Neuronal free Ca(2+)and BBB permeability and ultrastructure in head injury with secondary insult

Cristobalite and Hematite Particles in Human Brain

Foreign substances get into the internal environment of living bodies and accumulate in various organs. Cristobalite and hematite particles in the glial cells of pons cerebri of human brain with diagnosis of Behhet disease with scanning electron microscopy (SEM), energy-dispersive microanalysis (EDX), and transmission electron microscopy (TEM) with diffraction were identified. SEM with EDX revealed the matter of irregular micrometer-sized particles sometimes forming polyhedrons with fibrilar or stratified structure. It was found in some particles Ti, Fe, and Zn. Some particles contained Cu. TEM and electron diffraction showed particles of cristobalite and hematite. The presence of the particles can be a result of environmental effect, disruption of normal metabolism, and transformation of physiologically iron-ferrihydrite into more stable form-hematite. From the size of particles can be drawn the long-term accumulation of elements in glial cells.

Candesartan attenuates ischemic brain edema and protects the blood-brain barrier integrity from ischemia/reperfusion injury in rats

Background: Angiotensin II (Ang II) has an important role on cerebral microcirculation; however, its direct roles in terms of ischemic brain edema need to be clarified. This study evaluated the role of central Ang II by using candesartan, as an AT1 receptor blocker, in the brain edema formation and blood-brain barrier (BBB) disruption caused by ischemia/reperfusion (I/R) injuries in rat. Methods: Rats were exposed to 60-min middle cerebral artery (MCA) occlusion. Vehicle and non-hypotensive doses of candesartan (0.1 mg/kg) were administered one hour before ischemia. Neurological dysfunction scoring was evaluated following 24 h of reperfusion. Animals were then decapitated under deep anesthesia for the assessments of cerebral infarct size, edema formation, and BBB permeability. Results: The outcomes of 24 h reperfusion after 60-min MCA occlusion were severe neurological disability, massive BBB disruption (Evans blue extravasation = 12.5 ± 1.94 µg/g tissue), 4.02% edema, and cerebral infarction (317 ± 21 mm³). Candesartan at a dose of 0.1 mg/kg, without changing arterial blood pressure, improved neurological dysfunction scoring together with significant reductions in BBB disruption (54.9%), edema (59.2%), and cerebral infarction (54.9%). Conclusions: Inactivation of central AT1 receptors, if not accompanied with arterial hypotension, protected cerebral micro-vasculatures from damaging effects of acute stroke.

The combination of astragalus membranaceus and ligustrazine ameliorates micro-haemorrhage by maintaining blood-brain barrier integrity in cerebrally ischaemic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Haemorrhagic transformation is an asymptomatic event that frequently occurs after following ischaemic stroke, particularly when pharmaceutical thrombolysis is used. However, the mechanism responsible for haemorrhagic transformation remains unknown, and therapeutics have not been identified. In this study, we administered a combination of astragalus membranaceus and ligustrazine to rats with cerebral ischaemia that had undergone thrombolysis. We analysed the effect of this combination on the attenuation of haemorrhagic transformation and the maintenance of blood-brain barrier integrity.

METHODS

A rat model of focal cerebral ischaemia was induced with autologous blood clot injections. Thrombolysis was performed via the intravenous injection of rt-PA. Astragalus membranaceus, ligustrazine or a combination of Astragalus membranaceus and ligustrazine was administered immediately after the clot injection. The cerebral infarct area, neurological deficits, blood-brain barrier integrity, and cerebral haemorrhage status were determined after 3, 6 and 24h of ischaemia. The ultrastructure of the blood-brain barrier was examined with a transmission electron microscope. The expression of tight junction proteins, including claudin-1, claudin-5, occludin, and zonula occludens-1, and matrix metallopeptidase-9 activation was further evaluated in terms of their roles in the protective effects of the combination drug on the integrity of the blood-brain barrier.

RESULTS

Ischaemia-induced Evans blue leakage and cerebral haemorrhage were markedly reduced in the combination drug-treated rats compared to the rats treated with either astragalus membranaceus or ligustrazine alone (p<0.05). The disruption of the ultrastructure of the blood-brain barrier and the neurological deficits were ameliorated by the combination treatment (p<0.05). The reductions in the expression of laudin-1, claudin-5, occludin, and ZO-1 were smaller in the rats that received the combination treatment. In addition, MMP-9 activity was suppressed in the combination-treated rats compared to the controls (p<0.05).

