Effects of increased intracellular cAMP on carbachol-stimulated zymogen activation, secretion, and injury in the pancreatic acinar cell

Abstract

A characteristic of acute pancreatitis is the premature activation and retention of enzymes within the pancreatic acinar cell. Because ligands linked to cAMP production may prevent some forms of pancreatitis, we evaluated the effects of increased intracellular cAMP in the rat pancreatic acinar cell. Specifically, this study examined the effects of the cholinergic agonist carbachol and agents that increase cAMP [secretin and 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP)] on zymogen activation (trypsin and chymotrypsin), enzyme secretion, and cellular injury in isolated pancreatic acini. Although cAMP agonists affected the responses to physiological concentrations of carbachol (1 microM), their most prominent effects were observed with supraphysiological concentrations (1 mM). When secretin was added to 1 mM carbachol, there was a slight increase in zymogen activation, but no change in the secretion of amylase or chymotrypsin. Furthermore, coaddition of secretin increased parameters of cell injury (trypan blue exclusion, lactic dehydrogenase release, and morphological markers) compared with carbachol (1 mM) alone. Although directly increasing cellular cAMP by 8-Br-cAMP caused much greater zymogen activation than carbachol (1 mM) alone or with secretin, 8-Br-cAMP cotreatment reduced all parameters of injury to the level of unstimulated acini. Furthermore, 8-Br-cAMP dramatically enhanced the secretion of amylase and chymotrypsin from the acinar cell. This study demonstrates that increasing acinar cell cAMP can overcome the inhibition of enzyme secretion caused by high concentrations of carbachol and eliminate acinar cell injury.

New Insights into Cellular Mechanisms in Smoking-Related Acute Pancreatitis

“…Activation of these receptors can cause production of cyclic AMP through adenylate cyclase and this generation of cAMP can initiates or sensitize to pancreatitis responses [26]. Although Alexandre et al [24] detected β-adrenergic receptors in rat acini, NNK mediated zymogen activation was not inhibited when β-adrenergic receptors were blocked.…”

Genetic and pharmacologic manipulation of vacuolar ATPase: Effects on zymogen activation in pancreatic acini

“…18 In brief, samples were thawed, homogenized, and centrifuged at 1000 g for one minute. To each well of a 24-well Falcon tissue culture plate, the following were added: 100 µl of supernatant and 350 µl of trypsin assay buffer (50 mM Tris [pH 8.1], 150 mM NaCl, 1 mM CaCl 2 , 0.01% BSA).…”

“…18 Amylase secretion into the media was expressed as percent of total amylase (media/[media + cells]).…”

Smoking induced pancreatitis and pancreatic cancer

“…Furthermore, systematic review and metaanalyses, which include many of the studies detailed here, find conclusively that current smoking and former smoking are firmly connected with elevated risk for AP (6,126). One singlecenter prospective, cohort study of the natural history of AP, found that smoking was a dosedependent risk factor for recurrent acute pancreatitis (RAP) (18). Furthermore they validated the association of cigarette smoking with CP.…”

“…Collectively, evidence from these clinical studies supports a dose-dependent association between smoking and chronic pancreatitis; however, a similar association with acute pancreatitis (AP) has also been revealed (18,108,126). In a Danish study with a mean follow-up of 20.2 years, a link between smoking and increased risk of AP was observed, independent of alcohol consumption.…”