Differential activation of heme oxygenase-1 by chalcones and rosolic acid in endothelial cells

Rosolic acid as a novel activator of the Nrf2/ARE pathway in arsenic-induced male reproductive toxicity: An in silico study

Male reproductive toxicity as a result of arsenic exposure is linked with oxidative stress and excessive generation of reactive oxygen species (ROS). It leads to an imbalance between ROS production and antioxidant defense mechanisms ultimately resulting in male infertility. The nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) is a transcription factor that responds to cellular stressors controlling the oxidative state, mitochondrial dysfunction, inflammation, and proteostasis. This study aims to investigate the potential of Rosolic acid (ROA) to act as a novel Nrf2 activator by mitigating oxidative stress to combat arsenic-induced male reproductive toxicity. The protein and ligands were prepared in the BIOVIA Discovery Studio, followed by protein-ligand docking using auto dock vina integrated with the PyRx-Virtual Screening Tool. Then the ADME properties were analyzed using the SwissADME tool to get a clear idea about the physicochemical properties, lipophilicity, water solubility, pharmacokinetics, and drug likeliness of ROA. It was followed by molecular dynamics simulation (MDS) studies using GROMACS. The 3D and 2D interaction maps revealed the interactions of Keap 1 with ROA. Keap1-ROA complex was found to have a binding energy of -7.8 kcal/mol. ROA showed 0 violations for Lipinski and 0 alerts each for PAINS and Brenk and a bioavailability score of 0.55. The BOILED-Egg representation showcases that ROA is predicted as passively crossing the blood-brain barrier (BBB). The MDS described 2FLU-ROA as a stable system. This work portrays that ROA can be a potent Nrf2 activator by exhibiting an inhibitory activity against the Keap1 protein and thus mitigating oxidative stress in arsenic-induced male reproductive toxicity.

Therapeutic Potential of Small Molecules Targeting Oxidative Stress in the Treatment of Chronic Obstructive Pulmonary Disease (COPD): A Comprehensive Review

Chronic obstructive pulmonary disease (COPD) is an increasing and major global health problem. COPD is also the third leading cause of death worldwide. Oxidative stress (OS) takes place when various reactive species and free radicals swamp the availability of antioxidants. Reactive nitrogen species, reactive oxygen species (ROS), and their counterpart antioxidants are important for host defense and physiological signaling pathways, and the development and progression of inflammation. During the disturbance of their normal steady states, imbalances between antioxidants and oxidants might induce pathological mechanisms that can further result in many non-respiratory and respiratory diseases including COPD. ROS might be either endogenously produced in response to various infectious pathogens including fungi, viruses, or bacteria, or exogenously generated from several inhaled particulate or gaseous agents including some occupational dust, cigarette smoke (CS), and air pollutants. Therefore, targeting systemic and local OS with therapeutic agents such as small molecules that can increase endogenous antioxidants or regulate the redox/antioxidants system can be an effective approach in treating COPD. Various thiol-based antioxidants including fudosteine, erdosteine, carbocysteine, and N-acetyl-L-cysteine have the capacity to increase thiol content in the lungs. Many synthetic molecules including inhibitors/blockers of protein carbonylation and lipid peroxidation, catalytic antioxidants including superoxide dismutase mimetics, and spin trapping agents can effectively modulate CS-induced OS and its resulting cellular alterations. Several clinical and pre-clinical studies have demonstrated that these antioxidants have the capacity to decrease OS and affect the expressions of several pro-inflammatory genes and genes that are involved with redox and glutathione biosynthesis. In this article, we have summarized the role of OS in COPD pathogenesis. Furthermore, we have particularly focused on the therapeutic potential of numerous chemicals, particularly antioxidants in the treatment of COPD.

Synthesis of chitosan-based polymeric dyes as colorimetric pH-sensing materials: Potential for food and biomedical applications

pH-sensitive polymeric dyes were fabricated by grafting phenol red (PR) and rosolic acid (RA) onto chitosan (CS) by a facile method. Successful grafting was confirmed by ¹H NMR, FT-IR, UV-vis, XRD, and elemental analysis. The polymeric dyes exhibited no cell toxicity. The colorimetric pH-sensing films were fabricated by blending the polymeric dyes with CS to establish their pH-dependent color properties. The film color changed in the pH range 4-10, which may indicate food spoilage or wound status. Covalently grafting of polymeric dyes in the films led to excellent color stability, leaching resistance, and reversibility. Hence, the synthesized polymeric dyes had potential as pH-indicative colorants for food and biomedical fields.

Pharmacological Activation of Nrf2 by Rosolic Acid Attenuates Endoplasmic Reticulum Stress in Endothelial Cells

Endoplasmic reticulum (ER) plays a key role in the folding, modification, and trafficking of proteins. When the homeostasis of the ER is disturbed, un/misfolded proteins accumulate in the ER which leads to ER stress. Sustained ER stress results in apoptosis, which is associated with various diseases. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a major transcription factor in redox homeostasis by regulating various genes associated with detoxification and cell-protective mechanisms. We found that Rosolic acid (RA) treatment dose-dependently activates Nrf2 in endothelial cells using the enzyme fragment complementation assay. The cytoprotective role of RA against ER stress-induced endothelial apoptosis and its molecular mechanism was explored in the present study. The Nrf2 and its target genes, as well as ER stress marker expressions, were measured by qPCR in ER stress-exposed endothelial cells. The contribution of Nrf2 in RA-mediated defense mechanism in endothelial cells was established by knockout studies using Nrf2-CRISPR/Cas9. The treatment with RA to ER stress-induced endothelial cells exhibited activation of Nrf2, as demonstrated by Nrf2 translocation and reduction of ER stress markers. We found that the Nrf2 knockout sensitized the endothelial cells against ER stress, and further, RA failed to mediate its cytoprotective effect. Proteomic studies using LC-MS/MS revealed that among the 1370 proteins detected, we found 296 differentially regulated proteins in ER stress-induced endothelial cells, and RA administration ameliorated 71 proteins towards the control levels. Of note, the ER stress in endothelial cells was attenuated by the treatment with the RA, suggesting the role of the Nrf2 activator in the pathological conditions of ER stress-associated diseases.

