ACE2 activator diminazene aceturate ameliorates Alzheimer's disease-like neuropathology and rescues cognitive impairment in SAMP8 mice

COVID-19 and the impact on Alzheimer's disease pathology

Coronavirus disease 2019 (COVID-19) has rapidly escalated into a global pandemic that primarily affects older and immunocompromised individuals due to underlying clinical conditions and suppressed immune responses. Furthermore, COVID-19 patients exhibit a spectrum of neurological symptoms, indicating that COVID-19 can affect the brain in a variety of manners. Many studies, past and recent, suggest a connection between viral infections and an increased risk of neurodegeneration, raising concerns about the neurological effects of COVID-19 and the possibility that it may contribute to Alzheimer's disease (AD) onset or worsen already existing AD pathology through inflammatory processes given that both COVID-19 and AD share pathological features and risk factors. This leads us to question whether COVID-19 is a risk factor for AD and how these two conditions might influence each other. Considering the extensive reach of the COVID-19 pandemic and the devastating impact of the ongoing AD pandemic, their combined effects could have significant public health consequences worldwide.

The Role of ACE2 in Neurological Disorders: From Underlying Mechanisms to the Neurological Impact of COVID-19

Angiotensin-converting enzyme 2 (ACE2) has become a hot topic in neuroscience research in recent years, especially in the context of the global COVID-19 pandemic, where its role in neurological diseases has received widespread attention. ACE2, as a multifunctional metalloprotease, not only plays a critical role in the cardiovascular system but also plays an important role in the protection, development, and inflammation regulation of the nervous system. The COVID-19 pandemic further highlights the importance of ACE2 in the nervous system. SARS-CoV-2 enters host cells by binding to ACE2, which may directly or indirectly affect the nervous system, leading to a range of neurological symptoms. This review aims to explore the function of ACE2 in the nervous system as well as its potential impact and therapeutic potential in various neurological diseases, providing a new perspective for the treatment of neurological disorders.

A Mouse Model of Sporadic Alzheimer's Disease with Elements of Major Depression

After olfactory bulbectomy, animals are often used as a model of major depression or sporadic Alzheimer's disease and, hence, the status of this model is still disputable. To elucidate the nature of alterations in the expression of the genome after the operation, we analyzed transcriptomes of the cortex, hippocampus, and cerebellum of the olfactory bulbectomized (OBX) mice. Analysis of the functional significance of genes in the brain of OBX mice indicates that the balance of the GABA/glutamatergic systems is disturbed with hyperactivation of the latter in the hippocampus, leading to the development of excitotoxicity and induction of apoptosis in the background of severe mitochondrial dysfunction and astrogliosis. On top of this, the synthesis of neurotrophic factors decreases leading to the disruption of the cytoskeleton of neurons, an increase in the level of intracellular calcium, and the activation of tau protein hyperphosphorylation. Moreover, the acetylcholinergic system is deficient in the background of the hyperactivation of acetylcholinesterase. Importantly, the activity of the dopaminergic, endorphin, and opiate systems in OBX mice decreases, leading to hormonal dysfunction. On the other hand, genes responsible for the regulation of circadian rhythms, cell migration, and innate immunity are activated in OBX animals. All this takes place in the background of a drastic downregulation of ribosomal protein genes in the brain. The obtained results indicate that OBX mice represent a model of Alzheimer's disease with elements of major depression.

A53T α-synuclein mutation increases susceptibility to postoperative delayed neurocognitive recovery via hippocampal Ang-(1-7)/MasR axis

Delayed neurocognitive recovery (dNCR) is a common complication in geriatric surgical patients. The impact of anesthesia and surgery on patients with neurodegenerative diseases, such as Parkinson's disease (PD) or prion disease, has not yet been reported. In this study, we aimed to determine the association between a pre-existing A53T genetic background, which involves a PD-related point mutation, and the development of postoperative dNCR. We observed that partial hepatectomy induced hippocampus-dependent cognitive deficits in 5-month-old A53T transgenic mice, a model of early-stage PD without cognitive deficits, unlike in age-matched wild-type (WT) mice. We respectively examined molecular changes at 6 h, 1 day, and 2 days after partial hepatectomy and observed that cognitive changes were accompanied by weakened angiotensin-(1-7)/Mas receptor [Ang-(1-7)/MasR] axis, increased alpha-synuclein (α-syn) expression and phosphorylation, decreased methylated protein phosphatase-2A (Me-PP2A), and prompted microglia M1 polarization and neuronal apoptosis in the hippocampus at 1 day after surgery. Nevertheless, no changes in blood-brain barrier (BBB) integrity or plasma α-syn levels in either A53T or WT mice. Furthermore, intranasal administration of selective MasR agonist AVE 0991, reversed the mentioned cognitive deficits in A53T mice, enhanced MasR expression, reduced α-syn accumulation and phosphorylation, and attenuated microglia activation and apoptotic response. Our findings suggest that individuals with the A53T genetic background may be more susceptible to developing postoperative dNCR. This susceptibility could be linked to central α-syn accumulation mediated by the weakened Ang-(1-7)/MasR/methyl-PP2A signaling pathway in the hippocampus following surgery, independent of plasma α-syn level and BBB.

