Tongxinluo improves cognition by decreasing ß-amyloid in spontaneous hypertensive rats.

ß-Amyloid (Aß) accumulation in the brain is the major pathophysiology of Alzheimer disease (AD). Hypertension is a risk factor for AD by promoting Aß deposition. Traditional Chinese medicinal compound tongxinluo (TXL) can improve blood circulation and endothelium-dependent vasodilation. This study investigates the effects of TXL on cognition and Aß using spontaneously hypertensive rats (SHRs). TXL was intragastrically administered to SHRs at low-dose, mid-dose and high-dose for 15, 30 or 60days. Cognition was evaluated with a Morris Water Maze (MWM). Aß in the brain was detected by western blot, ELISA and Thioflavin-S staining. Western blot and RT-PCR were employed to exam the expression of receptor for advanced glycation end products (RAGE), low-density lipoprotein receptor-related protein-1 (LRP-1) and amyloid precursor protein (APP). After TXL treatment for 60days, compared with the vehicle, the number of crossed platform and the time spent in the target quadrant increased in parallel with the increasing length of treatment in MWM. Moreover, the Aß in the hippocampus significantly decreased compared to the vehicle group, both in western blot and ELISA. Additionally, TXL reduced RAGE expression in a dose- and time-depended manner, but LRP-1 expression had no difference between TXL groups and vehicle groups. Furthermore, the ß-secretase expression was significantly decreased compared to the vehicle group, but APP expression had no difference. In conclusion, TXL improved cognition and decreased Aß in SHRs in a dose- and time-dependent manner, the underlying mechanism may involved in inhibiting RAGE and ß-secretase expression.

Ginsenoside-Rd Promotes Neurite Outgrowth of PC12 Cells through MAPK/ERK- and PI3K/AKT-Dependent Pathways.

Panax ginseng is a famous herbal medicine widely used in Asia. Ginsenosides have been identified as the principle active ingredients for Panax ginseng's biological activity, among which ginsenoside Rd (Rd) attracts extensive attention for its obvious neuroprotective activities. Here we investigated the effect of Rd on neurite outgrowth, a crucial process associated with neuronal repair. PC12 cells, which respond to nerve growth factor (NGF) and serve as a model for neuronal cells, were treated with different concentrations of Rd, and then their neurite outgrowth was evaluated. Our results showed that 10 µM Rd significantly increased the percentages of long neurite- and branching neurite-bearing cells, compared with respective controls. The length of the longest neurites and the total length of neurites in Rd-treated PC12 cells were much longer than that of respective controls. We also showed that Rd activated ERK1/2 and AKT but not PKC signalings, and inhibition of ERK1/2 by PD98059 or/and AKT by LY294002 effectively attenuated Rd-induced neurite outgrowth. Moreover, Rd upregulated the expression of GAP-43, a neuron-specific protein involved in neurite outgrowth, while PD98059 or/and LY294002 decreased Rd-induced increased GAP-43 expression. Taken together, our results provided the first evidence that Rd may promote the neurite outgrowth of PC12 cells by upregulating GAP-43 expression via ERK- and ARK-dependent signaling pathways.

The protective effects of tanshinone IIA on neurotoxicity induced by ß-amyloid protein through calpain and the p35/Cdk5 pathway in primary cortical neurons.

The characteristic pathological change of Alzheimer's disease (AD) include deposits of ß-amyloid protein (Aß) in brain, neurofibrillary tangles (NFTs), as well as a few neuronal loss. Evidence shows that Aß causes calcium influx and induces the cleavage of p35 into p25. Furthermore, the binding of p25 to cyclin-dependent kinase 5 (Cdk5) constitutively activates Cdk5. The p25/Cdk5 complex then hyperphosphorylates tau. Tanshinone IIA (tanIIA), a natural product extracted from Chinese herbal medicine Salvia miltiorrhiza BUNGE, has been reported to exert antioxidative activity. However, its neuroprotective activity remains unclear. The present study determined whether tanIIA protects neurons against Aß(25-35)-induced cytotoxicity and detected the association of this protective effect with calpain and the p35/Cdk5 pathway. The results showed that tanIIA protected neurons against the neurotoxicity of Aß(25-35), increased the viability of neurons, decreased expression of phosphorylated tau in neurons induced by Aß(25-35), improved the impairment of the cell ultrastructure (such as nuclear condensation and fragmentation, and neurofibril collapse). Further more, we found that tanIIA maintained the normal expression of p35 on peripheral membranes, and decreased p25 expression in the cytoplasm. TanIIA also inhibited the translocation of Cdk5 from the nucleus into the cytoplasm of primary neurons induced by Aß(25-35). These data suggested that tanIIA possessed neuroprotective action and the protection may involve in calpain and the p35/Cdk5 pathway.

