Selective ATP hydrolysis inhibition in F1Fo ATP synthase enhances radiosensitivity in non-small-cell lung cancer cells (A549)

The Interplay between Autophagy and Mitochondria in Cancer

Besides producing cellular energy, mitochondria are crucial in controlling oxidative stress and modulating cellular metabolism, particularly under stressful conditions. A key aspect of this regulatory role involves the recycling process of autophagy, which helps to sustain energy homeostasis. Autophagy, a lysosome-dependent degradation pathway, plays a fundamental role in maintaining cellular homeostasis by degrading damaged organelles and misfolded proteins. In the context of tumor formation, autophagy significantly influences cancer metabolism and chemotherapy resistance, contributing to both tumor suppression and surveillance. This review focuses on the relationship between mitochondria and autophagy, specifically in the context of cancer progression. Investigating the interaction between autophagy and mitochondria reveals new possibilities for cancer treatments and may result in the development of more effective therapies targeting mitochondria, which could have significant implications for cancer treatment. Additionally, this review highlights the increasing understanding of autophagy's role in tumor development, with a focus on modulating mitochondrial function and autophagy in both pre-clinical and clinical cancer research. It also explores the potential for developing more-targeted and personalized therapies by investigating autophagy-related biomarkers.

Adverse effects of SYP-3343 on zebrafish development via ROS-mediated mitochondrial dysfunction

As a newly-invented and highly-efficiency strobilurin fungicide, pyraoxystrobin (SYP-3343) has been recognized as a highly poisonous toxin for a variety of aquatic organisms. Nevertheless, the developmental toxicity and potential mechanism of SYP-3343 have not been well-documented. The results showed that SYP-3343 was relatively stable and maintained within the range of 20 % in 24 h, and the LC₅₀ value to embryos at 72 hpf was 17.13 μg/L. The zebrafish embryotoxicity induced by 1, 2, 4, and 8 μg/L SYP-3343 is demonstrated by repressive embryo incubation, enhancive mortality rate, abnormal heart rate, malformed morphological characteristic, and impaired spontaneous coiling, indicating SYP-3343 mostly exerted its toxicity in a dose- and time-dependent manner. Besides SYP-3343 was critically involved in regulating cell cycle, mitochondrial membrane potential, and reactive oxygen species production as well as zebrafish primary cells apoptosis, which can be mitigated using antioxidant N-acetyl-L-cysteine. A significant change occurred in total protein content, the biochemical indices, and antioxidant capacities owing to SYP-3343 exposure. Additionally, SYP-3343 altered the mRNA levels of heart development-, mitochondrial function-, and apoptosis-related genes in zebrafish embryos. These results indicated that SYP-3343 induced apoptosis accompanying reactive oxygen species-initiated mitochondrial dysfunction in zebrafish embryos.

ANTP-SMACN7 fusion peptide alone induced high linear energy transfer irradiation radiosensitization in non-small cell lung cancer cell lines

OBJECTIVE

The aim of the present study was to investigate the mechanisms responsible for the radiation-sensitizing effect of antennapedia proteins, ANTP-SMACN7, on lung cancer cells treated with accelerated carbon and Fe particle irradiation.

METHODS

The ANTP-SMACN7 fusion peptide was synthesized and linked to fluorescein isothiocyanate to determine its ability to penetrate cells. A549 and NCI-H460 cells, human non-small cell lung cancer (NSCLC) cell lines, were irradiated with X-ray or high linear energy transfer (LET) irradiation with or without ANTP-SMACN7 treatment. Cellular survival, apoptosis, and protein expression were studied by colony formation assays, flow cytometry, and western blot analyses, respectively.

RESULTS

ANTP-SMACN7 fusion proteins entered the cells and promoted A549 and NCI-H460 cell high LET irradiation radiosensitization. High LET irradiation was more efficient for clonogenic cell killing and the induction of apoptosis (P < 0.05). Treatment with ANTP-SMACN7 significantly reduced the A549 and NCI-H460 cell clone-forming percentages and increased apoptosis through inhibition of the X-linked inhibitor of apoptosis protein and the activation of caspase-3 and caspase-9.

CONCLUSIONS

Regarding pharmaceutical radiosensitization, these findings provided a way to improve high-LET clinical radiotherapy for NSCLC patients.

Inhibitors of F1F0-ATP synthase enzymes for the treatment of tuberculosis and cancer

The spectacular success of the mycobacterial F₁F₀-ATP synthase inhibitor bedaquiline for the treatment of drug-resistant tuberculosis has generated wide interest in the development of other inhibitors of this enzyme. Work in this realm has included close analogues of bedaquiline with better safety profiles and 'bedaquiline-like' compounds, some of which show potent antibacterial activity in vitro although none have yet progressed to clinical trials. The search has lately extended to a range of new scaffolds as potential inhibitors, including squaramides, diaminoquinazolines, chloroquinolines, dihydropyrazolo[1,5-a]pyrazin-4-ones, thiazolidinediones, diaminopyrimidines and tetrahydroquinolines. Because of the ubiquitous expression of ATP synthase enzymes, there has also been interest in inhibitors of other bacterial ATP synthases, as well as inhibitors of human mitochondrial ATP synthase for cancer therapy. The latter encompass both complex natural products and simpler small molecules. The review seeks to demonstrate the breadth of the structural types of molecules able to effectively inhibit the function of variants of this intriguing enzyme.

