Reactive oxygen species: role in the development of cancer and various chronic conditions

RelB regulates manganese superoxide dismutase gene and resistance to ionizing radiation of prostate cancer cells

Radiation therapy is in the front line for treatment of localized prostate cancer. However, a significant percentage of patients have radiation-resistant disease. The NF-kappaB pathway is an important factor for radiation resistance, and the classical (canonical) pathway is thought to confer protection of prostate cancer cells from ionizing radiation. Recently, the alternative (non-canonical) pathway, which is involved in prostate cancer aggressiveness, has also been shown to be important for radiation resistance in prostate cancer. The alternative NF-kappaB pathway component RelB protects prostate cancer cells from the detrimental effects of ionizing radiation, in part, by stimulating expression of the mitochondria-localized antioxidant enzyme manganese superoxide dismutase (MnSOD). Blocking RelB activation suppresses MnSOD expression and sensitizes prostate cancer cells to radiation. These results suggest that RelB-mediated modulation of the antioxidant capacity of prostate cancer cells is an important mechanism of radiation resistance. Therefore, targeting RelB activation may prove to be a valuable weapon in the oncologist's arsenal to defeat aggressive and radiation-resistant prostate cancer.

Manganese superoxide dismutase vs. p53: regulation of mitochondrial ROS

Coordination of mitochondrial and nuclear activities is vital for cellular homeostasis, and many signaling molecules and transcription factors are regulated by mitochondria-derived reactive oxygen species (ROS) to carry out this interorganellar communication. The tumor suppressor p53 regulates myriad cellular functions through transcription-dependent and -independent mechanisms at both the nucleus and mitochondria. p53 affect mitochondrial ROS production, in part, by regulating the expression of the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD). Recent evidence suggests mitochondrial regulation of p53 activity through mechanisms that affect ROS production, and a breakdown of communication amongst mitochondria, p53, and the nucleus can have broad implications in disease development.

Role of oxidative stress in stem, cancer, and cancer stem cells

The term ‘‘oxidative stress” refers to a cell’s state characterized by excessive production of reactive oxygen species (ROS) and oxidative stress is one of the most important regulatory mechanisms for stem, cancer, and cancer stem cells. The concept of cancer stem cells arose from observations of similarities between the self-renewal mechanism of stem cells and that of cancer stem cells, but compared to normal stem cells, they are believed to have no control over the cell number. ROS have been implicated in diverse processes in various cancers, and generally the increase of ROS in cancer cells is known to play an important role in the initiation and progression of cancer. Additionally, ROS have been considered as the most significant mutagens in stem cells; when elevated, blocking self-renewal and at the same time, serving as a signal stimulating stem cell differentiation. Several signaling pathways enhanced by oxidative stress are suggested to have important roles in tumorigenesis of cancer or cancer stem cells and the self-renewal ability of stem or cancer stem cells. It is now well established that mitochondria play a prominent role in apoptosis and increasing evidence supports that apoptosis and autophagy are physiological phenomena closely linked with oxidative stress. This review elucidates the effect and the mechanism of the oxidative stress on the regulation of stem, cancer, and cancer stem cells and focuses on the cell signaling cascades stimulated by oxidative stress and their mechanism in cancer stem cell formation, as very little is known about the redox status in cancer stem cells. Moreover, we explain the link between ROS and both of apoptosis and autophagy and the impact on cancer development and treatment. Better understanding of this intricate link may shed light on mechanisms that lead to better modes of cancer treatment.

Moving toward paradigm-shifting research in health disparities through translational, transformational, and transdisciplinary approaches

Translational, transdisciplinary, and transformational research stands to become a paradigm-shifting mantra for research in health disparities. A windfall of research discoveries using these 3 approaches has increased our understanding of the health disparities in racial, ethnic, and low socioeconomic status groups. These distinct but related research spheres possess unique environments, which, when integrated, can lead to innovation in health disparities science. In this article, we review these approaches and propose integrating them to advance health disparities research through a change in philosophical position and an increased emphasis on community engagement. We argue that a balanced combination of these research approaches is needed to inform evidence-based practice, social action, and effective policy change to improve health in disparity communities.

Improved survival in patients with end-stage cancer treated with coenzyme Q(10) and other antioxidants: a pilot study

This pilot study evaluated the survival of patients with end-stage cancer who received supplements of coenzyme Q(10) and a mixture of other antioxidants (e.g. vitamin C, selenium, folic acid and beta-carotene). During a period of 9 years, 41 patients who had end-stage cancer were included. Forty patients were followed until death and one patient was lost to follow-up and presumed dead. Primary cancers were located in the breast, brain, lungs, kidneys, pancreas, oesophagus, stomach, colon, prostate, ovaries and skin. The median predicted survival time was calculated from Kaplan-Meier curves for each patient at inclusion. Median predicted survival was 12 months (range 3 - 29 months), whereas median actual survival was 17 months (1 - 120 months), which is > 40% longer than the median predicted survival. Mean actual survival was 28.8 months versus 11.9 months for mean predicted survival. Ten patients (24%) survived for less time than predicted, whereas 31 (76%) survived for longer. Treatments were very well tolerated with few adverse effects.

