Proanthocyanidin exposure to B6C3F1 mice significantly attenuates dimethylnitrosamine-induced liver tumor induction and mortality by differentially modulating programmed and unprogrammed cell deaths

Evaluation of the medicinal herb Graptopetalum paraguayense as a treatment for liver cancer

Background

Hepatocellular carcinoma (HCC) is the fifth most common malignancy and the third most common cause of cancer-related death worldwide. Sorafenib is the only drug for patients with advanced-stage hepatocellular carcinoma (HCC) that has been shown to confer a survival benefit to patients with HCC; however, it has many side effects. Thus, alternate therapeutic strategies with improved safety and therapeutic efficacy for the management of HCC should be developed.

Methods and Findings

We demonstrate that an extract of Graptopetalum paraguayense (GP) down-regulated the expression levels of several onco-proteins, including AURKA, AURKB, and FLJ10540, in HCC cells. To isolate the active components in the GP extracts, we prepared extracts fractions and assessed their effects on the expression of onco-proteins in HCC cells. The fraction designated HH-F3 was enriched in active ingredients, exhibited cytotoxic effects, and suppressed the expression of the onco-proteins in HCC cells. The structure of the main active compound in HH-F3 was found to be similar to that of the proanthocyanidin compounds derived from Rhodiola rosea. In addition, a distinct new compound rich in 3, 4, 5-trihydroxy benzylic moieties was identified in the HH-F3 preparations. Mechanistic studies indicated that HH-F3 induced apoptosis in HCC cells by promoting the loss of mitochondrial membrane potential and the production of reactive oxygen species. HH-F3 also enhanced PTEN expression and decreased AKT phosphorylation at Ser473 in a concentration-dependent manner in HCC cells. Moreover combination of GP or HH-F3 and sorafenib synergistically inhibits the proliferation of Huh7 cells. The treatment of a rat model with diethylnitrosamine (DEN)-induced liver cancer with extracts of GP and HH-F3 decreased hepatic collagen contents and inhibited tumor growth.

Conclusions

These results indicate that GP extracts and HH-F3 can protect the liver by suppressing tumor growth; consequently, these compounds could be considered for the treatment of HCC.

Acute liver injury induced by low dose dimethylnitrosamine alters mediators of hepatic vascular flow

Alterations in liver vascular tone play an important role in chronic liver disease. The hepatic stellate cell (HSC) and mediators such as nitric oxide (NO) and hydrogen sulfide (H₂S) have been implicated in regulation of vascular tone and intra-hepatic pressure. Though these have been studied in chronic liver damage, changes in response to acute liver injury induced by hepatotoxins such as dimethyl nitrosamine are not well understood. Liver injury was induced in mice by a single intra-peritoneal injection of dimethylnitrosamine (DMN), following which animals were sacrificed at 24, 48 and 72 h. Changes in vascular mediators such as NO and H₂S as well as stellate cell activation was then examined. It was found that a single low dose of DMN in mice is sufficient to induce activation of hepatic stellate cells within 24 h, accompanied by oxidative stress, compromised metabolism of H₂S and decreased levels of the von Willebrand factor (vWF) cleaving protease; a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), which functions in intravascular thrombosis. A suppression of hepatic NO levels is also initiated at this time point, which progresses further and is sustained up to 72 h, at which point the HSC activation is still present. Compromised levels of ADAMTS13 and H₂S metabolism however, begin to recover by 48 h and are almost similar to control by 72 h. In conclusion, these data suggest that even moderate acute insults in the liver can have far reaching consequences on a number of mediators of vascular flow in the liver.

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.

Free radical scavenging, antioxidant and cancer chemoprevention by grape seed proanthocyanidin: an overview

