Chaudhury Nayab M A, Proctor Gordon B, Karlsson Niclas G, Carpenter Guy H, Flowers Sarah A
From the ‡Salivary Unit, Mucosal and Salivary Biology, Dental Institute, King's College London, Guy's Hospital, Floor 17, Tower Wing, London SE1 9RT, UK;
§Department of Medical Biochemistry, Institute of Biomedicine, University of Gothenburg, Medicinaregatan 9A, 405 30, Gothenburg, Sweden
Mol Cell Proteomics. 2016 Mar;15(3):1048-59. doi: 10.1074/mcp.M115.052993. Epub 2015 Dec 2.
Sjögren's syndrome is a chronic autoimmune disorder characterized by lymphocytic infiltration and hypofunction of salivary and lacrimal glands. This loss of salivary function leads to oral dryness, impaired swallowing and speech, and increased infection and is associated with other autoimmune diseases and an increased risk of certain cancers. Despite the implications of this prevalent disease, diagnosis currently takes years, partly due to the diversity in patient presentation. Saliva is a complicated biological fluid with major constituents, including heavily glycosylated mucins MUC5B and MUC7, important for its viscoelastic and hydrating and lubricating properties. This study investigated Sjögren's patient's perception of dryness (bother index questionnaires) along with the rheological, protein composition, and glycan analysis of whole mouth saliva and the saliva on the mucosal surface (residual mucosal saliva) to understand the properties that most affect patient wellbeing. Sjögren's patients exhibited a statistically significant reduction in residual mucosal saliva, salivary flow rate, and extensional rheology, spinnbarkeit (stringiness). Although the concentration of mucins MUC5B and MUC7 were similar between patients and controls, a comparison of protein Western blotting and glycan staining identified a reduction in mucin glycosylation in Sjögren's, particularly on MUC7. LC-MS/MS analysis of O-glycans released from MUC7 by β-elimination revealed that although patients had an increase in core 1 sulfation, the even larger reduction in sialylation resulted in a global decline of charged glycans. This was primarily due to the loss of the extended core 2 disialylated structure, with and without fucosylation. A decrease in the extended, fucosylated core 2 disialylated structure on MUC7, residual mucosal wetness, and whole mouth saliva flow rate appeared to have a negative and cumulative effect on the perception of oral dryness. The observed changes in MUC7 glycosylation could be a potential diagnostic tool for saliva quality and taken into consideration for future therapies for this multifactorial syndrome.
干燥综合征是一种慢性自身免疫性疾病，其特征为淋巴细胞浸润以及唾液腺和泪腺功能减退。唾液功能丧失会导致口腔干燥、吞咽和言语功能受损、感染风险增加，并且与其他自身免疫性疾病以及某些癌症的发病风险增加有关。尽管这种常见疾病有诸多影响，但目前诊断往往需要数年时间，部分原因是患者临床表现的多样性。唾液是一种复杂的生物流体，其主要成分包括高度糖基化的粘蛋白MUC5B和MUC7，这些成分对其粘弹性、保湿和润滑特性至关重要。本研究调查了干燥综合征患者对干燥的感受（困扰指数问卷），同时对全口唾液和黏膜表面唾液（残留黏膜唾液）进行了流变学、蛋白质组成和聚糖分析，以了解最影响患者健康的特性。干燥综合征患者的残留黏膜唾液、唾液流速和拉伸流变学（可纺性，即拉丝性）在统计学上显著降低。尽管患者和对照组之间粘蛋白MUC5B和MUC7的浓度相似，但蛋白质免疫印迹和聚糖染色比较发现，干燥综合征患者的粘蛋白糖基化减少，尤其是MUC7。通过β-消除法从MUC7释放的O-聚糖的液相色谱-串联质谱分析表明，尽管患者核心1硫酸化增加，但唾液酸化的更大程度降低导致带电荷聚糖总体减少。这主要是由于具有或不具有岩藻糖基化的延伸核心2双唾液酸化结构的丧失。MUC7上延伸的、岩藻糖基化的核心2双唾液酸化结构的减少、残留黏膜湿润度和全口唾液流速似乎对口腔干燥的感受产生了负面的累积影响。观察到的MUC7糖基化变化可能是唾液质量的潜在诊断工具，并可为这种多因素综合征的未来治疗提供参考。
