title: Native and reconstituted HDL activate Stat3 in ventricular cardiomyocytes via ERK1/2: role of sphingosine-1-phosphate.
abstract: OBJECTIVE
  High-density lipoprotein (HDL) has been reported to have cardioprotective properties independent from its cholesterol transport activity. The influence of native HDL and reconstituted HDL (rHDL) on Stat3, the transcription factor playing an important role in myocardium adaptation to stress, was analysed in neonatal rat ventricular cardiomyocytes. We have investigated modulating the composition of rHDL as a means of expanding its function and potential cardioprotective effects.
  
  
  RESULTS
  Stat3 phosphorylation and activation were determined by western blotting and electrophoretic mobility shift assay (EMSA). In ventricular cardiomyocytes, HDL and the HDL constituent sphingosine-1-phosphate (S1P) induce a concentration- and time-dependent increase in Stat3 activation. They also enhance extracellular signal-regulated kinases (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) phosphorylation. U0126, a specific inhibitor of MEK1/2, the upstream activator of ERK1/2, abolishes HDL- and S1P-induced Stat3 activation, whereas the p38 MAPK blocker SB203580 has no significant effect. Inhibition of the tyrosine kinase family Src (Src) caused a significant reduction of Stat3 activation, whereas inhibition of phosphatidylinositol 3-kinase (PI3K) had no effect. S1P and rHDL containing S1P have a similar strong stimulatory action on Stat3, ERK1/2, and p38 MAPK comparable to native HDL. S1P-free rHDL has a much weaker effect. Experiments with agonists and antagonists of the S1P receptor subtypes indicate that HDL and S1P activate Stat3 mainly through the S1P2 receptor.
  
  
  CONCLUSIONS
  In ventricular cardiomyocytes, addition of S1P to rHDL enhances its therapeutic potential by improving its capacity to activate Stat3. Activation of Stat3 occurs mainly via the S1P constituent and the lipid receptor S1P2 requiring stimulation of ERK1/2 and Src but not p38 MAPK or PI3K. The study underlines the therapeutic potential of tailoring rHDL to confront particular clinical situations.
authors.affiliation: Division of Endocrinology, Diabetology and Nutrition, University Hospital, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland. miguel.frias@unige.ch
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Frias
authors.forename: Richard W
authors.initials: RW
authors.lastname: James
authors.forename: Christine
authors.initials: C
authors.lastname: Gerber-Wicht
authors.forename: Ursula
authors.initials: U
authors.lastname: Lang
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000494:pharmacology*; D008246:Lysophospholipids / Q000378:metabolism* / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D049349:Receptors, Lysosphingolipid / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D008075:Lipoproteins, HDL; D008246:Lysophospholipids; D049349:Receptors, Lysosphingolipid; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; C060506:sphingosine 1-phosphate; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D013110:Sphingosine