Relaxation Assay Research Articles

Methotrexate improves perivascular adipose tissue/endothelial dysfunction via activation of AMPK/eNOS pathway.

Adipose and endothelial dysfunction is associated with cardiovascular disease. Perivascular adipose tissue (PVAT) directly surrounds vessels and influences vessel function via a paracrine effect, and adenosine monophosphate (AMP)-activated protein kinase (AMPK) modulates the metabolic pathway, thus, the present study hypothesized that activation of AMPK in PVAT may regulate endothelial function in pathological settings. The present study investigated the effect of methotrexate (MTX) on adipocytokine expression in PVAT with an emphasis on the regulation of endothelial function. The effects of MTX and the mechanisms involved were investigated using a relaxation assay and western blot analysis. Reverse transcription‑quantitative polymerase chain reaction and western blotting were used to detect the mRNA and protein expression levels. ELISA assay was used to quantify the level of TNF‑α and IL‑6. Palmitic acid (PA) stimulation induced inflammation and dysregulation of adipocytokine expression in PVAT. MTX treatment inhibited nuclear factor‑κB p65 phosphorylation and downregulated expression of pro‑inflammatory cytokines, including tumor necrosis factor‑α and interleukin-6, whereas adiponectin expression increased. MTX increased AMPK phosphorylation under basal and inflammatory conditions in PVAT, whereas knockdown of AMPK via small interfering RNA diminished its modulatory effect, indicating that MTX inhibits inflammation in an AMPK‑dependent manner. The present study prepared conditioned medium from PA‑stimulated PVAT to induce endothelial dysfunction and observed that pre‑treatment of PVAT with MTX effectively restored the loss of acetylcholine‑induced vasodilation and increased endothelial nitric oxide synthase phosphorylation in the rat aorta. The results of the present study demonstrated that MTX ameliorated inflammation-associated adipocytokine dysregulation and thus prevented endothelial dysfunction. These data provide further pharmacological evidence regarding the beneficial effects of MTX in cardiovascular diseases.

Development of an assay to assess genotoxicity by particulate matter extract.

The current study describes a method for assessing the oxidative potential of common environmental stressors (ambient air particulate matter), using a plasmid relaxation assay where the extract caused single-strand breaks, easily visualised through electrophoresis. This assay utilises a miniscule amount (11 µg) of particulate matter (PM) extract compared to other, cell-based methods (~3,000 µg). The negative impact of air pollution on human health has been extensively recognised. Among the air pollutants, PM plays an eminent role, as reflected in the broad scientific interest. PM toxicity highly depends on its composition (metals and organic compounds), which in turn has been linked to multiple health effects (such as cardiorespiratory diseases and cancer) through multiple toxicity mechanisms; the induction of oxidative stress is considered a major mechanism among these. In this study, the PM levels, oxidative potential, cytotoxicity and genotoxicity of PM in the region of Larissa, Greece were examined using the plasmid relaxation assay. Finally, coffee extracts from different varieties, derived from both green and roasted seeds, were examined for their ability to inhibit PM-induced DNA damage. These extracts also exerted an inhibitory effect on xanthine oxidase and catalase, but had no effect against superoxide dismutase. Overall, this study highlights the importance of assays for assessing the oxidative potential of widespread environmental stressors (PM), as well as the antioxidant capacity of beverages and food items, with the highlight being the development of a plasmid relaxation assay to assess the genotoxicity caused by PM using only a miniscule amount.

