Departamento de Tecnologia Medica, Santiago, Chile.
Programa de Biología Celular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Rheumatology (Oxford). 2020 Apr 1;59(4):742-753. doi: 10.1093/rheumatology/kez316.
Xerostomia in SS patients has been associated with low quality and quantity of salivary mucins, which are fundamental for the hydration and protection of the oral mucosa. The aim of this study was to evaluate if cytokines induce aberrant mucin expression and whether tauroursodeoxycholic acid (TUDCA) is able to counteract such an anomaly.
Labial salivary glands from 16 SS patients and 15 control subjects, as well as 3D acini or human submandibular gland cells stimulated with TNF-α or IFN-γ and co-incubated with TUDCA, were analysed. mRNA and protein levels of Mucin 1 (MUC1) and MUC7 were determined by RT-qPCR and western blot, respectively. Co-immunoprecipitation and immunofluorescence assays for mucins and GRP78 [an endoplasmic reticulum (ER)-resident protein] were also performed. mRNA levels of RelA/p65 (nuclear factor-κB subunit), TNF-α, IL-1β, IL-6, SEL1L and EDEM1 were determined by RT-qPCR, and RelA/p65 localization was evaluated by immunofluorescence.
MUC1 is overexpressed and accumulated in the ER of labial salivary gland from SS patients, while MUC7 accumulates throughout the cytoplasm of acinar cells; however, MUC1, but not MUC7, co-precipitated with GRP78. TUDCA diminished the overexpression and aberrant accumulation of MUC1 induced by TNF-α and IFN-γ, as well as the nuclear translocation of RelA/p65, together with the expression of inflammatory and ER stress markers in 3D acini.
Chronic inflammation alters the secretory process of MUC1, inducing ER stress and affecting the quality of saliva in SS patients. TUDCA showed anti-inflammatory properties decreasing aberrant MUC1 accumulation. Further studies are necessary to evaluate the potential therapeutic effect of TUDCA in restoring glandular homeostasis in SS patients.
干燥综合征（SS）患者的口干与唾液黏蛋白的数量和质量下降有关，而黏蛋白是口腔黏膜水合和保护的基础。本研究旨在评估细胞因子是否会诱导异常黏蛋白表达，以及牛磺熊脱氧胆酸（TUDCA）是否能够对抗这种异常。
分析了 16 名 SS 患者和 15 名对照者的唇腺，以及用 TNF-α或 IFN-γ刺激的 3D 腺泡或人颌下腺细胞，这些细胞与 TUDCA 共孵育。通过 RT-qPCR 和 Western blot 分别测定黏蛋白 1（MUC1）和 MUC7 的 mRNA 和蛋白水平。还进行了黏蛋白和 GRP78（内质网（ER）驻留蛋白）的共免疫沉淀和免疫荧光分析。通过 RT-qPCR 测定 RelA/p65（核因子-κB 亚基）、TNF-α、IL-1β、IL-6、SEL1L 和 EDEM1 的 mRNA 水平，并通过免疫荧光评估 RelA/p65 的定位。
SS 患者唇腺中 MUC1 过度表达并在 ER 中积累，而 MUC7 在腺泡细胞的细胞质中积累；然而，只有 MUC1 而不是 MUC7 与 GRP78 共沉淀。TUDCA 减少了 TNF-α和 IFN-γ诱导的 MUC1 过度表达和异常积累，以及 RelA/p65 的核转位，以及 3D 腺泡中炎症和 ER 应激标志物的表达。
慢性炎症改变了 MUC1 的分泌过程，导致 ER 应激，并影响 SS 患者的唾液质量。TUDCA 表现出抗炎特性，可减少异常 MUC1 积累。需要进一步研究以评估 TUDCA 在恢复 SS 患者腺体稳态方面的潜在治疗效果。
