Benoxaprofen photosensitization of cell membrane disruption

Computational Studies of the Photodegradation Mechanism of the Highly Phototoxic Agent Benoxaprofen

Computational quantum chemistry within the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) framework is used to investigate the photodegradation mechanism as well as the photochemical and photophysical properties of benoxaprofen (BP), a non steroid anti-inflammatory molecule (2-[2-(4-chlorophenyl)-1,3-benzoxazol-5-yl] propanoic acid). BP is a highly phototoxic agent that causes cutaneous phototoxicity shortly after its administration. On the grounds of concern about serious side effects, especially hepatotoxicity, it was withdrawn from the world market after only 2 years of its release. Our study shows that the drug has the capability to absorb radiation in the UV region, mainly between 300 and 340 nm, and undergoes spontaneous photoinduced decarboxylation from the triplet state. It shows very similar photochemical properties to the highly photolabile non-steroidal anti-inflammatory drugs (NSAIDs) ketoprofen, suprofen, and tiaprofenic acid. Like ketoprofen, BP can also decarboxylate from excited singlet states by overcoming low energy barriers. The differences in molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)) distributions between the neutral and deprotonated BP, their absorption spectra, and the energetics and fate of various photoproducts produced throughout the photodegradation are discussed. Initiation and termination of decarboxylated BP radical species and initiation of propagating lipid peroxidation reactions due to the addition of molecular oxygen giving rise to the corresponding peroxyl radical are also explored in detail.

Photosensitivity to Exogenous Agents

Objective:

To better understand cutaneous photosensitivity reactions, a review of its etiologic factors, clinical characteristics, pathogenesis, and treatment modalities was undertaken.

Methods:

Articles discussing the above aspects of phototoxic and photoallergic reactions were used to demonstrate what is currently known about photoinduced reactions and how to treat them.

Results:

Upon interaction of solar UV radiation with the chemical that is present in significant levels on the skin, one of two known reactions may occur in susceptible patients: a phototoxicity and/or photoallergy. Phototoxic and photoallergic reactions can be diagnosed separately on the basis of pathogenesis, clinical characteristics, and histology. Examples of drugs capable of inducing a phototoxic reaction include amiodarone, retinoids, nonsteroidal antiinflammatory agents, diuretics, and antibiotics. Substances known to cause a photoallergic response are fragrances, sunscreens, topical antimicrobials, NSAID, and psychiatric medications, such as chlorpromezine.

Conclusion:

Photoinduced reactions produced by exogenous chemicals are common skin disorders. Definitive therapy requires identifying and removing the offending agent, either the photosensitizing chemical or light. The use of fully protective clothing and a sunscreen of high SPF are important measures when light exposure is inevitable.

Principles and practice of drug photodegradation studies

A review is presented of the underlying principles and experimental techniques used for the study of the photochemical degradation of pharmaceuticals. Examples are given to illustrate their application.

Photosensitivity to Exogenous Agents

OBJECTIVE

To better understand cutaneous photosensitivity reactions, a review of its etiologic factors, clinical characteristics, pathogenesis, and treatment modalities was undertaken.

METHODS

Articles discussing the above aspects of phototoxic and photoallergic reactions were used to demonstrate what is currently known about photoinduced reactions and how to treat them.

RESULTS

Upon interaction of solar UV radiation with the chemical that is present in significant levels on the skin, one of two known reactions may occur in susceptible patients: a phototoxicity and/or photoallergy. Phototoxic and photoallergic reactions can be diagnosed separately on the basis of pathogenesis, clinical characteristics, and histology. Examples of drugs capable of inducing a phototoxic reaction include amiodarone, retinoids, nonsteroidal antiinflammatory agents, diuretics, and antibiotics. Substances known to cause a photoallergic response are fragrances, sunscreens, topical antimicrobials, NSAID, and psychiatric medications, such as chlorpromezine.

CONCLUSION

Photoinduced reactions produced by exogenous chemicals are common skin disorders. Definitive therapy requires identifying and removing the offending agent, either the photosensitizing chemical or light. The use of fully protective clothing and a sunscreen of high SPF are important measures when light exposure is inevitable.