Effect of Rosolic acid on endothelial dysfunction under ER stress in pancreatic microenvironment

Endothelial cell (EC) dysfunction is the underlying cause for the development of several pathologies, and the interdependency between the pancreatic β-cells and ECs has been established in the pathophysiology of diabetes. ECs release several factors that govern the expression of genes involved in the proliferation, physiology, and survival of the β-cells. Of the known factors that collapse this intricately balanced system, endothelial dysfunction is the crucial condition that manifests as the causative factor for micro and macrovascular diseases. Our earlier studies demonstrated that activation of nuclear factor erythroid-related factor (Nrf2) renders protection to the ECs experiencing ER stress. In this study, using a co-culture system, the crosstalk between pancreatic cells under ER stress and ECs and the effect of a novel Nrf2 activator Rosolic Acid (RA), on the crosstalk was investigated. ECs pre-treated with different concentrations RA and co-cultured with thapsigargin-induced ER stressed pancreatic β-cells showed increased levels of Nrf2 and its downstream targets such as heme oxygenase-1 (HO-1) and NADPH-quinone oxidoreductase-1 (NQO-1), and reduction of ER stress evinced by the decreased levels of glucose-regulated protein (GRP) 78 and C/ERB homologous protein (CHOP). The sensitization of ECs using RA, offered protection to pancreatic cells against ER stress as displayed by increased intracellular insulin and upregulated expression of cell survival and proliferative genes BCl2 and PDX-1. In addition, RA treatment resulted in elevated levels of various angiogenic factors, while inflammatory (TNF-α and IL-1β) and apoptotic markers (CXCL10 and CCL2) decreased. RA treatment normalized the levels of 115 proteins of the 277, which were differentially regulated as revealed by proteomic studies of ER stressed pancreatic β-cells in co-culture conditions. These findings clearly indicate the role of small molecule activators of Nrf2 not only in restoring the functioning of pancreatic cells but also in increasing the cell mass. Further, the study impinges on the strategies that can be developed to balance the pancreatic microenvironment, leading to the restoration of β-cell mass and their normophysiology in diabetic patients.

Heme Oxgenase-1, a Cardinal Modulator of Regulated Cell Death and Inflammation

Heme oxygenase catalyzes the rate-limiting step in heme degradation in order to generate biliverdin, carbon monoxide (CO), and iron. The inducible form of the enzyme, heme oxygenase-1 (HO-1), exerts a central role in cellular protection. The substrate, heme, is a potent pro-oxidant that can accelerate inflammatory injury and promote cell death. HO-1 has been implicated as a key mediator of inflammatory cell and tissue injury, as validated in preclinical models of acute lung injury and sepsis. A large body of work has also implicated HO-1 as a cytoprotective molecule against various forms of cell death, including necrosis, apoptosis and newly recognized regulated cell death (RCD) programs such as necroptosis, pyroptosis, and ferroptosis. While the antiapoptotic potential of HO-1 and its reaction product CO in apoptosis regulation has been extensively characterized, relatively fewer studies have explored the regulatory role of HO-1 in other forms of necrotic and inflammatory RCD (i.e., pyroptosis, necroptosis and ferroptosis). HO-1 may provide anti-inflammatory protection in necroptosis or pyroptosis. In contrast, in ferroptosis, HO-1 may play a pro-death role via enhancing iron release. HO-1 has also been implicated in co-regulation of autophagy, a cellular homeostatic program for catabolic recycling of proteins and organelles. While autophagy is primarily associated with cell survival, its occurrence can coincide with RCD programs. This review will summarize the roles of HO-1 and its reaction products in co-regulating RCD and autophagy programs, with its implication for both protective and detrimental tissue responses, with emphasis on how these impact HO-1 as a candidate therapeutic target in disease.

Targeting Quorum Sensing: High-Throughput Screening to Identify Novel LsrK Inhibitors

Since quorum sensing (QS) is linked to the establishment of bacterial infection, its inactivation represents one of the newest strategies to fight bacterial pathogens. LsrK is a kinase playing a key role in the processing of autoinducer-2 (AI-2), a quorum-sensing mediator in gut enteric bacteria. Inhibition of LsrK might thus impair the quorum-sensing cascade and consequently reduce bacterial pathogenicity. Aiming for the development of a target-based assay for the discovery of LsrK inhibitors, we evaluated different assay set-ups based on ATP detection and optimized an automation-compatible method for the high-throughput screening of chemical libraries. The assay was then used to perform the screening of a 2000-compound library, which provided 12 active compounds with an IC₅₀ ≤ 10 µM confirming the effectiveness and sensitivity of our assay. Follow-up studies on the positive hits led to the identification of two compounds, harpagoside and rosolic acid, active in a cell-based AI-2 QS interference assay, which are at the moment the most promising candidates for the development of a new class of antivirulence agents based on LsrK inhibition.

The winding road of the uvaretin class of natural products: from total synthesis to bioactive agent discovery

Herein, we disclose the development of a synthetic route to gain access to the uvaretin class of chalcone natural products. In this, the construction of a small library was achieved, and the collection was evaluated for cytotoxicity and other biological properties. Uvaretin (1) was accessed via a seven-step route in an overall yield of 15.1%. Within this route, the unsaturated enone variant of uvaretin (2), also a natural product, was accessed in a 16.7% yield over six steps. This route provides a nearly three-fold increase in yields of 1 and 2 in comparison to the previous synthetic route accessing them in 5.8% and 3.0% overall yields, respectively. Evaluation of 1 and 2 revealed IC₅₀ values between 2.0 and 5.1 μM in the cancerous cell lines HeLa, U937, A549, and MIA PaCa-2. Screening of the whole chalcone library set led to the discovery of over 30 compounds, within six cancerous cell lines, possessing single digit μM IC₅₀ activity as sole agents. Furthermore, multiple library members were found to possess promising potentiating properties with known chemotherapeutic agents.

A new chalcone derivative, 3-phenyl-1-(2,4,6-tris(methoxymethoxy)phenyl)prop-2-yn-1-one), inhibits phorbol ester-induced metastatic activity of colorectal cancer cells through upregulation of heme oxygenase-1

Chalcone (1,3-diphenyl-2-propen-1-one) derivatives exert anti-cancer activity by targeting key molecules that can lead to carcinogenesis. We synthesized the chalcone derivative 3-phenyl-1-(2,4,6-tris(methoxymethoxy)phenyl)prop-2-yn-1-one (KB-34) and previously reported its anti-inflammatory activity in macrophages. In this study, we examined the anti-metastatic activity of KB-34 against human colorectal cancer (CRC) cells and elucidated its underlying molecular mechanisms. KB-34 treatment significantly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced migration, as well as the invasion and proliferation of CRC cells (HT-29 and SW620). TPA-induced activation of NF-κB was also markedly suppressed by KB-34 in HT-29 cells. KB-34 suppressed the expression of matrix metalloproteinase-7 (MMP-7) at both the mRNA and protein levels in TPA-stimulated CRC cells (HT-29 and SW620). We also demonstrated that induced heme oxygenase-1 (HO-1) expression in CRC cells (HT-29 and SW620) and HO-1 is required for KB-34-mediated suppression of the expression of MMP-7 in TPA-stimulated HT-29 cells. Additionally, the cyclin-dependent kinase inhibitor p21 was significantly induced by treatment with KB-34 in CRC cells (HT-29 and SW620). Knockdown of HO-1 prevented the induction of p21 expression by KB-34 in HT-29 cells. Furthermore, we also demonstrated that 5-fluorouracil (5-FU) together with KB-34 produced a significantly greater inhibition of growth and stimulation of apoptosis of HT-29 cells than did 5-FU alone. In conclusion, KB-34 inhibits the TPA-stimulated metastatic potential of HT-29 cells by induction of HO-1 and may be a promising anti-cancer agent in chemotherapeutic strategies for CRC.

