Dysregulation of ACE-1 in normal aging and the early stages of Alzheimer's disease

Dysregulation of the renin-angiotensin system in vascular dementia

The renin-angiotensin system (RAS) regulates systemic and cerebral blood flow and is dysregulated in dementia. The major aim of this study was to determine if RAS signalling is dysregulated in vascular dementia. We measured markers of RAS signalling in white matter underlying the frontal and occipital cortex in neuropathologically confirmed cases of vascular dementia (n = 42), Alzheimer's disease (n = 50), mixed AD/VaD (n = 50) and age-matched controls (n = 50). All cases were stratified according to small vessel disease (SVD) severity across both regions. ACE-1 and ACE-2 protein and activity was measured by ELISA and fluorogenic peptide assays respectively, and angiotensin peptide (Ang-II, Ang-III and Ang-(1-7)) levels were measured by ELISA. ACE-1 protein level and enzyme activity, and Ang-II and Ang-III, were elevated in the white matter in vascular dementia in relation to SVD severity. ACE-1 and Ang-II protein levels were inversely related to MAG:PLP1 ratio, a biochemical marker of brain tissue oxygenation that when reduced indicates cerebral hypoperfusion, in a subset of cases. ACE-2 level was elevated in frontal white matter in vascular dementia. Ang-(1-7) level was elevated across all dementia groups compared to age-matched controls but was not related to SVD severity. RAS signalling was not altered in the white matter in Alzheimer's disease. In the overlying frontal cortex, ACE-1 protein was reduced and ACE-2 protein increased in vascular dementia, whereas angiotensin peptide levels were unchanged. These data indicate that RAS signalling is dysregulated in the white matter in vascular dementia and may contribute to the pathogenesis of small vessel disease.

Alzheimer's disease, aging, and cannabidiol treatment: a promising path to promote brain health and delay aging

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by progressive memory loss, neurodegeneration, and cognitive decline. Aging is one of the risk factors for AD. Although the mechanisms underlying aging and the incidence rate of AD are unclear, aging and AD share some hallmarks, such as oxidative stress and chronic inflammation. Cannabidiol (CBD), the major non-psychoactive phytocannabinoid extracted from Cannabis sativa, has recently emerged as a potential candidate for delaying aging and a valuable therapeutic tool for the treatment of aging-related neurodegenerative diseases due to its antioxidant and anti-inflammation properties. This article reviews the relevant literature on AD, CBD treatment for AD, cellular senescence, aging, and CBD treatment for aging in recent years. By analyzing these published data, we attempt to explore the complex correlation between cellular senescence, aging, and Alzheimer's disease, clarify the positive feedback effect between the senescence of neurocytes and Alzheimer's disease, and summarize the role and possible molecular mechanisms of CBD in preventing aging and treating AD. These data may provide new ideas on how to effectively prevent and delay aging, and develop effective treatment strategies for age-related diseases such as Alzheimer's disease.

Altered Gene Expression Within the Renin-Angiotensin System in Normal Aging and Dementia

The renin-angiotensin system (RAS) is dysregulated in Alzheimer's disease (AD). In this study, we have explored the hypothesis that an -age--related imbalance in brain RAS is a trigger for RAS dysregulation in AD. We characterized RAS gene expression in the frontal cortex from (i) a cohort of normal aging (n = 99, age range = 19-96 years) and (ii) a case-control cohort (n = 209) including AD (n = 66), mixed dementia (VaD + AD; n = 50), pure vascular dementia (VaD; n = 42), and age-matched controls (n = 51). The AD, mixed dementia, and age-matched controls were further stratified by Braak tangle stage (BS): BS0-II (n = 48), BSIII-IV (n = 44), and BSV-VI (n = 85). Gene expression was calculated by quantitative PCR (qPCR) for ACE1, AGTR1, AGTR2, ACE2, LNPEP, and MAS1 using the 2-∆∆Cq method, after adjustment for reference genes (RPL13 and UBE2D2) and cell-specific calibrator genes (NEUN, GFAP, PECAM). ACE1 and AGTR1, markers of classical RAS signaling, and AGTR2 gene expression were elevated in normal aging and gene expression in markers of protective downstream regulatory RAS signaling, including ACE2, MAS1, and LNPEP, were unchanged. In AD and mixed dementia, AGTR1 and AGTR2 gene expression were elevated in BSIII-IV and BSV-VI, respectively. MAS1 gene expression was reduced at BSV-VI and was inversely related to parenchymal Aβ and tau load. LNPEP gene expression was specifically elevated in VaD. These data provide novel insights into RAS signaling in normal aging and dementia.

