激活α7 nAChR通过抑制慢性炎症反应减轻饮食诱导的大鼠肥胖型高血压

Activation ofα7 nAChR attenuates diet-induced obesity-associated hypertension in rats by suppressing chronic inflammation

目的:探讨激活α7烟碱型乙酰胆碱受体(α7 nAChR)是否通过抑制IκB激酶β/核因子κB(IKKβ/NF-κB)介导的慢性炎症而阻止饮食诱导的肥胖大鼠高血压。方法:高脂(HF)饮食16周诱导肥胖高血压大鼠模型,分为模型对照组(HF con组,n=10)、α7 nAChR激动剂PUN-282987组(PNU组,n=10)和α7 nAChR抑制剂α-银环蛇毒素(α-BGT)+激动剂PUN-282987组(α-BGT+PNU组,n=12),另设空白对照组(NF con组,n=8)。PNU组持续6周腹腔注射α7 nAChR激动剂PNU-282987,α-BGT+PNU组持续6周腹腔注射α7 nAChR抑制剂α-BGT和激动剂PNU-282987。检测血浆和肾脏去甲肾上腺素(NE)含量以反映交感神经活性;检测下丘脑中α7 nAChR、IKKβ、NF-κB、白细胞介素1β(IL-1β)和肿瘤坏死因子α(TNF-α)的表达水平以反映IKKβ/NF-κB促炎信号通路活性;利用Western blot或RT-qPCR法检测下丘脑磷酸化信号转导及转录激活因子3(p-STAT3)、磷酸化磷脂酰肌醇3-激酶(pPI3K)、瘦素受体b(LepRb)、细胞因子信号转导抑制因子3(SOCS3)和蛋白酪氨酸磷酸酶1B(PTP1B)以反映瘦素信号敏感性。结果:与HF con组比较,PNU组大鼠体重、脂肪总重和血压均显著降低(P<0.05或P<0.01),且肾脏中NE水平显著降低(P<0.01),表明交感神经活性减低。与HF con组比较,PNU组大鼠下丘脑中p-IKKβ、NF-κB、IL-1β和TNF-α蛋白水平显著降低(P<0.05或P<0.01)。同时,与HF con组比较,PNU组下丘脑中p-STAT3蛋白水平和LepRb mRNA水平显著升高(P<0.05或P<0.01),而p-PI3K蛋白水平及SOCS3和PTP1B mRNA水平显著降低(P<0.05或P<0.01),表明PNU组瘦素敏感性增加。然而,当同时给予α-BGT可降低PNU-282987的上述作用。结论:使用激动剂激活α7 nAChR可抑制下丘脑中的慢性炎症,减轻瘦素抵抗,从而缓解大鼠肥胖型高血压。

AIM:To investigate whetherα7 nicotinic acetylcholine receptor(nAChR)activation attenuates hypertension in diet-induced obese rats by inhibiting IκB kinaseβ/nuclear factor-κB(IKKβ/NF-κB)signaling pathway.METHODS:High-fat(HF)diet for 16 weeks was used to induce obese rats,and these rats were randomly assigned to 3 groups:HF control group(HF con group,n=10),α7 nAChR agonist PNU-282987 group(PNU group,n=10),andα7 nAChR inhibitorα-bungarotoxin(α-BGT)and agonist PNU-282987 group(α-BGT+PNU group,n=12).The rats fed with normal-fat(NF)diet were set up as NF control group(NF con group,n=8).The rats in PNU group were intraperitoneally injected with PNU-282987 for 6 weeks,and the rats inα-BGT+PNU group were co-administered withα-BGT and PNU-282987 intraperitoneally for 6 weeks.Norepinephrine(NE)levels in the plasma and renal tissue were evaluated to reflect sympathetic activity.The levels of IKKβ,NF-κB,interleukin-1β(IL-1β)and tumor necrosis factor-α(TNF-α)in the hypothalamus were measured to reflect the anti-inflammatory effect ofα7 nAChR activation.Additionally,the protein levels of phosphorylated signal transducer and activator of transcription 3(p-STAT3)and phosphatidylinositol 3-kinase(pPI3 K),and the mRNA levels of leptin receptor isoform b(LepRb),suppressor of cytokine signaling 3(SOCS3)and protein-tyrosine phosphatase 1 B(PTP1 B)were determined by Western blot and RT-qPCR to evaluate hypothalamic leptin sensitivity.RESULTS:The rats in PNU group exhibited decreased body weight,total adipose mass and blood pressure compared with HF con group(P<0.05 or P<0.01).Moreover,the rats in PNU group had inhibited sympathetic activity reflected by decreased NE level in renal tissues(P<0.01).Compared with HF con group,the protein levels of p-IKKβ,NF-κB,IL-1βand TNF-αin hypothalamus of the rats in PNU group were lowered(P<0.05 or P<0.01).Simultaneously,compared with HF con group,the rats in PNU group exhibited increased p-STAT3 protein and LepRb mRNA levels(P<0.05 or P<0.01),and decreased p-PI3 K protein,SOCS3 mRNA and PTP1 B mRNA levels(P<0.05 or P<0.01)in hypothalamus,indicating improved leptin sensitivity in PNU group.However,the benefit effects ofα7 nAChR agonist PNU-282987 were weakened when co-administered withα7 nAChR antagonistα-BGT.CONCLUSION:Activation ofα7 nAChR by its agonist prevents obesity-associated hypertension in rats through suppressing chronic inflammation in hypothalamus and improving leptin resistance.