Increased Drp1 promotes autophagy and ESCC progression by mtDNA stress mediated cGAS-STING pathway

A Prospective Study of the Association of IL6 with the Critical Unit and Their Effect on in-Hospital Mortality in Critically Ill Patients

Purpose

We previously proposed a new concept, the "critical unit", which covers the structural integrity and function of mitochondria and endothelium. Injury of the critical unit plays a key role in the development of critical illnesses. High levels of inflammation may lead to abnormalities of the critical unit, which is an important mechanism for critical illnesses, and both inflammation and critical unit dysfunction may affect patient prognosis. Here we evaluated the correlation between interleukin-6 (IL6) and the critical unit biomarkers in critically ill patients and the impact of both on prognosis.

Patients and Methods

This study included adult patients admitted to the intensive care unit for various reasons from January 1st to May 31st, 2023. Baseline characteristics, intensive care unit parameters, and laboratory test and outcome data were obtained from the electronic medical records system. Critical unit parameters were measured using polymerase chain reaction and enzyme-linked immunosorbent assay methods. Correlations were examined between IL6, critical unit parameters, and various outcomes.

Results

In critically ill patients, IL6 was closely associated with all the critical unit biomarkers (activated partial thromboplastin time, sphingosine 1-phosphate, mitochondrial DNA, mitochondrial fission 1, and Parkin) and the prognoses of patients. A nomogram was constructed using the critical unit biomarkers to predict the in-hospital mortality of critically ill patients. The area under the curve for the mortality prediction model was 0.708. In sensitivity analyses, the predictive effect was better in the non-surgery and tumor groups compared with the surgery and non-tumor groups, with area under the curve values of 0.885 and 0.891, respectively.

Conclusion

Our study innovatively integrated mitochondrial and endothelial markers in the critical unit to comprehensively evaluate patient prognosis, which may be a trend in the future assessment of critically ill patients. There are few such studies, and ours may promote the progress of related research.

The role of cGAS in epithelial dysregulation in inflammatory bowel disease and gastrointestinal malignancies

The gastrointestinal tract is lined by an epithelial monolayer responsible for selective permeability and absorption, as well as protection against harmful luminal contents. Recognition of foreign or aberrant DNA within these epithelial cells is, in part, regulated by pattern recognition receptors such as cyclic GMP-AMP synthase (cGAS). cGAS binds double-stranded DNA from exogenous and endogenous sources, resulting in the activation of stimulator of interferon genes (STING) and a type 1 interferon response. cGAS is also implicated in non-canonical pathways involving the suppression of DNA repair and the upregulation of autophagy via interactions with PARP1 and Beclin-1, respectively. The importance of cGAS activation in the development and progression of inflammatory bowel disease and gastrointestinal cancers has been and continues to be explored. This review delves into the intricacies of the complex role of cGAS in intestinal epithelial inflammation and gastrointestinal malignancies, as well as recent therapeutic advances targeting cGAS pathways.

Enhancing myocardial infarction treatment through bionic hydrogel-mediated spatial combination therapy via mtDNA-STING crosstalk modulation

Myocardial infarction (MI)-induced impaired cardiomyocyte (CM) mitochondrial function and microenvironmental inflammatory cascades severely accelerate the progression of heart failure for compromised myocardial repair. Modulation of the crosstalk between CM mitochondrial DNA (mtDNA) and STING has been recently identified as a robust strategy in enhancing MI treatment, but remains seldom explored. To develop a novel approach that can address persistent myocardial injury using this crosstalk, we report herein construction of a biomimetic hydrogel system, Rb1/PDA-hydrogel comprised of ginsenoside Rb1/polydopamine nanoparticles (Rb1/PDA NPs)-loaded carboxylated chitosan, 4-arm-PEG-phenylboronic acid (4-arm-PEG-PBA), and 4-arm-PEG-dopamine (4-arm-PEG-DA) crosslinked networks. An optimized hydrogel formulation presents not only desired adhesion properties to the surface of the myocardium, but also adaptability for deep myocardial injection, resulting in ROS scavenging, CM mitochondrial function protection, M1 macrophage polarization inhibition through the STING pathway, and angiogenesis promotion via an internal-external spatial combination. The enhanced therapeutic efficiency is supported by the histological analysis of the infarcted area, which shows that the fibrotic area of the MI rats decreases from 58.4% to 5.5%, the thickness of the left ventricular wall increases by 1-fold, and almost complete recovery of cardiac function after 28 days of treatment. Overall, this study reported the first use of a strong adhesive and injectable hydrogel with mtDNA and STING signaling characteristics for enhanced MI treatment via an internal-external spatial combination strategy.

The anti-tumor activity of tangeretin in esophageal squamous cell carcinoma by inhibiting GLI2-mediated transcription of GPNMB

Tangeretin (Tan), a citrus flavonoid, possesses a strong anti-tumor efficacy in various human cancers. However, the precise role of Tan in the development of esophageal squamous cell carcinoma (ESCC) remains unclear. RNA sequencing (RNA-seq) analysis was performed to observe the Tan-related genes in Tan-treated TE-1 cells. The direct relationship between GLI family zinc finger 2 (GLI2) and the promoter of glycoprotein non-metastatic melanoma protein B (GPNMB) was predicted by bioinformatics analysis and validated by luciferase reporter and chromatin immunoprecipitation (ChIP) assays. Cell survival after Tan treatment was assessed by CCK8 assay. Gene expression levels were evaluated by a qRT-PCR, western blot, or immunofluorescence method. Cell migration and invasion were detected by wound-healing and transwell assays. The function of Tan in vivo was examined using xenograft studies. Our data indicated anti-migration and anti-invasion functions of Tan in ESCC cells in vitro. Tan also diminished tumor growth in vivo. Mechanistically, Tan diminished the expression and transcriptional activity of GLI2 in ESCC cells. Silencing of GLI2 resulted in decreased expression of GPNMB by inhibiting GPNMB transcription via the binding site at the GPNMB promoter at position +(1539-1550). Moreover, Tan down-regulated GPNMB expression in ESCC cells, and re-expression of GPNMB reversed anti-migration and anti-invasion functions of Tan in ESCC cells. Our findings uncover anti-migration and anti-invasion effects of Tan in ESCC cells by down-regulating GPNMB by suppressing GLI2-mediated GPNMB transcription, providing new evidence that Tan can function as a therapeutic agent against ESCC.

