Quinolone photoallergy: photosensitivity dermatitis induced by systemic administration of photohaptenic drugs

A laser flash photolysis and pulse radiolysis study of primary photochemical processes of flumequine

The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14,000 M(-1) cm(-1). The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2*- radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2,500 M(-1) cm(-1). In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3+) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2*- is formed but the photoreduction of Cyt Fe3+ by O2*- competes with an oxidizing pathway which involves photo-oxidation products of TrpH.

Alteration of the endocytotic pathway by photosensitization with fluoroquinolones

The endocytotic pathway is profoundly altered by the UVA-induced photosensitization of HS 68 fibroblasts by the fluoroquinolone (FQ) antibiotics lomefloxacin, BAYy 3118, norfloxacin and ciprofloxacin, which preferentially localize in lysosomes. The endocytosis of low-density lipoproteins (LDL) loaded with two carbocyanine dyes compatible for effective Forster-type resonance energy transfer (FRET), namely 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO) as the donor and 1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) as the acceptor, has been used as a model system. Binding of LDL to their cell surface receptors is impaired by irradiation with 10 J cm(-2) of UVA and/or treatment with 250 microM BAYy 3118 during 2 h. Perturbation of the plasma membrane by the FQ is revealed by the change in the rate of exchange of DiO from the LDL to the cell membrane as compared to untreated cells. The lysosomal degradation of LDL, demonstrated by the disappearance of FRET between DiO and DiI, is partly inhibited by the FQ. The actin filament network, involved in the fusion of mature endosomes with lysosomes, is readily destroyed upon photosensitization with the four FQ. However, actin depolymerization can be avoided by incubation of the cells with trans-epoxysuccinyl-1-leucylamido-(4-guanidino)butane, an inhibitor of lysosomal cathepsins prior to FQ photosensitization. All these data suggest that several components of the endocytotic pathway are impaired by photosensitization with these FQ.

Damage to mitochondria of cultured human skin fibroblasts photosensitized by fluoroquinolones

The phototoxic fluoroquinolones ofloxacin, lomefloxacin, norfloxacin, ciprofloxacin and BAYy 3118 have ionizable groups with pKa values close to neutrality. Different ionic species of these fluoroquinolones, therefore, partition in various compartments and organelles of living cells according to their ionic equilibria. While all these fluoroquinolones accumulate in lysosomes, they more or less stain the rest of the cytoplasm of living HS 68 fibroblasts. As a result, photosensitized damage to other cytoplasmic sites than lysosomes can also be expected. Using microfluorometry and rhodamine 123 (Rh 123) as a specific fluorescent probe which is released from mitochondria by light absorption, we show that under ultraviolet A (UVA) irradiation norfloxacin and ciprofloxacin readily damage mitochondrial membranes. as evidenced by the UVA dose-dependent strongly accelerated release of Rh 123 from mitochondria in cells treated with norfloxacin and ciprofloxacin. Damages are already noticeable at UVA doses as low as 2 J/cm2. By contrast, no such photoinduced damage can be observed with ofloxacin, lomefloxacin and BAYy 3118, the latter being the most phototoxic derivative towards HS 68 fibroblasts. The initial photodamage induced by norfloxacin and ciprofloxacin can then propagate after the irradiation as shown by the strongly increased rate of release of Rh 123 from mitochondria of cells that have been incubated with these two fluoroquinolones and left in the dark after a pre-irradiation with 18 J/cm2 of UVA. Interestingly, the same pre-irradiation after cells have been treated with BAYy 3118 and lomefloxacin induces similar post-irradiation effects, although they have no apparent immediate photosensitizing action on mitochondria.

Differences in the photogenotoxic potential of two fluoroquinolones as shown in diploid yeast strain (Saccharomyces cerevisae) and supercoiled plasmid DNA

Fluoroquinolones are antibiotics with a potential clinical side effect of phototoxicity and some are suspected to enhance UVA-induced tumorigenesis. The present study was designed to evaluate the recombinogenic and mutagenic potential of two highly photoreactive compounds, lomefloxacin and BAYy3118 when exposed to complete UVA (320-400 nm). In order to possibly increase the sensitivity of the test, we used a diploid mutant (D7-rad3) deficient in nucleotide excision repair and deriving from the tester strain D7 of the yeast Saccharomyces cerevisae. In agreement with previous reports, lomefloxacin had no effect in this system. Moreover, BAYy3118 was highly photocytotoxic and genotoxic especially when yeast cells were incubated in its presence in the dark before exposure to UVA radiation. Both fluoroquinolones were comparable in their ability to photo-induce DNA strand breaks or oxidative damage to purines and pyrimidines in supercoiled plasmid DNA, but agarose gel electrophoresis showed that BAYy3118 photoproducts could tightly interact with supercoiled plasmid DNA while lomefloxacin ones only induced strand breaks. These data suggest that phototoxicity of BAYy3118 was the result of a multistep mechanism: first, local photo oxidative stress is induced and secondly some of the photoproducts exerted genotoxic effects. This work also shows that very simple and complementary in vitro approaches can be very informative in the understanding of drug-induced phototoxicity.

