Protective Role And Mechanism Of Glycyrrhizic Acid In Neonatal Mice With Hypoxic Ischemic Brain Injury Based On Rac1/STAT3 Signaling

BackgroundThe neonatal hypoxic-ischemic encephalopathy(HIE)is a one of the most common causes of neonatal death and neurological dysfunction,which caused by HI in the perinatal period.Therapeutic hypothermia(TH)as the gold standard of neonatal HIE therapy is widely applied in the clinical treatment to reduce mortality and neurological disability.However,a substantial number of infants treated with TH still die or survive with severe long-term neurological disability,such as cerebral palsy,epilepsy,memory impairment due to its narrow time widow and limited neuroprotective role.Based on this,it is necessary to search for new potential neuroprotective agents to the replacement or adjuvant of TH hoping to develop therapeutic strategies of HIE in newborns.Glycyrrhizic acid(GA)is a vital bioactive ingredient from the root of licorice,which is known to possess robust anti-inflammatory character in multiple diseases.However,its role and specific mechanism in neonatal HIE have not been fully elucidated.ObjectiveTo explore the neuroprotective role and undlying mechanism of Glycyrrhizic acid after hypoxia-ischemiain(HI)insult in neonatal mice based on Rac1/STAT3 signaling,which aims to seek a new possibility for the clinical therapeutics of HIE in neonates.MethodsThe modified Rice-Vannucci method was used to construt a mouse model of neonatal hypoxic-ischemic encephalopathy(HIE)according to previous described.The TTC staining was used to verify successful construction of animal models and visualize the brain damage.After model establishment,the intuitive performance of mice and TTC staining were observed to verify the success of modeling,the body weight was monitored to evaluate the growth and development differences of mice in each group at the same time.The relative tests were carried at 3 days and 3weeks after modeling respectively.The brain water content,HE staining,q RT-PCR and Western Blot were carried to detect different indexs 3 days after modeling.The neurobehavioral tests were used to assess cognitive function(Novel Object Recognition test)and motor coordination(Cylinder test,Front-limb suspension test)3 weeks after modeling.ResultsCompared with the SHAM group,the mice showed obvious cerebral infarction,brain edema and significant growth retardation in the later period post HI insult.The infarct area,brain edema level and growth retardation were relieve to some extent after treated with GA.At the same time,the HE staining and neurobehavioral tests showed that GA significantly reduced HI-induced brain tissue damage and long-term neurobehavioral disorders.GA significantly inhibited the expression of pro-inflammatory cytokines(IL-1β,IL-6,TNF-α,i NOS)and the expression of RAC1 /STAT3 pathway related proteins(Rac1,STAT3,p-STAT3)as well.ConclusionOur study indicates that GA could promote neurofunctional recovery and relieve brain injury against neuroinflammation via suppressing Rac1/STAT3 signaling pathway,which may provide a novel therapeutic choice in ameliorating neonatal HIE.