A detrimental role for nitric oxide synthase-2 in the pathology resulting from acute cerebral injury

Nitric oxide (NO) synthesized from the inducible isoform of nitric oxide synthase (NOS-2) has been suggested to play both beneficial and deleterious roles in various neuropathologies. To define the role of nitric oxide in traumatic brain injury, we subjected male mice lacking a functional NOS-2 gene (NOS-2-/-) and their wild-type littermates (NOS-2+/+) to mild or severe aseptic cryogenic cerebral injury. Expression of NOS-2 mRNA and protein was observed in NOS-2+/+ animals following injury. Lesion volume (as measured by histology and brain imaging) and neurological outcome (using motor and cognitive behavioral paradigms) were assessed at various times after injury. While magnetic resonance imaging revealed the extent of edema of the 2 genotypes to be similar, histology showed a reduced (32%) lesion volume in severely injured NOS-2-/- compared with NOS-2+/+ mice. In addition, NOS-2-/- mice showed significant improvements in both contralateral sensorimotor deficits (grid test: p = 0.011) and cognitive function (Morris water maze: p = 0.009) after severe injury compared to their wild-type littermates. This indicates that lesion volume is reduced and neurological recovery is improved after acute traumatic injury in mice lacking a functional NOS-2 gene, and strongly suggests that the post-trauma production of NO from this source contributes to neuropathology.

Radiation-induced edema is dependent on cyclooxygenase 2 activity in mouse brain

Cerebrovascular dysfunction, characterized by compromise of the blood-brain barrier and formation of cerebral edema, is common during the acute period after brain irradiation and may contribute to delayed pathology (e.g. vascular collapse, white matter necrosis) that leads to functional deficits. Another response of normal brain tissue to radiation is the induction of inflammatory markers, such as cytokine expression and glial activation. In particular, radiation-induced neuroinflammation is associated with an elevation in cyclooxygenase 2 (COX2), one of two isoforms of the obligate enzyme in prostanoid synthesis and the principal target of non-steroid anti-inflammatory drugs. Since prostanoids serve as autocrine and paracrine mediators in numerous physiological and pathological processes, including vasoregulation, we investigated COX2 protein expression and COX2-mediated prostanoid production in radiation-induced cerebral edema in male C57/BL6 mice. We found that radiation induces COX2 protein that is accompanied by specific increases in prostaglandin E(2) and thromboxane A(2) within 4 and 24 h after brain irradiation. Furthermore, we showed that treatment with NS-398, a selective COX2 inhibitor, attenuated prostanoid induction and edema formation. These results suggest that radiation-induced changes in vascular permeability are dependent on COX2 activity, implicating this enzyme and its products as targets for potential therapeutic treatment/protection from the effects of radiation on normal brain tissue.

Treatment of cold injury-induced brain edema with a nonspecific matrix metalloproteinase inhibitor MMI270 in rats

