title: Heme oxygenase-1 does not mediate the effects of extracellular acidosis on vascular smooth muscle cell proliferation, migration, and susceptibility to apoptosis.
abstract: BACKGROUND
  Unbalanced vascular smooth muscle cell (VSMC) proliferation, migration, and apoptosis contribute to vascular disorders such as atherosclerosis, restenosis, and pulmonary hypertension. The effect of extracellular acidosis (EA) on VSMC homeostasis is incompletely understood but we previously reported that EA increases heme oxygenase-1 (HO-1) expression in VSMCs. Since HO-1 regulates VSMC proliferation and apoptosis we sought to define the role of HO-1 in VSMC responses to EA.
  
  
  METHODS
  Mouse aortic smooth muscle cells (MASMCs) were isolated from wild-type and HO-1-null mice. Cell proliferation and migration assays were done in a physiologic pH (7.4) or EA (pH 6.8). VSMC apoptosis in response to hydrogen peroxide was assessed by JC-1 staining, caspase-3 cleavage, annexin V, and Hoechst staining.
  
  
  RESULTS
  Wild-type MASMCs showed decreased proliferation and migration at pH 6.8 compared to pH 7.4. This observation was also true in HO-1-null MASMCs. Although wild-type and HO-1-null cells showed differences in the mode and kinetics of cell death, both genotypes exhibited increased susceptibility to hydrogen peroxide-induced apoptosis at pH 6.8 compared to 7.4.
  
  
  CONCLUSIONS
  EA inhibits VSMC proliferation and migration and increases susceptibility to oxidant-induced apoptosis. These effects of acidosis on VSMC homeostasis are independent of HO-1.
authors.affiliation: Division of Newborn Medicine, Brigham and Women's and Children's Hospitals and Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Lineke
authors.initials: L
authors.lastname: Brenninkmeijer
authors.forename: Constantin
authors.initials: C
authors.lastname: Kuehl
authors.forename: Adriana Miele
authors.initials: AM
authors.lastname: Geldart
authors.forename: Elena
authors.initials: E
authors.lastname: Arons
authors.forename: Helen
authors.initials: H
authors.lastname: Christou
mesh_terms: D000138:Acidosis / Q000201:enzymology / Q000473:pathology*; D000818:Animals; D017209:Apoptosis; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D051547:Heme Oxygenase-1 / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000633:toxicity; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*
chemical_list: D008565:Membrane Proteins; D006861:Hydrogen Peroxide; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse