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Ameliorative effects of hispidulin on high glucose-mediated endothelial dysfunction via inhibition of PKCβII-associated NLRP3 inflammasome activation and NF-κB signaling in endothelial cells

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Abstract

Endothelial dysfunction is closely relevant to atherosclerosis complications in diabetic patients. Hispidulin, a flavone derived from the herb Salvia plebeia R. Br., has numerous biological properties including anti-inflammatory and antioxidative effects, but the underlying mechanism of its anti-inflammatory action remains unclear. This study was designed to investigate the effects of hispidulin on endothelial homeostasis and its mechanism. Hispidulin effectively inhibited high glucose-induced oxidative stress by attenuating PKCβII phosphorylation and downstream reactive oxygen species (ROS) production, furthermore reversing the loss of mitochondria membrane potential. Moreover, hispidulin significantly suppressed the expression of NLRP3 inflammasome and IKKβ/NF-κB, and restored high glucose-impaired vasodilation in rat aorta. This study demonstrated that hispidulin ameliorated high glucose-mediated endothelial dysfunction via inhibiting PKCβII-associated NLRP3 inflammasome activation and NF-κB signaling. Besides, these findings indicate the beneficial effects of hispidulin on the improvement of endothelial dysfunction and explain its potential application in the prevention and treatment of diabetic vascular complications.

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... That is the major characteristic compound from Eriocaulon cinereum R.Br with iristectorigenin A (12) and irigenin(13) [6]. Hispidulin reported having activities inhibits of ROS production and improve the functions of mitochondria [7]. ROS reported can be a trigger become cancer. ...
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Endothelial dysfunction is tightly associated with cardiovascular complications in diabetic patients. This study aims to investigate the effects of mangiferin on the regulation of endothelial homeostasis under endoplasmic reticulum stress (ER stress) conditions.ResultsHigh glucose (25 mM) exposure induced ER stress and promoted ROS production in endothelial cells. Mangiferin effectively inhibited ER stress-associated oxidative stress by attenuating IRE1α phosphorylation and reducing ROS production. In response to ER stress, thioredoxin-interacting protein (TXNIP) expression increased, followed by NLRP3 inflammasome activation and increased IL-1β secretion. Mangiferin treatment attenuated the expressions of TXNIP and NLRP3 and reduced IL-1β and IL-6 production, demonstrating its inhibitory effects on TXNIP/NLRP3 inflammasome activation. NLRP3 inflammasome activation is responsible for mitochondrial cell death. Mangiferin restored the loss of the mitochondrial membrane potential (Δψm) and inhibited caspase-3 activity, and thereby protected cells from high glucose-induced apoptosis. Moreover, mangiferin inhibited ET-1 secretion and restored the loss of NO production when cells exposed to high glucose. Mangiferin enhanced AMPK phosphorylation and AMPK inhibitor compound C diminished its beneficial effects, indicating the potential role of AMPK in its action.Conclusion Our work showed the beneficial effects of mangiferin on the improvement of endothelial homeostasis and elucidated the molecular pathway through which mangiferin ameliorated endothelial dysfunction by inhibition of ER stress-associated TXNIP/NLRP3 inflammasome activation in endothelial cells.SignificanceThese findings demonstrated the beneficial effects of mangiferin on the regulation of endothelial homeostasis and indicated its potential application in the management of diabetic cardiovascular complications.
