Suppression of mitochondrial complex I influences cell metastatic properties

Transcriptomic meta-analysis and exploration of differentially expressed gene functions in wooden breast myopathy of broilers

Wooden breast (WB) myopathy is a common myopathy found in commercial broiler chickens worldwide. Although extensive research on WB has been conducted using transcriptomics, effectively screening and analyzing key target information remains a challenge. In this present study, 5 transcriptomic datasets obtained from the National Center for Biotechnology Information (NCBI) were used. A meta-analysis was conducted to identify meta-differentially expressed genes (meta-DEGs) involved in the response of broilers to WB myopathy. These meta-DEGs were further analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Gene Set Enrichment Analysis (GSEA), supplemented by protein-protein interaction (PPI) network construction to pinpoint hub genes. These analyses help to reveal key genes, pathways, and biological processes associated with WB myopathy. The results showed that 645 up-regulated and 99 down-regulated significant meta-DEGs (|log2FC| ≥0.6, P-Meta < 0.05, and present in at least 4 datasets) were identified. GO analysis showed that multiple fibrosis-related pathways/biological processes, such as cell adhesion, connective tissue development, and collagen-rich extracellular matrix, as well as calcium ion binding were significantly upregulated. PPI analysis identified TGFB3, COL1A1, COL1A2, and COL3A1 as central hub genes involved in the fibrotic processes. KEGG analysis revealed significant upregulation of apoptosis and lysosomal pathways, with an enrichment of Ca2+-related signals and lysosomal cathepsins within the apoptosis pathway. Additionally, GSEA indicated a suppression of the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain (ETC) in WB myopathy, with PPI analysis also identifying specific hub genes associated with these pathways. In conclusion, our comprehensive analysis of meta-DEGs elucidated key biological processes and pathways implicated in WB myopathy, including fibrosis, apoptosis, altered calcium signaling, and metabolic disruption. The identification of specific hub genes offers avenues for further investigation into the pathogenesis of this condition, potentially guiding targeted therapeutic strategies.

Tankyrase1/2 inhibitor XAV-939 reverts EMT and suggests that PARylation partially regulates aerobic activities in human hepatocytes and HepG2 cells

The maintenance of a highly functional metabolic epithelium in vitro is challenging. Metabolic impairments in primary human hepatocytes (PHHs) over time is primarily due to epithelial-to-mesenchymal transitioning (EMT). The immature hepatoma cell line HepG2 was used as an in vitro model to explore strategies for enhancing the hepatic phenotype. The phenotypic characterization includes measuring the urea cycle, lipid storage, tricarboxylic acid-related metabolites, reactive oxygen species, endoplasmic reticulum calcium efflux, mitochondrial membrane potentials, oxygen consumptions rate, and CYP450 biotransformation capacity. Expression studies were performed with transcriptomics, co-immunoprecipitation and proteomics. CRISPR/Cas9 was also employed to genetically engineer HepG2 cells. After confirming that PHHs develop an EMT phenotype, expression of tankyrase1/2 was found to increase over time. EMT was reverted when blocking tankyrases1/2-dependent poly-ADP-ribosylation (PARylation) activity, by biochemical and genetic perturbation. Wnt/β-catenin inhibitor XAV-939 blocks tankyrase1/2 and treatment elevated several oxygen-consuming reactions (electron-transport chain, OXHPOS, CYP450 mono-oxidase activity, phase I/II xenobiotic biotransformation, and prandial turnover), suggesting that cell metabolism was enhanced. Glutathione-dependent redox homeostasis was also significantly improved in the XAV-939 condition. Oxygen consumption rate and proteomics experiments in tankyrase1/2 double knockout HepG2 cells then uncovered PARylation as master regulator of aerobic-dependent cell respiration. Furthermore, novel tankyrase1/2-dependent PARylation targets, including mitochondrial DLST, and OGDH, were revealed. This work exposed a new mechanistic framework by linking PARylation to respiration and metabolism, thereby broadening the current understanding that underlies these vital processes. XAV-939 poses an immediate and straightforward strategy to improve aerobic activities, and metabolism, in (immature) cell cultures.

SGK3 deficiency in macrophages suppresses angiotensin II-induced cardiac remodeling via regulating Ndufa13-mediated mitochondrial oxidative stress

Infiltration of monocyte-derived macrophages plays a crucial role in cardiac remodeling and dysfunction. The serum and glucocorticoid-inducible protein kinase 3 (SGK3) is a downstream factor of PI3K signaling, regulating various biological processes via an AKT-independent signaling pathway. SGK3 has been implicated in cardiac remodeling. However, the contribution of macrophagic SGK3 to hypertensive cardiac remodeling remains unclear. A cardiac remodeling model was established by angiotensin II (Ang II) infusion in SGK3-Lyz2-CRE (f/f, +) and wild-type mice to assess the function of macrophagic SGK3. Additionally, a co-culture system of SGK3-deficient or wild-type macrophages and neonatal rat cardiomyocytes (CMs) or neonatal rat fibroblasts (CFs) was established to evaluate the effects of SGK3 and the underlying mechanisms. SGK3 levels were significantly elevated in both peripheral blood mononuclear cells and serum from patients with heart failure. Macrophage SGK3 deficiency attenuated Ang II-induced macrophage infiltration, myocardial hypertrophy, myocardial fibrosis, and mitochondrial oxidative stress. RNA sequencing suggested Ndufa13 as the candidate gene in the effect of SGK3 on Ang II-induced cardiac remolding. Downregulation of Ndufa13 in CMs and CFs prevented the suppression of cardiac remodeling caused by SGK3 deficiency in macrophages. Mechanistically, the absence of SGK3 led to a reduction in IL-1β secretion by inhibiting the NLRP3/Caspase-1/IL-1β pathway in macrophages, consequently suppressing upregulated Ndufa13 expression and mitochondrial oxidative stress in CMs and CFs. This study provides new evidence that SGK3 is a potent contributor to the pathogenesis of hypertensive cardiac remodeling, and targeting SGK3 in macrophages may serve as a potential therapy for cardiac remodeling.

Correction: Suppression of Mitochondrial Complex I Influences Cell Metastatic Properties

[This corrects the article DOI: 10.1371/journal.pone.0061677.].

Complex I activity in hypoxia: implications for oncometabolism

Certain cancer cells within solid tumors experience hypoxia, rendering them incapable of oxidative phosphorylation (OXPHOS). Despite this oxygen deficiency, these cells exhibit biochemical pathway activity that relies on NAD+. This mini-review scrutinizes the persistent, residual Complex I activity that oxidizes NADH in the absence of oxygen as the electron acceptor. The resulting NAD+ assumes a pivotal role in fueling the α-ketoglutarate dehydrogenase complex, a critical component in the oxidative decarboxylation branch of glutaminolysis - a hallmark oncometabolic pathway. The proposition is that through glutamine catabolism, high-energy phosphate intermediates are produced via substrate-level phosphorylation in the mitochondrial matrix substantiated by succinyl-CoA ligase, partially compensating for an OXPHOS deficiency. These insights provide a rationale for exploring Complex I inhibitors in cancer treatment, even when OXPHOS functionality is already compromised.

Anti-Cancer Potency of Copper-Doped Carbon Quantum Dots Against Breast Cancer Progression

Introduction

The anti-cancer potency of copper-doped carbon quantum dots (Cu-CDs) against breast cancer progression needs more detailed investigations.

Methods

With urea and ethylene glycol applied as carbon sources and copper sulfate used as a reactive dopant, Cu-CDs were synthesized in the current study by a one-step hydrothermal synthesis method, followed by the characterization and biocompatibility evaluations of Cu-CDs. Subsequently, the anti-cancer potency of Cu-CDs against breast cancer progression was confirmed by these biochemical, molecular, and transcriptomic assessments, including viability, proliferation, migration, invasion, adhesion, clonogenicity, cell cycle distribution, apoptosis, redox homeostasis, and transcriptomic assays of MDA-MB-231 cells.

Results

The biocompatibility of Cu-CDs was confirmed based on the non-significant changes in the pathological and physiological parameters in the Cu-CDs treated mice, as well as the noncytotoxic effect of Cu-CDs on normal cells. Moreover, the Cu-CDs treatments not only decreased the viability, proliferation, migration, invasion, adhesion, and clonogenicity of MDA-MB-231 cells but also induced the redox imbalance, cell cycle arrest, and apoptosis of MDA-MB-231 cells via ameliorating the mitochondrial dysfunctions and regulating the MAPK signaling pathway.

Conclusion

Our findings confirmed the biosafety and excellent anti-cancer potency of Cu-CDs against breast cancer progression by tapping into mechanisms that disrupt malignant behaviors and oxidative homeostasis of breast cancer cells.