Influence of Plant Growth Retardants on Quality of Codonopsis Radix

Plant growth retardant (PGR) refers to organics that can inhibit the cell division of plant stem tip sub-apical meristem cells or primordial meristem cell. They are widely used in the cultivation of rhizomatous functional plants; such as Codonopsis Radix, that is a famous Chinese traditional herb. However, it is still unclear whether PGR affects the medicinal quality of C. Radix. In the present study, amino acid analyses, targeted and non-targeted analyses by ultra-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLC-TOF-MS) and gas chromatography-MS were used to analyze and compare the composition of untreated C. Radix and C. Radix treated with PGR. The contents of two key bioactive compounds, lobetyolin and atractylenolide III, were not affected by PGR treatment. The amounts of polysaccharides and some internal volatiles were significantly decreased by PGR treatment; while the free amino acids content was generally increased. Fifteen metabolites whose abundance were affected by PGR treatment were identified by UPLC-TOF-MS. Five of the up-regulated compounds have been reported to show immune activity, which might contribute to the healing efficacy (“buqi”) of C. Radix. The results of this study showed that treatment of C. Radix with PGR during cultivation has economic benefits and affected some main bioactive compounds in C. Radix.

The influence of lipoic acid on caveolin-1-regulated antioxidative enzymes in the mouse model of acute ulcerative colitis

AIM

This study was undertaken to verify if two-weeks treatment of lipoic acid (LA) influence colon damage and pro-inflammatory cytokine synthesis during DSS-induced acute colitis. Moreover, as LA has anti-oxidative properties, we analyzed its influence on the level of antioxidative enzymes, HO-1 and eNOS, and their regulator- caveolin-1.

METHODS

LA was administrated to male C57/BALBc mice at a dose of 25 or 50mg/kg/day (i.p.) for 21days. Acute colitis was induced by administration of 4% DSS (w/v) in drinking water for 5days, followed by 2days of normal drinking water. Mice in LA+DSS groups were treated with LA (25 or 50mg/kg/day; i.p.) starting 14days prior to 4% DSS. Control group received saline for 21days. In the colon tissue we measured myeloperoxidase activity (MPO), IL-1β, IL-6, IL-17A, IL-23 (ELISA method), and tissue level of cav-1, phospho-eNOS, total eNOS and HO-1 (Western blot).

RESULTS

Administration of DSS significantly increased total colon damage (p<0.001), myeloperoxidase (MPO) activity (p<0.05) and pro-inflammatory IL-6 (p<0.05). There was also a tendency towards higher IL-1β, IL-17A, and IL-23 in the colon. LA alone did not influence total colon damage, MPO activity, and pro-inflammatory cytokines concentration compared to control (p<0.05). Notably, mice treated with LA and DSS had significantly decreased total colon damage score (p<0.001), despite augmented colon MPO activity (p<0.01), but similar (IL-17A) or even significantly higher level (IL-1β, IL-23) as compared to the DSS group (p<0.05). IL-6 was insignificantly decreased after LA treatment at a dose of 50mg/kg. In acute colitis there was a tendency towards an increase in cav-1 and HO-1 and a decrease p-eNOS/total eNOS ratio. Moreover, the LA+DSS groups had higher expression of HO-1 and p-eNOS/total eNOS (p<0.05) compared to the DSS group, and a tendency towards higher cav-1 level. The changes did not depend on LA dose.

CONCLUSION

Our study indicated that LA, at lower doses, may influence cav-1-regulated antioxidative enzyme levels (HO-1 and p-eNOS/total eNOS) despite an increase in colon pro-inflammatory cytokine levels during acute colitis. Hence, LA treatment may be - to some extent - beneficial in attenuation of acute colitis.

Enhancing the anti-inflammatory activity of chalcones by tuning the Michael acceptor site

Inflammatory signaling pathways orchestrate the cellular response to infection and injury. These pathways are known to be modulated by compounds that alkylate cysteinyl thiols. One class of phytochemicals with strong thiol alkylating activity is the chalcones. In this study we tested fourteen chalcone derivatives, α-X-substituted 2',3,4,4'-tetramethoxychalcones (α-X-TMCs, X = H, F, Cl, Br, I, CN, Me, p-NO2-C6H4, Ph, p-OMe-C6H4, NO2, CF3, COOEt, COOH), for their ability to modulate inflammatory responses, as monitored by their influence on heme oxygenase-1 (HO-1) activity, inducible nitric oxide synthase (iNOS) activity, and cytokine expression levels. We confirmed that the transcriptional activity of Nrf2 was activated by α-X-TMCs while for NF-κB it was inhibited. For most α-X-TMCs, anti-inflammatory activity was positively correlated with thiol alkylating activity, i.e. stronger electrophiles (X = CF3, Br and Cl) being more potent. Notably, this correlation did not hold true for the strongest electrophiles (X = CN and NO2) which were found to be ineffective as anti-inflammatory compounds. These results emphasize the idea that chemical fine-tuning of electrophilicity is needed to achieve and optimize desired therapeutic effects.

The anti-inflammatory effects of E-α-(p-methoxyphenyl)-2',3,4,4'-tetramethoxychalcone are mediated via HO-1 induction

Inflammation plays a central role in the pathophysiology of many diseases. The inducible enzyme heme oxygenase-1 (HO-1) protects cells against inflammation and can be induced by electrophilic compounds like the chalcones (1,3-diphenylprop-2-enones) from the class of α,β-unsaturated carbonyl compounds. We hypothesized that the synthetic chalcone E-α-(p-methoxyphenyl)-2',3,4,4'-tetramethoxychalcone (E-α-p-OMe-C6H4-TMC) exerts anti-inflammatory effects in RAW264.7, Jurkat lymphocytes and HK-2 cells via HO-1 induction. RAW264.7 cells were treated with lipopolysaccharide prior to E-α-p-OMe-C6H4-TMC treatment. Subsequently, HO-1 protein induction and activity were analyzed, as well as expression of pro- and anti-inflammatory mediators, transcription factors and mitogen-activated protein kinases to evaluate the possible molecular mechanism. These results were confirmed in human cell lines (Jurkat T-lymphocytes and HK-2 epithelial cells). We found that the E-α-p-OMe-C6H4-TMC exerts significant anti-inflammatory effects in a dose dependent manner, showing no toxic effects in LPS-treated RAW264.7 macrophages. E-α-p-OMe-C6H4-TMC induced HO-1 and SOD-1 protein expression and HO-1 enzyme activity, reduced the upregulation of COX-2 and iNOS, while inducing the translocation of Nrf2. NF-κB activity was attenuated following E-α-p-OMe-C6H4-TMC treatment accompanied by the downregulation of proinflammatory cytokines IL-1β, IL-6 and MCP-1. Pretreatment with E-α-p-OMe-C6H4-TMC revealed significant changes in phosphorylation of ERK and p38, but not JNK. These anti-inflammatory effects of E-α-p-OMe-C6H4-TMC were approved in Jurkat and HK-2 cells, furthermore revealing a downregulation of IL-8 and IL-10. In conclusion, it is tempting to speculate about E-α-p-OMe-C6H4-TMC as a new and non-toxic agent, inducing HO-1 in cells. This opens up new opportunities regarding the development of therapeutic agents using beneficial effects of HO-1 and its products.

