Intracellular Zn²⁺ promotes extracellular matrix remodeling in dexamethasone-treated trabecular meshwork

Abstract

Purpose : There is a consensus that glucocorticoids (GCs) influence Matrix metalloproteinases (MMPs) expression in trabecular meshwork (TM) cells, leading to extracellular matrix (ECM) deposition and intraocular pressure (IOP) elevation. However, the underlying mechanisms remain uncertain. Since Zn²⁺ is essential for structure and enzymatic activity of MMPs, we explored its role in ECM alterations induced by dexamethasone (DEX).

Methods : Human TM samples isolated from residual tissue after cornea transplantation underwent treatment with 1μM DEX. To manipulate Zn²⁺ concentration, we treated cells with TPEN, a selective Zn²⁺ chelator and ZnSO₄. Intracellular Zn²⁺ was detected by Zinpyr-1, a Zn²⁺ fluorescent sensor. Subconjunctival injection of mice with DEX acetate formulation (0.01 g/ml) was performed after weekly IOP monitoring. Statistical analyses included two-tailed Student's t-test and one-way analysis of variance for group comparisons.

Results : DEX-treated human TM cells showed decreased intracellular Zn²⁺ and impaired extracellular Zn²⁺ uptake. These changes correlated with Zrt-, Irt-related proteins (ZIP) and metallothionein alterations. ZIP8 knockdown impaired Zn²⁺ uptake, but Zn²⁺ chelation didn't affect ZIP8 expression. Mirroring DEX effects, chelating Zn²⁺ decreased MMP2 expression, increased ECM protein deposition and induced ECM structural disarray. Conversely, Zn²⁺ supplementation to DEX-treated cells mitigated these outcomes. Dietary zinc supplementation in mice significantly reduced DEX-induced IOP elevation and TM collagen content.

Conclusions : Zinc supplementation's potential in alleviating DEX-induced changes in both cellular and animal models suggests its therapeutic value in GC-induced IOP elevation, especially concerning ECM remodeling. These results enhanced our understanding of TM cell responses to GCs and provided valuable insights into managing GC-induced ocular complications. Future studies should delve deeper into the molecular mechanisms underlying the observed effects and explore the specific pathways through which zinc exerts its therapeutic effects.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Zn²⁺ concentration impact MMP2 expression levels and ECM density.

 

Zinc supplementation alleviated DEX-Induced IOP rise and collagen alterations in mice.