Senolytic therapy in mild Alzheimer's disease: a phase 1 feasibility trial

Aluminum chloride and D-galactose induced a zebrafish model of Alzheimer's disease with cognitive deficits and aging

Alzheimer's disease (AD) is an age-related neurodegenerative disorder. Transgenic and pharmacological AD models are extensively studied to understand AD mechanisms and drug discovery. However, they are time-consuming and relatively costly, which hinders the discovery of potential anti-AD therapeutics. Here, we established a new model of AD in larval zebrafish by co-treatment with aluminum chloride (AlCl3) and D-galactose (D-gal) for 72 h. In particular, exposure to 150 μM AlCl3 + 40 mg/mL D-gal, 200 μM AlCl3 + 30 mg/mL D-gal, or 200 μM AlCl3 + 40 mg/mL D-gal successfully induced AD-like symptoms and aging features. Co-treatment with AlCl3 and D-gal caused significant learning and memory deficits, as well as impaired response ability and locomotor capacity in the plus-maze and light/dark test. Moreover, increased acetylcholinesterase and β-galactosidase activities, β-amyloid 1-42 deposition, reduced telomerase activity, elevated interleukin 1 beta mRNA expression, and enhanced reactive oxygen species production were also observed. In conclusion, our zebrafish model is simple, rapid, effective and affordable, incorporating key features of AD and aging, thus may become a unique and powerful tool for high-throughput screening of anti-AD compounds in vivo.

A new clinical age of aging research

Aging is a major risk factor for a variety of diseases, thus, translation of aging research into practical applications is driven by the unmet need for existing clinical therapeutic options. Basic and translational research efforts are converging at a critical stage, yielding insights into how fundamental aging mechanisms are used to identify promising geroprotectors or therapeutics. This review highlights several research areas from a clinical perspective, including senescent cell targeting, alleviation of inflammaging, and optimization of metabolism with endogenous metabolites or precursors. Refining our understanding of these key areas, especially from the clinical angle, may help us to better understand and attenuate aging processes and improve overall health outcomes.

Cellular senescence: A novel therapeutic target for central nervous system diseases

The underlying mechanisms of diseases affecting the central nervous system (CNS) remain unclear, limiting the development of effective therapeutic strategies. Remarkably, cellular senescence, a biological phenomenon observed in cultured fibroblasts in vitro, is a crucial intrinsic mechanism that influences homeostasis of the brain microenvironment and contributes to the onset and progression of CNS diseases. Cellular senescence has been observed in disease models established in vitro and in vivo and in bodily fluids or tissue components from patients with CNS diseases. These findings highlight cellular senescence as a promising target for preventing and treating CNS diseases. Consequently, emerging novel therapies targeting senescent cells have exhibited promising therapeutic effects in preclinical and clinical studies on aging-related diseases. These innovative therapies can potentially delay brain cell loss and functional changes, improve the prognosis of CNS diseases, and provide alternative treatments for patients. In this study, we examined the relevant advancements in this field, particularly focusing on the targeting of senescent cells in the brain for the treatment of chronic neurodegenerative diseases (e.g., Alzheimer's disease, Parkinson's disease, and multiple sclerosis) and acute neurotraumatic insults (e.g., ischemic stroke, spinal cord injury, and traumatic brain injury).

Exploring senescence as a modifier of β cell extracellular vesicles in type 1 diabetes

Type 1 Diabetes (T1D) is a chronic metabolic disease resulting from insulin deficiency due to autoimmune loss of pancreatic β cells. In addition to β cell destruction, it is now accepted that β cell stress and dysfunction, such as senescence, plays a crucial role in the development of the disease. Accumulation of senescent β cells occurs during development of T1D in humans and contributes to the progression of T1D in the nonobese diabetic (NOD) mouse model. Senescent β cells are thought to exacerbate the inflammatory response within the islets by production and secretion of senescence-associated secretory phenotype (SASP). Extracellular vesicles (EVs) from β cells have been shown to carry protein and microRNAs (miRNAs), influencing cellular signaling and may contribute to the development of T1D but it remains to be addressed how senescence impacts β cell EV cargo. In this minireview, we discuss emerging evidence that EV cargo proteins and miRNAs associated with senescence could contribute to the development of T1D and could suggest potential biomarkers and therapeutic targets for the regulation of SASP and elimination of senescent β cells in T1D. Future investigation exploring the intricate relationship between β cell senescence, EVs and miRNAs could pave the way for the development of novel diagnostic techniques and therapeutic interventions.

Genetics of Cardiac Aging Implicate Organ-Specific Variation

Heart structure and function change with age, and the notion that the heart may age faster for some individuals than for others has driven interest in estimating cardiac age acceleration. However, current approaches have limited feature richness (heart measurements; radiomics) or capture extraneous data and therefore lack cardiac specificity (deep learning [DL] on unmasked chest MRI). These technical limitations have been a barrier to efforts to understand genetic contributions to age acceleration. We hypothesized that a video-based DL model provided with heart-masked MRI data would capture a rich yet cardiac-specific representation of cardiac aging. In 61,691 UK Biobank participants, we excluded noncardiac pixels from cardiac MRI and trained a video-based DL model to predict age from one cardiac cycle in the 4-chamber view. We then computed cardiac age acceleration as the bias-corrected prediction of heart age minus the calendar age. Predicted heart age explained 71.1% of variance in calendar age, with a mean absolute error of 3.3 years. Cardiac age acceleration was linked to unfavorable cardiac geometry and systolic and diastolic dysfunction. We also observed links between cardiac age acceleration and diet, decreased physical activity, increased alcohol and tobacco use, and altered levels of 239 serum proteins, as well as adverse brain MRI characteristics. We found cardiac age acceleration to be heritable (h2g 26.6%); a genome-wide association study identified 8 loci related to linked to cardiomyopathy (near TTN, TNS1, LSM3, PALLD, DSP, PLEC, ANKRD1 and MYO18B) and an additional 16 loci (near MECOM, NPR3, KLHL3, HDGFL1, CDKN1A, ELN, SLC25A37, PI15, AP3M1, HMGA2, ADPRHL1, PGAP3, WNT9B, UHRF1 and DOK5). Of the discovered loci, 21 were not previously associated with cardiac age acceleration. Mendelian randomization revealed that lower genetically mediated levels of 6 circulating proteins (MSRA most strongly), as well as greater levels of 5 proteins (LXN most strongly) were associated with cardiac age acceleration, as were greater blood pressure and Lp(a). A polygenic score for cardiac age acceleration predicted earlier onset of arrhythmia, heart failure, myocardial infarction, and mortality. These findings provide a thematic understanding of cardiac age acceleration and suggest that heart- and vascular-specific factors are key to cardiac age acceleration, predominating over a more global aging program.

Long COVID as a disease of accelerated biological aging: An opportunity to translate geroscience interventions

It has been four years since long COVID-the protracted consequences that survivors of COVID-19 face-was first described. Yet, this entity continues to devastate the quality of life of an increasing number of COVID-19 survivors without any approved therapy and a paucity of clinical trials addressing its biological root causes. Notably, many of the symptoms of long COVID are typically seen with advancing age. Leveraging this similarity, we posit that Geroscience-which aims to target the biological drivers of aging to prevent age-associated conditions as a group-could offer promising therapeutic avenues for long COVID. Bearing this in mind, this review presents a translational framework for studying long COVID as a state of effectively accelerated biological aging, identifying research gaps and offering recommendations for future preclinical and clinical studies.

