Effects of Brain-derived Neurotrophic Factor and Free Radical on the Retinal Ganglion Cell in Rats with Experimental Glaucoma

• Main Authors: Lany Mei Lan Ko, 柯美蘭
• Other Authors: 陳朝峰
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/19130819757218592097

博士 === 國立臺灣大學 === 生理學研究所 === 89 === We investigated the effect of brain-derived neurotrophic factor (BDNF) and free radical on retinal ganglion cell (RGC) after elevation of intraocular pressure (IOP). The whole experiment was divided into three parts. The first part was survival patterns of retinal ganglion cell after BDNF administration in hypertensive eyes of rats. The second part was the combined effect of BDNF and a free radical scavenger in the experimental glaucoma. The third part was the studies of superoxide anion activity in the retina of the experimental glaucoma. In adult Wistar rats, RGCs were labeled with 5% Fluorogold (FG) injected into the superior colliculus. Animals with 1.8-2.5 fold increase in IOP after cauterization of three episcleral vessels, were divided into 3 BDNF groups and 3 vehicle control groups, each receiving one, two or three injections. The RGC survival percentage on RGCs of the first, second and third injections were 93.9% (n=7), 91.3% (n=7), 82.7% (n=5) respectively in BDNF groups; 91.6% (n=6), 84.1% (n=6) and 73.5% (n=5) respectively in vehicle controls. The second and third injections of BDNF showed statistically significant survival effects. These findings demonstrated that BDNF has partial neuroprotection on RGCs in whole retina and enhances RGC survival in moderately chronic hypertensive eyes. We further investigated the combined treatment of BDNF and a non-specific free radical scavenger N-tert-butyl-(2-sulfophenyal)-nitrone (S-PBN) on the RGCs in hypertensive eyes of rats. Adult Wistar rats were separated into five groups: BDNF (0.5 mg) + S-PBN; BDNF (1.0 mg) + S-PBN; BDNF (1.0 mg); S-PBN+PBS and PBS. Right eyes served as normal controls (n=10). Three days after intratectal injection, the episcleral veins of the left eyes were cauterized. Intravitreal injection of BDNF was performed on days 5, 13, 21 and 29 after IOP elevation. S-PBN was injected intraperitoneally (100mg/kg body weight) every 12 hr starting 30 min after cauterization. The combination of BDNF and S-PBN significantly increased the survival of RGCs to 90.1%, compared to 81% in BDNF treatment alone. The systemic administration of S-PBN alone did not significantly rescue the RGCs. In order to investigate the generation of superoxide anion on retina after elevation of intraocular pressure in rats, three episcleral veins were cauterized in left eyes. The right eye served as normal control. The resting level of superoxide anion in detached retina of controls and experimental glaucoma on day 1, day3, one week, three weeks and five weeks were measured by an ultra-sensitive lucigenin-dependent Chemiluminescence (CL) analyzer. The detached retinas were also incubated with nitro blue tetrazolium (NBT) to demonstrate the changes of superoxide on the retina ganglion cell (RGC) layer on day1, day3, one week, three weeks and 5 weeks after IOP elevation. The whole retina CL level of glaucoma at day 3 (2819 + 194) and one week (2608+178) were significantly greater than that of controls (1889 + 109) (p< 0.01). However, the CL level of whole retina dropped to nearly normal state within five weeks (2006+187). The peak optical density of NBT staining was obtained on day 3 (0.2707 + 0.003), which was also significantly higher than controls (0.2516 + 0.002) (p<0.01). The maximal generation of superoxide anion or free radical was observed on day 3 after IOP elevation by these two different methods. Our findings demonstrated the increase of superoxide anion on the retinal ganglion cell layer might be related to the early stage of moderately hypertensive eyes in rats. The role of superoxide anion on apoptosis of RGC in experimental glaucoma is still unclear and further study is needed.