Procyanidin B2 and a cocoa polyphenolic extract inhibit acrylamide-induced apoptosis in human Caco-2 cells by preventing oxidative stress and activation of JNK pathway

Protection of cyanidin-3-glucoside against oxidative stress induced by acrylamide in human MDA-MB-231 cells

Acrylamide (AA) occurs in many cooked starchy foods and has caused widespread concern as a possible carcinogen. In the present study, we investigate the intervention of AA toxicity in MDA-MB-231 cells pretreated with cyanidin-3-glucoside (Cy-3-glu). Compared to the cells treated with AA, Cy-3-glu significantly inhibited AA-induced cytotoxicity, reduced reactive oxygen species (ROS) generation, recovered glutathione (GSH) depletion and decreased the activities of glutathione peroxidase (GPx) and glutathione S-transferase (GST). Moreover, the expression of GPx1, GSTP1 and gamma-glutamyl cysteine synthase (γ-GCS) were enhanced, and cytochrome P450 2E1 (CYP2E1) expression was inhibited by the pretreatment of Cy-3-glu. Cy-3-glu presents the protective role against oxidative stress induced by AA in MDA-MB-231 cells.

Cocoa polyphenols prevent inflammation in the colon of azoxymethane-treated rats and in TNF-α-stimulated Caco-2 cells

Numerous lines of evidence support a relationship between intestinal inflammation and cancer. Therefore, much attention has recently been focused on the identification of natural compounds with anti-inflammatory activities as a strategy to suppress the early stages of colorectal cancer. Because cocoa is a rich source of bioactive compounds, the present study investigated its anti-inflammatory properties in a rat model of azoxymethane (AOM)-induced colon carcinogenesis and in TNF-α-stimulated Caco-2 cells. A total of forty male rats were fed with control or cocoa-enriched diets (12 %) during 8 weeks and injected with saline or AOM (20 mg/kg body weight) during the third and fourth week (n10 rats/group). At the end of the experiment, colon samples were evaluated for markers of inflammation. The anti-inflammatory activity of a cocoa polyphenolic extract (10 μg/ml) was examined in TNF-α-stimulated Caco-2 cells, anin vitromodel of experimentally induced intestinal inflammation. The signalling pathways involved, including NF-κB and the mitogen-activated protein kinase family such as c-Jun NH2-terminal kinases (JNK), extracellular signal-regulated kinases and p38, were also evaluated. The results show that the cocoa-rich diet decreases the nuclear levels of NF-κB and the expression of pro-inflammatory enzymes such as cyclo-oxygenase-2 and inducible NO synthase induced by AOM in the colon. Additionally, the experiments in Caco-2 cells confirm that cocoa polyphenols effectively down-regulate the levels of inflammatory markers induced by TNF-α by inhibiting NF-κB translocation and JNK phosphorylation. We conclude that cocoa polyphenols suppress inflammation-related colon carcinogenesis and could be promising in the dietary prevention of intestinal inflammation and related cancer development.

Diallyl tetrasulfane activates both the eIF2α and Nrf2/HO-1 pathways

BACKGROUND

Diallyl polysulfanes have been shown to exert cell cycle arrest, anti-tumor and anti-inflammatory activities in a variety of in vitro and in vivo models. Although diallyl polysulfanes cause oxidative stress, little is known about the underlying signaling cascades leading to antioxidant defense or apoptosis.

METHODS

Cells were treated with DATTS at different concentrations and for different time periods. Reactive oxygen species and thiol concentrations were determined by commercially available kits. The expression levels of signal molecules were determined by Western Blot analysis. A direct influence of Nrf2 on the promoter of HO-1 gene was determined by a luciferase assay with the StRE promoter element from the HO-1 gene.

RESULTS

We found an immediate increase in the level of the superoxide anion radical O(2)(-) and hydrogen peroxide H(2)O(2) and an overall thiol depletion. DATTS treatment of HCT116 cells also caused an up-regulation of phospho-eIF2α, nuclear Nrf2 and HO-1 protein levels in a time and concentration-dependent manner. Pre-treatment of cells with antioxidants significantly reduced the elevated expression levels of these proteins. A direct contribution of Nrf2 was shown by its interaction with the stress-response element of the HO-1 promoter.

CONCLUSIONS

DATTS activates the ROS-eIF2α/Nrf2 HO-1 signaling cascades leading to the up-regulation of HO-1. However, this antioxidant defense is not sufficient to protect HCT116 cells from apoptosis.

GENERAL SIGNIFICANCE

This study shows for the first time a parallel but not equal activation of signaling pathways by DATTS with a competitive ultimate cellular outcome.

Immunomodulatory activity of polyphenols derived from Cassia auriculata flowers in aged rats

The immunomodulatory activity of Cassia auriculata (CA)-derived polyphenols was tested on aged rats. Rats (24-26 months old) were given CA polyphenols supplementation at doses of 25, 50, and 100 mg/kg for 28 days. Flow cytometry analysis of CA polyphenols-treated aged rats showed increased T and B cells percentage along with enhanced proliferation of splenocytes in both resting and LPS-stimulated cells. Increased percentage of pan T cells is further supported by an elevation of CD4+, CD8+, and CD4+CD25+ regulatory cells. In terms of innate immune cell activity, CA polyphenol supplementation reduced the oxidative burst activity of neutrophils in response to PMA and Escherichia coli activation. Our results collectively show that polyphenols derived from CA boost T cell immunity by increasing the number of T cells and its sensitivity towards stimulants and decreasing ROS production by neutrophils that could potentially harm multiple biological systems in aged individuals.