KoCVAM-led development of phototoxicity alternative test method using reconstructed human epidermis model (KeraSkin™)

Phototoxicity is an acute toxic reaction induced by topical skin exposure to photoreactive chemicals followed by exposure to environmental light and thus chemicals that absorb UV are recommended to be evaluated for phototoxic potential. There are currently three internationally harmonized alternative test methods for phototoxicity. One of them is the in vitro Phototoxicity: RhE Phototoxicity test method (OECD TG498). Korean center for the Validation of Alternative Methods (KoCVAM) developed an in vitro phototoxicity test method using a KeraSkin™ reconstructed human epidermis model (KeraSkin™ Phototoxicity Assay) as a 'me-too' test method of OECD TG498. For the development and optimization of KeraSkin™ Phototoxicity Assay, the following test chemicals were used: 6 proficiency chemicals in OECD TG498 (3 phototoxic and 3 non-phototoxic), 6 reference chemicals in OECD Performance Standard No. 356 (excluding the proficiency test chemicals, 3 phototoxic and 3 non-phototoxic) and 13 additional chemicals (7 phototoxic and 6 non-phototoxic). Based on the test results generated from the test chemicals above, the overall predictive capacity of KeraSkin™ Phototoxicity Assay was calculated. In particular, the assay exhibited 100 % accuracy, 100 % sensitivity, and 100 % specificity. Therefore, it fulfills the requirements to be included as a 'me-too' test method in OECD TG498.

Anti-tuberculosis drugs used in a directly observed treatment short course (DOTS) schedule alter endocrine patterns and reduce the ovarian reserve and oocyte quality in the mouse

CONTEXT

Tuberculosis is one of the major infectious diseases, with people of reproductive age group having a high risk of infection.

AIMS

The present study was designed to understand the consequences of anti-tuberculosis drugs (ATDs) used in DOTS (directly observed treatment short course) schedule on ovarian function.

METHODS

Adult female Swiss albino mice were orally administered with combinations of ATDs used in the DOTS schedule every day for 4weeks. At 2weeks after the cessation of ATDs administration, the endocrine changes and ovarian function were assessed in mice.

KEY RESULTS

Administration of ATDs to mice resulted in a prolonged estrous cycle, reduced ovarian follicle reserve, alteration in FSH, LH, and progesterone level, and decreased the number of ovulated oocytes. Further, the degree of fragmentation, degeneration, abnormal distribution of cytoplasmic organelles, abnormal spindle organisation, and chromosomal misalignment were higher in oocytes that were ovulated following superovulation. Blastocysts derived from ATDs treated mice had significantly lower total cell numbers and greater DNA damage. A marginal increase in the number of resorbed fetuses was observed in all the ATDs treated groups except in the multidrug resistance treatment group. Male progeny of ATDs treated mice had decreased sperm count and lower progressive motility, while female progeny exhibited a non-significant reduction in the number of oocytes ovulated.

CONCLUSIONS

Theresults of this study suggest that ATDs can have significant adverse effects on the ovarian reserve, cytoplasmic organisation of oocytes, and can potentially cause transgenerational changes.

IMPLICATIONS

The findings of the present study indicate ovarian toxicity of ATDs and warrant further research in the direction of identifying alternate drugs with minimal toxicity, and strategies to mitigate the ovarian toxicity induced by these drugs.

Evaluation of the skin phototoxicity of systemically administered pharmaceuticals in Sprague-Dawley rats

In vivo phototoxicity testing is important for predicting drug-induced phototoxicity in humans. Currently, there is no internationally validated in vivo test method for the photosafety evaluation of pharmaceuticals. In this study, we evaluated the phototoxicity of systemically administered drugs using SD rats. We first determined the appropriate ultraviolet A (UVA) dose using 8-methoxypsoralen, a well-known phototoxic drug. Compared to lower and higher UVA doses, we found that a UVA dose of 10 J/cm² allowed for the detection of phototoxic responses in both a dose- and time-dependent manner. We next performed a phototoxicity study using seven pharmaceutical drugs which included known phototoxic and non-phototoxic drugs using a UVA dose of 10 J/cm². In order to improve the accuracy of our assessment, we evaluated both gross skin findings as well as histopathological findings. Using gross skin findings alone resulted in an accuracy of 85.7% which could be increased to 100% accuracy when the gross skin findings were combined with histopathological findings. This study suggests that the inclusion of histopathological findings increases the accuracy of the phototoxicity evaluation of systemically administered drugs in SD rats. In conclusion, we found that for studying drug-induced phytotoxicity, a 10 J/cm² UVA dose serves as the optimal radiation dose, and that the inclusion of histopathological findings increases the accuracy of the phototoxicity evaluation of the drugs.

