Inflammasome Activation Triggers Caspase-1-Mediated Cleavage of cGAS to Regulate Responses to DNA Virus Infection

Inhibition of the cGAS-STING pathway: contributing to the treatment of cerebral ischemia-reperfusion injury

The cGAS-STING pathway plays an important role in ischemia-reperfusion injury in the heart, liver, brain, and kidney, but its role and mechanisms in cerebral ischemia-reperfusion injury have not been systematically reviewed. Here, we outline the components of the cGAS-STING pathway and then analyze its role in autophagy, ferroptosis, cellular pyroptosis, disequilibrium of calcium homeostasis, inflammatory responses, disruption of the blood-brain barrier, microglia transformation, and complement system activation following cerebral ischemia-reperfusion injury. We further analyze the value of cGAS-STING pathway inhibitors in the treatment of cerebral ischemia-reperfusion injury and conclude that the pathway can regulate cerebral ischemia-reperfusion injury through multiple mechanisms. Inhibition of the cGAS-STING pathway may be helpful in the treatment of cerebral ischemia-reperfusion injury.

Mitochondrial Dysfunction is a Crucial Immune Checkpoint for Neuroinflammation and Neurodegeneration: mtDAMPs in Focus

Neuroinflammation is a pivotal factor in the progression of both age-related and acute neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and stroke. Mitochondria, essential for neuronal health due to their roles in energy production, calcium buffering, and oxidative stress regulation, become increasingly susceptible to dysfunction under conditions of metabolic stress, aging, or injury. Impaired mitophagy in aged or injured neurons leads to the accumulation of dysfunctional mitochondria, which release mitochondrial-derived damage-associated molecular patterns (mtDAMPs). These mtDAMPs act as immune checkpoints, activating pattern recognition receptors (PRRs) and triggering innate immune signaling pathways. This activation initiates inflammatory responses in neurons and brain-resident immune cells, releasing cytokines and chemokines that damage adjacent healthy neurons and recruit peripheral immune cells, further amplifying neuroinflammation and neurodegeneration. Long-term mitochondrial dysfunction perpetuates a chronic inflammatory state, exacerbating neuronal injury and contributing additional immunogenic components to the extracellular environment. Emerging evidence highlights the critical role of mtDAMPs in initiating and sustaining neuroinflammation, with circulating levels of these molecules potentially serving as biomarkers for disease progression. This review explores the mechanisms of mtDAMP release due to mitochondrial dysfunction, their interaction with PRRs, and the subsequent activation of inflammatory pathways. We also discuss the role of mtDAMP-triggered innate immune responses in exacerbating both acute and chronic neuroinflammation and neurodegeneration. Targeting dysfunctional mitochondria and mtDAMPs with pharmacological agents presents a promising strategy for mitigating the initiation and progression of neuropathological conditions.

Diffuse traumatic brain injury induced stimulator of interferons (STING) signaling in microglia drives cortical neuroinflammation, neuronal dysfunction, and impaired cognition

Neuropsychiatric complications including depression and cognitive impairment develop, persist, and worsen in the years after traumatic brain injury (TBI), negatively affecting life and lifespan. Inflammatory responses mediated by microglia are associated with the transition from acute to chronic neuroinflammation after TBI. Moreover, type I interferon (IFN-I) signaling is a key mediator of inflammation during this transition. Thus, the purpose of this study was to determine the degree to which a microglia-specific knockout of the stimulator of interferons (STING) influenced TBI-induced neuroinflammation, neuronal dysfunction, and cognitive impairment. Here, microglial inducible STING knockout (CX₃CR1Cre/ERT2 x STINGfl/fl) mice were created and validated (mSTING-/-). Diffuse brain injury (midline fluid percussion) in male and female mice increased STING expression in microglia, promoted microglial morphological restructuring, and induced robust cortical inflammation and pathology 7 days post injury (dpi). These TBI-associated responses were attenuated in mSTING-/- mice. Increased cortical astrogliosis and rod-shaped microglia induced by TBI were independent of mSTING-/-. 7 dpi, TBI induced 237 differentially expressed genes (DEG) in the cortex of functionally wildtype (STINGfl/fl) associated with STING, NF-κB, and Interferon Alpha signaling and 85% were attenuated by mSTING-/-. Components of neuronal injury including reduced NeuN expression, increased cortical lipofuscin, and increased neurofilament light chain in plasma were increased by TBI and dependent on mSTING. TBI-associated cognitive tasks (novel object recognition/location, NOR/NOL) at 7 dpi were dependent on mSTING. Notably, the TBI-induced cognitive deficits in NOR/NOL and increased cortical inflammation 7 dpi were unaffected in global interferon-α/β receptor 1 knockout (IFNAR1) mice. In the final study, the RNA profile of neurons after TBI in STINGfl/fl and mSTING-/- mice was assessed 7 dpi by single nucleus RNA-sequencing. There was a TBI-dependent suppression of cortical neuronal homeostasis with reductions in CREB signaling, synaptogenesis, and oxytocin signaling and increases in cilium assembly and PTEN signaling. Overall, mSTING-/- prevented 50% of TBI-induced DEGs in cortical neurons. Collectively, ablation of STING in microglia attenuates TBI-induced interferon responses, cortical inflammation, neuronal dysfunction, neuronal pathology, and cognitive impairment.

Identification and development of cGAS inhibitors and their uses to treat Alzheimer's disease

Cyclic GMP-AMP (cGAMP) synthase (cGAS) is a key component of the evolutionary conserved immune response pathway, acting upstream stimulator of interferon genes (STING). It is implicated in various human diseases, including Alzheimer's Disease (AD) and other neurodegenerative disorders. Recent studies have shown that pharmacological inhibition of cGAS in tauopathy mice reduces cytokine expression and ameliorates memory and cognition function. This review summarizes the development and application of high-throughput screening (HTS) strategies for identifying cGAS inhibitor hits and transitioning from hits to leads. Such efforts have provided diverse array of potent cGAS inhibitors that may be beneficial in treating central nervous system (CNS) disorders, such as AD and other neurodegenerative diseases. We describe three HTS strategies: the classical HTS using a chemical library of drug like compounds by cell-free or cell-based assays and the fragment-based screening, where the activity of potential inhibitors was determined by measuring the levels of unreacted ATP or assessing the production of cGAMP or pyrophosphate (PPi). These methods were instrumental in discovering cGAS inhibitor hits and subsequent modifications produced potent leads. Finally, we discuss various post-translational modifications of cGAS and consider whether some of these modifications may serve as useful targets for inhibiting cGAS activity or for promoting protein degradation.

Cytosolic nucleic acid sensing as driver of critical illness: mechanisms and advances in therapy

Nucleic acids from both self- and non-self-sources act as vital danger signals that trigger immune responses. Critical illnesses such as acute respiratory distress syndrome, sepsis, trauma and ischemia lead to the aberrant cytosolic accumulation and massive release of nucleic acids that are detected by antiviral innate immune receptors in the endosome or cytosol. Activation of receptors for deoxyribonucleic acids and ribonucleic acids triggers inflammation, a major contributor to morbidity and mortality in critically ill patients. In the past decade, there has been growing recognition of the therapeutic potential of targeting nucleic acid sensing in critical care. This review summarizes current knowledge of nucleic acid sensing in acute respiratory distress syndrome, sepsis, trauma and ischemia. Given the extensive research on nucleic acid sensing in common pathological conditions like cancer, autoimmune disorders, metabolic disorders and aging, we provide a comprehensive summary of nucleic acid sensing beyond critical illness to offer insights that may inform its role in critical conditions. Additionally, we discuss potential therapeutic strategies that specifically target nucleic acid sensing. By examining nucleic acid sources, sensor activation and function, as well as the impact of regulating these pathways across various acute diseases, we highlight the driving role of nucleic acid sensing in critical illness.

