Joon Ha Park

Pre- and post-treatments with escitalopram protect against experimental ischemic neuronal damage via regulation of BDNF expression and oxidative stress

Selective serotonin re-uptake inhibitors (SSRI) have been widely used in treatment of major depression because of their efficacy, safety, and tolerability. Escitalopram, an SSRI, is known to decrease oxidative stress in chronic stress animal models. In the present study, we examined the neuroprotective effects of pre- and post-treatments with 20 mg/kg and 30 mg/kg escitalopram in the gerbil hippocampal CA1 region (CA1) after transient cerebral ischemia. Pre-treatment with escitalopram protected against ischemia-induced neuronal death in the CA1 after ischemia/reperfusion (I/R). Post-treatment with 30 mg/kg, not 20 mg/kg, escitalopram had a neuroprotective effect against ischemic damage. In addition, 20 mg/kg pre- and 30 mg/kg post-treatments with escitalopram increased brain-derived neurotrophic factor (BDNF) protein levels in the ischemic CA1 compared to vehicle-treated ischemia animals. In addition, 20 mg/kg pre- and 30 mg/kg post-treatments with escitalopram reduced microglia activation and decreased 4-hydroxy-2-nonenal and Cu,Zn-superoxide dismutase immunoreactivity and their levels in the ischemic CA1 compared to vehicle-treated ischemia animals after transient cerebral ischemia. In conclusion, these results indicated that pre- and post-treatments with escitalopram can protect against ischemia-induced neuronal death in the CA1 induced by transient cerebral ischemic damage by increase of BDNF as well as decrease of microglia activation and oxidative stress.

Increases of antioxidants are related to more delayed neuronal death in the hippocampal CA1 region of the young gerbil induced by transient cerebral ischemia

In age-related studies, young animals are resistant to ischemic damage. In present study, we investigated the neuronal death of pyramidal neurons and compared changes in the immunoreactivities and levels of antioxidants, Cu/Zn-SOD (SOD1), Mn-SOD (SOD2), catalase (CAT) and glutathione peroxidase (Gpx), in the hippocampal CA1 region between adult and young gerbils after 5 min of transient cerebral ischemia. In the adult ischemia-group, only a few (12%) of CA1 pyramidal neurons survived 4 days after ischemia-reperfusion (I-R); however, in the 4 days after I-R the young group, most of CA1 pyramidal neurons survived. Seven days after I-R, many (about 39%) of CA1 pyramidal neurons survived, thereafter, the neuronal death in the CA1 pyramidal neurons was not significantly changed. The immunoreactivities of all the antioxidants were well detected in CA1 pyramidal neurons in the adult sham-groups; in the young sham-groups, they were distinctively low compared to those in the adult sham-group. Four days after I-R in the adult group, all the immunoreactivities in the pyramidal neurons were dramatically deceased. However, at this time after I-R in the young groups, they were dramatically increased in the pyramidal neurons. From 7 days after I-R, all the immunoreactivities in the pyramidal neurons in the young ischemia-groups were distinctively decreased. In addition, the levels of all the antioxidants in the CA1 region of the young sham-groups were lower than those in the adult sham-group. Four days after I-R in the adult groups, the levels of all the antioxidants were dramatically deceased; however, at this time in the young ischemia-groups, they were distinctively increased in the CA1 region. Seven days after I-R, all the antioxidants levels in the CA1 region were distinctively decreased. In brief, we conclude that the increased antioxidants levels were related to a less and much delayed neuronal death in the CA1 pyramidal neurons in the young group following I-R injury.

Comparison of neuroprotective effects of five major lipophilic diterpenoids from Danshen extract against experimentally induced transient cerebral ischemic damage

We observed neuroprotective effects of five major lipophilic diterpenes derived from Danshen (Radix Salvia miltiorrhiza) extract, such as cryptotanshinone (CTs), dihydrotanshinone I (DTsI), tanshinone I (TsI), tanshinone IIA (TsIIA) and tanshinone IIB (TsIIB), in the hippocampal CA1 region (CA1) against transient ischemic damage in gerbils. These diterpenes were administered 30min before ischemia-reperfusion and the animals were sacrificed 4days after ischemia-reperfusion. In the vehicle-treated-group, cresyl violet positive (CV(+)) cells and neuronal nuclei (NeuN)(+) neurons were significantly decreased in the CA1. However, in the TsI- and CTs-treated-ischemia-groups, CV(+) and NeuN(+) neurons were abundant in the CA1. In the other groups, the number of CV(+) and NeuN(+) neurons was less than the TsI- and CTs-treated-ischemia-groups. In addition, gliosis induced by ischemic damage was apparently blocked in the TsI- and CTs-treated-ischemia-groups. These results suggest that TsI and CTs among five major lipophilic diterpenes have strong potentials for neuroprotection against ischemic damage.

