Eun Joo Bae

Impact of hyperthermia before and during ischemia–reperfusion on neuronal damage and gliosis in the gerbil hippocampus induced by transient cerebral ischemia

Hyperthermia can exacerbate the brain damage produced by ischemia. In the present study, we investigated the effects of hyperthermia before and during ischemia-reperfusion on neuronal damage and glial changes in the gerbil hippocampus following transient cerebral ischemia using cresyl violet staining, NeuN immunohistochemistry and Fluoro-Jade B histofluorescence staining. The animals were randomly assigned to 4 groups: (1) sham-operated animals with normothermia (normothermia + sham group); (2) ischemia-operated animals with normothermia (normothermia + ischemia group); (3) sham-operated animals with hyperthermia (hyperthermia + sham group); and (4) ischemia-operated animals with hyperthermia (hyperthermia + ischemia group). Hyperthermia (39.5 ± 0.2°C) was induced by exposing the gerbils to a heating pad connected to a rectal thermistor for 30 min before and during ischemia-reperfusion. In the normothermia+ischemia groups, a significant delayed neuronal death was observed in the stratum pyramidale (SP) of the hippocampal CA1 region (CA1) 5 days after ischemia-reperfusion. In the hyperthermia+ischemia groups, neuronal death in the SP of the CA1 occurred at 1 day post-ischemia, and neuronal death was observed in the SP of the CA2/3 region at 2 days post-ischemia. In addition, we examined activations of astrocytes and microglia using immunohistochemistry for anti-glial fibrillary acidic protein (GFAP) and anti-ionized calcium-binding adapter molecule 1 (Iba-1). GFAP-positive astrocytes and Iba-1-positive microglia in the ischemic hippocampus were activated much earlier and much more accelerated in the hyperthermia+ischemia groups than those in the normothermia+ischemia groups. Based on our findings, we suggest that an experimentally hyperthermic pre-condition before cerebral ischemic insult produces more extensive neuronal damage and glial activation in the ischemic hippocampus.

Delayed hippocampal neuronal death in young gerbil following transient global cerebral ischemia is related to higher and longer-term expression of p63 in the ischemic hippocampus.

The tumor suppressor p63 is one of p53 family members and plays a vital role as a regulator of neuronal apoptosis in the development of the nervous system. However, the role of p63 in mature neuronal death has not been addressed yet. In this study, we first compared ischemia-induced effects on p63 expression in the hippocampal regions (CA1- 3) between the young and adult gerbils subjected to 5 minutes of transient global cerebral ischemia. Neuronal death in the hippocampal CA1 region of young gerbils was significantly slow compared with that in the adult gerbils after transient global cerebral ischemia. p63 immunoreactivity in the hippocampal CA1 pyramidal neurons in the sham-operated young group was significantly low compared with that in the sham-operated adult group. p63 immunoreactivity was apparently changed in ischemic hippocampal CA1 pyramidal neurons in both ischemia-operated young and adult groups. In the ischemia-operated adult groups, p63 immunoreactivity in the hippocampal CA1 pyramidal neurons was significantly decreased at 4 days post-ischemia; however, p63 immunoreactivity in the ischemia-operated young group was significantly higher than that in the ischemia-operated adult group. At 7 days post-ischemia, p63 immunoreactivity was decreased in the hippocampal CA1 pyramidal neurons in both ischemia-operated young and adult groups. Change patterns of p63 level in the hippocampal CA1 region of adult and young gerbils after ischemic damage were similar to those observed in the immunohistochemical results. These findings indicate that higher and longer-term expression of p63 in the hippocampal CA1 region of the young gerbils after ischemia/reperfusion may be related to more delayed neuronal death compared to that in the adults.

Pretreated duloxetine protects hippocampal CA1 pyramidal neurons from ischemia-reperfusion injury through decreases of glial activation and oxidative stress

Duloxetine (DXT), a serotonin/norepinephrine reuptake inhibitor, is widely used for the treatment of major depressive disorders. In the present study, we investigated the neuroprotective effect of pre-treated DXT in the hippocampal CA1 region following transient global cerebral ischemia. Pre-treatment with 40mg/kg DXT protected pyramidal neurons in the CA1 region from ischemia-reperfusion injury. In addition, pre-treatment with DXT reduced ischemia-induced activations of microglia and astrocytes in the ischemic CA1 region. On the other hand, we found that pre-treatment with DXT did not increase 4-hydroxy-2-noneal (a marker for lipid peroxidation) and significantly increased the expression of Cu, Zn-superoxide dismutase, an antioxidant, in the CA1 pyramidal neurons compared with non-treated those after ischemia-reperfusion. These results indicate that pre-treated DXT has neuroprotective effect against transient global cerebral ischemia and suggest that the neuroprotective effect of DXT may be due to the attenuation of ischemia-induced glial activation as well as the decrease of oxidative stress.

