title: Dexamethasone effects on Na(v)1.6 in tooth pulp, dental nerves, and alveolar osteoclasts of adult rats.
abstract: Dexamethasone causes extensive physiologic reactions including the reduction of inflammation and pain. Here, we asked whether it also affected dental or periodontal cells or dental innervation by altering voltage-gated sodium channel Na(v)1.6 immunoreactivity (IR) or neural synaptophysin. Daily dexamethasone (0.2 mg/kg) given for 1 week to rats caused 12-fold increased intensity of Na(v)1.6-IR in dendritic pulpal cells of normal molars and incisors compared with vehicle treatment. These cells also co-localized monocyte (ED-1) or dendritic cell (CD11b/Ox42) markers, and their location in molars expanded during dexamethasone treatment to include deeper pulp. Furthermore, dexamethasone caused a 10-fold decrease in the number of Na(v)1.6-immunoreactive multinucleate osteoclasts along the alveolar bone of molar root sockets. No changes occurred for neural Na(v)1.6 at axonal nodes of Ranvier, even though IR for calcitonin gene-related peptide was greatly decreased, as expected, and neural synaptophysin-IR was decreased 59% by dexamethasone. At 4 days after tooth injury, pulpal vasodilation and increased Na(v)1.6-immunoreactive pulp cells were similar for all groups. Thus, dexamethasone changes dental pulp cell and alveolar osteoclast Na(v)1.6-IR in normal teeth, but different mechanisms occur after tooth injury when tissue reactions were similar for dexamethasone- and vehicle-treated rats. Steroid-induced alterations of dental pain and inflammation coincide with altered exocytic capability in dental nerve fibers as shown by synaptophysin-IR and with altered pulp cell Na(v)1.6-IR and osteoclast number, but not with any changes in Na(v)1.6-IR for nodes of Ranvier in myelinated dental axons.
authors.affiliation: Department of Anesthesiology, University of Washington, Box 356540, Seattle, WA 98195-6540, USA. byersm@u.washington.edu
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Byers
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Rafie
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Westenbroek
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002452:Cell Count; D003713:Dendritic Cells / Q000166:cytology / Q000187:drug effects; D003782:Dental Pulp / Q000166:cytology / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D008297:Male; D009000:Monocytes / Q000166:cytology / Q000187:drug effects; D062557:NAV1.6 Voltage-Gated Sodium Channel; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D011901:Ranvier's Nodes / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism*; D016708:Synaptophysin / Q000378:metabolism*; D018677:Tooth Injuries / Q000188:drug therapy / Q000473:pathology; D020390:Tooth Socket / Q000166:cytology / Q000187:drug effects; D014665:Vasodilator Agents / Q000378:metabolism
chemical_list: D062557:NAV1.6 Voltage-Gated Sodium Channel; C507811:Scn8a protein, rat; D015222:Sodium Channels; D016708:Synaptophysin; D014665:Vasodilator Agents; D003907:Dexamethasone; D015740:Calcitonin Gene-Related Peptide