A novel proanthocyanidin IH636 grape seed extract increases in vivo Bcl-XL expression and prevents acetaminophen-induced programmed and unprogrammed cell death in mouse liver.

Several molecular events in the apoptotic or necrotic death of hepatocytes induced by acetaminophen (AAP) now appear to be well defined. Recent studies also indicate that select expression of bcl-Xl is possibly modified during AAP-induced liver injury. The purpose of this study was several-fold: (i) to examine the hepatoprotective ability of short-term (3-day) and long-term (7-day) exposures of a grape seed proanthocyanidin extract (GSPE) on AAP-induced liver injury and animal lethality; (ii) to monitor effects of GSPE on one of the prime targets of AAP, i.e., hepatocellular genomic DNA and associated apoptotic and necrotic death; and (iii) to unravel changes in the pattern of expression of an antiapoptotic gene, bcl-Xl in the liver. In order to investigate these events, male ICR mice (30-40 g) were administered nontoxic doses of GSPE (3 or 7 days, 100 mg/kg, po), followed by hepatotoxic doses of AAP (400 and 500 mg/kg, ip), and sacrificed 24 h later. Serum was analyzed for alanine aminotransferase activity (ALT) and the liver for histopathological diagnosis of apoptosis/necrosis. The ability of AAP to promote apoptotic DNA fragmentation and its counteraction by GSPE in the liver was also evaluated quantitatively (by a sedimentation assay) and qualitatively (by agarose gel electrophoresis). Portions of livers were also subjected to Western blot analysis (27,000g fraction of liver homogenates) to examine the pattern of expression of cell death inhibitory gene bcl-Xl. Results indicate that 7-day GSPE preexposure induced dramatic protection and markedly decreased liver injury and animal lethality culminated by AAP, when compared to a short-term 3-day exposure. Abrogation of toxicity was also mirrored in DNA fragmentation. Histopathological evaluation of liver sections showed remarkable counteraction of AAP-toxicity by this novel GSPE and substantial inhibition of both apoptotic and necrotic liver cell death. Agarose gel electrophoresis revealed that 7-day GSPE preexposure prior to AAP administration completely blocked Ca(2+)/Mg(2+)-Ca(2+)/Mg(2+)-dependent-endonuclease-mediated ladder-like fragmentation of genomic DNA and significantly altered the bcl-Xl expression. The most dramatic changes observed in this study were: (i) substantial increase in the expression of bcl-Xl in the liver by 7-day GSPE exposure alone; (ii) significant modification bcl-Xl expression by AAP alone; and (iii) dramatic inhibition of AAP-induced modification of bcl-Xl (phosphorylation?) expression by GSPE. In summary, these observations demonstrate that GSPE preexposure may significantly attenuate AAP-induced hepatic DNA damage, apoptotic and necrotic cell death of liver cells, and, most remarkably, antagonize the influence of AAP-induced changes in bcl-Xl expression in vivo.     

Serum metabolites of proanthocyanidin-administered rats decrease lipid synthesis in HepG2 cells

The regular consumption of flavonoids has been associated with reduced mortality and a decreased risk of cardiovascular diseases. The proanthocyanidins found in plasma are very different from the original flavonoids in food sources. The use of physiologically appropriate conjugates of proanthocyanidins is essential for the in vitro analysis of flavonoid bioactivity.In this study, the effect of different proanthocyanidin-rich extracts, which were obtained from cocoa (CCX), French maritime pine bark (Pycnogenol extract, PYC) and grape seed (GSPE), on lipid homeostasis was evaluated. Hepatic human cells (HepG2 cells) were treated with 25 mg/L of CCX, PYC or GSPE. We also performed in vitro experiments to assess the effect on lipid synthesis that is induced by the bioactive GSPE proanthocyanidins using the physiological metabolites that are present in the serum of GSPE-administered rats. For this, Wistar rats were administered 1 g/kg of GSPE, and serum was collected after 2 h. The semipurified serum of GSPE-administered rats was fully characterized by liquid chromatography tandem triple quadrupole mass spectrometry (LC–QqQ/MS²). The lipids studied in the analyses were free cholesterol (FC), cholesterol ester (CE) and triglycerides (TG).All three proanthocyanidin-rich extracts induced a remarkable decrease in the de novo lipid synthesis in HepG2 cells. Moreover, GSPE rat serum metabolites reduced the total percentage of CE, FC and particularly TG; this reduction was significantly higher than that observed in the cells directly treated with GSPE. In conclusion, the bioactivity of the physiological metabolites that are present in the serum of rats after their ingestion of a proanthocyanidin-rich extract was demonstrated in Hep G2 cells.     

