Subacute treatment with vascular endothelial growth factor after traumatic brain injury increases angiogenesis and gliogenesis

Vascular endothelial growth factor (VEGF) is neuroprotective and induces neurogenesis and angiogenesis when given early after traumatic brain injury (TBI). However, the effects of VEGF administration in the subacute phase after TBI remain unknown. Mice were subjected to TBI and treated with vehicle or VEGF beginning 7 days later for an additional 7 days. The animals were injected with BrdU to label proliferating cells and examined with a motor-sensory scale at pre-determined time points. Mice were killed 90 days post injury and immunohistochemistry was used to study cell fates. Our results demonstrate that lesion volumes did not differ between the groups confirming the lack of neuroprotective effects in this paradigm. VEGF treatment led to significant increments in cell proliferation (1.9 fold increase vs. vehicle, P<0.0001) and angiogenesis in the lesioned cortex (1.7 fold increase vs. vehicle, P=0.0001) but most of the proliferating cells differentiated into glia and no mature newly-generated neurons were detected. In conclusion, VEGF induces gliogenesis and angiogenesis when given 7 days post TBI. However, treated mice had only insignificant motor improvements in this paradigm, suggesting that the bulk of the beneficial effects observed when VEGF is given early after TBI results from the neuroprotective effects.

Rapamycin is a neuroprotective treatment for traumatic brain injury

The mammalian target of rapamycin, commonly known as mTOR, is a serine/threonine kinase that regulates translation and cell division. mTOR integrates input from multiple upstream signals, including growth factors and nutrients to regulate protein synthesis. Inhibition of mTOR leads to cell cycle arrest, inhibition of cell proliferation, immunosuppression and induction of autophagy. Autophagy, a bulk degradation of sub-cellular constituents, is a process that keeps the balance between protein synthesis and protein degradation and is induced upon amino acids deprivation. Rapamycin, mTOR signaling inhibitor, mimics amino acid and, to some extent, growth factor deprivation. In the present study we examined the effect of rapamycin, on the outcome of mice after brain injury. Our results demonstrate that rapamycin injection 4 h following closed head injury significantly improved functional recovery as manifested by changes in the Neurological Severity Score, a neurobehavioral testing. To verify the activity of the injected rapamycin, we demonstrated that it inhibits p70S6K phosphorylation, reduces microglia/macrophages activation and increases the number of surviving neurons at the site of injury. We therefore suggest that rapamycin is neuroprotective following traumatic brain injury and as a drug used in the clinic for other indications, we propose that further studies on rapamycin should be conducted in order to consider it as a novel therapy for traumatic brain injury.

Immunohistochemical characterization of Fas (CD95) and Fas Ligand (FasL/CD95L) expression in the injured brain: relationship with neuronal cell death and inflammatory mediators

Traumatic brain injury causes progressive tissue atrophy and consequent neurological dysfunction, resulting from neuronal cell death in both animal models and patients. Fas (CD95) and Fas ligand (FasL/CD95L) are important mediators of apoptosis. However, little is known about the relationship between Fas and FasL and neuronal cell death in mice lacking the genes for inflammatory cytokines. In the present study, double tumor necrosis factor/lymphotoxin-alpha knockout (-/-) and interleukin-6-/- mice were subjected to closed head injury (CHI) and sacrificed at 24 hours or 7 days post-injury. Consecutive brain sections were evaluated for Fas and FasL expression, in situ DNA fragmentation (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling; TUNEL), morphologic characteristics of apoptotic cell death and leukocyte infiltration. A peak incidence of TUNEL positive cells was found in the injured cortex at 24 hours which remained slightly elevated at 7 days and coincided with maximum Fas expression. FasL was only moderately increased at 24 hours and showed maximum expression at 7 days. A few TUNEL positive cells were also found in the ipsilateral hippocampus at 24 hours. Apoptotic, TUNEL positive cells mostly co-localized with neurons and Fas and FasL immunoreactivity. The amount of accumulated polymorphonuclear leukocytes and CD11b positive cells was maximal in the injured hemispheres at 24 hours. We show strong evidence that Fas and FasL might be involved in neuronal apoptosis after CHI. Furthermore, Fas and FasL upregulation seems to be independent of neuroinflammation since no differences were found between cytokine-/- and wild-type mice.

Endothelial-mediated regulation of cerebral microcirculation

Vascular endothelial cells are important not only for maintaining homeostasis, but also in pathogenesis of vascular disorders. Cerebral capillary and microvascular endothelial cells play an active role in maintaining cerebral blood flow, microvascular tone and blood brain barrier functions. Factors produced and released by endothelial cells, other brain cells and circulating blood cells participate in these regulatory functions. In particular, endothelin-1 (ET-1) and nitric oxide (NO) are known to contribute to the functional vascular changes under pathological conditions (e.g., hypertension, arteriosclerosis, and stroke). This report describes the involvement of endothelial cell mediators in the post-ischemic hypoperfusion induced by brain ischemia and in vitro endothelial responses (Ca(2+) mobilization and cytoskeletal rearrangements) to ET-1 and its interactions with NO or 2-AG. The capacity of NO and endocannabinoids to counteract ET-1-induced cerebral capillary and microvascular endothelial responses indicates that they may actively participate in EC function and implicates them in physiological and pathophysiological conditions.

Erythropoietin is neuroprotective, improves functional recovery, and reduces neuronal apoptosis and inflammation in a rodent model of experimental closed head injury

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in young people in industrialized countries. Although various anti-inflammatory and antiapoptotic modalities have shown neuroprotective effects in experimental models of TBI, to date, no specific pharmacological agent aimed at blocking the progression of secondary brain damage has been approved for clinical use. Erythropoietin (Epo) belongs to the cytokine superfamily and has traditionally been viewed as a hematopoiesis-regulating hormone. The newly discovered neuroprotective properties of Epo lead us to investigate its effect in TBI in a mouse model of closed head injury. Recombinant human erythropoietin (rhEpo) was injected at 1 and 24 h after TBI, and the effect on recovery of motor and cognitive functions, tissue inflammation, axonal degeneration, and apoptosis was evaluated up to 14 days. Motor deficits were lower, cognitive function was restored faster, and less apoptotic neurons and caspase-3 expression were found in rhEpo-treated as compared with vehicle-treated animals (P<0.05). Axons at the trauma area in rhEpo-treated mice were relatively well preserved compared with controls (shown by their density; P<0.01). Immunohistochemical analysis revealed a reduced activation of glial cells by staining for GFAP and complement receptor type 3 (CD11b/CD18) in the injured hemisphere of Epo- vs. vehicle-treated animals. We propose that further studies on Epo in TBI should be conducted in order to consider it as a novel therapy for TBI.

