Glaucoma, Curcumin, and Autoimmunity: Exploring the Research
New Discoveries Related to Glaucoma
Glaucoma is a potentially serious eye problem. In the most common form of the disease, fluid builds up in the eyeball. The fluid creates pressure that damages the retinal ganglion cells located at the back of the eyeball. The long fibers of these cells are known as axons and form the optic nerve. The nerve is vital for vision because it transmits signals from the eye to the brain. If glaucoma is not treated and the optic nerve is damaged, vision loss and even blindness may result.
Researchers have recently discovered that a chemical called curcumin from turmeric helps to treat early glaucoma in rats when formulated correctly. The chemical may be helpful in humans as well. Other researchers have found evidence supporting the idea that glaucoma is an autoimmune disease. If this idea is true, new and more effective treatments may be created.
Parts of the Eye
In order to understand the problem that contributes to vision loss in glaucoma, it's helpful to know a little about the anatomy of the eye. The cornea is the transparent layer over the front of the eye. The iris is the colored part of the eye. It has a circular gap in the center called the pupil. The pupil allows light rays to reach and travel through the lens, which is located behind the iris. The size of the pupil varies, depending on light conditions. The light rays travel through the vitreous humour located behind the lens and then strike the retina.
The light triggers the creation of electrical nerve impulses in the retina. Retinal ganglion cells are located at the back of the retina. They send impulses along the optic nerve to the brain, which produces an image.
What Is Glaucoma?
The spaces between the cornea and the lens are filled with a fluid called aqueous humor, which provides nourishment to eye tissues. The aqueous humor is secreted by the ciliary body, moves through the posterior chamber behind the iris, and then travels through the anterior chamber in front of the iris. It's removed through drainage canals located between the edge of the iris and the cornea.
If the fluid exit area is narrowed or the drainage canals are blocked, an insufficient quantity of fluid may leave the eye. Intraocular pressure (the pressure inside the eyeball) may then increase. The pressure is transmitted through the largest chamber of the eye, which is filled with a gel known as vitreous humor, and then presses on the retina at the back of the eyeball. This damages the retinal ganglion cells and the optic nerve produced from their axons.
It should be noted that optic nerve damage and glaucoma sometimes develop without an increase in fluid pressure within the eyeball. This suggests that we don’t completely understand the condition yet. Unfortunately, people may not notice a vision problem or seek medical help until the disease is quite advanced and a considerable number of retinal ganglion cells have been lost.
The earliest symptoms of glaucoma include the loss of peripheral vision, as shown in the simulation at the start of this article. Initially, vision loss will probably be milder than that shown in the photo and the condition may progress slowly. Eventually, central vision may be lost.
Disease Description by an Eye Doctor
The Turmeric Plant and Spice
Turmeric is a flowering plant in the ginger family (the Zingiberaceae) that’s native to India and Southeast Asia. Its rhizome, or underground stem, is used to create a yellow-orange powder. The powder is used as a spice and is also known as turmeric. Curcumin is a chemical in the spice.
Turmeric and curcumin might be capable of providing several wonderful health benefits. It’s been hard to prove this, though. For example, turmeric is a popular component of the diet in India and Asia. It has been noted that the incidence of Alzheimer’s disease is significantly lower in these parts of the world than in other areas. The Alzheimer’s Society in the UK says that turmeric ingestion is unlikely to be responsible for this observation, however. Interestingly, they don’t completely dismiss the benefit of the spice. They note that in lab equipment curcumin has been found to have antioxidant, anti-inflammatory, and anti-amyloid properties. Abnormal brain deposits of a protein called beta-amyloid are a characteristic of Alzheimer’s disease.
We have some evidence, if you look at the in vitro cellular studies, if you look at animal studies, the evidence is very strong. But humans are not animals. We need to provide more evidence from clinical trials … to get solid evidence of the health benefits of curcumin.— Professor Manohar Garg, University of Newcastle, via the Australian Broadcasting Corporation
Improving the Absorption of Curcumin
One problem with obtaining the required proof for its benefit might be that curcumin is poorly absorbed by the gut. Benefits demonstrated in cells or tissue in lab equipment are not always duplicated in the body. A patient would have to take a huge dose of turmeric or curcumin in order to absorb enough to be helpful (assuming the substance is beneficial for the patient’s condition). This would not only be inconvenient but would likely cause gastrointestinal distress. There is hope that the absorption of curcumin will soon be improved, however.
Ingesting black pepper with curcumin or turmeric increases the bioavailability of curcumin by around 2,000 percent. Bioavailability is the proportion of a drug that has an active effect in the body. A new discovery may be even more helpful. Researchers in Britain have created a nanocarrier for curcumin that they say increases its solubility in eye drops by an amazing 400,000 times. In addition to the increased solubility, another advantage of the nanocarrier is that it would enable doctors to place the substance directly in the eyes instead of providing an oral medication.
A nanometer is a billionth of a meter. The word “nanoparticle” general refers to particles with a diameter of one to a hundred nanometers. A nanocarrier is a molecule or particle on the nanoscale that is used to carry medicinal drugs through the body. The carrier may be a little larger than a traditionally-defined nanoparticle but is still very tiny. A nanocarrier has features that enable it to effectively ferry a drug to the area where it’s needed. Without the carrier, the drug may not be absorbed by the correct area.