Loss of NDUFS1 promotes gastric cancer progression by activating the mitochondrial ROS-HIF1α-FBLN5 signaling pathway

BACKGROUND

Recent studies suggested that NDUFS1 has an important role in human cancers; however, the effects of NDUFS1 on gastric cancer (GC) are still not fully understood.

METHODS

We confirmed that NDUFS1 is downregulated in GC cells through western blot immunohistochemistry and bioinformation analysis. The effect of NDUFS1 on GC was studied by CCK-8, colony formation, transwell assay in vitro and Mouse xenograft assay in vivo. Expression and subcellular localization of NDUFS1 and the content of mitochondrial reactive oxygen species (mROS) was observed by confocal reflectance microscopy.

RESULTS

Reduced expression of NDUFS1 was found in GC tissues and cell lines. Also, NDUFS1 overexpression inhibited GC cell proliferation, migration, and invasion in vitro as well as growth and metastasis in vivo. Mechanistically, NDUFS1 reduction led to the activation of the mROS-hypoxia-inducible factor 1α (HIF1α) signaling pathway. We further clarified that NDUFS1 reduction upregulated the expression of fibulin 5 (FBLN5), a transcriptional target of HIF1α, through activation of mROS-HIF1α signaling in GC cells.

CONCLUSIONS

The results of this study indicate that NDUFS1 downregulation promotes GC progression by activating an mROS-HIF1α-FBLN5 signaling pathway.

The Interplay between Dysregulated Metabolism and Epigenetics in Cancer

Cellular metabolism (or energetics) and epigenetics are tightly coupled cellular processes. It is arguable that of all the described cancer hallmarks, dysregulated cellular energetics and epigenetics are the most tightly coregulated. Cellular metabolic states regulate and drive epigenetic changes while also being capable of influencing, if not driving, epigenetic reprogramming. Conversely, epigenetic changes can drive altered and compensatory metabolic states. Cancer cells meticulously modify and control each of these two linked cellular processes in order to maintain their tumorigenic potential and capacity. This review aims to explore the interplay between these two processes and discuss how each affects the other, driving and enhancing tumorigenic states in certain contexts.

The Oligostilbene Gnetin H Is a Novel Glycolysis Inhibitor That Regulates Thioredoxin Interacting Protein Expression and Synergizes with OXPHOS Inhibitor in Cancer Cells

Since aerobic glycolysis was first observed in tumors almost a century ago by Otto Warburg, the field of cancer cell metabolism has sparked the interest of scientists around the world as it might offer new avenues of treatment for malignant cells. Our current study claims the discovery of gnetin H (GH) as a novel glycolysis inhibitor that can decrease metabolic activity and lactic acid synthesis and displays a strong cytostatic effect in melanoma and glioblastoma cells. Compared to most of the other glycolysis inhibitors used in combination with the complex-1 mitochondrial inhibitor phenformin (Phen), GH more potently inhibited cell growth. RNA-Seq with the T98G glioblastoma cell line treated with GH showed more than an 80-fold reduction in thioredoxin interacting protein (TXNIP) expression, indicating that GH has a direct effect on regulating a key gene involved in the homeostasis of cellular glucose. GH in combination with phenformin also substantially enhances the levels of p-AMPK, a marker of metabolic catastrophe. These findings suggest that the concurrent use of the glycolytic inhibitor GH with a complex-1 mitochondrial inhibitor could be used as a powerful tool for inducing metabolic catastrophe in cancer cells and reducing their growth.

Recent advances of mitochondrial complex I inhibitors for cancer therapy: Current status and future perspectives

Mitochondrial complex I (CI) as a critical multifunctional respiratory complex of electron transport chain (ETC) in mitochondrial oxidative phosphorylation has been identified as vital and essence in ATP production, biosynthesis and redox balance. Recent progress in targeting CI has provided both insight and inspiration for oncotherapy, highlighting that the development of CI-targeting inhibitors is a promising therapeutic approach to fight cancer. Natural products possessing of ample scaffold diversity and structural complexity are the majority source of CI inhibitors, although low specificity and safety hinder their extensive application. Along with the gradual deepening in understanding of CI structure and function, significant progress has been achieved in exploiting novel and selective small molecules targeting CI. Among them, IACS-010759 had been approved by FDA for phase I trial in advanced cancers. Moreover, drug repurposing represents an effective and prospective strategy for CI inhibitor discovery. In this review, we mainly elaborate the biological function of CI in tumor progression, summarize the CI inhibitors reported in recent years and discuss the further perspectives for CI inhibitor application, expecting this work may provide insights into innovative discovery of CI-targeting drugs for cancer treatment.

GRIM-19 in asthenozoospermia regulates GC-2 spd cell proliferation, apoptosis and migration

Asthenozoospermia (AZS) is a severe form of male infertility with no clear pathogenesis, despite numerous research efforts, there is no consensus on this. This study was to investigate the expression of gene-associated with retinoid-interferon-induced mortality 19 (GRIM-19) in the sperm of patients with asthenozoospermia and the regulation of GC-2 spd cell proliferation, apoptosis and migration. We analyzed the sperm samples from 82 asthenozoospermia and normal patients were collected in the First People's Hospital of Shangqiu and the First Affiliated Hospital of Zhengzhou University. Immunofluorescence, western blots and RT-qPCR analyses were used to verify the expressions of GRIM-19. MTT assays were used to assess cell proliferations, flow cytometry was performed to assess cell apoptosis, wound‑healing was performed to measure cell migration. Immunofluorescence showed that GRIM-19 is predominantly expressed in the sperm mid-piece, the mRNA expressions of GRIM-19 in sperms of the asthenozoospermia group were significantly low, relative to the normal group (OR 0.266; 95% CI = 0.081-0.868; P = 0.028). The protein expressions of GRIM-19 in sperms of the asthenozoospermia group were significantly lower than that of the normal group as well (GRIM-19/GAPDH: 0.827 ± 0.063 vs 0.458 ± 0.033; P < 0.001). GRIM-19 overexpression promotes GC-2 spd cell proliferation and migration and reduces apoptosis, while GRIM-19-silenced reduces GC-2 spd cell proliferation and migration and increased apoptosis. GRIM-19 is closely related to the occurrence of asthenozoospermia and promotes GC-2 spd cell proliferation and migration and reduces apoptosis.

Energy metabolism pathways in breast cancer progression: The reprogramming, crosstalk, and potential therapeutic targets

Breast cancer (BC) is a malignant tumor that seriously endangers health in women. BC, like other cancers, is accompanied by metabolic reprogramming. Among energy metabolism-related pathways, BC exhibits enhanced glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway (PPP), glutamate metabolism, and fatty acid metabolism activities. These pathways facilitate the proliferation, growth and migration of BC cells. The progression of BC is closely related to the alterations in the activity or expression level of several metabolic enzymes, which are regulated by the intrinsic factors such as the key signaling and transcription factors. The metabolic reprogramming in the progression of BC is attributed to the aberrant expression of the signaling and transcription factors associated with the energy metabolism pathways. Understanding the metabolic mechanisms underlying the development of BC will provide a druggable potential for BC treatment and drug discovery.

Mitochondrial respiratory complexes: Significance in human mitochondrial disorders and cancers

Mitochondria are pivotal organelles that govern cellular energy production through the oxidative phosphorylation system utilizing five respiratory complexes. In addition, mitochondria also contribute to various critical signaling pathways including apoptosis, damage-associated molecular patterns, calcium homeostasis, lipid, and amino acid biosynthesis. Among these diverse functions, the energy generation program oversee by mitochondria represents an immaculate orchestration and functional coordination between the mitochondria and nuclear encoded molecules. Perturbation in this program through respiratory complexes' alteration results in the manifestation of various mitochondrial disorders and malignancy, which is alarmingly becoming evident in the recent literature. Considering the clinical relevance and importance of this emerging medical problem, this review sheds light on the timing and nature of molecular alterations in various respiratory complexes and their functional consequences observed in various mitochondrial disorders and human cancers. Finally, we discussed how this wealth of information could be exploited and tailored to develop respiratory complex targeted personalized therapeutics and biomarkers for better management of various incurable human mitochondrial disorders and cancers.

Increased COX-1 expression in benign prostate epithelial cells is triggered by mitochondrial dysfunction

BACKGROUND

Prostatic inflammation is closely linked to the development and progression of benign prostatic hyperplasia (BPH). Clinical studies of non-steroidal anti-inflammatory drugs, which inhibit cyclooxygenase-2 (COX-2), targeting prostate inflammation patients with symptomatic BPH have demonstrated conflicting results, with some studies demonstrating symptom improvement and others showing no impact. Thus, understanding the role of the cyclooxygenases in BPH and prostatic inflammation is important.

