II exerted a protective effect against neuronal injury induced by oxygen-glucose deprivation through decreasing cell apoptosis. Therefore, Ang II may be used as a potential therapeutic target in the future.

Endogenous nitric-oxide synthase inhibitor ADMA after acute brain injury

Previous results on nitric oxide (NO) metabolism after traumatic brain injury (TBI) show variations in NO availability and controversial effects of exogenous nitric oxide synthase (NOS)-inhibitors. Furthermore, elevated levels of the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA) were reported in cerebro-spinal fluid (CSF) after traumatic subarachnoid hemorrhage (SAH). Therefore, we examined whether ADMA and the enzymes involved in NO- and ADMA-metabolism are expressed in brain tissue after TBI and if time-dependent changes occur. TBI was induced by controlled cortical impact injury (CCII) and neurological performance was monitored. Expression of NOS, ADMA, dimethylarginine dimethylaminohydrolases (DDAH) and protein-arginine methyltransferase 1 (PRMT1) was determined by immunostaining in different brain regions and at various time-points after CCII. ADMA and PRMT1 expression decreased in all animals after TBI compared to the control group, while DDAH1 and DDAH2 expression increased in comparison to controls. Furthermore, perilesionally ADMA is positively correlated with neuroscore performance, while DDAH1 and DDAH2 are negatively correlated. ADMA and its metabolizing enzymes show significant temporal changes after TBI and may be new targets in TBI treatment.

Low dose of valproate improves motor function after traumatic brain injury

BACKGROUND

Traumatic brain injuries (TBIs) are a major health care problem worldwide. Approximately 1.5 million new TBI cases occur annually in the United States, with mortality rates ranging between 35% and 40% in severe patients. Despite the incidence of these injuries and their substantial socioeconomic implications, no specific pharmacological intervention is available for clinical use. Several studies have indicated that 300 mg/kg or 400 mg/kg of valproate (VPA) exhibits neuroprotective effects in animal models. However, humans cannot tolerate high doses of VPA. This study aims to investigate whether 30 mg/kg of VPA administered to rats affects TBIs.

METHODS

We used a rat model to test the effects of 30 mg/kg of VPA on TBIs. Molecular identifications for histone acetylation and phosphorylation of cAMP response element-binding protein (CREB) and phosphorylated extracellular signal regulated kinase (ERK) were performed.

RESULTS

The results indicated that treating adult rats with VPA after TBIs significantly decreased the contusion volume and recovery of contusion-related skilled forelimb reaching deficits. Applying VPA also increased histone acetylation, p-ERK, and p-CREB expression in the brain. Furthermore, applying VPA reduced inflammation, glial fibrillary acidic protein activation, and apoptosis. Conclusion. This study found that 30 mg/kg of VPA assists in treating TBIs in rat models.

Hydrogen sulfide offers neuroprotection on traumatic brain injury in parallel with reduced apoptosis and autophagy in mice

Hydrogen sulfide (H₂S), a novel gaseous mediator, has been recognized as an important neuromodulator and neuroprotective agent in the central nervous system. The present study was undertaken to study the effects of exogenous H₂S on traumatic brain injury (TBI) and the underlying mechanisms. The effects of exogenous H₂S on TBI were examined by using measurement of brain edema, behavior assessment, propidium iodide (PI) staining, and Western blotting, respectively. Compared to TBI groups, H₂S pretreatment had reduced brain edema, improved motor performance and ameliorated performance in Morris water maze test after TBI. Immunoblotting results showed that H₂S pretreatment reversed TBI-induced cleavage of caspase-3 and decline of Bcl-2, suppressed LC3-II, Beclin-1 and Vps34 activation and maintained p62 level in injured cortex and hippocampus post TBI. The results suggest a protective effect and therapeutic potential of H₂S in the treatment of brain injury and the protective effect against TBI may be associated with regulating apoptosis and autophagy.

Administration of low dose methamphetamine 12 h after a severe traumatic brain injury prevents neurological dysfunction and cognitive impairment in rats

We recently published data that showed low dose of methamphetamine is neuroprotective when delivered 3 h after a severe traumatic brain injury (TBI). In the current study, we further characterized the neuroprotective potential of methamphetamine by determining the lowest effective dose, maximum therapeutic window, pharmacokinetic profile and gene expression changes associated with treatment. Graded doses of methamphetamine were administered to rats beginning 8 h after severe TBI. We assessed neuroprotection based on neurological severity scores, foot fault assessments, cognitive performance in the Morris water maze, and histopathology. We defined 0.250 mg/kg/h as the lowest effective dose and treatment at 12 h as the therapeutic window following severe TBI. We examined gene expression changes following TBI and methamphetamine treatment to further define the potential molecular mechanisms of neuroprotection and determined that methamphetamine significantly reduced the expression of key pro-inflammatory signals. Pharmacokinetic analysis revealed that a 24-hour intravenous infusion of methamphetamine at a dose of 0.500 mg/kg/h produced a plasma Cmax value of 25.9 ng/ml and a total exposure of 544 ng/ml over a 32 hour time frame. This represents almost half the 24-hour total exposure predicted for a daily oral dose of 25mg in a 70 kg adult human. Thus, we have demonstrated that methamphetamine is neuroprotective when delivered up to 12 h after injury at doses that are compatible with current FDA approved levels.

Serum adhesion molecules, outcome and neuro-psychological function in acute traumatic brain injury patients

BACKGROUND

Serum concentrations of adhesion molecules may be associated with secondary brain injury after acute traumatic brain injury (TBI).

METHODS

Blood samples of 68 patients admitted within 24h after TBI were obtained on admission and on Days 4 and 7 after TBI. Patients received neuro-psychological testing on discharge and at 3 months after TBI.

RESULTS

Compared to controls, patients with acute TBI had markedly increased sICAM-1 and sVCAM-1 on presentation (p=0.002 and p=0.021, respectively), but markedly decreased sL-selectin and sE-selectin (p=0.009 and p≤0.001, respectively). Outcome was assessed upon discharge using the Glasgow Outcome Scale (GOS). Good outcome was defined as GOS ≥4 and poor outcome as GOS ≤3. Motor deficits on admission (p≤0.001), Glasgow Coma Scale score on admission (p=0.002), Injury Severity Score on admission (p=0.009), neuro-surgical intervention (p=0.004), post-traumatic seizure (p=0.04), and sVCAM-1 level on admission (p=0.033) were significant risk factors of outcome. A sVCAM-1 cut-off value of 752.5ng/ml on admission had 80.0% sensitivity and 68.1% specificity for predicting outcome.

CONCLUSION

Serum adhesion molecules are not specific for predicting outcome in patients with TBI. However, higher mean levels of these molecules on admission may imply more severe inflammatory response causing secondary brain injury and worse neuro-psychological function. These molecules may be added as evaluation markers in clinical practice.

