Cognitive Effects of Astaxanthin Pretreatment on Recovery From Traumatic Brain Injury

Traumatic brain injury (TBI), caused by mechanical impact to the brain, is a leading cause of death and disability among young adults, with slow and often incomplete recovery. Preemptive treatment strategies may increase the injury resilience of high-risk populations such as soldiers and athletes. In this work, the xanthophyll carotenoid Astaxanthin was examined as a potential nutritional preconditioning method in mice (sabra strain) to increase their resilience prior to TBI in a closed head injury (CHI) model. The effect of Astaxanthin pretreatment on heat shock protein (HSP) dynamics and functional outcome after CHI was explored by gavage or free eating (in pellet form) for 2 weeks before CHI. Assessment of neuromotor function by the neurological severity score (NSS) revealed significant improvement in the Astaxanthin gavage-treated group (100 mg/kg, ATX) during recovery compared to the gavage-treated olive oil group (OIL), beginning at 24 h post-CHI and lasting throughout 28 days (p < 0.007). Astaxanthin pretreatment in pellet form produced a smaller improvement in NSS vs. posttreatment at 7 days post-CHI (p < 0.05). Cognitive and behavioral evaluation using the novel object recognition test (ORT) and the Y Maze test revealed an advantage for Astaxanthin administration via free eating vs. standard chow during recovery post-CHI (ORT at 3 days, p < 0.035; improvement in Y Maze score from 2 to 29 days, p < 0.02). HSP profile and anxiety (open field test) were not significantly affected by Astaxanthin. In conclusion, astaxanthin pretreatment may contribute to improved recovery post-TBI in mice and is influenced by the form of administration.

Nerve growth factor plays a role in the neurotherapeutic effect of a CD45+ pan-hematopoietic subpopulation derived from human umbilical cord blood in a traumatic brain injury model

BACKGROUND AIMS

Human umbilical cord blood (HUCB) is an important source of stem cells for therapy of hematopoietic disorders and is a potential therapy for various neurological disorders, including traumatic brain injury (TBI). The expression of nerve growth factor (NGF) and its receptors TrkA, p75^NTR and α9β1 integrin on an HUCB CD45⁺ pan-hematopoietic subpopulation was investigated in the context of its neurotherapeutic potential after TBI.

METHODS

NGF and its receptors were detected on CD45⁺ cells by reverse transcriptase polymerase chain reaction, flow cytometry analysis and confocal microscopy. CD45⁺ cells were stimulated by TBI brain extracts, and NGF levels were measured by enzyme-linked immunosorbent assay. TBI mice were divided into six groups for xenogeneic intravenous transplantation, 1 day post-trauma, with 1 × 10⁶ CD45⁺ cells untreated or treated with the anti-NGF neutralizing antibody K252a, a TrkA antagonist; VLO5, an α9β1 disintegrin; or negative (vehicle) and positive (NGF) controls.

RESULTS

The HUCB CD45⁺ subpopulation constitutively expresses NGF and its receptors, mainly TrkA and p75^NTR and minor levels of α9β1. In vitro experiments provided evidence that trauma-related mediators from brain extracts of TBI mice induced release of NGF from HUCB CD45⁺ cell cultures. HUCB CD45⁺ cells induced a neurotherapeutic effect in TBI mice, abrogated by cell treatment with either anti-NGF antibody or K252a, but not VLO5.

CONCLUSIONS

These findings strengthen the role of NGF and its TrkA receptor in the HUCB CD45⁺ subpopulation's neurotherapeutic effect. The presence of neurotrophin receptors in the HUCB CD45⁺ pan-hematopoietic subpopulation may explain the neuroprotective effect of cord blood in therapy of a variety of neurological disorders.

Are the endocannabinoid-like compounds N-acyl aminoacids neuroprotective after traumatic brain injury?

In recent years, a library of approx. 70 N-acyl aminoacids (NAAAs) was discovered in the rat brain. A particular member of this family of compounds is arachidonoyl serine (AraS), which has generated special interest as a potential therapy for traumatic brain injury (TBI). This is due to its structural similarity to the endocannabinoid (eCB) 2-arachidonoyl glycerol (2-AG), which was previously shown to be beneficial in the recovery in a closed head injury model of TBI. Indeed, AraS exerted eCB-mediated neuroprotection, which was evident in numerous aspects related to the secondary damage characterizing TBI. These findings promoted broadening of the research to additional compounds of the NAAA family that share a structural similarity to AraS, namely, palmitoyl serine (PalmS) and oleoyl serine. The latter did not exhibit any improvement in recovery, whereas the former displayed some neuroprotection, albeit inferior to 2-AG and AraS, via unknown mechanisms. Interestingly, when a combined treatment of 2-AG, AraS and PalmS was tested, the overall effect on the severity score was inferior to their individual effects, suggesting not only a lack of direct or indirect synergism, but also possibly some spatial hindrance. Taken together, the complexity of the damage caused by TBI and the many open questions concerning the role of the eCB system in health and disease, the findings so far may serve as a small trace to the understanding of the eCB system, as well as of the mechanisms underlying TBI.

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

Correction to: Journal of Cerebral Blood Flow and Metabolism (2010) 30, 616–627; doi:10.1038/jcbfm.2009.234; published online 11 November 2009.

Following the publication of this article, the authors noticed that Dr Umschweif was misspelled. The complete and correct author names appear above.

Neuroprotection after traumatic brain injury in heat-acclimated mice involves induced neurogenesis and activation of angiotensin receptor type 2 signaling

Long-term exposure of mice to mild heat (34°C±1°C) confers neuroprotection against traumatic brain injury (TBI); however, the underling mechanisms are not fully understood. Heat acclimation (HA) increases hypothalamic angiotensin II receptor type 2 (AT2) expression and hypothalamic neurogenesis. Accumulating data suggest that activation of the brain AT2 receptor confers protection against several types of brain pathologies, including ischemia, a hallmark of the secondary injury occurring following TBI. As AT2 activates the same pro-survival pathways involved in HA-mediated neuroprotection (e.g., Akt phosphorylation, hypoxia-inducible factor 1α (HIF-1α), and brain-derived neurotrophic factor (BDNF)), we examined the role of AT2 in HA-mediated neuroprotection after TBI. Using an AT2-specific antagonist PD123319, we found that the improvements in motor and cognitive recovery as well as reduced lesion volume and neurogenesis seen in HA mice were all diminished by AT2 inhibition, whereas no significant alternations were observed in control mice. We also found that nerve growth factor/tropomyosin-related kinase receptor A (TrkA), BDNF/TrkB, and HIF-1α pathways are upregulated by HA and inhibited on PD123319 administration, suggesting that these pathways play a role in AT2 signaling in HA mice. In conclusion, AT2 is involved in HA-mediated neuroprotection, and AT2 activation may be protective and should be considered a novel drug target in the treatment of TBI patients.

Neurotherapeutic effect of cord blood derived CD45+ hematopoietic cells in mice after traumatic brain injury

Treatment of traumatic brain injury (TBI) is still an unmet need. Cell therapy by human umbilical cord blood (HUCB) has shown promising results in animal models of TBI and is under evaluation in clinical trials. HUCB contains different cell populations but to date, only mesenchymal stem cells have been evaluated for therapy of TBI. Here we present the neurotherapeutic effect, as evaluated by neurological score, using a single dose of HUCB-derived mononuclear cells (MNCs) upon intravenous (IV) administration one day post-trauma in a mouse model of closed head injury (CHI). Delayed (eight days post-trauma) intracerebroventricular administration of MNCs showed improved neurobehavioral deficits thereby extending the therapeutic window for treating TBI. Further, we demonstrated for the first time that HUCB-derived pan-hematopoietic CD45 positive (CD45(+)) cells, isolated by magnetic sorting and characterized by expression of CD45 and CD11b markers (96-99%), improved the neurobehavioral deficits upon IV administration, which persisted for 35 days. The therapeutic effect was in a direct correlation to a reduction in the lesion volume and decreased by pre-treatment of the cells with anti-human-CD45 antibody. At the site of brain injury, 1.5-2 h after transplantation, HUCB-derived cells were identified by near infrared scanning and immunohistochemistry using anti-human-CD45 and anti-human-nuclei antibodies. Nerve growth factor and vascular endothelial growth factor levels were differentially expressed in both ipsilateral and contralateral brain hemispheres, thirty-five days after CHI, measured by enzyme-linked immunosorbent assay. These findings indicate the neurotherapeutic potential of HUCB-derived CD45(+) cell population in a mouse model of TBI and propose their use in the clinical setting of human TBI.

