The Expression of Isoforms of Nitric Oxide Synthase (NOS) and Subunits of N-methyl-D-aspartate (NMDA) Receptor according to Administration of Mycophenolic Acid before or after Perinatal Hypoxic Ischemic Brain Injury

ABSTRACT

PURPOSE: Mycophenolic acid (MPA), a potent inhibitor of inosine-monophosphate dehydrogenase (IMPDH), was used as a new immunosuppressive drug since 1990s. It was reported that MPA increased neuronal survival after excitotoxic injury, induced apoptosis in microglial cells, inhibited the induction of inducible nitric oxide synthase (iNOS) in astrocytes. and inhibited microglial cell proliferation in N-methyl-D-aspartate (NMDA) induced hippocampal cells. However, the effects of MPA on the perinatal hypoxic-ischemic (HI) brain injury had not been yet evaluated. Therefore, we examined whether MPA could be neuroprotective in the HI brain injury. METHODS: Cortical cells were cultured using a 18-day-pregnant Sprague-Dawley (SD) rats and incubated in 1% O2 incubator for hypoxia. MPA (10 ug/mL) before or after a HI insult were treated. Seven-day-old SD rat pups were subjected to left carotid occlusion followed by 2.5 hours of hypoxic exposure (8% O2). MPA (10 mg/kg) were administrated intraperitoneally before or after a HI insult. Nitric oxide (NO) activity and expression of N-methyl-D-aspartate (NMDA) receptors also measured using Real-time PCR with primer pairs of isoforms of NOS; iNOS, endothelial NOS (eNOS), neuronal NOS (nNOS), and subunits of NMDA receptors; NR1, NR2A, NR2B, NR2C, NR2D. RESULTS: The expression of iNOS was decreased in the hypoxia group but increased in the MPA-treated group. However express or that eNOS and nNOS were inversed. The expression of all NMDA receptor subunits except NR2B was decreased in the hypoxia group but increased in the MPA-treated group. CONCLUSION: This study indicates that the administration of MPA before a HI insult could significantly protect against perinatal HI brain injury via some parts of NO-mediated or excitotoxic mechanisms.