Renoprotective mechanisms of Astragaloside IV in cisplatin-induced acute kidney injury

Nephrotoxicity remains a serious adverse effect of cisplatin chemotherapy, limiting its clinical usage. Numerous studies show that oxidative stress and inflammation are closely associated with cisplatin-induced renal damage. Astragaloside IV (AS-IV) has been found to possess antioxidant and anti-inflammation functions. Therefore, we investigated the potential curative effects of AS-IV against cisplatin-induced renal injury and the possible cellular mechanism for activity, both in vitro and in vivo. We found that pretreatment of HK-2 cells with AS-IV could mitigate cisplatin-induced cell damage caused by oxygen-free radicals and the inflammatory response, as evidenced by reduced formation of reactive oxygen species (ROS) and inflammatory cytokines. AS-IV improved cisplatin-induced renal dysfunction and histopathological injury in mice. Additionally, AS-IV enhanced the activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT). It also inhibited cisplatin-induced overproduction of kidney injury molecule-1 (KIM-1), malondialdehyde (MDA), tumour necrosis factor-α (TNF???α), and interleukin-1β (IL-1β) in kidney tissues. We found that the protective effects of AS-IV occurred via activation of the nuclear factor-erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) proteins and inhibition of nuclear factor-κappaB (NF-κB) activation. Further, small interfering RNA (siRNA) knockdown of Nrf2 abrogated the protective effects of AS-IV against cisplatin-induced oxidative stress and blocked the inhibitory effects of AS-IV on cisplatin-induced NF-κB activation and inflammatory cytokine production. In conclusion, our data suggested that AS-IV attenuated cisplatin-mediated renal injury, and these protective effects might be due to inhibition of both oxidative damage and inflammatory response via activation of Nrf2 system and suppression of NF-κB activation.     

Gambogenic acid induces Noxa-mediated apoptosis in colorectal cancer through ROS-dependent activation of IRE1α/JNK

BackgroundGambogenic acid (GNA), an active component of Garcinia hanburyi Hook.f. (Clusiaceae) (common name gamboge), exerts anti-inflammatory and antitumor properties. However, the underlying mechanism of GNA in colorectal cancer (CRC) is still not well understood.PurposeThis study aimed to investigate the antitumor effects and mechanisms of GNA on CRC in vitro and in vivo.MethodsCell viability, colony formation and cell apoptosis assays were performed to determine the antitumor effects of GNA. qRT-PCR and Western blotting were performed to evaluate the expression of genes or proteins affected by GNA in vitro and in vivo. HCT116 colon cancer xenografts and the APC^min/+ mice model were used to confirm the antitumor effects of GNA on CRC in vivo.ResultsGNA induced Noxa-mediated apoptosis by inducing reactive oxygen species (ROS) generation and c-Jun N-terminal kinase (JNK) activation. Moreover, GNA triggered endoplasmic reticulum (ER) stress, which subsequently activated inositol-requiring enzyme-1α (IRE1α) leading to JNK phosphorylation. ROS scavenger attenuated GNA-induced IRE1α activation and JNK phosphorylation. Knockdown of IRE1α also prevented GNA-induced JNK phosphorylation. In vivo, GNA suppressed tumor growth and progression in HCT116 colon cancer xenografts and the APC^min/+ mices model.ConclusionThese findings revealed that GNA induced Noxa-mediated apoptosis by activating the ROS/IRE1α/JNK signaling pathway in CRC both in vitro and in vivo. GNA is therefore a promising antitumor agent for CRC treatment.     

