ABSTRACT
Objective To observe the effect of hippocampal DNA methyltransferases (DNMTs)on neonatal cognitive impairments induced by sevoflurance exposure.Methods Sixty-four 7-day old male Sprague-Dawley rats were randomly divided into the following four groups (n =1 6):control group (group C),sevoflurane group (group S),sevoflurane+NaCl group (group SN),and sevoflurane+5-AZA group (group SA).Sevoflurane animals received 3% sevoflurane plus 30% oxy-gen for 2 hours daily for 3 consecutive days,and rats in group C were placed into the same container, which contained 30% oxygen only.Animals in group SA were intracerebroventricularly injected with 5-AZA (1 mg/kg),while group SN same volume of NaCl one hour before sevoflurane exposure. Open field and Morris water maze were given the four weeks after anesthesia (n =8).Rats without any behavior tests from each group (n =8)were euthanized 4 weeks after the treatment and the hip-pocampus was harvested.Quantitative real-time PCR and Western blot were used to detect the mRNA and protein levels of DNMT1,DNMT3a and DNMT3b.Results In the open field test,no significant difference was observed in the distance travelled and the time spent in the center of the arena.Com-pared with the group C,group S showed an increase in the latency,decreased time spent in the target quadrant,and the mRNA and protein levels of DNMT3a and DNMT3b in the hippocampus were sig-nificantly increased (P < 0.05).Compared with the group SN,group SA showed a decrease in the la-tency,more time spent in the target quadrant,and the mRNA and protein levels of DNMT3a and DNMT3b in the hippocampus were decreased (P < 0.05).There was no significant difference in the expression of DNMT1 among the four groups.Conclusion Sevoflurane exposure induces neonatal cog-nitive impairments later in life,which was accompanied by the increased mRNA and protein levels of DNMT3a and DNMT3b in the hippocampus.By contrast,pretreatment of 5-AZA decreased hipp-ocampal DNMT3a and DNMT3b,and ameliorated cognitive impairments.These results suggest that DNMTs are involved in sevoflurane induced neonatal cognitive impairments.
ABSTRACT
Objective To investigate the role of histone lysine methyltransferase G9a in sevoflurane-induced cognitive impairment in the developing brain of neonatal rats.Methods Thirty-six 5-day-old male SD rats were randomly divided into 3 groups (n =12):control group,sevoflurane group and Bix01294 (the inhibitor of histone lysine methyltransferase G9a)group.The rats in the sevoflurane group and the Bix01294 group received 3% sevoflurane anesthesia for 2 hours once a day at postnatal 5-7 days (P5-P7 ).The rats in the Bix01294 group received Bix01294 (10 mg/kg)subcu-taneously at 1 5 min before anesthesia,and the rats in the control group and sevoflurane group received normal saline for injection (0.1 ml)at the same time.The open-field test and fear condition-ing test were performed at P3 5 and P3 9-P41 ,respectively.The tissues of hippocampus were collected at P42 to measure the levels of G9a,histone H3 lysine 9 dimethylation (H3K9me 2 )and synapsin 1. Results Compared with the control group,the percentage of freezing time of sevoflurane group was significantly decreased in the contextual fear condition test,while the levels of G9a and H3K9me 2 were significantly increased and the level of synapsin 1 was significantly decreased (P <0.01).How-ever,the percentage of freezing time of Bix01294 group was significantly increased,while the levels of G9a and H3K9me 2 were significantly decreased and the level of synapsin 1 was significantly in-creased compared with the sevoflurane group (P <0.05).There was no difference in the total distance and residence time in the central grid in the open-field test,and the percentage of freezing time in the cued fear condition test among the three groups.Conclusion Histone lysine methyltransferase G9a is involved in the sevoflurane-induced long-term cognitive impairment in developing brain of neonatal rats,which may be associated with the increase of H3K9me 2 and the down-regulation of synapsin 1 in the hippocampus.