Fucoidan increases TNF-alpha-induced MMP-9 secretion in monocytic cell line U937

To investigate the effect of fucoidan on the expression of matrix metalloproteinase-9 (MMP-9) from monocytes.

Human monocytic cell line U937 was purchased from ATCC. During the experiment, FBS-free 1640 was used and U937 was cultivated with 20 ng/ml TNF-alpha and/or different concentrations of fucoidan for 24 h. RT-PCR experiments were used to determine the MMP-9 mRNA expression. ELISA and gelatin zymography detected MMP-9 amounts and activity in the supernatant. The intracellular level of MMP-9 was assayed by Western blot, and the level of CD44 on the surface was assayed by FACS.

In this study, we showed that pro-inflammatory cytokine TNF-alpha up-regulated U937 MMP-9 mRNA and protein levels (P < 0.05). Fucoidan can increase the TNF-alpha-induced MMP-9 secretion from U937 (P < 0.05), but no significant difference was observed in MMP-9 mRNA. The intracellular level of MMP-9 treated with TNF-alpha and fucoidan was lower (P < 0.05) than that treated with TNF-alpha alone. In addition, we demonstrated that fucoidan downregulated the surface level of CD44, the main molecule to which MMP-9 attaches.

We demonstrated that fucoidan post-translationally regulated MMP-9 secretion from U937. Reduced intracellular level and decreased membrane attachment may contribute to the increase in MMP-9 secretion.