Protective effect of flavonoids on drug-induced hepatotoxicity in vitro

Silymarin Encapsulated Liposomal Formulation: An Effective Treatment Modality against Copper Toxicity Associated Liver Dysfunction and Neurobehavioral Abnormalities in Wistar Rats

Wilson's disease causes copper accumulation in the liver and extrahepatic organs. The available therapies aim to lower copper levels by various means. However, a potent drug that can repair the damaged liver and brain tissue is needed. Silymarin has hepatoprotective, antioxidant, and cytoprotective properties. However, poor oral bioavailability reduces its efficacy. In this study, a "thin film hydration method" was used for synthesizing silymarin-encapsulated liposome nanoparticles (SLNPs) and evaluated them against copper toxicity, associated liver dysfunction and neurobehavioral abnormalities in Wistar rats. After copper toxicity induction, serological and behavioral assays were conducted to evaluate treatment approaches. Histological examination of the diseased rats revealed severe hepatocyte necrosis and neuronal vacuolation. These cellular degenerations were mild in rats treated with SLNPs and a combination of zinc and SLNPs (ZSLNPs). SLNPs also decreased liver enzymes and enhanced rats' spatial memory significantly (p = 0.006) in the diseased rats. During forced swim tests, SLNPs treated rats exhibited a 60-s reduction in the immobility period, indicating reduced depression. ZSLNPs were significantly more effective than traditional zinc therapy in decreasing the immobility period (p = 0.0008) and reducing liver enzymes, but not in improving spatial memory. Overall, SLNPs enhanced oral silymarin administration and managed copper toxicity symptoms.

Evaluation of Garlic Juice Processing Waste Supplementation in Juvenile Black Rockfish (Sebastes schlegelii) Diets on Growth Performance, Antioxidant and Digestive Enzyme Activity, Growth- and Antioxidant-Related Gene Expression, and Disease Resistance against Streptococcus iniae

An 8-week feeding trial was conducted to evaluate the effects of various dietary levels of garlic juice processing waste (GJPW) on the growth, feed utilization, digestive and antioxidant enzyme activity, growth- and antioxidant-related gene expression, and resistance to Streptococcus iniae infection of juvenile black rockfish (Sebastes schlegelii). A total of 450 juvenile rockfish were randomly distributed into 30 L rectangular tanks (30 fish per tank). Five experimental diets were prepared in triplicate. The fish were fed experimental diets supplemented with GJPW at concentrations of 0 (GJPW0, control), 2.5 (GJPW2.5), 5 (GJPW5), 7.5 (GJPW7.5), and 10 g kg^-1 (GJPW10) diet. All of the GJPW-supplemented treatments (2.5, 5, 7.5, and 10 g kg^-1) significantly enhanced weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER), and digestive enzyme activity (amylase, trypsin, and lipase). A decreasing trend was seen in plasma aspartate aminotransferase (ALT), alanine aminotransferase (AST), and glucose (GLU) content with increasing dietary levels of GJPW. In contrast, plasma lysozyme and antioxidant enzyme activities were significantly increased with increasing dietary GJPW levels. Furthermore, GJPW administration significantly upregulated the expression of insulin-like growth factor-1 (IGF-1), superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) in the liver of rockfish. A challenge test with S. iniae showed significantly higher resistance in the GJPW-supplemented treatments than in the control. In short, dietary supplementation GJPW enhanced growth performance and antioxidant response in juvenile black rockfish, with suitable effects in fish fed with 2.5 g kg^-1 GJPW for 8 weeks.

A Polyphenol-Rich Fraction from Eugenia uniflora Exhibits Antioxidant and Hepatoprotective Activities In Vivo

Leaves from Eugenia uniflora, the red Brazilian cherry, have a high content of flavonoids that possess several biological effects such as anti-inflammatory, antioxidant, and antidiabetic activities. However, their influence on carbon tetrachloride (CCl4)-induced acute liver injury in rats has not been investigated. In the current study, a bioguided fractionation assay revealed that the ethyl acetate fraction (EAF) of Eugenia uniflora is the safest and most active fraction. LC-MS analysis of the ethyl acetate fraction revealed 22 secondary metabolites, mainly myricetin and quercetin derivatives. EAF did not show toxicity up to 2000 mg/kg, and exhibited antioxidant activities in vitro in DPPH assay with IC50 of 3.35 µg/mL. Additionally, EAF exhibited substantial antioxidant activities in vivo by counteracting the oxidative damage of the prooxidant juglone [80 µM] in Caenorhabditis elegans model organism and increased its survival rate in a dose-dependent fashion through the DAF-16/Foxo pathway. Furthermore, the hepatoprotective activity of EAF (200 mg/kg against carbon tetrachloride (CCl4) intoxicated male Wistar rats was assessed. EAF significantly inhibited CCl4-induced elevation of alanine aminotransferase (ALT), aspartate transaminase (AST), total bilirubin (TB), total cholesterol (TC), and triglycerides (TG), in the blood serum and prevented lipid peroxidation and restored superoxide dismutase (SOD) activity and glutathione (GSH) content in liver tissues. The observed hepatoprotective effects of EAF, which were supported by histopathological observations as pretreatment with EAF, effectively attenuated the CCl4-induced histopathological changes. In conclusion, EAF of Eugenia uniflora leaves has substantial hepatoprotective activities against CCl4 induced acute liver injury in rats due to its antioxidant activity.