METHODS

The expression of COX-1 was analyzed in a cohort of donors and BPH patients by immunohistochemistry and compared to previously determined characteristics for this same cohort. The impact of mitochondrial dysfunction on COX-1 and COX-2 was determined in experiments treating human benign prostate epithelial cell lines BPH-1 and RWPE-1 with rotenone and MitoQ. RWPE-1 cells were transfected with small interfering RNA specific to complex 1 gene NDUFS3.

RESULTS

COX-1 expression was increased in the epithelial cells of BPH specimens compared to young healthy organ donor and normal prostate adjacent to BPH and frequently co-occurred with COX-2 alteration in BPH patients. COX-1 immunostaining was associated with the presence of CD8+ cytotoxic T-cells, but was not associated with age, prostate size, COX-2 or the presence of CD4+, CD20+ or CD68+ inflammatory cells. In cell line studies, COX protein levels were elevated following treatment with inhibitors of mitochondrial function. MitoQ significantly decreased mitochondrial membrane potential in RWPE-1 cells. Knockdown of NDUFS3 stimulated COX-1 expression.

CONCLUSION

Our findings suggest COX-1 is elevated in BPH epithelial cells and is associated with increased presence of CD8+ cytotoxic T-cells. COX-1 can be induced in benign prostate epithelial cells in response to mitochondrial complex I inhibition, and knockdown of the complex 1 protein NDUFS3. COX-1 and mitochondrial dysfunction may play more of a role than previously recognized in the development of age-related benign prostatic disease.

Mitochondrial dysfunction and epithelial to mesenchymal transition in head neck cancer cell lines

Mitochondrial dysfunction promotes cancer aggressiveness, metastasis, and resistance to therapy. Similar traits are associated with epithelial mesenchymal transition (EMT). We questioned whether mitochondrial dysfunction induces EMT in head and neck cancer (HNC) cell lines. We induced mitochondrial dysfunction in four HNC cell lines with carbonyl cyanide-4(trifluoromethoxy)phenylhydrazone (FCCP), a mitochondrial electron transport chain uncoupling agent, and oligomycin, a mitochondrial ATP synthase inhibitor. Extracellular flux analyses and expression of the cystine/glutamate antiporter system xc (xCT) served to confirm mitochondrial dysfunction. Expression of the EMT-related transcription factor SNAI2, the mesenchymal marker vimentin and vimentin/cytokeratin double positivity served to detect EMT. In addition, holotomographic microscopy was used to search for morphological features of EMT. Extracellular flux analysis and xCT expression confirmed that FCCP/oligomycin induced mitochondrial dysfunction in all cell lines. Across the four cell lines, mitochondrial dysfunction resulted in an increase in relative SNAI2 expression from 8.5 ± 0.8 to 12.0 ± 1.1 (mean ± SEM; p = 0.007). This effect was predominantly caused by the CAL 27 cell line (increase from 2.2 ± 0.4 to 5.5 ± 1.0; p < 0.001). Similarly, only in CAL 27 cells vimentin expression increased from 2.2 ± 0.5 × 10^-3 to 33.2 ± 10.2 × 10^-3 (p = 0.002) and vimentin/cytokeratin double positive cells increased from 34.7 ± 5.1 to 67.5 ± 9.8% (p = 0.003), while the other 3 cell lines did not respond with EMT (all p > 0.1). Across all cell lines, FCCP/oligomycin had no effect on EMT characteristics in holotomographic microscopy. Mitochondrial dysfunction induced EMT in 1 of 4 HNC cell lines. Given the heterogeneity of HNC, mitochondrial dysfunction may be sporadically induced by EMT, but EMT does not explain the tumor promoting effects of mitochondrial dysfunction in general.

Mitochondria-actin cytoskeleton crosstalk in cell migration

Mitochondria perform diverse functions in the cell and their roles during processes such as cell survival, differentiation, and migration are increasingly being appreciated. Mitochondrial and actin cytoskeletal networks not only interact with each other, but this multifaceted interaction shapes their functional dynamics. The interrelation between mitochondria and the actin cytoskeleton extends far beyond the requirement of mitochondrial ATP generation to power actin dynamics, and impinges upon several major aspects of cellular physiology. Being situated at the hub of cell signaling pathways, mitochondrial function can alter the activity of actin regulatory proteins and therefore modulate the processes downstream of actin dynamics such as cellular migration. As we will discuss, this regulation is highly nuanced and operates at multiple levels allowing mitochondria to occupy a strategic position in the regulation of migration, as well as pathological events that rely on aberrant cell motility such as cancer metastasis. In this review, we summarize the crosstalk that exists between mitochondria and actin regulatory proteins, and further emphasize on how this interaction holds importance in cell migration in normal as well as dysregulated scenarios as in cancer.

Identification of the Upregulation of MRPL13 as a Novel Prognostic Marker Associated with Overall Survival Time and Immunotherapy Response in Breast Cancer

Mitochondrial ribosomal protein (MRPL) genes have been reported to participate in many cellular processes, such as cell proliferation, apoptosis, and cell cycle. Meanwhile, the occurrence rate of breast cancer (BRCA) in China steadily increased. Exploring the prognostic value of MRPL genes in BRCA could provide novel biomarkers for BRCA. In this study, to identify prognosis-related genes in breast cancer, the P value and the hazard ratio (HR) of all genes are analyzed with TCGA database. We revealed higher expression level of CEL, PGK1, WNT3A, USP41, LINC02037, PCMT1, LRP11, MCTS1, TCP1, TMEM31, STK4-AS1, STXBP5, LOC100287036, SLC16A2, MRPL13, DERL1, and TARS was correlated to shorter OS time in BRCA. However, higher expression level of JCHAIN, KLRB1, and TNFRSF14 was correlated to longer OS time in BRCA. The further analysis demonstrated MRPL13 was overexpressed in BRCA. Subtype analysis showed that MRPL13 was overexpressed in luminal, HER2-positive BRCA, and TNBC samples and was highest in TNBC samples. Moreover, we revealed higher expression of MRPL13 was significantly correlated to shorter OS time and higher TMB levels in BRCA. Pan-cancer analysis further revealed the prognostic value of MRPL13 in human cancers. MRPL13 expression was significantly increased in multiple human cancers, such as bladder cancer, colon cancer, liver cancer, and prostate cancer. Pan-cancer TMB and overall survival time showed dysregulation of MRPL13 is significantly related to the OS and TMB levels in various cancers. These results further proved that MRPL13 may be a pan-cancer biomarker for predicting prognosis and the response to immunotherapy.

Mechanisms for the impacts of graphene oxide on the developmental toxicity and endocrine disruption induced by bisphenol A on zebrafish larvae

The huge production and application of bisphenol A (BPA) and graphene oxide (GO) inevitably lead to their co-presence in aquatic ecosystems, which might cause joint toxic effects to aquatic organisms. Herein, zebrafish larvae at 3 d post fertilization (dpf) were exposed to BPA, GO, and their mixtures until 7 dpf. GO was ingested and localized in the gut. 5000 μg/L BPA alone induced distinct ultrastructure damage, which was alleviated by GO, indicating that GO reduced the developmental toxicity of BPA. The levels of endocrine-related genes and steroid hormones were all modulated to the greatest extent by 500 μg/L BPA, suggesting that BPA exhibited a remarkable endocrine disruption effect. However, the responses of some of these genes were recovered by GO, indicating that GO also alleviated the BPA-induced endocrine disruption. The mRNA levels of five genes in the extracellular matrix-receptor interaction pathway, two in the oxidative phosphorylation pathway, 18 in the metabolic pathways, and five in the peroxisome proliferator-activated receptor signaling pathway were distinctly altered by 5000 μg/L BPA, but most of them were recovered in the presence of GO. GO might relieve the BPA-induced developmental toxicity and endocrine disruption by recovering the genes related to the corresponding pathways.

[Pathogenic role of NDUFA13 inactivation in spontaneous hepatitis in mice and the mechanism]

OBJECTIVE

To investigate the role of NDUFA13 inactivation in the pathogenesis of spontaneous hepatitis in mice and explore the possible mechanisms.

METHODS

Hepatocyte-specific NDUFA13 knockout (NDUFA13^fl/-) mice were generated by intercrossing NDUFA13^fl/fl and Alb-Cre mice based on Cre/loxP transgenic technology, and tail and liver DNA of the mice was genotyped by PCR analysis. Ten NDUFA13^fl/- mice and 10 littermate control NDUFA13^fl/fl mice were housed, and in each group, 5 mice were euthanized at the age of 4 weeks and the other 5 at two years for pathological examination of the liver tissues with HE staining. Immunohistochemistry was used to verify the expression levels of NDUFA13, NF-κB/p65, NF-κB/p-p65 and inflammasome NLRP3. The total intracellular ROS and mitochondrial ROS levels were measured with a ROS staining kit. The expressions of the inflammatory cell markers (CD45, MPO, and F4/80) and inflammatory cytokines (IL1β and IL33) in the liver were detected with immunohistochemistry and immunofluorescence assay.

