The Japanese Angelica acutiloba root and yokukansan increase hippocampal acetylcholine level, prevent apoptosis and improve memory in a rat model of repeated cerebral ischemia.

ETHNOPHARMACOLOGICAL RELEVANCE: Japanese Angelica acutiloba root (Angelica root) is included in several Kampo medicines including Yokukansan (YKS). Angelica root and YKS are used for the treatment of a variety of psychological and neurodegenerative disorders. Development of safe and effective therapeutic agents against cerebrovascular disorders will improve the treatment of patients with dementia. AIM OF THE STUDY: The effect of Angelica root and YKS on ischemia-impaired memory has not yet been fully investigated. The present study investigated whether Angelica root is also involved in memory improving and neuroprotective effect of YKS in a model of cerebrovascular ischemia. MATERIALS AND METHODS: Male Wistar rats grouped into sham rats received saline, and other three groups subjected to repeated cerebral ischemia induced by 4-vessel occlusion (4-VO), received a 7-day oral administration of either saline, Angelica root or YKS. Memory was evaluated by eight-arm radial maze task. Acetylcholine release (ACh) in the dorsal hippocampus was investigated by microdialysis-HPLC. Apoptosis was determined by terminal deoxynucleotidyl transferase (TdT)-mediated fluorescein-deoxyuridine triphosphate (dUTP) nick-end labeling. RESULTS: Ischemia induced apoptosis, reduced release of ACh, and impaired the memory (increased error choices and decreased correct choices). Angelica root and YKS improved the memory deficits, upregulated the release of ACh and prevented 4-VO-induced hippocampal apoptosis. CONCLUSION: The dual ACh-increasing and neuroprotective effect of Angelica root could make it a promising therapeutic agent useful for the treatment of symptoms of cerebrovascular dementia. Angelica root could be one of the components contributing to the memory-improving and neuroprotective effects of YKS.

Behavioral defects in a DCTN1G71A transgenic mouse model of Perry syndrome.

Perry syndrome is a rare neurodegenerative disease characterized by parkinsonism, depression/apathy, weight loss, and central hypoventilation. Our previously-conducted genome-wide association scan and subsequent studies identified nine mutations in DCTN1, the largest protein subunit of the dynactin complex, in patients with Perry syndrome. These included G71A in the microtubule-binding cytoskeleton-associated protein Gly-rich domain of p150Glued. The dynactin complex is essential for function of the microtubule-based cytoplasmic retrograde motor dynein. To test the hypothesis that the G71A mutation in the DCTN1 gene is sufficient to cause Perry syndrome, we generated DCTN1G71A transgenic mice. These mice initially developed normally, but young animals showed decreased exploratory activity and aged animals showed impaired motor coordination. These behavioral defects parallel apathy-like symptoms and parkinsonism encountered in Perry syndrome. TDP-43 aggregates were not detected in the substantia nigra and cerebral cortex of the transgenic mice, although pathological aggregates of TDP-43 have been considered a major neuropathological feature of Perry syndrome. Our study reveals that a single mutation in the DCTN1 gene recapitulates symptoms of Perry syndrome patients, and provides evidence that DCTN1G71A transgenic mice represent a novel rodent model of Perry syndrome.

Overexpression of Swedish mutant APP in aged astrocytes attenuates excitatory synaptic transmission.