Molecular mechanisms of cognitive dysfunction following traumatic brain injury

Traumatic brain injury (TBI) results in significant disability due to cognitive deficits particularly in attention, learning and memory, and higher-order executive functions. The role of TBI in chronic neurodegeneration and the development of neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic Lateral Sclerosis (ALS) and most recently chronic traumatic encephalopathy (CTE) is of particular importance. However, despite significant effort very few therapeutic options exist to prevent or reverse cognitive impairment following TBI. In this review, we present experimental evidence of the known secondary injury mechanisms which contribute to neuronal cell loss, axonal injury, and synaptic dysfunction and hence cognitive impairment both acutely and chronically following TBI. In particular we focus on the mechanisms linking TBI to the development of two forms of dementia: AD and CTE. We provide evidence of potential molecular mechanisms involved in modulating Aβ and Tau following TBI and provide evidence of the role of these mechanisms in AD pathology. Additionally we propose a mechanism by which Aβ generated as a direct result of TBI is capable of exacerbating secondary injury mechanisms thereby establishing a neurotoxic cascade that leads to chronic neurodegeneration.

Peptidergic drugs for the treatment of traumatic brain injury

Traumatic brain injury (TBI) is a devastating medical condition that has an enormous socioeconomic impact because it affects more than 10 million people annually worldwide and is associated with high rates of hospitalization, mortality and disability. Although TBI survival has improved continuously for decades, particularly in developing countries, implementation of an effective drug therapy for TBI represents an unmet clinical need. All confirmatory trials conducted to date with drugs targeting a single TBI pathological pathway failed to show clinical efficacy, probably because TBI pathophysiology involves multiple cellular and molecular mechanisms of secondary brain damage. According to current scientific evidence of the participation of peptide-mediated mechanisms in the processes of brain injury and repair after TBI, peptidergic drugs represent a multimodal therapy alternative to improve acute outcome and long-term recovery in TBI patients. Preliminary randomized-controlled clinical trials and open-label studies conducted to date with the peptidergic drug Cerebrolysin® (Ever Neuro Pharma GmbH, Unterach, Austria) and with the endogenous neuropeptides progesterone and erythropoietin, showed positive clinical results. Cerebrolysin-treated patients had a faster clinical recovery, a shorter hospitalization time and a better long-term outcome. Treatment with progesterone showed advantages over placebo regarding TBI mortality and clinical outcome, whereas erythropoietin only reduced mortality. Further validation of these promising findings in confirmatory randomized-controlled clinical trials is warranted. This article reviews the scientific basis and clinical evidence on the development of multimodal peptidergic drugs as a therapeutic option for the effective treatment of TBI patients.

Early ghrelin treatment attenuates disruption of the blood brain barrier and apoptosis after traumatic brain injury through a UCP-2 mechanism

Ghrelin has been shown to be anti-inflammatory and neuroprotective in models of neurologic injury. We hypothesize that treatment with ghrelin will attenuate breakdown of the blood brain barrier (BBB) and apoptosis 24h following traumatic brain injury (TBI). We believe this protection is at least in part mediated by up-regulation of UCP-2, thereby stabilizing mitochondria and preventing up-regulation of caspase-3. A weight drop model was used to create severe TBI. Balb/c mice were divided into 3 groups. Sham: no TBI or ghrelin treatment; TBI: TBI only; TBI/ghrelin: 20μg (IP) ghrelin at the time of TBI. BBB permeability to 70kDa FITC-Dextran was measured 24h following injury and quantified in arbitrary integrated fluorescence (afu). Brain tissue was subjected to TUNEL staining and TUNEL positive cells were quantified. Immunohistochemistry was performed on injured tissue to reveal patterns of caspase-3 and UCP-2 expression. TBI increased cerebral vascular permeability by three-fold compared to sham. Ghrelin treatment restored vascular permeability to the level of shams. TUNEL staining showed that ghrelin mitigated the significant increase in apoptosis that follows TBI. TBI increased both caspase-3 compared to sham. Treatment with ghrelin significantly increased UCP-2 compared to TBI alone and this increase in UCP-2 expression was associated with a decrease in expression of caspase-3. Early ghrelin treatment prevents TBI induced BBB disruption and TBI mediated apoptosis 24h following injury. These results demonstrate the neuroprotective potential of ghrelin as a therapy in TBI.

Poloxamer-188 attenuates TBI-induced blood-brain barrier damage leading to decreased brain edema and reduced cellular death

Plasmalemma permeability plays an important role in the secondary neuronal death induced by traumatic brain injury (TBI). Previous works showed that Poloxamer 188 (P188) could restore the intactness of the plasma membrane and play a cytoprotective action. However, the roles of P188 in blood-brain barrier (BBB) integrity and TBI-induced neural cell death are still not clear. In this study, mice were induced TBI by controlled cortical impact (CCI), and cerebral water content was measured to explore the profile of brain edema after CCI. Further, the regimen of P188 in mouse CCI models was optimized. The neurological test and BBB integrity assessment were performed, and the numbers of TBI-induced neural cell death were counted by propidium iodide (PI) labeling. The expression of apoptotic pathway associated proteins (Bax, cyt-c, caspase-8, caspase-9, caspase-3, P53) and aquaporin-4 (AQP4) was assessed by RT-PCR or immunoblotting. The data showed that the brain edema peaked at 24 h after TBI in untreated animals. Tail intravenous injection of P188 (4 mg/ml, 100 μl) 30 min before TBI or within 30 min after TBI could attenuate TBI-induced brain edema. P188 pre-treatment restored BBB integrity, suppressed TBI-induced neural cell death, and improved neurological function. TBI induced an up-regulation of Bax, cyt-c, caspase-8, caspase-9, caspase-3, and the expression of p53 was down-regulated by P188 pre-treatment. AQP4 mainly located on endothelial cells and astrocytes, and its expression was also regulated by P188 pretreatment. All these results revealed that P188 attenuates TBI-induced brain edema by resealing BBB and regulating AQP4 expression, and suppressed apoptosis through extrinsic or intrinsic pathway. Plasmalemma permeability may be a potential target for TBI treatment.

Salidroside improves behavioral and histological outcomes and reduces apoptosis via PI3K/Akt signaling after experimental traumatic brain injury

Background

Traumatic brain injury (TBI) induces a complex sequence of apopototic cascades that contribute to secondary tissue damage. The aim of this study was to investigate the effects of salidroside, a phenolic glycoside with potent anti-apoptotic properties, on behavioral and histological outcomes, brain edema, and apoptosis following experimental TBI and the possible involvement of the phosphoinositide 3-kinase/protein kinase B (PI3K)/Akt signaling pathway.