A large number of investigations have demonstrated a broad spectrum of pharmacological and therapeutic benefits of grape seed proanthocyanidins (GSP) against oxidative stress and degenerative diseases including cardiovascular dysfunctions, acute and chronic stress, gastrointestinal distress, neurological disorders, pancreatitis, various stages of neoplastic processes and carcinogenesis including detoxification of carcinogenic metabolites. GSP exhibited potent free radical scavenging abilities in both in vitro and in vivo models. GSP exerted significant in vivo protection against structurally diverse drug and chemical-induced hepatotoxicity, cardiotoxicity, neurotoxicity, nephrotoxicity and spleentoxicity. GSP also protected against idarubicin and 4-hydroxyperoxy-cyclophosphamide-induced cytotoxicity toward human normal liver cells. GSP exhibited selective cytotoxicity toward selected human cancer cells, while enhancing the growth and viability of normal cells. GSP exhibited potent modulatory effects of pro-apoptotic and apoptotic regulatory bcl-XL, p53, c-myc, c-JUN, JNK-1 and CD36 genes. Long-term exposure to GSP may serve as a novel chemoprotectant against three stages of DMN-induced liver carcinogenesis and tumorigenesis including initiation, promotion and progression. GSP may selectively protect against oxidative stress, genomic integrity and cell death patterns in vivo. These results demonstrate that GSP may serve as a novel therapeutic intervention against carcinogenesis.

Matrix metalloproteinase-9, -10, and -12, MDM2 and p53 expression in mouse liver during dimethylnitrosamine-induced oxidative stress and genomic injury

Treatment during early tumor development has greater success because tissue growth remains largely confined to its original locus. At later stages, malignant cells migrate from their original location, invade surrounding normal areas, and can disseminate widely throughout the body. Remodeling of the extracellular matrix (ECM) serves as a key facilitator of this dissemination. Proteolytic enzymes including plasmin and matrix metalloproteinases (MMPs) play an integral role in degrading the surrounding ECM proteins and clearing a path for tumor cell migration. Specific MMPs are highly expressed late during malignant tumor invasion. It is not understood whether early changes in MMPs influence apoptotic and necrotic cell death, processes known to govern the early stages of carcinogenesis. Similarly, the interaction between MDM2 and p53 is tightly controlled by a complex array of post-translational modifications, which in turn dictates the stability and activity of both p53 and MDM2. The present studies examine the hypothesis that model hepatotoxin dimethylnitrosamine (DMN), which is also a model carcinogen, will induce the MMP family of proteins after administration in hepatotoxic doses. Doses of 25, 50, and 100 mg/kg DMN were administered i.p. to male C3H mice. Changes in parameters associated with apoptotic and necrotic cell death, DNA damage, cell proliferation, and extracellular proteinases were examined in liver at 24 h. Serum ALT activity, oxidative stress [malondialdehyde], and caspase-activated DNAse mediated DNA laddering increased in a dose-dependent manner, as did the level of MDM2 protein. MMP-9, -10 and -12 (gelatinase-B, stromelysin-2, macrophage elastase), and p53 protein levels increased following 25 mg/kg DMN, but were successively decreased after higher DMN doses. The results of this study demonstrate changes in MDM2 and MMPs during DMN-induced acute liver injury and provide a plausible linkage between DMN-induced oxidative stress-mediated genomic injury and its likely involvement in setting the stage for initiating subsequent metastatic disease at later circumstances.

Protective effects of green and white tea against benzo(a)pyrene induced oxidative stress and DNA damage in murine model

In the current investigation, the ameliorative effect of green tea (GT) and white tea (WT) against benzo(a)pyrene (BaP) induced oxidative stress and DNA damage has been studied in the livers and lungs of Balb/c mice. A single dose of BaP (125 mg/kg, b.w. orally) increased the levels of lipid peroxidation (LPO) and decreased endogenous antioxidants such as superoxide dismutase (SOD), glutahione reductase (GR), catalase (CAT), and glutathione (GSH) significantly. Pretreatment with GT and WT for 35 days before a single dose of BaP elevated the decreased activity of GR, SOD, and CAT in liver tissue and also tended to normalize the levels of GSH and LPO in both hepatic and pulmonary tissues. The percentage of DNA in comet tail and 8-hydroxy-2'-deoxyguanosine levels reflected the decreasing pattern of DNA damage from the BaP-treated group to the groups that received pretreatment with GT and WT. Our study concludes that both GT and WT are effective in combating BaP induced oxidative insult and DNA damage. However, WT was found to be more protective than GT with respect to CAT (only in the liver), percentage of DNA in comet tail (only in the lungs), GST activity, and GSH content in both the tissues.

