Protective Effect Of Luteolin Research Articles

베타아밀로이드로 유도된 신경소교세포 사멸에 대한 루테올린의 보호효과 연구

Objectives : The purpose of this study is to investigate neuroprotective effects and molecular mechanisms of luteolin against β -amyloid (Aβ 25-35)-induced oxidative cell death in BV-2 cells. Methods : The protective effects of luteolin against Aβ25-35-induced cytotoxicity and apoptotic cell death were determined by MTT dye reduction assay and TUNEL staining, respectively. The apoptotic cell death was further analyzed by measuring mitochondrial transmembrane potential and expression of pro- and/or anti-apoptotic proteins. To elucidate the molecular mechanisms underlying the protective effects of luteolin, intracellular accumulation of reactive oxygen species, oxidative damages, and expression of antioxidant enzymes were examined. Results : Luteolin pretreatment effectively attenuated Aβ 25-35-induced apoptotic cell death indices such as DNA fragmentation, dissipation of mitochondrial transmembrane potential, increased Bax/Bcl-2 ratio, and activation of c-Jun N-terminal kinase and caspase-3 in BV-2 cells. Furthermore, Aβ 25-35-induced intracellular formation of reactive oxygen species and subsequent oxidative damages such as lipid peroxidation and depletion of endogenous antioxidant glutathione were suppressed by luteolin treatment. The neuroprotective effects of luteolin might be mediated by up-regulation of cellular antioxidant defense system via up-regulation of γ -glutamylcysteine ligase, a rate-limiting enzyme in the glutathione biosynthesis and superoxide dismutase, an enzyme involved in dismutation of superoxide anion into oxygen and hydrogen peroxide. Conclusions : These findings suggest that luteolin has a potential to protect against Aβ 25-35-induced neuronal cell death and damages thereby exhibiting therapeutic utilization for the prevention and/or treatment of Alzheimer’s disease.

Protective effects of luteolin on cognitive impairments induced by psychological stress in mice

In the present study, the protective effects of luteolin were investigated against psychological stress-induced cognitive impairment. To emulate the psychological stress, mice received restraint stress for six hours daily, between 9:00 and 15:00 hours, for 21 consecutive days. The results of step-through test, open-field test and Morris Water Maze test demonstrated that psychological stress treatment could result in cognitive impairments in mice. This cognition dysfunction was improved by treatment with low- and medium-dose luteolin. In addition, psychological stress induced an increased serum corticosterone concentration with a decreased serum norepinephrine and dopamine concentration. These alterations were attenuated by treatment with luteolin. Also, psychological stress significantly decreased the glutathione (GSH) concentrations and superoxide dismutase (SOD) activities in prefrontal cortex and hippocampus, while the malondialdehyde (MDA) concentrations were enhanced. However, these oxidative alterations in prefrontal cortex and hippocampus induced by psychological stress were significantly reversed by treatment of luteolin. Further, the current study indicated a decline of catalase (CAT) activities in the hippocampus of the ST group, which was significantly prevented by low, medium and high dose of luteolin. On the other hand, there was no significance in CAT activities of the prefrontal cortex among the six groups. Collectively, the present results suggest that luteolin treatment serves as a key role in improving the psychological stress-induced cognitive impairments.

Protective Effect of Luteolin on an Oxidative-Stress Model Induced by Microinjection of Sodium Nitroprusside in Mice

Accumulating lines of evidence showed that luteolin, a polyphenolic compound, has potent neuroprotective effects. The purpose of this study was to examine whether luteolin can protect against sodium nitroprusside (SNP)-induced oxidative damage in mouse brain. Intrastriatal co-injection of luteolin (3 – 30 nmol) with SNP (10 nmol) dose-dependently protected against brain damage and motor dysfunction. Oral administrations of luteolin (600 – 1200 mg/kg) dose-dependently protected against brain damage and motor dysfunction induced by striatal injection of SNP. Furthermore, luteolin (30 – 100 μM) concentration dependently protected against Fe2+-induced lipid peroxidation in mouse brain homogenate. Luteolin (1 – 100 μg/ml) showed potent DPPH radical scavenging ability, when compared with ascorbic acid and glutathione. Finally, a ferrozine assay showed that luteolin (30 – 100 μg/ml) has Fe2+-chelating ability, but this was weaker than that of ethylenediaminetetraacetic acid. These results suggest that intrastriatal or oral administration of luteolin protected mice brain from SNP-induced oxidative damage by scavenging and chelating effects.

