brevetoxins

Brevetoxins are a family of lipid-soluble neurotoxic polyether compounds produced by marine dinoflagellates, principally Karenia brevis. They accumulate in shellfish and fish during red tide events along warm coastal waters of the Atlantic and Gulf of Mexico. Humans are exposed mainly through ingestion of contaminated seafood, but inhalation of aerosolized seawater during blooms can also cause respiratory symptoms.

Chemically, brevetoxins are polyether ladder toxins that interact with voltage-gated sodium channels. They bind to site 5 on the alpha subunit of these channels, shifting activation to more negative potentials and delaying or preventing inactivation. The result is a persistent inward sodium current and heightened neuronal excitability, which disrupts nerve signaling and can affect muscle function.

In humans, brevetoxin exposure can cause Neurotoxic Shellfish Poisoning (NSP). Symptoms typically include tingling and numbness of the lips, face, and extremities, a reversal of hot and cold sensation, dizziness, ataxia, and nausea or diarrhea; in severe cases, respiratory distress may occur. Inhalation exposure to aerosolized toxins can provoke coughing, throat irritation, and wheezing, particularly in individuals with asthma. Brevetoxins are relatively heat-stable and cooking does not reliably destroy them.

Monitoring and regulation aim to prevent contaminated seafood from reaching consumers. Shellfish harvesting is closed or restricted when toxin levels exceed regulatory limits, and products are tested using chemical assays such as LC-MS or immunoassays; historically, mouse bioassays were used. Ecologically, blooms are seasonal in warm coastal waters, and toxins can degrade over time through sunlight and microbial processes, though they may persist in the environment and tissues for some period.