Extracellular ATP Induces Calcium Signaling in Odontoblasts. (February 2017)

• Record Type: Journal Article
• Authors: Lee, B.M.; Jo, H.; Park, G.; Kim, Y.H.; Park, C.K.; Jung, S.J.; Chung, G.; Oh, S.B.
• Is Part Of: Journal of dental research. Volume 96:Number 2(2017)
• Page Start: 200
• Page End: 207
• Publication Date: 2017-02
• Subjects: dental pulp -- odontoblasts -- dentin -- adenosine triphosphate -- single-cell analysis -- purinergic receptors; Dentistry -- Periodicals; Dentistry -- Social aspects -- Periodicals; Dentistry -- Periodicals; Research -- Periodicals; 617.6005
• DOI: 10.1177/0022034516671308
• Languages: English
• ISSNs: 0022-0345

Abstract

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 (P2X1 to P2X7 ) in tooth pulp, single-cell RT-PCR analysis of acutely isolated rat odontoblasts revealed P2Y2, P2Y4, P2X2, P2X4, P2X6, and P2X7 expression in only a subset (23% to 47%) of cells tested, with no evidence for P2X1, P2X3, and P2X5 expression. An increase of intracellular Ca 2+ concentration in response to 100μM ATP, which was repeated after pretreatment of thapsigargin or under the Ca 2+ -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 P2X4 subtype 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 P2X7 as 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 P2X4 and P2X7 in 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.