Protective Effect of Luteolin in Experimental Ischemic Stroke: Upregulated SOD1, CAT, Bcl-2 and Claudin-5, Down-Regulated MDA and Bax Expression

Luteolin recently has been proved to elicit a vanity of biological effects through its antioxidant and anti-apoptosis properties. Oxidative and apoptosis damage play an important role in cerebral ischemic pathogenesis and may represent a target for treatment. The aim of this study was to evaluate the neuroprotective effects of luteolin and the underlying mechanisms in cerebral ischemia. Focal cerebral ischemia was induced in adult male Sprague-Dawley rats by permanent middle cerebral artery occlusion (pMCAO). Luteolin was injected intraperitoneally at different doses of 10 or 25mg/kg immediately after pMCAO. Experiment 1, luteolin's neuroprotective effect was analyzed. Neurological deficits, brain water content and infarct volume were evaluated at 24 and 72h after pMCAO. SOD1, Bcl-2, and Bax expression were measured by immunohistochemistry, western blot and reverse transcription-polymerase chain reaction. Experiment 2, luteolin's anti-oxidative activities were evaluated. SOD1, CAT activities, and MDA content were measured by spectrophotometer. Experiment 3, the influence of luteolin on claudin-5 was detected. Compared with MCAO group, luteolin significantly increased the activities of SOD1, CAT, Bcl-2 and claudin-5 (P<0.05), decreased the levels of MDA and Bax (P<0.05), and alleviated the neurological deficits, infarct volume and brain water content (P<0.05). The results indicated that luteolin protected the brain from ischemic damage, and this effect may be through reduction of oxidative stress and apoptosis, and upregulation of the expressions of claudin-5.

Effects of Luteolin on Liver, Kidney and Brain in Pentylentetrazol-Induced Seizures: Involvement of Metalloproteinases and NOS Activities.

Flavonoids are an important group of recognized antioxidants in plants. Luteolin (LUT) is a natural flavonoid in the plant kingdom. This study was aimed to investigate the effects of the LUT in the liver, kidney and brain of pentylentetrazol (PTZ)-induced seizure and the relationship between nitric oxide synthases (iNOS, eNOS) and matrix metalloproteinases (MMP2, MMP9). LUT (10 mg/kg) was given intraperitoneally during two weeks prior to seizure induction. A single dose PTZ 80 mg/kg i.p. was administered and seizures were observed and evaluated with regard to latency, frequency and stage for one hour. Seizure frequen cy after PTZ administration was significantly decreased in LUT pretreated rats (p<0.05). An increase of immunhistochemical reactions of iNOS and MMP2, but a decrease of eNOS activity, were observed in rat hippocampus and peripheral tissues during the PTZ induced seizures. LUT pretreatment reversed the iNOS and MMP2 activity to the control levels and significantly increased the eNOS activity (p<0.001). LUT seems to have an effective role in reducing the seizure frequency and a protective role on peripheral organ injury in animal models of seizure. The protective effect of LUT in seizures and the seizure induced peripheral tissue damage warrant further investigations.

Protective Effects of Luteolin against Apoptotic Liver Damage Induced by d-Galactosamine/Lipopolysaccharide in Mice

In this study, the protective effects of luteolin (1, a major component of Cirsium japonicum) were examined against d-galactosamine (GalN)/lipopolysaccharide (LPS)-induced fulminant hepatic failure. Mice received an intraperitoneal injection of 1 (25, 50, 100, and 200 mg·kg(-1)) 1 h before treatment with GalN (700 mg·kg(-1))/LPS (10 μg·kg(-1)). Treatment with GalN/LPS resulted in increased mortality and serum aminotransferase activity. These increases were attenuated by pretreatment with 1. Treatment with GalN/LPS induced an increase in the serum level of tumor necrosis factor-α (TNF-α) and protein expression of TNF-α receptor-associated death domain, and these increases were prevented by 1. In addition, 1 attenuated apoptosis induced by GalN/LPS treatment, which was analyzed using a caspase-3 and -8 activity assay, as well as by proapoptotic BH3-only protein and cytochrome c protein expression, and by a terminal deoxynuleotidyl transferase-mediated dUTP nick end-labeling method. After GalN/LPS injection, nuclear phosphorylated c-Jun levels showed a significant increase, which were attenuated by 1. The present findings suggest that luteolin ameliorates D-GalN/LPS-induced liver injury and that this protection is likely due to inhibition of the extrinsic and intrinsic apoptotic pathways.

