Objectives: It is well known that smoking is a major risk factor in the development of periodontal diseases. In addition, an association between reduced healing response subsequent to periodontal therapies and cigarette smoking has been found. In the current study, we asked what signaling pathways are affected by nicotine during human gingival cell migration. Methods: Human gingival cells from healthy tissues were cultured and grown to confluence in cell culture medium (low glucose DMEM, 10% fetal bovine serum, 1% antimycotic/antibiotic). Cells were starved for 24 hours without serum, and then treated with nicotine (0 or 0.5 µM) right before in vitro wounding. To analyze cell migration, wound areas were measured at different time points. For cell polarity analysis, the cells were fixed and immunolabeled with antibodies specific for the Golgi apparatus. The percentage of cells having polarity, as defined by the position of the Golgi, was measured 0, 1, 2 and 3 hours after wounding with or without nicotine treatment. Rac activity was assessed in confluent cultures (6 cm dishes) following multiple wounds in the presence or absence of nicotine. Rac activity and phosphorylation level of p21-activated kinase 1/2 (PAK1/2) were assessed at various time points after wounding. Results: Nicotine treated cells had slower wound closure rates than control cells. Compared to controls, nicotine treatment changed the activation pattern of Rac and PAK1/2. However, the cell polarity was not changed by nicotine. Conclusions: Our results demonstrate that nicotine inhibits human gingival cell migration and affects the activation of Rac and PAK1/2.
Cite grants: Texas A&M University System Health Science Center, Tobacco Endowment Fund, NIH EY-08886