Salivary concentration of secretory leukocyte protease inhibitor, an antimicrobial protein, is decreased with advanced age

Background. Secretory leukocyte protease inhibitor (SLPI) exhibits antimicr obial activities that, in addition to other well-characterized proteins suc h as lysozyme and lactoferrin, is thought to play a critical role in mucosa l defenses. Although elderly individuals are particularly susceptible to mu cosal infections, salivary production of SLPI has not been assessed in an a ged cohort. Objectives: Hypothesizing that oral SLPI concentrations are red uced with advanced age, this cross-sectional study compared SLPI concentrat ions to concentrations of lysozyme, lactoferrin and total protein in unstim ulated salivary secretions of healthy, community-dwelling 79+year-old and y ounger adults. Methods: Study participants were 45 non-hospitalized dentate adults aged 79-89 (23 elderly) or 21-51 years (22 non-elderly). Home-based interviews and clinical examinations determined dentate status and confirm ed the absence of dentures, oral mucosal disease, anti-infective medication use, irradiation therapy for head and neck cancer and self-perceived xeros tomia. Whole unstimulated saliva was collected from all subjects and analyz ed for antimicrobial protein concentration by enzyme-linked immunosorbent a ssay and for total protein content by the bicinchoninic acid method. Bivari ate and multivariate (generalized linear modeling) analyses evaluated the r elationships between age, gender and salivary protein concentrations. Resul ts: Mean salivary levels of SLPI and lysozyme were lower in elderly compare d with non-elderly subjects (p < 0.001), unlike lactoferrin and total prote in levels. Similar results were obtained when concentrations of the individ ual proteins were normalized to the total protein concentration, suggesting that glandular production of SLPI and lysozyme preferentially decreases wi th aging. Gender differences were detected only for SLPI concentrations; ma les had lower SLPI levels than females regardless of age (p < 0.01). Genera lized linear models confirmed that age (p < 0.001) and gender (p < 0.05) we re each associated with the SLPI concentration and together accounted for 5 0% of the variation in SLPI concentration in this population. Conclusion: T hese findings indicate that SLPI production is diminished among healthy com munity-dwelling older adults, particularly elderly males. Further investiga tion should determine the impact of decreased local SLPI production on the increased risk of oral mucosal disease with advanced age. Copyright (C) 200 1 S. Karger AG, Basel.