Luteolin protects osteoblastic MC3T3-E1 cells from antimycin A-induced cytotoxicity through the improved mitochondrial function and activation of PI3K/Akt/CREB

Luteolin is a flavonoid found in many herbal extracts including celery, green pepper, parsley, perilla leaf and seeds, and chamomile. Antimycin A (AMA) is an inhibitor of the mitochondrial electron transport chain. In the present study, the protective effect of luteolin on AMA-induced cell damage was investigated in osteoblastic MC3T3-E1 cells. Luteolin significantly increased the viability of MC3T3-E1 cells in the presence of AMA and the effect of luteolin in increasing cell viability was completely prevented by the presence of LY294002, Akt inhibitor, or auranofin, suggesting that the effect of luteolin might be partly mediated from PI3K, Akt, and thioredoxin reductase. Pre-treatment with luteolin prior to AMA exposure significantly prevented mitochondrial membrane potential dissipation, ATP loss, inactivation of complex I and IV, ROS production, inactivation of thioredoxin reductase, intracellular calcium elevation, and cytochrome c release induced by AMA. Moreover, luteolin increased activities of PI3K (phosphoinositide 3-kinase) and Akt (protein kinase B), and CREB (cAMP-response element-binding protein) phosphorylation inhibited by AMA treatment. Collectively, these results suggest that luteolin protects MC3T3-E1 cells from AMA-induced cell damage through the improved mitochondrial function and activation of PI3K/Akt/CREB.

Protective Effects of Luteolin on Diabetic Nephropathy in STZ-Induced Diabetic Rats

Diabetic nephropathy is a long-term complication of diabetic mellitus. Many experimental evidences suggest that persistent hyperglycaemia generates intracellular reactive oxygen species (ROS) and upregulates transforming growth factor-b1 and extracellular matrix expression in mesangial and tubular epithelial cells, which is involved of free radicals in the pathogenesis of diabetes and more importantly in the development of diabetic complications. Antioxidants effectively inhibit high-glucose- and H2O2-induced transforming growth factor-b1 and fibronectin upregulation, thus providing evidence that ROS play an important role in high glucose-induced renal injury. The flavonoid luteolin has been shown to possess direct antioxidant activity, therefore we hypothesize that it may be useful in treatment of many chronic disease associated with oxidative stress, such as diabetic nephropathy via its antioxidant properties. Our results suggested that protection against development of diabetic nephropathy by luteolin treatment involved changes in superoxide dismutase (SOD) activity, the malondialdehyde (MDA) content and expression of Heme Oxygenase-1 (HO-1) protein.

The protective effect of luteolin on amyloid β protein (25–35)-induced neurotoxicity in primary rat cortical neuron cells and possible mechanisms

The protective effect of luteolin on amyloid β protein (25–35)-induced neurotoxicity in primary rat cortical neuron cells and possible mechanisms

Protective effects of luteolin against lipopolysaccharide-induced acute lung injury involves inhibition of MEK/ERK and PI3K/Akt pathways in neutrophils

