Pancreatic kallikrein gene expression: effects of glucocorticoids in vivo and in vitro

Possible role of corticosterone on behavioral, physiological, and immune responses in chicks

Glucocorticoids are one of steroid hormone and have a variety of functions including stress response, carbohydrate metabolism, and modulation of immune system in vertebrates. Corticosterone is the main glucocorticoid in birds, although the precise role of the glucocorticoid during immune challenge is not fully understood. Therefore, the purpose of the present study was to determine if a single subcutaneous injection of corticosterone could affect inflammation-related gene expressions in the spleen and liver of chicks (Gallus gallus). In addition, the effects of corticosterone injection on the food intake, cloacal temperature, formation of conditioned visual aversion, and plasma constituents were also measured. Corticosterone did not affect the food intake or cloacal temperature and did not cause conditioned visual aversion in chicks. The corticosterone injection was associated with a significant decrease in gene expression of several pro-inflammatory cytokines including inducible nitric oxide synthase and cyclooxygenase-2 in the spleen and liver at 1 and 3 h post-injection. Corticosterone increased the plasma glucose and uric acid concentrations and the antioxidant capacity. In summary, the present study suggests that corticosterone is likely not associated with food intake, cloacal temperature or the development of aversive sensation, but suppresses the synthesis of inflammation-associated bioactive molecules and increases the antioxidant capacity in chicks.

Effect of ornithokinin on feeding behavior, cloacal temperature, voluntary activity and crop emptying rate in chicks

Bradykinin is a well-studied bioactive peptide associated with several physiological functions, including vasodilation and inflammation, in mammals. However, its avian homolog, ornithokinin, has received less research attention in birds. Therefore this study aimed to investigate the effect of intraperitoneal (IP) and intracerebroventricular (ICV) injections of ornithokinin on feeding behavior, cloacal temperature, voluntary activity, crop emptying rate, and blood constituents in chicks (Gallus gallus). We also investigated the effect of lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria, on ornithokinin-associated gene expression was also investigated to determine whether activation of the ornithokinin system is induced by bacterial infection. Both IP and ICV injections of ornithokinin significantly decreased feed intake, cloacal temperature, voluntary activity, and crop emptying rate in chicks, but they did not affect the plasma concentration of corticosterone. Additionally, LPS significantly increased the expression of ornithokinin B2 receptor mRNA in several organs. Hence, ornithokinin is associated with a range of physiological responses in chicks and may be related to their response to bacterial infection.

Raf-1 kinase inhibitory protein (RKIP) mediates ethanol-induced sensitization of secretagogue signaling in pancreatic acinar cells

Excessive alcohol consumption is associated with most cases of chronic pancreatitis, a progressive necrotizing inflammatory disease that can result in pancreatic insufficiency due to acinar atrophy and fibrosis and an increased risk of pancreatic cancer. At a cellular level acute alcohol exposure can sensitize pancreatic acinar cells to secretagogue stimulation, resulting in dysregulation of intracellular Ca(2+) homeostasis and premature digestive enzyme activation; however, the molecular mechanisms by which ethanol exerts these toxic effects have remained undefined. In this study we identify Raf-1 kinase inhibitory protein as an essential mediator of ethanol-induced sensitization of cholecystokinin- and carbachol-regulated Ca(2+) signaling in pancreatic acinar cells. We show that exposure of rodent acinar cells to ethanol induces protein kinase C-dependent Raf-1 kinase inhibitory protein phosphorylation, sensitization of cholecystokinin-stimulated Ca(2+) signaling, and potentiation of both basal and cholecystokinin-stimulated extracellular signal-regulated kinase activation. Furthermore, we show that either suppression of Raf-1 kinase inhibitory protein expression using short hairpin RNA or gene ablation prevented the sensitizing effects of ethanol on cholecystokinin- and carbachol-stimulated Ca(2+) signaling and intracellular chymotrypsin activation in pancreatic acinar cells, suggesting that the modulation of Raf-1 inhibitory protein expression may have future therapeutic utility in the prevention or treatment of alcohol-associated pancreatitis.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

Rat pancreatic AR42J cells. Amphicrine cells as an in vitro model to study peptide hormone receptor regulation

