Thymol induces mitochondrial pathway-mediated apoptosis via ROS generation, macromolecular damage and SOD diminution in A549 cells.

BACKGROUND: Thymol is a monoterpene phenol found in thyme species plants. The present study was carried out to investigate the effect of thymol and its molecular mechanism on non-small lung cancer (A549) cells. METHODS: The cytotoxic effect of thymol on A549 cells was assessed via MTT assay. ROS production, macromolecular damage, apoptosis were determined using DCF-DA, PI, AO/EtBr stains, respectively. ROS-dependent effect of thymol was confirmed using NAC. The expression of caspase-9, Bcl-2, Bax and cell cycle profile was analyzed via western blot and FACS, respectively. RESULTS: The antiproliferative effect of thymol on A549 cells was found to be both dose and time dependent with IC50 values of 112 µg/ml (745 µM) at 24 h. Thymol treatment favored apoptotic cell death and caused G0/G1 cell cycle arrest. It mediated cellular and nuclear morphological changes, phosphatidylserine translocation, and mitochondrial membrane depolarization. Additionally, upregulation of Bax, downregulation of Bcl-2, and apoptotic fragmented DNA were also observed. Thymol induced ROS by reducing the SOD level which was confirmed via in vitro and in silico analysis. Furthermore, the levels of lipid peroxides and protein carbonyl content were elevated in thymol-treated groups. Notably, N-acetyl cysteine pretreatment reversed the efficacy of thymol on A549 cells. Moreover, thymol-treated human PBMC cells did not show any significant cytotoxicity. CONCLUSION: Overall, our results confirmed that thymol can act as a safe and potent therapeutic agent to treat NSCLC.

Thymol inhibits bladder cancer cell proliferation via inducing cell cycle arrest and apoptosis.

Thymol is a phenolic compound with various pharmacological activities such as anti-inflammatory, anti-bacterial and anti-tumor effects. However, the effect of thymol on bladder cancer cell growth is still elusive. The purpose of this study is to investigate the efficacy of thymol in bladder cancer cells and its underlying mechanism. Thymol inhibited bladder cancer cell proliferation in a dose and time-dependent manner. We also observed cell cycle arrest at the G2/M phase after the treatment of thymol. Moreover, thymol could induce apoptosis in bladder cancer cells via the intrinsic pathway along with caspase-3/9 activation, release of cytochrome c and down-regulation of anti-apoptotic Bcl-2 family proteins. The activation of JNK and p38 was also critical for thymol-induced apoptosis since it was abrogated by the treatment of JNK inhibitor (SP600125), and p38 inhibitor (SB203580) but not ERK inhibitor (SCH772984). Furthermore, the generation of ROS (reactive oxygen species) was detected after the treatment of thymol. ROS scavenger NAC (N-acetyl cysteine) could block the thymol-triggered apoptosis and activation of MAPKs. These findings offer a novel therapeutic approach for bladder cancer.

Factors that interact with the antibacterial action of thyme essential oil and its active constituents.

The viable counts of Salmonella typhimurium on nutrient agar (NA) decreased upon the addition of either the essential oil of thyme or its constituent thymol, especially under anaerobic conditions. Antagonistic effects of thymol against Staphylococcus aureus were also greater under anaerobic conditions. In contrast to the phenolic constituents of the oil, thymol and carvacrol, the chemically related terpenes p-cymene and gamma-terpinene had no antagonistic effects against Salm. typhimurium. The addition of Desferal to NA counteracted the antibacterial effects of both thyme oil and thymol. No support was obtained, however, for a possible role of iron in the oxygen-related antibacterial action of the thyme oil and thymol or for the observed effect of Desferal. In the presence of thymol, the viable counts of Salm. typhimurium obtained on a minimal medium (MM) were lower than those obtained on NA. Addition of bovine serum albumin (BSA) neutralized the antibacterial action of thymol. It is suggested that the effects of BSA or Desferal are due to their ability to bind phenolic compounds through their amino and hydroxylamine groups, respectively, thus preventing complexation reactions between the oil phenolic constituents and bacterial membrane proteins. This hypothesis is supported by the marked decrease in the viable counts of Salm. typhimurium caused by either thyme oil or thymol when the pH of the medium was changed from 6.5 to 5.5 or the concentration of Tween 80 in the medium was reduced.