Regulation of amylase and chymotrypsinogen expression by dexamethasone and caerulein in serum-free-cultured pancreatic acinar AR4-2J cells. Influence of glucose

Abstract

The direct effects of dexamethasone and caerulein on two pancreatic enzymes, amylase and chymotrypsin, were determined in AR4-2J cells cultured under serum-free conditions at two glucose concentrations (1.0 and 4.5 g/l). In the absence of any hormone, the higher glucose concentration resulted in a 1.6-1.8-fold increase in the basal levels of amylase and chymotrypsinogen. Dexamethasone (50 nM) increased the biosynthesis and mRNA levels of both enzymes at both glucose concentrations. However, dexamethasone had a more pronounced effect on amylase biosynthesis (5-fold induction) than on chymotrypsinogen biosynthesis (1.8-fold induction). The parallel increases in mRNA and protein indicated the existence of pre-translational regulation. This is in contrast with what was observed in serum-containing media, where a translational regulation of amylase biosynthesis took place, probably under the control of both glucose and some serum factors. By contrast, caerulein (10 nM) exerted a more specific action on chymotrypsinogen. The increases in chymotrypsinogen mRNA were 2.2-and 2.1-fold, and increases in chymotrypsin activity were 1.6-and 2.9-fold at 1.0 and 4.5 g of glucose/litre respectively. Thus the regulation by caerulein occurred mainly through the enhancement of chymotrypsinogen transcription and/or mRNA stabilization.

Extracellular Signal-Regulated Kinase 1/2 and c-Jun NH2-Terminal Kinase, through Nuclear Factor-κB and Activator Protein-1, Contribute to Caerulein-Induced Expression of Substance P and Neurokinin-1 Receptors in Pancreatic Acinar Cells

“…On the other hand, SP expression was significantly increased at a lower concentration of 10 Ϫ8 M. The up-regulation of SP was substantially stronger than the upregulation of its gene, PPT-A (3-to 1.5-fold compared with control). It is possible that RNA stabilization, increased translational activity, or reduced degradation of SP by neutral endopeptidases contributed to the observation, although these hypotheses remain to be elucidated (Estival et al, 1991;O'Connor et al, 2004). The 3-fold increase in SP levels is in line with previous experiments done in vivo, in which SP is increased with a similar magnitude in the pancreas after induction of AP (Lau and Bhatia, 2006).…”

Dexamethasone-induced differentiation of pancreatic AR42J cell involves p21(waf1/cip1)and MAP kinase pathway

“…These results indicated that dexamethasone inhibits growth and induces differentiation of AR42J cell toward an amylase-secreting exocrine phenotype. Our observation was similar to those of previously reported by others for dexamethasone-induced parameters of differentiation (Logsdon et al, 1985;Estival et al, 1991;Rajasekaran et al, 1993). We examined the effect of MAP kinase pathway on amylase mRNA expression induced by dexamethasone.…”

“…It has been demonstrated that dexamethasone converts them into matured exocrine cells expressing digestive enzymes (Logsdon et al, 1985;Rajasekaran et al, 1993), whereas activin A converts them into insulin-producing neuroendocrine cells (Ohnishi et al, 1995). The dexamethasone-induced phenotypic changes of AR42J cells include increases in secretory organelles (Rajasekaran et al, 1993), tissue specific gene expression (Estival et al, 1991) and receptors for cholecystokinin (Rosewicz et al, 1994). Moreover, glucocorticoids inhibit the growth of animal cells including AR42J cells (Guthrie et al, 1991), another hallmark of cellular differentiation.…”

Caerulein and gastrin(2–17 ds) regulate differently synthesis of secretory enzymes, mRNA levels and cell proliferation in pancreatic acinar cells (AR4-2J)

“…Enzyme secretion in serum-free culture media is linear for 48 h in both unstimulated and stimulated cells [20]. No chymotrypsin activity was detected in either the cells or the secretion before the addition of activating trypsin.…”