Cu/ZnSOD always responded stronger and rapider than MnSOD in Lymantria dispar larvae under the avermectin stress

Metalloenzyme SODs play important roles in insects dealing with environmental stress. Here, we cloned the Cu/ZnSOD (LdCZS) and MnSOD (LdMS) mRNA of Lymantria dispar by rapid amplification of cDNA ends (RACE). Afterwards their expression patterns were detected by quantitative real-time polymerase chain reaction (qPCR) after bioinformatic analysis. We found that both LdCZS and LdMS were widely detected in all gypsy moth larvae and all five tissues that we analyzed, and both of them were up-regulated after larvae were fed with avermectin of sublethal concentration and LC₁₀. The LdCZS expression value are always higher than LdMS after treating with avermectin of sublethal concentrations. In addition, temporal expression profile in avermectin treated larvae showed that LdCZS expressed highest at 2nd hour, and LdMS expressed highest at 6th hour. The cuticulas transcribed LdCZS and LdMS significantly higher than heads, fat bodies, Malpighian tubes, and midguts after spraying avermectin of sublethal concentration. These results suggested that both Cu/ZnSOD and MnSOD are important antioxidant enzymes in L. dispar defensing against pesticide stress, and LdCZS always responded rapider and stronger than LdMS.

Gelsolin-Cu/ZnSOD interaction alters intracellular reactive oxygen species levels to promote cancer cell invasion

The actin-binding protein, gelsolin, is a well known regulator of cancer cell invasion. However, the mechanisms by which gelsolin promotes invasion are not well established. As reactive oxygen species (ROS) have been shown to promote cancer cell invasion, we investigated on the hypothesis that gelsolin-induced changes in ROS levels may mediate the invasive capacity of colon cancer cells.

Herein, we show that increased gelsolin enhances the invasive capacity of colon cancer cells, and this is mediated via gelsolin's effects in elevating intracellular superoxide (O₂^.-) levels. We also provide evidence for a novel physical interaction between gelsolin and Cu/ZnSOD, that inhibits the enzymatic activity of Cu/ZnSOD, thereby resulting in a sustained elevation of intracellular O₂^.-. Using microarray data of human colorectal cancer tissues from Gene Omnibus, we found that gelsolin gene expression positively correlates with urokinase plasminogen activator (uPA), an important matrix-degrading protease invovled in cancer invasion. Consistent with the in vivo evidence, we show that increased levels of O₂^.- induced by gelsolin overexpression triggers the secretion of uPA. We further observed reduction in invasion and intracellular O₂^.- levels in colon cancer cells, as a consequence of gelsolin knockdown using two different siRNAs. In these cells, concurrent repression of Cu/ZnSOD restored intracellular O₂^.- levels and rescued invasive capacity.

Our study therefore identified gelsolin as a novel regulator of intracellular O₂^.- in cancer cells via interacting with Cu/ZnSOD and inhibiting its enzymatic activity. Taken together, these findings provide insight into a novel function of gelsolin in promoting tumor invasion by directly impacting the cellular redox milieu.

Relation Between Mitochondrial Membrane Potential and ROS Formation

Mitochondria are considered the main source of reactive oxygen species (ROS) in the cell. For this reason they have been recognized as a source of various pathological conditions as well as aging. Chronic increase in the rate of ROS production is responsible for the accumulation of ROS-associated damages in DNA, proteins, and lipids and may result in progressive cell dysfunctions and, in a consequence, apoptosis, increasing the overall probability of an organism's pathological conditions. The superoxide anion is the main undesired by-product of mitochondrial oxidative phosphorylation. Its production is triggered by a leak of electrons from the mitochondrial respiratory chain and the reaction of these electrons with O₂. Superoxide dismutase (MnSOD, SOD2) from the mitochondrial matrix, as well as superoxide dismutase (Cu/ZnSOD, SOD1) present in small amounts in the mitochondrial intramembrane space, converts superoxide anion to hydrogen peroxide, which can be then converted by catalase to harmless H₂O.In the chapter we describe a relation between mitochondrial membrane potential and the rate of ROS formation. We present different methods applicable for isolated mitochondria or intact cells. We also present experiments demonstrating that a magnitude and a direction (increase or decrease) of a change in mitochondrial ROS production depend on the metabolic state of this organelle.

Nfu1 Mediated ROS Removal Caused by Cd Stress in Tegillarca granosa

The blood clam Tegillarca granosa, a eukaryotic bottom-dwelling bivalve species has a strong ability to tolerate and accumulate cadmium. In our previous study, Nfu1 (iron-sulfur cluster scaffold protein), which is involved in Fe-S cluster biogenesis, was shown to be significantly up-regulated under Cd stress, as determined by proteomic analysis. To investigate the function of Nfu1 in cadmium (Cd) detoxification, the function of blood clam Nfu1 (designated as Tg-Nfu1) was investigated by integrated molecular and protein approaches. The full-length cDNA of Tg-Nfu1 is 1167 bp and encodes a protein of 272 amino acid residues. The deduced Tg-Nfu1 protein is 30 kDa contains a conserved Nfu-N domain and a Fe-S cluster binding motif (C-X-X-C). qRT-PCR analysis revealed that Tg-Nfu1 was ubiquitously expressed in all examined tissues; it was up-regulated in the hepatopancreas and gill, and kept a high level from 9 to 24 h after Cd exposure (250 μg/L). Western blot analysis further revealed that the Tg-Nfu1 protein was also highly expressed in the hepatopancreas and gill after 24 h of Cd stress. Further functional analysis showed that the production of ROS was increased and Cu/ZnSOD activity was inhibited in blood clam, treated with the specific Nfu1 siRNA and Cd stress, respectively. These results suggest that Tg-Nfu1 could protect blood clam from oxidative damage caused by Cd stress.

