Effects Of Unsaturated Fatty Acids On Oxidative Stress And Cell Apoptosis Of Red Tide Microalgae

In recent years, harmful algal blooms frequently wreak havoc in the world, seriously endanger the stability of the marine environment, sustainable development of offshore aquaculture and human health. Methods for controlling red tide are mainly physical, chemical and biological technologies, in which the use of allelopathic mechanism and the inhibitory effect of macroalgae on outbreaks of harmful algal blooms has a unique advantage. Currently studies on mechanism of allelopathy focus on the impact of algal cell membranes,photosynthetical system, extracellular enzymes.etc, while research of oxidative stress and cell apoptosis rarely reported.Unsaturated fatty acids- linoleic acid（LA） and eicosapentaenoic acid（EPA）, were screened and isolated from macroalgae,with high allelopathic activity,quick degradation in the environment, low toxicity on non-target organisms.etc. K. mikimotoi and Prorocentrum donghaiense is the new dominant species of red tide, they can form a bipolar tide.In this experimentalstudy, linoleic acid induced K. Mikimotoi oxidation stress, membrane lipid peroxidation, further causing the cell apoptosis phenomenon. The impact of EPA on Prorocentrum donghaiense is also true. It interpreted Inhibition mechanism of unsaturated fatty acids from a new perspective, also provided a theoretical basis for the further development and application in algaecide. There are results achieved:1. The effects of Linolic acid on the growth of K. Mikimotoi and the effects of Eicosapentaenoic acid on the growth of Prorocentrum donghaiense LuLow concentrations of linoleic acid played a catalytic role on the growth of K. mikimotoi.With the increase of linoleic acid concentration, inhibition intensified. The effects of different concentration of EPA on the growth of Prorocentrum donghaiense Lu is also true.2. Studies on oxidative stress of K. Mikimotoi linoleic acid induced and studies on oxidative stress of Prorocentrum donghaiense Lu Eicosapentaenoic acid induced（1） With the increase of Linolic acid concentration, the activities of SOD、POD、CAT and the content of GSH 、 AsA in K. Mikimotoi first accumulated and then decreased.Prorocentrum donghaiense Lu also exhibit the above rule under the EPA exposure.（2） Linolic acids induced over production of ROS in K. Mikimotoi and ·OH content H2O2 content and O₂^·- content accumulated. The impact of EPA on Prorocentrum donghaiense is also true. But O₂^·- content had no significant regularity the under two unsaturated fatty acids exposure.（3） Under low concentration of linoleic acid exposure, there was no significant effect onthe content of MDA in K. mikimotoi; MDA content increased sharply under high concentration of linoleic acid exposure. MDA content in Prorocentrum donghaiense Lu continued to increase with the increase of EPA concentration.（4） Allelopathy of unsaturated fatty acids had characteristics of universal and specific.3. Research on the mechanism of cell apoptosis in K. Mikimotoi under linoleic acid exposure and research on the mechanism of cell apoptosis in Prorocentrum donghaiense Lu under Eicosapentaenoic acid exposure（1） Trypan blue staining experiments showed linoleic acid can inhibit the cell viability of K. Mikimotoi, EPA can inhibit the cell viability of Prorocentrum donghaiense Lu.（2） TEM observed submicroscopic structure of algal cell, TEM pictures show that almost all normal cell organelles are indistinguishable, the outer membrane is dissolved, plastid boundaries are not clear, shape of algal cell changes, starch granules appeared, internal structural seriously damaged and so on. Based on flow cytometry, results showed that algal cells appeared apoptosis phenomenon.（3） By the decrease of mitochondrial membrane potential, activity of Caspase-3,9 increased,the release of cytochrome c and Bcl-2 family protein reduction and other related test results,further confirmed the effect of unsaturated fatty acid on apoptotic mechanism of red-tide microalgae.