Angiotensin receptor type 2 activation induces neuroprotection and neurogenesis after traumatic brain injury

Angiotensin II receptor type 2 (AT(2)) agonists have been shown to limit brain ischemic insult and to improve its outcome. The activation of AT(2) was also linked to induced neuronal proliferation and differentiation in vitro. In this study, we examined the therapeutic potential of AT(2) activation following traumatic brain injury (TBI) in mice, a brain pathology that displays ischemia-like secondary damages. The AT(2) agonist CGP42112A was continuously infused immediately after closed head injury (CHI) for 3 days. We have followed the functional recovery of the injured mice for 35 days post-CHI, and evaluated cognitive function, lesion volume, molecular signaling, and neurogenesis at different time points after the impact. We found dose-dependent improvement in functional recovery and cognitive performance after CGP42112A treatment that was accompanied by reduced lesion volume and induced neurogenesis in the neurogenic niches of the brain and also in the injury region. At the cellular/molecular level, CGP42112A induced early activation of neuroprotective kinases protein kinase B (Akt) and extracellular-regulated kinases ½ (ERK½), and the neurotrophins nerve growth factor and brain-derived neurotrophic factor; all were blocked by treatment with the AT(2) antagonist PD123319. Our results suggest that AT(2) activation after TBI promotes neuroprotection and neurogenesis, and may be a novel approach for the development of new drugs to treat victims of TBI.

Inosine improves functional recovery after experimental traumatic brain injury

Despite years of research, no effective therapy is yet available for the treatment of traumatic brain injury (TBI). The most prevalent and debilitating features in survivors of TBI are cognitive deficits and motor dysfunction. A potential therapeutic method for improving the function of patients following TBI would be to restore, at least in part, plasticity to the CNS in a controlled way that would allow for the formation of compensatory circuits. Inosine, a naturally occurring purine nucleoside, has been shown to promote axon collateral growth in the corticospinal tract (CST) following stroke and focal TBI. In the present study, we investigated the effects of inosine on motor and cognitive deficits, CST sprouting, and expression of synaptic proteins in an experimental model of closed head injury (CHI). Treatment with inosine (100 mg/kg i.p. at 1, 24 and 48 h following CHI) improved outcome after TBI, significantly decreasing the neurological severity score (NSS, p<0.04 vs. saline), an aggregate measure of performance on several tasks. It improved non-spatial cognitive performance (object recognition, p<0.016 vs. saline) but had little effect on sensorimotor coordination (rotarod) and spatial cognitive functions (Y-maze). Inosine did not affect CST sprouting in the lumbar spinal cord but did restore levels of the growth-associated protein GAP-43 in the hippocampus, though not in the cerebral cortex. Our results suggest that inosine may improve functional outcome after TBI.

The role and dynamics of β-catenin in precondition induced neuroprotection after traumatic brain injury

Preconditioning via heat acclimation (34°C 30 d) results in neuroprotection from traumatic brain injury due to constitutive as well as dynamic changes triggered by the trauma. Among these changes is Akt phosphorylation, which decreases apoptosis and induces HIF1α. In the present study we investigated the Akt downstream GSK3β/β -catenin pathway and focused on post injury alternations of β catenin and its impact on the cellular response in preconditioned heat acclimated mice. We found that the reduction in motor disability is accompanied with attenuation of depressive like behavior in heat acclimated mice that correlates with the GSK3β phosphorylation state. Concomitantly, a robust β catenin phosphorylation is not followed by its degradation, or by reduced nuclear accumulation. Enhanced tyrosine phosphorylation of β catenin in the injured area weakens the β catenin-N cadherin complex. Membrane β catenin is transiently reduced in heat acclimated mice and its recovery 7 days post TBI is accompanied by induction of the synaptic marker synaptophysin. We suggest a set of cellular events following traumatic brain injury in heat acclimated mice that causes β catenin to participate in cell-cell adhesion alternations rather than in Wnt signaling. These events may contribute to synaptogenesis and the improved motor and cognitive abilities seen heat acclimated mice after traumatic brain injury.

Carvacrol together with TRPC1 elimination improve functional recovery after traumatic brain injury in mice

Death of Central Nervous System (CNS) neurons following traumatic brain injury (TBI) is a complex process arising from a combination of factors, many of which are still unknown. It has been found that inhibition of transient receptor potential (TRP) channels constitutes an effective strategy for preventing death of CNS neurons following TBI. TRP channels are classified into seven related subfamilies, most of which are Ca(2+) permeable and involved in many cellular functions, including neuronal cell death. We hypothesized that TRP channels of the TRPC subfamily may be involved in post-TBI pathophysiology and that the compound 5-isopropyl-2-methylphenol (carvacrol), by inhibition of TRP channels, may exert neuroprotective effect after TBI. To test these suppositions, carvacrol was given to mice after TBI and its effect on their functional recovery was followed for several weeks. Our results show that neurological recovery after TBI was significantly enhanced by application of carvacrol. To better define the type of the specific channel involved, the effect of carvacrol on the extent and speed of recovery after TBI was compared among mice lacking TRPC1, TRPC3, or TRPC5, relative to wild type controls. We found that neurological recovery after TBI was significantly enhanced by combining carvacrol with TRPC1 elimination, but not by the absence of TRPC3 or TRPC5, showing a synergistic effect between carvacrol application and TRPC1 elimination. We conclude that TRPC1-sensitive mechanisms are involved in TBI pathology, and that inhibition of this channel by carvacrol enhances recovery and should be considered for further studies in animal models and humans.

Near infrared transcranial laser therapy applied at various modes to mice following traumatic brain injury significantly reduces long-term neurological deficits

Near-infrared transcranial laser therapy (TLT) has been found to modulate various biological processes including traumatic brain injury (TBI). Following TBI in mice, in this study we assessed the possibility of various near-infrared TLT modes (pulsed versus continuous) in producing a beneficial effect on the long-term neurobehavioral outcome and brain lesions of these mice. TBI was induced by a weight-drop device, and neurobehavioral function was assessed from 1 h to 56 days post-trauma using the Neurological Severity Score (NSS). The extent of recovery is expressed as the difference in NSS (dNSS), the difference between the initial score and that at any other later time point. An 808-nm Ga-Al-As diode laser was employed transcranially 4, 6, or 8 h post-trauma to illuminate the entire cortex of the brain. Mice were divided into several groups of 6-8 mice: one control group that received a sham treatment and experimental groups that received either TLT continuous wave (CW) or pulsed wave (PW) mode transcranially. MRI was taken prior to sacrifice at 56 days post-injury. From 5-28 days post-TBI, the NSS of the laser-treated mice were significantly lower (p<0.05) than those of the non-laser-treated control mice. The percentage of surviving mice that demonstrated full recovery at 56 days post-CHI (NSS=0, as in intact mice) was the highest (63%) in the group that had received TLT in the PW mode at 100 Hz. In addition, magnetic resonance imaging (MRI) analysis demonstrated significantly smaller infarct lesion volumes in laser-treated mice compared to controls. Our data suggest that non-invasive TLT of mice post-TBI provides a significant long-term functional neurological benefit, and that the pulsed laser mode at 100 Hz is the preferred mode for such treatment.

