Primary prevention of chronic anthracycline cardiotoxicity with ACE inhibitor is temporarily effective in rabbits, but benefits wane in post-treatment follow-up.

Angiotensin-converting enzyme inhibitors (ACEis) have been used to treat anthracycline (ANT)-induced cardiac dysfunction, and they appear beneficial for secondary prevention in high-risk patients. However, it remains unclear whether they truly prevent ANT-induced cardiac damage and provide long-lasting cardioprotection. The present study aimed to examine the cardioprotective effects of perindopril on chronic ANT cardiotoxicity in a rabbit model previously validated with the cardioprotective agent dexrazoxane (DEX) with focus on post-treatment follow-up (FU). Chronic cardiotoxicity was induced by daunorubicin (DAU; 3 mg/kg/week for 10 weeks). Perindopril (0.05 mg/kg/day) was administered before and throughout chronic DAU treatment. After the completion of treatment, significant benefits were observed in perindopril co-treated animals, particularly full prevention of DAU-induced mortality and prevention or significant reductions in cardiac dysfunction, plasma cardiac troponin T (cTnT) levels, morphological damage, and most of the myocardial molecular alterations. However, these benefits significantly waned during 3 weeks of drug-free FU, which was not salvageable by administering a higher perindopril dose. In the longer (10-week) FU period, further worsening of left ventricular function and morphological damage occurred together with heart failure (HF)-related mortality. Continued perindopril treatment in the FU period did not reverse this trend but prevented HF-related mortality and reduced the severity of the progression of cardiac damage. These findings contrasted with the robust long-lasting protection observed previously for DEX in the same model. Hence, in the present study, perindopril provided only temporary control of ANT cardiotoxicity development, which may be associated with the lack of effects on ANT-induced and topoisomerase II ß (TOP2B)-dependent DNA damage responses in the heart.

Prodrug of ICRF-193 provides promising protective effects against chronic anthracycline cardiotoxicity in a rabbit model in vivo.

The anthracycline (ANT) anticancer drugs such as doxorubicin or daunorubicin (DAU) can cause serious myocardial injury and chronic cardiac dysfunction in cancer survivors. A bisdioxopiperazine agent dexrazoxane (DEX) has been developed as a cardioprotective drug to prevent these adverse events, but it is uncertain whether it is the best representative of the class. The present study used a rabbit model of chronic ANT cardiotoxicity to examine another bisdioxopiperazine compound called GK-667 (meso-(butane-2,3-diylbis(2,6-dioxopiperazine-4,1-diyl))bis(methylene)-bis(2-aminoacetate) hydrochloride), a water-soluble prodrug of ICRF-193 (meso-4,4'-(butan-2,3-diyl)bis(piperazine-2,6-dione)), as a potential cardioprotectant. The cardiotoxicity was induced by DAU (3 mg/kg, intravenously, weekly, 10 weeks), and GK-667 (1 or 5 mg/kg, intravenously) was administered before each DAU dose. The treatment with GK-667 was well tolerated and provided full protection against DAU-induced mortality and left ventricular (LV) dysfunction (determined by echocardiography and LV catheterization). Markers of cardiac damage/dysfunction revealed minor cardiac damage in the group co-treated with GK-667 in the lower dose, whereas almost full protection was achieved with the higher dose. This was associated with similar prevention of DAU-induced dysregulation of redox and calcium homeostasis proteins. GK-667 dose-dependently prevented tumor suppressor p53 (p53)-mediated DNA damage response in the LV myocardium not only in the chronic experiment but also after single DAU administration. These effects appear essential for cardioprotection, presumably because of the topoisomerase IIß (TOP2B) inhibition provided by its active metabolite ICRF-193. In addition, GK-667 administration did not alter the plasma pharmacokinetics of DAU and its main metabolite daunorubicinol (DAUol) in rabbits in vivo. Hence, GK-667 merits further investigation as a promising drug candidate for cardioprotection against chronic ANT cardiotoxicity.

COVID-19 Prophylaxis Efforts Based on Natural Antiviral Plant Extracts and Their Compounds.

