Protective Effects Of Isoliquiritigenin Research Articles

Isoliquiritigenin alleviates myocardial ischemia-reperfusion injury by regulating the Nrf2/HO-1/SLC7a11/GPX4 axis in mice

Ischemia-reperfusion (I/R) injury, a multifaceted pathological process, occurs when the prolongation of reperfusion duration triggers ferroptosis-mediated myocardial damage. Isoliquiritigenin (ISL), a single flavonoid from licorice, exhibits a wide range of pharmacological impacts, but its function in ferroptosis caused by myocardial I/R injury remains unclear. This study delved into the protective effect of ISL on myocardial I/R injury-induced ferroptosis and its mechanism. Neonatal mouse cardiomyocytes (NMCM) underwent hypoxia/reoxygenation (H/R) to simulate the pathological process of myocardial I/R. ISL significantly attenuated H/R-triggered production of reactive oxygen species in NMCM, reduced the expression of malondialdehyde and the activity of lactate dehydrogenase, enhanced superoxide dismutase and catalase activity, and increased the expression of nuclear factor E2-related factor 2 (Nrf2) and its downstream heme oxygenase 1 (HO-1), thereby mitigating oxidative stress damage. CCK8 experiment revealed that the ferroptosis inhibitor Ferrostatin-1 significantly improved myocardial cell viability after 24 h of reoxygenation, and ISL treatment showed a similar effect. ISL reduced intracellular free iron accumulation, up-regulated glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) expression, and inhibited lipid peroxidation accumulation, thereby alleviating ferroptosis. The Nrf2-specific inhibitor ML385 counteracted ISL's defensive role against H/R-triggered oxidative stress damage and ferroptosis. In vivo experiments further confirmed that by regulating the translocation of Nrf2 into the nucleus, ISL treatment increased the levels of HO-1, GPX4, and SLC7A11, inhibited the expression of ACSL4, Drp1 to exert the antioxidant role, alleviated mitochondrial damage, and ferroptosis, ultimately reducing myocardial infarction area and injury induced by I/R. ML385 nearly abolished ISL's protective impact on the I/R model by inhibiting Nrf2 function. In summary, ISL is capable of mitigating oxidative stress, mitochondrial damage, and cardiomyocyte ferroptosis caused by I/R, thereby reducing myocardial injury. A key mechanism includes triggering the Nrf2/HO-1/SLC7A11/GPX4 pathway to prevent oxidative stress damage and cardiomyocyte ferroptosis caused by I/R.

Protective effect of isoliquiritigenin in amiodarone-induced damage of human umbilical vein endothelial cells.

Amiodarone (AM) is a drug commonly used in patients with ventricular arrhythmias. It can damage vascular endothelial cells and easily cause phlebitis. At present, the prevention and treatment of phlebitis induced by the use of AM is not clear due to the lack of corresponding primary research. Isoliquiritigenin (ISL) has an anti-inflammatory effect, but until now, has not been explored much in the field of research in primary care nursing. The purpose of this study is to investigate the efficacy and mechanism of action of ISL in treating phlebitis induced by AM. In our study, we used human umbilical vein endothelial cells (HUVECs) that were divided into three groups: the NC group (normal), the AM group (AM 30 μmol/L for 24 h), and the ISL pretreatment group (isoliquiritigenin 10 μmol/L after 1 h of pretreatment with amiodarone for 24 h). We used CCK-8 to detect cell proliferation, cell scratch assay to detect the migration capability of cells, flow cytometry to measure apoptosis, angiogenesis assay to check the total length and total branches of angiogenesis, and PCR and WB to detect the expression of PCNA, casepase-3, and VEGFA. WB was used to detect NF-κBp65 and p-NF-κBp65 expression. Compared with the AM group, the ISL pretreatment promoted cell proliferation and migration, inhibited cell apoptosis, increased the total length and total branches of angiogenesis, and downregulated p-NF-κBp65 expression. ISL shows promise in the prevention and treatment of clinical phlebitis and can be used as a potential therapeutic drug to prevent phlebitis.