The Alzheimer's Disease Brain, Its Microvasculature, and NADPH Oxidase

The deterioration of the brain's microvasculature, particularly in the hippocampus, appears to be a very early event in the development of Alzheimer's disease (AD), preceding even the deposition of amyloid-β. A damaged microvasculature reduces the supply of oxygen and glucose to this region and limits the production of energy, ATP. The damage may be a function of the rise with age in the expression and activity of NADPH oxidase (NOX) in these microvessels. This rise renders these vessels vulnerable to the effects of oxidative stress and inflammation. The rise in NOX activity with age is even more marked in the AD brain where an inverse correlation has been demonstrated between NOX activity and cognitive ability. Apocynin, a putative NOX inhibitor, has been shown to block the damaging effects of NOX activation. Apocynin acts as a strong scavenger of H2O2, and as a weak scavenger of superoxide. Like apocynin, sodium oxybate (SO) has also been shown to block the toxic effects of NOX activation. The application of SO generates NADPH and ATP. SO inhibits oxidative stress and maintains normal cerebral ATP levels under hypoxic conditions. Moreover, it acts epigenetically to attenuate the expression of NOX. SO may delay the onset and slow the progress of AD by suppling energy and maintaining an antioxidative environment in the brain throughout the night. The slow wave activity produced by SO may also activate the glymphatic system and promote the clearance of amyloid-β from the brain.

Past antihypertensive medication use is associated with lower levels of small vessel disease and lower Aβ plaque stage in the brains of older individuals

AIMS

This study assesses the association of antihypertensive medication use on the severities of neuropathological cerebrovascular disease (CVD excluding lobar infarction) in older individuals.

METHODS

Clinical and neuropathological data were retrieved for 149 autopsy cases >75 years old with or without CVD or Alzheimer's disease and no other neuropathological diagnoses. Clinical data included hypertension status, hypertension diagnosis, antihypertensive medication use, antihypertensive medication dose (where available) and clinical dementia rating (CDR). Neuropathological CVD severity was evaluated for differences with anti-hypertensive medication usage.

RESULTS

Antihypertensive medication use was associated with less severe white matter small vessel disease (SVD, mainly perivascular dilatation and rarefaction), with a 5.6-14.4 times greater likelihood of less severe SVD if medicated. No significant relationship was detected between infarction (presence, type, number and size), lacunes or cerebral amyloid angiopathy and antihypertensive medication use. Only increased white matter rarefaction/oedema and not perivascular dilation was associated with Alzheimer's pathology, with a 4.3 times greater likelihood of reduced Aβ progression through the brain if white matter rarefaction severity was none or mild. Antihypertensive medication use was associated with reduced Aβ progression but only in those with moderate to severe white matter SVD.

CONCLUSIONS

This histopathological study provides further evidence that antihypertensive medication use in older individuals is associated with white matter SVD and not with other CVD pathologies. This is mainly due to a reduction in white matter perivascular dilation and rarefaction/oedema. Even in those with moderate to severe white matter SVD, antihypertensive medication use reduced rarefaction and Aβ propagation through the brain.

Alzheimer's Disease: An Updated Overview of Its Genetics

Alzheimer's disease (AD) is the most common neurodegenerative disease in the world. It is classified as familial and sporadic. The dominant familial or autosomal presentation represents 1-5% of the total number of cases. It is categorized as early onset (EOAD; <65 years of age) and presents genetic mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2), or the Amyloid precursor protein (APP). Sporadic AD represents 95% of the cases and is categorized as late-onset (LOAD), occurring in patients older than 65 years of age. Several risk factors have been identified in sporadic AD; aging is the main one. Nonetheless, multiple genes have been associated with the different neuropathological events involved in LOAD, such as the pathological processing of Amyloid beta (Aβ) peptide and Tau protein, as well as synaptic and mitochondrial dysfunctions, neurovascular alterations, oxidative stress, and neuroinflammation, among others. Interestingly, using genome-wide association study (GWAS) technology, many polymorphisms associated with LOAD have been identified. This review aims to analyze the new genetic findings that are closely related to the pathophysiology of AD. Likewise, it analyzes the multiple mutations identified to date through GWAS that are associated with a high or low risk of developing this neurodegeneration. Understanding genetic variability will allow for the identification of early biomarkers and opportune therapeutic targets for AD.

Mini-review: Angiotensin- converting enzyme 1 (ACE1) and the impact for diseases such as Alzheimer's disease, sarcopenia, cancer, and COVID-19

Ageing has been associated with comorbidities, systemic low-grade of inflammation, and immunosenescence. Hypertension is the most common morbidity and anti-hypertensives are used for more than 50%. Angiotensin-converting enzyme 1 inhibitors (ACEi) and angiotensin II receptor blockers (ARB) control blood pressure but also seem to play a role in comorbidities such as Alzheimer's disease, sarcopenia and cancer. The impact of anti-hypertensives in comorbidities is due to the expression of renin-angiotensin system (RAS) in several tissues and body fluids. Angiotensin-converting enzyme 1 (ACE1) has been linked to oxidative stress, metabolism, and inflammation. The levels and activity of ACE1 are under genetic control and polymorphisms have been correlated with susceptibility to Alzheimer's disease. In addition, some results found that ACEi and ARB users present delayed cognitive decline and reduced risk of dementia. Regarding to sarcopenia, RAS has been linked to the catabolic and anabolic pathways for muscle mass maintenance. In some studies, older adults using ACEi were highly benefited by exercise training. In cancer, RAS and its products have been shown to play a role since their inhibition in animal models modulates tumor microenvironment and improves the delivery of chemotherapy drugs. Clinically, the incidence of colorectal cancer is reduced in patients using ACEi and ARB. During the pandemic COVID-19 it was found that ACE2 receptor plays a role in the entry of SARS-CoV-2 into the host cell. ACE1 genotypes have been linked to an increased risk for COVID-19 and severe disease. In some studies COVID-19 patients taking ARB or ACEi presented better outcome.

