Activation of CPP32-like protease in tumor necrosis factor-induced apoptosis is dependent on mitochondrial function

Digeda-4 decoction and its disassembled prescriptions improve dyslipidemia and apoptosis by regulating AMPK/SIRT1 pathway on tyloxapol-induced nonalcoholic fatty liver disease in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Nonalcoholic fatty liver disease (NAFLD) is a manifestation of metabolic syndrome in the liver and the leading cause of chronic liver disease worldwide. Digeda-4 decoction (DGD-4) is a commonly prescribed Mongolian herbal drug for treating acute and chronic liver injury and fatty liver. However, the mechanisms underlying the improvement of dislipidemia and liver injury via treatment with DGD-4 remain unclear. Disassembling a prescription is an effective approach to studying the effects and mechanisms underlying Mongolian medicine prescriptions. By disassembling a prescription, it is feasible to discover effective combinations of individual herbs to optimize a given prescription. Accordingly, we disassembled DGD-4 into two groups: the single Lomatogonium rotatum (L.) Fries ex Nym (LR) (DGD-1) and non-LR (DGD-3).

AIM OF THIS STUDY

To study whether DGD-4 and its disassembled prescriptions have protective effects against tyloxapol (TY)-induced NAFLD and to explore the underlying mechanisms of action and compatibility of prescriptions.

MATERIAL AND METHODS

NAFLD mice were developed by TY induction. Biochemical horizontal analyses, enzyme-linked immunosorbent assay, and liver histological staining were performed to explore the protective effects of DGD-4 and its disassembled prescriptions DGD-3 and DGD-1. Furthermore, we performed immunohistochemical analyses and Western blotting to further explore the expression of target proteins.

RESULTS

DGD-4 and its disassembled prescriptions could inhibit TY-induced dislipidemia and liver injury. In addition, DGD-4 and its disassembled prescriptions increased the levels of p-AMPKα and p-ACC, but decreased the levels of SREBP1c, SCD-1, SREBP-2, and HMGCS1 proteins. The activation of lipid metabolic pathways SIRT1, PGC-1α, and PPARα improved lipid accumulation in the liver. Moreover, DGD-4 could inhibit hepatocyte apoptosis and treat TY-induced liver injury by upregulating the Bcl-2 expression, downregulating the expression of Bax, caspase-3, caspase-8, and the ratio of Bax/Bcl-2, and positively regulating the imbalance of oxidative stress (OxS) markers (such as superoxide dismutase [SOD], catalase [CAT], malondialdehyde [MDA], and myeloperoxidase [MPO]). DGD-1 was superior to DGD-3 in regulating lipid synthesis-related proteins such as SREBP1c, SCD-1, SREBP-2, and HMGCS1. DGD-3 significantly affected the expression of lipid metabolic proteins SIRT1, PGC-1α, PPARα, apoptotic proteins Bcl-2, Bax, caspase-3, caspase-8, and the regulation of Bax/Bcl-2 ratio. However, DGD-1 showed no regulatory effects on Bax and Bcl-2 proteins.

CONCLUSION

This study demonstrates the protective effects of DGD-4 in the TY-induced NAFLD mice through a mechanism involving improvement of dyslipidemia and apoptosis by regulating the AMPK/SIRT1 pathway. Although the Monarch drug DGD-1 reduces lipid accumulation and DGD-3 inhibits apoptosis and protects the liver from injury, DGD-4 can be more effective overall as a therapy when compared to DGD-1 and DGD-3.

The F1Fo-ATPase inhibitor protein IF1 in pathophysiology

The endogenous inhibitor of ATP synthase is a protein of about 10 kDa, known as IF1 which binds to the catalytic domain of the enzyme during ATP hydrolysis. The main role of IF1 consists of limiting ATP dissipation under condition of severe oxygen deprivation or in the presence of dysfunctions of mitochondrial respiratory complexes, causing a collapse in mitochondrial membrane potential and therefore ATP hydrolysis. New roles of IF1 are emerging in the fields of cancer and neurodegeneration. Its high expression levels in tumor tissues have been associated with different roles favouring tumor formation, progression and evasion. Since discordant mechanisms of action have been proposed for IF1 in tumors, it is of the utmost importance to clarify them in the prospective of defining novel approaches for cancer therapy. Other IF1 functions, including its involvement in mitophagy, may be protective for neurodegenerative and aging-related diseases. In the present review we aim to clarify and discuss the emerging mechanisms in which IF1 is involved, providing a critical view of the discordant findings in the literature.

The Multifaceted ATPase Inhibitory Factor 1 (IF1) in Energy Metabolism Reprogramming and Mitochondrial Dysfunction: A New Player in Age-Associated Disorders?

Significance: The mitochondrial oxidative phosphorylation (OXPHOS) system, comprising the electron transport chain and ATP synthase, generates membrane potential, drives ATP synthesis, governs energy metabolism, and maintains redox balance. OXPHOS dysfunction is associated with a plethora of diseases ranging from rare inherited disorders to common conditions, including diabetes, cancer, neurodegenerative diseases, as well as aging. There has been great interest in studying regulators of OXPHOS. Among these, ATPase inhibitory factor 1 (IF1) is an endogenous inhibitor of ATP synthase that has long been thought to avoid the consumption of cellular ATP when ATP synthase acts as an ATP hydrolysis enzyme. Recent Advances: Recent data indicate that IF1 inhibits ATP synthesis and is involved in a multitude of mitochondrial-related functions, such as mitochondrial quality control, energy metabolism, redox balance, and cell fate. IF1 also inhibits the ATPase activity of cell-surface ATP synthase, and it is used as a cardiovascular disease biomarker. Critical Issues: Although recent data have led to a paradigm shift regarding IF1 functions, these have been poorly studied in entire organisms and in different organs. The understanding of the cellular biology of IF1 is, therefore, still limited. The aim of this review was to provide an overview of the current understanding of the role of IF1 in mitochondrial functions, health, and diseases. Future Directions: Further investigations of IF1 functions at the cell, organ, and whole-organism levels and in different pathophysiological conditions will help decipher the controversies surrounding its involvement in mitochondrial function and could unveil therapeutic strategies in human pathology. Antioxid. Redox Signal. 37, 370-393.

Paeoniflorin improves cardiac function and decreases adverse postinfarction left ventricular remodeling in a rat model of acute myocardial infarction

Background

Paeoniflorin (PF) is the active component of Paeonia lactiflora Pall. or Paeonia veitchii Lynch. This study was, therefore, aimed to evaluate the improvement and mechanism of the PF on ventricular remodeling in rats with acute myocardial infarction (AMI).

Materials and methods

In this study, AMI model was established by ligating the anterior descending coronary artery in Wistar rats. After 4 weeks gavage of PF, the apparent signs and the left ventricle weight index of Wistar rats were observed. The left ventricular ejection fraction (LVEF) was evaluated by Doppler ultrasonography. Changes in cardiac morphology were observed by pathologic examination, and apoptosis was observed by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In addition, enzyme-linked immunosorbent assay was used to detect the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) interleukin-10 (IL-10) and brain natriuretic peptide (BNP). Immunohistochemistry and Western blot method were applied to detect Caspase-3 and Caspase-9.

Results

Compared with the model control, the survival conditions of rats in all treatment groups were generally improved after PF treatment. LVEF was significantly increased, and both left ventricular end-diastolic inner diameter and left ventricular end-systolic inner diameter were significantly reduced. Moreover, pathologic examination showed that the myocardium degeneration of the rats treated with PF was decreased, including neater arrangement, more complete myofilament, more uniform gap and less interstitial collagen fibers. Furthermore, the mitochondrial structure of cardiomyocytes was significantly improved. The ultrastructure was clear, and the arrangement of myofilament was more regular. Also, the expression of Caspase-3 and Caspase-9 was inhibited, and apoptosis was obviously reduced in the PF treatment groups. BNP, TNF-α and IL-6 were also decreased and IL-10 was increased in the treated rats.

Conclusion

PF could significantly improve the LVEF of rats. It decreased adverse left ventricular remodeling after myocardial infarction in rat models. The potential mechanism could be that PF decreased and inhibited BNP, TNF-α and IL-6, increased IL-10 and further inhibited the expression of Caspase-3 and Caspase-9, thus promoting ventricular remodeling.

