Changes in expression of neuronal and glial glutamate transporters in lead-exposed adult rat brain.
Excitatory amino acid transporters (EAATs) are membrane-bound proteins localized in glial and neuronal cells which transport glutamate (Glu) in a process essential for terminating its action and protecting neurons from excitotoxic damage. Since Pb-induced neurotoxicity has a glutamatergic component and astrocytes serve as a cellular Pb deposition site, it was of interest to investigate the response of main glutamate transporters to short-term lead exposure in the adult rat brain (25mg/kg b.w. of lead acetate, i.p. for 3 days). We examined the expression of mRNA and protein of GLAST, GLT-1 and EAAC1 in homogenates obtained from cerebellum, hippocampus and forebrain. Molecular evidence is provided which indicates that, of the two glial transporters, GLT-1 is more susceptible than GLAST to the neurotoxic effect arising from Pb. RT-PCR analysis revealed highly decreased expression of GLT-1 mRNA in forebrain and hippocampus. In contrast, GLAST was overexpressed in forebrain and in cerebellum. In the case of EAAC1, the enhanced expression of mRNA and protein of transporter was observed only in forebrain. The results demonstrate regional differences in the expression of glutamate transporters after short-term exposure to Pb. In forebrain, downregulation of GLT-1 is compensated by enhanced expression of GLAST, while in hippocampus, the expression of both is lowered. This observation suggests that under conditions of Pb toxicity in adult rat brain, the hippocampus is most vulnerable to the excitotoxic cell damage arising from impaired clearance of the released glutamate.
Laboratory of Pathoneurochemistry, Department of Neurochemistry, Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland. lidkas@cmdik.pan.pl
Lidia
L
Struzyńska
Małgorzata
M
Chalimoniuk
Grzegorz
G
Sulkowski
D027322:Amino Acid Transport System X-AG / Q000096:biosynthesis* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects*; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D050580:Excitatory Amino Acid Transporter 3; D050491:Glutamate Plasma Membrane Transport Proteins; D007854:Lead / Q000097:blood / Q000378:metabolism / Q000633:toxicity*; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000378:metabolism
D027322:Amino Acid Transport System X-AG; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D050580:Excitatory Amino Acid Transporter 3; D050491:Glutamate Plasma Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C493398:Slc1a1 protein, rat; C493392:Slc1a3 protein, rat; D027981:Symporters; D007854:Lead