|M.Sc Student||Savulescu Dana|
|Subject||Characterization and Monitoring of Salivary Translocator|
Protein (TSPO) under Physiological Conditions and
Following Exposure to Cigarette Smoke
|Department||Department of Medicine||Supervisors||Professor Rafael M. Nagler|
|Professor Emeritus Moshe Gavish|
|Full Thesis text|
The 18 kDa Translocator protein (TSPO) is an intracellular receptor located on the outer mitochondrial membrane. Its presence has never been monitored in saliva in spite of the fact that TSPO levels are often related to cancer and that saliva may be used for various monitoring purposes. Oral cancer is the most common malignancy of the head and neck and its main inducer is exposure to cigarette smoke (CS).
Accordingly the purposes of our study were to monitor and to characterize TSPO in human saliva, under physiological conditions and following exposure to CS.
We detected the presence of the TSPO and its associated protein, VDAC in human saliva. Next, we determined the binding characteristics of the TSPO in human saliva. A saturation curve of its specific ligand, [3H]PK 11195 (final concentration: 0.18-12 nM) showed saturable binding. Next, we exposed saliva samples to CS in vitro and tested them for TSPO binding, Western blot analysis, cell viability and total amount of protein. We demonstrated a three-fold decrease in the ligand affinity to the TSPO (p<0.01), a 30% decrease in the ligand specific binding to the TSPO (p<0.05), and no significant change in the TSPO levels, total amount of protein and the cell viability in saliva exposed to CS, as compared to control. Next, we performed two assays aimed to explore the possible mediatory role of oxygen free radicals and volatile aldehydes in the effect of cigarette smoke on the TSPO. The results suggest that these molecules do not mediate the effect of CS on the salivary TSPO. Following the experiments of the in vitro CS exposure, we compared the TSPO specific binding and protein levels in saliva of smoking and non-smoking individuals, and in saliva of tongue cancer patients and healthy individuals. Both smoking individuals and tongue cancer patients were found to have reduced TSPO specific binding, and an insignificant change in the total amount of protein in their saliva, as compared to their control groups. We also detected lower TSPO and VDAC expression in saliva of smoking individuals, as compared to non-smoking individuals.
In summary these results demonstrate for the first time the presence of TSPO in human saliva. Moreover, the significant reduction in the salivary TSPO binding scores following exposure to CS in vitro and in vivo may have a significant role in the pathogenesis of CS induced oral cancer.