Impact of Smoking on p65 Nuclear Factor κB, p38 Mitogen-Activated Protein Kinase, and Inducible Nitric Oxide Synthase Expression Levels in Oral Mucosa

Abstract

Smoking plays an important role in oral cancer development; however, the molecular carcinogenesis mechanism in oral mucosa is not well understood. The aim of this study was to examine and compare the levels of p65 nuclear factor κB (NF-κB), p38 mitogen-activated protein kinase (MAPK), and inducible nitric oxide synthase (iNOS) expressions between oral mucosa of nonsmoker and smoker volunteers. Oral cheek mucosa was collected from 78 volunteers. Smokers were divided into 2 subgroups: light smokers (<40 pack years) and heavy smokers (≥ 40 pack years). Paraffinized tissue immunochemistry was carried out for p65 NF-κB, p38 MAPK, and iNOS expression with specific antibodies. Results were evaluated based on diffuseness and intensity of staining. Group 1 composed of 40 nonsmokers: 52.5% were female and 47.5% were male, with a mean age of 46.4 years. Group 2 composed of 38 smokers (20 light smokers, 18 heavy smokers): 39.5% were female and 60.5% were male, with a mean age of 48.9 years. Total immunohistochemical staining scores of smokers were significantly higher compared with those of nonsmokers in p65 NF-κB, p38 MAPK, and iNOS expression (P < 0.001). The highest p65 NF-κB, p38 MAPK, and iNOS expression levels were detected in the oral mucosa of heavy smokers. The expression of iNOS and p65 NF-κB in heavy smokers was significantly higher compared to that in light smokers (P < 0.01 and P < 0.05, respectively). Although p38 MAPK expressions were higher in heavy smokers compared with light smokers, the difference was not statistically significant (P > 0.05). Our results show for the first time the significant increase in the expression of p65 NF-κB and p38 MAPK in the oral mucosa of smokers. Levels of p65 NF-κB, p38 MAPK, and iNOS expression in the oral mucosa of smokers were related to the number of pack years.