Design, Synthesis and in vitro Anticancer Activity of a Cu(II) Complex of Carminic Acid: A Novel Small Molecule Inhibitor of Human DNA Topoisomerase I and Topoisomerase II

AbstractThe hydroxy‐9,10‐anthraquinones in anthracyclines form semiquinones and reactive oxygen species (ROS) that help in antitumor activity. ROS generation is cytotoxic to cells but cardiotoxic as well. Carminic acid (CA) with a sugar bound to a hydroxyanthraquinone resembles anthracyclines closely. Role of sugar in anthracyclines was realized from physicochemical parameters of CA that were found to be in between those of anthracyclines and hydroxy‐9,10‐anthraquinones. A Cu(II)complex of CA was prepared and its structure attempted from powder X‐ray diffraction. Studies with DNA revealed unlike CA, the complex did not show decrease in binding constant with increase in the pH of the medium. DNA relaxation assay showed the complex as a dual inhibitor of human DNA topoisomerase I and topoisomerase II stabilizing covalent topoisomerase‐DNA adducts in vitro. Inhibition of growth of ALL‐MOLT‐4 cells was higher for the complex supporting in vitro experiments. An enzyme assay revealed less superoxide formation for the complex suggesting that it might be less cardiotoxic. Decrease in superoxide for the complex does not affect anticancer activity, which was greater than CA.

Inhibitory effects of lapachol on rat C6 glioma in vitro and in vivo by targeting DNA topoisomerase I and topoisomerase II.

BackgroundLapachol is a natural naphthoquinone compound that possesses extensive biological activities. The aim of this study is to investigate the inhibitory effects of lapachol on rat C6 glioma both in vitro and in vivo, as well as the potential mechanisms.MethodsThe antitumor effect of lapachol was firstly evaluated in the C6 glioma model in Wistar rats. The effects of lapachol on C6 cell proliferation, apoptosis and DNA damage were detected by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS)/ phenazinemethosulfate (PMS) assay, hoechst 33358 staining, annexin V-FITC/PI staining, and comet assay. Effects of lapachol on topoisomerase I (TOP I) and topoisomerase II (TOP II) activities were detected by TOP I and TOP II mediated supercoiled pBR322 DNA relaxation assays and molecular docking. TOP I and TOP II expression levels in C6 cells were also determined.ResultsHigh dose lapachol showed significant inhibitory effect on the C6 glioma in Wistar rats (P < 0.05). It was showed that lapachol could inhibit proliferation, induce apoptosis and DNA damage of C6 cells in dose dependent manners. Lapachol could inhibit the activities of both TOP I and II. Lapachol-TOP I showed relatively stronger interaction than that of lapachol-TOP II in molecular docking study. Also, lapachol could inhibit TOP II expression levels, but not TOP I expression levels.ConclusionThese results showed that lapachol could significantly inhibit C6 glioma both in vivo and in vitro, which might be related with inhibiting TOP I and TOP II activities, as well as TOP II expression.

Combination of baicalein and 10-hydroxy camptothecin exerts remarkable synergetic anti-cancer effects

Background10-Hydroxy camptothecin (HCPT), a naturally occurring alkaloid, is a clinical drug for cancer chemotherapy. Baicalein (BA) is a flavonoid extracted from the root of Scutellaria baicalensis. The synergistic anti-cancer effect of BA and HCPT has not been reported. PurposeTo explore whether and how BA enhances the anti-cancer effect of HCPT in BGC823 cells. MethodsCell viability was measured by MTT assay. Apoptosis and cell cycle were analyzed through flow cytometry and western blotting analysis. DNA damage was determined by a comet assay. The activity of topoisomerase I (Topo I) was detected by the plasmid DNA relaxation assay. The synergistic anti-cancer effect of BA and HCPT in vivo was tested by BGC823 xenografted tumor model. ResultsBA at non-toxic doses prominently enhanced the anti-cancer activities of HCPT in BGC823, MCF7 and SMMC7721 cells. Combination treatment of BA and HCPT induced BGC823 cells apoptosis mainly via intrinsic rather than extrinsic pathways, and preferentially arresting cell cycle in G1 and G2 phases with the aid of p21. Of note, p53, the upstream regulator of cell apoptosis and cycle, was increased by 5 folds in combination group. It helped to further trigger DNA damage and inhibit Topo I catalytic activity after combination treatment of BA and HCPT. Moreover, the BGC823 xenografted tumor growth rate in nude mice was repressed in a greater degree (P< 0.01) in the combinational group than the single-drug group. ConclusionHCPT and BA, a new and effective combination therapy, synergistically target Topo I and up-regulate p53 to induce cell apoptosis and cell cycle arrest.

