Apple procyanidins activate apoptotic signaling pathway in human colon adenocarcinoma cells by a lipid-raft independent mechanism

Limiting glutamine utilization activates a GCN2/TRAIL-R2/Caspase-8 apoptotic pathway in glutamine-addicted tumor cells

Oncogenic transformation leads to changes in glutamine metabolism that make transformed cells highly dependent on glutamine for anabolic growth and survival. Herein, we investigated the cell death mechanism activated in glutamine-addicted tumor cells in response to the limitation of glutamine metabolism. We show that glutamine starvation triggers a FADD and caspase-8-dependent and mitochondria-operated apoptotic program in tumor cells that involves the pro-apoptotic TNF-related apoptosis-inducing ligand receptor 2 (TRAIL-R2), but is independent of its cognate ligand TRAIL. In glutamine-depleted tumor cells, activation of the amino acid-sensing general control nonderepressible-2 kinase (GCN2) is responsible for TRAIL-R2 upregulation, caspase-8 activation, and apoptotic cell death. Interestingly, GCN2-dependent ISR signaling induced by methionine starvation also leads to TRAIL-R2 upregulation and apoptosis. Moreover, pharmacological inhibition of transaminases activates a GCN2 and TRAIL-R2-dependent apoptotic mechanism that is inhibited by non-essential amino acids (NEAA). In addition, metabolic stress upon glutamine deprivation also results in GCN2-independent FLICE-inhibitory protein (FLIP) downregulation facilitating caspase-8 activation and apoptosis. Importantly, downregulation of the long FLIP splice form (FLIP_L) and apoptosis upon glutamine deprivation are inhibited in the presence of a membrane-permeable α-ketoglutarate. Collectively, our data support a model in which limiting glutamine utilization in glutamine-addicted tumor cells triggers a previously unknown cell death mechanism regulated by GCN2 that involves the TRAIL-R2-mediated activation of the extrinsic apoptotic pathway.

Bioactive phenolic components and potential health effects of chestnut shell: A review

Chestnut kernels are often used for direct consumption; or processed to produce marron glacé, chestnut purée, and gluten-free products, while chestnut by-products (inner shell and outer shell) are treated as waste residues. Many in vivo and in vitro studies have proved how chestnut shell extract functions as an antioxidant and exhibits anticancer, anti-inflammatory, antidiabetic, and anti-obesity activities. This review introduces the main components of phenolic compounds in chestnut shells, traditional and modern extraction methods, and reported potential health effects. The aim is to have a better understanding of the functional active ingredients in chestnut shells and their value-added uses, to increase understanding of future applications of this agricultural and sideline product in the food, pharmaceutical, and cosmetic industries. PRACTICAL APPLICATIONS: In recent years, chestnut shells have become a hot research topic because of their rich bioactive ingredients. Due to the large amount of phenolic compounds in chestnut shells and their potential health functions (antioxidant, anticancer, antibacterial, anti-inflammatory, hypoglycemic, and treatment of obesity), extracts of chestnut shells have high biological value in the treatment of diseases. Therefore, this review introduces the main components of phenolic compounds in chestnut shells, traditional and modern extraction methods, and the potential health effects of these compounds. The aim of this review is to better understand the functional, active ingredients in chestnut shells and their value-added uses, and to increase understanding of future applications of this agricultural and sideline product in the food, pharmaceutical, and cosmetic industries.

Understanding toward the Biophysical Interaction of Polymeric Proanthocyanidins (Persimmon Condensed Tannins) with Biomembranes: Relevance for Biological Effects

Persimmon condensed tannins (PT) are highly polymerized (mDP = 26) and highly galloylated (72%) proanthocyanidins. Its pleiotropic effects in oxidation resistance, neuroprotection, hypolipidemia, and cardio-protection both in vitro and in vivo were widely reported. Because large proanthocyanidins are unlikely to be absorbed in the gastrointestinal tract, it is believed that the interaction of PT with biological membranes may play a crucial role in its biological activities. In the present study, the capacities of PT adsorbing to membrane, partitioning into membrane, and its influence on the membrane fluidity were investigated by fluorescence quenching, isothermal titration calorimetry (ITC) and fluorescence anisotropy measurements in a biomembrane-mimetic system composed of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE), sphingomyelin (SPM), and cholesterol (CHOL). Besides, the effects of PT on the morphology and integrity of the cell membrane were studied by scanning electron microscopy (SEM) and fluorescence staining in the 3T3-L1 cell model. The results suggested that PT could affect cell membrane rafts domains, destroy the cell membrane morphology, and regulate cell membrane fluidity, which might contribute to its biological effects.

