Attenuation of dysfunction in the ischemia-reperfused liver by glycyrrhizin

Review of Constituents and Biological Activities of Triterpene Saponins from Glycyrrhizae Radix et Rhizoma and Its Solubilization Characteristics

Glycyrrhizae Radix et Rhizoma is regarded as one of the most popular and commonly used herbal medicines and has been used in traditional Chinese medicine (TCM) prescriptions for over 2000 years. Pentacyclic triterpene saponins are common secondary metabolites in these plants, which are synthesized via the isoprenoid pathway to produce a hydrophobic triterpenoid aglycone containing a hydrophilic sugar chain. This paper systematically summarizes the chemical structures of triterpene saponins in Glycyrrhizae Radix et Rhizoma and reviews and updates their main biological activities studies. Furthermore, the solubilization characteristics, influences, and mechanisms of Glycyrrhizae Radix et Rhizoma are elaborated. Solubilization of the triterpene saponins from Glycyrrhizae Radix et Rhizoma occurs because they contain the nonpolar sapogenin and water-soluble sidechain. The possible factors affecting the solubilization of Glycyrrhizae Radix et Rhizoma are mainly other crude drugs and the pH of the decoction. Triterpene saponins represented by glycyrrhizin from Glycyrrhizae Radix et Rhizoma characteristically form micelles due to amphiphilicity, which makes solubilization possible. This overview provides guidance regarding a better understanding of GlycyrrhizaeRadix et Rhizoma and its TCM compatibility, alongside a theoretical basis for the further development and utilization of Glycyrrhizae Radix et Rhizoma.

Natural products in licorice for the therapy of liver diseases: Progress and future opportunities

Liver diseases related complications represent a significant source of morbidity and mortality worldwide, creating a substantial economic burden. Oxidative stress, excessive inflammation, and dysregulated energy metabolism significantly contributed to liver diseases. Therefore, discovery of novel therapeutic drugs for the treatment of liver diseases are urgently required. Licorice is one of the most commonly used herbal drugs in Traditional Chinese Medicine for the treatment of liver diseases and drug-induced liver injury (DILI). Various bioactive components have been isolated and identified from the licorice, including glycyrrhizin, glycyrrhetinic acid, liquiritigenin, Isoliquiritigenin, licochalcone A, and glycycoumarin. Emerging evidence suggested that these natural products relieved liver diseases and prevented DILI through multi-targeting therapeutic mechanisms, including anti-steatosis, anti-oxidative stress, anti-inflammation, immunoregulation, anti-fibrosis, anti-cancer, and drug-drug interactions. In the current review, we summarized the recent progress in the research of hepatoprotective and toxic effects of different licorice-derived bioactive ingredients and also highlighted the potency of these compounds as promising therapeutic options for the treatment of liver diseases and DILI. We also outlined the networks of underlying molecular signaling pathways. Further pharmacology and toxicology research will contribute to the development of natural products in licorice and their derivatives as medicines with alluring prospect in the clinical application.

Effects of Preoperative Glycyrrhizin Infusion for the Prevention of Venous Thrombosis on the Tissue Expression of Antithrombin in a Rat Model

OBJECTIVE

Using a thrombus model prepared by ligation of the inferior vena cava (IVC), the influences of the glycoside, glycyrrhizin, on plasma antithrombin levels and antithrombin mRNA expression levels in the liver and IVC with the inhibition of venous thrombosis were investigated.

MATERIALS AND METHODS

The rat IVC was exposed and ligated for 24 h immediately after the intravenous administration of 300 mg/kg glycyrrhizin. Among antithrombotic drugs, the Xa inhibitor, fondaparinux sodium, was used as a control drug.

RESULTS

The mean thrombus weight was significantly smaller in the glycyrrhizin-treated group (18.3 mg) than in the saline-treated group (34.3 mg). In contrast, the inhibition of thrombosis was not observed in the fondaparinux-treated group. Antithrombin mRNA expression levels in the liver were significantly higher in the ligated groups than in the baseline control group. The mean plasma antithrombin level was significantly lower in the glycyrrhizin group (96.6%) than in the saline group (114.4%), but was not significantly different from that in the baseline control group (102.4%).

CONCLUSION

The pretreatment with glycyrrhizin inhibited venous thrombosis, and antithrombin mRNA expression levels in the liver and IVC as well as plasma antithrombin levels were significantly lower than those in the saline group.

Glycyrrhizin ameliorates metabolic syndrome-induced liver damage in experimental rat model