Phototoxicity to diuretics and antidiabetics in the cultured keratinocyte cell line HaCaT: evaluation by clonogenic assay and single cell gel electrophoresis Comet assay)

BACKGROUND

Potential phototoxicity has been described for a number of drugs and chemical substances. Psoralens, chlorpromazines and fluoroquinolones have been described as inducing photomutagenicity and photocarcinogenicity in vitro and in vivo. We wanted to investigate oral antidiabetics and diuretics for potential phototoxicity and possible DNA damage in the HaCaT cell line.

METHODS

: The oral antidiabetics tolbutamide, glibenclamide and glipizide, and the diuretics bendroflumethiazide, butizide, furosemide, hydrochlorothiazide and trichlormethiazide were dissolved in DMSO to final concentrations of 1 mM, 0.1 mM, and 0.01 mM, incubated together with the cells, and exposed to UVA1 (23 or 48 J/cm2). Cell survival was evaluated in a clonogenic assay and phototoxic DNA damage was investigated by single cell gel electrophoresis (comet assay). To investigate possible inhibiting effects of antioxidants, L-ascorbic acid and alpha-tocopherol were added at a final concentration of 1 mM 24 h before treatment with the drugs.

RESULTS

Bendroflumethiazide, furosemide, hydrochlorothiazide, trichlormethiazide and tolbutamide induced dose-dependent phototoxicity in the clonogenic assay. Cells incubated with bendroflumethiazide, tolbutamide and glibenclamide and irradiated with UVA1 demonstrated increased oxidative DNA damage, revealed as alkali-labile sites in the comet assay. Pretreatment with L-ascorbic acid or alpha-tocopherol suppressed the UVA-induced DNA damage in cells incubated with 1 mM bendroflumethiazide, furosemide, glibenclamide, glipizide, tolbutamide or trichloromethiazide.

CONCLUSION

Several oral antidiabetics and diuretics show phototoxic effects in the HaCaT cell line. Inhibiting effects of antioxidants point towards involvement of reactive oxygen species in phototoxic DNA damage, suggesting a link between the phototoxic and photocancerogenic potential of the sulfonamide-derived oral antidiabetic and diuretic drugs. Excessive exposure to UV light may be deleterious for patients treated with oral antidiabetic and diuretic drugs.

Light-induced decarboxylation of (o-acylphenyl)acetic acids

Near-UV irradiation of both o-acetylphenyl- and o-benzoylphenylacetic acids in benzene solution results in their efficient decarboxylation. Their meta and para isomers do not undergo this process. The O-deuterated acids yield deuterated o-acyltoluene products, suggesting the possibility of an intramolecular proton transfer step in the decarboxylation process, although intermolecular deuteration would achieve the same result. The corresponding esters and amides are essentially photoinert and, like the acids, do not undergo the benzocyclobutenol formation expected of o-alkylphenyl ketones.

Photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids with photosensitizing side effects

The photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids benoxaprofen, carprofen, naproxen, ketoprofen, tiaprofenic acid, and suprofen is reviewed with special emphasis on fundamental photophysical and photochemical properties. The absorption and emission properties of the excited states of these drugs as well as their main photodegradation routes are summarized. The photochemical mechanisms are discussed on the basis of product studies and detection of short-lived intermediates by means of laser flash photolysis. After dealing with the unimolecular processes, attention is focused on the photosensitized reactions of key biomolecules, such as lipids, proteins or nucleic acids. Finally, a short section on the photobiological effects on simple biological models is also included. Although some earlier citations are included, the literature coverage is in general limited to the last decade.

Drug-induced solar urticaria due to tetracycline

Solar urticaria is an uncommon disorder characterized by pruritus, erythema and whealing commencing within minutes of exposure to ultraviolet (UV) and visible light, and generally resolves in a few hours. We describe a 28-year-old woman who developed pruritus and erythema 5 min after sun exposure while on tetracycline for treatment of perioral dermatitis. Phototesting elicited urticarial reactions in the UVA, UVB and visible spectra. Repeat phototesting after cessation of tetracycline was negative. This report documents the first case of solar urticaria induced by tetracycline.

