RT Journal Article
SR Electronic
T1 Potentiation of Sulfonylurea Action by an EPAC-selective cAMP Analog in INS-1 Cells: Comparison of Tolbutamide and Gliclazide, and a Potential Role for EPAC Activation of a 2-APB-sensitive Ca2+ Influx.
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.112.081943
DO 10.1124/mol.112.081943
A1 Rachel E Jarrard
A1 Yuchen Wang
A1 Amy E Salyer
A1 Evan PS Pratt
A1 Ian M Soderling
A1 Marcy L Guerra
A1 Allison M Lange
A1 Hilary J Broderick
A1 Gregory H Hockerman
YR 2012
UL http://molpharm.aspetjournals.org/content/early/2012/10/15/mol.112.081943.abstract
AB Tolbutamide and gliclazide block the KATP channel Kir6.2/Sur1, causing membrane depolarization and stimulating insulin secretion in pancreatic beta cells. We examined the ability of the EPAC-selective cAMP analog 8-pCPT-2'-O-Me-cAMP-AM to potentiate the action of these drugs, and the mechanism that might account for it. Insulin secretion stimulated by both 200 μM tolbutamide and 20 μM gliclazide, concentrations that had equivalent effects on membrane potential, was inhibited by thapsigargin (1 μM) or the L-type Ca2+ channel blocker nicardipine (2 μM), and was potentiated by 8-pCPT-2'-O-Me-cAMP-AM at concentrations > 2 μM in INS-1 cells. Ca2+ transients stimulated by either tolbutamide or gliclazide were inhibited by thapsigargin or nicardipine and were significantly potentiated by 8-pCPT-2'-O-Me-cAMP-AM at 5 μM but not 1μM. Both tolbutamide and gliclazide stimulated phospholipase C activity; however, only gliclazide did so independently of its activity at KATP channels, and this activity was partially inhibited by pertussis toxin. 8-pCPT-2'-O-Me-cAMP-AM alone (5 μM) did not stimulate insulin secretion, but did increase intracellular Ca2+ concentration significantly, and this activity was inhibited by 25 μM 2-aminoethoxydiphenylborate (2-APB) or the removal of extracellular Ca2+. 8-pCPT-2'-O-Me-cAMP-AM potentiation of insulin secretion stimulated by tolbutamide was markedly inhibited by 2-APB (25 μM), and enhanced by the PKC inhibitor Bisindolylmaleimide I (1 μM). Our data demonstrate that the actions of both tolbutamide and gliclazide are strongly potentiated by 8-pCPT-2'-O-Me-cAMP-AM, that gliclazide can stimulate phospholipase C activity via a partially pertussis toxin-sensitive mechanism, and that 8-pCPT-2'-O-Me-cAMP-AM potentiation of tolbutamide action may involve activation of a 2-APB-sensitive Ca2+ influx.