The flavonoid glabridin attenuates 2-deoxy-D-ribose-induced oxidative damage and cellular dysfunction in MC3T3-E1 osteoblastic cells

Glabridin Alleviates Oxidative Stress-Induced Osteoporosis by Targeting the Akt/NF-ĸB and Akt/GSK-3β Pathways

Diabetes-related osteoporosis has been known to be a consequence of oxidative stress caused by excessive reactive oxygen species (ROS) production in the tissues. Despite the increase in the number of individuals with diabetes-related osteoporosis year on year, there is still no effective drug that does not induce adverse side effects. Glabridin, which exerts hypoglycemic effects and possesses antioxidant properties, may have beneficial effects in the treatment of diabetes-related osteoporosis. In this study, we aimed to investigate the preventive effects of glabridin in counteracting oxidative stress-induced bone loss and its underlying mechanisms. A diabetic rat model was established by a single intraperitoneal injection of streptozotocin into male Wistar rats. The diabetic rats were orally gavaged daily with glabridin or glyburide for 8 weeks. The presence of diabetes significantly decreased the rats' tibia length, bone thickness, epiphyseal plate length, and collagen deposition compared to the control rats; in comparison, treatment with glabridin for 8 weeks significantly reversed these effects. In our in vitro study, the treatment of MC3T3-E1 preosteoblasts with glabridin up to 7.5 µM for 48 h showed no cytotoxic effect. However, pretreatment with glabridin significantly prevented oxidative stress-induced inhibition of cell proliferation. In addition, glabridin significantly diminished ROS production, restored antioxidant enzyme activity, and mitigated cellular apoptosis. These effects occurred by stimulating the phosphorylation of Akt, GSK-3β, and P65 NF-ĸB proteins. The above results show that glabridin alleviated oxidative stress-induced bone loss and osteoblast cell apoptosis by modulating the expression of the Akt/NF-ĸB and Akt/GSK-3β pathways.

Subinhibitory concentrations of glabridin from Glycyrrhiza glabra L. reduce Listeria monocytogenes motility and hemolytic activity but do not exhibit antimicrobial activity

Increases in the virulence and survival of some pathogens in the presence of subinhibitory concentrations of antibiotics have been reported. However, research on the effects of subinhibitory concentrations of antimicrobial substances derived from traditional Chinese medicine on pathogens is still insufficient. Glabridin is a well-known active isoflavone found in licorice roots that possesses a wide range of biological activities. Therefore, in this study, Listeria monocytogenes (L. monocytogenes) exposed to subinhibitory concentrations of glabridin was used as the research object. The minimum inhibitory concentration (MIC) was determined for L. monocytogenes. We investigated the impacts of subinhibitory concentrations of glabridin on the morphology, motility, biofilm formation, adherence, and survival of L. monocytogenes. The results indicated that the MIC of glabridin for L. monocytogenes was 31.25 μg/mL. At 1/8, 1/4, or 1/2 of the MIC, glabridin did not affect the growth, morphology, flagellar production, or biofilm formation of L. monocytogenes. However, subinhibitory concentrations of glabridin inhibited bacterial swimming and swarming motility and decreased the hemolytic activity of L. monocytogenes. Glabridin reduced the hemolytic activity of L. monocytogenes culture supernatants. The results also showed that subinhibitory concentrations of glabridin had no toxic effect on RAW264.7 cells but decreased the intracellular growth of L. monocytogenes in RAW264.7 cells. Furthermore, subinhibitory concentrations of glabridin triggered ROS production but did not induce MET formation in macrophages. In addition, glabridin did not enhance the capacity of L. monocytogenes to trigger METs or the extracellular killing of macrophages by METs. Thus, we conclude that subinhibitory concentrations of glabridin reduce L. monocytogenes motility and hemolytic activity but do not exhibit antimicrobial activity. Glabridin could be an interesting food additive as a bacteriostatic agent with anti-Listeria activity.

