The peroxidase activity of mitochondrial superoxide dismutase

Trace and essential elements as vital components to improve the performance of the male reproductive system: Implications in cell signaling pathways

Successful male fertilization requires the main processes such as normal spermatogenesis, sperm capacitation, hyperactivation, and acrosome reaction. The progress of these processes depends on some endogenous and exogenous factors. So, the optimal level of ions and essential and rare elements such as selenium, zinc, copper, iron, manganese, calcium, and so on in various types of cells of the reproductive system could affect conception and male fertility rates. The function of trace elements in the male reproductive system could be exerted through some cellular and molecular processes, such as the management of active oxygen species, involvement in the action of membrane channels, regulation of enzyme activity, regulation of gene expression and hormone levels, and modulation of signaling cascades. In this review, we aim to summarize the available evidence on the role of trace elements in improving male reproductive performance. Also, special attention is paid to the cellular aspects and the involved molecular signaling cascades.

Association of SOD2 rs2758339, rs5746136 and rs2842980 polymorphisms with increased risk of breast cancer: a haplotype-based case-control study

BACKGROUND

A growing body of evidence indicates that oxidative stress, high levels of reactive oxygen species (ROS), is implicated in the pathogenesis of breast cancer (BC). Superoxide dismutase (SOD2), a mitochondria-resident antioxidant enzyme, protects cells from ROS by catalytically converting the superoxide radicals into less reactive species.

OBJECTIVE

We aimed to investigate whether SOD2 rs2758339, rs5746136 and rs2842980 polymorphisms are associated with increased risk of BC.

METHODS

A total of 100 patients with BC and 100 healthy controls were enrolled in the study. We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay for genotyping the SOD2 single-nucleotide polymorphisms (SNPs). Under co-dominant, dominant and recessive inheritance models, the genotypic and allelic associations of SOD2 SNPs with susceptibility to BC were evaluated using logistic regression analysis. The haplotype analysis was performed on the SOD2 SNPs to determine their combined effect on the BC risk.

RESULTS

We found that SOD2 rs5746136 was significantly associated with decreased risk of developing BC in co-dominant and dominant inheritance models (P < 0.05). The SOD2 rs5746136 T allele confers an apparent protective effect against breast carcinogenesis (OR: 1.956; 95% CI 1.312-2.916; P < 0.0001). The SOD2 rs5746136/rs2842980 combined genotypes (CT/AA, CT/AT and TT/AA) were significantly more frequent in healthy subjects compared to BC patients (P < 0.05). The CTA and ACA haplotypes (rs2758339, rs5746136, rs2842980) were found to be a protective and a risk factor for BC, respectively.

CONCLUSION

These data strongly suggest that SOD2 rs5746136 was significantly associated with reduced risk of BC, indicating its protective role in BC development.

The Body Status of Manganese and Activity of This Element-Dependent Mitochondrial Superoxide Dismutase in a Rat Model of Human Exposure to Cadmium and Co-Administration of Aronia melanocarpa L. Extract

The impact of a polyphenol-rich 0.1% aqueous extract from Aronia melanocarpa L. berries (AE) on the body status of manganese (Mn) and the activity of this essential element-dependent mitochondrial superoxide dismutase (MnSOD) during treatment with cadmium (Cd) was investigated in a rat model of low-level and moderate environmental human exposure to this xenobiotic (1 and 5 mg Cd/kg diet, respectively, for 3-24 months). The exposure to Cd, dose- and duration-dependently, affected the body status of Mn (apparent absorption, body retention, serum and tissue concentrations, content in some organs and total Mn body burden, and urinary and faecal excretion) and the activity of MnSOD in the mitochondria of the liver, kidney, and brain. The administration of AE during the exposure to Cd prevented or at least partially protected the animals from the perturbation of the metabolism of Mn, as well as ameliorated changes in the activity of MnSOD and the concentration of Mn and protected from Cd accumulation in the mitochondria. In conclusion, AE may protect from disorders in the body status of Mn and influence the antioxidative capacity of cells under chronic exposure to Cd. The findings confirm the protective impact of aronia berries products against Cd toxicity.

Lactobacillus fermentum ME-3: A Breakthrough in Glutathione Therapy

It is difficult to overstate the importance of glutathione because it performs many critical biological functions. The purpose of this article is to briefly review glutathione's functions, explain why most people have low levels of glutathione and make the case that increasing glutathione levels is one of the most important pro-active steps people can take to improve their health and slow down the onset of age-related diseases. This article will also introduce practitioners to Lactobacillus fermentum ME-3, which is a unique strain of probiotic bacteria that synthesizes glutathione.

Copper Chaperone for Superoxide Dismutase FoCCS1 in Frankliniella occidentalis May Be Associated with Feeding Adaptation after Host Shifting

Western flower thrips (Frankliniella occidentalis) pose a serious threat to the global vegetable and flower crop production. The regulatory mechanism for superoxide dismutase (SOD) in the feeding adaptation of F. occidentalis after host shifting remains unclear. In this study, the copper chaperone for SOD (CCS) and manganese SOD (MnSOD) genes in F. occidentalis were cloned, and their expression levels at different developmental stages was determined. The mRNA expression of FoCCS1 and FoMnSOD2 in F. occidentalis second-instar larvae and adult females of F₁, F₂, and F₃ generations was analyzed after shifting the thrips to kidney bean and broad bean plants, respectively. The F₂ and F₃ second-instar larvae and F₂ adult females showed significantly upregulated FoCCS1 mRNA expression after shifting to kidney bean plants. The F₁ second-instar larvae and F₂ adult females showed significantly upregulated FoCCS1 mRNA expression after shifting to broad bean plants. The RNA interference significantly downregulated the FoCCS1 mRNA expression levels and adult females showed significantly inhibited SOD activity after shifting to kidney bean and broad bean plants. F. occidentalis adult females subjected to RNA interference and released on kidney bean and broad bean leaves for rearing, respectively, significantly reduced the survival rate and fecundity. These findings suggest that FoCCS1 plays an active role in regulating the feeding adaptation ability of F. occidentalis after host shifting.

Hypoxia aggravates ferroptosis in RPE cells by promoting the Fenton reaction

Oxidative stress and hypoxia in the retinal pigment epithelium (RPE) have long been considered major risk factors in the pathophysiology of age-related macular degeneration (AMD), but systematic investigation of the interplay between these two risk factors was lacking. For this purpose, we treated a human RPE cell line (ARPE-19) with sodium iodate (SI), an oxidative stress agent, together with dimethyloxalylglycine (DMOG) which leads to stabilization of hypoxia-inducible factors (HIFs), key regulators of cellular adaptation to hypoxic conditions. We found that HIF stabilization aggravated oxidative stress-induced cell death by SI and iron-dependent ferroptosis was identified as the main cell death mechanism. Ferroptotic cell death depends on the Fenton reaction where H₂O₂ and iron react to generate hydroxyl radicals which trigger lipid peroxidation. Our findings clearly provide evidence for superoxide dismutase (SOD) driven H₂O₂ production fostering the Fenton reaction as indicated by triggered SOD activity upon DMOG + SI treatment as well as by reduced cell death levels upon SOD2 knockdown. In addition, iron transporters involved in non-transferrin-bound Fe²⁺ import as well as intracellular iron levels were also upregulated. Consequently, chelation of Fe²⁺ by 2'2-Bipyridyl completely rescued cells. Taken together, we show for the first time that HIF stabilization under oxidative stress conditions aggravates ferroptotic cell death in RPE cells. Thus, our study provides a novel link between hypoxia, oxidative stress and iron metabolism in AMD pathophysiology. Since iron accumulation and altered iron metabolism are characteristic features of AMD retinas and RPE cells, our cell culture model is suitable for high-throughput screening of new treatment approaches against AMD.

