ROS-generating Drugs Research Articles

Fabrication of a Dual-Targeted Liposome-Coated Mesoporous Silica Core-Shell Nanoassembly for Targeted Cancer Therapy.

Nanoparticles have been suggested as drug-delivery systems for chemotherapeutic drugs to allow for controlled drug release profiles and selectivity to target cancer cells. In addition, nanoparticles can be used for the in situ generation and amplification of reactive oxygen species (ROS), which have been shown to be a promising strategy for cancer treatment. Thus, a targeted nanoscale drug-delivery platform could be used to synergistically improve cancer treatment by the action of chemotherapeutic drugs and ROS generation. Herein, we propose a promising chemotherapy strategy where the drug-loaded nanoparticles generate high doses of ROS together with the loaded ROS-generating chemotherapeutic drugs, which can damage the mitochondria and activate cell death, potentiating the therapeutic outcome in cancer therapy. In the present study, we have developed a dual-targeted drug-delivery nanoassembly consisting of a mesoporous silica core loaded with the chemotherapeutic, ROS-generating drug, paclitaxel (Px), and coated with a liposome layer for controlled drug release. Two different lung cancer-targeting ligands, folic acid and peptide GE11, were used to target the overexpressed nonsmall lung cancer receptors to create the final nanoassembly (MSN@Px) L-GF. Upon endocytosis by the cancer cells, the liposome layer was degraded by the intracellular lipases, and the drug was rapidly released at a rate of 65% within the first 20 h. In vitro studies confirmed that this nanoassembly was 8-fold more effective in cancer therapy compared to the free drug Px.

Oxidative Stress Amplifying Polyprodrug Micelles as Drug Carriers for Combination Anticancer Therapy

Cancer cells are more vulnerable to reactive oxygen species (ROS)-mediated oxidative stress than normal cells due to disturbed redox balance. It can be postulated that ROS-generating drug carriers exert anticancer actions, leading to combination anticancer therapy with drug payloads. Here, we report a ROS-generating polyprodrug of cinnamaldehyde (CA) that not only serves as a drug carrier but also synergizes with drug payloads. The polyprodrug of CA (pCA) incorporates ROS-generating CA in the backbone of an amphiphilic polymer through an acid-cleavable acetal linkage. pCA could self-assemble with tumor-targeting lipopeptide (DSPE-PEG-RGD) and encapsulate doxorubicin (DOX) to form T-pCAD micelles. At acidic pH, T-pCAD micelles release both CA and DOX to exert synergistic anticancer actions. Animal studies using mouse xenograft models revealed that T-pCAD micelles accumulate in tumors preferentially and suppress the tumor growth significantly. Based on the oxidative stress amplification and acid-responsiveness, ROS-generating pCAD micelles hold tremendous potential as drug carriers for combination anticancer therapy.

One-pot fabrication of a polydopamine-based nanoplatform for GSH triggered trimodal ROS-amplification for cancer therapy.

Reactive oxygen species (ROS) based nanoplatforms have been considered as attractive and feasible candidates for cancer therapy. However, the activated endogenous antioxidant defense of cancer cells in response to the ROS attack greatly hinders their therapeutic efficacy. Although cancer-specific ROS amplification strategies have been widely explored, most of them suffer from tedious synthesis procedures and complex components, which will bring about undesired side effects and unsatisfactory results. Herein, we design a cancer-specific oxidative stress amplification nanomedicine (CA-Cu-PDA), which is simply fabricated through integrating the glutathione (GSH) responsive/depleting nanocarrier of copper-polydopamine (Cu-PDA) nanoparticles with a ROS-generating drug cinnamaldehyde (CA) via a facile one-pot polymerization route. It is verified that GSH could trigger the breakage of CA-Cu-PDA networks and the subsequent release of both copper ions and CA in cancer cells. The released copper ions efficiently oxidize GSH, thereby weakening the antioxidant system of cancer cells and increasing the ROS levels. On the other hand, extra ROS are generated by the reduced copper ions through a Fenton reaction, so that a synergistic ROS therapy with CA is achieved. Consequently, oxidative stress is specifically increased within cancer cells, leading to efficient cancer cell apoptosis, significant tumor suppression and minimized side effects. Such an ingenious structure realizes the interlocking cooperation and full utilization of each component's function, presenting promising perspectives for nanomedicine design.

