Redox regulation of transcriptional activators

Pulmonary endothelial cell NOX

Reactive oxygen species (ROS) have profound influences on cellular homeostasis. In excess, they can potentiate the oxidation of numerous molecules, including proteins, lipids, and nucleic acids, affecting function. Furthermore, ROS-mediated oxidation of proteins can directly or indirectly modulate gene expression via effects on redox-sensitive transcription factors or via effects on phospho-relay-mediated signal transduction. In doing so, ROS impact numerous fundamental cellular processes, and have thus been implicated as critical mediators of both homeostasis and disease pathogenesis. Vascular reduced nicotinamide adenine dinucleotide phosphate oxidase (NOX) is a major contributor of ROS within the lung. The generation of ROS in the pulmonary vasculature has a pivotal role in endothelial cell (EC) activation and function. Alterations in EC phenotype contribute to vascular tone, permeability, and inflammatory responses and, thus, have been implicated in numerous diseases of the lung, including pulmonary hypertension, ischemic-reperfusion injury, and adult respiratory distress syndrome. Thus, although a detailed understanding of NOX-derived ROS in pulmonary EC biology in the context of health and disease is nascent, there is mounting evidence implicating these enzymes as critical modifiers of diseases of the lung and pulmonary circulation. The purpose of this review is to focus specifically on known as well as putative roles for pulmonary EC NOX, with attention to studies on the intact lung.

The in vitro effects of zearalenone and T-2 toxins on Vero cells

The aim of the present study was to investigate in vitro, whether cytolethality and oxidative damage is enhanced by combination of both mycotoxins as compared to their individual effect. In our paper, we applied a tiered in vitro experimental approach in order to predict the possible health risk effects of two interactive fusarial toxins. Considering the concomitant production of zearalenone (ZEN) and T-2 toxin, it is very likely that humans and animals are always exposed to the mixture rather than to individual compounds. Our results clearly showed that cultured renal cells respond to individual (ZEN) or T-2 toxin exposure by a moderate inhibition of cell proliferation, respectively. However, when combined, they exert a more significant decrease in cell viability. Similar results were found for the investigated oxidative status endpoints. When combined, ZEN and T-2 toxin increased ROS production and heat shock protein (Hsp) 70 expression as compared to the effect of each mycotoxin taken alone. We can conclude that the mixture of ZEN and T-2 toxin increased their toxic effects. The health risk is heightened by the interactions between co-occurring mycotoxins.

Oxidative stress and antioxidant defense

Reactive oxygen species (ROS) are produced by living organisms as a result of normal cellular metabolism and environmental factors, such as air pollutants or cigarette smoke. ROS are highly reactive molecules and can damage cell structures such as carbohydrates, nucleic acids, lipids, and proteins and alter their functions. The shift in the balance between oxidants and antioxidants in favor of oxidants is termed “oxidative stress.” Regulation of reducing and oxidizing (redox) state is critical for cell viability, activation, proliferation, and organ function. Aerobic organisms have integrated antioxidant systems, which include enzymatic and nonenzymatic antioxidants that are usually effective in blocking harmful effects of ROS. However, in pathological conditions, the antioxidant systems can be overwhelmed. Oxidative stress contributes to many pathological conditions and diseases, including cancer, neurological disorders, atherosclerosis, hypertension, ischemia/perfusion, diabetes, acute respiratory distress syndrome, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, and asthma. In this review, we summarize the cellular oxidant and antioxidant systems and discuss the cellular effects and mechanisms of the oxidative stress.

Low interleukin-17A production in response to fungal pathogens in patients with chronic granulomatous disease

Patients with chronic granulomatous disease (CGD) cannot produce reactive oxygen species (ROS) due to a genetic defect in the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system. Dysregulation of the L-tryptophan metabolism in mice with defects in NADPH oxidase, resulting in overproduction of interleukin (IL)-17, has been proposed to link ROS defects with hyperinflammation and susceptibility to pulmonary aspergillosis. In this study, we assessed the L-tryptophan metabolism and cytokine profiles in response to fungal pathogens in CGD patients. Peripheral blood mononuclear cells (PBMCs) from CGD patients showed increased production of IL-6, tumor necrosis factor-α, and interferon-γ upon stimulation with Aspergillus or Candida species, while IL-17A production was strikingly low compared with healthy controls. Indoleamine 2,3-dioxygenase expression was similar in PBMCs and neutrophils from CGD patients compared with healthy controls. Conversion of L-tryptophan to L-kynurenine, as measured by high-performance liquid chromatography, did not differ between CGD patients and healthy controls. Moreover, adding L-kynurenine to the cell cultures did not suppress fungal-induced IL-17A production. Although PBMCs of CGD patients produced more proinflammatory cytokines after stimulation, IL-17A production was strikingly low in response to fungal pathogens when compared with healthy controls. In addition, cells from CGD patients did not display a defective L-tryptophan metabolism.

Basic principles and emerging concepts in the redox control of transcription factors

Convincing concepts of redox control of gene transcription have been worked out for prokaryotes and lower eukaryotes, whereas the knowledge on complex mammalian systems still resembles a patchwork of poorly connected findings. The article, therefore, reviews principles of redox regulation with special emphasis on chemical feasibility, kinetic requirements, specificity, and physiological context, taking well investigated mammalian transcription factor systems, nuclear transcription factor of bone marrow-derived lymphocytes (NF-κB), and kelch-like ECH-associated protein-1 (Keap1)/Nrf2, as paradigms. Major conclusions are that (i) direct signaling by free radicals is restricted to O(2)•- and •NO and can be excluded for fast reacting radicals such as •OH, •OR, or Cl•; (ii) oxidant signals are H(2)O(2), enzymatically generated lipid hydroperoxides, and peroxynitrite; (iii) free radical damage is sensed via generation of Michael acceptors; (iv) protein thiol oxidation/alkylation is the prominent mechanism to modulate function; (v) redox sensors must be thiol peroxidases by themselves or proteins with similarly reactive cysteine or selenocysteine (Sec) residues to kinetically compete with glutathione peroxidase (GPx)- and peroxiredoxin (Prx)-type peroxidases or glutathione-S-transferases, respectively, a postulate that still has to be verified for putative mammalian sensors. S-transferases and Prxs are considered for system complementation. The impact of NF-κB and Nrf2 on hormesis, management of inflammatory diseases, and cancer prevention is critically discussed.

