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Na Luo, Xinyao Hu, Min Qi, Yang Sun; The effect of TRPV4 in Primary Cilia Signaling. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3012.
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© 2017 Association for Research in Vision and Ophthalmology.
Oculocerebrorenal syndrome of Lowe (Lowe syndrome) is a rare X-linked recessive disease caused by mutations in OCRL which encodes an inositol phosphatase. Lowe syndrome is characterized by congenital cataracts, glaucoma, hypotonia, intellectual impairment, and renal dysfunction. Our previous work has shown that OCRL interacts with TRPV4, and the expression of glaucoma-causing mutation (OCRL-D499A) results in ciliary defects in trabecular meshwork cells. However, the molecular mechanisms of TRPV4 in ciliogenesis and in Lowe syndrome remains unknown. The goal of this study was to investigate the ocular effects of TRPV4 agonist GSK1016790A (GSK) on primary cilia signaling in Lowe syndrome.
Intraocular pressure (IOP) measurements in 9-12 week old C57bl/6J male wildtype mice were performed using TonoLab tonometer. Anterior chamber cannulation and computer-controlled flow pump systems were built to measure the conventional outflow facility in freshly enucleated mouse eyeballs. Treatments of TRPV4 agonist GSK 20ng/gram body weight/Day (ng/g/D), TRPV4 antagonist HC067047 (HC) (50ng/g/D), Rho kinase inhibitor Y-27632 (20ng/g/D) and sham control were carried out by intraperitoneal injection prior to IOP measurement and anterior chamber cannulation. Tissue integrity was determined by paraffin sectioning and H&E staining for cannulated eyes. Immunofluorescence and confocal microscopy were performed to assess primary cilia response to GSK treatment with ciliary markers.
Decreased IOP was detected in mice treated with GSK for 4 days when compared to controls (GSK 10.4±0.8 mmHg, N=10; control 12.6±0.9 mmHg, N=10; P<0.05). No IOP lowering was observed in the TRPV4 antagonist group (HC, 11.1±1.3 mmHg, N=10, P=0.07). GSK increased outflow facility by 45% (GSK, N=12; control, N=4; P<0.05). Similarly, increased outflow facility of 48% was observed after treatment of Y-27632 (Y-27632 N=6; control N=4, P<0.05). The shortened primary cilia lengths in Lowe fibroblasts (2.4±0.2μm vs control 4.5±0.2μm, P<0.001) and OCRL knockdown RPE cells (3.2±0.1μm vs control 4.3±0.1μm, P<0.001) were all rescued to 4.2±0.2μm after treated with 0.1uM GSK for 2 days.
This study showed that TRPV4 agonist treatment increases the outflow facility in mice and reversed the shortened cilia phenotype in OCRL-deficient cells, which indicates TRPV4 as a potential therapeutic target for Lowe syndrome.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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