Chlorin E6 Sound Dynamic Effects Of H-22 Tumor-bearing Mice

While Sonodynamic therapy (SDT) has been recognized as a promising therapeutic modality for the treatment of various cancers and diseases, developments of effective sonosensitizers are highly desired to improve the prospect for the use of SDT. In this study, we evaluated chlorin-e6 (Ce6), a new sonosensitizer, for anti-tumor SDT in vivo. Then, the biological mechanism of antitumor effect by Ce6-mediated SDT was discussed.In order to investigate the distribution and phamacokinetics of the sonosensitizer in Hepatoma-22 tumor-bearing female ICR mice after Ce6 intravenously injection, Fluorescence Spectrophotometry was used to analysis the distribution of Ce6 in plasma and tissues. To further characterize the distribution of Ce6 in H-22 tumor in vivo, the phamacokinetics of Ce6 was assessed by using a three-dimensional optical imaging system (1VIS spectrum) 0-24 hours after administration of Ce6 via the tail vein. Effectiveness of Ce6-mediated SDT was examined on Hepatoma-22 xenografts established subcutaneously in ICR mice. Anti-tumor effects were estimated by measuring tumor size. The levels of lipid peroxidation (MDA) and oxidative stress were assessed by measuring the activities of key antioxidant enzymes (ie, Superoxide dismutase[SOD], Glutathione peroxidase [GSH-PX], Catalase [CAT]) in H-22 tumor after SDT. The present experimental conclusions obtained are as follows:1. The results of pharmacokinetic study of Ce6 in Hepatoma-22 tumor-bearing mice indicated that the metabolism and distribution of Ce6 in tumors and other tissues was time-dependent, the drugs quickly metabolited into tissues within 2 hours after intravenous injection. Similar phamacokinetic trends of Ce6 in skin and muscle of the two kinds of tumor-bearing mice were observed, the drugs clearance rate from the two tissues was faster than other tissues. But from the metabolic trends of Ce6 in the solid tumor tissues, we can see that the clearance of Ce6 from tumor tissues were very slow, conforming the selective distribution of Ce6 in tumor tissues.2. The results of pharmacoskinetic study of Ce6 in Hepatoma-22 tumor-bearing mice by using in vivo optical imaging indicated that:fluorescence was not observed in the whole body of mice before Ce6 administration, weak fluorescence could be detected in tumor after Ce6 administration, and the tumor tissue could be distinguished from surrounding tissues according to the number of fluorescent photons. The anti-cancer drug targeted the tumor in a very short time, as the tumor uptake reached a maximum at 2 hours pi, remaining in the tumor for a long time, and washed out over time very slowly. This perfectly matched with the result of Fluorescence Spectrophotometry of the tumor.3. The results of in vivo imaging of some tissues of H-22 tumor-bearing mice after 4h administration of Ce6 indicated that:the fluorescent photons in tumor was the highest, then followed by liver, intestine, skin, stomach, kidney, heart, muscle, brain and spleen. Based on the phamacokinetics results of Ce6 detected by both Fluorescence Spectrophotometry and Bio-optical Imaging,4 h drug-ultrasound interval was selected in our experiment considering both the sonosensitizer concentration in tumor for sonodynamic treatmeat and minimal side effect to normal tissues, so that this can ensure the best anti-tumor efficacy of Ce6 mediated SDT.4. The results of anti-tumor effects caused by different parameters(drug dose and ultrasound intensity) revealed a strong dependence on the drug dosages as well as on the intensity of ultrasound. At an ultrasound intensity≥4 W/cm2 and a Ce6 dose≥10 mg/kg, a significant synergistic effect of ultrasound combined with Ce6 was observed, reducing tumor volume significantly; this synergistic effect was obviously stronger than ultrasound treatment alone, while Ce6 alone showed no significant effect.5. The results of biological mechanism of anti-tumor by Ce6 mediated SDT showed that the content of MDA significantly increased after treatment, while the activities of key antioxidant enzymes (SOD, GSH-Px and CAT) in tumor cells all decreased at different levels. Oxygen free radical may play an important role in improving the membrane lipid peroxidation, decrasing the activities of key antioxidant enzymes in cells, and the biological mechanism might be involved in mediating the killing effect of S180 cells in SDT.Optical imaging of tumors in mice offer a simple, effective, and rapid technique for noninvasive in vivo monitoring phamacokinetics of the sonosensitizer in tumor-bearing mice. Ce6 are a potential sonosensitizer for fluorescence imaging as well as for sonodynamic therapy for cancer. The antitumor effect of ultrasound could be enhanced in the presence of Ce6 which might be involved in a sonochemical mechanism. The activation of the sonotosensitizer through acoustic cavitation by ultrasound leads to conversion of molecular oxygen to various highly reactive oxygen species (ROS), which kills tumor cells directly or damages the tumor-associated vasculature.