Expression of prostaglandin E2 receptor in hamster buccal pouch: effect of benzo (a) pyrene and nicotine

Morphological alterations in the epithelium of the oral mucosa of rats (Rattus norvegicus) submitted to long-term systemic nicotine treatment

Smoking is considered to be the most albeit preventable cause of diseases and premature deaths in the history of mankind. The local action of tobacco on the oral mucosa can cause precancerous and cancerous lesions. However, there is not enough evidence to establish all the systemic effects caused by nicotine on the organism. Thus, the aim of the present study was to characterize the cellular changes of the cheek mucosa of rats submitted to long-term systemic nicotine treatment. Twenty male rats were divided into two experimental groups: a nicotine group and a control group, each consisting of 10 animals. The nicotine group was injected daily with 0.250 mg of nicotine per 100 g of body weight. All animals received a solid diet and water ad libitum. After 90 days of treatment, all animals were weighed and sacrificed. Samples of cheek mucosa were collected for light and transmission electron microscopy. The results revealed oral epithelium containing atypical cells that were characterized by atrophy, cell membrane disorganization and tissue damage. It was concluded that systemic administration of nicotine damaged the cellular integrity of the oral mucosa, impairing tissue function and predisposing the tissue to the action of different pathogenic agents and also to that of other carcinogenic substances present in tobacco.

Benzo[a]pyrene and nicotine alter prostaglandin E2 receptor and its functions in hamster buccal mucosa

This study investigated the in vivo effect of benzo[a]pyrene (BP) and nicotine (NC) on prostaglandin E2 (PGE2) receptor and its cellular responses in hamster buccal mucosa. Adult male Syrian hamsters were treated by apical swabbing the pouch with mineral oil (control), or 1 mM BP + NC, twice/day, 3 times/week, for 8 weeks. The BP + NC treatment significantly decreased the specific binding of PGE2 to buccal mucosal membranes (12.8 +/- 0.14 vs 8.7 +/- 1.13 fmol/mg protein; control vs. BP + NC; mean +/- S.D., n=6, P < 0.05). Scatchard analysis revealed that the reduction of receptor binding might be due to an alteration of the receptor binding properties, such as increase of the dissociation constant (Kd, 1.08 vs. 4.20 nM; control vs. BP + NC) and elimination of the low-affinity binding site. The addition of 16,16-dimethyl PGE2 (DMPGE2) into the control buccal tissue caused a 36% decrease of the overall protein synthesis. In contrast, DMPGE2 enhanced the [35S]methionine incorporation into several major proteins (i.e., 150, 120, 90, 75, 55, 38 and 26 kDa) in the BP + NC group. DMPGE2 showed no effect on DNA synthesis in both groups. Our data demonstrated that BP + NC in vivo altered PGE2 receptor properties and cellular functions in hamster buccal pouch.

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 10(4) cells/well into 48 well tissue culture plates and maintained in serum-free media at 37 degrees 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/10(4) 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-1 alpha and IL-1 beta 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-1 alpha 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.