Reduced fluoresceinamine as a fluorescent sensor for nitric oxide

A new fluorescent sensor for nitric oxide (NO) is presented that is based on its reaction with a non fluorescent substance, reduced fluoresceinamine, producing the highly fluorescent fluoresceinamine. Using a portable homemade stabilized light source consisting of 450 nm LED and fiber optics to guide the light, the sensor responds linearly within seconds in the NO concentration range between about 10–750 μM with a limit of detection (LOD) of about 1 μM. The system generated precise intensity readings, with a relative standard deviation of less than 1%. The suitability of the sensor was assessed by monitoring the NO generated by either the nitrous acid decomposition reaction or from a NO-releasing compound. Using relatively high incubation times, the sensor also responds quantitatively to hydrogen peroxide and potassium superoxide, however, using transient signal measurements results in no interfering species.

Lipophilic aroylhydrazone chelator HNTMB and its multiple effects on ovarian cancer cells

BACKGROUND

Metal chelators have gained much attention as potential anti-cancer agents. However, the effects of chelators are often linked solely to their capacity to bind iron while the potential complexation of other trace metals has not been fully investigated. In present study, we evaluated the effects of various lipophilic aroylhydrazone chelators (AHC), including novel compound HNTMB, on various ovarian cancer cell lines (SKOV-3, OVCAR-3, NUTU-19).

METHODS

Cell viability was analyzed via MTS cytotoxicity assays and NCI60 cancer cell growth screens. Apoptotic events were monitored via Western Blot analysis, fluorescence microscopy and TUNEL assay. FACS analysis was carried out to study Cell Cycle regulation and detection of intracellular Reactive Oxygen Species (ROS) RESULTS: HNTMB displayed high cytotoxicity (IC50 200-400 nM) compared to previously developed AHC (oVtBBH, HNtBBH, StBBH/206, HNTh2H/315, HNI/311; IC50 0.8-6 microM) or cancer drug Deferoxamine, a hexadentate iron-chelator (IC50 12-25 microM). In a NCI60 cancer cell line screen HNTMB exhibited growth inhibitory effects with remarkable differences in specificity depending on the cell line studied (GI50 10 nM-2.4 microM). In SKOV-3 ovarian cancer cells HNTMB treatment led to chromatin fragmentation and activation of the extrinsic and intrinsic pathways of apoptosis with specific down-regulation of Bcl-2. HNTMB caused delayed cell cycle progression of SKOV-3 through G2/M phase arrest. HNTMB can chelate iron and copper of different oxidation states. Complexation with copper lead to high cytotoxicity via generation of reactive oxygen species (ROS) while treatment with iron complexes of the drug caused neither cytotoxicity nor increased ROS levels.

CONCLUSIONS

The present report suggests that both, non-complexed HNTMB as a chelator of intracellular trace-metals as well as a cytotoxic HNTMB/copper complex may be developed as potential therapeutic drugs in the treatment of ovarian and other solid tumors.

Perchlorotrityl radical-fluorophore conjugates as dual fluorescence and EPR probes for superoxide radical anion

Perchlorotrityl radicals, mono-substituted with a fluorophore using an amide linker of varying chain length, were synthesized and characterized. Electron paramagnetic resonance (EPR) spectroscopic study indicated free-electron coupling with the aromatic hydrogen nuclei and long-range coupling with the methylene hydrogens of the linker group. Reactivity of the fluorophore-conjugated trityls with superoxide radical anion showed quenching of EPR signal and enhancement of fluorescence emission spectrum. This work presents the first example of a perchlorotrityl-fluorophore conjugate that can potentially be employed as a dual probe for the detection of superoxide under oxidative stress-mediated conditions in biological systems.

Biochemical and cellular toxicology of peroxynitrite: implications in cell death and autoimmune phenomenon

Reactive nitrogen species include nitric oxide (.NO), peroxynitrite (ONOO(-)) and nitrogen dioxide radical (NO2*). Peroxynitrite is a reactive oxidant, produced from nitric oxide (*NO) and superoxide anion (O(2*-), that reacts with a variety of biological macromolecules. It is produced in the body in response to physiological stress and environmental toxins. It is a potent trigger of oxidative protein and DNA damage-including DNA strand breakage and base modification. It activates the nuclear enzyme poly-ADP ribose polymerase (PARP) resulting in energy depletion and apoptosis/necrosis of cells. Peroxynitrite generation is a crucial pathological mechanism in stroke, diabetes, inflammation, neurodegeneration, cancer, etc. Peroxynitrite modified DNA may also lead to the generation of autoantibodies in various autoimmune disorders such as systemic lupus erythematosus (SLE). In chronic inflammatory diseases, peroxynitrite formed by phagocytic cells may cause damage to DNA, generating neoepitopes leading to the production of autoantibodies. Hence, understanding the pathophysiology of peroxynitrite could lead to important therapeutic interventions.

Oxidative stress and autophagy in cardiac disease, neurological disorders, aging and cancer

Autophagy is a catalytic process of the bulk degradation of long-lived cellular components, ultimately resulting in lysosomal digestion within mature cytoplasmic compartments known as autophagolysosomes. Autophagy serves many functions in the cell, including maintaining cellular homeostasis, a means of cell survival during stress (e.g., nutrient deprivation or starvation) or conversely as a mechanism for cell death. Increased reactive oxygen species (ROS) production and the resulting oxidative cell stress that occurs in many disease states has been shown to induce autophagy. The following review focuses on the roles that autophagy plays in response to the ROS generated in several diseases.

