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Effects of Oleanolic Acid and Hederagenin on Acute Alcohol-Induced Hepatotoxicity in Mice
Abstract
We studied the effects of oleanolic acid and hederagenin on acute alcohol-induced hepatotoxicity in mice. Oleanolic acid [10 and 20 mg/kg body weight (BW)/d] or hederagenin (10 and 20 mg/kg BW/d) was orally administered to the study group for 1 week. On the last day of treatment, ethanol (5 g/kg BW) was orally administered to induce acute liver injury. The oleanolic acid-treated group showed lower levels of alanine aminotransferase compared to the ethanol-treated group (EtOH). The mRNA expression level of alcohol dehydrogenase was significantly increased in the high dosage oleanolic acid-treated group compared with the control and EtOH groups. The glutathione levels of the oleanolic acid or hederagenin-treated groups were elevated significantly compared with those of the control and EtOH groups. The mRNA expression levels of glutathione synthetic enzymes were also elevated in the oleanolic acid-treated groups. The oleanolic acid or hederagenin-treated groups also showed lower levels of mRNA expression of tumor necrosis factor alpha. Thus, these results show that oleanolic acid and hederagenin could reduce oxidative stress and hepatotoxicity in ethanol-treated mouse liver.
... In the previous study, we demonstrated a potential hepatoprotective effect from A. quinata extract on acute alcohol-induced hepatotoxicity in mice (17). In addition, oleanolic acid and hederagenin, which are compounds found in A. quinata extract, demonstrated hepatoprotective effects and reduced blood ethanol concentration in mice with alcohol induced hepatotoxicity (18). Furthermore, we showed that A. quinata extracts relieved oxidative stress by increasing hepatic glutathione levels. ...
The present study was conducted to investigate the effects of beverages containing fermented Akebia quinata extracts on alcoholic hangover. For this study, 25 healthy young men were recruited. All participants consumed 100 mL of water (placebo), commercial hangover beverage A or B, fermented A. quinata leaf (AQL) or fruit (AQF) extract before alcohol consumption. After 1 h, all participants consumed a bottle of Soju, Korean distilled liquor (360 mL), containing 20% alcohol. Blood was collected at 0 h, 1 h, 3 h, and 5 h after alcohol consumption. The plasma alanine transaminase (ALT) activity was highest in the placebo group. Compared with the control group, the AQL and AQF groups showed decreased ALT activity at 5 h after alcohol consumption. Plasma ethanol concentration was increased after alcohol intake and peaked at 3 h after alcohol consumption. Compared with the control group, the A group showed a higher plasma ethanol concentration at 1 h (P<0.05). At 3 h after alcohol consumption, the AQF group showed the lowest mean plasma ethanol concentration compared to the other groups; however, there were no statistical differences. After 5 h of alcohol consumption, the AQL and AQF groups showed lower plasma ethanol concentrations compared with the B group. The sensory evaluation score for the fermented A. quinata fruit extract was lower than for the commercial hangover beverages. In conclusion, the present intervention study results suggest that fermented A. quinata extracts alleviate alcoholic hangover and reduce plasma ethanol concentrations.
The research tries to establish Wistar rat’s model of atherosclerosis for evaluating the antiatherosclerotic effect of hederagenin and exploring its antiatherosclerosis-related mechanisms. The statistical data have shown that hederagenin exhibits multiple pharmacological activities in the treatment of hyperlipidemia, antiplatelet aggregation, liver protection, and anti-inflammation, indicating that hederagenin may exert a protective effect on vascular walls by improving lipid metabolism disorders and lipid deposition. The results show that hederagenin can correct the imbalance of endothelial function by inhibiting the release of large amounts of iNOS and increasing eNOS contents and inhibits the IKK
β
/NF-
κ
B signaling pathway to reduce the release of IL-6, IFN-
γ
, TNF-
α
, and other inflammatory factors. The experimental results indicated that hederagenin can inhibit or ameliorate the pathological changes associated with AS, displaying an excellent preventive function against AS.
