Novel o-naphthoquinones induce apoptosis of EL-4 T lymphoma cells through the increase of reactive oxygen species

Anticancer Potential of Resveratrol, β-Lapachone and Their Analogues

This review aims to explore the potential of resveratrol, a polyphenol stilbene, and beta-lapachone, a naphthoquinone, as well as their derivatives, in the development of new drug candidates for cancer. A brief history of these compounds is reviewed along with their potential effects and mechanisms of action and the most recent attempts to improve their bioavailability and potency against different types of cancer.

Oxidative Stress Produced by Hyperthyroidism Status Induces the Antioxidant Enzyme Transcription through the Activation of the Nrf-2 Factor in Lymphoid Tissues of Balb/c Mice

Hyperthyroidism is an endocrine disorder characterized by excessive secretion of thyroid hormones T3 and T4. Thyroid hormones exert pleiotropic actions on numerous tissues and induce an overall increase in metabolism, with an increase in energy demand and oxygen consumption. Therefore, the purpose of this study was to investigate the effects of hyperthyroidism on the production of reactive oxygen species (ROS) in lymph node and spleen cells of euthyroid and hyperthyroid mice, analyzing antioxidant mechanisms involved in the restitution of the cellular redox state. For this, thirty female Balb/c (H-2d) mice were randomly divided into two groups: euthyroid (by treatment with placebo) and hyperthyroid (by treatment with 12 mg/l of T4 in drinking water for 30 days). We found a significant increase in ROS and an increase in the genomic and protein expression of the antioxidant enzymes catalase (CAT) and glutathione peroxidase-1 (GPx-1) in lymph node and spleen cells of hyperthyroid mice. In vitro treatment with H₂O₂ (250 μM) of the lymphoid cells of euthyroid mice increased the expression levels of CAT and GPx-1. The hyperthyroidism increased the phosphorylation levels of Nrf2 (nuclear factor erythroid 2-related factor) and the kinase activity of protein kinase C (PKC) and extracellular signal-regulated kinase (ERK). Additionally, we found an increase in the expression of the classic isoenzymes of PKCα, β and γ. In conclusion, these results indicated that the increase in ROS found in the hyperthyroid state induces the antioxidant enzyme transcription through the activation of the Nrf-2 factor in lymphoid tissues. This shows the influence of hyperthyroidism on the regulation of the cellular antioxidant system.

Effects of a novel β-lapachone derivative on Trypanosoma cruzi: Parasite death involving apoptosis, autophagy and necrosis

Natural products comprise valuable sources for new antiparasitic drugs. Here we tested the effects of a novel β-lapachone derivative on Trypanosoma cruzi parasite survival and proliferation and used microscopy and cytometry techniques to approach the mechanism(s) underlying parasite death. The selectivity index determination indicate that the compound trypanocidal activity was over ten-fold more cytotoxic to epimastigotes than to macrophages or splenocytes. Scanning electron microscopy analysis revealed that the R72 β-lapachone derivative affected the T. cruzi morphology and surface topography. General plasma membrane waving and blebbing particularly on the cytostome region were observed in the R72-treated parasites. Transmission electron microscopy observations confirmed the surface damage at the cytostome opening vicinity. We also observed ultrastructural evidence of the autophagic mechanism termed macroautophagy. Some of the autophagosomes involved large portions of the parasite cytoplasm and their fusion/confluence may lead to necrotic parasite death. The remarkably enhanced frequency of autophagy triggering was confirmed by quantitating monodansylcadaverine labeling. Some cells displayed evidence of chromatin pycnosis and nuclear fragmentation were detected. This latter phenomenon was also indicated by DAPI staining of R72-treated cells. The apoptotis induction was suggested to take place in circa one-third of the parasites assessed by annexin V labeling measured by flow cytometry. TUNEL staining corroborated the apoptosis induction. Propidium iodide labeling indicate that at least 10% of the R72-treated parasites suffered necrosis within 24 h. The present data indicate that the β-lapachone derivative R72 selectively triggers T. cruzi cell death, involving both apoptosis and autophagy-induced necrosis.

