Midkine inhibitors: application of a simple assay procedure to screening of inhibitory compounds

<p>Abstract</p> <p>Background</p> <p>Midkine is a heparin-binding cytokine and is involved in etiology of various diseases. Thus, midkine inhibitors are expected to be helpful in treatment of many diseases.</p> <p>Methods</p> <p>We developed a simple assay for midkine activity based on midkine-dependent migration of osteblastic cells. Midkine inhibitors were searched as materials that inhibit this midkine activity. To develop peptides that inhibit midkine activity, we constructed models in which C-terminal half of midkine interacted with α₄β₁-integrin. Low molecular weight compounds which are expected to bind to midkine with high affinity were searched by <it>in silico </it>screening with the aid of Presto-X2 program.</p> <p>Results</p> <p>Among peptides in putative binding sites of midkine and the integrin, a peptide derived from β₁-integrin and that derived from the first β sheet of the C-terminal half of midkine significantly inhibited midkine activity. Two low molecular weight compounds found by <it>in silico </it>screening exhibited no toxicity to target cells, but inhibited midkine activity. They are trifluoro compounds: one (PubChem 4603792) is 2-(2,6-dimethylpiperidin-1-yl)-4-thiophen-2-yl-6-(trifluoromethy)pyrimidine, and the other has a related structure.</p> <p>Conclusions</p> <p>The assay procedure is helpful in screening midkine inhibitors. All reagents described here might become mother material to develop clinically effective midkine inhibitors.</p