Central Angiotensin II Stimulation Promotes β Amyloid Production in Sprague Dawley Rats

Abstract

BackgroundStress and various stress hormones, including catecholamines and glucocorticoids, have recently been implicated in the pathogenesis of Alzheimer's disease (AD), which represents the greatest unresolved medical challenge in neurology. Angiotensin receptor blockers have shown benefits in AD and prone-to-AD animals. However, the mechanisms responsible for their efficacy remain unknown, and no studies have directly addressed the role of central angiotensin II (Ang II), a fundamental stress hormone, in the pathogenesis of AD. The present study focused on the role of central Ang II in amyloidogenesis, the critical process in AD neuropathology, and aimed to provide direct evidence for the role of this stress hormone in the pathogenesis of AD.Methodology/Principal FindingsIncreased central Ang II levels during stress response were modeled by intracerebroventricular (ICV) administration of graded doses of Ang II (6 ng/hr low dose, 60 ng/hr medium dose, and 600 ng/hr high dose, all delivered at a rate of 0.25 µl/hr) to male Sprague Dawley rats (280–310 g) via osmotic pumps. After 1 week of continuous Ang II infusion, the stimulation of Ang II type 1 receptors was accompanied by the modulation of amyloid precursor protein, α-, β-and γ-secretase, and increased β amyloid production. These effects could be completely abolished by concomitant ICV infusion of losartan, indicating that central Ang II played a causative role in these alterations.Conclusions/SignificanceCentral Ang II is essential to the stress response, and the results of this study suggest that increased central Ang II levels play an important role in amyloidogenesis during stress, and that central Ang II-directed stress prevention and treatment might represent a novel anti-AD strategy.

The peptide network regulated by angiotensin converting enzyme (ACE) in hematopoiesis

“…24 Also, neither Ang II nor losartan changed CFU-Meg formation in a defined megakaryocyte lineage assay. 24 These data suggest that Ang II facilitates hematopoietic proliferation at an early differentiation an important role of locally produced Ang II, [10][11][12] including a local RAS producing Ang II in bone marrow (BM). 13 Hematopoiesis is carefully controlled.…”

Autoantibodies Toward the Angiotensin 2 Type 1 Receptor: A Novel Autoantibody in Alzheimer’s Disease

“…Importantly, AD patients taking angiotensin receptor blockers were found to have reduced AD-related pathology postmortem [14]. In animal studies, stimulation of the angiotensin system increases leukocyte adhesion, increases permeability of the BBB, induces oxidative stress in the microcirculation of the brain [15], and leads to an increase in A␤ [16] and tau [17] pathologies. Neuronal cell death is also strongly linked to the presence of immunoglobulin G in AD patients' brains.…”

Combination of Antihypertensive Therapy in The Elderly, Multicenter Investigation (CAMUI) Trial

“…[24][25][26] In addition, it has been suggested that some ACE inhibitors and ARBs might have benefits not only for the prevention but also for the treatment of mild to moderate Alzheimer disease progression. [27][28][29] Thus the association between an antihypertensive treatment and cognitive function is becoming an important topic. In this trial, we hope to elucidate the relationship between blood pressure or drug combination and cognitive function.…”