Synthesis, Biological Evaluation and Docking Studies of Chalcone and Flavone Analogs as Antioxidants and Acetylcholinesterase Inhibitors

Several oxidative processes are related to a wide range of human chronic and degenerative diseases, like Alzheimer’s disease, which also has been related to cholinergic processes. Therefore, search for new or improved antioxidant molecules with acetylcholinesterase activity is essential to offer alternative chemotherapeutic agents to support current drug therapies. A series of chalcone (2a–2k) and flavone (3a–3k) analogs were synthesized, characterized, and evaluated as acetylcholinesterase (AChE) inhibitors, and antioxidant agents using 1,1-diphenyl-2-picrylhydrazyl (DPPH•), 2-2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS•), and β-carotene/linoleic acid bleaching assay. Compounds more active were 3j and 2k in DPPH with EC50 of 1 × 10−8 and 5.4 × 10−3 μg/mL, respectively; 2g and 3i in ABTS (1.14 × 10−2 and 1.9 × 10−3 μg/mL); 2e, 2f, 3f, 2j, and 3j exceeded the α-tocopherol control in the β-carotene assay (98–99% of antioxidant activity). At acetylcholinesterase inhibition assay, flavones were more active than chalcones; the best results were compounds 2d and 3d (IC50 21.5 and 26.8 µg/mL, respectively), suggesting that the presence of the nitro group enhances the inhibitory activity. The docking of these two structures were made to understand their interactions with the AChE receptor. Although further in vivo testing must be performed, our results represent an important step towards the identification of improved antioxidants and acetylcholinesterase inhibitors.

Hepatoprotective standardized EtOH-water extract of the leaves of Ziziphus jujuba

The hepatoprotective activity of the EtOH-water extract of Ziziphus jujuba leaves was evaluated against CCl₄-induced hepatic damage in mice. The EtOH-water extract significantly alleviated liver damage as indicated by the decreased levels of serum ALT and AST and the decreased MDA content, the increased levels of SOD, GSH and GSH-Px, and the reduced pathological tissue injury induced by CCl₄. A quantitative analysis of fifteen major constituents (1-15) of the EtOH-water extract of the leaves of Z. jujuba was conducted by HPLC-DAD. Based on our research results, it can be concluded that the EtOH-water extract of the leaves of Z. jujuba is efficacious for prevention and treatment of CCl₄-induced hepatic injury in mice. Flavonoids might be the active ingredients responsible for the biological and pharmacological activities towards hepatoprotection.

Protective effects of green tea and its main constituents against natural and chemical toxins: A comprehensive review

Toxins are natural or chemical poisonous substances with severe side effects on health. Humans are generally exposed by widespread toxic contaminations via air, soil, water, food, fruits and vegetables. Determining a critical antidote agent with extensive effects on different toxins is an ultimate goal for all toxicologists. Traditional medicine is currently perceived as a safe and natural approach against toxins. In this regard, we focused on the protective effects of green tea (Camellia sinensis) and its main components such as catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin and epigallocatechin gallate as a principal source of antioxidants against both natural and chemical toxins. This literate review demonstrates that protective effects of green tea and its constituents were mainly attributed to their anti-oxidative, radical scavenging, chelating, anti-apoptotic properties and modulating inflammatory responses. Although, some studies reveal they have protective effects by increasing toxin metabolism and neutralizing PLA₂, proteases, hyaluronidase and l-amino acid oxidase enzymes.

The effect of nutrition on chemical toxicity

The toxicity of chemicals, and of reactive oxygen species (ROS), are both affected by nutrition and diet. Calorific excess (continuous feeding), or deficiency (fasting), may increase production of ROS, which are also formed by interaction of toxic chemicals with cytochromes P450 (CYP2E or futile cycling). Both ROS (GSH reductase and peroxidase) and toxic chemicals (S-transferases) are detoxified by GSH enzymes; ROS are scavenged by a system comprising GSH, ascorbic acid and tocopherols, which may be regenerated by NADPH. Dietary protein is necessary for GSH or enzyme replacement, lipids are required for polyunsaturated fatty acids (PUFAs) and prostanoid biosynthesis, lipotropes and phospholipids for synthesis of endoplasmic reticulum, and folate is needed for dug metabolizing activity. Among required minerals, Se is necessary as the essential component of the antioxidant enzyme, glutathione peroxidase. Other dietary factors considered are the natural toxicants, gossypol, lathyrogens, glucosinolates, and saponins, and toxicants from food spoilage, food intoxication and food processing.

Luteolin and fisetin inhibit the effects of lipopolysaccharide obtained from Porphyromonas gingivalis in human gingival fibroblasts

Periodontitis is an inflammatory process of infectious origin that affects the gums and, in severe cases, destroys connective tissue, leading to loss of the dental organ. Gram-negative Porphyromonas gingivalis bacteria are recovered from patients with chronic periodontitis. The polysaccharide obtained from these bacteria induces the expression of interleukin (IL)-1 beta, tumor necrosis factor, and IL-6. Flavonoids are molecules that participate in the control of inflammatory processes. We studied the role of the flavonoids fisetin, luteolin, myricetin, and morin in inhibiting the activation of mitogen-activated protein kinase (MAPK) and AKT as well as their role in lipopolysaccharide (LPS)-induced cyclooxygenase-2 (COX-2) transcription. All four of these flavonoids were found to inhibit MAPK and AKT. Fisetin and luteolin blocked the activation of MAPK and AKT to levels below basal levels. All of these flavonoids also blocked LPS-mediated COX-2 expression.

