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

Abstract

Curcumin [1, -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 nutra-ceutical 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.

The Immunosuppressive Niche Established with a Curcumin-Loaded Electrospun Nanofibrous Membrane Promotes Cartilage Regeneration in Immunocompetent Animals

“…Hence, Cur—an anti-inflammatory drug—was added to the PLGA membrane to obtain the Cur/PLGA nanofibrous membrane. Although Cur has several drawbacks (e.g., instability, poor solubility, and low bioavailability) [ 36 ], the roles of Cur in suppressing inflammatory cytokines have been extensively studied [ 37 , 38 ]. Cur exerts anti-inflammatory activities through the following mechanisms: (1) Cur alleviates oxidative stress and inflammation in chronic diseases by modulating the Nrf2-keap1 signaling pathway.…”

The Age-Related Macular Degeneration (AMD)-Preventing Mechanism of Natural Products

“…In this study, the relation between AMD and the suppression of the three types of stress by natural products was reviewed. These natural products include anti-oxidants, including Nrf2/HO-1 stimulators, namely, canolol, genipin, hesperetin, narigenin, salvianolic acid, carotenoids, Arctium lappa L. leaves, delpinidin, polyphenols, and glabridin [62][63][64][65][66][67][68][69][70][71][72]; anti-inflammatory agents, such as baicalin, Lycium barbarum polysaccharides, puerarin, grape seed proanthocyanidin, C3G, curcumin, nepetin, resveratrol, saffron, and wogonin [80][81][82][83][84][85][86][87]90,91,93]; and anti-carbonyl stress suppressors, such as allicin, blueberries, grapes, quercetin, tomatoes, and nutritional supplements containing vitamin C, vitamin E, zinc, and lutein [42,82,94,96,[98][99][100]. However, there are several AMD-prevented mechanisms of natural products excluding anti-oxidation, anti-inflammation, and anticarbonylation.…”

“…Curcumin [1,7-bis-(4-hydroxy-3-methoxyphenyl)-hepta-1,6-diene-3,5-dione], which is one of the major constituents in Curcuma longa, has several biological effects, including anti-allergy, anti-oxidative, and anti-inflammatory effects; in particular, it suppresses bcl-2 family-related RPE cell death through the extracellular signal-regulated kinase (ERK)/NF-κB-COX-2 signaled anti-inflammation pathway [85]. Nepetin, which is called eupafolin or 6-methoxyluteolin, a flavonoid isolated from several herbs, such as Eupatorium ballotaefolium, Rosmarinus officinalis, and Clerodendrum petasites [86][87][88], decreases inflammation-related cytokines, such as IL-6 and IL-8, via the NF-κB/MAPK (ERK1/2, JNK and p38MAPK) pathway [89].…”

NUTRARET: Effect of 2-Year Nutraceutical Supplementation on Redox Status and Visual Function of Patients With Retinitis Pigmentosa: A Randomized, Double-Blind, Placebo-Controlled Trial

“…Curcumin, the main component of turmeric, was capable to slow down inflammation in AMD, diabetic retinopathy or RP through the downregulation of IL6, TNFα, etc. ( 65 ). Different studies evaluated the effect of the nutritional supplementation with β-carotene, vitamin A, docosahexaenoic acid (DHA), lutein or vitamin E in RP patients.…”