Drugs and acute porphyrias: reasons for a hazardous relationship

The porphyrias are a group of metabolic diseases caused by inherited or acquired enzymatic deficiency in the metabolic pathway of heme biosynthesis. Simplistically, they can be considered as storage diseases, because the partial enzymatic defect gives rise to a metabolic "bottleneck" in the biosynthetic pathway and hence to an accumulation of different metabolic intermediates, potentially toxic and responsible for the various (cutaneous or neurovisceral) clinical manifestations observed in these diseases. In the acute porphyrias (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and the very rare delta-aminolevulinic acid dehydratase ALAD-d porphyria), the characteristic severe neurovisceral involvement is mainly ascribed to a tissue accumulation of delta-aminolevulinic acid, a neurotoxic nonporphyrin precursor. Many different factors, both endogenous and exogenous, may favor the accumulation of this precursor in patients who are carriers of an enzymatic defect consistent with an acute porphyria, thus contributing to trigger the serious (and potentially fatal) clinical manifestations of the disease (acute porphyric attacks). To date, many different drugs are known to be able to precipitate an acute porphyric attack, so that the acute porphyrias are also considered as pharmacogenetic or toxygenetic diseases. This article reviews the different biochemical mechanisms underlying the capacity of many drugs to precipitate a porphyric acute attack (drug porphyrogenicity) in carriers of genetic mutations responsible for acute porphyrias, and addresses the issue of prescribing drugs for patients affected by these rare, but extremely complex, diseases.

Identification of heme oxygenase-1 stimulators by a convenient ELISA-based bilirubin quantification assay

The upregulation of heme oxygenase-1 (HO-1) has proven to be a useful tool for fighting inflammation. In order to identify new HO-1 inducers, an efficient screening method was developed which can provide new lead structures for drug research. We designed a simple ELISA-based HO-1 enzyme activity assay, which allows for the screening of 12 compounds in parallel in the setting of a 96-well plate. The well-established murine macrophage cell line RAW264.7 is used and only about 26µg of protein from whole cell lysates is needed for the analysis of HO-1 activity. The quantification of HO-1 activity is based on an indirect ELISA using the specific anti-bilirubin antibody 24G7 to quantify directly bilirubin in the whole cell lysate, applying a horseradish peroxidase-tagged antibody together with ortho-phenylenediamine and H2O2 for detection. The bilirubin is produced on the action of HO enzymes by converting their substrate heme to biliverdin and additional recombinant biliverdin reductase together with NADPH at pH 7.4 in buffer. This sensitive assay allows for the detection of 0.57-82pmol bilirubin per sample in whole cell lysates. Twenty-three small molecules, mainly natural products with an α,β-unsaturated carbonyl unit such as polyphenols, including flavonoids and chalcones, terpenes, an isothiocyanate, and the drug oltipraz were tested at typically 6 or 24h incubation with RAW264.7 cells. The activity of known HO-1 inducers was confirmed, while the chalcones cardamonin, flavokawain A, calythropsin, 2',3,4'-trihydroxy-4-methoxychalcone (THMC), and 2',4'-dihydroxy-3,4-dimethoxychalcone (DHDMC) were identified as new potent HO-1 inducers. The highest inductive power after 6h incubation was found at 10µM for DHDMC (6.1-fold), carnosol (3.9-fold), butein (3.1-fold), THMC (2.9-fold), and zerumbone (2.5-fold). Moreover, the time dependence of HO-1 protein production for DHDMC was compared to its enzyme activity, which was further evaluated in the presence of lipopolysaccharide and the specific HO-1 inhibitor tin protoporphyrin IX. Taken together, we developed a convenient and highly sensitive ELISA-based HO-1 enzyme activity assay, allowing the identification and characterization of molecules potentially useful for the treatment of inflammatory and autoimmune diseases.

The quinone methide aurin is a heat shock response inducer that causes proteotoxic stress and Noxa-dependent apoptosis in malignant melanoma cells

Pharmacological induction of proteotoxic stress is rapidly emerging as a promising strategy for cancer cell-directed chemotherapeutic intervention. Here, we describe the identification of a novel drug-like heat shock response inducer for the therapeutic induction of proteotoxic stress targeting malignant human melanoma cells. Screening a focused library of compounds containing redox-directed electrophilic pharmacophores employing the Stress & Toxicity PathwayFinder(TM) PCR Array technology as a discovery tool, a drug-like triphenylmethane-derivative (aurin; 4-[bis(p-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one) was identified as an experimental cell stress modulator that causes (i) heat shock factor transcriptional activation, (ii) up-regulation of heat shock response gene expression (HSPA6, HSPA1A, DNAJB4, HMOX1), (iii) early unfolded protein response signaling (phospho-PERK, phospho-eIF2α, CHOP (CCAAT/enhancer-binding protein homologous protein)), (iv) proteasome impairment with increased protein-ubiquitination, and (v) oxidative stress with glutathione depletion. Fluorescence polarization-based experiments revealed that aurin displays activity as a geldanamycin-competitive Hsp90α-antagonist, a finding further substantiated by molecular docking and ATPase inhibition analysis. Aurin exposure caused caspase-dependent cell death in a panel of human malignant melanoma cells (A375, G361, LOX-IMVI) but not in non-malignant human skin cells (Hs27 fibroblasts, HaCaT keratinocytes, primary melanocytes) undergoing the aurin-induced heat shock response without impairment of viability. Aurin-induced melanoma cell apoptosis depends on Noxa up-regulation as confirmed by siRNA rescue experiments demonstrating that siPMAIP1-based target down-regulation suppresses aurin-induced cell death. Taken together, our data suggest feasibility of apoptotic elimination of malignant melanoma cells using the quinone methide-derived heat shock response inducer aurin.

TI-I-174, a Synthetic Chalcone Derivative, Suppresses Nitric Oxide Production in Murine Macrophages via Heme Oxygenase-1 Induction and Inhibition of AP-1

Chalcones (1,3-diaryl-2-propen-1-ones), a flavonoid subfamily, are widely known for their anti-inflammatory properties. Propenone moiety in chalcones is known to play an important role in generating biological responses by chalcones. In the present study, we synthesized chalcone derivatives structurally modified in propenone moiety and examined inhibitory effect on nitric oxide (NO) production and its potential mechanisms. Among the chalcone derivatives used for this study, TI-I-174 (3-(2-Hydroxyphenyl)-1-(thiophen-3-yl)prop-2-en-1-one) most potently inhibited lipopolysaccharide (LPS)-stimulated nitrite production in RAW 264.7 macrophages. TI-I-174 treatment also markedly inhibited inducible nitric oxide synthase (iNOS) expression. However, TI-I-174 did not significantly affect production of IL-6, cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNF-α), implying that TI-I-174 inhibits production of inflammatory mediators in a selective manner. Treatment of macrophages with TI-I-174 significantly inhibited transcriptional activity of activator protein-1 (AP-1) as determined by luciferase reporter gene assay, whereas nuclear factor-κB (NF-κB) activity was not affected by TI-I-1744. In addition, TI-I-174 significantly inhibited activation of c-Jun-N-Terminal kinase (JNK) without affecting ERK1/2 and p38MAPK, indicating that down-regulation of iNOS gene expression by TI-I-174 is mainly attributed by blockade of JNK/AP-1 activation. We also demonstrated that TI-I-174 treatment led to an increase in heme oxygenase-1 (HO-1) expression both at mRNA and protein level. Transfection of siRNA targeting HO-1 reversed TI-I-174-mediated inhibition of nitrite production. Taken together, these results indicate that TI-I-174 suppresses NO production in LPS-stimulated RAW 264.7 macrophages via induction of HO-1 and blockade of AP-1 activation.

