Senescent Cell Mitochondrial DNA Release

Low-grade inflammation is a hallmark of old age and a central driver of ageing-associated impairment and disease1. Multiple factors can contribute to ageing-associated inflammation2; however, the molecular pathways that transduce aberrant inflammatory signalling and their impact in natural ageing remain unclear. Here we show that the cGAS-STING signalling pathway, which mediates immune sensing of DNA3, is a critical driver of chronic inflammation and functional decline during ageing. Blockade of STING suppresses the inflammatory phenotypes of senescent human cells and tissues, attenuates ageing-related inflammation in multiple peripheral organs and the brain in mice, and leads to an improvement in tissue function. Focusing on the ageing brain, we reveal that activation of STING triggers reactive microglial transcriptional states, neurodegeneration and cognitive decline. Cytosolic DNA released from perturbed mitochondria elicits cGAS activity in old microglia, defining a mechanism by wh

Recognition of foreign or misplaced nucleic acids is one of the principal modes by which the immune system detects pathogenic entities. When cytosolic DNA is sensed, a signal is relayed via the cGAS-STING pathway: this involves the activation of cyclic GMP-AMP (cGMP-AMP) synthase (cGAS) and generation of the cyclic dinucleotide cGAMP, followed by the induction of stimulator of interferon genes (STING). The cGAS-STING pathway responds to viral, bacterial, and self-DNA. Whereas it generally mediates immune surveillance and is often neuroprotective, excessive engagement of the system can be deleterious. This is relevant in aging and age-related neurological diseases, where neuroinflammation contributes to disease progression. This review focuses on cGAS-STING signaling in aging, neurodegeneration, and neuroinflammation, and on therapeutic implications.

In addition to constituting the genetic material of an organism, DNA is a tracer for the recognition of foreign pathogens and a trigger of the innate immune system. cGAS functions as a sensor of double-stranded DNA fragments and initiates an immune response via the adaptor protein STING. The cGAS-STING pathway not only defends cells against various DNA-containing pathogens but also modulates many pathological processes caused by the immune response to the ectopic localization of self-DNA, such as cytosolic mitochondrial DNA (mtDNA) and extranuclear chromatin. In addition, macrophages can cause inflammation by forming a class of protein complexes called inflammasomes, and the activation of the NLRP3 inflammasome requires the release of oxidized mtDNA. In innate immunity related to inflammasomes, mtDNA release is mediated by macropores that are formed on the outer membrane of mitochondria via VDAC oligomerization. These macropores are specifically formed in response to mitochondrial stre

Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP)1. Mitochondria are major regulators of the SASP; however, the underlying mechanisms have not been elucidated2. Mitochondria are often essential for apoptosis, a cell fate distinct from cellular senescence. During apoptosis, widespread mitochondrial outer membrane permeabilization (MOMP) commits a cell to die3. Here we find that MOMP occurring in a subset of mitochondria is a feature of cellular senescence. This process, called minority MOMP (miMOMP), requires BAX and BAK macropores enabling the release of mitochondrial DNA (mtDNA) into the cytosol. Cytosolic mtDNA in turn activates the cGAS-STING pathway, a major regulator of the SASP. We find that inhibition of MOMP in vivo decreases inflammatory markers and improves healthspan in aged mice. Our results reveal that apoptosis and senescence are regulated by similar mitochondria-dependent mec

The mechanism regulating cellular senescence of postmitotic muscle cells is still unknown. cGAS-STING innate immune signaling was found to mediate cellular senescence in various types of cells, including postmitotic neuron cells, which however has not been explored in postmitotic muscle cells. Here by studying the myofibers from Zmpste24-/- progeria aged mice [an established mice model for Hutchinson-Gilford progeria syndrome (HGPS)], we observed senescence-associated phenotypes in Zmpste24-/- myofibers, which is coupled with increased oxidative damage to mitochondrial DNA (mtDNA) and secretion of senescence-associated secretory phenotype (SASP) factors. Also, Zmpste24-/- myofibers feature increased release of mtDNA from damaged mitochondria, mitophagy dysfunction, and activation of cGAS-STING. Meanwhile, increased mtDNA release in Zmpste24-/- myofibers appeared to be related with increased VDAC1 oligomerization. Further, the inhibition of VDAC1 oligomerization in Zmpste24-/- myofibers

Neuroinflammation drives Alzheimer's disease (AD) pathogenesis. Z-DNA, a non-canonical left-handed DNA structure, activates innate immune signaling through Z-DNA-binding protein 1 (ZBP1). However, the functional significance of ZBP1-mediated Z-DNA detection in AD remains undefined. Here, we found that ZBP1 is amplified in AD microglia, driving innate immune responses and neuroinflammation through sensing Z-form mitochondrial DNA (mtDNA). We show that oxidized mtDNA, generated by amyloid-β (Aβ)-induced oxidative stress, was fragmented and released into the cytoplasm, forming Z-DNA. Z-DNA-activated ZBP1 engaged receptor-interacting protein kinase 1 (RIPK1), promoting its kinase activation and inducing transcription of pro-inflammatory molecules and inflammatory signaling mediators. Genetic deletion of Zbp1 or inhibition of RIPK1 attenuated neuroinflammation, Aβ pathology, and behavioral deficits in an AD mouse model. Our findings reveal that oxidation induces the Z conformer in mtDNA and