CONCLUSIONS

Treatment with a combination of astragalus membranaceus and ligustrazine alleviated ischaemia-induced micro-haemorrhage transformation by maintaining the integrity of the blood-brain barrier.

Enalapril attenuates ischaemic brain oedema and protects the blood-brain barrier in rats via an anti-oxidant action

1. In the present study, we investigated the effects of postischaemic angiotensin-converting enzyme (ACE) inhibition with enalapril on vasogenic oedema formation and blood-brain barrier (BBB) integrity following transient focal cerebral ischaemia in rats. 2. Cerebral ischaemia was induced by 60 min occlusion of the right middle cerebral artery, followed by 24 h reperfusion. Vehicle and a non-hypotensive dose of enalapril (0.03 mg/kg) were administered at the beginning of the reperfusion period. A neurological deficit score (NDS) was determined for all rats at the end of the reperfusion period. Then, brain oedema formation was investigated using the wet-dry weight method and BBB permeability was evaluated on the basis of extravasation of Evans blue (EB) dye. In addition, oxidative stress was assessed by measuring reduced glutathione (GSH) and malondialdehyde (MDA) in brain homogenates. 3. Inhibition of ACE by enalapril significantly reduced NDS and decreased brain oedema formation (P < 0.05 for both). Disruption of the BBB following ischaemia resulted in considerable leakage of EB dye into the brain parenchyma of the ipsilateral hemispheres of vehicle-treated rats. Enalapril significantly (P < 0.05) decreased EB extravasation into the lesioned hemisphere. Enalapril also augmented anti-oxidant activity in ischaemic brain tissue by increasing GSH concentrations and significantly (P < 0.05) attenuating the increased MDA levels in response to ischaemia. 4. In conclusion, inhibition of ACE with a non-hypotensive dose of enalapril may protect BBB function and attenuate oedema formation via anti-oxidant actions.

Attenuation of focal cerebral ischemic injury following post-ischemic inhibition of angiotensin converting enzyme (ACE) activity in normotensive rat

BACKGROUND

Central renin angiotensin system has an important role on the cerebral microcirculation and metabolism. Our previous work showed that inhibition of angiotensin converting enzyme (ACE) activity prior to induction of ischemia protected the brain from severe ischemia/reperfusion (I/R) injuries. This study evaluated the impacts of post-ischemic inhibition of ACE, enalapril, on brain infarction in normotensive rats.

METHODS

Rats were anesthetized with chloral hydrate (400 mg/kg). Focal cerebral ischemia was induced by 60-min intraluminal occlusion of right middle cerebral artery (MCA). Intraperitoneal injection of enalapril (0.03 or 0.1 mg/kg) was done after MCA reopening (reperfusion). Neurological deficit score (NDS) was evaluated after 24 h and the animals randomly assigned for the assessments of infarction, absolute brain water content (ABWC) and index of brain edema.

RESULTS

Severe impaired motor functions (NDS = 2.78 ± 0.28), massive infarction (cortex = 214 ± 19 mm3, striatum = 86 ± 5 mm3) and edema (ABWC = 83.1 ± 0.46%) were observed in non-treated ischemic rats. Non-hypotensive dose of enalapril (0.03 mg/kg) significantly reduced NDS (1.5 ± 0.22), infarction (cortex = 102 ± 16 mm3, striatum = 38 ± 5 mm3) and edema (ABWC = 80.9 ± 0.81%). Enalapril at dose of 0.1 mg/kg significantly lowered arterial pressure could not improve NDS (2.0 ± 0.45) and reduce infarction (cortex = 166 ± 26 mm3, striatum = 71 ± 11 mm3).

CONCLUSION

Post-ischemic ACE inhibition in the normotensive rats without affecting arterial pressure protects the brain from reperfusion injuries; however, this beneficial action is masked by hypotension.

