Biopharmaceutics, pharmacokinetics and pharmacology of psoralens

The psoralen derivative 8-methoxypsoralen (8-MOP) and to a lesser extent some other psoralens, including 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP) have acquired a place in the treatment of psoriasis and other dermatoses. They are only active when combined with long-wave ultraviolet light: PUVA therapy (Psoralen plus UVA). Successful PUVA therapy depends on sufficiently high psoralen concentrations coinciding with the time of irradiation. The use of oral or rectal pharmaceutical formulations with 8-MOP dissolved in liquid is preferable to conventional tablets or capsules. Since no formulation of 5-MOP with fast and predictable absorption is available 8-MOP should be preferred in PUVA therapy. The effectiveness of oral TMP is doubtful, because of low serum concentrations, probably due to malabsorption.     

Permeation Characteristics of 8-Methoxypsoralen Through Human Skin; Relevance to Clinical Treatment*

The permeation characteristics through human skin of 8-methoxypsoralen (8-MOP) and its physical attributes were investigated. The log octanol/water partition coefficient and saturated aqueous solubility of 8-MOP at 32°C were 1.98 and 55.8 μg mL^?1 respectively. 8-MOP showed Fickian diffusion, with its flux being linearly related to the concentration of drug in the donor solution. The permeability coefficient of 8-MOP through human skin from different concentrations of aqueous solutions and a 2.6 μg mL^?1 bath lotion (as used in clinics) were statistically identical with mean values of 1.76 ± 0.12 × 10^?2 and 1.70 ± 0.32 × 10^?1 cm h^?1 respectively (P ≥ 005). An ethanol/water (1:1 w/v) receptor solution did not improve the clearance of 8-MOP from the dermis when compared with an aqueous vehicle. Complete removal of the stratum corneum by tape stripping from full-thickness membranes produced a threefold increase in the flux of 8-MOP thus suggesting that the main barrier to 8-MOP permeation resides in the stratum corneum although the aqueous epidermal and dermal tissue provide a significant resistance to transdermal drug permeation. The equilibrium uptake of 8-MOP into psoriatic plaques and the 8-MOP aqueous/plaque partition coefficient were found to be more than twofold greater than for normal stratum corneum. The absorption of 8-MOP from the total applied topical dose (396 mg) was assessed as ～0.25% and only 2.5% of an oral dose, a significant reduction in the possible toxic hazard. The peak concentration of 8-MOP permeating through the skin was observed at about 35 min after limited exposure for 15 min. Our results suggest that following a 15 min bath in the drug solution, there may be a need for an interval of about 20 min before patients are irradiated to ensure the optimization of photosensitizer with UVA irradiation (PUVA) therapy. Alternatively, UV irradiation could be applied at a lower flux over a longer time.     

Effect of alpha-tocopherol and di-butyl-hydroxytoluene (BHT) on UV-A-induced photobinding of 8-methoxypsoralen to Wistar rat epidermal biomacromolecules in vivo

The possible formation of singlet oxygen via photoexcited psoralens has been associated with the occurrence of, amongst others, erythema. Therefore it has been suggested to combine PUVA with the topical or systemic administration of antioxidants. However, the effect of these antioxidants on the photobinding of psoralens to DNA, which is held responsible for the anti-proliferative effect, should be taken into account. In the present study the effect of two phenolic antioxidants, alpha-tocopherol (AT) and butylated hydroxytoluene (BHT), on the in vivo photobinding of 8-methoxypsoralen (8-MOP) to not only epidermal DNA, but also proteins and lipids was determined. After topical application of an ethanolic antioxidant solution onto the shaven skin of Wistar rats, labeled 8-MOP was applied using the same solvent. After this the rats were exposed to UV-A. By separating epidermal lipids, DNA/RNA and proteins by a selective extraction method, irreversible binding of 8-MOP to each of these biomacromolecules was determined. Both AT and BHT caused a decrease in the photobinding of 8-MOP to epidermal DNA and proteins. To investigate the underlying mechanism of this protection, the effect of AT was compared with that of AT-acetate. It also proved helpful to study the effects of the antiooxidants on the photobinding of another photosensitizer, namely chlorpromazine. From these experiments it was concluded that AT and BHT affect 8-MOP photobinding by quenching reactive 8-MOP intermediates, involving the phenolic hydroxyl group of the antioxidants. BHT offered protection against lipid binding of 8-MOP but AT, especially at high concentrations, enhanced the UV-A-induced binding of 8-MOP to lipids. This is noteworthy with respect to the current interest in the role of 8-MOP-lipid adducts in PUVA therapy.     

