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BioMed Research International
Volume 2013 (2013), Article ID 168765, 7 pages
http://dx.doi.org/10.1155/2013/168765
Research Article

Multimolecular Salivary Mucin Complex Is Altered in Saliva of Cigarette Smokers: Detection of Disulfide Bridges by Raman Spectroscopy

1Department of Functional Biology, Kanagawa Dental College, 82 Inaokacho, Yokosuka 238-8580, Japan
2Department of Maxillofacial Diagnostic Science, Kanagawa Dental College, 82 Inaokacho, Yokosuka 238-8580, Japan
3Department of Oral Medicine, Kanagawa Dental College, 82 Inaokacho, Yokosuka 238-8580, Japan
4Department of Dental Sociology, Kanagawa Dental College, 82 Inaokacho, Yokosuka 238-8580, Japan
5Yokohama Training Center, Kanagawa Dental College, 3-31-6 Turuyacho, Kanagawa-ku, Yokohama 221-0835, Japan
6Department of Pathology, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan
7Clinical Laboratory, Kanagawa Dental College, 82 Inaokacho, Yokosuka 238-8580, Japan

Received 24 April 2012; Revised 1 July 2012; Accepted 23 July 2012

Academic Editor: Y. James Kang

Copyright © 2013 Motoe Taniguchi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Saliva contains mucins, which protect epithelial cells. We showed a smaller amount of salivary mucin, both MG1 and MG2, in the premenopausal female smokers than in their nonsmoking counterparts. Smokers' MG1, which contains almost 2% cysteine/half cystine in its amino acid residues, turned out to be chemically altered in the nonsmoker’s saliva. The smaller acidic glycoprotein bands were detectable only in smoker’s saliva in the range of 20–25 kDa and at 45 kDa, suggesting that degradation, at least in part, caused the reduction of MG1 mucin. This is in agreement with the previous finding that free radicals in cigarette smoke modify mucins in both sugar and protein moieties. Moreover, proteins such as amylase and albumin are bound to other proteins through disulfide bonds and are identifiable only after reduction with DTT. Confocal laser Raman microspectroscopy identified a disulfide stretch band of significantly stronger intensity per protein in the stimulated saliva of smokers alone. We conclude that the saliva of smokers, especially stimulated saliva, contains significantly more oxidized form of proteins with increased disulfide bridges, that reduces protection for oral epithelium. Raman microspectroscopy can be used for an easy detection of the damaged salivary proteins.