Discovery of novel brain permeable and G protein-biased beta-1 adrenergic receptor partial agonists for the treatment of neurocognitive disorders

Comprehensive Overview of Alzheimer's Disease: Etiological Insights and Degradation Strategies

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and affects millions of individuals globally. AD is associated with cognitive decline and memory loss that worsens with aging. A statistical report using U.S. data on AD estimates that approximately 6.9 million individuals suffer from AD, a number projected to surge to 13.8 million by 2060. Thus, there is a critical imperative to pinpoint and address AD and its hallmark tau protein aggregation early to prevent and manage its debilitating effects. Amyloid-β and tau proteins are primarily associated with the formation of plaques and neurofibril tangles in the brain. Current research efforts focus on degrading amyloid-β and tau or inhibiting their synthesis, particularly targeting APP processing and tau hyperphosphorylation, aiming to develop effective clinical interventions. However, navigating this intricate landscape requires ongoing studies and clinical trials to develop treatments that truly make a difference. Genome-wide association studies (GWASs) across various cohorts identified 40 loci and over 300 genes associated with AD. Despite this wealth of genetic data, much remains to be understood about the functions of these genes and their role in the disease process, prompting continued investigation. By delving deeper into these genetic associations, novel targets such as kinases, proteases, cytokines, and degradation pathways, offer new directions for drug discovery and therapeutic intervention in AD. This review delves into the intricate biological pathways disrupted in AD and identifies how genetic variations within these pathways could serve as potential targets for drug discovery and treatment strategies. Through a comprehensive understanding of the molecular underpinnings of AD, researchers aim to pave the way for more effective therapies that can alleviate the burden of this devastating disease.

Locus Coeruleus and Noradrenergic Pharmacology in Neurodegenerative Disease

Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α₁-AR, α₂-AR, and β-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Identification and characterization of metamorphic proteins: Current and future perspectives

Proteins that can reversibly alternate between distinctly different folds under native conditions are described as being metamorphic. The "metamorphome" is the collection of all metamorphic proteins in the proteome, but it remains unknown the extent to which the proteome is populated by this class of proteins. We propose that uncovering the metamorphome will require a synergy of computational screening of protein sequences to identify potential metamorphic behavior and validation through experimental techniques. This perspective discusses computational and experimental approaches that are currently used to predict and characterize metamorphic proteins as well as the need for developing improved methodologies. Since metamorphic proteins act as molecular switches, understanding their properties and behavior could lead to novel applications of these proteins as sensors in biological or environmental contexts.

Meta-analysis of global and high throughput public gene array data for robust vascular gene expression discovery in chronic rhinosinusitis: Implications in controlled release

BACKGROUND

Chronic inflammation is known to cause alterations in vascular homeostasis that directly affects blood vessel morphogenesis, angiogenesis, and tissue permeability. These phenomena have been investigated and exploited for targeted drug delivery applications in the context of cancers and other disease processes. Vascular pathophysiology and its associated genes and signaling pathways, however, have not been systematically investigated in patients with chronic rhinosinusitis (CRS). Understanding the interplay between key vascular signaling pathways and top biomarkers associated with CRS may facilitate the development of new targeted delivery strategies and treatment paradigms. Herein, we report findings from a gene meta-analysis to identify key vascular pathways and top genes involved in CRS.

METHODS

Proprietary software (Illumina BaseSpace Correlation Engine) and open-access data sets were used to perform a gene meta-analysis to systematically determine significant differences between key vascular biomarkers and vascular signaling pathways expressed in sinonasal tissue biopsies of controls and patients with CRS.

RESULTS

Thirteen studies were initially identified, and then reduced to five after applying exclusion principle algorithms. Genes associated with vasculature development and blood vessel morphogenesis signaling pathways were identified to be overexpressed among the top 15 signaling pathways. Out of many significantly upregulated genes, the levels of pro angiogenic genes such as early growth response (EGR3), platelet endothelial cell adhesion molecule (PECAM1) and L-selectin (SELL) were particularly significant in patients with CRS compared to controls.

DISCUSSION

Key vascular biomarkers and signaling pathways were significantly overexpressed in patients with CRS compared to controls, suggesting a contribution of vascular dysfunction in CRS pathophysiology. Vascular dysregulation and permeability may afford opportunities to develop drug delivery systems to improve efficacy and reduce toxicity of CRS treatment.

Biased agonism at β-adrenergic receptors

The β-adrenergic receptors (βARs) include three subtypes, β₁, β₂ and β₃. These receptors are widely expressed and regulate numerous physiological processes including cardiovascular and metabolic functions and airway tone. The βARs are also important targets in the treatment of many diseases including hypertension, heart failure and asthma. In some cases, the use of current βAR ligands to treat a disease is suboptimal and can lead to severe side effects. One strategy to potentially improve such treatments is the development of biased agonists that selectively regulate a subset of βAR signaling pathways and responses. Here we discuss the compounds identified to date that preferentially activate a G_s- or β-arrestin-mediated signaling pathway through βARs. Mechanistic insight on how these compounds bias signaling sheds light on the potential development of even more selective compounds that should have increased utility in treating disease.

ADRB1 was identified as a potential biomarker for breast cancer by the co-analysis of tumor mutational burden and immune infiltration

Breast cancer (BRCA) has traditionally been considered as having poor immunogenicity and is characterized by relatively low tumor mutational burden (TMB). Improving immunogenicity may improve the response to clinical immunotherapy of BRCA. However, the relationship between TMB, immune infiltration, and prognosis in BRCA remains unclear. We aimed to explore their interrelations and potential biomarkers. In this study, based on somatic mutation data of BRCA from The Cancer Genome Atlas (TCGA), patients were categorized into high and low TMB groups utilizing the TMB values. CIBERSOFT algorithm indicated significant infiltration of activated partial immune cells in high TMB group. Besides, ADRB1 had been identified as a prognosis-related immune gene in the mutant genes by the combination of the ImmPort database and the univariate Cox analysis. ADRB1 mutation was associated with lower TMB and manifested a satisfactory clinical prognosis. Various database applications (Gene Set Enrichment Analysis, Tumor IMmune Estimation Resource, Connectivity Map, KnockTF) supported the selection of treatment strategies targeting ADRB1. In conclusion, TMB was not an independent prognostic factor for BRCA and high TMB was more likely to activate a partial immune response. ADRB1 was identified as a potential biomarker and may provide new insights for co-therapy of BRCA.

Beta-adrenergic receptor antagonism is proinflammatory and exacerbates neuroinflammation in a mouse model of Alzheimer's Disease

Adrenergic systems regulate both cognitive function and immune function. The primary source of adrenergic signaling in the brain is norepinephrine (NE) neurons of the locus coeruleus (LC), which are vulnerable to age-related degeneration and are one of the earliest sites of pathology and degeneration in neurodegenerative disorders such as Alzheimer's Disease (AD). Loss of adrenergic tone may potentiate neuroinflammation both in aging and neurodegenerative conditions. Importantly, beta-blockers (beta-adrenergic antagonists) are a common treatment for hypertension, co-morbid with aging, and may further exacerbate neuroinflammation associated with loss of adrenergic tone in the central nervous system (CNS). The present studies were designed to both examine proinflammatory consequences of beta-blocker administration in an acute lipopolysaccharide (LPS) model as well as to examine chronic effects of beta-blocker administration on neuroinflammation and behavior in an amyloid-beta protein precursor (APP) mouse model of AD. We provide evidence for robust potentiation of peripheral inflammation with 4 different beta-blockers in an acute model of LPS. However, beta-blockers did not potentiate CNS inflammation in this model. Notably, in this same model, the genetic knockdown of either beta1- or beta2-adrenergic receptors in microglia did potentiate CNS inflammation. Furthermore, in an APP mouse model of amyloid pathology, chronic beta-blocker administration did potentiate CNS inflammation. The beta-blocker, metoprolol, also induced markers of phagocytosis and impaired cognitive behavior in both wild-type and APP mice. Given the induction of markers of phagocytosis in vivo, we examined phagocytosis of synaptosomes in an in vitro primary microglia culture and showed that beta-blockers enhanced whereas beta-adrenergic agonists inhibited phagocytosis of synaptosomes. In conclusion, beta-blockers potentiated inflammation peripherally in a systemic model of inflammation and centrally in an amyloidosis model of neuroinflammation. Additionally, beta-blockers impaired learning and memory and modulated synaptic phagocytosis with implications for synaptic degeneration. These findings warrant further consideration of the proinflammatory consequences of chronic beta-blocker administration, which are not restricted to the periphery in patients with neurodegenerative disorders.

