Porphyrin synthesis from aminolevulinic acid esters in endothelial cells and its role in photodynamic therapy.
Photodynamic therapy (PDT) may cause tumour cell destruction by direct toxicity or by inducing microcirculatory shutdown. Protoporphyrin IX generated from 5-aminolevulinic acid (ALA) has been widely used as an endogenous photosensitiser in PDT. However, the hydrophilic nature of the ALA molecule limits its penetration through the stratum corneum of the skin and cell membranes and thus, ALA alkyl-esters have been developed to improve ALA permeation. The aim of this work was to study Protoporphyrin IX synthesis from ALA and its derivatives ALA methyl ester (Me-ALA) and ALA hexyl ester (He-ALA) in the microvascular endothelial cell line HMEC-1 derived from normal skin, and to evaluate their response to PDT. We found that lower light doses are required to photosensitise HMEC-1 endothelial cells than to photosensitise PAM212 transformed keratinocytes, showing some possible selectivity of ALA-PDT for vascularisation in skin. Employed at concentrations leading to equal Protoporphyrin IX synthesis, ALA, He-ALA and Me-ALA presented the same efficacy of HMEC-1 photosensitisation. However, He-ALA was a promising compound for the use in the enhancement of Protoporphyrin IX in HMEC-1 cells employed at low concentrations at both short and long time exposures whereas Me-ALA should be employed at high concentrations and longer time periods in order to surpass the Protoporphyrin IX levels obtained with ALA. The advantage of Me-ALA over ALA was based on its lower dark toxicity. This is the first work to report vascular cell photosensitisation employing alkyl-esters of ALA, and we demonstrated that these derivatives could exert the same effect as ALA and under certain conditions enhance photosensitisation of vasculature.
Rodriguez
Lorena
L
Centro de Investigaciones sobre Porfirinas y Porfirias (CIPYP), CONICET and Hospital de Clínicas José de San Martín, University of Buenos Aires, Córdoba 2351 1er subsuelo, Ciudad de Buenos Aires, CP 1120AAF, Argentina.
de Bruijn
Henriëtte S
HS
Di Venosa
Gabriela
G
Mamone
Leandro
L
Robinson
Dominic J
DJ
Juarranz
Angeles
A
Batlle
Alcira
A
Casas
Adriana
A
D000622:Aminolevulinic Acid / Q000031:analogs & derivatives* / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D042783:Endothelial Cells / Q000378:metabolism* / Q000528:radiation effects; D006801:Humans; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000378:metabolism*; D011524:Protoporphyrins / Q000096:biosynthesis* / Q000502:physiology; D014466:Ultraviolet Rays
D017319:Photosensitizing Agents; D011524:Protoporphyrins; C114767:delta-aminolevulinic acid methyl ester; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX