Intracellular reactive oxygen species in monocytes generated by photosensitive chromophores activated with blue light.
OBJECTIVE
Disinfection of the tooth pulp-canal system is imperative to successful endodontic therapy. Yet, studies suggest that 30-50% of current endodontic treatments fail from residual bacterial infection. Photodynamic therapy using red-light chromophores (630 nm) to induce antimicrobial death mediated by generated reactive oxygen species (ROS) has been reported, but red-light also may thermally damage resident tissues. In the current study, we tested the hypothesis that several blue light chromophores (380-500 nm) generate intracellular reactive oxygen species but are not cytotoxic to mammalian cells.


METHODS
THP1 monocytes were exposed to 10 microM of four chromophores (chlorin e6, pheophorbide-a, pheophorbide-a-PLL, and riboflavin) for 30 min before activation with blue light (27J/cm(2), 60s). After activation, intracellular ROS were measured using a dihydrofluorescein diacetate technique, and cytotoxicity was determined by measuring mitochondrial activity with the MTT method.


RESULTS
All photosensitizers produced intracellular ROS levels that were dependent on both the presence of the photosensitizer and blue light exposure. Riboflavin and pheophorbide-a-PLL produced the highest levels of ROS. Photosensitizers except riboflavin exhibited cytotoxicity above 10 microM, and all except pheophorbide-a-PLL were more cytotoxic after blue light irradiation.


CONCLUSIONS
The current study demonstrated the possible utility of blue light chromophores as producers of ROS that would be useful for endodontic disinfection.
Bouillaguet
Serge
S
Endodontics Unit, Section of Dental Medicine, University of Geneva, 19 rue B. Menn, 1205 Geneva, Switzerland. Serge.bouillaguet@medecine.unige.ch
Owen
Brandi
B
Wataha
John C
JC
Campo
Marino A
MA
Lange
Norbert
N
Schrenzel
Jacques
J
D002460:Cell Line; D002734:Chlorophyll / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D002735:Chlorophyllides; D004396:Coloring Agents; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006801:Humans; D008027:Light; D008928:Mitochondria / Q000187:drug effects; D009000:Monocytes / Q000187:drug effects*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000494:pharmacology; D011107:Polylysine / Q000008:administration & dosage / Q000494:pharmacology; D011166:Porphyrins / Q000008:administration & dosage / Q000494:pharmacology; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012256:Riboflavin / Q000008:administration & dosage / Q000494:pharmacology; D013385:Succinate Dehydrogenase / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles
D002735:Chlorophyllides; D004396:Coloring Agents; D005452:Fluoresceins; D005456:Fluorescent Dyes; D017319:Photosensitizing Agents; D011166:Porphyrins; D011838:Radiation-Sensitizing Agents; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts; D013844:Thiazoles; C110423:dihydrofluorescein; D002734:Chlorophyll; D011107:Polylysine; C062985:phytochlorin; D013385:Succinate Dehydrogenase; C022616:thiazolyl blue; C032623:pheophorbide a; D012256:Riboflavin