Blockade of Nitroxidative Stress by Roasted Licorice Extracts in High Glucose-exposed Endothelial Cells

Radix Glycyrrhizae Preparata Induces Cell Cycle Arrest and Induced Caspase-Dependent Apoptosis in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a highly aggressive and devastating brain tumor characterized by poor prognosis and high rates of recurrence. Despite advances in multidisciplinary treatment, GBM constinues to have a poor overall survival. The Radix Glycyrrhizae Preparata (RGP) has been reported to possess anti-allergic, neuroprotective, antioxidative, and anti-inflammatory activities. However, it not clear what effect it may have on tumorigenesis in GBM. This study demonstrated that RGP reduced glioma cell viability and attenuated glioma cell locomotion in GBM8401 and U87MG cells. RGP treated cells had significant increase in the percentage of apoptotic cells and rise in the percentage of caspase-3 activity. In addition, the results of study’s cell cycle analysis also showed that RGP arrested glioma cells at G₂/M phase and Cell failure pass the G2 checkpoint by RGP treatment in GBM8401 Cells. Based on the above results, it seems to imply that RGP activated DNA damage checkpoint system and cell cycle regulators and induce apoptosis in established GBM cells. In conclusion, RGP can inhibit proliferation, cell locomotion, cell cycle progression and induce apoptosis in GBM cells in vitro.

The anti-diabetic activity of licorice, a widely used Chinese herb

ETHNOPHARMACOLOGICAL RELEVANCE

A great deal of valuable experience has been accumulated in the traditional Chinese medicine (TCM) system for the treatment of "Xiaoke" disease which is known as diabetes mellitus now. As the most-commonly used Chinese herb, licorice has been used in TCM for more than two thousand years. It is often used in combination with other herbs to treat metabolic disorders, especially diabetes mellitus.

AIM OF THE STUDY

To summarize the characteristics, mechanisms, and clinical use of licorice and its active components for treating diabetes mellitus.

METHODS

PubMed, Web of Science, Research Gate, Science Direct, Google Scholar, and Academic Journals were used as information sources by the inclusion of the search terms 'diabetes', 'licorice', 'licorice extracts', 'flavonoids', 'triterpenoids', and their combinations, mainly from 2005 to 2019.

RESULTS

Licorice extracts, five flavonoids and three triterpenoids isolated from licorice possess great antidiabetic activities in vivo and in vitro. This was done by several mechanisms such as increasing the appetency and sensitivity of insulin receptor site to insulin, enhancing the use of glucose in different tissues and organs, clearing away the free radicals and resist peroxidation, correcting the metabolic disorder of lipid and protein, and improving microcirculation in the body. Multiple signaling pathways, including the PI3K/Akt, AMPK, AGE-RAGE, MAPK, NF-кB, and NLRP3 signaling pathways, are targets of the licorice compounds.

CONCLUSION

Licorice and its metabolites have a great therapeutic potential for the treatment of diabetes mellitus. However, a better understanding of their pharmacological mechanisms is needed for evaluating its efficacy and safety.

Licorice root components in dietary supplements are selective estrogen receptor modulators with a spectrum of estrogenic and anti-estrogenic activities

Licorice root extracts are often consumed as botanical dietary supplements by menopausal women as a natural alternative to pharmaceutical hormone replacement therapy. In addition to their components liquiritigenin (Liq) and isoliquiritigenin (Iso-Liq), known to have estrogenic activity, licorice root extracts also contain a number of other flavonoids, isoflavonoids, and chalcones. We have investigated the estrogenic activity of 7 of these components, obtained from an extract of Glycyrrhiza glabra powder, namely Glabridin (L1), Calycosin (L2), Methoxychalcone (L3), Vestitol (L4), Glyasperin C (L5), Glycycoumarin (L6), and Glicoricone (L7), and compared them with Liq, Iso-Liq, and estradiol (E2). All components, including Liq and Iso-Liq, have low binding affinity for estrogen receptors (ERs). Their potency and efficacy in stimulating the expression of estrogen-regulated genes reveal that Liq and Iso-Liq and L2, L3, L4, and L6 are estrogen agonists. Interestingly, L3 and L4 have an efficacy nearly equivalent to E2 but with a potency ca. 10,000-fold less. The other components, L1, L5 and L7, acted as partial estrogen antagonists. All agonist activities were reversed by the antiestrogen, ICI 182,780, or by knockdown of ERα with siRNA, indicating that they are ER dependent. In HepG2 hepatoma cells stably expressing ERα, only Liq, Iso-Liq, and L3 stimulated estrogen-regulated gene expression, and in all cases gene stimulation did not occur in HepG2 cells lacking ERα. Collectively, these findings classify the components of licorice root extracts as low potency, mixed ER agonists and antagonists, having a character akin to that of selective estrogen receptor modulators or SERMs.

