In Vitro Phototoxicity of Phenothiazines: Involvement of Stable UVA Photolysis Products Formed in Aqueous Medium (original) (raw)
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Excited-state Properties and In Vitro Phototoxicity Studies of Three Phenothiazine Derivatives¶
Photochemistry and Photobiology, 2007
This work concerns a combined photophysical, photochemical and photobiological study of three drugs (psychotherapeutic agents) of the phenothiazine series: perphenazine, fluphenazine hydrochloride and thioridazine hydrochloride. The excited-state properties were first investigated by stationary and time-resolved fluorimetry and by laser flash photolysis. The spectral description was assisted by quantum-mechanical calculations with the INDO/1-CI method. In organic media the lowest excited singlet state was found to decay by fluorescence (small quantum yield) and mainly by intersystem crossing to the lowest triplet state, which is responsible for oxygen photosensitization (high yields of singlet oxygen production) and photodegradation. A further decay pathway in aqueous solutions was the photoionization process, which led to the formation of the phenothiazine radical cations and the solvated electron. After the preliminary study of the photobehavior in organic solvents and in water, the phototoxicity of the three drugs was investigated on various biological substrates through a series of in vitro assays under UVA irradiation. Photohemolysis of mouse erythrocytes and phototoxicity on cultured murine fibroblasts were observed for all three compounds. Lipid photoperoxidation was then investigated using linoleic acid as the unsaturated lipid model and isolated red blood cell membranes. The drug-induced photodamage was also evaluated on proteins by measuring the photosensitizing cross-linking in erythrocyte ghosts. The combined approach proved to be useful in understanding the mechanism by which these phenothiazine derivatives induce skin photosensitization. In particular, the photophysical properties of the compounds under investigation and the results of the study on their phototoxicity are in agreement with a mechanism that involves the radical cation of the drugs as a main intermediate. ¶Posted on the website on
Toxicological Sciences, 2013
This study aimed to establish an efficient photosafety screening system, employing in vitro photochemical and cassette-dosing pharmacokinetic (PK) studies. Eight phenothiazine (PTZ) derivatives were selected as model chemicals, and photochemical characterization and cassette-dosing PK study were carried out. In vivo photosafety testing on oral PTZs (100 mg/kg) was also assessed in rats. All the tested PTZs exhibited potent UVA/B absorption with molar extinction coefficients of ca. 3400-4400 M −1 cm −1. Under exposure to simulated sunlight (2.0 mW/cm 2), all PTZs, especially fluphenazine 2HCl (FP) and trifluoperazine 2HCl (TF), tended to generate reactive oxygen species (ROS). Casset-dosing PK studies demonstrated high dermal deposition of FP and TF in rats, and from these findings, taken together with the potent photochemical reactivity, both FP and TF were deduced to be highly phototoxic. In contrast, the phototoxic potential of chlorpromazine HCl (CP) seemed to be low because of moderate ROS generation and limited dermal distribution. Predicted phototoxic risk for PTZs from photochemical and PK data appeared basically to agree with the observed phototoxicity in rats; however, oral CP (100 mg/kg) caused severe phototoxic responses in rats. Metabolites of CP have been recognized to be phototoxic, which might explain in part this false prediction. These findings might also suggest the necessity of complementary testing on drug metabolites for more reliable photosafety evaluation. The combined use of photochemical and PK data might be efficacious for simple and fast prediction of the phototoxic potential of new drug candidates.
Photosensitization of Biomolecules by Phenothiazine Derivatives
Current Drug Targets, 2006
It is well known that many drugs act as photosensitizers towards cells by interacting with various cellular components such as lipids, proteins and nucleic acids. The structural modifications of the cellular components may occur by direct interactions of the excited states (singlets or triplets) of the drugs with the biological substrate or indirectly, through reactive species of oxygen sensitised by the drug themselves. In particular, the phototoxic activity of various drugs correlated with their potential photomutagenic and photocarcinogenic effects, takes place through DNA modification. Phenothiazines, a class of antihistaminic (anti-H1) or neuroleptic drugs used in the therapy of mental illness, such as schizophrenia, organic psychoses and other mental disorders, are known to induce photosensitization of the skin by systemic use or by topical applications as antiallergic drugs. In this review we have focused our attention on the photosensitizing property of phenothiazines and related compounds both in vitro and in vivo systems. Particular attention has been given to the mechanism of photo reaction with biomolecules such as lipids, proteins and DNA. Moreover there is a growing interest in drugs having photobiological effects because of their possible application as phototherapeutics. It has been interesting in this context to mention briefly the possible application of phenothiazine derivatives as new photosensitizers for their therapeutic application in photodynamic therapy (PDT) or in the light inactivation of viruses and bacteria.
