Differentially expressed genes in the livers of mice exposed to microcystin-LR (MC-LR)

To explore the molecular mechanisms involved in the toxicity in the livers exposed to MC-LR at the environmental level, the hepatic transcriptome was performed. A total of 210 genes were differentially expressed (P<0.05, |fold change|≥2) in response to MC-LR exposure; among them, 143 genes were significantly upregulated, and 67 genes were downregulated. Pathway enrichment analysis identified the top biological functions associated with the genes differentially expressed in response to MC-LR exposure, which were circadian regulation of gene expression, negative regulation of glucocorticoid receptor signaling pathway, the epoxygenase P450 pathway, regulation of insulin secretion, lipid metabolic process, and cell cycle pathway. Six-week-old male BALB/c mice were assigned randomly to two groups (one control and one treatment). Mice in treatment were exposed to 100 μg/L microcystin-LR through drinking water for 12 months. The control mice were given normal sterile water. At the end of exposure time, three liver samples from independent mice in each group were obtained to analyze the gene expression by microarray assay. Total RNA was extracted, amplified and labeled using a One-Color LowInput Quick Amp Labeling Kit (Agilent, Santa Clara, CA, USA). Labeled cRNA was purified with an RNeasy Mini Kit (Qiagen, Hilden, Germany). The slides were then hybridized with Cy3-labeled cRNA using Gene Expression Hybridization Kit in a hybridization oven (Agilent, Santa Clara, CA, USA), followed by washing in staining dishes (Thermo, Waltham, MA, USA) with Gene Expression Wash Buffer Kit (Agilent, Santa Clara, CA, USA). An Agilent Microarray Scanner was used to scan the slides. Data were extracted by the Feature Extraction software and normalized by the Quantile algorithm of Gene Spring software.