Heme oxygenase-1 as a target for drug discovery

SIGNIFICANCE

Heme oxygenase enzymes, which exist as constitutive (HO-2) and inducible (HO-1) isoforms, degrade heme to carbon monoxide (CO) and the bile pigment biliverdin. In the last two decades, substantial scientific evidence has been collected on the function of HO-1 in cell homeostasis, emphasizing these two important features: (i) HO-1 is a fundamental "sensor" of cellular stress and directly contributes toward limiting or preventing tissue damage; (ii) the products of HO-1 activity dynamically participate in cellular adaptation to stress and are inherently involved in the mechanisms of defence.

RECENT ADVANCES

On the basis of its promising cytoprotective features, scientists have pursued the targeting of HO-1 as an attractive cellular pathway for drug discovery. Three different pharmacological approaches are currently being investigated in relation to HO-1, namely the use of CO gas, the development of CO-releasing molecules (CO-RMs), and small molecules possessing the ability to up-regulate HO-1 in cells and tissues. CRITICAL ISSUE: Studies on the regulation and amplification of the HO-1/CO pathway by selective pharmacological approaches may lead to the discovery of novel drugs for the treatment of a variety of diseases.

FUTURE DIRECTIONS

In this review, we will discuss in detail the importance of pharmacologically manipulating the HO-1 pathway and its products for conferring protection against a variety of conditions that are characterized by oxidative stress and inflammation. We will also evaluate each of the strategic approaches being developed by considering their intrinsic advantages and disadvantages, which may have implications for their use as therapeutics in specific pathological conditions.

Second monoclinic form of (E)-3-(4-fluoro-phen-yl)-1-phenyl-prop-2-en-1-one

The unit-cell dimensions and space group of the second monoclinic polymorph of the title compound, C15H11FO, differ from those of the previously reported form [Jing (2009 ▶). Acta Cryst. E65, o2515]. The title compound shows an E conformation of the C=C bond with the 4-fluoro-phenyl group opposite to the benzoyl group. The torsion angle of between the planes of the 4-fluoro-phenyl and benzoyl groups is 10.53 (6)°. In the crystal, weak C-H⋯O and C-H⋯F inter-actions form a cross-linked packing motif, building sheets parallel to (-102).

Small molecule activators of the Nrf2-HO-1 antioxidant axis modulate heme metabolism and inflammation in BV2 microglia cells

The nuclear factor erythroid derived 2-related factor 2 (Nrf2) and the antioxidant protein heme oxygenase-1 (HO-1) are crucial components of the cellular stress response. These two systems work together to combat oxidative stress and inflammation and are attractive drug targets for counteracting different pathologies, including neuroinflammation. We aimed to identify the most effective Nrf2/HO-1 activators that modulate the inflammatory response in microglia cells. In the present study, we searched the literature and selected 56 compounds reported to activate Nrf2 or HO-1 and analyzed them for HO-1 induction at 6 and 24h and cytotoxicity in BV2 microglial cells in vitro. Approximately 20 compounds up-regulated HO-1 at the concentrations tested (5-20 μM) with carnosol, supercurcumin, cobalt protoporphyrin-IX and dimethyl fumarate exhibiting the best induction/low cytotoxicity profile. Up-regulation of HO-1 by some compounds resulted in increased cellular bilirubin levels but did not augment the expression of proteins involved in heme synthesis (ALAS 1) or biliverdin reductase. Bilirubin production by HO-1 inducers correlated with their potency in inhibiting nitrite production after challenge with interferon-γ (INF-γ) or lipopolysaccharide (LPS). The compounds down-regulated the inflammatory response (TNF-α, PGE2 and nitrite) more strongly in cells challenged with INF-γ than LPS, and silencing HO-1 or Nrf2 with shRNA differentially affected the levels of inflammatory markers. These findings indicate that some small activators of Nrf2/HO-1 are effective modulators of microglia inflammation and highlight the chemical scaffolds that can serve for the synthesis of potent new derivatives to counteract neuroinflammation and neurodegeneration.

Chemical reactivity and biological activity of chalcones and other α,β-unsaturated carbonyl compounds

Abstract 1. Chalcones are structural analogues of benzalacetophenone (BAP). Several derivatives have been identified in plants and anticarcinogenic and anti-inflammatory properties were attributed to the compounds, probably related to their direct antioxidant activity or stimulatory effects on the expression of endogenous defence enzymes like hemeoxygenase-1 (HO-1). HO-1 expression is triggered by the Nrf2-Keap1 signalling pathway, initiated by the addition of chalcones to thiol groups of Keap1 via Michael-type reaction. 2. The present study used a model system estimating the reactivity of different synthetic chalcones and other α,β-unsaturated carbonyl compounds with thiols and compared the chemical reactivity with the biological activity, measured by HO-1 expression in human dermal fibroblasts. 3. Chemical reactivity with the thiol group of N-acetylcysteine was determined with 5,5'-dithiobis-(2-nitrobenzoic acid) and followed chemical principles of structure-reactivity relationship. Most reactive were sulforaphane, dimethylfumarate, chalcone 3 ((2E)-1-phenyl-3-pyrimidin-2-ylprop-2-en-1-one) and chalcone 7 (1,3-diphenylprop-2-yn-1-one). This result demonstrates that α,β-unsaturated carbonyl derivatives react with thiols differently. All compounds were also biologically active; however, expression of HO-1 was not only related to the chemical reactivity but also to the lipophilicity of the molecules which likely affected transmembrane uptake. Most efficient inducers of HO-1 expression were BAP, 4-hydroxynonenal and chalcone 1 (4-[(1E)-3-oxo-3-phenylprop-1-en-1-yl]benzonitrile), chalcone 5 ((2E)-1-phenyl-3-[4-(trifluoromethyl)-phenyl]prop-2-en-1-one) and chalcone 7.

