Zhongwei Liu1, Yanpeng Ma1, Qianwei Cui1, Jing Xu1, Zhiguo Tang1, Yuan Wang2, Chunhui He3, Xi Wang4. 1. Department of Cardiology, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi, China. 2. Department of Medical Prevention, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi, China. Electronic address: ooozkb@sina.com. 3. Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China. Electronic address: hechunhuiyisheng@163.com. 4. Department of Obstetrics and Gynecology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China. Electronic address: wangxi825@csu.edu.cn.
Abstract
OBJECTIVE: This study was aimed to investigate the role of Toll-like receptor 4 (TLR4) in advanced glycation end products (AGEs)- induced macrophage polarization toward M1. METHODS: Isolated primary macrophages were exposed to prepared AGEs at concentrations of 0, 2.5, 5 and 10 μmol/L. Macrophages were also exposed to hydrogen peroxide (H2O2) which provided exogenous reactive oxygen species (ROS). Receptor for AGEs (RAGE) was over-expressed by a vector. Specific siRNA silencing TLR4 and inhibitor TAK-242 were used to pre-treat the macrophages. Intracellular ROS was determined by DCFH-DA. Immunofluorescence staining was used to evaluate the expression of inducible nitric oxide synthase (iNOS) which is the marker of M1 macrophage phenotype. Real-time PCR was used to assess the mRNA expression level of TLR4 and RAGE. Protein expression levels of cytoplasmic RAGE, TLR4, nuclear signal transducers and activators of transcription 1 (STAT1) and phosphorylation levels of cytoplasmic STAT1 were evaluated by Western blotting. ELISA was used to measure concentrations of interleukin 6 (IL6), IL12 and tumor necrosis factor (TNF)α in supernatant of cell culture medium of macrophages. RESULTS: AGEs significantly elevated intracellular ROS generation, expression levels of iNOS, cytoplasmic RAGE, TLR4, nuclear STAT1, phosphorylation levels of cytoplasmic STAT1, as well as IL6, IL12 and TNFα contents in a concentration-dependent manner. TLR4 silencing and inhibitor pre-treatment reduced expression levels of cytoplasmic RAGE, TLR4, phosphorylation of STAT1 and nuclear STAT1 in AGEs-exposed macrophages without affecting RAGE expression and intracellular ROS production levels. RAGE over-expression elevated both ROS and TLR4 expression levels in macrophages. TLR4 expression elevation was also found in H2O2-treat macrophages. CONCLUSION: AGEs induced macrophage polarization toward M1 via activating RAGE/ROS/TLR4/STAT1 signaling pathway.
OBJECTIVE: This study was aimed to investigate the role of Toll-like receptor 4 (TLR4) in advanced glycation end products (AGEs)- induced macrophage polarization toward M1. METHODS: Isolated primary macrophages were exposed to prepared AGEs at concentrations of 0, 2.5, 5 and 10 μmol/L. Macrophages were also exposed to hydrogen peroxide (H2O2) which provided exogenous reactive oxygen species (ROS). Receptor for AGEs (RAGE) was over-expressed by a vector. Specific siRNA silencing TLR4 and inhibitor TAK-242 were used to pre-treat the macrophages. Intracellular ROS was determined by DCFH-DA. Immunofluorescence staining was used to evaluate the expression of inducible nitric oxide synthase (iNOS) which is the marker of M1 macrophage phenotype. Real-time PCR was used to assess the mRNA expression level of TLR4 and RAGE. Protein expression levels of cytoplasmic RAGE, TLR4, nuclear signal transducers and activators of transcription 1 (STAT1) and phosphorylation levels of cytoplasmic STAT1 were evaluated by Western blotting. ELISA was used to measure concentrations of interleukin 6 (IL6), IL12 and tumor necrosis factor (TNF)α in supernatant of cell culture medium of macrophages. RESULTS: AGEs significantly elevated intracellular ROS generation, expression levels of iNOS, cytoplasmic RAGE, TLR4, nuclear STAT1, phosphorylation levels of cytoplasmic STAT1, as well as IL6, IL12 and TNFα contents in a concentration-dependent manner. TLR4 silencing and inhibitor pre-treatment reduced expression levels of cytoplasmic RAGE, TLR4, phosphorylation of STAT1 and nuclear STAT1 in AGEs-exposed macrophages without affecting RAGE expression and intracellular ROS production levels. RAGE over-expression elevated both ROS and TLR4 expression levels in macrophages. TLR4 expression elevation was also found in H2O2-treat macrophages. CONCLUSION: AGEs induced macrophage polarization toward M1 via activating RAGE/ROS/TLR4/STAT1 signaling pathway.
Authors: Lisha Teng; Lingling Shen; Wenjun Zhao; Cuili Wang; Shi Feng; Yucheng Wang; Yan Bi; Song Rong; Nelli Shushakova; Hermann Haller; Jianghua Chen; Hong Jiang Journal: Front Immunol Date: 2022-04-01 Impact factor: 8.786