Aqueous extract of Glycyrrhiza inflata inhibits aggregation by upregulating PPARGC1A and NFE2L2-ARE pathways in cell models of spinocerebellar ataxia 3

Spinocerebellar ataxia (SCA) types 1, 2, 3, 6, 7, and 17 and dentatorubropallidoluysian atrophy, as well as Huntington disease, are a group of neurodegenerative disorders caused by a CAG triplet-repeat expansion encoding a long polyglutamine (polyQ) tract in the respective mutant proteins. The cytoplasmic and nuclear aggregate formation, a pathological hallmark of polyQ diseases, is probably the initial process triggering the subsequent pathological events. Compromised oxidative stress defense capacity and mitochondrial dysfunction have emerged as contributing factors to the pathogenesis of polyQ diseases. The roots of licorice (Glycyrrhiza species) have long been used as an herbal medicine. In this study, we demonstrate the aggregate-inhibitory effect of Glycyrrhiza inflata herb extract and its constituents licochalcone A and ammonium glycyrrhizinate (AMGZ) in both 293 and SH-SY5Y ATXN3/Q75 cells, SCA3 cell models. The reporter assay showed that G. inflata herb extract, licochalcone A, and AMGZ could enhance the promoter activity of peroxisome proliferator-activated receptor γ, coactivator 1α (PPARGC1A), a known regulator of mitochondrial biogenesis and antioxidative response genes. G. inflata extract, licochalcone A, and AMGZ upregulated PPARGC1A expression and its downstream target genes, SOD2 and CYCS, in the 293 ATXN3/Q75 cell model. The expression of nuclear factor erythroid 2-related factor 2 (NFE2L2), the principal transcription factor that binds to antioxidant-responsive elements (AREs) to promote ARE-dependent gene expression when the cells respond to oxidative stress, and its downstream genes, HMOX1, NQO1, GCLC, and GSTP1, was also increased by G. inflata herb extract, licochalcone A, and AMGZ. Knockdown of PPARGC1A increased aggregates in ATXN3/Q75 cells and also attenuated the aggregate-inhibiting effect of the tested compounds. G. inflata extract and its constituents significantly elevated GSH/GSSG ratio and reduced reactive oxidative species in ATXN3/Q75 cells. The study results suggest that the tested agents activate PPARGC1A activity and NFE2L2-ARE signaling to increase mitochondrial biogenesis, decrease oxidative stress, and reduce aggregate formation in SCA3 cellular models.

Nox as a target for diabetic complications

Oxidative stress has been linked to the pathogenesis of the major complications of diabetes in the kidney, the heart, the eye or the vasculature. NADPH oxidases of the Nox family are a major source of ROS (reactive oxygen species) and are critical mediators of redox signalling in cells from different organs afflicted by the diabetic milieu. In the present review, we provide an overview of the current knowledge related to the understanding of the role of Nox in the processes that control cell injury induced by hyperglycaemia and other predominant factors enhanced in diabetes, including the renin–angiotensin system, TGF-β (transforming growth factor-β) and AGEs (advanced glycation end-products). These observations support a critical role for Nox homologues in diabetic complications and indicate that NADPH oxidases are an important therapeutic target. Therefore the design and development of small-molecule inhibitors that selectively block Nox oxidases appears to be a reasonable approach to prevent or retard the complications of diabetes in target organs. The bioefficacy of these agents in experimental animal models is also discussed in the present review.