Photo-oxidative damage to isolated rat liver mitochondria induced by phenothiazines
2009
Photosensitization is a well-known side-effect of phenothiazines that could involve photochemically promoted oxidative damage to mitochondria, leading to the impairment of metabolic functions and apoptosis. In this work, for the first time, we investigated the effects of photoexcited thioridazine (TR), trifluoperazine (TFP) and fluphenazine (FP) on isolated rat liver mitochondria. Under UV irradiation, the presence of these phenothiazines led to a dose-dependent lack of the respiratory control ratio. These effects were not accompanied by significant swelling and oxidation of protein thiol groups but were accompanied by lipid peroxidation. Lycopene and sorbate, well-known quenchers of singlet oxygen and triplet species, respectively, were ineffective at protecting mitochondrial lipids against the damage promoted by the excited phenothiazines, suggesting that photochemically-produced cation radicals were the prooxidant species. Corroborating this proposal, butylated hydroxytoluene (BHT) completely inhibited the lipid peroxidation induced by UV irradiation in the presence of phenothiazines. These novel results make a significant contribution to the understanding of the photochemical properties of phenothiazines in biological systems.
Chemico-Biological Interactions, 1983
Inactivation of &X174 bacteriophages as a function of the irradiation time in the near-UV and in the presence of triflupromazine (TFt~), promazine (PZ), chlorpromazine (CPZ) or methoxypromazine (MTPZ) proceeds according to single hit kinetics. Acepromazine (ACPZ) has no significant activity. At low concentrations (0.1 mM) TFPZ and PZ are the most active compounds. Higher concentrations (up to 5 mM) result in a protective effect by these two compounds but cause increased inactivation rates in the case of MTPZ or CPZ. Photoinactivation mediated by TFPZ or CPZ increases the reversion frequency of a ~bXamber mutant. Neither MTPZ nor PZ sensitization induces mutagenesis. The effect of NaN3 on the phage inactivation rate varies depending upon both the sensitizer and the concentration of the quencher. Phage inactivation in an N2 atmosphere is measurable only in the presence of high concentrations of CPZ and MTPZ. The drugs do not show any selectivity for calf thymus DNA or bovine serum albumin, at least as measured by dialysis equilibrium experiments.
Photodegradation of 2-chloro Substituted Phenothiazines in Alcohols
Photochemistry and Photobiology, 2009
The mechanisms that trigger the phototoxic response to 2-chlorophenothiazine derivatives are still unknown. To better understand the relationship between the molecular structure of halogenated phenothiazines and their phototoxic activity, their photophysics and photochemistry were studied in several alcohols. The photodestruction quantum yields were determined under anaerobic conditions using monochromatic light (313 nm). Absorption-and emission-spectroscopy, 1 Hand 13 C-NMR, and GC-MS were used to characterize the photoproducts and reference compounds. An electron transfer mechanism had been previously proposed by Bunce and coworkers (J. Med. Chem. 22,[202][203][204] to explain the large difference between the photodestruction quantum yield of 2-chlorpromazine (φ = 0.46) and 2-chlorphenothiazine (φ = 0.20). According to these authors, the alkylamino chain transfers an electron to the phenothiazine moiety. Our results demonstrate that this mechanism is incorrect, because the photodestruction quantum yields of all chlorinated derivatives of this study are the same under the same conditions of solvent and irradiation wavelength. The quantum yield has no dependence on the 10substituent, but it depends on the solvent. The percentage of each photoproduct, on the other hand, strongly depends on that substituent, but not very much on the solvent. Finally, it is demonstrated that the phototoxic effect of chlorinated phenothiazines is not related to the photodechlorination, although both processes share the same transient.