Blood-brain barrier (BBB) disruption is a critical event leading to vasogenic brain edema and secondary brain damage after cold injury-induced brain trauma. Matrix metalloproteinases (MMPs), a family of proteolytic enzymes which degrade the extracellular matrix, are implicated in BBB disruption in this model. The purpose of this study was to examine the effects of MMI270 (N-hydroxy-2(R)-[(4-methoxysulfony) (3-picolyl)-amino]-3-metylbutaneamide hydrochloride monohydrate), a synthetic nonspecific MMP inhibitor, on cold injury-induced brain edema in rats. Cold injury was induced by applying a copper probe cooled with liquid nitrogen on the parietal skull for 30 sec in 38 rats. Treatment with MMI270, a bolus injection at a dose of 30 mg/kg, was started immediately after the induction of cold injury and was continued for 24 h at a dose of 40 mg/kg/day using an intraperitoneal osmotic minipump (n = 7). In the untreated control group (n = 7), rats were administered a vehicle and implanted with a vehicle-containing osmotic pump. Two percent Evans Blue (EB) in saline (1 mL/kg) was administrated intravenously immediately after the cold injury in another group of rats, six of which were untreated and six of which were treated with MMI270 at the above dose. At 24 h after the cold injury, the brain water content and the BBB permeability to EB were determined. To assess the protective effect of MMI270 on secondary brain lesion after the cold injury, the MMI270-treated rats received a bolus injection at a dose of 30 mg/kg, followed by a continuous administration of MMI270 for 7 days at a dose of 40 mg/kg/day using an osmotic minipump (n = 6). In the untreated control group (n = 6), the rats were administered the vehicle and implanted with a vehicle-containing osmotic pump. At 7 days after cold injury, the secondary brain lesion was assessed using hematoxylin and eosin (H-E) staining. Compared with the untreated control group, treatment with MMI270 significantly reduced the brain water content in the ipsilateral core and intermediate areas (p < 0.05 and p < 0.01) and protected the BBB integrity to EB in the ipsilateral core area (p < 0.05) at 24 h after the cold injury. The secondary lesion was significantly smaller in the MMI270-treated animals compared with the untreated animals (p < 0.05) a 7 days after the cold injury. O kur results indicate that treatment with MMI270 in rats exhibits protection in acute brain edema formation and secondary brain damage by attenuating the BBB permeability after cold injury.

[Endogenous protective effects of superoxide dismutases on infectious brain injury in rats]

We studied the alterations of MDA and three forms of SOD activities such as T-SOD, CuZn-SOD, and Mn-SOD in rat cerebral tissues injected by bordetella pertussis (BP) to elucidate protective mechanism of SOD against the infectious brain injury. The results were that water content(WC), Evans blue content(EB), MDA, and Mn-SOD activities in 4 h and 24 h BP-treated groups increased and T-SOD and CuZn-SOD decreased compared to corresponding normal saline(NS)-treated groups, respectively(P < 0.01); MDA increased and had a positive correlation with WC and EB in 4 h BP treated group (r = 0.9650, r = 0.9441, P < 0.01, P < 0.01, respectively); Mn-SOD activities were elevated and had a negative correlation with WC, EB, and MDA (r = -0.8650, r = -0.9021, r = -0.9346, P < 0.01, P < 0.01, P < 0.01, respectively) in 24 h BP-treated group. The results suggest that the increase of component Mn-SOD activities may play an important role in vivo endogenous protective mechanism against delayed infectious brain injury.

Differential regulation of aquaporin-5 and -9 expression in astrocytes by protein kinase A

Aquaporins (AQPs) transport water through the membranes of numerous tissues, but the molecular mechanisms for regulating water balance in brain are unknown. In this study, we investigated the effects of a protein kinase A (PKA) activator on the expression of AQP4, 5 and 9 in cultured rat astrocytes. Treatment of the cells with dbcAMP caused decreases in AQP5 mRNA and protein and increases in AQP9 mRNA and protein in time- and concentration-dependent manners. However, AQP4 mRNA and protein were not changed by treatment with dbcAMP. The dbcAMP-induced effects on AQP5 and AQP9 mRNAs were inhibited by PKA inhibitors. In addition, pretreating the cells with an inhibitor of protein synthesis, cycloheximide, inhibited the increase in AQP9 mRNA induced by dbcAMP, but not the decrease in AQP5 mRNA. These results suggest that signal transduction via PKA may play important roles in regulating the expression of AQP5 and AQP9, and the effect on AQP9 may be mediated by some factors induced by dbcAMP.

Nitric oxide synthase and cytochrome c oxidase changes in the tumoural and peritumoural cerebral cortex

BACKGROUND

We analysed changes in nitric oxide synthase (NOS) and cytochrome oxidase (CO) activities in the tumoural and peritumoural cerebral cortex in order to investigate: a) the role of NO in tumourigenesis, in TBF regulation, and in vasogenetic PBE; b) the metabolic changes caused by the neoplasm in the surrounding tissues.