Increase in peripheral benzodiazepine receptors and loss of glutamate NMDA receptors in a mouse model of closed head injury: a quantitative autoradiographic study⋆

Increases in peripheral type benzodiazepine receptors (PTBR) have been utilized for the detection of neuroinflammation and neurotoxicity in the brain. We have investigated the relationship between PTBR and NMDA receptor binding density in mice with closed head injury (CHI) using quantitative autoradiography. CHI was induced by a weight drop in nine mice, four of which received a single injection of the rat sarcoma (Ras) inhibitor famesyl thiosalicylate (FTS) 1 h after the insult. Sham controls received anesthesia but no contusion. The neurological status of the mice was evaluated at 1 h, and hence up to 7 days using a neurological severity score (NSS). Animals were killed 7 days after CHI and consecutive brain sections were incubated with [3H]PK11195, a PTBR antagonist, or [3H]MK801, an n-methyl-d-aspartate receptor (NMDAR) use-dependent antagonist. CHI produced large (two- to threefold), widespread increases in PK11195 binding in the traumatized hemisphere and a significant decrease (20%-40%) in NMDAR binding limited to regions at close proximity to the lesion. Histologically, these regions were characterized by glial proliferation and neuronal loss. Significant increases in PTBR binding, but no concomitant decrease in NMDAR, were identified in several regions remote from the lesion, including the contralateral ventrolateral striatum and the ipsilateral ventral thalamus. Drug treatment significantly improved the neurological deficits but had only a marginal effect on PTBR. These results support a complex role for glial activation and PTBR increases in the context of CHI.

Apolipoprotein e4 decreases whereas apolipoprotein e3 increases the level of secreted amyloid precursor protein after closed head injury

Apolipoprotein E (apoE4) and head trauma are important genetic and environmental risk factors for Alzheimer's disease. Furthermore, apoE4 increases both the acute and chronic consequences of head trauma. The latter are associated with the deposition of amyloid-beta, which is particularly elevated in apoE4 subjects. The short-term effects of head injury are associated with transiently increased metabolism of amyloid precursor protein (APP) and its secreted fragment, APPs. In the present study, we examined the possibility that the acute, short-term pathological effects of apoE4 following head trauma and the corresponding neuroprotective effects of apoE3 are related to isoform-specific effects of apoE on APP metabolism. Accordingly, male transgenic mice expressing human apoE3 or apoE4 on a null mouse apoE background and apoE-deficient and control mice were subjected to closed head injury (CHI). The resulting effects on brain APP, and on its secreted products, APPs and secreted product of the alpha-cleavage of APP (APPsalpha) were then determined 24 h following injury. Immunoblotting revealed no significant differences between the basal APP, APPs and APPsalpha levels of the hippocampus or the cortex of the control and the apoE3 and ApoE4 transgenic mice. The apoE-deficient mice also had similar cortical basal levels of APP and its metabolites, whereas their corresponding basal hippocampal APP and APPs levels were lower than those of the other groups. CHI lowered the hipppocampal APPs and APPsalpha levels of the apoE4 transgenic mice, whereas those of the apoE3 transgenic mice and of the control and apoE-deficient mice were not affected by this insult. In contrast, CHI raised the cortical APP and APPs levels of the apoE3 transgenic mice but had no significant effect on those of the other mice groups. These animal model findings suggest that the acute, short-term pathological effects of apoE4 following CHI and the corresponding neuroprotective effects of apoE3 may be mediated by their opposing effects on the expression and cleavage of cortical and hippocampal APP. Similar isoform-specific interactions between apoE and APP may play a role in the acute, short-term effects of head trauma in humans.

Experimental models of head trauma

Traumatic brain injury is one of the most common causes for chronic disability in young people. Despite this there are currently no widely available modes of therapy that would limit the extent of brain damage secondary to trauma. Therefore, new insights into the pathological mechanisms involved in head trauma possibly leading to the identification of new therapeutic targets are urgently needed. In order to attain these goals adequate animal models for traumatic brain injury are needed. In the following paper the authors will review the various animal models for head trauma and emphasize their potential strengths and weaknesses.

Antioxidant properties of the vasoactive endocannabinoid, 2-arachidonoyl glycerol (2-AG)

Reactive oxygen species (ROS) were shown to play a role in altering blood-brain barrier (BBB) permeability and formation of brain edema induced by trauma and/or ischemia. 2-arachidonoyl glycerol (2-AG), a novel, potent vasodilatory and cytoprotective endocannabinoid has been implicated to act as an antioxidative agent. This study examines: 1) the possible 2-AG modulation of BBB injury and edema formation induced by closed head injury (CHI); and 2) comparable effects between 2-AG and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TPL), a known antioxidant nitroxide on endothelial Ca2+ and cytoskeletal responses to H2O2 (ROS). 2-AG treatment reduced the CHI-induced increase in BBB permeability and brain edema. The endothelial H2O2-stimulated Ca2+ mobilization and cytoskeleton (vimentin) rearrangement was modified by either 2-AG or TPL. These findings provide evidence of 2-AG antioxidant activity and are consistent with the involvement of ROS in the pathomechanism of CHI-induced BBB injury and brain edema.

The nitroxide antioxidant tempol is cerebroprotective against focal cerebral ischemia in spontaneously hypertensive rats

Free radicals appear to participate in the final common pathway of neuronal death in ischemia and may therefore be an adequate target for therapy. Tempol is a nitroxide antioxidant with proven protective efficacy in several animal models, including myocardial ischemia, that has not been previously tested in models of permanent cerebral ischemia. Spontaneously hypertensive rats underwent permanent middle cerebral artery occlusion (PMCAO). Following dose-response and time-window-finding experiments rats were given vehicle or tempol (50 mg/kg) subcutaneously 1 h after PMCAO (n = 10/group). Five animals in each group were evaluated with a motor scale 24 h after the infarct and were then sacrificed and the injury volume was measured. The remaining animals were examined daily with the motor scale and also with a Morris water maze test on days 26-30 after PMCAO and sacrificed on day 30. Motor scores at all time points examined were significantly better in the tempol-treated animals (P < 0.05 for all). Significantly better performance in the water maze test for performance on days 26-30 was noted in the tempol group compared with the vehicle-treated group (P < 0.05). Injury volumes at days 1 and 30 were significantly reduced in the tempol group (9.83 +/- 1.05 vs 19.94 +/- 1.43% hemispheric volume, P = 0.0009, and 13.2 +/- 2.97 vs 24.4 +/- 2.38% hemispheric volume, P = 0.02, respectively). In conclusion, treatment with tempol led to significant motor and behavioral improvement and reduced injured tissue volumes both in the short and in the long term after stroke.

