黄芩苷对创伤性脑损伤模型大鼠的治疗作用及Akt/Nrf2信号通路的影响

Therapeutic effect of baicalin in a rat model of traumatic brain injury by regulating the Akt/Nrf2 signaling activity

目的探讨黄芩苷对创伤性脑损伤(TBI)模型大鼠的治疗作用及蛋白激酶B(Akt)/核因子E2相关因子2(Nrf2)信号通路的影响。方法建立TBI模型大鼠,按照随机数字表法分成模型组、阳性对照组(单唾液酸四己糖神经节苷脂钠注射液14 mg/kg)及黄芩苷低、中、高剂量组(50、100、200 mg/kg),每组12只;另取12只大鼠设为假手术组。检测大鼠神经功能缺损评分(mNSS)、脑组织含水量、脑组织Akt、Nrf2 mRNA和蛋白表达水平,并观察大鼠脑组织病理结构。结果假手术组大鼠脑组织细胞结构完整、排列整齐,未见出血及水肿;模型组大鼠脑组织细胞排列松散,且部分细胞点状坏死,大量炎性细胞浸润,出血和水肿明显;黄芩苷低、中、高剂量组大鼠脑组织出血、水肿面积和点状坏死细胞数量逐渐减少;阳性对照组和黄芩苷高剂量组效果相近。与假手术组比较,模型组大鼠mNSS评分[(8.43±1.72)分比(0.37±0.04)分,P<0.05]、脑组织含水量[(82.93±2.19)%比(68.72±1.36)%,P<0.05]升高,脑组织Akt、Nrf2 mRNA[Akt mRNA:(0.31±0.04)比(1.00±0.02),Nrf2 mRNA:(0.36±0.05)比(1.01±0.03),P均<0.05]和蛋白[Akt蛋白:(0.20±0.03)比(0.93±0.17),Nrf2蛋白:(0.34±0.06)比(1.41±0.23),P均<0.05]表达水平降低;与模型组比较,阳性对照组及黄芩苷低、中、高剂量组大鼠mNSS评分[(4.41±0.81)分、(7.21±1.31)分、(5.91±1.12)分、(4.48±0.84)分比(8.43±1.72)分,P均<0.05]、脑组织含水量[(70.19±1.32)%、(78.26±1.93)%、(74.01±1.60)%、(70.48±1.35)%比(82.93±2.19)%,P均<0.05]均降低,脑组织Akt、Nrf2 mRNA[Akt mRNA:(0.82±0.15)、(0.53±0.08)、(0.69±0.11)、(0.84±0.17)比(0.31±0.04),Nrf2 mRNA:(0.94±0.19)、(0.60±0.09)、(0.77±0.14)、(0.91±0.18)比(0.36±0.05),P均<0.05]和蛋白[Akt蛋白:(0.74±0.13)、(0.36±0.05)、(0.54±0.08)、(0.72±0.12)比(0.20±0.03),Nrf2蛋白:(1.27±0.20)、(0.65±0.10)、(0.91±0.15)、(1.24±0.18)比(0.34±0.06),P均<0.05]表达水平均升高,且黄芩苷各剂量组之间呈剂量依赖性(P<0.05);阳性对照组和黄芩苷高剂量组大鼠上述指标差异无统计学意义(P>0.05)。结论黄芩苷可有效治疗TBI造成的大鼠脑神经损伤,改善脑水肿,其机制可能与激活Akt/Nrf2信号通路,促进Akt、Nrf2 mRNA和蛋白表达有关。

Objective To investigate the therapeutic effect of baicalin in a rat model of traumatic brain injury(TBI)and then explore the underlying molecular events.Methods The TBI rat model was established and randomly divided into control,model,positive control(monosialote trahexosyl ganglioside sodium injection at a dose of14 mg/kg),model+positive control,and model+baicalin(low,medium of high dose,i.e.,50,100,and 200 mg/kg;n=12 peer group)groups.The modified neurological severity score(mNSS),brain water content,brain tissue level of protein kinase B(Akt)and nuclear factor E2 related factor 2(Nrf2)mRNA and protein were assessed using the corresponding assays,while change in rat brain tissue structures was also observed.Results Control rats had normal brain tissue structures,whereas the model rats showed loose arrangement of brain cells with some cells for punctate necrosis and a large number of inflammatory cell infiltration,bleeding,and edema.In contrast,baicalin treatment(all doses)showed reduced severity of cerebral hemorrhage,edema,and punctate necrotic cells,while the positive control rats and baicalin treatment(high dose)had similar findings.Moreover,compared with the control rats,the model rats showed increase in the mNSS score(8.43±1.72 vs.0.37±0.04;P<0.05)and brain water content(82.93±2.19 vs.68.72±1.36%;P<0.05),but decrease in brain tissue level of Akt(0.31±0.04 vs.1.00±0.02)and Nrf2 mRNA(0.36±0.05 vs.1.01±0.03;all P<0.05)and Akt(0.20±0.03 vs.0.93±0.17)and Nrf2 proteins(0.34±0.06vs.1.41±0.23;all P<0.05).Compared with model rats,the positive control and baicalin(all doses)reduced the mNSS score(4.41±0.81,7.21±1.31,5.91±1.12,and 4.48±0.84 vs.8.43±1.72,respectively;all P<0.05)and brain water content(70.19±1.32,78.26±1.93,74.01±1.60,and 70.48±1.35 vs.82.93±2.19%,respectively;all P<0.05),but the positive control and baicalin(all doses)increased brain tissue level of Akt(0.82±0.15,0.53±0.08,0.69±0.11,and 0.84±0.17 vs.0.31±0.04,respectively;all P<0.05)and Nrf2 mRNA(0.94±0.19,0.60±0.09,0.77±0.14,and0.91±0.18 vs.0.36±0.05,respectively;all P<0.05)and Akt(0.74±0.13,0.36±0.05,0.54±0.08,and 0.72±0.12 vs.0.20±0.03,respectively;all P<0.05)and Nrf2 proteins(1.27±0.20,0.65±0.10,0.91±0.15,and 1.24±0.18 vs.0.34±0.06,respectively;all P<0.05)in a dose-dependent manner(P<0.05).However,there was no significant difference in the above-named indexes between the positive control and baicalin(high dose)-treated rats(P>0.05).Conclusion Baicalin was able to effectively improve brain nerve injury induced by TBI and Akt and Nrf2 expression,indicating that baicalin could activate the Akt/Nrf2 signal in control of TBI in rat.