Angiotensin Converting Enzyme 1 Expression in the Leukocytes of Adults Aged 64 to 67 Years

The renin angiotensin system is composed of several enzymes and substrates on which angiotensin converting enzyme (ACE) 1 and renin act to produce angiotensin II. ACE1 and its substrates control blood pressure, affect cardiovascular and renal function, hematopoiesis, reproduction, and immunity. The increased expression of ACE1 has been observed in human monocytes during congestive heart failure and abdominal aortic aneurysm. Moreover, T lymphocytes from individuals with hypertension presented increased expression of ACE1 after in vitro stimulation with angiotensin II (ATII) with the highest ACE1 expression observed in individuals with hypertension with low-grade inflammation. Our group and others have shown that aging is associated with comorbidities, chronic inflammation, and immunosenescence, but there is a lack of data about ACE1 expression on immune cells during the aging process. Therefore, our aim was to evaluate the levels of ACE1 expression in nonlymphoid cells compared to lymphoid that in cells in association with the immunosenescence profile in adults older than 60 years. Cryopreserved peripheral blood mononuclear cells obtained from blood samples were used. Cells were stained with monoclonal antibodies and evaluated via flow cytometry. We found that ACE1 was expressed in 56.9% of nonlymphocytes and in more than 90% of lymphocytes (all phenotypes). All donors exhibited characteristics of immunosenescence, as evaluated by low frequencies of naïve CD4+ and CD8+ T cells, high frequencies of effector memory re-expressing CD45RA CD8+ T cells, and double-negative memory B cells. These findings, in addition to the increased C-reactive protein levels, are intriguing questions for the study of ACE1, inflammaging, immunosenescence, and perspectives for drug development or repurposing (Reviewed by the Plan P #PeerRef Community).

Deciphering mechanisms of action of ACE inhibitors in neurodegeneration using Drosophila models of Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder for which there is no cure. Recently, several studies have reported a significant reduction in the incidence and progression of dementia among some patients receiving antihypertensive medications such as angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin receptor blockers (ARBs). Why these drugs are beneficial in some AD patients and not others is unclear although it has been shown to be independent of their role in regulating blood pressure. Given the enormous and immediate potential of ACE-Is and ARBs for AD therapeutics it is imperative that we understand how they function. Recently, studies have shown that ACE-Is and ARBs, which target the renin angiotensin system in mammals, are also effective in suppressing neuronal cell death and memory defects in Drosophila models of AD despite the fact that this pathway is not conserved in flies. This suggests that the beneficial effects of these drugs may be mediated by distinct and as yet, identified mechanisms. Here, we discuss how the short lifespan and ease of genetic manipulations available in Drosophila provide us with a unique and unparalleled opportunity to rapidly identify the targets of ACE-Is and ARBs and evaluate their therapeutic effectiveness in robust models of AD.

Age-related reduction in brain ACE-2 is not exacerbated by Alzheimer's disease pathology in mouse models of Alzheimer's disease

An imbalance in the circulatory and organ-specific renin-angiotensin system (RAS) pathways is associated with age-related dysfunction and disease including cardiovascular burden and more recently Alzheimer's disease (AD). It is currently unclear whether an age-associated imbalance in components of the RAS within the brain precedes the onset of AD or whether a RAS imbalance is associated with the onset of disease pathology and cognitive decline. Angiotensin-converting enzyme-1 (ACE-1) and -2 (ACE-2) protein (ELISA) and enzyme activity (FRET assay), markers of the classical and counter-regulatory RAS axis respectively, and Ang-II and Ang-(1-7) peptide levels (ELISA), were measured in the left cortex across four transgenic AD mouse models of amyloid pathology (5xFAD - 2, 6, and 12 months of age; Apd9 - 3-4, 12, and 18 months of age; Tg2576 - 3-4 and 24 months of age; and PDAPP - 3-4, 7, 11, 15, and 18 months of age) and littermate wild-type (WT) controls. ACE-1 level, and enzyme activity, was unaltered in relation to age in WT mice and across all four models. In contrast, ACE-2 level and enzyme activity, was reduced and Ang-II increased with ageing in both WT animals and disease models. The changes in ACE-2 and Ang-II in AD models mirrored WT mice, except for the 5xFAD model, when the reduction in ACE-2 (and elevated Ang-II) was observed at a younger age. These data indicate an age-related dysregulation of brain RAS is likely to be driven by a reduction in ACE-2. The reduction in ACE-2 occurs at a young age, coinciding with early pathological changes and the initial deposition of Aβ, and preceding neuronal loss and cognitive decline, in the transgenic AD models. However, the age-related loss was mirrored in WT mice suggesting that the change was independent of pathological Aβ deposition.