Effect of 23‑hydroxybetulinic acid on lung adenocarcinoma and its mechanism of action

The present study aimed to investigate the effect and mechanism of Pulsatilla compounds on lung adenocarcinoma. The representative drug chosen was the compound 23-HBA. GeneCards, Swiss target prediction, DisGeNET and TCMSP were used to screen out related genes, and MTT and flow cytometry assays were used to verify the inhibitory effect of Pulsatilla compounds on the proliferation of lung adenocarcinoma cells. Subsequently, the optimal target, peroxisome proliferator-activated receptor (PPAR)-γ, was selected using bioinformatics analysis, and its properties of low expression in lung adenocarcinoma cells and its role as a tumor suppressor gene were verified by western blot assay. The pathways related to immunity and inflammation, vascular function, cell proliferation, differentiation, development and apoptosis with the highest degree of enrichment and the mechanisms were explored through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Finally, the clinical prognosis in terms of the survival rate of patients in whom the drug is acting on the target was analyzed using the GEPIA database. The results indicated that Pulsatilla compounds can inhibit the proliferation of lung adenocarcinoma cells by blocking the cell cycle at the G1 phase. Subsequently, the related PPAR-γ gene was verified as a tumor suppressor gene. Further analysis demonstrated that this finding was related to the PPAR signaling pathway and mitochondrial reactive oxygen species (ROS) production. Finally, the clinical prognosis was found to be improved, as the survival rate of patients was increased. In conclusion, Pulsatilla compounds were indicated to inhibit the viability and proliferation of lung adenocarcinoma H1299 cells, and the mechanism of action was related to PPAR-γ, the PPAR signaling pathway and mitochondrial ROS. The present study provides novel insight to further explore the treatment of lung adenocarcinoma.

Homocysteine-induced sustained GluN2A NMDA receptor stimulation leads to mitochondrial ROS generation and neurotoxicity

Homocysteine, a sulfur-containing amino acid derived from methionine metabolism, is a known agonist of N-methyl-D-aspartate receptor (NMDAR) and is involved in neurotoxicity. Our previous findings showed that neuronal exposure to elevated homocysteine levels leads to sustained low-level increase in intracellular Ca2+, which is dependent on GluN2A subunit-containing NMDAR (GluN2A-NMDAR) stimulation. These studies further showed a role of ERK MAPK in homocysteine-GluN2A-NMDAR mediated neuronal death. However, the intracellular mechanisms associated with such sustained GluN2A-NMDAR stimulation and subsequent Ca2+ influx have remained unexplored. Using live cell imaging with Fluo3-AM and biochemical approaches, we show that homocysteine-GluN2A NMDAR induced initial Ca2+ influx triggers sequential phosphorylation and subsequent activation of Pyk2 and Src family kinases (SFK), which in turn phosphorylates GluN2A-Tyr1325 residue of GluN2A-NMDARs to maintain channel activity. The continuity of this cycle of events leads to sustained Ca2+ influx through GluN2A-NMDAR. Our findings also show that lack of activation of the regulatory tyrosine phosphatase STEP, which can limit Pyk2 and SFK activity further contributes to the maintenance of this cycle. Additional studies using live cell imaging of neurons expressing a redox sensitive green fluorescent protein (RoGFP) targeted to the mitochondrial matrix show that treatment with homocysteine leads to a progressive increase in mitochondrial reactive oxygen species (ROS) generation, which is dependent on GluN2A-NMDAR mediated sustained ERK MAPK activation. This later finding demonstrates a novel role of GluN2A-NMDAR in homocysteine-induced mitochondrial ROS generation and highlights the role of ERK MAPK as the intermediary signaling pathway between GluN2A-NMDAR stimulation and mitochondrial ROS generation.

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

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

Mitochondrial protein and organelle quality control-Lessons from budding yeast

Mitochondria are essential for normal cellular function and have emerged as key aging determinants. Indeed, defects in mitochondrial function have been linked to cardiovascular, skeletal muscle and neurodegenerative diseases, premature aging, and age-linked diseases. Here, we describe mechanisms for mitochondrial protein and organelle quality control. These surveillance mechanisms mediate repair or degradation of damaged or mistargeted mitochondrial proteins, segregate mitochondria based on their functional state during asymmetric cell division, and modulate cellular fitness, the response to stress, and lifespan control in yeast and other eukaryotes.

Age-Dependent Changes in the Production of Mitochondrial Reactive Oxygen Species in Human Skeletal Muscle

A decrease in muscle mass and its functionality (strength, endurance, and insulin sensitivity) is one of the integral signs of aging. One of the triggers of aging is an increase in the production of mitochondrial reactive oxygen species. Our study was the first to examine age-dependent changes in the production of mitochondrial reactive oxygen species related to a decrease in the proportion of mitochondria-associated hexokinase-2 in human skeletal muscle. For this purpose, a biopsy was taken from m. vastus lateralis in 10 young healthy volunteers and 70 patients (26-85 years old) with long-term primary arthrosis of the knee/hip joint. It turned out that aging (comparing different groups of patients), in contrast to inactivity/chronic inflammation (comparing young healthy people and young patients), causes a pronounced increase in peroxide production by isolated mitochondria. This correlated with the age-dependent distribution of hexokinase-2 between mitochondrial and cytosolic fractions, a decrease in the rate of coupled respiration of isolated mitochondria and respiration when stimulated with glucose (a hexokinase substrate). It is discussed that these changes may be caused by an age-dependent decrease in the content of cardiolipin, a potential regulator of the mitochondrial microcompartment containing hexokinase. The results obtained contribute to a deeper understanding of age-related pathogenetic processes in skeletal muscles and open prospects for the search for pharmacological/physiological approaches to the correction of these pathologies.

Acute high-dose MitoQ does not increase urinary kidney injury markers in healthy adults: a randomized crossover trial

Several human studies have used the mitochondrial antioxidant MitoQ. Recent in vitro data indicating that MitoQ may induce nephrotoxicity caused concern regarding the safety of MitoQ on the kidneys, but the doses were supraphysiological. Therefore, we sought to determine whether acute MitoQ elicits changes in urinary biomarkers associated with tubular injury in healthy adults with our hypothesis being there would be no changes. Using a randomized crossover design, 32 healthy adults (16 females and 16 males, 29 ± 11 yr old) consumed MitoQ (100-160 mg based on body mass) or placebo capsules. We obtained serum samples and a 4- to 6-h postcapsule consumption urine sample. We assessed creatinine clearance and urine kidney injury biomarkers including the chitinase 3-like-1 gene product YKL-40, kidney-injury marker-1, monocyte chemoattractant protein-1, epidermal growth factor, neutrophil gelatinase-associated lipocalin, interleukin-18, and uromodulin using multiplex assays. We used t tests, Wilcoxon tests, and Hotelling's T2 to assess global differences in urinary kidney injury markers between conditions. Acute MitoQ supplementation did not influence urine flow rate (P = 0.086, rrb = 0.39), creatinine clearance (P = 0.085, rrb = 0.42), or urinary kidney injury markers (T22,8 = 30.6, P = 0.121, univariate ps > 0.064). Using exploratory univariate analysis, MitoQ did not alter individual injury markers compared with placebo (e.g., placebo vs. MitoQ: YKL-40, 507 ± 241 vs. 442 ± 236 pg/min, P = 0.241; kidney injury molecule-1, 84.1 ± 43.2 vs. 76.2 ± 51.2 pg/min, P = 0.890; and neutrophil gelatinase-associated lipocalin, 10.8 ± 10.1 vs. 9.83 ± 8.06 ng/min, P = 0.609). In conclusion, although longer-term surveillance and data are needed in clinical populations, our findings suggest that acute high-dose MitoQ had no effect on urinary kidney injury markers in healthy adults.NEW & NOTEWORTHY We found acute high-dose mitochondria-targeted antioxidant (MitoQ) supplementation was not nephrotoxic and had no effect on markers of acute kidney injury in healthy adults. These findings can help bolster further confidence in the safety of MitoQ, particularly for future investigations seeking to examine the role of mitochondrial oxidative stress, via acute MitoQ supplementation, on various physiological outcomes.

IGFBP1 Sustains Cell Survival during Spatially-Confined Migration and Promotes Tumor Metastasis

Cell migration is a pivotal step in metastatic process, which requires cancer cells to navigate a complex spatially-confined environment, including tracks within blood vessels and in the vasculature of target organs. Here it is shown that during spatially-confined migration, the expression of insulin-like growth factor-binding protein 1 (IGFBP1) is upregulated in tumor cells. Secreted IGFBP1 inhibits AKT1-mediated phosphorylation of mitochondrial superoxide dismutase (SOD2) serine (S) 27 and enhances SOD2 activity. Enhanced SOD2 attenuates mitochondrial reactive oxygen species (ROS) accumulation in confined cells, which supports tumor cell survival in blood vessels of lung tissues, thereby accelerating tumor metastasis in mice. The levels of blood IGFBP1 correlate with metastatic recurrence of lung cancer patients. This finding reveals a unique mechanism by which IGFBP1 sustains cell survival during confined migration by enhancing mitochondrial ROS detoxification, thereby promoting tumor metastasis.