Expressions of P53 and CD68 in mouse liver with Schistosoma mansoni infection and the protective role of silymarin

Schistosomiasis is one of the major human parasitic diseases in many developing countries and is one of the causes of morbidity and mortality in the human population. The present work has been planned to study the histopathological and immunohistochemical expression of P53 and CD68 in mouse liver tissues experimentally infected with Schistosoma mansoni, in addition to the ameliorating role of silymarin. A total of 50 adult male mice were divided into 5 groups (10 animals each). Groups 1 and 2 were the control and silymarin groups, respectively, while group 3 was the infected group in which the mice were infected with S. mansoni live cercariae for 6 weeks. Groups 4 and 5 were the cotreated and posttreated groups, respectively, in which mice were infected with cercariae of S. mansoni and treated with silymarin during and after Schistosoma infection, respectively. The major histopathological lesions were variable numbers of perioval granulomas, diffuse infiltration of inflammatory cells, mainly eosinophils and small mononuclear cells, and fibrosis of portal areas and interlobular septa. Treatment with silymarin led to a significant reduction in granuloma area in all treated infected mice compared with nontreated infected mice. Immunohistochemical observations of the liver tissues showed a significant increase in the apoptotic proteins P53 and CD68 after the infection with the cercariae of Schistosoma, compared with the control group. The expression of the cytoplasmic P53 and CD68 was very low in the control liver sections. A significant decrease in the expression of the cytoplasmic P53 and CD68 was observed after silymarin treatment.

Plant polyphenols in cancer and heart disease: implications as nutritional antioxidants

Certain dietary antioxidants such as vitamin E and vitamin C are important for maintaining optimum health. There is now much interest in polyphenolic products of the plant phenylpropanoid pathway as they have considerable antioxidant activity in vitro and are ubiquitous in our diet. Rich sources include tea, wine, fruits and vegetables although levels are affected by species, light, degree of ripeness, processing and storage. This confounds the formulation of databases for the estimation of dietary intakes. Most attention to date has focused on the flavonoids, a generic term which includes chalcones, flavones, flavanones, flavanols and anthocyanins. There is little convincing epidemiological evidence that intakes of polyphenols are inversely related to the incidence of cancer whereas a number of studies suggest that high intakes of flavonoids may be protective against CHD. In contrast, numerous cell culture and animal models indicate potent anticarcinogenic activity by certain polyphenols mediated through a range of mechanisms including antioxidant activity, enzyme modulation, gene expression, apoptosis, upregulation of gap junction communication and P-glycoprotein activation. Possible protective effects against heart disease may be due to the ability of some polyphenols to prevent the oxidation of LDL to an atherogenic form although anti-platelet aggregation activity and vasodilatory properties are also reported. However, some polyphenols are toxic in mammalian cells. Thus, until more is known about their bioavailability, metabolism and intracellular location, increasing intakes of polyphenols by supplements or food fortification may be unwise.

Effect of silymarin on pyrogallol- and rifampicin-induced hepatotoxicity in mouse

Rifampicin and pyrogallol, besides beneficial effects, elicit hepatotoxicity in experimental animals and humans. The present investigation was undertaken to elucidate the role of drug/toxicant-metabolizing enzymes in rifampicin- and pyrogallol-induced hepatotoxicity and the effect of silymarin, a herbal antioxidant, on rifampicin- and pyrogallol-induced alterations in mouse liver. Male Swiss albino mice were treated intraperitoneally with and without rifampicin (20 mg/kg) and/or pyrogallol (40 mg/kg) for 1, 2, 3 and 4 weeks. In some experiments, animals were treated with silymarin (40 mg/kg), 2 h prior to rifampicin and/or pyrogallol. The differential expression and catalytic activity of cytochrome P-450 (CYP) 1A1, CYP1A2 and CYP2E1, the activity of glutathione-S-transferase, glutathione peroxidase and glutathione reductase, and lipid peroxidation were measured in the liver of control and treated groups. CYP1A1 expression and catalytic activity were not altered following individual or combinational treatment. A significant augmentation in the expression and activity of CYP1A2 and CYP2E1 was observed following pyrogallol and rifampicin+pyrogallol treatment; however, rifampicin exhibited a significant induction of CYP2E1 only. Attenuation of glutathione-S-transferase, glutathione reductase and glutathione peroxidase activities and augmentation of lipid peroxidation were observed following rifampicin and/or pyrogallol treatment and a cumulative effect was seen when the two drugs were administered in combination. Silymarin restored the rifampicin- and/or pyrogallol-induced alterations in the expression and activity of CYP1A2 and CYP2E1, the activity of glutathione-S-transferase, glutathione reductase, and glutathione peroxidase, and lipid peroxidation. The results demonstrate the role of CYP1A2, CYP2E1, glutathione-S-transferase, glutathione reductase and glutathione peroxidase in rifampicin- and pyrogallol-induced hepatotoxicity and provide evidence for the involvement of silymarin in attenuation of drug-induced hepatotoxicity.

Thioacetamide induced liver damage in zebrafish embryo as a disease model for steatohepatitis

Steatohepatitis has recently been increasing as a cofactor influencing the progression of fibrosis, cirrhosis, adenoma and carcinoma in liver; however, the mechanisms by which it contributes to liver injury remain uncertain. We induced steatohepatitis in zebrafish embryos using thioacetamide (TAA). TUNEL assay revealed significant increasing of apoptosis in liver after 5 days post fertilization and the increasing of apoptosis was observed to be associated with the up-regulation of apoptotic genes such as, bad, bax, P-38a, caspase-3 and 8, and JNK-1. Histological sections by oil red O stain showed the accumulation of fatty droplets which causes the pushing of the nucleus towards one side. Up-regulation of steatosis markers such as, ACC, adiponectin, PTL, CEBP- alpha and beta, SREBP-1 was also observed. Furthermore, the elevation of glutathione peroxidase in TAA treated embryos indicated that TAA induces lipid peroxidation which leads to causes liver damage. Zebrafish has already been considered as a good human disease model and in this context; TAA-treated zebrafish may serve as a good animal model to study the molecular pathogenesis of steatohepatitis. Moreover, non-availability of specific drugs to prevent steatohepatitis, this animal model may serve as a powerful preclinical platform to study the therapeutic strategies and for evaluating chemoprevention strategies for this disease.