Eight immune-related genes predict survival outcomes and immune characteristics in breast cancer

Advancements in immunotherapy have improved our understanding of the immune characteristics of breast cancer. Here, we analyzed gene expression profiles and clinical data obtained from The Cancer Genome Atlas database to identify genes that were differentially expressed between breast tumor tissues and normal breast tissues. Comparisons with the Immunology Database and Analysis Portal (ImmPort) indicated that many of the identified differentially expressed genes were immune-related. Risk scores calculated based on an eight-gene signature constructed from these immune-related genes predicted both overall survival and relapse-free survival outcomes in breast cancer patients. The predictive value of the eight-gene signature was validated in different breast cancer subtypes using external datasets. Associations between risk score and breast cancer immune characteristics were also identified; in vitro experiments using breast cancer cell lines confirmed those associations. Thus, the novel eight-gene signature described here accurately predicts breast cancer survival outcomes as well as immune checkpoint expression and immune cell infiltration processes.

Ganoderic acid A protects neural cells against NO stress injury in vitro via stimulating β adrenergic receptors

Excessive nitric oxide (NO) causes extensive damage to the nervous system, and the adrenergic system is disordered in many neuropsychiatric diseases. However, the role of the adrenergic system in protection of the nervous system against sodium nitroprusside (SNP) injury remains unclear. In this study, we investigated the effect of ganoderic acid A (GA A) against SNP injury in neural cells and the role of adrenergic receptors in GA A neuroprotection. We found that SNP (0.125-2 mM) dose-dependently decreased the viability of both SH-SY5Y and PC12 cells and markedly increased NO contents. Pretreatment with GA A (10 μM) significantly attenuated SNP-induced cytotoxicity and NO increase in SH-SY5Y cells, but not in PC12 cells. Furthermore, pretreatment with GA A caused significantly higher adrenaline content in SH-SY5Y cells than in PC12 cells. In order to elucidate the mechanism of GA A-protecting SH-SY5Y cells, we added adrenaline, phentolamine, metoprolol, or ICI 118551 1 h before GA A was added to the culture medium. We found that addition of adrenaline (10 μM) significantly improved GA A protection in PC12 cells. The addition of β1-adrenergic receptor antagonist metoprolol (10 μM) or β2-adrenergic receptor antagonist ICI 118551 (0.1 μM) blocked the protective effect of GA A, whereas the addition of α-adrenergic receptor antagonist phentolamine (0.1 μM) did not affect GA A protection in SH-SY5Y cells. These results suggest that β-adrenergic receptors play an important role in the protection of GA A in SH-SY5Y cells against SNP injuries, and excessive adrenaline system activation caused great damage to the nervous system.