Melatonin: a ferroptosis inhibitor with potential therapeutic efficacy for the post-COVID-19 trajectory of accelerated brain aging and neurodegeneration

The unprecedented pandemic of COVID-19 swept millions of lives in a short period, yet its menace continues among its survivors in the form of post-COVID syndrome. An exponentially growing number of COVID-19 survivors suffer from cognitive impairment, with compelling evidence of a trajectory of accelerated aging and neurodegeneration. The novel and enigmatic nature of this yet-to-unfold pathology demands extensive research seeking answers for both the molecular underpinnings and potential therapeutic targets. Ferroptosis, an iron-dependent cell death, is a strongly proposed underlying mechanism in post-COVID-19 aging and neurodegeneration discourse. COVID-19 incites neuroinflammation, iron dysregulation, reactive oxygen species (ROS) accumulation, antioxidant system repression, renin-angiotensin system (RAS) disruption, and clock gene alteration. These events pave the way for ferroptosis, which shows its signature in COVID-19, premature aging, and neurodegenerative disorders. In the search for a treatment, melatonin shines as a promising ferroptosis inhibitor with its repeatedly reported safety and tolerability. According to various studies, melatonin has proven efficacy in attenuating the severity of certain COVID-19 manifestations, validating its reputation as an anti-viral compound. Melatonin has well-documented anti-aging properties and combating neurodegenerative-related pathologies. Melatonin can block the leading events of ferroptosis since it is an efficient anti-inflammatory, iron chelator, antioxidant, angiotensin II antagonist, and clock gene regulator. Therefore, we propose ferroptosis as the culprit behind the post-COVID-19 trajectory of aging and neurodegeneration and melatonin, a well-fitting ferroptosis inhibitor, as a potential treatment.

Generation and characterization of a humanized ACE2 mouse model to study long-term impacts of SARS-CoV-2 infection

Although the COVID-19 pandemic has officially ended, the persistent challenge of long-COVID or post-acute COVID sequelae (PASC) continues to impact societies globally, highlighting the urgent need for ongoing research into its mechanisms and therapeutic approaches. Our team has recently developed a novel humanized ACE2 mouse model (hACE2ki) designed explicitly for long-COVID/PASC research. This model exhibits human ACE2 expression in tissue and cell-specific patterns akin to mouse Ace2. When we exposed young adult hACE2ki mice (6 weeks old) to various SARS-CoV-2 lineages, including WA, Delta, and Omicron, at a dose of 5 × 105 PFU/mouse via nasal instillation, the mice demonstrated distinctive phenotypes characterized by differences in viral load in the lung, trachea, and nasal turbinate, weight loss, and changes in pro-inflammatory cytokines and immune cell profiles in bronchoalveolar lavage fluid. Notably, no mortality was observed in this age group. Further, to assess the model's relevance for long-COVID studies, we investigated tau protein pathologies, which are linked to Alzheimer's disease, in the brains of these mice post SARS-CoV-2 infection. Our findings revealed the accumulation and longitudinal propagation of tau, confirming the potential of our hACE2ki mouse model for preclinical studies of long-COVID.

The Renin Angiotensin System as a Therapeutic Target in Traumatic Brain Injury

Traumatic brain injury (TBI) is a major public health problem, with limited pharmacological options available beyond symptomatic relief. The renin angiotensin system (RAS) is primarily known as a systemic endocrine regulatory system, with major roles controlling blood pressure and fluid homeostasis. Drugs that target the RAS are used to treat hypertension, heart failure and kidney disorders. They have now been used chronically by millions of people and have a favorable safety profile. In addition to the systemic RAS, it is now appreciated that many different organ systems, including the brain, have their own local RAS. The major ligand of the classic RAS, Angiotensin II (Ang II) acts predominantly through the Ang II Type 1 receptor (AT1R), leading to vasoconstriction, inflammation, and heightened oxidative stress. These processes can exacerbate brain injuries. Ang II receptor blockers (ARBs) are AT1R antagonists. They have been shown in several preclinical studies to enhance recovery from TBI in rodents through improvements in molecular, cellular and behavioral correlates of injury. ARBs are now under consideration for clinical trials in TBI. Several different RAS peptides that signal through receptors distinct from the AT1R, are also potential therapeutic targets for TBI. The counter regulatory RAS pathway has actions that oppose those stimulated by AT1R signaling. This alternative pathway has many beneficial effects on cells in the central nervous system, bringing about vasodilation, and having anti-inflammatory and anti-oxidative stress actions. Stimulation of this pathway also has potential therapeutic value for the treatment of TBI. This comprehensive review will provide an overview of the various components of the RAS, with a focus on their direct relevance to TBI pathology. It will explore different therapeutic agents that modulate this system and assess their potential efficacy in treating TBI patients.

