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.

Telmisartan reduces progressive oxidative stress and phosphorylated α-synuclein accumulation in stroke-resistant spontaneously hypertensive rats after transient middle cerebral artery occlusion.

Telmisartan is an angiotensin receptor blocker with high lipid solubility, also called metabosartan, which exerts a special protective effect on both acute brain damage and chronic neurodegeneration. We examined the effects of telmisartan on oxidative stress by advanced glycation end product (AGE) and 4-hydroxynonenal (4-HNE) assays and the accumulation of phosphorylated α-synuclein (pSyn) in the brain of stroke-resistant spontaneously hypertensive rats (SHR-SR). At the age of 12 weeks, SHR-SR received transient middle cerebral artery occlusion (tMCAO) for 90 minutes and were divided into the following 3 groups: the vehicle group, the low-dose telmisartan group (.3 mg/kg/day), and the high-dose telmisartan group (3 mg/kg/day, postoperatively). Immunohistologic analysis was performed when rats were 6, 12, and 18 months old. AGE, 4-HNE, and pSyn-positive cells (per square millimeter) increased with age in the cerebral cortex and hippocampus of the vehicle group, in the low-dose telmisartan group, these parameters decreased without lowering blood pressure (BP), and in the high-dose telmisartan group, these parameters increased with lowering BP. The present study suggests that a persistent hypertension after tMCAO caused a progressive oxidative stress with the abnormal accumulation of pSyn, and that telmisartan reduced oxidative stress and the accumulation of pSyn without lowering BP (low dose) or improved these conditions with a reduction in BP (high dose) via its pleiotropic effects through a potential peroxisome proliferator-activated receptor gamma stimulation in the brain of SHR-SR.

Protective effect of telmisartan against progressive oxidative brain damage and synuclein phosphorylation in stroke-resistant spontaneously hypertensive rats.

Previously, we reported that reactive oxygen species and signaling molecules of angiotensin II produced lipid peroxides, degenerated proteins, and injured DNA after cerebral ischemia in normotensive Wistar rats. Here, we investigated the long-term effect of the angiotensin II type I receptor blocker telmisartan on oxidative stress and hyperphosphorylated α-synuclein accumulation in stroke-resistant spontaneously hypertensive rats (SHR-SR). At the age of 3 months, SHR-SR were divided into 3 treatment groups: SHR-SR vehicle (SHR/Ve), SHR-SR low-dose telmisartan (.3 mg/kg/day) (SHR/low), and SHR-SR high-dose telmisartan (3 mg/kg/day) (SHR/high). Immunohistologic analyses were conducted in these groups and Wistar rats at the age of 6, 12, and 18 months. The SHR/Ve group demonstrated more progressive increase in advanced glycation end product (AGE)-, 4-hydroxy-2-nonenal (4-HNE)-, and phosphorylated α-synuclein (pSyn)-positive cells in the cerebral cortex and hippocampus compared with the Wistar group at 18 months. These expressions were reduced in the SHR/low group even without lowering blood pressure (BP), and expressions were dramatically suppressed in the SHR/high group with lowering of BP. These data suggest that persistent hypertension in SHR-SR strongly potentiate the markers of oxidative damage (AGEs and 4-HNE) and abnormal accumulation of pSyn, which were greatly suppressed by telmisartan in a dose-dependent manner without and with lowering of BP.

Gelatin-siloxane hybrid scaffolds with vascular endothelial growth factor induces brain tissue regeneration.

In the brain after infarction or trauma, the tissue becomes pannecrotic and forms a cavity. In such situation, a scaffold is necessary to produce new tissue. In this study, we implanted a new porous gelatin-siloxane hybrid derived from gelatin and 3-(glycidoxypropyl) trimethoxysilane (gelatin-GPTMS) scaffolds into a brain defect, and investigated whether it makes a new brain tissue. In addition, vascular endothelial growth factor (VEGF) was added on gelatin-GPTMS scaffolds and its effect on tissue regeneration was examined. At 30 days after the implantation, the marginal territory of the scaffolds became occupied by newly formed tissue. Immunohistochemical analysis revealed that the new tissue was constituted by endothelial, astroglial and microglial cells, some of which were labeled for bromodeoxyuridine (BrdU). Addition of VEGF promoted numbers of these cells. Thus, combination of gelatin-GPTMS scaffolds and VEGF is preferable for brain regeneration.

Macrophage infiltration, lectin-like oxidized-LDL receptor-1, and monocyte chemoattractant protein-1 are reduced by chronic HMG-CoA reductase inhibition.

Statin reduces cerebrovascular events independent of its cholesterol lowering effect. We hypothesized that statin inhibits early atherosclerotic change in common carotid artery (CCA), and investigated its effect on lectin-like oxidized-LDL receptor-1 (LOX-1) and monocyte chemoattractant protein-1 (MCP-1) expression, both of which are early atherosclerotic markers. Stroke-prone spontaneous hypertensive rats (SHR-SP) of 8 weeks old were orally treated with vehicle or simvastatin (20mg/kg) daily. After 4 weeks of simvastatin or vehicle treatment, or 2 weeks of vehicle and 2 weeks of simvastatin treatment, CCA was removed. LOX-1 and MCP-1 expression as well as macrophage infiltration were histologically investigated. Lipid deposition was also investigated by Sudan III staining. Simvastatin groups showed significantly smaller amount of lipid deposition and LOX-1 and MCP-1 expression, independent of serum lipid levels. Macrophage infiltration was also decreased. Reduction of cerebrovascular events by statins may be brought by the direct inhibition of atherosclerotic change.

