内质网应激蛋白BiP在姜黄素抗2型糖尿病神经病理性疼痛大鼠的作用

Effect of endoplasmic reticulum stress protein BiP on type 2 diabetic neuropathic pain in rats treated with curcumin

目的:探讨姜黄素对2型糖尿病诱导的神经病理性疼痛(DNP)大鼠机械痛敏(MWT)、热痛敏(TWL)、脊髓背角和背根神经节(DRG)的保护作用及机制。方法:高脂高糖饲料喂养8周诱导胰岛素抵抗后,继以单次小剂量链脲佐菌素(STZ)35 mg/kg腹腔注射,在注射STZ前和14 d后采用Electronic Von Fery触觉测痛仪和甩尾/足底测试仪测大鼠MWT和TWL,注射STZ 3 d后血糖≥16.7 mmol/L且在注射STZ 14 d后痛阈下降至基础值85%以下者入选为D组(81只)。将D组随机分为3组(n=27):DNP组、DNP+姜黄素100 mg.kg-1.d-1组(DCur组)和DNP+溶剂组(DSC组),另取27只为正常对照组(C组),给予普通饲料喂养。给姜黄素3、7、14 d后测血糖、MWT与TWL,并在同时点取大鼠L4～L6脊髓和DRG,用免疫组化和免疫印迹法测定脊髓背角和DRG中免疫球蛋白重链结合蛋白(BiP)的表达。结果:与C组相比,DNP组各时点MWT降低,TWL缩短,血糖值升高,脊髓背角和DRG中BiP均出现表达上调(P<0.05)。与DNP组相比,DCur组在给姜黄素7 d后MWT升高,TWL延长;给姜黄素14 d后脊髓背角和DRG中BiP表达下调(P<0.05)。DSC组和DNP组相比差异无统计学意义。结论:BiP参与了2型糖尿病神经病理性疼痛的发病机制。姜黄素减轻2型糖尿病大鼠神经病理性疼痛的机制可能与抑制BiP表达有关。

AIM： To investigate the effects of immunoglobulin heavy chain - binding proteiia （ BiP）, an endo- plasmic reticulum stress protein, on mechanical withdrawal threshold （MWT）, thermal withdrawal latency （TWL）, spinal dorsal horn and dorsal root ganglion （DRG） in type II diabetic neuropathic pain rats treated with eurcumin. METHODS： The rats were fed with a high - fat and high - fructose diet for 8 weeks to induce insulin resistance, and then were intraperitoneally injected with streptozotocin （STZ, 35 mg/kg）. Eighty -one rats were selected into experimental design as their blood glucose ≥ 16.7 mmol/L 3 d after STZ injection and their MWT and TWL were decreased to 85% of the baseline values 14 d after STZ injection. The rats were divided into 3 groups （n =27 each） ： DNP group： type 2 diabetic neuropathic pain; DCur group： type 2 diabetic neuropathic pain and intraperitonal injection of curcumin at a dose of 100 mg·kg-1·d-1 ; DSC group： type 2 diabetic neuropathic pain and intraperitonal injection of corn oil at a dose of 4 mL/kg. Another 27 normal SD male rats fed with normal forage were adopted as control group （ C group）. MWT and TWL were measured at the time points of 3 d, 7 d and 14 d after curcumin injection. The lumbar segment 4 ~ 6 of the spinal cord and the corresponding DRG were removed at the same time. The expression of BiP was determined by immunohistochemical staining and West- ern blotting. RESULTS： Compared with C group, the rats in DNP group developed hyperglycemia and a decrease in MWT and TWL, as well as an increase in the activity of BiP in spinal dorsal horn and DRG （P 〈 0. 05 ）. Compared with DNP group, the rats in DCur group at the time point of 7 d significantly attenuated mechanical allodynia and thermal hyperalgesia, and these effects were correlated with the inhibition of BiP hyper - activation at the time point of 14 d after treatment with curcumin （ P 〈 0. 05 ）. No significant difference of MWT, TWL and the expression of BiP between DNP group and SC group was observed. CONCLUSION： BiP participates in the pathogenesis of type II diabetic neuropathic pain. Curcumin attenuates the MWT and TWL in type 2 diabetic neuropathic pain rats. The mechanism may be involved in the inhibition of BiP expression by curcumin.