Studies of intracellular angiotensin II

Role of angiotensin II in aging

Aging is an inevitable progressive decline in physiological organ function that increases the chance of disease and death. The renin-angiotensin system (RAS) is involved in the regulation of vasoconstriction, fluid homeostasis, cell growth, fibrosis, inflammation, and oxidative stress. In recent years, unprecedented advancement has been made in the RAS study, particularly with the observation that angiotensin II (Ang II), the central product of the RAS, plays a significant role in aging and chronic disease burden with aging. Binding to its receptors (Ang II type 1 receptor - AT1R in particular), Ang II acts as a mediator in the aging process by increasing free radical production and, consequently, mitochondrial dysfunction and telomere attrition. In this review, we examine the physiological function of the RAS and reactive oxygen species (ROS) sources in detail, highlighting how Ang II amplifies or drives mitochondrial dysfunction and telomere attrition underlying each hallmark of aging and contributes to the development of aging and age-linked diseases. Accordingly, the Ang II/AT1R pathway opens a new preventive and therapeutic direction for delaying aging and reducing the incidence of age-related diseases in the future.

A retrospective study on the short-term effect of high-dose spironolactone (80 mg/d) on chronic congestive heart failure

To explore the short-term effect of high-dose spironolactone (80 mg/d) on chronic congestive heart failure (CHF).The general clinical data of 211 patients with CHF from February 2016 to August 2019 were collected and analyzed. Patients were divided into Low-dose group (taking 40 mg/d spironolactone) and High-dose group (taking 80 mg/d spironolactone) according to the patient's previous dose of spironolactone. The changes of B-type brain natriuretic peptide (BNP), NT-pro BNP (N terminal pro B type natriuretic peptide), echocardiography, 6-minute walking test (6MWT), and comprehensive cardiac function assessment data were collected for analysis.Compared with before treatment, the blood potassium of the two groups increased significantly (P < .05), but the blood potassium did not exceed the normal range. Compared with before treatment, BNP, NT-pro BNP, LVEDD, LVEDV and NYHA grading were significantly decreased (P < .05), LVEF and 6-MWT were significantly increased (P < .05). Compared with the Low-dose group, the high-dose group BNP (117.49 ± 50.32 vs 195.76 ± 64.62, P < .05), NT-pro BNP (312.47 ± 86.28 vs 578.47 ± 76.73, P < .05), LVEDD (45.57 ± 5.69 vs 51.96 ± 5.41, P <.05), LVEDV (141.63 ± 51.14 vs 189.85 ± 62.49, P < .05) and NYHA grading (1.29 ± 0.41 vs 1.57 ± 0.49, P < .05) were significantly reduced, but, 6-MWT (386.57 ± 69.72 vs 341.73 ± 78.62, P < .05), LVEF (41.62 ± 2.76 vs 36.02 ± 2.18, P < .05) and total effective rate (92.68% vs 81.39%, P < .05) increased significantly.Compared with 40 mg spironolactone, 80 mg spironolactone can rapidly reduce BNP and NT-pro BNP concentration, enhance exercise tolerance, improve clinical signs and cardiac function classification, and has better efficacy.

The intracellular renin-angiotensin system: Friend or foe. Some light from the dopaminergic neurons

The renin-angiotensin system (RAS) is one of the oldest hormone systems in vertebrate phylogeny. RAS was initially related to regulation of blood pressure and sodium and water homeostasis. However, local or paracrine RAS were later identified in many tissues, including brain, and play a major role in their physiology and pathophysiology. In addition, a major component, ACE2, is the entry receptor for SARS-CoV-2. Overactivation of tissue RAS leads several oxidative stress and inflammatory processes involved in aging-related degenerative changes. In addition, a third level of RAS, the intracellular or intracrine RAS (iRAS), with still unclear functions, has been observed. The possible interaction between the intracellular and extracellular RAS, and particularly the possible deleterious or beneficial effects of the iRAS activation are controversial. The dopaminergic system is particularly interesting to investigate the RAS as important functional interactions between dopamine and RAS have been observed in the brain and several peripheral tissues. Our recent observations in mitochondria and nucleus of dopaminergic neurons may clarify the role of the iRAS. This may be important for the developing of new therapeutic strategies, since the effects on both extracellular and intracellular RAS must be taken into account, and perhaps better understanding of COVID-19 cell mechanisms.