The physicochemistry and toxicology of CFA particles

The term "technogenic particles" is used to describe airborne particulate matter (PM) produced during industrial processes. The most common of these is "fly ash" produced during combustion of solid and liquid fossil fuels. Coal fly ash is derived from the mineral and metal contaminants within coal in which particles (1) are distinctly spherical in shape, (2) are composed of 60-90% glass, and (3) often contain a range of contaminant metals. In addition, particles may contain recrystallized minerals, mainly quartz, mullite, and hematite; both quartz and mullite are recognized respiratory hazards. Fly ash particles from both UK and Chinese coal-burning power stations were characterized by field emission-scanning electron microscopy (morphology and size), x-ray diffraction (crystallinity and minerals), and inductively coupled plasma-mass spectroscopy (elemental composition). PM(10) samples were separated from bulk fly ash by a dry dust separator system. The plasmid scission assay (PSA) was used to measure damage produced by fly ash to plasmid bacteriophage PhiX174 RF DNA. The supercoiled DNA was either damaged or severely damaged by reactive oxygen species (ROS) generated by the fly ash at different concentrations. Geochemical analyses confirmed that the fly ash particles are predominantly glass, with a minor component of the minerals quartz, hematite, and mullite. Fly ash particles also contained a range of metals contaminants; however, these were mostly bound into the glass with only a small proportion potentially bioaccessible. PSA data showed that fly ash exhibited significant oxidative capacity when compared to negative control (MB H(2)O), indicating that ROS are likely to be the driving force underlying fly ash bioreactivity.

Examination of polymorphic glutathione S-transferase (GST) genes, tobacco smoking and prostate cancer risk among men of African descent: a case-control study

BACKGROUND

Polymorphisms in glutathione S-transferase (GST) genes may influence response to oxidative stress and modify prostate cancer (PCA) susceptibility. These enzymes generally detoxify endogenous and exogenous agents, but also participate in the activation and inactivation of oxidative metabolites that may contribute to PCA development. Genetic variations within selected GST genes may influence PCA risk following exposure to carcinogen compounds found in cigarette smoke and decreased the ability to detoxify them. Thus, we evaluated the effects of polymorphic GSTs (M1, T1, and P1) alone and combined with cigarette smoking on PCA susceptibility.

METHODS

In order to evaluate the effects of GST polymorphisms in relation to PCA risk, we used TaqMan allelic discrimination assays along with a multi-faceted statistical strategy involving conventional and advanced statistical methodologies (e.g., Multifactor Dimensionality Reduction and Interaction Graphs). Genetic profiles collected from 873 men of African-descent (208 cases and 665 controls) were utilized to systematically evaluate the single and joint modifying effects of GSTM1 and GSTT1 gene deletions, GSTP1 105 Val and cigarette smoking on PCA risk.

RESULTS

We observed a moderately significant association between risk among men possessing at least one variant GSTP1 105 Val allele (OR = 1.56; 95%CI = 0.95-2.58; p = 0.049), which was confirmed by MDR permutation testing (p = 0.001). We did not observe any significant single gene effects among GSTM1 (OR = 1.08; 95%CI = 0.65-1.82; p = 0.718) and GSTT1 (OR = 1.15; 95%CI = 0.66-2.02; p = 0.622) on PCA risk among all subjects. Although the GSTM1-GSTP1 pairwise combination was selected as the best two factor LR and MDR models (p = 0.01), assessment of the hierarchical entropy graph suggested that the observed synergistic effect was primarily driven by the GSTP1 Val marker. Notably, the GSTM1-GSTP1 axis did not provide additional information gain when compared to either loci alone based on a hierarchical entropy algorithm and graph. Smoking status did not significantly modify the relationship between the GST SNPs and PCA.

CONCLUSION

A moderately significant association was observed between PCA risk and men possessing at least one variant GSTP1 105 Val allele (p = 0.049) among men of African descent. We also observed a 2.1-fold increase in PCA risk associated with men possessing the GSTP1 (Val/Val) and GSTM1 (*1/*1 + *1/*0) alleles. MDR analysis validated these findings; detecting GSTP1 105 Val (p = 0.001) as the best single factor for predicting PCA risk. Our findings emphasize the importance of utilizing a combination of traditional and advanced statistical tools to identify and validate single gene and multi-locus interactions in relation to cancer susceptibility.

Regioselective synthesis of thiadiazolo[3,2-a]benzimidazole-5,8-diones

Regioselective synthesis of the novel 7-hydroxy-2-(alkylsulfanyl)-6-undecyl[1,3,4]thiadiazolo[3,2- a]benzimidazole-5,8-diones was achieved by the reaction of 2,5-dihydroxy-6-undecyl-1,4-bezoquinone (embelin) with 5-(alkyl/aralkyl/ phenacylsulfanyl)-1,3,4-thiadiazol-2-amines in refluxing acetic acid.

Beta-catenin is involved in alterations in mitochondrial activity in non-transformed intestinal epithelial and colon cancer cells

BACKGROUND

Alteration in respiratory activity and mitochondrial DNA (mtDNA) transcription seems to be an important feature of cancer cells. Leukotriene D(4) (LTD(4)) is a proinflammatory mediator implicated in the pathology of chronic inflammation and cancer. We have shown earlier that LTD(4) causes translocation of beta-catenin both to the mitochondria, in which it associates with the survival protein Bcl-2 identifying a novel role for beta-catenin in cell survival, and to the nucleus in which it activates the TCF/LEF transcription machinery.

METHODS

Here we have used non-transformed intestinal epithelial Int 407 cells and Caco-2 colon cancer cells, transfected or not with wild type and mutated (S33Y) beta-catenin to analyse its effect on mitochondria activity. We have measured the ATP/ADP ratio, and transcription of the mtDNA genes ND2, ND6 and 16 s in these cells stimulated or not with LTD(4).

RESULTS

We have shown for the first time that LTD(4) triggers a cellular increase in NADPH dehydrogenase activity and ATP/ADP ratio. In addition, LTD(4) significantly increased the transcription of mtDNA genes. Overexpression of wild-type beta-catenin or a constitutively active beta-catenin mutant mimicked the effect of LTD(4) on ATP/ADP ratio and mtDNA transcription. These elevations in mitochondrial activity resulted in increased reactive oxygen species levels and subsequent activations of the p65 subunit of NF-kappaB.

CONCLUSIONS

The present novel data show that LTD(4), presumably through beta-catenin accumulation in the mitochondria, affects mitochondrial activity, lending further credence to the idea that inflammatory signalling pathways are intrinsically linked with potential oncogenic signals.

Plumbagin induces ROS-mediated apoptosis in human promyelocytic leukemia cells in vivo

Plumbagin, a naphtoquinone from the roots of Plumbago zeylanica is known to possess anticancer and anti-bacterial activity. Based on the former finding of our group in vitro demonstrating its effectiveness in human promyelocytic leukemia cells, NB4, in this study we further revealed the mitochondrial pathway involved in plumbagin-induced apoptosis. We also found that the generation of ROS was a critical mediator in plumbagin-induced apoptosis, which would be abrogated completely by antioxidant, NAC. The anticancer effect of plumbagin was investigated in vivo using NB4 tumor xenograft in NOD/SCID mice. The incidence of formation, growth characteristics, body weight and volume of tumors were observed. The histopathologic examination of tumors and organs were made. The results showed that intraperitoneal injection of plumbagin (2mg/kg body weight) daily for 3 weeks resulted to a 64.49% reduction of tumor volume compared with the control. Furthermore, there was no overt manifestation of toxicity such as weight loss, tissue damage and behavior change which appeared in Doxorubicin-treated mice (1mg/kg thrice a week). These results indicate that plumbagin has potential as a novel therapeutic agent for myeloid leukemia.

Cytoprotective effect of polypeptide from Chlamys farreri on neuroblastoma (SH-SY5Y) cells following HO exposure involves scavenging ROS and inhibition JNK phosphorylation

Oxidative stress has long been linked to cell death in many neurodegenerative conditions. Treatment with antioxidants is a promising approach for slowing disease progression. In this study, we used the neuroblastoma SH-SY5Y cells as an in vitro model to first assess the effect of polypeptide from Chlamys farreri (PCF), a natural marine antioxidant, on H(2)O(2)-induced neuronal cell death. Pre-treatment of SH-SY5Y cells with PCF inhibited H(2)O(2)-induced cell death in a concentration-dependent manner. In parallel, intracellular reactive oxygen species generation and lipid peroxidation were inhibited by PCF. Under severe H(2)O(2) insult, PCF promoted endogenous antioxidant defense components including glutathione peroxidase, catalase, superoxide dismutase, and glutathione. PCF also protected DNA from oxidative damage and enhanced the removal of 8-oxo-7,8-dihydro-2'-deoxyguanosine from DNA. Further, we found that PCF potentially prevented H(2)O(2)-induced cell apoptosis. When investigated mitogen-activated protein kinase signaling pathway, we found that pre-treatment of cells with PCF significantly blocked H(2)O(2)-induced phosphorylation of c-Jun N-terminal kinase of the mitogen-activated protein kinase family. However, PCF had little inhibitory effect on the H(2)O(2)-induced activation of extracellular signal-regulated kinase. Taken together, these data demonstrate that PCF prevents oxidative stress-induced reactive oxygen species production and c-Jun N-terminal kinase activation and may be useful in the treatment of neurodegenerative diseases.

Antioxidant activity of sulfur and selenium: a review of reactive oxygen species scavenging, glutathione peroxidase, and metal-binding antioxidant mechanisms

It is well known that oxidation caused by reactive oxygen species (ROS) is a major cause of cellular damage and death and has been implicated in cancer, neurodegenerative, and cardiovascular diseases. Small-molecule antioxidants containing sulfur and selenium can ameliorate oxidative damage, and cells employ multiple antioxidant mechanisms to prevent this cellular damage. However, current research has focused mainly on clinical, epidemiological, and in vivo studies with little emphasis on the antioxidant mechanisms responsible for observed sulfur and selenium antioxidant activities. In addition, the antioxidant properties of sulfur compounds are commonly compared to selenium antioxidant properties; however, sulfur and selenium antioxidant activities can be quite distinct, with each utilizing different antioxidant mechanisms to prevent oxidative cellular damage. In the present review, we discuss the antioxidant activities of sulfur and selenium compounds, focusing on several antioxidant mechanisms, including ROS scavenging, glutathione peroxidase, and metal-binding antioxidant mechanisms. Findings of several recent clinical, epidemiological, and in vivo studies highlight the need for future studies that specifically focus on the chemical mechanisms of sulfur and selenium antioxidant behavior.