Diverse strategies utilized by coronaviruses to evade antiviral responses and suppress pyroptosis

Viral infections trigger inflammasome-mediated caspase-1 activation. Nevertheless, limited understanding exists regarding how viruses use the active caspase-1 to evade host immune response. Here, we use porcine epidemic diarrhea virus (PEDV) as a model of coronaviruses (CoVs) to illustrate the intricate regulation of CoVs to combat IFN-I signaling and pyroptosis. Our findings demonstrate that PEDV infection stabilizes caspase-1 expression via papain-like protease PLP2's deubiquitinase activity. This stabilization of caspase-1 disrupts IFN-I signaling by cleaving RIG-I at the D189 residue. Furthermore, we demonstrate that 6-thioguanine (6TG), a PLP2 inhibitor, reverses the inhibitory effect on IFN-I signaling mediated by PLP2 and significantly reduces PEDV replication. Additionally, PLP2 degrades GSDMD-p30 by removing its K27-linked ubiquitin chain at K275 to restrain pyroptosis. Papain-like proteases from other genera of CoVs (PDCoV and SARS-CoV-2) have the similar activity to degrade GSDMD-p30. We further demonstrate that SARS-CoV-2 N protein induced NLRP3 inflammasome activation also uses the active caspase-1 to counter IFN-I signaling by cleaving RIG-I. Therefore, our work unravels a novel antagonistic mechanism employed by CoVs to evade host antiviral response.

Diffuse Traumatic Brain Injury Induced Stimulator of Interferons (STING) Signaling in Microglia Drives Cortical Neuroinflammation, Neuronal Dysfunction, and Impaired Cognition

Neuropsychiatric complications including depression and cognitive impairment develop, persist, and worsen in the years after traumatic brain injury (TBI), negatively affecting life and lifespan. Inflammatory responses mediated by microglia are associated with the transition from acute to chronic neuroinflammation after TBI. Moreover, type I interferon (IFN-I) signaling is a key mediator of inflammation during this transition. Thus, the purpose of this study was to determine the degree to which a microglia-specific knockout of the stimulator of interferons (STING) influenced TBI-induced neuroinflammation, neuronal dysfunction, and cognitive impairment. Here, microglial inducible STING knockout (CX3CR1Cre/ERT2 × STINGfl/fl) mice were created and validated (mSTING-/-). Diffuse brain injury (midline fluid percussion) in male and female mice increased STING expression in microglia, promoted microglial morphological restructuring, and induced robust cortical inflammation and pathology 7 days post injury (dpi). These TBI-associated responses were attenuated in mSTING-/- mice. Increased cortical astrogliosis and rod-shaped microglia induced by TBI were independent of mSTING-/-. 7 dpi, TBI induced 237 differentially expressed genes (DEG) in the cortex of functionally wildtype (STING+/+) associated with STING, NF-κB, and Interferon Alpha signaling and 85% were attenuated by mSTING-/-. Components of neuronal injury including reduced NeuN expression, increased cortical lipofuscin, and increased neurofilament light chain in plasma were increased by TBI and dependent on mSTING. TBI-associated cognitive tasks (novel object recognition/location, NOR/NOL) at 7 dpi were dependent on mSTING. Notably, the TBI-induced cognitive deflcits in NOR/NOL and increased cortical inflammation 7 dpi were unaffected in global interferon-α/β receptor 1 knockout (IFNAR1) mice. In the final study, the RNA profile of neurons after TBI in STING+/+ and mSTING-/- mice was assessed 7 dpi by single nucleus RNA-sequencing. There was a TBI-dependent suppression of cortical neuronal homeostasis with reductions in CREB signaling, synaptogenesis, and oxytocin signaling and increases in cilium assembly and PTEN signaling. Overall, mSTING-/- prevented 50% of TBI-induced DEGs in cortical neurons. Collectively, ablation of STING in microglia attenuates TBI-induced IFN-dependent responses, cortical inflammation, neuronal dysfunction, neuronal pathology, and cognitive impairment.

HDAC6 deacetylates TRIM56 to negatively regulate cGAS-STING-mediated type I interferon responses

Histone deacetylase HDAC6 has been implicated in regulating antiviral innate immunity. However, its precise function in response to DNA virus infection remains elusive. Herein, we find that HDAC6 deficiency promotes the activation of cGAS-STING signaling and type I interferon (IFN) production, both in vitro and in vivo, resulting in a decrease in HSV-1 infection. Mechanistically, HDAC6 deacetylates tripartite motif protein 56 (TRIM56) at K110 in mice, thereby impairing the monoubiquitination cGAS and its DNA binding ability. Overexpression of TRIM56 K110Q protects mice against HSV-1 infection. Notably, different amino acids at position 110 of TRIM56 in human and mouse cause species-specific IFN responses. Further, we show that during early stages of HSV-1 infection, the viral protein US3 phosphorylates HDAC6 to inhibit the cGAS-mediated antiviral response. Our results suggest that HDAC6 inhibits cGAS activation through TRIM56 deacetylation in a species-specific manner.

Honokiol ameliorates silica-induced lung fibrosis by inhibiting macrophage pyroptosis via modulating cGAS/STING signaling

Silicosis is a life-threatening occupational disease because of inhaling silica dust, leading to chronic inflammation, pyroptosis, and fibrosis. Unfortunately, it is still lacking effective pharmacological intervention currently. Honokiol (HKL), a natural extract with biological activity from Magnolia bark, is known for its antioxidant and anti-inflammatory biological effects. The current work aimed to investigate the therapeutic potential of HKL in mitigating silica-induced lung fibrosis and pyroptosis, particularly focusing on the cGAS/STING signaling pathway. The pulmonary pathological results shown in H&E and Masson's trichrome staining images confirmed the protective effects of HKL on lung tissue structure. In addition, HKL significantly reduced lung inflammation, collagen deposition, and oxidative stress compared to mice in the silicosis group. HKL treatment also alleviated silica-induced pyroptosis by suppressing the activation of the cGAS/STING signaling pathway in lung tissues. Moreover, the in vitro experiments using J774A.1 macrophages demonstrated that HKL reduced pyroptosis and improved cell viability under exposure to silica combined lipopolysaccharide (LPS). These were attributed to HKL downregulating the activation of the cGAS/STING signaling pathway in pyroptotic J774A.1 cells induced by silica combined with LPS. Meanwhile, inhibition of STING signaling induced by DNase I significantly enhanced the protective effects of HKL on the inflammatory and pyroptotic processes induced by silica. Overall, HKL could attenuate silica-induced pyroptosis by modulating the cGAS/STING signaling pathway against pulmonary fibrosis. The current study offers a promising approach for treating silicosis and related inflammatory responses.

Curdione combined with borneol treats bacterial mixed HPV infection by regulating the crosstalk among immune cells

Background

Human papillomavirus (HPV) infection is a worldwide reproductive system disease. Baofukang suppository, a traditional herbal preparation that includes curdione and borneol, has been reported to treat bacterial vaginosis (BV) and HPV infection in China. However, the therapeutic mechanism is still unknown. This study aims to explore the molecular mechanisms of curdione and borneol in treating HPV infection.

Methods

We conducted a retrospective cohort analysis of medical records from a single-center study involving 205 HPV patients, focusing on the correlation between HPV clearance and co-infection with other pathogens, confirming the efficacy of Baofukang suppository. Bioinformatics and network pharmacology approaches were employed to identify therapeutic targets of Baofukang suppository for BV/HPV co-infections. qRT-PCR, Western blot, immunofluorescence staining, and flow cytometry were utilized to validate the therapeutic targets of curdione and borneol, along with the associated immune molecular changes. Finally, the molecular mechanisms and therapeutic efficacy of curdione and borneol were confirmed in vivo using an LPS/TC-1 cervical orthotopic injection model.

Results

Curdione and borneol selectively inhibit the secretion of interleukin-6 (IL-6) and interleukin-1β (IL-1β) by macrophages. The reduction in IL-6 and IL-1β levels effectively inhibits the expression of CD274 (Programmed death ligand 1, PD-L1) in infected epithelial cells by inhibiting STAT3 phosphorylation, thereby suppressing their immune evasion capabilities. Furthermore, curdione and borneol enhance the expression of tumor necrosis factor α (TNF-α) and caspase 1 (CASP1) in macrophages, as well as the expression of interleukin 12 (IL-12) and interleukin 23 (IL-23) in dendritic cells (DCs). The expression of these inflammatory factors effectively promotes the migration and differentiation of T cells to the site of infection, completing the clearance of infected epithelial cells.