Central role of mitochondria and p53 in PUVA-induced apoptosis in human keratinocytes cell line NCTC-2544

Despite strong evidence concerning the high efficiency of PUVA therapy (psoralen plus UVA light), its mechanism of action has not yet been fully elucidated. In this study, we have evaluated in a cell line of human keratinocytes (NCTC-2544) the effects of two linear psoralen derivatives, 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP), that are widely used in PUVA therapy and two angular derivatives, Angelicin (ANG) and 4,6,4'-trymetyl angelicin (TMA). All derivatives photoinduce cellular death, TMA being the most active compound. The cell cycle analysis showed that the four derivatives induce, 24 h after irradiation, a cell cycle arrest in G1 phase later followed by massive apoptosis. The G1 arrest is correlated to an increase in the expression of p21(Waf1/Cip1), a protein associated with the cell cycle block and apoptosis. Furthermore, treatment of NCTC-2544 resulted in p53 activation by 5-MOP, 8-MOP, and ANG but not TMA and its phosphorylation at serine-15. The levels of p21(Waf1/Cip1) paralleled p53 protein staining pattern suggesting that p53 activation correlated with p21(Waf1/Cip1) induction. Simultaneous to p53 activation, psoralens induced mitochondrial depolarization, cytochrome c release, mitochondrial production of reactive oxygen species, as well as caspase-3 and -9 activation. Thus these results strongly indicate the necessity of p53 activation and the induction of the apoptotic machinery downstream of mitochondria.     

Influence of food on the kinetics of 8-methoxypsoralen in serum and suction blister fluid in psoriatic patients

Summary The influence of food on the kinetics of 8-methoxypsoralen (8-MOP) in serum and suction blister fluid was evaluated in a cross-over study in 19 psoriatic patients under PUVA treatment. The peak serum concentration of 8-MOP was reached 1.5 h after ingestion on an empty stomach, and in suction blister fluid the maximum concentration was already present in the first sample taken after 2 h, the time when UVA radiation was given. The postprandial kinetics of 8-MOP in serum and suction blister fluid differed, the highest levels being reached, respectively, at 2.4 and 3 h after intake, i.e. in both body fluids after irradiation had started. The side effects of 8-MOP, such as nausea and dizziness, in the two groups were similar. The present results indicate that to optimize the therapeutic effect of PUVA in individual patients, 8-MOP should be given on an empty stomach.     

Toxicity of 8-methoxypsoralen, 5-methoxypsoralen, 3-carbethoxypsoralen, or 5-methylisopsoralen with ultraviolet radiation in the hairless (HRA/Skh) mouse

An experimental design to simulate PUVA therapy (oral 8-methoxypsoralen followed by uv radiation) has been tested in a 13-week subchronic study to determine the relative toxicities of 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP), 5-methylisopsoralen (5-MIP), and 3-carbethoxypsoralen (3-CEP) in inbred hairless mice (HRA/Skh). Drug was administered by 1-hr pulse feedings three times a week after mice were fasted overnight; individually housed animals were then exposed to uv radiation (320-400 nm; less than 2% output less than 320 nm). 8-MOP or 5-MOP administered orally (at doses of approximately 240 or 480 mg/m2 body surface area per week) followed one-half hour later with uv radiation of 2 J/cm2 for 13 weeks were found to cause skin toxicity including inflammation, hyperplasia, ulceration, and cellular atypia. Dose-related toxicity was not seen in other organ systems. Corresponding levels of 5-MIP or 3-CEP with uv radiation did not produce skin toxicity. These studies show that the psoralens with two potential DNA-binding sites (8-MOP and 5-MOP) were more toxic than psoralens with only one photoreactive site (5-MIP and 3-CEP).     

Inhibition and induction of drug metabolism by psoralens: alterations in duration of sleep induced by hexobarbital and in clearance of caffeine and hexobarbital in mice.