To investigate whether luteolin, the major polyphenolic components of Lonicera japonica, has beneficial effects against lipopolysaccharide (LPS)-induced acute lung injury (ALI) and to determine whether the protective mechanism involves anti-inflammatory effects on neutrophils. ALI was induced with intratracheal instillation of LPS in mice. The level of ALI was determined by measuring the cell count and protein content in bronchoalveolar lavage (BAL) fluid. Neutrophils were stimulated with formyl-Met-Leu-Phe (fMLP) or LPS in vitro. Chemotaxis and superoxide anion generation were measured to evaluate neutrophil activation. The potential involvement of intracellular signaling molecules in regulating neutrophil activation was analyzed by using Western blot. LPS induced ALI in mice, as evidenced with leukocyte infiltration and protein leakage into the lungs. Luteolin attenuated LPS-induced leukocyte infiltration and protein extravasation. In cell studies, luteolin attenuated the fMLP-induced neutrophil chemotaxis and respiratory burst (IC(50) 0.2+/-0.1 micromol/L and 2.2+/-0.8 micromol/L, respectively), but had a negligible effect on superoxide anion generation during phorbol myristate acetate stimulation. Furthermore luteolin effectively blocked MAPK/ERK kinase 1/2 (MEK), extracellular signal-regulated kinase (ERK), and Akt phosphorylation in fMLP- and LPS-stimulated neutrophils. These results indicate that luteolin has beneficial effects against LPS-induced ALI in mice, and the attenuation of neutrophil chemotaxis and respiratory burst by luteolin involves the blockade of MEK-, ERK-, and Akt-related signaling cascades.

Protective Effects of Luteolin against Amyloid β 25–35-induced Toxicity on Rat Cerebral Microvascular Endothelial Cells

Aim To evaluate the effects of luteolin against amyloid beta-peptide 25–35 (Aβ 25–35) on rat cerebral microvascular endothelial cells (CMECs). Methods CMECs were isolated from Wistar rats at 3-week-old, and randomly divided into 5 groups including control group, Aβ 25–35 group, 0.1, 1.0, and 10.0 μmol·L −1 luteolin groups. Cell viability was determined with MTS assay. Intracelluar ROS level and SOD activity were monitored by DCFH-DA and SOD inhibition assay, respectively. Transendothelial electrical resistance was measured using an EVOM resistance meter. γ-Glutamyl transpeptidase and alkaline phosphatase activities were detected using activity assay kits. Levels of TXA 2 and PGI 2 in culture medium were measured as their stable metabolites, TXB 2 and 6-keto-PGF 1α, by ELISA. Results Luteolin attenuated Aβ 25–35-induced toxicity at 0.1, 1.0, and 10 μmol·L −1, inhibited intracellular ROS generation, and increased SOD activity at 1.0 and 10 μmol·L −1. Luteolin was also found to preserve CMECs barrier function, involving the alleviation of TEER reduction, the increase of characteristic enzymatic activity, and regulation of TXA 2 and PGI 2 secretion. Conclusion Luteolin had the ability to protect rat CMECs against Aβ 25–35-induced toxicity.

Protective effects of luteolin on neurons against oxygen-glucose deprivation/reperfusion injury via improving Na+/K+-ATPase activity

Luteolin, a flavone, has considerable neuroprotective effects by its anti-oxidative mechanism. However, it is still unclear whether luteolin can protect neurons against oxygen-glucose deprivation/reperfusion (OGD/R) induced injury. After 2 hours oxygen-glucose deprivation and 24 hours reperfusion treatment in primary cultured hippocampal neurons, the neuron viability, survival rate and apoptosis rate were evaluated by MTT assay, lactate dehydrogenase (LDH) leakage assay and Hoechst staining, respectively. The activity of Na+/K+ -ATPase was examined in cultured neurons or in the hippocampus of SD rats treated by 10 minutes global cerebral ischemia and followed 24 hours reperfusion. Treatment by OGD/R markedly reduced neuronal viability, increased LDH leakage rate and increased apoptosis rate. Application of luteolin (10-100 micromol x L(-1)) during OGD inhibited OGD/R induced neuron injury and apoptosis in a dose-dependent manner. Compared to the control group or OGP/R-treated neurons, the activity of Na+/K+ -ATPase was significantly suppressed in global ischemia/reperfusion group or OGD/R-treated neurons. Application of luteolin during ischemia or OGD preserved the Na+/K+ -ATPase activity. Furthermore, inhibition of Na+/K+ -ATPase with ouabain attenuated the protective effect afforded by luteolin. The data provide the evidence that luteolin has neuroprotective effect against OGD/R induced injury and the protective effect may be associated with its ability to improve Na+/K+ -ATPase activity after OGD/R.

