Extracellular Superoxide Dismutase Research Articles

Extracellular Superoxide Dismutase (SOD3) mediates extracellular superoxide‐dependent signaling by TNFalpha.

Tumor necrosis factor‐α (TNFα) signaling requires superoxide (O2−•) to be produced extracellularly by NADPH oxidase 1 (Nox1). It remains unclear how this redox signal is transduced into activation of intracellular signaling pathways. We sought to identify steps in the TNFα signaling cascade that are directly O2−•‐dependent. We analyzed TNFα receptor endocytosis and activation of MAPKs and NF‐κB in cultured vascular smooth muscle cells (VSMC). JNK, p38 and ERK1/2 were activated with a similar concentration dependence. TNFα receptor endocytosis, MAPKs (p‐JNK and p‐ERK1/2) and NF‐κB activation were all inhibited by unmodified superoxide dismutase (SOD, 500 U/ml) added extracellularly, but not by catalase (1000 U/ml), or by overexpression of cytoplasmic CuZnSOD or catalase with adenovirus. This suggested a paramount importance of extracellular O2−•. We next sought to determine if endogenous, extracellular SOD (SOD3) modulated these responses by employing siRNA‐mediated downregulation. Surprisingly, siSOD3 blocked TNFα‐induced endocytosis (37 % reduction) and rather than enhancing MAPK and NF‐κB activation, these effects were blocked (Relative NF‐κB activation; siControl+TNFα 10.8 ± 1.0, siSOD3+TNFα 4.0 ± 0.3 fold, n=7, p<0.05). Similar results were obtained by pharmacologic inhibition of SOD3 using DETC (100 μM). These results demonstrate that enzymatic activity of endogenous SOD3 is required for signaling, however, the lack of effect of extracellular catalase calls into question the role of H2O2, the product of SOD3 activity. In order to directly assess the signaling impact of H2O2 we performed a dose‐response to this oxidant. MAPK activation occurred at a lower concentration (1 μM) while a higher concentration (10 μM) potently inhibited signaling (Figure 1). It remains to be determined how SOD3 modulates local H2O2 concentrations in the extracellular matrix following Nox1 activation by TNFα, and whether the H2O2 produced by SOD3 is accessible to catalase placed into that compartment. Taken together, these data suggest a novel role for SOD3 in transducing Nox1‐dependent inflammatory signaling activated by TNFα in VSMC.Support or Funding InformationThis work was supported by R01 HL128386 (FSL) and by a Scientist Development Award from the AHA (HC).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Endothelial TRPA1 Channels Are Activated by Hypoxia in Cerebral Arteries and Protect Against Ischemic Damage

Acute drops in cerebral perfusion can lead to rapid neuronal death, as seen during transient ischemic attacks and ischemic strokes. The extent of brain damage following hypoxia is linked to the ability of collateral blood vessels to adequately supply blood to the peri‐infarct region and thus prevent neuronal loss and infarct expansion. During hypoxia, reactive oxygen species (ROS) are increased and may activate the Ca2+‐permeable transient receptor potential ankyrin 1 (TRPA1) in endothelial cells, promoting vasodilation. Here, we tested the hypothesis that TRPA1 channels in endothelial cells are activated by hypoxia‐derived ROS, leading to cerebral artery dilation and reduced ischemic damage. Using a novel mouse model expressing the Ca2+ indicator GCaMP6f in endothelial cells (Tek:GCaMP6f), we show that 4‐hydroxynonenal (4‐HNE), a lipid peroxide, increased TRPA1 channel activity, detected as elementary Ca2+ influx events (TRPA1 sparklets). The TRPA1 inhibitor A967079 prevented 4‐HNE induction of TRPA1 sparklets in endothelial cells. Acute exposure of cerebral arteries to hypoxia (5% O2, 6% CO2, 89% N2) significantly increased 4‐HNE accumulation in cerebral arteries, which was linked to an increase in TRPA1 sparklets. Hypoxia induction of TRPA1 sparklets was blocked by the TRPA1 inhibitor A967079, and by PEGylated superoxide dismutase (PEG‐SOD), suggesting a role for intracellular generation of ROS. Incubation of arteries with the mitochondria‐targeted antioxidant mitoTEMPO prevented the hypoxia‐induced increase in TRPA1 sparklets, whereas extracellular SOD or the NADPH oxidase inhibitor apocynin had no effect. In pressure myography studies, hypoxia caused endothelium‐dependent dilation of isolated cerebral arteries, an effect that was prevented by the membrane‐permeable SOD mimetic tempol and by mitoTEMPO. Hypoxia‐induced dilation of cerebral arteries was partially inhibited by the TRPA1 antagonist A967079 and was reduced in arteries isolated from endothelial cell‐specific TRPA1 knockout mice (eTRPA1−/− mice). In vivo, loss of TRPA1 channels in endothelial cells increased infarct size following middle cerebral occlusion, a model of ischemic strokes. Reversely, TRPA1 activation with cinnamaldehyde (50 mg/kg) reduced infarct size in wildtype, but not eTRPA1−/−, mice. Together, these data suggest that TRPA1 channels in cerebral artery endothelial cells are early sensors of hypoxia and orchestrate a response that culminates with vasodilation, thereby reducing ischemic damage. Further, pharmacological activation of TRPA1 channels may be a putative therapeutic target to reduce cerebral ischemic damage.Support or Funding InformationSupported by the National Institutes of Health (R01HL091095 to SE) and the American Heart Association (15POST2472002 to PWP)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Redistribution of Extracellular Superoxide Dismutase Causes Neonatal Pulmonary Vascular Remodeling and PH but Protects Against Experimental Bronchopulmonary Dysplasia.