Deep learning-assisted high-content screening identifies isoliquiritigenin as an inhibitor of DNA double-strand breaks for preventing doxorubicin-induced cardiotoxicity

BackgroundAnthracyclines including doxorubicin are essential components of many cancer chemotherapy regimens, but their cardiotoxicity severely limits their use. New strategies for treating anthracycline-induced cardiotoxicity (AIC) are still needed. Anthracycline-induced DNA double-strand break (DSB) is the major cause of its cardiotoxicity. However, DSB-based drug screening for AIC has not been performed possibly due to the limited throughput of common assays for detecting DSB. To discover new therapeutic candidates for AIC, here we established a method to rapidly visualize and accurately evaluate the intranuclear anthracycline-induced DSB, and performed a screening for DSB inhibitors.ResultsFirst, we constructed a cardiomyocyte cell line stably expressing EGFP-53BP1, in which the formation of EGFP-53BP1 foci faithfully marked the doxorubicin-induced DSB, providing a faster and visible approach to detecting DSB. To quantify the DSB, we used a deep learning-based image analysis method, which showed the better ability to distinguish different cell populations undergoing different treatments of doxorubicin or reference compounds, compared with the traditional threshold-based method. Subsequently, we applied the deep learning-assisted high-content screening method to 315 compounds and found three compounds (kaempferol, kaempferide, and isoliquiritigenin) that exert cardioprotective effects in vitro. Among them, the protective effect of isoliquiritigenin is accompanied by the up-regulation of HO-1, down-regulation of peroxynitrite and topo II, and the alleviation of doxorubicin-induced DSB and apoptosis. The results of animal experiments also showed that isoliquiritigenin maintained the myocardial tissue structure and cardiac function in vivo. Moreover, isoliquiritigenin did not affect the killing of HeLa and MDA-MB-436 cancer cells by doxorubicin and thus has the potential to be a lead compound to exert cardioprotective effects without affecting the antitumor effect of doxorubicin.ConclusionsOur findings provided a new method for the drug discovery for AIC, which combines phenotypic screening with artificial intelligence. The results suggested that isoliquiritigenin as an inhibitor of DSB may be a promising drug candidate for AIC.

Isoliquiritigenin attenuates emodin-induced hepatotoxicity in vivo and in vitro through Nrf2 pathway

Emodin (EMO), the main bioactive component of Polygonum multiflorum, Rheum palmatum, Aloe vera and Cassia acutifolia, can cause severe hepatotoxicity. Isoliquiritigenin (ISL), a flavonoid compound from the Glycyrrhiza, has been reported to be the most potent antioxidant response element (ARE)-luciferase inducer among the main components of licorice. But the protective effect and underlying mechanism of ISL on liver injury induced by EMO has not been reported. This study aims to explore the role of nuclear transcription factor 2 (Nrf2) in EMO-induced hepatotoxicity and the protective effect of ISL. EMO treatment caused cytotoxicity in L-02 cells. Combined treatment of EMO with ISL effectively reversed changes in cell viability, reduced reactive oxygen species (ROS) generation and malondialdehyde (MDA) generation, enhanced the levels of glutathione (GSH) and super oxide dismutase (SOD) induced by EMO in L-02 cells. Furthermore, ISL could also phosphorylate mitogen-activated protein kinases (MAPKs) and up-regulate Kelth-like ECH-associated protein (Keap1). The pathways of MAPKs and Keap1 lead to the separation of Keap1 and Nrf2. Free Nrf2 transferred to the nucleus and enhanced the expression of phase II detoxification enzymes. In conclusion, our results are the first to highlight the beneficial role and relevant mechanisms of ISL in EMO-induced liver injury and provide novel insight into its application.

Long-Circulation and Brain Targeted Isoliquiritigenin Micelle Nanoparticles: Formation, Characterization, Tissue Distribution, Pharmacokinetics and Effectsfor Ischemic Stroke.

