Age-related macular degeneration: Study finds surprising culprit
18 May, 2020
A new study suggests that a molecule that always suppresses harmful blood vessel growth can do the opposite in a type of sight loss called age-related macular degeneration (AMD). If confirmed in future studies, the discovery could bring about more effective treatments.
A lot more than 1.8 million Americans aged 40 years and over have AMD, in line with the Centers for Disease Control and Prevention (CDC).
According to 1 source, 10-15% of men and women with AMD have a far more severe form of the condition referred to as “wet” AMD that progresses quicker.
Wet AMD involves inflammation and excessive growth of fragile arteries beneath the macular. This is the central section of the retina that allows the attention to see fine detail. These vessels leak blood and fluid, which damages photoreceptors in the macular and results in lack of central vision.
Research into other conditions involving nerve damage, such as for example Alzheimer’s and Parkinson’s disease, shows that an immune-signaling molecule called interleukin-4 (IL-4) may play an anti-inflammatory, protective role.
IL-4 is also known to suppress blood vessel growth, which may assist in preventing the growth of tumors.
In addition, bone marrow cells usually help your body repair damaged tissues, including blood vessels.
Aqueous humor
Researchers in the Division of Ophthalmology and Visual Science at Tottori University in Japan attempt to discover whether IL-4 and bone marrow cells protect the photoreceptors of individuals with wet AMD.
The team published their finding in the journal eLife.
First, they measured levels of IL-4 in the aqueous humor - the watery fluid in the eyes - of 234 people with wet AMD at their first treatment session. In addition they collected samples of aqueous humor from 104 older persons undergoing surgery for cataracts, who served as controls.
People with wet AMD had higher levels of IL-4 than those in the control group.
The researchers also discovered that mice with a condition that mimics AMD had raised degrees of IL-4 to them. To determine if the molecule is protective or harmful, they injected IL-4 in to the bloodstream of the mice and found it increased excessive blood vessel growth to them.
Injecting the mice with an antibody that blocks IL-4 production had the contrary effect, reducing blood vessel growth.
The researchers continued to use cell culture experiments to show that IL-4 really helps to control the response of mice bone marrow cells and the growth of new retinal blood vessels. In its absence, the fragile blood vessels that characterize AMD were not able to grow.
Crucial role
“Our results show that IL-4 plays an essential role in excessive blood-vessel growth by recruiting bone marrow cells that aid this growth to the lesion in the eye,” says Takashi Baba, co-first writer of the study.
The researchers conclude that far from protecting photoreceptors by inhibiting the growth of new arteries - which is what they expected - IL-4 promotes the growth of more blood vessels.
“These results were surprising and advise that normally helpful immune responses can instead cause more harm,” says co-first author Dai Miyazaki.
In their paper, the authors write that while IL-4 may reduce inflammation, avoid the growth of new blood vessels, and protect nerve cells, these functions appear to be reliant on the context.
Nonetheless, they think that their surprise finding offers new possibilities for treating AMD.
“As IL-4 plays a key disease-promoting role in AMD, it could serve as a target for new treatments to take care of this problem,” says Miyazaki.
These treatments could block either IL-4 itself or the receptors to which it binds.
For the present time, however, the findings remain preliminary and can ought to be investigated further to confirm the researchers’ conclusions.
Source: www.medicalnewstoday.com
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