Regulation of mitochondrial proliferation by PGC-1α induces cellular apoptosis in musculoskeletal malignancies

Exploring cuproptosis as a mechanism and potential intervention target in cardiovascular diseases

Copper (Cu) is a vital trace element for maintaining human health. Current evidence suggests that genes responsible for regulating copper influx and detoxification help preserve its homeostasis. Adequate Cu levels sustain normal cardiac and blood vessel activity by maintaining mitochondrial function. Cuproptosis, unlike other forms of cell death, is characterized by alterations in mitochondrial enzymes. Therapeutics targeting cuproptosis in cardiovascular diseases (CVDs) mainly include copper chelators, inhibitors of copper chaperone proteins, and copper ionophores. In this review, we expound on the primary mechanisms, critical proteins, and signaling pathways involved in cuproptosis, along with its impact on CVDs and the role it plays in different types of cells. Additionally, we explored the influence of key regulatory proteins and signaling pathways associated with cuproptosis on CVDs and determined whether intervening in copper metabolism and cuproptosis can enhance the outcomes of CVDs. The insights from this review provide a fresh perspective on the pathogenesis of CVDs and new targets for intervention in these diseases.

Annona muricate Extract Supplementation Contributes to Improve Aberrant Multi-Organ Energy Metabolism via Muscle-Brain Connectivity in Diabetic Mice

Type 2 diabetes mellitus (T2DM) is related with the incidence of sarcopenia and cognitive impairment that reduces quality of life in the elderly. Recent evidence has demonstrated that sarcopenia is associated with cognitive dysfunction, and muscle-derived endocrine factors might contribute to cognitive function by the skeletal muscle-brain endocrine loop. This study investigated the beneficial effects of Annona muricata (AM, graviola) on multi-organ energy metabolism with muscle-brain connectivity via brain function-related myokines in mice. Body composition, fasting blood glucose level, insulin, HbA1c%, histopathological changes, and the protein levels of insulin-signaling, energy metabolism, neuroprotection, inflammation, and protein-degradation pathways were measured. AM extract (AME) treatment selectively enhanced insulin signaling in the skeletal muscle and hippocampus of T2DM mice. Furthermore, AME treatment effectively increased muscle-derived fibroblast growth factor 21 (FGF21), cathepsin-B (CTSB), irisin, brain-derived neurotrophic factor (BDNF), and liver-derived FGF21 that contribute to whole-body energy homeostasis. In particular, AME increased the levels of circulating myokines (FGF21, BDNF, irisin, and CTSB), and these were accordance with the hippocampal neurotrophic factors (BDNF and CTSB) in T2DM mice. In conclusion, we suggest that AME would be a potential nutraceutical for improving the energy metabolism associated with muscle-brain connectivity via brain function-related myokines in T2DM.

Chemotherapy-Induced Molecular Changes in Skeletal Muscle

Paraneoplastic conditions such as cancer cachexia are often exacerbated by chemotherapy, which affects the patient’s quality of life as well as the response to therapy. The aim of this narrative review was to overview the body-composition-related changes and molecular effects of different chemotherapy agents used in cancer treatment on skeletal-muscle remodeling. A literature search was performed using the Web of Science, Scopus, and Science Direct databases and a total of 77 papers was retrieved. In general, the literature survey showed that the molecular changes induced by chemotherapy in skeletal muscle have been studied mainly in animal models and mostly in non-tumor-bearing rodents, whereas clinical studies have essentially assessed changes in body composition by computerized tomography. Data from preclinical studies showed that chemotherapy modulates several molecular pathways in skeletal muscle, including the ubiquitin–proteasome pathway, autophagy, IGF-1/PI3K/Akt/mTOR, IL-6/JAK/STAT, and NF-κB pathway; however, the newest chemotherapy agents are underexplored. In conclusion, chemotherapy exacerbates skeletal-muscle wasting in cancer patients; however, the incomplete characterization of the chemotherapy-related molecular effects on skeletal muscle makes the development of new preventive anti-wasting strategies difficult. Therefore, further investigation on molecular mechanisms and clinical studies are necessary.

Differential Stimulation of Pluripotent Stem Cell-Derived Human Microglia Leads to Exosomal Proteomic Changes Affecting Neurons

Microglial exosomes are an emerging communication pathway, implicated in fulfilling homeostatic microglial functions and transmitting neurodegenerative signals. Gene variants of triggering receptor expressed on myeloid cells-2 (TREM2) are associated with an increased risk of developing dementia. We investigated the influence of the TREM2 Alzheimer’s disease risk variant, R47H^het, on the microglial exosomal proteome consisting of 3019 proteins secreted from human iPS-derived microglia (iPS-Mg). Exosomal protein content changed according to how the iPS-Mg were stimulated. Thus lipopolysaccharide (LPS) induced microglial exosomes to contain more inflammatory signals, whilst stimulation with the TREM2 ligand phosphatidylserine (PS⁺) increased metabolic signals within the microglial exosomes. We tested the effect of these exosomes on neurons and found that the exosomal protein changes were functionally relevant and influenced downstream functions in both neurons and microglia. Exosomes from R47H^het iPS-Mg contained disease-associated microglial (DAM) signature proteins and were less able to promote the outgrowth of neuronal processes and increase mitochondrial metabolism in neurons compared with exosomes from the common TREM2 variant iPS-Mg. Taken together, these data highlight the importance of microglial exosomes in fulfilling microglial functions. Additionally, variations in the exosomal proteome influenced by the R47H^het TREM2 variant may underlie the increased risk of Alzheimer’s disease associated with this variant.

Osteosarcoma Cell Growth Inhibition by Isoxanthanol-Nanoparticles through Histone H3 Lysine 27 Trimethylation Downregulation and AMPK Activation

The present study was aimed to investigate the effect of isoxanthanol-nanoparticles (IXNP) on proliferation of osteosarcoma cells and evaluate the underlying mechanism. In MG-63 and U2-OS cells proliferative potential was reduced significantly (p < 0.05) in dose-dependent manner by IXNP treatment. The IXNP treatment at 15 mg/mL suppressed MG-63 cell viability to 39% and that U2-OS cells to 43% at 48 h. Treatment with IXNP led to a prominent up-regulation of caspases-3 and -9 cleavage compared to untreated cells. Moreover, PARP and Bax levels in the cells showed a remarkable increase on IXNP-treatment in comparison to the control cells. Phosphorylation of AMPKα, expression of p21 and replication of mtDNA was also promoted in MG-63 and U2-OS cells on treatment with IXNP. In MG-63 and U2-OS cells, IXNP-treatment elevated expression of PGC-1α and TFAM while as EED, EZH2, and SUZ12 expression was down-regulated. Thus, IXNP suppress proliferation of osteosarcoma cells through activates AMPK activation and elevation of Histone H3 lysine 27 trimethylation. Therefore, IXNP has therapeutic potential to be developed for treatment of osteosarcoma.

NUPR1: A Critical Regulator of the Antioxidant System

Simple Summary

Nuclear protein 1 (NUPR1) is activated in cellular stress and is expressed at high levels in cancer cells. Much evidence has been gathered supporting its critical role in regulating the antioxidant system. Our review aims to summarize the literature data on the impact of NUPR1 on the oxidative stress response via such a regulatory role and how its inhibition induces reactive oxygen species-mediated cell death, such as ferroptosis.

Abstract

Nuclear protein 1 (NUPR1) is a small intrinsically disordered protein (IDP) activated in response to various types of cellular stress, including endoplasmic reticulum (ER) stress and oxidative stress. Reactive oxygen species (ROS) are mainly produced during mitochondrial oxidative metabolism, and directly impact redox homeostasis and oxidative stress. Ferroptosis is a ROS-dependent programmed cell death driven by an iron-mediated redox reaction. Substantial evidence supports a maintenance role of the stress-inducible protein NUPR1 on cancer cell metabolism that confers chemotherapeutic resistance by upregulating mitochondrial function-associated genes and various antioxidant genes in cancer cells. NUPR1, identified as an antagonist of ferroptosis, plays an important role in redox reactions. This review summarizes the current knowledge on the mechanism behind the observed impact of NUPR1 on mitochondrial function, energy metabolism, iron metabolism, and the antioxidant system. The therapeutic potential of genetic or pharmacological inhibition of NUPR1 in cancer is also discussed. Understanding the role of NUPR1 in the antioxidant system and the mechanisms behind its regulation of ferroptosis may promote the development of more efficacious strategies for cancer therapy.

