A selective small-molecule nuclear factor-kappaB inhibitor from a high-throughput cell-based assay for "activator protein-1 hits"

Screening a small molecule library to identify inhibitors of NF-κB inducing kinase and pro-labor genes in human placenta

The non-canonical NF-κB signaling (RelB/p52) pathway drives pro-labor genes in the human placenta, including corticotropin-releasing hormone (CRH) and cyclooxygenase-2 (COX-2), making this a potential therapeutic target to delay onset of labor. Here we sought to identify small molecule compounds from a pre-existing chemical library of orally active drugs that can inhibit this NF-κB signaling, and in turn, human placental CRH and COX-2 production. We used a cell-based assay coupled with a dual-luciferase reporter system to perform an in vitro screening of a small molecule library of 1,120 compounds for inhibition of the non-canonical NF-κB pathway. Cell toxicity studies and drug efflux transport MRP1 assays were used to further characterize the lead compounds. We have found that 14 drugs have selective inhibitory activity against lymphotoxin beta complex-induced activation of RelB/p52 in HEK293T cells, several of which also inhibited expression of CRH and COX-2 in human term trophoblast. We identified sulfapyridine and propranolol with activity against CRH and COX-2 that deserve further study. These drugs could serve as the basis for development of orally active drugs to affect length of gestation, first in an animal model, and then in clinical trials to prevent preterm birth during human pregnancy.

Comparison of the toxicity of sintered and unsintered indium-tin oxide particles in murine macrophage and epidermal cells

Indium-tin oxide (ITO) is used to produce flat panel displays and several other technology products. Composed of 90% indium oxide (In₂O₃) and 10% tin oxide (SnO₂) by weight, ITO is synthesized under conditions of high heat via a process known as sintering. Indium lung disease, a recently recognized occupational illness, is characterized by pulmonary alveolar proteinosis, fibrosis, and emphysema. Murine macrophage (RAW 264.7) and epidermal (JB6) cells stably transfected with AP-1 to study tumor promoting potential, were used to differentiate between the toxicological profiles of sintered ITO (SITO) and unsintered mixture (UITO). We hypothesized that sintering would play a key role in free radical generation and cytotoxicity. Exposure of cells to both UITO and SITO caused a time and dose dependent decrease of the viability of cells. Intracellular ROS generation was inversely related to the dose of both UITO and SITO, a direct reflection of the decreased number of viable RAW 264.7 and JB6/AP-1 cells observed at higher concentrations. Electron spin resonance showed significantly increased hydroxyl radical (OH) generation in cells exposed to UITO compared to SITO. This is different from LDH release, which showed that SITO caused significantly increased damage to the cell membrane compared to UITO. Lastly, the JB6/AP-1 cell line did not show activation of the AP-1 pathway. Our results highlight both the differences in the mechanisms of cytotoxicity and the consistent adverse effects associated with UITO and SITO exposure.

Anti-inflammatory activity of chitosan nanoparticles carrying NF-κB/p65 antisense oligonucleotide in RAW264.7 macropghage stimulated by lipopolysaccharide

The purpose of this present study is to prepare NF-κB/p65 antisense oligonucleotide loaded chitosan nanoparticles (NPs) and evaluate their physicochemical characterization and antisense effects in RAW264.7 macrophages. Condensed nanoparticles with mean particle size of 128±16nm, average Zeta potential of 19.6±6.3mV and high entrapment efficiency (EE) of 98.6±0.11% were formed between NF-κB/p65 antisense gene (NAG) and chitosan by complex coacervation method. Trypan blue staining and MTT tests showed that NAG chitosan NPs had no toxic effect on RAW264.7 macrophages when the dose was no more than 20μg/mL. Confocal microscopy images showed that NAG chitosan NPs were capable to deliver NAG into cytoplasm of RAW264.7 macrophages and finally into nucleus. Real-time PCR tests verified that NAG chitosan NPs could significantly decrease the mRNA expression level of NF-κB/p65 and inflammatory cytokines including TNF-ɑ, IL-1 and IL-6. Accordingly, western blot study showed that NAG NPs uptaken in the cells could efficiently reversed the expression of NF-κB/p65 protein induced by LPS. At last, downstream release level of inflammatory factors including TNF-ɑ, IL-1 and IL-6 in LPS stimulated RAW264.7 macrophages was significantly decreased after treated by NAG chitosan NPs. It could be concluded that chitosan NPs were excellent delivery vectors to ferry the NAG into the cytoplasm and nucleus of macrophages. The NAG chitosan NPs might be a novel therapeutic apparatus for the treatment of LPS induced sepsis by inhibiting NF-κB-related pro-inflammatory cytokines secretion.

