Probucol protects against smooth muscle cell proliferation by upregulating heme oxygenase-1.
BACKGROUND
Evidence suggests that induction of heme oxygenase-1 (HO-1) inhibits proliferation of vascular smooth muscle cells and intimal thickening after arterial injury, and therapeutic molecules induce HO-1. Probucol is the only oral drug that inhibits restenosis in humans and intimal thickening in animals, although its underlying mechanism remains unclear.


RESULTS
Aortas were harvested from New Zealand White rabbits fed normal or 0.75% (wt/wt) probucol-fortified chow, with or without endothelial denudation of the abdominal aorta on day 21, and analyzed for heme oxygenase and apoptosis. Uninjured aortas were harvested on day 21 and balloon-injured aortas on days 22 and 25. Probucol significantly increased mRNA of HO-1 assessed by real-time PCR and HO activity in aortas at all time points. Probucol also enhanced apoptosis of medial cells in the injured aorta, as evidenced by the TUNEL assay. Furthermore, probucol (100 micromol/L) increased HO-1 mRNA and HO activity when added to rabbit aortic smooth muscle cells (RASMCs) cultured in serum-free medium for 24 hours. Induction of HO-1 mRNA was inhibited by actinomycin D and was associated with inhibition of RASMC proliferation. This probucol-induced increase in HO-1 mRNA and inhibition of RASMC proliferation was prevented by the HO inhibitor Sn(IV) protoporphyrin or transfection with small interference RNA (siRNA) to knockdown HO-1, but not by inactive Cu(II) protoporphyrin or scrambled siRNA.


CONCLUSIONS
Probucol induces HO-1, and this contributes to the inhibition of vascular SMC proliferation. This novel finding may explain how probucol inhibits restenosis and highlights HO-1 as a target for therapeutic intervention against occlusive vascular disease.
Deng
Yi-Mo
YM
Centre for Vascular Research, University of New South Wales, and the Department of Haematology, Prince of Wales Hospital, Sydney. Australia.
Wu
Ben J
BJ
Witting
Paul K
PK
Stocker
Roland
R
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology / Q000627:therapeutic use; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use; D001012:Aorta, Abdominal / Q000201:enzymology / Q000293:injuries / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects; D001161:Arteriosclerosis / Q000517:prevention & control; D002404:Catheterization / Q000009:adverse effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D004790:Enzyme Induction / Q000187:drug effects; D018390:Gene Targeting; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D051547:Heme Oxygenase-1; D006984:Hypertrophy; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D011341:Probucol / Q000494:pharmacology / Q000627:therapeutic use*; D011524:Protoporphyrins / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000494:pharmacology; D011817:Rabbits; D011897:Random Allocation; D014162:Transfection; D017539:Tunica Intima / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure
D000924:Anticholesteremic Agents; D000975:Antioxidants; D011524:Protoporphyrins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C092553:copper protoporphyrin IX; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D011341:Probucol