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.

Potential signaling pathway through which Notch regulates oxidative damage and apoptosis in renal tubular epithelial cells induced by high glucose

Diabetic nephropathy (DN) is one of the most common and serious complications of diabetes mellitus, and glomerular sclerosis and renal tubular interstitial fibrosis are the main pathological features. Current evidence indicates that the Notch pathway can mediate the impairment of renal tubular function and induce angiogenesis and renal interstitial fibrosis. This study was conducted to explore the potential signaling pathway through which Notch regulates oxidative damage and apoptosis in renal tubular epithelial cells induced by high glucose. mRNA and protein expression levels were assessed using real-time PCR and Western blot, respectively. The protein expression levels of Jaggedl, Notchl, pro-caspase-3, Drpl, and PGC-1α were increased by high glucose, but N-[N-(3,5-difluorohenacetyl)-l-alanyl]-S-phenylglycine tert-butyl ester (DAPT; an inhibitor of the Notch signaling pathway) reversed these effects. Furthermore, DAPT reduced the mRNA expression of Jaggedl, Notchl, MnSOD2, Drpl, and PGC-1α in renal tubular epithelial cells induced by high glucose. In conclusion, the Notch signaling pathway may regulate oxidative damage and apoptosis in renal tubular epithelial cells induced by high glucose by regulating mitochondrial dynein and biogenesis genes, which can accelerate renal interstitial fibrosis in DN. The Notch signaling pathway might be a potential therapeutic target for DN, and DAPT might become a potential drug for the treatment of DN.

PGC-1α isoforms coordinate to balance hepatic metabolism and apoptosis in inflammatory environments

Objective

The liver is regularly exposed to changing metabolic and inflammatory environments. It must sense and adapt to metabolic need while balancing resources required to protect itself from insult. Peroxisome proliferator activated receptor gamma coactivator-1 alpha (PGC-1α) is a transcriptional coactivator expressed as multiple, alternatively spliced variants transcribed from different promoters that coordinate metabolic adaptation and protect against inflammation. It is not known how PGC-1α integrates extracellular signals to balance metabolic and anti-inflammatory outcomes.

Methods

Primary mouse hepatocytes were used to evaluate the role(s) of different PGC-1α proteins in regulating hepatic metabolism and inflammatory signaling downstream of tumor necrosis factor alpha (TNFα). Gene expression and signaling analysis were combined with biochemical measurement of apoptosis using gain- and loss-of-function in vitro and in vivo.

Results

Hepatocytes expressed multiple isoforms of PGC-1α, including PGC-1α4, which microarray analysis showed had common and isoform-specific functions linked to metabolism and inflammation compared with canonical PGC-1α1. Whereas PGC-1α1 primarily impacted gene programs of nutrient metabolism and mitochondrial biology, TNFα signaling showed several pathways related to innate immunity and cell death downstream of PGC-1α4. Gain- and loss-of-function models illustrated that PGC-1α4 uniquely enhanced expression of anti-apoptotic gene programs and attenuated hepatocyte apoptosis in response to TNFα or lipopolysaccharide (LPS). This was in contrast to PGC-1α1, which decreased the expression of a wide inflammatory gene network but did not prevent hepatocyte death in response to cytokines.

Conclusions

PGC-1α variants have distinct, yet complementary roles in hepatic responses to metabolism and inflammation, and we identify PGC-1α4 as an important mitigator of apoptosis.

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Multiple isoforms of PGC-1α are expressed in hepatocytes, including PGC-1α4.

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PGC-1α1 and PGC-1α4 share many metabolic targets, but PGC-1α4 has unique functions linked to hepatic inflammatory signalling.

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PGC-1α4 attenuates hepatocyte apoptosis in response to TNFα and LPS in vitro and in vivo.

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Inflammatory signaling influences PGC-1α4 localization in hepatocytes.

