Proteomic Analysis of the Trabecular Meshwork of Rats in a Steroid-Induced Ocular Hypertension Model: Downregulation of Type I Collagen C-Propeptides

Abstract

Purpose: To investigate global protein expression profiles in the trabecular meshwork (TM) of normal and glucocorticoid-induced ocular hypertensive rat eyes by proteomic analysis, which has not yet been conducted to date. Materials and Methods: A rat ocular hypertension model was produced by topical application of dexamethasone (DEX) for 4 weeks. Age-matched untreated rats served as controls. Intraocular pressure (IOP) was monitored by an electronic tonometer. TM protein expression profiling and protein identification was carried out by a two-dimensional fluorescence differential gel electrophoresis (2-D DIGE) system and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, respectively. Results: In DEX-treated rats, average IOP was elevated significantly, as compared with controls. By the DEX treatment, 14 TM protein spots were up- or downregulated consistently in 2-D DIGE analyses. Proteins exhibiting more than 2-fold statistically significant change were identified by MALDI-TOF mass spectrometry. αA-Crystallin and βA₃-crystallin were upregulated, while the C-propeptides of type I collagen were downregulated. Conclusion: Relatively short-term glucocorticoid application induced alteration in the expression of a number of proteins, including downregulation of type I collagen C-propeptides. This could reflect impaired collagen turnover in the TM of glucocorticoid-treated eyes.

Persisent ocular hypertension following intravitreal ranibizumab

“…It is known that glucocorticoids affect extracellular matrix deposition in the trabecular meshwork [6], and alter aqueous proteomics [7] and gene expression. [8,9] There are no such studies on the effect of anti-VEGF agents.…”

Proteomic analysis of rat retina in a steroid-induced ocular hypertension model: Potential vulnerability to oxidative stress

“…Three rats (rats 4, 5, and 6) were treated with topical application of DEX on both eyes for 4 weeks to induce ocular hypertension as described previously. 10,11 The other rats (rats 1, 2, and 3) were treated with vehicle only and served as controls. At the end of treatment, they were used for experiments after IOP measurement conducted with an electronic tonometer as described.…”

“…At the end of treatment, they were used for experiments after IOP measurement conducted with an electronic tonometer as described. 10,11 All experiments were conducted in compliance with the University of the Ryukyus Animal Care and Use Committee Guidelines and the ARVO Statement for the Use of Animals in Vision Research.…”

“…10 We used a rat ocular hypertension model generated by relatively short-term topical DEX application, 11 and compared global protein expression profi les in the TM of control and DEX-treated rat eyes. 10 Type I collagen C propeptides, which are processing by-products of fi brillar collagen, were downregulated. The data strongly suggested that collagen turnover, a cycle of homeostatic degradation and repair by newly formed fi brils, is slowed in DEX-treated eyes.…”

Introduction of the Mini Review Series in <b><i>Ophthalmic Research</i></b>

“…in uveitic cystoid macula edema [2,4]. However, triamcinolone remained an off-label approach and side effects such as increase in intraocular pressure limit its use [5,6,7]. In addition, because of its short intraocular halftime, reinjections are often needed.…”