The role of cellular senescence in neurodegenerative diseases

Increasing evidence has revealed that cellular senescence drives NDs, including Alzheimer's disease (AD) and Parkinson's disease. Different senescent cell populations secrete senescence-associated secretory phenotypes (SASP), including matrix metalloproteinase-3, interleukin (IL)-1α, IL-6, and IL-8, which can harm adjacent microglia. Moreover, these cells possess high expression levels of senescence hallmarks (p16 and p21) and elevated senescence-associated β-galactosidase activity in in vitro and in vivo ND models. These senescence phenotypes contribute to the deposition of β-amyloid and tau-protein tangles. Selective clearance of senescent cells and SASP regulation by inhibiting p38/mitogen-activated protein kinase and nuclear factor kappa B signaling attenuate β-amyloid load and prevent tau-protein tangle deposition, thereby improving cognitive performance in AD mouse models. In addition, telomere shortening, a cellular senescence biomarker, is associated with increased ND risks. Telomere dysfunction causes cellular senescence, stimulating IL-6, tumor necrosis factor-α, and IL-1β secretions. The forced expression of telomerase activators prevents cellular senescence, yielding considerable neuroprotective effects. This review elucidates the mechanism of cellular senescence in ND pathogenesis, suggesting strategies to eliminate or restore senescent cells to a normal phenotype for treating such diseases.

Role of astrocytes in Alzheimer's disease pathogenesis and the impact of exercise-induced remodeling

Alzheimer's disease (AD) is a prevalent and debilitating brain disorder that worsens progressively with age, characterized by cognitive decline and memory impairment. The accumulation of amyloid-beta (Aβ) leading to amyloid plaques and hyperphosphorylation of Tau, resulting in intracellular neurofibrillary tangles (NFTs), are primary pathological features of AD. Despite significant research investment and effort, therapies targeting Aβ and NFTs have proven limited in efficacy for treating or slowing AD progression. Consequently, there is a growing interest in non-invasive therapeutic strategies for AD prevention. Exercise, a low-cost and non-invasive intervention, has demonstrated promising neuroprotective potential in AD prevention. Astrocytes, among the most abundant glial cells in the brain, play essential roles in various physiological processes and are implicated in AD initiation and progression. Exercise delays pathological progression and mitigates cognitive dysfunction in AD by modulating astrocyte morphological and phenotypic changes and fostering crosstalk with other glial cells. This review aims to consolidate the current understanding of how exercise influences astrocyte dynamics in AD, with a focus on elucidating the molecular and cellular mechanisms underlying astrocyte remodeling. The review begins with an overview of the neuropathological changes observed in AD, followed by an examination of astrocyte dysfunction as a feature of the disease. Lastly, the review explores the potential therapeutic implications of exercise-induced astrocyte remodeling in the context of AD.

Effects of intermittent senolytic therapy on bone metabolism in postmenopausal women: a phase 2 randomized controlled trial

Preclinical evidence demonstrates that senescent cells accumulate with aging and that senolytics delay multiple age-related morbidities, including bone loss. Thus, we conducted a phase 2 randomized controlled trial of intermittent administration of the senolytic combination dasatinib plus quercetin (D + Q) in postmenopausal women (n = 60 participants). The primary endpoint, percentage changes at 20 weeks in the bone resorption marker C-terminal telopeptide of type 1 collagen (CTx), did not differ between groups (median (interquartile range), D + Q -4.1% (-13.2, 2.6), control -7.7% (-20.1, 14.3); P = 0.611). The secondary endpoint, percentage changes in the bone formation marker procollagen type 1 N-terminal propeptide (P1NP), increased significantly (relative to control) in the D + Q group at both 2 weeks (+16%, P = 0.020) and 4 weeks (+16%, P = 0.024), but was not different from control at 20 weeks (-9%, P = 0.149). No serious adverse events were observed. In exploratory analyses, the skeletal response to D + Q was driven principally by women with a high senescent cell burden (highest tertile for T cell p16 (also known as CDKN2A) mRNA levels) in which D + Q concomitantly increased P1NP (+34%, P = 0.035) and reduced CTx (-11%, P = 0.049) at 2 weeks, and increased radius bone mineral density (+2.7%, P = 0.004) at 20 weeks. Thus, intermittent D + Q treatment did not reduce bone resorption in the overall group of postmenopausal women. However, our exploratory analyses indicate that further studies are needed testing the hypothesis that the underlying senescent cell burden may dictate the clinical response to senolytics. ClinicalTrials.gov identifier: NCT04313634 .

Advancing personalized medicine in neurodegenerative diseases: The role of epigenetics and pharmacoepigenomics in pharmacotherapy

About 80 % of brain disorders have a genetic basis. The pathogenesis of most neurodegenerative diseases is associated with a myriad of genetic defects, epigenetic alterations (DNA methylation, histone/chromatin remodeling, miRNA dysregulation), and environmental factors. The emergence of new sequencing technologies and tools to study the epigenome has led to identifying predictive biomarkers for earlier diagnosis, opening up the possibility of prophylactical interventions. As a result, advances in pharmacogenetics and pharmacoepigenomics now allow for personalized treatments based on the profile of each patient and the specific genetic and epigenetic mechanisms involved. This Review highlights the complexity of neurodegenerative diseases and the variability in patient responses to pharmacotherapy, emphasizing the influence of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of drugs used to treat those conditions. We specifically discuss the potential modulatory effect of several genetic polymorphisms associated with an increased risk of developing different neurodegenerative diseases. We explore genetic and genomic technologies and the potential of analyzing individual-specific drug metabolism to predict and influence drug response and associated clinical outcomes. We also provide insights into the mechanism of action of the drugs under investigation and their potential impact on disease-modifying pathways. Finally, the Review underscores the great potential of this field to enhance the effectiveness and safety of drug treatments through personalized medicine.

Anti-aging effects of medicinal plants and their rapid screening using the nematode Caenorhabditis elegans

BACKGROUND

Aging is the primary risk factor of most chronic diseases in humans, including cardiovascular diseases, osteoporosis and neurodegenerative diseases, which extensively damage the quality of life for elderly individuals. Aging is a multifaceted process with numerous factors affecting it. Efficient model organisms are essential for the research and development of anti-aging agents, particularly when investigating pharmacological mechanisms are needed.

PURPOSE

This review discusses the application of Caenorhabditis elegans for studying aging and its related signaling pathways, and presents an overview of studies exploring the mechanism and screening of anti-aging agents in C. elegans. Additionally, the review summarizes related clinical trials of anti-aging agents to inspire the development of new medications.

METHOD

Literature was searched, analyzed, and collected using PubMed, Web of Science, and Science Direct. The search terms used were "anti-aging", "medicinal plants", "synthetic compounds", "C. elegans", "signal pathway", etc. Several combinations of these keywords were used. Studies conducted in C. elegans or humans were included. Articles were excluded, if they were on studies conducted in silico or in vitro or could not offer effective data.