Cell damage induced by Angiovist-370 and 308nm excimer laser radiation

BACKGROUND AND OBJECTIVE

Radiographic contrast media containing iodine-labeled organic compounds can be present in the irradiated field during laser angioplasty using 308 nm excimer laser radiation. These compounds absorb light at 308 nm and may undergo photochemical reactions that produce products that damage cells.

STUDY DESIGN/MATERIALS AND METHODS

This study was undertaken to determine whether photoproducts that damage human lymphocytes in vitro are formed when Angiovist 370 (AV), a contrast medium containing triiodinated aromatic compounds, is exposed to 308 nm radiation.

RESULTS

The absorption spectrum of AV developed a new peak at 360 nm that extended to wavelengths greater than 500 nm when dilute AV solutions were exposed to 308 nm radiation indicating that photoproducts were formed. Irradiating dilute AV solutions above a layer of human lymphocytes caused a dose-dependent decrease in thymidine incorporation using fluence rates between 5.2 x 10(6) and 1.0 x 10(8) W/cm2. Decreased DNA synthesis was independent of the pulse length (10 ns vs. 230 ns) but was lower, at a given dose, when the highest fluence rate was used. Incubation of lymphocytes with preirradiated AV solutions also decreased incorporation of thymidine in a radiation dose-dependent manner. The cell damaging photoproducts in preirradiated AV solutions were unstable; within 15 min, the effectiveness had decreased by approximately 85%.

CONCLUSIONS

These results indicate that exposure of AV to 308 nm excimer laser radiation produces photochemical products that damage human cells in vitro.

Effect of the microenvironment on the efficiency of singlet oxygen (O2(1 delta g)) production by photosensitizing anti-inflammatory drugs

The influence of the medium on the quantum yields of singlet oxygen (O2(1 delta g)) production (phi delta) by a series of photosensitizing non-steroidal anti-inflammatory drugs (NSAID) derived from 2-arylpropionic acid (APA) has been investigated. Four-component oil-in-water and water-in-oil microemulsions, based on anionic and cationic surfactants, have been employed as the simplest models to mimic more complex biological environments. phi delta values have been determined by monitoring the singlet oxygen (1O2) luminescence at 1270 nm upon continuous excitation of the drugs under air-equilibrated conditions. Results indicate that phi delta values are highly affected by the medium, being higher in microheterogeneous systems than in (homogeneous) solution. Some of the anti-inflammatory derivatives are very efficient 1O2 sensitizers: e.g., values of apparent phi delta as high as 0.86 (+/- 0.04) and 0.70 (+/- 0.03) have been found for tiaprofenic acid and suprofen, respectively. The location of the drugs in the interfacial region of the microemulsions combined with their high phi delta values suggest that type II reactions may play a significant role in the overall photodynamic process in more complex organized media, such as biological membranes.

Nonsteroidal antiinflammatory drug-photosensitized formation of pyrimidine dimer in DNA

Phototoxic nonsteroidal antiinflammatory drugs (NSAIDs) may induce DNA damage in vitro upon irradiation. In this study, we investigated the ability of ketoprofen (KP), tiaprofenic acid (Tia), naproxen (NP) and indomethacin (IND) to photosensitize the formation of pyrimidine dimers and single strand breaks. Both kinds of damage were sought by analyzing DNA-drug mixtures irradiated at 313 nm by agarose gel electrophoresis. The formation of pyrimidine dimers was evidenced by using endonuclease V from bacteriophage T4 and compared to that induced by acetophenone, a well-known photosensitizer of thymine dimerization. Upon irradiation of DNA alone, pyrimidine dimers were observed while single strand breaks were not detected under our conditions. DNA, in the presence of NSAIDs, undergoes single strand breaks, the quantum yield of the DNA cleavage so induced (phiC) varying from 5 x 10(-4) for KP to 10(-5) for IND. The formation of dimers was only increased in the presence of KP or Tia. The quantum yields of pyrimidine dimers formed by photosensitization (phiD) were 2 x 10(-4) for KP and 10(-5) for Tia, respectively. The oxygen and concentration dependence of both processes was analyzed in the case of KP. In aerated solution, KP-photoinduced cleavage of DNA was predominant on the photodimerization process of pyrimidines, whereas in deaerated solution the cleavage was decreased and the dimerization increased. These results reflect competition between a radical process leading to DNA cleavage and a poorly efficient energy transfer between the drug and the pyrimidines at the origin of the dimerization process.

