Avaliação do efeito citotóxico da terapia fotodinâmica associada ao LED e ao Photogem® sobre a mucosa bucal de rato / Toxicity of the photodynamics therapy with LED associated to Photogem®: an in vivo study

A utilização da PDT para tratamento de diferentes tipos de infecções, tal como a candidose bucal, tem sido estudada. Entretanto, poucos são os dados científicos que relatam os possíveis efeitos tóxicos dessa terapia. Dessa forma, o objetivo deste estudo foi avaliar os efeitos da irradiação na mucosa bucal de ratos com LED azul (de 460 nm e potência de 200 mW/cm2) em presença do fotossensibilizador (FS) Photogem®, em duas diferentes concentrações (500 mg/L e 1000 mg/L). Para isso, foram utilizados 101 ratos (Rattus Norvegicus Albinus Holtzman) distribuídos em 6 grupos, de acordo com os seguintes tratamentos: Grupo 1 ­ controle; Grupo 2 ­ aplicação do FS (500 mg/L); Grupo 3 ­ aplicação do FS (500 mg/L) e irradiação com LED; Grupo 4 - aplicação do FS (1000 mg/L); Grupo 5 ­ aplicação do FS (1000 mg/L) e irradiação com LED; e Grupo 6 ­ irradiação com LED. O FS foi aplicado por 30 minutos (tempo de pré-incubação) e o tempo de irradiação da mucosa foi de 20 minutos (dose de 144 J/cm2 ). Decorridos os 4 períodos de avaliação propostos (0 dia, 1dia, 3 dias e 7 dias), os animais tiveram a mucosa palatina fotografada para análise macroscópica, sendo então imediatamente sacrificados para remoção cirúrgica do palato e posterior análise em microscopia de luz e de fluorescência. Um mapeamento térmico foi realizado a fim de avaliar a variação de temperatura ocorrida no tecido durante a irradiação com LED. Macroscopicamente, em todos os grupos experimentais e para todos os períodos de avaliação propostos na presente pesquisa, observou-se que a mucosa apresentava-se intacta, com aspecto de normalidade semelhante ao do Grupo 1 (controle). Microscopicamente, alterações teciduais, caracterizadas especialmente por discreta inflamação, puderam ser observadas na mucosa palatina de apenas 4 de um total de 80 animais submetidos a PDT. A penetração do fotossensibilizador na mucosa tratada pôde ser observada por meio da emissão de fluorescência do Photogem® , tendo este FS se mantido presente apenas no tecido epitelial. O mapeamento térmico revelou que a temperatura aumentou de 35ºC para 41ºC durante 20 minutos de irradiação. Dentro das condições experimentais avaliadas, foi possível concluir que a PDT, utilizando Photogem® nas concentrações de 500 mg/L e 1000 mg/L associado ou não à irradiação com LED (dose de 144 J/cm2), não foi tóxica para a mucosa palatina de ratos

The use of PDT has been investigated for the treatment of different types of infection, like oral candidosis. There are, however, few research-based data that report the possible toxic effects of this therapy. Therefore, this study evaluated the effects of irradiating the palatal mucosa of rats with blue LED (460 nm; 200 mW/cm²) in the presence of the photosensitizer Photogem® at two concentrations (500 and 1000 mg/L). Then, 101 rats (Rattus norvegicus albinus Holtzman) were randomly distributed in six groups, according to the treatment performed on the palatal mucosa: Group 1: control; Group 2: Photogem® (500 mg/L); Group 3: Photogem® (500 mg/L) + blue LED; Group 4 - Photogem® (1000 mg/L); Group 5: (1000 mg/L) + blue LED; and Group 6: blue LED. The exposure times to the photosensitizing agent and to the light source were 30 min (pre-incubation time) and 20 min (144 J/cm2 energy density), respectively. At 0, 1, 3 and 7 days posttreatment, the animals had their palatal mucosa photographed for macroscopic analysis and were immediately sacrificed. The palate was removed for further analysis by light and fluorescence microscopy. Thermal mapping was made to evaluate the temperature change occurred in the tissue during LED irradiation. In all experimental groups and periods, the macroscopic analysis revealed intact mucosa with normal aspect similar to that of Group 1 (control). Tissue alterations, characterized primarily by a mild inflammation, were observed microscopically on the mucosa of only 4 out of 80 animals subjected to PDT. Photosensitizer penetration into the treated mucosa was identified by the fluorescence emitted by Photogem® and was limited to the epithelial layer. The thermal mapping revealed a temperature increase from 35 to 41ºC during the 20-min irradiation. In conclusion, under the tested conditions, PDT using Photogem® at 500 and 1000 mg/L concentrations associated or not to LED irradiation (144 J/cm2) was not toxic to the rat palatal mucosa

Efeito citotóxico da terapia fotodinâmica associando Photogem® e LED azul e vermelho em cultura de células normais / Cytotoxic effect of the photodynamic therapy associating Photogem® and blue or red LED on normal cell culture

