Glycyrrhizin Suppresses RANKL-Induced Osteoclastogenesis and Oxidative Stress Through Inhibiting NF-κB and MAPK and Activating AMPK/Nrf2

The treatment for osteoporosis involves inhibiting bone resorption and osteoclastogenesis. Glycyrrhizin (GLY) is a triterpenoid saponin glycoside known to be as the most medically efficacious component of the licorice plant. It has strong anti-inflammatory, antioxidant, and antitumor properties. We investigated the effect of GLY on osteoclastogenesis, bone resorption, and intracellular oxidative stress and its molecular mechanisms. In vitro osteoclastogenesis assays were performed using bone marrow monocytes with and without glycyrrhizin. We also evaluated the effects of glycyrrhizin on the secretion of TNF-α, IL-1β, and IL-6 in LPS-stimulated RAW 264.7 cells using ELISA. The effects of glycyrrhizin on the expression of osteoclast-related genes, such as Nfatc1, c-fos, Trap, and cathepsin K (CK), were investigated by RT-PCR. Intracellular reactive oxygen species (ROS) were detected in receptor activator of nuclear factor kappa-Β ligand (RANKL)-stimulated osteoclasts in the presence and absence of glycyrrhizin. During the inhibition of osteoclastogenesis by glycyrrhizin, phosphorylation of AMPK, Nrf2, NF-κB, and MAPK was analyzed using western blotting. Our results showed that glycyrrhizin significantly inhibited RANKL-induced osteoclastogenesis, downregulated the expression of NFATc1, c-fos, TRAP, CK, DC-STAMP, and OSCAR, and inhibited p65, p38, and JNK. Glycyrrhizin was found to significantly decrease the secretion of inflammatory cytokines (TNF-α, IL-1β, and IL-6). Additionally, glycyrrhizin reduced the formation of ROS in osteoclasts by inducing AMPK phosphorylation and nuclear transfer of NRF2, resulting in an upregulation of antioxidant enzymes, such as HO-1, NQO-1, and GCLC. In summary, we found that glycyrrhizin inhibited RANKL-induced osteoclastogenesis. It was also indicated that glycyrrhizin could reduce oxidative stress by inhibiting the MAPK and NF-κB pathways and activating the AMPK/NRF2 signaling. Therefore, glycyrrhizin may be used as an effective therapeutic agent against osteoporosis and bone resorption.

Elicitation Enhanced the Yield of Glycyrrhizin and Antioxidant Activities in Hairy Root Cultures of Glycyrrhiza glabra L

Glycyrrhiza glabra L. has become an endangered medicinal plant due to the unabated extraction of glycyrrhizin. Glycyrrhizin is a triterpenoid saponin that is a root centric secondary metabolite having numerous pharmacological properties, such as anti-inflammatory, immunomodulatory, antiallergic, antiulcer, and is found to be effective even against HIV. Harvesting of the roots for high value glycyrrhizin destroys the whole plant causing existential threat to the plant itself and consequent damage to biodiversity. The present study establishes that hairy root cultures of G. glabra, using an optimized elicitor, can dramatically enhance focused production of glycyrrhizin at a much faster pace year-round without causing destruction of the plant. Hairy root cultures of G. glabra were developed using the Agrobacterium rhizogenes A4 strain. The glycyrrhizin content was enhanced using different biotic and abiotic elicitors, for example, PEG (polyethylene glycol), CdCl₂, cellulase, and mannan at different concentrations and durations. PEG at 1% concentration enhanced the yield of glycyrrhizin up to 5.4-fold after 24 h of exposure, whereas 200 µg mL^-1 cellulase enhanced glycyrrhizin yield to 8.6-fold after 7 days of treatment. Mannan at 10 mg L^-1 concentration enhanced the production of glycyrrhizin up to 7.8-fold after 10 days of stress. Among different antioxidant enzymes, SOD activity was significantly enhanced under drought, cellulase and mannan stress. This identification of elicitors can result in abundant supply of valuable glycyrrhizin to meet broad spectrum demand through commercial production without endangering G. glabra L.

Prevention of alcohol-induced DNA damage by a proprietary glycyrrhizin/D-mannitol product: A randomized, placebo-controlled, cross-over human study

OBJECTIVES

The purpose of the present study was to evaluate the ability of a proprietary combination of glycyrrhizin and D-mannitol to protect against oxidative damage to DNA associated with acute alcohol consumption by human subjects in a randomized, placebo-controlled cross-over designed study. Excessive alcohol consumption is associated with numerous diseases. Alcohol has been shown to generate reactive oxygen species that can result in DNA damage, leading to genetic and epigenetic changes.

METHODS

A total of 25 subjects (13 male and 12 female) were enrolled. Alcohol intake in the form of vodka (40% ethanol) was adjusted based on 1.275 g of 100% ethanol/kg body weight for men and 1.020 g/kg body weight for women, which was consumed with and without the study product. Blood samples were drawn at 2 h after alcohol consumption, lymphocytes were isolated, and were subjected to DNA comet electrophoresis on a blinded basis.

RESULTS

Acute alcohol consumption increased lymphocyte DNA damage by approximately 8.36%. Co-consumption of the glycyrrhizin/D-mannitol study product with alcohol reduced DNA damage to baseline levels. No adverse effects were associated with use of the study product, and no differences were observed in blood alcohol concentrations in the presence or absence of the study product in males and females.

CONCLUSIONS

Acute alcohol ingestion resulted in measurable increases in DNA damage, which were prevented by the addition of the proprietary glycyrrhizin/D-mannitol (NTX^®) study product to the alcohol, suggesting that the tissue-damaging effects of alcohol consumption can be ameliorated.

Glycyrrhizin ameliorates atopic dermatitis-like symptoms through inhibition of HMGB1

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease prevalent worldwide. This study investigated the effects of glycyrrhizin, an extract of licorice root, on the well-established model of 2,4-dinitrochlorobenzene-induced AD-like symptoms in mice. The severity of dermatitis, histopathological changes, serum IgE levels, changes in expression of high-mobility group box 1 (HMGB1), the receptor for advanced glycation end products (RAGE), nuclear factor (NF)-κB and inflammatory cytokines were evaluated. Treatment with glycyrrhizin inhibited the HMGB1 signaling cascade and ameliorated the symptoms of AD. Furthermore, in an in vitro study, the expression of RAGE was detected in a mouse mast cell line, P815 cells, and rmHMGB1 was found to be a potent inducer of mast cell activation by increasing Ca²⁺ influx, upregulating the CD117 and activating NF-κB signaling; these effects were also inhibited by glycyrrhizin. These findings implicate HMGB1 in the pathogenesis of AD and suggest that GL could be an effective therapeutic approach for cutaneous inflammation.

Derivatization, molecular docking and in vitro acetylcholinesterase inhibitory activity of glycyrrhizin as a selective anti-Alzheimer agent

Acetylcholinesterase inhibitors (AChE-Is) increase both level and duration of action of acetylcholine (ACh); thus, alleviate symptoms of Alzheimer's disease (AD). Glycyrrhizin, is the main active compound in liquorice root. Its aglycone, glycyrrhetinic acid, has shown several beneficial pharmacological activities. This study reports the synthesis and screening of a series of glycyrrhetinic acid analogs as AChE-Is. Fourteen derivatives were prepared, of which five derivatives are recorded as new viz., 3-phenyl-carbamoyl-18β-glycyrrhetinic acid (J9), 3-acetyl-18β-glycyrrhetinic-30-anilinamide (J10), 3-acetyl-18β-glycyrrhetinic-30-ethanolamide (J11), 3-acetyl-18β-glycyrrhetinic-30-n-butylamide (J12) and 18β-glycyrrhetinic acid-30-prenyl ester (J14), in addition to nine known derivatives (J1-J8 & J13). Compounds J12, J11, J0 and J3 showed remarkable AChE-I activity with IC₅₀ values of 3.43, 5.39, 6.27 and 8.68 μM, respectively. These results are in full agreement with the docking study. The active compounds were non-cytotoxic to normal cells (WI-38).