Background: A naturally occurring single nucleotide polymorphism (SNP), (R213G), in extracellular superoxide dismutase (SOD3), decreases SOD3 matrix binding affinity. Humans and mature mice expressing the R213G SNP exhibit increased cardiovascular disease but decreased lung disease. The impact of this SNP on the neonatal lung at baseline or with injury is unknown. Methods: Wild type and homozygous R213G mice were injected with intraperitoneal bleomycin or phosphate buffered saline (PBS) three times weekly for three weeks and tissue harvested at 22 days of life. Vascular and alveolar development were evaluated by morphometric analysis and immunostaining of lung sections. Pulmonary hypertension (PH) was assessed by right ventricular hypertrophy (RVH). Lung protein expression for superoxide dismutase (SOD) isoforms, catalase, vascular endothelial growth factor receptor 2 (VEGFR2), endothelial nitric oxide synthase (eNOS) and guanosine triphosphate cyclohydrolase-1 (GTPCH-1) was evaluated by western blot. SOD activity and SOD3 expression were measured in serum. Results: In R213G mice, SOD3 lung protein expression decreased, serum SOD3 protein expression and SOD serum activity increased compared to wild type (WT) mice. Under control conditions, R213G mice developed pulmonary vascular remodeling (decreased vessel density and increased medial wall thickness) and PH; alveolar development was similar between strains. After bleomycin injury, in contrast to WT, R213G mice were protected from impaired alveolar development and their vascular abnormalities and PH did not worsen. Bleomycin decreased VEGFR2 and GTPCH-1 only in WT mice. Conclusion: R213G neonatal mice demonstrate impaired vascular development and PH at baseline without alveolar simplification, yet are protected from bleomycin induced lung injury and worsening of pulmonary vascular remodeling and PH. These results show that vessel bound SOD3 is essential in normal pulmonary vascular development, and increased serum SOD3 expression and SOD activity prevent lung injury in experimental bronchopulmonary dysplasia (BPD) and PH.

Akt2 (Protein Kinase B Beta) Stabilizes ATP7A, a Copper Transporter for Extracellular Superoxide Dismutase, in Vascular Smooth Muscle: Novel Mechanism to Limit Endothelial Dysfunction in Type 2 Diabetes Mellitus.

Copper transporter ATP7A (copper-transporting/ATPase) is required for full activation of SOD3 (extracellular superoxide dismutase), which is secreted from vascular smooth muscle cells (VSMCs) and anchors to endothelial cell surface to preserve endothelial function by scavenging extracellular superoxide. We reported that ATP7A protein expression and SOD3 activity are decreased in insulin-deficient type 1 diabetes mellitus vessels, thereby, inducing superoxide-mediated endothelial dysfunction, which are rescued by insulin treatment. However, it is unknown regarding the mechanism by which insulin increases ATP7A expression in VSMCs and whether ATP7A downregulation is observed in T2DM (type2 diabetes mellitus) mice and human in which insulin-Akt (protein kinase B) pathway is selectively impaired. Here we show that ATP7A protein is markedly downregulated in vessels isolated from T2DM patients, as well as those from high-fat diet-induced or db/db T2DM mice. Akt2 (protein kinase B beta) activated by insulin promotes ATP7A stabilization via preventing ubiquitination/degradation as well as translocation to plasma membrane in VSMCs, which contributes to activation of SOD3 that protects against T2DM-induced endothelial dysfunction. Downregulation of ATP7A in T2DM vessels is restored by constitutive active Akt or PTP1B-/- (protein-tyrosine phosphatase 1B-deficient) T2DM mice, which enhance insulin-Akt signaling. Immunoprecipitation, in vitro kinase assay, and mass spectrometry analysis reveal that insulin stimulates Akt2 binding to ATP7A to induce phosphorylation at Ser1424/1463/1466. Furthermore, SOD3 activity is reduced in Akt2-/- vessels or VSMCs, which is rescued by ATP7A overexpression. Akt2 plays a critical role in ATP7A protein stabilization and translocation to plasma membrane in VSMCs, which contributes to full activation of vascular SOD3 that protects against endothelial dysfunction in T2DM.

