Hydrogen-containing saline attenuates doxorubicin-induced heart failure in rats

Interactions between doxorubicin (DOX) and iron generate reactive oxygen species and contribute to DOX-induced heart failure. Hydrogen, as a selective antioxidant, is a promising potential therapeutic option for the treatment of a variety of diseases. Therefore, we investigated the preventive effects of hydrogen treatment on DOX-induced heart failure in rats. We found that cardiac function was significantly improved and that the plasma levels of oxidative-stress markers and myocardial autophagic activity were decreased in animals treated with hydrogen-containing saline. Therefore, we conclude that hydrogen-containing saline may have beneficial effects for doxorubicin-induced heart failure.

Doxorubicin mediated cardiotoxicity in rats: protective role of felodipine on cardiac indices

Anthracyclines find vital uses in the treatment of solid tumors and other kind of malignancies. A typical side effect observed with few agents of this class is dose-dependent cardiotoxicity. Doxorubicin is one such agent which backs the generation of free radicals through metabolism of its quinone structure. This effect combined with induction of apoptotic and necrotic pathways leads to the development of irreversible cardiotoxicity. Reports showing the cardioprotective effects of felodipine have been published in the past. We chose to evaluate protective effect of felodipine in acute cardiotoxicity in rats induced by single dose of doxorubicin. Felodipine was assessed against doxorubicin-induced cardiotoxicity and we found that felodipine not only improves cardiac marker enzymes (P<0.001 for LDH; P<0.01 for CK-MB) but also prevents damage to myocardial tissue (20.61% necrosed area in doxorubicin intoxication; 11.52% necrosed area in felodipine treated group). Activation of apoptotic pathways is decelerated which is indicated by a significant reduction in myocardial caspase-3 activity (P<0.05) following felodipine pretreatment. Felodipine pretreatment was able to maintain normal cardiac morphology and histoarchitecture. Gravimetric analysis revealed beneficial effects following felodipine pretreatment. Abnormalities seen in the ECG after doxorubicin treatment were normalized to a significant extent (ST interval normalization was significant at P<0.01) in felodipine treated rats. In itself, felodipine was not found to have any detrimental effects on the myocardium or hemodynamic parameters of rats. Findings of the study suggest that pretreatment with felodipine prevents doxorubicin induced cardiotoxicity.

Evaluating the inhibitory potential of sulindac against the bleomycin-induced pulmonary fibrosis in wistar rats

The present study examined the protective effect of sulindac on bleomycin-induced lung fibrosis in rats. Animals were divided into saline group, bleomycin group (single intra-tracheal instillation of bleomycin) and bleomycin+sulindac (orally from day 1 to day 20). Bleomycin administration reduced the body weight, altered antioxidant status (such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione) while it increased the lung weight, hydroxyproline content, collagen deposition and lipid peroxidation. However, simultaneous administration of sulindac improved the body weight, antioxidant status and decreased the collagen deposition in lungs. Moreover, the levels of inflammatory cytokine tumour necrosis factor-α increased in bleomycin-induced group, whereas, on treatment with sulindac the levels of tumour necrosis factor-α were found reduced. Finally, histological evidence also supported the ability of sulindac to inhibit bleomycin-induced lung fibrosis. The results of the present study indicate that sulindac can be used as an agent against bleomycin-induced pulmonary fibrosis.

Ethanolic extract of Boswellia ovalifoliolata bark and leaf attenuates doxorubicin-induced cardiotoxicity in mice

The aim of the study was to investigate the potential protective effect of ethanolic extract of Boswellia ovalifoliolata (BO) bark and leaf against doxorubicin (DOX)-induced cardiotoxicity in mice. Ethanolic extracts of BO bark (400 mg/kg) and leaves (250 mg/kg) were given orally to mice for 9 consecutive days and DOX (15 mg/kg; i.p.) was administered on the seventh day. Extract protected against DOX-induced ECG changes. It significantly inhibited DOX-provoked glutathione depletion and accumulation of malondialdehyde. The decrease in antioxidant enzyme activities of catalase, superoxide dismutase, glutathione peroxidase in cardiac tissue were significantly (p<0.05) mitigated after treatment with BO bark and leaf extracts. Pretreatment with BO significantly (p<0.05) restored the levels of DOX-induced rise of SGPT, SGOT, serum lactate dehydrogenase and creatine kinase-MB levels. These findings suggest that ethanolic extract of BO has protective effects against DOX-induced cardiotoxicity.

Both aerobic exercise and resveratrol supplementation attenuate doxorubicin-induced cardiac injury in mice

Because doxorubicin (DOX)-containing chemotherapy causes left ventricular (LV) dysfunction and remodeling that can progress to heart failure, strategies to alleviate DOX cardiotoxicity are necessary to improve health outcomes of patients surviving cancer. Although clinical evidence suggests that aerobic exercise training (ET) can prevent cardiotoxicity in patients undergoing DOX chemotherapy, the physiological mechanisms involved have not been extensively studied, nor is it known whether compounds [such as resveratrol (RESV)] have similar beneficial effects. With the use of a murine model of chronic DOX exposure, this study compared the efficacy of modest ET to RESV treatment on exercise performance, LV remodeling, and oxidative stress resistance. Mice were divided into four groups that received saline, DOX (8 mg/kg ip, one time per week), DOX + RESV (4 g/kg diet, ad libitum), and DOX + ET (45 min of treadmill exercise, 5 days/wk) for 8 wk. LV function and morphology were evaluated by in vivo echocardiography. DOX caused adverse LV remodeling that was partially attenuated by modest ET and completely prevented by RESV. These effects were paralleled by improvements in exercise performance. The cardioprotective properties of ET and RESV were associated with reduced levels of atrial natriuretic peptide and the lipid peroxidation by-product, 4-hydroxy-2-nonenal. In addition, ET and RESV increased the expression of cardiac sarcoplasmic/endoplasmic reticulum calcium-ATPase 2a, superoxide dismutase, mitochondrial electron transport chain complexes, and mitofusin-1 and -2 in mice administered DOX. Compared with modest ET, RESV more effectively prevented DOX-induced LV remodeling and was associated with the reduction of DOX-induced oxidative stress. Our findings have important implications for protecting patients against DOX-associated cardiac injury.

Cardioprotective effect of grape-seed proanthocyanidins on doxorubicin-induced cardiac toxicity in rats

CONTEXT

Doxorubicin (Dox) is an anthracycline antibiotic used as anticancer agent. However, its use is limited due to its cardiotoxicity which is mainly attributed to accumulation of reactive oxygen species.

OBJECTIVE

This study was conducted to assess whether the antioxidant, proanthocyanidins (Pro) can ameliorate Dox-induced cardiotoxicity in rats.

MATERIALS AND METHODS

Male Sprague-Dawely rats were divided into four groups. Group I was control. Group II received Pro (70 mg/kg, orally) once daily for 10 days. Group III received doxorubicin 15 mg/kg i.p. as a single dose on the 7th day and Group IV animals were treated with Pro once daily for 10 days and Dox on the 7th day. The parameters of study were serum biomarkers, cardiac tissue antioxidant status, ECG, and effect on aconitine-induced cardiotoxicity.

RESULTS

Cardiac toxicity of doxorubicin was manifested as a significant increase in heart rate, elevation of the ST segment, prolongation of the QT interval and an increase in T wave amplitude. In addition, Dox enhanced aconitine-induced cardiotoxicity by a significant decrease in the aconitine dose producing ventricular tachycardia (VT). Administration of Pro significantly suppressed Dox-induced ECG changes and normalized the aconitine dose producing VT. The toxicity of Dox was also confirmed biochemically by significant elevation of serum CK-MB and LDH activities as well as myocardial MDA and GSH contents and decrease in serum catalase and myocardial SOD activities. Administration of Pro significantly suppressed these biochemical changes.

DISCUSSION AND CONCLUSION

These results suggest that proanthocyanidins might be a potential cardioprotective agent against Dox-induced cardiotoxicity due to its antioxidant properties.

Antigenotoxic activity of Thai Sangyod red rice extracts against a chemotherapeutic agent, doxorubicin, in human lymphocytes by sister chromatid exchange (SCE) assay in vitro

BACKGROUND

Nowadays, anticarcinogenic potential of pigmented brown rice and rice bran varieties have been increasingly stated. However, their mechanisms of action are still inconclusive. One of which might be their antigenotoxic activity that no study in human cells was reported before.

OBJECTIVE

To evaluate the antigenotoxic activities of Thai Sangyod red rice extracts against a chemotherapeutic agent, doxorubicin, by sister chromatid exchange (SCE) assay in human lymphocytes in vitro.

