TGF‐β1 Expression in Human Aortic Smooth Muscle Cells (VSMC) is Down‐regulated when Exposed to Nicotine In Vitro for Six Days

Objective Previous work from this lab has shown that exposure to nicotine causes an immediate (3 hour) increase in expression of TGF‐β1. We hypothesized that chronic exposure of VSMC to free‐base nicotine in vitro would cause sustained up regulation of TGF‐β1. Methods VSMC grown in vitro were exposed to 10−6 M FBN for 24 (day 1), 72 (day 3), and 144 hours (day 6). Control cells were exposed to growth media without FBN. Expression TGF‐β1 was determined by immunocytochemistry and an intensity stain index was measured quantitatively using digital image analysis. Results After 24 hour exposure to FBN, TGF‐β1 was down regulated when compared to control (132± 7.35 vs. 152± 5.31, p=.03). After 72, and 144 hours exposure, the decrease in expression of TGF‐β1, when compared to the 24 hours, continues and is significant, (114.4 ± 6.8 vs.132.8 ± 7.35, p=.05) and (95.2±3.9 vs. 132.8 ± 7.35, p=.004) Conclusion Although exposure of VSMC's to nicotine causes an acute increase of TGf‐β1, the long‐term impact is down regulation of TGF‐β1 expression. These observations imply that TGF‐β1 is only involved in the acute phase of the inflammatory response to nicotine.