The rat pancreatic acinar tumor cell line, AR42J, is widely used to study pancreatic acinar cell biology and biochemistry. In addition to the well-documented exocrine cell features, we have identified by immunofluorescence and by electron microscopy the co-expression of small neuroendocrine (NE) vesicles using the NE vesicle-specific markers synaptophysin and "protein S.V.2." AR24J cells store [3H]GABA, which is secreted upon potassium depolarization in a calcium-dependent manner. In addition, we found the expression of the receptor for the neurotransmitter substance P by using a receptor-specific cDNA probe. Glucocorticoid treatment, which profoundly inhibits cellular growth and induces differentiation, results in a rapid decrease of substance P receptor (SPR) gene expression as assessed by Northern blot analysis. Intracellular Ca2+ mobilization was then determined in response to substance P in control cells and glucocorticoid-pretreated cells by dual wavelength spectrophotometry using fura-2 in single cells. Glucocorticoid-mediated down-regulation of substance P receptors resulted in a dose- and time-dependent decrease of the intracellular Ca2+ mobilization stimulated by substance P. In summary, these data indicate that AR42J cells display an amphicrine phenotype with two differentially regulated secretory pathways; during glucocorticoid-induced differentiation, the cells become less sensitive to substance P stimulation as a consequence of reduced gene expression of the substance P receptor.

Trypsinogen expression by two human pancreatic cell lines CFPAC-1 and CAPAN-1. Modulation during spontaneous and induced cell growth

We previously demonstrated that two human pancreatic adenocarcinoma cell lines, CFPAC-1 (established from a patient with cystic fibrosis) and CAPAN-1, were able to secrete trypsinogens 1 and 2 specifically. In order to analyze the relation of trypsin secretion to differentiation and cell growth, we undertook a comparative study of immunoreactive trypsin 1 (IRT) secretion by the two cell lines during cell growth in the presence and in the absence of various differentiating agents: sodium butyrate (NaBut), dimethylsulfoxide (DMSO), and dexamethasone (DX). In the presence of NaBut, IRT levels in the supernatants of both cell lines were slightly increased, whereas the cellular growth of both cell lines decreased significantly. In the presence of DX, IRT levels in cell culture conditioned media immediately and dramatically decreased, but the cell growth of neither cell line was affected by DX. An important increase in IRT levels was observed when CFPAC-1 cells and CAPAN-1 cells were grown in the presence of DMSO, but for both cell lines the cellular growth decreased in the presence of DMSO. Our data show that neither the IRT secretion level nor the differentiation state of these cell lines correlates with cellular growth, and suggests that the expression of pancreatic proteases by these two tumor cell lines could be either related to a common stem cell with this potential or to a possible acinar origin of pancreatic cancer, as recently proposed by others.

Bombesin receptor gene expression in rat pancreatic acinar AR42J cells: transcriptional regulation by glucocorticoids

BACKGROUND/AIMS

This study investigated the correlation between glucocorticoid-regulated gene expression of the bombesin receptor (BR) and cellular sensitivity to bombesin stimulation in the rat pancreatic acinar cell line AR42J.

METHODS

BR gene expression was assessed using a cloned complementary DNA probe and radioligand binding assays. Intracellular Ca2+ mobilization was assessed by dual wavelength spectrophotometry using fura-2 in single cells.

RESULTS

Dexamethasone resulted in a rapid dose- and time-dependent decrease of BR messenger RNA levels with maximal inhibition to 25% +/- 2% of controls (n = 4) after 6 hours of hormone treatment. BR messenger RNA half-life was approximately 120 minutes and was not affected by dexamethasone pretreatment; nuclear run-on analysis showed a decreased transcription rate of the BR to approximately 25% of control after hormonal treatment. Radioligand binding studies showed a time-dependent decrease of specific bombesin binding to 25% +/- 8% of control after 48 hours of hormone treatment. Down-regulation of BR gene expression by dexamethasone resulted in a time- and dose-dependent decrease of intracellular Ca2+ mobilization after bombesin stimulation compared with untreated controls.

CONCLUSIONS

Glucocorticoids decrease BR gene transcription. The subsequent decrease in cellular BR number renders AR42J cells less sensitive for bombesin-stimulated intracellular Ca2+ mobilization.

