Mitochondrial Superoxide Levels Research Articles

M2 Macrophage-Derived Exosomal circ_0088494 Inhibits Ferroptosis via Promoting H3K4me1 Modification of STEAP3 in Cutaneous Squamous Cell Carcinoma.

Cutaneous squamous cell carcinoma (cSCC) is a common type of cutaneous cancer globally. M2 macrophage-derived exosomes (M2 exosomes) facilitate the development of cancer. Ferroptosis, a newly uncovered form of cell death, is linked to cancer progression. The present research planned to study the function and potential mechanism of M2 exosomes on ferroptosis in cSCC. Patients with cSCC were recruited to gather adjacent noncancerous specimens and cSCC tissues. Mononuclear macrophage (THP-1) cells were differentiated into M2 macrophages before exosome extraction, and then the exosomes were added into cSCC cells (A431 and SCL-1). Erastin was applied to induce ferroptosis. Cell viability, mitochondrial superoxide, lipid-ROS, malondialdehyde (MDA), and iron level were detected to validate ferroptosis in cSCC cells. Proteins and RNAs were tested by applying western blot and RT-qPCR. The combination between molecules was validated by ChIP and RIP. Six-transmembrane epithelial antigen of the prostate 3 (STEAP3) was elevated in cSCC specimens, which correlated to reduced ferroptosis. cSCC tissues presented an increase in the number of M2 macrophages. Erastin-elicited ferroptosis was repressed by M2 macrophages, while exosome inhibitor GW4869 neutralized the outcome of M2 macrophages. Furthermore, M2 exosomes repressed ferroptosis of cSCC cells via circ_0088494, which might be related to the upregulation of STEAP3. M2 exosomes-derived circ_0088494 promoted histone 3 lysine 4 monomethylation (H3K4me1) modification of STEAP3 by recruiting histone-lysine N-methyltransferase 2D (KMT2D). The effect of circ_0088494-silenced M2 exosomes on ferroptosis was antagonized by STEAP3 overexpression. M2 exosomes-derived circ_0088494 recruited KMT2D to promote H3K4me1 modification of STEAP3, thereby inhibiting ferroptosis in cSCC. This study might provide a novel target for cSCC treatment.

Loss of PTPN21 disrupted mitochondrial metabolic homeostasis and aggravated experimental pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a high-mortality lung disease with unclear pathogenesis. Convincing evidence suggests that an imbalance in mitochondrial homeostasis resulting from repeated injury to alveolar epithelial type 2 cells (AEC2) underlies IPF. Non-receptor protein tyrosine phosphatase 21 (PTPN21) performs various functions in cancer; however, its role in IPF has not been studied. This study aimed to investigate the role of PTPN21 in lung fibrosis. The experimental results showed that loss of PTPN21 exacerbated lung fibrosis by increasing cell numbers in bronchoalveolar lavage fluid, lung hydroxyproline content, and extracellular matrix protein expression of fibronectin and α-smooth muscle actin (α-SMA) in bleomycin-challenged mouse lungs. In A549 cells (AEC2), knockdown of PTPN21 suppressed focal adhesion and migration, reduced mitochondrial fission and increased fusion, increased the level of mitochondrial superoxide, decreased mitochondrial membrane potential and ATP levels. Simultaneously, knockdown of PTPN21 impaired autophagy, and increased intracellular reactive oxygen species levels. Treatment of fibroblasts (MRC-5) and primary human lung fibroblasts (PHLF)) with the supernatant from PTPN21-knockdown A549 cells increased the expression of fibronectin, collagen 1 and α-SMA. Conversely, overexpression of PTPN21 in A549 cells produced opposite effects. However, treatment of MRC-5 and PHLF with the supernatant from PTPN21-overexpressing A549 cells only slightly reduced the expression of fibronectin, collagen 1 in MRC-5 cells, but did not change the expression of α-SMA. In summary, this study revealed that the loss of PTPN21 in epithelial cells disrupted mitochondrial metabolic homeostasis, leading to epithelial cell inactivation and increased the deposition of extracellular matrix proteins in fibroblasts, thereby exacerbating experimental pulmonary fibrosis.

