Expression of IL-8 induced by Pseudomonas aeruginosa in differently differentiated U937 cells
Objective To study IL-8 expression of human monocytic leukemia cell lines (U937 cells) directly induced by Pseudomonas aeruginosa (Pa) and its mechanism through protein kinase C (PKC) and nuclear factor-kappa B (NF-κB). Methods RT-PCR and ELISA were performed to test the expression of IL-8 in differ- ently differentiated U937 cells infected by Pa. Western blot was employed to examine the expression of NF-κB pro- tein. In addition, U937 cells or PMA(phorbol 12-myristate 13-acetate)-differentiated U937 cells were cultured to- gether with PKC inhibitor, calphostin C, or NF-κB inhibitor, PDTC(pyrrolidine dithiocarbamate), respectively before Pa infection, then the expression of IL-8 and NF-κB were assayed using above methods. Results Pa was able to induce IL-8 mRNA expression and IL-8 protein secretion both in U937 cells and in PMA-differentiated U937 cells in marked time and concentration-dependent manner. Pa could also significantly promote the activation of NF-κB, which peaked at 1 h and then went down. PDTC and calphostin C could significantly decrease the activa- tion of NF-κB and the expression of IL-8. Conclusion IL-8 production induced by Pa might relate to the differ- entiated state of U937 cells. The directly induction of Pa could promote the activation of NF-κB by PKC signal pathway, leading to the expression and secretion of IL-8.