Botulinum Neurotoxins (BoNTs) and Their Biological, Pharmacological, and Toxicological Issues: A Scoping Review

Botulinum toxins or neurotoxins (BoNTs) are the most potent neurotoxins known, and are currently extensively studied, not only for their potential lethality, but also for their possible therapeutic and cosmetic uses. Currently, seven types of antigenically distinct toxins are known and characterized, produced by a rod-shaped bacterium, Clostridium botulinum. Human poisoning by botulism (presenting with severe neuromuscular paralytic disease) is usually caused by toxins A, B, E, and F type. Poisoning from contaminated food preparations is the most common cause of noniatrogenic botulism. The spores are highly resistant to heat but are easily destroyed at 80 °C for thirty minutes. Type A and B toxins are resistant to digestion by the enzymes of the gastrointestinal system. After their entry, BoNTs irreversibly bind to cholinergic nerve endings and block the release of acetylcholine from the synapses. In contrast, in wound botulism, the neurotoxin is instead product by the growth of C. botulium in infected tissues. The contamination by BoNT inhalation does not occur by a natural route but it is certainly the most dangerous. It can be caused by the dispersion of the botulinum toxin in the atmosphere in the form of an aerosol and therefore can be deliberately used for bioterrorist purposes (e.g., during CBRN (chemical, biological, radiological, and nuclear) unconventional events). In addition, BoNTs are currently used to treat a variety of diseases or alleviate their symptoms, such as the onabotulinumtoxinA for migraine attacks and for cosmetic use. Indeed, this paper aims to report on updated knowledge of BoNTs, both their toxicological mechanisms and their pharmacological action.