Breaking the defence: Blood-brain-barrier dysfunction in football players
There is an increasing number of retired football players that are developing neurodegenerative and neuropsychiatric disorders including Alzheimer’s, dementia, depression, and chronic traumatic encephalopathy. A new study published in JAMA Neurology reveals a new link between head trauma in football players and neural damage.
Football players frequently receive blows to the head, and evidence suggests that repeated mild traumatic brain injuries (mTBI), such as concussions, can lead to neurodegeneration. What isn’t clear, however, is how mTBIs that occur early in an athlete’s career lead to the development of neurodegenerative disorders many years later, after they have retired.
Recent evidence suggests that development of mTBI-related disorders may be due to a dysfunctional blood-brain-barrier (BBB). The BBB is a highly selective membrane that surrounds blood vessels in the central nervous system, allowing only certain molecules, typically nutrients necessary for neural function, to pass into the fluid surrounding the brain. Importantly, the BBB prevents the passage of potentially harmful molecules into the brain, which helps prevent neural damage. This includes blockade of even non-pathological molecules, such as proteins, which can become harmful if they accumulate in the brain.
Weissberg et al. tested the hypothesis that American football players have “leaky” BBBs. They used a technique called dynamic contrast enhanced MRI to measure the “leakiness” of the BBB in a group of football players, and in a group of track and field athletes that acted as a control cohort. Two months after each group had gone through a regular interval of training and competition, each athlete had a contrast dye, which is typically blocked by the BBB, injected into their blood stream. During the injection, athletes underwent an MRI on their brain to visualize how much dye leaked from their bloodstream and into their brain tissue.
The researchers found that 40% of the football players had significant BBB dysfunction, compared to only 8% of the control athletes. Although the authors say they were unable to find a correlation between BBB dysfunction and the number of concussions an athlete had experienced, they did not discount the possibility that sub-concussive injuries can also lead to BBB dysfunction, or that unreported concussions could be disrupting a potential correlation. However, this study provides a promising diagnostic tool, and importantly a potential target for preventing long term neurodegenerative and neuropsychiatric disorders associated with mTBIs.
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