During the time of the novel coronavirus disease 2019 (COVID-19) pandemic, it has been crucial to search for novel antiviral drugs from plants and well as other natural sources as alternatives for prophylaxis. This work reviews the antiviral potential of plant extracts, and the results of previous research for the treatment and prophylaxis of coronavirus disease and previous kinds of representative coronaviruses group. Detailed descriptions of medicinal herbs and crops based on their origin native area, plant parts used, and their antiviral potentials have been conducted. The possible role of plant-derived natural antiviral compounds for the development of plant-based drugs against coronavirus has been described. To identify useful scientific trends, VOSviewer visualization of presented scientific data analysis was used.

Ornamental Plant Efficiency for Heavy Metals Phytoextraction from Contaminated Soils Amended with Organic Materials.

Accumulation of heavy metals (HMs) by ornamental plants (OPs) from contaminated agriculture soils is a unique technique that can efficiently reduce the metal load in the food chain. Amaranthus tricolor L. has attractive characteristics acquiring a higher growth rate and large biomass when grown at heavy metal contaminated soils. Site-specific detailed information is not available on the use of A. tricolor plant in metal phytoremediation from the polluted sites. The study aimed to enhance the uptake of HMs (Pb, Zn, and Cu) via amending poultry litter extract (PLE), vinasse sugarcane (VSC), and humic acid (HA) as natural mobilized organic materials compared to ethylene diamine tetraacetic acid (EDTA), as a common mobilized chemical agent by A. tricolor plant. The studied soils collected from Helwan, El-Gabal El-Asfar (Cairo Governorate), Arab El-Madabeg (Assiut Governorate), Egypt, and study have been conducted under pot condition. Our results revealed all organic materials in all studied soils, except EDTA in EL-Gabal El-Asfar soil, significantly increased the dry weight of the A. tricolor plant compared to the control treatment. The uptake of Pb and Zn significantly (p > 0.05) increased due to applying all organic materials to the studied soils. HA application caused the highest uptake as shown in Pb concentration by more than 5 times in Helwan soil and EDTA by 65% in El-Gabal El-Asfar soil while VSC increased it by 110% in El-Madabeg soil. Also, an increase in Zn concentration due to EDTA application was 58, 42, and 56% for Helwan, El-Gabal El-Asfar, and El-Madabeg soil, respectively. In all studied soils, the application of organic materials increased the remediation factor (RF) than the control. El-Madabeg soil treated with vinasse sugarcane gave the highest RF values; 6.40, 3.26, and 4.02% for Pb, Zn, and Cu, respectively, than the control. Thus, we identified A. tricolor as a successful ornamental candidate that, along with organic mobilization amendments, most efficiently develop soil health, reduce metal toxicity, and recommend remediation of heavy metal-contaminated soils. Additionally, long-term application of organic mobilization amendments and continued growth of A. tricolor under field conditions could be recommended for future directions to confirm the results.

Investigation of Structure-Activity Relationships of Dexrazoxane Analogs Reveals Topoisomerase IIß Interaction as a Prerequisite for Effective Protection against Anthracycline Cardiotoxicity.

