Protection of human vascular smooth muscle cells from H2O2-induced apoptosis through functional codependence between HO-1 and AKT.
OBJECTIVE
Oxidative stress (OS) induces smooth muscle cell apoptosis in the atherosclerotic plaque, leading to plaque instability and rupture. Heme oxygenase-1 (HO-1) exerts cytoprotective effects in the vessel wall. Recent evidence suggests that PKB/Akt may modulate HO-1 activity. This study examined the role of Akt in mediating the cytoprotective effects of HO-1 in OS-induced apoptosis of human aortic smooth muscle cells (HASMCs).


RESULTS
HASMCs were transduced with retroviral vectors expressing HO-1, Akt, or GFP and exposed to H2O2. Cell viability was assessed by MTT assay. OS was determined by CM-H2DCFDA fluorescence, and apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), caspase-3 activity, and Bcl-2/Bad levels. Mitochondrial membrane potential (delta psi(m)) was assessed by fluorescence-activated cell sorter (FACS) using JC-1. HO-1 reduced H2O2-induced OS and apoptosis. Akt knockdown removed the protective effect of HO-1 on delta psi(m) during exposure to H2O2. Conversely, HO-1 knockdown removed the protective effect of Akt on delta psi(m). Inhibition of PI3K-Akt reduced induction of HO-1 protein expression by H2O2 and blocked its anti-apoptotic effects. The Akt-mediated upregulation of HO-1 was dependent on activation of HO-1 promoter by Nrf2.


CONCLUSIONS
HO-1 and Akt exert codependent cytoprotective effects against OS-induced apoptosis in HASMCs. These findings may have implications for the design of novel therapeutic strategies for plaque stabilization.
Brunt
Keith R
KR
Department of Physiology, Queen's University, 18 Stuart St, Kingston, Ontario, K7L 4S7. Canada.
Fenrich
Keith K
KK
Kiani
Gholam
G
Tse
M Yat
MY
Pang
Stephen C
SC
Ward
Christopher A
CA
Melo
Luis G
LG
D017209:Apoptosis / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D019610:Cytoprotection / Q000502:physiology; D051547:Heme Oxygenase-1 / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology*; D018384:Oxidative Stress; D011506:Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*
D051267:NF-E2-Related Factor 2; D016877:Oxidants; D011506:Proteins; D006861:Hydrogen Peroxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D051057:Proto-Oncogene Proteins c-akt