Nad+ and aging: a focus on novel molecular mechanisms of werner syndrome

La sindrome di Werner (WS) è una rara sindrome ereditaria caratterizzata da invecchiamento precoce causata da una mutazione nel gene Werner, codificante per la proteina WRN appartenente alla famiglia delle DNA elicasi RecQ. La mutazione a carico della proteina WRN si associa alla perdita dei meccanismi di riparazione del DNA con il conseguente accumularsi di danni al DNA, tipico segno della patologia. Tuttavia i meccanismi degli altri principali fenotipi della sindrome, quali la disfunzione mitocondriale, la compromissione del processo mitofagico e l’inefficienza delle cellule staminali, non sono ancora chiari. I nostri dati derivanti sia da modelli animali appartenenti alla classe degli Invertebrati sia da cellule di pazienti affetti mostrano come una significativa riduzione del coenzima NAD+ sia responsabile della disfunzione mitocondriale e dell’ invecchiamento prematuro. Inoltre WRN modula la trascrizione di NMNAT1 (nicotinamide nucleotide adeniltransferasi 1), un enzima chiave nella via biosintetica del cofattore NAD+. Il ripristino di valori fisiologici di NAD+ incrementa l’aspettativa di vita e migliora lo stato di salute nei nostri modelli animali, ristabilisce il profilo metabolico e potenzia il turnover mitocondriale attraverso la mitofagia dipendente dalle proteine DCT-1 e ULK-1. Al fine di identificare una correlazione tra la riduzione dei livelli di NAD+ e l’inefficienza delle cellule staminali, abbiamo valutato eventuali cambiamenti sia nelle cellule mitotiche della linea germinale nel nematode C. elegans sia la popolazione di cellule staminali intestinali (ISC) nel moscerino della frutta Drosophila melanogaster. Sorprendentemente il ripristino dei livelli di NAD+ ristabilisce quasi completamente la proliferazione delle cellule staminali in entrambi i modelli animali. Questo lavoro identifica un ruolo innovativo per il cofattore NAD+ nell’invecchiamento salutare e propone un possibile e nuovo approccio terapeutico per la sindrome di Werner, una patologia attualmente incurabile.The Werner syndrome (WS) is an autosomal recessive premature aging disease associated with mutation of the Werner gene, which encodes the RecQ family DNA helicase WRN. While accumulation of DNA damage in WS is contributed by the loss of DNA repair activity due to WRN dysfunction, mechanisms of other major WS phenotypes, such as mitochondrial dysfunction, impaired mitophagy and stem cell dysfunction, are largely elusive. WS patients exhibit severe metabolic phenotypes, but the underlying mechanisms are unknown and whether the metabolic deficit can be targeted for therapeutic intervention has not been determined. Our data from WS invertebrate models to human WS patient cells show depletion of a fundamental cofactor NAD+ induces mitochondrial dysfunction and premature aging. WRN also regulates transcription of NMNAT1 (nicotinamide nucleotide adenylytransferase 1), a key enzyme in NAD+ biosynthetic pathway. NAD+ repletion improves lifespan and healthspan in our WS animal models, restores metabolic profiles and improves mitochondrial quality through DCT-1 and ULK-1-dependent mitophagy. We further asked whether NAD+ depletion contributes to stem cell dysfunction in WS. We studied this hypothesis by investigating changes of both germ-line mitotic cells in WS C. elegans and intestinal stem cell (ISC) population in WS Drosophila. Intriguingly NAD+ repletion almost completely restored stem cell proliferation in both WS models. This work highlights a novel role of NAD+ in healthy aging and suggests a new therapeutic strategy for WS, a disease currently incurable

Dna damage‐induced neurodegeneration in accelerated ageing and alzheimer’s disease