SOD3 improves the tumor response to chemotherapy by stabilizing endothelial HIF-2\u03b1

One drawback of chemotherapy is poor drug delivery to tumor cells, due in part to hyperpermeability of the tumor vasculature. Extracellular superoxide dismutase (SOD3) is an antioxidant enzyme usually repressed in the tumor milieu. Here we show that specific SOD3 re-expression in tumor-associated endothelial cells (ECs) increases doxorubicin (Doxo) delivery into and chemotherapeutic effect on tumors. Enhanced SOD3 activity fostered perivascular nitric oxide accumulation and reduced vessel leakage by inducing vascular endothelial cadherin (VEC) transcription. SOD3 reduced HIF prolyl hydroxylase domain protein activity, which increased hypoxia-inducible factor-2α (HIF-2α) stability and enhanced its binding to a specific VEC promoter region. EC-specific HIF-2α ablation prevented both the SOD3-mediated increase in VEC transcription and the enhanced Doxo effect. SOD3, VEC, and HIF-2α levels correlated positively in primary colorectal cancers, which suggests a similar interconnection of these proteins in human malignancy.

Extracellular redox state shift: A novel approach to target prostate cancer invasion.

Extracellular superoxide dismutase (ECSOD) and the cysteine/glutamate transporter (Cys)/(xCT) are tumor microenvironment (TME) redox state homeostasis regulators. Altered expression of ECSOD and xCT can lead to imbalance of the TME redox state and likely have a profound effect on cancer invasion. In the present study, we investigated whether ECSOD and xCT could be therapeutic targets for prostate cancer (PCa) invasion. Immunohistochemistry of tumor microarray PCa tissues (N = 165) with high Gleason scores indicated that xCT protein expression is significantly increased while ECSOD protein expression is significantly decreased. Metastatic PCa indicated ECSOD protein expression is significantly decreased in epithelial area whereas xCT protein expression is significantly increased in stromal area. Furthermore, inhibition of extracellular O2•- by overexpression of ECSOD or alteration of the extracellular Cys/CySS ratio by knockdown of xCT protein inhibited PCa cell invasion. Simultaneous overexpression of ECSOD and knockdown xCT inhibited PCa cell invasion more than overexpression of ECSOD or knockdown of xCT alone. In the co-culturing system, simultaneous overexpression of ECSOD and knockdown of xCT in prostate stromal WPMY-1 cells inhibited PCa cell invasiveness more than overexpression of ECSOD alone. The decrease in PCa invasion correlated with increased of extracellular H2O2 levels. Notably, overexpression of catalase in TME reversed the inhibitory effect of ECSOD on cancer cell invasion. Impaired ECSOD activity and an upregulated of xCT protein expression may be clinical features of an aggressive PCa, particularly metastatic cancers and/or those with a high Gleason score. Therefore, shifting the extracellular redox state toward an oxidizing status by targeted modulation of ECSOD and xCT, in both cancer and stromal cells, may provide a greater strategy for potential therapeutic interventions of aggressive PCa.

Serum Extracellular Superoxide Dismutase Is Associated with Diabetic Retinopathy Stage in Chinese Patients with Type 2 Diabetes Mellitus.

Extracellular superoxide dismutase (ecSOD) is the major extracellular scavenger of reactive oxygen species and associated with the diabetic complication in patients with type 2 diabetes mellitus (T2DM). We aimed to investigate the serum ecSOD activity in Chinese patients with different stages of diabetic retinopathy (DR) and evaluate the association between the serum ecSOD activity and the severity of DR. A total of 343 T2DM patients were categorized into three groups: nondiabetic retinopathy (NDR) group, nonproliferative diabetic retinopathy (NPDR) group, and proliferative diabetic retinopathy (PDR) group. Serum ecSOD activities were measured by the autoxidation of the pyrogallol method. In this study, 271, 46, and 26 patients were enrolled in the NDR, NPDR, and PDR groups, respectively. We found a significantly decreased trend of serum ecSOD activity among NDR subjects (118.0 ± 11.5 U/mL) compared to NPDR subjects (108.5 ± 11.9 U/mL) (P < 0.001) and NPDR subjects compared to PDR subjects (102.7 ± 12.4 U/mL) (P = 0.041). Serum ecSOD activity was an independent risk factor for DR (OR = 0.920, P < 0.001) and was associated with the progression of DR. Serum ecSOD activity might be a biomarker for DR screening and evaluation of the clinical severity of DR in Chinese T2DM patients.