Photochemistry and Photobiology, 2004
(3-[dimethylamino]-2-methyl-propyl)-phenothiazine) have been investigated in neutral buffered aqueous solutions. The transient absorbances of the hydrated electrons, of the first excited triplet state (3CMZ*) with a characteristic absorption band peaking at 420 nm and of the radical cation ('CMZ+) (maximum absorbance at 500 nm) have been observed by 355 nm laser flash spectroscopy of deaerated solutions. All these transient species are formed by monophotonic processes and react with oxygen. Bimolecular reaction rate constants of TMZ+ and 3CMZ* with O2 are 2 X 10' M-' s-' and 4 X lo9 M-' s-l, respectively. The 3CMZ* reacts only sluggishly (reaction rate constant, 9 X 106 M-' s-l) with tryptophan chosen as a Type-I photodynamic substrate. Steady-state irradiations with 365 nm light demonstrate that CMZ is rapidly photolyzed (quantum yield, 0.04) in 02-saturated solutions leading to oxidation of the sulfur atom and of the side-chain nitrogen of CMZ. This photoproduct (2-cyano-10-(3-[dimethylamino, N-oxide]-2-methyl-propyl)-5-oxide-phenothiazine), is a good Type-I and Type-I1 photodynamic photosensitizer producing singlet oxygen in high yield (-0.45) and could play a major role in the phototoxicity of CMZ.
Journal of Photochemistry and Photobiology B: Biology, 2005
Phototoxic side effects of pharmaceutical and cosmetic products are of increasing concern for patients, dermatologists and the chemical industry. Moreover, the need of new chemicals and drugs puts pressure on pre-clinical test methods for side effects, especially interactive adverse-effects with UV-light. So, the predictive potential of different established test methods, which are used regularly in our departments in order to detect the phototoxic potential of chemicals, were analyzed. Namely the fibroblast 3T3 test, the photo henÕs egg test, a guinea pig test for measuring acute photoreactions, and a modified Local Lymph Node Assay, the Integrated Model for the Differentiation of Skin Reactions. Various agents with different photoreactive potential were tested: quinolones like Bay y 3118, ciprofloxacin, enoxacin, lomefloxacin, moxifloxacin, ofloxacin, sparfloxacin, as well as promethazine, chlorpromazine, 8-methoxypsoralen and olaquindox serving as control. Special emphasis was taken to evaluate the capability of the employed test procedures to predict phototoxic side effects in patients. Following our results, both in vitro assays were useful tools to detect photoirritancy while the photoallergic potentials of tested compounds were exclusively detected by an in vivo assay. As long as no in vitro model for photoallergy is available, the UV-IMDS should be considered to evaluate photoallergic properties of a supposed photoreactive agent.
The phototoxicity of phenothiazinium-based photosensitizers to bacterial membranes
FEMS Immunology & Medical Microbiology, 2006
The ability of phenothiazinium-based photosensitizers to induce photodamage to Escherichia coli membranes is investigated. Phenothiazinium-based photosensitizers were found to be somewhat lipophilic (log P 4 0.7) and to induce surfacepressure changes (3-12 mN m À 1 ) in lipid monolayers mimetic of bacterial membranes, implying that these molecules are able to penetrate biological membranes. Under dark and light conditions (3.15 J cm À 1 for 30 min), phenothiazinium-based photosensitizers were incubated with E. coli cells. These cells showed levels of dark bacteriolysis that ranged between 6% and 13%, with light conditions leading to no significant increase in these levels. Gas chromatographybased analyses showed such incubations to produce no significant changes in the levels of C 16 and C 18 fatty acid chain saturation found in E. coli whole lipidextracts. It is concluded that the phenothiazinium-based photosensitizers studied may not use E. coli membranes as their primary photodynamic target, but may inflict photodamage on cytoplasmic targets, possibly DNA.