The inhibitory effect of roasted licorice extract on human metastatic breast cancer cell-induced bone destruction

The aim of this study was to determine whether the ethanol extract of roasted licorice (rLE) could inhibit breast cancer-mediated bone destruction. rLE treatment reduced the viability of MDA-MB-231 human metastatic breast cancer cells but did not show any cytotoxicity in hFOB1.19 human osteoblastic cells and murine bone marrow-derived macrophages (BMMs). rLE inhibited expression and secretion of receptor activator of nuclear factor κB ligand (RANKL) as well as the mRNA and protein expression of cyclooxygenase-2 in osteoblastic cells exposed to the conditioned medium of breast cancer cells. rLE dramatically inhibited RANKL-induced osteoclastogenesis in BMMs, thereby reducing osteoclast-mediated pit formation. Moreover, treatment with licochalcone A and isoliquiritigenin as the active components, whose contents are increased by the roasting process, remarkably suppressed RANKL-induced osteoclast formation in BMMs, respectively. Furthermore, orally administered rLE substantially blocked tumor growth and bone destruction in mice inoculated with breast cancer cells in the tibiae. Serum levels of tartrate-resistant acid phosphatase and C-terminal cross-linking telopeptide of type I collagen and trabecular bone morphometric parameters were reversed to almost the same levels as the control mice by the rLE treatment. In conclusion, rLE may be a beneficial agent for preventing and treating bone destruction in patients with breast cancer.

HPLC method determination of isoliquiritin apioside and isoliquiritin in rat plasma for application in pharmacokinetic study after an oral administration of zhigancao extract

A sensitive HPLC method was developed for the quantitative determination of isoliquiritin apioside (ILA) and isoliquiritin (IL) in rat plasma. After protein precipitation with acetonitrile, chloroform was used to separate lipid-soluble impurities from the plasma samples and remove acetonitrile. A chromatography was carried out on Diamonsil C18 (150 × 4.6 mm; 5 μm) analytical column, using a mobile phase consisting of water (containing phosphoric acid 0.1%, v/v); acetonitrile (72 : 28, v/v) at a flow rate of 1.0 mL/min. The wavelength-switching technology was performed to determine ILA and IL at 360 nm and wogonoside (internal standard, IS) at 276 nm. The calibration curves of ILA and IL were fairly linear over the concentration ranges of 0.060-3.84 μg/mL (r = 0.9954) and 0.075-4.80 μg/mL (r = 0.9968), respectively. The average extract recoveries of ILA, IL, and IS were all over 80%. The precision and accuracy for all concentrations of quality controls and standards were within 15%. The lower limit of quantification (LLOQ) was 0.060 μg/mL for ILA and 0.075 μg/mL for IL. The method was used in pharmacokinetic study after an oral administration of Zhigancao extract to rats.

Grape seed procyanidin B2 inhibits advanced glycation end product-induced endothelial cell apoptosis through regulating GSK3β phosphorylation

To investigate the effects of GSPB2 (grape seed procyanidin B2) on the apoptosis of HUVECs (human umbilical endothelial cells) induced by AGEs (advanced glycation end products), HUVECs were treated with AGEs (200 μg/ml) in the presence or absence of GSPB2 (2.5, 5.0 and 10.0 μmol/l). Our findings showed that (i) AGEs induced HUVEC apoptosis and up-regulated the expression of caspase-3 activation and lactadherin and reduced the phosphorylation of GSK3β (glycogen synthase kinase 3β) at baseline. (ii) Treatment of HUVEC with GSPB2 significantly inhibited the cell apoptosis and the expression of caspase-3 activation and lactadherin induced by AGEs. Moreover, GSPB2 inhibited intracellular reactive oxygen species in a dose-dependent manner in AGEs-treated cells as determined by flow cytometry. (iii) GSPB2 increased the phosphorylation of GSK3β of HUVEC in response to AGEs. These findings suggest that the signalling pathway involving phosphorylation of GSK3β and lactadherin might play a key role in the endothelial apoptosis. GSPB2 therapy could become an effective approach to battling AGEs-induced endothelial apoptosis.

