title: Dexmedetomidine increases the activity of excitatory amino acid transporter type 3 expressed in Xenopus oocytes: the involvement of protein kinase C and phosphatidylinositol 3-kinase.
abstract: Dexmedetomidine, an α2 adrenergic agonist, has neuroprotective and anticonvulsant properties in addition to its sedative and anxiolytic effects. We hypothesized that dexmedetomidine would increase the activity of excitatory amino acid transporter type 3 (EAAT3) and that this effect would involve protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K), two protein kinases known to regulate EAAT3 activity. EAAT3 was expressed in Xenopus oocytes by injecting its mRNA. Two-electrode voltage clamping was used to record membrane currents before, during, and after application of 30 μM l-glutamate in the presence of 0.1-30 nM dexmedetomidine. Dexmedetomidine-treated oocytes were also exposed to a PKC activator (phorbol-12-myristate-13-acetate [PMA]), PKC inhibitors (chelerythrine, staurosporine, and calphostin C), and PI3K inhibitors (wortmannin and LY294002) before current measurement. Dexmedetomidine application resulted in a concentration-dependent increase in the EAAT3 activity in response to l-glutamate. The kinetic study showed that dexmedetomidine significantly increased the Vmax without changing Km. Treatment of oocytes with PMA significantly increased transporter currents compared with controls, but treatment with dexmedetomidine plus PMA did not further increase the response compared with PMA or dexmedetomidine alone. In addition, pre-treatment of oocytes with PKC inhibitors and PI3K inhibitors significantly abolished the dexmedetomidine-enhanced EAAT3 activity. These results suggest that dexmedetomidine increases the activity of EAAT3 expressed in Xenopus oocytes. PKC and PI3K seem to mediate this effect. These findings may explain the neuroprotective and anticonvulsant effects of dexmedetomidine.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea.
authors.forename: Sang-Hwan
authors.initials: SH
authors.lastname: Do
authors.affiliation: Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea.
authors.forename: Seong-Joo
authors.initials: SJ
authors.lastname: Park
authors.affiliation: Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea.
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Shin
authors.affiliation: Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Hye-Sun
authors.initials: HS
authors.lastname: Paik
authors.affiliation: Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA.
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Zuo
authors.affiliation: Department of Anesthesiology and Pain Medicine, Cheil General Hospital, Kwandong University, Seoul, South Korea.
authors.forename: Hea-Jo
authors.initials: HJ
authors.lastname: Yoon
authors.affiliation: Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea. Electronic address: jinaryu@lycos.co.kr.
authors.forename: Jung-Hee
authors.initials: JH
authors.lastname: Ryu
mesh_terms: D000818:Animals; D020927:Dexmedetomidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D050580:Excitatory Amino Acid Transporter 3 / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D009865:Oocytes / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D014981:Xenopus / Q000235:genetics*
chemical_list: D050580:Excitatory Amino Acid Transporter 3; D020927:Dexmedetomidine; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C
keywords: Dexmedetomidine; Glutamate transporters; Protein kinase C; Xenopus oocyte