Cocoa Polyphenol Extract Inhibits Cellular Senescence via Modulation of SIRT1 and SIRT3 in Auditory Cells

Cocoa, rich in polyphenols, has been reported to provide many health benefits due to its antioxidant properties. In this study, we investigated the effect of Cocoa polyphenols extract (CPE) against oxidative stress-induced cellular senescence using a hydrogen peroxide (H₂O₂)-induced cellular senescence model in three auditory cells lines derived from the auditory organ of a transgenic mouse: House Ear Institute-Organ of Corti 1 (HEI-OC1), Organ of Corti-3 (OC-k3), and Stria Vascularis (SV-k1) cells. Our results showed that CPE attenuated senescent phenotypes, including senescence-associated β-galactosidase expression, cell proliferation, alterations of morphology, oxidative DNA damage, mitochondrial dysfunction by inhibiting mitochondrial reactive oxygen species (mtROS) generation, and related molecules expressions such as forkhead box O3 (FOXO3) and p53. In addition, we determined that CPE induces expression of sirtuin 1 (SIRT1) and sirtuin 3 (SIRT3), and it has a protective role against cellular senescence by upregulation of SIRT1 and SIRT3. These data indicate that CPE protects against senescence through SIRT1, SIRT3, FOXO3, and p53 in auditory cells. In conclusion, these results suggest that Cocoa has therapeutic potential against age-related hearing loss (ARHL).

Stress Granules Inhibit Coxsackievirus B3-Mediated Cell Death via Reduction of Mitochondrial Reactive Oxygen Species and Viral Extracellular Release

Stress granules (SGs) are cytoplasmic aggregates of RNA-protein complexes that form in response to various cellular stresses and are known to restrict viral access to host translational machinery. However, the underlying molecular mechanisms of SGs during viral infections require further exploration. In this study, we evaluated the effect of SG formation on cellular responses to coxsackievirus B3 (CVB3) infection. Sodium arsenite (AS)-mediated SG formation suppressed cell death induced by tumor necrosis factor-alpha (TNF-a)/cycloheximide (CHX) treatment in HeLa cells, during which G3BP1, an essential SG component, contributed to the modulation of apoptosis pathways. SG formation in response to AS treatment blocked CVB3-mediated cell death, possibly via the reduction of mitochondrial reactive oxygen species. Furthermore, we examined whether AS treatment would affect small extracellular vesicle (sEV) formation and secretion during CVB3 infection and modulate human monocytic cell (THP-1) response. CVB3-enriched sEVs isolated from HeLa cells were able to infect and replicate THP-1 cells without causing cytotoxicity. Interestingly, sEVs from AS-treated HeLa cells inhibited CVB3 replication in THP-1 cells. These findings suggest that SG formation during CVB3 infection modulates cellular response by inhibiting the release of CVB3-enriched sEVs.

Inhibition of mitochondrial reactive oxygen species improves coronary endothelial function after cardioplegic hypoxia/reoxygenation

OBJECTIVE

Cardioplegic ischemia-reperfusion and diabetes mellitus are correlated with coronary endothelial dysfunction and inactivation of small conductance calcium-activated potassium channels. Increased reactive oxidative species, such as mitochondrial reactive oxidative species, may contribute to oxidative injury. Thus, we hypothesized that inhibition of mitochondrial reactive oxidative species may protect coronary small conductance calcium-activated potassium channels and endothelial function against cardioplegic ischemia-reperfusion-induced injury.

METHODS

Small coronary arteries and endothelial cells from the hearts of mice with and without diabetes mellitus were isolated and examined by using a cardioplegic hypoxia and reoxygenation model to determine whether the mitochondria-targeted antioxidant Mito-Tempo could protect against coronary endothelial and small conductance calcium-activated potassium channel dysfunction. The microvessels or mouse heart endothelial cells were treated with or without Mito-Tempo (0-10 μM) 5 minutes before and during cardioplegic hypoxia and reoxygenation. Microvascular function was assessed in vitro by vessel myography. K+ currents of mouse heart endothelial cells were measured by whole-cell patch clamp. The levels of intracellular cytosolic free calcium (Ca2+) concentration, mitochondrial reactive oxidative species, and small conductance calcium-activated potassium protein expression of mouse heart endothelial cells were measured by Rhod-2 fluorescence staining, MitoSox, and Western blotting, respectively.

RESULTS

Cardioplegic hypoxia and reoxygenation significantly attenuated endothelial small conductance calcium-activated potassium channel activity, caused calcium overload, and increased mitochondrial reactive oxidative species of mouse heart endothelial cells in both the nondiabetic and diabetes mellitus groups. In addition, treating mouse heart endothelial cells with Mito-Tempo (10 μM) reduced cardioplegic hypoxia and reoxygenation-induced Ca2+ and mitochondrial reactive oxidative species overload in both the nondiabetic and diabetes mellitus groups, respectively (P < .05). Treatment with Mito-Tempo (10 μM) significantly enhanced coronary relaxation responses to adenosine 5'-diphosphate and NS309 (P < .05), and endothelial small conductance calcium-activated potassium channel currents in both the nondiabetic and diabetes mellitus groups (P < .05).

CONCLUSIONS

Administration of Mito-Tempo improves endothelial function and small conductance calcium-activated potassium channel activity, which may contribute to its enhancement of endothelium-dependent vasorelaxation after cardioplegic hypoxia and reoxygenation.

Hif-1a suppresses ROS-induced proliferation of cardiac fibroblasts following myocardial infarction

We report that cardiac fibroblasts (CFs) and mesenchymal progenitors are more hypoxic than other cardiac interstitial populations, express more hypoxia-inducible factor 1α (HIF-1α), and exhibit increased glycolytic metabolism. CF-specific deletion of Hif-1a resulted in decreased HIF-1 target gene expression and increased mesenchymal progenitors in uninjured hearts and increased CF activation without proliferation following sham injury, as demonstrated using single-cell RNA sequencing (scRNA-seq). After myocardial infarction (MI), however, there was ∼50% increased CF proliferation and excessive scarring and contractile dysfunction, a scenario replicated in 3D engineered cardiac microtissues. CF proliferation was associated with higher reactive oxygen species (ROS) as occurred also in wild-type mice treated with the mitochondrial ROS generator MitoParaquat (MitoPQ). The mitochondrial-targeted antioxidant MitoTEMPO rescued Hif-1a mutant phenotypes. Thus, HIF-1α in CFs provides a critical braking mechanism against excessive post-ischemic CF activation and proliferation through regulation of mitochondrial ROS. CFs are potential cellular targets for designer antioxidant therapies in cardiovascular disease.

MCU overexpression evokes disparate dose-dependent effects on mito-ROS and spontaneous Ca2+ release in hypertrophic rat cardiomyocytes

Cardiac dysfunction in heart failure (HF) and diabetic cardiomyopathy (DCM) is associated with aberrant intracellular Ca2+ handling and impaired mitochondrial function accompanied with reduced mitochondrial calcium concentration (mito-[Ca2+]). Pharmacological or genetic facilitation of mito-Ca2+ uptake was shown to restore Ca2+ transient amplitude in DCM and HF, improving contractility. However, recent reports suggest that pharmacological enhancement of mito-Ca2+ uptake can exacerbate ryanodine receptor-mediated spontaneous sarcoplasmic reticulum (SR) Ca2+ release in ventricular myocytes (VMs) from diseased animals, increasing propensity to stress-induced ventricular tachyarrhythmia. To test whether chronic recovery of mito-[Ca2+] restores systolic Ca2+ release without adverse effects in diastole, we overexpressed mitochondrial Ca2+ uniporter (MCU) in VMs from male rat hearts with hypertrophy induced by thoracic aortic banding (TAB). Measurement of mito-[Ca2+] using genetic probe mtRCamp1h revealed that mito-[Ca2+] in TAB VMs paced at 2 Hz under β-adrenergic stimulation is lower compared with shams. Adenoviral 2.5-fold MCU overexpression in TAB VMs fully restored mito-[Ca2+]. However, it failed to improve cytosolic Ca2+ handling and reduce proarrhythmic spontaneous Ca2+ waves. Furthermore, mitochondrial-targeted genetic probes MLS-HyPer7 and OMM-HyPer revealed a significant increase in emission of reactive oxygen species (ROS) in TAB VMs with 2.5-fold MCU overexpression. Conversely, 1.5-fold MCU overexpression in TABs, that led to partial restoration of mito-[Ca2+], reduced mitochondria-derived reactive oxygen species (mito-ROS) and spontaneous Ca2+ waves. Our findings emphasize the key role of elevated mito-ROS in disease-related proarrhythmic Ca2+ mishandling. These data establish nonlinear mito-[Ca2+]/mito-ROS relationship, whereby partial restoration of mito-[Ca2+] in diseased VMs is protective, whereas further enhancement of MCU-mediated Ca2+ uptake exacerbates damaging mito-ROS emission.NEW & NOTEWORTHY Defective intracellular Ca2+ homeostasis and aberrant mitochondrial function are common features in cardiac disease. Here, we directly compared potential benefits of mito-ROS scavenging and restoration of mito-Ca2+ uptake by overexpressing MCU in ventricular myocytes from hypertrophic rat hearts. Experiments using novel mito-ROS and Ca2+ biosensors demonstrated that mito-ROS scavenging rescued both cytosolic and mito-Ca2+ homeostasis, whereas moderate and high MCU overexpression demonstrated disparate effects on mito-ROS emission, with only a moderate increase in MCU being beneficial.