Endocannabinoids and neuroprotection

Traumatic brain injury (TBI) releases harmful mediators that lead to secondary damage. On the other hand, neuroprotective mediators are also released, and the balance between these classes of mediators determines the final outcome after injury. Recently, it was shown that the endogenous brain cannabinoids anandamide and 2-Arachidonoyl glycerol (2-AG) are also formed after TBI in rat and mouse respectively, and when administered after TBI, they reduce brain damage. In the case of 2-AG, better results are seen when it is administered together with related fatty acid glycerol esters. Significant reduction of brain edema, better clinical recovery, and reduced infarct volume and hippocampal cell death are noted. This new neuroprotective mechanism may involve inhibition of transmitter release and of inflammatory response. 2-AG is also a potent modulator of vascular tone, and counteracts the endothelin (ET-1)-induced vasoconstriction that aggravates brain damage; it may thus help to restore blood supply to the injured brain.

Closed head injury increases extracellular levels of antioxidants in rat hippocampus in vivo: an adaptive mechanism?

Reactive oxygen species (ROS) are a major cause of secondary brain injury following head trauma. Low molecular weight antioxidants (LMWA) protect the tissue against oxidative damage caused by ROS. In the present study, we measured the extracellular levels of the LMWA ascorbic acid and uric acid in the rat brain before, during and after experimental closed head injury (CHI). A dialysis probe was inserted into the right ventral hippocampus through a chronically implanted guide. CHI was applied to the left hemisphere using a weight-drop device. CHI induced a rapid but transient increase in ascorbic acid levels. Uric acid levels increased to 250% of baseline shortly after CHI and remained elevated at 2 h after CHI. Previous results show that the overall reducing power of brain tissue decreases following CHI. Together with previous results, the current findings suggest that ascorbic acid and uric acid are mobilized from brain cells to the extracellular space.

An endogenous cannabinoid (2-AG) is neuroprotective after brain injury

Traumatic brain injury triggers the accumulation of harmful mediators that may lead to secondary damage. Protective mechanisms to attenuate damage are also set in motion. 2-Arachidonoyl glycerol (2-AG) is an endogenous cannabinoid, identified both in the periphery and in the brain, but its physiological roles have been only partially clarified. Here we show that, after injury to the mouse brain, 2-AG may have a neuroprotective role in which the cannabinoid system is involved. After closed head injury (CHI) in mice, the level of endogenous 2-AG was significantly elevated. We administered synthetic 2-AG to mice after CHI and found significant reduction of brain oedema, better clinical recovery, reduced infarct volume and reduced hippocampal cell death compared with controls. When 2-AG was administered together with additional inactive 2-acyl-glycerols that are normally present in the brain, functional recovery was significantly enhanced. The beneficial effect of 2-AG was dose-dependently attenuated by SR-141761A, an antagonist of the CB1 cannabinoid receptor.

N1-acetyl-N2-formyl-5-methoxykynuramine, a biogenic amine and melatonin metabolite, functions as a potent antioxidant

The biogenic amine The biogenic amine N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) was investigated for its potential antioxidative capacity. AFMK is a metabolite generated through either an enzymatic or a chemical reaction pathway from melatonin. The physiological function of AFMK remains unknown. To our knowledge, this report is the first to document the potent antioxidant action of this biogenic amine. Cyclic voltammetry (CV) shows that AFMK donates two electrons at potentials of 456 mV and 668 mV, and therefore it functions as a reductive force. This function contrasts with all other physiological antioxidants that donate a single electron only when they neutralize free radicals. AFMK reduced 8-hydroxydeoxyguanosine formation induced by the incubation of DNA with oxidants significantly. Lipid peroxidation resulting from free radical damage to rat liver homogenates was also prevented by the addition of AFMK. The inhibitory effects of AFMK on both DNA and lipid damage appear to be dose-response related. In cell culture, AFMK efficiently reduced hippocampal neuronal death induced by either hydrogen peroxide, glutamate, or amyloid b25-35 peptide. AFMK is a naturally occurring molecule with potent free radical scavenging capacity (donating two electrons/molecule) and thus may be a valuable new antioxidant for preventing and treating free radical-related disorders.

Regulation of chemokines and chemokine receptors after experimental closed head injury

The expression of the chemokines macrophage inflammatory protein (MIP)-2 and MIP-1alpha and of their receptors CXCR2 and CCR5 was assessed in wild type (WT) and TNF/lymphotoxin-alpha knockout (TNF/LT-alpha-/-) mice subjected to closed head injury (CHI). At 4 h after trauma intracerebral MIP-2 and MIP-1alpha levels were increased in both groups with MIP-2 concentrations being significantly higher in WT than in TNF/LT-alpha-/- animals (p < 0.05). Thereafter, MIP-2 production declined rapidly, whereas MIP-1alpha remained elevated for 7 days. Expression of CXCR2 was confined to astrocytes and increased dramatically within 24 h in both mouse types. Contrarily, CCR5 expression remained constitutively low and was mainly localized to microglia. These results show that after CHI, chemokines and their receptors are regulated differentially and with independent kinetics.

Communication strategies used during pediatric dental treatment: a pilot study

PURPOSE

Effective verbal communication is essential for successful dental treatment. The purpose of this study was to qualitatively and quantitatively examine communication techniques used by pediatric postdoctoral students during treatment. The operation of a communication model comprised of three linguistic approaches-permissive, empathic and personal-together with other strategies common to all three, was examined.

METHODS

The study group consisted of 24 children (14 boys and 10 girls), 3 to 12 years of age. All four dentists were 2nd year residents in pediatric dentistry. Conversations were taped and analyzed linguistically and statistically. The frequency of use of each approach was tabulated and correlated to the children's reported anxiety, cooperation during treatment, success of treatment, and mood at the end of treatment.

RESULTS

All dentists used the three approaches; the permissive approach, which supplied procedural information, was the most frequently used approach. The empathic approach was the least frequently used. Correlation tests showed that the empathic approach was most significantly related to the success of the treatment. Components of the permissive approach that contributed to the success of treatment were sensory information and supplying reasons.

CONCLUSIONS

Although generalization is limited because of the small sample, improving verbal conversational skills, emphasizing certain strategies, and improving linguistic abilities will contribute to better communication between child and pediatric dentist and to better cooperation and success in treatment.