DAP3 Is Involved in Modulation of Cellular Radiation Response by RIG-I-Like Receptor Agonist in Human Lung Adenocarcinoma Cells

Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) mediate anti-viral response through mitochondria. In addition, RLR activation induces anti-tumor effects on various cancers. We previously reported that the RLR agonist Poly(I:C)-HMW/LyoVec™ (Poly(I:C)) enhanced radiosensitivity and that cotreatment with Poly(I:C) and ionizing radiation (IR) more than additively increased cell death in lung adenocarcinoma cells, indicating that Poly(I:C) modulates the cellular radiation response. However, it remains unclear how mitochondria are involved in the modulation of this response. Here, we investigated the involvement of mitochondrial dynamics and mitochondrial ribosome protein death-associated protein 3 (DAP3) in the modulation of cellular radiation response by Poly(I:C) in A549 and H1299 human lung adenocarcinoma cell lines. Western blotting revealed that Poly(I:C) decreased the expression of mitochondrial dynamics-related proteins and DAP3. In addition, siRNA experiments showed that DAP3, and not mitochondrial dynamics, is involved in the resistance of lung adenocarcinoma cells to IR-induced cell death. Finally, we revealed that a more-than-additive effect of cotreatment with Poly(I:C) and IR on increasing cell death was diluted by DAP3-knockdown because of an increase in cell death induced by IR alone. Together, our findings suggest that RLR agonist Poly(I:C) modulates the cellular radiation response of lung adenocarcinoma cells by downregulating DAP3 expression.

The role of mitochondrial ATP synthase in cancer

The mitochondrial ATP synthase is a multi-subunit enzyme complex located in the inner mitochondrial membrane which is essential for oxidative phosphorylation under physiological conditions. In this review, we analyse the enzyme functions involved in cancer progression by dissecting specific conditions in which ATP synthase contributes to cancer development or metastasis. Moreover, we propose the role of ATP synthase in the formation of the permeability transition pore (PTP) as an additional mechanism which controls tumour cell death. We further describe transcriptional and translational modifications of the enzyme subunits and of the inhibitor protein IF1 that may promote adaptations leading to cancer metabolism. Finally, we outline ATP synthase gene mutations and epigenetic modifications associated with cancer development or drug resistance, with the aim of highlighting this enzyme complex as a potential novel target for future anti-cancer therapy.

Carbon ion combined with tigecycline inhibits lung cancer cell proliferation by inducing mitochondrial dysfunction

AIMS

Mitochondrial dysfunction is receiving considerable attention due to irreplaceable biological function of mitochondria. Ionizing radiation and tigecycline (TIG) alone can cause mitochondrial dysfunction, playing important role in tumor therapy. However, prior studies fail to investigate combined mechanism of carbon ion irradiation (IR) and TIG on tumor proliferation inhibition. The study aimed to explore the combined effects of both on autophagy and apoptosis.

MATERIALS AND METHODS

NSCLC cells A549 and H1299 were treated with carbon ion, TIG, or both. Cell survival rate, autophagy, apoptosis, expression of mitochondrial signaling proteins were determined by clone formation assay, immunofluorescence of LC3B, flow cytometry and western blotting, respectively; ATP content, mitochondrial membrane potential (MMP) and Ca²⁺ level in mitochondria were used to assessed mitochondrial function.

KEY FINDINGS

Results showed IR combined TIG inhibited cells proliferation by increasing apoptosis in both cells and enhancing autophagy in H1299 cells. Additionally, combination treatment induced the most severe mitochondrial dysfunction by sharply reducing ATP, MMP and increasing Ca²⁺ level of mitochondria. Up-regulation and down-regulation of mitochondrial translation proteins (EF-Tu, GFM1 and MRPS12) expression affected apoptosis and autophagy, while the level of p-mTOR was consistent with their expression in both cell types. In A549 cells, p-AMPK level decreased while p-Akt and p-mTOR increased after combination treatment.

SIGNIFICANCE

Overall, our results showed that p-Akt and p-AMPK antagonistically targeted p-mTOR to regulate mitochondrial translation proteins to affect autophagy and apoptosis. Furthermore, this study suggests that combination of carbon ion and TIG is a potential therapeutic option against tumors.

Natural products and other inhibitors of F1FO ATP synthase

F₁F_O ATP synthase is responsible for the production of >95% of all ATP synthesis within the cell. Dysregulation of its expression, activity or localization is linked to various human diseases including cancer, diabetes, and Alzheimer's and Parkinson's disease. In addition, ATP synthase is a novel and viable drug target for the development of antimicrobials as evidenced by bedaquiline, which was approved in 2012 for the treatment of tuberculosis. Historically, natural products have been a rich source of ATP synthase inhibitors that help unravel the role of F₁F_O ATP synthase in cellular bioenergetics. During the last decade, new modulators of ATP synthase have been discovered through the isolation of novel natural products as well as through a ligand-based drug design process. In addition, new data has been obtained with regards to the structure and function of ATP synthase under physiological and pathological conditions. Crystal structure studies have provided a significant insight into the rotary function of the enzyme and may provide additional opportunities to design a new generation of inhibitors. This review provides an update on recently discovered ATP synthase modulators as well as an update on existing scaffolds.

