Monitoring of singlet oxygen is useful for predicting the photodynamic effects in the treatment for experimental glioma.
OBJECTIVE
Singlet oxygen ((1)O(2)) generated in photodynamic therapy (PDT) plays a very important role in killing tumor cells. Using a new near-IR photomultiplier tube system, we monitored the real-time production of (1)O(2) during PDT and thus investigated the relationship between the (1)O(2) production and photodynamic effects.


METHODS
We did PDT in 9L gliosarcoma cells in vitro and in an experimental tumor model in vivo using 5-aminolevulinic acid and nanosecond-pulsed dye laser. During this time, we monitored (1)O(2) using this system. Moreover, based on the (1)O(2) monitoring, we set the different conditions of laser exposure and investigated whether they could affect the tumor cell death.


RESULTS
We could observe the temporal changes of (1)O(2) production during PDT in detail. At a low fluence rate the (1)O(2) signal gradually decreased with a low peak, whereas at a high fluence rate it decreased immediately with a high peak. Consequently, the cumulative (1)O(2) at a low fluence rate was higher, which thus induced a strong photodynamic effect. The proportion of apoptosis to necrosis might therefore be dependent on the peak and duration of the (1)O(2) signal. A low fluence rate tended to induce apoptotic change, whereas a high fluence rate tended to induce necrotic change.


CONCLUSIONS
The results of this study suggested that the monitoring of (1)O(2) enables us to predict the photodynamic effect, allowing us to select the optimal laser conditions for each patient.
Yamamoto
Junkoh
J
Department of Neurosurgery and Photon Medical Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan.
Yamamoto
Seiji
S
Hirano
Toru
T
Li
Shaoyi
S
Koide
Masayo
M
Kohno
Eiji
E
Okada
Mitsuo
M
Inenaga
Chikanori
C
Tokuyama
Tsutomu
T
Yokota
Naoki
N
Terakawa
Susumu
S
Namba
Hiroki
H
D000818:Animals; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D004354:Drug Screening Assays, Antitumor; D005910:Glioma / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D010778:Photochemotherapy / Q000295:instrumentation / Q000379:methods*; D017319:Photosensitizing Agents / Q000737:chemistry / Q000627:therapeutic use*; D011237:Predictive Value of Tests; D051381:Rats; D011916:Rats, Inbred F344; D026082:Singlet Oxygen / Q000032:analysis* / Q000378:metabolism; D013329:Structure-Activity Relationship; D016896:Treatment Outcome
D017319:Photosensitizing Agents; D026082:Singlet Oxygen