Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Yeongeondong 28, Chongnoku, Seoul 110-749, Korea.
Oral Dis. 2012 Mar;18(2):132-9. doi: 10.1111/j.1601-0825.2011.01853.x. Epub 2011 Sep 8.
Autoantibodies from the sera of Sjögren's syndrome patients (SS IgG) have been suggested to inhibit muscarinic receptor function. However, the acute nature of such an inhibitory effect remains controversial. In this study, we investigated the acute effects of SS IgG on muscarinic receptor function in human submandibular gland (HSG) cells.
The effects of autoantibodies on muscarinic receptor function were studied using microspectrofluorimetry, whole-cell patch clamp, immunofluorescence confocal microscopy, and a co-immunoprecipitation assay.
Carbachol (CCh) was found to consistently increase intracellular calcium concentration (Ca(2+) ) and activate K(+) current in HSG cells. However, pretreatment of the cells with SS IgG for 5 or 30 min significantly attenuated these responses, with a substantially more prominent effect after 30 min of treatment. Like CCh, adenosine 5'-triphosphate (ATP) also increased Ca(2+) and activated K(+) currents in HSG cells, although pretreatment with SS IgG did not affect the cellular response to ATP. CCh was found to reorganize α-fodrin in HSG cells in a Ca(2+) -dependent manner. However, pretreatment with SS IgG prevented the cytoskeletal reorganization of α-fodrin induced by CCh.
SS IgG acutely and reversibly inhibited muscarinic receptor function, thereby inhibiting the Ca(2+) mobilization necessary for the activation of K(+) currents and α-fodrin reorganization in HSG cells.
干燥综合征患者血清中的自身抗体（SS IgG）被认为可抑制毒蕈碱受体功能。然而，这种抑制作用的急性性质仍存在争议。本研究旨在探讨 SS IgG 对人颌下腺（HSG）细胞毒蕈碱受体功能的急性影响。
采用微光谱荧光法、全细胞膜片钳、免疫荧光共聚焦显微镜和共免疫沉淀检测，研究自身抗体对毒蕈碱受体功能的影响。
发现乙酰胆碱（CCh）可一致增加 HSG 细胞内钙离子浓度(Ca(2+) )并激活 K(+)电流。然而，用 SS IgG 预处理细胞 5 或 30 分钟可显著减弱这些反应，30 分钟后处理的效果更为明显。与 CCh 类似，三磷酸腺苷（ATP）也可增加 HSG 细胞中的Ca(2+) 并激活 K(+)电流，但 SS IgG 预处理并不影响细胞对 ATP 的反应。发现 CCh 以 Ca(2+) 依赖性方式重组 HSG 细胞中的α-辅肌动蛋白。然而，SS IgG 预处理可防止 CCh 诱导的α-辅肌动蛋白细胞骨架重组。
SS IgG 可急性和可逆地抑制毒蕈碱受体功能，从而抑制 HSG 细胞中激活 K(+)电流和α-辅肌动蛋白重组所需的 Ca(2+)动员。