Hepatoprotective effect of ginsenoside Rb1 and compound K on tert-butyl hydroperoxide-induced liver injury

BACKGROUND/AIM

The main component of Panax ginseng, which have been reported by many researchers, are ginsenoside Rb1, Rb2 and Rc. Orally administered ginsenosides are metabolized to 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol (compound K) by intestinal bacteria and absorbed to blood. To understand its hepatoprotective effect and its mechanism, the effects of ginsenoside Rb1 and its metabolite compound K on chemically injured HepG2 cells and mice were investigated.

METHODS

Ginsenoside Rb1 and compound K were isolated from ginseng. Hepatotoxicity of HepG2 cells and mice was induced by tert-butyl hydroperoxide (t-BHP). Cytotoxicity for HepG2 cells and serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) for mice as markers of hepatoprotective activity were measured.

RESULTS

Compound K protected HepG2 cell cytotoxicity induced by t-BHP. However, ginsenoside Rb1 did not inhibit cytotoxicity. Nevertheless, both ginsenoside Rb1 and compound K significantly inhibited the increment of ALT and AST induced by t-BHP in mice, when it was orally administered. However, intraperitoneally administered ginsenoside Rb1 did not inhibit the increment of plasma ALT and AST induced by t-BHP in mice. These compounds did not exhibit antioxidant activity. However, compound K showed the potent membrane stabilizing activity more than ginsenoside Rb1.

CONCLUSION

Compound K, which was produced from ginsenosides of Panax ginseng in intestine, could protect liver injury.

Free radical scavenging and hepatoprotective activity of jigrine against galactosamine induced hepatopathy in rats

Jigrine a polypharmaceutical herbal hepatoprotective formulation containing aqueous extracts of 14 medicinal plants is used in Indian system of medicine (Unani). Jigrine was evaluated for its hepatoprotective activity against galactosamine induced hepatopathy in rats. Galactosamine induced hepatotoxicity resembles human viral hepatitis. Biochemical parameters like AST, ALT and urea in serum, TBARS and glutathione in liver and whole blood glutathione were estimated to assess liver function. DPPH-free radical scavenging activity of jigrine was also evaluated. Biochemical data exhibited significant hepatoprotective activity of jigrine against galactosamine. Silymarin used as reference standard also exhibited significant hepatoprotective activity against galactosamine. The biochemical observations were supplemented with histopathological examination of rat liver sections.

Protection of tea melanin on hydrazine-induced liver injury

The protective activity of melanin derived from tea (MDFT) was studied using hydrazine as a DNA-reactive chemical agent. Intra-peritoneal administration of MDFT at the doses of 5 or 20 mg/kg dose-dependently prevented liver toxicity induced by hydrazine in rats. It normalized rises in serum alanine transferase activity and a decrease in the glutathione level in the liver. It also reduced the hepatic malondialdehyde concentration. Monitoring the intensity of chemiluminescence showed that MDFT could prevent the production of free radicals that are generated owing to metabolic transformation of hydrazine. It also prevented the formation 8-hydroxy-deoxyguanosine (8-OH-dG) DNA adducts. The results obtained in vivo and in vitro suggest that MDFT confers marked protection of the liver against hydrazine-induced oxidative toxicity.

Evaluation of hepatoprotective potential of jigrine post-treatment against thioacetamide induced hepatic damage

Jigrine a polypharmaceutical herbal formulation containing aqueous extracts of 14 medicinal plants developed on the principles of unani system of medicine is used for liver ailments. The hepatoprotective potential of jigrine post-treatment at the dose of 0.5 ml/kg per day p.o. for 21 days was evaluated against thiocetamide induced liver damage in rats. Biochemical parameters like AST, ALT in serum and TBARS and glutathione in tissues were estimated to assess liver function. Data on the biochemical parameters revealed hepatoprotective potential of jigrine post-treatment against thioacetamide induced hepatotoxicity in rats. Silymarin used as reference standard also exhibited significant hepatoprotective activity on post-treatment against thioacetamide-induced hepatotoxity in rats. The biochemical observations were supplemented with histopathological examination of rat liver sections.

Attenuation of luminol-amplified chemiluminescent intensity and lipid peroxidation in the livers of quercetin-fed mice

We assessed the antioxidative effects of quercetin-feeding on ddY strain male mice by measuring luminol-amplified chemiluminescence that was enhanced by a hydrophilic free radical initiator 2, 2'-azobis(2-amidinopropane) dihydrochloride. Quercetin suppressed chemiluminescent intensity in a dose-dependent manner in vitro with a half-inhibition concentration (IC(50)) of 3x10(-8) M, which was lower than the value of synthetic antioxidant 2, 6-di-tert-butyl-p-cresol (IC(50): 7x10(-7) M). Lysosomal (12000xg pellet) and supernatant fractions obtained from the livers of mice fed a diet containing 0.2% quercetin for 7 days showed more inhibition of chemiluminescent intensity than those from non-treated mice. Quercetin feeding also resulted in the inhibition of lipid peroxidation as determined by a thiobarbituric acid reactive substance test which detected suppression of the release of lysosomal enzymes induced by lipophilic free radical initiator 2, 2'-azobis(2,4-dimethylvaleronitrile). These results probably reflect radical quenching activity of quercetin, indicating that the measurement of chemiluminescence is a useful tool for the assessment of total antioxidant activity in biological systems.

