Low molecular weight chondroitin sulfate ameliorates pathological changes in 5XFAD mice by improving various functions in the brain.

Our previous study found that low molecular weight chondroitin sulfate (LMWCS) had neuroprotective effects against the toxicity of amyloid-ß (Aß) peptides both in vitro and in vivo, and we speculated that the effects might be related with its anti-oxidative activities. In this study, the anti-Alzheimer's disease (AD) activity of LMWCS was further studied in 5XFAD transgenic mice. After 4-month gavage, the levels of Aß1-42 level, amyloid precursor protein (APP) and presenilin 1 (PS1) were significantly decreased in the brains of 5XFAD mice, indicating the alteration of APP metabolism by LMWCS. Besides, LMWCS inhibited the secretions of pro-inflammatory cytokines, including interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and IL-6. Furthermore, the suppression of neuroinflammation by LMWCS was supported by the decreased expressions of glial fibrillary acidic protein (GFAP) and toll-like receptor 2 (TLR2) in the brains. LMWCS also reduced the production of reactive oxygen species (ROS) and the level of phospho-tau (Ser404) in the brains. Nevertheless, the changes in the behavior tests were moderate. In conclusion, LMWCS administration ameliorated APP metabolism, neuroinflammation, ROS production and tau protein abnormality in the brains of 5XFAD mice, displaying the potential to improve the pathological changes of AD mouse brain. LMWCS could be considered as a promising anti-AD drug candidate, nonetheless, the therapy regimen need to be optimized to improve its pharmacotherapy efficacy.

Isoorientin, a GSK-3ß inhibitor, rescues synaptic dysfunction, spatial memory deficits and attenuates pathological progression in APP/PS1 model mice.

ß-Amyloid (Aß) elevation, tau hyperphosphorylation, and neuroinflammation are major hallmarks of Alzheimer's disease (AD). Glycogen synthase kinase-3ß (GSK-3ß) is a key protein kinase implicated in the pathogenesis of AD. Blockade of GSK-3ß is an attractive therapeutic strategy for AD. Isoorientin, a 6-C-glycosylflavone, was previously shown to be a highly selective inhibitor of GSK-3ß, while exerting neuroprotective effects in neuronal models of AD. In the present study, we evaluated the in vivo effects of isoorientin on GSK-3ß, tau phosphorylation, Aß deposition, neuroinflammatory response, long-term potentiation, and spatial memory in amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice using biochemical, electrophysiological, and behavioral tests. Chronic oral administration of isoorientin to APP/PS1 mice at 8 months of age attenuated multiple AD pathogenic hallmarks in the brains, including GSK-3ß overactivation, tau hyperphosphorylation, Aß deposition, and neuroinflammation. For neuroinflammation, isoorientin treatment reduced the number of activated microglia associated with Aß-positive plaques, and in parallel reduced the levels of pro-inflammatory factors in the brains of APP/PS1 mice. Strikingly, isoorientin reversed deficits in synaptic long-term potentiation and spatial memory relevant to cognitive functions. Together, the findings suggest that isoorientin is a brain neuroprotector and may be a promising drug lead for treatment of AD and related neurodegenerative disorders.

Total flavonoid extract from Dracoephalum moldavica L. attenuates ß-amyloid-induced toxicity through anti-amyloidogenesic and neurotrophic pathways.

AIMS: Alzheimer's disease (AD) is an incurable neurodegenerative disorder characterized by global cognitive impairment that involves accumulation of amyloid-beta peptides (Aß) in the brain. Herbal approaches can be used as alternative medicines to slow the progression of AD. This study aimed to determine the beneficial effects and potential underlying mechanisms of total flavonoid extract from Dracoephalum moldavica L. (TFDM) for attenuating Alzheimer-related deficits induced by Aß. MAIN METHODS: We used amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mice and copper-injured APP Swedish mutation overexpressing SH-SY5Y cells to evaluate the beneficial effects of TFDM. Further, identifying the mechanisms of action was conducted on anti-amyloidogenic and neurotrophic transductions. KEY FINDINGS: Our results indicated that TFDM treatment ameliorated cognitive impairments and neurodegeneration and improved the antioxidant defense system in APP/PS1 mice. TFDM also reduced Aß burden by relieving Aß deposition, decreasing insoluble Aß levels, and inhibiting ß-amyloidogenic processing pathway involving downregulation of ß-secretase and ß-C-terminal fragment in the brain. In the in vitro model of AD, TFDM treatment protected injured cells, and combined with the beneficial effects of decreasing APP levels, lowered Aß1-42 and regulated the redox imbalance. Moreover, TFDM preserved the extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway both in vitro and in vivo. SIGNIFICANCE: In conclusion, TFDM clearly demonstrated neuroprotective effects by restoring the anti-amyloidogenic and neurotrophic transductions in the context of AD-associated deficits. These findings indicate the potential use of herb-based substances as supplements or potential alternative supplements for attenuating the progression of AD.

