Emodin enhances arsenic trioxide-induced apoptosis via generation of reactive oxygen species and inhibition of survival signaling

Ursolic acid regulates key EMT transcription factors, induces cell cycle arrest and apoptosis in MDA-MB-231 and MCF-7 breast cancer cells, an in-vitro and in silico studies

Epithelial-mesenchymal transition (EMT) is a vital process in tumorigenesis and metastasis of breast cancer. In our quest to explore effective anticancer alternatives, ursolic acid (UA) was purified from Capparis zeylanica and investigated for its anticancer activity against MDA-MB-231 and MCF-7 breast cancer cells. The apparent anticancer activity of UA on MDA-MB-231 and MCF-7 cells was evident from IC50 values of 14.98 and 15.99 μg/mL, respectively, in MTT assay and also through enhanced generation of ROS. When MDA-MB-231 and MCF-7 cells were treated with 20 μg/mL UA, an absolute decrease in cell viability of 47.6% and 48.6%, enhancement of 1.35% and 1.10% in early apoptosis, and 21.90% and 21.35% in late apoptosis, respectively and G0 /G1 phase, S phase, G2 /M phase cell cycle arrest was noticed. The gene expression studies revealed that UA could significantly (p < 0.001) downregulate the expression of EMT markers such as snail, slug, and fibronectin at molecular level. Further, the obtained in vitro results of snail, slug, and fibronectin were subjected to quantum-polarized-ligand (QM/MM) docking, which predicted that the in silico binding affinities of these three markers are in good correlation with strong hydrogen and van der Waal interactions to UA with -53.865, -48.971 and -40.617 MMGBSA (ΔGbind ) scores, respectively. The long-range molecular dynamics (50 ns) simulations have showed more consistency by UA. These findings conclude that UA inhibits breast cancer cells growth and proliferation through regulating the expression of key EMT marker genes, and thus UA is suggested as a potential anticancer agent.

Targeting TRPV1 and TRPA1: A feasible strategy for natural herbal medicines to combat postoperative ileus

Under physiological or pathological conditions, transient receptor potential (TRP) channel vanilloid type 1 (TRPV1) and TRP ankyrin 1 (TRPA1) possess the ability to detect a vast array of stimuli and execute diverse functions. Interestingly, increasing works have reported that activation of TRPV1 and TRPA1 could also be beneficial for ameliorating postoperative ileus (POI). Increasing research has revealed that the gastrointestinal (GI) tract is rich in TRPV1/TRPA1, which can be stimulated by capsaicin, allicin and other compounds. This activation stimulates a variety of neurotransmitters, leading to increased intestinal motility and providing protective effects against GI injury. POI is the most common emergent complication following abdominal and pelvic surgery, and is characterized by postoperative bowel dysfunction, pain, and inflammatory responses. It is noteworthy that natural herbs are gradually gaining recognition as a potential therapeutic option for POI due to the lack of effective pharmacological interventions. Therefore, the focus of this paper is on the TRPV1/TRPA1 channel, and an analysis and summary of the processes and mechanism by which natural herbs activate TRPV1/TRPA1 to enhance GI motility and relieve pain are provided, which will lay the foundation for the development of natural herb treatments for this disease.

Arsenic trioxide-induced cytotoxicity in A549 cells: The role of necroptosis

INTRODUCTION

Lung cancer is one of the deadliest cancers globally. Arsenic trioxide (ATO) is still present as a highly effective drug in treating acute promyelocytic leukemia (APL). Chemotherapy resistance is one of the major problems in cancer therapy. Necroptosis, can overcomes resistance to apoptosis, and can promote cancer treatment. This study examines the necroptosis pathway in A549 cancer cells exposed to ATO.

METHODS

We used the MTT test to determine the ATO effects on the viability of A549 cells at three different time intervals. Also, the reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were performed in three-time intervals. The effect of ATO on apoptosis was evaluated by Annexin V / PI staining and, the RIPK1 and MLKL gene expression were measured by Real-Time PCR.

RESULTS

The ATO has dose and time-dependent cytotoxic effects, so at 24, 48, and 72 h, the IC50 doses were 33.81 '11.44 '2.535 µM respectively. A 50 μM ATO is the most appropriate to increase the MMP loss significantly at all three times. At 24 and 48 h after exposure of cells to ATO, the ROS levels increased. The RIPK1 gene expression increased significantly compared to the control group at concentrations of 50 and 100 μM; however, MLKL gene expression decreased.

CONCLUSIONS

The A549 cells, after 48 h exposure to ATO at 50 and 100 μM, induces apoptosis and necroptosis. Due to the reduced expression of MLKL, it can be concluded that ATO is probably effective in the metastatic stage of cancer cells.

A Novel Oxidative Stress-Related lncRNA Signature That Predicts the Prognosis and Tumor Immune Microenvironment of Breast Cancer

Background

The association between oxidative stress and lncRNAs within the cancer-related researching field has been a controversial subject. At present, the exact function of oxidative stress as well as lncRNAs exert in breast cancer (BC) are still unclear. Therefore, the present study examined the lncRNAs oxidative stress-related in BC.

Methods

Transcriptome data of BC obtained from TCGA (The Cancer Genome Atlas) database were used to generate synthetic matrices. Patients with breast cancer were randomly assigned to training, testing, or combined groups. The prognostic signature of oxidative stress was created using the selection operator Cox regression method, and the difference in prognosis between groups was examined using Kaplan-Meier curves, the accuracy of which was calculated using a receiver-operating characteristic-area through the curve (ROC-AUC) analysis with internal validation. Also, the Gene Set Enrichment Analyses (GSEA) was applied for the analysis of the risk groups. To conclude, the half-maximal inhibitory concentration (IC50) of these groups were investigated by immunoassay assay.

Results

A model based on 7 lncRNAs related to oxidative stress was proposed, and the calibration plots and projected prognosis matched well. For prognosis at 5, 3, and 1 year, the area under the ROC curve (AUC) values were 0.777, 0.777, and 0.759. The functions of target genes identified by GSEA appear to be mainly expressed in metabolism, signal transduction, tumorigenesis, and also the progression. The remarkable differences in IC50 and gene expression between risk groups in this study provide a deep insight for further systemic treatment. Higher macrophage scores were acquired in the high-risk group, of which patients showed more response to conventional chemotherapy drugs, such as AKT inhibitor VIII and Lapatinib, as well as immunotherapy strategies including anti-CD80, TNF SF4, CD276, and NRP1.

Conclusion

The prognosis of breast cancer can be independently predicted by the markers, which sheds light on further research of the specific role of lncRNAs which are oxidative stress-related and clinical treatment of breast cancer.

Phytochemicals as Potential Chemopreventive and Chemotherapeutic Agents for Emerging Human Papillomavirus-Driven Head and Neck Cancer: Current Evidence and Future Prospects

Head and neck cancer (HNC) usually arises from squamous cells of the upper aerodigestive tract that line the mucosal surface in the head and neck region. In India, HNC is common in males, and it is the sixth most common cancer globally. Conventionally, HNC attributes to the use of alcohol or chewing tobacco. Over the past four decades, portions of human papillomavirus (HPV)-positive HNC are increasing at an alarming rate. Identification based on the etiological factors and molecular signatures demonstrates that these neoplastic lesions belong to a distinct category that differs in pathological characteristics and therapeutic response. Slow development in HNC therapeutics has resulted in a low 5-year survival rate in the last two decades. Interestingly, HPV-positive HNC has shown better outcomes following conservative treatments and immunotherapies. This raises demand to have a pre-therapy assessment of HPV status to decide the treatment strategy. Moreover, there is no HPV-specific treatment for HPV-positive HNC patients. Accumulating evidence suggests that phytochemicals are promising leads against HNC and show potential as adjuvants to chemoradiotherapy in HNC. However, only a few of these phytochemicals target HPV. The aim of the present article was to collate data on various leading phytochemicals that have shown promising results in the prevention and treatment of HNC in general and HPV-driven HNC. The review explores the possibility of using these leads against HPV-positive tumors as some of the signaling pathways are common. The review also addresses various challenges in the field that prevent their use in clinical settings.

