Alterations in brain protein kinase C after experimental brain injury

PKCγ promotes axonal remodeling in the cortico-spinal tract via GSK3β/β-catenin signaling after traumatic brain injury

Traumatic brain injury (TBI) is a common cause of death and disability. Enhancing the midline-crossing of the contralateral corticospinal tract (CST) to the denervated side of spinal cord facilitates functional recovery after TBI. Activation of the gamma isoform of PKC (PKCγ) in contralateral CST implicates its roles in promoting CST remodeling after TBI. In this study, we deployed loss and gain of function strategies in N2a cells and primary cortical neurons in vitro, and demonstrated that PKCγ is not only important but necessary for neuronal differentiation, neurite outgrowth and axonal branching but not for axonal extension. Mechanically, through the phosphorylation of GSK3β, PKCγ stabilizes the expression of cytosolic β-catenin and increase GAP43 expression, thus promoting axonal outgrowth. Further, rAAV2/9-mediated delivery of constitutive PKCγ in the corticospinal tract after unilateral TBI in vivo additionally showed that specifically delivery of active PKCγ mutant to cortical neuron promotes midline crossing of corticospinal fibers from the uninjured side to the denervated cervical spinal cord. This PKCγ-mediated injury response promoted sensorimotor functional recovery. In conclusion, PKCγ mediates stability of β-catenin through the phosphorylation of GSK3β to facilitate neuronal differentiation, neurite outgrowth and axonal branching, and PKCγ maybe a novel therapeutic target for physiological and functional recovery after TBI.

Therapeutic hypercapnia reduces blood-brain barrier damage possibly via protein kinase Cε in rats with lateral fluid percussion injury

Background

This study investigated whether therapeutic hypercapnia (TH) ameliorated blood–brain barrier (BBB) damage and improved the neurologic outcome in a rat model of lateral fluid percussion injury (FPI), and explored the possible underlying mechanism.

Methods

Rats underwent lateral FPI and received inhalation of 30%O₂–70%N₂ or 30%O₂–N₂ plus CO₂ to maintain arterial blood CO₂ tension (PaCO₂) between 80 and 100 mmHg for 3 h. To further explore the possible mechanisms for the protective effects of TH, a PKC inhibitor staurosporine or PKCαβ inhibitor GÖ6976 was administered via intracerebral ventricular injection.

Results

TH significantly improved neurological function 24 h, 48 h, 7 d, and 14 d after FPI. The wet/dry ratio, computed tomography values, Evans blue content, and histological lesion volume were significantly reduced by TH. Moreover, numbers of survived neurons and the expression of tight junction proteins (ZO-1, occludin, and claudin-5) were significantly elevated after TH treatment at 48-h post-FPI. TH significantly increased the expression of protein kinase Cε (PKCε) at 48-h post-FPI, but did not significantly change the expression of PKCα and PKCβII. PKC inhibitor staurosporine (but not the selective PKCαβ inhibitor-GÖ6976) inhibited the protective effect of TH.

Conclusions

Therapeutic hypercapnia is a promising candidate that should be further evaluated for clinical treatment. It not only protects the traumatic penumbra from secondary injury and improves histological structure but also maintains the integrity of BBB and reduces neurologic deficits after trauma in a rat model of FPI.

Traumatic Brain Injury Induces Alterations in Cortical Glutamate Uptake without a Reduction in Glutamate Transporter-1 Protein Expression

We hypothesize that the primary mechanism for removal of glutamate from the extracellular space is altered after traumatic brain injury (TBI). To evaluate this hypothesis, we initiated TBI in adult male rats using a 2.0 atm lateral fluid percussion injury (LFPI) model. In the ipsilateral cortex and hippocampus, we found no differences in expression of the primary glutamate transporter in the brain (GLT-1) 24 h after TBI. In contrast, we found a decrease in glutamate uptake in the cortex, but not the hippocampus, 24 h after injury. Because glutamate uptake is potently regulated by protein kinases, we assessed global serine-threonine protein kinase activity using a kinome array platform. Twenty-five kinome array peptide substrates were differentially phoshorylated between LFPI and controls in the cortex, whereas 19 peptide substrates were differentially phosphorylated in the hippocampus (fold change ≥ ± 1.15). We identified several kinases as likely to be involved in acute TBI, including protein kinase B (Akt) and protein kinase C (PKC), which are well-characterized modulators of GLT-1. Exploratory studies using an inhibitor of Akt suggest selective activation of kinases in LFPI versus controls. Ingenuity pathway analyses of implicated kinases from our network model found apoptosis and cell death pathways as top functions in acute LFPI. Taken together, our data suggest diminished activity of glutamate transporters in the prefrontal cortex, with no changes in protein expression of the primary glutamate transporter GLT-1, and global alterations in signaling networks that include serine-threonine kinases that are known modulators of glutamate transport activity.