Targeting Reactive Oxygen Species Metabolism to Induce Myeloma Cell Death.

Simple SummaryMultiple myeloma (MM) is a neoplastic disease of plasma cells, characterized by a complex array of clinical manifestations. Despite extensive efforts and progress in the care of MM patients, the disease is still fatal because of de novo or acquired resistance of malignant cells to standard chemotherapies. In turn, new therapies and/or combination therapies are urgently needed. Reactive oxygen species (ROS) are unstable and highly reactive chemical molecules, able to alter the main structural components of cells, such as proteins and lipids, and thus, modifying cell fates. ROS levels are tightly controlled in normal cells both for their production and degradation. In turn, an unbalance of the redox status might be exploited to induce cell death. This is indeed the case for myeloma cells even those that are resistant, opening new perspectives for refractory or relapsed MM patients.Multiple myeloma (MM) is a common hematological disease characterized by the accumulation of clonal malignant plasma cells in the bone marrow. Over the past two decades, new therapeutic strategies have significantly improved the treatment outcome and patients survival. Nevertheless, most MM patients relapse underlying the need of new therapeutic approaches. Plasma cells are prone to produce large amounts of immunoglobulins causing the production of intracellular ROS. Although adapted to high level of ROS, MM cells die when exposed to drugs increasing ROS production either directly or by inhibiting antioxidant enzymes. In this review, we discuss the efficacy of ROS-generating drugs for inducing MM cell death and counteracting acquired drug resistance specifically toward proteasome inhibitors.

Overcoming Cancer Cell Drug Resistance by a Folic Acid Targeted Polymeric Conjugate of Buthionine Sulfoximine.

Glutathione (GSH), which is the predominant low molecular weight intracellular thiol in mammals, has multiple functions, such as those of protecting against oxidative stress and detoxifying endogenous and exogenous electrophiles. High GSH levels, which have been observed in various types of tumors, have been thought to contribute to the resistance of neoplastic cells to apoptotic stimuli triggered by pro-oxidant therapy. Although L-(S,R)-Buthionine Sulfoximine (BSO), a selective irreversible inhibitor of glutamate cysteine ligase, depletes GSH in vitro and in in vivo and sensitizes tumor cells to radiation and some cancer chemotherapeutics, its toxicity and short in vivo half-life have limited its application to combination anticancer therapies. To demonstrate that a folate-targeted PEGylated BSO conjugate can sensitize cancer cells to a Reactive Oxygen Species (ROS)-generating anticancer agent by depleting GSH. A novel folate-targeted PEGylated-BSO conjugate was synthesized and tested in combination with gemcitabine in human cell lines that over-express (HeLa) or do not express (A549) the folate receptor. The prepared folate-PEG-GFLG-BSO conjugate proved to be efficacious in reducing GSH levels and, when used in combination with the pro-oxidant drug gemcitabine, it enhanced drug activity in the cell line overexpressing the folate receptor. The folate-PEG-GFLG-BSO conjugate studied was found to be effective in sensitizing folatereceptor positive cancer cells to the ROS-generating drug gemcitabine.