In Vitro Studies on Pesticide-Induced Oxidative DNA Damage

Pesticides are among the most extensively chemicals used in the world today and they are also among the most hazardous compounds for the human. This study was designed to use the plasmid relaxation assay to describe the association of markers of DNA damage with pesticide exposure. The DNA damage activity of fluoxastrobin and imazamox were checked on pBluescript M13+ plasmid DNA (3.2 kb) in the absence and presence of Cu(II) ions. It has been found that the fluoxastrobin and imazamox can effectively promote cleavage of plasmid DNA in the absence and presence of Cu(II) ions. DNA cleavage was found to be concentration and dependent. In conclusion, the present study showed that fluoxastrobin and imazamox can induce DNA damage, which warrants for further investigations to correctly evaluate the hazards of exposure to these chemicals.

Fluorescein hydrazones: A series of novel non-intercalative topoisomerase IIα catalytic inhibitors induce G1 arrest and apoptosis in breast and colon cancer cells

Fluorescein hydrazones (5 and 7) were synthesized in three/four steps with 82–92% yields. All synthesized compounds were evaluated by topoisomerase I (topo I) and topoisomerase IIα (topo IIα)-mediated relaxation and cell viability assays. Among them, most of the compounds showed topo I & IIα inhibitory activity and nineteen compounds showed strong anti-proliferative activity against various cell lines. In brief, 5e inhibited 53% topo IIα (etoposide 29%) at 20 μM and showed excellent antiproliferative activity against DU145 (1.43 ± 0.04 μM), HCT15 (2.4 ± 0.03 μM) and MCF7 (11.4 ± 0.5 μM) cell lines in comparison with adriamycin, etoposide, and camptothecin. Compounds 5e, 5g and 5h were further evaluated to determine their mode of action. Compounds 5e, 5g and 5h functioned as non-intercalative topo IIα catalytic inhibitor with induction of G1 arrest and activation of apoptotic proteins in dose-dependent manner.

Novel 2-aryl-4-(4′-hydroxyphenyl)-5H-indeno[1,2-b]pyridines as potent DNA non-intercalative topoisomerase catalytic inhibitors

On the basis of previous reports on the importance of thienyl, furyl or phenol group substitution on 5H-indeno[1,2-b]pyridine skeleton, a new series of rigid 2-aryl-4-(4′-hydroxyphenyl)-5H-indeno[1,2-b]pyridine derivatives were systematically designed and synthesized. Topoisomerase inhibitory activity and antiproliferative activity of all the synthesized compounds were determined using human colorectal (HCT15), breast (T47D), prostate (DU145) and cervix (HeLa) cancer cells. Compounds 9, 10, 12, 13, 15, 16, 18 and 19 with thienyl or furyl moiety at the 2-position and hydroxyl group at the meta or para positions of 4-phenyl ring displayed strong to moderate topoisomerase IIα (topo IIα) inhibitory activity and significant antiproliferative activity. The evaluation of compound 16 to determine its mechanism of action was performed with topo IIα-DNA cleavable complex, topo IIα-mediated ATPase assay, DNA unwinding and in vitro and ex vivo topo IIα relaxation assay. Compound 16 functioned as a DNA non-intercalative topo IIα catalytic inhibitor with better potency than etoposide in T47D breast cancer cells. Molecular docking study revealed that compound 16 cannot intercalate into regularly stacked base-pairs of DNA duplex but can interact or intercalate to topo IIα-bound DNA.

