Within the Brain: The Renin Angiotensin System

Pre and postnatal exposure to 900 MHz electromagnetic fields induce inflammation and oxidative stress, and alter renin-angiotensin system components differently in male and female offsprings

AIMS

This study was designed to investigate inflammation, oxidative stress and renin-angiotensin system components in brain and kidney tissues of female and male rats prenatally and/or postnatally exposed to 900 MHz electromagnetic field (EMF). It is aimed to evaluate the biological effects of 900 MHz EMF exposure due to the increase in mobile phone use and especially the more widespread use of the GSM 900 system.

MAIN METHODS

Male and female Wistar albino offsprings were divided into four groups of control, prenatal, postnatal, and prenatal+postnatal exposed to 900 MHz EMF for 1 h/day (23 days during pregnancy for prenatal period, 40 days for postnatal period). The brain and kidney tissues were collected when they reached puberty.

KEY FINDINGS

It was found that the total oxidant status, IL-2, IL-6, and TNF-α levels increased (p < 0.001) and the total antioxidant status levels decreased (p < 0.001) in all three EMF groups comparing to controls in both male and female brain and kidney tissues. The renin- angiotensin system components such as angiotensinogen, renin, angiotensin type 1 and type 2 receptors, and MAS1-like G protein-coupled receptor expression were higher (p < 0.001) in all three EMF exposure groups comparing to controls in both male and female brain and kidney tissues. Although there are some differences of the levels of proinflammatory markers, ROS components and RAS components in brain and kidney tissues between males and females, the common result of all groups was increase in oxidative stress, inflammation markers and angiotensin system components with exposure to 900 MHz EMF.

SIGNIFICANCE

In conclusion, our study suggested that the 900 MHz EMF can activate brain and kidney renin-angiotensin system, and this activation is maybe related to inflammation and oxidative stress in both male and female offsprings.

Renin-Angiotensin System-Modifying Antihypertensive Drugs Can Reduce the Risk of Cardiovascular Complications in Lupus: A Retrospective Cohort Study

BACKGROUND

Patients with systemic lupus erythematosus have a higher incidence of cardiovascular disease than the general population. Antihypertensive drugs that modify the renin-angiotensin system (RAS) are used to protect renal function in lupus nephritis and may also have extrarenal effects that lower cardiovascular disease risk due to their anti-inflammatory properties. In this study, we compared the effects of RAS vs non-RAS antihypertensive drugs on cardiovascular disease incidence in patients with lupus.

METHODS

Using a medical insurance claims dataset, 220,168 patients with lupus were identified, of which 31,647 patients (4018 patients prescribed RAS drugs, 27,629 patients prescribed non-RAS drugs) were eligible for the study. Patients had a mean age of 46.1 years, were 93.0% female, and healthy (96.9% Charlson Comorbidity Index score 0-4). Patients in the 2 drug groups were propensity score matched using demographic data, risk factors, and comorbidities.

RESULTS

Use of RAS vs non-RAS drugs lowered the relative risk (RR) of diagnosis of cardiovascular disease (RR 0.80; 95% confidence interval [CI], 0.74-0.87), which was more pronounced after propensity score matching (RR 0.62; 95% CI, 0.57-0.68). The decreased risk in cardiovascular disease occurred regardless of lupus nephritis status (with lupus nephritis: RR 0.51; 95% CI, 0.39-0.65; without lupus nephritis: RR 0.65; 95% CI, 0.59-0.72). RAS-modifying therapies significantly increased cardiovascular disease-free survival probability over a 5-year period (86.0% vs 78.3% probability).

CONCLUSIONS

RAS-modifying drugs reduced the risk of cardiovascular disease in patients with systemic lupus erythematosus in this dataset. These findings have the potential to impact clinical decision-making with regards to hypertension management in patients with lupus.

SARS-CoV-2 triggers pericyte-mediated cerebral capillary constriction

The SARS-CoV-2 receptor, ACE2, is found on pericytes, contractile cells enwrapping capillaries that regulate brain, heart and kidney blood flow. ACE2 converts vasoconstricting angiotensin II into vasodilating angiotensin-(1-7). In brain slices from hamster, which has an ACE2 sequence similar to human ACE2, angiotensin II evoked a small pericyte-mediated capillary constriction via AT1 receptors, but evoked a large constriction when the SARS-CoV-2 receptor binding domain (RBD, original Wuhan variant) was present. A mutated non-binding RBD did not potentiate constriction. A similar RBD-potentiated capillary constriction occurred in human cortical slices, and was evoked in hamster brain slices by pseudotyped virions expressing SARS-CoV-2 spike protein. This constriction reflects an RBD-induced decrease in the conversion of angiotensin II to angiotensin-(1-7) mediated by removal of ACE2 from the cell surface membrane and was mimicked by blocking ACE2. The clinically used drug losartan inhibited the RBD-potentiated constriction. Thus, AT1 receptor blockers could be protective in COVID-19 by preventing pericyte-mediated blood flow reductions in the brain, and perhaps the heart and kidney.

Pathogenesis of Chronic Kidney Disease Is Closely Bound up with Alzheimer's Disease, Especially via the Renin-Angiotensin System

Chronic kidney disease (CKD) is a clinical syndrome secondary to the definitive change in function and structure of the kidney, which is characterized by its irreversibility and slow and progressive evolution. Alzheimer's disease (AD) is characterized by the extracellular accumulation of misfolded β-amyloid (Aβ) proteins into senile plaques and the formation of neurofibrillary tangles (NFTs) containing hyperphosphorylated tau. In the aging population, CKD and AD are growing problems. CKD patients are prone to cognitive decline and AD. However, the connection between CKD and AD is still unclear. In this review, we take the lead in showing that the development of the pathophysiology of CKD may also cause or exacerbate AD, especially the renin-angiotensin system (RAS). In vivo studies had already shown that the increased expression of angiotensin-converting enzyme (ACE) produces a positive effect in aggravating AD, but ACE inhibitors (ACEIs) have protective effects against AD. Among the possible association of risk factors in CKD and AD, we mainly discuss the RAS in the systemic circulation and the brain.

AT1 receptor autoantibodies mediate effects of metabolic syndrome on dopaminergic vulnerability

The metabolic syndrome has been associated to chronic peripheral inflammation and related with neuroinflammation and neurodegeneration, including Parkinson's disease. However, the responsible mechanisms are unclear. Previous studies have involved the brain renin-angiotensin system in progression of Parkinson's disease and the angiotensin receptor type 1 (AT1) has been recently revealed as a major marker of dopaminergic vulnerability in humans. Dysregulation of tissue renin-angiotensin system is a key common mechanism for all major components of metabolic syndrome. Circulating AT1 agonistic autoantibodies have been observed in several inflammation-related peripheral processes, and activation of AT1 receptors of endothelial cells, dopaminergic neurons and glial cells have been observed to disrupt endothelial blood -brain barrier and induce neurodegeneration, respectively. Using a rat model, we observed that metabolic syndrome induces overactivity of nigral pro-inflammatory renin-angiotensin system axis, leading to increase in oxidative stress and neuroinflammation and enhancing dopaminergic neurodegeneration, which was inhibited by treatment with AT1 receptor blockers (ARBs). In rats, metabolic syndrome induced the increase in circulating levels of LIGHT and other major pro-inflammatory cytokines, and 27-hydroxycholesterol. Furthermore, the rats showed a significant increase in serum levels of proinflammatory AT1 and angiotensin converting enzyme 2 (ACE2) autoantibodies, which correlated with levels of several metabolic syndrome parameters. We also found AT1 and ACE2 autoantibodies in the CSF of these rats. Effects of circulating autoantibodies were confirmed by chronic infusion of AT1 autoantibodies, which induced blood-brain barrier disruption, an increase in the pro-inflammatory renin-angiotensin system activity in the substantia nigra and a significant enhancement in dopaminergic neuron death in two different rat models of Parkinson's disease. Observations in the rat models, were analyzed in a cohort of parkinsonian and non-parkinsonian patients with or without metabolic syndrome. Non-parkinsonian patients with metabolic syndrome showed significantly higher levels of AT1 autoantibodies than non-parkinsonian patients without metabolic syndrome. However, there was no significant difference between parkinsonian patients with metabolic syndrome or without metabolic syndrome, which showed higher levels of AT1 autoantibodies than non-parkinsonian controls. This is consistent with our recent studies, showing significant increase of AT1 and ACE2 autoantibodies in parkinsonian patients, which was related to dopaminergic degeneration and neuroinflammation. Altogether may lead to a vicious circle enhancing the progression of the disease that may be inhibited by strategies against production of these autoantibodies or AT1 receptor blockers (ARBs).

