Microcystins, are a family of toxins produced by freshwater cyanobacteria. They are cyclic heptapeptides, composed of seven amino acids. They exert a toxic effect by being specific inhibitors of the protein phosphatases 1 and 2A (PP1 and PP2A), but recent evidences also indicate its potential to generate oxidative stress. Oxidative stress is a general term used to describe the steady state level of oxidative damage in cells, tissues, or organs, caused by the reactive oxygen species (ROS). In this experiment,the toxic mechanism of MC-RR inducing oxidative stress was evaluated in tobacco BY-2 suspension cells. Changes of ROS formation and antioxidant system of tobacco BY-2 suspension cells were studied under the treatment of 2 mu g/mL, MC-RR, 2 mu g/mL MC-RR + 0.5% DMSO and 2 mu g/mL MC-RR + 2 mmol/L ASA. Under the treatment of 2 mu g/mL MC-RR,the contents of ROS, MDA and ASA as well as the activities of SOD and POD were higher than those in control after 5 days treatment. GSH content first decreased and then increased, and at the 6(th) day of treatment GSH content significantly increased compared with the control. The abundant accumulation of ROS and the change of antioxidant system both indicated that the cells suffered from oxidative stress induced by MC-RR. ROS may play an important role in its toxic effect on the cells. The MC-RR-induced oxidative stress in cells was further confirmed by exposing the cells to MC-RR in the presence of two ROS scavengers, ASA or DMSO. ASA has significant capacity of scavenging O-2(-) and H2O2, and DMSO is a kind of hydroxyl radical scavengers. When tobacco BY-2 suspension cells were exposed to 2 mu g/mL MC-RR with 0.5 % DMSO or 2 mmol/L ASA, the formation of ROS and MDA were prevented and the contents of GSH, ASA and activities of SOD and POD all decreased in contrast to MC-RR treatment. It concluded that tobacco BY-2 suspension cells suffered oxidative stress after MC-RR treatment and the exogenous ASA and DMSO can protect the cells from MC-RR induced oxidative stress.
Huang Wen-Min; Xing Wei; Li Dun-Hai; Liu Yong-Ding.Effects of exogenous DMSO and ASA on formation of reactive oxygen species and antioxidant systems of tobacco suspension cells under MC-RR stress,Acta Hydrobiologica Sinica,2007,31(6):869-873