DDDR-13. OPTIMIZING BRAIN CANCER THERAPY: BALANCING TUMOR ERADICATION AND NORMAL TISSUE PRESERVATION WITH BPM31510

Abstract The challenges translating glioblastoma therapies lie in safeguarding normal neuronal and glial tissue. Considering that the central nervous system has the lowest regenerative capacity, the exclusive focus on tumor eradication while neglecting normal tissue response, impedes proper healing. This oversight leads to toxicities ultimately culminating in patient demise with marginal gain in survival. BPM31510 is a nanodispersion encapsulating highly hydrophobic oxidized Coenzyme Q10 (CoQ10), allowing for delivery of supraphysiological CoQ10 concentrations into cancer cells. Initial investigations demonstrated differential responsiveness between cancer and non-cancer cells in vitro, an effect associated with high superoxide levels exclusively in cancer cells. To evaluate this divergence between cancer and non-cancer cells, a competitive co-culture cell-based assay was developed with labeled pairs of glioblastoma and non-cancer cells incubated up to three weeks with various concentrations of BPM31510 to ascertain optimal concentration leading to preferential growth of non-cancer cells. Human astrocyte (HA), mouse fibroblast (NIH 3T3), and rat astrocyte (TNC1) cells were paired with U251 human glioma, mouse GL261 and rat C6 glioma, respectively. Cell growth and spatial extent of the plate containing non-cancer or tumor cells were monitored every other day. Using doxorubicin as control, no dosage was discerned in which non-cancer cells exhibited advantage over tumor cells (i.e., either cultures became all tumor cells or both cell lines were eradicated). Using various concentrations of BPM31510, we identified an optimal dose in which cancer cells diminished while non-cancer cells predominated, reflected by markedly elevated mitochondrial superoxide levels in cancer cells prior to cell death. A co-culture cell-based assay was developed to identify an optimal dose of BPM31510 with selective preservation of non-cancer cells alongside tumor cell death. This approach elucidates developing a “fine tuning” strategy, wherein BPM31510 is titrated over time, thereby promoting normal tissue and healing, and ultimately leading to superior and prolonged functional outcomes.

PINK1-deficiency facilitates mitochondrial iron accumulation and colon tumorigenesis

ABSTRACT Mitophagy, the process by which cells eliminate damaged mitochondria, is mediated by PINK1 (PTEN induced kinase 1). Our recent research indicates that PINK1 functions as a tumor suppressor in colorectal cancer by regulating cellular metabolism. Interestingly, PINK1 ablation activated the NLRP3 (NLR family pyrin domain containing 3) inflammasome, releasing IL1B (interleukin 1 beta). However, inhibiting the NLRP3-IL1B signaling pathway with an IL1R (interleukin 1 receptor) antagonist or NLRP3 inhibitor did not hinder colon tumor growth after PINK1 loss. To identify druggable targets in PINK1-deficient tumors, ribonucleic acid sequencing analysis was performed on colon tumors from pink1 knockout and wild-type mice. Gene Set Enrichment Analysis highlighted the enrichment of iron ion transmembrane transporter activity. Subsequent qualitative polymerase chain reaction and western blot analysis revealed an increase in mitochondrial iron transporters, including mitochondrial calcium uniporter, in PINK1-deficient colon tumor cells and tissues. Live-cell iron staining demonstrated elevated cellular and mitochondrial iron levels in PINK1-deficient cells. Clinically used drugs deferiprone and minocycline reduced mitochondrial iron and superoxide levels, resulting in decreased colon tumor cell growth in vitro and in vivo. Manipulating the mitochondrial iron uptake protein MCU (mitochondrial calcium uniporter) also affected cell and xenograft tumor growth. This study suggests that therapies aimed at reducing mitochondrial iron levels may effectively inhibit colon tumor growth, particularly in patients with low PINK1 expression.

Sestrin2 balances mitophagy and apoptosis through the PINK1-Parkin pathway to attenuate severe acute pancreatitis

Mitophagy serves as a mitochondrial quality control mechanism to maintain the homeostasis of mitochondria and the intracellular environment. Studies have shown that there is a close relationship between mitophagy and apoptosis. Sestrin2 (Sesn2) is a highly conserved class of stress-inducible proteins that play important roles in reducing oxidative stress damage, inflammation, and apoptosis. However, the potential mechanism of how Sesn2 regulates mitophagy and apoptosis in severe acute pancreatitis (SAP) remains unclear. In the study, RAW264.7 (macrophage cell Line) cellular inflammation model established by lipopolysaccharide (LPS) treatment as well as LPS and CAE-induced SAP mouse model (wild-type and Sen2 Knockout mouse) were used. Our study showed that LPS stimulation significantly increased the level of Sesn2 in RAW264.7 cells, Sesn2 increased mitochondrial membrane potential, decreased inflammation levels, mitochondrial superoxide levels and apoptosis, and also promoted monocyte macrophages toward the M2 anti-inflammatory phenotype, suggesting a protective effect of Sesn2 on mitochondria. Further, Sesn2 increased mitophagy and decreased apoptosis via modulating the PINK1-Parkin signaling. Meanwhile, knockout of Sesn2 exacerbated pancreatic, mitochondrial damage and inflammation in a mouse model of SAP. In addition, the protective effect of Sesn2 against SAP was shown to be associated with mitophagy conducted by the PINK1-Parkin pathway via inhibiting apoptosis. These findings reveal that Sesn2 in balancing mitochondrial autophagy and apoptosis by modulating the PINK1-Parkin signaling may present a new therapeutic strategy for the treatment of SAP.