The Cytotoxicity of Doxorubicin Can Be Accelerated by a Combination of Hyperthermia and 5-Aminolevulinic Acid

Chemotherapy is cytotoxic to various cancer cells and as well as normal cells. Thus, treatments that demonstrate selective cytotoxicity for cancer cells are desired. The combination of chemotherapy and other cancer therapies can show synergic cytotoxicity, which may be a clue to the nature of the involved cancer cellar-specific damage. We previously reported a phenomenon whereby mitochondrial reactive oxygen species (mitROS) regulate the expression transporters involved in anticancer drug transport and mitROS production is increased by hyperthermia. Moreover, the uptake of 5-aminolevulinic acid (ALA) was enhanced by the increase in mitROS production. In this study, we investigated whether the combination of hyperthermia and ALA can enhance the cytotoxicity of doxorubicin. MitROS production and ALA-derived porphyrin accumulation by hyperthermia (HT) were increased in a murine breast cancer cell line. The expression of solute carrier 15A1 (SLC15A1) upregulated and an ATP-binding cassette subfamily G member 2 (ABCG2) downregulated by HT. Since SLC15A1 is an accumulating transporter for ALA, while ABCG2 is a porphyrin efflux transporter, porphyrin accumulation was enhanced. ABCG2 is also a doxorubicin efflux transporter. Thus, ALA treatment accelerates the intracellular concentration of porphyrin, which acts as a competitive inhibitor of doxorubicin. Indeed, the amount of intracellular doxorubicin was increased by a combination of HT and ALA. The cytotoxicity of doxorubicin was also enhanced. This enhancement was observed in the human breast cancer cell line while it was not seen in normal cells. The combination of HT and ALA treatment can enhance the cancer-specific cytotoxicity of doxorubicin.

Dabigatran Etexilate Induces Cytotoxicity in Rat Gastric Epithelial Cell Line via Mitochondrial Reactive Oxygen Species Production

Dabigatran is a novel oral anticoagulant that directly inhibits free and fibrin-bound thrombins and exerts rapid and predictable anticoagulant effects. While the use of this reagent has been associated with an increased risk of gastrointestinal bleeding, the reason why dabigatran use increases gastrointestinal bleeding risk remains unknown. We investigated the cytotoxicity of dabigatran etexilate and tartaric acid, the two primary components of dabigatran. The cytotoxicity of dabigatran etexilate and tartaric acid was measured in a cell viability assay. Intracellular mitochondrial reactive oxygen species (mitROS) production and lipid peroxidation were measured using fluorescence dyes. Cell membrane viscosity was measured using atomic force microscopy. The potential of ascorbic acid as an inhibitor of dabigatran cytotoxicity was also evaluated. The cytotoxicity of dabigatran etexilate was higher than that of tartaric acid. Dabigatran etexilate induced mitROS production and lipid peroxidation and altered the cell membrane viscosity. Ascorbic acid inhibited the cytotoxicity and mitROS production induced by dabigatran etexilate. Therefore, we attributed the cytotoxicity of dabigatran to dabigatran etexilate, and proposed that the cytotoxic effects of dabigatran etexilate are mediated via mitROS production. Additionally, we demonstrated that dabigatran cytotoxicity can be prevented via antioxidant treatment.

Mitochondrial reactive oxygen species scavenging attenuates thrombus formation in a murine model of sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is characterized by hemolysis-associated platelet dysfunction that leads to increased risk of thrombosis and plays a role in the high morbidity and mortality of the disease. The mechanisms by which hemolysis induces platelet activation remain unclear. We recently demonstrated that patients with SCD showed increased platelet mitochondrial reactive oxygen species (mtROS) production that correlates with markers of hemolysis and platelet activation. Experiments in isolated platelets demonstrated that mtROS stimulated platelet activation. However, the role of hemolysis-induced mtROS in thrombus formation in vivo remains unclear.

OBJECTIVES

Here, we hypothesize that scavenging of mtROS attenuates the propensity for thrombosis in mouse models of hemolysis.

METHODS

We used models of hemolysate infusion into wildtype mice as well as the Berkley transgenic mouse model of SCD, a chronic mode of hemolysis, to test the effect of hemolysis on platelet mtROS production and thrombosis.

RESULTS

We show that infusion of hemolysate in wildtype mice induces platelet mtROS production and decreases time to vessel occlusion in a model of ferric chloride-induced carotid artery thrombosis. Increased mtROS and propensity for thrombosis was also observed in the Berkley transgenic mouse model of SCD. Notably, treatment with mtROS scavengers decreased platelet mtROS levels and attenuated the propensity for thrombus formation in both models.

CONCLUSIONS

These data demonstrate that mtROS significantly contribute to the mechanism of hemolysis-induced thrombosis in vivo and suggest a potential role for mitochondrially targeted antioxidant therapy in hemolysis and SCD-related thrombosis.

[Inhibition of mitochondrial reactive oxygen species reduces high glucose-induced pyroptosis and ferroptosis in H9C2 cardiac myocytes]

OBJECTIVE

To observe the effect of inhibiting mitochondrial oxidative stress and NLRP3 inflammasomes on high glucose (HG)-induced pyroptosis and ferroptosis in H9C2 cardiac muscle cells and explore the possible interactions between mitochondrial reactive oxygen species (ROS) and inflammasomes.

METHODS

H9C2 cells exposed to high glucose (35 mmol/L) were treated with the mitochondrial antioxidant mitoquinone (MitoQ), the NLRP3 antagonist MCC950, or both MCC950 and rotenone (a mitochondrial electron transport antagonist), and the cell viability was measured with CCK-8 assay. The cellular and mitochondrial ROS levels were measured using CellRox and Mitosox fluorescent probes, respectively. The cellular NLRP3 inflammasome level was detected with immunofluorescence assay, and the expressions of the key proteins related with pyroptosis and ferroptosis were determined with Western blotting.

RESULTS

HG exposure significantly lowered the viability of H9C2 cells (P < 0.01), reduced the expression of GPX4 protein (a key protein related with ferroptosis) (P < 0.01), and increased the fluorescence intensities of NLRP3 (P < 0.01) and ROS (at both the cellular and mitochondrial levels, P < 0.01) and the protein expressions of NLRP3 and GSDMD-NT (P < 0.01). Treatment with either MitoQ or MCC950 significantly increased the viability of HG-exposed cells (P < 0.01), increased GPX4 expression (P < 0.01), and reduced the fluorescence intensities of NLRP3 (P < 0.01) and cellular and mitochondrial ROS (P < 0.01) and the protein expressions of NLRP3 and GSDMD-NT (P < 0.05). Compared with MCC950 treatment, treatment with both MCC950 and rotenone significantly reduced the viability of HG-exposed cells (P < 0.01), lowered GPX4 expression (P < 0.01), and increased the fluorescence intensities of ROS and NLRP3 (P < 0.01) and the protein levels of NLRP3 and GSDMD-NT (P < 0.05).

CONCLUSION

MitoQ inhibits mitochondrial ROS production to reduce HGinduced NLRP3 inflammasome activation and thus suppress pyroptosis and ferroptosis of cardiac muscle cells. There may be an interaction between mitochondrial ROS and NLRP3 inflammasomes.

Sirtuin 3 is essential for host defense against Mycobacterium abscessus infection through regulation of mitochondrial homeostasis

The global incidence of Mycobacterium abscessus (Mabc), a rapidly growing nontuberculous mycobacterial strain that causes treatment-refractory pulmonary diseases, is increasing. Despite this, the host factors that allow for protection against infection are largely unknown. In this study, we found that sirtuin 3 (SIRT3), a mitochondrial protein deacetylase, plays a critical role in host defense against Mabc infection. Mabc decreased SIRT3 and upregulated mitochondrial oxidative stress in macrophages. SIRT3 deficiency led to increased bacterial loads, histopathological, and mitochondrial damage, and pathological inflammation during Mabc infection. Administration of scavengers of mitochondrial reactive oxygen species significantly decreased the in vivo Mabc burden and excessive inflammation, and induced SIRT3 expression in infected lungs. Notably, SIRT3 agonist (resveratrol) significantly decreased Mabc growth and attenuated inflammation in mice and zebrafishes, indicating the key role for SIRT3 in metazoan host defense. Collectively, these data strongly suggest that SIRT3 is a host-directed therapeutic target against Mabc infection by controlling mitochondrial homeostasis.

Doxorubicin-Induced Fetal Mesangial Cell Death Occurs Independently of TRPC6 Channel Upregulation but Involves Mitochondrial Generation of Reactive Oxygen Species

Doxorubicin (DOX), a category D pregnancy drug, is a chemotherapeutic agent that has been shown in animal studies to induce fetal toxicity, including renal abnormalities. Upregulation of the transient receptor potential cation (TRPC) 6 channel is involved in DOX-induced podocyte apoptosis. We have previously reported that TRPC6-mediated Ca²⁺ signaling promotes neonatal glomerular mesangial cell (GMC) death. However, it is unknown whether DOX alters mesangial TRPC expression or viability in the fetus. In this study, cell growth was tracked in control and DOX-treated primary GMCs derived from fetal pigs. Live-cell imaging demonstrated that exposure to DOX inhibited the proliferation of fetal pig GMCs and induced cell death. DOX did not alter the TRPC3 expression levels. By contrast, TRPC6 protein expression in the cells was markedly reduced by DOX. DOX treatment also attenuated the TRPC6-mediated intracellular Ca²⁺ elevation. DOX stimulated mitochondrial reactive oxygen species (mtROS) generation and mitophagy by the GMCs. The DOX-induced mtROS generation and apoptosis were reversed by the mitochondria-targeted antioxidant mitoquinone. These data suggest that DOX-induced fetal pig GMC apoptosis is independent of TRPC6 channel upregulation but requires mtROS production. The mtROS-dependent GMC death may contribute to DOX-induced fetal nephrotoxicity when administered prenatally.