Changes of mGluR4 and the effects of its specific agonist L-AP4 in a rodent model of diffuse brain injury

OBJECTIVE

Excessive release of glutamate from nerve terminals following diffuse brain injury (DBI) is thought to contribute to neuronal calcium overload leading to calcium-mediated cell damage. Metabotropic glutamate receptor subtype 4 (mGluR4) is regarded as one of the neuroprotective receptors in mammalian brains. Therefore, the mGluR4 specific agonists might exert neuroprotective effects after DBI. The focus of this study is to examine the changes of expression of mGluR4 after DBI and the role of its specific agonist L-AP4 in vivo.

METHODS

One hundred and sixty-one male SD rats were randomized into two groups. Group A included normal control, sham-operated control and DBI group. DBI was produced by Marmarou's diffuse head injury model. The mRNA expression of mGluR4 was detected by hybridization in situ. Group B included DBI alone, DBI treated with normal saline and DBI treated with L-AP4. All DBI rats were trained in a series of performance tests, following which they were subjected to DBI. At 1 and 12 h, animals were injected intracerebroventricularly with L-AP4 (100 mM, 10 microl) or normal saline, respectively. The rats were tested for motor and cognitive performance at 1, 3, 7, 14 days post-injury and the damaged neurons were detected.

RESULTS

There was no significant difference between the normal control group and sham-operated group in the expression of mGluR4 (P>0.05). The animals exposed to DBI showed a significant increased expression of mRNA of mGluR4 compared with that of the sham-operated animals 1 h after injuries (P<0.05). At 6 h, the evolution of neuronal expression of mGluR4 in the trauma alone group was relatively static. Compared with saline-treated control animals, rats treated with L-AP4 showed decreased number of damaged neurons and a better motor and cognitive performance.

CONCLUSIONS

The increased expression of mGluR4 is an important process in the pathophysiological of DBI and its specific agonist L-AP4 can provide a remarkable neuroprotection against DBI not only at the histopathological level but also in the motor and cognitive performance.

Differences in cell death between high and low energy brain injury in adult rats

BACKGROUND

Traumatic brain damage is dependent on energy transfer to the brain at impact. Different injury mechanisms may cause different types of brain injury. It is, however, unknown if the relative distribution between apoptotic cell-death and necrotic cell- death in different populations of brain cells varies depending on energy transfer.

METHOD

Experimental contusions were produced with a modified weight drop onto the exposed dura of rats. Animals were divided into two groups. They received a weight drop from two different heights to vary energy transfer to be higher or lower. Animals were sacrificed at 24 hours post injury (1 DPI) or 6 days (6 DPI); brains were frozen and processed for TUNEL (TdT mediated dUTP nick end labelling), light microscopy and immunochemistry.

FINDINGS

The total number of TUNEL positive cells was higher in the higher energy group on the first day after the injury. At the same time point, relatively fewer cells were apoptotic than necrotic, while relatively more glial cells than neurons were TUNEL-positive in higher energy trauma. At 6 day after the injury fewer cells were TUNEL positive and there were no longer significant differences between the high and low energy groups.

CONCLUSIONS

Increasing energy transfer in a model for brain contusion demonstrated qualitative and quantitative changes in the pattern of cell death. This complexity must be considered when evaluating brain-protection as treatment results may vary depending on which cellular population and which mechanism of cell death is treated under the exact experimental and clinical conditions.

Posttraumatic secondary brain insults exacerbates neuronal injury by altering metabotropic glutamate receptors

Background

Our previous studies indicated that metabotropic glutamate receptors (mGluRs) are deeply involved in the secondary processes after diffuse brain injury (DBI). In the present study, we used a rodent DBI model to determine whether hypotension exacerbates neuronal injury as a secondary brain insult (SBI) after traumatic brain injury (TBI) by changing the expression of metabotropic glutamate receptors (mGluRs) in the cerebral cortex.

Results

Three hundred and eleven male Sprague-Dawley rats were randomly assigned into five groups: normal control, sham-operated control, SBI alone, DBI alone, or DBI with SBI. DBI was produced in rats by Marmarou's methods and the SBI model was produced by hypotension. The alteration of neuronal expression of mGluRs after DBI and DBI coupled with SBI was observed by hybridization in situ at different time points in the experiment. We found a higher mortality and neurological severity score (NSS) for rats in the DBI with SBI group compared with those in the DBI alone group. Although there was a significant rise in the expression of group I and group III mGluRs (except mGluR6) and a decrease in the expression of group II mGluRs after DBI (P < 0.05), the changes were more severe when DBI was coupled with SBI (P < 0.05). The expression of group I mGluRs peaked at 24 hours, while the expression of the group III mGluRs peaked at 6 hours after injuries, which may reflect a self-protection first mechanism of the damaged neurons. Moreover, the overall neuro-harmful effects of mGluRs on neurons were seemly associated with higher mortality and NSS in the DBI with SBI group.