SLC34A2 promotes cell proliferation by activating STX17-mediated autophagy in esophageal squamous cell carcinoma

BACKGROUND

Solute carrier family 34 member 2 (SLC34A2) has been implicated in the development of various malignancies. However, the clinical significance and underlying molecular mechanisms of SLC34A2 in esophageal squamous cell carcinoma (ESCC) remain elusive.

METHODS

Western blotting, quantitative real-time PCR and immunohistochemistry were utilized to evaluate the expression levels of SLC34A2 mRNA/protein in ESCC cell lines or tissues. Kaplan-Meier curves were employed for survival analysis. CCK-8, colony formation, EdU and xenograft tumor model assays were conducted to determine the impact of SLC34A2 on ESCC cell proliferation. Cell cycle was examined using flow cytometry. RNA-sequencing and enrichment analysis were carried out to explore the potential signaling pathways. The autophagic flux was evaluated by western blotting, mRFP-GFP-LC3 reporter system and transmission electron microscopy. Immunoprecipitation and mass spectrometry were utilized for identification of potential SLC34A2-interacting proteins. Cycloheximide (CHX) chase and ubiquitination assays were conducted to test the protein stability.

RESULTS

The expression of SLC34A2 was significantly upregulated in ESCC and correlated with unfavorable clinicopathologic characteristics particularly the Ki-67 labeling index and poor prognosis of ESCC patients. Overexpression of SLC34A2 promoted ESCC cell proliferation, while silencing SLC34A2 had the opposite effect. Moreover, SLC34A2 induced autophagy to promote ESCC cell proliferation, whereas inhibition of autophagy suppressed the proliferation of ESCC cells. Further studies showed that SLC34A2 interacted with an autophagy-related protein STX17 to promote autophagy and proliferation of ESCC cells by inhibiting the ubiquitination and degradation of STX17.

CONCLUSIONS

These findings indicate that SLC34A2 may serve as a prognostic biomarker for ESCC.

Mitochondrial DNA drives neuroinflammation through the cGAS-IFN signaling pathway in the spinal cord of neuropathic pain mice

Neuroinflammation is pivotal in the development of neuropathic pain (NeP). While mitochondrial deoxyribonucleic acid (mtDNA) and cyclic GMP-AMP synthase (cGAS) are recognized for inducing inflammation in various neurological disorders, their involvement in NeP remains ambiguous. In this study, we examined: (1) the changes in mtDNA and cGAS in mice with NeP induced by chronic constriction injury (CCI) of the sciatic nerve, whether mtDNA triggers inflammation via the cGAS signaling; (2) the effects of RU.521, a cGAS antagonist, on CCI-induced nociception (allodynia and hyperalgesia) and relative inflammatory protein expression; (3) the activation of microglia and the cGAS-IFN pathway mediated by mtDNA in BV2 cell; (4) the effect of RU.521 on mtDNA-induced inflammatory response in BV2 cells. Results revealed reduced mtDNA levels in the sciatic nerve but increased levels in the spinal cord of CCI mice, along with elevated cGAS expression and inflammatory factors. RU.521 alleviated nociceptive behaviors in CCI mice, possibly by normalizing cGAS levels and suppressing inflammation. Neuron-derived mtDNA provoked cellular activation and upregulated cGAS signaling in BV2 cells. Additionally, RU.521 and DNase I effectively inhibited cGAS-induced inflammation. These findings underscore the critical role of mtDNA accumulation and mtDNA-mediated cGAS signaling in NeP development after peripheral nerve injury.

BIBR1532 combined with radiotherapy induces ferroptosis in NSCLC cells and activates cGAS-STING pathway to promote anti-tumor immunity

BACKGROUND

Telomerase, by safeguarding damaged telomeres and bolstering DNA damage repair, has the capacity to heighten the radioresistance of tumour cells. Thus, in turn, can compromise the efficacy of radiotherapy (RT) and radioimmunotherapy. Our previous studies have revealed that the highly selective telomerase inhibitor, BIBR1532, possesses the potential to enhance the radiosensitivity of Non-small cell lung cancer (NSCLC). In this study, we delve further into the impact of BIBR1532 on the immune activation induced by RT and elucidate the underlying mechanisms.

METHODS

Biological information analyses, immunofluorescence assays, western blot assays, flow cytometry analysis were conducted to elucidate the functions of the combination of BIBR1532 with radiotherapy in NSCLC. Intracellular levels of lipid peroxides, glutathione, malondialdehyde, and Fe2+ were measured as indicators of ferroptosis status. Both in vitro and in vivo studies were conducted to examine the antitumor effects.

RESULTS

Our findings indicate that the confluence of BIBR1532 with RT significantly augments the activation of the cGAS-STING pathway in both in vivo and in vitro settings, thereby fostering an effective anti-tumoral immune response. The effects can be ascribed to two key processes. Firstly, ionizing radiation, in precipitating DNA double-strand breaks (DSBs), prompts the release of tumour-derived double-stranded DNA (dsDNA) into the cytoplasm. Subsequently, BIBR1532 amplifies the activation of antigen-presenting cells by dsDNA post-RT and instigates the cGAS-STING pathway. Secondly, BIBR1532 enhances the ferroptosis response in NSCLC following RT, thereby promoting unrestrained lipid peroxidation and elevated levels of reactive oxygen species (ROS) within tumour cells. This ultimately leads to mitochondrial stress and the release of endogenous mitochondrial DNA (mtDNA) into the cytoplasm, thus facilitating the activation of the STING pathway and the induction of a type I interferon (IFN)-linked adaptive immune response.