MATERIAL AND METHOD

Two fractions of water-soluble of Sangyod rice extracts were used: (i) the washed water extract of brown rice (WWBR) and (ii) the water extract of rice bran (WERB). Human lymphocytes were pretreated with each extracts at concentrations of 6.2, 12.5, 25, 50 and 100 microg/ml for 2 h followed by a genotoxic agent, doxorubicin (DXR) (0.1 microg/ml) for 2 h. SCE level, mitotic index (MI) and proliferation index (PI) were evaluated. Statistical analysis by Dunnett's t-test was performed.

RESULTS

The results indicated that the pretreatment of WERB fraction only at concentration of 6.2 microg/ml could significantly decrease SCE level as compared to that of the DXR treated alone (p < 0.05). On the other hand, WERB fraction at other concentrations and all WWBR pretreatments could not. In addition, there was no significant difference in MI and PI levels between all pretreated extracts as compared to the DXR treated alone.

CONCLUSION

Our data revealed that WERB pretreatment only at specific low concentration of 6.2 microg/ml possessed the antigenotoxic potential against genotoxic damage but not anticytotoxic induced by DXR. Further work is still needed to clarify more the antigenotoxic and anticytotoxic potentials from other fractions of Sangyod rice extracts.

Exendin-4 protects pancreatic beta cells from the cytotoxic effect of rapamycin by inhibiting JNK and p38 phosphorylation

It has been reported that the immunosuppressant rapamycin decreases the viability of pancreatic beta cells. In contrast, exendin-4, an analogue of glucagon-like peptide-1, has been found to inhibit beta cell death and to increase beta cell mass. We investigated the effects of exendin-4 on the cytotoxic effect of rapamycin in beta cells. Incubation with 10 nM rapamycin induced cell death in 12 h in murine beta cell line MIN6 cells and Wistar rat islets, but not when coincubated with 10 nM exendin-4. Rapamycin was found to increase phosphorylation of c-Jun amino-terminal kinase (JNK) and p38 in 30 minutes in MIN6 cells and Wistar rat islets while exendin-4 decreased their phosphorylation. Akt and extracellular signal-regulated kinase (ERK) were not involved in the cytoprotective effect of exendin-4. These results indicate that exendin-4 may exert its protective effect against rapamycin-induced cell death in pancreatic beta cells by inhibiting JNK and p38 signaling.

CDC25B mediates rapamycin-induced oncogenic responses in cancer cells

Because the mammalian target of rapamycin (mTOR) pathway is commonly deregulated in human cancer, mTOR inhibitors, rapamycin and its derivatives, are being actively tested in cancer clinical trials. Clinical updates indicate that the anticancer effect of these drugs is limited, perhaps due to rapamycin-dependent induction of oncogenic cascades by an as yet unclear mechanism. As such, we investigated rapamycin-dependent phosphoproteomics and discovered that 250 phosphosites in 161 cellular proteins were sensitive to rapamycin. Among these, rapamycin regulated four kinases and four phosphatases. A siRNA-dependent screen of these proteins showed that AKT induction by rapamycin was attenuated by depleting cellular CDC25B phosphatase. Rapamycin induces the phosphorylation of CDC25B at Serine375, and mutating this site to Alanine substantially reduced CDC25B phosphatase activity. Additionally, expression of CDC25B (S375A) inhibited the AKT activation by rapamycin, indicating that phosphorylation of CDC25B is critical for CDC25B activity and its ability to transduce rapamycin-induced oncogenic AKT activity. Importantly, we also found that CDC25B depletion in various cancer cell lines enhanced the anticancer effect of rapamycin. Together, using rapamycin phosphoproteomics, we not only advance the global mechanistic understanding of the action of rapamycin but also show that CDC25B may serve as a drug target for improving mTOR-targeted cancer therapies.

Protective effect of Zingiber officinale roscoe against anticancer drug doxorubicin-induced acute nephrotoxicity

Oxidative stress due to abnormal production of reactive oxygen species has been implicated in the nephrotoxicity induced by a commonly used anticancer antibiotic doxorubicin (DXN). The nephroprotective effect of aqueous ethanol extract of Zingiber officinale (200 and 400mg/kg, p.o) was evaluated against doxorubicin-induced (15mg/kg, i.p) acute renal damage in rat. Serum urea and creatinine levels were evaluated as the markers of renal failure. Renal antioxidant status such as activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and level of reduced glutathione (GSH) were determined. Level of lipid peroxidation as equivalents of malondialdehyde (MDA), and glutathione-S-transferase (GST) activity were determined in the kidneys. Serum urea and creatinine levels were reduced in the Z. officinale (200 and 400mg/kg, p.o) plus DXN treated groups. The renal antioxidant enzymes activities such as SOD, CAT GPx, levels of GSH and GST activity were restored and that of MDA declined significantly (p<0.001) in the Z. officinale (400mg/kg) plus DXN treated group. The nephroprotection is mediated by preventing the DXN-induced decline of renal antioxidant status, and also by increasing the activity of GST.

Acute doxorubicin nephrotoxicity in rats with malignant neoplasm can be successfully treated with fullerenol C60(OH)24 via suppression of oxidative stress

Oxidative stress has an important role in the pathogenesis of doxorubicin (DOX)-induced nephrotoxicity. The aim of this study was to investigate the nephroprotective effects of fullerenol (FLR), an antioxidant agent, on DOX-induced nephrotoxicity. The investigation was carried out on adult female Sprague Dawley outbred rats with chemically induced breast cancer (1-methyl-1-nitrosourea; 50 mg/kg; ip). Rats were divided into the following groups: control healthy, control cancer, DOX alone (8 mg/kg, ip, cancer), DOX plus FLR as a pre-treatment (8 mg/kg and 100 mg/kg, respectively, ip, cancer), and FLR alone (100 mg/kg, ip, cancer). At the end of the 2nd day after drug administration, blood and kidney tissues were taken for analysis. The activity of lactate dehydrogenase and alpha-hydroxybutyrate dehydrogenase as serum enzymes, as well as level of malondialdehyde, glutathione, glutathione peroxidase, glutathione reductases, catalase and superoxide dismutase, were determined. DOX caused nephrotoxicity, but FLR pre-treatment prevented oxidative stress, lipid peroxidation and the disbalance of GSH/GSSG levels in kidney tissue caused by DOX. Our results confirm satisfactory nephroprotective efficacy of FLR in the acute phase of toxicity and encourage further studies regarding its use as a potential nephroprotector.

Alpha(1) and alpha(2)-adrenoreceptor antagonists in streptozotocin- and vincristine-induced hyperalgesia

The effect of alpha(1)- and alpha(2)-adrenoreceptor antagonists (prazosin and yohimbine, respectively) on streptozotocin (STZ)- and vincristine (VIN)-induced hyperalgesia in rats was studied. In two experimental models, yohimbine (1.0 mg/kg ip) completely abolished STZ and VIN-induced hyperalgesia. This effect was markedly prolonged in diabetic rats. Prazosin (0.3 mg/kg ip) attenuated and delayed development of STZ-induced hyperalgesia. In VIN-elicited neuropathy, the administration of prazosin not only delayed hyperalgesia but also produced antinociception. After cessation of drug administration, a significant decrease in nociceptive threshold was observed. The obtained results seem to indicate that both alpha(1)- and alpha(2)-adrenoreceptors are engaged in diabetic (STZ) and toxic (VIN) neuropathy.

The volume-sensitive chloride channel inhibitors prevent both contractile dysfunction and apoptosis induced by doxorubicin through PI3kinase, Akt and Erk 1/2

Contractile dysfunction and cardiomyopathies secondary to apoptotic cell death are limiting factors for treating cancer with doxorubicin. Inhibition of volume-sensitive chloride currents (I(Cl,vol)) has been reported to blunt doxorubicin-induced apoptosis in cardiomyocytes. To investigate cellular contractility during acute induction of apoptosis by doxorubicin and to determine whether I(Cl,vol) inhibitors are able to prevent the subsequent contractile dysfunction, electrically paced ventricular myocytes freshly isolated from adult rabbits were acutely exposed to doxorubicin in the presence and absence of I(Cl,vol) inhibitors IAA-94 or DIDS. Doxorubicin induced increases in both annexin V labelling and caspase-3 activity and decreases in cell volume. Alteration in cardiac contractility was observed after doxorubicin exposure. Both IAA-94 and DIDS abolished the doxorubicin-induced decreases in peak shortening and cell volume as well as the increases in caspase-3 activity and annexin V labelling. These protective effects of I(Cl,vol) inhibitors were abolished by previous inhibition of PI(3)kinase, Akt and Erk 1/2. Thus, I(Cl,vol) inhibitors prevent doxorubicin-induced apoptosis and subsequent contractile dysfunction through PI(3)kinase/Akt and Erk 1/2. Inhibition of I(Cl,vol) may represent a new pharmacological strategy for developing cytoprotective drugs against apoptotic cell death and contractile dysfunction.