Review on the Diverse Biological Effects of Glabridin

Glabridin is a prenylated isoflavan from the roots of Glycyrrhiza glabra Linne and has posed great impact on the areas of drug development and medicine, due to various biological properties such as anti-inflammation, anti-oxidation, anti-tumor, anti-microorganism, bone protection, cardiovascular protection, neuroprotection, hepatoprotection, anti-obesity, and anti-diabetes. Many signaling pathways, including NF-κB, MAPK, Wnt/β-catenin, ERα/SRC-1, PI3K/AKT, and AMPK, have been implicated in the regulatory activities of glabridin. Interestingly, glabridin has been considered as an inhibitor of tyrosinase, P-glycoprotein (P-gp), and CYP2E1 and an activator of peroxisome proliferator-activated receptor γ (PPARγ), although their molecular regulating mechanisms still need further investigation. However, poor water solubility and low bioavailability have greatly limited the clinical applications of glabridin. Hopefully, several effective strategies, such as nanoemulsions, microneedles, and smartPearls formulation, have been developed for improvement.

The toxicity mechanism of glabridin in prostate cancer cells is involved in reactive oxygen species-dependent PI3K/Akt pathway: Integrated utilization of bioinformatic analysis and in vitro test validation

Glabridin is a prenylated isoflavonoid with considerable anticancer property. Reactive oxygen species (ROS) have evolved as regulators of many cellular signaling pathways in prostate cancer (PC). However, the role of ROS signaling in the anticancer activity of glabridin has not been investigated. Here, we attempted to evaluate the effect of glabridin on PC and the involvement of ROS signaling. Intracellular ROS and mitochondrial ROS (mitoROS) production in PC cell lines, DU-145 and LNCaP, were measured by H2DCFDA and MitoSOX Red staining, respectively. MTT assay was used to analyze the cellular viability. EdU staining assay was conducted to analyze the cell proliferation. To analyze apoptotic rate, TUNEL assay was performed. Caspase-3 activity was detected to reflect cell apoptosis. Western blot was carried out to detect the expression levels of Akt and p-Akt. We found that intracellular ROS and mitoROS levels were dose-dependently upregulated after glabridin treatment in both DU-145 and LNCaP cells, which was reversed by the treatment of ROS inhibitor, N-acetyl-L-cysteine (NAC). Glabridin inhibited the cell viability and reduced the number of EdU-positive DU-145 and LNCaP cells, which were respectively proved by MTT assay and EdU staining assay. Glabridin promoted cell death with increased apoptotic rate and caspase-3 activity in DU-145 and LNCaP cells. The effects of glabridin on cell proliferation and apoptosis were reversed by NAC. Moreover, glabridin suppressed the ratio of p-Akt/Akt, while NAC mitigated the decreased p-Akt/Akt ratio. In addition, the effects of glabridin on cell proliferation and apoptosis were also attenuated by Akt activator, SC79. Collectively, our results demonstrated that glabridin suppressed proliferation and induced apoptosis in PC cells via regulating ROS-mediated PI3K/Akt pathway. These findings suggested that glabridin might hold a promising prospective as a therapeutic agent against PC.

Investigating the Effect of Hydroalcoholic Extract of Licorice Root to Prevent Ovariectomy-Mediated Complications

Introduction. The importance of women’s health and the quality of life after menopause is a critical issue. To prevent disability and menopause complications as well as avoid the side effects of hormone replacement therapy (HRT), in this study, licorice hydroalcoholic extract (Glycyrrhiza uralensis roots) was evaluated as a natural remedy. Methods. Seventy-two female Sprague-Dawley rats were divided into six groups: control group, Sham-operated group, Glycyrrhiza (Gly) 30% group, and ovariectomized group as well as two ovariectomized groups treated with Gly 10% and Gly 30%. Normal saline and different treatments were administered orally for 8 weeks. At the end of the study, calcium, alkaline phosphatase, estrogen, and progesterone levels in the ovariectomized rats were determined. Moreover, the stereological and histopathological changes in uterine tissue in all groups were determined. Phytochemical analyses were also performed to determine the total phenolic content and antioxidant potential of the extract. Result. The hydroalcoholic extract of licorice root exhibited considerable effect to improve calcium, estrogen, and progesterone levels in the ovariectomized rats. Also, hydroalcoholic extract of licorice root successfully decreases the amount of alkaline phosphatase (ALP) level. The stereological and histopathological findings confirmed the therapeutic potential of this extract. The considerable effects of hydroalcoholic extract of licorice root could be due to high amounts of phytoestrogens with similar estrogen-like structures. Considerable total phenolic content and antioxidant activity were also seen in licorice root extract. Conclusion. Hydroalcoholic extract of licorice root due to containing high amounts of phytoestrogens with similar chemical structures to estradiol notably improves biochemical parameters as well as stereological and histopathological markers of uterine tissues in ovariectomy rats, so it could be a potential agent for prevention and/or treatment as hormone replacement therapy in healthy middle-aged and/or older women.