The Protecting Effect of Deoxyschisandrin and Schisandrin B on HaCaT Cells against UVB-Induced Damage

Schisandra chinensis is a traditional Chinese medicine that has multiple biological activities, including antioxidant, anticancer, tonic, and anti-aging effects. Deoxyschisandrin (SA) and schisandrin B (SB), the two major lignans isolated from S. chinensis, exert high antioxidant activities in vitro and in vivo by scavenging free radicals, such as reactive oxygen species (ROS). Ultraviolet B-ray (UVB) radiation induces the production of ROS and DNA damage, which eventually leads to cell death by apoptosis. However, it is unknown whether SA or SB protects cells against UVB-induced cellular DNA damage. Our study showed that both SA and SB effectively protected HaCaT cells from UVB-induced cell death by antagonizing UVB-mediated production of ROS and induction of DNA damage. Our results showed that both SA and SB significantly prevented UVB-induced loss of cell viability using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assays. Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assays showed that the production of ROS following UVB exposure was inhibited by treatment with SA and SB. Moreover, SA and SB decreased the UVB-induced DNA damage in HaCaT cells by comet assays. In addition, SA and SB also prevented UVB-induced cell apoptosis and the cleavage of caspase-3, caspase-8 and caspase-9. In a word, our results imply that the antioxidants SA and SB could protect cells from UVB-induced cell damage via scavenging ROS.     

Ginsenoside F2 induces apoptosis in humor gastric carcinoma cells through reactive oxygen species-mitochondria pathway and modulation of ASK-1/JNK signaling cascade in vitro and in vivo

Ginsenoside F₂ (F₂) is a potential bioactive metabolite of major ginsenosides. The potential anti-cancer effect of F₂ in gastric cancer cells has not been appraised. This study investigated the effects of F₂ on the production of reactive oxygen species (ROS). We also investigated the in vitro and in vivo effects of F₂ on the downstream signaling pathways leading to apoptosis in human gastric cancer cells. The in vitro data revealed that F₂ induces ROS accumulation followed by a decrease in mitochondrial transmembrane potential (MTP), and the release of cytochrome c (cyto c), which induced the caspase-dependent apoptosis. Further assay indicated that modulation of ASK-1/JNK pathway contributes to apoptosis. In vivo, F₂ exhibits the obvious anti-cancer effect compared with cisplatin with no obvious toxicity. Jointly, these results suggest that F₂ induces apoptosis by causing an accumulation of ROS and activating the ASK-1/JNK signaling pathway. This provides further support for the use of F₂ as a novel anticancer therapeutic candidate.     

Suppression of basal autophagy reduces lung cancer cell proliferation and enhances caspase-dependent and -independent apoptosis by stimulating ROS formation

Autophagy is a catabolic process involved in the turnover of organelles and macromolecules which, depending on conditions, may lead to cell death or preserve cell survival. We found that some lung cancer cell lines and tumor samples are characterized by increased levels of lipidated LC3. Inhibition of autophagy sensitized non-small cell lung carcinoma (NSCLC) cells to cisplatin-induced apoptosis; however, such response was attenuated in cells treated with etoposide. Inhibition of autophagy stimulated ROS formation and treatment with cisplatin had a synergistic effect on ROS accumulation. Using genetically encoded hydrogen peroxide probes directed to intracellular compartments we found that autophagy inhibition facilitated formation of hydrogen peroxide in the cytosol and mitochondria of cisplatin-treated cells. The enhancement of cell death under conditions of inhibited autophagy was partially dependent on caspases, however, antioxidant NAC or hydroxyl radical scavengers, but not the scavengers of superoxide or a MnSOD mimetic, reduced the release of cytochrome c and abolished the sensitization of the cells to cisplatin-induced apoptosis. Such inhibition of ROS prevented the processing and release of AIF (apoptosis-inducing factor) and HTRA2 from mitochondria. Furthermore, suppression of autophagy in NSCLC cells with active basal autophagy reduced their proliferation without significant effect on the cell-cycle distribution. Inhibition of cell proliferation delayed accumulation of cells in the S phase upon treatment with etoposide that could attenuate the execution stage of etoposide-induced apoptosis. These findings suggest that autophagy suppression leads to inhibition of NSCLC cell proliferation and sensitizes them to cisplatin-induced caspase-dependent and -independent apoptosis by stimulation of ROS formation.     