The attenuating effect of memantine on staurosporine-, salsolinol- and doxorubicin-induced apoptosis in human neuroblastoma SH-SY5Y cells

Memantine, a clinically used N-methyl-D-aspartate (NMDA)-receptor antagonist, has been shown to prevent apoptotic neuronal damage connected with the over-activity of NMDA receptors. In the present study, we examined the effect of memantine on staurosporine-, salsolinol- and doxorubicin-induced apoptosis in the SH-SY5Y cell line which does not possess functional NMDA receptors. Electrophysiological recordings and toxicity studies showed no response to NMDA-evoked currents in this cell line, irrespective of the stage of its neuronal differentiation. Memantine (0.1-2 microM) attenuated staurosporine-induced apoptosis as evidenced by reversal of the changes in mitochondrial membrane potential (DeltaPsi(m)) and decreased caspase-3 activity, lactate dehydrogenase (LDH) release and DNA fragmentation. Wortmannin (10 nM) and LY 294002 (10 microM) (inhibitors of phosphatidylinositol-3-kinase, PI3-K) reversed the inhibitory effect of memantine on the staurosporine-induced LDH release, suggesting that the PI3-K/Akt prosurvival pathway is a possible target for antiapoptotic action of memantine. Memantine at low micromolar concentrations also attenuated salsolinol- and doxorubicin-induced LDH release and DNA fragmentation, but only in the case of salsolinol was this effect accompanied by a decrease in caspase-3 activity. The present data indicate that memantine attenuates the toxic effects of various proapoptotic agents and the cytoprotective effect of memantine does not seem to be connected with its action on NMDA receptor but rather with its influence on intracellular pathways engaged in cellular survival/apoptotic processes.

Cytoprotective effect of anthocyanins against doxorubicin-induced toxicity in H9c2 cardiomyocytes in relation to their antioxidant activities

The effect of six anthocyanidins and seven anthocyanins against doxorubicin (Dox)-induced cardiotoxicity in relation to their antioxidant properties was investigated in H9c2 cardiomyocytes. The exposure to Dox, a highly effective cytotoxic agent against cancer cells, induced significant cell death, intracellular reactive oxygen species (ROS), and lipid peroxidation in non-tumorigenic cardiac cell culture. All anthocyanidins (50 and/or 100 microM) significantly increased cell survival up to 40% compared to the Dox-treated controls. Especially, cyanidin and delphinidin, which have an ortho-dihydroxyl moiety (3',4'-OH) on the flavylium skeleton, demonstrated the most potent protection against cytotoxicity (EC(50) of 113 and 179 microM, respectively) as well as lipid peroxidation induced by Dox treatment. In contrast, seven anthocyanins having a glycosidic moiety showed little effect in cytoprotection and lipid peroxidation, although they markedly blocked intracellular ROS generation. All anthocyanidins and anthocyanins had higher TEAC values than ascorbic acid, and efficaciously scavenged superoxide anion (O(2)(-)), hydrogen peroxide (H(2)O(2)), peroxynitrite (ONOO(-)) and nitric oxide (NO), but not hydroxyl radical (OH()). Their O(2)(-) scavenging activity was well correlated with the observed cytoprotection (r=0.67, p<0.05). These results suggest that anthocyanidins can ameliorate Dox-induced cardiotoxicity by, at least in part, scavenging of O(2)(-) generated by Dox.

Fungal malformins inhibit bleomycin-induced G2 checkpoint in Jurkat cells

A DNA-damaging agent, bleomycin, arrests the cell cycle at the G2 phase of Jurkat cells, which are defective in the G1 checkpoint, while microtubule-disrupting colchicine arrests it at M phase. Fungal cyclopeptides, malformin A1 and malformin C, were found to abrogate bleomycin-induced G2 arrest (IC(50); 0.48 microM and 0.9 nM, respectively), resulting in a drastic decrease in cells in G2 phase and increase in cells in subG1 phase. On the other hand, malformins showed little effect on the colchicine-induced M phase arrest in Jurkat cells (IC(50); 2.7 microM and 24 nM, respectively). Malformin C (0.026 microM) also abrogated bleomycin-induced G2 arrest in colon cancer-derived HCT-116 cells. These data strongly suggest that malformin C disrupted the cell cycle at the G2 checkpoint of cancer cells, leading to sensitization of the cancer cells to the anti-cancer reagent.

Topoisomerase IIbeta mediated DNA double-strand breaks: implications in doxorubicin cardiotoxicity and prevention by dexrazoxane

Doxorubicin is among the most effective and widely used anticancer drugs in the clinic. However, cardiotoxicity is one of the life-threatening side effects of doxorubicin-based therapy. Dexrazoxane (Zinecard, also known as ICRF-187) has been used in the clinic as a cardioprotectant against doxorubicin cardiotoxicity. The molecular basis for doxorubicin cardiotoxicity and the cardioprotective effect of dexrazoxane, however, is not fully understood. In the present study, we showed that dexrazoxane specifically abolished the DNA damage signal gamma-H2AX induced by doxorubicin, but not camptothecin or hydrogen peroxide, in H9C2 cardiomyocytes. Doxorubicin-induced DNA damage was also specifically abolished by the proteasome inhibitors bortezomib and MG132 and much reduced in top2beta(-/-) mouse embryonic fibroblasts (MEF) compared with TOP2beta(+/+) MEFs, suggesting the involvement of proteasome and DNA topoisomerase IIbeta (Top2beta). Furthermore, in addition to antagonizing Top2 cleavage complex formation, dexrazoxane also induced rapid degradation of Top2beta, which paralleled the reduction of doxorubicin-induced DNA damage. Together, our results suggest that dexrazoxane antagonizes doxorubicin-induced DNA damage through its interference with Top2beta, which could implicate Top2beta in doxorubicin cardiotoxicity. The specific involvement of proteasome and Top2beta in doxorubicin-induced DNA damage is consistent with a model in which proteasomal processing of doxorubicin-induced Top2beta-DNA covalent complexes exposes the Top2beta-concealed DNA double-strand breaks.

Curcumin prevents streptozotocin-induced islet damage by scavenging free radicals: a prophylactic and protective role

Pancreatic islet cell death is the cause of deficient insulin production in diabetes mellitus. Approaches towards prevention of cell death are of prophylactic importance in control and management of hyperglycemia. Generation of oxidative stress is implicated in streptozotocin, a beta cell specific toxin-induced islet cell death. In this context, antioxidants raise an interest for therapeutic purposes. Curcumin, a common dietary spice is a well known antioxidant and hence we investigated its effect on streptozotocin-induced islet damage in vitro. Isolated islets from C57/BL6J mice were incubated with curcumin for 24 h and later exposed to streptozotocin for 8 h. The effect of streptozotocin exposure to islets was determined with respect to islet viability and functionality, cellular reactive oxygen species concentrations and levels of activated poly (ADP-ribose) polymerase-1. Cellular antioxidant potential (Cu/Zn superoxide dismutase) and advanced glycation end-product related damage was assessed to determine the metabolic status of treated and untreated islets. Islet viability and secreted insulin in curcumin pretreated islets were significantly higher than islets exposed to streptozotocin alone. Curcumin retarded generation of islet reactive oxygen species along with inhibition of Poly ADP-ribose polymerase-1 activation. Although curcumin did not cause overexpression of Cu/Zn superoxide dismutase, it prevented reduction in levels of cellular free radical scavenging enzymes. Our data shows that curcumin protects islets against streptozotocin-induced oxidative stress by scavenging free radicals. We show here for the first time, that prophylactic use of curcumin may effectively rescue islets from damage without affecting the normal function of these cellular structures.

Protection by flavonoids against anthracycline cardiotoxicity: from chemistry to clinical trials

Cardiotoxic side-effects of doxorubicin limit the clinical use of this anti-cancer agent. Iron chelators have been studied as protectors against doxorubicin-induced cardiotoxicity. These iron chelators do not provide optimal protection and have certain drawbacks. We therefore looked for new protectors and decided that these new compounds should combine iron chelating and antioxidant activity. Flavonoids appeared to possess those combined iron chelating and antioxidant properties. Quantum chemical evaluation of radical stabilization and determination of physico-chemical properties of a series of flavonoids brought our attention to the semi-synthetic flavonoid 7-monohydroxyetylrutoside (monoHER). Both in vitro (using an electrically paced mouse left atrium model) and in vivo (using a mouse ECG telemetry model) experiments corroborated the protective effect of monoHER. MonoHER also showed anti-inflammatory properties. A subsequent clinical phase I study showed that an i.v. dose of 1,500mg/m2 is a feasible and safe dose to be evaluated in a phase II study to investigate the protective properties of monoHER against doxorubicin-induced cardiotoxicity in cancer patients.

