Nicotine and smokeless tobacco effects on gingival and peripheral blood mononuclear cells

The pathogenesis of tobacco-related periodontal diseases is not well understood. The purpose of this study was therefore to investigate smokeless tobacco extract (ST) and nicotine effects on prostaglandin E-2 (PGE(2)) and interleukin-1 beta (IL-1 beta) secretion by peripheral blood mononuclear cells (PBMC, consisting of monocytes and lymphocytes) and gingival mononuclear cells (GMC). Both peripheral blood and gingival tissue adjacent to the alveolar crest were taken from non-smoking adult periodontitis patients. Gingival tissue was treated with collagenase and deoxyribonuclease and GMC and PBMC were isolated by Ficoll-Hypaque centrifugation. GMC and PBMC (100,000 cells/200 mu l) were cultured for 24 hours in supplemented RPMI 1640 alone (control), or in supplemented RPMI 1640 containing 1% ST, 100 mu g/ml nicotine, 1 mu g/ml Porphyromonas gingivalis LPS, or 1 mu g/ml P. gingivalis LPS and either 100 mu g/ml nicotine or 1% ST. Enzyme immunoassays were used to quantify PGE(2) and IL-1 beta. Treatments were compared by repeated measures ANOVA. 100 mu g/ml nicotine (7-fold, p<0.02) and 1% ST (3.5-fold, p<0.004) significantly increased secretion of PGE(2) by PBMC relative to control cultures. 100 mu g/ml nicotine and 1% ST, however, had no effect on IL-1 beta secretion by PBMC. Enhanced PGE(2) secretion also was seen when PBMC were treated with P. gingivalis LPS + 100 mu g/ml nicotine relative to P. gingivalis LPS alone (p<0.007). In contrast, 100 mu g/ml nicotine significantly downregulated IL-1 beta secretion by GMC relative to medium alone (p<0.008) and had no effect on PGE(2) secretion by GMC. These data indicate that while nicotine and ST can stimulate PBMC to secrete PGE(2), they cannot activate further mononuclear cells extracted from gingiva, possibly due to maximal previous stimulation in the periodontitis lesion.