CONCLUSION

This study underscores the potential of BIBR1532 as an efficacious and safe radiosensitizer and radioimmunotherapy synergist, providing robust preclinical research evidence for the treatment of NSCLC.

Second messenger 2'3'-cyclic GMP-AMP (2'3'-cGAMP): the cell autonomous and non-autonomous roles in cancer progression

Cytosolic double-stranded DNA (dsDNA) is frequently accumulated in cancer cells due to chromosomal instability or exogenous stimulation. Cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, which is activated upon binding to dsDNA to synthesize the crucial second messenger 2'3'-cyclic GMP-AMP (2'3'-cGAMP) that in turn triggers stimulator of interferon genes (STING) signaling. The canonical role of cGAS-cGAMP-STING pathway is essential for innate immunity and viral defense. Recent emerging evidence indicates that 2'3'-cGAMP plays an important role in cancer progression via cell autonomous and non-autonomous mechanisms. Beyond its role as an intracellular messenger to activate STING signaling in tumor cells, 2'3'-cGAMP also serves as an immunotransmitter produced by cancer cells to modulate the functions of non-tumor cells especially immune cells in the tumor microenvironment by activating STING signaling. In this review, we summarize the synthesis, transmission, and degradation of 2'3'-cGAMP as well as the dual functions of 2'3'-cGAMP in a STING-dependent manner. Additionally, we discuss the potential therapeutic strategies that harness the cGAMP-mediated antitumor response for cancer therapy.

IFNα-induced BST2+ tumor-associated macrophages facilitate immunosuppression and tumor growth in pancreatic cancer by ERK-CXCL7 signaling

Pancreatic ductal adenocarcinoma (PDAC) features an immunosuppressive tumor microenvironment (TME) that resists immunotherapy. Tumor-associated macrophages, abundant in the TME, modulate T cell responses. Bone marrow stromal antigen 2-positive (BST2+) macrophages increase in KrasG12D/+; Trp53R172H/+; Pdx1-Cre mouse models during PDAC progression. However, their role in PDAC remains elusive. Our findings reveal a negative correlation between BST2+ macrophage levels and PDAC patient prognosis. Moreover, an increased ratio of exhausted CD8+ T cells is observed in tumors with up-regulated BST2+ macrophages. Mechanistically, BST2+ macrophages secrete CXCL7 through the ERK pathway and bind with CXCR2 to activate the AKT/mTOR pathway, promoting CD8+ T cell exhaustion. The combined blockade of CXCL7 and programmed death-ligand 1 successfully decelerates tumor growth. Additionally, cGAS-STING pathway activation in macrophages induces interferon (IFN)α synthesis leading to BST2 overexpression in the PDAC TME. This study provides insights into IFNα-induced BST2+ macrophages driving an immune-suppressive TME through ERK-CXCL7 signaling to regulate CD8+ T cell exhaustion in PDAC.

High glucose-induced p66Shc mitochondrial translocation regulates autophagy initiation and autophagosome formation in syncytiotrophoblast and extravillous trophoblast

BACKGROUND

p66Shc, as a redox enzyme, regulates reactive oxygen species (ROS) production in mitochondria and autophagy. However, the mechanisms by which p66Shc affects autophagosome formation are not fully understood.

METHODS

p66Shc expression and its location in the trophoblast cells were detected in vivo and in vitro. Small hairpin RNAs or CRISPR/Cas9, RNA sequencing, and confocal laser scanning microscope were used to clarify p66Shc's role in regulating autophagic flux and STING activation. In addition, p66Shc affects mitochondrial-associated endoplasmic reticulum membranes (MAMs) formation were observed by transmission electron microscopy (TEM). Mitochondrial function was evaluated by detected cytoplastic mitochondrial DNA (mtDNA) and mitochondrial membrane potential (MMP).

RESULTS

High glucose induces the expression and mitochondrial translocation of p66Shc, which promotes MAMs formation and stimulates PINK1-PRKN-mediated mitophagy. Moreover, mitochondrial localized p66Shc reduces MMP and triggers cytosolic mtDNA release, thus activates cGAS/STING signaling and ultimately leads to enhanced autophagy and cellular senescence. Specially, we found p66Shc is required for the interaction between STING and LC3II, as well as between STING and ATG5, thereby regulates cGAS/STING-mediated autophagy. We also identified hundreds of genes associated several biological processes including aging are co-regulated by p66Shc and ATG5, deletion either of which results in diminished cellular senescence.

CONCLUSION

p66Shc is not only implicated in the initiation of autophagy by promoting MAMs formation, but also helps stabilizing active autophagic flux by activating cGAS/STING pathway in trophoblast.

Focusing on mitochondria in the brain: from biology to therapeutics

Mitochondria have multiple functions such as supplying energy, regulating the redox status, and producing proteins encoded by an independent genome. They are closely related to the physiology and pathology of many organs and tissues, among which the brain is particularly prominent. The brain demands 20% of the resting metabolic rate and holds highly active mitochondrial activities. Considerable research shows that mitochondria are closely related to brain function, while mitochondrial defects induce or exacerbate pathology in the brain. In this review, we provide comprehensive research advances of mitochondrial biology involved in brain functions, as well as the mitochondria-dependent cellular events in brain physiology and pathology. Furthermore, various perspectives are explored to better identify the mitochondrial roles in neurological diseases and the neurophenotypes of mitochondrial diseases. Finally, mitochondrial therapies are discussed. Mitochondrial-targeting therapeutics are showing great potentials in the treatment of brain diseases.

