Study On The Biological Activity Of Extracellular Polymeric Substances From Aphanizomenon Flos-aquae

Lake Dianchi is the sixth freshwater of China and it has lost its lucidity and beauty because Aphanizomenon flos-aquae blooms often take place now. Aphanizomenon flos-aquae is the dominant bloom-forming species in spring and winter while microcystin instead of Aphanizomenon flos-aquae in summer and autumn of Lake Dianchi, so we should notice biological diversity of watershed and blooms condition which will happen. Aphanizomenon flos-aquae excreted amout of extracellular polymeric substances (EPSs) into the surrounding matrix when they grow, and these EPSs probably play important roles to maintain the dominant species of Aphanizomenon flos-aquae and biological diversity variety of water ecosystem. In order to approve the function, in this paper, the effects of EPS-A on A431 cells and astrocytes of zebrafish were studied. The main results are as follows:1. EPS-A in Lake Dianchi were extracted and used 0.45 fibrous filter to get rid of algae first, and then culture medium which had not algae was condensed and puritied.2. EPS-A affected the morphology of A431 cells and astrocytes of zebrafish. When the cells were treated by different concentration of EPS-A, there were a lot of suspension cells if concentration of EPS-A was increased and treated time was extended, and the morphology of cells had not any changes.3. EPS-A can restrain the multiplication of A431 cells and astrocytes of zebrafish. When the cells were treated by different concentration of EPS-A, survival rate of the cells were reduced with increased concentration and extended time. Lethal concentration 50 of astrocytes of zebrafish is 2.35mg/mL and Lethal concentration 50 of A431 cells is 3.17mg/mL.4. EPS-A can affect the cell cycle of A431 cells and the cell cycle was determined by flow cytometry. The rate of apoptosis is small after 48h and the rate of apoptosis is 26.59% after 72h, and apoptotic peak is not obvious. So the effects of EPS-A on the cell cycle is the main reason which had induced A431 cell apoptosis, but the clear mechanism is not known.5. EPS-A can affect the cell membrane potential of mitochondrion. The cell membrane potential of mitochondrion was decreased from 24h to 72h after EPS-A treated the cells.6. PI and Rhl23 both dyed A431 cell. In order to know the cell membrane potential of mitochondrion and the cell membrane integrality. Some treated cell moved PI^-Rh⁺ to PI^-Rh^- after 48h. The result is some cell membrane integrality and the cell membrane potential of mitochondrion was decreased.7. EPS-A can affect the ultrastructure of A431 cell. By transmission electron microscope we found that nucleolus is obvious of the control cell, chromatin distribution is uniform and cell organ is abundant, cell membrane and karyotheca are integrated. Chromatin contracted and cell membrane happened rupture after the cell was treated 48h by low concentration of EPS-A. Chromatin contracted heavily and cell shape happened the severity change, rough endoplasmic reticulum expanded the pool, but karyotheca had no rupture and during the whole process there were not apoptosis body formation.8. EPS-A can affect antioxidant system of A431 cell. Antioxidant enzyme changed after the cells were treated by EPS-A. SOD activity is higher than that of control while CAT and POD activities are lower than that of control after 24h and 48h. the result explained that SOD activity was activated while CAT and POD activities were restrained by EPS-A. When the treated time was extended, SOD,CAT and POD activities were restrained, whatmore, the activities of all were lower than that of control. SOD activity was probably restrained by superfluous H₂O₂, CAT and POD can not effectively get rid of H₂O₂, so apoptosis of cell happened because of lost balance of antioxidant system.So we can get the conclusion, EPS-A can affect the morphology and the multiplication of astrocytes from zebrafish; EPS-A had obvious antitumor activity to A431 cell And antitumor mechanism of EPS-A lies in mitochondrion approach, the stagnation of cell cycle and decrease of membrane potential of mitochondria might the main reason of tumor cell apoptosis and apoptosis of cell happened because of lost balance of antioxidant system. So EPS-A had important biological activity function and can decrease biological diversity of other biology.