Amyloid precursor protein (APP), a type I transmembrane protein, has different aspects, namely, performs essential physiological functions and produces ß-amyloid peptide (Aß). Overexpression of neuronal APP is responsible for synaptic dysfunction. In the central nervous system, astrocytes - a major glial cell type - have an important role in the regulation of synaptic transmission. Although APP is expressed in astrocytes, it remains unclear whether astrocytic overexpression of mutant APP affects synaptic transmission. In this study, the effect of astrocytic overexpression of a mutant APP on the excitatory synaptic transmission was investigated using coculture system of the transgenic (Tg) cortical astrocytes that express the human APP695 polypeptide with the double mutation K670N + M671L found in a large Swedish family with early onset Alzheimer's disease, and wild-type hippocampal neuron. Significant secretion of Aß 1-40 and 1-42 was observed in cultured cortical astrocytes from the Tg2576 transgenic mouse that genetically overexpresses Swedish mutant APP. Under the condition, Tg astrocytes did not affect excitatory synaptic transmission of cocultured wild-type neurons. However, aged Tg astrocytes cultured for 9 weeks elicited a significant decrease in excitatory synaptic transmission in cocultured neurons. Moreover, a reduction in the number of readily releasable synaptic vesicles accompanied a decrease in the number of excitatory synapses in neurons cocultured with aged Tg astrocytes. These observations indicate that astrocytic expression of the mutant APP is involved in the downregulation of synaptic transmission with age.

Rheb activation disrupts spine synapse formation through accumulation of syntenin in tuberous sclerosis complex.

Rheb is a small GTP-binding protein and its GTPase activity is activated by the complex of Tsc1 and Tsc2 whose mutations cause tuberous sclerosis complex (TSC). We previously reported that cultured TSC neurons showed impaired spine synapse morphogenesis in an mTORC1-independent manner. Here we show that the PDZ protein syntenin preferentially binds to the GDP-bound form of Rheb. The levels of syntenin are significantly higher in TSC neurons than in wild-type neurons because the Rheb-GDP-syntenin complex is prone to proteasomal degradation. Accumulated syntenin in TSC neurons disrupts spine synapse formation through inhibition of the association between syndecan-2 and calcium/calmodulin-dependent serine protein kinase. Instead, syntenin enhances excitatory shaft synapse formation on dendrites by interacting with ephrinB3. Downregulation of syntenin in TSC neurons restores both spine and shaft synapse densities. These findings suggest that Rheb-syntenin signalling may be a novel therapeutic target for abnormalities in spine and shaft synapses in TSC neurons.

Activation of Rheb, but not of mTORC1, impairs spine synapse morphogenesis in tuberous sclerosis complex.

Mutations in the Tsc1 or Tsc2 genes cause tuberous sclerosis complex (TSC). Tsc1 and Tsc2 proteins form a complex that inhibits mammalian target of rapamycin complex 1 (mTORC1) signalling through Rheb-GTPase. We found that Tsc2(+/-) neurons showed impaired spine synapse formation, which was resistant to an mTORC1 inhibitor. Knockdown of mTOR also failed to restore these abnormalities, suggesting mTORC may not participate in impaired spinogenesis in Tsc2(+/-) neurons. To address whether Rheb activation impairs spine synapse formation, we expressed active and inactive forms of Rheb in WT and Tsc2(+/-) neurons, respectively. Expression of active Rheb abolished dendritic spine formation in WT neurons, whereas inactive Rheb restored spine synapse formation in Tsc2(+/-) neurons. Moreover, inactivation of Rheb with farnesyl transferase inhibitors recovered spine synapse morphogenesis in Tsc2(+/-) neurons. In conclusion, dendritic spine abnormalities in TSC neurons may be caused through activation of Rheb, but not through of mTORC1.

Facilitation of memory impairment and cholinergic disturbance in a mouse model of Alzheimer's disease by mild ischemic burden.

Epidemiological studies suggest that cerebral ischemia may contribute to the onset and progression of Alzheimer's disease (AD). However, the mechanism by which ischemic events trigger the onset and progression of AD is poorly understood. Acetylcholine (ACh) is one of the key factors in memory, and cholinergic disturbance is a primary feature of AD. To clarify whether cholinergic disturbance is implicated in the exacerbation of AD symptoms by cerebral ischemia, memory impairment and hippocampal ACh release were examined in young (4-6 month-old) Tg2576 (Tg) mice, an AD transgenic mouse model, and in age-matched control mice with or without transient cerebral ischemia (bilateral common carotid artery occlusion: 2VO). 2VO induced memory impairment and decreased high-K(+)-evoked ACh release in Tg mice, but not in control mice. There were no differences in memory and ACh release between sham-operated control and Tg mice. Increases in ß-amyloid (Aß) 40 and Aß42 were also observed in 2VO-operated Tg mice compared with sham-operated Tg mice, but no evident amyloid plaques or neuronal loss were found in the hippocampus of these mice. These results suggest that the memory of Tg mice is affected by 2VO, and the memory impairment may be due to cholinergic dysfunction induced by Aß. Our findings support the idea that cerebral hypoperfusion could be a risk factor for AD.