METHOD

Intra-operative samples of cerebral cortex were studied by means of immunohistochemistry for nNOS and iNOS, and by histochemistry for NADPH-diaphorase (NADPH-d) and CO.

FINDINGS

In contrast with normal cortex, reactive glial cells and the endothelium of small blood vessels displayed strong NADPH-d and iNOS activities in oedematous peritumoural tissue. In the tumoural cortex, NADPH-d and nNOS-positive neurones were reduced in number and their dendrites were thin and interrupted, and infiltrates of NADPH-d and iNOS-positive tumoural cells were frequent. CO activity was decreased in the deep layers of peritumoural cortex, and it was almost absent in the tumoural cortex.

INTERPRETATION

In peritumoural and tumoural cortex changes in NOS and CO activities suggest that the coupling between neuronal activity and blood flow is impaired in the damaged cerebral cortex, and that the increase in NOS activity may play a role in tumour vascularization and progression.

Time profile of neuron specific enolase serum levels after experimental brain injury in rat

The aim of this study was to investigate the time course of NSE serum levels after traumatic brain injury in rats. 65 male Wistar rats were subjected to severe cortical impact injury (100 PSI, 2 mm deformation). Blood samples were drawn directly after trauma, after 1 h, 6 h, 12 h, 24 h, and 48 h in the trauma group as well as in sham operated animals directly after craniotomy, after 6 h and after 48 h. NSE serum levels were estimated with a commercially available enzyme immuno assay (LIA-mat Sangtec). The control animals showed a NSE serum level of 8.82 micrograms/l (mean, n = 10). We demonstrated a time dependent release of NSE into the serum after trauma. The highest NSE serum values were detected six hours after trauma (31.5 micrograms/l, mean, n = 10). NSE serum level seems to reflect neuronal damage after cortical contusion in the rat in a time dependent manner.

The role of proteolytic enzymes in focal ischaemic brain damage

Although various neuroprotective and fibrinolytic drugs are currently under evaluation in the acute stages of ischaemic stroke, their therapeutic potential is likely to be limited by unwanted side effects and a narrow time window of opportunity for intervention. Proteolytic enzymes are involved in the catabolism of peptide neurotransmitters and structural cellular proteins in normal brain and have been implicated in the pathogenesis of neurodegenerative disorders. We hypothesised that activation of these enzymes might also play a crucial role in effecting ischaemic neuronal injury, thereby providing a potential site for therapeutic intervention in human stroke. Focal cerebral ischaemia was induced by thermocoagulation of the left middle cerebral artery in aged (30 month) male Wistar rats who were pre-treated with saline or the competitive N-methyl-D-Aspartate antagonist D-CPP-ene, which has been shown to be neuroprotective in young animal models of stroke. Major protease activities were analysed in the left (ischaemic) and right (non-ischaemic) hemispheres, following tissue homogenisation. Data have been analysed using Mann-Whitney tests and are presented as means +/- standard errors. Enzyme activity decreased in ischaemic brain; for example, the mean activity of dipeptidyl aminopeptidase I was 23 +/- 3 and 43 +/- 6 nmol substrate/hour/ml brain extract in the left and right hemispheres respectively (n = 10, p < 0.05). Ischaemic neuronal injury is not effected by the early activation of proteolytic enzymes and protease inhibitors are therefore unlikely to be of benefit in human stroke.

