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David Krizaj, Monika Lakk, Tam Thi Thanh Phuong; Mechanical strain modulates TRPV4-dependent cytoskeletal reorganization in the trabecular meshwork. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3013.
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© ARVO (1962-2015); The Authors (2016-present)
The Rho kinase signaling pathway in the trabecular meshwork (TM) has been proposed to regulate the conventional outflow pathway in part by regulating IOP-sensitive actin dynamics. However, how Rho kinases might sense pressure and how this pathway could be perturbed in glaucoma remains unknown.
Immortalized and primary human TM cells were stimulated with uniaxial and biaxial strain (1-12%; Strex, Flexcell stimulation paradigms) in the presence/absence of Rho kinase (ROCK) inhibitors and modulators of putative mechanosensitive ion channels. mRNA and protein levels were measured with qRT-PCR and Western blots. Changes in transcription and/or translation were assessed 0.5-6 hours post-exposure. Calcium levels in TM cells were measured with optical imaging and electrophysiological methods.
Mechanical strain potentiated the transcript levels of Rho pathway signaling components. Some, but not all, cytoskeletal markers were dysregulated, including the phosphorylated (p)-focal adhesion kinase (FAK) protein and p-zyxin; however, mechanical force did not affect total protein levels. Stretch-induced expression of p-FAK was suppressed by the Rho kinase (ROCK) blocker Y-27632. Moreover, exposure to selective activators and blockers of the TRPV4 signaling pathway modulated stretch-dependent changes in RhoA signals measured at mRNA, protein and [Ca2+]i levels.
Our results show that (i) stretch modulates transcription of Rho pathway signals and (ii) cytoskeletal remodeling at translational and post-translational levels, due to strain-sensitive kinase activation; (iii) RhoA signaling in TM interfaces with TRPV4 signaling. Thus, the role of ROCK in the regulation of conventional outflow resistance and glaucomatous remodeling in the anterior eye is likely linked to strain-dependent modulation of TRPV4.
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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