Angiotensin receptor blocker use is associated with upregulation of the memory-protective angiotensin type 4 receptor (AT4R) in the postmortem brains of individuals without cognitive impairment

The reported primary dementia-protective benefits of angiotensin II type 1 receptor (AT1R) blockers (ARB) are believed, at least in part, to arise from systemic effects on blood pressure. However, there is a specific and independently regulated brain renin-angiotensin system (RAS). Brain RAS acts mainly through three receptor subtypes; AT1R, AT2R, and AT4R. The AT1R promotes inflammation and mitochondrial reactive oxygen species generation. AT2R increases nitric oxide. AT4R is essential for dopamine and acetylcholine release. It is unknown whether ARB use is associated with changes in the brain RAS. Here, we compared the impact of treatment with ARB on not cognitively impaired individuals and individuals with Alzheimer's dementia using postmortem frontal-cortex samples of age- and sex-matched participants (70-90 years old, n = 30 in each group). We show that ARB use is associated with higher brain AT4R, lower oxidative stress, and amyloid-β burden in NCI participants. In AD, ARB use was associated with lower brain AT1R but had no impact on inflammation, oxidative stress, or amyloid-β burden. Our results may suggest a potential role for AT4R in the salutary effects for ARB on the brains of not cognitively impaired older adults.

Impact of genetic deletion of MrgD or Mas receptors in depressive-like behaviour in mice

OBJECTIVES

To evaluate the impact of genetic deletion of receptors of the counterregulatory arms of the renin-angiotensin system in depressive-like behaviours.

METHODS

8-12 weeks-old male mice wild type (WT, C57BL/6J) and mice with genetic deletion of MrgD (MrgD KO) or Mas receptors (Mas KO) were subjected to the Forced Swim Test (FST) and the Tail Suspension Test (TST). Brain-derived neurotrophic factor (BDNF) levels were measured by enzyme-linked immunosorbent assay (ELISA). Blockade of Mas was performed by acute intracerebroventricular (icv) injection of its selective antagonist, A779.

RESULTS

No statistical difference in immobility time was observed between MrgD KO and WT male animals subjected to FST and TST. However, acute icv injection of A779 significantly increased the immobility time of MrgD KO male mice subjected to FST and TST, suggesting the involvement of Mas in preventing depressive-like behaviour. Indeed, Mas KO male animals showed increased immobility time in FST and TST, evidencing a depressive-like behaviour in these animals, in addition to a reduction in BDNF levels in the prefrontal cortex and hippocampus. No changes in BDNF levels were observed in MrgD KO male animals.

CONCLUSION

Our data showed that Mas plays an important role in the neurobiology of depression probably by modulating BDNF expression. On the contrary, lack of MrgD did not alter depressive-like behaviour, which was supported by the lack of alterations in BDNF levels.

A review of literature on Compound 21-loaded gelatin nanoparticle: a promising nose-to-brain therapy for multi-infarct dementia

Multi-infarct dementia (MID) is described as a chronic progressive decline in cortical cognitive function due to the occurrence of multiple infarcts in the cerebral vascularization throughout the gray and white matter. Current therapies of MID mostly focus only on slowing down MID progression and symptomatic medications. A novel therapy which is able to provide both preventive and curative properties for MID is of high interest. The purpose of this review is to identify the potential of Compound 21 (C21) gelatin nanoparticle through the nose-to-brain route as therapy for MID. C21, an angiotensin II type 2 receptor (AT2R) agonist, has shown to reduce the size of cerebral infarct in rodent models, resulting in the preservation and improvement of overall cognitive function and prevention of secondary neurodegenerative effects. It is also shown that C21 decreases neuronal apoptosis, improves damaged axons, and encourage synapse development. The challenge remains in preventing systemic AT2R activation and increasing its low oral bioavailability which can be overcome through nose-to-brain administration of C21. Nose-to-brain drug delivery of C21 significantly increases drug efficiency and limits C21 exposure in order to specifically target the multiple infarcts located in the cerebral cortex. Adhering C21 onto gelatin nanoparticles may enable longer contact time with the olfactory and the trigeminal nerve endings, increasing the potency of C21. In summary, treatment of C21 gelatin nanoparticle through nose-to-brain delivery shows high potential as therapy for vascular dementia. However, clinical trials must be further studied in order to test the safety and efficacy of C21.

Chronic Neuroinflammation and Cognitive Decline in Patients with Cardiac Disease: Evidence, Relevance, and Therapeutic Implications

Acute and chronic cardiac disorders predispose to alterations in cognitive performance, ranging from mild cognitive impairment to overt dementia. Although this association is well-established, the factors inducing and accelerating cognitive decline beyond ageing and the intricate causal pathways and multilateral interdependencies involved remain poorly understood. Dysregulated and persistent inflammatory processes have been implicated as potentially causal mediators of the adverse consequences on brain function in patients with cardiac disease. Recent advances in positron emission tomography disclosed an enhanced level of neuroinflammation of cortical and subcortical brain regions as an important correlate of altered cognition in these patients. In preclinical and clinical investigations, the thereby involved domains and cell types of the brain are gradually better characterized. Microglia, resident myeloid cells of the central nervous system, appear to be of particular importance, as they are extremely sensitive to even subtle pathological alterations affecting their complex interplay with neighboring astrocytes, oligodendrocytes, infiltrating myeloid cells, and lymphocytes. Here, we review the current evidence linking cognitive impairment and chronic neuroinflammation in patients with various selected cardiac disorders including the aspect of chronic neuroinflammation as a potentially druggable target.

Role of angiotensin receptor blockers in the context of Alzheimer's disease

As the world's population ages, the prevalence of age-related neurological disorders such as Alzheimer's disease (AD) is increasing. There is currently no treatment for Alzheimer's disease, and the few approved medications have a low success rate in lowering symptoms. As a result, several attempts are underway worldwide to identify new targets for the therapy of Alzheimer's disease. In preclinical studies of Alzheimer's disease, it was recently found that inhibition of angiotensin-converting enzyme (ACE) and blocking of the angiotensin II receptors reduce symptoms of neurodegeneration, Aβ plaque development, and tau hyperphosphorylation. Angiotensin II type I (AT1) blockers, such as telmisartan, candesartan, valsartan, and others, have a wide safety margin and are commonly used to treat hypertension. Renal and cardiovascular failures are reduced due to their vascular protective actions. Inhibition of AT1 receptors in the brain has a neuroprotective impact in humans, reducing the risk of stroke, increasing cognition, and slowing the progression of Alzheimer's disease. The review focuses on the mechanisms via which AT1 blockers may act beneficially in Alzheimer's disease. Although their effect is evident in preclinical studies, clinical trials, on the other hand, are in short supply to validate the strategy. More dose-response experiments with possible AT1 blockers and brain-targeted administration will be needed in the future.

Sex-dependent effects of microglial reduction on impaired fear extinction induced by single prolonged stress

Single prolonged stress (SPS) is a preclinical rodent model for studying post-traumatic stress disorder (PTSD)-like behaviors. Previously we found that increased expression of the microglial marker Iba-1 in the ventral hippocampus after SPS exposure was associated with impaired fear extinction, suggesting that microglial activity contributed to the SPS-induced behavioral changes. To test this, we examined whether reducing microglia with the colony-stimulating factor 1 receptor blocker, PLX3397, in the diet would prevent the SPS-induced extinction impairment. Male rats exposed to SPS showed enhanced fear acquisition and impaired fear extinction memory. Adding PLX3397 to the diet prevented these behavioral changes. In contrast, PLX3397 did not prevent SPS from impairing fear extinction memory in the female rats. Despite the sex-dependent behavioral effects, we found a reduced number and area fraction of Iba-1+ microglia in both male and female rats suggesting that PLX3397 had similar effects on microglia in both sexes. Altogether, these results suggest that microglia contribute to the behavioral changes induced by SPS in male but not female rats.

Diminazene Ameliorates Neuroinflammation by Suppression of Astrocytic miRNA-224-5p/NLRP3 Axis in Alzheimer's Disease Model

Purpose

ACE2/Ang(1-7)/Mas Receptor, the momentous component of the renin-angiotensin system, has been shown to be involved in Alzheimer's disease (AD). We had previously found that enhancing brain ACE2 activity ameliorated cognitive impairment and attenuated brain neuroinflammation in SAMP8 mice, an animal model of AD. However, the exact mechanism of action of Diminazene (DIZE) has not been revealed.

Methods

APP/PS1 mice were injected intraperitoneally with DIZE. Cognitive functions, neuronal and synaptic integrity, and inflammation-related markers were assessed by Morris water maze, Nissl staining, Western blotting and ELISA, respectively. Since astrocytes played a crucial role in AD-related neuroinflammation whilst miRNAs were reported to participate in modulating inflammatory responses, astrocytes of APP/PS1 mice were then isolated for high-throughput miRNAs sequencing to identify the most differentially expressed miRNA following DIZE treatment. Afterward, the downstream pathway of this miRNA in the anti-inflammatory action of DIZE was investigated using primary astrocytes.