Bisdioxopiperazine agent dexrazoxane (ICRF-187) has been the only effective and approved drug for prevention of chronic anthracycline cardiotoxicity. However, the structure-activity relationships (SARs) of its cardioprotective effects remain obscure owing to limited investigation of its derivatives/analogs and uncertainties about its mechanism of action. To fill these knowledge gaps, we tested the hypothesis that dexrazoxane derivatives exert cardioprotection via metal chelation and/or modulation of topoisomerase IIß (Top2B) activity in chronic anthracycline cardiotoxicity. Dexrazoxane was alkylated in positions that should not interfere with the metal-chelating mechanism of cardioprotective action; that is, on dioxopiperazine imides or directly on the dioxopiperazine ring. The protective effects of these agents were assessed in vitro in neonatal cardiomyocytes. All studied modifications of dexrazoxane molecule, including simple methylation, were found to abolish the cardioprotective effects. Because this challenged the prevailing mechanistic concept and previously reported data, the two closest derivatives [(±)-4,4'-(propane-1,2-diyl)bis(1-methylpiperazine-2,6-dione) and 4-(2-(3,5-dioxopiperazin-1-yl)ethyl)-3-methylpiperazine-2,6-dione] were thoroughly scrutinized in vivo using a rabbit model of chronic anthracycline cardiotoxicity. In contrast to dexrazoxane, both compounds failed to protect the heart, as demonstrated by mortality, cardiac dysfunction, and myocardial damage parameters, although the pharmacokinetics and metal-chelating properties of their metabolites were comparable to those of dexrazoxane. The loss of cardiac protection was shown to correlate with their abated potential to inhibit and deplete Top2B both in vitro and in vivo. These findings suggest a very tight SAR between bisdioxopiperazine derivatives and their cardioprotective effects and support Top2B as a pivotal upstream druggable target for effective cardioprotection against anthracycline cardiotoxicity. SIGNIFICANCE STATEMENT: This study has revealed the previously unexpected tight structure-activity relationships of cardioprotective effects in derivatives of dexrazoxane, which is the only drug approved for the prevention of cardiomyopathy and heart failure induced by anthracycline anticancer drugs. The data presented in this study also strongly argue against the importance of metal-chelating mechanisms for the induction of this effect and support the viability of topoisomerase IIß as an upstream druggable target for effective and clinically translatable cardioprotection.

Betacyanins and Betaxanthins in Cultivated Varieties of Beta vulgaris L. Compared to Weed Beets.

There are 11 different varieties of Beta vulgaris L. that are used in the food industry, including sugar beets, beetroots, Swiss chard, and fodder beets. The typical red coloration of their tissues is caused by the indole-derived glycosides known as betalains that were analyzed in hypocotyl extracts by UV/Vis spectrophotometry to determine the content of betacyanins (betanin) and of betaxanthins (vulgaxanthin I) as constituents of the total betalain content. Fields of beet crops use to be also infested by wild beets, hybrids related to B. vulgaris subsp. maritima or B. macrocarpa Guss., which significantly decrease the quality and quantity of sugar beet yield; additionally, these plants produce betalains at an early stage. All tested B. vulgaris varieties could be distinguished from weed beets according to betacyanins, betaxanthins or total betalain content. The highest values of betacyanins were found in beetroots 'Monorubra' (9.69 mg/100 mL) and 'Libero' (8.42 mg/100 mL). Other beet varieties contained less betacyanins: Sugar beet 'Labonita' 0.11 mg/100 mL; Swiss chard 'Lucullus,' 0.09 mg/100 mL; fodder beet 'Monro' 0.15 mg/100 mL. In contrast with weed beets and beetroots, these varieties have a ratio of betacyanins to betaxanthins under 1.0, but the betaxanthin content was higher in beetcrops than in wild beet and can be used as an alternative to non-red varieties. Stability tests of selected varieties showed that storage at 22 °C for 6 h, or at 7 °C for 24 h, did not significantly reduce the betalain content in the samples.

In vitro and in vivo investigation of cardiotoxicity associated with anticancer proteasome inhibitors and their combination with anthracycline.

Although proteasome inhibitors (PIs) are modern targeted anticancer drugs, they have been associated with a certain risk of cardiotoxicity and heart failure (HF). Recently, PIs have been combined with anthracyclines (ANTs) to further boost their anticancer efficacy. However, this raised concerns regarding cardiac safety, which were further supported by several in vitro studies on immature cardiomyocytes. In the present study, we investigated the toxicity of clinically used PIs alone (bortezomib (BTZ), carfilzomib (CFZ)) as well as their combinations with an ANT (daunorubicin (DAU)) in both neonatal and adult ventricular cardiomyocytes (NVCMs and AVCMs) and in a chronic rabbit model of DAU-induced HF. Using NVCMs, we found significant cytotoxicity of both PIs around their maximum plasma concentration (cmax) as well as significant augmentation of DAU cytotoxicity. In AVCMs, BTZ did not induce significant cytotoxicity in therapeutic concentrations, whereas the toxicity of CFZ was significant and more profound. Importantly, neither PI significantly augmented the cardiotoxicity of DAU despite even more profound proteasome-inhibitory activity in AVCMs compared with NVCMs. Furthermore, in young adult rabbits, no significant augmentation of chronic ANT cardiotoxicity was noted with respect to any functional, morphological, biochemical or molecular parameter under study, despite significant inhibition of myocardial proteasome activity. Our experimental data show that combination of PIs with ANTs is not accompanied by an exaggerated risk of cardiotoxicity and HF in young adult animal cardiomyocytes and hearts.

