Cytokines increase CRE binding but decrease CRE-mediated reporter activity in rat hepatocytes by increasing c-Jun

Abstract

The cyclic AMP response element (CRE) has been implicated in the regulation of the expression of many genes and cellular processes important in hepatocyte function. CRE sites exist in the promoter regions of several genes expressed during inflammation. Numerous studies on the role of CRE in hepatocyte gene expression have been performed in resting hepatocytes, but the role of CRE during inflammation is unknown. To evaluate the regulation of CRE-mediated transcription during sepsis, cultured hepatocytes were exposed to proinflammatory cytokines and lipopolysaccharide (LPS) was injected into rats. Nuclear proteins were collected and CRE binding activity measured by electromobility shift assay (EMSA) using a consensus CRE oligonucleotide. CRE binding activity was increased in vitro by cytokines and in vivo by LPS administration but CRE-dependent reporter activity was decreased by cytokine stimulation. A c-jun N-terminal kinase (JNK) inhibitor reversed the cytokine-induced increase in CRE binding and increased CRE-dependent reporter activity. Supershift assays indicated that cyclic AMP response element binding protein (CREB) and c-Jun proteins were included in the CRE binding complex. CREB induced and c-Jun suppressed reporter activity using a CRE-dependent construct transfected into cultured primary hepatocytes. In conclusion, these data demonstrate that proinflammatory cytokines regulate CRE binding and activity in cultured hepatocytes and suggest that sepsis-induced changes in CRE binding may participate in the cellular response to inflammation.

Nonclassical Action of Retinoic Acid on the Activation of the cAMP Response Element-binding Protein in Normal Human Bronchial Epithelial Cells

“…The rapid activation of CREB by RA resulted in increased DNA binding of the active CREB to its cognate CRE binding sequence. This result is in consistent with several studies showing increased DNA binding after CREB activation by various stimuli (Zhang et al, 2004) In contrast, there are few reports that activation of CREB did not lead to increased DNA binding activity in vitro (Hagiwara et al, 1993). Interestingly, most, if not all, of the CREB was present in an active phosphorylated form in the presence of RA, as suggested by the finding that most of the retarded band was supershifted by pCREB antibody.…”

Restoration of CREB function ameliorates cisplatin cytotoxicity in renal tubular cells

“…1C). In this regard, cisplatin would seem to be similar to LPS-induced stress in hepatocytes, where LPS treatment increases CREB phosphorylation but CREB-mediated reporter activity actually falls (21). In those studies, it is thought that the inhibition is served by cytokine activation of c-Jun.…”

CREB mediates ERK-induced survival of mouse renal tubular cells after oxidant stress

“…This biphasic response to H 2 O 2 has not been explored before. In several models, moderate oxidative stress induces prosurvival signals through CREB activation [12,13], which may or may not be a result of changes in phosphorylated CREB level or CREB binding to its cognate sequence [14,28,29]. Indeed, several models of oxidant injury revealed a decreased CREB-binding activity [14,15,30] but the effect of levels of oxidant stress was not explored.…”