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Inflammatory bowel disease (IBD) affects millions of people worldwide. Although the etiology of this disease is uncertain, accumulating evidence indicates a key role for the activated mucosal immune system. In the present study, we examined the effects of the natural compound fraxinellone on dextran sulfate sodium (DSS)-induced colitis in mice, an animal model that mimics IBD. Treatment with fraxinellone significantly reduced weight loss and diarrhea in mice and alleviated the macroscopic and microscopic signs of the disease. In addition, the activities of myeloperoxidase and alkaline phosphatase were markedly suppressed, while the levels of glutathione were increased in colitis tissues following fraxinellone treatment. This compound also decreased the colonic levels of interleukin (IL)-1β, IL-6, IL-18 and tumor necrosis factor (TNF)-α in a concentration-dependent manner. These effects of fraxinellone in mice with experimental colitis were attributed to its inhibition of CD11b(+) macrophage infiltration. The mRNA levels of macrophage-related molecules in the colon, including intercellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2), were also markedly inhibited following fraxinellone treatment. The results from in vitro assays showed that fraxinellone significantly reduced lipopolysaccharide (LPS)-induced production of nitric oxide (NO), IL-1β and IL-18 as well as the activity of iNOS in both THP-1 cells and mouse primary peritoneal macrophages. The mechanisms responsible for these effects were attributed to the inhibitory role of fraxinellone in NF-κB signaling and NLRP3 inflammasome activation. Overall, our results support fraxinellone as a novel drug candidate in the treatment of colonic inflammation. Copyright © 2014 Elsevier Inc. All rights reserved.
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Objective Metformin and glucagon like peptide-1 (GLP-1) prevent diabetic cardiovascular complications and atherosclerosis. However, the direct effects on hyperglycemia-induced oxidative stress in endothelial cells are not fully understood. Thus, we aimed to evaluate the effects of metformin and a GLP-1 analog, liraglutide on high glucose-induced oxidative stress.Methods Production of reactive oxygen species (ROS), activation of protein kinase C (PKC) and NAD(P)H oxidase, and changes in signaling molecules in response to high glucose exposure were evaluated in human aortic endothelial cells with and without treatment of metformin and liraglutide, alone or in combination. PKC-NAD(P)H oxidase pathway was assessed by translocation of GFP-fused PKCβ2 isoform and GFP-fused p47phox, a regulatory subunit of NAD(P)H oxidase, in addition to endogenous PKC phosphorylation and NAD(P)H oxidase activity.ResultsHigh glucose-induced ROS overproduction was blunted by metformin or liraglutide treatment, with a further decrease by a combination of these drugs. Exposure to high glucose caused PKCβ2 translocation and a time-dependent phosphorylation of endogenous PKC but failed to induce its translocation and phosphorylation in the cells treated with metformin and liraglutide. Furthermore, both drugs inhibited p47phox translocation and NAD(P)H oxidase activation, and prevented the high glucose-induced changes in intracellulalr diacylglycerol (DAG) level and phosphorylation of AMP-activated protein kinase (AMPK). A combination of these drugs further enhanced all of these effects.Conclusions Metformin and liraglutide ameliorate high glucose-induced oxidative stress by inhibiting PKC-NAD(P)H oxidase pathway. A combination of these two drugs provides augmented protective effects, suggesting the clinical usefulness in prevention of diabetic vascular complications.
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Aims: Endothelial cells play a pivotal role in vascular intimal inflammation during cardiovascular diseases. The chemerin/ChemR23 system in endothelial cells is one of physiological mechanisms that regulate inflammatory responses. Our previous studies indicated that stimulation of non-neuronal muscarinic receptor (NNMR) improved endothelial dysfunction. However, the relationship between the chemerin/ChemR23 signaling axis and NNMR in endothelial cell is poorly understood. Here, we first investigated whether the modulation of chemerin/ChemR23 signaling axis is involved in NNMR-mediated endothelial protection. Main methods: Cultured rat aortic endothelial cells (RAECs) were used. The ChemR23 protein expression and chemerin secretion were measured using Western blot analysis. The gene expression level of ChemR23 was examined with reverse transcriptase PCR (RT-PCR). The production of nitric oxide (NO) was determined by a nitrate reductase assay kit. Key findings: A sharp decline of chemerin secretion and ChemR23 protein/gene expression was observed in RAECs after exposed to homocysteine at concentration of 0.5 mmol/L. Arecoline (10 μmol/L) pretreatment increased ChemR23 protein expression as well as mRNA expression, and enhanced the secretion of chemerin. Arecoline could also reverse the decreased ChemR23 mRNA expression induced by uric acid, high glucose, or oxidized low-density lipoprotein. Furthermore, the modulation of arecoline on chemerin/ChemR23 signaling axis was absolutely abolished in the presence of the nonselective muscarinic receptors antagonist atropine 1 μmol/L. Additionally, arecoline improved endothelial dysfunction by increasing the reduced NO production induced by uric acid, which was blocked by anti-ChemR23 antibody. Significance: The chemerin/ChemR23 signaling axis participates in NNMR-mediated protection against endothelial dysfunction in cardiovascular system.