Effect of mitochondrial oxidative stress on regulatory T cell manufacturing for clinical application in transplantation: Results from a pilot study

The manufacturing process of regulatory T (Treg) cells for clinical application begins with the positive selection of CD25+ cells using superparamagnetic iron oxide nanoparticle (SPION)-conjugated anti-CD25 antibodies (spCD25) and immunomagnetic cell separation technology. Our findings revealed that the interaction of spCD25 with its cell target induced the internalization of the complex spCD25–interleukin-2 receptor. Accumulation of intracellular spCD25 triggered oxidative stress, causing delayed Treg expansion and temporary reduction in suppressor activity. This activation delay hindered the efficient generation of clinically competent cells. During this early phase, Treg cells exhibited elevated mitochondrial superoxide and lipid peroxidation levels, with a concomitant decrease in mitochondrial respiration rates. The results uncovered the increased mitochondrial unfolded protein response. This protective, redox-sensitive activity is inherent in Tregs when contrasted with homologous, spCD25-treated, conventional T cells. Although the temporary effects of spCD25 on clinically competent cells did not impede their use in a safety/feasibility pilot study with kidney transplant recipients, it is reasonable to anticipate a potential reduction in their therapeutic efficacy. The mechanistic understanding of the adverse effects triggered by spCD25 is crucial for improving the manufacturing process of clinically competent Treg cells, a pivotal step in the successful implementation of immune cell therapy in transplantation.

Frequency-Dependent Antioxidant Responses in HT-1080 Human Fibrosarcoma Cells Exposed to Weak Radio Frequency Fields.

This study explores the complex relationship between radio frequency (RF) exposure and cancer cells, focusing on the HT-1080 human fibrosarcoma cell line. We investigated the modulation of reactive oxygen species (ROS) and key antioxidant enzymes, including superoxide dismutase (SOD), peroxidase, and glutathione (GSH), as well as mitochondrial superoxide levels and cell viability. Exposure to RF fields in the 2-5 MHz range at very weak intensities (20 nT) over 4 days resulted in distinct, frequency-specific cellular effects. Significant increases in SOD and GSH levels were observed at 4 and 4.5 MHz, accompanied by reduced mitochondrial superoxide levels and enhanced cell viability, suggesting improved mitochondrial function. In contrast, lower frequencies like 2.5 MHz induced oxidative stress, evidenced by GSH depletion and increased mitochondrial superoxide levels. The findings demonstrate that cancer cells exhibit frequency-specific sensitivity to RF fields even at intensities significantly below current safety standards, highlighting the need to reassess exposure limits. Additionally, our analysis of the radical pair mechanism (RPM) offers deeper insight into RF-induced cellular responses. The modulation of ROS and antioxidant enzyme activities is significant for cancer treatment and has broader implications for age-related diseases, where oxidative stress is a central factor in cellular degeneration. The findings propose that RF fields may serve as a therapeutic tool to selectively modulate oxidative stress and mitochondrial function in cancer cells, with antioxidants playing a key role in mitigating potential adverse effects.