Nuclear-localized, iron-bound superoxide dismutase-2 antagonizes epithelial lineage programs to promote stemness of breast cancer cells via a histone demethylase activity

The dichotomous behavior of superoxide dismutase-2 (SOD2) in cancer biology has long been acknowledged and more recently linked to different posttranslational forms of the enzyme. However, a distinctive activity underlying its tumor-promoting function is yet to be described. Here, we report that acetylation, one of such posttranslational modifications (PTMs), increases SOD2 affinity for iron, effectively changing the biochemical function of this enzyme from that of an antioxidant to a demethylase. Acetylated, iron-bound SOD2 localizes to the nucleus, promoting stem cell gene expression via removal of suppressive epigenetic marks such as H3K9me3 and H3K927me3. Particularly, H3K9me3 was specifically removed from regulatory regions upstream of Nanog and Oct-4, two pluripotency factors involved in cancer stem cell reprogramming. Phenotypically, cells expressing nucleus-targeted SOD2 (NLS-SOD2) have increased clonogenicity and metastatic potential. FeSOD2 operating as H3 demethylase requires H2O2 as substrate, which unlike cofactors of canonical demethylases (i.e., oxygen and 2-oxoglutarate), is more abundant in tumor cells than in normal tissue. Therefore, our results indicate that FeSOD2 is a demethylase with unique activities and functions in the promotion of cancer evolution toward metastatic phenotypes.

Manganese Superoxide Dismutase Acetylation and Regulation of Protein Structure in Breast Cancer Biology and Therapy

The loss and/or dysregulation of several cellular and mitochondrial antioxidants' expression or enzymatic activity, which leads to the aberrant physiological function of these proteins, has been shown to result in oxidative damage to cellular macromolecules. In this regard, it has been surmised that the disruption of mitochondrial networks responsible for maintaining normal metabolism is an established hallmark of cancer and a novel mechanism of therapy resistance. This altered metabolism leads to aberrant accumulation of reactive oxygen species (ROS), which, under specific physiological conditions, leads to a potential tumor-permissive cellular environment. In this regard, it is becoming increasingly clear that the loss or disruption of mitochondrial oxidant scavenging enzymes may be, in specific tumors, either an early event in transformation or exhibit tumor-promoting properties. One example of such an antioxidant enzyme is manganese superoxide dismutase (MnSOD, also referred to as SOD2), which detoxifies superoxide, a ROS that has been shown, when its normal physiological levels are disrupted, to lead to oncogenicity and therapy resistance. Here, we will also discuss how the acetylation of MnSOD leads to a change in detoxification function that leads to a cellular environment permissive for the development of lineage plasticity-like properties that may be one mechanism leading to tumorigenic and therapy-resistant phenotypes.

Targeting prooxidant MnSOD effect inhibits triple-negative breast cancer (TNBC) progression and M2 macrophage functions under the oncogenic stress

Triple-negative breast cancer (TNBC) has been shown with high mitochondrial oxidative phosphorylation and production of reactive oxygen species (ROS). MnSOD (SOD2) is a mitochondrial antioxidant defense that has been implicated in inhibition of human malignancies. However, the impact of MnSOD on immunosuppressive macrophage functions and TNBC aggressiveness has never been explored. We found here that SOD2^high is primarily observed in the aggressive subtypes of HER2(+) breast cancers and TNBCs patients. Further analyses demonstrated that the oncoprotein multiple copies in T-cell malignancy-1 (MCT-1 or MCTS1) induces mitochondrial superoxide dismutase (MnSOD) in TNBC cells by stabilizing the transcription factor Nrf2. SOD2^high/MCTS1^high expression correlates with a poor prognosis in breast cancer patients. MnSOD in TNBC cells functions as a prooxidant peroxidase that increases mitochondrial ROS (mROS) and adaptation to oxidative stress under the oncogenic effect. Interleukin-6 (IL-6) in the MCT-1 pathway elevates Nrf2/MnSOD and mROS levels. Knockdown of MnSOD inhibits TNBC cell invasion, breast cancer stem cells (BCSCs), mROS, and IL-6 excretion promoted by MCT-1. TNBC cells deficient in MnSOD prevent the polarization and chemotaxis of M2 macrophages but improve the ability of M1 macrophages to engulf cancer cells. Quenching mROS with MitoQ, a mitochondria-targeted non-metal-based antioxidant MnSOD mimics, effectively suppresses BCSCs and M2 macrophage invasion exacerbated by MnSOD and MCT-1. Consistently, silencing MnSOD impedes TNBC progression and intratumoral M2 macrophage infiltration. We revealed a novel stratagem for TNBC management involving targeting the MCT-1 oncogene-induced mitochondrial prooxidant MnSOD pathway, which prevents the development of an immunosuppressive tumor microenvironment.

Valproic acid promotes SOD2 acetylation: A potential mechanism of valproic acid-induced oxidative stress in developing systems

Valproic acid (VPA) is an antiepileptic, bipolar and migraine medication, which is associated with embryonic dysmorphology, more specifically neural tube defects (NTDs), if taken while pregnant. One mechanism by which VPA may cause NTDs is through oxidative stress that cause disruption of cell signaling. However, mechanisms of VPA-induced oxidative stress are not fully understood. Since VPA is a deacetylase inhibitor, we propose that VPA promotes mitochondrial superoxide dismutase-2 (SOD2) acetylation, decreasing SOD2 activity and increasing oxidant levels. Using the pluripotent embryonal carcinoma cell line, P19, VPA effects were evaluated in undifferentiated and neurodifferentiated cells. VPA treatments increased oxidant levels, oxidized the glutathione (GSH)/glutathione disulfide (GSSG) redox couple, and decreased total SOD and SOD2 activity in undifferentiated P19 cells but not in differentiated P19 cells. VPA caused a specific increase in mitochondrial oxidants in undifferentiated P19 cells, VPA did not alter respirometry measurements. Immunoblot analyses demonstrated that VPA increased acetylation of SOD2 at lysine⁶⁸ (AcK68 SOD2) in undifferentiated P19 cells but not in differentiated P19 cells. Pretreatments with the Nrf2 inducer, dithiol-3-thione (D3T), in undifferentiated P19 cells prevented increased oxidant levels, GSH/GSSG redox oxidation and restored total SOD and SOD2 activity, correlating with a decrease in AcK68 SOD2 levels. In embryos, VPA decreased total SOD and SOD2 activity and increased levels of AcK68 SOD2, and D3T pretreatments prevented VPA effects, increasing total SOD and SOD2 activity and lowering levels of AcK68 SOD2. These data demonstrate a potential, contributing oxidizing mechanism by which VPA incites teratogenesis in developing systems. Moreover, these data also suggest that Nrf2 interventions may serve as a means to protect developmental signaling and inhibit VPA-induced malformations.