The aging population worldwide is facing a significant increase in age-related non-communicable diseases, including cardiovascular and brain pathologies. This comprehensive review paper delves into the impact of the exposome, which encompasses the totality of environmental exposures, on unhealthy aging. It explores how environmental factors contribute to the acceleration of aging processes, increase biological age, and facilitate the development and progression of a wide range of age-associated diseases. The impact of environmental factors on cognitive health and the development of chronic age-related diseases affecting the cardiovascular system and central nervous system is discussed, with a specific focus on Alzheimer's disease, Parkinson's disease, stroke, small vessel disease, and vascular cognitive impairment (VCI). Aging is a major risk factor for these diseases. Their pathogenesis involves cellular and molecular mechanisms of aging such as increased oxidative stress, impaired mi

In idiopathic Parkinson’s disease (PD), pathologic αSyn aggregates drive oxidative and nitrative stress that may cause genomic and mitochondrial DNA damage. These events are associated with activation of the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) immune pathway, but it is not known whether STING is activated in or contributes to α-synucleinopathies. Herein, we used primary cell cultures and the intrastriatal αSyn preformed fibril (αSyn-PFF) mouse model of PD to demonstrate that αSyn pathology causes STING-dependent neuroinflammation and dopaminergic neurodegeneration. In microglia-astrocyte cultures, αSyn-PFFs induced DNA double-strand break (DSB) damage response signaling (γH2A.X), as well as TBK1 activation that was blocked by STING inhibition. In the αSyn-PFF mouse model, we similarly observed TBK1 activation and increased γH2A.X within striatal microglia prior to the onset of dopaminergic neurodegeneration. Using STING-deficient (Stinggt) mice, we dem

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect fo

Cytoplasmic accumulation of TDP-43 is a disease hallmark for many cases of amyotrophic lateral sclerosis (ALS), associated with a neuroinflammatory cytokine profile related to upregulation of nuclear factor κB (NF-κB) and type I interferon (IFN) pathways. Here we show that this inflammation is driven by the cytoplasmic DNA sensor cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS) when TDP-43 invades mitochondria and releases DNA via the permeability transition pore. Pharmacologic inhibition or genetic deletion of cGAS and its downstream signaling partner STING prevents upregulation of NF-κB and type I IFN induced by TDP-43 in induced pluripotent stem cell (iPSC)-derived motor neurons and in TDP-43 mutant mice. Finally, we document elevated levels of the specific cGAS signaling metabolite cGAMP in spinal cord samples from patients, which may be a biomarker of mtDNA release and cGAS/STING activation in ALS. Our results identify mtDNA release and cGAS/STING activation as critical de

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission

Ageing is the primary risk factor for most neurodegenerative diseases, including Alzheimer disease (AD) and Parkinson disease (PD). One in ten individuals aged ≥65 years has AD and its prevalence continues to increase with increasing age. Few or no effective treatments are available for ageing-related neurodegenerative diseases, which tend to progress in an irreversible manner and are associated with large socioeconomic and personal costs. This Review discusses the pathogenesis of AD, PD and other neurodegenerative diseases, and describes their associations with the nine biological hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, mitochondrial dysfunction, cellular senescence, deregulated nutrient sensing, stem cell exhaustion and altered intercellular communication. The central biological mechanisms of ageing and their potential as targets of novel therapies for neurodegenerative diseases are also discussed, with potential the

Senescence is a cellular state linked to ageing and age-onset disease across many mammalian species1,2. Acutely, senescent cells promote wound healing3,4 and prevent tumour formation5; but they are also pro-inflammatory, thus chronically exacerbate tissue decline. Whereas senescent cells are active targets for anti-ageing therapy6-11, why these cells form in vivo, how they affect tissue ageing and the effect of their elimination remain unclear12,13. Here we identify naturally occurring senescent glia in ageing Drosophila brains and decipher their origin and influence. Using Activator protein 1 (AP1) activity to screen for senescence14,15, we determine that senescent glia can appear in response to neuronal mitochondrial dysfunction. In turn, senescent glia promote lipid accumulation in non-senescent glia; similar effects are seen in senescent human fibroblasts in culture. Targeting AP1 activity in senescent glia mitigates senescence biomarkers, extends fly lifespan and health span, and