Inhibiting effects of antioxidants on drug-induced phototoxicity in cell cultures. Investigations with sulphonamide-derived oral antidiabetics and diuretics

The sulphonamide-derived oral antidiabetics chlorpropamide, glibenclamide, glipizide, gliquidone, glymidine, tolazamide and tolbutamide, and the diuretics bemetizide, bendroflumethiazide, benzylhydrochlorothiazide, bumetanide, butizide, chlortalidone, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, piretanide, polythiazide, trichlormethiazide and xipamide were investigated for phototoxicity in a cell culture model. Cell death dependent on ultraviolet A (UVA) radiation fluence and test substance concentration was observed in the presence of the oral antidiabetics glibenclamide and gliquidone, as well as the diuretics bemetizide, bendroflumethiazide, benzylhydrochlorothiazide, bumetanide, butizide, hydrochlorothiazide, hydroflumethiazide, piretanide, polythiazide and trichlormethiazide. Bendroflumethiazide was phototoxic at concentrations of 0.05 mM and above; bemetizide, benzylhydrochlorothiazide, bumetanide and hydroflumethiazide were phototoxic at concentrations of 0.25 mM or more; the oral antidiabetics glibenclamide and gliquidone, as well as the diuretics butizide, hydrochlorothiazide, piretanide, polythiazide and trichlormethiazide were phototoxic at concentrations of 0.5 mM. To evaluate the effects of antioxidants, ascorbic acid, alpha-tocopherol, beta-carotene or ubiquinone was added to the tissue culture flasks before irradiation. The phototoxic inhibition of the colony-forming ability was largely reduced by the addition of ascorbic acid and alpha-tocopherole, indicating the involvement of reactive oxygen species in the phototoxic process.

Drug photosensitivity, idiopathic photodermatoses, and sunscreens

Photosensitization may be defined as a process in which a reaction to normally innocuous radiation is induced by the introduction of a specific radiation-absorbing substance (the photosensitizer) that causes another component (the substrate) to be changed by the radiation. This review focuses on photosensitization produced by exogenous chemicals. Idiopathic photodermatoses, including polymorphous light eruption and its variants, solar urticaria and chronic actinic dermatitis, are also discussed. Clinical recognition patterns of the photodermatoses are stressed as well as several diagnostic procedures available for confirmation of the condition. Finally, descriptions, therapeutic uses, and adverse reactions of sunscreens are provided.

Photohemolytic potency of oral antidiabetic drugs in vitro: effects of antioxidants and a nitrogen atmosphere

The sulphonamide-derived oral antidiabetic drugs carbutamide, chlorpropamide, glibenclamide, glibornuride, gliclazide, glipizide, gliquidone, glisoxepide, glymidine, tolazamide and tolbutamide were investigated for photohemolytic properties in vitro. Irradiation with a SOL 3 apparatus (solar simulating irradiation) revealed hemolysis in the presence of chlorpropamide, glipizide, gliquidone, glymidine and tolbutamide (all in the concentration 10(-3) mol/l). Except for glymidine, which exerted photohemolysis in the concentration 10(-4) mol/l, no hemolytic effects were seen in the concentration of 10(-4) mol/l or 10(-5) mol/l. Irradiation with TL 12 light bulbs (UVB), a UVASUN 5000 apparatus (UVA) or an experimental lamp (visible light) did not induce phototoxic hemolysis with either of the test substances. Addition of the antioxidants ascorbic acid, alpha-tocopherol or superoxide dismutase significantly inhibited the phototoxic hemolysis. Investigations carried out in a nitrogen-rich atmosphere reduced the hemolysis as well. These findings indicate an involvement of reactive oxygen species in the mechanism of action of the hemolytic process in the presence of oral antidiabetic drugs.

