The adenosine A2B receptor is involved in anion secretion in human pancreatic duct Capan-1 epithelial cells.

M Hayashi,A Inagaki,I Novak,H Matsuda

doi:10.1007/s00424-016-1806-9

Abstract

Adenosine modulates a wide variety of biological processes via adenosine receptors. In the exocrine pancreas, adenosine regulates transepithelial anion secretion in duct cells and is considered to play a role in acini-to-duct signaling. To identify the functional adenosine receptors and Cl− channels important for anion secretion, we herein performed experiments on Capan-1, a human pancreatic duct cell line, using open-circuit Ussing chamber and gramicidin-perforated patch-clamp techniques. The luminal addition of adenosine increased the negative transepithelial potential difference (Vte) in Capan-1 monolayers with a half-maximal effective concentration value of approximately 10 μM, which corresponded to the value obtained on whole-cell Cl− currents in Capan-1 single cells. The effects of adenosine on Vte, an equivalent short-circuit current (Isc), and whole-cell Cl− currents were inhibited by CFTRinh-172, a cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel inhibitor. The adenosine A2B receptor agonist, BAY 60-6583, increased Isc and whole-cell Cl− currents through CFTR Cl− channels, whereas the A2A receptor agonist, CGS 21680, had negligible effects. The A2B receptor antagonist, PSB 603, inhibited the response of Isc to adenosine. Immunohistochemical analysis showed that the A2A and A2B receptors colocalized with Ezrin in the luminal membranes of Capan-1 monolayers and in rat pancreatic ducts. Adenosine elicited the whole-cell Cl− currents in guinea pig duct cells. These results demonstrate that luminal adenosine regulates anion secretion by activating CFTR Cl− channels via adenosine A2B receptors on the luminal membranes of Capan-1 cells. The present study endorses that purinergic signaling is important in the regulation of pancreatic secretion.

Highlights

The pancreas plays a pivotal role in digestion
In order to determine whether adenosine regulated transepithelial anion secretion in pancreatic duct cells, we measured the electrophysiological parameters of the Capan-1 monolayer in Ussing chambers
We demonstrated that the luminal adenosine A2B receptor regulated the CFTR Cl− channels necessary for anion secretion in Capan-1 cells

Summary

Introduction

Pancreatic acini secrete digestive enzymes, and ducts secrete a HCO3−-rich pancreatic juice that neutralizes acid chyme in the duodenum. The generally accepted model for HCO3− transport involves Cl−–HCO3− exchangers that operate in parallel with cAMPactivated Cl− channels [cystic fibrosis transmembrane conductance regulator (CFTR)] and Ca2+-activated Cl− channels, such as TMEM16A/ANO1, on the luminal membranes of duct cells [46, 50]. Extracellular adenosine has been shown to modulate a wide variety of biological processes via cell surface adenosine receptors [6, 10]. There are four known adenosine receptors denoted adenosine A1, A2A, A2B, and A3 receptors. A2A and A2B receptors generally increase, whereas A1 and A3 receptors decrease cAMP levels [11]. Previous studies reported that adenosine activated A1, A2A, A2B, and A3 receptors with half-maximal effective concentration (EC50) values of 0.1, 0.3, 15, and 0.3 μM, respectively [10]

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