Reactive Oxygen Species Regulate T Cell Immune Response in the Tumor Microenvironment

Reactive oxygen species (ROS) produced by cellular metabolism play an important role as signaling messengers in immune system. ROS elevated in the tumor microenvironment are associated with tumor-induced immunosuppression. T cell-based therapy has been recently approved to be effective for cancer treatment. However, T cells often become dysfunctional after reaching the tumor site. It has been reported that ROS participate extensively in T cells activation, apoptosis, and hyporesponsiveness. The sensitivity of T cells to ROS varies among different subsets. ROS can be regulated by cytokines, amino acid metabolism, and enzymatic activity. Immunosuppressive cells accumulate in the tumor microenvironment and induce apoptosis and functional suppression of T cells by producing ROS. Thus, modulating the level of ROS may be important to prolong survival of T cells and enhance their antitumor function. Combining T cell-based therapy with antioxidant treatment such as administration of ROS scavenger should be considered as a promising strategy in cancer treatment, aiming to improve antitumor T cells immunity.

Polyphenol-Rich Fraction from Larrea divaricata and its Main Flavonoid Quercetin-3-Methyl Ether Induce Apoptosis in Lymphoma Cells Through Nitrosative Stress

Larrea divaricata is a plant with antiproliferative principles. We have previously identified the flavonoid quercetin-3-methyl ether (Q-3-ME) in an ethyl acetate fraction (EA). Both the extract and Q-3-ME were found to be effective against the EL-4 T lymphoma cell line. However, the mechanism underlying the inhibition of tumor cell proliferation remains to be elucidated. In this work, we analyzed the role of nitric oxide (NO) in the induction of apoptosis mediated by Q-3-ME and EA. Both treatments were able to induce apoptosis in a concentration-dependent and time-dependent manner. The western blot analysis revealed a sequential activation of caspases-9 and 3, followed by poly-(ADP-ribose)-polymerase cleavage. EA and Q-3-ME lowered the mitochondrial membrane potential, showing the activation of the intrinsic pathway of apoptosis. Q-3-ME and EA increased NO production and inducible NO synthase expression in tumor cells. The involvement of NO in cell death was confirmed by the nitric oxide synthases inhibitor L-NAME. In addition, EA and Q-3-ME induced a cell cycle arrest in G0/G1 phase. These drugs did not affect normal cell viability. This data suggested that EA and Q-3-ME induce an increase in NO production that would lead to the cell cycle arrest and the activation of the intrinsic pathway of apoptosis. Copyright © 2016 John Wiley & Sons, Ltd.

Polychlorinated Biphenyl Quinone Metabolite Promotes p53-Dependent DNA Damage Checkpoint Activation, S-Phase Cycle Arrest and Extrinsic Apoptosis in Human Liver Hepatocellular Carcinoma HepG2 Cells

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants. The toxic behavior and mechanism of PCBs individuals and congeners have been extensively investigated. However, there is only limited information on their metabolites. Our previous studies have shown that a synthetic PCB metabolite, PCB29-pQ, causes oxidative damage with the evidence of cytotoxicity, genotoxicity, and mitochondrial-derived intrinsic apoptosis. Here, we investigate the effects of PCB29-pQ on DNA damage checkpoint activation, cell cycle arrest, and death receptor-related extrinsic apoptosis in human liver hepatocellular carcinoma HepG2 cells. Our results illustrate that PCB29-pQ increases the S-phase cell population by down-regulating cyclins A/D1/E, cyclin-dependent kinases (CDK 2/4/6), and cell division cycle 25A (CDC25A) and up-regulating p21/p27 protein expressions. PCB29-pQ also induces apoptosis via the up-regulation of Fas/FasL and the activation of caspase 8/3. Moreover, p53 plays a pivotal role in PCB29-pQ-induced cell cycle arrest and apoptosis via the activation of ATM/Chk2 and ATR/Chk1 checkpoints. Cell cycle arrest and apoptotic cell death were attenuated by the pretreatment with antioxidant N-acetyl-cysteine (NAC). Taken together, these results demonstrate that PCB29-pQ induces oxidative stress and promotes p53-dependent DNA damage checkpoint activation, S-phase cycle arrest, and extrinsic apoptosis in HepG2 cells.