Pharmacologic Activation of Angiotensin-Converting Enzyme II Alleviates Diabetic Cardiomyopathy in db/db Mice by Reducing Reactive Oxidative Stress

BACKGRUOUND

Diabetes mellitus is one of the most common chronic diseases worldwide, and cardiovascular disease is the leading cause of morbidity and mortality in diabetic patients. Diabetic cardiomyopathy (DCM) is a phenomenon characterized by a deterioration in cardiac function and structure, independent of vascular complications. Among many possible causes, the renin-angiotensin-aldosterone system and angiotensin II have been proposed as major drivers of DCM development. In the current study, we aimed to investigate the effects of pharmacological activation of angiotensin-converting enzyme 2 (ACE2) on DCM.

METHODS

The ACE2 activator diminazene aceturate (DIZE) was administered intraperitoneally to male db/db mice (8 weeks old) for 8 weeks. Transthoracic echocardiography was used to assess cardiac mass and function in mice. Cardiac structure and fibrotic changes were examined using histology and immunohistochemistry. Gene and protein expression levels were examined using quantitative reverse transcription polymerase chain reaction and Western blotting, respectively. Additionally, RNA sequencing was performed to investigate the underlying mechanisms of the effects of DIZE and identify novel potential therapeutic targets for DCM.

RESULTS

Echocardiography revealed that in DCM, the administration of DIZE significantly improved cardiac function as well as reduced cardiac hypertrophy and fibrosis. Transcriptome analysis revealed that DIZE treatment suppresses oxidative stress and several pathways related to cardiac hypertrophy.

CONCLUSION

DIZE prevented the diabetes mellitus-mediated structural and functional deterioration of mouse hearts. Our findings suggest that the pharmacological activation of ACE2 could be a novel treatment strategy for DCM.

COVID-19 and Diarylamidines: The Parasitic Connection

As emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants (Omicron) continue to outpace and negate combinatorial vaccines and monoclonal antibody therapies targeting the spike protein (S) receptor binding domain (RBD), the appetite for developing similar COVID-19 treatments has significantly diminished, with the attention of the scientific community switching to long COVID treatments. However, treatments that reduce the risk of "post-COVID-19 syndrome" and associated sequelae remain in their infancy, particularly as no established criteria for diagnosis currently exist. Thus, alternative therapies that reduce infection and prevent the broad range of symptoms associated with 'post-COVID-19 syndrome' require investigation. This review begins with an overview of the parasitic-diarylamidine connection, followed by the renin-angiotensin system (RAS) and associated angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSSR2) involved in SARS-CoV-2 infection. Subsequently, the ability of diarylamidines to inhibit S-protein binding and various membrane serine proteases associated with SARS-CoV-2 and parasitic infections are discussed. Finally, the roles of diarylamidines (primarily DIZE) in vaccine efficacy, epigenetics, and the potential amelioration of long COVID sequelae are highlighted.

Aging, Plasminogen Activator Inhibitor 1, Brain Cell Senescence, and Alzheimer's Disease

The etiology for late-onset Alzheimer's disease (LOAD), which accounts for >95% of Alzheimer's disease (AD) cases, is unknown. Emerging evidence suggests that cellular senescence contributes importantly to AD pathophysiology, although the mechanisms underlying brain cell senescence and by which senescent cells promote neuro-pathophysiology remain unclear. In this study we show for the first time that the expression of plasminogen activator inhibitor 1 (PAI-1), a serine protease inhibitor, is increased, in correlation with the increased expression of cell cycle repressors p53 and p21, in the hippocampus/cortex of senescence accelerated mouse prone 8 (SAMP8) mice and LOAD patients. Double immunostaining results show that astrocytes in the brain of LOAD patients and SAMP8 mice express higher levels of senescent markers and PAI-1, compared to astrocytes in the corresponding controls. In vitro studies further show that overexpression of PAI-1 alone, intracellularly or extracellularly, induced senescence, whereas inhibition or silencing PAI-1 attenuated H2O2-induced senescence, in primary mouse and human astrocytes. Treatment with the conditional medium (CM) from senescent astrocytes induced neuron apoptosis. Importantly, the PAI-1 deficient CM from senescent astrocytes that overexpress a secretion deficient PAI-1 (sdPAI-1) has significantly reduced effect on neurons, compared to the PAI-1 containing CM from senescent astrocytes overexpressing wild type PAI-1 (wtPAI-1), although sdPAI-1 and wtPAI-1 induce similar degree of astrocyte senescence. Together, our results suggest that increased PAI-1, intracellularly or extracellularly, may contribute to brain cell senescence in LOAD and that senescent astrocytes can induce neuron apoptosis through secreting pathologically active molecules, including PAI-1.

