Modeling the metabolism of idarubicin to idarubicinol in rat heart: effect of rutin and phenobarbital

Natural Products Counteracting Cardiotoxicity during Cancer Chemotherapy: The Special Case of Doxorubicin, a Comprehensive Review

Cardiotoxicity is a frequent undesirable phenomenon observed during oncological treatment that limits the therapeutic dose of antitumor drugs and thus may decrease the effectiveness of cancer eradication. Almost all antitumor drugs exhibit toxic properties towards cardiac muscle. One of the underlying causes of cardiotoxicity is the stimulation of oxidative stress by chemotherapy. This suggests that an appropriately designed diet or dietary supplements based on edible plants rich in antioxidants could decrease the toxicity of antitumor drugs and diminish the risk of cardiac failure. This comprehensive review compares the cardioprotective efficacy of edible plant extracts and foodborne phytochemicals whose beneficial activity was demonstrated in various models in vivo and in vitro. The studies selected for this review concentrated on a therapy frequently applied in cancer, anthracycline antibiotic-doxorubicin-as the oxidative stress- and cardiotoxicity-inducing agent.

A Heart-Breast Cancer-on-a-Chip Platform for Disease Modeling and Monitoring of Cardiotoxicity Induced by Cancer Chemotherapy

Cardiotoxicity is one of the most serious side effects of cancer chemotherapy. Current approaches to monitoring of chemotherapy-induced cardiotoxicity (CIC) as well as model systems that develop in vivo or in vitro CIC platforms fail to notice early signs of CIC. Moreover, breast cancer (BC) patients with preexisting cardiac dysfunctions may lead to different incident levels of CIC. Here, a model is presented for investigating CIC where not only induced pluripotent stem cell (iPSC)-derived cardiac tissues are interacted with BC tissues on a dual-organ platform, but electrochemical immuno-aptasensors can also monitor cell-secreted multiple biomarkers. Fibrotic stages of iPSC-derived cardiac tissues are promoted with a supplement of transforming growth factor-β 1 to assess the differential functionality in healthy and fibrotic cardiac tissues after treatment with doxorubicin (DOX). The production trend of biomarkers evaluated by using the immuno-aptasensors well-matches the outcomes from conventional enzyme-linked immunosorbent assay, demonstrating the accuracy of the authors' sensing platform with much higher sensitivity and lower detection limits for early monitoring of CIC and BC progression. Furthermore, the versatility of this platform is demonstrated by applying a nanoparticle-based DOX-delivery system. The proposed platform would potentially help allow early detection and prediction of CIC in individual patients in the future.

Scutellarin protects against doxorubicin-induced acute cardiotoxicity and regulates its accumulation in the heart

The clinical use of doxorubicin (DOX) is limited by its dose-dependent cardiotoxicity. The present study investigated the effects of scutellarin against DOX-induced cardiotoxicity in rats using pharmacodynamic and pharmacokinetic approaches. DOX (20 mg/kg) was injected intraperitoneally (i.p.) as a single dose, and scutellarin (5 mg/kg/day) was injected intravenously (i.v.) for 3 days. Rats treated with DOX showed acute cardiotoxicity as indicated by the elevated serum lactate dehydrogenase (LDH) activity (4057.8 ± 107.2 vs. 2032.7 ± 70.95), tissue malondialdehyde (MDA) level (2.083 ± 0.10 vs. 1.103 ± 0.09), cardiac troponin T (cTnT) concentration (0.1695 ± 0.0114 ng/mL), the decreased left ventricular ejection fraction (LVEF) (47.75 ± 15.79 vs. 78.72 ± 7.25) and left ventricular fractional shortening (LVFS) (20.66 ± 8.06 vs. 43.7 ± 6.76) compared with those of the control group. Cotreatment with scutellarin significantly decreased the LDH activity (2595.9 ± 72.73), MDA level (1.380 ± 0.06), cTnT concentration (0.0222 ± 0.0041 ng/m L), increased LVEF (76.70 ± 3.91) and LVFS (40.28 ± 3.68). Histopathological studies showed disruption of cardiac tissues in the DOX groups. Cotreatment with scutellarin reduced the damage to cardiac tissues. In the pharmacokinetic and tissue distribution study, scutellarin reduced the heart tissue exposure to DOX but did not change the AUC of plasma. These results suggest that scutellarin can protect against DOX-induced acute cardiotoxicity through its antioxidant activity and alterations of heart concentrations.

