Common Bacteria Found in Eyes May Contribute to Cognitive Decline
Chlamydia pneumoniae, a bacterium known for causing pneumonia and sinus infections, can persist in the eye and brain for extended periods. A recent study from Cedars-Sinai suggests this bacterium might aggravate Alzheimer’s disease. The findings, published in Nature Communications, indicate that it could play a role in intensifying Alzheimer’s symptoms and hint at potential interventions like therapies aimed at reducing inflammation and early antibiotic use.
Bacteria Found in Eye and Brain
This study reveals that Chlamydia pneumoniae can reach the retina, the eye’s inner lining, where it provokes immune responses associated with inflammation, nerve cell death, and cognitive decline.
“Our consistent findings of Chlamydia pneumoniae across various human tissues, cell cultures, and animal models highlighted a previously overlooked connection between bacterial infections, inflammation, and neurodegeneration,” noted Maya Koronyo-Hamaoui, Ph.D., a professor at Cedars-Sinai Health Sciences University and the primary author of the research.
Koronyo-Hamaoui added, “The eye serves as an indicator for the brain, and this study supports the idea that retinal infections and ongoing inflammation may reveal brain pathology, offering a noninvasive method to identify individuals at risk for Alzheimer’s through retinal imaging.”
Methodology of the Study
Researchers utilized advanced imaging techniques, genetic analysis, and protein testing to inspect retinal tissue from 104 individuals, encompassing those with normal cognition, mild cognitive impairment, and Alzheimer’s disease.
They discovered significantly elevated levels of Chlamydia pneumoniae in the retinas and brains of people suffering from Alzheimer’s compared to those with normal cognitive function. Moreover, higher bacterial levels correlated with more severe brain alterations and cognitive decline.
Individuals possessing the APOE4 gene variant, a recognized Alzheimer’s risk factor, exhibited increased levels of this bacterium.
Inflammation Links and Treatment Insights
The research team also investigated human neurons in a lab setting and in mice with Alzheimer’s. The presence of Chlamydia pneumoniae was linked to heightened inflammation, nerve cell death, and cognitive deterioration, suggesting that this bacterium could speed up disease progress. Additionally, the infection led to increased production of amyloid-beta, a protein associated with Alzheimer’s.
Timothy Crother, Ph.D., co-corresponding author of the study, remarked, “This discovery opens the door to potentially targeting the infection-inflammation link for Alzheimer’s treatment.” The research indicates that addressing chronic bacterial infections and the resulting inflammation could provide a new strategy for treatment. It also supports the idea of using retinal assessments as a noninvasive tool for diagnosing and monitoring the disease.
