Objectives Steroid-induced ocular hypertension and glaucoma are associated with extracellular matrix remodeling at the trabecular meshwork (TM) of the eye due to reduced secretion of matrix metalloproteinases (MMPs), a family of enzymes regulating extracellular matrix proteolysis. Several biological functions of steroids are known to involve regulation of adenosine A1 receptors (A1AR) and nuclear factor kappa B (NFKB). Since MMPs expression in TM has been shown to be regulated by A1AR as well as transcription factors, it is likely that dexamethasone-induced changes in aqueous humor dynamics involve reduced MMP and A1AR expression and reduced NFKB activation. Hence, the current study investigated the association of dexamethasone-induced reduction in MMP secretion with reduced NFKB activation and A1AR expression. Methods Human trabecular meshwork cells (HTMCs) were characterized by estimating myocilin and alpha smooth muscle actin expression and then were treated with dexamethasone 100 nM for 2, 5 and 7 days. The MMP secretion was estimated in culture media using Western blot. Immunocytochemistry (ICC) and ELISA were done to investigate the effect of dexamethasone on NFKB phosphorylation. A1AR expression in HTMCs was determined using Western blot and ELISA. Results Dexamethasone caused a significant reduction in both MMP-2 and -9 expression compared to untreated group after five and seven days but not after two days of culture. Significantly reduced phosphorylated NFKB and A1AR protein levels were detected in dexamethasone treated compared to vehicle treated HTMCs after five days of culture. Conclusions Dexamethasone reduces MMP-2 and -9 secretion by HTMCs and this effect of dexamethasone is associated with reduced NFKB phosphorylation and A1AR expression.
BACKGROUND: Steroid-induced ocular hypertension is currently treated in the same way as primary open-angle glaucoma. However, the treatment is often suboptimal and is associated with adverse effects. We evaluated the oculohypotensive effects of topical trans-resveratrol in rats with steroid-induced ocular hypertension and involvement of adenosine receptors (AR) in intraocular pressure (IOP) lowering effect of trans-resveratrol.
METHODS: The oculohypotensive effect of unilateral single-drop application of various concentrations of trans-resveratrol was first studied in oculonormotensive rats. Concentration with maximum effect was similarly studied in rats with steroid-induced ocular hypertension. Involvement of AR was studied by observing the alterations of IOP in response to trans-resveratrol after pretreating animals with AR subtype-specific antagonists. Additionally, we used computational methods, including 3D modelling, 3D structure generation and protein-ligand interaction, to determine the AR-trans-resveratrol interaction.
RESULTS: All concentrations of trans-resveratrol produced significant IOP reduction in normotensive rat eyes. Maximum mean IOP reduction of 15.1% was achieved with trans-resveratrol 0.2%. In oculohypertensive rats, trans-resveratrol 0.2% produced peak IOP reduction of 25.2%. Pretreatment with A₁ antagonist abolished the oculohypotensive effect of trans-resveratrol. Pretreatment with A₃ and A₂A AR antagonists produced significant IOP reduction in both treated and control eyes, which was further augmented by trans-resveratrol application in treated eyes. Computational studies showed that trans-resveratrol has highest affinity for A₂B and A₁, followed by A2A and A₃ AR.
CONCLUSION: Topically applied trans-resveratrol reduces IOP in rats with steroid-induced ocular hypertension. Trans-resveratrol-induced oculohypotension involves its agonistic activity at the A₁ AR.
KEYWORDS: adenosine receptors; docking simulation; intraocular pressure; resveratrol; topical
Steroid-induced hypertension and glaucoma is associated with increased extracellular meshwork (ECM) deposition in trabecular meshwork (TM). Previous studies have shown that single drop application of trans-resveratrol lowers IOP in steroid-induced ocular hypertensive (SIOH) rats. This IOP lowering is attributed to activation of adenosine A1 receptors, which may lead to increased matrix metalloproteinase (MMP)-2 activity. This study evaluated the effect of repeated topical application of trans-resveratrol for 21 days in SIOH animals on IOP, changes in MMP-2 level in aqueous humor, trabecular meshwork and retinal morphology and retinal redox status. We observed that treatment with trans-resveratrol results in significant and sustained IOP reduction in SIOH rats. This IOP reduction is associated with significantly higher aqueous humor total MMP-2 level; significantly reduced TM thickness and increased number of TM cells. Treatment with trans-resveratrol also significantly increased ganglion cell layer (GCL) thickness, the linear cell density in the GCL and inner retina thickness; and significantly reduced retinal oxidative stress compared to the SIOH vehicle-treated group. In conclusion, repeated dose topical application of trans-resveratrol produces sustained IOP lowering effect, which is associated with increased level of aqueous humor MMP-2, normalization of TM and retinal morphology and restoration of retinal redox status.