Bovine milk-derived α-lactalbumin prevents hepatic fibrosis induced by dimethylnitrosamine via nitric oxide pathway in rats

The present study was designed to evaluate the hepatoprotective potential of α-lactalbumin (αLA) against dimethylnitrosamine (DMN)-induced toxic insults in the rat liver. The liver damage was induced in rats by the repeated administration of DMN (10 mg/kg, i.p.) on three consecutive days per week for three weeks. The rats were maintained on either a standard AIN-93 M or αLA-enriched diet starting one week before the DMN injection until the termination of the experiment. The DMN treatment produced a progressive increase in the plasma markers (aspartate aminotransferase, alanine aminotransferase, total bililbin, hyarulonic acid, and matrix metalloproteinase-2) in 28 days after the first DMN injection. Dietary treatment with αLA significantly reduced the DMN-induced damage toward normalcy. N^Ｇ-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, significantly attenuated the hepatoprotective effect of αLA. These findings show that αLA has a marked suppressive effect on hepetic fibrosis through a nitric oxide-mediated mechanism.     

The co-administration of proanthocyanidins and an obesogenic diet prevents the increase in intestinal permeability and metabolic endotoxemia derived to the diet

The consumption of Westernized diets leads to hyperphagia and obesity, as well as intestinal alterations. In the present study, we evaluated the effect of the administration of a grape seed proanthocyanidin extract (GSPE) at different time points on the modulation of intestinal barrier function (intestinal permeability and metabolic endotoxemia), in rats with high-fat/high-carbohydrate diet-induced obesity. Animals were fed a cafeteria diet (CAF) supplemented with a preventive (PRE-CAF) or simultaneously intermittent (SIT-CAF) GSPE treatment (500 mg/kg bw). Changes in the plasma levels of an orally administered marker of intestinal permeability (ovalbumin, OVA), lipopolysaccharide (LPS) and tumor necrosis factor-α (TNF-α) were analyzed after animals were fed the obesogenic diet for 8, 12 and 17 weeks. In addition, ex vivo variations in transepithelial electrical resistance (TEER), the expression of tight junction (TJ) genes and the activity of myeloperoxidase (MPO) in the small and large intestines were monitored at the end of the experiment. The CAF diet increased OVA, LPS, MPO and TNF-α levels, accompanied by decreased TEER values in the small and large intestines. Interestingly, both GSPE treatments prevented these detrimental effects of the CAF diet, being the SIT-CAF group the most effective after 17 weeks of diet intervention. For the first time, this study provides evidence of the ameliorative effect of a proanthocyanidin extract, administered before or together with an obesogenic diet, on barrier dysfunction, as measured by intestinal permeability and metabolic endotoxemia.     

