A mechanistic study on the phototoxicity of atorvastatin: singlet oxygen generation by a phenanthrene-like photoproduct

Atorvastatin calcium (ATV) is one of the most frequently prescribed drugs worldwide. Among the adverse effects observed for this lipid-lowering agent, clinical cases of cutaneous adverse reactions have been reported and associated with photosensitivity disorders. Previous work dealing with ATV photochemistry has shown that exposure to natural sunlight in aqueous solution leads to photoproducts resulting from oxidation of the pyrrole ring and from cyclization to a phenanthrene derivative. Laser flash photolysis of ATV, at both 266 and 308 nm, led to a transient spectrum with two maxima at λ ) 360 and λ ) 580 nm (τ ) 41 μs), which was assigned to the primary intermediate of the stilbene-like photocyclization. On the basis of the absence of a triplet-triplet absorption, the role of the parent drug as singlet oxygen photosensitizer can be discarded. By contrast, a stable phenanthrene-like photoproduct would be a good candidate to play this role. Laser flash photolysis of this compound showed a triplet-triplet transient absorption at λmax ) 460 nm with a lifetime of 26 μs, which was efficiently quenched by oxygen (kq ) 3 ((0.2) × 109 M-1 s-1). Its potential to photosensitize formation of singlet oxygen was confirmed by spin trapping experiments, through conversion of TEMP to the stable free radical TEMPO. The photoreactivity of the phenanthrene-like photoproduct was investigated using Trp as a marker. The disappearance of the amino acid fluorescence (λmax ) 340 nm) after increasing irradiation times at 355 nm was taken as a measurement of photodynamic oxidation. To confirm the involvement of a type II mechanism, the same experiment was also performed in D2O; this resulted in a significant enhancement of the reaction rate. On the basis of the obtained photophysical and photochemical results, the phototoxicity of atorvastatin can be attributed to singlet oxygen formation with the phenanthrene-like photoproduct as a photosensitizer

Assessing physical properties of amphoteric fluoroquinolones using phosphorescence spectroscopy