Tissue distribution of silibinin, the major active constituent of silymarin, in mice and its association with enhancement of phase II enzymes: implications in cancer chemoprevention

Polyphenolic antioxidants are being identified as cancer preventive agents. Recent studies in our laboratory have identified and defined the cancer preventive and anticarcinogenic potential of a polyphenolic flavonoid antioxidant, silymarin (isolated from milk thistle). More recent studies by us found that these effects of silymarin are due to the major active constituent, silibinin, present therein. Here, studies are done in mice to determine the distribution and conjugate formation of systemically administered silibinin in liver, lung, stomach, skin, prostate and pancreas. Additional studies were then performed to assess the effect of orally administered silibinin on phase II enzyme activity in liver, lung, stomach, skin and small bowel. For tissue distribution studies, SENCAR mice were starved for 24 h, orally fed with silibinin (50 mg/kg dose) and killed after 0.5, 1, 2, 3, 4 and 8 h. The desired tissues were collected, homogenized and parts of the homogenates were extracted with butanol:methanol followed by HPLC analysis. The column eluates were detected by UV followed by electrochemical detection. The remaining homogenates were digested with sulfatase and beta-glucuronidase followed by analysis and quantification. Peak levels of free silibinin were observed at 0.5 h after administration in liver, lung, stomach and pancreas, accounting for 8.8 +/- 1.6, 4. 3 +/- 0.8, 123 +/- 21 and 5.8 +/- 1.1 (mean +/- SD) microg silibinin/g tissue, respectively. In the case of skin and prostate, the peak levels of silibinin were 1.4 +/- 0.5 and 2.5 +/- 0.4, respectively, and were achieved 1 h after administration. With regard to sulfate and beta-glucuronidate conjugates of silibinin, other than lung and stomach showing peak levels at 0.5 h, all other tissues showed peak levels at 1 h after silibinin administration. The levels of both free and conjugated silibinin declined after 0.5 or 1 h in an exponential fashion with an elimination half-life (t((1/2))) of 57-127 min for free and 45-94 min for conjugated silibinin in different tissues. In the studies examining the effect of silibinin on phase II enzymes, oral feeding of silibinin at doses of 100 and 200 mg/kg/day showed a moderate to highly significant (P < 0.1-0.001, Student's t-test) increase in both glutathione S-transferase and quinone reductase activities in liver, lung, stomach, skin and small bowel in a dose- and time-dependent manner. Taken together, the results of the present study clearly demonstrate the bioavailability of and phase II enzyme induction by systemically administered silibinin in different tissues, including skin, where silymarin has been shown to be a strong cancer chemopreventive agent, and suggest further studies to assess the cancer preventive and anticarcinogenic effects of silibinin in different cancer models.

Astilbin selectively induces dysfunction of liver-infiltrating cells--novel protection from liver damage

The present study aimed to examine the effect of astilbin, a flavanoid, on liver injury. When administered during the effector but not induction phase, astilbin significantly decreased the liver injury induced by delayed-type hypersensitivity to picryl chloride in mice. The pretreatment of nonparenchymal cells but not hepatocytes with astilbin in vitro caused a concentration- and time-dependent inhibition against the damage. Nonparenchymal cells isolated from astilbin-administered mice also showed a significant incompetence of hepatotoxicity, correlated with the inhibition of serum transaminase elevation. However, astilbin did not protect from CCl4-induced liver damage. Furthermore, the flavanoid markedly promoted the apoptosis of nonparenchymal cells from liver-injured mice, whereas did not influence those from naive mice. These results suggest that astilbin provides improvement against liver injury through a selective dysfunction of liver-infiltrating cells rather than by protecting the hepatocyte membrane. Such characteristics will be of significance to pave a new way for treating immunologically related liver diseases and for developing new drugs.