Levels of protein kinase C and nitric oxide synthase activity in rats exposed to sub chronic low level lead

Previous studies from our laboratories have linked the protective abilities of IH636 grape seed proanthocyanidin extract (GSPE) with inactivation of anti-apoptotic gene bcl-XL, and modification of several other critical molecular targets such as DNA-damage/DNA-repair, lipid peroxidation and intracellular Ca²⁺ homeostasis. Especially, GSPE provided dramatic protection against acetaminophen (APAP)-induced hepatotoxicity, significantly increased bcl-XL expression in the liver [1], and antagonized both necrotic and apoptotic deaths of liver cells in vivo. However, it was not clear from this study whether anti-apoptogenic and anti-necrotic effects of GSPE were: (i) due to its interference with endonuclease activity, (ii) due to its antioxidant effect, or, (iii) due to its ability to inhibit microsomal drug metabolizing enzyme(s), such as CYP-4502E1. Since CYP-4502E1 primarily metabolizes acetaminophen in mice and rats, this study specifically focused on CYP-4502E1's catalytic activity in vitro. Overall this investigation compared the in vitro aniline hydroxylation patterns of: (i) in vivo GSPE-exposed and unexposed (control) mouse liver microsomes, (ii) induced (1% acetone in drinking water for 3 days) and uninduced rat liver microsomes in the presence and absence of GSPE in vitro, and (iii) control rat liver microsomes in the presence of an anti-APAP agent 4-aminobenzamide (4-AB) in vitro. For the in vivo assessment, male B6C3F1 mice were fed GSPE diet (ADI 100 mg/kg body wt) for 4 weeks, and liver microsomes were isolated from both control and GSPE-fed mice for aniline hydroxylation, a specific marker of CYP-4502E1 activity. Data show that hydroxylation was 40% less in microsomes from GSPE-exposed livers compared to control microsomes. Similarly, when rat liver microsomes were incubated with various concentrations of GSPE in vitro (100 and 250 g/ml), aniline hydroxylation was inhibited to various degrees (uninduced: 40 and 60% and induced: 25 and 50%, respectively with 100 and 250 g/ml). Influence of GSPE on hydroxylation patterns were compared with another hepatoprotective agent 4-aminobenzamide (4-AB), a well-known modulator of nuclear enzyme poly(ADP-ribose) polymerase, and the data shows that 4-AB did not alter aniline hydroxylation at all. Collectively, these results may suggest that GSPE has the ability to inhibit CYP-4502E1, and this is an additional cytoprotective attribute, in conjunction with its novel antioxidant and/or antiendonucleolytic potential.     

Dietary grape seed procyanidin extract protects against lead-induced heart injury in rats involving endoplasmic reticulum stress inhibition and AKT activation

To investigate the protective role of grape seed procyanidin extract (GSPE) against lead-induced heart injury and the possible molecular mechanism associated with this event, Wistar rats were orally given GSPE (200 mg/kg) daily with or without lead acetate (PbA) (0.5 g/L) in drinking water for 56 d. GSPE attenuated oxidative stress, heart dysfunction, and lead accumulation in lead-exposed rat hearts. Meanwhile, GSPE inhibited the protein kinase RNA-like endoplasmic reticulum (ER) kinase/eukaryotic initiation factor 2α signaling pathway, and promoted protein kinase B (AKT) and glycogen synthase kinase 3β phosphorylation altered by lead, and regulated lead-activated apoptosis and its related signaling pathway. This study suggests that dietary GSPE ameliorates lead-induced heart injury associated with ER stress inhibition and AKT activation. Dietary GSPE may be a protector against lead-induced heart injury and a novel therapy for lead exposure.     

Persistence and accumulation of (potential) single strand breaks in liver DNA of rats treated with diethylnitrosamine or dimethylnitrosamine: correlation with hepatocarcinogenicity.

