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.

Hydrogen sulfide protects against bleomycin-induced pulmonary fibrosis in rats by inhibiting NF-κB expression and regulating Th1/Th2 balance.

Hydrogen sulfide (H2S) displays vasodilative, anti-oxidative, anti-inflammatory and cytoprotective activities. The objective of this study was to evaluate the inhibitory effect of H2S on bleomycin (BLM)-induced pulmonary fibrosis in rats and its possible mechanisms. Fifty-four pathogen-free Male Wistar rats were randomly divided into three groups: control, BLM and H2S treated groups with 18 rats in each group. Each group was then divided into three subgroups based on time of study (7, 14 and 28 day). Pulmonary fibrosis model was established by a single intratracheal instillation of BLM A5 (5 mg/kg). While control rats received saline, rats of the treated group simultaneously were administered intraperitoneal injections of NaHS (the H2S donor, 28 µmol/kg) once daily. BLM induced pulmonary inflammation and fibrosis, increased lung hydroxyproline levels, lung index, total cell counts, neutrophils and eosinophils counts and expression of NF-κB p65 in lung tissue, decreased lymphocytes and macrophages counts. In addition, Th1 response is suppressed as shown by diminished IFN-γ in bronchoalveolar lavage fluid (BALF) after BLM exposure, and enhancement of Th2 response is marked by increased IL-4 in BALF. H2S administration significantly attenuated these effects. The findings reveal the therapeutic potential of H2S for BLM-induced pulmonary fibrosis in male rats, which were at least partly due to inhibition NF-κB p65 expression and regulation of Th1/Th2 balance.

Sodium ferulate protects against daunorubicin-induced cardiotoxicity by inhibition of mitochondrial apoptosis in juvenile rats.

Daunorubicin (DNR) is a widely used chemotherapeutic agent; however, its clinical use is limited because of its cardiotoxicity. This study was aimed to investigate the protective effect of sodium ferulate (SF), an effective component from traditional Chinese herbs, against DNR-induced cardiotoxicity in juvenile rats. DNR was administered intraperitoneally to rats at the dosage of 2.5 mg·kg(-1)·wk(-1) for 5 consecutive weeks (cumulative dose of 12.5 mg/kg) or in combination with intraperitoneal injection of SF at 50 mg·kg(-1)·d(-1) over a period of 30 days. The animals were killed 6 days after the last injection of DNR. SF significantly ameliorated the DNR-induced cardiac dysfunction, structural damage of the myocardium, and release of lactate dehydrogenase and creatine kinase. Treatment with SF also reversed DNR-induced oxidative stress as evidenced by a decrease in malondialdehyde levels with a concomitant increase in myocardical superoxide dismutase activities. Furthermore, SF afforded significant cardioprotection against DNR-induced apoptosis in vivo and effectively suppressed the complex mitochondrion-dependent apoptotic signaling triggered by DNR. This study indicates that SF may improve cardiac function by inhibition of oxidative stress and apoptosis, thus providing a beneficial effect on the prevention of DNR-induced cardiotoxicity.

Chronic alcohol ingestion primes the lung for bleomycin-induced fibrosis in mice.

BACKGROUND: Alcohol abuse increases the risk for acute lung injury (ALI). In both experimental models and in clinical studies, chronic alcohol ingestion causes airway oxidative stress and glutathione depletion and increases the expression of transforming growth factor beta-1 (TGFß1), a potent inducer of fibrosis, in the lung. Therefore, we hypothesized that alcohol ingestion could promote aberrant fibrosis following experimental ALI and that treatment with the glutathione precursor s-adenosylmethionine (SAMe) could mitigate these effects. METHODS: Three-month-old C57BL/6 mice were fed standard chow ± alcohol (20% v/v) in their drinking water for 8 weeks and ±SAMe (4% w/v) during the last 4 weeks. ALI was induced by intratracheal instillation of bleomycin (2.5 units/kg), and lungs were assessed histologically at 7 and 14 days for fibrosis and at 14 days for the expression of extracellular matrix proteins and TGFß1. RESULTS: Alcohol ingestion had no apparent effect on lung inflammation at 7 days, but at 14 days after bleomycin treatment, it increased lung tissue collagen deposition, hydroxyproline content, and the release of activated TGFß1 into the airway. In contrast, SAMe supplementation completely mitigated alcohol-induced priming of these aberrant fibrotic changes through decreased TGFß1 expression in the lung. In parallel, SAMe decreased alcohol-induced TGFß1 and Smad3 mRNA expressions by lung fibroblasts in vitro. CONCLUSIONS: These new experimental findings demonstrate that chronic alcohol ingestion renders the experimental mouse lung susceptible to fibrosis following bleomycin-induced ALI, and that these effects are likely driven by alcohol-mediated oxidative stress and its induction and activation of TGFß1.