Glycyrrhizin, a major constituent of licorice (Glycyrrhiza glabra) root, has been reported to ameliorate insulin resistance, hyperglycemia, dyslipidemia, and obesity in rats with metabolic syndrome. Liver dysfunction is associated with this syndrome. The objective of this study is to investigate the effect of glycyrrhizin treatment on metabolic syndrome-induced liver damage. After induction of metabolic syndrome in rats by high fructose (60%) diet for 6 weeks, the rats were treated with glycyrrhizin (50 mg/kg body weight, single intra-peritoneal injection). After 2 weeks of treatment, rats were sacrificed to collect blood samples and liver tissues. Compared to normal, elevated activities of serum alanine transaminase, alkaline phosphatase and aspartate transaminase, increased levels of liver advanced glycation end products, reactive oxygen species, lipid peroxidation, protein carbonyl, protein kinase Cα, NADPH oxidase-2, and decreased glutathione cycle components established liver damage and oxidative stress in fructose-fed rats. Activation of nuclear factor κB, mitogen-activated protein kinase pathways as well as signals from mitochondria were found to be involved in liver cell apoptosis. Increased levels of cyclooxygenase-2, tumor necrosis factor, and interleukin-12 proteins suggested hepatic inflammation. Metabolic syndrome caused hepatic DNA damage and poly-ADP ribose polymerase cleavage. Fluorescence-activated cell sorting using annexin V/propidium iodide staining confirmed the apoptotic hepatic cell death. Histology of liver tissue also supported the experimental findings. Treatment with glycyrrhizin reduced oxidative stress, hepatic inflammation, and apoptotic cell death in fructose-fed rats. The results suggest that glycyrrhizin possesses therapeutic potential against hepatocellular damage in metabolic syndrome.

Potential drug interactions associated with glycyrrhizin and glycyrrhetinic acid

Glycyrrhizin (GZ), the main active component of licorice, is a widely used therapeutic in the clinic. Depending on the disease, the treatment may involve a long course of high dose GZ. Another component of licorice, glycyrrhetinic acid (GA), is the main active metabolite of GZ and is thought to be responsible for the majority of the pharmacological properties of GZ. Therefore, GZ and GA are both used for therapeutic purposes. In addition, GZ and GA are also widely used to sweeten and flavor foods. Due to this widespread, multifaceted use of these substances, potential drug interactions with GZ and GA have recently gained attention. Along these lines, this review covers the known effects of GZ and GA on drug-metabolizing enzymes and efflux transporters. We conclude that both GZ and GA may have an effect on the activity of CYPs. For example, GZ may induce CYP3A activity through activation of PXR. Also, GZ and GA may affect glucuronidation in rats and humans. Furthermore, 18β-GA is a potent inhibitor of P-gp, while GZ and GA are inhibitors of MRP1, MRP2 and BCRP. The pharmacokinetics and pharmacodynamics of many medications may be altered when used concurrently with GZ or GA, which is also covered in this review. Overall, GZ, GA or related products should be taken with caution when taken with additional medications due to the possible drug interactions.

Protective effect of the combinations of glycyrrhizic, ferulic and cinnamic acid pretreatment on myocardial ischemia-reperfusion injury in rats

The aim of this study was to find an effective drug cocktail pretreatment to protect myocardial tissue of the heart from ischemia-reperfusion (I/R) injury. The mechanisms underlying the effects of the drug cocktail were subsequently explored in order to expand the application of Dang-gui-si-ni-tang (DGSN), a Traditional Chinese Medicine. The active components of DGSN in the serum following oral administration were investigated using high-performance liquid chromatography. The activity of superoxide dismutase (SOD) and malondialdehyde (MDA) levels were then analyzed to show the effect of the active components in the treatment of myocardial I/R injury. An L16 (4⁴) orthogonal experiment was utilized to determine the most effective cocktail mix and the mechanism underlying the effect of this mix on myocardial I/R injury was investigated. It was observed that FCG, a mixture of glycyrrhizic (50 mg/kg), cinnamic (200 mg/kg) and ferulic (300 mg/kg) acid, was the optimal drug cocktail present in DGSN. This was absorbed into the blood following oral administration and was shown to decrease MDA levels and increase the activity of SOD. In conclusion, the findings suggest that FCG, a combination of active ingredients in the DGSN decoction, can be absorbed into the blood and protect the myocardium from I/R injury.

Application of spray granulation for conversion of mixed phospholipid-bile salt micelles to dry powder form: influence of drug hydrophobicity on nanoparticle reagglomeration

The aim of this study was to investigate the feasibility of using spray granulation as a drying method to convert phospholipid (PL)-sodium deoxycholate (SDC)-mixed micelles (MMs) containing a water-insoluble drug to a solid dosage form and to evaluate how drugs with significantly different physicochemical properties affect the spray granulation process and subsequent in vitro and in vivo processes. Cucurbitacin B (Cu B) and glycyrrhizin (GL) were used as the model drugs. After spray granulation, the dried Cu B-PL/SDC-MM powder was completely redispersible within 15 minutes in vitro. Meanwhile, the area under the curve during 24 hours (AUC_0–24) and peak serum concentration from the dried powder were significantly (P<0.05) lower than the values from Cu B-PL/SDC-MMs in vivo. However, a better result was obtained for GL, ie, the drug was redispersed completely within 5 minutes in vitro. Further, absorption from the dried GL-PL/SDC-MM powder was increased to the same level as that for GL-PL/SDC-MMs in vivo compared with the control group. The difference in these results can be found in Cu B and GL. Cu B nanoparticles reagglomerated when released, resulting in slower redispersibility and less absorption compared with the original PL-SDC-MMs. However, no agglomeration or delay was observed for GL. A possible explanation is the difference in surface hydrophobicity between Cu B and GL. The results of this study not only show that spray granulation is an effective drying technique that can complement spray-drying and freeze-drying, but also confirm that the physicochemical properties of a drug have a significant influence on the in vitro and in vivo performance of the dried powder obtained after spray granulation.

