New insights into generalized hepatoprotective effects of oleanolic acid: key roles of metallothionein and Nrf2 induction

Oleanolic acid improves pulmonary morphofunctional parameters in experimental sepsis by modulating oxidative and apoptotic processes

We compared the effects of oleanolic acid (OA) vs. dexamethasone on lung mechanics and histology, inflammation, and apoptosis in lung and distal organs in experimental sepsis. Seventy-eight BALB/c mice were randomly divided into two groups. Sepsis was induced by cecal ligation and puncture, while the control group underwent sham surgery. 1h after surgery, all animals were further randomized to receive saline (SAL), OA and dexamethasone (DEXA) intraperitoneally. Both OA and DEXA improved lung mechanics and histology, which were associated with fewer lung neutrophils and less cell apoptosis in lung, liver, and kidney than SAL. However, only animals in the DEXA group had lower levels of interleukin (IL)-6 and KC (murine analog of IL-8) in bronchoalveolar lavage fluid than SAL animals. Conversely, OA was associated with lower inducible nitric oxide synthase expression and higher superoxide dismutase than DEXA. In the experimental sepsis model employed herein, OA and DEXA reduced lung damage and distal organ apoptosis through distinct anti-inflammatory mechanisms.

Protective effects of metallothionein on isoniazid and rifampicin-induced hepatotoxicity in mice

Isoniazid (INH) and Rifampicin (RFP) are widely used in the world for the treatment of tuberculosis, but the hepatotoxicity is a major concern during clinical therapy. Previous studies showed that these drugs induced oxidative stress in liver, and several antioxidants abated this effect. Metallothionein (MT), a member of cysteine-rich protein, has been proposed as a potent antioxidant. This study attempts to determine whether endogenous expression of MT protects against INH and RFP-induced hepatic oxidative stress in mice. Wild type (MT+/+) and MT-null (MT−/−) mice were treated intragastrically with INH (150 mg/kg), RFP (300 mg/kg), or the combination (150 mg/kg INH +300 mg/kg RFP) for 21 days. The results showed that MT−/− mice were more sensitive than MT+/+ mice to INH and RFP-induced hepatic injuries as evidenced by hepatic histopathological alterations, increased serum AST levels and liver index, and hepatic oxidative stress as evidenced by the increase of MDA production and the change of liver antioxidant status. Furthermore, INH increased the protein expression of hepatic CYP2E1 and INH/RFP (alone or in combination) decreased the expression of hepatic CYP1A2. These findings clearly demonstrate that basal MT provides protection against INH and RFP-induced toxicity in hepatocytes. The CYP2E1 and CYP1A2 were involved in the pathogenesis of INH and RFP-induced hepatotoxicity.

Oleanolic acid alters bile acid metabolism and produces cholestatic liver injury in mice

Oleanolic acid (OA) is a triterpenoids that exists widely in plants. OA is effective in protecting against hepatotoxicants. Whereas a low dose of OA is hepatoprotective, higher doses and longer-term use of OA produce liver injury. This study characterized OA-induced liver injury in mice. Adult C57BL/6 mice were given OA at doses of 0, 22.5, 45, 90, and 135 mg/kg, s.c., daily for 5 days, and liver injury was observed at doses of 90 mg/kg and above, as evidenced by increases in serum activities of alanine aminotransferase and alkaline phosphatase, increases in serum total bilirubin, as well as by liver histopathology. OA-induced cholestatic liver injury was further evidenced by marked increases of both unconjugated and conjugated bile acids (BAs) in serum. Gene and protein expression analysis suggested that livers of OA-treated mice had adaptive responses to prevent BA accumulation by suppressing BA biosynthetic enzyme genes (Cyp7a1, 8b1, 27a1, and 7b1); lowering BA uptake transporters (Ntcp and Oatp1b2); and increasing a BA efflux transporter (Ostβ). OA increased the expression of Nrf2 and its target gene, Nqo1, but decreased the expression of AhR, CAR and PPARα along with their target genes, Cyp1a2, Cyp2b10 and Cyp4a10. OA had minimal effects on PXR and Cyp3a11. Taken together, the present study characterized OA-induced liver injury, which is associated with altered BA homeostasis, and alerts its toxicity potential.