Is Emodin with Anticancer Effects Completely Innocent? Two Sides of the Coin

Many anticancer active compounds are known to have the capacity to destroy pathologically proliferating cancer cells in the body, as well as to destroy rapidly proliferating normal cells. Despite remarkable advances in cancer research over the past few decades, the inclusion of natural compounds in researches as potential drug candidates is becoming increasingly important. However, the perception that the natural is reliable is an issue that needs to be clarified. Among the various chemical classes of natural products, anthraquinones have many biological activities and have also been proven to exhibit a unique anticancer activity. Emodin, an anthraquinone derivative, is a natural compound found in the roots and rhizomes of many plants. The anticancer property of emodin, a broad-spectrum inhibitory agent of cancer cells, has been detailed in many biological pathways. In cancer cells, these molecular mechanisms consist of suppressing cell growth and proliferation through the attenuation of oncogenic growth signaling, such as protein kinase B (AKT), mitogen-activated protein kinase (MAPK), HER-2 tyrosine kinase, Wnt/-catenin, and phosphatidylinositol 3-kinase (PI3K). However, it is known that emodin, which shows toxicity to cancer cells, may cause kidney toxicity, hepatotoxicity, and reproductive toxicity especially at high doses and long-term use. At the same time, studies of emodin, which has poor oral bioavailability, to transform this disadvantage into an advantage with nano-carrier systems reveal that natural compounds are not always directly usable compounds. Consequently, this review aimed to shed light on the anti-proliferative and anti-carcinogenic properties of emodin, as well as its potential toxicities and the advantages of drug delivery systems on bioavailability.

Stable W/O/W multiple nanoemulsion encapsulating natural tocotrienols and caffeic acid with cisplatin synergistically treated cancer cell lines (A549 and HEP G2) and reduced toxicity on normal cell line (HEK 293)

This work aimed to evaluate the effects of encapsulated tocotrienols (TRF) and caffeic acid (CA) in water-in-oil-in-water (W/O/W) multiple nanoemulsion with cisplatin towards cancer cells. This work is important considering the limited efficacy of cisplatin due to tumour resistance, as well as its severe side effects. A549 and HEP G2 cancer cell lines were utilised for evaluating the efficacy of the encapsulated W/O/W while HEK 293 normal cell line was used for evaluating the toxicity. TRF, CA and CIS synergistically improved apoptosis in the late apoptotic phase in A549 and HEP G2 by 23.1% and 24.9%, respectively. The generation of ROS was enhanced using TRF:CA:CIS by 16.9% and 30.2% for A549 and HEP G2, respectively. Cell cycle analysis showed an enhanced cell arrest in the G0/G1 phase for both A549 and HEP G2. TRF, CA and CIS led to cell death in A549 and HEP G2. For HEK 293, ~33% cell viability was found when only CIS was used while >95% cell viability was observed when TRF, CA and CIS were used. This study demonstrates that the encapsulated TRF and CA in W/O/W with CIS synergistically improved therapeutic efficacy towards cancer cells, as well as lowered the toxicity effects towards normal cells.

Molecular Mechanisms of Action of Emodin: As an Anti-Cardiovascular Disease Drug

Emodin is a natural occurring anthraquinone derivative isolated from roots and barks of numerous plants, molds, and lichens. It is found to be an active ingredient in different Chinese herbs including Rheum palmatum and Polygonam multiflorum, and it is a pleiotropic molecule with diuretic, vasorelaxant, anti-bacterial, anti-viral, anti-ulcerogenic, anti-inflammatory, and anti-cancer effects. Moreover, emodin has also been shown to have a wide activity of anti-cardiovascular diseases. It is mainly involved in multiple molecular targets such as inflammatory, anti-apoptosis, anti-hypertrophy, anti-fibrosis, anti-oxidative damage, abnormal, and excessive proliferation of smooth muscle cells in cardiovascular diseases. As a new type of cardiovascular disease treatment drug, emodin has broad application prospects. However, a large amount of evidences detailing the effect of emodin on many signaling pathways and cellular functions in cardiovascular disease, the overall understanding of its mechanisms of action remains elusive. In addition, by describing the evidence of the effects of emodin in detail, the toxicity and poor oral bioavailability of mice have been continuously discovered. This review aims to describe a timely overview of emodin related to the treatment of cardiovascular disease. The emphasis is to summarize the pharmacological effects of emodin as an anti-cardiovascular drug, as well as the targets and its potential mechanisms. Furthermore, the treatment of emodin compared with conventional cardiovascular drugs or target inhibitors, the toxicity, pharmacokinetics and derivatives of emodin were discussed.

A natural flavonoid, apigenin isolated from Clerodendrum viscosum leaves, induces G2/M phase cell cycle arrest and apoptosis in MCF-7 cells through the regulation of p53 and caspase-cascade pathway

BACKGROUND

With 9.6 million deaths in 2018, cancer remains the second leading cause of death worldwide. Breast cancer is the most deadly type of cancer among females, with 55.2% of crude incidence rate and 16.6% of crude mortality rate.

PURPOSE

The present study was aimed to investigate the anti-breast cancer potential of natural dietary flavonoid, apigenin isolated from Clerodendrum viscosum leaves.

METHODS

Apigenin was evaluated for in-depth anticancer activity in MCF-7 cells using cell viability assay, cell cycle analysis, Annexin-V-FLUOS staining, ROS induction, morphological analysis, and western blot analysis.

RESULTS

Apigenin showed selective cytotoxicity on MCF-7 cells with an IC₅₀-56.72 ± 2.35 µM, while negligible cytotoxicity was observed on WI-38 cells. Further, the flow cytometer-based analysis showed that apigenin halted MCF-7 cells in the G2/M phase arrest followed by dose-dependent apoptosis. Moreover, the FACS and confocal microscopy results confirmed the elevation of intracellular ROS and nuclear fragmentation in apigenin-treated MCF-7 cells. Western blots showed up-regulation of cell cycle regulatory proteins, increased p53 expression, Bax/Bcl-2 ratio, activation of caspases, and cleavage of PARP. Finally, apigenin treatment in the presence of Pifithrin-µ showed decreased apoptotic population and it was further confirmed through western blotting study. The results revealed the vital role of p53 in apigenin-induced apoptosis in MCF-7 cells.

CONCLUSIONS

In the present findings, treatment of apigenin-induced intracellular ROS in MCF-7 cells followed by induction of G2/M phase cell cycle arrest and further apoptosis through the regulation of p53 and caspase-cascade signaling pathway.

Antinociceptive Effects of Emodin on CFA-Induced Inflammatory Pain in Rats

The effect of emodin on complete Freund’s adjuvant (CFA)-induced inflammatory pain in rats and its potential molecular mechanism was investigated. For this, a rat model of inflammatory pain induced by CFA was established and rats were treated with emodin by intraperitoneal injection. The pain threshold was evaluated by the von Frey, thermo hyperalgesia, and cold plate tests. The mRNA expression of transient receptor potential channel ankyrin type-1 ( Trpa1) and transient receptor potential vanilloid 1 ( Trpv1) was detected by quantitative reverse transcription polymerase chain reaction, and the level of inflammatory cytokines was determined by enzyme-linked immunosorbent assay. The mechanical and thermal pain thresholds of CFA-treated rats were significantly lower than those of the control rats, while the paw withdrawal responses in response to cold stimulation were higher than that of the control group. Emodin treatment significantly improved CFA-induced hyperalgesia. Further results showed that emodin inhibits the upregulation of Trpa1 and Trpv1 mRNA expression in the dorsal root ganglion (DRG) of rats with inflammatory pain compared with the control group. Emodin also significantly reduced the levels of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6) in the serum of rats with inflammatory pain. Thus, emodin may inhibit hyperalgesia induced by inflammatory stimulation by downregulating the mRNA expression of Trpa1 and Trpv1 in DRG neurons and reducing the levels of TNF-α, IL-1β, and IL-6.

L-Ascorbic Acid and α-Tocopherol Synergistically Triggers Apoptosis Inducing Antileukemic Effects of Arsenic Trioxide via Oxidative Stress in Human Acute Promyelocytic Leukemia Cells

Chemosensitization is an effective strategy to overcome the drawbacks of arsenic trioxide (As₂O₃) treatment, which may be possible through the use of dietary supplements in combination. The present investigation evaluates the synergistic mechanism of action of vitamins, such as L-ascorbic acid (L-AA) and α-tocopherol (α-TOC) in As₂O₃ chemotherapy using human leukemia (HL-60) cells. In vitro assays on the cytotoxicity of As₂O₃ and vitamins and cellular apoptotic evidences were done; a proteomic investigation with mass spectrometry was also performed. The combination of L-AA and α-TOC potentiates As₂O₃ cytotoxicity in HL-60 cells, substantiated by depletion in antioxidant status, mitochondrial transmembrane potential, and inhibition of nuclear factor erythroid 2-related factor 2 and B-cell lymphoma 2 transcription factors. Mass spectrometry results showed decreased expression of proteins regulating cell cycle and translation in cells treated with As₂O₃, L-AA, and α-TOC when compared with As₂O₃-treated sample. In addition, this combination treatment identified numerous proteins associated with apoptosis and cell stress. HL-60 cells became more prone to As₂O₃ on exposure to L-AA and α-TOC, indicating that this combination may be a promising approach to increase the outcome of As₂O₃ chemotherapy.

