Efeitos de furocumarinas associadas à luz ultravioleta B (312mn) em staphylococcus aerus

Abstract

Furocoumarins (FCs) are an important class of photoactive compounds which may potentially bind to DNA forming intermolecular complexes, and once excited by UVA light (~ 365 nm) they re able to form photoadducts, which may result in mutagenicity and lethality. However, when the 8-methoxypsoralen (8-MOP) is added to the post-irradiation plating medium increases the sensitization probably by inhibiting repairs in damaged DNA. The FCs also have a protective effect against UVC (~254 nm) attributed to the inhibition of pyrimidine dimers. FCs associated with UVB light (312 nm), remain few known. The aim of the present study was to investigate the lethal effect of UVB light alone, and combined with solutions of 8-MOP, 4,5',8-trimethylpsoralen (TMP) and 3-carbetoxypsoralen (3-CPs) at different concentrations on Staphylococcus aureus growth. We also evaluated the effect of these FCs in the plating medium. Treatment with 8-MOP-UVB and TMP-UVB were more effective in inducing lethality than the UVB treatment alone. Increasing the solution concentration of 8-MOP resulted in a higher mortality while the increase in the concentration of the TMP led to a reduction in the lethality. For other hand, 3-CPs displayed a photoprotective effect against UVB damage in all concentrations tested. The results of FCs in the plating medium showed that the 8-MOP induzed a higher lethal effect and also increased mortality from bacterial strain treated by FC-UVB. The different behaviors shown by FCs may be related with differences in the sequence specificity of binding and photoreaction, inhibition of pyrimidine dimers formation by intercalated molecules and efficacy of repair systems. These results emphasize the need for further studies to elucidate the participation of FCs as photosensitizing and photoprotective agents in biological systems, when combined with UVB.