Glycyrrhizin attenuates histamine-mediated MUC5AC upregulation, inflammatory cytokine production, and aquaporin 5 downregulation through suppressing the NF-κB pathway in human nasal epithelial cells

Allergic rhinitis (AR) is a chronic respiratory inflammatory disease. Glycyrrhizin is a main bioactive component of the licorice root extract and exhibits anti-inflammatory activity. However, the role of glycyrrhizin in AR has not been studied. The aim of the present study was to investigate the effect of glycyrrhizin on histamine-induced human nasal epithelial cells (HNEpCs). Here, we found that glycyrrhizin (20 or 40 μM) inhibited histamine-induced the mRNA expression and secretion of mucin 5 subtype AC (MUC5AC), interleukin (IL)-6 and IL-8 in HNEpCs. The expression levels of aquaporin 5 (AQP5) and phosphorylated cyclic adenosine monophosphate-responsive element binding protein (p-CREB) were decreased by histamine in HNEpCs and increased in cells treated with glycyrrhizin. The glycyrrhizin treatment inhibited histamine-induced expressions of p-NF-κB p65 and p-IκBα in HNEpCs, indicating that glycyrrhizin inhibited the activation of NF-κB pathway in histamine-induced HNEpCs. In addition, inhibition of the NF-κB pathway exhibited the similar effect with glycyrrhizin on histamine-induced HNEpCs. In summary, the results showed that glycyrrhizin reversed the effect of histamine on MUC5AC expression, inflammatory cytokine production, and AQP5 expression in HNEpCs, and the NF-κB pathway was involved in the effect. Glycyrrhizin might be used for complementary and alternative therapeutics of AR.

Inhibition of HMGB1 mediates neuroprotection of traumatic brain injury by modulating the microglia/macrophage polarization

Microglia/Macrophages have a double-edged role in secondary brain damage after traumatic brain injury (TBI) depending on polarization toward proinflammatory M1 or anti-inflammatory M2 phenotypes. Recently, high-mobility group box 1 (HMGB1) was found to influence the polarization of macrophages. In this study, glycyrrhizin (GL), an inhibitor of HMGB1, was used to investigate whether the inhibition of HMGB1 could modulate microglia/macrophage polarization after TBI. The results showed that treatment with GL improved the neurological function recovery, reduced the lesion volume, and inhibited the release and expression of HMGB1 after TBI. In addition, the administration of GL suppressed M1 phenotype activation and promoted M2 phenotype activation of microglia/macrophages. In conclusion, the results suggested that GL attenuated TBI by inhibiting M1 phenotype while inducing M2 phenotype activation of microglia/macrophages, at least partly through inhibiting HMGB1. Also, targeting HMGB1 to modulate the microglia/macrophage polarization should be one potential therapeutic approach for TBI.

Evaluation of the hepatoprotective effect of combination between hinokiflavone and Glycyrrhizin against CCl4 induced toxicity in rats

Liver diseases are one of the fatal syndromes due to the vital role of the liver. Most of the effective treatment of liver conditions are of natural origin. Silymarin (SI) is the standard drug used for treatment of impaired liver functions. Two natural compounds possessing promising liver protection and with different chemical structures namely; the bioflavonoid hinokiflavone (HF) isolated from Junipers phoenicea family Cupressaceae and the sweet saponin Glycyrrhizin (GL) present in Glycyrrhiza glabra (liquorice) were selected for the current study. Since the two compounds are of different nature, they may act by different mechanisms and express synergistic effect. Combination of the two compounds using to dose levels were challenged with single doses of HF, GL and SI as well. The comparison was monitored via measuring serum biochemical parameters including, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyltranspeptidase (GGT), alkaline phosphatase (ALP) and total bilirubin, tissue parameters such as MDA, NP-SH and TP, histopathological study using light and electron microscope. Protective effect on kidney was also monitored histopathologically and biochemically through observing the levels of LDH, creatinine, creatinine-kinase, urea and uric acid. The combinations of HF and GL showed protective effect more than the used single doses of HF and GL alone. However, SI was superior to the used combination in the two used doses in all the measured parameters. The liver and kidney cells appearance under normal and electron microscope showed that SI treated groups showed almost normal cells with slight toxic signs. Cells from group treated with the higher doses of the combination of HF and GL showed slight signs of intoxication under light and electron microscope indicating good level of protection. Although the combination of HF and GL expressed good protection in the higher dose, however, the combination did not exceed the protective effect of SI.

Glycyrrhizin ameliorates high fat diet-induced obesity in rats by activating NrF2 pathway

AIM

Obesity based on insulin resistance is a state of chronic oxidative stress and inflammation that are highly regulated through nuclear factor Erythroid 2-related factor 2 (NrF2) pathway.

MATERIALS AND METHODS

70 male Wistar rats were randomized into two models. The prophylactic model was 10weeks and rats were grouped into: normal group, GL group (received glycyrrhizin 50mg/kg/day orally along with normal pellet diet), HFD group and HFD+ GL group (received glycyrrhizin along with HFD). The treatment model was 14weeks and rats were grouped into: normal group, HFD group and HFD+GL group (received glycyrrhizin from the week 10).