α-Tocopheryl Succinate Affects Malignant Cell Viability, Proliferation, and Differentiation

The widespread occurrence of malignant tumors motivates great attention to finding and investigating effective new antitumor preparations. Such preparations include compounds of the vitamin E family. Among them, α-tocopheryl succinate (vitamin E succinate (VES)) has the most pronounced antitumor properties. In this review, various targets and mechanisms of the antitumor effect of vitamin E succinate are characterized. It has been shown that VES has multiple intracellular targets and effects, and as a result VES is able to induce apoptosis in tumor cells, inhibit their proliferation, induce differentiation, prevent metastasizing, and inhibit angiogenesis. However, VES has minimal effects on normal cells and tissues. Due to the variety of targets and selectivity of action, VES is a promising agent against malignant neoplasms. More detailed studies in this area can contribute to development of effective and safe chemotherapeutic preparations.

Use of the Prostate Core Mitomic Test in Repeated Biopsy Decision-Making: Real-World Assessment of Clinical Utility in a Multicenter Patient Population

BACKGROUND

Prostate cancer is the most common cancer diagnosed in men in developed countries. Using molecular testing may help to improve outcomes in this clinically challenging group. Since 2011, the Prostate Core Mitomic Test (PCMT), which quantifies a 3.4-kb mitochondrial DNA deletion strongly associated with prostate cancer, has been used by more than 50 urology practices accessing pathology services through our laboratory in New Jersey. However, the use of a molecular test can only be beneficial if it affects patient management and improves outcomes.

OBJECTIVE

To determine whether repeated biopsy decision-making was affected in a quantifiable manner through the adjunct use of molecular testing with the PCMT.

METHODS

In this observational study we conducted 2 independent, structured query language database queries of our patient records at our laboratory, QDx Pathology Services, in Cranford, NJ. Query 1 included all men who had a negative prostate biopsy and a negative PCMT between February 1, 2011, and June 30, 2013. Men with a previous diagnosis of cancer were excluded. Query 2 included all men who had a negative prostate biopsy and a repeated biopsy between February 1, 2011, and September 30, 2013. The data exported for each query included the unique specimen number for an index biopsy, the interval between biopsies where present, the unique specimen number for a follow-up biopsy where present, histopathology for all biopsies, the biopsy procedure dates, the patient's date of birth, and the PCMT result when utilized. The patient rebiopsy rates and intervals were compared between the patients who were using PCMT and those who were not to assess whether the adjunct use of the PCMT impacted the rebiopsy decision-making process.

RESULTS

Query 1 identified 644 men who had a negative biopsy and a negative PCMT result within the study period. Query 2 identified 823 men with a repeat biopsy after the initial negative index biopsy within the study period. Of these men, 132 had PCMT to inform their care. This patient population of 1467 men originated from US-based clinical urology practices. Evaluation of the impact on physician behavior demonstrated a general trend toward the earlier detection of prostate cancer on repeat biopsy by an average of 2.5 months and a coincident increase in cancer detection rates for urologists using the deletion assay in their rebiopsy decision-making process. Importantly, this trend was only observed when men with atypical small acinar proliferation (ASAP) on index biopsy were not considered. In the 644 men with a negative PCMT result, only 35 (5.4%) were subjected to a follow-up biopsy, with 5 (14.3%) of the 35 men identified as having cancer. Finally, the cohort of 132 men who had PCMT and repeat biopsy was compared with the published data supporting PCMT's ability to predict rebiopsy outcome. The key metrics of sensitivity and negative predictive value were comparable and within the 95% confidence intervals of the reported work.

CONCLUSION

Molecular tests, such as the PCMT, are useful in addressing the sampling error of prostate needle biopsy and providing additional evidence to inform the clinical uncertainty regarding initial negative prostate biopsy when ASAP is not present. Longitudinal monitoring of clinical impact indicators provides the necessary inputs to better allocation of healthcare resources in the short- and long-term.

Mitochondrial DNA copy number in peripheral blood leukocytes and the aggressiveness of localized prostate cancer

We investigated whether low mitochondrial DNA copy number (mtDNAcn) in peripheral blood leukocytes at diagnosis was associated with an increased risk of the aggressive form of the tumor and disease progression among localized prostate cancer (PCa) patients. We recruited 1,751 non-Hispanic white men with previously untreated PCa from The University of Texas MD Anderson Cancer Center. mtDNAcn was categorized into three groups according to tertiles. We used multivariate logistic regression to estimate the odds ratios (ORs) and 95 percent confidence intervals (95% CIs) for the association of mtDNAcn with the risk of having aggressive PCa at diagnosis. We used Cox proportional hazards model to estimate hazard ratios (HRs) and 95% CIs for disease progression. We observed an inverse association between aggressiveness of PCa and mtDNAcn (P < 0.001). In multivariate analysis, compared to patients in the highest tertile of mtDNAcn, those in the second and lowest tertiles had significantly increased risks of presenting with the high-risk form of PCa, as defined by the D'Amico criteria, with ORs of 1.33 (95% CI, 0.89–1.98; P = 0.17) and 1.53 (95% CI, 1.02–2.30; P = 0.04), respectively. Furthermore, PCa patients in the lowest and second tertiles combined relative to those in the highest tertile had a 56% increased risk of disease progression (HR, 1.56; 95% CI, 0.96–2.54; P = 0.07). In summary, our results suggested that low mtDNAcn in peripheral blood leukocytes was associated with aggressive PCa at diagnosis and might further predict poor progression-free survival among localized PCa patients.

Mitochondrial DNA depletion causes decreased ROS production and resistance to apoptosis

Mitochondrial DNA (mtDNA) depletion occurs frequently in many diseases including cancer. The present study was designed in order to examine the hypothesis that mtDNA‑depleted cells are resistant to apoptosis and to explore the possible mechanisms responsible for this effect. Parental human osteosarcoma 143B cells and mtDNA‑deficient (Rho˚ or ρ˚) 206 cells (derived from 143B cells) were exposed to different doses of solar-simulated ultraviolet (UV) radiation. The effects of solar irradiation on cell morphology were observed under both light and fluorescence microscopes. Furthermore, apoptosis, mitochondrial membrane potential (MMP) disruption and reactive oxygen species (ROS) production were detected and measured by flow cytometry. In both cell lines, apoptosis and ROS production were clearly increased, whereas MMP was slightly decreased. However, apoptosis and ROS production were reduced in the Rho˚206 cells compared with the 143B cells. We also performed western blot analysis and demonstrated the increased release of cytosolic Cyt c from mitochondria in the 143B cells compared with that in the Rho˚206 cells. Thus, we concluded that Rho˚206 cells exhibit more resistance to solar‑simulated UV radiation‑induced apoptosis at certain doses than 143B cells and this is possibly due to decreased ROS production.

Mitochondria and Mitochondrial ROS in Cancer: Novel Targets for Anticancer Therapy

Mitochondria are indispensable for energy metabolism, apoptosis regulation, and cell signaling. Mitochondria in malignant cells differ structurally and functionally from those in normal cells and participate actively in metabolic reprogramming. Mitochondria in cancer cells are characterized by reactive oxygen species (ROS) overproduction, which promotes cancer development by inducing genomic instability, modifying gene expression, and participating in signaling pathways. Mitochondrial and nuclear DNA mutations caused by oxidative damage that impair the oxidative phosphorylation process will result in further mitochondrial ROS production, completing the "vicious cycle" between mitochondria, ROS, genomic instability, and cancer development. The multiple essential roles of mitochondria have been utilized for designing novel mitochondria-targeted anticancer agents. Selective drug delivery to mitochondria helps to increase specificity and reduce toxicity of these agents. In order to reduce mitochondrial ROS production, mitochondria-targeted antioxidants can specifically accumulate in mitochondria by affiliating to a lipophilic penetrating cation and prevent mitochondria from oxidative damage. In consistence with the oncogenic role of ROS, mitochondria-targeted antioxidants are found to be effective in cancer prevention and anticancer therapy. A better understanding of the role played by mitochondria in cancer development will help to reveal more therapeutic targets, and will help to increase the activity and selectivity of mitochondria-targeted anticancer drugs. In this review we summarized the impact of mitochondria on cancer and gave summary about the possibilities to target mitochondria for anticancer therapies. J. Cell. Physiol. 231: 2570-2581, 2016. © 2016 Wiley Periodicals, Inc.

