Peizhi Li1, Zhao Zhang2, Jianping Gong3, Yan Zhang4, Xiwen Zhu5. 1. Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, 74# Linjiang Road, Chongqing, 400010, China. lipeizhi@163.com. 2. Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, 74# Linjiang Road, Chongqing, 400010, China. djxiaosen@sohu.com. 3. Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, 74# Linjiang Road, Chongqing, 400010, China. gongjianping11@126.com. 4. Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, 74# Linjiang Road, Chongqing, 400010, China. candy8001@126.com. 5. Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, 74# Linjiang Road, Chongqing, 400010, China. doctor115@126.com.
Abstract
PURPOSE: S-Adenosylmethionine (SAM) is beneficial for lipopolysaccharide (LPS)-induced liver injury, but its molecular basis is not fully understood. The present study was carried out to investigate the effects of SAM on LPS signal transduction and its possible mechanism. METHODS: An animal model of LPS-induced liver injury was established by intraperitoneally injecting mice with 10 mg/kg LPS pretreatment with or without SAM (170 μmol/kg body weight). Toll-like receptor 4 (TLR4) protein expression in liver tissues and the tumor necrosis factor alpha (TNF-α) secretion level in serum were detected by immunohistochemistry and enzyme-linked immunosorbent assay, respectively. Then, Kupffer cells (KCs) were isolated and challenged with LPS, with or without SAM pretreatment (1,000 μM), and the expressions of TLR4 and myeloid differentiation primary response protein (MYD88) were assayed at the mRNA and protein levels. The activities of nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) were also analyzed using Western blotting. RESULTS: SAM significantly improved the survival rate of endotoxemic mice (p < 0.05) and decreased TNF-α levels in serum (p < 0.05). Simultaneously, SAM also attenuated LPS-induced liver injury and expression of TLR4 and MYD88 in the hepatic sinusoid. Moreover, TLR4 and MYD88 gene and protein expressions were downregulated by SAM pretreatment in LPS-stimulated KCs. Finally, SAM did not affect NF-κB-p65 translocation into the nucleus (p > 0.05), but significantly inhibited p38 MAPK activation (p < 0.05). CONCLUSIONS: SAM attenuated liver injury and improved the survival rate in endotoxemic mice by decreasing the TNF-α expression. The downregulative effect of SAM on TNF-α was mediated by suppressing activation of the TLR4/MAPK signaling pathway.
PURPOSE:S-Adenosylmethionine (SAM) is beneficial for lipopolysaccharide (LPS)-induced liver injury, but its molecular basis is not fully understood. The present study was carried out to investigate the effects of SAM on LPS signal transduction and its possible mechanism. METHODS: An animal model of LPS-induced liver injury was established by intraperitoneally injecting mice with 10 mg/kg LPS pretreatment with or without SAM (170 μmol/kg body weight). Toll-like receptor 4 (TLR4) protein expression in liver tissues and the tumor necrosis factor alpha (TNF-α) secretion level in serum were detected by immunohistochemistry and enzyme-linked immunosorbent assay, respectively. Then, Kupffer cells (KCs) were isolated and challenged with LPS, with or without SAM pretreatment (1,000 μM), and the expressions of TLR4 and myeloid differentiation primary response protein (MYD88) were assayed at the mRNA and protein levels. The activities of nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) were also analyzed using Western blotting. RESULTS:SAM significantly improved the survival rate of endotoxemic mice (p < 0.05) and decreased TNF-α levels in serum (p < 0.05). Simultaneously, SAM also attenuated LPS-induced liver injury and expression of TLR4 and MYD88 in the hepatic sinusoid. Moreover, TLR4 and MYD88 gene and protein expressions were downregulated by SAM pretreatment in LPS-stimulated KCs. Finally, SAM did not affect NF-κB-p65 translocation into the nucleus (p > 0.05), but significantly inhibited p38 MAPK activation (p < 0.05). CONCLUSIONS:SAMattenuated liver injury and improved the survival rate in endotoxemic mice by decreasing the TNF-α expression. The downregulative effect of SAM on TNF-α was mediated by suppressing activation of the TLR4/MAPK signaling pathway.
Authors: Z J Liu; X L Liu; J Zhao; Y J Shi; L N Yan; X F Chen; X H Li; H B You; F L Xu; J P Gong Journal: Dig Liver Dis Date: 2008-04-02 Impact factor: 4.088