Xanthine oxidase activity in patients with age-related cataract associated with hypertension.

Reactive oxygen species and lipid peroxidation are important factors that contribute to the development of age-related cataract. The study included 130 patients with age-related cataract, 69 of whom were diagnosed with hypertension (HT), 20 with hypertension and type 2 diabetes mellitus (DM), and 41 had no accompanying condition. The following parameters were measured in the serum of the examinees: products of lipid peroxidation malondialdehyde (MDA) and lipofuscin-like fluorophores (LLF), activity of prooxidative enzymes xanthine oxidase (XO) and myeloperoxidase (MPO), antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), the concentration of thiol groups, and the ferric reducing activity of plasma. The activity of prooxidative enzymes XO and MPO was higher in the plasma of patients with HT (XO=9.0±1.2 U/L; MPO=77.3±8.4 U/L) and with HT and DM (XO=11.9±0.9 U/L; MPO=89.5±5.0 U/L) compared to patients with age-related cataract (XO=6.2±0.9 U/L; MPO=52.4±6.3 U/L; P<0.01). Our research has shown that patients with age-related cataract and hypertension were exposed to increased oxidative damage of biomolecules, based on the increased plasma LLF and MDA content and decreased levels of thiol groups. Oxidative changes of biomolecules in these patients were associated with increased activity of the XO, MPO, and GPx enzymes and a lower extracellular SOD activity and total ferric reductive ability of plasma.

Cu,Zn Superoxide Dismutase Genes in Tribolium castaneum: Evolution, Molecular Characterisation, and Gene Expression during Immune Priming.

The production of reactive oxygen species (ROS) is a normal consequence of the aerobic cell metabolism. Despite their high and potentially detrimental reactivity with various biomolecules, the endogenous production of ROS is a vital part of physiological, immunological, and molecular processes that contribute to fitness. The role of ROS in host–parasite interactions is frequently defined by their contribution to innate immunity as effectors, promoting parasite death during infections. In vertebrates, ROS and antioxidant system enzymes, such as superoxide dismutase (SOD) are also involved in acquired immune memory, where they are responsible for T-cell signalling, activation, proliferation, and viability. Based on recent findings, ROS are now also assumed to play a role in immune priming, i.e., a form of memory in invertebrates. In this study, the potential involvement of Cu,Zn SODs in immunity of the red flour beetle Tribolium castaneum is described for the first time, applying an approach that combines an in silico gene characterisation with an in vivo immune priming experiment using the Gram-positive entomopathogen Bacillus thuringiensis. We identified an unusually high number of three different transcripts for extracellular SOD and found that priming leads to a fine-tuned modulation of SOD expression, highlighting the potential of physiological co-adaptations for immune phenotypes.

100 Days of marine Synechococcus-Ruegeria pomeroyi interaction: A detailed analysis of the exoproteome.

SummaryMarine phototroph and heterotroph interactions are vital in maintaining the nutrient balance in the oceans as essential nutrients need to be rapidly cycled before sinking to aphotic layers. The aim of this study was to highlight the molecular mechanisms that drive these interactions. For this, we generated a detailed exoproteomic time‐course analysis of a 100‐day co‐culture between the model marine picocyanobacterium Synechococcus sp. WH7803 and the Roseobacter strain Ruegeria pomeroyi DSS‐3, both in nutrient‐enriched and natural oligotrophic seawater. The proteomic data showed a transition between the initial growth phase and stable‐state phase that, in the case of the heterotroph, was caused by a switch in motility attributed to organic matter availability. The phototroph adapted to seawater oligotrophy by reducing its selective leakiness, increasing the acquisition of essential nutrients and secreting conserved proteins of unknown function. We also report a surprisingly high abundance of extracellular superoxide dismutase produced by Synechococcus and a dynamic secretion of potential hydrolytic enzyme candidates used by the heterotroph to cleave organic groups and hydrolase polymeric organic matter produced by the cyanobacterium. The time course dataset we present here will become a reference for understanding the molecular processes underpinning marine phototroph‐heterotroph interactions.

