Mei Mei1, Ling-Han Qu2, Xin Cong3, Yan Zhang3, Ruo-Lan Xiang3, Guang-Yan Yu2, Jia-Zeng Su4, Li-Ling Wu5. 1. Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, and Beijing Key Laboratory of Digital Stomatology, Beijing, China; First Clinical Division, Peking University School and Hospital of Stomatology, Beijing, China. 2. Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, and Beijing Key Laboratory of Digital Stomatology, Beijing, China. 3. Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing, China. 4. Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, and Beijing Key Laboratory of Digital Stomatology, Beijing, China. Electronic address: sujiazeng@163.com. 5. Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing, China. Electronic address: pathophy@bjmu.edu.cn.
Abstract
BACKGROUND: C1q/tumour necrosis factor-related protein 3 (CTRP3) plays important roles in metabolism and inflammatory responses in various cells and tissues. However, the expression and function of CTRP3 in salivary glands have not been explored. METHODS: The expression and distribution of CTRP3 were detected by western blot, polymerase chain reaction, immunohistochemical and immunofluorescence staining. The effects of CTRP3 on tumour necrosis factor (TNF)-α-induced apoptosis and barrier dysfunction were detected by flow cytometry, western blot, co-immunoprecipitation, and measurement of transepithelial resistance and paracellular tracer flux. RESULTS: CTRP3 was distributed in both acinar and ductal cells of human submandibular gland (SMG) and was primarily located in the ducts of rat and mouse SMGs. TNF-α increased the apoptotic rate, elevated expression of cleaved caspase 3 and cytochrome C, and reduced B cell lymphoma-2 (Bcl-2) levels in cultured human SMG tissue and SMG-C6 cells, and CTRP3 further enhanced TNF-α-induced apoptosis response. Additionally, CTRP3 aggravated TNF-α-increased paracellular permeability. Mechanistically, CTRP3 promoted TNF-α-enhanced TNF type I receptor (TNFR1) expression, inhibited the expression of cellular Fas-associated death domain (FADD)-like interleukin-1β converting enzyme inhibitory protein (c-FLIP), and increased the recruitment of FADD with receptor-interacting protein kinase 1 and caspase 8. Moreover, CTRP3 was significantly increased in the labial gland of Sjögren's syndrome patients and in the serum and SMG of nonobese diabetic mice. CONCLUSIONS: These findings suggest that the salivary glands are a novel source of CTRP3 synthesis and secretion. CTRP3 might promote TNF-α-induced cell apoptosis through the TNFR1-mediated complex II pathway.
BACKGROUND: C1q/tumour necrosis factor-related protein 3 (CTRP3) plays important roles in metabolism and inflammatory responses in various cells and tissues. However, the expression and function of CTRP3 in salivary glands have not been explored. METHODS: The expression and distribution of CTRP3 were detected by western blot, polymerase chain reaction, immunohistochemical and immunofluorescence staining. The effects of CTRP3 on tumour necrosis factor (TNF)-α-induced apoptosis and barrier dysfunction were detected by flow cytometry, western blot, co-immunoprecipitation, and measurement of transepithelial resistance and paracellular tracer flux. RESULTS: CTRP3 was distributed in both acinar and ductal cells of human submandibular gland (SMG) and was primarily located in the ducts of rat and mouse SMGs. TNF-α increased the apoptotic rate, elevated expression of cleaved caspase 3 and cytochrome C, and reduced B cell lymphoma-2 (Bcl-2) levels in cultured human SMG tissue and SMG-C6 cells, and CTRP3 further enhanced TNF-α-induced apoptosis response. Additionally, CTRP3 aggravated TNF-α-increased paracellular permeability. Mechanistically, CTRP3 promoted TNF-α-enhanced TNF type I receptor (TNFR1) expression, inhibited the expression of cellular Fas-associated death domain (FADD)-like interleukin-1β converting enzyme inhibitory protein (c-FLIP), and increased the recruitment of FADD with receptor-interacting protein kinase 1 and caspase 8. Moreover, CTRP3 was significantly increased in the labial gland of Sjögren's syndrome patients and in the serum and SMG of nonobese diabetic mice. CONCLUSIONS: These findings suggest that the salivary glands are a novel source of CTRP3 synthesis and secretion. CTRP3 might promote TNF-α-induced cell apoptosis through the TNFR1-mediated complex II pathway.