Mitochondrial respiratory function induces endogenous hypoxia

Hypoxia influences many key biological functions. In cancer, it is generally believed that hypoxic condition is generated deep inside the tumor because of the lack of oxygen supply. However, consumption of oxygen by cancer should be one of the key means of regulating oxygen concentration to induce hypoxia but has not been well studied. Here, we provide direct evidence of the mitochondrial role in the induction of intracellular hypoxia. We used Acetylacetonatobis [2-(2′-benzothienyl) pyridinato-kN, kC3’] iridium (III) (BTP), a novel oxygen sensor, to detect intracellular hypoxia in living cells via microscopy. The well-differentiated cancer cell lines, LNCaP and MCF-7, showed intracellular hypoxia without exogenous hypoxia in an open environment. This may be caused by high oxygen consumption, low oxygen diffusion in water, and low oxygen incorporation to the cells. In contrast, the poorly-differentiated cancer cell lines: PC-3 and MDAMB231 exhibited intracellular normoxia by low oxygen consumption. The specific complex I inhibitor, rotenone, and the reduction of mitochondrial DNA (mtDNA) content reduced intracellular hypoxia, indicating that intracellular oxygen concentration is regulated by the consumption of oxygen by mitochondria. HIF-1α was activated in endogenously hypoxic LNCaP and the activation was dependent on mitochondrial respiratory function. Intracellular hypoxic status is regulated by glucose by parabolic dose response. The low concentration of glucose (0.045 mg/ml) induced strongest intracellular hypoxia possibly because of the Crabtree effect. Addition of FCS to the media induced intracellular hypoxia in LNCaP, and this effect was partially mimicked by an androgen analog, R1881, and inhibited by the anti-androgen, flutamide. These results indicate that mitochondrial respiratory function determines intracellular hypoxic status and may regulate oxygen-dependent biological functions.

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

A number of studies have reported that decreased mitochondrial numbers are linked with neoplastic transformation and/or tumor progression, including resistance to apoptosis. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) is a multi-functional transcriptional coactivator that regulates the activities of multiple nuclear receptors and transcriptional factors involved in mitochondrial biogenesis. In this study, we observed that the number of mitochondria in sarcoma tissues, such as osteosarcoma and malignant fibrous histiocytoma, is significantly lower than that in normal muscle tissue or benign tumors and that increasing the number of mitochondria by PGC-1α overexpression induces mitochondrial apoptosis in human sarcoma cell lines. The findings suggest that decreased mitochondrial numbers may contribute to musculoskeletal tumor progression and that regulation of mitochondrial numbers by PGC-1α could be a potent therapeutic tool for human malignancies.

Mitochondrial DNA mutations and breast tumorigenesis

Breast cancer is a heterogeneous disease and genetic factors play an important role in its genesis. Although mutations in tumor suppressors and oncogenes encoded by the nuclear genome are known to play a critical role in breast tumorigenesis, the contribution of the mitochondrial genome to this process is unclear. Like the nuclear genome, the mitochondrial genome also encodes proteins critical for mitochondrion functions such as oxidative phosphorylation (OXPHOS), which is known to be defective in cancer including breast cancer. Mitochondrial DNA (mtDNA) is more susceptible to mutations due to limited repair mechanisms compared to nuclear DNA (nDNA). Thus changes in mitochondrial genes could also contribute to the development of breast cancer. In this review we discuss mtDNA mutations that affect OXPHOS. Continuous acquisition of mtDNA mutations and selection of advantageous mutations ultimately leads to generation of cells that propagate uncontrollably to form tumors. Since irreversible damage to OXPHOS leads to a shift in energy metabolism towards enhanced aerobic glycolysis in most cancers, mutations in mtDNA represent an early event during breast tumorigenesis, and thus may serve as potential biomarkers for early detection and prognosis of breast cancer. Because mtDNA mutations lead to defective OXPHOS, development of agents that target OXPHOS will provide specificity for preventative and therapeutic agents against breast cancer with minimal toxicity.

Reduced mitochondrial DNA content associates with poor prognosis of prostate cancer in African American men

Reduction or depletion of mitochondrial DNA (mtDNA) has been associated with cancer progression. Although imbalanced mtDNA content is known to occur in prostate cancer, differences in mtDNA content between African American (AA) and Caucasian American (CA) men are not defined. We provide the first evidence that tumors in AA men possess reduced level of mtDNA compared to CA men. The median tumor mtDNA content was reduced in AA men. mtDNA content was also reduced in normal prostate tissues of AA men compared to CA men, suggesting a possible predisposition to cancer in AA men. mtDNA content was also reduced in benign prostatic hyperplasia (BPH) tissue from AA men. Tumor and BPH tissues from patients ≥ 60 years of age possess reduced mtDNA content compared to patients <60 years of age. In addition, mtDNA content was higher in normal tissues from patients with malignant T3 stage disease compared to patients with T2 stage disease. mtDNA levels in matched normal prostate tissues were nearly doubled in Gleason grade of >7 compared to ≤ 7, whereas reduced mtDNA content was observed in tumors of Gleason grade >7 compared to ≤ 7. Together, our data suggest that AA men possess lower mtDNA levels in normal and tumor tissues compared to CA men, which could contribute to higher risk and more aggressive prostate cancer in AA men.

Transcutaneous application of carbon dioxide (CO2) induces mitochondrial apoptosis in human malignant fibrous histiocytoma in vivo

Mitochondria play an essential role in cellular energy metabolism and apoptosis. Previous studies have demonstrated that decreased mitochondrial biogenesis is associated with cancer progression. In mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) regulates the activities of multiple nuclear receptors and transcription factors involved in mitochondrial proliferation. Previously, we showed that overexpression of PGC-1α leads to mitochondrial proliferation and induces apoptosis in human malignant fibrous histiocytoma (MFH) cells in vitro. We also demonstrated that transcutaneous application of carbon dioxide (CO₂) to rat skeletal muscle induces PGC-1α expression and causes an increase in mitochondrial proliferation. In this study, we utilized a murine model of human MFH to determine the effect of transcutaneous CO₂ exposure on PGC-1α expression, mitochondrial proliferation and cellular apoptosis. PGC-1α expression was evaluated by quantitative real-time PCR, while mitochondrial proliferation was assessed by immunofluorescence staining and the relative copy number of mitochondrial DNA (mtDNA) was assessed by real-time PCR. Immunofluorescence staining and DNA fragmentation assays were used to examine mitochondrial apoptosis. We also evaluated the expression of mitochondrial apoptosis related proteins, such as caspases, cytochorome c and Bax, by immunoblot analysis. We show that transcutaneous application of CO₂ induces PGC-1α expression, and increases mitochondrial proliferation and apoptosis of tumor cells, significantly reducing tumor volume. Proteins involved in the mitochondrial apoptotic cascade, including caspase 3 and caspase 9, were elevated in CO₂ treated tumors compared to control. We also observed an enrichment of cytochrome c in the cytoplasmic fraction and Bax protein in the mitochondrial fraction of CO₂ treated tumors, highlighting the involvement of mitochondria in apoptosis. These data indicate that transcutaneous application of CO₂ may represent a novel therapeutic tool in the treatment of human MFH.

A case-control study of peripheral blood mitochondrial DNA copy number and risk of renal cell carcinoma

BACKGROUND

Low mitochondrial DNA (mtDNA) copy number is a common feature of renal cell carcinoma (RCC), and may influence tumor development. Results from a recent case-control study suggest that low mtDNA copy number in peripheral blood may be a marker for increased RCC risk. In an attempt to replicate that finding, we measured mtDNA copy number in peripheral blood DNA from a U.S. population-based case-control study of RCC.

METHODOLOGY/PRINCIPAL FINDINGS

Relative mtDNA copy number was measured in triplicate by a quantitative real-time PCR assay using DNA extracted from peripheral whole blood. Cases (n = 603) had significantly lower mtDNA copy number than controls (n = 603; medians 0.85, 0.91 respectively; P = 0.0001). In multiple logistic regression analyses, the lowest quartile of mtDNA copy number was associated with a 60% increase in RCC risk relative to the highest quartile (OR = 1.6, 95% CI = 1.1-2.2; P(trend) = 0.009). This association remained in analyses restricted to cases treated by surgery alone (OR (Q1) = 1.4, 95% CI = 1.0-2.1) and to localized tumors (2.0, 1.3-2.8).