ACE2/ANG-(1-7)/Mas receptor axis activation prevents inflammation and improves cognitive functions in streptozotocin induced rat model of Alzheimer's disease-like phenotypes

Activation of the renin-angiotensin system (RAS), by Angiotensin converting enzyme/Angiotensin II/Angiotensin receptor-1 (ACE/Ang II/AT1 R) axis elicits amyloid deposition and cognitive impairment. Furthermore, ACE2 induced release of Ang-(1-7) binds with the Mas receptor and autoinhibits ACE/Ang II/AT1 axis activation. Inhibition of ACE by perindopril has been reported to improve memory in preclinical settings. However, the functional significance and mechanism by which ACE2/Mas receptor regulate cognitive functions and amyloid pathology is not known. The present study is aimed to determine the role of ACE2/Ang-(1-7)/Mas receptor axis in STZ induced rat model of Alzheimer's disease (AD). We have used pharmacological, biochemical and behavioural approaches to identify the role of ACE2/Ang-(1-7)/Mas receptor axis activation on AD-like pathology in both in vitro and invivo models. STZ treatment enhances ROS formation, inflammation markers and NFκB/p65 levels which are associated with reduced ACE2/Mas receptor levels, acetylcholine activity and mitochondrial membrane potential in N2A cells. DIZE mediated ACE2/Ang-(1-7)/Mas receptor axis activation resulted in reduced ROS generation, astrogliosis, NFκB level and inflammatory molecules and improved mitochondrial functions along with Ca²⁺ influx in STZ treated N2A cells. Interestingly, DIZE induced activation of ACE2/Mas receptor significantly restored acetylcholine levels and reduced amyloid-beta and phospho-tau deposition in cortex and hippocampus that resulted in improved cognitive function in STZ induced rat model of AD-like phenotypes. Our data indicate that ACE2/Mas receptor activation is sufficient to prevented cognitive impairment and progression of amyloid pathology in STZ induced rat model of AD-like phenotypes. These findings suggest the potential role of ACE2/Ang-(1-7)/Mas axis in AD pathophysiology by regulating inflammation cognitive functions.

Links between COVID-19 and Alzheimer's Disease-What Do We Already Know?

Alzheimer's disease (AD) is a life-changing condition whose etiology is explained by several hypotheses. Recently, a new virus contributed to the evidence of viral involvement in AD: the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the COVID-19 coronavirus disease. AD was found to be one of the most common COVID-19 comorbidities, and it was found to increase mortality from this disease as well. Moreover, AD patients were observed to present with the distinct clinical features of COVID-19, with delirium being prevalent in this group. The SARS-CoV-2 virus enters host cells through the angiotensin-converting enzyme 2 (ACE2) receptor. ACE2 is overexpressed in brains with AD, which thus increases the viral invasion. Furthermore, the inhibition of the ACE2 receptor by the SARS-CoV-2 virus may also decrease the brain-derived neurotrophic factor (BDNF), contributing to neurodegeneration. The ApoE ε4 allele, which increases the risk of AD, was found to facilitate the SARS-CoV-2 entry into cells. Furthermore, the neuroinflammation and oxidative stress existing in AD patients enhance the inflammatory response associated with COVID-19. Moreover, pandemic and associated social distancing measures negatively affected the mental health, cognitive function, and neuro-psychiatric symptoms of AD patients. This review comprehensively covers the links between COVID-19 and Alzheimer's disease, including clinical presentation, molecular mechanisms, and the effects of social distancing.

Lamotrigine protects against cognitive deficits, synapse and nerve cell damage, and hallmark neuropathologies in a mouse model of Alzheimer’s disease

Lamotrigine (LTG) is a widely used drug for the treatment of epilepsy. Emerging clinical evidence suggests that LTG may improve cognitive function in patients with Alzheimer’s disease. However, the underlying molecular mechanisms remain unclear. In this study, amyloid precursor protein/presenilin 1 (APP/PS1) double transgenic mice were used as a model of Alzheimer’s disease. Five-month-old APP/PS1 mice were intragastrically administered 30 mg/kg LTG or vehicle once per day for 3 successive months. The cognitive functions of animals were assessed using Morris water maze. Hyperphosphorylated tau and markers of synapse and glial cells were detected by western blot assay. The cell damage in the brain was investigated using hematoxylin and eosin staining. The levels of amyloid-β and the concentrations of interleukin-1β, interleukin-6 and tumor necrosis factor-α in the brain were measured using enzyme-linked immunosorbent assay. Differentially expressed genes in the brain after LTG treatment were analyzed by high-throughput RNA sequencing and real-time polymerase chain reaction. We found that LTG substantially improved spatial cognitive deficits of APP/PS1 mice; alleviated damage to synapses and nerve cells in the brain; and reduced amyloid-β levels, tau protein hyperphosphorylation, and inflammatory responses. High-throughput RNA sequencing revealed that the beneficial effects of LTG on Alzheimer’s disease-related neuropathologies may have been mediated by the regulation of Ptgds, Cd74, Map3k1, Fosb, and Spp1 expression in the brain. These findings revealed potential molecular mechanisms by which LTG treatment improved Alzheimer’s disease. Furthermore, these data indicate that LTG may be a promising therapeutic drug for Alzheimer’s disease.

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.

A postpartum enriched environment rescues impaired cognition and oxidative markers in aged mice with gestational inflammation

INTRODUCTION

Previous studies have shown that gestational inflammation can accelerate age-associated cognitive decline (AACD) in maternal mice; enriched environments (EEs) have been reported to protect normally aging mice from AACD and improve mitochondrial function. However, it is unclear whether the nitrosative stress-related proteins tet methylcytosine dioxygenase 1 (TET1) and S-nitrosoglutathione reductase (GSNOR) are involved in the accelerated aging process of gestational inflammation and whether EEs can slow this process.