The glutathionylation of p65 modulates NF-κB activity in 15-deoxy-Δ¹²,¹⁴-prostaglandin J₂-treated endothelial cells

Protein glutathionylation is a posttranslational modification of cysteine residues with glutathione in response to mild oxidative stress. Because 15-deoxy-Δ12,14-prostaglandin J(2) (15d-PGJ(2)) is an electrophilic prostaglandin that can increase glutathione (GSH) levels and augment reactive oxygen species (ROS) production, we hypothesized that it induces NF-κB-p65 glutathionylation and would exert anti-inflammatory effects. Herein, we show that 15d-PGJ(2) suppresses the expression of ICAM-1 and NF-κB-p65 nuclear translocation. 15d-PGJ(2) upregulates the Nrf2-related glutathione synthase gene and thereby increases the GSH levels. Consistent with this, Nrf2 siRNA molecules abolish the inhibition of p65 nuclear translocation in 15d-PGJ(2)-induced endothelial cells (ECs). ECs treated with GSSG show increased thiol modifications of p65 and also a block in TNFα-induced p65 nuclear translocation and ICAM-1 expression, but not in IκBα degradation. However, the overexpression of glutaredoxin 1 was found to be accompanied by a modest increase in NF-κB activity. Furthermore, we found that multiple cysteine residues in p65 are responsible for glutathionylation. 15d-PGJ(2) was observed to induce p65 glutathionylation and is suppressed by a GSH synthesis inhibitor, buthionine sulfoximine, by catalase, and by Nrf2 siRNA molecules. Our results thus indicate that the GSH/ROS-dependent glutathionylation of p65 is likely to be responsible for 15d-PGJ(2)-mediated NF-κB inactivation and for the enhanced inhibitory effects of 15d-PGJ(2) on TNFα-treated ECs.

Antioxidant pharmacological therapies for COPD

Increased oxidative stress occurs in the lungs and systemically in COPD, which plays a role in many of the pathogenic mechanisms in COPD. Hence, targeting local lung and systemic oxidative stress with agents that modulate the antioxidants/redox system or boost endogenous antioxidants would be a useful therapeutic approach in COPD. Thiol antioxidants (N-acetyl-l-cysteine [NAC] and N-acystelyn, carbocysteine, erdosteine, and fudosteine) have been used to increase lung thiol content. Modulation of cigarette smoke (CS) induced oxidative stress and its consequent cellular changes have also been reported to be effected by synthetic molecules, such as spin traps (α-phenyl-N-tert-butyl nitrone), catalytic antioxidants (superoxide dismutase [ECSOD] mimetics), porphyrins, and lipid peroxidation and protein carbonylation blockers/inhibitors (edaravone and lazaroids/tirilazad). Preclinical and clinical trials have shown that these antioxidants can reduce oxidative stress, affect redox and glutathione biosynthesis genes, and proinflammatory gene expression. In this review the approaches to enhance lung antioxidants in COPD and the potential beneficial effects of antioxidant therapy on the course of the disease are discussed.

Microcantilevers and organic transistors: two promising classes of label-free biosensing devices which can be integrated in electronic circuits

Most of the success of electronic devices fabricated to actively interact with a biological environment relies on the proper choice of materials and efficient engineering of surfaces and interfaces. Organic materials have proved to be among the best candidates for this aim owing to many properties, such as the synthesis tunability, processing, softness and self-assembling ability, which allow them to form surfaces that are compatible with biological tissues. This review reports some research results obtained in the development of devices which exploit organic materials' properties in order to detect biologically significant molecules as well as to trigger/capture signals from the biological environment. Among the many investigated sensing devices, organic field-effect transistors (OFETs), organic electrochemical transistors (OECTs) and microcantilevers (MCLs) have been chosen. The main factors motivating this choice are their label-free detection approach, which is particularly important when addressing complex biological processes, as well as the possibility to integrate them in an electronic circuit. Particular attention is paid to the design and realization of biocompatible surfaces which can be employed in the recognition of pertinent molecules as well as to the research of new materials, both natural and inspired by nature, as a first approach to environmentally friendly electronics.

A synthetic chalcone as a potent inducer of glutathione biosynthesis

Chalcones continue to attract considerable interest due to their anti-inflammatory and antiangiogenic properties. We recently reported the ability of 2',5'-dihydroxychalcone (2',5'-DHC) to induce both breast cancer resistance protein-mediated export of glutathione (GSH) and c-Jun N-terminal kinase-mediated increased intracellular GSH levels. Herein, we report a structure-activity relationship study of a series of 30 synthetic chalcone derivatives with hydroxyl, methoxyl, and halogen (F and Cl) substituents and their ability to increase intracellular GSH levels. This effect was drastically improved with one or two electrowithdrawing groups on phenyl ring B and up to three methoxyl and/or hydroxyl groups on phenyl ring A. The optimal structure, 2-chloro-4',6'-dimethoxy-2'-hydroxychalcone, induced both a potent NF-E2-related factor 2-mediated transcriptional response and an increased formation of glutamate cysteine ligase holoenzyme, as shown using a human breast cancer cell line stably expressing a luciferase reporter gene driven by antioxidant response elements.

Pharmacological antioxidant strategies as therapeutic interventions for COPD

Cigarette/tobacco smoke/biomass fuel-induced oxidative and aldehyde/carbonyl stress are intimately associated with the progression and exacerbation of chronic obstructive pulmonary disease (COPD). Therefore, targeting systemic and local oxidative stress with antioxidants/redox modulating agents, or boosting the endogenous levels of antioxidants are likely to have beneficial effects in the treatment/management of COPD. Various antioxidant agents, such as thiol molecules (glutathione and mucolytic drugs, such as N-acetyl-L-cysteine and N-acystelyn, erdosteine, fudosteine, ergothioneine, and carbocysteine), have been reported to modulate various cellular and biochemical aspects of COPD. These antioxidants have been found to scavenge and detoxify free radicals and oxidants, regulate of glutathione biosynthesis, control nuclear factor-kappaB (NF-kappaB) activation, and hence inhibiting inflammatory gene expression. Synthetic molecules, such as specific spin traps like α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a superoxide dismutase mimetic M40419, iNOS and myeloperoxidase inhibitors, lipid peroxidation inhibitors/blockers edaravone, and lazaroids/tirilazad have also been shown to have beneficial effects by inhibiting cigarette smoke-induced inflammatory responses and other carbonyl/oxidative stress-induced cellular alterations. A variety of oxidants, free radicals, and carbonyls/aldehydes are implicated in the pathogenesis of COPD, it is therefore, possible that therapeutic administration or supplementation of multiple antioxidants and/or boosting the endogenous levels of antioxidants will be beneficial in the treatment of COPD. This review discusses various novel pharmacological approaches adopted to enhance lung antioxidant levels, and various emerging beneficial and/or prophylactic effects of antioxidant therapeutics in halting or intervening the progression of COPD. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Modulation of Nrf2/ARE pathway by food polyphenols: a nutritional neuroprotective strategy for cognitive and neurodegenerative disorders

In recent years, there has been a growing interest, supported by a large number of experimental and epidemiological studies, for the beneficial effects of some phenolic substances, contained in commonly used spices and herbs, in preventing various age-related pathologic conditions, ranging from cancer to neurodegenerative diseases. Although the exact mechanisms by which polyphenols promote these effects remain to be elucidated, several reports have shown their ability to stimulate a general xenobiotic response in the target cells, activating multiple defense genes. Data from our and other laboratories have previously demonstrated that curcumin, the yellow pigment of curry, strongly induces heme-oxygenase-1 (HO-1) expression and activity in different brain cells via the activation of heterodimers of NF-E2-related factors 2 (Nrf2)/antioxidant responsive element (ARE) pathway. Many studies clearly demonstrate that activation ofNrf2 target genes, and particularly HO-1, in astrocytes and neurons is strongly protective against inflammation, oxidative damage, and cell death. In the central nervous system, the HO system has been reported to be very active, and its modulation seems to play a crucial role in the pathogenesis of neurodegenerative disorders. Recent and unpublished data from our group revealed that low concentrations of epigallocatechin-3-gallate, the major green tea catechin, induces HO-1 by ARE/Nrf2 pathway in hippocampal neurons, and by this induction, it is able to protect neurons against different models of oxidative damages. Furthermore, we have demonstrated that other phenolics, such as caffeic acid phenethyl ester and ethyl ferulate, are also able to protect neurons via HO-1 induction. These studies identify a novel class of compounds that could be used for therapeutic purposes as preventive agents against cognitive decline.

