Expression of c-jun, hsp72 and gfap following repeated unilateral common carotid artery occlusion in gerbils-correlates of delayed ischemic injury

Hypoxic/ischemic conditions induce expression of the putative pro-death gene Clca1 via activation of extrasynaptic N-methyl-D-aspartate receptors

The stimulation of extrasynaptic N-methyl-D-aspartate (NMDA) receptors triggers cell death pathways and has been suggested to play a key role in cell degeneration and neuron loss associated with glutamate-induced excitotoxicity. In contrast, synaptic NMDA receptors promote neuronal survival. One mechanism through which extrasynaptic NMDA receptors damage neurons may involve Clca1, which encodes a putative calcium-activated chloride channel. Here we show that Clca1 expression is induced in cultured rat hippocampal neurons exposed to oxygen/glucose-free media; this induction is mediated by a signaling pathway activated by extrasynaptic NMDA receptors. Clca1 mRNA levels also increased in the gerbil hippocampus following a transient forebrain ischemia caused by bilateral carotid occlusion. Microelectrode array recordings revealed that oxygen-glucose deprivation enhances hippocampal network firing rates, which induces c-fos transcription through a signaling pathway that, in contrast to Clca1, is activated by synaptic but not extrasynaptic NMDA receptors. Thus, conditions of low oxygen/glucose lead to the activation of both extrasynaptic and synaptic NMDA receptors that regulate distinct target genes. Clca1 may be part of the genomic death program triggered by extrasynaptic NMDA receptors; it could be a marker for ischemic brain damage and a possible target for therapeutic interventions.

Human neural stem/progenitor cells, expanded in long-term neurosphere culture, promote functional recovery after focal ischemia in Mongolian gerbils

Transplantation of human neural stem cells (NSCs) is a promising potential therapy for neurologic dysfunctions after the hyperacute stage of stroke in humans, but large amounts of human NSCs must be expanded in long-term culture for such therapy. To determine their possible therapeutic potential for human stroke, human fetal neural stem/progenitor cells (NSPCs) (i.e., neurosphere-forming cells) were isolated originally from forebrain tissues of one human fetus, and expanded in long-term neurosphere culture (exceeding 24 weeks), then xenografted into the lesioned areas in the brains of Mongolian gerbils 4 days after focal ischemia. Sensorimotor and cognitive functions were evaluated during the 4 weeks after transplantation. The total infarction volume in the NSPC-grafted animals was significantly lower than that in controls. Approximately 8% of the grafted NSPCs survived, mainly in areas of selective neuronal death, and were costained with antibodies against neuronal nuclei antibody (NeuN), microtubule associated protein (MAP-2), glial fibrillary acidic protein (GFAP), and anti-2'3' cyclic nucleotide 3'-phosphodiesterase (CNPase). Synaptic structures between NSPCs-derived neurons and host neurons were observed. Furthermore, gradual improvement of neurologic functions was observed clearly in the NSPC-grafted animals, compared to that in controls. Human NSPCs, even from long-term culture, remarkably improved neurologic functions after focal ischemia in the Mongolian gerbil, and maintained their abilities to migrate around the infarction, differentiate into mature neurons, and form synapses with host neuronal circuits. These results indicate that in vitro-expanded human neurosphere cells are a potential source for transplantable material for treatment of stroke.

Protective effect of green tea polyphenol EGCG against neuronal damage and brain edema after unilateral cerebral ischemia in gerbils