Molecular basis of drug phototoxicity: photosensitized cell damage by the major photoproduct of tiaprofenic acid

Tiaprofenic acid is a photosensitizing nonsteroidal anti-inflammatory drug, whose major photoproduct (decarboxytiaprofenic acid) is also a potent photosensitizer. Because of the lack of the carboxylate moiety, this photoproduct is more lipophilic and might bind more efficiently to cell membranes, thereby causing phototoxic damage. To verify the feasibility of this hypothesis, we have prepared the 3H-labeled analogs of tiaprofenic acid and its photoproduct and examined the binding, persistence and phototoxicity of the photoproduct using poorly metabolizing (fibroblasts) and actively metabolizing cells (hepatocytes). The photoproduct of tiaprofenic acid accumulates in both cell types as it is formed. Upon removal of the photoproduct from the culture medium, it rapidly disappears from hepatocytes but not from fibroblasts. Consequently, irradiation of fibroblasts previously incubated with the photoproduct and kept in culture in the dark for 20 h results in generalized cell damage while this effect is not observed in hepatocytes. Because of its long persistence in poorly metabolizing skin cells and its reluctance to photobleaching, the formation of this photoproduct in skin may be of relevance to explain the in vivo phototoxicity of tiaprofenic acid.

Photochemical and photobiological properties of ketoprofen associated with the benzophenone chromophore

Irradiation of ketoprofen in neutral aqueous medium gave rise to 3-ethylbenzophenone as the major photoproduct. Its formation is justified via protonation of a benzylic carbanion or hydrogen abstraction by a benzylic radical. Minor amounts of eight additional compounds were isolated. Four of them are derived from the benzylic radical: 3-(1-hydroperoxyethyl)benzophenone, 3-(1-hydroxyethyl)benzophenone, 3-acetylbenzophenone and 2,3-bis-(3-benzoylphenyl)butane. The other four products involve initial hydrogen abstraction by the excited benzophenone chromophore of ketoprofen: 1,2-bis-(3-ethylphenyl)-1,2-diphenyl-1,2-ethanediol, 2-(3-benzoylphenyl)-1-(3-ethylphenyl)-1-phenylpropan-1-ol, alpha-(3-ethylphenyl)phenylmethanol, 1,2-bis-[3-(2-hydroxycarbonylethyl) phenyl]-1,2-diphenyl-1,2-ethanediol. The latter process was found to mediate the photoperoxidation of linoleic acid through a type I mechanism, as evidenced by the inhibition produced by the radical scavengers butylated hydroxyanisole and reduced glutathione. The major photoproduct, which contains the benzophenone moiety but lacks the propionic acid side chain, also photosensitized linoleic acid peroxidation. Because lipid peroxidation is indicative of cell membrane lysis, the above findings are highly relevant to explain the photobiological properties of ketoprofen.

Photodynamic lipid peroxidation by the photosensitizing nonsteroidal antiinflammatory drugs suprofen and tiaprofenic acid

The photochemistry of the photosensitizing nonsteroidal antiinflammatory drugs tiaprofenic acid and suprofen involves the intermediacy of short-lived species (i.e. radicals). The data obtained in the present work strongly suggest that such intermediates may be responsible for the phototoxicity of 2-arylpropionic acids by inducing photodynamic lipid peroxidation at drug concentrations likely to be reached in the skin. This has been investigated using linoleic acid as a model lipid and determining the amount of hydroperoxides by measuring the spectrophotometric absorption at 233 nm, associated with the formation of dienic hydroperoxides. The major photoproducts of tiaprofenic acid and suprofen are derivatives bearing an ethyl side chain. Photoproducts of this type, due to the lack of polar moieties, are highly lipophilic and likely to accumulate in the lipid bilayer of cell membranes. Taking into account their ability to induce photodynamic lipid peroxidation and their marked photostability, it is conceivable that such photoproducts can participate in many catalytic cycles, playing a significant role in the mechanism of photosensitization by tiaprofenic acid and suprofen.