Endurance training alleviates MCP-1 and TERRA accumulation at old age in human skeletal muscle

Both oxidative stress and telomere transcription are up-regulated by acute endurance exercise in human skeletal muscle. Whether and how life-long exercise training influences the antioxidant system response at transcriptional level and TERRA expression is unknown, especially during aging. Response to acute endurance exercise was investigated in muscle biopsies of 3 male subjects after 45 min of cycling. MCP-1 and SOD1 mRNA levels increased up to, 15-fold and 63%, respectively, after the cycling session while the mRNA levels of SOD2 were downregulated by 25%. The effects of chronic endurance exercise and aging were tested in the blood and muscle of 34 male subjects divided into four groups: young (YU) or old (OU) untrained, young (YT) or old (OT) trained cyclists. Long-term endurance training limited the age-dependent elevation in SOD1 (OT vs OU, -26%, P = 0.03) and the decline in SOD2 mRNA levels (OU vs YU, -41%, P = 0.04). A high endurance training status alleviated the age-related increase in the aging biological marker MCP-1 in plasma (OU vs YU, +48%, P = 0.005). Similar results were observed for telomeric transcription as the age-associated increase in 16p TERRA levels (OU vs YU, +39%, P = 0.001) was counteracted by a high endurance training status (OT vs OU, -63%, P = 0.0005). In conclusion, as MCP-1, we propose that the age-related TERRA accumulation might represent a novel biological marker of aging. Those aging-related increase expression might be alleviated by a high endurance training status. Whether those biological markers of aging are linked to an elevation of oxidative stress is still an open question. Therefore, whether the positive adaptations provided by endurance training indeed reduce oxidative stress, including at telomeres, and whether TERRA plays any role in this, need to be further investigated.

Regulatory Effects of Cannabidiol on Mitochondrial Functions: A Review

Cannabidiol (CBD) is part of a group of phytocannabinoids derived from Cannabissativa. Initial work on CBD presumed the compound was inactive, but it was later found to exhibit antipsychotic, anti-depressive, anxiolytic, and antiepileptic effects. In recent decades, evidence has indicated a role for CBD in the modulation of mitochondrial processes, including respiration and bioenergetics, mitochondrial DNA epigenetics, intrinsic apoptosis, the regulation of mitochondrial and intracellular calcium concentrations, mitochondrial fission, fusion and biogenesis, and mitochondrial ferritin concentration and mitochondrial monoamine oxidase activity regulation. Despite these advances, current data demonstrate contradictory findings with regard to not only the magnitude of effects mediated by CBD, but also to the direction of effects. For example, there are data indicating that CBD treatment can increase, decrease, or have no significant effect on intrinsic apoptosis. Differences between studies in cell type, cell-specific response to CBD, and, in some cases, dose of CBD may help to explain differences in outcomes. Most studies on CBD and mitochondria have utilized treatment concentrations that exceed the highest recorded plasma concentrations in humans, suggesting that future studies should focus on CBD treatments within a range observed in pharmacokinetic studies. This review focuses on understanding the mechanisms of CBD-mediated regulation of mitochondrial functions, with an emphasis on findings in neural cells and tissues and therapeutic relevance based on human pharmacokinetics.

Neferine inhibits proliferation and migration of human prostate cancer stem cells through p38 MAPK/JNK activation

Cancer stem cells (CSCs) are one of the significant causes of cancer treatment failure and metastasis, as they have significant chemo-and radio-resistance leading to tumor recurrence. Here we investigated the possible anticancer properties of neferine, a natural alkaloid, on human prostate cancer (PCa) cells and their stem cells. CD44⁺ CSCs were isolated from androgen-insensitive PC3 cells by magnetic-activated cell sorting system (MACS). Neferine dose-and time-dependently inhibited the viability of PC3 and CSCs as well as androgen-sensitive LNCaP cells through inducing apoptosis and cell cycle arrest at G1 phase. Neferine was shown to downregulate the expression of Bcl-2 and CDK4, and upregulate caspase 3, clePARP, p21, p27, and p53. The treatment significantly inhibits the migration of CSCs. Neferine induces JNK and p38 MAPK phosphorylation, and downregulates PI3K and NF-ĸβ signaling. In conclusion, neferine may have a therapeutic effect inhibiting the PCa cell proliferation as well as by eliminating CSCs. PRACTICAL APPLICATIONS: Neferine is an alkaloid found in the seed embryo of Nelumbo nucifera and has recently been shown to have anticancer effects on various human cancer cells. More than 90% of cancer-related deaths develop after metastasis, and CSCs are considered to be largely responsible for the cell migration and invasion. It has been shown that treatment of neferine kills not only PCa cells but also CSCs, and may contribute to the prevention of progression of PCa and metastasis by inhibiting cell proliferation and migration.

Mitochondrial Superoxide Dismutase: What the Established, the Intriguing, and the Novel Reveal About a Key Cellular Redox Switch

Significance: Reactive oxygen species (ROS) are now widely recognized as central mediators of cell signaling. Mitochondria are major sources of ROS. Recent Advances: It is now clear that mitochondrial ROS are essential to activate responses to cellular microenvironmental stressors. Mediators of these responses reside in large part in the cytosol. Critical Issues: The primary form of ROS produced by mitochondria is the superoxide radical anion. As a charged radical anion, superoxide is restricted in its capacity to diffuse and convey redox messages outside of mitochondria. In addition, superoxide is a reductant and not particularly efficient at oxidizing targets. Because there are many opportunities for superoxide to be neutralized in mitochondria, it is not completely clear how redox cues generated in mitochondria are converted into diffusible signals that produce transient oxidative modifications in the cytosol or nucleus. Future Directions: To efficiently intervene at the level of cellular redox signaling, it seems that understanding how the generation of superoxide radicals in mitochondria is coupled with the propagation of redox messages is essential. We propose that mitochondrial superoxide dismutase (SOD2) is a major system converting diffusion-restricted superoxide radicals derived from the electron transport chain into highly diffusible hydrogen peroxide (H₂O₂). This enables the coupling of metabolic changes resulting in increased superoxide to the production of H₂O₂, a diffusible secondary messenger. As such, to determine whether there are other systems coupling metabolic changes to redox messaging in mitochondria as well as how these systems are regulated is essential.

CNP mediated selective toxicity on melanoma cells is accompanied by mitochondrial dysfunction

Cerium (Ce) oxide nanoparticles (CNP; nanoceria) are reported to have cytotoxic effects on certain cancerous cell lines, while at the same concentration they show no cytotoxicity on normal (healthy) cells. Redox-active CNP exhibit both selective prooxidative as well as antioxidative properties. The former is proposed to be responsible for impairment of tumor growth and invasion and the latter for rescuing normal cells from reactive oxygen species (ROS)-induced damage. Here we address possible underlying mechanisms of prooxidative effects of CNP in a metastatic human melanoma cell line. Malignant melanoma is the most aggressive form of skin cancer, and once it becomes metastatic the prognosis is very poor. We have shown earlier that CNP selectively kill A375 melanoma cells by increasing intracellular ROS levels, whose basic amount is significantly higher than in the normal (healthy) counterpart, the melanocytes. Here we show that CNP initiate a mitochondrial increase of ROS levels accompanied by an increase in mitochondrial thiol oxidation. Furthermore, we observed CNP-induced changes in mitochondrial bioenergetics, dynamics, and cristae morphology demonstrating mitochondrial dysfunction which finally led to tumor cell death. CNP-induced cell death is abolished by administration of PEG-conjugated catalase. Overall, we propose that cerium oxide nanoparticles mediate cell death via hydrogen peroxide production linked to mitochondrial dysfunction.