Oleanolic acid is abundantly distributed in Swertia mussotii Franch, a Chinese traditional herb for the treatment of jaundice. However, the hepatoprotective role of oleanolic acid in obstructive cholestasis and its underlying molecular mechanism are unclear.
Normal rats and bile duct-ligated (BDL) rats were given oleanolic acid and serum biochemistry, bile salts, and pro-inflammatory factors were measured, as well as the expression levels of liver bile acid synthesis and detoxification enzymes, membrane transporters, nuclear receptors, and transcriptional factors.
Oral administration of oleanolic acid at 100 mg/kg did not cause rat liver injury. However, it significantly reduced the serum levels of alanine aminotransferase (ALT) on days 7 and 14, aspartate aminotransferase (AST) and TNF-α on day 14, and alkaline phosphatase (ALP) and IL-1β on days 3, 7, and 14 in the BDL rats. Furthermore, the serum levels of total bile acid (TBA) and bile acids, including CDCA, CA, DCA, and Tα/βMCA were significantly reduced by oleanolic acid on day 3 in the BDL rats. In addition, the expression levels of detoxification enzymes Cyp3a, Ugt2b, Sult2a1, Gsta1-2, and Gstm1-3, membrane transporters Mrp3, Mrp4, Ostβ, Mdr1, Mdr2, and Bsep, nuclear receptors Pxr, Vdr, Hnf4α, Rxrα, Rarα, Lxr, and Lrh-1, and transcriptional factors Nrf2, Hnf3β, and Ahr were significantly increased in oleanolic acid-treated rats.
We demonstrated that the oral administration of oleanolic acid attenuates liver injury, inflammation, and cholestasis in BDL rats. The anti-cholestatic effect may be associated with the induction of hepatic detoxification enzymes and efflux transporters mediated by nuclear receptors and transcriptional factors.
Chronic ethanol (EtOH) abuse results in the development of steatosis, alcoholic hepatitis, and cirrhosis. Augmented TNF-alpha production by macrophages and Kupffer cells and signaling via the p55 TNF receptor have been shown to be critical for these effects of chronic EtOH; however, the molecular mechanisms leading to augmented TNF-alpha production remain unclear. Using cell culture models and in vivo studies we demonstrate that chronic EtOH results in increased TNF-alpha transcription, which is independent of NF-kappaB. Using reporter assays and chromatin immunoprecipitation we found that this increased transcription is due to increased IRF-3 binding to and transactivation of the TNF promoter. As IRF-3 is downstream from the TLR4 adaptor TIR-domain-containing adapter-inducing IFN-beta (Trif), we demonstrate that macrophages from Trif-/- mice are resistant to this dysregulation of TNF-alpha transcription by EtOH in vitro as well as EtOH-induced steatosis and TNF dysregulation in vivo. These data demonstrate that the Trif/IRF-3 pathway is a target to ameliorate liver dysfunction associated with chronic EtOH.
Endotoxemia participates in the pathogenesis of many liver injuries. Lipopolysaccharide (LPS) was shown to inactivate hepatic methionine adenosyltransferase (MAT), the enzyme responsible for S-adenosylmethionine (SAMe) biosynthesis. SAMe treatment was shown to prevent the LPS-induced increase in tumor necrosis factor-alpha, which may be one of its beneficial effects. SAMe is also an important precursor of glutathione (GSH) and GSH was shown to ameliorate LPS-induced hepatotoxicity. The aims of this work were to examine changes in SAMe and GSH homeostasis during endotoxemia and the effect of SAMe. Mice received SAMe or vehicle pretreatment followed by LPS and were killed up to 18 h afterward. Unexpectedly, we found hepatic SAMe level increased 67% following LPS treatment while S-adenosylhomocysteine level fell by 26%, suggesting an increase in SAMe biosynthesis and/or block in transmethylation. The mRNA and protein levels of MAT1A and MAT2A were increased following LPS. However, despite increased MAT1A expression, MAT activity remained inhibited 18 h after LPS. The major methyltransferase that catabolizes hepatic SAMe is glycine N-methyltransferase, whose expression fell by 65% following LPS. Hepatic GSH level fell more than 50% following LPS, coinciding with a comparable fall in the mRNA and protein levels of glutamate-cysteine ligase (GCL) catalytic (GCLC) and modifier subunits (GCLM). SAMe pretreatment prevented the fall in GCLC and attenuated the fall in GCLM expression and GSH level. SAMe pretreatment prevented the LPS-induced increase in plasma alanine transaminases levels but not the LPS-induced increase in hepatic mRNA levels of proinflammatory cytokines. It further enhanced LPS-induced increase in interleukin-10 mRNA level. Taken together, the hepatic response to LPS is to upregulate MAT expression and inhibit SAMe utilization. GSH is markedly depleted largely due to lower expression of GCL. Interestingly, SAMe treatment prevented the fall in GCL and helped to preserve the GSH store and prevent liver injury.