Novel antioxidants in anthracycline cardiotoxicity

It has been suggested nitroxides and their amine precursors prevent incidence of damage caused by superoxide and hydroxyl radicals formed during the oxidative metabolism of doxorubicin (DOX) and daunorubicin (DAU). Both doxorubicin and daunorubicin have been associated with cardiac toxicity in both adults and children. The authors herein suggest that cardioprotective molecules modified by nitroxides and their secondary amine precursors can prevent or diminish the anthracycline-induced cardiomyopathy by accumulating in cardiomiocytes.

Other uses of dexrazoxane: savene, the first proven antidote against anthracycline extravasation injuries

Dexrazoxane has been in clinical use for more than 25 years for prevention of cardiotoxicity in anthracycline based anticancer therapy. However, we discovered another property of the compound, i.e. the ability to prevent the devastating tissue necrosis after accidental extravasation of anthracyclines. The preclinical and clinical studies leading to the clinical implementation of Savene (dexrazoxane) as the first and only proven antidote in anthracycline extravasation are described in short.

Antioxidant defense against anthracycline cardiotoxicity by metallothionein

Anthracycline cardiotoxicity is related to oxidative stress generated from the metabolism of anthracyclines in the heart. Studies using transgenic mice with high levels of antioxidants such as catalase or metallothionein (MT) specifically in the heart have demonstrated that elevation of cardiac antioxidant defense leads to intervention of anthracycline cardiotoxicity. MT protection against anthracycline-induced cardiac toxicity is related to its anti-apoptotic effect by inhibiting both p38-MAPK-mediated and mitochondrial cytochrome c-release-mediated apoptotic signaling. The anti-apoptotic effect of MT is closely related to its antioxidant action, which involves regulation of zinc homeostasis by the MT redox cycle. MT interferes with oxidant-mediated detrimental process through at least in part zinc release and zinc transfers directly from MT to acceptor proteins. In addition, MT posttranslationally modulates critical proteins involved in mitochondrial respiration and energy metabolism. All of these processes constitute the mechanisms by which MT protects from anthracycline cardiotoxicity.

Carvedilol: just another Beta-blocker or a powerful cardioprotector?

Beta-blockers have been used to treat ischemic heart disease, due to negative chronotropic and inotropic properties, thus inducing a decrease in myocardial consumption of oxygen and nutrients, allowing a better balance between nutritional needs and the supply provided by the coronary blood flow. Recent developments in cell biology allowed us to understand that not all beta-blockers are equal, as their intracellular mechanisms of action can be very different. This paper will focus on carvedilol, a non-selective beta-blocker with alfa-blocker properties, currently used to treat hypertension, heart failure and coronary artery disease. Effects of carvedilol on cardiac mitochondria, their relation to its antioxidant properties, and how these can improve cardiomyocyte resistance to aggression and cardiac function will be discussed. We will begin by depicting the effect of carvedilol on mitochondrial parameters, namely oxidative phosphorylation, calcium homeostasis and energy production. Then we will focus on the mitochondrial permeability transition (MPT) and how the antioxidant properties of carvedilol can be used to minimize oxidative stress, a powerful inducer of MPT. Carvedilol will also be highlighted as an enzyme modulator, focusing on its importance to prevent doxorubicin (DOX) cardiotoxicity. The mitochondrial-related mechanism of cardioprotection involving carvedilol will also be addressed, as we will discuss some clinical pieces of evidence showing the importance of mechanisms previously depicted. In conclusion, based upon its molecular mechanisms of action, carvedilol seems to be a unique beta-blocker. These unique characteristics can help us understand the positive impact of carvedilol on the prognosis of patients with heart disease.

Lovastatin protects human endothelial cells from the genotoxic and cytotoxic effects of the anticancer drugs doxorubicin and etoposide

BACKGROUND AND PURPOSE

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) are frequently used lipid-lowering drugs. Moreover, they exert pleiotropic effects on cellular stress responses and death. Here, we analysed whether lovastatin affects the sensitivity of primary human endothelial cells (HUVEC) to the anticancer drug doxorubicin.

EXPERIMENTAL APPROACH

We investigated whether pretreatment of HUVEC with low dose of lovastatin influences the cellular sensitivity to doxorubicin. To this end, cell viability, proliferation and apoptosis as well as DNA damage-triggered stress response were analysed.

KEY RESULTS

Lovastatin reduced the cytotoxic potency of doxorubicin in HUVEC. Lovastatin attenuated the doxorubicin-induced increase in p53 as well as activation of checkpoint kinase (Chk-1) and stress-activated protein kinase/c-Jun-N-terminal kinase (SAPK/JNK). Acquired doxorubicin resistance was independent of alterations in doxorubicin efflux and cell cycle progression. Also, doxorubicin-triggered production of reactive oxygen species (ROS) and formation of oxidative DNA lesions remained unaffected by lovastatin. However, lovastatin impaired DNA strand break formation induced by doxorubicin. Notably, lovastatin also conferred cross-resistance to the cytotoxic and genotoxic effects of etoposide, indicating that lovastatin shields topoisomerase II against poisons.

CONCLUSIONS AND IMPLICATIONS

Based on these data, we suggest that lovastatin-mediated resistance to topoisomerase II inhibitors is due to a reduction in DNA damage and, hence, it attenuates stress responses leading to cell death that are triggered by DNA damage. Therefore, lovastatin might be useful clinically for alleviating side-effects of anticancer therapies that include topoisomerase II inhibitors.

The selective effect of cystathionine on doxorubicin hepatotoxicity in tumor-bearing mice

The aim of the present study was to examine the protective effect of cystathionine as a cysteine precursor on doxorubicin toxicity in the liver of Ehrlich ascites tumor (EAT)-bearing mice and in the EAT cells. Both compounds were injected intraperitoneally alone or in combination at the following doses: cystathionine at 10 mg and doxorubicin at 5 mg per kg of body weight. In the liver of EAT-bearing mice, glutathione (GSH), cysteine and sulfane sulfur levels as well as the activities of: glutathione S-transferase, gamma-glutamyl transpeptidase, rhodanese and gamma-cystathionase significantly dropped in comparison with healthy animals. Administration of cystathionine elevated GSH and cysteine levels in the livers of EAT-bearing mice and reduced lipid peroxidation. Furthermore, cystathionine increased gamma-glutamyl transpeptidase activity, thereby activating gamma-glutamyl cycle, responsible for proper glutathione metabolism in the cells. Cystationine did not influence sulfane sulfur level and rhodanese and gamma-cystathionase activity in the livers of EAT-bearing mice. It was next shown that cystathionine administered in combination with doxorubicin protected against the drug toxicity since it elevated thiol level, lowering reactive oxygen species content and suppressing lipid peroxidation. This means that, cystathionine in the liver of EAT-bearing mice can both correct harmful effects of carcinogenesis, and protect the liver from doxorubicin cytotoxicity. In contrast, in EAT cells, cystathionine lowered GSH and cysteine levels and did not alter reactive oxygen species level, lipid peroxidation, and gamma-glutamyl transpeptidase activity. All these data indicate that cystathionine action is selectively beneficial for normal cells because it corrects harmful effects induced by EAT development and protects the organism against doxorubicin cytotoxicity without impairing cytotoxicity of this drug to tumor cells.

The anti-hepatitis drug DDB chemosensitizes multidrug resistant cancer cells in vitro and in vivo by inhibiting P-gp and enhancing apoptosis

PURPOSE

DDB (dimethyl-4,4'-dimethoxy-5,6,5'6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate) is a synthetic hepatoprotectant which has been widely used to treat chronic viral hepatitis B patients in China for more than 20 years. In this study, we evaluated DDB as a multidrug resistance (MDR) chemosensitizing agent.

METHODS

A panel of sensitive and resistant cancer cell lines were treated with various concentration of DDB, and the effect on chemosensitivity and accumulation of anticancer drugs; promotion of apoptosis and P-glycoprotein (P-gp) expression were determined by MTT (Dimethyl thiazolyl-2,5-diphenyltetrazolium bromide) assay, fluorospectrometry and flow cytometry respectively. Drug resistance reversal activity of DDB was also examined in BALB/c nude mice bearing both acquired MDR human nasopharyngeal carcinoma KBv200 and parental KB xenografts. The effect of DDB on the pharmacokinetics of Dox and hematological toxicity induced by Dox was measured in ICR and C(57)/BL mice, respectively.

