Preliminary Experimental Anticancer Activity Of Synthetical Antimicrobial Peptide Tachyplesin-Ⅰ

Antimicrobial peptides, the majority of which are cationic and amphipathic, are small peptides. They can strongly act on many kinds of bacterial and cancer cells, while at the same concentrations they act weakly on normal cells. The ability is due to their unique structures. This selective toxicity has attracted much attention. Now some progress has made on the linear antimicrobial peptides in inhibiting bacterial and cancer cells but not in the case of cyclic peptides. Tachyplesin- I , a small antimicrobial peptide from the hemocytes of the horseshoe crab (Tachypleus tridentatus ) , which has a cyclic anti-parallel 3 -sheet structure held together by two disulfide bonds, permeabilizes both bacterial and artificial lipid membranes at low concentrations. It suggests that tachyplesin-1 is also a potent anticancer agent.In this experiment, we aim at exploring whether, how and to what extent the synthetical antimicrobial peptide tachyplesin inhibits human gastric adenocarcinoma BGC-823 cell. Firstly, we test the effect of tachyplesin- I on cell proliferation, livability and morphology , and then we test the integrity of vital membranes via the change of intensity and distribution of FDA Dextran-FITC JC-1 and YO-PRO-1 probes.The results show that tachyplesin-1 inhibited the proliferation of BGC-823 cell and reduced the survival ratio of cancer cells. Observation from transmission electron microscope shows tachyplesin- I broke cell membranes and nucleus membranes,induced mitochondria swelling and increased the number of secondary lysosome. Staining with fluorescent probes of FDA Dextran-FITC JC-1 and YO-PRO-1 indicated that tachyplesin- I could permeabilize cell membranes, induce potential shift of mitochondria membrane and damage on nucleus membranes. Hemolytic test indicated tachyplesin- I could damage on human erymrocyte membranes at low level.Based on what we have found, we can give a general idea about the anticancer mechanism of tachyplesin- I : 1 ) Synthetical antimicrobial peptide tachyplesin-1 inhibits the BGC-823 cell via the pass way of cytotoxicity; 2) Interaction of the peptide with membrane is the first step, and then possibly there are two ways, the big pores form, or the peptide enters the cell to reach an alternative target, including mitochondria and nucleus; 3 ) Tachyplesin- I interacts with membrane via two ways depending on its concentrations.