Selective clearance of macrophages in atherosclerotic plaques by the protein synthesis inhibitor cycloheximide.
Macrophages are an essential component of unstable atherosclerotic plaques and play a pivotal role in the destabilization process. We have demonstrated previously that local delivery of the mammalian target of rapamycin (mTOR) inhibitor everolimus selectively clears macrophages in rabbit plaques. Because mTOR controls mRNA translation, inhibition of protein synthesis might induce selective macrophage cell death. We therefore investigated in the present study the effect of the protein synthesis inhibitor cycloheximide on macrophage and smooth muscle cell (SMC) viability. In vitro studies with cultured macrophages and SMCs showed that cycloheximide induced selective apoptosis of macrophages in a concentration- and time-dependent manner. Moreover, macrophages could be selectively depleted in rabbit carotid artery rings with collar-induced atherosclerotic plaques after in vitro treatment with cycloheximide. Local in vivo administration of cycloheximide via osmotic minipumps to rabbit carotid arteries with collar-induced atherosclerotic plaques significantly reduced the macrophage but not the SMC content. Cycloheximide-treated plaques showed signs of apoptosis (increased terminal deoxynucleotidyl transferase end labeling and fluorescein isothiocyanate-Val-Ala-dl-Asp(O-methyl)-fluoromethylketone labeling) that did not colocalize with SMCs. Organ chamber studies demonstrated that the functionality of SMCs and the endothelium were not influenced by cycloheximide treatment. All together, these findings demonstrate that cycloheximide decreases the macrophage load in atherosclerotic plaques by induction of apoptosis without changing SMC content or contractility.
Croons
Valerie
V
Division of Pharmacology, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium.
Martinet
Wim
W
Herman
Arnold G
AG
Timmermans
Jean-Pierre
JP
De Meyer
Guido R Y
GR
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002340:Carotid Artery Diseases / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003513:Cycloheximide / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D007150:Immunohistochemistry; D007260:Infusion Pumps; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D032390:Myoblasts, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011500:Protein Synthesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D011817:Rabbits; D013997:Time Factors
D011500:Protein Synthesis Inhibitors; D003513:Cycloheximide