PurposeWe designed a novel isoliquiritigenin (ISL) loaded micelle prepared with DSPE-PEG2000 as the drug carrier modified with the brain-targeting polypeptide angiopep-2 to improve the poor water solubility and low bioavailability of ISL for the treatment of acute ischemic stroke.MethodsThin film evaporation was used to synthesize the ISL micelles (ISL-M) modified with angiopep-2 as the brain targeted ligands. The morphology of the micelles was observed by the TEM. The particle size and zeta potential were measured via the nanometer particle size analyzer. The drug loading, encapsulation and in vitro release rates of micelles were detected by the HPLC. The UPLC-ESI-MS/MS methods were used to measure the ISL concentrations of ISL in plasma and main tissues after intravenous administration, and compared the pharmacokinetics and tissue distributions between ISL and ISL-M. In the MCAO mice model, the protective effects of ISL and ISL-M were confirmed via the behavioral and molecular biology experiments.ResultsThe results showed that the drug loading of ISL-M was 7.63 ± 2.62%, the encapsulation efficiency was 68.17 ± 6.23%, the particle size was 40.87 ± 4.82 nm, and the zeta potential was −34.23 ± 3.35 mV. The in vitro release experiments showed that ISL-M had good sustained-release effect and pH sensitivity. Compared with ISL monomers, the ISL-M could significantly prolong the in vivo circulation time of ISL and enhance the accumulation in the brain tissues. The ISL-M could ameliorate the brain injury induced by the MCAO mice via inhibition of cellular autophagy and neuronal apoptosis. There were no the cellular structural damages and other adverse effects for ISL-M on the main tissues and organs.ConclusionThe ISL-M could serve as a promising and ideal drug candidate for the clinical application of ISL in the treatment of acute ischemic stroke.

The protective effect of isoliquiritigenin against doxorubicin-induced nephropathy in rats entails activation of Nrf2 signaling as one key mechanism

ObjectivesThis study aimed to evaluate if the protective effect of Isoliquiritigenin (ISL) against doxorubicin-induced nephropathy in rats entails activation of Nrf2 signaling. MethodsAdult male Wistart rats were treated as control, ISL, DOX, DOX, and ISL + DOX + ISL + Nrf2 inhibitor (brusatol) (n = 8/group). Treatments with ISL (25 mg//kg, oral) were carried out 10 days before and 10 days after the single dose of DOX (15 mg/kg, i.p). ResultsTreatment with ISL attenuated the glomerular and tubular damage and reduced interstitial fibrosis and collagen accumulation in the kidneys of DOX-intoxicated animals. It also increased urinary flow and volume, stimulated urinary creatinine excretion, and decreased albumin excretion. These effects were associated with high transcription of Bcl2, suppression of ROS, MDA, and inflammatory cytokines production (i.e., TNF-α, IL-6, and IL-1β), downregulation of apoptotic markers (Bax and caspase-3/9), TGF-β1, Collagen I/III. Besides, ISL stimulated renal expression, translation, and nuclear localization of Nrf2, as well as levels of GSH and SOD, independent of keap-1. All these effects afforded by ISL were reversed by suppressing Nrf2 with brusatol. ConclusionPre-treatment with ISL is an effective strategy to alleviate DOX-induced nephropathy in rats by stimulating the Nrf2/antioxidant axis, which encourages further pre-clinical studies.

Isoliquiritigenin Confers Neuroprotection and Alleviates Amyloid-β42-Induced Neuroinflammation in Microglia by Regulating the Nrf2/NF-κB Signaling.

