Rong-Rong Lu

Curcumin protects mouse neuroblastoma Neuro-2A cells against hydrogen-peroxide-induced oxidative stress

Curcumin has been traditionally used in China and India for food and medicinal purposes. It has been shown to possess potent antioxidative activity both in vitro and in vivo. In the present study, the neuroprotective effects and the potential mechanisms of curcumin against H2O2-induced oxidative stress in mouse neuroblastoma Neuro-2A cells were investigated. Treatment with curcumin at 20 and 25μg/mL for 1h prior to H2O2 exposure significantly attenuated cell viability loss, reduced apoptosis, suppressed the elevation of intracellular reactive oxygen species (ROS) and calcium levels, and stabilised mitochondrial membrane potential. Furthermore, curcumin could block H2O2-mediated degradation of the protein IκBα and subsequent activation of nuclear factor κB, thus inhibiting the expression of its target gene cyclooxygenase 2. These results indicate that curcumin has potential protective effects against H2O2-induced oxidative stress in neuron cells, which might make curcumin a suitable therapeutic agent for prevention and treatment of neurodegenerative diseases associated with oxidative stress.

Protective effect of whey protein hydrolysates on H2O2-induced PC12 cells oxidative stress via a mitochondria-mediated pathway

Whey protein hydrolysates (WPHs) were prepared with pepsin and trypsin. A PC12 cell model was built to observe the protective effect of WPHs against H2O2-induced oxidative stress. The results indicated that WPHs reduced apoptosis by 14% and increased antioxidant enzyme activities. Flow cytometry was used to assess the accumulation of reactive oxygen species (ROS), Ca(2+) levels and the mitochondrial membrane potential (MMP). The results showed that WPHs suppressed ROS elevation and Ca(2+) levels and stabilised MMP by 16%. The anti-apoptosis/pro-apoptosis proteins Bcl-2/Bax and poly (ADP-ribose) polymerase (PARP) were investigated by Western-blot analysis, which indicated that WPHs increased the expression of Bcl-2 while inhibiting the expression of Bax and the degradation of PARP. WPHs also blocked Caspase-3 activation by 62%. The results demonstrate that WPHs can significantly protect PC12 cells against oxidative stress via a mitochondria-mediated pathway. These findings indicate the potential benefits of WPHs as valuable food antioxidative additives.

Exopolysaccharide from Lactobacillus planterum LP6: antioxidation and the effect on oxidative stress.

An exopolysaccharide (EPS-3) was isolated from the culture of Lactobacillus planterum LP6 and purified by ion exchange and gel chromatography. The concentrations required to scavenge 50% of the initial radical for DPPH·, OH· and O2(·-) radicals were 1.38, 3.43 and 0.11 mg/mL, respectively. The reducing power (A700 nm) was 0.632 at 5mg/mL. The cell viability of PC12 was improved by 21.67% at 200 μg/mL of EPS-3. Compared with the H2O2 group, the total-antioxidant capacity, activities of superoxide dismutase and catalase were enhanced by 65.81%, 41.34% and 59.05%, respectively. Meanwhile, the level of malondialdehyde and lactate dehydrogenase were decreased by 52.80% and 30.24%. The result indicated that EPS-3 had a notable protective effect against oxidative damage on PC12 cells. The study might lay a theoretical foundation for the comprehensive utilization of lactic acid bacteria source which could result in its application in food systems.

Curcumin inhibits invasion and metastasis in K1 papillary thyroid cancer cells

Curcumin, the active constituent of dietary spice turmeric, possesses a strong potential for cancer prevention and treatment. However, there is no study to address the effects of curcumin on invasion and metastasis of thyroid cancers. Thyroid cancer is the most common malignancy of endocrine organs, and its incidence rates have steadily increased over recent decades. Although most indolent tumours can be effectively managed, metastatic tumours at distant secondary sites behave aggressively and currently there is no effective form of treatment. Here, for the first time it has been reported that curcumin inhibit multiple metastasis steps of K1 papillary thyroid cancer cells. Curcumin dose-dependently suppressed viability of K1 cells as well as its cell attachment, spreading, migration and invasion abilities. Moreover, curcumin could also down-regulate the expression and activity of matrix metalloproteinase-9 (MMP-9). The findings showed that curcumin might be an effective tumouristatic agent for the treatment of aggressive papillary thyroid carcinomas.

Isolation and identification of antioxidant peptides derived from whey protein enzymatic hydrolysate by consecutive chromatography and Q-TOF MS

To isolate and identify antioxidant peptides from enzymatically hydrolysed whey protein, whey protein isolate was hydrolysed by different protease (trypsin, pepsin, alcalase 2·4L, promatex, flavourzyme, protease N). The hydrolysate generated by alcalase 2·4L had the highest antioxidant activities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, superoxide radicals and in a linoleic acid peroxidation system induced by Fe2+. The IC50 values of DPPH and superoxide radical scavenging activities of the hydrolysate decreased significantly (6·89 and 38·88%, respectively) after treatment with macroporous adsorption resin. Seven different peptides showing strong antioxidant activities were isolated from the hydrolysate using consecutive chromatographic methods including gel filtration chromatography and high-performance liquid chromatography. The molecular mass and amino acids sequences of the purified peptides were determined using a Quadrupole time-of-flight mass spectrometer (Q-TOF MS). One of the antioxidative peptides, Trp-Tyr-Ser-Leu, displayed the highest DPPH radical scavenging activity (IC50=273·63 μm) and superoxide radical scavenging activity (IC50=558·42 μm). These results suggest that hydrolysates from whey proteins are good potential source of natural antioxidants.