12234 Gα13 Promotes Clonogenic Growth By Increasing Tolerance To Oxidative Metabolic Stress In Prostate Cancer Cells

Abstract Disclosure: D. Wu: None. W. Lim: None. X. Chai: None. V.P. Seshachalam: None. S.A. Rasheed: None. S. Ghosh: None. P.J. Casey: None. Gα13 and Gα12 are members of the G12 family of Gα proteins that, along with their associated Gβγ subunits, mediate signaling from specific G protein-coupled receptors. Analyses of tumor specimens indicate that Gα13 expression correlates with patient survival in several solid cancers. We previously reported a role for Gα13 in cell migration and invasion in prostate cancer cell lines. Interestingly, patient data supports the notion that mitochondrial superoxide dismutase 2 (SOD2) correlates with prostate cancer risk and prognostic Gleason scores. Gα13 lower-expressing LNCaP cells also have lower SOD2 protein levels compared to the Gα13 higher-expressing PC3 cells. Hence, we explored the role of Gα13 in prostate tumorigenesis, and its effect on cellular processes such as cell survival and mitochondrial metabolism, in human prostate cancer cell lines PC3 and LNCaP. We stably knocked-down GNA13 expression in PC3 cells and overexpressed GNA13 in LNCaP cells. We found that Gα13 promoted anchorage-independent cell growth in PC3 and LNCaP cell lines, as assessed by soft agar colony formation, spheroid formation, and xenograft tumor growth. Whole-genome transcriptome analyses suggested that Gα13-regulated genes are functionally enriched in the mitochondria compartment and that GNA13 expression positively correlated to SOD2 transcript levels in PC3 cells. We found that silencing GNA13 sensitized PC3 cells to long-term oxidative metabolic stress when cultured in media containing non-glycolytic metabolites, namely galactose, glutamate plus malate, and succinate. Furthermore, Gα13 levels impacted the abundance of SOD2 protein in the mitochondria, as well as SOD2 promoter activity and mRNA expression. In addition, silencing GNA13 increased mitochondrial superoxide levels in PC3 cells when cultured in galactose medium, as assessed by MitoSOX staining and flow cytometry. Moreover, overexpression of SOD2 could rescue the effect of Gα13 loss on suppression of anchorage-independent cell growth in PC3 cells. Importantly, anchorage-independent cell growth was not rescued when a catalytically-inactive SOD2(Q167A) mutant was expressed. Likewise, stable knockdown of SOD2 suppressed the effect of overexpression of Gα13 on anchorage-independent cell growth in LNCaP cells. We propose a novel biological route of Gα13-mediated anchorage-independent growth and response to oxidative metabolic stress through regulation of SOD2 expression in prostate cancer cells. Given that SOD2 protein levels correlate with prostate cancer Gleason grade, identifying the upregulated GPCRs that signal through Gα13 in prostate cancer could lead to novel preventive or therapeutic strategies. Presentation: 6/1/2024

HECTD2 as a target for veratric acid in the regulation of ferroptosis in renal cell carcinoma

Function of HECTD2 in renal cell carcinoma malignant progression is undefined. Molecular mechanism behind anti-cancer effects of veratric acid (VA) from traditional Chinese medicine (TCM) is underexplored. The Cancer Genome Atlas was leveraged to study HECTD2 expression in renal cell carcinoma and its relationship with histological grading. Kaplan–Meier survival analysis was performed. HECTD2 expression was detected in cancer cells and tissues via qRT-PCR and immunohistochemistry. GPX4 and SLC7A11 expression in tumor samples with high or low HECTD2 expression was examined by immunohistochemistry, cell viability by CCK8, cell proliferation by colony formation assay, lipid ROS and mitochondrial superoxide levels by flow cytometry, Fe2+ and MDA content by assay kits, and GPX4 and SLC7A11 proteins by western blot. SeeSAR software screened TCM small molecule compounds with highest affinity to HECTD2, confirmed with cellular thermal shift assay. VA IC50 was measured by CCK8. Xenograft model was developed and treated with VA. Tumor size and weight were monitored, with immunohistochemistry to detect HECTD2 expression in tumors and assess ferroptosis-related markers. HECTD2 was overexpressed in tumor tissues and cells, which positively correlated with histological grading. HECTD2 depletion inhibited cell vitality and proliferation, raised intracellular lipid ROS, mitochondrial superoxide, Fe2+, and MDA. HECTD2 was a target with highest VA affinity. In vitro and vivo experiments concurred that VA treatment hindered malignancy of renal cell carcinoma and enhanced its susceptibility to ferroptosis. HECTD2 supports ferroptosis resistance in renal cell carcinoma, but VA, through its targeting of HECTD2, initiates ferroptosis, showcasing its anti-cancer efficacy.

Antimony exposure affects oocyte quality and early embryo development via excessive mitochondrial oxidation and dysfunction

Antimony (Sb) is a metalloid, widely presents in the environment and associates with human health. In this study, we aimed to decipher whether Sb exposure is harmful to female reproduction and explore the underlying mechanisms. The ICR mice were exposed to 0, 5, 10, and 20 mg/kg acetate potassium Sb tartrate trihydrate by intraperitoneal injection for 10 days, then mouse oocytes were collected for further analysis. We first found a significant decrease in the proportion of MII-stage oocytes obtained from supernumerary ovulation in the fallopian tubes and early embryo development under Sb treatment. Then a series of tests showed Sb affects oocyte maturation by damaging the cytoskeleton of microtubule and actin. Moreover, the abnormal distribution of cortical granules and their component Ovastacin in oocytes, combined with reduced expression levels of Juno, affected sperm-oocyte binding and led to fertilization failure. Based on the sequencing results and experimental validation, it was demonstrated that Sb exposure impairs mitochondrial distribution and membrane potential, elevated levels of mitochondrial superoxide, finally caused energy supply deficits. Mitochondrial damage in oocytes after Sb exposure results in the excessive oxidative stress and early apoptosis. Taken together, these data suggest that Sb exposure decreases oocyte quality and female fertilization ability by impairing mitochondrial function and redox perturbation.

Simultaneous Targeting of NQO1 and SOD1 Eradicates Breast Cancer Stem Cells via Mitochondrial Futile Redox Cycling.

Triple negative breast cancer (TNBC) contains the highest proportion of cancer stem-like cells (CSCs), which display intrinsic resistance to currently available cancer therapies. This therapeutic resistance is partially mediated by an antioxidant defense coordinated by the transcription factor NRF2 and its downstream targets including NQO1. Here, we identified the antioxidant enzymes NQO1 and SOD1 as therapeutic vulnerabilities of ALDH+ epithelial-like CSCs and CD24-/loCD44+/hi mesenchymal-like CSCs in TNBC. Effective targeting of these CSC states was achieved by utilizing IB-DNQ, a potent and specific NQO1-bioactivatable futile redox cycling molecule, which generated large amounts of reactive oxygen species (ROS) including superoxide and hydrogen peroxide. Furthermore, the CSC killing effect was specifically enhanced by genetic or pharmacological inhibition of SOD1, a copper-containing superoxide dismutase highly expressed in TNBC. Mechanistically, a significant portion of NQO1 resided in the mitochondrial intermembrane space, catalyzing futile redox cycling from IB-DNQ to generate high levels of mitochondrial superoxide, and SOD1 inhibition markedly potentiated this effect resulting in mitochondrial oxidative injury, cytochrome c release, and activation of the caspase 3-mediated apoptotic pathway. Treatment with IB-DNQ alone or together with SOD1 inhibition effectively suppressed tumor growth, metastasis, and tumor-initiating potential in xenograft models of TNBC expressing different levels of NQO1. This futile oxidant-generating strategy, which targets CSCs across the epithelial-mesenchymal continuum, could be a promising therapeutic approach for treating TNBC patients.

Hydramethylnon induces mitochondria-mediated apoptosis in BEAS-2B human bronchial epithelial cells

Typically used household chemicals comprise numerous compounds. Determining mixture toxicity, as observed when using household chemicals containing multiple substances, is of considerable importance from a regulatory perspective. Upon examining the toxic effects of household chemical mixtures, we observed that hydramethylnon combined with tetramethrin resulted in synergistic toxicity. To determine the unknown toxicity mechanism of hydramethylnon, which carries the risk of inhalation exposure when using household chemicals, we conducted a further investigation using BEAS-2B cells, a human bronchial epithelial cell line. Hydramethylnon-induced cytotoxicity was determined following 24 and 48 h of exposure using the water-soluble tetrazolium 1 and lactate dehydrogenase assays. To elucidate the toxicity mechanism, we utilized flow cytometry and measured the levels of apoptosis-related proteins and caspase activities. Given that hydramethylnon, as an insecticide, disrupts the mitochondrial electron transfer chain, we analyzed the relevant mechanisms, including mitochondrial superoxide levels as well as the mitochondrial membrane potential (MMP). Hydramethylnon dose-dependently induced BEAS-2B cell apoptosis via the intrinsic pathway. Furthermore, it significantly increased mitochondrial superoxide levels and disrupted the MMP. Pre-treatment with a caspase inhibitor (Z-DEVD-FMK) confirmed that hydramethylnon induced caspase-dependent apoptosis. Apoptosis, a key event in the toxicological process of chemicals, can lead to lung diseases, including fibrosis and cancer. The results of the present study suggest a mechanism of toxicity of hydramethrylnon, an organofluorine biocide whose toxicity has been little studied, to the lung epithelium. Considering the potential risks associated with inhalation exposure, these results highlight the need for careful management and regulation of hydramethylnon.

Prenylated xanthones from mangosteen (Garcinia mangostana) target oxidative mitochondrial respiration in cancer cells

Mangosteen (Garcinia mangostana) is well-known for its nutritional value and health benefits. Breast cancer is the most common cancer and the leading cause of cancer-related mortality among females worldwide. Here we show that the prenylated xanthones, α-mangostin, γ-mangostin, 9-hydroxycalabaxanthone (9-HCX), and garcinone E from the mangosteen pericarp exhibit cytotoxicity against a panel of human cancer cell lines including lung adenocarcinoma (A549), cervical carcinoma (HeLa), prostatic carcinoma (DU 145), pancreatic carcinoma (MIA PaCa-2), hepatocellular carcinoma (Hep G2), bladder urothelial cancer (5637), as well as the triple-negative breast cancer cells MDA-MB-231. In line with its higher predicted bioactivity score compared to other prenylated xanthones, 9-HCX induced the strongest antiproliferative and proapoptotic effects in MDA-MB-231 breast cancer xenografts in vivo. In different in vitro models, we demonstrate that prenylated xanthones from G. mangostana target mitochondria in cancer cells by inhibition of the mitochondrial respiratory chain complex II (α-mangostin, γ-mangostin, and garcinone E) and complex III (9-HCX) as shown in isolated mitochondria. Accordingly, oxidative mitochondrial respiration (OXPHOS) was inhibited, mitochondrial proton leak increased, and adenosine triphosphate (ATP) synthesis decreased as analyzed by Seahorse assay in MDA-MB-231 cells. Hence, the prenylated xanthones increased mitochondrial superoxide levels, induced mitochondrial membrane permeabilization, and initiated caspase 3/7-mediated apoptosis in MDA-MB-231 triple-negative breast cancer cells. Thus, prenylated xanthones from Garcinia mangostana exhibit anticancer activity based on interference with the mitochondrial respiration.