MCU-Dependent mROS Generation Regulates Cell Metabolism and Cell Death Modulated by the AMPK/PGC-1α/SIRT3 Signaling Pathway

The mitochondrial calcium uniporter is an intensively investigated calcium channel, and its molecular components, structural features, and encoded genes have long been explored. Further studies have shown that the mitochondrial calcium unidirectional transporter (MCU) is a macromolecular complex related to intracellular and extracellular calcium regulation. Based on the current understanding, the MCU is crucial for maintaining cytosolic Ca²⁺ (cCa²⁺) homeostasis by modulating mitochondrial Ca²⁺ (mCa²⁺) uptake. The elevation of MCU-induced calcium levels is confirmed to be the main cause of mitochondrial reactive oxygen species (mROS) generation, which leads to disordered cellular metabolic patterns and cell death. In particular, in an I/R injury model, cancer cells, and adipocytes, MCU expression is maintained at high levels. As is well accepted, the AMPK/PGC-1α/SIRT3 pathway is believed to have an affinity for mROS formation and energy consumption. Therefore, we identified a link between MCU-related mROS formation and the AMPK/PGC-1α/SIRT3 signaling pathway in controlling cell metabolism and cell death, which may provide a new possibility of targeting the MCU to reverse relevant diseases.

Enhanced IL-1β Release Following NLRP3 and AIM2 Inflammasome Stimulation Is Linked to mtROS in Airway Macrophages in Pulmonary Fibrosis

Fibrotic Interstitial lung diseases (ILDs) are complex disorders of variable clinical behaviour. The majority of them cause significant morbidity, whilst Idiopathic Pulmonary Fibrosis (IPF) is recognised as the most relentless. NLRP3, AIM2, and NLRC4 inflammasomes are multiprotein complexes driving IL-1β release; a proinflammatory and profibrotic cytokine. Several pathogenetic factors associated with IPF are identified as inflammasome activators, including increases in mtROS and bacterial burden. Mitochondrial oxidation and alterations in bacterial burden in IPF and other ILDs may lead to augmented inflammasome activity in airway macrophages (AMs). IPF (n=14), non-IPF-ILDs (n=12) patients and healthy subjects (n=12) were prospectively recruited and AMs were isolated from bronchoalveolar lavage. IL-1β release resulting from NLRP3, AIM2 and NLRC4 inflammasomes stimulation in AMs were determined and baseline levels of mitochondrial ROS and microbial burden were also measured. Our results showed that NLRP3 was more inducible in IPF and other ILDs compared to controls. Additionally, following AIM2 activation IL-1β release was significantly higher in IPF compared to controls, whereas similar trends were observed in Non-IPF-ILDs. NLRC4 activation was similar across groups. mtROS was significantly associated with heightened NLRP3 and AIM2 activation, and mitochondrial antioxidant treatment limited inflammasome activation. Importantly, microbial burden was linked to baseline IL-1β release and AIM2 and IL-18 relative expression independently of mtROS. In conclusion, the above findings suggested a link between the overactivation of NLRP3 and AIM2 inflammasomes, driven by mitochondrial oxidation, in the pathogenesis of lung fibrosis while changes in the microbiota may prime the inflammasome in the lungs.

Inhibition of oxidative stress and NLRP3 inflammasome by Saikosaponin-d alleviates acute liver injury in carbon tetrachloride-induced hepatitis in mice

NLRP3 inflammasome activation results in severe liver inflammation and injury. Saikosaponin-d (SSd) possesses anti-inflammatory and hepatoprotective effects. This study aimed to determine the protective effects of SSd on carbon tetrachloride (CCl₄)-induced acute liver injury in mice, and whether oxidative stress and NLRP3 inflammasome activation participate in the process.

The CCl₄ mice model and controls were induced. The mice were treated with SSd at 1, 1.5, or 2.0 mg/kg in a total volume of 100 µl/25 g of body weight. Liver injury was assessed by histopathology. Oxidative stress was determined using mitochondrial superoxide production (MSP), malondialdehyde (MDA) content, and superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities. NLRP3, ASC, and Caspase 1 were determined by real-time PCR and western blot. IL-1β and IL-18 levels were determined by ELISA.

Significantly elevated oxidative stress was induced in the liver by CCl₄, as demonstrated by histopathology and increases of MDA and MSP levels and decreases of SOD, GPx, and CAT activities (all P < 0.01). SSd significantly decreased the MDA and MSP levels and increased the activities of SOD, GPx, and CAT (all P < 0.05). The mRNA expression of NLRP3, ASC, and Caspase 1, and the protein expression of Caspase 1-p10, NLRP3, ASC, IL-1β, and IL-18 were significantly increased after CCl₄ induction (all P < 0.01). These changes were reversed by SSd (all P < 0.05).

Suppression of the oxidative stress and NLRP3 inflammasome activation were involved in SSd-alleviated acute liver injury in CCl₄-induced hepatitis.

Mitochondria-dependent synthetic small-molecule vaccine adjuvants for influenza virus infection

Vaccine adjuvants enhance and prolong pathogen-specific protective immune responses. Recent reports indicate that host factors-such as aging, pregnancy, and genetic polymorphisms-influence efficacies of vaccines adjuvanted with Toll-like receptor (TLR) or known pattern-recognition receptor (PRR) agonists. Although PRR independent adjuvants (e.g., oil-in-water emulsion and saponin) are emerging, these adjuvants induce some local and systemic reactogenicity. Hence, new TLR and PRR-independent adjuvants that provide greater potency alone or in combination without compromising safety are highly desired. Previous cell-based high-throughput screenings yielded a small molecule 81 [N-(4-chloro-2,5-dimethoxyphenyl)-4-ethoxybenzenesulfonamide], which enhanced lipopolysaccharide-induced NF-κB and type I interferon signaling in reporter assays. Here compound 81 activated innate immunity in primary human peripheral blood mononuclear cells and murine bone marrow-derived dendritic cells (BMDCs). The innate immune activation by 81 was independent of TLRs and other PRRs and was significantly reduced in mitochondrial antiviral-signaling protein (MAVS)-deficient BMDCs. Compound 81 activities were mediated by mitochondrial dysfunction as mitophagy inducers and a mitochondria specific antioxidant significantly inhibited cytokine induction by 81. Both compound 81 and a derivative obtained via structure-activity relationship studies, 2F52 [N-benzyl-N-(4-chloro-2,5-dimethoxyphenyl)-4-ethoxybenzenesulfonamide] modestly increased mitochondrial reactive oxygen species and induced the aggregation of MAVS. Neither 81 nor 2F52 injected as adjuvants caused local or systemic toxicity in mice at effective concentrations for vaccination. Furthermore, vaccination with inactivated influenza virus adjuvanted with 2F52 demonstrated protective effects in a murine lethal virus challenge study. As an unconventional and safe adjuvant that does not require known PRRs, compound 2F52 could be a useful addition to vaccines.

Hypoglycemia Induces Mitochondrial Reactive Oxygen Species Production Through Increased Fatty Acid Oxidation and Promotes Retinal Vascular Permeability in Diabetic Mice

Aims: Hypoglycemia is associated with increased reactive oxygen species (ROS) production and vascular events. We have previously reported that low-glucose (LG) conditions induce mitochondrial ROS (mtROS) production in aortic endothelial cells (ECs). However, the mechanism by which hypoglycemia promotes diabetic retinopathy (DR) is unclear. Blood-retinal barrier (BRB) disruption occurs in the early stages of DR. We hypothesized that the mechanisms underlying hypoglycemia-induced DR are associated with BRB breakdown due to mtROS generation during hypoglycemia. Here, we aimed to determine whether hypoglycemia exacerbated mtROS production and induced BRB disruption. Results: We observed that hypoglycemia induced mtROS production by increasing fatty acid oxidation (FAO), which was suppressed by overexpression of mitochondrial-specific manganese superoxide dismutase (MnSOD) in retinal ECs. Furthermore, FAO blockade decreased the hypoglycemia-induced mtROS production. Recurrent hypoglycemia increased albumin leak in diabetic mice retina, which was suppressed in diabetic vascular endothelial cell-specific MnSOD transgenic (eMnSOD-Tg) mice. Pharmacological FAO blockade also reduced mtROS production, reduced vascular endothelial growth factor (VEGF) production during hypoglycemia, and prevented retinal vascular permeability in diabetic mice. MnSOD overexpression or carnitine palmitoyltransferase I (CPT1) blockade suppressed vascular endothelial-cadherin phosphorylation under LG in retinal ECs. Innovation and Conclusion: Reduction of mtROS and VEGF production via pharmacological FAO and/or CPT1 blockade may prevent hypoglycemia-induced worsening of DR.

Mitochondrial ROS control neuronal excitability and cell fate in frontotemporal dementia

INTRODUCTION

The second most common form of early-onset dementia-frontotemporal dementia (FTD)-is often characterized by the aggregation of the microtubule-associated protein tau. Here we studied the mechanism of tau-induced neuronal dysfunction in neurons with the FTD-related 10+16 MAPT mutation.

METHODS

Live imaging, electrophysiology, and redox proteomics were used in 10+16 induced pluripotent stem cell-derived neurons and a model of tau spreading in primary cultures.

RESULTS

Overproduction of mitochondrial reactive oxygen species (ROS) in 10+16 neurons alters the trafficking of specific glutamate receptor subunits via redox regulation. Increased surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors containing GluA1 and NR2B subunits leads to impaired glutamatergic signaling, calcium overload, and excitotoxicity. Mitochondrial antioxidants restore the altered response and prevent neuronal death. Importantly, extracellular 4R tau induces the same pathological response in healthy neurons, thus proposing a mechanism for disease propagation.

DISCUSSION

These results demonstrate mitochondrial ROS modulate glutamatergic signaling in FTD, and suggest a new therapeutic strategy.

