Neuroprotective effect of the ethanol extract of Artemisia capillaris on transient forebrain ischemia in mice via nicotinic cholinergic receptor / 中国天然药物

Artemisia capillaris Thunberg is a medicinal plant used as a traditional medicine in many cultures. It is an effective remedy for liver problems including hepatitis. Recent pharmacological reports have indicated that Artemisia species can exert various neurological effects. Previously, we reported a memory-enhancing effect of Artemisia species. However, the mechanisms underlying the neuroprotective effect of A. capillaris (AC) are still unknown. In the present study, we investigated the effect of an ethanol extract of AC on ischemic brain injury in a mouse model of transient forebrain ischemia. The mice were treated with AC for seven days, beginning one day before induction of transient forebrain ischemia. Behavioral deficits were investigated using the Y-maze. Nissl and Fluoro-jade B staining were used to indicate the site of injury. To determine the underlying mechanisms for the drug, we measured acetylcholinesterase activity. AC (200 mg·kg) treatment reduced transient forebrain ischemia-induced neuronal cell death in the hippocampal CA1 region. The AC-treated group also showed significant amelioration in the spontaneous alternation of the Y-maze test performance, compared to that in the untreated transient forebrain ischemia group. Moreover, AC treatment showed a concentration-dependent inhibitory effect on acetylcholinesterase activity in vitro. Finally, the effect of AC on forebrain ischemia was blocked by mecamylamine, a nonselective nicotinic acetylcholine receptor antagonist. Our results suggested that in a model of forebrain ischemia, AC protected against neuronal death through the activation of nicotinic acetylcholine receptors.

Neuroprotective effect of the ethanol extract of Artemisia capillaris on transient forebrain ischemia in mice via nicotinic cholinergic receptor / 中国天然药物

Artemisia capillaris Thunberg is a medicinal plant used as a traditional medicine in many cultures. It is an effective remedy for liver problems including hepatitis. Recent pharmacological reports have indicated that Artemisia species can exert various neurological effects. Previously, we reported a memory-enhancing effect of Artemisia species. However, the mechanisms underlying the neuroprotective effect of A. capillaris (AC) are still unknown. In the present study, we investigated the effect of an ethanol extract of AC on ischemic brain injury in a mouse model of transient forebrain ischemia. The mice were treated with AC for seven days, beginning one day before induction of transient forebrain ischemia. Behavioral deficits were investigated using the Y-maze. Nissl and Fluoro-jade B staining were used to indicate the site of injury. To determine the underlying mechanisms for the drug, we measured acetylcholinesterase activity. AC (200 mg·kg) treatment reduced transient forebrain ischemia-induced neuronal cell death in the hippocampal CA1 region. The AC-treated group also showed significant amelioration in the spontaneous alternation of the Y-maze test performance, compared to that in the untreated transient forebrain ischemia group. Moreover, AC treatment showed a concentration-dependent inhibitory effect on acetylcholinesterase activity in vitro. Finally, the effect of AC on forebrain ischemia was blocked by mecamylamine, a nonselective nicotinic acetylcholine receptor antagonist. Our results suggested that in a model of forebrain ischemia, AC protected against neuronal death through the activation of nicotinic acetylcholine receptors.

Characterization of nestin expression in astrocytes in the rat hippocampal CA1 region following transient forebrain ischemia / 대한해부학회지

Recent studies have suggested that nestin facilitates cellular structural remodeling in vasculature-associated cells in response to ischemic injury. The current study was designed to investigate the potential role of post-ischemic nestin expression in parenchymal astrocytes. With this aim, we characterized ischemia-induced nestin expression in the CA1 hippocampal region, an area that undergoes a delayed neuronal death, followed by a lack of neuronal generation after transient forebrain ischemia. Virtually all of the nestin-positive cells in the ischemic CA1 hippocampus were reactive astrocytes. However, induction of nestin expression did not correlate simply with astrogliosis, but rather showed characteristic time- and strata-dependent expression patterns. Nestin induction in astrocytes of the pyramidal cell layer was rapid and transient, while a long-lasting induction of nestin was observed in astrocytes located in the CA1 dendritic subfields, such as the stratum oriens and radiatum, until at least day 28 after ischemia. There was no detectable expression in the stratum lacunosum moleculare despite the evident astroglial reaction. Almost all of the nestin-positive cells also expressed a transcription factor for neural/glial progenitors, i.e., Sox-2 or Sox-9, and some cells were also positive for Ki-67. However, all of the nestin-positive astrocytes expressed the calcium-binding protein S100beta, which is known to be expressed in a distinct, post-mitotic astrocyte population. Thus, our data indicate that in the ischemic CA1 hippocampus, nestin expression was induced in astroglia that were becoming reactive, but not in a progenitor/stem cell population, suggesting that nestin may allow for the structural remodeling of these cells in response to ischemic injury.

Iron mediates endothelial cell damage and blood-brain barrier opening in the hippocampus after transient forebrain ischemia in rats

Blood cells are transported into the brain and are thought to participate in neurodegenerative processes following hypoxic ischemic injury. We examined the possibility that transient forebrain ischemia (TFI) causes the blood-brain barrier (BBB) to become permeable to blood cells, possibly via dysfunction and degeneration of endothelial cells in rats. Extravasation of Evans blue and immunoglobulin G (IgG) was observed in the hippocampal CA1-2 areas within 8 h after TFI, and peaked at 48 h. This extravasation was accompanied by loss of tight junction proteins, occludin, and zonula occludens-1, and degeneration of endothelial cells in the CA1-2 areas. Iron overload and mitochondrial free radical production were evident in the microvessel endothelium of the hippocampus before endothelial cell damage occurred. Administration of deferoxamine (DFO), an iron chelator, or Neu2000, an antioxidant, blocked free radical production and endothelial cell degeneration. Our findings suggest that iron overload and iron-mediated free radical production cause loss of tight junction proteins and degeneration of endothelial cells, opening of the BBB after TFI.