Neuroprotective effect of luteolin on amyloid β protein (25–35)‐induced toxicity in cultured rat cortical neurons

The present study was carried out to investigate the neuroprotective effect of luteolin on amyloid beta (Abeta) (25-35)-induced neurotoxicity using cultured rat cortical neurons. After exposure of primary cultures of rat cortical cells to 10 muM Abeta (25-35) for 48 h, cortical cell cultures exhibited marked apoptotic death. Pretreatment with luteolin (1, 10 microM) significantly protected cortical cell cultures against Abeta (25-35)-induced toxicity. Luteolin (1, 10 microM) showed a concentration-dependent inhibition on 10 muM Abeta (25-35)-induced apoptotic neuronal death, as assessed by MTT assay. Furthermore, luteolin reduced apoptotic characteristics by DAPI staining. For Western blot analysis, the results showed that the protective effect of luteolin on Abeta (25-35)-induced neurotoxicity was mediated by preventing of ERK-p, JNK, JNK-p, P38-p and caspase 3 activations in rat primary cortical cultures. Taken together, the results suggest that luteolin prevents Abeta (25-35)-induced apoptotic neuronal death through inhibiting the protein level of JNK, ERK and p38 MAP kinases and caspase 3 activations.

Luteolin inhibits cell proliferation during Azoxymethane-induced experimental colon carcinogenesis via Wnt/ β-catenin pathway

The protective role of Luteolin (LUT) against Azoxymethane (AOM)-induced mouse colon carcinogenesis has been documented earlier. The aim of this study is to investigate on the mechanism of chemopreventive action exhibited by LUT employing AOM-induced colon carcinogenesis in mice as an experimental model. LUT inhibited AOM-induced colon tumorigenesis by decreasing tumor incidence and size. LUT reduced the cell proliferation by decreasing the number of Argyrophillic nucleolar organizer region (AgNOR)/nucleus and Proliferating Cell Nuclear Antigen (PCNA) index. It was known that β-catenin is a key effector in Wingless and Int (Wnt) signaling pathway and 90% of colon tumors arise from mutations in this pathway. In this study, we show evidence that LUT inhibited colon carcinogenesis by decreasing AOM-induced cell proliferation through the involvement of β-catenin, Glycogen synthase kinase (GSK)-3β and cyclin D1, the key components in Wnt signaling pathway. In conclusion, the protective effect of LUT could be attributed to inhibition of AOM-induced cellular proliferation probably through the involvement of β-catenin, GSK-3β and cyclin D1.

The anti-amnesic effects of luteolin against amyloid β25–35 peptide-induced toxicity in mice involve the protection of neurovascular unit

Luteolin (3′,4′,5,7-tetrahydroxyflavone) is an important member of the flavonoid family. It exhibits strongly anti-inflammatory, antioxidant and phytoestrogen-like activities. In the present study, we examined the anti-amnesic and protective effects of luteolin against Aβ25-35-induced toxicity in mice. Mice were given an i.c.v. injection of aggregated Aβ25-35 peptide. The learning and memory impairments, ultrastructural changes of cerebral cortex, cerebrovascular dysfunction and neuronal changes were detected after oral administration of luteolin continuously for 8 days. Our results demonstrate that oral administration of luteolin for 8 days for those Aβ25-35-induced amnesic mice conferred robust neurovascular protection in Aβ25-35-induced amnesia, involving the improvement of the spatial learning and memory capabilities, the modulation of microvascular function, the increase of regional cerebral blood flow values, the clearance of reactive oxygen species, the improvement of cholinergic neuronal system, and the increase of brain-derived neurotrophic factor level and its receptor tyrosine kinase B expression in cerebral cortex.

