Abstract
BackgroundRecently, topical dexamethasone-induced ocular hypertension and a consequent loss of retinal ganglion cells (RGCs) have been described in mice. This has been proposed as a model of steroid-induced glaucoma. In this study, we set up and evaluated a similar model in rats.ResultsTen-week old Sprague Dawley (SD) rats (N = 12) were used to evaluate the effect of topical 0.1 % dexamethasone (50 μl) administered 3 times daily for 4 weeks. Sodium chloride (0.9 %) was used in another group of rats (N = 12) that served as the controls. After 1 week, we observed a progressive decrease in body weight in the dexamethasone-treated rats compared both to the pre-treatment baseline and the vehicle-treated rats. In contrast to earlier work that showed elevated Intraocular pressure (IOP) following dexamethasone instillation in mice, IOP in the rats unexpectedly fell to 11.3 ± 1.3 mmHg in the treated eyes, compared to 14.8 ± 2.4 mmHg in the untreated eyes, after 3 weeks of topical dexamethasone (P = 0.032). Blood tests performed after 4 weeks of treatment showed a 3.3-fold increase in both plasma cholesterol (P < 0.001) and alanine transaminase (P = 0.019) in the dexamethasone-treated rats compared to the control rats. Meanwhile, topical steroid did not induce changes in either plasma blood glucose or glycated hemoglobin (HbA1c). We also did not detect changes in the expression of RGC markers (with real-time PCR) following the treatment.ConclusionsIn contrast to mice, which previously showed increased IOP following the topical administration of dexamethasone, the rats displayed a paradoxical reduction in IOP following a similar treatment. This was accompanied by a loss of body weight without affecting the level of blood glucose.Electronic supplementary materialThe online version of this article (doi:10.1186/s12952-016-0048-x) contains supplementary material, which is available to authorized users.
Highlights
Topical dexamethasone-induced ocular hypertension and a consequent loss of retinal ganglion cells (RGCs) have been described in mice
The body weight of the steroid-treated rats continued to show a steady decline in the following weeks, and had decreased to ~66.6 % of that of the saline-treated group after treatment for 4 weeks
We observed that this decline in body weight was accompanied by a reduction in intraocular pressure (IOP) starting after 2 weeks of treatment
Summary
Topical dexamethasone-induced ocular hypertension and a consequent loss of retinal ganglion cells (RGCs) have been described in mice. This has been proposed as a model of steroid-induced glaucoma. The condition is characterized by a selective loss of the retinal ganglion cells (RGCs) and their nerve fibers, resulting in a progressive narrowing of the visual field [3]. Glucocorticoid, which is a class of steroid hormone, has anti-inflammatory effects, and is used in the clinical treatment of patients with diseases such as autoimmune disorders, allergies, and intraocular inflammation including uveitis and optic neuritis [7,8,9]. Glucocorticoid treatment has numbers of adverse effects, such as gain of weight, increased blood glucose, triglyceride, and cholesterol as well as elevated blood pressure [10, 11]
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