Effect of hydrogen sulfide on 5-aminolevulinic acid- photodynamic therapy (ALA-PDT) in murine mammary adenocarcinoma cells.

CALVO G; DI VENOSA G; VALLECORSA P; MAMONE L; BATLLE A; CASAS A; SAENZ D

Dusseldorf

Congreso; International Congress on Porphyrins and Porphyrias; 2015

Photodynamic therapy (PDT) is a technique for inducing tissue damage with light following administration of a light-activated photosensitizing drug, which in the presence of oxygen, produce cytotoxic species. 5-Aminolevulinic acid is the precursor of the photosensitizer Protoporphyrin IX, and (ALA)-mediated PDT (ALA-PDT) is one of the most widely employed PDT techniques. Hydrogen sulfide (H2S) has been recognized as an important signalling molecule, contributing to many physiological and pathological processes. It is proposed to be one of the so-called ?gasotransmitters? along with nitric oxide (NO) and carbon monoxide. Gasotransmitters exist as gases, are freely membrane permeable, are endogenously and enzymatically generated and have defined functions at physiological concentrations. In addition, these gasotransmitters have been recognized as toxic gases.The aim of this work was to study the impact of H2S on the outcome of ALA-PDT. We employed the LM3 and LM2 mammary adenocarcinoma cell lines. The first line is NO producer whereas the second is non NO producer. Exposure of the cells to NaHS, which is a H2S donor, was non toxic in the concentration range employed (0.05-10 mM) in both cell lines. We performed ALA-PDT under the following conditions: cells were exposed 3 h to 1 mM ALA and illuminated with different light doses.In LM3 cells, previous exposure to NaHS did not modify the outcome of ALA-PDT in all the concentration range. On the other hand, exposure of LM2 cells to increasing NaHS concentrations higher than 0.5 mM NaHS, gradually prevented cell death induced by ALA-PDT and complete abrogation of the PDT effect was obtained employing 1 mM.We determined the intracellular endogenous H2S levels synthesised from L-cysteine and observed that LM2 produce higher levels than LM3 cells.By means of a singlet oxygen probe we demostrated that NaHS significantly decreases the in vitro production of singlet oxygen upon illumination of a porphyrin photosensitizer, thus showing that H2S modulates the cellular response to PDT by inhibiting reactive oxygen species production.