Oxidative stress induces Z-DNA-binding protein 1-dependent activation of microglia via mtDNA released from retinal pigment epithelial cells

Reduction of D2 receptors on microglia leads to ZBP1-mediated PANoptosis of mPFC in Parkinson's disease depression mice

Parkinson's disease depression (PDD) is a common non-motor symptom of Parkinson's disease (PD), characterized by complex neurobiological mechanisms that remain poorly understood. This study identifies ZBP1-mediated PANoptosis as a critical mechanism linking neuroinflammation, neuronal loss, and depressive behaviors in PDD. Using a 6-hydroxydopamine (6-OHDA)-induced PDD mouse model, we observed significant reductions in dopaminergic projections from the substantia nigra (SN) to the medial prefrontal cortex (mPFC), accompanied by neuronal loss and depressive-like behaviors. Microglial activation, driven by DRD2 downregulation, was found to impair mPFC neuronal function, as evidenced by altered local field potentials and reduced gamma, beta, and theta oscillations. Furthermore, ZBP1 expression was significantly upregulated in the mPFC of PDD mice, where it colocalized with CaMKII-positive neurons and facilitated the formation of PANoptosomes, a multimeric complex driving pyroptosis, apoptosis, and necroptosis. Knockdown of ZBP1 in the mPFC effectively suppressed PANoptosome formation, reduced neuronal injury, restored local field potentials, and alleviated depressive-like behaviors. These findings highlight ZBP1-mediated PANoptosis as a key pathological mechanism in PDD and suggest that targeting ZBP1 may represent a promising therapeutic strategy for mitigating neuronal loss and depressive symptoms in PDD.

ZBP1 synchronized with periodontopathogenesis as the essential pattern recognition receptor

BACKGROUND

Periodontitis is a chronic inflammatory disease impacting quality of life. Understanding its pathogenesis is key to developing effective treatments. This study aimed to identify key pattern recognition receptors (PRRs) involved in periodontitis and elucidate their roles in disease progression.

METHODS

Periodontal tissues from healthy individuals and those with periodontitis were analyzed using RNA-sequencing, quantitative real-time PCR(qRT-PCR), and immunohistochemical analysis. Paired tissues collected before and after non-surgical treatment were analyzed via 4D-microDIA proteomics and Western blot.

RESULTS

RNA-sequencing showed significantly higher expression of Z-DNA binding protein 1(ZBP1) and absent in melanoma 2(AIM2) in periodontitis tissues compared to healthy controls, confirmed by qRT-PCR. Post-treatment proteomics indicated significant downregulation of ZBP1, with a non-significant trend for AIM2. Immunohistochemical staining localized ZBP1 to the middle and superficial layers of the gingival epithelium and around deep pockets in periodontitis, while AIM2 was detected in the junctional epithelium and extended throughout the pocket epithelium in periodontitis.

CONCLUSIONS

ZBP1 is highlighted as a key PRR in periodontitis, with significant regulatory potential. AIM2 may play a secondary role. Their distinct spatial distributions suggest involvement in specific microenvironments within periodontal tissues, mediating responses to microbial and inflammatory challenges. ZBP1 may be a critical receptor initiating periodontitis.

On the quest for undiscovered plant DNA receptors

The presence of unexpected DNA in cellular compartments acts as a danger signal that activates immune responses. In mammals, delocalized self-DNA triggers strong inflammatory responses crucial for antiviral immunity and cancer control. In plants, application of exogenous self-DNA increases resistance to pathogens and herbivores. Although several mammalian DNA receptors have been identified with distinct subcellular localizations and mechanisms to discriminate between microbial and mitochondrial DNA, no DNA receptors have been identified in plants. Here, we show current evidence for different potential response mechanisms for DNA perception and consider several hypothetical mechanisms for its recognition in plants. Finally, we provide a potential framework for finding plant self-DNA receptors in the future.

Mitochondrial DNA signals driving immune responses: Why, How, Where?

There has been a recent expansion in our understanding of DNA-sensing mechanisms. Mitochondrial dysfunction, oxidative and proteostatic stresses, instability and impaired disposal of nucleoids cause the release of mitochondrial DNA (mtDNA) from the mitochondria in several human diseases, as well as in cell culture and animal models. Mitochondrial DNA mislocalized to the cytosol and/or the extracellular compartments can trigger innate immune and inflammation responses by binding DNA-sensing receptors (DSRs). Here, we define the features that make mtDNA highly immunogenic and the mechanisms of its release from the mitochondria into the cytosol and the extracellular compartments. We describe the major DSRs that bind mtDNA such as cyclic guanosine-monophosphate-adenosine-monophosphate synthase (cGAS), Z-DNA-binding protein 1 (ZBP1), NOD-, LRR-, and PYD- domain-containing protein 3 receptor (NLRP3), absent in melanoma 2 (AIM2) and toll-like receptor 9 (TLR9), and their downstream signaling cascades. We summarize the key findings, novelties, and gaps of mislocalized mtDNA as a driving signal of immune responses in vascular, metabolic, kidney, lung, and neurodegenerative diseases, as well as viral and bacterial infections. Finally, we define common strategies to induce or inhibit mtDNA release and propose challenges to advance the field.

Epidermal ZBP1 stabilizes mitochondrial Z-DNA to drive UV-induced IFN signaling in autoimmune photosensitivity

Photosensitivity is observed in numerous autoimmune diseases and drives poor quality of life and disease flares. Elevated epidermal type I interferon (IFN) production primes for photosensitivity and enhanced inflammation, but the substrates that sustain and amplify this cycle remain undefined. We show that IFN-induced Z-DNA binding protein 1 (ZBP1) stabilizes ultraviolet (UV) B-induced cytosolic Z-DNA derived from oxidized mitochondrial DNA. ZBP1 is up-regulated in the epidermis of adult and pediatric patients with autoimmune photosensitivity. In patient-derived samples, lupus keratinocytes accumulate extensive cytosolic Z-DNA after UVB exposure, and transfection of keratinocytes with Z-DNA results in stronger IFN production through cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes (cGAS-STING) activation compared with the more conventional B-DNA. ZBP1 knockdown abrogates UVB-induced IFN responses, whereas overexpression results in a lupus-like phenotype with spontaneous Z-DNA accumulation and IFN production. Our results highlight Z-DNA and ZBP1 as critical mediators for UVB-induced inflammation and uncover how type I IFNs prime for cutaneous inflammation in photosensitivity.

Mitochondrial DNA leakage: underlying mechanisms and therapeutic implications in neurological disorders

Mitochondrial dysfunction is a pivotal instigator of neuroinflammation, with mitochondrial DNA (mtDNA) leakage as a critical intermediary. This review delineates the intricate pathways leading to mtDNA release, which include membrane permeabilization, vesicular trafficking, disruption of homeostatic regulation, and abnormalities in mitochondrial dynamics. The escaped mtDNA activates cytosolic DNA sensors, especially cyclic gmp-amp synthase (cGAS) signalling and inflammasome, initiating neuroinflammatory cascades via pathways, exacerbating a spectrum of neurological pathologies. The therapeutic promise of targeting mtDNA leakage is discussed in detail, underscoring the necessity for a multifaceted strategy that encompasses the preservation of mtDNA homeostasis, prevention of membrane leakage, reestablishment of mitochondrial dynamics, and inhibition the activation of cytosolic DNA sensors. Advancing our understanding of the complex interplay between mtDNA leakage and neuroinflammation is imperative for developing precision therapeutic interventions for neurological disorders.