The anti-inflammatory drug carprofen improves long-term outcome and induces gliogenesis after traumatic brain injury

Traumatic brain injury (TBI) initiates acute and chronic inflammatory processes involving cyclooxygenase-2 (COX-2), which may have detrimental effects on outcome and especially on brain regeneration. Therefore we aimed to study whether carprofen, a COX-2 inhibitor, would improve outcome and increase neurogenesis after TBI. TBI was induced in Sabra mice that were then treated with vehicle or carprofen for 7 days. Functional outcome was evaluated with the Neurological Severity Score (NSS).Cytokine levels were assessed 4 h post-TBI and water content was measured 24 h post TBI. Mice were given BrdU to label newborn cells for 10 days. The animals were killed 90 days post-TBI and the lesion size as well as newborn cell fate were assessed. Carprofen significantly reduced lesion size (p=0.002), decreased water content in the lesioned cortex (p=0.03), reduced the number of microglia in the lesioned cortex (p<0.0001), and lowered the levels of proinflammatory cytokines (IL-1β, p=0.03; IL-6, p=0.02). Carprofen led to significantly larger improvements in functional outcome (p≤0.008) which were durable over 90 days. Carprofen also induced a threefold increase in the proliferation of new cells in the peri-lesion area (p≤0.002), but newborn cells differentiated mainly into glia in both groups. Carprofen is neuroprotective and induces cell proliferation and gliogenesis after TBI. Treatment with carprofen is consistently associated with better functional outcome. Our results imply that anti-inflammatory drugs may represent novel therapeutic options for TBI.

N-arachidonoyl-L-serine is neuroprotective after traumatic brain injury by reducing apoptosis

N-arachidonoyl-L-serine (AraS) is a brain component structurally related to the endocannabinoid family. We investigated the neuroprotective effects of AraS following closed head injury induced by weight drop onto the exposed fronto-parietal skull and the mechanisms involved. A single injection of AraS following injury led to a significant improvement in functional outcome, and to reduced edema and lesion volume compared with vehicle. Specific antagonists to CB2 receptors, transient receptor potential vanilloid 1 (TRPV1) or large conductance calcium-activated potassium (BK) channels reversed these effects. Specific binding assays did not indicate binding of AraS to the GPR55 cannabinoid receptor. N-arachidonoyl-L-serine blocked the attenuation in phosphorylated extracellular-signal-regulated kinase 1/2 (ERK) levels and led to an increase in pAkt in both the ipsilateral and contralateral cortices. Increased levels of the prosurvival factor Bcl-xL were evident 24 hours after injury in AraS-treated mice, followed by a 30% reduction in caspase-3 activity, measured 3 days after injury. Treatment with a CB2 antagonist, but not with a CB1 antagonist, reversed this effect. Our results suggest that administration of AraS leads to neuroprotection via ERK and Akt phosphorylation and induction of their downstream antiapoptotic pathways. These protective effects are related mostly to indirect signaling via the CB2R and TRPV1 channels but not through CB1 or GPR55 receptors.

Regional sensitivity to neuroinflammation: in vivo and in vitro studies

BACKGROUND

Neuroinflammation is involved in several acute-onset neuropathologies such as meningitis, encephalitis, stroke, and traumatic brain injury as well as in neurodegenerative diseases. All of these patholologies are associated with cognitive deficits. Using a model of pure neuroinflammation (intracisternal injection of endotoxin in mice), we tested the hypothesis that brain regions involved in cognition are the most vulnerable to inflammatory insults, and this vulnerability is an inherent property of neocortical neurons.

METHODS

Mice (n = 10/group) injected with endotoxin (LPS) or saline in the cisterna magna underwent neurobehavioral and cognitive testing followed by quantitative autoradiographic assessment of regional neuroinflammation with [3H]PK11195, an established marker of microgliosis. In parallel, cocultures of cortical and striatal neurons taken from embryonic day 19 rat embryos or postnatal day 1 mice expressing green fluorescent protein were exposed for 24 h to the proinflammatory cytokine TNFalpha, glutamate, or a combination of the two agents.

RESULTS

LPS-treated mice exhibited significant deficits in memory and significant increases in specific PK11195 binding in cortical and hippocampal regions, but not in striatum. Cultured neurons of cortical origin showed significantly lower survival rate relative to striatal neurons in response to TNFalpha, glutamate, or a combination of the two agents. Furthermore, TNFalpha exerted neuroprotective rather than neurotoxic effects in the striatal but not in the cortical neurons.

CONCLUSIONS

These results suggest that the cortex is inherently more sensitive than the striatum to the deleterious effects of neuroinflammation, and may offer an explanation for the preponderance of cognitive deficits in neuropathologies with a neuroinflammatory component.

CD38 facilitates recovery from traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. It causes progressive tissue atrophy and consequent neurological dysfunctions. TBI is accompanied by neuroinflammation, a process mediated largely by microglia. CD38 is an ectoenzyme that promotes transmembrane signaling via the synthesis of potent calcium mobilizing agents or via its receptor activity. CD38 is expressed in the brain in various cell types including microglia. In previous studies, we showed that CD38 regulates microglial activation and response to chemokines. In view of the important role of neuroinflammation in TBI and the effects of CD38 on microglial responses, the present study examines the role of CD38 in the recovery of mice from closed head injury (CHI), a model of focal TBI. For this purpose, CD38-deficient and wild-type (WT) mice were subjected to a similar severity of CHI and the effect of the injury on neurobehavioral and cognitive functions was assessed by the Neurological Severity Score (NSS) and the Object Recognition Test, at various time points post-injury. The results show that recovery after CHI (as indicated by the NSS) was significantly lower in CD38-deficient mice than in WT mice and that the object recognition performance after injury was significantly impaired in injured CD38-deficient mice than in WT mice. In addition, we also observed that the amount of activated microglia/macrophages at the injury site was significantly lower in CD38-deficient mice compared with WT mice. Taken together, our findings indicate that CD38 plays a beneficial role in the recovery of mice from CHI and that this effect is mediated, at least in part, via the effect of CD38 on microglia responses.

D-cycloserine improves functional outcome after traumatic brain injury with wide therapeutic window

It has been long thought that hyperactivation of N-methyl-D-aspartate (NMDA) receptors underlies neurological decline after traumatic brain injury. However, all clinical trials with NMDA receptor antagonists failed. Since NMDA receptors are down-regulated from 4h to 2weeks after brain injury, activation at 24h, rather than inhibition, of these receptors, was previously shown to be beneficial in mice. Here, we tested the therapeutic window, dose regimen and mechanism of action of the NMDA receptor partial agonist D-cycloserine (DCS) in traumatic brain injury. Male mice were subjected to trauma using a weight-drop model, and administered 10mg/kg (i.p.) DCS or vehicle once (8, 16, 24, or 72h) twice (24 and 48h) or three times (24, 48 and 72h). Functional recovery was assessed for up to 60days, using a Neurological Severity Score that measures neurobehavioral parameters. In all groups in which treatment was begun at 24 or 72h neurobehavioral function was significantly better than in the vehicle-treated groups. Additional doses, on days 2 and 3 did not further improve recovery. Mice treated at 8h or 16h post injury did not differ from the vehicle-treated controls. Co-administration of the NMDA receptor antagonist MK-801 completely blocked the protective effect of DCS given at 24h. Infarct volume measured by 2,3,5-triphenyltetrazolium chloride staining at 48h or by cresyl violet at 28days was not affected by DCS treatment. Since DCS is used clinically for other indications, the present study offers a novel approach for treating human traumatic brain injury with a therapeutic window of at least 24h.