Long term cerebroprotective effects of dexanabinol in a model of focal cerebral ischemia

In order to test the long-term cerebroprotective effects of dexanabinol, a synthetic non-competitive NMDA antagonist that also has anti-TNFalpha effects, spontaneously hypertensive rats underwent permanent middle cerebral artery occlusion (PMCAO). Rats were given vehicle or dexanabinol (4.5 mg/kg) 1, 3 or 6 h after PMCAO. The research consisted of 2 stages. In the short-term set of experiments animals (n=5/group), were tested with a motor disability scale 24 h post PMCAO, then sacrificed and the infarct volume was measured using 2,3,5-Triphenyltetrazolium chloride (TTC) staining. In the long-term set of experiments the rats (n=7/group) were examined daily with a motor disability scale up to 30 days after PMCAO and then sacrificed and infarct volumes were determined using TTC staining. Motor scores were significantly improved in the dexanabinol treated rats (P<0.05 for all groups) at all the time points examined. Infarct volumes were significantly reduced 24 h after PMCAO in the groups treated 1 or 3 h, but not 6 h after PMCAO compared with vehicle (Mean+/-S.D., 11.5+/-2.02, 12+/-3.2 and 14.4+/-2.4% vs. 20.8+/-1.3% hemispheric volume respectively). The lesions remained significantly smaller in the dexanabinol groups 30 days after PMCAO (Mean+/-S.D., 24.49+/-1.9% vs. 8.1+/-0.6, 11.1+/-2.3 and 13.8+/-2.5% hemispheric volume in animals treated with vehicle vs. dexanabinol 1, 3 or 6 h after PMCAO respectively; P<0.05 for all). In conclusion, the extended therapeutic window and the multi-mechanistic durable neuroprotective effects of dexanabinol make it a promising candidate for future stroke therapy.

TNF-alpha stimulates caspase-3 activation and apoptotic cell death in primary septo-hippocampal cultures

Primary septo-hippocampal cell cultures were incubated in varying concentrations of tumor necrosis factor (TNF-alpha; 0.3-500 ng/ml) to examine proteolysis of the cytoskeletal protein alpha-spectrin (240 kDa) to a signature 145 kDa fragment by calpain and to the apoptotic-linked 120-kDa fragment by caspase-3. The effects of TNF-alpha incubation on morphology and cell viability were assayed by fluorescein diacetate-propidium iodide (FDA-PI) staining, assays of lactate dehydrogenase (LDH) release, nuclear chromatin alterations (Hoechst 33258), and internucleosomal DNA fragmentation. Incubation with varying concentrations of TNF-alpha produced rapid increases in LDH release and nuclear PI uptake that were sustained over 48 hr. Incubation with 30 ng/ml TNF-alpha yielded maximal, 3-fold, increase in LDH release and was associated with caspase-specific 120-kDa fragment but not calpain-specific 145-kDa fragment as early as 3.5 hr after injury. Incubation with the pan-caspase inhibitor, carbobenzosy- Asp-CH(2)-OC (O)-2-6-dichlorobenzene (Z-D-DCB, 50-140 microM) significantly reduced LDH release produced by TNF-alpha. Apoptotic-associated oligonucleosomal-sized DNA fragmentation on agarose gels was detected from 6 to 72 hr after exposure to TNF-alpha. Histochemical changes included chromatin condensation, nuclear fragmentation, and formation of apoptotic bodies. Results of this study suggest TNF-alpha may induce caspase-3 activation but not calpain activation in septo-hippocampal cultures and that this activation of caspase-3 at least partially contributes to TNF-alpha-induced apoptosis.

Susceptibility of transgenic mice expressing human apolipoprotein E to closed head injury: the allele E3 is neuroprotective whereas E4 increases fatalities

Apolipoprotein E, the major brain lipid-binding protein, is expressed in humans as three common isoforms (E2, E3 and E4). Previous studies revealed that the allele apolipoprotein E4 is a major genetic risk factor of Alzheimer's disease and that traumatic brain injury is associated with increased risk for developing this disease. Furthermore, it has been suggested that the effects of traumatic head injury and apolipoprotein E4 in Alzheimer's disease are synergistic. To test the hypothesis that the apolipoprotein E genotype affects susceptibility to brain injury, we subjected transgenic mice, expressing either human apolipoprotein E3 or human apolipoprotein E4 on a null mouse apolipoprotein E background and apolipoprotein E-deficient knockouts, to closed head injury and compared mortality, neurological recovery and the extent of brain damage of the survivors. More than 50% of the transgenic mice expressing human apolipoprotein E4 died following closed head injury, whereas only half as many of the transgenic mice expressing human apolipoprotein E3, and of the control and apolipoprotein E-deficient mice died during this period (P<0.02). A neurological severity score used for clinical assessment of the surviving mice up to 11 days after closed head injury revealed that the four mouse groups displayed similar severity of damage at 1h following injury. At three and 11 days post-injury, however, the neurological severity scores of the transgenic mice expressing human apolipoprotein E3 were significantly lower than those of the other three groups whose scores were similar, indicating better recovery of the transgenic mice expressing human apolipoprotein E3. Histopathological examination of the mice performed 11 days post-injury revealed, consistent with the above neurological results, that the size of the damaged brain area of the transgenic mice expressing human apolipoprotein E3 was smaller than that of the other head-injured groups. These findings show that transgenic mice expressing human apolipoprotein E4 are more susceptible than those expressing apolipoprotein E3 to closed head injury. We suggest that this effect is due to both a protective effect of apolipoprotein E3 and an apolipoprotein E4-related pathological function.

Antisense prevention of neuronal damages following head injury in mice

Closed head injury (CHI) is an important cause of death among young adults and a prominent risk factor for nonfamilial Alzheimer's disease. Emergency intervention following CHI should therefore strive to improve survival, promote recovery, and prevent delayed neuropathologies. We employed high-resolution nonradioactive in situ hybridization to determine whether a single intracerebro-ventricular injection of 500 ng 2'-O-methyl RNA-capped antisense oligonucleotide (AS-ODN) against acetylcholinesterase (AChE) mRNA blocks overexpression of the stress-related readthrough AChE (AChE-R) mRNA splicing variant in head-injured mice. Silver-based Golgi staining revealed pronounced dendrite outgrowth in somatosensory cortex of traumatized mice 14 days postinjury that was associated with sites of AChE-R mRNA overexpression and suppressed by anti-AChE AS-ODNs. Furthermore, antisense treatment reduced the number of dead CA3 hippocampal neurons in injured mice, and facilitated neurological recovery as determined by performance in tests of neuromotor coordination. In trauma-sensitive transgenic mice overproducing AChE, antisense treatment reduced mortality from 50% to 20%, similar to that displayed by head-injured control mice. These findings demonstrate the potential of antisense therapeutics in treating acute injury, and suggest antisense prevention of AChE-R overproduction to mitigate the detrimental consequences of various traumatic brain insults.