We studied the effects of Akebia quinata fruit extract (AQ) on acute alcohol-induced hepatotoxicity in mice. AQ (30-1,000 mg/kg body weight (BW) per day) was orally administered to the study group, once daily for 1 week. On the last day of AQ treatment, ethanol (6 mg/kg BW) was orally administered to induce acute liver injury. The AQ-treated group showed significantly lower levels of alanine aminotransferase and aspartate aminotransferase, compared to the only ethanol-treated group (ETG). The glutathione level in the AQ-treated group elevated up to 20.6%, compared to that observed in the ETG. The mRNA expression of glutathione synthetic enzymes was also higher in the AQ-treated group, compared to the ETG. The AQ-treated group also exhibited lower levels of expression of NADPH oxidase 4 and tumor necrosis factor alpha mRNA. Thus, these results show that AQ treatment can be a potential method to reduce oxidative stress and inflammation in ethanol-treated mouse liver and also that AQ can be a useful therapeutic agent for acute alcohol-induced hepatotoxicity.
Two free triterpenoids and twelve triterpenoid saponins were isolated from the fresh pericarps of Akebia quinata DECNE. (Lardizabalaceae). Ten saponins, PA-G, PJ2, PJ3 and PK, of the above twelve were characterized as follows : PA (I), hederagenin (hederag.) 3-O-α-L-ara·pyranoside ; PF (II), hederag. 3-O-β-D-glc·pyr-(1→2)-α-L-ara·pyranoside ; PB (III), oleanolic acid (ol. acid) 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranoside ; Pc (VI), hederag. 3-O-β-D-xyl·pyr-(1→3)-α-L-ara·pyranoside ; PD (IX), hederag. 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranoside ; PE (XI), ol, acid 3-O-β-D-glc·pyr-(1→2)-α-L-ara·pyranoside ; PG (XIII), hederag. 3-O-β-D-xyl·pyr-(1→3)-α-L-rha·pyr-(1→2)-α-L-ara·pyranoside ; PJz (XV') 3-O-α-L-ara·pyranosyl-hederag. 28-O-α-L-rha·pyr-(1→4)-β-D-glc·pyr-(1→6)-β-D-glc·pyranoside ; PJs (XIX'), 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranosyl-ol. acid 28-O-α-L-rha·pyr-(1→4)-β-D-glc·pyr-(1→6)-β-D-glc·pyranoside ; PK (XXI), 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranosyl-hederag. 28-O-α-L-rha·pyr-(1→4)-β-D-glc·pyr-(1→6)-β-D-glc·pyranoside. VI, XI and XV'are new members of the group of hederagenin and oleanolic acid oligoglycosides. It is noted that they all have the common unit, 3-O-α-L-ara·pyranoside, and that XV', XIX'and XX, having the same trisaccharide combined with the 28-carboxyl group of the aglycone, are corresponding to I, III and IX, respectively.