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Recent clinical and experimental evidence suggests that endoplasmic reticulum (ER) stress contributes to the life-and-death decisions of β cells during the progression of type 1 and type 2 diabetes. Although crosstalk between inflammation and ER stress has been suggested to play a significant role in β cell dysfunction and death, a key molecule connecting ER stress to inflammation has not been identified. Here we report that thioredoxin-interacting protein (TXNIP) is a critical signaling node that links ER stress and inflammation. TXNIP is induced by ER stress through the PERK and IRE1 pathways, induces IL-1β mRNA transcription, activates IL-1β production by the NLRP3 inflammasome, and mediates ER stress-mediated β cell death. Collectively, our results suggest that TXNIP is a potential therapeutic target for diabetes and ER stress-related human diseases such as Wolfram syndrome.
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We investigated whether diosgenin, a widely used steroidal sapogenin, exerted protection against palmitate (PA)-induced inflammation and insulin resistance in the endothelium. Human umbilical vein endothelial cells (HUVECs) were pretreated with diosgenin for 30 min, and then incubated with 100 μmol/L PA for 30 min or 24 h with or without insulin. IKKβ, p65 phosphorylation, serine phosphorylation of insulin receptor substrate-1 (IRS-1) at S307, tyrosine phosphorylation of IRS-1, Akt and eNOS activation were determined by Western blot analysis. Levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), endothelin-1 (ET-1) and plasminogen activator inhibitor-1 (PAI-1) were measured with ELISA Kits. Intracellular nitric oxide (NO) was viewed with fluorescence microscopy. Effects of diosgenin on insulin-mediated vasodilation was investigated in the isolated rat aortic rings. Diosgenin significantly reduced PA-enhanced IKKβ and NF-κB phosphorylation with inhibition of TNF-α and IL-6 production in endothelial cells at the concentrations of 0.1, 1 and 10 μmol/L, well demonstrating its anti-inflammatory activity in an IKKβ/NF-κB-dependent fashion. Meanwhile, diosgenin attenuated PA-induced serine phosphorylation (S307) of IRS-1 and restored IRS-1 tyrosine phosphorylation in response to insulin. The beneficial modulation of serine/tyrosine phosphorylation of IRS-1 by diosgenin contributed to the improvement of insulin signaling along PI3K/Akt/eNOS pathways and thereby increased insulin-mediated NO production. Salicylate (5 mmol/L), an inhibitor of IKKβ, showed similar activities as diosgenin. Diosgenin also remarkably inhibited ET-1 and PAI-1 production in the endothelial cells, and markedly restored the loss of insulin-mediated vasodilation in the presence of PA. The above-mentioned evidence suggests that diosgenin ameliorated endothelial dysfunction involved in insulin resistance through an IKKβ/IRS-1-dependent manner, shows potential application in the treatment for the cardiovascular diseases including atherosclerosis.
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Hyperglycemic memory may explain why intensive glucose control has failed to improve cardiovascular outcomes in patients with diabetes. Indeed, hyperglycemia promotes vascular dysfunction even after glucose normalization. However, the molecular mechanisms of this phenomenon remain to be elucidated. The present study investigated the role of mitochondrial adaptor p66(Shc) in this setting. In human aortic endothelial cells (HAECs) exposed to high glucose and aortas of diabetic mice, activation of p66(Shc) by protein kinase C βII (PKCβII) persisted after returning to normoglycemia. Persistent p66(Shc) upregulation and mitochondrial translocation were associated with continued reactive oxygen species (ROS) production, reduced nitric oxide bioavailability, and apoptosis. We show that p66(Shc) gene overexpression was epigenetically regulated by promoter CpG hypomethylation and general control nonderepressible 5-induced histone 3 acetylation. Furthermore, p66(Shc)-derived ROS production maintained PKCβII upregulation and PKCβII-dependent inhibitory phosphorylation of endothelial nitric oxide synthase at Thr-495, leading to a detrimental vicious cycle despite restoration of normoglycemia. Moreover, p66(Shc) activation accounted for the persistent elevation of the advanced glycated end product precursor methylglyoxal. In vitro and in vivo gene silencing of p66(Shc), performed at the time of glucose normalization, blunted ROS production, restored endothelium-dependent vasorelaxation, and attenuated apoptosis by limiting cytochrome c release, caspase 3 activity, and cleavage of poly (ADP-ribose) polymerase. p66(Shc) is the key effector driving vascular hyperglycemic memory in diabetes. Our study provides molecular insights for the progression of diabetic vascular complications despite glycemic control and may help to define novel therapeutic targets.
