Mechanisms involved in the photosensitized inactivation of Acanthamoeba palestinensis trophozoites.
OBJECTIVE
To advance our understanding of the mechanisms involved in the RLP068 phthalocyanine-photosensitized inactivation of Acanthamoeba palestinensis trophozoites through a precise identification of the targets of the photoprocess in both the cytosolic and mitochondrial compartments.


RESULTS
We followed the activities of selected marker enzymes as well as we performed fluorescence and transmission electron microscopy investigations of the alterations induced by the photoprocess in the fine structure of subcellular compartments. RLP068 is preferentially located in the contractile vacuole: the fluorescence in that site is particularly evident in the unirradiated cells and becomes more diffused after irradiation. Electron microscopic analysis of photosensitized A. palestinensis cells clearly shows that the swelling of trophozoites and the appearance of vacuoles spread throughout the cytoplasm after phototreatment. The activity of a typical cytoplasmic enzyme, such as lactate dehydrogenase, underwent a 35% decrease as a consequence of the photoprocess, reflecting the photodamage induced by migrating phthalocyanine molecules in their micro-environment.


CONCLUSIONS
The presence of multiple targets for the phthalocyanine-photosensitized process is of utmost importance because this pattern of cell damage makes it unlikely that photoresistant A. palestinensis strains are gradually selected or mutagenic phenomena are developed as a consequence of the photoinduced damage.


CONCLUSIONS
Photosensitization via phthalocyanines appears to represent an efficient and safe approach for achieving a close control of the population of a potentially pathogenic protozoan such as A. palestinensis, opening new perspectives for the disinfection of microbiologically polluted waters.
Ferro
S
S
Department of Biology, University of Padova, Padova, Italy.
Guidolin
L
L
Tognon
G
G
Jori
G
G
Coppellotti
O
O
D000048:Acanthamoeba / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D053148:Caspase 3 / Q000032:analysis; D007211:Indoles / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D019344:Lactic Acid / Q000032:analysis; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000528:radiation effects; D009942:Organometallic Compounds / Q000494:pharmacology*; D010778:Photochemotherapy / Q000379:methods; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013053:Spectrophotometry; D019802:Succinic Acid / Q000032:analysis; D053058:Trophozoites / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects
D007211:Indoles; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; C477806:RLP068; D019344:Lactic Acid; D019802:Succinic Acid; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3