骨边刺电针干预对骨癌痛吗啡耐受大鼠蓝斑核的影响

Bone-edge electroacupuncture relieves pain by regulating expression of GRK5, β-arrestin 2 and PKCα proteins in locus coeruleus in bone cancer pain rats with morphine tolerance

目的:观察骨边刺电针对骨癌痛吗啡耐受大鼠蓝斑核G蛋白耦联受体激酶5(GRK5)、β-抑制蛋白2(β-arrestin2)、蛋白激酶Cα(PKCα)及其磷酸化(p-PKCα)表达的影响,部分揭示骨边刺电针干预骨癌痛吗啡耐受的中枢机制。方法:SD大鼠随机分为假骨癌痛组、骨癌痛组、吗啡耐受组、骨边刺电针组和假电针组,每组8只。采用胫骨骨髓腔内注射3μL MRMT-1大鼠乳腺癌细胞建立骨癌痛模型,在此基础上通过腹腔多次注射盐酸吗啡注射液(10 mg/kg)建立骨癌痛吗啡耐受模型。骨边刺电针组于成功建立骨癌痛吗啡耐受模型后,开始介入骨边刺电针干预,每日1次,持续7 d。动态观察各组大鼠患侧足跖机械痛阈。采用免疫印迹法观察各组大鼠患侧蓝斑核GRK5、β-arrestin2、PKCα、p-PKCα蛋白表达。结果:与假骨癌痛组比较,癌细胞接种后10 d骨癌痛组大鼠患侧足跖机械痛阈显著降低(P<0.01);吗啡注射后,与骨癌痛组比较,吗啡耐受组、骨边刺电针组和假电针组大鼠患侧足跖机械痛阈显著升高(P<0.01),而吗啡注射11 d后,吗啡耐受组机械痛阈显著降低,与骨癌痛组比较差异无统计学意义(P>0.05),出现耐受现象;与吗啡耐受组、假电针组比较,骨边刺电针组干预后机械痛阈明显升高(P<0.01)。与假骨癌痛组比较,吗啡耐受组大鼠蓝斑核GRK5蛋白表达显著降低(P<0.01);与吗啡耐受组和假电针组比较,骨边刺电针组蓝斑核GRK5蛋白表达显著升高(P<0.01)。与假骨癌痛组比较,骨癌痛组大鼠蓝斑核β-arrestin2、p-PKCα蛋白表达显著增多(P<0.01);与吗啡耐受组和假电针组比较,骨边刺电针组蓝斑核β-arrestin2、p-PKCα蛋白表达显著降低(P<0.01)。与吗啡耐受组和假电针组比较,骨边刺电针组蓝斑核PKCα蛋白表达显著降低(P<0.01)。结论:骨边刺电针可有效干预骨癌痛吗啡耐受现象,其机制可能与增加蓝斑核GRK5,抑制β-arrestin2、PKCα及其磷酸化水平有关。

Objective To observe the effect of bone-edge electroacupuncture(EA) intervention on mechanical pain threshold(PT) and expression of G protein-coupled receptor kinase(GRK5), β-arrestin 2, total and phosphorylated PKC alpha(p-PKCα) proteins in the locus coeruleus(LC) of rats with bone cancer pain induced morphine tolerance, so as to reveal its partial central mechanisms underlying pain relief. Methods Forty SD rats were randomly divided into 5 groups, namely sham bone cancer, bone cancer pain, morphine tolerance, bone-edge EA, and sham EA(n= 8 rats in each group). The bone cancer with morphine tolerance model was established by intramedullary injection of MRMT-1 cells into the tibial cavity, and then intraperitoneal injection of morphine hydrochloride injection. After successful establishment of morphine tolerance model, the bone-edge EA(2 Hz/100 Hz,0.5-1.5 mA) was applied to bilateral "Zusanli"(ST36) and "Kunlun"(BL60) for 30 min, once a day for 7 days, after inserting the needle-tip to the tibial bone surface. The ipsilateral mechanical paw withdrawal thresholds(PWTs) were detected dynamically. The expression levels of GRK5, β-arrestin 2, PKCα and p-PKCα in the LC area were measured by Western blot. Results The PWTs of bone cancer pain rats were decreased on day 10 after inoculation of cancer cells(P<0.01). After i.p. of morphine for 11 days, no analgesic effect and pain tolerance appeared(P>0.05). The PWTs were significantly increased in the bone-edge EA intervention group(P<0.01), not in the sham EA group(P>0.05). In comparison with the sham bone cancer group, the expression of GRK5 protein in morphine tolerance group was significantly decreased(P<0.01);compared with morphine tolerance group, the expression of GRK5 protein in bone-edge EA group was increased(P<0.01). In comparison with the sham bone cancer group, the expression of β-arrestin 2 and p-PKCα in bone cancer group significantly increased(P<0.01). After the intervention, the increased β-arrestin 2 and p-PKCα expressions were reversed in the bone-edge EA group(P<0.01);compared with morphine tolerance group and sham EA group, the expression of PKCα protein was decreased(P<0.01). Conclusion Bone-edge EA can effectively relieve morphine tolerance in bone cancer pain rats, which may be related to its functions in up-regulating GRK5 protein and down-regulating β-arrestin 2, PKCα and p-PKCα proteins in LC.