Ethylene Glycol and Amino Acid Derivatives of 5-Aminolevulinic Acid as New Photosensitizing Precursors of Protoporphyrin IX in Cells

Abstract

Protoporphyrin IX (PpIX) is used as a photosensitizing agent in photodynamic detection and therapy (PDT) of cancer and is synthesized intracellularly from aminolevulinic acid (ALA) precursors. To evaluate means to specifically target ALA derivatives to defined cells, we have synthesized and characterized ethylene glycol esters and amino acid pseudodipeptide derivatives of ALA as potential specific substrates for cellular esterases and aminopeptidases, respectively. The PpIX formation induced by these products was investigated using cultures of human and rat cell lines of carcinoma and endothelial origins. The cytotoxicity of these compounds in the absence of light was also controlled. The results have shown that ethylenglycol esters can induce high levels of PpIX and are useful at concentrations below their cytotoxicity threshold. From the ALA-amino acid derivatives which were evaluated, the highest PpIX production was obtained using ALA derivatives of neutral amino acids, as compared to acidic or basic amino acids.

Protoporphyrin IX enhancement by 5-aminolaevulinic acid peptide derivatives and the effect of RNA silencing on intracellular metabolism

“…This problem has partly been addressed through the synthesis of lipophilic ester prodrugs that provide improved cellular uptake and are metabolised into PpIX following the action of nonspecific intracellular esterases (Lopez et al, 2004). A more recent development concerns the preparation of peptide-based ALA prodrugs, and we (Casas et al, 1999;Rogers et al, 2005) and others (Berger et al, 2000(Berger et al, , 2003 have described the synthesis and evaluation of short ALA peptide derivatives in which either the amino or the carboxyl functions of the latter are masked, thereby providing improved physical properties and the potential for cell line-specific ALA release, according to which peptidases are expressed. We have shown earlier the feasibility of using L-phenylalanyl-ALA derivatives (Bourré et al, 2008) to enhance intracellular porphyrin production and improve the efficacy of photodynamic treatment.…”

“…In conclusion, the nature of the N terminus appears to play an important role in the efficacy of these compounds, which indicates that the release of the substituted amino acid intracellularly is probably conditioned by a specific enzymatic activity. Berger et al (2000) have described the evaluation of several L-amino-acid ALA derivatives and their PpIX production in different cell lines (rat endothelial EC212, human endothelial HCEC and lung carcinoma A549 cells). Included in this study was compound 8, which showed high yields of PpIX in all cell lines compared with other neutral and charged amino-acid derivatives investigated.…”

“…To overcome this problem, several chemical approaches have been attempted to improve the incorporation of ALA and also its selectivity. One approach has been to use more lipophilic ALA derivatives, such as alkyl or ethyleneglycol esters, which are potential substrates for cellular esterases (Kloek and Beijersbergen, 1996;Gaullier et al, 1997;Berger et al, 2000;Uehlinger et al, 2000), or different delivery systems including dendrimers (Battah et al, 2001Di Venosa et al, 2006), or liposomes (Casas et al, 2002;Casas and Batlle, 2006). 5-Aminolaevulinic acid prodrug ester derivatives have been widely studied (Kloek and Beijersbergen, 1996;Peng et al, 1996;Gaullier et al, 1997;Kloek et al, 1998;Casas et al, 1999;Eleouet et al, 2000;Brunner et al, 2003;Lopez et al, 2004), in particular the methyl and hexyl ester derivatives, and approval has been granted for the treatment of actinic keratosis and basal cell carcinoma using the methyl ester derivative in Europe and Australia.…”

“…The use of alkyl esters of ALA results in a nonspecific distribution of ALA in all cell types, but with an increased PpIX production (Webber et al, 1997;Uehlinger et al, 2000) in tumour cells. In this regard, Casas et al (1999) and Berger et al (2000Berger et al ( , 2003 have conjectured that the incorporation of 5-ALA into a short peptide derivative would provide a suitable means of both facilitating transdermal delivery and also improved targeting to cancerous cells.…”

Inativação fotodinâmica de microrganismos

“…Embora formação altamente regulada de protoporfirina IX (PpIX) exista em quase todas as células nucleadas, PpIX acumula preferencialmente em tecidos com alta atividade celular 52 . PpIX pode ser sintetizada em todas as células contendo mitocôndria 53 .…”