title: Sensitization of cutaneous neuronal purinergic receptors contributes to endothelin-1-induced mechanical hypersensitivity.
abstract: Endothelin (ET-1), an endogenous peptide with a prominent role in cutaneous pain, causes mechanical hypersensitivity in the rat hind paw, partly through mechanisms involving local release of algogenic molecules in the skin. The present study investigated involvement of cutaneous ATP, which contributes to pain in numerous animal models. Pre-exposure of ND7/104 immortalized sensory neurons to ET-1 (30nM) for 10min increased the proportion of cells responding to ATP (2μM) with an increase in intracellular calcium, an effect prevented by the ETA receptor-selective antagonist BQ-123. ET-1 (3nM) pre-exposure also increased the proportion of isolated mouse dorsal root ganglion neurons responding to ATP (0.2-0.4μM). Blocking ET-1-evoked increases in intracellular calcium with the IP3 receptor antagonist 2-APB did not inhibit sensitization to ATP, indicating a mechanism independent of ET-1-mediated intracellular calcium increases. ET-1-sensitized ATP calcium responses were largely abolished in the absence of extracellular calcium, implicating ionotropic P2X receptors. Experiments using quantitative polymerase chain reaction and receptor-selective ligands in ND7/104 showed that ET-1-induced sensitization most likely involves the P2X4 receptor subtype. ET-1-sensitized calcium responses to ATP were strongly inhibited by broad-spectrum (TNP-ATP) and P2X4-selective (5-BDBD) antagonists, but not antagonists for other P2X subtypes. TNP-ATP and 5-BDBD also significantly inhibited ET-1-induced mechanical sensitization in the rat hind paw, supporting a role for purinergic receptor sensitization in vivo. These data provide evidence that mechanical hypersensitivity caused by cutaneous ET-1 involves an increase in the neuronal sensitivity to ATP in the skin, possibly due to sensitization of P2X4 receptors.
authors.affiliation: Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA, USA Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden Neurobiology Department, Children's Hospital Boston, Harvard Medical School, Boston, MA, USA Harvard School of Dental Medicine, Boston, MA, USA Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
authors.forename: Travis P
authors.initials: TP
authors.lastname: Barr
authors.forename: Alen
authors.initials: A
authors.lastname: Hrnjic
authors.forename: Alla
authors.initials: A
authors.lastname: Khodorova
authors.forename: Jared M
authors.initials: JM
authors.lastname: Sprague
authors.forename: Gary R
authors.initials: GR
authors.lastname: Strichartz
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000633:toxicity*; D006930:Hyperalgesia / Q000139:chemically induced* / Q000378:metabolism*; D008297:Male; D051379:Mice; D051381:Rats; D017207:Rats, Sprague-Dawley; D058848:Receptors, Purinergic P2X4 / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000378:metabolism*; D012867:Skin / Q000187:drug effects / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D058848:Receptors, Purinergic P2X4
keywords: ATP; Endothelin; Mechanosensitivity; Pain; Sensitization