Nucleotide coordinated polymers, a ROS-based immunomodulatory antimicrobial, doubly kill Pseudomonas aeruginosa biofilms of implant infections

Pseudomonas aeruginosa causes high morbidity and mortality in nosocomial infections, and newly approved antibiotics have been declining for decades. A green and universal deprotonation-driven strategy is used to screen the guanylic acid-metal ion coordination polymer nanoparticles (GMC), instead of the failure of binding occurs when specific metal ion participation. We find that the precise pH-dependent oxidase-like activity of GMC-2 orchestrates a duple symphony of immune modulation for Pseudomonas aeruginosa biofilm infections. Specifically, GMC-2-mediated reactive oxygen species (ROS) regulation triggers mitochondrial dysfunction and releases damage-associated molecular patterns, engaging pattern recognition receptors and resulting in endogenous innate immune activation. Meanwhile, GMC-2-triggered ROS generation in a mildly acidic biofilm environment destroys the biofilm, exposing exogenous pathogen-associated molecular patterns. GMC-2 cannot cause resistance for Pseudomonas aeruginosa compared with conventional antibiotics. In an infected implant mouse model, Pseudomonas aeruginosa biofilms were effectively eliminated by GMC-2-mediated triggering of innate and adaptive immunity. These findings provide a universal approach for facilitating the binding of biomolecules with metal ions and highlight the precise ROS-regulating platform plays a critical role in initiating endogenous and exogenous immune activation targeted for bacterial biofilm infection.

ZBP1-mediated PANoptosis is a crucial lethal form in diverse keratinocyte death modalities in UVB-induced skin injury

UVB irradiation induces diverse modalities of regulatory cell death in keratinocytes. Recently, the pattern of coexistence of pyroptosis, apoptosis, and necroptosis has been termed PANoptosis; however, whether PANoptosis occurs in keratinocytes in UVB-induced skin injury remains unclear. We observed that the key molecules of GSDMD-mediated pyroptosis, apoptosis, and necroptosis, which are N-terminal GSDMD, cleaved caspase-3/PARP, and phosphorylated MLKL, respectively, were elevated in keratinocytes of UVB-challenged mice and human skin tissue. Through keratinocyte-specific gene knockout or using corresponding inhibitors, we found that individual inhibition of GSDMD-mediated pyroptosis, caspase-3-mediated apoptosis, or MLKL-mediated necroptosis did not reduce the overall level of keratinocyte death after UVB exposure, and that the other two pathways maintained the activation. However, when the PANoptosome sensor ZBP1 was knocked out, keratinocyte death was reduced and epidermal thickening was alleviated in UVB-challenged mice. In conclusion, our study demonstrated that UVB irradiation induces ZBP1-mediated PANoptosis in keratinocytes, which is a crucial lethal form in diverse keratinocyte death modalities in UVB-induced skin injury. The above findings provide a new insight on the complexity of regulated cell death modalities in keratinocytes exposed to UV irradiation.

Lethal COVID-19 associates with RAAS-induced inflammation for multiple organ damage including mediastinal lymph nodes

Lethal COVID-19 outcomes are attributed to classic cytokine storm. We revisit this using RNA sequencing of nasopharyngeal and 40 autopsy samples from patients dying of SARS-CoV-2. Subsets of the 100 top-upregulated genes in nasal swabs are upregulated in the heart, lung, kidney, and liver, but not mediastinal lymph nodes. Twenty-two of these are "noncanonical" immune genes, which we link to components of the renin-angiotensin-activation-system that manifest as increased fibrin deposition, leaky vessels, thrombotic tendency, PANoptosis, and mitochondrial dysfunction. Immunohistochemistry of mediastinal lymph nodes reveals altered architecture, excess collagen deposition, and pathogenic fibroblast infiltration. Many of the above findings are paralleled in animal models of SARS-CoV-2 infection and human peripheral blood mononuclear and whole blood samples from individuals with early and later SARS-CoV-2 variants. We then redefine cytokine storm in lethal COVID-19 as driven by upstream immune gene and mitochondrial signaling producing downstream RAAS (renin-angiotensin-aldosterone system) overactivation and organ damage, including compromised mediastinal lymph node function.

The emerging role of PANoptosis in viral infections disease

PANoptosis is a distinct inflammatory cell death mechanism that involves interactions between pyroptosis, apoptosis, and necroptosis. It can be regulated by diverse PANoptosome complexes built by integrating components from various cell death modalities. There is a rising interest in PANoptosis' process and functions. Viral infection is an important trigger of PANoptosis. Viruses invade host cells through their unique mechanisms and utilize host cell resources for replication and proliferation. In this process, viruses interfere with the normal physiological functions of host cells, including cell death mechanisms. A variety of viruses, such as influenza A virus (IAV), herpes simplex virus 1 (HSV1) and coronaviruses, have been found to induce PANoptosis in host cells. Given the importance of PANoptosis across the disease spectrum, this review briefly describes the relationships between pyroptosis, apoptosis, and necroptosis, highlights the key molecules in PANoptosome formation and activation, and outlines the multifaceted roles of PANoptosis in viral diseases, including potential therapeutic targets. We also talk about key principles and significant concerns for future PANoptosis research. Improved understanding of PANoptosis and its mechanisms is critical for discovering new treatment targets and methods.

The crosstalk between DNA-damage responses and innate immunity

DNA damage is typically caused during cell growth by DNA replication stress or exposure to endogenous or external toxins. The accumulation of damaged DNA causes genomic instability, which is the root cause of many serious disorders. Multiple cellular organisms utilize sophisticated signaling pathways against DNA damage, collectively known as DNA damage response (DDR) networks. Innate immune responses are activated following cellular abnormalities, including DNA damage. Interestingly, recent studies have indicated that there is an intimate relationship between the DDR network and innate immune responses. Diverse kinds of cytosolic DNA sensors, such as cGAS and STING, recognize damaged DNA and induce signals related to innate immune responses, which link defective DDR to innate immunity. Moreover, DDR components operate in immune signaling pathways to induce IFNs and/or a cascade of inflammatory cytokines via direct interactions with innate immune modulators. Consistently, defective DDR factors exacerbate the innate immune imbalance, resulting in severe diseases, including autoimmune disorders and tumorigenesis. Here, the latest progress in understanding crosstalk between the DDR network and innate immune responses is reviewed. Notably, the dual function of innate immune modulators in the DDR network may provide novel insights into understanding and developing targeted immunotherapies for DNA damage-related diseases, even carcinomas.

DAMP sensing and sterile inflammation: intracellular, intercellular and inter-organ pathways

Damage-associated molecular patterns (DAMPs) are endogenous molecules that are released from host cells as a result of cell death or damage. The release of DAMPs in tissues is associated with loss of tissue homeostasis. Sensing of DAMPs by innate immune receptors triggers inflammation, which can be beneficial in initiating the processes that restore tissue homeostasis but can also drive inflammatory diseases. In recent years, the sensing of intracellular DAMPs has received extensive attention in the field of sterile inflammation. However, emerging studies have shown that DAMPs that originate from neighbouring cells, and even from distal tissues or organs, also mediate sterile inflammatory responses. This multi-level sensing of DAMPs is crucial for intercellular, trans-tissue and trans-organ communication. Here, we summarize how DAMP-sensing receptors detect DAMPs from intracellular, intercellular or distal tissue and organ sources to mediate sterile inflammation. We also discuss the possibility of targeting DAMPs or their corresponding receptors to treat inflammatory diseases.