BackgroundNeuroinflammation and oxidative stress are two major pathological characteristics of Alzheimer’s disease (AD). Amyloid-β oligomers (AβO), a toxic form of Aβ, promote the neuroinflammation and oxidative stress in the development of AD. Isoliquiritigenin (ISL), a natural flavonoid isolated from the root of liquorice, has been shown to exert inhibitory effects on inflammatory response and oxidative stress.ObjectivesThe main purpose of this study is to assess the influence of ISL on inflammatory response and oxidative stress in BV2 cells stimulated with AβO, and to explore the underlying molecular mechanisms.Methods3-(4,5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H- tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) cytotoxicity assays were used to assess the toxic or protective effects of ISL. The expression levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assays. Morphological changes in BV2 cells were assessed by immunofluorescence method. Nitric oxide (NO) assay kit was used to determinate the NO production. Western blot, qRT-PCR and immunofluorescence were used to explore the underlying molecular mechanisms.ResultsISL treatment reduced the production of inflammatory cytokines and NO, and alleviated the morphological changes in BV2 cells induced by AβO. ISL treatment further protected N2a cells from the toxic medium of AβO-stimulated BV2 cells. ISL activated nuclear factor erythroid-2 related factor 2 (Nrf2) signaling and suppressed nuclear factor-κB (NF-κB) signaling in BV2 cells.ConclusionISL suppresses AβO-induced inflammation and oxidative stress in BV2 cells via the regulation of Nrf2/NF-κB signaling. Therefore, ISL indirectly protects neurons from the damage of toxic conditioned media.

Protective effect of isoliquiritigenin on experimental diabetic nephropathy in rats: Impact on Sirt-1/NFκB balance and NLRP3 expression

The prevalence of diabetes mellitus (DM) drastically increases worldwide. Persistent hyperglycemia affects body microvasculature causing injuries to kidney producing diabetic nephropathy (DNE). Manifestation of these microvascular complications is associated with disturbed redox homeostasis. The current study evaluated the effect of isoliquiritigenin (ISLQ), a bioactive chalcone found in licorice which is known for its antioxidant effect, on diabetes-induced renal injury. DM was prompted in male rats by streptozotocin (STZ, 50 mg/kg, intraperitoneally). ISLQ was administrated by oral gavage for 8 weeks at a dose (20 mg/kg/day). Features of renal injury were observed in kidneys of diabetic rats including, albuminuria and deteriorated renal function. Renal dysfunction was associated with reduced sirtuin-1 (Sirt-1) expression, increased renal oxidative stress, nucleotide-binding domain and leucine-rich repeat containing protein-3 (NLRP3), nuclear factor-κB (NFκB) and inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Moreover, there was significant downregulation of anti-inflammatory cytokine interleukin-10 (IL-10), glomerular and tubular injury and collagen accumulation. ISLQ administration preserved renal function and architecture, restored Sirt1 and renal oxidant-antioxidant balance, dampened inflammation and attenuated collagen accumulation. It can be inferred that ISLQ possess a protective effect and could have a potential as a food supplement to halt development and progression of DNE.

488-P: Isoliquiritigenin Protects Renal Tubular Epithelial Cells from Inflammatory and Oxidative Injuries via Directly Activating SIRT1 in Type 1 Diabetic Nephropathy

Emerging evidence shows that increasing fibrosis and apoptosis have been observed in the tubular epithelia in the progression of type 1 diabetic nephropathy (DN). Excessive inflammatory response and oxidative stress contribute to the pathogenesis of progression. Isoliquiritigenin (ISL), a natural chalcone compound, has been reported to exert anti-inflammatory and anti-oxidative properties. However, little is known about the effects of ISL on diabetic nephropathy and its mechanism. In this study, we investigated the potential protective effects and pharmacological mechanisms of ISL on DN in vivo and in vitro. We test beneficial activities of ISL on streptozotocin (STZ)-induced type 1 diabetes mellitus mice and renal tubular epithelial NRK-52E cells. The study showed that ISL attenuated diabetic nephropathy by decreasing both pro-fibrotic and pro-apoptotic biomarkers. Diabetes or high glucose (HG) induced inflammatory response and oxidative stress were eliminated by ISL administration. The molecular docking using the multiple ligand simultaneous docking (MLSD) software indicated that three molecules of ISL might bound to the binding site of SIRT1 and formation of a stable complex. We also found ISL could neutralize HG-mediated inactivation of SIRT1. Activation of SIRT1 could attenuate HG-induced inflammation, oxidative stress, fibrosis and apoptosis in NRK-52E cells, paralleled with the effects of ISL. While inhibition of SIRT1 could significantly abrogate the protective effects of ISL. Our study implicated that ISL might have great pharmacological actions on attenuating tubular damage of diabetic nephropathy. The beneficial effects of ISL are likely associated with inhibiting excessive inflammatory response and oxidative stress via directly activating SIRT1. Disclosure X. Chen: None. F. Shen: None. Funding Wenzhou Science and Technology Bureau (Y20190125); First Affiliated Hospital of Wenzhou Medical University (FHY2019015)