Immunopharmacologic agents in the amelioration of hepatic injuries

A number of immunomodulating agents of different origin have been shown to reduce liver injury of various etiologies. Immunostimulants like levamisole, BCG, a protein polysaccharide from myceria Coriolus vesicolor PS-K, a streptoccocal preparation OK-432 and immunomodulators like N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and its analogs. Selective T-cell suppressors like the polypeptide cyclosporine A (CsA) and the macrolide FK 506 (tacrolimus) have also been claimed to possess hepatoprotrophic or hepatoprotective properties at low doses. The aim of this review article is to highlight the interplay between the administration of immunomodulating agents and the amelioration of hepatic injuries. Hepatic effects of exogenous immunomodulators are discussed with special focus on the most widely used immunosuppressive agents, CsA and tacrolimus. An important question exists as to whether these potential hepatoprotective effects are related mechanistically to the immune system or are working at different levels. Due to the differences in effects and modes of actions of various immunoactive substances presented herein, a common mechanism for their cytoprotective effects cannot be formulated at this stage. Levamisole and cyanidanol may protect cells against necrosis by acting as free radical scavengers. MDP and its analogs reduce carbon tetrachloride-elevated (CCl4) lipid peroxides and their protective effects are primarily on hepatic cytoplasmic membranes where lipid peroxidation and calcium homeostasis interact. MDP reduced CCl4-elevated calcium in both intact hepatocytes and in the post microsomal supernatant suggest that the influx of extracellular calcium across plasma membrane is affected. Elevations of intracellular calcium above a threshold are involved in: the stimulation of Ca2+-sensitive enzymes such as phospholipase A2, endonucleases and proteases, the conversion of xanthine dehydrogenase to xanthine oxidase and the formation of free radicals, all of which disturb biomembranes. MDP and its analogs, in a specific dose range, may act to maintain intracellular calcium within physiological ranges. Highly complex cellular signalling systems, including calcium, are involved in the explanation of the mechanism of the immunosuppressive effect of CsA and tacrolimus. The hepatoprotective effects of these selective immunosuppressive agents, however, are independent of the inhibition of T-cell activation. The cyclophilin and tacrolimus binding proteins of the mitochondria are the receptors for these compounds and play a key role in the regulation of mitochondrial permeability transition pores. CsA or tacrolimus inhibition of mitochondrial permeability transition pores does not require interaction with calcineurin, indicating a dissociation between immunosuppression and mitochondrial protection. The involvement of intracellular or intramitochondrial proteins in the modulation of mitochondrial permeability transition pores with the creation of a partially impermeable state for Ca2+ movement in drug-treated mitochondria and the dissociation of this effect from immunomodulatory actions potentially offers new and promising approaches for the development of new pharmacologicals targeted at therapeutic intervention. Clinical trials of these drugs as hepatoprotective agents are limited. Use of CsA in patients with primary biliary cirrhosis and autoimmune chronic hepatitis and in cirrhotic animal models produced by chronic administration of CCl4 have yielded encouraging results. It seems that this class of compounds may be of substantial benefit in liver protection against many pathological conditions where disturbance in mitochondrial function and in Ca2+ homeostasis appear to be prerequisites for cell injury.

Quercetin and myricetin protect against hydrogen peroxide-induced DNA damage (strand breaks and oxidised pyrimidines) in human lymphocytes

The effects of the flavonoids quercetin and myricetin, and the antihepatotoxic agent silymarin, on hydrogen peroxide-mediated DNA damage in human lymphocytes were determined using alkaline single-cell gel electrophoresis (the comet assay). Treatment with hydrogen peroxide increased the levels of DNA strand breaks and oxidised pyrimidine bases in these cells. Quercetin was protective at concentrations above 10 microM and myricetin decreased oxidant-induced DNA strand breakage at concentrations of 100 microM. Cellular metabolism may alter the antioxidant efficacy of the flavonoids. Silymarin had no protective effect at any of the concentrations tested. None of these flavonoids was itself genotoxic. Neither alpha-tocopherol nor beta-carotene decreased hydrogen peroxide-induced DNA breakage. The differences in effectiveness of these dietary compounds against oxidative DNA damage may be explained by differences in their chemical structure or location within the cell.

Liver injury model induced in mice by a cellular immunologic mechanism--study for use in immunopharmacological evaluations

Various drugs for clinical hepatitis were applied to a new model of liver injury induced in mice by delayed-type hypersensitivity to picryl chloride (PCI-DTH). The hepatoprotective agent, biphenyl dimethyl dicarboxylate showed a remarkable improvement against the elevation of serum transaminase levels as well as the histopathological changes when given during the induction phase but not during the effector phase of DTH reaction. Cyclophosphamide (Cy), an immunosuppressive agent, significantly inhibited the enzymatic elevation given in both induction and effector phases. However, Cy did not affect the sustaining of liver injury 4 weeks after the liver injury eliciting. Moreover, the consecutive administration of prednisolone (Pred), in both induction phase and sustaining process of liver injury, conversely caused a more severe liver damage. Such exacerbation by Pred might be resulted from its toxic action to hepatocytes. As an immunomodulatory and antiinflammatory agent, glycyrrhizin remarkably improved the sustaining process but not the acute phase of the liver injury. Krestin and malotilate also showed an improving effect on the sustaining development of liver injury. These findings that most of above drugs showed an improving action in their respective manner suggest that this model may be useful for the pharmacological evaluation of drugs especially immunomodulating agents for hepatitis.

S-(1,2-dichlorovinyl)-L-cysteine-induced nephrotoxicity in the New Zealand white rabbit: characterization of proteinuria and examination of the potential role of oxidative injury

S-(1,2-dichlorovinyl)-L-cysteine (DCVC)-induced nephrotoxicity in vivo was investigated in New Zealand White rabbits. A primary emphasis in these studies was further characterization of DCVC-induced nephrotoxicity using a variety of serum and urinary analytes, including sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Additionally, the role of oxidative injury was assessed to address the dichotomy between reports indicating that such a mechanism is important in vivo and those indicating that such mechanisms do not contribute substantially to the mechanism of effects observed in vitro. Urine was collected prior to and at 8 and 24 hr after iv administration of DCVC. Serum was collected 15 min prior to and 24 hr after DCVC administration. Rabbits were euthanized 24 hr post-DCVC administration, and kidneys were fixed in formalin and further processed for light microscopic examination. DCVC (10 mg/kg, iv) induced a 45-50-fold increase in total urinary protein excretion, a 10-15-fold increase in urinary N-acetyl-beta-D-glucosaminidase concentration, plus a marked glucosuria by 24 hr postadministration. Additionally, DCVC increased serum creatinine levels by about 2-fold, with a trend toward increased blood urea nitrogen. SDS-PAGE analysis of rabbit urine confirmed the clinical finding of marked proteinuria in DCVC-treated animals, which in contrast to previously reported data was due to the presence of both low and high molecular weight proteins. Antioxidants had no significant effect on DCVC-dependent renal injury, nor was there evidence for DCVC-induced lipid peroxidation, as measured by either thiobarbituric acid-reactive substances or a commercial assay for malondialdehyde and hydroxalkenals.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid peroxidation and irreversible damage in the rat hepatocyte model. Protection by the silybin-phospholipid complex IdB 1016

