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 E2 (PGE2) and interleukin-1beta (IL-1beta) 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 microl) were cultured for 24 hours in supplemented RPMI 1640 alone (control), or in supplemented RPMI 1640 containing 1% ST, 100 microg/ml nicotine, 1 microg/ml Porphyromonas gingivalis LPS, or 1 microg/ml P. gingivalis LPS and either 100 microg/ml nicotine or 1% ST. Enzyme immunoassays were used to quantify PGE2 and IL-1beta. Treatments were compared by repeated measures ANOVA. 100 microg/ml nicotine (7-fold, p<0.02) and 1% ST (3.5-fold, p<0.004) significantly increased secretion of PGE2 by PBMC relative to control cultures. 100 microg/ml nicotine and 1% ST, however, had no effect on IL-1beta secretion by PBMC. Enhanced PGE2 secretion also was seen when PBMC were treated with P. gingivalis LPS+ 100 microg/ml nicotine relative to P. gingivalis LPS alone (p<0.007). In contrast, 100 microg/ml nicotine significantly downregulated IL-1beta secretion by GMC relative to medium alone (p<0.008) and had no effect on PGE2 secretion by GMC. These data indicate that while nicotine and ST can stimulate PBMC to secrete PGE2, they cannot activate further mononuclear cells extracted from gingiva, possibly due to maximal previous stimulation in the periodontitis lesion.

Enriched preparations of histidine-rich polypeptides (HRPs) and isolated HRP pairs (1-2, 3-4 and 5-6) degrade in the presence of fresh autologous whole saliva to a series of low-molecular-weight cationic peptides (HRPs 6a-c and 7). Analysis of the HRPs during degradation indicates that: HRP 1 is not the parent molecule of the HRPs; the HRP pairs do not convert to each other in a cascade-like sequence in saliva; and the HRPs can be separated into 2 groups consisting of HRPs 1-2 and 3-7. Preparations containing HRPs 1-7, 1-2, and 3-7 were obtained by fractionation and separation on Bio-Rex 70, and tested for aggregating and antibacterial effects against Streptococcus mutans BHT, S. mutans GS-5 and Streptococcus sanguis G9B. HRPs 1-2 had significant aggregating effects on all 3 strains but the other HRPs had little to no agglutinating ability. The HRPs did not inhibit the growth of S. sanguis, and HRPs 1-2 enhanced its growth. No growth enhancement by the HRPs was observed for the 2 S. mutans strains. However, significant bacterial inhibition of the S. mutans strains was noted after incubation with HRPs 3-7. The data suggest that the dissimilar effects of HRPs 1-2 and 3-7 may be of importance in the colonization and growth of S. mutans and S. sanguis in vivo.