METHODS

In this study, CD-1 female mice on the 15th day of pregnancy were injected with bacterial lipopolysaccharide (50 μg/kg; LPS group) or an equivalent amount of normal saline (CON group) from the abdominal cavity for 4 consecutive days. Twenty-one days after delivery, half of the LPS-treated mice were randomly selected for EE until the end of the behavioral experiment (LPS-E group). When the female rats were raised to 6 months and 18 months of age, the Morris water maze (MWM) was used to detect spatial learning and memory ability; RT-PCR and Western blots were used to measure the mRNA and protein levels of hippocampal TET1 and GSNOR.

RESULTS

As for the control group, compared with 6-month-old mice, the spatial learning and memory ability of 18-month-old mice decreased, and the hippocampal TET1 and GSNOR mRNA and protein levels were decreased. Gestational inflammation exacerbated these age-related changes, but an EE alleviated the effects. Pearson's correlation analysis indicated that performance during the learning and memory periods in the MWM correlated with the levels of hippocampal TET1 and GSNOR.

CONCLUSIONS

Our findings suggest that gestational inflammation accelerates age-related learning and memory impairments and that postpartum EE exposure could alleviate these changes. These effects may be related to hippocampal TET1 and GSNOR expression.

ACE2, Circumventricular Organs and the Hypothalamus, and COVID-19

The SARS-CoV-2 virus gains entry to cells by binding to angiotensin-converting enzyme 2 (ACE2). Since circumventricular organs and parts of the hypothalamus lack a blood-brain barrier, and immunohistochemical studies demonstrate that ACE2 is highly expressed in circumventricular organs which are intimately connected to the hypothalamus, and the hypothalamus itself, these might be easy entry points for SARS-CoV-2 into the brain via the circulation. High ACE2 protein expression is found in the subfornical organ, area postrema, and the paraventricular nucleus of the hypothalamus (PVH). The subfornical organ and PVH are parts of a circuit to regulate osmolarity in the blood, through the secretion of anti-diuretic hormone into the posterior pituitary. The PVH is also the stress response centre in the brain. It controls not only pre-ganglionic sympathetic neurons, but is also a source of corticotropin-releasing hormone, that induces the secretion of adrenocorticotropic hormone from the anterior pituitary. It is proposed that the function of ACE2 in the circumventricular organs and the PVH could be diminished by binding with SARS-CoV-2, thus leading to a reduction in the ACE2/Ang (1-7)/Mas receptor (MasR) signalling axis, that modulates ACE/Ang II/AT1R signalling. This could result in increased presympathetic activity/neuroendocrine secretion from the PVH, and effects on the hypothalamic-pituitary-adrenal axis activity. Besides the bloodstream, the hypothalamus might also be affected by SARS-CoV-2 via transneuronal spread along the olfactory/limbic pathways. Exploring potential therapeutic pathways to prevent or attenuate neurological symptoms of COVID-19, including drugs which modulate ACE signalling, remains an important area of unmet medical need.

The Pharmacorank Search Tool for the Retrieval of Prioritized Protein Drug Targets and Drug Repositioning Candidates According to Selected Diseases

We present the Pharmacorank search tool as an objective means to obtain prioritized protein drug targets and their associated medications according to user-selected diseases. This tool could be used to obtain prioritized protein targets for the creation of novel medications or to predict novel indications for medications that already exist. To prioritize the proteins associated with each disease, a gene similarity profiling method based on protein functions is implemented. The priority scores of the proteins are found to correlate well with the likelihoods that the associated medications are clinically relevant in the disease's treatment. When the protein priority scores are plotted against the percentage of protein targets that are known to bind medications currently indicated to treat the disease, which we termed the pertinency score, a strong correlation was observed. The correlation coefficient was found to be 0.9978 when using a weighted second-order polynomial fit. As the highly predictive fit was made using a broad range of diseases, we were able to identify a general threshold for the pertinency score as a starting point for considering drug repositioning candidates. Several repositioning candidates are described for proteins that have high predicated pertinency scores, and these provide illustrative examples of the applications of the tool. We also describe focused reviews of repositioning candidates for Alzheimer's disease. Via the tool's URL, https://protein.som.geisinger.edu/Pharmacorank/, an open online interface is provided for interactive use; and there is a site for programmatic access.

Renin-Angiotensin System in Huntington's Disease: Evidence from Animal Models and Human Patients

The Renin-Angiotensin System (RAS) is expressed in the central nervous system and has important functions that go beyond blood pressure regulation. Clinical and experimental studies have suggested that alterations in the brain RAS contribute to the development and progression of neurodegenerative diseases. However, there is limited information regarding the involvement of RAS components in Huntington's disease (HD). Herein, we used the HD murine model, (BACHD), as well as samples from patients with HD to investigate the role of both the classical and alternative axes of RAS in HD pathophysiology. BACHD mice displayed worse motor performance in different behavioral tests alongside a decrease in the levels and activity of the components of the RAS alternative axis ACE2, Ang-(1-7), and Mas receptors in the striatum, prefrontal cortex, and hippocampus. BACHD mice also displayed a significant increase in mRNA expression of the AT1 receptor, a component of the RAS classical arm, in these key brain regions. Moreover, patients with manifest HD presented higher plasma levels of Ang-(1-7). No significant changes were found in the levels of ACE, ACE2, and Ang II. Our findings provided the first evidence that an imbalance in the RAS classical and counter-regulatory arms may play a role in HD pathophysiology.