Conclusion

The main components of Baofukang suppository, curdione and borneol, inhibit the progression of HPV infection and the occurrence of cervical cancer by modulating the communication between innate and adaptive immunity, promoting the recruitment and recognition of CD8+ T cells to eliminate HPV-infected epithelial cells.

MYO1F positions cGAS on the plasma membrane to ensure full and functional signaling

Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS) detects viral or endogenous DNA, activating the innate immune response to infections and autoimmune diseases. Upon binding to double-stranded DNA, cGAS synthesizes 2'3' cGMP-AMP, which triggers type I interferon production. Besides its presence in the cytosol and nucleus, cGAS is found at the plasma membrane, although its significance remains unclear. Here, we report that cGAS associates with myosin 1F (MYO1F) at the plasma membrane of human and mouse macrophages. During viral infection, phosphorylation of MYO1F by spleen-associated tyrosine kinase (SYK) facilitates the recruitment of lysine acetyltransferase 2A (KAT2A), which acetylates cGAS at lysine residues 421, 292, and 131, essential for its activation. Moreover, membrane-localized cGAS is crucial for signaling activation and type I interferon production triggered by virus-cell fusion due to Mn2+ release from organelles. Our results highlight the importance of MYO1F-mediated cGAS localization for its full activation in response to viral infection.

Zinc homeostasis regulates caspase activity and inflammasome activation

Inflammasome activation drives pyroptotic cell death and the release of inflammatory cytokines, and many diseases involve its overactivation. Zinc is essential for all organisms as a trace element, but its functions in innate immunity remain undefined. Here, we reported that Zn2+ inhibits caspase-1 to hinder inflammasome activation. We first identified the zinc exporter solute carrier family 30 member 1 (SLC30A1) as an inflammasome regulator, using a genome-wide CRISPR-Cas9-mediated screen. SLC30A1 deficiency suppressed multiple inflammasomes by increasing intracellular levels of Zn2+, which bound and inhibited caspase-1 at its active site residues H237, C244 and C285. Mutation of these residues almost completely blocked zinc binding. Similarly, Zn2+ also inhibited caspase-4/5/11-mediated noncanonical inflammasome activation. Importantly, zinc supplementation significantly relieved cecal ligation and puncture (CLP)-induced sepsis, Imiquimod (IMQ)-induced psoriasis and Alzheimer's disease. Thus, zinc might be used to treat inflammasome-related diseases as a broad-spectrum inflammasome inhibitor.

Crosstalk of pyroptosis and cytokine in the tumor microenvironment: from mechanisms to clinical implication

In the realm of cancer research, the tumor microenvironment (TME) plays a crucial role in tumor initiation and progression, shaped by complex interactions between cancer cells and surrounding non-cancerous cells. Cytokines, as essential immunomodulatory agents, are secreted by various cellular constituents within the TME, including immune cells, cancer-associated fibroblasts, and cancer cells themselves. These cytokines facilitate intricate communication networks that significantly influence tumor initiation, progression, metastasis, and immune suppression. Pyroptosis contributes to TME remodeling by promoting the release of pro-inflammatory cytokines and sustaining chronic inflammation, impacting processes such as immune escape and angiogenesis. However, challenges remain due to the complex interplay among cytokines, pyroptosis, and the TME, along with the dual effects of pyroptosis on cancer progression and therapy-related complications like cytokine release syndrome. Unraveling these complexities could facilitate strategies that balance inflammatory responses while minimizing tissue damage during therapy. This review delves into the complex crosstalk between cytokines, pyroptosis, and the TME, elucidating their contribution to tumor progression and metastasis. By synthesizing emerging therapeutic targets and innovative technologies concerning TME, this review aims to provide novel insights that could enhance treatment outcomes for cancer patients.

The role of post-translational modifications of cGAS in γδ T cells

Cyclic GMP-AMP (cGAMP) synthase (cGAS) senses DNA in a sequence-independent manner, triggering cGAMP synthesis, which activates stimulator of interferon genes (STING) and the subsequent expression of type I interferons, tumour necrosis factor alpha (TNF-α) and other proinflammatory factors in two downstream pathways. However, the function of the cGASSTING pathway in γδ T cells remains unclear. The γδ T-cell population differs from the innate-like lymphocyte population, particularly with respect to tissue distribution, indicating the unique potential of γδ T cells in treating infections and cancers. On the basis of accumulating evidence, cGAS activity is modulated by protein posttranslational modifications (PTMs), including phosphorylation, O-GlcNAcylation, acetylation, ubiquitylation and methylation, which affect multiple cGAS functions. Thus, here, we summarize recent research on PTMs of the cGAS protein that modulate γδ T-cell function. An understanding of cGAS features and modulation mechanisms may facilitate the design of therapies for γδ T-cell-related immune diseases and cancer.

Review of Excessive Cytosolic DNA and Its Role in AIM2 and cGAS-STING Mediated Psoriasis Development

In psoriasis, keratinocytes are triggered by factors, such as infection or tissue damage, to release DNA, which thereby activates plasmacytoid dendritic cells and macrophages to induce inflammation, thickened epidermis, and parakeratosis. The recognition of double-stranded (ds)DNA facilitates the activation of cytoplasmic DNA sensors absent in melanoma 2 (AIM2) inflammasome assembly and cyclic guanosine monophosphate adenosine monophosphate (cGAMP) synthase (cGAS) - stimulator of interferon gene (STING) pathway, both of which play a pivotal role in mediating the inflammatory response and driving the progression of psoriasis. Additionally, secreted proinflammatory cytokines can stimulate further DNA release from keratinocytes. Notably, the activation of AIM2 and cGAS-STING signaling pathways also mediates programmed cell death, potentially enhancing DNA overproduction. As a result, excessive DNA can activate these pathways, amplifying persistent inflammatory responses that contribute to the maintenance of psoriasis. Several studies have validated that targeting DNA and its mediated activation of AIM2 and cGAS-STING offers promising therapeutic strategies for psoriasis. Here, we postulate a hypothesis that excessive cytosolic DNA can activate AIM2 and cGAS-STING, mediating inflammation and programmed cell death, ultimately fostering DNA accumulation and contributing to the development of psoriasis.

Cytoplasmic DNA and AIM2 inflammasome in RA: where they come from and where they go?

Rheumatoid arthritis is a chronic autoimmune disease of undetermined etiology characterized by symmetric synovitis with predominantly destructive and multiple joint inflammation. Cytoplasmic DNA sensors that recognize protein molecules that are not themselves or abnormal dsDNA fragments play an integral role in the generation and perpetuation of autoimmune diseases by activating different signaling pathways and triggering innate immune signaling pathways and host defenses. Among them, melanoma deficiency factor 2 (AIM2) recognizes damaged DNA and double-stranded DNA and binds to them to further assemble inflammasome, initiating the innate immune response and participating in the pathophysiological process of rheumatoid arthritis. In this article, we review the research progress on the source of cytoplasmic DNA, the mechanism of assembly and activation of AIM2 inflammasome, and the related roles of other cytoplasmic DNA sensors in rheumatoid arthritis.

Identification of a novel caspase cleavage motif AEAD

Infections of many viruses induce caspase activation to regulate multiple cellular pathways, including programmed cell death, immune signaling and etc. Characterizations of caspase cleavage sites and substrates are important for understanding the regulation mechanisms of caspase activation. Here, we identified and analyzed a novel caspase cleavage motif AEAD, and confirmed its caspase dependent cleavage activity in natural substrate, such as nitric oxide-associated protein 1 (NOA1). Fusing the enhanced green fluorescent protein (EGFP) with the mitochondrial marker protein Tom20 through the AEAD motif peptide localized EGFP to the mitochondria. Upon the activation of caspase triggered by Sendai virus (SeV) or herpes simplex virus type 1 (HSV-1) infection, EGFP diffusely localized to the cell due to the caspase-mediated cleavage, thus allowing visual detection of the virus-induced caspase activation. An AEAD peptide-derived inhibitor Z-AEAD-FMK were developed, which significantly inhibited the activities of caspases-1, -3, -6, -7, -8 and -9, exhibiting a broad caspase inhibition effect. The inhibitor further prevented caspases-mediated cleavage of downstream substrates, including BID, PARP1, LMNA, pro-IL-1β, pro-IL-18, GSDMD and GSDME, protecting cells from virus-induced apoptotic and pyroptotic cell death. Together, our findings provide a new perspective for the identification of novel caspase cleavage motifs and the development of new caspase inhibitors and anti-inflammatory drugs.

