Protoporphyrin IX fluorescence kinetics in UV-induced tumours and normal skin of hairless mice after topical application of 5-aminolevulinic acid methyl ester.
Accumulation of protoporphyrin IX (PpIX) was investigated in normal skin and UV-induced tumours in hairless mice after topical application of a cream containing 2, 8 or 16% of 5-aminolevulinic acid methyl ester (ALA-Me). Higher levels of PpIX were measured in tumours compared to normal skin. The maximal amount of PpIX was reached at 1.5, 3 and 4 h after 2, 8 and 16% ALA-Me application, respectively. Higher tumour to normal skin PpIX fluorescence ratios were measured after application of 8 and 16% ALA-Me than after application of 2%. After irradiation with a broad spectrum of visible light from a slide projector, more than 90% of PpIX was bleached by fluences of 36 and 48 J/cm2, at fluence rates of 10 and 40 mW/cm2 respectively. At these fluences, the PpIX photobleaching rate was significantly higher (P<0.05) in normal mouse skin than in tumours. In addition, for a given fluence, more PpIX was photobleached at the lower fluence rate (10 mW/cm2) than at the higher fluence rate (40 mW/cm2) in normal skin (P<0.001) as well as in tumours (P<0.05) after exposure to 24 J/cm2 of light. In conclusion, the highest tumour to normal skin PpIX ratio was observed 3 h after application of 8% ALA-Me, suggesting that light exposure should be performed at this time in order to achieve an optimal PDT effect in this tumour model.
Juzenas
Petras
P
Division of Dermatology, Notre-Dame Hospital, Montreal University Hospital Center, 1560 Sherbrooke Street East, Rm. K-5201, Québec, H2L 4M1, Montreal, Canada.
Sharfaei
Soraya
S
Moan
Johan
J
Bissonnette
Robert
R
D000287:Administration, Topical; D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000009:adverse effects* / Q000031:analogs & derivatives*; D000818:Animals; D005260:Female; D005453:Fluorescence; D007700:Kinetics; D051379:Mice; D008812:Mice, Hairless; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000009:adverse effects*; D011524:Protoporphyrins / Q000378:metabolism*; D012867:Skin / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D012878:Skin Neoplasms / Q000378:metabolism*; D014466:Ultraviolet Rays
D017319:Photosensitizing Agents; D011524:Protoporphyrins; C114767:delta-aminolevulinic acid methyl ester; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX