Pancreas transcription factor 1alpha expression is regulated in pancreatitis.

BACKGROUND: Expression of acinar cell-specific genes requires the pancreas transcription factor 1alpha (Ptf1alpha). p48 is the only component of Ptf1alpha that is involved in both acinar gene regulation and pancreatic ontogenesis. MATERIALS AND METHODS: To determine whether Ptf1alpha/p48 expression is regulated during pancreatitis, acute pancreatitis was induced in rats by repeated caerulein injections; early chronic pancreatitis by the combined administration of caerulein and cyclosporin A; and focal pancreas fibrosis by trinitrobenzene sulfonic acid infusion into the pancreatic duct. AR42J cells were used to examine caerulein effects on acinar cells. Ptf1alpha/p48 expression was examined using immunohistochemistry, Western blotting, and qRT-PCR methods. RESULTS: In acute pancreatitis, Ptf1alpha/p48 decreased markedly within 6 h as determined by Western blotting and immunohistochemistry. After 24 h, Ptf1alpha/p48 increased continuously and normalized at day six. In contrast, pancreas amylase reached a nadir at 48 h, when Ptf1alpha/p48 had largely recovered. In the early chronic pancreatitis model Ptf1alpha/p48 levels did not completely recover even at day 14, and this was associated with a failure to restore normal histology and amylase content. qRT-PCR showed that p48 mRNA were reduced after pancreatitis induction and were followed by a decrease in elastase mRNA. In the focal pancreas fibrosis model, Ptf1alpha/p48 expression was undetectable in areas with substantial acinar cell loss and tubular complexes. Caerulein did not affect Ptf1alpha/p48 expression in AR42J cells. CONCLUSIONS: Ptf1alpha/p48 protein and mRNA levels are regulated in acute and chronic experimental pancreatitis. Inability to re-express Ptf1alpha/p48 after injury may preclude acinar cell differentiation and appropriate pancreatic regeneration.

Interaction and functional cooperation of NF-kappa B with Smads. Transcriptional regulation of the junB promoter.

The transforming growth factor-beta (TGF-beta) family of cytokines regulates diverse cellular processes through control of the expression of target genes. Smad proteins are a recently identified family of signal transducers for members of the TGF-beta family. Smads act as transcriptional regulators through binding to DNA and interacting with a variety of transcription factors. Here, we identified a kappaB site as a TGF-beta-responsive region in the 3'-downstream junB promoter region. We also demonstrate that kappaB sites alone are sufficient to mediate immediate transcriptional activation by TGF-beta. Transactivation of kappaB sites by TGF-beta requires an intact NF-kappaB pathway, cooperates with known activators of this pathway, and is mediated by Smad family members. Furthermore, we show that Smad3 interacts with p52 in vivo. These data expand the model in which Smad proteins undergo multiple interactions with several transcription factors that could induce either activation or repression of gene expression.

A zinc-finger transcription factor induced by TGF-beta promotes apoptotic cell death in epithelial Mv1Lu cells.

Transforming growth factor-beta (TGF-beta) superfamily members constitute a group of multifunctional factors that are able to stimulate apoptotic cell death in a variety of cells. In this report, we show that a zinc-finger transcription factor (TIEG) is an immediate early gene transcriptionally induced by TGF-beta in the epithelial Mv1Lu cell line. We also demonstrate that, mimicking TGF-beta effects, ectopic overexpression of TIEG is sufficient to trigger the apoptotic cell program in these cells, which is preceded by a decrease of Bcl-2 protein levels. Finally, apoptotic events elicited by TIEG overexpression can be effectively prevented by ectopic co-expression of Bcl-2. On the basis of these results we suggest that induction of TIEG expression has a role in the pro-apoptotic properties of TGF-beta.

JunB is involved in the inhibition of myogenic differentiation by bone morphogenetic protein-2.

Bone morphogenetic proteins (BMPs) constitute a family of multifunctional growth and differentiation factors structurally related to transforming growth factor-beta. BMPs were first identified by their osteoinductive effects, inducing ectopic bone formation when implanted in skeletal muscle, and have an important role as regulators of skeletal development in vivo. In vitro, BMP-2 is able to transdifferentiate myogenic C2C12 cells into the osteoblastic phenotype. In this report, we show that the osteoinductive effects of BMP-2 in C2C12 cells are mediated by bone morphogenetic protein receptor type-IA in combination with both activin receptor type II and bone morphogenetic protein receptor type II. We also analyzed the expression levels of nuclear protooncogenes to understand early transcriptional events induced by BMP-2. We show that junB is an immediate early gene induced by BMP-2 and transforming growth factor-beta. BMP-2 induces transcriptional activation of JunB expression as early as 30 min after ligand addition, reaching maximal levels after 90 min. Increase of JunB mRNA correlates with a higher AP-1 binding activity. Furthermore, ectopic overexpression of JunB is sufficient to inhibit expression of myoblast differentiation markers in C2C12 cells. These data, taken together, show the involvement of JunB in the early steps of inhibition of myogenic differentiation induced by transforming growth factor-beta family members.

Beta 3-adrenergic receptors are responsible for the adrenergic inhibition of insulin-stimulated glucose transport in rat adipocytes.

The inhibition of insulin-stimulated glucose transport by isoprenaline, a mixed beta-adrenergic-receptor (AR) agonist, is well documented in rat adipocytes. Since it has been described that rat adipocytes possess not only beta 1- and beta 2- but also beta 3-ARs, the influence of various subtype-selective beta-AR agonists and antagonists on 2-deoxyglucose (2-DG) transport was assessed in order to characterize the beta-AR subtype involved in the adrenergic counter-regulation of the insulin effect. The stimulation of 2-DG transport by insulin was counteracted, in a dose-dependent manner, by all the beta-AR agonists tested, and the magnitude of the inhibition followed the rank order: BRL 37344 > isoprenaline = noradrenaline >> dobutamine = procaterol. The same rank order of potency was obtained for lipolysis activation. This is not in accordance with the pharmacological definition of a beta 1- or a beta 2-adrenergic effect, but agrees with the pharmacological pattern of a beta 3-adrenergic effect. The inhibitory effect of the beta 3-agonist BRL 37344 on insulin-stimulated 2-DG transport was not reversed by either the selective beta 1-antagonist ICI 89406 or the beta 2-antagonist ICI 118551. In addition, neither of these beta-antagonists was able to block the isoprenaline and noradrenaline effects, supporting major beta 3-adrenoceptor-subtype involvement in the adrenergic inhibition of insulin-stimulated 2-DG transport. Like isoprenaline, BRL 37344 inhibited (60% inhibition) insulin-stimulated glucose transport only when adenosine deaminase was present in the assay. Furthermore, the maximal inhibitory effects of isoprenaline and BRL 37344 were not additive, and were both dependent on albumin concentration in the incubation medium: they increased when the albumin concentration decreased in the medium from 3.5 to 1%. To conclude, the similarities between isoprenaline and BRL 37344 action on insulin-stimulated 2-DG transport, the poor efficacy of the beta 1-/beta 2-agonists and the lack of effect of selective beta 1- and beta 2-antagonists are compelling arguments to support the important role of beta 3-adrenoceptors in the adrenergic inhibition of glucose transport in rat adipocytes.