Inducible cyclooxygenase-2 expression after experimental intracerebral hemorrhage

Cyclooxygenase-2 (COX-2) is an inducible isoform of cyclooxygenase, which catalyzes the conversion of arachidonic acid to prostaglandins and thromboxane. Recent evidence suggests it has a pathological role in cerebral insults, but its involvement in intracerebral hemorrhage (ICH) is unknown. The present study investigates the temporal and anatomic distribution of COX-2 as well as the effect of the selective COX-2 inhibitor NS-398 on brain edema formation and cerebral blood flow in a rat model of ICH. Immunohistochemistry for COX-2 was performed in control rats and 6 h, as well as 1, 3, 7 and 10 days after the injection of 100 microl autologous blood into the right basal ganglia. Double-labeling immunohistochemistry was used to determine the type of COX-2 immunoreactive microvascular-associated cells. Western blot analysis was used to quantify COX-2 protein. The effect of NS-398 on brain water content, ion concentration and cerebral blood flow were assessed 24 h after ICH. The results demonstrated that COX-2 protein was expressed in control brain tissue and induced significantly in the ipsilateral hemisphere at 6 h, as well as 1 and 3 days after ICH. Increased staining of COX-2 in neurons was observed around the blood clot with a peak at 6 h. COX-2 was induced in endothelial cells, perivascular cells as well as infiltrating leukocytes 1 day after ICH. Brain water and ion contents and cerebral blood flow were unaffected by NS-398 administration. Thus, although COX-2 expression was increased in the ipsilateral hemisphere after an autologous blood injection, its products do not appear to be major regulators of blood flow or edema formation following ICH.

Effects of deferoxamine on tissue superoxide dismutase and glutathione peroxidase levels in experimental head trauma

BACKGROUND

This study aims to evaluate the effects of deferoxamine on tissue superoxide dismutase (SOD) and glutathione peroxidase (GPx) brain levels after head trauma.

METHODS

Thirty rabbits were divided equally into three groups: group 1 was the sham-operated group, group 2 suffered head trauma (no treatment was given), and group 3 received deferoxamine 50 mg/kg after the trauma. Head trauma was applied unilaterally. One hour after trauma, brain cortices were resected and SOD and GPx levels were determined. One-way analysis of variance and Tukey-HSD tests were used for analysis. Significance was defined as p < 0.05.

RESULTS

Baseline SOD levels are preserved in the traumatized side of the deferoxamine-treated group. Although GPx level of the traumatized side of the deferoxamine-treated group decreased significantly, the decrease was significantly less than the nontreated group.

CONCLUSION

Trauma leads to a decrease in brain tissue SOD and GPx levels. Deferoxamine suppresses this decrease completely in SOD level and partially in GPx level when given after trauma.

Reduction of copper, zinc-superoxide dismutase in knockout mice does not affect edema or infarction volumes and the early release of mitochondrial cytochrome c after permanent focal cerebral ischemia

Copper,zinc-superoxide dismutase (SOD1) was shown to be highly protective against ischemia/reperfusion injury in the brain. We have recently reported that SOD1 prevents the release of mitochondrial cytochrome c and subsequent apoptosis after ischemia/reperfusion in mice. To investigate its dose dependent effect on permanent focal cerebral ischemia, we examined neurological deficit scores, infarction volume, and the amount of hemisphere enlargement after 24 h of focal cerebral ischemia in both knockout mutants of SOD1 (Sod1 -/+ and Sod1 -/-) and wild-type littermates. We also examined the release of cytochrome c and subsequent DNA fragmentation after ischemia. There were no differences in the neurological deficit scores, infarction volumes and edema formation. There was also no difference of the amount cytosolic cytochrome c at 2 h and of the amount of DNA fragmentation at 24 h after focal cerebral ischemia. The results indicate that the SOD1 enzyme does not appear to affect cerebral infarction, cerebral edema nor the mitochondrial signaling pathway for apoptosis following permanent focal cerebral ischemia where there is no reperfusion injury.