Changes in regional energy metabolism after closed head injury in the rat

We examined in the present investigation regional ATP, glucose, and lactate content in the cortical and subcortical structures, in a rat model of closed head injury (CHI). In serial tissue sections bioluminescence imaging of ATP, glucose, and lactate was performed at 4 h, 12 h and 24 h (n = 4/5 per time point with) after the induction of CHI or sham surgery. Bioluminescence images were analyzed by computer-assisted densitometry, at the lesion site, in remote cortical areas, and in the subcortical structures (thalamus and caudate nucleus). ATP content was significantly decreased at the lesion site after 4 h and in the remote cortex at 12 h post-injury. At 12 h, the ATP content reached baseline levels on the ipsilateral side and at 24 h also at remote lateral parietal sites. In the contralateral cortex, ATP increased transiently above the baseline at 12 h. No significant changes in ATP were found in the thalamus and caudate nucleus. Cortical glucose and lactate contents could not be discerned over time. Following CHI there is an acute and progressive, yet transient, ischemic cortical profile, which is not reflected in subcortical areas.

A peptide derived from activity-dependent neuroprotective protein (ADNP) ameliorates injury response in closed head injury in mice

Brain injury induces disruption of the blood-brain barrier, edema, and release of autodestructive factors that produce delayed neuronal damage. NAPSVIPQ (NAP), a femtomolar-acting peptide, is shown to be neuroprotective in a mouse model of closed head injury. NAP injection after injury reduced mortality and facilitated neurobehavioral recovery (P < 0.005). Edema was reduced by 70% in the NAP-treated mice (P < 0.01). Furthermore, in vivo magnetic resonance imaging demonstrated significant brain-tissue recovery in the NAP-treated animals. NAP treatment decreased tumor necrosis factor-alpha levels in the injured brain and was shown to protect pheochromocytoma (PC12 cells) against tumor necrosis factor-alpha-induced toxicity. Thus, NAP provides significant amelioration from the complex array of injuries elicited by head trauma.

Tumor necrosis factor and reactive oxygen species cooperative cytotoxicity is mediated via inhibition of NF-kappaB

BACKGROUND

Tumor necrosis factor alpha (TNFalpha) plays a key role in pathogenesis of brain injury. However, TNFalpha exhibits no cytotoxicity in primary cultures of brain cells. This discrepancy suggests that other pathogenic stimuli that exist in the setting of brain injury precipitate TNFalpha cytotoxicity. The hypothesis was tested that reactive oxygen species (ROS), that are released early after brain injury, act synergistically with TNFalpha in causing cell death.

MATERIALS AND METHODS

Cultured human and rat brain capillary endothelial cells (RBEC), and cortical astrocytes were treated with TNFalpha alone or together with different doses of H2O2, and apoptotic cell death and DNA fragmentation were measured by means of 3'-OH-terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and Hoechst fluorescence assay, respectively. The effect of H2O2 on TNFalpha-induced activation of nuclear factor kappa B (NF-kappaB) was measured by Western blots of cytoplasmic and nuclear extracts of RBEC using anti-inhibitor of NF-kappaB (IkappaB) and anti-p65 subunit of NF-kappaB antibodies. Nuclear translocation of NF-kappaB was investigated by immunofluorescent staining of RBEC with anti-p65 antibodies.

RESULTS

TNFalpha alone had no cytotoxic effect in brain endothelial cells and astrocytes at concentrations up to 100 ng/ml. Co-treatment with 5-10 microM of H2O2 caused a two-fold increase in the number of apoptotic cells 24 hr later. Similar doses (1-3 microM) of H2O2 initiated early DNA fragmentation. H2O2 inhibited TNFalpha-induced accumulation of p65 in the nucleus, although it had no effect on degradation of the IkappaB in cytoplasm. Immunostaining confirmed that H2O2 inhibited p65 transport to the nucleus.

CONCLUSIONS

Reactive oxygen species could act synergistically with TNFalpha in causing cytotoxicity via inhibition of a cytoprotective branch of TNFalpha signaling pathways, which starts with NF-kappaB activation.

Closed head injury induces up-regulation of ErbB-4 receptor at the site of injury

ErbB-4 receptor tyrosine kinase and its ligand neu differentiation factor (NDF/neuregulin) are widely expressed in the brain. The closed head injury model was used to investigate the possible role of ErbB-4 receptor in neurodegeneration. It is demonstrated that levels of ErbB-4 are dramatically increased at the site of injury. Activated microglia/macrophages constitute the major population of cells with the highest receptor levels at the site of injury. In addition ErbB-4 expression after injury is elevated also in neurons but not in astrocytes. Confocal microscopy analysis suggests that the high level of ErbB-4 protein in activated microglia/macrophages is probably due to phagocytosis of neuronal cells. These findings show for the first time that ErbB-4 receptors play a role in brain responses to head trauma. Overexpression of ErbB-4 receptors may be important for directing activated microglia/macrophages to the lesion site.

Selective antagonism of endothelin-A-receptors improves outcome in both head trauma and focal stroke in rat

Increased levels of endothelin (ET) have been demonstrated in the ischemic brain, and ET receptor antagonism has been shown to improve outcome in cerebral ischemia. However, no previous work has been carried out evaluating the role of ET and its antagonism in brain trauma as compared to experimental stroke. In this study, we evaluated changes in brain ET levels following closed head injury (CHI) and the effects of SB 234551, an endothelin-A- (ET(A)) selective antagonist, and SB 209670, a mixed endothelin-A- and -B- (ET(A)/ET(B)) antagonist, on outcome in CHI and focal stroke. Male Sabra rats were subjected to CHI (weight drop model). Male Sprague Dawley rats were subjected to focal stroke (intraluminal suture model). Motor function(s) were assessed and immunoreactive ET (irET) and the degree of cerebral edema were measured for 24 h after CHI. Brain swelling (edema), neurological deficits and forebrain infarct volumes were measured 24 h after focal stroke. Antagonists (total doses of 7.5, 15, 30 or 60 mg/kg) were administered intravenously for 6-24 h (beginning 15 min after injury). Control rats were infused with vehicle. CHI resulted in increased ET levels in the directly contused hemisphere at 12 and 24 h. In addition, SB 234551 significantly reduced neurological deficits (decreased 30%) and brain edema (decreased 40%) following CHI (p < 0.05 at 60 mg/kg dose). SB 209670 had no effects on CHI outcome. Focal stroke studies yielded similar results. SB 234551 reduced focal stroke-induced neurological deficits by 50%, brain swelling by 54% and the degree of infarction by 36% (p < 0.05 at 30 mg/kg). SB 209670 did not provide any neuroprotection in focal stroke. These data indicate that ET plays a significant role in the pathophysiology of CHI, and that selectively targeting ET(A)-receptors similarly in both CHI and stroke might be a therapeutic opportunity.