Previous studies have demonstrated that a green tea polyphenol, (-)-epigallocatechine gallate (EGCG), has a potent free radical scavenging and antioxidant effect. Glutamate leads to excitotoxicity and oxidative stress, which are important pathophysiologic responses to cerebral ischemia resulting in brain edema and neuronal damage. We investigated the effect of EGCG on excitotoxic neuronal damage in a culture system and the effect on brain edema formation and lesion after unilateral cerebral ischemia in gerbils. In vitro, excitotoxicity was induced by 24-hr incubation with N-methyl-D-aspartate (NMDA; 10 microM), AMPA (10 microM), or kainate (20 microM). EGCG (5 microM) was added to the culture media alone or with excitotoxins. We examined malondialdehyde (MDA) level and neuronal viability to evaluate the effect of EGCG. In vivo, unilateral cerebral ischemia was induced by occlusion of the right common carotid artery for 30, 60, or 90 min and followed by reperfusion of 24 hr. Brain edema, MDA, and infarction were examined to evaluate the protective effect of EGCG. EGCG (25 or 50 mg/kg, intraperitoneally) was administered twice, at 30 min before and immediately after ischemia. EGCG reduced excitotoxin-induced MDA production and neuronal damage in the culture system. In the in vivo study, treatment of gerbils with the lower EGCG dose failed to show neuroprotective effects; however, the higher EGCG dose attenuated the increase in MDA level caused by cerebral ischemia. EGCG also reduced the formation of postischemic brain edema and infarct volume. These results demonstrate EGCG may have future possibilities as a neuroprotective agent against excitotoxicity-related neurologic disorders such as brain ischemia.

Expression of c-jun, mitogen-activated protein kinase phosphatase-1, caspase-3 and glial fibrillary acidic protein following cortical cold injury in rats: relationship to metabolic disturbances and delayed cell death

The expression of c-jun, mitogen-activated protein kinase phosphatase-1 (mkp-1), caspase-3 and glial fibrillary acidic protein (gfap) was examined at 1, 3 and 7 days after cortical cold injury in rats by in situ hybridisation and immunocytochemistry. Alterations of gene expression were related to metabolic disturbances and delayed cell death, as revealed by cerebral protein synthesis autoradiography, ATP bioluminescence, pH fluorescence and terminal transferase biotinylated dUTP nick end labelling (TUNEL). Protein synthesis autoradiographies depicted sharply demarcated cortex lesions, which were almost congruent with areas exhibiting ATP depletion (lesion volume: 16.9+/-11.8 mm(3) after 7 days). Lesions were surrounded by a region of tissue alkalosis, which was most prominent 1 day after trauma. Delayed cell injury, as revealed by TUNEL, was noticed in a thin rim around the lesion border on day 1 (tissue volume: 1.7+/-0.8 mm(3)) and, to lesser extent, days 3 and 7 post-lesioning. However, only a small percentage of cells in this area were positive for activated caspase-3 protein. TUNEL(+) cells were further seen in the ventrobasal thalamus after 7 days. In the thalamus, the appearance of DNA-fragmented cells was closely accompanied by activated caspase-3 expression. In situ hybridisations revealed that cell injury both in the peri-lesion rim and ventrobasal thalamus was associated with increased c-jun and gfap, but not mkp-1 and caspase-3 mRNA levels. Gene responses were not confined to areas revealing irreversible cell death: mkp-1 mRNA was bilaterally upregulated in the lesion-remote entorhinal cortex, cingulate cortex and reticular thalamus at 7 days after trauma, and caspase-3 mRNA was slightly, but significantly downregulated in the entorhinal cortex after 3 and 7 days. Gfap mRNA was elevated in all regions exhibiting tissue alkalosis. Our data suggest that delayed cell injury after cortex trauma may be apoptotic in the ventrobasal thalamus, but not the peri-lesion rim. The dissociated responses of c-jun, mkp-1 and caspase-3 mRNAs may represent important factors influencing tissue viability.

Neurological dysfunctions versus regional infarction volume after focal ischemia in Mongolian gerbils

BACKGROUND AND PURPOSE

With advances in the therapy of stroke at the postacute phase, the use of animal models for chronological and region-specific evaluation of neurological function has become increasingly important. Our aim was to test long-term behavioral dysfunction in gerbils after focal ischemia and to correlate the results with the regional distribution of infarction in the coordinating cortical regions.

METHODS

Repetitive unilateral hemispheric ischemia (two 10-minute occlusions, 5-hour interval) was induced in Mongolian gerbils. The elevated body swing test (EBST), bilateral asymmetry test (BAT), and T-maze test were performed to assess asymmetrical motor behavior, somatosensory deficit, and spatial cognitive dysfunction during 4 weeks after ischemia. The results were correlated against the regional infarction volume of the primary motor, somatosensory, and primary visual cortices at 4 weeks after ischemia.