Article
Oxidative stress and glucose affect the expression of various genes that contribute to both reactive oxygen species generation and antioxidant systems. However, systemic alteration of oxidative stress-related gene expression in normal brains and in brains with a high-glucose status after ischemic-reperfusion has not been explored. Using a polymerase chain reaction array system, we demonstrate that thioredoxin-interacting protein (Txnip) is induced by both oxidative stress and glucose. We found that Txnip mRNA is induced by ischemic-reperfusion injury and that Txnip is located in the cytoplasm of neurons. Moreover, in vitro oxygen-glucose deprivation (OGD) and subsequent reoxygenation without glucose and in vivo administration of 3-nitropropionic acid also promoted an increase in Txnip in a time-dependent manner, indicating that oxidative stress without glucose can induce Txnip expression in the brain. However, calcium channel blockers inhibit induction of Txnip after OGD and reoxygenation. Using the polymerase chain reaction array with ischemic and hyperglycemic-ischemic samples, we confirmed that enhanced expression of Txnip was observed in hyperglycemic-ischemic brains after middle cerebral artery occlusion. Finally, transfection of Txnip small interfering RNA into primary neurons reduced lactate dehydrogenase release after OGD and reoxygenation. This is the first report showing that Txnip expression is induced in neurons after oxidative or glucose stress under either ischemic or hyperglycemic-ischemic conditions, and that Txnip is proapoptotic under these conditions.
Article
Hyperglycemia, via peroxynitrite-mediated endothelial nitric oxide synthase (eNOS) enzymatic uncoupling, induced endothelial dysfunction. Propofol has been reported to improve high glucose-induced endothelial dysfunction. However, its mechanisms of action remain unclear. We hypothesized that propofol could improve hyperglycemia-induced endothelial dysfunction by decreasing the peroxynitrite level and thus restoring eNOS coupling. At the end of 3 days of incubation in medium with 30 mM glucose, human umbilical vein endothelial cells were treated with different concentrations (0.2, 1, 5, and 25 μM) of propofol for different times (0.5, 1, 2, and 4 hours). In parallel experiments, cells were cultured in 5 mM glucose for 3 days as a control. Nitric oxide (NO) production was measured with a nitrate reductase assay. Superoxide anion (O(2)(·-)) accumulation was measured with the reduction of ferricytochrome c and dihydroethidine fluorescence assay. The treatment that had maximal effect on 30 mM glucose-induced NO production and O(2)(·-) accumulation was applied in the following studies to examine the underlying signaling pathways. eNOS total protein, eNOS dimer and monomer expression, eNOS phosphorylation at Ser(1177), inducible NO synthase total protein, inducible NO synthase dimer and monomer expression, peroxynitrite, and guanosine triphosphate cyclohydrolase I expression were measured by Western blot. Tetrahydrobiopterin (BH(4)) level was measured with liquid chromatography-mass spectrometry. Compared with 5 mM glucose treatment, 30 mM glucose significantly decreased NO production by 60% (P < 0.001) and increased O(2)(·-) accumulation by 175% (P = 0.0026), which were both attenuated by propofol in a concentration- and time-dependent manner. Compared with 5 mM glucose treatment, total eNOS protein expression was increased by 30 mM glucose (P < 0.001), whereas the ratio of eNOS dimer/monomer (P = 0.0001) and eNOS phosphorylation (P < 0.001) were decreased by 30 mM glucose. Propofol did not affect 30 mM glucose-induced total eNOS protein expression, but restored the ratio of eNOS dimer/monomer (P = 0.0005) and increased eNOS phosphorylation (P < 0.001). 30 mM glucose-induced O(2)(·-) accumulation was inhibited by the eNOS inhibitor hydrochloride. Furthermore, compared with 5 mM glucose treatment, 30 mM glucose decreased the BH(4) level (P = 0.0001) and guanosine triphosphate cyclohydrolase I expression (P < 0.001), whereas it increased peroxynitrite level (P = 0.0003), which could all be reversed by propofol (P = 0.0045, P < 0.001, P = 0.0001 vs 30 mM glucose treatment, respectively). Propofol has beneficial effects on 30 mM glucose-induced NO reduction and O(2)(·-) accumulation in human umbilical vein endothelial cells. This may be mediated through inhibiting peroxynitrite-mediated BH(4) reduction, and restoring eNOS coupling.