1. Hexobarbital (100 mg/kg i.p.) sleeping times in male CD-1 mice pretreated (-1 h) with a single i.p. injection of 150 mumol/kg of psoralen or coumarin analogues were increased, most markedly (6-fold) by linear, methoxy-substituted psoralens. 2. Hexobarbital sleeping times of mice which received three daily injections (231 mumol/kg; 50 mg/kg) of 8-methoxypsoralen (8-MOP) were 44% of controls (corn oil). 3. The whole-body half-life of caffeine (1 mg) in mice was 10.2, 1.2, and 0.37 h following 8-MOP (50 mg/kg per day) x 1, vehicle, and 8-MOP x 3 respectively. 4. The whole-body concentrations of hexobarbital (100 mg/kg dose) in mice 30 min after dosing were 14.3 +/- 0.9, 8.4 +/- 0.3, and 5.2 +/- 0.5 micrograms/ml (1 mouse = 150 ml) following 8-MOP (50 mg/kg per day) x 1, vehicle, and 8-MOP x 3 respectively. 5. It is concluded that, administered acutely, psoralen analogues inhibit hexobarbital metabolism in mice; and 8-MOP administered acutely inhibits the metabolism of caffeine and hexobarbital, but administered repeatedly increases their metabolism.     

Induction of apoptosis in Jurkat cells by photoexcited psoralen derivatives: Implication of mitochondrial dysfunctions and caspases activation.

The prevailing form of cell death in lymphocytes exposed to psoralen plus UVA light (PUVA), was investigated. We studied the well known drug 8-methoxypsoralen (8-MOP) and an angular derivatives: angelicin (ANG). We evaluated the induction of apoptosis in a human tumor T-cell line (Jurkat). Both compounds provoke a significant induction of apoptosis at 24h from irradiation as demonstrated by a remarkable percentage of cells Annexin-V positive. We investigated the effects of the psoralen derivatives upon UVA irradiation on the cell cycle. The flow cytometric analysis of propidium labeled cells indicates that treatment induces, in a dose dependent manner, a massive accumulation of cells, for both compounds, in G2-S phase after 24h from the irradiation. We have focused our attention on the mitochondrial functionality after irradiation in the presence of psoralen derivatives. We evaluated, by flow cytometry, (i) the mitochondrial potential (Deltapsi(mt)), (ii) the production of reactive oxygen species (ROS) and (iii) the oxidation of cardiolipin, a phospholipid restricted to the inner mitochondrial membrane. Furthermore the activation of caspases -3, -8 and -9 was also investigated. The obtained data indicated that, upon UVA irradiation, the two compounds induce a strong decrease in mitochondrial functions and activate caspase-3, -8 and -9.     

Psoralen binding and inhibition of epidermal growth factor binding by psoralen/ultraviolet light (PUVA) in human epithelial cells.

The psoralen analogs 8-methoxypsoralen (8-MOP) and 4,5',8-trimethylpsoralen (TMP), in combination with ultraviolet light (UVA, 320-400 nm), are potent modulators of epidermal cell growth and differentiation and are commonly used in photochemotherapy of psoriasis and vitiligo. We have used KB cells, a human epithelial cell line, to examine the mechanism of action of these compounds. In KB cells, 8-MOP was found to bind to specific, saturable receptor sites. Binding of [3H]-8-MOP to its receptor was inhibited by TMP as well as psoralen. We found that binding of these analogs to the cells followed by UVA light treatment was associated with inhibition of epidermal growth factor (EGF) receptor binding. Inhibition of EGF binding was temperature dependent, occurred immediately following UVA light exposure, and appeared to be due to a decrease in the number of EGF receptors. In KB cells, 125I-labeled EGF surface receptor binding is followed by its rapid internalization and degradation. We found that photoactivated psoralens also inhibited internalization of 125I-EGF, but had no apparent effect on EGF metabolism. These data indicate that the cell surface membrane may be an important target for the photoactivated psoralens. In addition, since photoactivated psoralens regulate cell proliferation, the interaction of these compounds with EGF receptor function may underlie their biological activity.     

The pharmacokinetics of 8-methoxypsoralen following i.v. administration in humans.