CONCLUSIONS/SIGNIFICANCE

Our findings from this investigation, to our knowledge the largest of its kind, offer important confirmatory evidence that low mtDNA copy number is associated with increased RCC risk. Additional research is needed to assess whether the association is replicable in prospective studies.

Induction of the permeability transition pore in cells depleted of mitochondrial DNA

Respiratory complexes are believed to play a role in the function of the mitochondrial permeability transition pore (PTP), whose dysregulation affects the process of cell death and is involved in a variety of diseases, including cancer and degenerative disorders. We investigated here the PTP in cells devoid of mitochondrial DNA (ρ(0) cells), which lack respiration and constitute a model for the analysis of mitochondrial involvement in several pathological conditions. We observed that mitochondria of ρ(0) cells maintain a membrane potential and that this is readily dissipated after displacement of hexokinase (HK) II from the mitochondrial surface by treatment with either the drug clotrimazole or with a cell-permeant HK II peptide, or by placing ρ(0) cells in a medium without serum and glucose. The PTP inhibitor cyclosporin A (CsA) could decrease the mitochondrial depolarization induced by either HK II displacement or by nutrient depletion. We also found that a fraction of the kinases ERK1/2 and GSK3α/β is located in the mitochondrial matrix of ρ(0) cells, and that glucose and serum deprivation caused concomitant ERK1/2 inhibition and GSK3α/β activation with the ensuing phosphorylation of cyclophilin D, the mitochondrial target of CsA. GSK3α/β inhibition with indirubin-3'-oxime decreased PTP-induced cell death in ρ(0) cells following nutrient ablation. These findings indicate that ρ(0) cells are equipped with a functioning PTP, whose regulatory mechanisms are similar to those observed in cancer cells, and suggest that escape from PTP opening is a survival factor in this model of mitochondrial diseases. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

Cytokines in alcoholic liver disease

Alcoholic liver disease (ALD) is associated with a spectrum of liver injury ranging from steatosis and steatohepatitis to fibrosis and cirrhosis. While multifactorial pathogenesis plays a role in the disease progression, enhanced inflammation in the liver during ethanol exposure is a major feature of ALD. Dysregulated cytokine metabolism and activity are crucial to the initiation of alcohol-induced liver injury. The pro-inflammatory cytokine tumor necrosis factor (TNF-α) has been demonstrated to be one of the key factors in the various aspects of pathophysiology of ALD. The immunomodulatory cytokines such as interleukin 10 and interleukin 6 play roles in exerting hepatic protective effects. Adiponectin is an adipose tissue-derived hormone, which displays protective actions on ethanol-induced liver injury. Treatment for mice with adiponectin decreases TNF-α expression, steatosis and prevents alcohol-induced liver injury. Adiponectin exerts its anti-inflammatory effects via suppression of TNF-α expression and induction of anti-inflammatory cytokines such as IL-10. Adiponectin attenuates alcoholic liver injury by the complex network of multiple signaling pathways in the liver, leading to enhanced fatty acid oxidation and reduced steatosis. Interactions between pro- and anti-inflammatory cytokines such as TNFα and adiponectin and other cytokines are likely to play important roles in the development and progression of alcoholic liver disease.

Consumption of oxygen: a mitochondrial-generated progression signal of advanced cancer

Changes in mitochondrial genome such as mutation, deletion and depletion are common in cancer and can determine advanced phenotype of cancer; however, detailed mechanisms have not been elucidated. We observed that loss of mitochondrial genome reversibly induced overexpression and activation of proto-oncogenic Ras, especially K-Ras 4A, responsible for the activation of AKT and ERK leading to advanced phenotype of prostate and breast cancer. Ras activation was induced by the overexpression of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), the rate-limiting enzyme of the mevalonate pathway. Hypoxia is known to induce proteasomal degradation of HMGR. Well differentiated prostate and breast cancer cells with high mitochondrial DNA content consumed a large amount of oxygen and induced hypoxia. Loss of mitochondrial genome reduced oxygen consumption and increased in oxygen concentration in the cells. The hypoxic-to-normoxic shift led to the overexpression of HMGR through inhibiting proteasomal degradation. Therefore, reduction of mitochondrial genome content induced overexpression of HMGR through hypoxic to normoxic shift and subsequently the endogenous induction of the mevalonate pathway activated Ras that mediates advanced phenotype. Reduction of mitochondrial genome content was associated with the aggressive phenotype of prostate cancer in vitro cell line model and tissue specimens in vivo. Our results elucidate a coherent mechanism that directly links the mitochondrial genome with the advanced progression of the disease.

The awakening of an advanced malignant cancer: an insult to the mitochondrial genome

BACKGROUND

In only months-to-years a primary cancer can progress to an advanced phenotype that is metastatic and resistant to clinical treatments. As early as the 1900s, it was discovered that the progression of a cancer to the advanced phenotype is often associated with a shift in the metabolic profile of the disease from a state of respiration to anaerobic fermentation - a phenomenon denoted as the Warburg Effect.

SCOPE OF REVIEW

Reports in the literature strongly suggest that the Warburg Effect is generated as a response to a loss in the integrity of the sequence and/or copy number of the mitochondrial genome content within a cancer.

MAJOR CONCLUSIONS

Multiple studies regarding the progression of cancer indicate that mutation, and/or, a flux in the copy number, of the mitochondrial genome content can support the early development of a cancer, until; the mutational load and/or the reduction-to-depletion of the copy number of the mitochondrial genome content induces the progression of the disease to an advanced phenotype.

GENERAL SIGNIFICANCE

Collectively, evidence has revealed that the human cell has incorporated the mitochondrial genome content into a cellular mechanism that, when pathologically actuated, can de(un)differentiate a cancer from the parental tissue of origin into an autonomous disease that disrupts the hierarchical structure-and-function of the human body. This article is part of a Special Issue entitled: Biochemistry of Mitochondria.

Skewed ratios between CD3(+) T cells and monocytes are associated with poor prognosis in patients with HBV-related acute-on-chronic liver failure

Tempering of the innate immune response by T lymphocytes has been demonstrated to play a critical role in protecting animals from inflammation-induced death; however, its role in humans remains unknown. Patients with HBV-related acute-on-chronic liver failure (ACLF) share a striking similarity to the inflammatory response in septic shock where a hyperactive innate response is observed. The present study attempted to characterize the features of CD3(+) T cells and monocytes and evaluate their clinical implications in 55 patients with HBV-related ACLF, 30 patients with chronic hepatitis B (CHB) and 30 healthy controls (HC). We found that the ratio between circulating CD3(+) T cells and monocytes (T/M) was decreased in ACLF patients, due to decreased CD3 counts and increased monocyte counts compared with CHB and HC subjects. We also found that the T/M ratios were decreased from the early to the intermediate stage and reached the lowest value at the late stage in ACLF patients. Analyses with clinical parameters revealed that T/M ratios were negatively correlated with the Model for End-Stage Liver Disease Score and direct bilirubin, and positively correlated with prothrombin activity. Moreover, increased T/M ratios were observed in patients with good prognosis, but not in patients with a poor outcome; and ACLF patients who received liver transplantation exhibited an increased T/M ratio. Importantly, we found that programmed death-1 receptor (PD-1) was drastically upregulated on both CD4(+) T and CD8(+) T cells in ACLF, which at least in part contributed to the T-cell loss in these patients. Mechanically, the in vitro co-culture assay revealed that both CD4(+) T and CD8(+) T cells, as well as regulatory T cells, could inhibit TNF-α secretion by monocytes. In addition, the TNF-α levels in ACLF serum were negatively correlated with T/M ratios. In conclusion, our study identified the novel potential role of T/M ratio in predicting disease progression and provided novel evidences for further studies of the immunopathogenesis in ACLF.

Expression of Bcl-2 and Bax in hepatocytes in nonalcoholic fatty liver disease

AIM: To investigate the role of apoptosis-regulated proteins Bcl-2 and Bax in the progression of nonalcoholic fatty liver disease (NAFLD) in rats.