A novel dietary supplement containing multiple phytochemicals and vitamins elevates hepatorenal and cardiac antioxidant enzymes in the absence of significant serum chemistry and genomic changes

A novel dietary supplement composed of three well-known phytochemicals, namely, Salvia officinalis (sage) extract, Camellia sinensis (oolong tea) extract, and Paullinia cupana (guarana) extract, and two prominent vitamins (thiamine and niacin) was designed to provide nutritional support by enhancing metabolism and maintaining healthy weight and energy. The present study evaluated the safety of this dietary supplement (STG; S=sage; T=tea; G=guarana) and assessed changes in target organ antioxidant enzymes (liver, kidneys and heart), serum chemistry profiles and organ histopathology in Fisher 344 rats. Adult male and female Fisher 344 rats were fed control (no STG) or STG containing (1X and 7X, 1X=daily human dose) diets and sacrificed after 2 and 4 months. Serum chemistry analysis and histopathological examination of three vital target organs disclosed no adverse influence on protein, lipid and carbohydrate profiles, genomic integrity of the liver and/or the tissue architecture. However, analysis of the most important antioxidant components in the liver, kidney and heart homogenates revealed a dramatic increase in total glutathione concentrations, glutathione peroxidase and superoxide dismutase enzyme activities. Concomitantly, oxidative stress levels (malondialdehyde accumulation) in these three organs were less than control. Organ specific serum markers (ALT/AST for the liver; CPK/AST for the heart; BUN/creatinine for kidneys) and the genomic integrity disclosed no STG-induced alteration. Some of the serum components (lipid and protein) showed insignificant changes. Overall, STG-exposed rats were more active, and the results suggest that STG exposure produces normal serum chemistry coupled with elevated antioxidant capacity in rats fed up to seven times the normal human dose and does not adversely influence any of the vital target organs. Additionally, this study reiterates the potential benefits of exposure to a pharmacologically relevant combination of phytochemicals compared to a single phytochemical entity.

Silymarin modulates doxorubicin-induced oxidative stress, Bcl-xL and p53 expression while preventing apoptotic and necrotic cell death in the liver

The emergence of silymarin (SMN) as a natural remedy for liver diseases, coupled with its entry into NIH clinical trial, signifies its hepatoprotective potential. SMN is noted for its ability to interfere with apoptotic signaling while acting as an antioxidant. This in vivo study was designed to explore the hepatotoxic potential of Doxorubicin (Dox), the well-known cardiotoxin, and in particular whether pre-exposures to SMN can prevent hepatotoxicity by reducing Dox-induced free radical mediated oxidative stress, by modulating expression of apoptotic signaling proteins like Bcl-xL, and by minimizing liver cell death occurring by apoptosis or necrosis. Groups of male ICR mice included Control, Dox alone, SMN alone, and Dox with SMN pre/co-treatment. Control and Dox groups received saline i.p. for 14 days. SMN was administered p.o. for 14 days at 16 mg/kg/day. An approximate LD(50) dose of Dox, 60 mg/kg, was administered i.p. on day 12 to animals receiving saline or SMN. Animals were euthanized 48 h later. Dox alone induced frank liver injury (>50-fold increase in serum ALT) and oxidative stress (>20-fold increase in malondialdehyde [MDA]), as well as direct damage to DNA (>15-fold increase in DNA fragmentation). Coincident genomic damage and oxidative stress influenced genomic stability, reflected in increased PARP activity and p53 expression. Decreases in Bcl-xL protein coupled with enhanced accumulation of cytochrome c in the cytosol accompanied elevated indexes of apoptotic and necrotic cell death. Significantly, SMN exposure reduced Dox hepatotoxicity and associated apoptotic and necrotic cell death. The effects of SMN on Dox were broad, including the ability to modulate changes in both Bcl-xL and p53 expression. In animals treated with SMN, tissue Bcl-xL expression exceeded control values after Dox treatment. Taken together, these results demonstrated that SMN (i) reduced, delayed onset, or prevented toxic effects of Dox which are typically associated with hydroxyl radical production, (ii) performed as an antioxidant limiting oxidative stress, (iii) protected the integrity of the genome, and (iv) antagonized apoptotic and necrotic cell death while increasing antiapoptotic Bcl-xL protein levels and minimizing the leakage of proapoptotic cytochrome c from liver mitochondria. These observations demonstrate the protective actions of SMN in liver, and raise the possibility that such protection may extend to other organs during Dox treatment including the heart.

Protective Effects of Proanthocyanidin on Cerulein-induced Acute Pancreatic Inflammation in Rats

Background

The aim of this study was to assess the possible protective effect of proanthocyanidin against cerulein-induced acute pancreatic inflammation (AP) and oxidative injury.

