L-Glutamine Protects Mouse Brain And Promotes Recovery After Ischemic Injury

INTRODUCTION: Oxidative stress plays an important role in stroke pathophysiology.L-glutamine(L-GLN)has been shown to have antioxidant activity and was approved by the FDA in July 2017 for the treatment of sickle cell disease.In this study,I aim to investigate the effect of L-GLN in ischemic brain injury.METHODS: Ninety-minute transient middle cerebral artery occlusion(tMCAO)model was used to induce a focal cerebral ischemic injury in mice.Adult male ICR mice(n=135)were divided into four groups:(1)Sham,(2)Saline,(3)L-GLN,and(4)L-GLN plus Apoptozole(AZ),a HSP70 ATPase inhibitor.Treatments were delivered intraperitoneally once daily for the first three days after tMCAO.Neurobehavioral tests were performed before tMCAO and at 1,3,7 and 14 days after tMCAO by an investigator blinded to the experimental design using the modified neurological severity score(mNSS),elevated body swing test(EBST),and rotarod test.Infarction volume was assessed by cresyl violet staining of brain sections.The expression levels of heat shock proteins and their signaling pathway related proteins were evaluated by Western Blot and real-time PCR.The level of oxidative stress was evaluated by malondialdehyde(MDA),superoxide dismutase(SOD),and glutathione(GSH)assays.Astrocyte,BEND.3 and neuron cell cultures and oxygen glucose deprivation(OGD)model was used to further examine the molecular pathways involved in the protective effects by L-GLN.RESULTS: We found that L-GLN treatment reduced brain infarct volume and promoted neurobehavioral recovery in mice after ischemic injury.Such beneficial effect was abolished by the coadministration of AZ.L-GLN induced the up-regulation of HSP70 and Nuclear factor erythroid 2-related factor 2(NRF2),reduced oxidative stress level and neuronal apoptosis.In the L-GLN group,SOD and GSH levels were significantly increased compared to the saline group.Cell culture study further revealed that the conditioned medium(CM)from astrocytes cultured with L-GLN effectively reduced the apoptosis of neurons after OGD.CONCLUSION: L-GLN attenuated ischemic brain injury and promoted functional recovery via HSP70,suggesting a new avenue for treating ischemic stroke.