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

Drug-Induced Photosensitivity-An Update: Culprit Drugs, Prevention and Management

Photosensitive drug eruptions are cutaneous adverse events due to exposure to a medication and either ultraviolet or visible radiation. In this review, the diagnosis, prevention and management of drug-induced photosensitivity is discussed. Diagnosis is based largely on the history of drug intake and the appearance of the eruption primarily affecting sun-exposed areas of the skin. This diagnosis can also be aided by tools such as phototesting, photopatch testing and rechallenge testing. The mainstay of management is prevention, including informing patients of the possibility of increased photosensitivity as well as the use of appropriate sun protective measures. Once a photosensitivity reaction has occurred, it may be necessary to discontinue the culprit medication and treat the reaction with corticosteroids. For certain medications, long-term surveillance may be indicated because of a higher risk of developing melanoma or squamous cell carcinoma at sites of earlier photosensitivity reactions. A large number of medications have been implicated as causes of photosensitivity, many with convincing clinical and scientific supporting evidence. We review the medical literature regarding the evidence for the culpability of each drug, including the results of phototesting, photopatch testing and rechallenge testing. Amiodarone, chlorpromazine, doxycycline, hydrochlorothiazide, nalidixic acid, naproxen, piroxicam, tetracycline, thioridazine, vemurafenib and voriconazole are among the most consistently implicated and warrant the most precaution by both the physician and patient.

Drug and chemical induced photosensitivity from a clinical perspective

Drug photosensitivity is a relatively common occurrence and a range of mechanisms may be involved. Some of these mechanisms will be discussed, including the most common, that of drug phototoxicity. Different types of photosensitivity are addressed with respect to clinical presentation, mechanisms and additionally the contribution to our understanding through clinically directed investigations and regulatory requirements. Repeated controlled therapeutic use of drug phototoxicity, with psoralen-UVA (PUVA) photochemotherapy and photodynamic therapy (PDT) will also be discussed. Finally, the potential for drug-induced photocarcinogenesis will also be covered.

Natural extracellular nanovesicles and photodynamic molecules: is there a future for drug delivery?

Photodynamic molecules represent an alternative approach for cancer therapy for their property (i) to be photo-reactive; (ii) to be not-toxic for target cells in absence of light; (iii) to accumulate specifically into tumour tissues; (iv) to be activable by a light beam only at the tumour site and (v) to exert cytotoxic activity against tumour cells. However, to date their clinical use is limited by the side effects elicited by systemic administration. Extracellular vesicles are endogenous nanosized-carriers that have been recently introduced as a natural delivery system for therapeutic molecules. We have recently shown the ability of human exosomes to deliver photodynamic molecules. Therefore, this review focussed on extracellular vesicles as a novel strategy for the delivery of photodynamic molecules at cancer sites. This completely new approach may enhance the delivery and decrease the toxicity of photodynamic molecules, therefore, represent the future for photodynamic therapy for cancer treatment.

Risk assessment of three fluoroquinolone antibiotics in the groundwater recharge system

Three fluoroquinolone antibiotics agents (FQs) in groundwater and reclaimed water have been investigated in Changzhou and Beijing, China. The occurrence of ofloxacin (OFL), enrofloxacin (ENR) and norfloxacin (NOR) is in nanograms per liter and has 100% frequency. The concentration order of FQs in reclaimed water is NOR>OFL>ENR, whilst the order in groundwater is NOR>ENR>OFL. And then the single and mixture adsorption-desorption have been studied and showed that (i) silty clay loam has higher sorption capacity than loamy sand, (ii) competitive adsorption exists when the three selected FQs coexist, (iii) ENR has a significantly priority sorption to NOR, whilst OFL has a least sorption among the mixture, (iv) there is no significant difference between the desorption results of mixture and the indivdual compound in relatively low concentration, (v) the formed chemical bonds and the irreversible combination of adsorption point are the significant influential factors for explaining desorption hysteresis of the selected FQs. Based on the above study, transport model and risk quotient have been performed, and the calculated risk quotient reveals that: (i) the selected FQs risk order in reclaimed water is OFL>ENR>NOR, (ii) in groundwater, OFL and ENR pose a higher risk than NOR no matter whether considering the long time groundwater recharge. This study will help policy makers to decide which FQs need to be covered in the priority substance lists defined in legislative frameworks.

The phototoxicity of vemurafenib: An investigation of clinical monochromator phototesting and in vitro phototoxicity testing

BACKGROUND

Vemurafenib is a targeted therapy approved for the treatment of patients with metastatic melanoma harbouring the BRAF V600E mutation. Photosensitivity has been reported in over 50% of patients and has been demonstrated to involve at least the broadband UVA spectrum in most patients. Erythrocyte protoporphyrin levels have also been reported as elevated in some patients.

OBJECTIVES

We report the results of monochromator phototesting in one patient recorded before and while taking vemurafenib. Analysis of porphyrin levels was also conducted.