Autophagy attenuates the oxidative stress-induced apoptosis of Mc3T3-E1 osteoblasts.

The oxidative stress-induced osteoblast apoptosis plays an important role in the pathological process of osteoporosis, but the roles of autophagy in oxidative stress and apoptosis of osteoblasts remain unclear. This study aimed to observe the role of autophagy in oxidative stress injury of osteoblasts and the relationship between autophagy and apoptosis. Mc3T3-E1 cells were stimulated with different concentrations (0.1, 0.5, and 1 mM) of hydrogen peroxide. The cell viability was detected via cell counting kit 8 (CCK8) at different time points (0, 2, 6, 8, and 12 h), the apoptosis was detected via Western blotting and flow cytometry, and the autophagy was detected via macrophage-derived chemokine (MDC) and transmission electron microscope. The changes in expression of autophagy-associated protein, Beclin1, and LC3II/I ratio, were detected via Western blotting. Moreover, the intracellular reactive oxygen species (ROS) level and extracellular superoxide dismutase (SOD) level were observed using the autophagy regulators, rapamycin (Rap) and 3-methyladenine (3-MA), so as to clarify the interaction between autophagy and cellular oxidation. Hydrogen peroxide-induced apoptosis and autophagy of osteoblasts were in dose- and time-dependent manners; the hydrogen peroxide inhibitors could inhibit the autophagy level, and autophagy inhibitor (3-MA) could significantly enhance the hydrogen peroxide-induced ROS level and apoptosis rate in cells. Besides, Western blotting confirmed that the cleaved caspase-3 and cleaved poly adenosine diphosphate ribose polymerase (PARP) proteins were increased. The autophagy inducer (Rap) partially inhibited the hydrogen peroxide-induced oxidative stress and apoptosis. Autophagy inhibits the oxidative stress-mediated apoptosis of osteoblasts, which is a potential target for the osteoporosis treatment.

Inhalation of Fine Particulate Matter Impairs Endothelial Progenitor Cell Function Via Pulmonary Oxidative Stress.

Exposure to fine particulate matter (PM2.5) air pollution is associated with the depletion of circulating endothelial progenitor cells (EPCs), as well as vascular injury and dysfunction. Nevertheless, it remains unclear whether PM2.5 exposure leads to significant impairments in EPC function. Hence, we studied the effects of PM2.5 on EPC-mediated recovery of vascular perfusion after hindlimb ischemia and examined the mechanisms whereby PM2.5 exposure affects EPC abundance and function. In comparison with EPCs isolated from mice breathing filtered air, EPCs from mice exposed for 9 consecutive days (6 hours per day) to concentrated ambient PM2.5 (CAP) had defects in both proliferation and tube formation. However, CAP exposure of mice overexpressing extracellular superoxide dismutase (ecSOD-Tg) in the lungs did not affect EPC tube formation. Exposure to CAP also suppressed circulating EPC levels, VEGF (vascular endothelial growth factor)-stimulated aortic Akt phosphorylation, and plasma NO levels in wild-type but not in ecSOD-Tg mice. EPCs from CAP-exposed wild-type mice failed to augment basal recovery of hindlimb perfusion when injected into unexposed mice subjected to hindlimb ischemia; however, these deficits in recovery of hindlimb perfusion were absent when using EPCs derived from CAP-exposed ecSOD-Tg mice. The improved reparative function of EPCs from CAP-exposed ecSOD-Tg mice was also reflected by greater expression of Mmp-9 and Nos3 when compared with EPCs from CAP-exposed wild-type mice. Exposure to PM2.5 impairs EPC abundance and function and prevents EPC-mediated vascular recovery after hindlimb ischemia. This defect is attributed, in part, to pulmonary oxidative stress and was associated with vascular VEGF resistance and a decrement in NO bioavailability.

Extracellular Superoxide Dismutase Attenuates Renal Oxidative Stress Through the Activation of Adenosine Monophosphate-Activated Protein Kinase in Diabetic Nephropathy.

