Xiaohuan Zhong1, Huixin Wang1, Shenggao Huang2. 1. Department of Stomatology, Xiangya Hospital, Central South University, Changsha 410008, Hunan, PR China. 2. Dental Center, The Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, PR China. Electronic address: huangsg1964@126.com.
Abstract
OBJECTIVE: Both endothelin-1 (ET-1) and interleukin (IL)-18 induce osteoblast proliferation under normal and pathophysiological conditions. In the present study, we explored the interaction between the two proteins by examining the effect of ET-1 on IL-18 expression in cultured human osteoblasts. METHODS: Human osteoblasts were treated with ET-1 in different concentrations (1, 10, 20, 40, or 50 nM) for different length of time (1, 6, 12, 18, or 24 h) in the presence or absence of ET A receptor (ETAR) blocker BQ123, ET B receptor (ETBR) blocker BQ788, p38 mitogen-activated protein kinase (MAPK) siRNA, or different kinase inhibitors. RESULTS: ET-1 increased the IL-18 mRNA level in a statistically significant dose- and time-dependent manner within 18 h, which was reflected in dose-dependent induction of the human IL-18 gene promoter activity and IL-18 protein/secreted protein expression. BQ123 (1μ M) and p38 MAPK siRNA and inhibitor PD169316 (25 μM) completely abolished the promoting effect of ET-1 on IL-18 expression. [(3)H]thymidine incorporation assays showed that ET-1 lost a major part (57%) of its promoting effect on osteoblast proliferation when the endogenous IL-18 expression in osteoblasts was knocked down by 75%. CONCLUSIONS: ET-1 induces IL-18 expression in human osteoblasts at the gene promoter/transcription level via ETAR by a p38 MAPK-dependent mechanism, and that IL-18 mediates a major part of ET-1 induced osteoblast proliferation. This study provides the first evidence of interaction between ET-1 and IL-18 in osteoblast and adds new insights into bone physiology and pathophysiology.
OBJECTIVE: Both endothelin-1 (ET-1) and interleukin (IL)-18 induce osteoblast proliferation under normal and pathophysiological conditions. In the present study, we explored the interaction between the two proteins by examining the effect of ET-1 on IL-18 expression in cultured human osteoblasts. METHODS:Human osteoblasts were treated with ET-1 in different concentrations (1, 10, 20, 40, or 50 nM) for different length of time (1, 6, 12, 18, or 24 h) in the presence or absence of ET A receptor (ETAR) blocker BQ123, ET B receptor (ETBR) blocker BQ788, p38 mitogen-activated protein kinase (MAPK) siRNA, or different kinase inhibitors. RESULTS:ET-1 increased the IL-18 mRNA level in a statistically significant dose- and time-dependent manner within 18 h, which was reflected in dose-dependent induction of the humanIL-18 gene promoter activity and IL-18 protein/secreted protein expression. BQ123 (1μ M) and p38 MAPK siRNA and inhibitor PD169316 (25 μM) completely abolished the promoting effect of ET-1 on IL-18 expression. [(3)H]thymidine incorporation assays showed that ET-1 lost a major part (57%) of its promoting effect on osteoblast proliferation when the endogenous IL-18 expression in osteoblasts was knocked down by 75%. CONCLUSIONS:ET-1 induces IL-18 expression in human osteoblasts at the gene promoter/transcription level via ETAR by a p38 MAPK-dependent mechanism, and that IL-18 mediates a major part of ET-1 induced osteoblast proliferation. This study provides the first evidence of interaction between ET-1 and IL-18 in osteoblast and adds new insights into bone physiology and pathophysiology.
Authors: Ali Aydin; Zekai Halici; Erol Akpinar; A Murat Aksakal; Murat Saritemur; Muhammed Yayla; C Semih Kunak; Elif Cadirci; H Tarik Atmaca; S Sena Karcioglu Journal: J Bone Miner Metab Date: 2014-10-09 Impact factor: 2.626