Cholinergic involvement and synaptic dynamin 1 expression in Yokukansan-mediated improvement of spatial memory in a rat model of early Alzheimer's disease.

The aim of this study was to investigate the effect of Yokukansan (YKS) on the impairment of spatial memory and cholinergic involvement in a rat model of early-phase Alzheimer's disease (AD). In this model, rats underwent four-vessel transient cerebral ischemia and then were treated with beta amyloid oligomers injected intracerebroventricularly once daily for 7 days. These animals showed memory impairment in an eight-arm radial maze task without histological evidence of apoptosis but with a decrease in expression of hippocampal dynamin 1, an important factor in synaptic vesicle endocytosis. Oral administration of YKS for 2 weeks significantly increased the number of correct choices and decreased the number of error choices in the eight-arm radial maze task (P < 0.05). Moreover, YKS significantly increased high K⁺-evoked potentiation of acetylcholine (ACh) release (P < 0.05) and significantly increased the expression of dynamin 1 (P < 0.01) in the hippocampus. The ameliorative effect of YKS on spatial memory impairment in our rat model of early-phase AD may be mediated in part by an increase in ACh release and modulation of dynamin 1 expression, leading to improved synaptic function. Future studies will determine whether YKS is similarly useful in the treatment of memory defects in patients diagnosed with early-stage AD.

Ameliorative effects of telmisartan on the inflammatory response and impaired spatial memory in a rat model of Alzheimer's disease incorporating additional cerebrovascular disease factors.

Telmisartan, an angiotensin type 1 receptor blocker, is used in the management of hypertension to control blood pressure. In addition, telmisartan has a partial agonistic effect on peroxisome proliferator activated receptor γ (PPARγ). Recently, the effects of telmisartan on spatial memory or the inflammatory response were monitored in a mouse model of Alzheimer's disease (AD). However, to date, no studies have investigated the ameliorative effects of telmisartan on impaired spatial memory and the inflammatory response in an AD animal model incorporating additional cerebrovascular disease factors. In this study, we examined the effect of telmisartan on spatial memory impairment and the inflammatory response in a rat model of AD incorporating additional cerebrovascular disease factors. Rats were subjected to cerebral ischemia and an intracerebroventricular injection of oligomeric or aggregated amyloid-ß (Aß). Oral administration of telmisartan (0.3, 1, 3 mg/kg/d) seven days after ischemia and Aß treatment resulted in better performance in the eight arm radial maze task in a dose-dependent manner. Telmisartan also reduced tumor necrosis factor α mRNA expression in the hippocampal region of rats with impaired spatial memory. These effects of telmisartan were antagonized by GW9662, an antagonist of PPARγ. These results suggest that telmisartan has ameliorative effects on the impairment of spatial memory in a rat model of AD incorporating additional cerebrovascular disease factors via its anti-inflammatory effect.

Long-term culture of astrocytes attenuates the readily releasable pool of synaptic vesicles.

