Abstract: Objective　To investigate the cytotoxic effect of spirulina platensis polysaccharides (SPP) on acute T lymphocyte leukemia Jurkat cells. Methods　SPP was obtained by water extraction and ethanol precipitation. The effect of SPP on cell proliferation was determined by MTT assay. Caspase-3 was tested by Western blot assay. Furthermore, the cell surface expression of CD45 and CD71, and the expression levels of p-ERK, p-JNK, t-ERK and t-JNK were also evaluated. Results　SPP inhibited Jurkat cell proliferation in a dose-dependent manner (1 g/L, 2 g/L and 5 g/L), the inhibitory rates were 53.286%±3.112%, 80.075%±4.240% and 86.430%±4.614%, respectively. The expression levels of cleaved caspase-3 were higher in 2 g/L and 5 g/L SPP groups than those in the control group, and that in 5 g/L SPP group was higher than that in 1 g/L SPP group (P＜0.05). The expression levels of CD45 were higher in 1 g/L and 2 g/L SPP groups than those in the control group (P＜0.05), while there was no significant difference in the expression level of CD71 between the two groups. The expression levels of CD45 were higher in 5 g/L SPP group than those in control group, 1 g/L SPP group and 2 g/L SPP group. The expression level of CD71 was lower in 5 g/L SPP group than that in control group (P＜0.05), and there was no significant difference in the expression level of CD71 between 1 g/L and 2 g/L SPP groups. The expression levels of p-ERK were increased significantly in turn in the control group, 1 g/L, 2 g/L and 5 g/L SPP groups. There were no significant differences in expression levels of t-ERK, p-JNK and t-JNK between groups. Conclusion　SPP could inhibit Jurkat cell growth and induce cell death, which might through affecting CD45 and CD71 expression on cell surface, then activating ERK and finally activating caspase-3 to induce cell apoptosis.

Key words: spirulina, polysaccharide, leukemia, Jurkat cells, apoptosis, extracellular signal-regulated MAP kinases