Long-term effect of telmisartan on Alzheimer's amyloid genesis in SHR-SR after tMCAO.

Telmisartan is expected to reduce not only the level of blood pressure but also neuroinflammation and neurotoxicity via pleiotrophic effects as a metabo-sartan. We examined the effects of telmisartan on Alzheimer's disease (AD) pathology in spontaneously hypertensive rat stroke resistant (SHR-SR) after transient middle cerebral artery occlusion (tMCAO) by giving either telmisartan at 0 (vehicle), 0.3 mg/kg/day (low dose, with no reduction of blood pressure), or 3 mg/kg/day (high dose, with a significant reduction of blood pressure) p.o. from 3 months (M) of age, and performed immunohistological analysis at 6, 12, and 18 M of age. The numbers of amyloid ß (Aß)-positive neurons in the cerebral cortex and hippocampus and senile plaque (SP) in the ipsilateral cerebral cortex progressively increased with age until 18 M in the SHR-SR after tMCAO. On the other hand, low-dose telmisartan significantly reduced the number of Aß-positive neuron as well as SP at 6, 12, and 18 M. High-dose telmisartan showed further reductions of the above AD pathology. The present study suggests that telmisartan reduced both intracellular Aß and extracellular SP accumulations after tMCAO in SHR-SR, with a further improvement by combined BP lowering. Such a strong effect of telmisartan could provide a preventative approach for AD in post-stroke patients with hypertension.

Telmisartan reduces progressive accumulation of cellular amyloid beta and phosphorylated tau with inflammatory responses in aged spontaneously hypertensive stroke resistant rat.

BACKGROUND: In addition to reducing the level of blood pressure (BP), telmisartan was expected to show the long-term neuroprotective effects preventing accumulation of cellular amyloid beta peptide (Aß) and phosphorylated tau (pτ) by ameliorating neuroinflammation. METHODS: We examined effects of telmisartan on cellular Aß and pτ with inflammatory responses in the brain of a spontaneously hypertensive stroke resistant (SHR-SR) rat by giving either telmisartan at 0 (vehicle), .3 mg/kg/day or 3 mg/kg/day, orally, from 3 months of age and performed immunohistologic analysis at 6, 12, and 18 months. Compared with normotensive Wistar rats, numbers of Aß- and pτ-positive neurons in the cerebral cortex progressively increased with age until 18 months in the SHR-SR rats, as did the numbers of ionized calcium-binding adapter molecule 1 (Iba-1)-positive microglia, tumor necrosis factor alpha (TNF-α)-positive neurons, and monocyte chemotactic protein 1 (MCP-1)-positive neurons. RESULTS: Low-dose telmisartan significantly decreased the numbers of Aß- and pτ-positive neuron as well as the numbers of TNF-α-positive neurons, Iba-1-positive microglia, and MCP-1-positive neurons at 6, 12, and 18 months. High-dose telmisartan reduced BP and showed a further reduction of cellular Aß and pτ. CONCLUSIONS: The present study suggests that accumulation of cellular Aß and pτ and the inflammatory responses were decreased via improving metabolic syndrome with low-dose telmisartan and improving both metabolic syndrome and hypertension with high-dose telmisartan.

Statins have therapeutic potential for the treatment of Alzheimer's disease, likely via protection of the neurovascular unit in the AD brain.

Structural and functional abnormalities in the neurovascular unit (NVU) have been recently observed in Alzheimer's disease (AD). Statins, which are used clinically for reducing cholesterol levels, can also exert beneficial vascular actions, improve behavioral memory and reduce senile plaque (SP). Thus, we examined cognitive function, the serum level of lipids, senile plaque (SP), and the protective effects of statins on NVU disturbances in a mouse AD model. Amyloid precursor protein (APP) transgenic (Tg) mice were used as a model of AD. Atorvastatin (30 mg/kg/day, p.o.) or pitavastatin (3mg/kg/day, p.o.) were administered from 5 to 20 months of age. These 2 statins improved behavioral memory and reduced the numbers of SP at 15 and 20 M without affecting serum lipid levels. There was a reduction in immunopositive staining for N-acetyl glucosamine oligomer (NAGO) in the endothelium and in collagen IV in the APP vehicle (APP/Ve) group, with collagen IV staining most weakest near SP. There was also an increase in intensity and numbers of glial fibrillary acidic protein (GFAP) positive astrocytes, particularly around the SP, where MMP-9 was more strongly labeled. Double immunofluorescent analysis showed that astrocytic endfeet had detached from the capillary endothelium in the APP/Ve group. Overall, these data suggest that statins may have therapeutic potential for AD by protecting NVU.

