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Title: Fenofibrate activates AMPK and increases eNOS phosphorylation in HUVEC

Abstract

Fenofibrate improves endothelial function by lipid-lowering and anti-inflammatory effects. Additionally, fenofibrate has been demonstrated to upregulate endothelial nitric oxide synthase (eNOS). AMP-activated protein kinase (AMPK) has been reported to phosphorylate eNOS at Ser-1177 and stimulate vascular endothelium-derived nitric oxide (NO) production. We report here that fenofibrate activates AMPK and increases eNOS phosphorylation and NO production in human umbilical vein endothelial cells (HUVEC). Incubation of HUVEC with fenofibrate increased the phosphorylation of AMPK and acetyl-CoA carboxylase. Fenofibrate simultaneously increased eNOS phosphorylation and NO production. Inhibitors of protein kinase A and phosphatidylinositol 3-kinase failed to suppress the fenofibrate-induced eNOS phosphorylation. Neither bezafibrate nor WY-14643 activated AMPK in HUVEC. Furthermore, fenofibrate activated AMPK without requiring any transcriptional activities. These results indicate that fenofibrate stimulates eNOS phosphorylation and NO production through AMPK activation, which is suggested to be a novel characteristic of this agonist and unrelated to its effects on peroxisome proliferator-activated receptor {alpha}.

Authors:
 [1];  [2];  [3];  [3];  [1];  [1];  [1];  [1];  [1];  [3];  [1]
  1. Department of Cardiology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-8550 (Japan)
  2. Department of Cardiology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-8550 (Japan). E-mail: ryuichi@med.nagoya-u.ac.jp
  3. Department of Endocrinology and Metabolism, Division of Molecular and Cellular Adaptation, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)
Publication Date:
OSTI Identifier:
20798850
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 341; Journal Issue: 4; Other Information: DOI: 10.1016/j.bbrc.2006.01.052; PII: S0006-291X(06)00131-8; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; AMP; CARBOXYLASE; ENDOTHELIUM; INCUBATION; INFLAMMATION; LIPIDS; NITRIC OXIDE; PHOSPHORYLATION; RECEPTORS; VEINS