KEY FINDINGS

Glycyrrhizin decreased significantly rat weights and insulin resistance, normalized lipid profile and reduced significantly the adipocytes size in adipose tissue and lipid deposition in the liver tissue through histopathologic examination. Furthermore, glycyrrhizin ameliorated obesity-induced oxidative stress which indicated by significant decrease in liver malondialdehyde level (P<0.001) and increase in the total antioxidant capacity (P<0.001). Interestingly, molecular mechanism of glycyrrhizin was explored, that included significant reduction of liver gluconeogenic enzymes mRNA expression (P<0.001), a significant increase of liver insulin receptor, NrF2 and homooxygenase-1 mRNA expressions (P<0.001) and significant increase and nuclear translocation of NrF2 in liver tissue.

SIGNIFICANCE

Glycyrrhizin ameliorates HFD-induced obesity in rats that may be attributed to its ability to increase insulin receptor expression and to activate NrF2 and subsequent homooxygenase-1 pathway. Thus, this work represents a safe natural compound (glycyrrhizin) that has a great role either as prophylaxis or treatment for insulin resistance related to obesity.

Glycyrrhizin suppresses the expressions of HMGB1 and ameliorates inflammative effect after acute subarachnoid hemorrhage in rat model

High-mobility group box 1 (HMGB1), a nuclear protein that has endogenous cytokine-like activity, is involved in early brain injury after subarachnoid hemorrhage (SAH) by mediating inflammatory response. This study was conducted to investigate the effect of glycyrrhizin as an inhibitor of HMGB1 in a rat SAH model. Experimental SAH was induced by using autologous blood injection to prechiasmatic cistern. 15 mg/kg glycyrrhizin was administered immediately after SAH induction, and then administered once at 6, 12 and 18 h. All the rats were sacrificed at 24 h after neurological assessment and frontal brain tissue was taken for assay. Blood-brain barrier (BBB) permeability was determined by Evans blue (EB) extravasation. The expression of HMGB1 were detected by immunofluorescence, western blot and quantitative real-time PCR. Inflammatory mediators (TNF-α, IL-1β) were measured using specific ELISA. Fluoro-Jade C staining and TUNEL staining was performed for the quantitative assessment of neuronal injury. We found the use of glycyrrhizin significantly improved neurological scores, reduced HMGB1-positive cells, down-regulated mRNA and protein levels of HMGB1, inhibited BBB permeability, and attenuated neuronal cell death and apoptosis after SAH. The up-regulations of inflammation-related molecules (TNF-α, IL-1β) in SAH rats were suppressed by glycyrrhizin treatment. These findings suggest that glycyrrhizin is a potential candidate for the treatment of inflammatory brain injury after SAH.

Probing the contractile vacuole as Achilles' heel of the biotrophic grapevine pathogen Plasmopara viticola

The causative agent of Grapevine Downy Mildew, the oomycete Plasmopara viticola, poses a serious threat to viticulture. In the current work, the contractile vacuole of the zoospore is analysed as potential target for novel plant protection strategies. Using a combination of electron microscopy, spinning disc confocal microscopy, and video differential interference contrast microscopy, we have followed the genesis and dynamics of this vacuole required during the search for the stomata, when the non-walled zoospore is exposed to hypotonic conditions. This subcellular description was combined with a pharmacological study, where the functionality of the contractile vacuole was blocked by manipulation of actin, by Na, Cu, and Al ions or by inhibition of the NADPH oxidase. We further observe that RGD peptides (mimicking binding sites for integrins at the extracellular matrix) can inhibit the function of the contractile vacuole as well. Finally, we show that an extract from Chinese liquorice (Glycyrrhiza uralensis) proposed as biocontrol for Downy Mildews can efficiently induce zoospore burst and that this activity depends on the activity of NADPH oxidase. The effect of the extract can be phenocopied by its major compound, glycyrrhizin, suggesting a mode of action for this biologically safe alternative to copper products.