[EN] The self-association of fluoroquinolones (FQ) in water would play a relevant role in their translocations across lipid membranes. Triplet excited states of these drugs have been shown as reporters of FQ self-association using laser flash photolysis technique. A study using low-temperature phosphorescence technique was performed with quinolone derivatives such as enoxacin (ENX), norfloxacin (NFX), pefloxacin (PFX), ciprofloxacin (CPX, ofloxacin (OFX), nalidixic acid (NLA), pipemidic acid (PPA) and piromidic acid (PRA) to explore emission changes associated with self-associations and to shed some light on the triplet excited state energy (E-T) discrepancies described in the literature for most of these drugs. The emissions obtained at 77 K in buffered aqueous medium revealed that the amphoteric nature of the quinolones CPX, NFX, PFX, ENX, OFX and PPA must generate their self-associations because a redshift of their phosphorescence maxima is produced by FQ concentrations increases. Hence, this effect was not observed for NLA and PRA or when all quinolones were analysed using ethanol or ethylene glycol aqueous mixtures as glassed solvents. Interestingly, the presence of these organic mixtures produced a blue-shift in the phosphorescence emission maximum of each FQ. Additionally, laser flash photolysis experiments with PRA and the amphoteric quinolone PPA, compounds with the same skeleton but different peripheral substituent, confirm the expected correlations between the amphoteric nature of compounds and their self-associations in aqueous media because the excimer generation was only detected for PPA. Now, the discrepancies described in the literature for the ET of FQs can be understood considering that changes of medium polarity or proticity as well as the temperature can considerably modify their ET values. Thereby, low-temperature phosphorescence technique, is an effective way to detect molecular self-associations and surrounding changes in quinolones that opens the possibility to evaluate these effects in other drug families. (C) 2019 Elsevier B.V. All rights reserved.Financial support from Spanish government (grant CTQ2014-54729-C2-2-P) and the Generalitat Valenciana (PROMETEO program, 2017-075).Soldevila Serrano, S.; Bosca Mayans, F. (2020). Assessing physical properties of amphoteric fluoroquinolones using phosphorescence spectroscopy. Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy. 227:1-7. https://doi.org/10.1016/j.saa.2019.117569S17227Domagala, J. M., Hanna, L. D., Heifetz, C. L., Hutt, M. P., Mich, T. F., Sanchez, J. P., & Solomon, M. (1986). New structure-activity relationships of the quinolone antibacterials using the target enzyme. The development and application of a DNA gyrase assay. Journal of Medicinal Chemistry, 29(3), 394-404. doi:10.1021/jm00153a015Cramariuc, O., Rog, T., Javanainen, M., Monticelli, L., Polishchuk, A. V., & Vattulainen, I. (2012). Mechanism for translocation of fluoroquinolones across lipid membranes. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1818(11), 2563-2571. doi:10.1016/j.bbamem.2012.05.027Sun, J., Sakai, S., Tauchi, Y., Deguchi, Y., Chen, J., Zhang, R., & Morimoto, K. (2002). Determination of lipophilicity of two quinolone antibacterials, ciprofloxacin and grepafloxacin, in the protonation equilibrium. European Journal of Pharmaceutics and Biopharmaceutics, 54(1), 51-58. doi:10.1016/s0939-6411(02)00018-8Sun, J., Sakai, S., Tauchi, Y., Deguchi, Y., Cheng, G., Chen, J., & Morimoto, K. (2003). Protonation equilibrium and lipophilicity of olamufloxacin (HSR-903), a newly synthesized fluoroquinolone antibacterial. European Journal of Pharmaceutics and Biopharmaceutics, 56(2), 223-229. doi:10.1016/s0939-6411(03)00099-7Furet, Y. X., Deshusses, J., & Pechère, J. C. (1992). Transport of pefloxacin across the bacterial cytoplasmic membrane in quinolone-susceptible Staphylococcus aureus. Antimicrobial Agents and Chemotherapy, 36(11), 2506-2511. doi:10.1128/aac.36.11.2506Maurer, N., Wong, K. F., Hope, M. J., & Cullis, P. R. (1998). Anomalous solubility behavior of the antibiotic ciprofloxacin encapsulated in liposomes: a 1H-NMR study. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1374(1-2), 9-20. doi:10.1016/s0005-2736(98)00125-4Cuquerella, M. C., Andreu, I., Soldevila, S., & Bosca, F. (2012). Triplet Excimers of Fluoroquinolones in Aqueous Media. The Journal of Physical Chemistry A, 116(21), 5030-5038. doi:10.1021/jp301800qLhiaubet-Vallet, V., Sarabia, Z., Boscá, F., & Miranda, M. A. (2004). Human Serum Albumin-Mediated Stereodifferentiation in the Triplet State Behavior of (S)- and (R)-Carprofen. Journal of the American Chemical Society, 126(31), 9538-9539. doi:10.1021/ja048518gBosca, F. (2012). Seeking to Shed Some Light on the Binding of Fluoroquinolones to Albumins. The Journal of Physical Chemistry B, 116(11), 3504-3511. doi:10.1021/jp208930qCuquerella, M. C., Lhiaubet-Vallet, V., Miranda, M. A., & Bosca, F. (2017). Drug–DNA complexation as the key factor in photosensitized thymine dimerization. Physical Chemistry Chemical Physics, 19(7), 4951-4955. doi:10.1039/c6cp08485kAlfredson, T. V., Maki, A. H., & Waring, M. J. (1991). Optically detected triplet-state magnetic resonance studies of the DNA complexes of the bisquinoline analog of echinomycin. Biochemistry, 30(40), 9665-9675. doi:10.1021/bi00104a014Alfredson, T. V., & Maki, A. H. (1990). Phosphorescence and optically detected magnetic resonance studies of echinomycin-DNA complexes. Biochemistry, 29(38), 9052-9064. doi:10.1021/bi00490a024Li, J., Li, J., Shuang, S., & Dong, C. (2005). Study of the luminescence behavior of seven quinolones on a paper substrate. Analytica Chimica Acta, 548(1-2), 134-142. doi:10.1016/j.aca.2005.04.053Sun, C., Ping, H., Zhang, M., Li, H., & Guan, F. (2011). Spectroscopic studies on the lanthanide sensitized luminescence and chemiluminescence properties of fluoroquinolone with different structure. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 82(1), 375-382. doi:10.1016/j.saa.2011.07.065Rieutord, A., Vazquez, L., Soursac, M., Prognon, P., Blais, J., Bourget, P., & Mahuzier, G. (1994). Fluoroquinolones as sensitizers of lanthanide fluorescence: application to the liquid chromatographic determination of ciprofloxacin using terbium. Analytica Chimica Acta, 290(1-2), 215-225. doi:10.1016/0003-2670(94)80058-8Sortino, S., De Guidi, G., Giuffrida, S., Monti, S., & Velardita, A. (1998). pH Effects on the Spectroscopic and Photochemical Behavior of Enoxacin: A Steady-State and Time-Resolved Study. Photochemistry and Photobiology, 67(2), 167. doi:10.1562/0031-8655(1998)0672.3.co;2Martínez, L., Bilski, P., & Chignell, C. F. (1996). Effect of Magnesium and Calcium Complexation on the Photochemical Properties of Norfloxacin. Photochemistry and Photobiology, 64(6), 911-917. doi:10.1111/j.1751-1097.1996.tb01855.xBilski, P., Martinez, L. J., Koker, E. B., & Chignell, C. F. (1996). Photosensitization by Norfloxacin is a Function of pH. Photochemistry and Photobiology, 64(3), 496-500. doi:10.1111/j.1751-1097.1996.tb03096.xBosca, F., Lhiaubet-Vallet, V., Cuquerella, M. C., Castell, J. V., & Miranda, M. A. (2006). The Triplet Energy of Thymine in DNA. Journal of the American Chemical Society, 128(19), 6318-6319. doi:10.1021/ja060651gLhiaubet-Vallet, V., Cuquerella, M. C., Castell, J. V., Bosca, F., & Miranda, M. A. (2007). Triplet Excited Fluoroquinolones as Mediators for Thymine Cyclobutane Dimer Formation in DNA. The Journal of Physical Chemistry B, 111(25), 7409-7414. doi:10.1021/jp070167fCuquerella, M. C., Lhiaubet-Vallet, V., Bosca, F., & Miranda, M. A. (2011). Photosensitised pyrimidine dimerisation in DNA. Chemical Science, 2(7), 1219. doi:10.1039/c1sc00088hLhiaubet-Vallet, V., Bosca, F., & Miranda, M. A. (2009). Photosensitized DNA Damage: The Case of Fluoroquinolones. Photochemistry and Photobiology, 85(4), 861-868. doi:10.1111/j.1751-1097.2009.00548.xAlbini, A., & Monti, S. (2003). Photophysics and photochemistry of fluoroquinolones. Chemical Society Reviews, 32(4), 238. doi:10.1039/b209220bCuquerella, M. C., Miranda, M. A., & Bosca, F. (2006). Role of Excited State Intramolecular Charge Transfer in the Photophysical Properties of Norfloxacin and Its Derivatives. The Journal of Physical Chemistry A, 110(8), 2607-2612. doi:10.1021/jp0559837Lorenzo, F., Navaratnam, S., & Allen, N. S. (2008). Formation of Secondary Triplet Species after Excitation of Fluoroquinolones in the Presence of Relatively Strong Bases. Journal of the American Chemical Society, 130(37), 12238-12239. doi:10.1021/ja804471