Upregulation of Mitochondrial Redox Sensitive Proteins in LPS-Treated Stefin B-Deficient Macrophages

Stefin B (cystatin B) is an intracellular inhibitor of cysteine cathepsins and mutations in the stefin B gene, resulting in the development of Unverricht–Lundborg disease, which is a form of myoclonic epilepsy. It was suggested that a key mechanism behind stefin B-mediated disease progression was impaired redox homeostasis. Stefin B-deficient mice were found more sensitive to lipopolysaccharide (LPS)-induced sepsis as a consequence of increased expression of caspase-11 and Nucleotide-binding oligomerization domain, Leucine rich Repeat and Pyrin domain containing (NLRP nflammasome activation and higher levels of mitochondrial reactive oxygen species (ROS). In the present study, we investigated if LPS-triggered oxidative stress affected the protein levels and redox status of redox sensitive proteins—thioredoxin, peroxiredoxins, and superoxide dismutases in macrophages and spleens of LPS-injected mice. LPS challenge was found to result in a marked elevation in mitochondrial peroxiredoxin 3 (Prx3), sulfiredoxin, and superoxide dismutase 2 (Sod2) in stefin B-deficient macrophages and spleens. We determined that sulfiredoxin is targeted to mitochondria after LPS challenge. In conclusion, the upregulation of mitochondrial redox-sensitive proteins Prx3 and Sod2 in stefin B-deficient cells implies a protective role of stefin B in mitochondrial function.

SOD2 acetylation on lysine 68 promotes stem cell reprogramming in breast cancer

Mitochondrial superoxide dismutase (SOD2) suppresses tumor initiation but promotes invasion and dissemination of tumor cells at later stages of the disease. The mechanism of this functional switch remains poorly defined. Our results indicate that as SOD2 expression increases acetylation of lysine 68 ensues. Acetylated SOD2 promotes hypoxic signaling via increased mitochondrial reactive oxygen species (mtROS). mtROS, in turn, stabilize hypoxia-induced factor 2α (HIF2α), a transcription factor upstream of "stemness" genes such as Oct4, Sox2, and Nanog. In this sense, our findings indicate that SOD2K68Ac and mtROS are linked to stemness reprogramming in breast cancer cells via HIF2α signaling. Based on these findings we propose that, as tumors evolve, the accumulation of SOD2K68Ac turns on a mitochondrial pathway to stemness that depends on HIF2α and may be relevant for the progression of breast cancer toward poor outcomes.

Lysine 68 acetylation directs MnSOD as a tetrameric detoxification complex versus a monomeric tumor promoter

Manganese superoxide dismutase (MnSOD) functions as a tumor suppressor; however, once tumorigenesis occurs, clinical data suggest MnSOD levels correlate with more aggressive human tumors, implying a potential dual function of MnSOD in the regulation of metabolism. Here we show, using in vitro transformation and xenograft growth assays that the MnSOD-K68 acetylation (Ac) mimic mutant (MnSODK68Q) functions as a tumor promoter. Interestingly, in various breast cancer and primary cell types the expression of MnSODK68Q is accompanied with a change of MnSOD's stoichiometry from a known homotetramer complex to a monomeric form. Biochemical experiments using the MnSOD-K68Q Ac-mimic, or physically K68-Ac (MnSOD-K68-Ac), suggest that these monomers function as a peroxidase, distinct from the established MnSOD superoxide dismutase activity. MnSODK68Q expressing cells exhibit resistance to tamoxifen (Tam) and cells selected for Tam resistance exhibited increased K68-Ac and monomeric MnSOD. These results suggest a MnSOD-K68-Ac metabolic pathway for Tam resistance, carcinogenesis and tumor progression.

Effect of resveratrol on vitrified in vitro produced bovine embryos: Recovering the initial quality

Although vitrification is the current routine method for human embryo cryopreservation, it may cause detrimental effects. The aim of this study was to evaluate the effect of supplementing in vitro culture (IVC) media and/or vitrification solutions (VS) with Resveratrol on the presence of apoptotic markers, reactive oxygen species (ROS) level, glutathione (GSH) content and relative gene abundance. Abattoir-derived oocytes were matured and fertilized in vitro according to a standard procedure. Zygotes were cultured in IVC medium supplemented with or without 0.5 μM Resveratrol (C^R, C^- respectively). On day 7, blastocysts were vitrified using the minimum volume vitrification method supplementing VS with (C^-V^R, C^RV^R) or without (C^-V^-, C^RV^-) 0.5 μM Resveratrol. After warming, embryonic quality parameters were evaluated. Survival rates were significantly lower in C^RV^R group compared with C^RV^- group, but no differences in hatching rate were observed between groups. Vitrification/warming process did not alter total cell number or the presence of apoptotic or dead cells, but C^RV^- and C^RV^R groups presented a significant increase in dead cells (P < 0.05 by ANOVA). Resveratrol supplementation in VS (C^-V^R) restored GSH content (P < 0.05) to the level found in the C^R group. Vitrification/warming process significantly increased the expression of FOXO3A, PNPLA2, BCL2L1 and BAX genes (P < 0.05). Resveratrol addition to IVC medium or VS partially compensated this increase for FOXO3A and PNPLA2 (P < 0.05) but not for BCL2L1 and BAX. In conclusion, supplementation of IVC media or VS with 0.5 μM resveratrol may help embryos to partially restore the initial quality they had before the cryopreservation process.

Intranasal administration of erythropoietin rescues the photoreceptors in degenerative retina: a noninvasive method to deliver drugs to the eye

Inherited retinopathies typically lead to photoreceptor loss and severe visual impairments in the subjects. Intranasal administration is an efficient approach to deliver therapeutic agents to the targeted tissue. The present study is designed to deliver the erythropoietin (EPO) into the N-methyl-N-nitrosourea (MNU) induced mice, a pharmacological retinopathy model via intranasal or intravenous route. The mice were then subjected to bioavailability assay and therapeutic effects evaluation. Our results showed that the intranasal delivery of EPO is effective to alleviate the morphological disruptions in the MNU induced mice. The intranasal delivery of EPO also ameliorated the visual impairments in the MNU induced mice. Immunostaining experiment showed that both the M-cone and S-cone populations in the degenerative retinas are rescued by the intranasal delivery of EPO. In particular, the M-cone photoreceptors in dorsal-temporal (DT) quadrant and the S-cone photoreceptors in ventral-nasal (VN) quadrant were preferentially preserved by the intranasal delivery of EPO. Mechanism studies showed that the intranasal delivery of EPO could the modulate apoptosis and restrict oxidation in the degenerative retina. Compared with intravenous delivery, the intranasal delivery led to the significantly higher EPO concentration in the retina. The intranasal delivery resulted in more potent protection and had less erythropoiesis-stimulating activity than the intravenous delivery. Our results suggest that the intranasal administration is a noninvasive and efficient approach to deliver EPO into the retinas. These findings lay the groundwork for further intranasal administration of EPO in ophthalmological practice.

iTRAQ-based proteomics reveals SOD2 as a potential salivary biomarker in liver cancer

BACKGROUND

Salivary proteomic analysis has been extensively used in a wide range of cancer, but not in hepatocellular carcinoma. The aim of this study was to identify potential salivary biomarkers for hepatocellular carcinoma clinical screening.

