Inflammatory involvement into phototoxic reaction in erythropoietic protoporphyria (EPP) patients.

Phototoxic reaction is a known feature of EPP at least in part triggered by the oxidative status, complement system activation, and mast cell response. The aim of this study was to verify some aspects involved in phototoxic reaction during a season. The complement system was evaluated by C3 assay, alternative pathway by factor-B, and classical pathway by C1q; oxidative status was tested with malondialdehyde (MDA) and mast cell by IL-10 assay. The serum samples were collected in winter and summer from 19 EPP patients and 13 controls. The reaction to sun exposure within each group was monitored without any invasive treatment. In summer, C3 and factor B were higher in patients than in controls (p = 0.002 and < 0.0001 respectively), while no change was detected for C1q. The oxidative stress was increased in summer in comparison with the control group (p = 0.04), and IL-10 an assay was normal in both seasons. The correlation between the C3 and factor-B in summer was significant. This study shows that the phototoxic reaction is not limited to the dermis but can also exert a systemic response, which could affect the general health of a patient. The knowledge of the pathophysiology of phototoxic reaction is essential for identifying new disease markers useful for improving clinical studies of known and future drugs.

Photosafety screening of phenothiazine derivatives with combined use of photochemical and cassette-dosing pharmacokinetic data.

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.

Vemurafenib: an unusual UVA-induced photosensitivity.

Vemurafenib is a new-targeted therapy approved for the treatment of patients with V600E BRAF-mutant metastatic melanoma. Among the cutaneous adverse events reported, the photosensitivity is frequently experienced. We aimed to characterize more deeply the mechanism leading to this photosensitivity as well as the corresponding UV spectrum. Phototests showed that the phototoxicity was UVA-dependent since from normal value prior to vemurafenib treatment, the UVA-minimal erythema dose decreased in 17 of 18 patients (94.4%) while the minimal erythema dose remained unchanged. Furthermore, a vemurafenib-induced erythema appeared quickly during the UVA exposure contrarily to what is observed with a conventional drug-induced phototoxicity showing an erythema 12-24 h after the phototesting. Vitamin PP concentration decreased, and porphyrin level significantly increased after 2 months of vemurafenib. Our study confirms the high risk of vemurafenib-induced photosensitivity and indicates that it is possibly vitamin PP- and porphyrin dependent.

Isolation and identification of the photodegradation products of the photosensitizing antidepressant drug clomipramine. Phototoxicity studies on erythrocytes.

The isolation and identification of the photodegradation products of clomipramine (CIP) in phosphate buffered saline (PBS pH 7.4 and 6.0) solution and methanol under aerobic conditions were studied. Six compounds were identified and four of them were isolated and characterized by spectroscopic methods. A radical mechanism with the participation of the solvent is proposed for the photodegradation of CIP which undergoes homolytic cleavage of the carbon-chlorine bond and also photooxidation of the amine group. CIP was able to induce photohemolysis when it was irradiated in PBS pH 7.4 and in PBS pH 6.0 containing a suspension of human red blood cells (RBCs). The photohemolysis experiments in the presence of additives DABCO and GSH showed nearly total inhibition of drug-induced photohemolysis. The efficient inhibition of photohemolysis by the radical scavenger GSH compared with the inhibition show by DABCO suggests a moderate effect by singlet oxygen. Clomipramine-N-oxide was the unique photoproduct able to induce hemolysis and photohemolysis when it was incubated and irradiated with RBCs for 1 h. A mechanism involving singlet oxygen, radicals and photoproducts is suggested for the reported phototoxicity.

The effect of whole-body sunbed ultraviolet A exposure on the pharmacokinetics of the photolabile drug nifedipine.

The calcium antagonist nifedipine absorbs ultraviolet A (UVA) radiation and readily photodegrades in vitro to a toxic nitroso-pyridine photoproduct. We examined whether whole body exposure of normal subjects to sunbed UVA radiation would affect the pharmacokinetics of nifedipine. Eight healthy, male, Caucasian volunteers (phototypes I-III) participated in this ethically approved, randomised, cross-over study. Each subject attended on 2 occasions, one week apart, and on each occasion was given a single oral dose (10 mg) of nifedipine following which blood samples were collected at 0, 0.5, 1. 1.5, 2, 2.5, 3, 3.5, 4, 5, 6 and 7 h. During one of the visits, 15 min after nifedipine ingestion, a whole-body UVA (sunbed comprising Philips R-UVA lamps) dose of 70% of the individual's predetermined minimal phototoxic dose was delivered over a period of 17-36 min. Plasma nifedipine levels were measured using a standard reverse-phase high-performance liquid chromatography method. The area under the plasma concentration-time curve (AUC) of nifedipine during the UVA irradiation session (median 206 ng x ml(-1) x h(-1)) was significantly higher than during the non-irradiation control session (median 174.5 ng x ml(-1) x h(-1)) (P=0.03; 95% C.I. for difference in medians 9.9 to 55.9 ng x ml(-1) x h(-1)). UVA irradiation did not significantly affect any of the other measured pharmacokinetic parameters (Cmax, t 1/2, tmax). We demonstrate that sunbed UVA irradiation does not lead to in vivo photodegradation of nifedipine in healthy humans after a single dose. The apparent increase in AUC during UVA irradiation may be due to slightly slower metabolism of nifedipine in the presence of toxic photoproduct(s) or due to blood distribution changes affecting liver blood flow.

Photobiological properties of nabumetone (4-[6-methoxy-2-naphthalenyl]-2-butanone), a novel non-steroidal anti-inflammatory and analgesic agent.