1. 8-methoxypsoralen (8-MOP) is a naturally occurring photoreactive substance which, in the presence of u.v. light, forms covalent adducts with pyrimidine bases in nucleic acids. For many years, 8-MOP has been used in PUVA therapy for treatment of psoriasis. Recently, the drug has been found to inactivate effectively bacteria spiked into platelet concentrates. The purpose of this study was to determine the pharmacokinetics and safety of 8-MOP administered intravenously in the bactericidal dosage range. 2. Eighteen volunteers were divided into three treatment groups to receive, respectively, 5, 10, and 15 mg 8-MOP infused over 60 min. Frequent arterial samples were gathered, and the blood and plasma were assayed for 8-MOP concentration. The pharmacokinetic parameters were determined by moment and compartmental population analysis, the latter performed with the program NONMEM. Haemodynamics, ventilatory pattern, and subjective effects were recorded throughout the study. 3. The intravenously administered 8-MOP was well tolerated in all individuals, and no acute toxicity was observed. 4. The pharmacokinetics of 8-MOP were best described by a three-compartment mammillary model in which the volumes and clearances were proportional to weight. The mean pharmacokinetic parameters for the plasma concentrations were: V1 = 0.045 1 kg-1, V2 = 0.57 1 kg-1, V3 = 0.15 1 kg-1, CL1 (systemic) = 0.010 1 kg-1 min-1, CL2 = 0.0067 1 kg-1 min-1, CL3 = 0.012 1 kg-1 min-1. The mean pharmacokinetic parameters for the blood concentrations were: V1 = 0.061 1 kg-1, V2 = 1.15 1 kg-1, V3 = 0.21 1 kg-1, CL1 (systemic) = 0.015 1 kg-1 min-1, CL2 = 0.011 1 kg-1 min-1 and CL3 = 0.015 1 kg-1 min-1. 5. The plasma pharmacokinetic model described the observations with a median absolute error of 17%, and the blood pharmacokinetic model described the observations with a median absolute error of 18%. Analysis of the relative concentration of 8-MOP between plasma and red blood cells suggested concentration-dependent partitioning. 6. The addition of 7.5 mg 8-MOP to 300 ml platelet concentrate would produce bactericidal concentrations of 25 micrograms ml-1. Simulations based upon our data show that intravenous administration of 7.5 mg over 60 min would result in systemic concentrations of 8-MOP similar to those observed with conventional PUVA therapy. We conclude that the extensive safety history established in PUVA therapy will be applicable to this new application of 8-MOP.     

Dietary intake and risk assessment of phototoxic furocoumarins in humans

The question of whether the furocoumarin content of vegetables is sufficient to induce phototoxic skin reactions after ultraviolet irradiation was examined in two experiments with four human volunteers. In a first experiment, 300 g of celery roots (total phototoxic furocoumarin content 28.2 micrograms/g) was ingested. No skin reactions were observed after UVA exposure (1.5-9 J/cm2), and the blood levels of the furocoumarins--psoralen, 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP)--were below the analytical detection limit of 2 ng/ml. To investigate the phototoxic effects of a mixture of the two most important furocoumarins in vegetables, after gastro-intestinal uptake, 8-MOP and 5-MOP (15 mg each) were ingested separately in a 50% alcoholic solution. A strong and persistent erythema was induced in three out of the four subjects (UVA dose: 3-25 J/cm2). The blood levels immediately before UVA irradiation varied between 14 and 114 ng/ml (8-MOP), and 17 and 70 ng/ml (5-MOP). In the subject who did not show phototoxicity, the blood levels remained at trace levels (3 ng/ml). Two subjects were also tested with a mixture of 10 mg 8-MOP plus 10 mg 5-MOP; in one subject the mixture induced pigmentation only, while in the other a mild-to-medium erythema was induced. The blood levels of the furocoumarins in the two subjects were similar (12-15 ng/ml for 8-MOP and 5-MOP). It is concluded that in humans the phototoxic threshold dose of furocoumarin mixtures is of the order of 10 mg 8-MOP plus 10 mg 5-MOP, which is equivalent to about 15 mg 8-MOP per person (blood levels of 8-MOP and 5-MOP at 30 min after ingestion of about 10-15 ng/ml each). This phototoxic threshold dose was not reached by the consumption of celery roots and other conventional vegetables under normal dietary habits (experimental intake of 2-8 mg per subject of the potentially phototoxic furocoumarin mixture). However, the safety factor between the possible actual intake of furocoumarins and the phototoxic threshold dose is about 2-10, which is relatively small.     

