Inhibition of cGAS-STING by JQ1 alleviates oxidative stress-induced retina inflammation and degeneration

Contribution of ferroptosis and SLC7A11 to light-induced photoreceptor degeneration

JOURNAL/nrgr/04.03/01300535-202601000-00043/figure1/v/2025-06-09T151831Z/r/image-tiff Progressive photoreceptor cell death is one of the main pathological features of age-related macular degeneration and eventually leads to vision loss. Ferroptosis has been demonstrated to be associated with retinal degenerative diseases. However, the molecular mechanisms underlying ferroptosis and photoreceptor cell death in age-related macular degeneration remain largely unexplored. Bioinformatics and biochemical analyses in this study revealed xC - , solute carrier family 7 member 11-regulated ferroptosis as the predominant pathological process of photoreceptor cell degeneration in a light-induced dry age-related macular degeneration mouse model. This process involves the nuclear factor-erythroid factor 2-related factor 2-solute carrier family 7 member 11-glutathione peroxidase 4 signaling pathway, through which cystine depletion, iron ion accumulation, and enhanced lipid peroxidation ultimately lead to photoreceptor cell death and subsequent visual function impairment. We demonstrated that solute carrier family 7 member 11 overexpression blocked this process by inhibiting oxidative stress in vitro and in vivo . Conversely, solute carrier family 7 member 11 knockdown or the solute carrier family 7 member 11 inhibitor sulfasalazine and ferroptosis-inducing agent erastin aggravated H 2 O 2 -induced ferroptosis of 661W cells. These findings indicate solute carrier family 7 member 11 may be a potential therapeutic target for patients with retinal degenerative diseases including age-related macular degeneration.

Targeting mitochondrial DNA-STING-NF-κB Axis-mediated microglia activation by cryptotanshinone alleviates ischemic retinopathy

BACKGROUND

Ischemic retinopathy, a leading cause of vision impairment, involves oxidative stress and dysregulated inflammation, with microglia playing a key role. Cryptotanshinone (CTS), a bioactive compound from Salvia miltiorrhiza, exhibits anti-inflammatory and antioxidant properties and thus has the potential for development as a therapeutic agent. However, the actual mechanism of action of CTS in ischemic retinopathy is not known. Overactivation of the STING pathway in microglia is critical in ischemic retinopathy pathogenesis and a potential target of CTS.

PURPOSE

This study aimed to explore whether CTS alleviates ischemic retinopathy by modulating microglial STING signaling.

METHODS

Oxygen-induced retinopathy (OIR) mice and hypoxia-induced microglial cells were used. CTS efficacy in ischemic retinopathy was evaluated at multiple stages using fluorescein fundus angiography, electroretinogram, H&E staining, and Western blotting of relevant proteins. Network pharmacology and RNA sequencing identified STING as a key target. Furthermore, surface plasmon resonance (SPR), molecular docking, and site-directed mutagenesis were systematically employed to elucidate the precise binding interface between CTS and the STING protein. STING activation and knockout models were employed to further investigate the mechanisms of action of CTS.

RESULTS

CTS treatment reduced microglial activation and pathological retinal angiogenesis, and protected both retinal function and structure in OIR mice. Network pharmacology, RNA sequencing, and experimental validation demonstrated a significant link between the protective effect of CTS and the inhibition of STING signaling. Mechanistically, CTS suppressed cytosolic mtDNA release, blocked STING translocation from the ER to the Golgi, and enhanced lysosomal STING degradation. These CTS-mediated effects were abolished by STING activation and absent in Sting-deficient OIR mice. Notably, CTS combined with anti-VEGF therapy showed synergistic efficacy in suppressing pathological retinal neovascularization.

CONCLUSION

CTS, a natural inhibitor of STING, alleviated ischemic retinopathy by inhibiting the mtDNA-STING-NF-κB signaling pathway via multifaceted mechanisms in microglia.

Dietary resveratrol alleviates liver and intestinal injury in ducks under cage rearing system

Cage rearing is a promising farming method. However, our previous studies have demonstrated that changes in farming practices induce oxidative stress and inflammation in the liver and duodenum of ducks. Resveratrol (RES), a natural plant polyphenol, possesses antioxidant, anti-inflammatory, and cytoprotective properties. This study evaluated the alleviating effects of RES against cage-rearing-induced duck health problems, emphasizing the involvement of redox imbalance, inflammatory response, endoplasmic reticulum (ER) stress, apoptosis, and PI3K/AKT and MAPK/ERK pathways. A total of 120 healthy 12-week-old female ducks were transferred to a cage system and randomly assigned to two dietary RES groups with 6 replicates each (10 ducks per replicate), including basal diet + 0 mg/kg RES (control group, CON), and basal diet + 500 mg/kg RES (RES-treated group, RES). During the early stages (within 10 days) of cage rearing, blood, liver, and duodenal samples were collected for analysis. The results demonstrated that RES reduced histopathological damage in the liver and duodenum of cage-reared ducks. It also reduced serum albumin levels, increased serum aspartate aminotransferase and alanine aminotransferase levels, and enhanced antioxidant (increased CAT, GSH-Px, SOD, and T-AOC activities in the serum, liver, and duodenum, and reduced the increase in MDA) and anti-inflammatory properties (reduced pro-inflammatory cytokines interleukin (IL)-1β and IL-6 secretion and increased anti-inflammatory cytokine IL-4 levels). Additionally, quantitative real-time polymerase chain reaction revealed that RES intervention reversed the abnormal mRNA abundance of biomarkers associated with inflammatory injury (iNOS and COX2) in the liver, and ER stress (GRP78) and apoptosis (Bax and Bcl2) in the liver and duodenum of cage-reared ducks. Further analysis of key proteins in the PI3K/AKT and ERK MAPK signaling pathways revealed that RES promoted AKT phosphorylation in the liver and duodenum of cage-reared ducks and reduced cleaved caspase-3 protein content. Overall, RES prevents cage-rearing stimuli-induced liver and intestinal injury in ducks by enhancing liver function, improving antioxidant properties, inhibiting inflammation, ER stress, and apoptosis, and activating the PI3K/AKT signaling pathway.

Unraveling immunosenescence in sepsis: from cellular mechanisms to therapeutics

Sepsis is a life-threatening multiple organ dysfunction resulting from a dysregulated host response to infection, and patients with sepsis always exhibit a state of immune disorder characterized by both overwhelming inflammation and immunosuppression. The aging of immune system, namely "immunosenescence", has been reported to be correlated with high morbidity and mortality in elderly patients with sepsis. Initially, immunosenescence was considered as a range of age-related alterations in the immune system. However, increasing evidence has proven that persistent inflammation or even a short-term inflammatory challenge during sepsis could trigger accelerated aging of immune cells, which might further exacerbate inflammatory cytokine storm and promote the shift towards immunosuppression. Thus, premature immunosenescence is found in young sepsis individuals, which further aggravates immune disorders and induces the progression of sepsis. Furthermore, in old sepsis patients, the synergistic effects of both sepsis and aging may cause immunosenescence-associated alterations more significantly, resulting in more severe immune dysfunction and a worse prognosis. Therefore, it is necessary to explore the potential therapeutic strategies targeting immunosenescence during sepsis.

Natural products for the treatment of age-related macular degeneration: New insights focusing on mitochondrial quality control and cGAS/STING pathway

Age-related macular degeneration (AMD) is a disease that affects the vision of elderly individuals worldwide. Although current therapeutics have shown effectiveness against AMD, some patients may remain unresponsive and continue to experience disease progression. Therefore, in-depth knowledge of the mechanism underlying AMD pathogenesis is urgently required to identify potential drug targets for AMD treatment. Recently, studies have suggested that dysfunction of mitochondria can lead to the aggregation of reactive oxygen species (ROS) and activation of the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) innate immunity pathways, ultimately resulting in sterile inflammation and cell death in various cells, such as cardiomyocytes and macrophages. Therefore, combining strategies targeting mitochondrial dysfunction and inflammatory mediators may hold great potential in facilitating AMD management. Notably, emerging evidence indicates that natural products targeting mitochondrial quality control (MQC) and the cGAS/STING innate immunity pathways exhibit promise in treating AMD. Here, we summarize phytochemicals that could directly or indirectly influence the MQC and the cGAS/STING innate immunity pathways, as well as their interconnected mediators, which have the potential to mitigate oxidative stress and suppress excessive inflammatory responses, thereby hoping to offer new insights into therapeutic interventions for AMD treatment.

Ferroptosis: An Energetic Villain of Age-Related Macular Degeneration

Iron homeostasis plays an important role in maintaining cellular homeostasis; however, excessive iron can promote the production of reactive oxygen species (ROS). Ferroptosis is iron-dependent programmed cell death that is characterized by excessive iron accumulation, elevated lipid peroxides, and the overproduction of ROS. The maintenance of iron homeostasis is contingent upon the activity of the transferrin receptor (TfR), ferritin (Ft), and ferroportin (FPn). In the retina, iron accumulation and lipid peroxidation can contribute to the development of age-related macular degeneration (AMD). This phenomenon can be explained by the occurrence of the Fenton reaction, in which the interaction between divalent iron and hydrogen peroxide leads to the generation of highly reactive hydroxyl radicals. The hydroxyl radicals exhibit a propensity to attack proteins, lipids, nucleic acids, and carbohydrates, thereby instigating oxidative damage and promoting lipid peroxidation. Ultimately, these processes culminate in cell death and retinal degeneration. In this context, a comprehensive understanding of the exact mechanisms underlying ferroptosis may hold significant importance for developing therapeutic interventions. This review summarizes recent findings on iron metabolism, cellular ferroptosis, and lipid metabolism in the aging retina. We also introduce developments in the therapeutic strategies using iron chelating agents. Further refinements of these knowledges would deepen our comprehension of the pathophysiology of AMD and advance the clinical management of degenerative retinopathy. A comprehensive search strategy was employed to identify relevant studies on the role of ferroptosis in AMD. We performed systematic searches of the PubMed and Web of Science electronic databases from inception to the current date. The keywords used in the search included "ferroptosis", "AMD", "age-related macular degeneration", "iron metabolism", "oxidative stress", and "ferroptosis pathways". Peer-reviewed articles, including original research, reviews, meta-analyses, and clinical studies, were included in this paper, with a focus on the molecular mechanisms of ferroptosis in AMDs. Studies not directly related to ferroptosis, iron metabolism, or oxidative stress in the context of AMD were excluded. Furthermore, articles that lacked sufficient data or were not peer-reviewed (e.g., conference abstracts, editorials, or opinion pieces) were not considered.