PARP1 Inhibition Augments UVB-Mediated Mitochondrial Changes-Implications for UV-Induced DNA Repair and Photocarcinogenesis

Keratinocytes provide the first line of defense of the human body against carcinogenic ultraviolet (UV) radiation. Acute and chronic UVB-mediated cellular responses were widely studied. However, little is known about the role of mitochondrial regulation in UVB-induced DNA damage. Here, we show that poly (ADP-ribose) polymerase 1 (PARP1) and ataxia-telangiectasia-mutated (ATM) kinase, two tumor suppressors, are important regulators in mitochondrial alterations induced by UVB. Our study demonstrates that PARP inhibition by ABT-888 upon UVB treatment exacerbated cyclobutane pyrimidine dimers (CPD) accumulation, cell cycle block and cell death and reduced cell proliferation in premalignant skin keratinocytes. Furthermore, in human keratinocytes UVB enhanced oxidative phosphorylation (OXPHOS) and autophagy which were further induced upon PARP inhibition. Immunoblot analysis showed that these cellular responses to PARP inhibition upon UVB irradiation strongly alter the phosphorylation level of ATM, adenosine monophosphate-activated kinase (AMPK), p53, protein kinase B (AKT), and mammalian target of rapamycin (mTOR) proteins. Furthermore, chemical inhibition of ATM led to significant reduction in AMPK, p53, AKT, and mTOR activation suggesting the central role of ATM in the UVB-mediated mitochondrial changes. Our results suggest a possible link between UVB-induced DNA damage and metabolic adaptations of mitochondria and reveal the OXPHOS-regulating role of autophagy which is dependent on key metabolic and DNA damage regulators downstream of PARP1 and ATM.

Nitric oxide represses the proliferation of Caco-2 cells by inducing S-G2/M cell cycle arrest

There is conflicting data regarding the ability of nitric oxide (NO) to promote or inhibit colorectal cancer cell proliferation. Furthermore, NO reacts rapidly with endogenous superoxide at a diffusion-controlled rate to give peroxynitrite (ONOO-), a strong oxidant and nitrating agent. The aim of this study was to assess the effects of exogenous NO and ONOO- on the proliferation of the colorectal cancer cell line Caco-2. NOR5 and SIN-1 were used as NO and ONOO- donors, respectively. Both NOR5 and SIN-1 inhibited the proliferation of the Caco-2 cells; however, the effect of NOR5 was slightly stronger than that of SIN-1. The results also indicated that NO plays a major role in the inhibition of SIN-1-induced proliferation of Caco-2 cells. The results of a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, cell cycle analysis, and p21 protein expression measurement further indicated that NO induced S-G2/M phase arrest, but not apoptosis, in the Caco-2 cells. The results suggest that NO, rather than ONOO-, has the potential to repress the proliferation of Caco-2 cells by inducing S-G2/M cell cycle arrest.

MiR-138-5p exacerbates hypoxia/reperfusion-induced heart injury through the inactivation of SIRT1-PGC-1α

OBJECTIVES

A drastic reduction in myocardial cell apoptosis plays a crucial role in the treatment/management of myocardial infarction, a major cardiovascular health challenge confronting the world, especially the Western world. Accumulating evidence indicates that the cardiotoxicity caused by the apoptotic machinery is partly regulated by miRNAs. The aim of this research is to investigate the role of miR-138-5p on hypoxia/reperfusion-induced heart injury.

METHODS

The expression of miR-138-5p was determined in heart tissue from myocardial infarction patients and rats. Rats were transfection with a miR-138-5p inhibitor to silence miR-138-5p. The cardiac function of rats was detected via echocardiography. SIRT1 and PGC-1α expression in cardiac infarction was detected via quantitative Real-time PCR (qPCR) and Western blot analysis, while the TUNEL assay was used to determine myocardial apoptosis.

RESULTS

Our observations showed that miR-138-5p expression was upregulated after the induction of myocardial infarction. The miR-138-5p inhibitor significantly improved cardiac function, increased the expression of SIRT1 and PGC-1α, and decreased the rate of myocardial apoptosis, whereas siRNA-SIRT1 reversed these protective effects.

CONCLUSIONS

In conclusion, our study demonstrated that miR-138-5p could promote cardiac ischemia injury via inhibition of the silent information regulator 1 and peroxisome proliferator-initiated receptor gamma and coactivator 1 alpha (SIRT1-PGC-1α) axis.

