RESUMO
UNLABELLED: The mechanisms of action of propolis can be studied in detail by comparing the effects of propolis and the effects of its constituent components. AIM: To clarify and compare the effects of Bulgarian propolis and caffeic acid phenethyl ester (CAPE, a chemically synthesized component of propolis)--by using a set of cellular, molecular-biological and immunological techniques. MATERIAL AND METHODS: The McCoy-Plovdiv cell line was treated with propolis and CAPE in increasing concentrations (0.01, 0.1, 1.0, 10 mg/L, and 2.5, 4, 8, 16 mg/L, respectively). The expression of the proliferating cell nuclear antigen (PCNA) and the tumour-suppressor protein p53 was studied immunocytochemically. Apoptosis was measured using a highly sensitive microgel electrophoresis technique (comet assay). RESULTS: The results of the study showed corresponding changes in the expression of the examined proliferative antigens. PCNA was detected in all examined concentrations of the tested substances the expression being dose-dependent. Molecule localization changed from the nucleus to the cytoplasm. Treatment with CAPE brought about gradual attenuation of PCNA expression. High propolis concentrations induced increased synthesis of p53. No p53 expression was found when cells were treated with CAPE. The studied substances in their highest concentrations (10 mg/L propolis and 16 mg/L CAPE) had a cytotoxic effect. The comet assay showed DNA degradation kinetics characteristic for apoptosis. CONCLUSIONS: The present study demonstrates that high concentrations of propolis and CAPE cause apoptosis-induced cell death in McCoy-Plovdiv cells.