Combinative effects of β-Lapachone and APO866 on pancreatic cancer cell death through reactive oxygen species production and PARP-1 activation

Pancreatic cancer (PC) is one of the most lethal human malignancies and a major health problem. Patients diagnosed with PC and treated with conventional approaches have an overall 5-year survival rate of less than 5%. Novel strategies are needed to treat this disease. Herein, we propose a combinatorial strategy that targets two unrelated metabolic enzymes overexpressed in PC cells:

NAD(P)H

quinone oxidoreductase-1 (NQO1) and nicotinamide phosphoribosyl transferase (NAMPT) using β-lapachone (BL) and APO866, respectively. We show that BL tremendously enhances the antitumor activity of APO866 on various PC cell lines without affecting normal cells, in a PARP-1 dependent manner. The chemopotentiation of APO866 with BL was characterized by the following: (i) nicotinamide adenine dinucleotide (NAD) depletion; (ii) catalase (CAT) degradation; (iii) excessive H2O2 production; (iv) dramatic drop of mitochondrial membrane potential (MMP); and finally (v) autophagic-associated cell death. H2O2 production, loss of MMP and cell death (but not NAD depletion) were abrogated by exogenous supplementation with CAT or pharmacological or genetic inhibition of PARP-1. Our data demonstrates that the combination of a non-lethal dose of BL and low dose of APO866 optimizes significantly cell death on various PC lines over both compounds given separately and open new and promising combination in PC therapy.

Sesquiterpene lactones from Ambrosia spp. are active against a murine lymphoma cell line by inducing apoptosis and cell cycle arrest

Sesquiterpene lactones (STLs) are natural terpenoid compounds. They have been recognized as antitumor agents. The purpose of this investigation was to explore the antiproliferative effects of psilostachyin, psilostachyin C, peruvin and cumanin on the murine lymphoma cell line BW5147. Cells were treated with the STLs at different concentrations. Tritiated thymidine uptake was employed to determine cell proliferation. MTT assay was used to analyze cell viability. Flow cytometry assay with annexin V-FITC and propidium iodide was employed to evaluate cell death. Reactive oxygen species (ROS), mitochondrial membrane potential and cell cycle analysis were also evaluated by flow cytometry. Antioxidant enzymes activities were determined spectrophotometrically by kinetic assays. Results showed that these STLs inhibited cell proliferation in a concentration-dependent manner by exerting cytotoxicity through apoptosis. Psilostachyin C was the most active and the less toxic compound. This STL induced apoptosis with an impairment in mitochondrial membrane potential. Psilostachyin C was able to induce ROS generation, related to a modulation of the antioxidant enzymes activity. In addition, it induced cell cycle arrest in S phase. In conclusion, psilostachyin C was found to be active against lymphoma cells exerting both cytostatic and cytotoxic effects. These findings may provide a novel approach for lymphoma treatment.

Antiproliferative and apoptosis inducing effect of essential oil extracted from Cyrtomium fortumei (J.) Smith leaves