Protective effect of luteolin on neurons against cerebral ischemia/reperfusion injury via regulating the activity of ATPase

The aim of this study was to determine whether luteolin protects neurons against cerebral ischemia/reperfusion injury and its underlying mechanism. We cultivated hippocampal neurons from new‐born Sprague‐Dawley rats, and established the model of oxygen‐glucose deprivation/reperfusion (2 h/24 h). Neuronal viability was assessed by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, and cell injury was evaluated by lactate dehydrogenase (LDH) leakage rate. The percentage of apoptotic cells was measured by using Hoechst 33258 staining. Adult male Sprague‐Dawley rats were subjected to four‐vessel‐occlusion for 10 min followed by reperfusion for 24 h, and the activities of Na+, K+‐ATPase and Ca2+, Mg2+‐ATPase were measured by spectrophotometry. Oxygen‐glucose deprivation/reperfusion decreased the cell viability and increased LDH leakage rate and percentage of apoptotic cells. Compared with oxygen‐glucose deprivation/reperfusion group, luteolin (1‐100 μmol/L) treatment significantly increased the cell viability, decreased LDH leakage rate and the percentage of apoptotic cells in a dose‐dependent manner. Luteolin (200 mg·kg−1, i.p.) markedly inhibited the decrease of ATPase activities induced by global cerebral ischemia/reperfusion. These results demonstrate that luteolin protects neurons against ischemia/reperfusion‐induced cell injury via, at least partly, regulating the activity of ATPase.

Luteolin Suppresses Cisplatin-Induced Apoptosis in Auditory Cells: Possible Mediation Through Induction of Heme Oxygenase-1 Expression

Luteolin has been shown to possess antitumorigenic, antioxidant, and anti-inflammatory properties. In the present study, we investigated the protective mechanism of luteolin against cisplatin-induced apoptosis in auditory (House Ear Institute-Organ of Corti 1 [HEI-OC1]) cells. Luteolin was found to induce the expression of heme oxygenase-1 (HO-1) in a dose- and time-dependent manner. Luteolin also activated the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase pathway, which plays an important role in the expression of HO-1. Luteolin protected the cells against cisplatin-induced apoptotic cell death. The protective effect of luteolin was abrogated by zinc protoporphyrin IX (ZnPP IX), an HO inhibitor, and antisense oligodeoxynucleotides against the HO-1 gene. Furthermore, pretreatment with luteolin inhibited the activation of caspase-3 and the mitochondrial dysfunction, and the effect of luteolin on the activation of caspase-3 disappeared in the presence of ZnPP IX or PD098059. These results demonstrate that the expression of HO-1 by luteolin is mediated by the ERK pathway, and also that the activating of HO-1 inhibits cisplatin-induced apoptosis in HEI-OC1 1 cells.

Protective Effect of Luteolin on Inflammatory Factor‐Mediated Insulin Resistance in 3T3‐L1 Adipocytes

Obesity and insulin resistance have been recently linked to a low‐grade chronic inflammatory response characterized by increased macrophage infiltration, altered cytokine production, and activation of inflammatory signaling pathway in adipose tissue. Pharmacological agents and natural products capable of reducing inflammatory activity possess anti‐diabetic properties. Luteolin, a naturally occurring flavonoid, has been demonstrated to inhibit LPS‐induced TNFα release and activation of NF‐κB pathway in macrophages. However, little is known about the role and mechanism of luteolin on anti‐insulin resistance and diabetes. In this study, we investigated the role of luteolin in the regulation of inflammatory factor‐mediated insulin resistance in 3T3‐L1 adipocytes. Here we show that luteolin treatment for 24 hrs increased insulin‐stimulated glucose uptake in a dose‐dependent manner in 3T3‐L1 adipocytes. Our results also demonstrated that 24 hour treatment of luteolin enhanced insulin‐stimulated PPARγ expression in 3T3‐L1 adipocytes. Interestingly, time‐dependent serine phosphorylation of insulin receptor substrate 1 (IRS‐1) by TNFα was blocked in 3T3‐L1 adipocytes with pretreatment of luteolin for 30 min. Furthermore, luteolin treatment for 24 hrs attenuated LPS‐stimulated TNF‐α secretion from both 3T3‐L1 preadipocytes and adipocytes. When added to 3T3‐L1 cells together with LPS during the entire differentiation process, luteolin antagonized the effect of LPS on the induction of IL‐6 gene expression in 3T3‐L1 adipocytes. Thus, our data demonstrate that luteolin plays a protective role in inflammation‐mediated adipocyte dysfunction and insulin resistance.