Bithionol eliminates acute myeloid leukaemia stem-like cells by suppressing NF-κB signalling and inducing oxidative stress, leading to apoptosis and ferroptosis

Acute myeloid leukaemia (AML) is a lethal bone marrow neoplasm caused by genetic alterations in blood cell progenitors. Leukaemic stem cells (LSCs) are responsible for the development of AML, drug resistance and relapse. Bithionol is an old anthelmintic drug with potential antibacterial, antiviral, antifungal, anti-Alzheimer, and antitumour properties. In this work, we focused on the anti-AML LSC properties of bithionol. This compound inhibited the viability of both solid and haematological cancer cells, suppressed AML stem-like cells, and inhibited AML growth in NSG mice at a dosage of 50 mg/kg, with tolerable systemic toxicity. Bithionol significantly reduced the levels of phospho-NF-κB p65 (Ser529) and phospho-NF-κB p65 (Ser536) and nuclear NF-κB p65 translocation in AML cells, indicating that this molecule can suppress NF-κB signalling. DNA fragmentation, nuclear condensation, cell shrinkage, phosphatidylserine externalisation, loss of transmembrane mitochondrial potential, caspase-3 activation and PARP-(Asp 214) cleavage were detected in bithionol-treated AML cells, indicating the induction of apoptosis. Furthermore, this compound increased mitochondrial superoxide levels, and bithionol-induced cell death was partially prevented by cotreatment with the selective ferroptosis inhibitor ferrostatin-1, indicating the induction of ferroptosis. In addition, bithionol synergised with venetoclax in AML cells, indicating the translational potential of bithionol to enhance the effects of venetoclax in patients with AML. Taken together, these data indicate that bithionol is a potential new anti-AML drug.

Abstract Tu140: Evaluation of the effects of mitoquinone on doxorubicin-induced acute cardiac damage

Background: Doxorubicin (DOX)-induced cardiotoxicity remains a high priority to overcome due to irreversibility and lack of abundant preventions. DOX damages the heart tissue principally by overproduction of mitochondrial superoxide and intercalation with the topoisomerase II in the nucleus. Ultimately, cardiac cells become apoptotic, and heart function declines. Our lab has shown that Mitoquinone (MQ), a mitochondria-targeted antioxidant, improves H9c2 cell viability in the presence of DOX. We hypothesize that MQ would counteract DOX to preserve cardiac cells and function in isolated rat hearts, possibly by reducing mitochondrial superoxide production and intracellular accumulation. Methods: H9c2 cells (passages < 18) were incubated with DOX (40 µM) with or without MQ (0.005 μM - 5 μM) for 24 hours before measuring mitochondrial superoxide anion levels and DOX intracellular accumulation. Furthermore, heart rate (HR) and left ventricular end-systolic pressure (LVESP) were recorded before and after a 60-minute infusion of DOX or DOX with MQ in isolated rat hearts. TUNEL staining was performed on heart tissue slides to assess apoptosis. All the data was expressed as a ratio between treatment and DOX alone or between final to initial values. Statistical significance was evaluated using ANOVA with Student Newman Keuls post-hoc analysis. Results: Hearts perfused with DOX (25 µM, n = 5) displayed lower final LVESP with 39 ± 5% of the initial baseline. By contrast, hearts treated with 0.25 µM MQ (n = 4) or 1 µM MQ (n = 5) manifested exhibited a higher final LVESP to 44 ± 8% and 90 ± 6% of initial baselines, respectively. Additionally, MQ administration significantly reduced cardiac cell apoptosis to 8 ± 1% (0.25 µM, n = 2) and 6 ± 1% (1 µM, n = 5, p < 0.05) when compared to DOX (88 ± 2%, n = 4). In contrast to DOX, MQ (1 µM, n = 4) showed 27 ± 9% (n = 4) reduction in mitochondrial superoxide levels and 54 ± 6% (n = 6, p < 0.05) less intracellular DOX deposition in H9c2 cells. Conclusion: This study suggests acute DOX administration to the heart severely compromises cardiac systolic function with higher induction of cell apoptosis. MQ exerts cardio-protection with higher systolic function and cell viability by attenuating mitochondrial superoxide levels and intracellular DOX accumulation.