FOXO3-NF-κB RelA Protein Complexes Reduce Proinflammatory Cell Signaling and Function

Tumor-associated myeloid cells, including dendritic cells (DCs) and macrophages, are immune suppressive. This study demonstrates a novel mechanism involving FOXO3 and NF-κB RelA that controls myeloid cell signaling and impacts their immune-suppressive nature. We find that FOXO3 binds NF-κB RelA in the cytosol, impacting both proteins by preventing FOXO3 degradation and preventing NF-κB RelA nuclear translocation. The location of protein-protein interaction was determined to be near the FOXO3 transactivation domain. In turn, NF-κB RelA activation was restored upon deletion of the same sequence in FOXO3 containing the DNA binding domain. We have identified for the first time, to our knowledge, a direct protein-protein interaction between FOXO3 and NF-κB RelA in tumor-associated DCs. These detailed biochemical interactions provide the foundation for future studies to use the FOXO3-NF-κB RelA interaction as a target to enhance tumor-associated DC function to support or enhance antitumor immunity.

Sinulolides A-H, new cyclopentenone and butenolide derivatives from soft coral Sinularia sp

Eight new compounds, sinulolides A-H (1-8), along with two known compounds, α-methoxy-2,3-dimethyl-butenolide (9) and sinularone D (10), were isolated from the soft coral Sinularia sp. The structures of these compounds were elucidated on the basis of extensive spectroscopic analysis. The absolute configurations were determined on the basis of electronic circular dichroism (ECD) data analysis. Compounds 5 and 10 exhibited moderate effects for the inhibition of NF-κB activation.

Importance of purity evaluation and the potential of quantitative ¹H NMR as a purity assay

In any biomedical and chemical context, a truthful description of chemical constitution requires coverage of both structure and purity. This qualification affects all drug molecules, regardless of development stage (early discovery to approved drug) and source (natural product or synthetic). Purity assessment is particularly critical in discovery programs and whenever chemistry is linked with biological and/or therapeutic outcome. Compared with chromatography and elemental analysis, quantitative NMR (qNMR) uses nearly universal detection and provides a versatile and orthogonal means of purity evaluation. Absolute qNMR with flexible calibration captures analytes that frequently escape detection (water, sorbents). Widely accepted structural NMR workflows require minimal or no adjustments to become practical ¹H qNMR (qHNMR) procedures with simultaneous qualitative and (absolute) quantitative capability. This study reviews underlying concepts, provides a framework for standard qHNMR purity assays, and shows how adequate accuracy and precision are achieved for the intended use of the material.

The small molecule NSC676914A is cytotoxic and differentially affects NFκB signaling in ovarian cancer cells and HEK293 cells

Background

The small molecule NSC676914A was previously identified as an NF-κB inhibitor in TPA-stimulated HEK293 cells (Mol Can Ther 8:571-581, 2009). We hypothesized that this effect would also be seen in ovarian cancer cells, and serve as its mechanism of cytotoxicity. OVCAR3 and HEK293 cell lines stably containing a NF-κB luciferase reporter gene were generated.

Methods

Levels of NF-κB activity were assessed by luciferase reporter assays, after stimulation with LPA, LPS, TPA, and TNFα, in the presence or absence of a known NF-κB inhibitor or NSC676914A, and cytotoxicity was measured.

Results

NSC676914A was toxic to both OVCAR3 and HEK293 cells. We also investigated the cytotoxicity of NSC676914A on a panel of lymphoma cell lines with well characterized mutations previously shown to determine sensitivity or resistance to NF-κB inhibition. The compound did not show predicted patterns of effects on NF-κB activity in either lymphoma, ovarian or HEK293 cell lines. In HEK293 cells, the small molecule inhibited NF-κB when cells were stimulated, while in OVCAR3 cells it only partially inhibited NF-κB. Interestingly, we observed rescue of cell death with ROS inhibition.