Synthesis and biological evaluation of imidazopyridinyl-1,3,4-oxadiazole conjugates as apoptosis inducers and topoisomerase IIα inhibitors

A series of imidazopyridinyl-1,3,4-oxadiazole conjugates were synthesized and investigated for their cytotoxic activity and some compounds showed promising cytotoxic activity. Compound 8q (NSC: 763639) exhibited notable growth inhibition that satisfies threshold criteria at single dose (10μM) on all human cancer cell lines. This compound was further evaluated at five dose levels (0.01, 0.1, 1, 10 and 100μM) to obtain GI50 values ranging from 1.30 to 5.64μM. Flow cytometric analysis revealed that compound 8q arrests the A549 cells in sub G1 phase followed by induction of apoptosis which was further confirmed by Annexin-V-FITC, Hoechst nuclear staining, caspase 3 activation, measurement of mitochondrial membrane potential and ROS generation. Topo II mediated DNA relaxation assay results showed that conjugate 8q could significantly inhibit the activity of topo II. Moreover, molecular docking studies also indicated binding to the topoisomerase enzyme (PDBID 1ZXN).

Supercritical Fluid Technology-Based Trans-Resveratrol SLN for Long Circulation and Improved Radioprotection

To alleviate the harmful effects of radiations during occupational radiology, radiotherapy and diagnosis, radioprotective system with lower toxicity and extended activity is imperative. Trans-resveratrol (RVL) acts through free radical scavenging/antioxidant mechanism to mitigate the radiation-induced damage. But, its poor solubility and fast metabolism impede its efficacy. Thus, encapsulation of RVL into long circulating solid lipid nanoparticle (SLN) is aimed. Supercritical CO2 solution of RVL, Gelucire®50/02 and Gelucire®50/13 SLN, was rapidly expanded into aqueous phase containing Tween 80, sonicated and lyophilized to get SLN. Particle size, polydispersity index (PDI), entrapment efficiency (%EE), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), drug release, in vivo pharmacokinetics, antioxidant assays, radiation-induced lipid peroxidation and plasmid DNA relaxation assays were studied. Stability studies were performed to analyze drug degradation and shelf life. Optimized formulation (F9) had %yield, particle size, PDI, %EE and %drug release (after 72 h) of 68.48 ± 5.73 %, 276.7 ± 5.33 nm, 0.18 ± 0.032, 62.66 ± 4.52 % and 70.05 ± 3.003 %, respectively. Electron microscopy revealed nearly spherical particles, while DSC and XRD showed reduced crystalline peaks. F9 showed higher AUC and sustained release of RVL in rats (i.v. bolus) and increased antioxidant activities and radioprotection as compared to RVL solution. Shelf life of >2 years was predicted for F9 (at 8 °C). Results are encouraging to use F9 for radiation exposure prophylaxis.

Assessment of the chemotherapeutic potential of a new camptothecin derivative, ZBH-1205

CPT-11 (irinotecan) is a derivative of camptothecin which is a natural product derived from the Chinese tree Camptotheca acuminta and widely used in antitumor therapy. Here, the in vitro anti-tumor activity and associated mechanisms of a novel derivative of camptothecin, ZBH-1205, were investigated in a panel of 9 human tumor cell lines, as well as in HEK 293 and SK-OV-3/DPP, a multi-drug resistant (MDR) cell line, and compared to CPT-11 and 7-ethyl-10-hydroxy-camptothecin (SN38). Comparisons between the different compounds were made on the basis of IC50 values as determined by the MTT assay, and flow cytometry was used to evaluate cell cycle progression, apoptosis, and the levels of pro- and active caspase-3 among different treatment groups. Interaction between the molecules and topoisomerase-1 (Topo-1)-DNA complexes was detected by a DNA relaxation assay. Our results demonstrated that IC50 values for ZBH-1205 ranged from 0.0009 μmol/L to 2.5671 μmol/L, which were consistently lower than IC50 values of CPT-11 or SN38 in the panel of cell lines, including SK-OV-3/DPP. Furthermore, ZBH-1205 was more effective than CPT-11 or SN38 at stabilizing Topo-1-DNA complexes and inducing tumor cell apoptosis. Therefore, ZBH-1205 is a promising chemotherapeutic agent to be further assessed in large-scale clinical trials.

