刺激迷走神经对抑郁模型大鼠炎性因子和细胞凋亡的影响

Effects of vagus nerve stimulation on inflammatory factors and apoptosis in depression model rats

目的研究刺激迷走神经(vagus nerve stimulation,VNS)对慢性不可预知性应激(chronic unpredictable stress,CUS)诱导的抑郁模型大鼠血清、孤束核炎性因子及海马细胞凋亡的影响。方法选取32只成年清洁级雄性SD大鼠,鼠龄8~9周。随机选取8只作为对照组,另24只采用慢性不可预知性应激方法建立大鼠抑郁模型,造模成功后大鼠随机分为CUS组,氟西汀组,VNS组,每组8只。对照组和CUS组大鼠给予生理盐水,氟西汀组和VNS组大鼠左侧颈部植入VNS刺激电极进行VNS电刺激,连续干预刺激28 d。实验前、造模后、干预后,采用糖水偏爱实验和旷场实验评定大鼠抑郁水平;Elisa法检测各组大鼠血清、孤束核组织TNF-α、IL-6、IL-1β表达水平,Tunel染色观察海马CA1区细胞凋亡率。结果(1)糖水消耗实验和旷场实验显示,与CUS组比较,VNS组大鼠糖水消耗量、糖水偏爱率、垂直运动次数和水平运动次数均升高[糖水消耗量:(11.78±2.67)ml,(8.06±2.85)ml;糖水偏爱率:(72.31±9.98)%,(63.67±8.95)%;垂直运动次数:(16.61±3.98 )次,(10.31±3.86)次;水平运动次数:(44.25±9.59)次,(36.21±7.21)次],差异有统计学意义(t=4.87,7.98,5.87,9.12,均P<0.05)。VNS组与氟西汀组相比[糖水消耗量[(11.32±2.66)ml];糖水偏爱率[(71.31±9.03)%];垂直运动次数[(15.63±4.11)次]和水平运动次数[(45.61±8.54)次]差异无统计学意义(t=-0.32,-1.83,0.98,-1.13,均P>0.05)。(2)与CUS组相比,VNS组血清TNF-α、IL-6和IL-1β水平均降低,差异有统计学意义[血清TNF-α:(46.72±11.63)pg/ml,(125.47±15.18)pg/ml;IL-6[(243.65±38.90)pg/ml,(441.39±83.31)pg/ml;IL-1β:(209.31±32.45)pg/ml,(339.21±76.37)pg/ml;t=-70.38,-196.25,-131.13,均P<0.05),且VNS组TNF-α、IL-6、IL-1β水平较氟西汀组[血清TNF-α(58.76±12.64)pg/ml;血清IL-6(308.83±64.31)pg/ml;血清IL-1β(249.18±43.6)pg/ml]降低,差异有统计学意义(t=-15.38,-64.25,-18.83,均P<0.05)。VNS组孤束核TNF-α、IL-6和IL-1β水平显著低于CUS组[TNF-α:(53.52±12.31)pg/ml,(135.51±20.64)pg/ml;IL-6:(265.31±45.63)pg/ml,(465.32±60.21)pg/ml;IL-1β:(212.66±43.32 )pg/ml,(365.96±76.32)pg/ml;t=-79.38,-189.13,-127.50,均P<0.05)]和氟西汀组[TNF-α:(63.42±10.64)pg/ml;IL-6:(315.62±53.21)pg/ml;IL-1β:(278.32±65.38)pg/ml](t=-10.25,-39.00,-83.00,均P<0.05)。(3)VNS组海马CA1细胞凋亡率[(21.41±5.86)%]低于CUS组[(32.78±8.32)%,t=-10.75,P<0.05],与氟西汀组[(22.54±6.31)%]相比差异无统计学意义(t=-1.75,P>0.05)。结论VNS可改善CUS诱导大鼠模型抑郁行为学指标,其机制与抑制血清、孤束核TNF-α、IL-6、IL-1β表达及海马CA1区细胞凋亡有关。

