Assessing the toxicity of ingested Taihu Lake water on mice via hepatic histopathology and matrix metalloproteinase expression

Abstract

Water from Taihu Lake (China) is used as a drinking source. The frequency of contamination in Taihu Lake has increased over the past decade and the bloom-forming cyanobacteria are the dominant species during eutrophication. Cyanobacteria can produce various harmful secondary substances including microcystins capable of endangering human health and ecological safety. This study investigated toxicity of ingested Taihu Lake water on mice via hepatic histopathology and matrix metalloproteinase (MMP) expression. Water was sampled from four Taihu Lake locations, Meiliang Bay 2 group (M2), Meiliang Bay 1 group (M1), Lake Center (H) and Xukou Bay (X), along a gradient of decreasing degree of eutrophication. The experimental design consists of five groups of male mice (Mus musculus, ICR): one control and four groups ingesting water from the four sampling sites for 90 days. Compared to control, M1 and M2 mice showed hepatic histopathological changes including swollen, vacuolar degeneration or inflammatory. Immunohistochemical staining demonstrated a higher expression of MMP-2 proteins in M2 group and a lower expression of MMP-9 in M1. Enzyme-linked immunosorbent assay indicated that MMP-9 concentration was significantly reduced from 0.55 to 0.28 ng/g liver weight in M2 (p < 0.05). Real time PCR revealed a down-regulation of MMP-9 mRNA by 2.2 fold in M1 and an up-regulation of MMP-2 mRNA by 1.73 fold in H. Using this mouse model as a gauge of water toxicity, our results revealed that potential health risks induced by Taihu Lake water might arise from the use of this source water by local resident.