Ginkgolide B inactivates the NLRP3 inflammasome by promoting autophagic degradation to improve learning and memory impairment in Alzheimer's disease

The NLR family, pyrin domain containing 3 (NLRP3) inflammasome drives the progression of Alzheimer's disease (AD). Ginkgolide B (GB) is a potential anti-inflammatory compound that controls neuro-inflammation. The aim of this study was to evaluate the effect of GB on the NLRP3 inflammasome in AD. The effect of GB on the conversion between the M1 and M2 microglial phenotype was examined using quantitative real-time PCR and immunostaining. Western blotting assays and ELISA were used to detect changes in neuro-inflammation following GB treatment, including the NLRP3 inflammasome pathway and autophagy. In order to evaluate the cognitive function of male senescence-accelerated mouse prone 8 (SAMP8) mice, behavioral tests, including the Morris water maze and novel object recognition tests, were performed. GB significantly decreased the intracellular pro-inflammatory cytokine levels in lipopolysaccharide-treated BV2 cells and improved cognitive behavior in SAMP8 mice. Moreover, GB deactivated the NLRP3 inflammasome, and this effect was dependent on autophagy. Ubiquitination was associated with GB-induced autophagic NLRP3 degradation. These results were further validated in the hippocampus of SAMP8 mice. Thus, GB exerted a neuroprotective effect on the cognitive function of SAMP8 mice by suppressing the activation of NLRP3 inflammasome via autophagic degradation.

Can SARS-CoV-2 Infection Exacerbate Alzheimer's Disease? An Overview of Shared Risk Factors and Pathogenetic Mechanisms

The current coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus (SARS-CoV)-2, is affecting every aspect of global society, including public healthcare systems, medical care access, and the economy. Although the respiratory tract is primarily affected by SARS-CoV-2, emerging evidence suggests that the virus may also reach the central nervous system (CNS), leading to several neurological issues. In particular, people with a diagnosis of Alzheimer's disease (AD) are a vulnerable group at high risk of contracting COVID-19, and develop more severe forms and worse outcomes, including death. Therefore, understanding shared links between COVID-19 and AD could aid the development of therapeutic strategies against both. Herein, we reviewed common risk factors and potential pathogenetic mechanisms that might contribute to the acceleration of neurodegenerative processes in AD patients infected by SARS-CoV-2.

Angiotensin-(1-7) Analogue AVE0991 Modulates Astrocyte-Mediated Neuroinflammation via lncRNA SNHG14/miR-223-3p/NLRP3 Pathway and Offers Neuroprotection in a Transgenic Mouse Model of Alzheimer's Disease

Objective

Emerging evidence suggests that brain angiotensin-(1–7) (Ang-(1–7)) deficiency contributes to the pathogenesis of Alzheimer’s disease (AD). Meanwhile, our previous studies revealed that restoration of brain Ang-(1–7) levels provided neuroprotection by inhibition of inflammatory responses during AD progress. However, the potential molecular mechanisms by which Ang-(1–7) modulates neuroinflammation remain unclear.

Materials and Methods

APP/PS1 mice were injected intraperitoneally with AVE0991 (a nonpeptide analogue of Ang-(1–7)) once a day for 30 consecutive days. Cognitive functions, neuronal and synaptic integrity, and inflammation-related markers were assessed. Since astrocytes played a crucial role in AD-related neuroinflammation whilst long noncoding RNAs (lncRNAs) were reported to participate in modulating inflammatory responses, astrocytes of APP/PS1 mice were isolated for high-throughput lncRNA sequencing to identify the most differentially expressed lncRNA following AVE0991 treatment. Afterward, the downstream pathways of this lncRNA in the anti-inflammatory action of AVE0991 were investigated using primary astrocytes.

Results

AVE0991 rescued spatial cognitive impairments and alleviated neuronal and synaptic damage in APP/PS1 mice. The levels of Aβ_1-42 in the brain of APP/PS1 mice were not affected by AVE0991. By employing high-throughput lncRNA sequencing, our in vitro study demonstrated for the first time that AVE0991 suppressed astrocytic NLRP3 inflammasome-mediated neuroinflammation via a lncRNA SNHG14-dependent manner. SNHG14 acted as a sponge of miR-223-3p while NLRP3 represented a direct target of miR-223-3p in astrocytes. In addition, miR-223-3p participated in the AVE0991-induced suppression of astrocytic NLRP3 inflammasome.

Conclusion

Our results suggest that Ang-(1–7) analogue AVE0991 inhibits astrocyte-mediated neuroinflammation via SNHG14/miR-223-3p/NLRP3 pathway and offers neuroprotection in APP/PS1 mice. These findings reveal the underlying mechanisms by which Ang-(1–7) inhibits neuroinflammation under AD condition and uncover the potential of its nonpeptide analogue AVE0991 in AD treatment.