Antioxidant, lipid lowering, and membrane stabilization effect of sesamol against doxorubicin-induced cardiomyopathy in experimental rats.

The present study was designed to evaluate the cardioprotective effect of sesamol against doxorubicin-induced cardiomyopathy in rats. In this study, the cardioprotective effect of sesamol against doxorubicin induced cardiomyopathy in experimental rats was evaluated at the dosage of 50 mg/kg bw. Doxorubicin was administered to rats at a total cumulative dose of 15 mg/kg through intraperitoneal route for 2 weeks in six-divided dose on 8th, 10th, 14th, 16th, 18th, and 21st day. After the last dose administration, the endogenous antioxidants and lipid peroxidation were estimated in heart tissue homogenate. Cardiac biomarkers such as troponin T, LDH, CK, and AST and lipid profiles such as cholesterol, triglycerides, HDL, LDL, and VLDL were estimated in serum. Sesamol has cardioprotective activity through normalization of doxorubicin-induced-altered biochemical parameters. Biochemical study was further supported by histopathological study, which shows that sesamol offered myocardial protection from necrotic damage. From these findings, it has been concluded that the sesamol has significant cardioprotection against doxorubicin induced cardiomyopathy via amelioration of oxidative stress, lipid lowering, and membrane stabilization effect.

Salidroside improves doxorubicin-induced cardiac dysfunction by suppression of excessive oxidative stress and cardiomyocyte apoptosis.

Doxorubicin (DOX) is a potent available antitumor drug; however, its clinical use is limited by the cardiotoxicity. Salidroside (SLD), with strong antioxidative and cytoprotective actions, is of particular interest in the development of antioxidative therapies for oxidative injury in cardiac diseases. Now, the protection and underlying mechanisms of SLD against DOX-induced cardiotoxicity are still unknown. In the present study, we revealed both antioxidative mechanism and Bcl2-dependent survival signaling involved in SLD's protection. We observed that DOX exposure induced mortality elevation, body weight loss, and cardiac dysfunction in mice, increased lactate dehydrogenase leakage and cardiomyocyte apoptosis, but decreased cell viability and size in cardiac tissues and cultured H9c2 cells, respectively, which were effectively antagonized by SLD supplement. We further observed that SLD significantly reduced the intercellular oxidative stress level, partly by inhibiting NOX1 expression and augmenting the expression and activities of the endogenous antioxidative enzymes, catalase, and manganese superoxide dismutase. In addition, SLD treatment upregulated the antiapoptotic Bcl2 and downregulated the proapoptotic Bax and inhibited a downstream pathway of Bcl2/Bax and caspase-3 activity. Our results indicated that SLD effectively protected the cardiomyocytes against DOX-induced cardiotoxicity by suppressing the excessive oxidative stress and activating a Bcl2-mediated survival signaling pathway.

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.

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.

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.

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.

Neuregulin-1 attenuates doxorubicin-induced autophagy in neonatal rat cardiomyocytes.

