Extracellular ATP Induces Calcium Signaling in Odontoblasts.
Odontoblasts form dentin at the outermost surface of tooth pulp. An increasing level of evidence in recent years, along with their locational advantage, implicates odontoblasts as a secondary role as sensory or immune cells. Extracellular adenosine triphosphate (ATP) is a well-characterized signaling molecule in the neuronal and immune systems, and its potential involvement in interodontoblast communications was recently demonstrated. In an effort to elaborate the ATP-mediated signaling pathway in odontoblasts, the current study performed single-cell reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescent detection to investigate the expression of ATP receptors related to calcium signal in odontoblasts from incisal teeth of 8- to 10-wk-old rats, and demonstrated an in vitro response to ATP application via calcium imaging experiments. While whole tissue RT-PCR analysis detected P2Y2, P2Y4, and all 7 subtypes (P2X1to P2X7) in tooth pulp, single-cell RT-PCR analysis of acutely isolated rat odontoblasts revealed P2Y2, P2Y4, P2X2, P2X4, P2X6, and P2X7expression in only a subset (23% to 47%) of cells tested, with no evidence for P2X1, P2X3, and P2X5expression. An increase of intracellular Ca2+concentration in response to 100μM ATP, which was repeated after pretreatment of thapsigargin or under the Ca2+-free condition, suggested function of both ionotropic and metabotropic ATP receptors in odontoblasts. The enhancement of ATP-induced calcium response by ivermectin and inhibition by 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]-1,4-diazepin-2-one (5-BDBD) confirmed a functional P2X4subtype in odontoblasts. Positive calcium response to 2',3'-O-(benzoyl-4-benzoyl)-ATP (BzATP) and negative response to α,β-methylene ATP suggested P2X2, P2X4, and P2X7as functional subunits in rat odontoblasts. Single-cell RT-PCR analysis of the cells with confirmed calcium response and immunofluorescent detection further corroborated the expression of P2X4and P2X7in odontoblasts. Overall, this study demonstrated heterogeneous expression of calcium-related ATP receptor subtypes in subsets of individual odontoblasts, suggesting extracellular ATP as a potential signal mediator for odontoblastic functions.
1 Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
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BM
Lee
1 Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
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Jo
1 Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
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Park
1 Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
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YH
Kim
2 Department of Physiology, Graduate School of Medicine, Gachon University, Incheon, Republic of Korea.
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CK
Park
3 Department of Physiology, College of Medicine, Hanyang University, Seoul, Republic of Korea.
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Jung
1 Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
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G
Chung
1 Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea.|4 Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea.
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Oh
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D002478:Cells, Cultured; D009804:Odontoblasts / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058476:Receptors, Purinergic P2X2 / Q000378:metabolism; D058848:Receptors, Purinergic P2X4 / Q000378:metabolism; D058486:Receptors, Purinergic P2X7 / Q000378:metabolism; D058473:Receptors, Purinergic P2Y2 / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D058848:Receptors, Purinergic P2X4; D058486:Receptors, Purinergic P2X7; D058473:Receptors, Purinergic P2Y2; C110590:purinoceptor P2X6; C104749:purinoceptor P2Y4; D000255:Adenosine Triphosphate
adenosine triphosphate; dental pulp; dentin; odontoblasts; purinergic receptors; single-cell analysis