Xylitol is well-known to have an anti-caries effect by inhibiting the replication of cariogenic bacteria. In addition, xylitol enhances saliva secretion. However, the precise molecular mechanism of xylitol on saliva secretion is yet to be elucidated. Thus, in this study, we aimed to investigate the stimulatory effect of xylitol on saliva secretion and to further evaluate the involvement of xylitol in muscarinic type 3 receptor (M3R) signaling. For determining these effects, we measured the saliva flow rate following xylitol treatment in healthy individuals and patients with dry mouth. We further tested the effects of xylitol on M3R signaling in human salivary gland (HSG) cells using realtime quantitative reverse-transcriptase polymerase chain reaction, immunoblotting, and immunostaining. Xylitol candy significantly increased the salivary flow rate and intracellular calcium release in HSG cells via the M3R signaling pathway. In addition, the expressions of M3R and aquaporin 5 were induced by xylitol treatment. Lastly, we investigated the distribution of M3R and aquaporin 5 in HSG cells. Xylitol was found to activate M3R, thereby inducing increases in Ca2+ concentration. Stimulation of the muscarinic receptor induced by xylitol activated the internalization of M3R and subsequent trafficking of aquaporin 5. Taken together, these findings suggest a molecular mechanism for secretory effects of xylitol on salivary epithelial cells.

Introduction
 Materials and Methods
  1. Cell culture
  2. Reagents
  3. Subjects
  4. Measurement of intracellular calcium concentration
  5. Real-time quantitative reverse-transcriptasepolymerase chain reaction (qRT-PCR)
  6. Western blotting
  7. Membrane protein purification
  8. Immunostaining
  9. Statistics
 Results
  1. Xylitol stimulates salivary secretion in both healthyand dry mouth patients
  2. Xylitol increases intracellular calcium concentrationin HSG cells via M3R signaling pathway
  3. Xylitol induces M3R expression in HSG cells viastimulation of M3R signaling pathway
  4. Xylitol induces AQP5 expression via M3R signalingpathway
 Discussion
 References

• Eunjoo Park(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Hee Sam Na(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Sunghee Jeong(Department of Oral Medicine, School of Dentistry, Pusan National University)
• Jin Chung(Department of Oral Microbiology, School of Dentistry, Pusan National University) Correspondence to