The use of natural compounds for the targeting and chemoprevention of ovarian cancer

Among gynaecological cancers, ovarian cancer represents the leading cause of death in women. Current treatment for ovarian cancer entails surgery followed by combined chemotherapy with platinum and taxane, which are associated, particularly cisplatin, with severe side effects. While this treatment approach appears to be initially effective in a high number of patients, nearly 70% of them suffer a relapse within a few months after initial treatment. Therefore, more effective and better-tolerated treatment options are clearly needed. In recent years, several natural compounds (such as curcumin, epigallocatechin 3-gallate (EGCG), resveratrol, sulforaphane and Withaferin-A), characterized by long-term safety and negligible and/or inexistent side effects, have been proposed as possible adjuvants of traditional chemotherapy. Indeed, several in vitro and in vivo studies have shown that phytocompounds can effectively inhibit tumor cell proliferation, stimulate autophagy, induce apoptosis, and specifically target ovarian cancer stem cells (CSCs), which are generally considered to be responsible for tumor recurrence in several types of cancer. Here we review current literature on the role of natural products in ovarian cancer chemoprevention, highlighting their effects particularly on the regulation of inflammation, autophagy, proliferation and apoptosis, chemotherapy resistance, and ovarian CSC growth.

A-type ECG and EGCG dimers inhibit 3T3-L1 differentiation by binding to cholesterol in lipid rafts

The present study aimed to explore the underlying mechanisms of epicatechin-3-gallate-(4β→8, 2β→O→7)-epicatechin-3-gallate (A-type ECG dimer) and epigallocatechin-3-gallate-(4β→8, 2β→O→7)-epigallocatechin-3-gallate (A-type EGCG dimer) involved in their strong inhibitory effects on 3T3-L1 preadipocytes differentiation. In the synthetic "lipid raft-like" liposome, A-type ECG and EGCG dimers incorporated into the liposome with high affinity and decreased the fluidity of the liposome. In 3T3-L1 preadipocytes, A-type ECG and EGCG dimers possibly bonded to lipid rafts cholesterol and disrupted the integrity of lipid rafts, thus exerting their notable inhibitory effects on 3T3-L1 preadipocytes differentiation by suppressing mitotic clonal expansion process and mRNA levels of PPARγ, C/EBPα and SREBP1C. A highly positive correlation between the cholesterol binding capacity of the two dimers and their inhibitory effect on 3T3-L1 preadipocytes differentiation (R²=0.9328) was observed. Molecular dynamics simulation further verified that A-type ECG and EGCG dimers could bond to cholesterol via hydrogen bonding. The results of this study suggested that the disruption of A-type ECG and EGCG dimers on membrane lipid rafts by targeting cholesterol in the lipid rafts was involved in the underlying mechanisms of their strong inhibitory effects on 3T3-L1 preadipocytes differentiation. This broadens the understanding of the molecular mechanisms of polyphenols on modulating and controlling of metabolic dysregulation, particularly adipocyte differentiation, which is a significant risk factor associated with the development of cardiovascular disease.

Restoring TRAIL Induced Apoptosis Using Naturopathy. Hercules Joins Hand with Nature to Triumph Over Lernaean Hydra

Cancer is a multifaceted disease. Our deepened knowledge about genetic and biological mechanisms of cancer cells presents an opportunity to explore the inter-individual differences in the body’s ability to metabolize and respond to different nutrients. It is becoming progressively more understandable that the deregulation of several signaling pathways and the alterations in apoptotic response are some of the major determinants that underpin carcinogenesis. Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL)-mediated signaling has gained a remarkable appreciation because of its ability to selectively induce apoptosis in cancer cells leaving normal cells intact. However, technological advances have started to shed light on underlying mechanisms of resistance against TRAIL-induced apoptosis in cancer cells. The impairment of TRAIL-mediated apoptosis includes various factors ranging from the loss or down regulation of TRAIL receptors or pro-apoptotic proteins to the up regulation of anti-apoptotic proteins. Intriguingly to mention that there is an ever-increasing number of natural herbal extracts (phytometabolites), which have been explored to date for their potential action in restoring apoptosis TRAIL-mediated in cancer cells. In this review, we will highlight the progress in understanding the mechanisms opted by phenolic compounds in overcoming TRAIL resistance.