The mechanism underlying proliferation-inhibitory and apoptosis-inducing effects of curcumin on papillary thyroid cancer cells

Recently, many studies on health benefits associated with curcumin have been reported. In this study, the effects of curcumin on apoptosis of papillary thyroid cancer cell line K1 and its potential mechanisms were investigated. Curcumin was found to significantly inhibit cell viability and promoted cell apoptosis in a dose-dependent manner. Moreover, curcumin-induced cell apoptosis was characterized with a rapid stimulation of reactive oxygen species (ROS) production. Furthermore, curcumin-induced ROS generation led to the loss of mitochondrial membrane potential (MMP) and the disturbance of intracellular Ca(2+) concentration. A decrease in expression of Bcl-2 and the cleavage of poly ADP-ribose polymerase (PARP) were observed after exposure to curcumin. Results of this study may elucidate the curcumin-induced apoptosis effects on K1 cells. Thus, our results indicate a role of curcumin as health-promoting food ingredient, as well as a potential chemotherapeutic agent which is able to fight against papillary thyroid cancer.

Characterization of surface layer proteins and its role in probiotic properties of three Lactobacillus strains.

The objective of this study was the characterization of the surface layer proteins (SLPs) and their functional role in the probiotic activity of Lactobacillus helveticus fb213, L. acidophilus fb116 and L. acidophilus fb214. SLPs were extracted and identified by SDS-PAGE, circular dichroism spectra and LC-MS analysis. The results revealed that the molecular masses of the three proteins were 49.7 kDa, 46.0 kDa and 44.6 kDa, respectively. The secondary structures and amino acid compositions of the three proteins were found to be similar. After removing SLPs, the survival of the three lactobacilli in simulated gastric and intestinal juices was reduced by 2-3log as compared with survival of the intact cells. And the adhesion ability of the three strains to HT-29 cells decreased by 61%, 65% and 92%, respectively. SLPs also inhibited the adhesion and invasion of Escherichia coli ATCC 43893 to HT-29 cells. These results suggest that SLPs are advantageous barriers for lactobacilli in the gastrointestinal tract, and these proteins help make it possible for lactobacilli to serve their probiotic functions.

Curcumin inhibits hypoxia-induced migration in K1 papillary thyroid cancer cells.

Curcumin, traditionally used as food and medicinal purposes, has recently been reported to have protective efficacy against hypoxia. Hypoxia is one of the important reactive factors in tumor metastasis, which is a key problem in clinical thyroid cancer therapy. In present study, we investigate the anti-metastatic effect of curcumin on the K1 papillary thyroid cancer cells as well as its potential mechanisms. The results show that curcumin effectively inhibits hypoxia-induced reactive oxygen species (ROS) upregulation and significantly decreases the mRNA and protein expression levels of hypoxia-inducible factor-1α (HIF-1α) in K1 cells. Curcumin also decreases the DNA binding ability of HIF-1α to hypoxia response element (HRE). Furthermore, curcumin enhances E-cadherin expression, inhibits metalloproteinase-9 (MMP-9) enzyme activity, and weakens K1 cells migration under hypoxic conditions. In summary, these results indicate that curcumin possesses a potent anti-metastatic effect and might be an effective tumoristatic agent for the treatment of aggressive papillary thyroid cancers.

Curcumin inhibits metastasis in human papillary thyroid carcinoma BCPAP cells via down-regulation of the TGF-β/Smad2/3 signaling pathway

Thyroid cancers usually possess a good prognosis while the risks of recurrence and metastasis turn out to be a disturbing issue. Curcumin [bis(4-hydroxy-3-methoxy-phenyl)-1,6-heptadiene-3,5-dione] is a natural polyphenolic compound mainly found in turmeric (Curcuma longa). Our previous studies have demonstrated that curcumin showed proliferation-inhibitory and apoptosis-inducing effects on K1 papillary thyroid cancer cells. However, the mechanism underlying the inhibition effects of curcumin on thyroid cancer cells remains unclear. Herein, we demonstrated that curcumin remarkably increased the expression of the epithelial marker E-cadherin and repressed the expression of the mesenchymal marker vimentin in human papillary thyroid carcinoma BCPAP cells. Curcumin also suppressed multiple metastatic steps of BCPAP cells, including cell attachment, spreading as well as migration. In addition, the transcription, secretion and activation of matrix metalloproteinases (MMPs) induced by transforming growth factor-β1 (TGF-β1) in BCPAP cells were mitigated upon curcumin treatment. Further evidence showed that curcumin decreased TGF-β1-mediated phosphorylation of Smad2 and Smad3. These results revealed that curcumin inhibited the TGF-β1-induced epithelial-mesenchymal transition (EMT) via down-regulation of Smad2/3 signaling pathways. Our findings provide new evidence that the anti-metastatic and anti-EMT activities of curcumin may contribute to the development of chemo-preventive agents for thyroid cancer treatment.

Murein hydrolase activity of surface layer proteins from Lactobacillus acidophilus against Escherichia coli

The aim of this study was to investigate the murein hydrolase activities of the surface layer proteins (SLPs) from two strains of Lactobacillus acidophilus using zymography. The influence of these hydrolase activities on Escherichia coli ATCC 43893 was also evaluated by analysing their growth curve, cell morphology and physiological state. After the incubation of E. coli with SLPs, growth was inhibited, the number of viable cells was significantly reduced, examination by transmission electron microscopy showed that the cell wall was damaged and flow cytometry results indicated that the majority of the cells were sublethally injured. All of these results suggested that the SLPs of both L. acidophilus strains possessed murein hydrolase activities that were sublethal to E. coli cells.