Andrea Breuer

DNA adduct formation by the anticancer drug ellipticine in rats determined by 32P postlabeling

Ellipticine is a potent antineoplastic agent whose mode of action is considered to be based mainly on DNA intercalation and/or inhibition of topoisomerase II. Recently, we found that ellipticine also forms covalent DNA adducts in vitro and that the formation of the major adduct is dependent on the activation of ellipticine by cytochrome P450 (CYP). Here, we investigated the capacity of ellipticine to form DNA adducts in vivo. Male Wistar rats were treated with ellipticine, and DNA from various organs was analyzed by 32P postlabeling. Ellipticine‐specific DNA adduct patterns, similar to those found in vitro, were detected in most test organs. Only DNA of testes was free of the ellipticine‐DNA adducts. The highest level of DNA adducts was found in liver (19.7 adducts per 107 nucleotides), followed by spleen, lung, kidney, heart and brain. One major and one minor ellipticine‐DNA adducts were found in DNA of all these organs of rats exposed to ellipticine. Besides these, 2 or 3 additional adducts were detected in DNA of liver, kidney, lung and heart. The predominant adduct formed in rat tissues in vivo was identical to the deoxyguanosine adduct generated in DNA by ellipticine in vitro as shown by cochromatography in 2 independent systems. Correlation studies showed that the formation of this major DNA adduct in vivo is mediated by CYP3A1‐ and CYP1A‐dependent reactions. The results presented here are the first report showing the formation of CYP‐mediated covalent DNA adducts by ellipticine in vivo and confirm the formation of covalent DNA adducts as a new mode of ellipticine action.

Aristolactam I a metabolite of aristolochic acid I upon activation forms an adduct found in DNA of patients with Chinese herbs nephropathy.

Aristolochic acid (AA) a naturally occuring nephrotoxin and carcinogen is implicated in a unique type of renal fibrosis, designated Chinese herbs nephropathy (CHN). We identified AA-specific DNA adducts in kidneys and in a ureter obtained from CHN patients after renal transplantation. AA is a plant extract of aristolochia species containing AA I as the major component. Aristolactams are the principal detoxication metabolites of AA, which were detected in urine and faeces from animals and humans. They are activated by cytochrome P450 (P450) and peroxidase to form DNA adducts. Using the 32P-postlabelling assay we investigated the formation of DNA adducts by aristolactam I in these two activation systems. A combination of two independent chromatographic systems (ion-exchange chromatography TLC and reversed-phase HPLC) with reference compounds was used for the identification of adducts. Aristolactam I activated by peroxidase led to the formation of several adducts. Two major adducts were identical to adducts previously observed in vivo. 7-(deoxyguanosin-N2-yl)aristolactam I (dG-AAI) and 7-(deoxyadenosin-N6-yl)aristolactam I (dA-AAI) were formed in DNA during the peroxidase-mediated one-electron oxidation of aristolactam I. Aristolactam I activated by P450 led to one major adduct and four minor ones. Beside the principal AA-DNA adducts identified recently in the ureter of one patient with CHN, an additional minor adduct was detected, which was found to have indistinguishable chromatographic properties on TLC and HPLC from the major adduct formed from aristolactam I by P450 activation. Thus, this minor AA-adduct might be evolved from the AAI detoxication metabolite (aristolactam I) by P450 activation. These results indicate a potential carcinogenic effect of aristolactam I in humans.

Evidence for reductive activation of carcinogenic aristolochic acids by prostaglandin H synthase - 32P-postlabeling analysis of DNA adduct formation

Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, is implicated in an unique type of renal fibrosis, designated Chinese herbs nephropathy (CHN), which can develop to urothelial cancer. Understanding which enzymes are involved in AA activation and/or detoxication is important in the assessment of an individual susceptibility to this natural carcinogen. We examined the ability of prostaglandin H synthase (PHS) to activate AA to metabolites forming DNA adducts with the nuclease P1 and 1-butanol extraction enrichment procedure of the (32)P-postlabeling assay. PHS is a prominent enzyme in the kidney and urothelial tissues. Ram seminal vesicle (RSV) microsomes, which contain high levels of PHS, generated AA-DNA adduct patterns reproducing those found in renal tissues in CHN patients. 7-(Deoxyadenosin-N(6)-yl)aristolactam I, 7-(deoxyguanosin-N(2)-yl)aristolactam I and 7-(deoxyadenosin-N(6)-yl)aristolactam II were identified as AA-DNA adducts formed by AAI. Two adducts, 7-(deoxyguanosin-N(2)-yl)aristolactam II and 7-(deoxyadenosin-N(6)-yl)aristolactam II, were generated from AAII. According to the structures of the DNA adducts identified, nitroreduction is the crucial pathway in the metabolic activation of AA. The identity of PHS as the activating enzyme in RSV microsomes was proven with different cofactors and inhibitors. Only indomethacin, a selective inhibitor of PHS, significantly decreased the amount of adducts formed by RSV microsomes. The inhibitor of NADPH:CYP reductase (alpha-lipoic acid) and some selective inhibitors of cytochromes P450 (CYP) were not effective. Likewise, only cofactors of PHS, arachidonic acid and hydrogen peroxide, supported the DNA adduct formation of AAI and AAII, while NADPH and NADH were ineffective. These results demonstrate a key role of PHS in the activation pathway of AAI and AAII in the RSV microsomal system and were corroborated with the purified enzyme, namely ovine PHS-1. The results presented here are the first report demonstrating a reductive activation of nitroaromatic compounds by PHS-1.

Induction of metallothionein by zinc protects from daunorubicin toxicity in rats

Daunorubicin (DNR) is an anthracyline antibiotic used in the treatment of a variety of human cancers. Reactive oxygen species (ROS) produced in the metabolism of DNR have severe cardiotoxicity which consequently compromises its clinical use as anticancer drug. This study aimed to investigate the effect of DNR administration on both cardiac and hepatic tissues, and the possible protective role of zinc on the cardiotoxicity and hepatotoxicity produced by DNR. Administration of 10 or 20 mg/kg DNR to Sprague-Dawley rats, increases serum creatine kinase activity, and blood troponin T levels (as cardiotoxicity indices), alanine aminotransferase activity (as hepatotoxicity index), as well as cardiac and hepatic 2-thiobarbituric acid reactive substances (as an index of lipid peroxidation). Treatment with 20 mg/kg Zn prior to DNR, dramatically induced metallothionein-1 (MT-1) mRNA and MT protein in both heart and liver while DNR alone induced MT, but to a much lower degree than Zn. The analysis of MT protein isoforms revealed that MT-1 was the form induced, while metallothionein-2 (MT-2) levels remained practically unchanged. The increases in both MT protein and MT-1 mRNA ran parallel with the reduction of cardiac and hepatic toxicities. Our results indicate that MT induction by Zn is a highly effective approach in preventing cardiotoxicity and hepatotoxicity caused by DNR. These animal data suggest the use of Zn to reduce DNR-induced cardiotoxicity and hepatotoxicity in the chemotherapy of cancer patients.

N-nitrososdimethylamine is activated in microsomes from hepatocytes to reactive metabolites which damage DNA of non-parenchymal cells in rat liver.

The liver carcinogen N-nitrosodimethylamine (NDMA) has to be metabolically activated by specific cytochromes before it can react with cellular macromolecules (e.g. proteins or DNA). Although hepatocytes are believed to be responsible for this activation, the liver tumours originate mainly from non-parenchymal cells (NPC). To investigate their activation capacity we determined NDMA-demethylase activity in isolated microsomes from both liver cell types. The results demonstrate that only hepatocytes have activation capacity. Additional experiments were performed with hepatocytes and NPC using the single cell microgel electrophoresis assay (MGE). DNA damage appears in both cell types following in vivo exposure. Tested in vitro, however, the carcinogens induce DNA damages only in hepatocytes (the cells which activate these compounds). N-nitroso-hydroxymethyl-methylamine could be the responsible metabolite as it is stable enough to be transported from hepatocytes to NPC in an intact liver.

