Effect of (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol (CP55,940) on intracellular Ca2+ levels in human osteosarcoma cells.
The study was undertaken to explore the effect of CP55,940 ((-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol), a drug commonly used as a CB1/CB2 cannabinoid receptor agonist, on intracellular free Ca2+ levels ([Ca2+]i) in MG63 human osteoblast-like epithelial cells. [Ca2+]i was measured in suspended cells by using the fluorescent dye fura-2 as an indicator. At concentrations between 2-20 microM, CP55,940 increased [Ca2+]i in a concentration-dependent manner with an EC50 of 8 microM. The [Ca2+] signal comprised an initial rise, a slow decay, and a sustained phase. CP55940 (10 microM)-induced [Ca2+]i signal was not altered by 5 microM of two cannabinoid receptor antagonists (AM-251, N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole3-carboxamide; AM-281, 1-(2,4-Dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide). Extracellular Ca2+ removal decreased the maximum value of the Ca2+ signals by 50%. CP55,940 induced quench of fura-2 fluorescence by Mn2+ (50 microM), suggesting the presence of Ca2+ influx across the plasma membrane. CP55,940 (10 microM)-induced [Ca2+]i increase in Ca(2+)-free medium was inhibited by 84% by pretreatment with 1 microM thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor. Conversely, pretreatment with 10 microM CP55,940 in Ca(2+)-free medium abolished thapsigargin-induced [Ca2+]i increase. At 1 microM, nifedipine, verapamil, and diltiazem did not alter CP55, 940 (10 microM)-induced [Ca2+]i increase. CP55,940 (20 microM)-induced Ca2+ release was not affected when phospholipase C was inhibited by 2 microM U73122 (1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino) hexyl)-1H-pyrrole-2,5-dione). CP55,940 (20 microM) did not induce acute cell death after incubation for 30 min as assayed by trypan blue exclusion. Collectively, CP55,940 induced significant [Ca2+]i increases in osteoblasts by releasing store Ca2+ from thapsigargin-sensitive stores and by causing Ca2+ entry. The CP55,940's action appears to be independent of stimulation of CB1 cannabinoid receptors.
Lu
Yih-Chau
YC
Department of Orthopaedic Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan 813, Rupublic of China.
Su
Warren
W
Jiann
Bang-Ping
BP
Chang
Hong-Tai
HT
Huang
Jong-Khing
JK
Jan
Chung-Ren
CR
D002118:Calcium / Q000493:pharmacokinetics*; D003511:Cyclohexanols / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012516:Osteosarcoma; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D003511:Cyclohexanols; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D019284:Thapsigargin; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D010738:Type C Phospholipases; D002118:Calcium