Results

The results showed that DIZE alleviated cognitive impairment and neuronal and synaptic damage in APP/PS1 mice. Simultaneously, DIZE suppressed the secretion of pro-inflammatory cytokines and the expression of NLRP3 inflammasome. Importantly, miR-224-5p was significantly up-regulated in the astrocytes of APP/PS1 mice treated by DIZE, and NLRP3 is one of the targets of miR-224-5p. Upregulation of miR-224-5p inhibited the expression of NLRP3 in Aβ1-42-stimulated cells, whereas miR-224-5p downregulation reversed this effect. Furthermore, the inhibition of miR-224-5p could reverse the inhibitory effect of DIZE on astrocytic NLRP3 inflammasome.

Conclusion

These findings firstly suggested that DIZE could inhibit astrocyte-regulated neuroinflammation via miRNA-224-5p/NLRP3 pathway. Furthermore, our study reveals the underlying mechanism by which DIZE suppresses neuroinflammatory responses in AD mice and uncovers the potential of DIZE in AD treatment.

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.

A New Perspective on the Renin-Angiotensin System

Cardiovascular disease (CVD) is the leading cause of death in the world. Hypertension is a serious medical problem not only in adults but also in children and adolescents. The renin-angiotensin-aldosterone system (RAAS) is one of the most important mechanisms regulating blood pressure and the balance of water and electrolytes. According to the latest reports, RAAS acts not only on endocrine but also on paracrine, autocrine, and intracrine. Moreover, RAAS has a component associated with hypotension and cardioprotective effects. These components are called alternative pathways of RAAS. The most important peptide of the alternative pathway is Ang 1-7, which is related to the Mas receptor. Mas receptors have widely known antihypertension properties, including vasodilatation, the release of nitric oxide, and increased production of anti-inflammatory cytokines. Another interesting peptide is angiotensin A, which combines the properties of the classical and alternative pathways. No less important components of RAAS are the proteolytic enzymes angiotensin convertase enzyme type 1 and 2. They are responsible for the functioning of the RAAS system and are a hypertension therapeutic target. Also involved are tissue-specific enzymes that form a local renin-angiotensin system. Currently, a combination of drugs is used in hypertension treatment. These drugs have many undesirable side effects that cannot always be avoided. For this reason, new treatments are being sought, and the greatest hope comes from the ACE2/ang 1-7/MasR axis.

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.

Renin-angiotensin-system increases phosphorylated tau and Reactive Oxygen Species in human cortical neuron cell line

Alzheimer's Disease (AD) is the most common cause of dementia. AD patients had increased extracellular amyloid β plaques and intracellular hyperphosphorylated tau (p-tau) in neurons. Recent studies have shown an association between the Renin-Angiotensin System (RAS) and AD. The involvement of RAS has been mediated through Angiotensin II (AngII), which is overexpressed in aging brains. However, the exact mechanism of how AngII contributes to AD is unknown. Thus, we hypothesize that AngII increases p-tau by activating its kinases, CDK5 and MAPK. In the human cortical neuron cell line, HCN2, treatment with AngII upregulated the gene expression of CDK5 (2.9 folds, p < 0.0001) and MAPTK (1.9 folds, p < 0.001). The AT1R antagonist, Losartan, blocked the changes in tau kinases. Also, AngII-induced the MAPK activation, increasing its phosphorylation by 400% (p < 0.0001), an increase that was also blocked by Losartan. An increase in p-tau by AngII was observed using fluorescent microscopy. We then quantified Reactive Oxygen Species (ROS) production, and it was significantly increased by AngII (p < 0.01), and treatment with Losartan blunted their production (p < 0.05). The data obtained demonstrated that AngII might contribute to the pathogenesis of AD.

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Angiotensin II increases CDK5 and MAPK gene expression in human cortical neuron cell line.

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Angiotensin II increases tau phosphorylation in human cortical neuron cell line.

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Angiotensin II increases Reactive Oxygen Species production in human cortical neuron cell line.

Microglial angiotensin type 2 receptors mediate sex-specific expression of inflammatory cytokines independently of circulating estrogen

There are sex differences in microglia, which can maintain sex-related gene expression and functional differences in the absence of circulating sex steroids. The angiotensin type 2 (AT2) receptors mediate anti-inflammatory actions in different tissues, including brain. In mice, we performed RT-PCR analysis of microglia isolated from adult brains and RNA scope in situ hybridization from males, females, ovariectomized females, orchiectomized males and brain masculinized females. We also compared wild type and AT2 knockout mice. The expression of AT2 receptors in microglial cells showed sex differences with much higher AT2 mRNA expression in females than in males, and this was not dependent on circulating gonadal hormones, as observed using ovariectomized females, brain masculinized females and orchiectomized males. These results suggest genomic reasons, possibly related to sex chromosome complement, for sex differences in AT2 expression in microglia, as the AT2 receptor gene is located in the X chromosome. Furthermore, sex differences in expression of AT2 receptors were associated to sex differences in microglial expression of key anti-inflammatory cytokines such as interleukin-10 and pro-inflammatory cytokines such as interleukin-1β and interleukin-6. In conclusion, sex differences in microglial AT2 receptor expression appear as a major factor contributing to sex differences in the neuroinflammatory responses beyond the effects of circulating steroids.

Microglia autophagy in ischemic stroke: A double-edged sword

Ischemic stroke (IS) is one of the major types of cerebrovascular diseases causing neurological morbidity and mortality worldwide. In the pathophysiological process of IS, microglia play a beneficial role in tissue repair. However, it could also cause cellular damage, consequently leading to cell death. Inflammation is characterized by the activation of microglia, and increasing evidence showed that autophagy interacts with inflammation through regulating correlative mediators and signaling pathways. In this paper, we summarized the beneficial and harmful effects of microglia in IS. In addition, we discussed the interplay between microglia autophagy and ischemic inflammation, as along with its application in the treatment of IS. We believe this could help to provide the theoretical references for further study into IS and treatments in the future.

The effect of AT1R-1166A/C and AT2R-1675A/G polymorphisms on susceptibility to preeclampsia: A systematic review and meta-analysis

BACKGROUND

The aim of this meta-analysis is to investigate the association between Angiotensin II type 1 receptor (AT1R)-1166A/C, Angiotensin II type 2 receptor (AT2R)-1675A/G polymorphisms and susceptibility to preeclampsia (PE).

METHODS

Online databases, including Web of Science, PubMed, EMBASE, CINAHL, CENTRAL, Scopus, Lilacs/SciELO, and Chinese National Knowledge Infrastructure, China Wan Fang, China Science and Technology Journal Database, were used to perform the literature search up to April 2022. The odds ratio (OR) and 95% confidence interval (CI) were used as effect size. The data was analyzed by Stata 15.0 software.

RESULTS

According to the inclusion and exclusion criteria, a total of 22 case-control studies were identified, including 3524 cases and 6308 controls. Our meta-analysis showed that the AT1R -1166 A/C allele was significantly associated with susceptibility to PE (A vs C: OR = 0.82, 95% CI: 0.69-0.96, P = .013), and there was significant difference in recessive gene model (AA vs AC + CC: OR = 0.81, 95% CI: 0.67-0.97, P = .021). However, no association was found between AT2R-1675A/G polymorphism and susceptibility to PE.

CONCLUSION

our meta-analysis suggested that AT1R-1166A/C polymorphism had an association with susceptibility to PE, but AT2R-1675A/G polymorphism had no association with susceptibility to PE.

Soluble ANPEP Released From Human Astrocytes as a Positive Regulator of Microglial Activation and Neuroinflammation: Brain Renin-Angiotensin System in Astrocyte-Microglia Crosstalk

Astrocytes are major supportive glia and immune modulators in the brain; they are highly secretory in nature and interact with other cell types via their secreted proteomes. To understand how astrocytes communicate during neuroinflammation, we profiled the secretome of human astrocytes following stimulation with proinflammatory factors. A total of 149 proteins were significantly upregulated in stimulated astrocytes, and a bioinformatics analysis of the astrocyte secretome revealed that the brain renin-angiotensin system (RAS) is an important mechanism of astrocyte communication. We observed that the levels of soluble form of aminopeptidase N (sANPEP), an RAS component that converts angiotensin (Ang) III to Ang IV in a neuroinflammatory milieu, significantly increased in the astrocyte secretome. To elucidate the role of sANPEP and Ang IV in neuroinflammation, we first evaluated the expression of Ang IV receptors in human glial cells because Ang IV mediates biological effects through its receptors. The expression of angiotensin type 1 receptor was considerably upregulated in activated human microglial cells but not in human astrocytes. Moreover, interleukin-1β release from human microglial cells was synergistically increased by cotreatment with sANPEP and its substrate, Ang III, suggesting the proinflammatory action of Ang IV generated by sANPEP. In a mouse neuroinflammation model, brain microglial activation and proinflammatory cytokine expression levels were increased by intracerebroventricular injection of sANPEP and attenuated by an enzymatic inhibitor and neutralizing antibody against sANPEP. Collectively, our results indicate that astrocytic sANPEP-induced increase in Ang IV exacerbates neuroinflammation by interacting with microglial proinflammatory receptor angiotensin type 1 receptor, highlighting an important role of indirect crosstalk between astrocytes and microglia through the brain RAS in neuroinflammation.