Isoangustone A suppresses mesangial fibrosis and inflammation in human renal mesangial cells

Development of diabetic nephropathy with fibrosis is associated with hypereglycemia-linked inflammation. Increased levels of proinflammatory factors have been found in diabetic patients with nephropathy. The present study was to test the hypothesis that isoangustone A, a novel compound present in licorice, can inhibit renal fibrosis and inflammation inflamed by high glucose (HG) in human mesangial cells through disturbing transforming growth factor β (TGF- β) and nuclear facor κB (NF- κB) pathways. Serum-starved mesangial cells were cultured in 33 mmol/L glucose media. Cells were treated with 1–20 μmol/L isoangustone A isolated from Glycyrrhiza uralensis licorice for three days. Exposure of cells to HG elevated connective tissue growth factor and collagen production, which was dose-dependently reversed by isoangustone A. Isoangustone A boosted HG-plummeted membrane type matrix metalloproteinase (MMP)-1 expression and diminished HG-elevated tissue inhibitor of MMP-2 expression. HG activated mesangial TGF- β1-SMAD-responsive signaling, which was repealed by ≥10 μmol/L isoangustone A. Furthermore, HG upregulated intracellular cell adhesion molecule-1 (ICAM-1) level and monocyte chemoattractant protein-1 (MCP-1) mRNA expression, and such increases were dose-dependently suppressed by isoangustone A most likely through hampering TGF- β signaling pathways. Blockade of NF- κB signaling appeared to be responsible for attenuating HG-triggered induction of ICAM-1 and MCP-1. Our findings provide the first evidence that isoangustone A dampens mesangial sclerosis associated with inflammation in response to HG through hindering TGF- β and NF- κB signaling.

Hyperglycemia induces apoptosis of pancreatic islet endothelial cells via reactive nitrogen species-mediated Jun N-terminal kinase activation

Hyperglycemia significantly stimulates pancreatic islet endothelial cell apoptosis; however, the precise mechanisms are not fully understood. In the present study, treating pancreatic islet endothelial (MS-1) cells with high glucose (30mmol/l) but not mannitol significantly increased the number of apoptotic cells as compared with a physiological glucose concentration (5.5mmol/l). Hyperglycemia significantly stimulated the expression of inducible nitric oxide synthase (iNOS) and production of NO and peroxynitrite (ONOO(-)), relevant to MS-1 cell apoptosis. Moreover, induced reactive nitrogen species (RNS) significantly increased the expression of bax, cleaved caspase-3 and poly adenosine diphosphate (ADP)-ribose polymerase (PARP) via JNK activation, but the expression of bcl-2 was not altered. Furthermore, SP600125 (a specific inhibitor of JNK) and 1400W (a specific inhibitor of iNOS) significantly attenuated cell apoptosis induced by high glucose. Therefore, hyperglycemia triggers MS-1 cell apoptosis by activating an intrinsic-dependent apoptotic pathway via RNS-mediated JNK activation.

Roasted licorice extracts dampen high glucose-induced mesangial hyperplasia and matrix deposition through blocking Akt activation and TGF-beta signaling

Diabetic nephropathy (DN) characterized as nephrotic syndrome and diffuse glomerulosclerosis can cause renal failure and end-stage kidney disease. Expansion of mesangial matrix around capillaries in the kidney glomeruli is a prominent feature of DN. This study investigated whether licorice extracts inhibited mesangial cell (MC) proliferation and matrix accumulation induced by high glucose (HG). Human renal MC were cultured in media containing 5.5 mM glucose plus 27.5 mM mannitol as an osmotic control or 33 mM glucose for 3 d in the presence of water or ethanol extracts from raw licorice (LW, LE) or roasted licorice (RLW, RLE). Non-polar components including glycyrrhetic acid were elevated during licorice roasting, whereas polar components soluble in water extracts were diminished. Exposure of cells to HG caused significant increases in collagen IV secretion and connective tissue growth factor (CTGF) expression, which was appeased by RLW and RLE at transcriptional levels. The inhibitory potency was high in the order of RLE > or = RLW > or = LE > > LW. Non-polar glycyrrhetic acid but not glycyrrhizin retarded HG-stimulated mesangial matrix deposition through diminishing CTGF expression. In addition, RLW and RLE but not LW modulated membrane type matrix metalloproteinase-1 (MT-1 MMP) expression, MMP-2 activity and tissue inhibitor of MMP-2 (TIMP-2), which facilitated the degradation of mesangial matrix. Furthermore, the augmented expression of CTGF and TIMP-2 in HG-exposed cells was mediated by Akt activation and TGF-beta/Smad signaling through PKCbeta2-responsive signaling pathways. However, HG-down-regulated MT-1 MMP expression was independent of activation of ERK1/2 and Akt when using their inhibitors of DB98059 (ERK1/2) and LY294002 (Akt) alone or in combination. These results demonstrate that extracts from roasted licorice may be highly potent therapeutic agents for the prevention and treatment of mesangial fibrosis and glomerulosclerosis leading to diabetes nephropathy due to longstanding diabetes mellitus.

