Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.
Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.
Kidney Int. 2020 May;97(5):951-965. doi: 10.1016/j.kint.2019.09.035. Epub 2019 Nov 2.
The endothelial glycocalyx is a key component of the glomerular filtration barrier. We have shown that matrix metalloproteinase (MMP)-mediated syndecan 4 shedding is a mechanism of glomerular endothelial glycocalyx damage in vitro, resulting in increased albumin permeability. Here we sought to determine whether this mechanism is important in early diabetic kidney disease, by studying streptozotocin-induced type 1 diabetes in DBA2/J mice. Diabetic mice were albuminuric, had increased glomerular albumin permeability and endothelial glycocalyx damage. Syndecan 4 mRNA expression was found to be upregulated in isolated glomeruli and in flow cytometry-sorted glomerular endothelial cells. In contrast, glomerular endothelial luminal surface syndecan 4 and Marasmium oreades agglutinin lectin labelling measurements were reduced in the diabetic mice. Similarly, syndecan 4 protein expression was significantly decreased in isolated glomeruli but increased in plasma and urine, suggesting syndecan 4 shedding. Mmp-2, 9 and 14 mRNA expression were upregulated in isolated glomeruli, suggesting a possible mechanism of glycocalyx damage and albuminuria. We therefore characterised in detail the activity of MMP-2 and 9 and found significant increases in kidney cortex, plasma and urine. Treatment with MMP-2/9 inhibitor I for 21 days, started six weeks after diabetes induction, restored endothelial glycocalyx depth and coverage and attenuated diabetes-induced albuminuria and reduced glomerular albumin permeability. MMP inhibitor treatment significantly attenuated glomerular endothelial and plasma syndecan 4 shedding and inhibited plasma MMP activity. Thus, our studies confirm the importance of MMPs in endothelial glycocalyx damage and albuminuria in early diabetes and demonstrate that this pathway is amenable to therapeutic intervention. Hence, treatments targeted at glycocalyx protection by MMP inhibition may be of benefit in diabetic kidney disease.
内皮糖萼是肾小球滤过屏障的关键组成部分。我们已经表明，基质金属蛋白酶（MMP）介导的连接蛋白 4 脱落是体外肾小球内皮糖萼损伤的一种机制，导致白蛋白通透性增加。在这里，我们通过研究链脲佐菌素诱导的 DBA2/J 小鼠 1 型糖尿病，试图确定这种机制在早期糖尿病肾病中的重要性。糖尿病小鼠出现白蛋白尿，肾小球白蛋白通透性和内皮糖萼损伤增加。发现分离的肾小球和流式细胞术分选的肾小球内皮细胞中连接蛋白 4 mRNA 表达上调。相比之下，糖尿病小鼠肾小球内皮细胞管腔表面连接蛋白 4 和 Marasmium oreades agglutinin 凝集素标记测量值减少。同样，分离的肾小球中连接蛋白 4 蛋白表达显著降低，但在血浆和尿液中增加，提示连接蛋白 4 脱落。Mmp-2、9 和 14 mRNA 表达在分离的肾小球中上调，提示糖萼损伤和白蛋白尿的可能机制。因此，我们详细描述了 MMP-2 和 9 的活性，发现肾皮质、血浆和尿液中的活性显著增加。从糖尿病诱导后六周开始，用 MMP-2/9 抑制剂 I 治疗 21 天，可恢复内皮糖萼深度和覆盖率，并减轻糖尿病引起的白蛋白尿和降低肾小球白蛋白通透性。MMP 抑制剂治疗可显著减轻肾小球内皮和血浆连接蛋白 4 的脱落，并抑制血浆 MMP 活性。因此，我们的研究证实了 MMP 在早期糖尿病中内皮糖萼损伤和白蛋白尿中的重要性，并表明该途径可进行治疗干预。因此，通过 MMP 抑制靶向糖萼保护的治疗方法可能对糖尿病肾病有益。
