Induction of topoisomerase II-mediated DNA cleavage by the plant naphthoquinones plumbagin and shikonin

Abstract

Plumbagin and shikonin, plant metabolites which have naphthoquinone structures, induced mammalian topoisomerase II-mediated DNA cleavage in vitro. Treatment of a reaction mixture containing these naphthoquinones and topoisomerase II at an elevated temperature (65°C) resulted in a great reduction in DNA cleavage, suggesting that the mechanism of the topoisomerase II-mediated DNA cleavage induced by these naphthoquinones is through formation of a cleavable complex, as seen with antitumor agents such as 4'-(9-acridinylamino)methanesulfon-m-anisidide and demethylepipodophyllotoxin ethylidene-13-glucoside.Lawson and lapacol, which are structurally related plant metabolites with naphthoquinone moieties, could not induce topoisomerase U-mediated DNA cleavage. Plumbagin and shikonin induced a similar DNA cleavage pattern with topoisomerase II which was different from the cleavage patterns induced with other known topoisomerase II-active drugs. A DNA-unwinding assay with T4 DNA ligase showed that shikonin, lawson, and lapacol did not intercalate into DNA, while plumbagin and 2-methyl-1,4-naphthoquinone intercalate into DNA, but to a lower degree than 4'-(9-acridinylamino)methanesulfon-m-anisidide does.DNA topoisomerases are a class of enzymes that alter DNA conformation through a concerted breaking and rejoining of the DNA molecule, thereby controlling the topological state of DNA. They are reported to be involved in many important processes of DNA metabolism including replication, transcription, recombination, and chromosome segregation (38). In addition, topoisomerases have been potential targets for chemotherapy. Bacterial topoisomerase II (DNA gyrase) is well known as the primary target of quinolone antibacterial agents. Mammalian topoisomerase II has also been identified as the primary cellular target for a number of clinically important antitumor agents which include intercalating agents [e.g., 4'-(9-acridinylamino)methanesulfon-manisidide {m-AMSA}, adriamycin, and ellipticine] as well as nonintercalating agents (e.g., VP16 and VM26 [epipodophyllotoxin]) (6,29,34,35). All of these drugs trap topoisomerase II in an intermediary conformation with DNA, termed the "cleavable complex," which can be detected as DNA double-strand breaks upon treatment of the complex with protein denaturants. Structure-activity studies of a large number of acridine derivatives, epipodophyllotoxin congeners, and antitumor quinolones have shown a strong correlation between antitumor activity and the ability to induce the cleavable complex (23,31,39). In addition, there is now good evidence that mammalian topoisomerase I is the cellular target of camptothecin, an alkaloid with antitumor activity which was isolated from the Chinese tree Camptotheca acuminata. Camptothecin derivatives have shown promising activities in clinical studies (12,16 purified mammalian topoisomerases. We found that the plant naphthoquinones plumbagin and shikonin are potent inducers of the cleavable complex formation with topoisomerase II in vitro.In this report, we de...

Identification of a Molecular Activator for Insulin Receptor with Potent Anti-diabetic Effects

“…Most of these quinoids belong to DNA-intercalating agents (16,17). For instance, Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), derived from Plumbagineae and Droseraceae families, can induce mammalian topoisomerase II-mediated DNA cleavage in vitro (18). Therefore, they are effective anticancer agents against murine fibrosarcoma, P388 lymphocytic leukemia, and A549 non-small cell lung cancer cells (19 -21).…”

Cytotoxicity of synthesized 1,4-naphthoquinone analogues on selected human cancer cell lines

“…The cytotoxic effects of these quinones are mainly due to the inhibition of DNA topoisomerase -II. 1,2 Naphthoquinones are widely distributed in plants, fungi and some animals, and most of these are found to exhibit an interesting range of pharmacological properties. 1,4-Naphthoquinone is an important example of quinone family and is used as a raw material in pharmaceutical industries.…”

“…Recently, 1,4-Naphthoquinone derivatives were proved to be human DNA topoisomerase I and II inhibitors. 2 The presence of two carbonyl groups in naphthoquinones that have the ability to accept one or two electrons to form the corresponding radical anion or di-anion species and their acid-base properties is responsible for the various biological activities. 17,18 In another study, it was found that the presence of hydroxy groups at 5 and 8 positions, which facilitate the tautomerism in the structure of 1,4-naphthoquinone, reduced the electrophilicity of the naphthoquinone ring.…”

SH‐7, a new synthesized shikonin derivative, exerting its potent antitumor activities as a topoisomerase inhibitor

“…4 Shikonin is one of the active ingredients isolated from the roots of the traditional oriental medicinal herb Lithospermium erythrorhizon. 5 Many studies showed that shikonin exerted antitumor effects by inhibiting cancer cell growth, 6 inducing apoptosis 7 and inhibiting DNA topoisomerase I/II activity, [8][9][10] antitelomerase activity 11 and antiangiogenesis. 12 Because of its poor solubility and toxicity, shikonin have little potential to be an anticancer drug.…”