Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile.
Departamento de Reumatología, Clínica INDISA, Santiago, Chile.
Rheumatology (Oxford). 2015 Aug;54(8):1518-27. doi: 10.1093/rheumatology/kev026. Epub 2015 Mar 22.
A hallmark characteristic of SS patients is the ectopic presence of the mucins MUC5B and MUC7 in the extracellular matrix of salivary glands that have lost apical-basolateral acinar-cell polarity. This study aims to determine whether exogenous salivary mucins induce gene expression of pro-inflammatory cytokines, as well as to evaluate whether the Toll-like receptor-4 (TLR4) pathway is involved in this response.
Differentiated human submandibular gland (HSG) cells were stimulated with mucins or oligosaccharide residues at different concentrations and for different periods of time. The expression of pro-inflammatory cytokines and their receptors was determined by semi-quantitative real time PCR (sqPCR). TLR4-mediated responses induced by mucin were evaluated with the Toll-IL-1 receptor domain containing adaptor protein (TIRAP) inhibitory peptide or using anti-hTLR4 blocking antibody. TLR4-receptor expression was also determined in SS patients, controls and HSG cells.
Mucins induced a significant increase in CXCL8, TNF-α, IFN-α, IFN-β, IL-6 and IL-1β, but not B cell activating factor (BAFF). Cytokine induction was mediated by TLR4, as shown using TIRAP or using anti-hTLR4 antibody. Sugar residues present in MUC5B, such as sulpho-Lewis (SO3-3Galβ1-3GlcNAc), also induced cytokines. Unexpectedly, mucins induced MUC5B, but not MUC7 expression.
Salivary mucins were recognized by TLR4 in epithelial cells initiating a pro-inflammatory response that could attract inflammatory cells to amplify and perpetuate inflammation and thereby contribute to the development of a chronic state characteristic of SS. The ectopic localization of MUC5B and MUC7 in the salivary gland extracellular matrix from SS patients and the current results reveal the importance of salivary epithelial cells in innate immunity, as well as in SS pathogenesis.
SS 患者的一个显著特征是，在外周唾液腺中，黏蛋白 MUC5B 和 MUC7 异常存在于失去顶端-基底外侧腺泡细胞极性的细胞外基质中。本研究旨在确定外源性唾液黏蛋白是否会诱导促炎细胞因子的基因表达，并评估 Toll 样受体 4（TLR4）途径是否参与这一反应。
用不同浓度和不同时间的黏蛋白或寡糖残基刺激分化的人颌下腺（HSG）细胞。通过半定量实时 PCR（sqPCR）测定促炎细胞因子及其受体的表达。用 Toll-IL-1 受体结构域包含衔接蛋白（TIRAP）抑制肽或使用抗 hTLR4 阻断抗体评估黏蛋白诱导的 TLR4 介导的反应。还在 SS 患者、对照和 HSG 细胞中测定 TLR4 受体表达。
黏蛋白诱导 CXCL8、TNF-α、IFN-α、IFN-β、IL-6 和 IL-1β显著增加，但不增加 B 细胞激活因子（BAFF）。TLR4 介导了细胞因子的诱导，TIRAP 或抗 hTLR4 抗体的使用证明了这一点。MUC5B 中存在的糖残基，如磺酸-Lewis（SO3-3Galβ1-3GlcNAc），也诱导了细胞因子。出乎意料的是，黏蛋白诱导了 MUC5B 的表达，但没有诱导 MUC7 的表达。
唾液黏蛋白被上皮细胞中的 TLR4 识别，启动促炎反应，从而吸引炎症细胞，放大并维持炎症，从而有助于 SS 特征性的慢性状态的发展。SS 患者唾液腺细胞外基质中 MUC5B 和 MUC7 的异位定位以及目前的结果揭示了唾液上皮细胞在固有免疫以及 SS 发病机制中的重要性。