Atorvastatin and pitavastatin reduce senile plaques and inflammatory responses in a mouse model of Alzheimer's disease.

OBJECTIVES: To examine and compare the pleiotropic anti-inflammatory effects and the long-term effects of atorvastatin and pitavasatin in mouse model of Alzheimer's disease (AD). METHODS: We examined the effects of two strong statins on senile plaque (SP) size and inflammatory responses in the brain of an amyloid precursor protein (APP) transgenic (Tg) mouse. We gave the Tg mice either atorvastatin or pitavastatin from 5-20 months of age, and performed immunohistological analysis [SP area, monocyte chemotactic protein 1 (MCP-1)-positive neurons, ionized calcium-binding adaptor molecule 1 (Iba-1)-1-positive microglia, and tumor necrosis factor α (TNF-α)-positive neurons] every 5 months. RESULTS: In the APP-Tg mice treated with both statins, the number of MCP-1-positive neurons was reduced at 10 months, that of Iba-1-positive microglia was reduced at 15 months, and that of TNF-α-positive neurons and the mean total SP area decreased at 15-20 months, compared with APP-Tg mice with vehicle treatment. DISCUSSION: The protective effect of these statins took 5 months to reach significance in these mice, and the order of sensitivity to statin treatment was MCP-1>Iba-1>TNF-α>SPs. Proinflammatory responses including MCP-1, Iba-1, and TNF-α preceded and possibly contributed to SP formation. Pitavastatin has the same significant pleiotrophic effect to prevent and ameliorate inflammation and also has a long-term effect compared with atorvastatin, and both of them have high potential for a preventative approach in patients at risk of AD.

Atorvastatin and pitavastatin protect cerebellar Purkinje cells in AD model mice and preserve the cytokines MCP-1 and TNF-α.

In contrast to cerebral cortical neurons, the extent of damage to cells of the cerebellum in Alzheimer's disease (AD) is still a matter of debate. Here, we examined pathological changes in the cerebellar Purkinje cells (PCs) of AD model mice (amyloid precursor protein transgenic (APP-Tg) mice) at 10, 15, and 20 months (M) of age, and investigated the possible protective effect of two strong statins (atorvastatin at 30 mg/kg/day or pitavastatin at 3mg/kg/day, p.o.) by administering these statins from 5 to 20 M. The number of PCs detected by hematoxylin-eosin staining in APP-Tg mice was approximately 60% of the number in non-Tg mice at 10 M, and this progressively reduced with age until 20 M. Moreover, the number of monocyte chemotactic protein 1 (MCP-1)-positive PCs and tumor necrosis factor alpha (TNF-α)-positive PCs was also reduced in the transgenics. In contrast, the APP-Tg mice treated with either of the two statins showed a significant recovery in the number of PCs, and MCP-1 (at 20 M) and TNF-α (at 15 and 20 M) staining in PCs was preserved. Because MCP-1 and TNF-α play important roles in maintaining the synaptic network in PCs, the present study suggests that atorvastatin and pitavastatin can maintain the number of PCs and their synaptic networks in the AD cerebellum.

Atorvastatin and pitavastatin improve cognitive function and reduce senile plaque and phosphorylated tau in aged APP mice.

In addition to simply reducing the serum level of cholesterol, 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have various pleiotrophic effects such as reducing oxidative stress, neuroinflammation, and neurotoxicity. However, such a pleiotrophic effect has not been fully studied in a new statin (pitavastatin). We examined and compared the effects of two strong statins (atorvastatin, 30 mg/kg/day, p.o.; pitavastatin, 3mg/kg/day, p.o.) on the serum level of lipids, cognitive dysfunction, senile plaque (SP) and phosphorylated tau-positive dystrophic neuritis (pτDN) in amyloid precursor protein (APP) transgenic (Tg) mice from 5 months (M) of age to 20 M. These two statins improved behavioral memory and reduced the numbers of SP and pτDN at 15 and 20 M without affecting serum lipid levels, but preserved mice brain weight in pitavastatin group at 20 M. These protective effects of statins took 10 M from the beginning of treatment to show an improvement in the present model mice, and sensitivity to the statin treatment was linked to behavioral memory, SP and pτDN in this order. These findings suggest that early treatment with both atorvastatin and pitavastatin prevented subsequent worsening of cognitive function and the amyloidogenic process, probably due to pleiotrophic effects, suggesting a therapeutic potential for Alzheimer's disease (AD).