The Effect Of Hypericin On Retinal Glutamate And Ganglion Cell In Chronic Ocular Hypertension Rabbits

[Objective] Research has proved that the apoptosis of retinal ganglion cells is closely linked to the retinal excitotoxicity induced by glutamate, and glutamate plays an important role in the pathogenesis and progress of glaucoma. The present study was to explore the effect of hypericin, a specific protein kinase C antagonist, on retinal glutamate levels in chronic ocular hypertension rabbits.[Methods] Thirty-two rabbits were used to establish chronic ocular hypertension model by posterior chamber injection of alpha-chymotrypsin to elevate the intraocular pressure(IOP) to 30mmHg or more. Ten days after modeled, 0.1ml hypericin or saline was injected into the vitreous cavity of 24 successful models. Three rabbits from the each group were sacrificed for retinal glutamate detect by High Performance Liquid Chromatography (HPLC) at 1 day, 4 days, 7 days and 14 days after the injection. Three more successful models without intravitreous injection and 3 normal rabbits without any treatment were served as controls.[Results] The mean IOP was (19.32±1.45)mmHg in normal rabbit eyes and (34.12±2.31) mmHg in experimental rabbit eyes. The mean retinal glutamate level was (1.71×10-5±0.23×10-5) mmol/g in the normal rabbit eyes and(4.65×10-5±0.12×10-5)mmol/g in chronic ocular hypertension group.The latter increased significantly in comparison with the former(t=6.318,P=0.021). Retinal glutamate levels was significantly decreased in the hypericin-treated eyes in comparison with saline-treated eyes at various time points(t=7.156, P=0.019, t=7.933, P=0.016, t=11.993, P=0.007, t=5.276, P=0.034).[Conclusion] Chronic ocular hypertension can induce the increase of retinal glutamate level. Intravitreal injection of hypericin can inhibit the increase of the retinal glutamate level. [Objective] To explore the effect of hypericin on retinal ganglion cell in chronic ocular hypertension rabbits.[Methods] Twenty–eight rabbits were used to establish chronic ocular hypertension model by posterior chamber injection of alpha-chymotrypsin to elevate the intraocular pressure(IOP) to 30mmHg or more. Ten days after modeled, 0.1ml hypericin or saline was injected into the vitreous cavity of 16 successful models once a week for two weeks. Other eight successful models and four normal rabbits were as controls .All rabbits from each group were sacrificed and eight eyeballs were extracted. Retinal ganglion cells of these rabbit eyes were observed by light microscopy and electron microscopy .Also the mean thinckness of inner retina layer(MTIRL) were examined .[Results] The number of retinal ganglion cells in saline control group and control group decreased significantly.There was serious cell degradation with perinuclear condensation of chromatin and swelling organelles. But the change was slight in hypericin-treatedt group.The normal MTIRL was(78.62±1.87)μm.The difference of MTIRL between the normal group and the control group was significant(t=3.254,P=0.005). Also the MTIRL was significantly decreased in the saline-treated eyes in comparison with hypericin-treated eyes(t=3.189,P=0.003).[Conclusion] Intravitreal injection of hypericin as a protein kinase C antagonist can protect the retinal ganglion cell in chronic ocular hypertension rabbits .