Restoration of Brain Angiotensin-Converting Enzyme 2 Alleviates Neurological Deficits after Severe Traumatic Brain Injury via Mitigation of Pyroptosis and Apoptosis

Clinically, the renin-angiotensin-aldosterone system is intensely activated in moderate to severe traumatic brain injury (TBI) patients. Increased angiotensin II in circulatory blood after TBI can enter the brain through the disrupted blood-brain barrier. Angiotensin-converting enzyme 2 (ACE2) is an enzyme that metabolizes angiotensin II into angiotensin (1-7), which has been shown to have neuroprotective results. However, the expression and role of ACE2 in the brain after TBI remains elusive. We found that ACE2 protein abundance was downregulated around the contusional area in the brains of both humans and mice. Endogenous ACE2 was expressed in neurons, astrocytes, and microglia in the cortex of the mouse brain. Administration of recombinant human ACE2 intracerebroventricularly alleviated neurological defects after TBI in mice. Treatment of recombinant human ACE2 suppressed TBI-induced increase of angiotensin II and the decrease of angiotensin (1-7) in the brain, mitigated neural cell death, reduced the activation of NLRP3 and Caspase3, decreased phosphorylation of mitogen-activated protein kinases, and nuclear factor kappa B, and reduced inflammatory cytokines TNF-α and IL-1β. Administration of ACE2 enzyme activator diminazene aceturate intraperitoneally rescued downregulation of ACE2 enzymatic activity and protein abundance in the brain. Diminazene aceturate treatment once per day in the acute stage after TBI alleviated long-term cognitive defects and neuronal loss in mice. Collectively, these results indicated that restoration of ACE2 alleviated neurological deficits after TBI by mitigation of pyroptosis and apoptosis.

AngIV-Analog Dihexa Rescues Cognitive Impairment and Recovers Memory in the APP/PS1 Mouse via the PI3K/AKT Signaling Pathway

The renin-angiotensin system (RAS) is a paracrine RAS within the central nervous system (CNS) and is closely related to Alzheimer’s disease (AD). The endogenous hexapeptide angiotensin IV (Ang IV), an important component of the brain RAS, was found to rescue cognitive impairment and recover memory in previous studies. In our study, we used different doses of Dihexa, which can be orally administered and cross the BBB in APP/PS1 mice. We found that the amount of AngIV in mouse tissue increased after the administration of Dihexa compared to that in the WT group. Meanwhile, Dihexa restored spatial learning and cognitive functions in the Morris water maze test. Dihexa increased the neuronal cells and the expression of SYP protein in APP/PS1 mice in Nissl staining. Furthermore, Dihexa decreased the activation of astrocytes and microglia, markedly reduced levels of the pro-inflammatory cytokines IL-1β and TNF-α and increased the levels of the anti-inflammatory cytokine IL-10. Dihexa activated the PI3K/AKT signaling pathway, while PI3K inhibitor wortmannin significantly reversed the anti-inflammatory and anti-apoptotic effects of APP/PS1 mice. These findings highlight the brain AngIV/PI3K/AKT axis as a potential target for the treatment of AD.

A non-peptidic MAS1 agonist AVE0991 alleviates hippocampal synaptic degeneration in rats with chronic cerebral hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is a contributing factor for neurodegenerative diseases. As a recently identified heptapeptide of the brain renin-angiotensin system, angiotensin-(1-7) was revealed to activate its receptor MAS1 and thus ameliorated cognitive impairments in rats with CCH. Since hippocampal synaptic degeneration represents an important pathological basis of cognitive deficits, we hypothesize that activation of MAS1-mediated signaling may alleviate CCH-induced synaptic degeneration in the hippocampus.

METHODS

In this study, we tested this hypothesis and uncovered the underlying mechanisms in a rat model of CCH induced by bilateral common carotid artery ligation surgery. At 1 week after the surgery, rats received a daily intraperitoneal injection of vehicle or a non-peptidic MAS1 agonist AVE0991 for 8 weeks. During this procedure, cerebral blood flow (CBF) was recorded. The levels of MAS1, amyloid-β (Aβ), neuroinflammatory cytokines, glial cell markers and synaptophysin in the hippocampus were assessed at the end of the treatment period.

RESULTS

We showed that AVE0991 significantly alleviated hippocampal synaptic degeneration in rats with CCH. This protection might be achieved by facilitating CBF recovery, reducing hippocampal Aβ levels and suppressing neuroinflammatory responses.

CONCLUSIONS

These findings indicate that MAS1-mediated signaling may represent a novel therapeutic target for CCH-related neurodegenerative diseases.