Neurological recovery from closed head injury is impaired in diabetic rats

Diabetes mellitus is a metabolic disorder associated with central nervous system impairments. Recent studies implicate oxidative stress mediated by reactive oxygen species (ROS) in the pathogenesis of diabetic complications. ROS have been shown to play role in the pathophysiology of brain injury. In the present study, closed head injury (CHI) was induced in diabetic rats to test the hypothesis that chronic oxidative stress exacerbates brain damage following CHI. Neurological recovery, edema, levels of low molecular weight antioxidants (LMWA), and markers of lipid peroxidation were determined at different intervals after injury. Diabetic rats (4 weeks after induction with streptozotocin) were subjected to CHI. Brain edema (percent water) and clinical status (neurological severity score) were assessed during 7 days. Brain LMWA were determined using cyclic voltammetry (CV) and HPLC-EC. In addition, conjugated dienes and thiobarbituric acid reactive substances (TBARS) were measured. Diabetic-CHI rats exhibited a lower rate of recovery and greater and more sustained edema (p < 0.01), as compared with the controls. At all times diabetic rats had higher levels of TBARS and conjugated dienes and lower concentrations of LMWA, and of vitamins C and E, suggesting chronic oxidative stress. At 5 min of CHI, the amounts of LMWA in control-CHI brains decreased (approximately 50%, p < 0.01) and returned to normal by 48 h and 7 days. In the diabetic-CHI brain only one class of LMWA slightly declined but remained low for 7 days. The present results support the hypothesis that diabetic rats are under chronic oxidative stress, and suffer greater neurological dysfunction, associated with further lipid peroxidation following CHI.

Intracerebral complement C5a receptor (CD88) expression is regulated by TNF and lymphotoxin-alpha following closed head injury in mice

The anaphylatoxin C5a is a potent mediator of inflammation in the CNS. We analyzed the intracerebral expression of the C5a receptor (C5aR) in a model of closed head injury (CHI) in mice. Up-regulation of C5aR mRNA and protein expression was observed mainly on neurons in sham-operated and head-injured wild-type mice at 24 h. In contrast, in TNF/lymphotoxin-alpha knockout mice, the intracerebral C5aR expression remained at low constitutive levels after sham operation, whereas it strongly increased in response to trauma between 24 and 72 h. Interestingly, by 7 days after CHI, the intrathecal C5aR expression was clearly attenuated in the knockout animals. These data show that the posttraumatic neuronal expression of the C5aR is, at least in part, regulated by TNF and lymphotoxin-alpha at 7 days after trauma.

Human brain capillary endothelium: 2-arachidonoglycerol (endocannabinoid) interacts with endothelin-1

In brain, the regulatory mechanism of the endothelial reactivity to nitric oxide and endothelin-1 may involve Ca(2+), cytoskeleton, and vasodilator-stimulated phosphoprotein changes mediated by the cGMP/cGMP kinase system.(1) Endothelium of human brain capillaries or microvessels is used to examine the interplay of endothelin-1 with the putative vasorelaxant 2-arachidonoyl glycerol, an endogenous cannabimimetic derivative of arachidonic acid. This study demonstrates that 2-arachidonoyl glycerol counteracts Ca(2+) mobilization and cytoskeleton rearrangement induced by endothelin-1. This event is independent of nitric oxide, cyclooxygenase, and lipoxygenase and is mediated in part by cannabimimetic CB1 receptor, G protein, phosphoinositol signal transduction pathway, and Ca(2+)-activated K(+) channels. The induced rearrangements of cellular cytoskeleton (actin or vimentin) are partly prevented by inhibition of protein kinase C or high levels of potassium chloride. The 2-arachidonoyl glycerol-induced phosphorylation of vasodilator-stimulated phosphoprotein is mediated by cAMP. These findings suggest that 2-arachidonoyl glycerol may contribute to the regulation of cerebral capillary and microvascular function.

Tau hyperphosphorylation in apolipoprotein E-deficient and control mice after closed head injury

Apolipoprotein E (apoE)-deficient mice have learning and memory impairments that are associated with specific neurochemical changes and hyperphosphorylation of distinct epitopes of the cytoskeletal protein tau. Furthermore, such mice are highly susceptible to the sequelae of brain trauma and their ability to recover from head injury is impaired. In the present study we investigated the extent that the neuronal maintenance and repair impairments of apoE-deficient mice are related to aberrations at the tau phosphorylation level. This was pursued by subjecting control and apoE-deficient mice to closed head injury (CHI) and examination, utilizing immunoblot assays, of the resulting effects on tau phosphorylation. The results thus obtained revealed that tau of apoE-deficient mice is hyperphosphorylated before CHI and that this insult results in transient tau hyperphosphorylation, whose extent and time course in the two mouse groups varied markedly. Tau hyperphosphorylation in the injured controls was maximal by about 4 hr after injury and reverted to basal levels by 24 hr. In contrast, almost no head injury-induced tau hyperphosphorylation was observed in the apoE-deficient mice at 4 hr after injury. Some tau hyper-phosphorylation was detected in the head-injured apoE-deficient mice after longer time intervals, but its extent was markedly lower than the maximal values obtained in the head injured controls. These findings show that the chronic neuronal impairments brought about by apoE deficiency and the acute response to head injury are both associated with hyperphosphorylation of the same tau domain and that the ability of apoE-deficient mice to mount the acute tau hyperphosphorylation response to head injury is impaired.

Increased levels of intracellular iron in the brains of ApoE-deficient mice with closed head injury

Previous studies have revealed that apolipoprotein E (apoE)-deficient mice have distinct memory deficits and neurochemical derangements and are oxidatively stressed prior to and following closed head injury. The objective of this study was to evaluate the possibility that the enhanced susceptibility of apoE-deficient mice to closed head injury is related to impairments in their antioxidative iron-chelating mechanisms. ApoE-deficient and control mice were subjected to closed had injury, after which the extent of brain-damage and the level of iron-containing cells were assessed. Examination of the brain-damaged areas in the injured mice revealed that, by Day 3 post injury, animals of both groups were maximally and similarly affected. While the size of the damaged area of the injured control mice diminished significantly by Day 7, however recovery was not observed in injured apoE-deficient mice up to at least 14 days post-injury. Histopathologically, the decrease in the damaged areas in the control mice was interpreted as related to decreased edema. Numbers of iron-containing cells at Days 3 and 7 after injury were greater in the brains of control mice than in the apoE-deficient mice. Whereas the number of iron-containing cells in injured control mice decreased at days 9 and 14-post injury, that of the injured apoE-deficient mice plateaued by Day 9 at a level more than two-fold higher than the maximal level seen for controls. The size of the damaged areas and the number of iron-containing cells were correlated (P < 0.03) for both mouse groups at days 9 and 14 after injury. The data suggest that the increased susceptibility of apoE-deficient mice to closed head injury may be due, at least in part, to impaired iron scavenging and sustained oxidative stress.