The Effect of Fluoxetine on Behaviors in Transient Forebrain Ischemic Gerbil / 대한정신약물학회지

OBJECTIVE: This study aims to explore the effect of fluoxetine on memory, locomotor and depressive behavior in transient forebrain ischemic model of gerbil. METHODS: Doses of fluoxetine (10, 40 mg/kg) or vehicle were intraperitoneally administered once 30 min before ischemic surgery in gerbil. Novel object recognition test, spontaneous motor activity, learned helplessness test were performed 4 days, 8 days, or 9 days, respectively, after sham or ischemic surgery. RESULTS: Fluoxetine treatment (40 mg/kg) significantly reduced recognition memory in sham operated gerbil. However, fluoxetine (10, 40 mg/kg) did not affect ischemia-induced impairment in recognition memory. The treatment of fluoxetine (10, 40 mg/kg) significantly inhibited locomotor hyperactivity induced by transient ischemia even though fluoxetine (40 mg/kg) did not affect spontaneous motor activity in the sham operated gerbils. Fluoxetine did not affect depressive behavior in sham and ischemic gerbils. CONCLUSION: The treatment of fluoxetine inhibited ischemia-induced hyperactivity, but did not affect memory and depressive behavior in transient forebrain ischemic gerbils.

Postischemic Treatment with Aminoguanidine Inhibits Peroxynitrite Production in the Rat Hippocampus Following Transient Forebrain Ischemia

Transient forebrain ischemia results in the delayed neuronal death in the CA1 area of the hippocampus. The present study was performed to determine effects of aminoguanidine, a selective iNOS inhibitor, on the generation of peroxynitrite and delayed neuronal death occurring in the hippocampus following transient forebrain ischemia. Transient forebrain ischemia was produced in the conscious rats by four-vessel occlusion for 10 min. Treatment with aminoguanidine (100 mg/kg or 200 mg/kg, i.p.) or saline (0.4 ml/100 g, i.p.) was started 30 min following ischemia-reperfusion and the animals were then injected twice daily until 12 h before sacrifice. Immunohistochemical method was used to detect 3-nitrotyrosine, a marker of peroxynitrite production. Posttreatment of aminoguanidine (200 mg/kg) significantly attenuated the neuronal death in the hippocampal CA1 area 3 days, but not 7 days, after ischemia-reperfusion. 3-Nitrotyrosine immunoreactivity was enhanced in the hippocampal CA1 area 3 days after reperfusion, which was prevented by the treatment of aminoguanidine (100 mg/kg and 200 mg/kg). Our findings showed that (1) the generation of peroxynitrite in the hippocampal CA1 area 3 days after ischemia-reperfusion was dependent on the iNOS activity; (2) the postischemic delayed neuronal death was attenuated in the early phase through the prevention of peroxynitrite generation by an iNOS inhibitor.

Morphological Analysis of Short and Long Term Changes after Ligation of Unilateral Common Carotid Artery in Gerbils

BACKGROUND: The ligation of the unilateral common carotid artery (CCA) in the gerbil has been known as an ischemic animal model showing various changes including selective neuronal necrosis as well as infarction. This study was performed to analyze the short and long term morphological changes of transient unilateral forebrain ischemia with special attention to astroglial proliferation. METHODS: 67 mongolian gerbils were subjected to 2 hr, 3 hr, 4 hr, or 5 hr of forebrain ischemia by the unilateral CCA ligation method. Each of the ischemic groups were examined after a 1 day, 3 day, or 7 day period of reperfusion. Long term reperfusion groups consisted of 2, 3, and 4 weeks of reperfusion after 5hr of unilateral CCA ligation. Morphological changes were analyzed by H-E staining and an immunohistochemical reaction with GFAP antibody. RESULTS: The ligation of the unilateral CCA, induced unilateral hemispheric infarction in 14 gerbils, selective neuronal necrosis (SNN) involving caudate in 1 gerbil, and delayed neuronal necrosis (DND) of the hippocampal CA1 neurons in 2 gerbils. Infarction was most frequent in 1 day reperfusion groups and did not show any differences according to the duration of ischemia. The GFAP reaction was strongly positive in the center of infarction at a 1 day period and negative at a 3 & 7 day period. The surrounding brain parenchyme progressively revealed increased positive reactions. Gerbils with SNN and DND showed moderately or markedly increased GFAP positive reactions in the unilateral caudate, thalamus, and hippocampus, whereas no apparent changes were shown by a H-E stain. CONCLUSIONS: Reactive astrogliosis is a stereotyped reaction of ischemic brain injury and is a more sensitive parameter than neuronal changes.

Behamioral Change and Memory Inpairment Following Transient Forebrain Ischemia in Rats / 대한마취과학회지

This study examined the behavioral change and memory impairment following transient forebrain ischemia in 20 male rats: ten rats were subjected to sham operation. Inchemia was induced by a combination of bilateral common carotid artery occlusion and induced hypotension. During the recovery period, behavioral change was evaluated by open-field method. Histopathological examination was performed 7 days after ischemic insult. The results were as follows 1) Hippocampus CA 1 neuron was the most vulnerable to 10-minute forebrain ischemia. 2) There was increase in locomotor activity and rearing during early post-ischemic period. 3) Ischemia resulted in suppressed preening and grooming. From the above mentioned results, authors suggested that transient forebrain ischemia produced severe neuronal damage in CA l sector of hippocampus, therefore produced behavioral change and memory impairment.