Transcriptional regulation of the human manganese superoxide dismutase gene: the role of specificity protein 1 (Sp1) and activating protein-2 (AP-2)

Heregulin-β1 Activates NF-E2-related Factor 2 and Induces Manganese Superoxide Dismutase Expression in Human Breast Cancer Cells via Protein Kinase B and Extracellular Signal-regulated Protein Kinase Signaling Pathways

Heregulin-β1, a ligand of ErbB-2 and ErbB-3/4 receptors, has been reported to potentiate oncogenicity and metastatic potential of breast cancer cells. In the present work, treatment of human mammary cancer (MCF-7) cells with heregulin-β1 resulted in enhanced cell migration and expression of manganese superoxide dismutase (MnSOD) and its mRNA transcript. Silencing of MnSOD abrogated clonogenicity and migrative ability of MCF-7 cells. Heregulin-β1 treatment also increased nuclear translocation, antioxidant response element binding and transcriptional activity of NF-E2-related factor 2 (Nrf2). A dominant-negative mutant of Nrf2 abrogated heregulin-β1-induced MnSOD expression. Treatment with heregulin-β1 caused activation of protein kinase B (Akt) and extracellular signal-regulated protein kinase (ERK). The pharmacological inhibitors of phosphatidylinositol 3-kinase and mitogen-activated protein kinase kinase 1/2, which are upstream of Akt and ERK, respectively, attenuated heregulin-β1-induced MnSOD expression and nuclear localization of Nrf2. In conclusion, heregulin-1 induces upregulation of MnSOD and activation of Nrf2 via the Akt and ERK signaling in MCF-7 cells, which may confer metastatic potential and invasiveness of these cells.

Manganese Superoxide Dismutase Dysfunction and the Pathogenesis of Kidney Disease

The mitochondria are a major source of reactive oxygen species (ROS). Superoxide anion (O₂^•–) is produced by the process of oxidative phosphorylation associated with glucose, amino acid, and fatty acid metabolism, resulting in the production of adenosine triphosphate (ATP) in the mitochondria. Excess production of reactive oxidants in the mitochondria, including O₂^•–, and its by-product, peroxynitrite (ONOO^–), which is generated by a reaction between O₂^•– with nitric oxide (NO^•), alters cellular function via oxidative modification of proteins, lipids, and nucleic acids. Mitochondria maintain an antioxidant enzyme system that eliminates excess ROS; manganese superoxide dismutase (Mn-SOD) is one of the major components of this system, as it catalyzes the first step involved in scavenging ROS. Reduced expression and/or the activity of Mn-SOD results in diminished mitochondrial antioxidant capacity; this can impair the overall health of the cell by altering mitochondrial function and may lead to the development and progression of kidney disease. Targeted therapeutic agents may protect mitochondrial proteins, including Mn-SOD against oxidative stress-induced dysfunction, and this may consequently lead to the protection of renal function. Here, we describe the biological function and regulation of Mn-SOD and review the significance of mitochondrial oxidative stress concerning the pathogenesis of kidney diseases, including chronic kidney disease (CKD) and acute kidney injury (AKI), with a focus on Mn-SOD dysfunction.

The HIV-Tat protein interacts with Sp3 transcription factor and inhibits its binding to a distal site of the sod2 promoter in human pulmonary artery endothelial cells

Redox imbalance results in damage to cellular macromolecules and interferes with signaling pathways, leading to an inflammatory cellular and tissue environment. As such, the cellular oxidative environment is tightly regulated by several redox-modulating pathways. Many viruses have evolved intricate mechanisms to manipulate these pathways for their benefit, including HIV-1, which requires a pro-oxidant cellular environment for optimal replication. One such virulence factor responsible for modulating the redox environment is the HIV Transactivator of transcription (Tat). Tat is of particular interest as it is actively secreted by infected cells and internalized by uninfected bystander cells where it can elicit pro-oxidant effects resulting in inflammation and damage. Previously, we demonstrated that Tat regulates basal expression of Superoxide Dismutase 2 (sod2) by altering the binding of the Sp-transcription factors at regions relatively near (approx. -210 nucleotides) upstream of the transcriptional start site. Now, using in silico analysis and a series of sod2 promoter reporter constructs, we have identified putative clusters of Sp-binding sites located further upstream of the proximal sod2 promoter, between nucleotides -3400 to -210, and tested their effect on basal transcription and for their sensitivity to HIV-1 Tat. In this report, we demonstrate that under basal conditions, maximal transcription requires a cluster of Sp-binding sites in the -584 nucleotide region, which is extremely sensitive to Tat. Using chromatin immunoprecipitation (ChIP) we demonstrate that Tat results in altered occupancy of Sp1 and Sp3 at this distal Tat-sensitive regulatory element and strongly stimulated endogenous expression of SOD2 in human pulmonary artery endothelial cells (HPAEC). We also report altered expression of Sp1 and Sp3 in Tat-expressing HPAEC as well as in the lungs of HIV-1 infected humanized mice. Lastly, Tat co-immunoprecipitated with endogenous Sp3 but not Sp1 and did not alter the acetylation state of Sp3. Thus, here, we have defined a novel and important cis-acting factor in HIV-1 Tat-mediated regulation of SOD2, demonstrated that modulation of Sp1 and Sp3 activity by Tat promotes SOD2 expression in primary human pulmonary artery endothelial cells and determined that pulmonary levels of Sp3 as well as SOD2 are increased in the lungs of a mouse model of HIV infection.

Up-regulation of microRNA-375 ameliorates the damage of dopaminergic neurons, reduces oxidative stress and inflammation in Parkinson's disease by inhibiting SP1

Background: This study is conducted to investigate the protective role of elevated microRNA-375 (miR-375) in dopaminergic neurons in Parkinson’s disease through down-regulating transcription factor specificity protein 1 (SP1).

Results: The successfully modeled rats with Parkinson’s disease showed aggregated neurobehavioral change, increased neuroinflammatory response and oxidative stress, and lowered dopamine content. Parkinson’s disease rats treated with overexpressed miR-375 displayed improved neurobehavioral change, ameliorated neuroinflammatory response and oxidative stress, heightened dopamine content and abated neuronal apoptosis by down-regulating SP1. Up-regulation of SP1 reversed the protective effect of upregulated miR-375 on Parkinson’s disease.

Conclusion: Up-regulation of miR-375 ameliorated the damage of dopaminergic neurons, reduced oxidative stress and inflammation in Parkinson’s disease by inhibiting SP1.

Methods: Parkinson’s disease rat model was established by targeted injection of 6-hydroxydopamine to damage the substantia nigra striatum. The successfully modeled Parkinson’s disease rats were intracerebroventricularly injected with miR-375 mimics or pcDNA3.1-SP1. The functions of miR-375 and SP1 in neurobehavioral change, neuroinflammatory response, oxidative stress, dopamine content and expression of apoptosis-related proteins in the substantia nigra of Parkinson’s disease rats were evaluated. The target relation of miR-375 and SP1 was confirmed by bioinformatics analysis and dual luciferase reporter gene assay.

Entrainment of superoxide rhythm by menadione in HCT116 colon cancer cells

Reactive oxygen species (ROS) are primary effectors of cytotoxicity induced by many anti-cancer drugs. Rhythms in the pseudo-steady-state (PSS) levels of particular intracellular ROS in cancer cells and their relevance to drug effectiveness are unknown thus far. We report that the PSS levels of intracellular superoxide (SOX), an important ROS, exhibit an inherent rhythm in HCT116 colon cancer cells, which is entrained (reset) by the SOX inducer, menadione (MD). This reset was dependent on the expression of p53, and it doubled the sensitivity of the cells to MD. The period of oscillation was found to have a linear correlation with MD concentration, given by the equation, T, in h = 23.52 - 1.05 [MD concentration in µM]. Further, we developed a mathematical model to better understand the molecular mechanisms involved in rhythm reset. Biologically meaningful parameters were obtained through parameter estimation techniques; the model can predict experimental profiles of SOX, establish qualitative relations between interacting species in the system and serves as an important tool to understand the profiles of various species. The model was also able to successfully predict the rhythm reset in MD treated hepatoma cell line, HepG2.