Elevated uric acid correlates with wound severity

Chronic venous leg ulcers are a major health issue and represent an often overlooked area of biomedical research. Nevertheless, it is becoming increasingly evident that new approaches to enhance healing outcomes may arise through better understanding the processes involved in the formation of chronic wounds. We have for the first time shown that the terminal purine catabolite uric acid (UA) is elevated in wound fluid (WF) from chronic venous leg ulcers with relative concentrations correlating with wound chronicity. We have also shown a corresponding depletion in UA precursors, including adenosine, with increased wound severity. Further, we have shown that xanthine oxidase, the only enzyme in humans that catalyses the production of UA in conjunction with a burst of free radicals, is active in chronic WF. Taken together, this provides compelling evidence that xanthine oxidase may play a critical role in the formation of chronic wounds by prolonging the inflammatory process.

Ryanodine receptor: a new therapeutic target to control diabetic cardiomyopathy

Diabetes mellitus is a major risk factor for cardiovascular complications. Intracellular Ca(2+) release plays an important role in the regulation of muscle contraction. Sarcoplasmic reticulum Ca(2+) release is controlled by dedicated molecular machinery, composed of a complex of cardiac ryanodine receptors (RyR2s). Acquired and genetic defects in this complex result in a spectrum of abnormal Ca(2+) release phenotypes in heart. Cardiovascular dysfunction is a leading cause for mortality of diabetic individuals due, in part, to a specific cardiomyopathy, and to altered vascular reactivity. Cardiovascular complications result from multiple parameters, including glucotoxicity, lipotoxicity, fibrosis, and mitochondrial uncoupling. In diabetic subjects, oxidative stress arises from an imbalance between production of reactive oxygen and nitrogen species and capability of the system to readily detoxify reactive intermediates. To date, the etiology underlying diabetes-induced reductions in myocyte and cardiac contractility remains incompletely understood. However, numerous studies, including work from our laboratory, suggest that these defects stem in part from perturbation in intracellular Ca(2+) cycling. Since the RyR2s are one of the well-characterized redox-sensitive ion channels in heart, this article summarizes recent findings on redox regulation of cardiac Ca(2+) transport systems and discusses contributions of redox regulation to pathological cardiac function in diabetes.

Superoxide dismutase 1 (SOD1) is a target for a small molecule identified in a screen for inhibitors of the growth of lung adenocarcinoma cell lines

We previously described four small molecules that reduced the growth of lung adenocarcinoma cell lines with either epidermal growth factor receptor (EGFR) or KRAS mutations in a high-throughout chemical screen. By combining affinity proteomics and gene expression analysis, we now propose superoxide dismutase 1 (SOD1) as the most likely target of one of these small molecules, referred to as lung cancer screen 1 (LCS-1). siRNAs against SOD1 slowed the growth of LCS-1 sensitive cell lines; conversely, expression of a SOD1 cDNA increased proliferation of H358 cells and reduced sensitivity of these cells to LCS-1. In addition, SOD1 enzymatic activity was inhibited in vitro by LCS-1 and two closely related analogs. These results suggest that SOD1 is an LCS-1-binding protein that may act in concert with mutant proteins, such as EGFR and KRAS, to promote cell growth, providing a therapeutic target for compounds like LCS-1.

Hemoglobin attenuates the effects of inspired oxygen on plasma isofurans in humans during upper-limb surgery

Reperfusion injury is characterized by significant oxidative stress. F(2)-isoprostanes (F(2)-IsoP's) and isofurans (IsoF's), the latter preferentially produced during increased oxygen tension, are recognized markers of in vivo oxidative stress. We aimed to determine whether increasing oxygen tension during reperfusion modified levels of plasma total IsoF's and F(2)-IsoP's. Forty-five patients undergoing upper-limb surgery were randomized to receive inspired oxygen concentrations of 30, 50, or 80% during the last 15 min of surgery. Venous blood samples were taken before the change in inspired oxygen, after 10 min (before reperfusion), and after 15 min (5 min after reperfusion). IsoF's and F(2)-IsoP's were measured by gas chromatography-mass spectrometry. Venous oxygen tension and hemoglobin concentrations were also measured. Plasma IsoF and F(2)-IsoP levels in the 50 and 80% O(2) groups were not significantly different from those of the 30% O(2) group. In secondary analyses, using data combining all groups, levels of IsoF's, but not F(2)-IsoP's, associated with higher venous oxygen tension (P=0.038). Hemoglobin negatively modified the influence of oxygen tension on levels of IsoF's (P=0.014). This study has shown, for the first time, that plasma IsoF levels associate with higher oxygen tension in a human model of reperfusion, and this effect is significantly attenuated by hemoglobin.

Comparative proteomic analysis of irinotecan-sensitive colorectal carcinoma cell line and its chemoresistant counterpart

In this study, we used two-dimensional gel electrophoresis and MALDI-Q-TOF-MS/MS analysis to examine the global protein expression of a pair of colorectal carcinoma cell lines, SW620 and irinotecan-resistant SW620. Of the 30 spots identified as differentially expressed proteins (±over twofold, P<0.05) between the two cell lines, 26 spots (corresponding to 26 unique proteins) were positively identified by MALDI-Q-TOF-MS/MS analysis. These proteins could be grouped into main classes including metabolism (15.38%), cell SSproliferation/differentiation (11.53%), molecular chaperone (11.53%), mRNA splicing (11.53%), and so on. The proteins, which might be involved in the development of tumor drug resistance, such as α-enolase, cofilin, and thioredoxin-dependent peroxide 1, have been validated by western blot analysis and have been discussed. The proteins identified in this study may be useful in showing the mechanisms underlying irinotecan resistance.

Superoxide production by macrophages and T cells is critical for the induction of autoreactivity and type 1 diabetes

OBJECTIVE

The role of reactive oxygen species (ROS) and their dissipation in type 1 diabetes pathogenesis have garnered considerable controversy. Our recent work has demonstrated the importance of NADPH oxidase (NOX) activity for type 1 diabetes development and modulating T-cell autoreactivity. We previously linked decreased monocyte ROS with diabetes resistance in the alloxan-resistant mouse, and NOD-Ncf1(m1J) mice with a genetic ablation of NOX activity had reduced and delayed type 1 diabetes compared with NOD mice.