Vanadium elicitation of Trifolium pratense L. cell culture and possible pathways of produced isoflavones transport across the plasma membrane.

KEY MESSAGE: Vanadium compounds increased the content and release of distinct isoflavones in a Trifolium pratense suspension culture. Regarding transport-mechanism inhibitors, the process was mostly facilitated by ABC proteins and vesicular transport. The transport of isoflavones and other secondary metabolites is an important part of metabolism within plants and cultures in vitro regarding their role in defence against various abiotic and biotic stressors. This research focuses on the way how to increase production and exudation of isoflavones by application of chemical elicitor and the basic identification of their transport mechanisms across cell membranes. The release of five isoflavones (genistin, genistein, biochanin A, daidzein, and formononetin) into a nutrient medium was determined in a Trifolium pratense var. DO-8 suspension culture after two vanadium compound treatments and cultivation for 24 and 48 h. The NH4VO3 solution caused a higher concentration of isoflavones in the medium after 24 h. This increased content of secondary metabolites was subsequently suppressed by distinct transport-mechanism inhibitors. The transport of isoflavones in T. pratense was mostly affected by ABC inhibitors from the multidrug-resistance-associated protein subfamily, but the genistein concentration in the medium was lower after treatment with multidrug-resistance protein subfamily inhibitors. Brefeldin A, which blocks vesicular transport, also decreased the concentration of some isoflavones in the nutrient medium.

Changes in Content of Polyphenols and Ascorbic Acid in Leaves of White Cabbage after Pest Infestation.

Crops, such as white cabbage (Brassica oleracea L. var. capitata (L.) f. alba), are often infested by herbivorous insects that consume the leaves directly or lay eggs with subsequent injury by caterpillars. The plants can produce various defensive metabolites or free radicals that repel the insects to avert further damage. To study the production and effects of these compounds, large white cabbage butterflies, Pieris brassicae and flea beetles, Phyllotreta nemorum, were captured in a cabbage field and applied to plants cultivated in the lab. After insect infestation, leaves were collected and UV/Vis spectrophotometry and HPLC used to determine the content of stress molecules (superoxide), primary metabolites (amino acids), and secondary metabolites (phenolic acids and flavonoids). The highest level of superoxide was measured in plants exposed to fifty flea beetles. These plants also manifested a higher content of phenylalanine, a substrate for the synthesis of phenolic compounds, and in activation of total phenolics and flavonoid production. The levels of specific phenolic acids and flavonoids had higher variability when the dominant increase was in the flavonoid, quercetin. The leaves after flea beetle attack also showed an increase in ascorbic acid which is an important nutrient of cabbage.

2,6-Dihydroxybenzaldehyde Analogues of the Iron Chelator Salicylaldehyde Isonicotinoyl Hydrazone: Increased Hydrolytic Stability and Cytoprotective Activity against Oxidative Stress.

Salicylaldehyde isonicotinoyl hydrazone (SIH) is a small molecule and lipophilic chelating agent that firmly binds ferric ions from the cellular labile iron pool and is able to protect various tissues against oxidative damage. Previously, SIH possessed the best ratio of cytoprotective efficiency to toxicity among various iron chelators, including the desferrioxamine, deferiprone, and deferasirox used in clinical practice. Here, we prepared a series of 2,6-dihydroxybenzaldehyde aroylhydrazones as SIH analogues with an additional hydroxyl group that can be involved in the chelation of metal ions. Compound JK-31 (2,6-dihydroxybenzaldehyde 4-chlorobenzohydrazone) showed the best cytoprotective efficiency among the studied compounds including SIH. This compound significantly protected H9c2 cardiomyoblast cells against oxidative stress induced by various pro-oxidants, such as hydrogen peroxide, tert-butyl hydroperoxide, paraquat, epinephrine, N-acetyl- p-benzoquinone imine (a toxic metabolite of paracetamol), and 6-hydroxydopamine. The exceptional cytoprotective activity of JK-31 was confirmed using epifluorescence microscopy, where JK-31-treated H9c2 cells maintained a higher mitochondrial inner membrane potential in the presence of a lethal dose of hydrogen peroxide than was observed with cells treated with SIH. Hence, this study demonstrates the deleterious role of free iron ions in oxidative injury and the potential of 2,6-dihydroxybenzaldehyde aroylhydrazones in the prevention of various types of cardiac injuries, highlighting the need for further investigations into these compounds.

