Therapeutic Implications of Renin-Angiotensin System Modulators in Alzheimer's Dementia.

The Renin-Angiotensin System (RAS) has attracted considerable interest beyond its traditional cardiovascular role due to emerging data indicating its potential involvement in neurodegenerative diseases, including Alzheimer's dementia (AD). This review investigates the therapeutic implications of RAS modulators, specifically focusing on angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), and renin inhibitors in AD. ACEIs, commonly used for hypertension, show promise in AD by reducing angiotensin (Ang) II levels. This reduction is significant as Ang II contributes to neuroinflammation, oxidative stress, and ß-amyloid (Aß) accumulation, all implicated in AD pathogenesis. ARBs, known for vasodilation, exhibit neuroprotection by blocking Ang II receptors, improving cerebral blood flow and cognitive decline in AD models. Renin inhibitors offer a novel approach by targeting the initial RAS step, displaying anti-inflammatory and antioxidant effects that mitigate AD degeneration. Preclinical studies demonstrate RAS regulation's favorable impact on neuroinflammation, neuronal damage, cognitive function, and Aß metabolism. Clinical trials on RAS modulators in AD are limited, but with promising results, ARBs being more effective that ACEIs in reducing cognitive decline. The varied roles of ACEIs, ARBs, and renin inhibitors in RAS modulation present a promising avenue for AD therapeutic intervention, requiring further research to potentially transform AD treatment strategies.

The Impact of Some Modulators of the Renin-Angiotensin System on the Scopolamine-Induced Memory Loss Mice Model.

As some of the renin-angiotensin-aldosterone system (RAAS)-dependent mechanisms underlying the cognitive performance modulation could include oxidative balance alterations, in this study we aimed to describe some of the potential interactions between RAAS modulators (Losartan and Ramipril) and oxidative stress in a typical model of memory impairment. In this study, 48 white male Swiss mice were divided into six groups and received RAAS modulators (oral administration Ramipril 4 mg/kg, Losartan 20 mg/kg) and a muscarinic receptors inhibitor (intraperitoneal injection scopolamine, 0.5 mg/kg) for 8 consecutive days. Then, 24 h after the last administration, the animals were euthanized and whole blood and brain tissues were collected. Biological samples were then processed, and biochemical analysis was carried out to assess superoxide dismutase and glutathione activities and malondialdehyde concentrations. In the present experimental conditions, we showed that RAAS modulation via the angiotensin-converting enzyme inhibition (Ramipril) and via the angiotensin II receptor blockage (Losartan) chronic treatments could lead to oxidative stress modulation in a non-selective muscarinic receptors blocker (scopolamine) animal model. Our results showed that Losartan could exhibit a significant systemic antioxidant potential partly preventing the negative oxidative effects of scopolamine and a brain antioxidant potential, mainly by inhibiting the oxidative-stress-mediated cellular damage and apoptosis. Ramipril could also minimize the oxidative-mediated damage to the lipid components of brain tissue resulting from scopolamine administration. Both blood serum and brain changes in oxidative stress status were observed following 8-day treatments with Ramipril, Losartan, scopolamine, and combinations. While the serum oxidative stress modulation observed in this study could suggest the potential effect of RAAS modulation and scopolamine administration on the circulatory system, blood vessels endothelia, and arterial tension modulation, the observed brain tissues oxidative stress modulation could lead to important information on the complex interaction between renin-angiotensin and cholinergic systems.

A Comparative Study on the Memory-Enhancing Actions of Oral Renin-Angiotensin System Altering Drugs in Scopolamine-Treated Mice.

This study was designed to evaluate the spatial working memory (as studied in Y-maze) or short-term and long-term spatial memory (assessed in radial 8 arms-maze task), in a scopolamine-induced memory deficits model in mice, by the oral administration of 2 angiotensin-converting enzyme inhibitors-captopril and ramipril and also the effects of the AT1 receptor antagonist, losartan. The present article was initiated as a reaction to the clinical setting of hypertensive disease, which involves lifelong administration of antihypertensive drugs, dietary or lifestyle constraints, and aging, which all take a toll on the higher functions of the nervous system. Most of the patients with cognitive decline suffer of various metabolic imbalances, hypertension, cardiac and kidney disease, many of them which are treated with oral administration of Renin-angiotensin aldosterone system-altering agents like those presented above. Our results showed a protective effect of captopril, ramipril, and losartan prescopolamine administration on spontaneous alternation in Y-maze task, as compared to scopolamine-alone treated mice, as well as decreased number of working memory errors and reference memory errors in radial-arm maze for both losartan + scopolamine and ramipril + scopolamine groups versus scopolamine alone. This could have a therapeutical relevance, especially since oral administration was preferred in our report, as it is used in the therapeutic procedures in humans, further enhancing the similarities with the clinical conditions.