METHODS: An experimental rat model of NAFLD was established by feeding rats a fat-rich diet (NAFLD group). Control animals were fed a standard diet (control group). Hepatic steatosis, inflammation and fibrosis were graded by routine HE staining of liver sections. The expression levels of Bcl-2 and Bax proteins in the liver were determined by Western blot.

RESULTS: The NAFLD model rats exhibited mild steatosis at week 4, simple fatty liver at week 8, and severe steatohepatitis with fibrosis at week 12. Western blot analysis showed that hepatic expression of Bax protein in the NAFLD group was more pronounced from week 4, and continued to rise at weeks 8 and 12 when compared with the control group (0.61 ± 0.03, 0.78 ± 0.03 and 1.02 ± 0.03 vs 0.51 ± 0.03, respectively; all P < 0.01), while the expression of Bcl-2 decreased with the progression of fatty liver (0.39 ± 0.01, 0.28 ± 0.01 and 0.15 ± 0.01 vs 0.52 ± 0.01, respectively; all P < 0.01). Bcl-2/Bax ratio in the NAFLD group decreased in a time-dependent manner, particularly prominent at week 12.

CONCLUSION: NAFLD may cause increased hepatic expression of Bax but decreased expression of Bcl-2, and the decrease in Bcl-2/Bax ratio may accelerate hepatocyte apoptosis.

Vitamin E analogues as mitochondria-targeting compounds: from the bench to the bedside?

Despite considerable effort focusing on designing and finding efficient anti-cancer drugs over the last decade, little progress has been achieved, in particular in case of highly recalcitrant malignancies. Also, since there is a trend suggesting that deaths from cancers may be more frequent than from cardiovascular diseases, it is important to look for novel efficient and selective therapeutic approaches to gradually start winning the battle with cancer. Redox-silent vitamin E analogues, epitomised by alpha-tocopheryl succinate, give some hope in the quest for drugs with such properties. Thus far, these agents have been successfully tested in experimental animals with different types of cancer, showing high efficacy against malignancies including HER2-positive breast carcinomas or malignant mesotheliomas. Further research will provide additional, necessary data to launch clinical trials, possibly in near future, translating into development of innovative anti-cancer drugs acting by targeting mitochondria selectively in cancer cells.

Constitutive activation of AKT pathway inhibits TNF-induced apoptosis in mitochondrial DNA-deficient human myelogenous leukemia ML-1a

TNF plus protein synthesis inhibitor cycloheximide-induced apoptosis in human myelogenous leukemia ML-1a but not in C19, respiration minus mitochondrial DNA-deficient C19 cells, derived from ML-1a. To investigate how mitochondrial DNA depletion inhibits apoptosis, we investigated AKT. Both AKT and its phosphorylated form were observed only in C19, indicating that depletion of mtDNA increased protein and the active form of AKT. Treatment of C19 with LY294002, which inhibits PI-3 kinase and inhibits AKT, significantly increased apoptosis induction by TNF plus cycloheximide and eliminated phosphorylation of AKT. These results indicate that AKT activation was induced by the depletion of mtDNA and inhibited TNF-induced apoptosis.

Increased distributional variance of mitochondrial DNA content associated with prostate cancer cells as compared with normal prostate cells

BACKGROUND

Mitochondria are key organelles for apoptosis, and mitochondrial DNA (mtDNA) content can regulate cancer progression. Increases in mtDNA mutations and deletions have been reported in cancer; however, a detailed investigation of mtDNA content in cancer cells has not yet been conducted.

METHODS

Quantitative real-time PCR and improved extraction method were established to investigate the mtDNA content in a single prostate cell.

RESULTS

The heterogeneity of mtDNA content was demonstrated between the clones of prostate cancer cell line LNCaP and individual cells in each clone. To investigate whether large distributional variance of mtDNA content is associated with cancer initiation and/or progression, we first compared PZ-HPV-7, an HPV-transformed normal prostate epithelial cell line, with CA-HPV-10, transformed from prostate cancer cells derived from the same donor. We found an enhanced distributional variance of mtDNA content in CA-HPV-10. Then, we investigated mtDNA content in individual cells in laser microdisssected cancer and adjacent normal cells from prostate cancer tissue specimens using quantitative real-time PCR method. Results showed that the mtDNA content per cell follows a higher skewed distribution in cancer cells as compared in normal cells. We also observed that mtDNA content was increased in seven of nine (78%) of prostate cancers compared to normal prostate tissue.

CONCLUSIONS

These results indicate that prostate carcinogenesis may involve dysregulation of mtDNA content.

Induction of acquired resistance to antiestrogen by reversible mitochondrial DNA depletion in breast cancer cell line

Although the net benefits of tamoxifen in adjuvant breast cancer therapy have been proven, the recurrence of the cancer in an aggressive and hormone independent form has been highly problematic. We previously demonstrated the important role mitochondrial DNA (mtDNA) plays in hormone-independence in prostate cancer. Here, the role of mtDNA in breast cancer progression was investigated. We established hydroxytamoxifen (4-OHT) resistant HTRMCF by growing MCF-7, human breast adenocarcinoma cells, in the presence of 4-OHT. HTRMCF was cross-resistant to 4-OHT and ICI182,780 concurrent with the depletion of mtDNA. To further investigate the role of mtDNA depletion, MCF-7 was depleted of mtDNA by treatment with ethidium bromide. MCF Rho 0 was resistant to both 4-OHT and ICI182,780. Furthermore, cybrid (MCFcyb) prepared by fusion MCF Rho 0 with platelet to transfer mtDNA showed susceptibility to antiestrogen. Surprisingly, after withdrawal of 4-OHT for 8 weeks, HTRMCF and their clones became susceptible to both drugs concurrent with a recovery of mtDNA. Herein, our results substantiated the first evidence that the depletion of mtDNA induced by hormone therapy triggers a shift to acquired resistance to hormone therapy in breast cancer. In addition, we showed that mtDNA depletion can be reversed, rendering the cancer cells susceptible to antiestrogen. The fact that the hormone independent phenotype can be reversed should be a step toward more effective treatments for estrogen-responsive breast cancer.

Vitamin E analogues inhibit angiogenesis by selective induction of apoptosis in proliferating endothelial cells: the role of oxidative stress

"Mitocans" from the vitamin E group of selective anticancer drugs, alpha-tocopheryl succinate (alpha-TOS) and its ether analogue alpha-TEA, triggered apoptosis in proliferating but not arrested endothelial cells. Angiogenic endothelial cells exposed to the vitamin E analogues, unlike their arrested counterparts, readily accumulated reactive oxygen species (ROS) by interfering with the mitochondrial redox chain and activating the intrinsic apoptotic pathway. The vitamin E analogues inhibited angiogenesis in vitro as assessed using the "wound-healing" and "tube-forming" models. Endothelial cells deficient in mitochondrial DNA (mtDNA) were resistant to the vitamin E analogues, both in ROS accumulation and apoptosis induction, maintaining their angiogenic potential. alpha-TOS inhibited angiogenesis in a mouse cancer model, as documented by ultrasound imaging. We conclude that vitamin E analogues selectively kill angiogenic endothelial cells, suppressing tumor growth, which has intriguing clinical implications.

Mitochondria transmit apoptosis signalling in cardiomyocyte-like cells and isolated hearts exposed to experimental ischemia-reperfusion injury

Ischemia-reperfusion (I/R) is a condition leading to serious complications due to death of cardiac myocytes. We used the cardiomyocyte-like cell line H9c2 to study the mechanism underlying cell damage. Exposure of the cells to simulated I/R lead to their apoptosis. Over-expression of Bcl-2 and Bcl-x(L) protected the cells from apoptosis while over-expression of Bax sensitized them to programmed cell death induction. Mitochondria-targeted coenzyme Q (mitoQ) and superoxide dismutase both inhibited accumulation of reactive oxygen species (ROS) and apoptosis induction. Notably, mtDNA-deficient cells responded to I/R by decreased ROS generation and apoptosis. Using both in situ and in vivo approaches, it was found that apoptosis occurred during reperfusion following ischemia, and recovery was enhanced when hearts from mice were supplemented with mitoQ. In conclusion, I/R results in apoptosis in cultured cardiac myocytes and heart tissue largely via generation of mitochondria-derived superoxide, with ensuing apoptosis during the reperfusion phase.