Mitochondrial Succinate Metabolism and Reactive Oxygen Species Are Important but Not Essential for Eliciting Carotid Body and Ventilatory Responses to Hypoxia in the Rat

Reflex increases in breathing in response to acute hypoxia are dependent on activation of the carotid body (CB)—A specialised peripheral chemoreceptor. Central to CB O₂-sensing is their unique mitochondria but the link between mitochondrial inhibition and cellular stimulation is unresolved. The objective of this study was to evaluate if ex vivo intact CB nerve activity and in vivo whole body ventilatory responses to hypoxia were modified by alterations in succinate metabolism and mitochondrial ROS (mitoROS) generation in the rat. Application of diethyl succinate (DESucc) caused concentration-dependent increases in chemoafferent frequency measuring approximately 10–30% of that induced by severe hypoxia. Inhibition of mitochondrial succinate metabolism by dimethyl malonate (DMM) evoked basal excitation and attenuated the rise in chemoafferent activity in hypoxia. However, approximately 50% of the response to hypoxia was preserved. MitoTEMPO (MitoT) and 10-(6′-plastoquinonyl) decyltriphenylphosphonium (SKQ1) (mitochondrial antioxidants) decreased chemoafferent activity in hypoxia by approximately 20–50%. In awake animals, MitoT and SKQ1 attenuated the rise in respiratory frequency during hypoxia, and SKQ1 also significantly blunted the overall hypoxic ventilatory response (HVR) by approximately 20%. Thus, whilst the data support a role for succinate and mitoROS in CB and whole body O₂-sensing in the rat, they are not the sole mediators. Treatment of the CB with mitochondrial selective antioxidants may offer a new approach for treating CB-related cardiovascular–respiratory disorders.

The Relationship between Mitochondrial Reactive Oxygen Species Production and Mitochondrial Energetics in Rat Tissues with Different Contents of Reduced Coenzyme Q

We investigated the relationship between mitochondrial production of reactive oxygen species (ROS) and mitochondrial energetics in various rat tissues with different contents of the reduced coenzyme Q (Q) pool (Q9 + Q10). Our results indicate that similar to the tissue level, mitochondrial H₂O₂ release under nonphosphorylating conditions was strongly dependent on the amount of the reduced Q pool. Namely, in brain and lung mitochondria, less H₂O₂ release corresponded to a less reduced Q pool, while in liver and heart mitochondria, higher H₂O₂ release corresponded to a more reduced Q pool. We can conclude that the differences observed in rat tissues in the size of the reduced Q pool reflect different levels of ROS production and hence may reflect different demands for reduced Q as an antioxidant. Moreover, differences in mitochondrial H₂O₂ release were observed in different types of rat mitochondria during the oxidation of succinate (complex II substrate), malate plus glutamate (complex I substrate), and their mixture under phosphorylating and nonphosphorylating conditions. Our results indicate the existence of a tissue-specific maximum respiratory chain capacity in ROS production, possibly related to the membrane potential-mediated control of oxidative phosphorylation. We propose the use of a new parameter for the study of isolated mitochondria, RCR_ROS, the ratio between the formation of mitochondrial ROS under nonphosphorylating and phosphorylating conditions, which represents the maximum factorial increase in mitochondrial ROS formation that can be achieved after all ADP is phosphorylated.

Regulatory effect of mitoQ on the mtROS-NLRP3 inflammasome pathway in leptin-pretreated BEAS-2 cells

Obese asthma is a phenotype of asthma whose occurrence is gradually increasing in both adults and children. The majority of studies have demonstrated that obesity is a major risk factor for asthma and the effect of obesity on the lungs is considerable. NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome has been previously demonstrated to serve a role in obese asthma mediated by mitochondrial reactive oxygen species (mtROS). The aim of the present in vitro study was to investigate the effect of leptin on airway epithelial cells and the protective effect of the mitochondrial-targeted antioxidant mitoquinone (mitoQ). Human normal bronchial epithelial cell lines BEAS-2 cells were used and divided into 6 groups: Control group (negative control), DMSO group (solvent control), lipopolysaccharide (LPS) group (positive control), LPS + mitoQ group, Leptin group and Leptin + mitoQ group. CCK8 assay was used to establish the optimal concentration and incubation time of the drugs. mitoTracker probe and mitoSOX reagent were used to detect the integrity of mitochondrial membranes and the content of mtROS. mRNA expression levels were detected by reverse transcription-quantitative PCR analysis. It was revealed that the mitochondrial membrane was disrupted in the Leptin group, which recovered after treatment with mitoQ. As a result, the production of mitochondrial reactive oxygen species (mtROS) in the Leptin group was significantly increased (P<0.01), but following treatment with mitoQ, this overproduction of mtROS was significantly decreased to normal levels (P<0.01). Furthermore, the expression levels of NOD-, LRR- and pyrin domain-containing protein 3 NLRP3 and caspase-1 mRNA in the leptin-pretreated BEAS-2 cells were significantly increased compared with those in the control group (P<0.01), while they were decreased following mitoQ treatment (P<0.01). Taken together, these data suggested that leptin may promote airway inflammation partially through upregulating the mtROS-NLRP3 inflammasome signaling pathway in airway epithelial cells and mitoQ may be a potential treatment for obese asthma.

Chronic Inhibition of mROS Protects Against Coronary Endothelial Dysfunction in Mice With Diabetes

Diabetes is associated with coronary endothelial dysfunction. Persistent oxidative stress during diabetes contributes to coronary endothelial dysfunction. The mitochondria are main sources of reactive oxygen species (ROS) in diabetes, and mitochondria-targeted antioxidant mito-Tempo can prevent mitochondrial reactive oxygen species (mROS) generation in a variety of disorders. Inhibition/inactivation of small-conductance Ca²⁺-activated K⁺ (SK) channels contribute to diabetic downregulation of coronary endothelial function/relaxation. However, few investigated the role of mROS on endothelial dysfunction/vasodilation and endothelial SK channel downregulation in diabetes. The aim of present study was to investigate the chronic administration of mito-Tempo, on coronary vasodilation, and endothelial SK channel activity of mice with or without diabetes. Mito-Tempo (1 mg/kg/day) was applied to the mice with or without diabetes (n = 10/group) for 4 weeks. In vitro relaxation response of pre-contracted arteries was examined in the presence or absence of the vasodilatory agents. SK channel currents of the isolated mouse heart endothelial cells were measured using whole-cell patch clamp methods. At baseline, coronary endothelium-dependent relaxation responses to ADP and the selective SK channel activator NS309 and endothelial SK channel currents were decreased in diabetic mice compared with that in non-diabetic (ND) mice (p < 0.05). After a 4-week treatment with mito-Tempo, coronary endothelium-dependent relaxation response to ADP or NS309 and endothelial SK channel currents in the diabetic mice was significantly improved when compared with that in untreated diabetic mice (p < 0.05). Interestingly, coronary relaxation responses to ADP and NS309 and endothelial SK channel currents were not significantly changed in ND mice after mito-Tempo treatment, as compared to that of untreated control group. Chronic inhibition of endothelial mROS appears to improve coronary endothelial function/dilation and SK channel activity in diabetes, and mROS inhibitors may be a novel strategy to treat vascular complications in diabetes.

Unique Cellular and Biochemical Features of Human Mitochondrial Peroxiredoxin 3 Establish the Molecular Basis for Its Specific Reaction with Thiostrepton

A central hallmark of tumorigenesis is metabolic alterations that increase mitochondrial reactive oxygen species (mROS). In response, cancer cells upregulate their antioxidant capacity and redox-responsive signaling pathways. A promising chemotherapeutic approach is to increase ROS to levels incompatible with tumor cell survival. Mitochondrial peroxiredoxin 3 (PRX3) plays a significant role in detoxifying hydrogen peroxide (H₂O₂). PRX3 is a molecular target of thiostrepton (TS), a natural product and FDA-approved antibiotic. TS inactivates PRX3 by covalently adducting its two catalytic cysteine residues and crosslinking the homodimer. Using cellular models of malignant mesothelioma, we show here that PRX3 expression and mROS levels in cells correlate with sensitivity to TS and that TS reacts selectively with PRX3 relative to other PRX isoforms. Using recombinant PRXs 1–5, we demonstrate that TS preferentially reacts with a reduced thiolate in the PRX3 dimer at mitochondrial pH. We also show that partially oxidized PRX3 fully dissociates to dimers, while partially oxidized PRX1 and PRX2 remain largely decameric. The ability of TS to react with engineered dimers of PRX1 and PRX2 at mitochondrial pH, but inefficiently with wild-type decameric protein at cytoplasmic pH, supports a novel mechanism of action and explains the specificity of TS for PRX3. Thus, the unique structure and propensity of PRX3 to form dimers contribute to its increased sensitivity to TS-mediated inactivation, making PRX3 a promising target for prooxidant cancer therapy.

SIRT3 deficiency increases mitochondrial oxidative stress and promotes migration of retinal pigment epithelial cells

Retinal pigment epithelial cells are closely associated with the pathogenesis of diabetic retinopathy. The mechanism by which diabetes impacts retinal pigment epithelial cell function is of significant interest. Sirtuins are an important class of proteins that primarily possess nicotinamide adenine dinucleotide-dependent deacetylases activity and involved in various cellular physiological and pathological processes. Here, we aimed to examine the role of sirtuins in the induction of diabetes-associated retinal pigment epithelial cell dysfunction. High glucose and platelet-derived growth factor (PDGF) treatment induced epithelial-mesenchymal transition and the migration of retinal pigment epithelial cells, and decreased sirtuin-3 expression. Sirtuin-3 knockdown using siRNA increased epithelial-mesenchymal transition and migration of retinal pigment epithelial cells. In contrast, sirtuin-3 overexpression attenuated the effects caused by high glucose and PDGF on epithelial-mesenchymal transition and migration of retinal pigment epithelial cells, suggesting that sirtuin-3 deficiency contributed to retinal pigment epithelial cell dysfunction induced by high glucose and PDGF. Mechanistically, sirtuin-3 deficiency induced retinal pigment epithelial cell dysfunction by the overproduction of mitochondrial reactive oxygen species. These results suggest that sirtuin-3 deficiency mediates the migration of retinal pigment epithelial cells, at least partially by increasing mitochondrial oxidative stress, and shed light on the importance of sirtuin-3 and mitochondrial reactive oxygen species as potential targets in diabetic retinopathy therapy.