Oxidative stress induces senescence in breast cancer stem cells

Cancer stem cells (CSCs) have been shown to be resistant to current anticancer therapies and the induction of oxidative stress is an important mechanism of action for many anticancer agents. However, it is still largely unknown how CSCs respond to hydrogen peroxide (H2O2)-induced oxidative stress. Here, we show that the levels of reactive oxygen species (ROS) are markedly lower in breast CSCs (BCSCs) than that in non-cancer stem cells (NCSCs). A transient exposure of breast cancer cells to sublethal doses of H2O2 resulted in a dose-dependent increase of the epithelium-specific antigen (ESA)+/CD44+/CD24- subpopulations, a known phenotype for BCSCs. Although BCSCs survived sublethal doses of H2O2 treatment, they lost the ability to form tumor spheres and failed to generate colonies as demonstrated by mammosphere-formation and clonogenic assays, respectively. Mechanistic studies revealed that H2O2 treatment led to a marked increase of senescence-associated β-galactosidase activity but only minimal apoptotic cell death in BCSCs. Furthermore, H2O2 triggers p53 activation and promotes p21 expression, indicating a role for the p53/p21 signaling pathway in oxidative stress-induced senescence in BCSCs. Taken together, these results demonstrate that the maintenance of a lower level of ROS is critical for CSCs to avoid oxidative stress and H2O2-induced BCSC loss of function is likely attributable to oxidative stress-triggered senescence induction, suggesting that ROS-generating drugs may have the therapeutic potential to eradicate drug-resistant CSCs via induction of premature senescence.

Targeting the Achilles' heel of cancer cells via integrin-mediated delivery of ROS-generating dihydrolipoamide dehydrogenase.

Cancer cells frequently exhibit higher levels of reactive oxygen species (ROS) than normal cells and when ROS levels increase beyond a cellular tolerability threshold, cancer cell death is enhanced. The mitochondrial dihydrolipoamide dehydrogenase (DLDH) is an enzyme which produces ROS in association with its oxidoreductive activity and may be thus utilized as an exogenous anticancer agent. As cancer cells often overexpress integrins that recognize RGD-containing proteins, we have bioengineered the human DLDH with RGD motifs (DLDHRGD) for integrin-mediated drug delivery. The modified protein fully retained its enzyme activity and ROS-production capability. DLDHRGD uptake by cells was shown to depend on the presence of cell-associated integrin αvβ3, as comparatively demonstrated with normal kidney cells (HEK293) transfected with either β1 (αvβ1 positive) or β3 integrins (αvβ3 positive). The interaction with β3 integrins was shown to be competitively inhibited by an RGD peptide. In mice melanoma cells (B16F10), which highly express an endogenous αvβ3 integrin, fast cellular uptake of DLDHRGD which resulted in cell number reduction, apoptosis induction, and a parallel intracellular ROS production was shown. Similar results were obtained with additional human melanoma cell models (A375, WM3314, and WM3682). In contrast, HEK293β3 cells remained intact following DLDHRGD uptake. The high pharmacological safety profile of DLDHRGD has been observed by several modes of administrations in BALB/C or C57Bl/6 mouse strains. Treatments with DLDHRGD in a subcutaneous melanoma mice model resulted in significant tumor inhibition. Our study demonstrated, in vitro and in vivo, the development of a unique platform, which targets cancer cells via integrin-mediated drug delivery of an exogenous ROS-generating drug.

Fluidic shear stress increases the anti-cancer effects of ROS-generating drugs in circulating tumor cells.

Many anti-cancer drugs are used in chemotherapy; however, little is known about their efficacy against circulating tumor cells (CTCs). In this study, we investigated whether the pulsatile fluidic shear stress (SS) in human arteries can affect the efficacy of anti-cancer drugs. Cancer cells were circulated in our microfluidic circulatory system, and their responses to drug and SS treatments were determined using various assays. Breast and cervical cancer cells that stably expressed apoptotic sensor proteins were used to determine apoptosis in real-time by fluorescence resonance energy transfer (FRET)-based imaging microscopy. The occurrence of cell death in non-sensor cells were revealed by annexin V and propidium iodide staining. Cell viability was determined by MTT assay. Intracellular reactive oxygen species (ROS) levels were determined by staining cells with two ROS-detecting dyes: 2',7'-dichlorofluorescin diacetate and dihydroethidium. Fluidic SS significantly increased the potency of the ROS-generating drugs doxorubicin (DOX) and cisplatin but had little effect on the non-ROS-generating drugs Taxol and etoposide. Co-treatment with SS and ROS-generating drugs dramatically elevated ROS levels in CTCs, while the addition of antioxidants abolished the pro-apoptotic effects of DOX and cisplatin. More importantly, the synergistic killing effects of SS and DOX or cisplatin were confirmed in circulated lung, breast, and cervical cancer cells, some of which have a strong metastatic ability. These findings suggest that ROS-generating drugs are more potent than non-ROS-generating drugs for destroying CTCs under pulsatile fluidic conditions present in the bloodstream. This new information is highly valuable for developing novel therapies to eradicate CTCs in the circulation and prevent metastasis.

