Thromboxane receptor activates the AMP-activated protein kinase in vascular smooth muscle cells via hydrogen peroxide.
Thromboxane A2 receptor (TPr) stimulation induces cellular hypertrophy in vascular smooth muscle cells (VSMCs); however, regulation of VSMC hypertrophy remains poorly understood. Here we show that TPr stimulation activates AMP-activated kinase (AMPK), which in turn limits TPr-induced protein synthesis in VSMCs. Exposure of cultured VSMCs to either TPr agonists, IBOP and U46619, or exogenous hydrogen peroxide (H2O2) caused time- and dose-dependent AMPK activation, as evidenced by increased phosphorylation of both AMPK-Thr172 and acetyl-coenzyme A carboxylase-Ser79, a downstream enzyme of AMPK, whereas SQ29548, a selective TPr antagonist, significantly attenuated TPr-enhanced AMPK activation. In parallel, both IBOP and U46619 significantly increased the production of reactive oxygen species such as H2O2. Furthermore, adenoviral overexpression of catalase (an H2O2 scavenger) abolished, whereas superoxide dismutase (which catalyzes H2O2 formation) enhanced, IBOP-induced AMPK activation, suggesting that TPr-activated AMPK was mediated by H2O2. Consistently, exposure of VSMCs to either TPr agonists or exogenous H2O2 dose-dependently increased the phosphorylation of LKB1 (at serines 428 and 307), an AMPK kinase, as well as coimmunoprecipitation of AMPK with LKB1. In addition, direct mutagenesis of either Ser428 or Ser307 of LKB1 into alanine, like the kinase-dead LKB1 mutant, abolished both TPr-stimulated AMPK activation and coimmunoprecipitation. Finally, genetic inhibition of AMPK significantly accentuated IBOP-enhanced protein synthesis, whereas adenoviral overexpression of constitutively active AMPK abolished IBOP-enhance protein synthesis in VSMCs. We conclude that TPr stimulation triggers reactive oxygen species-mediated LKB1-dependent AMPK activation, which in return inhibits cellular protein synthesis in VSMCs.
Division of Endocrinology and Diabetes, Department of Medicine, University of Oklahoma Health Science Center, 941 Stanton L. Young Blvd, Oklahoma City, OK 73104, USA.
Miao
M
Zhang
Yunzhou
Y
Dong
Jian
J
Xu
Zhonglin
Z
Xie
Yong
Y
Wu
Ping
P
Song
Melissa
M
Guzman
Jiliang
J
Wu
Ming-Hui
MH
Zou
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases; D000256:Adenoviridae; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006984:Hypertrophy; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000201:enzymology* / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D016877:Oxidants / Q000494:pharmacology; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000819:agonists* / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D014161:Transduction, Genetic; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D009097:Multienzyme Complexes; D016877:Oxidants; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D014662:Vasoconstrictor Agents; C061750:7-(3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo(2.2.1)heptan-2-yl)-5-heptenoic acid; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D017346:Protein Serine-Threonine Kinases; C488755:Stk11 protein, rat; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases