68-4

29/136

and catalytic and metabolic proteins were more expressed in epithelium than stroma. Diffusion, ultrafiltration, and active secretion are physiolog-ical processes that participate in the production of aqueous humor, especially active secretion4). Blood flows through the CB, and aqueous humor is produced from the blood plasma by the non-pig-mented ciliary epithelium. The proteins in the aqueous humor differ both quantitatively and qual-itatively from those in the plasma4, 22, 23), indicating that the CB must be involved in the secretion of proteins into the aqueous humor. In comparison of Figure 3　 Effect of dexamethasone on the expression of Rab8 in monkey ciliary epithelial cellsA: Western blot analysis with an antibody against Rab8 showed a tendency of decrease in the expression of Rab8 in monkey ciliary epithelial cells after exposure to dexamethasone (Dex) for 5 days. Western blot analysis with an antibody against actin was the control. The relative amount of Rab8/actin was quantified. B: Western blot analysis of ciliary epithelial cells after exposure to timolol maleate for five days. No change was seen in the expression of Rab8 proteins. C: Western blot analysis of ciliary epithelial cells after exposure to acetazolamide for five days. No change was seen in the expression of Rab8 proteins.CB with aqueous humor, Chowdhury et al reported that 355 proteins were identified from human aqueous humor by narrow liquid chromatography electrospray ionization tandem mass spectrometry, and most of the proteins had catalytic, enzymatic, and structural properties23). Catalytic and meta-bolic proteins are almost 30% each of top 50 distri-bution by function by Gene Ontology in CB, and approximately 20% each in aqueous humor. Struc-ture proteins take up around 35% in CB, whereas 9.9% in aqueous humor23), though simple compar-ison is not possible according to different way of classification.Myocilin, a glaucoma gene, is found in the aqueous humor, and the trabecular meshwork cells are known to secrete exosomes into the aqueous humor24). The CB appears to secrete proteins into the aqueous humor in the same way. Rab8, one of the proteins identified by our proteomic analysis, is a small GTP-binding protein that is related to optineurin, a glaucoma gene18-20). It is known to be involved in protein localization and transportation in the small intestine and can affect the morphology of microvilli18). Although no reports have described the role that Rab8 plays in the CB, it is quite reasonable to assume that it is involved in protein secretion. Our proteomic analysis also identified the ERM family proteins, which are core proteins of the microvilli and are found directly beneath the cell membranes. They act as linker proteins and connect actin filaments to the cell membranes25, 26). Rab8 and moesin have been reported to interact to regulate the transport of rhodopsin in photore-ceptor cells21). Both proteins appear to be related to protein transport and to be active in the CB. We double immunostained for Rab8, ezrin, radixin, and moesin in cynomolgus monkey CB tissues and also in cultured non-pigmented ciliary epithelial cells. Confocal microscopy showed a co-expression of Rab8 and the ERM family in the non-pigmented epithelium of the CB, suggesting that these proteins are involved in the function of the non-pigmented epithelium of the CB. The secondary glaucoma caused by glucocorti-coids is both clinically and morphologically similar to primary open angle glaucoma. Thus, glucocorti-coids have been used in both in vivo and in vitro glaucoma research27-31). When trabecular mesh-349