Cognitive dysfunction in SLE: An understudied clinical manifestation

Neuropsychiatric lupus (NPSLE) is a debilitating manifestation of SLE which occurs in a majority of SLE patients and has a variety of clinical manifestations. In the central nervous system, NPSLE may result from ischemia or penetration of inflammatory mediators and neurotoxic antibodies through the blood brain barrier (BBB). Here we focus on cognitive dysfunction (CD) as an NPSLE manifestation; it is common, underdiagnosed, and without specific therapy. For a very long time, clinicians ignored cognitive dysfunction and researchers who might be interested in the question struggled to find an approach to understanding mechanisms for this manifestation. Recent years, however, propelled by a more patient-centric approach to disease, have seen remarkable progress in our understanding of CD pathogenesis. This has been enabled through the use of novel imaging modalities and numerous mouse models. Overall, these studies point to a pivotal role of an impaired BBB and microglial activation in leading to neuronal injury. These insights suggest potential therapeutic modalities and make possible clinical trials for cognitive impairment.

Role of the renin-angiotensin system in the development of COVID-19-associated neurological manifestations

SARS-CoV-2 causes COVID-19, which has claimed millions of lives. This virus can infect various cells and tissues, including the brain, for which numerous neurological symptoms have been reported, ranging from mild and non-life-threatening (e.g., headaches, anosmia, dysgeusia, and disorientation) to severe and life-threatening symptoms (e.g., meningitis, ischemic stroke, and cerebral thrombosis). The cellular receptor for SARS-CoV-2 is angiotensin-converting enzyme 2 (ACE2), an enzyme that belongs to the renin-angiotensin system (RAS). RAS is an endocrine system that has been classically associated with regulating blood pressure and fluid and electrolyte balance; however, it is also involved in promoting inflammation, proliferation, fibrogenesis, and lipogenesis. Two pathways constitute the RAS with counter-balancing effects, which is the key to its regulation. The first axis (classical) is composed of angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and angiotensin type 1 receptor (AT1R) as the main effector, which -when activated- increases the production of aldosterone and antidiuretic hormone, sympathetic nervous system tone, blood pressure, vasoconstriction, fibrosis, inflammation, and reactive oxygen species (ROS) production. Both systemic and local classical RAS' within the brain are associated with cognitive impairment, cell death, and inflammation. The second axis (non-classical or alternative) includes ACE2, which converts Ang II to Ang-(1-7), a peptide molecule that activates Mas receptor (MasR) in charge of opposing Ang II/AT1R actions. Thus, the alternative RAS axis enhances cognition, synaptic remodeling, cell survival, cell signal transmission, and antioxidant/anti-inflammatory mechanisms in the brain. In a physiological state, both RAS axes remain balanced. However, some factors can dysregulate systemic and local RAS arms. The binding of SARS-CoV-2 to ACE2 causes the internalization and degradation of this enzyme, reducing its activity, and disrupting the balance of systemic and local RAS, which partially explain the appearance of some of the neurological symptoms associated with COVID-19. Therefore, this review aims to analyze the role of RAS in the development of the neurological effects due to SARS-CoV-2 infection. Moreover, we will discuss the RAS-molecular targets that could be used for therapeutic purposes to treat the short and long-term neurological COVID-19-related sequelae.

Inhibition of cGAS in Paraventricular Nucleus Attenuates Hypertensive Heart Injury Via Regulating Microglial Autophagy

Neuroinflammation in the cardiovascular center plays a critical role in the progression of hypertensive heart disease. And microglial autophagy is involved in the regulation of neuroinflammation. Cyclic GMP-AMP synthase (cGAS), a cytosolic DNA sensor, senses mitochondrial DNA (mtDNA) and regulates autophagy. The detailed mechanisms of central cGAS affects neuroinflammatory response in hypertensive heart disease via regulating autophagy remain unknown. Angiotensin II (Ang II, 1.5 mg·kg⁻¹·12 h⁻¹, 2 weeks) was intraperitoneally injected to induce hypertension in mice. The cGAS-STING pathway was activated in the paraventricular nucleus (PVN) of Ang II-induced hypertensive mice. The contractile dysfunction of heart was alleviated in Ang II-induced hypertensive cGAS^−/− mice. To observe the central effects of cGAS on regulating hypertensive heart disease, the RU.521 (a cGAS inhibitor) was intracisternally infused in hypertensive mice. Intracisternal infusion of the RU.521-alleviated myocardial interstitial fibrosis, cardiomyocyte hypertrophy, and the contractile dysfunction in Ang II-induced hypertensive mice. Intracisternal infusion of RU.521 attenuated the microglial activation, neuroinflammation, sympathetic/parasympathetic activity ratio, and lowered blood pressure. The autophagic flux in the PVN cells was blocked, while intracisternal infusion of RU.521 alleviated this effect in the Ang II-induced hypertensive mice. In vitro, it was found that cGAS-STING activation-induced autophagic flux blockage, while when the impaired autophagic flux was facilitated by rapamycin, an autophagy inducer, the microglial M1 polarization was decreased correspondingly. In conclusion, cGAS induces the inflammatory phenotype of microglia via impairing autophagic flux, thereby participating in neuroinflammation, which leads to sympathetic overactivation in hypertension and further caused hypertensive myocardial injury.

Contralesional angiotensin type 2 receptor activation contributes to recovery in experimental stroke

We and others have previously shown that angiotensin II receptor type 2 receptor (AT2R) is upregulated in the contralesional hemisphere after stroke in normoglycemic Wistar rats. In this study, we examined the expression of AT2R in type 2 diabetic Goto-Kakizaki (GK) rats and control Wistars after stroke. We also tested the contribution of the contralesional AT2R in recovery after stroke through a specific knockdown of the AT2R in this hemisphere only. Two experiments were conducted. In the first experiment, GK rats were subjected to middle cerebral artery occlusion (MCAO) and treated with the angiotensin II receptor type 1 receptor (AT1R) blocker candesartan or saline at reperfusion. Stroke outcomes, as well as AT2R expression, were examined and compared to control Wistars at 24 h. In the second experiment, localized AT2R knockdown was achieved through intrastriatal injection of short hairpin RNA (shRNA) lentiviral particles or non-targeting control into the left-brain hemisphere of Wistar rats. After 14 days, rats were subjected to right MCAO and treated with the AT2R agonist, Compound 21 (C21), or saline for 7 days. Behavioral outcomes were assessed for up to 10 days. In the first experiment, stroke reduced the expression of AT2R in GK rats. Candesartan treatment failed to improve the neurobehavioral outcomes, preserve vascular integrity or reduce oxidative/nitrative stress or apoptotic markers at 24 h post stroke in these animals. In the second experiment, contralesional AT2R knockdown reduced the C21-mediated functional recovery after stroke. In conclusion, contralesional AT2R upregulation after stroke is blunted in diabetic rats which show reduced sensitivity to post-stroke candesartan treatment. Contralesional AT2R could be involved in C21-mediated functional recovery after stroke.

The neuropeptide landscape of human prefrontal cortex

The neuropeptide system encompasses the most diverse family of neurotransmitters, but their expression, cellular localization, and functional role in the human brain have received limited attention. Here, we study human postmortem samples from prefrontal cortex (PFC), a key brain region, and employ RNA sequencing and RNAscope methods integrated with published single-cell data. Our aim is to characterize the distribution of peptides and their receptors in 17 PFC subregions and to explore their role in chemical signaling. The results suggest that the well-established anatomical and functional heterogeneity of human PFC is also reflected in the expression pattern of the neuropeptides. Our findings support ongoing efforts from academia and pharmaceutical companies to explore the potential of neuropeptide receptors as targets for drug development.