Histone deacetylase inhibitor ITF2357 is neuroprotective, improves functional recovery, and induces glial apoptosis following experimental traumatic brain injury

Despite efforts aimed at developing novel therapeutics for traumatic brain injury (TBI), no specific pharmacological agent is currently clinically available. Here, we show that the pan-histone deacetylase (HDAC) inhibitor ITF2357, a compound shown to be safe and effective in humans, improves functional recovery and attenuates tissue damage when administered as late as 24 h postinjury. Using a well-characterized, clinically relevant mouse model of closed head injury (CHI), we demonstrate that a single dose of ITF2357 administered 24 h postinjury improves neurobehavioral recovery from d 6 up to 14 d postinjury (improved neurological score vs. vehicle; P< or =0.05), and that this functional benefit is accompanied by decreased neuronal degeneration, reduced lesion volume (22% reduction vs. vehicle; P< or =0.01), and is preceded by increased acetylated histone H3 levels and attenuation of injury-induced decreases in cytoprotective heat-shock protein 70 kDa and phosphorylated Akt. Moreover, reduced glial accumulation and activation were observed 3 d postinjury, and total p53 levels at the area of injury and caspase-3 immunoreactivity within microglia/macrophages at the trauma area were elevated, suggesting enhanced clearance of these cells via apoptosis following treatment. Hence, our findings underscore the relevance of HDAC inhibitors for ameliorating trauma-induced functional deficits and warrant consideration of applying ITF2357 for this indication.

Targeting cell death in vivo in experimental traumatic brain injury by a novel molecular probe

Traumatic brain injury (TBI) remains a frequent and major challenge in neurological and neurosurgical practice. Apoptosis may play a role in cerebral tissue damage induced by the traumatic insult, and thus its detection and inhibition may advance patient care. DDC (N,N'-didansyl-L-cystine) is a novel fluorescent probe for detection of apoptotic cells. We now report on the performance of DDC in experimental TBI. Closed head injury was induced in mice by weight-drop. DDC was administered intravenously in vivo. Two hours later, animals were sacrificed, and brain tissue was subjected to fluorescent microcopy, for assessment of DDC uptake, in correlation with histopathological assessment of apoptosis by TUNEL and caspase substrates, and also in correlation with the neurological deficits, as assessed by Neurological Severity Score (NSS). Selective uptake of DDC was observed at the primary site of injury, and also at remote sites. Uptake was at the cellular level, with accumulation of DDC in the cytoplasm. Cells manifesting DDC uptake were confirmed as apoptotic cells by detection of the characteristic apoptotic DNA fragmentation (positive TUNEL staining) and detection of activated caspases. The damaged region stained by DDC fluorescence correlated with the severity of neuronal deficits. Our study confirms the role of apoptosis in TBI, and proposes DDC as a useful tool for its selective targeting and detection in vivo. Such imaging of apoptosis, following future radiolabeling of DDC, may advance care for patients with head injury, by allowing real-time evaluation of the extent of tissue damage, assessment of novel therapeutic strategies, and optimization of treatment for the individual patient.

The cannabinoid CB1 receptor regulates bone formation by modulating adrenergic signaling

We have recently reported that in bone the cannabinoid CB1 receptor is present in sympathetic terminals. Here we show that traumatic brain injury (TBI), which in humans enhances peripheral osteogenesis and fracture healing, acutely stimulates bone formation in a distant skeletal site. At this site we demonstrate i) a high level of the main endocannabinoid, 2-arachidonoylglycerol (2-AG), and expression of diacylglycerol lipases, enzymes essential for 2-AG synthesis; ii) that the TBI-induced increase in bone formation is preceded by elevation of the 2-AG and a decrease in norepinephrine (NE) levels. The TBI stimulation of bone formation was absent in CB1-null mice. In wild-type animals it could be mimicked, including the suppression of NE levels, by 2-AG administration. The TBI- and 2-AG-induced stimulation of osteogenesis was restrained by the beta-adrenergic receptor agonist isoproterenol. NE from sympathetic terminals is known to tonically inhibit bone formation by activating osteoblastic beta2-adrenergic receptors. The present findings further demonstrate that the sympathetic control of bone formation is regulated through 2-AG activation of prejunctional CB1. Elevation of bone 2-AG apparently suppresses NE release from bone sympathetic terminals, thus alleviating the inhibition of bone formation. The involvement of osteoblastic CB2 signaling in this process is minimal, if any.

low-level laser therapy applied transcranially to mice following traumatic brain injury significantly reduces long-term neurological deficits

Low-level laser therapy (LLLT) has been evaluated in this study as a potential therapy for traumatic brain injury (TBI). LLLT has been found to modulate various biological processes. Following TBI in mice, we assessed the hypothesis that LLLT might have a beneficial effect on their neurobehavioral and histological outcome. TBI was induced by a weight-drop device, and motor function was assessed 1 h post-trauma using a neurological severity score (NSS). Mice were then divided into three groups of eight mice each: one control group that received a sham LLLT procedure and was not irradiated; and two groups that received LLLT at two different doses (10 and 20 mW/cm(2) ) transcranially. An 808-nm Ga-As diode laser was employed transcranially 4 h post-trauma to illuminate the entire cortex of the brain. Motor function was assessed up to 4 weeks, and lesion volume was measured. There were no significant changes in NSS at 24 and 48 h between the laser-treated and non-treated mice. Yet, from 5 days and up to 28 days, the NSS of the laser-treated mice were significantly lower (p < 0.05) than the traumatized control mice that were not treated with the laser. The lesion volume of the laser treated mice was significantly lower (1.4%) than the non-treated group (12.1%). Our data suggest that a non-invasive transcranial application of LLLT given 4 h following TBI provides a significant long-term functional neurological benefit. Further confirmatory trials are warranted.

D‐cycloserine improves functional recovery and reinstates long‐term potentiation (LTP) in a mouse model of closed head injury

Traumatic brain injury triggers a massive glutamate efflux, activation of NMDA receptor channels, and cell death. Recently, we reported that NMDA receptors in mice are down-regulated from hours to days following closed head injury (CHI), and treatment with NMDA improved recovery of motor and cognitive functions up to 14 d post-injury. Here we show that a single injection of a low dose of D-cycloserine (DCS), a partial NMDA receptor agonist, in CHI mice 24 h post-injury, resulted in a faster and greater recovery of motor and memory functions as assessed by neurological severity score and object recognition tests, respectively. Moreover, DCS treatment of CHI mice led to a significant improvement of hippocampal long-term potentiation (LTP) in the CA1 region that was completely blunted in CHI control mice. However, DCS did not improve CHI-induced impairment in synaptic glutamate release measured by paired pulse facilitation (PPF) ratio in hippocampal CA1 region. Finally, CHI-induced reduction of brain-derived neurotrophic factor (BDNF) was fully restored following DCS treatment. Since DCS is in clinical use for other indications, the present study offers a novel approach to treat human brain injury.

Depression induces bone loss through stimulation of the sympathetic nervous system

Major depression is associated with low bone mass and increased incidence of osteoporotic fractures. However, causality between depression and bone loss has not been established. Here, we show that mice subjected to chronic mild stress (CMS), an established model of depression in rodents, display behavioral depression accompanied by impaired bone mass and structure, as portrayed by decreases in trabecular bone volume density, trabecular number, and trabecular connectivity density assessed in the distal femoral metaphysis and L3 vertebral body. Bone remodeling analysis revealed that the CMS-induced skeletal deficiency is accompanied by restrained bone formation resulting from reduced osteoblast number. Antidepressant therapy, which prevents the behavioral responses to CMS, completely inhibits the decrease in bone formation and markedly attenuates the CMS-induced bone loss. The depression-triggered bone loss is associated with a substantial increase in bone norepinephrine levels and can be blocked by the beta-adrenergic antagonist propranolol, suggesting that the sympathetic nervous system mediates the skeletal effects of stress-induced depression. These results define a linkage among depression, excessive adrenergic activity, and reduced bone formation, thus demonstrating an interaction among behavioral responses, the brain, and the skeleton, which leads to impaired bone structure. Together with the common occurrence of depression and bone loss in the aging population, the present data implicate depression as a potential major risk factor for osteoporosis and the associated increase in fracture incidence.