Loss of the DNA repair protein, polynucleotide kinase/phosphatase, activates the type 1 interferon response independent of ionizing radiation

DNA damage has been implicated in the stimulation of the type 1 interferon (T1IFN) response. Here, we show that downregulation of the DNA repair protein, polynucleotide kinase/phosphatase (PNKP), in a variety of cell lines causes robust phosphorylation of STAT1, upregulation of interferon-stimulated genes and persistent accumulation of cytosolic DNA, all of which are indicators for the activation of the T1IFN response. Furthermore, this did not require damage induction by ionizing radiation. Instead, our data revealed that production of reactive oxygen species (ROS) synergises with PNKP loss to potentiate the T1IFN response, and that loss of PNKP significantly compromises mitochondrial DNA (mtDNA) integrity. Depletion of mtDNA or treatment of PNKP-depleted cells with ROS scavengers abrogated the T1IFN response, implicating mtDNA as a significant source of the cytosolic DNA required to potentiate the T1IFN response. The STING signalling pathway is responsible for the observed increase in the pro-inflammatory gene signature in PNKP-depleted cells. While the response was dependent on ZBP1, cGAS only contributed to the response in some cell lines. Our data have implications for cancer therapy, since PNKP inhibitors would have the potential to stimulate the immune response, and also to the neurological disorders associated with PNKP mutation.

ZBP1-mediated PANoptosis: A possible novel mechanism underlying the therapeutic effects of penehyclidine hydrochloride on myocardial ischemia-reperfusion injury

Although penehyclidine hydrochloride (PHC) has been identified to alleviate myocardial injury induced by ischemia/reperfusion (I/R), the regulatory molecules and related mechanisms are unknown. In this study, bioinformatics, molecular biology, and biochemistry methods were used to explore the molecular mechanisms and targets of PHC. In the myocardial ischemia-reperfusion injury (MIRI)-induced rat model, PHC pretreatment significantly improved cardiac function (p < 0.01). Multiple differentially expressed genes, including Z-DNA binding protein 1 (ZBP1), were identified through mRNA sequencing analysis of myocardial ischemic penumbra tissue in MIRI rats. The transduction of the ZBP1 adenovirus vector (Ad-Zbp1) in PHC-pretreated rats exhibited a reversible augmentation in myocardial infarct size (p < 0.01), pronounced pathological damage to the myocardial tissue, as well as a significant elevation of serum myocardial enzymes (p < 0.05). The interaction among ZBP1, fas-associating via death domain (FADD), and receptor-interacting serine/threonine-protein kinase 3 (RIPK3) leads to a remarkable up-regulation of cleaved-Caspase-1 (Cl-Casp-1), N-terminal gasdermin D (N-GSDMD), phospho-mixed lineage kinase domain-like Ser358 (p-MLKLS358), and other regulatory proteins, thereby triggering pyroptosis, apoptosis, and necroptosis (PANoptosis) in cardiomyocytes of MIRI rats. Moreover, the transduction of Ad-Zbp1 in the oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced H9c2 cell model also dramatically augmented the number of cell deaths. However, the intervention of PHC considerably enhanced cell viability (p < 0.01), effectively mitigated the release of myocardial enzymes (p < 0.05), and markedly attenuated the expression levels of PANoptosis regulatory proteins through restraint of ZBP1 expression. Therefore, the therapeutic efficacy of PHC in improving MIRI might be attributed to targeting ZBP1-mediated PANoptosis.

Elabela ameliorates neuronal pyroptosis and mitochondrial fission via APJ/ZBP1 signaling in ischemic stroke

Pyroptosis signifies a significant form of programmed neuronal demise subsequent to ischemic stroke. In our prior investigations, we demonstrated that the Elabela (ELA)-Apelin receptor (APJ) axis alleviated neuronal death by improving collateral circulation and mitigating ferroptosis in a murine model of middle cerebral artery occlusion (MCAO). However, the connection between ELA and neuronal pyroptosis remains further elucidation. Here, we observed an upregulation of ELA and APJ expression in both murine brain specimens and cultured HT-22 hippocampal neurons exposed to experimental ischemic stroke. ELA administration markedly diminished the infarct size in comparison to controls. ELA treatment ameliorated neurological deficits and anxiety-like symptoms in mice with stroke, concurrently inhibiting pyroptosis and mitochondria fission in neurons. Conversely, ELA knockdown yielded the opposite effects. Utilizing RNA-sequencing analysis, we identified a candidate for pyroptosis priming, Z-DNA-binding protein 1 (ZBP1), which was suppressed in ELA-treated HT-22 neurons during oxygen-glucose deprivation/reperfusion (OGD/R). Subsequent co-immunoprecipitation analyses demonstrated the binding between APJ and ZBP1. Specifically, APJ suppressed ZBP1 to inhibit NLRP3 inflammasome activation and dynamin-related protein 1-mediated mitochondrial fission in neurons. In summary, our findings suggest that ELA functions as a stroke-induced signal limiting neuronal pyroptosis and mitochondrial fission via APJ/ZBP1 signaling, thereby underscoring ELA as a potential therapeutic target for ischemic stroke treatment.

IRF1 regulation of ZBP1 links mitochondrial DNA and chondrocyte damage in osteoarthritis

BACKGROUND

Z-DNA binding protein 1 (ZBP1) is a nucleic acid sensor that is involved in multiple inflammatory diseases, but whether and how it contributes to osteoarthritis (OA) are unclear.

METHODS

Cartilage tissues were harvested from patients with OA and a murine model of OA to evaluate ZBP1 expression. Subsequently, the functional role and mechanism of ZBP1 were examined in primary chondrocytes, and the role of ZBP1 in OA was explored in mouse models.

RESULTS

We showed the upregulation of ZBP1 in articular cartilage originating from OA patients and mice with OA after destabilization of the medial meniscus (DMM) surgery. Specifically, knockdown of ZBP1 alleviated chondrocyte damage and protected mice from DMM-induced OA. Mechanistically, tumor necrosis factor alpha induced ZBP1 overexpression in an interferon regulatory factor 1 (IRF1)-dependent manner and elicited the activation of ZBP1 via mitochondrial DNA (mtDNA) release and ZBP1 binding. The upregulated and activated ZBP1 could interact with receptor-interacting protein kinase 1 and activate the transforming growth factor-beta-activated kinase 1-NF-κB signaling pathway, which led to chondrocyte inflammation and extracellular matrix degradation. Moreover, inhibition of the mtDNA-IRF1-ZBP1 axis with Cyclosporine A, a blocker of mtDNA release, could delay the progression of DMM-induced OA.

CONCLUSIONS

Our data revealed the pathological role of the mtDNA-IRF1-ZBP1 axis in OA chondrocytes, suggesting that inhibition of this axis could be a viable therapeutic approach for OA.

Experimental investigation for nonalcoholic fatty pancreas management using probiotics

BACKGROUND

Nonalcoholic fatty pancreatitis (NAFP) presents a pressing challenge within the domain of metabolic disorders, necessitating further exploration to unveil its molecular intricacies and discover effective treatments. Our focus was to delve into the potential therapeutic impact of ZBiotic, a specially engineered strain of probiotic B. subtilis, in managing NAFP by targeting specific genes linked with necroptosis and the TNF signaling pathway, including TNF, ZBP1, HSPA1B, and MAPK3, along with their upstream epigenetic regulator, miR-5192, identified through bioinformatics.

METHODS

Rats were subjected to either a standard or high-fat, high-sucrose diet (HFHS) for eight weeks. Subsequently, they were divided into groups: NAFP model, and two additional groups receiving daily doses of ZBiotic (0.5 ml and 1 ml/kg), and the original B. subtilis strain group (1 ml/kg) for four weeks, alongside the HFHS diet.