Design, synthesis, topoisomerase I & II inhibitory activity, antiproliferative activity, and structure–activity relationship study of pyrazoline derivatives: An ATP-competitive human topoisomerase IIα catalytic inhibitor

A series of pyrazoline derivatives (5) were synthesized in 92–96% yields from chalcones (3) and hydrazides (4). Subsequently, topo-I and IIα-mediated relaxation and antiproliferative activity assays were evaluated for 5. Among the tested compounds, 5h had a very strong topo-I activity of 97% (Camptothecin, 74%) at concentration of 100μM. Nevertheless, all the compounds 5a–5i showed significant topo II inhibitory activity in the range of 90–94% (Etoposide, 96%) at the same concentration. Cytotoxic potential of these compounds was tested in a panel of three human tumor cell lines, HCT15, BT474 and T47D. All the compounds showed strong activity against HCT15 cell line with IC50 at the range of 1.9–10.4μM (Adriamycin, 23.0; Etoposide, 6.9; and Camptothecin, 7.1μM). Moreover, compounds 5c, 5f and 5i were observed to have strong antiproliferative activity against BT474 cell lines. Since, compound 5d showed antiproliferative activity at a very low IC50 thus 5d was then selected to study on their mode of action with diverse methods of ATP competition assay, ATPase assay and DNA-topo IIα cleavable complex assay and the results revealed that it functioned as a ATP-competitive human topoisomerase IIα catalytic inhibitor. Further evaluation of endogenous topo-mediated DNA relaxation in cells has been conducted to find that, 5d inhibited endogenous topo-mediated pBR322 plasmid relaxation is more efficient (78.0±4.7% at 50μM) than Etoposide (36.0±1.7% at 50μM).

The combined effects of proteasome inhibitor bortezomib with topoisomerase I and II inhibitors on topoisomerase enzymes.

DNA topoisomerases are ubiquitous enzymes that regulate conformational changes in DNA topology during essential cellular processes, and, for this reason, have been characterized as the cellular targets of a number of anticancer drugs. Bortezomib is a powerful proteasome inhibitor used in the treatment of hematological malignancies. In this study, we investigated the inhibitory effects of bortezomib on human topoisomerase I and II enzymes both alone and in combination modes with camptothecin and etoposide. The interactions of these drugs with topoisomerase enzymes were evaluated by relaxation assay in cell-free systems. IC50 values of the drugs on topoisomerase enzymes were calculated using the S probit analysis program. Bortezomib showed a very weak inhibition effect on topoisomerase I (IC50 = 87.11 mM). On the other hand, it had a strong inhibitory effect on topoisomerase II (IC50 = 1.41 mM). Our results indicated that bortezomib is effective not only on proteasome but also on topoisomerase II. In addition, bortezomib possesses an increased synergistic effect when used in combination with camptothecin and etoposide than when used alone. The results of this study point out that these data may build a framework for combination studies with bortezomib, camptothecin, and etoposide in the treatment of cancer.

Dextran and poly(butyl methacrylate) graft copolymers as non-adherent materials for vascular applications

