Abstract
The increasing cyanobacterial blooms have recently been considered a severe environmental problem. Microcystin-leucine arginine (MC-LR) is one of the secondary products of cyanobacteria metabolism and most harmful cyanotoxins found in water bodies. Studies show MC-LR negatively affects various human organs when exposed to it. The phenotype of the jejunal chronic toxicity induced by MC-LR has not been well described. The aim of this paper was to investigate the effects of MC-LR on the jejunal microstructure and expression level of inflammatory-related factors in jejunum. Mice were treated with different doses (1, 30, 60, 90 and 120 μg/L) of MC-LR for six months. The microstructure and mRNA expression levels of inflammation-related factors in jejunum were analyzed. Results showed that the microstructure of the jejunum was destroyed and expression levels of inflammation-related factors interleukin (IL)-1β, interleukin (IL)-8, tumor necrosis factor alpha, transforming growth factor-β1 and interleukin (IL)-10 were altered at different MC-LR concentrations. To the best of our knowledge, this is the first study that mice were exposed to a high dose of MC-LR for six months. Our data demonstrated MC-LR had the potential to cause intestinal toxicity by destroying the microstructure of the jejunum and inducing an inflammatory response in mice, which provided new insight into understanding the prevention and diagnosis of the intestinal diseases caused by MC-LR.
Highlights
The rapid development of industries and agriculture has led to the increasing discharge of wastewater containing nitrogen and phosphorus into water bodies
No death or symptoms in Microcystin-leucine arginine (MC-LR) treated mice were recorded during the six-month experiment
Compared to the control group, no differences were observed in the MC-LR treated (g)significant mice heights groups in terms of weight gain, diet, water consumption and activity, nor did the intestinal
Summary
The rapid development of industries and agriculture has led to the increasing discharge of wastewater containing nitrogen and phosphorus into water bodies. These activities may result in eutrophication and development of cyanobacterial blooms [1,2]. The monocyclic heptapeptide microcystins (MCs) are the secondary products of cyanobacteria metabolism and most harmful cyanotoxin found in water bodies [3,4,5]. Previous studies showed that animals and humans are mainly exposed to MC-LR through drinking polluted water, body contact, hemodialysis, consumption of contaminated food and algal dietary supplements [8,9,10]. When MC-LR is ingested, it first enters the intestine where most of these toxins are absorbed through the intestinal mucosal barrier (mucosal epithelial cells and mucosal lamina propria), and the absorbed MC-LR are transported through the bloodstream and Toxins 2019, 11, 482; doi:10.3390/toxins11090482 www.mdpi.com/journal/toxins
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