Guanine Oxidation in Double-stranded DNA by MnTMPyP/KHSO5: At Least Three Independent Reaction Pathways

In order to better define the mechanism and the products of guanine oxidation within DNA, we investigated the details of the mechanism of guanine oxidation by a metalloporphyrin, Mn-TMPyP, associated to KHSO5 on oligonucleotides. We found that the three major products of guanine oxidation are formed by independent reaction routes. The oxidized guanidinohydantoin (1) and the proposed spiro compound 3 derivatives are not precursors of imidazolone lesion (Iz). These guanine lesions as well as their degradation products, may account for non-detected guanine oxidation products on oxidatively damaged DNA

Ethical Screening and Financial Performance: Evidence from US Mutual Funds.

This paper investigates the performance of US SRI Funds, over the time period January 2011 to April 2016. The paper focuses on heterogeneity of screening methodologies by using panel data analysis, which extends the research about SRI funds’ performance. Using different measures of performance, the study examines the effect of ethical screening on financial performance and financial risk. I find that screening intensity has a curvilinear effect on financial performance, and on risk as well, what makes the choice of screens really sensitive. Therefore, I also analyse the impact of screening areas and approaches. I find that Governance screening has a positive impact on fund’s performance, whereas restricted screening and avoiding industries badly impact financial performance

Tool Embodiment Is Reflected in Movement Multifractal Nonlinearity

Recent advances in neuroscience have linked dynamical systems theory to cognition. The main contention is that extended cognition relies on a unitary brain-body-tool system showing the expected signatures of interaction-dominance reflected in a multifractal behavior. This might be particularly relevant when it comes to understanding how the brain is able to embody a tool to perform a task. Here we applied the multifractal formalism to the dynamics of hand movement while one was performing a computer task (the herding task) using a mouse or its own hand as a tool to move an object on the screen. We applied a focus-based multifractal detrended fluctuation analysis to acceleration time series. Then, multifractal nonlinearity was assessed by comparing original series to a finite set of surrogates obtained after Iterated Amplitude Adjusted Fourier transformation, a method that removes nonlinear multiscale dependencies while preserving the linear structure of the time series. Both hand and mouse task execution demonstrated multifractal nonlinearity, a typical form of across-scales interactivity in cognitive control. In addition, a wider multifractal spectrum was observed in mouse condition, which might highlight a richer set of interactions when the cognitive system is extended to the embodied mouse. We conclude that the emergence of multifractal nonlinearity from a brain-body-tool system pleads for recent theories of radical tool embodiment. Multifractal nonlinearity may be a promising metric to appreciate how physical objects—but also virtual tools and potentially prosthetics—are efficiently embodied by the brain

Antitrypanosomatid Pharmacomodulation at Position 3 of the 8-Nitroquinolin-2(1H)-one Scaffold Using Palladium-Catalysed Cross-Coupling Reactions

International audienceAn antikinetoplastid pharmacomodulation study at position 3 of the recently described hit molecule 3-bromo-8-nitroquinolin-2(1H)-one was conducted. Twenty-four derivatives were synthesised using the Suzuki-Miyaura cross-coupling reaction and evaluated in vitro on both Leishmania infantum axenic amastigotes and Trypanosoma brucei brucei trypomastigotes. Introduction of a para-carboxyphenyl group at position 3 of the scaffold led to the selective antitrypanosomal hit molecule 3-(4-carboxyphenyl)-8-nitroquinolin-2(1H)-one (21) with a lower reduction potential (-0.56 V) than the initial hit (-0.45 V). Compound 21 displays micromolar antitrypanosomal activity (IC50 =1.5 μm) and low cytotoxicity on the human HepG2 cell line (CC50 =120 μm), having a higher selectivity index (SI=80) than the reference drug eflornithine. Contrary to results previously obtained in this series, hit compound 21 is inactive toward L. infantum and is not efficiently bioactivated by T. brucei brucei type I nitroreductase, which suggests the existence of an alternative mechanism of action

Novel 8-nitroquinolin-2(1H)-ones as NTR-bioactivated antikinetoplastid molecules:Synthesis, electrochemical and SAR study