The antioxidative activities of various solvent extracts of Hsian-tsao (Mesona procumbens Hemsl.) were investigated. The results showed that for the same concentration of 0.2 g/kg, the antioxidative activities of various Hsian-tsao extracts, especially the ethyl acetate extract, which exhibited 93% inhibition of peroxidation of linoleic acid, were greater than those of BHA and α -tocopherol. When the ethyl acetate extract of Hsian-tsao (EEHT) was separated into nine fractions by silica gel chromatography, fraction II showed high yield and high antioxidative activity. Fraction II was further separated into five subfractions using silica gel chromatography. Subfraction IIC was then isolated by preparative HPLC equipped with a silica column and four components were identified as stigmasterol, β -sitosterol, oleanolic acid, and ursolic acid by UV, EI-MS,1H-, and13SC-NMR. The descending order of antioxidative activity for those compounds was: EEHT>BHA>α -tocopherol>ursolic acid>oleanolic acid>β -sitosterol>stigmasterol.
A new triterpene was isolated from the methanol extracts of Akebia quinata tissue culture. The structure was determined by spectra and chemical transformations to be 3α,24-dihydroxy-30-norolean-12,20(29)-dien-28-oic acid.
Four triterpenoid saponins [1-4], including three new compounds, were isolated as major saponins from callus tissues Akebia trifoliata. The structures of these new glycosides, named trifosides A-C, were elucidated as 3 beta-hydroxyolean-12-en-28,23-dioic acid 3-0-beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->3)-beta-D-glucopyranoside [2], 3 beta-hydroxy-30-nor-olean-12,20(29)-dien-28-oic acid 3-0-beta-D-xylopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranoside[3], and 3 beta,23-dihydroxy-30-nor-olean-12,20(29)-dien-28-oic acid 3-0-beta-D-xylopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranoside [4], respectively. The known saponin was identified as mubenoside A [1]. Additionally, nine known triterpene aglycones were isolated and identified by comparing their spectral data and tlc R(f)values with those of authentic samples. The compounds identified in the present study were compared with the terpenoid profiles of callus cultures of other planes in the Lardizabalaceae.
Male Sprague-Dawley rats were exposed to increasing concentrations (15–22 mg/l) of ethanol vapor over a 4-day period. The hepatic lipid peroxide level as well as the sensitivity of mitochondria and microsomes to peroxidative attacks were studied during the early stage of alcohol intoxication, at the end of the inhalation period and, finally, during withdrawal. The level of hepatic lipid peroxide started to increase significantly after the first day of ethanol inhalation, whereas the in vitro mitochondrial sensitivity to peroxidation induced by ADP · Fe3+ in the presence of an O2−-generating system was still unaltered after a 2-day inhalation period. Both the hepatic peroxide level and the mitochondrial sensitivity to peroxidation were significantly enhanced at the end of the 4-day inhalation period. Such an enhancement was still apparent 24 h after withdrawal, a time at which no more ethanol was present in the blood. Lipid peroxidation returned to normal values only 48 h after withdrawal. Microsomes were less affected than mitochondria by the ethanol treatment. It is suggested that the alterations of lipid peroxidation are related to the presence and/or the metabolism of ethanol at an early stage of inhalation, whereas changes in the membrane structure would be responsible for the maintenance of enhanced lipid peroxidation 24 h after ethanol withdrawal.
Background/Aims: Several liver diseases that are characterized by chronic steatosis lead to steatohepatitis lesions in some susceptible subjects. We tested the hypothesis that acute or chronic steatosis may lead to lipid peroxidation.Methods: Diverse steatogenic treatments were administered to mice, and lipid peroxidation was assessed by measuring thiobarbituric acid reactants in the liver and the exhalation of ethane in breath.Results: Administration of ethanol (5 g/kg), tetracycline, chlortetracycline, demeclocycline (0.25 mmol/kg each), amineptine (1 mmol/kg), amiodarone (1 mmol/kg), pirprofen (2 mmol/kg), or valproate (2 mmol/kg) led to microvesicular steatosis of the liver and lipid peroxidation. After tetracycline administration, hepatic triglycerides reached a maximum at 24 h and then declined; ethane exhalation followed a similar time course. Microvesicular steatosis and lipid peroxidation were also observed after 4 days of treatment with either ethionine (0.02 mmol/kg daily) or dexamethasone (0.25 mmol/kg daily) or after 7 days of tetracycline (0.25 mmol/kg daily) administration. Administration of ethanol in the drinking water for 5.5 months led to macrovacuolar and microvesicular steatosis, lipid peroxidation, and a few necrotic hepatocytes.Conclusions: We conclude that acute or chronic fat deposition due to a variety of compounds was associated with lipid peroxidation in mice. We suggest that the presence of oxidizable fat in the liver leads to peroxidation, and that chronic lipid peroxidation might represent the common (but not exclusive) mechanism for the possible development of steatohepatitis lesions in conditions characterized by chronic steatosis.
