Neuroprotection in glaucoma: old concepts, new ideas

Nanoparticles Enhance Solubility and Neuroprotective Effects of Resveratrol in Demyelinating Disease

Resveratrol is a natural polyphenol which may be useful for treating neurodegenerative diseases such as multiple sclerosis (MS). To date, current immunomodulatory treatments for MS aim to reduce inflammation with limited effects on the neurodegenerative component of this disease. The purpose of the current study is to develop a novel nanoparticle formulation of resveratrol to increase its solubility, and to assess its ability to prevent optic nerve and spinal cord degeneration in an experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Resveratrol nanoparticles (RNs) were made using a thin rehydration technique. EAE mice received a daily oral administration of vehicle, RNs or unconjugated resveratrol for one month. They were assessed daily for clinical signs of paralysis and weekly for their visual acuity with optokinetic responses (OKR). After one month, their spinal cords and optic nerves were stained for inflammation and demyelination and retinal ganglion cells immunostained for Brn3a. RNs were stable for three months. The administration of RNs did not have any effect on clinical manifestation of EAE and did not preserve OKR scores but reduced the intensity of the disease. It did not reduce inflammation and demyelination in the spinal cord and the optic nerve. However, RNs were able to decrease RGC loss compared to the vehicle. Results demonstrate that resveratrol is neuroprotective by reducing RGC loss. Interestingly, neuroprotective effects and decreased disease severity occurred without reduction of inflammation or demyelination, suggesting this therapy may fill an unmet need to limit the neurodegenerative component of MS.

Astrocyte Networks as Therapeutic Targets in Glaucomatous Neurodegeneration

Astrocytes are intimately involved in the response to neurodegenerative stress and have become an attractive target for the development of neuroprotective therapies. However, studies often focus on astrocytes as single-cell units. Astrocytes are densely interconnected by gap junctions that are composed primarily of the protein connexin-43 (Cx43) and can function as a broader network of cells. Such networks contribute to a number of important processes, including metabolite distribution and extracellular ionic buffering, and are likely to play an important role in the progression of neurodegenerative disease. This review will focus on the pro-degenerative and pro-survival influence of astrocyte Cx43 in disease progression, with a focus on the roles of gap junctions and hemichannels in the spread of degenerative stress. Finally, we will highlight the specific evidence for targeting these networks in the treatment of glaucomatous neurodegeneration and other optic neuropathies.

Apoptosis in health and diseases of the eye and brain

Apoptosis is a form of programmed cell death (PCD) and enables the immunologically silent disposal of senescent or unwanted cells, causing minimal damage to the surrounding environment. Apoptosis can occur via intrinsic or extrinsic pathways that initiate a series of intracellular and extracellular signaling events. This ultimately leads to the clearance of the cell by phagocytes. This normal physiological mechanism may be accelerated in several diseases including those involving the eyes and brain, leading to loss of structure and function. This review presents the role of PCD in the health of the eyes and brain, and the evidence presented for its aberrant role in disease.

Curcumin as a Therapeutic Option in Retinal Diseases

The retina is subjected to oxidative stress due to its high vascularization, long time light exposition and a high density of mitochondria. Oxidative stress can lead to pathological processes, like cell apoptosis, angiogenesis and inflammation ending in retinal pathologies. Curcumin, a major bioactive component obtained from the spice turmeric (Curcuma longa) rhizome has been used for centuries in Asian countries for cooking and for curing all kinds of diseases like dysentery, chest congestion and pain in general, due to its antioxidant effects. Curcumin prevents the formation of reactive oxygen species and so it is a good protective agent. Curcumin has shown also anti-inflammatory, and antitumor properties. Curcumin is a natural product, which can be a therapeutic option in a variety of retinal diseases due to its pleiotropic properties. Some drawbacks are its poor solubility, bioavailability and lack of stability at physiological conditions; which have been shown in curcumin skeptical publications. In this review, we provide some lights and shadows on curcumin administration on the major retinal pathologies.

Does Retinal Ganglion Cell Loss Precede Visual Field Loss in Glaucoma?

It is often said that substantial retinal ganglion cells are lost before glaucomatous damage is detected by standard automated perimetry. There are 4 key articles referenced to support this belief. To test the hypothesis that the 4 key articles are incorrectly cited, the publications in the first 6 months of 2019 that reference 1 or more of these 4 articles were examined. In particular, the degree to which the quotes from these 2019 publications accurately reflected the evidence in the 4 key articles was assessed. These quotes are inadequately supported by the data, and in some cases even by the conclusions found in the abstracts of the key articles. This is despite several review articles that have questioned the evidence in these key articles. Further, a case can be made that the evidence in the key articles better supports the opposite conclusion. That is, the data suggest that sensitivity loss can be seen on standard automated perimetry before retinal ganglion cells are missing.