Conclusions

The current study suggests that the effect of NSC676914A on NF-κB depends on cell type and the manner in which the pathway is stimulated. Furthermore, as it is similarly toxic to lymphoma, OVCAR3 and HEK293 cells, NSC676914A shows promising NF-κB-independent anti-cancer activity in ovarian tumor cells.

Bioactivities of six sterols isolated from marine invertebrates

CONTEXT

Epidioxy sterols and sterols with special side chains, such as hydroperoxyl sterols, usually obtained from marine natural products, are attractive for bioactivities.

OBJECTIVE

To isolate and screen bioactive and special sterols from China Sea invertebrates.

MATERIALS AND METHODS

Two hydroperoxyl sterols (1 and 2) from the sponge Xestospongia testudinaria Lamarck (Petrosiidae), three epidioxy sterols (3-5) from the sea urchin Glyptocidaris crenularis A. Agassiz (Glyptocidaridae), sponge Mycale sp. (Mycalidae) and gorgonian Dichotella gemmacea Milne Edwards and Haime (Ellisellidae) and an unusual sterol with 25-acetoxy-19-oate (6) also from D. gemmacea were obtained and identified. Using high-throughput screening, their bioactivities were tested toward Forkhead box O 3a (Foxo3a), 3-hydroxy-3-methylglutaryl CoA reductase gene fluorescent protein (HMGCR-GFP), nuclear factor kappa B (NF-κB) luciferase, peroxisome proliferator-activated receptor-γ co-activator 1α (PGC-1α), protein-tyrosine phosphatase 1B (PTP1B), mitochondrial membrane permeabilization (MMP) and adenosine monophosphate-activated protein kinase.

RESULTS

Their structures were determined by comparing their nuclear magnetic resonance data with those reported in the literature. Three epidioxy sterols (3-5) showed inhibitory activities toward Foxo3a, HMGCR-GFP and NF-κB-luciferase with the IC50 values 4.9-6.8 μg/mL. The hydroperoxyl sterol 29-hydroperoxystigmasta-5,24(28)-dien-3-ol (2) had diverse inhibitory activities against Foxo3a, HMGCR-GFP, NF-κB-luciferase, PGC-1α, PTP1B and MMP, with IC50 values of 3.8-19.1 μg/mL.

DISCUSSION AND CONCLUSION

The bioactivities of 3-5 showed that 5α,8α-epidioxy is the active group. Otherwise, the most plausible biosynthesis pathway for 1 and 2 in sponge involves the abstraction of an allylic proton by an activated oxygen, such as O2, along with migration of carbon-carbon double bond. Therefore, the bioactive and unstable steroid should be biosynthesized in sponge under a special ecological environment to act as a defensive strategy against invaders.

Synthesis of 2',3',4'-trihydroxyflavone (2-D08), an inhibitor of protein sumoylation

Protein sumoylation is a dynamic posttranslational modification involved in diverse biological processes during cellular homeostasis and development. Recently sumoylation has been shown to play a critical role in cancer, although to date there are few small molecule probes available to inhibit enzymes involved in the SUMO conjugation process. As part of a program to identify and study inhibitors of sumoylation we recently reported the discovery that 2',3',4'-trihydroxyflavone (2-D08) is a cell permeable, mechanistically unique inhibitor of protein sumoylation. The work reported herein describes an efficient synthesis of 2-D08 as well as a structurally related but inactive isomer. We also report an unanticipated Wessely-Moser rearrangement that occurs under vigorous methyl ether deprotection conditions. This rearrangement likely gave rise to 2-D08 during a deprotection step, resulting in 2-D08 appearing as a contaminant in a screening well from a commercial supplier.

BRITER: a BMP responsive osteoblast reporter cell line

Background

BMP signaling pathway is critical for vertebrate development and tissue homeostasis. High-throughput molecular genetic screening may reveal novel players regulating BMP signaling response while chemical genetic screening of BMP signaling modifiers may have clinical significance. It is therefore important to generate a cell-based tool to execute such screens.