Modulation of reactive oxygen species via ERK and STAT3 dependent signalling are involved in the response of mesothelioma cells to exemestane.

Pleural mesothelioma is a deadly form of cancer. The prognosis is extremely poor due to the limited treatment modalities. Uptake of asbestos fibres, the leading cause of mesothelioma, lead to the accumulation of reactive-oxygen-species (ROS). Interestingly, increasing ROS production by using ROS-generating drugs may offer a strategy to selectively trigger cell death. Exemestane, an aromatase inhibitor, has previously shown anti-tumor properties in mesothelioma preclinical models suggesting a role of G protein-coupled receptor 30 (GPR30) in the drug response. As exemestane, in addition to blocking estrogen biosynthesis, generates ROS that are able to arrest the growth of breast cancer, we explored the role of ROS, antioxidant defense system, and ROS-induced signalling pathways in mesothelioma cells during exemestane response. Here we report that exemestane treatment reduced cell proliferation with an increase in ROS production and reduction of cyclic adenosine monophosphate (cAMP) levels in MSTO-H211, Ist-Mes1, Ist-Mes2 and MPP89 exemestane-sensitive mesothelioma cell lines, but not in NCI-H2452 exemestane-insensitive mesothelioma cells. Exemestane induced a significant antioxidant response in NCI-H2452 cells, as highlighted by an increase in γ-glutamylcysteine levels, catalase (Cat), superoxide-dismutase and (SOD) and glutathione-peroxidase (GSH-Px) activity and nuclear factor E2-related factor 2 (Nrf2) activation, responsible for drug insensitivity. Conversely, exemestane elevated ROS levels along with increased ERK phosphorylation and a reduction of p-STA3 in exemestane-sensitive mesothelioma cells. ROS generation was the crucial event of exemestane action because ROS inhibitor N-acetyl-L-cysteine (NAC) abrogated p-ERK and p-STAT3 modulation and cellular death. Exemestane also modulates ERK and STAT3 signalling via GPR30. Results indicate an essential role of ROS in the antiproliferative action of exemestane in mesothelioma cells. It is likely that the additional oxidative insults induced by exemestane results in the lethal effects of mesothelioma cells by increasing ROS production. As such, manipulating ROS levels with exemestane seems to be a feasible strategy to selectively kill mesothelioma cells with less toxicity to normal cells by regulating ERK and STAT3 activity.

Power frequency magnetic field promotes a more malignant phenotype in neuroblastoma cells via redox-related mechanisms

In accordance with the classification of the International Agency for Research on Cancer, extremely low frequency magnetic fields (ELF-MF) are suspected to promote malignant progression by providing survival advantage to cancer cells through the activation of critical cytoprotective pathways. Among these, the major antioxidative and detoxification defence systems might be targeted by ELF-MF by conferring cells significant resistance against clinically-relevant cytotoxic agents. We investigated whether the hyperproliferation that is induced in SH-SY5Y human neuroblastoma cells by a 50 Hz, 1 mT ELF magnetic field was supported by improved defence towards reactive oxygen species (ROS) and xenobiotics, as well as by reduced vulnerability against both H2O2 and anti-tumor ROS-generating drug doxorubicin. ELF-MF induced a proliferative and survival advantage by activating key redox-responsive antioxidative and detoxification cytoprotective pathways that are associated with a more aggressive behavior of neuroblastoma cells. This was coupled with the upregulation of the major sirtuins, as well as with increased signaling activity of the erythroid 2-related nuclear transcription factor 2 (NRF2). Interestingly, we also showed that the exposure to 50 Hz MF as low as 100 µT may still be able to alter behavior and responses of cancer cells to clinically-relevant drugs.

