Protective effects of angiotensin II type 1 receptor blocker on cerebral circulation independent of blood pressure.
ABSTRACT Angiotensin II type 1 receptor (AT1R) blocker (ARB) has been reported to modify hypertensive cerebrovascular changes; however, it is not clear whether its protective effects are independent of blood pressure. The aim of this study was to clarify the role of AT1R-mediated signals in cerebral circulation by the chronic treatment with telmisartan, an ARB, at a dose that did not lower the blood pressure. Male spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were treated for 4 weeks from 16 weeks of ages with telmisartan (SHR-L: 0.3 mg/kg/day, SHR-H: 3 mg/kg/day, WKY-H: 3 mg/kg/day) or vehicle (SHR-V, WKY-V). Superoxide measured by a chemiluminescent assay or dihydroethidium fluorescence and vascular morphology were examined for the thoracic aorta (Ao), common carotid (CCA), middle cerebral (MCA) and basilar arteries (BA). After 4 weeks of treatment, the blood pressure significantly declined in SHR-H but not in SHR-L in comparison to SHR-V. The lower limit of cerebral blood flow (CBF) autoregulation, evaluated by hemorrhagic hypotension, was significantly lower in SHR-L and SHR-H than SHR-V. In both SHR and WKY, the superoxide levels in the arteries were significantly attenuated by both doses of ARB. ARB also reversed vascular hypertrophy in Ao, CCA and BA and the inward remodeling in MCA. These results suggest that chronic treatment with telmisartan may therefore improve CBF autoregulation with a restoration of the vascular structure and an attenuation of superoxide generation, even at a dose that does not lower the blood pressure.
SourceAvailable from: Marius C Staiculescu[Show abstract] [Hide abstract]
ABSTRACT: The microcirculation is a portion of the vascular circulatory system that consists of resistance arteries, arterioles, capillaries and venules. It is the place where gases and nutrients are exchanged between blood and tissues. In addition the microcirculation is the major contributor to blood flow resistance and consequently to regulation of blood pressure. Therefore, structural remodeling of this section of the vascular tree has profound implications on cardiovascular pathophysiology. This review is focused on the role that reactive oxygen species (ROS) play on changing the structural characteristics of vessels within the microcirculation. Particular attention is given to the resistance arteries and the functional pathways that are affected by ROS in these vessels and subsequently induce vascular remodeling. The primary sources of ROS in the microcirculation are identified and the effects of ROS on other microcirculatory remodeling phenomena such as rarefaction and collateralization are briefly reviewed.International Journal of Molecular Sciences 12/2014; 15(12):23792-23835. DOI:10.3390/ijms151223792 · 2.46 Impact Factor
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ABSTRACT: Telmisartan is expected to ameliorate not only hypertension, but also metabolic syndrome as a metabosartan. We examined the effects of telmisartan on metabolic syndrome-related molecules such as insulin receptor (IR), peroxisome proliferator-activated receptor gamma (PPAR-γ), and angiotensin 2 type 1 receptor (AT1R) in stroke-resistant spontaneously hypertensive rat (SHR-SR) after transient middle cerebral artery occlusion (tMCAO), by administering telmisartan at either 0 (vehicle), .3 mg/kg/day (low dose), or 3 mg/kg/day (high dose), postoperatively, from 3 months of age and performed immunohistologic analysis at 6, 12, and 18 months of age. Compared with the vehicle group, the 2 telmisartan groups dose dependently decreased the number of IR- and AT1R-positive neurons in the cerebral cortex in the ipsilateral cerebral cortex from 6 to 18 months after tMCAO. On the other hand, the number of PPAR-γ-positive neurons increased in a dose-dependent manner in the 2 telmisartan groups from 6 to 18 months. The present study suggests that telmisartan dose-dependently ameliorated metabolic syndrome-related changes in the poststroke brain of SHR-SR with a direct protective effect (low dose) and an additive benefit, an antihypertensive effect at a high dose, for long-term protection after tMCAO.Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 10/2014; 23(10). DOI:10.1016/j.jstrokecerebrovasdis.2014.06.012 · 1.99 Impact Factor
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ABSTRACT: 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 (Aβ) and phosphorylated tau (pτ) by ameliorating neuroinflammation. Methods We examined effects of telmisartan on cellular Aβ 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 Aβ- 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 Aβ- 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 Aβ and pτ. Conclusions The present study suggests that accumulation of cellular Aβ 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.Journal of Stroke and Cerebrovascular Diseases 09/2014; 23(10). DOI:10.1016/j.jstrokecerebrovasdis.2014.05.023 · 1.99 Impact Factor