RESULTS

Four compounds mainly derived through synthesis (metformin, rapamycin, nicotinamide mononucleotide, alpha-ketoglutarate) and four active ingredients chiefly obtained from plants (resveratrol, quercetin, Astragalus polysaccharide, ginsenosides) are introduced emphatically. These compounds and active ingredients exhibit potential anti-aging effects in preclinical and clinical studies. The screening of these anti-aging agents and the investigation of their pharmacological mechanisms can benefit from the use of C. elegans.

CONCLUSION

Medicinal plants provide valuable resource for the treatment of diseases. A wide source of raw materials for the particular plant medicinal compounds having anti-aging effects meet diverse pharmaceutical requirements, such as immunomodulatory, anti-inflammation and alleviating oxidative stress. C. elegans possesses advantages in scientific research including short life cycle, small size, easy maintenance, genetic tractability and conserved biological processes related to aging. C. elegans can be used for the efficient and rapid evaluation of compounds with the potential to slow down aging.

Looking for the philosopher's stone: Emerging approaches to target the hallmarks of aging in the skin

Senescence and epigenetic alterations are two important hallmarks of cellular aging. During aging, cells subjected to stress undergo many cycles of damage and repair before finally entering either apoptosis or senescence, a permanent state of cell cycle arrest. The first biomarkers of senescence to be identified were increased ß-galactosidase activity and induction of p16INK4a. Another feature of senescent cells is the senescence-associated secretory phenotype (SASP), a complex secretome containing more than 80 pro-inflammatory factors including metalloproteinases, growth factors, chemokines and cytokines. The secretome is regulated through a dynamic process involving a self-amplifying autocrine feedback loop and activation of the immune system. Senescent cells play positive and negative roles depending on the composition of their SASP and may participate in various processes including wound healing and tumour suppression, as well as cell regeneration, embryogenesis, tumorigenesis, inflammation and finally aging. The SASP is also a biomarker of age, biological aging and age-related diseases. Recent advances in anti-age research have shown that senescence can be now prevented or delayed by clearing the senescent cells or mitigating the effects of SASP factors, which can be achieved by a healthy lifestyle (exercise and diet), and senolytics and senomorphics, respectively. An alternative is tissue rejuvenation, which can be achieved by stimulating aged stem cells and reprogramming deprogrammed aged cells. These non-clinical findings will open up new avenues of clinical research into the development of treatments capable of preventing or treating age-related pathologies in humans.

Addition of Polyphenols to Drugs: The Potential of Controlling "Inflammaging" and Fibrosis in Human Senescent Lung Fibroblasts In Vitro

The combination of a polyphenol, quercetin, with dasatinib initiated clinical trials to evaluate the safety and efficacy of senolytics in idiopathic pulmonary fibrosis, a lung disease associated with the presence of senescent cells. Another approach to senotherapeutics consists of controlling inflammation related to cellular senescence or "inflammaging", which participates, among other processes, in establishing pulmonary fibrosis. We evaluate whether polyphenols such as caffeic acid, chlorogenic acid, epicatechin, gallic acid, quercetin, or resveratrol combined with different senotherapeutics such as metformin or rapamycin, and antifibrotic drugs such as nintedanib or pirfenidone, could present beneficial actions in an in vitro model of senescent MRC-5 lung fibroblasts. A senescent-associated secretory phenotype (SASP) was evaluated by the measurement of interleukin (IL)-6, IL-8, and IL-1β. The senescent-associated β-galactosidase (SA-β-gal) activity and cellular proliferation were assessed. Fibrosis was evaluated using a Picrosirius red assay and the gene expression of fibrosis-related genes. Epithelial-mesenchymal transition (EMT) was assayed in the A549 cell line exposed to Transforming Growth Factor (TGF)-β in vitro. The combination that demonstrated the best results was metformin and caffeic acid, by inhibiting IL-6 and IL-8 in senescent MRC-5 cells. Metformin and caffeic acid also restore cellular proliferation and reduce SA-β-gal activity during senescence induction. The collagen production by senescent MRC-5 cells was inhibited by epicatechin alone or combined with drugs. Epicatechin and nintedanib were able to control EMT in A549 cells. In conclusion, caffeic acid and epicatechin can potentially increase the effectiveness of senotherapeutic drugs in controlling lung diseases whose pathophysiological component is the presence of senescent cells and fibrosis.

Fyn Kinase in Alzheimer's Disease: Unraveling Molecular Mechanisms and Therapeutic Implications

Alzheimer's disease, characterized by the accumulation of abnormal protein aggregates and neuronal damage in the brain, leads to a gradual decline in cognitive function and memory. As a complex neurodegenerative disorder, it involves disruptions in various biochemical pathways and neurotransmitter systems, contributing to the progressive loss of neurons and synaptic connections. The complexity of Alzheimer's signaling pathways complicates treatment, presenting a formidable challenge in the quest for effective therapeutic interventions. A member of the Src family of kinases (SFKs), Fyn, is a type of non-receptor tyrosine kinase that has been linked to multiple essential CNS processes, such as myelination and synaptic transmission. Fyn is an appealing target for AD treatments because it is uniquely linked to the two major pathologies in AD by its interaction with tau, in addition to being activated by amyloid-beta (Aβ) through PrPC. Fyn mediates neurotoxicity and synaptic impairments caused by Aβ and is involved in regulating the process of Aβ synthesis.Additionally, the tau protein's tyrosine phosphorylation is induced by Fyn. Fyn is also a challenging target because of its widespread body expression and strong homology with other kinases of the Src family, which could cause unintentional off-target effects. This review emphasizes signaling pathways mediated by Fyn that govern neuronal development and plasticity while also summarizing the most noteworthy recent research relevant to Fyn kinase's function in the brain. Additionally, the therapeutic inhibition of Fyn kinase has been discussed, with a focus on the Fyn kinase inhibitors that are in clinical trials, which presents a fascinating opportunity for targeting Fyn kinase in the creation of possible therapeutic approaches for the management of Alzheimer's disease.

Polyphenols and Diets as Current and Potential Nutrition Senotherapeutics in Alzheimer's Disease: Findings from Clinical Trials

Cellular senescence, a hallmark of aging, plays an important role in age-related conditions among older adults. Targeting senescent cells and its phenotype may provide a promising strategy to delay the onset or progression of Alzheimer's disease (AD). In this review article, we investigated efficacy and safety of nutrition senotherapy in AD, with a focus on the role of polyphenols as current and potential nutrition senotherapeutic agents, as well as relevant dietary patterns. Promising results with neuroprotective effects of senotherapeutic agents such as quercetin, resveratrol, Epigallocatechin-gallate, curcumin and fisetin were reported from preclinical studies. However, in-human trials remain limited, and findings were inconclusive. In future, nutrition senotherapeutic agents should be studied both individually and within dietary patterns, through the perspective of cellular senescence and AD. Further studies are warranted to investigate bioavailability, dosing regimen, long term effects of nutrition senotherapy and provide better understanding of the underlying mechanisms. Collaboration between researchers needs to be established, and methodological limitations of current studies should be addressed.

