Effect of hydroxy substituent on the prooxidant action of naphthoquinone compounds

doi:10.1016/j.tiv.2009.11.018

Toxicology in Vitro

Volume 24, Issue 3, April 2010, Pages 905-909

https://doi.org/10.1016/j.tiv.2009.11.018 Get rights and content

Abstract

Prooxidant activity of naphthoquinone compounds was analyzed by lipid peroxidation, and the formation of base adduct in DNA. Naphthoquinones with electron-repelling hydroxyl group in the benzene moiety such as juglone and shikonin of lower concentrations stimulated the microsomal lipid peroxidation, but lawsone and lapachol with hydroxyl group in the quinone moiety did not enhance the formation of lipid peroxides. Naphthoquinone-dependent lipid peroxidation was closely related to the enhancement of Fe²⁺ autooxidation. Treatment of DNA with juglone a representative of 5-hydroxylated naphthoquinone stimulated the formation of 8-hydroxy-2′-deoxyguanosine, whereas lawsone and lapachol showed negligible formation of DNA base adduct. ESR spectra showed that juglone can form semiquinone radical in the presence of ferrous ion, but lawsone cannot. Biological toxicity of juglone with the potent electron-repelling group at 5-position may be due to the reactive oxygen species formed by semiquinone radical, but naphthoquinone compounds with an electron-repelling group in the quinone moiety, lawsone shows weak toxicity with only a little ability producing reactive oxygen species by the negligible formation of semiquinone.

Introduction

Naphthoquinone compounds, widely distributed in plants have pharmacological and toxicological importance, and are often used as cancer chemotherapeutic drugs, antimalarials, antibacterial agents and fungicides (O’Brien, 1991, Monks et al., 1992). Cytotoxic action of naphthoquinones varies depending on the structure of the compounds: juglone, 5-hydroxy-1,4-naphthoquinone causes cell death of some types of cells, whereas lawsone, 2-hydroxy-1,4-napthoquinone shows little or no cytotoxicity (Kumbhar et al., 1996) (Fig. 1). These cytotoxic effects have been explained by the decrease in glutathione due to the enzymatic redox cycling of naphthoquinones (Ross et al., 1986, Öllinger and Brunmark, 1991), and by the formation of adducts to DNA and protein (Rossi et al., 1986). In the present work, we analyzed the direct prooxidant action of naphthoquinone compounds with a focus on the lipid peroxidation, and the formation of DNA base adduct, 8-hydroxy-2′-deoxyguanosine. Prooxidant properties of naphthoquinones were closely related to the enhancement of autooxidation of reduced iron. Juglone with the electron-repelling hydroxyl group in the benzene moiety was suggested to form semiquinone radical causing potent oxidative damage of DNA and lipids, whereas naphthoquinones with hydroxyl group in the quinone moiety showed a weak cytotoxicity that was ascribed to the reduction of transition metals forming oxygen radicals.

Section snippets

Materials

Juglone, plumbagin, shikonin, menadione, lawsone, lapachol, DMPO (5,5′-dimethyl-1-pyrroline N-oxide), 8-hydroxy-2′-deoxyguanosine, enzymes for DNA hydrolysis, and bathophenanthroline disulfonate were obtained from Sigma–Aldrich Chemicals (Tokyo, Japan). NADP-Isocitrate dehydrogenase is a product of Oriental Yeast Co. (Osaka, Japan). Other chemicals were obtained from commercial sources.

Lipid peroxidation of liver microsomes

Microsomes were prepared from the livers of adult male rats by standard differential centrifugation techniques

Effect of napththoquinone compounds on the microsomal lipid peroxidation

We examined the effect of naphthoquinone compounds (Fig. 1) on the lipid peroxidation of microsomes from rat liver (Fig. 2). Naphthoquinone compounds with 5-hydroxyl group enhanced lipid peroxidation. Juglone and shikonin of lower concentration markedly increased the thiobarbituric acid-reactive substances as a marker of lipid peroxidation, but these compounds of higher concentrations rather tended to decrease the formation of thiobarbituric acid-reactive substances. Plumbagin at its higher

Discussion

Quinones are widely distributed in nature and play an essential biological role in mitochondrial respiration and photosynthesis. Some quinone compounds such as benzoquinone and naphthoquinones show potent cytotoxic and anti-proliferative effects on various cells and organisms (Öllinger and Brunmark, 1991, Kumbhar et al., 1996, Inbaraj and Chignell, 2004), and have been used for topical treatment of certain diseases (O’Brien, 1991, Monks et al., 1992). Quinone toxicity has been studied

