Via Greta, at Bloomberg, Botox May Move From Face to Brain, Study in Rats Says
Botulinum neurotoxin type A, sold as Allergan Inc.’s Botox remedy for wrinkles, can move from its injection site to the brain, a study shows.
Scientists injected rats’ whisker muscles with botulism toxin. Tests of the rodents’ brain tissue found that botulism had been transported to the brain stems, the researchers said in the Journal of Neuroscience published April 2.
You can read the Journal of Neuroscience article abstract here:
Botulinum toxins (BoNTs) are used increasingly to treat maladies from spasms and migraines to obesity and wrinkles. It has been assumed that the toxin remains localized at the injection site, where it cleaves proteins involved in vesicle fusion, thereby blocking neurotransmitter release. But now Antonucci et al. demonstrate that BoNT/A is retrogradely transported along microtubules, transcytosed, and taken up by afferent terminals. When BoNT/A was injected into one hippocampus in rats, it cleaved its target — synaptosomal-associated protein of 25 kDa (SNAP-25)—in the contralateral hippocampus, resulting in reduced neuronal activity. Similarly, when BoNT/A was injected into the superior colliculus or whisker pads, SNAP-25 was cleaved in the retina and facial nucleus, respectively. In the retina, BoNT/A remained active for at least 25 d after injection. Although cleaved SNAP-25 was detected only in afferents that projected directly to the injection site, it is not clear whether further transcytosis would occur over time.
The Bloomberg article says,
Scientists injected botulism toxin into one side of the hippocampus in each rodent brain, and into their superior colliculus, a visual center. From one side of the hippocampus, the toxin migrated to the opposite. From the visual center, the drug went to the animals’ eyes.
The effects of the injection into the hippocampus were still present six months later, the scientists wrote.
The FDA is evaluating reports of breathing difficulties and death after use of Botox and Myobloc, according to a posting in February on the agency’s Web site. Many of the most serious cases involved children who received the injections to treat arm and leg spasms associated with cerebral palsy, a use not approved by the FDA.
Prescribing literature for Botox and Myobloc now carries warnings about the risk of breathing and swallowing difficulties in patients with neuromuscular disorders. The FDA said the new data suggest that life-threatening side effects may occur in patients with other conditions, including children with cerebral palsy.
On a lighter mode, considering some of the statements regular Botox users make, these new findings are not really surprising.