Methodology/Principal Findings

Mice subjected to controlled cortical impact injury received intraperitoneal salidroside (20, or 50 mg/kg) or vehicle injection 10 min after injury. Behavioral studies, histology analysis and brain water content assessment were performed. Levels of PI3K/Akt signaling-related molecules, apoptosis-related proteins, cytochrome C (CytoC), and Smac/DIABLO were also analyzed. LY294002, a PI3K inhibitor, was administered to examine the mechanism of protection. The protective effect of salidroside was also investigated in primary cultured neurons subjected to stretch injury. Treatment with 20 mg/kg salidroside_significantly improved functional recovery and reduced brain tissue damage up to post-injury day 28. Salidroside_also significantly reduced neuronal death, apoptosis, and brain edema at day 1. These changes were associated with significant decreases in cleaved caspase-3, CytoC, and Smac/DIABLO at days 1 and 3. Salidroside increased phosphorylation of Akt on Ser473 and the mitochondrial Bcl-2/Bax ratio at day 1, and enhanced phosphorylation of Akt on Thr308 at day 3. This beneficial effect was abolished by pre-injection of LY294002. Moreover, delayed administration of salidroside at 3 or 6 h post-injury reduced neuronal damage at day 1. Salidroside treatment also decreased neuronal vulnerability to stretch-induced injury in vitro.

Conclusions/Significance

Post-injury salidroside improved long-term behavioral and histological outcomes and reduced brain edema and apoptosis following TBI, at least partially via the PI3K/Akt signaling pathway.

Staurosporine induces necroptotic cell death under caspase-compromised conditions in U937 cells

For a long time necrosis was thought to be an uncontrolled process but evidences recently have revealed that necrosis can also occur in a regulated manner. Necroptosis, a type of programmed necrosis is defined as a death receptor-initiated process under caspase-compromised conditions. The process requires the kinase activity of receptor-interacting protein kinase 1 and 3 (RIPK1 and RIPK3) and mixed lineage kinase domain-like protein (MLKL), as a substrate of RIPK3. The further downstream events remain elusive. We applied known inhibitors to characterize the contributing enzymes in necroptosis and their effect on cell viability and different cellular functions were detected mainly by flow cytometry. Here we report that staurosporine, the classical inducer of intrinsic apoptotic pathway can induce necroptosis under caspase-compromised conditions in U937 cell line. This process could be hampered at least partially by the RIPK1 inhibitor necrotstin-1 and by the heat shock protein 90 kDa inhibitor geldanamycin. Moreover both the staurosporine-triggered and the classical death ligand-induced necroptotic pathway can be effectively arrested by a lysosomal enzyme inhibitor CA-074-OMe and the recently discovered MLKL inhibitor necrosulfonamide. We also confirmed that the enzymatic role of poly(ADP-ribose)polymerase (PARP) is dispensable in necroptosis but it contributes to membrane disruption in secondary necrosis. In conclusion, we identified a novel way of necroptosis induction that can facilitate our understanding of the molecular mechanisms of necroptosis. Our results shed light on alternative application of staurosporine, as a possible anticancer therapeutic agent. Furthermore, we showed that the CA-074-OMe has a target in the signaling pathway leading to necroptosis. Finally, we could differentiate necroptotic and secondary necrotic processes based on participation of PARP enzyme.

Near-infrared photobiomodulation in an animal model of traumatic brain injury: improvements at the behavioral and biochemical levels

OBJECTIVE

The purpose of this was to evaluate the neuroprotective effects of near-infrared (NIR) light using an in-vivo rodent model of traumatic brain injury (TBI), controlled cortical impact (CCI), and to characterize changes at the behavioral and biochemical levels.

BACKGROUND DATA

NIR upregulates mitochondrial function, and decreases oxidative stress. Mitochondrial oxidative stress and apoptosis are important in TBI. NIR enhanced cell viability and mitochondrial function in previous in-vitro TBI models, supporting potential NIR in-vivo benefits.

METHODS

Sprague-Dawley rats were divided into three groups: severe TBI, sham surgery, and anesthetization only (behavioral response only). Cohorts in each group were administered either no NIR or NIR. They received two 670 nm LED treatments (5 min, 50 mW/cm(2), 15 J/cm(2)) per day for 72 h (chemical analysis) or 10 days (behavioral). During the recovery period, animals were tested for locomotor and behavioral activities using a TruScan device. Frozen brain tissue was obtained at 72 h and evaluated for apoptotic markers and reduced glutathione (GSH) levels.

RESULTS

Significant differences were seen in the TBI plus and minus NIR (TBI+/-) and sham plus and minus NIR (S+/-) comparisons for some of the TruScan nose poke parameters. A statistically significant decrease was found in the Bax pro-apoptotic marker attributable to NIR exposure, along with lesser increases in Bcl-2 anti-apoptotic marker and GSH levels.

CONCLUSIONS

These results show statistically significant, preclinical outcomes that support the use of NIR treatment after TBI in effecting changes at the behavioral, cellular, and chemical levels.

Necrostatin-1 suppresses autophagy and apoptosis in mice traumatic brain injury model

Traumatic brain injury (TBI) results in neuronal apoptosis, autophagic cell death and necroptosis. Necroptosis is a newly discovered caspases-independent programmed necrosis pathway which can be triggered by activation of death receptor. Previous works identified that necrostatin-1 (NEC-1), a specific necroptosis inhibitor, could reduce tissue damage and functional impairment through inhibiting of necroptosis process following TBI. However, the role of NEC-1 on apoptosis and autophagy after TBI is still not very clear. In this study, the amount of TBI-induced neural cell deaths were counted by PI labeling method as previously described. The expression of autophagic pathway associated proteins (Beclin-1, LC3-II, and P62) and apoptotic pathway associated proteins (Bcl-2 and caspase-3) were also respectively assessed by immunoblotting. The data showed that mice pretreated with NEC-1 reduced the amount of PI-positive cells from 12 to 48 h after TBI. Immunoblotting results showed that NEC-1 suppressed TBI-induced Beclin-1 and LC3-II activation which maintained p62 at high level. NEC-1 pretreatment also reversed TBI-induced Bcl-2 expression and caspase-3 activation, as well as the ratio of Beclin-1/Bcl-2. Both 3-MA and NEC-1 suppressed TBI-induced caspase-3 activation and LC3-II formation, Z-VAD only inhibited caspase-3 activation but increased LC3-II expression at 24 h post-TBI. All these results revealed that multiple cell death pathways participated in the development of TBI, and NEC-1 inhibited apoptosis and autophagy simultaneously. These coactions may further explain how can NEC-1 reduce TBI-induced tissue damage and functional deficits and reflect the interrelationship among necrosis, apoptosis and autophagy.