DNA repair ensures genomic stability to achieve healthy ageing, including cognitive maintenance. Mutations on genes encoding key DNA repair proteins can lead to diseases with accelerated ageing phenotypes. Some of these diseases are xeroderma pigmentosum group A (XPA, caused by mutation of XPA), Cockayne syndrome group A and group B (CSA, CSB, and are caused by mutations of CSA and CSB, respectively), ataxia-telangiectasia (A-T, caused by mutation of ATM), and Werner syndrome (WS, with most cases caused by mutations in WRN). Except for WS, a common trait of the aforementioned progerias is neurodegeneration. Evidence from studies using animal models and patient tissues suggests that the associated DNA repair deficiencies lead to depletion of cellular nicotinamide adenine dinucleotide (NAD+), resulting in impaired mitophagy, accumulation of damaged mitochondria, metabolic derailment, energy deprivation, and finally leading to neuronal dysfunction and loss. Intriguingly, these features are also observed in Alzheimer’s disease (AD), the most common type of dementia affecting more than 50 million individuals worldwide. Further studies on the mechanisms of the DNA repair deficient premature ageing diseases will help to unveil the mystery of ageing and may provide novel therapeutic strategies for AD

Crosstalk among DNA Damage, Mitochondrial Dysfunction, Impaired Mitophagy, Stem Cell Attrition, and Senescence in the Accelerated Ageing Disorder Werner Syndrome

Werner syndrome (WS) is an accelerated ageing disease caused by multiple mutations in the gene encoding the Werner DNA helicase (WRN). The major clinical features of WS include wrinkles, grey hair, osteoporosis, and metabolic phenomena such as atherosclerosis, diabetes, and fatty liver, and resemble those seen in normal ageing, but occur earlier, in middle age. Defective DNA repair resulting from mutations in WRN explain the majority of the clinical features of WS, but the underlying mechanisms driving the larger metabolic dysfunction remain elusive. Recent studies in animal models of WS and in WS patient cells and blood samples suggest the involvement of impaired mitophagy, NAD<sup>+</sup> depletion, and accumulation of damaged mitochondria in metabolic dysfunction. This mini-review summarizes recent progress in the understanding of the molecular mechanisms of metabolic dysfunction in WS, with the involvement of DNA damage, mitochondrial dysfunction, mitophagy reduction, stem cell impairment, and senescence. Future studies on NAD<sup>+</sup> and mitophagy may shed light on potential therapeutic strategies for the WS patients

Residual pesticides reduction on table grapes in post-harvest using ozonated water washing

Nowadays, different systems for reducing pesticides in table grapes are being tested at different production stages either in the field or in post-harvest. The present study tested ozonated water treatments at the beginning of the cold storage on Melissa seedless table grape variety to reduce residue contents of some pesticides. An ozone generator capable of producing ozone concentrations ranging from 18 to 65 Nm3 was utilized for obtaining three ozone concentration levels in water: 3, 5 and 10 mg/L. Ozonated water was placed into a 70 L plastic box where 500 g grape samples closed in perforated plastic clamshell containers were immersed utilizing two washing times (5 and 10 min). Overall, six ozonated water treatments were tested. After ozonated water treatments, all samples were stored for 30 days at 2 °C and 95% relative humidity to simulate commercial practice. Pesticide residue contents were determined before ozonated water treatments (T0) and 30 days after the cold storage (T1). The comparison highlighted the different degradation rates as regards Fludioxonil and Fluxapyroxad. The best results were reached among the non-systemic pesticide such as Fludioxonil. Using 3 mg/L ozonated water to wash grapes for 10 min represented the optimal degradation conditions for the analyzed pesticides

Studying Werner syndrome to elucidate mechanisms and therapeutics of human aging and age-related diseases

Aging is a natural and unavoidable part of life. However, aging is also the primary driver of the dominant human diseases, such as cardiovascular disease, cancer, and neurodegenerative diseases, including Alzheimer’s disease. Unraveling the sophisticated molecular mechanisms of the human aging process may provide novel strategies to extend ‘healthy aging’ and the cure of human aging-related diseases. Werner syndrome (WS), is a heritable human premature aging disease caused by mutations in the gene encoding the Werner (WRN) DNA helicase. As a classical premature aging disease, etiological exploration of WS can shed light on the mechanisms of normal human aging and facilitate the development of interventional strategies to improve healthspan. Here, we summarize the latest progress of the molecular understandings of WRN protein, highlight the advantages of using different WS model systems, including Caenorhabditis elegans, Drosophila melanogaster and induced pluripotent stem cell (iPSC) systems. Further studies on WS will propel drug development for WS patients, and possibly also for normal age-related diseases