RESULTS

Liver-specific NDUFA13 heterozygous knockout mice were successfully constructed as verified by PCR results. HE staining revealed severe liver damage in both 4- week-old and 2-year-old NDUFA13^fl/- mice as compared with their littermate controls. Immunohistochemistry showed a significant decrease of NDUFA13 expression in both 4-week-old and 2-year-old NDUFA13^fl/- mice (P < 0.05). The expression levels of NF-κB signals p65, p-p65 and NLRP3 inflammasomes were all significantly increased in NDUFA13^fl/- mice (P < 0.05). The total intracellular ROS and mitochondrial ROS levels in NDUFA13^fl/- mice were also significantly increased. NDUFA13 knockout obviously promoted the expression of the inflammatory cell markers (CD45, MPO and F4/80) and the secretion of IL-1β and IL-33 in the liver tissue of the mice (P < 0.05).

CONCLUSIONS

Hepatocytes-specific NDUFA13 ablation can trigger spontaneous hepatitis in mice possibly mediated by the activation of ROS/NF-κB/NLRP3 signaling.

Bioinformatics analysis reveals TSPAN1 as a candidate biomarker of progression and prognosis in pancreatic cancer

Pancreatic cancer (PCC) is a common malignant tumor of the digestive system that is resistant to traditional treatments and has an overall 5-year survival rate of <7%. Transcriptomics research provides reliable biomarkers for diagnosis, prognosis, and clinical precision treatment, as well as the identification of molecular targets for the development of drugs to improve patient survival. We sought to identify new biomarkers for PCC by combining transcriptomics and clinical data with current knowledge regarding molecular mechanisms. Consequently, we employed weighted gene co-expression network analysis and differentially expressed gene analysis to evaluate genes co-expressed in tumor versus normal tissues using pancreatic adenocarcinoma data from The Cancer Genome Atlas and dataset GSE16515 from the Gene Expression Omnibus. Twenty-one overlapping genes were identified, with enrichment of key Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways, including epidermal growth factor receptor signaling, cadherin, cell adhesion, ubiquinone, and glycosphingolipid biosynthesis pathways, and retinol metabolism. Protein-protein interaction analysis highlighted 10 hub genes, according to Maximal Clique Centrality. Univariate and multivariate COX analyses indicated that TSPAN1 serves as an independent prognostic factor for PCC patients. Survival analysis distinguished TSPAN1 as an independent prognostic factor among hub genes in PCC. Finally, immunohistochemical staining results suggested that the TSPAN1 protein levels in the Human Protein Atlas were significantly higher in tumor tissue than in normal tissue. Therefore, TSPAN1 may be involved in PCC development and act as a critical biomarker for diagnosing and predicting PCC patient survival.

The intervention mechanism of emodin on TLR3 pathway in the process of central nervous system injury caused by herpes virus infection

Background and purpose: To investigate the effect of Emodin on the inflammatory response of brain tissue and the expression of the TLR3 pathway in mice with herpes virus encephalitis.Method: Twenty male BALB/c mice were randomly divided into the NS group, HSV-1 group, HSV-1 + Emodin group and HSV-1 + ACV group. The histopathological features and the effect of TLR3 expression were observed by staining and immunohistochemistry (IHC) respectively. The gene expression of TLR3, trif, TRADD, TRAF6, traf3, p38, Nemo and IRF3 was detected by polymerase chain reaction (PCR). The protein production of TLR3 and its downstream molecules was detected by Western blot. The expression of IL-6, TNF-α and IFN-β in the brain tissues was detected by ELISA.Result: Compared to the HSV-1 group, the pathological changes (inflammatory cell infiltration, necrotic temporal lobe and massive hemorrhage) were not as obvious as those in the HSV-1+emodin and HSV-1+ACV groups. The TLR3 staining increased significantly in the HSV-1 groups and decreased in the HSV-1 + emodin group. Compared with the NS group, the mRNA expression of TLR3, TRIF, TRADD, TRAF6, traf3, p38, NEMO and IRF3 decreased by 20%-60% in the HSV-1 + emodin group and 30% in the HSV-1 + ACV group, respectively. The expression of IL-6, TNF-α and IFN-β decreased by 30%-50% in the HSV-1 + emodin group and showed no significant change in the HSV-1 + ACV group, respectively.Conclusion: Emodin could inhibit the inflammatory response in the brain of mice with herpes virus encephalitis. The inhibition of TLR3 expression may play an important role in this process.

Differential regulation of mitochondrial complex I and oxidative stress based on metastatic potential of colorectal cancer cells

Mitochondria serve a vital role in cellular homeostasis as they regulate cell proliferation and death pathways, which are attributed to mitochondrial bioenergetics, free radicals and metabolism. Alterations in mitochondrial functions have been reported in various diseases, including cancer. Colorectal cancer (CRC) is one of the most common metastatic cancer types with high mortality rates. Although mitochondrial oxidative stress has been associated with CRC, its specific mechanism and contribution to metastatic progression remain poorly understood. Therefore, the aims of the present study were to investigate the role of mitochondria in CRC cells with low and high metastatic potential and to evaluate the contribution of mitochondrial respiratory chain (RC) complexes in oncogenic signaling pathways. The present results demonstrated that cell lines with low metastatic potential were resistant to mitochondrial complex I (C-I)-mediated oxidative stress, and had C-I inhibition with impaired mitochondrial functions. These adaptations enabled cells to cope with higher oxidative stress. Conversely, cells with high metastatic potential demonstrated functional C-I with improved mitochondrial function due to coordinated upregulation of mitochondrial biogenesis and metabolic reprogramming. Pharmacological inhibition of C-I in high metastatic cells resulted in increased sensitivity to cell death and decreased metastatic signaling. The present findings identified the differential regulation of mitochondrial functions in CRC cells, based on CRC metastatic potential. Specifically, it was suggested that a functional C-I is required for high metastatic features of cancer cells, and the role of C-I could be further examined as a potential target in the development of novel therapies for diagnosing high metastatic cancer types.

Targeting the Redox Landscape in Cancer Therapy

Reactive oxygen species (ROS) are produced predominantly by the mitochondrial electron transport chain and by NADPH oxidases in peroxisomes and in the endoplasmic reticulum. The antioxidative defense counters overproduction of ROS with detoxifying enzymes and molecular scavengers, for instance, superoxide dismutase and glutathione, in order to restore redox homeostasis. Mutations in the redox landscape can induce carcinogenesis, whereas increased ROS production can perpetuate cancer development. Moreover, cancer cells can increase production of antioxidants, leading to resistance against chemo- or radiotherapy. Research has been developing pharmaceuticals to target the redox landscape in cancer. For instance, inhibition of key players in the redox landscape aims to modulate ROS production in order to prevent tumor development or to sensitize cancer cells in radiotherapy. Besides the redox landscape of a single cell, alternative strategies take aim at the multi-cellular level. Extracellular vesicles, such as exosomes, are crucial for the development of the hypoxic tumor microenvironment, and hence are explored as target and as drug delivery systems in cancer therapy. This review summarizes the current pharmaceutical and experimental interventions of the cancer redox landscape.

Mitochondrial DNA mutations in Malaysian female breast cancer patients

Cancer development has been ascribed with diverse genetic variations which are identified in both mitochondrial and nuclear genomes. Mitochondrial DNA (mtDNA) alterations have been detected in several tumours which include lung, colorectal, renal, pancreatic and breast cancer. Several studies have explored the breast tumour-specific mtDNA alteration mainly in Western population. This study aims to identify mtDNA alterations of 20 breast cancer patients in Malaysia by next generation sequencing analysis. Twenty matched tumours with corresponding normal breast tissues were obtained from female breast cancer patients who underwent mastectomy. Total DNA was extracted from all samples and the entire mtDNA (16.6kb) was amplified using long range PCR amplification. The amplified PCR products were sequenced using mtDNA next-generation sequencing (NGS) on an Illumina Miseq platform. Sequencing involves the entire mtDNA (16.6kb) from all pairs of samples with high-coverage (~ 9,544 reads per base). MtDNA variants were called and annotated using mtDNA-Server, a web server. A total of 18 of 20 patients had at least one somatic mtDNA mutation in their tumour samples. Overall, 65 somatic mutations were identified, with 30 novel mutations. The majority (59%) of the somatic mutations were in the coding region, whereas only 11% of the mutations occurred in the D-loop. Notably, somatic mutations in protein-coding regions were non-synonymous (49%) in which 15.4% of them are potentially deleterious. A total of 753 germline mutations were identified and four of which were novel mutations. Compared to somatic alterations, less than 1% of germline missense mutations are harmful. The findings of this study may enhance the current knowledge of mtDNA alterations in breast cancer. To date, the catalogue of mutations identified in this study is the first evidence of mtDNA alterations in Malaysian female breast cancer patients.