Apelin-13 attenuates cisplatin-induced cardiotoxicity through inhibition of ROS-mediated DNA damage and regulation of MAPKs and AKT pathways

Platinum-based chemotherapy represents one of the most effective ways in combating human cancers. However, the cardiotoxicity subsequent severely limited its clinical application. Increased evidences indicate that oxidative stress plays a crucial role in the pathological process of platinum-induced cardiotoxicity. It is reported that apelin-13 a bioactive peptide has the scavenging capacity of free radical, and it has the potential to regulate the cardiovascular system. Hence, the potential of apelin-13 to antagonize cisplatin-induced cardiotoxicity was evaluated in H9c2 rat myocardial cells in vitro and in C57 mice in vivo. The results showed that cisplatin indeed caused DNA damage in H9c2 cells by promoting the accumulation of intracellular reactive oxygen species (ROS) and superoxide anion, which led to cell apoptosis and resulted in overt cardiotoxicity. However, apelin-13 pre-treatment effectively attenuated the cisplatin-induced ROS and superoxide anion generation, inhibited DNA damage, and suppressed the PARP cleavage and caspases activation. Further investigation revealed that apelin-13 blocked cisplatin-induced H9c2 cells apoptosis involving the regulation of MAPKs and PI3K/Akt signaling pathway. Importantly, apelin-13 co-treatment also significantly attenuated cisplatin-induced cardiotoxicity in vivo by inhibiting myocardial cells apoptosis and improving angiogenesis in mice heart. Taken together, our results suggest that the use of apelin-13 may be an effective strategy for antagonizing the cardiotoxicity-induced by platinum-based chemotherapy.     

The Antioxidant and Antigenotoxic Effects of Pycnogenol<Superscript>®</Superscript> on Rats Treated With Cisplatin

Oxidative stress and inflammation are implicated in the pathogenesis of cisplatin-induced toxicity. Pycnogenol® is known for its strong antioxidant and anti-inflammatory effects. In this study, the possible protective effects of pycnogenol on kidney, bone marrow, and red blood cells in rats treated with cisplatin were investigated. The rats were divided into four groups. Group 1 was the control and groups 2, 3, and 4 were orally treated with pycnogenol (200 mg/kg bw, o.p) for 5 days, treated with cisplatin (7 mg/kg bw, i.p.) on the fifth day and treated with cisplatin plus pycnogenol, respectively. Antioxidative parameters in kidney and red blood cells were measured. Chromosome anomalies in bone marrow and renal histopathology were also investigated. Activities of pro-oxidant enzymes (myeloperoxidase and xanthine oxidase), malondialdehyde, and nitric oxide levels significantly increased but antioxidant enzymes activities decreased in the kidneys and red blood cells after cisplatin treatment. Pycnogenol treatment prior to the administration of cisplatin significantly decreased cisplatin-induced injury, as evidenced by its normalizing these parameters. Chromosomal aberrations decreased and mitotic index frequencies increased in bone marrow treated with cisplatin plus pycnogenol. These findings suggest that pycnogenol may be a useful protective agent against the toxicity associated with cisplatin therapy.     

Protection against cisplatin-induced nephrotoxicity by Cu(II)2(3,5-diisopropylsalicylate)4