Increased mitochondrial DNA induces acquired docetaxel resistance in head and neck cancer cells

Docetaxel is one of the most effective chemotherapeutic agents against cancer; nevertheless, some patients develop resistance. Unfortunately, their causes and mechanisms remain unknown. We created docetaxel-resistant DRHEp2 from human laryngeal cancer HEp2 and investigated the roles of mitochondrial DNA (mtDNA) and reactive oxygen species (ROS) on docetaxel resistance. DRHEp2 had greatly increased mtDNA content. Reduction of mtDNA content in DRHEp2 by ethidium bromide treatment reduced the resistance. These results indicate the possible roles of mtDNA-coded enzymes in mitochondrial respiratory chain (MRC) in resistant mechanisms. Oligomycin A, an Fo-ATPase inhibitor, eliminated docetaxel resistance in DRHEp2; in contrast, inhibitors of other MRC did not. RNA interference targeted to Fo-ATPase d-subunit restored docetaxel-induced cytotoxicity to DRHEp2. These results indicate the roles of Fo-ATPase for resistant mechanisms. Docetaxel induced ROS generation in HEp2 but not in DRHEp2 and antioxidant pyrrolidine dithiocarbamate eliminated docetaxel-induced cytotoxicity, suggesting roles of ROS in docetaxel-induced cell death. Furthermore, inhibition of Fo-ATPase by Oligomycin A induced docetaxel-mediated ROS generation in DRHEp2. Taken together, DRHEp2 acquired docetaxel resistance through increasing Fo-ATPase, which led to diminish docetaxel-induced ROS generation and subsequently inhibited cell death. In conclusion, mtDNA plays an important role in developing docetaxel resistance through the reduction of ROS generation by regulating Fo-ATPase.

Vitamin E analogues as a novel group of mitocans: anti-cancer agents that act by targeting mitochondria

Mitochondria have recently emerged as new and promising targets for cancer prevention and therapy. One of the reasons for this is that mitochondria are instrumental to many types of cell death and often lie downstream from the initial actions of anti-cancer drugs. Unlike the tumour suppressor gene encoding p53 that is notoriously prone to inactivating mutations but whose function is essential for induction of apoptosis by DNA-targeting agents (such as doxorubicin or 5-fluorouracil), mitochondria present targets that are not so compromised by genetic mutation and whose targeting overcomes problems with mutations of upstream targets such as p53. We have recently proposed a novel class of anti-cancer agents, mitocans that exert their anti-cancer activity by destabilising mitochondria, promoting the selective induction of apoptotic death in tumour cells. In this communication, we review recent findings on mitocans and propose a common basis for their mode of action in inducing apoptosis of cancer cells. We use as an example the analogues of vitamin E that are proving to be cancer cell-specific and may soon be developed into efficient anti-cancer drugs.

Regulation of mitochondrial DNA content and cancer

Enzymatic activities of the proteins encoded in nuclear genome are regulated by transcriptional, translational and post-transcriptional level. Enzymatic activities of proteins encoded in mitochondrial DNA (mtDNA) have been considered to be regulated by the same steps although detailed mechanisms might differ. However, dynamic change of the number of mtDNA, from some hundred to more than ten thousand, should be considered as another novel mechanism to regulate mtDNA-encoded proteins. Recently, we showed the connection of mtDNA depletion and deletion to cancer progression [Higuchi, M., Kudo, T., Suzuki, S., Evans, T.T., Sasaki, R., Wada, Y., Shirakawa, T., Sawyer, J.R., Gotoh, A., 2006. Mitochondrial DNA determines androgen dependence in prostate cancer cell lines. Oncogene 25, 1437-1445]. This review focuses and describes the possible connections of the mitochondrial DNA depletion and deletion to cancer.

Vitamin E analogs, a novel group of "mitocans," as anticancer agents: the importance of being redox-silent

The search for a selective and efficient anticancer agent for treating all neoplastic disease has yet to deliver a universally suitable compound(s). The majority of established anticancer drugs either are nonselective or lose their efficacy because of the constant mutational changes of malignant cells. Until recently, a largely neglected target for potential anticancer agents was the mitochondrion, showing a considerable promise for future clinical applications. Vitamin E (VE) analogs, epitomized by alpha-tocopheryl succinate, belong to the group of "mitocans" (mitochondrially targeted anticancer drugs). They are selective for malignant cells, cause destabilization of their mitochondria, and suppress cancer in preclinical models. This review focuses on our current understanding of VE analogs in the context of their proapoptotic/anticancer efficacy and suggests that their effect on mitochondria may be amplified by modulation of alternative pathways operating in parallel. We show here that the analogs of VE that cause apoptosis (which translates into their anticancer efficacy) generally do not possess antioxidant (redox) activity and are prototypical of the mitocan group of anticancer compounds. Therefore, by analogy to Oscar Wilde's play The Importance of Being Earnest, we use the motto in the title "the importance of being redox-silent" to emphasize an essentially novel paradigm for cancer therapy, in which redox-silence is a prerequisite property for most of the anticancer activities described in this communication.

The evolving role of leptin and adiponectin in chronic liver diseases

Leptin and adiponectin, the main metabolic products of adipose tissue, have been implicated in a wide spectrum of human diseases. Given the frequent presence of hepatic steatosis in several chronic liver diseases, there is currently increasing interest in the role of these adipokines in the development of hepatic steatosis and also in necroinflammation and fibrosis, mostly in patients with nonalcoholic fatty liver disease or chronic hepatitis C. According to experimental data, reduced adiponectin levels and increased leptin levels associated with leptin resistance, which are usually observed in obese patients with or without metabolic syndrome, may result in fat accumulation in the liver and in the enhancement of liver inflammation and mostly fibrogenesis. Increased leptin and decreased adiponectin serum levels have been detected initially in patients with nonalcoholic steatohepatitis and more recently in patients with chronic hepatitis C compared to healthy controls in most but not all studies, while the data on the associations between these adipokine levels and the severity of hepatic steatosis or fibrosis are still rather conflicting. However, several potential confounding parameters were not evaluated in all studies. Therefore, the associations between adipokines and liver histological lesions and their effects on liver cells should be evaluated further in prospective, carefully designed studies, including larger cohorts of patients with detailed assessment of metabolic and other potential confounding factors.

Vitamin E analogues as anticancer agents: lessons from studies with alpha-tocopheryl succinate

The new millennium has witnessed considerable decrease in a number of previously fatal pathologies, largely due to the advancement in molecular medicine and modern approaches to treatment. In spite of this success, neoplastic disease remains a serious problem due to several reasons. These include an exceedingly high variability of cancer cells even within the same type of tumour. Cancer cells, albeit of clonal origin, mutate so that they escape established treatments, resulting in the fatal outcome of current therapies. Moreover, there are types of cancer, such as mesotheliomas, that cannot be treated at present. A novel group of clinically interesting anticancer drugs has been a recent focus in the literature that hold substantial promise as selective anticancer drugs. These compounds, epitomised by alpha-tocopheryl succinate, comprise redox-silent analogues of vitamin E that have been shown to suppress several types of cancer in animal models, including breast, colon and lung cancer as well as mesotheliomas and melanomas, while being nontoxic to normal cells and tissues. It is now proven that the strong anticancer effect of vitamin E analogues stems from their propensity to induce selective apoptosis in malignant cells. The results point to the novel group of vitamin E analogues as promising agents applicable to different types of tumours.

Regulation of signal transduction through protein cysteine oxidation

The production of reactive oxygen species (ROS) accompanies many signaling events. Antioxidants and ROS scavenging enzymes in general have effects that indicate a critical role for ROS in downstream signaling, but a mechanistic understanding of the contribution of ROS as second messengers is incomplete. Here, the role of reactive oxygen species in cell signaling is discussed, emphasizing the ability of ROS to directly modify signaling proteins through thiol oxidation. Examples are provided of protein thiol modifications that control signal transduction effectors that include protein kinases, phosphatases, and transcription factors. Whereas the effects of cysteine oxidation on these proteins in experimental systems is clear, it has proven more difficult to demonstrate these modifications in response to physiologic stimuli. Improved detection methods for analysis of thiol modification will be essential to define these regulatory mechanisms. Bridging these two areas of research could reveal new regulatory mechanisms in signaling pathways, and identify new therapeutic targets.