Hepatoprotection of 1β-hydroxyeuscaphic acid - the major constituent from Rubus aleaefolius against CCl4-induced injury in hepatocytes cells

CONTEXT

Rubus aleaefolius Poir. (Rosaceae) is used as a folk medicine to treat various types of hepatitis with significant effects in Fujian Province of China. The ethyl acetate fraction of R. aleaefolius root ethanol extract proved effective after our testing in vivo animal experiments.

OBJECTIVE

The protective effects of a major constituent, 1β-hydroxyeuscaphic acid isolated from R. aleaefolius was first investigated against carbon tetrachloride (CCl4)-induced injury in liver cells from hepatocytes cell line (BRL-3A).

MATERIALS AND METHODS

Treatment of BRL-3A with CCl4 led to generation of free radicals detected after a 2 h incubation and produced cell injury demonstrated by increased leakage of alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) in the media. Exposure to CCl4 caused apoptosis to cells but did not induce lipid peroxidation. Following treatment with 1β-hydroxyeuscaphic acid at doses ranging from 1 to 100 µg/mL for 24 h, cellular morphology, cell growth function (MTT assay), ALT, AST, malondialdehyde (MDA) and superoxide dismutase (SOD) were assessed and evaluated under control and exposed conditions.

RESULTS

The IC50 of 1β-hydroxyeuscaphic acid was 15 μg/mL. Exposure of injured BRL-3A at 20 μg/mL changed abnormal size, cellular shrinkage, and enhanced regulation. ALT, AST, MDA enzyme levels were reduced and SOD activity was increased.

DISCUSSION AND CONCLUSION

Treatment with 1β-hydroxyeuscaphic acid has significant hepatoprotective activity by lowering the leakage of intracellular enzymes, reducing the oxidation of proteins and decreasing the incidence of apoptosis. These results provide a basis for confirming the traditional uses of R. aleaefolius in treating hepatic diseases.

Prevention by sulforaphane of diabetic cardiomyopathy is associated with up-regulation of Nrf2 expression and transcription activation

This study was to investigate whether sulforaphane (SFN) can prevent diabetic cardiomyopathy. Type 1 diabetes was induced in FVB mice by multiple intraperitoneal injections with low-dose streptozotocin. Hyperglycemic and age-matched control mice were treated with or without SFN at 0.5mg/kg daily in five days of each week for 3 months and then kept until 6 months. At 3 and 6 months of diabetes, blood pressure and cardiac function were assessed. Cardiac fibrosis, inflammation, and oxidative damage were assessed by Western blot, real-time qPCR, and histopathological examination. SFN significantly prevented diabetes-induced high blood pressure and cardiac dysfunction at both 3 and 6 months, and also prevented diabetes-induced cardiac hypertrophy (increased the ratio of heart weight to tibia length and the expression of atrial natriuretic peptide mRNA and protein) and fibrosis (increased the accumulation of collagen and expression of connective tissue growth factor and tissue growth factor-β). SFN also almost completely prevented diabetes-induced cardiac oxidative damage (increased accumulation of 3-nitrotyrosine and 4-hydroxynonenal) and inflammation (increased tumor necrotic factor-α and plasminogen activator inhibitor 1 expression). SFN up-regulated NFE2-related factor 2 (Nrf2) expression and transcription activity that was reflected by increased Nrf2 nuclear accumulation and phosphorylation as well as the mRNA and protein expression of Nrf2 downstream antioxidants. Furthermore, in cultured H9c2 cardiac cells silencing Nrf2 gene with its siRNA abolished the SFN's prevention of high glucose-induced fibrotic response. These results suggest that diabetes-induced cardiomyopathy can be prevented by SFN, which was associated with the up-regulated Nrf2 expression and transcription function.

Efficacy of MK615 for the treatment of patients with liver disorders

AIM: To investigate the hepatoprotective effect of MK615, a Japanese apricot extract, in an animal model, and its clinical therapeutic effect.

METHODS: Wistar rats were administered physiological saline (4 mL/kg) or MK615 solution (4 mL/kg) for 7 d. On the sixth d, acute hepatic injury was induced by administering a single intraperitoneal injection (ip) of D-galactosamine hydrochloride (D-GalN) (600 mg/kg). Plasma levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined, and liver tissues were used for histopathological analysis. Fifty-eight patients with liver disorders [hepatitis C (n = 40), non-alcoholic fatty liver disease (n = 15), and autoimmune liver disease (n = 3)] were orally administered commercially available Misatol ME-containing MK615 (13 g/d) daily for 12 wk. Blood and urine were sampled immediately before and 6 wk, 12 wk, and 16 wk after the start of intake to measure various biochemical parameters. The percentage change in ALT and AST levels after 12 wk from the pre-intake baseline served as a primary endpoint.

