Blindness from some inherited eye diseases may be caused by gut bacteria, new study suggests

Key Takeaways

• In eyes with sight loss caused by a particular genetic mutation known to cause eye diseases that lead to blindness, gut bacteria were found within the damaged areas of the eye. 
• Treating these bacteria with antimicrobials, such as antibiotics, was able to prevent sight loss in mice with the mutation.

Sight loss in certain inherited eye diseases may be caused by gut bacteria, and is potentially treatable by antimicrobials, finds a new study in mice co-led by a UCL and Moorfields researcher. The international study observed that in eyes with sight loss caused by a particular genetic mutation known to cause eye diseases that lead to blindness, gut bacteria were found within the damaged areas of the eye. The authors of the new paper, published in Cell and jointly led by researchers in China, say their findings suggest that the genetic mutation may relax the body’s defenses, thus allowing harmful bacteria to reach the eye and cause blindness.

The researchers investigated the impact of the Crumbs homolog 1 (CBR1) gene, which is known to be expressed in the retina and is crucial to building the blood-retina barrier to regulate what flows in and out of the eye. The CRB1 gene is associated with inherited eye disease, most commonly forms of Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP); the gene is the cause of 10% of LCA cases and 7% of RP cases worldwide. Using mouse models, the research team discovered the CRB1 gene is key to combating pathogens and harmful bacteria by regulating what passes between the contents of the gut and the rest of the body.

The team also found that when the gene has a particular mutation, dampening its expression (reducing its effect), barriers in both the retina and the gut can be breached, enabling bacteria in the gut to move through the body and into the eye. This leads to lesions in the retina that cause sight loss.

Crucially, treating these bacteria with antimicrobials, such as antibiotics, was able to prevent sight loss in the mice even though it did not rebuild the affected cell barriers in the eye. The findings of this study suggest that simply using antimicrobials might help prevent deterioration in CRB1-associated inherited eye diseases. Future work will investigate whether this applies in humans. 

Edited by Suditi Kedambadi and Miriam Kaplan, PhD.

Source: University College London, Medical Xpress, February 26, 2024; see source article