Middlemas A B, Agthong S, Tomlinson D R
Faculty of Life Sciences, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK.
Diabetologia. 2006 Mar;49(3):580-7. doi: 10.1007/s00125-005-0133-z. Epub 2006 Feb 3.
AIMS/HYPOTHESIS: This study was designed to determine whether diabetes in rats is associated with phosphorylation of c-Jun N-terminal kinase (JNK) and one of its transcription factors, c-Jun, in sensory neurones innervating the lower limb. We also sought to determine which neuronal phenotypes are affected and to examine the effect of aldose reductase inhibition on JNK and c-Jun phosphorylation.
Diabetes was induced in rats using streptozotocin. Phosphorylation of JNK and c-Jun in lumbar dorsal root ganglia was determined by binding of phospho-specific antibodies using western blots and immunocytochemistry. Neuronal phenotypes were characterised by binding of N52 (an antibody that recognises the heavy neurofilament protein; for large-diameter mechanoceptors) and of calcitonin gene-related peptide and the plant glycoprotein lectin IB4 (for nociceptors). The efficacy of the aldose reductase inhibitor fidarestat was determined by measuring polyol pathway metabolites in sciatic nerve, and functionally by measuring the conduction velocity of motor and sensory nerves.
In control rats, activated JNK and c-Jun were primarily associated with mechanoceptors; in diabetes this was increased, but a greater increase was seen in nociceptors. Phosphorylation was prevented in all cells by fidarestat, which normalised polyol pathway metabolites as well as motor nerve and sensory nerve conduction velocity.
CONCLUSIONS/INTERPRETATION: Fidarestat-sensitive phosphorylation of JNK and c-Jun occurs in fast-conduction mechanoceptors-the same class of neurones that registers the changes in sensory nerve conduction velocity-and in nociceptors. This supports the notion that mitogen-activated protein kinase phosphorylation, via the polyol pathway, may convert the direct effects of raised glucose into impaired nerve conduction and neuropathic pain. For proof of this we await the availability of specific JNK antagonists formulated for in vivo use.
目的/假设：本研究旨在确定大鼠糖尿病是否与支配下肢的感觉神经元中c-Jun氨基末端激酶（JNK）及其转录因子之一c-Jun的磷酸化有关。我们还试图确定哪些神经元表型受到影响，并研究醛糖还原酶抑制对JNK和c-Jun磷酸化的作用。
使用链脲佐菌素诱导大鼠患糖尿病。通过蛋白质免疫印迹法和免疫细胞化学法，利用磷酸特异性抗体结合来测定腰段背根神经节中JNK和c-Jun的磷酸化情况。通过N52（一种识别重链神经丝蛋白的抗体，用于识别大直径机械感受器）、降钙素基因相关肽和植物糖蛋白凝集素IB4（用于识别伤害感受器）的结合来鉴定神经元表型。通过测量坐骨神经中的多元醇途径代谢产物来确定醛糖还原酶抑制剂非达司他的疗效，并通过测量运动神经和感觉神经的传导速度来进行功能测定。
在对照大鼠中，活化的JNK和c-Jun主要与机械感受器相关；在糖尿病大鼠中，这种情况有所增加，但在伤害感受器中增加更为明显。非达司他可防止所有细胞中的磷酸化，使多元醇途径代谢产物以及运动神经和感觉神经传导速度恢复正常。
结论/解读：JNK和c-Jun的非达司他敏感型磷酸化发生在快速传导的机械感受器（与记录感觉神经传导速度变化的同一类神经元）和伤害感受器中。这支持了这样一种观点，即丝裂原活化蛋白激酶磷酸化可能通过多元醇途径将血糖升高的直接影响转化为神经传导受损和神经性疼痛。为了证明这一点，我们期待有可用于体内的特异性JNK拮抗剂。