The key role of the level of ACE2 gene expression in SARS-CoV-2 infection

SARS-CoV-2 more readily affects the elderly, especially as they present co-morbidities. In the COVID-19 pathogeny, ACE2 appears to be the key cell receptor for SARS-CoV-2 to infect humans. The level of ACE2 gene expression influences the susceptibility of contracting SARS-CoV-2. In circumstances in which the ACE2 level is low, the incidence of Covid-19 seems to be fewer. Two clinical patterns illustrate this observation, i. e., in infants and in Alzheimer's disease (AD). Very young children and AD patients get little COVID-19, in part probably due to decreased expression of ACE2. The determination of the nasal level of ACE2 gene expression could provide a useful scale to predict the susceptibility to contract the SARS-CoV-2 infection.

Multifunctional angiotensin converting enzyme 2, the SARS-CoV-2 entry receptor, and critical appraisal of its role in acute lung injury

The recent emergence of coronavirus disease-2019 (COVID-19) as a pandemic affecting millions of individuals has raised great concern throughout the world, and the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was identified as the causative agent for COVID-19. The multifunctional protein angiotensin converting enzyme 2 (ACE2) is accepted as its primary target for entry into host cells. In its enzymatic function, ACE2, like its homologue ACE, regulates the renin-angiotensin system (RAS) critical for cardiovascular and renal homeostasis in mammals. Unlike ACE, however, ACE2 drives an alternative RAS pathway by degrading Ang-II and thus operates to balance RAS homeostasis in the context of hypertension, heart failure, and cardiovascular as well as renal complications of diabetes. Outside the RAS, ACE2 hydrolyzes key peptides, such as amyloid-β, apelin, and [des-Arg9]-bradykinin. In addition to its enzymatic functions, ACE2 is found to regulate intestinal amino acid homeostasis and the gut microbiome. Although the non-enzymatic function of ACE2 as the entry receptor for SARS-CoV-2 has been well established, the contribution of enzymatic functions of ACE2 to the pathogenesis of COVID-19-related lung injury has been a matter of debate. A complete understanding of this central enzyme may begin to explain the various symptoms and pathologies seen in SARS-CoV-2 infected individuals, and may aid in the development of novel treatments for COVID-19.

ACE2 and ACE: structure-based insights into mechanism, regulation and receptor recognition by SARS-CoV

Angiotensin converting enzyme (ACE) is well-known for its role in blood pressure regulation via the renin–angiotensin aldosterone system (RAAS) but also functions in fertility, immunity, haematopoiesis and diseases such as obesity, fibrosis and Alzheimer’s dementia. Like ACE, the human homologue ACE2 is also involved in blood pressure regulation and cleaves a range of substrates involved in different physiological processes. Importantly, it is the functional receptor for severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 responsible for the 2020, coronavirus infectious disease 2019 (COVID-19) pandemic. Understanding the interaction between SARS-CoV-2 and ACE2 is crucial for the design of therapies to combat this disease. This review provides a comparative analysis of methodologies and findings to describe how structural biology techniques like X-ray crystallography and cryo-electron microscopy have enabled remarkable discoveries into the structure–function relationship of ACE and ACE2. This, in turn, has enabled the development of ACE inhibitors for the treatment of cardiovascular disease and candidate therapies for the treatment of COVID-19. However, despite these advances the function of ACE homologues in non-human organisms is not yet fully understood. ACE homologues have been discovered in the tissues, body fluids and venom of species from diverse lineages and are known to have important functions in fertility, envenoming and insect–host defence mechanisms. We, therefore, further highlight the need for structural insight into insect and venom ACE homologues for the potential development of novel anti-venoms and insecticides.

Effects of Embryonic Inflammation and Adolescent Psychosocial Environment on Cognition and Hippocampal Staufen in Middle-Aged Mice

Accumulating evidence has indicated that embryonic inflammation could accelerate age-associated cognitive impairment, which can be attributed to dysregulation of synaptic plasticity-associated proteins, such as RNA-binding proteins (RBPs). Staufen is a double-stranded RBP that plays a critical role in the modulation of synaptic plasticity and memory. However, relatively few studies have investigated how embryonic inflammation affects cognition and neurobiology during aging, or how the adolescent psychosocial environment affects inflammation-induced remote cognitive impairment. Consequently, the aim of this study was to investigate whether these adverse factors can induce changes in Staufen expression, and whether these changes are correlated with cognitive impairment. In our study, CD-1 mice were administered lipopolysaccharides (LPS, 50 μg/kg) or an equal amount of saline (control) intraperitoneally during days 15–17 of gestation. At 2 months of age, male offspring were randomly exposed to stress (S), an enriched environment (E), or not treated (CON) and then assigned to five groups: LPS, LPS+S, LPS+E, CON, and CON+S. Mice were evaluated at 3-month-old (young) and 15-month-old (middle-aged). Cognitive function was assessed using the Morris water maze test, while Staufen expression was examined at both the protein and mRNA level using immunohistochemistry/western blotting and RNAscope technology, respectively. The results showed that the middle-aged mice had worse cognitive performance and higher Staufen expression than young mice. Embryonic inflammation induced cognitive impairment and increased Staufen expression in the middle-aged mice, whereas adolescent stress/an enriched environment would accelerated/mitigated these effects. Meanwhile, Staufen expression was closely correlated with cognitive performance. Our findings suggested embryonic inflammation can accelerate age-associated learning and memory impairments, and these effects may be related to the Staufen expression.