Comparison of an in vitro cellular phototoxicity model against controlled clinical trials of fluoroquinolone skin phototoxicity

Many therapeutic drugs induce phototoxic skin responses following exposure to solar or artificial ultraviolet radiation sources. Several in vitro model systems have been developed to predict drug phototoxicity but none have been conducted in parallel with controlled clinical phototoxicity studies on systemically administered pharmaceuticals. The in vitro phototoxicity of eight fluoroquinolone (FQ) antibiotics (ciprofloxacin, grepafloxacin, lomefloxacin, norfloxacin, ofloxacin, trovafloxacin, BAYy3118, moxifloxacin) was determined by exposing Chinese hamster fibroblasts to UVA radiation. Cell damage was quantified with standard MTT or neutral red assays and an in vitro phototoxic index calculated (PI(vit)=% cell viability with UVA alone /% cell viability with UVA+FQ) for each endpoint. Clinical photosensitizing ability of the eight systemically administered FQ was investigated using double-blind, placebo and positive controlled, clinical skin phototesting of normal subjects. Minimal erythema doses at 365+/-30nm were determined before and after 6-7 days of FQ ingestion and PI(clin) (minimal erythema dose without FQ/minimal erythema dose with FQ) calculated. Linear regression analysis of PI(vit) vs PI(clin) gave correlations of up to 0.893. Principal components analysis of PI(vit), daily dose, plasma levels and photophysical (absorption) properties of the eight FQ showed that phototoxic (arbitrarily defined as PI(clin)> or =2) and non-phototoxic (PI(clin)<2) FQ could be completely discriminated using these parameters, and that the in vitro models were able to rank the relative phototoxic potential of the eight FQ.

Immune responses to photohaptens: implications for the mechanisms of photosensitivity to exogenous agents

A photohaptenic moiety is one of the salient properties of photoallergic chemicals. Clinically, it is likely that photohaptens are the main causative substances in photoallergic contact dermatitis and drug photoallergy. Photohaptens bind covalently to protein under exposure to ultraviolet A light (UVA). Because of this photocoupling ability, cells are easily photoderivatized with a photohapten by UVA irradiation, becoming immunogenic photohapten-modified cells. Langerhans cells photomodified with a photohapten can stimulate immune T cells when photomodification is performed with a non-phototoxic dose of UVA.

Formation of antigenic quinolone photoadducts on Langerhans cells initiates photoallergy to systemically administered quinolone in mice

Quinolone antibacterial agents are well known to cause photoallergy as a side-effect. Murine photoallergy to fluoroquinolones is a T cell-mediated immune response, evoked either by systemic fluoroquinolone and subsequent exposure of skin to ultraviolet A light or by subcutaneous injection of fluoroquinolone-photomodified epidermal cells. In this photosensitivity, epidermal Langerhans cells may be photomodified initially with the drug and thus present photohaptenic moieties to sensitize and restimulate T cells. Although we have shown that Langerhans cells photocoupled in vitro with fluoroquinolones are capable of stimulating sensitized T cells, it remains unclear whether systemically given fluoroquinolone photomodifies Langerhans cells upon ultraviolet A irradiation of the skin and the Langerhans cells become photohapten-bearing, T cell-stimulatory cells. In a murine model of fleroxacin photoallergy induced by intraperitoneal injection of the drugs plus ultraviolet A irradiation of skin, we found that Langerhans cells as well as keratinocytes are photoderivatized with fleroxacin as demonstrated with a fluoroquinolone-specific monoclonal antibody. Langerhans-cell-enriched epidermal cells prepared from mice treated with fleroxacin and ultraviolet A induced proliferation of sensitized T cells, indicating that photomodified Langerhans cells are functional. There was an optimal range of ultraviolet A dose to quantitatively and qualitatively form fleroxacin-photomodified Langerhans cells, as excess ultraviolet A rather reduced the photoantigen-presenting capacity of Langerhans cells presumably because of drug phototoxicity. Our study suggests that Langerhans cells serve as photoantigen-presenting cells in drug photoallergy.

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.