Effect of smokeless tobacco extract on human gingival keratinocyte levels of prostaglandin E₂ and interleukin-1

Gingival recession and white mucosal lesions frequently occur at sites of smokeless tobacco (ST) placement. The etiology of these alterations is presumably related to the irritating effects of tobacco components. The purpose of this study was to examine the effect of an aqueous ST extract (STE) on gingival keratinocyte production of prostaglandin E₂ (PGE₂) and interleukin-1 (IL-1), mediators involved in periodontal destruction and keratinocyte proliferation. Keratinocyte cultures were established from healthy tissues discarded from 8 subjects undergoing crown lengthening procedures. Cells (passage 2-3) were seeded at 2.5 x 10⁴ cells/well into 48 well tissue culture plates and maintained in serum-free media at 37°C. On day 4 or 5, the wells were divided into 4 groups receiving either 10%, 5%, 2.5% or 0% STE for time periods ranging from 30 to 240 minutes. PGE₂ levels (pg/10⁴ cells), as measured by enzyme immunoassay, were significantly (P < 0.05) increased in the 10% (215.66 ± 34.58) and 5% STE (151.82 ± 27.97) treated cultures compared to untreated cells (46.16 ± 9.58). IL-1α and IL-1β proteins were elevated (P < 0.05) in cell lysates (299.45 ± 38.69 and 28.45 ± 5.18, respectively) from 5% STE exposed cultures compared to control wells. At 10% STE, secreted IL-1α was decreased (P < 0.05) relative to 2.5% STE. This may reflect a toxic effect, as 10% STE significantly (P < 0.05) depressed cell numbers and viability. Lower tobacco concentrations did not affect cell numbers or viability, but significantly (P < 0.05) increased PGE₂ and IL-1 levels. Tobacco-induced synthesis of these mediators may play a role in the development of tobacco-related oral disease.