Targeting Reactive Oxygen Species in Cancer via Chinese Herbal Medicine

Recently, reactive oxygen species (ROS), a class of highly bioactive molecules, have been extensively studied in cancers. Cancer cells typically exhibit higher levels of basal ROS than normal cells, primarily due to their increased metabolism, oncogene activation, and mitochondrial dysfunction. This moderate increase in ROS levels facilitates cancer initiation, development, and progression; however, excessive ROS concentrations can lead to various types of cell death. Therefore, therapeutic strategies that either increase intracellular ROS to toxic levels or, conversely, decrease the levels of ROS may be effective in treating cancers via ROS regulation. Chinese herbal medicine (CHM) is a major type of natural medicine and has greatly contributed to human health. CHMs have been increasingly used for adjuvant clinical treatment of tumors. Although their mechanism of action is unclear, CHMs can execute a variety of anticancer effects by regulating intracellular ROS. In this review, we summarize the dual roles of ROS in cancers, present a comprehensive analysis of and update the role of CHM—especially its active compounds and ingredients—in the prevention and treatment of cancers via ROS regulation and emphasize precautions and strategies for the use of CHM in future research and clinical trials.

Combined treatment with emodin and a telomerase inhibitor induces significant telomere damage/dysfunction and cell death

G-quadruplex telomeric secondary structures represent natural replication fork barriers and must be resolved to permit efficient replication. Stabilization of telomeric G4 leads to telomere dysfunctions demonstrated by telomere shortening or damage, resulting in genome instability and apoptosis. Chemical compounds targeting G4 structures have been reported to induce telomere disturbance and tumor suppression. Here, virtual screening was performed in a natural compound library using PyRx to identify novel G4 ligands. Emodin was identified as one of the best candidates, showing a great G4-binding potential. Subsequently, we confirmed that emodin could stabilize G4 structures in vitro and trigger telomere dysfunctions including fragile telomeres, telomere loss, and telomeric DNA damage. However, this telomere disturbance could be rescued by subsequent elevation of telomerase activity; in contrast, when we treated the cells with the telomerase inhibitor BIBR1532 upon emodin treatment, permanent telomere disturbance and obvious growth inhibition of 4T1-cell xenograft tumors were observed in mice. Taken together, our results show for the first time that emodin-induced telomeric DNA damage can upregulate telomerase activity, which may weaken its anticancer effect. The combined use of emodin and the telomerase inhibitor synergistically induced telomere dysfunction and inhibited tumor generation.

Inhibition of Mitochondrial Complex Function-The Hepatotoxicity Mechanism of Emodin Based on Quantitative Proteomic Analyses

Emodin is the main component of traditional Chinese medicines including rhubarb, Polygonum multiflorum, and Polygonum cuspidatum. It has confirmed hepatotoxicity and may be the main causative agent of liver damage associated with the above-mentioned traditional Chinese medicines. However, current research does not explain the mechanism of emodin in hepatotoxicity. In this study, L02 cells were used as a model to study the mechanism of emodin-induced hepatocyte apoptosis using quantitative proteomics, and the results were verified by Western blot. A total of 662 differentially expressed proteins were discovered and analyzed using Gene Ontology (GO) and pathway enrichment analysis. The results show that the oxidative phosphorylation pathway is highly represented. Abnormalities in this pathway result in impaired mitochondrial function and represent mitochondrial damage. This result is consistent with mitochondria membrane potential measurements. Analysis of differentially expressed proteins revealed that emodin mainly affects oxidative phosphorylation pathways by inhibiting the function of the mitochondrial respiratory chain complexes; the mitochondrial respiratory chain complex activity assay result also confirmed that emodin could inhibit the activity of all mitochondrial complexes. This results in an increase in caspase-3, a decrease in mitochondrial membrane potential (MMP,) an increase in reactive oxygen species (ROS), and disorders in ATP synthesis, etc., eventually leading to mitochondrial damage and hepatocyte apoptosis in vitro.

A conjugated-polymer-based ratiometric nanoprobe for evaluating in-vivo hepatotoxicity induced by herbal medicine via MSOT imaging

Herbal medicines are widely used around the world, while some of them are associated with adverse effects like herb-induced liver injury due to oxidative/nitrosative stress resulted from hepatically-generated ROS/RNS. It is of significance to accurately evaluate herbal-medicine-induced hepatotoxicity, since it would help provide effective monitoring method of the safety of herbal remedies. Herein we designed a ratiometric nanoprobe for in vivo imaging hepatic injury induced by herbal medicine (polygonum multiflorum, PM) via specifically responding to NO generated in liver by PM, and with MSOT imaging the precise location of liver injury can be identified. The liposomal nanoprobe consists of a responsive dye (IX-2NH₂) which could specifically respond to NO and the diketopyrrolopyrrole-based conjugated polymer (DPP-TT) as the internal reference. Thus we can realize ratiometric optoacoustic detection of herbal-medicine-induced liver injury with 3D information in mouse model in a noninvasive way.

Evaluation of phyto-medicinal efficacy of thymoquinone against Arsenic induced mitochondrial dysfunction and cytotoxicity in SH-SY5Y cells

BACKGROUND

It is evaluated that a few million individuals worldwide are experiencing Arsenic (As) harmfulness coming about because of anthropogenic discharges. There is likewise proof to propose that As can affect the peripheral, as well as, the central nervous system (CNS). On the contrary, thymoquinone (TQ), a biologically active ingredient of Nigella sativa has exhibited numerous neuro-pharmacological traits since ancient times.

HYPOTHESIS/PURPOSE

In the present study, the neuroprotective efficacy of TQ was explored by primarily studying its antioxidant and anti-apoptotic potential against Arsenic trioxide (As₂O₃) induced toxicity in SH-SY5Y human neuroblastoma cell lines.

STUDY DESIGN

For experimentation, cells were seeded in 96 well tissue culture plates and kept undisturbed for 24 h to attain proper adhesion. After 75-80% confluence, cells were pretreated with 10 µM and 20 µM thymoquinone (TQ) for 1 h After adding 2 µM As, cells were set aside for incubation for 24 h without changing the medium.

METHODS

The mitigatory effects of TQ with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied.

RESULTS

Pretreatment of SH-SY5Y cells with TQ (10 and 20 μM) for an hour and subsequent exposure to 2 μM As₂O₃ protected the SH-SY5Y cells against the neuro-damaging effects of the latter. Also, the SH-SY5Y cells were better preserved with increased viability, repaired DNA, less free radical generation and balanced transmembrane potential than those exposed to As₂O₃ alone. TQ pretreatment also inhibited As₂O₃-induced exacerbation in protein levels of BAX and PARP-1 and restored the loss of Bcl₂ levels.

CONCLUSION

The findings of this study suggest that TQ may prevent neurotoxicity and As₂O₃-induced apoptosis and cytotoxicity. It is, therefore, worth studying further for its potential to reduce the risks of arsenic-related neurological implications.

Emodin induces liver injury by inhibiting the key enzymes of FADH/NADPH transport in rat liver

Emodin is a natural anthraquinone derivative that occurs in many Chinese medicinal herbs. It might induce liver damage, but the mechanism is not clear. In this research, seven groups of Sprague-Dawley (SD) rats with three doses of emodin were used. The liver injury was examined by analyzing biochemical indexes and histopathology. Altered proteins between the control group (CG) and the liver injury group were determined by proteomic technology. The results showed that emodin causes liver injury in a time- and dose-dependent manner. In the high-dosage 1-week group (HG1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was downregulated, and the activity of malate dehydrogenase (MDH) was inhibited by emodin. These might cause the inhibition of FADH or NADH/NADPH transport from the cytoplasm to mitochondria. The WB results showed that the inhibition of FADH/NADPH transport induced a high activity of caspase-9 and caspase-3, and the expressions of cytochrome c (Cyt C), caspase-9 and caspase-3 were high in HG1, which might lead to mitochondrial apoptosis pathway activation. In addition, whatever the HG1 or low-dose group (LG), the effects of emodin on mitochondria were observed. Overall, for the first time, we showed that emodin inhibited proton transport and induced the activation of the mitochondrial apoptosis pathway, which might be the reason for liver injury.