Discovery of a triphenylamine-based ligand that targets mitochondrial DNA G-quadruplexes and activates the cGAS-STING immunomodulatory pathway

Stabilization of G-quadruplex (G4) structures in mitochondria leads to the damage of mitochondrial DNA (mtDNA), making mtDNA G4s a promising target in the field of cancer therapy in recent years. Damaged mtDNA released into the cytosol can stimulate cytosolic DNA-sensing pathways, and cGAS-STING pathway is a typical one with potent immunostimulatory effects. A few small molecule ligands of mtDNA G4s are identified with antitumor efficacy, but little is known about their results and mechanisms on immunomodulation. In this study, we engineered a series of triphenylamine-based analogues targeting mtDNA G4s, and A6 was determined as the most promising compound. Cellular studies indicated that A6 caused severe mtDNA damage. Then, damaged mtDNA stimulated cGAS-STING pathway, resulting in the following cytokine production of tumor cells and the maturation of DCs. In vivo experiments certified that A6 exerted suppressive influences on tumor growth and metastasis in 4T1 cell-bearing mice by the regulation of TME, including the remodeling of macrophages and the activation of T cells. To our knowledge, it is the first time to report a ligand targeting mtDNA G4s to activate the cGAS-STING immunomodulatory pathway, providing a novel strategy for the future development of mtDNA G4-based antitumor agents.

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.

Drp1: Focus on Diseases Triggered by the Mitochondrial Pathway

Drp1 (Dynamin-Related Protein 1) is a cytoplasmic GTPase protein encoded by the DNM1L gene that influences mitochondrial dynamics by mediating mitochondrial fission processes. Drp1 has been demonstrated to play an important role in a variety of life activities such as cell survival, proliferation, migration, and death. Drp1 has been shown to play different physiological roles under different physiological conditions, such as normal and inflammation. Recently studies have revealed that Drp1 plays a critical role in the occurrence, development, and aggravation of a series of diseases, thereby it serves as a potential therapeutic target for them. In this paper, we review the structure and biological properties of Drp1, summarize the biological processes that occur in the inflammatory response to Drp1, discuss its role in various cancers triggered by the mitochondrial pathway and investigate effective methods for targeting Drp1 in cancer treatment. We also synthesized the phenomena of Drp1 involving in the triggering of other diseases. The results discussed herein contribute to our deeper understanding of mitochondrial kinetic pathway-induced diseases and their therapeutic applications. It is critical for advancing the understanding of the mechanisms of Drp1-induced mitochondrial diseases and preventive therapies.

p53-dependent HIF-1α /autophagy mediated glycolysis to support Cr(VI)-induced cell growth and cell migration

Cr(VI) is known to be seriously toxic and carcinogenic. Hypoxia-inducible factor-1α (HIF-1α) is a crucial regulator to promote tumor development. In this study, we found that Cr(VI) significantly increased the expression of HIF-1α in A549 cells and in lung of BALB/c mice but not in HELF cells. Treatment with Lificiguat (YC-1), HIF-1α inhibitor, or CoCl2, HIF-1α inducer, could alter Cr(VI)-induced autophagy, glycolysis, and cell growth in A549 cells but not in HELF cells, validating the involvement of HIF-1α in these effects of Cr(VI) in A549 cells. Co-treatments of pcATG4B with YC-1, or siATG4B with CoCl2 demonstrated the role of HIF-1α / autophagy axis in inducing glycolysis and cell growth in A549 cells. In HELF cells, however, only autophagy but not HIF-1α played a role in inducing glycolysis. The protein level of p53 was significantly lower in A549 cells than in HELF cells. RITA, a p53 inducer, attenuated Cr(VI)-induced HIF-1α and LC3-II in A549 cells, suggesting that p53 might be the mechanism underlying the different effects of Cr(VI) on HIF-1α in A549 and HELF cells. Thus, p53-dependent HIF-1α / autophagy-mediated glycolysis plays a role in facilitating Cr(VI)-induced carcinogenesis.

The critical roles of STING in mitochondrial homeostasis

The stimulator of interferon genes (STING) is a crucial signaling hub in the immune system's antiviral and antimicrobial defense by detecting exogenous and endogenous DNA. The multifaceted functions of STING have been uncovered gradually during past decades, including homeostasis maintenance and overfull immunity or inflammation induction. However, the subcellular regulation of STING and mitochondria is poorly understood. The main functions of STING are outlined in this review. Moreover, we discuss how mitochondria and STING interact through multiple mechanisms, including the release of mitochondrial DNA (mtDNA), modulation of mitochondria-associated membrane (MAM) and mitochondrial dynamics, alterations in mitochondrial metabolism, regulation of reactive oxygen species (ROS) production, and mitochondria-related cell death. Finally, we discuss how STING is crucial to disease development, providing a novel perspective on its role in cellular physiology and pathology.

Conjugated Linoleic Acid Ameliorates Hydrogen Peroxide-Induced Mitophagy and Inflammation via the DRP1-mtDNA-STING Pathway in Bovine Hepatocytes

Oxidative stress is tightly associated with liver dysfunction and injury in dairy cows. Previous studies have shown that cis-9, trans-11 conjugated linoleic acid (CLA) possesses anti-inflammatory and antioxidative abilities. In this study, the bovine hepatocytes were pretreated with CLA for 6 h, followed by treatment with hydrogen peroxide (H2O2) for another 6 h to investigate the antioxidative effect of CLA and uncover the underlying mechanisms. The results demonstrated that H2O2 treatment elevated the level of mitophagy, promoted mitochondrial DNA (mtDNA) leakage into the cytosol, and activated the stimulator of interferon genes (STING)/nuclear factor kappa B (NF-κB) signaling pathway to trigger an inflammatory response in bovine hepatocytes. In addition, the dynamin-related protein 1(DRP1)-mtDNA-STING-NF-κB axis contributed to the H2O2-induced oxidative injury of bovine hepatocytes. CLA could reduce mitophagy and the inflammatory response to attenuate oxidative damage via the DRP1/mtDNA/STING pathway in bovine hepatocytes. These findings offer a theoretical foundation for the hepatoprotective effect of CLA against oxidative injury in dairy cows.