Article
Hispidulin, an active component from Artemisia vestita, a traditional Tibetan medicinal plant, has been shown to possess anti-inflammatory and anti-oxidative activities. However, the functional role of hispidulin on tumor growth and angiogenesis has not been elucidated. We found that hispidulin significantly inhibited human pancreatic tumor growth in xenograft mice when s.c. treated at a dosage of 20 mg/kg daily, and this effect was accompanied with a potent inhibition on angiogenesis. When examining the cytotoxicity of hispidulin on HUVECs and pancreatic cancer cells in vitro, we found that HUVECs were more susceptible to the treatment, suggesting angiogenesis might be the primary target of hispidulin. Our results further showed that hispidulin inhibited vascular endothelial growth factor (VEGF)-induced cell migration, invasion, and capillary-like structure formation of HUVECs in a dose-dependent manner. In ex vivo and in vivo angiogenesis assays, we showed that hispidulin suppressed VEGF-induced microvessel sprouting of rat aortic rings and corneal neovascularization in C57/BL6 mice. To understand the underlying molecular basis, we next examined the effects of hispidulin on different molecular components in treated HUVECs, and found that hispidulin suppressed the VEGF-triggered activation of VEGF receptor 2, PI3K, Akt, mTOR, and ribosomal protein S6 kinase, but had little effect on focal adhesion kinase or extracellular signal-regulated kinase at an effective concentration. Taken together, our results indicate that hispidulin targets the VEGF receptor 2-mediated PI3K/Akt/mTOR signaling pathway in endothelial cells, leading to the suppression of pancreatic tumor growth and angiogenesis.
Article
Glioblastoma multiforme (GBM) is the most common and lethal type of primary brain tumor. Despite recent therapeutic advances in other cancers, the treatment of GBM remains ineffective and essentially palliative. The current focus lies in the finding of components that activate the AMP-activated protein kinase (AMPK), one key enzyme thought to be activated during the caloric restriction (CR). In the present study, we found that treatment of hispidulin, a flavone isolated from Saussurea involucrate Kar. et Kir., resulted in dose-dependent inhibition of GBM cellular proliferation. Interestingly, we show that hispidulin activated AMPK in GBM cells. The activation of AMPK suppressed downstream substrates, such as the mammalian target of rapamycin (mTOR) and eukaryotic initiation factor 4E-binding protein-1 (4E-BP1), and resulted in a general decrease in mRNA translation. Moreover, hispidulin-activated AMPK decreases the activity and/or expression of lipogenic enzymes, such as fatty acid synthase (FASN) and acetyl-CoA carboxylase (ACC). Furthermore, hispidulin blocked the progression of the cell cycle at the G1 phase and induced apoptosis by inducing p53 expression and further upregulating p21 expression in GBM cells. On the basis of these results, we demonstrated that hispidulin has the potential to be a chemopreventive and therapeutic agent against human GBM.