Targeting the Mitochondrial Metabolic Network: A Promising Strategy in Cancer Treatment

Metabolic reprogramming is a hallmark of cancer, which implements a profound metabolic rewiring in order to support a high proliferation rate and to ensure cell survival in its complex microenvironment. Although initial studies considered glycolysis as a crucial metabolic pathway in tumor metabolism reprogramming (i.e., the Warburg effect), recently, the critical role of mitochondria in oncogenesis, tumor progression, and neoplastic dissemination has emerged. In this report, we examined the main mitochondrial metabolic pathways that are altered in cancer, which play key roles in the different stages of tumor progression. Furthermore, we reviewed the function of important molecules inhibiting the main mitochondrial metabolic processes, which have been proven to be promising anticancer candidates in recent years. In particular, inhibitors of oxidative phosphorylation (OXPHOS), heme flux, the tricarboxylic acid cycle (TCA), glutaminolysis, mitochondrial dynamics, and biogenesis are discussed. The examined mitochondrial metabolic network inhibitors have produced interesting results in both preclinical and clinical studies, advancing cancer research and emphasizing that mitochondrial targeting may represent an effective anticancer strategy.

Deletion of the Mitochondrial Complex-IV Cofactor Heme A:Farnesyltransferase Causes Focal Segmental Glomerulosclerosis and Interferon Response

Mutations in mitochondrial DNA as well as nuclear-encoded mitochondrial proteins have been reported to cause tubulointerstitial kidney diseases and focal segmental glomerulosclerosis (FSGS). Recently, genes and pathways affecting mitochondrial turnover and permeability have been implicated in adult-onset FSGS. Furthermore, dysfunctioning mitochondria may be capable of engaging intracellular innate immune-sensing pathways. To determine the impact of mitochondrial dysfunction in FSGS and secondary innate immune responses, we generated Cre/loxP transgenic mice to generate a loss-of-function deletion mutation of the complex IV assembly cofactor heme A:farnesyltransferase (COX10) restricted to cells of the developing nephrons. These mice develop severe, early-onset FSGS with innate immune activation and die prematurely with kidney failure. Mutant kidneys showed loss of glomerular and tubular epithelial function, epithelial apoptosis, and, in addition, a marked interferon response. In vitro modeling of Cox10 deletion in primary kidney epithelium compromises oxygen consumption, ATP generation, and induces oxidative stress. In addition, loss of Cox10 triggers a selective interferon response, which may be caused by the leak of mitochondrial DNA into the cytosol activating the intracellular DNA sensor, stimulator of interferon genes. This new animal model provides a mechanism to study mitochondrial dysfunction in vivo and demonstrates a direct link between mitochondrial dysfunction and intracellular innate immune response.

Ameliorating mitochondrial dysfunction restores carbon ion-induced cognitive deficits via co-activation of NRF2 and PINK1 signaling pathway

Carbon ion therapy is a promising modality in radiotherapy to treat tumors, however, a potential risk of induction of late normal tissue damage should still be investigated and protected. The aim of the present study was to explore the long-term cognitive deficits provoked by a high-linear energy transfer (high-LET) carbon ions in mice by targeting to hippocampus which plays a crucial role in memory and learning. Our data showed that, one month after 4 Gy carbon ion exposure, carbon ion irradiation conspicuously resulted in the impaired cognitive performance, neurodegeneration and neuronal cell death, as well as the reduced mitochondrial integrity, the disrupted activities of tricarboxylic acid cycle flux and electron transport chain, and the depressed antioxidant defense system, consequently leading to a decline of ATP production and persistent oxidative damage in the hippocampus region. Mechanistically, we demonstrated the disruptions of mitochondrial homeostasis and redox balance typically characterized by the disordered mitochondrial dynamics, mitophagy and glutathione redox couple, which is closely associated with the inhibitions of PINK1 and NRF2 signaling pathway as the key regulators of molecular responses in the context of neurotoxicity and neurodegenerative disorders. Most importantly, we found that administration with melatonin as a mitochondria-targeted antioxidant promoted the PINK1 accumulation on the mitochondrial membrane, and augmented the NRF2 accumulation and translocation. Moreover, melatonin pronouncedly enhanced the molecular interplay between NRF2 and PINK1. Furthermore, in the mouse hippocampal neuronal cells, overexpression of NRF2/PINK1 strikingly protected the hippocampal neurons from carbon ion-elicited toxic insults. Thus, these data suggest that alleviation of the sustained mitochondrial dysfunction and oxidative stress through co-modulation of NRF2 and PINK1 may be in charge of restoration of the cognitive impairments in a mouse model of high-LET carbon ion irradiation.