Manuka honey synergistically enhances the chemopreventive effect of 5-fluorouracil on human colon cancer cells by inducing oxidative stress and apoptosis, altering metabolic phenotypes and suppressing metastasis ability
The development of chemo-sensitizers is urgently needed to overcome 5-fluorouracil (5-FU) therapeutic resistance and adverse toxicity in colorectal cancer. This work aims to evaluate the synergic effects of 5-FU and Manuka honey (MH), a rich source of bioactive compounds, in enhancing the anticancer effects of this drug on human colon cancer HCT-116 and LoVo cells. Compared to 5-FU alone, MH synergistically enhanced the chemotherapeutic effects of 5-FU, by reducing cell proliferation through the suppression of EGFR, HER2, p-Akt and p-mTOR expression, and promoting apoptosis by the modulation pro-apoptotic (p53, Bax, Cyto c, FasL caspase-3, -8, -9 and cleave-PARP) and anti-apoptotic (Bcl-2) markers. The activations of p-p38MAPK and p-Erk1/2 pathways and ROS production were also involved in this process. Downregulation of transcription factor (NF-κB and Nrf2) and antioxidant enzyme activity (SOD, catalase, glutathione peroxidase and glutathione reductase) and expression (SOD, catalase and HO-1) were more evident after the combined treatment, leading to more cell death by oxidative stress. Moreover, additive effects were also observed by increasing lipid and protein oxidation and arresting cell cycle. All the parameters of mitochondrial respiration and glycolysis function decreased and both cells entered the quiescent stage after the combined treatments. MH also influenced the anti-metastasis effects of 5-FU by decreasing migration ability, suppressing the expression of MMP-2, MMP-9 and increasing N-cadherin and E-cadherin. In conclusion, MH could be a useful preventive or adjuvant agent in the treatment of colorectal cancer with 5-FU.
Protective effects of Manuka honey on LPS-treated RAW 264.7 macrophages. Part 2: Control of oxidative stress induced damage, increase of antioxidant enzyme activities and attenuation of inflammation
The redox-system is altered by oxidative stress that is initiated by oxidative agents such as lipopolysaccharides (LPS) and reactive oxygen species (ROS), which are strongly involved in chronic inflammation. Even if Manuka honey (MH) is a good source of polyphenol rich antioxidants, its antioxidant and anti-inflammatory effects are still elusive. The aim of the present work was to explore the protective effects of MH against E.coli LPS stimulated oxidative stress and inflammatory condition and the underlying mechanisms on murine RAW 264.7 macrophages. Pre-treatment with MH markedly inhibited LPS induced ROS and nitrite accumulation and increased the protection against cellular biomolecules such as lipids, proteins, and DNA. Stimulation by LPS suppressed both antioxidant enzyme activities and expressions, and Keap1-Nrf2 signaling pathway which was significantly (p < 0.05) increased in the presence of MH. The pro-inflammatory cytokines, such as TNF-α, IL-1β and IL-6, and other inflammatory mediators (iNOS) were enhanced after LPS treatment, whereas MH suppressed the expression of these inflammatory markers. Moreover, MH also inhibited the expression of TLR4/NF-кB via IкB phosphorylation in LPS-stressed RAW 264.7 macrophages. In conclusion, MH acted as a natural agent for preventing oxidative and inflammatory-related diseases.
The inhibitory effect of Manuka honey on human colon cancer HCT-116 and LoVo cell growth. Part 2: Induction of oxidative stress, alteration of mitochondrial respiration and glycolysis, and suppression of metastatic ability
Despite its high content of phenolic compounds, the chemopreventive activity of Manuka honey (MH) is still elusive. The aim of the present work was to evaluate the effects of MH on oxidative stress, antioxidant enzymes, cellular metabolism and the metastatic ability in HCT-116 and LoVo cells, paying particular attention to the molecular mechanisms involved. We observed a strong induction of oxidative stress after MH treatment since it augmented the accumulation of reactive oxygen species and increased the damage to proteins, lipids and DNA. Furthermore, MH suppressed the Nrf2-dependent antioxidant enzyme expression (superoxide dismutase (SOD), catalase and heme oxygenase-1) and the activity of SOD, catalase, glutathione peroxidase and glutathione reductase. Cell metabolisms were markedly disrupted after MH treatment. It decreased maximal oxygen consumption and spare respiratory capacity, which could reduce the mitochondrial function that is correlated with cell survival potential. Simultaneously, MH decreased the extracellular acidification rate (glycolysis) of HCT-116 and LoVo cells. Furthermore, MH suppressed the p-AMPK/AMPK, PGC1α and SIRT1 activation, involved in the survival of HCT-116 and LoVo cells under metabolic stress conditions. Dose-dependently, MH reduced the migration and invasion (MMP-2 and MMP-9) ability, and concurrently regulated EMT-related markers (E cadherin, N cadherin, and β-catenin) in both cell types. The above findings indicate that MH induces HCT-116 and LoVo cell death partly by enhancing oxidative stress, as well as by regulating the energy metabolism in both aerobic and anaerobic pathways and suppressing the metastatic ability.