ROS modifiers and NOX4 affect the expression of the survivin-associated radio-adaptive response

The survivin-associated radio-adaptive response can be induced following exposure to ionizing radiation in the dose range from 5 to 100 mGy, and its magnitude of expression is dependent upon the TP53 mutational status of cells and ROS signaling. The purpose of the study was to investigate the potential role of ROS in the development of the survivin-associated adaptive response. Utilizing human colon carcinoma HCT116 TP53 wild type (WT) and HCT116 isogenic TP53 null mutant (Mut) cell cultures, the roles of inter- and intracellular ROS signaling on expression of the adaptive response as evidenced by changes in intracellular translocation of survivin measured by ELISA, and cell survival determined by a standard colony forming assay were investigated using ROS modifying agents that include emodin, N-acetyl-L-cysteine (NAC), fulvene-5, honokiol, metformin and rotenone. The role of NADPH oxidase 4 (NOX4) in the survivin-associated adaptive response was investigated by transfecting HCT116 cells, both WT and Mut, with two different NOX4 siRNA oligomers and Western blotting. A dose of 5 mGy or a 15 min exposure to 50 µM of the ROS producing drug emodin were equally effective in inducing a pro-survival adaptive response in TP53 WT and a radio-sensitization adaptive response in TP53 Mut HCT116 cells. Each response was associated with a corresponding translocation of survivin into the cytoplasm or nucleus, respectively. Exposure to 10 mM NAC completely inhibited both responses. Exposure to 10 µM honokiol induced responses similar to those observed following NAC exposure in TP53 WT and Mut cells. The mitochondrial complex 1 inhibitor rotenone was effective in reducing both cytoplasmic and nuclear survivin levels, but was ineffective in altering the expression of the adaptive response in either TP53 WT or Mut cells. In contrast, both metformin and fulvene-5, inhibitors of NOX4, facilitated the reversal of TP53 WT and Mut adaptive responses from pro-survival to radio-sensitization and vice versa, respectively. These changes were accompanied by corresponding reversals in the translocation of survivin to the nuclei of TP53 WT and to the cytoplasm of TP53 Mut cells. The potential role of NOX4 in the expression of the survivin-associated adaptive response was investigated by transfecting HCT116 cells with NOX4 siRNA oligomers to inhibit NOX4 expression. Under these conditions NOX4 expression was inhibited by about 50%, resulting in a reversal in the expression of the TP53 WT and Mut survivin-associated adaptive responses as was observed following metformin and fulvene-5 treatment. Exposure to 5 mGy resulted in enhanced NOX4 expression by about 40% in both TP53 WT and Mut cells, in contrast to only a 1-2% increase following a 2 Gy only exposure. Utilizing mixed cultures of HCT116 TP53 WT and isogenic null Mut cells, as few as 10% TP53 Mut cells were sufficient to control the expression of the remaining 90% WT cells and resulted in an overall radio-sensitization response accompanied by the nuclear translocation of survivin characteristic of homogeneous TP53 Mut populations.

Arsenic trioxide induces apoptosis and the formation of reactive oxygen species in rat glioma cells

Background

Arsenic trioxide (As₂O₃) has a dramatic therapeutic effect on acute promyelocytic leukemia (APL) patients. It can also cause apoptosis in various tumor cells. This study investigated whether As₂O₃ has an antitumor effect on glioma and explored the underlying mechanism.

Results

MTT and trypan blue assays showed that As₂O₃ remarkably inhibited growth of C6 and 9 L glioma cells. Cell viability decreased in glioma cells to a greater extent than in normal glia cells. The annexin V-FITC/PI and Hoechest/PI staining assays revealed a significant increase in apoptosis that correlated with the duration of As₂O₃ treatment and occurred in glioma cells to a greater extent than in normal glial cells. As₂O₃ treatment induced reactive oxygen species (ROS) production in C6 and 9 L cells in a time-dependent manner. Cells pretreated with the antioxidant N-acetylcysteine (NAC) showed significantly lower As₂O₃-induced ROS generation. As₂O₃ significantly inhibited the expression of the anti-apoptotic gene Bcl-2, and upregulated the proapoptotic gene Bax in both C6 and 9 L glioma cells in a time-dependent manner.

Conclusions

As₂O₃ can significantly inhibit the growth of glioma cells and it can induce cell apoptosis in a time- and concentration-dependent manner. ROS were found to be responsible for apoptosis in glioma cells induced by As₂O₃. These results suggest As₂O₃ is a promising agent for the treatment of glioma.

Environmental arsenic exposure: From genetic susceptibility to pathogenesis

More than 200 million people in 70 countries are exposed to arsenic through drinking water. Chronic exposure to this metalloid has been associated with the onset of many diseases, including cancer. Epidemiological evidence supports its carcinogenic potential, however, detailed molecular mechanisms remain to be elucidated. Despite the global magnitude of this problem, not all individuals face the same risk. Susceptibility to the toxic effects of arsenic is influenced by alterations in genes involved in arsenic metabolism, as well as biological factors, such as age, gender and nutrition. Moreover, chronic arsenic exposure results in several genotoxic and epigenetic alterations tightly associated with the arsenic biotransformation process, resulting in an increased cancer risk. In this review, we: 1) review the roles of inter-individual DNA-level variations influencing the susceptibility to arsenic-induced carcinogenesis; 2) discuss the contribution of arsenic biotransformation to cancer initiation; 3) provide insights into emerging research areas and the challenges in the field; and 4) compile a resource of publicly available arsenic-related DNA-level variations, transcriptome and methylation data. Understanding the molecular mechanisms of arsenic exposure and its subsequent health effects will support efforts to reduce the worldwide health burden and encourage the development of strategies for managing arsenic-related diseases in the era of personalized medicine.

Dual Roles of Oxidative Stress in Metal Carcinogenesis

It has been well established that environmental and occupational exposure to heavy metal causes cancer in several organs. Although the exact mechanism of heavy metal carcinogenesis remains elusive, metal-generated reactive oxygen species (ROS) are essential. ROS can play two roles in metal carcinogenesis; two stages in the process of metal carcinogenesis differ in the amounts of ROS activating a dual redox-mediated mechanism. In the early stage of metal carcinogenesis, ROS acts in an oncogenic role. However, in the late stage of metal carcinogenesis, ROS plays an antioncogenic role. Similarly, NF-E2-related factor 2 (Nrf2) also has two different roles, which makes it a key molecule for separating metal carcinogenesis into two different stages. In the early stage, inducible Nrf2 fights against elevated ROS to decrease cell transformation by its antioxidant protection property. In the late stage, constitutively activated Nrf2 manipulates reduced ROS to perform a comfortable environment for apoptosis resistance through an oncogenic role. Interestingly, a cunning carcinogenic mechanism takes advantage of the dual role of Nrf2 to implement the dual role of ROS through a series of redox adaption mechanisms. In this review, we discuss the paradox in the rationales behind the two opposite ROS roles and focus on their potential pharmacological application. The dual role of ROS represents a 'double-edged sword' with many possible novel ROS-mediated strategies in cancer therapy in metal carcinogenesis.

Ellagic acid mitigates arsenic-trioxide-induced mitochondrial dysfunction and cytotoxicity in SH-SY5Y cells

In the current study, neuroprotective significance of ellagic acid (EA, a polyohenol) was explored by primarily studying its antioxidant and antiapoptotic potential against arsenic trioxide (As₂ O₃ )-induced toxicity in SH-SY5Y human neuroblastoma cell lines. The mitigatory effects of EA with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied. Pretreatment of SH-SY5Y cells with EA (10 and 20 μM) for 60 min followed by exposure to 2 μM As₂ O₃ protected the SH-SY5Y cells against the harmful effects of the second. Also, EA pre-treated groups expressed improved viability, repaired DNA, reduced free radical generation, and maintained altered mitochondrial membrane potential than those exposed to As₂ O₃ alone. EA supplementation also inhibited As₂ O₃ -induced cytochrome c expression that is an important hallmark for determining mitochondrial dynamics. Thus, the current investigations are more convinced for EA as a promising candidate in modulating As₂ O₃ -induced mitochondria-mediated neuronal toxicity under in vitro system.

