The influence of melatonin and dexamethasone instillations on the clinical course of uveitis and the biochemical processes in the aqueous humour of the anterior chamber of the eye (an experimental study)

Abstract

Introduction. The problem of the treatment of uveitis has the important socio-medical implications bearing in mind the high prevalence of this pathological condition frequently affecting the subjects of the employable age. Uveitis is characterized by the enhanced production of free radicals in the eye tissues and marked activation of oxidative reactions that gradually aggravate the pronounced changes in the immune system that, in their turn, promote the development of oxidative stress. Aim. This study was designed to evaluate and compare the influence of melatonin and dexamethasone or their combination on the clinical symptoms and local metabolic processes in the aqueous humour of the anterior chamber of the rabbit eyes. Materials and methods. The present study was based on the rabbit model of immunogenic anterior uveitis developed by the subcutaneous injections of the normal equine serum followed by its intravitreal administration. We investigated the influence of instillations of a 0.1% melatonin solution and a 0.4% dexamethasone solution or their combinations on the clinical course of uveitis and the biochemical processes in the aqueous humour of the anterior chamber of the eye including the anti-oxidative activity, total protein and alpha-2 macroglobulin contents as well as the leukocyte count. Results. It was shown that instillation of melatonin either alone or in a combination with the dexamethasone solution reduced the severity of the inflammatory processes associated with uveitis. Melatonin, similar to dexamethasone, decreased palpebral oedema and iridial swelling. The two medication instilled successively produced a synergic effect on palpebral oedema, conjunctival hyperemia, corneal and iridial oedema. A significant decrease of protein and alpha-2 macroglobulin levels in comparison with the same values in the aqueous humour of the anterior chamber of the eye of the untreated animals was documented within 8 days after the induction of experimental uveitis. The similar effects of dexamethasone was even more pronounced. At the same time, the instillation of melatonin more significantly than that of dexamethasone reduced the number of leukocytes in the aqueous humour of the anterior chamber. It is worthwhile to note that instillations of melatonin, unlike those of dexamethasone, caused a significant increase in the anti-oxidative activity in the aqueous humour of the anterior chamber. Discussion. The instillations of melatonin make it possible to reduce the intensity of the inflammatory processes associated with experimental uveitis, enhance the anti-oxidative potential in the eye tissues, and decrease the permeability of the blood-ocular barrier. Conclusion. It is concluded that the introduction of melatonin instillations in the combined treatment of uveitis may improve the effectiveness of therapy of this condition.