Carcinogenesis and Reactive Oxygen Species Signaling: Interaction of the NADPH Oxidase NOX1-5 and Superoxide Dismutase 1-3 Signal Transduction Pathways

SIGNIFICANCE

Reduction/oxidation (redox) balance could be defined as an even distribution of reduction and oxidation complementary processes and their reaction end products. There is a consensus that aberrant levels of reactive oxygen species (ROS), commonly observed in cancer, stimulate primary cell immortalization and progression of carcinogenesis. However, the mechanism how different ROS regulate redox balance is not completely understood. Recent Advances: In the current review, we have summarized the main signaling cascades inducing NADPH oxidase NOX1-5 and superoxide dismutase (SOD) 1-3 expression and their connection to cell proliferation, immortalization, transformation, and CD34+ cell differentiation in thyroid, colon, lung, breast, and hematological cancers.

CRITICAL ISSUES

Interestingly, many of the signaling pathways activating redox enzymes or mediating the effect of ROS are common, such as pathways initiated from G protein-coupled receptors and tyrosine kinase receptors involving protein kinase A, phospholipase C, calcium, and small GTPase signaling molecules.

FUTURE DIRECTIONS

The clarification of interaction of signal transduction pathways could explain how cells regulate redox balance and may even provide means to inhibit the accumulation of harmful levels of ROS in human pathologies.

QTL Mapping of Genome Regions Controlling Manganese Uptake in Lentil Seed

This study evaluated Mn concentration in the seeds of 120 RILs of lentil developed from the cross “CDC Redberry” × “ILL7502”. Micronutrient analysis using atomic absorption spectrometry indicated mean seed manganese (Mn) concentrations ranging from 8.5 to 26.8 mg/kg, based on replicated field trials grown at three locations in Turkey in 2012 and 2013. A linkage map of lentil was constructed and consisted of seven linkage groups with 5,385 DNA markers. The total map length was 973.1 cM, with an average distance between markers of 0.18 cM. A total of 6 QTL for Mn concentration were identified using composite interval mapping (CIM). All QTL were statistically significant and explained 15.3–24.1% of the phenotypic variation, with LOD scores ranging from 3.00 to 4.42. The high-density genetic map reported in this study will increase fundamental knowledge of the genome structure of lentil, and will be the basis for the development of micronutrient-enriched lentil genotypes to support biofortification efforts.

Insights into the Dichotomous Regulation of SOD2 in Cancer

While loss of antioxidant expression and the resultant oxidant-dependent damage to cellular macromolecules is key to tumorigenesis, it has become evident that effective oxidant scavenging is conversely necessary for successful metastatic spread. This dichotomous role of antioxidant enzymes in cancer highlights their context-dependent regulation during different stages of tumor development. A prominent example of an antioxidant enzyme with such a dichotomous role and regulation is the mitochondria-localized manganese superoxide dismutase SOD2 (MnSOD). SOD2 has both tumor suppressive and promoting functions, which are primarily related to its role as a mitochondrial superoxide scavenger and H₂O₂ regulator. However, unlike true tumor suppressor- or onco-genes, the SOD2 gene is not frequently lost, or rarely mutated or amplified in cancer. This allows SOD2 to be either repressed or activated contingent on context-dependent stimuli, leading to its dichotomous function in cancer. Here, we describe some of the mechanisms that underlie SOD2 regulation in tumor cells. While much is known about the transcriptional regulation of the SOD2 gene, including downregulation by epigenetics and activation by stress response transcription factors, further research is required to understand the post-translational modifications that regulate SOD2 activity in cancer cells. Moreover, future work examining the spatio-temporal nature of SOD2 regulation in the context of changing tumor microenvironments is necessary to allows us to better design oxidant- or antioxidant-based therapeutic strategies that target the adaptable antioxidant repertoire of tumor cells.

Specificity protein 1-modulated superoxide dismutase 2 enhances temozolomide resistance in glioblastoma, which is independent of O6-methylguanine-DNA methyltransferase

Acquisition of temozolomide (TMZ) resistance is a major factor leading to the failure of glioblastoma (GBM) treatment. The exact mechanism by which GBM evades TMZ toxicity is not always related to the expression of the DNA repair enzyme O⁶-methylguanine-DNA methyltransferase (MGMT), and so remains unclear. In this study, TMZ-resistant variants derived from MGMT-negative GBM clinical samples and cell lines were studied, revealing there to be increased specificity protein 1 (Sp1) expression associated with reduced reactive oxygen species (ROS) accumulation following TMZ treatment. Analysis of gene expression databases along with cell studies identified the ROS scavenger superoxide dismutase 2 (SOD2) as being disease-related. SOD2 expression was also increased, and it was found to be co-expressed with Sp1 in TMZ-resistant cells. Investigation of the SOD2 promoter revealed Sp1 as a critical transcriptional activator that enhances SOD2 gene expression. Co-treatment with an Sp1 inhibitor restored the inhibitory effects of TMZ, and decreased SOD2 levels in TMZ-resistant cells. This treatment strategy restored susceptibility to TMZ in xenograft animals, leading to prolonged survival in an orthotopic model. Thus, our results suggest that Sp1 modulates ROS scavengers as a novel mechanism to increase cancer malignancy and resistance to chemotherapy. Inhibition of this pathway may represent a potential therapeutic target for restoring treatment susceptibility in GBM.

Specificity protein 1-zinc finger protein 179 pathway is involved in the attenuation of oxidative stress following brain injury

After sudden traumatic brain injuries, secondary injuries may occur during the following days or weeks, which leads to the accumulation of reactive oxygen species (ROS). Since ROS exacerbate brain damage, it is important to protect neurons against their activity. Zinc finger protein 179 (Znf179) was shown to act as a neuroprotective factor, but the regulation of gene expression under oxidative stress remains unknown. In this study, we demonstrated an increase in Znf179 protein levels in both in vitro model of hydrogen peroxide (H₂O₂)-induced ROS accumulation and animal models of traumatic brain injury. Additionally, we examined the sub-cellular localization of Znf179, and demonstrated that oxidative stress increases Znf179 nuclear shuttling and its interaction with specificity protein 1 (Sp1). Subsequently, the positive autoregulation of Znf179 expression, which is Sp1-dependent, was further demonstrated using luciferase reporter assay and green fluorescent protein (GFP)-Znf179-expressing cells and transgenic mice. The upregulation of Sp1 transcriptional activity induced by the treatment with nerve growth factor (NGF) led to an increase in Znf179 levels, which further protected cells against H₂O₂-induced damage. However, Sp1 inhibitor, mithramycin A, was shown to inhibit NGF effects, leading to a decrease in Znf179 expression and lower cellular protection. In conclusion, the results obtained in this study show that Znf179 autoregulation through Sp1-dependent mechanism plays an important role in neuroprotection, and NGF-induced Sp1 signaling may help attenuate more extensive (ROS-induced) damage following brain injury.

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Znf179 levels increase in vitro after hydrogen peroxide treatment.

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Znf179 levels increase in vivo in traumatic brain injury mouse model.

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Oxidative stress increases Znf179 translocation to nucleus.

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Znf179 autoregulates its expression through Sp1-dependent mechanism.

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Sp1-Znf179 pathway plays an important role in neuroprotection.

Down-regulation of EPHX2 gene transcription by Sp1 under high-glucose conditions

sEH (soluble epoxide hydrolase), which is encoded by the EPHX2 gene, regulates the actions of bioactive lipids, EETs (epoxyeicosatrienoic acids). Previously, we found that high-glucose-induced oxidative stress suppressed sEH levels in a hepatocarcinoma cell line (Hep3B) and sEH was decreased in streptozotocin-induced diabetic mice in vivo. In the present study, we investigated the regulatory mechanisms underlying EPHX2 transcriptional suppression under high-glucose conditions. The decrease in sEH was prevented by an Sp1 (specificity protein 1) inhibitor, mithramycin A, and overexpression or knockdown of Sp1 revealed that Sp1 suppressively regulated sEH expression, in contrast with the general role of Sp1 on transcriptional activation. In addition, we found that AP2α (activating protein 2α) promoted EPHX2 transcription. The nuclear transport of Sp1, but not that of AP2α, was increased under high glucose concomitantly with the decrease in sEH. Within the EPHX2 promoter -56/+32, five Sp1-binding sites were identified, and the mutation of each of these sites showed that the first one (SP1_1) was important in both suppression by Sp1 and activation by AP2α. Furthermore, overexpression of Sp1 diminished the binding of AP2α by DNA-affinity precipitation assay and ChIP, suggesting competition between Sp1 and AP2α on the EPHX2 promoter. These findings provide novel insights into the role of Sp1 in transcriptional suppression, which may be applicable to the transcriptional regulation of other genes.

