An Uncoupling Effect of Reactive Oxygen Species on the Retinal Horizontal Cells
Glutathione is a potent endogenous scavenger of oxygen free radicals in living cells. Decreased levels of glutathione are involved in aging and some neurodegenerative diseases. To investigate an effect of glutathione depletion in the horizontal cells of carp retina, the gap junctional intercellular communication between horizontal cells was studied using both techniques of intracellular recording of light-induced responses and dye coupling of the fluorescence, Lucifer Yellow (LY). The glutathione depletion was accomplished by single injection of 2.5μmol L-buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis. Intravitreal injection of BSO induced a dramatic reduction of retinal level of glutathione 2 days after treatment. The low level of glutathione continued for a further 4–5 days and thereafter was gradually recovered to about 70% of the control level by 50 days after injection. In normal retinas, the response amplitude of horizontal cells was monotonically enhanced as the diameter of the spot increased (0.5–4.0mm) and correspondingly the dye diffusion area was wide, as the injected LY normally diffused to several neighboring cells. Depletion of glutathione by BSO significantly altered the spatial properties of horizontal cells by increasing the response amplitude to central spots and slightly decreasing that to peripheral annuli, which were observed by 4 days after treatment. It also restricted intracellular LY to one or two cells. Accompanying the recovery of the cellular level of glutathione, the spatial properties and dye coupling of horizontal cells were recovered to normal. These alterations of spatial and dye coupling properties of horizontal cells were well correlated with accumulation of reactive oxygen species (H2O2) during glutathione depletion. The present data have demonstrated for the first time that neuronal gap junctional channels can be modified by intracellular glutathione via oxidative stress.
KeywordsResponse Amplitude Intravitreal Injection Reactive Oxygen Species Accumulation Horizontal Cell Central Spot
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