ROS-modulated therapeutic approaches in cancer treatment

PURPOSE

Reactive oxygen species (ROS) are produced in cancer cells as a result of increased metabolic rate, dysfunction of mitochondria, elevated cell signaling, expression of oncogenes and increased peroxisome activities. Certain level of ROS is required by cancer cells, above or below which lead to cytotoxicity in cancer cells. This biochemical aspect can be exploited to develop novel therapeutic agents to preferentially and selectively target cancer cells.

METHODS

We searched various electronic databases including PubMed, Web of Science, and Google Scholar for peer-reviewed english-language articles. Selected articles ranging from research papers, clinical studies, and review articles on the ROS production in living systems, its role in cancer development and cancer treatment, and the role of microbiota in ROS-dependent cancer therapy were analyzed.

RESULTS

This review highlights oxidative stress in tumors, underlying mechanisms of different relationships of ROS and cancer cells, different ROS-mediated therapeutic strategies and the emerging role of microbiota in cancer therapy.

CONCLUSION

Cancer cells exhibit increased ROS stress and disturbed redox homeostasis which lead to ROS adaptations. ROS-dependent anticancer therapies including ROS scavenging anticancer therapy and ROS boosting anticancer therapy have shown promising results in vitro as well as in vivo. In addition, response to cancer therapy is modulated by the human microbiota which plays a critical role in systemic body functions.

HMGB1 contributes to glomerular endothelial cell injury in ANCA-associated vasculitis through enhancing endothelium-neutrophil interactions

Our previous studies demonstrated that high mobility group box‐1 (HMGB1), a typical damage‐associated molecular pattern (DAMP) protein, is associated with the disease activity of antineutrophil cytoplasmic antibody (ANCA)‐associated vasculitis (AAV). Moreover, HMGB1 participates in ANCA‐induced neutrophil activation. The current study aimed to investigate whether HMGB1 regulated the interaction between neutrophils and glomerular endothelial cells (GEnC) in the presence of ANCA. Correlation analysis on HMGB1 levels in AAV patients and soluble intercellular cell adhesion molecule‐1 (sICAM‐1) levels or vascular endothelial growth factor (VEGF) levels, which are markers of endothelial cell activation, was performed. The effect of HMGB1 on neutrophil migration towards GEnC, respiratory burst and degranulation of neutrophils in coculture conditions with GEnC was measured. The activation of neutrophils, the activation and injury of GEnC, and the consequent pathogenic role of injured GEnC were evaluated. Plasma levels of HMGB1 correlated with sICAM‐1 and VEGF (r = 0.73, P < 0.01; r = 0.41, P = 0.04) in AAV patients. HMGB1 increased neutrophil migration towards GEnC, as well as respiratory burst and degranulation of neutrophils in the presence of ANCA in the coculture system. In the presence of robust neutrophil activation, GEnC were further activated and injured in the coculture system of GEnC and neutrophils. In addition, injured GEnC could produce TF‐positive leuco‐endothelial microparticles and endothelin‐1 (ET‐1), while NF‐κB was phosphorylated (S529) in the injured GEnC. Plasma levels of HMGB1 correlated with endothelial cell activation in AAV patients. HMGB1 amplified neutrophil activation and the activation and injury of GEnC in the presence of ANCA.

Phenylethyl isothiocyanate reverses cisplatin resistance in biliary tract cancer cells via glutathionylation-dependent degradation of Mcl-1

Biliary tract cancer (BTC) is a highly malignant cancer. BTC exhibits a low response rate to cisplatin (CDDP) treatment, and therefore, an understanding of the mechanism of CDDP resistance is urgently needed. Here, we show that BTC cells develop CDDP resistance due, in part, to upregulation of myeloid cell leukemia 1 (Mcl-1). Phenylethyl isothiocyanate (PEITC), a natural compound found in watercress, could enhance the efficacy of CDDP by degrading Mcl-1. PEITC-CDDP co-treatment also increased the rate of apoptosis of cancer stem-like side population (SP) cells and inhibited xenograft tumor growth without obvious toxic effects. In vitro, PEITC decreased reduced glutathione (GSH), which resulted in decreased GSH/oxidized glutathione (GSSG) ratio and increased glutathionylation of Mcl-1, leading to rapid proteasomal degradation of Mcl-1. Furthermore, we identified Cys16 and Cys286 as Mcl-1 glutathionylation sites, and mutating them resulted in PEITC-mediated degradation resistant Mcl-1 protein. In conclusion, we demonstrate for the first time that CDDP resistance is partially associated with Mcl-1 in BTC cells and we identify a novel mechanism that PEITC can enhance CDDP-induced apoptosis via glutathionylation-dependent degradation of Mcl-1. Hence, our results provide support that dietary intake of watercress may help reverse CDDP resistance in BTC patients.

Aniline Induces Oxidative Stress and Apoptosis of Primary Cultured Hepatocytes

The toxicity and carcinogenicity of aniline in humans and animals have been well documented. However, the molecular mechanism involved in aniline-induced liver toxicity and carcinogenesis remains unclear. In our research, primary cultured hepatocytes were exposed to aniline (0, 1.25, 2.50, 5.0 and 10.0 μg/mL) for 24 h in the presence or absence of N-acetyl-l-cysteine (NAC). Levels of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH), activities of superoxide dismutase (SOD) and catalase (CAT), mitochondrial membrane potential, DNA damage, cell viability, and apoptosis were detected. Levels of ROS and MDA were significantly increased and levels of GSH and CAT, activity of SOD, and mitochondrial membrane potential in hepatocytes were significantly decreased by aniline compared with the negative control group. The tail moment and DNA content of the tail in exposed groups were significantly higher than those in the negative control group. Cell viability was reduced and apoptotic death was induced by aniline in a concentration-dependent manner. The phenomena of ROS generation, oxidative damage, loss of mitochondrial membrane potential, DNA damage and apoptosis could be prevented if ROS inhibitor NAC was added. ROS generation is involved in the loss of mitochondrial membrane potential and DNA injury, which may play a role in aniline-induced apoptosis in hepatocytes. Our study provides insight into the mechanism of aniline-induced toxicity and apoptosis of hepatocytes.

IDH2 knockdown sensitizes tumor cells to emodin cytotoxicity in vitro and in vivo

Although reactive oxygen species (ROS) work as second messengers at sublethal concentrations, higher levels of ROS can kill cancer cells. Since cellular ROS levels are determined by a balance between ROS generation and removal, the combination of ROS generators, and the depletion of reducing substances greatly enhance ROS levels. Emodin (1,3,8-trihydroxy-6-methyl anthraquinone), a natural anthraquinone derivative from the root and rhizome of numerous plants, is a ROS generator that induces apoptosis in cancer cells. The major enzyme to generate mitochondrial NADPH is the mitochondrial isoenzyme of NADP⁺-dependent isocitrate dehydrogenase (IDH2). In this report, we demonstrate that IDH2 knockdown effectively enhances emodin-induced apoptosis of mouse melanoma B16F10 cells through the regulation of ROS generation. Our findings suggest that suppression of IDH2 activity results in perturbation of the cellular redox balance and, ultimately, exacerbate emodin-induced apoptotic cell death in B16F10 cells. Our results strongly support a therapeutic strategy in the management of cancer that alters the intracellular redox status by the combination of a ROS generator and the suppression of antioxidant enzyme activity.

The effects of buthionine sulfoximine on the proliferation and apoptosis of biliary tract cancer cells induced by cisplatin and gemcitabine

Patients with biliary tract cancer (BTC) have a poor prognosis. Advanced BTC patients have been treated with cisplatin in combination with gemcitabine, however, the treatment has had little impact on survival rates, and more effective treatments are urgently required for this disease. Previous studies discovered that buthionine sulfoximine (BSO), a potent inhibitor of glutathione (GSH) synthesis, was able to enhance the cytotoxic effect of various drugs in cancer cells. Phase I studies demonstrated that continuous-infusion of BSO was relatively non-toxic and resulted in the depletion of tumor GSH. However, the synergistic effect of BSO and cisplatin in BTC cells remains unknown, and no reports are available regarding sensitization to gemcitabine by BSO. In the present study, the effect of BSO in combination with cisplatin or gemcitabine in the treatment of BTC cells was examined in vitro. Cytotoxic effects were measured using an MTT assay, Annexin V assay and fluorescence-activated cell sorting analysis. Antiapoptotic protein expression levels were examined using western blot analysis. The results revealed that a sub-toxic concentration of BSO was capable of significantly enhancing cisplatin-induced apoptosis in BTC cells. The mechanisms of BSO's effect on BTC cells may be attributable to the reduction of GSH levels and downregulation of the expression of antiapoptotic proteins (Bcl-2, Bcl-xL and Mcl-1). Furthermore, BSO enhanced the antiproliferative effect of gemcitabine. In conclusion, the present data are the first results to indicate that BSO may sensitize BTC cells to standard first-line chemotherapeutic agents (cisplatin and gemcitabine). Combining BSO with cisplatin and gemcitabine is a promising therapeutic strategy for the treatment of BTC.

