Effect of superoxide dismutase-entrapped liposomes and protein transduction domain-superoxide dismutase on human umbilical vein endothelial cells

Superoxide dismutases (SOD) are able to remove the superoxide anion free radicals produced by environmental stress and thereby protect cells from being injured by reactive oxygen species. However, SOD is unable to transduce automatically across cell membranes. Protein transduction domains (PTDs) are peptides able to mediate protein delivery into cells and were first observed in the HIV-1 Tat protein. In the present study, PTD (RKKRRQRRR) was fused to Dunaliella salina (Ds)MnSOD to form PTD-DsMnSOD. This was inserted into pET32a to construct the recombinant plasmid pET32a-PTD-DsMnSOD and transduced into E. coli BL21(DE3) to obtain purified PTD-DsMnSOD proteins. Liposome-encapsulated proteins are also able to cross cell membranes. In this study, DsMnSOD proteins were purified and encapsulated by liposomes. The obtained MnSOD, PTD-MnSOD and liposome MnSOD were used to protect human umbilical vein endothelial cells (HUVECs) from injury under oxygen pressure. A cell counting kit 8 was used to test the survival rate of HUVECs and results indicated that the protective effect of MnSOD was limited compared with that of PTD-MnSOD and liposome MnSOD. Thus, PTD and liposomes exhibited improved effects when MnSOD was present in cells.