RESULTS

After one month of vemurafenib therapy the patient demonstrated markedly increased light sensitivity in the UVA spectrum between 335 ± 27 nm, 365 ± 27 nm and 400 ± 27 nm. However responses in the UVB (305 ± 5 nm) and blue light (430 ± 27 nm) regions were normal. There was no abnormal immediate erythemal response. Pre-vemurafenib baseline phototesting was normal, as was repeat testing two months later when the patient was taking high doses of systemic steroid. No abnormal porphyrins were detected and the antinuclear antibody test was normal. In parallel studies, HaCaT keratinocytes incubated with vemurafenib were killed by UVA but not by visible (blue) light and did not show evidence of detectable intracellular porphyrin in the presence of the drug.

CONCLUSION

These data confirm vemurafenib induced UVA photosensitivity with a probable phototoxic mechanism not mediated via enhanced porphyrin.

Cytotoxicity Induced by Tetracyclines via Protein Photooxidation

Background. Bacterial ribosomes have been considered the principal targets of tetracyclines. Recently, new clinical data has shown how other biomacromolecules are involved in the cellular damage of bacteria. Researchers are now reconsidering the pharmacological classification of tetracyclines, not only based on their semisynthetic or synthetic generations but also following the new mechanisms of action that are progressively being discovered. Materials and Methods. The toxicity properties of seven tetracycline derivatives (tetracycline, oxytetracycline, demeclocycline, chlortetracycline, doxycycline, minocycline, and meclocycline) were investigated in vitro using a cell line of human keratinocytes. Cells were irradiated in the presence of tetracyclines for different durations and at three different intensities of light. The investigation of protein oxidation was set up using model proteins to quantify the formation of carbonyl groups. Results. After incubation and irradiation with UV light, the viability of keratinocytes was assessed with half the maximal inhibitory concentration for doxycycline, demeclocycline, chlortetracycline, and tetracycline. No phototoxicity was observed for oxytetracycline, meclocycline, and minocycline. Conclusions. This study provides evidence that tetracycline’s derivatives show different photobehaviour according to their chemical properties due to different reactive groups on the same molecular skeleton.

Effect of norfloxacin and moxifloxacin on melanin synthesis and antioxidant enzymes activity in normal human melanocytes

Fluoroquinolone antibiotics provide broad-spectrum coverage for a number of infectious diseases, including respiratory as well as urinary tract infections. One of the important adverse effects of these drugs is phototoxicity which introduces a serious limitation to their use. To gain insight the molecular mechanisms underlying the fluoroquinolones-induced phototoxic side effects, the impact of two fluoroquinolone derivatives with different phototoxic potential, norfloxacin and moxifloxacin, on melanogenesis and antioxidant enzymes activity in normal human melanocytes HEMa-LP was determined. Both drugs induced concentration-dependent loss in melanocytes viability. The value of EC50 for these drugs was found to be 0.5 mM. Norfloxacin and moxifloxacin suppressed melanin biosynthesis; antibiotics were shown to inhibit cellular tyrosinase activity and to reduce melanin content in melanocytes. When comparing the both analyzed fluoroquinolones, it was observed that norfloxacin possesses greater inhibitory effect on tyrosinase activity in melanocytes than moxifloxacin. The extent of oxidative stress in cells was assessed by measuring the activity of antioxidant enzymes: SOD, CAT, and GPx. It was observed that norfloxacin caused higher depletion of antioxidant status in melanocytes when compared with moxifloxacin. The obtained results give a new insight into the mechanisms of fluoroquinolones toxicity directed to pigmented tissues. Moreover, the presented differences in modulation of biochemical processes in melanocytes may be an explanation for various phototoxic activities of the analyzed fluoroquinolone derivatives in vivo.

Differential sensitivity in cell lines to photodynamic therapy in combination with ABCG2 inhibition

BACKGROUND

ABCG2 is an ATP-binding cassette transporter protein which has a role in the regulation of endogenous protoporphyrin IX (PpIX) levels.

OBJECTIVE

To understand the influence of ABCG2 on porphyrin-based photodynamic therapy (PDT) and fluorescence diagnosis (FD), we examined the role of endogenous ABCG2 in four human cell lines from the epidermis (HaCaT keratinocytes), oesophagus (OE19 adenocarcinoma), brain (SH-SY5Y neuroblastoma) and bladder (HT1197 carcinoma).

METHODS

Cells were incubated with ALA or MAL in the presence or absence of the ABCG2 activity inhibitor Ko-143. Porphyrin accumulation was detected by spectrofluorimetric analysis and high performance liquid chromatography (HPLC) with porphyrin localisation observed by confocal laser scanning microscopy. PDT efficacy was assessed 24h post irradiation (1.5J/cm(2) red light) by the neutral red (NR) assay.

RESULTS

We show cell-specific differences when Ko-143 was co-incubated with ALA or, in particular with, MAL. Enhanced PDT-induced cell kill was shown in HaCaT, OE19 and HT1197 cells, but not SH-SY5Y cells and could be explained by porphyrin accumulation and expression of ABCG2. We have also found that despite high levels of intracellular PpIX, the OE19 cells were protected from phototoxic cell death by PpIX compartmentalisation. This could be reversed by Ko-143.

CONCLUSION

The results from this study show a possible cause of reduced sensitivity to ALA/MAL-PDT, with a potential solution to overcome this effect in certain tissue types. The potential to improve PDT with Ko-143 remains promising.