Pro- and antitumor effects of mitochondrial reactive oxygen species

In cancer, mitochondrial functions are commonly altered. Directly involved in metabolic reprogramming, mitochondrial plasticity confers to cancer cells a high degree of adaptability to a wide range of stresses and to the harsh tumor microenvironment. Lack of nutrients or oxygen caused by altered perfusion, metabolic needs of proliferating cells, co-option of the microenvironment, control of the immune system, cell migration and metastasis, and evasion of exogenous stress (e.g., chemotherapy) are all, at least in part, influenced by mitochondria. Mitochondria are undoubtedly one of the key contributors to cancer development and progression. Understanding their protumoral (dys)functions may pave the way to therapeutic strategies capable of turning them into innocent entities. Here, we will focus on the production and detoxification of mitochondrial reactive oxygen species (mtROS), on their impact on tumorigenesis (genetic, prosurvival, and microenvironmental effects and their involvement in autophagy), and on tumor metastasis. We will also summarize the latest therapeutic approaches involving mtROS.

Alteration of Gene Associated with Retinoid-interferon-induced Mortality-19-expressing Cell Types in the Mouse Hippocampus Following Pilocarpine-induced Status Epilepticus

The gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) plays several significant roles in cellular processes, including ATP synthesis, reactive oxygen species formation, and the regulation of glycolytic enzyme activity, which are closely related to the pathophysiological mechanisms of epilepsy. Therefore, we investigated the expression pattern of GRIM-19 in the CA1 area of the hippocampus in 8-week-old male C57BL/6 mice following pilocarpine-induced status epilepticus (SE). Neuronal death in the hippocampal CA1 area was prominently observed at 4 and 7 days after SE, and astrocytes and microglia became progressively activated beginning at 1 day after SE. GRIM-19 immunoreactivity was decreased in the damaged pyramidal cell layer but markedly increased in the stratum radiatum and stratum lacunosum-moleculare of the hippocampus at 4 and 7 days after SE. In addition, the cell types of GRIM-19-expressing cells in the epileptic hippocampus were identified. GRIM-19 was mainly co-localized in neurons but only slightly expressed in glia in the normal hippocampus. Most of the GRIM-19-positive cells induced by SE in the stratum radiatum and stratum lacunosum-moleculare were glial fibrillary acidic protein-expressing reactive astrocytes. Moreover, we observed that both GRIM-19 and pyruvate kinase isozyme M2, a glycolytic enzyme, were highly expressed in reactive astrocytes after SE. These results indicate that expression of GRIM-19 in the hippocampus is mainly observed in neurons under normal conditions but is altered in the SE mouse model as evidenced by its increased expression in reactive astrocytes. The possible role of GRIM-19 in the glycolytic activity of reactive astrocytes is also discussed.

Inhibition of Alternative Cancer Cell Metabolism of EGFR Mutated Non-Small Cell Lung Cancer Serves as a Potential Therapeutic Strategy

Targeted therapy is an efficient treatment for patients with epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC). Therapeutic resistance invariably occurs in NSCLC patients. Many studies have focused on drug resistance mechanisms, but only a few have addressed the metabolic flexibility in drug-resistant NSCLC. In the present study, we found that during the developing resistance to tyrosine kinase inhibitor (TKI), TKI-resistant NSCLC cells acquired metabolic flexibility in that they switched from dependence on glycolysis to oxidative phosphorylation by substantially increasing the activity of the mitochondria. Concurrently, we found the predominant expression of monocarboxylate transporter 1 (MCT-1) in the TKI-resistant NSCLC cells was strongly increased in those cells that oxidized lactate. Thus, we hypothesized that inhibiting MCT-1 could represent a novel treatment strategy. We treated cells with the MCT-1 inhibitor AZD3965. We found a significant decrease in cell proliferation and cell motility in TKI-sensitive and TKI-resistant cells. Taken together, these results demonstrated that gefitinib-resistant NSCLC cells harbored higher mitochondrial bioenergetics and MCT-1 expression. These results implied that targeting mitochondrial oxidative phosphorylation proteins or MCT-1 could serve as potential treatments for both TKI-sensitive and -resistant non-small cell lung cancer.

Aberrant mitochondrial function in ageing and cancer

Alterations in mitochondrial metabolism have been described as one of the major hallmarks of both ageing cells and cancer. Age is the biggest risk factor for the development of a significant number of cancer types and this therefore raises the question of whether there is a link between age-related mitochondrial dysfunction and the advantageous changes in mitochondrial metabolism prevalent in cancer cells. A common underlying feature of both ageing and cancer cells is the presence of somatic mutations of the mitochondrial genome (mtDNA) which we postulate may drive compensatory alterations in mitochondrial metabolism that are advantageous for tumour growth. In this review, we discuss basic mitochondrial functions, mechanisms of mtDNA mutagenesis and their metabolic consequences, and review the evidence for and against a role for mtDNA mutations in cancer development.

Complex I and II are required for normal mitochondrial Ca2+ homeostasis

Cytosolic calcium (_cCa²⁺) entry into mitochondria is facilitated by the mitochondrial membrane potential (ΔΨm), an electrochemical gradient generated by the electron transport chain (ETC). Is has been assumed that as long as mutations that affect the ETC do not affect the ΔΨm, the mitochondrial Ca²⁺ (_mCa²⁺) homeostasis remains normal. We show that knockdown of NDUFAF3 and SDHB reduce ETC activity altering _mCa²⁺ efflux and influx rates while ΔΨm remains intact. Shifting the equilibrium toward lower [Ca²⁺]_m accumulation renders cells resistant to death. Our findings reveal an unexpected relationship between complex I and II with the _mCa²⁺ homeostasis independent of ΔΨm.

CHCHD4 confers metabolic vulnerabilities to tumour cells through its control of the mitochondrial respiratory chain

Background

Tumour cells rely on glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) to survive. Thus, mitochondrial OXPHOS has become an increasingly attractive area for therapeutic exploitation in cancer. However, mitochondria are required for intracellular oxygenation and normal physiological processes, and it remains unclear which mitochondrial molecular mechanisms might provide therapeutic benefit. Previously, we discovered that coiled-coil-helix-coiled-coil-helix domain-containing protein 4 (CHCHD4) is critical for regulating intracellular oxygenation and required for the cellular response to hypoxia (low oxygenation) in tumour cells through molecular mechanisms that we do not yet fully understand. Overexpression of CHCHD4 in human cancers correlates with increased tumour progression and poor patient survival.

Results

Here, we show that elevated CHCHD4 expression provides a proliferative and metabolic advantage to tumour cells in normoxia and hypoxia. Using stable isotope labelling with amino acids in cell culture (SILAC) and analysis of the whole mitochondrial proteome, we show that CHCHD4 dynamically affects the expression of a broad range of mitochondrial respiratory chain subunits from complex I-V, including multiple subunits of complex I (CI) required for complex assembly that are essential for cell survival. We found that loss of CHCHD4 protects tumour cells from respiratory chain inhibition at CI, while elevated CHCHD4 expression in tumour cells leads to significantly increased sensitivity to CI inhibition, in part through the production of mitochondrial reactive oxygen species (ROS).

Conclusions

Our study highlights an important role for CHCHD4 in regulating tumour cell metabolism and reveals that CHCHD4 confers metabolic vulnerabilities to tumour cells through its control of the mitochondrial respiratory chain and CI biology.

Mitochondrial dysfunction induces the invasive phenotype, and cell migration and invasion, through the induction of AKT and AMPK pathways in lung cancer cells

Mitochondria are well known for their important roles in oxidative phosphorylation, amino acid metabolism, fatty acid oxidation and ion homeostasis. Although the effects of mitochondrial dysfunction on tumorigenesis in various cancer cells have been reported, the correlation between mitochondrial dysfunction and epithelial‑to‑mesenchymal transition (EMT) in lung cancer development and metastasis has not been well elucidated. In the present study, the effects of mitochondrial dysfunction on EMT and migration in lung cancer cells were investigated using inhibitors of mitochondrial respiration, oligomycin A and antimycin A. Oligomycin A and antimycin A induced distinct mesenchymal‑like morphological features in H23, H1793 and A549 lung cancer cells. In addition, they decreased the expression levels of the epithelial marker protein E‑cadherin, but increased the expression levels of the mesenchymal marker proteins Vimentin, Snail and Slug. The results of immunofluorescence staining indicated that oligomycin A and antimycin A downregulated cortical E‑cadherin expression and upregulated the expression of Vimentin. In addition, oligomycin A and antimycin A increased the migration and invasion of A549 lung cancer cells, and promoted the expression levels of phosphorylated (p)‑protein kinase B (AKT) and p‑AMP‑activated protein kinase (AMPK). Notably, the production of reactive oxygen species by oligomycin A and antimycin A did not affect the expression of EMT protein markers. Conversely, treatment with the AKT inhibitor wortmannin and the AMPK inhibitor Compound C upregulated E‑cadherin and downregulated Vimentin expression. These results suggested that oligomycin A and antimycin A may induce migration and invasion of lung cancer cells by inducing EMT via the upregulation of p‑AKT and p‑AMPK expression.