Increased hepatic lipid soluble antioxidant capacity as compared to other organs of streptozotocin-induced diabetic rats: a cyclic voltammetry study

It has been suggested that oxidative stress plays an important role in the chronic complications of diabetes. The experimental findings regarding the changes in tissue antioxidant enzymes and lipid peroxidation of diabetic tissues have been inconsistent. Previous studies in our laboratory demonstrated that the reducing power of a specific tissue correlates with its low molecular weight antioxidant (LMWA) capacity. In the present study, the overall LMWA capacity (reducing equivalents) of plasma and tissues of streptozotocin (STZ)-induced diabetic rats (1-4 weeks) and insulin treated diabetic rats were measured by cyclic voltammetry. Levels of water and lipid soluble LMWA capacity progressively decreased in the diabetic plasma, kidney, heart and brain, while the diabetic liver, at 2, 3 and 4 weeks after STZ injection, showed a significant increase in the overall lipid soluble LMWA capacity (p < 0.001). Subsequently, analysis of specific components by high pressure liquid chromatography (electrochemical detection) showed decreased levels of ascorbic acid in plasma, kidney, heart and brain of diabetic animals. The alpha-tocopherol level dropped in all tissues, except for the liver in which there was a significant increase (p < 0.01 and p < 0.001 at 2-4 weeks). Lipid peroxidation was assessed by conjugated diene levels, which increased significantly in all diabetic tissues except the liver. Insulin treatment that was started after 3 weeks of diabetes and continued for 3 weeks showed no change in the conjugated dienes and in the overall LMWA capacity in all organs. Our results suggest a unique behavior of the liver in the STZ-induced diabetic rats to the stress and indicate its higher capacity to cope with oxidative stress as compared to other organs.

Experimental closed head injury: analysis of neurological outcome, blood-brain barrier dysfunction, intracranial neutrophil infiltration, and neuronal cell death in mice deficient in genes for pro-inflammatory cytokines

Cytokines are important mediators of intracranial inflammation following traumatic brain injury (TBI). In the present study, the neurological impairment and mortality, blood-brain barrier (BBB) function, intracranial polymorphonuclear leukocyte (PMN) accumulation, and posttraumatic neuronal cell death were monitored in mice lacking the genes for tumor necrosis factor (TNF)/lymphotoxin-alpha (LT-alpha) (TNF/LT-alpha-/-) and interleukin-6 (IL-6) and in wild-type (WT) littermates subjected to experimental closed head injury (total n = 107). The posttraumatic mortality was significantly increased in TNF/LT-alpha-/- mice (40%; P < 0.02) compared with WT animals (10%). The IL-6-/- mice also showed a higher mortality (17%) than their WT littermates (5.6%), but the difference was not statistically significant (P > 0.05). The neurological severity score was similar among all groups from 1 to 72 hours after trauma, whereas at 7 days, the TNF/LT-alpha-/- mice showed a tendency toward better neurological recovery than their WT littermates. Interestingly, neither the degree of BBB dysfunction nor the number of infiltrating PMNs in the injured hemisphere was different between WT and cytokine-deficient mice. Furthermore, the analysis of brain sections by in situ DNA nick end labeling (TUNEL histochemistry) at 24 hours and 7 days after head injury revealed a similar extent of posttraumatic intracranial cell death in all animals. These results show that the pathophysiological sequelae of TBI are not significantly altered in mice lacking the genes for the proinflammatory cytokines TNF, LT-alpha, and IL-6. Nevertheless, the increased posttraumatic mortality in TNF/LT-alpha-deficient mice suggests a protective effect of these cytokines by mechanisms that have not been elucidated yet.

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.

Diffusion and perfusion magnetic resonance imaging following closed head injury in rats

Diffusion-, perfusion-, T1-, and T2-weighted magnetic resonance imaging (MRI) were performed at 1-2 h, 24 h, and 1 week following closed head injury (CHI) in rats, and data was compared with hematoxylin and eosin histology. At 1-2 h, large areas of low perfusion in the damaged hemisphere overestimate the histological damage. In the first 2 h, the histological damage seems to be a superposition of abnormalities in the T1- and diffusion-weighted images. In areas with more than 10% reduction in the apparent diffusion coefficients (ADCs), reduced regional cerebral blood volume (r-CBV) was also observed. The decrease in ADCs and rCBV correlated with r = 0.78. Changes in the MRI parameters revealed the following: (a) Further reduction in ADC occurred from 83+/-15% at 1-2 h after trauma to 69+/-9% at 24 h, and 1 week later a marked elevation in the ADC values is observed. (b) Blood perfusion measurements performed 1-2 h posttrauma revealed a pronounced reduction in r-CBV (53+/-18%) in the damaged hemisphere in all rats. At 24 h postimpact, areas of hyper- and hypoperfusion were observed. One week later, similar perfusion was found in both hemispheres of all rats. (c) T2 hyperintensity at 24 h overestimated the histological damage found at 1 week. At one week following the trauma, the T2 hyperintensity underestimated the histological damage. It is concluded that CHI, which is a heterogeneous insult, should be studied by a combination of MRI techniques. The superposition of the abnormalities seen on T1 and on the diffusion-weighted MR images at early time point represents best the histological damage. Both T2 and rCBV images are less informative in terms of actual histological damage.

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.

Serum-mediated osteogenic effects of head injury on cultured rat marrow stromal cells

Central nervous system (CNS) injuries in humans are frequently associated with heterotopic ossification (HO) and with enhanced fracture healing. In search for an experimental HO model we tested sera, from an established rat model of closed head injury (CHI), for their osteogenic effects on rat marrow stromal cells. Most normal rat sera increased cell proliferation not discriminating between osteoprogenitors and other stromal cells. Rats followed longitudinally by sequential blood sampling were bled 24 hours before and 24 hours, 48 hours, and 7 days after CHI. Sera obtained 24 and 48 hours after CHI progressively decreased cell proliferation and specific alkaline phosphatase (ALP) activity compared with pre-CHI sera of the same rats. Sera obtained from these rats, 7 days post-CHI, partially recovered proliferation induction, more than recovering induction of specific ALP activity. A positive correlation between day 11 ALP activity and day 21 mineralization was found under stimulation by pre-CHI sera. However, no correlation was found on stimulation with sera obtained 48 hours after CHI. Correlation between ALP and mineralization partially recovered in cultures exposed to sera obtained 7 days after CHI. In cross-sectional experiments where rats were subjected to single blood sampling, sera of 24 hours and 7 days post-CHI induced proliferation, whereas sera of 48 hours and 14 days post-CHI did not. The results indicate that 48 hours post-CHI, the mitogenicity of sera decreased in both cross-sectional and longitudinal blood sampling. In addition, 48 hours post-CHI, the specific ALP activity increases in cultured marrow stromal cells. Thus, changes in bone-seeking factors, causing serum-mediated osteogenic activity in rats, are expected close on 48 hour post-CNS injury.

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.