Glycyrrhizin and glycyrrhetinic acid inhibits alpha-naphthyl isothiocyanate-induced liver injury and bile acid cycle disruption

Alpha-naphthyl isothiocyanate (ANIT) is a common hepatotoxicant experimentally used to reproduce the pathologies of drug-induced liver injury in humans, but the mechanism of its toxicity remains unclear. To determine the metabolic alterations following ANIT exposure, metabolomic analyses was performed by use of liquid chromatography-mass spectrometry. Partial least squares discriminant analysis (PLS-DA) of liver, serum, bile, ileum, and cecum of vehicle- and ANIT-treated mice revealed significant alterations of individual bile acids, including increased tauroursodeoxycholic acid, taurohydrodeoxycholic acid, taurochenodeoxycholic acid, and taurodeoxycholic acid, and decreased ω-, β- and tauro-α/β- murideoxycholic acid, cholic acid, and taurocholic acid in the ANIT-treated groups. In accordance with these changes, ANIT treatment altered the expression of mRNAs encoded by genes responsible for the metabolism and transport of bile acids and cholesterol. Pre-treatment of glycyrrhizin (GL) and glycyrrhetinic acid (GA) prevented ANIT-induced liver damage and reversed the alteration of bile acid metabolites and Cyp7a1, Npc1l1, Mttp, and Acat2 mRNAs encoding bile acid transport and metabolism proteins. These results suggested that GL/GA could prevent drug-induced liver injury and ensuing disruption of bile acid metabolism in humans.

Role of Glycyrrhizin in the Reduction of Inflammation in Diabetic Kidney Disease

BACKGROUND

Diabetic kidney disease (DKD) is one of the most debilitating complications of type 2 diabetes. Recent evidence suggests chronic inflammation to be one of the causal factors of DKD. The mechanisms entailed are not completely elucidated except that a variety of cytokines play a major role in this process. High mobility group box 1 (HMGB1) is a pro-inflammatory toll-like receptor-4 (TLR4)-binding cytokine that is involved in inflammation-associated gene expression. This investigation was designed to assess the involvement of HMGB1, TLR-4, and nuclear factor (NF)-κB in the development of DKD and to evaluate that whether blocking HMGB1 by its natural inhibitor Glycyrrhizin (GLC) can reduce the progression of the disease.

METHODS

Studies were carried out in 8-10-weeks old Zucker diabetic fatty (ZDF) and lean, age- and gender-matched rats. At 10 weeks of age, ZDF rats as compared to controls, showed hyperglycemia, without proteinuria. After 8-10 weeks of the development of diabetes, ZDF animals that showed proteinuria were treated with GLC for 4 weeks. In addition, normal rat kidney (NRK-52E) cells with epithelial-like morphology were comparatively treated with GLC under hyperglycemic condition in vitro.

RESULTS

Substantial increase in the expression of HMGB1, TLR4, and NF-κB in vivo and in vitro under hyperglycemic conditions was observed as compared to normoglycemic conditions. The overexpression of HMGB1, TLR4, NF-κB, and glomerular injury marker nestin was significantly ameliorated by GLC administration.

CONCLUSION

Our findings suggest that hyperglycemia-induced HMGB1 activation in ZDF rats may contribute to the progression of DKD.

Glycyrrhizin Ameliorate Ischemia Reperfusion Lung Injury through Downregulate TLR2 Signaling Cascade in Alveolar Macrophages

This experiment was conducted to study whether pretreatment with Glycyrrhizin (GL) could ameliorate ischemia-reperfusion (I/R) lung injury and investigate the mechanisms of its protective effects in a mice model. Six-eight weeks male BALB/C mice were randomly assigned to four groups (n = 6): Control, Glycyrrhizin, I/R and I/R+Glycyrrhizin. Lung I/R was achieved by clamping the left hilus pulmonis. GL (200 mg/kg) was injected intraperitoneally 30 min before anesthesia. Measurement of pathohistological lung injury score, pulmonary permeability, isolated alveolar macrophages, inflammatory mediators, TLR2 and its downstream factors (MyD88, NF-κB) were performed. The results were as anticipated. Pathohistological evaluation indicated that GL significantly ameliorated I/R-induced lung injury, pulmonary permeability and edema. Pretreatment with GL significantly inhibited I/R-induced inflammation in lung tissues and BALF. In addition, GL significantly decreased I/R-induced isolated alveolar macrophages and suppressed I/R-induced expression of TLR2 and its downstream factors in lung tissues and alveolar macrophages. Collectively, our data indicated that pretreatment with GL could ameliorate I/R lung injury. The mechanisms of its protective effects might be inhibit I/R-induced inflammatory response through downregulate TLR2 signaling cascade in alveolar macrophages.