RESULTS

ZBiotic exhibited remarkable efficacy in modulating gene expression, leading to the downregulation of miR-5192 and its target mRNAs (p < 0.001). Treatment resulted in the reversal of fibrosis, inflammation, and insulin resistance, evidenced by reductions in body weight, serum amylase, and lipase levels (p < 0.001), and decreased percentages of Caspase and Nuclear Factor Kappa-positive cells in pancreatic sections (p < 0.01). Notably, high-dose ZBiotic displayed superior efficacy compared to the original B. subtilis strain, highlighting its potential in mitigating NAFP progression by regulating pivotal pancreatic genes.

CONCLUSION

ZBiotic holds promise in curbing NAFP advancement, curbing fibrosis and inflammation while alleviating metabolic and pathological irregularities observed in the NAFP animal model. This impact was intricately linked to the modulation of necroptosis/TNF-mediated pathway-related signatures.

Z-DNA binding protein 1 orchestrates innate immunity and inflammatory cell death

Innate immunity is not only the first line of host defense against microbial infections but is also crucial for the host responses against a variety of noxious stimuli. Z-DNA binding protein 1 (ZBP1) is a cytosolic nucleic acid sensor that can induce inflammatory cell death in both immune and nonimmune cells upon sensing of incursive virus-derived Z-form nucleic acids and self-nucleic acids via its Zα domain. Mechanistically, aberrantly expressed or activated ZBP1 induced by pathogens or noxious stimuli enables recruitment of TANK binding kinase 1 (TBK1), interferon regulatory factor 3 (IRF3), receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and RIPK3 to drive type I interferon (IFN-I) responses and activation of nuclear factor kappa B (NF-κB) signaling. Meanwhile, ZBP1 promotes the assembly of ZBP1- and absent in melanoma 2 (AIM2)-PANoptosome, which ultimately triggers PANoptosis through caspase 3-mediated apoptosis, mixed lineage kinase domain like pseudokinase (MLKL)-mediated necroptosis, and gasdermin D (GSDMD)-mediated pyroptosis. In response to damaged mitochondrial DNA, ZBP1 can interact with cyclic GMP-AMP synthase to augment IFN-I responses but inhibits toll like receptor 9-mediated inflammatory responses. This review summarizes the structure and expression pattern of ZBP1, discusses its roles in human diseases through immune-dependent (e.g., the production of IFN-I and pro-inflammatory cytokines) and -independent (e.g., the activation of cell death) functions, and highlights the attractive prospect of manipulating ZBP1 as a promising therapeutic target in diseases.

Neurotoxic β-amyloid oligomers cause mitochondrial dysfunction-the trigger for PANoptosis in neurons

As the global population ages, the incidence of elderly patients with dementia, represented by Alzheimer's disease (AD), will continue to increase. Previous studies have suggested that β-amyloid protein (Aβ) deposition is a key factor leading to AD. However, the clinical efficacy of treating AD with anti-Aβ protein antibodies is not satisfactory, suggesting that Aβ amyloidosis may be a pathological change rather than a key factor leading to AD. Identification of the causes of AD and development of corresponding prevention and treatment strategies is an important goal of current research. Following the discovery of soluble oligomeric forms of Aβ (AβO) in 1998, scientists began to focus on the neurotoxicity of AβOs. As an endogenous neurotoxin, the active growth of AβOs can lead to neuronal death, which is believed to occur before plaque formation, suggesting that AβOs are the key factors leading to AD. PANoptosis, a newly proposed concept of cell death that includes known modes of pyroptosis, apoptosis, and necroptosis, is a form of cell death regulated by the PANoptosome complex. Neuronal survival depends on proper mitochondrial function. Under conditions of AβO interference, mitochondrial dysfunction occurs, releasing lethal contents as potential upstream effectors of the PANoptosome. Considering the critical role of neurons in cognitive function and the development of AD as well as the regulatory role of mitochondrial function in neuronal survival, investigation of the potential mechanisms leading to neuronal PANoptosis is crucial. This review describes the disruption of neuronal mitochondrial function by AβOs and elucidates how AβOs may activate neuronal PANoptosis by causing mitochondrial dysfunction during the development of AD, providing guidance for the development of targeted neuronal treatment strategies.

Contribution of extracellular vesicles for the pathogenesis of retinal diseases: shedding light on blood-retinal barrier dysfunction

Retinal degenerative diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), loom as threats to vision, causing detrimental effects on the structure and function of the retina. Central to understanding these diseases, is the compromised state of the blood-retinal barrier (BRB), an effective barrier that regulates the influx of immune and inflammatory components. Whether BRB breakdown initiates retinal distress, or is a consequence of disease progression, remains enigmatic. Nevertheless, it is an indication of retinal dysfunction and potential vision loss.The intricate intercellular dialogues among retinal cell populations remain unintelligible in the complex retinal milieu, under conditions of inflammation and oxidative stress. The retina, a specialized neural tissue, sustains a ceaseless demand for oxygen and nutrients from two vascular networks. The BRB orchestrates the exchange of molecules and fluids within this specialized region, comprising the inner BRB (iBRB) and the outer BRB (oBRB). Extracellular vesicles (EVs) are small membranous structures, and act as messengers facilitating intercellular communication in this milieu.EVs, both from retinal and peripheral immune cells, increase complexity to BRB dysfunction in DR and AMD. Laden with bioactive cargoes, these EVs can modulate the retinal microenvironment, influencing disease progression. Our review delves into the multifaceted role of EVs in retinal degenerative diseases, elucidating the molecular crosstalk they orchestrate, and their microRNA (miRNA) content. By shedding light on these nanoscale messengers, from their biogenesis, release, to interaction and uptake by target cells, we aim to deepen the comprehension of BRB dysfunction and explore their therapeutic potential, therefore increasing our understanding of DR and AMD pathophysiology.

Crosstalk Between Microglia and Müller Glia in the Age-Related Macular Degeneration: Role and Therapeutic Value of Neuroinflammation

Age-related macular degeneration (AMD) is a progressive neurodegeneration disease that causes photoreceptor demise and vision impairments. In AMD pathogenesis, the primary death of retinal neurons always leads to the activation of resident microglia. The migration of activated microglia to the ongoing retinal lesion and their morphological transformation from branching to ameboid-like are recognized as hallmarks of AMD pathogenesis. Activated microglia send signals to Müller cells and promote them to react correspondingly to damaging stimulus. Müller cells are a type of neuroglia cells that maintain the normal function of retinal neurons, modulating innate inflammatory responses, and stabilize retinal structure. Activated Müller cells can accelerate the progression of AMD by damaging neurons and blood vessels. Therefore, the crosstalk between microglia and Müller cells plays a homeostatic role in maintaining the retinal environment, and this interaction is complicatedly modulated. In particular, the mechanism of mutual regulation between the two glia populations is complex under pathological conditions. This paper reviews recent findings on the crosstalk between microglia and Müller glia during AMD pathology process, with special emphasis on its therapeutic potentials.

The regulation of the apoptotic pore-An immunological tightrope walk

Apoptotic pore formation in mitochondria is the pivotal point for cell death during mitochondrial apoptosis. It is regulated by BCL-2 family proteins in response to various cellular stress triggers and mediates mitochondrial outer membrane permeabilization (MOMP). This allows the release of mitochondrial contents into the cytosol, which triggers rapid cell death and clearance through the activation of caspases. However, under conditions of low caspase activity, the mitochondrial contents released into the cytosol through apoptotic pores serve as inflammatory signals and activate various inflammatory responses. In this chapter, we discuss how the formation of the apoptotic pore is regulated by BCL-2 proteins as well as other cellular or mitochondrial proteins and membrane lipids. Moreover, we highlight the importance of sublethal MOMP in the regulation of mitochondrial-activated inflammation and discuss its physiological consequences in the context of pathogen infection and disease and how it can potentially be exploited therapeutically, for example to improve cancer treatment.

