title: Photosensitization of isolated rat liver mitochondria by tetra(m-hydroxyphenyl)chlorin.
abstract: Tetra(m-hydroxyphenyl)chlorin (mTHPC) is used as a photosensitizer in photodynamic therapy (PDT), a novel modality for cancer treatment. Since little is known about mTHPC-mediated damage in vitro, we chose isolated rat liver mitochondria as a model system to study its photodynamic effects. Incubation of isolated mitochondria with mTHPC plus irradiation with light of a wavelength of 652 nm resulted in protein oxidation and lipid peroxidation, as measured by the mitochondrial content of carbonyl groups and thiobarbituric acid-reactive substances, respectively. Type I and type II photochemical reactions contribute to this oxidative damage as shown by the use of scavengers. Photodynamically treated mitochondria had a reduced membrane potential, and their Ca2+ uptake was impaired. Oxygen consumption of complex I of the respiratory chain was stimulated at a low concentration of mTHPC plus irradiation, but decreased at higher concentrations, whereas oxygen consumption at complex II and IV decreased with all mTHPC concentrations offered. No mitochondrial changes were seen with mTHPC in the absence of irradiation. Our results confirm the sensitivity of mitochondria to PDT and may help to understand the mechanisms by which PDT using mTHPC kills cells.
authors.affiliation: Department of Gynecology and Obstetrics, University Hospital, Zurich, Switzerland.
authors.forename: S D
authors.initials: SD
authors.lastname: Klein
authors.forename: H
authors.initials: H
authors.lastname: Walt
authors.forename: C
authors.initials: C
authors.lastname: Richter
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005260:Female; D016166:Free Radical Scavengers / Q000378:metabolism; D007834:Lasers; D008027:Light; D015227:Lipid Peroxidation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008652:Mesoporphyrins / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013053:Spectrophotometry; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D008652:Mesoporphyrins; D017319:Photosensitizing Agents; D017392:Thiobarbituric Acid Reactive Substances; D000244:Adenosine Diphosphate; C072269:temoporfin; D002118:Calcium