Phototoxicity of lumidoxycycline

Doxycycline (DOTC) is a photosensitizing drug whose mechanism of phototoxicity is complicated by the large variety of stable photoproducts formed. To assess the role of a DOTC photoproduct, lumidoxycycline (LuDOTC), in the photosensitization mechanism of DOTC, MGH-U1 human bladder carcinoma cells were treated in vitro with either DOTC or LuDOTC, and irradiated with the 351-nm emission of an argon-ion laser. Both DOTC and LuDOTC were phototoxic and caused radiant-exposure-dependent inhibition of cellular incorporation of tritiated thymidine. On an absorbed-photon basis, DOTC was about five times as phototoxic as LuDOTC. Cellular uptake of DOTC was about five times as great as that of LuDOTC. Epifluorescence microscopy showed localization of LuDOTC predominantly within cellular membranes, particularly of mitochondria, as well as a low level of LuDOTC fluorescence diffusely within the cytoplasm. Epifluorescence microscopy of cells labeled with the mitochondrial probe, rhodamine 123, showed mitochondrial fragmentation and altered mitochondrial membrane integrity after LuDOTC photosensitization; these effects depended on radiant exposure and were partially reversible by 24 h after irradiation. For both DOTC and LuDOTC, phototoxicity was increased by irradiation in the presence of deuterium oxide and decreased in the presence of sodium azide, effects consistent with an important mechanistic role for singlet oxygen, O2(1 delta g), in the injury. In solution, LuDOTC and DOTC had similar quantum yields for generation of O2(1 delta g) as measured by time-resolved spectroscopy and by O2(1 delta g) trapping. LuDOTC was photostable in solution, but DOTC underwent significant photodegradation. These data demonstrate that DOTC photo-products such as LuDOTC have significant photobiologic activity and may play an important role in the phototoxicity mechanism of DOTC.

Haemolysis by ultraviolet B of red blood cells from different animal species

Photohaemolysis of erythrocytes was studied under ultraviolet B (UVB) light, which emitted radiation predominantly in the 290-320 nm region. Maximum haemolysis was obtained with rat red blood cells (RBCs), followed by human, fish, sheep, pigeon, lizard and frog RBCs. The rate of UVB-induced haemolysis was almost identical to that produced by UVC (200-290 nm), both causing extensive damage to RBCs. On the other hand, natural sunlight or UVA (320-400 nm) caused very little damage to RBCs. The results indicated that exposure to UVB is detrimental to RBCs and photomodification of RBCs is induced even with small increments in UVB level due to stratospheric ozone depletion.

Phototoxicity of non-steroidal anti-inflammatory drugs: in vitro testing of the photoproducts of Butibufen and Flurbiprofen

In this work, the phototoxicity of two non-steroidal anti-inflammatory drugs, Butibufen and Flurbiprofen, was examined. Both were unstable to light, to give several photoproducts which were isolated and identified. The different photoproducts were formed by a primary photochemical mechanism which involves an initial cleavage of the C-C bond alpha to the carbonyl group, followed by several secondary processes. The cytotoxic effects of the xenobiotics were evaluated using two well-established biological in vitro tests: (a) enzyme leakage lactate dehydrogenase and glutamate-oxaloacetate transaminase from cultured fibroblasts and (b) lysis of red blood cells. The benzylic alcohols caused extensive leakage from cultured fibroblasts at the different concentrations assayed. The alcohol obtained from Butibufen was a potent lytic agent for human red blood cells. The other photoproducts, Butibufen and Flurbiprofen did not produce observable toxic effects on cells.

