Monocytes and macrophages play important roles in many inflammatory reactions. Phorbol-12-myristate-13-acetate (PMA) is stimuli commonly used to induce macrophage differentiation in monocytic cell lines, but the extent of differentiation in comparison to primary tissue macrophages is unclear. Major functions of macrophages include maintaining tissue homeostasis and responding to microorganisms. They can mediate immune and inflammation processes via the production and release of a variety of soluble mediators such as radicals like superoxide anions, cytokines and eicosanoids. These biologically active agents are also known to modulate cell differentiation and proliferation. Midkine is a fibrinolytic, anti-apoptotic, mitogenic, transforming, angiogenic, and chemotactic molecule which takes part in inflammatory conditions. THP-1 cell line were exposed to different dosage and time duration protocols of PMA. Cells are compared as morphology. Midkine, TNF-a, IL-10, IFN-g secretion functions are measured by ELISA. PMA stimuli induced changes in cell morphology indicative of differentiation. PMA differentiation induced midkine, TNF-a, IL-10, IFN-g secretions in monocytic cells even in lowest dosage (10 ng/ml). Moreover, with increasing dosage PMA (>20 ng/ml) induced cytotoxicity in cells. There was no difference in cytokine profile and midkine secretion between different dosages of PMA induced cells. These findings suggest a modified PMA differentiation protocol (20 ng/ml and 48 h incubation) can enhance macrophage differentiation of THP-1 cells without induced cell death (viability 92.2%) and cytokine secretion and midkine responses as important discriminators of the level of macrophage differentiation for transformed cells.

This study was supported by TUBITAK-BMBF (SBAG108S262 and SBAG110S242).