Multi-System-Level Analysis with RNA-Seq on Pterygium Inflammation Discovers Association between Inflammatory Responses, Oxidative Stress, and Oxidative Phosphorylation

A pterygium is a common conjunctival degeneration and inflammatory condition. It grows onto the corneal surface or limbus, causing blurred vision and cosmetic issues. Ultraviolet is a well-known risk factor for the development of a pterygium, although its pathogenesis remains unclear, with only limited understanding of its hereditary basis. In this study, we collected RNA-seq from both pterygial tissues and conjunctival tissues (as controls) from six patients (a total of twelve biological samples) and retrieved publicly available data, including eight pterygium samples and eight controls. We investigated the intrinsic gene regulatory mechanisms closely linked to the inflammatory reactions of pterygiums and compared Asian (Korea) and the European (Germany) pterygiums using multiple analysis approaches from different perspectives. The increased expression of antioxidant genes in response to oxidative stress and DNA damage implies an association between these factors and pterygium development. Also, our comparative analysis revealed both similarities and differences between Asian and European pterygiums. The decrease in gene expressions involved in the three primary inflammatory signaling pathways-JAK/STAT, MAPK, and NF-kappa B signaling-suggests a connection between pathway dysfunction and pterygium development. We also observed relatively higher activity of autophagy and antioxidants in the Asian group, while the European group exhibited more pronounced stress responses against oxidative stress. These differences could potentially be necessitated by energy-associated pathways, specifically oxidative phosphorylation.

Protection against Oxidative Stress by Coenzyme Q10 in a Porcine Retinal Degeneration Model

Oxidative stress plays an important role in neurodegenerative diseases, including glaucoma. Therefore, we analyzed if the antioxidant coenzyme Q10 (CoQ10), which is also commercially available, can prevent retinal degeneration induced by hydrogen peroxide (H2O2) in a porcine organ culture model. Retinal explants were cultivated for eight days, and H2O2 (500 µM, 3 h) induced the oxidative damage. CoQ10 therapy was applied (700 µM, 48 h). Retinal ganglion cells (RGCs) and microglia were examined immunohistologically in all groups (control, H2O2, H2O2 + CoQ10). Cellular, oxidative, and inflammatory genes were quantified via RT-qPCR. Strong RGC loss was observed with H2O2 (p ≤ 0.001). CoQ10 elicited RGC protection compared to the damaged group at a histological (p ≤ 0.001) and mRNA level. We detected more microglia cells with H2O2, but CoQ10 reduced this effect (p = 0.004). Cellular protection genes (NRF2) against oxidative stress were stimulated by CoQ10 (p ≤ 0.001). Furthermore, mitochondrial oxidative stress (SOD2) increased through H2O2 (p = 0.038), and CoQ10 reduced it to control level. Our novel results indicate neuroprotection via CoQ10 in porcine retina organ cultures. In particular, CoQ10 appears to protect RGCs by potentially inhibiting apoptosis-related pathways, activating intracellular protection and reducing mitochondrial stress.

When DNA-damage responses meet innate and adaptive immunity

When cells proliferate, stress on DNA replication or exposure to endogenous or external insults frequently results in DNA damage. DNA-Damage Response (DDR) networks are complex signaling pathways used by multicellular organisms to prevent DNA damage. Depending on the type of broken DNA, the various pathways, Base-Excision Repair (BER), Nucleotide Excision Repair (NER), Mismatch Repair (MMR), Homologous Recombination (HR), Non-Homologous End-Joining (NHEJ), Interstrand Crosslink (ICL) repair, and other direct repair pathways, can be activated separately or in combination to repair DNA damage. To preserve homeostasis, innate and adaptive immune responses are effective defenses against endogenous mutation or invasion by external pathogens. It is interesting to note that new research keeps showing how closely DDR components and the immune system are related. DDR and immunological response are linked by immune effectors such as the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway. These effectors act as sensors of DNA damage-caused immune response. Furthermore, DDR components themselves function in immune responses to trigger the generation of inflammatory cytokines in a cascade or even trigger programmed cell death. Defective DDR components are known to disrupt genomic stability and compromise immunological responses, aggravating immune imbalance and leading to serious diseases such as cancer and autoimmune disorders. This study examines the most recent developments in the interaction between DDR elements and immunological responses. The DDR network's immune modulators' dual roles may offer new perspectives on treating infectious disorders linked to DNA damage, including cancer, and on the development of target immunotherapy.

Mono-quinoxaline-induced DNA structural alteration leads to ZBP1/RIP3/MLKL-driven necroptosis in cancer cells

Evading the cellular apoptosis mechanism by modulating multiple pathways poses a sturdy barrier to effective chemotherapy. Cancer cell adeptly resists the apoptosis signaling pathway by regulating anti and pro-apoptotic proteins to escape cell death. Nevertheless, bypassing the apoptotic pathway through necroptosis, an alternative programmed cell death process, maybe a potential therapeutic modality for apoptosis-resistant cells. However, synthetic mono-quinoxaline-based intercalator-induced cellular necroptosis as an anti-cancer perspective remains under-explored. To address this concern, we undertook the design and synthesis of quinoxaline-based small molecules (3a-3l). Our approach involved enhancing the π-surface of the mandatory benzyl moiety to augment its ability to induce DNA structural alteration via intercalation, thereby promoting cytotoxicity across various cancer cell lines (HCT116, HT-29, and HeLa). Notably, the potent compound 3a demonstrated the capacity to induce DNA damage in cancer cells, leading to the induction of ZBP1-mediated necroptosis in the RIP3-expressed cell line (HT-29), where Z-VAD effectively blocked apoptosis-mediated cell death. Interestingly, we observed that 3a induced RIP3-driven necroptosis in combination with DNA hypomethylating agents, even in the RIP3-silenced cell lines (HeLa and HCT116). Overall, our synthesized compound 3a emerged as a promising candidate against various cancers, particularly in apoptosis-compromised cells, through the induction of necroptosis.

Multi-System-Level Analysis Reveals Differential Expression of Stress Response-Associated Genes in Inflammatory Solar Lentigo

Although the pathogenesis of solar lentigo (SL) involves chronic ultraviolet (UV) exposure, cellular senescence, and upregulated melanogenesis, underlying molecular-level mechanisms associated with SL remain unclear. The aim of this study was to investigate the gene regulatory mechanisms intimately linked to inflammation in SL. Skin samples from patients with SL with or without histological inflammatory features were obtained. RNA-seq data from the samples were analyzed via multiple analysis approaches, including exploration of core inflammatory gene alterations, identifying functional pathways at both transcription and protein levels, comparison of inflammatory module (gene clusters) activation levels, and analyzing correlations between modules. These analyses disclosed specific core genes implicated in oxidative stress, especially the upregulation of nuclear factor kappa B in the inflammatory SLs, while genes associated with protective mechanisms, such as SLC6A9, were highly expressed in the non-inflammatory SLs. For inflammatory modules, Extracellular Immunity and Mitochondrial Innate Immunity were exclusively upregulated in the inflammatory SL. Analysis of protein-protein interactions revealed the significance of CXCR3 upregulation in the pathogenesis of inflammatory SL. In conclusion, the upregulation of stress response-associated genes and inflammatory pathways in response to UV-induced oxidative stress implies their involvement in the pathogenesis of inflammatory SL.