The endocannabinoid 2-AG protects the blood–brain barrier after closed head injury and inhibits mRNA expression of proinflammatory cytokines

Endocannabinoids are involved in neuroprotection through numerous biochemical pathways. We have shown that the endocannabinoid 2-arachidonoyl glycerol (2-AG) is released in mouse brain after closed head injury (CHI), and treatment with exogenous 2-AG exerts neuroprotection via the central cannabinoid receptor CB1. This process involves inhibition of inflammatory signals that are mediated by activation of the transcription factor NF-kB. The present study was designed to examine the effect of 2-AG on the blood-brain barrier (BBB) and the possible inhibition of the early expression of proinflammatory cytokines, which are implicated in BBB disruption. We found that 2-AG decreased BBB permeability and inhibited the acute expression of the main proinflammatory cytokines: TNF-alpha, IL-1beta and IL-6. It also augmented the levels of endogenous antioxidants. We suggest that 2-AG exerts neuroprotection in part by inhibition of the early (1-4 h) inflammatory response and augmentation of the brain reducing power.

Decrease in reducing power of aqueous humor originating from glaucomatous rabbits

AIM

To evaluate changes in the reducing power of aqueous humor (AH) with cyclic voltammetry (CV) and HPLC-EC.

METHODS

NZW Rabbits exhibiting a sporadic mutation causing bilaterally buphthalmus eyes were set for intra ocular pressure (IOP) and eye size measurements. AH was obtained under anesthesia, from congenital glaucomatic rabbits (CGR, n=6) and age-matched controls (CON; n=6). The AH samples were analysed by CV and HPLC-EC.

RESULTS

CGR IOP was found to be significantly higher than in CON (33.5+/-1.1 and 14.2+/-1.0 mmHg, respectively), eye size was 18.25 and 13.9 cm, respectively. CV analysis revealed two anodic currents representing two groups of low molecular weight antioxidant (LMWA). The two anodic potentials were equal for the two tested groups, indicating the same components of LMWA. The first anodic current of CGR was only 30% of the CON rabbits (2.11 vs7.17 microA/mg protein, t-test: P<0.05). As the main hydrophilic components of the first anodic current are known to be uric acid (UA) and ascorbic acid (AA), they were analysed for exact content by HPLC-EC. UA and AA levels were significantly lower in the CGR group (UA: 17.1+/-3.2 and 189.1+/-75.70 microM/mg, AA: 1.1+/-0.3 and 4.8+/-2.0 microM/mg protein respectively).

CONCLUSIONS

Changes in the reducing power, as indicated by CV analysis, of CGR AH, is probably a result of chronic oxidative stress caused by the pathology. The differences in the first anodic wave are mainly due to a fall in the concentration of UA and AA.

Brain injury-dependent expression of activity-dependent neuroprotective protein

Activity-dependent neuroprotective protein (ADNP), a crucial brain development factor, contains a unique sequence, termed NAPVSIPQ, which protects mice against closed head injury (CHI). The aim of this study was to determine whether CHI affects ADNP mRNA expression in the injured brain hemisphere. Male C57JBL/6J mice were subjected to CHI. Brains were removed 5 h, 24 h, 7 d, and 29 d post-CHI. A comparison was made between ADNP mRNA in the injured versus the noninjured hemisphere using real-time polymerase chain reaction. A nonsignificant change (p >0.05) was found 5 h, 24 h, and 7 d post-CHI. However, a significant increase (p <0.05) in ADNP mRNA expression was detected in the injured cerebral hemisphere 29 d post-CHI. The data presented may be associated with ADNP's crucial involvement in brain development and response to injury.

The influence of the peptide NAP on Mac-1-deficient mice following closed head injury

A single administration of the neuroprotective peptide NAP was previously shown to protect against death associated with closed head injury (CHI) and enhance recovery of the surviving mice. The protective effect was accompanied by down-regulation of the relative mRNA content of the complement receptor 3 (Mac-1, a marker for inflammation) as measured about a month after the injury. In contrast, the mRNA transcripts for activity-dependent neuroprotective protein (ADNP, the NAP containing protein) were shown to increase 29 days post CHI in the injured hemisphere of Mac-1 expressing mice. The present study was set out to investigate: (1) are Mac-1-deficient mice less susceptible to the adverse outcome of traumatic head injury; (2) does NAP treatment affect Mac-1-deficient mice subjected to head injury; and (3) is Mac-1 expression associated with ADNP expression. Results showed that (1) Mac-1-deficient mice were partially protected against death associated with severe head injury as compared to Mac-1 expressing mice. (2) Significant protection against death was observed in NAP-treated mice and an increase in recovery was observed in the NAP-treated Mac-1 mice 4 weeks after injury. (3) ADNP expression did not change in the Mac-1-deficient mice following head injury. Our working hypothesis is that a month following injury, gene expression in the injured brain is altered and competing proteins are expressed such as Mac-1 that is associated with inflammation and ADNP that is associated with neuroprotection. Obviously, this plasticity in gene expression is intimately interwoven with the genetic background of the animal. NAP treatment tilts the balance toward neuroprotection.

Ischemic preconditioning increases antioxidants in the brain and peripheral organs after cerebral ischemia

BACKGROUND AND PURPOSE

Low molecular weight antioxidants (LMWA), which reflect tissue reducing power, are among the endogenous mechanisms for neutralizing reactive oxygen species (ROS). Ischemic preconditioning (IPC) was associated with decreased oxidative stress. We examined the effect of focal ischemia on LMWA and on prostaglandin E(2) (PGE(2), a product of arachidonic acid oxidation) in the brain, heart, liver, and lungs of rats subjected to 90 min of ischemia and in IPC rats subjected to similar insult.

METHODS

Transient right middle cerebral artery occlusion (MCAO) was performed for 90 min and at 0, 5, 30, 60, or 240 min of reperfusion, LMWA and PGE(2) were evaluated by cyclic voltametry (CV) and radioimmunoassay, respectively. IPC was induced by 2 min of MCAO, 24 h prior to the major ischemic episode.

RESULTS

LMWA decreased at 5 min of reperfusion in the brain, heart, liver, and lung and rose 4 h later only in the brain. PGE(2) levels increased three to fivefold in all tissues examined. Surprisingly, in IPC rats a dramatic increase of LMWA occurred at 5 min of reperfusion in the brain and in the peripheral organs. Uric acid, but not ascorbic, is the major LMWA increased.

CONCLUSIONS

We propose that after ischemia, ROS rapidly consume the antioxidants reserves in the brain and also in peripheral organs, suggesting that the whole body is under oxidative stress. Moreover, part of the neuroprotection afforded by IPC is mediated by the brain's ability to mobilize antioxidants, especially uric acid, that attenuate the massive ROS-mediated oxidative stress.

Synergism between tumor necrosis factor-α and H2O2 enhances cell damage in rat PC12 cells

Tumor necrosis factor-alpha (TNFalpha) is harmful in the early phase and beneficial in the long-term phase after brain injury. Reactive oxygen species (ROS) are among the most toxic mediators activated by injury. We speculate that part of the TNFalpha toxicity is mediated by its synergism with ROS. Thus, toxicity of TNFalpha and ROS, alone or together, were studied in PC12 cells. PC12 cells were exposed for 18 h to TNFalpha (0-100 ng/ml), to H2O2 (1-300 microM) or to both, each at sub-toxic concentrations. Lactic dehydrogenase release, prostaglandin E2 accumulation and morphology indicated cell death and stress response. TNFalpha toxicity was seen at >50 ng/ml, and that of H2O2 at >150 microM, however, when together, sub-lethal levels (25 ng/ml TNFalpha and 30 microM H2O2) induced toxicity. Dexanabinol, an N-methyl-D-aspartate antagonist with antioxidant and anti-TNFalpha properties, completely rescued the cells. These findings corroborate our hypothesis on the cooperative toxicity exerted by TNFalpha and ROS after brain injury.