Effects of diethylnitrosamine (DEN) and dimethylnitrosamine (DMN) on the sedimentation pattern of [3H]thymidine-labelled Sprague-Dawley female rat liver DNA in alkaline sucrose gradients were studied with regard to time and dose dependency. In experiments at 1--56 days after a single injection it was observed that (potential) single strand breaks induced by DEN were repaired at a low rate. At 56 days the sedimentation pattern was still grossly abnormal. Half-life values of 27 and 46 days were observed after 134 mg/kg DEN (approx. 45% of the LD50) and 13.4 mg/kg DEN, respectively. Identical experiments after DMN (10 mg/kg, corresponding to about 35% of the LD50) showed return to (almost) completely control sedimentation patterns within 56 days after injection (t 1/2 = 8 days). Experiments at 6 or 56 days after the last of a series of 5 or 10 weekly injections of DEN (13.4 mg/kg) showed that a major part of DEN-induced damage (measured as single strand breaks) is of a persistent and accumulating character. No accumulation of DMN-induced rat liver lesions was observed. It is concluded that DNA fragmentation and lack of DNA repair is not a consequence of hepatotoxicity. Since at equimolar doses DEN gives appreciably less DNA alkylation (including O6-alkylguanine) but is much more effective both as an inducer of preneoplastic liver lesions and as a hepatocarcinogen when compared with DMN, we believe that the formation of persistent (and accumulating) DNA damage after DEN administration might be relevant in the process of liver tumour formation.     

Study of the therapeutic effects of Lactobacillus and α-lipoic acid against dimethylnitrosamine-induced liver fibrosis in rats

Lactobacillus (LB) and α-lipoic acid (ALA) were investigated to compare their protective effects against dimethylnitrosamine (DMN)-induced liver fibrosis in rats. Animals were either injected intraperitoneally with DMN to induce hepatic fibrosis, or were left untreated (negative control). For the DMN + LB and DMN + ALA treatment groups, at two weeks of DMN treatment LB or ALA was added to the feed and supplementation continued until the experimental endpoint at sixty days. At the study endpoint, expression of IL-1β, IL-6, IL-10, TNF-α, IFN-γ, TGF-β1, COL1-α1 genes and the concentration of glutathione and malondialdehyde were measured in liver tissues, while GOT, GPT, and ALP concentrations were measured in blood. Body weights remained higher in NC and DMN + LB groups compared to DMN and DMN + ALA groups, while activity of GOT and GPT in serum was lower in DMN + LB and DMN + ALA groups compared to the DMN group. Compared to other treatment groups, in the DMN group expression of both TGF-β1 and, COL1-α1 mRNAs and pro-inflammatory cytokines increased, while that of 1L-10 decreased. Furthermore, LB and ALA treatments increased antioxidant activity of glutathione and decreased malondialdehyde in comparison to the DMN group. Between LB and ALA treatments, glutathione concentration was higher in the DMN + LB group, while malondialdehyde was lower. Our results indicate that both LB and ALA exert hepatoprotective effects against DMN-induced liver fibrosis. Their beneficial effects may be partly associated with down-regulation of both TGF-β1 and COL1-α1 signaling, which may be accounted for reduction of increased oxidative stress and TNF-α production.     

A Grape Seed Procyanidin Extract Ameliorates Fructose-Induced Hypertriglyceridemia in Rats via Enhanced Fecal Bile Acid and Cholesterol Excretion and Inhibition of Hepatic Lipogenesis

The objective of this study was to determine whether a grape seed procyanidin extract (GSPE) exerts a triglyceride-lowering effect in a hyperlipidemic state using the fructose-fed rat model and to elucidate the underlying molecular mechanisms. Rats were fed either a starch control diet or a diet containing 65% fructose for 8 weeks to induce hypertriglyceridemia. During the 9^th week of the study, rats were maintained on their respective diet and administered vehicle or GSPE via oral gavage for 7 days. Fructose increased serum triglyceride levels by 171% after 9 weeks, compared to control, while GSPE administration attenuated this effect, resulting in a 41% decrease. GSPE inhibited hepatic lipogenesis via down-regulation of sterol regulatory element binding protein 1c and stearoyl-CoA desaturase 1 in the fructose-fed animals. GSPE increased fecal bile acid and total lipid excretion, decreased serum bile acid levels and increased the expression of genes involved in cholesterol synthesis. However, bile acid biosynthetic gene expression was not increased in the presence of GSPE and fructose. Serum cholesterol levels remained constant, while hepatic cholesterol levels decreased. GSPE did not modulate expression of genes responsible for esterification or biliary export of the newly synthesized cholesterol, but did increase fecal cholesterol excretion, suggesting that in the presence of GSPE and fructose, the liver may secrete more free cholesterol into the plasma which may then be shunted to the proximal small intestine for direct basolateral to apical secretion and subsequent fecal excretion. Our results demonstrate that GSPE effectively lowers serum triglyceride levels in fructose-fed rats after one week administration. This study provides novel insight into the mechanistic actions of GSPE in treating hypertriglyceridemia and demonstrates that it targets hepatic de novo lipogenesis, bile acid homeostasis and non-biliary cholesterol excretion as important mechanisms for reducing hypertriglyceridemia and hepatic lipid accumulation in the presence of fructose.     

