The differential expression of the salivary peptidome in radiotherapy-induced Xerostomia

Abstract

Abstract Background Head and neck cancer patients always suffer from xerostomia after radiotherapy. The parasympathomimetic is an effective drug to relieve the radiotherapy-induced xerostomia. However, the unwanted side effect annoys patient a lot. The saliva substitute is commonly used replacement of the natural saliva for relieving the xerostomia symptom and improve the quality of life. The peptides in the saliva are the main compounds to keep the moisture of the oral cavity. In this study, we would like to analyze the differential expression of the peptide in the saliva of the subjects who had xerostomia and underwent head and neck radiotherapy and compared with normal subjects. We aim to find a specific peptide as a new ingredient for developing new saliva substitute which is more compatible with oral microenvironment of the patient to maintain the oral health and quality of life like the real saliva. Methods We collected the stimulated saliva from 10 head and neck cancer patients who underwent radiotherapy and had xerostomia symptom and from 10 age- and sex-matched controls. The xerostomia was evaluated with xerostomia inventory short version. The average xerostomia score of the patient group is 11.5, and the normal group is 5.5. We separated the peptide from saliva specimens with a 10K cut off filter. The differential expression of the peptide was performed with MALDI-TOF/TOF Ultraflex mass spectrometer and plausible neural network pattern recognition software. Results We found patients who receive radiotherapy lacks two major peaks of m/z 555.19 and 754.35. Those indicated the small fragment of the several possible peptides that lacking in the patient group and contribute to xerostomia symptom. Conclusion In the future work, we will add the candidate peptides into artificial saliva and perform the in vivo study to evaluate the potential of the peptide as a new ingredient of saliva substitute.