Hyposmotically induced amino acid release from the rat cerebral cortex: role of phospholipases and protein kinases

In an evaluation of the contribution of swelling-induced amino acid release, through the regulatory volume decrease (RVD) process, to cerebral ischemic injury, studies of the role of phospholipases and protein kinases in the response to hyposmotic stress were undertaken using an in vivo rat cortical cup model. Hyposmotic stress induced significant releases of aspartate, glutamate, glycine, phosphoethanolamine, taurine and GABA from the rat cerebral cortex. Taurine release was most affected, exhibiting a greater than 9-fold increase during the hyposmotic stimulus. The phospholipase A2 (PLA2) inhibitors 4-bromophenacyl bromide (1 microM) and 7,7-dimethyleicosadienoic acid (5 microM) had no significant effects on hyposmotically induced amino acid release. AACOCF3 (50 microM), an inhibitor of cytosolic PLA2 decreased taurine release to 84% of DMSO controls. The release of the other amino acids was not affected. The phospholipase C inhibitor U73122 (5 microM) had no significant effects on amino acid release. The protein kinase C (PKC) inhibitor chelerythrine (5 microM) significantly reduced hyposmotically induced taurine release to 72% of saline controls but had no significant effects on the other amino acids. Stimulation of PKC with phorbol 12-myristate, 13-acetate (10 microM) did not significantly change taurine, glutamate, glycine or phosphethanolamine release. The releases of aspartate and GABA were enhanced 2 to 3 fold. Phorbol 12,13-didecanoate (10 microM), another potent stimulator of PKC, significantly increased taurine release to 122% of DMSO controls. The releases of aspartate, glutamate and glycine were enhanced 2.5 to 3.5 fold. Similarly, stimulation of protein kinase A with forskolin (100 microM) significantly increased taurine, aspartate, and glycine release 1.5- to 2-fold compared to DMSO controls. In summary, phospholipases may play a minor role in volume regulation. These studies also support the hypothesis that protein kinases play a modulatory role in the RVD response. The results show that although RVD may play a role, additional mechanisms, including phospholipase activation, must be involved in the ischemia-evoked release of excitotoxic amino acids.

Early decrease in apurinic/apyrimidinic endonuclease is followed by DNA fragmentation after cold injury-induced brain trauma in mice

Apurinic/apyrimidinic endonuclease, a multifunctional protein in the DNA base excision repair pathway, plays a central role in repairing DNA damage caused by reactive oxygen species. We examined protein expression of apurinic/apyrimidinic endonuclease before and after cold injury-induced brain trauma in mice, where we have previously shown reactive oxygen species to participate. Immunohistochemistry showed the nuclear expression of apurinic/apyrimidinic endonuclease in the entire region of control brains. One hour after cold injury-induced brain trauma, nuclear immunoreactivity was predominantly decreased in the inner boundary of the lesion, whereas there was a slight increase in the outer boundary area. Four hours after cold injury-induced brain trauma, nuclear immunoreactivity was almost absent in the entire lesion, and remained so until 24 h. At this time, a marked increase in apurinic/apyrimidinic endonuclease immunoreactivity was seen in the outer boundary zone. Western blot analysis of the sample from the non-ischemic area showed a characteristic 37,000 mol. wt band, which decreased markedly 24 h after cold injury-induced brain trauma. A time-dependent increase in DNA fragmentation was also observed after cold injury-induced brain trauma. Our data provide the first evidence that apurinic/apyrimidinic endonuclease decreased rapidly in the lesion after cold injury-induced brain trauma, whereas it was significantly increased at the outer boundary zone. Although further examination is necessary to elucidate the direct relationship between apurinic/apyrimidinic endonuclease alteration and the pathogenesis of cold injury-induced brain trauma, our results suggest the possibility that an early decrease in apurinic/apyrimidinic endonuclease and failure of the DNA repair mechanism may contribute to DNA-damaged neuronal cell death after cold injury-induced brain trauma.