Paeonol protects mitochondrial injury and prevents pulmonary vascular remodeling in hypoxia

Mitochondrial injury of pulmonary artery smooth muscle cells (PASMCs) is an important stage in the development of pulmonary arterial hypertension (PAH). Recent studies revealed that Paeonol exerts anti-proliferative effects on vascular smooth muscle cells. However, whether Paeonol is directly involved in mitochondrial injury related to PAH remains unknown. Here, we found that hypoxia-induced mitochondrial injury in vivo was alleviated in the presence of Paeonol. Hypoxia mediated the mitochondrial injuries in PASMCs in vitro, including decreased ATP generation, morphological alterations, mitochondrial polarization and increased reactive oxygen species production, which were suppressed by Paeonol. Our results also indicated that the expression of peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) was regulated by Paeonol. Paeonol caused significant alterations in mitochondrion-dependent apoptosis through PGC-1α in PASMCs. Taken together, these results provide the first evidence confirming the protective effect of Paeonol in mediating mitochondrial injury under hypoxia and elucidating the necessary role of PGC-1α in the effects of Paeonol in inducing PASMC apoptosis.

miR-23b-3p suppressing PGC1α promotes proliferation through reprogramming metabolism in osteosarcoma

Metabolic shift from oxidative phosphorylation (OXPHOS) to glycolysis is a hallmark of osteosarcoma (OS). However, the mechanisms of the metabolic switch have not been completely elucidated. Here we reported that the miR-23b-3p was significantly upregulated in OS cells. Functional studies suggested that knockdown of miR-23b-3p could inhibit OS cell proliferation in vitro or in vivo. In addition, suppression of miR-23b-3p could lead to upregulation of OXPHOS and suppression of glycolysis. Mechanistically, miR-23b-3p promoted OS cell proliferation and inhibited OXPHOS in OS, at least in part, by directly targeting peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC1α) and inhibiting its expression. Our data highlights important roles of miR-23b-3p and PGC1α in glucose metabolism reprogram of OS. The suppression of miR-23b-3p may provide effective therapeutic strategies for the treatment of OS.

Identification of Compounds That Inhibit Estrogen-Related Receptor Alpha Signaling Using High-Throughput Screening Assays

The nuclear receptor, estrogen-related receptor alpha (ERRα; NR3B1), plays a pivotal role in energy homeostasis. Its expression fluctuates with the demands of energy production in various tissues. When paired with the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), the PGC/ERR pathway regulates a host of genes that participate in metabolic signaling networks and in mitochondrial oxidative respiration. Unregulated overexpression of ERRα is found in many cancer cells, implicating a role in cancer progression and other metabolism-related diseases. Using high throughput screening assays, we screened the Tox21 10K compound library in stably transfected HEK293 cells containing either the ERRα-reporter or the reporter plus PGC-1α expression plasmid. We identified two groups of antagonists that were potent inhibitors of ERRα activity and/or the PGC/ERR pathway: nine antineoplastic agents and thirteen pesticides. Results were confirmed using gene expression studies. These findings suggest a novel mechanism of action on bioenergetics for five of the nine antineoplastic drugs. Nine of the thirteen pesticides, which have not been investigated previously for ERRα disrupting activity, were classified as such. In conclusion, we demonstrated that high-throughput screening assays can be used to reveal new biological properties of therapeutic and environmental chemicals, broadening our understanding of their modes of action.

Increase in carbon dioxide accelerates the performance of endurance exercise in rats

Endurance exercise generates CO2 via aerobic metabolism; however, its role remains unclear. Exogenous CO2 by transcutaneous delivery promotes muscle fibre-type switching to increase endurance power in skeletal muscles. Here we determined the performance of rats running in activity wheels with/without transcutaneous CO2 exposure to clarify its effect on endurance exercise and recovery from muscle fatigue. Rats were randomised to control, training and CO2 groups. Endurance exercise included activity-wheel running with/without transcutaneous CO2 delivery. Running performance was measured after exercise initiation. We also analysed changes in muscle weight and muscle fibres in the tibialis anterior muscle. Running performance improved over the treatment period in the CO2 group, with a concomitant switch in muscle fibres to slow-type. The mitochondrial DNA content and capillary density in the CO2 group increased. CO2 was beneficial for performance and muscle development during endurance exercise: it may enhance recovery from fatigue and support anabolic metabolism in skeletal muscles.