Influence of resveratrol on liver fibrosis induced by dimethylnitrosamine in male rats

Liver fibrosis is a significant health problem which represents the liver’s scarring process and response to injury through deposition of collagen and extracellular matrix, and ultimately leads to cirrhosis. Resveratrol is a naturally occurring phytoalexin found predominantly in grapes. This study aimed to investigate the antifibrotic role of resveratrol on dimethylnitrosamine (DMN)-induced liver fibrosis in rats. Rats were divided into four groups and treated for three weeks; control, resveratrol administered orally (20 mg/kg daily), DMN intraperitoneally injected (10 mg/kg 3 days/week), and the last group was pre-treated daily with resveratrol then injected with DMN, 3 days/week. DMN administration induced severe liver pathological alterations. However, oral administration of resveratrol before DMN significantly prevented the induced loss in body weight, as well as the increase in liver weight which arise from DMN administration. Resveratrol has also inhibited the elevation of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin levels. Furthermore, resveratrol significantly increased hepatic reduced glutathione (GSH) levels and reduced the levels of malondialdehyde (MDA) due to its antioxidants effect as well as increased serum protein levels. In addition, DMN induced elevation in hydroxyproline content. On the other hand, hydroxyproline level was significantly reduced in the resveratrol pretreated rats. Resveratrol has also remarkably maintained the normal liver lobular architecture. Moreover, resveratrol had displayed potent potentials to prevent collagen deposition, lymphocytic infiltration, necrosis, steatosis, vascular damage, blood hypertention, cholangiocyte proliferation. It can be concluded that resveratrol has a marked protective role on DMN-induced liver fibrosis in rats, and can be considered as antiproliferative, antihypertensive, as well as antifibrotic agent and may be used to block the development of liver fibrosis.     

Effects of pretreatment with pyrazole and inducers of mixed function oxidases on DNA repair elicited by dimethylnitrosamine in rat hepatocytes in vivo and in vitro

Experiments were performed to investigate the relationship between the rate of oxidative metabolism of dimethylnitrosamine (DMN) by rat liver microsomes (i.e., DMN demethylase activity, DMNd) and its genotoxicity in liver, as assessed by the in vitro and in vivo/in vitro rat hepatocyte primary culture/DNA repair (HPC/DR) assays. Pretreatment of rats with pyrazole (PYR) resulted in a 4-fold increase in DMNd and a 3-fold greater DNA repair response to in vivo administration of 5 mg DMN/kg body weight. Pretreatment with phenobarbital (PB), dichlorodiphenyltrichloroethane (DDT), 3-methylcholanthrene (3-MC), beta-naphthoflavone (beta-NF) or Aroclor 1254 (ARO) produced a variable degree of inhibition of DMNd and had no significant effects on the response to DMN in the in vivo/in vitro HPC/DR assay. DNA repair elicited by DMN in vitro was decreased in hepatocytes from rats pretreated with 3-MC, while PB, DDT, beta-NF and ARO pretreatments had little effect on the response. In contrast, PYR pretreatment produced a 4.5-6.7-fold increase in the in vitro DNA repair response to DMN, and extended detection of positive responses to lower concentrations. Most of the inducers had no effect on DNA repair elicited by the direct acting alkylator, methyl methanesulfonate (MMS). Thus, the pretreatment-related changes in DMN-induced DNA repair were probably due to alterations in DMNd rather than to effects on the DNA repair capacity of the hepatocytes.     

