Regulation of 5-aminolevulinic acid-mediated protoporphyrin IX accumulation in human urothelial carcinomas.

Abstract

PURPOSE:

The purpose of this study was to clarify the regulatory mechanism of protoporphyrin IX (PpIX) synthesis mediated by 5-aminolevulinic acid (ALA) in human urothelial carcinoma (UC), leading to improved accuracy in photodynamic diagnosis and therapy using ALA.

EXPERIMENTAL DESIGN:

PpIX accumulation in cultured UC cells after incubation for 1-5 h with 0.5-5 mM ALA was analyzed by fluorescence analysis using fluorescence microscopy and flow cytometry technique.

RESULTS:

PpIX fluorescence mediated by ALA was increased, and the intensity of PpIX fluorescence was time-dependently increased in UC cells compared to noncancerous cells. The distribution of endogenous PpIX fluorescence primarily coincided with mitochondria, and then increased at a specific perinuclear region in the cells during the time of incubation. The ALA-mediated PpIX synthesis in UC cells was suppressed by beta-alanine, an inhibitor of beta-transporters of cell membrane, and carbonylcyanide p-trifluoromethoxyphenyl hydrazone, an uncoupler of mitochondrial oxidative phosphorylation. In contrast, the ALA-mediated PpIX accumulation was increased by deferoxamine, an iron chelator, manganese and nitric oxide, which is contributed to PpIX metabolism by inhibiting ferrochelatase activity, generated by a nitric oxide-generating reagent NOC-18. As observed above, ALA-mediated PpIX synthesis in human UC cells was regulated by the process of ALA uptake, ALA conversion to PpIX and metabolism of accumulated PpIX to heme.

CONCLUSIONS:

This shows that the suppression of ferrochelatase increased PpIX accumulation in UC cells using small amount of ALA, thus leading to an improved clinical practicability of photodynamic diagnosis and therapy.

• Authors: Keiji Inoue, Takashi Karashima, Masayuki Kamada, Taro Shuin, Atsushi Kurabayashi, Mutsuo Furihata, Hirofumi Fujita, Kozo Utsumi, Junzo Sasaki
• Journal: Pathobiology : journal of immunopathology, molecular and cellular biology (Pathobiology) Vol. 76 Issue 6 Pg. 303-14 ( 2009) ISSN: 1423-0291 [Electronic] Switzerland
• PMID: 19955842 (Publication Type: Journal Article)
• Copyright: Copyright 2009 S. Karger AG, Basel.

Chemical References

• NOC 18
• Nitroso Compounds
• Photosensitizing Agents
• Protoporphyrins
• beta-Alanine
• Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone
• Aminolevulinic Acid
• protoporphyrin IX
• Ferrochelatase
• Deferoxamine

Topics

• Aminolevulinic Acid (pharmacology)
• Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone (pharmacology)
• Carcinoma, Transitional Cell (drug therapy, metabolism)
• Cell Line, Tumor
• Deferoxamine (pharmacology)
• Ferrochelatase (antagonists & inhibitors, metabolism)
• Flow Cytometry
• Humans
• Microscopy, Fluorescence
• Mitochondria (drug effects, metabolism)
• Nitroso Compounds (pharmacology)
• Oxidative Phosphorylation (drug effects)
• Photosensitizing Agents (pharmacology)
• Protoporphyrins (biosynthesis)
• Time Factors
• Urinary Bladder Neoplasms (drug therapy, metabolism)
• Urothelium (drug effects, metabolism)
• beta-Alanine (pharmacology)