The Oncojanus Paradigm of Respiratory Complex I

Mitochondrial respiratory function is now recognized as a pivotal player in all the aspects of cancer biology, from tumorigenesis to aggressiveness and chemotherapy resistance. Among the enzymes that compose the respiratory chain, by contributing to energy production, redox equilibrium and oxidative stress, complex I assumes a central role. Complex I defects may arise from mutations in mitochondrial or nuclear DNA, in both structural genes or assembly factors, from alteration of the expression levels of its subunits, or from drug exposure. Since cancer cells have a high-energy demand and require macromolecules for proliferation, it is not surprising that severe complex I defects, caused either by mutations or treatment with specific inhibitors, prevent tumor progression, while contributing to resistance to certain chemotherapeutic agents. On the other hand, enhanced oxidative stress due to mild complex I dysfunction drives an opposite phenotype, as it stimulates cancer cell proliferation and invasiveness. We here review the current knowledge on the contribution of respiratory complex I to cancer biology, highlighting the double-edged role of this metabolic enzyme in tumor progression, metastasis formation, and response to chemotherapy.

Implication of SPARC in the modulation of the extracellular matrix and mitochondrial function in muscle cells

Secreted protein, acidic and rich in cysteine (SPARC) is differentially associated with cell proliferation and extracellular matrix (ECM) assembly. We show here the effect of exogenous SPARC inhibition/induction on ECM and mitochondrial proteins expression and on the differentiation of C2C12 cells. The cells were cultured in growth medium (GM) supplemented with different experimental conditions. The differentiation of myoblasts was studied for 5 days, the expressions of ECM and mitochondrial proteins were measured and the formation of the myotubes was quantified after exogenous induction/inhibition of SPARC. The results indicate that the addition of recombinant SPARC protein (rSPARC) in cell culture medium increased the differentiation of C2C12 myoblasts and myogenin expression during the myotube formation. However, the treatment with antibody specific for SPARC (anti-SPARC) prevented the differentiation and decreased myogenin expression. The induction of SPARC in the proliferating and differentiating C2C12 cells increased collagen 1a1 protein expression, whereas the inhibition decreased it. The effects on fibronectin protein expression were opposite. Furthermore, the addition of rSPARC in C2C12 myoblast increased the expression of mitochondrial proteins, ubiquinol-cytochrome c reductase core protein II (UQCRC2) and succinate dehydrogenase iron-sulfur subunit (SDHB), whereas the anti-SPARC decreased them. During the differentiation, only the anti-SPARC had the effects on mitochondrial proteins, NADH dehydrogenase ubiquinone 1 beta subcomplex subunit 8 (NADHB8), SDHB and cytochrome c oxidase 1 (MTCO1). Thus, SPARC plays a crucial role in the proliferation and differentiation of C2C12 and may be involved in the link between the ECM remodeling and mitochondrial function.

Ghrelin protects retinal ganglion cells against rotenone via inhibiting apoptosis, restoring mitochondrial function, and activating AKT-mTOR signaling

Ghrelin, a 28-amino acid peptide hormone, has protective effects on neuronal cells. The present study aimed to examine the neuroprotective effects of ghrelin on the rat retinal ganglion cells in the rotenone-induced in vitro model of Parkinson's disease (PD). Cell viability and cell apoptosis were determined by MTT assay and flow cytometry, respectively. Mitochondrial functions were detected by mitochondrial complex I activity assay and mitochondrial membrane potential (MMP) assay. The mRNA and protein expression levels were determined by qRT-PCR and western blot, respectively. Rotenone significantly suppressed cell viability and increased cell apoptosis, also decreased the mitochondrial complex I activity as well as MMP in rat retinal ganglion cell line (RGC-5). Growth hormone secretagogue receptor (Ghsr) siRNA transfection significantly suppressed the expression of Ghsr in RGC-5 cells. Ghrelin treatment attenuated the effects of rotenone-induced changes in cell viability, cell apoptosis and mitochondrial functions in RGC-5 cells. Post-transcriptional suppression by Ghsr siRNA transfection and treatment with GHS-R antagonist, YIL781, both significantly attenuated the effects of ghrelin in RGC-5 cells. Rotenone decreased the protein levels of Bcl-2 and increased the protein levels of Bax, cleaved caspase-3 and cleaved caspase-9, and this effect was reversed by ghrelin treatment. Ghrelin also prevented the inhibitory effects of rotenone on the AKT-mTOR signaling. The effects of ghrelin on the rotenone-induced changes in apoptosis-related protein levels and AKT-mTOR signaling were attenuated by Ghsr siRNA transfection and treatment with YIL781 in the RGC-5 cells. In addition, both rapamycin and AKT inhibitor IV pre-treatment significantly attenuated the effects of ghrelin on rotenone-induced changes in cell viability and cell apoptosis. In conclusion, ghrelin by acting on the GSH-R to protect rat retinal ganglion cells against rotenone via inhibiting apoptosis and restore mitochondrial functions in RGC-5 cells, and this effect was partially associated with the AKT-mTOR signaling pathway in RGC-5 cells.

Lipoamide Inhibits NF1 Deficiency-induced Epithelial-Mesenchymal Transition in Murine Schwann Cells

BACKGROUND AND AIMS

Neurofibromatosis type I (NF1) is one of the most common neurocutaneous syndromes characterized by development of adult neurofibromas which is mainly made up of Schwann cells. The disease is generally accepted to be caused by inactivation mutation of Nf1 gene. And Nf1 deficiency had been reported to lead to ROS overproduction and epithelial-mesenchymal transition (EMT) phenotype. This study was designed to investigate whether excessive ROS conferred to Nf1 deficiency-induced EMT in Schwann cells.

METHODS

Colony formation, wound healing assay and transwell assay was used to evaluate the effects of stable Nf1 knockdown in SW10 Schwann cells. Western blot and ROS assay was conducted to explore the molecular mechanisms of Nf1 inactivation in tumorigenesis. Animal experiments were performed to assess the inhibitory effects of lipoamide, which is the neutral amide of α-lipoic acid and functions as a potent antioxidant to scavenge ROS, on Nf1-deficiency tumor growth in vivo.

RESULTS

Nf1 knockdown enhanced the cellular capacities of proliferation, migration and invasion, promoted ROS generation, decreased the expression of epithelial surface marker E-cadherin, and up-regulated several EMT-associated molecules in Schwann cells. Moreover, lipoamide dose-dependently inhibited not only Nf1 deficiency-induced EMT but also spontaneous EMT. Furthermore, lipoamide markedly suppresses tumor growth in a mouse model of NF1-associated neurofibroma.

CONCLUSIONS

Our results clearly reveal that ROS overproduction is responsible for Nf1 deficiency-induced EMT and plays a crucial role in NF1 tumor growth. The findings presented herein shed light on the potential of antioxidant therapy to prevent the progression of NF1-associated neurofibroma.

Lactate-mediated mitoribosomal defects impair mitochondrial oxidative phosphorylation and promote hepatoma cell invasiveness

Impaired mitochondrial oxidative phosphorylation (OXPHOS) capacity, accompanied by enhanced glycolysis, is a key metabolic feature of cancer cells, but its underlying mechanism remains unclear. Previously, we reported that human hepatoma cells that harbor OXPHOS defects exhibit high tumor cell invasiveness via elevated claudin-1 (CLN1). In the present study, we show that OXPHOS-defective hepatoma cells (SNU354 and SNU423 cell lines) exhibit reduced expression of mitochondrial ribosomal protein L13 (MRPL13), a mitochondrial ribosome (mitoribosome) subunit, suggesting a ribosomal defect. Specific inhibition of mitoribosomal translation by doxycycline, chloramphenicol, or siRNA-mediated MRPL13 knockdown decreased mitochondrial protein expression, reduced oxygen consumption rate, and increased CLN1-mediated tumor cell invasiveness in SNU387 cells, which have active mitochondria. Interestingly, we also found that exogenous lactate treatment suppressed MRPL13 expression and oxygen consumption rate and induced CLN1 expression. A bioinformatic analysis of the open RNA-Seq database from The Cancer Genome Atlas (TCGA) liver hepatocellular carcinoma (LIHC) cohort revealed a significant negative correlation between MRPL13 and CLN1 expression. Moreover, in patients with low MRPL13 expression, two oxidative metabolic indicators, pyruvate dehydrogenase B expression and the ratio of lactate dehydrogenase type B to type A, significantly and negatively correlated with CLN1 expression, indicating that the combination of elevated glycolysis and deficient MRPL13 activity was closely linked to CLN1-mediated tumor activity in LIHC. These results suggest that OXPHOS defects may be initiated and propagated by lactate-mediated mitoribosomal deficiencies and that these deficiencies are critically involved in LIHC development.

