Preventing the expression of the protein claudin-5 in the blood brain barrier after traumatic brain injury alleviates the swelling and improves brain function reports a paper in Nature Communications this week. These findings identify a novel way of reversibly modifying the blood brain barrier to reduce the amount of fluid build-up in the brain which often leads to long term damage.

The blood brain barrier is pivotal in keeping the brain separated from circulating blood. After brain injury, there is a dramatic reduction in water diffusion across the blood brain to the circulating blood from the brain, which contributes to swelling and potential brain damage. The protein claudin-5 is known to contribute to the permeability of the blood brain barrier.

Matthew Campbell and colleagues now show that use of the protein in alleviate the symptoms associated with swelling. They team administered interfering RNA in a mouse model of brain injury to suppress the expression of claudin-5. They find that there is enhanced exchange of water from the brain to the circulating blood that lasts up to 72 hours post treatment, which reduces the swelling in the brain as well as improves cognitive function.

The authors suggest that these findings could have major implications in a range of neurological conditions where fluid build-up in the brain is the central cause of morbidity and mortality.