Anti-inflammatory role of curcumin in retinal disorders (Review)

Abstract

Curcumin [1,7-bis-(4-hydroxy-3-methoxyphenyl)-hepta-1,6-diene-3,5-dione], the main component of turmeric (Curcuma longa, a flowering plant of the ginger family, Zingiberaceae), is known to possess different pharmacological activities, particularly anti-inflammatory and antioxidant properties. Since an underlying inflammatory process exists in several ocular conditions, such as anterior uveitis, glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy (DR), the aim of the present review was to summarize the pleiotropic effects exerted by this molecule, focusing in particular on its beneficial role in retinal diseases. The anti-inflammatory activity of curcumin has also been described in numerous systemic inflammatory pathologies and tumors. Specifically, the biological, pharmaceutical and nutraceutical properties of curcumin are associated with its ability to downregulate the expression of the following genes: IκBα, cyclooxygenase 2, prostaglandin E2, interleukin (IL)-1, IL-6, IL-8 and tumor necrosis factor-α. According to this finding, curcumin may be useful in the treatment of some retinal disorders. In DR, proliferative vitreoretinopathy and AMD, beneficial effects have been observed following treatment with curcumin, including slowing down of the inflammatory process. Despite the aforementioned evidence, the main disadvantage of this substance is that it possesses a low solubility, as well as poor oral bioavailability due to its reduced absorption, rapid metabolism and rapid elimination. Therefore, several curcumin analogues have been synthesized and tested over the years, in order to improve the possible obtainable therapeutic effects. The purpose of the present review was to identify new aspects that could guide future research on this important traditional medicine, which is a well-tolerated natural product, and is widely considered safe and economical.

Keywords: DR; ROS; curcumin; epidermal growth factor; polymeric micelles; protein kinases.

Figure 1

Curcuma longa. (A) Turmeric flowers, (B) root and (C) its chemical structure.

Figure 2

OCT. Wet age-related macular degeneration with choroidal neovascularization. Subretinal fluid and fibrovascular pigment epithelial detachment were also evident on the OCT. Diagnostic images provided by Professor M. Nebbioso. OCT, optical coherence tomography.

Figure 3

OCT. Diabetic retinopathy with cystoid macular edema. OCT showed a retinal section with cystic spaces at the macula. Diagnostic images provided by Professor M. Nebbioso. OCT, optical coherence tomography.