Human prefrontal cortex (hPFC) is a complex brain region involved in cognitive and emotional processes and several psychiatric disorders. Here, we present an overview of the distribution of the peptidergic systems in 17 subregions of hPFC and three reference cortices obtained by microdissection and based on RNA sequencing and RNAscope methods integrated with published single-cell transcriptomics data. We detected expression of 60 neuropeptides and 60 neuropeptide receptors in at least one of the hPFC subregions. The results reveal that the peptidergic landscape in PFC consists of closely located and functionally different subregions with unique peptide/transmitter–related profiles. Neuropeptide-rich PFC subregions were identified, encompassing regions from anterior cingulate cortex/orbitofrontal gyrus. Furthermore, marked differences in gene expression exist between different PFC regions (>5-fold; cocaine and amphetamine–regulated transcript peptide) as well as between PFC regions and reference regions, for example, for somatostatin and several receptors. We suggest that the present approach allows definition of, still hypothetical, microcircuits exemplified by glutamatergic neurons expressing a peptide cotransmitter either as an agonist (hypocretin/orexin) or antagonist (galanin). Specific neuropeptide receptors have been identified as possible targets for neuronal afferents and, interestingly, peripheral blood-borne peptide hormones (leptin, adiponectin, gastric inhibitory peptide, glucagon-like peptides, and peptide YY). Together with other recent publications, our results support the view that neuropeptide systems may play an important role in hPFC and underpin the concept that neuropeptide signaling helps stabilize circuit connectivity and fine-tune/modulate PFC functions executed during health and disease.

Antihypertensive drugs and brain function: mechanisms underlying therapeutically beneficial and harmful neuropsychiatric effects

A bidirectional relationship exists between hypertension and psychiatric disorders, including unipolar and bipolar depression, anxiety, post-traumatic stress disorder (PTSD), psychosis, schizophrenia, mania, and dementia/cognitive decline. Repurposing of antihypertensive drugs to treat mental disorders is thus being explored. A systematic knowledge of the mechanisms of action and clinical consequences of the use of antihypertensive agents on neuropsychiatric functions has not been achieved yet. In this article, we review the putative role of antihypertensive agents in psychiatric disorders, discuss the targets and mechanisms of action, and examine how and to what extent specific drug classes/molecules may trigger, worsen, or mitigate psychiatric symptoms. In addition, we review pharmacokinetics (brain penetration of drugs) and pharmacogenetics data that add important information to assess risks and benefits of antihypertensive drugs in neuropsychiatric settings. The scientific literature shows robust evidence of a positive effect of α1 blockers on PTSD symptoms, nightmares and sleep quality, α2 agonists on core symptoms, executive function and quality of life in Attention-Deficit/Hyperactivity Disorder, PTSD, Tourette's syndrome, and β blockers on anxiety, aggression, working memory, and social communication. Renin-angiotensin system modulators exert protective effects on cognition, depression, and anxiety, and the loop diuretic bumetanide reduced the core symptoms of autism in a subset of patients. There is no evidence of clear benefits of calcium channel blockers in mood disorders in the scientific literature. These findings are mainly from preclinical studies; clinical data are still insufficient or of anecdotal nature, and seldom systematic. The information herewith provided can support a better therapeutic approach to hypertension, tailored to patients with, or with high susceptibility to, psychiatric illness. It may prompt clinical studies exploring the potential benefit of antihypertensive drugs in selected patients with neuropsychiatric comorbidities that include outcomes of neuropsychiatric interest and specifically assess undesirable effects or interactions.

Angiotensin type-1 receptor and ACE2 autoantibodies in Parkinson´s disease

The role of autoimmunity in neurodegeneration has been increasingly suggested. The renin-angiotensin system (RAS) autoantibodies play a major role in several peripheral inflammatory processes. Dysregulation of brain RAS has been involved in neuroinflammation and neurodegeneration. We aimed to know whether angiotensin type-1 receptor (AT1) autoantibodies (AT1 agonists) and angiotensin-converting enzyme 2 (ACE2) autoantibodies (ACE2 antagonists) may be involved in Parkinson's disease (PD) progression and constitute a new therapeutical target. Both AT1 and ACE2 serum autoantibodies were higher in a group of 117 PD patients than in a group of 106 controls. Serum AT1 autoantibodies correlated with several cytokines, particularly Tumor Necrosis Factor Ligand Superfamily Member 14 (TNFSF14, LIGHT), and 27-hydroxycholesterol levels. Serum ACE2 autoantibodies correlated with AT1 autoantibodies. Both autoantibodies were found in cerebrospinal fluid (CSF) of four PD patients with CSF samples. Consistent with the observations in patients, experimental dopaminergic degeneration, induced by 6-hydroxydopamine, increased levels of autoantibodies in serum and CSF in rats, as well as LIGHT levels and transglutaminase activity in rat substantia nigra. In cultures, administration of AT1 autoantibodies enhanced dopaminergic neuron degeneration and increased levels of neuroinflammation markers, which was inhibited by the AT1 antagonist candesartan. The results suggest dysregulation of RAS autoantibodies as a new mechanism that can contribute to PD progression. Therapeutical strategies blocking the production, or the effects of these autoantibodies may be useful for PD treatment, and the results further support repurposing AT1 blockers (ARBs) as treatment against PD progression.

Cross-translational models of late-onset cognitive sequelae and their treatment in pediatric brain tumor survivors

Pediatric brain tumor treatments have a high success rate, but survivors are at risk of cognitive sequelae that impact long-term quality of life. We summarize recent clinical and animal model research addressing pathogenesis or evaluating candidate interventions for treatment-induced cognitive sequelae. Assayed interventions encompass a broad range of approaches, including modifications to radiotherapy, modulation of immune response, prevention of treatment-induced cell loss or promotion of cell renewal, manipulation of neuronal signaling, and lifestyle/environmental adjustments. We further emphasize the potential of neuroimaging as a key component of cross-translation to contextualize laboratory research within broader clinical findings. This cross-translational approach has the potential to accelerate discovery to improve pediatric cancer survivors' long-term quality of life.

The Pathophysiology of Long COVID throughout the Renin-Angiotensin System

COVID-19 has expanded across the world since its discovery in Wuhan (China) and has had a significant impact on people’s lives and health. Long COVID is a term coined by the World Health Organization (WHO) to describe a variety of persistent symptoms after acute SARS-CoV-2 infection. Long COVID has been demonstrated to affect various SARS-CoV-2-infected persons, independently of the acute disease severity. The symptoms of long COVID, like acute COVID-19, consist in the set of damage to various organs and systems such as the respiratory, cardiovascular, neurological, endocrine, urinary, and immune systems. Fatigue, dyspnea, cardiac abnormalities, cognitive and attention impairments, sleep disturbances, post-traumatic stress disorder, muscle pain, concentration problems, and headache were all reported as symptoms of long COVID. At the molecular level, the renin-angiotensin system (RAS) is heavily involved in the pathogenesis of this illness, much as it is in the acute phase of the viral infection. In this review, we summarize the impact of long COVID on several organs and tissues, with a special focus on the significance of the RAS in the disease pathogenesis. Long COVID risk factors and potential therapy approaches are also explored.

Chinese Classical Music Lowers Blood Pressure and Improves Left Ventricular Hypertrophy in Spontaneously Hypertensive Rats

High blood pressure (BP) plays an important role in the pathogenesis and development of cardiovascular diseases and multi-organ damages. Music has been well known to elicit emotional changes, such as anxiolytic effects. However, whether music therapy lowers BP in spontaneously hypertensive rats (SHR) and the potential mechanism remains unknown. SHRs were, respectively exposed to white noise (WN), Western classical music (WM), Chinese classical music (CCM), rock music (RM), and bisoprolol treatment. WN and WM did not lower systemic BP, but CCM and RM significantly lowered BPs in SHRs. The effects of CCM therapy on lowering systemic BPs is comparable to that of bisoprolol at the dose of low to medium. Combination of CCM treatment with bisoprolol further improved systemic BPs and myocardial hypertrophy in SHRs, compared to CCM treatment or bisoprolol alone. Furthermore, IHC and WB analysis indicated that CCM therapy inhibited the β1/cAMP/PKA and α1/PLC/PKC signalings, but didn’t alter the β2/PI3K/Akt signaling. Above all, CCM therapy lowers systemic BPs and alleviates myocardial hypertrophy in hypertensive rats, which may be caused by the inhibitions of β1/cAMP/PKA and α1/PLC/PKC signalings.