Lycopene: A potent antioxidant to alleviate kidney disease

Kidney disease is a major public health problem worldwide and one of the common causes of death in patients. How to effectively treat or alleviate renal diseases has not only attracted the attention of a large number of scholars, but is likewise a great challenge. Oxidative stress is the main mechanism leading to kidney injury. Natural antioxidant substances not only have efficient antioxidant capacity, but also have the advantage of high safety and low side effects. Lycopene is a naturally occurring carotenoid found mainly in tomatoes or tomato products. Epidemiologic investigations have shown that lycopene has potent antioxidant properties, scavenges reactive substances, and has a protective role in kidney disease. This paper summarizes the biochemical properties and antioxidant mechanisms of lycopene in the context of animal experiments and clinical studies of lycopene in renal diseases. We found that lycopene exerts its protective effects against kidney injury mainly through anti-oxidative stress and anti-inflammatory effects. Meanwhile, lycopene has been found to reduce the incidence of Chronic Kidney Disease (CKD) as well as mortality in some CKD patients. In addition to this, lycopene intake is negatively correlated with the incidence of kidney cancer and also mitigates the nephrotoxic damage of cisplatin. Therefore, lycopene has a promising application in the treatment of kidney diseases. However, there are relatively few clinical studies on lycopene in renal diseases, and subsequent research studies in large-scale populations are still needed to determine the value of lycopene in renal diseases even further.

Circulating cell-free DNA promotes inflammation in dermatomyositis patients with anti-NXP2 antibodies via the cGAS/STING pathway

OBJECTIVES

DM is a rare type I IFN (IFN-I)-driven autoimmune disease, and anti-nuclear matrix protein 2 (NXP2) antibody is related to severe muscle disease and poor prognosis. Circulating cell-free DNA (ccf-DNA), including ccf-mitochondrial DNA and ccf-nuclear DNA, activates the cGAS/STING pathway to induce IFN-I production in autoimmune diseases. We investigated whether serum-derived ccf-DNA had a pathogenic effect on skeletal muscle in anti-NXP2 antibody-positive DM.

METHODS

Serum ccf-DNA levels were measured, and correlations between ccf-DNA and clinicopathological indicators were performed. RNA sequencing, immunofluorescence, western blotting and reverse transcriptase quantitative polymerase chain reaction were performed on skeletal muscle samples. The serum-induced expression of p-STING in C2C12 cells was assessed in vitro.

RESULTS

We found that increased ccf-DNA levels were positively correlated with MYOACT scores in anti-NXP2 antibody-positive DM. RNA sequencing and immunofluorescence results revealed that the cytosolic DNA-sensing pathway was upregulated and that increased cytosolic dsDNA was colocalized with cGAS in skeletal muscle in anti-NXP2 antibody-positive DM. Western blot analysis revealed activation of the cGAS/STING pathway in patients with perifascicular atrophy (PFA) but not in patients without PFA. Reverse transcriptase quantitative polymerase chain reaction showed increased IFN-I scores in both patients with PFA and patients without PFA. Sera from patients with PFA increased p-STING expression in C2C12 cells, and DNase I treatment and STING inhibitor efficiently inhibited p-STING expression, respectively.

CONCLUSION

Increased ccf-DNA levels may be potential biomarkers for monitoring disease activity in anti-NXP2 antibody-positive DM. Activation of the cGAS/STING pathway is associated with PFA. Our findings identified a pathogenic effect of ccf-DNA on skeletal muscle via the cGAS/STING pathway.

BRD4 Mediates Cadmium-Induced Oxidative Stress and Kidney Injury in Mice via Disruption of Redox Homeostasis

Cadmium (Cd) is a toxic heavy metal that threatens public health, with kidney injury being one of the common manifestations after Cd exposure. Oxidative stress plays a crucial role in Cd-induced kidney injury, arising from an imbalance between cellular oxidation and antioxidation processes. Bromodomain-containing protein 4 (BRD4) has been identified as a significant factor in the initiation and advancement of multiple diseases, primarily due to its regulatory role in oxidative stress. Nevertheless, the specific role of BRD4 in Cd-induced kidney oxidative injury remains poorly understood. The present study demonstrates that BRD4 is activated in the kidney after Cd exposure, while JQ1 (a BRD4 inhibitor) treatment inhibits Cd-induced oxidative stress and kidney injury. Subsequently, we investigate the mechanisms by which Cd regulates oxidative stress both in vivo and in vitro. The results indicate that JQ1 treatment reduces the expression levels of NADPH oxidase 4 (Nox4), thereby alleviating mitochondrial damage and reducing reactive oxygen species (ROS) generation. Furthermore, JQ1 treatment facilitates nuclear translocation levels of Nuclear factor erythroid-derived 2-like 2 (Nrf2), thereby enhancing the antioxidant defense system in the kidney after Cd exposure. In conclusion, this study reveals that BRD4 is significantly involved in the process of Cd-induced oxidative damage in the kidney, while inhibiting BRD4 is observed to attenuate ROS generation by regulating Nox4 and enhance ROS scavenging by regulating Nrf2, which, in turn, suppresses the oxidative stress level in the kidney after Cd exposure. These findings suggest that targeting BRD4 may represent an effective strategy for the prevention and treatment of Cd-induced kidney diseases.

Sodium Iodate-Induced Ferroptosis in Photoreceptor-Derived 661W Cells Through the Depletion of GSH

Oxidative stress-induced photoreceptor cell death is closely associated with the etiology of age-related macular degeneration (AMD), and sodium iodate (SI) has been widely used as an oxidant stimulus in AMD models to induce retinal pigment epithelium (RPE) and photoreceptor cell death. However, the mechanism underlying SI-induced photoreceptor cell death remains controversial and unclear. In this study, we elucidate that ferroptosis is a critical form of cell death induced by SI in photoreceptor-derived 661W cells. SI disrupts system Xc-, leading to glutathione (GSH) depletion and triggering lipid peroxidation, thereby promoting ferroptosis in photoreceptor-derived 661W cells. Additionally, SI enhances intracellular Fe2+ levels, which further facilitates reactive oxygen species (ROS) accumulation, making the 661W cells more susceptible to ferroptosis. Exogenous GSH, as well as specific inhibitors of ferroptosis such as Fer-1 and antioxidants like NAC, significantly attenuate SI-induced ferroptosis in photoreceptor-derived 661W cells. These findings provide new insights into the mechanisms of ferroptosis as a key pathway in SI-induced photoreceptor-derived 661W cell death.

cGAMP promotes inner blood-retinal barrier breakdown through P2RX7-mediated transportation into microglia

BACKGROUND

Impairment of the inner blood-retinal barrier (iBRB) leads to various blinding diseases including diabetic retinopathy (DR). The cGAS-STING pathway has emerged as a driving force of cardiovascular destruction, but its impact on the neurovascular system is unclear. Here, we show that cGAMP, the endogenous STING agonist, causes iBRB breakdown and retinal degeneration thorough P2RX7-mediated transport into microglia.

METHODS

Extracellular cGAMP and STING pathway were determined in tissue samples from patients with proliferative DR (PDR) and db/db diabetic mice. Histological, molecular, bioinformatic and behavioral analysis accessed effects of cGAMP on iBRB. Single-cell RNA sequencing identified the primary retinal cell type responsive to cGAMP. Specific inhibitors and P2RX7-deficienct mice were used to evaluate P2RX7' role as a cGAMP transporter. The therapeutic effects of P2RX7 inhibitor were tested in db/db mice.

RESULTS

cGAMP was detected in the aqueous humor of patients with PDR and elevated in the vitreous humor with STING activation in db/db mouse retinas. cGAMP administration led to STING-dependent iBRB breakdown and neuron degeneration. Microglia were the primary cells responding to cGAMP, essential for cGAMP-induced iBRB breakdown and visual impairment. The ATP-gated P2RX7 transporter was required for cGAMP import and STING activation in retinal microglia. Contrary to previous thought that mouse P2RX7 nonselectively transports cGAMP only at extremely high ATP concentrations, human P2RX7 directly binds to cGAMP and activates STING under physiological conditions. Clinically, cGAMP-induced microglial signature was recapitulated in fibrovascular membranes from patients with PDR, with P2RX7 being predominantly expressed in microglia. Inhibiting P2RX7 reduced cGAMP-STING activation, protected iBRB and improved neuron survival in diabetic mouse retinas.

CONCLUSIONS

Our study reveals a mechanism for cGAMP-mediated iBRB breakdown and suggests that targeting microglia and P2RX7 may mitigate the deleterious effects of STING activation in retinal diseases linked to iBRB impairment.

Cytosolic mtDNA-cGAS-STING axis mediates melanocytes pyroptosis to promote CD8+ T-cell activation in vitiligo

BACKGROUND

The cGAS-STING axis, a DNA sensor pathway, has recently emerged as a key hub in sensing stress signals and initiating the immune cascade in several diseases. However, its role in the pathogenesis of vitiligo remains unclear.

OBJECTIVE

To explore the pathogenic role of the cGAS-STING axis in linking oxidative stress and CD8+ T-cell-mediated anti-melanocytic immunity in vitiligo.

METHODS

The expression status of the cGAS-STING axis and cytosolic mtDNA were evaluated in the oxidatively stressed epidermal cells and vitiligo perilesional skin, respectively. Then, we investigated the activation of cGAS-STING axis in mtDNA-treated melanocytes, and the influence of cGAS or STING silencing on mtDNA-induced melanocytes pyroptosis. Finally, the paracrine effects of melanocytes pyroptosis on CD8+ T cell activation were explored.

RESULTS

We initially demonstrated that the cGAS-STING axis in melanocytes was highly susceptible to oxidative stress and activated in the vitiliginous melanocytes of perilesional skin, accompanied by enhanced cytosolic mtDNA accumulation. Our mechanistic in vitro experiments confirmed that oxidative stress-induced mitochondrial damage in epidermal cells led to cytosolic mtDNA accumulation, which served as a trigger in activating the cGAS-STING axis in melanocytes. Furthermore, the cytosolic mtDNA-cGAS-STING axis was verified to mediate melanocytes pyroptosis. More importantly, we found that IL-1β and IL-18 produced by pyroptotic melanocytes promoted the activation of CD8+ T cells from patients with vitiligo.