RESEARCH DESIGN AND METHODS

To determine the required cellular sources of ROS that are necessary for type 1 diabetes initiation, we used antibody depletion and adoptive transfer experiments into NOD and NOD-Scid females, respectively. After receiving treatment, female mice were monitored for hyperglycemia and overt diabetes.

RESULTS

Depletion of macrophages and neutrophils fully protected NOD mice from type 1 diabetes. However, elimination of neutrophils alone showed no significant reduction or delay. Type 1 diabetes induction in NOD-Scid mice by adoptive transfer with NOD-Ncf1(m1J) splenocytes was significantly delayed compared with NOD splenocytes, suggesting macrophage ROS and modulation of effector responses are critical for diabetes. The adaptive immune response was also altered by the absence of NOX activity, as purified T cells from NOD-Ncf1(m1J) mice exhibited delayed transfer kinetics. Cotransfer experiments demonstrated the defect was intrinsic to NOX-deficient CD8(+) T cells. After stimulation, cytotoxic T cells exhibited decreased effector function in the absence of superoxide production.

CONCLUSIONS

These data demonstrate that the impaired autoreactive response of NOX-deficient NOD-Ncf1(m1J) immune system results from an alteration in the antigen-presenting cell-T-cell axis rather than failure of neutrophils to act as effector cells and that ROS signaling is important for the initiation of β-cell-directed autoimmunity by T cells.

Mitochondrial superoxide dismutase--signals of distinction

Mitochondrial superoxide dismutase (MnSOD) neutralizes the highly reactive superoxide radical (O(2)(˙-)), the first member in a plethora of mitochondrial reactive oxygen species (ROS). Over the past decades, research has extended the prevailing view of mitochondrion well beyond the generation of cellular energy to include its importance in cell survival and cell death. In the normal state of a cell, endogenous antioxidant enzyme systems maintain the level of reactive oxygen species generated by the mitochondrial respiratory chain. Mammalian mitochondria are important to the production of reactive oxygen species, which underlie oxidative damage in many pathological conditions and contribute to retrograde redox signaling from the organelle to the cytosol and nucleus. Mitochondria are further implicated in various metabolic and aging-related diseases that are now postulated to be caused by misregulation of physiological systems rather than pure accumulation of oxidative damage. Thus, the signaling mechanisms within mitochondria, and between the organelle and its environment, have gained interest as potential drug targets. Here, we discuss redox events in mitochondria that lead to retrograde signaling, the role of redox events in disease, and their potential to serve as therapeutic targets.

Hydroxytyrosol glucuronides protect renal tubular epithelial cells against H(2)O(2) induced oxidative damage

Hydroxytyrosol (2-(3',4'-dihydroxyphenyl)ethanol; HT), the most active ortho-diphenolic compound, present either in free or esterified form in extravirgin olive oil, is extensively metabolized in vivo mainly to O-methylated, O-sulfated and glucuronide metabolites. We investigated the capacity of three glucuronide metabolites of HT, 3'-O-β-d-glucuronide and 4'-O-β-d-glucuronide derivatives and 2-(3',4'-dihydroxyphenyl)ethanol-1-O-β-d-glucuronide, in comparison with the parent compound, to inhibit H(2)O(2) induced oxidative damage and cell death in LLC-PK1 cells, a porcine kidney epithelial cell line. H(2)O(2) treatment exerted a toxic effect inducing cell death, interacting selectively within the pro-death extracellular-signal relate kinase (ERK 1/2) and the pro-survival Akt/PKB signaling pathways. It also produced direct oxidative damage initiating the membrane lipid peroxidation process. None of the tested glucuronides exhibited any protection against the loss in renal cell viability. They also failed to prevent the changes in the phosphorylation states of ERK and Akt, probably reflecting their inability to enter the cells, while HT was highly effective. Notably, pretreatment with glucuronides exerted a protective effect at the highest concentration tested against membrane oxidative damage, comparable to that of HT: the formation of malondialdehyde, fatty acid hydroperoxides and 7-ketocholesterol was significantly inhibited.

Antioxidants in foods: state of the science important to the food industry

Antioxidant foods and ingredients are an important component of the food industry. In the past, antioxidants were used primarily to control oxidation and retard spoilage, but today many are used because of putative health benefits. However, the traditional message that oxidative stress, which involves the production of reactive oxygen species (ROS), is the basis for chronic diseases and aging is being reexamined. Accumulating evidence suggests that ROS exert essential metabolic functions and that removal of too many ROS can upset cell signaling pathways and actually increase the risk of chronic disease. It is imperative that the food industry be aware of progress in this field to present the science relative to foods in a forthright and clear manner. This may mean reexamining the health implications of adding large amounts of antioxidants to foods.

Redox modulation of p53: mechanisms and functional significance

The tumor suppressor protein p53 functions as a stress-responsive transcription factor. In response to oxidative, nitrosative, and electrophilic insults, p53 undergoes post-translational modifications, such as oxidation and covalent modification of cysteines, nitration of tyrosines, acetylation of lysines, phosphorylation of serine/threonine residues, etc. Because p53 plays a vital role in the transcriptional regulation of genes encoding proteins involved in a wide spectrum of biochemical processes including DNA repair, cell-cycle regulation, and programmed cell death, the redox-modification of p53 appears to be an important determinant of cell fate. This review highlights the redox regulation of p53 and its consequences on cellular function.