Isoflavones Production and Possible Mechanism of Their Exudation in Genista tinctoria L. Suspension Culture after Treatment with Vanadium Compounds.

The family Fabaceae traditionally serves as a food and herbal remedies source. Certain plants serve for treatment of menopausal symptoms based on a presence of typical secondary metabolites, isoflavones. Beside soybean and clovers, other plants or cultures in vitro can produce these molecules. A cultivation in vitro can be enhanced by elicitation that stimulates metabolites biosynthesis via stress reaction. Vanadium compounds have been already described as potential elicitors, and the aim of this study was to determine the impact of NH4VO3 and VOSO4 solutions on isoflavones production in Genista tinctoria L. cell cultures. The significant increase of isoflavones content, such as genistin, genistein, or formononetin, was measured in a nutrient medium or dry mass after NH4VO3 treatment for 24 or 48 h. The possible transport mechanism of isoflavones release as a result of elicitation was further evaluated. An incubation with different transport inhibitors prior to elicitation took effect on isoflavones content in the medium. However, there was a non-ended result for particular metabolites such as genistein and daidzein, where ATP-binding cassette (ABC) or, alternatively, multidrug and toxin extrusion (MATE) proteins can participate. Possible elicitation by some inhibitors was discussed as a result of their pleiotropic effect. Despite this outcome, the determination of the transport mechanism is an important step for identification of the specific transporter.

Zinc oxide nanoparticles application alleviates salinity stress by modulating plant growth, biochemical attributes and nutrient homeostasis in Phaseolus vulgaris L.

Salt stress poses a significant challenge to global agriculture, adversely affecting crop yield and food production. The current study investigates the potential of Zinc Oxide (ZnO) nanoparticles (NPs) in mitigating salt stress in common beans. Salt-stressed bean plants were treated with varying concentrations of NPs (25 mg/L, 50 mg/L, 100 mg/L, 200 mg/L) using three different application methods: foliar application, nano priming, and soil application. Results indicated a pronounced impact of salinity stress on bean plants, evidenced by a reduction in fresh weight (24%), relative water content (27%), plant height (33%), chlorophyll content (37%), increased proline (over 100%), sodium accumulation, and antioxidant enzyme activity. Application of ZnO NPs reduced salt stress by promoting physiological growth parameters. The NPs facilitated enhanced plant growth and reduced reactive oxygen species (ROS) generation by regulating plant nutrient homeostasis and chlorophyll fluorescence activity. All the tested application methods effectively mitigate salt stress, with nano-priming emerging as the most effective approach, yielding results comparable to control plants for the tested parameters. This study provides the first evidence that ZnO NPs can effectively mitigate salt stress in bean plants, highlighting their potential to address salinity-induced growth inhibition in crops.

Exploring the effects of topoisomerase II inhibitor XK469 on anthracycline cardiotoxicity and DNA damage.

