Supporting data for Neuroprotective role of α-Melanocyte-stimulating hormone on ischemia/reperfusion-induced brain and retinal damage in type 1 diabetic mouse

Persons with type 1 diabetes have an increased risk of stroke compared
with the general population. Because
vision loss is frequently connected with stroke, it is essential to find a
strategy that effectively preserves vision by protecting retina in addition to
the brain. α-Melanocyte-stimulating
hormone (α-MSH) is a neuropeptide that has protective effects against
ischemia/reperfusion (I/R) induced organ damages. In this study, we aimed to investigate the
neuroprotective role of α-MSH on I/R-induced brain and retinal damages after
experimental stroke associated with hyperglycemia using C57BL/6J Ins2Akita/+
mice. Experimental stroke was induced by
blocking the right middle cerebral artery (MCA) for 2 h with reperfusion for 2 h
and 22 h, respectively using the intraluminal method. Since the opening of ophthalmic artery is proximal
to the origin of the MCA, blood supply to the retina was also blocked by the
filament. Animals were treated
intraperitoneally with or without α-MSH at 1 h after ischemia and 1 h after
reperfusion. Significantly higher percent
survival and lower neurological scores were recorded in animals injected with
α-MSH. Similarly, neuron death, glial
cells activation as well as oxidative and nitrosative stress were significantly
decreased in the α-MSH-treated brains. Relative intensities of matrix
metallopeptidases 9, cyclooxygenase 2 and nuclear factor-κB were significantly
decreased while intensities of Akt, heme oxygenase (HO) 1, HO-2 and B-cell
lymphoma 2 were significantly increased in α-MSH treated brain. In addition, gene expressions of
monocarboxylate transporter (MCT) 1, MCT-2 and activity-regulated
cytoskeleton-associated protein were significantly higher in brain samples
treated with α-MSH, suggesting an involvement of lactate metabolism in α-MSH
neuroprotective effects. In the retina,
α-MSH significantly increased the amplitude of b-wave as well as oscillatory
potentials in electroretinogram, a measure of retinal function. α-MSH also prevented I/R-induced histological
alterations and inhibited the development of retinal swelling. Loss of retinal ganglion cells as well as
oxidative stress were significantly attenuated in α-MSH-treated diabetic retina
after I/R injury. Expression of interleukin
10 was significantly increased in the retina after α-MSH treatment. In addition, gene expression of MCT-1, MCT-2
and glutamate aspartate transporter 1 were significantly higher after α-MSH
administration. In conclusion, α-MSH is
neuroprotective under hyperglycemic condition against I/R-induced brain and
retinal damage by its anti-inflammatory, anti-oxidative and anti-apoptotic
properties. These effects of α-MSH may
have important therapeutic implication against cerebral and retinal I/R injury
under hyperglycemic condition.

一型糖尿病患者相较于普通人群，其发生中风的风险有所上升。鉴于视力丧失常与中风相关联，探寻一种有效保护视网膜并维护脑部健康的策略显得尤为迫切。α-黑色素细胞刺激激素（α-MSH）作为一种神经肽，能够对因缺血再灌注（I/R）引起的器官损伤发挥保护作用。本研究旨在探讨α-MSH在实验性中风伴高血糖条件下，对脑部和视网膜缺血再灌注损伤的神经保护作用，实验对象为C57BL/6J Ins2Akita/+小鼠。通过阻断右侧大脑中动脉（MCA）2小时并分别进行2小时和22小时的再灌注，诱导实验性中风。由于眼动脉开口位于MCA起源的近端，视网膜的血液供应也因丝线而被阻断。动物在缺血和再灌注后1小时接受腹腔注射α-MSH或未接受注射。接受α-MSH注射的动物显示出显著更高的存活率和较低的神经学评分。类似地，α-MSH处理后的脑部神经细胞死亡、胶质细胞激活以及氧化和硝化应激显著降低。在α-MSH处理的脑组织中，基质金属蛋白酶9、环氧化酶2和核因子-κB的相对强度显著降低，而Akt、血红素加氧酶（HO）1、HO-2和B细胞淋巴瘤2的强度则显著增加。此外，经α-MSH处理的脑组织样本中，单羧酸转运蛋白（MCT）1、MCT-2和活性调节的细胞骨架相关蛋白的基因表达显著升高，这表明乳酸代谢在α-MSH的神经保护作用中发挥重要作用。在视网膜中，α-MSH显著增加了视网膜电图（ERG）中b波振幅以及振荡电位，这是衡量视网膜功能的一个指标。α-MSH还能防止I/R引起的组织学改变，并抑制视网膜肿胀的发展。在I/R损伤后，α-MSH处理的糖尿病视网膜中视网膜神经节细胞的丧失以及氧化应激显著减轻。α-MSH治疗后视网膜中白细胞介素10的表达显著增加。此外，MCT-1、MCT-2和谷氨酸-天冬氨酸转运蛋白1的基因表达在α-MSH给药后也显著升高。综上所述，α-MSH在血糖升高的条件下，通过其抗炎、抗氧化和抗凋亡的特性，对I/R引起的脑部和视网膜损伤具有神经保护作用。这些作用可能对血糖升高条件下的脑部和视网膜I/R损伤的治疗具有重要的临床意义。