Glabridin inhibits osteoarthritis development by protecting chondrocytes against oxidative stress, apoptosis and promoting mTOR mediated autophagy

Osteoarthritis (OA) is a common chronic degenerative disease that affects the elderly. Thus far, no pharmacological therapy approved by regulators has shown a convincing effect on OA. Glabridin, a small molecule, is a well-known and powerful natural antioxidant, which has a strong scavenging effect on free radicals. This study attempted to explore the role and underlying mechanisms of Glabridin on OA both in vitro and in vivo. In the in vitro study, Glabridin was found to increase the expression levels of extracellular matrix (ECM) related genes, Collagen II, Aggrecan (ACAN), SRY-box 9 (SOX9) and proteoglycan 4 (PRG4). Moreover, Glabridin was observed to significantly reduce the level of oxidative stress in OA chondrocytes while effectively reducing the apoptosis of chondrocytes. Glabridin was also found to significantly increase the autophagy of human OA chondrocytes. During the in vivo study, intraarticular injection of Glabridin was observed to alleviate OA progression and protect chondrocytes against apoptosis following anterior cruciate ligament transection (ACLT) in rats. Furthermore, the mammalian target of rapamycin (mTOR) mediated autophagy was identified as one of the potential mediators of Glabridin activity. Overall, Glabridin protects articular cartilage from damage in rats with OA by protecting chondrocytes against oxidative stress, apoptosis and promoting mTOR mediated autophagy.

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.

Tetrabromobisphenol A Promotes the Osteoclastogenesis of RAW264.7 Cells Induced by Receptor Activator of NF-kappa B Ligand In Vitro

BACKGROUND

Tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame-retardants, is a representative persistent organic pollutants group. Studies on TBBPA toxicity have been conducted using various target cells; however, few studies have investigated TBBPA toxicity in bone cells. Therefore, this study investigated the in vitro effects of TBBPA on osteoclasts, a cell type involved in bone metabolism.

METHODS

RAW264.7 cells were cultured in medium containing 50 ng/mL receptor activator of nuclear factor kappa B ligand (RANKL) and varying concentrations of TBBPA. To evaluate the effects of TBBPA on the differentiation and function of osteoclasts, osteoclast-specific gene expression, tartrate-resistant acid phosphatase (TRAP) activity, bone resorbing activity, mitochondrial membrane potential (MMP) and mitochondrial superoxide were measured.

RESULTS

The presence of 20 μ TBBPA significantly increased TRAP activity in RANKL-stimulated RAW264.7 cells, the bone resorbing activity of osteoclasts, and the gene expression of Akt2, nuclear factor of activated T-cells cytoplasmic 1, and chloride channel voltage-sensitive 7. However, TBBPA treatment caused no change in the expression of carbonic anhydrase II, cathepsin K, osteopetrosis-associated transmembrane protein 1, Src, extracellular signal-related kinase, GAB2, c-Fos, or matrix metalloproteinase 9. Furthermore, 20 μ TBBPA caused a significant decrease in MMP and a significant increase in mitochondrial superoxide production.

CONCLUSION

This study suggests that TBBPA promotes osteoclast differentiation and activity. The mechanism of TBBPA-stimulated osteoclastogenesis might include increased expression of several genes involved in osteoclast differentiation and reactive oxygen species production.