Dual role of tumor necrosis factor alpha in brain injury

Brain injury (ischemia, trauma) is among the leading cause of mortality and disability in the western world. It induces increased production of tumor necrosis factor (TNF alpha) by brain resident cells. There is conflicting evidence on the role of this response in the injured brain, showing its potential effect in both processes of repair and of damage. This review presents data from clinical and experimental studies on the stimulation of TNF alpha production in brain injury and on the deleterious consequence of this acute response. Its inhibition by pharmacologic agents, neutralizing antibodies or soluble receptors has protective effects. In contrast, there are reports (from in-vitro studies or knock-out mice) on the beneficial effects of TNF alpha. To reconcile these apparently conflicting reports, the exact timing and extent of TNF alpha activation must be taken into account, as well as the presence of other mediators such as reactive oxygen species. It is suggested that the appropriate context of mediators, at any given time after brain injury may well determine whether the effect of TNF alpha is protective or toxic.

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.

Neuroprotective effect of rasagiline, a selective monoamine oxidase-B inhibitor, against closed head injury in the mouse

The potential neuroprotective effects of rasagiline, N-propargyl-1R-aminoindan, a selective monoamine oxidase-B inhibitor and its inactive enantiomer TVP 1022, N-propargyl-1S-aminoindan were assessed against the sequelae of closed head injury in the mouse. Injury was induced in the left hemisphere under ether anaesthesia. Rasagiline (0.2 and 1 mg/kg) or TVP1022 (1 and 2 mg/kg) injected 5 min after injury accelerated the recovery of motor function and spatial memory and reduced the cerebral oedema by about 40-50%, (P < 0.01). The neuroprotective effects on motor function and spatial memory, but not on cerebral oedema, were prevented by scopolamine (0.2 mg/kg). Daily injection of rasagiline (1 mg/kg) from day 3 after injury accelerated the recovery of spatial memory but not motor function.

CONCLUSIONS

Early administration of rasagiline or TVP1022 can reduce the immediate sequelae of brain injury. The mechanism of action does not appear to involve monoamine oxidase-B inhibition but could be mediated by the maintenance of cholinergic transmission in brain neurons.

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.

Dexanabinol; a novel neuroprotective drug in experimental focal cerebral ischemia

The permanent middle cerebral artery occlusion (PMCAO) model was used to investigate the cerebroprotective effects of the synthetic cannabinoid, dexanabinol (HU-211). Dexanabinol is a noncompetitive N-methyl-D-aspartate antagonist, with antioxidant and anti-TNFalpha properties. Twenty hypertensive rats were subjected to PMCAO. Eight were given 4 mg/kg dexanabinol, i.v., 1 h after PMCAO, eight received vehicle and four were not injected Five rats underwent sham surgery. Infarct volumes were assessed, as well as TNFalpha concentrations and NOS activity in brain homogenates. Dexanabinol significantly decreased infarct volumes. It also significantly lowered TNFalpha levels in the ipsilateral hemisphere although not to the level of sham operated rats. No effect could be demonstrated on NOS activity. In conclusion, dexanabinol may be a pluripotent cerebroprotective agent.

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.

The effects of the acetylcholinesterase inhibitor ENA713 and the M1 agonist AF150(S) on apolipoprotein E deficient mice

Apolipoprotein E (apoE)-deficient and control mice were treated chronically with either the acetylcholinesterase (AChE) inhibitor ENA713, or the M1 muscarinic agonist AF150(S). Both treatments reversed the spatial working memory impairment of apoE-deficient mice but they differed in their effects on the levels of brain AChE activity. AF150(S) enhanced the brain AChE activity of apoE-deficient mice and rendered it similar to that of the untreated controls, whereas ENA713 reduced the brain AChE activity of control mice but had no effect on that of apoE-deficient mice. These findings suggest that AChE inhibition and M1 muscarinic activation have similar beneficial cognitive effects on apoE-deficient mice, but that the cellular and molecular mechanisms underlying these effects differ.

Rivastigmine, a brain-selective acetylcholinesterase inhibitor, ameliorates cognitive and motor deficits induced by closed-head injury in the mouse

The effects of Rivastigmine, a novel centrally-acting anticholinesterase agent, were evaluated on cerebral edema, neurological and motor deficits, and impairment of spatial memory induced in mice by closed-head injury (CHI). Severe injury was induced in the left hemisphere of mice under ether anesthesia. Rivastigmine (1 or 2 mg/kg) or saline (10 ml/kg) was injected SC 5 min later. Rivastigmine (2 mg/kg) reduced cerebral edema by at least 50% (p < 0.01), 24 h after CHI and accelerated the recovery of motor function 7 and 14 days after CHI. Control mice (n = 24), previously trained to find the goal platform in a Morris water maze failed to recall or relearn its position for at least 11 days post-injury. Those given a single injection of Rivastigmine (2 mg/kg) regained their pre-test latencies by the third day after CHI. The neuroprotective effects of Rivastigmine on brain edema, neurological and motor function, and performance in the Morris water maze were completely antagonized by simultaneous SC injection of either scopolamine (0.5 mg/kg) or mecamylamine (2.5 mg/kg). The antagonists alone had no significant effect on any of these parameters. These data show that the reduction by Rivastigmine of the immediate and long-term sequelae of brain injury are mediated by increased cholinergic activity at both muscarinic and nicotinic receptors.

Cerebro-protective effects of ENA713, a novel acetylcholinesterase inhibitor, in closed head injury in the rat

Focal ischemic brain damage and diffuse brain swelling occur in severe cases of traumatic head injury. Ischemia decreases brain acetylcholine (ACh) levels and head trauma upregulates acetylcholinesterase (AChE) in experimental animal models. The present study determined whether a brain-selective AChE inhibitor, ENA713, given once, up to 2 h after closed head injury (CHI) could reduce the vasogenic edema and accelerate recovery from neurological deficits induced by the injury in rats. ENA713 1-5 mg/kg produced a dose-related inhibition of AChE ranging from 40-85% in the cortex and hippocampus. Doses of 1, 2 and 5 mg/kg, significantly reduced the motor and neurological deficits and speeded recovery, as indicated by measurements made 7 and 14 days after injury. The two larger doses were still effective when injected 1 or 2 h after CHI. The acceleration by ENA713 of recovery of motor function was independent of its reduction in body temperature and was prevented by the simultaneous injection of mecamylamine (2.5 mg/kg), but not by scopolamine (0.2 or 1 mg/kg). Edema in the contused hemisphere (24 h after injury) and disruption of the blood brain barrier (4 h after injury) were significantly reduced (about 50%) by doses of 2 and 5 mg/kg, but not by 1 mg/kg. The data support the hypothesis that ENA713 exerts a neuroprotective effect in brain injury by preventing the decrease in cholinergic activity in cerebral vessels and in neurones.

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.