Glycyrrhizin protects spinal cord and reduces inflammation in spinal cord ischemia-reperfusion injury

OBJECTIVE

Inflammation, which is detrimental to the neurologic defect after ischemia-reperfusion, provides a potential target for therapeutic approach for spinal cord ischemia-reperfusion injury. High mobility group box 1 (HMGB-1) was recently discovered to be a crucial cytokine that mediates the response to infection, injury and inflammation. The present study aimed to gain a deep insight into the neuroprotective effect of glycyrrhizin in the process of ischemia and reperfusion injury in spinal cord of mice.

METHODS

Spinal cord ischemia was induced in male C57BL/6 mice by occlusion of the thoracic aorta. The experimental groups (n = 6 per group) included sham operation, control (receiving phosphate buffered saline (PBS)) and glycyrrhizin (10 mg/kg, when cross-clamped). Neurologic function was assessed by the motor function score of the hind limbs at 72 hours after reperfusion. Histologic changes were studied using hematoxylin and eosin staining. Expression changes of inflammatory cytokines or their receptors at messenger RNA level or protein level were determined by real-time transcription polymerase chain reaction or enzyme-linked immunosorbent assay at different time points post reperfusion. Nuclear factor κB (NF-κB) activity was examined with Western blotting.

RESULTS

Compared with the control group, the glycyrrhizin group showed significantly improved neurologic outcome, reduced apoptosis of motoneurons of spinal anterior horn, decreased the activation of NF-κB and subsequent inflammatory cytokines expression [tumor necrosis factor (TNF) and interleukin 1β (IL-1β)], and alleviated neutrophil infiltration in ischemic spinal cord. HMGB-1 treatment also reduced the expressions of itself.

CONCLUSIONS

Treatment with glycyrrhizin exerted a neuroprotective effect against spinal cord ischemia-reperfusion injury. The anti-inflammatory effect was believed to be one of the contributing mechanisms. Our findings provided experimental and therapeutic options for the treatment of spinal cord ischemia-reperfusion injury.

Some Haematological and Biochemical Investigations on Duck Virus Hepatitis following Administration of Glycyrrhizin

The present study aimed to investigate the protective effect of glycyrrhizin (locally isolated and purified from licorice root) against duck hepatitis virus through the assessment of some hematological and biochemical parameters. One hundred and sixty white Pekin ducklings—one day old—were randomly divided into four equal groups. Group (1) was kept as normal control. Group (2) was inoculated I/P with 10 mg glycyrrhizin/kg BW, three times per week for four weeks. Group (3) was inoculated I/M with 0.5 ml of live attenuated DHV vaccine. Group (4) was inoculated with both glycyrrhizin (10 mg/kg BW I/P, three times per week for four weeks) and live attenuated DHV vaccine (0.5 ml, I/M). Then, all groups of treatment were challenged using virulent DHV except for 20 ducklings from the normal control group which were continued to be kept as negative control. The results revealed that duck hepatitis virus (DHV) caused macrocytic hypochromic anemia, leukopenia, hypoproteinemia, hypoalbuminemia, hyperglycemia, hypercholesterolemia, and marked elevation of liver enzymes and renal parameters. In conclusion, glycyrrhizin injected alone or in combination with DHV vaccine protected or ameliorated the deteriorating effects induced by DHV vaccine and/or duck hepatitis virus infection by improvement of erythrogram and leukogram, as well as liver and kidney functions.

Improvement of oral bioavailability of glycyrrhizin by sodium deoxycholate/phospholipid-mixed nanomicelles

Glycyrrhizin (GL), extracted from the Glycyrrhiza glabra L., is active triterpenoid saponin components. However, due to its impermeability across the gastrointestinal mucosa, oral bioavailability of the drug was relatively low. To improve its oral bioavailability, formulation of GL as sodium deoxycholate/phospholipid-mixed nanomicelles (SDC/PL-MMs) has been performed in this study. GL-SDC/PL-MMs were produced by a film dispersion method and then investigated using photon correlation spectroscopy (PCS), zeta potential measurement, as well as its physical stability after storage for 10, 20, 30, 60, 90 and 120 days. To verify the theoretical hypothesis, pharmacokinetics and pharmacodynamic studies based on carbon tetrachloride (CCl(4))-induced acute liver injury was investigated. Results showed that a narrow size distributed nanomicelles with a mean particle size of 82.99 ± 7.5 nm and a zeta potential of -32.23 ± 1.05 mV was obtained. In the pharmacokinetics, GL-SDC/PL-MMs show a significant superiority in AUC(0-t), C(max) and other pharmacokinetic parameters compared with the control group. In the pharmacodynamic studies, compared with the bifendate control group, GL-SDC/PL-MMs showed an equivalent effect in reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST) and improving the pathological changes of liver tissue. These results revealed that SDC/PL-MMs could enhance GL absorption in gastrointestinal tract and pharmacodynamic effect in the treatment of acute liver injury caused by CCl(4), and SDC/PL-MMs might be a good choice for oral delivery of poor bioavailability drug like GL.