A Sunscreen-Based Photocage for Carbonyl Groups

Photolabile protecting groups (PPGs) have been exploited in a wide range of chemical and biological applications, due to their ability to provide spatial and temporal control over light-triggered activation. In this work, we explore the concept of a new photocage compound based on the commercial UVA/UVB filter oxybenzone (OB; 2-hydroxy-4-methoxybenzophenone) for photoprotection and controlled release of carbonyl groups. The point here is that oxybenzone not only acts as a mere PPG, but also provides, once released, UV photoprotection to the carbonyl derivative. This design points to a possible therapeutic approach to reduce the severe photoadverse effects of drugs containing a carbonyl chromophore.This work was supported by the Spanish Government (project PGC2018‐096684‐B‐I00) and the Universitat Politècnica de València (FPI grant to M.L.‐R.). Carmen Clemente Martínez is acknowledged for her technical help during the UPLC‐HRMS experiments

Photosensitivity to triflusal: formation of a photoadduct with ubiquitin demonstrated by photophysical and proteomic techniques

8 p.-7 fig.1 tab.Triflusal is a platelet aggregation inhibitor chemically related to acetylsalicylic acid, which is used for the prevention and/or treatment of vascular thromboembolisms, which acts as a prodrug. Actually, after oral administration it is absorbed primarily in the small intestine, binds to plasma proteins (99%) and is rapidly biotransformed in the liver into its deacetylated active metabolite 2-hydroxy-4-trifluoromethylbenzoic acid (HTB). In healthy humans, the half-life of triflusal is ca. 0.5 h, whereas for HTB it is ca. 35 h. From a pharmacological point of view, it is interesting to note that HTB is itself highly active as a platelet anti-aggregant agent. Indeed, studies on the clinical profile of both drug and metabolite have shown no significant differences between them. It has been evidenced that HTB displays ability to induce photoallergy in humans. This phenomenon involves a cell-mediated immune response, which is initiated by covalent binding of a light-activated photosensitizer (or a species derived therefrom) to a protein. In this context, small proteins like ubiquitin could be appropriate models for investigating covalent binding by means of MS/MS and peptide fingerprint analysis. In previous work, it was shown that HTB forms covalent photoadducts with isolated lysine. Interestingly, ubiquitin contains seven lysine residues that could be modified by a similar reaction.With this background, the aim of the present work is to explore adduct formation between the triflusal metabolite and ubiquitin as model protein upon sunlight irradiation, combining proteomic and photophysical (fluorescence and laser flash photolysis) techniques. Photophysical and proteomic analysis demonstrates monoadduct formation as the major outcome of the reaction. Interestingly, addition can take place at any of the +-amino groups of the lysine residues of the protein and involves replacement of the trifluoromethyl moiety with a new amide function. This process can in principle occur with other trifluoroaromatic compounds and may be responsible for the appearance of undesired photoallergic side effects.Financial supportfromtheGeneralitatValenciana(Prometeo Program), the Spanish Government (MINECOCTQ2015-70164- P toVL-Vand SAF2012-36519 to DP-S) and the Carlos III Institute of Health(Grant RIRAAF,RETIC Sprogram, RD12/0013/0009 to MM and RD12/0013/0008 to DP-S,and Miguel Servet Contract CP11/00154forIA) is gratefully acknowledged.Peer reviewe

Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer

For many biological and biomedical studies, it is essential to detect the production of O-1(2) and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6-tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been widely employed, it can produce misleading data. This is demonstrated by the present study, in which the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method are compared for a set of well-known photosensitizers. The results reveal that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizer is efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP+(center dot) radical cation, followed by deprotonation and reaction with molecular oxygen, gives rise to an EPR-detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological, and medical studies.The Spanish government (CTQ2012-32621, RyC-2007-00476, PFIS FI09/00312, Severo Ochoa Program SEV-2012-0267), the Carlos III Institute of Health (Grant RIRAAF, RETICS Program RD12/0013/0009), and the Generalitat Valenciana (Prometeo II/2013/005) are gratefully acknowledged for financial support. Dr. A. Vidal-Moya is acknowledged for his help with the EPR measurements.Nardi, G.; Manet, I.; Monti, S.; Miranda Alonso, MÁ.; Lhiaubet-Vallet, V. (2014). Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer. Free Radical Biology and Medicine. 77:64-70. https://doi.org/10.1016/j.freeradbiomed.2014.08.020S64707

Interacció entre filtres solars

Els protectors solars s'utilitzen per protegir la pell de la radiació solar ultraviolada (UV), particularment de l'UVA i UVB. Una característica important que hauria de tenir un filtre solar és la fotoestabilitat. És a dir, després d'irradiar un filtre UVA o UVB aquest hauria de romandre invariable. Tanmateix, molts filtres presenten certa reactivitat. Un conegut exemple és el del tert-butilmetoxidibenzoilmetà (BM-DBM, també conegut com avobenzona) que, malgrat la seua fotolabilitat, és un filtre UVA utilitzat habitualment. En la formulació de molts protectors solars s'utilitzen almenys dos filtres per tal de cobrir tot l'espectre UV. Això pot donar lloc bé a un efecte sinergètic que afavoreix la fotoestabilització dels filtres, o bé a una acceleració de la descomposició d'aquestos. La millora de l'estabilitat dels filtres solars UV rau en el fet d'entendre les propietats fotoquímiques i fotofísiques d'aquestes combinacions de filtres. Tot i això, fins ara no existia una metodologia generalment acceptada per tal d'estudiar de manera sistemàtica els efectes d'aquestes combinacions. En aquest treball s'ha centrat l'atenció en l'estudi de les interaccions de l'avobenzona combinada amb sis filtres UV comercials. A partir d'aquests compostos s'ha dissenyat una estratègia per tal d'investigar la fotoestabilitat dels protectors solars d'una manera més sistemàtica, tenint en compte els diferents processos que poden donar-se considerant aquestes combinacions.Sunscreens are used to protect against ultraviolet (UV) radiation reaching earth i.e. UVA and UVB regions of the solar spectrum. Among the different characteristics a sunscreen should possess, photostability is important not only to maintain an efficient protection along exposition time but also to avoid adverse effects like phototoxicity and photoallergy. However, many filters are photoreactive. This is the case of the well-known tert-butylmethoxydibenzoylmethane (BM-DBM, also known as avobenzone) which, in spite of its photolability, is a widely used UVA filter. In sunscreen formulation, at least two filters are generally present in order to cover all the UV spectra. This could produce a synergistic effect that favours filter stabilization or, on the other hand, could accelerate filter decomposition. Thus, improvement of UV filter stability is a key factor in sunscreen development that relies on the understanding of photochemical and photophysical properties of the filter combination. However, until now a general methodology to study systematically these combinations does not exist. In this work, we have focused the attention on the interactions between avobenzone and six commercial UV filters. In order to investigate the photostability of sunscreens in a more systematic way, the designed strategy takes into account all the different processes that could occur between the different single components

Pterin-lysine photoadduct: A potential candidate for photoallergy

Photoallergy is a photosensitivity disorder associated with a modified ability of the skin to react to the combined effect of drugs and sunlight. It has been attributed to the covalent conjugation of proteins with a photosensitizer, yielding modified macromolecules that can act as antigen provoking the immune system response. The potential role of some endogenous compounds as photoallergens has not been fully established. It has been previously proposed that pterins, which are endogenous photosensitizers present in human skin under pathological conditions, are able to covalently bind to proteins. Here, we evaluated the capability of pterin (Ptr) to form photoadducts with free Lysine (Lys) and poly-l-lysine (poly-Lys). The findings obtained using chromatographic and spectroscopic tools, confirm the formation of photoadducts of Ptr with Lys residues. With poly-Lys the resulting adduct retains the spectroscopic properties of the photosensitizer, suggesting that the aromatic Ptr structure is conserved. On the other hand, the photoproduct formed with free Lys does not behave like Ptr, which suggests that if this product is a photoadduct, a chemical modification may have occurred during the photochemical reaction that alters the pterin moiety.Fil: Farías, Jesuán Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Lizondo Aranda, Paloma. Universidad Politécnica de Valencia; EspañaFil: Thomas, Andrés Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; ArgentinaFil: Lhiaubet Vallet, Virginie. Universidad Politécnica de Valencia; EspañaFil: Dantola, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; Argentin

Stereoselective Fluorescence Quenching in the Electron Transfer Photooxidation of Nucleobase-Related Azetidines by Cyanoaromatics

