PMA and IL4 sequentially induced human monocyte cell line into M2 type macrophages in vitro

Objective To study if U937 and THP-1 human monocyte cell lines were induced into the M2 type macrophages by in vitro stimulation, and to explore the effect of rapamycin on this process. Methods The U937 and THP-1 cell lines were stimulated by phorbol 12-Myristate 13-Acetate(PMA) and interleukin-4(IL-4) sequentially. The expressions of M1/M2 markers protein and m RNA in the stimulated macrophages were examined by q RT-PCR and ELISA, respectively. Results Both of U937 and THP-1 human monocytes were induced into macrophages by PMA, and with pseudopods further by the subsequent stimulation with IL-4. The expression levels of M1 associated markers(IL-1β、IL-6、IL-12 and i NOS) m RNA were downregulated significantly( 0.01), but the expression levels of M2 associated markers(IL-10、CD163) m RNA were upregulated significantly. At the same time, the expression level of CCL18 protein and m RNA was highly elevated by the stimulation of IL4, but the elevated CCL18 expression level was downregulated by further stimulation of rapamycin. Conclusion The sequential stimulation by PMA and IL4 induces human monocytes into M2 type macrophages, but rapamycin could reverse this process.