Neuroprotective effects of isoliquiritigenin against cognitive impairment via suppression of synaptic dysfunction, neuronal injury, and neuroinflammation in rats with kainic acid-induced seizures

Epileptogenesis is a dynamic process initiated by insults to brain and commonly accompanied by cognitive impairment. Isoliquiritigenin (ISL), a flavonoid in licorice, has a broad spectrum of biological effects including anti-inflammatory and antioxidant activities. However, the protective effects of ISL against cognitive impairment in epileptic processes and the underlying molecular mechanism are not well understood. To address these questions, we established an reproducible seizure model by intracerebroventricular injection of kainic acid (KA) in 21-day-old rats; ISL was intraperitoneally administered three times prior to KA injection, and changes in cognitive function; synaptic plasticity; neuronal injury; number of glial cells; and expression of pro-inflammatory cytokines and nuclear factor-like (NRF)2 signaling and NACHT, LRR, and PYD domains-containing protein (NLRP)3 inflammasome components in the hippocampus were examined. Rats with KA-induced seizures showed longer average escape latency and decreases in the number of platform crossings and average time spent in the target quadrant in the Morris water maze; ISL pretreatment reversed this decline in cognitive impairment and increased the protein levels of synaptophysin, postsynaptic density-95 and brain-derived neurotrophic factor while reducing the number of Fluoro Jade B-positive cells, microglia, and astrocytes; cleaved-Caspase-3 and -9 protein levels; and tumor necrosis factor-α, interleukin (IL)-1β, and IL-18 production. It also enhanced the nuclear localization of NRF2, hemeoxygenase-1, and NAD(P)H:quinone oxidoreductase (NQO) 1, and reversed the upregulation of NLRP3 inflammasome components NLRP3 and Caspase-1 induced by KA injection. Thus, ISL protects against cognitive impairment in KA-induced epileptic processes possibly through regulation of NRF2 signaling and the NLRP3 inflammasome pathway.

Isoliquiritigenin Provides Protection and Attenuates Oxidative Stress-Induced Injuries via the Nrf2-ARE Signaling Pathway After Traumatic Brain Injury.

Traumatic brain injury (TBI) is a serious public health and medical problem worldwide. Oxidative stress plays a vital role in the pathogenesis of TBI. Nuclear factor erythroid 2-related factor 2 (Nrf2), an important factor in the cellular defense against oxidative stress, is activated following TBI. In this study, the protective effects of Isoliquiritigenin (ILG), a promising antioxidant stress drug, was evaluated as a protective agent against TBI. In a mouse model of controlled cortical impact Injury, we found that the ILG administration reduced the Garcia neuroscore, injury histopathology, brain water content, cerebral vascular permeability, the expression of cleaved caspase3, aquaporin-4, glial fibrillary acidic protein and the increased the expression of neurofilament light chain protein, indicating the protective effects against TBI in vivo. ILG treatment after TBI also restored the oxidative stress and promoted the Nrf2 protein transfer from the cytoplasm to the nucleus. We then used Nrf2-/- mice to test the protective effect of Nrf2 during ILG treatment of TBI. Our findings indicated that Nrf2-/- mice had greater brain injury and oxidative stress than wild-type (WT) mice and ILG was less effective at inhibiting oxidative stress and repairing the brain injury than in the WT mice. In vitro studies in SY5Y cells under oxygen glucose deprivation/re-oxygenation stimulation yielded results that were consistent with those obtained in vivo showing that ILG promotes Nrf2 protein transfer from the cytoplasm to the nucleus. Taken together, our findings demonstrate that Nrf2 is an important protective factor against TBI-induced injuries, which indicates that the protective effects of ILG are mediated by inhibiting oxidative stress after TBI via a mechanism that involves the promotion of Nrf2 protein transfer from the cytoplasm to the nucleus.