SIRT1/PGC-1α Signaling Promotes Mitochondrial Functional Recovery and Reduces Apoptosis after Intracerebral Hemorrhage in Rats

Silent information regulator 1 (SIRT1) exerts neuroprotection in many neurodegenerative diseases. However, it is not clear if SIRT1 has protective effects after intracerebral hemorrhage (ICH)-induced brain injury in rats. Thus, our goal was to examine the influence of SIRT1 on ICH injuries and any underlying mechanisms of this influence. Brain injury was induced by autologous arterial blood (60 μL) injection into rat brains, and data show that activation of SIRT1 with SRT1720 (5 mg/kg) restored nuclear SIRT1, deacetylation of PGC-1α, and mitochondrial biogenesis and decreased mortality, behavioral deficits, and brain water content without significant changes in phosphorylated AMP-activated protein kinase (pAMPK) induced by ICH. Activation of SIRT1 with SRT1720 also restored mitochondrial electron transport chain proteins and decreased apoptotic proteins in ICH; however, these changes were reversed after ICH. In contrast, treatment with PGC-1α siRNA yielded opposite effects. To explore the protective effects of SIRT1 after ICH, siRNAs were used to knockdown SIRT1. Treatment with SIRT1 siRNA increased mortality, behavioral deficits, brain water content, mitochondrial dysfunction, and neurocyte apoptosis after ICH. Thus, activation of SIRT1 promotes recovery of mitochondrial protein and function by increasing mitochondrial biogenesis and reduces apoptosis after ICH via the PGC-1α mitochondrial pathway. These data may suggest a new therapeutic approach for ICH injuries.

Bioenergetics of acquired cisplatin resistant H1299 non-small cell lung cancer and P31 mesothelioma cells

Acquired cisplatin resistance is a common feature of tumours following cancer treatment with cisplatin and also of non-small cell lung cancer (H1299) and mesothelioma (P31) cell lines exposed to cisplatin. To elucidate the cellular basis of acquired cisplatin resistance, a comprehensive bioenergetic analysis was undertaken. We demonstrate that cellular oxygen consumption was significantly decreased in cisplatin resistant cells and that the reduction was primarily due to reduced mitochondrial activity as a result of reduced mitochondrial abundance. The differential mitochondrial abundance was supported by data showing reduced sirtuin 1 (SIRT1), peroxisome-proliferator activator receptor-γ co-activator 1-alpha (PGC1α), sirtuin 3 (SIRT3) and mitochondrial transcription factor A (TFAM) protein expression in resistant cells. Consistent with these data we observed increased reactive oxygen species (ROS) production and increased hypoxia inducible factor 1-alpha (HIF1α) stabilization in cisplatin resistant cells when compared to cisplatin sensitive controls. We also observed an increase in AMP kinase subunit α2 (AMPKα2) transcripts and protein expression in resistant H1299 cells. mRNA expression was also reduced for cisplatin resistant H1299 cells in these genes, however the pattern was not consistent in resistant P31 cells. There was very little change in DNA methylation of these genes, suggesting that the cells are not stably reprogrammed epigenetically. Taken together, our data demonstrate reduced oxidative metabolism, reduced mitochondrial abundance, potential for increased glycolytic flux and increased ROS production in acquired cisplatin resistant cells. This suggests that the metabolic changes are a result of reduced SIRT3 expression and increased HIF-1α stabilization.

Sulforaphane induces differential modulation of mitochondrial biogenesis and dynamics in normal cells and tumor cells

Antioxidant-based chemotherapy has been intensely debated. Herein, we show that sulforaphane (SFN) induced mitochondrial biogenesis followed by mitochondrial fusion in a kidney cell line commonly used in nephroprotective models. At the same concentration and exposure time, SFN induced cell death in prostate cancer cells accompanied by mitochondrial biogenesis and fragmentation. Stabilization of the nuclear factor E2-related factor-2 (Nrf2) could be associated with these effects in the tumor cell line. An increase in the peroxisome proliferator-activated receptor-γ co-activator-1α (PGC1α) level and a decrease in the hypoxia-inducible factor-1α (HIF1α) level would suggest a possible metabolic shift. The knockdown in the nuclear respiratory factor-1 (NRF1) attenuated the SFN-induced effect on prostate cancer cells demonstrating that mitochondrial biogenesis plays an important role in cell death for this kind of tumor cells. This evidence supports SFN as a potential antineoplastic agent that could inhibit tumor development and could protect normal tissues by modulating common processes.