Bryostatin-1 Restores Blood Brain Barrier Integrity following Blast-Induced Traumatic Brain Injury

Recent wars in Iraq and Afghanistan have accounted for an estimated 270,000 blast exposures among military personnel. Blast traumatic brain injury (TBI) is the 'signature injury' of modern warfare. Blood brain barrier (BBB) disruption following blast TBI can lead to long-term and diffuse neuroinflammation. In this study, we investigate for the first time the role of bryostatin-1, a specific protein kinase C (PKC) modulator, in ameliorating BBB breakdown. Thirty seven Sprague-Dawley rats were used for this study. We utilized a clinically relevant and validated blast model to expose animals to moderate blast exposure. Groups included: control, single blast exposure, and single blast exposure + bryostatin-1. Bryostatin-1 was administered i.p. 2.5 mg/kg after blast exposure. Evan's blue, immunohistochemistry, and western blot analysis were performed to assess injury. Evan's blue binds to albumin and is a marker for BBB disruption. The single blast exposure caused an increase in permeability compared to control (t = 4.808, p < 0.05), and a reduction back toward control levels when bryostatin-1 was administered (t = 5.113, p < 0.01). Three important PKC isozymes, PKCα, PKCδ, and PKCε, were co-localized primarily with endothelial cells but not astrocytes. Bryostatin-1 administration reduced toxic PKCα levels back toward control levels (t = 4.559, p < 0.01) and increased the neuroprotective isozyme PKCε (t = 6.102, p < 0.01). Bryostatin-1 caused a significant increase in the tight junction proteins VE-cadherin, ZO-1, and occludin through modulation of PKC activity. Bryostatin-1 ultimately decreased BBB breakdown potentially due to modulation of PKC isozymes. Future work will examine the role of bryostatin-1 in preventing chronic neurodegeneration following repetitive neurotrauma.

Activation of microglia with lipopolysaccharide leads to the prolonged decrease of conventional protein kinase C activity

The activation of microglia by lipopolysaccharide (LPS) results in the induction of harmful factors including nitric oxide and tumor necrosis factor alpha (TNFalpha). Such microglial activation was suggested to be mediated by PKC activity based on the results of an inhibitor experiment. To clarify the relationship between microglial activation and PKC activity, conventional PKC (cPKC) activity was measured by enzyme-linked immunosorbent assay (ELISA) in LPS-activated microglia. LPS stimulation caused a time- and dose-dependent decrease (70%) of specific activity of cPKC, ascribed to the decreasing amounts of PKCalpha. However, the remaining PKC activity (30%) was sustained despite longer incubation or higher LPS concentration. Therefore, it is suggested that LPS-stimulated microglia require priming by PKC activation for the induction of harmful factors, while only a part (30%) of original PKC activity is sufficient for durable microglial activation.

Protein kinase C isoforms as therapeutic targets in nervous system disease states

Neuronal tissues display high levels of protein kinase C (PKC) activity and isoform expression. The activation of this enzymatic system is important in the control of short and long term brain functions (ion channel regulation, receptor modulation, neurotransmitter release, synaptic potentiation/depression, neuronal survival) that are related to diverse brain pathologies. This review will describe recent developments in PKC regulation and changes in levels, isoforms and activation in acute and chronic neurodegenerative pathologies as well as in affective and psychic disorders. The recent availability of isoform selective inhibitors and activators may help to understand better the relevance of PKC in central nervous system (CNS) physiology and pathology and to identify new and safer pharmacologic strategies to be tested in different disease states.

