A water channel (AQP9) in retinal ganglion cell apoptosis and glaucoma

Abstract

Aquaporin-9 (AQP9) is a neutral channel, permeable to water, glycerol, and a number of solutes. The presence of AQP9 in retinal ganglion cells (RGCs) was confirmed. AQP9 and a number of proteins responded differently to two animal models of glaucoma. Inhibition of AQP9 may protect RGCs under hypoxia conditions. The expression of AQP9 responded to hypotonic shock in a time-dependent matter. Aquaporin in the RGCs and astrocytes may play a role in cell survival or death, depending on the stimulus. Under some conditions, increasing AQP4 may also be protective, such as in vasogenic edema, whereas under cytotoxic edema it becomes detrimental. This work describes possible physiological and pathophysiological roles of AQP9. Aquaporin-4 is expressed in astrocytes, which are considered RGCs supportive cells. AQP4 may be targeted by the proteasome system, so inhibition of this pathway may be protective in vasogenic brain edema.