Putative Effects of Nutritive Polyphenols on Bone Metabolism In Vivo-Evidence from Human Studies

For the prevention and treatment of bone loss related diseases, focus has been put on naturally derived substances such as polyphenols. Based on human intervention studies, this review gives an overview of the effects of dietary significant polyphenols (flavonoids, hydroxycinnamic acids, and stilbenes) on bone turnover. Literature research was conducted using PubMed database and articles published between 01/01/2008 and 31/12/2018 were included (last entry: 19/02/2019). Randomized controlled trials using oral polyphenol supplementation, either of isolated polyphenols or polyphenols-rich foods with healthy subjects or study populations with bone disorders were enclosed. Twenty articles fulfilled the inclusion criteria and the average study quality (mean Jadad score: 4.5) was above the pre-defined cut-off of 3.0. Evidence from these studies does not allow an explicit conclusion regarding the effects of dietary important polyphenols on bone mineral density and bone turnover markers. Differences in study population, habitual diet, lifestyle factors, applied polyphenols, used doses, and polyphenol bioavailability complicate the comparison of study outcomes.

Glabridin inhibits the activation of myofibroblasts in human fibrotic buccal mucosal fibroblasts through TGF-β/smad signaling

Oral submucous fibrosis (OSF) has been recognized as one of the oral potentially malignant disorders. Areca nut chewing is implicated in this pathological fibrosis, and it causes chronic inflammation and persistent activation of myofibroblasts. As yet, existing treatments only provide temporary symptomatic relief and there is a lack of an effective intervention to cure OSF. Therefore, development of approaches to ameliorate myofibroblast activities becomes a crucial objective to prevent the malignant progression of OSF. In this study, we examined the inhibitory effect of glabridin, an isoflavane extracted from licorice root, on the myofibroblast characteristics in human fibrotic buccal mucosal fibroblasts (fBMFs). Our results showed that myofibroblast activities, including collagen gel contractility, migration, invasion and wound healing abilities were reduced after exposure of glabridin in a dose-dependent manner. Most importantly, we demonstrated that the arecoline-induced myofiroblast activities were abolished by glabridin treatment. Additionally, the expression of the myofibroblast marker α-smooth muscle actin and other fibrogenic marker, type I collagen, in fBMFs were dose-dependently downregulated. Moreover, we showed that the production of TGF-β was suppressed by glabridin in fBMFs and the protein expression of phospho-Smad2 was decreased as well. In summary, our data suggested that glabridin repressed the myofibroblast features in fBMFs via TGF-β/Smad2 signaling pathway. Glabridin also prevented the arecoline-increased myofibroblast activities, and could serve as a natural anti-fibrosis compound for OSF.

The Flavonoid Glabridin Induces OCT4 to Enhance Osteogenetic Potential in Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are a promising tool for studying intractable diseases. Unfortunately, MSCs can easily undergo cellular senescence during in vitro expansion by losing stemness. The aim of this study was to improve the stemness and differentiation of MSCs by using glabridin, a natural flavonoid. Assessments of cell viability, cell proliferation, β-galactosidase activity, differentiation, and gene expression by reverse transcription PCR were subsequently performed in the absence or presence of glabridin. Glabridin enhanced the self-renewal capacity of MSCs, as indicated by the upregulation of the OCT4 gene. In addition, it resulted in an increase in the osteogenic differentiation potential by inducing the expression of osteogenesis-related genes such as DLX5 and RUNX2. We confirmed that glabridin improved the osteogenesis of MSCs with a significant elevation in the expression of OSTEOCALCIN and OSTEOPONTIN genes. Taken together, these results suggest that glabridin enhances osteogenic differentiation of MSCs with induction of the OCT4 gene; thus, glabridin could be useful for stem cell-based therapies.