Photochemical properties and phototoxicity of Pazufloxacin: a stable and transient study

Photochemical properties and phototoxicity of Pazufloxacin (PAX) were systematically investigated in aqueous solutions using UV-Vis, fluorescence, laser flash photolysis, pulse radiolysis and SDS-PAGE gel electrophoresis techniques. PAX triplet-state ((3)PAX(*)) absorption spectra (λ(max)=570 nm) was determined. (3)PAX(*) was quenched by PAX and O(2), with rate constants of 6.9×10(8) and 3.2×10(8) dm(3) mol(-1) s(-1), respectively. The pK(a) values (5.7 and 8.6) for the protonation equilibrium were determined by UV-Vis and fluorescence techniques. The PAX triplet energy (E(T)=260.3 kJ/mol) was obtained using energy transfer method. The reaction of electron transfer from tryptophan (TrpH) and dGMP to (3)PAX(*) was found with rate constants of 8.8×10(7) and 8.7×10(6) dm(3) mol(-1) s(-1), respectively. The rate constants for reactions of ()OH, SO(4)(-) and hydrated electron with PAX were found to be 5.8×10(8), 2.1×10(9) and 9×10(9)d m(3) mol(-1) s(-1), respectively. Based on the results obtained, a rational scheme for dGMP, TrpH and lysozyme photodamage induced by PAX was proposed.

Trans,trans,trans-[PtIV(N3)2(OH)2(py)(NH3)]: a light-activated antitumor platinum complex that kills human cancer cells by an apoptosis-independent mechanism

Photoactivatable Pt(IV) diazido complexes have unusual photobiologic properties. We show here that trans,trans,trans-[Pt(IV)(N(3))(2)(OH)(2)(py)(NH(3))] complex 3 is a potent photoactivated cytotoxin toward human cancer cells in culture, with an average IC(50) value in 13 cell lines of 55 ± 28 μmol/L after 30 minutes (0.12 mW/cm(2)) photoactivation with UVA, although visible light was also effective. Photoactivated complex 3 was noncross-resistant to cisplatin in 3 of 4 resistant cell lines. Cell swelling but very little blebbing was seen for HL60 cells treated with irradiated complex 3. Unlike cisplatin and etoposide, both of which cause apoptosis in HL60 cells, no apoptosis was observed for UVA-activated complex 3 by the Annexin V/propidium iodide flow cytotometry assay. Changes in the levels of the autophagic proteins LC3B-II and p62 in HL60 cells treated with UVA-activated complex 3 indicate autophagy is active during cell death. In a clonogenic assay with the SISO human cervix cancer cell line, 3 inhibited colony formation when activated by UVA irradiation. Antitumor activity of complex 3 in mice bearing xenografted OE19 esophageal carcinoma tumors was photoaugmented by visible light. Insights into the novel reaction pathways of complex 3 have been obtained from (14)N{(1)H} nuclear magnetic resonance studies, which show that photoactivation pathways can involve release of free azide in buffered solution. Density functional theory (DFT) and time-dependent DFT calculations revealed the dissociative character of singlet and triplet excited states of complex 3, which gives rise to reactive, possibly cytotoxic azidyl radicals.

Drug-induced photosensitivity: culprit drugs, management and prevention

Photo-induced drug eruptions are cutaneous adverse events due to exposure to a drug and either ultraviolet or visible radiation. Based on their pathogenesis, they can be classified as phototoxic or photoallergic drug eruptions, although in many cases it is not possible to determine whether a particular eruption is due to a phototoxic or photoallergic mechanism. In this review, the diagnosis, prevention and management of drug-induced photosensitivity are discussed. Diagnosis is based primarily on the history of drug intake and the clinical appearance of the eruption, primarily affecting sun-exposed areas of the skin. Phototesting and photopatch testing can be useful adjuncts in making a diagnosis. The mainstay of management is prevention, including informing patients of the possibility of increased sun sensitivity and the use of sun protective measures. However, once the eruption has occurred, it may be necessary to discontinue the culprit medication and treat the eruption with a potent topical corticosteroid. Drugs that have been implicated in causing photosensitive eruptions are reviewed. Tetracycline, doxycycline, nalidixic acid, voriconazole, amiodarone, hydrochlorothiazide, naproxen, piroxicam, chlorpromazine and thioridazine are among the most commonly implicated medications. We review the medical literature regarding evidence for the culpability of each drug, including the results of phototesting, photopatch testing and rechallenge testing.

Radiation-Inducedin VitroPhototoxic Potential of Some Fluoroquinolones

Photosensitizing drugs that can damage cellular biomolecules is a matter of concern. Lomefloxacin, norfloxacin, ofloxacin, and enoxacin (broad-spectrum antibiotics of fluoroquinolone group) are used for the treatment of Gram-positive and Gram-negative bacterial infections. Phototoxicity and possible mechanism of their action was assessed under the exposure of ambient levels of UV-A, UV-B, and sunlight at a concentration generally used in the treatment of various diseases. Singlet oxygen (1O2), superoxide anion radical (O2.-) generation, DNA damage, and lipid peroxidation in human blood were studied. All the fluoroquinolones tested in this study produced 1O2 and O2.- under exposure to UV-A, UV-B, and sunlight depending on the concentrations (0 to 60 microg/mL) of the drugs. Enoxacin showed a higher yield of 1O2 and O2.- than other drugs. These materials also degraded deoxyguanosine and induced lipid peroxidation in vitro under exposure to UV-A, UV-B, and sunlight (depending on the dose of radiation). The formation of the reactive oxygen species (ROS) by the photoexcited drugs may be considered as a possible mechanism of their action.