In the land of not-unhappiness: On the state-of-the-art of targeting aging and age-related diseases by biomedical research

The concept of the Land of Not-Unhappiness refers to the potential achievement of eliminating the pathologies of the aging process. To inform of how close we are to settling in the land, we summarize and review the achievements of research on anti-aging interventions over the last hundred years with a specific focus on strategies that slow down metabolism, compensate for aging-related losses, and target a broad range of age-related diseases. We critically evaluate the existing interventions labeled as "anti-aging," such as calorie restriction, exercise, stem cell administration, and senolytics, to provide a down-to-earth evaluation of their current applicability in counteracting aging. Throughout the text, we have maintained a light tone to make it accessible to non-experts in biogerontology, and provide a broad overview for those considering conducting studies, research, or seeking to understand the scientific basis of anti-aging medicine.

Cellular senescence, DNA damage, and neuroinflammation in the aging brain

Aging may lead to low-level chronic inflammation that increases the susceptibility to age-related conditions, including memory impairment and progressive loss of brain volume. As brain health is essential to promoting healthspan and lifespan, it is vital to understand age-related changes in the immune system and central nervous system (CNS) that drive normal brain aging. However, the relative importance, mechanistic interrelationships, and hierarchical order of such changes and their impact on normal brain aging remain to be clarified. Here, we synthesize accumulating evidence that age-related DNA damage and cellular senescence in the immune system and CNS contribute to the escalation of neuroinflammation and cognitive decline during normal brain aging. Targeting cellular senescence and immune modulation may provide a logical rationale for developing new treatment options to restore immune homeostasis and counteract age-related brain dysfunction and diseases.

Chronological and Biological Aging in Amyotrophic Lateral Sclerosis and the Potential of Senolytic Therapies

Amyotrophic Lateral Sclerosis (ALS) is a group of sporadic and genetic neurodegenerative disorders that result in losses of upper and lower motor neurons. Treatment of ALS is limited, and survival is 2-5 years after disease onset. While ALS can occur in younger individuals, the risk significantly increases with advancing age. Notably, both sporadic and genetic forms of ALS share pathophysiological features overlapping hallmarks of aging including genome instability/DNA damage, mitochondrial dysfunction, inflammation, proteostasis, and cellular senescence. This review explores chronological and biological aging in the context of ALS onset and progression. Age-related muscle weakness and motor unit loss mirror aspects of ALS pathology and coincide with peak ALS incidence, suggesting a potential link between aging and disease development. Hallmarks of biological aging, including DNA damage, mitochondrial dysfunction, and cellular senescence, are implicated in both aging and ALS, offering insights into shared mechanisms underlying disease pathogenesis. Furthermore, senescence-associated secretory phenotype and senolytic treatments emerge as promising avenues for ALS intervention, with the potential to mitigate neuroinflammation and modify disease progression.

Senescent-like microglia limit remyelination through the senescence associated secretory phenotype

The capacity to regenerate myelin in the central nervous system (CNS) diminishes with age. This decline is particularly evident in multiple sclerosis (MS), which has been suggested to exhibit features of accelerated biological aging. Whether cellular senescence, a hallmark of aging, contributes to remyelination impairment remains unknown. Here, we show that senescent cells (SCs) accumulate within demyelinated lesions after injury, and their elimination enhances remyelination in young mice but not in aged mice. In young mice, we observed the upregulation of senescence-associated transcripts primarily in microglia after demyelination, followed by their reduction during remyelination. However, in aged mice, senescence-associated factors persisted within lesions, correlating with inefficient remyelination. We found that SC elimination enhanced remyelination in young mice but was ineffective in aged mice. Proteomic analysis of senescence-associated secretory phenotype (SASP) revealed elevated levels of CCL11/Eotaxin-1 in lesions, which was found to inhibit efficient oligodendrocyte maturation. These results suggest therapeutic targeting of SASP components, such as CCL11, may improve remyelination in aging and MS.

Senolytic Therapy Enabled by Senescent Cell-Sensitive Biomimetic Melanin Nano-Senolytics

Cellular senescence is a significant risk factor for aging and age-related diseases (ARD). The canonical senolytics Dasatinib and Quercetin (DQ) have shown promise in clearing senescent cells (SnCs); however, the lack of selectivity poses a challenge in achieving optimal outcomes. Despite the recent occurrence of nanomaterial-based approaches targeting SnCs, limited therapeutic effects, and potential toxicity still remain a major concern. Herein, a "double locks-like" nanoplatform is developed that integrated Galactan coating and mesoporous polydopamine to encase the senolytic drug DQ. By this way, DQ is only released in SnCs that are featured with higher levels of β-galactosidase (β-gal) and low PH. Additionally, the nanoparticles are equipped with 2,2,6,6-Tetramethylpiperidine-1-oxyl (Tempo) to gain enhanced photothermal converting potential. Consequently, the synthesized nanosenolytics demonstrate remarkable specificity and efficacy in eradicating SnCs, and accordingly reverse pulmonary fibrosis in mice without affecting normal tissues. Upon exposure of near-infrared (NIR) light, the nanoparticles demonstrate to efficiently remove senescent tumor cells inducted by chemotherapy, thereby hindering the outgrowth and metastasis or breast cancer. Collectively, the present study develops an "On/Off" switchable nanoplatform in response to SnCs, and produces a more safe, efficient, and feasible way to delay aging or alleviate age-associated diseases.

The potential for senotherapy as a novel approach to extend life quality in veterinary medicine

Cellular senescence, a condition where cells undergo arrest and can assume an inflammatory phenotype, has been associated with initiation and perpetuation of inflammation driving multiple disease processes in rodent models and humans. Senescent cells secrete inflammatory cytokines, proteins, and matrix metalloproteinases, termed the senescence associated secretory phenotype (SASP), which accelerates the aging processes. In preclinical models, drug interventions termed "senotherapeutics" selectively clear senescent cells and represent a promising strategy to prevent or treat multiple age-related conditions in humans and veterinary species. In this review, we summarize the current available literature describing in vitro evidence for senotheraputic activity, preclinical models of disease, ongoing human clinical trials, and potential clinical applications in veterinary medicine. These promising data to date provide further justification for future studies identifying the most active senotherapeutic combinations, dosages, and routes of administration for use in veterinary medicine.

Endothelial cellular senescence and tau accumulation: An interplay full of opportunities?

Recent research has shown that tau protein can be passed to neighboring cells, leading to cellular senescence in the endothelial cells present in the central nervous system (CNS). This discovery could potentially open new doors for testing novel therapeutic compounds that specifically target senescent cells (senolytics) or for identifying new biomarkers that can enable early detection of tauopathies and dementia.