Para considerar a Terapia Fotodinâmica (PDT) como tratamento clínico da estomatite protética, é necessário conhecer tanto o potencial antifúngico, como efeito citotóxico desta terapia sobre células normais do indivíduo. Assim, o objetivo desse estudo in vitro foi avaliar a citotoxicidade da PDT antifúngica com o fotossensibilizador Photogem® associado ao LED azul e ao LED vermelho em cultura de fibroblastos L929 e células odontoblastóides MDPC-23. As células foram cultivadas (30.000 células/cm2) em placas de 24 compartimentos por 48 horas e ambos os tipos celulares foram incubados com Photogem® (0, 10, 25, 50, 100 ou 150 mg/L) e irradiados ou não pelo LED azul (460 ± 3 nm; 25,5 ou 37,5 J/cm2; 22 mW/cm2) ou LED vermelho (630 ± 3 nm; 70 ou 100 J/cm2; 25 mW/cm2) . O metabolismo celular foi determinado 0, 12 e 24 horas após a PDT utilizando o teste do metiltetrazolium (MTT), e a morfologia celular avaliada pela microscopia eletrônica de varredura (MEV). A técnica de citometria de fluxo foi utilizada para avaliar o tipo de morte celular (necrose ou apoptose) assim como estimar os níveis intracelulares das espécies reativas de oxigênio (EROs). Observou-se redução do metabolismo celular estatisticamente significante para todas as concentrações do Photogem® quando irradiadas em qualquer dose de luz, sendo essa redução de 90 a 97% tanto para as células L929 quanto MDPC-23 (ANOVA and Dunnet's post hoc tests; p<0.05). Essa redução da atividade mitocondrial não foi dependente da concentração do fotossensibilizador e nem da dose de luz empregada. Também, foi demonstrado que a atividade mitocondrial das células submetidas a PDT não foi recuperada após 12 ou 24 horas, caracterizando um dano irreversível. A presença do Photogem® e da luz isoladamente não alterou estatisticamente a atividade mitocondrial de ambas as linhagens. As células submetidas à PDT tiveram sua morfologia alterada, não sendo possível observação dos limites celulares. Em ambas as linhagens, foi observado predomínio de morte celular por necrose quando em contato com o fotossensibilizador. A presença do Photogem® e a exposição à luz aumentaram os níveis de EROs intracelulares de uma forma dosedependente para L929 e MDPC-23. A associação do Photogem® com LED azul ou vermelho causou intensos efeitos tóxicos sobre cultura de células normais, caracterizados pela redução da atividade mitocondrial, alterações morfológicas e indução de morte celular por necrose

In order to consider the photodynamic therapy (PDT) as a clinical treatment for candidosis, it is necessary to know its antifungal potential and its cytotoxicity effect on normal cells. Therefore, the purpose of this in vitro study was to evaluate the cytotoxicity of PDT with Photogem® associated to blue and red LED on L929 and MDPC-23 cell cultures. The cells (30.000 cells/cm2) were seeded in 24-well plates for 48 hours, incubated with Photogem® (10, 25, 50, 100 or 150 mg/L) and were irradiated or not with a blue LED source (460 ± 3 nm; 25.5 or 37.5 J/cm2; 22 mW/cm2) or with a red LED source (630 ± 3 nm; 75 or 100 J/cm2; 22 mW/cm2). Cell metabolism was evaluated by the MTT assay (ANOVA and Dunnet's post hoc tests; p<0.05) and cell morphology was examined by scanning electron microscopy. Flow cytometry was employed to analyze the type of PDT-induced cell death (necrosis or apoptosis) as well as to estimate intracellular production of reactive oxygen species (ROS). There was a statistically significant decrease of mitochondrial activity for all Photogem® concentrations associated to blue or red LED regardless irradiation time; this reduction ranged from 90 to 97% for both cell lines. This reduction, however, was not dependent on the photosensitizer concentration. It was also demonstrated that the mitochondrial activity of the cells submitted to PDT was not recovered after 12 or 24 hours, characterizing irreversible cell damage. PDT-treated cells presented an altered morphology with ill-defined limits. In both cell lines, there was a predominance of necrotic cell death when in contact with the photosensitizer. The presence of Photogem® and exposure to blue and red LED increased the intracellular levels of ROS in both L929 and MDPC23 cells in a dose-dependent manner. The association of Photogem® and blue LED caused severe toxic effects on normal cell culture, characterized by the reduction of the mitochondrial activity, morphological alterations and induction of necrotic cell death

Photo hen's egg test: a model for phototoxicity.

The aim of this investigation was to establish a new model for phototoxicity which is more advanced than the widely used cultures of yeasts, bacteria or cells of various origin, and at the same time to avoid animal testing. We studied the extraembryonal vasculature of the incubated hen's egg. This model was originally introduced by toxicologists as an alternative to the rabbit's eye irritation test (Draize test). In the photo hen's egg test, substances are applied to the embryo's yolk-sac blood vessel system at a non-toxic concentration and are irradiated with 5 J/cm2 ultraviolet A (UVA) (320-400 nm). Promethazine, haematoporphyrin, ciprofloxacin and 8-methoxypsoralen were tested in this system. Death of the embryo, membrane discoloration and haemorrhage are parameters for phototoxic damage, which were recorded during an observation period of 24 h. These well-known phototoxic substances induced pronounced damage of the yolk-sac membrane and blood vessels which was not found in the controls (test substance alone, UVA alone or untreated) using a 2 x 2 factorial test design. The photo hen's egg test serves as a valid screening model for substances supposed to be photosensitizers owing to a phototoxic mechanism.