In vitro cytotoxicity and phototoxicity of N-piperazinyl quinolone derivatives with a 2-thienyl group

We examined the cytotoxic potential of nine N-[2-substituted-2-(2-thienyl)ethyl] piperazinyl quinolone derivatives on human oral epithelial mouth carcinoma (KB) and human squamous carcinoma (A431) cell lines. Phototoxic properties of these compounds were also evaluated by mouse 3T3 fibroblast under ultraviolet-A (UVA) irradiation. The percent of cell viability was evaluated by MTT assay. Compound 6 having a 4-[2-(phenylmethoxyimino)-2-(2-thienyl)ethyl] group attached to N4 position of piperazine ring of enoxacin showed the highest cytotoxicity potential on both A431 and KB cell lines (IC50 of 3.11+/-0.52 and 4.91+/-1.94 microg/ml, respectively). While some of the other tested compounds exhibited clear phototoxic potential in 3T3 cell line, compound 6 showed only a minor potential of phototoxicity. These findings suggest the high potential of 4-[2-(phenylmethoxyimino)-2-(2-thienyl)ethyl] derivative of enoxacin as a cytotoxic compound with low potency of phototoxic reactions. The mentioned chemical was identified to be of special interest for further characterization.

Photosensitizing Potential of Ciprofloxacin at Ambient Level of UV Radiation

Ciprofloxacin is a widely used fluoroquinolone drug with broad spectrum antibacterial activities. Clinical experience has shown incidences of adverse effects related to skin, hepatic, central nervous system, gastrointestinal and phototoxicity. India is a tropical country and sunlight is abundant throughout the day. In this scenario exposure to ambient levels of ultraviolet radiation (UV-R) in sunlight may lead to harmful effects in ciprofloxacin users. Phototoxicity assessment of ciprofloxacin was studied by two mouse fibroblast cell lines L-929 and NIH-3T3. Generation of reactive oxygen species (ROS) like singlet oxygen (1O2), superoxide anion radical (O2*-) and hydroxyl radical (*OH) was studied under the exposure of ambient intensities of UV-A (1.14, 1.6 and 2.2 mW cm(-2)), UV-B (0.6, 0.9 and 1.2 mW cm(-2)) and sunlight (60 min). The drug was generating 1O2, O2*- and *OH in a concentration and dose-dependent manner. Sodium azide (NaN3) and 1,4-diazabicyclo 2-2-2-octane (DABCO) inhibited the generation of 1O2. Superoxide dismutase (SOD) inhibited 90-95% O2*- generation. The drug (5-40 microg mL(-1)) was responsible for linoleic acid peroxidation. Quenching study of linoleic acid peroxidation with SOD (25 and 50 U mL(-1)) confirms the involvement of ROS in drug-induced lipid peroxidation. The generation of *OH radical was further confirmed by using specific quenchers of *OH such as mannitol (0.5 M) and sodium benzoate (0.5 M). 2'-deoxyguanosine (2'-dGuO) assay and linoleic acid peroxidation showed that ROS were mainly responsible for ciprofloxacin-sensitized photo-degradation of guanine base. L-929 cell line showed 29%, 34% and 54% reduced cell viability at higher drug concentration (300 microg mL(-1)) under UV-A, UV-B and sunlight, respectively. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay in NIH-3T3 cell line at higher drug concentration (300 microg mL(-1)) showed a decrease in cell viability by 54%, 56% and 59% under UV-A, UV-B and sunlight, respectively. Results of neutral red uptake assay (NRU) in L-929 cell line were in accordance with MTT assay. The NIH-3T3 cell line showed a higher photosensitizing potential than L-929. The phototoxicity end point shows a time- and concentration-dependent statistically significant (P<0.001) damage. Ciprofloxacin produced ROS by Type I and Type II photodynamic reactions, interacted with nucleic acid moiety and inhibited cell viability. Further, UV-induced photo-peroxidation of linoleic acid accorded the involvement of ROS in the manifestation of drug phototoxicity. Appearance of ciprofloxacin-induced phototoxicity at the ambient level of sunlight is a real risk for the people of India and for those of other tropical countries. We suggest that sunlight exposure should be avoided (especially peak hours) during ciprofloxacin treatment.

In vitro phototoxicity test using artificial skin with melanocytes

BACKGROUND

Exposure to ultraviolet radiation (UVR) has been shown to induce cutaneous biological changes and phototoxic reactions.

OBJECTIVE

This study was designed to evaluate the usefulness of artificial skin (AS) composed of keratinocytes and melanocytes as an in vitro phototoxicity model for topical agents.