The astrocyte is a major glial cell type of the brain, and plays key roles in the formation, maturation, stabilization and elimination of synapses. Thus, changes in astrocyte condition and age can influence information processing at synapses. However, whether and how aging astrocytes affect synaptic function and maturation have not yet been thoroughly investigated. Here, we show the effects of prolonged culture on the ability of astrocytes to induce synapse formation and to modify synaptic transmission, using cultured autaptic neurons. By 9 weeks in culture, astrocytes derived from the mouse cerebral cortex demonstrated increases in ß-galactosidase activity and glial fibrillary acidic protein (GFAP) expression, both of which are characteristic of aging and glial activation in vitro. Autaptic hippocampal neurons plated on these aging astrocytes showed a smaller amount of evoked release of the excitatory neurotransmitter glutamate, and a lower frequency of miniature release of glutamate, both of which were attributable to a reduction in the pool of readily releasable synaptic vesicles. Other features of synaptogenesis and synaptic transmission were retained, for example the ability to induce structural synapses, the presynaptic release probability, the fraction of functional presynaptic nerve terminals, and the ability to recruit functional AMPA and NMDA glutamate receptors to synapses. Thus the presence of aging astrocytes affects the efficiency of synaptic transmission. Given that the pool of readily releasable vesicles is also small at immature synapses, our results are consistent with astrocytic aging leading to retarded synapse maturation.

Yokukansan enhances pentobarbital-induced sleep in socially isolated mice: possible involvement of GABA(A)-benzodiazepine receptor complex.

In the present study, we investigated the effect of the Kampo medicine Yokukansan (YKS) on pentobarbital-induced sleep in group-housed and socially isolated mice. Socially isolated mice showed shorter sleeping time than the group-housed mice. YKS (300 mg/kg, p.o.) prolonged the pentobarbital-induced sleeping time in socially isolated mice without affecting pentobarbital sleep in group-housed mice. The prolongation of sleeping time by YKS was reversed by bicuculline (3 mg/kg, i.p.) and flumazenil (3 mg/kg, i.p.), but not WAY100635. These findings suggest that the GABA(A)-benzodiazepine receptor complex, but not 5-HT(1A) receptors, is involved in the reversal effect of YKS on the decrease of pentobarbital sleep by social isolation.

Yokukansan Enhances Pentobarbital-Induced Sleep in Socially Isolated Mice: Possible Involvement of GABA(A) - Benzodiazepine Receptor Complex.

In the present study, we investigated the effect of the Kampo medicine Yokukansan (YKS) on pentobarbital-induced sleep in group-housed and socially isolated mice. Socially isolated mice showed shorter sleeping time than the group-housed mice. YKS (300 mg/kg, p.o.) prolonged the pentobarbital-induced sleeping time in socially isolated mice without affecting pentobarbital sleep in group-housed mice. The prolongation of sleeping time by YKS was reversed by bicuculline (3 mg/kg, i.p.) and flumazenil (3 mg/kg, i.p.), but not WAY100635. These findings suggest that the GABA(A) - benzodiazepine receptor complex, but not 5-HT(1A) receptors, is involved in the reversal effect of YKS on the decrease of pentobarbital sleep by social isolation.

Neuroprotective effects of citidine-5-diphosphocholine on impaired spatial memory in a rat model of cerebrovascular dementia.

Citidine-5-diphosphocholine or citicoline (CDP-choline) is used as a neuroprotective and memory-enhancing drug in cerebral stroke, Alzheimer's disease, and other neurovascular diseases. Non-clinical studies have demonstrated the neuroprotective effects of CDP-choline in ischemic animal models. However, the relationship between the neuroprotective effect and the memory enhancing effect of CDP-choline is still unknown. No studies have demonstrated the ameliorative effect on impaired spatial memory and the suppressive effect on neuronal cell death of CDP-choline in the same model. In this study, we examined the effect of CDP-choline on impaired spatial memory and hippocampal CA1 neuronal death in rats subjected to repeated cerebral ischemia, and we compared the mechanism of CDP-choline to that of donepezil. Seven days post administration of CDP-choline (100, 300, 1000 mg/kg per day, p.o.) or donepezil increased correct choices and reduced error choices in an eight-arm radial maze task in a dose-dependent manner. Neuronal cell death of caspase-3 protein-positive neurons in the hippocampus were reduced by repeated administration of CDP-choline at the highest dose. These results suggest that CDP-choline has ameliorative effects on the impairment of spatial memory via hippocampal neuronal cell death in a rat model of cerebral ischemia.