Pardaxin stimulation of phospholipases A2 and their involvement in exocytosis in PC-12 cells

Pardaxin (PX) is a voltage-dependent ionophore that stimulates catecholamine exocytosis from PC-12 pheochromocytoma cells both in the presence and absence of extracellular calcium. Using a battery of phospholipase A(2) inhibitors we show that PX stimulation of phospholipase A(2) (PLA(2)) enzymes is coupled with induction of exocytosis. We investigated the relationship between PX-induced PLA(2) activity and neurotransmitter release by measuring the levels of arachidonic acid (AA), prostaglandin E(2) (PGE(2)), and dopamine release. In the presence of extracellular calcium, the cytosolic PLA(2) inhibitor arachidonyl trifluoromethyl ketone (AACOCF(3)) inhibited by 100, 70, and 73%, respectively, the release of AA, PGE(2), and dopamine induced by PX. The mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor 2'-amino-3'-methoxyflavone (PD98059) reduced by 100 and 82%, respectively, the release of AA and PGE(2) induced by PX. In the absence of extracellular calcium, the calcium-independent PLA(2) (iPLA(2)) inhibitors methyl arachidonyl fluorophosphonate, AACOCF(3), and bromoenol lactone (BEL) inhibited by 80 to 90% PX stimulation of AA release, by 65 to 85% PX stimulation of PGE(2) release, and by 80 to 90% PX-induced dopamine release. Using vesicle fusion-based enzyme-linked immunosorbent assay we found similar levels of inhibition of PX-induced exocytosis by these inhibitors. Also, PX induced the formation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor complexes, an effect that was augmented by N-methylmaleimide. This complex formation was completely inhibited by BEL. Botulinum toxins type C1 and F significantly inhibited the release of AA, PGE(2), and dopamine induced by PX. Our data suggest that PX stimulates exocytosis by activating cystolic PLA(2) and iPLA(2), leading to the generation of AA and eicosanoids, which, in turn, stimulate vesicle competence for fusion and neurotransmitter release.

Neuroprotective and neurotoxic effects of monoamine oxidase-B inhibitors and derived metabolites under ischemia in PC12 cells

Selegiline and rasagiline are selective and irreversible monoamine oxidase-B inhibitors that exert neuroprotective effects in various preclinical models. The aim of the present study was to examine the effect of selegiline and its major metabolite, L-methamphetamine in comparison to rasagiline and its major metabolite, 1-R-aminoindan on oxygen-glucose deprivation induced cell death in nerve growth factor (NGF)-differentiated pheochromocytoma (PC12) cells. Our results show that selegiline reduces oxygen-glucose deprivation induced cell death by 30%. When the cultures were treated with rasagiline at similar concentrations, cell death induced by oxygen-glucose deprivation was reduced by 45-55%. L-methamphetamine, a major selegiline metabolite, but not 1-R-aminoindan, the major rasagiline metabolite, enhanced oxygen-glucose deprivation-induced cell death by 70%. Under normoxic conditions, both metabolites lack neurotoxicity. Concomitant exposure of the cultures under oxygen-glucose deprivation, to a combination of either selegiline and L-methamphetamine or rasagiline and 1-R-aminoindan, indicated that L-methamphetamine, but not 1-R-aminoindan, blocked the neuroprotective effect of the parental drug. These results suggest there may be a neuroprotective advantage of rasagiline over selegiline.

Induction of antitumor immunity by indomethacin

Irradiated tumor cells given, together with indomethacin, to syngeneic mice induced an antitumor response and conferred protection against a challenge of a lethal dose of murine mammary (4T1) and lung (3LL) carcinoma cells. Continuous administration of indomethacin was crucial throughout the entire period of immunization and challenge, as no protection was achieved when the drug was given during only one of these procedures. Antitumor immunity was long-lasting and, when tested in the 4T1 model, 48% of mice were resistant to a second challenge of lethal tumor cells. Tumor-free immune mice that were given indomethacin for more than 300 days remained healthy with normal white blood cell counts and normal spleen size. Cells isolated from immune mice were able to kill tumor cells in culture after in vitro activation by interleukin-2, in a manner similar to cells from naive normal control mice. In addition, the mitogenic response of their T cells was as high as that of the control naive mice. While indomethacin was able to induce antitumor immunity to 4T1 and 3LL murine carcinoma cells, both of which contain a high concentration of endogenic prostaglandin E(2) (PGE2), no such immunity was achieved to murine tumor cells with a low concentration of endogenic PGE2. These results suggest a correlation between PGE2 concentration and the ability of indomethacin to induce antitumor immunity. We therefore suggest that an immunotherapy protocol with long-term dispensation of a tolerable dose of an immunomodulator, given together with irradiated autologous tumor cells, may stimulate antitumor responses to tumors containing high concentrations of endogenic PGE2.

Rasagiline, a monoamine oxidase-B inhibitor, protects NGF-differentiated PC12 cells against oxygen-glucose deprivation

In our in vitro model, rasagiline a selective irreversible monoamine oxidase-B (MAO-B) inhibitor, protected nerve growth factor (NGF)-differentiated PC12 cells from cell death under oxygen and glucose deprivation (OGD). The severity of the OGD insult, as expressed by cell death, was time-dependent. Exposure of the cells to OGD for 3 hr followed by 18 hr of reoxygenation caused about 30-40% cell death. Under these conditions, the neuroprotective effect of rasagiline was dose-dependent: rasagiline reducing OGD-induced cell death by 68% and 80% at 100 nM and 1 microM, respectively. The neuroprotective effect of rasagiline was also observed when added after the OGD insult (55% reduction in cell death). Under rasagiline treatment, there was a lesser decrease in ATP content in cultures exposed to OGD compared with that in untreated cultures. OGD followed by reoxygenation resulted in a several fold increase in PGE(2) release into the extracellular medium. Rasagiline (100 nM-1 microM) markedly inhibited OGD-induced PGE(2) release. Clorgyline, a monoamine oxidase-A (MAO-A) inhibitor, did not protect NGF-differentiated PC12 cells against OGD-induced cell death. As NGF-differentiated PC12 cells contain exclusively MAO type A, these data suggest that the neuroprotective effect of rasagiline under OGD conditions is independent of MAO inhibition.

Antioxidants attenuate acute toxicity of tumor necrosis factor-alpha induced by brain injury in rat

Tumor necrosis factor-alpha alpha (TNF-alpha) and reactive oxygen species (ROS) are produced in the brain after traumatic injury and have deleterious effects. In a rat model of closed head injury (CHI), the synthetic antioxidant from the nitroxide family, Tempol, improved recovery and protected the blood-brain barrier. Similar protection was found after CHI in heat-acclimated rats, in which the endogenous antioxidants have been shown to be elevated after CHI. The present study examined the relationship between TNF-alpha and ROS after CHI, namely, whether after CHI, antioxidants that afforded cerebroprotection also attenuated brain levels of TNF-alpha. Three groups of rats were subjected to CHI: (1) control, nontreated, (2) Tempol-treated, and (3) heat-acclimated (30 days at 34 degrees C). Four hours after injury (time for peak production of TNF-alpha), the activity of TNF-alpha was measured. Although clinical recovery was facilitated in rats of the two treated groups, TNF-alpha activity was as high as in the traumatized, untreated rats. Moreover, direct injection of TNF-alpha into mouse brain induced disruption of the blood-brain barrier, indicating its acute harmful effect. This toxic effect was attenuated by before and after treatment with Tempol. Our results support the hypothesis that in vivo antioxidants neutralize TNF-alpha toxicity, probably by interfering with activation of the transcription factor NF-kappa-B.