Evaluation of new benzoporphyrin derivatives with enhanced PDT efficacy.

A first report on the biological evaluation of a series of isomerically pure benzoporphyrin derivatives (cis- and trans-isomers) as methyl esters is described. In preliminary in vivo studies, the n-hexyl ether analogues of both cis- and trans-isomers of benzoporphyrin derivatives were found to be more active than the industrially prepared benzoporphyrin derivative, a mixture of monocarboxylic acids (BPDMA, Quadralogic Technologies, Vancouver). Further studies with 4-de-vinyl-4- (1-hexyloxyethyl) benzoporphyrin derivative showed that, like BPDMA, it had reduced residual skin phototoxicity compared in mice with Photofrin. The uptake and clearance characteristics of BPDMA were also compared with the 4-(1-hexyloxyethyl)-derivative by in vivo reflection spectroscopy.

Local neurotoxicity of hematoporphyrin derivative following intracerebral injection.

The present study reports on toxicity of hematoporphyrin derivative (HpD) for normal brain tissue in vivo without the addition of light. Hematoporphyrin derivative was injected by slow infusion in rat brains. Histological examination was carried out for intervals after HpD administration, ranging from 0 h to 15 days. Ultrastructural changes were examined with transmission electron microscopy. The extent of the necrosis was determined for different HpD concentrations and compared with control animals infused with 0.9% saline. Leukocytic infiltration was observed at day 5. Transmission electron microscopy showed that nuclei of neurons were completely disintegrated 4 h after HpD administration. Furthermore disruption of myelin sheaths was observed. The extent of the necrosis decreased with lower HpD doses. Injection of 2 micrograms HpD in a volume of 4 microL (0.5 mg/mL) resulted in a virtually equal extension of the tissue damage, as compared to the mechanical damage in the control animals caused by the infusion procedure.

Comparative skin phototoxicity in mice with two photosensitizing drugs: benzoporphyrin derivative monoacid ring A and porfimer sodium (Photofrin).

Benzoporphyrin derivative monoacid ring A (BPD-MA) and Photofrin (porfimer sodium) are photodynamic anticancer agents. The chemical structures of the two regioisomers of BPD-MA are 9-methyl trans-(+/-)-18-ethenyl-4,4 alpha-dihydro-3,4- bis(methoxycarbonyl)-4 alpha, 8,14,19-tetramethyl-4,4 alpha-dihydro-3,4- bis(methoxycarbonyl)-4 alpha, 8,14,19-tetramethyl-23H,25H-benzo(b)porphine- 9,13-dipropanoate and 13-methyl-trans-(+/-)-18-ethenyl-4,4 alpha-dihydro-3,4- bis(methoxycarbonyl)-4 alpha, 8,14,19-tetramethyl-23H,25H-benzo(b)porphine- 9,13-dipropanoate. Photofrin (a registered trademark of American Cyanamid Co.) is a polyporphrin oligomer containing ester and ether linkages. The ability of BPD-MA or Photofrin to cause skin phototoxicity was investigated in mice exposed to simulated sunlight (light) 3, 24, or 48 hr after receiving a single intravenous injection of vehicle or 2, 10, or 20 mg/kg of BPD-MA or Photofrin. The data were from two studies conducted using male and female CD1 mice (approximately 7 weeks old). The hair of the dorsal thoracic area was clipped 24 hr prior to exposure to light. Mice were exposed to light for 5 min. The clipped area of skin was the primary site for the evaluation of phototoxicity. Mice were observed for 2 weeks after treatment. There were no significant findings in controls or in mice given 2 mg/kg of BPD-MA. When mice were exposed to light 3 hr after dosing, both BPD-MA (10 or 20 mg/kg) and Photofrin (2, 10 or 20 mg/kg) caused phototoxicity. Death occurred in all mice given 20 mg/kg of BPD-MA or Photofrin, and in the majority of mice given 10 mg/kg of Photofrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on inactivation of pathogenic microorganisms in culture media and in bovine semen by photosensitive agents.

The application of three photosensitive agents for disinfection of bovine semen was investigated. Bovine microbial pathogens suspended in tissue culture medium and/or PBS and also added to bovine semen were exposed to the photosensitive agents followed by irradiation. Hematoporphyrin, hematoporphyrin derivative and thiopyronine were effective against bovine herpes virus-1, bovine viral diarrhoea virus, Mycoplasma bovigenitalium, Mycoplasma canadense, and Ureaplasma diversum in culture media. In addition, thiopyronine was effective against Leptospira pomona. Similar treatments were not effective against Leptospira hardjo, Mycoplasma bovis, or Campylobacter fetus subsp. venerealis. When microorganisms were added to bovine semen, only bovine herpes virus-1 was controlled by the photosensitive agents used at concentrations which did not appear harmful to sperm cells.