The superoxide dismutase inhibitor diethyldithiocarbamate has antagonistic effects on apoptosis by triggering both cytochrome c release and caspase inhibition

Tumor necrosis factor-alpha (TNF-alpha) and etoposide both trigger a large and rapid production of reactive oxygen species (ROS) in HeLa cells. This occurs before translocations of the proapoptotic Bax and cytochrome c proteins, the loss of mitochondrial membrane potential (DeltaPsim), and apoptosis. We have used diethyldithiocarbamate (DDC), a well-known inhibitor of Cu, Zn superoxide dismutase to study the role of ROS in this system. We report that DDC strongly inhibits caspase activation, loss of DeltaPsim, and cell death induced by TNF-alpha or etoposide. Surprisingly, DDC does not inhibit Bax and cytochrome c translocations. On the contrary, we have observed that DDC can trigger the translocations of these proteins by itself, without altering DeltaPsim. Here, we report that DDC has at least two antagonistic apoptosis regulation functions. First, DDC triggers ROS-dependent Bax and cytochrome c translocations, which are potentially proapoptotic, and second, DDC inhibits caspase activation and activity, loss of DeltaPsim, and cell death, in a ROS-independent manner. Our results suggest an interesting model in which ROS-dependent Bax and cytochrome c translocations can be studied without interference from later apoptotic events.

Mitochondrial DNA determines androgen dependence in prostate cancer cell lines

Prostate cancer progresses from an androgen-dependent to androgen-independent stage after androgen ablation therapy. Mitochondrial DNA plays a role in cell death and metastatic competence. Further, heteroplasmic large-deletion mitochondrial DNA is very common in prostate cancer. To investigate the role of mitochondrial DNA in androgen dependence of prostate cancers, we tested the changes of normal and deleted mitochondrial DNA in accordance with the progression of prostate cancer. We demonstrated that the androgen-independent cell line C4-2, established by inoculation of the androgen-dependent LNCaP cell line into castrated mice, has a greatly reduced amount of normal mitochondrial DNA and an accumulation of large-deletion DNA. Strikingly, the depletion of mitochondrial DNA from androgen-dependent LNCaP resulted in a loss of androgen dependence. Reconstitution of normal mitochondrial DNA to the mitochondrial DNA-depleted clone restored androgen dependence. These results indicate that mitochondrial DNA determines androgen dependence of prostate cancer cell lines. Further, mitochondrial DNA-deficient cells formed tumors in castrated athymic mice, whereas LNCaP did not. The accumulation of large deletion and depletion of mitochondrial DNA may thus play a role in the development of androgen independence, leading to progression of prostate cancers.

Mitochondrial reactive oxygen species regulate the temporal activation of nuclear factor kappaB to modulate tumour necrosis factor-induced apoptosis: evidence from mitochondria-targeted antioxidants

ROS (reactive oxygen species) from mitochondrial and non-mitochondrial sources have been implicated in TNFalpha (tumour necrosis factor alpha)-mediated signalling. In the present study, a new class of specific mitochondria-targeted antioxidants were used to explore directly the role of mitochondrial ROS in TNF-induced apoptosis. MitoVit E {[2-(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)ethyl]triphenylphosphonium bromide} (vitamin E attached to a lipophilic cation that facilitates accumulation of the antioxidant in the mitochondrial matrix) enhanced TNF-induced apoptosis of U937 cells. In time course analyses, cleavage and activation of caspase 8 in response to TNF were not affected by MitoVit E, whereas the activation of caspase 3 was significantly increased. Furthermore, there was an increased cleavage of the proapoptotic Bcl-2 family member Bid and an increased release of cytochrome c from mitochondria, in cells treated with TNF in the presence of MitoVit E. We considered several mechanisms by which MitoVit E might accelerate TNF-induced apoptosis including mitochondrial integrity (ATP/ADP levels and permeability transition), alterations in calcium homoeostasis and transcription factor activation. Of these, only the transcription factor NF-kappaB (nuclear factor kappaB) was implicated. TNF caused maximal nuclear translocation of NF-kappaB within 15 min, compared with 1 h in cells pretreated with MitoVit E. Thus the accumulation of an antioxidant within the mitochondrial matrix enhances TNF-induced apoptosis by decreasing or delaying the expression of the protective antiapoptotic proteins. These results demonstrate that mitochondrial ROS production is a physiologically relevant component of the TNF signal-transduction pathway during apoptosis, and reveal a novel functional role for mitochondrial ROS as a temporal regulator of NF-kappaB activation and NF-kappaB-dependent antiapoptotic signalling.

Mitochondria: A novel target for the chemoprevention of cancer

The mitochondria have emerged as a novel target for anticancer chemotherapy. This tenet is based on the observations that several conventional and experimental chemotherapeutic agents promote the permeabilization of mitochondrial membranes in cancerous cells to initiate the release of apoptogenic mitochondrial proteins. This ability to engage mitochondrial-mediated apoptosis directly using chemotherapy may be responsible for overcoming aberrant apoptosis regulatory mechanisms commonly encountered in cancerous cells. Interestingly, several putative cancer chemopreventive agents also possess the ability to trigger apoptosis in transformed, premalignant, or malignant cells in vitro via mitochondrial membrane permeabilization. This process may occur through the regulation of Bcl-2 family members, or by the induction of the mitochondrial permeability transition. Thus, by exploiting endogenous mitochondrial-mediated apoptosis-inducing mechanisms, certain chemopreventive agents may be able to block the progression of premalignant cells to malignant cells or the dissemination of malignant cells to distant organ sites as means of modulating carcinogenesis in vivo. This review will examine cancer chemoprevention with respect to apoptosis, carcinogenesis, and the proapoptotic activity of various chemopreventive agents observed in vitro. In doing so, I will construct a paradigm supporting the notion that the mitochondria are a novel target for the chemoprevention of cancer.

High rate of seropositivity of Chlamydia pneumoniae IgA in male patients with nonalcoholic steatohepatitis

The aim of this study was to investigate if there was any relationship between nonalcoholic steatohepatitis and the rate of Chlamydia pneumoniae seropositivity in a male population. Fifteen men with nonalcoholic steatohepatitis and 20 healthy men were enrolled in the study. The seropositivity rate of Chlamydia pneumoniae immunoglobulin A in the nonalcoholic steatohepatitis and control groups was 53.3 and 5%, respectively. The rate of Chlamydia pneumoniae immunoglobulin A positivity was significantly higher in the nonalcoholic steatohepatitis group than the controls (P = 0.002), while such a difference did not occur for Chlamydia pneumoniae immunoglobulin G positivity (P > 0.05). There is an association between nonalcoholic steatohepatitis and persistent Chlamydia pneumoniae infection as a probable causative or triggering agent. These findings suggest that further studies are necessary to clarify this association.

Redox regulation of apoptosis by members of the TNF superfamily

Tumor necrosis factor (TNF), fibroblast-associated cell surface (Fas) ligand, and TNF-related apoptosisinducing ligand (TRAIL), all members of the TNF superfamily, are arguably the most potent inducers of cell death. These cytokines induce cell death through sequential recruitment by the death receptors TNFR1- associated death domain protein (TRADD), Fas-associated death domain protein (FADD), FADD-like interleukin-1beta-converting enzyme (FLICE), and downstream caspases. Increasing evidence indicates that mitochondria play a critical role in cytokine receptor-mediated apoptosis. There is also now ample evidence that apoptosis induced by TNF and its family members is mediated through the production of reactive oxygen intermediates (also known as reactive oxygen species). Here we review the evidence linking reactive oxygen intermediates to cytokine-induced cell death mediated by TNF-alpha/beta, Fas, TRAIL, TNF-like weak inducer of apoptosis (TWEAK), and vascular endothelial cell growth inhibitor (VEGI).