RESULTS

DDB at nontoxic concentrations of 12.5, 25 and 50 microM partly reversed the resistance to vincristine, doxorubicin, paclitaxel in acquired MDR breast carcinoma MCF-7/Adr cells, KBv200 and intrinsic MDR human hepatocarcinoma Bel(7402) cells, whereas no chemosensitizing effect of DDB was observed in sensitive KB and MCF-7 cells. DDB increased the intracellular accumulation of doxorubicin and inhibited surface P-gp expression in MCF-7/Adr cells. Furthermore, it was found that DDB promoted doxorubicin-induced apoptosis of Bel(7402) cells through enhanced caspase-3 activation. Co-administration of DDB at 300 and 500 mg/kg orally to nude mice increased the antitumor activity of vincristine to KBv200 xenografts without a significant increase in toxicity. In contrast, Co-administration of DDB did not inhibit the growth of KB xenografts. DDB also markedly reduced the decrease of leukocytes in doxorubicin-treated C(57)/BL mice. Co-administration of DDB increased Dox concentration in ICR mice bearing S180 sarcoma, but no pharmacokinetical interaction with Dox was observed.

CONCLUSION

These results indicate that DDB has MDR reversal activity by inhibiting P-gp and when used in combination with anti-cancer drugs, it could potentially be used as a clinical treatment for P-gp-mediated MDR cancers.

Effects of melatonin in reducing the toxic effects of doxorubicin

Anthracycline antibiotics, such as doxorubicin and daunorubicin, constitute a group of wide spectrum therapeutic agents. Application of these drugs in chemotherapy is limited because of their toxic effects. Melatonin, the main secretory product of pineal gland, was recently found as a free radical scavenger and antioxidant. We decided to evaluate the tissue protective effect of melatonin against toxic effects of doxorubicin in six groups of rats. Rats were given doxorubicin (Dx) (45 mg/kg dose), melatonin (MEL) (10 mg/kg), first doxorubicin and then melatonin (DM), first melatonin and then doxorubicin (MD). The degree of kidney, lung, liver and brain cells' alterations were examined biochemically. In doxorubicin-treated group, malondialdehyde (MDA) levels of kidney, lung, liver and brain tissues were significantly increased but glutathione (GSH) levels were decreased compared to control rats. In the group in which first doxorubicin and then melatonin were given, MDA levels were significantly decreased compared to the doxorubicin-treated group. In doxorubicin-treated group, serum levels of creatinine, uric acid, blood urea nitrogen (BUN), Gamma-glutamyl transpeptidase (GGT) and Lactic acid dehydrogenase (LDH) were significantly increased while serum albumin and total protein levels were significantly decreased compared to control rats. Melatonin decreased the intensity of the changes produced by the administration of doxorubicin alone. Melatonin was quite efficient in reducing the formation of lipid peroxidation, restoring the tissue GSH contents and alterations of serum levels.

Prevention of chronic anthracycline cardiotoxicity in the adult Fischer 344 rat by dexrazoxane and effects on iron metabolism

PURPOSE

Anthracyclines, such as doxorubicin and daunorubicin, continue to be widely used in the treatment of cancer, although they share the adverse effect of chronic, cumulative dose-related cardiotoxicity. The only approved treatment in prevention of anthracycline cardiotoxicity is dexrazoxane, a putative iron chelator. Previous in vitro studies have shown that disorders of iron metabolism, including altered IRP1-IRE binding, may be an important mechanism of anthracycline cardiotoxicity.

METHODS

This study examined the role of IRP1-IRE binding ex vivo in a chronic model of daunorubicin cardiotoxicity in the Fischer 344 rat and whether dexrazoxane could prevent any daunorubicin-induced changes in IRP1 binding. Young adult (5-6 months) Fischer 344 rats received daunorubicin (2.5 mg/kg iv once per week for 6 weeks) with and without pretreatment with dexrazoxane (50 mg/kg ip). Other groups received saline (controls) or dexrazoxane alone. Rats were killed either 4 h or 2 weeks after the last dose of daunorubicin to assess IRP1-IRE binding.

RESULTS

Contractility (dF/dt) of atrial tissue, obtained from rats 2 weeks after the last dose of daunorubicin, was significantly reduced in daunorubicin-treated compared to control rats. Dexrazoxane pretreatment protected against the daunorubicin-induced decrease in atrial dF/dt. However, left ventricular IRP1/IRE binding was not affected by daunorubicin treatment either 4 h or 2 weeks after the last dose of daunorubicin.

CONCLUSIONS

IRP1 binding may not be altered in the rat model of chronic anthracycline cardiotoxicity.

Src inhibits adriamycin-induced senescence and G2 checkpoint arrest by blocking the induction of p21waf1

DNA-damaging drugs stop tumor cell proliferation by inducing apoptosis, necrosis, or senescence. Cyclin-dependent kinase inhibitor p21waf1 is an important regulator of these responses, promoting senescence and preventing aberrant mitosis that leads to cell death. Because tumors expressing oncogenic tyrosine kinases are relatively resistant to DNA-damaging agents, the effects of Src on cellular responses to anticancer drug Adriamycin were investigated. Src expression increased drug survival in HT1080 fibrosarcoma cells, as measured by the colony formation assay, and strongly inhibited Adriamycin-induced senescence. Src also decreased the number of apoptotic cells while increasing the fraction of cells dying through necrosis. In addition, Src inhibited the G2 and G1 tetraploidy checkpoints of Adriamycin-treated cells, permitting these cells to proceed into mitosis and subsequently double their DNA content. Inhibition of senescence and G2-G1 checkpoints in Src-expressing cells was associated with the failure of these cells to up-regulate p21waf1 in response to Adriamycin. The failure of p21waf1 induction, despite increased expression of p53 and its binding to p21waf1 promoter, was mediated by the up-regulation of c-Myc, a negative regulator of p21waf1 transcription. Conversely, ectopic expression of p21waf1 inhibited Myc transcription in Src-expressing cells, an effect that was associated with the interaction of p21waf1 with the STAT3 transcription factor at the Myc promoter. These results reveal a complex effect of Src on cellular drug responses and provide an explanation for the effect of this oncogene on cellular drug resistance.

Rapamycin-Sensitive Pathway Regulates Mitochondrial Membrane Potential, Autophagy, and Survival in Irradiated MCF-7 Cells

Radiation-induced inhibition of rapamycin-sensitive pathway and its effect on the cellular response to radiation were studied in the human breast cancer cell line MCF-7. Both radiation and rapamycin shared molecular targets and induced similar physiologic responses. Each of these treatments increased immunostaining of mammalian target of rapamycin (mTOR) in the nucleus, and radiation led to decreased phosphorylation of its autophosphorylation site Ser2481. In addition to dephosphorylation of established mTOR downstream effectors 4E-binding protein 1 and p70 ribosomal S6 kinase, both treatments decreased the level of eukaryotic initiation factor 4G. Experiments with the potentiometric dye, JC-1, revealed an oligomycin-dependent increase in mitochondrial membrane potential following radiation or rapamycin treatment, suggesting that both lead to reversal of F0F1ATPase activity. Both radiation and rapamycin induced sequestration of cytoplasmic material in autophagic vacuoles. In both cases, appearance of autophagic vacuoles involved the participation of microtubule-associated protein 1 light chain 3 (LC3). Transient cotransfection of green fluorescent protein-LC3 with either wild-type or dominant-negative mTOR further showed that inactivation of mTOR pathway is sufficient to induce autophagy in these cells. Finally, administration of rapamycin in combination with radiation led to enhanced mitochondria hyperpolarization, p53 phosphorylation, and increased cell death. Taken together, these experiments show that radiation-induced inhibition of rapamycin-sensitive pathway in MCF-7 cells causes changes in mitochondria metabolism, development of autophagy, and an overall decrease in cell survival.