RESULTS

In all postischemic gerbils, persistent sensorimotor and cognitive dysfunctions were detectable throughout the postischemic period. Histological examination revealed that a cortical zone of infarction surrounded the selective neuronal death in the ipsilateral cerebral hemisphere. The regional infarction volumes of the primary motor, somatosensory, and visual cortices were significantly correlated with the scores of the EBST, BAT, and T-maze test, respectively. These combinations had the highest regression coefficient of all pairs.

CONCLUSIONS

Postischemic motor and somatosensory functions were significantly correlated with regional infarction volumes in the corresponding cortical regions. In gerbils, visual abnormality could be independently detected by the T-maze test. Such regional analyses of ischemic lesions would be useful for investigating the functional outcomes of stroke therapy.

Relationship between metabolic dysfunctions, gene responses and delayed cell death after mild focal cerebral ischemia in mice

The evolution of brain injury was examined in mice subjected to focal cerebral ischemia as induced by 30 min of intraluminar thread occlusion of the middle cerebral artery, followed by 3 h to 3 days of reperfusion. Metabolic dysfunctions were studied by 3H-leucine autoradiography for the measurement of cerebral protein synthesis and by regional ATP bioluminescent imaging. Metabolic changes were compared with responses of the genes c-fos, c-jun, heat-shock protein gene (hsp)72, p53-activated gene (pag)608 and caspase-3, which were investigated by in situ hybridization histochemistry and immunocytochemistry, and correlated with the degree of DNA fragmentation, as assessed by the terminal TdT-mediated dUTP-biotin nick end labeling method. Intraluminar thread occlusion led to a reproducible reduction of cerebral laser Doppler flow to 20-30% of control. Thread withdrawal was followed by a short-lasting post-ischemic hyperperfusion to approximately 120%. In non-ischemic control animals, fractional protein synthesis values of 0.81+/-0.26 and 0.94+/-0.23 were obtained. Thread occlusion resulted in a suppression of protein synthesis throughout the territory of the middle cerebral artery after 3 h of reperfusion (0.04+/-0.08 in caudate-putamen and 0.14+/-0.19 in somatosensory cortex, P<0.05). Protein synthesis partly recovered in the cortex after 24 h and 3 days (0.71+/-0.40 and 0.63+/-0.26, respectively), but remained suppressed in the caudate-putamen (0.14+/-0.22 and 0.28+/-0.28). Regional ATP levels did not show any major disturbances at the reperfusion times examined. Thread occlusion resulted in a transient increase of c-fos mRNA levels in ischemic and non-ischemic parts of the cortex and caudate-putamen at 3 h after ischemia, which suggests that spreading depressions were elicited in the tissue. At the same time, c-jun and hsp72 mRNAs were elevated only in ischemic brain areas showing inhibition of protein synthesis. C-fos and c-jun responses completely disappeared within 24 h of reperfusion. Hsp72 mRNA levels remained elevated in the cortex after 24 h, but decreased to basal values in the caudate-putamen. Twenty-four hours after reperfusion, pag608 and caspase-3 mRNA levels increased in the caudate-putamen, where protein synthesis rates were still reduced, and remained elevated even after 3 days. However, pag608 and caspase-3 mRNA levels did not increase in the cortex, where protein synthesis recovered. After 24 h and 3 days, functionally active p20 fragment of caspase-3 was detected in the caudate-putamen, closely associated with the appearance of DNA fragmented cells. Neither activated caspase-3 nor DNA fragmentation were noticed in the cortex.In summary, the suppression of protein synthesis is reversible in the ischemia-resistant cortex following 30 min of thread occlusion in mice, but persists in the vulnerable caudate-putamen. In the caudate-putamen, apoptotic programs are induced, closely in parallel with the manifestation of delayed cell death. Thus, the recovery of protein synthesis may be a major factor influencing tissue survival after transient focal ischemia.