NAD+ augmentation restores mitophagy and limits accelerated aging in Werner syndrome

Metabolic dysfunction is a primary feature of Werner syndrome (WS), a human premature aging disease caused by mutations in the gene encoding the Werner (WRN) DNA helicase. WS patients exhibit severe metabolic phenotypes, but the underlying mechanisms are not understood, and whether the metabolic deficit can be targeted for therapeutic intervention has not been determined. Here we report impaired mitophagy and depletion of NAD+, a fundamental ubiquitous molecule, in WS patient samples and WS invertebrate models. WRN regulates transcription of a key NAD+ biosynthetic enzyme nicotinamide nucleotide adenylyltransferase 1 (NMNAT1). NAD+ repletion restores NAD+ metabolic profiles and improves mitochondrial quality through DCT-1 and ULK-1-dependent mitophagy. At the organismal level, NAD+ repletion remarkably extends lifespan and delays accelerated aging, including stem cell dysfunction, in Caenorhabditis elegans and Drosophila melanogaster models of WS. Our findings suggest that accelerated aging in WS is mediated by impaired mitochondrial function and mitophagy, and that bolstering cellular NAD+ levels counteracts WS phenotypes.publishe

Mitophagy inhibits amyloid-β and tau pathology and reverses cognitive deficits in models of Alzheimer's disease

Accumulation of damaged mitochondria is a hallmark of aging and age-related neurodegeneration, including Alzheimer’s disease (AD). The molecular mechanisms of impaired mitochondrial homeostasis in AD are being investigated. Here we provide evidence that mitophagy is impaired in the hippocampus of AD patients, in induced pluripotent stem cell-derived human AD neurons, and in animal AD models. In both amyloid-β (Aβ) and tau Caenorhabditis elegans models of AD, mitophagy stimulation (through NAD+ supplementation, urolithin A, and actinonin) reverses memory impairment through PINK-1 (PTEN-induced kinase-1)-, PDR-1 (Parkinson’s disease-related-1; parkin)-, or DCT-1 (DAF-16/FOXO-controlled germline-tumor affecting-1)-dependent pathways. Mitophagy diminishes insoluble Aβ1–42 and Aβ1–40 and prevents cognitive impairment in an APP/PS1 mouse model through microglial phagocytosis of extracellular Aβ plaques and suppression of neuroinflammation. Mitophagy enhancement abolishes AD-related tau hyperphosphorylation in human neuronal cells and reverses memory impairment in transgenic tau nematodes and mice. Our findings suggest that impaired removal of defective mitochondria is a pivotal event in AD pathogenesis and that mitophagy represents a potential therapeutic intervention

NAD+ augmentation restores mitophagy and limits accelerated aging in Werner syndrome

Metabolic dysfunction is a primary feature of Werner syndrome (WS), a human premature aging disease caused by mutations in the gene encoding the Werner (WRN) DNA helicase. WS patients exhibit severe metabolic phenotypes, but the underlying mechanisms are not understood, and whether the metabolic deficit can be targeted for therapeutic intervention has not been determined. Here we report impaired mitophagy and depletion of NAD+, a fundamental ubiquitous molecule, in WS patient samples and WS invertebrate models. WRN regulates transcription of a key NAD+ biosynthetic enzyme nicotinamide nucleotide adenylyltransferase 1 (NMNAT1). NAD+ repletion restores NAD+ metabolic profiles and improves mitochondrial quality through DCT-1 and ULK-1-dependent mitophagy. At the organismal level, NAD+ repletion remarkably extends lifespan and delays accelerated aging, including stem cell dysfunction, in Caenorhabditis elegans and Drosophila melanogaster models of WS. Our findings suggest that accelerated aging in WS is mediated by impaired mitochondrial function and mitophagy, and that bolstering cellular NAD+ levels counteracts WS phenotypes