Cytosolic DNA sensors in neurodegenerative diseases: from physiological defenders to pathological culprits

Cytosolic DNA sensors are a group of pattern recognition receptors (PRRs) that vary in structures, molecular mechanisms, and origins but share a common function to detect intracellular microbial DNA and trigger the innate immune response like type 1 interferon production and autophagy. Cytosolic DNA sensors have been proven as indispensable defenders against the invasion of many pathogens; however, growing evidence shows that self-DNA misplacement to cytoplasm also frequently occurs in non-infectious circumstances. Accumulation of cytosolic DNA causes improper activation of cytosolic DNA sensors and triggers an abnormal autoimmune response, that significantly promotes pathological progression. Neurodegenerative diseases are a group of neurological disorders characterized by neuron loss and still lack effective treatments due to a limited understanding of pathogenesis. But current research has found a solid relationship between neurodegenerative diseases and cytosolic DNA sensing pathways. This review summarizes profiles of several major cytosolic DNA sensors and their common adaptor protein STING. It also discusses both the beneficial and detrimental roles of cytosolic DNA sensors in the genesis and progression of neurodegenerative diseases.

Blocking reverse electron transfer-mediated mitochondrial DNA oxidation rescues cells from PANoptosis

PANoptosis is a new type of cell death featured with pyroptosis, apoptosis and necroptosis, and is implicated in organ injury and mortality in various inflammatory diseases, such as sepsis and hemophagocytic lymphohistiocytosis (HLH). Reverse electron transport (RET)-mediated mitochondrial reactive oxygen species (mtROS) has been shown to contribute to pyroptosis and necroptosis. In this study we investigated the roles of mtROS and RET in PANoptosis induced by TGF-β-activated kinase 1 (TAK1) inhibitor 5Z-7-oxozeaenol (Oxo) plus lipopolysaccharide (LPS) as well as the effects of anti-RET reagents on PANoptosis. We showed that pretreatment with anti-RET reagents 1-methoxy PMS (MPMS) or dimethyl fumarate (DMF) dose-dependently inhibited PANoptosis in macrophages BMDMs and J774A.1 cells induced by Oxo/LPS treatment assayed by propidium iodide (PI) staining. The three arms of the PANoptosis signaling pathway, namely pyroptosis, apoptosis and necroptosis signaling, as well as the formation of PANoptosomes were all inhibited by MPMS or DMF. We demonstrated that Oxo/LPS treatment induced RET and mtROS in BMDMs, which were reversed by MPMS or DMF pretreatment. Interestingly, the PANoptosome was co-located with mitochondria, in which the mitochondrial DNA was oxidized. MPMS and DMF fully blocked the mtROS production and the formation of PANoptosome induced by Oxo plus LPS treatment. An HLH mouse model was established by poly(I:C)/LPS challenge. Pretreatment with DMF (50 mg·kg-1·d-1, i.g. for 3 days) or MPMS (10 mg·kg-1·d-1, i.p. for 2 days) (DMF i.g. MPMS i.p.) effectively alleviated HLH lesions accompanied by decreased hallmarks of PANoptosis in the liver and kidney. Collectively, RET and mtDNA play crucial roles in PANoptosis induction and anti-RET reagents represent a novel class of PANoptosis inhibitors by blocking oxidation of mtDNA, highlighting their potential application in treating PANoptosis-related inflammatory diseases. PANoptotic stimulation induces reverse electron transport (RET) and reactive oxygen species (ROS) in mitochondia, while 1-methoxy PMS and dimethyl fumarate can inhibit PANoptosis by suppressing RETmediated oxidation of mitochondrial DNA.

Epidermal ZBP1 stabilizes mitochondrial Z-DNA to drive UV-induced IFN signaling in autoimmune photosensitivity

Photosensitivity is observed in numerous autoimmune diseases and drives poor quality of life and disease flares. Elevated epidermal type I interferon (IFN) production primes for photosensitivity and enhanced inflammation, but the substrates that sustain and amplify this cycle remain undefined. Here, we show that IFN-induced Z-DNA binding protein 1 (ZBP1) stabilizes ultraviolet (UV)B-induced cytosolic Z-DNA derived from oxidized mitochondrial DNA. ZBP1 is significantly upregulated in the epidermis of adult and pediatric patients with autoimmune photosensitivity. Strikingly, lupus keratinocytes accumulate extensive cytosolic Z-DNA after UVB, and transfection of keratinocytes with Z-DNA results in stronger IFN production through cGAS-STING activation compared to B-DNA. ZBP1 knockdown abrogates UV-induced IFN responses, whereas overexpression results in a lupus-like phenotype with spontaneous Z-DNA accumulation and IFN production. Our results highlight Z-DNA and ZBP1 as critical mediators for UVB-induced inflammation and uncover how type I IFNs prime for cutaneous inflammation in photosensitivity.

Extracellular vesicles in degenerative retinal diseases: A new therapeutic paradigm

Nanoscale extracellular vesicles (EVs), consisting of exomers, exosomes and microvesicles/ectosomes, have been extensively investigated in the last 20 years, although their biological role is still something of a mystery. EVs are involved in the transfer of lipids, nucleic acids and proteins from donor to recipient cells or distant organs as well as regulating cell-cell communication and signaling. Thus, EVs are important in intercellular communication and this is not limited to sister cells, but may also mediate the crosstalk between different cell types even over long distances. EVs play crucial functions in both cellular homeostasis and the pathogenesis of diseases, and since their contents reflect the status of the donor cell, they represent an additional valuable source of information for characterizing complex biological processes. Recent advances in isolation and analytical methods have led to substantial improvements in both characterizing and engineering EVs, leading to their use either as novel biomarkers for disease diagnosis/prognosis or even as novel therapies. Due to their capacity to carry biomolecules, various EV-based therapeutic applications have been devised for several pathological conditions, including eye diseases. In the eye, EVs have been detected in the retina, aqueous humor, vitreous body and also in tears. Experiences with other forms of intraocular drug applications have opened new ways to use EVs in the treatment of retinal diseases. We here provide a comprehensive summary of the main in vitro, in vivo, and ex vivo literature-based studies on EVs' role in ocular physiological and pathological conditions. We have focused on age-related macular degeneration, diabetic retinopathy, glaucoma, which are common eye diseases leading to permanent blindness, if not treated properly. In addition, the putative use of EVs in retinitis pigmentosa and other retinopathies is discussed. Finally, we have reviewed the potential of EVs as therapeutic tools and/or biomarkers in the above-mentioned retinal disorders. Evidence emerging from experimental disease models and human material strongly suggests future diagnostic and/or therapeutic exploitation of these biological agents in various ocular disorders with a good possibility to improve the patient's quality of life.

Type I Interferon: Monkeypox/Mpox Viruses Achilles Heel?

Poxviruses are notorious for having acquired/evolved numerous genes to counteract host innate immunity. Chordopoxviruses have acquired/evolved at least three different inhibitors of host necroptotic death: E3, which blocks ZBP1-dependent necroptotic cell death, and vIRD and vMLKL that inhibit necroptosis downstream of initial cell death signaling. While this suggests the importance of the necroptotic cell death pathway in inhibiting chordopoxvirus replication, several chordopoxviruses have lost one or more of these inhibitory functions. Monkeypox/mpox virus (MPXV) has lost a portion of the N-terminus of its E3 homologue. The N-terminus of the vaccinia virus E3 homologue serves to inhibit activation of the interferon-inducible antiviral protein, ZBP1. This likely makes MPXV unique among the orthopoxviruses in being sensitive to interferon (IFN) treatment in many mammals, including humans, which encode a complete necroptotic cell death pathway. Thus, IFN sensitivity may be the Achille's Heel for viruses like MPXV that cannot fully inhibit IFN-inducible, ZBP1-dependent antiviral pathways.