Regulatory role of DEPTOR‑mediated cellular autophagy and mitochondrial reactive oxygen species in angiogenesis in multiple myeloma

DEPTOR, an inhibitor of mammalian target of rapamycin (mTOR), is essential for the survival of multiple myeloma (MM) cells. The expression level of DEPTOR is closely related to the prognosis of patients with MM treated with the antiangiogenic agent thalidomide; however, its role in the regulation of angiogenesis has not yet been elucidated. In the present study, the expression levels of DEPTOR and vascular endothelial growth factor (VEGF), and the microvessel density (MVD) of bone marrow (BM) from patients with MM assessed. DEPTORoverexpression plasmid or CRISPR-associated protein 9 (Cas9) and single guided RNAs (sgRNAs) were used to modulate DEPTOR expression. The DEPTOR-mediated angiogenic effects were assessed using a tube formation assay of human umbilical vein endothelial cells (HUVECs) cultured in the collected conditioned medium from MM cell lines with different expression levels of DEPTOR. It was found that the expression level of DEPTOR negatively correlated with the VEGF level and BM MVD in MM. Autophagic activity was regulated by DEPTOR expression, but was not related to thalidomide-binding protein CRBN, which is required for thalidomide to play an anti-tumor and antiangiogenic role in MM cells. The disruption of DEPTOR protein decreased cellular autophagy, increased VEGF expression in MM cells, and inhibited the tube formation of HUVECs, while a high expression of DEPTOR exerted the opposite effect. Moreover, targeting DEPTOR also resulted in the production of mitochondrial reactive oxygen species (mtROS), the phosphorylation of nuclear factor-κB (NF-κB) and an increase in interleukin 6 (IL-6) secretion. Of note, these effects are fully abrogated by treatment with autophagy activator (SMER28) or mitochondrial-specific antioxidant (Mito-TEMPO). Taken together, the present study demonstrates the role of DEPTOR in the regulation of autophagy/mtROS and subsequent angiogenesis. The results provide a novel mechanism for the further understanding of the therapeutic effects of thalidomide on MM.

Albanol B from Mulberries Exerts Anti-Cancer Effect through Mitochondria ROS Production in Lung Cancer Cells and Suppresses In Vivo Tumor Growth

Albanol B (ABN-B), an arylbenzofuran derivative isolated from mulberries, has been shown to have anti-Alzheimer’s disease, anti-bacterial and antioxidant activities. The aim of this study was to investigate the anti-cancer effect of this compound against lung cancer cells. The results show that ABN-B inhibited the proliferation of four human lung cancer cell lines (A549, BZR, H1975, and H226) and induced apoptosis, based on the cleavage of caspase-7 and PARP (poly (ADP-ribose) polymerase), as well as the downregulation of Bcl-2. ABN-B also induced cell cycle arrest at G₂/M by down-regulating the expression of CKD1 (cyclin-dependent kinase 1) and cyclin B1, but up-regulating p21 (cyclin-dependent kinase inhibitor 1) expression. Notably, ABN-B increased the production of mitochondrial reactive oxygen species (ROS); however, treatment with mito-TEMPO (a specific mitochondrial antioxidant) blocked ABN-B-induced cell cycle arrest at G₂/M and apoptosis, as well as the up-regulation of p21 and down-regulation of CDK1 and cyclin B1 induced by ABN-B. At the molecular level, ABN-B-induced mitochondrial ROS production increased the phosphorylation levels of AKT (protein kinase B) and ERK1/2 (extracellular signal-regulated kinase 1/2), while the inhibition of these kinases blocked the ABN-B-induced up-regulation of p21 and down-regulation of CDK1 and cyclin B1. Moreover, ABN-B significantly suppressed tumor growth in Ex-3LL (Lewis lung carcinoma) tumor-bearing mice. Taken together, these results suggest that ABN-B can exert an anti-cancer effect by inducing apoptosis and cell cycle arrest at G₂/M through mitochondrial ROS production in lung cancer cells.

Cardiolipin deficiency in Barth syndrome is not associated with increased superoxide/H2 O2 production in heart and skeletal muscle mitochondria

Barth syndrome (BTHS) is a rare X-linked genetic disorder caused by mutations in the gene encoding the transacylase tafazzin and characterized by loss of cardiolipin and severe cardiomyopathy. Mitochondrial oxidants have been implicated in the cardiomyopathy in BTHS. Eleven mitochondrial sites produce superoxide/hydrogen peroxide (H₂ O₂ ) at significant rates. Which of these sites generate oxidants at excessive rates in BTHS is unknown. Here, we measured the maximum capacity of superoxide/H₂ O₂ production from each site and the ex vivo rate of superoxide/H₂ O₂ production in the heart and skeletal muscle mitochondria of the tafazzin knockdown mice (tazkd) from 3 to 12 months of age. Despite reduced oxidative capacity, superoxide/H₂ O₂ production was indistinguishable between tazkd mice and wild-type littermates. These observations raise questions about the involvement of mitochondrial oxidants in BTHS pathology.

Nitrate partially inhibits lipopolysaccharide-induced inflammation by maintaining mitochondrial function

Objective

Nitrate has been reported to protect cells via the nitrate-nitrite-nitric oxide (NO) pathway. Most studies tend to use nitrite to investigate the mechanisms of this pathway. However, the latest studies have confirmed that mammals can directly degrade nitrate via xanthine oxidoreductase (XOR). The hypothesis is that nitrate could play a protective role in inflammatory responses independent of bacterial nitrate reductases.

Methods

Mouse RAW264.7 macrophages were pre-incubated with sodium nitrate (10, 100, and 500 µM) for 2 hours, and then treated with lipopolysaccharide (LPS) for 2 hours to induce inflammation. The Quantikine Immunoassay was used to measure interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) concentrations in the supernatant. The fluorescence intensity ratio of red/green from JC-1 was used to assay mitochondrial membrane potential. The fluorescence intensity of MitoSOX Red was used to indicate the generation of mitochondrial reactive oxygen species.

Results

Nitrate partially reduced IL-6 and TNF-α secretion via reducing NF-κB signaling in LPS-induced macrophages. Nitrate also reduced the generation of mitochondrial reactive oxygen species by regulating mitochondrial function. These effects depended on XOR-derived NO but were independent of inducible nitric oxide synthase-derived NO.

Conclusion

Nitrate regulates mitochondrial function via XOR-derived NO to partially inhibit LPS-induced inflammation.

Pathological and Pharmacological Roles of Mitochondrial Reactive Oxygen Species in Malignant Neoplasms: Therapies Involving Chemical Compounds, Natural Products, and Photosensitizers

Oxidative stress plays an important role in cellular processes. Consequently, oxidative stress also affects etiology, progression, and response to therapeutics in various pathological conditions including malignant tumors. Oxidative stress and associated outcomes are often brought about by excessive generation of reactive oxygen species (ROS). Accumulation of ROS occurs due to dysregulation of homeostasis in an otherwise strictly controlled physiological condition. In fact, intracellular ROS levels are closely associated with the pathological status and outcome of numerous diseases. Notably, mitochondria are recognized as the critical regulator and primary source of ROS. Damage to mitochondria increases mitochondrial ROS (mROS) production, which leads to an increased level of total intracellular ROS. However, intracellular ROS level may not always reflect mROS levels, as ROS is not only produced by mitochondria but also by other organelles such as endoplasmic reticulum and peroxisomes. Thus, an evaluation of mROS would help us to recognize the biological and pathological characteristics and predictive markers of malignant tumors and develop efficient treatment strategies. In this review, we describe the pathological significance of mROS in malignant neoplasms. In particular, we show the association of mROS-related signaling in the molecular mechanisms of chemically synthesized and natural chemotherapeutic agents and photodynamic therapy.

Corticosteroids alleviate lipopolysaccharide-induced inflammation and lung injury via inhibiting NLRP3-inflammasome activation

The role of corticosteroids in acute lung injury (ALI) remains uncertain. This study aims to determine the underlying mechanisms of corticosteroid treatment for lipopolysaccharide (LPS)-induced inflammation and ALI. We used corticosteroid treatment for LPS-induced murine ALI model to investigate the effect of corticosteroid on ALI in vivo. Moreover, LPS-stimulated macrophages were used to explore the specific anti-inflammatory effects of corticosteroids on NLRP3-inflammasome in vitro. We found corticosteroids attenuated LPS-induced ALI, which manifested in reduction of the alveolar structure destruction, the infiltration of neutrophils and the inflammatory cytokines release of interleukin-1β (IL-1β) and interleukin-18 (IL-18) in Lung. In vitro, when NLRP3-inflammasome was knocked out, inflammatory response of caspase-1 activation and IL-1β secretion was obviously declined. Further exploration, our results showed that when corticosteroid preprocessed macrophages before LPS primed, it obviously inhibited the activation of caspase-1 and the maturation of IL-1β, which depended on inhibiting the nuclear factor-κB (NF-κB) signal pathway activation. However, when corticosteroids intervened the LPS-primed macrophages, it also negatively regulated NLRP3-inflammasome activation through suppressing mitochondrial reactive oxygen species (mtROS) production. Our results revealed that corticosteroids played a protection role in LPS-induced inflammation and ALI by suppressing both NF-κB signal pathway and mtROS-dependent NLRP3 inflammasome activation.