Oxygen in human health from life to death--An approach to teaching redox biology and signaling to graduate and medical students

In the absence of oxygen human life is measured in minutes. In the presence of oxygen, normal metabolism generates reactive species (ROS) that have the potential to cause cell injury contributing to human aging and disease. Between these extremes, organisms have developed means for sensing oxygen and ROS and regulating their cellular processes in response. Redox signaling contributes to the control of cell proliferation and death. Aberrant redox signaling underlies many human diseases. The attributes acquired by altered redox homeostasis in cancer cells illustrate this particularly well. This teaching review and the accompanying illustrations provide an introduction to redox biology and signaling aimed at instructors of graduate and medical students.

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The ability to sense oxygen and respond to oxidative stress is ancient.

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Chemical and kinetic properties of ROS are key to understanding redox signaling.

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Redox signaling participates in normal control of cell proliferation and death.

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Aberrant redox signaling contributes to the hallmarks of cancer.

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Novel redox-based chemotherapeutics are being developed.

MnTM-4-PyP modulates endogenous antioxidant responses and protects primary cortical neurons against oxidative stress

AIMS

Oxidative stress is a direct cause of injury in various neural diseases. Manganese porphyrins (MnPs), a large category of superoxide dismutase (SOD) mimics, shown universally to have effects in numerous neural disease models in vivo. Given their complex intracellular redox activities, detailed mechanisms underlying the biomedical efficacies are not fully elucidated. This study sought to investigate the regulation of endogenous antioxidant systems by a MnP (MnTM-4-PyP) and its role in the protection against neural oxidative stress.

METHODS

Primary cortical neurons were treated with MnTM-4-PyP prior to hydrogen peroxide-induced oxidative stress.

RESULTS

MnTM-4-PyP increased cell viability, reduced intracellular level of reactive oxygen species, inhibited mitochondrial apoptotic pathway, and ameliorated endoplasmic reticulum function. The protein levels and activities of endogenous SODs were elevated, but not those of catalase. SOD2 transcription was promoted in a transcription factor-specific manner. Additionally, we found FOXO3A and Sirt3 levels also increased. These effects were not observed with MnTM-4-PyP alone.

CONCLUSION

Induction of various levels of endogenous antioxidant responses by MnTM-4-PyP has indispensable functions in its protection for cortical neurons against hydrogen peroxide-induced oxidative stress.

A novel murrel Channa striatus mitochondrial manganese superoxide dismutase: gene silencing, SOD activity, superoxide anion production and expression

We have reported the molecular characterization including gene silencing, superoxide activity, superoxide anion production, gene expression and molecular characterization of a mitochondrial manganese superoxide dismutase (mMnSOD) from striped murrel Channa striatus (named as CsmMnSOD). The CsmMnSOD polypeptide contains 225 amino acids with a molecular weight of 25 kDa and a theoretical isoelectric point of 8.3. In the N-terminal region, CsmMnSOD carries a mitochondrial targeting sequence and a superoxide dismutases (SOD) Fe domain (28-109), and in C-terminal region, it carries another SOD Fe domain (114-220). The CsmMnSOD protein sequence shared significant similarity with its homolog of MnSOD from rock bream Oplegnathus fasciatus (96%). The phylogenetic analysis showed that the CsmMnSOD fell in the clade of fish mMnSOD group. The monomeric structure of CsmMnSOD possesses 9 α-helices (52.4%), 3 β-sheets (8.8%) and 38.8% random coils. The highest gene expression was noticed in liver, and its expression was inducted with fungal (Aphanomyces invadans) and bacterial (Aeromonas hydrophila) infections. The gene silencing results show that the fish that received dsRNA exhibited significant (P < 0.05) changes in expression when compared to their non-injected and fish physiological saline-injected controls. The SOD activity shows that the activity increases with the spread of infection and decreases once the molecule controls the pathogen. The capacity of superoxide anion production was determined by calculating the granular blood cell count during infection in murrel. It shows that the infection influenced the superoxide radical production which plays a major role in killing the pathogens. Overall, this study indicated the defense potentiality of CsmMnSOD; however, further research is necessary to explore its capability at protein level.

RORα decreases oxidative stress through the induction of SOD2 and GPx1 expression and thereby protects against nonalcoholic steatohepatitis in mice

AIMS

Increased hepatic oxidative stress and inflammation is the main cause of exacerbating nonalcoholic steatohepatitis (NASH). Retinoic acid-related orphan receptor α (RORα) regulates diverse target genes associated with lipid metabolism, and its expression level is low in the liver of patients with NASH. Here, we investigated the role of RORα in regulating hepatic oxidative stress and inflammation.

RESULTS

First, cholesterol sulfate (CS), an agonist of RORα, lowered oxidative stress that was induced by 1.5 mM oleic acid in the primary cultures of hepatocytes. Second, exogenously introduced RORα or CS treatment induced the mRNA level of antioxidant enzymes, superoxide dismutase 2 (SOD2) and glutathione peroxidase 1 (GPx1), through the RORα response elements located in the upstream promoters of Sod2 and Gpx1. Third, RORα significantly decreased reactive oxygen species levels and mRNA levels of tumor necrosis factor α (TNFα) and interleukin-1β that were induced by lipopolysaccharide or TNFα in Kupffer cells. Finally, the administration of JC1-40 decreased the signs of liver injury, lipid peroxidation, and inflammation in the MCD diet-induced NASH mice.

INNOVATION AND CONCLUSION

We showed for the first time that RORα and its ligands protect NASH in mice by reducing hepatic oxidative stress and inflammation. Further, the molecular mechanism of the protective function of RORα against oxidative stress in the liver was revealed. These findings may offer a rationale for developing therapeutic strategies against NASH using RORα ligands.

FUsed in sarcoma is a novel regulator of manganese superoxide dismutase gene transcription

AIMS

FUsed in sarcoma (FUS) is a multifunctional DNA/RNA-binding protein that possesses diverse roles, such as RNA splicing, RNA transport, DNA repair, translation, and transcription. The network of enzymes and processes regulated by FUS is far from being fully described. In this study, we have focused on the mechanisms of FUS-regulated manganese superoxide dismutase (MnSOD) gene transcription.

RESULTS

Here we demonstrate that FUS is a component of the transcription complex that regulates the expression of MnSOD. Overexpression of FUS increased MnSOD expression in a dose-dependent manner and knockdown of FUS by siRNA led to the inhibition of MnSOD gene transcription. Reporter analyses, chromatin immunoprecipitation assay, electrophoretic mobility shift assay, affinity chromatography, and surface plasmon resonance analyses revealed the far upstream region of MnSOD promoter as an important target of FUS-mediated MnSOD transcription and confirmed that FUS binds to the MnSOD promoter and interacts with specificity protein 1 (Sp1). Importantly, overexpression of familial amyotropic lateral sclerosis (fALS)-linked R521G mutant FUS resulted in a significantly reduced level of MnSOD expression and activity, which is consistent with the decline in MnSOD activity observed in fibroblasts from fALS patients with the R521G mutation. R521G-mutant FUS abrogates MnSOD promoter-binding activity and interaction with Sp1.

INNOVATION AND CONCLUSION

This study identifies FUS as playing a critical role in MnSOD gene transcription and reveals a previously unrecognized relationship between MnSOD and mutant FUS in fALS.