Neuronal damage in hippocampal subregions induced by various durations of transient cerebral ischemia in gerbils using Fluoro-Jade B histofluorescence

Although there are many studies on ischemic brain damage in the gerbil, which is a good model of transient cerebral ischemia, studies on neuronal damage according to the duration of ischemia-reperfusion (I-R) time are limited. We carried out neuronal damage in the gerbil hippocampus after various durations of I-R (5, 10, 15 and 20 min) using Fluoro-Jade B (F-J B, a maker for neuronal degeneration) histofluorescence as well as cresyl violet (CV) staining. The changes of CV positive ((+)) neurons were well detected in the hippocampal CA1 region, not in the other regions. F-J B histofluorescence staining showed apparent neuronal damage in all the hippocampal subregions. In the CA1, most of the pyramidal neurons of the stratum pyramidale (SP) were stained with F-J B (about 100/mm(2) in a section), and F-J B(+) neurons in the other ischemia-groups were not changed. In the CA2, a few F-J B(+) neurons were detected in the SP of the 5 min ischemia-group, and F-J B(+) neurons were gradually increased with the longer time of ischemia: in the 20 min ischemia-group, the mean number of F-J B(+) neurons was about 85/mm(2) in a section. In the CA3, some F-J B(+) neurons were observed only in the SP of the 20 min ischemia-group. In the dentate gyrus, some F-J B positive neurons were detected only in the polymorphic layer (PL) of the 5 min ischemia-group, and the number of F-J B(+) neurons were gradually increased with the longer ischemic time. Our findings indicate that F-J B histofluorescence showed a very high quality of neuronal damage in all the hippocampal subregions.

Long-Term Exercise Improves Memory Deficits via Restoration of Myelin and Microvessel Damage, and Enhancement of Neurogenesis in the Aged Gerbil Hippocampus After Ischemic Stroke.

Background. The positive correlation between therapeutic exercise and memory recovery in cases of ischemia has been extensively studied; however, long-term exercise begun after ischemic neuronal death as a chronic neurorestorative strategy has not yet been thoroughly examined. Objective. The purpose of this study is to investigate possible mechanisms by which exercise ameliorates ischemia-induced memory impairment in the aged gerbil hippocampus after transient cerebral ischemia. Methods. Treadmill exercise was begun 5 days after ischemia-reperfusion (I-R) and lasted for 1 or 4 weeks. The animals were sacrificed 31 days after the induction of ischemia. Changes in short-term memory, as well as the hippocampal expression of markers of cell proliferation, neuroblast differentiation, neurogenesis, myelin and microvessel repair, and growth factors were examined by immunohistochemistry and/or western blots. Results. Four weeks of exercise facilitated memory recovery despite neuronal damage in the stratum pyramidale (SP) of the hippocampal CA1 region and in the polymorphic layer (PoL) of the dentate gyrus (DG) after I-R. Long-term exercise enhanced cell proliferation and neuroblast differentiation in a time-dependent manner, and newly generated mature cells were found in the granule cell layer of the DG, but not in the SP of the CA1 region or in the PoL of the DG. In addition, long-term exercise ameliorated ischemia-induced damage of myelin and microvessels, which was correlated with increased BDNF expression in the CA1 region and the DG. Conclusions. These results suggest that long-term treadmill exercise after I-R can restore memory function through replacement of multiple damaged structures in the ischemic aged hippocampus.

Ischemic preconditioning-induced neuroprotection against transient cerebral ischemic damage via attenuating ubiquitin aggregation

Ubiquitin binds to short-lived proteins, and denatured proteins are produced by various forms of injuries. In the present study, we investigated the effect of ischemic preconditioning (IPC) on free ubiquitin and its mutant form (ubiquitin(+1)) in the gerbil hippocampus induced by transient cerebral ischemia. The animals were randomly assigned to 4 groups (sham-operated-group, ischemia-operated-group, IPC plus (+)-sham-operated-group, and IPC+ischemia-operated-group). IPC was induced by subjecting gerbils to a 2 min of ischemia followed by 1 day of recovery. A significant loss of neurons was observed in the stratum pyramidale (SP) of the hippocampal CA1 region (CA1) in the ischemia-operated-groups 5 days after ischemia-reperfusion (I-R). In all the IPC+ischemia-operated-groups, neurons in the SP were well protected. We found that strong ubiquitin immunoreactivity was detected in the SP in the sham-operated-group and the immunoreactivity was decreased with time after I-R. In all the IPC+ischemia-operated-groups, ubiquitin immunoreactivity in the SP was similar to that in the sham-operated group. Moderate ubiquitin(+1) immunoreactivity was detected in the SP of the sham-operated-group, and the immunoreactivity was markedly increased 2 days after I-R. Five days after I-R, ubiquitin(+1) immunoreactivity was very weak in the SP. In all the IPC+ischemia-operated-groups, ubiquitin(+1) immunoreactivity in the SP was slightly decreased with time after I-R. Western blot analysis showed that, in all the IPC+ischemia-ischemia-groups, the levels of ubiquitin and ubiquitin(+1) proteins were well maintained after I-R. In brief, our findings suggest that the inhibition of the depletion of free ubiquitin and the formation of ubiquitin(+1) may have an essential role in inducing cerebral ischemic tolerance by IPC.