CONCLUSION

The present study confirmed that the cytosolic mtDNA-cGAS-STING axis of melanocytes played an important role in oxidative stress-triggered CD8+ T-cell response, providing novel insights into mechanisms underlying vitiligo onset.

Oxidative stress mediates retinal damage after corneal alkali burn through the activation of the cGAS/STING pathway

Retinal damage accounts for irreversible vision loss following ocular alkali burn (OAB), but the underlying mechanisms remain largely unexplored. Herein, using an OAB mouse model, we examined the impact of oxidative stress (OS) in retinal damage and its molecular mechanism. Results revealed that OS in the retina was enhanced soon after alkali injury. Antioxidant therapy with N-acetylcysteine (NAC) preserved the retinal structure, suppressed cell apoptosis and decreased retinal inflammation, confirming the role of OS. Moreover, enhanced OS was linked to mitochondrial dysfunction, mtDNA leakage and initiation of the cytosolic DNA-sensing signaling. The activation of the major DNA sensors cyclic GMP-AMP Synthase (cGas) and cGAS-Stimulator of Interferon Genes (cGAS/STING) pathway was then identified. Notably, inhibiting cGAS/STING signaling with C-176 markedly reduced inflammation and cell apoptosis and ultimately protected the retina against OAB. Overall, our study reveals the vital function of OS in the occurrence of OAB-induced retinal damage and the involvement of cGAS/STING activation. Furthermore, our provides preclinical validation of the use of an antioxidant or a STING inhibitor as a potential therapeutic approach to protect the retina after OAB.

β-Hydroxybutyrate-induced mitochondrial DNA (mtDNA) release mediated innate inflammatory response in bovine mammary epithelial cells by inhibiting autophagy

BACKGROUND

In perinatal dairy cows, ketosis is a prevalent metabolic disorder that lowers milk output and performance. Mitochondrial dysfunction and chronic inflammation in mammary tissue are linked to elevated blood ketone levels, particularly β-hydroxybutyrate (BHB). Recent research has linked cytosolic mitochondrial DNA (mtDNA) with chronic aseptic inflammation by activating the cGAS-STING pathway during metabolic disorders, while autophagy activation effectively reverses this process. However, whether it is involved in mammary gland damage during ketosis is poorly understood. Therefore, this study aimed to explore the underlying mechanisms of mtDNA-induced inflammation under BHB stress and evaluate the potential therapeutic strategy of autophagy activation in mitigating this damage.

RESULTS

Our study found an increased cytoplasmic mtDNA abundance in mammary gland tissues of dairy cows with ketosis and bovine mammary epithelial cell line (MAC-T) subjected to BHB stress. Further investigations revealed the activation of the cGAS-STING pathway and inflammatory response, indicated by elevated levels of cGAS and STING, along with increased phosphorylation levels of TBK1, P65, and IκB, and higher transcript levels of pro-inflammatory factors (IL-1B, IL-6, and TNF-α) in both in vivo and in vitro experiments. Notably, STING inhibition via si-STING transfection reversed BHB-induced inflammation. Additionally, autophagy activation appeared to protect against BHB stress by facilitating the removal of cytoplasmic mtDNA and preventing cGAS-STING pathway-mediated inflammation.

CONCLUSIONS

The findings illustrate that elevated BHB levels lead to the release of cytoplasmic mtDNA, which in turn activates the cGAS-STING pathway and triggers an inflammatory response in the mammary glands during hyperketonemia. Conversely, autophagy activation has been shown to alleviate this process by promoting cytoplasmic mtDNA degradation.

Spermidine alleviates diabetic periodontitis by reversing human periodontal ligament stem cell senescence via mitophagy

Type 2 Diabetes Mellitus (T2DM) exacerbates periodontal disease lesions, and human periodontal ligament stem cells (PDLSCs) depletion may be the key to periodontal healing impair by T2DM. This study aims to explore the mechanism of PDLSCs depletion in diabetes periodontitis (DP). Firstly, we observed aggravated periodontal destruction in the DP animal model, accompanied by oxidative damage and accumulation of senescent cells. In the high-glucose inflammatory environment in vitro, we revealed that PDLSCs underwent senescence, oxidative stress, mitochondrial dysfunction, and activation of cGAS-STING signaling pathway triggered by mitochondrial DNA. Lineage tracing confirmed that SPD recruited Tdtomato-Gli1+ PDLSCs to the damaged area and alleviated periodontal destruction in DP models. Evidence in vitro further showed that SPD inhibited PDLSCs senescence and oxidative stress, enhanced mitochondrial function, reduced membrane permeability transition pore opening, and reduced DNA leakage, which blocked the STING activation. Mechanistically, SPD reduced STING-TBK1 phosphorylation by scavenging mitochondrial-derived dsDNA in a mitophagy-dependent manner, its therapeutic effect was abolished by incorporation of cGAMP, a STING activator. In summary, our study reveals the mechanism of PDLSCs depletion due to excessive oxidative damage in the DP environment. Local injection of SPD reactivates mitophagy, recruits Gli1+ stem cells by inhibiting STING activation for periodontal regeneration.

Circulating mitochondria carrying cGAS promote endothelial Secreted group IIA phospholipase A2-mediated neuroinflammation through activating astroglial/microglial Integrin-alphavbeta3 in subfornical organ to augment central sympathetic overdrive in heart failure rats

BACKGROUND

Sympathoexcitation, a manifestation of heart-brain axis dysregulation, contributes to the progression of heart failure (HF). Our recent study revealed that circulating mitochondria (C-Mito), a newly identified mediator of multi-organ communication, promote sympathoexcitation in HF by aggravating endothelial cell (EC)-derived neuroinflammation in the subfornical organ (SFO), the cardiovascular autonomic neural center. The precise molecular mechanism by which C-Mito promotes SFO-induced endothelial neuroinflammation has not been fully elucidated.

OBJECTIVE

C-Mito carrying cGAS promote sympathoexcitation by targeting PLA2G2A in ECs of the SFO in HF rats.

METHODS

Male Sprague-Dawley (SD) rats received a subcutaneous injection of isoprenaline (ISO) at a dosage of 5 mg/kg/day for seven consecutive days to establish a HF model. C-Mito were isolated from HF rats and evaluated. The level of cGAS, a dsDNA sensor recently discovered to be directly localized on the outer membrane of mitochondria, was detected in C-Mito. C-Mito from HF rats (C-MitoHF) or control rats (C-MitoCtrl) were intravenously infused into HF rats. The accumulation of C-Mito in the ECs in the SFO was detected via double immunofluorescence staining. The SFO was processed for RNA sequencing (RNA-Seq) analysis. Secreted group IIA phospholipase A2 (PLA2G2A), the key gene involved in C-MitoHF-associated SFO dysfunction, was identified via bioinformatics analysis. Upregulation of PLA2G2A in the SFO ECs was assessed via immunofluorescence staining and immunoblotting, and PLA2G2A activity was evaluated. The interaction between cGAS and PLA2G2A was detected via co-immunoprecipitation. The dowstream molecular mechanisms of which PLA2G2A induced astroglial/microglial activation were also investigated. AAV9-TIE-shRNA (PLA2G2A) was introduced into the SFO to specifically knockdown endothelial PLA2G2A. Neuronal activation and glial proinflammatory polarization in the SFO were also evaluated. Renal sympathetic nerve activity (RSNA) was measured to evaluate central sympathetic output. Cardiac sympathetic hyperinnervation, myocardial remodeling, and left ventricular systolic function were assessed in C-Mito-treated HF rats.

RESULTS

Respiratory functional incompetence and oxidative damage were observed in C-MitoHF compared with C-MitoCtrl. Surprisingly, cGAS protein levels in C-MitoHF were significantly higher than those in C-MitoCtrl, while blocking cGAS with its specific inhibitor, RU.521, mitigated respiratory dysfunction and oxidative injury in C-MitoHF. C-Mito entered the ECs of the SFO in HF rats. RNA sequencing revealed that PLA2G2A is a key molecule for the induction of SFO dysfunction by C-MitoHF. The immunoblotting and immunofluorescence results confirmed that, compared with C-MitoCtrl, C-MitoHF increased endothelial PLA2G2A expression in the SFO of HF rats, which could be alleviated by attenuating C-MitoHF-localized cGAS. Furthermore, we found that cGAS directly interacts with PLA2G2A, increased the activity of PLA2AG2, which produced arachidonic acid, and also promoted PLA2G2A secretion in brain ECs. In addition, the inhibition of PLA2G2A in brain ECs significantly mitigated the proinflammatory effect of conditioned cell culture medium from C-MitoHF-treated ECs on astroglia and microglia. Also, we found that PLA2G2A secreted from ECs insulted by C-Mito induced neuroinflammation through activating astriglial/microglial Integrin-alphavbeta3 in the SFO, which further promote central sympathetic overdrive in HF rats. Specific knockdown of endothelial PLA2G2A in the SFO mitigated C-MitoHF-induced presympathetic neuronal sensitization, cardiac sympathetic hyperinnervation, RSNA activation, myocardial remodeling, and systolic dysfunction in HF rats.

CONCLUSION

C-Mito carrying cGAS promoted cardiac sympathoexcitation by directly targeting PLA2G2A in the ECs of the SFO in HF rats. Secreted PLA2G2A derived from ECs insulted by C-Mito induced neuroinflammation through activating astriglial/microglial Integrin-alphavbeta3 in the SFO, which further promote central sympathetic overdrive in HF rats. Our study indicated that inhibiting cGAS in C-Mito might be a potential treatment for central sympathetic overdrive in HF.

Mitochondrial damage causes inflammation via cGAS-STING signaling in ketamine-induced cystitis

BACKGROUND

Mitochondrial dysfunction and damage can result in the release of mitochondrial DNA (mtDNA) into the cytoplasm, which subsequently activates the cGAS-STING pathway, promoting the onset of inflammatory diseases. Various factors, such as oxidative stress, viral infection, and drug toxicity, have been identified as inducers of mitochondrial damage. This study aims to investigate the role of mtDNA as a critical inflammatory mediator in the pathogenesis of ketamine (KET)-induced cystitis (KC) through the cGAS-STING pathway.

METHODS

To investigate the role of the cGAS-STING pathway in KET-induced cystitis, we assessed the expression of cGAS and STING in rats with KET cystitis. Additionally, we evaluated STING expression in conditionally deficient Simian Virus-transformed Human Uroepithelial Cell Line 1 (SV-HUC-1) cells in vitro. Morphological changes in mitochondria were examined using transmission electron microscopy. We measured intracellular reactive oxygen species (ROS) production through flow cytometry and immunofluorescence techniques. Furthermore, alterations in associated inflammatory factors and cytokines were quantified using real-time quantitative PCR with fluorescence detection.