Article
The NLRP3 inflammasome has a major role in regulating innate immunity. Deregulated inflammasome activity is associated with several inflammatory diseases, yet little is known about the signaling pathways that lead to its activation. Here we show that NLRP3 interacted with thioredoxin (TRX)-interacting protein (TXNIP), a protein linked to insulin resistance. Inflammasome activators such as uric acid crystals induced the dissociation of TXNIP from thioredoxin in a reactive oxygen species (ROS)-sensitive manner and allowed it to bind NLRP3. TXNIP deficiency impaired activation of the NLRP3 inflammasome and subsequent secretion of interleukin 1beta (IL-1beta). Akin to Txnip(-/-) mice, Nlrp3(-/-) mice showed improved glucose tolerance and insulin sensitivity. The participation of TXNIP in the NLRP3 inflammasome activation may provide a mechanistic link to the observed involvement of IL-1beta in the pathogenesis of type 2 diabetes.
Article
Although it is now well established that the deleterious effects of chronic hyperglycaemia (i.e., glucose toxicity) play an important role in the progressive impairment of insulin secretion and sensitivity, the two major actors of the pathogenesis of type 2 diabetes mellitus, the precise biochemical and molecular mechanisms responsible for the defects induced by glucose toxicity still remain to be defined. here we will briefly report on convincing evidence that glucose toxicity acts through oxidative stress, modifications in the exosamine pathway, protein kinase C and others. After inducing or contributing to the genesis of type 2 diabetes, these same mechanisms are considered responsible for the appearance and worsening of diabetic specific microvascular complications, while its role in increasing the risk of cardiovascular diseases is less clear. Recent intervention studies (ADVANCE, ACCORD, VADT), conducted to evaluate the effects of strict glycaemic control, apparently failed to demonstrate an effect of glucose toxicity on cardiovascular diseases, at least in secondary prevention or when diabetes is present for a prolonged time. The re-examination, 20 years later, of the population studied in the UKPDS study, however, clearly demonstrated that the earliest is the strict glycaemic control reached, the lowest is the incidence of cardiovascular diseases observed, including myocardial infarction. The acquaintance of the role of glucose toxicity should strongly influence the usual therapeutic choices and glycaemic targets where the reduced or absent risk of hypoglycaemia, durability of action, and data on prolonged safety should be the preferred characteristics of the drug of choice in the treatment of type 2 diabetes mellitus.
Article
The central therapeutic problem in diabetes mellitus is prevention and treatment of the chronic vascular disease associated with this disorder. Prolonged exposure to hyperglycemia is the primary factor associated with the development of diabetes-specific microvascular disease, and the relationship between deranged glucose metabolism and arterial disease is complicated by many other factors that influence atherogenesis in nondiabetics. Until relatively recently, knowledge about diabetic vascular disease was limited mainly to clinical description. New information about abnormal vascular physiology, ultrastructure, biochemistry, cell biology, and molecular biology now makes it possible to understand in an integrated fashion the major specific mechanisms by which hyperglycemia damages diabetic vessels. Continued progress in this area will further optimize the development of safe and effective drugs for the treatment of diabetic vascular disease.
Article
In addition to beta-sitosterol and alpha-amyrin detected in all the investigated species, the extract of the aerial parts of Artemisia giraldii var. giraldii gave stigmasterol, daucosterol, sesamine, luteolin, eupafolin, hispidulin, eupatilin, belamcanidin, pinitol, artemin, ridentin, and a new antifungal monoterpene (named santolinylol) while that of the aerial parts of A. mongolica afforded sesamine, eupafolin, eupatilin, matricarin, and a new germacranolide (3-oxo-11 alpha H-germacra-1(10)E,4Z-dien-12,6 alpha-olide), and that of the aerial parts of A. vestita yielded stigmasterol, daucosterol, umbelliferone, scopolin, scoparone, and isoscopoletin-O-glucoside. Pinitol, first reisolated from Artemisia genus, was shown to inhibit the growth of the human pathogenic fungi Candida albicans, Aspergillus flavus, A. niger, Geotrichun candidum, Trichophyton rubrum, and Epidermophyton floccosum. Umbelliferone was also active against Candida tropicalis, A. flavus, G. candidum, T. rubrum, and E. floccosum. The flavones hispidulin and belamcanidin were almost equally inhibitory to the growth of A. flavus, G. candidum, T. rubrum, and E. floccosum, and santolinylol to C. albicans, A. flavus, A. niger, G. candidum, T. rubrum, and E. floccosum. In addition, ridentin was active against the growth of the plant pathogenic fungus Cladosporium cucumerinum.