MnTE-2-PyP modulates thiol oxidation in a hydrogen peroxide-mediated manner in a human prostate cancer cell

To improve the treatment of advanced prostate cancer, the development of effective and innovative antitumor agents is needed. Our previous work demonstrated that the ROS (reactive oxygen species) scavenger, MnTE-2-PyP, inhibited human prostate cancer growth and also inhibited prostate cancer migration and invasion. We showed that MnTE-2-PyP treatment altered the affinity of the histone acetyltransferase enzyme, p300, to bind to DNA. We speculate that this may be one mechanism by which MnTE-2-PyP inhibits prostate cancer progression. Specifically, MnTE-2-PyP decreased p300/HIF-1/CREB complex (p300/hypoxia-inducible factor-1/cAMP response element-binding protein) binding to a specific hypoxia-response element (HRE) motif within the plasminogen activator inhibitor-1 (PAI-1) gene promoter region, and consequently, repressed PAI-1 expression. However, it remains unclear how MnTE-2-PyP reduces p300 complex binding affinity to the promoter region of specific genes. In this study, we found that overexpression of Cu/ZnSOD (superoxide dismutase 1, SOD1) significantly suppressed PAI-1 gene expression and p300 complex binding to the promoter region of PAI-1 gene, just as was observed in cells treated with MnTE-2-PyP. Furthermore, catalase (CAT) overexpression rescued the inhibition of PAI-1 expression and p300 binding by MnTE-2-PyP. Taken together, the above findings suggest that hydrogen peroxide (H₂O₂) is likely the mediator through which MnTE-2-PyP inhibits the PAI-1 expression and p300 complex binding in PC3 cells. To confirm this, we measured the production of H₂O₂ following overexpression of SOD1 or catalase with MnTE-2-PyP treatment in the presence or absence of radiation. We found that MnTE-2-PyP increased the intracellular steady-state levels of H₂O₂ and increased nuclear H₂O₂ levels. As expected, catalase overexpression significantly decreased the levels of intracellular H₂O₂ induced by MnTE-2-PyP. We then determined if this increased H₂O₂ production could result in oxidized protein thiol groups. In the presence of MnTE-2-PyP, there was a significant increase in oxidized thiols in PC3 cell lysates and this was reversed with catalase overexpression. Specifically, we showed that p300 was oxidized after MnTE-2-PyP treatment, indicating that MnTE-2-PyP is creating a more oxidizing environment and this is altering the oxidation state of p300 thiol residues. Our data provide an in depth mechanism by which MnTE-2-PyP regulates gene transcription through induced H₂O₂ mediated oxidation of particular proteins, supporting an important role for MnTE-2-PyP as an effective and innovative antitumor agent to enhance treatment outcomes in prostate cancer radiotherapy.

The effect of sarafloxacin on Cu/ZnSOD structure and activity

The effect of sarafloxacin to Cu/ZnSOD was evaluated via investigating the change in Cu/ZnSOD structure and the structure basis activity upon sarafloxacin binding. Multi-spectroscopic methods, isothermal titration microcalorimetry (ITC) and molecular docking method were adopted in this study. Sarafloxacin binds to Cu/ZnSOD mainly through hydrophobic and hydrogen bond forces and tends to be saturated as the molar ratio of sarafloxacin to Cu/ZnSOD reaches 4. The binding changed the microenvironment around Tyr and the secondary structure of Cu/ZnSOD but did not affect the activity of Cu/ZnSOD. Molecular docking study revealed that sarafloxacin binds into a hydrophobic area with possibility to form hydrogen bonds with Tyr 108, Asp 25, Pro 100 and Ser 103 of Cu/ZnSOD. The binding area locates on the surface of β-barrel close to the second Greek key loop (GK2) and V-loop but far away from the active site and active site channel of Cu/ZnSOD. These promoted the understanding of the experiment phenomenons. The binding of sarafloxacin does not affect the activity of Cu/ZnSOD should attribute to the binding not to change the microenvironment of Cu/ZnSOD active site and active site channel.

Probing the interactions between carboxylated multi-walled carbon nanotubes and copper-zinc superoxide dismutase at a molecular level

In order to evaluate the toxicity of multi-walled carbon nanotubes (MWCNTs-COOH) at a molecular level, the effect of MWCNTs-COOH on antioxidant enzyme copper-zinc superoxide dismutase (Cu/ZnSOD) was investigated using fluorescence spectroscopy, UV/vis absorption spectroscopy, circular dichroism (CD) spectroscopy and isothermal titration calorimetry (ITC). By deducting the inner filter effect (IFE), the fluorescence emission spectra and synchronous fluorescence spectra indicated that there were interactions between MWCNTs-COOH and Cu/ZnSOD. Moreover, the microenvironment of the amino acid residues in the enzyme was changed slightly. The UV/vis absorption and CD spectroscopic results showed appreciable conformational changes in Cu/ZnSOD. However, the results of a Cu/ZnSOD activity determination did not show any significant difference. In other words, MWCNTs-COOH has no significant effect on enzyme activity. The ITC results showed that the binding of MWCNTs-COOH to Cu/ZnSOD was a weak endothermic process, indicating that the predominant force of the binding was hydrophobic interaction. Moreover, it was essential to consider the IFE in fluorescence assays, which might affect the accuracy and precision of the results. The above results are helpful in evaluating the oxidative stress induced by MWCNTs-COOH in vivo.