Bacteriophage interactions with phagocytes and their potential significance in experimental therapy

Bacteriophages are among the most numerous creatures on earth and they are omnipresent. They are thus in constant natural contact with humans and animals. However, the clinical and technological use of bacteriophages has also become more frequent, which is why all aspects of phage-mammal interactions need to be explored. Bacteriophages are able to interact with mammalian phagocytes. They may inhibit the phagocytosis of bacteria, but they may also undergo phagocytosis themselves. The ability of bacteriophages to reduce reactive oxygen species production by polymorphonuclear leukocytes in the presence of bacteria or their endotoxins was also confirmed. Studies show that the high immunogenicity of bacteriophages may also be employed in anti-tumor treatment. The present knowledge of phage interactions with cellular components of the mammalian immune system is sparse and insufficient, especially considering the increasing interest in the application of these viruses in human life. We believe that continuation of such research is indispensable.

Comparative study of antioxidant activity and antiproliferative effect of hot water and ethanol extracts from the mushroom Inonotus obliquus

The medicinal mushroom Inonotus obliquus is a traditional and widely used multi-functional fungus. Hot water (50 degrees C, 70 degrees C, and 80 degrees C) and ethanol crude extracts of I. obliquus were investigated for their antioxidant activity with superoxide dismutase (SOD) and (1,1-diphenyl-2-picryhydrazyl) (DPPH) radical-scavenging activity assays. We also investigated the antiproliferative effects and ability of the extracts to induce apoptosis in human colon cancer DLD-1 cells. Among the four extracts, the ethanol extract (EE) exhibited the strongest SOD-like activity and antiproliferative effect on DLD-1 cells, and exposure to the EE resulted in the induction of apoptosis, whereas no apoptosis was observed in DLD-1 cells exposed to the hot water extracts (HWEs). HWE at 70 degrees C (HWE70) exhibited the strongest DPPH radical-scavenging activity (EC50, 126 microg/ml), whereas the EE showed the weakest activity (EC50, 224 microg/ml). The different biological activities among the four extracts may be attributed to differences in their chemical composition, partially supported by polysaccharide, protein and phenolic content, and the 1H-NMR spectra.

Comparison of eumelanin and pheomelanin content between cultured uveal melanoma cells and normal uveal melanocytes

Levels of eumelanin (EM) and pheomelanin (PM) of uveal melanoma cells have not been measured and compared with those of normal uveal melanocytes. EM and PM amounts in four immortal human uveal melanoma cell lines were measured by chemical degradation and microanalytical high-performance liquid chromatography and compared with those from 39 normal human uveal melanocyte cell lines reported earlier by us. Uveal melanoma cells had a very low EM/PM ratio (0.41), which was very significantly lower than that from normal melanocytes isolated both from eyes with light-colored irides (1.31) or dark-colored irides (7.32). The low EM/PM ratio was caused by a low level of EM in melanoma cells, which was only 1/8 and 1/31 of that in melanocytes from eyes with light-colored irides and dark-colored irides, respectively. The PM level in uveal melanoma cells was not statistically different from normal melanocytes from eyes with light-colored irides or dark-colored irides. The total quantity of EM and PM in uveal melanoma cells was significantly less than that in normal melanocytes. This difference was because of the low level of EM in uveal melanoma cells. The results of these studies indicate that the changes of melanin content in uveal melanoma cells mainly relate to the decrease of EM content. Low melanin and EM content may make melanoma cells more susceptible to mutagenic effects of ultraviolet radiation and oxidative stress, which may enhance the proliferation of melanoma cells and accelerate progression of melanoma.

Watching the watcher: regulation of p53 by mitochondria

p53 has been referred to as the 'guardian of the genome' because of its role in protecting the cell from DNA damage. p53 performs its duties by regulating cell-cycle progression and DNA repair and, in cases of irreparable DNA damage, by executing programmed cell death. Mitochondria are an important target of transcription-dependent and -independent actions of p53 to carry out the apoptotic function. However, increasing evidence suggests that p53 activity is regulated by mitochondria. Cellular insults that alter mitochondrial function can have important consequences on p53 activity. In light of these new findings, the following review focuses on p53/mitochondria connections, in particular how reactive oxygen species generated at mitochondria regulate p53 activity. A better understanding of the mechanisms by which mitochondria regulate p53 may have an impact on our understanding of the development and progression of many diseases, especially cancer.

Myeloid-derived suppressor cells as regulators of the immune system

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that expand during cancer, inflammation and infection, and that have a remarkable ability to suppress T-cell responses. These cells constitute a unique component of the immune system that regulates immune responses in healthy individuals and in the context of various diseases. In this Review, we discuss the origin, mechanisms of expansion and suppressive functions of MDSCs, as well as the potential to target these cells for therapeutic benefit.