QUANTIFICATION OF GLYCYRRHIZIN BIOMARKER IN GLYCYRRHIZA GLABRA RHIZOME AND BABY HERBAL FORMULATIONS BY VALIDATED RP-HPTLC METHODS

BACKGROUND

A simple and sensitive thin-layer chromatographic method has been established for quantification of glycyrrhizin in Glycyrrhiza glabra rhizome and baby herbal formulations by validated Reverse Phase HPTLC method.

MATERIALS AND METHODS

RP-HPTLC Method was carried out using glass coated with RP-18 silica gel 60 F254S HPTLC plates using methanol-water (7: 3 v/v) as mobile phase.

RESULTS

The developed plate was scanned and quantified densitometrically at 256 nm. Glycyrrhizin peaks from Glycyrrhiza glabra rhizome and baby herbal formulations were identified by comparing their single spot at R_f = 0.63 ± 0.01. Linear regression analysis revealed a good linear relationship between peak area and amount of glycyrrhizin in the range of 2000-7000 ng/band.

CONCLUSION

The method was validated, in accordance with ICH guidelines for precision, accuracy, and robustness. The proposed method will be useful to enumerate the therapeutic dose of glycyrrhizin in herbal formulations as well as in bulk drug.

Purification of high-purity glycyrrhizin from licorice using hydrophilic interaction solid phase extraction coupled with preparative reversed-phase liquid chromatography

Glycyrrhizin (GA), a major bioactive compound in licorice, has been extensively used throughout the world as a medicine to treat chronic viral hepatitis and allergic dermatitis. In this study, a new method based on hydrophilic interaction solid phase extraction (HILIC-SPE) and preparative reversed-phase liquid chromatography (prep-RPLC) was developed to purify GA with high purity from the complex licorice extract. Via evaluation of retention behavior of GA and flavonoids in different commercially available columns, a hydrophilic column--Click XIon was finally chosen for the purification due to its excellent resolution toward GA and flavonoids under HILIC mode. To optimize the SPE elution conditions, relative factors including water content, pH and ionic strength had been investigated in chromatographic condition. The result indicated that the most appropriate water content was 30% and pH at 4.00, as well as salt concentration should be controlled at 5mM. In addition, the optimization revealed that GA experiences both hydrophilic interaction and ion-exchange interaction on the Click XIon material. According to the chromatographic evaluation, the optimized conditions were applied to HILIC-SPE to enrich GA from licorice, which leads to an increased content of GA from 13.67% to 64.22%. Finally, prep-RPLC was performed to obtain GA with purity higher than 99.00%，which demonstrating great prospect in large-scale preparation of GA.

Glycyrrhizin protects against focal cerebral ischemia via inhibition of T cell activity and HMGB1-mediated mechanisms

Background

Glycyrrhizin (Gly) protects against brain injury induced by stroke. We studied whether Gly achieves its protection by inhibiting T cell activity and high-mobility group box 1 (HMGB1) release in the ischemic brain.

Methods

Stroke was induced by transient middle cerebral artery occlusion in rats and mice. Gly was injected intraperitoneally before or after stroke. We measured infarction, neuroinflammatory cells, gene expressions of interferon-γ (IFNγ), IL-4, and IL-10 in CD4 T cells, HMGB1 release, and T cell proliferation in cultured splenocytes.

Results

Gly treatment reduced infarctions and neuroinflammation characterized by the infiltration of CD68-positive macrophages and myeloperoxidase-positive neutrophils, which corresponds to a reduction in the number of T cells and their subsets, CD4 and CD8 T cells, in the ischemic brain, as measured by flow cytometry. Unlike in wild-type animals, Gly did not offer protection in nude rats and severe combined immunodeficient (SCID) mice who had no T cells, while Gly reduced infarction in both nude rats and SCID mice whose T cells were reconstituted, suggesting that T cells should be the target of Gly. In addition, Gly administration inhibited T cell proliferation stimulated by ConA in in vitro assays and inhibited HMGB1 release from the ischemic brain. Furthermore, Gly attenuated gene expression of IFNγ, but not IL-4 and IL-10 in CD4 T cells. Lastly, HMGB1 promoted T cell proliferation stimulated by ConA, which was inhibited by the addition of Gly.

Conclusions

Gly blocks infarction by inhibiting IFNγ-mediated T cell activity, which is at least partly modulated by HMGB1 activity.

