Xinjiang Medical University, Urumqi 830054, China.
Dept. of Oral and Maxillofacial Surgery, People,s Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China.
Hua Xi Kou Qiang Yi Xue Za Zhi. 2021 Jun 1;39(3):267-273. doi: 10.7518/hxkq.2021.03.004.
This study aims to investigate the effects of ionizing radiation on the secretion of the paracellular pathway in rat submandibular glands (SMGs) and reveal the changes in the tight junction (TJ) protein claudin-4.
A total of 24 Wistar rats were randomly divided into control and irradiation groups. The irradiation groups were further divided into 1, 4, and 12 weeks groups after irradiation. One-time 20 Gy irradiation was given to the SMG area on the experimental side of the irradiation group. At 1, 4, and 12 weeks after irradiation, the secretion of SMGs was measured using the Schirmer's test. The pathological changes in the gland tissues were observed under light microscopy after hematoxylin⁃eosin (HE) staining. The changes in the TJ ultrastructure were observed under transmission electron microscopy. The immunofluorescence staining and Western blot were used to detect the expression levels of muscarinic acetylcholine M3 receptor, aquaporin 5 (AQP5), and claudin-4 protein.
At 1, 4, and 12 weeks after irradiation, the secretion of SMGs in the irradiation group was significantly decreased and lower than that in the control group (<0.01). At 1 week, the interstitial edema was observed in SMG tissues. Nuclear pyknosis, decreased number of acinar cells, and small focal necrosis with inflammatory infiltration were also observed over time. However, these changes were most evident at 12 weeks after irradiation. In the irradiation group, the TJ ultrastructure of glands at different times appeared to be fuzzy, collapsed, and had decreased electron density. Moreover, the width of TJs was remarkably decreased (<0.01). The expression levels of M3 and AQP5 were decreased in a time-dependent manner, and the fluorescence intensity was significantly reduced after irradiation. However, the expression levels and fluorescence intensity of claudin-4 were enhanced in different degrees.
The changes in the TJ structure, the upregulation of the claudin-4 expression, and the damage in the paracellular pathway were involved in the hyposecretion of SMGs after irradiation.
本研究旨在探讨电离辐射对大鼠颌下腺（SMG）旁细胞途径分泌的影响，并揭示紧密连接（TJ）蛋白闭合蛋白-4 的变化。
将 24 只 Wistar 大鼠随机分为对照组和照射组。照射组再分为照射后 1、4 和 12 周组。对照射组 SMG 区域进行一次性 20 Gy 照射。照射后 1、4 和 12 周，采用 Schirmer 试验测量 SMG 的分泌情况。苏木精-伊红（HE）染色后，在光镜下观察腺体组织的病理变化。透射电镜观察 TJ 超微结构的变化。采用免疫荧光染色和 Western blot 检测毒蕈碱乙酰胆碱 M3 受体、水通道蛋白 5（AQP5）和闭合蛋白-4 蛋白的表达水平。
照射后 1、4 和 12 周，照射组 SMG 分泌明显减少，低于对照组（<0.01）。1 周时，SMG 组织间质水肿，随时间推移，还观察到核固缩、腺泡细胞数量减少、小灶状坏死伴炎症浸润。然而，这些变化在照射后 12 周最为明显。在照射组，不同时间腺体的 TJ 超微结构显示模糊、塌陷，电子密度降低。此外，TJ 宽度明显减小（<0.01）。M3 和 AQP5 的表达呈时间依赖性下降，照射后荧光强度明显降低。然而，闭合蛋白-4 的表达水平和荧光强度呈不同程度增强。
TJ 结构的变化、闭合蛋白-4 表达的上调以及旁细胞途径的损伤参与了照射后 SMG 的分泌减少。