International audienceTo study the antiparasitic 8-nitroquinolin-2(1H)-one pharmacophore, a series of 31 derivatives was synthesized in 1-5 steps and evaluated in vitro against both Leishmania infantum and Trypanosoma brucei brucei. In parallel, the reduction potential of all molecules was measured by cyclic voltammetry. Structure-activity relationships first indicated that antileishmanial activity depends on an intramolecular hydrogen bond (described by X-ray diffraction) between the lactam function and the nitro group, which is responsible for an important shift of the redox potential (+0.3 V in comparison with 8-nitroquinoline). With the assistance of computational chemistry, a set of derivatives presenting a large range of redox potentials (from -1.1 to -0.45 V) was designed and provided a list of suitable molecules to be synthesized and tested. This approach highlighted that, in this series, only substrates with a redox potential above -0.6 V display activity toward L. infantum. Nevertheless, such relation between redox potentials and in vitro antiparasitic activities was not observed in T. b. brucei. Compound 22 is a new hit compound in the series, displaying both antileishmanial and antitrypanosomal activity along with a low cytotoxicity on the human HepG2 cell line. Compound 22 is selectively bioactivated by the type 1 nitroreductases (NTR1) of L. donovani and T. brucei brucei. Moreover, despite being mutagenic in the Ames test, as most of nitroaromatic derivatives, compound 22 was not genotoxic in the comet assay. Preliminary in vitro pharmacokinetic parameters were finally determined and pointed out a good in vitro microsomal stability (half-life > 40 min) and a 92% binding to human albumin

8-Aryl-6-chloro-3-nitro-2-(phenylsulfonylmethyl)imidazo[1,2-a]pyridines as potent antitrypanosomatid molecules bioactivated by type 1 nitroreductases

Based on a previously identified antileishmanial 6,8-dibromo-3-nitroimidazo[1,2-a]pyridine derivative, a Suzuki-Miyaura coupling reaction at position 8 of the scaffold was studied and optimized from a 8-bromo-6-chloro-3-nitroimidazo[1,2-a]pyridine substrate. Twenty-one original derivatives were prepared, screened in vitro for activity against L infantum axenic amastigotes and T. brucei brucei trypomastigotes and evaluated for their cytotoxicity on the HepG2 human cell line. Thus, 7 antileishmanial hit compounds were identified, displaying IC50 values in the 1.1-3 mu M range. Compounds 13 and 23, the 2 most selective molecules (SI = >18 or >17) were additionally tested on both the promastigote and intramacrophage amastigote stages of L donovani. The two molecules presented a good activity (IC50 = 1.2-1.3 mu M) on the promastigote stage but only molecule 23, bearing a 4-pyridinyl substituent at position 8, was active on the intracellular amastigote stage, with a good IC50 value (2.3 mu M), slightly lower than the one of miltefosine (IC50 = 4.3 mu M). The antiparasitic screening also revealed 8 antitrypanosomal hit compounds, including 14 and 20, 2 very active (IC50 = 0.04-0.16 mu M) and selective (SI = >313 to 550) molecules toward T brucei brucei, in comparison with drug-candidate fexinidazole (IC50 = 0.6 & SI > 333) or reference drugs suramin and eflornithine (respective IC50 = 0.03 and 13.3 mu M). Introducing an aryl moiety at position 8 of the scaffold quite significantly increased the antitrypanosomal activity of the pharmacophore. Antikinetoplastid molecules 13, 14, 20 and 23 were assessed for bioactivation by parasitic nitroreductases (either in L donovani or in T. brucei brucei), using genetically modified parasite strains that over-express NTRs: all these molecules are substrates of type 1 nitroreductases (NTRI), such as those that are responsible for the bioactivation of fexinidazole. Reduction potentials measured for these 4 hit compounds were higher than that of fexinidazole (-0.83 V), ranging from -0.70 to -0.64 V

New 8-nitroquinolinone derivative displaying submicromolar in vitro activities against both Trypanosoma brucei and cruzi

International audienceAn antikinetoplastid pharmacomodulation study was conducted at position 6 of the 8-nitroquinolin-2(1H)-one pharmacophore. Fifteen new derivatives were synthesized and evaluated in vitro against L. infantum, T. brucei brucei, and T. cruzi, in parallel with a cytotoxicity assay on the human HepG2 cell line. A potent and selective 6-bromo-substituted antitrypanosomal derivative 12 was revealed, presenting EC50 values of 12 and 500 nM on T. b. brucei trypomastigotes and T. cruzi amastigotes respectively, in comparison with four reference drugs (30 nM ≤ EC50 ≤ 13 μM). Moreover, compound 12 was not genotoxic in the comet assay and showed high in vitro microsomal stability (half life >40 min) as well as favorable pharmacokinetic behavior in the mouse after oral administration. Finally, molecule 12 (E° = −0.37 V/NHE) was shown to be bioactivated by type 1 nitroreductases, in both Leishmania and Trypanosoma, and appears to be a good candidate to search for novel antitrypanosomal lead compounds

Oxidation of single-stranded oligonucleotides by carbonate radical anions: generating intrastrand cross-links between guanine and thymine bases separated by cytosines