METHODS

In this study, we performed isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics analysis to detect differentially expressed proteins between saliva samples from 15 hepatocellular carcinoma patients and 15 healthy controls. Enzyme-linked immunosorbent assay (ELISA) verification was undertaken in saliva samples from 14 hepatocellular carcinoma patients and 14 healthy controls.

RESULTS

Overall, 133 proteins with significant differential expression level (ratio > 1.5 or < 0.67) were detected. Using bioinformatic analysis, two candidate proteins were selected and subsequently verified by ELISA. The increased expression of superoxide dismutase 2, mitochondrial (SOD2) in hepatocellular carcinoma patients was confirmed by ELISA, with an area under the curve value of 0.9082.

CONCLUSIONS

iTRAQ-based quantitative proteomics revealed that SOD2 might serve as a potential salivary biomarker for hepatocellular carcinoma detection. Our results indicated that a noninvasive and inexpensive salivary test might be established for hepatocellular carcinoma detection.

Switch of Mitochondrial Superoxide Dismutase into a Prooxidant Peroxidase in Manganese-Deficient Cells and Mice

Superoxide radical anion (O₂^⋅‒) and other reactive oxygen species are constantly produced during respiration. In mitochondria, the dismutation of O₂^⋅‒ is accelerated by the mitochondrial superoxide dismutase 2 (SOD2), an enzyme that has been traditionally associated with antioxidant protection. However, increases in SOD2 expression promote oxidative stress, indicating that there may be a prooxidant role for SOD2. Here we show that SOD2, which normally binds manganese, can incorporate iron and generate an alternative isoform with peroxidase activity. The switch from manganese to iron allows FeSOD2 to utilize H₂O₂ to promote oxidative stress. We found that FeSOD2 is formed in cultured cells and in vivo. FeSOD2 causes mitochondrial dysfunction and higher levels of oxidative stress in cultured cells and in vivo. We show that formation of FeSOD2 converts an antioxidant defense into a prooxidant peroxidase that leads to cellular changes seen in multiple human diseases.

Immuno-spin trapping of macromolecules free radicals in vitro and in vivo - One stop shopping for free radical detection

The only general technique that allows the unambiguous detection of free radicals is electron spin resonance (ESR). However, ESR spin trapping has severe limitations especially in biological systems. The greatest limitation of ESR is poor sensitivity relative to the low steady-state concentration of free radical adducts, which in cells and in vivo is much lower than the best sensitivity of ESR. Limitations of ESR have led to an almost desperate search for alternatives to investigate free radicals in biological systems. Here we explore the use of the immuno-spin trapping technique, which combine the specificity of the spin trapping to the high sensitivity and universal use of immunological techniques. All of the immunological techniques based on antibody binding have become available for free radical detection in a wide variety of biological systems.

Alterations in Sod2-Induced Oxidative Stress Affect Endocrine Cancer Progression

CONTEXT

Although important advances have been made in understanding the genetics of endocrine tumors, cellular physiology is relatively understudied as a determinant of tumor behavior. Oxidative stress and reactive oxygen species are metabolic factors that may affect tumor behavior, and these are, in part, controlled by manganese-dependent superoxide dismutase (MnSod), the mitochondrial superoxide dismutase (encoded by SOD2).

OBJECTIVE

We sought to understand the role of MnSod in the prognosis of aggressive human endocrine cancers and directly assessed the effect of MnSod under- or overexpression on tumor behavior, using established mouse thyroid cancer models.

METHODS

We performed transcriptome analysis of human and mouse models of endocrine cancer. To address the role of Sod2 in endocrine tumors, we introduced a Sod2 null allele or a transgenic Sod2 overexpression allele into mouse models of benign thyroid follicular neoplasia or aggressive, metastatic follicular thyroid cancer (FTC) and monitored phenotypic changes in tumor initiation and progression.

RESULTS

In the thyroid, SOD2/Sod2 was downregulated in FTC but not papillary thyroid cancer. Reduced expression of SOD2 was correlated with poorer survival of patients with aggressive thyroid or adrenal cancers. In mice with benign thyroid tumors, Sod2 overexpression increased tumor burden. In contrast, in mice with aggressive FTC, overexpression of Sod2 reduced tumor proliferation and improved mortality rates, whereas its deficiency enhanced tumor growth.

CONCLUSION

Overall, our results indicate that SOD2 has dichotomous roles in cancer progression and acts in a context-specific manner.

Emerging evidence for targeting mitochondrial metabolic dysfunction in cancer therapy

Mammalian cells use a complex network of redox-dependent processes necessary to maintain cellular integrity during oxidative metabolism, as well as to protect against and/or adapt to stress. The disruption of these redox-dependent processes, including those in the mitochondria, creates a cellular environment permissive for progression to a malignant phenotype and the development of resistance to commonly used anticancer agents. An extension of this paradigm is that when these mitochondrial functions are altered by the events leading to transformation and ensuing downstream metabolic processes, they can be used as molecular biomarkers or targets in the development of new therapeutic interventions to selectively kill and/or sensitize cancer versus normal cells. In this Review we propose that mitochondrial oxidative metabolism is altered in tumor cells, and the central theme of this dysregulation is electron transport chain activity, folate metabolism, NADH/NADPH metabolism, thiol-mediated detoxification pathways, and redox-active metal ion metabolism. It is proposed that specific subgroups of human malignancies display distinct mitochondrial transformative and/or tumor signatures that may benefit from agents that target these pathways.

Static Magnetic Fields Modulate the Response of Different Oxidative Stress Markers in a Restraint Stress Model Animal

Stress is a state of vulnerable homeostasis that alters the physiological and behavioral responses. Stress induces oxidative damage in several organs including the brain, liver, kidney, stomach, and heart. Preliminary findings suggested that the magnetic stimulation could accelerate the healing processes and has been an effective complementary therapy in different pathologies. However, the mechanism of action of static magnetic fields (SMFs) is not well understood. In this study, we demonstrated the effects of static magnetic fields (0.8 mT) in a restraint stressed animal model, focusing on changes in different markers of oxidative damage. A significant increase in the plasma levels of nitric oxide (NO), malondialdehyde (MDA), and advanced oxidation protein products (AOPP), and a decrease in superoxide dismutase (SOD), glutathione (GSH), and glycation end products (AGEs) were observed in restraint stress model. Exposure to SMFs over 5 days (30, 60, and 240 min/day) caused a decrease in the NO, MDA, AGEs, and AOPP levels; in contrast, the SOD and GSH levels increased. The response to SMFs was time-dependent. Thus, we proposed that exposure to weak-intensity SMFs could offer a complementary therapy by attenuating oxidative stress. Our results provided a new perspective in health studies, particularly in the context of oxidative stress.