Disruption of glucose homeostasis by bacterial infection orchestrates host innate immunity through NAD+/NADH balance

Metabolic reprogramming is crucial for activating innate immunity in macrophages, and the accumulation of immunometabolites is essential for effective defense against infection. The NAD+/NADH (ratio of nicotinamide adenine dinucleotide and its reduced counterpart) redox couple serves as a critical node that integrates metabolic pathways and signaling events, but how this metabolite couple engages macrophage activation remains unclear. Here, we show that the NAD+/NADH ratio serves as a molecular signal that regulates proinflammatory responses and type I interferon (IFN) responses divergently. Salmonella Typhimurium infection leads to a decreased NAD+/NADH ratio by inducing the accumulation of NADH. Further investigation shows that an increased NAD+/NADH ratio correlates with attenuated proinflammatory responses and enhanced type I IFN responses. Conversely, a decreased NAD+/NADH ratio is linked to intensified proinflammatory responses and restrained type I IFN responses. These results show that the NAD+/NADH ratio is an essential cell-intrinsic factor that orchestrates innate immunity, which enhances our understanding of how metabolites fine-tune innate immunity.

Tumor microenvironment-responsive manganese-based nano-modulator activate the cGAS-STING pathway to enhance innate immune system response

BACKGROUND

Manganese ions (Mn2+) combined with adjuvants capable of damaging and lysing tumor cells form an antitumor nano-modulator that enhances the immune efficacy of cancer therapy through the cascade activation of the cyclic GMP-AMP interferon gene synthase-stimulator (cGAS-STING) pathway, which underscores the importance of developing antitumor nano-modulators, which induce DNA damage and augment cGAS-STING activity, as a critical future research direction. METHODS AND RESULTS: We have successfully synthesized an antitumor nano-modulator, which exhibits good dispersibility and biosafety. This nano-modulator is engineered by loading manganese dioxide nanosheets (M-NS) with zebularine (Zeb), known for its immunogenicity-enhancing effects, and conducting targeted surface modification using hyaluronic acid (HA). After systemic circulation to the tumor site, Mn2+, Zeb, and reactive oxygen species (ROS) are catalytically released in the tumor microenvironment by H+ and H2O2. These components can directly or indirectly damage the DNA or mitochondria of tumor cells, thereby inducing programmed cell death. Furthermore, they promote the accumulation of double-stranded DNA (dsDNA) in the cytoplasm, enhancing the activation of the cGAS-STING signalling pathway and boosting the production of type I interferon and the secretion of pro-inflammatory cytokines. Additionally, Zeb@MH-NS enhances the maturation of dendritic cells, the infiltration of cytotoxic T lymphocytes, and the recruitment of natural killer cells at the tumor site.

CONCLUSIONS

This HA-modified manganese-based hybrid nano-regulator can enhance antitumor therapy by boosting innate immune activity and may provide new directions for immunotherapy and clinical translation in cancer.

Genetic and epigenetic regulation of inflammasomes: Role in atherosclerosis

The cardiovascular complications of atherosclerosis are thought to arise from an inflammatory response to the accumulation of cholesterol-rich lipoproteins in the arterial wall. The positive outcome of CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcome Study) provided key evidence to support this concept and suggested that inflammasomes and IL-1β are important inflammatory mediators in human atherosclerotic cardiovascular diseases (ACVD). In specific settings NLRP3 or AIM2 inflammasomes can induce inflammatory responses in the arterial wall and promote the formation of unstable atherosclerotic plaques. Clonal hematopoiesis (CH) has recently emerged as a major independent risk factor for ACVD. CH mutations arise during ageing and commonly involves variants in genes mediating epigenetic modifications (TET2, DNMT3A, ASXL1) or cytokine signaling (JAK2). Accumulating evidence points to the role of inflammasomes in the progression of CH-induced ACVD events and has shed light on the regulatory pathways and possible therapeutic approaches that specifically target inflammasomes in atherosclerosis. Epigenetic dynamics play a vital role in regulating the generation and activation of inflammasome components by causing changes in DNA methylation patterns and chromatin assembly. This review examines the genetic and epigenetic regulation of inflammasomes, the intersection of macrophage cholesterol accumulation with inflammasome activation and their roles in atherosclerosis. Understanding the involvement of inflammasomes in atherosclerosis pathogenesis may lead to customized treatments that reduce the burden of ACVD.

Type I interferon governs immunometabolic checkpoints that coordinate inflammation during Staphylococcal infection

Macrophage metabolic plasticity is central to inflammatory programming, yet mechanisms of coordinating metabolic and inflammatory programs during infection are poorly defined. Here, we show that type I interferon (IFN) temporally guides metabolic control of inflammation during methicillin-resistant Staphylococcus aureus (MRSA) infection. We find that staggered Toll-like receptor and type I IFN signaling in macrophages permit a transient energetic state of combined oxidative phosphorylation (OXPHOS) and aerobic glycolysis followed by inducible nitric oxide synthase (iNOS)-mediated OXPHOS disruption. This disruption promotes type I IFN, suppressing other pro-inflammatory cytokines, notably interleukin-1β. Upon infection, iNOS expression peaks at 24 h, followed by lactate-driven Nos2 repression via histone lactylation. Type I IFN pre-conditioning prolongs infection-induced iNOS expression, amplifying type I IFN. Cutaneous MRSA infection in mice constitutively expressing epidermal type I IFN results in elevated iNOS levels, impaired wound healing, vasculopathy, and lung infection. Thus, kinetically regulated type I IFN signaling coordinates immunometabolic checkpoints that control infection-induced inflammation.

Complementary dual-virus strategy drives synthetic target and cognate T-cell engager expression for endogenous-antigen agnostic immunotherapy

Targeted antineoplastic immunotherapies have achieved remarkable clinical outcomes. However, resistance to these therapies due to target absence or antigen shedding limits their efficacy and excludes tumours from candidacy. To address this limitation, here we engineer an oncolytic rhabdovirus, vesicular stomatitis virus (VSVΔ51), to express a truncated targeted antigen, which allows for HER2-targeting with trastuzumab. The truncated HER2 (HER2T) lacks signaling capabilities and is efficiently expressed on infected cell surfaces. VSVΔ51-mediated HER2T expression simulates HER2-positive status in tumours, enabling effective treatment with the antibody-drug conjugate trastuzumab emtansine in vitro, ex vivo, and in vivo. Additionally, we combine VSVΔ51-HER2T with an oncolytic vaccinia virus expressing a HER2-targeted T-cell engager. This dual-virus therapeutic strategy demonstrates potent curative efficacy in vivo in female mice using CD3+ infiltrate for anti-tumour immunity. Our findings showcase the ability to tailor the tumour microenvironment using oncolytic viruses, thereby enhancing compatibility with "off-the-shelf" targeted therapies.

Identifying selection signatures for immune response and resilience to Aleutian disease in mink using genotype data

Aleutian disease (AD) brings tremendous financial losses to the mink industry. Selecting AD-resilient mink has been conducted to control AD. Such selections could have altered the patterns of genetic variation responding to selection pressures. This study aimed to identify selection signatures for immune response (IRE) and resilience to AD. A total of 1,411 mink from an AD-positive facility were used. For IRE, 264 animals were categorized according to the combined results of enzyme-linked immunosorbent assay (ELISA) and counterimmunoelectrophoresis (CIEP). For resilience, two grouping methods were used: 1) general resilience performance (GRP, n = 30) was evaluated based on the feed conversion ratio, Kleiber ratio, and pelt quality; and 2) female reproductive performance (FRP, n = 36) was measured based on the number of kits alive 24 h after birth. Detection methods were the pairwise fixation index, nucleotide diversity, and cross-population extended haplotype homozygosity. A total of 619, 569, and 526 SNPs were identified as candidates for IRE, GRP, and FRP, respectively. The annotated genes were involved in immune system process, growth, reproduction, and pigmentation. Two olfactory-related Gene Ontology (GO) terms were significant (q < 0.05) for all traits, suggesting the impact of AD on the sense of smell of infected mink. Differences in detected genes and GO terms among different color types for IRE indicated variations in immune response to AD among color types. The mitogen-activated protein kinase (MAPK) signaling pathway was significant (q < 0.05) for FRP, suggesting that AD may disrupt MAPK signaling and affect FRP. The findings of this research contribute to our knowledge of the genomic architecture and biological mechanisms underlying AD resilience in mink.