Oxidative stress plays a crucial role in the pathogenesis of diabetic nephropathy (DN). We evaluated whether extracellular superoxide dismutase (EC-SOD) has a renoprotective effect through activation of adenosine monophosphate-activated protein kinase (AMPK) in diabetic kidneys. Human recombinant EC-SOD (hEC-SOD) was administered to 8-week-old male C57BLKS/J db/db mice through intraperitoneal injection once a week for 8 weeks. Renal SOD3 expression was suppressed in db/db mice, which was significantly enhanced by hEC-SOD treatment. hEC-SOD improved albuminuria, mesangial expansion, and interstitial fibrosis in db/db mice. At the molecular level, hEC-SOD increased phosphorylation of AMPK, activation of peroxisome proliferative-activated receptor γ coactivator 1α (PGC-1α), and dephosphorylation of forkhead box O transcription factor (FoxO)1 and FoxO3a. The protective effects of hEC-SOD were attributed to enhanced nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) and subsequently increased expression of NAD(P)H dehydrogenase 1 and heme oxygenase-1. Consequently, hEC-SOD recovered from systemic and renal inflammation and apoptosis, as reflected by the decreases of serum and renal monocyte chemoattractant protein-1 and tumor necrosis factor-α levels and increases of BCL-2/BAX ratio in diabetic kidney. hEC-SOD also improved oxidative stress and resulted in increased renal and urinary 8-hydroxy-2'-deoxyguanosine and 8-isoprostane levels in db/db mice. In cultured human glomerular endothelial cells, hEC-SOD ameliorated apoptosis and oxidative stress caused by high glucose exposure through activation of AMPK and PGC-1α and dephosphorylation of FoxOs. These findings demonstrated for the first time that EC-SOD can potentially ameliorate hyperglycemia-induced oxidative stress, apoptosis, and inflammation through activation of AMPK and its downstream pathways in diabetic kidneys. EC-SOD is a potential therapeutic target for treatment of type 2 DN through intrarenal AMPK-PGC-1α-Nrf2 and AMPK-FoxOs signaling. Antioxid. Redox Signal. 28, 1543-1561.

Extracellular superoxide dismutase inhibits hepatocyte growth factor-mediated breast cancer-fibroblast interactions.

We have previously shown tumor suppressive effects of extracellular superoxide dismutase, EcSOD in breast cancer cells. In this study, an RTK signaling array revealed an inhibitory effect of EcSOD on c-Met phosphorylation and its downstream kinase c-Abl in MDA-MB231 cells. Moreover, an extracellular protein array showed that thrombospondin 1 (TSP-1), a scavenger of the c-Met ligand, hepatocyte growth factor (HGF) is significantly up-regulated in EcSOD overexpressing cells (Ec.20). We further determined the effects of EcSOD on HGF/c-Met-mediated cancer-fibroblast interactions by co-culturing normal fibroblasts (RMF) or RMF which overexpresses HGF (RMF-HGF) with MDA-MB231 cells. We observed that while RMF-HGF significantly promoted Matrigel growth of MDA-MB231, overexpression of EcSOD inhibited the HGF-stimulated growth. Similarly, a SOD mimetic, MnTE-2-PyP, inhibited HGF-induced growth and invasion of MDA-MB231. In addition, a long-term heterotypic co-culture study not only showed that Ec.20 cells are resistant to RMF-HGF-induced invasive stimulation but RMF-HGF that were co-cultured with Ec.20 cells showed an attenuated phenotype, suggesting an oxidative-mediated reciprocal interaction between the two cell types. In addition, we demonstrated that RMF-HGF showed an up-regulation of an ROS-generating enzyme, NADPH oxidase 4 (Nox4). Targeting this pro-oxidant significantly suppressed the activated phenotype of RMF-HGF in a collagen contraction assay, suggesting that RMF-HGF contributes to the oxidative tumor microenvironment. We have further shown that scavenging ROS with EcSOD significantly inhibited RMF-HGF-stimulated orthotopic tumor growth of MDA-MB231. This study suggests the loss of EcSOD in breast cancer plays a pivotal role in promoting the HGF/c-Met-mediated cancer-fibroblast interactions.

27 - The Irony of Cu-only Superoxide Dismutases in Fungal Pathogens

Superoxide dismutases (SODs) are metal containing enzymes that catalyze the disproportionation of superoxide radicals to hydrogen peroxide and molecular oxygen. Extracellular Cu-only SODs are a new class of SODs found in fungi. Unlike the common Cu/Zn SODs, they lack the zinc site and have an unusually open access copper site. Interestingly, the human fungal pathogen Candida albicans encodes three of these enzymes, SOD4, 5, 6. The evolutionary advantage for the multiplicity of Cu-only SOD enzymes and their potentially divergent roles was unknown. Our recent studies have focused on a comparison of the highly homologous SOD4 and SOD5 of C. albicans. Using pulse radiolysis we find that SOD4 has similar enzyme kinetics to SOD5 and can react with superoxide at rates that are limited by diffusion. SOD4 and SOD5 appear virtually identical at the biochemical level, other than some possible differences in surface charges. However, these proteins strongly diverge at the expression level in C. albicans. SOD5 is predominantly expressed during morphogenesis of C. albicans from a budding state to an invasive filamentous form. Conversely, SOD4 is specifically upregulated during iron starvation, suggesting it may have a role in iron acquisition within the host where reactive oxygen species are present. We have also identified another Cu-only SOD in the emerging fungal pathogen Candida auris that is upregulated during iron restriction, suggesting this link to Fe homeostasis is conserved. The potential role for extracellular Cu-only SODs in protecting fungal pathogens in the iron starved environment of the host will be discussed.