Recombinant human neuregulin-1 (rhNRG-1) improves cardiac function in animal models of doxorubicin (DOX)-induced cardiomyopathy, but the underlying mechanism remains largely unknown. Here, we confirm a role for rhNRG-1 in attenuating DOX-induced autophagy and define the signaling pathways through which it mediates some of its effects. Neonatal rat ventricular myocytes were subjected to different treatments both to induce autophagy and to determine the effects of rhNRG-1 on the process. The rhNRG-1 inhibited DOX-induced autophagy, reduced reactive oxygen species production and increased protein expression of Bcl-2, effects that were recapitulated when the cells were treated with the antioxidant N-acetylcysteine. These effects were blocked by the phosphatidylinositol 3-kinase inhibitor LY294002, pointing to the involvement of the Akt pathway in mediating the process. Inhibition of Bcl-2 expression with small interfering RNA silencing also inhibited rhNRG-1's ability to attenuate DOX-induced autophagy. The rhNRG-1 is a potent inhibitor of DOX-induced autophagy and multiple signaling pathways, including Akt and activation of reactive oxygen species, play important roles in the anti-autophagy effect. The rhNRG-1 is a novel drug that may be effectively therapeutically in protecting further damage in DOX-induced damaged myocardium.

FGF-2 and FGF-16 protect isolated perfused mouse hearts from acute doxorubicin-induced contractile dysfunction.

The anti-cancer drug doxorubicin is associated with an increased risk of cardiac damage and dysfunction, which can be acute as well as chronic. Fibroblast growth factor 2 (FGF-2) provides cardioprotection from ischemia-reperfusion injury but its effects on doxorubicin-induced damage are not known. We investigated the acute effects of doxorubicin administered in the absence and presence of FGF-2 pre-treatment, on isolated mouse perfused heart function over a period of 120 min. Doxorubicin elicited a significant decrease in left ventricular developed pressure (DP) at 30 min that persisted throughout the study. No effect on lactate dehydrogenase levels was detected in the perfusate, suggesting a lack of significant plasma membrane damage. FGF-2 pre-treatment lessened the deleterious effect of doxorubicin on DP significantly, and this beneficial effect of FGF-2 was blunted by protein kinase C inhibition with chelerythrine. Pre-treatment with a non-mitogenic FGF-2 mutant or FGF-16 also protected against a doxorubicin-induced decrease in DP. FGF-16 as well as FGF-2 pre-treatment elicited a small and transient negative inotropic effect. In conclusion, FGF-2 and FGF-16 increase resistance to acute doxorubicin-induced cardiac dysfunction, and protein kinase C activation is implicated in this response.

Preventive effects of ellagic acid against doxorubicin-induced cardio-toxicity in mice.

Preventive effects of ellagic acid against doxorubicin-induced cardiac oxidative, inflammatory and apoptotic stress were examined. This agent at 0.25, 0.5 or 1% was added in feed and supplied to mice for 8 weeks, and followed by doxorubicin treatment. Ellagic acid intake increased its deposit in heart. Pre-intake of this compound at 0.5 and 1% significantly attenuated doxorubicin caused increase in plasma creatine phosphokinase activity. Doxorubicin treatment decreased glutathione content, increased reactive oxygen species (ROS), malonyldialdehyde (MDA), interleukin (IL)-6, IL-10, monocyte chemoattractant protein-1 and tumor necrosis factor-alpha levels, declined glutathione peroxidase (GPX) and superoxide dismutase (SOD) activities, and enhanced xanthine oxidases (XO) activity in heart. Ellagic acid intake dose-dependently reserved glutathione content, lowered ROS and MDA levels, and reduced XO activity. This compound at 0.5 and 1% retained GPX and SOD activities, and decreased cytokines in heart. Doxorubicin treatment raised cardiac activity and protein production of caspase-3, nuclear factor kappa B (NF-κB) p50 and p65. Ellagic acid dose-dependently lowered caspase-3 activity and cleaved caspase-3 formation, and at 0.5 and 1% declined activity and protein level of NF-κB. Doxorubicin treatment also up-regulated cardiac expression of p-p38, p-ERK 1/2 and p-JNK, and ellagic acid at 0.5 and 1% suppressed p-p38 expression and at 1% down-regulated p-ERK 1/2 expression. These findings suggest that ellagic acid is a potent cardiac protective agent against doxorubicin.

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.

Antioxidant and anti-apoptotic effects of onion (Allium cepa) extract on doxorubicin-induced cardiotoxicity in rats.