Non-oncogene dependencies: Novel opportunities for cancer therapy

Targeting oncogene addictions have changed the history of subsets of malignancies and continues to represent an excellent therapeutic opportunity. Nonetheless, alternative strategies are required to treat malignancies driven by undruggable oncogenes or loss of tumor suppressor genes and to overcome drug resistance also occurring in cancers addicted to actionable drivers. The discovery of non-oncogene addiction (NOA) uncovered novel therapeutically exploitable "Achilles' heels". NOA refers to genes/pathways not oncogenic per sé but essential for the tumor cell growth/survival while dispensable for normal cells. The clinical success of several classes of conventional and molecular targeted agents can be ascribed to their impact on both tumor cell-associated intrinsic as well as microenvironment-related extrinsic NOA. The integration of genetic, computational and pharmacological high-throughput approaches led to the identification of an expanded repertoire of synthetic lethality interactions implicating NOA targets. Only a few of them have been translated into the clinics as most NOA vulnerabilities are not easily druggable or appealing targets. Nonetheless, their identification has provided in-depth knowledge of tumor pathobiology and suggested novel therapeutic opportunities. Here, we summarize conceptual framework of intrinsic and extrinsic NOA providing exploitable vulnerabilities. Conventional and emerging methodological approaches used to disclose NOA dependencies are reported together with their limits. We illustrate NOA paradigmatic and peculiar examples and outline the functional/mechanistic aspects, potential druggability and translational interest. Finally, we comment on difficulties in exploiting the NOA-generated knowledge to develop novel therapeutic approaches to be translated into the clinics and to fully harness the potential of clinically available drugs.

Focus on senescence: Clinical significance and practical applications

The older population is increasing worldwide, and life expectancy is continuously rising, predominantly thanks to medical and technological progress. Healthspan refers to the number of years an individual can live in good health. From a gerontological viewpoint, the mission is to extend the life spent in good health, promoting well-being and minimizing the impact of aging-related diseases to slow the aging process. Biologically, aging is a malleable process characterized by an intra- and inter-individual heterogeneous and dynamic balance between accumulating damage and repair mechanisms. Cellular senescence is a key component of this process, with senescent cells accumulating in different tissues and organs, leading to aging and age-related disease susceptibility over time. Removing senescent cells from the body or slowing down the burden rate has been proposed as an efficient way to reduce age-dependent deterioration. In animal models, senotherapeutic molecules can extend life expectancy and lifespan by either senolytic or senomorphic activity. Much research shows that dietary and physical activity-driven lifestyle interventions protect against senescence. This narrative review aims to summarize the current knowledge on targeting senescent cells to reduce the risk of age-related disease in animal models and their translational potential for humans. We focused on studies that have examined the potential role of senotherapeutics in slowing the aging process and modifying age-related disease burdens. The review concludes with a general discussion of the mechanisms underlying this unique trajectory and its implications for future research.

Adipose tissue as a linchpin of organismal ageing

Ageing is a conserved biological process, modulated by intrinsic and extrinsic factors, that leads to changes in life expectancy. In humans, ageing is characterized by greatly increased prevalence of cardiometabolic disease, type 2 diabetes and disorders associated with impaired immune surveillance. Adipose tissue displays species-conserved, temporal changes with ageing, including redistribution from peripheral to central depots, loss of thermogenic capacity and expansion within the bone marrow. Adipose tissue is localized to discrete depots, and also diffusely distributed within multiple organs and tissues in direct proximity to specialized cells. Thus, through their potent endocrine properties, adipocytes are capable of modulating tissue and organ function throughout the body. In addition to adipocytes, multipotent progenitor/stem cells in adipose tissue play a crucial role in maintenance and repair of tissues throughout the lifetime. Adipose tissue may therefore be a central driver for organismal ageing and age-associated diseases. Here we review the features of adipose tissue during ageing, and discuss potential mechanisms by which these changes affect whole-body metabolism, immunity and longevity. We also explore the potential of adipose tissue-targeted therapies to ameliorate age-associated disease burdens.

Cellular senescence of granulosa cells in the pathogenesis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age, but its pathology has not been fully characterized and the optimal treatment strategy remains unclear. Cellular senescence is a permanent state of cell-cycle arrest that can be induced by multiple stresses. Senescent cells contribute to the pathogenesis of various diseases, owing to an alteration in secretory profile, termed 'senescence-associated secretory phenotype' (SASP), including with respect to pro-inflammatory cytokines. Senolytics, a class of drugs that selectively eliminate senescent cells, are now being used clinically, and a combination of dasatinib and quercetin (DQ) has been extensively used as a senolytic. We aimed to investigate whether cellular senescence is involved in the pathology of PCOS and whether DQ treatment has beneficial effects in patients with PCOS. We obtained ovaries from patients with or without PCOS, and established a mouse model of PCOS by injecting dehydroepiandrosterone. The expression of the senescence markers p16INK4a, p21, p53, γH2AX, and senescence-associated β-galactosidase and the SASP-related factor interleukin-6 was significantly higher in the ovaries of patients with PCOS and PCOS mice than in controls. To evaluate the effects of hyperandrogenism and DQ on cellular senescence in vitro, we stimulated cultured human granulosa cells (GCs) with testosterone and treated them with DQ. The expression of markers of senescence and a SASP-related factor was increased by testosterone, and DQ reduced this increase. DQ reduced the expression of markers of senescence and a SASP-related factor in the ovaries of PCOS mice and improved their morphology. These results indicate that cellular senescence occurs in PCOS. Hyperandrogenism causes cellular senescence in GCs in PCOS, and senolytic treatment reduces the accumulation of senescent GCs and improves ovarian morphology under hyperandrogenism. Thus, DQ might represent a novel therapy for PCOS.

Frailty trajectories preceding dementia: an individual-level analysis of four cohort studies in the United States and United Kingdom

Frailty may represent a modifiable risk factor for dementia, but the direction of that association remains uncertain. We investigated frailty trajectories in the years preceding dementia onset using data from 23,672 participants (242,760 person-years of follow-up, 2,906 cases of incident dementia) across four cohort studies in the United States and United Kingdom. Bayesian non-linear models revealed accelerations in frailty trajectories 4-9 years before incident dementia. Among participants whose time between frailty measurement and incident dementia exceeded that prodromal period, frailty remained positively associated with dementia risk (adjusted hazard ratios ranged from 1.20 [95% confidence interval, CI = 1.15-1.26] to 1.43 [95% CI = 1.14-1.81]). This observational evidence suggests that frailty increases dementia risk independently of any reverse causality. These findings indicate that frailty measurements can be used to identify high-risk population groups for preferential enrolment into clinical trials for dementia prevention and treatment. Frailty itself may represent a useful upstream target for behavioural and societal approaches to dementia prevention.

Revolutionizing Diabetic Foot Ulcer Care: The Senotherapeutic Approach

Diabetic foot ulcers (DFUs) are a prevalent and profoundly debilitating complication that afflicts individuals with diabetes mellitus (DM). These ulcers are associated with substantial morbidity, recurrence rates, disability, and mortality, imposing substantial economic, psychological, and medical burdens. Timely detection and intervention can mitigate the morbidity and disparities linked to DFU. Nevertheless, current therapeutic approaches for DFU continue to grapple with multifaceted limitations. A growing body of evidence emphasizes the crucial role of cellular senescence in the pathogenesis of chronic wounds. Interventions that try to delay cellular senescence, eliminate senescent cells (SnCs), or suppress the senescence-associated secretory phenotype (SASP) have shown promise for helping chronic wounds to heal. In this context, targeting cellular senescence emerges as a novel therapeutic strategy for DFU. In this comprehensive review, we look at the pathology and treatment of DFU in a systematic way. We also explain the growing importance of investigating SnCs in DFU and highlight the great potential of senotherapeutics that target SnCs in DFU treatment. The development of efficacious and safe senotherapeutics represents a pioneering therapeutic approach aimed at enhancing the quality of life for individuals affected by DFU.