MATERIALS AND METHODS

AS was manufactured with three-dimensionally cultured keratinocytes and melanocytes on a de-epidermized dermis (DED). The photobiological responses in AS with and without melanocytes were comparatively examined after ultraviolet A (UVA) exposure. Three test chemicals (8-methoxypsoralen, 6-methylcoumarin and tetracycline) were topically applied onto the AS with melanocytes and after UVA irradiation, the released inflammatory cytokines (IL-1alpha, IL-beta and IL-6) were analyzed.

RESULTS

AS with melanocytes showed better epidermal structures, stronger resistance to UVA exposure and photobiological responses closer to in vivo human skin. Releases of inflammatory cytokines were well correlated with the increased phototoxicities of test chemicals. Among the measured cytokines, IL-6 could be the most reliable in vitro marker indicative of phototoxic potential, because it showed statistically significant increase only in case of concurrent exposure to chemicals and UVA.

CONCLUSION

The AS with melanocytes may be a useful tool especially for examining UV-induced cutaneous changes and a promising in vitro phototoxicity test model for topical agents.

The EpiSkin phototoxicity assay (EPA): development of an in vitro tiered strategy using 17 reference chemicals to predict phototoxic potency

The aim of the study was to investigate the ability of human reconstructed epidermis EpiSkin(LM) to identify the phototoxic potency of topically or systemically applied chemicals (EPA: EpiSkin phototoxicity assay). Three classes, according to their available human phototoxic potential, were evaluated: systemic phototoxic compounds, topical phototoxic chemicals and non-phototoxic compounds. Non-cytotoxic concentrations of chemicals were applied topically or directly added to the underlying culture medium in order to mimic a systemic-like administration. Following treatment, tissues were exposed to non-cytotoxic dose of UVA (50 J cm(-2)). Cell viability and pro-inflammatory mediators (IL-1alpha) were investigated 22 h after UVA exposure. Our results show that the phototoxic potential of chemicals can be determined using cell viability combined with inflammatory mediator measurements (cytokine IL-1alpha) in a 3-D epidermis model. Moreover, the EPA was able to discriminate efficiently between phototoxic and non-phototoxic products. Furthermore, the EPA is sensitive to the administration route in the prediction of the phototoxic potency of the tested chemical. Differences observed between the two routes of administration (topical or systemic-like) may be linked in part to chemicals bioavailability which depends on specific penetration potential, epidermis barrier function and also on keratinocytes absorption/metabolization processes. Results were very promising and showed a very good sensitivity (92.3%) and an excellent specificity (100%) with an overall accuracy of 94.1%. The performances of the EPA showed that the EpiSkin(LM) model is an interesting tool able to integrate decision-making processes to address the question of phototoxicity linked to the application site.

Rufloxacin-induced photosensitization in yeast

The fluoroquinolone Rufloxacin (RFX) is active as specific inhibitor of bacterial gyrase. The adverse effects of the photosensitization induced by fluoroquinolones are well known. A predominant type II photosensitizing activity of Rufloxacin has already been demonstrated on simpler models (free nucleosides, calf thymus DNA), whereas a cooperative mechanism was corroborated on more complex ones (plasmid and fibroblast). The purpose of this study is to examine the drug photocytoxicity in another complex cellular model, a wild-type eukaryotic fast-growing microorganism whose cultivation is cheap and easily managed, Saccharomyces cerevisiae. This work represents the first report of the potential photogenotoxicity of Rufloxacin. Particular emphasis was given to DNA modifications caused in yeast by the formation of Rufloxacin photomediated toxic species, such as hydrogen peroxide and formaldehyde. Drug phototoxicity on yeast was evaluated by measuring DNA fragmentation (single/double strand breaks) using single cell gel electrophoresis assay and 8-OH-dGuo, a DNA photooxidation biomarker, by HPLC-ECD. Cellular sensitivity was also assessed by cell viability test. The extra- and intracellular RFX concentration (as well as its main photoproduct) was verified by HPLC-MS, whereas the cytotoxic species were evaluated by colorimetric assays. The results confirm the phototoxicity of Rufloxacin on yeast cell and are in agreement with those previously obtained with human fibroblast and with simpler models used recently, and provide a clear link between DNA photosensitization and overall phototoxicity.

Broad-spectrum sunscreens prevent the secretion of proinflammatory cytokines in human keratinocytes exposed to ultraviolet A and phototoxic lomefloxacin

The combination of phototoxic drugs and ultraviolet (UV) radiation can trigger the release of proinflammatory cytokines. The present study measured the ability of sunscreens to prevent cytokine secretion in human keratinocytes following cotreatment of these cells with a known photoreactive drug and UVA. Keratinocytes were treated for 1 h with increasing concentrations of lomefloxacin (LOM) or norfloxacin (NOR), exposed to 15 J/cm2 UVA, and incubated for 24 h. NOR, owing to the absence of a fluorine atom in position 8, was non-phototoxic and used as a negative control. Cell viability and the release of 3 cytokines were assessed, namely interleukin-1alpha (IL-1alpha), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-alpha). The measurement of these cytokines may be a useful tool for detecting photoreactive compounds. To measure their ability to prevent cytokine secretion, various sunscreens were inserted between the UVA source and the cells. Treatment with NOR, NOR plus UVA, or LOM had no effect on the cells. LOM plus UVA, however, had an effect on cell viability and on cytokine secretion. IL-1alpha levels increased with LOM concentration. The release of TNF-alpha and IL-6 followed the same pattern at lower concentrations of LOM but peaked at 15 micromol/L and decreased at higher concentrations. Sunscreens protected the cells from the effects of LOM plus UVA, as cell viability and levels of cytokines remained the same as in the control cells. In conclusion, the application of broad-spectrum sunscreen by individuals exposed to UVA radiation may prevent phototoxic reactions initiated by drugs such as LOM.

