Cannabinoid receptor subtype 2 (CB2R) agonist, GW405833 reduces agonist-induced Ca2+ oscillations in mouse pancreatic acinar cells

Abstract

Emerging evidence demonstrates that the blockade of intracellular Ca2+ signals may protect pancreatic acinar cells against Ca2+ overload, intracellular protease activation, and necrosis. The activation of cannabinoid receptor subtype 2 (CB2R) prevents acinar cell pathogenesis in animal models of acute pancreatitis. However, whether CB2Rs modulate intracellular Ca2+ signals in pancreatic acinar cells is largely unknown. We evaluated the roles of CB2R agonist, GW405833 (GW) in agonist-induced Ca2+ oscillations in pancreatic acinar cells using multiple experimental approaches with acute dissociated pancreatic acinar cells prepared from wild type, CB1R-knockout (KO), and CB2R-KO mice. Immunohistochemical labeling revealed that CB2R protein was expressed in mouse pancreatic acinar cells. Electrophysiological experiments showed that activation of CB2Rs by GW reduced acetylcholine (ACh)-, but not cholecystokinin (CCK)-induced Ca2+ oscillations in a concentration-dependent manner; this inhibition was prevented by a selective CB2R antagonist, AM630, or was absent in CB2R-KO but not CB1R-KO mice. In addition, GW eliminated L-arginine-induced enhancement of Ca2+ oscillations, pancreatic amylase, and pulmonary myeloperoxidase. Collectively, we provide novel evidence that activation of CB2Rs eliminates ACh-induced Ca2+ oscillations and L-arginine-induced enhancement of Ca2+ signaling in mouse pancreatic acinar cells, which suggests a potential cellular mechanism of CB2R-mediated protection in acute pancreatitis.

Heterogeneity of cannabinoid ligand-induced modulations in intracellular Ca2+ signals of mouse pancreatic acinar cells in vitro

“…Taken together, our data demonstrate that the ACEA-induced inhibition of cellular Ca 2+ oscillations is achieved through a non-CBR mechanism. This functional study supports our previous work, in which we failed to detect CB 1 R mRNA expression in mouse pancreatic acinar cells [4]. The reason for the differences between previous reports and ours may be the use of different preparations.…”

“…Both CB 1 R and CB 2 R mRNA and proteins have been detected in pancreatic tissue [3,18]. Using real-time RT-PCR, our recent work detected CB 2 R but not CB 1 R mRNA in freshly isolated mouse pancreatic acinar cells [4]. Therefore, in this study, we examined the effects of a CB 1 R agonist on the ACh-induced Ca 2+ oscillations in isolated single mouse pancreatic acinar cells.…”

“…Effect of the CB 1 R agonist on ACh-induced Ca 2+ oscillations It has been reported that both CB 1 R and CB 2 R are expressed in mouse pancreatic tissue [3], but in our acute dissociated mouse pancreatic acinar cells, the CB 1 R mRNA was not detected [4]. Here, we tested the effect of CB 1 R agonists on ACh-induced Ca 2+ oscillations.…”

“…The reason for the differences between previous reports and ours may be the use of different preparations. Previous reports that tested CB 1 R and CB 2 R mRNA expression used pancreatic tissue [3], while we used dissociated pancreatic acinar cells [4]. In pancreatic tissue, there are other types of cells, such as beta-cells, which have been reported to express both CB 1 R and CB 2 R [3,18].…”

“…Additionally, a recent study showed that in animal models of pancreatitis, CB 2 R mRNA and protein levels are changed in pancreatic acinar cells and CB 2 R agonists can reduce the pathological changes in acinar cells [2,3]. In acutely dissociated mouse pancreatic acinar cells, we reported that the selective CB 2 R agonist GW405833 (GW) inhibited both the acetylcholine (ACh)-induced Ca 2+ oscillations and the L-arginine-induced elevation of intracellular Ca 2+ oscillations, indicating that CB 2 R plays important roles in regulating the physiology and pathophysiology of pancreatic acinar cells [4].…”