Alteration in superoxide dismutase 1 causes oxidative stress and p38 MAPK activation following RVFV infection

Rift Valley fever (RVF) is a zoonotic disease caused by Rift Valley fever virus (RVFV). RVFV is a category A pathogen that belongs to the genus Phlebovirus, family Bunyaviridae. Understanding early host events to an infectious exposure to RVFV will be of significant use in the development of effective therapeutics that not only control pathogen multiplication, but also contribute to cell survival. In this study, we have carried out infections of human cells with a vaccine strain (MP12) and virulent strain (ZH501) of RVFV and determined host responses to viral infection. We demonstrate that the cellular antioxidant enzyme superoxide dismutase 1 (SOD1) displays altered abundances at early time points following exposure to the virus. We show that the enzyme is down regulated in cases of both a virulent (ZH501) and a vaccine strain (MP12) exposure. Our data demonstrates that the down regulation of SOD1 is likely to be due to post transcriptional processes and may be related to up regulation of TNFα following infection. We also provide evidence for extensive oxidative stress in the MP12 infected cells. Concomitantly, there is an increase in the activation of the p38 MAPK stress response, which our earlier published study demonstrated to be an essential cell survival strategy. Our data suggests that the viral anti-apoptotic protein NSm may play a role in the regulation of the cellular p38 MAPK response. Alterations in the host protein SOD1 following RVFV infection appears to be an early event that occurs in multiple cell types. Activation of the cellular stress response p38 MAPK pathway can be observed in all cell types tested. Our data implies that maintaining oxidative homeostasis in the infected cells may play an important role in improving survival of infected cells.

Dexamethasone inhibits the Nox-dependent ROS production via suppression of MKP-1-dependent MAPK pathways in activated microglia

BACKGROUND

Nox-2 (also known as gp91phox), a subunit component of NADPH oxidases, generates reactive oxygen species (ROS). Nox-dependent ROS generation and nitric oxide (NO) release by microglia have been implicated in a variety of diseases in the central nervous system. Dexamethasone (Dex) has been shown to suppress the ROS production, NO release and inflammatory reaction of activated microglial cells. However, the underlying mechanisms remain unclear.

RESULTS

The present study showed that the increased ROS production and NO release in activated BV-2 microglial cells by LPS were associated with increased expression of Nox-2 and iNOS. Dex suppressed the upregulation of Nox-2 and iNOS, as well as the subsequent ROS production and NO synthesis in activated BV-2 cells. This inhibition caused by Dex appeared to be mediated by upregulation of MAPK phosphatase-1 (MKP-1), which antagonizes the activity of mitogen-activated protein kinases (MAPKs). Dex induced-suppression of Nox-2 and -upregulation of MKP-1 was also evident in the activated microglia from corpus callosum of postnatal rat brains. The overexpression of MKP-1 or inhibition of MAPKs (by specific inhibitors of JNK and p38 MAPKs), were found to downregulate the expression of Nox-2 and iNOS and thereby inhibit the synthesis of ROS and NO in activated BV-2 cells. Moreover, Dex was unable to suppress the LPS-induced synthesis of ROS and NO in BV-2 cells transfected with MKP-1 siRNA. On the other hand, knockdown of Nox-2 in BV-2 cells suppressed the LPS-induced ROS production and NO release.

CONCLUSION

In conclusion, it is suggested that downregulation of Nox-2 and overexpression of MKP-1 that regulate ROS and NO may form the potential therapeutic strategy for the treatment of neuroinflammation in neurodegenerative diseases.

Oxidative stress and redox modulation potential in type 1 diabetes

Redox reactions are imperative to preserving cellular metabolism yet must be strictly regulated. Imbalances between reactive oxygen species (ROS) and antioxidants can initiate oxidative stress, which without proper resolve, can manifest into disease. In type 1 diabetes (T1D), T-cell-mediated autoimmune destruction of pancreatic β-cells is secondary to the primary invasion of macrophages and dendritic cells (DCs) into the islets. Macrophages/DCs, however, are activated by intercellular ROS from resident pancreatic phagocytes and intracellular ROS formed after receptor-ligand interactions via redox-dependent transcription factors such as NF-κB. Activated macrophages/DCs ferry β-cell antigens specifically to pancreatic lymph nodes, where they trigger reactive T cells through synapse formation and secretion of proinflammatory cytokines and more ROS. ROS generation, therefore, is pivotal in formulating both innate and adaptive immune responses accountable for islet cell autoimmunity. The importance of ROS/oxidative stress as well as potential for redox modulation in the context of T1D will be discussed.

Reactive oxygen species-activated p38/ERK 1/2 MAPK signaling pathway in the Mycobacterium bovis bacillus Calmette Guérin (BCG)-induced CCL2 secretion in human monocytic cell line THP-1

BACKGROUND AND AIMS

CCL2 plays an important role in mycobacterial infection by inducing leukocyte recruitment and activation. Here we assess the role of reactive oxygen species (ROS) in the secretion of the CCL2 and the activation of mitogen-activated protein kinases (MAPKs) by human monocytic cells infected with Mycobacterium bovis bacillus Calmette Guérin (BCG).

METHODS

CCL2 mRNA and protein expression were measured by reverse transcriptase polymerase chain reaction (RT-PCR), quantitative PCR and ELISA. Kinase phosphorylation was determined by immunoblotting.

RESULTS

Treatment of human monocytic cells with M. bovis BCG activated rapid superoxide generation. mRNA expression of CCL2 was increased in M. bovis BCG-infected monocytic cells, and this increase was abrogated by administration of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenyleneiodonium (DPI). Importantly, M. bovis BCG-induced CCL2 protein secretion was also inhibited by the NADPH oxidase inhibitor DPI, the selective inhibitor of NADPH oxidase apocynin, the mitochondrial electron transfer chain subunit I inhibitor rotenone and H(2)O(2) scavenging enzyme catalase, indicating that the inhibition is through the NADPH/ROS pathway. Analysis of downstream signals showed that inhibition of NADPH oxidase inhibited M. bovis BCG-induced phosphorylation of MAPK (extracellular signal-regulated kinase (ERK) 1/2 and p38).

CONCLUSIONS

These results strongly suggest that NADPH oxidase-derived ROS-mediated activation of p38 and ERK 1/2 is essential for the M. bovis BCG-induced CCL2 production.

