Olfactory Viral Inflammation Associated with Accelerated Onset of Alzheimer's Disease
Published:09 Jan.2023    Source:University of Colorado Anschutz Medical Campus
Viruses can inflame and disrupt connections between the olfactory system, which governs the sense of smell, and the part of the brain associated with memory and learning, possibly accelerating the onset of Alzheimer's disease, according to a new study from researchers at the University of Colorado Anschutz Medical Campus.
 
The findings, published Tuesday in the journal Neurobiology of Aging, could lead to new therapies that detect Alzheimer's disease (AD) earlier while helping to illuminate the role that viruses and the olfactory system play in driving the illness.
 
"We know that one of the early signs of Alzheimer's disease is losing the sense of smell," said the study's lead author Andrew Bubak, PhD, assistant research professor in the division of neurology at the University of Colorado School of Medicine.
 
Bubak's team focused on the olfactory tract, olfactory bulb and the hippocampus, the area of the brain which manages memory and learning.
 
They examined messenger RNA in the brain tissue of six individuals from Colombia who had Familial Alzheimer's disease (FAD) and tissue from a control group without AD. They found signatures of viral infection in the olfactory bulbs of the FAD group and inflammation in the olfactory tract which carries information to the hippocampus. They also discovered altered myelination in the olfactory tract. Myelin is a protective fatty layer around nerves that allows electrical impulses to move quickly and smoothly. If it's damaged, signaling stalls.
 
"These findings raise the possibility that viral infection and associated inflammation and dysregulation of myelination of the olfactory system may disrupt hippocampal function, contributing to the acceleration of FAD progression," the study said.
 

The study's senior author, Diego Restrepo, PhD, professor of cell and developmental biology at the CU School of the Medicine, said viruses have long been suspected of playing a role in cognition problems. Some studies have associated the SARS-CoV-2 virus, which causes COVID-19, with dementia. The virus, which travels through the nose, causes some of those infected to lose their sense of smell.