Anthracyclines, such as doxorubicin (adriamycin), daunorubicin, or epirubicin, rank among the most effective agents in classical anticancer chemotherapy. However, cardiotoxicity remains the main limitation of their clinical use. Topoisomerase IIß has recently been identified as a plausible target of anthracyclines in cardiomyocytes. We examined the putative topoisomerase IIß selective agent XK469 as a potential cardioprotective and designed several new analogs. In our experiments, XK469 inhibited both topoisomerase isoforms (α and ß) and did not induce topoisomerase II covalent complexes in isolated cardiomyocytes and HL-60, but induced proteasomal degradation of topoisomerase II in these cell types. The cardioprotective potential of XK469 was studied on rat neonatal cardiomyocytes, where dexrazoxane (ICRF-187), the only clinically approved cardioprotective, was effective. Initially, XK469 prevented daunorubicin-induced toxicity and p53 phosphorylation in cardiomyocytes. However, it only partially prevented the phosphorylation of H2AX and did not affect DNA damage measured by Comet Assay. It also did not compromise the daunorubicin antiproliferative effect in HL-60 leukemic cells. When administered to rabbits to evaluate its cardioprotective potential in vivo, XK469 failed to prevent the daunorubicin-induced cardiac toxicity in either acute or chronic settings. In the following in vitro analysis, we found that prolonged and continuous exposure of rat neonatal cardiomyocytes to XK469 led to significant toxicity. In conclusion, this study provides important evidence on the effects of XK469 and its combination with daunorubicin in clinically relevant doses in cardiomyocytes. Despite its promising characteristics, long-term treatments and in vivo experiments have not confirmed its cardioprotective potential.

Hydrophobicity-enhanced ferritin nanoparticles for efficient encapsulation and targeted delivery of hydrophobic drugs to tumor cells.

Ferritin, a naturally occurring iron storage protein, has gained significant attention as a drug delivery platform due to its inherent biocompatibility and capacity to encapsulate therapeutic agents. In this study, we successfully genetically engineered human H ferritin by incorporating 4 or 6 tryptophan residues per subunit, strategically oriented towards the inner cavity of the nanoparticle. This modification aimed to enhance the encapsulation of hydrophobic drugs into the ferritin cage. Comprehensive characterization of the mutants revealed that only the variant carrying four tryptophan substitutions per subunit retained the ability to disassemble and reassemble properly. As a proof of concept, we evaluated the loading capacity of this mutant with ellipticine, a natural hydrophobic indole alkaloid with multimodal anticancer activity. Our data demonstrated that this specific mutant exhibited significantly higher efficiency in loading ellipticine compared to human H ferritin. Furthermore, to evaluate the versatility of this hydrophobicity-enhanced ferritin nanoparticle as a drug carrier, we conducted a comparative study by also encapsulating doxorubicin, a commonly used anticancer drug. Subsequently, we tested both ellipticine and doxorubicin-loaded nanoparticles on a promyelocytic leukemia cell line, demonstrating efficient uptake by these cells and resulting in the expected cytotoxic effect.

Arsenic Soil Contamination and Its Effects on 5-Methylcytosine Levels in Onions and Arsenic Distribution and Speciation.

Arsenic represents a serious health threat in localities with a high arsenic-polluted environment and can easily get into the human food chain through agronomy production in areas affected by arsenic contamination. Onion plants that were grown in controlled conditions in arsenic-contaminated soil (5, 10, and 20 ppm) were harvested 21 days after contamination. Arsenic levels (from 0.43 ± 0.03 µg g-1 to 1761.11 ± 101.84 µg g-1) in the onion samples were high in the roots and low in the bulbs and leaves, which is probably caused by a reduced ability of the onions to transport arsenic from roots to bulbs and leaves. Arsenic species As(V) and As(III) in As(V)-contaminated soil samples were represented strongly in favor of the As(III) species. This indicates the presence of arsenate reductase. Levels of 5-methylcytosine (5-mC) (from 5.41 ± 0.28% to 21.17 ± 1.33%) in the onion samples were also higher in the roots than in the bulbs and leaves. Microscopic sections of the roots were examined, and the most damage was found in the 10 ppm As variant. Photosynthetic parameters pointed to a significant decrease in photosynthetic apparatus activity and the deterioration of the physiological state of plants as arsenic content increased in the soil.

Effect of Arsenic Soil Contamination on Stress Response Metabolites, 5-Methylcytosine Level and CDC25 Expression in Spinach.

