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Toxicol Appl Pharmacol. 2019 Aug 15;377:114626. doi: 10.1016/j.taap.2019.114626. Epub 2019 Jun 12.

Microcystin-LR promotes necroptosis in primary mouse hepatocytes by overproducing reactive oxygen species.

Author information

1
Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
2
Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Fuzhou, China.
3
Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China; Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Fuzhou, China. Electronic address: linxu@mail.fjmu.edu.cn.

Abstract

Microcystin-LR (MC-LR) is a type of cyclic heptapeptide toxin produced by cyanobacteria during bloom events. MC-LR-induced cell death is critically involved in its potent specific hepatotoxicity. Many studies have demonstrated that prototypical apoptosis as a form of programmed cell death after MC-LR is associated with liver injury. However, whether another form of programmed cell death exists and the underlying mechanism have not been reported. Here, we demonstrate that MC-LR can induce necroptosis via ROS overactivation in primary mouse hepatocytes. Various potential pathways of programmed cell death induced by MC-LR were evaluated by annexin V/PI dual staining for flow cytometric analysis, image-based PI staining analysis and western blot analysis. Cell viability was determined by the CCK8 assay. Rupture of the plasma membrane was indicated by lactate dehydrogenase release. ROS was evaluated with the carboxy-H2DCFDA fluorescent probe. It was found that in MC-LR-treated cells, as the plasma membrane was damaged, annexin V/PI-stained double-positive cells were significantly induced and PI-stained nuclei were more diffuse. Western blot analysis showed that MC-LR treatment significantly upregulated the expression of necroptotic and apoptotic proteins. Mechanistically, MC-LR induced ROS overproduction by dysregulating the expression and activity of the pro-oxidants SOD1, MAOA, and NOX4 and the antioxidant GPX1. These results indicate the presence of a novel mechanism for MC-LR-mediated liver injury and present a novel target in the treatment of MC-LR-exposed patients.

KEYWORDS:

Apoptosis; Cyanbacteria; Eutrophication; Liver injury; Microcystins; Necroptosis

PMID:
31201821
DOI:
10.1016/j.taap.2019.114626

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