The main catechin of green tea, (-)-epigallocatechin-3-gallate (EGCG), reduces bleomycin-induced DNA damage in human leucocytes

Interest in the beneficial effects of green tea has led to investigations on activities by the main catechin (-)-epigallocatechin-3-gallate (EGCG). This antioxidative compound could contribute to cancer chemoprevention by acting antigenotoxic. To further explore this hypothesis we investigated antigenotoxic potentials of low EGCG concentrations in human peripheral leucocytes. Leucocytes isolated from whole blood were (1) stimulated with phytohaemagglutinin, (2) damaged with genotoxic bleomycin, and (3) post-incubated to allow DNA repair. After each phase DNA integrity was measured with the comet assay. EGCG (2, 20, 100 microM) was added either during phases 1, 2 or 3 or during the whole process (1-3), to delineate mechanisms of antigenotoxicity reflecting induction of detoxification (phase 1), scavenging of radicals (phase 2), stimulation of repair (phase 3), respectively. Bleomycin induced breaks and endonuclease III specific damage, but EGCG did not affect damage or repair of these lesions when added during phases 1, 2 or 3. However, the application of EGCG during phases 1 and 2 significantly reduced both bleomycin-induced breaks and endonuclease III sensitive sites. EGCG added during all phases impaired persistence of damage. Our studies show that the continuous presence of EGCG can reduce radical-induced DNA damage in primary leucocytes, possibly due to a combination of different mechanisms. Together the findings support the hypotheses that EGCG acts protective in human cells.

Rho GDP dissociation inhibitor protects cancer cells against drug-induced apoptosis

Rho GDP dissociation inhibitor (RhoGDI) plays an essential role in control of a variety of cellular functions through interactions with Rho family GTPases, including Rac1, Cdc42, and RhoA. RhoGDI is frequently overexpressed in human tumors and chemo-resistant cancer cell lines, raising the possibility that RhoGDI might play a role in the development of drug resistance in cancer cells. We found that overexpression of RhoGDI increased resistance of cancer cells (MDA-MB-231 human breast cancer cells and JLP-119 lymphoma cells) to the induction of apoptosis by two chemotherapeutic agents: etoposide and doxorubicin. Conversely, silencing of RhoGDI expression by DNA vector-mediated RNA interference (small interfering RNA) sensitized MDA-MB-231 cells to drug-induced apoptosis. Resistance to apoptosis was restored by reintroduction of RhoGDI protein expression. The mechanism for the anti-apoptotic activity of RhoGDI may derive from its ability to inhibit caspase-mediated cleavage of Rac1 GTPase, which is required for maximal apoptosis to occur in response to cytotoxic drugs. Taken together, the data show that RhoGDI is an anti-apoptotic molecule that mediates cellular resistance to these chemotherapy agents.

Lipopolysaccharide Prevents Doxorubicin-Induced Apoptosis in RAW 264.7 Macrophage Cells by Inhibiting p53 Activation

The effect of lipopolysaccharide on doxorubicin-induced cell death was studied by using mouse RAW 264.7 macrophage cells. Pretreatment with lipopolysaccharide at 10 ng/mL prevented doxorubicin-induced cell death and the inhibition was roughly dependent on the concentration of lipopolysaccharide. Posttreatment with lipopolysaccharide for 1 hour also prevented doxorubicin-induced cell death. Lipopolysaccharide inhibited DNA fragmentation and caspase-3 activation in doxorubicin-treated RAW 264.7 cells, suggesting the prevention of doxorubicin-induced apoptosis. Lipopolysaccharide did not significantly inhibit doxorubicin-induced DNA damage detected by single-cell gel electrophoresis (comet) assay. Lipopolysaccharide definitely inhibited the stabilization and nuclear translocation of p53 in doxorubicin-treated RAW 264.7 cells. Lipopolysaccharide, as well as being an inhibitor of p53, abolished doxorubicin-induced apoptosis. Therefore, p53 was suggested to play a pivotal role in the prevention of doxorubicin-induced apoptosis in RAW 264.7 cells by lipopolysaccharide.

Screening of antioxidants from medicinal plants for cardioprotective effect against doxorubicin toxicity

Doxorubicin is an important and effective anticancer drug widely used for the treatment of various types of cancer but its clinical use is limited by dose-dependent cardiotoxicity. Elevated tissue levels of cellular superoxide anion/oxidative stress are a mechanism by which doxorubicin-induced cardiotoxicity. Selected medicinal plant extracts were tested for their antioxidant capacity and cardioprotective effect against doxorubicin-induced cardiotoxicity. The cardiac myoblasts H9c2 were incubated with the antioxidants ascorbic acid, trolox, N-acetylcysteine or selected medicinal plant extracts including; 1) ethanolic extracts from Curcuma longa L-EtOH Phyllanthus emblica L-EtOH, and Piper rostratum Roxb-EtOH; and 2) water extracts from Curcuma longa L-H2O and Morus alba L-H2O. The cardioprotective effects of these extracts were evaluated by crystal violet cytotoxicity assay. IC50s of doxorubicin were compared in the presence or absence of ascorbic acids, trolox, N-acetylcysteine or plant extracts. Morus alba L-H2O showed the highest antioxidant properties evaluated by ferric reducing/antioxidant power assay. Ascorbic acid and N-acetylcysteine had modest effects on the protection of doxorubicin-induced cytotoxicity while trolox showed insignificant protective effect. All plant extracts protected cardiac toxicity at different degrees except that Curcuma longa L-EtOH had no protective effect. Phyllanthus emblica-EtOH (100 microg/ml) showed the highest cardioprotective effect (approximately 12-fold doxorubicin IC50 increase). The data demonstrate that antioxidants from natural sources may be useful in the protection of cardiotoxicity in patients who receive doxorubicin.

Effect of melatonin on the cardiotoxicity of doxorubicin

This study was designed to investigate the preventive effect of melatonin on doxorubicin's most important side effect, cardiotoxicity. Forty male albino Wistar rats were utilized and the rats were divided into five groups: group I, 0.9% NaCl for 4 days; group II, doxorubicin 3 mg/kg/day for 4 days; group III, 2.5 % ethanol for 15 days; group IV, melatonin 6 mg/kg/day for 15 days; and group V, a doxorubicin and melatonin combination were administered intraperitoneally. At the end of the experiment, tissue samples obtained from the cardiac muscle of the left ventricle of the rats were processed for measurement of malondialdehyde and for electron microscopic examination. Malondialdehyde, a product of lipid peroxidation, was found to be significantly higher in the doxorubicin group. However, in the doxorubicin and melatonin combination group the level of malondialdehyde was decreased statistical significant. The histological examination revealed destruction of myofibrils, disorganization of sarcomeres, mitochondrial degeneration and formation of giant mitochondria and lipid accumulation in the doxorubicin group. Also, accumulation of filamentous structures in the sarcoplasma in some of the cells, structural changes in capillaries and an increase in collagen fibers forming bundles were observed. When melatonin was added to the doxorubicin treatment all structural changes were reduced. The cardiotoxic side effect of doxorubicin used as a chemotherapeutic agent and was probably developed as a result of suppression of the antioxidant system and lipid peroxidation. Therefore, it could be assumed that the addition of melatonin in the treatment of doxorubicin could prevent the cardiotoxicity of doxorubicin.

Saeng-Ji-Hwang has a protective effect on adriamycin-induced cytotoxicity in cardiac muscle cells

This study examined the effect of Saeng-Ji-Hwang (SJH: Radix Rehmanniae) on cardiac muscle cells. Adriamycin-exposed H9C2 cardiac muscle cells were treated with a water extract of SJH. The adriamycin induced cell death and caspase-3 activation were significantly inhibited by SJH (2 mg/ml), which can be explained by the increase in Bcl-2 expression and the inhibition of Bax expression. Adriamycin reduced the Mn-SOD protein expression level in H9C2 cardiac muscle cells but a SJH treatment partially but significantly reversed this effect. Manganese (Mn)-TBAP or Mn-TMyM--mitochondria-specific SOD mimetic agent--reduced the adriamycin-induced cytotoxicity. It was also shown that SJH inhibits the release of H2O2 and prevents lipid peroxidation in the presence of adriamycin. This study examined the intracellular GSH level, which showed that adriamycin significantly decreased the intracellular GSH level but SJH increased it. BSO, a selective inhibitor of glutamyl cysteinyl ligase, which is a rate-limiting enzyme in GSH synthesis, did not affect the viability of the cardiac muscle cells. However, a combination of BSO with SJH in the presence of adriamycin reversed the SJH-induced protection. Overall, the results suggest that SJH-associated Mn-SOD and GSH are important factors in the mechanism of the SJH-induced protective mechanism in H9C2 cardiac muscle cells.