Aldehyde Dehydrogenase 2 Protects Against Post-Cardiac Arrest Myocardial Dysfunction Through a Novel Mechanism of Suppressing Mitochondrial Reactive Oxygen Species Production

Post-cardiac arrest myocardial dysfunction significantly contributes to early mortality after the return of spontaneous circulation. However, no effective therapy is available now. Aldehyde dehydrogenase 2 (ALDH2) enzyme has been shown to protect the heart from aldehyde toxicity such as 4-hydroxy-2-nonenal (4-HNE) and oxidative stress. In this study, we evaluated the effect of enhanced activity or expression of ALDH2 on post-cardiac arrest myocardial dysfunction and survival in a rat cardiac arrest model. Furthermore, we elucidated the underlying mechanisms with a focus on mitochondrial reactive oxygen species (ROS) production in a cell hypoxia/reoxygenation model. A total of 126 rats were used for the ALDH2 activation or cardiac overexpression of ALDH2 studies. Randomization was done 10 min before the respective agonist injection or in vivo gene delivery. We showed that enhanced activity or expression of ALDH2 significantly improved contractile function of the left ventricle and survival rate in rats subjected to cardiac arrest-cardiopulmonary resuscitation procedure. Moreover, ALDH2 prevented cardiac arrest-induced cardiomyocyte death from apoptosis and mitochondrial damage. Mechanistically, 4-HNE, a representative substrate of ALDH2, was dominantly increased in the hypoxia/reoxygenation-exposed cardiomyocytes. Direct addition of 4-HNE led to significantly augmented succinate accumulation and mitochondrial ROS production. Through metabolizing 4-HNE, ALDH2 significantly inhibited mitochondrial ROS production. Our findings provide compelling evidence of the cardioprotective effects of ALDH2 and therapeutic targeting this enzyme would provide an important approach for treating post-cardiac arrest myocardial dysfunction.

TGF-β induces corneal endothelial senescence via increase of mitochondrial reactive oxygen species in chronic corneal allograft failure

The corneal endothelium (CE) dysfunction impairs optical transparency and leads to corneal allograft failure. Morphologically, CE cells are characterized by premature senescence at the late stage of corneal graft. However, the detailed molecular mechanisms are largely unknown. Here we found that transforming growth factor-β (TGF-β) is elevated in the CE of late graft failure. In addition, senescence-associated gene p21 and p16 are increased as well, which is consistent with their elevation upon TGF-β treatment in human corneal endothelial cell B4G12. Furthermore, TGF-β treatment leads to high positive ratio of SA-β-gal, indicating B4G12 cells undergo cellular senescence. Mechanistically, we demonstrated that TGF-β could induce mitochondrial ROS (mtROS) production and mtROS scavenger could rescue CE cell senescence upon TGF-β treatment. Our study provides new evidence that elevated TGF-β plays a crucial role in the CE cell senescence and loss in chronic corneal graft failure, which could be potential targets for clinical treatment.

Blockade of endogenous angiotensin II type I receptor agonistic autoantibody activity improves mitochondrial reactive oxygen species and hypertension in a rat model of preeclampsia

Preeclampsia (PE) is characterized by new-onset hypertension that usually occurs in the third trimester of pregnancy and is associated with oxidative stress and angiotensin II type 1 receptor agonistic autoantibodies (AT₁-AAs). Inhibition of the AT₁-AAs in the reduced uterine perfusion pressure (RUPP) rat, a model of PE, attenuates hypertension and many other characteristics of PE. We have previously shown that mitochondrial oxidative stress (mtROS) is a newly described PE characteristic exhibited by the RUPP rat that contributes to hypertension. However, the factors that cause mtROS in PE or RUPP are unknown. Thus, the objective of the current study is to use pharmacologic inhibition of AT₁-AAs to examine their role in mtROS in the RUPP rat model of PE. AT₁-AA inhibition in RUPP rats was achieved by administration of an epitope-binding peptide ('n7AAc'). Female Sprague-Dawley rats were divided into the following two groups: RUPP and RUPP + AT₁-AA inhibition (RUPP + 'n7AAc'). On day 14 of gestation (GD), RUPP surgery was performed; 'n7AAc' peptide (2 µg/μL) was administered by miniosmotic pumps in a subset of RUPP rats; and on GD19, sera, placentas, and kidneys were collected. mitochondrial respiration and mtROS were measured in isolated mitochondria using the Oxygraph 2K and fluorescent microplate reader, respectively. Placental and renal mitochondrial respiration and mtROS were improved in RUPP + 'n7AAc' rats compared with RUPP controls. Moreover, endothelial cells (human umbilical vein endothelial cells) treated with RUPP + 'n7AAc' sera exhibited less mtROS compared with those treated with RUPP sera. Overall, our findings suggest that AT₁-AA signaling is one stimulus of mtROS during PE.

Peroxisome Proliferator-Activated Receptor-γ Coactivator-1α Inhibits Vascular Calcification Through Sirtuin 3-Mediated Reduction of Mitochondrial Oxidative Stress

Aims: Vascular calcification is associated with cardiovascular death in patients with chronic kidney disease (CKD). Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) plays an important role in various cardiovascular diseases. However, its role in vascular calcification remains unknown. Results: Adenine-induced rat CKD model was used to induce arterial medial calcification. The level of PGC-1α decreased in abdominal aorta of CKD rats. Overexpression of PGC-1α significantly ameliorated calcium deposition in rat abdominal aorta, isolated carotid rings, and cultured vascular smooth muscle cells (VSMCs). Mitochondrial reactive oxygen species (mtROS) increased in calcifying aorta and VSMCs. Upregulation of PGC-1α inhibited, whereas PGC-1α depletion promoted β-glycerophosphate-induced mtROS production and calcium deposition. Moreover, PGC-1α increased superoxide dismutase 1 (SOD1) and SOD2 contents in vivo and in vitro, whereas SOD2 deletion eliminated PGC-1α-mediated mtROS change and promoted calcium deposition. Mechanistically, sirtuin 3 (SIRT3) expression declined in calcifying aorta and VSMCs, while PGC-1α overexpression restored SIRT3 expression. Inhibition of SIRT3 by 3-TYP or siRNA (small interfering RNA) reduced PGC-1α-induced upregulation of SOD1 and SOD2, and abolished the protective effect of PGC-1α on calcification of VSMCs. Importantly, PGC-1α was reduced in calcified femoral arteries in CKD patients. In phosphate-induced human umbilical arterial calcification, upregulation of PGC-1α attenuated calcium nodule formation, while this protective effect was abolished by SIRT3 inhibitor. Innovation: We showed for the first time that PGC-1α is an important endogenous regulator against vascular calcification. Induction of PGC-1α could be a potential strategy to treat vascular calcification in CKD patients. Conclusions: PGC-1α protected against vascular calcification by SIRT3-mediated mtROS reduction.

p66Shc Contributes to Liver Fibrosis through the Regulation of Mitochondrial Reactive Oxygen Species

Background: p66Shc is a redox enzyme that mediates mitochondrial reactive oxygen species (ROS) generation. p66Shc inhibition confers protection against liver injury, however, its functional contribution to liver fibrosis remains unclear. The aim of this study is to explore the involvement of p66Shc in liver fibrosis and underlying mechanism of p66Shc by focusing on mitochondrial ROS. Methods: p66Shc-silenced mice were injected with carbon tetrachloride (CCl₄). Primary hepatic stellate cells (HSCs) were performed with p66Shc silencing or overexpression prior to TGF-β1 stimulation. Results: p66Shc expression was progressively elevated in mice with CCl₄-induced liver fibrosis, and p66Shc silencing in vivo significantly attenuated fibrosis development, reducing liver damage, oxidative stress and HSC activation, indicated by the decreased α-SMA, CTGF and TIMP1 levels. Furthermore, in primary HSCs, p66Shc-mediated mitochondrial ROS production played a vital role in mitochondrial morphology and cellular metabolism. Knockdown of p66Shc significantly inhibited mitochondrial ROS production and NOD-like receptor protein 3 (NLRP3) inflammasome activation, which were closely associated with HSC activation, indicated by the decreased α-SMA, CTGF and TIMP1 levels. However, p66Shc overexpression exerted the opposite effects, which were suppressed by a specific mitochondrial ROS scavenger (mito-TEMPO). More importantly, p66Shc expression was significantly increased in human with liver fibrosis, accompanied by NLRP3 inflammasome activation. Conclusions: p66Shc is a key regulator of liver fibrosis by mediating mitochondrial ROS production, which triggers NLRP3 inflammasome activation.

Mitochondrial regulation of diabetic vascular disease: an emerging opportunity

Diabetes-related vascular complication rates remain unacceptably high despite guideline-based medical therapies that are significantly more effective in individuals without diabetes. This critical gap represents an opportunity for researchers and clinicians to collaborate on targeting mechanisms and pathways that specifically contribute to vascular pathology in patients with diabetes mellitus. Dysfunctional mitochondria producing excessive mitochondrial reactive oxygen species (mtROS) play a proximal cell-signaling role in the development of vascular endothelial dysfunction in the setting of diabetes. Targeting the mechanisms of production of mtROS or mtROS themselves represents an attractive method to reduce the prevalence and severity of diabetic vascular disease. This review focuses on the role of mitochondria in the development of diabetic vascular disease and current developments in methods to improve mitochondrial health to improve vascular outcomes in patients with DM.