Modulation of MnSOD in Cancer:Epidemiological and Experimental Evidence

Since it was first observed in late 1970s that human cancers often had decreased manganese superoxide dismutase (MnSOD) protein expression and activity, extensive studies have been conducted to verify the association between MnSOD and cancer. Significance of MnSOD as a primary mitochondrial antioxidant enzyme is unquestionable; results from in vitro, in vivo and epidemiological studies are in harmony. On the contrary, studies regarding roles of MnSOD in cancer often report conflicting results. Although putative mechanisms have been proposed to explain how MnSOD regulates cellular proliferation, these mechanisms are not capitulated in epidemiological studies. This review discusses most recent epidemiological and experimental studies that examined the association between MnSOD and cancer, and describes emerging hypotheses of MnSOD as a mitochondrial redox regulatory enzyme and of how altered mitochondrial redox may affect physiology of normal as well as cancer cells.

B-cell translocation gene 2 mediates crosstalk between PI3K/Akt1 and NFκB pathways which enhances transcription of MnSOD by accelerating IκBα degradation in normal and cancer cells

BACKGROUND

B-cell translocation gene 2 (BTG2) belongs to antiproliferative (ARPO) gene family and the expression of BTG2, human ortholog of rat PC3 and mouse TIS21 gene, has been shown to render cancer cells more sensitive to doxorubicin treatment by upregulating MnSOD expression without regulating any other reactive oxygen species (ROS) scavenging enzymes.

RESULTS

In the present study, by employing exogenous and endogenous BTG2/TIS21/Pc3 expression by transfection and transduction analyses, and by knockdown of gene expression using RNA interference or using gene knockout cells, we observed that BTG2 increased the binding of activated NF-κB (p65/RelA) to the enhancer element of MnSOD gene in the 2nd intron, which was regulated by p-Akt1, and the induction of MnSOD by BTG2 was accompanied with subsequent downregulation of ROS level and cyclin B1 biosynthesis along with the increase of p21WAF1, resulting in the G2/M arrest independent of p53.

CONCLUSIONS

These results show for the first time that BTG2 mediates crosstalk between PI3K-Akt1 and NF-κB pathways, which regulates p53-independent induction of G2/M phase arrest both in normal and cancer cells.

Curbing cancer's sweet tooth: is there a role for MnSOD in regulation of the Warburg effect?

Reactive oxygen species (ROS), while vital for normal cellular function, can have harmful effects on cells, leading to the development of diseases such as cancer. The Warburg effect, the shift from oxidative phosphorylation to glycolysis, even in the presence of adequate oxygen, is an important metabolic change that confers many growth and survival advantages to cancer cells. Reactive oxygen species are important regulators of the Warburg effect. The mitochondria-localized antioxidant enzyme manganese superoxide dismutase (MnSOD) is vital to survival in our oxygen-rich atmosphere because it scavenges mitochondrial ROS. MnSOD is important in cancer development and progression. However, the significance of MnSOD in the regulation of the Warburg effect is just now being revealed, and it may significantly impact the treatment of cancer in the future.

Epigenetic modification of Sod2 in the development of diabetic retinopathy and in the metabolic memory: role of histone methylation

PURPOSE

Mitochondrial superoxide levels are elevated in the retina in diabetes, and their scavenging enzyme, MnSOD, becomes subnormal. The objective of this study is to investigate the role of histone methylation of Sod2, the gene that encodes MnSOD, in the development of diabetic retinopathy and in the metabolic memory phenomenon associated with its continued progression after termination of hyperglycemia.

METHODS

Effect of high glucose on monomethyl H3K4 (H3K4me1), dimethyl H3K4 (H3K4me2), and lysine-specific demethylase-1 (LSD1) was quantified at Sod2 by chromatin immunoprecipitation in isolated retinal endothelial cells. The role of histone methylation in the metabolic memory phenomenon was investigated in the retina of rats maintained in poor glycemic control (PC, approximately 12% glycated hemoglobin [GHb]) for 3 months followed by in good glycemic control (GC, approximately 6% GHb) for 3 months.

RESULTS

Hyperglycemia reduced H3K4me1 and -me2, and increased the binding of LSD1 and Sp1 at Sod2. Regulation of LSD1 by LSD1-siRNA ameliorated glucose-induced decrease in H3K4 methylation at Sod2, and prevented decrease in Sod2 gene expression. In rats, re-institution of GC failed to reverse decrease in H3K4me1 and -me2 at Sod2, and LSD1 remained active with increased binding of LSD1 and Sp1 at Sod2. Retina from human donors with diabetic retinopathy also had decreased H3K4me2 and increased LSD1 at Sod2.

CONCLUSIONS

Histone methylation of retinal Sod2 has an important role in the development of diabetic retinopathy and in the metabolic memory phenomenon associated with its continued progression. Targeting enzymes important for histone methylation may serve as a potential therapy to halt the development of diabetic retinopathy.

A manganese superoxide dismutase with potent antioxidant activity identified from Oplegnathus fasciatus: genomic structure and transcriptional characterization

In this study, we describe the identification and characterization of manganese superoxide dismutase, an important antioxidant enzyme acting as the chief reactive oxygen species (ROS) scavenger, from rock bream Oplegnathus fasciatus (Of-mMnSOD) at genomic- and transcriptional-levels as well as the biological activity of recombinant protein. The Of-mMnSOD protein portrayed distinct MnSOD family features including signature motifs, metal association sites and the typical active site topology. It was also predicted to be localized in mitochondrial matrix. The Of-mMnSOD had a quinquepartite genome organization encompassing five exons interrupted by four introns. Comparison of its sequence and gene structure with that of other lineages emphasized its strong conservation among different vertebrates. The Of-mMnSOD was ubiquitously transcribed in different rock bream tissues with higher levels in blood cells and metabolically active tissues. Transcription of Of-mMnSOD was kinetically modulated in response to investigational challenges using mitogens (lipopolysaccharide and poly I:C) and live-pathogens (Edwardsiella tarda and rock bream irido virus) in blood cells and liver tissue. The purified recombinant Of-mMnSOD possessed potential antioxidant capacity and actively survived over a range of pH (7.5-11) and temperature (15-40 °C) conditions. Collectively, findings of this study suggest that Of-mMnSOD combats against oxidative stress and cellular damages induced by mitogen/pathogen-mediated inflammation, by detoxifying harmful ROS (O(2)(●-)) in rock bream.

CyclinB1/Cdk1 phosphorylates mitochondrial antioxidant MnSOD in cell adaptive response to radiation stress

Manganese superoxide dismutase (MnSOD), a major antioxidant enzyme within the mitochondria, is responsible for the detoxification of free radicals generated by cellular metabolism and environmental/therapeutic irradiation. Cell cycle-dependent kinase Cdk1, along with its regulatory partner CyclinB1, plays important roles in the regulation of cell cycle progression as well as in genotoxic stress response. Herein, we identified the presence of the minimal Cdk1 phosphorylation consensus sequence ([S/T]-P; Ser106) in human MnSOD, suggesting Cdk1 as a potential upstream kinase of MnSOD. A substantial amount of CyclinB1/Cdk1 was found to localize in the mitochondrion upon irradiation. The enhanced Cdk1/MnSOD interaction and MnSOD phosphorylation were detected in both the irradiated human cells and mouse tissues. We report that CyclinB1/Cdk1 can regulate MnSOD through reversible Ser106 phosphorylation, both in vivo and in vitro. The CyclinB1/Cdk1-mediated MnSOD Ser106 resulted in increased MnSOD activity and stability, along with improved mitochondrial function and cellular resistance to radiation-induced apoptosis. These results demonstrate a unique pro-survival mechanism by which cells enhance the survival via CyclinB1/Cdk1-mediated MnSOD activation under genotoxic stress conditions.

