title: GPCR agonist-induced transactivation of the EGFR upregulates MLC II expression and promotes hypertension in insulin-resistant rats.
abstract: OBJECTIVE
  The presence of metabolic abnormalities such as insulin resistance and elevated levels of various vasoconstrictor G-protein-coupled receptor (GPCR) agonists contributes to the development of hypertension. Recent studies have suggested a link between disease progression and activation of growth factor receptor signalling pathways such as the epidermal growth factor receptor (EGFR) by matrix metalloproteinases (MMPs). We hypothesized that excessive stimulation of GPCRs such as alpha(1)-adrenergic receptors activates MMP-dependent EGFR transactivation and contributes to the development of hypertension by promoting increased synthesis of contractile proteins in vascular smooth muscle (VSM).
  
  
  RESULTS
  We tested this concept in experiments using insulin-resistant VSM cells (VSMCs) and fructose hypertensive rats (FHRs), a model of acquired systolic hypertension and insulin resistance. We found that insulin resistance and agonist stimulation increased the expression and activity of MMPs (MMP-2 and MMP-7), the EGFR, contractile proteins such as myosin light chain kinase and MLC II, and their transcriptional activators including P90 ribosomal kinase (P90RSK) and serum response factor, possibly via the activation of extracellular signal-regulated kinase (ERK1/2) in VSMCs. Further, in insulin-resistant VSMCs and arteries from FHRs, disruption of MMP-EGFR signalling either by a pharmacological or small interfering RNA approach normalized the increased expression and activity of contractile proteins and their transcriptional activators and prevented the development of hypertension in FHRs.
  
  
  CONCLUSIONS
  Our data suggest that the MMP-EGFR pathway could be a potential target in the treatment of hypertension in insulin resistance and/or hyperglycaemic conditions such as type 2 diabetes.
authors.affiliation: Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, BC, Canada, V6T 1Z3.
authors.forename: Prabhakara Reddy
authors.initials: PR
authors.lastname: Nagareddy
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: MacLeod
authors.forename: John H
authors.initials: JH
authors.lastname: McNeill
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D024722:Cardiac Myosins / Q000378:metabolism*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005632:Fructose; D006973:Hypertension / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D007333:Insulin Resistance; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology*; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D017208:Rats, Wistar; D020239:Receptor Cross-Talk; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation; D014661:Vasoconstriction / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists; D061965:Matrix Metalloproteinase Inhibitors; D018994:Myosin Light Chains; D011480:Protease Inhibitors; D047428:Protein Kinase Inhibitors; D018340:Receptors, Adrenergic, alpha-1; C107184:myosin light chain 2; D010656:Phenylephrine; D005632:Fructose; C483803:Egfr protein, rat; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020783:Matrix Metalloproteinase 7; D020778:Matrix Metalloproteinase 2; C522363:Mmp2 protein, rat; D024722:Cardiac Myosins