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Michael H Elliott, Mark E. McClellan, Willard M. Freeman, W Daniel Stamer; ROLE OF CAVEOLAE AS MECHANOSENSORS IN SCHLEMM’S CANAL. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3477.
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© ARVO (1962-2015); The Authors (2016-present)
Polymorphisms at the caveolin (CAV)1/2 gene locus are associated with primary open angle glaucoma (POAG) risk and elevated intraocular pressure (IOP). Caveolins are signature proteins of caveolae that are abundant in Schlemm’s canal (SC) and trabecular meshwork (TM). We and others have reported that Cav1/caveolae ablation in mice results in ocular hypertension from reduced aqueous humor drainage but the SC-intrinsic contributions of caveolae are unknown. We hypothesize that caveolae in SC modulate IOP through mechanical control of endothelial nitric oxide synthase (eNOS) activity.
We measured IOP by rebound tonometry in endothelium-specific Cav1 knockout (Endo-Cav1 KO) and Cav1/eNOS double KO (DKO) mice. We evaluated eNOS phosphorylation and tyrosine nitration by immunoblotting iridocorneal angle tissue from Endo-Cav1 KO mice. We tested whether caveolae in primary human SC cells respond to mechanical stretch by examining binding partners by immunoprecipitation and Cav1 phosphorylation by immunoblotting. We present preliminary expression analyses of caveolae genes in human SC cells harboring a common POAG-associated polymorphism (rs4236601).
Endothelium-specific Cav1 deletion was confirmed in Endo-Cav1 KO SC by immunohistochemistry. Endo-Cav1 KO mice had significantly elevated IOP compared to littermate controls (p≤0.003, unpaired t-test, n=20-22). Compared to C57BL/6J controls, IOP was similarly and significantly elevated in Cav1/eNOS DKO, Cav1 KO, and eNOS KO mice (p≤0.05; ANOVA with Newman-Keuls post hoc test; n = 12-22 mice) but was not significantly different between KO or DKO strains (P>0.05). Basal eNOS phosphorylation was increased in iridocorneal angle tissues from Endo-Cav1 KO mice compared to littermate controls. Experimental IOP elevation increased eNOS phosphorylation in control but not Endo-Cav1-KO tissue. Protein nitration was not different between genotypes. Human SC cells harboring the POAG-associated rs4236601A variant had reduced CAV2 and increased PTRF/CAVIN1 expression.
Deletion of Cav1 in SC and vascular endothelia induces dysregulation of eNOS and similar IOP elevation as global Cav1 ablation. We provide the first evidence that a POAG-associated polymorphism affects caveolae gene expression in a POAG-relevant cell. These results demonstrate an important role of Cav1 in eNOS regulation in the SC endothelium that may impact TM contractility.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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