Mechanisms of resistance to methotrexate in childhood acute lymphoblastic leukemia: circumvention of thymidylate synthase inhibition

Purpose: In about 25% of patients suffering from acute lymphoblastic leukemia (ALL) treatment failures occur that are most likely due to development of resistance to methotrexate (MTX). Blasts from patients with ALL were evaluated for MTX uptake, formation of long-chain MTX polyglutamates (MTX-Glu5+6), cytotoxicity and thymidylate synthase inhibition by MTX and compared to blasts from patients with acute myelogenous leukemia (AML). Methods: Radioactively labeled MTX-Glun were analyzed by means of HPLC. Thymidylate synthase activity was measured by a tritium-release assay. Cytotoxicity was determined by trypan blue exclusion. Results: In most ALL blasts (n = 9) large amounts of MTX-Glu5+6 (1.06–7.03 pmol/107cells) and high cytotoxicity (43.5%–92.7%) were found, while in others small amounts of MTX-Glu5+6 (0.0–0.39 pmol/107cells) caused only weak cytotoxicity (6.0%–27.9%) (n = 5, 2 relapsed patients). Resistance to MTX in blasts from AML patients (n = 5) was also caused by reduced synthesis of MTX-Glu5+6 (0.0–0.42 pmol/107cells). In contrast, some ALL blasts (n = 7, 4 relapsed patients) were able to survive MTX treatment despite large amounts of MTX-Glu5+6 (1.5–5.05 pmol/107cells) and extensive thymidylate synthase inhibition. Conclusions: Since the majority of ALL patients were examined at first diagnosis, an inherent mechanism of resistance seems most likely. We propose a mechanism based on the switch of thymidylate synthesis to the salvage pathway.

Pesticide analysis in coffee leaves using a quick, easy, cheap, effective, rugged and safe approach and liquid chromatography tandem mass spectrometry: Optimization of the clean-up step☆

An analytical method using a quick, easy, cheap, effective, rugged and safe (QuEChERS) procedure for multi-residue determination of 52 pesticides in coffee leaf extractshas been developed and validated according to SANTE/11945/2015 guidelines. Different sorbent combinations for dispersive solid phase extraction (d-SPE) clean-up as well as dispersive liquid-liquid microextraction (DLLME) were tested. The relative standard deviations (RSDs) for the recovery of 87-94% of pesticides added to coffee leaf extracts,was ≤20% for samples spiked at concentrations up to 50ng*g-1 depending on the clean-up procedures. However, samples spiked with a 100ng*g-1 pesticide mixture gave RSDs>20% for most pesticides when d-SPE was carried out adding Supelclean ENVI-Carb 120/400. To explain this fact,the secondary metabolic profile was analyzed in all the extraction and clean-up procedures. Only in the clean-up procedure with the addition of Supel QuE Z-Sep+, does caffeine show a constant adsorption between blank and spiked samples. In other clean-up procedures, the amount of caffeine was higher in those samples spiked with pesticides. This indicates competition between caffeine and pesticides for adsorption to the sorbent. Addition of Supel QuE Z-Sep+ to the procedure revealed only a 32% matrix effect, whereas using PSA+ C18 the matrix effect was close to 97%. The process efficiency is up to 54% with the addition of Supel QuE Z-Sep+ and just up to 7% for the other clean-up procedures. The method was successfully tested in coffee leaves from different types of cultivars. Pesticides were not detected in organic coffee leaf extracts, but thiametoxan was clearly detected in 50% of coffee leaf extracts harvested from coffee trees grown under traditional conditions as determined by UHPLC-TOFMSLC/QqTOF-MS/MS.

