Immunoquantification of human salivary mucins MG1 and MG2: determination of mucin levels in a sample population, examination of mucin secretory physiology and investigation of racial differences in mucin output

PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.Thesis (D.Sc.D.)--Boston University, Henry M. Goldman School of Dental Medicine. 2000.xi, 150 leaves : chartsIncludes bibliographical references (leaves 132-147).Human whole saliva is a complex mixture comprised of secretions of the major and minor salivary glands, gingival crevicular fluid, sloughed epithelial cells as well as various other components. This fluid coats both hard and soft tissues in the oral cavity, helps to maintain the integrity of oral tissues and facilitates basic functions such as speech, swallowing and digestion. While it has been reported that there are over 200 distinct proteins present in whole saliva, there are approximately 10 major families of salivary proteins. Human salivary mucins represent one of the major families of salivary proteins and consist of a high molecular weight mucin, MG1, and a low molecular weight mucin, MG2. Numerous aspects of salivary function have been ascribed to the salivary mucins. Human salivary mucins have proven difficult to study primarily because of their size (MG1 [greater than] 1000 kDa; MG2 150-200 kDa), but also because of their unique structure. Mucins are comprised of between 70-80% carbohydrate by weight and have a large central tandem repeat region that contains many potential O-glycosylation sites. While the biochemical properties of these glycoproteins have been described, little is known regarding their concentration in whole saliva and glandular secretions. Thus, one of the main goals of this work was to develop immunological methods for quantifying MG1 and MG2. Once these assays had been shown to be accurate and reliable, measurement of the concentration of MG1 and MG2 in whole saliva was undertaken in a limited number of subjects to establish baseline mucin levels. Assessment of mucin levels in whole saliva is challenging because of the complex nature of whole saliva. More importantly, there are a number of factors that can influence the composition of whole saliva, such as, the proportion of different glandular secretions, the flow rate, the type and intensity of stimulation as well as the level of oral health. However, whole saliva is the liquid that is present in the oral cavity and it is in this milieu that mucins function in the mouth. Therefore, to more fully understand the roles of MG1 and MG2 in the oral cavity, it is necessary to also investigate those factors that may influence their concentration. Finally, having developed the immunological techniques for quantification of MG1 and MG2, determining their baseline levels in whole saliva and investigating some of the parameters that may influence their concentration, these assays were used to investigate the potential role of salivary mucin in disease. Gastroesophageal reflux disease is one of the most prevalent diseases in this country as well as abroad. While the etiology of the disease is usually impaired lower esophageal sphincter function, it has been demonstrated that salivary mucins are important in the disease process as they protect esophageal tissue from acid and pepsin during regurgitation. Furthermore, it has been shown that African Americans are less likely to develop gastroesophageal reflux disease than Caucasians, suggesting the possibility that differences in salivary mucin levels might be a factor in the lower prevalence of gastroesophageal reflux disease in African-Americans. This could have significant impact on the treatment of this chronic disease. Therefore, to further investigate the role of salivary mucin in gastroesophageal reflux disease, levels of salivary mucin in African Americans and Caucasians were examined using the recently developed mucin capture ELISAs