Progress in understanding of relationship between inflammation and tumors

Over the past decade, there has been clear evidence that inflammation plays a key role in tumorigenesis. Tumor extrinsic inflammation is caused by many factors, including bacterial and viral infections, autoimmune diseases, obesity, smoking, excessive alcohol consumption, etc., all of which can increase cancer risk and stimulate malignant progression. Conversely, inflammation inherent in cancer or caused by cancer can be triggered by cancer-initiating mutations and can promote malignant progression through recruitment and activation of inflammatory cells. Both exogenous and endogenous inflammation can lead to immunosuppression, thus providing a preferred opportunity for tumor development. Studies have confirmed that chronic inflammation is involved in various steps of tumorigenesis, including cell transformation, promotion, survival, prolifer-ation, invasion, angiogenesis, and metastasis. Recent research has shed new light on the molecular and cellular circuits between inflammation and cancer. Two pathways have been preliminarily identified: Intrinsic and extrinsic. In the intrinsic pathway, genetic events leading to tumors initiate the expression of inflammatory related programs and guide the construction of the inflammatory microenvironment. In the extrinsic pathway, inflammatory conditions promote the development of cancer. This article reviews the recent progress in the understanding of the relationship between inflammation and tumors.

MTFR2-dependent mitochondrial fission promotes HCC progression

BACKGROUND

The role of mitochondrial dynamics, encompassing fission, fusion, and mitophagy, in cancer progression has been extensively studied. However, the specific impact of mitochondrial dynamics on hepatocellular carcinoma (HCC) is still under investigation.

METHODS

In this study, mitochondrial dynamic genes were obtained from the MitoCarta 3.0 database, and gene expression data were collected from The Cancer Genome Atlas (TCGA) database. Based on the expression of these dynamic genes and differentially expressed genes (DEGs), patients were stratified into two clusters. Subsequently, a prognostic model was constructed using univariate COX regression and the least absolute shrinkage and selection operator (LASSO) regression, and the prognostic signature was evaluated. We analyzed the interaction between these model genes and dynamic genes to identify hub genes and reveal mitochondrial status. Furthermore, we assessed immune infiltration, tumor mutational burden (TMB), tumor stemness indices (TSI), and the response to immune checkpoint block (ICB) therapy using the TIDE algorithm and risk scores. Additionally, transmission electron microscopy (TEM), hematoxylin-eosin (H&E) staining, immunohistochemistry (IHC), western blotting (WB), and immunofluorescence (IF) were conducted to afford detailed visualization of the morphology of the mitochondria and the expression patterns of fission-associated proteins.

RESULTS

Patients in Cluster 2 exhibited heightened mitochondrial fission and had a worse prognosis. The up-regulated dynamic genes in Cluster 2 were identified as fission genes. GO/KEGG analyses reconfirmed the connection of Cluster 2 to augmented mitochondrial fission activities. Subsequently, a ten-gene prognostic signature based on the differentially expressed genes between the two clusters was generated, with all ten genes being up-regulated in the high-risk group. Moreover, the potential links between these ten signature genes and mitochondrial dynamics were explored, suggesting their involvement in mediating mitochondrial fission through interaction with MTFR2. Further investigation revealed that the high-risk group had an unfavorable prognosis, with a higher mutation frequency of TP53, increased immune checkpoint expression, a higher TIS score, and a lower TIDE score. The mitochondrial imbalance characterized by increased fission and upregulated MTFR2 and DNM1L expression was substantiated in both HCC specimens and cell lines.

CONCLUSIONS

In conclusion, we developed a novel MTFR2-related prognostic signature comprising ten mitochondrial dynamics genes. These genes play crucial roles in mitochondrial fission and have the potential to serve as important predictors and therapeutic targets for HCC.

Research progress on mitochondria regulating tumor immunity

Tumor cells adapt their metabolism to meet the demands for energy and biosynthesis. Mitochondria, pivotal organelles in the metabolic reprogramming of tumor cells, contribute to tumorigenesis and cancer progression significantly through various dysfunctions in both tumor and immune cells. Alterations in mitochondrial dynamics and metabolic signaling pathways exert crucial regulatory influence on the activation, proliferation, and differentiation of immune cells. The tumor microenvironment orchestrates the activation and functionality of tumor-infiltrating immune cells by reprogramming mitochondrial metabolism and inducing shifts in mitochondrial dynamics, thereby facilitating the establishment of a tumor immunosuppressive microenvironment. Stress-induced leakage of mitochondrial DNA contributes multifaceted regulatory effects on anti-tumor immune responses and the immunosuppressive microenvironment by activating multiple natural immune signals, including cGAS-STING, TLR9, and NLRP3. Moreover, mitochondrial DNA-mediated immunogenic cell death emerges as a promising avenue for anti-tumor immunotherapy. Additionally, mitochondrial reactive oxygen species, a crucial factor in tumorigenesis, drives the formation of tumor immunosuppressive microenvironment by changing the composition of immune cells within the tumor microenvironment. This review focuses on the intrinsic relationship between mitochondrial biology and anti-tumor immune responses from multiple angles. We explore the core role of mitochondria in the dynamic interplay between the tumor and the host to facilitate the development of targeted mitochondrial strategies for anti-tumor immunotherapy.

cGAS-STING at the crossroads in cancer therapy

DNA is highly immunogenic, both exogenous and endogenous DNA can activate the pathogen-associated molecular pattern (PAMP) and danger-associated molecular pattern (DAMP), respectively, and hence activate the evolutionarily conserved cGAS-STING pathway for inflammatory responses. The cGAS-STING signaling pathway plays a very important role in the pathogenesis and progression of neoplastic diseases. For cancer therapy, there are some discrepancies on whether cGAS-STING should be inhibited or activated. Deregulated cGAS-STING signaling pathway might be the origin and pathogenesis of tumor, understanding and modulating cGAS-STING signaling holds great promise for cancer therapy. In this review article, we discuss the molecular mechanisms underlying cGAS-STING deregulation, highlighting the tumor inhibiting and promoting roles and challenges with cGAS-STING agonists in the context of cancer therapies.