Impact of Procyanidins from Different Berries on Caspase 8 Activation in Colon Cancer

Scope. The aim of this work is to identify which proapoptotic pathway is induced in human colon cancer cell lines, in contact with proanthocyanidins extracted from various berries. Methods and Results. Proanthocyanidins (Pcys) extracted from 11 berry species are monitored for proapoptotic activities on two related human colon cancer cell lines: SW480-TRAIL-sensitive and SW620-TRAIL-resistant. Apoptosis induction is monitored by cell surface phosphatidylserine (PS) detection. Lowbush blueberry extract triggers the strongest activity. When tested on the human monocytic cell line THP-1, blueberry Pcys are less effective for PS externalisation and DNA fragmentation is absent, highlighting a specificity of apoptosis induction in gut cells. In Pcys-treated gut cell lines, caspase 8 (apoptosis extrinsic pathway) but not caspase 9 (apoptosis intrinsic pathway) is activated after 3 hours through P38 phosphorylation (90 min), emphasizing the potency of lowbush blueberry Pcys to eradicate gut TRAIL-resistant cancer cells. Conclusion. We highlight here that berries Pcys, especially lowbush blueberry Pcys, are of putative interest for nutritional chemoprevention of colorectal cancer in view of their apoptosis induction in a human colorectal cancer cell lines.

Differential modulation of apoptotic processes by proanthocyanidins as a dietary strategy for delaying chronic pathologies

Apoptosis is a biological process necessary for maintaining cellular homeostasis. Several diseases can result if it is deregulated. For example, inhibition of apoptotic signaling pathways is linked to the survival of pathological cells, which contributes to cancer, whereas excessive apoptosis is linked to neurodegenerative diseases, partially via oxidative stress. The activation or restoration of apoptosis via extrinsic or intrinsic pathways combined with cell signaling pathways triggered by reactive oxygen specises (ROS) formation is considered a key strategy by which bioactive foods can exert their health effects. Proanthocyanidins, a class of flavonoids naturally found in fruits, vegetables, and beverages, have attracted a great deal of attention not only because they are strong antioxidants but also because they appear to exert a different modulation of apoptosis, stimulating apoptosis in damaged cells, thus preventing cancer or reducing apoptosis in healthy cells, and as a result, preserving the integrity of normal cells and protecting against neurodegenerative diseases. Therefore, proanthocyanidins could provide a defense against apoptosis induced by oxidative stress or directly inhibit apoptosis, and they could also provide a promising treatment for a variety of diseases. Emerging data suggest that proanthocyanidins, especially those that humans can be persuaded to consume, may be used to prevent and manage cancer and mental disorders.

Application of an Optimized HPLC Method for the Detection of Various Phenolic Compounds in Apples from Lithuanian Cultivars

A specific analytical procedure including sample preparation and HPLC analysis was developed and validated for the detection of phenolic compounds in the samples of different apples from popular Lithuanian cultivars “Aldas,” “Auksis,” “Ligol,” and “Šampion.” The conditions for phenol extraction were optimized: the solvent of the extraction was 70% (v/v) ethanol, and the extraction was performed in an ultrasound bath for 20 min at the temperature of 40°C. The HPLC mobile phase consisted of 2% (v/v) acetic acid in water and 100% (v/v) acetonitrile. Using the HPLC technique, 11 analytes were identified, and their specificity was confirmed: procyanidin B1, (+)-catechin, chlorogenic acid, procyanidin B2, (−)-epicatechin, rutin, hyperoside, isoquercitrin, avicularin, quercitrin, and phloridzin. Chlorogenic acid was the major component in “Aldas,” “Auksis,” and “Ligol” and procyanidin B2 in “Šampion.” Hyperoside and avicularin were the dominant compounds of all the identified quercetin derivatives in “Aldas” and “Auksis;” hyperoside in “Šampion;” and quercitrin in “Ligol.” The total content of phenolic compounds varied from 1641.0 ± 47.9 μg/g (cv. “Ligol”) to 4291.3 ± 154.2 μg/g (cv. “Aldas”).