Conclusion

The results suggest posttraumatic SBI may exacerbate neuronal injury or brain injury by altering expression of mGluRs, and more emphasis should therefore be put on the prevention and treatment of SBI.

Temporal relationship of peroxynitrite-induced oxidative damage, calpain-mediated cytoskeletal degradation and neurodegeneration after traumatic brain injury

We assessed the temporal and spatial characteristics of PN-induced oxidative damage and its relationship to calpain-mediated cytoskeletal degradation and neurodegeneration in a severe unilateral controlled cortical impact (CCI) traumatic brain injury (TBI) model. Quantitative temporal time course studies were performed to measure two oxidative damage markers: 3-nitrotyrosine (3NT) and 4-hydroxynonenal (4HNE) at 30 min, 1, 3, 6, 12, 24, 48, 72 h and 7 days after injury in ipsilateral cortex of young adult male CF-1 mice. Secondly, the time course of Ca(++)-activated, calpain-mediated proteolysis was also analyzed using quantitative western-blot measurement of breakdown products of the cytoskeletal protein alpha-spectrin. Finally, the time course of neurodegeneration was examined using de Olmos silver staining. Both oxidative damage markers increased in cortical tissue immediately after injury (30 min) and elevated for the first 3-6 h before returning to baseline. In the immunostaining study, the PN-selective marker, 3NT, and the lipid peroxidation marker, 4HNE, were intense and overlapping in the injured cortical tissue. alpha-Spectrin breakdown products, which were used as biomarker for calpain-mediated cytoskeletal degradation, were also increased after injury, but the time course lagged behind the peak of oxidative damage and did not reach its maximum until 24 h post-injury. In turn, cytoskeletal degradation preceded the peak of neurodegeneration which occurred at 48 h post-injury. These studies have led us to the hypothesis that PN-mediated oxidative damage is an early event that contributes to a compromise of Ca(++) homeostatic mechanisms which causes a massive Ca(++) overload and calpain activation which is a final common pathway that results in post-traumatic neurodegeneration.

Cerebral oxidative stress and depression of energy metabolism correlate with severity of diffuse brain injury in rats

OBJECTIVE

The combined effect of traumatic brain injury (TBI) and secondary insult on biochemical changes of cerebral tissue is not well known. For this purpose, we studied the time-course changes of parameters reflecting ROS-mediated oxidative stress and modifications of cell energy metabolism determined in rats subjected to cerebral insult of increasing severity.

METHODS

Rats were divided into four groups: 1) sham-operated, 2) subjected to 10 minutes of hypoxia and hypotension (HH), 3) subjected to severe diffuse TBI, and 4) subjected to severe diffuse TBI + HH. Rats were killed at different times after injury, and analyses of malondialdehyde, ascorbate, high-energy phosphates, nicotinic coenzymes, oxypurines, nucleosides, and N-acetylaspartate (NAA) were made by high-performance liquid chromatography on whole-brain tissue extracts.

RESULTS

Data indicated a close relationship between degree of oxidative stress and severity of brain insult, as evidenced by the highest malondialdehyde values and lowest ascorbate levels in rats subjected to TBI + HH. Similarly, modifications of parameters related to cell energy metabolism were modulated by increasing severity of brain injury, as demonstrated by the lowest values of energy charge potential, nicotinic coenzymes, and NAA and the highest levels of oxypurines and nucleosides recorded in TBI + HH rats. Both the intensity of oxidative stress-mediated cerebral damage and perturbation of energy metabolism were minimally affected in rats subjected to HH only.

CONCLUSION

These results showed that the severity of brain insult can be graded by measuring biochemical modifications, specifically, reactive oxygen species-mediated damage, energy metabolism depression, and NAA, thereby validating the rodent model of closed-head diffuse TBI coupled with HH and proposing NAA as a marker with diagnostic relevance to monitor the metabolic state of postinjured brain.