Salvianolic acid A shows selective cytotoxicity against multidrug-resistant MCF-7 breast cancer cells

Multidrug resistance (MDR) is a major cause for incurable breast cancer. Salvianolic acid A (SAA), the hydrophilic polyphenolic derivative of Salvia miltiorrhiza Bunge (Danshen/Red Sage), was examined for cytotoxicities to MDR MCF-7 human breast cancer cells and their parental counterparts. We have shown that SAA inhibited proliferation, caused cell cycle arrest at the S phase, and induced apoptosis dose dependently to the two kinds of cancer cells. However, the resistant cells were significantly susceptible to the inhibition of SAA compared with the parental cells. SAA increased the level of reactive oxygen species (ROS) by 6.2-fold in the resistant cells, whereas the level of SAA-induced ROS changed only by 1.6-fold in their parental counterparts. Thus, the data showed that the selective cytotoxicity resulted from the hypersensitivity of the resistant cells to the strongly elevated ROS by SAA. In addition, SAA-triggered apoptosis was associated with increased caspase-3 activity, disrupted mitochondrial membrane potential, downregulated Bcl-2 expression, and upregulated Bax expression in the resistant cells. Moreover, SAA downregulated the level of P-glycoprotein, which was overexpressed in the resistant cells. This indicated that SAA modulated MDR. Furthermore, SAA showed higher antitumor activity than did doxorubicin in xenografts established from the resistant cells. The present work raised a possibility that SAA might be considered a potential choice to overcome MDR for the selective susceptibility of the resistant breast cancer cells to SAA treatment.

BME, a novel compound of anthraquinone, down regulated P-glycoprotein expression in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells via generation of reactive oxygen species

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) in tumor cells is still a main obstacle for the chemotherapeutic treatment of cancers. Thus, development of effective MDR reversing agents is an important approach in the clinic. The present study revealed that BME, a novel compound of anthraquinone, elevated intracellular accumulation of the P-gp substrates and reduced concentration resulting in 50% inhibition of cell growth (IC50) values for doxorubicin (DOX) in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells. Further more, BME was also reported to down regulated P-gp expression accompanying with generation of nontoxic low level of intracellular reactive oxygen species (iROS) and activation of extracellular signal-regulated kinase (ERK)1/2 as well as c-JUN N-terminal kinase (JNK). However, treatment with N-acetyl-cysteine (NAC), U0216 and SP600125 almost abolished actions of the BME mentioned above. These results indicated that the effect of the BME on the P-gp may be involved in generation of nontoxic low level of iROS and activation of ERK1/2 or JNK, which suggested valuable clues to screen and develop P-gp reversing agents.

Effect of piperine on the bioavailability and pharmacokinetics of emodin in rats

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) has been widely used as a traditional medicine and was shown to possess a multitude of health-promoting properties in pre-clinical studies, but its bioavailability was low due to the extensive glucuronidation in liver and intestine, hindering the development of emodin as a feasible chemopreventive agent. In this study, piperine, as a bioenhancer, was used to enhance the bioavailability of emodin by inhibiting its glucuronidation. The pharmacokinetic profiles of emodin after oral administration of emodin (20mg/kg) alone and in combination with piperine (20mg/kg) to rats were investigated via a validated LC/MS/MS method. As the in vivo pharmacokinetic studies had indicated, the AUC and Cmax of emodin were increased significantly after piperine treatment, and the glucuronidation of emodin was markedly inhibited. Our study demonstrated that piperine significantly improved the in vivo bioavailability of emodin and the influence of piperine on the pharmacokinetics of emodin may be attributed to the inhibition of glucuronidation of emodin. Further research is needed to investigate the detailed mechanism of improved bioavailability of emodin via its combination with piperine.

Arsenic trioxide-induced cytotoxicity in small cell lung cancer via altered redox homeostasis and mitochondrial integrity

Arsenic trioxide (ATO) has demonstrated anticancer activity in different malignancies, especially acute promyelocytic leukemia, with a wide array of putative mechanisms. In this study, we aimed to elucidate the activity and mechanisms of ATO in small cell lung cancer (SCLC). A panel of SCLC cell lines (H841, DMS79, H526, H69 and H187) was employed to demonstrate the activity of ATO. Cell viability, apoptosis and mitochondrial membrane depolarization were assessed. Western blotting was performed to determine the alteration of pro-apoptotic and anti-apoptotic mediators. Reactive oxygen species (ROS) (hydrogen peroxide and superoxide) and intracellular glutathione (GSH) were measured. Antioxidants, N-acetyl-L-cysteine (NAC) and butylated hydroxyanisole (BHA), were applied to restore GSH content and reduce production of ROS. All SCLC cell lines were relatively sensitive to ATO with IC50 values below 10 µM. ATO induced cell death mainly through apoptosis in H841 cells in a dose-dependent manner. Hydrogen peroxide was the major ROS in SCLC cells induced by ATO. Along with GSH depletion and Bcl-2 downregulation, mitochondrial membrane permeabilization was enhanced, followed by release of AIF and SMAC from mitochondria to initiate different cell death pathways. NAC reversed cell death and molecular changes induced by ATO via restoring GSH and reducing ROS content. BHA inhibited hydrogen peroxide production completely and partially restored GSH content accounting for partial reversal of cell inhibition and mitochondrial dysfunction. Nonetheless, ATO reduced both reduced and oxidized form of thioredoxin 1 (Trx1) with no effect on Trx1 redox potential. ATO led to cell death in SCLC mainly through mitochondrial dysfunction, resulting from altered cellular redox homeostasis, namely, hydrogen peroxide generation, GSH depletion and Trx1 downregulation.

Emodin augments cisplatin cytotoxicity in platinum-resistant ovarian cancer cells via ROS-dependent MRP1 downregulation

The intracellular level of reactive oxygen species (ROS) is closely associated with chemosensitivity of cancer cells. Overexpression of ATP binding cassette transporter MRP1 is correlated with resistance to platinum drugs. In this study, we tested the hypothesis that emodin, a potent ROS generator, may increase sensitivity of cisplatin-(cDDP-) resistant ovarian carcinoma cells to cDDP cytotoxicity via ROS-mediated suppression of MRP1 expression. Using the isogenic pair of the human ovarian carcinoma cell line COC1 and its cDDP resistant variant COC1/DDP, we found that ROS level in the cDDP-sensitive ovarian cancer cells was significantly higher than that in the cDDP-resistant cells. Emodin enhanced ROS production in COC1/DDP cells and consequently sensitized them to cDDP-induced apoptosis. These effects were reversed by addition of the antioxidant N-acetyl-L-cysteine (NAC). Cotreatment with emodin and cDDP inhibited the tumor growth in vivo by increasing tumor cell apoptosis. The emodin-enhanced cDDP cytotoxicity was attributable to downregulation of multidrug resistance-related protein 1 (MRP1) expression. Together, these results suggest that emodin could act as an adjunct to enhance the anticancer effect of cDDP likely through ROS-related downregulation of MRP1 expression, and may be of therapeutic potential in cDDP-refractory ovarian carcinomas.

G226, a new epipolythiodioxopiperazine derivative, triggers DNA damage and apoptosis in human cancer cells in vitro via ROS generation

AIM

G226 is a novel derivative of epipolythiodioxopiperazines with potent inhibitory activity against cancer cells. Here, we sought to identify potential targets involved in the anti-cancer activity of G226.

METHODS

Cell proliferation assay was conducted in a panel of 12 human cancer cell lines. The activities of topoisomerase I (Topo I) and Topo II were studied using supercoiled pBR322 DNA relaxation and kDNA decatenation assays. ROS production was assessed with probes DCFH-DA and H&E. Western blot analysis and flow cytometry were used to examine DNA damage, apoptosis and cell cycle changes.

