Dexamethasone effects on Na(v)1.6 in tooth pulp, dental nerves, and alveolar osteoclasts of adult rats.
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.
Byers
Margaret R
MR
Department of Anesthesiology, University of Washington, Box 356540, Seattle, WA 98195-6540, USA. byersm@u.washington.edu
Rafie
Matthew M
MM
Westenbroek
Ruth E
RE
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
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