The aim of this study was to investigate the antioxidant and anti-apoptotic effects of onion (Allium cepa) extracts (ACE) on doxorubicin (DOX)-induced cardiotoxicity. The rats in the ACE-pretreated group were given a daily dose of 1 ml ACE for 14 days. To induce cardiotoxicity, DOX (30 mg kg(-1) body weight) was injected intraperitoneally by a single dose and the rats were sacrificed after 48 h. To date, no such studies have been performed on the cardioprotective and anti-apoptotic potential of ACE on DOX-induced cardiotoxicity. Our data indicate a significant reduction in the activity of in situ identification of apoptosis using terminal dUTP nick end-labeling in cardiomyocytes of the DOX-treated group with ACE therapy. The DOX-treated with ACE groups showed a significant decrease in malondialdehyde levels, and increased activities of superoxide dismutase, glutathione and glutathione peroxidase in comparison with the DOX-treated group. Creatine kinase, creatine kinase MB, lactate dehydrogenase activities and cardiac troponin I levels were significantly decreased in the DOX + ACE group in comparison with the DOX group. These biochemical and histological disturbances were effectively attenuated on pretreatment with ACE. The present study showed that ACE may be a suitable cardioprotector against toxic effects of DOX.

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.

Inhibition of doxorubicin-induced autophagy in hepatocellular carcinoma Hep3B cells by sorafenib--the role of extracellular signal-regulated kinase counteraction.

A multikinase inhibitor of the Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway, sorafenib, is increasingly being used in the management of hepatocellular carcinoma, and its combination with conventional chemotherapeutics has stimulated particular interest. Although the combination of sorafenib with doxorubicin (DOX) is presently being investigated in a phase III randomized trial, little is known about the molecular mechanisms of their interaction. Because DOX causes cell death through upregulation of the MEK/ERK pathway, and sorafenib has an opposite influence on the same cascade, we hypothesized that co-treatment with these drugs may lead to an antagonistic effect. DOX treatment arrested proliferation and induced autophagic cell death in Hep3B cells, whereas apoptotic changes were not conspicuous. Sorafenib alone affected viability and caused massive mitochondrial degradation. However, when added together with DOX, sorafenib facilitated cell cycle progression, increased survival, and reduced autophagy. To evaluate the molecular mechanisms of this phenomenon, we examined the expression of ERK1/2, protein kinase B (Akt), and cyclin D1, as well as the members of Bcl-2 family. ERK1/2 activation induced by DOX was suppressed by sorafenib. Similarly, ERK targeting with the selective inhibitor U0126 impaired DOX-induced toxicity. Treatment with sorafenib, either alone or in combination with DOX, resulted in Akt activation. The role of sorafenib-induced degradation of cyclin D1 in the suppression of DOX efficiency is discussed. In conclusion, MEK/ERK counteraction, stimulation of survival via Akt and dysregulation of cyclin D1 could contribute to the escape from DOX-induced autophagy and thus promote cancer cell survival. The use of MEK/ERK inhibitors in combination with chemotherapeutics, intended to enhance anticancer efficacy, requires the consideration of possible antagonistic effects.

Protection from doxorubicin-induced cardiomyopathy using the modified anthracycline N-benzyladriamycin-14-valerate (AD 198).

The anthracycline doxorubicin (Dox) is an effective antitumor agent. However, its use is limited because of its toxicity in the heart. N-Benzyladriamycin-14-valerate (AD 198) is a modified anthracycline with antitumor efficacy similar to that of Dox, but with significantly less cardiotoxicity and potentially cardioprotective elements. In the present study, we investigated the possibility of in vivo protective effects of low-dose AD 198 against Dox-induced cardiomyopathy. To do this, rats were divided into four groups: vehicle, Dox (20 mg/kg; single injection day 1), AD 198 (0.3 mg/kg per injection; injections on days 1, 2, and 3), or a combination treatment of Dox + AD 198. Seventy-two hours after beginning treatment, hearts from the Dox group had decreased phosphorylation of AMP kinase and troponin I and reduced poly(ADP-ribose) polymerase, ß-tubulin, and serum albumin expression. Dox also increased the phosphorylation of phospholamban and expression of inducible nitric-oxide synthase in hearts. Each of these Dox-induced molecular changes was attenuated in the Dox + AD 198 group. In addition, excised hearts from rats treated with Dox had a 25% decrease in left ventricular developed pressure (LVDP) and a higher than normal increase in LVDP when perfused with a high extracellular Ca(2+) solution. The Dox-induced decrease in baseline LVDP and hyper-responsiveness to [Ca(2+)] was not observed in hearts from the Dox + AD 198 group. Thus Dox, with well established and efficient antitumor protocols, in combination with low levels of AD 198, to counter anthracycline cardiotoxicity, may be a promising next step in chemotherapy.