Hypothermia inhibits the propagation of acute ischemic injury by inhibiting HMGB1

Acute ischemic stroke causes significant chronic disability worldwide. We designed this study to clarify the mechanism by which hypothermia helps alleviate acute ischemic stroke. In a middle cerebral artery occlusion model (4 h ischemia without reperfusion), hypothermia effectively reduces mean infarct volume. Hypothermia also prevents neurons in the infarct area from releasing high mobility group box 1 (HMGB1), the most well-studied damage-associated molecular pattern protein. By preventing its release, hypothermia also prevents the typical middle cerebral artery occlusion-induced increase in serum HMGB1. We also found that both glycyrrhizin-mediated inhibition of HMGB1 and intracerebroventricular neutralizing antibody treatments before middle cerebral artery occlusion onset diminish infarct volume. This suggests a clear neuroprotective effect of HMGB1 inhibition by hypothermia in the brain. We next used real-time polymerase chain reaction to measure the levels of pro-inflammatory cytokines in peri-infarct regions. Although middle cerebral artery occlusion increases the expression of interleukin-1β and tissue necrosis factor-α, this elevation is suppressed by both hypothermia and glycyrrhizin treatment. We show that hypothermia reduces the production of inflammatory cytokines and helps salvage peri-infarct regions from the propagation of ischemic injury via HMGB1 blockade. In addition to suggesting a potential mechanism for hypothermia’s therapeutic effects, our results suggest HMGB1 modulation may lengthen the therapeutic window for stroke treatments.

One-pot synthesis of glycyrrhetic acid polyglycosides based on grafting-from method using cyclic sulfite

Glycyrrhetic acid polyglycosides were synthesized in one-pot via cationic ring-opening condensation polymerization of cyclic sulfite (4) initiated by glycyrrhetic acid as an aglycon. Sulfite 4 worked as a practical monomer for the preparation of (1 → 2)-linked polysaccharide skeletons. The chemical stability of 4 was evaluated by the comparison of thermodynamic parameters with those of conventional epoxide (2). The grafting reaction of 4 from glycyrrhetic acid (5) was performed in the presence of TfOH and MS 3A in CH2Cl2 at room temperature. The polymerization degree was moderately controllable by the change of feed ratio of initiator.

Glycyrrhizin ameliorates oxidative stress and inflammation in hippocampus and olfactory bulb in lithium/pilocarpine-induced status epilepticus in rats

Glycyrrhizin (GL) is a triterpene present in the roots and rhizomes of Glycyrrhiza glabra that has anti-inflammatory, hepatoprotective and neuroprotective effects. Recently, it was demonstrated that GL produced neuroprotective effects on the postischemic brain as well as on the kainic acid injury model in rats. In addition to this, GL also prevented excitotoxic effects on primary cultures. The aims of the present study were to evaluate GL scavenging properties and to investigate GL's effect on oxidative stress and inflammation in the lithium/pilocarpine-induced seizure model in two cerebral regions, hippocampus and olfactory bulb, at acute time intervals (3 or 24h) after status epilepticus (SE). Fluorometric methods showed that GL scavenged three reactive oxygen species: hydrogen peroxide, peroxyl radicals and superoxide anions. In contrast, GL was unable to scavenge peroxynitrite, hydroxyl radicals, singlet oxygen and 2,2-diphenil-1-picrylhydrazyl (DPPH) radicals suggesting that GL is a weak scavenger. Additionally, administration of GL (50mg/kg, i.p.) 30min before pilocarpine administration significantly suppressed oxidative stress. Moreover, malondialdehyde levels were diminished and glutathione levels were maintained at control values in both cerebral regions at 3 and 24 after SE. At 24h after SE, glutathione S-transferase and superoxide dismutase activity increased in the hippocampus, while both glutathione reductase and glutathione peroxidase activity were unchanged in the olfactory bulb at that time. In addition, GL suppressed the induction of the proinflammatory cytokines interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in both cerebral regions evaluated. These results suggest that GL confers protection against pilocarpine damage via antioxidant and anti-inflammatory effects.