RESULTS

G226 displayed potent cytotoxicity in the 12 human cancer cell lines with a mean IC50 value of 92.7 nmol/L. This compound (1-100 μmol/L) selectively inhibited the activity of Topo II, and elevated the expression of phosphorylated-H2AX in a dose-dependent manner. In Topo II-deficient HL60/MX2 cells, however, G226-induced DNA damage, apoptosis and cytotoxicity were only partially reduced, suggesting that Topo II was not essential for the anti-tumor effects of G226. Furthermore, G226 (0.125-2 μmol/L) dose-dependently elevated the intracellular levels of H2O2 and in the cancer cells, and pretreatment with GSH, NAC or DTT not only blocked G226-induced intracellular accumulation of ROS, but also abrogated G226-mediated phosphorylation of H2AX, apoptosis and cytotoxicity.

CONCLUSION

G226-mediated ROS production contributes to the anti-cancer activity of this compound.

The roles of mitoferrin-2 in the process of arsenic trioxide-induced cell damage in human gliomas

Background

Among glioma treatment strategies, arsenic trioxide (As₂O₃) has shown efficacy as a therapeutic agent against human gliomas. However, the exact antitumor mechanism of action of As₂O₃ is still unclear. Mitochondria are considered to be the major source of intracellular reactive oxygen species (ROS), which are known to be associated with As₂O₃-induced cell damage. Therefore, we investigated whether mitoferrin-2, a mitochondrial iron uptake transporter, participates in As₂O₃-induced cell killing in human gliomas.

Methods

Human glioma cell lines were used to explore the mechanism of As₂O₃’s antitumor effects. First, expression of mitoferrin-2 was analyzed in glioma cells that were pretreated with As₂O_3. Changes in ROS production and apoptosis were assessed. Furthermore, cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT).

Results

In the present study we found that As₂O₃ induced ROS production and apoptosis in glioma cells. In addition, gene expression of mitoferrin-2, a mitochondrial iron uptake transporter, was increased 4 to 5 fold after exposure to As₂O₃ (5 μM) for 48 hours. Furthermore, apoptosis and cytotoxicity induced by As₂O₃ in glioma cells were decreased after silencing the mitoferrin-2 gene.

Conclusions

Our findings indicated that mitoferrin-2 participates in mitochondrial ROS-dependent mechanisms underlying As₂O₃-mediated damage in glioma cells.

Apoptosis of Dalton's lymphoma due to in vivo treatment with emodin is associated with modulations of hydrogen peroxide metabolizing antioxidant enzymes

The evolving concept of pro-oxidative mechanism-based antitumor activity of emodin (1,3,8-trihydroxy-6-methyl anthraquinone), derived mainly from in vitro studies, needs to be defined for in vivo tumor models. The present article describes apoptosis and regression of Dalton's lymphoma (DL) in mice by emodin vis a vis modulations of hydrogen peroxide (H2O2) metabolizing antioxidant enzymes in the tumor cells in vivo. A non-toxic dose (40 mg/kg bw) of emodin, given intraperitoneally to the DL bearing mice daily up to 12th post DL transplantation day, caused a significant decline (P < 0.05) in the number of viable DL cells and could significantly increase life span of the DL mice (P < 0.01). A significant decline in Bcl2/Bax ratio consistent with the release of mitochondrial cytochrome c release in DL cells from emodin-treated DL mice suggested that emodin could induce mitochondrial pathway of apoptosis in the DL cells in vivo. Apoptosis of DL cells by emodin was further confirmed by the appearance of smaller DNA fragments on DNA ladder analysis. Over activation of both, the Cu-Zn-superoxide dismutases (SOD1) and Mn-SOD (SOD2), has been found correlated with the tumor suppression. Emodin caused significant increases in the expression and activity of SOD1 and SOD2 in the DL cells. H2O2 produced by SODs is degraded by catalase and glutathione peroxidase in the cells. Both these enzymes were observed to be declined significantly with a concomitant increment in H2O2 concentration (P < 0.01) in the DL cells from emodin-treated DL mice. It is concluded that emodin is able to induce mitochondrial pathway of apoptosis in the DL cells in vivo via reciprocal modulations of H2O2 producing and degrading antioxidant enzymes.

Polysaccharides from dioscorea ( shān yào) and other phytochemicals enhance antitumor effects induced by DNA vaccine against melanoma

Adjuvants can be used to enhance the immunogenicity of antigens and improve the efficacy of vaccines. Potent adjuvant action is known to often correlate with the activation of the transcription factor, nuclear factor-κB (NF-κB). Specific plant polysaccharides and a variety of phytochemicals from foods and traditional medicinal herbs have been shown to modulate NF-κB activation. In the present study, selected plant polysaccharides and phytochemicals were evaluated for use as a DNA vaccine adjuvant in a murine melanoma model. We observed that a specific ethanol extract fraction (DsCE-I) from the tuber of a key Traditional Chinese Medicine plant, Dioscorea (山藥 Shān Yào), enhanced the protection against melanoma after immunization with a gene-based vaccine. A number of anti-inflammatory phytochemicals tested were able to partially diminish the inflammation-associated tumorigenesis elicited by LPS. Among the several phytochemical combinations investigated, the use of an adjuvant containing LPS in combination with emodin resulted in smaller tumors and higher survival rate in test mice than the use of other adjuvant treatments and the control sets in this DNA cancer vaccine model. A Dioscorea polysaccharide fraction (DsCE-I) and several specific phytochemicals warrant further exploration as useful adjuvants for anticancer vaccines.

Endoplasmic reticulum stress-mediated apoptosis in imatinib-resistant leukemic K562-r cells triggered by AMN107 combined with arsenic trioxide

The first tyrosine kinase inhibitor (TKI) imatinib mesylate (imatinib) targets the kinase domain of BCR-ABL and induces apoptosis in newly diagnosed chronic myeloid leukaemia (CML). However, resistant and relapse are common problems in imatinib-treated patients. Although second-generation TKI such as AMN107 appears to improve the treatment of CML, TKI resistance and relapse are also frequently occurred in the patients. To test whether arsenic trioxide (ATO) could potentiate the efficacy of AMN107 in imatinib-resistant cells, we conducted a series of assays in TKI-resistant K562-r cells treated with AMN107 and ATO. Based on a time-course cDNA microarray analysis, we found many genes typically involved in the endoplasmic reticulum (ER) stress signalling were significantly up-regulated, implicating the occurrence of ER stress-mediated apoptosis in K562-r cells treated with the combination of ATO and AMN107. Such implication was also supported by the data showing the activation of members in the JNK pathway, which are known to be characteristic markers bridging ER-stress and apoptosis. Partial knock-down of the JNK activities alleviated the effects of apoptosis (p < 0.05) triggered by combining AMN107 with ATO. In conclusion, this study for the first time demonstrates a synergistic effect of AMN107 with ATO, allowing insights into the possible mechanisms underlying imatinib-induced resistance in CML. Our data also suggest that combination of AMN107 with ATO may represent a new strategy for the treatment of imatinib-resistant CML patients.

New Strategies to Direct Therapeutic Targeting of PML to Treat Cancers

The tumor suppressor function of the promyelocytic leukemia (PML) protein was first identified as a result of its dysregulation in acute promyelocytic leukemia, however, its importance is now emerging far beyond hematological neoplasms, to an extensive range of malignancies, including solid tumors. In response to stress signals, PML coordinates the regulation of numerous proteins, which activate fundamental cellular processes that suppress tumorigenesis. Importantly, PML itself is the subject of specific post-translational modifications, including ubiquitination, phosphorylation, acetylation, and SUMOylation, which in turn control PML activity and stability and ultimately dictate cellular fate. Improved understanding of the regulation of this key tumor suppressor is uncovering potential opportunities for therapeutic intervention. Targeting the key negative regulators of PML in cancer cells such as casein kinase 2, big MAP kinase 1, and E6-associated protein, with specific inhibitors that are becoming available, provides unique and exciting avenues for restoring tumor suppression through the induction of apoptosis and senescence. These approaches could be combined with DNA damaging drugs and cytokines that are known to activate PML. Depending on the cellular context, reactivation or enhancement of tumor suppressive PML functions, or targeted elimination of aberrantly functioning PML, may provide clinical benefit.