Beta-blocker therapy and risk of vascular dementia: A population-based prospective study

There are a few studies that report cognitive impairment as a complication of treatment with beta- blockers. We aimed to evaluate the longitudinal association between use of beta-blockers, as a class, and incident risk of all-cause dementia, vascular dementia, Alzheimer's and mixed dementia in the prospective population-based Malmö Preventive Project. We included 18,063 individuals (mean age 68.2, males 63.4%) followed up for 84,506 person-years. Dementia cases were retrieved from the Swedish National Patient Register and validated by review of medical records and neuroimaging data. We performed propensity score matching analysis, resulting in 3720 matched pairs of beta-blocker users and non-users at baseline, and multivariable Cox proportional-hazards regression. Overall, 122 study participants (1.6%) were diagnosed with dementia during the follow-up. Beta-blocker therapy was independently associated with increased risk of developing vascular dementia, regardless of confounding factors (HR: 1.72, 95%CI 1.01-3.78; p = .048). Conversely, treatment with beta-blockers was not associated with increased risk of all-cause, Alzheimer's and mixed dementia (HR:1.15; 95%CI 0.80-1.66; p = .44; HR:0.85; 95%CI 0.48-1.54; P = .59 and HR:1.35; 95%CI 0.56-3.27; p = .50, respectively). We observed that use of beta-blockers, as a class, is associated with increased longitudinal risk of vascular dementia in the general elderly population, regardless of cardiovascular risk factors, prevalent or incident history of atrial fibrillation, stroke, coronary events and heart failure. Further studies are needed to confirm our findings in the general population and to explore the mechanisms underlying the relationship between use of beta- blockers and increased risk of vascular dementia.

Inhibitory designer receptors aggravate memory loss in a mouse model of down syndrome

The pontine nucleus locus coeruleus (LC) is the primary source of noradrenergic (NE) projections to the brain and is important for working memory, attention, and cognitive flexibility. Individuals with Down syndrome (DS) develop Alzheimer's disease (AD) with high penetrance and often exhibit working memory deficits coupled with degeneration of LC-NE neurons early in the progression of AD pathology. Designer receptors exclusively activated by designer drugs (DREADDs) are chemogenetic tools that allow targeted manipulation of discrete neuronal populations in the brain without the confounds of off-target effects. We utilized male Ts65Dn mice (a mouse model for DS), and male normosomic (NS) controls to examine the effects of inhibitory DREADDs delivered via an AAV vector under translational control of the synthetic PRSx8, dopamine β hydroxylase (DβH) promoter. This chemogenetic tool allowed LC inhibition upon administration of the inert DREADD ligand, clozapine-N-oxide (CNO). DREADD-mediated LC inhibition impaired performance in a novel object recognition task and reversal learning in a spatial task. DREADD-mediated LC inhibition gave rise to an elevation of α-adrenoreceptors both in NS and in Ts65Dn mice. Further, microglial markers showed that the inhibitory DREADD stimulation led to increased microglial activation in the hippocampus in Ts65Dn but not in NS mice. These findings strongly suggest that LC signaling is important for intact memory and learning in Ts65Dn mice and disruption of these neurons leads to increased inflammation and dysregulation of adrenergic receptors.

Hybridization of β-Adrenergic Agonists and Antagonists Confers G Protein Bias

Starting from the β-adrenoceptor agonist isoprenaline and beta-blocker carvedilol, we designed and synthesized three different chemotypes of agonist/antagonist hybrids. Investigations of ligand-mediated receptor activation using bioluminescence resonance energy transfer biosensors revealed a predominant effect of the aromatic head group on the intrinsic activity of our ligands, as ligands with a carvedilol head group were devoid of agonistic activity. Ligands composed of a catechol head group and an antagonist-like oxypropylene spacer possess significant intrinsic activity for the activation of Gα_s, while they only show weak or even no β-arrestin-2 recruitment at both β₁- and β₂-AR. Molecular dynamics simulations suggest that the difference in G protein efficacy and β-arrestin recruitment of the hybrid ( S)-22, the full agonist epinephrine, and the β₂-selective, G protein-biased partial agonist salmeterol depends on specific hydrogen bonding between Ser^5.46 and Asn^6.55, and the aromatic head group of the ligands.

