In the fight to link brain injuries and Alzheimer’s Disease (AD) in humans, researchers at the University of Pennsylvania Medical Center have found a strong contender in the molecular weight category. Abnormal tau proteins, which form fibrous tangles in the brains of AD sufferers, are identical to the abnormal tau proteins found in patients with Dementia Pugilistica (DP), a memory disorder also known as Punch Drunk – or Boxer’s – Syndrome.
Researchers from Penn’s Center for Neurodegenerative Disease Research (CNDR) compared the brains of people with a genetic history of AD and the brains of DP sufferers to discover if there is a molecular basis in humans for the notion that brain injuries could predispose a person to AD. Their findings, published in the June issue of the international neurology journal Acta Neuropathologica, suggest that lesions in the two disorders arise through similar means.
“Our findings suggest that brain injury can cause Boxer’s Syndrome by activating mechanisms like the ones that cause tau lesions in Alzheimer’s,’ said M. Luise Schmidt, PhD, a senior research investigator at the CNDR. “By extension, it also suggests that a head injury can increase susceptibility to Alzheimer’s later in life.”
Tau lesions, which form as fibrous clumps of abnormal tau protein amass, are one part of the assortment of problems that characterize AD. The human brain produces six forms of tau protein, which researchers believe have a role in forming the network of microtubules that serve as a kind of transport system within brain cells.
Alzheimer’s Disease and Dementia Pugilistica are both part of a subset of brain diseases known as tauopathies, and are both marked by similar physical and memory disorders. That does not mean, however, that the diseases are the same. Although they share the pathology, the fibrous lesions in AD and DP are generally found in different parts of the brain.
“These findings lead us to believe that the events of brain injury lead to the same sort of biochemical effects that cause the tau lesions in Alzheimer’s,” said John Q. Trojanowski, MD, PhD, co-director of the CNDR and professor in the Department of Pathology and Laboratory Medicine in Penn’s School of Medicine.
“The abnormal tau proteins found in people with Boxer’s Syndrome are indistinguishable from those found in patients with a familial history of Alzheimer’s, and we are exploring how they got that way.”
The researchers believe that, by understanding the similarities in the diseases, they can find the common roots. In this article, they compared the brains of people who had a post mortem diagnosis of an inherited from of AD with the brains of deceased ex-boxers who had a diagnosis of DP. The findings – that they share pathology in humans – will further clarify the relationship of DP and AD as well as other tauopathies.
The researchers also stress the need for care and protection of the brain, especially in sporting activities. Boxers, of course, participate in a sport that exposes them to repeated acts of brain trauma. Even those who seem fine after a traumatic event may not realize the injury’s full impact until years later.
“The effects of these self inflicted brain injuries are not always readily apparent, and we are only beginning to understand the long-term secondary effects of the trauma,” comments Tracy K. McIntosh, PhD, director of Penn’s Head Injury Center. “It also goes to show that people have an unfortunate tendency to willingly replicate a natural disorder.”