Metabolic carbonyl reduction of anthracyclines - role in cardiotoxicity and cancer resistance. Reducing enzymes as putative targets for novel cardioprotective and chemosensitizing agents

Anthracycline antibiotics (ANT), such as doxorubicin or daunorubicin, are a class of anticancer drugs that are widely used in oncology. Although highly effective in cancer therapy, their usefulness is greatly limited by their cardiotoxicity. Possible mechanisms of ANT cardiotoxicity include their conversion to secondary alcohol metabolites (i.e. doxorubicinol, daunorubicinol) catalyzed by carbonyl reductases (CBR) and aldo-keto reductases (AKR). These metabolites are suspected to be more cardiotoxic than their parent compounds. Moreover, overexpression of ANT-reducing enzymes (CBR and AKR) are found in many ANT-resistant cancers. The secondary metabolites show decreased cytotoxic properties and are more susceptible to ABC-mediated efflux than their parent compounds; thus, metabolite formation is considered one of the mechanisms of cancer resistance. Inhibitors of CBR and AKR were found to reduce the cardiotoxicity of ANT and the resistance of cancer cells, and therefore are being investigated as prospective cardioprotective and chemosensitizing drug candidates. In this review, the significance of a two-electron reduction of ANT, including daunorubicin, epirubicin, idarubicin, valrubicin, amrubicin, aclarubicin, and especially doxorubicin, is described with respect to toxicity and efficacy of therapy. Additionally, CBR and AKR inhibitors, including monoHER, curcumin, (−)-epigallocatechin gallate, resveratrol, berberine or pixantrone, and their modulating effect on the activity of ANT is characterized and discussed as potential mechanism of action for novel therapeutics in cancer treatment.

Idarubicin and idarubicinol effects on breast cancer multicellular spheroids

Despite extensive preclinical evaluation in several experimental models, no studies have determined the effect of idarubicin and its metabolite idarubicinol on multicellular spheroids, a model which mimics the microregions of solid tumors. The principal aim of the present study was to investigate the in vitro cytotoxicity of idarubicin and its metabolite idarubicinol on MCF-7 breast cancer cells growing as monolayers or multicellular spheroids and to evaluate the influence of the length of exposure on the cytotoxic effect of both drugs. Cytoxicity was evaluated on monolayer and spheroid cultures exposed to idarubicin and idarubicinol 0.01-1000 ng/ml for 24 h or treated for 6, 12, 24 and 48 h to 100 ng/ml of both drugs. The IC50 of idarubicin and idarubicinol were 3.3+/-0.4 and 3.6+/-0.7 ng/ml, respectively, on MCF-7 monolayers and 7.9+/-1.1 and 5.3+/-0.7 ng/ml in multicellular spheroids, respectively. The antiproliferative effects of 100 ng/ml idarubicin and idarubicinol on MCF-7 spheroids was characterized by a marked time-dependence, which was less evident on MCF-7 growing as monolayer. In conclusion, the present experimental data demonstrate, for the first time, that idarubicin and idarubicinol have significant cytotoxic activity against multicellular spheroids, comparable to the antiproliferative effects on monolayer cells. In contrast, spheroids displayed substantial resistance after short exposure times that was not present in the two dimensional cultures.

Effects of idarubicin and idarubicinol on rat coronary resistance and vasoconstrictor responsiveness of isolated aorta and mesentery

It has been hypothesized that coronary vasoconstriction is involved in the cardiotoxic action of anthracyclines. The purpose of this study was to determine whether an increase in coronary resistance induced by idarubicin (IDA) or its primary circulating metabolite idarubicinol (IDOL) is correlated with a decrease in vascular sensitivity to vasoconstrictor agonists. Coronary vasoconstriction was studied in single-pass perfused rat hearts after a 10-min infusion of 0.5 mg IDA or IDOL. In the endothelium-intact rat thoracic aorta and mesentery we measured the inhibition of phenylephrine (PE)- and KCl-induced contraction in the presence of IDA and IDOL, respectively. The increase in coronary vascular resistance evoked by IDOL (121%) exceeded that of IDA (75%). IDA (10-100 micromol/l) concentration-dependently diminished vascular sensitivity to PE and KCl due to a reduction in maximal contractile response (Emax), i.e. the antagonism by IDA of PE- or KCl-induced vasoconstriction was non-competitive, indicating a post-receptor cellular mechanism. These reductions of PE or KCl efficacy elicited by IDOL were significantly larger than those elicited by the corresponding doses of IDA. The decrease in efficacy of PE in the presence of IDA and IDOL was characterized by IC50 estimates of 44.3 and 30.7 mumol/l, respectively. With a 10-fold lower IC50, IDA inhibited the reactivity of small mesenteric arteries to noradrenaline with 10-fold higher potency. The correlation between the increase in coronary resistance and the decrease in vasoconstrictor responsiveness may suggest that these anthracyclines act through a common cellular mechanism.