Exercise training during chemotherapy preserves skeletal muscle fiber area, capillarization, and mitochondrial content in patients with breast cancer

Exercise has been suggested to ameliorate the detrimental effects of chemotherapy on skeletal muscle. The aim of this study was to compare the effects of different exercise regimens with usual care on skeletal muscle morphology and mitochondrial markers in patients being treated with chemotherapy for breast cancer. Specifically, we compared moderate-intensity aerobic training combined with high-intensity interval training (AT-HIIT) and resistance training combined with high-intensity interval training (RT-HIIT) with usual care (UC). Resting skeletal muscle biopsies were obtained pre- and postintervention from 23 randomly selected women from the OptiTrain breast cancer trial who underwent RT-HIIT, AT-HIIT, or UC for 16 wk. Over the intervention, citrate synthase activity, muscle fiber cross-sectional area, capillaries per fiber, and myosin heavy chain isoform type I were reduced in UC, whereas RT-HIIT and AT-HIIT were able to counteract these declines. AT-HIIT promoted up-regulation of the electron transport chain protein levels vs. UC. RT-HIIT favored satellite cell count vs. UC and AT-HIIT. There was a significant association between change in citrate synthase activity and self-reported fatigue. AT-HIIT and RT-HIIT maintained or improved markers of skeletal muscle function compared with the declines found in the UC group, indicating a sustained trainability in addition to the preservation of skeletal muscle structural and metabolic characteristics during chemotherapy. These findings highlight the importance of supervised exercise programs for patients with breast cancer during chemotherapy.-Mijwel, S., Cardinale, D. A., Norrbom, J., Chapman, M., Ivarsson, N., Wengström, Y., Sundberg, C. J., Rundqvist, H. Exercise training during chemotherapy preserves skeletal muscle fiber area, capillarization, and mitochondrial content in patients with breast cancer.

An ex vivo abomasal ovine model to study the immediate immune response in the context of Haemonchus contortus larval-stage

We have set up an ex vivo ovine abomasal model, which can mimic the multicellular process to explore the early steps in haemonchine nematode infection using RNA-seq technology. Ovine abomasal explants were collected for histological and transcriptional analysis and supernatants collected to quantitate lactate dehydrogenase (LDH) enzymes. Atotal of 233 were substantially induced genes between L₄-inoculated and uninoculated-control tissues, respectively. However, a total of 14 were considerably down-regulated genes between the 51 aforementioned tissues. Fifteen pathways were annotated by Kyoto Encyclopedia of Genes, and Genomes pathway analysis accounted for the significant percentage in immediate response to larval-stage of H. contortus. Key genes upregulated in response to the addition of L₄-inoculum of H. contortus were IL-6, IL-8, C1q, Atypical chemokine receptor-3, chemokine ligand-2, manganese superoxide dismutase, integrin alpha-7, -8, -9, integrin subunit beta-1, integrin subunit beta 6, intercellular adhesion molecule-1 and actin alpha-1. This study shows for the first time that galectin-1 is up-regulated in an ex vivo abomasal segment model exposed to L₄-inoculum of H. contortus following 6 h of incubation. The abomasal segment model has been shown to be a suitable tool to study the haemonchine larval-stage effects on the ovine abomasal tissues prior to in vivo assessment.

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.

Extracellular superoxide dismutase and its role in cancer

Reactive oxygen species (ROS) are increasingly recognized as critical determinants of cellular signaling and a strict balance of ROS levels must be maintained to ensure proper cellular function and survival. Notably, ROS is increased in cancer cells. The superoxide dismutase family plays an essential physiological role in mitigating deleterious effects of ROS. Due to the compartmentalization of ROS signaling, EcSOD, the only superoxide dismutase in the extracellular space, has unique characteristics and functions in cellular signal transduction. In comparison to the other two intracellular SODs, EcSOD is a relatively new comer in terms of its tumor suppressive role in cancer and the mechanisms involved are less well understood. Nevertheless, the degree of differential expression of this extracellular antioxidant in cancer versus normal cells/tissues is more pronounced and prevalent than the other SODs. A significant association of low EcSOD expression with reduced cancer patient survival further suggests that loss of extracellular redox regulation promotes a conducive microenvironment that favors cancer progression. The vast array of mechanisms reported in mediating deregulation of EcSOD expression, function, and cellular distribution also supports that loss of this extracellular antioxidant provides a selective advantage to cancer cells. Moreover, overexpression of EcSOD inhibits tumor growth and metastasis, indicating a role as a tumor suppressor. This review focuses on the current understanding of the mechanisms of deregulation and tumor suppressive function of EcSOD in cancer.

Opposite effects of catalase and MnSOD ectopic expression on stress induced defects and mortality in the desmin deficient cardiomyopathy model

Oxidative stress has been linked strongly to cell death and cardiac remodeling processes, all hallmarks of heart failure. Mice deficient for desmin (des-/-), the major muscle specific intermediate filament protein, develop dilated cardiomyopathy and heart failure characterized by mitochondrial defects and cardiomyocyte death. The cellular and biochemical alterations in the hearts of these mice strongly suggest that oxidative stress is one of the mechanisms contributing to the pathogenesis of the phenotype. Recently, we showed that indeed the desmin deficient cardiomyocytes are under increased oxidative stress. In order to verify these findings in vivo, we generated transgenic animals overexpressing SOD2 (MnSOD) and/or catalase in the heart and crossed them with des-/- mice, thus allowing us to evaluate the contribution of oxidative injury in inherited cardiomyopathies, as well as the therapeutic potential of antioxidant strategies. Moderate MnSOD and/or catalase overexpression in des-/- hearts leads to a marked decrease in intracellular reactive oxygen species (ROS), ameliorates mitochondrial and other ultrastructural defects, minimizes myocardial degeneration and leads to a significant improvement of cardiac function. Importantly, catalase overexpression increased the 50% survival rate of des-/- mice in an obligatory exercise to 100%. In contrast, MnSOD overexpression enhanced the lethality of des-/- mice, underscoring the importance of a fine balanced cellular redox status. Overall, the present study supports the contribution of oxidative stress in the development of des-/- cardiomyopathy and points to a well-considered antioxidant treatment as therapeutic for cardiomyopathies.

Early and late gene expression profiles of the ovine mucosa in response to Haemonchus contortus infection employing Illumina RNA-seq technology

We conducted herein transcriptome sequencing of the ovine abomasal tissues using the Illumina HiSeq 4000 platform to segregate early and late H. contortus-infected sheep (7 and 50days post-infected groups, respectively) from the control naive ones. A total of 548, 357 and 7 were substantially induced genes in 7days post-infection versus uninfected-control group, 50days post-infection versus 7days post-infection (7dpi), and 50days post-infection (50dpi) versus uninfected-control group, respectively. However, a total of 301, 355 and 11 were significantly repressed genes between 7dpi versus uninfected-control group, 50dpi versus 7dpi, and 50dpi versus uninfected-control group, correspondingly. This indicates that H. contortus infection induced a more potent activation of abomasal gene expression in the early stage of infection as compared to the late stage. Seven pathways were annotated by Kyoto Encyclopedia of Genes, and Genomes pathway analysis accounted for the significant percentage in early H. contortus infection. This study shows for the first time that both galectin-11 and matricellular protein osteopontin are up-regulated in abomasal tissue after chronic H. contortus infection, while galectin-4 is specifically down-regulated in the early infection. Additionally, our results showed that the induction or repression of these molecules is likely to determine the infection progression.