Characterization and quantitation of the polyphenolic compounds detected in methanol extracts of Pistacia atlantica Desf. fruits from the Guelmim region of Morocco

HIGHLIGHTSTwenty seven polyphenols have been identified in fruits of Pistacia atlantica Desf.Major polyphenol classes are gallates, flavonoids and ellagic acid derivatives.Pentagallate, luteolin and ellagic acid are predominant in these classes.Twenty four polyphenols in Pistacia atlantica Desf are described for the first time. ABSTRACT High performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC‐ESI–MS) was used for the identification of the major phenolic compounds in mature P. atlantica fruits from the Guelmim region (southeast of Morocco). In this study twenty seven polyphenolic compounds are identified and quantitated. To date, this is the most comprehensive report on the polyphenolic content of Pistacia fruits. The profiles comprise, three major polyphenolic classes, namely gallates (18.76 g/kg; 63.92%), flavonoids (10.12 g/kg; 34.48%) and ellagic acid derivatives (0.47 g/kg; 1.60%) with a total of 29.35 g/kg detected. The major gallate was pentagalloyl glucoside (5.0 g/kg; 17.04% of total polyphenolics), the major flavonoid luteolin (3.18 g/kg; 10.83% of total polyphenolics) and the major ellagic acid derivative ellagic acid (0.25 g/kg; 0.85% of total polyphenolics). Identification of galloyl quinate, digalloyl quinates (x 2), galloyl glucoside, digalloyl glucosides (x 2), trigalloyl glucoside, tetragalloyl glucosides (x 2), pentagalloyl glucoside, 2″‐O‐galloyl‐quercetin‐3‐O‐galactoside, quercetin‐3‐O‐rhamnogalactoside, quercetin‐3‐O‐galactoside, ellagic acid diglucoside, luteolin‐4′‐O‐glucoside, 2″‐O‐galloyl‐luteolin‐4′‐O‐glucoside, quercetin‐3‐O‐glucuronide, kaempferol‐3‐O‐glucoside, eriodictyol, apigenin, ellagic acid diglucoside, ellagic acid glucoside, methyl ellagic acid glucoside, and ellagic acid are described as phytochemical components of Pistacia fruits for the first time.

Comparison of the major polyphenols in mature Argan fruits from two regions of Morocco

Previous studies have shown that Argan fruits contain a large variety of polyphenolic compounds. Recently, another class of polyphenolic compounds, namely amino phenols have been detected and identified in immature Argan fruits. The objective of this study, was to establish whether or not, these novel compounds are also present in mature Argan fruits. To this end, a comparison was made between mature fruits from two regions of Morocco. Nineteen major compounds were identified and quantitated, including amino phenols, flavonoids, and phenolic acids by chromatographic methods in mature Argan fruits from the two regions of Morocco (Essaouira and Agadir). The phenolic acids were identified as gallic acid and 3,4-dihydroxybenzoic acid; the amino phenols as Arganimide A, and argaminolics A-C, and the flavonoids as rutin pentoside, quercetin-3-O-arabinoside, quercetin glycogallate, quercetin-3-O-rhamnogalactoside, rutin, quercetin-3-O-galactoside (hyperoside), quercetin-3-O-glucoside (quercitrin), quercetin-3-O-arabinoside, quercetin glycohydroxybenzoate, quercetin glycosinapate, quercetin glycoferulate, quercetin glycocoumarate and quercetin. n=145.

Ethnobotanic, Ethnopharmacologic Aspects and New Phytochemical Insights into Moroccan Argan Fruits

This review summarizes available data on argan fruit botany, geographical distribution, traditional uses, environmental interest, socioeconomic role, phytochemistry, as well as health beneficial effects and examination of future prospects. In particular, ethnomedical uses of argan fruits are carried out throughout Morocco where it has been used against various diseases. Different classes of bioactive compounds have been characterized including essential oils, fatty acids, triacylglycerols, flavonoids and their newly reported acylglycosyl derivatives, monophenols, phenolic acids, cinnamic acids, saponins, triterpenes, phytosterols, ubiquinone, melatonin, new aminophenols along with vitamin E among other secondary metabolites. The latter have already shown a wide spectrum of in vitro, and ex vivo biologicalactivities including antioxidant, anti-inflammatory, anti-diabetic, antihypertensive, anti-hypercholesterolemia, analgesic, antimicrobial, molluscicidal anti-nociceptive and anticancer potential. Argan flesh (pulp) contains a broad spectrum of polyphenolic compounds which may have utility for incorporation into nutraceuticals and cosmeceuticals relevant to the food, cosmetic and health industries. Further research is recommended, especially on the health beneficial effects of the aminophenols.