3-Alkyl- and 3-aryl-7H-furo[3,2-g]-1-benzopyran-7-ones: synthesis,photoreactivity, and fluorescence properties

A series of 3-alkyl- and 3-aryl-7H-furo[3, 2-g]-1-benzopyran-7-ones, known as linear furocoumarins, was synthesized and evaluated for their dark- and photobinding (crosslink formation) with DNA as well as for their spectrophotometric and fluorescent properties, lipophilicity, and ability to photobleach N, N-dimethyl-p-nitrosoaniline (RNO) after irradiation with UVA light. 8-Methoxypsoralen (8-MOP, 9-methoxy-7H-furo[3, 2-g]-1-benzopyran-7-one) and 4, 5', 8-trimethylpsoralen (TMP, 2, 5, 9-trimethyl-7H-furo[3, 2-g]-1-benzopyran-7-one) were used as reference compounds in all tests. The investigations support the formation of a molecular complex between the furocoumarins and DNA.Crosslink formation with DNA after irradiation with UVA light was detectable for compounds with a methyl or phenyl substituent in position 3, but not for those bearing either a tert-butyl, a 4-methoxyphenyl, or a 2, 5-dimethoxyphenyl group. All furocoumarins exhibited sufficient absorption in the UVA wavelength range and are fluorescent. All compounds showed a higher lipophilicity than 8-MOP. Generally the 3-alkyl substituted furocoumarins had a capacity to photobleach RNOwhich was higher than that of the 3-aryl substituted ones. Some of the 3-aryl substituted furocoumarins displayed a photobleaching ability which was similar to or lower than that of 8-MOP.     

Studies on 8-methoxypsoralen tolbutamide interactions. 2. Studies after U.V.-A irradiation in vitro and in vivo.

Previous studies had evidenced that tolbutamide has influence on the complex formation between 8-methoxypsoralen (8-MOP) and serum albumin, both in vitro and in vivo, partially displacing it from its binding site. We have now extended this research by studying competition under UV-A irradiation, thus approaching the conditions which occur during PUVA therapy more closely. Research was first carried out in vitro, studying tolbutamide competing with bound 8-MOP in human serum after irradiation with UV-A. From the data obtained, it appears that the displacement is not influenced to any significant extent by irradiation. Experiments were then carried out in vivo on mice treated with the two drugs and irradiated with UV-A in conditions analogous to those generally used for PUVA therapy; the amount of 8-MOP localized in blood serum and in various organs was then determined. Concerning distribution of 8-MOP, results confirmed what had been previously obtained; concerning irradiation, results showed that the effect on the 8-MOP displacement by tolbutamide was not statistically significative in the most organs considered. A slight difference in respect to the results obtained without irradiation was observed only in the cases of skin, eyes and ears.     

Pharmacokinetics of tazarotene cream 0.1% after a single dose and after repeat topical applications at clinical or exaggerated application rates in patients with acne vulgaris or photodamaged skin

OBJECTIVE: To evaluate the safety and pharmacokinetics of tazarotene cream 0.1% under standard (face only) or exaggerated (15% body surface area, including the face) application conditions after a single dose and after repeat topical applications once daily to patients with acne vulgaris or photodamaged skin. METHODS: Two separate, randomised, single-centre, nonblinded, parallel-group pharmacokinetic studies were conducted. In one study, tazarotene cream 0.1% was applied either to the face of eight female patients with moderate acne or to 15% body surface area of ten female patients with severe acne. In the other study, tazarotene cream 0.1% was applied either to the face (six females, two males) or to 15% body surface area (8 females, 8 males) of patients with photodamaged skin. In both studies, tazarotene cream 0.1% was applied once daily (except on days 1 and 2) for 30 days. Blood was drawn for measurement of plasma concentrations of tazarotenic acid at defined time intervals after application of the cream. Plasma tazarotenic acid concentrations were determined by a validated gas chromatography-tandem mass spectrometry method with a lower limit of quantification of 0.005 microg/L. RESULTS: At exaggerated application rates in patients with acne vulgaris, the maximum average peak concentration (C(max)) and 24-hour area under the concentration-time curve (AUC) values of tazarotenic acid were (mean +/- SD) 1.20 +/- 0.41 microg/L (n = 10) and 17.0 +/- 6.1 microg. h/L (n = 10), respectively, and occurred on day 15. The single highest C(max) was 1.91 microg/L. At standard application rates in patients with acne vulgaris, the maximum average C(max) and AUC values of tazarotenic acid were 0.10 +/- 0.06 microg/L (n = 8) and 1.54 +/- 1.01 microg. h/L (n = 8), respectively, and occurred on day 15. At exaggerated application rates in patients with photodamaged skin, the maximum average C(max) and AUC values of tazarotenic acid were (mean +/- SD) 1.75 +/- 0.53 microg/L (n = 16) and 23.8 +/- 7.0 microg. h/L (n = 16), respectively, and occurred on day 22. The single highest C(max) was 3.43 microg/L on day 29. At standard application rates in patients with photodamaged skin, the maximum average C(max) and AUC values of tazarotenic acid were 0.236 +/- 0.255 microg/L (n = 8) and 2.44 +/- 1.38 microg. h/L (n = 8), respectively, and occurred on day 15. Gender had no influence on the systemic exposure of tazarotenic acid. The most common treatment-related adverse events were signs and symptoms of local irritation, of mild or moderate severity. CONCLUSIONS: The pharmacokinetics of tazarotene cream 0.1% in patients with acne vulgaris or photodamaged skin are similar. The maximum average plasma concentrations of tazarotenic acid after topical application of tazarotene cream 0.1% to the face were less than 0.25 microg/L. The maximum average plasma concentrations of tazarotenic acid following application to an exaggerated body surface area (15%) were less than 1.8 microg/L.     