葡萄籽原花青素对大鼠烟雾吸入性肺损伤的保护作用

目的:探讨葡萄籽原花青素(grape seed proanthocyanidin extract,GSPE)对大鼠烟雾吸入性肺损伤的保护作用。方法:将48只大鼠随机分为正常对照组、烟雾吸入性肺损伤模型组、GSPE治疗组(500mg/kg),分别于致伤后2、4、12、24h监测动脉血气分析,分批处死大鼠,分别进行肺组织湿/干重测定,制备组织匀浆测超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、一氧化氮合酶(NOS)活性及一氧化氮(NO)、丙二醛(MDA)含量和HE染色。结果:与模型组比较,GSPE治疗组各时间点动脉血氧分压均显著升高(P<0.01),肺组织含水量显著降低(P<0.05),肺组织中SOD活性均明显升高(P<0.01),GSH-Px活性均明显升高(P<0.05),NOS活性及NO、MDA含量均明显降低(P<0.05)。肺组织病理学观察GSPE治疗组较模型组肺间质水肿减轻,炎性细胞浸润减少。结论:GSPE可能通过其显著增加组织的抗氧化能力而对烟雾吸入性肺损伤起到一定保护作用。     

Beneficial effects of a novel IH636 grape seed proanthocyanidin extract and a niacin-bound chromium in a hamster atherosclerosis model

Atherosclerosis is a disease of the arteries in which fatty plaques develop on the inner arterial wall, which eventually obstructs blood flow. Identified risk factors for atherosclerosis include genetics, diet, lifestyle, smoking, circulating lipid and cholesterol levels, and molecular and circulating signals of chronic vascular inflammation. The link between flavonoids and atherosclerosis is based partly on the evidence that some flavonoids possess antioxidant properties and have been shown to be potent inhibitors of LDL oxidation in vitro. Hypercholesterolemia, a significant cardiovascular risk factor is prevalent in the American population. Grape seed proanthocyanidin extracts are known to exhibit a broad spectrum of chemopreventive and cardioprotective properties against oxidative stress. A recent study has shown that a combination of IH636 grape seed proanthocyanidin extract (GSPE) and a niacin-bound chromium (NBC) can decrease total cholesterol, LDL and oxidized LDL levels in hypercholesterolemic human subjects. In this study, we assessed the efficacy of GSPE supplementation in hamsters, singly and in combination with NBC, since these animals have a similar lipid profile to hypercholesterolemic humans when fed a hypercholesterolemic diet of 0.2% cholesterol and 10% coconut oil (HCD). After 10 weeks of feeding HCD, these animals developed foam cells, which is a biomarker of early stages of atherosclerosis. Atherosclerosis (% of aorta covered with foam cells) was reduced by approximately 50% and 63% following supplementation of these animals with 50 mg/kg and 100 mg/kg of GSPE, respectively, in conjunction with a HCD, while approximately 32% reduction was observed following supplementation of GSPE plus NBC. A minimum of 7–9 animals were used in each study group. GSPE alone and in combination with NBC exerted a pronounced effect on the cholesterol, and triglyceride levels, as well as oxidative lipid damage as demonstrated by the formation of thiobarbituric acid reactive substances (TBARS). This data demonstrates that GSPE and NBC may provide significant health benefits by dramatically ameliorating the incidence of atherosclerosis as demonstrated by reducing the formation of foam cells.     

GSPE is superior to NAC in the prevention of contrast-induced nephropathy: Might this superiority be related to caspase 1 and calpain 1?

Aims

Our study was intended to evaluate the role of inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), caspases 1 and 3 and calpain 1 in the pathogenesis of contrast-induced nephropathy (CIN) and to compare the protective effects of N acetyl cysteine (NAC) and grape seed proanthocyanidin extract (GSPE) against the development of CIN.

Main methods

32 rats were divided into four groups; control, contrast media (CM), CM + NAC and CM + GSPE. CIN was induced by administration of 7 ml/kg diatrizoate. The experiment was discontinued on the ninth day. Blood was collected for blood urea nitrogen (BUN) and creatinine measurement. Rat kidney tissues were removed for histopathological evaluation and the investigation of caspases 1 and 3, iNOS, eNOS, TUNEL and calpain 1.

Key findings

A significant increase in BUN, creatinine, renal histopathological injury, TUNEL, caspases 1, 3, calpain 1, iNOS and eNOS was observed in the CM group compared to the control group. There was amelioration in all these parameters in the CM + GSPE group, while there was no significant amelioration in BUN, creatinine and renal histopathological injury in the CM + NAC group. In addition, calpain 1 staining and creatinine were significantly lower in the CM + GSPE group compared to the CM + NAC group.

Significance

Our study showed, for the first time in the literature, that GSPE has a greater renoprotective effect compared with NAC and that this effective protection may be related to decrease in calpain 1 levels.     

Grape Seed Procyanidins and Cholestyramine Differentially Alter Bile Acid and Cholesterol Homeostatic Gene Expression in Mouse Intestine and Liver

Bile acid (BA) sequestrants, lipid-lowering agents, may be prescribed as a monotherapy or combination therapy to reduce the risk of coronary artery disease. Over 33% of adults in the United States use complementary and alternative medicine strategies, and we recently reported that grape seed procyanidin extract (GSPE) reduces enterohepatic BA recirculation as a means to reduce serum triglyceride (TG) levels. The current study was therefore designed to assess the effects on BA, cholesterol and TG homeostatic gene expression following co-administration with GSPE and the BA sequestrant, cholestyramine (CHY). Eight-week old male C57BL/6 mice were treated for 4 weeks with either a control or 2% CHY-supplemented diet, after which, they were administered vehicle or GSPE for 14 hours. Liver and intestines were harvested and gene expression was analyzed. BA, cholesterol, non-esterified fatty acid and TG levels were also analyzed in serum and feces. Results reveal that GSPE treatment alone, and co-administration with CHY, regulates BA, cholesterol and TG metabolism differently than CHY administration alone. Notably, GSPE decreased intestinal apical sodium-dependent bile acid transporter (Asbt) gene expression, while CHY significantly induced expression. Administration with GSPE or CHY robustly induced hepatic BA biosynthetic gene expression, especially cholesterol 7α-hydroxylase (Cyp7a1), compared to control, while co-administration further enhanced expression. Treatment with CHY induced both intestinal and hepatic cholesterologenic gene expression, while co-administration with GSPE attenuated the CHY-induced increase in the liver but not intestine. CHY also induced hepatic lipogenic gene expression, which was attenuated by co-administration with GSPE. Consequently, a 25% decrease in serum TG levels was observed in the CHY+GSPE group, compared to the CHY group. Collectively, this study presents novel evidence demonstrating that GSPE provides additive and complementary efficacy as a lipid-lowering combination therapy in conjunction with CHY by attenuating hepatic cholesterol synthesis, enhancing BA biosynthesis and decreasing lipogenesis, which warrants further investigation.     

Potentiation of dimethylnitrosamine genotoxicity in rat hepatocytes isolated following ethanol treatment in vivo

Unscheduled DNA synthesis (UDS), following exposure to dimethylnitrosamine (DMN), was potentiated in cultured hepatocytes isolated following treatment of rats for 14 or 28 days with 20% ethanol/5% sucrose solution. Ethanol treatment was associated with increased UDS, a concomitant increase in hepatic microsomal protein concentration and DMN N-demethylase activity. Increased aniline hydroxylase activity of hepatic microsomes from ethanol-treated rats preceded the measured increase in microsomal protein content or DMN metabolism. The increase in metabolism of DMN in vitro and potentiation of DMN-induced UDS associated with ethanol treatment may contribute to a synergistic effect of ethanol on DMN hepatotoxicity and carcinogenicity. In contrast, ethanol pretreatment did not increase the cytotoxicity of DMN as characterized by enzyme release.     

Grape seed procyanidin extract ameliorates lead-induced liver injury via miRNA153 and AKT/GSK-3β/Fyn-mediated Nrf2 activation

Lead-induced hepatotoxicity is characterized by an extensive oxidative stress. Grape seed procyanidin extract (GSPE) possesses abundant biological activities. Herein, we investigated the protective role of GSPE against lead-induced liver injury and determined the potential molecular mechanisms. In vivo, rats were treated with/without lead acetate (PbAc) (0.05%, w/v) in the presence/absence of GSPE (200 mg/kg). In vitro, hepatocytes were pretreated with/without GSPE (100 μg/ml) in the presence/absence of PbAc (100 μM). PbAc administration to rats resulted in anemia, liver dysfunction, lead accumulation in the bone and liver, oxidative stress, DNA damage and apoptosis. GSPE significantly attenuated these adverse effects, except lead accumulation in liver. GSPE also decreased the expression of miRNA153 and increased the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and levels of its downstream protein, and protein kinase B (AKT) phosphorylation in PbAc-induced liver injury. In primary hepatocytes treated with PbAc, GSPE increased hepatocyte viability and decreased lactate dehydrogenase release and reactive oxygen species levels. Dietary GSPE attenuated PbAc-induced liver injury in rats via an integrated mechanism associated with the miRNA153 and AKT/glycogen synthase kinase 3 beta/Fyn-mediated Nrf2 activation.     

Effect of Grape Seed Proanthocyanidin Extracts on Methylmercury-Induced Neurotoxicity in Rats

As a highly toxic environmental pollutant, methylmercury (MeHg) can cause neurotoxicity in animals and humans. Considering the antioxidant property of grape seed proanthocyanidin extracts (GSPE), this study was aimed to evaluate the effect of GSPE on MeHg-induced neurotoxicity in rats. Rats were exposed to MeHg by intraperitoneal injection (4, 12 μmol/kg, respectively) and GSPE was administered by gavage (250 mg/kg) 2 h later. After a 4-week treatment, phosphate-activated glutaminase, glutamine synthetase, glutathione peroxidase and superoxide dismutase activities, glutamate, glutamine, malondialdehyde and glutathione contents in cerebral cortex were measured. Reactive oxygen species (ROS) and apoptosis were also estimated in cells. The results showed that the MeHg-induced neurotoxicity was significantly attenuated. GSPE significantly decreased the production of ROS, counteracted oxidative damage and increased the antioxidants and antioxidant enzymes activities in rats prior to MeHg exposure. Moreover, the effects on the rate of apoptotic cells and the disturbance of glutamate homeostasis were correspondingly modulated. These observations highlighted the potential of GSPE in offering protection against MeHg-induced neurotoxicity.     

Studies on the relationship between dimethylnitrosamine-demethylase activity and dimethylnitrosamine-dependent mutagenesis in Drosophila melanogaster

The relationship between dimethylnitrosamine (DMN) demethylase activity and DMN-induced mutagenesis was investigated in Drosophila melanogaster. The activity of DMN-demethylase was at least 10-fold greater in the Hikone-R strain than in three other Drosophila strains. However, the sex-linked recessive lethal (SLRL) mutations induced by DMN in the four strains differed by less than 2-fold. Several possibilities to explain the lack of correlation between DMN-demethylase activity and DMN-induced mutations were tested and eliminated. They include: (i) the presence of inhibitors of DMN-demethylase in extracts of low-activity strains, (ii) a sex bias in the Hikone-R strain in which the enzyme activity is confined to the females, (iii) the possibility that DMN treatment induces DMN-demethylase activity in the low-activity strains and (iv) the possibility that Hikone-R has a much more efficient DNA repair system than the other strains. The results are discussed in terms of what is known about the role of DMN-demethylase in the metabolic activation of DMN in other systems.