The ability of Cu(II)(2)(3,5-diisopropylsalicylate)(4), CuDIPS, which exhibits superoxide dismutase (SOD)-like activity, to prevent cisplatin-induced nephrotoxicity was examined in rats. Rats were divided into four groups and treated as follows: (i) vehicle control; (ii) cisplatin (16 mg/kg, intraperitoneally); (iii) CuDIPS (10 mg/kg, intraperitoneally); and (iv) cisplatin plus CuDIPS. Rats were sacrificed 3 days post-treatment. Cisplatin alone resulted in significantly increased plasma creatinine and urea. Administration of 10 mg/kg CuDIPS prevented the cisplatin-induced elevation of plasma creatinine and urea and protected against kidney damage. Relative to controls, rats that received cisplatin treatment displayed a decrease of reduced glutathione (GSH) and elevated platinum and thiobarbituric acid reactive substances (TBARS) levels in the kidney. In comparison with controls, activities of antioxidant enzymes (SOD, CAT, GSH-Px and GSH-Rd) were also reduced in the kidney of rats treated with cisplatin. Administration of 10 mg/kg CuDIPS prevented cisplatin-induced alterations in renal platinum, GSH, TBARS, and antioxidant enzyme activities. This study suggests that the protection offered by CuDIPS against cisplatin-induced nephrotoxicity is partly related to maintenance of renal antioxidant systems.     

Carvedilol protects against cisplatin-induced oxidative stress, redox state unbalance and apoptosis in rat kidney mitochondria

Cisplatin is a highly effective chemotherapeutic agent which causes severe nephrotoxicity. Studies have suggested that reactive oxygen species, mainly generated in mitochondria, play a central role in cisplatin-induced renal damage. A wide range of antioxidants have been evaluated as possible protective agents against cisplatin-induced nephrotoxicity; however a safe and efficacious compound has not yet been found. The present study is the first to evaluate the protective potential of carvedilol, a beta-blocker with strong antioxidant properties, against the mitochondrial oxidative stress and apoptosis in kidney of rats treated with cisplatin. The following cisplatin-induced toxic effects were prevented by carvedilol: increased plasmatic levels of creatinine and blood urea nitrogen (BUN); lipid peroxidation, oxidation of cardiolipin; oxidation of protein sulfhydryls; depletion of the non-enzymatic antioxidant defense and increased activity of caspase-3. Carvedilol per se did not present any effect on renal mitochondria. It was concluded that carvedilol prevents mitochondrial dysfunction and renal cell death through the protection against the oxidative stress and redox state unbalance induced by cisplatin. The association of carvedilol to cisplatin chemotherapy was suggested as a possible strategy to minimize the nephrotoxicity induced by this antitumor agent.     

Role of CFTR in oxidative stress and suicidal death of renal cells during cisplatin-induced nephrotoxicity

The clinical use of the antineoplastic drug cisplatin is limited by its deleterious nephrotoxic side effect. Cisplatin-induced nephrotoxicity is associated with an increase in oxidative stress, leading ultimately to renal cell death and irreversible kidney dysfunction. Oxidative stress could be modified by the cystic fibrosis transmembrane conductance regulator protein (CFTR), a Cl⁻ channel not only involved in chloride secretion but as well in glutathione (GSH) transport. Thus, we tested whether the inhibition of CFTR could protect against cisplatin-induced nephrotoxicity. Using a renal proximal cell line, we show that the specific inhibitor of CFTR, CFTR_inh-172, prevents cisplatin-induced cell death and apoptosis by modulating the intracellular reactive oxygen species balance and the intracellular GSH concentration. This CFTR_inh-172-mediated protective effect occurs without affecting cellular cisplatin uptake or the formation of platinum-DNA adducts. The protective effect of CFTR_inh-172 in cisplatin-induced nephrotoxicity was also investigated in a rat model. Five days after receiving a single cisplatin injection (5 mg/kg), rats exhibited renal failure, as evidenced by the alteration of biochemical and functional parameters. Pretreatment of rats with CFTR_inh-172 (1 mg/kg) prior to cisplatin injection significantly prevented these deleterious cisplatin-induced nephrotoxic effects. Finally, we demonstrate that CFTR_inh-172 does not impair cisplatin-induced cell death in the cisplatin-sensitive A549 cancer cell line. In conclusion, the use of a specific inhibitor of CFTR may represent a novel therapeutic approach in the prevention of nephrotoxic side effects during cisplatin treatment without affecting its antitumor efficacy.     