Treatment of Chronic Hepatitis due to Hepatitis C Virus (CH-C) in India: A Randomized Controlled Trial Comparing Daily Interferon-alfa-2b and Ribavirin with Daily Interferon-alfa-2b and Glycyrrhizin-A Multicenter Study

BACKGROUND AND AIM

Pegylated-interferon-alfa (PEG-IFN-α) with ribavirin is an established treatment in chronic hepatitis due to hepatitis C virus (HCV) (CH-C). Such treatment is expensive and in resource-poor countries such as India, alternative less expensive therapy is needed.

METHODS

Multicenter randomized controlled trial comparing two treatment regimens (interferon-alfa-2b [IFN-α-2b] 3 million unit/day [MU/day] and ribavirin 1000 mg/day [I+R] vs IFN-α-2b 3 MU/day and glycyrrhizin 250 mg [I+G]) in CH-C. Viral, host characteristics and therapeutic responses were assessed (ICMR-6 months trial for chronic hepatitis-CTRI/2008/091/000105).

RESULTS

One hundred and thirty-one patients meeting the inclusion criteria were randomized to I + G (n=64) or I+R (n=67) during the period February 2002 to May 2005. About 85% (I+G=53, I+R=58) completed 6 months of treatment and 89% of them (I+G=46, I+R=53) completed 6 months of follow-up after completion of treatment. Hepatitis C virus genotype 3 was the major type detected (71% patients). The mean log10 viral load (copies/mL), histological activity index, and fibrosis stage for all patients were 5.1 ± 0.98, 5 ± 2, and 2± 1.5, respectively. Sustained viral response (SVR) was significantly higher in I + R group than in I + G group (65.7% vs 46.9%, OR=2.2, P = 0.03). Treatment with I + G was associated with significantly lower frequencies of leukopenia (2% vs 17%, P <0.01) and anemia (8% vs 40%, P <0.001) as compared to treatment with I + R.

CONCLUSION

Genotype 3 HCV infection with low viral load is prevalent in India. Daily IFN with ribavirin showed significantly better responses. Leukopenia and anemia were significantly more in ribavirin group. Responses observed with IFN + ribavirin were similar to the reported response rates with PEG-IFN suggesting that this modality may be considered as a cheaper alternative of treatment for chronic hepatitis C.

The use of Stronger Neo-Minophagen C, a glycyrrhizin-containing preparation, in robust neuroprotection in the postischemic brain

Stronger Neo-Minophagen C (SNMC) is a glycyrrhizin-containing preparation that is approved in Japan for the treatment of chronic hepatic diseases and is marketed in Japan, China, Korea, Taiwan, and India. Glycyrrhizin, a triterpene present in the roots and rhizomes of licorice (Glycyrrhiza glabra) has been shown to have anti-inflammatory, anti-oxidative, and anti-viral effects. In the present study, we demonstrated the marked neuroprotective effects of SNMC in the postischemic rat brain after middle cerebral artery occlusion (MCAO). We used 1 ml/kg of SNMC, which is within the dose range used for the treatment of patients with chronic hepatic disease. The administration of SNMC intravenously at 30 minutes before or 30 minutes and 3 hours after MCAO (60 minutes) reduces mean infarct volumes to 27.0±4.2%, 37.1±12.4%, and 67.8±5.8% of that of untreated controls, respectively. This neuroprotective effect is accompanied by improvements in motor impairment and neurological deficits. The administration of SNMC is shown to suppress microglia activation and neutrophil infiltration in the postischemic brain. In addition, SNMC suppresses lipopolysaccharide-induced nitrite production and proinflammatory cytokine induction in a microglia cell line, BV2. This indicates that the neuroprotective effect of SNMC might be due, at least in part, to an anti-inflammatiory effect. Interestingly, SNMC shows significantly higher neuroprotective potency compared to an equivalent dose of pure glycyrrhizin, in terms of reducing infarct volume and improving neurological deficits. Together these results indicate that SNMC, a glycyrrhizin-containing preparation developed for chronic liver disease, has a marked neuroprotective function in the postischemic brain via its anti-inflammatory effects.

Glycyrrhizin prevents liver injury by inhibition of high-mobility group box 1 production by Kupffer cells after ischemia-reperfusion in rats

High-mobility group box 1 (HMGB1) acts as an early mediator of inflammation and organ damage in hepatic ischemia-reperfusion (I/R) injury. Glycyrrhizin is a natural anti-inflammatory and antiviral triterpene in clinical use. The purpose of this study was to investigate the effect of glycyrrhizin on liver injury caused by I/R and production of HMGB1 by Kupffer cells in rats. In the first test period, rats were given saline or glycyrrhizin 20 min before segmental hepatic warm I/R. Serum alanine aminotransferase and HMGB1 levels and hepatic histopathological findings were evaluated after I/R. Furthermore, expression of HMGB1 in the liver was assessed by immunohistochemical staining after I/R. Kupffer cells were isolated by collagenase digestion and differential centrifugation, and production of HMGB1 was assessed. In another set of experiments, the effect of inhibition of Kupffer cells by injection of liposome-entrapped dichloromethylene diphosphonate (lipo-MDP) on liver injury and expression of HMGB1 were investigated after I/R. Liver injury was prevented in the glycyrrhizin group compared with the control group. Furthermore, serum HMGB1 levels were also significantly blunted in the glycyrrhizin group compared with the control group. Cells expressing HMGB1 were detected in the hepatic sinusoid by immunohistochemistry and recognized morphologically as Kupffer cells. Furthermore, the expression of HMGB1 was reduced in the glycyrrhizin group compared with the control group. Production of HMGB1 was reduced in Kupffer cells isolated from the glycyrrhizin group compared with the control group. It is noteworthy that treatment with lipo-MDP significantly blunted serum HMGB1 levels and prevented liver injury after I/R. These results suggest that glycyrrhizin has the therapeutic potential to prevent warm I/R-induced injury during hepato-biliary surgery.

