When someone suffers a traumatic spinal cord injury, injured tissue at the lesion site releases an excessive amount of a chemical called adenosine triphosphate (ATP) that activates a receptor called P2X7. The activation of P2X7 receptors causes further irreversible tissue damage or secondary injury.

In 2004, Maiken Nedergaard and colleagues at the University of Rochester Medical Center (NY) showed that a compound that blocked the P2X7 receptors reduced spinal cord damage and improved motor function recovery in rats that had experienced spinal cord injury (Nat. Med. 10, 821–827; 2004). This compound, however, is toxic and cannot cross the blood-brain barrier, so it has only limited clinical utility.

Nedergaard and her team have now tested another compound, called Brilliant blue G (BBG), that also blocks P2X7. BBG is cheap and non-toxic, crosses the brain-blood barrier and is very similar to FD&C blue dye No. 1, the compound used to dye Gatorade and M&Ms blue. When given to rats with spinal cord injuries, BBG reduced tissue damage and improved motor recovery (Proc. Natl. Acad. Sci. USA 106, 12489–12493; 2009).

To evaluate BBG, the research team anesthetized the rats and gave the rats a weight drop injury in the thoracic region of the spinal cord. They then injected the rats with either a control solution or a solution of BBG (at a dose of 10 or 50 mg/kg) 10–15 min after injury and once daily for the next two days. The researchers monitored motor recovery and injury size for the six weeks following injury.

The rats that received one of the BBG doses recovered motor function faster than did the control animals. From 10 through 42 days after injury (the end of the experiment), the BBG rats had significantly better motor function than the non-treated rats. Additionally, the rats that received either dose of BBG lost significantly less spinal cord tissue after the injury than did the rats treated with the control solution. Importantly, the BBG injections had a greater effect on mitigating tissue atrophy than on suppressing lesion size, which fits with the hypothesis that BBG blocks the response that causes secondary injury.

The only noticeable side effect was that the eyes of the rats that received either of the BBG doses and the skin of the rats that received the 50 mg/kg BBG dose became temporarily blue. Though these results are promising, more extensive research is needed to determine whether this therapy could be useful for humans.