Alzheimer's disease and related dementias (ADRD) are among the top contributors to disability and mortality in later life. As with many chronic conditions, aging is the single most influential factor in the development of ADRD. Even among older adults who remain free of dementia throughout their lives, cognitive decline and neurodegenerative changes are appreciable with advancing age, suggesting shared pathophysiological mechanisms. In this Review, we provide an overview of changes in cognition, brain morphology, and neuropathological protein accumulation across the lifespan in humans, with complementary and mechanistic evidence from animal models. Next, we highlight selected aging processes that are differentially regulated in neurodegenerative disease, including aberrant autophagy, mitochondrial dysfunction, cellular senescence, epigenetic changes, cerebrovascular dysfunction, inflammation, and lipid dysregulation. We summarize research across clinical and translational studies to li

The stimulator of interferon genes (STING) pathway plays a unique role in antitumor immunity, bridging innate and adaptive immune responses to initiate a sustained and highly effective antitumor immune response. However, due to the widespread expression of the STING pathway and the lack of clearly distinguishable physiological and pathological features, its excessive or systemic activation can trigger severe adverse effects, such as cytokine storms, thereby limiting its clinical applicability. With the development of nanotechnology, stimuli-responsive nanoplatforms designed based on tumor microenvironment (TME) signals (such as pH, glutathione, reactive oxygen species, hypoxia, and enzymes) and exogenous stimuli (including light, ultrasound, radiation, and magnetic fields) provide a promising strategy for the precise activation of the STING pathway. These nanoplatforms can achieve tumor-specific and controllable STING activation, thereby minimizing off-target toxicity, and can be combi

Recent advancements in gene expression modulation and RNA delivery systems have underscored the immense potential of nucleic acid-based therapies (NA-BTs) in biological research. However, the blood-brain barrier (BBB), a crucial regulatory structure that safeguards brain function, presents a significant obstacle to the delivery of drugs to glial cells and neurons. The BBB tightly regulates the movement of substances from the bloodstream into the brain, permitting only small molecules to pass through. This selective permeability poses a significant challenge for effective therapeutic delivery, especially in the case of NA-BTs. Extracellular vesicles, particularly exosomes, are recognized as valuable reservoirs of potential biomarkers and therapeutic targets. They are also gaining significant attention as innovative drug and nucleic acid delivery (NAD) carriers. Their unique ability to safeguard and transport genetic material, inherent biocompatibility, and capacity to traverse physiolog

The convergence of peptides and nanoparticles through bionanoconjugation has emerged as a transformative strategy to address the persistent challenges in treating neurodegenerative disorders. Peptides, particularly short sequences (< 45 amino acids), offer unique advantages as protein mimetics, including structural flexibility, target specificity and blood-brain barrier permeability. Their clinical translation is hindered by rapid enzymatic degradation, short half-life, and poor bioavailability. Conjugation with nanoparticles, overcomes these limitations by enhancing stability, prolonging circulation, and enabling precise targeting. Peptide-nanoparticle conjugates, including TAT-functionalized gold nanoparticles and RGD-decorated polymeric systems, have shown significant improvements in blood brain barrier penetration. These advancements are associated with a reduction in amyloid-beta aggregation and the inhibition of tau hyperphosphorylation in preclinical models. These hybrids levera

Alzheimer's disease (AD) is the most common neurodegenerative disorder associated with dementia. Cellular senescence, widely acknowledged as a key hallmark of aging, has increasingly been recognized as a significant factor in the pathogenesis of AD, although the precise mechanisms underlying this relationship have yet to be fully understood. In the brains of individuals with AD, neurons, glial cells, and cerebrovascular endothelial cells exhibit premature senescence, characterized by irreversible cell cycle arrest, resistance to apoptosis, and the secretion of a diverse range of bioactive molecules collectively referred to as the senescence-associated secretory phenotype (SASP). These senescent cells profoundly influence the neural microenvironment through the release of SASP factors, thus exacerbating Aβ- and tau-induced neurotoxicity, promoting neuroinflammatory responses, and impairing the integrity of the blood-brain barrier (BBB), ultimately giving rise to a self-sustaining "senes

Phylogenetic analyses of DNA glycosylases that function in the initiation step of base excision repair reveal a high degree of conservation within the genes encoding Nei-like DNA glycosylase 1 (NEIL1). In concert with other glycosylases, this enzyme is an important player in cleansing both nuclear and mitochondrial genomes of a wide variety of damaged DNA bases. The relative efficiency of NEIL1 to catalyze release of ring-opened formamido-pyrimidines (Fapy) and alkylated-Fapy adducts, multiple ring-saturated pyrimidines, secondary oxidation products of 8-oxoguanine, and psoralen-derived crosslinks is augmented by pre-mRNA editing at codon 242, resulting in cells containing both NEIL1-Lys242 and edited Arg242. The biological significance of NEIL1 was revealed through investigations of mutagenesis and carcinogenesis in murine models, primarily using aflatoxin B1 (AFB1) as a genotoxicant challenge, which forms stable AFB1-FapyGua adducts. Specifically, Neil1 knockout mice were > 3-fold mo