Effect of necrosis modulator necrox-7 on hepatic ischemia-reperfusion injury in beagle dogs

OBJECTIVE

The liver is susceptible to ischemia-reperfusion (IR) injury during inflow occlusion for hepatectomy. There is no effective pharmacologic agent available to prevent the release of high-mobility-group box 1 (HMGB1) or to ameliorate IR injury. This pilot study sought to develop a model in beagle dogs for the purpose of testing the efficacy of a necrosis modulator, necrox-7, to prevent hepatic IR injury in beagle dogs.

METHODS

Six male beagle dogs were randomly assigned to the control group (group A; n = 3) or the treatment group (group B; n = 3). Under general anesthesia, group B received intravenous infusion of necrox-7 (13 mg/kg over 20 minutes) followed by 60 minutes of left hepatic inflow occlusion and 60 minutes of reperfusion. Both groups were tested for serum biochemicals, hematology values, liver biopsies, and plasma HMGB1 levels over a 48-hour period.

RESULTS

The maximum alanine transferase (ALT), aspartate transferase (AST), and lactate dehydrogenase (LDH) levels among group A versus group B were: ALT 868.3 ± 337.4 IU/L vs 274.3 ± 72.6 IU/L (P = .041); AST 1,024.7 ± 246.5 IU/L vs 505.3 ± 66.7 IU/L (P = .024); and LDH 962.7 ± 226.2 IU/L vs 552.7 ± 62.4 IU/L (P = .039). Liver biopsy demonstrated marked necrosis and inflammatory infiltrates in group A, whereas group B showed little evidence of IR injury. The plasma HMGB1 concentration was significantly lower among group B versus A.

CONCLUSION

This pilot study developed a hepatic IR injury model, demonstrating that necrox-7 reduced hepatic necrosis secondary to IR injury in a large animal setting.

Hepatoprotective and antioxidant effects of Glycyrrhiza glabra extract against carbon tetrachloride (CCl(4))-induced hepatocyte damage in common carp (Cyprinus carpio)

The present study is aiming at evaluating the hepatoprotective and antioxidant effects of Glycyrrhiza glabra extract (2.5, 5 and 10 μg/ml) on the carbon tetrachloride (CCl(4))-induced carp hepatocyte damage in vitro. Glycyrrhiza glabra extract was added to the carp primary hepatocytes before (pre-treatment), after (post-treatment) and both before and after (pre- and post-treatment) the incubation of the hepatocytes with CCl(4). CCl(4) at 8 mM in the culture medium produced significantly elevated levels of lactate dehydrogenase (LDH), glutamate oxalate transaminase (GOT), glutamate pyruvate transaminase (GPT) and malondialdehyde (MDA) and significantly reduced levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Pre-treatment (5 μg/ml) and pre- and post-treatment (5 and 10 μg/ml) of the hepatocytes with Glycyrrhiza glabra extract significantly reduced the elevated levels of LDH, GOT, GPT and MDA and increased the reduced levels of SOD and GSH-Px by CCl(4); post-treatment of the hepatocytes with Glycyrrhiza glabra extract at 5 μg/ml reduced the GPT and GOT levels and increased the GSH-Px level, but had no effect on the other parameters at all the studied concentrations. The results support the use of Glycyrrhiza glabra extract as a hepatoprotective and antioxidant agent in fish.

Prevention of venous thrombosis by preoperative glycyrrhizin infusion in a rat model

BACKGROUND

Glycyrrhizin is an agent with the capacity to bind to selectin molecules expressed on vascular endothelial cells and potentially prevent the adherence of neutrophils to the vascular endothelial surface. It has been found to prevent intravenous thrombus formation.

METHODS

Venous thrombosis was induced in male rats by ligation of the inferior vena cava (IVC) for 6 h. Before the ligation, the study rats were given intravenous injections of glycyrrhizin through the IVC. After 6 h of venous ligation, the rats were sacrificed and the IVC segments were harvested. Thrombus within the IVC was collected to measure the wet weight. Gene expression of P-, L-, and E-selectin was detected by reverse transcriptase polymerase chain reaction using extracts of mRNA from the IVC vein wall. As baseline controls, IVC samples without ligation were harvested immediately after laparotomy. Neutrophil adhesion to the luminal surface of IVC was assessed on histological sections stained with hematoxylin and eosin. Blood samples were collected through the IVC proximal to the ligation after 6 h to estimate activated partial thromboplastin time (APTT) and prothrombin time (PT). To investigate the effect of glycyrrhizin on binding capacity of P-selectin to human neutrophils, real-time biospecific interaction analysis was performed with the Biacore 2000 system.