Colloidal silver nanoparticles improve anti-leukemic drug efficacy via amplification of oxidative stress

Recently, increased reactive oxygen species (ROS) levels and altered redox status in cancer cells have become a novel therapeutic strategy to improve cancer selectivity over normal cells. It has been known that silver nanoparticles (AgNPs) display anti-leukemic activity via ROS overproduction. Hence, we hypothesized that AgNPs could improve therapeutic efficacy of ROS-generating agents against leukemia cells. In the current study, N-(4-hydroxyphenyl)retinamide (4-HPR), a synthetic retinoid, was used as a drug model of ROS induction to investigate its synergistic effect with AgNPs. The data exhibited that AgNPs with uniform size prepared by an electrochemical method could localize in the lysosomes, mitochondria and cytoplasm of SHI-1 cells. More importantly, AgNPs together with 4-HPR could exhibit more cytotoxicity and apoptosis via overproduction of ROS in comparison with that alone. Taken together, these results reveal that AgNPs combined with ROS-generating drugs could potentially enhance therapeutic efficacy against leukemia cells, thereby providing a novel strategy for AgNPs in leukemia therapy.

OP1-1 - Peroxiredoxin 1 knockdown sensitizes cancer cells to reactive oxygen species-generating drugs – an alternative approach for chemotherapy

Peroxiredoxins have multiple cellular functions as major antioxidants, signaling regulators and tumor suppressors. Peroxiredoxin 1 (PRX1) is the most abundant among the six isoforms of human peroxiredoxins, catalyzing the reduction of peroxides utilizing thioredoxin 1as an electron donor. PRX1 is frequently over-expressed in various cancer cells, which is thought to be associated with carcinogenesis, metastasis and resistance to radiotherapy or chemotherapy. We investigated how modulations of intracellular redox system, especially PRX1, affect cancer cell sensitivity to reactive oxygen species (ROS)-generating drugs. We observed that stable and transient Prx1 knockdown (Prx1–) significantly enhances HeLa cell sensitivity to β-lapachone (β-lap), a potential anticancer agent, and to other ROS-generating molecules. ROS accumulation played a crucial role in drug-enhanced Prx1– cell death. For β-lap, Prx1– cells sensitization is achieved through combined action of accumulation of ROS and enhancement of mitogen-activated protein kinase pathway activation. The effect of other ROS-inducing drugs on Prx1– cell survival will also be presented and discussed. Taken together, our data provide evidence that PRX1 could be an interesting anticancer target and modulation of intracellular redox states through PRX1 inhibition could be an alternative approach to enhance cancer cell sensitivity to ROS-generating drugs.

Superparamagnetic Iron Oxide Nanoparticles: Amplifying ROS Stress to Improve Anticancer Drug Efficacy

Superparamagnetic iron oxide nanoparticles (SPION) are an important and versatile nano- platform with broad biological applications. Despite extensive studies, the biological and pharmacological activities of SPION have not been exploited in therapeutic applications. Recently, β-lapachone (β-lap), a novel anticancer drug, has shown considerable cancer specificity by selectively increasing reactive oxygen species (ROS) stress in cancer cells. In this study, we report that pH-responsive SPION-micelles can synergize with β-lap for improved cancer therapy. These SPION-micelles selectively release iron ions inside cancer cells, which interact with hydrogen peroxide (H2O2) generated from β-lap in a tumor-specific, NQO1-dependent manner. Through Fenton reactions, these iron ions escalate the ROS stress in β-lap-exposed cancer cells, thereby greatly enhancing the therapeutic index of β-lap. More specifically, a 10-fold increase in ROS stress was detected in β-lap-exposed cells pretreated with SPION-micelles over those treated with β-lap alone, which also correlates with significantly increased cell death. Catalase treatment of cells or administration of an iron chelator can block the therapeutic synergy. Our data suggest that incorporation of SPION-micelles with ROS-generating drugs can potentially improve drug efficacy during cancer treatment, thereby provides a synergistic strategy to integrate imaging and therapeutic functions in the development of theranostic nanomedicine.

