According to a study in the Feb 9 issue in the Open Access journal PLoS Pathogens, the cause of seizures in patients whose brains are infected by the pork tapeworm Taenia solium has been identified by researchers from Baylor College of Medicine as a neuropeptide called ‘Substance P”.
Neurocysticercosis (NCC) is the largest cause of seizures worldwide and is caused by a parasitic tapeworm infection of the brain. Until now, the mediators responsible for seizures in NCC have been unknown, but Prema Robinson and her team recognized that Substance P plays a role in inflammation and discovered Substance P in autopsies of patients’ brains with the tapeworm infection. The neuropeptide Substance P is a small protein-like molecule that plays a part in communication between neurons, and was not found in uninfected brains.
Substance P, which is produced by neurons, endothelial cells, i.e. cells that line blood vessels, and cells involved in host defense, was discovered in the 1930s and has long been recognized as a pain transmitter, although since a few years it has also been discovered that it impacts many other functions.
Robinson explained that: “As long as the parasite is alive, nothing happens.” As soon as the worm dies however, it causes inflammation, which is brought on by the body’s chemical response of recruiting immune system cells to the site of infection. Robinson’s studies demonstrate that the cells producing Substance P are most prevalent in inflamed areas that are near the dead worms.
Robinson’s team observed severe seizures in mice that were either injected with Substance P alone or infected animals that were injected with extracts from the inflamed areas (granulomas) close to the worms. They noted that rodents that were administered with the drug that blocks the Substance P receptor did not have seizures.
Furthermore, they observed no induced seizures in mice with a Substance P receptor deficiency, even when the animals were injected with the extracts of granulomas from infected mice and neither did granuloma extracts from mice that lacked the cells that make Substance P.
These results are significant for those who frequently suffer seizures during treatment for this tapeworm infection, considering that seizures start when inflammatory cells migrate to the inflamed areas as the worms die. Drugs that block the receptor for Substance P are available, and these drugs may be the most effective in the treatment and prevention of seizures in these patients.
Written by Petra Rattue