title: Effect of dexamethasone on voltage-gated Na+ channel in cultured human bronchial smooth muscle cells.
abstract: Voltage-gated Na(+) channel (I(Na)) encoded by SCN9A mRNA is expressed in cultured human bronchial smooth muscle cells. We investigated the effects of dexamethasone on I(Na), by using whole-cell voltage clamp techniques, reverse transcriptase/polymerase chain reaction (RT-PCR), and quantitative real-time RT-PCR. Acute application of dexamethasone (10(-6) M) did not affect I(Na). However, the percentage of the cells with I(Na) was significantly less in cells pretreated with dexamethasone for 48 h, and the current-density of I(Na) adjusted by cell capacitance in cells with I(Na) was also decreased in cells treated with dexamethasone. RT-PCR analysis showed that alpha and beta subunits mRNA of I(Na) mainly consisted of SCN9A and SCN1beta, respectively. Treatment with dexamethasone for 24-48 h inhibited the expression of SCN9A mRNA. The inhibitory effect of dexamethasone was concentration-dependent, and was observed at a concentration higher than 0.1 nM. The effect of dexamethasone on SCN9A mRNA was not blocked by spironolactone, but inhibited by mifepristone. The inhibitory effects of dexamethasone on SCN9A mRNA could not be explained by the changes of the stabilization of mRNA measured by using actinomycin D. These results suggest that dexamethasone inhibited I(Na) encoded by SCN9A mRNA in cultured human bronchial smooth muscle cells by inhibiting the transcription via the glucocorticoid receptor.
authors.affiliation: Department of Ischemia Circulatory Physiology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. masamasa@pb4.so-net.ne.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Nakajima
authors.forename: Taisuke
authors.initials: T
authors.lastname: Jo
authors.forename: Kentaro
authors.initials: K
authors.lastname: Meguro
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Oonuma
authors.forename: Ji
authors.initials: J
authors.lastname: Ma
authors.forename: Nami
authors.initials: N
authors.lastname: Kubota
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imuta
authors.forename: Haruhito
authors.initials: H
authors.lastname: Takano
authors.forename: Haruko
authors.initials: H
authors.lastname: Iida
authors.forename: Takahide
authors.initials: T
authors.lastname: Nagase
authors.forename: Taiji
authors.initials: T
authors.lastname: Nagata
mesh_terms: D000328:Adult; D001980:Bronchi / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D062556:NAV1.7 Voltage-Gated Sodium Channel; D018408:Patch-Clamp Techniques; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015222:Sodium Channels / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D062556:NAV1.7 Voltage-Gated Sodium Channel; C486866:SCN9A protein, human; D015222:Sodium Channels; D003907:Dexamethasone