Mechanism of DNA cleavage mediated by photoexcited non-steroidal antiinflammatory drugs

DNA damage photoinduced by four nonsteroidal antiinflammatory drugs (NSAID) have been investigated by neutral agarose gel electrophoresis. Upon irradiation at 300 nm, in phosphate buffered solution, benoxaprofen, naproxen, ketoprofen, tiaprofenic acid photosensitized the formation of single-strand breaks (SSB) in double stranded supercoiled phi X174 DNA. The efficiency of the cleavage is higher in argon saturated solutions than in aerated solutions and it is not correlated with the quantum yield of photodegradation of the drugs. Simultaneously with the DNA strand breaks, NSAID promote a weak reduction of the electrophoretic mobility of the supercoiled form that may be attributed to the formation of pyrimidine dimers or other DNA unwinding products. These photodimerization processes suggest the involvement of a triplet-triplet energy transfer between NSAID and DNA. Addition of mannitol and superoxide dismutase decreases the efficiency of the cleavage suggesting that HO. and O2.- are involved in the DNA cleavage. Unexpectedly, addition of sodium azide quenches the cleavage both in aerated or in deaerated solutions. Substituting H2O by D2O does not change the number of SSB thus suggesting that 1O2 does not take an important place in the cleavage of DNA. From our data we tentatively assume that the cleavage occurs through a radical mechanism that may involve in a first step an energy or an electron transfer. Gel sequencing on NSAID-photoinduced DNA breakage exhibits no particular specificity except in the case of benoxaprofen where a slight selectivity for cytosine is observed.

Comparison of the pro-oxidative interactions of flunoxaprofen and benoxaprofen with human polymorphonuclear leucocytes in vitro

At concentrations of 3.75 micrograms/ml and greater the non-steroidal anti-inflammatory drugs, benoxaprofen and to a lesser extent flunoxaprofen, caused dose-related spontaneous activation of both luminol- and lucigenin-enhanced chemiluminescence in human polymorphonuclear leucocytes (PMNL) in vitro. Flunoxaprofen- and benoxaprofen-mediated activation of oxidant release by PMNL was increased by UV-radiation. Pre-incubation of PMNL with sub-stimulatory concentrations of both drugs greatly enhanced the release of reactive oxygen species on subsequent exposure of the cells to various standard stimuli of membrane-associated oxidative metabolism. The protein kinase C inhibitor, H-7, and the phospholipase A2 inhibitor, BPB, both prevented drug-mediated activation of superoxide generation by PMNL. Flunoxaprofen-mediated stimulation of PMNL membrane-associated oxidative metabolism is, like benoxaprofen, due to apparent activation of protein kinase C. These findings establish the pro-oxidative properties of flunoxaprofen.

Photochemical studies on the anti-inflammatory drug diclofenac

Irradiation with UVA light of the anti-inflammatory drug diclofenac [2-(2,6-dichloroanilino)phenylacetic acid] in aqueous buffer or methanol solution leads to sequential loss of both chlorine substituents and ring closure to carbazole-1-acetic acid as the major product. Minor products result from substitution by the solvent. The photosensitizing properties of diclofenac and its major photoproduct were tested with singlet oxygen substrates and in the free radical polymerization of acrylamide. Although the major carbazole product is a weakly phototoxic agent, able to generate singlet oxygen more efficiently than diclofenac, the free radical photodechlorination process is postulated as the probable initiation step of in vivo photosensitivity responses.

DNA strand breaks photosensitized by benoxaprofen and other non steroidal antiinflammatory agents