Regional expression of Par-4 mRNA and protein after fluid percussion brain injury in the rat

Regional levels of prostate apoptosis response-4 (Par-4) protein and mRNA were measured after lateral fluid percussion (FP) brain injury in rats. Immunochemical studies indicated that Par-4 immunoreactivity (ir) is present in cortical neurons and hippocampal CA1-CA3 pyramidal neurons in uninjured rats. Increases of Par-4-ir were observed in the CA3 neurons of the ipsilateral hippocampus (IH), but not in injured left cortex (IC) at 48 h after FP brain injury. Levels of the Par-4 mRNA measured by RT-PCR assay and protein measured by Western blot procedure were significantly increased in the injured IC and IH, but not in the contralateral right cortex and hippocampus after brain injury. Levels of both Par-4 protein and mRNA were significantly increased in the IC and IH as early as 2 h and stayed elevated at 24 and 48 h after injury. These data show that the induction of proapoptotic Par-4 mRNA and protein occurs only in the IC and IH that have been observed to undergo apoptosis and neuronal cell loss after lateral FP brain injury. Because increased expression of Par-4 has been observed to contribute to apoptosis and cell death in cultured neurons, the present temporal pattern of Par-4 expression is consistent with a role for Par-4 in apoptosis and neuronal cell death after traumatic brain injury.

Regional expression of Bcl-2 mRNA and mitochondrial cytochrome c release after experimental brain injury in the rat

Regional levels of anti-apoptotic Bcl-2 mRNA and the cytosolic cytochrome c protein were measured after lateral fluid percussion (FP) brain injury in rats. Levels of Bcl-2 mRNA were significantly decreased in the injured left cortex (IC) and ipsilateral hippocampus (IH), but not in the contralateral right cortex (CC) and hippocampus (CH) after brain injury. Levels of Bcl-2 mRNA were significantly decreased as early as 2 h and stayed decreased as long as 48 h in the IC and IH after injury. Levels of the cytosolic cytochrome c protein were significantly increased in the IC and IH, but not in the CC and CH after brain injury. Levels of cytosolic cytochrome c were significantly increased in the IC at 30 min, 48 and 72 h, and in the IH at 2 h and as long as 72 h after injury. The increase of cytosolic cytochrome c suggests that the mitochondrial release of cytochrome is increased in the IC and IH after lateral FP brain injury. These data show that the reduction of anti-apoptotic Bcl-2 and increases of mitochondrial release of cytochrome c protein occur only in the IC and IH, regions which have been observed to undergo apoptosis and neuronal cell loss after lateral FP brain injury. Therefore, it is likely that the reduction of Bcl-2 and the increased cytochrome c protein in the cytosol contribute to the observed apoptosis and neuronal cell death in the IC and IH after lateral FP brain injury in rats.

The effect of protein kinase C activation on colonic epithelial cellular integrity

We have investigated whether activation of protein kinase C has a direct cytotoxic effect on colonic mucosal epithelial cells and whether oxidant-induced damage to colonocytes is mediated by activation of cellular protein kinase C. Incubation of freshly harvested cells from rat colon with the protein kinase C activator, phorbol 12-myristate, resulted in a concentration-dependent increase in the extent of cell injury. Phorbol 12-myristate acetate (0.1-10 microM) also increased cellular protein kinase C activity and this was reduced significantly by treating cells with the antagonists staurosporine or 2-[1-(3-dimethylaminopropyl)-indol-3-yl]3-(-indol-3-yl)maleimide (GF 109203X; 10 microM). Phorbol 12-myristate acetate treatment also resulted in increased translocation of proteins for protein kinase C isoforms alpha, delta and epsilon from cytosol to membrane particulate fractions. The antagonists reduced the extent of cell damage in response to phorbol 12-myristate acetate. Furthermore, cell injury in response to the phorbol acetate was also inhibited by the addition of the oxidant scavengers, superoxide dismutase or catalase to the cell suspension. Addition of H(2)O(2) to the incubation medium (0.1-100 microM) resulted in an increase in cellular protein kinase C activity, an increase in the expression of the alpha, beta and zeta isoforms and a reduction in cell integrity. The cellular damaging actions of H(2)O(2) were significantly reduced by the protein kinase C antagonists, staurosporine or 2-[1-(3-dimethylaminopropyl)-indol-3-yl]-3-(-indol-3-yl)maleimide (GF 109203X). These findings suggest that protein kinase C activation results in colonic cellular injury and this damage is mediated, at least in part, by release of reactive oxidants. Furthermore, oxidant-mediated damage to these cells also involves protein kinase C activation.

