Stress-adaptive enzyme and ion channels in xerostomia model mouse

Objectives: Xerostomia is caused by salivary gland dysfunction. Therefore investigating stress-adaptive enzyme AMP-activated protein kinase (AMPK) and AMPK-regulated ion channels involved in saliva secretion will be help for restoring the salivary gland cell function. To determine the key molecules for restoration of salivary gland cell function, we analyzed expression and activation of AMPK and expression of cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium ion channel (ENaC) in xerostomia model mouse.

Methods: Xerostomia model mouse was prepared by X-ray irradiation as described by Takeda et al.. Sublingual (SLG) and submandibular (SMG) glands were isolated and total RNA and protein were extracted. RNA and protein expression was analyzed by real-time quantitative RT-PCR using SYBR Green I and western blotting, respectively. Significances are determined by two-paired multiple t-test with Bonferroni correction following one-way ANOVA. CFTR expression was also analyzed by indirect immunofluorescent staining.

Results: AMPK, CFTR and ENaC expressed in SLG and SMG. After X-ray irradiation, increased expression and activation of AMPK were observed in SLG and SMG. ENaC expression increased by 2 to 3-fold in SLG, but decreased to 50% in SMG. CFTR expression had no significant change in SLG, but decreased to 50% in SMG.

Conclusion: Increased expression and activation of AMPK after X-ray irradiation and changes in expression of ENaC indicate that AMPK might protect cells from injury by activating cell protective pathway and controlling channel expression.