Anti-inflammatory effects of licorice and roasted licorice extracts on TPA-induced acute inflammation and collagen-induced arthritis in mice

The anti-inflammatory activity of licorice (LE) and roated licorice (rLE) extracts determined in the murine phorbol ester-induced acute inflammation model and collagen-induced arthritis (CIA) model of human rheumatoid arthritis. rLE possessed greater activity than LE in inhibiting phorbol ester-induced ear edema. Oral administration of LE or rLE reduced clinical arthritis score, paw swelling, and histopathological changes in a murine CIA. LE and rLE decreased the levels of proinflammatory cytokines in serum and matrix metalloproteinase-3 expression in the joints. Cell proliferation and cytokine secretion in response to type II collagen or lipopolysaccharide stimulation were suppressed in spleen cells from LE or rLE-treated CIA mice. Furthermore, LE and rLE treatment prevented oxidative damages in liver and kidney tissues of CIA mice. Taken together, LE and rLE have benefits in protecting against both acute inflammation and chronic inflammatory conditions including rheumatoid arthritis. rLE may inhibit the acute inflammation more potently than LE.

Isoliquiritigenin entails blockade of TGF-beta1-SMAD signaling for retarding high glucose-induced mesangial matrix accumulation

Diabetic nephropathy characterized as mesangial fibrosis and glomerulosclerosis results in renal failure and end-stage renal diseases. Enhanced expression and secretion of connective tissue growth factor (CTGF) play an important role in the expansion of glomerular mesangial matrix mostly composed of type IV collagen. Isoliquiritigenin can prevent various renal injuries via its anti-inflammatory action. However, the effect of isoliquiritigenin on diabetic nephropathy has never been explored. The present study was to investigate whether nontoxic isoliquiritigenin inhibited high glucose (HG)-induced mesangial fibrosis by retarding formation of type IV collagen as well as CTGF in human mesangial cells (HRMC). Serum starved cells were cultured in media containing 5.5 mM glucose plus 27.5 mM mannitol as an osmotic control or 33 mM glucose for 3 days with and without 1-20 microM isoliquiritigenin. Exposure of cells to HG caused marked increases in collagen secretion and CTGF expression, which was dose-dependently reversed by isoliquiritigenin at the transcriptional levels. Additionally, isoliquiritigenin boosted HG-plummeted type matrix metalloproteinase-1 (MT-1 MMP) expression and dampened HG-elevated tissue inhibitor of MMP-2 (TIMP-2) expression, facilitating the degradation of mesangial matrix. Isoliquiritigenin inhibited HG-upregulated CTGF and TIMP-2 expression via disturbing TGF-beta1 signaling in HRMC, as evidenced by TGF-beta receptor I kinase (TGF-beta RI) inhibitor. HG-activated SMAD2 through autocrine TGF-beta signaling was repealed by > or =10 microM isoliquiritigenin. HG induced SMAD4 expression of HRMC and obliterated antagonistic SMAD7, whereas isoliquiritigenin suppressed induction of TGF-beta RII and TGF-beta RI with blunting their downstream SMAD signaling. The results demonstrate that the bioactive isoliquiritigenin in licorice diminished mesangial matrix accumulation in response to ambient HG through retarding TGF-beta1-SMAD signaling transduction. Therefore, isoliquiritigenin may be a potential therapeutic agent for the prevention and treatment of mesangial fibrosis and glomerulosclerosis leading to diabetic nephropathy due to longstanding diabetes mellitus.