RESULTS

The mean weight of thrombus in the glycyrrhizintreated group was 12.9 +/- 11.1 mg, which is significantly lower than that of the saline-treated control group (21.3 +/- 12.5 mg). The expression level of P-and L-selectin mRNA in both saline-and glycyrrhizin-treated groups was significantly higher than that of the baseline control. Histological studies of cross sections of IVC showed significantly fewer neutrophils adhering to the luminal surface with glycyrrhizin treatment than in the saline-treated controls. There was no significant difference in the values of coagulation parameters with or without glycyrrhizin treatment. In vitro analysis showed that glycyrrhizin caused a dose-dependent reduction of neutrophils binding to immobilized recombinant P-selectin.

CONCLUSIONS

Preoperative treatment with glycyrrhizin is potentially useful for preventing venous thrombosis by suppressing the adherence of neutrophils to the venous endothelium during the initial phase of thrombus formation without reducing coagulation capacity and the subsequent risk for increased bleeding.

Use of glycyrrhizin in prevention of tissue damage caused by ischemia-reperfusion in rabbit hind limbs

BACKGROUND

Glycyrrhizin, an agent that can bind to selectins and inhibit their ability to bind neutrophils, was found to be effective in preventing tissue edema caused by ischemia-reperfusion in a rabbit model.

METHODS

Complete ischemia was produced by applying a tight Esmarch tourniquet to the hind limbs of 24 Japanese white rabbits. Immediately before and 1 h after release of the tourniquet, 12 animals were given glycyrrhizin intravenously; 12 controls received saline.

RESULTS

The mean relative increase in the circumference of the shins before and after ischemia-reperfusion with or without glycyrrhizin treatment was 4.6% +/- 2.4% and 9.6% +/- 4.2%, respectively, indicating that tissue edema caused by the ischemia-reperfusion was significantly attenuated by glycyrrhizin. Histological studies of cross sections of the anterior tibial muscle 24 h after reperfusion showed a significant reduction in the incidence of necrotic muscle fibers in the glycyrrhizin-treated animals compared with the controls that did not receive glycyrrhizin. The mRNA levels of P- and E-selectin 24 h after reperfusion were significantly higher in the ischemic anterior tibial muscle than in the nonischemic normal muscle. After 24 h of reperfusion, the mean activity of myeloperoxidase, a neutrophil-specific enzyme, in the anterior tibial muscles of the group given glycyrrhizin (0.0022 +/- 0.0013 absorbance units) was lower than that of the untreated group (0.027 +/- 0.026 absorbance units).

CONCLUSIONS

These data suggest that glycyrrhizin treatment is effective in suppressing the acute inflammatory reaction or edema following ischemia-reperfusion and might be potentially useful in clinical practice for preventing ischemia-reperfusion injuries to the extremities.

The contemporary role of antioxidant therapy in attenuating liver ischemia-reperfusion injury: a review

Oxidative stress is an important factor in many pathological conditions such as inflammation, cancer, ageing and organ response to ischemia-reperfusion. Humans have developed a complex antioxidant system to eliminate or attenuate oxidative stress. Liver ischemia-reperfusion injury occurs in a number of clinical settings, including liver surgery, transplantation, and hemorrhagic shock with subsequent fluid resuscitation, leading to significant morbidity and mortality. It is characterized by significant oxidative stress but accompanied with depletion of endogenous antioxidants. This review has 2 aims: firstly, to highlight the clinical significance of liver ischemia-reperfusion injury, the underlying mechanisms and the main pathways by which the antioxidants function, and secondly, to describe the new developments that are ongoing in antioxidant therapy and to present the experimental and clinical evidence about the role of antioxidants in modulating hepatic ischemia-reperfusion injury.

Profound difference of metabolic pharmacokinetics between pure glycyrrhizin and glycyrrhizin in licorice decoction

To investigate the difference of metabolic pharmacokinetics between pure glycyrrhizin (GZ) and GZ in licorice decoction, six New Zealand White rabbits were orally given pure GZ and licorice decoction containing equivalent content of GZ in a randomized crossover design. HPLC methods were used for the quantitation of GZ and glycyrrhetic acid (GA) in serum. The results indicated that the areas under curves (AUCs) of GZ and GA after administration of licorice decoction were significantly higher than those after pure GZ. This result was contradictory with that obtained in rats. To explore the mechanism of the pharmacokinetic difference, feces of rabbits, rats, pigs and humans were used to investigate the presystemic metabolism of pure GZ and GZ in licorice decoction. The results indicated that pure GZ was hydrolyzed to GA more rapidly and to a greater extent than that in licorice decoction by various feces. In addition, when pure GZ was fermented, the metabolic profiles of GA and 3-dehydroGA in rabbit feces were quite different from other feces. In conclusion, the bioavailabilities of GZ and GA are significantly better from licorice than from pure GZ in rabbits but the presystemic metabolism of pure GZ in rabbit is rather different from that in rat, pig and human.

