Photodynamic and light independent action of 8 to 2 carboxylic free porphyrins on some haem-enzymes

Effects on gram-negative and gram-positive bacteria mediated by 5-aminolevulinic Acid and 5-aminolevulinic acid derivatives

Due mainly to the extensive use of antibiotics, the spread of multiresistant bacterial strains is one of the most worrying threats to public health. One strategy that can be used to overcome potential shortcomings might be the inactivation of these microorganisms by 5-aminolevulinic acid (5-ALA) or 5-ALA derivative-mediated photodynamic therapy (PDT). 5-ALA has no photoactive properties, but when it is given exogenously, it acts as a precursor of photosensitive porphyrins predominantly in tissues or organisms that are characterized by a high metabolic turnover, such as tumors, macrophages, and bacteria. However, the weak ability of 5-ALA to cross biological barriers has led to the introduction of more lipophilic derivatives, such as methyl aminolevulinate or hexyl aminolevulinate, which display improved capacities to reach the cytoplasm. Starting from the hypothesis that more lipophilic compounds carrying only a permanent positive charge under physiological conditions may more easily cross the bacterial multilayer barrier, we have tested the efficacies of some 5-ALA n-alkyl esters for the inactivation of bacteria. For this purpose, different bacterial strains were incubated with 5-ALA or its corresponding esters of different lipophilicities. Then, the bacteria were irradiated with light and the numbers of CFU post-PDT were counted and compared to those for the controls, which were kept in the dark. Furthermore, the total amount of accumulated porphyrins was quantified by high-pressure liquid chromatography analysis. In our studies, analysis of the bacterial extracts revealed the presence of all the porphyrins involved in heme biosynthesis, from uroporphyrin to protoporphyin IX. The efficacy of bacterial inactivation was a function of the total amount of porphyrins produced, independently of their nature. The 5-ALA methyl and butyl esters were the most effective compounds with respect to the photodynamic inactivation of bacteria. We observed significant differences in terms of the optimal drug concentration, bactericidal activities, and porphyrin production.

Meso-substituted tetra-cationic porphyrins photosensitize the death of human fibrosarcoma cells via lysosomal targeting

In this paper we present a study on the intracellular localisation and the efficiency of cell photoinactivation of a series of derivatives of 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphine (C1), whose degree of lipophilicity was varied through replacement of one methyl group with an alkyl chain of various length. Human HT1080 fibrosarcoma cells exposed to the various C1 derivatives (0.25 microM) for 24 h and irradiated with increasing doses of red-light (0.45-27 J/cm2) were inactivated with different efficiencies. The efficiency of cell photoinactivation increased with the increasing length of the hydrocarbon tail and lipophilicity and correlated with the efficiency of the porphyrin accumulation into the cells. Despite the presence of positive charges, these porphyrins did localise rather selectively in lysosomes while mitochondrial localisation was not evident, as demonstrated by fluorescence microscopy studies. Studies on isolated mitochondria provided evidence that the porphyrin uptake and distribution in these organelles were not modulated by the transmembrane potential but were exclusively controlled by partitioning phenomena which might have prevented mitochondria localization in whole cells. Our findings demonstrated that these porphyrins entered the cells through the endocytotic pathway and were transported to lysosomes whose pH increased rapidly upon irradiation. Lysosomal damage did not cause any intracellular redistribution of the porphyrin and represented the primary event causing cell death, very likely via necrosis.

Photoreaction generating active oxygens of In(3+)-tetrakis(4-methylpyridyl)-porphine in the presence of albumins

The complex formation of In(3+)-tetrakis(4-N-methylpyridyl)-porphine (In-TMPyP) with albumin was studied by resonance Raman spectroscopy. Albumin coordinated to In(3+) through the -S(-) group(s). The photoreaction was investigated using the visible spectral change and In-TMPyP-thiourea complex was used as a model. It was demonstrated that the complex in a weak basic solution (pH 8.5) is excited by light and the excited complex converts oxygen to superoxide anion, which finally cleavages the porphine ring of In-TMPyP.