Decreased excretion of antimicrobial proteins and peptides in saliva of patients with oral candidiasis

Background: Antimicrobial peptides in saliva appear to play a crucial role in the regulation of oral Candida growth, and study on antimicrobial excretion in saliva and oral candidiasis appears useful for the analysis of pathophysiology of oral candidiasis. Methods: To clarify the role of saliva in the regulation of oral Candida growth, the levels of antimicrobial proteins and peptides and their excretion rates were examined in saliva obtained from 50 patients with oral candidiasis and 35 healthy individuals. Results: The inhibitory activities of patients' saliva against Candida adhesion with HeLa cells and against Candida growth (radiolabeled glucose incorporation) were lower than those of saliva from the healthy controls. The salivary levels of lactoferrin (Lf; 11 +/- 9 mug/ml), secretory immunoglobulin A (sIgA; 160 +/- 37 mug/ml), beta-defensin 1 (375 +/- 37 ng/ml), and beta-defensin 2 (412 +/- 51 ng/ml) in the patients were largely lower than those in the control group (33 +/- 14 mug/ml, 204 +/- 51 mug/ml, 452 +/- 89 ng/ml, and 530 +/- 142 ng/ml, respectively), although the transferrin (Tf) and secretory component (SC) levels were almost same in both groups, and alpha-defensin 1 was slightly increased in the patient group (660 +/- 115 ng/ml vs. 467 +/- 168 ng/ml). In addition, the excretion rates of the proteins and peptides were largely decreased in the patients (Tf: 14 +/- 2 mug/10 min vs. 34 +/- 7 mug/10 min; Lf: 18 +/- 11 mug/10 min vs. 139 +/- 43 mug/10 min; sIgA: 300 +/- 132 mug/10 min vs. 900 +/- 207 mug/10 min; SC: 112 +/- 46 mug/10 min vs. 292 +/- 64 mug/10 min; alpha-defensin 1: 1223 +/- 431 ng/10 min vs. 2044 +/- 612 ng/10 min; beta-defensin 1: 687 +/- 243 ng/10 min vs. 1985 +/- 295 ng/10 min; and beta-defensin 2: 784 +/- 299 ng/10 min vs. 2288 +/- 278 ng/10 min). Conclusion: These results conclusively suggest that oral candidiasis is associated with salivary gland hypofunction and that decreases of salivary antibacterial proteins induce Candida overgrowth.