Nicotine and its metabolite cotinine are mitogenic for human vascular smooth muscle cells.
OBJECTIVE
Intimal hyperplasia caused by smooth muscle cell (SMC) proliferation is the major cause of infrainguinal graft failure within the first 12 months. Tobacco smoking is associated with a twofold increase in graft failure within the first year of extremity bypass surgery, but the mechanism is not clearly understood. This study evaluated the effect of nicotine and its major stable metabolite cotinine on vascular SMC proliferation in vitro.


METHODS
SMC were harvested from human arteries and grown in culture with standard methods. Cells were seeded at a density of 1.8 x 10(4) cells/well in 24 multiwell dishes and cell cycle-synchronized. Subsequently the SMC were incubated with media containing 0.1% or 15% fetal bovine serum and nicotine or cotinine at concentrations ranging from 10(-9) mol/L to 10(-6) mol/L. Control samples were incubated with corresponding media but without the drugs. SMC proliferation was determined at 4 days with a cell counter. DNA synthesis was assessed at 24 hours with 3H-thymidine uptake. The results were expressed as a percentage change compared with the control samples (mean +/- SEM). Results were analyzed by analysis of variance and t tests.


RESULTS
In the presence of serum both nicotine and cotinine at concentrations of 10(-7) and 10(-8) mol/L were mitogenic for SMC in vitro (p < 0.05). A weak mitogenic effect was observed at a low serum concentration for cotinine but not nicotine. Cotinine at a concentration of 10(-9) mol/L, a level seen among passive smokers, was a statistically significant stimulus for DNA synthesis in both minimum serum and serum-supplemented media. At high concentrations both substances were toxic for the cells.


CONCLUSIONS
We have demonstrated a potential role for nicotine and cotinine in the development of intimal hyperplasia and ultimately failure of the vascular reconstruction.
Carty
C S
CS
Department of Surgery, State University of New York at Buffalo, USA.
Huribal
M
M
Marsan
B U
BU
Ricotta
J J
JJ
Dryjski
M
M
D000704:Analysis of Variance; D000818:Animals; D001011:Aorta / Q000166:cytology; D002417:Cattle; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003367:Cotinine / Q000009:adverse effects*; D003470:Culture Media; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D005312:Fetal Blood; D006085:Graft Survival; D006801:Humans; D006965:Hyperplasia; D007083:Iliac Artery / Q000166:cytology; D008934:Mitogens / Q000009:adverse effects*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D009538:Nicotine / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D017539:Tunica Intima / Q000166:cytology / Q000187:drug effects; D014656:Vascular Surgical Procedures
D003470:Culture Media; D008934:Mitogens; D014316:Tritium; D009538:Nicotine; D004247:DNA; D003367:Cotinine; D013936:Thymidine