Protective effects of a polysaccharide from Spirulina platensis on dopaminergic neurons in an MPT-Pinduced Parkinson's disease model in C57BL/6J mice

The present study aimed to determine whether a polysaccharide obtained fromSpirulina platensis shows protective effects on dopaminergic neurons. A Parkinson’s disease model was established through the intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyr-idine （MPTP） in C57BL/6J mice. Prior to the MPTP injection, some mice were pretreated with intraperitoneal injections of a polysaccharide derived fromSpirulina platensis once daily for 10 days. The results showed that the immunoreactive staining and mRNA expression of the dopa-mine transporter and tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis, in the substantia nigra, were signiifcantly increased in mice pretreated with 800 mg/kg of the poly-saccharide compared with those in MPTP-treated mice. The activities of superoxide dismutase and glutathione peroxidase in the serum and midbrain were also increased signiifcantly in mice injected with MPTP after pretreatment with the polysaccharide fromSpirulina platensis. By con-trast, the activity of monoamine oxidase B in serum and midbrain maintained unchanged. These experimental ifndings indicate that the polysaccharide obtained fromSpirulina platensis plays a protective role against the MPTP-induced loss of dopaminergic neurons in C57BL/6J mice, and that the antioxidative properties of this polysaccharide likely underlie its neuroprotective effect.

Effects of the polysaccharides from Spirulina platensis on the activities of hepatitis B virus

To investigate the effects of the polysaccharides from Spirulina platensis (PSP) on hepatitis B virus (HBV), the cytotoxic effect of PSP was assessed by choosing the maximal concentration of PSP without cytotoxic effect on HepG2 2.2.15 cell line for further experiments. Four concentrations (400-50 μg/ml) of PSP were adopted to treat the cells, and the supernatants or cells were collected after 24, 48, 72 and 144 h respectively. HBsAg and HBeAg in the supernatants of cell cultures were tested with ELISA and copies of HBV DNA in supernatants were measured by real-time fluorescence quantitative PCR (FQ-PCR). Meanwhile, DNA/RNA hybridization was performed to evaluate the expression of IFN-α receptor (IFN-αR) on the cells. The experimental results showed that the secretion of HBV antigens decreased under the influence of PSP in a dose and time-dependent manner. PSP in concentration of 400 μg/ml could significantly decrease the secretion of HBsAg in 24 h. Although no obvious effect was observed on the secretion of HBeAg at that time, the inhibitory effects were observed in a dose-dependent manner from 48 to 144 h. In addition, the copies of HBV DNA were declined under the influence of PSP in the same manner, moreover, the maximal suppressive effect of PSP in concentration of 400 μg/ml was as great as that of lamivudine. The expression of IFN-αR was much higher in PSP-treated cells than that of the un-treated cells also in dose and time-dependent manner. It is concluded that PSP in non-cytotoxic concentration not only significantly decreases the secretion of the HBV antigens and the replication of HBV DNA, but also increases the expression of IFN-αR on HepG2 2.2.15 cell line. The results of the present investigation strongly support the notion that PSP exerts the anti-HBV effect both through enhancing the anti-HBV immunity and acting on HBV directly.

Antiviral effect of polysaccharide from Spirulina platensis(PSP) on HSV-2 in vitro

To explore the antiviral effect and mechanism of polysaccharide from Spirulina platensis （PSP） on herpes simplex virus type 2 （HSV-2）, a standard strain of HSV-2 （333 strain） was used to investigate the antiviral effect of PSP in vitro. PSP in various concentrations was applied to different stages of HSV-2 replication cycle. Finally, the virus infectivity （TCID50）, cytopathic effect （CPE）, and MTT staining method for viable cells （MTT assay） were used as markers to evaluate the effect of PSP on HSV-2. The quantity of HSV-DNA was detected by real-time fluorescence quantitative PCR （FQ-PCR）. The HSV-2 infected Vero cell tdtrastructures were observed by transmission electron microscopy （TEM）. The results showed that PSP had little cytotoxic effect on Vero cells, it could not directly inactivate HSV-2 infectivity. PSP not only interfered in adsorption of HSV-2 to Vero cells but also inhibited HSV-2 biosynthesis in the ceils. FQ-PCR results showed that the inhibitory rate on HSV- DNA also increased in a dose-dependent and time-dependent manner. TEM also confirmed that PSP exhibited pronounced inhibitory effect on HSV-2. In conclusion, the antiviral effect of PSP on HSV-2 may be attributed to the inhibition of virus adsorption, virus replication and synthesis in cells.