Closed head injury in the rat induces whole body oxidative stress: overall reducing antioxidant profile

Traumatic injury to the brain triggers the accumulation of harmful mediators, including highly toxic reactive oxygen species (ROS). Endogenous defense mechanism against ROS is provided by low molecular weight antioxidants (LMWA), reflected in the reducing power of the tissue, which can be measured by cyclic voltammetry (CV). CV records biological peak potential (type of scavenger), and anodic current intensity (scavenger concentration). The effect of closed head injury (CHI) on the reducing power of various organs was studied. Water and lipid soluble extracts were prepared from the brain, heart, lung, kidney, intestine, skin, and liver of control and traumatized rats (1 and 24 h after injury) and total LMWA was determined. Ascorbic acid, uric acid, alpha-tocopherol, carotene and ubiquinol-10 were also identified by HPLC. The dynamic changes in LMWA levels indicate that the whole body responds to CHI. For example, transient reduction in LMWA (p<0.01) in the heart, kidney, lung and liver at 1 h suggests their consumption, probably due to interaction with locally produced ROS. However, in some tissues (e.g., skin) there was an increase (p<0.01), arguing for recruitment of higher than normal levels of LMWA to neutralize the ROS. alpha-Tocopherol levels in the brain, liver, lung, skin, and kidney were significantly reduced (p<0.01) even up to 24 h. We conclude that although the injury was delivered over the left cerebral hemisphere, the whole body appeared to be under oxidative stress, within 24 h after brain injury.

Antioxidant mechanisms in apolipoprotein E deficient mice prior to and following closed head injury

Apolipoprotein E deficient mice have distinct memory deficits and neurochemical derangements and their recovery from closed head injury is impaired. In the present study, we examined the possibility that the neuronal derangements of apolipoprotein E deficient mice are associated with oxidative stress, which in turn affects their ability to recover from close head injury. It was found that brain phospholipid levels in apolipoprotein E deficient mice are lower than those of the controls (55+/-15% of control, P<0. 01), that the cholesterol levels of the two mice groups are similar and that the levels of conjugated dienes of the apolipoprotein E deficient mice are higher than those of control mice (132+/-15% of P<0.01). Brains of apolipoprotein E deficient mice had higher Mn-superoxide dismutase (134+/-7%), catalase (122+/-8%) and glutathione reductase (167+/-7%) activities than control (P<0.01), whereas glutathione peroxidase activity and the levels of reduced glutathione and ascorbic acid were similar in the two mouse groups. Closed head injury increased catalase and glutathione peroxidase activities in both mouse groups, whereas glutathione reductase increased only in control mice. The superoxide dismutase activity was unaffected in both groups. These findings suggest that the antioxidative metabolism of apolipoprotein E deficient mice is altered both prior to and following head injury and that antioxidative mechanisms may play a role in mediating the neuronal maintenance and repair derangements of the apolipoprotein E deficient mice.

Characterization of pardaxin-induced dopamine release from pheochromocytoma cells: role of calcium and eicosanoids

Pardaxin, an excitatory neurotoxin, induced dopamine release from pheochromocytoma (PC12) cells both in the presence and absence of extracellular calcium ([Ca]o). In the presence of extracellular calcium, nifedipine, an L-type calcium channel blocker, did not affect dopamine release, whereas 1,2-bis (2-aminophenoxy) ethane N,N, N'N'-tetra-acetic acid (BAPTA), a chelator of cytosolic calcium, and dantrolene, a blocker of calcium release from intracellular stores, inhibited only partially (30-40%) pardaxin-induced dopamine release. In the absence of [Ca]o, BAPTA and dantrolene were ineffective. Pardaxin stimulated the arachidonic acid (AA) cascade in PC12 cells independently of [Ca]o. The phospholipase inhibitors mepacrine and bromophenacyl bromide inhibited both pardaxin-induced AA release and pardaxin-induced dopamine release. Dopamine release induced by pardaxin also was blocked by the lipoxygenase inhibitors nordihydroguaiaretic acid, esculetin, and 2-(12-hydroxydodeca-5, 10-diynyl)-3,5,6-trimethyl-1,4-benzoquinone. Under these conditions, a parallel reduction in 5-hydroxyeicosatetranoic acid release also was observed. Suppression of pardaxin-induced dopamine release by inhibitors of phospholipase A2 and lipoxygenase was more pronounced in calcium-free medium. These results indicate the involvement of the lipoxygenase pathway in pardaxin-induced dopamine release and suggest the use of this toxin as a novel pharmacological tool for investigating the mechanism of calcium-independent neurotransmitter release.

Pardaxin, a new pharmacological tool to stimulate the arachidonic acid cascade in PC12 cells

The effect of Pardaxin, a neurotoxin that induces neurotransmitter release from neurons, on the arachidonic acid (AA) cascade was studied in PC12 cells. Both native and the synthetic Pardaxin selectively stimulated phospholipase A2 (PLA2) activity (measured by [3H]AA release) in the presence as well as in the absence of extracellular calcium. Pardaxin-stimulated PLA2 activity was also evident in the increased formation of lysophosphatidylcholine. Pardaxin analogs, lacking the alpha-helical structure that is essential for insertion into the plasma membrane, were ineffective in stimulating the AA cascade in PC12 cells. Pardaxin stimulation of PLA2 was markedly inhibited by the nonselective PLA2 inhibitors bromophenacyl bromide and mepacrine, by methyl arachidonyl fluorophosphonate, a dual inhibitor of calcium-dependent cytosolic PLA2 and the calcium-independent PLA2 and by bromoenol lactone[(E)-6-(bromoethylene)tetrahydro-3-(1-naphthalenyl-2H-pyran -2- one], a highly specific inhibitor of calcium-independent PLA2. After Pardaxin treatment, there was increased release of AA metabolites produced by the cyclooxygenase pathway as expressed in an 8-fold increase of PGE2 release. The release of other eicosanoids, such as 6-keto-PGF1alpha and thromboxane B2, was also augmented. Pardaxin-induced PGE2 release was observed in calcium-free medium and in the absence of any increase in cytosolic calcium. Dexamethasone partially inhibited Pardaxin-induced PGE2 release. This effect was reversed by the type II corticosteroid receptor antagonist RU-38486. Our results indicate that Pardaxin stimulates release of AA and eicosanoids, independently of calcium, and suggest that calcium-independent PLA2 plays an important role in Pardaxin stimulation of the AA cascade.

Neuroprotection against oxidative stress by serum from heat acclimated rats

Exposure of PC12 cells, to 1% serum derived from normothermic (CON) rats resulted in 79% cell death. Sister cultures treated with 1% serum derived from heat acclimated (ACC) rats, were neuroprotected and expressed a significant reduction in cell death. In PC12 cells exposed to a free radical generator causing an oxidative stress, 90% cell death was measured in CON serum treated cultures, while ACC serum treated cultures were neuroprotected. Xanthine oxidase activity and uric acid (UA) levels were lower in ACC serum compared to CON. Addition of UA to both sera abolished the difference in cell viability, and toxicity of ACC serum reached that of CON. These findings suggest a causal relationship between the lower levels of UA in ACC and the neuroprotective effect observed. The present study proposes heat acclimation as an experimental and/or clinical tool for the achievement of neuroprotection.

Mechanism of brain protection by nitroxide radicals in experimental model of closed-head injury

Reactive oxygen-derived species were previously implicated in mediation of post-traumatic brain damage; however, the efficacy of traditional antioxidants in preventing/reversing the damage is sometimes limited. The present work focused on the mechanisms underlying the neuroprotective activity of cell permeable, nontoxic, antioxidants, namely stable nitroxide radicals in an experimental model of rat closed-head injury. Brain damage was induced by the weight-drop method and the clinical status was evaluated according to a neurological severity score at 1 h and 24 h, where the difference between these scores reflects the extent of recovery. The metal chelator deferoxamine as well as three nitroxide derivatives, differing in hydrophilicity and charge, and one hydroxylamine (a reduced nitroxide) facilitated the clinical recovery and decreased the brain edema. The nitroxides, but neither the hydroxylamine nor deferoxamine, protected the integrity of the blood-brain barrier. Superoxide dismutase also improved the clinical recovery but did not affect brain edema or the blood-brain barrier. The results suggest that by switching back and forth between themselves, the nitroxide and hydroxylamine act catalytically as self-replenishing antioxidants, and protect brain tissue by terminating radical-chain reactions, oxidizing deleterious metal ions, and by removal of intracellular superoxide.