Mammalian alcohol dehydrogenase (ADH) can be divided into six classes, ADH1-ADH6, according to primary structure and function, where the classes are further subdivided into isozymes and allelic forms. With the increasing amount of available genomic data a general pattern is possible to trace within the mammalian ADH gene and protein families. The transcriptional order for the ADH genes in all mammalian genomes is the same (ADH4-ADH1-ADH6-ADH5-ADH2-ADH3), but the cluster is found on different chromosomes in different species. However, in primates only ADH1-ADH5 are present, where the loss of ADH6 may have occurred simultaneously as the split into ADH1 isoforms. ADH3, also denoted glutathione-dependent formaldehyde dehydrogenase and S-nitrosoglutathione reductase, is identified as the last gene in the ADH transcriptional order, but several pseudogenes for ADH3 have been traced at other chromosomes. The flanking genes outside the ADH genome are similar or identical for all species showing that a larger DNA region has been duplicated and further evolved. However, the only entirely completed ADH genomes are those from primates and rodents. The latest identified ADH forms, ADH5 (class V) and ADH6 (class VI), are truly different classes and both are very diverged in contrast to ADH3, which is the most conserved class of all ADHs. ADH5 and ADH6 have been identified at the gene and transcriptional levels only, and their functions are still an enigma.
In a search for plant products against cancer, the protective effect of two plant products, ursolic acid isolated from Ocimum sanctum and oleanolic acid from Eugenia jumbolana against free radical induced damage was studied. Three different standard systems viz., ascorbic acid, carbon tetrachloride, ADP/Iron were used to induce lipid peroxidation in isolated rat liver microsomes in vitro. Both oleanolic acid and ursolic acid offered remarkable protection of 90% and 60% respectively. Both the compounds did not induce lipid peroxidation by themselves that improved the therapeutic application.
Male Sprague-Dawley rats were exposed to increasing concentrations (15-22 mg/l) of ethanol vapor over a 4-day period. The hepatic lipid peroxide level as well as the sensitivity of mitochondria and microsomes to peroxidative attacks were studied during the early stage of alcohol intoxication, at the end of the inhalation period and, finally, during withdrawal. The level of hepatic lipid peroxide started to increase significantly after the first day of ethanol inhalation, whereas the in vitro mitochondrial sensitivity to peroxidation induced by ADP X Fe3+ in the presence of an O(2)-generating system was still unaltered after a 2-day inhalation period. Both the hepatic peroxide level and the mitochondrial sensitivity to peroxidation were significantly enhanced at the end of the 4-day inhalation period. Such an enhancement was still apparent 24 h after withdrawal, a time at which no more ethanol was present in the blood. Lipid peroxidation returned to normal values only 48 h after withdrawal. Microsomes were less affected than mitochondria by the ethanol treatment. It is suggested that the alterations of lipid peroxidation are related to the presence and/or the metabolism of ethanol at an early stage of inhalation, whereas changes in the membrane structure would be responsible for the maintenance of enhanced lipid peroxidation 24 h after ethanol withdrawal.
Kupffer's cells participate in alcohol-induced liver injury, and endotoxemia is observed in human alcoholics and in a rat model. This study evaluated the effect of reducing bacterial endotoxin production by intestinal sterilization on alcohol-induced liver injury.
Male Wistar rats were exposed to ethanol continuously for up to 3 weeks via intragastric feeding. The gut was sterilized with polymyxin B and neomycin.