Prognostic value and immune regulatory role of dynamin 1-like in lung adenocarcinoma

Background

Lung adenocarcinoma (LUAD) is the most common histological subtype of non-small cell lung cancer (NSCLC), with poor treatment outcomes worldwide. Dynamin-related protein 1 (DRP1), which is encoded by the dynamin 1-like (DNM1L) gene, acts as a regulator of mitochondrial fission and plays crucial roles in tumor initiation and progression. However, the clinical value and immune regulation of DNM1L in LUAD have not been explored.

Methods

We comprehensively analyzed the expression of DNM1L in the LUAD cohort of the Human Protein Atlas (HPA) and the University of The ALabama at Birmingham CANcer data analysis Portal (UALCAN) databases. Kaplan-Meier plotter, in addition to the PrognoScan database, was used to estimate the correlation between DNM1L expression and survival outcome of LUAD patients. The association between the immune tumor microenvironment (TME) and DNM1L expression in LUAD was evaluated based on the Tumor IMmune Estimation Resource (TIMER)2.0 database. Finally, the functions of DNM1L were validated in vitro experiments, including reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot, wound healing assays, and transwell assays.

Results

DNM1L was overexpressed in LUAD compared to healthy control tissues and was regarded as an independent prognostic factor. Overexpression of DNM1L was significantly related to clinical variables and poor survival outcomes of LUAD patients. Moreover, DNM1L expression was positively associated with the expression of key genes involved in the regulation of immune cell subsets, including T helper (Th)2 cells, Th cells, B cells, CD8 T cells, dendritic cells, and mast cells. In contrast, DNM1L was negatively correlated with the infiltrating levels of myeloid dendritic cells and B cells. Furthermore, DNM1L may play a role in regulating immune cell infiltration and have prognostic value in LUAD patients. Finally, the in vitro experiments showed that increased DNM1L significantly promoted the proliferation and migration of LUAD cells.

Conclusions

This study suggested that DNM1L may play an important role in regulating the proliferation and migration of LUAD cells as well as the infiltration of tumor-related immune cells, which suggests DNM1L was a potential therapeutic target in LUAD. Further studies are however warranted to define its exact mechanism of action and potential therapeutic significance in LUAD patients.

cGAS-STING signaling in the tumor microenvironment

The cGAS-STING signaling is an important pathway involved in the regulation of tumor microenvironment, which affects many cellular functions including immune activation. Its role in combating tumor progression is widely recognized, especially with its function in inducing innate and adaptive immune responses, on which many immunotherapies have been developed. However, a growing number of findings also suggest a diversity of its roles in shaping tumor microenvironment, including functions that promote tumor progression. Here, we summarize the functions of the cGAS-STING signaling in tumor microenvironment to maintain tumor survival and proliferation through facilitating the forming of an immunosuppressive tumor microenvironment and discuss the current advances of STING-related immunotherapies.

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.

The role of mitochondrial dysfunction in periodontitis: From mechanisms to therapeutic strategy

Periodontitis is an inflammatory and destructive disease of tooth-supporting tissue and has become the leading cause of adult tooth loss. The most central pathological features of periodontitis are tissue damage and inflammatory reaction. As the energy metabolism center of eukaryotic cells, mitochondrion plays a notable role in various processes, such as cell function and inflammatory response. When the intracellular homeostasis of mitochondrion is disrupted, it can lead to mitochondrial dysfunction and inability to generate adequate energy to maintain basic cellular biochemical reactions. Recent studies have revealed that mitochondrial dysfunction is closely related to the initiation and development of periodontitis. The excessive production of mitochondrial reactive oxygen species, imbalance of mitochondrial biogenesis and dynamics, mitophagy and mitochondrial DNA damage can all affect the development and progression of periodontitis. Thus, targeted mitochondrial therapy is potentially promising in periodontitis treatment. In this review, we summarize the above mitochondrial mechanism in the pathogenesis of periodontitis and discuss some potential approaches that can exert therapeutic effects on periodontitis by modulating mitochondrial activity. The understanding and summary of mitochondrial dysfunction in periodontitis might provide new research directions for pathological intervention or treatment of periodontitis.

LRRK2 aggravates kidney injury through promoting MFN2 degradation and abnormal mitochondrial integrity

Mitochondrial dysfunction is one of the key features of acute kidney injury (AKI) and associated fibrosis. Leucine-rich repeat kinase 2 (LRRK2) is highly expressed in kidneys and regulates mitochondrial homeostasis. How it functions in AKI is unclear. Herein we reported that LRRK2 was dramatically downregulated in AKI kidneys. Lrrk2-/- mice exhibited less severity of AKI when compared to wild-type counterparts with less mitochondrial fragmentation and decreased reactive oxygen species (ROS) production in proximal renal tubular cells (PTCs) due to mitofusin 2 (MFN2) accumulation. Overexpression of LRRK2 in human PTC cell lines promoted LRRK2-MKK4/JNK-dependent phosphorylation of MFN2Ser27 and subsequently ubiquitination-mediated MFN2 degradation, which in turn exaggerated mitochondrial damage upon ischemia/reperfusion (I/R) mimicry treatment. Lrrk2 deficiency also alleviated AKI-to-chronic kidney disease (CKD) transition with less fibrosis. In vivo pretreatment of LRRK2 inhibitors attenuated the severity of AKI as well as CKD, potentiating LRRK2 as a novel target to alleviate AKI and fibrosis.

Cancer cell-specific cGAS/STING Signaling pathway in the era of advancing cancer cell biology

Pattern-recognition receptors (PRRs) are critical to recognizing endogenous and exogenous threats to mount a protective proinflammatory innate immune response. PRRs may be located on the outer cell membrane, cytosol, and nucleus. The cGAS/STING signaling pathway is a cytosolic PRR system. Notably, cGAS is also present in the nucleus. The cGAS-mediated recognition of cytosolic dsDNA and its cleavage into cGAMP activates STING. Furthermore, STING activation through its downstream signaling triggers different interferon-stimulating genes (ISGs), initiating the release of type 1 interferons (IFNs) and NF-κB-mediated release of proinflammatory cytokines and molecules. Activating cGAS/STING generates type 1 IFN, which may prevent cellular transformation and cancer development, growth, and metastasis. The current article delineates the impact of the cancer cell-specific cGAS/STING signaling pathway alteration in tumors and its impact on tumor growth and metastasis. This article further discusses different approaches to specifically target cGAS/STING signaling in cancer cells to inhibit tumor growth and metastasis in conjunction with existing anticancer therapies.

