Microcystin: From Blooms to Brain Toxicity

Abstract

An increase in the temperature of lakes and ponds facilitates the over-growth of photosynthetic cyanobacteria that produce a class of toxins called cyanotoxins. The abundance of cyanobacteria poses a significant threat to drinking and irrigation water supplies, and therefore, cyanotoxins have become a major class of environmental pollutants. Microcystins, the most common cyanotoxins, are cyclic peptides produced by cyanobacteria through non-ribosomal peptide synthases, and currently, approximately 279 microcystins have been identified to date. Exposure to microcystins can cause liver and brain cytotoxicity, dermatologic, gastrointestinal, respiratory, and neurologic signs and symptoms, and affect human health. Notably, microcystin-leucine arginine can breach the blood-brain barrier by the transporter proteins, organic anion transporting polypeptides, leading to neuroinflammation, and changes in neurocircuitry resulting in behavioral alterations. In this review, we provide an update of the current literature on the detrimental effects of microcystins on the brain, focusing on their potential role in Alzheimer's and Parkinson's diseases. We discuss the current findings along with the cellular mechanisms involved and provide a brief narrative of the scope of future studies, especially to address the effects of microcystins along with genetic and other risk factors (like alcohol and other drugs) on neurodegenerative disease.

Keywords: Cyanotoxins; Microcystins; Neuro-cytotoxicity; Neurodegenerative diseases.

Figure 1.

Structure of MC-LR where X and Z are Leucine and Arginine at the 2 and 4 positions, respectively.

Figure 2.

A schematic of how MCs cause neurodegenerative diseases.