RESULTS: D-GalN effectively induced acute hepatic injury in the rats. At 48 h after the ip injection of D-GalN, the plasma levels of ALT (475.6 ± 191.5 IU/L vs 225.3 ± 194.2 IU/L, P < 0.05) and AST (1253.9 ± 223.4 IU/L vs 621.9 ± 478.2 IU/L, P < 0.05) in the MK615 group were significantly lower than the control group. Scattered single cell necrosis, loss of hepatocytes, and extensive inflammatory cell infiltration were observed in hepatic tissue samples collected from the control group. However, these findings were less pronounced in the group receiving MK615. At the end of the clinical study, serum ALT and AST levels were significantly decreased compared with pre-intake baseline levels from 103.5 ± 58.8 IU/L to 71.8 ± 39.3 IU/L (P < 0.05) and from 93.5 ± 55.6 IU/L to 65.5 ± 34.8 IU/L (P < 0.05), respectively. A reduction of ≥ 30% from the pre-study baseline ALT level was observed in 26 (45%) of the 58 patients, while 25 (43%) patients exhibited similar AST level reductions. The chronic hepatitis C group exhibited significant ALT and AST level reductions from 93.4 ± 51.1 IU/L to 64.6 ± 35.1 IU/L (P < 0.05) and from 94.2 ± 55.5 IU/L to 67.2 ± 35.6 IU/L (P < 0.05), respectively. A reduction of ≥ 30% from the pre-study baseline ALT level was observed in 20 (50%) of the 40 patients. ALT levels in both the combined ursodeoxycholic acid (UDCA) treatment and the UDCA uncombined groups were significantly lower after Misatol ME administration. MK615 protected hepatocytes from D-GalN-induced cytotoxicity in rats. Misatol ME decreased elevated ALT and AST levels in patients with liver disorders.

CONCLUSION: These results suggest that MK615 and Misatol ME are promising hepatoprotective agents for patients with liver disorders.

Oleanolic acid arrests cell cycle and induces apoptosis via ROS-mediated mitochondrial depolarization and lysosomal membrane permeabilization in human pancreatic cancer cells

Oleanolic acid (OA), a pentacyclic triterpenoid, exhibits potential anti-tumor activity against many tumor cell lines. This study aims to examine the anti-tumor activity of OA on pancreatic cancer cells and its potential molecular mechanism. The results showed that the proliferation of Panc-28 cells was inhibited by OA in a concentration-dependent manner, with an IC50 (The half maximal inhibitory concentration) value of 46.35 µg ml(-1) , as determined by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The cell cycle was arrested in S phase and G2/M phase by OA. The study also showed that OA could induce remarkable apoptosis, evidenced by an increased percentage of early/late apoptotic cells, DNA ladder and nuclear morphology change. Further study revealed that OA could induce Reactive Oxygen Species (ROS) generation, mitochondrial depolarization, release of cytochrome C, lysosomal membrane permeabilization and leakage of cathepin B. The expression of apoptosis-correlated proteins was also affected in cells treated with OA, including activation of caspases-3/9 and cleavage of PARP. Further study confirmed that ROS scavenger vitamin C could reverse the apoptosis induced by OA in Panc-28 cells. Our results provide evidence that OA arrests the cell cycle and induces apoptosis, possibly via ROS-mediated mitochondrial and a lysosomal pathway in Panc-28 cells.

Oleanolic acid

Oleanolic acid (3β-hydroxyolean-12-en-28-oic acid) is a pentacyclic triterpenoid compound with a widespread occurrence throughout the plant kingdom. In nature, the compound exists either as a free acid or as an aglycone precursor for triterpenoid saponins, in which it can be linked to one or more sugar chains. Oleanolic acid and its derivatives possess several promising pharmacological activities, such as hepatoprotective effects, and anti-inflammatory, antioxidant, or anticancer activities. With the recent elucidation of its biosynthesis and the imminent commercialization of the first oleanolic acid-derived drug, the compound promises to remain important for various studies. In this review, the recent progress in understanding the oleanolic acid biosynthesis and its pharmacology are discussed. Furthermore, the importance and potential application of synthetic oleanolic acid derivatives are highlighted, and research perspectives on oleanolic acid are given.