Cerium Oxide-Incorporated Calcium Silicate Coating Protects MC3T3-E1 Osteoblastic Cells from H2O2-Induced Oxidative Stress

Oxidative stress regulates cellular functions in multiple pathological conditions, including bone formation by osteoblastic cells. In this work, the protective effects of cerium oxide (CeO₂)-incorporated calcium silicate (CeO₂-CS) coating on the response of osteoblasts to H₂O₂-induced oxidative stress and the related mechanism were examined. CeO₂ incorporation significantly improved osteoblast viability and reduced cell apoptosis caused by H₂O₂ when compared with the control. H₂O₂-induced reduction of differentiation marker alkaline phosphatase (ALP) was recovered in the presence of the CeO₂-CS coating. The above effects were mediated by the antioxidant effect of CeO₂. The CeO₂-CS coating immersed in 0.1 mM H₂O₂ aqueous solution was able to degrade 64 % of it in 1 week. In addition, CeO₂ incorporation decreased reactive oxygen species (ROS) production and suppressed malondialdehyde (MDA) formation in H₂O₂-treated osteoblasts. Taken together, CeO₂-CS biomedical coatings with antioxidant property would be promising for bone regeneration under oxidative stress.

Glabridin induces apoptosis and autophagy through JNK1/2 pathway in human hepatoma cells

BACKGROUND

Extensive research results support the use of herbal medicine or natural food to augment therapy for various cancers. Studies have associated glabridin with numerous biological activities, such as regulating energy metabolism and estrogenic, neuroprotective, antiosteoporotic, and skin-whitening activities.

HYPOTHESIS/PURPOSE

However, how glabridin affects tumor cell autophagy has not been clearly determined.

METHODS

Autophagy is a lysosomal degradation pathway essential for cell survival and tissue homeostasis. In this study, the roles of autophagy and related signaling pathways during glabridin-induced autophagy in human liver cancer cells were investigated. Additionally, the molecular mechanism of the anticancer effects of glabridin in human hepatoma cells was investigated.

RESULTS

The results revealed that glabridin significantly inhibited cell proliferation in human hepatoma cells. Glabridin induced apoptosis dose-dependently in Huh7 cells through caspase-3, -8, and -9 activation and PARP cleavage. Furthermore, autophagy was detected as early as 12h after exposure to a low dose of glabridin, as indicated by the up-regulated expression of LC3-II and beclin-1 proteins. The inhibition of JNK1/2 and p38 MAPK by specific inhibitors significantly reduced glabridin-induced activation of caspases-3, -8, and -9. Blocking autophagy sensitize the Huh7 cells to apoptosis.

CONCLUSION

This study demonstrated for the first time that autophagy occurs earlier than apoptosis does during glabridin-induced apoptosis in human liver cancer cell lines. Glabridin induces Huh7 cell death through apoptosis through the p38 MAPK and JNK1/2 pathways and is a potential chemopreventive agent against human hepatoma.

Biphasic Response to Luteolin in MG-63 Osteoblast-Like Cells under High Glucose-Induced Oxidative Stress

BACKGROUND

Clinical evidence indicates the diabetes-induced impairment of osteogenesis caused by a decrease in osteoblast activity. Flavonoids can increase the differentiation and mineralization of osteoblasts in a high-glucose state. However, some flavonoids such as luteolin may have the potential to induce cytotoxicity in osteoblast-like cells. This study was performed to investigate whether a cytoprotective concentration range of luteolin could be separated from a cytotoxic concentration range in human MG-63 osteoblast-like cells in high-glucose condition.

METHODS

Cells were cultured in a normal- or high-glucose medium. Cell viability was determined with the MTT assay. The formation of intracellular reactive oxygen species (ROS) was measured using probe 2',7' -dichlorofluorescein diacetate, and osteogenic differentiation was evaluated with an alkaline phosphatase bioassay.

RESULTS

ROS generation, reduction in alkaline phosphatase activity, and cell death induced by high glucose were inhibited by lower concentrations of luteolin (EC50, 1.29±0.23 µM). Oxidative stress mediated by high glucose was also overcome by N-acetyl-L-cysteine. At high concentrations, luteolin caused osteoblast cell death in normal- and high-glucose states (IC50, 34±2.33 and 27±2.42 µM, respectively), as represented by increased ROS and decreased alkaline phosphatase activity.

