1,8-Cineole promotes G0/G1 cell cycle arrest and oxidative stress-induced senescence in HepG2 cells and sensitizes cells to anti-senescence drugs.

AIMS: 1,8-Cineole is a plant-derived monoterpene and a major constituent of Eucalyptus essential oil. Previously, we demonstrated that 1,8-cineole inhibited hepatocellular carcinoma (HCC) HepG2 cell growth. However, the underlying mechanisms remain unknown. Here, we evaluated the mechanisms of action of 1,8-cineole and the potential benefits of its combination with anticancer compounds harboring "anti-senescence" properties in HepG2 cells. MAIN METHODS: Cell viability was determined by the MTT assay. Cell cycle was assessed through flow cytometry (FC) and western blot (WB). Senescence was determined by the SA-ß-galactosidase assay, and apoptosis by caspase-3 activity, WB, and TUNEL. MAPKs (ERK, JNK, and p38), AMPK, and Akt/mTOR were analyzed by WB. Reactive oxygen species (ROS) and mitochondrial membrane potential (ΔΨm) were evaluated by FC and fluorescence microscopy. KEY FINDINGS: 1,8-Cineole inhibited cell proliferation by promoting G0/G1 arrest. While 1,8-cineole was unable to trigger apoptosis, it induced cellular senescence. 1,8-Cineole promoted ROS production, ΔΨm depolarization, AMPK, ERK, and p38 activation and mTOR inhibition. Antioxidants, like N-acetyl-L-cysteine and vitamins, prevented HepG2 cell growth inhibition and senescence induced by 1,8-cineole. Pre-incubation with 1,8-cineole sensitized HepG2 cells to the anti-senescence compounds, quercetin, simvastatin, U0126, and SB202190. Combinations of 1,8-cineole and each compound synergistically inhibited cell viability, and combined treatment with 1,8-cineole and simvastatin induced apoptosis. SIGNIFICANCE: 1,8-Cineole induces G0/G1 arrest and senescence in HepG2 cells through oxidative stress and MAPK, AMPK, and Akt/mTOR pathways, and sensitizes cells to anti-senescence drugs, suggesting that 1,8-cineole has potential as an antineoplastic and adjuvant compound in combination with anti-senescence drugs in HCC therapy.

Is 1,8-Cineole-Rich Extract of Small Cardamom Seeds More Effective in Preventing Alzheimer's Disease than 1,8-Cineole Alone?

The present study demonstrates the efficacies of synthetic 1,8-cineole and an 1,8-cineole-rich supercritical carbon dioxide (SC-CO2) extract of small cardamom seeds in preventing oligomerization of amyloid beta peptide (Aß42) and inhibiting iron-dependent oxyradical production in vitro. The oligomerization of Aß42 was monitored by thioflavin T assay and MALDI-TOF analysis of the oligomers. The iron-dependent production of oxygen free radicals was detected by fluorometric benzoate hydroxylation assay. We observed that both pure 1,8-cineole and 1,8-cineole-rich extract of small cardamom seeds at concentrations of 50 µM and 100 µM prevented the production of reactive hydroxyl radicals from a mixture of Fe2+ and ascorbate. However, the 1,8-cineole-rich extract of small cardamom seeds prevented in vitro Aß42 oligomerization more effectively vis-à-vis the synthetic (99% pure) 1,8-cineole. Additional study on SHSY5Y cells indicated that both pure 1,8-cineole and 1,8-cineole-rich SC-CO2 extract of small cardamom seeds prevented iron-dependent cell death. Since oxidative damage, Aß42 aggregation and loss of cell viability (iron-induced) are characteristics of onset of Alzheimer's disease pathology, our results suggest a putative therapeutic role of 1,8-cineole-rich extract of small cardamom seeds over pure 1,8-cineole in preventing this neurodegenerative disease.

The prophylactic effect of a Eugenia aquea extract against oxidative stress and inflammation associated with the development of arthritis in an adjuvant-induced arthritis rat model.

Rheumatoid arthritis (RA) is the most common human autoimmune disease. A petroleum ether extract of Eugenia aquea (E. aquea) was analyzed by GC/MS. Antioxidant and anti-inflammatory activities were investigated in rats with adjuvant-induced arthritis (AIA). An AIA rat model received orally/daily a vehicle, diclofenac (100 mg per kg b.w.), and E. aquea extract (50 or 100 or 200 mg per kg b.w.; for 21 days). Fifty-five out of 70 compounds (97.77%) were identified: eucalyptol (34.14%), α-pinene (15.91%), l-verbenone (8.01%), camphor (7.38%) and borneol (6.74%). In an acute oral toxicity study, the E. aquea extract did not show any toxic effects in rats at 2000 mg/ kg-1. Only a high dose of the E. aquea extract or diclofenac significantly alleviated (P < 0.05-0.001) all complications observed in arthritic rats, including body weight loss, articular/extra-articular oxidative injury and synovial joint inflammation by increasing food intake as well as improving the antioxidant defense system and inflammatory marker. The dose-dependent modulatory activity of the E. aquea extract was statistically significant. It was equivalent to and sometimes even better than that of diclofenac. The present study proved the antioxidant and anti-inflammatory activities of the E. aquea extract, which could be attributed to the presence of eucalyptol and α-pinene.