title: GPR55-dependent stimulation of insulin secretion from isolated mouse and human islets of Langerhans.
abstract: The novel cannabinoid receptor GPR55 is expressed by rodent islets and it has been implicated in β-cell function in response to a range of ligands. This study evaluated the effects of GPR55 ligands on intracellular calcium ([Ca2+]i) levels and insulin secretion from islets isolated from GPR55 knockout (GPR55-/-) mice, age-matched wildtype (WT) mice and human pancreas.
  
  
  
  GPR55 expression was determined by Western blotting and fluorescent immunohistochemistry. Changes in [Ca2+]iwere measured by Fura-2 microfluorimetry. Dynamic insulin secretion was quantified by radioimmunoassay following perifusion of isolated islets. RhoA activity was monitored using a Rho binding domain pull down assay.
  
  
  
  Western blotting indicated that MIN6 β-cells, mouse and human islets express GPR55 and its localization on human β-cells was demonstrated by fluorescent immunohistochemistry. The pharmacological GPR55 agonist O-1602 (10 μM) significantly stimulated [Ca2+]iand insulin secretion from WT mouse islets and these stimulatory effects were abolished in islets isolated from GPR55-/-mice. In contrast, while the putative endogenous GPR55 agonist lysophosphatidylinositol (LPI, 5 µM) and the GPR55 antagonist cannabidiol (CBD, 1 µM) also elevated [Ca2+]iand insulin secretion, these effects were sustained in islets from GPR55-/-mice. Stimulatory effects of O-1602 on [Ca2+]iand insulin secretion were also observed in experiments using human islets, but O-1602 did not activate RhoA in MIN6 β-cells.
  
  
  
  Our results therefore suggest that GPR55 plays an important role in the regulation of mouse and human islet physiology, but LPI and CBD exert stimulatory effects on islet function by a GPR55-independent pathway(s).
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Bo
authors: B
authors: Liu
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Shuang
authors: S
authors: Song
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Inmaculada
authors: I
authors: Ruz-Maldonado
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Attilio
authors: A
authors: Pingitore
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Guo C
authors: GC
authors: Huang
authors: Centre for Neuroscience and Trauma, Barts and The London School of Medicine and Dentistry, London, UK.
authors: David
authors: D
authors: Baker
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Peter M
authors: PM
authors: Jones
authors: Division of Diabetes and Nutritional Sciences, Diabetes Research Group, King's College London, London, UK.
authors: Shanta J
authors: SJ
authors: Persaud
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002185:Cannabidiol / Q000494:pharmacology* / Q000031:analogs & derivatives; D063386:Cannabinoid Receptor Agonists / Q000494:pharmacology*; D063387:Cannabinoid Receptor Antagonists / Q000494:pharmacology*; D002460:Cell Line; D003510:Cyclohexanes / Q000494:pharmacology*; D003592:Cytophotometry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D061848:Optical Imaging; D043882:Receptors, Cannabinoid / Q000235:genetics* / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D012118:Resorcinols / Q000494:pharmacology*; D059010:Single-Cell Analysis; D020742:rhoA GTP-Binding Protein / Q000187:drug effects / Q000378:metabolism
chemical_list: D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D003510:Cyclohexanes; C524885:GPR55 protein, human; C526692:GPR55 protein, mouse; D007328:Insulin; D008246:Lysophospholipids; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled; D012118:Resorcinols; C025449:lysophosphatidylinositol; D002185:Cannabidiol; C568537:O-1602 compound; D020742:rhoA GTP-Binding Protein; D002118:Calcium
keywords: antidiabetic drug; beta cell; cannabinoids; islets; mouse model