| Summary: | 碩士 === 國立陽明大學 === 生理學研究所 === 102 === All-trans retinoic acid (ATRA) can induce acute promyelocytic leukemia (APL) cells differentiation into granulocytes. CD14 and Toll-like receptor 4 (TLR4) play important role in the phagocytic activity of macrophage, however, their role in granulocytic differentiation is still unclear. In this study, we determined the role of CD14/TLR4 in the phagocytic activity of APL cells during the process of granulocytic differentiation. The phagocytic activity of ATRA-NB4 was analyzed by flow cytometry to determine their ability in engulfing either fluorescein-latex beads or idarubicin-induced apoptotic cells. Our results indicated that the phagocytic activity of NB4 cells increased in a time-dependent manner during ATRA treatment for 6 days, in which the level of CD14 expression was minimal before ATRA treatment and was increased later in a time-dependent manner after ATRA treatment. On the contrary, TLR4 was constitutional expressed without significant change during early stage of ATRA treatment (before 3 days), and its level was significantly enhanced at the 6th day of ATRA treatment. Further study demonstrates that the phagocytic activity of ATRA-NB4 cells was significantly inhibited when their surface CD14 and TLR-4 were pretreated with their specific antibodies before phagocytosis assay. Furthermore, we investigate the CD14/TLR4-associated signal pathway. Our results indicate that the phagocytic activity of ATRA-NB4 cells on engulfing fluorescein-latex beads was significantly inhibited when ATRA-NB4 cells were pretreated with either BAY 11-7082 (a NF-κB inhibitor) or SP600125 (an IRF-3 inhibitor) before phagocytosis assay. However, the activity on engulfing apoptotic cells was only significantly inhibited only by treated with BAY 11-7082, but not by SP600125. On the other hand, we demonstrated that microparticles is derived from apoptotic cells also expressed CD14, and these CD14(+) microparticles can interact with ATRA-NB4 cells to enhance their phagocytic activity on engulfing apoptotic cells. In conclusion, we suggest that CD14 is essential for mediating phagocytic activity of ATRA-NB4 cells to engulf apoptotic cells during granulocytic differentiation.
|
|---|