Mean diffusivity in the amygdala correlates with anxiety in pediatric TBI

Traumatic brain injury (TBI) and orthopedic injury (OI) patients are prone to anxiety and mood disorders. In the present study, we integrated anatomical and diffusion tensor neuroimaging to investigate structural properties of the amygdala and hippocampus, gray matter regions implicated in anxiety and mood disorders. Children and adolescents were evaluated during the late sub-acute phase of recovery following trauma resulting from either moderate to severe TBI or OI. Mean diffusivity (MD) of the amygdala and hippocampus was elevated following TBI. An interaction of hemisphere, structure, and group revealed that MD of the right amygdala was elevated in females with TBI. Self-reported anxiety scores were not related to either volume or microstructure of the hippocampus, or to volume or fractional anisotropy of the amygdala. Left amygdala MD in the TBI group accounted for 17.5% of variance in anxiety scores. Anxiety symptoms may be mediated by different mechanisms in patients with TBI or OI.

Changes in apoptotic mechanisms following penetrating ballistic-like brain injury

We investigated apoptotic pathways in a model of severe traumatic brain injury, penetrating ballistic-like brain injury (PBBI). TUNEL staining identified increasing apoptosis within 24 h. From targeted arrays, 11 genes were identified for temporal mRNA evaluation. In addition, mRNA levels and enzyme activity for caspases 3, 8, and 9 were examined. In the death receptor-mediated apoptosis pathway, the relative quantities (RQs) of mRNA for tnfr1, fas, and tnf were upregulated while trail mRNA was downregulated. In the anti-apoptotic TNF-R2 pathway, tnfr2 and flip were upregulated while xiap was downregulated. These findings indicate that increases in tnf levels following injury are not only pro-apoptotic but may also signal competing anti-apoptotic mechanisms. For the mitochondria-mediated apoptosis pathway, RQs of anti-apoptotic factors bcl2a1d and birc3 were upregulated while both bcl2 and bax were downregulated. RQs for casp 3 and casp 8 increased while casp9 decreased. Enzymatic activity increased for caspases 3, 8, and 9. While multiple mechanisms promoting and inhibiting apoptosis are at play during the first week after a PBBI, the cumulative result remains increased apoptosis. The ability to understand and dissect these events will assist in the development and evaluation of treatments targeting apoptosis following severe brain injury.

Postinjury treatment with rolipram increases hemorrhage after traumatic brain injury

The pathology caused by traumatic brain injury (TBI) is exacerbated by the inflammatory response of the injured brain. Two proinflammatory cytokines that contribute to inflammation after TBI are tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). From previous studies using the parasagittal fluid-percussion brain injury model, we reported that the anti-inflammatory drug rolipram, a phosphodiesterase 4 inhibitor, reduced TNF-α and IL-1β levels and improved histopathological outcome when administered 30 min prior to injury. We now report that treatment with (±)-rolipram given 30 min after injury significantly reduced TNF-α levels in the cortex and hippocampus. However, postinjury administration of (±)-rolipram significantly increased cortical contusion volume and increased atrophy of the cortex compared with vehicle-treated animals at 10 days postinjury. Thus, despite the reduction in proinflammatory cytokine levels, histopathological outcome was worsened with post-TBI (±)-rolipram treatment. Further histological analysis of (±)-rolipram-treated TBI animals revealed significant hemorrhage in the contused brain. Given the well-known role of (±)-rolipram of increasing vasodilation, it is likely that (±)-rolipram worsened outcome after fluid-percussion brain injury by causing increased bleeding.

Mechanisms and consequences of acquired brain injury during development

The brain of the infant and young child is a developing, dynamic, structure subject to functional remodelling under the influence of factors responsible for optimal neuronal development and synaptogenesis. It exhibits age dependent variation in metabolic rate, blood flow, and ability to tolerate oxidative stress. It is also characterized by an exuberance of neurotransmitter activity, particularly in the first few years of life. The dynamic evolution and adaptability of early brain function permits the organization of neuronal networks to be influenced by environmental stimulation, and, to reduce the functional impact of injury. However, these same processes may also exacerbate the harm sustained by the brain following an acquired brain injury (ABI). The developing neurons are susceptible to excitotoxicity, oxidative stress, and, inflammation, often leading to cellular necrosis and apoptosis. Despite being immunologically privileged via the blood brain barrier, the developing brain is susceptible to injury from systemic inflammation through alteration of normally protective cerebrovascular endothelial cell function. Finally, many of the therapeutic agents currently employed in post-ABI hospital care may also compromise ABI outcome via non-intended pharmacological effects. These agents include analgesic, sedative and anti-convulsant medications. This review emphasizes those physiological considerations in the developing brain which may impact the outcome after ABI, including, the cellular mechanisms of neuronal and cerebrovascular endothelial cell injury, ABI outcome and future therapeutic directions.

Rapid analytical methods for on-site triage for traumatic brain injury

Traumatic brain injury (TBI) results from an event that causes rapid acceleration and deceleration of the brain or penetration of the skull with an object. Responses to stimuli and questions, loss of consciousness, and altered behavior are symptoms currently used to justify brain imaging for diagnosis and therapeutic guidance. Tests based on such symptoms are susceptible to false-positive and false-negative results due to stress, fatigue, and medications. Biochemical markers of neuronal damage and the physiological response to that damage are being identified. Biosensors capable of rapid measurement of such markers in the circulation offer a solution for on-site triage, as long as three criteria are met: (a) Recognition reagents can be identified that are sufficiently sensitive and specific, (b) the biosensor can provide quantitative assessment of multiple markers rapidly and simultaneously, and (c) both the sensor and reagents are designed for use outside the laboratory.

Involvement of the glycogen synthase kinase-3 signaling pathway in TBI pathology and neurocognitive outcome

BACKGROUND

Traumatic brain injury (TBI) sets in motion cascades of biochemical changes that result in delayed cell death and altered neuronal architecture. Studies have demonstrated that inhibition of glycogen synthase kinase-3 (GSK-3) effectively reduces apoptosis following a number of stimuli. The Wnt family of proteins, and growth factors are two major factors that regulate GSK-3 activity. In the absence of stimuli, GSK-3 is constitutively active and is complexed with Axin, adenomatous polyposis coli (APC), and casein kinase Iα (CK1α) and phosphorylates ß-Catenin leading to its degradation. Binding of Wnt to Frizzled receptors causes the translocation of GSK-3 to the plasma membrane, where it phosphorylates and inactivates the Frizzled co-receptor lipoprotein-related protein 6 (LRP6). Furthermore, the translocation of GSK-3 reduces ß-Catenin phosphorylation and degradation, leading to ß-Catenin accumulation and gene expression. Growth factors activate Akt, which in turn inhibits GSK-3 activity by direct phosphorylation, leading to a reduction in apoptosis.