On mitochondrial metabolism in tumor biology

PURPOSE OF REVIEW

To provide examples of mitochondria-specific metabolic events that influence tumor cell biology, and of metabolism-related mitochondrial biomarkers and therapeutic targets in cancer cells.

RECENT FINDINGS

Cancer cell mitochondria are rewired to optimally serve the cancer cell under various conditions of cellular stress. The nonexhaustive list of mitochondrial alterations that support cancer cell proliferation, survival, and/or progression includes upregulation of oxidative metabolism and use of alternative substrates, oncometabolites, increased superoxide production, mutated mitochondrial DNA, and altered mitochondrial morphology and dynamics. Potential therapeutic targets include fatty acid oxidation, voltage-dependent anion channel-1, the pyruvate dehydrogenase complex, and Complex I.

SUMMARY

Some phenotypical traits, for example, chemoresistance and metastasis, are likely regulated by a fine-tuned balance between several metabolic processes and events that are upregulated in parallel and are also dependent on microenvironmental cues. Many metabolism-related mitochondrial biomarkers show prognostic value, but the biological interpretation of the data may be confounded by the overall metabolic status and context. Understanding metabolic regulation of stemness is important for targeting cancer stem cells. Therapeutic targeting of cancer cell mitochondria remains experimental but promising, and more predictive markers will be needed for metabolism-based treatments and personalized medicine.

Constitutive Reprogramming of Fibroblast Mitochondrial Metabolism in Pulmonary Hypertension

Remodeling of the distal pulmonary artery wall is a characteristic feature of pulmonary hypertension (PH). In hypoxic PH, the most substantial pathologic changes occur in the adventitia. Here, there is marked fibroblast proliferation and profound macrophage accumulation. These PH fibroblasts (PH-Fibs) maintain a hyperproliferative, apoptotic-resistant, and proinflammatory phenotype in ex vivo culture. Considering that a similar phenotype is observed in cancer cells, where it has been associated, at least in part, with specific alterations in mitochondrial metabolism, we sought to define the state of mitochondrial metabolism in PH-Fibs. In PH-Fibs, pyruvate dehydrogenase was markedly inhibited, resulting in metabolism of pyruvate to lactate, thus consistent with a Warburg-like phenotype. In addition, mitochondrial bioenergetics were suppressed and mitochondrial fragmentation was increased in PH-Fibs. Most importantly, complex I activity was substantially decreased, which was associated with down-regulation of the accessory subunit nicotinamide adenine dinucleotide reduced dehydrogenase (ubiquinone) Fe-S protein 4 (NDUFS4). Owing to less-efficient ATP synthesis, mitochondria were hyperpolarized and mitochondrial superoxide production was increased. This pro-oxidative status was further augmented by simultaneous induction of cytosolic nicotinamide adenine dinucleotide phosphate reduced oxidase 4. Although acute and chronic exposure to hypoxia of adventitial fibroblasts from healthy control vessels induced increased glycolysis, it did not induce complex I deficiency as observed in PH-Fibs. This suggests that hypoxia alone is insufficient to induce NDUFS4 down-regulation and constitutive abnormalities in complex I. In conclusion, our study provides evidence that, in the pathogenesis of vascular remodeling in PH, alterations in fibroblast mitochondrial metabolism drive distinct changes in cellular behavior, which potentially occur independently of hypoxia.

The Mitochondrial Complex(I)ty of Cancer

Recent evidence highlights that the cancer cell energy requirements vary greatly from normal cells and that cancer cells exhibit different metabolic phenotypes with variable participation of both glycolysis and oxidative phosphorylation. NADH-ubiquinone oxidoreductase (Complex I) is the largest complex of the mitochondrial electron transport chain and contributes about 40% of the proton motive force required for mitochondrial ATP synthesis. In addition, Complex I plays an essential role in biosynthesis and redox control during proliferation, resistance to cell death, and metastasis of cancer cells. Although knowledge about the structure and assembly of Complex I is increasing, information about the role of Complex I subunits in tumorigenesis is scarce and contradictory. Several small molecule inhibitors of Complex I have been described as selective anticancer agents; however, pharmacologic and genetic interventions on Complex I have also shown pro-tumorigenic actions, involving different cellular signaling. Here, we discuss the role of Complex I in tumorigenesis, focusing on the specific participation of Complex I subunits in proliferation and metastasis of cancer cells.

GRIM-19, a gene associated with retinoid-interferon-induced mortality, affects endometrial receptivity and embryo implantation

GRIM-19 is associated with apoptosis, abnormal proliferation, immune tolerance and malignant transformation, and it also plays an important role in early embryonic development. Although the homologous deletion of GRIM-19 causes embryonic lethality in mice, the precise role of GRIM-19 in embryo implantation has not been elucidated. Here we show that GRIM-19 plays an important role in endometrial receptivity and embryo implantation. Day 1 to Day 6 pregnant mouse uteri were collected. Immunohistochemistry studies revealed the presence of GRIM-19 on the luminal epithelium and glandular epithelium throughout the implantation period in pregnant mice. The protein and mRNA levels of GRIM-19 were markedly decreased on Day 4 of pregnancy in pregnant mice, but there was no change in GRIM-19 levels in a group of pseudopregnant mice. Overexpression of GRIM-19 decreased the adhesion rate of RL95–2–BeWo co-cultured spheroids and increased apoptosis. Furthermore, STAT3 and IL-11 mRNA and protein levels were reduced by overexpressing GRIM-19, but protein and mRNA levels of TNF-α were increased. These findings indicate the involvement of GRIM-19 in the embryo implantation process by regulating adhesion, apoptosis and immune tolerance.

Migration and invasion of drug-resistant lung adenocarcinoma cells are dependent on mitochondrial activity

A small proportion of cancer cells have stem-cell-like properties, are resistant to standard therapy and are associated with a poor prognosis. The metabolism of such drug-resistant cells differs from that of nearby non-resistant cells. In this study, the metabolism of drug-resistant lung adenocarcinoma cells was investigated. The expression of genes associated with oxidative phosphorylation in the mitochondrial membrane was negatively correlated with the prognosis of lung adenocarcinoma. Because the mitochondrial membrane potential (MMP) reflects the functional status of mitochondria and metastasis is the principal cause of death due to cancer, the relationship between MMP and metastasis was evaluated. Cells with a higher MMP exhibited greater migration and invasion than those with a lower MMP. Cells that survived treatment with cisplatin, a standard chemotherapeutic drug for lung adenocarcinoma, exhibited increased MMP and enhanced migration and invasion compared with parental cells. Consistent with these findings, inhibition of mitochondrial activity significantly impeded the migration and invasion of cisplatin-resistant cells. RNA-sequencing analysis indicated that the expression of mitochondrial complex genes was upregulated in cisplatin-resistant cells. These results suggested that drug-resistant cells have a greater MMP and that inhibition of mitochondrial activity could be used to prevent metastasis of drug-resistant lung adenocarcinoma cells.

Heme oxygenase-1 in macrophages controls prostate cancer progression

Innate immune cells strongly influence cancer growth and progression via multiple mechanisms including regulation of epithelial to mesenchymal transition (EMT). In this study, we investigated whether expression of the metabolic gene, heme oxygenase-1 (HO-1) in tumor microenvironment imparts significant effects on prostate cancer progression.

We showed that HO-1 is expressed in MARCO-positive macrophages in prostate cancer (PCa) xenografts and human prostate cancers. We demonstrated that macrophage specific (LyzM-Cre) conditional deletion of HO-1 suppressed growth of PC3 xenografts in vivo and delayed progression of prostate intraepithelial neoplasia (PIN) in TRAMP mice. However, initiation and progression of cancer xenografts in the presence of macrophages lacking HO-1 resulted in loss of E-cadherin, a known marker of poor prognosis as well as EMT. Application of CO, a product of HO-1 catalysis, increased levels of E-cadherin in the adherens junctions between cancer cells. We further showed that HO-1-driven expression of E-cadherin in cancer cells cultured in the presence of macrophages is dependent on mitochondrial activity of cancer cells.

In summary, these data suggest that HO-1-derived CO from tumor-associated macrophages influences, in part, E-cadherin expression and thus tumor initiation and progression.