Superoxide dismutase 3 is induced by antioxidants, inhibits oxidative DNA damage and is associated with inhibition of estrogen-induced breast cancer

Epidemiological data and studies in rodent models strongly support the role of estrogens in the development of breast cancers. Oxidative stress has been implicated in this carcinogenic process. We have recently demonstrated that antioxidants vitamin C or butylated hydroxyanisole (BHA) severely inhibit 17β-estradiol (E2)-induced breast tumor development in female ACI rats. The objective of this study was to characterize the mechanism of antioxidant-mediated prevention of breast cancer. Female August Copenhagen Irish (ACI) rats were treated with E2, vitamin C, vitamin C + E2, BHA and BHA + E2 for up to 8 months. Superoxide dismutase 3 (SOD3) was suppressed in E2-exposed mammary tissues and in mammary tumors of rats treated with E2. This suppression was overcome by co-treatment of rats with E2 and vitamin C or BHA. 8-Hydroxydeoxyguanosine (8-OHdG) levels determined as a marker of oxidative DNA damage were higher in E2-exposed mammary tissues and in mammary tumors compared with age-matched controls. Vitamin C or BHA treatment significantly decreased E2-mediated increase in 8-OHdG levels in the mammary tissues and in MCF-10A cells. Increased DNA damage, colony and mammosphere formation, and migration in SOD3 knocked down MCF-10A cells, and nuclear translocation of SOD3 in vitamin C-treated mammary tissues and in MCF-10A cells suggest protective role of SOD3 against DNA damage and mammary carcinogenesis. Our studies further demonstrate that SOD3, but not SOD2 and SOD1, is induced by antioxidants and is regulated through NRF2. SOD3 may thus be an important gene in defense against oxidative stress and in the prevention of estrogen-mediated breast cancer.

Manganese superoxide dismutase regulation and cancer

Mitochondria are the power plants of the eukaryotic cell and the integrators of many metabolic activities and signaling pathways important for the life and death of a cell. Normal aerobic cells use oxidative phosphorylation to generate ATP, which supplies energy for metabolism. To drive ATP production, electrons are passed along the electron transport chain, with some leaking as superoxide during the process. It is estimated that, during normal respiration, intramitochondrial superoxide concentrations can reach 10⁻¹² M. This extremely high level of endogenous superoxide production dictates that mitochondria are equipped with antioxidant systems that prevent consequential oxidative injury to mitochondria and maintain normal mitochondrial functions. The major antioxidant enzyme that scavenges superoxide anion radical in mitochondria is manganese superoxide dismutase (MnSOD). Extensive studies on MnSOD have demonstrated that MnSOD plays a critical role in the development and progression of cancer. Many human cancer cells harbor low levels of MnSOD proteins and enzymatic activity, whereas some cancer cells possess high levels of MnSOD expression and activity. This apparent variation in MnSOD level among cancer cells suggests that differential regulation of MnSOD exists in cancer cells and that this regulation may be linked to the type and stage of cancer development. This review summarizes current knowledge of the relationship between MnSOD levels and cancer with a focus on the mechanisms regulating MnSOD expression.

Clair DK. Manganese superoxide dismutase: beyond life and death

Manganese superoxide dismutase (MnSOD) is a nuclear-encoded antioxidant enzyme that localizes to the mitochondria. Expression of MnSOD is essential for the survival of aerobic life. Transgenic mice expressing a luciferase reporter gene under the control of the human MnSOD promoter demonstrate that the level of MnSOD is reduced prior to the formation of cancer. Overexpression of MnSOD in transgenic mice reduces the incidences and multiplicity of papillomas in a DMBA/TPA skin carcinogenesis model. However, MnSOD deficiency does not lead to enhanced tumorigenicity of skin tissue similarly treated because MnSOD can modulate both the p53-mediated apoptosis and AP-1-mediated cell proliferation pathways. Apoptosis is associated with an increase in mitochondrial levels of p53 suggesting a link between MnSOD deficiency and mitochondrial-mediated apoptosis. Activation of p53 is preventable by application of a SOD mimetic (MnTE-2-PyP(5+)). Thus, p53 translocation to mitochondria and subsequent inactivation of MnSOD explain the observed mitochondrial dysfunction that leads to transcription-dependent mechanisms of p53-induced apoptosis. Administration of MnTE-2-PyP(5+) following apoptosis but prior to proliferation leads to suppression of protein carbonyls and reduces the activity of AP-1 and the level of the proliferating cellular nuclear antigen, without reducing the activity of p53 or DNA fragmentation following TPA treatment. Remarkably, the incidence and multiplicity of skin tumors are drastically reduced in mice that receive MnTE-2-PyP(5+) prior to cell proliferation. The results demonstrate the role of MnSOD beyond its essential role for survival and suggest a novel strategy for an antioxidant approach to cancer intervention.

Manganese superoxide dismutase is a p53-regulated gene that switches cancers between early and advanced stages

Manganese superoxide dismutase (MnSOD) plays a critical role in the survival of aerobic life, and its aberrant expression has been implicated in carcinogenesis and tumor resistance to therapy. However, despite extensive studies in MnSOD regulation and its role in cancer, when and how the alteration of MnSOD expression occurs during the process of tumor development in vivo are unknown. Here, we generated transgenic mice expressing a luciferase reporter gene under the control of human MnSOD promoter-enhancer elements and investigated the changes of MnSOD transcription using the 7,12-dimethylbenz(α)anthracene (DMBA)/12-O-tetradecanoylphorbol-l3-acetate (TPA) multistage skin carcinogenesis model. The results show that MnSOD expression was suppressed at a very early stage but increased at late stages of skin carcinogenesis. The suppression and subsequent restoration of MnSOD expression were mediated by two transcription-factors, Sp1 and p53. Exposure to DMBA and TPA activated p53 and decreased MnSOD expression via p53-mediated suppression of Sp1 binding to the MnSOD promoter in normal-appearing skin and benign papillomas. In squamous cell carcinomas, Sp1 binding increased because of the loss of functional p53. We used chromatin immunoprecipitation, electrophoretic mobility shift assay, and both knockdown and overexpression of Sp1 and p53 to verify their roles in the expression of MnSOD at each stage of cancer development. The results identify MnSOD as a p53-regulated gene that switches between early and advanced stages of cancer. These findings also provide strong support for the development of means to reactivate p53 for the prevention of tumor progression.

The role of manganese superoxide dismutase in inflammation defense

Antioxidant enzymes maintain cellular redox homeostasis. Manganese superoxide dismutase (MnSOD), an enzyme located in mitochondria, is the key enzyme that protects the energy-generating mitochondria from oxidative damage. Levels of MnSOD are reduced in many diseases, including cancer, neurodegenerative diseases, and psoriasis. Overexpression of MnSOD in tumor cells can significantly attenuate the malignant phenotype. Past studies have reported that this enzyme has the potential to be used as an anti-inflammatory agent because of its superoxide anion scavenging ability. Superoxide anions have a proinflammatory role in many diseases. Treatment of a rat model of lung pleurisy with the MnSOD mimetic MnTBAP suppressed the inflammatory response in a dose-dependent manner. In this paper, the mechanisms underlying the suppressive effects of MnSOD in inflammatory diseases are studied, and the potential applications of this enzyme and its mimetics as anti-inflammatory agents are discussed.

Dual function of protein kinase C (PKC) in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced manganese superoxide dismutase (MnSOD) expression: activation of CREB and FOXO3a by PKC-alpha phosphorylation and by PKC-mediated inactivation of Akt, respectively

12-O-tetradecanoylphorbol-13-acetate (TPA) has been shown to induce transcriptional activation of human manganese superoxide dismutase (MnSOD) mRNA in human lung carcinoma cells, A549, mediated by a protein kinase C (PKC)-dependent activation of cAMP-responsive element-binding protein (CREB)-1/ATF-1-like factors. In this study, we showed that MnSOD protein expression was elevated in response to TPA or TNF-α, but not to hydrogen peroxide treatment. TPA-induced generation of reactive oxygen species (ROS) was blocked by pretreatment of the PKC inhibitor BIM and NADPH oxidase inhibitor DPI. Small interfering RNA (siRNA) experiments indicated that knocking down the NADPH oxidase components e.g. Rac1, p22(phox), p67(phox), and NOXO1 in A549 cells impaired TPA-induced MnSOD expression. To identify the PKC isozyme involved, we used a sod2 gene response reporter plasmid, pSODLUC-3340-I2E-C, capable of sensing the effect of TNF-α and TPA, to monitor the effects of PKC isozyme-specific inhibitors and siRNA-induced knockdown of specific PKC isozyme. Our data indicate that TPA-induced MnSOD expression was independent of p53 and most likely mediated by PKC-α-, and -ε-dependent signaling pathways. Furthermore, siRNA-induced knock-down of CREB and Forkhead box class O (FOXO) 3a led to a reduction in TPA-induced MnSOD gene expression. Together, our results revealed that TPA up-regulates, in part, two PKC-dependent transcriptional pathways to induce MnSOD expression. One pathway involves PKC-α catalyzed phosphorylation of CREB and the other involves a PKC-mediated the PP2A catalyzed dephosphorylation of Akt at Ser(473) which in turn leads to FOXO3a Ser(253) dephosphorylation and its activation.