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Impact of cytotoxic plant naphthoquinones, juglone, plumbagin, lawsone and 2-methoxy-1,4-naphthoquinone, on Chlamydomonas reinhardtii reveals the biochemical mechanism of juglone toxicity by rapid depletion of plastoquinol
2023, Plant Physiology and Biochemistry
Hydrophilic, untethered 1,4-naphthoquinones (1,4-NQs) are plant secondary metabolites that are often excreted into the environment and play a role in various plant–microbial, plant–fungal, plant–insect and plant–plant interactions. The biological activity of 1,4-NQs is mainly related to their redox properties, i.e. the ability to undergo redox cycling in cells. These compounds may also undergo electrophilic addition to thiol-containing compounds. The aim of this study was to compare the impact of juglone, plumbagin, lawsone and 2-methoxy-1,4-naphthoquinone (2-met-NQ) on the antioxidant response of the green microalga Chlamydomonas reinhardtii. The algae were incubated with the examined compounds under low light for 6 h and the content of photosynthetic pigments, prenyllipid antioxidants, ascorbate, soluble thiols, proline, and superoxide dismutase activity was assessed. To examine the interaction between photosynthetic activity and naphthoquinone toxicity, we carried out the second experiment, in which C. reinhardtii was incubated with 1,4-NQs for 1 h under high light or in darkness. The pro-oxidant action of the examined 1,4-NQs depended on their reduction potentials, which decrease in order: juglone > plumbagin > 2-met-NQ > lawsone. Lawsone did not display pro-oxidant properties. Exposure to high light strongly enhanced the pro-oxidant effect of juglone, plumbagin, and 2-met-NQ, which is thought to result from the interception of the electrons from photosynthetic electron transfer chain. Only juglone was able to cause a fast depletion of plastoquinol, which may be an important mode of action of this allelochemical, responsible for its high toxicity to plants.
Reactivities of 1,2-, 1,3-, and 1,4-dihydroxynaphthalenes toward electrogenerated superoxide in N,N-dimethylformamide through proton-coupled electron transfer
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Conversely, members of this family of compounds also include harmful environmental contaminants. The harmful effects of H2NQ on living organisms are thought to be due to cytotoxicity and at the same time to be related to antitumor activities [5–9]. These diverse reactivities are mainly caused by the redox activities of naphthoquinone (NQ), oxidized form of 1,n-dihydroxynaphthalenes (1nH2NQ, n = 2, 3, 4) having two OHs on the same ring.
We have carried out an electrochemical and theoretical study on the reactivity of 1,2-, 1,3-, and 1,4-dihydroxynaphthalenes (1nH₂NQ, n = 2, 3, 4) toward electrogenerated superoxide radical anion (O₂^•−) in N,N-dimethylformamide. Cyclicvoltammetry and in situ electrolytic electron spin resonance measurements revealed that the quinone–hydroquinone π-conjugation plays an important role in a successful O₂^•− scavenging by 12H₂NQ and 14H₂NQ through proton-coupled electron transfer (PCET) reaction. The reactivities of 12H₂NQ and 14H₂NQ toward O₂^•− were mediated by the ortho- (catechol) or para-diphenol (hydroquinone) moieties, as experimentally confirmed in comparative analyses with catechol, hydroquinone, and 13H₂NQ, aided by density functional theory (DFT) calculations. The electrochemical and DFT results suggested that a concerted PCET mechanism involving two-proton transfers and one-electron transfer proceeds, demonstrating a successful O₂^•− scavenging by 12H₂NQ and 14H₂NQ. Furthermore, a subsequent electron transfer between molecular dioxygen and product-naphthoquinone-radicals was observed, where O₂^•− was regenerated. The DFT analysis suggested that the spin distribution on the planar naphthalene ring embodies the superior kinetics of the PCET and the subsequent generation of O₂^•− from dioxygen demonstrated in the electrochemical results.
Synthesis, molecular docking, and biological activity of thioether derived from juglone in preclinical models of chronic myeloid leukemia
2021, Computational Toxicology
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Several studies show that the presence of hydroxyl groups at the C-5 or C-8 positions of the aromatic ring provides greater efficiency in the redox cycle, thus inducing a higher toxic effect on the cells [25]. Yoshino and co-workers [26] revealed that juglone with a hydroxyl group in the benzene moiety induced lipid peroxidation and caused potent DNA damage. DNA topoisomerase I (TOP1) enzyme regulates DNA topology by transiently cleaving and replicating DNA strands and performs catalytic functions during replication and transcription [27].