Modulation of protein kinase C isoforms by PAF in cerebral cortex

The effect of platelet activating factor (PAF) on subcellular distribution of protein kinase C isoforms in rat cerebral cortex was investigated. PAF induced an increase in levels of protein kinase C epsilon and gamma in membrane fraction. Results also indicate that PAF induced an increase in protein kinase C delta levels in both cytosolic and membrane fraction. This effect is possibly due to an increase in enzyme synthesis, as indicated by the results obtained from the experiments performed in the presence of cycloheximide and actinomycin. All the effects induced by PAF were time- and dose-dependent, and were mediated through the activation of PAF receptor. These findings indicate that the three isoforms may be involved in signal transduction of PAF in the brain.

Alterations in BDNF and trkB mRNA levels in the cerebral cortex following experimental brain trauma in rats

Recent studies have suggested that brain-derived neurotrophic factor (BNDF) and its receptor, trkB, may provide neuroprotection following injury to the central nervous system. Conversely, other studies have implicated BDNF as a contributing factor to neurodegenerative events that occur following injury. In order to further investigate the role of BDNF in neuroprotection, we subjected adult rats to a lateral fluid percussion (FP) injury of moderate severity (2.0-2.1 atm) or sham injury. After survival periods of 1, 3, 6, 24, or 72 h, the brains were processed for the in situ hybridization localization of BDNF and trkB mRNAs using 35S-labeled cRNA probes. Hybridization levels were compared between injured and sham animals for regions of the cortex that were located within, adjacent to, and remote from the site of the cortical contusion. BDNF mRNA levels were significantly decreased in the injured cortex at 72 h, increased in adjacent cortical areas at 3 h, and increased bilaterally in the piriform cortex from 3 to 24 h post-FP injury. Expression of trkB mRNA was significantly decreased at all postinjury time-points in the injured cortex and at 24 h in the adjacent cortex. These results demonstrate that, following lateral FP injury, BDNF and trkB mRNA levels are decreased in cortical regions that contain degenerating neurons, generally unchanged in adjacent regions, and increased in remote areas. Thus, injury-induced decreases in the expression of BDNF and trkB may confer vulnerability to neurons within the cortical contusion.

Regional activities of phospholipase C after experimental brain injury in the rat

Regional activities of phosphoinositide-specific phospholipase C (PLC) were measured after lateral fluid percussion (FP) brain injury in rats. The activity of PLC on phosphatidylinositol 4,5-bisphosphate (PIP2) in the rat cortex required calcium, and at 45 microM concentration it increased PLC activity by about ten-fold. The activity of PLC was significantly increased in the cytosol fraction in the injured (left) cortex (IC) at 5 min, 30 min and 120 min after brain injury. However, in the same site, increases were observed in the membrane fraction only at 5 min after brain injury. In both the contralateral (right) cortex (CC) and ipsilateral hippocampus (IH), the activity of PLC was increased in the cytosol only at 5 min after brain injury. These results suggest that increased activity of PLC may contribute to increases in levels of cellular diacylglycerol and inositol trisphosphate in the IC (the greatest site of injury), and to a smaller extent in the IH and CC, after lateral FP brain injury. It is likely that this increased PLC activity is caused by alteration in either the levels or activities of one or more of its isozymes (PLCbeta, PLCgamma, and PLCdelta) after FP brain injury.

Mediation by membrane protein kinase C of zinc-induced oxidative neuronal injury in mouse cortical cultures

Transsynaptic movement of endogenous zinc may play a key role in selective neuronal death after brain ischemia and prolonged seizures. As to the mechanism, we have reported recently that zinc-induced neuronal death occurs mainly by oxidative stress in cortical cultures. Here we present evidence supporting the idea that activation of membrane protein kinase C (PKC) in neurons is likely to play a key role in zinc-induced oxidative neuronal injury. Exposure of cortical cultures to 300 microM zinc for 15 min induced increases in the activity, without changing the amount, of membrane PKC to two- to threefold of control values, followed by neuronal death over the next day. Addition of a zinc chelator, Ca-EDTA, or PKC inhibitors with zinc completely abolished the zinc-induced increase in the membrane PKC activity. Indicating the participation of PKC in zinc-induced oxidative stress and neuronal death, the selective PKC inhibitor GF109203X attenuated both. Furthermore, as in zinc-induced neuronal death, activation of PKC with phorbol esters induced free radical generation and neuronal death, which were blocked by GF109203X or an antioxidant, Trolox. The present results support the idea that zinc influx activates PKC in the membrane, which contributes to free radical generation and neuronal death. As an increasing body of evidence suggests that zinc neurotoxicity is an important mechanism of pathological neuronal death, timely prevention of PKC activation after acute brain insult may prove useful in ameliorating this type of neuronal death.