A Novel Danshensu Derivative Prevents Cardiac Dysfunction and Improves the Chemotherapeutic Efficacy of Doxorubicin in Breast Cancer Cells

Doxorubicin (Dox) is an anthracycline antibiotic widely used in clinics as an anticancer agent. However, the use of Dox is limited by its cardiotoxicity. We have previously shown that a Danshensu (DSS) derivative, ADTM, displayed strong cardioprotective effects. With improved chemical stability and activity, a novel DSS derivative, D006, based on the structure of ADTM, was synthesized. In the present study, the protective effects of D006, indexed by attenuation of the cardiotoxicity induced by Dox as well as chemosensitizing effects that increase the antitumor activity of Dox, were investigated. Our results showed that D006 was more potent than either parental compound, or their use in combination, in ameliorating Dox-induced toxicity in H9c2 cells. In our zebrafish model, D006, but not DSS, alone significantly preserved the ventricular function of zebrafish after Dox treatment. Moreover, D006 upregulated mitochondrial biogenesis and increased mtDNA copy number after Dox treatment of H9c2 cells. D006 promoted the expression of HO-1 protein in a time-dependent manner while the HO-1 inhibitor, Znpp, reversed the protective effects of D006. In human breast tumor MCF-7 cells, D006 enhanced Dox-induced cytotoxicity by increasing apoptosis. In conclusion, our results indicate that a new DSS derivative exhibits promising protective effects against Dox-induced cardiotoxicity both in vivo and in vitro, an effect at least partially mediated by induction of HO-1 expression and the activation of mitochondrial biogenesis. Meanwhile, D006 also potentiated the anti-cancer effects of Dox in breast tumor cells.

AICAR induces mitochondrial apoptosis in human osteosarcoma cells through an AMPK-dependent pathway

The AMP-activated protein kinase (AMPK) activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) modulates cellular energy metabolism, and promotes mitochondrial proliferation and apoptosis. Previous studies have shown that AICAR has anticancer effects in various cancers, however the roles of AMPK and/or the effects of AICAR on osteosarcoma have not been reported. In the present study, we evaluated the effects of AICAR on tumor growth and mitochondrial apoptosis in human osteosarcoma both in vitro and in vivo. For in vitro experiments, two human osteosarcoma cell lines, MG63 and KHOS, were treated with AICAR, and the effects of AICAR on cell growth and mitochondrial apoptosis were assessed by WST assays, TUNEL staining, and immunoblot analyses. In vivo, human osteosarcoma-bearing mice were treated with AICAR, and the mitochondrial proliferation and apoptotic activity in treated tumors were assessed. In vitro experiments revealed that AICAR activated AMPK, inhibited cell growth, and induced mitochondrial apoptosis in both osteosarcoma cell lines. In vivo, AICAR significantly reduced osteosarcoma growth without apparent body weight loss and AICAR increased both mitochondrial proliferation and apoptotic activity in treated tumor tissues. AICAR showed anticancer effects in osteosarcoma cells through an AMPK-dependent peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α)/mitochondrial transcription factor A (TFAM)/mitochondrial pathway. The findings in this study strongly suggest that AICAR could be considered as a potent therapeutic agent for the treatment of human osteosarcoma.

Decreased mitochondrial copy numbers in oral squamous cell carcinoma

BACKGROUND

Mitochondrial dysfunction and altered respiration have long been suspected to affect the development and progression of cancer. Although quantitative changes in mitochondrial DNA (mtDNA) have been reported in head and neck squamous cell carcinoma (SCC), differences in mtDNA copy numbers between normal and cancerous tissues from same patients have not been assessed.

METHODS

We compared mtDNA copy numbers and expressions of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and mitochondrial transcription factor A (TFAM) between normal mucous membrane and cancerous tissues resected from 35 patients with oral SCC, using TaqMan quantitative real-time polymerase chain reaction (PCR) and immunohistochemical staining.