Experimental spinach plants grown in soil with (5, 10 and 20 ppm) arsenic (As) contamination were sampled in 21 days after As(V) contamination. Levels of As in spinach samples (from 0.31 ± 0.06 µg g-1 to 302.69 ± 11.83 µg g-1) were higher in roots and lower in leaves, which indicates a low ability of spinach to translocate As into leaves. Species of arsenic, As(III) and As(V), were represented in favor of the As (III) specie in contaminated variants, suggesting enzymatic arsenate reduction. In relation to predominant As accumulation in roots, changes in malondialdehyde levels were observed mainly in roots, where they decreased significantly with growing As contamination (from 11.97 ± 0.54 µg g-1 in control to 2.35 ± 0.43 µg g-1 in 20 ppm As). Higher values in roots than in leaves were observed in the case of 5-methylcytosine (5-mC). Despite that, a change in 5-mC by As contamination was further deepened in leaves (from 0.20 to 14.10%). In roots of spinach, expression of the CDC25 gene increased by the highest As contamination compared to the control. In the case of total phenolic content, total flavonoid content, total phenolic acids content and total antioxidant capacity were higher levels in leaves in all values, unlike the roots.

2,6-Disubstituted 7-(naphthalen-2-ylmethyl)-7H-purines as a new class of potent antitubercular agents inhibiting DprE1.

Phenotypic screening of an in-house library of small molecule purine derivatives against Mycobacterium tuberculosis (Mtb) led to the identification of 2-morpholino-7-(naphthalen-2-ylmethyl)-1,7-dihydro-6H-purin-6-one 10 as a potent antimycobacterial agent with MIC99 of 4 µM. Thorough structure-activity relationship studies revealed the importance of 7-(naphthalen-2-ylmethyl) substitution for antimycobacterial activity, yet opened the possibility of structural modifications at positions 2 and 6 of the purine core. As the result, optimized analogues with 6-amino or ethylamino substitution 56 and 64, respectively, were developed. These compounds showed strong in vitro antimycobacterial activity with MIC of 1 µM against Mtb H37Rv and against several clinically isolated drug-resistant strains, had limited toxicity to mammalian cell lines, medium clearance with respect to phase I metabolic deactivation (27 and 16.8 µL/min/mg), sufficient aqueous solubility (>90 µM) and high plasma stability. Interestingly, investigated purines, including compounds 56 and 64, lacked activity against a panel of Gram-negative and Gram-positive bacterial strains, indicating a specific mycobacterial molecular target. To investigate the mechanism of action, Mtb mutants resistant to hit compound 10 were isolated and their genomes were sequenced. Mutations were found in dprE1 (Rv3790), which encodes decaprenylphosphoryl-ß-d-ribose oxidase DprE1, enzyme essential for the biosynthesis of arabinose, a vital component of the mycobacterial cell wall. Inhibition of DprE1 by 2,6-disubstituted 7-(naphthalen-2-ylmethyl)-7H-purines was proved using radiolabelling experiments in Mtb H37Rv in vitro. Finally, structure-binding relationships between selected purines and DprE1 using molecular modeling studies in tandem with molecular dynamic simulations revealed the key structural features for effective drug-target interaction.

Structure-Activity Relationship Study of Dexrazoxane Analogues Reveals ICRF-193 as the Most Potent Bisdioxopiperazine against Anthracycline Toxicity to Cardiomyocytes Due to Its Strong Topoisomerase IIß Interactions.

Cardioprotective activity of dexrazoxane (ICRF-187), the only clinically approved drug against anthracycline-induced cardiotoxicity, has traditionally been attributed to its iron-chelating metabolite. However, recent experimental evidence suggested that the inhibition and/or depletion of topoisomerase IIß (TOP2B) by dexrazoxane could be cardioprotective. Hence, we evaluated a series of dexrazoxane analogues and found that their cardioprotective activity strongly correlated with their interaction with TOP2B in cardiomyocytes, but was independent of their iron chelation ability. Very tight structure-activity relationships were demonstrated on stereoisomeric forms of 4,4'-(butane-2,3-diyl)bis(piperazine-2,6-dione). In contrast to its rac-form 12, meso-derivative 11 (ICRF-193) showed a favorable binding mode to topoisomerase II in silico, inhibited and depleted TOP2B in cardiomyocytes more efficiently than dexrazoxane, and showed the highest cardioprotective efficiency. Importantly, the observed ICRF-193 cardioprotection did not interfere with the antiproliferative activity of anthracycline. Hence, this study identifies ICRF-193 as the new lead compound in the development of efficient cardioprotective agents.