Cellular Senescence as a Targetable Risk Factor for Cardiovascular Diseases: Therapeutic Implications: JACC Family Series

The prevalence of cardiovascular diseases markedly rises with age. Cellular senescence, a hallmark of aging, is characterized by irreversible cell cycle arrest and the manifestation of a senescence-associated secretory phenotype, which has emerged as a significant contributor to aging, mortality, and a spectrum of chronic ailments. An increasing body of preclinical and clinical research has established connections between senescence, senescence-associated secretory phenotype, and age-related cardiac and vascular pathologies. This review comprehensively outlines studies delving into the detrimental impact of senescence on various cardiovascular diseases, encompassing systemic atherosclerosis (including coronary artery disease, stroke, and peripheral arterial disease), as well as conditions such as hypertension, congestive heart failure, arrhythmias, and valvular heart diseases. In addition, we have preclinical studies demonstrating the beneficial effects of senolytics-a class of drugs designed to eliminate senescent cells selectively across diverse cardiovascular disease scenarios. Finally, we address knowledge gaps on the influence of senescence on cardiovascular systems and discuss the future trajectory of strategies targeting senescence for cardiovascular diseases.

Targeting vascular senescence in cardiovascular disease with aging

Aging is a major risk factor for atherosclerosis and cardiovascular disease (CVD). Two major age-associated arterial phenotypes, endothelial dysfunction and large elastic arterial stiffness, are autonomous predictors of future CVD diagnosis and contribute to the progression of CVD in older adults. Senescent cells lose the capacity to proliferate but remain metabolically active and secrete inflammatory factors termed senescence-associated secretory phenotype (SASP), leading to an increase in inflammation and oxidative stress. Accumulation of senescent cells is linked with the progression of age-related diseases and has been known to play a role in cardiovascular disease. In this brief review, we describe the characteristics and mechanisms of senescent cell accumulation and how senescent cells promote endothelial dysfunction and arterial stiffness. We focus on a range of novel therapeutic strategies aimed at reducing the burden of endothelial dysfunction leading to atherosclerosis through targeting senescent cells. Studies have begun to investigate a specific class of drugs that are able to selectively eliminate senescent cells, termed senolytics, which have shown great promise in reversing the aging phenotype and ameliorating pathologies in age-related disorders, creating a new opportunity for aging research. Generating therapies targeting the elimination of senescent cells would improve health span and increase longevity, making senolytics a promising therapy for cardiovascular diseases.

Cellular senescence: Neither irreversible nor reversible

Cellular senescence is a critical stress response program implicated in embryonic development, wound healing, aging, and immunity, and it backs up apoptosis as an ultimate cell-cycle exit mechanism. In analogy to replicative exhaustion of telomere-eroded cells, premature types of senescence-referring to oncogene-, therapy-, or virus-induced senescence-are widely considered irreversible growth arrest states as well. We discuss here that entry into full-featured senescence is not necessarily a permanent endpoint, but dependent on essential maintenance components, potentially transient. Unlike a binary state switch, we view senescence with its extensive epigenomic reorganization, profound cytomorphological remodeling, and distinctive metabolic rewiring rather as a journey toward a full-featured arrest condition of variable strength and depth. Senescence-underlying maintenance-essential molecular mechanisms may allow cell-cycle reentry if not continuously provided. Importantly, senescent cells that resumed proliferation fundamentally differ from those that never entered senescence, and hence would not reflect a reversion but a dynamic progression to a post-senescent state that comes with distinct functional and clinically relevant ramifications.

Circulating biomarkers of inflammaging and Alzheimer's disease to track age-related trajectories of dementia: Can we develop a clinically relevant composite combination?

Alzheimer's disease (AD) is a rapidly growing global concern due to a consistent rise of the prevalence of dementia which is mainly caused by the aging population worldwide. An early diagnosis of AD remains important as interventions are plausibly more effective when started at the earliest stages. Recent developments in clinical research have focused on the use of blood-based biomarkers for improve diagnosis/prognosis of neurodegenerative diseases, particularly AD. Unlike invasive cerebrospinal fluid tests, circulating biomarkers are less invasive and will become increasingly cheaper and simple to use in larger number of patients with mild symptoms or at risk of dementia. In addition to AD-specific markers, there is growing interest in biomarkers of inflammaging/neuro-inflammaging, an age-related chronic low-grade inflammatory condition increasingly recognized as one of the main risk factor for almost all age-related diseases, including AD. Several inflammatory markers have been associated with cognitive performance and AD development and progression. The presence of senescent cells, a key driver of inflammaging, has also been linked to AD pathogenesis, and senolytic therapy is emerging as a potential treatment strategy. Here, we describe blood-based biomarkers clinically relevant for AD diagnosis/prognosis and biomarkers of inflammaging associated with AD. Through a systematic review approach, we propose that a combination of circulating neurodegeneration and inflammatory biomarkers may contribute to improving early diagnosis and prognosis, as well as providing valuable insights into the trajectory of cognitive decline and dementia in the aging population.

Repurposing Drugs for Senotherapeutic Effect: Potential Senomorphic Effects of Female Synthetic Hormones

Repurposing previously approved drugs may fast track the route to the clinic for potential senotherapeutics and improves the inefficiency of the clinical drug development pipeline. We performed a repurposing screen of 240 clinically approved molecules in human primary dermal fibroblasts for their effects on CDKN2A expression. Molecules demonstrating effects on CDKN2A expression underwent secondary screening for senescence-associated beta galactosidase (SAB) activity, based on effect size, direction, and/or molecule identity. Selected molecules then underwent a more detailed assessment of senescence phenotypes including proliferation, apoptosis, DNA damage, senescence-associated secretory phenotype (SASP) expression, and regulators of alternative splicing. A selection of the molecules demonstrating effects on senescence were then used in a new bioinformatic structure-function screen to identify common structural motifs. In total, 90 molecules displayed altered CDKN2A expression at one or other dose, of which 15 also displayed effects on SAB positivity in primary human dermal fibroblasts. Of these, 3 were associated with increased SAB activity, and 11 with reduced activity. The female synthetic sex hormones-diethylstilboestrol, ethynyl estradiol and levonorgestrel-were all associated with a reduction in aspects of the senescence phenotype in male cells, with no effects visible in female cells. Finally, we identified that the 30 compounds that decreased CDKN2A activity the most had a common substructure linked to this function. Our results suggest that several drugs licensed for other indications may warrant exploration as future senotherapies, but that different donors and potentially different sexes may respond differently to senotherapeutic compounds. This underlines the importance of considering donor-related characteristics when designing drug screening platforms.