Event Abstract Back to Event Dextran and poly(butyl methacrylate) graft copolymers as non-adherent materials for vascular applications Eléonore Michel1, 2, Pascale Chevallier1, Caroline Loy1, Lucie Lévesque1, Didier Letourneur2 and Diego Mantovani1 1 CHU de Québec Research Center, Laval University, Lab. Biomaterials and Bioengineering, CRC-I, Dept Min-Met-Materials Eng., Canada 2 Institut Galilée, Université Paris 13, Sorbonne Paris Cité, INSERM, U1148, Laboratory for Vascular Translational Science, France Introduction: Various polymers have been investigated and developed to resist to non-specific adhesion to avoid or limit adsorption of proteins, cells, bacterial or platelets adhesion, known to lead to inflammation, infections and to be the main responsible for the eventual failure of the implant. Thus, a major challenge in the field aims to decrease the hydrophobicity for enhancing the biocompatibility in an effort for compromising biological and mechanical properties. Polysaccharides, polyacrylates and their derivatives have been reported in many biomedical fields as potential candidates for antifouling, tissue engineering or hemocompatible applications[1]-[3]. This work aimed to develop and investigate copolymers of carboxymethyldextran and polybutylmethacrylate which are susceptible to show interesting mechanical and non-adherent properties especially suitable for vascular applications. Material and Methods: Graft copolymers (CMD-PBMA) have been synthesized by radical copolymerization with Ce(IV) ions, from butyl methacrylate monomers (BMA) and carboxymethyldextran (CMD) (Table 1)[4],[5]. Synthesis were characterized by mass balance, and copolymers by solid state 13C-NMR, FTIR as well as by SEC/HPLC after acid hydrolysis allowing to differentiate PBMA and CMD chains. Films have been prepared by dispersion of CMD-PBMA (50 mg/mL) in THF/water (90:10) poured in a mold and placed under THF atmosphere with CaCl2 overnight. Relaxation assay (ɛ = 3 %) were performed on dumbbell-shaped films with an Instron 5944 system, at 10 mm/min, until 25% of deformation and then up to rupture. Cytotoxicity and proliferation assays were performed with 3T3 fibroblast (15000 cells/cm²) and HUVEC (40000 cell/cm²). Cytotoxicity was investigated after 24h by resazurin with 1 and 7 days extracts. Cells viability was tested with resazurin prior observation of proliferation by fluorescence microscopy after 1, 4 and 7 days. Clotting assay was evaluated after 25 min of contact with whole blood by measuring free hemoglobin in absorbance. Results and Discussion: NMR and FTIR spectra of copolymers clearly evidenced the characteristic peaks of both CMD and PBMA. Whatever the copolymer considered, they were mostly made of PBMA chains (80-90%) which were 10 times larger than CMD ones as seen in Table 1. Furthermore, the reaction yield was quite low mainly due to PBMA homopolymer formation. It has been noticed that for both ratios of CMD/BMA used, CMD 0.2 led to higher yields than CMD 0.4, due to more available substitution sites (less COOH) for radical copolymerization. Latest observations, get along with the polymerization scheme involving PBMA macro-radicals formation and their recombination on the CMD backbone. Despite these differences, all copolymers films showed equivalent composition after XPS analyses and higher hydrophilicity than PBMA (80° vs 95°). Mechanical relaxation assays on CMD-PBMA films showed quasi-total relaxation of stress and elongations to fracture up to 60% whereas PBMA films were too brittle to be unmolded. Copolymer films did not induce cytotoxicity and HUVECs and 3T3 fibroblasts did not adhere, therefore no further proliferation has been observed (Figure 1). No difference in hemocompatibility was observed between copolymers and PBMA. Conclusions: The presence of CMD in the copolymer lead to increase mechanical resistance while antifouling properties of PBMA are preserved, as no cells adhere, and non-cytotoxicity is shown. Regardless the substitution degree of CMD and the BMA/CMD ratio considered, copolymers exhibit similar biological and mechanical properties. Therefore, these copolymers appear as promising materials for non-adherent coatings or polymers for vascular applications. This work was supported by Inserm-FRSQ, FP7 european program PRESTIGE, the Natural Science and Engineering Research Council of Canada, the Quebec Ministry for International Relations, the Centre Franco-Québecois de Coopération Universitaire, Centre d’Études et de Recherche sur les Matériaux Avancés (CERMA-ULaval), the CHU de Québec Research Center, the Centre Franco-Québecois de Coopération Universitaire, and the Research Center of CHU de Québec. The authors would like to express their gratitude to all the volunteers who donated blood and all technicians involved.

Synthesis and Mechanism Studies of 1,3-Benzoazolyl Substituted Pyrrolo[2,3-b]pyrazine Derivatives as Nonintercalative Topoisomerase II Catalytic Inhibitors.