Peroxiredoxin 1 knockdown potentiates -lapachone cytotoxicity through modulation of reactive oxygen species and mitogen-activated protein kinase signals

Peroxiredoxin (Prx) 1 is a member of the thiol-specific peroxidases family and plays diverse roles such as H2O2 scavenger, redox signal transducer and molecular chaperone. Prx1 has been reported to be involved in protecting cancer cells against various therapeutic challenges. We investigated how modulations of intracellular redox system affect cancer cell sensitivity to reactive oxygen species (ROS)-generating drugs. We observed that stable and transient Prx1 knockdown significantly enhanced HeLa cell sensitivity to β-lapachone (β-lap), a potential anticancer agent. Prx1 knockdown markedly potentiated 2 µM β-lap-induced cytotoxicity through ROS accumulation. This effect was largely NAD(P)H:quinone oxidoreductase 1 dependent and associated with a decrease in poly(ADP-ribose) polymerase 1 protein levels, phosphorylation of JNK, p38 and Erk proteins in mitogen-activated protein kinase (MAPK) pathways and a decrease in thioredoxin 1 (Trx1) protein levels. Trx1 serves as an electron donor for Prx1 and is overexpressed in Prx1 knockdown cells. Based on the fact that Prx1 is a major ROS scavenger and a partner of at least ASK1 and JNK, two key components of MAPK pathways, we propose that Prx1 knockdown-induced sensitization to β-lap is achieved through combined action of accumulation of ROS and enhancement of MAPK pathway activation, leading to cell apoptosis. These data support the view that modulation of intracellular redox state could be an alternative approach to enhance cancer cell sensitivity to ROS-generating drugs or to overcome some types of drug resistance.

Thermal sensitization through ROS modulation: A strategy to improve the efficacy of hyperthermic intraperitoneal chemotherapy

The purpose of this study was to investigate whether modulation of cellular reactive oxygen species (ROS) provides a synergistic effect with hyperthermia to induce tumor cell death in a colon cancer cell line. HT-29 colon cancer cells were exposed to heat (43 degrees C) in the presence of the ROS-generating drug, 2-2'-azobis-(2-amidinopropane) dihydrochloride (AAPH) for 1 h. Viable cell mass and apoptosis was measured by MTT and annexin V staining, respectively. Oxidative stress was evaluated by DCFH fluorescence. Protein levels were determined by Western blot analysis. A synergistic effect on cell viability with AAPH was noted under hyperthermic conditions as compared with hyperthermia alone (P < .05). The number of nonviable cells after hyperthermia and AAPH exposure was also significantly increased compared with AAPH at 37 degrees C (42% vs 20%, P < .05). ROS levels were increased modestly with AAPH at 37 degrees C, whereas they increased significantly in a dose-dependent manner with AAPH at 43 degrees C. Transient increases of phosphorylated-p38 and ERK and decreases in phosphorylated-AKT were observed in the cells exposed to AAPH at 43 degrees C. Pretreatment of inhibitors of p38 yielded additional decreases in cell mass when used in combination with AAPH and hyperthermia (P < .05). Increased expression of HSP 27 observed at 43 degrees C was abrogated with AAPH exposure. Oxidative stress increased the cytotoxic effects of hyperthermia in colon cancer cells. Thermal sensitization through modulation of cellular ROS may represent a novel approach to increase the efficacy of hyperthermia as an anticancer modality.

Generation of 8-epi-prostaglandin F(2alpha) in isolated rat kidney glomeruli by a radical-independent mechanism.