Glaucoma is a group of eye conditions affecting over 60 million people worldwide that leads to irreversible blindness in 1 in 10 cases.— University College London, via ScienceDaily
Curcumin in a Rat Model of Glaucoma
The term “animal model” is often used by researchers. The term means that although it seems that a lab animal has the same disease as humans, we can’t be absolutely certain that the disorder is the same or is occurring by the same processes as in the human body. A discovery in lab animals often applies to humans, but this isn’t always the case.
Scientists at University College London and Imperial College London recently used a rat model to study the effect of curcumin attached to a nanocarrier on glaucoma. The scientists administered the eye drop medication twice a day over a period of three weeks to rats who had retinal ganglion loss. Another group of rats with the same condition was untreated. The further loss of retinal ganglion cells was significantly reduced in the treated rats compared to the untreated ones and there were no signs of eye irritation from the treatment.
Current treatments for glaucoma include eye drops, laser treatment, and surgery. Eye drops containing one of a variety of drugs are commonly used. The drugs reduce fluid buildup and pressure in the eye by various methods. They are often helpful but can also produce side effects. In addition, in some patients retinal ganglion cells continue to be harmed even when intraocular pressure is normal. A medication such as curcumin might be very useful in protecting cells in the retina.
Types of Glaucoma
There are several kinds of T cells, or T lymphocytes as they are sometimes called. They are a type of white blood cell and are a very important part of our immune system. They are known as "T" cells because they mature in the thymus gland.
The Possible Role of T Cells
An autoimmune condition is one in which our immune system mistakenly attacks our body’s own tissues. The immune system is supposed to protect us from pathogens that cause disease or harm, which it often does admirably (though it sometimes needs help). Its attack on our cells can cause a range of health problems.
A team of researchers from the Massachusetts Institute of Technology, the Massachusetts Eye and Ear Institute, and other institutions has found evidence suggesting that glaucoma is—or is at least sometimes—an autoimmune disease. Like other observers, the researchers have noticed that in both humans and mice, even when intraocular pressure decreases, vision sometimes continues to get worse. This has suggested to the researchers that some other progressive condition occurs in the disease.
The researchers found T cells in the retina of mice with glaucoma (or with a disease closely resembling it). T cells are important in the immune system’s attack on an invader. The discovery was puzzling because T cells are normally prevented from entering the retina by the blood-retina barrier, which is a tightly-packed layer of cells. In mice, when intraocular pressure was high, the T cells were able to pass through this barrier.
Other researchers involved in the study had mice without T cells in their lab. The scientists triggered an increase in intraocular pressure in the mice, which caused a small amount of damage to their retina. When the scientists reduced the pressure, no further damage to the retina occurred.
Heat Shock Proteins and Autoimmunity
Additional studies by the Massachusetts researchers discovered how T cells may damage the retina in glaucoma patients. The presence of the cells appears to hinder molecules known as heat shock proteins. These molecules help cells to respond to stress and injuries.
Heat shock proteins in bacteria and humans are quite similar. The researchers suspect that the T cells that entered the retina had been “programmed” to target the human proteins after coming into contact with the bacterial ones.
Perhaps very significantly, the researchers found that people with glaucoma had five times the usual level of T cells that target heat shock proteins. The researchers don’t believe that a specific bacterium is required to create these T cells but think that the production is a response to the presence of bacteria in general. Interestingly, when the researchers tried to trigger glaucoma in a group of mice that contained no bacteria, they were unable to do so.
T cells in our body normally don't target our own heat shock proteins, but in glaucoma patients some may do so. This is a type of autoimmune response. When the abnormal T cells enter the retina due to high intraocular pressure, they may damage the retinal ganglion cells and may continue to do so after the pressure is reduced.
The disease often goes undetected at first; patients may not realize they have the disease until half of their retinal ganglion cells have been lost.— Anne Trayvon, MIT News Office
The Hope of Improved Treatments
The new discoveries are intriguing, but further research is needed. We need to discover whether the specially-formulated curcumin helps humans as well as rats. We also need to understand glaucoma better. An autoimmune response may be involved in some people with the disease but not in everyone. It's puzzling that some people suffer from glaucoma without developing high intraocular pressure.
Despite the need for further investigations, the recent discoveries could be very significant and may lead to better treatments for the disease. In addition, the discoveries related to T cells may occur in other diseases, including some that occur in the brain and some other autoimmune conditions. T cells are common and important cells in our body, so if they “misbehave” the results can be serious.
It would be wonderful if the latest research eventually helps not only glaucoma patients but also people with other diseases. With respect to glaucoma, however, diagnosing the condition as soon as possible is important with current treatments and will probably still be important if new ones are created. This is one reason why it's important to get our eyes checked regularly by an ophthalmologist. A checkup is especially important for older people, who are more likely to get glaucoma than younger ones. An eye doctor can detect problems before a patient is aware of them. Fighting glaucoma by all of the methods that are currently available is advisable.
Information about glaucoma from the Glaucoma Research Foundation
Turmeric and dementia from the Alzheimer’s Society in the UK (Alzheimer's disease is a type of dementia.)
What does the evidence say about turmeric's health benefits? from the Australian Broadcasting Corporation
A review of curumin's effects on human health from the Foods journal, National Institutes of Health
Eye drops derived from turmeric might treat glaucoma from the ScienceDaily news service
Glaucoma may be an autoimmune disease from MIT (Massachusetts Institute of Technology)
Commensal microflora-induced T cell responses mediate progressive neurodegeneration in glaucoma from Nature Communications
Questions & Answers
© 2018 Linda Crampton