Ischemic preconditioning protects neurons from damage and maintains the immunoreactivity of kynurenic acid in the gerbil hippocampal CA1 region following transient cerebral ischemia

Pyramidal neurons in region I of hippocampus proper (CA1) are particularly vulnerable to excitotoxic processes following transient forebrain ischemia. Kynurenic acid (KYNA) is a small molecule derived from tryptophan when this amino acid is metabolized through the kynurenine pathway. In the present study, we examined the effects of ischemic preconditioning (IPC) on the immunoreactivity and protein levels of KYNA following 5 min of transient forebrain ischemia in gerbils. The animals were randomly assigned to 4 groups (sham-operated group, ischemia-operated group, IPC + sham-operated group and IPC + ischemia-operated group). IPC was induced by subjecting the gerbils to 2 min of ischemia followed by 1 day of recovery. In the ischemia-operated group, we observed a significant loss of pyramidal neurons in the CA1 stratum pyramidale (SP) at 5 days post-ischemia; however, in the IPC + ischemia-operated group, the pyramidal neurons were well protected. KYNA immunoreactivity in the SP of the ischemia-operated group was significantly altered following ischemia-reperfusion and was very low 5 days following ischemia-reperfusion. In the IPC + ischemia-operated group, however, KYNA immunoreactivity was constitutively detected in the SP of the CA1 region after the ischemic insult. We also found that the alteration pattern of the KYNA protein level in the CA1 region following ischemia was generally similar to the immunohistochemical changes observed. In brief, our findings demonstrated that IPC maintained and even increased KYNA immunoreactivity in the SP of the CA1 region following ischemia-reperfusion. The data from the present study thus indicate that the enhancement of KYNA expression by IPC may be necessary for neuronal survival following transient ischemic injury.

Ethanol extract of Oenanthe javanica increases cell proliferation and neuroblast differentiation in the adolescent rat dentate gyrus

Oenanthe javanica is an aquatic perennial herb that belongs to the Oenanthe genus in Apiaceae family, and it displays well-known medicinal properties such as protective effects against glutamate-induced neurotoxicity. However, few studies regarding effects of Oenanthe javanica on neurogenesis in the brain have been reported. In this study, we examined the effects of a normal diet and a diet containing ethanol extract of Oenanthe javanica on cell proliferation and neuroblast differentiation in the subgranular zone of the hippocampal dentate gyrus of adolescent rats using Ki-67 (an endogenous marker for cell proliferation) and doublecortin (a marker for neuroblast). Our results showed that Oenanthe javanica extract significantly increased the number of Ki-67-immunoreactive cells and doublecortin-immunoreactive neuroblasts in the subgranular zone of the dentate gyrus in the adolescent rats. In addition, the immunoreactivity of brain-derived neurotrophic factor was significantly increased in the dentate gyrus of the Oenanthe javanica extract-treated group compared with the control group. However, we did not find that vascular endothelial growth factor expression was increased in the Oenanthe javanica extract-treated group compared with the control group. These results indicate that Oenanthe javanica extract improves cell proliferation and neuroblast differentiation by increasing brain-derived neurotrophic factor immunoreactivity in the rat dentate gyrus.

Ischemic preconditioning inhibits expression of Na+/H+ exchanger 1 (NHE1) in the gerbil hippocampal CA1 region after transient forebrain ischemia

The participation of Na(+)/H(+) exchanger (NHE) in neuronal damage/death in the hippocampal CA1 region (CA1) induced by transient forebrain ischemia has not been well established, although acidosis may be involved in neuronal damage/death. In the present study, we examined the effect of ischemic preconditioning (IPC) on NHE1 immunoreactivity following a 5min of transient forebrain ischemia in gerbils. The animals used in the study were randomly assigned to four groups (sham-operated-group, ischemia-operated-group, IPC plus (+) sham-operated-group and IPC+ischemia-operated-group). IPC was induced by subjecting animals to 2min of ischemia followed by 1day of recovery. A significant neuronal loss was found in the stratum pyramidale (SP) of the CA1, not the CA2/3, of the ischemia-operated-group at 5days post-ischemia. However, in the IPC+ischemia-operated-group, neurons in the SP of the CA1 were well protected. NHE1 immunoreactivity was not detected in any regions of the CA1-3 of the sham- and IPC+sham-operated-groups. However, the immunoreactivity was apparently expressed in the SP of the CA1-3 after ischemia, and the NHE1immunoreactivity was very weak 5days after ischemia; however, at this point in time, strong NHE1immunoreactivity was found in astrocytes in the CA1. In the CA2/3, NHE1immunoreactivity was slightly changed, although NHE1immunoreactivity was expressed in the SP. In the IPC+ischemia-operated-groups, NHE1 immunoreactivity was also expressed in the SP of the CA1-3; however, the immunoreactivity was more slightly changed than that in the ischemia-operated-groups. In brief, our findings show that IPC dramatically protected CA1 pyramidal neurons and strongly inhibited NHE1 expression in the SP of the CA1 after ischemia-reperfusion. These findings suggest that the inhibition of NHE1 expression may be necessary for neuronal survival from transient ischemic damage.