Isoprostanes comprise a group of free radical-catalyzed products of arachidonic acid. However, there is recent evidence pointing towards an enzyme-dependent formation of isoprostanes. With the use of isolated rat glomeruli we addressed the mechanisms of isoprostane generation. Synthesis of prostanoids and isoprostanes, including 8-epi-PGF(2alpha), was studied under conditions favouring radical formation. Cultured glomeruli formed different prostanoids including 8-epi-PGF(2alpha). Upon LPS challenge cyclo-oxygenase (COX)-2 expression was enhanced, and this was paralleled by a 2 - 9-fold increase in prostanoid formation, including isoprostanes. Addition of COX-isoform unselective inhibitors (diclofenac, indomethacin) or a selective inhibitor (NS-398) suppressed the synthesis of prostanoids, 8-epi-PGF(2alpha) and total isoprostane fraction; however, inhibition of the latter was less pronounced. Antioxidants such as butylated hydroxytoluene (BHT), nordihydroguaiaretic acid (NDGA), or dimethylurea exhibited an only minimal inhibitory effect on 8-epi-PGF(2alpha) synthesis. Moreover, ROS-generating drugs (menadione, methylviologen) or NADPH-driven radical formation were unable to cause the generation of significant amounts of 8-epi-PGF(2alpha) by rat glomeruli. In contrast, the total isoprostane fraction could be increased by menadione addition. These data provide further evidence for a radical-independent, but COX-dependent formation of 8-epi-PGF(2alpha) in renal tissue. Regarding the other isoprostanes, both radicals and COX enzymes contribute to their formation. Based on our data we assume that elevated release of vasoactive 8-epi-PGF(2alpha) has to be expected under conditions when the prostanoid system in the kidney is stimulated, e.g. under inflammatory conditions. Regarding renal oxidative injuries, the usefulness of 8-epi-PGF(2alpha) as a representative marker molecule of oxidative stress has to be questioned.

Post-transcriptional control of increased hepatic catalase gene expression in response to oxidative stress.

Catalase is an important member of the antioxidant network that protects the cell against reactive oxygen species (ROS). We studied catalase gene expression in the liver of rats exposed to oxidative stress induced by the ROS-generating drug nitrofurantoin (NF). Catalase enzymatic activity and content are enhanced by NF treatment. The corresponding increase in the steady state level of the messenger ribonucleic acid (mRNA) occurs without significant changes in transcription and seems therefore controlled post-transcriptionally. Indeed, RNA band-shift assays demonstrated a reduced binding of redox-sensitive cytoplasmic protein(s) to the 3' region of catalase mRNA in NF-treated rats, thus suggesting that the redox state of protein that binds to an antioxidant enzyme mRNA may play a role in the hepatic response to oxidative stress.

Towards more efficacious chemotherapy of trypanosomiasis: Combination of alpha-difluoromethylornithine (DFMO) with reactive oxygen generating drugs

Trypanosomiasis (whether African sleeping sickness, or American Chaga's disease) is caused by an infection with a protozoan parasite, i.e. the trypanosome. This carries fatal sequences in the untreated host. Currently available chemotherapeutic drugs (some of which cure by involving reactive oxygen species (ROS)) are not optimally adequate. They are toxic as well, and may also be carcinogenic. It is therefore desirable to devise better chemotherapeutic regimens. ROS destroy the parasite, but excess ROS damage host tissue and are potentially carcinogenic. Alpha-difluoromethylornithine (DFMO) inhibits ornithine decarboxylase and so lowers the levels of spermine and spermidine. This singular effect in the parasite inhibits its multiplication, whereas in the host tissue it prevents carcinogenesis by preventing cell proliferation. Thus, combination of ROS-generating drugs with DFMO would be very effective against trypanosomiasis, and would be without cancer risk too. The combination is therefore advocated for chemotherapy of trypanosoma infections. This necessities experimental investigations specifically directed towards establishing the optimally efficacious combination of DFMO with the drugs.