RESULTS

We observed up-regulation of cGAS and STING expressions in the bladder tissue of rats in the KET group, stimulation with KET also led to increased cGAS and STING levels in SV-HUC-1 cells. Notably, the knockdown of STING inhibited the nuclear translocation of NF-κB p65 and IRF3, resulting in a decrease in the expression of inflammatory cytokines, including IL-6, IL-8, and CXCL10. Additionally, KET induced damage to the mitochondria of SV-HUC-1 cells, facilitating the release of mtDNA into the cytoplasm. This significant depletion of mtDNA inhibited the activation of cGAS-STING pathway, subsequently affecting the expression of NF-κB p65 and IRF3. Importantly, the reintroduction of mtDNA after STING knockdown partially restored the inflammatory response.

CONCLUSION

Our findings confirmed the activation of the cGAS-STING pathway in KC rats and revealed mitochondrial damage in vitro. These results highlight the involvement of the cGAS-STING pathway in the pathogenesis of KC, suggesting its potential as a therapeutic target for intervention.

Macrophage STING signaling promotes fibrosis in benign airway stenosis via an IL6-STAT3 pathway

Acute and chronic inflammation are important pathologies of benign airway stenosis (BAS) fibrosis, which is a frequent complication of critically ill patients. cGAS-STING signalling has an important role in inflammation and fibrosis, yet the function of STING in BAS remains unclear. Here we demonstrate using scRNA sequencing that cGAS‒STING signalling is involved in BAS, which is accompanied by increased dsDNA, expression and activation of STING. STING inhibition or deficiency effectively alleviates tracheal fibrosis of BAS mice by decreasing both acute and chronic inflammation. Macrophage depletion also effectively ameliorates BAS. Mechanistically, dsDNA from damaged epithelial cells activates the cGAS-STING pathway of macrophages and induces IL-6 to activate STAT3 and promote fibrosis. In summary, the present results suggest that cGAS-STING signalling induces acute inflammation and amplifies the chronic inflammation and tracheal fibrosis associated with benign airway stenosis, highlighting the mechanism and potential drug target of BAS.

Potential antiviral activity of rhamnocitrin against influenza virus H3N2 by inhibiting cGAS/STING pathway in vitro

Influenza remains a serious issue for public health and it's urgent to discover more effected drugs against influenza virus. Rhamnocitrin, as a flavonoid, its effect on influenza virus infection remains poorly explored. In this study, rhamnocitrin showed antiviral effect and anti-apoptosis on influenza virus A/Aichi/2/1968 (H3N2) in MDCK cells and A549 cells. In addition, molecular docking revealed that rhamnocitrin have good binding activity with the target proteins cGAS and STING, molecular dynamic simulation and surface plasmon resonance showed that rhamnocitrin could form a stable complex with the above proteins. Moreover, the qPCR and western blot assays further verified that rhamnocitrin could reduce type I IFN and proinflammatory cytokines production by inhibiting the cGAS/STING pathway. Taken together, the results suggest that rhamnocitrin could be a potential anti-viral agent against influenza.

Gastrodin ameliorates oxidative stress-induced RPE damage by facilitating autophagy and phagocytosis through PPARα-TFEB/CD36 signal pathway

Age-related macular degeneration (AMD), the leading cause of irreversible blindness in the elderly, is primarily characterized by the degeneration of the retinal pigment epithelium (RPE). However, effective therapeutic options for dry AMD are currently lacking, necessitating further exploration into preventive and pharmaceutical interventions. This study aimed to investigate the protective effects of gastrodin on RPE cells exposed to oxidative stress. We constructed an in vitro oxidative stress model of 4-hydroxynonenal (4-HNE) and performed RNA-seq, and demonstrated the protective effect of gastrodin through mouse experiments. Our findings reveal that gastrodin can inhibit 4-HNE-induced oxidative stress, effectively improving the mitochondrial and lysosomal dysfunction of RPE cells. We further elucidated that gastrodin promotes autophagy and phagocytosis through activating the PPARα-TFEB/CD36 signaling pathway. Interestingly, these outcomes were corroborated in a mouse model, in which gastrodin maintained retinal integrity and reduced RPE disorganization and degeneration under oxidative stress. The accumulation of LC3B and SQSTM1 in mouse RPE-choroid was also reduced. Moreover, activating PPARα and downstream pathways to restore autophagy and phagocytosis, thereby countering RPE injury from oxidative stress. In conclusion, this study demonstrated that gastrodin maintains the normal function of RPE cells by reducing oxidative stress, enhancing their phagocytic function, and restoring the level of autophagic flow. These findings suggest that gastrodin is a novel formulation with potential applications in the development of AMD disease.

The role of the cGAS-STING pathway in chronic pulmonary inflammatory diseases

The innate immune system plays a vital role in the inflammatory process, serving as a crucial mechanism for the body to respond to infection, cellular stress, and tissue damage. The cGAS-STING signaling pathway is pivotal in the onset and progression of various autoimmune diseases and chronic inflammation. By recognizing cytoplasmic DNA, this pathway initiates and regulates inflammation and antiviral responses within the innate immune system. Consequently, the regulation of the cGAS-STING pathway has become a prominent area of interest in the treatment of many diseases. Chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis, are characterized by persistent or recurrent lung inflammation and tissue damage, leading to diminished respiratory function. This paper explores the mechanism of action of the cGAS-STING signaling pathway in these diseases, examines the development of STING inhibitors and nanomaterial applications, and discusses the potential clinical application prospects of targeting the cGAS-STING pathway in chronic inflammatory lung diseases.

Role of cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes pathway in diabetes and its complications

Diabetes mellitus (DM) is one of the major causes of mortality worldwide, with inflammation being an important factor in its onset and development. This review summarizes the specific mechanisms of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway in mediating inflammatory responses. Furthermore, it comprehensively presents related research progress and the subsequent involvement of this pathway in the pathogenesis of early-stage DM, diabetic gastroenteropathy, diabetic cardiomyopathy, non-alcoholic fatty liver disease, and other complications. Additionally, the role of cGAS-STING in autonomic dysfunction and intestinal dysregulation, which can lead to digestive complications, has been discussed. Altogether, this study provides a comprehensive analysis of the research advances regarding the cGAS-STING pathway-targeted therapeutic agents and the prospects for their application in the precision treatment of DM.

Continuous Theta Burst Stimulation Inhibits Oxidative Stress-Induced Inflammation and Autophagy in Hippocampal Neurons by Activating Glutathione Synthesis Pathway, Improving Cognitive Impairment in Sleep-Deprived Mice

Sleep deprivation (SD) has been reported to have a negative impact on cognitive function. Continuous theta burst stimulation (cTBS) shows certain effects in improving sleep and neurological diseases, and its molecular or cellular role in SD-induced cognition impairment still need further exploration. In this study, C57BL/6 mice were subjected to 48 h of SD and cTBS treatment, and cTBS treatment significantly improved SD-triggered impairment of spatial learning and memory abilities in mice. Additionally, cTBS reduced malondialdehyde levels, increased superoxide dismutase activities, and inhibited the production of inflammatory cytokines, alleviating oxidative stress and inflammation levels in hippocampal tissues of SD model mice. cTBS decreased LC3II/LC3I ratio, Beclin1 protein levels, and LC3B puncta intensity, and elevated p62 protein levels to suppress excessive autophagy in hippocampal tissues of SD-stimulated mice. Then, we proved that inhibiting oxidative stress alleviated inflammation, autophagy, and death of hippocampal neuron cells through an in vitro cellular model for oxidative stress, and cTBS treatment promoted the production of glutathione (GSH), the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the mRNA expression of GSH synthesis-related genes to enhance antioxidant capacity in hippocampal tissues of SD mice. An Nrf2 inhibitor ML385 or a GSH synthesis inhibitor BSO reversed the alleviating effects of cTBS treatment on oxidative stress-associated damage of hippocampal tissues and cognitive impairment in SD model mice. Altogether, our study demonstrated that cTBS mitigates oxidative stress-associated inflammation and autophagy through activating the Nrf2-mediated GSH synthesis pathway, improving cognitive impairment in SD mice.

Role and Mechanism of Sialic Acid in Alleviating Acute Lung Injury through In Vivo and In Vitro Models

Excessive inflammatory reactions are the most important pathological injury factor in acute lung injury (ALI). Our recent study found that sialic acid had an anti-colitis effect. In this study, the effect of sialic acid (SA) on acute lung inflammation was investigated. A lipopolysaccharide (LPS)-induced ALI animal model and LPS-stimulated HUVEC cell model were used to evaluate the anti-inflammatory effect of SA and study its molecular mechanisms. Compared with the LPS group, the lung index of the SA group decreased from 0.79 ± 0.05% to 0.58 ± 0.06% (LPS + 50 SA) and 0.62 ± 0.02% (LPS + 100 SA), with p < 0.01, suggesting that SA could improve the pulmonary edema of mice and alleviate LPS-induced lung injury. Transcriptome research identified 26 upregulated genes and 25 downregulated genes involved in the protection of SA against ALI. These genes are mainly related to the MAPK and NF-κB signaling pathways. Our study also proved that SA markedly downregulated the expression of inflammatory factors and blocked the JNK/p38/PPAR-γ/NF-κB pathway. Meanwhile, SA treatment also upregulated the expression of HO-1 and NQO1 in ALI mice. In vitro, SA obviously repressed the expressions of inflammatory cytokines and the JNK/p38-NF-κB/AP-1 pathway. SA also regulated the expression of oxidative stress-related genes through the Nrf2 pathway. Taken together, SA exhibits a protective role by modulating the anti-inflammatory and anti-oxidation pathways in ALI, and it may be a promising candidate for functional foods to prevent ALI.