Targeting brain Renin-Angiotensin System for the prevention and treatment of Alzheimer's disease: Past, present and future

Alzheimer's disease (AD) is a well-known neurodegenerative disease characterized by the presence of two main hallmarks - Tau hyperphosphorylation and Aβ deposits. Notwithstanding, in the last few years the scientific evidence about the drivers of AD have been changing and nowadays age-related vascular alterations and several cardiovascular risk factors have been shown to trigger the development of AD. In this context, drugs targeting the Renin Angiotensin System (RAS), commonly used for the treatment of hypertension, are evidencing a high potential to delay AD development due to their action on brain RAS. Indeed, the ACE 1/Ang II/AT1R axis is believed to be upregulated in AD and to be responsible for deleterious effects such as increased oxidative stress, neuroinflammation, blood-brain barrier (BBB) hyperpermeability, astrocytes dysfunction and a decrease in cerebral blood flow. In contrast, the alternative axis - ACE 1/Ang II/AT2R; ACE 2/Ang (1-7)/MasR; Ang IV/ AT4R(IRAP) - seems to counterbalance the deleterious effects of the principal axis and to exert beneficial effects on memory and cognition. Accordingly, retrospective studies demonstrate a reduced risk of developing AD among people taking RAS medication as well as several in vitro and in vivo pre-clinical studies as it is herein critically reviewed. In this review, we first revise, at a glance, the pathophysiology of AD focused on its classic hallmarks. Secondly, an overview about the impact of the RAS on the pathophysiology of AD is also provided, focused on their four essential axes ACE 1/Ang II/AT2R; ACE 2/Ang (1-7)/MasR; Ang IV/ AT4R(IRAP) and ACE 1/Ang II/AT1R. Finally, the therapeutic potential of available drugs targeting RAS on AD, namely angiotensin II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs), is highlighted and data supporting this hope will be presented, from in vitro and in vivo pre-clinical to clinical studies.

NF-κB Signaling-Mediated Activation of WNK-SPAK-NKCC1 Cascade in Worsened Stroke Outcomes of Ang II-Hypertensive Mice

BACKGROUND

Worsened stroke outcomes with hypertension comorbidity are insensitive to blood pressure-lowering therapies. In an experimental stroke model with comorbid hypertension, we investigated causal roles of ang II (angiotensin II)-mediated stimulation of the brain WNK (with no lysine [K] kinases)-SPAK (STE20/SPS1-related proline/alanine-rich kinase)-NKCC1 (Na-K-Cl cotransporter) complex in worsened outcomes.

METHODS

Saline- or ang II-infused C57BL/6J male mice underwent stroke induced by permanent occlusion of the distal branches of the middle cerebral artery. Mice were randomly assigned to receive either vehicle dimethyl sulfoxide/PBS (2 mL/kg body weight/day, IP), a novel SPAK inhibitor, 5-chloro-N-(5-chloro-4-((4-chlorophenyl)(cyano)methyl)-2-methylphenyl)-2-hydroxybenzamide (ZT-1a' 5 mg/kg per day, IP) or a NF-κB (nuclear factor-κB) inhibitor TAT-NBD (transactivator of transcription-NEMO-binding domain' 20 mg/kg per day, IP). Activation of brain NF-κB and WNK-SPAK-NKCC1 cascade as well as ischemic stroke outcomes were examined.

RESULTS

Stroke triggered a 2- to 5-fold increase of WNK (isoforms 1, 2, 4), SPAK/OSR1 (oxidative stress-responsive kinase 1), and NKCC1 protein in the ang II-infused hypertensive mouse brains at 24 hours after stroke, which was associated with increased nuclear translocation of phospho-NF-κB protein in the cortical neurons (a Pearson correlation r of 0.77, P<0.005). The upregulation of WNK-SPAK-NKCC1 cascade proteins resulted from increased NF-κB recruitment on Wnk1, Wnk2, Wnk4, Spak, and Nkcc1 gene promoters and was attenuated by NF-κB inhibitor TAT-NBD. Poststroke administration of SPAK inhibitor ZT-1a significantly reduced WNK-SPAK-NKCC1 complex activation, brain lesion size, and neurological function deficits in the ang II-hypertensive mice without affecting blood pressure and cerebral blood flow.

CONCLUSIONS

The ang II-induced stimulation of NF-κB transcriptional activity upregulates brain WNK-SPAK-NKCC1 cascade and contributes to worsened ischemic stroke outcomes, illustrating the brain WNK-SPAK-NKCC1 complex as a therapeutic target for stroke with comorbid hypertension.

Insights Into Vascular Anomalies, Cancer, and Fibroproliferative Conditions: The Role of Stem Cells and the Renin-Angiotensin System

Cells exhibiting embryonic stem cell (ESC) characteristics have been demonstrated in vascular anomalies (VAs), cancer, and fibroproliferative conditions, which are commonly managed by plastic surgeons and remain largely unsolved. The efficacy of the mTOR inhibitor sirolimus, and targeted therapies that block the Ras/BRAF/MEK/ERK1/2 and PI3KCA/AKT/mTOR pathways in many types of cancer and VAs, further supports the critical role of ESC-like cells in the pathogenesis of these conditions. ESC-like cells in VAs, cancer, and fibroproliferative conditions express components of the renin-angiotensin system (RAS) – a homeostatic endocrine signaling cascade that regulates cells with ESC characteristics. ESC-like cells are influenced by the Ras/BRAF/MEK/ERK1/2 and PI3KCA/AKT/mTOR pathways, which directly regulate cellular proliferation and stemness, and interact with the RAS at multiple points. Gain-of-function mutations affecting these pathways have been identified in many types of cancer and VAs, that have been treated with targeted therapies with some success. In cancer, the RAS promotes tumor progression, treatment resistance, recurrence, and metastasis. The RAS modulates cellular invasion, migration, proliferation, and angiogenesis. It also indirectly regulates ESC-like cells via its direct influence on the tissue microenvironment and by its interaction with the immune system. In vitro studies show that RAS inhibition suppresses the hallmarks of cancer in different experimental models. Numerous epidemiological studies show a reduced incidence of cancer and improved survival outcomes in patients taking RAS inhibitors, although some studies have shown no such effect. The discovery of ESC-like cells that express RAS components in infantile hemangioma (IH) underscores the paradigm shift in the understanding of its programmed biologic behavior and accelerated involution induced by β-blockers and angiotensin-converting enzyme inhibitors. The findings of SOX18 inhibition by R-propranolol suggests the possibility of targeting ESC-like cells in IH without β-adrenergic blockade, and its associated side effects. This article provides an overview of the current knowledge of ESC-like cells and the RAS in VAs, cancer, and fibroproliferative conditions. It also highlights new lines of research and potential novel therapeutic approaches for these unsolved problems in plastic surgery, by targeting the ESC-like cells through manipulation of the RAS, its bypass loops and converging signaling pathways using existing low-cost, commonly available, and safe oral medications.

Potential Neuroprotective Effect of Cannabinoids in Covid-19 Patients

The global pandemic caused by the SARS-CoV-2 virus began in early 2020 and is still present. The respiratory symptoms caused by COVID-19 are well established, however, neurological manifestations that may result from direct or indirect neurological damage after SARS-CoV-2 infection have been reported frequently. The main proposed pathophysiological processes leading to neurological damage in COVID-19 are cerebrovascular disease, and indirect mechanisms of inflammatory / autoimmune origin. A growing number of studies confirm that neuroprotective measures should be maintained in COVID-19 patients. On the other hand, cannabinoids have been the subject of various studies that propose them as potential promising drugs in chronic neurodegenerative diseases due to their powerful neuroprotective potential. In this review we address the possible mechanism of action of cannabinoids as a neuroprotective treatment in patients infected by SARS-CoV-2. The endocannabinoid system is found in multiple systems within the body, including the immune system. Its activation can lead to beneficial results, such as a decrease in viral entry, a decrease in viral replication, and a decrease in pro-inflammatory cytokines such as IL-2, IL-4, IL-6, IL-12, TNF-α or IFN-c through CB2R expression induced during inflammation by SARS-CoV-2 infection in the central nervous system.

Higher Angiotensin II Type 1 Receptor Levels and Activity in the Postmortem Brains of Older Persons with Alzheimer's Dementia

Aging is a key risk factor in Alzheimer's dementia (AD) development and progression. The primary dementia-protective benefits of angiotensin II subtype 1 receptor (AT1R) blockers are believed to arise from systemic effects on blood pressure. However, a brain-specific renin-angiotensin system (b-RAS) exists, which can be altered by AT1R blockers. Brain RAS acts mainly through 3 angiotensin receptors: AT1R, AT2R, and AT4R. Changes in these brain angiotensin receptors may accelerate the progression of AD. Using postmortem frontal cortex brain samples of age- and sex-matched cognitively normal individuals (n = 30) and AD patients (n = 30), we sought to dissect the b-RAS changes associated with AD and assess how these changes correlate with brain markers of oxidative stress, inflammation, and mitochondrial dysfunction as well as amyloid-β and paired helical filament tau pathologies. Our results show higher protein levels of the pro-inflammatory AT1R and phospho-ERK (pERK) in the brains of AD participants. Brain AT1R levels and pERK correlated with higher oxidative stress, lower cognitive performance, and higher tangle and amyloid-β scores. This study identifies molecular changes in b-RAS and offers insight into the role of b-RAS in AD-related brain pathology.

