Anticancer effects of Thymus vulgaris and Thymus serpyllum essential oils from Montenegro

Introduction The phytochemicals present in essential oils derived from aromatic plants of genus Thymus have been reported to exert antioxidant, anti-inflammatory, and anticancer effects. The aim of the research was to examine the cytotoxic activity and the mechanisms of anticancer action of the two essential oils obtained from Thymus vulgaris and Thymus serpyllum grown in Montenegro. Material and Methods The cytotoxic activity was determined against four human cancer cell lines: cervical adenocarcinoma HeLa, malignant melanoma A375, colorectal adenocarcinoma LS 174T, and lung carcinoma A549, as well as against normal lung fibroblasts MRC-5 by MTT assay. The cell cycle phase distribution of HeLa cells and the potential activation of caspase-3, caspase-8, and caspase-9 were investigated by flow cytometry. Gene and microRNA expression levels in HeLa cells were measured using RT-qPCR. The intracellular levels of reactive oxygen species (ROS) in MRC-5 cells were measured by flow cytometry. Results and Discussions Both essential oils exerted strong cytotoxicity against cancer cell lines with IC50 concentrations in the range from 0,20 to 0,24 µL/mL for T. vulgaris and from 0.32 to 0.49 µL/mL for T. serpyllum. Strong cytotoxicity was observed against lung fibroblasts MRC-5. The remarkable increases in the percentage of HeLa cells in the subG1 phase of the cell cycle after 24 h treatment with T. vulgaris and T. serpyllum essential oils were observed in comparison to the control cells. Pretreatment of HeLa cells with caspase inhibitors showed that T. vulgaris oil induced apoptotic cell death through caspase-3 and caspase-8, while T. serpyllum oil induced apoptosis through caspase-3 activation. Both essential oils decreased intracellular ROS levels in MRC-5 cells and reduced levels of oxidative stress induced by hydrogen peroxide. The treatment of HeLa cells with T. vulgaris oil lowered the MMP2 expression levels, increased MMP9 and VEGFA levels when compared with control cell