Upregulation of chemoprotective enzymes and glutathione by Nigella sativa (black seed) and thymoquinone in CCl4-intoxicated rats

To examine the hepatoprotective activities of Nigella sativa (Ns) and thymoquinone (TQ) against carbon tetrachloride (CCl(4))-induced hepatotoxicity, the effects of water extract of Ns seeds (50 mg/kg) or TQ (5 mg/kg in corn oil) by gavage for 5 days on detoxifying enzymes and glutathione were compared in healthy and CCl(4)-challenged (1 mL/kg in corn oil, intraperitoneally [ip], a single dose) rats. Both Ns and TQ countered the elevations in serum alanine aminotransferase activity, oxidized glutathione level, and stress ratio caused by CCl(4). Both Ns and TQ ameliorated the reductions in the activities and messenger RNA (mRNA) levels of glutathione S-transferase, NAD(P)H-quinone oxidoreductase, and microsomal epoxide hydrolase, as well as the reductions in reduced glutathione and cysteine levels produced by CCl(4). In many instances, Ns was much superior to TQ in providing protection against the damaging effects caused by CCl(4). This protection could be attributed to the induction of chemoprotective enzymes probably through increasing transcription.

The cap'n'collar transcription factor Nrf2 mediates both intrinsic resistance to environmental stressors and an adaptive response elicited by chemopreventive agents that determines susceptibility to electrophilic xenobiotics

Transcription factor Nrf2 regulates genes encoding drug-metabolising enzymes and drug transporters, as well as enzymes involved in the glutathione, thioredoxin and peroxiredoxin antioxidant pathways. Using mouse embryonic fibroblast (MEF) cells from Nrf2(+/+) and Nrf2(-/-) mice, in conjunction with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay, we have shown that loss of Nrf2 diminishes the intrinsic resistance of mutant fibroblasts towards isothiocyanates (i.e. sulforaphane), epoxides (i.e. (2S,3S)-(-)-3-phenylglycidol, ethyl 3-phenylglycidate and styrene-7,8-epoxide), peroxides, hydroquinones and quinones (i.e. tert-butylhydroperoxide, tert-butylhydroquinone and 2,3-dimethoxynaphthoquinone), NaAsO(2), and various mutagens, including β-propiolactone, cisplatin, mechlorethamine and methyl methanesulfonate to ∼50% of that observed in equivalent wild-type cells. Exposure of Nrf2(+/+) fibroblasts, but not Nrf2(-/-) fibroblasts, to a non-toxic dose (3μmol/l) of the chemopreventive agent sulforaphane (Sul) stimulated an adaptive response that, 18h after first being subjected to the isothiocyanate, caused an induction of between 2- and 10-fold in the levels of mRNA for glutamate-cysteine ligase catalytic (Gclc) and modifier (Gclm) subunits, glutathione S-transferases and NAD(P)H:quinone oxidoreductase-1 (Nqo1); this was accompanied by an increase in total glutathione of between 1.5- and 1.9-fold. Pre-treatment of Nrf2(+/+) MEF cells with 3μM Sul for 18h prior to challenge with xenobiotics, conferred between 2.0- and 4.0-fold protection against isothiocyanates, reactive carbonyls, peroxides, quinones, NaAsO(2), and the anticancer nitrogen mustard chlorambucil, but pre-treatment with 3μM Sul produced no such increased tolerance in Nrf2(-/-) MEF cells. The inducible resistance towards acrolein, cumene hydroperoxide and chlorambucil, produced by pre-treating wild-type fibroblasts with 3μM Sul, was dependent on glutathione because simultaneous pre-treatment with 5μmol/l buthionine sulfoximine abolished the increased tolerance of these xenobiotics. However, inducible resistance towards menadione that occurred upon pre-treatment with 3μM Sul was independent of glutathione and may be due to upregulation of Nqo1. Thus Nrf2 controls cellular resistance against electrophiles.

Nrf2-Keap1 antioxidant system and hepatic diseases

NF-E2-related factor 2 (Nrf2) is an important transcription factor. When oxidative stress occurs, Nrf2 dissociates from Keap1 (Kelch-like ECH-associating protein 1), translocates to the nucleus, and regulates the expression of genes encoding phase II detoxifying enzymes and antioxidant proteins, thereby increasing the resistance to oxidative stress and electrophilic agents. Reactive oxygen species and oxidative stress play an important role in the development of hepatic diseases. In this article, we will summarize the relationship between the Nrf2-Keap1 system and hepatic diseases.