Reduced levels of antioxidants in brains of apolipoprotein E-deficient mice following closed head injury

Recent animal model studies using apolipoprotein E (apoE)-deficient (knockout) mice revealed that these mice have memory deficits and neurochemical derangements and that they recover from closed head injury less adequately than control mice. In the present study, we examined the possibility that the diminished recovery of apoE-deficient mice from head injury is related to a reduction in their ability to counteract oxidative damage. Measurements of reducing agents by cyclic voltammetry revealed that cortical homogenates of apoE-deficient and control mice contain similar levels of these compounds whose oxidation potentials for the two groups of mice are at 400 +/- 40 mV and 900 +/- 50 mV. The responses of the apoE-deficient and control groups to closed head injury were both biphasic and were composed of initial reductions followed by subsequent increases in the levels of reducing antioxidant equivalents. However, the two groups differed markedly in the magnitude of their response. This difference was most pronounced with the 400-mV reducing compounds, such that at 4 h after injury their levels in injured control mice increased over twofold relative to the noninjured control mice, whereas the corresponding anodic current of the apoE-deficient mice recovered only to its original level and did not increase further even by 24 h after injury. In vitro studies using recombinant apoE allele E3 and beta very low density lipoprotein revealed that this lipoprotein can delay Cu(2+)-induced lipid peroxidation. This suggests that the inability of the apoE-deficient mice to respond to brain injury by a surge in brain reducing compounds may be related, at least in part to direct antioxidant activity of apoE.

Changes of biological reducing activity in rat brain following closed head injury: a cyclic voltammetry study in normal and heat-acclimated rats

Reactive oxygen species (ROS) are normally generated in the brain during metabolism, and their production is enhanced by various insults. Low molecular weight antioxidants (LMWA) are one of the defense mechanisms of the living cell against ROS. The reducing capacity of brain tissue (total LMWA) was measured by cyclic voltammetry (CV), which records biological oxidation potential specific to the type of scavenger(s) present and anodic current intensity (Ia), which depends on scavenger concentration. In the present study, the reducing capacity of rat brain following closed head injury (CHI) was measured. In addition, CV of heat-acclimated traumatized rats was used to correlate endogenous cerebroprotection after CHI with LMWA activity. Sham-injured rat brains displayed two anodic potentials: at 350 +/- 50 mV (Ia = 0.75 +/- 0.06 microA/mg protein) and at 750 +/- 50 mV (Ia = 1.00 +/- 0.05 microA/mg protein). Following CHI, the anodic waves appeared at the same potentials as in the sham animals. However, within 5 min of CHI, the total reducing capacity was transiently decreased by 40% (p < 0.01). A second dip was detected at 24 h (60%, p < 0.005). By 48 h and at 7 days, the Ia levels normalized. The acclimated rats displayed anodic potentials identical to those of normothermic rats. However, the Ia of both potentials was lower (60% of control, p < 0.001). The Ia profile after CHI was the direct opposite of the normothermic Ia profile: no immediate decrease of Ia and an increase from 4 h and up to 7 days (40-50%, p < 0.001). We suggest that the lowered levels of LMWA in the post-CHI period reflect their consumption due to overproduction of free radicals. The augmented concentration of LMWA found in the brain of the heat-acclimated rats suggests that these rats are better able to cope with these harmful radicals, resulting in a more favorable outcome following CHI.

An experimental model of closed head injury in mice: pathophysiology, histopathology, and cognitive deficits

The present study describes the characterization of an experimental model of closed head injury (CHI) in the mouse. This model is a modification of a setup described and used previously in the rat. The weight-drop device was modified and adapted to the size and weight of the mouse and the typical parameters that define the severity of the injury and its outcome were evaluated. The posttraumatic accumulation of water, i.e., cerebral edema, the disruption of the blood-brain barrier (BBB), histopathology, motor and cognitive functions were studied up to 30 days following CHI. Increases in cerebral water content and of BBB permeability were observed in the injured hemisphere at 4 h (p < 0.05) and 24 h (p < 0.01) postinjury, respectively. By 7 days, edema disappeared, while the BBB remained open for up to 30 days. The motor function was evaluated by a set of criteria termed neurological severity score (NSS). NSS was severely impaired immediately after CHI and later showed a spontaneous progressive recovery, although some residual deficits, mainly of beam-walk and balance, were still present at 30 days. Mice trained in the Morris water maze before the injury demonstrated highly significant deficits in memory retention up to at least 11 days postinjury (p < 0.01). Histopathological analysis revealed significant neuronal cell death in CA1, CA2, and CA3 regions of the left hippocampus following CHI. However, in the right hippocampus, overt neuronal cell death was observed only in area CA3 at 7 days after CHI. These results suggest that the modified model of CHI in mice can reproduce the posttraumatic sequelae observed in rats and show that some of the data obtained in this model are essentially similar to those observed in human head injury. The experimental model of CHI in mice may be a useful tool for studies in animals that carry specific genetic alterations, aimed at manipulating neurochemical pathways involved in the pathophysiology of brain damage.

Cerebroprotective effect of stable nitroxide radicals in closed head injury in the rat

Nitroxide stable radicals are unreactive toward most diamagnetic molecules, but readily undergo one-electron redox reactions with paramagnetic species such as free radicals and transition metals, thus serving as cell permeable antioxidants. The involvement of reactive oxygen species in the pathophysiology of neurotrauma has been well established. The neuroprotective properties of three nitroxides: 2,2,6,6-tetramethylpiperidine-1-N-oxyl (TPO), the hydrophilic analog: TPL, and its reduced form: TPH, were tested in a rat model of closed head injury (CHI). CHI was induced in ether anesthetized rats by a weight drop device and recovery was followed for up to 24 h. The "clinical status' was evaluated according to a "Neurological Severity Score' (NSS), at 1 h and 24 h, the difference between these scores, delta NSS, reflecting the extent of recovery. Edema was assessed by measurement of water content at 24 h. The integrity of the blood-brain barrier (BBB) was investigated using Evans Blue extravasation. TPL, TPH and TPO facilitated clinical recovery, the latter causing a more pronounced effect (delta NSS = 7.63 +/- 0.26 in treated rats vs 4.94 +/- 0.48 in control rats, P < 0.001). TPL was found to significantly reduce edema formation (80.13% +/- 0.26 vs 83.65% +/- 0.49, P < 0.001) and to ameliorate BBB disruption (P < 0.001). The therapeutic window of TPL was found to be in the range of 4 h after CHI. The mechanisms underlying the nitroxide neuroprotective activity presumably involve: (a) reoxidation of reduced transition metal ions; (b) a selective radical-radical reaction; and (c) catalytic removal of intracellular and extracellular .O2-. The results indicate that nitroxides could be used in neuroprotective treatment of CHI.

A novel nonpsychotropic cannabinoid, HU-211, in the treatment of experimental pneumococcal meningitis

Typical features of pneumococcal meningitis have been demonstrated in rats inoculated with Streptococcus pneumoniae. HU-211, a novel noncompetitive N-methyl-D-aspartate antagonist recently demonstrated to inhibit tumor necrosis factor-alpha production under various conditions, improves recovery in some experimental models of brain injury. The present study tested the efficacy of HU-211 in combination with antimicrobial therapy in reducing brain damage in experimental pneumococcal meningitis. S. pneumoniae-infected rats were treated with saline alone, ceftriaxone alone, or with combination of ceftriaxone and HU-211 18 h after inoculation of the bacteria. Brain edema and blood-brain barrier impairment 48 h after infection were significantly (P<.05) reduced suggest that HU-211 when given concomitantly with antibiotics attenuates brain damage in the rat model of pneumococcal meningitis.