Article
Generation of Interleukin (IL)-1beta via cleavage of its proform requires the activity of caspase-1 (and caspase-11 in mice), but the mechanism involved in the activation of the proinflammatory caspases remains elusive. Here we report the identification of a caspase-activating complex that we call the inflammasome. The inflammasome comprises caspase-1, caspase-5, Pycard/Asc, and NALP1, a Pyrin domain-containing protein sharing structural homology with NODs. Using a cell-free system, we show that proinflammatory caspase activation and proIL-1beta processing is lost upon prior immunodepletion of Pycard. Moreover, expression of a dominant-negative form of Pycard in differentiated THP-1 cells blocks proIL-1beta maturation and activation of inflammatory caspases induced by LPS in vivo. Thus, the inflammasome constitutes an important arm of the innate immunity.
Article
The metabolic syndrome is a highly prevalent multifaceted clinical entity produced through the interaction of genetic, hormonal, and lifestyle factors. A distinctive constellation of abnormalities precedes and predicts the accelerated development of inflammation and coagulation represent emerging risk contributors associated with obesity and insulin resistance, central components of the metabolic syndrome, which act in concert with traditional abnormalities to increase cardiovascular risk. The initiation and progression of atherosclerosis may have its origins in impaired endothelial function that can be detected at the earliest stages of development of the syndrome. The basic elements of the metabolic syndrome and accelerated phase of atherogenesis are often silent partners that present many years before the onset of type 2 diabetes mellitus. The ability to detect and monitor subclinical vascular disease, as a reflection of the multiple factors that contribute to impair arterial wall integrity, holds potential to further refine cardiovascular risk stratification. Noninvasive assessment of vascular health may also aid the clinical decision-making process by guiding therapeutic interventions to optimize vascular protection in the metabolic syndrome.
Article
The functional characterization of hispidulin (4′,5,7-trihydroxy-6-methoxyflavone), a potent benzodiazepine (BZD) receptor ligand, was initiated to determine its potential as a modulator of central nervous system activity. After chemical synthesis, hispidulin was investigated at recombinant GABAA/BZD receptors expressed by Xenopus laevis oocytes. Concentrations of 50 nM and higher stimulated the GABA-induced chloride currents at tested receptor subtypes (α1−3,5,6β2γ2S) indicating positive allosteric properties. Maximal stimulation at α1β2γ2S was observed with 10 μM hispidulin. In contrast to diazepam, hispidulin modulated the α6β2γ2S-GABAA receptor subtype. When fed to seizure-prone Mongolian gerbils (Meriones unguiculatus) in a model of epilepsy, hispidulin (10 mg kg−1 body weight (BW) per day) and diazepam (2 mg kg−1 BW per day) markedly reduced the number of animals suffering from seizures after 7 days of treatment (30 and 25% of animals in the respective treatment groups, vs 80% in the vehicle group). Permeability across the blood–brain barrier for the chemically synthesized, 14C-labelled hispidulin was confirmed by a rat in situ perfusion model. With an uptake rate (Kin) of 1.14 ml min−1 g−1, measurements approached the values obtained with highly penetrating compounds such as diazepam. Experiments with Caco-2 cells predict that orally administered hispidulin enters circulation in its intact form. At a concentration of 30 μM, the flavone crossed the monolayer without degradation as verified by the absence of glucuronidated metabolites. British Journal of Pharmacology (2004) 142, 811–820. doi:10.1038/sj.bjp.0705828
Article
Free fatty acids (FFA) are commonly elevated in diabetes and obesity and have been shown to impair nitric oxide (NO) production by endothelial cells. However, the signaling pathways responsible for FFA impairment of NO production in endothelial cells have not been characterized. Insulin receptor substrate-1 (IRS-1) regulation is critical for activation of endothelial nitric oxide synthase (eNOS) in response to stimulation by insulin or fluid shear stress. We demonstrate that insulin-mediated tyrosine phosphorylation of IRS-1 and serine phosphorylation of Akt, eNOS, and NO production are significantly inhibited by treatment of bovine aortic endothelial cells with 100 micromol/L FFA composed of palmitic acid for 3 hours before stimulation with 100 nM insulin. This FFA preparation also increases, in a dose-dependent manner, IKKbeta activity, which regulates activation of NF- kappaB, a transcriptional factor associated with inflammation. Similarly, elevation of other common FFA such as oleic and linoleic acid also induce IKKbeta activation and inhibit insulin-mediated eNOS activation. Overexpression of a kinase inactive form of IKKbeta blocks the ability of FFA to inhibit insulin-dependent NO production, whereas overexpression of wild-type IKKbeta recapitulates the effect of FFA on insulin-dependent NO production. Elevated levels of common FFA found in human serum activate IKKbeta in endothelial cells leading to reduced NO production, and thus may serve to link pathways involved in inflammation and endothelial dysfunction.