Isoliquiritigenin alleviated the Ang II-induced hypertensive renal injury through suppressing inflammation cytokines and oxidative stress-induced apoptosis via Nrf2 and NF-κB pathways

PurposeHypertensive renal injury plays important role in the pathogenesis of end-stage nephropathy and the need for dialysis. Isoliquiritigenin (ISL) is a natural compound with antioxidant and anti-inflammatory activities. In this study, the protective effects of ISL on Angiotensin II (Ang II)- induced apoptosis, inflammation and extracellular matrix production in HK-2 cells were observed and its mechanisms were elucidated. MethodsCell survival was determined with MTT assay. Cell cycle and apoptosis was assessed with flow cytometric analysis. The production of cytokines including IL-1β and TNF-α were evaluated with Elisa. Western blotting assay was used to determine protein levels of apoptosis related signaling, oxidative stress, NF-κB and ECM related molecules. mRNA levels of fibronectin and collagen Ⅳ were detected by RT-qPCR. ResultsAng II significantly inhibited cell survival, induced cell cycle arrest and enhanced cell apoptosis. However, the above effects were markedly alleviated by ISL treatment in a dose-dependent manner. In addition, Ang II significantly induced oxidative stress and NF-κB signaling activation, as well as inflammatory cytokines release. In contrast, these effects were remarkably reversed by ISL via regulation of Nrf2. Notably, Ang II also triggered generation of extracellular matrix, including fibronectin and collagen Ⅳ, which was abolished upon ISL treatment. ConclusionsTaken together, ISL alleviated the Ang II-induced hypertensive renal injury through suppressing inflammation cytokines, excessive deposition of extracellular matrix and oxidative stress-induced apoptosis via Nrf2 and NF-κB pathways. Our findings provided the evidences for exploring the possible mechanism of hypertensive renal injury pathogenesis and identifying novel therapeutic targets.

Isoliquiritigenin Inhibits Cigarette Smoke-Induced COPD by Attenuating Inflammation and Oxidative Stress via the Regulation of the Nrf2 and NF-κB Signaling Pathways.

Chronic obstructive pulmonary disease (COPD) is the major leading cause of disease with high-mortality worldwide. Cigarette smoke (CS) is a major factor for COPD. CS causes chronic inflammation and oxidative stress, which contributes to lung dysfunction in COPD. Isoliquiritigenin (ILG), a natural flavonoid derived from the root of liquorice, has been reported to possess antiinflammatory and antioxidant activity. In the present study, we tested the mechanism and protective effects of ILG on CS-induced COPD. Mice were exposed to CS for 2 h twice a day for 4 weeks. ILG was given orally 1 h before CS exposure twice a day for 4 weeks. The bronchial alveolar lavage fluid was collected to test the levels of inflammatory cytokines and the number of inflammatory cells. The lung tissues were obtained to evaluate the pathological changes, lung edema, myeloperoxidase (MPO) activity, malondialdehyde (MDA) level, as well as the expression of the nuclear factor-erythroid 2 (Nrf2) and nuclear factor κB (NF-κB) signaling pathways. The results showed that ILG reduced the infiltration of inflammatory cells and the production of inflammatory cytokines. ILG also reversed CS-induced lung pathological injuries, wet/dry ratio, MPO activity, and MDA level. Further research also showed that ILG dose-dependently up-regulated the expression of Nrf2 and down-regulated the expression of NF-κB signaling pathways induced by CS. In conclusion, ILG protected against CS-induced COPD by inhibiting inflammatory and oxidative stress via the regulation of the Nrf2 and NF-κB signaling pathways.

Protective effect of isoliquiritigenin against cerebral injury in septic mice via attenuation of NF-κB.