Lower serum extracellular superoxide dismutase levels are associated with polyneuropathy in recent-onset diabetes

Increased oxidative stress is implicated in the pathogenesis of experimental diabetic neuropathy, but translational evidence in recent-onset diabetes is scarce. We aimed to determine whether markers of systemic oxidative stress are associated with diabetic sensorimotor polyneuropathy (DSPN) in recent-onset diabetes. In this cross-sectional study, we measured serum concentrations of extracellular superoxide dismutase (SOD3), thiobarbituric acid reactive substances (TBARS), and reduced glutathione (GSH) in 107 type 1 and 215 type 2 diabetes patients from the German Diabetes Study baseline cohort and 37 glucose-tolerant individuals (controls). DSPN was defined by electrophysiological and clinical criteria (Toronto Consensus, 2011). SOD3 and GSH concentrations were lower in individuals with type 1 and type 2 diabetes compared with concentrations in controls (P<0.0001). In contrast, the TBARS concentration was higher in participants with type 1 diabetes and type 2 diabetes compared with levels in controls (P<0.0001). In addition, the SOD3 concentration was higher in participants with type 1 diabetes compared to concentrations in those with type 2 diabetes (P<0.0001). A low SOD3 concentration was associated with DSPN in individuals with type 1 diabetes (β=−0.306, P=0.002), type 2 diabetes (β=−0.164, P=0.017), and in both groups combined (β=−0.206, P=0.0003). Lower SOD3 concentrations were associated with decreased motor nerve conduction velocity (NCV) in men and, to a lesser degree, with reduced sensory NCV in women with diabetes. In conclusion, several biomarkers of oxidative stress are altered in recent-onset diabetes, with only a lower SOD3 concentration being linked to the presence of DSPN, suggesting a role for reduced extracellular antioxidative defense against superoxide in the early development of DSPN.

The SOD3 R213G Polymorphism Promotes Resolution of Innate Immune Activation and Blocks Induction of miR29b in Bleomycin Induced Lung Inflammation and Fibrosis

A naturally occurring single nucleotide polymorphism (SNP) (R213G) in extracellular superoxide dismutase (SOD3), a key lung and vascular antioxidant enzyme, decreases tissue binding and increases SOD3 in epithelial lining fluid and plasma. Mice harboring the R213G SNP are protected against bleomycin-induced alveolar inflammation and fibrosis. We hypothesized that the redistribution of SOD3 due to the R213G SNP, through site specific changes in the redox environment, modulates key miRNA and mRNA signaling networks responsible for macrophage activation and fibrosis. Plasma, lung and BALF O2•‒ was measured by electron paramagnetic resonance using the CMH spin probe. Bleomycin increased O2•‒ in all three compartments; the increase in O2•‒ was attenuated in the blood of R213G mice. We performed high throughput RNAseq and bioinformatics analyses in lung mRNA and miRNA 7 days post-bleomycin in WT and R213G mice. We identified distinct mRNA and miRNA profiles between strains in response to bleomycin. By pathway analysis, key immune and inflammatory pathways were activated in WT mice but suppressed in R213G mice at 7 days, the timepoint associated with resolution of inflammation in the R213G mice. Predicted upstream regulators included multiple signaling molecules within the TLR4/NF-ks/IKKe/IRF3 pathway. Distinct strain specific miRNA responses were observed, including miR29, a key miRNA implicated in fibrosis, which decreased only in R213G mice. In bone marrow derived macrophages (BMDM) from WT and R213G mice, the response to classic “M1” LPS + IFN polarizing stimuli was similar between strains but attenuated by pretreatment with exogenous extracellular SOD. Using bioinformatics and molecular approaches, we conclude that the redistribution of ecSOD, due to its impact on O2•‒ , can suppress innate immune responses by regulating macrophage plasticity, accounting for the ability of the R213G SNP to protect against bleomycin-induced lung fibrosis. The role of miRNA regulation in this process requires further study.

