Mir-34a Inhibitor May Effectively Protect Against Sevoflurane-Induced Hippocampal Apoptosis Through The Wnt/?-Catenin Pathway By Targeting Wnt1

BackgroundIncreasing studies have revealed the neuronal toxicity induced by commonly used anesthetics both in animals and humans and have suggested that these anesthetics would unavoidably induce neurodegeneration and apoptosis in hippocampus,thereby leading to learning and memory impairment.Sevoflurane is one of the most commonly used volatile anesthetics and is administered by inhalation for both induction and maintenance of anesthesia in clinical surgery for paediatric patients.Research has shown that sevoflurane-induced toxicity elicits apoptosis of rat hippocampal neurons and cognitive dysfunction in the developing brain.Unfortunately,the underlying mechanism by which sevoflurane induces hippocampal neurodegeneration is still undefined.Accumulating evidence has well documented the association between neurological impairments induced by sevoflurane and changes in the expression of multiple genes involved in brain development.It has been well-acknowledged that sevoflurane anesthesia causes alterations in expression levels of microRNAs(miRNAs)in the rat hippocampus.miRNAs are a group of short-sequenced,small noncoding RNAs that negatively regulate gene expression through binding to the 3'untranslated region(UTR)of target mRNA,promoting translation inhibition or mRNA degradation.There is striking evidence that miRNAs play a fundamental role in various cellular processes,such as cell death,survival and differentiation.Moreover,emerging evidence has shown that miRNAs are abundantly expressed in various cortical regions,including hippocampus,and play prominent roles in regulating brain development,including neurogenesis and maturation,cortical neuropathy and neurodegenerative diseases.Among cortically expressed miRNAs,miR-34a,which belongs to the miR-34 family that is highly conserved among different species,is constitutively expressed in the brains and plays critical roles in many aspects of cortical development and tumorigenesis.miR-34a has been reported to negatively regulate ketamine-induced hippocampal apoptosis and memory impairment.However,the role of miR-34a in sevoflurane-induced hippocampal neurodegeneration remains largely unclear.In the present study,we aimed to explore the role of miR-34a in sevoflurane-induced neurodegeneration in the hippocampus and to further investigate the association between miR-34a and the Wnt/?-catenin pathway.ObjectiveResearch has shown that sevoflurane-induced toxicity causes neurodegeneration in the developing brain.miR-34a has been found to negatively regulate ketamine-induced hippocampal apoptosis and memory impairment.However,the role of miR-34a in sevoflurane-induced hippocampal neurodegeneration remains largely unc ear.MethodsC57BL/6 mice(7-day-old)inhaled 2.3%sevoflurane for 2 h/day over 3 consecutive days.miR-34a expression was reduced through intracerebroventricular injection with miR-34a interference lentivirus vector(LV-anti-miR-34a)into mouse hippocampus after anaesthesia on the first day of exposure.Hippocampal apoptosis was detected by TUNEL assay and flow cytometry analysis.Spatial memory ability was evaluated by the Morris water maze test.The interaction between miR-34a and Wntl was confirmed by luciferase reporter assay.RNA immunoprecipitation,Western blot,and immunofluorescence staining.The effects of miR-34a on protein levels of B-cell lymphoma 2(Bcl-2),bcl-2-like protein 4(Bax),and Wnt/?-catenin pathway-related proteins were evaluated using Western blot analysis.ResultsSevoflurane upregulated hippocampal miR-34a,and miR-34a inhibitor attenuated sevoflurane-induced hippocampal apoptosis and memory impairment.miR-34a negatively regulated Wnt1 expression by targeting miR-34a in hippocampal neurons.Moreover,forced expression of Wnt1 markedly undermined miR-34a-mediated enhancement of sevoflurane-induced apoptosis of hippocampal neurons while Wnt1 silencing greatly restored anti-miR-34a-mediated repression of sevoflurane-induced apoptosis of hippocampal neurons.Increased expression of miR-34a inhibited the Wnt/?-catenin pathway in hippocampal neurons exposed to sevoflurane,while anti-miR-34a exerted the opposite effects.ConclusionmiR-34a inhibitor may effectively protect against sevoflurane-induced hippocampal apoptosis via activation of the Wnt/?-catenin pathway by targeting Wnt1.