Cellular Redox Status Regulates Emodin-Induced Radiosensitization of Nasopharyngeal Carcinoma Cells In Vitro and In Vivo

Here, we report that regulation of cellular redox status is required for radiosensitization of nasopharyngeal carcinoma (NPC) cells by emodin. We evaluated emodin's radiosensitivity-enhancing ability by using NPC cells in vitro and xenografts in vivo. A clonogenic assay was performed to evaluate NPC cell survival and to determine dose modification factors. Flow cytometry, western blot analysis, and in vivo radiation-induced tumor regrowth delay assays were performed to characterize emodin's effects. Exposure of CNE-1 NPC cells to emodin enhanced their radiosensitivity. HIF-1α expression significantly increased under hypoxic conditions but did not change after treatment with emodin alone. Emodin downregulated mRNA and protein expression of HIF-1α. Cells exposed to radiation and emodin underwent significant cell cycle arrest at the G₂/M phase. The percentage of apoptotic cells and reactive oxygen species (ROS) levels were significantly higher in the group exposed to emodin and radiation hypoxic group than in the other groups. Compared to the CNE-1 xenografts exposed to radiation alone, CNE-1 xenografts exposed to radiation with emodin showed significantly enhanced radiation effects. Our data suggest that emodin effectively enhanced the radiosensitivity of CNE-1 cells in vitro and in vivo. The mechanism appears to involve ROS generation and ROS-mediated inhibition of HIF-1α expression.

Phytochemicals as chemosensitizers: from molecular mechanism to clinical significance

This review provides an overview of the clinical relevance of chemosensitization, giving special reference to the phenolic phytochemicals, curcumin, genistein, epigallocatechin gallate, quercetin, emodin, and resveratrol, which are potential candidates due to their ability to regulate multiple survival pathways without inducing toxicity. We also give a brief summary of all the clinical trials related to the important phytochemicals that emerge as chemosensitizers. The mode of action of these phytochemicals in regulating the key players of the death receptor pathway and multidrug resistance proteins is also abridged. Rigorous efforts in identifying novel chemosensitizers and unraveling their molecular mechanism have resulted in some of the promising candidates such as curcumin, genistein, and polyphenon E, which have gone into clinical trials. Even though considerable research has been conducted in identifying the salient molecular players either contributing to drug efflux or inhibiting DNA repair and apoptosis, both of which ultimately lead to the development of chemoresistance, the interdependence of the molecular pathways leading to chemoresistance is still the impeding factor in the success of chemotherapy. Even though clinical trials are going on to evaluate the chemosensitizing efficacy of phytochemicals such as curcumin, genistein, and polyphenon E, recent results indicate that more intense study is required to confirm their clinical efficacy. Current reports also warrant intense investigation about the use of more phytochemicals such as quercetin, emodin, and resveratrol as chemosensitizers, as all of them have been shown to modulate one or more of the key regulators of chemoresistance.

Combination of single walled carbon nanotubes/graphene oxide with paclitaxel: a reactive oxygen species mediated synergism for treatment of lung cancer

Heterogeneity in tumors has led to the development of combination therapies that enable enhanced cell death. Previously explored combination therapies mostly involved the use of bioactive molecules. In this work, we explored a non-conventional strategy of using carbon nanostructures (CNs) [single walled carbon nanotube (SWNT) and graphene oxide (GO)] for potentiating the efficacy of a bioactive molecule [paclitaxel (Tx)] for the treatment of lung cancer. The results demonstrated enhanced cell death following combination treatment of SWNT/GO and Tx indicating a synergistic effect. In addition, synergism was abrogated in the presence of an anti-oxidant, N-acetyl cysteine (NAC), and was therefore shown to be reactive oxygen species (ROS) dependent. It was further demonstrated using bromodeoxyuridine (BrdU) incorporation assay that treatment with CNs was associated with enhanced mitogen associated protein kinase (MAPK) activation that was ROS mediated. Hence, these results for the first time demonstrated the potential of SWNT/GO as co-therapeutic agents with Tx for the treatment of lung cancer.

Emodin regulates glucose utilization by activating AMP-activated protein kinase

AMP-activated protein kinase has been described as a key signaling protein that can regulate energy homeostasis. Here, we aimed to characterize novel AMP-activated kinase (AMPK)-activating compounds that have a much lower effective concentration than metformin. As a result, emodin, a natural anthraquinone derivative, was shown to stimulate AMPK activity in skeletal muscle and liver cells. Emodin enhanced GLUT4 translocation and [(14)C]glucose uptake into the myotube in an AMPK-dependent manner. Also, emodin inhibited glucose production by suppressing the expression of key gluconeogenic genes, such as phosphoenolpyruvate carboxykinase and glucose-6-phosphatase, in hepatocytes. Furthermore, we found that emodin can activate AMPK by inhibiting mitochondrial respiratory complex I activity, leading to increased reactive oxygen species and Ca(2+)/calmodulin-dependent protein kinase kinase activity. Finally, we confirmed that a single dose administration of emodin significantly decreased the fasting plasma glucose levels and improved glucose tolerance in C57Bl/6J mice. Increased insulin sensitivity was also confirmed after daily injection of emodin for 8 days using an insulin tolerance test and insulin-stimulated PI3K phosphorylation in wild type and high fat diet-induced diabetic mouse models. Our study suggests that emodin regulates glucose homeostasis in vivo by AMPK activation and that this may represent a novel therapeutic principle in the treatment of type 2 diabetic models.

Mechanisms of verapamil-enhanced chemosensitivity of gallbladder cancer cells to platinum drugs: glutathione reduction and MRP1 downregulation

Gallbladder cancer (GBC) is highly malignant with a low response rate after chemotherapy and platinum drugs are currently prominent in the treatment of biliary tract cancers. Therefore, the development of novel strategies to enhance the sensitivity of GBC to platinum drugs is required. In the present study, we examined the effects of verapamil, a classic chemosensitizer whose reported mechanisms of action include inhibiting the transport function of P-glycoprotein (MDR1) or stimulating glutathione (GSH) transport by multidrug resistance-related protein 1 (MRP1), in combination with cisplatin (CDDP), carboplatin (CBP) or oxaliplatin on the GBC cell lines, SGC996 and GBC-SD. Our results demonstrated that the co-treatment with verapamil markedly enhanced the chemosensitivity of GBC cells in comparison with platinum drug treatment alone. The mechanisms involved included GSH reduction and MRP1 downregulation. Verapamil/CDDP co-treatment inhibited tumor xenograft growth via the downregulation of MRP1 expression. MRP1 was highly expressed in human GBC tissue compared to non-tumorous gallbladder tissue. Our data demonstrate that verapamil may be used as a safe chemosensitizer for platinum drugs in the treatment of GBC. It functions by ROS and ATP-binding cassette transporter-related mechanisms.

Emodin as an effective agent in targeting cancer stem-like side population cells of gallbladder carcinoma

Side population (SP) cells are previously identified from bone marrow based on their capacity to efflux of the fluorescent dye Hoechst 33342. Recent studies demonstrate that SP cells isolated from various cancer cell lines and primary tumors possess stem-cell-like properties. Thus, targeting tumor SP cells may provide new strategies for treatment in clinic. We previously showed that 1,3,8-trihydroxy-6-methylanthraquinone (emodin), a reactive oxygen species (ROS) generator, enhanced sensitivity of gallbladder cancer SGC-996 cells to cisplatin (CDDP) via generation of ROS and downregulation of multidrug-resistance-associated protein 1 (MRP1). To determine whether emodin also acts effectively on cancer stem cells of gallbladder carcinoma, we use SP cells as a model of cancer stem-cell-like cells. Here, we found that emodin, via ROS-related mechanism and suppressing the function of ATP-binding cassette super-family G member (ABCG2), which is known to be associated with Hoechst dye efflux activity of SP cells, not only reduced the ratio, inhibited clone formation, and eliminated sphere formation of SP cells effectively, but also promoted obviously the intracellular accumulation of doxorubicin, the main substrate of the efflux pump ABCG2. In addition, emodin could sensitize CDDP, via inhibition of expression of ABCG2, to overcome chemoresistance of SP cells. Importantly, similar to the experiment in vitro, emodin/CDDP co-treatment in vivo suppressed the tumor growth derived from SP cells through downregulating ABCG2 expression. Our results suggest that emodin is an effective agent targeting cancer stem-like SP cells of gallbladder carcinoma, either alone or acts as a chemotherapy enhancer.