In this work, 16 new thio-1,4-naphthoquinones were synthesized, and their antiproliferative effects against tumor cell lines SK-MEL-19, AGP-01, ACP-02, HL-60, K-562, K-562-Lucena-1, FEPS, and non-neoplastic human fibroblast MRC-5, were examined. The compounds were selective active against leukemia cell lines. Based on the screening results for cytotoxic activity, naphthoquinone 11a showed higher cytotoxicity on the chemoresistant leukemia (FEPS) cell line when compared to the chemosensitive (K-562) cell line. Moreover, naphthoquinone 11a presented excellent ADME/T and did not violate Lipinski’s rule of five, indicating good oral absorption. Target prediction revealed DNA topoisomerase I (TOP1) as a possible target of 11a. The molecular docking prediction showed an − 11.94 kcal/mol binding affinity interaction of 11a with TOP1, involving three hydrogen bonds to ARG364, A113, and G11 from the active site of the enzyme. In addition, naphthoquinone 11a significantly suppressed the expression of the TOP1 gene in K-562 and FEPS leukemia cell lines. The naphthoquinone 11a induced significant changes in cell morphology, demonstrating cell and nuclear shrinkage, blebbing formation as well and fragmentation of the cell into apoptotic bodies. Thus, 11a could be a drug that leads to a new set of TOP1 major inhibitors. In summary, the present study showed a cytotoxic effect of 11a against chemoresistant and chemosensitive leukemia cell lines with TOP1 as a possible target.
Details in the catalytic mechanism of mammalian thioredoxin reductase 1 revealed using point mutations and juglone-coupled enzyme activities
2016, Free Radical Biology and Medicine
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This finding would be compatible with the idea of a “guiding bar” indeed assisting movement and access of the C-terminus of the enzyme to the dithiol/FAD site of the N-terminal domain and, furthermore, that such access is important for the activity of the enzyme when coupled to juglone. It is well known that juglone is a highly cytotoxic compound, with the mechanisms of cytotoxicity involving increased oxidative stress and redox cycling processes with both one- and two-electron transfer reactions [55–57]. It was also shown that targeting of TrxR1 and Sec-compromised forms of the enzyme may underpin several of these reactions with juglone [24–26,53].
The mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a key enzyme in redox regulation, antioxidant defense, and cellular growth. TrxR1 can catalyze efficient reduction of juglone (5-hydroxy-1,4-naphthoquinone; walnut toxin) in a reaction which, in contrast to reduction of most other substrates of TrxR1, is not dependent upon an intact selenocysteine (Sec, U) residue of the enzyme. Using a number of TrxR1 mutant variants, we here found that a sole Cys residue at the C-terminal tail of TrxR1 is required for high-efficiency juglone-coupled NADPH oxidase activity of Sec-deficient enzyme, occurring with mixed one- and two-electron reactions producing superoxide. The activity also utilizes the FAD and the N-terminal redox active disulfide/dithiol motif of TrxR1. If a sole Cys residue at the C-terminal tail of TrxR1, in the absence of Sec, was moved further towards the C-terminal end of the protein compared to its natural position at residue 497, juglone reduction was, surprisingly, further increased. Ala substitutions of Trp407, Asn418 and Asn419 in a previously described “guiding bar”, thought to mediate interactions of the C-terminal tail of TrxR1 with the FAD/dithiol site at the N-terminal domain of the other subunit in the dimeric enzyme, lowered turnover with juglone about 4.5-fold. Four residues of Sec-deficient TrxR1 were found to be easily arylated by juglone, including the Cys residue at position 497. Based upon our observations we suggest a model for involvement of the juglone-arylated C-terminal motif of TrxR1 to explain its high activity with juglone. This study thus provides novel insights into the catalytic mechanisms of TrxR1. One-electron juglone reduction by TrxR1 producing superoxide should furthermore contribute to the well-known prooxidant cytotoxicity of juglone.
Redox Properties, Bioactivity and Health Effects of Indicaxanthin, a Bioavailable Phytochemical from Opuntia ficus indica, L.: A Critical Review of Accumulated Evidence and Perspectives
2022, Antioxidants
Functional Group Transformation in Naphthoquinones: Strategies for the Synthesis of Mono-and Bis(Amino-1,4-Naphthoquinones)
2021, Current Organic Chemistry

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Effect of hydroxy substituent on the prooxidant action of naphthoquinone compounds

Abstract

Introduction

Section snippets

Materials

Lipid peroxidation of liver microsomes

Effect of napththoquinone compounds on the microsomal lipid peroxidation

Discussion

Methods in Enzymology

Biochemical and Biophysical Research Communications

Journal of Biological Chemistry

Archives of Biochemistry and Biophysics

Toxicology and Applied Pharmacology

Chemico-Biological Interactions

Journal of Biological Chemistry

Biochimica et Biophysica Acta