Phase separation as a new form of regulation in innate immunity

Innate immunity is essential for the host against pathogens, cancer, and autoimmunity. The innate immune system encodes many sensor, adaptor, and effector proteins and relies on the assembly of higher-order signaling complexes to activate immune defense. Recent evidence demonstrates that many of the core complexes involved in innate immunity are organized as liquid-like condensates through a mechanism known as phase separation. Here, we discuss phase-separated condensates and their diverse functions. We compare the biochemical, structural, and mechanistic details of solid and liquid-like assemblies to explore the role of phase separation in innate immunity. We summarize the emerging evidence for the hypothesis that phase separation is a conserved mechanism that controls immune responses across the tree of life. The discovery of phase separation in innate immunity provides a new foundation to explain the rules that govern immune system activation and will enable the development of therapeutics to treat immune-related diseases properly.

Neuroimmune cell interactions and chronic infections in oral cancers

Inflammation is a process that is associated with the activation of distal immunosuppressive pathways that have evolved to restore homeostasis and prevent excessive tissue destruction. However, long-term immunosuppression resulting from systemic and local inflammation that may stem from dysbiosis, infections, or aging poses a higher risk for cancers. Cancer incidence and progression dramatically increase with chronic infections including HIV infection. Thus, studies on pro-tumorigenic effects of microbial stimulants from resident microbiota and infections in the context of inflammation are needed and underway. Here, we discuss chronic infections and potential neuro-immune interactions that could establish immunomodulatory programs permissive for tumor growth and progression.

The multiple faces of cGAS-STING in antitumor immunity: prospects and challenges

As a key sensor of double-stranded DNA (dsDNA), cyclic GMP-AMP synthase (cGAS) detects cytosolic dsDNA and initiates the synthesis of 2'3' cyclic GMP-AMP (cGAMP) that activates the stimulator of interferon genes (STING). This finally promotes the production of type I interferons (IFN-I) that is crucial for bridging innate and adaptive immunity. Recent evidence show that several antitumor therapies, including radiotherapy (RT), chemotherapy, targeted therapies and immunotherapies, activate the cGAS-STING pathway to provoke the antitumor immunity. In the last decade, the development of STING agonists has been a major focus in both basic research and the pharmaceutical industry. However, up to now, none of STING agonists have been approved for clinical use. Considering the broad expression of STING in whole body and the direct lethal effect of STING agonists on immune cells in the draining lymph node (dLN), research on the optimal way to activate STING in tumor microenvironment (TME) appears to be a promising direction. Moreover, besides enhancing IFN-I signaling, the cGAS-STING pathway also plays roles in senescence, autophagy, apoptosis, mitotic arrest, and DNA repair, contributing to tumor development and metastasis. In this review, we summarize the recent advances on cGAS-STING pathway's response to antitumor therapies and the strategies involving this pathway for tumor treatment.

DNA sensing of dendritic cells in cancer immunotherapy

Dendritic cells (DCs) are involved in the initiation and maintenance of immune responses against malignant cells by recognizing conserved pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) through pattern recognition receptors (PRRs). According to recent studies, tumor cell-derived DNA molecules act as DAMPs and are recognized by DNA sensors in DCs. Once identified by sensors in DCs, these DNA molecules trigger multiple signaling cascades to promote various cytokines secretion, including type I IFN, and then to induce DCs mediated antitumor immunity. As one of the potential attractive strategies for cancer therapy, various agonists targeting DNA sensors are extensively explored including the combination with other cancer immunotherapies or the direct usage as major components of cancer vaccines. Moreover, this review highlights different mechanisms through which tumor-derived DNA initiates DCs activation and the mechanisms through which the tumor microenvironment regulates DNA sensing of DCs to promote tumor immune escape. The contributions of chemotherapy, radiotherapy, and checkpoint inhibitors in tumor therapy to the DNA sensing of DCs are also discussed. Finally, recent clinical progress in tumor therapy utilizing agonist-targeted DNA sensors is summarized. Indeed, understanding more about DNA sensing in DCs will help to understand more about tumor immunotherapy and improve the efficacy of DC-targeted treatment in cancer.

cGAS-STING, an important signaling pathway in diseases and their therapy

Since cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway was discovered in 2013, great progress has been made to elucidate the origin, function, and regulating mechanism of cGAS-STING signaling pathway in the past decade. Meanwhile, the triggering and transduction mechanisms have been continuously illuminated. cGAS-STING plays a key role in human diseases, particularly DNA-triggered inflammatory diseases, making it a potentially effective therapeutic target for inflammation-related diseases. Here, we aim to summarize the ancient origin of the cGAS-STING defense mechanism, as well as the triggers, transduction, and regulating mechanisms of the cGAS-STING. We will also focus on the important roles of cGAS-STING signal under pathological conditions, such as infections, cancers, autoimmune diseases, neurological diseases, and visceral inflammations, and review the progress in drug development targeting cGAS-STING signaling pathway. The main directions and potential obstacles in the regulating mechanism research and therapeutic drug development of the cGAS-STING signaling pathway for inflammatory diseases and cancers will be discussed. These research advancements expand our understanding of cGAS-STING, provide a theoretical basis for further exploration of the roles of cGAS-STING in diseases, and open up new strategies for targeting cGAS-STING as a promising therapeutic intervention in multiple diseases.

IUPHAR ECR review: The cGAS-STING pathway: Novel functions beyond innate immune and emerging therapeutic opportunities

Stimulator of interferon genes (STING) is a crucial innate immune sensor responsible for distinguishing pathogens and cytosolic DNA, mediating innate immune signaling pathways to defend the host. Recent studies have revealed additional regulatory functions of STING beyond its innate immune-related activities, including the regulation of cellular metabolism, DNA repair, cellular senescence, autophagy and various cell deaths. These findings highlight the broader implications of STING in cellular physiology beyond its role in innate immunity. Currently, approximately 10 STING agonists have entered the clinical stage. Unlike inhibitors, which have a maximum inhibition limit, agonists have the potential for infinite amplification. STING signaling is a complex process that requires precise regulation of STING to ensure balanced immune responses and prevent detrimental autoinflammation. Recent research on the structural mechanism of STING autoinhibition and its negative regulation by adaptor protein complex 1 (AP-1) provides valuable insights into its different effects under physiological and pathological conditions, offering a new perspective for developing immune regulatory drugs. Herein, we present a comprehensive overview of the regulatory functions and molecular mechanisms of STING beyond innate immune regulation, along with updated details of its structural mechanisms. We discuss the implications of these complex regulations in various diseases, emphasizing the importance and feasibility of targeting the immunity-dependent or immunity-independent functions of STING. Moreover, we highlight the current trend in drug development and key points for clinical research, basic research, and translational research related to STING.

Identification of Pyroptosis-Related Genes Regulating the Progression of Chronic Rhinosinusitis with Nasal Polyps

INTRODUCTION

Chronic rhinosinusitis with nasal polyps (CRSwNP) is an immunologic disease, and pyroptosis, an inflammation-based cellular death, strictly modulates CRSwNP pathology, whereas the pyroptosis genes and mechanisms involved in CRSwNP remain unclear. Herein, we explored disease biomarkers and potential therapeutic targets for pyroptosis and immune regulation in CRSwNP using bioinformatics analysis and tissue-based verification.

METHODS

We retrieved the transcriptional profiles of the high-throughput dataset GSE136825 from the Gene Expression Omnibus database, as well as 170 pyroptosis-related gene expressions from GeneCards. Using R, we identified differentially expressed pyroptosis-related genes and examined the potential biological functions of the aforementioned genes using Gene Ontology, Kyoto Encyclopedia of the Genome pathway, immune infiltration, and protein-protein interaction (PPI) network analyses, thereby generating a list of hub genes. The hub genes were, in turn, verified using real-time quantitative polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC), and Western blotting (WB). Ultimately, using the StarBase and miRTarBase databases, we estimated the targeting microRNAs and long chain non-coding RNAs.