SOD2 and the Mitochondrial UPR: Partners Regulating Cellular Phenotypic Transitions

ATP and reactive oxygen species (ROS) are signaling molecules that control cellular function and phenotype. Mitochondria produce both ATP and ROS. Since the electrons needed to generate either ATP or ROS originate from NADH/FADH2, the mechanism through which electrons flow towards oxygen determines yields and whether ATP or ROS prevails. Alterations in the electron flow impact cells dramatically, such as by supporting specialization (which requires high ATP) or imposing dedifferentiation. High ROS, facilitated by enzymes such as superoxide dismutase 2 (SOD2) that enhance mitochondrial hydrogen peroxide (mtH2O2), are normally linked to dedifferentiation of somatic cells. Here we propose that combined high mtH2O2 and mitochondrial unfolded protein response (UPR(mt)) activation are essential for somatic dedifferentiation programs and the acquisition of stem-like properties in reparative processes and disease.

Identification and Analysis of the Role of Superoxide Dismutases Isoforms in the Pathogenesis of Paracoccidioides spp

The ability of Paracoccidioides to defend itself against reactive oxygen species (ROS) produced by host effector cells is a prerequisite to survive. To counteract these radicals, Paracoccidioides expresses, among different antioxidant enzymes, superoxide dismutases (SODs). In this study, we identified six SODs isoforms encoded by the Paracoccidioides genome. We determined gene expression levels of representative isolates of the phylogenetic lineages of Paracoccidioides spp. (S1, PS2, PS3 and Pb01-like) using quantitative RT-PCR. Assays were carried out to analyze SOD gene expression of yeast cells, mycelia cells, the mycelia-to-yeast transition and the yeast-to-mycelia germination, as well as under treatment with oxidative agents and during interaction with phagocytic cells. We observed an increased expression of PbSOD1 and PbSOD3 during the transition process, exposure to oxidative agents and interaction with phagocytic cells, suggesting that these proteins could assist in combating the superoxide radicals generated during the host-pathogen interaction. Using PbSOD1 and PbSOD3 knockdown strains we showed these genes are involved in the response of the fungus against host effector cells, particularly the oxidative stress response, and in a mouse model of infection. Protein sequence analysis together with functional analysis of knockdown strains seem to suggest that PbSOD3 expression is linked with a pronounced extracellular activity while PbSOD1 seems more related to intracellular requirements of the fungus. Altogether, our data suggests that P. brasiliensis actively responds to the radicals generated endogenously during metabolism and counteracts the oxidative burst of immune cells by inducing the expression of SOD isoforms.

Paracoccidioidomycosis is a health-threatening human systemic mycosis, endemic to some Latin America countries. The disease is caused by species belonging to the Paracoccidioides genus. Once inside the human host, Paracoccidioides must face the host innate immune system, escaping from the cytotoxic capacity of innate immune cells (ROS production and liberation of polypeptide antibiotics). To do so, they express and synthetize superoxide dismutases (SODs). We aimed to identify and characterize the SOD isoforms present in the Paracoccidioides genome. We identified six isoforms, among which we found an increased expression of PbSOD1 and PbSOD3 during the transition-to-yeast process, exposure to oxidative agents and interaction with phagocytic cells. Additionally, we found that PbSOD3 expression might be linked with a pronounced extracellular activity while PbSOD1 and the other isoforms seem more related to intracellular requirements of the fungus. We propose that the defence against endogenous-produced ROS may depend on intracellular Sods (mostly SOD1, but possibly also SOD2, SOD4 and SOD5), but defence against extracellular ROS (produced during host-pathogen interactions) might rely to a greater extent on SOD3, which is endowed with an extracellular activity.

Mitochondrial Superoxide Dismutase Has a Protumorigenic Role in Ovarian Clear Cell Carcinoma

Epithelial ovarian cancer (EOC) is the fourth leading cause of death due to cancer in women and comprises distinct histologic subtypes, which vary widely in their genetic profiles and tissues of origin. It is therefore imperative to understand the etiology of these distinct diseases. Ovarian clear cell carcinoma (OCCC), a very aggressive subtype, comprises >10% of EOCs. In the present study, we show that mitochondrial superoxide dismutase (Sod2) is highly expressed in OCCC compared with other EOC subtypes. Sod2 is an antioxidant enzyme that converts highly reactive superoxide (O2 (•-)) to hydrogen peroxide (H2O2) and oxygen (O2), and our data demonstrate that Sod2 is protumorigenic and prometastatic in OCCC. Inhibiting Sod2 expression reduces OCCC ES-2 cell tumor growth and metastasis in a chorioallantoic membrane (CAM) model. Similarly, cell proliferation, migration, spheroid attachment and outgrowth on collagen, and Akt phosphorylation are significantly decreased with reduced expression of Sod2. Mechanistically, we show that Sod2 has a dual function in supporting OCCC tumorigenicity and metastatic spread. First, Sod2 maintains highly functional mitochondria, by scavenging O2 (•-), to support the high metabolic activity of OCCC. Second, Sod2 alters the steady-state ROS balance to drive H2O2-mediated migration. While this higher steady-state H2O2 drives prometastatic behavior, it also presents a doubled-edged sword for OCCC, as it pushed the intracellular H2O2 threshold to enable more rapid killing by exogenous sources of H2O2. Understanding the complex interaction of antioxidants and ROS may provide novel therapeutic strategies to pursue for the treatment of this histologic EOC subtype.

Iron incorporation into MnSOD A (bacterial Mn-dependent superoxide dismutase) leads to the formation of a peroxidase/catalase implicated in oxidative damage to bacteria

BACKGROUND

Mn/Fe-superoxide dismutase (SOD) is a family of enzymes essential for organisms to be able to cope with oxygen. These enzymes bound to their classical metals catalyze the dismutation of the free radical superoxide anion (O2(-)) to H2O2 and molecular oxygen. E. coli has the manganese-dependent SOD A and the iron-dependent SOD B.

METHODS

Strains of E. coli overexpressing SOD A or SOD B were grown in media with different metal compositions. SODs were purified and their metal content and SOD activity were determined. Those proteins were incubated with H2O2 and assayed for oxidation of Amplex red or o-phenylenediamine, consumption of H2O2, release of iron and protein radical formation. Cell survival was determined in bacteria with MnSOD A or FeSOD A after being challenged with H2O2.

RESULTS

We show for the first time that the bacterial manganese-dependent SOD A when bound to iron (FeSOD A) has peroxidase activity. The in vivo formation of the peroxidase FeSOD A was increased when media had higher levels of iron because of a decreased manganese metal incorporation. In comparison to bacteria with MnSOD A, cells with FeSOD A had a higher loss of viability when exposed to H2O2.

GENERAL SIGNIFICANCE

The biological occurrence of this fundamental antioxidant enzyme in an alternative iron-dependent state represents an important source of free radical formation.

MnSOD upregulation sustains the Warburg effect via mitochondrial ROS and AMPK-dependent signalling in cancer

Manganese superoxide dismutase (MnSOD/SOD2) is a mitochondria-resident enzyme that governs the types of reactive oxygen species egressing from the organelle to affect cellular signaling. Here, we demonstrate that MnSOD upregulation in cancer cells establishes a steady flow of H₂O₂ originating from mitochondria that sustains AMP-activated kinase (AMPK) activation and the metabolic shift to glycolysis. Restricting MnSOD expression or inhibiting AMPK suppress the metabolic switch and dampens the viability of transformed cells indicating that the MnSOD/AMPK axis is critical in support cancer cell bioenergetics. Recapitulating in vitro findings, clinical and epidemiologic analyses of MnSOD expression and AMPK activation indicated that the MnSOD/AMPK pathway is most active in advanced stage and aggressive breast cancer subtypes. Taken together, our results indicate that MnSOD serves as a biomarker of cancer progression and acts as critical regulator of tumor cell metabolism.

Natural allelic variations in glutathione peroxidase-1 affect its subcellular localization and function

Glutathione peroxidase 1 (GPx-1) has been implicated in the etiology of several common diseases due to the association between specific allelic variations and cancer risk. The most common among these variations are the codon 198 polymorphism that results in either a leucine or proline and the number of alanine repeat codons in the coding sequence. The molecular and biologic consequences of these variations remain to be characterized. Toward achieving this goal, we have examined the cellular location of GPx-1 encoded by allelic variants by ectopically expressing these genes in MCF-7 human breast carcinoma cells that produce undetectable levels of GPx-1, thus achieving exclusive expression in the same cellular environment. A differential distribution between the cytoplasm and mitochondria was observed, with the allele expressing the leucine-198 polymorphism and 7 alanine repeats being more cytoplasmically located than the other alleles examined. To assess whether the distribution of GPx-1 between the cytoplasm and mitochondria had a biologic consequence, we engineered derivative GPx-1 proteins that were targeted to the mitochondria by the addition of a mitochondria targeting sequence and expressed these proteins in MCF-7 cells. These cells were examined for their response to oxidative stress, energy metabolism, and impact on cancer-associated signaling molecules. The results obtained indicated that both primary GPx-1 sequence and cellular location have a profound impact on cellular biology and offer feasible hypotheses about how expression of distinct GPx-1 alleles can affect cancer risk. Cancer Res; 74(18); 5118-26. ©2014 AACR.

SOD therapeutics: latest insights into their structure-activity relationships and impact on the cellular redox-based signaling pathways

SIGNIFICANCE

Superoxide dismutase (SOD) enzymes are indispensable and ubiquitous antioxidant defenses maintaining the steady-state levels of O2·(-); no wonder, thus, that their mimics are remarkably efficacious in essentially any animal model of oxidative stress injuries thus far explored.

RECENT ADVANCES

Structure-activity relationship (half-wave reduction potential [E1/2] versus log kcat), originally reported for Mn porphyrins (MnPs), is valid for any other class of SOD mimics, as it is dominated by the superoxide reduction and oxidation potential. The biocompatible E1/2 of ∼+300 mV versus normal hydrogen electrode (NHE) allows powerful SOD mimics as mild oxidants and antioxidants (alike O2·(-)) to readily traffic electrons among reactive species and signaling proteins, serving as fine mediators of redox-based signaling pathways. Based on similar thermodynamics, both SOD enzymes and their mimics undergo similar reactions, however, due to vastly different sterics, with different rate constants.

CRITICAL ISSUES

Although log kcat(O2·(-)) is a good measure of therapeutic potential of SOD mimics, discussions of their in vivo mechanisms of actions remain mostly of speculative character. Most recently, the therapeutic and mechanistic relevance of oxidation of ascorbate and glutathionylation and oxidation of protein thiols by MnP-based SOD mimics and subsequent inactivation of nuclear factor κB has been substantiated in rescuing normal and killing cancer cells. Interaction of MnPs with thiols seems to be, at least in part, involved in up-regulation of endogenous antioxidative defenses, leading to the healing of diseased cells.

FUTURE DIRECTIONS

Mechanistic explorations of single and combined therapeutic strategies, along with studies of bioavailability and translational aspects, will comprise future work in optimizing redox-active drugs.

Free radicals: how do we stand them? Anaerobic and aerobic free radical (chain) reactions involved in the use of fluorogenic probes and in biological systems

Biologically significant conclusions have been based on the use of fluorogenic and luminogenic probes for the detection of reactive species. The basic mechanisms of the processes involved have not been satisfactorily elucidated. In the present work, the mechanism of the enzyme and photosensitized oxidation of NAD(P)H by resorufin is analyzed and appears to involve both aerobic and anaerobic free radical chain reactions. There are two major fallouts of this analysis. Many of the conclusions about the participation of radicals based on the use of probes such as resorufin and Amplex red need reevaluation. It is also concluded that anaerobic free radical reactions may be biologically significant, and the possible existence of enzymatic systems to eliminate certain free radicals is discussed.

Regulation of Cu-Zn superoxide dismutase on SCN2A in SH-SY5Y cells as a potential therapy for temporal lobe epilepsy

In order to evaluate SCN2A as a candidate gene for epileptic susceptibility and the use of a Cu-Zn superoxide dismutase (SOD) supplement as a potential therapy for epilepsy, SCN2A expression in the cortex and the correlation between SCN2A and Cu-Zn SOD in SH-SY5Y cells were examined. SCN2A expression and the concentration of Cu-Zn SOD in the cerebral cortexes of patients with primary and secondary temporal lobe epilepsy and normal brain cortex tissues were detected. By transfecting SH-SY5Y cells, the expression of SCN2A and the concentration of Cu-Zn SOD was analyzed and the single-cell patch clamp technique was employed in order to investigate the changes in sodium ion levels following SCN2A knockdown. SCN2A level restoration was also investigated with a Cu-Zn SOD supplement using an expression study and evaluated the changes in sodium ion levels following SCN2A knockdown. SCN2A expression and Cu-Zn SOD concentration decreased in the epileptic cerebral cortex. Following SCN2A knockdown, the concentration of Cu-Zn SOD declined and the si-SCN2A vector group showed a repeated discharge. Furthermore, the Cu-Zn SOD concentration was capable of restoring the expression of SCN2A following SCN2A knockdown in SH-SY5Y cells and the overexpression of Cu-Zn SOD prevented the repeated discharge caused by si-SCN2A. The results indicated that there is a low expression of SCN2A and Cu-Zn SOD in the epileptic cerebral cortex and provided novel insights into potential therapies for temporal lobe epilepsy.

Immuno-spin trapping from biochemistry to medicine: advances, challenges, and pitfalls. Focus on protein-centered radicals

BACKGROUND

Immuno-spin trapping (IST) is based on the reaction of a spin trap with a free radical to form a stable nitrone adduct, followed by the use of antibodies, rather than traditional electron paramagnetic resonance spectroscopy, to detect the nitrone adduct. IST has been successfully applied to mechanistic in vitro studies, and recently, macromolecule-centered radicals have been detected in models of drug-induced agranulocytosis, hepatotoxicity, cardiotoxicity, and ischemia/reperfusion, as well as in models of neurological, metabolic and immunological diseases.

SCOPE OF THE REVIEW

To critically evaluate advances, challenges, and pitfalls as well as the scientific opportunities of IST as applied to the study of protein-centered free radicals generated in stressed organelles, cells, tissues and animal models of disease and exposure.

MAJOR CONCLUSIONS

Because the spin trap has to be present at high enough concentrations in the microenvironment where the radical is formed, the possible effects of the spin trap on gene expression, metabolism and cell physiology have to be considered in the use of IST and in the interpretation of results. These factors have not yet been thoroughly dealt with in the literature.

GENERAL SIGNIFICANCE

The identification of radicalized proteins during cell/tissue response to stressors will help define their role in the complex cellular response to stressors and pathogenesis; however, the fidelity of spin trapping/immuno-detection and the effects of the spin trap on the biological system should be considered. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.