Toxicity evaluation of Wanzhou watershed of Yangtze Three Gorges Reservior in the flood season in Caenorhabditis elegans

Abstract

Three Gorges Reservoir (TGR) in the upper stream of Yangtze River in China is a reservoir with the largest and the longest yearly water-level drop. Considering the fact that most of safety assessments of water samples collected from TGR region were based on chemical analysis, we here employed Caenorhabditis elegans to perform in vivo safety assessment of original surface water samples collected from TGR region in the flood season in Wanzhou, Chongqing. Among the examined five original surface water samples, only exposure to original surface water sample collected from backwater area could induce the significant intestinal ROS production, enhance the intestinal permeability, and decrease the locomotion behavior. Additionally, exposure to original surface water sample collected from backwater area altered the expressions of sod-2, sod-5, clk-1, and mev-1. Moreover, mutation of sod-2 or sod-5 was susceptible to the potential toxicity of original surface water sample collected from backwater area on nematodes. Together, our results imply that exposure to surface water sample from the backwater area may at least cause the adverse effects on intestinal function and locomotion behavior in nematodes.

Figure 1

Sampling sites in the Three Gorges Reservoir.

Figure 2

Effects of different surface water samples in the TGR region on survival and development of wild-type nematodes. (a) Effects of different surface water samples on survival. (b) Effects of different surface water samples on development. Development was assessed by the endpoint of body length. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD.

Figure 3

Effect of different surface water samples in the TGR region on induction of oxidative stress in wild-type nematodes. (a) Effect of different surface water samples on induction of intestinal ROS production. The left shows the pictures of intestinal ROS production, and the right indicates the comparison of relative fluorescence intensity for signals labeling ROS production in intestine. (b) Effect of different surface water samples on GST-4::GFP expression. Thirty animals were analyzed per treatment. (c) Comparison of expression patterns for genes required for oxidative stress. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD. ^**P < 0.01 vs control.

Figure 4

Effect of different surface water samples in the TGR region on intestinal permeability in wild-type nematodes. (a) Analysis on the dye distribution and leakage from the intestinal lumen into the body cavity. Arrowheads indicate the dye leakage from the intestinal lumen into the body cavity. (b) Effect of exposure to the sample of W5 on expressions of genes required for the control of intestinal development. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD. ^**P < 0.01 vs control.

Figure 5

Effects of different surface water samples in the TGR region on locomotion behavior and reproduction in wild-type nematodes. (a) Effect of different surface water samples on locomotion behavior. Locomotion behavior was assessed by the endpoints of head thrash and body bend. (b) Effect of different surface water samples on reproduction. Reproduction was assessed by the endpoint of brood size. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD. ^**P < 0.01 vs control.

Figure 6

Effects of different surface water samples in the TGR region on lifespan of wild-type nematodes. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD.

Figure 7

Effect of sod-2 or sod-5 mutation on the induction of ROS production (a), the locomotion behavior (b), and the brood size (c) in nematodes exposed to the examined different surface water samples in the TGR region. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD. ^**P < 0.01 vs control (if not specially indicated).

Figure 8

Effect of liquid phase or solid phase of the sample of W5 on the induction of intestinal ROS production (a) the locomotion behavior (b) in nematodes. Exposures were performed from L4-larvae for 24-h. Bars represent means ± SD. ^**P < 0.01 vs control.