[EN] Electron transfer involving nucleic acids and their derivatives is an important field in bioorganic chemistry, specifically in connection with its role in the photo-driven DNA damage and repair. Four-membered ring heterocyclic oxetanes and azetidines have been claimed to be the intermediates involved in the repair of DNA (6-4) photoproduct by photolyase. In this context, we examine here the redox properties of the two azetidine isomers obtained from photocycloaddition between 6-aza-1,3-dimethyluracil and cyclohexene. Steady-state and time-resolved fluorescence experiments using a series of photoreductants and photooxidants have been run to evaluate the efficiency of the electron transfer process. Analysis of the obtained quenching kinetics shows that the azetidine compounds can act as electron donors. Additionally, it appears that the cis isomer is more easily oxidized than its trans counterpart. This result is in agreement with electrochemical studies performed on both azetidine derivatives.Spanish Government (CTQ2015-70164-P, RIRAAF RETICS RD12/0013/0009, Red de Fotoquimica Biologica CTQ2015-71896-REDT, Severo Ochoa program/SEV-2012-0267 and SVP-2013-068057 for A. B. F.-R. grant) and Generalitat Valenciana (Prometeo II/2013/005) are gratefully acknowledged.Fraga-Timiraos, AB.; Rodríguez Muñiz, GM.; Peiro-Penalba, V.; Miranda Alonso, MÁ.; Lhiaubet, VL. (2016). Stereoselective Fluorescence Quenching in the Electron Transfer Photooxidation of Nucleobase-Related Azetidines by Cyanoaromatics. Molecules. 21(12). https://doi.org/10.3390/molecules21121683S2112Arnold, A. R., Grodick, M. A., & Barton, J. K. (2016). DNA Charge Transport: from Chemical Principles to the Cell. Cell Chemical Biology, 23(1), 183-197. doi:10.1016/j.chembiol.2015.11.010Jia, C., Ma, B., Xin, N., & Guo, X. (2015). Carbon Electrode–Molecule Junctions: A Reliable Platform for Molecular Electronics. Accounts of Chemical Research, 48(9), 2565-2575. doi:10.1021/acs.accounts.5b00133Beratan, D. N., Liu, C., Migliore, A., Polizzi, N. F., Skourtis, S. S., Zhang, P., & Zhang, Y. (2014). Charge Transfer in Dynamical Biosystems, or The Treachery of (Static) Images. Accounts of Chemical Research, 48(2), 474-481. doi:10.1021/ar500271dKawai, K., & Majima, T. (2013). Hole Transfer Kinetics of DNA. Accounts of Chemical Research, 46(11), 2616-2625. doi:10.1021/ar400079sSancar, A. (2003). Structure and Function of DNA Photolyase and Cryptochrome Blue-Light Photoreceptors. Chemical Reviews, 103(6), 2203-2238. doi:10.1021/cr0204348Kanvah, S., Joseph, J., Schuster, G. B., Barnett, R. N., Cleveland, C. L., & Landman, U. (2010). Oxidation of DNA: Damage to Nucleobases. Accounts of Chemical Research, 43(2), 280-287. doi:10.1021/ar900175aKelley, S. O. (1999). Electron Transfer Between Bases in Double Helical DNA. Science, 283(5400), 375-381. doi:10.1126/science.283.5400.375Breeger, S., von Meltzer, M., Hennecke, U., & Carell, T. (2006). Investigation of the Pathways of Excess Electron Transfer in DNA with Flavin-Donor and Oxetane-Acceptor Modified DNA Hairpins. Chemistry - A European Journal, 12(25), 6469-6477. doi:10.1002/chem.200600074Boussicault, F., & Robert, M. (2008). Electron Transfer in DNA and in DNA-Related Biological Processes. Electrochemical Insights. Chemical Reviews, 108(7), 2622-2645. doi:10.1021/cr0680787The Nobel Prize in Chemistry 2015—Advanced Informationhttp://www.nobelprize.org/nobel_prizes/chemistry/laureates/2015/advanced.htmlBrettel, K., & Byrdin, M. (2010). Reaction mechanisms of DNA photolyase. Current Opinion in Structural Biology, 20(6), 693-701. doi:10.1016/j.sbi.2010.07.003Dandliker, P. J. (1997). Oxidative Thymine Dimer Repair in the DNA Helix. Science, 275(5305), 1465-1468. doi:10.1126/science.275.5305.1465Vicic, D. A., Odom, D. T., Núñez, M. E., Gianolio, D. A., McLaughlin, L. W., & Barton, J. K. (2000). Oxidative Repair of a Thymine Dimer in DNA from a Distance by a Covalently Linked Organic Intercalator. Journal of the American Chemical Society, 122(36), 8603-8611. doi:10.1021/ja000280iHartman, T., & Cibulka, R. (2016). Photocatalytic Systems with Flavinium Salts: From Photolyase Models to Synthetic Tool for Cyclobutane Ring Opening. Organic Letters, 18(15), 3710-3713. doi:10.1021/acs.orglett.6b01743Scannell, M. P., Fenick, D. J., Yeh, S.-R., & Falvey, D. E. (1997). Model Studies of DNA Photorepair:  Reduction Potentials of Thymine and Cytosine Cyclobutane Dimers Measured by Fluorescence Quenching. Journal of the American Chemical Society, 119(8), 1971-1977. doi:10.1021/ja963360oPérez-Ruiz, R., Jiménez, M. C., & Miranda, M. A. (2014). Hetero-cycloreversions Mediated by Photoinduced Electron Transfer. Accounts of Chemical Research, 47(4), 1359-1368. doi:10.1021/ar4003224Boussicault, F., & Robert, M. (2006). Electrochemical Approach to the Repair of Oxetanes Mimicking DNA (6−4) Photoproducts. The Journal of Physical Chemistry B, 110(43), 21987-21993. doi:10.1021/jp062425zPrakash, G., & Falvey, D. E. (1995). Model studies of the (6-4) photoproduct DNA photolyase: Synthesis and photosensitized splitting of a thymine-5,6-oxetane. Journal of the American Chemical Society, 117(45), 11375-11376. doi:10.1021/ja00150a050Friedel, M. G., Cichon, M. K., & Carell, T. (2005). Model compounds for (6–4) photolyases: a comparative flavin induced cleavage study of oxetanes and thietanes. Organic & Biomolecular Chemistry, 3(10), 1937. doi:10.1039/b503205aFraga-Timiraos, A. B., Lhiaubet-Vallet, V., & Miranda, M. A. (2016). Repair of a Dimeric Azetidine Related to the Thymine-Cytosine (6- 4) Photoproduct by Electron Transfer Photoreduction. Angewandte Chemie International Edition, 55(20), 6037-6040. doi:10.1002/anie.201601475Andreu, I., Delgado, J., Espinós, A., Pérez-Ruiz, R., Jiménez, M. C., & Miranda, M. 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Photosensitivity to Triflusal: Formation of a Photoadduct with Ubiquitin Demonstrated by Photophysical and Proteomic Techniques

