Using BRET assay, we further confirmed that ectopic expressed GCGR and Lrp5 do interact specifically on the cell surface

natural killer cells after stimulation with cytokines such as IL-12, IL-18 and IL-2 were significantly reduced. However, the role C/EBPc Suppresses IL-6 BQ123 production of C/EBPc in inflammation remains largely unknown. In the current study, we demonstrate that C/EBPc expression is induced by IL-1b in lung epithelial cells, “2859375 and apparently contributes to the inhibition of IL-1b-mediated IL-6 production. Furthermore, we show that C/EBPc inhibits IL-6 expression by inhibiting C/EBPb stimulatory activity. In sharp contrast, NF-kB activity is not impaired by C/EBPc. The data suggest that C/EBPc may play an important regulatory role in lung inflammatory responses. C/EBPc suppresses IL-1b-induced IL-6 expression in primary alveolar type II epithelial cells To further confirm the inhibitory role of C/EBPc in IL-6 expression observed in the MLE12 cells, we isolated primary alveolar type II epithelial cells from mouse lung. As shown in Fig. 3A and B, expression of the surfactant protein C was confirmed using fluorescent staining with a pro-SP-C monoclonal antibody. The successful isolation of primary alveolar type II epithelial cells was verified using TEM assay that shows the lamellar bodies of characteristic features. Primary alveolar type II epithelial cells were infected with Adeno-GFP and Adeno-C/EBPc, respectively. Our preliminary study shows that adenoviral transfection efficiency is about 40%. Consistent with the results obtained from MLE12 cells, we found that over-expression of C/EBPc significantly inhibited IL-6 secretion after IL-1b stimulation. Taken together, these results support the inhibitory role of C/EBPc on IL-1b-induced IL-6 production in alveolar type II epithelial cells. Results C/EBPc suppresses IL-1b-induced IL-6 production in MLE12 cells Little is known about the expression and function of C/EBPc during inflammation. We evaluated the time course of C/EBP activation in lung epithelial cells by EMSA, using nuclear extracts from MLE12, a lung epithelial cell line, obtained at various time points after IL-1b treatment. As shown in Fig. 1A, at time 0, low levels of constitutive C/EBPs were observed. C/EBP activation became stronger by 3 h, then decreased to control levels. To determine if increased oligonucleotide binding to C/EBPc was caused by increased transcriptional expression of C/EBPc, we conducted Real Time PCR experiments. As shown in Fig. 1B, constitutive levels of C/ EBPc mRNA expression in MLE12 cells were observed at 0, 3, and 6 h after IL-1b treatment, with modest decreases at 12 and 24 h. These data suggest that the C/EBPc DNA binding was mainly regulated at post-transcriptional level. C/EBPb has been shown to participate in IL-1b signaling such as mediating IL-6 production. However, the role of C/EBPc in IL-1b signaling is unclear. We therefore determined whether C/EBPc expression in MLE12 cells has any effect on IL-1b-induced IL-6 production. MLE 12 cells were transfected with control siRNA or C/EBPc siRNA before IL-1b challenge. We demonstrated that C/EBPc siRNA could effectively suppress the endogenous C/EBPc expression in MLE12 cells. We found that knockdown of C/EBPc significantly increased IL-1b-stimulated IL-6 expression at mRNA level. Moreover, we show that IL-6 production at protein level was ” increasingly elevated in a timedependent manner when the MLE12 cells were stimulated with IL-1b. Importantly, knockdown of C/EBPc in MLE12 cells led to a significant increase of IL-1b-stimulated IL-6 secretion at all