Glycine bidirectionally regulates ischemic tolerance via different mechanisms including NR2A‐dependent CREB phosphorylation

Abstract

The exact effect of glycine pre-treatment on brain ischemic tolerance (IT) remains quite controversial. The objective of this study was to investigate the potential effects of glycine on IT. We used rat models of both in vitro ischemia (oxygen and glucose deprivation) and in vivo ischemia (transient middle cerebral artery occlusion). Low doses of glycine (L-Gly) significantly decreased hippocampal ischemic LTP (i-LTP), infarct volume, and neurological deficit scores which were administered before ischemia was induced in rats, whereas high doses of glycine exerted deteriorative effects under the same condition. These findings suggested that exogenous glycine may induce IT in a dose-dependent manner. Furthermore , L-Gly-dependent neuronal protection was inversed by L689, a selective NMDAR glycine site antagonist both in vitro (abolished i-LTP depression) and in vivo (increased infarct size reduction), but not glycine receptor (GlyR) inhibitor strychnine. Importantly, L-Gly-induced IT was achieved by NR2A-dependent cAMP-response element binding protein phosphorylation. These data imply that glycine pre-treatment may represent a novel strategy for inducing IT based on synaptic NMDAR-dependent neuronal transmission.

Geniposide Attenuates Post-Ischaemic Neurovascular Damage via GluN2A/AKT/ ERK-Dependent Mechanism

“…The membranes were then incubated with pAKT, pERK, AKT, ERK, Bcl-2, Bax, GAPDH (Cell Signalling Technology, USA), GluN2A, GluN2B and PSD-95 (Santa Cruz Biotechnology, USA) antibodies at 4°C overnight. After incubating the membranes with secondary antibodies (horseradish peroxidase-conjugated IgG), the immunoreactive bands were visualized [24, 25, 26]. The images were scanned and quantified with Quantity One software (Bio-Rad, USA).…”

“…The transient middle cerebral artery occlusion (tMCAO) surgery was conducted as previously described [4, 24]. The animals were anaesthetized with chloral hydrate (0.3 mg/kg) intraperitoneally.…”

“…Each brain was sliced into coronal sections (2 mm thickness). Cerebral infarct size was analysed by incubating these sections for 30 minutes at 37℃ with 2% 2, 3,5-triphenyltetrazolium chloride (TTC) solution [4, 24]. …”

“…Finally, the sections were mounted on slides and analysed using a digital microscope (Leica Microsystems, Germany). The GluN2A-/GluN2B-positive and Nissl-positive cells in the hippocampal DG region were quantified (at approximately -3 and -4.5 mm posterior to bregma) using light microscopy [24]. …”

“…Neurological severity scores (NSSs) were tested using a six-grade scale to assess post-stroke behavioural deficits [4, 24]. …”