Myeloid-derived suppressor cells as regulators of the immune system

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that expand during cancer, inflammation and infection, and that have a remarkable ability to suppress T-cell responses. These cells constitute a unique component of the immune system that regulates immune responses in healthy individuals and in the context of various diseases. In this Review, we discuss the origin, mechanisms of expansion and suppressive functions of MDSCs, as well as the potential to target these cells for therapeutic benefit.

The use of magnetic field effects on photosensitizer luminescence as a novel probe for optical monitoring of oxygen in photodynamic therapy

The effect of a magnetic field on the steady-state and time-resolved optical emission of a custom fullerene-linked photosensitizer (PS) in liposome cell phantoms was studied at various oxygen concentrations (0.19-190 microM). Zeeman splitting of the triplet state and hyperfine coupling, which control intersystem crossing between singlet and triplet states, are altered in the presence of low magnetic fields (B < 320 mT), perturbing the luminescence intensity and lifetime as compared to the triplet state at B = 0. Measurements of the luminescence intensity and lifetime were performed using a time-domain apparatus integrated with a magnet. We propose that by probing magnet-affected optical emissions, one can monitor the state of oxygenation throughout the course of photodynamic therapy. Since the magnetic field effect (MFE) operates primarily by affecting the radical ion pairs related to type I photodynamic action, the enhancement or suppression of the MFE can be used as a measure of the dynamic equilibrium between the type I and II photodynamic pathways. The unique photo-initiated charge-transfer properties of the PS used in this study allow it to serve as both cytotoxic agent and oxygen probe that can provide in situ dosimetric information at close to real time.

Modulation of tricarboxylic acid cycle dehydrogenases during hepatocarcinogenesis induced by hexachlorocyclohexane in mice

The sequential distribution of key tricarboxylic acid (TCA) cycle enzymes have been investigated during hexachlorocyclohexane (HCH)-induced hepatocarcinogenesis in Swiss mice. Animals were continuously exposed to HCH (500ppm) for 2, 4, and 6 months until liver tumor developed. The activity of TCA cycle enzymes such as isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH) have been studied. The activity of all the enzymes declined after 2 months of exposure of HCH in the liver. The neoplastic nodules and tumors developed after an exposure of HCH for 4 and 6 months, respectively. Neoplastic nodule and tumor showed wide variations in the activity and distribution of TCA cycle enzymes. The decreasing pattern in the activity of enzymes persisted in the non-neoplastic and non-tumor regions of the liver except SDH. However, the cells in nodular area and tumor showed intense enzymatic activities at cellular level. In the nodular region SDH activity declined prominently, whereas the non-nodular area showed positive reaction. Conspicuously, the tumor showed islands of positive and negative zones for TCA cycle dehydrogenases. The significance and relevance of such a distribution pattern still remains a mystery. The results are discussed in the light of HCH-induced toxicity on energy metabolism in exposed animals and possible role of such enzymes in the tumor formation.

The JmjC domain histone demethylase Ndy1 regulates redox homeostasis and protects cells from oxidative stress

The histone H3 demethylase Ndy1/KDM2B protects cells from replicative senescence. Changes in the metabolism of reactive oxygen species (ROS) are important for establishing senescence, suggesting that Ndy1 may play a role in redox regulation. Here we show that Ndy1 protects from H(2)O(2)-induced apoptosis and G(2)/M arrest and inhibits ROS-mediated signaling and DNA damage, while knockdown of Ndy1 has the opposite effects. Consistent with these observations, whereas Ndy1 overexpression promotes H(2)O(2) detoxification, Ndy1 knockdown inhibits it. Ndy1 promotes the expression of genes encoding the antioxidant enzymes aminoadipic semialdehyde synthase (Aass), NAD(P)H quinone oxidoreductase-1 (Nqo1), peroxiredoxin-4 (Prdx4), and serine peptidase inhibitor b1b (Serpinb1b) and represses the expression of interleukin-19. At least two of these genes (Nqo1 and Prdx4) are regulated directly by Ndy1, which binds to specific sites within their promoters and demethylates promoter-associated histone H3 dimethylated at K36 and histone H3 trimethylated at K4. Simultaneous knockdown of Aass, Nqo1, Prdx4, and Serpinb1b in Ndy1-expressing cells to levels equivalent to those detected in control cells was sufficient to suppress the Ndy1 redox phenotype.

[Mitochondrial DNA mutations in the pathogenesis in the head and neck squamous cell carcinoma]

Data reported until today suggested a pivotal role of nuclear DNA mutations in the process of carcinogenesis. Recently more and more authors claim that disruption of mitochondrial DNA should not be excluded from this analysis. mtDNA have been reported in many cancers of head and neck region. Mitochondrial D-loop has been proven to be mutation hot - spot with majority of mutations in the positions 303 to 315 of poly-C tract. Data show that 37% of patients with premalignant lesions and 62% with carcinoma in situ are positive for mtDNA mutations. Moreover mutations in genes encoding ND2, ND5, COIII, CYTB, and ATP6 were observed in 17% of patients. Mutations in mitochondrial rRNA genes occured in similar number of cases. Neoplastic cells undifferentiation and disease progression is accompanied by multiplication of mtDNA number and increased mtDNA content. mtDNA content corellates with the stage of the disease. mtDNA mutations faciliate cell proliferation and inhibit apoptosis by increasing the production of ractive oxygen species (ROS). Cells harbouring mutated mtDNA have increased proliferation rate, as increased ROS concentration may act as an endogenous growth factor.