NADPH oxidase subunit 4-mediated reactive oxygen species contribute to cycling hypoxia-promoted tumor progression in glioblastoma multiforme

Background

Cycling and chronic tumor hypoxia are involved in tumor development and growth. However, the impact of cycling hypoxia and its molecular mechanism on glioblastoma multiforme (GBM) progression remain unclear.

Methodology

Glioblastoma cell lines, GBM8401 and U87, and their xenografts were exposed to cycling hypoxic stress in vitro and in vivo. Reactive oxygen species (ROS) production in glioblastoma cells and xenografts was assayed by in vitro ROS analysis and in vivo molecular imaging studies. NADPH oxidase subunit 4 (Nox4) RNAi-knockdown technology was utilized to study the role of Nox4 in cycling hypoxia-mediated ROS production and tumor progression. Furthermore, glioblastoma cells were stably transfected with a retroviral vector bearing a dual reporter gene cassette that allowed for dynamic monitoring of HIF-1 signal transduction and tumor cell growth in vitro and in vivo, using optical and nuclear imaging. Tempol, an antioxidant compound, was used to investigate the impact of ROS on cycling hypoxia-mediated HIF-1 activation and tumor progression.

Principal Findings

Glioblastoma cells and xenografts were compared under cycling hypoxic and normoxic conditions; upregulation of NOX4 expression and ROS levels were observed under cycling hypoxia in glioblastoma cells and xenografts, concomitant with increased tumor cell growth in vitro and in vivo. However, knockdown of Nox4 inhibited these effects. Moreover, in vivo molecular imaging studies demonstrated that Tempol is a good antioxidant compound for inhibiting cycling hypoxia-mediated ROS production, HIF-1 activation, and tumor growth. Immunofluorescence imaging and flow cytometric analysis for NOX4, HIF-1 activation, and Hoechst 3342 in glioblastoma also revealed high localized NOX4 expression predominantly in potentially cycling hypoxic areas with HIF-1 activation and blood perfusion within the endogenous solid tumor microenvironment.

Conclusions

Cycling hypoxia-induced ROS via Nox4 is a critical aspect of cancer biology to consider for therapeutic targeting of cycling hypoxia-promoted HIF-1 activation and tumor progression in GBM.     

20(S)-Ginsenoside Rh1 inhibits cisplatin-induced hearing loss by inhibiting the MAPK signaling pathway and suppressing apoptosis in vitro

As an anticancer drug, cisplatin is widely used, but its clinical application is restricted due to its severe side effects of ototoxicity. Therefore, this study was dedicated to assessing the benefit of ginsenoside extract, 20(S)-Ginsenoside Rh1 (Rh1), on cisplatin-induced ototoxicity. HEI-OC1 cells and neonatal cochlear explants were cultured. Cleaved caspase-3, TUNEL, and MitoSOX Red were observed in vitro by immunofluorescence staining. CCK8 and LDH cytotoxicity assays were detected to measure cell viability and cytotoxicity. Our results showed that Rh1 significantly increased cell viability, reduced cytotoxicity, and alleviated cisplatin-induced apoptosis. In addition, Rh1 pretreatment decreased the excessive accumulation of intracellular reactive oxygen species. Mechanistic studies indicated that Rh1 pretreatment reversed the increase of apoptotic protein expression, accumulation of mitochondrial ROS, and activation of the MAPK signaling pathway. These results suggested that Rh1 can act as an antioxidant and anti-apoptotic agent against cisplatin-induced hearing loss by suppressing the excessive accumulation of mitochondrial ROS, activation of MAPK signaling pathway and apoptosis.     