Spatiotemporal expression patterns of ZBP1 in the brain of mouse experimental stroke model

Z-DNA binding protein 1 (ZBP1) is a cytosolic nucleic acid sensor, functioning as a critical mediator of inflammation and cell death pathways. Since neuroinflammation could occur in response to damage-associated molecular patterns (DAMPs), ZBP1 might be involved in neuroinflammation after stroke. However, the spatiotemporal expression profile of ZBP1 in the post-stroke brain remains to be elucidated. The aim of this study is to demonstrate the spatiotemporal expression patterns of ZBP1 in the post-stroke brain using a mouse photothrombotic stroke model. Real-time PCR assays showed that ZBP1 is induced on days 3-14 post stroke. ZBP1 immunoreactivity was observed in Iba1-positive microglia/macrophages in peri-infarct regions by immunohistochemistry. ZBP1-positive cells were spread in layers surrounding the infarct core by 7-14 days post stroke. Interestingly, ZBP1 immunoreactivity was also detected in CD206-positive border-associated macrophages (BAMs) in the meninges. Furthermore, ZBP1-expressing cells were positive for antibodies against inflammatory mediators such as Toll-like receptor 4 (TLR4), Toll/IL-1R domain-containing adaptor-inducing IFN-β (TRIF), and receptor-interacting serine/threonine-protein kinase 1 (RIPK1). Morphological analysis with confocal microscopy showed that the co-localization signals of ZBP1 and its adaptor, TRIF, are increased by glucose oxidase (GOx) treatment, which has been reported to induce mitochondrial DNA (mtDNA) release. These results suggest that ZBP1 is induced in peri-infarct microglia/macrophages and may be involved in DAMPs-mediated neuroinflammation involving mtDNA in the post-infarct brain.

Flipons and small RNAs accentuate the asymmetries of pervasive transcription by the reset and sequence-specific microcoding of promoter conformation

The role of alternate DNA conformations such as Z-DNA in the regulation of transcription is currently underappreciated. These structures are encoded by sequences called flipons, many of which are enriched in promoter and enhancer regions. Through a change in their conformation, flipons provide a tunable mechanism to mechanically reset promoters for the next round of transcription. They act as actuators that capture and release energy to ensure that the turnover of the proteins at promoters is optimized to cell state. Likewise, the single-stranded DNA formed as flipons cycle facilitates the docking of RNAs that are able to microcode promoter conformations and canalize the pervasive transcription commonly observed in metazoan genomes. The strand-specific nature of the interaction between RNA and DNA likely accounts for the known asymmetry of epigenetic marks present on the histone tetramers that pair to form nucleosomes. The role of these supercoil-dependent processes in promoter choice and transcriptional interference is reviewed. The evolutionary implications are examined: the resilience and canalization of flipon-dependent gene regulation is contrasted with the rapid adaptation enabled by the spread of flipon repeats throughout the genome. Overall, the current findings underscore the important role of flipons in modulating the readout of genetic information and how little we know about their biology.

The Z-nucleic acid sensor ZBP1 in health and disease

Nucleic acid sensing is a central process in the immune system, with far-reaching roles in antiviral defense, autoinflammation, and cancer. Z-DNA binding protein 1 (ZBP1) is a sensor for double-stranded DNA and RNA helices in the unusual left-handed Z conformation termed Z-DNA and Z-RNA. Recent research established ZBP1 as a key upstream regulator of cell death and proinflammatory signaling. Recognition of Z-DNA/RNA by ZBP1 promotes host resistance to viral infection but can also drive detrimental autoinflammation. Additionally, ZBP1 has interesting roles in cancer and other disease settings and is emerging as an attractive target for therapy.

Exosome-based crosstalk in glaucoma pathogenesis: a focus on oxidative stress and neuroinflammation

Exosomes are membrane-bound tiny particles that are released by all live cells that contain multiple signal molecules and extensively participate in numerous normal physical activities and pathologies. In glaucoma, the crucial role of exosome-based crosstalk has been primarily revealed in animal models and ex vivo cell studies in the recent decade. In the aqueous drainage system, exosomes derived from non-pigment ciliary epithelium act in an endocrine manner and specifically regulate the function of the trabecular meshwork to cope with persistent oxidative stress challenges. In the retina, a more complicated regulatory network among microglia, retinal neurons, retinal ganglial cells, retinal pigment epithelium, and other immune effector cells by exosomes are responsible for the elaborate modulation of tissue homeostasis under physical state and the widespread propagation of neuroinflammation and its consequent neurodegeneration in glaucoma pathogenesis. Accumulating evidence indicates that exosome-based crosstalk depends on numerous factors, including the specific cargos they carried (particularly micro RNA), concentration, size, and ionization potentials, which largely remain elusive. In this narrative review, we summarize the latest research focus of exosome-based crosstalk in glaucoma pathogenesis, the current research progress of exosome-based therapy for glaucoma and provide in-depth perspectives on its current research gap.

Cooperative sensing of mitochondrial DNA by ZBP1 and cGAS promotes cardiotoxicity

Mitochondrial DNA (mtDNA) is a potent agonist of the innate immune system; however, the exact immunostimulatory features of mtDNA and the kinetics of detection by cytosolic nucleic acid sensors remain poorly defined. Here, we show that mitochondrial genome instability promotes Z-form DNA accumulation. Z-DNA binding protein 1 (ZBP1) stabilizes Z-form mtDNA and nucleates a cytosolic complex containing cGAS, RIPK1, and RIPK3 to sustain STAT1 phosphorylation and type I interferon (IFN-I) signaling. Elevated Z-form mtDNA, ZBP1 expression, and IFN-I signaling are observed in cardiomyocytes after exposure to Doxorubicin, a first-line chemotherapeutic agent that induces frequent cardiotoxicity in cancer patients. Strikingly, mice lacking ZBP1 or IFN-I signaling are protected from Doxorubicin-induced cardiotoxicity. Our findings reveal ZBP1 as a cooperative partner for cGAS that sustains IFN-I responses to mitochondrial genome instability and highlight ZBP1 as a potential target in heart failure and other disorders where mtDNA stress contributes to interferon-related pathology.

Mitochondrial DNA Release in Innate Immune Signaling

According to the endosymbiotic theory, most of the DNA of the original bacterial endosymbiont has been lost or transferred to the nucleus, leaving a much smaller (∼16 kb in mammals), circular molecule that is the present-day mitochondrial DNA (mtDNA). The ability of mtDNA to escape mitochondria and integrate into the nuclear genome was discovered in budding yeast, along with genes that regulate this process. Mitochondria have emerged as key regulators of innate immunity, and it is now recognized that mtDNA released into the cytoplasm, outside of the cell, or into circulation activates multiple innate immune signaling pathways. Here, we first review the mechanisms through which mtDNA is released into the cytoplasm, including several inducible mitochondrial pores and defective mitophagy or autophagy. Next, we cover how the different forms of released mtDNA activate specific innate immune nucleic acid sensors and inflammasomes. Finally, we discuss how intracellular and extracellular mtDNA release, including circulating cell-free mtDNA that promotes systemic inflammation, are implicated in human diseases, bacterial and viral infections, senescence and aging.

The cGAS-STING pathway in diabetic retinopathy and age-related macular degeneration

Diabetic retinopathy and age-related macular degeneration are common retinal diseases with shared pathophysiology, including oxidative stress-induced inflammation. Cellular mechanisms responsible for converting oxidative stress into retinal damage are ill-defined but have begun to clarify. One common outcome of retinal oxidative stress is mitochondrial damage and subsequent release of mitochondrial DNA into the cytosol. This leads to activation of the cGAS-STING pathway, resulting in interferon release and disease-amplifying inflammation. This review summarizes the evolving link between aberrant cGAS-STING signaling and inflammation in common retinal diseases and provides prospective for targeting this system in diabetic retinopathy and age-related macular degeneration. Further defining the roles of this system in the retina is expected to reveal new disease pathology and novel therapeutic approaches.