Spectrofluorimetry and chemometrics for investigation of norfloxacin distribution in multilamellar liposomes

Norfloxacin (NFX), a fluoroquinolone, was encapsulated in multilamellar liposomes (MLV) of soy-bean phosphatidylcholine at pH 7.0. The observed affinity of this class of drugs for hydrophobic environments, such as phospholipid bilayers, could lead to a better understanding of the mechanism of uptake in bacteria. The fluorescent properties of NFX were examined both free in solution and in MLV, using anisotropy and fluorescence quenching measurements. The latter data was treated with a chemometric method to deconvolute the overlapped spectra of zwitterionic and neutral species of NFX in equilibrium at this pH. The results show that NFX incorporates into the lipidic bilayers with two different distributions of species: the zwitterionic form in the lipid/aqueous interface, and the neutral one, more towards the center of the bilayer.

Evaluation of phototoxic and photoallergic potentials of 13 compounds by different in vitro and in vivo methods

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 hen's 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.

Rufloxacin induced photosensitization in bio-models of increasing complexity

Rufloxacin belongs to the class of fluoroquinolones that act mainly as specific inhibitors of bacterial Topoisomerase II. These drugs are widely known to be involved in various diseases ranging from cutaneous reactions to aging. The type II photosensitizing activity of Rufloxacin has been already demonstrated on calf thymus DNA and free nucleosides. The aim of this study is to examine in control untreated and UVA irradiated human fibroblasts the modifications on DNA status induced by Rufloxacin added in the culture medium. This allows to investigate the photosensitizing activity of Rufloxacin in a more complex cell model. Fibroblasts, either in the presence or in the absence of Rufloxacin, were exposed to UVA irradiation for different times. An experimental protocol was followed in order to evaluate the amount of single-strand breaks (SSB) and double-strand breaks (DSB) DNA fragmentation by comet assay, and plasmid photocleavage. The presence of oxidized bases was also evaluated using the 8-OH-dGuo test. The comet assay test was also employed to assess cellular repair capacity. The intracellular drug concentration was verified by HPLC-MS. The results confirming the role of Rufloxacin as photosensitizer were: (i) a time-dependent increase in DNA fragmentation when fibroblasts were irradiated in the presence of Rufloxacin; (ii) the efficiency of the cellular repair machinery to be exhaustive after 2 h (whereas no correlation between irradiation time and DNA damage repair was observed with a higher level of DNA fragmentation after shorter irradiation times); (iii) the increased number of cells exhibiting high DNA fragmentation, seen as comets with long tails, was not accompanied by a similar large extent of oxidised DNA base formation, as measured by 8-OH-dGuo analysis; (iv) the double helix SSB, formed in plasmid photosensitization, agreed with the comet assay results, pointing out a good correlation among the cell system and the simpler models used.

6-Aminoquinolones: photostability, cellular distribution and phototoxicity

Three selected aminoquinolones endowed with a potent antibacterial (compounds 1 and 2) and antiviral activity (compound 3) have been evaluated for their phototoxic properties in vitro. Photostability studies of these compounds indicate that compound 3 is photostable whereas compound 1 and in particular, compound 2 are rapidly photodegraded upon UVA irradiation, yielding a toxic photoproduct. Intracellular localization of these compounds has been evaluated by means of fluorescence microscopy using tetramethylrhodamine methyl ester and acridine orange, which are specific fluorescent probes for mitochondria and lysosomes, respectively. No co-staining was observed with lysosomal stain for all the test compounds. On the contrary compound 3 was found to be specifically incorporated in mitochondria. The compounds exhibited remarkable phototoxicity in two cell culture lines: human promyelocytic leukaemia (HL-60) and human fibrosarcoma (HT-1080). The quinolone-induced photodamage was also evaluated measuring the photosensitizing cross-linking in erythrocyte ghost membranes, the strand breaks activity and oxidative damage on plasmid DNA. The results show that these derivatives are able to photoinduce crosslink of erythrocytes spectrin, whereas do not significantly photocleavage DNA directly, but single strand breaks were observed after treatment of photosensitized DNA with two base excision repair enzymes, Fpg and Endo III respectively.

A randomized controlled trial (volunteer study) of sitafloxacin, enoxacin, levofloxacin and sparfloxacin phototoxicity

BACKGROUND

Fluoroquinolone antibiotics (FQs) are associated with phototoxic skin reactions following exposure to sunlight.

OBJECTIVES

We aimed to compare the phototoxic potential of sitafloxacin, a novel FQ with three others: sparfloxacin, enoxacin, levofloxacin and placebo in Caucasian volunteers. In a second study, two dosage regimens of sitafloxacin were compared with placebo in Oriental subjects.