Monoamines and their Derivatives on GPCRs: Potential Therapy for Alzheimer's Disease

Albeit cholinergic depletion remains the key event in Alzheimer's Disease (AD), recent information describes stronger links between monoamines (trace amines, catecholamines, histamine, serotonin, and melatonin) and AD than those known in the past century. Therefore, new drug design strategies focus efforts to translate the scope on these topics and to offer new drugs which can be applied as therapeutic tools in AD. In the present work, we reviewed the state-of-art regarding genetic, neuropathology and neurochemistry of AD involving monoamine systems. Then, we compiled the effects of monoamines found in the brain of mammals as well as the reported effects of their derivatives and some structure-activity relationships. Recent derivatives have triggered exciting effects and pharmacokinetic properties in both murine models and humans. In some cases, the mechanism of action is clear, essentially through the interaction on G-protein-coupled receptors as revised in this manuscript. Additional mechanisms are inhibition of enzymes for their biotransformation, regulation of free-radicals in the central nervous system and others for the effects on Tau phosphorylation or amyloid-beta accumulation. All these data make the monoamines and their derivatives attractive potential elements for AD therapy.

β-Arrestin Based Receptor Signaling Paradigms: Potential Therapeutic Targets for Complex Age-Related Disorders

G protein coupled receptors (GPCRs) were first characterized as signal transducers that elicit downstream effects through modulation of guanine (G) nucleotide-binding proteins. The pharmacotherapeutic exploitation of this signaling paradigm has created a drug-based field covering nearly 50% of the current pharmacopeia. Since the groundbreaking discoveries of the late 1990s to the present day, it is now clear however that GPCRs can also generate productive signaling cascades through the modulation of β-arrestin functionality. β-Arrestins were first thought to only regulate receptor desensitization and internalization - exemplified by the action of visual arrestin with respect to rhodopsin desensitization. Nearly 20 years ago, it was found that rather than controlling GPCR signal termination, productive β-arrestin dependent GPCR signaling paradigms were highly dependent on multi-protein complex formation and generated long-lasting cellular effects, in contrast to G protein signaling which is transient and functions through soluble second messenger systems. β-Arrestin signaling was then first shown to activate mitogen activated protein kinase signaling in a G protein-independent manner and eventually initiate protein transcription - thus controlling expression patterns of downstream proteins. While the possibility of developing β-arrestin biased or functionally selective ligands is now being investigated, no additional research has been performed on its possible contextual specificity in treating age-related disorders. The ability of β-arrestin-dependent signaling to control complex and multidimensional protein expression patterns makes this therapeutic strategy feasible, as treating complex age-related disorders will likely require therapeutics that can exert network-level efficacy profiles. It is our understanding that therapeutically targeting G protein-independent effectors such as β-arrestin will aid in the development of precision medicines with tailored efficacy profiles for disease/age-specific contextualities.

Importance of GPCR-Mediated Microglial Activation in Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with impairment of cognition, memory deficits and behavioral abnormalities. Accumulation of amyloid beta (Aβ) is a characteristic hallmark of AD. Microglia express several GPCRs, which, upon activation by modulators, mediate microglial activation and polarization phenotype. This GPCR-mediated microglial activation has both protective and detrimental effects. Microglial GPCRs are involved in amyloid precursor protein (APP) cleavage and Aβ generation. In addition, microglial GPCRs are featured in the regulation of Aβ degradation and clearance through microglial phagocytosis and chemotaxis. Moreover, in response to Aβ binding on microglial Aβ receptors, they can trigger multiple inflammatory pathways. However, there is still a lack of insight into the mechanistic link between GPCR-mediated microglial activation and its pathological consequences in AD. Currently, the available drugs for the treatment of AD are mostly symptomatic and dominated by acetylcholinesterase inhibitors (AchEI). The selection of a specific microglial GPCR that is highly expressed in the AD brain and capable of modulating AD progression through Aβ generation, degradation and clearance will be a potential source of therapeutic intervention. Here, we have highlighted the expression and distribution of various GPCRs connected to microglial activation in the AD brain and their potential to serve as therapeutic targets of AD.