CONCLUSION

Our results indicated that the cytoprotective action of luteolin in glucotoxic condition was manifested in much lower concentrations, by a factor of approximately 26 and 20, than was its cytotoxic activity, which occurred under normal or glucotoxic condition, respectively.

Glabridin Alleviates the Toxic Effects of Methylglyoxal on Osteoblastic MC3T3-E1 Cells by Increasing Expression of the Glyoxalase System and Nrf2/HO-1 Signaling and Protecting Mitochondrial Function

Methylglyoxal (MG) contributes to the pathogenesis of age- and diabetes-associated complications. The present study investigated the effects of glabridin on MG-induced cytotoxicity in MC3T3-E1 osteoblastic cells. MC3T3-E1 cells were treated with glabridin in the presence of MG, and markers of mitochondrial function and oxidative damage were examined. Pretreatment of MC3T3-E1 osteoblastic cells with glabridin prevented MG-induced cell death, the production of intracellular reactive oxygen species and mitochondrial superoxides, cardiolipin peroxidation, and the production of inflammatory cytokines. The soluble form of receptor for advanced glycation end products (sRAGEs)/RAGE ratio increased upon MG treatment, but less so after pretreatment with glabridin, which also increased the level of reduced glutathione and the activities of glyoxalase I and heme oxygenase-1, all of which were reduced by MG. In addition, glabridin elevated the level of nuclear factor erythroid 2-related factor 2. These findings suggest that glabridin protects against MG-induced cell damage by inhibiting oxidative stress and increasing MG detoxification. Pretreatment of MC3T3-E1 osteoblastic cells with glabridin reduced MG-induced mitochondrial dysfunction. Additionally, the nitric oxide level significantly increased upon glabridin pretreatment. Together, these data show that glabridin may potentially serve to prevent the development of diabetic bone disease associated with MG-induced oxidative stress.

Glycyrrhiza glabra

Liquorice foliage

Natural Flavonoids as Potential Herbal Medication for the Treatment of Diabetes Mellitus and its Complications

Diabetes mellitus, together with its various complications, is becoming a serious threat to human health. Natural products are secondary metabolites widely distributed in plants, having a broad range of biological activities. The development of antidiabetic medication from natural products, especially those originating from plants with a traceable folk-usage history in treating diabetes, is receiving more attention. Many studies highlighted not only the benefits of natural flavonoids with hypoglycemic effects, but also their importance in the management of diabetic complications. This review describes selected natural flavonoids that have been validated for their hypoglycemic properties, together with their mechanisms of action. Also discussed are their activities in the treatment of diabetic complications demonstrated via laboratory diabetic animal models, in vitro and clinical trials using human subjects. Published papers from 2000 to date on flavonoids and diabetes were covered through accessing Web of Science and multiple databases for biomedical sciences. The major potential benefits of natural flavonoids discussed in this review clearly suggest that these substances are lead compounds with sufficient structural diversity of great importance in the antidiabetic drug developing process.

Glabridin mediate caspases activation and induces apoptosis through JNK1/2 and p38 MAPK pathway in human promyelocytic leukemia cells

Background

Glabridin, a prenylated isoflavonoid of G. glabra L. roots, has been associated with a wide range of biological properties such as regulation of energy metabolism, estrogenic, neuroprotective, anti-osteoporotic, and skin-whitening in previous studies. However, the effect of glabridin on tumor cells metastasis has not been clearly clarified. Here, the molecular mechanism by which glabridin anticancer effects in human promyelocytic leukemia cells was investigated.

Methodology and Principal Findings

The results showed that glabridin significantly inhibited cell proliferation of four AML cell lines (HL-60, MV4-11, U937, and THP-1). Furthermore, glabridin induced apoptosis of HL-60 cells through caspases-3, -8, and -9 activations and PARP cleavage in dose- and time-dependent manner. Moreover, western blot analysis also showed that glabridin increase phosphorylation of ERK1/2, p38 MAPK and JNK1/2 in dose- and time-dependent manner. Inhibition of p38 MAPK and JNK1/2 by specific inhibitors significantly abolished the glabridin-induced activation of the caspase-3, -8 and -9.