Ventralization of an indirect developing hemichordate by NiCl₂ suggests a conserved mechanism of dorso-ventral (D/V) patterning in Ambulacraria (hemichordates and echinoderms)

One of the earliest steps in embryonic development is the establishment of the future body axes. Morphological and molecular data place the Ambulacraria (echinoderms and hemichordates) within the Deuterostomia and as the sister taxon to chordates. Extensive work over the last decades in echinoid (sea urchins) echinoderms has led to the characterization of gene regulatory networks underlying germ layer specification and axis formation during embryogenesis. However, with the exception of recent studies from a direct developing hemichordate (Saccoglossus kowalevskii), very little is known about the molecular mechanism underlying early hemichordate development. Unlike echinoids, indirect developing hemichordates retain the larval body axes and major larval tissues after metamorphosis into the adult worm. In order to gain insight into dorso-ventral (D/V) patterning, we used nickel chloride (NiCl₂), a potent ventralizing agent on echinoderm embryos, on the indirect developing enteropneust hemichordate, Ptychodera flava. Our present study shows that NiCl₂ disrupts the D/V axis and induces formation of a circumferential mouth when treated before the onset of gastrulation. Molecular analysis, using newly isolated tissue-specific markers, shows that the ventral ectoderm is expanded at expense of dorsal ectoderm in treated embryos, but has little effect on germ layer or anterior-posterior markers. The resulting ventralized phenotype, the effective dose, and the NiCl₂ sensitive response period of Ptychodera flava, is very similar to the effects of nickel on embryonic development described in larval echinoderms. These strong similarities allow one to speculate that a NiCl₂ sensitive pathway involved in dorso-ventral patterning may be shared between echinoderms, hemichordates and a putative ambulacrarian ancestor. Furthermore, nickel treatments ventralize the direct developing hemichordate, S. kowalevskii indicating that a common pathway patterns both larval and adult body plans of the ambulacrarian ancestor and provides insight in to the origin of the chordate body plan.

Glucose Oxidase Incorporated Collagen Matrices for Dermal Wound Repair in Diabetic Rat Models: A Biochemical Study

Impaired wound healing in diabetes is a well-documented phenomenon. Emerging data favor the involvement of free radicals in the pathogenesis of diabetic wound healing. We investigated the beneficial role of the sustained release of reactive oxygen species (ROS) in diabetic dermal wound healing. In order to achieve the sustained delivery of ROS in the wound bed, we have incorporated glucose oxidase in the collagen matrix (GOIC), which is applied to the healing diabetic wound. Our in vitro proteolysis studies on incorporated GOIC show increased stability against the proteases in the collagen matrix. In this study, GOIC film and collagen film (CF) are used as dressing material on the wound of streptozotocin-induced diabetic rats. A significant increase in ROS ( p < 0.05) was observed in the fibroblast of GOIC group during the inflammation period compared to the CF and control groups. This elevated level up regulated the antioxidant status in the granulation tissue and improved cellular proliferation in the GOIC group. Interestingly, our biochemical parameters nitric oxide, hydroxyproline, uronic acid, protein, and DNA content in the healing wound showed that there is an increase in proliferation of cells in GOIC when compared to the control and CF groups. In addition, evidence from wound contraction and histology reveals faster healing in the GOIC group. Our observations document that GOIC matrices could be effectively used for diabetic wound healing therapy.

Protein misfolding and cellular stress: an overview

Cell survival and death are complex matters. Too much survival may lead to cancer and too much cell death may result in tissue degeneration. In this chapter, we will first of all focus on the cellular survival mechanisms that promote correct folding and maintenance of protein function. These mechanisms include protein quality control (PQC) systems comprising molecular chaperones and intracellular proteases in the cytosol, endoplasmatic reticulum (ER) and in the mitochondria. In addition to the PQC systems, mechanisms elicited by misfolded proteins, known as unfolded protein responses (UPRs), including induction/activation of antioxidant systems are also present in the three compartments of the cell. Second, we will discuss the mechanisms by which misfolded proteins lead to the generation of oxidative stress in the form of reactive oxygen species (ROS) and reactive nitrogen species (RNS). These species are produced mainly from superoxide (O2-) generated in the mitochondrial respiratory chain and from nitrogen oxide (NO) produced by the mitochondrial nitrogen oxide synthetase (mtNOS). Third, the effects of oxidative stress will be discussed, both with respect to mitochondrial dynamics, i.e., fission and fusion, and the related elimination of dysfunctional mitochondria by cellular cleaning systems, i.e., mitophagy or mitoptosis, and related to the generation and cellular effects of oxidatively modified proteins, which closes a vicious cycle of protein misfolding and oxidative stress.

Oxidative stress in schizophrenia: an integrated approach

Oxidative stress has been suggested to contribute to the pathophysiology of schizophrenia. In particular, oxidative damage to lipids, proteins, and DNA as observed in schizophrenia is known to impair cell viability and function, which may subsequently account for the deteriorating course of the illness. Currently available evidence points towards an alteration in the activities of enzymatic and nonenzymatic antioxidant systems in schizophrenia. In fact, experimental models have demonstrated that oxidative stress induces behavioral and molecular anomalies strikingly similar to those observed in schizophrenia. These findings suggest that oxidative stress is intimately linked to a variety of pathophysiological processes, such as inflammation, oligodendrocyte abnormalities, mitochondrial dysfunction, hypoactive N-methyl-d-aspartate receptors and the impairment of fast-spiking gamma-aminobutyric acid interneurons. Such self-sustaining mechanisms may progressively worsen producing the functional and structural consequences associated with schizophrenia. Recent clinical studies have shown antioxidant treatment to be effective in ameliorating schizophrenic symptoms. Hence, identifying viable therapeutic strategies to tackle oxidative stress and the resulting physiological disturbances provide an exciting opportunity for the treatment and ultimately prevention of schizophrenia.

A nuclear glutathione cycle within the cell cycle

The complex antioxidant network of plant and animal cells has the thiol tripeptide GSH at its centre to buffer ROS (reactive oxygen species) and facilitate cellular redox signalling which controls growth, development and defence. GSH is found in nearly every compartment of the cell, including the nucleus. Transport between the different intracellular compartments is pivotal to the regulation of cell proliferation. GSH co-localizes with nuclear DNA at the early stages of proliferation in plant and animal cells. Moreover, GSH recruitment and sequestration in the nucleus during the G1- and S-phases of the cell cycle has a profound impact on cellular redox homoeostasis and on gene expression. For example, the abundance of transcripts encoding stress and defence proteins is decreased when GSH is sequestered in the nucleus. The functions of GSHn (nuclear GSH) are considered in the present review in the context of whole-cell redox homoeostasis and signalling, as well as potential mechanisms for GSH transport into the nucleus. We also discuss the possible role of GSHn as a regulator of nuclear proteins such as histones and PARP [poly(ADP-ribose) polymerase] that control genetic and epigenetic events. In this way, a high level of GSH in the nucleus may not only have an immediate effect on gene expression patterns, but also contribute to how cells retain a memory of the cellular redox environment that is transferred through generations.