Simvastatin increases notch signaling activity and promotes arteriogenesis after stroke.

BACKGROUND AND PURPOSE: Notch signaling activity regulates arteriogenesis. Presenilin 1 (PS1) mediates Notch signaling activity via cleavage of Notch, liberating Notch intracellular domain (NICD). We tested the hypothesis that simvastatin enhances arteriogenesis after stroke by increasing PS1 activation of the Notch signaling pathway. METHODS: Rats were subjected to middle cerebral artery occlusion (MCAo) and treated with or without simvastatin (1 mg/kg) starting 24 hours after stroke and daily for 7 days; they were euthanized 14 days after stroke. Immunostaining, Western blot, and real-time polymerase chain reaction assays were performed. RESULTS: Simvastatin significantly increased arterial diameter, density, and vascular smooth muscle cell proliferation, and upregulated PS1, Notch1, and NICD expression in the ischemic border tissue and in the cerebral arteries compared with MCAo control rats, respectively. However, simvastatin did not increase arteriogenesis, PS1, and NICD expression in sham control animals. To investigate the mechanisms of simvastatin-induced arteriogenesis, primary cerebral artery cultures were used. Rats were subjected to MCAo and treated with or without simvastatin daily for 7 days. The cerebral arteries derived from these stroke rats were cultured in matrigel and treated with or without a gamma40-secretase inhibitor II, which blocks Notch signaling activity, inhibiting NICD production. Arterial cell migration was measured. simvastatin treatment significantly increased arterial cell migration compared to control MCAo artery, whereas inhibition of Notch signaling activity by the gamma40-secretase inhibitor II significantly attenuated simvastatin-induced arterial cell migration. CONCLUSIONS: These data indicate that simvastatin increases arteriogenesis after stroke, and that simvastatin upregulation of PS1 expression and Notch signaling activity may facilitate an increase in arteriogenesis.

GABA(A) receptor-mediated acceleration of aging-associated memory decline in APP/PS1 mice and its pharmacological treatment by picrotoxin.

Advanced age and mutations in the genes encoding amyloid precursor protein (APP) and presenilin (PS1) are two serious risk factors for Alzheimer's disease (AD). Finding common pathogenic changes originating from these risks may lead to a new therapeutic strategy. We observed a decline in memory performance and reduction in hippocampal long-term potentiation (LTP) in both mature adult (9-15 months) transgenic APP/PS1 mice and old (19-25 months) non-transgenic (nonTg) mice. By contrast, in the presence of bicuculline, a GABA(A) receptor antagonist, LTP in adult APP/PS1 mice and old nonTg mice was larger than that in adult nonTg mice. The increased LTP levels in bicuculline-treated slices suggested that GABA(A) receptor-mediated inhibition in adult APP/PS1 and old nonTg mice was upregulated. Assuming that enhanced inhibition of LTP mediates memory decline in APP/PS1 mice, we rescued memory deficits in adult APP/PS1 mice by treating them with another GABA(A) receptor antagonist, picrotoxin (PTX), at a non-epileptic dose for 10 days. Among the saline vehicle-treated groups, substantially higher levels of synaptic proteins such as GABA(A) receptor alpha1 subunit, PSD95, and NR2B were observed in APP/PS1 mice than in nonTg control mice. This difference was insignificant among PTX-treated groups, suggesting that memory decline in APP/PS1 mice may result from changes in synaptic protein levels through homeostatic mechanisms. Several independent studies reported previously in aged rodents both an increased level of GABA(A) receptor alpha1 subunit and improvement of cognitive functions by long term GABA(A) receptor antagonist treatment. Therefore, reduced LTP linked to enhanced GABA(A) receptor-mediated inhibition may be triggered by aging and may be accelerated by familial AD-linked gene products like Abeta and mutant PS1, leading to cognitive decline that is pharmacologically treatable at least at this stage of disease progression in mice.