METHODS

Randomized, placebo-controlled, assessor-blinded clinical trial. In 40 healthy Caucasians, sitafloxacin 100 mg twice a day (n = 8), sparfloxacin 200 mg day-1 (n = 8), enoxacin 200 mg three times a day (n = 8), levofloxacin 100 mg three times a day (n = 8) and placebo (n = 8) were given in oral doses for 6 days. In the second study, sitafloxacin 50 mg and 100 mg, both twice daily, were compared with placebo in 17 healthy Oriental subjects. Using an established monochromator technique, baseline threshold erythema levels were established pre-drug and on-drug. The phototoxic index (PI) baseline, minimal erythema dose (MED) divided by on-drug MED for each medication at each wavelength was determined and related to sitafloxacin peak plasma levels. The duration of susceptibility to phototoxicity was assessed by repeat phototesting daily after stopping medication.

RESULTS

In the Caucasian study, sitafloxacin 100 mg twice a day produced mild ultraviolet (UV) A-dependent phototoxicity (median PI = 1.45) at 365 +/- 30 nm (half-maximum bandwidth), maximal at 24 h with normalization by 24 h postdrug cessation. The sparfloxacin group experienced severe phototoxicity maximal at 24 h and, unusually for an FQ, extended in the visible region (430 +/- 30 nm), maximal at 400 +/- 30 nm (median PI = 12.35) with abnormal pigmentation at on-drug phototest sites lasting, although fading, for up to 1 year. Enoxacin showed UVA-dependent phototoxicity (335-365 +/- 30 nm) median PI 3.94 (at 365 +/- 30 nm) returning to normal 48 h after stopping the drug. Fading pigmentation at phototoxic sites also lasted up to 1 year. Phototoxicity was not detected in the levofloxacin or placebo groups. In the Oriental study, no clinically relevant phototoxicity was seen with either sitafloxacin or placebo groups.

CONCLUSIONS

We conclude that 100 mg twice a day sitafloxacin in Caucasians is associated with a mild degree of cutaneous phototoxicity. Enoxacin 200 mg three times a day and sparfloxacin 200 mg day-1 are much more photoactive. Sparfloxacin phototoxicity is induced by UVA and visible wavelengths. Levofloxacin and placebo failed to show a phototoxic effect. In the Oriental study, sitafloxacin 50 mg twice a day and 100 mg twice a day failed to demonstrate a clinically significant phototoxic effect.

In vitro phototoxic properties of new 6-desfluoro and 6-fluoro-8-methylquinolones

A representative set of potent antibacterial 6-desfluoro-8-methylquinolones, in which the C-6 fluorine atom is replaced by -NH(2) or -H, and their 6-fluoro counterparts, were investigated to evaluate their phototoxic potential and to explore the mechanism behind their phototoxicity. The capacity to photosensitize biological substrates (lipids, proteins, DNA) has been analyzed, as well as their photocytotoxicity on red blood cells and 3T3 murine fibroblasts. The results obtained show that the quinolones studied are able to photosensitize red blood cell lysis in an oxygen-dependent way and induce a high decrease in cell viability after UVA irradiation. A major correlation with phototoxicity lies in the structure of the individual antibacterials and their hydrophobicity; in particular, 6-amino derivatives are less phototoxic than corresponding unsubstituted and fluorinated compounds. Cellular phototoxicity was inhibited by the addition of free radical and hydroxyl radical scavengers (BHA, GSH and DMTU), suggesting the involvement of a radical mechanism in their cytotoxicity. A good correlation was observed between lipid peroxidation and phototoxicity, indicating that the test compounds exert their toxic effects mainly in the cellular membrane. Preliminary experiments on pBR322 DNA show that these derivatives do not photocleave DNA, differently from the two photogenotoxic fluoroquinolones, ciprofloxacin and lomefloxacin, used as reference compounds.

Evaluation of UV-radiation induced singlet oxygen generation potential of selected drugs

Photosensitization reaction of drugs leading to the formation of reactive oxygen species under ultraviolet radiation (UVR) can cause tissue injury, resulting in damage to various cellular macromolecules. The aim of this study was to determine the singlet oxygen generation potential of some commonly used antibiotics so that due precautions can be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce singlet oxygen (1O2) under artificial UVA (320-400 nm). Singlet oxygen generation of various screened antibiotics under UVA is of the following order: Nalidixic acid > Amphotericin-B > Cephradine > Cefazolin > Nafcillin > Cephalothin > Ampicillin > Cephalexin > Puromycin > Kanamycin > Lincomycin > Tetracycline > Nystatin > Gentamicin sulphate. Nalidixic acid, the most potent generator of 1O2 among the screened antibiotics, was selected to carry out further studies. Certain specific quenchers of 1O2 such as beta-carotene, 1,4-diazabicyclo[2.2.2] octane (DABCO), and sodium azide (NaN3) accorded significant inhibition in the production of 1O2. The results suggest that precautions are necessary to avoid ultraviolet radiation after the intake of photoreactive drugs, especially in tropical countries such as India. These findings are significant because UVB radiation is reportedly increasing on earth surface in part due to depletion of stratospheric ozone layer. The selected drugs are commonly used for the treatment of various diseases. Thus, the synergistic action of both can lead to undesirable phototoxic responses.