Hepatoprotective activity of bacoside A against N-nitrosodiethylamine-induced liver toxicity in adult rats

N-Nitrosodiethylamine (DEN) is a notorious carcinogen, present in many environmental factors. DEN induces oxidative stress and cellular injury due to enhanced generation of reactive oxygen species; free radical scavengers protect the membranes from DEN-induced damage. The present study was designed to evaluate the protective effect of bacoside A (the active principle isolated from Bacopa monniera Linn.) on carcinogen-induced damage in rat liver. Adult male albino rats were pretreated with 15 mg/kg body weight/day of bacoside A orally (for 14 days) and then intoxicated with single necrogenic dose of N-nitrosodiethylamine (200 mg/kg bodyweight, intraperitonially) and maintained for 7 days. The liver weight, lipid peroxidation (LPO), and activity of serum marker enzymes (aspartate transaminases, alanine transaminases, lactate dehydrogenase, alkaline phosphatase, and gamma-glutamyl transpeptidase) were markedly increased in carcinogen-administered rats, whereas the activities of marker enzymes were near normal in bacoside A-pretreated rats. Activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutatione-S-transferase, and reduced glutathione) in liver also decreased in carcinogen-administered rats, which were significantly elevated in bacoside A-pretreated rats. It is concluded that pretreatment of bacoside A prevents the elevation of LPO and activity of serum marker enzymes and maintains the antioxidant system and thus protects the rats from DEN-induced hepatotoxicity.

Health effects of quercetin: from antioxidant to nutraceutical

Quercetin, a member of the flavonoids family, is one of the most prominent dietary antioxidants. It is ubiquitously present in foods including vegetables, fruit, tea and wine as well as countless food supplements and is claimed to exert beneficial health effects. This includes protection against various diseases such as osteoporosis, certain forms of cancer, pulmonary and cardiovascular diseases but also against aging. Especially the ability of quercetin to scavenge highly reactive species such as peroxynitrite and the hydroxyl radical is suggested to be involved in these possible beneficial health effects. Consequently, numerous studies have been performed to gather scientific evidence for these beneficial health claims as well as data regarding the exact mechanism of action and possible toxicological aspects of this flavonoid. The purpose of this review is to evaluate these studies in order to elucidate the possible health-beneficial effects of the antioxidant quercetin. Firstly, the definitions as well as the most important aspects regarding free radicals, antioxidants and oxidative stress will be discussed as background information. Subsequently, the mechanism by which quercetin may operate as an antioxidant (tested in vitro) as well as the potential use of this antioxidant as a nutraceutical (tested both ex vivo and in vivo) will be discussed.

Epithelial to mesenchymal transition in human breast epithelial cells transformed by 17beta-estradiol

The estrogen dependence of breast cancer has long been recognized; however, the role of 17beta-estradiol (E(2)) in cancer initiation was not known until we showed that it induces complete neoplastic transformation of the human breast epithelial cells MCF-10F. E(2) treatment of MCF-10F cells progressively induced high colony efficiency and loss of ductulogenesis in early transformed (trMCF) cells and invasiveness in Matrigel invasion chambers. The cells that crossed the chamber membrane were collected and identified as bsMCF; their subclones were designated bcMCF; and the cells harvested from carcinoma formation in severe combined immunodeficient mice were designated caMCF. These phenotypes correlated with gene dysregulation during the progression of the transformation. The highest number of dysregulated genes was observed in caMCF, being slightly lower in bcMCF, and lowest in trMCF. This order was consistent with the extent of chromosome aberrations (caMCF > bcMCF >>> trMCF). Chromosomal amplifications were found in 1p36.12-pter, 5q21.1-qter, and 13q21.31-qter. Losses of the complete chromosome 4 and 8p11.21-23.1 were found only in tumorigenic cells. In tumor-derived cell lines, additional losses were found in 3p12.1-14.1, 9p22.1-pter, and 18q11.21-qter. Functional profiling of dysregulated genes revealed progressive changes in the integrin signaling pathway, inhibition of apoptosis, acquisition of tumorigenic cell surface markers, and epithelial-mesenchymal transition. In tumorigenic cells, the levels of E-cadherin, epithelial membrane antigen, and various keratins were low and CD44E/CD24 were negative, whereas SNAI2, vimentin, S100A4, FN1, HRAS, transforming growth factor beta1, and CD44H were high. The phenotypic and genomic changes triggered by estrogen exposure that lead normal cells to tumorigenesis confirm the role of this steroid hormone in cancer initiation.

Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers

The present work is focussed on the principles of photodynamic therapy (PDT), emphasizing the photochemical mechanisms of reactive oxygen species formation and the consequent biochemical processes generated by the action of reactive oxygen species on various biological macromolecules and organelles. This paper also presents some of the most used photosensitizers, including Photofrin, and the new prototypes of photosensitizers, analysing their physicochemical and spectroscopic properties. At this point, the review discusses the therapeutic window of absorption of specific wavelengths involving first- and second-generation photosensitizers, as well as the principal light sources used in PDT. Additionally, the aggregation process, which consists in a phenomenon common to several photosensitizers, is studied. J-aggregates and H-aggregates are discussed, along with their spectroscopic effects. Most photosensitizers have a significant hydrophobic character; thus, the study of the types of aggregation in aqueous solvent is very relevant. Important aspects of the coordination chemistry of metalloporphyrins and metallophthalocyanines used as photosensitizers are also discussed. The state-of-the-art in PDT is evaluated, discussing recent articles in this area. Furthermore, macrocyclic photosensitizers, such as porphyrins and phthalocyanines, are specifically described. The present review is an important contribution, because PDT is one of the most auspicious advances in the therapy against cancer and other non-malignant diseases.