Regulation of the high basal expression of the manganese superoxide dismutase gene in aggressive breast cancer cells

A high basal expression of manganese superoxide dismutase (MnSOD) has been reported in aggressive breast cancer cells, according to an unknown mechanism, and contributes to their invasive abilities. Here, we report the involvement of Sp1 and nuclear factor-κB (NF-κB) transcription factors in this high basal expression of MnSOD in aggressive breast cancer cells. Suppression or inactivation of Sp1 showed that it plays an essential role in the high MnSOD expression in aggressive breast cancer cells through a unique binding site identified by chromatin immunoprecipitation (ChIP) assay and functional analysis of the MnSOD proximal promoter. Treatment of cells with a specific NF-κB inhibitor peptide decreased significantly high basal MnSOD expression. A ChIP assay showed binding of a constitutive p50/p65 NF-κB complex to the MnSOD intronic enhancer element, associated with hyperacetylation of the H3 histone. Finally, high basal expression of MnSOD resulted in the lack of expression of Damaged DNA binding 2 (DDB2) protein in aggressive breast cancer cells. DDB2 overexpression prevented the binding of Sp1 as well as of NF-κB to their respective elements on the MnSOD gene. These results contribute to a better understanding of MnSOD up-regulation, which may be clinically important in the prediction of breast tumor progression.

Hypoxia activates constitutive luciferase reporter constructs

Hypoxia has been identified as a contributing factor in the pathophysiology of several diseases and oxygen regulation is important during stem cell development, particularly in early embryogenesis. One aspect that has emerged is the role of hypoxia-inducible factors, or HIFs in regulating the effect of hypoxia. Studies in our laboratory sought to examine the hypoxic regulation of HIF activity in placental trophoblast cells, through the use of dual-reporter luciferase assays. Our study demonstrates that hypoxic conditions cause a significant increase in the level of constitutive luciferase reporter activity. We also show that this induction is not a cell type or species-specific phenomenon and provides an alternative method for normalizing transfection efficiency in luciferase assays under hypoxic conditions. Our results suggest that in studies dealing with hypoxic conditions, caution should be used when interpreting measurements of transcriptional activity by traditional dual-reporter assays.

Colored potato extracts induce superoxide dismutase-2 mRNA via ERK1/2 pathway in HepG2 cells

Rats fed a diet containing Shadow Queen (SQ), an anthocyanin-rich potato cultivar, previously showed an increase in the hepatic superoxide dismutase (SOD)-2 mRNA level. We investigated whether an extract of SQ would directly increase the hepatic SOD-2 mRNA level in HepG2 cells. Furthermore, we estimated the intracellular signaling pathway for the induction of SOD-2 mRNA expression. HepG2 cells were stimulated using extracts of four crops, including SQ, for 12 h; only extracts of colored potatoes induced SOD-2 mRNA expression significantly. This induction of SOD-2 mRNA expression was blocked by an inhibitor of the extracellular signal-related kinase (ERK) 1/2 pathway. Furthermore, an extract of SQ increased the phosphorylation of ERK1/2 after 15 or 30 min of stimulation. These data indicate that an extract of SQ directly induces hepatic SOD-2 mRNA expression via activation of ERK1/2 pathway in HepG2 cells.

Influence of the polymorphism in candidate genes on late cardiac damage in patients treated due to acute leukemia in childhood

Anthracyclines have contributed significantly to the increased cure rate in pediatric oncology. Cardiac toxicity is an important late effect after anthracycline treatment and is thought to occur by reactive oxygen species mediated cardiac damage. We hypothesized that deactivating variants of superoxide dismutase II (SOD2) [rs4880 (-9Val > Ala)], catalase (CAT) [rs1001179 (-262C > T) and rs10836235 (c.66 + 78C > T)], GSTT1, and GSTM1 may increase the risk of developing cardiac toxicity, in patients exposed to anthracyclines. The hypothesis was tested in a cohort of 76 long-term survivals of acute lymphoblastic leukemia in childhood. Cardiac damage was evaluated as an attributive variable and compared to gene polymorphisms. In our study group, we show statistically significant correlation between CC homozygosity for CAT (rs10836235 (c.66 + 78C > T)) and cardiac damage after anthracycline exposure (p = 0.020). We found no statistically significant correlation between cardiac damage after anthracycline exposure and deactivating variants of SOD2 [rs4880 (-9Val > Ala)], CAT [rs1001179 (-262C > T), GSTT1, and GSTM1.

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.

Nicotine stimulates PPARbeta/delta expression in human lung carcinoma cells through activation of PI3K/mTOR and suppression of AP-2alpha

We previously showed that nicotine stimulates non-small cell lung carcinoma (NSCLC) cell proliferation through nicotinic acetylcholine receptor (nAChR)-mediated signals. Activation of peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) has also been shown to induce NSCLC cell growth. Here, we explore the potential link between nicotine and PPARbeta/delta and report that nicotine increases the expression of PPARbeta/delta protein; this effect was blocked by an alpha7 nAChR antagonist (alpha-bungarotoxin), by alpha7 nAChR short interfering RNA, and by inhibitors of phosphatidylinositol 3-kinase (PI3K; wortmannin and LY294002) and mammalian target of rapamycin (mTOR; rapamycin). In contrast, this effect was enhanced by PUN282987, an alpha7 nAChR agonist. Silencing of PPARbeta/delta attenuated the stimulatory effect of nicotine on cell growth, which was overcome by transfection of an exogenous PPARbeta/delta expression vector. Of note, nicotine induced complex formation between alpha7 nAChR and PPARbeta/delta protein and increased PPARbeta/delta gene promoter activity through inhibition of AP-2alpha as shown by reduced AP-2alpha binding using electrophoretic gel mobility shift and chromatin immunoprecipitation assays. In addition, silencing of Sp1 attenuated the effect of nicotine on PPARbeta/delta. Collectively, our results show that nicotine increases PPARbeta/delta gene expression through alpha7 nAChR-mediated activation of PI3K/mTOR signals that inhibit AP-2alpha protein expression and DNA binding activity to the PPARbeta/delta gene promoter. Sp1 seems to modulate this process. This study unveils a novel mechanism by which nicotine promotes human lung carcinoma cell growth.

Modulation of detoxification enzymes by watercress: in vitro and in vivo investigations in human peripheral blood cells

BACKGROUND

Epidemiological studies indicate that consumption of cruciferous vegetables (CV) can reduce the risk of cancer. Supposed mechanisms are partly the inhibition of phase I and the induction of phase II enzymes.

AIM

The aim of this study was to investigate in vitro and in vivo effects of watercress (WC), a member of the CV family, on chemopreventive parameters using human peripheral blood mononuclear cells (PBMC) as surrogate cells. We investigated the hypothesis that WC reduces cancer risk by inducing detoxification enzymes in a genotype-dependent manner.

METHODS

In vitro gene expression and enzyme activity experiments used PBMC incubated with a crude extract from fresh watercress (WCE, 0.1-10 microL/mL with 8.2 g WC per 1 mL extract) or with one main key compound phenethyl isothiocyanate (PEITC, 1-10 microM). From an in vivo perspective, gene expression and glutathione S-transferase (GST) polymorphisms were determined in PBMC obtained from a human intervention study in which subjects consumed 85 g WC per day for 8 weeks. The influence of WC consumption on gene expression was determined for detoxification enzymes such as superoxide dismutase 2 (SOD2) and glutathione peroxidase 1 (GPX1), whilst the SOD and GPX activities in red blood cells were also analysed with respect to GST genotypes.

RESULTS

In vitro exposure of PBMC to WCE or PEITC (24 h) increased gene expression for both detoxification enzymes GPX1 (5.5-fold, 1 microL/mL WCE, 3.7-fold 1 microM PEITC) and SOD2 (12.1-fold, 10 microL/mL WCE, 7.3-fold, 10 microM PEITC), and increased SOD2 activity (1.9-fold, 10 microL/mL WCE). The WC intervention had no significant effect on in vivo PBMC gene expression, as high individual variations were observed. However, a small but significant increase in GPX (p = 0.025) and SOD enzyme activity (p = 0.054) in red blood cells was observed in GSTM1*0, but not in GSTM1*1 individuals, whilst the GSTT1 genotype had no impact.

