microcistinas

Microcystins, also called microcistinas in some languages, are a family of potent hepatotoxic cyclic peptide toxins produced by freshwater cyanobacteria during algal blooms. They are most commonly associated with the genera Microcystis, Planktothrix, and Anabaena, and can contaminate drinking water and recreational waters in lakes and reservoirs around the world.

Chemically, microcystins are cyclic heptapeptides that contain unusual amino acids, most notably the Adda moiety, which is essential for their biological activity. More than 200 congeners have been identified; the best known are microcystin-LR, -YR, and -RR. The structural diversity among congeners influences toxicity and occurrence, but all share a common mechanism of action.

The primary mechanism is inhibition of serine/threonine protein phosphatases 1 and 2A (PP1 and PP2A). Microcystins covalently bind to active-site residues, leading to hyperphosphorylation of cellular proteins, disruption of cytoskeletal integrity, and hepatocellular injury. Clinically, exposure can cause abdominal pain, vomiting, and acute liver failure in severe cases; chronic exposure is linked to liver disease and is classified by IARC as possibly carcinogenic to humans (Group 2B) for microcystin-LR.

Exposure occurs mainly through contaminated drinking water or recreational waters, and via consumption of fish or shellfish from affected areas. Monitoring employs ELISA and liquid chromatography–mass spectrometry (LC-MS). Guideline values exist to protect public health; the World Health Organization has issued provisional drinking-water limits for microcystin-LR (about 1 µg/L). Water treatment strategies include activated carbon, oxidation, and advanced oxidation processes to reduce toxin levels. There is no specific antidote; management is supportive in cases of poisoning.