Mitochondrial pores at the crossroad between cell death and inflammatory signaling

Mitochondria are cellular organelles with a major role in many cellular processes, including not only energy production, metabolism, and calcium homeostasis but also regulated cell death and innate immunity. Their proteobacterial origin makes them a rich source of potent immune agonists, normally hidden within the mitochondrial membrane barriers. Alteration of mitochondrial permeability through mitochondrial pores thus provides efficient mechanisms not only to communicate mitochondrial stress to the cell but also as a key event in the integration of cellular responses. In this regard, eukaryotic cells have developed diverse signaling networks that sense and respond to the release of mitochondrial components into the cytosol and play a key role in controlling cell death and inflammatory pathways. Modulating pore formation at mitochondria through direct or indirect mechanisms may thus open new opportunities for therapy. In this review, we discuss the current understanding of the structure and molecular mechanisms of mitochondrial pores and how they function at the interface between cell death and inflammatory signaling to regulate cellular outcomes.

Oxidized mitochondrial DNA: a protective signal gone awry

Despite the emergence of mitochondria as key regulators of innate immunity, the mechanisms underlying the generation and release of immunostimulatory alarmins by stressed mitochondria remains nebulous. We propose that the major mitochondrial alarmin in myeloid cells is oxidized mitochondrial DNA (Ox-mtDNA). Fragmented Ox-mtDNA enters the cytosol where it activates the NLRP3 inflammasome and generates IL-1β, IL-18, and cGAS-STING to induce type I interferons and interferon-stimulated genes. Inflammasome activation further enables the circulatory release of Ox-mtDNA by opening gasdermin D pores. We summarize new data showing that, in addition to being an autoimmune disease biomarker, Ox-mtDNA converts beneficial transient inflammation into long-lasting immunopathology. We discuss how Ox-mtDNA induces short- and long-term immune activation, and highlight its homeostatic and immunopathogenic functions.

On the other end of the line: Extracellular vesicle-mediated communication in glaucoma

In the last decade, extracellular vesicles (EVs) have emerged as a promising field of research due to their ability to participate in cell-to-cell communication via the transfer of their very diverse and complex cargo. The latter reflects the nature and physiological state of the cell of origin and, as such, EVs may not only play a pivotal role in the cellular events that culminate into disease, but also hold great potential as drug delivery vehicles and biomarkers. Yet, their role in glaucoma, the leading cause of irreversible blindness worldwide, has not been fully studied. Here, we provide an overview of the different EV subtypes along with their biogenesis and content. We elaborate on how EVs released by different cell types can exert a specific function in the context of glaucoma. Finally, we discuss how these EVs provide opportunities to be used as biomarkers for diagnosis and monitoring of disease.

Z-DNA/RNA Binding Protein 1 Senses Mitochondrial DNA to Induce Receptor-Interacting Protein Kinase-3/Mixed Lineage Kinase Domain-Like-Driven Necroptosis in Developmental Sevoflurane Neurotoxicity

Developmental sevoflurane exposure leads to widespread neuronal cell death known as sevoflurane-induced neurotoxicity (SIN). Receptor-interacting protein kinase-3 (RIPK3) and mixed lineage kinase domain-like (MLKL)-driven necroptosis plays an important role in cell fate. Previous research has shown that inhibition of RIPK1 activity alone did not attenuate SIN. Since RIPK3/MLKL signaling could also be activated by Z-DNA/RNA binding protein 1 (ZBP1), the present study was designed to investigate whether ZBP1-mediated and RIPK3/MLKL-driven necroptosis is involved in SIN through in vitro and in vivo experiments. We found that sevoflurane priming triggers neuronal cell death and LDH release in a time-dependent manner. The expression levels of RIPK1, RIPK3, ZBP1 and membrane phosphorylated MLKL were also dramatically enhanced in SIN. Intriguingly, knockdown of RIPK3, but not RIPK1, abolished MLKL-mediated neuronal necroptosis in SIN. Additionally, inhibition of RIPK3-mediated necroptosis with GSK'872, rather than inhibition of apoptosis with zVAD, significantly ameliorated SIN. Further investigation showed that sevoflurane treatment causes mitochondrial DNA (mtDNA) release into the cytosol. Accordingly, ZBP1 senses cytosolic mtDNA and consequently activates RIPK3/MLKL signaling. This conclusion was reinforced by the evidence that knockdown of ZBP1 or depleting mtDNA with ethidium bromide remarkably improved SIN. Finally, the administration of the RIPK3 inhibitor GSK'872 relieved sevoflurane-induced spatial and emotional disorders without influence on locomotor activity. Altogether, these results illustrate that ZBP1 senses cytosolic mtDNA to induce RIPK3/MLKL-driven necroptosis in SIN. Elucidating the role of necroptosis in SIN will provide new insights into understanding the mechanism of anesthetic exposure in the developing brain.

ZBP1: A Powerful Innate Immune Sensor and Double-Edged Sword in Host Immunity

Z-conformation nucleic acid binding protein 1 (ZBP1), a powerful innate immune sensor, has been identified as the important signaling initiation factor in innate immune response and the multiple inflammatory cell death known as PANoptosis. The initiation of ZBP1 signaling requires recognition of left-handed double-helix Z-nucleic acid (includes Z-DNA and Z-RNA) and subsequent signaling transduction depends on the interaction between ZBP1 and its adapter proteins, such as TANK-binding kinase 1 (TBK1), interferon regulatory factor 3 (IRF3), receptor-interacting serine/threonine-protein kinase 1 (RIPK1), and RIPK3. ZBP1 activated innate immunity, including type-I interferon (IFN-I) response and NF-κB signaling, constitutes an important line of defense against pathogenic infection. In addition, ZBP1-mediated PANoptosis is a double-edged sword in anti-infection, auto-inflammatory diseases, and tumor immunity. ZBP1-mediated PANoptosis is beneficial for eliminating infected cells and tumor cells, but abnormal or excessive PANoptosis can lead to a strong inflammatory response that is harmful to the host. Thus, pathogens and host have each developed multiplex tactics targeting ZBP1 signaling to maintain strong virulence or immune homeostasis. In this paper, we reviewed the mechanisms of ZBP1 signaling, the effects of ZBP1 signaling on host immunity and pathogen infection, and various antagonistic strategies of host and pathogen against ZBP1. We also discuss existent gaps regarding ZBP1 signaling and forecast potential directions for future research.

Targeting mitochondria in cancer therapy: Insight into photodynamic and photothermal therapies

Mitochondria are critical multifunctional organelles in cells that generate power, produce reactive oxygen species, and regulate cell survival. Mitochondria that are dysfunctional are eliminated via mitophagy as a way to protect cells under moderate stress and physiological conditions. However, mitophagy is a double-edged sword and can trigger cell death under severe stresses. By targeting mitochondria, photodynamic (PD) and photothermal (PT) therapies may play a role in treating cancer. These therapeutic modalities alter mitochondrial membrane potential, thereby affecting respiratory chain function and generation of reactive oxygen species promotes signaling pathways for cell death. In this regard, PDT, PTT, various mitochondrion-targeting agents and therapeutic methods could have exploited the vital role of mitochondria as the doorway to regulated cell death. Targeted mitochondrial therapies would provide an excellent opportunity for effective mitochondrial injury and accurate tumor erosion. Herein, we summarize the recent progress on the roles of PD and PT treatments in regulating cancerous cell death in relation to mitochondrial targeting and the signaling pathways involved.