Regional levels of brain phospholipase Cgamma in Alzheimer's disease

The levels of PLCgamma, a phospholipase C (PLC) isozyme, were higher in the cytosol fraction than in the membrane fraction in several control brain regions. The levels of PLCgamma were significantly elevated in the membrane, but not in the cytosolic fraction of the hippocampus of AD subjects. In the superior and middle temporal gyri (SMTG) of AD subjects, the levels of PLCgamma were significantly elevated in both the membrane and cytosolic fractions. In the inferior parietal lobule and cerebellum of AD subjects, no significant changes were found in the PLCgamma levels of either cytosolic or membrane fractions. These results suggest that the increased levels of PLCgamma, by increasing the hydrolysis of PIP2 in the hippocampus and SMTG, may contribute to pathophysiology of AD. These results also support a role for excitatory neurotransmitters and their receptors in AD.

Traumatic brain injury in rats results in increased expression of Gap-43 that correlates with behavioral recovery

Traumatic brain injury is associated with behavioral deficits, often in the absence of histopathological or ultrastructural changes. To determine whether membrane remodeling occurs, immunocytochemical techniques were used and the density and distribution of GAP-43 were measured. GAP-43 is a membrane-bound protein, which, when phosphorylated, is thought to regulate metabolic pathways involved in membrane remodeling and neurite growth. Moderate central fluid percussion injury (FPI, 1.9-2.2 atm.) was performed on anesthetized, spontaneously hypertensive Wistar rats (SHR). Behavioral reflex recovery was consistent with moderate levels of brain injury. One, 3, 5, 7 and 9 days after injury, both sham control (n = 4) and FPI (n = 4) animals were sacrificed, the brains were removed, cryosectioned and processed. Density measurements were taken from histological sections taken at interaural 6.20 mm and bregma -2.80 mm and were found to be statistically greater (P < 0.05) than background grey matter readings in the agranular cortices, the frontal, hindlimb, parietal 1 and 2 cortices, and the hippocampus and dentate gyrus, excluding the pyramidal and granular cell layers. Density measurements taken in forelimb and hindlimb cortical regions correlate with forelimb and hindlimb recovery in foot-fault and beam balance tests (P < 0.05). We interpret these data to indicate neuronal membrane remodeling as a result of the disruption of neuronal membranes due to the impact and shearing forces associated with the FPI. The disruption and remodeling of neuronal membranes are in areas that are consistent with the loss and recovery of locomotor and spatial behavior as a result of FPI.

Regional levels of phospholipase Cgamma after fluid percussion brain injury in the rat

Levels of PLCgamma, a phospholipase C (PLC) isozyme, were significantly increased in the cytosol in the injured left cortex (LC) at 5, 30 and 120 min after brain injury. In the same site, although levels of membrane PLCgamma did not alter at 5 and 30 min, they were found to be decreased at 2 h after brain injury. In general, the levels of both cytosolic and membrane PLCgamma were unaltered in the contralateral right cortex (RC), ipsilateral left hippocampus (LH) and contralateral right hippocampus (RH) between 5 and 120 min after brain injury. These results suggest that, in addition to well-proposed excitatory neurotransmitter-receptor systems, increased levels of PLCgamma may also contribute to alterations in PIP2 signal transduction pathway, particularly in the greatest injury site (LC) after lateral FP brain injury.

Role of protein kinase C in acidosis induced glial swelling--current understanding

A major factor in secondary brain injury following cerebral trauma is accumulation of lactic acid resulting in glial swelling. Further, evidence obtained in this context demonstrates activation of protein kinase C (PKC) under these circumstances. Glial swelling from acidosis is attributable to activation of the Na+/H(+)-exchanger, mediating influx of Na(+)-ions in exchange for the extrusion of H+ ions. The antiporter is activated following phosphorylation by PKC. The current study was made to elucidate the role of PKC activation in acidosis-induced glial swelling. For that purpose, suspended C6 glioma cells were used to examine changes of the cell volume and intracellular pH (pHi). Acidosis was induced by administration of isotonic lactic acid. Stimulation of PKC by the phorbol-ester PMA was significantly enhancing glial swelling from severe acidosis (pH 6.2), whereas the decrease of pHi was somewhat attenuated. On the other side, inhibition of PKC by staurosporine did not affect cell swelling nor the decrease of pHi from acidosis. The results indicate that activation of PKC in cerebral trauma or ischemia may enhance glial swelling from lactacidosis.