METHODOLOGY/PRINCIPAL FINDINGS

Using a rodent model, we found that TBI caused a rapid, but transient, increase in LRP6 phosphorylation that is followed by a modest decrease in ß-Catenin phosphorylation. Phospho-GSK-3β immunoreactivity was found to increase three days post injury, a time point at which increased Akt activity following TBI has been observed. Lithium influences several neurochemical cascades, including inhibiting GSK-3. When the efficacy of daily lithium was assessed, reduced hippocampal neuronal cell loss and learning and memory improvements were observed. These influences were partially mimicked by administration of the GSK-3-selective inhibitor SB-216763, as this drug resulted in improved motor function, but only a modest improvement in memory retention and no overt neuroprotection.

CONCLUSION/SIGNIFICANCE

Taken together, our findings suggest that selective inhibition of GSK-3 may offer partial cognitive improvement. As a broad spectrum inhibitor of GSK-3, lithium offers neuroprotection and robust cognitive improvement, supporting its clinical testing as a treatment for TBI.

CSF Bcl-2 and cytochrome C temporal profiles in outcome prediction for adults with severe TBI

The biochemical cascades associated with cell death after traumatic brain injury (TBI) involve both pro-survival and pro-apoptotic proteins. We hypothesized that elevated cerebrospinal fluid (CSF) Bcl-2 and cytochrome C (CytoC) levels over time would reflect cellular injury response and predict long-term outcomes after TBI. Cerebrospinal fluid Bcl-2 and CytoC levels were measured for 6 days after injury for adults with severe TBI (N=76 subjects; N=277 samples). Group-based trajectory analysis was used to generate distinct temporal biomarker profiles that were compared with Glasgow Outcome Scale (GOS) and Disability Rating Scale (DRS) scores at 6 and 12 months after TBI. Subjects with persistently elevated temporal Bcl-2 and CytoC profiles compared with healthy controls had the worst outcomes at 6 and 12 months (P≤0.027). Those with CytoC profiles near controls had better long-term outcomes, and those with declining CytoC levels over time had intermediate outcomes. Subjects with Bcl-2 profiles that remained near controls had better outcomes than those with consistently elevated Bcl-2 profiles. However, subjects with Bcl-2 values that started near controls and steadily rose over time had 100% good outcomes by 12 months after TBI. These results show the prognostic value of Bcl-2 and CytoC profiles and suggest a dynamic apoptotic and pro-survival response to TBI.

Necroptosis: biochemical, physiological and pathological aspects

Programmed cell death is a key component of tissue homeostasis, normal development and wide variety of diseases. Conventional view refers to programmed cell death form as caspase-mediated apoptosis while necrosis is considered as an accidental and unwanted cell demise, carried out in a non-regulated manner and caused by extreme conditions. However, accumulating evidences indicate that necrotic cell death can also be a regulated process. The term necroptosis has been introduced to describe a cell death receptor-induced, caspase-independent, highly regulated type of programmed cell death process with morphological resemblance of necrosis. Necroptosis recently has been found to contribute to a wide range of pathologic cell death forms including ischemic brain injury, neurodegenerative diseases and viral infection, therefore a better understanding of the necroptotic signaling machinery has clinical relevance.

Systems-scale analysis reveals pathways involved in cellular response to methamphetamine

Background

Methamphetamine (METH), an abused illicit drug, disrupts many cellular processes, including energy metabolism, spermatogenesis, and maintenance of oxidative status. However, many components of the molecular underpinnings of METH toxicity have yet to be established. Network analyses of integrated proteomic, transcriptomic and metabolomic data are particularly well suited for identifying cellular responses to toxins, such as METH, which might otherwise be obscured by the numerous and dynamic changes that are induced.

Methodology/Results

We used network analyses of proteomic and transcriptomic data to evaluate pathways in Drosophila melanogaster that are affected by acute METH toxicity. METH exposure caused changes in the expression of genes involved with energy metabolism, suggesting a Warburg-like effect (aerobic glycolysis), which is normally associated with cancerous cells. Therefore, we tested the hypothesis that carbohydrate metabolism plays an important role in METH toxicity. In agreement with our hypothesis, we observed that increased dietary sugars partially alleviated the toxic effects of METH. Our systems analysis also showed that METH impacted genes and proteins known to be associated with muscular homeostasis/contraction, maintenance of oxidative status, oxidative phosphorylation, spermatogenesis, iron and calcium homeostasis. Our results also provide numerous candidate genes for the METH-induced dysfunction of spermatogenesis, which have not been previously characterized at the molecular level.

Conclusion

Our results support our overall hypothesis that METH causes a toxic syndrome that is characterized by the altered carbohydrate metabolism, dysregulation of calcium and iron homeostasis, increased oxidative stress, and disruption of mitochondrial functions.

Early and sustained increase in the expression of hippocampal IGF-1, but not EPO, in a developmental rodent model of traumatic brain injury

Pediatric traumatic brain injury (pTBI) is the leading cause of traumatic death and disability in children in the United States. Impaired learning and memory in these young survivors imposes a heavy toll on society. In adult TBI (aTBI) models, cognitive outcome improved after administration of erythropoietin (EPO) or insulin-like growth factor-1 (IGF-1). Little is known about the production of these agents in the hippocampus, a brain region critical for learning and memory, after pTBI. Our objective was to describe hippocampal expression of EPO and IGF-1, together with their receptors (EPOR and IGF-1R, respectively), over time after pTBI in 17-day-old rats. We used the controlled cortical impact (CCI) model and measured hippocampal mRNA levels of EPO, IGF-1, EPOR, IGF-1R, and markers of caspase-dependent apoptosis (bcl2, bax, and p53) at post-injury days (PID) 1, 2, 3, 7, and 14. CCI rats performed poorly on Morris water maze testing of spatial working memory, a hippocampally-based cognitive function. Apoptotic markers were present early and persisted for the duration of the study. EPO in our pTBI model increased much later (PID7) than in aTBI models (12 h), while EPOR and IGF-1 increased at PID1 and PID2, respectively, similar to data from aTBI models. Our data indicate that EPO expression showed a delayed upregulation post-pTBI, while EPOR increased early. We speculate that administration of EPO in the first 1-2 days after pTBI would increase hippocampal neuronal survival and function.

Autophagy in acute brain injury: feast, famine, or folly?

