Purchase this article with an account.
C R. Ethier, Yuan Lei, Alex Boussommier-Calleja, Darryl R. Overby, W Daniel Stamer; Nitric Oxide Overexpression Facilitates Aqueous Humour Drainage in the Mouse Eye. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6618.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To better understand molecular factors controlling aqueous humour (AH) drainage, we measured intraocular pressure (IOP) and AH dynamics in wild-type and transgenic C57BL/6 mice overexpressing a fusion protein of active endothelial nitric oxide synthase (eNOS) and GFP (Haperin et al., Am J Pathology, 2003).
IOP was measured by rebound tonometry (TonoLab) and pressure vs. flow data was measured by ex vivo perfusion at multiple perfusion pressures between 4 and 35 mmHg, using either mock AH or mock AH + 100 mM L-NAME. A subset of eyes was examined histologically using standard techniques or labelled to identify the distribution of eNOS, while eNOS expression was assayed in other eyes by Western blotting.
In transgenic mice, IOP was lower (9.6 ± 0.6 vs 11.5 ± 0.5 mmHg; mean ± SD; p = 0.026) and conventional (pressure-dependent) AH conventional outflow facility, defined as the slope of the regression line fit to the flow vs pressure data, was 19% higher, as compared to wild-type controls, while unconventional AH drainage was unaffected. Increased conventional facility in transgenic animals was abolished by the NOS inhibitor L-NAME. Western blots showed higher levels of eNOS expression in ocular tissues, while histology showed increased eNOS/GFP fusion protein expression in the trabecular meshwork and inner wall of Schlemm’s canal without structural changes in outflow tissue architecture. For IOPs > 35mmHg, the nature of the IOP-outflow curve changed so that conventional facility in wild-type mice increased to match that in transgenic mice at low IOP. Theoretical calculations showed that the expected shear stress due to AH flow in Schlemm's canal was comparable to that in human and in a range known to affect eNOS expression.
eNOS overexpression lowers IOP by increasing conventional (trabecular) aqueous drainage in the mouse eye. Our data are consistent with NO having a regulatory role in IOP control, specifically with eNOS induction at high IOPs/AH drainage rates. This represents an interesting pharmacologic target (see e.g. Borghi et al, J Ocul Pharmacol Ther. 2010), especially in light of recent reports of polymorphisms in the NOS3 gene associating with ocular hypertension in glaucoma.
This PDF is available to Subscribers Only