The study was conducted to scrutinize the outcome of isoliquiritigenin (ISL) against cerebral injury in septic mice. The sepsis was introduced using cecal ligation and puncture (CLP) method in experimental mice. The effect of ISL was quantified using the content of brain water and blood brain barrier (BBB) permeability. The effect on the levels of myeloperoxidase (MPO), superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione (GSH) in brain homogenates was also determined. The effect of ISL on the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in serum was also estimated. The levels of various inflammatory biomarkers (COX-2 and PGE2) were also studied. The expression of NF-κB signalling cascade and inducible nitric oxide synthase (iNOS) was estimated by Western blot. Compared with CLP group, the brain water content was found to be reduced significantly together with the enhanced BBB integrity in ISL treated group. The level of MDA was reduced together with enhanced level of SOD and GSH in the ISL treated group. The levels of TNF-α, IL-1β, and IL-6 were also found to be modulated in ISL group. The level of COX-2 and PGE2 was reduced to near normal after ISL administration together with increase in the IκBα expression and reduction of p65 and p-p65 expression in a concentration-dependent manner. The expression of iNOS was also found to be reduced in ISL group. These results demonstrate that ISL causes protection of CLP-induced sepsis in experimental mice via multiple pathways.

Protective Effects of Isoliquiritigenin on LPS-Induced Acute Lung Injury by Activating PPAR-γ.

Isoliquiritigenin (ILG), a major ingredient of licorice, has been reported to have anti-oxidative and anti-inflammatory effects. The aim of this study was to investigate the protective effects of ILG on lung injury using an animal model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Male BALB/c mice were conditioned with ILG 1h before intranasal instillation of LPS. The effects of ILG on lung injury were assessed by measuring lung histopathological examination, MPO assay, wet/dry (W/D) ratio, and inflammatory cytokine production. The results showed that ILG significantly inhibited LPS-induced lung histopathological changes and the MPO activity. Meanwhile, it attenuated the wet/dry (W/D) ratio in the lung tissues. The results also indicated that ILG inhibited LPS-induced ALI in the expression of inflammatory cytokines in the BALF. Furthermore, ILG can decrease the activity of NF-κB and can increase the expression of PPAR-γ. These findings suggested that ILG inhibited the inflammatory of LPS-induced lung injury by activating PPAR-γ and inhibiting NF-κB activation.

Protective Effect of Isoliquiritigenin against Ethanol-Induced Hepatic Steatosis by Regulating the SIRT1-AMPK Pathway

Ethanol-induced fat accumulation, the earliest and most common response of the liver to ethanol exposure, may be involved in the pathogenesis of liver diseases. Isoliquiritigenin (ISL), an important constituent of Glycyrrhizae Radix, is a chalcone derivative that exhibits antioxidant, anti-inflammatory, and phytoestrogenic activities. However, the effect of ISL treatment on lipid accumulation in hepatocytes and alcoholic hepatitis remains unclear. Therefore, we evaluated the effect and underlying mechanism of ISL on ethanol-induced hepatic steatosis by treating AML-12 cells with 200 mM ethanol and/or ISL (0∼50 μM) for 72 hr. Lipid accumulation was assayed by oil red O staining, and the expression of sirtuin1 (SIRT1), sterol regulatory element-binding protein-1c (SREBP-1c), AMP-activated protein kinase (AMPK), and peroxisome proliferator-activated receptor alpha (PPARα) was studied by western blotting. Our results indicated that ISL treatment upregulated SIRT1 expression and downregulated SREBP-1c expression in ethanol-treated cells. Similarly, oil red O staining revealed a decrease in ethanolinduced fat accumulation upon co-treatment of ethanol-treated cells with 10, 20, and 50 μM of ISL. These findings suggest that ISL can reduce ethanol induced-hepatic lipogenesis by activating the SIRT1-AMPK pathway and thus improve lipid metabolism in alcoholic fatty livers.

The Protective Effects of Isoliquiritigenin and Glycyrrhetinic Acid against Triptolide-Induced Oxidative Stress in HepG2 Cells Involve Nrf2 Activation.