Levofloxacin-Loaded Nanosonosensitizer as a Highly Efficient Therapy for Bacillus Calmette-Guérin Infections Based on Bacteria-Specific Labeling and Sonotheranostic Strategy

Purpose

The rapid emergence of multidrug-resistant Mycobacterium tuberculosis (MTB) poses a significant challenge to the treatment of tuberculosis (TB). Sonodynamic antibacterial chemotherapy (SACT) combined with sonosensitizer-loaded nanoparticles with targeted therapeutic function is highly expected to eliminate bacteria without fear of drug resistance. This study aimed to investigate the antibacterial effect and underlying mechanism of levofloxacin-loaded nanosonosensitizer with targeted therapeutic function against Bacillus Calmette-Guérin bacteria (BCG, an MTB model).

Methods

This study developed levofloxacin-loaded PLGA-PEG (poly lactide-co-glycolide-polyethylene glycol) nanoparticles with BM2 aptamer conjugation on its surface using the crosslinking agents EDC and NHS (BM2-LVFX-NPs). The average diameter, zeta potential, morphology, drug-loading properties, and drug release efficiency of the BM2-LVFX-NPs were investigated. In addition, the targeting and toxicity of BM2-LVFX-NPs in the subcutaneous BCG infection model were evaluated. The biosafety, reactive oxygen species (ROS) production, cellular phagocytic effect, and antibacterial effect of BM2-LVFX-NPs in the presence of ultrasound stimulations (42 kHz, 0.67 W/cm², 5 min) were also systematically evaluated.

Results

BM2-LVFX-NPs not only specifically recognized BCG bacteria in vitro but also gathered accurately in the lesion tissues. Drugs loaded in BM2-LVFX-NPs with the ultrasound-responsive feature were effectively released compared to the natural state. In addition, BM2-LVFX-NPs exhibited significant SACT efficiency with higher ROS production levels than others, resulting in the effective elimination of bacteria in vitro. Meanwhile, in vivo experiments, compared with other options, BM2-LVFX-NPs also exhibited an excellent therapeutic effect in a rat model with BCG infection after exposure to ultrasound.

Conclusion

Our work demonstrated that a nanosonosensitizer formulation with LVFX could efficiently translocate therapeutic drugs into the cell and improve the bactericidal effects under ultrasound, which could be a promising strategy for targeted therapy for MTB infections with high biosafety.

Chemical tuning for potential antitumor fluoroquinolones

Phototoxic effects of 6,8 dihalogenated quinolones confers to this type of molecules a potential property as photochemotherapeutic agents. Two photodehalogenation processes seem to be involved in the remarkable photoinduced cellular damage. In this context, a new 6,8 dihalogenated quinolone 1 (1-methyl-6,8-difluoro-4-oxo-7-aminodimethyl-1,4-dihydroquinoline-3-carboxylic acid) was synthetized looking for improving the phototoxic properties of fluoroquinolones (FQ) and to determine the role of the photodegradation pathways in the FQ phototoxicity. With this purpose, fluorescence emissions, laser flash photolysis experiments and photodegradation studies were performed with compound 1 using 1-ethyl-6,8-difluoro-4-oxo-7-aminodimethyl-1,4-dihidroquinoline-3-carboxylic acid (2) and lomefloxacin (LFX) as reference compounds. The shortening of alkyl chain of the N(1) of the quinolone ring revealed a lifetime increase of the reactive aryl cation generated from photolysis of the three FQ and a significant reduction of the FQ photodegradation quantum yield. The fact that these differences were smaller when the same study was done using a hydrogen donor solvent (ethanol-aqueous buffer, 50/50 v/v) evidenced the highest ability of the reactive intermediate arising from 1 to produce intermolecular alkylations. These results were correlated with in vitro 3T3 NRU phototoxicity test. Thus, when Photo-Irritation-Factor (PIF) was determined for 1, 2 and LFX using cytotoxicity profiles of BALB/c 3T3 fibroblasts treated with each compound in the presence and absence of UVA light, a PIF more higher than 30 was obtained for 1 while the values for 2 and LFX were only higher than 8 and 10, respectively. Thereby, the present study illustrates an approach to modulate the photosensitizing properties of FQ with the purpose to improve the chemotherapeutic properties of antitumor quinolones. Moreover, the results obtained in this study also evidence that the key pathway responsible for the phototoxic properties associated with dihalogenated quinolones is the aryl cation generation.