Oxidative stress induces autophagic cell death independent of apoptosis in transformed and cancer cells

Autophagy is a self-digestion process that degrades intracellular structures in response to stresses leading to cell survival. When autophagy is prolonged, this could lead to cell death. Generation of reactive oxygen species (ROS) through oxidative stress causes cell death. The role of autophagy in oxidative stress-induced cell death is unknown. In this study, we report that two ROS-generating agents, hydrogen peroxide (H(2)O(2)) and 2-methoxyestradiol (2-ME), induced autophagy in the transformed cell line HEK293 and the cancer cell lines U87 and HeLa. Blocking this autophagy response using inhibitor 3-methyladenine or small interfering RNAs against autophagy genes, beclin-1, atg-5 and atg-7 inhibited H(2)O(2) or 2-ME-induced cell death. H(2)O(2) and 2-ME also induced apoptosis but blocking apoptosis using the caspase inhibitor zVAD-fmk (benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone) failed to inhibit autophagy and cell death suggesting that autophagy-induced cell death occurred independent of apoptosis. Blocking ROS production induced by H(2)O(2) or 2-ME through overexpression of manganese-superoxide dismutase or using ROS scavenger 4,5-dihydroxy-1,3-benzene disulfonic acid-disodium salt decreased autophagy and cell death. Blocking autophagy did not affect H(2)O(2)- or 2-ME-induced ROS generation, suggesting that ROS generation occurs upstream of autophagy. In contrast, H(2)O(2) or 2-ME failed to significantly increase autophagy in mouse astrocytes. Taken together, ROS induced autophagic cell death in transformed and cancer cells but failed to induce autophagic cell death in non-transformed cells.

Attenuation of N-nitrosodiethylamine-induced hepatocellular carcinogenesis by a novel flavonol-Morin

Morin (3,5,7,2',4'-pentahydroxyflavone), a plant-derived flavonoid belonging to the subclass of flavonol is believed to play a role in chemoprevention and cancer chemotherapy. In this study, we found that the cotreatment of morin (500 ppm in diet) for 16 weeks to N-nitosodiethylamine-induced (200 mg/kg bodyweight in drinking water) rats provides protection against the oxidative stress caused by the carcinogen and thereby prevents hepatocellular carcinogenesis. On administration of the carcinogen, the level of lipid peroxidation increased markedly, but was found to be significantly lowered by morin treatment. On the contrary, the antioxidant levels in both liver and serum were decreased in carcinogen-administered animals, which was improved to normalcy upon morin administration. Cotreatment with morin prevented the elevation of marker enzymes induced by N-nitrosodiethylamine. The body weight of the animals decreased and their relative liver weight increased significantly on N-nitrosodiethylamine administration when compared to control group. However, cotreatment with morin significantly prevented the decrease of the body weight and increase in relative liver weight caused by DEN. Histological observations of liver tissue too correlated with the biochemical observations. In conclusion, these findings indicate that morin prevents lipid peroxidation, hepatic cell damage and protects the antioxidant system in N-nitrosodiethylamine-induced hepatocellular carcinogenesis.

Top-down and bottom-up mass spectrometric characterization of human myoglobin-centered free radicals induced by oxidative damage

In an effort to determine the utility of top-down mass spectrometric methodologies for the characterization of protein radical adducts, top-down approaches were investigated and compared to the traditional bottom-up approaches. Specifically, the nature of the radicals on human myoglobin induced by the addition of hydrogen peroxide and captured by the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was investigated. The most abundant ion observed in the electrospray mass spectrum of this reaction mixture corresponds in mass to the human myoglobin plus one DMPO molecule. In addition, a second ion of lower abundance is observed, which corresponds to a second DMPO molecule being trapped on myoglobin. Top-down analyses using Fourier transform ion cyclotron resonance mass spectrometry can be used to characterize proteins and, thus, were performed on several different charge-state ions of both the native and the mono-DMPO nitrone adduct of human myoglobin. Data produced from the top-down analyses are very complex yet information rich. In the case of DMPO-modified human myoglobin, the top-down data localized the DMPO spin trap to residues 97-110 of the myoglobin. The observation of the y43+5 fragment ion arising from C-terminal cleavage to the cysteine-110 residue in the MS/MS spectrum of DMPO-modified myoglobin and not in the unmodified myoglobin implicates a change to this residue, specifically, DMPO adduction. On the other hand, using the traditional bottom-up approach of peptide mapping and MS sequencing methodologies, two DMPO radical adducts on human myoglobin were identified, Cys-110 and Tyr-103. The bottom-up approach is more proven and robust than the top-down methodologies. Nonetheless, the bottom-up and top-down approaches to protein characterization are complementary rather than competitive approaches with each having its own utility.