TGRL Lipolysis Products Induce Stress Protein ATF3 via the TGF-β Receptor Pathway in Human Aortic Endothelial Cells

• Published in: PloS one 2015-12, Vol.10 (12), p.e0145523-e0145523
• Main Authors: Eiselein, Larissa, Nyunt, Tun, Lamé, Michael W, Ng, Kit F, Wilson, Dennis W, Rutledge, John C, Aung, Hnin H
• Format: Article
• Language: English
• Subjects: Accumulation; Activating transcription factor 3; Activating Transcription Factor 3 - biosynthesis; Active Transport, Cell Nucleus; Activin; Animals; Aorta; Aorta - metabolism; Apoptosis; Atherosclerosis; c-Jun protein; Caspase; Caspase 3 - metabolism; Caspase-3; Cell cycle; Cells, Cultured; Cytosol; Endothelial cells; Endothelial Cells - metabolism; Gene expression; Gene regulation; Homocysteine; Humans; Inflammation; Inhibition; Internal medicine; Kinases; Lipolysis; Lipoproteins; Lipoproteins - genetics; Lipoproteins - metabolism; MAP kinase; Mice; Oxidative stress; p53 Protein; Phosphorylation; Physiology; Proteins; Receptors, Transforming Growth Factor beta - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; Signal Transduction; Signaling; Smad2 protein; Smad2 Protein - metabolism; Smad4 protein; Smad4 Protein - metabolism; Stress response; Stress, Physiological; Stresses; Studies; Transcription factors; Transforming Growth Factor beta1 - metabolism; Transforming growth factor-a; Transforming growth factor-b1; Translocation; Triglycerides; Triglycerides - genetics; Triglycerides - metabolism; Tumor necrosis factor-TNF; Tumor Suppressor Protein p53 - metabolism; Veterinary colleges; Veterinary medicine
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0145523

Studies have suggested a link between the transforming growth factor beta 1 (TGF-β1) signaling cascade and the stress-inducible activating transcription factor 3 (ATF3). We have demonstrated that triglyceride-rich lipoproteins (TGRL) lipolysis products activate MAP kinase stress associated JNK/c-Jun pathways resulting in up-regulation of ATF3, pro-inflammatory genes and induction of apoptosis in human aortic endothelial cells. Here we demonstrate increased release of active TGF-β at 15 min, phosphorylation of Smad2 and translocation of co-Smad4 from cytosol to nucleus after a 1.5 h treatment with lipolysis products. Activation and translocation of Smad2 and 4 was blocked by addition of SB431542 (10 μM), a specific inhibitor of TGF-β-activin receptor ALKs 4, 5, 7. Both ALK receptor inhibition and anti TGF-β1 antibody prevented lipolysis product induced up-regulation of ATF3 mRNA and protein. ALK inhibition prevented lipolysis product-induced nuclear accumulation of ATF3. ALKs 4, 5, 7 inhibition also prevented phosphorylation of c-Jun and TGRL lipolysis product-induced p53 and caspase-3 protein expression. These findings demonstrate that TGRL lipolysis products cause release of active TGF-β and lipolysis product-induced apoptosis is dependent on TGF-β signaling. Furthermore, signaling through the stress associated JNK/c-Jun pathway is dependent on TGF-β signaling suggesting that TGF-β signaling is necessary for nuclear accumulation of the ATF3/cJun transcription complex and induction of pro-inflammatory responses.