IdB 1016 is a new silybin-phospholipid complex which is more bioavailable than the flavonoid silybin itself and displays free radical scavenging and antioxidant properties in liver microsomes. We report here that the addition of increasing concentrations of IdB 1016 to isolated rat hepatocytes caused a dose-dependent inhibition of lipid peroxidation induced by ADP-Fe3+ or cumene hydroperoxide. Moreover, IdB 1016 at the concentration which completely prevented MDA formation also protected isolated hepatocytes against the toxicity of pro-oxidant agents such as allyl alcohol, cumene hydroperoxide and bromotrichloromethane, without interfering with the activation mechanism of these xenobiotics. Similar protection was also obtained in hepatocytes prepared from animals pretreated in vivo with IdB 1016 while rat supplementation with pure silybin was totally inefficient. These results indicate IdB 1016 as being a potentially useful protective agent against free radical-mediated toxic liver injury.

Protective effect of diosmetin on in vitro cell membrane damage and oxidative stress in cultured rat hepatocytes

Primary cultures of rat hepatocytes were used to study the effects of the flavonoids diosmin and its main metabolite diosmetin on the cell membrane damage caused by erythromycin estolate (EE) and oxidative stress caused by tert-butylhydroperoxide (TBHP). The damage was evaluated by the leakage of intracellular enzymes lactate dehydrogenase, aspartate-aminotransferase and the residual cell content of a lysosomal marker acid phosphatase (AP). After treating the cells for 40 h with diosmetin EE induced less enzyme leakage. The content of AP was kept higher by diosmetin pretreatment after 6 h exposure to EE. Diosmin at the same concentrations had barely any effect. Diosmetin, but not diosmin, also protected against TBHP toxicity and this was related to lower lipid peroxidation and higher glutathione content caused by pretreatment with the flavonoid. When the cells were treated simultaneously with TBHP and diosmetin after 21 h of culture, the protection by the flavonoid was even higher. In fact the antioxidant activity of diosmetin was considerably greater than that of diosmin. After 40 h exposure to both flavonoids diosmin but not diosmetin was detectable in the cell membrane fraction, suggesting that the latter's protective effect is associated with its metabolites.

Nutritional requirements for detoxication of environmental chemicals

The biological defence systems against oxygen radical toxicity and chemical toxicity, and their component enzymes, are described, and the nutritional requirements for biological defence against chemical and oxygen toxicity, including calories, protein, lipids and lipotropes, vitamins and minerals, are reviewed in the context of their contribution to the mechanisms of detoxication. Modulation of the cytochromes P-450, and hence toxicity, by dietary components are considered; the P450I family, induced by food pyrolysis mutagens, and the P450IIE family, induced by alcohol and fasting, contribute substantially to chemical toxicity and carcinogenicity. It is concluded that: (i) the detoxication system of terrestrial fauna has evolved over greater than 300 million years to protect animals from dietary plant toxins; (ii) protection against chemical and oxygen toxicity requires all categories of nutrients; and (iii) the rôle of food and nutrition in detoxication is essential to survival.

Protection from chlordecone-amplified carbon tetrachloride toxicity by cyanidanol: regeneration studies

Previous work has shown that chlordecone (CD)-amplified CCl4 hepatotoxicity and lethality can be mitigated by pretreatment with cyanidanol. These studies also revealed that stimulated hepatocellular regeneration might play an important role in the cyanidanol protection of CD-amplified CCl4 toxicity. The present studies conducted over a time course of 0 to 120 hr after CCl4 challenge describe sequential changes in hepatic [3H]thymidine incorporation into hepatocellular nuclear DNA, polyamines and related enzymes, and histomorphometry of liver sections from variously treated rats. Male Sprague-Dawley rats (125-150 g) were maintained on a control diet or on a diet contaminated with CD (10 ppm) for 15 days and/or pretreated with cyanidanol (250 mg/kg, ip) at 48, 24, and 2 hr before a single ip injection of either a standard protocol dose (100 microliters/kg) or a low dose (50 microliters/kg, L) of CCl4 on Day 16 of the dietary protocol. Cyanidanol pretreatment significantly stimulated the hepatic [3H]thymidine incorporation into hepatocellular nuclear DNA of control rats irrespective of CD pretreatment. Similarly, polyamine metabolism was altered favorably for cell division, although mitotic index (metaphase) was not increased. Cyanidanol-stimulated [3H]thymidine incorporation was highly suppressed in rats receiving the CD + CCl4 standard dose combination treatment up to 36 hr, but after this time point a marked increase was observed. Hepatocellular regeneration, quantified histomorphometrically as volume density of cells in metaphase, was progressively increased in rats protected from CD + CCl4 interaction by cyanidanol, starting at 36 hr and lasting until 72 hr. Favorably altered polyamine metabolism was evident from the stimulated ornithine decarboxylase, as well as from the stimulated interconversion of the higher polyamines to maintain increased concentration of putrescine. Challenge by the same dose of CCl4 (100 microliters/kg) to CD-pretreated rats not protected by cyanidanol failed to cause any increase in [3H]thymidine incorporation up to 36 hr and resulted in animal death starting at 36 hr. In the surviving rats, [3H]thymidine incorporation at 48 hr was increased, but was less than 50% of the increase observed in the cyanidanol group. In these rats, attenuation in the stimulation of cell division and insufficiently increased putrescine levels were observed, which are consistent with the inadequate level of hepatocellular regeneration. With rats receiving CD + CCl4(L) combination, the [3H]thymidine incorporation at 48 hr was less than 50% of the increase of cyanidanol-protected rats. Cyanidanol pretreatment to the CD + CCl4 group of rats prevented the decrease in the hepatic DNA levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Hepatoprotective agent (+)-cyanidanol increases the synthetic phase of hepatocellular regeneration