Cyclic guanosine monophosphate-adenosine monophosphate synthetase/stimulator of interferon genes signaling aggravated corneal allograft rejection through neutrophil extracellular traps

The activation of innate immunity following transplantation has been identified as a crucial factor in allograft inflammation and rejection. However, the role of cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/stimulator of interferon genes (STING) signaling-mediated innate immunity in the pathogenesis of allograft rejection remains unclear. Utilizing a well-established murine model of corneal transplantation, we demonstrated increased expression of cGAS and STING in rejected-corneal allografts compared with syngeneic (Syn) and normal (Nor) corneas, along with significant activation of the cGAS/STING pathway, as evidenced by the enhanced phosphorylation of TANK-binding kinase 1and interferon regulatory factor 3. Pharmacological and genetic inhibition of cGAS/STING signaling markedly delayed corneal transplantation rejection, resulting in prolonged survival time and reduced inflammatory infiltration. Furthermore, we observed an increase in the formation of neutrophil extracellular traps (NETs) in rejected allografts, and the inhibition of NET formation through targeting peptidylarginine deiminase 4 and DNase I treatment significantly alleviated immune rejection and reduced cGAS/STING signaling activity. Conversely, subconjunctival injection of NETs accelerated corneal transplantation rejection and enhanced the activation of the cGAS/STING pathway. Collectively, these findings demonstrate that NETs contribute to the exacerbation of allograft rejection via cGAS/STING signaling, highlighting the targeting of the NETs/cGAS/STING signaling pathway as a potential strategy for prolonging allograft survival.

The cGAS-STING Pathway: A New Therapeutic Target for Ischemia-Reperfusion Injury in Acute Myocardial Infarction?

The innate immune system is the body's natural defense system, which recognizes a wide range of microbial molecules (such as bacterial DNA and RNA) and abnormal molecules within cells (such as misplaced DNA, self-antigens) to play its role. DNA released into the cytoplasm activates the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway to initiate an immune response. Ischemia-reperfusion injury (IRI) after acute myocardial infarction refers to the phenomenon where myocardial tissue suffers further damage upon the restoration of blood flow. This issue is a significant clinical problem in the treatment of myocardial infarction, as it can diminish the effectiveness of reperfusion therapy and lead to further deterioration of cardiac function. Studies have found that the cGAS-STING signaling pathway is closely related to this phenomenon. Therefore, this review aims to describe the role of the cGAS-STING signaling pathway in ischemia-reperfusion injury after myocardial infarction and summarize the current development status of cGAS-STING pathway inhibitors and the application of nanomaterials to further elucidate the potential of this pathway as a therapeutic target.

Mitophagy and cGAS-STING crosstalk in neuroinflammation

Mitophagy, essential for mitochondrial health, selectively degrades damaged mitochondria. It is intricately linked to the cGAS-STING pathway, which is crucial for innate immunity. This pathway responds to mitochondrial DNA and is associated with cellular stress response. Our review explores the molecular details and regulatory mechanisms of mitophagy and the cGAS-STING pathway. We critically evaluate the literature demonstrating how dysfunctional mitophagy leads to neuroinflammatory conditions, primarily through the accumulation of damaged mitochondria, which activates the cGAS-STING pathway. This activation prompts the production of pro-inflammatory cytokines, exacerbating neuroinflammation. This review emphasizes the interaction between mitophagy and the cGAS-STING pathways. Effective mitophagy may suppress the cGAS-STING pathway, offering protection against neuroinflammation. Conversely, impaired mitophagy may activate the cGAS-STING pathway, leading to chronic neuroinflammation. Additionally, we explored how this interaction influences neurodegenerative disorders, suggesting a common mechanism underlying these diseases. In conclusion, there is a need for additional targeted research to unravel the complexities of mitophagy-cGAS-STING interactions and their role in neurodegeneration. This review highlights potential therapies targeting these pathways, potentially leading to new treatments for neuroinflammatory and neurodegenerative conditions. This synthesis enhances our understanding of the cellular and molecular foundations of neuroinflammation and opens new therapeutic avenues for neurodegenerative disease research.

Polystyrene Microplastics Causes Diarrhea and Impairs Intestinal Angiogenesis through the ROS/METTL3 Pathway

Due to the immature intestinal digestion, immunity, and barrier functions, weaned infants are more susceptible to pathogens and develop diarrhea. Microplastics (MPs), pervasive contaminants in food, water, and air, have unknown effects on the intestinal development of weaned infants. This study explored the impact of polystyrene MPs on intestinal development using a weaned piglet model. Piglets in the control group received a basal diet, and those in the experimental groups received a basal diet contaminated with 150 mg/kg polystyrene MPs. The results showed that exposure to polystyrene MPs increased the diarrhea incidence and impaired the intestinal barrier function of weaned piglets. Notably, the exposure led to oxidative stress and inflammation in the intestine. Furthermore, polystyrene MPs-treated weaned piglets showed a reduced level of intestinal angiogenesis. Mechanistically, polystyrene MPs suppressed methyltransferase-like 3 (METTL3) expression by increasing reactive oxygen species (ROS) production, consequently destabilizing angiogenic factors' mRNA and hindering intestinal angiogenesis. In summary, polystyrene MPs contamination in the diet increases diarrhea and compromises intestinal angiogenesis through the ROS/METTL3 pathway, demonstrating their toxic effects on the intestine health of weaned infants.

Therapeutic intervention in neuroinflammation for neovascular ocular diseases through targeting the cGAS-STING-necroptosis pathway

The microglia-mediated neuroinflammation have been shown to play a crucial role in the ocular pathological angiogenesis process, but specific immunotherapies for neovascular ocular diseases are still lacking. This study proposed that targeting GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) might be a novel immunotherapy for these angiogenesis diseases. We found a significant upregulation of CGAS and STING genes in the RNA-seq data derived from retinal tissues of the patients with proliferative diabetic retinopathy. In experimental models of ocular angiogenesis including laser-induced choroidal neovascularization (CNV) and oxygen-induced retinopathy (OIR), the cGAS-STING pathway was activated as angiogenesis progressed. Either genetic deletion or pharmacological inhibition of STING resulted in a remarkable suppression of neovascularization in both models. Furthermore, cGAS-STING signaling was specifically activated in myeloid cells, triggering the subsequent RIP1-RIP3-MLKL pathway activation and leading to necroptosis-mediated inflammation. Notably, targeted inhibition of the cGAS-STING pathway with C-176 or SN-011 could significantly suppress pathological angiogenesis in CNV and OIR. Additionally, the combination of C-176 or SN-011 with anti-VEGF therapy led to least angiogenesis, markedly enhancing the anti-angiogenic effectiveness. Together, our findings provide compelling evidence for the importance of the cGAS-STING-necroptosis axis in pathological angiogenesis, highlighting its potential as a promising immunotherapeutic target for treating neovascular ocular diseases.

Pharmacological potential of cyclic nucleotide signaling in immunity

Cyclic nucleotides are important signaling molecules that play many critical physiological roles including controlling cell fate and development, regulation of metabolic processes, and responding to changes in the environment. Cyclic nucleotides are also pivotal regulators in immune signaling, orchestrating intricate processes that maintain homeostasis and defend against pathogenic threats. This review provides a comprehensive examination of the pharmacological potential of cyclic nucleotide signaling pathways within the realm of immunity. Beginning with an overview of the fundamental roles of cAMP and cGMP as ubiquitous second messengers, this review delves into the complexities of their involvement in immune responses. Special attention is given to the challenges associated with modulating these signaling pathways for therapeutic purposes, emphasizing the necessity for achieving cell-type specificity to avert unintended consequences. A major focus of the review is on the recent paradigm-shifting discoveries regarding specialized cyclic nucleotide signals in the innate immune system, notably the cGAS-STING pathway. The significance of cyclic dinucleotides, exemplified by 2'3'-cGAMP, in controlling immune responses against pathogens and cancer, is explored. The evolutionarily conserved nature of cyclic dinucleotides as antiviral agents, spanning across diverse organisms, underscores their potential as targets for innovative immunotherapies. Findings from the last several years have revealed a striking diversity of novel bacterial cyclic nucleotide second messengers which are involved in antiviral responses. Knowledge of the existence and precise identity of these molecules coupled with accurate descriptions of their associated immune defense pathways will be essential to the future development of novel antibacterial therapeutic strategies. The insights presented herein may help researchers navigate the evolving landscape of immunopharmacology as it pertains to cyclic nucleotides and point toward new avenues or lines of thinking about development of therapeutics against the pathways they regulate.

BRD4 promotes LPS-induced endothelial cells senescence via activating and cooperating STING-IRF3 pathway

Endothelial cells (ECs) senescence is closely associated with the initiation and development of multiple age-related cardiovascular diseases. It is necessary to explore the underlying molecular mechanisms of ECs senescence, which is not only the basis to decipher cellular senescence, but also a novel therapeutic target for the endothelial senescence-related diseases. BRD4, a key epigenetic regulator, is universally related to gene expression regulation and has been reported to accelerate cell senescence. Besides, emerging evidence has suggested that the stimulator of interferon genes protein (STING) can regulate inflammatory and senescence-related diseases. However, whether STING pathway activation is regulated by BRD4 in the context of ECs senescence remains largely unclear. Here, we observed that elevated BRD4 and activated STING-IRF3 signaling pathway during ECs senescence and further confirmed that BRD4 could abolish STING activation. We demonstrated that BRD4 could inhibit E3 ubiquitin ligase HRD1-mediated ubiquitination degradation of STING via inhibiting HRD1 transcription. In addition to the direct regulatory effect of BRD4 on STING activation, we have confirmed that BRD4 cooperates with IRF3 and P65 to promote SASP gene expression, thereby accelerating ECs senescence. Here, we proposed a novel mechanism underlying BRD4' key dual role in activating the STING pathway during ECs senescence.

miR-92b-3p protects retinal tissues against DNA damage and apoptosis by targeting BTG2 in experimental myopia

BACKGROUND

Myopia is one of the eye diseases that can damage the vision of young people. This study aimed to explore the protective role of miR-92b-3p against DNA damage and apoptosis in retinal tissues of negative lens-induced myopic (LIM) guinea pigs by targeting BTG2.

METHODS

Biometric measurements of ocular parameters, flash electroretinogram (FERG), and retinal thickness (RT) were performed after miR-92b-3p intravitreal injection in LIM guinea pigs. The apoptotic rate was detected by Annexin V-FITC/PI double staining, and the change in mitochondrial membrane potential was measured by JC-1 staining. Retinal apoptosis and expression of p53, BTG2, and CDK2 were explored by TdT-mediated dUTP-biotin nick labeling (TUNEL) and immunofluorescence staining assays, respectively. BTG2 and its upstream and downstream molecules at gene and protein levels in retinal tissues were measured by real-time quantitative PCR (qPCR) and Western blotting.