Suppression of basal autophagy reduces lung cancer cell proliferation and enhances caspase-dependent and -independent apoptosis by stimulating ROS formation

Autophagy is a catabolic process involved in the turnover of organelles and macromolecules which, depending on conditions, may lead to cell death or preserve cell survival. We found that some lung cancer cell lines and tumor samples are characterized by increased levels of lipidated LC3. Inhibition of autophagy sensitized non-small cell lung carcinoma (NSCLC) cells to cisplatin-induced apoptosis; however, such response was attenuated in cells treated with etoposide. Inhibition of autophagy stimulated ROS formation and treatment with cisplatin had a synergistic effect on ROS accumulation. Using genetically encoded hydrogen peroxide probes directed to intracellular compartments we found that autophagy inhibition facilitated formation of hydrogen peroxide in the cytosol and mitochondria of cisplatin-treated cells. The enhancement of cell death under conditions of inhibited autophagy was partially dependent on caspases, however, antioxidant NAC or hydroxyl radical scavengers, but not the scavengers of superoxide or a MnSOD mimetic, reduced the release of cytochrome c and abolished the sensitization of the cells to cisplatin-induced apoptosis. Such inhibition of ROS prevented the processing and release of AIF (apoptosis-inducing factor) and HTRA2 from mitochondria. Furthermore, suppression of autophagy in NSCLC cells with active basal autophagy reduced their proliferation without significant effect on the cell-cycle distribution. Inhibition of cell proliferation delayed accumulation of cells in the S phase upon treatment with etoposide that could attenuate the execution stage of etoposide-induced apoptosis. These findings suggest that autophagy suppression leads to inhibition of NSCLC cell proliferation and sensitizes them to cisplatin-induced caspase-dependent and -independent apoptosis by stimulation of ROS formation.     

Niazirin from Moringa oleifera Lam. attenuates high glucose-induced oxidative stress through PKCζ/Nox4 pathway

BackgroundDiabetic complications-coronary atherosclerosis is closely related to the increased reactive oxygen species (ROS) induced by hyperglycemia. ROS are reported to induce the abnormal proliferation of vascular smooth muscle cells (VSMCs) under high glucose conditions. Leaf and seed extracts from Moringa oleifera are found to exhibit antioxidant activity. However, few studies are evaluating the antioxidant activities of chemical compounds isolated from the M. oleifera especially in cardiovascular field.PurposeThe aim of this study is to explore the antioxidative effect during hyperglycemia of niazirin from M. oleifera.Study designA cell model was applied.MethodsAfter the taking the in vitro antioxidant experiment including ferric reducing antioxidant power (FRAP), 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Cell viability was carried out using high glucose-induced VSMCs model. ROS production was tested by 2′,7′-dichlorofluorescein diacetate (DCF-DA) assay. The protein kinase C zeta (PKCζ) and NADPH oxidase 4 (Nox 4) expression in vitro and in vivo were measured by western blot analysis.ResultsNiazirin showed good free radical scavenging activity. Niazirin significantly attenuated the proliferation of high glucose-induced VSMCs. Furthermore, it could decrease the ROS and malondialdehyde (MDA) productions, while increased total antioxidant capacity (T-AOC), superoxide dismutase (SOD) as well as glutathione peroxidase (GPx) levels in high glucose-induced VSMCs and streptozotocin-induced mice. In addition, niazirin could eliminate the high glucose-induced PKCζ activation, indicated by Thr410 phosphorylation and inhibition of the Nox4 protein expression in vitro and in vivo.ConclusionNiazirin from M. oleifera exhibited notably antioxidant activities and could be utilized as a potential natural antioxidant in preventing diabetic atherosclerosis.     