Article
Endothelial dysfunction contributes to cardiovascular diseases, including hypertension, atherosclerosis, and coronary artery disease, which are also characterized by insulin resistance. Insulin resistance is a hallmark of metabolic disorders, including type 2 diabetes mellitus and obesity, which are also characterized by endothelial dysfunction. Metabolic actions of insulin to promote glucose disposal are augmented by vascular actions of insulin in endothelium to stimulate production of the vasodilator nitric oxide (NO). Indeed, NO-dependent increases in blood flow to skeletal muscle account for 25% to 40% of the increase in glucose uptake in response to insulin stimulation. Phosphatidylinositol 3-kinase-dependent insulin-signaling pathways in endothelium related to production of NO share striking similarities with metabolic pathways in skeletal muscle that promote glucose uptake. Other distinct nonmetabolic branches of insulin-signaling pathways regulate secretion of the vasoconstrictor endothelin-1 in endothelium. Metabolic insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase-dependent signaling, which in endothelium may cause imbalance between production of NO and secretion of endothelin-1, leading to decreased blood flow, which worsens insulin resistance. Therapeutic interventions in animal models and human studies have demonstrated that improving endothelial function ameliorates insulin resistance, whereas improving insulin sensitivity ameliorates endothelial dysfunction. Taken together, cellular, physiological, clinical, and epidemiological studies strongly support a reciprocal relationship between endothelial dysfunction and insulin resistance that helps to link cardiovascular and metabolic diseases. In the present review, we discuss pathophysiological mechanisms, including inflammatory processes, that couple endothelial dysfunction with insulin resistance and emphasize important therapeutic implications.
Article
Interleukin-2 (IL-2) can modulate cardiovascular functions, but the effect of IL-2 on vascular endothelial function in diabetes is not known. We hypothesized that IL-2 may attenuate endothelial dysfunction induced by high glucose or diabetes. So the aim of this study was to investigate the effect of IL-2 on endothelium-response of aortas incubated with high glucose or from diabetic rats and its underlying mechanism. Acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR), sodium nitroprusside (SNP)-induced endothelium-independent relaxation (EIR), superoxide dismutase (SOD) and nitric oxide synthase (NOS) were measured in aortas isolated from non-diabetic rats and exposed to a high glucose concentration and from streptozotocin-induced diabetic rats. Incubation of aortic rings with high glucose (44 mM) for 4 h resulted in a significant inhibition of EDR, but had no effects on EIR. Co-incubation with IL-2 for 40 min prevented the inhibition of EDR caused by high glucose in a concentration-dependent manner. Similarly, high glucose decreased SOD and NOS activity in aortic tissue. IL-2 (1000 U/ml) significantly attenuated the decrease of SOD and NOS activity caused by high glucose. In addition, EDR declined along with the decrease of serum NO level in aortas from STZ-induced diabetic rats. Injection of IL-2 (5000 and 50,000 U kg(-1) d(-1), s.c.) for 5 weeks prevented the inhibition of EDR and the decrease of serum NO levels caused by diabetes. IL-2 significantly ameliorated the endothelial dysfunction induced by hyperglycemia, in which the activation of the NO pathway and SOD may be involved.