Breviscapine improves functions of spatial learning and memory of focal cerebral ischemia rats.

OBJECTIVE: To investigate the effects of breviscapine on the functions of spatial learning and memory of focal cerebral ischemia rats. METHODS: Rots withl the left middle cerebral artery occluded were made by an intraluminal filament. Then breviscapine (20 mg/kg,40 mg/kg) in experimental group and 10% glucose in control group were administered intraperitoneally once a day for 2 weeks, and the Morris water maze tasks were carried out for 5 days. RESULTS: Compared with sham-operation group,the animals of ischemia-control group exhibited seriously impaired spatial learning and memory in both place navigation test and spatial probe test. In the place navigation test, the mean value of escape latency in breviscapine group was significantly shorter than that in ischemia control group (P < 0.01 for lower-dose and P < 0.05 for higher-dose breviscapine group, respectively). In the spatial probe test,compared with sham-operation (P < 0.01) and breviscapine group (P < 0.01), the rats of ischemia-control group spent more time in the no-former platform quadrant, and showed reduced frequency of crossing former platform site significantly. The numbers of neurons with Nissl staining and choline acetyltransferase (ChAT) immunopositive neurons in ipssilateral cortex in the breviscapine group were significantly more than those in the ischemia-control group (P < 0.01). In hippocampus, the numbers of neurons with Nissl staining and ChAT immunopositive neurons in the stratum pyramidale of CA area were similar among the groups. CONCLUSION: These results indicate that breviscapine can improve the functions of spatial learning and memory of focal cerebral ischemia rats and the protection against the loss of ChAT immunopositive neuron in new cortex may be involved in its mechanisms.

[Effect of ligustrazine on migration of neuronal precursors after focal cerebral ischemia in adult rats].

OBJECTIVE: To study the effect of ligustrazine on the migration of neuronal precursors (NPs) after focal cerebral ischemia in adult rats and explore its acting mechanism on recovery of function. METHODS: Rat model of left middle cerebral artery occlusion (MCAO) was established by thread ligation. Ligustrazine 40 mg/kg was injected peritoneally once a day 2 h after modeling. On the 3rd, 7th, 14th and 21st day after operation, the migration of Doublecortin (DCX, the marker of NPs) in subventricular zone (SVZ) and the rostral migratory stream (RMS) were observed with immunohistochemistry. RESULTS: The migration of DCX-positive cells in SVZ (abbrev. as migration below) through RMS into the olfactory bulb started from the 3rd day after ischemia, and lasted to the 21st day; the migration directly or through RMS into the ischemic penumbra of the adjacent striatum started on the 7th day, and increased significantly on the 14th day; and a few of DCX positive cells migrated through corpus callosum into the ischemic cortex on the 21st day. The migration was similar in the two groups in its pathway, but the extent in the ligustrazine group was more intensive. CONCLUSION: Ligustrazine could promote direct migration of NPs into the ischemic cerebral cortex and striatum, suggesting that it might play an important role in promoting self-recovery of brain function after ischemia through accelerating the migration of NPs.

[Effect of ligustrazine on cell proliferation in subventricular zone of lateral cerebral ventricle after adult rat suffering from focal cerebral ischemia].

OBJECTIVE: To explore the effect of ligustrazine on cell proliferation in subventricular zone of lateral cerebral ventricle after middle cerebral artery occluded (MACO) in adult rat. METHODS: SD male rats were randomly divided into three group: sham operation group, ischemic model group and Ligustrazine group. The model of the middle cerebral artery occlusion was established by placement of an intraluminal filament at the origin of left MCA. Ligustrazine was administered intraperitoneally with a dose of 80 mg/kg daily starting at 2 hours after MCAO. BrdU (50 mg/kg) was injected once a day intraperitoneally starting at 4 hours after operation. Number of BrdU-positive cells and expression of doublecortin (DCX) in subventricular zone (SVZ) were measured by immunohistochemistry on day 7, 14, 24 after operation. RESULTS: Compared with sham operation group, BrdU-positive cells in ischemic model group increased on day 7, reached the peak on day 14, then decreased on day 21 after operation. On day 7 and 14, the numbers of BrdU-positive cells in Ligustrazine group were markedly augmented and significantly more than those in ischemic model group (P < 0.01), but decreased on day 21. The expressions of DCX in SVZ in ischemic model group were enhanced on day 7 with lasting into day 14, and reduced on day 21, but still higher than those in sham operation group on day 7, 14, and 21, respectively. The expressions of DCX in SVZ in Ligustrazine group increased gradually along with prolong of ischemia and kept the high level up to day 21 after operation, and were higher than those in ischemic model group on day 14 and 21. CONCLUSION: Our results suggest that Ligustrazine may promote the cells of SVZ, which the adult rats suffer from the focal cerebral ischemia, to go into cell proliferation.