Novel topoisomerase II (Topo II) inhibitors have gained considerable interest for the development of anticancer agents. In this study, a series of 1,3-benzoazolyl-substituted pyrrolo[2,3-b]pyrazine derivatives were designed, synthesized, and evaluated as potential Topo II catalytic inhibitors. It was found that some of derivatives had good antiproliferative activity on seven cancer cell lines, especially on HL-60/MX2, a cancer cell line derivative from HL-60 that is resistant to Topo II poison. Topo II mediated DNA relaxation assay results showed that derivatives could significantly inhibit the activity of Topo II, and the structure-activity relationship studies indicated the importance of the alkylamino side chain and the benzoazolyl group. Further mechanism studies revealed that derivatives function as Topo II nonintercalative catalytic inhibitors and may block the ATP binding site of Topo II. Moreover, flow cytometric analysis showed that this class of compounds could induce apoptosis of HL-60 cells.

Single-Molecule Supercoil Relaxation Assay as a Screening Tool to Determine the Mechanism and Efficacy of Human Topoisomerase IB Inhibitors.

Human nuclear type IB topoisomerase (Top1) inhibitors are widely used and powerful anticancer agents. In this study, we introduce and validate a single-molecule supercoil relaxation assay as a molecular pharmacology tool for characterizing therapeutically relevant Top1 inhibitors. Using this assay, we determined the effects on Top1 supercoil relaxation activity of four Top1 inhibitors; three clinically relevant: camptothecin, LMP-400, LMP-776 (both indenoisoquinoline derivatives), and one natural product in preclinical development, lamellarin-D. Our results demonstrate that Top1 inhibitors have two distinct effects on Top1 activity: a decrease in supercoil relaxation rate and an increase in religation inhibition. The type and magnitude of the inhibition mode depend both on the specific inhibitor and on the topology of the DNA substrate. In general, the efficacy of inhibition is significantly higher with supercoiled than with relaxed DNA substrates. Comparing single-molecule inhibition with cell growth inhibition (IC50) measurements showed a correlation between the binding time of the Top1 inhibitors and their cytotoxic efficacy, independent of the mode of inhibition. This study demonstrates that the single-molecule supercoil relaxation assay is a sensitive method to elucidate the detailed mechanisms of Top1 inhibitors and is relevant for the cellular efficacy of Top1 inhibitors.

Nano-silymarin provides protection against γ-radiation-induced oxidative stress in cultured human embryonic kidney cells

Radiation can produce biological damage, mainly oxidative stress, via production of free radicals, including reactive oxygen species (ROS). Nanoparticles are of interest as radioprotective agents, particularly due to their high solubility and bioavailability. Silymarin is a hepatoprotective agent but has poor oral bioavailability. Silymarin was formulated as a nanoemulsion with the aim of improving its bioavailability and therapeutic efficacy. In the present study, we evaluated self-nanoemulsifying drug delivery systems (SNEDDS) formulated with surfactants and co-surfactants. Nano-silymarin was characterized by estimating % transmittance, globule size, and polydispersity index, and by transmission electron microscopy (TEM). The nano-silymarin obtained was in the range of 3–8nm diameter. With regard to DNA damage, measured by a plasmid relaxation assay, maximum protection was obtained at 10μg/mL. Cytotoxicity of nano-silymarin to human embryonic kidney (HEK) cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Protective efficacy against γ-radiation was assessed by reduction in micronucleus frequency and ROS generation, using the 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) assay. Radiation-induced apoptosis was estimated by microscopic analysis and cell-cycle estimation. Nano-silymarin was radioprotective, supporting the possibility of developing new approaches to radiation protection via nanotechnology.