Nitric oxide in the pathophysiology of hyperthermic brain injury. Influence of a new anti-oxidant compound H-290/51. A pharmacological study using immunohistochemistry in the rat

The possibility that nitric oxide (NO) is involved in the pathophysiology of brain injury caused by heat stress (HS) was examined using neuronal nitric oxide synthase (NOS) immunohistochemistry in a rat model. In addition, to find out a role of oxidative stress in NOS upregulation and cell injury, the effect of a new antioxidant compound H-290/51 (Astra Hässle, Mölndal, Sweden) was examined in this model. Subjection of conscious young rats to 4 h HS in a biological oxygen demand (BOD) incubator at 38 degrees C resulted in a marked upregulation of NOS in many brain regions compared to control rats kept at room temperature (21 +/- 1 degree C). This NOS immunoreactivity was found mainly in distorted neurons located in the edematous regions not normally showing NOS activity. Breakdown of the blood-brain barrier (BBB) permeability, increase in brain water content and marked neuronal, glial and myelin reaction were common findings in several brain regions exhibiting upregulation of NOS activity. Pretreatment with H-290/51 significantly attenuated the upregulation of NOS in rats subjected to HS. In these animals breakdown of the BBB permeability, edema and cell changes were considerably reduced. Our results suggest that hyperthermic brain injury is associated with a marked upregulation of NOS activity in the CNS and this upregulation of NOS and concomitant cell injury can be reduced by prior treatment with an antioxidant compound H 290/51. These observations indicate that oxidative stress seems to be an important endogenous signals for NOS upregulation and cell reaction in hyperthermic brain injury.

Nitric oxide synthase immunoreactivity related to cold-induced brain edema

To determine the relationship between brain edema and the expression of nitric oxide synthase (NOS), we immunohistochemically studied the distribution and level of NOS in rat brain cold injury model. Vasogenic brain edema was produced by cortical freezing lesion. NOS immunohistochemical studies were performed 4 and 8 h, 1, 3, 5, 7, 14 and 21 days after injury. In control normotensive rats, immunoreactivity for NOS was observed in scattered neuronal cells as reported previously, but there was no reactivity in glial cells. In the present study in the cold injury model, however, fibrinogen staining showed extravasated plasma fluid extending to the white matter contralateral to the site of cold injury. NOS immunoreactivity was observed in most reactive astrocytes and a proportion of the microglial cells and macrophages in the white matter not only just beneath the area of cold injury but also in the contralateral side. The nerve cells in the edematous region scarcely showed additional immunoreactivity for NOS. The distribution of increased NOS relatively corresponded with the sites of extravasated plasma fluid demonstrated by fibrinogen staining. Electron microscopically, NOS was observed in astrocytes along the rough endoplasmic reticulum suggesting that NOS was produced in the cells and not taken up from the surroundings. Based on these findings, we postulate that brain edema and the simultaneously generated free radicals or some extravasated plasma components may induce expression of NOS in the reactive cells, and that the NO thus generated may be involved in the development of diffuse degeneration of the white matter which accompanies brain edema.

Reduced fertility and postischaemic brain injury in mice deficient in cytosolic phospholipase A2

Phospholipase A2 (PLA2) enzymes are critical regulators of prostaglandin and leukotriene synthesis and can directly modify the composition of cellular membranes. PLA2 enzymes release fatty acids and lysophospholipids, including the precursor of platelet-activating factor, PAF, from phospholipids. Free fatty acids, eicosanoids, lysophospholipids and PAF are potent regulators of inflammation, reproduction and neurotoxicity. The physiological roles of the various forms of PLA2 are not well defined. The cytosolic form, cPLA2, preferentially releases arachidonic acid from phospholipids and is regulated by changes in intracellular calcium concentration. We have now created 'knockout' (cPLA2-/-) mice that lack this enzyme, in order to evaluate its physiological importance. We find that cPLA2-/- mice develop normally, but that the females produce only small litters in which the pups are usually dead. Stimulated peritoneal macrophages from cPLA2-/- animals did not produce prostaglandin E2 or leukotriene B4 or C4. After transient middle cerebral artery occlusion, cPLA2-/- mice had smaller infarcts and developed less brain oedema and fewer neurological deficits. Thus cPLA2 is important for macrophage production of inflammatory mediators, fertility, and in the pathophysiology of neuronal death after transient focal cerebral ischaemia.