In the central nervous system, increased autophagy has now been reported after traumatic brain and spinal cord injury, cerebral ischemia, intracerebral hemorrhage, and seizures. This increase in autophagy could be physiologic, converting damaged or dysfunctional proteins, lipids, and/or organelles to their amino acid and fatty acid components for recycling. On the other hand, this increase in autophagy could be supraphysiologic, perhaps consuming and eliminating functional proteins, lipids, and/or organelles as well. Whether an increase in autophagy is beneficial (feast) or detrimental (famine) in brain likely depends on both the burden of intracellular substrate targeted for autophagy and the capacity of the cell's autophagic machinery. Of course, increased autophagy observed after brain injury could also simply be an epiphenomenon (folly). These divergent possibilities have clear ramifications for designing therapeutic strategies targeting autophagy after acute brain injury and are the subject of this review. This article is part of a Special Issue entitled "Autophagy and protein degradation in neurological diseases."

BCL2 genotypes: functional and neurobehavioral outcomes after severe traumatic brain injury

Traumatic brain injury (TBI) triggers a cascade of apoptotic-related events that include BCL2 expression, a pro-survival protein in the apoptosis pathway. The purpose of this study was to use tagging single nucleotide polymorphism (tSNP) genotypes to screen the BCL2 gene to determine if genetic variability in the BCL2 gene influences outcomes in 205 patients with severe TBI. Outcomes (Glasgow Outcome Scale [GOS], Disability Rating Scale [DRS], mortality, and Neurobehavioral Rating Scale-Revised [NRS-R]) were analyzed at 3, 6, 12, and 24 months. Multivariate analysis demonstrates that there were four tSNPs of significant interest: rs17759659, rs1801018, rs7236090, and rs949037. Presence of the variant allele for rs17759659 was associated with poorer outcomes (GOS p = 0.001; DRS p = 0.002), higher mortality (p = 0.02; OR = 4.23; CI 1.31,13.61), and worse NRS-R scores (p = 0.05). Presence of the variant allele for rs1801018 was associated with poorer outcomes (GOS p = 0.02; DRS p = 0.009), and mortality (p = 0.03; OR = 3.86; CI 1.18,12.59). Being homozygous for the wild-type allele for rs7236090 was associated with favorable outcomes on the NRS-R (p = 0.007), while homozygosity for the variant genotype was associated with favorable outcomes on the GOS (p = 0.007) and DRS (p = 0.006). The homozygous variant for rs949037 was associated with favorable outcomes (GOS p = 0.04; DRS p = 0.03), and the homozygous wild-type was associated with increased mortality at 3 months (p = 0.005; OR = 3.67; CI 1.08,12.49). The only finding that stood up to Bonferroni correction was rs17759659 for GOS. These data support the possibility that genetic variability for pro-survival proteins, particularly genetic variation in the BCL2 gene, impacts outcomes after severe TBI.

Neuroprotective effect and cognitive outcome of chronic lithium on traumatic brain injury in mice

In vitro and in vivo studies have demonstrated that lithium treatment can protect neurons against excitotoxic and ischemic damage. Yet the possible beneficial effect of chronic low dose lithium on a model of traumatic brain injury (TBI) has not been intensively investigated. In this study, lithium (1 mmol/kg) was given daily, intraperitonealy, for 14 days before the onset of moderate controlled TBI and was continued until the mice were sacrificed. The results showed that in brain injured animals, chronic lithium treatment attenuated the loss of hemispheric tissue, cerebral edema and the expression of pro-inflammatory cytokine interleukin-1β. The neuronal degeneration in hippocampal CA3 and dentate gyrus sub-regions was also attenuated in the chronic lithium-treated mice as shown by Fluoro-Jade B staining. Moreover, chronic lithium treatment enhanced spatial learning and memory performance of injured mice in the Morris water maze. Our current study extended the protective role of lithium in the model of TBI and suggested that chronic lithium treatment might be a helpful therapeutic strategy for brain injury with multiple beneficial effects.

Valproate administered after traumatic brain injury provides neuroprotection and improves cognitive function in rats

BACKGROUND

Traumatic brain injury (TBI) initiates a complex series of neurochemical and signaling changes that lead to pathological events including neuronal hyperactivity, excessive glutamate release, inflammation, increased blood-brain barrier (BBB) permeability and cerebral edema, altered gene expression, and neuronal dysfunction. It is believed that a drug combination, or a single drug acting on multiple targets, may be an effective strategy to treat TBI. Valproate, a widely used antiepileptic drug, has a number of targets including GABA transaminase, voltage-gated sodium channels, glycogen synthase kinase (GSK)-3, and histone deacetylases (HDACs), and therefore may attenuate a number of TBI-associated pathologies.

METHODOLOGY/PRINCIPAL FINDINGS

Using a rodent model of TBI, we tested if post-injury administration of valproate can decrease BBB permeability, reduce neural damage and improve cognitive outcome. Dose-response studies revealed that systemic administration of 400 mg/kg (i.p.), but not 15, 30, 60 or 100 mg/kg, increases histone H3 and H4 acetylation, and reduces GSK-3 activity, in the hippocampus. Thirty min post-injury administration of 400 mg/kg valproate improved BBB integrity as indicated by a reduction in Evans Blue dye extravasation. Consistent with its dose response to inhibit GSK-3 and HDACs, valproate at 400 mg/kg, but not 100 mg/kg, reduced TBI-associated hippocampal dendritic damage, lessened cortical contusion volume, and improved motor function and spatial memory. These behavioral improvements were not observed when SAHA (suberoylanilide hydroxamic acid), a selective HDAC inhibitor, was administered.

CONCLUSION/SIGNIFICANCE

Our findings indicate that valproate given soon after TBI can be neuroprotective. As clinically proven interventions that can be used to minimize the damage following TBI are not currently available, the findings from this report support the further testing of valproate as an acute therapeutic strategy.

Effect of endogenous androgens on 17beta-estradiol-mediated protection after spinal cord injury in male rats

Several groups have recently shown that 17beta-estradiol is protective in spinal cord injury (SCI). Testosterone can be aromatized to 17beta-estradiol and may increase estrogen-mediated protection. Alternatively, testosterone has been shown to increase excitotoxicity in models of central nervous system (CNS) injury. These experiments test the hypothesis that endogenous testosterone in male rats alters 17beta-estradiol-mediated protection by evaluating a delayed administration over a clinically relevant dose range and manipulating testicular-derived testosterone. Adult male Sprague Dawley rats were either gonadectomized or left gonad-intact prior to SCI. SCI was produced by a midthoracic crush injury. At 30 min post SCI, animals received a subcutaneous pellet of 0.0, 0.05, 0.5, or 5.0 mg of 17beta-estradiol, released over 21 days. Hindlimb locomotion was analyzed weekly in the open field. Spinal cords were collected and analyzed for cell death, expression of Bcl-family proteins, and white-matter sparing. Post-SCI administration of the 0.5- or 5.0-mg pellet improved hindlimb locomotion, reduced urinary bladder size, increased neuronal survival, reduced apoptosis, improved the Bax/Bcl-xL protein ratio, and increased white-matter sparing. In the absence of endogenous testicular-derived androgens, SCI induced greater apoptosis, yet 17beta-estradiol administration reduced apoptosis to the same extent in gonadectomized and gonad-intact male rats. These data suggest that delayed post-SCI administration of a clinically relevant dose of 17beta-estradiol is protective in male rats, and endogenous androgens do not alter estrogen-mediated protection. These data suggest that 17beta-estradiol is an effective therapeutic intervention for reducing secondary damage after SCI in males, which could be readily translated to clinical trials.