Hepatoprotective effects of Rubus aleaefolius Poir. and identification of its active constituents

The purpose of this study was to study the hepatoprotective effects of the most promising extract of the root from Rubus aleaefolius Poir. and to isolate and identify the active components. Various crude forms of Rubus aleaefolius have been evaluated for their effects on CCl(4)-induced acute liver injury in mice vivo experimental model. Treatment groups contained 5 sub-groups that were ethanol crude extract; the high/low dosage ethyl acetate or n-butanol fraction; extracted with ethyl acetate or n-butanol after the residues and major constituent; intragastrically administrated with 35 mg/kg; 35, 4.6 mg/kg; 35, 5.8 mg/kg; 35 mg/kg and 3.5 mg/kg for 7 days. The serum samples were collected for biological analysis and also carried out histopathological studies. The low-dosage ethyl acetate fraction was the most active when the fractions were compared. It was found to decrease AST, ALT; to prevent formation of hepatic MDA, NO and intensify the activity of SOD. The histopathological changes induced by CCl(4) were also significantly reduced. The separation revealed the presence of six constituents by a bioassay-guided fractionation, beta-Sitosterol (1), 1beta-Hydroxyeuscaphic acid (2), Oleanolic acid (3), Myrianthic acid (4), Euscaphic acid (5), and Tomentic acid (6). Among them, compounds 2, 4, 5 in Rubus aleaefolius root is reported here for the first time. 1beta-Hydroxyeuscaphic acid (major constituent) showed a tremendous activity and the results confirm the traditional uses of Rubus aleaefolius in treating hepatitis.

Nrf2 the rescue: effects of the antioxidative/electrophilic response on the liver

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that positively regulates the basal and inducible expression of a large battery of cytoprotective genes. These gene products include proteins that catalyze reduction reactions (NAD(P)H:quinone oxidoreductase 1, Nqo1), conjugation reactions (glutathione-S-transferases, Gsts and UDP-glucuronosyltransferases, Ugts), as well as the efflux of potentially toxic xenobiotics and xenobiotic conjugates (multidrug resistance-associated proteins, Mrps). The significance of Nrf2 in the liver has been established, as livers of Nrf2-null mice are more susceptible to various oxidative/electrophilic stress-induced pathologies than wild-type mice. In contrast, both pharmacological and genetic models of hepatic Nrf2 activation are protective against oxidative/electrophilic stress. Furthermore, because certain Nrf2-target genes in the liver could affect the distribution, metabolism, and excretion of xenobiotics, the effects of Nrf2 on the kinetics of drugs and other xenobiotics should also be considered, with a special emphasis on metabolism and excretion. Therefore, this review highlights the research that has contributed to the understanding of the importance of Nrf2 in toxicodynamics and toxicokinetics, especially that which pertains to the liver.

Oleanolic acid activates Nrf2 and protects from acetaminophen hepatotoxicity via Nrf2-dependent and Nrf2-independent processes

Oleanolic acid is a plant-derived triterpenoid, which protects against various hepatotoxicants in rodents. In order to determine whether oleanolic acid activates nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor known to induce various antioxidant and cytoprotective genes, wild-type and Nrf2-null mice were treated with oleanolic acid (90 mg/kg, i.p.) once daily for 3 days. Oleanolic acid increased nuclear accumulation of Nrf2 in wild-type but not Nrf2-null mice, as determined by Western blot and immunofluorescence. Oleanolic acid-treated wild-type mice had increased hepatic mRNA expression of the Nrf2 target genes NAD(P)H:quinone oxidoreductase 1 (Nqo1); glutamate-cysteine ligase, catalytic subunit (Gclc); heme oxygenase-1 (Ho-1); as well as Nrf2 itself. In addition, oleanolic acid increased protein expression and enzyme activity of the prototypical Nrf2 target gene, Nqo1, in wild-type, but not in Nrf2-null mice. Oleanolic acid protected against acetaminophen hepatotoxicity in wild-type mice but to a lesser extent in Nrf2-null mice. Oleanolic acid-mediated Nrf2-independent protection from acetaminophen is, in part, due to induction of Nrf2-independent cytoprotective genes, such as metallothionein. Collectively, the present study demonstrates that oleanolic acid facilitates Nrf2 nuclear accumulation, causing induction of Nrf2-dependent genes, which contributes to protection from acetaminophen hepatotoxicity.