Oxidative stress drives disulfide bond formation between basic helix-loop-helix transcription factors

Basic helix-loop-helix (bHLH) transcription factors including Twist1 and E2a proteins regulate essential processes. These factors bind DNA as homo- or heterodimers and the choice of binding partners determines their functional output. To investigate potential regulators of bHLH dimerization, cells were exposed to the oxidative agent hydrogen peroxide (H(2)O(2)). Western blot analysis in the presence or absence of reducing agents, revealed that H(2)O(2) induces the rapid formation of an intermolecular disulfide bond between Twist1 homodimers and Twist/E2a proteins heterodimers. The disulfide bond is first observed between Twist1 homodimers at 25 mM H(2)O(2) and between Twist1 heterodimers at 75 mM H(2)O(2). This response is dependent upon cell density as H(2)O(2) did not induce disulfide bridge formation between bHLH proteins in cells seeded at high density. In the presence of E proteins, the formation of Twist1/E2a proteins heterodimers is favored over Twist1 homodimers, identifying an oxidative stimulus as an important factor in modulating binding partner specificity. We further demonstrated that a cysteine residue located at the C-terminus of Twist1 and E2a proteins is involved in this response. Disulfide bond formation between Twist1 homodimers significantly reduced its ability to interact with two of its binding partners, Runx2 and HDAC4, indicating that disulfide dimerization in response to H(2)O(2) has functional significance. These data support the conclusion that disulfide bond formation in response to an oxidative stimulus contributes to Twist1 homo- and heterodimerization and raises the possibility that the redox status of a cell may represent an important step in bHLH transcriptional regulation.

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.

Regulation of redox signaling by selenoproteins

The unique chemistry of oxygen has been both a resource and threat for life on Earth for at least the last 2.4 billion years. Reduction of oxygen to water allows extraction of more metabolic energy from organic fuels than is possible through anaerobic glycolysis. On the other hand, partially reduced oxygen can react indiscriminately with biomolecules to cause genetic damage, disease, and even death. Organisms in all three superkingdoms of life have developed elaborate mechanisms to protect against such oxidative damage and to exploit reactive oxygen species as sensors and signals in myriad processes. The sulfur amino acids, cysteine and methionine, are the main targets of reactive oxygen species in proteins. Oxidative modifications to cysteine and methionine can have profound effects on a protein's activity, structure, stability, and subcellular localization. Non-reversible oxidative modifications (oxidative damage) may contribute to molecular, cellular, and organismal aging and serve as signals for repair, removal, or programmed cell death. Reversible oxidation events can function as transient signals of physiological status, extracellular environment, nutrient availability, metabolic state, cell cycle phase, immune function, or sensory stimuli. Because of its chemical similarity to sulfur and stronger nucleophilicity and acidity, selenium is an extremely efficient catalyst of reactions between sulfur and oxygen. Most of the biological activity of selenium is due to selenoproteins containing selenocysteine, the 21st genetically encoded protein amino acid. The most abundant selenoproteins in mammals are the glutathione peroxidases (five to six genes) that reduce hydrogen peroxide and lipid hydroperoxides at the expense of glutathione and serve to limit the strength and duration of reactive oxygen signals. Thioredoxin reductases (three genes) use nicotinamide adenine dinucleotide phosphate to reduce oxidized thioredoxin and its homologs, which regulate a plethora of redox signaling events. Methionine sulfoxide reductase B1 reduces methionine sulfoxide back to methionine using thioredoxin as a reductant. Several selenoproteins in the endoplasmic reticulum are involved in the regulation of protein disulfide formation and unfolded protein response signaling, although their precise biological activities have not been determined. The most widely distributed selenoprotein family in Nature is represented by the highly conserved thioredoxin-like selenoprotein W and its homologs that have not yet been assigned specific biological functions. Recent evidence suggests selenoprotein W and the six other small thioredoxin-like mammalian selenoproteins may serve to transduce hydrogen peroxide signals into regulatory disulfide bonds in specific target proteins.

Effect of N-[Imino(4-morpholyl)methyl]guanidine on the oxidative status in rats with toxic hepatitis

The hepatoprotective and antioxidant properties of a synthetic biguanide N-[imino(4-morpholyl)methyl]guanidine (IMMG) were prognosticated by the method of computer prediction. Administration of IMMG was accompanied by a decrease in serum transaminase activity in rats with toxic hepatitis, which reflects inhibition of hepatocyte cytolysis. IMMG treatment was followed by a decrease in biochemiluminescence parameters reflecting the intensity of free radical oxidation. We revealed an increase in activity of aconitase, which was reduced during toxic hepatitis. The content of citrate in the liver and serum was returned to normal under these conditions. IMMG also increased activities of superoxide dismutase and catalase and total antioxidant activity in rat liver. Our results suggest that the hepatoprotective effect of IMMG is associated with its antioxidant activity.

Signal transduction pathways and transcription factors triggered by arsenic trioxide in leukemia cells

Arsenic trioxide (As(2)O(3)) is widely used to treat acute promyelocytic leukemia (APL). Several lines of evidence have indicated that As(2)O(3) affects signal transduction and transactivation of transcription factors, resulting in the stimulation of apoptosis in leukemia cells, because some transcription factors are reported to associate with the redox condition of the cells, and arsenicals cause oxidative stress. Thus, the disturbance and activation of the cellular signaling pathway and transcription factors due to reactive oxygen species (ROS) generation during arsenic exposure may explain the ability of As(2)O(3) to induce a complete remission in relapsed APL patients. In this report, we review recent findings on ROS generation and alterations in signal transduction and in transactivation of transcription factors during As(2)O(3) exposure in leukemia cells.

