Photodynamic activity of aluminium (III) and zinc (II) phthalocyanines in Leishmania promastigotes

Abstract

Introduction. Photodynamic therapy is a two-step procedure, involving the use ofphotosensitizing agents followed by selective illumination of the target lesion with visible light.It produces highly reactive oxygen species and subsequent cellular damage.

Objective. This study was designed to determine whether Leishmania chagasi and L.panamensis promastigotes were sensitive to photodynamic therapy in vitro.

Material and methods. Leishmania promastigotes were treated with aluminium phthalocyaninechloride and zinc phthalocyanine photosensitizers before illumination with visible light at 670nm. The parasite photoactivity was calculated by sigmoidal regression analysis.

Results. Leishmania chagasi promastigotes were highly photosensitive to aluminiumphthalocyanine chloride treatment with effective inhibitory dose50 (ED50) concentration values of0.0033, 0.0083 and 0.0093 μM upon exposure to 10.0, 5.0, and 2.5 J/cm2 light intensitiesrespectively. By contrast, the activity of aluminium phthalocyanine chloride on L. panamensiswas significantly lower (P<0.01) with ED50 values of 0.17, 0.25, 0.34 μM at the same lightintensities. Zinc phthalocyanine activity was significantly (P<0.01) less active than aluminiumphthalocyanine chloride on both strains of these two species and no differences in zincphthalocyanine activity were found between them. A dose-response phototoxic effect with bothphthalocyanines was observed. Parasite inhibition was not observed after aluminiumphthalocyanine chloride or zinc phthalocyanine treatment in the dark. The reference drugshexadecylphosphocholine and amphotericin B were not photoactive.

Conclusion. Treatment of Leishmania promastigotes with aluminium phthalocyanine chlorideand zinc phthalocyanine followed by illumination with visible light at 670 nm inhibited in vitrogrowth of promastigotes of L. chagasi and L. panamensis. Photodynamic therapy againstLeishmania could be a promising strategy for leishmaniasis treatment.