Methodology/Principal Findings

We have established a BMP responsive reporter cell line by stably integrating a BMP responsive dual luciferase reporter construct in the immortalized calvarial osteoblast cells isolated from tamoxifen inducible Bmp2; Bmp4 double conditional knockout mouse strain. This cell line, named BRITER (BMP Responsive Immortalized Reporter cell line), responds robustly, promptly and specifically to exogenously added BMP2 protein. The sensitivity to added BMP may be further increased by depleting the endogenous BMP2 and BMP4 proteins.

Conclusion

As the dynamic range of the assay (for BMP responsiveness) is very high for BRITER and as it responds specifically and promptly to exogenously added BMP2 protein, BRITER may be used effectively for chemical or molecular genetic screening for BMP signaling modifiers. Identification of novel molecular players capable of influencing BMP signaling pathway may have clinical significance.

Synthetic lethal screen identifies NF-κB as a target for combination therapy with topotecan for patients with neuroblastoma

Background

Despite aggressive multimodal treatments the overall survival of patients with high-risk neuroblastoma remains poor. The aim of this study was to identify novel combination chemotherapy to improve survival rate in patients with high-risk neuroblastoma.

Methods

We took a synthetic lethal approach using a siRNA library targeting 418 apoptosis-related genes and identified genes and pathways whose inhibition synergized with topotecan. Microarray analyses of cells treated with topotecan were performed to identify if the same genes or pathways were altered by the drug. An inhibitor of this pathway was used in combination with topotecan to confirm synergism by in vitro and in vivo studies.

Results

We found that there were nine genes whose suppression synergized with topotecan to enhance cell death, and the NF-κB signaling pathway was significantly enriched. Microarray analysis of cells treated with topotecan revealed a significant enrichment of NF-κB target genes among the differentially altered genes, suggesting that NF-κB pathway was activated in the treated cells. Combination of topotecan and known NF-κB inhibitors (NSC 676914 or bortezomib) significantly reduced cell growth and induced caspase 3 activity in vitro. Furthermore, in a neuroblastoma xenograft mouse model, combined treatment of topotecan and bortezomib significantly delayed tumor formation compared to single-drug treatments.

Conclusions

Synthetic lethal screening provides a rational approach for selecting drugs for use in combination therapy and warrants clinical evaluation of the efficacy of the combination of topotecan and bortezomib or other NF-κB inhibitors in patients with high risk neuroblastoma.

Identification and characterization of a novel class of c-Jun N-terminal kinase inhibitors

In efforts to identify novel small molecules with anti-inflammatory properties, we discovered a unique series of tetracyclic indenoquinoxaline derivatives that inhibited lipopolysaccharide (LPS)-induced nuclear factor-κB/activating protein 1 activation. Compound IQ-1 (11H-indeno[1,2-b]quinoxalin-11-one oxime) was found to be a potent, noncytotoxic inhibitor of pro-inflammatory cytokine [interleukin (IL)-1α, IL-1β, IL-6, IL-10, tumor necrosis factor (TNF)-α, interferon-γ, and granulocyte-macrophage colony-stimulating factor] and nitric oxide production by human and murine monocyte/macrophages. Three additional potent inhibitors of cytokine production were identified through further screening of IQ-1 analogs. The sodium salt of IQ-1 inhibited LPS-induced TNF-α and IL-6 production in MonoMac-6 cells with IC(50) values of 0.25 and 0.61 μM, respectively. Screening of 131 protein kinases revealed that derivative IQ-3 [11H-indeno[1,2-b]quinoxalin-11-one-O-(2-furoyl)oxime]was a specific inhibitor of the c-Jun N-terminal kinase (JNK) family, with preference for JNK3. This compound, as well as IQ-1 and three additional oxime indenoquinoxalines, were found to be high-affinity JNK inhibitors with nanomolar binding affinity and ability to inhibit c-Jun phosphorylation. Furthermore, docking studies showed that hydrogen bonding interactions of the active indenoquinoxalines with Asn152, Gln155, and Met149 of JNK3 played an important role in enzyme binding activity. Finally, we showed that the sodium salt of IQ-1 had favorable pharmacokinetics and inhibited the ovalbumin-induced CD4(+) T-cell immune response in a murine delayed-type hypersensitivity model in vivo. We conclude that compounds with an indenoquinoxaline nucleus can serve as specific small-molecule modulators for mechanistic studies of JNKs as well as a potential leads for the development of anti-inflammatory drugs.