Alterations in BDNF and NT-3 mRNAs in rat hippocampus after experimental brain trauma

Previous studies have suggested that the neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) are neuroprotective or neurotrophic for certain subpopulations of hippocampal neurons following various brain insults. In the present study, the expression of BDNF and NT-3 mRNAs in rat hippocampus was examined after traumatic brain injury. Following lateral fluid percussion (FP) brain injury of moderate severity (2.0-2.1 atm) or sham injury, the hippocampi from adult rats were processed for the in situ hybridization localization of BDNF and NT-3 mRNAs using 35S-labeled cRNA probes at post-injury survival times of 1, 3, 6, 24 and 72 h. Unilateral FP injury markedly increased hybridization for BDNF mRNA in the dentate gyrus bilaterally which peaked at 3 h and remained above control levels for up to 72 h post-injury. A moderate increase in BDNF mRNA expression was also observed bilaterally in the CA3 region of the hippocampus at 1, 3, and 6 h after FP injury, but expression declined to control levels by 24 h. Conversely, NT-3 mRNA was significantly decreased in the dentate gyrus following FP injury at the 6 and 24 h survival times. These results demonstrate that FP brain injury differentially modulates expression of BDNF and NT-3 mRNAs in the hippocampus, and suggest that neurotrophin plasticity is a functional response of hippocampal neurons to brain trauma.

Lack of delayed effects of amphetamine, methoxamine, and prazosin (adrenergic drugs) on behavioral outcome after lateral fluid percussion brain injury in the rat

This study examined the delayed effects of the administration of d-amphetamine, methoxamine (an alpha1-adrenergic receptor agonist), and prazosin (an alpha1-adrenergic receptor antagonist) on the behavioral outcome of lateral fluid-percussion (FP) brain injury. Rats trained to perform a beam-walking task were subjected to brain injury of moderate severity (2.1 to 2.2 atm). Twenty-four hours after injury, rats were treated with amphetamine, methoxamine, or prazosin at two or three different dose levels. Amphetamine-treated animals displayed no significant improvement in beam-walking ability either during or after drug intoxication (from days 3 to 5 after brain injury). Similarly, neither methoxamine nor prazosin significantly affected beam-walking ability during or after drug intoxication. Neither amphetamine treatment at three different doses nor treatment with methoxamine or prazosin at two different doses affected the spatial learning disabilities of brain-injured animals. These results suggest that (1) unlike amphetamine administration after sensorimotor cortex (SMC) ablation or contusion brain injury models, amphetamine administration at 24 h after concussive FP brain injury does not improve beam-walking performance; (2) unlike amphetamine administration 10 min after concussive FP brain injury amphetamine administration 24 h after injury does not improve cognitive function; and (3) unlike prazosin administration after SMC ablation brain injury, prazosin administration 24 h after concussive FP brain injury does not effect beam-walking performance.

Regional generation of leukotriene C4 after experimental brain injury in anesthetized rats

Regional concentrations of leukotriene C4 and extravasation of Evans blue were measured after lateral fluid-percussion brain injury in rats. Tissue levels of LTC4 were elevated in the injured cortex at 10 min, 30 min, and 1 h after injury; these levels returned to normal by 2 h after injury. Increases in the levels of LTC4 were also observed in the ipsilateral hippocampus after brain injury, and these elevations persisted for 2 h after injury. No significant increase in levels of LTC4 was observed in the contralateral cortex at any time after injury. A substantial extravasation of Evans blue was observed only in the ipsilateral cortex and hippocampus at 3 h and 6 h after brain injury. Although a temporal association between LTC4 and blood-brain barrier (BBB) breakdown is suggested by these data, no cause-and-effect relationship has been addressed in this study. However, it is possible that, as is true for cerebral ischemia, LTC4 may play a role as a mediator in the BBB breakdown associated with fluid-percussion brain injury in rats.