Inhibition of protein phosphatase 2A with the small molecule LB100 overcomes cell cycle arrest in osteosarcoma after cisplatin treatment

Osteosarcoma is the most common primary malignant bone tumor and affects a significant portion of pediatric oncology patients. Although surgery and adjuvant chemotherapy confer significant survival benefits, many patients go on to develop metastatic disease, particularly to the lungs, secondary to development of drug resistance. Inhibition of protein phosphatase 2A with the small molecule, LB100, has demonstrated potent chemo- and radio-sensitizing properties in numerous pre-clinical tumor models. In this study, we showed that LB100 overcame DNA repair mechanisms in osteosarcoma cells treated with cisplatin, in vitro, and recapitulated these findings in an in vivo xenograft model. Notably, the addition of LB100 to cisplatin prevented development of pulmonary metastases in the majority of treated animals. Our data indicated the mechanism of chemo-sensitization by LB100 involved abrogation of the ATM/ATR-activated DNA damage response, leading to hyperphosphorylation of Chk proteins and persistent cyclin activity. In addition, LB100 exposure suppressed Akt signaling, leading to Mdm2-mediated proteasomal degradation of functional p53. Taken together, LB100 prevented repair of cisplatin-induced DNA damage, resulting in mitotic catastrophe and cell death.     

Growth inhibition and pro-apoptotic activity of violacein in Ehrlich ascites tumor

The continuing threat to biodiversity lends urgency to the need of identification of sustainable source of natural products. This is not so much trouble if there is a microbial source of the compound. Herein, violacein, a natural indolic pigment extracted from Chromobacterium violaceum, was evaluated for its antitumoral potential against the Ehrlich ascites tumor (EAT) in vivo and in vitro. Evaluation of violacein cytotoxicity using different endpoints indicated that EAT cells were twofold (IC₅₀ = 5.0 μM) more sensitive to the compound than normal human peripheral blood lymphocytes. In vitro studies indicated that violacein cytotoxicity to EAT cells is mediated by a rapid (8–12 h) production of reactive oxygen species (ROS) and a decrease in intracellular GSH levels, probably due to oxidative stress. Additionally, apoptosis was primarily induced, as demonstrated by an increase in Annexin-V positive cells, concurrently with increased levels of DNA fragmentation and increased caspase-2, caspase-9 and caspase-3 activities up to 4.5-, 6.0- and 5.5-fold, respectively, after 72 h of treatment. Moreover, doses of 0.1 and 1.0 μg kg^?1 violacein, administered intraperitoneally (i.p.) to EAT-bearing mice throughout the lifespan of the animals significantly inhibited tumor growth and increased survival of mice. In view of these results, a 35-day toxicity study was conducted in vivo. Complete hematology, biochemistry (ALT, AST and creatinine levels) and histopathological analysis of liver and kidney indicated that daily doses of violacein up to 1000 μg kg^?1 for 35 days are well tolerated and did not cause hematotoxicity nor renal or hepatotoxicity when administered i.p. to mice. Altogether, these results indicate that violacein causes oxidative stress and an imbalance in the antioxidant defense machinery of cells culminating in apoptotic cell death. Furthermore, this is the first report of its antitumor activity in vivo, which occurs in the absence of toxicity to major organs.     

Hybrids of arenobufagin and benzoisoselenazol reducing the cardiotoxicity of arenobufagin

Arenobufagin is a naturally occurring bufadienolide showing promising antitumor activity accompanied however with apparent cardiac toxicity. Following the recent discovery that oxidative damage possibly be an important cause of the cardiac toxicity of cardenolides, a strategy fusing the antitumor agent arenobufagin with a benzoisoselenazol fragment, a reactive oxygen species (ROS) scavenger, has been developed. Six novel hybrids were synthesized and their ROS scavenging activities as well as their in vitro cytotoxicity against the human hepatocellular carcinoma cell line HepG2, an adriamycin-resistant subline HepG2/ADM, and the human myocardial cell line AC16 were evaluated. The results indicate that the hybrids exhibit various degrees of in vitro ROS scavenging activities, and weaker cytotoxicity than that of arenobufagin against the myocardial cell line AC16. These findings suggest the feasibility of a strategy in which the cardiotoxicity of the potential antitumor agent arenobufagin is reduced.