Citation Formats

Murakami, Hisashi, Murakami, Ryuichiro, Kambe, Fukushi, Cao, Xia, Takahashi, Ryotaro, Asai, Toru, Hirai, Toshihisa, Numaguchi, Yasushi, Okumura, Kenji, Seo, Hisao, and Murohara, Toyoaki. Fenofibrate activates AMPK and increases eNOS phosphorylation in HUVEC. United States: N. p., 2006. Web. doi:10.1016/j.bbrc.2006.01.052.
Murakami, Hisashi, Murakami, Ryuichiro, Kambe, Fukushi, Cao, Xia, Takahashi, Ryotaro, Asai, Toru, Hirai, Toshihisa, Numaguchi, Yasushi, Okumura, Kenji, Seo, Hisao, & Murohara, Toyoaki. Fenofibrate activates AMPK and increases eNOS phosphorylation in HUVEC. United States. doi:10.1016/j.bbrc.2006.01.052.
Murakami, Hisashi, Murakami, Ryuichiro, Kambe, Fukushi, Cao, Xia, Takahashi, Ryotaro, Asai, Toru, Hirai, Toshihisa, Numaguchi, Yasushi, Okumura, Kenji, Seo, Hisao, and Murohara, Toyoaki. Fri . "Fenofibrate activates AMPK and increases eNOS phosphorylation in HUVEC". United States. doi:10.1016/j.bbrc.2006.01.052.
@article{osti_20798850,
title = {Fenofibrate activates AMPK and increases eNOS phosphorylation in HUVEC},
author = {Murakami, Hisashi and Murakami, Ryuichiro and Kambe, Fukushi and Cao, Xia and Takahashi, Ryotaro and Asai, Toru and Hirai, Toshihisa and Numaguchi, Yasushi and Okumura, Kenji and Seo, Hisao and Murohara, Toyoaki},
abstractNote = {Fenofibrate improves endothelial function by lipid-lowering and anti-inflammatory effects. Additionally, fenofibrate has been demonstrated to upregulate endothelial nitric oxide synthase (eNOS). AMP-activated protein kinase (AMPK) has been reported to phosphorylate eNOS at Ser-1177 and stimulate vascular endothelium-derived nitric oxide (NO) production. We report here that fenofibrate activates AMPK and increases eNOS phosphorylation and NO production in human umbilical vein endothelial cells (HUVEC). Incubation of HUVEC with fenofibrate increased the phosphorylation of AMPK and acetyl-CoA carboxylase. Fenofibrate simultaneously increased eNOS phosphorylation and NO production. Inhibitors of protein kinase A and phosphatidylinositol 3-kinase failed to suppress the fenofibrate-induced eNOS phosphorylation. Neither bezafibrate nor WY-14643 activated AMPK in HUVEC. Furthermore, fenofibrate activated AMPK without requiring any transcriptional activities. These results indicate that fenofibrate stimulates eNOS phosphorylation and NO production through AMPK activation, which is suggested to be a novel characteristic of this agonist and unrelated to its effects on peroxisome proliferator-activated receptor {alpha}.},
doi = {10.1016/j.bbrc.2006.01.052},
journal = {Biochemical and Biophysical Research Communications},
number = 4,
volume = 341,
place = {United States},
year = {Fri Mar 24 00:00:00 EST 2006},
month = {Fri Mar 24 00:00:00 EST 2006}
}
  • Research highlights: {yields} Low-concentration oxidized LDL enhances angiogenesis through nitric oxide (NO). {yields} Oxidized LDL increases intracellular NO levels via eNOS phosphorylation. {yields} Akt/PI3K signaling mediates oxidized LDL-induced eNOS phosphorylation. -- Abstract: It has long been considered that oxidized low-density lipoprotein (oxLDL) causes endothelial dysfunction and is remarkably related to the development of atherosclerosis. However, the effect of oxLDL at very low concentration (<10 {mu}g/ml) on the endothelial cells remains speculative. Nitric oxide (NO) has a crucial role in the endothelial cell function. In this study, we investigated the effect of oxLDL at low concentration on NO production and proliferation,more » migration, tube formation of the human coronary artery endothelial cells (HCAEC). Results showed that oxLDL at 5 {mu}g/ml enhanced HCAEC proliferation, migration and tube formation. These phenomena were accompanied by an increased intracellular NO production. L-NAME (a NOS inhibitor), LY294002 and wortmannin (PI3K inhibitors) could abolish oxLDL-induced angiogenic effects and prevent NO production in the HCAEC. The phosphorylation of Akt, PI3K and eNOS were up-regulated by oxLDL, which was attenuated by LY294002. Our results suggested that oxLDL at low concentration could promote in-vitro angiogenesis and activate nitric oxide synthesis through PI3K/Akt/eNOS pathway in HCAEC.« less