Guidelines for the treatment of vitiligo.

At present, there is no universally effective drug for vitiligo therapy; there are, however, various therapeutic modalities that may be beneficial. Therapeutic regimens used to treat vitiligo include psoralens and ultraviolet A light (PUVA), topical corticosteroids, fluorouracil locally applied with skin abrasion, a variety of surgical techniques to transplant autologous melanocytes from pigmented skin to nonpigmenting areas, a new photochemotherapeutic regimen using oral khellin with UVA phototherapy, and a recently proposed treatment with oral phenylalanine in combination with UVA exposure. PUVA and topical corticosteroids are the 2 most frequently used modalities. The use of effective sunscreens with a high sun protection factor (SPF) is of help in preventing the vitiliginous areas from burning and normal skin from becoming tanned. Cosmetic camouflage is also useful to disguise the white areas of skin. Finally, depigmentation should be considered in patients with greater than 50% cutaneous involvement who fail to respond or are unwilling to undergo treatment. The selection of patients for therapy should take into consideration the patient's motivation, the psychological impact of the disease and the clinical presentation of vitiligo, and should weigh the risks and benefits of prolonged therapy.     

Examination of psoralens-induced photodermatitis in Wistar rats under scanning electron microscopy.

The psoralens are photoactivated plant biosynthetic compounds which are found in several plant families, including common fruits and vegetables. Synthetic forms of the psoralens bergapten (5-methoxypsoralen) and xanthotoxin (8-methoxypsoralen) are extensively used in skin chemotherapy in combination with long-wave ultraviolet radiation (PUVA). Side effects of PUVA therapy are not, however, desirable, and this therapy has been linked with increased incidence of skin cancer in humans. The psoralens are known to be carcinogenic, mutagenic and teratogenic, and to cause photodermatitis. The main objective of this study was to document the effect of PUVA on the epidermis of rats. Female Wistar rats were administered dietary bergapten and/or xanthotoxin (0-200 mg/kg body) and exposed to UVA radiation (45 min./day) for four weeks. At the end of the four-week period the rats were sacrificed; skin samples were taken from the ears and the top part of the tail and fixed for examination by Scanning Electron Microscopy. The animals subjected to PUVA had significantly smaller scales on the tail epidermis (mean scale size for the control 926 mu vs. 725 to 805 mu for the psoralen treatment groups. The rats that received dietary psoralens also had significantly less hair on the ears compared with the control animals (mean number of hairs per millimeter over the ear edge for the control 54.9 vs. 2.00 to 10.7 for the treatment groups). The two compounds were synergistic in their ability to reduce scale size on the tail epidermis.     

人参皂苷Rg1对细胞光老化模型中p53信号转导途径的影响

目的观察人参皂苷Rg1对光老化p53信号转导途径中相关基因损伤及蛋白表达水平的影响。方法采用8-MOP/UVA(8-methoxypsoralen and subsequent ultraviolet A irradiation)联合处理人皮肤成纤维细胞建立光老化模型,用流式细胞周期分析、SA-β-半乳糖苷酶(senescence associatedβ-galactosidase)化学染色,免疫荧光及Western blot等方法检测人参皂苷Rg1对培养真皮成纤维细胞多项细胞衰老指标及p53信号途径中蛋白表达的影响。结果人参皂苷Rg1可明显抑制细胞和组织老化的指标表达(包括SA-β-Gal表达减少及细胞周期G1阻滞率降低);减少基因氧化应激损伤产物8-oxo-dG及老化相关蛋白p53,p21WAF-1及p16INK-4a的表达。结论人参皂苷Rg1可能通过缓解基因的氧化应激损伤,抑制相关信号转导,从而缓解细胞光老化进程。     