RESULTS

We found mtDNA copy numbers and expressions of PGC-1α and TFAM were decreased in cancerous tissues compared with normal tissues from the same patients.

CONCLUSION

The PGC-1α-TFAM mitochondrial pathway may be associated with malignant potential in human oral SCC, and could be an attractive therapeutic target. © 2016 Wiley Periodicals, Inc. Head Neck 38:1170-1175, 2016.

Effects of nitric oxide on the biological behavior of HepG2 human hepatocellular carcinoma cells

Many studies have found the function of nitric oxide (NO) in cancer as a pro-neoplastic vs. an anti-neoplastic effector, but the role of NO in hepatocellular carcinoma (HCC) remains unclear. The present study aimed to investigate the effects of nitric oxide (NO) on the biological behavior of the human hepatocellular carcinoma cell line HepG2. HepG2 cell was cultured in vitro and treated with or without sodium nitroprusside (SNP), a NO donor. Subsequently, we evaluated the effects of NO in cell proliferation, cell cycle, apoptosis, migration and invasion by MTT assay, flow cytometry, wound healing assay and Matrigel invasion assay. We demonstrate that NO significantly inhibited HepG2 cell proliferation by inducing G0/G1 phase arrest in a dose-dependent manner. In addition, compared to the control group, cells treated with SNP showed obviously higher apoptosis ratios in a dose-dependent manner. Furthermore, we revealed that NO effectively inhibited the ability of migration and invasion of HepG2 cells. Taken together, our results suggested that NO has an important role in the regulation of biological behavior in HepG2 cells and the potential for use in the prevention and treatment of HCC.

Transcutaneous carbon dioxide induces mitochondrial apoptosis and suppresses metastasis of oral squamous cell carcinoma in vivo

Squamous cell carcinoma (SCC) is the main histological type of oral cancer. Its growth rate and incidence of metastasis to regional lymph nodes is influenced by various factors, including hypoxic conditions. We have previously reported that transcutaneous CO₂ induces mitochondrial apoptosis and decreases lung metastasis by reoxygenating sarcoma cells. However, previous studies have not determined the sequential mechanism by which transcutaneous CO₂ suppresses growth of epithelial tumors, including SCCs. Moreover, there is no report that transcutaneous CO₂ suppresses lymphogenous metastasis using human cell lines xenografts. In this study, we examined the effects of transcutaneous CO₂ on cancer apoptosis and lymphogenous metastasis using human SCC xenografts. Our results showed that transcutaneous CO₂ affects expressions of PGC-1α and TFAM and protein levels of cleavage products of caspase-3, caspase-9 and PARP, which relatives mitochondrial apoptosis. They also showed that transcutaneous CO₂ significantly inhibits SCC tumor growth and affects expressions of HIF-1α, VEGF, MMP-2 and MMP-9, which play essential roles in tumor angiogenesis, invasion and metastasis. In conclusion, transcutaneous CO₂ suppressed tumor growth, increased mitochondrial apoptosis and decreased the number of lymph node metastasis in human SCC by decreasing intra-tumoral hypoxia and suppressing metastatic potential with no observable effect in vivo. Our findings indicate that transcutaneous CO₂ could be a novel therapeutic tool for treating human SCC.

Cancer cells recovering from damage exhibit mitochondrial restructuring and increased aerobic glycolysis

Instead of relying on mitochondrial oxidative phosphorylation, most cancer cells rely heavily on aerobic glycolysis, a phenomenon termed as "the Warburg effect". We considered that this effect is a direct consequence of damage which persists in cancer cells that recover from damage. To this end, we studied glycolysis and rate of cell proliferation in cancer cells that recovered from severe damage. We show that in vitro Damage-Recovered (DR) cells exhibit mitochondrial structural remodeling, display Warburg effect, and show increased in vitro and in vivo proliferation and tolerance to damage. To test whether cancer cells derived from tumor microenvironment can show similar properties, we isolated Damage-Recovered (T(DR)) cells from tumors. We demonstrate that T(DR) cells also show increased aerobic glycolysis and a high proliferation rate. These findings show that Warburg effect and its consequences are induced in cancer cells that survive severe damage.