[Endogenous porphyrins for photodynamic therapy of cataracts in vitro].
Photodynamic therapy is based on accumulation of a photosensitizing substance in tissues and excitement by light of a suitable wavelength. Because of high levels of locally absorbed energy this process may also enable the selective destruction of proliferating lens epithelial cells. Delta-aminolaevulinic acid (ALA) is a natural precursor of hemoglobin. An accumulation of porphyrin derivates occurs following ingestion of ALA, of which one, protoporphyrin IX (P IX), is a potent photosensitizer.


METHODS
Bovine lens epithelial cells were removed from the anterior lens capsule and cultivated in Waymouth/Ham's F12 (1:2) with 10% serum. Cells of an epithelial tumor cell line were cultivated. Cultures were incubated with various concentrations of ALA and irradiated with an argon-pulsed dye laser (630 nm).


RESULTS
Fluorescence typical for porphyrin was detectable following incubation with 200 micrograms/ml ALA. Irradiation of such cultures with 10 J/cm2 resulted in death of the cells; 75% of the cells were lethally damaged at 3 J/cm2. Addition of P IX to the medium at a concentration of 50 micrograms/ml resulted in cell death at the low energy of 1 J/cm2. No lethal effect was observed following laser treatment without addition of ALA or P IX.


CONCLUSIONS
Our results show for the first time that photodynamic destruction of lens epithelial cells can be achieved by a photosensitizer, which is the product of cellular metabolism.
Joussen
A M
AM
Augenklinik, Universität Heidelberg.
Kruse
F E
FE
Kaus
M
M
Völcker
H E
HE
D000622:Aminolevulinic Acid / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D002460:Cell Line; D004848:Epithelium / Q000187:drug effects / Q000473:pathology; D006414:Hematoporphyrin Photoradiation; D066298:In Vitro Techniques; D007908:Lens, Crystalline / Q000187:drug effects* / Q000473:pathology; D008858:Microscopy, Phase-Contrast; D011166:Porphyrins / Q000378:metabolism
D011166:Porphyrins; D000622:Aminolevulinic Acid