RESULTS

Compared with normal controls (NC), the ocular axial length of LIM guinea pig significantly increased, whereas refraction decreased. Meanwhile, dMax-a and -b wave amplitudes of ERG declined, retinal thickness was decreased, the number of apoptotic cells and apoptotic rate in LIM eyes was exaggerated, and the mitochondrial membrane potential significantly decreased. In addition, results of qPCR and Western blot assays showed that the expression levels of p53, BTG2, CDK2, and BAX in LIM guinea pigs were higher than the levels of the NC group, whereas the BCL-2 expression level was decreased. By contrast, the miR-92b-3p intravitreal injection in LIM guinea pigs could significantly inhibit axial elongation, alleviate DNA damage and apoptosis, and thus protect guinea pigs against myopia.

CONCLUSION

In conclusion, p53 and BTG2 were activated in the retinal tissue of myopic guinea pigs, and the activated BTG2 could elevate the expression of CDK2 and BAX, and attenuate the expression of BCL-2, which in turn promote apoptosis and eventually lead to retinal thinning and impaired visual function in myopic guinea pigs. The miR-92b-3p intravitreal injection can attenuate the elongation of ocular length and retinal thickness, and inhibit the CDK2, BAX, and p53 expression by targeting BTG2, thereby ameliorating DNA damage and apoptosis in LIM guinea pigs and protecting ocular tissues.

Kaempferol alleviates adipose tissue inflammation and insulin resistance in db/db mice by inhibiting the STING/NLRP3 signaling pathway

Chronic inflammation induced by obesity plays a crucial role in the pathogenesis of insulin resistance. The infiltration of macrophages into adipose tissues contributes to adipose tissue inflammation and insulin resistance. Kaempferol, a flavonoid present in various vegetables and fruits, has been shown to possess remarkable anti-inflammatory properties. In this study, we used leptin receptor-deficient obese mice (db/db) as an insulin-resistant model and investigated the effects of kaempferol treatment on obesity-induced insulin resistance. Our findings revealed that the administration of kaempferol (50 mg/kg/day, for 6 weeks) significantly reduced body weight, fat mass, and adipocyte size. Moreover, it effectively ameliorated abnormal glucose tolerance and insulin resistance in db/db mice. In the adipose tissue of obese mice treated with kaempferol, we observed a reduction in macrophage infiltration and a downregulation of mRNA expression of M1 marker genes TNF-α and IL-1β, accompanied by an upregulation of Arg1 and IL-10 mRNA expression. Additionally, kaempferol treatment significantly inhibited the STING/NLRP3 signaling pathway in adipose tissue. In vitro experiments, we further discovered that kaempferol treatment suppressed LPS-induced inflammation through the activation of NLRP3/caspase 1 signaling in RAW 264.7 macrophages. Our results suggest that kaempferol may effectively alleviate inflammation and insulin resistance in the adipose tissue of db/db mice by modulating the STING/NLRP3 signaling pathway.

Inhibition of spinal BRD4 alleviates pyroptosis and M1 microglia polarization via STING-IRF3 pathway in morphine-tolerant rats

BACKGROUND

Morphine tolerance has been a challenging medical issue. Neuroinflammation is considered as a critical mechanism for the development of morphine tolerance. Bromodomain-containing protein 4 (BRD4), a key regulator in cell damage and inflammation, participates in the development of chronic pain. However, whether BRD4 is involved in morphine tolerance and the underlying mechanisms remain unknown.

METHODS

The morphine-tolerant rat model was established by intrathecal administration of morphine twice daily for 7 days. Behavior test was assessed by a tail-flick latency test. The roles of BRD4, pyroptosis, microglia polarization and related signaling pathways in morphine tolerance were elucidated by Western blot, real-time quantitative polymerase chain reaction, and immunofluorescence.

RESULTS

Repeated morphine administration upregulated BRD4 level, induced pyroptosis, and promoted microglia M1-polarization in spinal cord, accompanied by the release of proinflammatory cytokines, such as TNF-α and IL-1β. JQ-1, a BRD4 antagonist, alleviated the development of morphine tolerance, diminished pyroptosis and induced the switch of microglia from M1 to M2 phenotype. Mechanistically, stimulator of interferon gene (STING)- interferon regulatory factor 3 (IRF3) pathway was activated and the protective effect of JQ-1 against morphine tolerance was at least partially mediated by inhibition of STING-IRF3 pathway.

CONCLUSION

This study demonstrated for the first time that spinal BRD4 contributes to pyroptosis and switch of microglia polarization via STING-IRF3 signaling pathway during the development of morphine tolerance, which extend the understanding of the neuroinflammation mechanism of morphine tolerance and provide an alternative strategy for the precaution against of this medical condition.

Mitochondrial DNA-Activated cGAS-STING Signaling in Environmental Dry Eye

Purpose

The cGAS-STING pathway has been shown to be an important mediator of inflammation. There is emerging evidence of the importance of this signaling cascade in a variety of inflammatory diseases settings. Here, we present evidence that the mitochondrial DNA (mtDNA) damage-mediated cGAS-STING pathway plays an important role in the induction of inflammation in environmental dry eye (DE).

Methods

RT-qPCR and Western blot were used to assess the induction of the cGAS-STING pathway and inflammatory cytokines in environmental DE mouse model, primary human corneal epithelial cells (pHCECs), and patients with DE. RNA sequencing was used to determine mRNA expression patterns of high osmotic pressure (HOP)-stimulated pHCECs. mtDNA was detected with electron microscopy, flow cytometry, and immunofluorescent staining. mtDNA was isolated and transfected into pHCECs for evaluating the activation of the cGAS-STING pathway.

Results

The expression levels of cGAS, STING, TBK1, IRF3, and IFNβ were significantly increased in an environmental DE model and HOP-stimulated pHCECs. The STING inhibitor decreased the expression of inflammatory factors in DE. An upregulation of STING-mediated immune responses and IRF3 expression mediated by TBK1 were observed in the HOP group. HOP stimulation induced mitochondrial oxidative damage and the leakage of mtDNA into the cytoplasm. Then, mtDNA activated the cGAS-STING pathway and induced intracytoplasmic STING translocated to the Golgi apparatus. Finally, we also found activated cGAS-STING signaling in the human conjunctival blot cell of patients with DE.

Conclusions

Our findings suggest that the cGAS-STING pathway is activated by recognizing cytoplasmic mtDNA leading to STING translocation, further exacerbating the development of inflammation in environmental DE.

The combination of Tanshinone IIA and Astragaloside IV attenuates myocardial ischemia-reperfusion injury by inhibiting the STING pathway

BACKGROUND

Astragaloside IV (As-IV) and Tanshinone IIA (Ta-IIA) are the main ingredients of traditional Chinese medicinal Astragalus membranaceus (Fisch.) Bunge and Salvia miltiorrhiza Bunge, respectively, both of which have been employed in the treatment of cardiovascular diseases. Nevertheless, the efficacy of the combination (Co) of Ta-IIA and As-IV for cardiovascular diseases remain unclear and warrant further investigation. This study aimed to investigate the efficacy and the underlying molecular mechanism of Co in treating myocardial ischemia-reperfusion injury (MIRI).

METHODS

In order to assess the efficacy of Co, an in vivo MIRI mouse model was created by temporarily blocking the coronary arteries for 30 min and then releasing the blockage. Parameters such as blood myocardial enzymes, infarct size, and ventricular function were measured. Additionally, in vitro experiments were conducted using HL1 cells in both hypoxia-reoxygenation model and oxidative stress models. The apoptosis rate, expression levels of apoptosis-related proteins, oxidative stress indexes, and release of inflammatory factors were detected. Furthermore, molecular docking was applied to examine the binding properties of Ta-IIA and As-IV to STING, and western blotting was performed to analyze protein expression of the STING pathway. Additionally, the protective effect of Ta-IIA, As-IV and Co via inhibiting STING was further confirmed in models of knockdown STING by siRNA and adding STING agonist.

RESULTS

Both in vitro and in vivo data demonstrated that, compared to Ta-IIA or As-IV alone, the Co exhibited superior efficacy in reducing the area of myocardial infarction, lowering myocardial enzyme levels, and promoting the recovery of myocardial contractility. Furthermore, the Co showed more potent anti-apoptosis, antioxidant, and anti-inflammation effects. Additionally, the Co enhanced the inhibitory effects of Ta-IIA and As-IV on STING phosphorylation and the activation of STING signaling pathway. However, the administration of a STING agonist attenuated the protective effects of the Co, Ta-IIA, and As-IV by compromising their anti-apoptotic, antioxidant, and anti-inflammatory effects in MIRI.

CONCLUSION

Compared to the individual administration of Ta-IIA or As-IV, the combined treatment demonstrated more potent ability in inhibiting apoptosis, oxidative stress, inflammation, and the STING signaling pathway in the context of MIRI, indicating a more powerful protective effect against MIRI.

Circulating mitochondria promoted endothelial cGAS-derived neuroinflammation in subfornical organ to aggravate sympathetic overdrive in heart failure mice

BACKGROUND

Sympathoexcitation contributes to myocardial remodeling in heart failure (HF). Increased circulating pro-inflammatory mediators directly act on the Subfornical organ (SFO), the cardiovascular autonomic center, to increase sympathetic outflow. Circulating mitochondria (C-Mito) are the novel discovered mediators for inter-organ communication. Cyclic GMP-AMP synthase (cGAS) is the pro-inflammatory sensor of damaged mitochondria.

OBJECTIVES

This study aimed to assess the sympathoexcitation effect of C-Mito in HF mice via promoting endothelial cGAS-derived neuroinflammation in the SFO.

METHODS

C-Mito were isolated from HF mice established by isoprenaline (0.0125 mg/kg) infusion via osmotic mini-pumps for 2 weeks. Structural and functional analyses of C-Mito were conducted. Pre-stained C-Mito were intravenously injected every day for 2 weeks. Specific cGAS knockdown (cGAS KD) in the SFO endothelial cells (ECs) was achieved via the administration of AAV9-TIE-shRNA (cGAS) into the SFO. The activation of cGAS in the SFO ECs was assessed. The expression of the mitochondrial redox regulator Dihydroorotate dehydrogenase (DHODH) and its interaction with cGAS were also explored. Neuroinflammation and neuronal activation in the SFO were evaluated. Sympathetic activity, myocardial remodeling, and cardiac systolic dysfunction were measured.

