1 Medical Research Institute, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Republic of Korea.
2 Division of Endocrinology and Metabolism, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Republic of Korea.
Mol Pain. 2018 Jan-Dec;14:1744806918775482. doi: 10.1177/1744806918775482. Epub 2018 Apr 24.
Background Diabetic neuropathy originating in distal lower extremities is associated with pain early in the disease course, overwhelming in the feet. However, the pathogenesis of diabetic neuropathy remains unclear. Macrophage migration inhibitory factor has been implicated in the onset of neuropathic pain and the development of diabetes. Objective of this study was to observe pain syndromes elicited in the footpad of diabetic neuropathy rat model and to assess the contributory role of migration inhibitory factor in the pathogenesis of diabetic neuropathy. Methods Diabetic neuropathy was made in Sprague Dawley rats by streptozotocin. Pain threshold was evaluated using von Frey monofilaments for 24 weeks. On comparable experiment time after streptozotocin injection, all footpads were prepared for following procedures; glutathione assay, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling staining, immunohistochemistry staining, real-time reverse transcription polymerase chain reaction, and Western blot. Additionally, human HaCaT skin keratinocytes were treated with methylglyoxal, transfected with migration inhibitory factor/control small interfering RNA, and prepared for real-time reverse transcription polymerase chain reaction and Western blot. Results As compared to sham group, pain threshold was significantly reduced in diabetic neuropathy group, and glutathione was decreased in footpad skin, simultaneously, cell death was increased. Over-expression of migration inhibitory factor, accompanied by low expression of glyoxalase-I and intraepidermal nerve fibers, was shown on the footpad skin lesions of diabetic neuropathy. But, there was no significance in expression of neurotransmitters and inflammatory mediators such as transient receptor potential vanilloid 1, mas-related G protein coupled receptor D, nuclear factor kappa B, tumor necrosis factor-alpha, and interleukin-6 between diabetic neuropathy group and sham group. Intriguingly, small interfering RNA-transfected knockdown of the migration inhibitory factor gene in methylglyoxal-treated skin keratinocytes increased expression of glyoxalase-I and intraepidermal nerve fibers in comparison with control small interfering RNA-transfected cells, which was decreased by induction of methylglyoxal. Conclusions Our findings suggest that migration inhibitory factor can aggravate diabetic neuropathy by suppressing glyoxalase-I and intraepidermal nerve fibers on the footpad skin lesions and provoke pain. Taken together, migration inhibitory factor might offer a pharmacological approach to alleviate pain syndromes in diabetic neuropathy.
起源于下肢远端的糖尿病周围神经病变与疾病早期的足部疼痛有关，但发病机制尚不清楚。巨噬细胞移动抑制因子已被认为与神经病理性疼痛的发生和糖尿病的发展有关。本研究旨在观察糖尿病周围神经病变大鼠模型足底诱发的疼痛综合征，并评估移动抑制因子在糖尿病周围神经病变发病机制中的作用。
链脲佐菌素诱导 Sprague Dawley 大鼠糖尿病周围神经病变。使用 von Frey 单丝评估 24 周的疼痛阈值。在链脲佐菌素注射后相当的实验时间，所有足底均进行谷胱甘肽测定、末端脱氧核苷酸转移酶介导的生物素化 UTP 缺口末端标记染色、免疫组织化学染色、实时逆转录聚合酶链反应和 Western blot。此外，人 HaCaT 皮肤角质形成细胞用甲基乙二醛处理，用移动抑制因子/对照小干扰 RNA 转染，并进行实时逆转录聚合酶链反应和 Western blot。
与假手术组相比，糖尿病周围神经病变组的疼痛阈值显著降低，足底皮肤谷胱甘肽减少，同时细胞死亡增加。糖尿病周围神经病变足底皮肤病变中，移动抑制因子过度表达，同时糖氧酶-I 和表皮神经纤维表达降低。但糖尿病周围神经病变组与假手术组之间，神经递质和炎症介质如瞬时受体电位香草醛 1、mas 相关 G 蛋白偶联受体 D、核因子 kappa B、肿瘤坏死因子-α和白细胞介素-6 的表达均无差异。有趣的是，与对照小干扰 RNA 转染细胞相比，甲基乙二醛处理的皮肤角质形成细胞中移动抑制因子基因小干扰 RNA 转染的敲低可增加糖氧酶-I 和表皮神经纤维的表达，而甲基乙二醛诱导则降低了这种表达。
我们的研究结果表明，移动抑制因子可通过抑制足底皮肤病变中的糖氧酶-I 和表皮神经纤维来加重糖尿病周围神经病变，并引起疼痛。综上所述，移动抑制因子可能为缓解糖尿病周围神经病变的疼痛综合征提供一种药理学方法。
