Abstract
Purpose :
Global deletion of Cav1, the primary protein of caveolae, results in ocular hypertension and reduced aqueous humor drainage which is paradoxical to its established role in endothelial nitric oxide synthase (eNOS) regulation. Here, we examined the effect of targeted Cav1 gene deletion in vascular endothelium (Schlemm’s canal and distal vasculature, but not trabecular meshwork) on intraocular pressure (IOP), outflow facility, outflow pathway morphology, and eNOS activity.
Methods :
To interrogate Cav1 function in the SC and distal vasculature, we generated endothelium-specific Cav1 knockout mice (Endo-Cav1 KO). In these mice, we measured IOP, outflow facility, and distal vascular morphology in anterior segment wholemounts immunostained with antibodies against CD31, α-smooth muscle actin, and Cav1. Morphometric analyses of vessel diameters were done using ImageJ. Additionally, we examined IOP-induced activation of eNOS by Western blotting of iridocorneal angle tissue for phosphorylation of eNOS.
Results :
Efficient endothelium-specific Cav1 deletion was confirmed by immunohistochemistry. Endo-Cav1 KO mice displayed significantly elevated IOP compared to littermate controls (p≤0.01, unpaired t-test, n=20-22). Surprisingly, outflow facility was modestly elevated in Endo-Cav1 KO mice compared to controls (p=0.07, unpaired t-test, n=8-9). Veins distal to SC were significantly enlarged in both Endo-Cav1 KO (p≤0.001, unpaired t-test, n = 4 cre-negative control and n = 3 Endo-Cav1 KO mice) and global Cav1 KO mice (p≤0.001, unpaired t-test, n = 5 WT controls and n = 6 Cav1 KO mice). Arterial and capillary diameters were not significantly different between any genotype. The distal venous enlargement was consistent with increased activation/phosphorylation of eNOS in iridocorneal angle tissues from Endo-Cav1 KO mice compared to controls. Consistent with distal venous enlargement, basal eNOS phosphorylation was elevated in Endo-Cav1 KOs, and experimental IOP elevation only stimulated eNOS phosphorylation in WT, not Endo-Cav1 KO mice.
Conclusions :
Our results suggest that Cav1 is an endogenous regulator of eNOS in the SC and distal vasculature, and that Cav1 deficiency results in eNOS uncoupling, distal vascular enlargement, and increased outflow facility. The paradoxically increased IOP in this model and differences in outflow facility between it and global KOs merits further mechanistic study.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.