RESULTS

C-Mito were successfully isolated, which showed typical structural characteristics of mitochondria with double-membrane and inner crista. Further analysis showed impaired respiratory complexes activities of C-Mito from HF mice (C-MitoHF) accompanied by oxidative damage. C-Mito entered ECs, instead of glial cells and neurons in the SFO of HF mice. C-MitoHF increased the level of ROS and cytosolic free double-strand DNA (dsDNA), and activated cGAS in cultured brain endothelial cells. Furthermore, C-MitoHF highly expressed DHODH, which interacted with cGAS to facilitate endothelial cGAS activation. C-MitoHF aggravated endothelial inflammation, microglial/astroglial activation, and neuronal sensitization in the SFO of HF mice, which could be ameliorated by cGAS KD in the ECs of the SFO. Further analysis showed C-MitoHF failed to exacerbate sympathoexcitation and myocardial sympathetic hyperinnervation in cGAS KD HF mice. C-MitoHF promoted myocardial fibrosis and hypertrophy, and cardiac systolic dysfunction in HF mice, which could be ameliorated by cGAS KD.

CONCLUSION

Collectively, we demonstrated that damaged C-MitoHF highly expressed DHODH, which promoted endothelial cGAS activation in the SFO, hence aggravating the sympathoexcitation and myocardial injury in HF mice, suggesting that C-Mito might be the novel therapeutic target for sympathoexcitation in HF.

Regulated cell death pathways in the sodium iodate model: Insights and implications for AMD

The sodium iodate (NaIO3) model of increased oxidative stress recapitulates dry AMD features such as patchy RPE loss, secondary photoreceptors, and underlying choriocapillaris death, allowing longitudinal evaluation of the retinal structure. Due to the time- and dose-dependent degeneration observed in diverse animal models, this preclinical model has become one of the most studied models. The events leading to RPE cell death post- NaIO3 injection have been extensively studied, and here we have reviewed different modalities of cell death, including apoptosis, necroptosis, ferroptosis, and pyroptosis with a particular focus on findings associated with in vivo and in vitro NaIO3 studies on RPE cell death. Because the fundamental cause of vision loss in patients with dry AMD is the death of these same cells affected by NaIO3, studies using NaIO3 can provide valuable insights into RPE and photoreceptor cell death mechanisms and can help understand mechanisms behind RPE degeneration in AMD.

Circ-CARD6 inhibits oxidative stress-induced apoptosis and autophagy in ARPE-19 cells via the miR-29b-3p/PRDX6/PI3K/Akt axis

BACKGROUND

Oxidative stress-induced damage and dysfunction of retinal pigment epithelium (RPE) cells are important pathogenetic factors of age-related macular degeneration (AMD) and hereditary retinopathy diseases (HRDs). This study aimed to elucidate the roles and mechanisms of circ-CARD6 and miR-29b-3p in oxidative stress-induced RPE and provide new ideas for the diagnosis and treatment of retinopathy disease (RD).

METHODS

A model of oxidative stress-induced RPE (ARPE-19) was established, and the level of malondialdehyde (MDA) and concentration of reactive oxygen species (ROS) were detected by a DCFH-DA fluorescent probe and MDA kit. The cell viability was measured by a CCK-8 assay. The expression of PRDX6/PI3K/Akt axis genes and proteins related to apoptosis and autophagy were determined by RT‒qPCR and Western blot analyses. The dual-luciferase reporter system confirmed the targeting relationship between miR-29b-3p and circ-CARD6 and between miR-29b-3p and PRDX6.

RESULTS

In H2O2-treated ARPE-19 cells, the expression of circ-CARD6 and PRDX6 was decreased, while the expression of miR-29b-3p was increased. The overexpression of circ-CARD6 inhibits oxidative stress-induced increases in ROS, apoptosis and autophagy in ARPE-19 cells. circ-CARD6 targets miR-29b-3p, miR-29b-3p targets PRDX6, and circ-CARD6 regulates PRDX6 via miR-29b-3p. Further studies showed that circ-CARD6 acts as a competitive endogenous RNA of miR-29b-3p to affect the expression of PRDX6, thereby inhibiting autophagy and apoptosis in ARPE-19 cells.

CONCLUSION

circ-CARD6 can inhibit oxidative stress and apoptosis by regulating the miR-29b-3p/PRDX6/PI3K/Akt axis.

Tafluprost promotes axon regeneration after optic nerve crush via Zn2+-mTOR pathway

PURPOSE

To investigate whether Tafluprost could promote optic nerve regeneration in mice after optic nerve crush (ONC) and determine the underlying molecular mechanism.

METHODS

Tafluprost was injected into the vitreous body immediately after ONC. The level of Zn2+ in the inner plexiform layer (IPL) of the retina was stained using autometallography (AMG). The number of survival retinal ganglion cells (RGCs) was determined via dual staining with RGC markers Tuj1 and RBPMS. Individual axons that regenerated to 0.25, 0.5, 0.75 and 1 mm were manually counted in the whole-mount optic nerve labeled by cholera toxin B fragment (CTB). Immunofluorescence and Western blot were performed to detect protein expression levels. Pattern electroretinogram was used to evaluate RGCs function.

RESULTS

Tafluprost promoted RGC survival in a dose-dependent manner with an optimal concentration of 1 μM. Tafluprost significantly decreased ZnT-3 expression and Zn2+ accumulation in the IPL of retina. Tafluprost stimulated intense axonal regeneration and maintained RGCs function compared to control. Mechanistically, Tafluprost and Zn2+ elimination treatment (TPEN or ZnT-3 deletion) can activate the mTOR pathway with an improved percentage of pS6+ RGCs in the retina. However, rapamycin, a specific inhibitor of the mTOR1, inhibited the activation of the mTOR pathway and abolished the regenerative effect mediated by Tafluprost. Tafluprost also inhibited the upregulation of p62, LC3 and Beclin-1, attenuated the overactivation of microglia/macrophages and downregulated the expression of TNFα and IL-1β.

CONCLUSIONS

Our results suggest that Tafluprost promoted axon regeneration via regulation of the Zn2+-mTOR pathway, and provide novel research directions for glaucomatous optic nerve injury mechanisms.

Modeling aging and retinal degeneration with mitochondrial DNA mutation burden

Somatic mitochondrial DNA (mtDNA) mutation accumulation has been observed in individuals with retinal degenerative disorders. To study the effects of aging and mtDNA mutation accumulation in the retina, a Polymerase gamma (POLG) deficiency model, the POLGD257A mutator mice (PolgD257A), was used. POLG is an enzyme responsible for regulating mtDNA replication and repair. Retinas of young and older mice with this mutation were analyzed in vivo and ex vivo to provide new insights into the contribution of age-related mitochondrial dysfunction due to mtDNA damage. Optical coherence tomography (OCT) image analysis revealed a decrease in retinal and photoreceptor thickness starting at 6 months of age in mice with the POLGD257A mutation compared to wild-type (WT) mice. Electroretinography (ERG) testing showed a significant decrease in all recorded responses at 6 months of age. Sections labeled with markers of different types of retinal cells, including cones, rods, and bipolar cells, exhibited decreased labeling starting at 6 months. However, electron microscopy analysis revealed differences in retinal pigment epithelium (RPE) mitochondria morphology beginning at 3 months. Interestingly, there was no increase in oxidative stress observed in the retina or RPE of POLGD257A mice. Additionally, POLGD257A RPE exhibited an accelerated rate of autofluorescence cytoplasmic granule formation and accumulation. Mitochondrial markers displayed decreased abundance in protein lysates obtained from retina and RPE samples. These findings suggest that the accumulation of mitochondrial DNA mutations leads to impaired mitochondrial function and accelerated aging, resulting in retinal degeneration.

BET Protein Inhibitor JQ1 Ameliorates Experimental Peritoneal Damage by Inhibition of Inflammation and Oxidative Stress

Peritoneal dialysis (PD) is a current replacement therapy for end-stage kidney diseases (ESKDs). However, long-term exposure to PD fluids may lead to damage of the peritoneal membrane (PM) through mechanisms involving the activation of the inflammatory response and mesothelial-to-mesenchymal transition (MMT), leading to filtration failure. Peritoneal damage depends on a complex interaction among external stimuli, intrinsic properties of the PM, and subsequent activities of the local innate-adaptive immune system. Epigenetic drugs targeting bromodomain and extra-terminal domain (BET) proteins have shown beneficial effects on different experimental preclinical diseases, mainly by inhibiting proliferative and inflammatory responses. However the effect of BET inhibition on peritoneal damage has not been studied. To this aim, we have evaluated the effects of treatment with the BET inhibitor JQ1 in a mouse model of peritoneal damage induced by chlorhexidine gluconate (CHX). We found that JQ1 ameliorated the CHX-induced PM thickness and inflammatory cell infiltration. Moreover, JQ1 decreased gene overexpression of proinflammatory and profibrotic markers, together with an inhibition of the nuclear factor-κB (NF-κB) pathway. Additionally, JQ1 blocked the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and restored changes in the mRNA expression levels of NADPH oxidases (NOX1 and NOX4) and NRF2/target antioxidant response genes. To corroborate the in vivo findings, we evaluated the effects of the BET inhibitor JQ1 on PD patients' effluent-derived primary mesothelial cells and on the MeT-5A cell line. JQ1 inhibited tumor necrosis factor-α (TNF-α)-induced proinflammatory gene upregulation and restored MMT phenotype changes, together with the downmodulation of oxidative stress. Taken together, these results suggest that BET inhibitors may be a potential therapeutic option to ameliorate peritoneal damage.

Alleviation of Photoreceptor Degeneration Based on Fullerenols in rd1 Mice by Reversing Mitochondrial Dysfunction via Modulation of Mitochondrial DNA Transcription and Leakage

Poor therapeutic outcomes of antioxidants in ophthalmologic clinical applications, including glutathione during photoreceptor degeneration in retinitis pigmentosa (RP), are caused by limited anti-oxidative capacity. In this study, fullerenols are synthesized and proven to be highly efficient in vitro radical scavengers. Fullerenol-based intravitreal injections significantly improve the flash electroretinogram and light/dark transition tests performed for 28 days on rd1 mice, reduce the thinning of retinal outer nuclear layers, and preserve the Rhodopsin, Gnat-1, and Arrestin expressions of photoreceptors. RNA-sequencing, RT-qPCR, and Western blotting validate that mitochondrial DNA (mt-DNA)-encoded genes of the electron transport chain (ETC), such as mt-Nd4l, mt-Co1, mt-Cytb, and mt-Atp6, are drastically downregulated in the retinas of rd1 mice, whereas nuclear DNA (n-DNA)-encoded genes, such as Ndufa1 and Atp5g3, are abnormally upregulated. Fullerenols thoroughly reverse the abnormal mt-DNA and n-DNA expression patterns of the ETC and restore mitochondrial function in degenerating photoreceptors. Additionally, fullerenols simultaneously repress Flap endonuclease 1 (FEN1)-mediated mt-DNA cleavage and mt-DNA leakage via voltage-dependent anion channel (VDAC) pores by downregulating the transcription of Fen1 and Vdac1, thereby inactivating the downstream pro-inflammatory cGAS-STING pathway. These findings demonstrate that fullerenols can effectively alleviate photoreceptor degeneration in rd1 mice and serve as a viable treatment for RP.