  • Peroxisome proliferator-activated receptor α (PPARα) activates the β-oxidation of fatty acids in the liver. Fenofibrate is a potent agonist of PPARα and is used in the treatment of hyperlipidemia. Fenofibrate treatment often induces the production of intracellular reactive oxygen species (ROS), leading to cell death. The nuclear factor erythroid 2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) pathway is an essential component of the defense mechanism against oxidative stress. However, the molecular mechanism underlying the regulation of the Nrf2-Keap1 pathway in fenofibrate-induced cell death is not known. In this study, we demonstrated that fenofibrate induces Keap1 degradation and Nrf2 activation.more » This fenofibrate-mediated Keap1 degradation is partly dependent on autophagy. Furthermore, fenofibrate-induced Keap1 degradation followed by Nrf2 activation is mainly mediated by p62, which functions as an adaptor protein in the autophagic pathway. Consistent with these findings, ablation of p62 increased fenofibrate-mediated apoptotic cell death associated with ROS accumulation. These results strongly suggest that p62 plays a crucial role in preventing fenofibrate-induced cell death. - Highlights: • Fenofibrate induces cell death by increasing ROS production. • The underlying defense mechanism against this effect is unknown. • Fenofibrate induces autophagy-dependent Keap1 degradation and Nrf2 activation. • This process is p62-dependent; lack of p62 enhanced fenofibrate-mediated apoptosis. • p62 plays a crucial role in preventing fenofibrate-induced cell death.« less
  • Purpose: Adenosine monophosphate (AMP)-activated kinase (AMPK) is a molecular energy sensor regulated by the tumor suppressor LKB1. Starvation and growth factors activate AMPK through the DNA damage sensor ataxia-telangiectasia mutated (ATM). We explored the regulation of AMPK by ionizing radiation (IR) and its role as a target for radiosensitization of human cancer cells. Methods and Materials: Lung, prostate, and breast cancer cells were treated with IR (2-8 Gy) after incubation with either ATM or AMPK inhibitors or the AMPK activator metformin. Then, cells were subjected to either lysis and immunoblotting, immunofluorescence microscopy, clonogenic survival assays, or cell cycle analysis. Results:more » IR induced a robust phosphorylation and activation of AMPK in all tumor cells, independent of LKB1. IR activated AMPK first in the nucleus, and this extended later into cytoplasm. The ATM inhibitor KU-55933 blocked IR activation of AMPK. AMPK inhibition with Compound C or anti-AMPK {alpha} subunit small interfering RNA (siRNA) blocked IR induction of the cell cycle regulators p53 and p21{sup waf/cip} as well as the IR-induced G2/M arrest. Compound C caused resistance to IR, increasing the surviving fraction after 2 Gy, but the anti-diabetic drug metformin enhanced IR activation of AMPK and lowered the surviving fraction after 2 Gy further. Conclusions: We provide evidence that IR activates AMPK in human cancer cells in an LKB1-independent manner, leading to induction of p21{sup waf/cip} and regulation of the cell cycle and survival. AMPK appears to (1) participate in an ATM-AMPK-p21{sup waf/cip} pathway, (2) be involved in regulation of the IR-induced G2/M checkpoint, and (3) may be targeted by metformin to enhance IR responses.« less
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  • Honokiol is a bioactive neolignan compound isolated from the species of Magnolia. This study was designed to elucidate the cellular mechanism by which honokiol alleviates the development of non-alcoholic steatosis. HepG2 cells were treated with honokiol for 1 h, and then exposed to 1 mM free fatty acid (FFA) for 24 h to simulate non-alcoholic steatosis in vitro. C57BL/6 mice were fed with a high-fat diet for 28 days, and honokiol (10 mg/kg/day) was daily treated. Honokiol concentration-dependently attenuated intracellular fat overloading and triglyceride (TG) accumulation in FFA-exposed HepG2 cells. These effects were blocked by pretreatment with an AMP-activated proteinmore » kinase (AMPK) inhibitor. Honokiol significantly inhibited sterol regulatory element-binding protein-1c (SREBP-1c) maturation and the induction of lipogenic proteins, stearoyl-CoA desaturase-1 (SCD-1) and fatty acid synthase (FAS) in FFA-exposed HepG2 cells, but these effects were blocked by pretreatment of an AMPK inhibitor. Honokiol induced AMPK phosphorylation and subsequent acetyl-CoA carboxylase (ACC) phosphorylation, which were inhibited by genetic deletion of liver kinase B1 (LKB1). Honokiol stimulated LKB1 phosphorylation, and genetic deletion of LKB1 blocked the effect of honokiol on SREBP-1c maturation and the induction of SCD-1 and FAS proteins in FFA-exposed HepG2 cells. Honokiol attenuated the increases in hepatic TG and lipogenic protein levels and fat accumulation in the mice fed with high-fat diet, while significantly induced LKB1 and AMPK phosphorylation. Taken together, our findings suggest that honokiol has an anti-lipogenic effect in hepatocytes, and this effect may be mediated by the LKB1–AMPK signaling pathway, which induces ACC phosphorylation and inhibits SREBP-1c maturation in hepatocytes. - Highlights: • Honokiol attenuates lipid accumulation induced by free fatty acid in hepatocyte. • Honokiol inhibits the increase in lipogenic enzyme levels induced by free fatty acid. • Honokiol induces the phosphorylation of AMPK and ACC and inhibits SREBP-1c maturation. • LKB1–AMPK signaling pathway mediates anti-lipogenic effect of honokiol in hepatocyte. • Honokiol activates LKB1 and AMPK and inhibits nonalcoholic steatosis in HFD-fed mice.« less