ys. Furthermore, the stable expression of C/EBPb in a murine B lymphoblast cell line is sufficient to confer LPS inducibility of IL-6 expression. Importantly, NF-kB and C/EBPb synergistically activate the IL-6 promoter, and consistent with this, direct interaction between the C/EBPb bZIP and the NF-kB Rel homology domain has been observed, as well as cooperative binding of the two factors. In addition, the NF-kB site of the IL-6 promoter is required for the activity of the C/EBPb bZIP in the absence of aminoterminal motifs. All of these studies suggested a mechanism for IL-6 activation whose essential feature is the requirement for the bZIP region of C/EPBb to synergize with NF-kB, although this remains to be further investigated. In addition, it has been recently shown that IL-1b-induced IL-6 production in alveolar type II cells is associated with the activation of both IL-1 receptorassociated kinase-4 and phosphatidylinositol 3-kinase. However, in alveolar type II cells, molecular mechanisms involved in IL-1b-induced IL-6 production remains largely unknown. In the current study, we find that the binding activity of both NF-kB and C/EBPb to their Danoprevir chemical information regulatory elements in the IL-6 promoter is significantly elevated by IL-1b stimulation in alveolar epithelial cells. Our data further indicate that both C/EBPb and p65 are indispensable for IL-1b-induced IL-6 expression, which is consistent with the observation in other cell types. Our finding that C/EBPc can regulate IL-1b-induced IL-6 production in alveolar type II epithelial cells is interesting. C/ EBPc has been considered as an inhibitor of other C/EBP family members. For example, C/EBPc inhibits C/EBPb-mediated HIV-1 long terminal repeat-driven transcription in human brain cells. In addition, C/EBPc represses C/EBPb-mediated induction of alcohol dehydrogenase expression in the rat livers. These results are consistent with the fact that C/EBPc lacks known activation domains and is essentially a C/EBP bZIP domain. In contrast, C/EBPc can also act as a transcription activator. 11753686” For example, C/EBPc has been shown to be a positive regulator of IFN-c expression in splenocytes and NK cells, and gamma-globin expression in fetal liver. Furthermore, previous studies demonstrated that augmentation of C/EBPb activity on the IL-6 and IL-8 promoters by C/EBPc required formation of a heterodimeric leucine zipper and 
co-expression of NF-kB. Interestingly, C/EBPc inhibits C/EBPb- and C/ EBPd-mediated transactivation of a reporter gene in fibroblasts in a leucine zipper-dependent manner, but it has no suppressive function in HepG2 hepatoma cells. These findings together indicate that C/EBPc has complex effects on gene transcription. Our current finding that C/EBPc suppresses IL-1b-induced IL-6 production in alveolar type II epithelial cells further suggests that its function may be cell specific. The exact molecular mechanism whereby C/EBPc regulates gene expression is not clear. In IL-1b-stimulated alveolar epithelial cells, C/EBPc exists as both homodimers and heterodimers . It is possible that the lack of one transactivation domain in C/EBPc:b heterodimers may contribute to the inhibitory effect of C/EBPc. On the other hand, in C/EBPc-overexpressed cells, the major C/EBPc binding species is C/EBPc:c homodimers, suggesting that C/ EBPc:c homodimers may compete with the stimulatory C/EBP b:b to bind to IL-6 promoter region. In addition, we observed an increased C/EBPc:b heterodimers binding to IL-6 promo