Triptolide (TP), an active ingredient of Tripterygium wilfordii Hook f., possesses a wide range of biological activities. Oxidative stress likely plays a role in TP-induced hepatotoxicity. Isoliquiritigenin (ISL) and glycyrrhetinic acid (GA) are potent hepatoprotection agents. The aim of the present study was to investigate whether Nrf2 pathway is associated with the protective effects of ISL and GA against TP-induced oxidative stress or not. HepG2 cells were treated with TP (50 nM) for 24 h after pretreatment with ISL and GA (5, 10, and 20 μM) for 12 h and 24 h, respectively. The results demonstrated that TP treatment significantly increased ROS levels and decreased GSH levels. Both ISL and GA pretreatment decreased ROS and meanwhile enhanced intracellular GSH content. Additionally, TP treatment obviously decreased the protein expression of Nrf2 and its target genes including HO-1 and MRP2 except NQO1. Moreover, both ISL and GA displayed activities as inducers of Nrf2 and increased the expression of HO-1, NQO1, and MRP2. Taken together the current data confirmed that ISL and GA could activate the Nrf2 antioxidant response in HepG2 cells, increasing the expression of its target genes which may be partly associated with their protective effects in TP-induced oxidative stress.

Protective Effects of Isoliquiritigenin Against Methamphetamine-Induced Neurotoxicity in Mice

Isoliquiritigenin (ISL) suppresses cocaine-induced extracellular dopamine levels and has a neuroprotective effect in cocaine-treated rat brain. Here, we examine the effect of ISL on methamphetamine-induced striatal neurotoxicity. Repeated injections of methamphetamine cause the loss of striatal dopamine transporter (DAT) and tyrosine hydroxylase (TH). Intraperitoneal injection of ISL prior to methamphetamine injection significantly prevented methamphetamine-induced reduction of DAT and TH. ISL also suppressed methamphetamine-induced activation of glial cells. Moreover, ISL impeded the expression of nitric oxide synthase and the activation of NF-κB through blockage of its phosphorylation. Our results suggest that ISL protects against methamphetamine-induced neurotoxicity by inhibition of NF-κB activation.

Protective effects of isoliquiritigenin in transient middle cerebral artery occlusion-induced focal cerebral ischemia in rats

Epidemiological studies indicate that the intake of flavonoids is inversely associated with risk of stroke, cardiovascular diseases and cancer. Isoliquiritigenin (ISL), a flavonoid constituent in the root of Glycyrrhiza glabra, is known to have vasorelaxant effect, antioxidant, anti-platelet, anti-tumor, anti-allergic, antiviral activities and estrogenic properties. However, there is no report on the effects of ISL in cerebral ischemia. Evidence demonstrate that the impaired energy metabolism and the excessive generation of reactive oxygen radicals (ROS) contribute to the brain injury associated with cerebral ischemia. In the present study, the protective effects of ISL were investigated in transient middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia–reperfusion injury in rats. Male Sprague–Dawley rats were divided into five groups: sham-operated group, vehicle-pretreated group, and three ISL-pretreated groups (5, 10 and 20 mg kg −1, i.g.). ISL were administered once a day, for 7 days prior to ischemia. The rats were subjected to 2 h right MCAO via the intraluminal filament technique and 22 h reperfusion. Pretreatment with ISL significantly reduced the cerebral infarct volume and edema and produced significant reduction in neurological deficits. In this study, in order to clarify the mechanism of ISL's protection against cerebral ischemia damage, cerebral energy metabolism, brain Na +K +ATPase activity, malondialdehyde (MDA) content and antioxidant enzyme activities were measured. ISL pretreatment increased the brain ATP content, energy charge (EC) and total adenine nucleotides (TAN) in a dose-dependent manner. The brain Na +K +ATPase activity was protected significantly by pretreatment of ISL for 7 days. Pretreatment with ISL significantly inhibited the increases of brain MDA content and prevented the activities of brain superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) from declines caused by cerebral ischemia–reperfusion. All these findings indicate that ISL has the protective potential against cerebral ischemia injury and its protective effects may be due to the amelioration of cerebral energy metabolism and its antioxidant property.