1. (+)-Cyanidanol (250 mg/kg) administration to male rats resulted in a concentration-dependent increase in [3H]-thymidine incorporation into hepatic nuclear DNA as well as a corresponding increase in the per cent of labelled cells. 2. The increase in [3H]-thymidine incorporation and per cent labelled cells was significant by 24 hr, maximal between 48 and 96 hr, and declined very slowly to normal by 15 days (360 hr). 3. Administration of (+)-cyanidanol resulted in an increase in heptic putrescine levels and ornithine decarboxylase activity at 6 hr but not at 24 hr. However, S-adenosylmethionine decarboxylase and spermidine acetyltransferase activities were unaltered. 4. Inspite of these favorable conditions, for cell division, mitotic index (per cent cells in metaphase) was not increased by (+)-cyanidanol. 5. These results along with previous findings indicate that (+)-cyanidanol stimulates the S-phase activity of hepatocellular regeneration, but the commitment to M-phase depends on the occurrence of liver injury.

Dermal intoxication of mice with bis(2-chloroethyl)sulphide and the protective effect of flavonoids

The influence of dermal application of sulphur mustard (SM) on hepatic lipid peroxidation and the protective effect of flavonoids in SM toxicity was investigated. SM applied on the skin of mice (0.25 or 0.5 LD50) depleted glutathione (GSH) in blood and liver. Malondialdehyde (MDA) levels in the liver showed an increase indicating lipid peroxidation. Administration of vitamin E or two flavonoids, gossypin (GN) and hydroxyethyl rutosides (HR) after dermal application of SM did not alter depletion of GSH but did reduce the MDA level significantly. Survival time of mice with 1 LD50 SM applied dermally was increased by GN and HR to a greater extent than by vitamin E or sodium thiosulphate probably due to one or more of the analgesic, anti-inflammatory, antihepatotoxic, antihistaminic, mast cell stabilization, lipid peroxidation inhibitory and free radical scavenging actions of the flavonoids. The present study indicates that dermally applied SM can induce lipid peroxidation and GSH depletion, and flavonoids may be beneficial in reducing the toxicity.

Cytotoxicity induced by papaverine hydrochloride in fungal cell systems

Cunninghamella echinulata was used to assess the cytotoxicity of papaverine (papaver), at concentrations ranging from 1 x 10(-5) to 1 x 10(-3) M for 1-6 days. Leakage of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT), and changes in alkaline phosphatase (AP) activity and lactate/pyruvate (L/P) ratios were used as indices of cytotoxicity. Leakage of LDH occurred at the 6th day with 1 x 10(-3) M; AP activity and L/P ratios decreased after 6 days treatment with 1 x 10(-4) M, after 1 day with 1 x 10(-3) M, and after 3 days with 1 x 10(-4) M, respectively. This study provides support for the use of fungal cell systems to evaluate the toxicity of drugs and chemicals.

Toxicity assessment of papaverine hydrochloride and papaverine-derived metabolites in primary cultures of rat hepatocytes

The present study was undertaken to assess and compare the toxic effects of papaverine hydrochloride and its metabolites. Primary cell cultures of rat hepatocytes were treated with papaverine (papaver), 3'-O-desmethyl (3'-OH), 4'-O-desmethyl (4'-OH), and 6-O-desmethyl (6-OH) papaverine at 1 x 10(-5), 1 x 10(-4), and 1 x 10(-3) M for 4, 8, 12, and 24-h periods. Cell injury was determined by: a) cell viability using the trypan blue exclusion test; b) cytosolic enzyme leakage of lactate dehydrogenase and aspartate aminotransferase; c) morphologic alterations; and d) lactate:pyruvate (L:P) ratios. Cell cultures showed concentration- and time-dependent toxic responses. For example, a decrease in cell viability and an increase in enzyme leakage were observed after cell treatment with 1 x 10(-4) and 1 x 10(-3) M papaver for 8 h; 1 x 10(-3) M 6-OH papaverine for 8 h and 1 x 10(-4) M for 24 h; and 1 x 10(-3) M 4'-OH papaverine for 24 h (P less than 0.05). Furthermore, changes in morphology correlated to cell viability and enzyme release in those cultures treated with papaver, 4'-OH and 6-OH papaverine. Some of these changes included size deformation, cell detachment from the dishes, and cell necrosis. On the other hand, an increase in L:P ratios (P less than 0.05) was detected with papaver as early as 8 h with 1 x 10(-4) and 1 x 10(-3) M and 12 h with 1 x 10(-5) M; 6-OH showed an increase in L:P ratios at 8 h with 1 x 10(-3) M and 12 h with 1 x 10(-4) M; these changes were evident with with 4'-OH at 12 h with 1 x 10(-3) M. In contrast, cells treated with 3'-OH papaverine did not show significant damage with any time period and concentration used in this study. The results of this study indicate that papaverine-derived metabolites are less cytotoxic than its parent compound, papaver. The toxicity was ranked as follows: papaver greater than 6-OH greater than 4'-OH greater than -3'-OH.