Cyrtomium fortumei (J.) Smith is an endemic species in China, which has been proved to be an important Chinese herbal medicine. However, chemical composition and bioactivity of essential oil (EO) of C. fortumei (J.) Smith leaves remain unclear. In present study, we isolated EO from the plant by supercritical carbon dioxide extraction assay (SFE-CO₂), and investigated on cancer cells MGC-803, MCF-7, BGC-823, Bcap-37, A375, and A549 in vitro by MTT assay. 26 compounds were identified by GC–MS analysis, and the EO showed significant antitumor activities against MGC-803, Bcap-37, and A549 cancer cell lines (IC₅₀ values ranging from 0.15 to 0.24 mg/mL), and the activities of its main component were also studied. Subsequent fluorescence staining and flow cytometry analysis indicated that the EO could induce apoptosis in MGC-803, Bcap-37, and A549 cell lines, and the apoptosis ratios reached 26.44 % after 48 h of treatment at 0.15 mg/mL in MGC-803 cells. Caspase 3 activity in MGC-803 cells was also determined when the cells treated with the oil, and the activity of caspase 3 enzyme was increased compared to the control. This study suggests that the EO isolated from C. fortumei (J.) Smith could inhibit the growth of human carcinoma cells, and it could induce apoptosis of cancer cells.

A small library of synthetic di-substituted 1, 4-naphthoquinones induces ROS-mediated cell death in murine fibroblasts

Synthesis of compound libraries and their concurrent assessment as selective reagents for probing and modulating biological function continues to be an active area of chemical biology. Microwave-assisted solid-phase Dötz benzannulation reactions have been used to inexpensively synthesize 2, 3-disubstituted-1, 4-naphthoquinone derivatives. Herein, we report the biological testing of a small library of such compounds using a murine fibroblast cell line (L929). Assessment of cellular viability identified three categories of cytotoxic compounds: no toxicity, low/intermediate toxicity and high toxicity. Increased levels of Annexin-V-positive staining and of caspase 3 activity confirmed that low, intermediate, and highly toxic compounds promote cell death. The compounds varied in their ability to induce mitochondrial depolarization and formation of reactive oxygen species (ROS). Both cytotoxic and non-cytotoxic compounds triggered mitochondrial depolarization, while one highly cytotoxic compound did not. In addition, all cytotoxic compounds promoted increased intracellular ROS but the cells were only partially protected from compound-induced apoptosis when in the presence of superoxide dismutase, catalase, or ascorbic acid suggesting utilization of additional pro-death mechanisms. In summary, nine of twelve (75%) 1, 4-naphthoquinone synthetic compounds were cytotoxic. Although the mitochondria did not appear to be a central target for induction of cell death, all of the cytotoxic compounds induced ROS formation. Thus, the data demonstrate that the synthesis regime effectively created cytotoxic compounds highlighting the potential use of the regime and its products for the identification of biologically relevant reagents.

Potential of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones against Leishmania (L.) infantum: biological activity and structure-activity relationships

Naphtoquinones have been used as promising scaffolds for drug design studies against protozoan parasites. Considering the highly toxic and limited therapeutic arsenal, the global negligence with tropical diseases and the elevated prevalence of co-morbidities especially in developing countries, the parasitic diseases caused by various Leishmania species (leishmaniasis) became a significant public health threat in 98 countries. The aim of this work was the evaluation of antileishmanial in vitro potential of thirty-six 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones obtained by a three component reaction of lawsone, the appropriate aldehyde and thiols adequately substituted, exploiting the in situ generation of o-quinonemethides (o-QM) via the Knoevenagel condensation. The antileishmanial activity of the naphthoquinone derivatives was evaluated against promastigotes and intracellular amastigotes of Leishmania (Leishmania) infantum and their cytotoxicity was verified in mammalian cells. Among the thirty-six compounds, twenty-seven were effective against promastigotes, with IC₅₀ values ranging from 8 to 189 µM; fourteen compounds eliminated the intracellular amastigotes, with IC₅₀ values ranging from 12 to 65 µM. The compounds containing the phenyl groups at R₁ and R₂ and with the fluorine substituent at the phenyl ring at R₂, rendered the most promising activity, demonstrating a selectivity index higher than 15 against amastigotes. A QSAR (quantitative structure activity relationship) analysis yielded insights into general structural requirements for activity of most compounds in the series. Considering the in vitro antileishmanial potential of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones and their structure-activity relationships, novel lead candidates could be exploited in future drug design studies for leishmaniasis.