Synthesis and biological evaluation of 6-substituted indolizinoquinolinediones as catalytic DNA topoisomerase I inhibitors

In our previous work, indolizinoquinolinedione derivative 1 was identified as a Top1 catalytic inhibitor. Herein, a series of 6-substituted indolizinoquinolinedione derivatives were synthesized through modification of the parent compound 1. Top1 cleavage and relaxation assays indicate that none of these novel compounds act as classical Top1 poison, and that the compounds with alkylamino terminus at C-6 side chain, including 8, 11–16, 18–21, 25, 26 and 28–30, are the most potent Top1 catalytic inhibitors. Top1-mediated unwinding assay demonstrated that 14, 22 and 26 were Top1 catalytic inhibitors without Top1-mediated unwinding effect. Moreover, MTT results showed that compounds 26, 28–30 exhibit significant cytotoxicity against human leukemia HL-60 cells, and that compound 26 exerts potent cytotoxicity against A549 lung cancer cells at nanomolar range.

The Topoisomerase 1 Inhibitor Austrobailignan-1 Isolated from Koelreuteria henryi Induces a G2/M-Phase Arrest and Cell Death Independently of p53 in Non-Small Cell Lung Cancer Cells.

Koelreuteria henryi Dummer, an endemic plant of Taiwan, has been used as a folk medicine for the treatment of hepatitis, enteritis, cough, pharyngitis, allergy, hypertension, hyperlipidemia, and cancer. Austrobailignan-1, a natural lignan derivative isolated from Koelreuteria henryi Dummer, has anti-oxidative and anti-cancer properties. However, the effects of austrobailignan-1 on human cancer cells have not been studied yet. Here, we showed that austrobailignan-1 inhibited cell growth of human non-small cell lung cancer A549 and H1299 cell lines in both dose- and time-dependent manners, the IC50 value (48 h) of austrobailignan-1 were 41 and 22 nM, respectively. Data from flow cytometric analysis indicated that treatment with austrobailignan-1 for 24 h retarded the cell cycle at the G2/M phase. The molecular event of austrobailignan-1-mediated G2/M phase arrest was associated with the increase of p21Waf1/Cip1 and p27Kip1 expression, and decrease of Cdc25C expression. Moreover, treatment with 100 nM austrobailignan-1 for 48 h resulted in a pronounced release of cytochrome c followed by the activation of caspase-2, -3, and -9, and consequently induced apoptosis. These events were accompanied by the increase of PUMA and Bax, and the decrease of Mcl-1 and Bcl-2. Furthermore, our study also showed that austrobailignan-1 was a topoisomerase 1 inhibitor, as evidenced by a relaxation assay and induction of a DNA damage response signaling pathway, including ATM, and Chk1, Chk2, γH2AX phosphorylated activation. Overall, our results suggest that austrobailignan-1 is a novel DNA damaging agent and displays a topoisomerase I inhibitory activity, causes DNA strand breaks, and consequently induces DNA damage response signaling for cell cycle G2/M arrest and apoptosis in a p53 independent manner.

Antitumor activity of a 2-pyridinecarboxaldehyde 2-pyridinecarboxylic acid hydrazone copper complex and the related mechanism.

In the present study, 2-pyridinecarboxaldehyde 2-pyridinecarboxylic acid hydrazone (PPAH) was prepared and its antitumor activity was evaluated. The inhibition of proliferation of PPAH against the HepG2 and HCT-116 cell lines was less effective, yet in the presence of copper ions, the mixture demonstrated excellent antitumor activity (IC50 at 2.75±0.30µM for the HepG2 cell line, and 1.90±0.20µM for the HCT-116 cell line, respectively) and the new active species was confirmed to be a PPAH copper complex with a 1:1 ratio by spectral analysis. The excellent antitumor activity of the copper complex prompted us to investigate the underlying mechanism. RT-PCR was performed to detect the changes in the expression of apoptotic genes induced by PPAH and its copper complex. However, no changes were observed when the cells were treated by the agents for 24 or 48h, indicating that ROS were unlikely involved. Cell cycle analysis showed that both PPAH and its copper complex led to Sphase arrest of the cells. The sDNA relaxation assay revealed that the PPAH-copper complex displayed dual topoisomerase inhibition for typeI and II. The data suggest that the inhibition of proliferation exhibited by the PPAH copper complex may stem from its dual topoisomerase inhibition, which is rarely observed for a metal complex.