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The proinflammatory LTB4/BLT1 signal axis confers resistance to TGF-?1-induced growth inhibition by targeting Smad3 linker region.

ABSTRACT: Leukotriene B4 (LTB4) is a potent pro-inflammatory eicosanoid that is derived from arachidonic acid, and its signaling is known to have a tumor-promoting role in several cancer types. In this study, we investigated whether enhanced LTB4 signaling confers resistance to the cytostatic transforming growth factor-?1 (TGF-?1) response. We found that LTB4 pretreatment or ectopic expression of BLT1, a high affinity LTB4 receptor, fully abrogated TGF-?1-induced cell cycle arrest and expression of p15INK4B and p27KIP1. Mechanism study revealed that LTB4-mediated suppression of TGF-?1-induced Smad3 activation and growth inhibition was due to enhanced phosphorylation of Smad3 linker region (pSmad3L) through activation of BLT1-NAD(P)H oxidase (NOX)-reactive oxygen species (ROS)-epidermal growth factor receptor (EGFR)-phosphatidylinositol 3-kinase (PI3-K)-extracellular signal-activated kinase1/2 (ERK1/2)-linked signaling cascade. Furthermore, the LTB4/BLT1 signaling pathway leading to pSmad3L was constitutively activated in breast cancer cells and was correlated with TGF-?1-resistant growth of the cells in vitro and in vivo. In human breast cancer tissues, the expression level of pSmad3L (Thr179) had a positive correlation with BLT1 expression. Collectively, our data demonstrate for the first time that the induction of pSmad3L through BLT1-NOX-ROS-EGFR-PI3K-ERK1/2 signaling pathway is a key mechanism by which LTB4 blocks the anti-proliferative responses of TGF-?1, providing a novel mechanistic insight into the connection between enhanced inflammatory signal and cancer cell growth.

SUBMITTER: Jeon WK

PROVIDER: S-EPMC4747179 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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The proinflammatory LTB4/BLT1 signal axis confers resistance to TGF-β1-induced growth inhibition by targeting Smad3 linker region.

Jeon Woo-Kwang WK Choi Jiyeon J Park Seong Ji SJ Jo Eun Ji EJ Lee Young K YK Lim Seunghwan S Kim Jae-Hong JH Letterio John J JJ Liu Fang F Kim Seong-Jin SJ Kim Byung-Chul BC

Oncotarget 20151201 39

Leukotriene B4 (LTB4) is a potent pro-inflammatory eicosanoid that is derived from arachidonic acid, and its signaling is known to have a tumor-promoting role in several cancer types. In this study, we investigated whether enhanced LTB4 signaling confers resistance to the cytostatic transforming growth factor-β1 (TGF-β1) response. We found that LTB4 pretreatment or ectopic expression of BLT1, a high affinity LTB4 receptor, fully abrogated TGF-β1-induced cell cycle arrest and expression of p15INK ...[more]

PMID: 26497676

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Project description:AIM:To study the molecular mechanisms involved in the hepatoprotective effects of naringenin (NAR) on carbon tetrachloride (CCl4)-induced liver fibrosis. METHODS:Thirty-two male Wistar rats (120-150 g) were randomly divided into four groups: (1) a control group (n = 8) that received 0.7% carboxy methyl-cellulose (NAR vehicle) 1 mL/daily p.o.; (2) a CCl4 group (n = 8) that received 400 mg of CCl4/kg body weight i.p. 3 times a week for 8 wk; (3) a CCl4 + NAR (n = 8) group that received 400 mg of CCl4/kg body weight i.p. 3 times a week for 8 wk and 100 mg of NAR/kg body weight daily for 8 wk p.o.; and (4) an NAR group (n = 8) that received 100 mg of NAR/kg body weight daily for 8 wk p.o. After the experimental period, animals were sacrificed under ketamine and xylazine anesthesia. Liver damage markers such as alanine aminotransferase (ALT), alkaline phosphatase (AP), ?-glutamyl transpeptidase (?-GTP), reduced glutathione (GSH), glycogen content, lipid peroxidation (LPO) and collagen content were measured. The enzymatic activity of glutathione peroxidase (GPx) was assessed. Liver histopathology was performed utilizing Masson's trichrome and hematoxylin-eosin stains. Zymography assays for MMP-9 and MMP-2 were carried out. Hepatic TGF-?, ?-SMA, CTGF, Col-I, MMP-13, NF-?B, IL-1, IL-10, Smad7, Smad3, pSmad3 and pJNK proteins were detected via western blot. RESULTS:NAR administration prevented increases in ALT, AP, ?-GTP, and GPx enzymatic activity; depletion of GSH and glycogen; and increases in LPO and collagen produced by chronic CCl4 intoxication (P < 0.05). Liver histopathology showed a decrease in collagen deposition when rats received NAR in addition to CCl4. Although zymography assays showed that CCl4 produced an increase in MMP-9 and MMP-2 gelatinase activity; interestingly, NAR administration was associated with normal MMP-9 and MMP-2 activity (P < 0.05). The anti-inflammatory, antinecrotic and antifibrotic effects of NAR may be attributed to its ability to prevent NF-?B activation and the subsequent production of IL-1 and IL-10 (P < 0.05). NAR completely prevented the increase in TGF-?, ?-SMA, CTGF, Col-1, and MMP-13 proteins compared with the CCl4-treated group (P < 0.05). NAR prevented Smad3 phosphorylation in the linker region by JNK since this flavonoid blocked this kinase (P < 0.05). CONCLUSION:NAR prevents CCl4 induced liver inflammation, necrosis and fibrosis, due to its antioxidant capacity as a free radical inhibitor and by inhibiting the NF-?B, TGF-?-Smad3 and JNK-Smad3 pathways.

Dataset Information

The proinflammatory LTB4/BLT1 signal axis confers resistance to TGF-?1-induced growth inhibition by targeting Smad3 linker region.

Publications

The proinflammatory LTB4/BLT1 signal axis confers resistance to TGF-β1-induced growth inhibition by targeting Smad3 linker region.

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