Neuroprotective effect of nitric oxide against NMDA-induced neurotoxicity in the rat retina is associated with tyrosine hydroxylase expression.
N-methyl-D-aspartate (NMDA) may affect dopaminergic cells, which contain tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine synthesis. To clarify the involvement of TH in the neuroprotective effects of nitric oxide (NO), we investigated whether NMDA alters TH mRNA and TH protein levels and whether NO inhibits NMDA-induced changes in the rat retina. Dopamine levels in the retina were measured by high-performance liquid chromatography (HPLC). Reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR showed that intravitreal injection of NMDA caused a significant reduction in TH mRNA levels in the retina. Similarly, Western blot analysis showed that NMDA decreased the production of TH protein. These reductions in TH mRNA and TH protein levels were attenuated by concomitant injection of NOC 18, an NO donor. HPLC analysis showed that NMDA reduced dopamine levels in the retina and that NO attenuated this reduction. Furthermore, morphological analysis showed that NO prevents NMDA-induced neurotoxicity through dopamine D(1) receptors. These results suggest that the neuroprotective effect of NO may be associated with the induction of TH expression and increased levels of dopamine.
Kitaoka
Yasushi
Y
Department of Ophthalmology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki-shi, Kanagawa 216-8511, Japan. kitaoka@marianna-u.ac.jp
Kumai
Toshio
T
Isenoumi
Kazuyuki
K
Kitaoka
Yuka
Y
Motoki
Masamitsu
M
Kobayashi
Shinichi
S
Ueno
Satoki
S
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D015153:Blotting, Western; D002452:Cell Count; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004294:Domperidone / Q000494:pharmacology; D004298:Dopamine / Q000032:analysis; D018492:Dopamine Antagonists / Q000494:pharmacology; D004347:Drug Interactions; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D016166:Free Radical Scavengers / Q000627:therapeutic use*; D005786:Gene Expression Regulation / Q000187:drug effects*; D008297:Male; D016202:N-Methylaspartate / Q000633:toxicity; D020258:Neurotoxicity Syndromes / Q000209:etiology / Q000517:prevention & control*; D009569:Nitric Oxide / Q000627:therapeutic use*; D020030:Nitric Oxide Donors / Q000627:therapeutic use; D009603:Nitroso Compounds / Q000627:therapeutic use; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism*
D001552:Benzazepines; D018492:Dopamine Antagonists; D018690:Excitatory Amino Acid Agonists; D016166:Free Radical Scavengers; C093285:NOC 18; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D009569:Nitric Oxide; D004294:Domperidone; D016202:N-Methylaspartate; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine