Editorial Article

Microcystins Threat Human Health

Massey Isaac Yaw, Shu Yang, Fei Yang*
Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, China
*Corresponding author:

Fei Yang, Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, China, Email: phfyang@csu.edu.cn

Microcystins (MCs) pose great threat to human health, which are a group of cyclic hepatotoxic peptides produced by freshwater cyanobacteria and are mostly found in water bodies worldwide [1]. MCs can damage the liver, colorectal, brain, small intestines, lungs and kidney [2]. This paper elucidated the effects and some toxic mechanisms of MCs on human health.

MCs share a general cyclic structure which makes them possible to resist physical and chemical factors. The common structure of microcystin is cyclo-(-D-Ala1-L-X-DisoMeAsp-L- Z-ADDA-D-isoGlu-Mdha), where D-MeAsp is D-erythro -b-methylaspartic acid, Mdha is N-methyldehydroalanine, ADDA is (2S, 3S, 8S, 9S)3- amino-9 methoxy-2,6,8- trimethyl-10-phenyldeca-4, 6-dienoic acid, and X and Z are highly variable L-amino acids [3]. MCs have more than 100 isoforms isolated from water blooms, with a size of approximately 3 nm in diameter and a molecular weight ranging from 900 to 1,100 Da [4].

The toxins of MCs are structurally diverse in their effects. MCs are toxic to human when intoxicated and may cause:

Liver cancer

The major symptom of MCs exposure is liver injury [5]. Risk of cancer from direct ingestion of contaminated drink-ing water and exposure to some foods has become more rampant than before. MCs are transported straight to the liver since the toxin first get to the portal vein circulation and then reach the liver finally [6]. MCs’ ability to inhibit protein phosphatases PP1 and PP2 causes liver cancer and may lead to cell blebbing, cell fragmenting, and cell separa-tion from each other [7], subsequently to its failure in its function in the human body system [8]. Abnormalities such as hepatocellular hyperplastic foci, vascular hyperplasia, bile ductular hyperplasia, fibrosis, cholestasis, necrosis and inflammation may also be caused [9]. MCs are also able to bring proliferation at low doses, which cause potential cancer and its other effects on the human liver [10].

Colorectal cancer

Another tumor related to MCs is colorectal cancer. Colo-rectal cancer may be associated with the consumption of meat [11], animal fats [12] and sea foods such as shellfish contaminated with MCs [13]. The toxic effect is due to the inhibition of protein phosphatases (PP1 and PP2). Colo-rectal cancer is rapidly on the increase in many countries, especially in the developed countries [1].

Brain damage

MCs can be transported across the blood-brain barrier (BBB) mediated by the human organ anion-transporting peptides (OATPs) which induces neurotoxicity [5]. The neurotoxic effects caused by MCs then lead to various symptoms including neurostructural, functional and behavioural changes in the human body such as blocked memory retrieval [14].

Small intestines damage

Orally administered toxin may damage both the villi and the individual cells of the gastrointestinal lining [15]. The presence of MCs in the human system may damage the duodenum, jejunum and ileum. An increase in MCs may also induce apoptosis in the cells of the duodenum, jejunum and ileum [16].

Kidney damage

Chronic intoxication of MCs is capable of damaging the cortex and medulla of the human kidney. MCs may have a direct effect on the glomeruli which can result in intense amount of protein in the urinary space, increase of glomerular filtration, which may further lead to an increase in urinary flow [17, 18].

Lung cancer

MCs can accumulate in the human lungs through blood circulation. Although the effect of MCs on the lungs re-mains unclear, chronic and low-dose MCs exposure are capable of inducing alveolar collapse, lung cell apoptosis, break of cell junction integrity [19], rapid increase in lung impedance, inflammatory response with interstitial edema and inflammatory cell [20].


Exposure of the human body to water contaminated with MCs can result in some serious irritations. MCs come in contact with the skin which may lead to skin ir-ritation, eye irritation, ear irritation [21], nausea, vomiting [22], vertigo, myalgia, cough, blistering in the mouth and severe headache [23].

There are some reports of human poisoning and death resulting from intoxication by MCs. A serious incidence of liver failure and human death in Caruaru, Brazil dur-ing1996 were due to the use of untreated water from a reservoir contaminated with MCs toxins at a hemodialysis center. Hematological investigations showed that, the MCs exposure caused normocytic anemia in the patients at the hemodialysis unit [22]. Furthermore, the high incidence of hepatic tumors in the population of China has been considered to be associated with the consumption of raw waters containing MCs [24]. It is reported MCs existed in serum samples of fishermen at Lake Chaohu, China[25]. Human health effects caused by MCs toxin vary in severity.

MCs have been regarded as one of the biggest water pollution problems in the world, which have a lot of adverse effects on the human health. In order to protect human health, a number of techniques need to be developed to analyze and remove MCs. Moreover, a further extensive study should be enhanced on the molecular toxic mecha-nism of MCs because the toxic mechanisms are obscure until now. In addition, active-wise policies need to be drawn up and implemented. Furthermore, effective and efficient drugs need to be invented and produced to inhibit the binding of MCs to protein phosphatase.

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Published: 10 May 2017


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