Protection Mechanism Of Traditional Chinese Medicine Compound VIS On Acute High Intraocular Pressure Induced Ganglion Cell Apoptosis In Rat

Objective:To investigate the intervention of Chinese herbal compound VIS on retinal ganglion cell (RGC) damage in a rat acute ocular hypertension model, and to explore the possible mechanisms underlying optic nerve protection of VIS.Methods:Firstly, we reproduced acute ocular hypertension model by using the technique of the anterior chamber infusion of saline to increase intraocular pressure for 1 h. Then the animals were treated with Chinese Compound VIS, and the retinal ganglion cells were acutely isolated at 1,3,7 and 14 days after the operation. Outward potassium currents in these retinal ganglion cells were studied by whole-cell patch-clamp techniques. Outward K+ currents were induced by a series of depolarizing voltage pulses from a holding potential of -70 mV to +20 mV in an increment of 10 mV. The changes in current amplitude of outward potassium currents were observed at different times after the operation. Secondly, we examined the effects of DSX, the extract of Erigeron breviscapus and the composition of VIS, on outward potassium currents. DSX, at a concentration of 0.1g/L, was directly applied to the retinal ganglion cells acutely isolated from normal rats in the same whole-cell patch-clamp technique, so as to examine whether DSX may have effect on outward potassium currents. Then we studied whether the effects of DSX on outward potassium currents in a concentration-dependentl manner. TUNEL and Western blot techniques were used to examine retinal ganglion cell apoptosis and the apoptotic related protein expression at 7th day after the operation in acute ocular hypertension model under different conditions.Results:Chinese herbal compound VIS rescured acute ocular hypertension-induced changes of outward potassium currents in RGCs. Extracellular application of DSX voltage-dependently suppressed both the steady-state and peak current amplitudes of outward K+ currents in the cells. Furthermore, DSX reversibly and dose-dependently inhibited the amplitudes of outward K+ currents. At+20 mV membrane potential DSX at the concentrations of 0.02g/L and 0.05 g/L showed no significant effects on the currents. In contrast, DSX at higher concentrations (0.1 g/L,0.2 g/L and 0.5 g/L) significantly suppressed the current amplitudes. TUNEL and Western blot experiments showed that LY294002, a specific PI3K/AKT signaling pathway inhibitor, could attenuate the protection of VIS on retinal ganglion cells in the rat acute ocular hypertension model.Conclusions:The traditional Chinese medicine compound VIS provides a protective effect against retinal ganglion cell damage in the rat acute intraocular hypertension model, which may be mediated by stabilizing the outward potassium currents, and activating the intracellular PI3K/Akt signaling pathway. DSX reversibly and dose-dependently inhibits the outward K+ current amplitudes, which may be one of the possible mechanisms underlying VIS prevents vision loss and RGCs damage caused by glaucoma.