Effects of yokukansan on anxiety-like behavior in a rat model of cerebrovascular dementia.

Behavioral and psychological symptoms of dementia (BPSD) are commonly seen in patients with dementia. Current pharmacological approaches to treatment are inadequate, despite the availability of serotonergic agents to ameliorate anxiety, one of the symptoms of BPSD. The herbal medicine yokukansan has been demonstrated to improve BPSD in a randomized, single-blinded, placebo-controlled study. However, the mechanisms of the anxiolytic effect of yokukansan have not been clarified. There are also no reports on the anxiolytic effect of yokukansan in cerebrovascular ischemia models. In this study, we examined whether rats subjected to repeated cerebral ischemia exhibited anxiety-like behavior in a plus-maze task, a light/dark box test and an open-field task. We then investigated the effect of yokukansan on anxiety-like behavior in ischemic rats. Repeated ischemia was induced by the four-vessel occlusion method in which a 10-min ischemic episode was repeated once after 60 min. Yokukansan was orally administered once a day for 14 days from 7 days before ischemia induction. The last administration was performed 1 h before the behavioral experiments. The ischemic rats showed anxiety-like behavior in all three tasks, suggesting that this rat may be a good model for anxiety in cerebrovascular dementia. Yokukansan exhibited anxiolytic effects on the anxiety-like behavior in rats subjected to repeated cerebral ischemia, and exerted antagonistic effects on the wet-dog shakes induced by 1-(2,5-dimethoxy-4-indophenyl)-2-amino propane, a serotonin receptor (5-HT(2A)) agonist. This study revealed that yokukansan shows anxiolytic effects not only in normal animals but also in cerebrovascular model rats.

Telmisartan, a partial agonist of peroxisome proliferator-activated receptor gamma, improves impairment of spatial memory and hippocampal apoptosis in rats treated with repeated cerebral ischemia.

Telmisartan, an angiotensin type 1 receptor blocker (ARB), is used for hypertension to control blood pressure and has been shown to have a partial agonistic effect on peroxisome proliferator-activated receptor gamma (PPARgamma). Recently, the ligand of PPARgamma has been implicated in cerebroprotection due to its anti-inflammatory effect. In this study, we investigated whether telmisartan has a cerebroprotective effect on memory impairment and neuronal cell death induced by repeated cerebral ischemia. Repeated cerebral ischemia (RI: 10 min x 2) significantly induced impairment of spatial memory and hippocampal apoptosis in rats. Fourteen-day pre- and post-ischemic administration of telmisartan (0.3, 1, 3mg/kg/day, p.o.) increased the number of correct choices and reduced the number of errors made in the eight-arm radial maze task in a dose-dependent manner in RI treated rats. TUNEL-positive cells in the hippocampus CA1 areas were also reduced following 14-day administration of telmisartan (3mg/kg/day, p.o.). Seven-day post-ischemic administration of telmisartan improved spatial memory and reduced TUNEL-positive cells while 7-day pre-ischemic administration of telmisartan did not. These effects of telmisartan were inhibited by the PPARgamma antagonist, GW9662. On further experiment, 7-day post-ischemic administration of telmisartan reduced the expression of caspase-3 in the hippocampus, and this effect was also inhibited by GW9662. These results suggest that telmisartan improves memory impairment and reduces neuronal apoptosis via a PPARgamma-dependent caspase-3 inhibiting mechanism. Telmisartan, which has the unique character of having both ARB and PPARgamma agonistic effect, will be useful for preventing memory impairment after cerebrovascular disease.

Dynamin 1 depletion and memory deficits in rats treated with Abeta and cerebral ischemia.

