海马内DNA甲基转移酶在七氟醚所致新生大鼠远期认知功能损伤中的作用

目的观察海马内DNA甲基转移酶(DNMTs)在七氟醚所致新生大鼠远期认知功能损伤中的作用。方法出生7d雄性SD大鼠64只,随机均分为四组(n=16):对照组(C组)、七氟醚组(S组)、七氟醚+生理盐水组(SN组)及七氟醚+5-杂氮胞苷组(5-AZA,DNMTs抑制剂,SA组)。C组吸入30%O22h,连续3d;S组、SN组和SA组吸入3%七氟醚+30%O22h,连续3d;SA组在七氟醚吸入前1h时侧脑室注入5-AZA 1mg/kg;SN组则注射等容量生理盐水。4周后,一部分大鼠行旷场实验和Morris水迷宫实验(n=8),另一部分取海马组织(n=8),采用实时荧光定量PCR和Western blot分别检测DNMT1、DNMT3a、DNMT3b的mRNA和蛋白含量。结果旷场实验中,四组大鼠探索路程和中央格停留时间差异无统计学意义。与C组比较,S组在Morris水迷宫实验中逃逸潜伏期明显延长,目标象限探索时间明显缩短,海马内DNMT3a及DNMT3b的mRNA和蛋白含量明显增加(P0.05);与SN组比较,SA组逃逸潜伏期明显缩短,目标象限探索时间明显延长,海马内DNMT3a及DNMT3b的mRNA和蛋白含量明显减少(P0.05);四组海马内DNMT1的mRNA和蛋白含量差异无统计学意义。结论七氟醚可致新生大鼠远期认知功能损伤伴海马内DNMT3a和DNMT3b表达增加;5-AZA可降低海马内DNMT3a及DNMT3b表达,减轻七氟醚所致新生大鼠远期认知功能损伤,表明DNMTs参与了七氟醚所致新生大鼠远期认知功能损伤的过程。

Effect of hippocampal DNA methyltransferases in sevoflurane induced neonatal cognitive impairments

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.