Heat shock protein 90 and its cochaperone, p23, are markedly increased in the aged gerbil hippocampus.

In the present study, we compared HSP90 and its co-chaperone, p23, immunoreactivity and their protein levels in the hippocampus between adult (postnatal month 6) and aged (postnatal month 24) gerbils using immunohistochemistry and western blot analysis. HSP90 immunoreactivity was markedly increased in pyramidal cells in the hippocampus proper and in polymorphic cells in the dentate gyrus of the aged group compared to the adult group. p23 immunoreactivity was slightly increased in pyramidal cells of the hippocampus proper and in granule cells of the dentate gyrus in the aged group. In addition, HSP90 and p23 protein levels in the aged hippocampus were much higher than the adult hippocampus. These results indicate that HSP90 and p23 immunoreactivity and protein levels in the hippocampus are distinctively increased in the aged gerbils compared to the adult gerbils.

Neuroprotective effect of a new synthetic aspirin-decursinol adduct in experimental animal models of ischemic stroke.

Stroke is the second leading cause of death. Experimental animal models of cerebral ischemia are widely used for researching mechanisms of ischemic damage and developing new drugs for the prevention and treatment of stroke. The present study aimed to comparatively investigate neuroprotective effects of aspirin (ASA), decursinol (DA) and new synthetic aspirin-decursinol adduct (ASA-DA) against transient focal and global cerebral ischemic damage. We found that treatment with 20 mg/kg, not 10 mg/kg, ASA-DA protected against ischemia-induced neuronal death after transient focal and global ischemic damage, and its neuroprotective effect was much better than that of ASA or DA alone. In addition, 20 mg/kg ASA-DA treatment reduced the ischemia-induced gliosis and maintained antioxidants levels in the corresponding injury regions. In brief, ASA-DA, a new synthetic drug, dramatically protected neurons from ischemic damage, and neuroprotective effects of ASA-DA may be closely related to the attenuation of ischemia-induced gliosis and maintenance of antioxidants.

Neuroprotective effects of tanshinone I from Danshen extract in a mouse model of hypoxia-ischemia

Hypoxia-ischemia leads to serious neuronal damage in some brain regions and is a strong risk factor for stroke. The aim of this study was to investigate the neuroprotective effect of tanshinone I (TsI) derived from Danshen (Radix Salvia miltiorrhiza root extract) against neuronal damage using a mouse model of cerebral hypoxia-ischemia. Brain infarction and neuronal damage were examined using 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin and eosin histochemistry, and Fluoro-Jade B histofluorescence. Pre-treatment with TsI (10 mg/kg) was associated with a significant reduction in infarct volume 1 day after hypoxia-ischemia was induced. In addition, TsI protected against hypoxia-ischemia-induced neuronal death in the ipsilateral region. Our present findings suggest that TsI has strong potential for neuroprotection against hypoxic-ischemic damage. These results may be used in research into new anti-stroke medications.

Changes and expressions of Redd1 in neurons and glial cells in the gerbil hippocampus proper following transient global cerebral ischemia.

Redd1 (known as RTP801/Dig2/DDIT4) is a stress-induced protein, and it is known to be regulated in response to some stresses including hypoxia and oxidative stress. In the present study, we investigated the time-dependent changes in Redd1 immunoreactivity and its protein levels in the gerbil hippocampus proper (CA1-3 regions) after 5 min of transient global cerebral ischemia using immunohistochemistry and Western blot analysis. Redd1 immunoreactivity was apparently changed in the pyramidal neurons of the ischemic CA1 region, not in the pyramidal neurons of the ischemic CA2/3 region. Redd1 immunoreactivity in the CA1 pyramidal neurons was significantly increased at 6 h post-ischemia, decreased until 1 day post-ischemia, increased again at 2 days post-ischemia and weakly observed at 5 days post-ischemia. Especially, at 5 days after ischemic damage, Redd1 immunoreactivity was newly expressed in astrocytes and GABAergic interneurons in the CA1 region. Redd1 protein levels in the ischemic CA1 region were changed like the pattern of the Redd1 immunoreactivity. These results indicate that Redd1 immunoreactivity and protein levels are increased in the ischemic CA1 region at an early time after ischemic damage and that the increased Redd1 expression may be closely related to the delayed neuronal death of the CA1 pyramidal neurons following 5 min of transient global cerebral ischemia.