Kotaro Sakata1, Satoshi Eda2, Eun-Seo Lee2, Mitsuko Hara2, Masaya Imoto3, Soichi Kojima4. 1. Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan; Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan; Drug Discovery Laboratory, Wakunaga Pharmaceutical Co., Ltd., Akitakata, Hiroshima 739-1195, Japan. 2. Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan. 3. Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan. 4. Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan. Electronic address: skojima@riken.jp.
Abstract
AIM: Hepatic fibrosis and angiogenesis occur in parallel during the progression of liver disease. Fibrosis promotes angiogenesis via inducing vascular endothelial growth factor (VEGF) from the activated hepatic stellate cells (HSCs). In turn, increased neovessel formation causes fibrosis, although the underlying molecular mechanism remains undetermined. In the current study, we aimed to address a role of endothelial cells (ECs) as a source of latent transforming growth factor (TGF)-β, the precursor of the most fibrogenic cytokine TGF-β. METHODS: After recombinant VEGF was administered to mice via the tail vein, hepatic angiogenesis and fibrogenesis were evaluated using immunohistochemical and biochemical analyses in addition to investigation of TGF-β activation using primary cultured HSCs and liver sinusoidal ECs (LSECs). RESULTS: In addition to increased hepatic levels of CD31 expression, VEGF-treated mice showed increased α-smooth muscle actin (α-SMA) expression, hepatic contents of hydroxyproline, and latency associated protein degradation products, which reflects cell surface activation of TGF-β via plasma kallikrein (PLK). Liberating the PLK-urokinase plasminogen activator receptor complex from the HSC surface by cleaving a tethering phosphatidylinositol linker with its specific phospholipase C inhibited the activating latent TGF-β present in LSEC conditioned medium and subsequent HSC activation. CONCLUSION: Neovessel formation (angiogenesis) accelerates liver fibrosis at least in part via provision of latent TGF-β that activated on the surface of HSCs by PLK, thereby resultant active TGF-β stimulates the activation of HSCs.
AIM: Hepatic fibrosis and angiogenesis occur in parallel during the progression of liver disease. Fibrosis promotes angiogenesis via inducing vascular endothelial growth factor (VEGF) from the activated hepatic stellate cells (HSCs). In turn, increased neovessel formation causes fibrosis, although the underlying molecular mechanism remains undetermined. In the current study, we aimed to address a role of endothelial cells (ECs) as a source of latent transforming growth factor (TGF)-β, the precursor of the most fibrogenic cytokine TGF-β. METHODS: After recombinant VEGF was administered to mice via the tail vein, hepatic angiogenesis and fibrogenesis were evaluated using immunohistochemical and biochemical analyses in addition to investigation of TGF-β activation using primary cultured HSCs and liver sinusoidal ECs (LSECs). RESULTS: In addition to increased hepatic levels of CD31 expression, VEGF-treated mice showed increased α-smooth muscle actin (α-SMA) expression, hepatic contents of hydroxyproline, and latency associated protein degradation products, which reflects cell surface activation of TGF-β via plasma kallikrein (PLK). Liberating the PLK-urokinase plasminogen activator receptor complex from the HSC surface by cleaving a tethering phosphatidylinositol linker with its specific phospholipase C inhibited the activating latent TGF-β present in LSEC conditioned medium and subsequent HSC activation. CONCLUSION: Neovessel formation (angiogenesis) accelerates liver fibrosis at least in part via provision of latent TGF-β that activated on the surface of HSCs by PLK, thereby resultant active TGF-β stimulates the activation of HSCs.
Authors: Mitsuko Hara; Ikuyo Inoue; Yuta Yamazaki; Akiko Kirita; Tomokazu Matsuura; Scott L Friedman; Daniel B Rifkin; Soichi Kojima Journal: Fibrogenesis Tissue Repair Date: 2015-09-15