Expression of nitric oxide synthase isoforms and N-methyl-D-aspartate receptor subunits according to transforming growth factor-β1 administration after hypoxic-ischemic brain injury in neonatal rats

Abstract

Purpose : Transforming growth factor (TGF)- reportedly increases neuronal survival by inhibiting the induction of inducible nitric oxide synthase (NOS) in astrocytes and protecting neurons after excitotoxic injury. However, the neuroprotective mechanism of TGF- on hypoxic-ischemic (HI) brain injury in neonatal rats is not clear. The aim of this study was to determine whether TGF- has neuroprotective effects via a NO-mediated mechanism and N-methyl-D-aspartate (NMDA) receptor modulation on perinatal HI brain injury. Methods : Cortical cells were cultured using 19-day-pregnant Sprague-Dawley (SD) rats treated with TGF- (1, 5, or 10 ng/mL) and incubated in a 1% O2 incubator for hypoxia. Seven-day-old SD rat pups were subjected to left carotid occlusion followed by 2 h of hypoxic exposure (7.5% O2). TGF- (0.5 ng/kg) was administered intracerebrally to the rats 30 min before HI brain injury. The expressions of NOS and NMDA receptors were measured. Results : In the in vitro model, the expressions of endothelial NOS (eNOS) and neuronal NOS (nNOS) increased in the hypoxic group and decreased in the 1 ng/mL TGF--treated group. In the in vivo model, the expression of inducible NOS (iNOS) decreased in the hypoxia group and increased in the TGF--treated group. The expressions of eNOS and nNOS were reversed compared with the expression of iNOS. The expressions of all NMDA receptor subunits decreased in hypoxia group and increased in the TGF--treated group except NR2C. Conclusion : The administration of TGF- could significantly protect against perinatal HI brain injury via some parts of the NO-mediated or excitotoxic mechanism.