Candida Albicans FRE8 Encodes a Member of the NADPH Oxidase Family that Produces a Burst of ROS Important for Morphogenesis

NADPH oxidase (NOX) enzymes, which produce reactive oxygen species (ROS), were until recently thought to occur only in multicellular organisms. ROS have important physiological effects such as acting as signaling molecules in biological processes or as defense mechanisms against invading microbes through oxidative damage. In this work, we demonstrate that the unicellular fungus Candida albicans is capable of producing an extracellular ROS burst using a member of the NOX enzyme family identified as Fre8. C. albicans is an opportunistic human fungal pathogen which undergoes morphologic transition between yeast, pseudohyphal, and hyphal forms. During morphogenesis, FRE8 is induced to produce ROS specifically at the growing tip of the polarized cell. The extracellular superoxide dismutase, Sod5, is also induced during morphogenesis and our findings are consistent with a model in which Sod5 acts as a partner for Fre8, converting Fre8-derived superoxide to the diffusible hydrogen peroxide molecule. Fre8∆/∆ mutants exhibit a morphogenesis defect in vitro and are specifically impaired in the development or maintenance of elongated hyphae in high density cultures. A fre8∆/∆ defect in hyphal formation was similarly observed in a disseminated candidiasis model. Moreover, in a rat catheter model, C. albicans fre8∆/∆ mutants showed deficiencies in biofilm formation. Together these studies demonstrate that like multicellular organisms, the unicellular C. albicans expresses NOX to produce ROS and this signal helps drive fungal morphogenesis in the animal host.

26 - Copper-only Superoxide Dismutases as Novel Drug Targets for Fungal Pathogens

Superoxide dismutases (SODs) are metalloenzymes that disproportionate superoxide produced by aerobic metabolism as well as the oxidative bursts present at the host-pathogen interface. Bimetallic eukaryotic Cu/Zn SOD molecules are potent antioxidants found in most intracellular compartments and in extracellular locations. Our lab has recently discovered a new class of extracellular copper-only SODs found only in the fungal kingdom that are structurally distinct from bimetallic Cu/Zn SODs while still retaining equivalent catalytic efficiency. This novel class of copper only SODs are unique in that they lack zinc-binding residues and an electrostatic loop, creating an open active site that is accessible to solvent. Importantly these copper only SODs have been shown to be virulence factors in fungal pathogens such as Candida albicans and Histoplasma capsulatum. The uniquely accessible active site of these copper only SODs and their role in pathogenesis make them good candidates for selective drug design. We screened for compounds that selectively inhibit copper-only C. albicans SOD5 over mammalian Cu/Zn SOD1. We found that pyrithione zinc (PZ), a well-known antifungal in dandruff shampoo, has highly selective and potent activity against C. albicans copper only SOD5. The metal complex of pyrithione (Zn or Cu) appears to be more effective against SOD5 than pyrithione alone, suggesting the di-pyrithione structure selectively targets the open active site of fungal Cu-only SODs. Metal-pyrithione complexes are promising candiates for new anti-fungals that target the curious family of fungal Cu-only SODs.

Allele-Specific Effects of ecSOD in Bacterial Infection

Extracellular superoxide dismutase (ecSOD) is the only enzyme that scavenges superoxide specifically in the extracellular compartment. Recent studies indicate that ecSOD is important for protecting tissues from oxidative damage by dampening immune responses but imply that the immunosuppressive effect may be counterproductive during acute infections against invading microorganisms. Although many studies have revealed the importance of the reactive oxygen species (ROS) in bacterial killing, the role of ecSOD during bacterial infection is beginning to be understood. In this study, Listeria monogytogene and Streptococcus pneumoniae were used to infect mice expressing various level of ecSOD: congenic mice sod3129 (relatively high), sod3wt and sod3 KO mice (none). ecSOD expression is inversely related to bacterial clearance. On the other hand, bacterial infection significantly decreases ecSOD activity in infected tissues, while the protein levels are not affected. The induction of iNOS expression is significantly lower in the liver and spleen of sod3 KO mice when compared to those of congenic sod3129 and sod3wt mice. The NO levels in liver and spleen were independent on the level of iNOS induction. However, the NO levels in plasma were significantly induced regardless of the genotype. The oxidative stress levels measured by nitrotyrosine immunoblotting in plasma and liver were significantly higher in sod3 KO mice compared to the congenic sod3129 and sod3wt mice. In conclusion, high ecSOD expression impairs the bacterial clearance and the infection diminishes the ecSOD activity. These data provide a potential target for therapeutic intervention for acute infection.