Studies On The Pollution Of Anatoxin-a In Dianshan Lake And Neurotoxicity Of Anatoxin-a

With progressive eutrophication of surface water, water bloom and red tide break out frequently in freshwater and seawater. Contamination of algae (including algal toxins) has been an important public health concern. Algal toxins can give birth to the damage of many tissues. Anatoxin-a (ANTX-A) is one of the most familiar neurotoxical algal toxins. There were lots of domestic fowls and livestock and wild animals poisoning incidents caused by ANTX-A. Different amounts of ANTX-A were detected from lakes and reservoirs in many countries. Moreover, conventional chlorination water treatment procedure is not sufficient to totally remove ANTX-A, humans are potentially exposed to low-level ANTX-A. Some toxicological tests suggested that low-dose ANTX-A might be associated with central nerve system toxicity. Therefore, it's necessary to study the low-dose neurotoxicity of ANTX-A.The present study is aimed to investigate the distribution of ANTX-A from Dianshan Lake and to explore the effect of ANTX-A on CNS and its possible mechanism. This study includes three parts: 1) investigation on the pollution of ANTX-A in Dianshan Lake; 2) in vivo neurotoxical test of ANTX-A; 3) in vitro neurotoxical test of ANTX-A.Part 1: Investigation on the Pollution of Anatoxin-a in Dianshan Lake Objectives: To study the eutrophication status and the distribution of ANTX-A in Dianshan Lake, and discuss the correlation between ANTX-A and various environmental elements. Methods: During the summer and autumn in 2002, some physical-chemical elements associated to eutrophication and algae cell density were investigated, the concentration of ANTX-A in the lake and water-bloom algae were measured by the high-performance liquid chromatography (HPLC), the correlation between ANTX-A and environmental elements was analyzed by general estimated equations (GEE). Results: The concentration of total nitrogen (TN) and total phosphorus (TP) in the Lake were higher than the III level guideline of surface water environmental quality standard. The average algae cell density was 3×106 /liter. The average level of ANTX-A in the lake was 7 ng/liter. And the pollution of ANTX-A was most serious in July. The concentration of ANTX-A in water-bloom algae was 15ng/mg dry algae. The level of ANTX-A was correlated with illumination, turbidity, TP and chlorophyll a (Chla). And the correlation between turbidity and ANTX-A was more significant than others (p<0.05). Conclusion: Dianshan Lake presented serious eutriphication. There was the pollution of ANTX-A, and it was most serious in July. The concentration of ANTX-A was significant correlative with turbidity of lake. Part 2: in vivo Neurotoxical Test of Anatoxin-a Objectives: To study the effect of sub-acute exposure of ANTX-A on CNS in mouse and explore its possible mechanism. Methods: Mice were administered by i.p. with ANTX-A at the concentrations of 0, 12.5, 50, 200ug/kg.bw/day for 30 days. Body weight increase was observed during the administration period, neurobehavioral function was measured using step-through test and Morris water maze test, the CNS neuropathological changes were examined. The changes of calcium-mediated signal transduction system including intracellular calcium, ATPase, calcineurin (PP2B), c-fos and CREB-1 and free radical signal system comprised of reactive oxygen species (ROS) and nitric oxide (NO) were measured. Results: The body weight increase of the mice in ANTX-A 200ug/kg.bw group decreased obviously (p<0.05). The passive evade activity and special learning and memory function of the mice in ANTX-A 200ug/kg.bw group weakened significantly (p<0.05). Degeneration and necrosis of neuron were observed in the cortex and hippocampus of ANTX-A 200ug/kg.bw-treated mice. And no such changes were observed in the other ANTX-A group. In ANTX-A 12.5ug/kg.bw, 50ug/kg.bw, 200ug/kg.bw group, the concentration of intracellular calcium in the brain increased significantly (p<0.05). The activity of PP2B and the gene and protein expression of c-fos and CREB-1 improved in ANTX-A 200ug/kg.