Molecular, genetic and epigenetic pathways of peroxynitrite-induced cellular toxicity

Oxidative stress plays a key role in the pathogenesis of cancer and many metabolic diseases; therefore, an effective antioxidant therapy would be of great importance in these circumstances. Nevertheless, convincing randomized clinical trials revealed that antioxidant supplementations were not associated with significant reduction in incidence of cancer, chronic diseases and all-cause mortality. As oxidation of essential molecules continues, it turns to nitro-oxidative stress because of the involvement of nitric oxide in pathogenesis processes. Peroxynitrite damages via several distinctive mechanisms; first, it has direct toxic effects on all biomolecules and causes lipid peroxidation, protein oxidation and DNA damage. The second mechanism involves the induction of several transcription factors leading to cytokine-induced chronic inflammation. Finally, it causes epigenetic perturbations that exaggerate nuclear factor kappa-B mediated inflammatory gene expression. Lessons-learned from the treatment of several chronic disorders including pulmonary diseases suggest that, chronic inflammation and glucocorticoid resistance are regulated by prolonged peroxynitrite production.

Regulatory regions responsive to oxidative stress in the promoter of the human DNA glycosylase gene NEIL2

Reactive oxygen species (ROS) generated endogenously or from exogenous sources produce mutagenic DNA lesions. If not repaired, these lesions could lead to genomic instability and, potentially, to cancer development. NEIL2 (EC 4.2.99.18), a mammalian base excision repair (BER) protein and ortholog of the bacterial Fpg/Nei, excises oxidized DNA lesions from bubble or single-stranded structures, suggesting its involvement in transcription-coupled DNA repair. Perturbation in NEIL2 expression may, therefore, significantly impact BER capacity and promote genomic instability. To characterize the genetic and environmental factors regulating NEIL2 gene expression, we mapped the human NEIL2 transcriptional start site and partially characterized the promoter region of the gene using a luciferase reporter assay. We identified a strong positive regulatory region from nucleotide -206 to +90 and found that expression from this region was contingent on its being isolated from an adjacent strong negative regulatory region located downstream (+49 to +710 bp), suggesting that NEIL2 transcription is influenced by both these regions. We also found that oxidative stress, induced by glucose oxidase treatment, reduced the positive regulatory region expression levels, suggesting that ROS may play a significant role in regulating NEIL2 transcription. In an initial attempt to characterize the underlying mechanisms, we used in silico analysis to identify putative cis-acting binding sites for ROS-responsive transcription factors within this region and then used site-directed mutagenesis to investigate their role. A single-base change in the region encompassing nucleotides -206 to +90 abolished the effect of oxidative stress that was observed in the absence of the mutation. Our study is the first to provide an initial partial characterization of the NEIL2 promoter and opens the door for future research aimed at understanding the role of genetic and environmental factors in regulating NEIL2 expression.

Neferine, a bisbenzylisoquinline alkaloid attenuates bleomycin-induced pulmonary fibrosis

In this study, we evaluated the potential anti-fibrotic property of neferine, a bisbenzylisoquinline alkaloid extracted from the seed embryo of Nelumbo mucifera Gaertn. Intratracheal bleomycin administration resulted in pulmonary fibrosis 14 and 21 days posttreatment, as evidenced by increased hydroxyproline content in bleomycin group (255.77+/-97.17 microg/lung and 269.74+/-40.92 microg/lung) compared to sham group (170.78+/-76.46 microg/lung and 191.24+/-60.45 microg/lung), and the hydroxyproline was significantly suppressed (193.07+/-39.55 microg/lung and 201.08+/-71.74 microg/lung) by neferine administration (20mg/kg, b.i.d). The attenuated-fibrosis condition was also validated by histological observations. Biochemical measurements revealed that bleomycin caused a significant decrease in lung superoxidae dismutase (SOD) activity, which was accompanied with a significant increase in malondialdehyde (MDA) levels and myeloperoxidase (MPO) activity on the 7th and 14th days. However, neferine reversed the decrease in SOD activity as well as the increase in MDA and MPO activity. Enzyme-linked immunosorbent assay and radio-immunity assay showed that treatment with neferine alleviated bleomycin-induced increase of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and endothelin-1 in plasma or in tissue. Additionally, neferine blocked bleomycin-induced increases of NF-kappaB in nuclear extracts and TGF-beta(1) in total protein extracts of murine RAW264.7 macrophages. In summary, neferine attenuates bleomycin-induced pulmonary fibrosis in vitro and in vivo. The beneficial effect of neferine might be associated with its activities of anti-inflammation, antioxidation, cytokine and NF-kappaB inhibition.

Hydrogen peroxide as a cell-survival signaling molecule

Reactive oxygen species (ROS) were seen as destructive molecules, but recently, they have been shown also to act as second messengers in varying intracellular signaling pathways. This review concentrates on hydrogen peroxide (H2O2), as it is a more stable ROS, and delineates its role as a survival molecule. In the first part, the production of H2O2 through the NADPH oxidase (Nox) family is investigated. Through careful examination of Nox proteins and their regulation, it is determined how they respond to stress and how this can be prosurvival rather than prodeath. The pathways on which H2O2 acts to enable its prosurvival function are then examined in greater detail. The main survival pathways are kinase driven, and oxidation of cysteines in the active sites of various phosphatases can thus regulate those survival pathways. Regulation of transcription factors such as p53, NF-kappaB, and AP-1 also are reviewed. Finally, prodeath proteins such as caspases could be directly inhibited through their cysteine residues. A better understanding of the prosurvival role of H2O2 in cells, from the why and how it is generated to the various molecules it can affect, will allow more precise targeting of therapeutics to this pathway.

Regulation of pentraxin-3 by antioxidants

BACKGROUND

Pentraxin-3 (PTX3) may be a useful biomarker in sepsis, but its regulatory mechanisms are still unclear. Oxidative stress is well defined in patients with sepsis and has a role in regulation of inflammatory pathways which may include PTX3. We undertook an in vitro study of the effect of antioxidants on regulation of PTX3 in endothelial cells combined with a prospective observational pilot study of PTX3 in relation to markers of antioxidant capacity and oxidative stress in patients with sepsis.