Targeting metabolic flexibility by simultaneously inhibiting respiratory complex I and lactate generation retards melanoma progression

Melanoma is a largely incurable skin malignancy owing to the underlying molecular and metabolic heterogeneity confounded by the development of resistance. Cancer cells have metabolic flexibility in choosing either oxidative phosphorylation (OXPHOS) or glycolysis for ATP generation depending upon the nutrient availability in tumor microenvironment. In this study, we investigated the involvement of respiratory complex I and lactate dehydrogenase (LDH) in melanoma progression. We show that inhibition of complex I by metformin promotes melanoma growth in mice via elevating lactate and VEGF levels. In contrast, it leads to the growth arrest in vitro because of enhanced extracellular acidification as a result of increased glycolysis. Inhibition of LDH or lactate generation causes decrease in glycolysis with concomitant growth arrest both in vitro and in vivo. Blocking lactate generation in metformin-treated melanoma cells results in diminished cell proliferation and tumor progression in mice. Interestingly, inhibition of either LDH or complex I alone does not induce apoptosis, whereas inhibiting both together causes depletion in cellular ATP pool resulting in metabolic catastrophe induced apoptosis. Overall, our study suggests that LDH and complex I play distinct roles in regulating glycolysis and cell proliferation. Inhibition of these two augments synthetic lethality in melanoma.

GRIM-19 inhibition induced autophagy through activation of ERK and HIF-1α not STAT3 in Hela cells

Gene associated with retinoid-interferon-induced mortality (GRIM-19), an important subunit of mitochondrial complex I, has been identified as a tumor suppressor, and its reduced expression has been reported to be associated with tumorigenesis and metastasis. Autophagy has been proposed as a protective mechanism for cell survival under various stresses, including chemotherapy. However, it remains unknown whether GRIM-19 is linked to autophagy and chemotherapy resistance. Here, we showed that suppression of GRIM-19 by shRNA enhanced cell-type-dependent autophagy by activating extracellular regulated protein kinase (ERK) and hypoxia inducible factor-1a (HIF-1a) in a reactive oxygen species (ROS)-mediated manner, and thereby conferred resistance to paclitaxel. Besides, the antioxidant N-acetyl-L-cysteine (NAC) and autophagy inhibitor 3-MA could in part overcome this resistance. We also found that GRIM-19 expression was significantly correlated with clinical stage and grade in patients with cervical cancers. Taken together, our results indicated that GRIM-19 inhibition induced autophagy and chemotherapy resistance, which could affect prognosis of cervical cancers. Our study has identified new function of GRIM-19 and its underlying mechanism, and it will provide possible avenues for therapeutic targeting in cervical cancers.

Identification of a mitochondrial defect gene signature reveals NUPR1 as a key regulator of liver cancer progression

Many cancer cells require more glycolytic adenosine triphosphate production due to a mitochondrial respiratory defect. However, the roles of mitochondrial defects in cancer development and progression remain unclear. To address the role of transcriptomic regulation by mitochondrial defects in liver cancer cells, we performed gene expression profiling for three different cell models of mitochondrial defects: cells with chemical respiratory inhibition (rotenone, thenoyltrifluoroacetone, antimycin A, and oligomycin), cells with mitochondrial DNA depletion (Rho0), and liver cancer cells harboring mitochondrial defects (SNU354 and SNU423). By comparing gene expression in the three models, we identified 10 common mitochondrial defect-related genes that may be responsible for retrograde signaling from cancer cell mitochondria to the intracellular transcriptome. The concomitant expression of the 10 common mitochondrial defect genes is significantly associated with poor prognostic outcomes in liver cancers, suggesting their functional and clinical relevance. Among the common mitochondrial defect genes, we found that nuclear protein 1 (NUPR1) is one of the key transcription regulators. Knockdown of NUPR1 suppressed liver cancer cell invasion, which was mediated in a Ca(2+) signaling-dependent manner. In addition, by performing an NUPR1-centric network analysis and promoter binding assay, granulin was identified as a key downstream effector of NUPR1. We also report association of the NUPR1-granulin pathway with mitochondrial defect-derived glycolytic activation in human liver cancer.

CONCLUSION

Mitochondrial respiratory defects and subsequent retrograde signaling, particularly the NUPR1-granulin pathway, play pivotal roles in liver cancer progression.

From cell senescence to age-related diseases: differential mechanisms of action of senescence-associated secretory phenotypes

Cellular senescence is a process by which cells enter a state of permanent cell cycle arrest. It is commonly believed to underlie organismal aging and age-associated diseases. However, the mechanism by which cellular senescence contributes to aging and age-associated pathologies remains unclear. Recent studies showed that senescent cells exert detrimental effects on the tissue microenvironment, generating pathological facilitators or aggravators. The most significant environmental effector resulting from senescent cells is the senescence-associated secretory phenotype (SASP), which is constituted by a strikingly increased expression and secretion of diverse pro-inflammatory cytokines. Careful investigation into the components of SASPs and their mechanism of action, may improve our understanding of the pathological backgrounds of age-associated diseases. In this review, we focus on the differential expression of SASP-related genes, in addition to SASP components, during the progress of senescence. We also provide a perspective on the possible action mechanisms of SASP components, and potential contributions of SASP-expressing senescent cells, to age-associated pathologies.

Mitochondrial Respiratory Dysfunction Induces Claudin-1 Expression via Reactive Oxygen Species-mediated Heat Shock Factor 1 Activation, Leading to Hepatoma Cell Invasiveness

Although mitochondrial dysfunction has been implicated in tumor metastasis, it is unclear how it regulates tumor cell aggressiveness. We have reported previously that human hepatoma cells harboring mitochondrial defects have high tumor cell invasion activity via increased claudin-1 (Cln-1) expression. In this study, we demonstrated that mitochondrial respiratory defects induced Cln-1 transcription via reactive oxygen species (ROS)-mediated heat shock factor 1 (HSF1) activation, which contributed to hepatoma invasiveness. We first confirmed the inverse relationship between mitochondrial defects and Cln-1 induction in SNU hepatoma cells and hepatocellular carcinoma tissues. We then examined five different respiratory complex inhibitors, and complex I inhibition by rotenone most effectively induced Cln-1 at the transcriptional level. Rotenone increased both mitochondrial and cytosolic ROS. In addition, rotenone-induced Cln-1 expression was attenuated by N-acetylcysteine, an antioxidant, and exogenous H2O2 treatment was enough to increase Cln-1 transcription, implying the involvement of ROS. Next we found that ROS-mediated HSF1 activation via hyperphosphorylation was the key event for Cln-1 transcription. Moreover, the Cln-1 promoter region (from -529 to +53) possesses several HSF1 binding elements, and this region showed increased promoter activity and HSF1 binding affinity in response to rotenone treatment. Finally, we demonstrated that the invasion activity of SNU449 cells, which harbor mitochondrial defects, was blocked by siRNA-mediated HSF1 knockdown. Taken together, these results indicate that mitochondrial respiratory defects enhance Cln-1-mediated hepatoma cell invasiveness via mitochondrial ROS-mediated HSF1 activation, presenting a potential role for HSF1 as a novel mitochondrial retrograde signal-responsive transcription factor to control hepatoma cell invasiveness.

Hitting the Bull's-Eye in Metastatic Cancers-NSAIDs Elevate ROS in Mitochondria, Inducing Malignant Cell Death

Tumor metastases that impede the function of vital organs are a major cause of cancer related mortality. Mitochondrial oxidative stress induced by hypoxia, low nutrient levels, or other stresses, such as genotoxic events, act as key drivers of the malignant changes in primary tumors to enhance their progression to metastasis. Emerging evidence now indicates that mitochondrial modifications and mutations resulting from oxidative stress, and leading to OxPhos stimulation and/or enhanced reactive oxygen species (ROS) production, are essential for promoting and sustaining the highly metastatic phenotype. Moreover, the modified mitochondria in emerging or existing metastatic cancer cells, by their irreversible differences, provide opportunities for selectively targeting their mitochondrial functions with a one-two punch. The first blow would block their anti-oxidative defense, followed by the knockout blow—promoting production of excess ROS, capitulating the terminal stage—activation of the mitochondrial permeability transition pore (mPTP), specifically killing metastatic cancer cells or their precursors. This review links a wide area of research relevant to cellular mechanisms that affect mitochondria activity as a major source of ROS production driving the pro-oxidative state in metastatic cancer cells. Each of the important aspects affecting mitochondrial function are discussed including: hypoxia, HIFs and PGC1 induced metabolic changes, increased ROS production to induce a more pro-oxidative state with reduced antioxidant defenses. It then focuses on how the mitochondria, as a major source of ROS in metastatic cancer cells driving the pro-oxidative state of malignancy enables targeting drugs affecting many of these altered processes and why the NSAIDs are an excellent example of mitochondria-targeted agents that provide a one-two knockout activating the mPTP and their efficacy as selective anticancer metastasis drugs.