Fecal culture of stool samples from ethanol-fed rats treated with antibiotics showed virtually no growth of gram-negative bacteria. Endotoxin levels of 80-90 pg/mL in plasma of ethanol-fed rats were reduced to < 25 pg/mL by antibiotics. Antibiotic treatment also completely prevented elevated aspartate aminotransferase levels and significantly reduced the average hepatic pathological score in rats exposed to ethanol. Oxygen tension on the surface of the liver measured in vivo was decreased significantly from control values of 48 +/- 1 to 39 +/- 1 mumol/L in ethanol-treated rats. This hypoxia was prevented by treatment with antibiotics. Moreover, the increase in rates of ethanol elimination due to long-term ethanol treatment was prevented by antibiotic treatment.
Intestinal sterilization prevented alcohol-induced liver injury in the rat, supporting the idea that hypermetabolism and consequent hypoxia caused by activation of Kupffer's cells by endotoxin is involved in the mechanism.
Oleanolic acid and ursolic acid are triterpenoid compounds that exist widely in food, medicinal herbs and other plants. This review summarizes the pharmacological studies on these two triterpenoids. Both oleanolic acid and ursolic acid are effective in protecting against chemically induced liver injury in laboratory animals. Oleanolic acid has been marketed in China as an oral drug for human liver disorders. The mechanism of hepatoprotection by these two compounds may involve the inhibition of toxicant activation and the enhancement of the body defense systems. Oleanolic acid and ursolic acid have also been long-recognized to have antiinflammatory and antihyperlipidemic properties in laboratory animals, and more research is warranted to develop a therapy for patients. Recently, both compounds have been noted for their antitumor-promotion effects, which are stimulating additional research in this field. Oleanolic acid and ursolic acid are relatively non-toxic, and have been used in cosmetics and health products. The possible mechanisms for the pharmacological effects and the prospects for these two compounds are discussed.
The protective effects of oleanolic acid-type saponins and their derivatives on in vitro immunological liver injury of primary cultured rat hepatocytes were studied. A known antihepatotoxic saponin (chikusetsusaponin IVa, 1) showed hepatoprotective activity in this model. Although a rhamnosyl derivative (2) of 1 similarly showed hepatoprotective activity, its prosapogenin (5) did not show any hepatoprotective activity. On the contrary, 5 exhibited cytotoxicity toward liver cells. In the absence of antiserum, monodesmosyl saponins showed hepatotoxicity, while the bisdesmosyl saponins except for 1, did not show such hepatotoxicity. In order to clarify the effects of the sugar residues at C-3 and C-28 responsible for hepatoprotective and hepatotoxic actions, oleanolic acid 3-O-glucuronide (2a) and oleanolic acid 28-O-glucoside (2b) were prepared and tested. 2b showed neither hepatoprotective action nor hepatotoxicity. In contrast, 2a was effective at 90 microM on hepatoprotection, although it showed strong hepatotoxicity. Oleanolic acid (2c) itself showed both hepatoprotective action and weak hepatotoxicity. Therefore, the hepatoprotective activity of these types of saponins could represent a balance between hepatoprotective action and hepatotoxicity.
Ethanol metabolism causes oxidative stress and lipid peroxidation not only in liver but also in extra-hepatic tissues. Ethanol administration has been shown to cause oxidative degradation and depletion of hepatic mitochondrial DNA (mtDNA) in rodents, but its in vivo effects on the mtDNA of extra-hepatic tissues have not been assessed. We studied the effects of an acute intragastric ethanol administration (5 g/kg) on brain, heart, skeletal muscle, and liver mtDNA in mice. Ethanol administration caused mtDNA depletion and replacement of its supercoiled form by linearized forms in all tissues examined. Maximal mtDNA depletion was about similar (ca. 50%) in all organs studied. It occurred 2 h after ethanol administration in heart, skeletal muscle, and liver but after 10 h in brain. This mtDNA depletion was followed by increased mtDNA synthesis. A secondary, transient increase in mtDNA levels occurred 24 h after ethanol administration in all organs. In hepatic or extra-hepatic tissues, mtDNA degradation and depletion were prevented by 4-methylpyrazole, an inhibitor of ethanol metabolism, and attenuated by vitamin E, melatonin, or coenzyme Q, three antioxidants. In conclusion, our study shows for the first time that ethanol metabolism also causes oxidative degradation of the mitochondrial genome in brain, heart, and skeletal muscles. These effects could contribute to the development of (cardio)myopathy and brain injury in some alcoholic patients. Antioxidants prevent these effects in mice and could be useful in persevering drinkers.