Blood-brain barrier breakdown as a therapeutic target in traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of death in young adults and children. The treatment of TBI in the acute phase has improved substantially; however, the prevention and management of long-term complications remain a challenge. Blood-brain barrier (BBB) breakdown has often been documented in patients with TBI, but the role of such vascular pathology in neurological dysfunction has only recently been explored. Animal studies have demonstrated that BBB breakdown is involved in the initiation of transcriptional changes in the neurovascular network that ultimately lead to delayed neuronal dysfunction and degeneration. Brain imaging data have confirmed the high incidence of BBB breakdown in patients with TBI and suggest that such pathology could be used as a biomarker in the clinic and in drug trials. Here, we review the neurological consequences of TBI, focusing on the long-term complications of such injuries. We present the clinical evidence for involvement of BBB breakdown in TBI and examine the primary and secondary mechanisms that underlie such pathology. We go on to consider the consequences of BBB injury, before analyzing potential mechanisms linking vascular pathology to neuronal dysfunction and degeneration, and exploring possible targets for treatment. Finally, we highlight areas for future basic research and clinical studies into TBI.

Heat acclimation provides sustained improvement in functional recovery and attenuates apoptosis after traumatic brain injury

Heat acclimation (HA) offers functional neuroprotection in mice after traumatic brain injury (TBI). This study further characterizes endogenous neuroprotection acquired by HA (34+/-1 degrees C, 30 d) after TBI. We establish here the ability of HA to induce sustained functional benefits and to reduce activation of apoptotic pathways. Neurobehavioral recovery, assessed by the Neurological Severity Score, was greater in HA mice up to 8 days after injury as compared with normothermic controls (P<0.05) and lesion volume was also smaller in the HA group (P<0.05). Reduced apoptotic cell death in HA mice was confirmed using caspase-3 activity measurements and immunohistochemistry. To investigate the underlying molecular pathways, expression levels of intrinsic apoptotic pathway-related proteins were examined. HA mice displayed higher mitochondrial levels of antiapoptotic Bcl-xL, accompanied by lower proapoptotic Bad levels and decreased cytochrome c release, suggesting a higher apoptotic threshold. Taken together with our previous reports, indicating increased Akt phosphorylation and antioxidative capacity, alongside with reduced tumor necrosis alpha levels after TBI in HA animals, the current results support the involvement of an antiapoptotic effect in HA-induced neuroprotection. Current results warrant further study as TBI-induced apoptosis may persist over weeks after injury, possibly providing a target for belated therapeutic intervention.

Traumatic brain injury: an overview of pathobiology with emphasis on military populations

This review considers the pathobiology of non-impact blast-induced neurotrauma (BINT). The pathobiology of traumatic brain injury (TBI) has been historically studied in experimental models mimicking features seen in the civilian population. These brain injuries are characterized by primary damage to both gray and white matter and subsequent evolution of secondary pathogenic events at the cellular, biochemical, and molecular levels, which collectively mediate widespread neurodegeneration. An emerging field of research addresses brain injuries related to the military, in particular blast-induced brain injuries. What is clear from the effort to date is that the pathobiology of military TBIs, particularly BINT, has characteristics not seen in other types of brain injury, despite similar secondary injury cascades. The pathobiology of primary BINT is extremely complex. It comprises systemic, local, and cerebral responses interacting and often occurring in parallel. Activation of the autonomous nervous system, sudden pressure-increase in vital organs such as lungs and liver, and activation of neuroendocrine-immune system are among the most important mechanisms significantly contributing to molecular changes and cascading injury mechanisms in the brain.

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

In this investigation, we evaluated the effect of post-traumatic mild hypothermia on cell death in the hippocampus after fluid percussion traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were randomly divided into three groups (n = 40/group): TBI with hypothermia treatment (32 degrees C), TBI with normothermia (37 degrees C), and sham injury. The TBI model was induced by a fluid percussion TBI device. Mild hypothermia (32 degrees C) was achieved by partial immersion in a water bath (0 degrees C) under general anesthesia for 4h. All rats were killed at 24 or 72h after TBI. The ipsilateral hippocampal CA1 in all rats were analyzed by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL), and 4',6-diamidino-2-phenylindole (DAPI) staining for determining cell death. Caspase-3 expression was examined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. At 24h, based on TUNEL and DAPI results, the cell death index was 28.80 +/- 2.60% and 32.10 +/- 1.40% in the normothermia TBI group, while reaching only 14.30 +/- 2.70% and 18.40 +/- 2.10% in the hypothermic TBI group (p < 0.01). Based on RT-PCR and Western blotting results, the expression of caspase-3 was 210.20 +/- 5.30% and 170.30 +/- 4.80% in the normothermic TBI group, while reaching only 165.10 +/- 3.70% and 130.60 +/- 4.10% in the hypothermic TBI group (p < 0.05). At 72h, based on TUNEL and DAPI results, the cell death index was 20.80 +/- 2.50% and 25.50 +/- 1.80% in the normothermic TBI group, while reaching only 10.20 +/- 2.60% and 15.50 +/- 2.10% in the hypothermic TBI group (p < 0.01). Based on RT-PCR and Western blotting results, the expression of caspase-3 was 186.20 +/- 6.20% and 142.30 +/- 5.10% in the normothermic TBI group, versus only 152.10 +/- 3.60% and 120.60 +/- 3.90% in the hypothermic TBI group (p < 0.05). Based on our findings, we conclude that post-traumatic hypothermia significantly attenuates cell death within the hippocampus following fluid percussion injury. Taken together with other studies, these observations support the premise that post-traumatic mild hypothermia can provide cerebral protection for patients with TBI.

c-Jun N-terminal kinase pathway activation in human and experimental cerebral contusion

The c-Jun N-terminal kinase (JNK) pathway is involved in cell stress and apoptosis. We tested the hypothesis that this pathway plays a role in traumatic brain injury (TBI) by assessing JNK activation in human brain tissues and in brains of mice subjected to controlled cortical impact brain injury. We also assessed the effects of specific inhibition of the JNK pathway by the cell-permeable JNK inhibitor peptide, D-JNKI1, on neurobehavioral function and posttraumatic cell loss in mice. The inhibitor was administered intraperitoneally 10 minutes after injury. The JNK pathway showed robust activation both in human contusion specimens and in injured cortex and hippocampi of TBI-injured mice, 1, 4, and 48 hours after injury. D-JNKI1 treatment significantly improved motor performance at 48 hours and 7 days after injury and reduced the contusion volume compared with saline treatment; the numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were significantly decreased in the hippocampi of injured mice 48 hours after treatment. Thus, because the JNK pathway is activated after human and experimental TBI and the inhibitor peptide D-JNKI1 affords significant neuroprotection and amelioration of neurobehavioral deficits after experimental TBI, therapeutic targeting of the JNK activation pathway may hold promise for future clinical applications.

