Investigation On The Antiviral And Anticancer Activities Of Polysaccharides From Spirulina Platensis

In this paper, the antiviral and anticancer activities of polysaccharides from Spirulina platensis (PSP) were reported. A modified TCA(trichloroacetic acid) method for extraction of PSP was conducted in our experiment, and the purity of the polysaccharides reaches to 92%. This method is more convenient, rapid and economical than the traditional Sevag method. A standard strain of herpes simplex virus type 1(HSV-1, SM44 strain) was used to investigate the antiviral activities of PSP in vitro and in vivo. In vitro experiments were carried out in Vero cells, firstly the activity of PSP against HSV-1 was proved to be better than acidovir, which is the most widely used antiviral agent in clinic. Then various concentrations of PSP were applied to different steps of HSV-1 replication cycle, virus infectivity (TCIDso), cytopathic effect (CPE), plaque forming unit (PFU), methyl thiazolyl tetrazolium (MTT) method and in situ hybridization were used for estimating the influence of the polysaccharides on the virus. The in vitro results indicate that some of the mechanisms of PSP against HSV-1 may be explained by the inhibitory effects on virus adsorption, virus replication and HSV-1 gG gene transcription. When tested in vivo, the results also prove that PSP has a significant and efficient protection against HSV-1 infection. The anticancer properties PSP were also studied, in vitro experiments, the antiproliferation effects of PSP on tumor cells were evaluated by MTT assay, the HeLa cell morphological changes were observed under light microscope, HeLa cell division cycles and apoptosis were measured by flow cytometry. It was found that PSP could inhibit HeLa cell proliferation and induce apoptosis in HeLa cell. PSP not only exerts inhibitory effects on HepG-2 cell proliferations but also on insulin-like growth factor 2 (IGF-2) mRNA expression; PSP also has the ability to inhibit gastric cancer, colic and rectal cancercells in vitro. In vivo experiments, the inhibition of PSP on the transplanted tumor cells of Sarcinoma 180 were studied, it is proved that with the dosage of 50~200 mg/kg , PSP could inhibit the Sarcinoma 180. To establish a simple, direct, rapid and sensitive model for screening antiviral agents, the recombiant expressive vector of HSV- pEGFP was constructed and transfected into the Vero ceil. These results not only indicate that PSP exerts inhibitory activity on ICP6 promoter, but also may provide an easy and rapid method for monitoring HSV infections and screening antiviral agents.