Angiotensin-(1-7) as a Potential Therapeutic Strategy for Delayed Cerebral Ischemia in Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a substantial cause of mortality and morbidity worldwide. Moreover, survivors after the initial bleeding are often subject to secondary brain injuries and delayed cerebral ischemia, further increasing the risk of a poor outcome. In recent years, the renin-angiotensin system (RAS) has been proposed as a target pathway for therapeutic interventions after brain injury. The RAS is a complex system of biochemical reactions critical for several systemic functions, namely, inflammation, vascular tone, endothelial activation, water balance, fibrosis, and apoptosis. The RAS system is classically divided into a pro-inflammatory axis, mediated by angiotensin (Ang)-II and its specific receptor AT₁R, and a counterbalancing system, presented in humans as Ang-(1-7) and its receptor, MasR. Experimental data suggest that upregulation of the Ang-(1-7)/MasR axis might be neuroprotective in numerous pathological conditions, namely, ischemic stroke, cognitive disorders, Parkinson's disease, and depression. In the presence of SAH, Ang-(1-7)/MasR neuroprotective and modulating properties could help reduce brain damage by acting on neuroinflammation, and through direct vascular and anti-thrombotic effects. Here we review the role of RAS in brain ischemia, with specific focus on SAH and the therapeutic potential of Ang-(1-7).

Neuroinflammation and COVID-19 Ischemic Stroke Recovery—Evolving Evidence for the Mediating Roles of the ACE2/Angiotensin-(1–7)/Mas Receptor Axis and NLRP3 Inflammasome

Cerebrovascular events, notably acute ischemic strokes (AIS), have been reported in the setting of novel coronavirus disease (COVID-19) infection. Commonly regarded as cryptogenic, to date, the etiology is thought to be multifactorial and remains obscure; it is linked either to a direct viral invasion or to an indirect virus-induced prothrombotic state, with or without the presence of conventional cerebrovascular risk factors. In addition, patients are at a greater risk of developing long-term negative sequelae, i.e., long-COVID-related neurological problems, when compared to non-COVID-19 stroke patients. Central to the underlying neurobiology of stroke recovery in the context of COVID-19 infection is reduced angiotensin-converting enzyme 2 (ACE2) expression, which is known to lead to thrombo-inflammation and ACE2/angiotensin-(1–7)/mitochondrial assembly receptor (MasR) (ACE2/Ang-(1-7)/MasR) axis inhibition. Moreover, after AIS, the activated nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome may heighten the production of numerous proinflammatory cytokines, mediating neuro-glial cell dysfunction, ultimately leading to nerve-cell death. Therefore, potential neuroprotective therapies targeting the molecular mechanisms of the aforementioned mediators may help to inform rehabilitation strategies to improve brain reorganization (i.e., neuro-gliogenesis and synaptogenesis) and secondary prevention among AIS patients with or without COVID-19. Therefore, this narrative review aims to evaluate the mediating role of the ACE2/Ang- (1-7)/MasR axis and NLRP3 inflammasome in COVID-19-mediated AIS, as well as the prospects of these neuroinflammation mediators for brain repair and in secondary prevention strategies against AIS in stroke rehabilitation.

Shared Molecular Targets in Parkinson’s Disease and Arterial Hypertension: A Systematic Review

(1) Background: Parkinson’s disease and arterial hypertension are likely to coexist in the elderly, with possible bidirectional interactions. We aimed to assess the role of antihypertensive agents in PD emergence and/or progression. (2) We performed a systematic search on the PubMed database. Studies enrolling patients with Parkinson’s disease who underwent treatment with drugs pertaining to one of the major antihypertensive drug classes (β-blockers, diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and calcium-channel blockers) prior to or after the diagnosis of parkinsonism were scrutinized. We divided the outcome into two categories: neuroprotective and disease-modifying effect. (3) We included 20 studies in the qualitative synthesis, out of which the majority were observational studies, with only one randomized controlled trial. There are conflicting results regarding the effect of antihypertensive drugs on Parkinson’s disease pathogenesis, mainly because of heterogeneous protocols and population. (4) Conclusions: There is low quality evidence that antihypertensive agents might be potential therapeutic targets in Parkinson’s disease, but this hypothesis needs further testing.

Determinants and Mechanisms of the Renin-Aldosterone Stress Response

OBJECTIVE

The renin-angiotensin-aldosterone system (RAAS) plays a relevant role in regulating blood pressure and thus maintaining cardiovascular homeostasis. Although it was recently shown that RAAS parameters are responsive to acute psychosocial stress, the psychobiological determinants of the acute stress-induced RAAS activation have not yet been investigated. In a randomized placebo-controlled design, we investigated potential psychological and physiological determinants of the RAAS response and underlying mechanisms.

METHODS

Fifty-seven young healthy male participants underwent either an acute standardized psychosocial stress test or a nonstress placebo task. We measured aldosterone in plasma and saliva, as well as renin, and the stress-reactive endocrine measures adrenocorticotropic hormone (ACTH), epinephrine, and norepinephrine in plasma at rest, immediately after the task and several times up to 3 hours thereafter. Moreover, we assessed stress-reactive psychological (anticipatory cognitive stress appraisal, mood, physical discomfort) and basal demographic-physiological measures (age, body mass index, blood pressure).

RESULTS

Acute psychosocial stress elicited changes in all assessed endocrine (p values ≤ .028, ηp2 values ≥ 0.07) and stress-reactive psychological measures (p values ≤ .003, ηp2 values ≥ 0.15). The basal parameter body mass index, the stress-reactive endocrine parameters ACTH and norepinephrine, and the psychological parameter anticipatory stress appraisal were identified as determinants of higher RAAS parameter reactivity to acute psychosocial stress. The association between anticipatory cognitive stress appraisal and plasma RAAS measures was fully mediated by ACTH increases (p values ≤ .044, ηp2 values ≥ 0.05).

CONCLUSIONS

Cognitive stress appraisal processes seem to modulate RAAS stress reactivity. This points to potential clinical implications for psychoeducative therapeutical interventions targeting stress appraisal processes to reduce endocrine stress reactivity.

Implications of testicular ACE2 and the renin-angiotensin system for SARS-CoV-2 on testis function

Although many studies have focused on SARS-CoV-2 infection in the lungs, comparatively little is known about the potential effects of the virus on male fertility. SARS-CoV-2 infection of target cells requires the presence of furin, angiotensin-converting enzyme 2 (ACE2) receptors, and transmembrane protease serine 2 (TMPRSS2). Thus, cells in the body that express these proteins might be highly susceptible to viral entry and downstream effects. Currently, reports regarding the expression of the viral entry proteins in the testes are conflicting; however, other members of the SARS-CoV family of viruses - such as SARS-CoV - have been suspected to cause testicular dysfunction and/or orchitis. SARS-CoV-2, which displays many similarities to SARS-CoV, could potentially cause similar adverse effects. Commonalities between SARS family members, taken in combination with sparse reports of testicular discomfort and altered hormone levels in patients with SARS-CoV-2, might indicate possible testicular dysfunction. Thus, SARS-CoV-2 infection has the potential for effects on testis somatic and germline cells and experimental approaches might be required to help identify potential short-term and long-term effects of SARS-CoV-2 on male fertility.

Renin-angiotensin system: Basic and clinical aspects-A general perspective

The renin–angiotensin system (RAS) is one of the most complex hormonal regulatory systems, involving several organs that interact to regulate multiple body functions. The study of this system initially focused on investigating its role in the regulation of both cardiovascular function and related pathologies. From this approach, pharmacological strategies were developed for the treatment of cardiovascular diseases. However, new findings in recent decades have suggested that the RAS is much more complex and comprises two subsystems, the classic RAS and an alternative RAS, with antagonistic effects that are usually in equilibrium. The classic system is involved in pathologies where inflammatory, hypertrophic and fibrotic phenomena are common and is related to the development of chronic diseases that affect various body systems. This understanding has been reinforced by the evidence that local renin–angiotensin systems exist in many tissue types and by the role of the RAS in the spread and severity of COVID-19 infection, where it was discovered that viral entry into cells of the respiratory system is accomplished through binding to angiotensin-converting enzyme 2, which is present in the alveolar epithelium and is overexpressed in patients with chronic cardiometabolic diseases. In this narrative review, preclinical and clinical aspects of the RAS are presented and topics for future research are discussed some aspects are raised that should be clarified in the future and that call for further investigation of this system.