CONCLUSION

The results indicate that WC is able to modulate the enzymes SOD and GPX in blood cells in vitro and in vivo, and suggest that the capacity of moderate intake of CV to induce detoxification is dependent in part on the GSTM1 genotype.

Regulation of Mn-superoxide dismutase activity and neuroprotection by STAT3 in mice after cerebral ischemia

Cerebral ischemia and reperfusion increase superoxide anions (O(2)(*-)) in brain mitochondria. Manganese superoxide dismutase (Mn-SOD; SOD2), a primary mitochondrial antioxidant enzyme, scavenges superoxide radicals and its overexpression provides neuroprotection. However, the regulatory mechanism of Mn-SOD expression during cerebral ischemia and reperfusion is still unclear. In this study, we identified the signal transducer and activator of transcription 3 (STAT3) as a transcription factor of the mouse Mn-SOD gene, and elucidated the mechanism of O(2)(*-) overproduction after transient focal cerebral ischemia (tFCI). We found that Mn-SOD expression is significantly reduced by reperfusion in the cerebral ischemic brain. We also found that activated STAT3 is usually recruited into the mouse Mn-SOD promoter and upregulates transcription of the mouse Mn-SOD gene in the normal brain. However, at early postreperfusion periods after tFCI, STAT3 was rapidly downregulated, and its recruitment into the Mn-SOD promoter was completely blocked. In addition, transcriptional activity of the mouse Mn-SOD gene was significantly reduced by STAT3 inhibition in primary cortical neurons. Moreover, we found that STAT3 deactivated by reperfusion induces accumulation of O(2)(*-) in mitochondria. The loss of STAT3 activity induced neuronal cell death by reducing Mn-SOD expression. Using SOD2-/+ heterozygous knock-out mice, we found that Mn-SOD is a direct target of STAT3 in reperfusion-induced neuronal cell death. Our study demonstrates that STAT3 is a novel transcription factor of the mouse Mn-SOD gene and plays a crucial role as a neuroprotectant in regulating levels of reactive oxygen species in the mouse brain.

Identification of DDB2 protein as a transcriptional regulator of constitutive SOD2 gene expression in human breast cancer cells

Manganese superoxide dismutase plays a role in breast tumor cell growth, which depends on its constitutive expression. However, the mechanisms responsible for the regulation of constitutive SOD2 gene expression at different malignant phenotype in breast cancers remain to be determined. The present study reports the identification and characterization of a DNA sequence located in the proximal promoter of the SOD2 gene, which forms a complex with a nuclear protein from breast tumor MCF-7 cells. Purification of this complex showed that it contained DDB2 (damaged DNA binding 2), a well known protein involved in nucleotide excision DNA repair and cell cycle regulation. Functional analysis of the proximal promoter of the SOD2 gene or modulation of DDB2 expression allowed us to demonstrate that DDB2 regulates negatively the constitutive expression of the SOD2 gene in breast cancer cells. We demonstrate that the binding of DDB2 was associated with the loss of acetylated H3 histones and the decrease in the binding of Sp1 but not AP-2alpha transcription factors to the SOD2 proximal promoter. In addition, we show that DDB2 exerts, at least in part, a control of breast cancer cell growth through its negative regulation of constitutive expression of the SOD2 gene. For the first time, these data give supporting evidence that DDB2 is a new transcriptional regulator, and they provide insight into the molecular function of breast cancer cell growth, which will have an important clinical interest.

[Advances in the expression and regulation of MnSOD gene]

MnSOD, which is an important oxygen free radical scavenger in organisms, has an effect to resist oxidative stress and tumor. The expression and regulation of MnSOD gene is a complicated process, which includes many kinds of transcription factors, cell signal molecules and cell signal pathways. It refers to three aspects including transcription regulation, post-transcription regulation and translation regulation. Transcription regulation is the primary step for MnSOD gene expression and plays a key role during the expression of MnSOD gene. The activity of transcription factors, which controls MnSOD gene expression, such as SP-1, AP-2, AP-1, NF-kB and so on, can be changed in the course of transcription regulation. Drugs and metalions can also affect those transcription factors' activity. Furthermore some genes mutation and depletion also have an influence on the activity of those transcription factors. Post-transcription regulation is in a way of changing the stability of mRNA and its translation. Translation regulation is a process to regulate edition, modification, binding to metalion and site-specific of MnSOD polypeptide. Recently a kind of manganese trafficking factor for mitochondrial MnSOD called MTMl which is very important for activation of MnSOD has been discovered. Here, we review the advances in this field with an emphasis on transcription regulation and translation regulation of MnSOD gene. And at last, we discussed the prospect of MnSOD gene expression and regulation.

Epigenetic inactivation of galanin receptor 1 in head and neck cancer

PURPOSE

One copy of the galanin receptor 1 (GALR1) locus on 18q is often deleted and expression is absent in some head and neck squamous cell carcinoma (HNSCC) cell lines. To determine if loss of heterozygosity and hypermethylation might silence the GALR1 gene, promoter methylation status and gene expression were assessed in a large panel of HNSCC cell lines and tumors.

EXPERIMENTAL DESIGN

Promoter methylation of GALR1 in 72 cell lines and 100 primary tumor samples was analyzed using methylation-specific PCR. GALR1 expression and methylation status were analyzed further by real-time PCR and bisulfite sequencing analysis.

RESULTS

The GALR1 promoter was fully or partially methylated in 38 of 72 (52.7%) HNSCC cell lines but not in the majority 18 of 20 (90.0%) of nonmalignant lines. GALR1 methylation was also found in 38 of 100 (38%) primary tumor specimens. Methylation correlated with decreased GALR1 expression. In tumors, methylation was significantly correlated with increased tumor size (P = 0.0036), lymph node status (P = 0.0414), tumor stage (P = 0.0037), cyclin D1 expression (P = 0.0420), and p16 methylation (P = 0.0494) and survival (P = 0.045). Bisulfite sequencing of 36 CpG sites upstream of the transcription start site revealed that CpG methylation within transcription factor binding sites correlated with complete suppression of GALR1 mRNA. Treatment with trichostatin A and 5-azacytidine restored GALR1 expression. In UM-SCC-23 cells that have total silencing of GALR1, exogenous GALR1 expression and stimulation with galanin suppressed cell proliferation.

CONCLUSIONS

Frequent promoter hypermethylation, gene silencing, association with prognosis, and growth suppression after reexpression support the hypothesis that GALR1 is a tumor suppressor gene in HNSCC.

Mutations in the SOD2 promoter reveal a molecular basis for an activating protein 2-dependent dysregulation of manganese superoxide dismutase expression in cancer cells

A primary antioxidant enzyme in mitochondria, manganese superoxide dismutase (MnSOD), plays a critical role in the survival of aerobic life. It is well documented that, compared with normal cell counterparts, MnSOD level is decreased in neoplastic transformed cells but is increased in aggressive cancers. However, the underlying mechanism for the observed dysregulation of MnSOD in cancer is unknown. We have identified previously a unique set of mutations located in the promoter region of the SOD2 gene in several types of cancer cells. We found that a C-to-T transition at -102 and an insertion of A at -93 down-regulate MnSOD transcription by interrupting the formation of a single-stranded loop that is essential for a high level of promoter activity. Here, we show that the additional downstream mutation, C-to-G transversion at -38, creates a binding site for the transcription factors specificity protein 1 (Sp1) and activating protein 2 (AP-2). The promoter function is regulated by the relative levels of Sp1 and AP-2. In cytokine-induced expression of the SOD2 gene, Sp1 cooperates with a transcriptional complex containing nuclear factor-kappaB and nucleophosmin. The presence of AP-2 attenuates this induction. Our results suggest that the high level of MnSOD observed in aggressive cancer cells may be due, in part, to the absence of AP-2 transcriptional repression.