Methods

Sprague-Dawley rats were pretreated with proanthocyanidine (100 mg/kg, orally) or saline 15 min before cerulein was given by 20 µg/kg subcutaneously at 1-h intervals within 4 hours. Six hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1b). Pancreas tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na⁺, K⁺-ATPase and myeloperoxidase (MPO) activities. Formation of reactive oxygen species in pancreatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes, while the extent of tissue injury was analyzed microscopically.

Results

Acute pancreatitis caused a significant decrease in tissue GSH level and Na⁺, K⁺-ATPase activity, which was accompanied with significant increases in the pancreatic MDA, luminol and lucigenin chemiluminescences (CL) levels and MPO activity. Similarly TNF-α and IL-1β levels were elevated in the pancreatic group as compared to control group. On the other hand, proanthocyanidin treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by cerulein.

Conclusions

Proanthocyanidine can ameliorate pancreatic injury induced by cerulein in rats, this result suggests that proanthocyanidin may have utility in treating acute pancreatititis.

Inhibition of U-87 human glioblastoma cell proliferation and formyl peptide receptor function by oligomer procyanidins (F2) isolated from grape seeds

Gliomas are the most common and lethal tumor type in the brain. The present study investigated the effect of oligomer procyanidins (F2) (F2, degree of polymerization 2-15), a natural fraction isolated from grape seeds on the biological behavior of glioblastoma cells. We found that F2 significantly inhibited the glioblastoma growth, with little cytotoxicity on normal cells, induced G2/M arrest and decreased mitochondrial membrane potential in U-87 cells. It also induced a non-apoptotic cell death phenotype resembling paraptosis in U-87 cells. In addition, it was found for the first time that F2 in non-cytotoxic concentrations selectively inhibited U-87 cell chemotaxis mediated by a G-protein coupled receptor formyl peptide receptor FPR, which is implicated in tumor cell invasion and metastasis. Further experiments indicated that F2 inhibited fMLF-induced U-87 cell calcium mobilization and MAP kinases ERK1/2 phosphorylation. Moreover, F2 attenuated the glioblastoma FPR expression, a new molecular target for glioma therapeutics, which has been shown to play important roles in glioma cells chemotaxis, proliferation and angiogenesis in addition to its promotion to tumor progression, but did not affect FPR mRNA expression in U-87 cells. Taken together, our results suggest that F2 may be a promising candidate for the development of novel anti-tumor therapeutics.

Flavonoid-rich grapeseed extracts: a new approach in high cardiovascular risk patients?

The management of traditional risk factors such as hypertension and dyslipidaemia has been successful in reducing the development of cardiovascular disease. However, this has not resulted in the amelioration of complications; prompting attention to be focused on novel markers of vascular risk such as endothelial dysfunction (a determinant of vascular tone), vascular inflammation, oxidative stress and insulin resistance. With an ever-growing interest in plant-derived products, agents that could have a beneficial effect on this complex web of pathophysiology have thus been a major area of research and interest. Flavonoids have been a major focus of attention since the days of the French paradox and the presence of high quantity of flavonoids in grapeseed extracts has prompted research looking at its effects on novel markers of vascular risk. This review briefly summarises mechanisms implicated in the development of vascular disease and then focuses upon the potential role of the antioxidant properties of flavonoid-rich grapeseed extracts in the reversal of these processes.

Pre-exposure to a novel nutritional mixture containing a series of phytochemicals prevents acetaminophen-induced programmed and unprogrammed cell deaths by enhancing BCL-XL expression and minimizing oxidative stress in the liver