Influence of honey on the gastrointestinal metabolism and disposition of glycyrrhizin and glycyrrhetic acid in rabbits

To investigate the effects of honey on the pharmacokinetics of glycyrrhizin and glycyrrhetic acid, administration of glycyrrhizin or glycyrrhetic acid with and without honey was carried out in rabbits in a randomized crossover design. An in vitro study using rabbit fecal flora was employed to elucidate the mechanism of the interaction. HPLC methods were used for the determination of glycyrrhizin, glycyrrhetic acid and 3-dehydroglycyrrhetic acid concentrations in serum and feces. Paired and unpaired Student's t-tests were used for statistical comparisons for in vivo and in vitro studies, respectively. Our study indicated that the area under the curve (AUC0-t) of glycyrrhetic acid was significantly enhanced by 53% when honey was concomitantly given with glycyrrhizin, whereas that of glycyrrhizin was not significantly altered. Nevertheless, lack of effect was observed when honey was concurrently given with glycyrrhetic acid. Fecal study indicated that both the hydrolysis of glycyrrhizin to glycyrrhetic acid and subsequent oxidation of glycyrrhetic acid to 3-dehydroglycyrrhetic acid were significantly affected in the presence of honey to result in more glycyrrhetic acid available for absorption. It could be concluded that honey significantly affected the gastrointestinal metabolism of glycyrrhizin and resulted in the increased glycyrrhetic acid exposure. Therefore, honey might enhance the efficacy and adverse effects of glycyrrhizin.

Efficient method for determining the glycyrrhizin content of fresh and dried roots, and root extracts, of Glycyrrhiza species

A reliable and efficient method suitable for the selective analysis of the glycyrrhizin content of fresh and dried roots of Glycyrrhiza species and of root extracts is described. The method was optimised for recovery and analysis of glycyrrhizin after conversion to its aglycone, 18 beta-glycyrrhetinic acid. The reversed-phase HPLC system was developed using a sterically protected C8 column that allowed UV detection of the aglycone at 254 mm without interference from co-occurring components. The average recovery through the method was determined at 83%, with a range of 65-99%. Analysis of 150 dried root samples gave levels of glycyrrhizin consistent with earlier reported values. A comparison of post-harvest treatment conditions. showed that the drying of root samples at up to 65 degrees C did not result in any measurable reduction in glycyrrhizin.

Glycyrrhizin-induced reduction of ALT in European patients with chronic hepatitis C

OBJECTIVE

In Japan, ALT normalization induced by long-term i.v. glycyrrhizin treatment reportedly reduces the progression of liver disease to hepatocellular carcinoma in chronic hepatitis C patients. The aim of this study was to evaluate the short-term (4-wk) feasibility and efficacy on serum ALT of three or six times per week i.v. glycyrrhizin therapy in European patients.

METHODS

Patients with chronic hepatitis C, nonresponders, or unlikely to respond (genotype 1/cirrhosis) to interferon therapy were included in this study. Medication was administered i.v. three or six times per week for 4 wk; follow-up also lasted 4 wk.

RESULTS

Sixty-nine out of 72 treatment courses were completed according to protocol. There were no significant changes in ALT levels within the placebo group (n = 13). The mean percentage ALT decrease from baseline at the end of treatment was 26% and 47% for the three times per week and six times per week treatment group, respectively (both p < 0.001 vs placebo). At the end of active treatment, 10% (four of 41) and 20% (three of 15) of the patients reached normal ALT levels for the three times per week and six times per week treatment group, respectively. The ALT lowering effect disappeared after cessation of treatment. No major side effects were observed.

CONCLUSION

It appeared feasible to treat European outpatients with chronic hepatitis C three or six times per week with i.v. glycyrrhizin. Glycyrrhizin treatment induces a significant ALT decrease in patients with chronic hepatitis C. Six times per week treatment appears more effective than three times per week.

Determination of glycyrrhizic acid and 18-beta-glycyrrhetinic acid in biological fluids by micellar electrokinetic chromatography

A micellar electrokinetic chromatographic technique for determining acid (GZA) and 18 beta-glycyrrhetinic acid (GRA) in human plasma and urine was developed. Sample clean-up and analyte concentration were carried out by solid-phase extraction (with C18 sorbent). The buffer solution used for MEKC contained 20 mM sodium dihydrogenphosphate, 20 mM sodium tetraborate, 20 mM tetrabutylammonium bromide and 50 mM sodium dodecylsulphate, at a pH of 8.7. Good linearities for both GZA and GRA in plasma and urine were obtained. The recoveries of the method were in the range 86.5 to 107%. The detection limits for GZA in urine (0.5 ml) and plasma (1 ml) were 1.6 micrograms ml-1 and 0.8 micrograms ml-1, respectively, while for GRA in urine (0.5 ml) and plasma (1 ml) were 2 micrograms ml-1 and 1 micrograms ml-1, respectively.

