Angiotensin receptor type 1 antagonists protect against neuronal injury induced by oxygen-glucose depletion.
OBJECTIVE
Several clinical trials and in vivo animal experiments have suggested that blockade of angiotensin receptor type 1 (AT(1)) improves ischaemic outcomes. However, the mechanism(s) underlying these effects has not been elucidated. Here, we have investigated the protective effects of pretreatment with AT(1) receptor antagonists, losartan or telmisartan, against ischaemic insult to neurons in vitro.


METHODS
Primary rat neuron-astrocyte co-cultures and astrocyte-defined medium (ADM)-cultured pure astrocyte cultures were prepared. Ischaemic injury was modelled by oxygen-glucose depletion (OGD) and lactate dehydrogenase release after OGD was measured with or without AT(1) receptor antagonists or agonists (L162313), AT(2) receptor antagonist (PD123319) or agonist (CGP-42112A) pretreatment, for 48 h. Activity of glutamate transporter 1 (GLT-1) was evaluated by [(3)H]-glutamate uptake assays, after AT(1) receptor agonists or antagonists. Immunoblot and real-time PCR were used for analysis of protein and mRNA levels of GLT-1.


RESULTS
AT(1) receptor agonists augmented OGD-induced cellular damage, which was attenuated by AT(1) receptor antagonists. AT(1) receptor antagonists also suppressed OGD-induced extracellular glutamate release, reactive oxygen species production and nitric oxide generation. GLT-1 expression and glutamate uptake activity were significantly enhanced by AT(1) receptor antagonists and impaired by AT(1) receptor agonists. AT(1) receptor stimulation suppressed both ADM-induced GLT-1 protein expression and mRNA levels. AT(1)b receptor knock-down with siRNA enhanced GLT-1 expression. In postnatal (P1-P21) rat brains, protein levels of GLT-1 and AT(1) receptors were inversely correlated.


CONCLUSIONS
Suppression of AT(1) receptor stimulation induced GLT-1 up-regulation, which ameliorated effects of ischaemic injury.
Wu
X
X
Department of Neuroscience for Drug Discovery, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Kihara
T
T
Hongo
H
H
Akaike
A
A
Niidome
T
T
Sugimoto
H
H
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes; D001562:Benzimidazoles / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000494:pharmacology; D016923:Cell Death; D018920:Coculture Techniques; D027342:Excitatory Amino Acid Transporter 2 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D019808:Losartan / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D000077333:Telmisartan
D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001565:Benzoates; D001713:Biphenyl Compounds; D027342:Excitatory Amino Acid Transporter 2; D007093:Imidazoles; C091630:L 162313; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D018698:Glutamic Acid; D005947:Glucose; D019808:Losartan; D010100:Oxygen; D000077333:Telmisartan