Alzheimer's disease (AD) is progressive dementia with senile plaques composed of beta-amyloid (Abeta). Recent studies suggest that synaptic dysfunction is one of the earliest events in the pathogenesis of AD. Here we provide the first experimental evidence that a change in the level of dynamin 1 induced by Abeta correlates with memory impairment in vivo. We treated rats with transient cerebral ischemia with oligomeric forms of Abeta (Abeta oligomers), including dimers, trimers, and tetramers, intracerebroventricularly. The combination of Abeta oligomers and cerebral ischemia, but not cerebral ischemia alone, significantly impaired memory and decreased the level of dynamin 1, which plays a critical role in synaptic vesicle recycling, but did not affect the levels of other synaptic proteins, such as synaptophysin and synaptobrevin, in the hippocampus. Furthermore, the N-methyl-D-aspartate (NMDA) receptor antagonist memantine prevented memory impairment and dynamin 1 degradation, suggesting that these changes might be mediated by NMDA receptors. These results suggest that Abeta oligomers induce memory impairment via dynamin 1 degradation, which may imply that dynamin 1 degradation is one of the causes of synaptic dysfunction in AD.

Cerebroprotective action of telmisartan by inhibition of macrophages/microglia expressing HMGB1 via a peroxisome proliferator-activated receptor gamma-dependent mechanism.

Telmisartan is known to block angiotensin (Ang) II type-1 receptors (AT(1)R), and also activate peroxisome proliferator-activated receptor gamma (PPARgamma) signaling. Recently, PPARgamma has been implicated as a regulator of cellular proliferation and inflammatory responses. In the present study, we investigated the anti-inflammatory effects of telmisartan on middle cerebral artery (MCA) occlusion in mice. Telmisartan was administered orally to mice at 2h before and 2h after MCA occlusion. Infarct size was determined at 24h after MCA occlusion. In addition, cerebral blood flow (CBF) was measured during MCA occlusion. The effect of telmisartan on inflammatory markers, including Iba1 (macrophage/microglia marker) immunoreactivity and plasma high-mobility group box1 (HMGB1), was also investigated at 24h after MCA. Telmisartan significantly decreased the infarct area in dose-dependent manner without affecting CBF. Furthermore, the cerebroprotective effect of telmisartan was inhibited by GW9662, PPARgamma antagonist. Telmisartan significantly decreased the number of Iba1-positive cells expressing HMGB1 and decreased plasma HMGB1 levels. These effects were partially inhibited by GW9662. These data suggest that telmisartan may be a potential treatment for post-ischemic injury by partially inhibiting the inflammatory reaction after cerebral ischemia via a PPARgamma-dependent HMGB1 inhibiting mechanism.

Mice lacking ganglioside GM3 synthase exhibit complete hearing loss due to selective degeneration of the organ of Corti.

The ganglioside GM3 synthase (SAT-I), encoded by a single-copy gene, is a primary glycosyltransferase for the synthesis of complex gangliosides. In SAT-I null mice, hearing ability, assessed by brainstem auditory-evoked potentials (BAEP), was impaired at the onset of hearing and had been completely lost by 17 days after birth (P17), showing a deformity in hair cells in the organ of Corti. By 2 months of age, the organ of Corti had selectively and completely disappeared without effect on balance or motor function or in the histology of vestibule. Interestingly, spatiotemporal changes in localization of individual gangliosides, including GM3 and GT1b, were observed during the postnatal development and maturation of the normal inner ear. GM3 expressed in almost all regions of cochlea at P3, but at the onset of hearing it distinctly localized in stria vascularis, spiral ganglion, and the organ of Corti. In addition, SAT-I null mice maintain the function of stria vascularis, because normal potassium concentration and endocochlear potential of endolymph were observed even when they lost the BAEP completely. Thus, the defect of hearing ability of SAT-I null mice could be attributed to the functional disorganization of the organ of Corti, and the expression of gangliosides, especially GM3, during the early part of the functional maturation of the cochlea could be essential for the acquisition and maintenance of hearing function.