Is an unruly immune system responsible for dementia?
Scientists have struggled for years to understand the causes of dementia and other neurodegenerative diseases. Genetic factors, the formation of amyloid plaques in the brain, damage to blood vessels, traumatic brain injury, and numerous other lifestyle and environmental factors have been explored, but researchers at Australia’s University of Adelaide have a new theory involving a runaway immune system.
The scientists believe that the neurological decline common to all of the diseases is caused by “auto-inflammation,” where the body’s own immune system develops a persistent inflammatory response that causes brain cells to die.
“Dementia, including the most common form Alzheimer’s disease, and related neurodegenerative conditions are dramatically rising in frequency as people live longer and our population ages,” says study leader professor Robert Richards.
“Currently we have no effective treatments to assist the millions of affected people, and these diseases are an enormous burden on families and the public healthcare system.”
Alzheimer’s disease is the most common form of dementia. Currently, about 5.4 million Americans suffer from Alzheimer’s, and according to the Alzheimer’s Association, that number may almost triple by 2050.
There are many distinct forms of neurodegeneration including Alzheimer’s, Parkinson’s and Huntington’s Diseases. Although when they first appear, the conditions are distinguished by the different types of symptoms and brain nerve cells that are first affected, the diseases become more similar as they progress.
Richards believes that all of the neurological diseases have the same underlying mechanism, and there is a common pathway of nerve cell loss.
“Our interest in the body’s own (innate) immune system as the culprit began when we discovered that immune system agents become activated in a laboratory model of Huntington’s Disease,” he says.
“Remarkably, researchers from other laboratories were at the same time reporting similar features in other neurodegenerative diseases. When we pulled the evidence together, it made a very strong case that uncontrolled innate immunity is indeed the common cause.”
The immune system is the body’s first line of defense. Normally, it differentiates the body’s own cells from foreign cells that cause disease or abnormal cells like those that cause cancer, and triggers the invasive and abnormal cells to self-destruct.
Malfunctions can occur because of various triggers including genetic mutations, infection, toxins or physical injury, all of which have been linked with different forms of neurodegeneration. Initially the immune system protects against the triggers, but prolonged activation becomes self-perpetuating, causing brain cell death to occur.
“We hope this new way of understanding neurodegeneration will lead to new treatments,” Richards says, adding that further study may identify new drug targets that will delay the onset or stop the progression of the diseases.
Image: Is an Unruly Immune System Responsible for Dementia? Copyright AP)
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