The carbonate radical anion is a biologically important one-electron oxidant that can directly abstract an electron from guanine, the most easily oxidizable DNA base. Oxidation of the 5′-d(CCTACGCTACC) sequence by photochemically generated CO3·− radicals in low steady-state concentrations relevant to biological processes results in the formation of spiroiminodihydantoin diastereomers and a previously unknown lesion. The latter was excised from the oxidized oligonucleotides by enzymatic digestion with nuclease P1 and alkaline phosphatase and identified by LC-MS/MS as an unusual intrastrand cross-link between guanine and thymine. In order to further characterize the structure of this lesion, 5′-d(GpCpT) was exposed to CO3·− radicals, and the cyclic nature of the 5′-d(G*pCpT*) cross-link in which the guanine C8-atom is bound to the thymine N3-atom was confirmed by LC-MS/MS, 1D and 2D NMR studies. The effect of bridging C bases on the cross-link formation was studied in the series of 5′-d(GpCnpT) and 5′-d(TpCnpG) sequences with n = 0, 1, 2 and 3. Formation of the G*-T* cross-links is most efficient in the case of 5′-d(GpCpT). Cross-link formation (n = 0) was also observed in double-stranded DNA molecules derived from the self-complementary 5′-d(TTACGTACGTAA) sequence following exposure to CO3·− radicals and enzymatic excision of the 5′-d(G*pT*) product

Quantification of the 2-Deoxyribonolactone and Nucleoside 5 '-Aldehyde Products of 2-Deoxyribose Oxidation in DNA and Cells by Isotope-Dilution Gas Chromatography Mass Spectrometry: Differential Effects of gamma-Radiation and Fe2+-EDTA

The oxidation of 2-deoxyribose in DNA has emerged as a critical determinant of the cellular toxicity of oxidative damage to DNA, with oxidation of each carbon producing a unique spectrum of electrophilic products. We have developed and validated an isotope-dilution gas chromatography-coupled mass spectrometry (GC−MS) method for the rigorous quantification of two major 2-deoxyribose oxidation products: the 2-deoxyribonolactone abasic site of 1′-oxidation and the nucleoside 5′-aldehyde of 5′-oxidation chemistry. The method entails elimination of these products as 5-methylene-2(5H)-furanone (5MF) and furfural, respectively, followed by derivatization with pentafluorophenylhydrazine (PFPH), addition of isotopically labeled PFPH derivatives as internal standards, extraction of the derivatives, and quantification by GC−MS analysis. The precision and accuracy of the method were validated with oligodeoxynucleotides containing the 2-deoxyribonolactone and nucleoside 5′-aldehyde lesions. Further, the well-defined 2-deoxyribose oxidation chemistry of the enediyne antibiotics, neocarzinostatin and calicheamicin γ1I, was exploited in control studies, with neocarzinostatin producing 10 2-deoxyribonolactone and 300 nucleoside 5′-aldehyde per 106 nt per μM in accord with its established minor 1′- and major 5′-oxidation chemistry. Calicheamicin unexpectedly caused 1′-oxidation at a low level of 10 2-deoxyribonolactone per 106 nt per μM in addition to the expected predominance of 5′-oxidation at 560 nucleoside 5′-aldehyde per 106 nt per μM. The two hydroxyl radical-mediated DNA oxidants, γ-radiation and Fe2+−EDTA, produced nucleoside 5′-aldehyde at a frequency of 57 per 106 nt per Gy (G-value 74 nmol/J) and 3.5 per 106 nt per μM, respectively, which amounted to 40% and 35%, respectively, of total 2-deoxyribose oxidation as measured by a plasmid nicking assay. However, γ-radiation and Fe2+−EDTA produced different proportions of 2-deoxyribonolactone at 7% and 24% of total 2-deoxyribose oxidation, respectively, with frequencies of 10 lesions per 106 nt per Gy (G-value, 13 nmol/J) and 2.4 lesions per 106 nt per μM. Studies in TK6 human lymphoblastoid cells, in which the analytical data were corrected for losses sustained during DNA isolation, revealed background levels of 2-deoxyribonolactone and nucleoside 5′-aldehyde of 9.7 and 73 lesions per 106 nt, respectively. γ-Irradiation of the cells caused increases of 0.045 and 0.22 lesions per 106 nt per Gy, respectively, which represents a 250-fold quenching effect of the cellular environment similar to that observed in previous studies. The proportions of the various 2-deoxyribose oxidation products generated by γ-radiation are similar for purified DNA and cells. These results are consistent with solvent exposure as a major determinant of hydroxyl radical reactivity with 2-deoxyribose in DNA, but the large differences between γ-radiation and Fe2+−EDTA suggest that factors other than hydroxyl radical reactivity govern DNA oxidation chemistry.National Institute of Environmental Health Sciences (ES002109)National Center for Research Resources (U.S.) (RR023783-01)National Center for Research Resources (U.S.) (RR017905-01)National Cancer Institute (U.S.) (CA103146