The Studies of Photodynamic Activities and Pharmacokinetics of Pheophytin a in 4T1 Tumor-bearing Mice

• Main Authors: Jheng-Huan Yeh, 葉政瓛
• Other Authors: Wen-Tyng Li
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/31792399092462697622

碩士 === 中原大學 === 生物醫學工程研究所 === 100 === Photodynamic therapy (PDT) is an alternative modality for cancer treatment. Tumor site is damaged by cytototoxic reactive oxygen species (ROS) produced by the activated photosensitizer selectively accumulated in cancerous cells and specific tissues after light irradiation with specific excitation wavelength. The aim of this study was to the efficacies of pheophytin mediated PDT combined with 660 nm light emitting diodes (LEDs) against murine mammary gland adenocarcinoma 4T1 cells and 4T1 tumor bearing Balb/c mice. First of all, the maximal concentration of pheophytin a in 4T1 cells was found 2 hrs after incubation with the photosensitizer. Cell viability decreased as the photosensitizer concentration, incubation time and light dose increased. When incubated with pheophytin a for 2 hrs, half lethal dose (LD50) for 4T1 cells was 459.3 ± 28.9 ng/mL with 2.55 J/cm2 irradiation and 320.2 ± 23.3 ng/mL with 5.10 J/cm2 irradiation. For pheophytin b, LD50 was 303.8 ± 25.1 and 226.7 ± 5.4 ng/mL with 2.55 and 5.10 J/cm2 irradiation, respectively. TUNEL assay revealed that the percentage of apoptotic cells increased as the increase of incubation time with pheophytin a. Acute toxicity was studied in mice with single dose injection of 87.25 mg/kg pheophytin a. It was found that bodyweight of mice did not decline and no major organs damage was observed in tissue section within 14 days post photosensitizer administration. No subacute toxicity was seen in 4T1 tumor bearing mice after daily injection of 2 mg/kg pheophytin a. Biodistribution of pheophytin a in normal and 4T1 tumor bearing mice were analyzed after intravenous injection through the tail vein. At 4 hr post-injection, pheophytin a accumulated most in the liver of the normal mice, whereas it accumulated most at tumor site of tumor bearing mice. Tumor growth was inhibited in 4T1 tumor-bearing mice with daily intravenous injection of pheophytin a at the concentration of 2 mg/kg and light dose of 10.2 J/cm2. Histochemical staining further showed that more apoptotic cells and more tumor tissue damage post-PDT. To sum up, this study demonstrated that pheophytin a is selectively accumulated in tumor tissue, possesses phototoxicity against urine mammary gland adenocarcinoma 4T1 cells, and effectively inhibits tumor growth when combined with red light irradiation.