Effects of lomefloxacin on survival, growth and reproduction of Daphnia magna under simulated sunlight radiation

Lomefloxacin, an antibacterial agent with known photo-induced toxicity in clinical studies, is frequently detected in aquatic environments. Investigating the photo-induced toxicity of lomefloxacin in aquatic organisms is therefore of importance for assessing its ecological risks. In this study, the effects of lomefloxacin on survival, growth and reproduction of Daphnia magna under simulated sunlight radiation (SSR) were investigated, and the mechanism of action was revealed. Results indicated that SSR containing UV radiation increased the acute toxicity of lomefloxacin to Daphnia magna relative to white fluorescent light irradiation. Under SSR, 100 μM lomefloxacin significantly enhanced reactive oxygen species (ROS) generation and lipid peroxidation, and decreased activities of superoxide dismutase and catalase. The biochemical observations and apparent effects on the organism indicate that oxidative stress plays a central role in the acute photo-induced toxicity. Chronic toxicity results showed that SSR significantly affected growth and reproduction of Daphnia magna, whereas lomefloxacin reduced the damage of UV radiation in SSR through light shielding. This study provides insight into the mechanism of photo-induced toxicity and can support the risk assessment of chemicals in the aquatic environment by including the impacts of sunlight irradiation on toxicity.

Assessment of phototoxicity in pigmented Long-Evans rat: sparfloxacin and 8-methoxypsoralen

The aim of the present work was to evaluate the effects of photo-activated toxicity induced after administration of two known melanin-binding phototoxic compounds, sparfloxacin (SPX) and 8-methoxypsoralen (8-MOP), followed or not by UVA/Vis exposure, in pigmented rats (Long Evans: LE) and albino rats (Sprague Dawley: SD). Groups of three rats were treated with SPX or 8-MOP by oral gavage for six consecutive days. Irradiated animals were submitted to a UVA/Vis light dose standardized to 10 J/cm² UVA daily. Clinical signs, cutaneous reactions and body weight were monitored throughout the study period. Ear biopsy weight, lymph node weight and lymph node cell count were determined at necropsy. Ophthalmologic examinations were performed before the first treatment and on the day of sacrifice. Microscopic examinations were performed on skin biopsies and eyes. Phototoxicity was demonstrated for both SPX and 8-MOP in the pigmented and albino strains, in terms of auricular irritation, lymph node weight and proliferation index, cutaneous reactions and ocular histopathology. LE rats were less sensitive than SD rats, especially at the ocular level, supporting the notion that pigmentation may provide protection against photo-activation. The pigmented rat may be a more relevant model than the albino rat for human safety evaluation.

Identification of influential events concerning the Antarctic ozone hole over southern Brazil and the biological effects induced by UVB and UVA radiation in an endemic treefrog species

The increased incidence of solar ultraviolet radiation (UV) due to ozone depletion has been affecting both terrestrial and aquatic ecosystems and it may help to explain the enigmatic decline of amphibian populations in specific localities. In this work, influential events concerning the Antarctic ozone hole were identified in a dataset containing 35 years of ozone measurements over southern Brazil. The effects of environmental doses of UVB and UVA radiation were addressed on the morphology and development of Hypsiboas pulchellus tadpole (Anura: Hylidae), as well as on the induction of malformation after the conclusion of metamorphosis. These analyzes were complemented by the detection of micronucleus formation in blood cells. 72 ozone depletion events were identified from 1979 to 2013. Surprisingly, their yearly frequency increased three-fold during the last 17 years. The results clearly show that H. pulchellus tadpole are much more sensitive to UVB than UVA light, which reduces their survival and developmental rates. Additionally, the rates of micronucleus formation by UVB were considerably higher compared to UVA even after the activation of photolyases enzymes by a further photoreactivation treatment. Consequently, a higher occurrence of malformation was observed in UVB-irradiated individuals. These results demonstrate the severe genotoxic impact of UVB radiation on this treefrog species and its importance for further studies aimed to assess the impact of the increased levels of solar UVB radiation on declining species of the Hylidae family.

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.