Ficolin B secreted by alveolar macrophage exosomes exacerbates bleomycin-induced lung injury via ferroptosis through the cGAS-STING signaling pathway

Pathogenesis exploration and timely intervention of lung injury is quite necessary as it has harmed human health worldwide for years. Ficolin B (Fcn B) is a recognition molecule that can recognize a variety of ligands and play an important role in mediating the cell cycle, immune response, and tissue homeostasis in the lung. However, the role of Fcn B in bleomycin (BLM)-induced lung injury is obscure. This study aims to investigate the sources of Fcn B and its mechanism in BLM-induced lung injury. WT, Fcna-/-, and Fcnb-/- mice were selected to construct the BLM-induced lung injury model. Lung epithelial cells were utilized to construct the BLM-induced cell model. Exosomes that were secreted from alveolar macrophages (AMs) were applied for intervention by transporting Fcn B. Clinical data suggested M-ficolin (homologous of Fcn B) was raised in plasma of interstitial lung disease (ILD) patients. In the mouse model, macrophage-derived Fcn B aggravated BLM-induced lung injury and fibrosis. Fcn B further promoted the development of autophagy and ferroptosis. Remarkably, cell experiment results revealed that Fcn B transported by BLM-induced AMs exosomes accelerated autophagy and ferroptosis in lung epithelial cells through the activation of the cGAS-STING pathway. In contrast, the application of 3-Methyladenine (3-MA) reversed the promotion effect of Fcn B from BLM-induced AMs exosomes on lung epithelial cell damage by inhibiting autophagy-dependent ferroptosis. Meanwhile, in the BLM-induced mice model, the intervention of Fcn B secreted from BLM-induced AMs exosomes facilitated lung injury and fibrosis via ferroptosis. In summary, this study demonstrated that Fcn B transported by exosomes from AMs exacerbated BLM-induced lung injury by promoting lung epithelial cells ferroptosis through the cGAS-STING signaling pathway.

PRRSV infection activates NLRP3 inflammasome through inducing cytosolic mitochondrial DNA stress

Porcine reproductive and respiratory syndrome virus (PRRSV) infection causes severe interstitial pneumonia and inflammatory response in piglets and growing pigs. IL-1β is implicated in PRRSV-mediated inflammatory response and the pathogenesis of PRRSV infection. Mitochondria are critical intracellular organelles which is served as signaling platform for antiviral immunity response to participate in immune response of virus infection. The role of mitochondria in PRRSV-mediated inflammatory response and the pathogenesis of PRRSV infection has not been elucidated. Here, our data suggested that PRRSV infection facilitates mitochondrial dysfunction, which induces cytosolic mitochondrial DNA (mtDNA) stress and ROS accumulation, severally activates the NLRP3 inflammasome and NF-κB signaling pathway, and consequently stimulates IL-1β production in PAMs. Furthermore, mtDNA degradation by DNase I abrogates the activation of NLRP3 inflammasome and IL-1β secretion during PRRSV infection. Scavenging ROS significantly inhibits NF-κB signaling activation and the subsequently transcription and secretion of IL-1β. In conclusion, our results indicate that cytosolic mtDNA stress and ROS accumulation after PRRSV infection-induced mitochondrial dysfunction activate NLRP3 inflammasome and NF-κB signaling pathway to promote IL-1β production, revealing a new strategy for vaccine and drug development to PRRSV.

Increased mitochondrial fission induces NLRP3/cGAS-STING mediated pro-inflammatory pathways and apoptosis in UVB-irradiated immortalized human keratinocyte HaCaT cells

Ultraviolet B (UVB) irradiation causes skin inflammation and apoptosis. Mitochondria are highly dynamic and undergo constant fusion and fission that are essential for maintaining physiological functions of cells. Although dysfunction of mitochondria has been implicated in skin damages, little is known about the roles of mitochondrial dynamics in these processes. UVB irradiation increases abnormal mitochondrial content but decreases mitochondrial volume in immortalized human keratinocyte HaCaT cells. UVB irradiation resulted in marked upregulation of mitochondrial fission protein dynamin-related protein 1 (DRP1) and downregulation of mitochondrial outer membrane fusion proteins 1 and 2 (MFN1 and MFN2) in HaCaT cells. Mitochondrial dynamics was discovered to be crucial for NLRP3 inflammasome and cGAS-STING pathway activation, as well as the induction of apoptosis. Inhibition of mitochondrial fission by treatments with a DRP1 inhibitor, mdivi-1, or with DRP1-targeted siRNA, efficiently prevented UVB-induced NLRP3/cGAS-STING mediated pro-inflammatory pathways or apoptosis in the HaCaT cells, whereas inhibition of mitochondrial fusion with MFN1and 2 siRNA increased these pro-inflammatory pathways or apoptosis. The enhanced mitochondrial fission and reduced fusion caused the up-regulation of reactive oxygen species (ROS). Application of an antioxidant, N-acetyl-l-cysteine (NAC), which scavenges excessive ROS, attenuated inflammatory responses through suppressing NLRP3 inflammasome and cGAS-STING pathway activation, and rescued cells from apoptosis caused by UVB-irradiation. Together, our findings revealed the regulation of NLRP3/cGAS-STING inflammatory pathways and apoptosis by mitochondrial fission/fusion dynamics in UVB-irradiated HaCaT cells, providing a new strategy for the therapy of UVB skin injury.