Development of water-soluble prodrugs of the bisdioxopiperazine topoisomerase IIß inhibitor ICRF-193 as potential cardioprotective agents against anthracycline cardiotoxicity.

The bisdioxopiperazine topoisomerase IIß inhibitor ICRF-193 has been previously identified as a more potent analog of dexrazoxane (ICRF-187), a drug used in clinical practice against anthracycline cardiotoxicity. However, the poor aqueous solubility of ICRF-193 has precluded its further in vivo development as a cardioprotective agent. To overcome this issue, water-soluble prodrugs of ICRF-193 were prepared, their abilities to release ICRF-193 were investigated using a novel UHPLC-MS/MS assay, and their cytoprotective effects against anthracycline cardiotoxicity were tested in vitro in neonatal ventricular cardiomyocytes (NVCMs). Based on the obtained results, the bis(2-aminoacetoxymethyl)-type prodrug GK-667 was selected for advanced investigations due to its straightforward synthesis, sufficient solubility, low cytotoxicity and favorable ICRF-193 release. Upon administration of GK-667 to NVCMs, the released ICRF-193 penetrated well into the cells, reached sufficient intracellular concentrations and provided effective cytoprotection against anthracycline toxicity. The pharmacokinetics of the prodrug, ICRF-193 and its rings-opened metabolite was estimated in vivo after administration of GK-667 to rabbits. The plasma concentrations of ICRF-193 reached were found to be adequate to achieve cardioprotective effects in vivo. Hence, GK-667 was demonstrated to be a pharmaceutically acceptable prodrug of ICRF-193 and a promising drug candidate for further evaluation as a potential cardioprotectant against chronic anthracycline toxicity.

Clinically Translatable Prevention of Anthracycline Cardiotoxicity by Dexrazoxane Is Mediated by Topoisomerase II Beta and Not Metal Chelation.

BACKGROUND: Anthracycline-induced heart failure has been traditionally attributed to direct iron-catalyzed oxidative damage. Dexrazoxane (DEX)-the only drug approved for its prevention-has been believed to protect the heart via its iron-chelating metabolite ADR-925. However, direct evidence is lacking, and recently proposed TOP2B (topoisomerase II beta) hypothesis challenged the original concept. METHODS: Pharmacokinetically guided study of the cardioprotective effects of clinically used DEX and its chelating metabolite ADR-925 (administered exogenously) was performed together with mechanistic experiments. The cardiotoxicity was induced by daunorubicin in neonatal ventricular cardiomyocytes in vitro and in a chronic rabbit model in vivo (n=50). RESULTS: Intracellular concentrations of ADR-925 in neonatal ventricular cardiomyocytes and rabbit hearts after treatment with exogenous ADR-925 were similar or exceeded those observed after treatment with the parent DEX. However, ADR-925 did not protect neonatal ventricular cardiomyocytes against anthracycline toxicity, whereas DEX exhibited significant protective effects (10-100 µmol/L; P<0.001). Unlike DEX, ADR-925 also had no significant impact on daunorubicin-induced mortality, blood congestion, and biochemical and functional markers of cardiac dysfunction in vivo (eg, end point left ventricular fractional shortening was 32.3±14.7%, 33.5±4.8%, 42.7±1.0%, and 41.5±1.1% for the daunorubicin, ADR-925 [120 mg/kg]+daunorubicin, DEX [60 mg/kg]+daunorubicin, and control groups, respectively; P<0.05). DEX, but not ADR-925, inhibited and depleted TOP2B and prevented daunorubicin-induced genotoxic damage. TOP2B dependency of the cardioprotective effects was probed and supported by experiments with diastereomers of a new DEX derivative. CONCLUSIONS: This study strongly supports a new mechanistic paradigm that attributes clinically effective cardioprotection against anthracycline cardiotoxicity to interactions with TOP2B but not metal chelation and protection against direct oxidative damage.