METHODS

Human endothelial cells were cultured with lipopolysaccharide 2 microg ml(-1), peptidoglycan G 20 microg ml(-1), tumour necrosis factor (TNF) alpha 10 ng ml(-1), interleukin-1 (IL-1) beta 20 ng ml(-1), or killed Candida albicans yeast cells plus either N-acetylcysteine (NAC) 25 mM, trolox 100 mM, or idebenone 1 microM. Plasma samples were obtained from 15 patients with sepsis and 11 healthy volunteers.

RESULTS

PTX3 levels in plasma were higher in patients with sepsis than in healthy people [26 (1-202) ng ml(-1) compared with 6 (1-12) ng ml(-1), P=0.01]. Antioxidant capacity was lower in patients with sepsis than healthy controls [0.99 (0.1-1.7) mM compared with 2.2 (1.3-3.3) mM, P=0.01]. In patients with sepsis, lipid hydroperoxide levels were 3.32 (0.3-10.6) nM and undetectable in controls. We found no relationship between PTX3 and antioxidant capacity or lipid hydroperoxides. Cell expression of PTX3 increased with all inflammatory stimulants but was highest in cells treated with TNFalpha plus IL-1beta. PTX3 concentrations were lower in cells co-treated with antioxidants (all P<0.05), associated with lower nuclear factor kappaB expression for NAC and trolox (P<0.05).

CONCLUSIONS

PTX3 expression is down-regulated in vitro by antioxidants. Plasma levels of PTX3 are elevated in sepsis but seem to be unrelated to markers of oxidant stress or antioxidant capacity.

Intracellular prooxidant activity of melatonin induces a survival pathway involving NF-kappaB activation

We have shown that melatonin exerts a prooxidant activity in U937 cells, a tumor human promonocytic cell line. (1) Here we show that melatonin induces a strong canonical activation of NF-kappaB, inducing IkappaBalpha degradation and the consequential nuclear translocation of p50/p65 subunits. The timing of NF-kappaB activation overlaps with the timing of reactive oxygen species (ROS) production due to melatonin. Overexpression of dominant-negative IkappaB, which prevents a possible NF-kappaB activation, transformed melatonin in a proapoptotic molecule. These data indicate for the first time that melatonin can trigger NF-kappaB activation and might suggest a possible role for ROS induced by melatonin. Results indicate a possible involvement in the survival pathway of melatonin-generated ROS as secondary messengers.

Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells

Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-kappaB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P(+)). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P(+) cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-kappaB more efficiently in JB6(+/+) cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6(+/+) cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

Clair DK. Regulation of superoxide dismutase genes: implications in disease

Numerous short-lived and highly reactive oxygen species (ROS) such as superoxide (O2(.-)), hydroxyl radical, and hydrogen peroxide are continuously generated in vivo. Depending upon concentration, location, and intracellular conditions, ROS can cause toxicity or act as signaling molecules. The cellular levels of ROS are controlled by antioxidant enzymes and small-molecule antioxidants. As major antioxidant enzymes, superoxide dismutases (SODs), including copper-zinc superoxide dismutase (Cu/ZnSOD), manganese superoxide dismutase, and extracellular superoxide dismutase, play a crucial role in scavenging O2(.-). This review focuses on the regulation of the sod genes coding for these enzymes, with an emphasis on the human genes. Current knowledge about sod structure and regulation is summarized and depicted as diagrams. Studies to date on genes coding for Cu/ZnSOD (sod1) are mostly focused on alterations in the coding region and their associations with amyotrophic lateral sclerosis. Evaluation of nucleotide sequences reveals that regulatory elements of the sod2 gene reside in both the noncoding and the coding region. Changes associated with sod2 lead to alterations in expression levels as well as protein function. We also discuss the structural basis for the changes in SOD expression associated with pathological conditions and where more work is needed to establish the relationship between SODs and diseases.

The depletion of nuclear glutathione impairs cell proliferation in 3t3 fibroblasts

Background

Glutathione is considered essential for survival in mammalian cells and yeast but not in prokaryotic cells. The presence of a nuclear pool of glutathione has been demonstrated but its role in cellular proliferation and differentiation is still a matter of debate.

Principal Findings

We have studied proliferation of 3T3 fibroblasts for a period of 5 days. Cells were treated with two well known depleting agents, diethyl maleate (DEM) and buthionine sulfoximine (BSO), and the cellular and nuclear glutathione levels were assessed by analytical and confocal microscopic techniques, respectively. Both agents decreased total cellular glutathione although depletion by BSO was more sustained. However, the nuclear glutathione pool resisted depletion by BSO but not with DEM. Interestingly, cell proliferation was impaired by DEM, but not by BSO. Treating the cells simultaneously with DEM and with glutathione ethyl ester to restore intracellular GSH levels completely prevented the effects of DEM on cell proliferation.

Conclusions

Our results demonstrate the importance of nuclear glutathione in the control of cell proliferation in 3T3 fibroblasts and suggest that a reduced nuclear environment is necessary for cells to progress in the cell cycle.

Metabolic defects provide a spark for the epigenetic switch in cancer

Cancer is a pathology that is associated with aberrant gene expression and an altered metabolism. Whereas changes in gene expression have historically been attributed to mutations, it has become apparent that epigenetic processes also play a critical role in controlling gene expression during carcinogenesis. Global changes in epigenetic processes, including DNA methylation and histone modifications, have been observed in cancer. These epigenetic alterations can aberrantly silence or activate gene expression during the formation of cancer; however, the process leading to this epigenetic switch in cancer remains unknown. Carcinogenesis is also associated with metabolic defects that increase mitochondrially derived reactive oxygen species, create an atypical redox state, and change the fundamental means by which cells produce energy. Here, we summarize the influence of these metabolic defects on epigenetic processes. Metabolic defects affect epigenetic enzymes by limiting the availability of cofactors like S-adenosylmethionine. Increased production of reactive oxygen species alters DNA methylation and histone modifications in tumor cells by oxidizing DNMTs and HMTs or through direct oxidation of nucleotide bases. Last, the Warburg effect and increased glutamine consumption in cancer influence histone acetylation and methylation by affecting the activity of sirtuins and histone demethylases.

Curcumin and cancer cells: how many ways can curry kill tumor cells selectively?

Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.