Carvedilol prevents doxorubicin-induced free radical release and apoptosis in cardiomyocytes in vitro

The clinical use of doxorubicin, a highly active anticancer drug, is limited by its severe cardiotoxic side effects. Increased oxidative stress and apoptosis have been implicated in the cardiotoxicity of doxorubicin. Carvedilol is an adrenergic blocking agent with potent anti-oxidant activity. In this study we investigated whether carvedilol has protective effects against doxorubicin-induced free radical production and apoptosis in cultured cardiac muscle cells, and we compared the effects of carvedilol to atenolol, a beta-blocker with no anti-oxidant activity. Reactive oxygen species (ROS) generation in cultured cardiac muscle cells (H9c2 cells) was evaluated by flow cytometry using dichlorofluorescein (DCF) and hydroethidine (HE). Apoptosis was assessed by measuring annexin V-FITC/propidium iodide double staining, DNA laddering, levels of expression of the pro-apoptotic protein Bax-alpha and the anti-apoptotic protein Bcl-2, and caspase-3 activity. Pre-treatment with carvedilol significantly attenuated the doxorubicin-induced increases in DCF (P < 0.001 compared to cells not pre-treated with carvedilol) and HE (P < 0.01) fluorescence. Doxorubicin increased the fraction of annexin V-FITC-positive fluorescent cells, while pre-treatment with carvedilol reduced the number of positive fluorescent cells (P < 0.01). Doxorubicin-induced DNA fragmentation to a clear ladder pattern, while carvedilol prevented DNA fragmentation. Doxorubicin-induced a fall in mRNA expression of the anti-apoptotic Bcl-2 and an increase in the expression of the pro-apoptotic Bax-alpha. Carvedilol pre-treatment blunted both the decrease of Bcl-2 (P < 0.01) and the increase of Bax-alpha mRNA expression (P < 0.01). Caspase-3 activity significantly increased after the addition of doxorubicin. Concurrently, carvedilol partially inhibited the doxorubicin-induced activation of caspase-3 (P < 0.01). Atenolol did not produce any effect in preventing doxorubicin-induced ROS generation and cardiac apoptosis. Our results suggest that carvedilol is potentially protective against doxorubicin cardiotoxicity by decreasing free radical release and apoptosis in cardiomyocytes.

α-Tocopherol Suppresses Mammary Tumor Sensitivity to Anthracyclines in Fish Oil-Fed Rats

Polyunsaturated fatty acids (PUFAs) have been reported to enhance the efficacy of chemotherapeutic agents that produce reactive oxygen species such as anthracyclines. We previously reported in a human breast cancer cell line that the increased cytotoxic activity of anthracyclines by several PUFAs was abolished by antioxidants and enhanced by pro-oxidants, suggesting that lipid peroxidation was involved in this effect. To determine the relevance of this observation in vivo, we examined the effect of the oxidative status of the diet on the activity of epirubicin against N-methylnitrosourea-induced mammary tumors in Sprague-Dawley rats. Three groups of rats were fed a basal diet enriched with dietary n-3 PUFA (sardine oil, 15%) alone (control group), with addition of an antioxidant (alpha-tocopherol, 100 UI/kg diet), or with addition of an oxidant system (dehydroascorbate/naphthoquinone). When the first mammary tumor reached 1 cm2, epirubicin was administrated weekly for 3 wk, and subsequent change in tumor size was documented over time. Two weeks after the end of epirubicin injections, tumor size was increased by 34% in the control group. In the pro-oxidant group, tumor size was decreased by 50%. In contrast, tumor size was increased by 188% in the antioxidant group. Thus, addition of pro-oxidants in a fish oil-enriched diet increased the sensitization of mammary tumors to chemotherapy, whereas addition of alpha-tocopherol suppressed tumor response in vivo, indicating that interaction between components of the diet has to be carefully controlled during chemotherapy.

Dietary Vitamin E Decreases Doxorubicin- Induced Oxidative Stress Without Preventing Mitochondrial Dysfunction

Doxorubicin (DOX) is a widely prescribed antineoplastic and although the precise mechanism(s) have yet to be identified, DOX-induced oxidative stress to mitochondrial membranes is implicated in the pathogenic process. Previous attempts to protect against DOX-induced cardiotoxicity with alpha-tocopherol (vitamin E) have met with limited success, possibly as a result of inadequate delivery to relevant subcellular targets such as mitochondrial membranes. The present investigation was designed to assess whether enrichment of cardiac membranes with alpha-ocopherol is sufficient to protect against DOX-induced mitochondrial cardiotoxicity. Adult male Sprague-Dawley rats received seven weekly subcutaneous injections of 2 mg/kg DOX and fed either standard diet or diet supplemented with alpha-tocopherol succinate. Treatment with a cumulative dose of 14 mg/kg DOX caused mitochondrial cardiomyopathy as evidenced by histology, accumulation of oxidized cardiac proteins, and a significant decrease in mitochondrial calcium loading capacity. Maintaining rats on the alpha-tocopherol supplemented diet resulted in a significant (two- to four-fold) enrichment of cardiac mitochondrial membranes with alpha-tocopherol and diminished the content of oxidized cardiac proteins associated with DOX treatment. However, dietary alpha-tocopherol succinate failed to protect against mitochondrial dysfunction and cardiac histopathology. From this we conclude that although dietary vitamin E supplementation enriches cardiac mitochondrial membranes with alpha-tocopherol, either (1) this tocopherol enrichment is not sufficient to protect cardiac mitochondrial membranes from DOX toxicity or (2) oxidative stress alone is not responsible for the persistent mitochondrial cardiomyopathy caused by long-term DOX therapy.

The modulating effects of quercetin and rutin on the mitomycin C induced DNA damage

The present study was carried out to investigate the modulating effects of the two flavonoids quercetin and rutin on the mutagenic anticancer drug mitomycin C by single cell gel electrophoresis (Comet assay) in human lymphocytes. Lymphocytes were incubated with different concentrations of quercetin and rutin, with or without mitomycin C, and DNA damage was evaluated. Concentrations of 0.03, 0.15, 0.3, 0.6, 1.5 and 3mM quercetin significantly reduced the DNA strand breakage induced by mitomycin C (P<0.001) but the highest concentration of 6mM quercetin did not show a protective effect. The frequency of damaged cells induced by mitomycin C was not changed at 0.02 mM, and also at the highest concentrations of 1.64 and 3.28 mM rutin. However, at concentrations of 0.08, 0.16, 0.33 and 0.82 mM rutin cells were protected from DNA damage. Thus, in human lymphocytes quercetin and rutin displayed protective effects on DNA damage induced by mitomycin C, in a concentration-dependent manner.

Potent induction of cellular antioxidants and phase 2 enzymes by resveratrol in cardiomyocytes: protection against oxidative and electrophilic injury

Resveratrol is known to be protective against oxidative cardiovascular disorders. However, the underlying mechanisms remain unclear. This study was undertaken to determine if resveratrol could increase endogenous antioxidants and phase 2 enzymes in cardiomyocytes, and if such increased cellular defenses could provide protection against oxidative and electrophilic cell injury. Incubation of cardiac H9C2 cells with low micromolar resveratrol resulted in a significant induction of a scope of cellular antioxidants and phase 2 enzymes in a concentration- and/or time-dependent fashion. To investigate the protective effects of the resveratrol-induced cellular defenses on oxidative and electrophilic cell injury, H9C2 cells were first incubated with resveratrol, and then exposed to xanthine oxidase (XO)/xanthine, 4-hydroxy-2-nonenal or doxorubicin. We observed that resveratrol pretreatment afforded a marked protection against the above agent-mediated cytotoxicity in H9C2 cells. Moreover, the resveratrol pretreatment led to a great reduction in XO/xanthine-induced intracellular accumulation of ROS. Taken together, this study demonstrates that resveratrol induces antioxidants and phase 2 enzymes in cardiomyocytes, which is accompanied by increased resistance to oxidative and electrophilic cell injury.

Genotoxicity of streptozotocin in normal and cancer cells and its modulation by free radical scavengers

Streptozotocin (STZ) is an antibiotic which can be used to induce diabetes in experimental animals in order to have an insight into pathogenesis of this disease. To use STZ as a diabetogenic substance, its molecular mode of action should be elucidated. Using the alkaline comet assay, we showed that STZ at concentrations in the range 0.01-100 micromol/L induced DNA damage in normal human lymphocytes and HeLa cancer cells in a dose-dependent manner. Lymphocytes were able to remove damage to their DNA within a 30-min repair incubation, whereas HeLa cells completed the repair in 60 min. Vitamins C and E at 10 and 50 micromol/L diminished the extent of DNA damage induced by 50 micromol/L STZ. Pretreatment of the lymphocytes with the nitrone spin trap, alpha-(4-pyridil-1-oxide)-N-tert-butylnitrone (POBN) or ebselen, which mimics glutathione peroxidase, or pyrrolidine dithiocarbamate (PDTC) reduced the extent of DNA damage evoked by STZ. The cells exposed to STZ and treated with endonuclease III (Endo III), formamidopyrimidine-DNA glycosylase (Fpg) and 3-methyladenine-DNA glycosylase II (AlkA), the enzymes recognizing oxidized and alkylated bases, displayed greater extent of DNA damage than those not treated with these enzymes. These results suggest that free radicals may be involved in the formation of DNA lesions induced by streptozotocin. The drug can also alkylate DNA bases. This broad range of DNA damage induced by STZ indicates that the drug may seriously affect genomic stability in normal and pathological cells.