Conclusion

Taken together, our results suggest that glabridin induced HL-60 cell apoptosis through p38 MAPK and JNK1/2 pathways and could serve as a potential additional chemotherapeutic agent for treating AML.

Protective effect of apigenin against oxidative stress-induced damage in osteoblastic cells

Apigenin, a plant-derived flavonoid, was investigated to determine whether it could influence hydrogen peroxide (H2O2)-induced oxidative damage and cellular dysfunction in the MC3T3-E1 mouse osteoblastic cell line. In the present study, osteoblastic cells were treated with H2O2 in the presence or absence of apigenin. Cell viability, apoptosis, reactive oxygen species (ROS) production and mitochondrial membrane potential (ΔΨm) were subsequently examined. It was observed that H2O2 reduced cell survival and ΔΨm, while it markedly increased the intracellular levels of ROS and apoptosis. However, pretreatment of cells with apigenin attenuated all the H2O2-induced effects. The antioxidants, catalase and N-acetyl-L-cysteine (NAC) also prevented H2O2-induced oxidative cell damage. In addition, treatment with apigenin resulted in a significant elevation of osteoblast differentiation genes including alkaline phosphatase (ALP), collagen, osteopontin (OPN), osteoprotegerin (OPG), bone sialoprotein (BSP), osterix (OSX) and osteocalcin (OC) and bone morphogenetic proteins (BMPs) genes (BMP2, BMP4 and BMP7). In the mechanistic studies of cell signaling by the antioxidative potential of apigenin, it was found that apigenin activated the H2O2-induced decreased expression of phosphatidylinositol 3'-kinase (PI3K), protein kinase B2 (AKT2) genes and extracellular signal-related kinase (EPK) 2, which are key regulators of survival-related signaling pathways. By contrast, there were no changes in the expression of nuclear facor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) gene exposed to H2O2 in the present study. Apigenin also upregulated the gene expression of antioxidant enzymes, superoxide dismutase (SOD) 1, SOD2 and glutathione peroxidase (GPx) 1. Taken together, these results suggested that apigenin attenuated oxidative-induced cell damage in osteoblastic cells and may be useful for the treatment of oxidative-related bone disease.

Phytochemistry and biological properties of glabridin

Glabridin, a prenylated isoflavonoid of G. glabra L. roots (European licorice, Fabaceae), has been associated with a wide range of biological properties such as antioxidant, anti-inflammatory, anti-atherogenic, regulation of energy metabolism, estrogenic, neuroprotective, anti-osteoporotic, and skin-whitening. While glabridin is one of the most studied licorice flavonoids, a comprehensive literature survey linked to its numerous bioactivities is unavailable. The present review provides a comprehensive description of glabridin as a key chemical and biological marker of G. glabra, by covering both its phytochemical characterization and reported biological activities. Both glabridin and standardized licorice extracts have significant impact on food, dietary supplements (DSs) and cosmetic markets, as evidenced by the amount of available patents and scientific articles since 1976, when glabridin was first described. Nevertheless, a thorough literature survey also reveals that information about the isolation and chemical characterization of this important marker is scattered and less detailed than expected. Accordingly, the first part of this review gathers and provides all analytical and spectroscopic data required for the comprehensive phytochemical characterization of glabridin. The four most frequently described and most relevant bioactivities of glabridin are its anti-inflammatory, anti-atherogenic, estrogenic-like effects, and its capacity to regulate energy metabolism. While all bioactivities reported for glabridin belong to a wide array of targets, its principal biological properties are likely interconnected. To this end, the current state of the literature suggests that the biological activity of glabridin mainly results from its capacity to down-regulate intracellular reactive oxygen species, bind to antioxidant effectors, and act on estrogen receptors, potentially as a plant-based Selective Estrogen Receptor Modulator (phytoSERM).