The pharmacokinetics of alcohol determines the time course of alcohol concentration in blood after the ingestion of an alcoholic beverage and the degree of exposure of organs to its effects. The interplay between the kinetics of absorption, distribution and elimination is thus important in determining the pharmacodynamic responses to alcohol. There is a large degree of variability in alcohol absorption, distribution and metabolism, as a result of both genetic and environmental factors. The between-individual variation in alcohol metabolic rates is, in part due to allelic variants of the genes encoding the alcohol metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). This review summarizes recent developments in the investigation of the following influences on alcohol elimination rate: gender, body composition and lean body mass, liver volume, food and food composition, ethnicity, and genetic polymorphisms in alcohol metabolizing enzymes as well as in the promoter regions of the genes for these enzymes. Evaluation of the factors regulating the rates of alcohol and acetaldehyde metabolism, both genetic and environmental, will help not only to explain the risk for development of alcoholism, but also the risk for development of alcohol-related organ damage and developmental problems.
In order to further determine the nature of structure-activity relationship on the cytotoxicities of saponins with 1-->2 and 1-->3 linkages of disaccharides, we isolated guaianin N, collinsonidin, kalopanaxsaponin A and hederoside D(2) as disaccharides, and patrinia glycoside B-II as a trisaccharide, from the n-BuOH extract of Akebia quinata (Lardizabalaceae). Complete acid hydrolysis of the extract afforded oleanolic acid (1) and hederagenin (2). By sulforhodamine B (SRB) assay, kalopanaxsaponin A containing an alpha-L-rhap-(1-->2)-alpha-L-arap moiety exhibited distinctly higher cytotoxicity (IC(50) 1.8-2.7 microg/ml) against all of the tested cell lines than the other saponins (IC(50), 4-8 microg/ml). These results suggest that the alpha-L-rhap-(1-->2)-alpha-L-arap moiety has a unique structural significance in terms of its cell biochemistry, compared to those oleanane glycosides with other sugar linkages. On the other hand, kalopanaxsaponin A exhibited a significant inhibitory effect on nitric oxide production by lipopolysaccharide (LPS)-activated macrophage 264.7, whereas other saponins had weaker activities.
The concentration of glutathione (GSH), the most abundant intracellular nonprotein thiol and important antioxidant, declines with age and in some age-related diseases. The underlying mechanism, however, is not clear. The previous studies from our laboratory showed that the age-dependent decline in GSH content in Fisher 344 rats was associated with a downregulation of glutamate cysteine ligase (GCL), the rate-limiting enzyme in de novo GSH synthesis. Our recent studies further indicated that the activity and mRNA content of glutathione synthase (GS), which catalyzes the second reaction in de novo GSH synthesis, were also decreased with age in some tissues. No age-associated change was observed in glutathione reductase or gamma-glutamyl transpeptidase activities. Also, although GSH content declined with age in both male and female mice, male mice experienced more dramatic age-associated decline in many tissues/organs than female mice. Furthermore, we found that GSH content was significantly decreased in the red blood cells from male Alzheimer disease patients, which was associated with decreases in GCL and GS activities. Finally, we showed that estrogen increased GSH content, GS and GR activities, and GCL gene expression in the liver of both male and female mice. Taken together, our results suggest that (1) GCL plays a critical role in maintaining GSH homeostasis under both physiological and pathological conditions; (2) decreased GSH content may be involved in AD pathology in humans; and (3) estrogen increases GSH content in mice by multiple mechanisms.