Role of mitochondrial phospholipid hydroperoxide glutathione peroxidase (PHGPx) as an antiapoptotic factor

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a unique antioxidant enzyme that markedly reduces lipid hydroperoxide generated in biomembranes. Overexpression of mitochondrial PHGPx potentially suppresses the release of cytochrome c (cyt. c) from mitochondria and apoptosis. The hydroperoxide level in mitochondria was elevated in 2-deoxyglucose (2DG)-induced apoptosis, but not in apoptosis-resistant cells in which mitochondrial PHGPx was overexpressed. From studies of the overexpression of PHGPx, the generation of hydrogen peroxide and lipid hydroperoxide in mitochondria might be important triggers of apoptosis. In particular lipid hydroperoxide could be involved in the initiation of cyt. c liberation from mitochondria in 2DG-induced apoptosis since lipid hydroperoxide is a primary substrate for PHGPx. The release of cyt. c from mitochondria is an important proapoptotic signal in the mitochondrial death pathway. Several reports demonstrated the reactive oxgen species could be involved in cyt. c liberation, although its mechanism is still unknown. Cardiolipin (CL), which exclusively locates in the innermembrane of mitochondria, shows strong affinity for cyt. c is required for the adenine nucleotide translocator (ANT) that controls the opening and closing of the permeability transition pore. Association of cyt. c with CL is lost upon peroxidation. CL hydroperoxide (CLOOH), in contrast to CL, does not bind to cyt. c. Furthermore, CLOOH can open the permeability transion pore by the inactivation of ANT. These previous results suggest that mitochondrial PHGPx inhibits the release of cyt. c from mitochondria by the scavenging CLOOH and could prevent apoptosis.

Induction of apoptosis by TNF receptor 2 in a T-cell hybridoma is FADD dependent and blocked by caspase-8 inhibitors

Previously we reported that both human TNFR1 and TNFR2 mediate TNF-induced apoptosis in the transfected rat/mouse T cell hybridoma PC60. We show here that TNFR2-mediated apoptosis in PVC60 cells can be blocked by the broad-spectrum caspase inhibitor zVAD-fmk, the caspase-8 inhibitor zIETD-fmk and by CrmA, a viral inhibitor of caspase-1 and caspase-8. This suggests an involvement of caspase-8 in TNFR2-mediated apoptosis. The upstream adaptor of caspase-8, FADD, is also involved in TNFR2-induced cell death, since transient overexpression of a dominant negative deletion mutant of FADD inhibited apoptosis induced by this receptor. TNFR2-induced apoptosis is independent of endogenous TNF or other death-inducing ligand production and subsequent activation of TNFR1 or other death receptors. Furthermore, TNFR2 stimulation does not enhance sensitivity for a subsequent TNFR1-induced apoptotic signal, as has been reported for Jurkat cells. TRAF2 downregulation, which has been proposed as the mechanism by which TNFR2 enhances TNFR1 signaling, was observed in PC60 cells, but the TNRF1 signal was not modulated. These data confirm the capacity of TNFR2 to generate an apoptotic cell death signal independent of TNFR1.

Vitamin E analogs trigger apoptosis in HER2/erbB2-overexpressing breast cancer cells by signaling via the mitochondrial pathway

Alpha-tocopheryl succinate (alpha-TOS) is a redox-silent vitamin E (VE) analog with high pro-apoptotic and anti-neoplastic activity. Here we investigated whether alpha-TOS and several novel VE analogs kill breast cancer cells over-expressing the anti-apoptotic receptor protein HER2/erbB2. The agents induced apoptosis at comparable levels in both erbB2-low and -high cells. Generation of reactive oxygen species (ROS) preceded mitochondrial destabilization and execution of apoptosis, as evidenced by the anti-apoptotic effects of exogenous superoxide dismutase and mitochondrially targeted coenzyme Q. Dissipation of DeltaPsi(m) was followed by cytochrome c and Smac/Diablo re-localization and caspase-dependent cleavage of death substrate. A resistance to apoptosis for the corresponding rho(0) counterparts confirmed a critical dependency for mitochondria during the induction of apoptosis in breast cancer cells mediated by VE analogs and linked apoptosis to generation of radicals as judged by the delayed accumulation of ROS in the cybrid cell types. We conclude that alpha-TOS causes efficient apoptosis in breast cancer cells independent of their erbB2 status. Since erbB2 is frequently over-expressed in breast cancers and renders the neoplastic disease resistant to established treatment, our findings are of clinical interest.

Pathophysiological effects of albumin dialysis in acute-on-chronic liver failure: a randomized controlled study

The pathophysiological basis of acute-on-chronic liver failure (ACLF) is unclear but systemic inflammatory response is thought to be important. In patients with ACLF, the molecular adsorbents recirculating system (MARS) improves individual organ function, but the effect of MARS on the proposed mediators of systemic inflammatory response is unclear. The present study was designed to determine the effect of MARS on the cytokine profile, oxidative stress, nitric oxide, and ammonia. A total of 18 patients with alcohol-related ACLF due to inflammation-related precipitants were randomized to receive standard medical therapy (SMT) alone, or with MARS therapy over 7 days. Plasma cytokines, malondialdehyde (MDA), free radical production, nitrate / nitrite (NOx), and ammonia were measured. Encephalopathy improved significantly with MARS (P < .01), but not with SMT. Mean arterial pressure and renal function remained unchanged. No significant change of plasma cytokines and ammonia levels were observed in either group. Plasma MDA levels did not change either. There was a fall in NOx (P < .05) with MARS, but not with SMT. In conclusion, in inflammation-related ACLF patients, albumin dialysis using MARS results in improvement of encephalopathy, independent of changes of ammonia or cytokines, without improving blood pressure or renal function. These results should temper the liberal use of MARS until further data is available.

Inhibition of tumor necrosis factor-induced apoptosis in transgenic mouse liver expressing creatine kinase

BACKGROUND

The mitochondrion acts as a pivotal decision center in many types of apoptotic responses. To clarify the effects of the enhanced mitochondrial function on tumor necrosis factoralpha (TNFalpha)-induced apoptosis, we studied hepatic injuries in transgenic mice whose livers express creatine kinase (CK).

METHODS

Mice fed a diet containing 10% creatine, came to accumulate phosphocreatine and to enhance hepatic ATP levels and mitochondrial oxidative phosphorylation activities. TNFalpha-mediated hepatic apoptosis in normally fed and Cr-feeding CK transgenic mice were assessed.

RESULTS

TNFalpha and actinomycin D cause severe liver failure in normally fed transgenic mice, and in the wild-type mice. In contrast, no significant elevations in transaminase levels after injection were observed in Cr feeding transgenic mice. The disruption of the mitochondrial transmembrane potential at 2 h after TNFalpha injection, prior to ATP depletion, activation of caspase 3 like protease, and DNA fragmentation at 4-6 h after injection, were observed in normally fed transgenic mice. These were fully suppressed in Cr feeding transgenic mice. However, anti-Fas antibody-induced apoptosis was not inhibited in both groups.

CONCLUSIONS

The results indicate that TNFalpha-induced apoptosis was inhibited in CK transgenic mice livers by maintaining mitochondrial function.

Mitochondrial disease: mutations and mechanisms

The mitochondrial diseases encompass a diverse group of disorders that can exhibit various combinations of clinical features. Defects in mitochondrial DNA (mtDNA) have been associated with these diseases, and studies have been able to assign biochemical defects. Deficiencies in mitochondrial oxidative phosphorylation appear to be the main pathogenic factors, although recent studies suggest that other mechanisms are involved. Reactive oxygen species (ROS) generation has been implicated in a wide variety of neurodegenerative diseases, and mitochondrial ROS generation may be an important factor in mitochondrial disease pathogenesis. Altered apoptotic signaling as a consequence of defective mitochondrial function has also been observed in both in vitro and in vivo disease models. Our current understanding of the contribution of these various mechanisms to mitochondrial disease pathophysiology will be discussed.

Mitochondrial disease: mutations and mechanisms

The mitochondrial diseases encompass a diverse group of disorders that can exhibit various combinations of clinical features. Defects in mitochondrial DNA (mtDNA) have been associated with these diseases, and studies have been able to assign biochemical defects. Deficiencies in mitochondrial oxidative phosphorylation appear to be the main pathogenic factors, although recent studies suggest that other mechanisms are involved. Reactive oxygen species (ROS) generation has been implicated in a wide variety of neurodegenerative diseases, and mitochondrial ROS generation may be an important factor in mitochondrial disease pathogenesis. Altered apoptotic signaling as a consequence of defective mitochondrial function has also been observed in both in vitro and in vivo disease models. Our current understanding of the contribution of these various mechanisms to mitochondrial disease pathophysiology will be discussed.