Reduced sensitivity of HeLa cells to cis-platinum by simultaneous overexpression of copper, zinc-superoxide dismutase and catalase

The Investigation of the Antitumor Agent Toxicity and Capsaicin Effect on the Electron Transport Chain Enzymes, Catalase Activities and Lipid Peroxidation Levels in Lung, Heart and Brain Tissues of Rats

Cisplatin is one of the most active cytotoxic agents in cancer treatment. To clarify the interaction with mitochondria, we hypothesize that the activities of mitochondrial electron transport chain (ETC) enzymes succinate dehydrogenase (SDH) and cytochrome c oxidase (COX), nucleotide levels, as well as levels of catalase (CAT) enzyme and membrane lipid peroxidation (LPO) can be affected by cisplatin. There was a significant decrease of both SDH and COX activities in the lung, heart, and brain tissues at the 1st day after cisplatin exposure, and the observed decreased levels of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) in comparison with the control could be because of cisplatin-induced mitochondrial dysfunction. The investigations suggested that cisplatin inhibits SDH, COX, and ATP synthase. The higher LPO level in the studied tissues after 1 and 4 days post-exposure to cisplatin compared to control can be inferred to be a result of elevated electron leakage from the ETC, and reactive oxygen species (ROS) can lead to wide-ranging tissue damage such as membrane lipid damage. Consequently, it was observed that capsaicin may have a possible protective effect on ETC impairment caused by cisplatin. The activities of SDH and COX were higher in heart and brain exposed to cisplatin + capsaicin compared to cisplatin groups, while LPO levels were lower. The investigated results in the cisplatin + capsaicin groups suggested that the antioxidant capacity of capsaicin scavenges ROS and prevents membrane destruction.

Effects of the loss of Atox1 on the cellular pharmacology of cisplatin

Previous work has demonstrated that the copper (Cu) transporters Ctr1, Atp7a and Atp7b regulate the cellular pharmacology of cisplatin (CDDP) by mediating its uptake and efflux. It was also shown that, in the process of uptake by Ctr1, CDDP triggers the rapid proteasomal degradation of its own transporter. The current study examined the role of the metallochaperone Atox1 in the regulation of uptake, efflux and subcellular distribution of CDDP by using a pair of fibroblast cell lines established from Atox1(+/+) and Atox1(-/-) mice. Atox1 is a metallochaperone that is known to play a central role in distributing Cu within the cells and was recently shown to act as a Cu-dependent transcription factor. Loss of Atox1 increased Cu accumulation and reduced efflux. In contrast, loss of Atox1 reduced the influx of CDDP and subsequent accumulation in vesicular compartments and in DNA. Loss of Atox1 was found to block the CDDP-induced down regulation of Ctr1. Ctr1 was found to be polyubiquitinated in an Atox1-dependent manner during CDDP exposure. In conclusion, Atox1 is required for the polyubiquitination of Ctr1 and the Ctr1-mediated uptake of CDDP.

Induction of apoptosis by chemotherapeutic drugs without generation of reactive oxygen species

Studies in a variety of cell types have suggested that cancer chemotherapy drugs induce tumor cell apoptosis in part by inducing formation of reactive oxygen species (ROS). Using human B lymphoma cells as the targets, we have found that apoptosis can be induced in the absence of any detectable oxidative stress. Apoptosis was induced with the chemotherapy drugs VP-16 and cisplatin. To determine whether oxidants are formed as part of the drug-induced apoptotic process, intracellular markers of oxidative stress were examined. These included measurement of (1) protein carbonyl groups by Western blot immunoassay, (2) protein methionine sulfoxide residues by amino acid analysis, (3) protein sulfhydryl oxidation by Western blot immunoassay, (4) F2-isoprostanes by GC/MS, and (5) intracellular ROS production using the oxidant-sensitive dyes DCFDA and dihydrorhodamine 123. Apoptosis was quantified using fluorescence microscopy to assess nuclear morphology. The results show that VP-16 and cisplatin induce extensive apoptosis in the absence of any detectable protein or lipid oxidation, measured in both the cytosolic and mitochondrial compartments of the cell. In contrast, H2O2, which kills the cells by nonapoptotic pathways, caused increases in both protein and lipid oxidation. Three different antioxidant compounds (N-acetyl cysteine, Tempol, and MnTBAP) failed to inhibit VP-16-induced apoptosis, while inhibiting H2O2-induced cell death. Only N-acetyl cysteine inhibited cisplatin-induced cell death and this is attributed to its known ability to react directly with and inactivate cisplatin before it enters the cell. The results demonstrate that, at least in B lymphoma cells, chemotherapy-induced apoptosis occurs using a mechanism that does not involve oxidants.