Oxidative stress modulation in hepatitis C virus infected cells

Hepatitis C virus (HCV) replication is associated with the endoplasmic reticulum, where the virus can induce cellular stress. Oxidative cell damage plays an important role in HCV physiopathology. Oxidative stress is triggered when the concentration of oxygen species in the extracellular or intracellular environment exceeds antioxidant defenses. Cells are protected and modulate oxidative stress through the interplay of intracellular antioxidant agents, mainly glutathione system (GSH) and thioredoxin; and antioxidant enzyme systems such as superoxide dismutase, catalase, GSH peroxidase, and heme oxygenase-1. Also, the use of natural and synthetic antioxidants (vitamin C and E, N-acetylcysteine, glycyrrhizin, polyenylphosphatidyl choline, mitoquinone, quercetin, S-adenosylmethionine and silymarin) has already shown promising results as co-adjuvants in HCV therapy. Despite all the available information, it is not known how different agents with antiviral activity can interfere with the modulation of the cell redox state induced by HCV and decrease viral replication. This review describes an evidence-based consensus on molecular mechanisms involved in HCV replication and their relationship with cell damage induced by oxidative stress generated by the virus itself and cell antiviral machinery. It also describes some molecules that modify the levels of oxidative stress in HCV-infected cells.

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.

Two activators of in vitro fertilization in mice from licorice

Systems for artificial insemination have been established in some animals. However, due to limited availability of sperm and oocytes, more effective treatment methodologies are required. Recently, it was demonstrated that the rate of in vitro fertilization (IVF) in mice was improved by adding a water extract of licorice (Glycyrrhiza uralensis), but not glycyrrhizic acid, to the artificial insemination culture medium. In this study, we examined licorice extract for active compounds using bioassay-guided separation. The results indicated that isoliquiritigenin and formononetin were the active molecules in licorice that contributed to the improved rate of IVF.

Delivery of liquorice extract by liposomes and hyalurosomes to protect the skin against oxidative stress injuries

Liquorice extract, obtained by percolation in ethanol of Glycyrrhiza glabra L. roots, was incorporated in liposomes and hyalurosomes, new phospholipid-sodium hyaluronate vesicles, and their protective effect against oxidative stress skin damages was probed. As a comparison, raw glycyrrhizin was also tested. All the vesicles were small in size (≤ 100 nm), with a highly negative zeta potential ensuring long-term stability, and able to incorporate a high amount of the extract. In vitro tests showed that the liquorice extract loaded in vesicles was able to scavenge DPPH free radical (80% inhibition) and to protect 3T3 fibroblasts against H2O2-induced oxidative stress, restoring the normal conditions. By contrast, glycyrrhizin showed poor antioxidant activity, and was not able to efficiently counteract the oxidative effect of H2O2. In addition, the incorporation of the liquorice extract into the vesicular systems promoted the proliferation and migration of 3T3 fibroblasts, favouring the closure of the scratched area. In vivo anti-inflammatory tests on mice confirmed the ability of the proposed nanosystems to improve the local efficacy of the extract, favouring the re-epitelization process.

Glycyrrhizin, silymarin, and ursodeoxycholic acid regulate a common hepatoprotective pathway in HepG2 cells

BACKGROUND

Glycyrrhizin, silymarin, and ursodeoxycholic acid are widely used hepatoprotectants for the treatment of liver disorders, such as hepatitis C virus infection, primary biliary cirrhosis, and hepatocellular carcinoma.

PURPOSE

The gene expression profiles of HepG2 cells responsive to glycyrrhizin, silymarin, and ursodeoxycholic acid were analyzed in this study.

METHODS

HepG2 cells were treated with 25 µM hepatoprotectants for 24 h. Gene expression profiles of hepatoprotectants-treated cells were analyzed by oligonucleotide microarray in triplicates. Nuclear factor-κB (NF-κB) activities were assessed by luciferase assay.

RESULTS

Among a total of 30,968 genes, 252 genes were commonly regulated by glycyrrhizin, silymarin, and ursodeoxycholic acid. These compounds affected the expression of genes relevant various biological pathways, such as neurotransmission, and glucose and lipid metabolism. Genes involved in hepatocarcinogenesis, apoptosis, and anti-oxidative pathways were differentially regulated by all compounds. Moreover, interaction networks showed that NF-κB might play a central role in the regulation of gene expression. Further analysis revealed that these hepatoprotectants inhibited NF-κB activities in a dose-dependent manner.

CONCLUSION

Our data suggested that glycyrrhizin, silymarin, and ursodeoxycholic acid regulated the expression of genes relevant to apoptosis and oxidative stress in HepG2 cells. Moreover, the regulation by these hepatoprotectants might be relevant to the suppression of NF-κB activities.