Cytosolic Release of Mitochondrial DNA and Associated cGAS Signaling Mediates Radiation-Induced Hematopoietic Injury of Mice

Mitochondrion is an important organelle of eukaryotic cells and a critical target of ionizing radiation (IR) outside the nucleus. The biological significance and mechanism of the non-target effect originating from mitochondria have received much attention in the field of radiation biology and protection. In this study, we investigated the effect, role, and radioprotective significance of cytosolic mitochondrial DNA (mtDNA) and its associated cGAS signaling on hematopoietic injury induced by IR in vitro culture cells and in vivo total body irradiated mice in this study. The results demonstrated that γ-ray exposure increases the release of mtDNA into the cytosol to activate cGAS signaling pathway, and the voltage-dependent anion channel (VDAC) may contribute to IR-induced mtDNA release. VDAC1 inhibitor DIDS and cGAS synthetase inhibitor can alleviate bone marrow injury and ameliorate hematopoietic suppression induced by IR via protecting hematopoietic stem cells and adjusting subtype distribution of bone marrow cells, such as attenuating the increase of the F4/80⁺ macrophage proportion in bone marrow cells. The present study provides a new mechanistic explanation for the radiation non-target effect and an alternative technical strategy for the prevention and treatment of hematopoietic acute radiation syndrome.

Association of mitochondrial homeostasis and dynamic balance with malignant biological behaviors of gastrointestinal cancer

Mitochondria determine the physiological status of most eukaryotes. Mitochondrial dynamics plays an important role in maintaining mitochondrial homeostasis, and the disorder in mitochondrial dynamics could affect cellular energy metabolism leading to tumorigenesis. In recent years, disrupted mitochondrial dynamics has been found to influence the biological behaviors of gastrointestinal cancer with the potential to be a novel target for its individualized therapy. This review systematically introduced the role of mitochondrial dynamics in maintaining mitochondrial homeostasis, and further elaborated the effects of disrupted mitochondrial dynamics on the cellular biological behaviors of gastrointestinal cancer as well as its association with cancer progression. We aim to provide clues for elucidating the etiology and pathogenesis of gastrointestinal cancer from the perspective of mitochondrial homeostasis and disorder.

The cyclic guanosine monophosphate synthase-stimulator of interferon genes pathway as a potential target for tumor immunotherapy

Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) detects infections or tissue damage by binding to microbial or self-DNA in the cytoplasm. Upon binding DNA, cGAS produces cGAMP that binds to and activates the adaptor protein stimulator of interferon genes (STING), which then activates the kinases IKK and TBK1 to induce the secretion of interferons and other cytokines. Recently, a series of studies demonstrated that the cGAS-STING pathway, a vital component of host innate immunity, might play an important role in anticancer immunity, though its mechanism remains to be elucidated. In this review, we highlight the latest understanding of the cGAS-STING pathway in tumor development and the advances in combination therapy of STING agonists and immunotherapy.

Mitochondrial quality control mechanisms as molecular targets in diabetic heart

Mitochondrial dysfunction has been regarded as a hallmark of diabetic cardiomyopathy. In addition to their canonical metabolic actions, mitochondria influence various other aspects of cardiomyocyte function, including oxidative stress, iron regulation, metabolic reprogramming, intracellular signaling transduction and cell death. These effects depend on the mitochondrial quality control (MQC) system, which includes mitochondrial dynamics, mitophagy and mitochondrial biogenesis. Mitochondria are not static entities, but dynamic units that undergo fission and fusion cycles to maintain their structural integrity. Increased mitochondrial fission elevates the number of mitochondria within cardiomyocytes, a necessary step for cardiomyocyte metabolism. Enhanced mitochondrial fusion promotes communication and cooperation between pairs of mitochondria, thus facilitating mitochondrial genomic repair and maintenance. On the contrary, erroneous fission or reduced fusion promotes the formation of mitochondrial fragments that contain damaged mitochondrial DNA and exhibit impaired oxidative phosphorylation. Under normal/physiological conditions, injured mitochondria can undergo mitophagy, a degradative process that delivers poorly structured mitochondria to lysosomes. However, defective mitophagy promotes the accumulation of nonfunctional mitochondria, which may induce cardiomyocyte death. A decline in the mitochondrial population due to mitophagy can stimulate mitochondrial biogenesis), which generates new mitochondrial offspring to maintain an adequate mitochondrial number. Energy crises or ATP deficiency also increase mitochondrial biogenesis, because mitochondrial DNA encodes 13 subunits of the electron transport chain (ETC) complexes. Disrupted mitochondrial biogenesis diminishes the mitochondrial mass, accelerates mitochondrial senescence and promotes mitochondrial dysfunction. In this review, we describe the involvement of MQC in the pathogenesis of diabetic cardiomyopathy. Besides, the potential targeted therapies that could be applied to improve MQC during diabetic cardiomyopathy are also discussed and accelerate the development of cardioprotective drugs for diabetic patients.

Mitochondrial oxidative stress in the tumor microenvironment and cancer immunoescape: foe or friend?

The major concept of "oxidative stress" is an excess elevated level of reactive oxygen species (ROS) which are generated from vigorous metabolism and consumption of oxygen. The precise harmonization of oxidative stresses between mitochondria and other organelles in the cell is absolutely vital to cell survival. Under oxidative stress, ROS produced from mitochondria and are the major mediator for tumorigenesis in different aspects, such as proliferation, migration/invasion, angiogenesis, inflammation, and immunoescape to allow cancer cells to adapt to the rigorous environment. Accordingly, the dynamic balance of oxidative stresses not only orchestrate complex cell signaling events in cancer cells but also affect other components in the tumor microenvironment (TME). Immune cells, such as M2 macrophages, dendritic cells, and T cells are the major components of the immunosuppressive TME from the ROS-induced inflammation. Based on this notion, numerous strategies to mitigate oxidative stresses in tumors have been tested for cancer prevention or therapies; however, these manipulations are devised from different sources and mechanisms without established effectiveness. Herein, we integrate current progress regarding the impact of mitochondrial ROS in the TME, not only in cancer cells but also in immune cells, and discuss the combination of emerging ROS-modulating strategies with immunotherapies to achieve antitumor effects.