RESULTS

We demonstrated that the identified pyroptosis-related genes primarily modulated bacterial defense activities, as well as inflammasome immune response and assembly. Moreover, they were intricately linked to neutrophil and macrophage infiltration. Furthermore, we validated the tissue contents of hub genes AIM2, NLPR6, and CASP5 and examined potential associations with clinical variables. We also developed a competitive endogenous RNA (ceRNA) modulatory axis to examine possible underlying molecular mechanisms.

CONCLUSION

We found AIM2, CASP5, and NLRP6, three hub genes for pyroptosis in chronic rhinosinusitis with nasal polyps, by biological analysis, experimental validation, and clinical variable validation.

The cGAS-STING pathway in viral infections: a promising link between inflammation, oxidative stress and autophagy

The host defence responses play vital roles in viral infection and are regulated by complex interactive networks. The host immune system recognizes viral pathogens through the interaction of pattern-recognition receptors (PRRs) with pathogen-associated molecular patterns (PAMPs). As a PRR mainly in the cytoplasm, cyclic GMP-AMP synthase (cGAS) senses and binds virus DNA and subsequently activates stimulator of interferon genes (STING) to trigger a series of intracellular signalling cascades to defend against invading pathogenic microorganisms. Integrated omic and functional analyses identify the cGAS-STING pathway regulating various host cellular responses and controlling viral infections. Aside from its most common function in regulating inflammation and type I interferon, a growing body of evidence suggests that the cGAS-STING signalling axis is closely associated with a series of cellular responses, such as oxidative stress, autophagy, and endoplasmic reticulum stress, which have major impacts on physiological homeostasis. Interestingly, these host cellular responses play dual roles in the regulation of the cGAS-STING signalling axis and the clearance of viruses. Here, we outline recent insights into cGAS-STING in regulating type I interferon, inflammation, oxidative stress, autophagy and endoplasmic reticulum stress and discuss their interactions with viral infections. A detailed understanding of the cGAS-STING-mediated potential antiviral effects contributes to revealing the pathogenesis of certain viruses and sheds light on effective solutions for antiviral therapy.

cGLRs Join Their Cousins of Pattern Recognition Receptor Family to Regulate Immune Homeostasis

Pattern recognition receptors (PRRs) recognize danger signals such as PAMPs/MAMPs and DAMPs to initiate a protective immune response. TLRs, NLRs, CLRs, and RLRs are well-characterized PRRs of the host immune system. cGLRs have been recently identified as PRRs. In humans, the cGAS/STING signaling pathway is a part of cGLRs. cGAS recognizes cytosolic dsDNA as a PAMP or DAMP to initiate the STING-dependent immune response comprising type 1 IFN release, NF-κB activation, autophagy, and cellular senescence. The present article discusses the emergence of cGLRs as critical PRRs and how they regulate immune responses. We examined the role of cGAS/STING signaling, a well-studied cGLR system, in the activation of the immune system. The following sections discuss the role of cGAS/STING dysregulation in disease and how immune cross-talk with other PRRs maintains immune homeostasis. This understanding will lead to the design of better vaccines and immunotherapeutics for various diseases, including infections, autoimmunity, and cancers.

Salmonella T3SS-elicited inflammatory innate immune response inhibits type I IFN response in macrophages

As a gram-negative intracellular bacterial pathogen, Salmonella enterica serovar Typhimurium (S. Typhimurium) invades different cell types including macrophages. Its infection in macrophages induces robust innate immune responses that are featured by proinflammatory and type I interferon (IFN) responses. The type III secretion systems (T3SSs) of S. Typhimurium play a crucial role in activating host inflammasome pathways. It has been recognized that the inflammasome pathways inhibit the type I IFN cascade. However, the potential role of T3SS in regulating the type I IFN response and the underlying mechanisms are largely unknown. In this study, we showed that S. Typhimurium infection activated strong proinflammatory, type I IFN and IFN-stimulated genes (ISGs) expression in macrophages. Furthermore, we showed that T3SS-defective S. Typhimurium mutant ΔinvC elicited attenuated inflammatory response but enhanced type I IFN and ISGs expression. Additionally, the inhibition of caspase-1 by a specific inhibitor VX-765 resulted in increased type I IFN response. Moreover, cell-permeable pan-caspase inhibitor Z-VAD-FMK also enhanced the type I IFN response upon S. Typhimurium infection. Intriguingly, compared with exponential phase S. Typhimurium infection, stationary phase bacteria triggered higher levels of type I IFN responses. Finally, the inhibition of caspase-1 by VX-765 substantially increased the intracellular S. Typhimurium burden. In conclusion, we demonstrated that the proinflammatory response induced by S. Typhimurium T3SS can inhibit the type I IFN response, which provides insight into the role of T3SS in orchestrating innate immunity during S. Typhimurium infection.

Cardiovascular diseases crossroads: cGAS-STING signaling and disease progression

It is now widely accepted that inflammation is critical in cardiovascular diseases (CVD). Here, studies are being conducted on how cyclic GMP-AMP synthase (cGAS), a component of innate immunity's DNA-sensing machinery, communicates with the STING receptor, which is involved in activating the immune system's antiviral response. Significantly, a growing body of research in recent years highlights the strong activation of the cGAS-STING signalling pathways in several cardiovascular diseases, such as myocardial infarction, heart failure, and myocarditis. This developing collection of research emphasises these pathways' crucial role in initiating and advancing cardiovascular disease. In this extensive narrative, we explore the role of the cGAS-STING pathway in the development of CVD. We elaborate on the basic mechanisms involved in the onset and progression of CVD. This review explores the most recent developments in the recognition and characterization of cGAS-STING pathway. Additionally, it considers the field's future prospects while examining how cGAS-STING pathway might be altered and its clinical applications for cardiovascular diseases.

cGAS-STING, inflammasomes and pyroptosis: an overview of crosstalk mechanism of activation and regulation

BACKGROUND

Intracellular DNA-sensing pathway cGAS-STING, inflammasomes and pyroptosis act as critical natural immune signaling axes for microbial infection, chronic inflammation, cancer progression and organ degeneration, but the mechanism and regulation of the crosstalk network remain unclear. Cellular stress disrupts mitochondrial homeostasis, facilitates the opening of mitochondrial permeability transition pore and the leakage of mitochondrial DNA to cell membrane, triggers inflammatory responses by activating cGAS-STING signaling, and subsequently induces inflammasomes activation and the onset of pyroptosis. Meanwhile, the inflammasome-associated protein caspase-1, Gasdermin D, the CARD domain of ASC and the potassium channel are involved in regulating cGAS-STING pathway. Importantly, this crosstalk network has a cascade amplification effect that exacerbates the immuno-inflammatory response, worsening the pathological process of inflammatory and autoimmune diseases. Given the importance of this crosstalk network of cGAS-STING, inflammasomes and pyroptosis in the regulation of innate immunity, it is emerging as a new avenue to explore the mechanisms of multiple disease pathogenesis. Therefore, efforts to define strategies to selectively modulate cGAS-STING, inflammasomes and pyroptosis in different disease settings have been or are ongoing. In this review, we will describe how this mechanistic understanding is driving possible therapeutics targeting this crosstalk network, focusing on the interacting or regulatory proteins, pathways, and a regulatory mitochondrial hub between cGAS-STING, inflammasomes, and pyroptosis.

SHORT CONCLUSION

This review aims to provide insight into the critical roles and regulatory mechanisms of the crosstalk network of cGAS-STING, inflammasomes and pyroptosis, and to highlight some promising directions for future research and intervention.

Decoding immunogenic cell death from a dendritic cell perspective

Dendritic cells (DCs) are myeloid cells bridging the innate and adaptive immune system. By cross-presenting tumor-associated antigens (TAAs) liberated upon spontaneous or therapy-induced tumor cell death to T cells, DCs occupy a pivotal position in the cancer immunity cycle. Over the last decades, the mechanisms linking cancer cell death to DC maturation, have been the focus of intense research. Growing evidence supports the concept that the mere transfer of TAAs during the process of cell death is insufficient to drive immunogenic DC maturation unless this process is coupled with the release of immunomodulatory signals by dying cancer cells. Malignant cells succumbing to a regulated cell death variant called immunogenic cell death (ICD), foster a proficient interface with DCs, enabling their immunogenic maturation and engagement of adaptive immunity against cancer. This property relies on the ability of ICD to exhibit pathogen-mimicry hallmarks and orchestrate the emission of a spectrum of constitutively present or de novo-induced danger signals, collectively known as damage-associated molecular patterns (DAMPs). In this review, we discuss how DCs perceive and decode danger signals emanating from malignant cells undergoing ICD and provide an outlook of the major signaling and functional consequences of this interaction for DCs and antitumor immunity.