Neuroprotective effects of ebselen are associated with the regulation of Bcl-2 and Bax proteins in cultured mouse cortical neurons.

There is little information available on the mechanisms underlying the neuroprotective actions of the organoselenium compound ebselen. In this study, we sought to determine the relationship between alterations in the expression of Bcl-2 and Bax proteins and intracellular levels of calcium and the protective effects of ebselen with a concentration range of 0.01-20 microM against glutamate toxicity in cultured mouse cortical neurons. Pretreatment with ebselen at moderate doses (4-12 microM), but not at lower or higher doses, significantly improved glutamate-induced suppression of cell viability. Pretreatment with ebselen (8 microM) also prevented apoptotic alterations, completely reversed the suppression of Bcl-2 expression, and significantly inhibited Bax overexpression, but did not alter elevated intracellular concentrations of calcium induced by glutamate. Pre-, co-, and post-treatment with ebselen (8 microM) had similar potency in improving the decreased viability of glutamate-exposed cells. These results indicate that the neuroprotective effects of ebselen at low doses are associated with the regulation of Bcl-2 and Bax proteins but appear to be independent of glutamate-mediated elevation of intracellular calcium, suggesting that different mechanisms are involved in the actions of low and high dose regimens. Ebselen may be an effective agent used for early treatment of acute brain injuries.

The herbal medicine Dipsacus asper wall extract reduces the cognitive deficits and overexpression of beta-amyloid protein induced by aluminum exposure.

Excess aluminum (Al) exposure impairs neurocognitive function in humans and animals. Epidemiologic studies have shown a potential link between chronic Al exposure and Alzheimer's disease. In the present study, we sought to evaluate the protective effects of the herbal medicine Dipsacus asper extract against the cognitive impairment and overexpression of hippocampal beta-amyloid protein (Abeta) induced by chronic Al exposure in rats. Vitamin E (VE) was used as a positive control. Following exposure to 0.3% aluminum chloride (AlCl(3)) solution for 90 days in their drinking water, animals displayed a striking decrease (>80%) in step-through latency in the passive avoidance task and a significant increase (123%) in the number of Abeta immunoreactive cells in the hippocampus compared to controls. Al-exposed animals were then randomly assigned to receive vehicle, Dipsacus asper extract (4 g/kg), or VE (40 mg/kg) treatment up to 5 months. Both Dipsacus asper extract and VE significantly ameliorated animal's performance impairment in the passive avoidance task and suppressed the overexpression of hippocampal Abeta immunoreactivity. The effects of Dipsacus asper extract, but not VE, increased with time of treatment. The present results suggest that Dipsacus asper extract may possess therapeutic effects against Alzheimer's disease.

The effects of the total saponin of Dipsacus asperoides on the damage of cultured neurons induced by beta-amyloid protein 25-35.

According to the pathogenesis of Alzheimer's disease (AD), beta-amyloid protein (A beta) was directly toxic to neurons, leading to neurodegeneration. Total saponin of Dipsacus asperoides (tSDA) is one of the main ingredients of Dipsacus asperoide, a traditional Chinese medicine. To explore the effects of tSDA on neuronal damage induced by A beta in vitro, biochemical analysis combining primary cultured neurons were adopted. Neurons were treated with 35 mmol/L A beta for 24 h, and tSDA at concentrations of 1-300 mg/L were added to A beta-treated cultures 24 h in advance, A beta for 24 h, the survival rate of neurons decreased closely by 50%. Lactate dehydrogenase release and the Malondialdehyde (MDA) level increased substantially. However, if neurons were pretreated with tSDA, the survival rate of neurons was higher than A beta-treated alone. Lactate dehydrogenase release and the MDA level decreased distinctly. Results demonstrated that tSDA possessed a neuroprotective action and that tSDA protected neurons against the toxicity of A beta, most likely by relieving oxidative stress or inhibiting the process of A beta, inducing free radical generation.