[EN] Triflusal is a platelet aggregation inhibitor chemically related to acetylsalicylic acid, which is used for the prevention and/or treatment of vascular thromboembolisms, which acts as a prodrug. Actually, after oral administration it is absorbed primarily in the small intestine, binds to plasma proteins (99%) and is rapidly biotransformed in the liver into its deacetylated active metabolite 2-hydroxy-4-trifluoromethylbenzoic acid (HTB). In healthy humans, the half-life of triflusal is ca. 0.5 h, whereas for HTB it is ca. 35 h. From a pharmacological point of view, it is interesting to note that HTB is itself highly active as a platelet anti-aggregant agent. Indeed, studies on the clinical profile of both drug and metabolite have shown no significant differences between them. It has been evidenced that HTB displays ability to induce photoallergy in humans. This phenomenon involves a cell-mediated immune response, which is initiated by covalent binding of a light-activated photosensitizer (or a species derived therefrom) to a protein. In this context, small proteins like ubiquitin could be appropriate models for investigating covalent binding by means of MS/MS and peptide fingerprint analysis. In previous work, it was shown that HTB forms covalent photoadducts with isolated lysine. Interestingly, ubiquitin contains seven lysine residues that could be modified by a similar reaction. With this background, the aim of the present work is to explore adduct formation between the triflusal metabolite and ubiquitin as model protein upon sunlight irradiation, combining proteomic and photophysical (fluorescence and laser flash photolysis) techniques. Photophysical and proteomic analysis demonstrates monoadduct formation as the major outcome of the reaction. Interestingly, addition can take place at any of the E-amino groups of the lysine residues of the protein and involves replacement of the trifluoromethyl moiety with a new amide function. This process can in principle occur with other trifluoroaromatic compounds and may be responsible for the appearance of undesired photoallergic side effects.Financial support from the Generalitat Valenciana (Prometeo Program), the Spanish Government (MINECO CTQ2015-70164-P to VL-V and SAF2012-36519 to DP-S) and the Carlos III Institute of Health (Grant RIRAAF, RETICS program, RD12/0013/0009 to MM and RD12/0013/0008 to DP-S, and Miguel Servet Contract CP11/00154 for IA) is gratefully acknowledged.Nuin Pla, NE.; Pérez-Sala, D.; Lhiaubet-Vallet, VL.; Andreu Ros, MI.; Miranda Alonso, MÁ. (2016). Photosensitivity to Triflusal: Formation of a Photoadduct with Ubiquitin Demonstrated by Photophysical and Proteomic Techniques. Frontiers in Pharmacology. 7(277). https://doi.org/10.3389/fphar.2016.00277S727