Mono, dual and triple moxifloxacin-based therapies for Helicobacter pylori eradication

BACKGROUND

Moxifloxacin is a broad spectrum fluoroquinolone with single daily administration, currently used, above all, for respiratory tract infections.

AIM

To compare the efficacy of different 1-week moxifloxacin-based Helicobacter pylori eradication regimens.

METHODS

One hundred and twenty H. pylori-positive subjects were randomized to receive moxifloxacin (400 mg/day), moxifloxacin (400 mg/day) and lansoprazole (30 mg/day) or moxifloxacin (400 mg/day), lansoprazole (30 mg/day) and clarithromycin (500 mg b.d.). H. pylori status was reassessed 6 weeks after the end of therapy, and both intention-to-treat and per protocol analyses were performed.

RESULTS

One hundred and nineteen of the 120 patients completed the study. H. pylori eradication was achieved in 22.5% of patients treated with moxifloxacin, in 33.3% of subjects treated with moxifloxacin and lansoprazole and in 90% of patients treated with moxifloxacin, clarithromycin and lansoprazole.

CONCLUSIONS

Mono and dual moxifloxacin-based therapies are not acceptable for H. pylori eradication; conversely, moxifloxacin-based triple therapy may be considered as a new, effective, first-line therapy option.

In vitro method for prediction of the phototoxic potentials of fluoroquinolones

The phototoxic potential of eight fluoroquinolones (norfloxacin, ofloxacin, enoxacin, ciprofloxacin, lomefloxacin, tosufloxacin, sparfloxacin and gatifloxacin) was evaluated by using three in vitro methods of cytotoxicity against mammalian cells, erythrocyte lysis and DNA strand breakage. All fluoroquinolones tested with the exception of gatifloxacin, an 8-methoxy quinolone, showed DNA strand breaking activities under UV-A irradiation. Their cytotoxicity against HeLa cells was also enhanced by UV-A irradiation. In particular, the phototoxic potential of sparfloxacin, enoxacin and lomefloxacin was high in both methods. Ofloxacin is very photocytotoxic against HeLa cells, while it has low potential to cause DNA strand breakage. Norfloxacin, ciprofloxacin and enoxacin were very photohemolytic, but sparfloxacin was not, indicating that the in vivo phototoxic potencies of fluoroquinolones might not be predictable by the photohemolysis study. Gatifloxacin, a non-phototoxic quinolone, showed no phototoxic potential in any of these three in vitro tests. These results suggest that determination of DNA strand breaking activity, combined with cytotoxicity against mammalian cells, is available to predict the phototoxic potential of fluoroquinolones without laboratory animals.

EVALUATION OF UV-INDUCED SUPEROXIDE RADICAL GENERATION POTENTIAL OF SOME COMMON ANTIBIOTICS

Photosensitization reaction of drugs leading to the formation of reactive oxygen species (ROS) cause tissue injury causing damage to various cellular macromolecules. The aim of this study was to determine the superoxide anion (O2-) generation potential of commonly used antibiotics so that due precaution could be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce (O2-) under sunlight and artificial UVA (320-400 nm) and UVB (290-320 nm). Lincomycin, cephalothin and erythromycin generated significant amount of O2- under various irradiation conditions. Superoxide dismutase (SOD), an enzymatic quencher of O2- inhibited O2- production in all drugs tested. The results suggest that due precaution are necessary to avoid ultraviolet radiation (UVR) after the intake of photoreactive drugs, especially in tropical and sub tropical countries.

The phototumorigenic fluoroquinolone, lomefloxacin, photosensitises p53 accumulation and transcriptional activity in human skin cells

The fluoroquinolone antibiotic, lomefloxacin, is phototoxic in human skin exposed to UVA radiation, photosensitises DNA strand breaks and pyrimidine dimers in human keratinocytes in vitro, and is phototumorigenic in mouse skin. The p53 tumour suppressor protein is activated by a variety of cellular insults including UV radiation, to become a transcription factor for downstream markers such as the cyclin-kinase inhibitor p21CIP1/WAF1 or cause caspase transactivation which cleaves poly ADP ribose polymerase (PARP) as an early step in apoptosis. We have investigated these molecular defence responses in human skin cells treated with lomefloxacin and UVA radiation in vitro. Western blots revealed that lomefloxacin photosensitised the stabilisation of p53 protein in human fibroblasts. Lomefloxacin also photosensitised p53 transcriptional activity in amelanotic melanoma cells expressing wild-type p53 and stably transfected with a construct containing a beta-galactosidase reporter gene downstream from a p53 consensus binding sequence. Neither photosensitised production of H2O2 nor the resultant DNA strand breaks, appeared to be involved in this effect. Interestingly, p21CIP1/WAFI protein was upregulated by lomefloxacin in the dark by a p53-independent mechanism. Lomefloxacin also photosensitised the degradation of nuclear PARP, suggestive of caspase mediated, early apoptotic events.