Manganese superoxide dismutase attenuates Cisplatin-induced renal injury: importance of superoxide

Cisplatin is a potent chemotherapeutic agent that is used to treat many human malignancies. Unfortunately, in addition to side effects such as ototoxicity, anaphylaxis, and bone marrow suppression, a significant percentage of patients receiving cisplatin develop severe nephrotoxicity. Mitochondrial dysfunction that is mediated via the generation of reactive oxygen species has been implicated in the pathogenesis of cisplatin-induced renal injury. To address the mechanism, it was hypothesized that overexpression of antioxidant enzymes, such as mitochondria-localized manganese superoxide dismutase (MnSOD) or mitochondria-targeted catalase (mito-Cat), would be cytoprotective in cisplatin-induced cell injury. To this end, human MnSOD or a mito-Cat vector were stably transfected into human embryonic kidney 293 cells. Cells that overexpressed MnSOD exhibited significantly less cell rounding and detachment compared with both mito-Cat and vector controls after exposure to 20 microM cisplatin. Cell injury as assessed by DNA fragmentation and annexin V binding assays was significantly decreased in the cells that overexpressed MnSOD compared with vector alone and mito-Cat. In addition, elevated levels of MnSOD were strongly associated with increased clonogenic potential after cisplatin challenge. Thus, overexpression of MnSOD, and not catalase, protects against cisplatin-induced renal epithelial cell injury. These results demonstrate the importance of reactive oxygen species in the mechanism that underlies cisplatin-induced renal injury and specifically implicate the superoxide radical, and not hydrogen peroxide, as the mediator.

Expression and prognostic significance of catalase in malignant mesothelioma

BACKGROUND

Free radicals and antioxidant enzymes (AOEs) may play a critical role in cell proliferation and in the resistance of malignant cells against cytotoxic drugs and radiation. Malignant mesothelioma is a resistant tumor with high levels of manganese superoxide dismutase, a central superoxide scavenging AOE. In the current study, the authors assessed the expression and prognostic role of catalase, an important hydrogen peroxide scavenging AOE, in malignant pleural mesothelioma.

METHODS

Catalase expression was investigated by immunohistochemistry in 5 cases of nonmalignant healthy pleura and in tumor tissue of 32 mesothelioma patients, and by Western blot in 7 continuous human mesothelioma cell lines. The distribution of catalase in mesothelioma cells was assessed by immunoelectron microscopy. Furthermore, to investigate the effect of catalase inhibition in the drug resistance of these cells in vitro, the authors exposed mesothelioma cells with the highest catalase level to epirubicin with and without aminotriazole pretreatment.

RESULTS

Nonmalignant mesothelial cells showed no catalase immunoreactivity whereas most mesothelioma cases (24 of 32, 75%) were catalase positive, 17 cases (53%) showing moderate or high expression. Higher catalase expression in mesothelioma was associated with a better prognosis, mean survival rate from diagnosis being 6 and 24 months for negative/low expression and moderate/high expression, respectively. Furthermore, a coordinately high expression of both manganese-superoxide dismutase (Mn-SOD) and catalase predicted even more favorable outcome of the mesothelioma patients. Catalase also could be detected in all mesothelioma cell lines, the most resistant cell line showing the highest protein expression and compartmentalization of catalase mainly to peroxisomes. Aminotriazole inhibition of catalase had a marginal effect on the toxicity caused by epirubicin.

CONCLUSIONS

Catalase may have multifactorial effects in malignant cells; high catalase and/or coordinated high expression of Mn-SOD and catalase may decrease tumor progression by modulating the cellular redox state, but enhanced antioxidant capacity of mesothelioma cells also may protect tumor cells against exogenous oxidants, at least in vitro.

Role of antioxidant systems in human androgen-independent prostate cancer cells

BACKGROUND

Most prostate cancer cells respond to initial hormonal therapy; however, some of them eventually acquire resistance to the hormonal therapy. Hormone-independent prostate cancer usually exhibits resistance to chemotherapy and radiotherapy. Antioxidant systems are known to be involved in the resistance of cancer cells to chemotherapy and radiotherapy. Therefore, it is of significance to examine antioxidant systems of hormone-independent prostate cancer for enhancing the efficacy of cancer therapy.

METHODS

Three cell lines of human hormone-independent prostate cancer (PC-3, PC-3 MA2, and HPC36M) were examined for activities of superoxide dismutase, catalase, and glutathione peroxidase, and for levels of protein and nonprotein thiols such as metallothionein, glutathione, and thioredoxin. Sensitivity of these cells to anticancer drugs and inducers of reactive oxygen species such as paraquat, tert-butylhydroperoxide, and hydrogen peroxide was determined by microtiter assay.

RESULTS

PC-3 and PC-3 MA2, which were derived from bone metastases, were resistant to paraquat, hydrogen peroxide, and cisplatin compared with HPC36M, which was obtained from the primary prostate cancer. However, HPC36M was resistant to vinblastine compared with PC-3 and PC-3 MA2. Both PC-3 and PC-3 MA2 had higher activities of catalase and glutathione peroxidase and higher levels of glutathione and metallothionein than HPC36M.

CONCLUSIONS

These data suggest that enhanced ability in scavenging free radicals by antioxidant enzymes and thiol compounds may, at least in part, contribute to the resistance of bone metastatic prostate cancer during chemotherapy.