Identification of a common recognition center for a photoactive non-steroidal antiinflammatory drug in serum albumins of different species

[EN] The non-steroidal anti-inflammatory drug (S)-carprofen (CPF) has been used as a photoactive probe to investigate the possible existence of a common recognition center in serum albumins (SAs) of different species. The methodology involves irradiation of the CPF/SA complexes, coupled with gel filtration chromatography or proteomic analysis of the photolysates, docking and molecular dynamics simulations. Photolysis of CPF/SA complexes at = 320 nm, and gel filtration chromatography, revealed that the protein fraction still contained the drug fluorophore, in agreement with covalent attachment of the photogenerated radical intermediate CBZ to SAs. After trypsin digestion and ESI-MS/MS, the incorporation of CBZ was detected at several positions in the different albumins. Remarkably, modifications at the IB/IIIA interface were observed in all cases (Tyr452 in HSA, RbSA and RtSA and Tyr451 in BSA, PSA and SSA). The molecular basis of this common recognition, studied by docking and molecular dynamics simulation studies on the corresponding non-covalent complexes, corroborated the experimentally observed covalent modifications. Our computational studies also revealed that the previously reported displacement of CPF by (S)-ibuprofen, a site II specific drug, would be due to an allosteric effect in site II, rather than a direct molecular displacement, as expected.Financial support from the Spanish Ministry of Economy and Competiveness (CTQ2016-78875-P, SAF2016-75638-R and BES-2014-069404), Generalitat Valenciana (PROMETEO2017/075), Conselleria de Cultura, Educacion e Ordenacion Universitaria (Centro singular de investigacion de Galicia accreditation 2016-2019, ED431G/09) and the European Regional Development Fund (ERDF) is acknowledged. This work was also supported by Instituto de Salud Carlos III (ISCIII) co-funded by Fondo Europeo de Desarrollo Regional FEDER for the Thematic Networks and Co-operative Research Centres: ARADyAL (RD16/0006/0030). EL thanks the Xunta de Galicia for his postdoctoral fellowship. We are also grateful to the Centro de Supercomputacion de Galicia (CESGA) for use of the Finis Terrae II supercomputer. The proteomic analysis was performed in the proteomics facility of SCSIE University of Valencia that belongs to ProteoRed PRB2-ISCIII and is supported by grant PT13/0001, of the PE I+D+I 2013-2016, funded by ISCIII and FEDER.Molins-Molina, O.; Lence, E.; Limones-Herrero, D.; González-Bello, C.; Miranda Alonso, MÁ.; Jiménez Molero, MC. (2019). Identification of a common recognition center for a photoactive non-steroidal antiinflammatory drug in serum albumins of different species. 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