Science Current Events | Science News | Brightsurf.com
 

Bacterium present in eyes with 'wet' age-related macular degeneration

November 08, 2005

BOSTON - Researchers at the Massachusetts Eye and Ear Infirmary (MEEI) have found that Chlamydia pneumoniae, a bacterium linked to heart disease and capable of causing chronic inflammation, was present in the diseased eye tissue of five out of nine people with neovascular, or "wet," age-related macular degeneration (AMD). However, it was not found in the eyes of more than 20 individuals without AMD, providing more evidence that this disease may be caused by inflammation. The study is described in the November issue of Graefe's Archive for Clinical and Experimental Ophthalmology.

AMD is the leading cause of blindness in Americans over the age of 55. The majority of vision loss is due to neovascular AMD, the advanced form of the disease characterized by the formation of blood vessels in the macula, the center part of the eye's retina. These blood vessels often leak, thus giving neovascular AMD the name of "wet" AMD.

Researchers at the MEEI and Harvard Medical School (HMS) examined nine wet AMD membranes for the presence of C. pneumoniae and also determined whether this pathogen can change the function of eye cells in ways that can cause wet AMD. They found C. pneumoniae in the eyes of five out of the nine patients with wet AMD. They also tested tissue from more than 20 people who did not have AMD and did not find C. pneumoniae in any of these normal eye tissues.

"The paper showed that C. pneumoniae is capable of modifying the function of important cell types involved in regulating normal eye function," said lead author Murat Kalayoglu, MD, PhD. "We found that C. pneumoniae infection led to increased production of vascular endothelial growth factor (VEGF), the key protein involved in wet AMD. That C. pneumoniae infection of human eye cell types increases VEGF production is therefore significant and could explain in part why VEGF levels are increased in many people with wet AMD." Kalayoglu is an HMS research fellow in ophthalmology at MEEI.

Most of the new medications either marketed or being developed to treat wet AMD, such as Macugen (EyeTech Pharmaceuticals) and Lucentis (Genetech) block VEGF.

The study comes at a time of great interest in inflammatory mediators of AMD. Over the past seven months, a flurry of high-impact papers have shown, in aggregate, that nearly 50 percent of AMD can be explained by variations in a gene called Complement Factor H (CFH). This gene makes a protein that regulates the immune and inflammatory responses of the body.

"Our hypothesis is that C. pneumoniae may be the key link between CFH and AMD," Kalayoglu said. "That is, patients with CFH variations may be particularly susceptible to the damaging effects of chronic infection, and an infectious organism like C. pneumoniae may be particularly effective in accelerating inflammation and driving progression of AMD in these patients."

Kalayoglu and colleagues are currently collaborating with CFH researchers to study this hypothesis. "It may be possible to stop or reverse progression of AMD by identifying susceptible patients by diagnostic testing, and then treating these susceptible patients. Although C. pneumoniae is a bacterium that might respond to some antibiotics, much more work needs to be done before considering antibiotic therapy for AMD," he said.

"This is an important study suggesting that infection with C. pneumoniae may be a critical link between a genetic predisposition to AMD and actual progression to disease," said Gerald I. Byrne, Ph.D., professor and chairman of the Department of Molecular Sciences University of Tennessee Health Sciences Center. "This is yet another example of how an infection may unexpectedly contribute to a chronic disease. Certainly the association of C. pneumoniae with heart disease sets the stage for this pathogen's involvement in other chronic conditions. This work is, in some ways, reminiscent of studies done more than 15 years ago on infections and ulcers. Those studies were viewed with skepticism, but Drs. Marshal and Warren, the researchers who pioneered that work received the Nobel Prize this year."

The Graefe's paper builds on data from the same group that showed, for the first time, that an infectious agent is associated with AMD by epidemiological studies (Archives of Ophthalmology, April 2003).

Harvard Medical School


Related Macular Degeneration Current Events and Macular Degeneration News Articles


Potential new approaches to treating eye diseases
Potential new approaches to treating eye diseases such as age-related macular degeneration (AMD) are described in a new study, "IL-33 amplifies an innate immune response in the degenerating retina," in the February Journal of Experimental Medicine.

The connection between excess iron and Parkinson's disease
It's long been known that excess iron is found in the brains of patients with Parkinson's disease (PD), an incurable neurodegenerative condition that affects motor function. The mechanism by which the iron wreaks damage on neurons involved in PD has not been clear.

Vegetables fried with olive oil have more healthy properties than boiled ones
Researchers from the University of Granada (UGR) have proven that frying in Extra Virgin Olive Oil (EVOO) is the cooking method that increases the phenolic fraction present in raw vegetables used in Mediterranean diet (potato, pumpkin, tomato and eggplant) the most.

Recently approved heart drug poses potential risk to brain & eye, Temple researcher warns
Patients with mild heart failure stand to benefit from a new drug that can halt the progression of their disease and reduce their risk of cardiovascular-related death.

Nearsightedness progression in children slowed down by medicated eye drops
Researchers say medicated eye drops may be the key to fighting rapidly worsening eyesight in children with myopia.

UA-led research: Prevention of macular degeneration possible
A University of Arizona-led study on age-related macular degeneration - the eye disease that gradually destroys the ability to read, drive, write and see close-up in 30 percent of older Americans - likely will lead to a way to delay or prevent the disease, researchers say.

New study: Leading cause of blindness could be prevented or delayed
In a major scientific breakthrough, a drug used to treat Parkinson's and related diseases may be able to delay or prevent macular degeneration, the most common form of blindness among older Americans.

New drug candidate is promising therapeutic option for angiogenic retinal diseases
A research team led by scientists at Beth Israel Deaconess Medical Center (BIDMC) and the University of New Mexico School of Medicine has identified a small molecule that treats animal models of aged macular degeneration (AMD) and retinopathy of prematurity (ROP) by preventing the overgrowth of blood vessels that are characteristic of these two retinal diseases.

Restoring vision with stem cells
Age-related macular degeneration (AMRD) could be treated by transplanting photoreceptors produced by the directed differentiation of stem cells, thanks to findings published today by Professor Gilbert Bernier of the University of Montreal and its affiliated Maisonneuve-Rosemont Hospital.

Do patients with age-related macular degeneration have trouble with touch screens?
Older adults with central vision loss caused by age-related macular degeneration (AMD) have no problem with accuracy in performing touch screen tasks, according to a study in the October issue of Optometry and Vision Science, official journal of the American Academy of Optometry.
More Macular Degeneration Current Events and Macular Degeneration News Articles

© 2016 BrightSurf.com