Atorvastatin promotes presenilin-1 expression and Notch1 activity and increases neural progenitor cell proliferation after stroke.

BACKGROUND AND PURPOSE: Presenilin1 (PS1) regulates Notch1 signaling activity, which liberates Notch intracellular domain (NICD). Notch activation promotes neural progenitor cell (NPC) self-renewal in the developing brain. In this study, we tested whether atorvastatin-induced NPC proliferation after stroke is mediated by PS1 and Notch1 activation. METHODS: PS1 and NICD expressions were measured in retired breeder rats subjected to middle cerebral artery occlusion that were left untreated or treated with atorvastatin. To investigate the mechanisms of atorvastatin-induced NPC self-renewal, subventricular zone (SVZ) neurosphere culture and knockdown of Notch1 gene expression by short interfering RNA were used. SVZ neurosphere formation, cell proliferation, real-time polymerase chain reaction, and Western blotting were performed. RESULTS: Atorvastatin significantly increased the numbers of newly generated neuroblasts and promoted PS1 and NICD expression in the ipsilateral and homologous contralateral SVZ compared with saline-treated control rats. Increased SVZ neurosphere formation and cell proliferation were found in cultured neurospheres derived from normal rat and poststroke rat SVZs treated in vitro with atorvastatin compared with untreated neurospheres (P<0.05). Atorvastatin significantly increased PS1 and hairy and enhancer of split1 (Hes1) gene expression in cultured SVZ neurospheres. Inhibition of PS1 significantly decreased NICD expression. Short interfering RNA knockdown of Notch1 expression, decreased NPC proliferation, and NICD and hairy and enhancer of split1 expression in cultured neurosphere cells. CONCLUSIONS: These data indicate that atorvastatin increases the NPC pool in older rats and that it also upregulates PS1 expression and Notch1 signaling activity, which in turn, facilitate an increase in SVZ NPC proliferation.

Caffeine protects Alzheimer's mice against cognitive impairment and reduces brain beta-amyloid production.

A recent epidemiological study suggested that higher caffeine intake over decades reduces the risk of Alzheimer's disease (AD). The present study sought to determine any long-term protective effects of dietary caffeine intake in a controlled longitudinal study involving AD transgenic mice. Caffeine (an adenosine receptor antagonist) was added to the drinking water of amyloid precursor protein, Swedish mutation (APPsw) transgenic (Tg) mice between 4 and 9 months of age, with behavioral testing done during the final 6 weeks of treatment. The average daily intake of caffeine per mouse (1.5 mg) was the human equivalent of 500 mg caffeine, the amount typically found in five cups of coffee per day. Across multiple cognitive tasks of spatial learning/reference memory, working memory, and recognition/identification, Tg mice given caffeine performed significantly better than Tg control mice and similar to non-transgenic controls. In both behaviorally-tested and aged Tg mice, long-term caffeine administration resulted in lower hippocampal beta-amyloid (Abeta) levels. Expression of both Presenilin 1 (PS1) and beta-secretase (BACE) was reduced in caffeine-treated Tg mice, indicating decreased Abeta production as a likely mechanism of caffeine's cognitive protection. The ability of caffeine to reduce Abeta production was confirmed in SweAPP N2a neuronal cultures, wherein concentration-dependent decreases in both Abeta1-40 and Abeta1-42 were observed. Although adenosine A(1) or A(2A) receptor densities in cortex or hippocampus were not affected by caffeine treatment, brain adenosine levels in Tg mice were restored back to normal by dietary caffeine and could be involved in the cognitive protection provided by caffeine. Our data demonstrate that moderate daily intake of caffeine may delay or reduce the risk of AD.