Proteomic biomarkers for blast neurotrauma: targeting cerebral edema, inflammation, and neuronal death cascades

Proteomics for blast traumatic brain injury (bTBI) research represents an exciting new approach that can greatly help to address the complex pathology of this condition. Antibody-based platforms, antibody microarrays (AbMA), and reverse capture protein microarrays (RCPM) can complement the classical methods based on 2D gel electrophoresis and mass spectrometry (2DGE/MS). These new technologies can address problematic issues, such as sample complexity, sensitivity, quantitation, reproducibility, and analysis time, which are typically associated with 2DGE/MS. Combined with bioinformatics analysis and interpretation of primary microarray data, these methods will generate a new level of understanding about bTBI at the level of systems biology. As biological and clinical knowledge and the availability of these systems become more widely established, we expect that AbMA and RCPM will be used routinely in clinical diagnostics, and also for following therapeutic progress. At the technical level, we anticipate that these platforms will evolve to accommodate comprehensive, high-speed, label-free analysis on a human proteome-wide scale.

Histone deactylase inhibition combined with behavioral therapy enhances learning and memory following traumatic brain injury

Traumatic brain injury (TBI) induces a number of pathological events ranging from neuronal degeneration and tissue loss to impaired neuronal plasticity and neurochemical dysregulation. In rodents, exposure of brain-injured animals to environmental enrichment has been shown to be an effective means of enhancing learning and memory post-injury. Recently, it has been discovered that environmental enrichment may enhance neuronal plasticity through epigenetic changes that involve enhanced histone acetylation, a property that can be mimicked by the use of histone deactylase (HDAC) inhibitors. We therefore evaluated the consequences of the HDAC inhibitor sodium butyrate on the learning and memory of brain-injured mice. In contrast to a previous report using a mouse neurodegeneration model, sodium butyrate (1.2 g/kg daily for four weeks) did not improve learning and memory when tested after the completion of the drug treatment paradigm. In addition, sodium butyrate administration during the reported period of neurodegeneration (days 0-5) also offered no benefit. However, when administered concurrently with training in the Morris water maze task (beginning on day 14 post-injury), sodium butyrate improved learning and memory in brain-injured mice. Interestingly, when these mice were subsequently tested in an associative fear conditioning task, an improvement was observed. Taken together, our findings indicate that HDAC inhibition may mimic some of the cognitive improvements seen following enriched environment exposure, and that the improvement is observed when the treatment is carried out current with behavioral testing.

Sex differences in XIAP cleavage after traumatic brain injury in the rat

Sex influences histological and behavioral outcomes following traumatic brain injury (TBI), but the underlying sex-dependent pathomechanisms regulating outcome measures remain poorly defined. Here, we investigated the TBI-induced regulation of the X-linked inhibitor of apoptosis protein (XIAP) that, in addition to suppressing cell death by inhibition of caspases, is involved in signaling cascades, including immune regulation and cell migration. Since estrogen has been shown to have anti-apoptotic properties, we specifically examined sex differences and the influence of estrogen on XIAP processing after TBI. Sprague-Dawley male (TBI-M), female (TBI-F), ovariectomized female (TBI-OVX) and ovariectomized females supplemented with estrogen (TBI-OVX+EST) were subjected to moderate (1.7-2.2atm) fluid percussion (FP) injury. Animals were sacrificed 24h after FP injury; cortical tissue (ipsilateral and contralateral) was dissected and analyzed for XIAP processing by immunoblot analysis (n=6-7/group) or confocal microscopy (n=2-3/group). Significant differences in XIAP cleavage products in the ipsilateral cortex were found between groups (p<0.03). Post hoc analysis showed an increase in XIAP processing in both TBI-F and TBI-OVX+EST compared to TBI-M and TBI-OVX (p<0.05), indicating that more XIAP is cleaved following injury in intact females and TBI-OVX+EST than in TBI-M and TBI-OVX groups. Co-localization of XIAP within neurons also demonstrated sex-dependent changes. Based on these data, it appears that the processing of XIAP after injury is different between males and females and may be influenced by exogenous estrogen treatment.

Melatonin reduces induction of Bax, caspase and cell death in methamphetamine-treated human neuroblastoma SH-SY5Y cultured cells

Several studies demonstrated that methamphetamine (MA)-treated human neuroblastoma cells exhibit increased oxidative stress, which regulates intracellular signaling cascades leading to cell death. Melatonin has a potential as a direct free radical scavenger and protects against cell death caused by MA. The objective of this study was to investigate the neuroprotective properties of melatonin on MA-induced induction of death signaling cascade and neuronal cell degeneration in human neuroblastoma SH-SY5Y cultured cells. The results of the present study demonstrate that MA significantly reduced cell viability in SH-SY5Y cultured cells. Desipramine, a monoamine uptake blocker, and melatonin reversed the toxic effect of MA in reducing cell viability. Induction of Bax, Bcl-2 and cleaved caspase-3 protein levels were observed in SH-SY5Y cultured cells treated with MA, whereas the induction of Bax and cleaved caspase-3 was diminished by melatonin. Visualization of the induction of Bax using immunofluorescence but a reduction in mitochondrial sites using red-fluorescent mitochondria-staining dye was more obviously apparent in MA-treated cells than in untreated control cells and, again, this effect was abolished by melatonin. These findings demonstrate important roles of Bax and caspase in death signaling cascade, and the protective effects of melatonin in MA-treated SH-SY5Y cells.

Amyloid precursor protein secretases as therapeutic targets for traumatic brain injury

Amyloid-beta (Abeta) peptides, found in Alzheimer's disease brain, accumulate rapidly after traumatic brain injury (TBI) in both humans and animals. Here we show that blocking either beta- or gamma-secretase, enzymes required for production of Abeta from amyloid precursor protein (APP), can ameliorate motor and cognitive deficits and reduce cell loss after experimental TBI in mice. Thus, APP secretases are promising targets for treatment of TBI.