Reduced brain edema and infarction volume in mice lacking the neuronal isoform of nitric oxide synthase after transient MCA occlusion

Infarct volume and edema were assessed after transient focal ischemia in mice lacking neuronal nitric oxide synthase (NOS) gene expression. With use of an 8-0 coated monofilament, the middle cerebral artery (MCA) of mutant (n = 32) and wild-type mice [SV-129 (n = 31), C57Black/6 (n = 18)] were occluded for 3 h and reperfused for up to 24 h. Regional CBF (rCBF), neurological deficits, water content, and infarct volume were examined in all three strains. rCBF, blood pressure, and heart rate did not differ between groups when measured for 1 h after reperfusion. Neurological deficits were less severe in mutant mice after MCA occlusion. Brain water content at 3 h after reperfusion and infarct volume at 24 h after reperfusion were greater in wild-type mice. These data indicate that genetic deletion of neuronal NOS confers resistance to focal ischemic injury in a reperfusion model. The findings agree with previous studies showing that tissue injury is less extensive after both permanent MCA occlusion and global ischemia in mice lacking neuronal NOS gene expression. Hence, NO may play a pivotal role in the pathogenesis of ischemic brain damage.

Multiple actions of the coumarine derivative cloricromene and its protective effects on ischemic brain injury

The effects of different doses (0.25, 0.5, 1 and 2 mg/kg i.p.) of cloricromene, a coumarine derivative, have been investigated on brain malondialdehyde levels, brain edema, myeloperoxidase activity, survival, locomotor hyperactivity and hippocampal neuronal loss following transient cerebral ischemia induced by temporary bilateral carotid occlusion in the Mongolian gerbil. Cloricromene reduced brain lipid peroxidation, measured through the evaluation of malondialdehyde (-82.9% with the highest dose), and the formation of post-ischemic brain edema, evaluated by water content. The increase in myeloperoxidase activity observed in the hippocampus of postischemic animals was also reduced: 0.7 +/- 0.3 U x 10(-3) vs. 3.3 +/- 0.3 U x 10(-3)/g tissue. The same treatment increased survival and reduced hyperactivity linked to neurodegeneration induced by cerebral ischemia and reperfusion. Histological observations of the pyramidal layer of CA1 showed a reduction of neuronal loss in animals that received the drug before occlusion but not in those that were treated after the occlusion. These results show that cloricromene, a drug with multiple actions, improves brain injury induced by transient cerebral ischemia.

Relations of intracranial pressure, creatine kinase and brainstem auditory evoked potential in patients with traumatic brain edema

We studied the relations of intracranial pressure (ICP), creatine kinase (CK) and brainstem auditory evoked potential (BAEP) in 44 patients with traumatic brain edema who were admitted to our hospital from June 1990 to February 1991. There were 30 males and 14 females, with age range from 9 to 67 years. The results showed that the abnormal BAEP could reflect the severity of cerebral edema in acute head injury and was related to ICP and serum CK levels. When ICP > 30 mmHg (4kPa), the abnormality of BAEP was more obvious than that of the control group (P < 0.05); the serum CK levels were also elevated markedly. In patients with ICP over and below 4kPa, the rate of abnormal BAEP was 38.46% and 77.78% respectively (P < 0.05). The serum CK level in the normal group or in the group with moderate abnormality of BAEP was significantly different from that in the group with severe abnormality or lack of BAEP (274.8 +/- 98.24 U/L vs 705.3 +/- 364.27 U/L; P < 0.001). After treatment, the ICP returned to normal, and the BAEP normalized too, but the serum CK level decreased. The results showed that BAEP may provide some indirect evidences for the relevant biochemical and biophysical changes after the occurrence of traumatic brain edema and an important clinical index for judging the severity of the edema.