From a disease-prevention perspective, recent progress in phytochemical and nutraceutical research clearly suggests (benefits outweigh the risk pattern). Although powerful antioxidant properties have been the most acclaimed mechanism of action for these entities, the individual antioxidants studied in clinical trials do not appear to have consistent preventative effects. The actions of the antioxidant nutrients alone do not explain the observed health benefits of diets rich in fruits and vegetables for chronic diseases. Therefore, we proposed that the additive and synergistic effects of phytochemicals in fruits and vegetables are responsible for these potent antioxidant and anticancer activities, and that the benefit of a diet rich in fruits and vegetables is attributed to the complex mixture of phytochemicals present in plants [1]. Surprisingly, however, no studies have attempted to evaluate the combined antitoxic potential of a phytochemical-nutraceutical mixture (PNM) in in vivo models. Therefore, this study, for the first time, was designed to investigate whether pre-exposure to a unique PNM has the ability to impede mechanistic events involved in acetaminophen (APAP)-induced hepatotoxicity. Besides several vitamins and minerals in balanced proportions (approximately US RDA), the PNM used in this investigation contained several well-known phytochemicals such as citrus flavonoids, red wine polyphenols, Garcinia, Gymnema, Ginkgo, Ephedra sinica, Camellia sinensis, Silybum, Guarana, Eluthero, Allium sativum and Ocimum basilicum extracts. To evaluate PNM's antitoxic potential, groups of animals ICR mice, 3 months old) received either a control diet or PNM containing diets (1X and 10X) for 4 weeks. On day-28, animals were divided into two subgroups. Half the animals were administered normal saline and the other half received 400mg/kg ip injections of APAP. All the animals were sacrificed 24h after APAP exposure. Serum and tissue (liver and kidneys) samples were analyzed. APAP alone caused massive liver injury (nearly 495-fold increase in ALT) and oxidative stress (Lipid peroxidation: 268% increase in MDA) coupled with genomic DNA fragmentation (288% increase). Exposure to 1X-PNM for 28 days significantly reduced animal mortality and all the APAP-induced biochemical events (In 1X-PNM + AP: ALT leakage decreased to 54 fold; MDA accumulation decreased to 125%, and DNA fragmentation decreased to 122%), whereas 10X-PNM + APAP slightly escalated both oxidative stress and genomic DNA fragmentation preceding liver injury. Liver homogenates subjected to western blot analysis disclosed the ability of 1X-PNM to counteract APAP-induced decrease in Bcl-xL expression. Histopathological evaluation of stained liver tissue sections indicated anti-apoptogenic and anti-necrogenic reponses coupled with near complete prevention of glycogen depletion by 1X-PNM. Collectively, our investigation suggests that a mixture containing an assortment of phytochemicals/nutraceuticals may serve as a much more powerful blend in preventing drug or chemical-induced organ injuries than a single phytochemical or nutraceutical entity. In addition, ephedra and caffeine containing PNM-exposure in a controlled manner may potentially shield vital target organs from toxicities caused by intentional, unintentional or accidental exposures to structurally and functionally diverse drug and chemical entities.

Assessment of the DNA damaging potency and chemopreventive effects towards BaP-induced genotoxicity in human derived cells by Monimiastrum globosum, an endemic Mauritian plant

Naturally occurring compounds have protective effects towards mutagens and carcinogens. The leaf extract of Monimiastrum globosum (Bois de Clous), a Mauritian endemic plant from the Myrtaceae family, was studied for its potency to induce DNA damage in human HepG2 hepatoma cells using DNA migration as a biological endpoint in the alkaline single cell gel electrophoresis (SCGE) assay. This was contrasted with the ability to modulate the benzo[a]pyrene (BaP)-dependent DNA damage in human hepatoma cells. M. globosum caused genotoxicity in HepG2 cells at concentrations exceeding 3mg fresh weight (FW) per ml cell culture in the absence of cytotoxicity. Pre-treatment of the cells with 12.2 microg FW/ml to 1.56 mg FW/ml led to a pronounced antigenotoxic effect towards BaP-induced DNA damage. DNA migration (OTM) was reduced by 66%, 81.5% and 74% for 49, 98 and 195 microg FW/ml, respectively. A U-shaped dose-response curve was derived for M. globosum indicating genotoxic effects in high doses and antigenotoxic effects in low doses. M. globosum extract had total phenolics (15 mg/g FW) with flavonoids (aglycones and conjugates: 8 mg/g FW) and proanthocyanidins (3mg/g FW) as major phenolic subclasses. The hydrolysis of conjugated flavonoids yielded the aglycones quercetin (606 microg/g FW) and kaempferol (117.8 microg/g FW) while HPLC-MS/MS analysis of the total extract revealed free flavonoids such as quercetin (19.2 microg/g FW) and myricetin (2.5 microg/g FW). The antioxidant activity of the extract of M. globosum, assessed by the FRAP and TEAC assays yielded values of 275+/-3.82 micromol/g FW and 346+/-4.2 micromol/g FW, respectively.