Inflammasome activity is controlled by ZBTB16-dependent SUMOylation of ASC

Inflammasome activity is important for the immune response and is instrumental in numerous clinical conditions. Here we identify a mechanism that modulates the central Caspase-1 and NLR (Nod-like receptor) adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD). We show that the function of ASC in assembling the inflammasome is controlled by its modification with SUMO (small ubiquitin-like modifier) and identify that the nuclear ZBTB16 (zinc-finger and BTB domain-containing protein 16) promotes this SUMOylation. The physiological significance of this activity is demonstrated through the reduction of acute inflammatory pathogenesis caused by a constitutive hyperactive inflammasome by ablating ZBTB16 in a mouse model of Muckle-Wells syndrome. Together our findings identify an further mechanism by which ZBTB16-dependent control of ASC SUMOylation assembles the inflammasome to promote this pro-inflammatory response.

Inflammasomes cross-talk with lymphocytes to connect the innate and adaptive immune response

BACKGROUND

Innate and adaptive immunity are two different parts of the immune system that have different characteristics and work together to provide immune protection. Inflammasomes are a major part of the innate immune system that are expressed widely in myeloid cells and are responsible for inflammatory responses. Recent studies have shown that inflammasomes are also expressed and activated in lymphocytes, especially in T and B cells, to regulate the adaptive immune response. Activation of inflammasomes is also under the control of lymphocytes. Therefore, we propose that inflammasomes act as a bridge and they provide crosstalk between the innate and adaptive immune systems to obtain a fine balance in immune responses.

AIM OF REVIEW

This review systematially summarizes the interaction between inflammasomes and lymphocytes and describes the crosstalk between the innate and adaptive immune systems induced by inflammasomes, with the aim of providing new directions and important areas for further research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

When considering the novel function of inflammasomes in various lymphocytes, attention should be given to the activity of specific inflammasomes in studies of lymphocyte function. Moreover, research on the function of various inflammasomes in lymphocytes will help advance knowledge on the mechanisms and treatment of various diseases, including autoimmune diseases and tumors. In addition, when studying inflammatory responses, inflammasomes in both lymphocytes and myeloid cells need to be considered.

The poxvirus F17 protein counteracts mitochondrially orchestrated antiviral responses

Poxviruses are unusual DNA viruses that replicate in the cytoplasm. To do so, they encode approximately 100 immunomodulatory proteins that counteract cytosolic nucleic acid sensors such as cGAMP synthase (cGAS) along with several other antiviral response pathways. Yet most of these immunomodulators are expressed very early in infection while many are variable host range determinants, and significant gaps remain in our understanding of poxvirus sensing and evasion strategies. Here, we show that after infection is established, subsequent progression of the viral lifecycle is sensed through specific changes to mitochondria that coordinate distinct aspects of the antiviral response. Unlike other viruses that cause extensive mitochondrial damage, poxviruses sustain key mitochondrial functions including membrane potential and respiration while reducing reactive oxygen species that drive inflammation. However, poxvirus replication induces mitochondrial hyperfusion that independently controls the release of mitochondrial DNA (mtDNA) to prime nucleic acid sensors and enables an increase in glycolysis that is necessary to support interferon stimulated gene (ISG) production. To counter this, the poxvirus F17 protein localizes to mitochondria and dysregulates mTOR to simultaneously destabilize cGAS and block increases in glycolysis. Our findings reveal how the poxvirus F17 protein disarms specific mitochondrially orchestrated responses to later stages of poxvirus replication.

STING in tumors: a focus on non-innate immune pathways

Cyclic GMP-AMP synthase (cGAS) and downstream stimulator of interferon genes (STING) are involved in mediating innate immunity by promoting the release of interferon and other inflammatory factors. Mitochondrial DNA (mtDNA) with a double-stranded structure has greater efficiency and sensitivity in being detected by DNA sensors and thus has an important role in the activation of the cGAS-STING pathway. Many previous findings suggest that the cGAS-STING pathway-mediated innate immune regulation is the most important aspect affecting tumor survival, not only in its anti-tumor role but also in shaping the immunosuppressive tumor microenvironment (TME) through a variety of pathways. However, recent studies have shown that STING regulation of non-immune pathways is equally profound and also involved in tumor cell progression. In this paper, we will focus on the non-innate immune system pathways, in which the cGAS-STING pathway also plays an important role in cancer.

Secretion of mitochondrial DNA via exosomes promotes inflammation in Behçet's syndrome

Mitochondrial DNA (mtDNA) leakage into the cytoplasm can occur when cells are exposed to noxious stimuli. Specific sensors recognize cytoplasmic mtDNA to promote cytokine production. Cytoplasmic mtDNA can also be secreted extracellularly, leading to sterile inflammation. However, the mode of secretion of mtDNA out of cells upon noxious stimuli and its relevance to human disease remain unclear. Here, we show that pyroptotic cells secrete mtDNA encapsulated within exosomes. Activation of caspase-1 leads to mtDNA leakage from the mitochondria into the cytoplasm via gasdermin-D. Caspase-1 also induces intraluminal membrane vesicle formation, allowing for cellular mtDNA to be taken up and secreted as exosomes. Encapsulation of mtDNA within exosomes promotes a strong inflammatory response that is ameliorated upon exosome biosynthesis inhibition in vivo. We further show that monocytes derived from patients with Behçet's syndrome (BS), a chronic systemic inflammatory disorder, show enhanced caspase-1 activation, leading to exosome-mediated mtDNA secretion and similar inflammation pathology as seen in BS patients. Collectively, our findings support that mtDNA-containing exosomes promote inflammation, providing new insights into the propagation and exacerbation of inflammation in human inflammatory diseases.

Longitudinal proteomic investigation of COVID-19 vaccination

Although the development of COVID-19 vaccines has been a remarkable success, the heterogeneous individual antibody generation and decline over time are unknown and still hard to predict. In this study, blood samples were collected from 163 participants who next received two doses of an inactivated COVID-19 vaccine (CoronaVac®) at a 28-day interval. Using TMT-based proteomics, we identified 1,715 serum and 7,342 peripheral blood mononuclear cells (PBMCs) proteins. We proposed two sets of potential biomarkers (seven from serum, five from PBMCs) at baseline using machine learning, and predicted the individual seropositivity 57 days after vaccination (AUC = 0.87). Based on the four PBMC's potential biomarkers, we predicted the antibody persistence until 180 days after vaccination (AUC = 0.79). Our data highlighted characteristic hematological host responses, including altered lymphocyte migration regulation, neutrophil degranulation, and humoral immune response. This study proposed potential blood-derived protein biomarkers before vaccination for predicting heterogeneous antibody generation and decline after COVID-19 vaccination, shedding light on immunization mechanisms and individual booster shot planning.

cGAS-STING signaling in cell death: Mechanisms of action and implications in pathologies

Cyclic GMP-AMP synthase (cGAS) monitors dsDNA in the cytosol in response to pathogenic invasion or tissue injury, initiating cGAS-STING signaling cascades that regulate various cellular physiologies, including IFN /cytokine production, autophagy, protein synthesis, metabolism, senescence, and distinct types of cell death. cGAS-STING signaling is crucial for host defense and tissue homeostasis; however, its dysfunction frequently leads to infectious, autoimmune, inflammatory, degenerative, and cancerous diseases. Our knowledge regarding the relationships between cGAS-STING signaling and cell death is rapidly evolving, highlighting their essential roles in pathogenesis and disease progression. Nevertheless, the direct control of cell death by cGAS-STING signaling, rather than IFN/NF-κB-mediated transcriptional regulation, remains relatively unexplored. This review examines the mechanistic interplays between cGAS-STING cascades and apoptosis, necroptosis, pyroptosis, ferroptosis, and autophagic/lysosomal cell death. We will also discuss their pathological implications in human diseases, particularly in autoimmunity, cancer, and organ injury scenarios. We hope that this summary will stimulate discussion for further exploration of the complex life-or-death responses to cellular damage mediated by cGAS-STING signaling.