Evolution of energy failure after repeated cerebral ischemia in gerbils

We have examined the regional differences in the evolution of energy failure in experimental focal cerebral ischemia. In gerbil brain subjected to repeated unilateral common carotid artery occlusion, the tissue ATP content, pH and succinic dehydrogenase activity decreased at different rates after the circulation had been restored in various cerebral regions. Light microscopical infarction became apparent at different rates following the impairment of the energy metabolism in these regions. In brain cortex with selective neuronal necrosis, only minor alterations in energy metabolism were detectable over a 7-day period following the restoration of the circulation. The present data show that the rate of energy failure is significantly different in various cerebral regions after repeated periods of cerebral ischemia in the gerbil. A slowly evolving impairment of the cerebral energy metabolism after circulation of the brain has been restored appears to be indispensable for the delayed formation of infarction after transient cerebral ischemia.

Expression of redox factor-1, p53-activated gene 608 and caspase-3 messenger RNAs following repeated unilateral common carotid artery occlusion in gerbils--relationship to delayed cell injury and secondary failure of energy state

The temporospatial expression pattern of the nuclear DNA repair enzyme redox factor-1 (ref-1), the p53-activated gene (pag) 608 and the effector caspase-3 was examined by in situ hybridization histochemistry in gerbils subjected to two 10-min episodes of unilateral common carotid artery occlusion, separated by 5h. Gene responses were correlated with the metabolic state, as revealed by regional adenosine 5'-triphosphate bioluminescent imaging, and with the degree of histological damage, as assessed by haematoxylin-eosin staining and terminal deoxynucleotidyl transferase-mediated-dUTP nick end labeling (TUNEL), in order to evaluate the role of these genes in the maturation of injury. Focal infarcts developed in the dorsolateral cerebral cortex at the bregma level and the nucleus caudate-putamen within four days after repeated unilateral ischemia, as indicated by a secondary adenosine 5'-triphosphate loss after initial adenosine 5'-triphosphate recovery and by histomorphological signs of pannecrosis. The more caudal cortex at hippocampal levels and the hippocampus (CA1>CA3 area), however, exhibited selective neuronal injury without adenosine 5'-triphosphate depletion. TUNEL+ cells appeared starting 5h after repeated unilateral ischemia. TUNEL+ cells reached maximum levels in the caudate-putamen at 12-24h, but much later in the cortex and hippocampus at two days after ischemia. Remarkably few TUNEL+ cells were noticed in the thalamus, where adenosine 5'-triphosphate state did not recover after reperfusion. Following repeated unilateral ischemia, a transient elevation of ref-1 mRNA was detected after 5h in the cerebral cortex and hippocampal CA1 area. Ref-1 mRNA levels decreased within 12-24h, before the onset of tissue damage. Subsequently, pag608 and caspase-3 mRNA levels increased, closely in parallel with the appearance of DNA fragmented cells, but slightly prior to the deterioration of adenosine 5'-triphosphate state. In the caudate-putamen, pag608 and caspase-3 mRNAs reached maximum levels already 12-24h after repeated common carotid artery occlusion, when DNA fragmentation was most prominent, and declined thereafter. In the cortex and hippocampal CA1-3 areas, where DNA damage appeared more slowly, pag608 and caspase-3 mRNAs were induced starting 24h after ischemia, and remained elevated even after two to four days. The levels of pag608 and caspase-3 mRNAs were similar at rostral and caudal levels of the cortex, as well as in the hippocampal CA1 and CA3 area, although the degree of injury differed considerably between these structures. Notably, pag608 and caspase-3 mRNAs were not elevated in the thalamus after repeated unilateral ischemia. The present report shows a close temporal association between the induction of ref-1, pag608 and caspase-3 mRNAs, the manifestation of cell injury and the secondary adenosine 5'-triphosphate depletion in infarcting brain areas, suggesting (i) that de novo responses of these genes may be involved in the maturation of cell injury and (ii) that apoptotic programs and the secondary deterioration of cerebral energy state may interfere with each other after ischemia.