title: Primary cultures of rat cortical microglia treated with nicotine increases in the expression of excitatory amino acid transporter 1 (GLAST) via the activation of the α7 nicotinic acetylcholine receptor.
abstract: Although the clearance of glutamate from the synapse under physiological conditions is performed by astrocytic glutamate transporters, their expression might be diminished under pathological conditions. Microglia glutamate transporters, however, might serve as a back-up system when astrocytic glutamate uptake is impaired, and could have a prominent neuroprotective function under pathological conditions. In the current study, the effect of nicotine, well known as a neuroprotective molecule, on the function of glutamate transporters in cultured rat cortical microglia was examined. Reverse transcription polymerase chain reaction and pharmacological approaches demonstrated that, glutamate/aspartate transporter (GLAST), not glutamate transporter 1 (GLT-1), is the major functional glutamate transporter in cultured cortical microglia. Furthermore, the α7 subunit was demonstrated to be the key subunit comprising nicotinic acetylcholine (nACh) receptors in these cells. Treatment of cortical microglia with nicotine led to a significant increase of GLAST mRNA expression and (14)C-glutamate uptake in a concentration- and time-dependent manner, which were markedly inhibited by pretreatment with methyllycaconitine, a selective α7 nACh receptor antagonist. The nicotine-induced expression of GLAST mRNA and protein is mediated through an inositol trisphosphate (IP3) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) depend intracellular pathway, since pretreatment with either xestospongin C, an IP3 receptor antagonist, or KN-93, a CaMKII inhibitor, blocked GLAST expression. Together, these findings indicate that activation of nACh receptors, specifically those expressing the α7 subunit, on cortical microglia could be a key mechanism of the neuroprotective effect of nACh receptor ligands such as nicotine.
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan. Electronic address: mnori@hiroshima-u.ac.jp.
authors.forename: N
authors.initials: N
authors.lastname: Morioka
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tokuhara
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Idenoshita
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Harano
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: F F
authors.initials: FF
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hisaoka-Nakashima
authors.affiliation: Department of Pharmacology, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakata
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018722:Nicotinic Agonists; D012333:RNA, Messenger; C493395:Slc1a2 protein, rat; C493392:Slc1a3 protein, rat; D064569:alpha7 Nicotinic Acetylcholine Receptor; D018698:Glutamic Acid; D009538:Nicotine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D002118:Calcium
keywords: BSS; Ca(2+)/calmodulin-dependent protein kinase II; CaMKII; DHK; DMEM; Dulbecco’s modified Eagle’s medium; EAATs; GAPDH; GLAST; GLT-1; IP(3); Iba1; L-trans-pyrrolidine-2,4-dicarboxylic acid; MLA; SDS; TGF; TNF; balanced salt solution; dihydrokainic acid; excitatory amino acid transporters; glutamate transporter; glutamate transporter 1; glutamate/aspartate transporter; glyceraldehydes-3-phosphate dehydrogenase; inositol triphosphate; inositol trisphosphate; ionized Ca(2+)-binding adaptor 1; methyllycaconitine; microglia; nACh; nicotinic acetylcholine; nicotinic acetylcholine receptor; sodium dodecyl sulfate; t-PDC; transforming growth factor; tumor necrosis factor; xesC; xestospongin C