The photolability of nabumetone (NB, 1, 4-[6-methoxy-2-naphthalenyl]-2-butanone) and its photobiological properties were studied under aerobic and anaerobic conditions using a variety of in vitro phototoxicity assays: photohemolysis, photoperoxidation of linoleic acid, and photosensitized degradation of histidine and thymine. The photodegradation rate of NB in methanol and phosphate buffered saline (PBS) was enhanced under oxygenated media. NB was phototoxic in vitro. The photohemolysis rate was enhanced by deuterium oxide and inhibited by the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO), butylated hydroxyanisole (BHA), sodium azide (NaN3) and reduced gluthathione (GSH). The induced photoperoxidation of linoleic acid was inhibited significantly by sodium azide and reduced gluthathione. Histidine and thymine were photodegraded by a photosensitized reaction induced by NB. A mechanism involving singlet oxygen, radicals and photoproducts is suggested for the observed photoxicity.

Lymphocyte stimulation test with drug-photomodified cells in patients with quinolone photosensitivity.

Quinolone antibacterial agents, known to elicit photosensitive dermatitis as an adverse effect, have both phototoxicity and photoallergenicity. The latter potency is mainly derived from their photohaptenic moiety; quinolones covalently bind to protein and cells upon exposure to ultraviolet A (UVA) light. Our previous study has shown the in vivo and in vitro antigenicity of quinolone-photomodified cells in mice. Here, we examined the presence of sensitized lymphocytes that react with quinolone-photomodified autologous cells in patients with photosensitivity to quinolones. A flow cytometric analysis using a monoclonal antibody specific to quinolone photoadducts demonstrated that peripheral blood mononuclear cells (PBMC) were successfully photomodified with quinolones upon exposure to UVA. PBMC from quinolone-photosensitive patients were cocultured with autologous PBMC photomodified with the causative drug. Modest but significant proliferative responses of responder lymphocytes were found in patients photosensitive to lomefloxacin, fleroxacin, and enoxacin, indicating photoallergic mechanism in these patients. On the other hand, sparfloxacin-photosensitive patients exhibited negative lymphocyte stimulation test, suggesting that its photosensitivity is mainly phototoxic. When UVA-preirradiated quinolones were used as stimulators, only fleroxacin exceptionally stimulated patients' PBMC, indicating its prohaptenic as well as photohaptenic properties. These findings suggest the presence of circulating sensitized T cells in patients with photosensitivity to certain quinolones.

Evaluation of phototoxic properties of oral antidiabetics and diuretics. Photohemolysis model as a screening method for recognizing potential photosensitizing drugs.

The oral hypoglycemic drugs carbutamide, chlorpropamide, glibenclamide, glubornuride, gliclazide, glipizide, gliquidone, glisoxepide, glymidine, tolazamide and tolbutamide, and the diuretics acetazolamide, bemetizide, bendroflumethiazide, benzthiazide, benzylhydrochlorothiazide, bumetanide, butizide, chlorazanile, chlorothiazide, chlortalidone, clopamide, cyclopenthiazide, cyclothiazide, diazoxide, etozoline, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, mefruside, metolazone, piretanide, polythiazide, trichlormethiazide, and xipamide were investigated for photohemolytic properties in vitro. Irradiation with a SOL 3 apparatus (solar simulating irradiation) revealed hemolysis in the presence of five oral hypoglycemic agents and in the presence of 19 out of the 25 tested diuretics. Photohemolysis was induced in the presence of three substances, respectively, after exposure to UVA or visible light. UVB alone did not induce phototoxic hemolysis in the presence of the tested drugs. Compared to clinical reports on photosensitivity reactions, the photohemolysis model seems a good predictive model in recognizing potential photosensitizing sulfonamides.

Detection of circulating T cells with CD4+CD7- immunophenotype in patients with benign and malignant lymphoproliferative dermatoses.

BACKGROUND: Cutaneous T-cell lymphomas (CTCLs) are malignancies of CD4+ T cells that involve the skin. CD4+CD7- cells may represent a malignant population in CTCL. OBJECTIVE: Our purpose was to compare the percentage of CD4+CD7- cells and the expression of pan-T-cell antigens in blood lymphocytes from 31 patients with benign dermatoses with 35 patients who had CTCL. METHODS: The patients with CTCL were classified as follows: 10 with mycosis fungoides (MF), seven with pre-Sézary syndrome (pre-SS), and 18 with Sézary syndrome (SS). Flow cytometry was used to determine the percentage of CD4+CD7- cells and the CD4/CD8 ratio and to detect aberrant expression of the pan-T-cell antigens CD2, CD3, and CD5. RESULTS: We found a mean of 5.8% CD4+CD7- cells for the 16 normal control subjects and 9.3% for the benign cases (p = 0.13). The patients with pre-SS and SS had a higher percentage of CD4+CD7- cells (22.4% and 35.5%, respectively) than patients with benign dermatoses (p < 0.01); no difference was found between patients with benign dermatoses and those with MF (p = 0.80). The mean CD4/CD8 ratio was 3.1 for the normal control subjects compared with 7.4 for the patients with benign dermatoses (p < 0.01). Patients with SS had a ratio of 49, which was higher than the ratio for those with benign dermatoses (p < 0.01); however, the ratio for patients with MF and pre-SS did not differ from that of the group with benign dermatoses (p = 0.71 and 0.55, respectively). Aberrant CD2, CD3, or CD5 expression was observed in 66% of patients with SS, 29% with pre-SS, 30% with MF, but in none of the patients with a benign dermatosis. CONCLUSION: Small numbers of CD4+CD7- cells can be found by flow cytometry in patients with a benign dermatosis and in normal control subjects. This T-cell subset is expanded in pre-SS and SS but not in MF. Aberrant pan-T-cell antigen expression is commonly observed in patients with SS but not in patients with a benign dermatosis.