Stimulator of interferon genes (STING): Key therapeutic targets in ischemia/reperfusion injury

The Stimulator of Interferon Genes (STING) is predominantly expressed in immune cells, including macrophages, natural killer cells, dendritic cells, and T cells, functioning as a pattern recognition receptor. STING activation upon detecting cytosolic DNA released from damaged cells initiates downstream pathways, leading to the production of inflammatory cytokines such as IFNs, IL-6, and TNF-α. Dysregulated STING activation has been implicated in inflammatory and metabolic diseases. Ischemia/reperfusion injury (I/RI) is common in stroke, acute myocardial infarction, organ transplantation, and surgeries for certain end-stage diseases. Recent studies suggest that STING could be a novel therapeutic target for I/RI treatment. In this review, we provide a concise overview of the cGAS-STING signaling pathway's general functions and summarize STING's role in I/RI across various organs, including the heart, liver, kidney, and lung. Moreover, we explore potential therapeutic approaches for I/RI by targeting STING.

Myocardial Mitochondrial DNA Drives Macrophage Inflammatory Response through STING Signaling in Coxsackievirus B3-Induced Viral Myocarditis

Coxsackievirus B3 (CVB3), a single-stranded positive RNA virus, primarily infects cardiac myocytes and is a major causative pathogen for viral myocarditis (VMC), driving cardiac inflammation and organ dysfunction. However, whether and how myocardial damage is involved in CVB3-induced VMC remains unclear. Herein, we demonstrate that the CVB3 infection of cardiac myocytes results in the release of mitochondrial DNA (mtDNA), which functions as an important driver of cardiac macrophage inflammation through the stimulator of interferon genes (STING) dependent mechanism. More specifically, the CVB3 infection of cardiac myocytes promotes the accumulation of extracellular mtDNA. Such myocardial mtDNA is indispensable for CVB3-infected myocytes in that it induces a macrophage inflammatory response. Mechanistically, a CVB3 infection upregulates the expression of the classical DNA sensor STING, which is predominantly localized within cardiac macrophages in VMC murine models. Myocardial mtDNA efficiently triggers STING signaling in those macrophages, resulting in strong NF-kB activation when inducing the inflammatory response. Accordingly, STING-deficient mice are able to resist CVB3-induced cardiac inflammation, exhibiting minimal inflammation with regard to their functional cardiac capacities, and they exhibit higher survival rates. Moreover, our findings pinpoint myocardial mtDNA as a central element driving the cardiac inflammation of CVB3-induced VMC, and we consider the DNA sensor, STING, to be a promising therapeutic target for protecting against RNA viral infections.

Light damage induces inflammatory factors in mouse retina and vitreous humor

Purpose

Increased inflammatory factor levels have been reported in the vitreous humor (VH) of diabetic retinopathy and neovascular age-related macular degeneration, ocular diseases generally associated with the formation of new retinal blood vessels and leakage. However, the levels of inflammatory mediators are less known in retinal degeneration without neovascularization. Human retinitis pigmentosa (RP) and animal models of light-induced retinal degeneration (LIRD) share several features, such as photoreceptor death and retinal inflammation. Here, we aimed to determine the levels of inflammatory factors in the VH of the LIRD mouse model.

Methods

LIRD was induced by exposing BALB/c mice to white light (15,000 lx, 2 h), and the mice were recovered for 2 days before analysis (n = 50 mice). We assessed retinal morphology using optical coherence tomography and hematoxylin and eosin staining; retinal cell viability was determined using terminal deoxynucleotidyl transferase dUTP nick-end labeling, and retinal responses were measured based on electroretinogram signals. Total retinal RNAs were extracted and subjected to RNA sequencing analysis. VH samples from control (n = 4) and LIRD mice (n = 9) were assayed in triplicate for a panel of four inflammatory mediators using the Simple Plex Cartridge on an Ella System.

Results

Retinal degeneration, photoreceptor death, infiltration of microglia/macrophages into the photoreceptor layer, and loss of a- and b-waves were obviously detected after LIRD. RNA sequencing revealed that light damage (LD) led to the significant upregulation of inflammatory factors in mouse retinas. In the VH, LD increased the total protein concentration. Dramatic induction of CCL2 (~3000 fold) and IL6 (~10 fold) was detected in VH in response to LD. Increased but not significant levels of TNFα and IL1β were also detected in light-exposed VH.

Conclusions

Given that the LIRD model mimics RP pathogenesis in some aspects, these results suggest a causative link between retinal degeneration and VH inflammation in RP progression, and the increased CCL2 level in VH may reflect similar elevated CCL2 expression in the degenerative retina.

Emerging Roles of cGAS-STING Signaling in Mediating Ocular Inflammation

Cyclic GMP-AMP (cGAMP) synthase (cGAS), a sensor of cytosolic DNA, recognizes cytoplasmic nucleic acids to activate the innate immune responses via generation of the second messenger cGAMP and subsequent activation of the stimulator of interferon genes (STINGs). The cGAS-STING signaling has multiple immunologic and physiological functions in all human vital organs. It mediates protective innate immune defense against DNA-containing pathogen infection, confers intrinsic antitumor immunity via detecting tumor-derived DNA, and gives rise to autoimmune and inflammatory diseases upon aberrant activation by cytosolic leakage of self-genomic and mitochondrial DNA. Disruptions in these functions are associated with the pathophysiology of various immunologic and neurodegenerative diseases. Recent evidence indicates important roles of the cGAS-STING signaling in mediating inflammatory responses in ocular inflammatory and inflammation-associated diseases, such as keratitis, diabetic retinopathy, age-related macular degeneration, and uveitis. In this review, we summarize the recently emerging evidence of cGAS-STING signaling in mediating ocular inflammatory responses and affecting pathogenesis of these complex eye diseases. We attempt to provide insightful perspectives on future directions of investigating cGAS-STING signaling in ocular inflammation. Understanding how cGAS-STING signaling is modulated to mediate ocular inflammatory responses would allow future development of novel therapeutic strategies to treat ocular inflammation and autoimmunity.

IQGAP1 promotes mitochondrial damage and activation of the mtDNA sensor cGAS-STING pathway to induce endothelial cell pyroptosis leading to atherosclerosis

Atherosclerosis (AS) is the most common cardiovascular disease and has limited therapeutic options. IQ motif-containing GTPase-activating protein 1 (IQGAP1) is an important scaffolding protein regulating mitochondrial function influencing endothelial cell activity. Evidence suggests that mitochondrial damage can lead to leakage of mtDNA into the cytoplasm to activate the DNA sensor cGAS-STING to mediate pyroptosis. However, whether IQGAP1 induces NLRP3-mediated endothelial cell pyroptosis by regulating mitochondrial function and activating the DNA sensor cGAS-STING, and its underlying mechanisms remain unclear. In vivo, ApoE-/- C57BL/J and Ldlr-/- C57BL/J mice were pre-injected with adeno-associated virus (AAV) by the tail vein to specifically silence IQGAP1 expression and were fed a high-fat diet (HFD) for 12 weeks. IQGAP1 knockdown reduced mtDNA release and decreased the expression of DNA receptors and pyroptosis-related molecules as determined by immunohistochemistry and immunofluorescence. In vitro, palmitic acid (0.3 mmol/L) was incubated with human umbilical vein endothelial cells (HUVECs) for 24 h. Overexpression of IQGAP1 in HUVECs, flow cytometry, and mitochondrial superoxide staining revealed increased levels of ROS. Moreover, the mitochondrial tracker with dsDNA co-localization showed the release of mtDNA into the cytoplasm increased, which activated the DNA receptor cGAS-STING. Protein blotting and TUNEL staining revealed that IQGAP1 promoted NLRP3-mediated pyroptosis. Furthermore, cGAS or STING small-molecule inhibitors RU.521 or C-176 reverse IQGAP1-promoted HUVECs from undergoing NLRP3-mediated pyroptosis. These results suggest that IQGAP1 promotes oxidative stress and mtDNA release, activates the DNA sensor cGAS-STING, and leads to NLRP3-mediated pyroptosis. The present study provides new insights into the mechanisms underlying AS and identifies new pharmacological targets for treatment.

TGR5 supresses cGAS/STING pathway by inhibiting GRP75-mediated endoplasmic reticulum-mitochondrial coupling in diabetic retinopathy

Diabetic retinopathy (DR) is a serious and relatively under-recognized complication of diabetes. Müller glial cells extend throughout the retina and play vital roles in maintaining retinal homeostasis. Previous studies have demonstrated that TGR5, a member of the bile acid-activated GPCR family, could ameliorate DR. However, the role of TGR5 in regulating Müller cell function and the underlying mechanism remains to be ascertained. To address this, high glucose (HG)-treated human Müller cells and streptozotocin-treated Sprague-Dawley rats were used in the study. The IP3R1-GRP75-VDAC1 axis and mitochondrial function were assessed after TGR5 ablation or agonism. Cytosolic mitochondrial DNA (mtDNA)-mediated cGAS-STING activation was performed. The key markers of retinal vascular leakage, apoptosis, and inflammation were examined. We found that mitochondrial Ca2+ overload and mitochondrial dysfunction were alleviated by TGR5 agonist. Mechanically, TGR5 blocked the IP3R1-GRP75-VDAC1 axis mediated Ca2+ efflux from the endoplasmic reticulum into mitochondria under diabetic condition. Mitochondrial Ca2+ overload led to the opening of the mitochondrial permeability transition pore and the release of mitochondrial DNA (mtDNA) into the cytosol. Cytoplasmic mtDNA bound to cGAS and upregulated 2'3' cyclic GMP-AMP. Consequently, STING-mediated inflammatory responses were activated. TGR5 agonist prevented retinal injury, whereas knockdown of TGR5 exacerbated retinal damage in DR rats, which was rescued by the STING inhibitor. Based on the above results, we propose that TGR5 might be a novel therapeutic target for the treatment of DR.