Recent Advances and Disputes About Curcumin in Retinal Diseases

Abstract

Curcumin belongs to the group of so-called phytocompounds, biologically active molecules produced by plants exerting a beneficial effect on health. Curcumin shows a wide spectrum of different properties, being an anti-inflammatory, antioxidant, antimicrobial and antimutagenic molecule. The purpose of the review is to examine what literature reported on the characteristics of curcumin, particularly, on the beneficial and controversial aspects of this molecule, aiming for a better therapeutic management of retinal diseases. The retina is a constant target of oxidative stress, this tissue being characterized by cells rich in mitochondria and by vessels and being, obviously, continuously reached from photons affecting its layers. Particularly, the retinal ganglion cells and the photoreceptors are extremely sensitive to oxidative stress damage and it is well known that an imbalance in reactive oxygen species is often involved in several retinal diseases, such as uveitis, age-related macular degeneration, diabetic retinopathy, central serous chorioretinopathy, macular edema, retinal ischemia-reperfusion injury, proliferative vitreoretinopathy, hereditary tapeto-retinal degenerations, and retinal and choroidal tumors. To date, several studies suggest that oral treatment with curcumin is generally well tolerated in humans and, in addition, it seems to have no negative effects: therefore, curcumin is a promising candidate as a retinal disease therapy. Unfortunately, the primary limitation of curcumin is represented by its poor bioavailability, in fact only a minimal fraction of this substance can reach the blood stream in the form of a biologically active compound. However, many steps have been made in several fields. In the future, it is expected that the strategies developed until now to allow curcumin to reach the target tissues in adequate concentrations could be ameliorated and, above all, large in vivo studies on humans are needed to demonstrate the total safety of these compounds and their effectiveness in different eye diseases.

Potential Properties of Natural Nutraceuticals and Antioxidants in Eye Protection

“…Most retinal diseases, as already mentioned, imply abundance of ROS and reduced levels of scavenger antioxidants. In particular, RGC and photoreceptors are extremely sensitive to oxidative stress damage and it is known that the accumulation of ROS is often involved in several diseases of the retina, such as uveitis, age-related macular degeneration, diabetic retinopathy, retinal tumors and proliferative vitreoretinopathy (PVR) [135]. In order to know the effect of curcumin after an oxidative stress insult, Munia et al, have shown that this nutraceutical compound was capable of protecting human retinal epithelial cells from death [136].…”

Detection of macular ganglion cell complex loss and correlation with choroidal thickness in chronic and recurrent central serous chorioretinopathy

“…The superficial capillary plexus (SCP) is primarily located within the ganglion cell layer. A significant reduction in SCP vessel density has been found in the loss of ganglion cells [39] . We found that SCP flow density was inversely associated with FLV in a proportion of patients with CCSC and RCSC.…”

The Pathomechanism, Antioxidant Biomarkers, and Treatment of Oxidative Stress-Related Eye Diseases

“…The oral administration of curcumin can relieve chronic diabetic macular edema and improve visual acuity [259]. The above reports demonstrate the therapeutic value of natural antioxidants in ophthalmic diseases [248,260].…”