Cold-induced brain edema in mice. Involvement of extracellular superoxide dismutase and nitric oxide

The role of extracellular superoxide in the pathogenesis of vasogenic edema was studied using transgenic mice expressing a 5-fold increase in extracellular superoxide dismutase (EC-SOD) activity in their brains. Increased EC-SOD expression offered significant protection against edema development after cold-induced injury (44% less edema than nontransgenic littermates, p < 0.05). Since iron may contribute to vasogenic edema by catalyzing the production of hydroxyl radical from superoxide and hydrogen peroxide, the effects of the chelator deferoxamine were studied. Deferoxamine reduced edema formation after cold-induced injury (43% less edema than controls, p < 0.05); however, treatment with iron-saturated deferoxamine also reduced edema development in mice (32-48% less edema, p < 0.05). This suggested that the protection offered by deferoxamine was independent of its ability to chelate iron. An iron-independent mechanism by which superoxide can contribute to vasogenic edema is via reaction with nitric oxide to produce the potentially toxic peroxynitrite anion, which is also scavenged by deferoxamine. Mice treated with an inhibitor of nitric oxide synthase were protected against cold-induced edema (37% less edema, p < 0.05). EC-SOD transgenic mice received no additional protection by inhibition of nitric oxide synthesis, supporting this novel alternative mechanism of edema formation.

[The permeability of the hemato-encephalic barrier for superoxide dismutase following the unilateral intracarotid hyperperfusion of the cerebral vessels]

On the model of acute blood-brain barrier injury in rats after a short-term hyperperfusion of one brain hemisphere with blood, the injection of exogenic superoxide dismutase (SOD) was accompanied by pronounced increase in the activity of SOD in the damaged brain tissue. This fact and other data of the authors on this model confirm the penetration of SOD over the microvessel endothelium into the extracellular space of the same damaged brain areas that are permeable for plasma albumin.

The prognostic value of the brain sodium-potassium ATPase enzyme concentration in head injury

Sodium-potassium adenosine triphosphatase (ATPase) enzyme was determined in the brain tissue of 11 patients with head injury and 6 control patients. Patients with head injury included in this study were selected from two categories: (a) patients in deep coma due to severe head injury [Glasgow Coma Scale (GCS) less than 8; 6 cases]; (b) patients with depressed skull fractures with dural tears who were conscious and able to give an adequate verbal response (GCS greater than 10; 5 cases). The level of the enzyme was significantly reduced in comatose patients with severe head injury as compared to the controls (P less than 0.001) or to conscious patients with depressed fractures (P less than 0.001). In the group of conscious patients with depressed fractures, the enzyme level was no different from that of the controls (P = 0.4215). All comatose patients with severely reduced enzyme levels subsequently died, whereas those with depressed fractures with normal enzyme levels survived. The relationship between a low enzyme level and brain edema in severe head injury is discussed.

Cold-induced brain edema and infarction are reduced in transgenic mice overexpressing CuZn-superoxide dismutase

It has been proposed that oxygen-derived radicals, superoxide in particular, are involved in the alteration of blood-brain barrier permeability and the pathogenesis of brain edema following trauma, ischemia, and reperfusion injury. Using transgenic mice that overexpress the human gene for copper-zinc-superoxide dismutase, we studied the role of superoxide radicals in the blood-brain permeability changes, edema development, and delayed infarction resulting from cold-trauma brain injury. At 2 hours after a 30-second cold injury, cerebral water and Evans blue contents were reduced, respectively, from 80 +/- 0.2% and 132.7 +/- 12.9 micrograms/gm of dry weight for nontransgenic mice to 78.5 +/- 0.3% and 87.1 +/- 9.9 micrograms/gm of dry weight for transgenic mice. Infarction, as measured by 2,3,5-triphenyltetrazolium chloride staining, was reduced by 52% in transgenic brains. These data indicate that an increased level of superoxide dismutase activity in the brain reduces the development of vasogenic brain edema and infarction. Superoxide radicals play an important role in the pathogenesis of these lesions in cold-traumatized brain.