Inhibition of Osteopontin Synthesis in THP-1 Cells Stimulated with Phorbol 12-Myristate 13-Acetate by Brefelamide Derivatives

Plasma osteopontin (OPN) levels are elevated in mycobacterium tuberculosis patients and may involve granuloma formation. New inhibitors using brefelamide, an aromatic amide isolated from Dictyostelium cellular slim molds which may inhibit OPN transcription at concentration of 1M, were synthesized as compounds C, D and E. Their inhibitory activity against OPN synthesis in phorbol 12-myristate 13-acetate (PMA)-stimulated THP-1 cells was confirmed using enzyme-linked immunosorbent assay (ELISA), a multicolor immune-fluorescent microscope and western blot analysis. For the ELISA performed using the full-length OPN, each compound showed significant inhibition. Detailed analysis were done using C and D. They also showed inhibitory activity when used on another ELISA system to detect the immune-related form of OPN and their IC50 were 0.6 and 1.2 M for compounds C and D, respectively. Fluorescent particle count of stained cell numbers by O-17 showed the inhibition. Antibodies for O-17 and 34E3, which recognize OPN N-terminus and thrombin-cleaved site, respectively, detected distinct bands on the western blots following PMA stimulation. The decrease in full-length OPN detected by O-17 in the compound-treated cells was identified via western blot analysis. These newly-developed compounds may therefore be used in clinical trials for cancer and infectious diseases.