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Glaucoma is a degenerative optic neuropathy that is associated with elevated intraocular pressure. Primary open angle glaucoma is the most common type of glaucoma in canines, and its highest incidence among dog breeds has been reported in Shiba-Inus, followed by Shih-Tzus. These breeds are known to have an abnormal iridocorneal angle and dysplastic prectinate ligament. However, the hereditary and genetic backgrounds of these dogs have not yet been clarified. In this study, we investigated the association between polymorphisms of the glaucoma candidate genes, SRBD1, ELOVL5, and ADAMTS10, and glaucoma in Shiba-Inus and Shih-Tzus. We analyzed 11 polymorphisms in these three genes using direct DNA sequencing. Three SRBD1 SNPs, rs8655283, rs22018514 and rs22018513 were significantly associated with glaucoma in Shiba-Inus, while rs22018513, a synonymous SNP in exon 4, showed the strongest association (P = 0.00039, OR = 3.03). Conditional analysis revealed that rs22018513 could account for most of the association of these SNPs with glaucoma in Shiba-Inus. In Shih-Tzus, only rs9172407 in the SRBD1 intron 1 was significantly associated with glaucoma (P = 0.0014, OR = 5.25). There were no significant associations between the ELOVL5 or ADAMTS10 polymorphisms and glaucoma in Shiba-Inus and Shih-Tzus. The results showed that SRBD1 polymorphisms play an important role in glaucoma pathology in both Shiba-Inus and Shih-Tzus. SRBD1 polymorphisms have also been associated with normal- and high-tension glaucomas in humans. Therefore, SRBD1 may be a common susceptibility gene for glaucoma in humans and dogs. We anticipate that the nucleotide sequencing data from this study can be used in genetic testing to determine for the first time, the genetic status and susceptibility of glaucoma in dogs, with high precision. Moreover, canine glaucoma resulting from SRBD1 polymorphisms could be a useful animal model to study human glaucoma. [ABSTRACT FROM AUTHOR]

Purpose: sigma-1 Receptor ligands prevent neuronal death associated with glutamate excitotoxicity both in vitro and in vivo. However, the molecular mechanism of the neuroprotective effect remains to be elucidated. The present study was undertaken to determine whether sigma-1 receptor agonists provide neuroprotection by decreasing glutamate-induced calcium mobilization and preventing apoptotic gene expression., Methods: Cell death was measured by using a calcein-AM/propidium iodide cell-survival assay. Western blot analysis determined the expression levels of Bax in normal RGC-5 cells. Caspase-3 activation after glutamate treatment was determined with a carboxyfluorescein caspase-3 detection kit. Glutamate-induced intracellular calcium mobilization was measured by using ratiometric calcium imaging., Results: sigma-1 Receptor-overexpressing RGC-5 (RGC-5-S1R) cells had lower glutamate-induced intracellular calcium mobilization than did normal RGC-5 cells, and the sigma-1 receptor ligand (+)-SKF10047 reduced the glutamate calcium response in normal and RGC-5-S1R cells. (+)-SKF10047 protected RGC-5 cells from glutamate-induced cell death, and the RGC-5-S1R cells showed a significant resistance to glutamate-induced apoptosis compared with the control RGC-5 cells. BD1047, a sigma-1 receptor antagonist, blocked the protective effect of (+)-SKF10047. Western blot analysis showed that (+)-SKF10047 inhibited the increase in Bax after glutamate treatments. Glutamate-mediated cell death involved activation of caspase-3, and sigma-1 receptor activation prevented an increase in caspase-3 expression., Conclusions: The results suggest that sigma-1 receptors regulate intracellular calcium levels and prevent activation of proapoptotic genes, thus promoting retinal ganglion cell survival. The sigma-1 ligands appear to be neuroprotective and are a potential target for neuroprotective therapeutics.