Molecular aspects of kallikrein and kininogen in the maturing kidney

Kinins are vasoactive paracrine peptides which participate in a wide range of functions, including the regulation of local organ blood flow, systemic blood pressure, transepithelial water and electrolyte transport, cellular growth, capillary permeability and inflammatory response, and pain. The recent introduction of specific bradykinin receptor subtype antagonists has greatly advanced our understanding of the role of the kallikrein-kinin system (KKS) in various physiological and disease states. However, a major gap remains in our knowledge of the role of kinins in early development. In this review, evidence is presented that the developing nephron expresses both tissue kallikrein and kininogen, and that the genes encoding the components of the KKS are subject to considerable developmental regulation. The activity of the intrarenal kinin-generating system is lowest in the developing kidney and increases with age. Completion of nephrogenesis is characterized by a marked surge in intrarenal kallikrein synthesis and gene transcription. Maturation is associated with redistribution of intrarenal kallikrein and its messenger RNA from the inner to outer cortical nephrons following the centrifugal pattern of nephron development. Challenges for the future include delineation of the direct role of kinins in the maturation of renal functions and elucidation of the molecular mechanisms underlying the developmental expression of the KKS.

Laminin binding in membranes of a rat pancreatic acinar cell line are targets for glucocorticoids

The adhesive properties of tumor cells to basement membranes are known to play a crucial role in the complex process of tumor invasion and metastasis. Therefore, the interaction between the rat pancreatic acinar cell line AR42J and various extracellular matrix components along the route of differentiation induced by glucocorticoids was investigated. AR42J cells displayed a significantly higher affinity to laminin than to type IV collagen and fibronectin. Flow cytometric analysis showed expression of the 67-kilodalton laminin receptor and the integrin VLA-6 as potential laminin binding proteins in AR42J cells. Cell adhesion inhibition studies revealed that binding of undifferentiated AR42J cells to laminin was mediated predominantly by the 67-kilodalton laminin receptor. Dexamethasone pretreatment, which results in a more differentiated phenotype of AR42J cells, reduced the adhesion to laminin. In contrast to undifferentiated cells, interaction of differentiated AR42J cells to laminin was mediated by VLA-6. Dexamethasone-induced differentiation of pancreatic AR42J cells was paralleled by a decreased expression of 67-kilodalton laminin receptors, most likely because of a downregulation of the steady-state concentration of 67-kilodalton laminin receptor messenger RNA induced by dexamethasone. The hormonal modulation of cell matrix interactions opens interesting perspectives to the potential regulation of infiltrative growth and metastasis in pancreatic cancer.

Regulation of renal kallikrein synthesis and activation by glucocorticoids

The effects of endogenous and exogenous glucocorticoids on renal active and prokallikrein levels (ng/mg protein) and in vivo kallikrein synthesis rate were studied in the conscious rat. Within two hours after low dose methylprednisolone (MP, 0.0125 to 0.05 mg/100 g body wt), active kallikrein and prokallikrein fell (29.1 +/- 2.3 and 35.1 +/- 2.7 ng/mg protein, respectively, compared to 38.4 +/- 3.7 and 42.7 +/- 3.4 in vehicle-treated rats, P less than 0.05 or less). These changes were accompanied by a significant fall in prokallikrein synthesis rate relative to total protein synthesis. The reductions in active and prokallikrein levels were transient, dissipating by six hours. With increasing MP doses, there was further dose-dependent reduction in active kallikrein. However, prokallikrein levels increased to normal as the MP dose was increased despite continued suppression of synthesis, suggesting that prokallikrein activation was inhibited. Renal kallikrein levels were also examined in relation to changes in endogenous glucocorticoid levels. In intact rats, three hours after plasma corticosterone peaked (10 p.m.), active and prokallikrein levels were 30.2 +/- 2.9 and 27.0 +/- 1.6 ng/mg protein, respectively, compared to 36.9 +/- 2.3 and 37.2 +/- 2.6 (P less than 0.005) three hours after the corticosterone nadir (11 a.m.). Furthermore, adrenalectomy increased active and prokallikrein (47.3 +/- 4.8 and 87.3 +/- 6.0 ng/mg protein, respectively), compared to levels in intact or shamoperated rats (intact: 32.9 +/- 2.9 and 54.9 +/- 5.3 ng/mg protein, P less than 0.01 or less). Adrenalectomy also eliminated the diurnal changes in kallikrein levels seen in intact rats. These data suggest that renal prokallikrein synthesis and activation are physiologically regulated by glucocorticoids.