Effects of pyrroline and pyrrolidine nitroxides on lipid peroxidation in heart tissue of rats treated with doxorubicin

Protection from doxorubicin-induced lipid peroxidation in vivo by two pyrroline and pyrrolidine nitroxides, Pirolin, PL, and Pirolid, PD, was examined in the heart tissue of rats treated with this drug. The level of lipid peroxidation was estimated on the basis of MDA content. A considerable (three-fold) increase in the MDA amount was found in heart homogenates from rats injected with doxorubicin, whereas no significant changes in MDA content compared to control were observed in cardiomyocytes treated with the nitroxides (Pirolin or Pirolid) only. Pirolin injected simultaneously with doxorubicin showed antioxidative effect and markedly attenuated lipid peroxidation in the heart tissue caused by this drug. In contrast to Pirolin, structurally related Pirolid was ineffective in the protection of heart myocytes from DOX-induced lipid peroxidation.

The nitroxides pirolin and pirolid protect the plasma membranes of rat cardiomyocytes against damage induced by anthracyclines

This study was performed to evaluate the protective effects of pyrroline and pyrrolidine nitroxides Pirolin, PL, and Pirolid, PD, on the plasma membranes of rat cardiomyocytes treated in vitro with anthracycline drugs aclarubicin (ACL) and doxorubicin (DOX). The influence of two concentrations of drugs (10 and 20 microM) and nitroxides (0.1 and 1 mM) as well as their combinations (a drug and a nitroxide) on membrane fluidity was investigated. The plasma membranes of cardiomyocytes were labelled with a hydrophobic fluorescence probe 12-AS and membrane fluidity was estimated on the basis of the fluorescence anisotropy of the probe. We found that aclarubicin and doxorubicin induced a significant dose-dependent decrease in membrane fluidity, whereas the nitroxides (PL and PD) caused its increase. Preincubation of cardiomyocytes with Pirolin entirely protected plasma membranes of these cells against damage caused by DOX. In the same conditions no protective effect of Pirolid was observed. What is more, Pirolid in combination with DOX caused fluidisation of the plasma membranes of cardiomyocytes. Both nitroxides at low concentration (0.1 mM) protected plasma membranes against rigidification induced by aclarubicin, while high concentration (1 mM) was ineffective and caused fluidisation of the plasma membranes of cardiomyocytes.

mTOR as a Target for Cancer Therapy

The target of rapamycin, mTOR, acts as a sensor for mitogenic stimuli, such as insulin-like growth factors and cellular nutritional status, regulating cellular growth and division. As many tumors are driven by autocrine or paracrine growth through the type-I insulin-like growth factor receptor, mTOR is potentially an attractive target for molecular-targeted treatment. Further, a rationale for anticipating tumor-selective activity based on transforming events frequently identified in malignant disease is becoming established.

The activities of tissue xanthine oxidase and adenosine deaminase and the levels of hydroxyproline and nitric oxide in rat hearts subjected to doxorubicin: protective effect of erdosteine

The aim of this experimental study was to investigate the effects of erdosteine, an antioxidant agent, on doxorubicin (DXR)-induced cardio-toxicity through nitric oxide (NO) levels, collagen synthesis, xanthine oxidase (XO) and adenosine deaminase (ADA) activities in rats. Rats were treated with erdosteine (10 mg/kg b.wt. per day, orally) or saline starting 2 days before administrating a single dose of DXR (20 mg/kg i.p.) or saline. At the 10th day of the DXR administration, hearts were removed under anesthesia for biochemical measurements. Enzyme activities as well as OH-proline and NO levels were found to be significantly increased in DXR group compared with the control group. All of the parameters studied except ADA activity were decreased significantly approximating to the control levels upon erdosteine administration. In conclusion, erdosteine seems to be an alternative agent for protection of cardiac tissue against DXR-induced cardio-toxicity through its regulatory effect on XO activity and NO level.

Rapamycin inhibits telomerase activity by decreasing the hTERT mRNA level in endometrial cancer cells

Rapamycin exerts its biological activity by inhibiting the kinase mammalian target of rapamycin (mTOR), which regulates important cellular processes such as control of cell cycle and cell size, translation initiation, and transcription. The ability of rapamycin to inhibit cancer cell proliferation has led to efforts to develop rapamycin and related mTOR inhibitors as anticancer agents. Some investigators have hypothesized that loss of the PTEN tumor suppressor may sensitize tumor cells to the antiproliferative activity of rapamycin because PTEN loss leads to activation of the mTOR pathway. Because PTEN loss is frequent in endometrial cancer, we have characterized the effect of rapamycin in endometrial cancer cells. We show that rapamycin in the nanomolar concentration range exerts a potent growth-inhibitory effect on endometrial cancer cells through induction of cell cycle arrest. This effect is independent of PTEN status because PTEN-positive ECC-1 cells are as sensitive to rapamycin as PTEN-null Ishikawa and Hec-1B cells, suggesting that rapamycin may be effective against a broad range of endometrial cancers. We also show that rapamycin rapidly inhibits telomerase activity by decreasing the mRNA level of hTERT, the catalytic subunit of telomerase. This implies that rapamycin leads to inhibition of hTERT gene transcription. We demonstrate that rapamycin inhibits phosphorylation of downstream targets of mTOR such as p70(S6K) kinase and 4E-BP1 translation repressor. This work suggests that rapamycin is a potentially useful targeted therapy for endometrial cancer and that loss of telomerase activity may be a good surrogate biomarker for assessing antitumor activity of rapamycin.

Geldanamycin induction of grp78 requires activation of reactive oxygen species via ER stress responsive elements in 9L rat brain tumour cells

The molecular mechanism whereby anticancer agent geldanamycin (GA) impacts endoplasmic reticulum (ER) stress pathway is largely unknown. Here, we investigate the effect of GA on the expression of grp78 coding for ER stress protein and the mechanistic relationship of GA signalling to ER stress. GA induces the expression of mRNA and protein of grp78 by Northern blot analysis and metabolic labelling experiment in cultured rat brain tumour 9L cells. The induced grp78 expression is sensitive to antioxidant N-acetylcysteine (NAC) addition, indicating the involvement of reactive oxygen species (ROS) in GA-induced ER stress. Results from direct determination of oxidation status using dichlorodihydrofluorescein diacetate (H(2)DCFDA) showed that accumulation of ROS elicited GA was quenched by addition of NAC. Reporter genes harbouring deletions of transcription elements from grp78 promoter demonstrated that controlling elements of ERSE1, ERSE2 and CRE are required in GA treatment. The critical ROS-dependent elements in grp78 promoter can be confined within ER stress responsive element (ERSE) region, since reporter constructs loss of ERSE elements that lost the susceptibility to be modulated by NAC after GA treatment. Hence, ER stress elements correlate well with ROS-mediated elements in grp78 promoter. Reporter construct loss of ERSE element retains the susceptibility by NAC after GA treatment, indicating that CRE element might represent a ROS-independent, GA-inductive element. Conclusively, we show that ROS is required for GA to launch the transactivation of grp78, and a firm link was established between the ROS signalling pathway to specific promoter elements-ERSE1 and ERSE2 elements in ER stress marker gene grp78 promoter.

Receptor activator of nuclear factor kappaB ligand plays a nonredundant role in doxorubicin-induced apoptosis

Doxorubicin induces apoptosis in a variety of cells. We investigated the expression and function of various tumor necrosis factor (TNF)alpha-homologues and their receptors. CEM cells did not differentially express any one of the TNFalpha-homologous receptors investigated nor TNF-related apoptosis-inducing ligand or TNF-related weakly apoptosis-inducing ligand (TWEAK) in the presence of doxorubicin. In addition to CD95 ligand, however, receptor activator of nuclear factor kappaB ligand (RANKL) was strongly up-regulated. Doxorubicin-induced apoptosis was greatly suppressed in the presence of either neutralizing antibody or RANK-Fc fusion protein. Moreover, neutralizing RANKL also prevented cytochrome c release from mitochondria. RANKL alone was unable to induce significant levels of apoptosis in CEM cells. However, doxorubicin-induced apoptosis was increased >2-fold when exogenous RANKL was added. Therefore, RANKL is necessary but not sufficient to account for early doxorubicin-induced apoptosis in CEM cells. This finding suggests improved chemotherapeutic efficiency of the anthracyclin against susceptible malignant cells in the presence with RANKL.