Serine racemase inhibition induces nitric oxide-mediated neurovascular protection during cerebral ischemia.
There are no effective neuroprotectant drugs for acute cerebral ischemia. Serine racemase (SR) synthesizes d-serine, which is involved in N-methyl-d-aspartate (NMDA) receptor-induced neurotoxicity. Recently, SR deletion was reported to protect against focal cerebral ischemia. However, regulatory mechanisms controlling SR-activity in the neurovascular unit (NVU) during cerebral ischemia remain to be clarified. We investigated the effects of SR inhibition on neurovascular protection after ischemia. The SR inhibitor phenazine methosulfate (PMS) alleviated neuronal damage in an ex vivo ischemic model (oxygen glucose deprivation [OGD]) using primary neuronal cultures, and in an in vivo mouse model of ischemia (middle cerebral artery occlusion [MCAO]). Ischemic preconditioning (IP) and PMS-treatment inhibited SR phosphorylation after ischemia ex vivo. In addition, SR phosphorylation after MCAO was also decreased in PMS-treated mice. Reductions in regional cerebral blood flow (CBF) after MCAO were improved by administration of PMS. Treatment with PMS increased phosphorylation of endothelial nitric oxide synthase (eNOS) in the ischemic core and penumbra region. In neuron-endothelial cell co-cultures, PMS promoted nitric oxide production after OGD. These findings indicate that SR inhibition acts as a neuroprotectant in the NVU and ameliorant of CBF abnormalities post-stroke. Thus, pharmacologic SR inhibition has potential clinical applications.
Department of Neurology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: watanabe@neurol.med.osaka-u.ac.jp.
Akihiro
A
Watanabe
Department of Neurology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Tsutomu
T
Sasaki
Department of Neurology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Toshiro
T
Yukami
Department of Neurology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Hideaki
H
Kanki
Department of Neurology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Manabu
M
Sakaguchi
Laboratory of Cell Signaling and Metabolism, National Institute of Biomedical Innovation, Saito, Ibaraki, Osaka 567-0085, Japan.
Hiroshi
H
Takemori
Department of Neurology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
Kazuo
K
Kitagawa
Department of Neurology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Hideki
H
Mochizuki
D000818:Animals; D002545:Brain Ischemia / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D005947:Glucose / Q000172:deficiency; D008297:Male; D008773:Methylphenazonium Methosulfate / Q000494:pharmacology*; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019998:Racemases and Epimerases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011897:Random Allocation; D017208:Rats, Wistar; D000099300:Serine Racemase
D005947:Glucose; D008773:Methylphenazonium Methosulfate; D018696:Neuroprotective Agents; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D019998:Racemases and Epimerases; D000099300:Serine Racemase; C496315:Nos3 protein, mouse
brain ischemia; endothelium; ischemic preconditioning and induced tolerance; nitric oxide; serine racemase