Expression of netrin-1 and its receptors DCC and neogenin in rat brain after ischemia.

It is very important to investigate the mechanism of axonal growth in the ischemic brain in order to consider a novel mean of therapy for stroke. Netrins are chemotropic factors for axon with chemoattractant or chemorepellant guidance activities, and deleted in colorectal cancer (DCC) and neogenin are receptors for netrins. In this study, we examined expressions of netrin-1, DCC, and neogenin in the brain after 90 min of transient middle cerebral artery occlusion (tMCAO). Netrin-1 was expressed in neurons at the peri-ischemic area with a peak at 14 days. DCC was expressed both in neurons and astrocytic feet with a peak at 14 days, though neogenin was expressed in endothelial cells at MCA territory with a peak at the same time point. These results suggest that netrin-1 is involved in the promotion of axonal growth. The expression of netrin-1 and DCC was overlapped both in the spatial and temporal patterns, indicating that DCC plays a role in netrin-1's axonal growth promoting effects. The location of neogenin positive cells differed from that of netrin-1 positive cells, thus its angiogenic activity may not have relevance with netrin-1.

Decreased focal inflammatory response by G-CSF may improve stroke outcome after transient middle cerebral artery occlusion in rats.

Recent studies have shown that administration of granulocyte colony-stimulating factor (G-CSF) is neuroprotective. However, the precise mechanisms of the neuroprotective effect of G-CSF are not entirely known. We carried out 90-min transient middle cerebral occlusion (tMCAO) of rats. The rats were injected with vehicle or G-CSF (50 mug/kg) immediately after reperfusion and sacrificed 8, 24, or 72 hr later. 2,3,5-Triphenyltetrazolium chloride (TTC) staining was carried out using brain sections of 72 hr, and immunohistochemistry was carried out with those of 8, 24, and 72 hr. TTC-staining showed a significant reduction of infarct volume in the G-CSF-treated group (**P < 0.01). Immunohistochemistry showed a significant decrease of the number of cells expressing tumor necrosis factor-alpha (TNF-alpha) at 8-72 hr, transforming growth factor-beta (TGF-beta) and inducible nitric oxide synthase (iNOS) at 24 and 72 hr after tMCAO in the peri-ischemic area (*P < 0.05 each). Our data suggest that the suppression of inflammatory cytokines and iNOS expression may be one mechanism of neuroprotection by G-CSF.

Potentiation of neurogenesis and angiogenesis by G-CSF after focal cerebral ischemia in rats.

Recently, granulocyte colony-stimulating factor (G-CSF) is expected to demonstrate beneficial effects on cerebral ischemia. Here, we showed the potential benefit of G-CSF administration after transient middle cerebral artery occlusion (tMCAO). Adult male Wistar rats received vehicle or G-CSF (50 microg/kg) subcutaneously after reperfusion, and were treated with 5-bromodeoxyuridine (BrdU, 50 mg/kg) once daily by the intraperitoneal route for 3 days after tMCAO. Nissl-stained sections at 7 days after tMCAO showed significant reduction of the infarction area (31%, P<0.01). At 7 days after tMCAO, BrdU plus NeuN double-positive cells increased by 43.3% in the G-CSF-treated group (P<0.05), and BrdU-positive endothelial cells were increased 2.29 times in the G-CSF-treated group, to a level as high as that in the vehicle-treated group (P<0.01), in the periischemic area. Our results indicate that G-CSF caused potentiation of neuroprotection and neurogenesis and is expected to have practical therapeutic potential in treating individuals after ischemic brain injury.

G-CSF enhances stem cell proliferation in rat hippocampus after transient middle cerebral artery occlusion.

Granulocyte colony-stimulating factor (G-CSF) enhances the survival and stimulates the proliferation of neutrophil progenitors. Recently, the neurogenerative effect of G-CSF has been intensely investigated. In this study, we explored the possibility that G-CSF enhanced the cell proliferation in the rat dentate gyrus (DG) after focal cerebral ischemia, using a rat transient middle cerebral artery occlusion (tMCAO) model. At 7 days after tMCAO, the number of 5-bromodeoxyuridine (BrdU)-positive cells in the G-CSF-treated group was significantly increased compared with that in the vehicle-treated group in the ipsilateral SGZ (16.6+/-5.5/mm(2) in the vehicle-treated group versus 33.0+/-7.2/mm(2) in the G-CSF-treated group, **p<0.01) and in the ipsilateral GCL (14.2+/-2.8/mm(2) in the vehicle-treated group versus 21.0+/-3.8/mm(2) in the G-CSF-treated group, *p<0.05). This result showed the possibility of a neurogenerative role of G-CSF after tMCAO in rats.