Objective To explore the influence of vagus nerve stimulation (VNS) on inflammatory factors in serum and nucleus of the solitary tract, and hippocampal apoptosis in rats with depression induced by chronic unpredictable stress(CUS). Methods Totally 32 male Sprague Dawley (SD) rats aged 8-9 weeks were selected.Eight rats were chosen as control group, and the other 24 rats were treated as the depression model with CUS. The rats were randomly divided into CUS, fluoxetine and VNS group, with 8 rats in each group after successful modeling. The control group and CUS group were induced by normal saline. Fluoxetine group and VNS group were implanted with VNS stimulation electrode. The VNS stimulation lasted for 28 d. On the time points of before experiment, after modeling and after treatment, the sucrose consumption test and open-field test (OFT) were performed to observe the behavioral changes of rats. Elisa was used to detect the levels of TNF-α, IL-6 and IL-1β in serum and nucleus of the solitary tract. Cell apoptosis was observed with TUNEL staining in hippocampal CA1 region. Results (1) Sucrose consumption experiment and OFT showed that, compared with the CUS group, the consumption of sucrose, percentage of sucrose consumption, scores of vertical and horizontal movement increased significantly in the VNS group (consumption of sucrose:(11.78±2.67) ml,(8.06±2.85) ml;percentage of sucrose consumption:(72.31±9.98)%,(63.67±8.95)%;score of vertical movement:(16.61±3.98),(10.31±3.86);score of horizontal movement:(44.25±9.59),(36.21±7.21))(t=4.87, 7.98, 5.87, 9.12, all P<0.05). There was no significant difference between VNS and fluoxetine groups (consumption of sucrose:(11.32±2.66) ml;percentage of sucrose consumption:(71.31±9.03)%;score of vertical movement:(15.63±4.11);score of horizontal movement:(45.61±8.54))(t=-0.32,-1.83, 0.98,-1.13, all P>0.05).(2) Compared with the CUS group, levels of TNF-α, IL-6 and IL-1β in serum decreased in the VNS group (serum TNF-α:(46.72±11.63) pg/ml,(125.47±15.18) pg/ml;serum IL-6:(243.65±38.90) pg/ml,(441.39±83.31) pg/ml;serum IL-1β:(209.31±32.45) pg/ml,(339.21±76.37) pg/ml)(t=-70.38,-196.25,-131.13, all P<0.05). The results in the VNS group were lower than those in the fluoxetine group (serum TNF-α:(58.76±12.64) pg/ml;serum IL-6:(308.83±64.31) pg /ml, serum IL-1β:(249.18±43.6) pg/ml)(t=-15.38,-64.25,-18.83, both P<0.05). The levels of TNF-α, IL-6 and IL-1β in nucleus of the solitary tract in the VNS group were lower than those in the CUS (TNF-α:(53.52±12.31) pg/ml,(135.51±20.64)pg/ml;IL-6:(265.31±45.63) pg/ml,(465.32±60.21) pg/ml;IL-1β:(212.66±43.32)pg/ml,(365.96±76.32) pg/ml)(t=-79.38,-189.13,-127.50, all P<0.05) and fluoxetine groups (TNF-α:(63.42±10.64) pg/ml;IL-6:(315.62±53.21) pg/ml;IL-1β:(278.32±65.38) pg/ml )(t=-10.25,-39.00,-83.00, all P<0.05).(3) The apoptotic rate of hippocampal CA1 region in VNS group ((21.41±5.86)%) was lower than that in the CUS group ((32.78±8.32)%)(t=-10.75, P<0.05);and there was no difference between VNS group and fluoxetine group ((22.54±6.31)%)(t=-1.75, P>0.05). Conclusion VNS can improve the depression behavior in rats with depression induced by CUS and the mechanism maybe related to inhibiting the expression of TNF-α, IL-6 and IL-1β in serum and nucleus of the solitary tract and cell apoptosis in hippocampal CA1 region.