Effect of Oenanthe Javanica Extract on Antioxidant Enzyme in the Rat Liver

Background:Oenanthe javanica (O. javanica) has been known to have high antioxidant properties via scavenging reactive oxygen species. We examined the effect of O. javanica extract (OJE) on antioxidant enzymes in the rat liver. Methods:We examined the effect of the OJE on copper, zinc-superoxide dismutase (SOD1), manganese superoxide dismutase (SOD2), catalase (CAT), and glutathione peroxidase (GPx) in the rat liver using immunohistochemistry and western blot analysis. Sprague-Dawley rats were randomly assigned to three groups; (1) normal diet fed group (normal-group), (2) diet containing ascorbic acid (AA)-fed group (AA-group) as a positive control, (3) diet containing OJE-fed group (OJE-group). Results:In this study, no histopathological finding in the rat liver was found in all the experimental groups. Numbers of SOD1, SOD2, CAT, and GPx immunoreactive cells and their protein levels were significantly increased in the AA-fed group compared with those in the normal-group. On the other hand, in the OJE-group, numbers of SOD1, SOD2, CAT, and GPx immunoreactive cells in the liver were significantly increased by about 190%, 478%, 685%, and 346%, respectively, compared with those in the AA-group. In addition, protein levels of SOD1, SOD2, CAT, and GPx in the OJE-group were also significantly much higher than those in the AA-group. Conclusion:OJE significantly increased expressions of SOD1 and SOD2, CAT, and GPx in the liver cells of the rat, and these suggests that significant enhancements of endogenous enzymatic antioxidants by OJE might be a legitimate strategy for decreasing oxidative stresses in the liver.

Immunoreactivities of calbindin‑D28k, calretinin and parvalbumin in the somatosensory cortex of rodents during normal aging

Calbindin-D28k (CB), calretinin (CR) and parvalbumin (PV), which regulate cytosolic free Ca2+ concentrations in neurons, are chemically expressed in γ-aminobutyric acid (GABA)ergic neurons that regulate the degree of glutamatergic excitation and output of projection neurons. The present study investigated age-associated differences in CB, CR and PV immunoreactivities in the somatosensory cortex in three species (mice, rats and gerbils) of young (1 month), adult (6 months) and aged (24 months) rodents, using immunohistochemistry and western blotting. Abundant CB-immunoreactive neurons were distributed in layers II and III, and age-associated alterations in their number were different according to the species. CR-immunoreactive neurons were not abundant in all layers; however, the number of CR-immunoreactive neurons was the highest in all adult species. Many PV-immunoreactive neurons were identified in all layers, particularly in layers II and III, and they increased in all layers with age in all species. The present study demonstrated that the distribution pattern of CB-, CR- and PV-containing neurons in the somatosensory cortex were apparently altered in number with normal aging, and that CB and CR exhibited a tendency to decrease in aged rodents, whereas PV tended to increase with age. These results indicate that CB, CR and PV are markedly altered in the somatosensory cortex, and this change may be associated with normal aging. These findings may aid the elucidation of the mechanisms of aging and geriatric disease.

Differences in the protein expression levels of Trx2 and Prx3 in the hippocampal CA1 region between adult and aged gerbils following transient global cerebral ischemia

The thioredoxin (Trx) and peroxiredoxin (Prx) redox system is associated with neuronal damage and neuroprotective effects via the regulation of oxidative stress in brain ischemia. In the present study, ischemia-induced changes in the protein expression levels of Trx2 and Prx3 in the stratum pyramidale (SP) of the hippocampal CA1 region were investigated in adult and aged gerbils, subjected to 5 min of transient global cerebral ischemia, using immunohistochemistry and western blot analysis. In the adult ischemia-group, minimal Trx2 immunoreactivity was detected in the SP 2 days after ischemia-reperfusion. In the aged animals, the Trx2 immunoreactivity in the sham-group was marginally lower compared with that in the adult sham-group. In the aged ischemia-group, Trx2 immunoreactivity in the SP was significantly higher 1, 2 and 4 days post-ischemia, compared with that in the adult ischemia-group and, in the 5 days post-ischemia group, Trx2 immunoreactivity was significantly decreased in the SP. Prx3 immunoreactivity in the SP of the adult ischemia-group was significantly decreased from 4 days after ischemia-reperfusion. In the aged animals, Prx3 immunoreactivity in the sham-group was also marginally lower compared with that in the adult sham-group. Prx3 immunoreactivity in the aged ischemia-group was also significantly higher 1, 2 and 4 days post-ischemia, compared with the adult ischemia-group; however, the Prx3 immunoreactivity was significantly decreased 5 days post-ischemia. The western blot analyses revealed that the pattern of changes in the protein levels of Trx2 and Prx3 in the adult and aged hippocampal CA1 region following ischemic damage were similar to the results obtained in the immunohistochemical data. These findings indicated that cerebral ischemia lead to different protein expression levels of Trx2 and Prx3 in the hippocampal CA1 region between adult and aged gerbils, and these differences may be associated with more delayed neuronal death in the aged gerbil hippocampus following transient global cerebral ischemia.