Abstract We095: Using Human Cardiac Organoids to Elucidate the Cardioprotective Potential of Mitochondrial-Targeted Therapies in a Preclinical Model of Diabetic Cardiomyopathy

Introduction: Mitochondrial dysregulation is implicated in many complications of type 2 diabetes (T2D). Mitochondrial-targeted therapies SkQ1, AP39 and SS31 limit renal T2D complications. We sought to obtain the first evidence of the cardioprotective potential of SkQ1, AP39 and SS31 in T2D, using a human induced pluripotent stem cell (iPSC)-derived 3D multicellular cardiac organoid model of diabetic cardiomyopathy. Methods: Human cardiac organoids (foreskin-2 cell-line) generated from human iPSC-derived cardiomyocytes, cardiac fibroblasts and endothelial cells were subjected to 5.55mM glucose (control) or T2D-like conditions (20mM glucose, fatty acids, endothelin-1 and cortisol) for 4 days with supplementation of either SkQ1 (50nM), AP39 (50nM) or SS31 (1µM) on day 2. On day 4, endpoint parameters were evaluated in cardiac organoids, including contractile function (captured via Olympus IX71), mitochondrial superoxide levels (MitoSOX assay), mitochondrial membrane potential (TMRM assay), and cellular injury (lactate dehydrogenase; LDH). Data are expressed as mean±SEM (fold control) with n =4-6 from 2-3 independent experiments. One-way ANOVA with Dunnett`s post hoc analysis was performed with P<0.05 considered significant. Results: After 4 days, T2D-conditions increased total contraction duration (1.55±0.10-fold control), time-to-peak (1.71±0.11-fold control, indicative of systolic dysfunction) and relaxation duration (1.46±0.13-fold control, indicative of diastolic dysfunction) in cardiac organoids. All 3 functional parameters were attenuated by AP39 (to 1.15±0.06, 1.32±0.09 and 1.04±0.04-fold control, respectively), or by SS31 (to 1.10±0.05, 1.12±0.15 and 1.09±0.12-fold control, respectively; all P<0.05), but not SkQ1. T2D-conditions increased mitochondrial superoxide (2.68±0.16-fold control), which was blunted by all 3 interventions, SkQ1 to 2.00±0.29, AP39 to 1.82±0.16 and SS31 to 1.89±0.17 (all P<0.05). Cellular injury was evident in T2D cardiac organoids (2.07±0.23-fold control), which was again limited by SkQ1 (to 1.06±0.11), AP39 (to 1.18±0.09) or SS31 (to 1.08±0.07), all P<0.05. Conclusion: These findings in human cardiac organoids highlight the cardioprotective potential of mitochondrial-targeted therapies to limit T2D-induced cardiac dysfunction, mitochondrial dysregulation and cellular injury, potentially facilitating clinical progression of candidates such as AP39 and SS31 as new therapies for patients with diabetic cardiomyopathy.

Cell stiffening is a label-free indicator of reactive oxygen species-induced intracellular acidification

Reactive oxygen species (ROS) are important secondary messengers involved in a variety of cellular processes, including activation, proliferation, and differentiation. Hydrogen peroxide (H2O2) is a major ROS typically kept in low nanomolar range that causes cell and tissue damage at supraphysiological concentrations. While ROS have been studied in detail at molecular scale, little is known about their impact on cell mechanical properties as label-free biomarker for stress response. Here, we exposed human myeloid precursor cells, T-lymphoid cells and neutrophils to varying concentrations of H2O2 and show that elevated levels of mitochondrial superoxide are accompanied by an increased Young’s modulus. Mechanical alterations do not originate from global modifications in filamentous actin and microtubules but from cytosolic acidification due to lysosomal degradation. Finally, we demonstrate our findings to be independent of the presence of H2O2 and that stiffening seems to be a general response of cells to stress factors lowering cytosolic pH.