2',5'-Dihydroxychalcone-induced glutathione is mediated by oxidative stress and kinase signaling pathways

Hydroxychalcones are naturally occurring compounds that continue to attract considerable interest because of their anti-inflammatory and antiangiogenic properties. They have been reported to inhibit the synthesis of the inducible nitric oxide synthase and to induce the expression of heme oxygenase-1. This study examines the mechanisms by which 2',5'-dihydroxychalcone (2',5'-DHC) induces an increase in cellular glutathione (GSH) levels using a cell line stably expressing a luciferase reporter gene driven by antioxidant-response elements (MCF-7/AREc32). The 2',5'-DHC-induced increase in cellular GSH levels was partially inhibited by the catalytic antioxidant MnTDE-1,3-IP(5+), suggesting that reactive oxygen species (ROS) mediate the antioxidant adaptive response. 2',5'-DHC treatment induced phosphorylation of the c-Jun N-terminal kinase (JNK) pathway, which was also inhibited by MnTDE-1,3-IP(5+). These findings suggest a ROS-dependent activation of the AP-1 transcriptional response. However, whereas 2',5'-DHC triggered the NF-E2-related factor 2 (Nrf2) transcriptional response, cotreatment with MnTDE-1,3-IP(5+) did not decrease 2',5'-DHC-induced Nrf2/ARE activity, showing that this pathway is not dependent on ROS. Moreover, pharmacological inhibitors of mitogen-activated protein kinase (MAPK) pathways showed a role for JNK and p38MAPK in mediating the 2',5'-DHC-induced Nrf2 response. These findings suggest that the 2',5'-DHC-induced increase in GSH levels results from a combination of ROS-dependent and ROS-independent pathways.

Novel chalcone derivatives as potent Nrf2 activators in mice and human lung epithelial cells

Nrf2-mediated activation of antioxidant response element is a central part of molecular mechanisms governing the protective function of phase II detoxification and antioxidant enzymes against carcinogenesis, oxidative stress, and inflammation. Nrf2 is sequestered in the cytoplasm by its repressor, Keap1. We have designed and synthesized novel chalcone derivatives as Nrf2 activators. The potency of these compounds was measured by the expression of Nrf2 dependent antioxidant genes GCLM, NQO1, and HO1 in human lung epithelial cells, while the cytotoxicity was analyzed using MTT assay. In vivo potency of identified lead compounds to activate Nrf2 was evaluated using a mouse model. Our studies showed 2-trifluoromethyl-2'-methoxychalone (2b) to be a potent activator of Nrf2, both in vitro and in mice. Additional experiments showed that the activation of Nrf2 by this compound is independent of reactive oxygen species or redox changes. We have discussed a quantitative structure-activity relationship and proposed a possible mechanism of Nrf2 activation.

Curcumin mediates both dilation and constriction of peripheral arterioles via adrenergic receptors

Curcumin has wound healing attributes mediated through a plethora of biological activities that in general are not ascribed to specific receptors. Recently we have demonstrated that i.v. curcumin limits burn injury progression in a rat model. Since decreased microvascular perfusion is a central element of burn injury progression, we hypothesized that curcumin may induce vasodilation in peripheral arterioles, to improve perfusion. Using mucosal microcirculation as an in situ assay, cheek pouch tissue was exteriorized in anesthetized (phentobarbital 70 mg/kg i.p.) male hamsters (N=60) to observe the terminal feed arterioles (~8μm diameter) and the immediately upstream arcade arterioles (~20μm). Curcumin (10⁻¹² – 10⁻⁴mol/L) was applied dose-wise (micropipette, 60 seconds). Subnanomolar curcumin dilated whereas micromolar doses constricted the arterioles. For the terminal arteriole: vasodilation logEC50 −10.3±0.2, peak dilation +39±1%; vasconstriction logEC50 −8.0±0.4, peak constriction −14±2%. Simultaneous atropine (muscarinic antagonist) or PD142893 (endothelin antagonist) had no effect. Propranolol (β-Ad antagonist) enhanced constriction by removing the vasodilation response to curcumin. Phentolamine (α-Ad antagonist) enhanced dilation to curcumin by removing the vasoconstriction response. Thus, the curcumin vasomotor activity on microcirculation was α-Ad and β-Ad receptor-dependent and its net vasoactive effect was concentration and time dependent.

The role of chalcones in suppression of NF-κB-mediated inflammation and cancer

Although consumption of fruits, vegetables, spices, cereals and pulses has been associated with lower incidence of cancer and other chronic diseases, how these dietary agents and their active ingredients minimize these diseases, is not fully understood. Whether it is oranges, kawa, hops, water-lilly, locorice, wax apple or mulberry, they are all connected by a group of aromatic ketones, called chalcones (1,3-diaryl-2-propen-1-ones). Some of the most significant chalcones identified from these plants include flavokawin, butein, xanthoangelol, 4-hydroxyderricin, cardamonin, 2',4'-dihydroxychalcone, isoliquiritigenin, isosalipurposide, and naringenin chalcone. These chalcones have been linked with immunomodulation, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, anticancer, and antidiabetic activities. The current review, however, deals with the role of various chalcones in inflammation that controls both the immune system and tumorigenesis. Inflammatory pathways have been shown to mediate the survival, proliferation, invasion, angiogenesis and metastasis of tumors. How these chalcones modulate inflammatory pathways, tumorigenesis and immune system is the focus of this review.

Cancer chemoprevention mechanisms mediated through the Keap1-Nrf2 pathway

The cap'n'collar (CNC) bZIP transcription factor Nrf2 controls expression of genes for antioxidant enzymes, metal-binding proteins, drug-metabolising enzymes, drug transporters, and molecular chaperones. Many chemicals that protect against carcinogenesis induce Nrf2-target genes. These compounds are all thiol-reactive and stimulate an adaptive response to redox stress in cells. Such agents induce the expression of genes that posses an antioxidant response element (ARE) in their regulatory regions. Under normal homeostatic conditions, Nrf2 activity is restricted through a Keap1-dependent ubiquitylation by Cul3-Rbx1, which targets the CNC-bZIP transcription factor for proteasomal degradation. However, as the substrate adaptor function of Keap1 is redox-sensitive, Nrf2 protein evades ubiquitylation by Cul3-Rbx1 when cells are treated with chemopreventive agents. As a consequence, Nrf2 accumulates in the nucleus where it heterodimerizes with small Maf proteins and transactivates genes regulated through an ARE. In this review, we describe synthetic compounds and phytochemicals from edible plants that induce Nrf2-target genes. We also discuss evidence for the existence of different classes of ARE (a 16-bp 5'-TMAnnRTGABnnnGCR-3' versus an 11-bp 5'-RTGABnnnGCR-3', with or without the embedded activator protein 1-binding site 5'-TGASTCA-3'), species differences in the ARE-gene battery, and the identity of critical Cys residues in Keap1 required for de-repression of Nrf2 by chemopreventive agents.