Senescent T Cells in Age-Related Diseases

Age-induced alterations in human immunity are often considered deleterious and are referred to as immunosenescence. The immune system monitors the number of senescent cells in the body, while immunosenescence may represent the initiation of systemic aging. Immune cells, particularly T cells, are the most impacted and involved in age-related immune function deterioration, making older individuals more prone to different age-related diseases. T-cell senescence can impact the effectiveness of immunotherapies that rely on the immune system's function, including vaccines and adoptive T-cell therapies. The research and practice of using senescent T cells as therapeutic targets to intervene in age-related diseases are in their nascent stages. Therefore, in this review, we summarize recent related literature to investigate the characteristics of senescent T cells as well as their formation mechanisms, relationship with various aging-related diseases, and means of intervention. The primary objective of this article is to explore the prospects and possibilities of therapeutically targeting senescent T cells, serving as a valuable resource for the development of immunotherapy and treatment of age-related diseases.

Evaluation of Exploratory Fluid Biomarker Results from a Phase 1 Senolytic Trial in Mild Alzheimer's Disease

Senescent cell accumulation contributes to the progression of age-related disorders including Alzheimer's disease (AD). Clinical trials evaluating senolytics, drugs that clear senescent cells, are underway, but lack standardized outcome measures. Our team recently published data from the first open-label trial to evaluate senolytics (dasatinib plus quercetin) in AD. After 12-weeks of intermittent treatment, we reported brain exposure to dasatinib, favorable safety and tolerability, and modest post-treatment changes in cerebrospinal fluid (CSF) inflammatory and AD biomarkers using commercially available assays. Herein, we present more comprehensive exploratory analyses of senolytic associated changes in AD relevant proteins, metabolites, lipids, and transcripts measured across blood, CSF, and urine. These analyses included mass spectrometry for precise quantification of amyloid beta (Aß) and tau in CSF; immunoassays to assess senescence associated secretory factors in plasma, CSF, and urine; mass spectrometry analysis of urinary metabolites and lipids in blood and CSF; and transcriptomic analyses relevant to chronic stress measured in peripheral blood cells. Levels of Aß and tau species remained stable. Targeted cytokine and chemokine analyses revealed treatment-associated increases in inflammatory plasma fractalkine and MMP-7 and CSF IL-6. Urinary metabolites remained unchanged. Modest treatment-associated lipid profile changes suggestive of decreased inflammation were observed both peripherally and centrally. Blood transcriptomic analysis indicated downregulation of inflammatory genes including FOS, FOSB, IL1β, IL8, JUN, JUNB, PTGS2. These data provide a foundation for developing standardized outcome measures across senolytic studies and indicate distinct biofluid-specific signatures that will require validation in future studies. ClinicalTrials.gov: NCT04063124.

Emerging role of senescent microglia in brain aging-related neurodegenerative diseases

Brain aging is a recognized risk factor for neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease), but the intricate interplay between brain aging and the pathogenesis of these conditions remains inadequately understood. Cellular senescence is considered to contribute to cellular dysfunction and inflammaging. According to the threshold theory of senescent cell accumulation, the vulnerability to neurodegenerative diseases is associated with the rates of senescent cell generation and clearance within the brain. Given the role of microglia in eliminating senescent cells, the accumulation of senescent microglia may lead to the acceleration of brain aging, contributing to inflammaging and increased vulnerability to neurodegenerative diseases. In this review, we propose the idea that the senescence of microglia, which is notably vulnerable to aging, could potentially serve as a central catalyst in the progression of neurodegenerative diseases. The senescent microglia are emerging as a promising target for mitigating neurodegenerative diseases.

Current senolytics: Mode of action, efficacy and limitations, and their future

Senescence is a cellular state characterized by its near-permanent halted cell cycle and distinct secretory phenotype. Although senescent cells have a variety of beneficial physiological functions, progressive accumulation of these cells due to aging or other conditions has been widely shown to provoke deleterious effects on the normal functioning of the same or higher-level biological organizations. Recently, erasing senescent cells in vivo, using senolytics, could ameliorate diseases identified with an elevated number of senescent cells. Since then, researchers have struggled to develop new senolytics each with different selectivity and potency. In this review, we have gathered and classified the proposed senolytics and discussed their mechanisms of action. Moreover, we highlight the heterogeneity of senolytics regarding their effect sizes, and cell type specificity as well as comment on the exploited strategies to improve these features. Finally, we suggest some prospective routes for the novel methods for ablation of senescent cells.

A randomized placebo-controlled trial of nicotinamide riboside in older adults with mild cognitive impairment

Nicotinamide riboside (NR) increases blood levels of NAD+, a cofactor central to energy metabolism, and improves brain function in some rodent models of neurodegeneration. We conducted a placebo-controlled randomized pilot study with the primary objective of determining safety of NR in older adults with mild cognitive impairment (MCI). Twenty subjects with MCI were randomized to receive placebo or NR using dose escalation to achieve, and maintain, a final dose of 1 g/day over a 10-week study duration. The primary outcome was post-treatment change from baseline measures of cognition (Montreal Cognitive Assessment, MoCA). Predefined secondary outcomes included post-treatment changes in cerebral blood flow (CBF); blood NAD+ levels; and additional neurocognitive, psychometric, and physical performance tests. DNA methylation was assessed in peripheral blood mononuclear cells (PBMCs) as an exploratory outcome. The target NR dose was safely achieved as evidenced by a 2.6-fold increase in blood NAD+ in the NR group (p < 0.001, 95% CI [17.77, 43.49]) with no between-group difference in adverse event reporting. MoCA and other neurocognitive and psychometric metrics remained stable throughout the study. NR reduced CBF in the default mode network (DMN) with greatest differences observed in the left inferior parietal lobe (IPL) (DMN p = 0.013, μ = 0.92, 95% CI [0.23, 1.62]; left IPL p = 0.009, μ = 1.66, 95% CI [0.5, 2.82]). Walking speed in the placebo group significantly improved across the study duration suggestive of a practice effect but did not change in the NR group (p = 0.0402 and p = 0.4698, respectively). Other secondary outcome measures remained stable. Global methylation analyses indicated a modest NR-associated increase in DNA methylation and concomitant reduction in epigenetic age as measured by PhenoAge and GrimAge epigenetic clock analyses. In summary, NR significantly increased blood NAD+ concentrations in older adults with MCI. NR was well tolerated and did not alter cognition. While CBF was reduced by NR treatment, statistical significance would not have withstood multiple comparisons correction. A larger trial of longer duration is needed to determine the potential of NR as a strategy to improve cognition and alter CBF in older adults with MCI. ClinicalTrials.gov NCT02942888.

Emerging epigenetic insights into aging mechanisms and interventions

Epigenetic dysregulation emerges as a critical hallmark and driving force of aging. Although still an evolving field with much to explore, it has rapidly gained significance by providing valuable insights into the mechanisms of aging and potential therapeutic opportunities for age-related diseases. Recent years have witnessed remarkable strides in our understanding of the epigenetic landscape of aging, encompassing pivotal elements, such as DNA methylation, histone modifications, RNA modifications, and noncoding (nc) RNAs. Here, we review the latest discoveries that shed light on new epigenetic mechanisms and critical targets for predicting and intervening in aging and related disorders. Furthermore, we explore burgeoning interventions and exemplary clinical trials explicitly designed to foster healthy aging, while contemplating the potential ramifications of epigenetic influences.