Review article: glycyrrhizin as a potential treatment for chronic hepatitis C

Chronic hepatitis C is a slowly progressive liver disease that may evolve into cirrhosis with its potential complications of liver failure or hepatocellular carcinoma. Current therapy with alpha-interferon is directed at viral clearance, but sustained response is only achieved in 20-40% of patients without cirrhosis, and less than 20% in patients with cirrhosis who have the greatest need for therapy. Treatment for those who do not respond to anti-viral therapy is highly desirable. In Japan glycyrrhizin has been used for more than 20 years as treatment for chronic hepatitis. In randomized controlled trials, glycyrrhizin induced a significant reduction of serum aminotransferases and an improvement in liver histology compared to placebo. Recently, these short-term effects have been amplified by a well-conducted retrospective study suggesting that long-term usage of glycyrrhizin prevents development of hepatocellular carcinoma in chronic hepatitis C. The mechanism by which glycyrrhizin improves liver biochemistry and histology are undefined. Metabolism, pharmacokinetics, side-effects, and anti-viral and hepatoprotective effects of glycyrrhizin are discussed.

Analysis and pharmacokinetics of glycyrrhizic acid and glycyrrhetinic acid in humans and experimental animals

Glycyrrhizic acid (GZA) and glycyrrhetinic acid (GRA) can be determined rapidly and precisely by high-performance liquid chromatography (HPLC) in biological fluids and tissues from experimental animals and humans. From plasma and tissues, GZA and GRA are extracted by organic solvents and the extracts can directly be used for HPLC. From bile or urine, extraction and determination of GZA and GRA are more difficult due to interfering endogenous compounds and conjugation of GRA with glucuronides or sulfates. Extraction of GZA and GRA from urine or bile can be performed by ion-pairing followed by extraction with organic solvents or by solid phase extraction. GRA conjugates can be determined by chromatographic separation or by pretreatment with beta-glucuronidase. The pharmacokinetics of GRA and GZA can be described by a biphasic elimination from the central compartment with a dose-dependent second elimination phase. Depending on the dose, the second elimination phase in humans has a half-life of 3.5 hours for GZA and between 10-30 hours for GRA. The major part of both GRA or GZA is eliminated by the bile. While GZA can be eliminated unmetabolized and undergoes enterohepatic cycling, GRA is conjugated to GRA glucuronide or sulfate prior to biliary excretion. Orally administered GZA is almost completely hydrolyzed by intestinal bacteria and reaches the systemic circulation as GRA.

Determination of 18 beta-glycyrrhetinic acid in biological fluids from humans and rats by solid-phase extraction and high-performance liquid chromatography

Methods have been developed and characterized allowing rapid isolation and quantification of 18 beta-glycyrrhetinic acid (GRA) in biological fluids from both humans and rats. Sample preparation includes extraction with urea-methanol for plasma samples, and solid-phase extraction (SPE) for urine and bile samples. Hydrolysis of GRA glucuronides in urine and bile was performed by treatment with beta-glucuronidase. MGRA, the 3-O-methyl derivative of GRA was synthesized as an internal standard resistant to hydrolysis. High-performance liquid chromatography (HPLC) was performed with an isocratic system using methanol-water-acetic acid (83:16.8:0.2, v/v/v) as solvent on a Lichrocart RP-18 column at 30 degrees C with ultraviolet detection. The methods allowed base line separation of GRA and MGRA from all biological fluids tested, with a detection limit of 0.15 mg/l. Validation of the methods included determination of recovery, accuracy and precision in plasma, bile and urine from humans and rats. The methods were further evaluated by investigating the pharmacokinetics of GRA in normal rats and in rats with a bile fistula. Following an intravenous dose of 10 mg/kg, the plasma concentration-time curve of GRA could be fitted to a one compartment model both in control and bile fistula rats. The elimination half life averaged 15.0 +/- 2.2 versus 16.8 +/- 2.4 min in control and bile fistula rats (difference not significant). Within 90 min following administration of GRA, urinary elimination of GRA and GRA glucuronides was less than 1% in both groups whereas biliary elimination averaged 51.3 +/- 3.1%. The results show that the methods developed allow pharmacokinetic studies of GRA in humans and rats.

Investigation of the renal injury caused by liver ischemia-reperfusion in rats

To explain the mechanism of renal injury caused by liver ischemia-reperfusion, we investigated biochemical and morphological changes in the liver and kidney in rats. After reperfusion following 60 min of liver ischemia, numerous changes were found. The level of serum transaminases and lipid peroxide formation in the liver tissue increased significantly. Electron microscopic studies revealed that most of the hepatocytes had swollen mitochondria and clumping of the nuclear chromatin. The sinusoidal endothelium was disrupted and the sinusoidal lumen was filled with numerous erythrocytes. Blood endotoxin concentration, plasma lipid peroxide levels, and serum beta-glucuronidase activities were significantly higher than in the control group. Biochemical and morphological renal injury was also observed. Tissue lipid peroxide levels increased in both the kidney and the liver. Microscopic examination revealed damage to the renal tubules, including interstitial edema, dilatation of the lumen, and granular casts derived from necrotic cells in the proximal convoluted tubule. The levels of urinary N-acetyl-beta-D-glucosaminidase (NAG) in the liver ischemia-reperfusion group were also higher than in the control group. These results suggest that the renal injury was caused by an increase in endotoxin, lipid peroxide, and lysosomal enzymes in the blood following the liver injury induced by the ischemia-reperfusion.