(Pro)renin Receptor and Blood Pressure Regulation: A Focus on the Central Nervous System

The renin-angiotensin system (RAS) is classically described as a hormonal system in which angiotensin II (Ang II) is one of the main active peptides. The action of circulating Ang II on its cognate Ang II type-1 receptor (AT1R) in circumventricular organs has important roles in regulating the autonomic nervous system, blood pressure (BP) and body fluid homeostasis, and has more recently been implicated in cardiovascular metabolism. The presence of a local or tissue RAS in various tissues, including the central nervous system (CNS), is well established. However, because the level of renin, the rate-limiting enzyme in the systemic RAS, is very low in the brain, how endogenous angiotensin peptides are generated in the CNS-the focus of this review-has been the subject of considerable debate. Notable in this context is the identification of the (pro)renin receptor (PRR) as a key component of the brain RAS in the production of Ang II in the CNS. In this review, we highlight cellular and anatomical locations of the PRR in the CNS. We also summarize studies using gain- and loss-of function approaches to elucidate the functional importance of brain PRR-mediated Ang II formation and brain RAS activation, as well as PRR-mediated Ang II-independent signaling pathways, in regulating BP. We further discuss recent developments in PRR involvement in cardiovascular and metabolic diseases and present perspectives for future directions.

Localization and expression of the Mas-related G-protein coupled receptor member D (MrgD) in the mouse brain

Numerous studies in the last decades have provided evidence for the existence of a local renin-angiotensin system (RAS) in the central nervous system (CNS). Widespread distribution of the different RAS components in the brain demonstrates the pleiotropic role of this system in the structure and function of CNS. With the advent of new molecular techniques, a novel receptor has been identified within the beneficial arm of the RAS, the Mas-related G-protein coupled receptor D (MrgD), which can be stimulated by two heptapeptides, Ala¹-(Ang-(1-7), also named alamandine, and Ang-(1-7). However, the biological and physiological relevance of this interaction remains obscure. Since several recent studies hinted at a role of MrgD in the CNS, we determined the distribution pattern of MrgD receptors in the adult mouse brain by using a genetic mouse model with tracers of MrgD expression. MrgD-positive cells could be identified in some forebrain areas, including cortex, hippocampus, amygdala, hypothalamus, habenular nuclei, striatum and pallidum, as well as in some mid-brain nuclei in a region-specific manner. The specific localization of MrgD in the reward- and limbic-related areas can hint at a role of MrgD in processes such as pain perception/modulation, synaptic plasticity, learning, memory and cognition.

Countering the classical renin-angiotensin system

It is well-established that Ang-(1-7) counteracts the effects of Ang II in the periphery, while stimulating vasopressin release and mimicking the activity of Ang II in the brain, through interactions with various receptors. The rapid metabolic inactivation of Ang-(1-7) has proven to be a limitation to therapeutic administration of the peptide. To circumvent this problem, Alves et al. (Clinical Science (2021) 135(18), https://doi.org/10.1042/CS20210599) developed a new transgenic rat model that overexpresses an Ang-(1-7)-producing fusion protein. In this commentary, we discuss potential concerns with this model while also highlighting advances that can ensue from this significant technical feat.

Chronic Renin-Angiotensin System Activation Induced Neuroinflammation: Common Mechanisms Underlying Hypertension and Dementia?

Hypertension is a major risk factor for the pathogenesis of vascular dementia and Alzheimer's disease. Chronic activation of the renin-angiotensin system (RAS) contributes substantially to neuroinflammation. We propose that neuroinflammation arising from chronic RAS activation can initiate and potentiate the onset of hypertension and related dementia. Neuroinflammation induced by chronic activation of the RAS plays a key role in the pathogenesis of dementia. Increased levels of pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and transforming growth factor (TGF)-β have been reported in brain tissue of vascular dementia patients and animal models of vascular dementia induced by either angiotensin II infusion or transverse aortic coarctation. It is proposed that neuronal cell death and synaptic dysfunction induced by neuroinflammation lead to cognitive impairment in dementia. The neuroprotective RAS pathway, regulated by angiotensin-converting enzyme 2 (ACE2) which converts angiotensin II into angiotensin-(1-7), can attenuate hypertension and dementia. Furthermore, the use of anti-hypertensive medications in preventing dementia or cognitive decline in hypertensive patients and animal models of dementia have mostly been beneficial. Current evidence suggests a strong link between RAS induced neuroinflammation and the onset of hypertension and dementia, which warrants further investigation. Strategies to counteract an overactive RAS and enhance the neuroprotective arm of the RAS may help prevent or improve cognitive impairment associated with hypertension.

Stimulation of angiotensin II receptor 2 preserves cognitive function and is associated with an enhanced cerebral vascular density after stroke

Angiotensin signaling is known to be sexually dimorphic. Although it is a well-studied target for intervention in stroke and cognitive impairment, female studies are rare. With females suffering a disproportionately greater negative impact of stroke and dementia vs. males, effective interventions are of utmost urgency. The aim of the current study was to determine the impact of activation of the angiotensin II type 2 receptor (AT2R) with the agonist compound 21 (C21) on the development of post-stroke cognitive impairment, after experimental ischemic stroke. Ovariectomized (OVX) spontaneously hypertensive rats (SHRs) were subjected to 1 h of middle cerebral artery occlusion (MCAO). At 24 h, rats with a significant neurologic deficit were randomized to receive either saline or C21 (0.03 mg/kg/day) intraperitoneally (IP) for 5 days, then orally (0.12 mg/kg/day) for a total of 6 weeks. Cognitive function, brain structure by MRI and vascular architecture by microCT angiography were measured. C21 preserved cognitive function, specifically spatial memory, and improved vascular density in the ischemic hemisphere at 6 weeks, reflecting both arteriogenesis and angiogenesis. In conclusion, C21 prevented cognitive impairment after stroke, likely through a mechanism involving vascular protection and restoration.

The Protective Effects of AT2R Agonist, CGP42112A, Against Angiotensin II-Induced Oxidative Stress and Inflammatory Response in Astrocytes: Role of AT2R/PP2A/NFκB/ROS Signaling

Angiotensin II receptor type 2 (AT2R) agonists have been known to promote neuroprotection by limiting ischemic insult, neuronal proliferation, and differentiation. Further, AT2R agonists have also been associated with the suppression of neuroinflammation and neurodegeneration. Of note, brain astrocytes play a critical role in these neuroinflammatory and neurodegenerative processes. However, the role of AT2R in astrocytic activation remains elusive. Therefore, this study evaluated the role and molecular mechanism of AT2R agonist CGP42112A (CGP) against Angiotensin II (Ang II)-induced astrocytic activation in primary astrocytes, and in a rat model of hypertension. Here, we demonstrated that AT2R activation by CGP abrogated Ang II-induced astrocytic activation, by mitigating the ROS production, mitochondrial dysfunction, IκB-α degradation, NFκB nuclear translocation, and release of TNF-α in astrocytes. However, AT2R-mediated anti-inflammatory effects were reversed by AT2R antagonist, PD123319 (PD), in both in vitro and in vivo conditions. Mechanistically, AT2R via protein phosphatase-2A (PP2A) abrogated the Ang II-induced NFκB activation, ROS generation, and subsequent astrocytic activation. Importantly, PP2A antagonist, okadaic acid, reversed the anti-inflammatory effects of AT2R in Ang II-stimulated primary astrocytes and in the cortex of hypertensive rats. Thus, the present study suggests that AT2R by activating PP2A inhibits oxidative stress and NFκB activation, thereby preventing the astrocytic pro-inflammatory activation. Therefore, AT2R might be advantageous therapeutic target for neuroinflammatory/neurodegenerative diseases perpetuated by astrocytic activation.

Angiotensin II and the Cardiac Parasympathetic Nervous System in Hypertension

The renin-angiotensin-aldosterone system (RAAS) impacts cardiovascular homeostasis via direct actions on peripheral blood vessels and via modulation of the autonomic nervous system. To date, research has primarily focused on the actions of the RAAS on the sympathetic nervous system. Here, we review the critical role of the RAAS on parasympathetic nerve function during normal physiology and its role in cardiovascular disease, focusing on hypertension. Angiotensin (Ang) II receptors are present throughout the parasympathetic nerves and can modulate vagal activity via actions at the level of the nerve endings as well as via the circumventricular organs and as a neuromodulator acting within brain regions. There is tonic inhibition of cardiac vagal tone by endogenous Ang II. We review the actions of Ang II via peripheral nerve endings as well as via central actions on brain regions. We review the evidence that Ang II modulates arterial baroreflex function and examine the pathways via which Ang II can modulate baroreflex control of cardiac vagal drive. Although there is evidence that Ang II can modulate parasympathetic activity and has the potential to contribute to impaired baseline levels and impaired baroreflex control during hypertension, the exact central regions where Ang II acts need further investigation. The beneficial actions of angiotensin receptor blockers in hypertension may be mediated in part via actions on the parasympathetic nervous system. We highlight important unknown questions about the interaction between the RAAS and the parasympathetic nervous system and conclude that this remains an important area where future research is needed.