A cell-penetrating peptide suppresses inflammation by inhibiting NF-κB signaling

Nuclear factor-κB (NF-κB) is a central regulator of immune response and a potential target for developing anti-inflammatory agents. Mechanistic studies suggest that compounds that directly inhibit NF-κB DNA binding may block inflammation and the associated tissue damage. Thus, we attempted to discover peptides that could interfere with NF-κB signaling based on a highly conserved DNA-binding domain found in all NF-κB members. One such small peptide, designated as anti-inflammatory peptide-6 (AIP6), was characterized in the current study. AIP6 directly interacted with p65 and displayed an intrinsic cell-penetrating property. This peptide demonstrated significant anti-inflammatory effects in vitro and in vivo. In vitro, AIP6 inhibited the DNA-binding and transcriptional activities of the p65 NF-κB subunit as well as the production of inflammatory mediators in macrophages upon stimulation. Local administration of AIP6 significantly inhibited inflammation induced by zymosan in mice. Collectively, our results suggest that AIP6 is a promising lead peptide for the development of specific NF-κB inhibitors as potential anti-inflammatory agents.

Isolation, structural elucidation, and absolute stereochemistry of enigmazole A, a cytotoxic phosphomacrolide from the Papua New Guinea marine sponge Cinachyrella enigmatica

Enigmazole A (1), a novel phosphate-containing macrolide, was isolated from a Papua New Guinea collection of the marine sponge Cinachyrella enigmatica. The structure of 1, including the absolute stereochemistry at all eight chiral centers, was determined by a combination of spectroscopic analyses and a series of microscale chemical derivatization studies. Compound 1 is comprised of an 18-membered phosphomacrolide that contains an embedded exomethylene-substituted tetrahydropyran ring and an acyclic portion that spans an embedded oxazole moiety. Two additional analogues, 15-O-methylenigmazole A and 13-hydroxy-15-O-methylenigmazole A, were also isolated and assigned. The enigmazoles are the first phosphomacrolides from a marine source and 1 exhibited significant cytotoxicity in the NCI 60-cell line antitumor screen, with a mean GI(50) of 1.7 microM.

Antineoplastic mechanisms of niclosamide in acute myelogenous leukemia stem cells: inactivation of the NF-kappaB pathway and generation of reactive oxygen species

NF-kappaB may be a potential therapeutic target for acute myelogenous leukemia (AML) because NF-kappaB activation is found in primitive human AML blast cells. In this report, we initially discovered that the potent antineoplastic effect of niclosamide, a Food and Drug Administration-approved antihelminthic agent, was through inhibition of the NF-kappaB pathway in AML cells. Niclosamide inhibited the transcription and DNA binding of NF-kappaB. It blocked tumor necrosis factor-induced IkappaBalpha phosphorylation, translocation of p65, and expression of NF-kappaB-regulated genes. Niclosamide inhibited the steps TAK1-->IkappaB kinase (IKK) and IKK-->IkappaBalpha. Niclosamide also increased the levels of reactive oxygen species (ROS) in AML cells. Quenching ROS by the glutathione precursor N-acetylcysteine attenuated niclosamide-induced apoptosis. Our results together suggest that niclosamide inhibited the NF-kappaB pathway and increased ROS levels to induce apoptosis in AML cells. On translational study of the efficacy of niclosamide against AML, niclosamide killed progenitor/stem cells from AML patients but spared those from normal bone marrow. Niclosamide was synergistic with the frontline chemotherapeutic agents cytarabine, etoposide, and daunorubicin. It potently inhibited the growth of AML cells in vitro and in nude mice. Our results support further investigation of niclosamide in clinical trials of AML patients.