Cardiac-targeted delivery of a novel Drp1 inhibitor for acute cardioprotection

Dynamin-related protein 1 (Drp1) is a mitochondrial fission protein and a viable target for cardioprotection against myocardial ischaemia-reperfusion injury. Here, we reported a novel Drp1 inhibitor (DRP1i1), delivered using a cardiac-targeted nanoparticle drug delivery system, as a more effective approach for achieving acute cardioprotection. DRP1i1 was encapsulated in cubosome nanoparticles with conjugated cardiac-homing peptides (NanoDRP1i1) and the encapsulation efficiency was 99.3 ± 0.1 %. In vivo, following acute myocardial ischaemia-reperfusion injury in mice, NanoDRP1i1 significantly reduced infarct size and serine-616 phosphorylation of Drp1, and restored cardiomyocyte mitochondrial size to that of sham group. Imaging by mass spectrometry revealed higher accumulation of DRP1i1 in the heart tissue when delivered as NanoDRP1i1. In human cardiac organoids subjected to simulated ischaemia-reperfusion injury, treatment with NanoDRP1i1 at reperfusion significantly reduced cardiac cell death, contractile dysfunction, and mitochondrial superoxide levels. Following NanoDRP1i1 treatment, cardiac organoid proteomics further confirmed reprogramming of contractile dysfunction markers and enrichment of the mitochondrial protein network, cytoskeletal and metabolic regulation networks when compared to the simulated injury group. These proteins included known cardioprotective regulators identified in human organoids and in vivo murine studies following ischaemia-reperfusion injury. DRP1i1 is a promising tool compound to study Drp1-mediated mitochondrial fission and exhibits promising therapeutic potential for acute cardioprotection, especially when delivered using the cardiac-targeted cubosome nanoparticles.

The NADPH oxidase inhibitor diphenyleneiodonium suppresses Ca2+ signaling and contraction in rat cardiac myocytes.

Diphenyleneiodonium (DPI) has been widely used as an inhibitor of NADPH oxidase (Nox) to discover its function in cardiac myocytes under various stimuli. However, the effects of DPI itself on Ca2+ signaling and contraction in cardiac myocytes under control conditions have not been understood. We investigated the effects of DPI on contraction and Ca2+ signaling and their underlying mechanisms using video edge detection, confocal imaging, and whole-cell patch clamp technique in isolated rat cardiac myocytes. Application of DPI suppressed cell shortenings in a concentration-dependent manner (IC50 of ≅0.17 µM) with a maximal inhibition of ~70% at ~100 µM. DPI decreased the magnitude of Ca2+ transient and sarcoplasmic reticulum Ca2+ content by 20%-30% at 3 µM that is usually used to remove the Nox activity, with no effect on fractional release. There was no significant change in the half-decay time of Ca2+ transients by DPI. The L-type Ca2+ current (ICa) was decreased concentration-dependently by DPI (IC50 of ≅40.3 µM) with ≅13.1%-inhibition at 3 µM. The frequency of Ca2+ sparks was reduced by 3 µM DPI (by ~25%), which was resistant to a brief removal of external Ca2+ and Na+. Mitochondrial superoxide level was reduced by DPI at 3-100 µM. Our data suggest that DPI may suppress L-type Ca2+ channel and RyR, thereby attenuating Ca2+-induced Ca2+ release and contractility in cardiac myocytes, and that such DPI effects may be related to mitochondrial metabolic suppression.

A novel marine-derived mitophagy inducer ameliorates mitochondrial dysfunction and thermal hypersensitivity in paclitaxel-induced peripheral neuropathy.

Mitochondrial dysfunction contributes to the pathogenesis and maintenance of chemotherapy-induced peripheral neuropathy (CIPN), a significant limitation of cancer chemotherapy. Recently, the stimulation of mitophagy, a pivotal process for mitochondrial homeostasis, has emerged as a promising treatment strategy for neurodegenerative diseases, but its therapeutic effect on CIPN has not been explored. Here, we assessed the mitophagy-inducing activity of 3,5-dibromo-2-(2',4'-dibromophenoxy)-phenol (PDE701), a diphenyl ether derivative isolated from the marine sponge Dysidea sp., and investigated its therapeutic effect on a CIPN model. Mitophagy activity was determined by a previously established mitophagy assay using mitochondrial Keima (mt-Keima). Mitophagy induction was further verified by western blotting, immunofluorescence, and electron microscopy. Mitochondrial dysfunction was analysed by measuring mitochondrial superoxide levels in SH-SY5Y cells and Drosophila larvae. A thermal nociception assay was used to evaluate the therapeutic effect of PDE701 on the paclitaxel-induced thermal hyperalgesia phenotype in Drosophila larvae. PDE701 specifically induced mitophagy but was not toxic to mitochondria. PDE701 ameliorated paclitaxel-induced mitochondrial dysfunction in both SH-SY5Y cells and Drosophila larvae. Importantly, PDE701 also significantly ameliorated paclitaxel-induced thermal hyperalgesia in Drosophila larvae. Knockdown of ATG5 or ATG7 abolished the effect of PDE701 on thermal hyperalgesia, suggesting that PDE701 exerts its therapeutic effect through mitophagy induction. This study identified PDE701 as a novel mitophagy inducer and a potential therapeutic compound for CIPN. Our results suggest that mitophagy stimulation is a promising strategy for the treatment of CIPN and that marine organisms are a potential source of mitophagy-inducing compounds.