Significance of the cGAS-STING Pathway in Health and Disease

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a significant role in health and disease. In this pathway, cGAS, one of the major cytosolic DNA sensors in mammalian cells, regulates innate immunity and the STING-dependent production of pro-inflammatory cytokines, including type-I interferon. Moreover, the cGAS-STING pathway is integral to other cellular processes, such as cell death, cell senescence, and autophagy. Activation of the cGAS-STING pathway by "self" DNA is also attributed to various infectious diseases and autoimmune or inflammatory conditions. In addition, the cGAS-STING pathway activation functions as a link between innate and adaptive immunity, leading to the inhibition or facilitation of tumorigenesis; therefore, research targeting this pathway can provide novel clues for clinical applications to treat infectious, inflammatory, and autoimmune diseases and even cancer. In this review, we focus on the cGAS-STING pathway and its corresponding cellular and molecular mechanisms in health and disease.

Yi-Shen-Xie-Zhuo formula alleviates cisplatin-induced AKI by regulating inflammation and apoptosis via the cGAS/STING pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Yi-Shen-Xie-Zhuo formula (YSXZF) is a traditional Chinese medicine prescription developed from the classic prescription Mulizexie powder documented in the book of Golden Chamber Synopsis and the Buyanghuanwu Decoction recorded in the book of Correction of Errors in Medical Classics. According to our years of clinical experience, YSXZF can effectively improve qi deficiency and blood stasis in kidney disease. However, its mechanisms need further clarification.

AIM OF THE STUDY

Apoptosis and inflammation play key roles in acute kidney disease (AKI). The Yi-Shen-Xie-Zhuo formula, consisting of four herbs, is commonly used for treating renal disease. However, the underlying mechanism and bioactive components remain unexplored. This study aimed to investigate the protective effects of YSXZF against apoptosis and inflammation in a cisplatin-treated mouse model, and identify the main bioactive components of YSXZF.

MATERIALS AND METHODS

C57BL/6 mice were administered cisplatin (15 mg/kg) with or without YSXZF (11.375 or 22.75 g/kg/d). HKC-8 cells were treated with cisplatin (20 μM) with or without YSXZF (5% or 10%) for 24 h. Renal function, morphology, and cell damage were evaluated. UHPLC-MS was used to analyze the herbal components and metabolites in the YSXZF-containing serum.

RESULTS

Blood urea nitrogen (BUN), serum creatinine, serum and urine neutrophil gelatinase-associated lipocalin (NGAL) levels were clearly increased in the cisplatin-treated group. Administration of YSXZF reversed these changes; it improved renal histology, downregulated kidney injury molecule 1 (KIM-1) expression, and lowered the number of TdT-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells. YSXZF significantly downregulated cleaved caspase-3 and BAX, and upregulated BCL-2 proteins in renal tissues. YSXZF suppressed increase in cGAS/STING activation and inflammation. In vitro treatment with YSXZF markedly reduced cisplatin-induced HKC-8 cell apoptosis, relieved cGAS/STING activation and inflammation, improved mitochondrial membrane potential (MMP), and lowered reactive oxygen species (ROS) overgeneration. Small RNA interference (siRNA)-mediated silencing of cGAS or STING inhibited the protective effects of YSXZF. Twenty-three bioactive constituents from the YSXZF-containing serum were identified as key components.

CONCLUSION

This is the first study to demonstrate that YSXZF protects against AKI by suppressing inflammation and apoptosis via the cGAS/STING signaling pathway.

A 360° view of the inflammasome: Mechanisms of activation, cell death, and diseases

Inflammasomes are critical sentinels of the innate immune system that respond to threats to the host through recognition of distinct molecules, known as pathogen- or damage-associated molecular patterns (PAMPs/DAMPs), or disruptions of cellular homeostasis, referred to as homeostasis-altering molecular processes (HAMPs) or effector-triggered immunity (ETI). Several distinct proteins nucleate inflammasomes, including NLRP1, CARD8, NLRP3, NLRP6, NLRC4/NAIP, AIM2, pyrin, and caspases-4/-5/-11. This diverse array of sensors strengthens the inflammasome response through redundancy and plasticity. Here, we present an overview of these pathways, outlining the mechanisms of inflammasome formation, subcellular regulation, and pyroptosis, and discuss the wide-reaching effects of inflammasomes in human disease.

Comparative analyses of bat genomes identify distinct evolution of immunity in Old World fruit bats

Bats have been identified as natural reservoir hosts of several zoonotic viruses, prompting suggestions that they have unique immunological adaptations. Among bats, Old World fruit bats (Pteropodidae) have been linked to multiple spillovers. To test for lineage-specific molecular adaptations in these bats, we developed a new assembly pipeline to generate a reference-quality genome of the fruit bat Cynopterus sphinx and used this in comparative analyses of 12 bat species, including six pteropodids. Our results reveal that immunity-related genes have higher evolutionary rates in pteropodids than in other bats. Several lineage-specific genetic changes were shared across pteropodids, including the loss of NLRP1, duplications of PGLYRP1 and C5AR2, and amino acid replacements in MyD88. We introduced MyD88 transgenes containing Pteropodidae-specific residues into bat and human cell lines and found evidence of dampened inflammatory responses. By uncovering distinct immune adaptations, our results could help explain why pteropodids are frequently identified as viral hosts.

Interplay between RNA viruses and cGAS/STING axis in innate immunity

While the function of cGAS/STING signalling axis in the innate immune response to DNA viruses is well deciphered, increasing evidence demonstrates its significant contribution in the control of RNA virus infections. After the first evidence of cGAS/STING antagonism by flaviviruses, STING activation has been detected following infection by various enveloped RNA viruses. It has been discovered that numerous viral families have implemented advanced strategies to antagonize STING pathway through their evolutionary path. This review summarizes the characterized cGAS/STING escape strategies to date, together with the proposed mechanisms of STING signalling activation perpetrated by RNA viruses and discusses possible therapeutic approaches. Further studies regarding the interaction between RNA viruses and cGAS/STING-mediated immunity could lead to major discoveries important for the understanding of immunopathogenesis and for the treatment of RNA viral infections.

Inflammation, Mitochondria and Natural Compounds Together in the Circle of Trust

Human diseases are characterized by the perpetuation of an inflammatory condition in which the levels of Reactive Oxygen Species (ROS) are quite high. Excessive ROS production leads to DNA damage, protein carbonylation and lipid peroxidation, conditions that lead to a worsening of inflammatory disorders. In particular, compromised mitochondria sustain a stressful condition in the cell, such that mitochondrial dysfunctions become pathogenic, causing human disorders related to inflammatory reactions. Indeed, the triggered inflammation loses its beneficial properties and turns harmful if dysregulation and dysfunctions are not addressed. Thus, reducing oxidative stress with ROS scavenger compounds has proven to be a successful approach to reducing inflammation. Among these, natural compounds, in particular, polyphenols, alkaloids and coenzyme Q10, thanks to their antioxidant properties, are capable of inhibiting the activation of NF-κB and the expression of target genes, including those involved in inflammation. Even more, clinical trials, and in vivo and in vitro studies have demonstrated the antioxidant and anti-inflammatory effects of phytosomes, which are capable of increasing the bioavailability and effectiveness of natural compounds, and have long been considered an effective non-pharmacological therapy. Therefore, in this review, we wanted to highlight the relationship between inflammation, altered mitochondrial oxidative activity in pathological conditions, and the beneficial effects of phytosomes. To this end, a PubMed literature search was conducted with a focus on various in vitro and in vivo studies and clinical trials from 2014 to 2022.

Molecular mechanisms of mitochondrial DNA release and activation of the cGAS-STING pathway

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 stress and tissue damage, and the inhibition of VDAC oligomerization mitigates this inflammatory response. The rapidly expanding area of research on the mechanisms by which mtDNA is released and triggers inflammation has revealed new treatment strategies not only for inflammation but also, surprisingly, for neurodegenerative diseases such as amyotrophic lateral sclerosis.