Benoxaprofen, a non steroidal antiinflammatory drug is known to be highly phototoxic. Upon irradiation at 300 nm, benoxaprofen is shown to enhance the cleavage of phi X 174 DNA in buffered aqueous solution (pH 7.4). A linear relationship between the number of single strand breaks and the irradiation time is found. In deaerated solutions, these breaks are three times greater in the presence than in the absence of benoxaprofen. In both cases the rate of cleavage decreases in the presence of air. The rate of DNA damage increases with the drug per base pair ratio up to approximatively 0.2 and then decreases at higher ratios. Other NSAIDs, naproxen, ketoprofen, diflunisal, sulindac and indomethacin have been tested as photocleavers of DNA by using the same experimental conditions. A comparison of the efficiency of cleavage of all these drugs (including BNP) was obtained at drug concentrations such that the light absorbance was the same. Benoxaprofen, naproxen, ketoprofen and diflunisal induce single strand breaks. Sulindac and indomethacin do not cause breaks, and they can in some conditions even act as screening agents. The most efficient of the series are naproxen and ketoprofen. In the presence of oxygen, at the same concentrations as above, the efficiency of benoxaprofen, ketoprofen and diflunisal is decreased while that of naproxen is increased. This suggests that all these compounds do not interact with DNA by the same mechanism. In the case of BNP, the mechanism of photoinduced DNA cleavage is discussed in detail. It is shown that the photoactive agent is the decarboxylated derivative of benoxaprofen, as the photodecarboxylation of benoxaprofen is much faster than the photocleavage of DNA.

A study of persistent photosensitivity as a sequel of the prior administration of the drug benoxaprofen

Cutaneous photosensitivity is a recognized side-effect of a number of commonly used groups of drugs, among which are the non-steroidal anti-inflammatory agents (NSAIDs) one of which, benoxaprofen, was withdrawn from use in 1982. The abnormal reaction of the skin to light usually occurs during the period of the systemic administration of the drug, but may with some drugs persist for longer, even for months. Chronic photosensitivity, i.e. 'persistent light reaction' of some years duration, continuing after the withdrawal of the primary cause, has so far only been reliably reported when the initial exposure of the skin to the photoactive substance has been by external contact and not following ingestion. A suggestion that photosensitivity could persist for a period of years as a sequel of initial benoxaprofen-induced photosensitivity was studied in a group of 42 subjects said to be affected in this way. The results failed to confirm the presence of persistent photosensitivity. It appeared that the probable explanation for the episodic abnormal reactions to light over the years since 1982 was the systemic administration of other photoactive drugs including a series of NSAIDs.

Photolytic degradation of benorylate: effects of the photoproducts on cultured hepatocytes

The photodegradation of benorylate [4'-(acetamido)phenyl-2-acetoxybenzoate], a drug frequently used in rheumatoid arthritis therapy, has been examined under different sets of experimental conditions. Several photoproducts have been isolated and identified on the basis of their IR, NMR, and MS spectra. The most significant photochemical process is the photo-Fries rearrangement of benorylate, leading to 5-acetamido-2'-acetoxy-2-hydroxybenzophenone (1). This compound undergoes a rapid transacylation to the isomeric 5'-acetamido-2'-acetoxy-2-hydroxybenzophenone (2). A primary culture of rat hepatocytes has been used to evaluate the possible toxicity of these two benzophenones, keeping in mind the following criteria: leakage of cytosolic enzymes, attachment index to culture plates, gluconeogenesis from lactate and fructose, glycogen balance, and albumin synthesis. At the concentrations assayed, neither of the two major photoproducts of benorylate (benzophenones 1 and 2) had significant toxic effects on liver cells in culture.

Lipid peroxidative potency of photosensitized thiazide diuretics

We examined the lipid peroxidative potency and photohemolytic activity of thiazide diuretics, especially penflutizide (PFZ), to determine the molecular mechanism of thiazide phototoxicity. Ultraviolet A irradiation of squalene in the presence of PFZ, hydrochlorothiazide, methiclothiazide, benzylhydrochlorothiazide, or trichlormethiazide induced in vitro peroxidation as measured by production of the hydroperoxides and thiobarbituric acid-reactive substances. Among the thiazides, PFZ showed the highest potency to photooxidize lipids. PFZ-photosensitized peroxidation of squalene was repressed by the presence of sodium azide or 2,5-dimethylfuran and was accelerated in a D2O suspension. These findings suggest the participation of singlet oxygen in PFZ photoperoxidation of squalene (type II mechanism). PFZ-photosensitized lysis of red blood cells (RBC) accompanied by formation of hydroperoxides in RBC membrane lipids was also noted. These results suggest that membrane lipids can be one of the target molecules of thiazide phototoxicity.