Antiproliferative mechanisms of the flavonoids 2,2'-dihydroxychalcone and fisetin in human prostate cancer cells

We have previously demonstrated the antiproliferative effect of two flavonoids-2,2'-dihydroxychalcone (DHC), a novel synthetic flavonoid, and fisetin, a naturally occurring flavonol-in prostate cancer cells. In this study, we further examine the mechanisms of these compounds on survival and proliferation pathways. DHC and fisetin (1-50 microM) caused a dose-dependent reduction in viability, a concomitant increase in apoptosis in PC3 cells at 72 h, and a decrease in clonogenic survival at 24 h treatment. DHC was considerably more potent than fisetin in these cytotoxicity assays. The mechanism of accelerated cellular senescence was not activated by either compound in PC3 or lymph node carcinoma of the prostate (LNCaP) cells. Gene expression alterations in PC3 and LNCaP cells treated with 15 muM DHC and 25 microM fisetin for 6 to 24 h were determined by oligonucleotide array. Amongst the most highly represented functional categories of genes altered by both compounds was the cell cycle category. In total, 100 cell cycle genes were altered by DHC and fisetin including 27 genes with key functions in G2/M phase that were downregulated by both compounds. Other functional categories altered included chromosome organization, apoptosis, and stress response. These results demonstrate the multiple mechanisms of antitumor activity of DHC and fisetin in prostate cancer cells in vitro.

The glutaredoxin/glutathione system modulates NF-kappaB activity by glutathionylation of p65 in cinnamaldehyde-treated endothelial cells

Reversible protein glutathionylation is an important posttranslational modification that provides protection against oxidation. In endothelial cells (ECs), cinnamaldehyde is an electrophilic compound that can increase the intracellular glutathione (GSH) levels or reactive oxygen species (ROS) production depending on the treatment duration. ECs treated with GSH and H(2)O(2) show increased sulfhydryl modifications of the p65 subunit of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB), which are responsible for NF-kappaB inactivation, and also a block in TNF-alpha-induced p65 nuclear translocation and inter-cellular adhesion molecule-1 (ICAM-1) expression. In our current study, we find that cinnamaldehyde induces p65 glutathionylation and inhibits TNF-alpha-induced p65 nuclear translocation and ICAM-1 expression within 12 h of treatment. Our analyses also reveal that p65 glutathionylation is suppressed by a GSH synthesis inhibitor, buthionine sulfoximine (BSO), and we further observed that the inhibitory effects of p65 nuclear translocation and ICAM-1 expression are also suppressed by BSO. NF-E2-related factor-2 small interfering RNA (siRNA) molecules not only inhibit glutamate-cysteine ligase catalytic subunit (GCLC) and glutamate-cysteine ligase modifier subunit (GCLM) induction and increases in GSH but also abolish cinnamaldehyde-induced p65 glutathionylation and its inhibitory effects. The gene expression and activity of glutaredoxin-1 (Grx-1), which catalyzes the formation of protein-glutathione mixed disulfides (protein-SSG), were also found to be increased after cinnamaldehyde treatment. A knock down of endogenous Grx-1 by siRNA or pretreatment with an inhibitor of Grx-1 activity, CdCl(2), abolishes p65-SSG formation. In addition, Grx-1 siRNA blocks the inhibition of p65 nuclear translocation and ICAM-1 expression, suggesting that this enzyme is involved in the cinnamaldehyde-mediated NF-kappaB inhibition. Our current results thus indicate that the GSH/Grx-1-dependent glutathionylation of p65 is likely to be responsible for cinnamaldehyde-mediated NF-kappaB inactivation and for the enhanced inhibitory effects of cinnamaldehyde upon TNF-alpha-treated ECs.

Heme oxygenase-1, a critical arbitrator of cell death pathways in lung injury and disease

Increases in cell death by programmed (i.e., apoptosis, autophagy) or nonprogrammed mechanisms (i.e., necrosis) occur during tissue injury and may contribute to the etiology of several pulmonary or vascular disease states. The low-molecular-weight stress protein heme oxygenase-1 (HO-1) confers cytoprotection against cell death in various models of lung and vascular injury by inhibiting apoptosis, inflammation, and cell proliferation. HO-1 serves a vital metabolic function as the rate-limiting step in the heme degradation pathway and in the maintenance of iron homeostasis. The transcriptional induction of HO-1 occurs in response to multiple forms of chemical and physical cellular stress. The cytoprotective functions of HO-1 may be attributed to heme turnover, as well as to beneficial properties of its enzymatic reaction products: biliverdin-IXalpha, iron, and carbon monoxide (CO). Recent studies have demonstrated that HO-1 or CO inhibits stress-induced extrinsic and intrinsic apoptotic pathways in vitro. A variety of signaling molecules have been implicated in the cytoprotection conferred by HO-1/CO, including autophagic proteins, p38 mitogen-activated protein kinase, signal transducer and activator of transcription proteins, nuclear factor-kappaB, phosphatidylinositol 3-kinase/Akt, and others. Enhanced HO-1 expression or the pharmacological application of HO end-products affords protection in preclinical models of tissue injury, including experimental and transplant-associated ischemia/reperfusion injury, promising potential future therapeutic applications.

Heme oxygenase-1 mediates the anti-allergic actions of quercetin in rodent mast cells

OBJECTIVE AND DESIGN

We investigated the involvement of heme oxygenase (HO)-1 in the anti-allergic action of quercetin against degranulation of rat basophilic leukemia (RBL-2H3) cells, rat peritoneal mast cells, and mouse bone marrow-derived mast cells.

METHODS

The strength of allergic reaction was evaluated by the extent of degranulation in mast cells sensitized with various stimulants. The levels of HO-1, HO-2, and nuclear factor erythroid 2-related factor 2 (Nrf2) expressions were determined by quantitative RT-PCR, western blotting, or immunocytochemistry.

RESULTS

Heme oxygenase activity was upregulated after short exposure to quercetin, followed by the induction of HO-1 expression after long exposure to quercetin. The inhibition of degranulation by quercetin was reversed using tin protoporphyrin IX (SnPP), an HO-1 inhibitor. HO-1 metabolites, bilirubin and CO, led to inhibit degranulation, and quercetin translocated Nrf2 from cytoplasm into nucleus in RBL-2H3 cells.

CONCLUSION

These results strongly suggest that quercetin exerted anti-allergic actions via activation of Nrf2-HO-1 pathway.