Disposition of 4,6,4'-trimethylangelicin in mice maintained in the dark and after UVA irradiation

The disposition of the furocoumarin 4,6,4'-trimethylangelicin (4,6,4'-TMA) was studied in mice. After oral administration of (3)H 4,6,4'-TMA, radioactivity measured in serum shows fast absorption and slow elimination. Serum protein binding is higher as compared to 8-methoxypsoralen (8-MOP), currently used in photochemotherapy (PUVA) and linearly declines from 30 min to 6 h after administration. Distribution in the various organs was similar to that of 8-MOP and was relatively uninfluenced by UVA radiation, required for the biological effects of 4,6,4'-TMA. Mice eliminate (3)H 4,6,4'-TMA mostly through the urine, but also through the faeces. Two metabolites were identified in the urine and serum of the treated mice, one of which proved to be a derivative of 4,6,4'-TMA, formed by hydrogenation of the double 4',5' bond of the furocoumarin nucleus.     

Inhibition and induction of drug metabolism by psoralens: Alterations in duration of sleep induced by hexobarbital and in clearance of caffeine and hexobarbital in mice

1. Hexobarbital (100?mg/kg i.p.) sleeping times in male CD-1 mice pretreated (-1?h) with a single i.p. injection of 150 μmol/kg of psoralen or coumarin analogues were increased, most markedly (6-fold) by linear, methoxy-substituted psoralens.

2. Hexobarbital sleeping times of mice which received three daily injections (231 μmol/kg; 50?mg/kg) of 8-methoxypsoralen (8-MOP) were 44% of controls (corn oil).

3. The whole-body half-life of caffeine (1?mg) in mice was 10˙2, 1˙2, and 0˙37?h following 8-MOP (50?mg/kg per day) × 1, vehicle, and 8-MOP × 3 respectively.

4. The whole-body concentrations of hexobarbital (100?mg/kg dose) in mice 30?min after dosing were 14˙3±0˙9, 8˙4±0˙3, and 5˙2±0˙5 μg/ml (1 mcuse = 150 ml) following 8-MOP (50?mg/kg per day) × 1, vehicle, and 8-MOP × 3 respectively.

5. It is concluded that, administered acutely, psoralen analogues inhibit hexobarbital metabolism in mice; and 8-MOP administered acutely inhibits the metabolism of caffeine and hexobarbital, but administered repeatedly increases their metabolism.     

8-Methoxypsoralen Induces Apoptosis by Upregulating p53 and Inhibits Metastasis by Downregulating MMP-2 and MMP-9 in Human Gastric Cancer Cells

Furanocoumarin 8-methoxypsoralen (8-MOP) is the parent compound that naturally occurs in traditional medicinal plants used historically. 8-MOP has been employed as a photochemotherapeutic component of Psoralen + Ultraviolet A (PUVA) therapy for the treatment of vitiligo and psoriasis. Although the role of 8-MOP in PUVA therapy has been studied, little is known about the effects of 8-MOP alone on human gastric cancer cells. In this study, we observed anti-proliferative effect of 8-MOP in several human cancer cell lines. Among these, the human gastric cancer cell line SNU1 is the most sensitive to 8-MOP. 8-MOP treated SNU1 cells showed G1-arrest by upregulating p53 and apoptosis by activating caspase-3 in a dose-dependent manner, which was confirmed by loss-of-function analysis through the knockdown of p53-siRNA and inhibition of apoptosis by Z-VAD-FMK. Moreover, 8-MOP-induced apoptosis is not associated with autophagy or necrosis. The signaling pathway responsible for the effect of 8-MOP on SNU1 cells was confirmed to be related to phosphorylated PI3K, ERK2, and STAT3. In contrast, 8-MOP treatment decreased the expression of the typical metastasis-related proteins MMP-2, MMP-9, and Snail in a p53-independent manner. In accordance with the serendipitous findings, treatment with 8-MOP decreased the wound healing, migration, and invasion ability of cells in a dose-dependent manner. In addition, combination treatment with 8-MOP and gemcitabine was effective at the lowest concentrations. Overall, our findings indicate that oral 8-MOP has the potential to treat early human gastric cancer, with fewer side effects.