Reversal of TNP-470-induced endothelial cell growth arrest by guanine and guanine nucleosides.

The mechanism of action of TNP-470 [O-(chloroacetyl-carbamoyl) fumagillol], which potently and selectively inhibits the proliferation of endothelial cells, is incompletely understood. Previous studies have established its binding protein and the most distal effector of its growth arrest activity as methionine aminopeptidase 2 (MetAP-2) and p21(WAF1/CIP1), respectively. However, the mechanistic steps between these two effectors have not been identified. We have found that addition of exogenous guanine and guanine-containing nucleosides to culture medium will completely reverse the cytostatic effect of TNP-470 on both cultured bovine aortic and mouse pulmonary endothelial cells. Western blotting showed that supplementation with exogenous guanosine reverses the induction of p21(WAF1/CIP1) by TNP-470. This "rescue" by guanine/guanosine was abolished when the guanine salvage pathway of nucleotide biosynthesis was inhibited with Immucillin H, suggesting that TNP-470 might reduce de novo guanine synthesis in endothelial cells. However, an analysis of inosine 5'-monophosphate dehydrogenase, the rate-limiting enzyme in de novo guanine synthesis and target of the antiangiogenic drug mycophenolic acid, showed no TNP-470-induced changes. Curiously, quantitation of cellular nucleotides confirmed that GTP levels were not reduced after TNP-470 treatment. Addition of guanosine at the start of G(1) phase causes a doubling in GTP levels that persists to the G(1)/S phase transition, where commitment to TNP-470 growth arrest occurs. Thus, guanine rescue involves an augmentation of cellular GTP beyond physiological levels rather than a restoration of a drug-induced GTP deficit. Determining the mechanism whereby this causes restoration of endothelial cell proliferation is an ongoing investigation.

Long-acting phosphodiesterase-5 inhibitor tadalafil attenuates doxorubicin-induced cardiomyopathy without interfering with chemotherapeutic effect.

Doxorubicin (DOX) is one of the most effective anticancer drugs. However, its cardiotoxicity remains a clinical concern that severely restricts its therapeutic usage. We designed this study to investigate whether tadalafil, a long-acting phosphodiesterase-5 (PDE-5) inhibitor, protects against DOX-induced cardiotoxicity. We also sought to delineate the cellular and molecular mechanisms underlying tadalafil-induced cardioprotection. Male CF-1 outbred mice were randomized into three groups (n = 15-24/group) to receive either saline (0.2 ml i.p.), DOX (15 mg/kg, given by a single intraperitoneal injection), or tadalafil (4 mg/kg p.o. daily for 9 days) plus DOX. Left ventricular function was subsequently assessed by transthoracic echocardiography and Millar conductance catheter. Cardiac contractile function was impaired by DOX, and it was significantly improved by cotreatment with tadalafil. Tadalafil attenuated DOX-induced apoptosis and depletion of prosurvival proteins, including Bcl-2 and GATA-4, in myocardium. Cardiac oxidative stress was attenuated and antioxidant capacity was enhanced by tadalafil possibly via up-regulation of mitochondrial superoxide dismutase (MnSOD). Moreover, the tadalafil-treated group demonstrated increased cardiac cGMP level and protein kinase G (PKG) activity. Tadalafil did not interfere with the efficacy of DOX in killing human osteosarcoma cells in vitro or its antitumor effect in vivo in tumor xenograft model. We conclude that tadalafil improved left ventricular function and prevented cardiomyocyte apoptosis in DOX-induced cardiomyopathy through mechanisms involving up-regulation of cGMP, PKG activity, and MnSOD level without interfering with the chemotherapeutic benefits of DOX.