Vildagliptin improves high glucose-induced endothelial mitochondrial dysfunction via inhibiting mitochondrial fission

The dipeptidyl peptidase 4 inhibitor vildagliptin (VLD), a widely used anti-diabetic drug, exerts favourable effects on vascular endothelium in diabetes. We determined for the first time the improving effects of VLD on mitochondrial dysfunction in diabetic mice and human umbilical vein endothelial cells (HUVECs) cultured under hyperglycaemic conditions, and further explored the mechanism behind the anti-diabetic activity. Mitochondrial ROS (mtROS) production was detected by fluorescent microscope and flow cytometry. Mitochondrial DNA damage and ATP synthesis were analysed by real time PCR and ATPlite assay, respectively. Mitochondrial network stained with MitoTracker Red to identify mitochondrial fragmentation was visualized under confocal microscopy. The expression levels of dynamin-related proteins (Drp1 and Fis1) were determined by immunoblotting. We found that VLD significantly reduced mtROS production and mitochondrial DNA damage, but enhanced ATP synthesis in endothelium under diabetic conditions. Moreover, VLD reduced the expression of Drp1 and Fis1, blocked Drp1 translocation into mitochondria, and blunted mitochondrial fragmentation induced by hyperglycaemia. As a result, mitochondrial dysfunction was alleviated and mitochondrial morphology was restored by VLD. Additionally, VLD promoted the phosphorylation of AMPK and its target acetyl-CoA carboxylase in the setting of high glucose, and AMPK activation led to a decreased expression and activation of Drp1. In conclusion, VLD improves endothelial mitochondrial dysfunction in diabetes, possibly through inhibiting Drp1-mediated mitochondrial fission in an AMPK-dependent manner.

Heat stress induces distinct responses in porcine cumulus cells and oocytes associated with disrupted gap junction and trans-zonal projection colocalization

Cumulus cells (CCs), the granulosa cells surrounding the oocytes, play critical roles in oocytes maturation through intercellular communication by extending trans-zonal projections (TZPs) to contact oocytes via gap junctions (GJs). The adverse effect of heat stress (HS) on oocyte maturation has been well documented, whereas the HS responses of CCs and the oocytes in association with GJ/TZP colocalization remain unclear. In this study, porcine cumulus-oocyte complexes (COCs) were subjected to HS at 41.5°C for 24 hr during in vitro maturation. Cumulus expansion was impaired and oocyte quality was reduced with lower survival rate, polar body extrusion rate, and early embryo developmental potentials. CCs and oocytes isolated from COCs demonstrated distinct responses to HS. The messenger RNA abundance of heat shock protein-related genes and mitochondrial DNA-encoded genes, together with ATP content, were significantly increased in CCs, yet decreased in oocytes, despite activation of caspase 3 detected in both CCs and oocytes. Similar changes were observed when denuded oocytes and isolated CCs subjected to HS separately, except mitochondria reactive oxygen species (mROS). In heat-stressed COCs, mROS was significantly increased only in oocytes. However, when isolated CCs and denuded oocytes were heat-stressed separately, mROS was significantly increased only in CCs. Moreover, F-actin, a TZP marker, and its colocalization with a GJ protein connexin-45, were significantly reduced in heat-exposed COCs. These results indicate that HS induces distinct responses in porcine CCs and oocytes in association with disrupted GJ and TZP colocalization.

Mitochondrial ROS activate interleukin-1β expression in allergic rhinitis

Allergic rhinitis (AR) is the most common cause of inflammation of the nasal mucosa. It is also the most common form of non-infectious rhinitis associated with an immunoglobulin E (IgE)-mediated immune response against allergens. Previous studies have indicated that interleukin-1β (IL-1β) has a pathological role in the development of allergic asthma. The present study was designed to assess whether IL-1β participates in the pathogenesis of AR. A total of 45 patients with AR were enrolled in the present study and were identified to have increased IL-1β expression expressed by peripheral blood mononuclear cells (PBMCs), and the mitochondrial reactive oxygen species (ROS) and NLRP3 are required for IL-1β synthesis in monocytes/macrophages and PBMCs from patients with AR. The levels of IL-1β and interleukin-17 (IL-17) were increased in patients with AR and were positively correlated with each other. The results of the present study suggested that patients with AR have raised mitochondrial ROS levels, which may upregulate the expression of IL-1β, affecting IL-17-production and serving a role in the pathogenesis of AR.

Lysophospholipids and Their Receptors Serve as Conditional DAMPs and DAMP Receptors in Tissue Oxidative and Inflammatory Injury

Significance: We proposed lysophospholipids (LPLs) and LPL-G-protein-coupled receptors (GPCRs) as conditional danger-associated molecular patterns (DAMPs) and conditional DAMP receptors as a paradigm shift to the widely accepted classical DAMP and DAMP receptor model. Recent Advances: The aberrant levels of LPLs and GPCRs activate pro-inflammatory signal transduction pathways, trigger innate immune response, and lead to tissue oxidative and inflammatory injury. Critical Issues: Classical DAMP model specifies only the endogenous metabolites that are released from damaged/dying cells as DAMPs, but fails to identify elevated endogenous metabolites secreted from viable/live cells during pathologies as DAMPs. The current classification of DAMPs also fails to clarify the following concerns: (i) Are molecules, which bind to pattern recognition receptors (PRRs), the only DAMPs contributing to inflammation and tissue injury? (ii) Are all DAMPs acting only via classical PRRs during cellular stress? To answer these questions, we reviewed the molecular characteristics and signaling mechanisms of LPLs, a group of endogenous metabolites and their specific receptors and analyzed the significant progress achieved in characterizing oxidative stress mechanisms of LPL mediated tissue injury. Future Directions: Further LPLs and LPL-GPCRs may serve as potential therapeutic targets for the treatment of pathologies induced by sterile inflammation. Antioxid. Redox Signal. 28, 973-986.

Depletion of mitochondrial reactive oxygen species downregulates epithelial-to-mesenchymal transition in cervical cancer cells

In the course of cancer progression, epithelial cells often acquire morphological and functional characteristics of mesenchymal cells, a process known as epithelial-to-mesenchymal transition (EMT). EMT provides epithelial cells with migratory, invasive, and stem cell capabilities. Reactive oxygen species produced by mitochondria (mtROS) could be of special importance for pro-tumorigenic signaling and EMT.

In our study, we used mitochondria-targeted antioxidant SkQ1 to lower the mtROS level and analyze their role in the regulation of the actin cytoskeleton, adhesion junctions, and signaling pathways critical for tumorigenesis of cervical carcinomas. A decrease in mtROS was found to induce formation of β-cytoplasmic actin stress fibers and circumferential rings in cervical cancer SiHa and Ca-Ski cells. It was accompanied by an upregulation of E-cadherin in SiHa cells and a downregulation of N-cadherin in Ca-Ski cells. In SiHa cells, an increase in E-cadherin expression was accompanied by a reduction of Snail, E-cadherin negative regulator. A stimulation of mtROS by epidermal growth factor (EGF) caused a Snail upregulation in SiHa cells that could be downregulated by SkQ1. SkQ1 caused a decrease in activation of extracellular-signal-regulated kinases 1 and 2 (ERK1/2) in SiHa and Ca-Ski. EGF produced an opposite effect. Incubation with SkQ1 suppressed EGF-induced p-ERK1/2 upregulation in SiHa, but not in Ca-Ski cells. Thus, we showed that scavenging of mtROS by SkQ1 initiated reversal of EMT and suppressed proliferation of cervical cancer cells.

Mitochondrial ROS contribute to oridonin-induced HepG2 apoptosis through PARP activation

Oridonin, the main active constituent of Rabdosia rubescens, is known to exert antitumor activity via the induction of apoptosis in numerous types of human cancer cells. However, the underlying regulatory mechanisms of mitochondrial ROS in oridonin-induced HepG2 apoptosis remain largely unknown, due to limitations of subcellular imaging resolution. Previously, it has been suggested that mitochondria serve a potential role in sensing and signaling cellular redox changes in vital biological processes such as cell death and the abiotic stress response, based on studies involving the mitochondrial-targeted redox-sensitive green fluorescent protein (GFP). To address this, a mitochondrial-targeted Grx1-roGFP2 (mtGrx1-roGFP2) biosensor was implemented to monitor real-time mitochondrial redox changes of HepG2 cells in response to either H₂O₂/DTT or oridonin/SS31 treatment. It was determined that oridonin caused a perturbation in mitochondrial redox status, which in turn contributed to oridonin-induced apoptosis. Furthermore, a novel mechanism underlying the regulation of mitochondrial redox changes in oridonin-induced HepG2 apoptosis, presumably dependent on PARP cleavage, was proposed. In conclusion, the present study provides evidence in support of mitochondrial redox changes as a potential mediator in the apoptotic activities of oridonin in HepG2 cells, which provides insight into the molecular mechanisms by which mitochondrial redox signaling regulates oridonin-induced apoptosis in cancer therapy, and the development of mitochondria-specific oridonin as a promising novel anticancer therapeutic strategy.

Ochratoxin A-Induced Apoptosis of IPEC-J2 Cells through ROS-Mediated Mitochondrial Permeability Transition Pore Opening Pathway

With the purpose to explore the mechanisms associated with the intestinal toxicity of Ochratoxin A (OTA), an intestinal porcine epithelial cell line (IPEC-J2) was applied in this study as in vitro models for intestinal epithelium. The results confirmed that OTA induced IPEC-J2 cell toxicity by MTT assay and apoptosis by Hoechst 33258 staining and flow cytometer analysis. We also observed that OTA induced the mitochondrial reactive oxygen species (ROS) production and mitochondrial permeability transition pore (mPTP) opening by confocal microscopy. Western blot showed that OTA induced cytochrome c (cyt-c) release and caspase-3 activation, which could be suppressed by inhibition of mPTP opening with cyclosporin A. Treatment with Mito-TEMPO, the mitochondria-targeted ROS scavenger, blocked OTA-induced mitochondrial ROS generation and mPTP opening and prevented cyt-c release, caspase-3 activation, and apoptosis in IPEC-J2 cells.