Quercetin and epigallocatechin gallate induce in vitro a dose-dependent stiffening and hyperpolarizing effect on the cell membrane of human mononuclear blood cells

The bioactivity of polyphenols is closely linked to their ability to interact with biological membranes. The study evaluates the in vitro effect of quercetin and epigallocatechin on the membrane anisotropy and transmembrane potential of peripheral blood mononuclear cells (PBMCs) isolated from 26 type 2 diabetes mellitus patients compared to 25 age matched controls. The in vitro assays were analyzed in correlation with the biochemical and inflammatory profile of the subjects and with insulin resistance parameters (HOMA-IR, plasma resistin) as well. For type 2 diabetes patients, the increase of HOMA-IR and resistin concentration was associated with a significant decrease of the PBMCs membrane anisotropy. The two tested polyphenols induced a dose-dependent hyperpolarizing effect and stiffening of the cell membranes for all tested subjects. Physiological levels of quercetin and epigallocatechin gallate had the tendency to normalize the PBMCs membrane anisotropy of the cells isolated from diabetes patients, bringing it to the level of cells isolated from normoglycemic ones. Epigallocatechin gallate induced higher effects compared to quercetin on the membranes isolated from subjects with higher cardiovascular risk. The decrease of membrane fluidity and the hyperpolarizing effect could explain the cardiovascular protective action of the tested compounds.

Proanthocyanidins: Oligomeric Structures with Unique Biochemical Properties and Great Therapeutic Promise

Proanthocyanidins represent a unique class of oligomeric and polymeric secondary metabolites found ubiquitously and in considerable amounts in plants and some algae. These substances exhibit a range of rather surprising physical and chemical properties which, once applied to living organisms, are translated into a multitude of biological activities. The latter include antioxidant properties, cancer chemoprevention, anti-inflammatory and anti-diabetic effects as well as some exceptional, yet highly interesting activities, such as anti-nutritional and antimicrobial activity. Despite the wide range of activities and possible medical/agricultural applications of proanthocyanidins, many questions still remain, including issues related to bioavailability, metabolism and the precise biochemical, extra- and intracellular targets and mode(s) of action of these highly potent materials. Among the various physical and chemical interactions of such substances, strong binding to proteins appears to form the basis of many of their biological activities. Once easy-to-use synthetic methods to produce appropriate quantities of pure proanthocyanidins are available, it will be possible to identify the prime biological targets of these oligomers, study oligomer-protein interactions in more detail and develop possible practical applications in medicine and agriculture.

Regulating TRAIL receptor-induced cell death at the membrane : a deadly discussion

The use of TRAIL/APO2L and monoclonal antibodies targeting TRAIL receptors for cancer therapy holds great promise, due to their ability to restore cancer cell sensitivity to apoptosis in association with conventional chemotherapeutic drugs in a large variety of tumors. TRAIL-induced cell death is tightly regulated right from the membrane and at the DISC (Death-Inducing Signaling Complex) level. The following patent and literature review aims to present and highlight recent findings of the deadly discussion that determines tumor cell fate upon TRAIL engagement.

Basic biochemical mechanisms behind the health benefits of polyphenols

Polyphenols and consequently many flavonoids have several beneficial actions on human health. However, the actual molecular interactions of polyphenols with biological systems remain mostly speculative. This review addresses the potential mechanisms of action that have been so far identified, as well as the feasibility that they could occur in vivo. Those mechanisms include: i) non specific actions, based on chemical features common to most polyphenols, e.g. the presence of a phenol group to scavenge free radicals; and ii) specific mechanisms; based on particular structural and conformational characteristics of select polyphenols and the biological target, e.g. proteins, or defined membrane domains. A better knowledge about the nature and biological consequences of polyphenol interactions with cell components will certainly contribute to develop nutritional and pharmacological strategies oriented to prevent the onset and/or the consequences of human disease.