The interaction between ageing and Alzheimer's disease: insights from the hallmarks of ageing

Ageing is a crucial risk factor for Alzheimer's disease (AD) and is characterised by systemic changes in both intracellular and extracellular microenvironments that affect the entire body instead of a single organ. Understanding the specific mechanisms underlying the role of ageing in disease development can facilitate the treatment of ageing-related diseases, such as AD. Signs of brain ageing have been observed in both AD patients and animal models. Alleviating the pathological changes caused by brain ageing can dramatically ameliorate the amyloid beta- and tau-induced neuropathological and memory impairments, indicating that ageing plays a crucial role in the pathophysiological process of AD. In this review, we summarize the impact of several age-related factors on AD and propose that preventing pathological changes caused by brain ageing is a promising strategy for improving cognitive health.

A Need for Refined Senescence Biomarkers and Measures of Senolytics in the Brain

Cellular senescence contributes to Alzheimer's disease (AD) pathogenesis. Treatments that remove senescent cells, senolytics, improve brain outcomes in AD mice with amyloid-β or tau deposition. 3xTgAD mice develop both AD neuropathologies; however, Ng et al. report low p16INK4a-associated senescence in the brain. Senolytic treatment by genetic removal; dasatinib with quercetin (D+Q), which enter the brain; and ABT-263 with limited brain penetrance all reduced AD neuropathology. Refined measures of senescence and brain exposure would help clarify the benefits of senolytics despite low p16INK4a-associated senescence and potential limited brain penetrance.

Delaying Brain Aging or Decreasing Tau Levels as Strategies to Prevent Alzheimer's Disease: In Memoriam of Mark A. Smith

Aging is the main risk for neurodegenerative disorders like Alzheimer's disease. In this short review, I will comment on how delaying brain aging through the addition of Yamanaka Factors or small compounds that bind to the folate receptor alpha, which promote the expression of the Yamanaka Factors or by the decrease tau levels in brain cells from older subjects could serve as strategies to prevent Alzheimer's disease.

Alzheimer's disease: the role of extrinsic factors in its development, an investigation of the environmental enigma

In the realm of Alzheimer's disease, the most prevalent form of dementia, the impact of environmental factors has ignited intense curiosity due to its substantial burden on global health. Recent investigations have unveiled these environmental factors as key contributors, shedding new light on their profound influence. Notably, emerging evidence highlights the detrimental role of various environmental contaminants in the incidence and progression of Alzheimer's disease. These contaminants encompass a broad spectrum, including air pollutants laden with ozone, neurotoxic metals like lead, aluminum, manganese, and cadmium, pesticides with their insidious effects, and the ubiquitous presence of plastics and microplastics. By meticulously delving into the intricate web connecting environmental pollutants and this devastating neurological disorder, this comprehensive chapter takes a deep dive into their involvement as significant risk factors for Alzheimer's disease. Furthermore, it explores the underlying molecular mechanisms through which these contaminants exert their influence, aiming to unravel the complex interactions that drive the pathogenesis of the disease. Additionally, this chapter proposes potential strategies to mitigate the detrimental effects of these environmental contaminants on brain health, with the ultimate goal of restoring and preserving typical cognitive function. Through this comprehensive exploration, we aim to enhance our understanding of the multifaceted relationship between neurotoxins and Alzheimer's disease, providing a solid foundation for developing innovative in-vivo models and advancing our knowledge of the intricate pathological processes underlying this debilitating condition.

Exploring Multitarget Strategies for Membrane Protection in Alzheimer's Disease

The exploration of multitarget molecules presents a promising avenue in the quest for effective therapeutic strategies against Alzheimer's disease (AD), a multifactorial neurodegenerative disorder. Traditional single-target drugs have shown limited success due to the complex interplay of pathological processes involved in AD. Multitarget-directed ligands (MTDLs), designed to interact with multiple targets simultaneously, offer a more holistic approach to address the multifaceted nature of neurodegenerative diseases. Recent studies have highlighted the potential of chalcones and huprine derivatives in mitigating amyloid-β peptide-associated toxicity and preserving membrane integrity, crucial for cellular homeostasis. The interaction of these compounds with lipid bilayers may modulate biological responses, opening a new realm of investigation in membrane-centric phenomena. This approach not only broadens the mechanistic understanding of bioactive compounds but also underscores the need for a paradigm shift in AD research, focusing on both intracellular targets and plasma membrane protection for more effective treatment strategies.

Mechanism and therapeutic potential of targeting cGAS-STING signaling in neurological disorders

DNA sensing is a pivotal component of the innate immune system that is responsible for detecting mislocalized DNA and triggering downstream inflammatory pathways. Among the DNA sensors, cyclic GMP-AMP synthase (cGAS) is a primary player in detecting cytosolic DNA, including foreign DNA from pathogens and self-DNA released during cellular damage, culminating in a type I interferon (IFN-I) response through stimulator of interferon genes (STING) activation. IFN-I cytokines are essential in mediating neuroinflammation, which is widely observed in CNS injury, neurodegeneration, and aging, suggesting an upstream role for the cGAS DNA sensing pathway. In this review, we summarize the latest developments on the cGAS-STING DNA-driven immune response in various neurological diseases and conditions. Our review covers the current understanding of the molecular mechanisms of cGAS activation and highlights cGAS-STING signaling in various cell types of central and peripheral nervous systems, such as resident brain immune cells, neurons, and glial cells. We then discuss the role of cGAS-STING signaling in different neurodegenerative conditions, including tauopathies, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as aging and senescence. Finally, we lay out the current advancements in research and development of cGAS inhibitors and assess the prospects of targeting cGAS and STING as therapeutic strategies for a wide spectrum of neurological diseases.

Translating the Biology of Aging into New Therapeutics for Alzheimer's Disease: Senolytics

The recent FDA-approval for amyloid lowering therapies reflects an unwavering commitment from the Alzheimer's disease (AD) research community to identify treatments for this leading cause of dementia. The clinical benefits achieved by reducing amyloid, though modest, provide evidence that disease modification is possible. Expanding the same tenacity to interventions targeting upstream drivers of AD pathogenesis could significantly impact the disease course. Advanced age is the greatest risk factor for developing AD. Interventions targeting biological aging offer the possibility of disrupting a foundational cause of AD. Senescent cells accumulate with age and contribute to inflammation and age-related diseases like AD. Senolytic drugs that clear senescent cells improve healthy aging, halt AD disease progression in animal models and are undergoing clinical testing. This review explores the biology of aging, the role of senescent cells in AD pathology, and various senotherapeutic approaches such as senolytics, dampening the SASP (senescence associated secretory phenotype), senescence pathway inhibition, vaccines, and prodrugs. We highlight ongoing clinical trials evaluating the safety and efficacy of the most advanced senolytic approach, dasatinib and quercetin (D+Q), including an ongoing Phase II senolytic trial supported by the Alzheimer's Drug Discovery Foundation (ADDF). Challenges in the field of senotherapy for AD, including target engagement and biomarker development, are addressed. Ultimately, this research pursuit may lead to an effective treatment for AD and provide the field with another disease-modifying therapy to be used, alone or in combination, with other emerging treatment options.