Cellular Mechanisms of Valvular Thickening in Early and Intermediate Calcific Aortic Valve Disease

Background:

Calcific aortic valve disease is common in an aging population. It is an ac-tive atheroinflammatory process that has an initial pathophysiology and similar risk factors as athero-sclerosis. However, the ultimate disease phenotypes are markedly different. While coronary heart dis-ease results in rupture-prone plaques, calcific aortic valve disease leads to heavily calcified and ossi-fied valves. Both are initiated by the retention of low-density lipoprotein particles in the subendotheli-al matrix leading to sterile inflammation. In calcific aortic valve disease, the process towards calcifica-tion and ossification is preceded by valvular thickening, which can cause the first clinical symptoms. This is attributable to the accumulation of lipids, inflammatory cells and subsequently disturbances in the valvular extracellular matrix. Fibrosis is also increased but the innermost extracellular matrix layer is simultaneously loosened. Ultimately, the pathological changes in the valve cause massive calcifica-tion and bone formation - the main reasons for the loss of valvular function and the subsequent myo-cardial pathology.

Conclusion:

Calcification may be irreversible, and no drug treatments have been found to be effec-tive, thus it is imperative to emphasize lifestyle prevention of the disease. Here we review the mecha-nisms underpinning the early stages of the disease.

The intracellular angiotensin system buffers deleterious effects of the extracellular paracrine system

The 'classical' renin-angiotensin system (RAS) is a circulating system that controls blood pressure. Local/paracrine RAS, identified in a variety of tissues, including the brain, is involved in different functions and diseases, and RAS blockers are commonly used in clinical practice. A third type of RAS (intracellular/intracrine RAS) has been observed in some types of cells, including neurons. However, its role is still unknown. The present results indicate that in brain cells the intracellular RAS counteracts the intracellular superoxide/H₂O₂ and oxidative stress induced by the extracellular/paracrine angiotensin II acting on plasma membrane receptors. Activation of nuclear receptors by intracellular or internalized angiotensin triggers a number of mechanisms that protect the cell, such as an increase in the levels of protective angiotensin type 2 receptors, intracellular angiotensin, PGC-1α and IGF-1/SIRT1. Interestingly, this protective mechanism is altered in isolated nuclei from brains of aged animals. The present results indicate that at least in the brain, AT1 receptor blockers acting only on the extracellular or paracrine RAS may offer better protection of cells.

Menopause and Parkinson's disease. Interaction between estrogens and brain renin-angiotensin system in dopaminergic degeneration

The neuroprotective effects of menopausal hormonal therapy in Parkinson's disease (PD) have not yet been clarified, and it is controversial whether there is a critical period for neuroprotection. Studies in animal models and clinical and epidemiological studies indicate that estrogens induce dopaminergic neuroprotection. Recent studies suggest that inhibition of the brain renin-angiotensin system (RAS) mediates the effects of estrogens in PD models. In the substantia nigra, ovariectomy induces a decrease in levels of estrogen receptor-α (ER-α) and increases angiotensin activity, NADPH-oxidase activity and expression of neuroinflammatory markers, which are regulated by estrogen replacement therapy. There is a critical period for the neuroprotective effect of estrogen replacement therapy, and local ER-α and RAS play a major role. Astrocytes play a major role in ER-α-induced regulation of local RAS, but neurons and microglia are also involved. Interestingly, treatment with angiotensin receptor antagonists after the critical period induced neuroprotection.

Age-Related Macular Degeneration and Intracrine Biology: An Hypothesis

This laboratory has studied the intracellular actions of angiotensin II and other signaling proteins that can act in the intracellular space-peptides/proteins we have called intracrines. Moreover, we have suggested that general principles of intracrine action exist and can help explain the progression of some chronic degenerative diseases such as diabetic nephropathy and congestive heart failure. Here, a similar analysis is carried out in the case of age-related macular degeneration. We propose that intracrine mechanisms are operative in this disorder. In particular, we hypothesize that intracrine loops involving renin, angiotensin II, transforming growth factor-beta, vascular endothelial growth factor, bone morphogenetic protein-4, and p53, among other factors, are involved. If this analysis is correct, it suggests a commonality of mechanism linking chronic progressive renal diseases, congestive heart failure, and macular degeneration.