Anthracyclines: Molecular Advances and Pharmacologic Developments in Antitumor Activity and Cardiotoxicity

The clinical use of anthracyclines like doxorubicin and daunorubicin can be viewed as a sort of double-edged sword. On the one hand, anthracyclines play an undisputed key role in the treatment of many neoplastic diseases; on the other hand, chronic administration of anthracyclines induces cardiomyopathy and congestive heart failure usually refractory to common medications. Second-generation analogs like epirubicin or idarubicin exhibit improvements in their therapeutic index, but the risk of inducing cardiomyopathy is not abated. It is because of their janus behavior (activity in tumors vis-à-vis toxicity in cardiomyocytes) that anthracyclines continue to attract the interest of preclinical and clinical investigations despite their longer-than-40-year record of longevity. Here we review recent progresses that may serve as a framework for reappraising the activity and toxicity of anthracyclines on basic and clinical pharmacology grounds. We review 1) new aspects of anthracycline-induced DNA damage in cancer cells; 2) the role of iron and free radicals as causative factors of apoptosis or other forms of cardiac damage; 3) molecular mechanisms of cardiotoxic synergism between anthracyclines and other anticancer agents; 4) the pharmacologic rationale and clinical recommendations for using cardioprotectants while not interfering with tumor response; 5) the development of tumor-targeted anthracycline formulations; and 6) the designing of third-generation analogs and their assessment in preclinical or clinical settings. An overview of these issues confirms that anthracyclines remain "evergreen" drugs with broad clinical indications but have still an improvable therapeutic index.

Anthracycline secondary alcohol metabolite formation in human or rabbit heart: biochemical aspects and pharmacologic implications

Clinical use of the anticancer anthracyclines doxorubicin (DOX) and daunorubicin (DNR) is limited by development of cardiotoxicity upon chronic administration. Secondary alcohol metabolites, formed after two-equivalent reduction of a carbonyl group in the side chain of DOX or DNR, have been implicated as potential mediators of chronic cardiotoxicity. In the present study we characterized how human heart converted DOX or DNR to their alcohol metabolites DOXol or DNRol. Experiments were carried out using post-mortem myocardial samples obtained by ethically-acceptable procedures, and results showed that DOXol and DNRol were formed by flavin-independent cytoplasmic reductases which shared common features like pH-dependence and requirement for NADPH, but not NADH, as a source of reducing equivalents. However, studies performed with inhibitors exhibiting absolute or mixed specificity toward best known cytoplasmic reductases revealed that DOX and DNR were metabolized to DOXol or DNRol through the action of distinct enzymes. Whereas DOX was converted to DOXol by aldehyde-type reductase(s) belonging to the superfamily of aldo-keto reductases, DNR was converted to DNRol by carbonyl reductase(s) belonging to the superfamily of short-chain dehydrogenase/reductases. This pattern changed in cardiac cytosol derived from rabbit, a laboratory animal often exploited to reproduce cardiotoxicity induced by anthracyclines and to develop protectants for use in cancer patients. In fact, only carbonyl reductases were involved in metabolizing DOX and DNR in rabbit cardiac cytosol, although with different K(m) and V(max). Collectively, these results demonstrate that human myocardium convert DOX and DNR to DOXol or DNRol by virtue of different reductases, an information which may be of value to prevent alcohol metabolite formation during the course of anthracycline-based anticancer therapy. These results also raise caution on the preclinical value of animal models of anthracycline cardiotoxicity, as they demonstrate that the metabolic routes leading to DOXol in a laboratory animal may not be the same as those occurring in patients.

Pharmacokinetics of idarubicin in the isolated perfused rat lung: effect of cinchonine and rutin

This study was designed to examine the effect of rutin and cinchonine on the uptake and metabolism of idarubicin (IDA) in the isolated perfused rat lung. IDA (2 mg) was infused for 2 min into the truncus pulmonalis in the presence of P-glycoprotein (P-gp) modulators cinchonine (1 microM) or rutin (6 microM). (Rutin is also known as an aldo-keto reductase inhibitor.) Venous outflow samples were collected up to 60 min, and the concentration of IDA and its primary metabolite idarubicinol (IDOL) were measured by high-performance liquid chromatography) with fluorescence detection. Thereafter, the tissue concentrations of IDA and IDOL were determined in the lung (n = 5 in each group). The estimated mean transit times for IDA in the treatment groups (MTT(cinchonine) = 21.8+/-3.5 min; MTT(rutin) = 20.1+/-5.0 min) were significantly higher than in the control group (11.6+/-2.1 min). Both cinchonine and rutin significantly enhanced the lung tissue concentrations of IDA (1.7- and 2.4-fold), as well as of IDOL (2.1- and 2.4-fold). Cinchonine and rutin also increased the outflow recovery of IDOL 2.6- and 2.7-fold, respectively. The results suggest that uptake kinetics of IDA into the rat lung is partly controlled by a P-gp efflux pump and its inhibition enhances the accumulation of IDA.