Neuroprotective effect of Qinggan Lishui formula on retinal ganglion cell apoptosis in a microbead-induced rat chronic glaucoma model

OBJECTIVE: To investigate a possible mechanism for protective effects of a decoction of the Qinggan Lishui formula(QF) on retinal ganglion cells(RGCs)in a rat model of microbead-induced chronic intraocular hypertension(COH).METHODS: The COH model was generated by injecting microbeads(superparamagnetic iron oxide)into the anterior chamber of rat eyes. QF was given by intragastric administration(gavage) once daily at a dose of 6.2 g/kg until day 28, following microbead injection. Cholera toxin B subunit(CTB) retrograde labeling and immunohistochemistry were used to evaluate changes in the number of RGCs in the retina. Terminal d UTP nick end labeling(TUNEL) staining was used to assess apoptotic changes in RGCs.RESULTS: Microbead injection induced a steady increase in intraocular pressure(IOP) of rats. Elevated IOP resulted in a progressive reduction in the number of CTB-labeled RGCs, 2-4 weeks after microbead injection. QF administration may moderately reduce IOP in the rat COH model and attenuate reduction of the number of CTB-labeled RGCs in COH rats. Furthermore, elevated IOP resulted in a progressive increase in the number of TUNEL-positive RGCs, 2-4 weeks after microbead injection, suggestive of an increase in the extent of RGC apoptosis.There was a significant reduction in the number of TUNEL-positive signals in QF-treated COH retinas,compared with untreated COH retinas.CONCLUSION: QF decoction may provide a protective effect for RGCs in COH retinas by reducing RGC loss; these effects may be mediated by inhibition of RGC apoptosis.