title: Oxysterol-induced apoptosis of smooth muscle cells is under the control of a soluble adenylyl cyclase.
abstract: OBJECTIVE
  Apoptosis of vascular smooth muscle cells (VSMC) in advanced atherosclerotic plaques is an important cause of plaque instability. Oxysterols have been suggested as important inducers of apoptosis in VSMC, but the precise mechanism is still poorly understood. Here we aimed to analyse the role of the soluble adenylyl cyclase (sAC).
  
  
  RESULTS
  VSMC derived from rat aorta were treated with either 25-hydroxycholesterol or 7-ketocholesterol for 24 h. Apoptosis was detected by TUNEL staining and caspases cleavage. Oxysterols treatment led to the activation of the mitochondrial pathway of apoptosis (cytochrome c release and caspase-9 cleavage) and mitochondrial ROS formation, which were suppressed by the pharmacological inhibition or knockdown of sAC. Scavenging ROS with N-acetyl-l-cysteine prevented oxysterol-induced apoptosis. Analyses of the downstream pathway suggest that protein kinase A (PKA)-dependent phosphorylation and the mitochondrial translocation of the pro-apoptotic protein Bax is a key link between sAC and oxysterol-induced ROS formation and apoptosis. To distinguish between intra-mitochondrial and extra-mitochondrial/cytosolic sAC pools, sAC was overexpressed in mitochondria or in the cytosol. sAC expression in the cytosol, but not in mitochondria, significantly promoted apoptosis and ROS formation during oxysterol treatment.
  
  
  CONCLUSIONS
  These results suggest that the sAC/PKA axis plays a key role in the oxysterol-induced apoptosis of VSMC by controlling mitochondrial Bax translocation and ROS formation and that cytosolic sAC, rather than the mitochondrial pool, is involved in the apoptotic mechanism.
authors.affiliation: Department of Clinical Pharmacology, Ruhr-University Bochum, Germany.
authors.forename: Avinash
authors.initials: A
authors.lastname: Appukuttan
authors.forename: Sascha Andreas
authors.initials: SA
authors.lastname: Kasseckert
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Kumar
authors.forename: H Peter
authors.initials: HP
authors.lastname: Reusch
authors.forename: Yury
authors.initials: Y
authors.lastname: Ladilov
mesh_terms: D000262:Adenylyl Cyclases / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D006888:Hydroxycholesterols / Q000494:pharmacology*; D007653:Ketocholesterols / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000502:physiology
chemical_list: C494828:Bax protein, rat; D006888:Hydroxycholesterols; D007653:Ketocholesterols; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; C007997:25-hydroxycholesterol; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; C003001:7-ketocholesterol
keywords: Apoptosis; Bax; Oxysterol; Protein kinase A; Soluble adenylyl cyclase