We previously reported a link between ethanol-induced elevation of homocysteine, endoplasmic reticulum (ER) stress, and alcoholic liver injury in the murine model of intragastric ethanol feeding. We studied the role of TNFalpha in this setting by using TNFR1 knockout mice (C57 BL/6). There was a 7.4-fold increase of homocysteine in wild-type and a 6-fold increase in TNFR1 knockout mice with intragastric alcohol exposure for 4 weeks. Plasma TNFalpha increased in the wild-type (18.4 +/- 3.3 pg/mL vs. 8.4 +/- 1.3 pg/mL (control)) and in the knockouts (12.9 +/- 1.4 pg/mL vs. 7.2 +/- 1.6 pg/mL (control)). Similar extent of fatty liver was observed in both types. Increased ALT was observed in both groups. Necroinflammatory foci were increased significantly in ethanol-fed knockouts but not to the same extent as in the ethanol-fed wild type. Increase of hepatic apoptosis and reduction of S-adenosyl-L-methionine was detected in both types of animals fed ethanol. ER stress demonstrated by RT-PCR of mRNA of selective ER stress markers GRP78, CHOP, and SREBP1 was increased equivalently in both types of mice. Betaine administration decreased ER stress in conjunction with attenuation of the elevated plasma homocysteine in both types of animals. Betaine increased hepatic S-adenosyl-L-methionine by 28 fold in the knockouts and by 24-fold in wild type. In conclusion, TNFalpha makes a moderate contribution to the ALT elevation, necroinflammation, apoptosis, a small contribution to the fatty liver and no contribution to hyperhomocysteinemia and ER stress in intragastric alcohol fed mice.
The stem of Akebia quinata Decasisne (Lardizabalaceae) has been used to treat urinary tract inflammatory disease. It has been reported that saponins in medicinal plants may act as bioactive components after biodegradation to sapogenins in the gastrointestinal tract. To find the active components, we obtained the methanol (MeOH) extract from A. quinata stems and fractionated this extract into CHCl(3), butanol (BuOH), and H(2)O fractions. A saponin-containing BuOH fraction was refluxed in an acidic solution to yield the hydrolyzed fraction. Silica gel column chromatography separated kalopanaxsaponin A (1) from the BuOH fraction, and oleanolic acid (2) and hederagenin (3) were obtained from the hydrolyzed fraction. The antinociceptive effect was tested by hot plate-writhing and tail-flicks methods using mice, and the anti-inflammatory effect was assayed using carrageenan-induced rat edema against the following samples: the MeOH extract of A. quinata stems, its fractions, the isolated saponin, kalopanaxsaponin A, and the sapogenins hederagenin and oleanolic acid. The MeOH extract exhibited antinociceptive/anti-inflammatory effects by oral administration of 100 and 250 mg/kg doses, indicating that the MeOH extract has an antinociceptive/anti-inflammatory activity. The BuOH fraction (crude saponin) also significantly exhibited those bioactivities. Treatments with 10 and 30 mg/kg perorally of these two sapogenins produced significant antinociceptive/ anti-inflammatory effects in the rat, suggesting that the sapogenins may act as resultant active compounds. Compounds 2 and 3 inhibited dye leakage into the peritoneal cavity induced by acetic acid, and the latter was more active than the former. The anti-inflammtory effects were further supported by the reduction of carrageenan-induced lipid peroxidation and hydroxy radical content in serum. These results suggest that the antinociceptive/anti-inflammatory properties of the stem of A. quinata can be attributed to the sapogenins oleanolic acid and hederagenin.
Chronic inflammation induced by biological, chemical and physical factors has been associated with increased risk of human cancer at various sites. Inflammation facilitates the initiation of normal cells and their growth and progression to malignancy through production of pro-inflammatory cytokines and diverse reactive oxygen and nitrogen species. These also activate signaling molecules involved in inflammation and carcinogenesis such as nuclear transcription factor (NF-kappaB), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Several chemopreventive agents act through inhibition of signaling pathways (e.g. NF-kappaB), inhibition of oxidant-generating enzymes (e.g. iNOS) and mediators of inflammation (e.g. COX-2), scavenging reactive oxygen and nitrogen species, and modulation of xenobiotic-metabolizing enzymes (especially phase II enzyme induction). Some anti-inflammatory drugs have been tested in clinical trials to prevent human cancer at several sites. Better understanding of the molecular mechanisms by which chronic inflammation increases cancer risk will lead to further development of new strategies for cancer prevention at many sites.