Background: Acute exposure to high concentrations of microcystin-LR (MC-LR) can cause significant hepatocyte injury.
Aim: To document the effects of long-term, low-dose MC-LR exposure on hepatic inflammation and fibrosis in mice with healthy and diseased livers.
Material and methods: Male CD1 mice (N = 20/group) were exposed to 1.0 μg/L of MC-LR in drinking water; 1.0 μg/L MC-LR plus 300 mg/L of the hepatotoxin thioacetamide (MC-LR/TAA); or 300 mg/L TAA alone for 28 weeks. Liver biochemistry and histology were documented at the end of the study period. In addition, hepatic stellate cells (HSCs), were exposed in vitro to MC-LR (0.1-10,000 μg/L) and monitored for changes in cell metabolism, proliferation and activation.
Results: Liver biochemistry and histology were essentially normal in MC-LR alone exposed mice. MC-LR/TAA and TAA alone exposed mice had significant hepatic inflammation and fibrosis but the extent of the changes were similar in the two groups. In vitro, MC-LR had no effect on HSC metabolism, proliferation or activation.
Conclusion: Long-term, low-dose exposure to MC-LR is unlikely to lead to chronic liver disease in the setting of a normal liver or exacerbate existing liver disease in the setting of ongoing hepatitis.
Keywords: Cyanobacteria. Blue-green algae. Cyanotoxins. Microcystins. Hepatic fibrosis. Cirrhosis. Chronic liver disease. Hepatic stellate cells..