PKC-dependent stimulation of the human MCT1 promoter involves transcription factor AP2

Monocarboxylate transporter (MCT1) plays an important role in the absorption of short-chain fatty acids (SCFA) such as butyrate in the human colon. Previous studies from our laboratory have demonstrated that phorbol ester, PMA (1 microM, 24 h), upregulates butyrate transport and MCT1 protein expression in human intestinal Caco-2 cells. However, the molecular mechanisms involved in the transcriptional regulation of MCT1 gene expression by PMA in the intestine are not known. In the present study, we showed that PMA (0.1 microM, 24 h) increased the MCT1 promoter activity (-871/+91) by approximately fourfold. A corresponding increase in MCT1 mRNA abundance in response to PMA was also observed. PMA-induced stimulation of MCT1 promoter activity was observed as early as 1 h and persisted until 24 h, suggesting that the effects of PMA are attributable to initial PKC activation. Kinase inhibitor and phosphorylation studies indicated that these effects may be mediated through activation of the atypical PKC-zeta isoform. 5'-deletion studies demonstrated that the MCT1 core promoter region (-229/+91) is the PMA-responsive region. Site-directed mutagenesis studies showed the predominant involvement of potential activator protein 2 (AP2) binding site in the activation of MCT1 promoter activity by PMA. In addition, overexpression of AP2 in Caco-2 cells significantly increased MCT1 promoter activity in a dose-dependent manner. These findings showing the regulation of MCT1 promoter by PKC and AP2 are of significant importance for an understanding of the molecular regulation of SCFA absorption in the human intestine.

Polymorphisms affecting gene transcription and mRNA processing in pharmacogenetic candidate genes: detection through allelic expression imbalance in human target tissues

BACKGROUND

Genetic variation in mRNA expression plays a critical role in human phenotypic diversity, but it has proven difficult to detect regulatory polymorphisms - mostly single nucleotide polymorphisms (rSNPs). Additionally, variants in the transcribed region, termed here 'structural RNA SNPs' (srSNPs), can affect mRNA processing and turnover. Both rSNPs and srSNPs cause allelic mRNA expression imbalance (AEI) in heterozygous individuals. We have used AEI to discover and characterize regulatory polymorphisms in OPRM1, TPH2, MDR1, DRD2, and VKORC1. The objective of this study was to use AEI to determine the extent of cis-regulatory factors in pharmacogenetic genes.

METHODS

We applied a rapid and accurate AEI methodology for testing 42 genes implicated in cardiovascular and central nervous system diseases, and affecting drug metabolism and transport. Each gene was analyzed in physiologically relevant human autopsy tissues, including brain, heart, liver, intestines, and lymphocytes.

RESULTS

Substantial AEI was observed in approximately 55% of the surveyed genes. Focusing on cardiovascular candidate genes in human hearts, AEI analysis revealed frequent cis-acting regulatory factors in ACE and SOD2 mRNA expression, having potential clinical significance. SNP scanning to locate regulatory polymorphisms in a number of genes failed to support several previously proposed promoter SNPs discovered with use of reporter gene assays in heterologous tissues, while srSNPs appear more frequent than expected. Computational analysis of mRNA folding indicates that approximately 90% of srSNPs affect mRNA folding, and hence potentially function.

CONCLUSION

Our results indicate that both rSNPs and srSNPs represent a still largely untapped reservoir of variants that contribute to human phenotypic diversity.

Maintenance of manganese superoxide dismutase (SOD2)-mediated delayed radioprotection induced by repeated administration of the free thiol form of amifostine

Thiol-containing drugs such as WR1065, the free thiol form of amifostine, have been shown to induce a delayed radioprotective effect in both malignant and non-malignant cells. In mammalian cells exposed to a dose as low as 40 microM WR1065, the redox-sensitive nuclear transcription factor kappaB (NFkappaB) is activated, leading to an elevation in the expression of the antioxidant gene manganese superoxide dismutase (SOD2) and a concomitant increase in active SOD2 enzyme levels that peaks 24 to 32 h later. Exposure of cells to ionizing radiation during the period of elevated SOD2 enzymatic activity results in an enhanced radiation resistance. This is seen as an increase in surviving fraction as determined by standard colony formation assays. To determine whether this delayed radioprotection can be maintained over a prolonged period in cells of either malignant or non-malignant origin, both human microvascular endothelial cells (HMEC) and SA-NH mouse sarcoma cells were grown to confluence and exposed to 40 muM WR1065 using three administration protocols: (1) daily drug exposure for 10 days followed each day by irradiation with 2 Gy; (2) drug exposure once every 48 h followed by irradiation with 2 Gy 48 h later for 14 days; and (3) drug exposure every 72 h followed by irradiation with 2 Gy 72 h later for 12 days. As a function of each experimental condition, cell numbers and associated SOD2 enzymatic activities were measured at the time of each irradiation. None of the treatment conditions were toxic to either HMEC or SA-NH cells. SOD2 activity was elevated 5.3- and 1.8-fold over background on average for HMEC exposed to 40 microM WR1065 every 24 or 48 h, respectively. Likewise, SOD2 activity was elevated in SA-NH mouse sarcoma cells 7.8- and 4.9-fold after daily exposure to WR1065 or exposure to WR1065 once every 48 h, respectively. Both HMEC and SA-NH cells exhibited enhanced radiation resistance that correlated with the increase in SOD2 activity. The average respective increases in cell survival were 1.33 +/- 0.01 (SEM), 1.23 +/- 0.01 and 1.04 +/- 0.01 for HMEC exposed to WR1065 every 24, 48 and 72 h, respectively, and 1.27 +/- 0.01, 1.18 +/- 0.02 and 1.02 +/- 0.02 for SA-NH cells exposed to WR1065 every 24, 48 and 72 h, respectively. Both the elevation in WR1065-induced SOD2 enzymatic activity and the corresponding increase in radiation resistance were completely inhibited in HMEC and SA-NH cells transfected with human or mouse SOD2 siRNA oligomers and irradiated 24 h later. These data demonstrate that a delayed radioprotective effect can be induced and maintained over a prolonged period in both non-malignant and malignant cells exposed to thiol-containing drugs such as WR1065. For non-malignant cells this represents a novel paradigm for radiation protection. The ability of WR1065 to induce a persistent elevated radiation resistance in malignant cells, however, suggests a new potential concern regarding the issue of tumor protection in patients exposed to thiol-containing drugs.

Oxidative stress and transcriptional regulation in Alzheimer disease

Alzheimer disease (AD) is defined by progressive impairments in memory and cognition and by the presence of extracellular neuritic plaques and intracellular neurofibrillary tangles. However, oxidative stress and impaired mitochondrial function always accompany AD. Mitochondria are a major site of production of free radicals [ie, reactive oxygen species (ROS)] and primary targets of ROS. ROS are cytotoxic, and evidence of ROS-induced damage to cell membranes, proteins, and DNA in AD is overwhelming. Nevertheless, therapies based on antioxidants have been disappointing. Thus, alternative strategies are necessary. ROS also act as signaling molecules including for transcription. Thus, chronic exposure to ROS in AD could activate cascades of genes. Although initially protective, prolonged activation may be damaging. Thus, therapeutic approaches based on modulation of these gene cascades may lead to effective therapies. Genes involved in several pathways including antioxidant defense, detoxification, inflammation, etc, are induced in response to oxidative stress and in AD. However, genes that are associated with energy metabolism, which is necessary for normal brain function, are mostly down-regulated. Redox-sensitive transcription factors such as activator protein-1, nuclear factor-kappaB, specificity protein-1, and hypoxia-inducible factor are important in redox-dependent gene regulation. Peroxisome proliferators-activated receptor-gamma coactivator (PGC-1alpha) is a coactivator of several transcription factors and is a potent stimulator of mitochondrial biogenesis and respiration. Down-regulated expression of PGC-1alpha has been implicated in Huntington disease and in several Huntington disease animal models. PGC-1alpha role in regulation of ROS metabolism makes it a potential candidate player between ROS, mitochondria, and neurodegenerative diseases. This review summarizes the current progress on how oxidative stress regulates the expression of genes that might contribute to AD pathophysiology and the implications of the transcriptional modifications for AD. Finally, potential therapeutic strategies based on the updated understandings of redox state-dependent gene regulation in AD are proposed to overcome the lack of efficacy of antioxidant therapies.