[Show abstract][Hide abstract] ABSTRACT: The front cover picture shows the pronounced impact of a nido-dicarbaborate cluster on the binding mode of a cyclooxygenase (COX) inhibitor. The commercially available COX-1-selective inhibitor indomethacin was converted to a highly potent and selective inhibitor (nido-indoborin) of the pathogenic isoform COX-2 by replacing the chlorophenyl ring with a boron cluster. Introduction of the cluster leads to a binding mode in the COX-2 site in which the indole moiety is flipped, compared with the orientation of indomethacin. Remarkably, the cluster opens up a subpocket by causing rotation of a leucine residue. The nido cluster is a promising pharmacophore and increases the stability and solubility of the inhibitor. More information can be found in the Communication by Evamarie Hey-Hawkins et al. on page 175 in Issue 2, 2016 (DOI: 10.1002/cmdc.201500199).
[Show abstract][Hide abstract] ABSTRACT: The cyclooxygenase enzymes (COX-1 and COX-2) are the therapeutic targets of non-steroidal anti-inflammatory drugs (NSAIDs). Neutralization of the carboxylic acid moiety of the NSAID indomethacin to an ester or amide functionality confers COX-2 selectivity, but the molecular basis for this selectivity has not been completely revealed through mutagenesis studies and/or x-ray crystallographic attempts. We expressed and assayed a number of divergent secondary shell COX-2 active site mutants and found that a COX-2 to COX-1 change at position 472 (Leu in COX-2, Met in COX-1) reduced the potency of enzyme inhibition by a series of COX-2-selective indomethacin amides and esters. In contrast, the potencies of indomethacin, arylacetic acid, propionic acid, and COX-2-selective diarylheterocycle inhibitors were either unaffected or only mildly affected by this mutation. Molecular dynamics simulations revealed identical equilibrium enzyme structures around residue 472; however, calculations indicated that the L472M mutation impacted local low-frequency dynamical COX constriction site motions by stabilizing the active site entrance and slowing constriction site dynamics. Kinetic analysis of inhibitor binding is consistent with the computational findings.
[Show abstract][Hide abstract] ABSTRACT: Cyclooxygenase (COX) is a homodimeric enzyme that catalyzes the oxygenation of arachidonic acid (AA) in the committed step of prostaglandin (PG) biosynthesis. Two isoforms of COX exist: COX-1, a housekeeping enzyme that maintains homeostatic PG synthesis, and COX-2, an inducible form involved in inflammatory and mitogenic processes. COX-2 can also oxygenate the endocannabinoids, 2-arachidonoyl glycerol (2-AG) and arachidonoyl ethanolamide (AEA) to their respective PG glyceryl ester and ethanolamide derivatives, respectively. PG biosynthesis occurs through COX's two distinct, interdependent peroxidase and cyclooxygenase activities. Hydroperoxides play a multifaceted role in COX catalysis by acting as substrates for the peroxidase reaction, initiators or activators for the cyclooxygenase reaction, and inactivators of enzymatic activity. Thus, regulation of peroxide levels, primarily by glutathione peroxidase, suppresses PG biosynthesis, while peroxides generated during the cyclooxygenase reaction impose an upper limit on PG production through enzyme inactivation. Within this context, functional differences between the COX isoforms with regard to their peroxide-dependent activation allow differential control of PG biosynthesis, even when both enzymes are present in the same intracellular compartment. Furthermore, substrate-specific differences in sensitivity to peroxide tone may play a role in determining the relative rate of oxygenation of AA versus the endocannabinoids.
[Show abstract][Hide abstract] ABSTRACT: Chronic inflammation results in increased production of reactive oxygen species (ROS), which can oxidize cellular molecules including lipids and DNA. Our laboratory has shown that 3-(2-deoxy-β-D-erythro-pentofuranosyl)pyrimido[1,2-α]purin-10(3H)-one (M1dG) is the most abundant DNA adduct formed from the lipid peroxidation product, malondialdehyde, or the DNA peroxidation product, base propenal. M1dG is mutagenic in bacterial and mammalian cells and is repaired via the nucleotide excision repair system. Here, we report that M1dG levels in intact DNA were increased from basal levels of 1 adduct per 108 nucleotides to 2 adducts per 106 nucleotides following adenine propenal treatment of RKO, HEK293 or HepG2 cells. We also found that M1dG in genomic DNA was oxidized in a time-dependent fashion to a single product, 6-oxo-M1dG, (to ~ 5 adducts per 107 nucleotides) and that this oxidation correlated with a decline in M1dG levels. Investigations in RAW264.7 macrophages indicate the presence of high basal levels of M1dG (1 adduct per 106 nucleotides) and the endogenous formation of 6-oxo-M1dG. This is the first report of the production of 6-oxo-M1dG in genomic DNA in intact cells and it has significant implications for understanding the role of inflammation in DNA damage, mutagenesis and repair.
No preview · Article · Oct 2015 · Chemical Research in Toxicology
[Show abstract][Hide abstract] ABSTRACT: A polypharmacologic approach to prostanoid based anti-inflammatory therapeutics was undertaken in order to exploit both the anti- and proinflammatory properties attributed to the various prostanoid receptors. Multitargeting of selected prostanoid receptors yielded a prototype compound, compound 1 (AGN 211377), that antagonizes prostaglandin D2 receptors DP1 (49) and DP2 (558), prostaglandin E2 receptors EP1 (266) and EP4 (117), prostaglandin F2α receptor (61), and thromboxane A2 receptor (TP) (11) while sparing EP2, EP3, and prostaglandin I2 receptors (IP); Kb values (in nanomoles) are given in parentheses. Compound 1 evoked a pronounced inhibition of cytokine/chemokine secretion from lipopolysaccharide or TNF-α stimulated primary human macrophages. These cytokine/chemokines included cluster of designation 40 receptor (CD40), epithelial-derived neutrophil-activating protein 78 (ENA-78), granulocyte colony stimulating factor (G-CSF), granulocyte macrophage colony stimulating factor (GM-CSF), IL-8, IL-18, monocyte chemotactic protein-1 (CCL2) (MCP-1), tissue plasminogen activator inhibitor (PAI-1), and regulated on activation, normal T cell expressed and secreted. In contrast, the inhibitory effects of most antagonists selective for a single receptor were modest or absent, and selective EP2 receptor blockade increased cytokine release in some instances. Compound 1 also showed clear superiority to the cyclooxygenase inhibitors diclofenac and rofecoxib. These findings reveal that blockade of multiple prostanoid receptors, with absent antagonism of EP2 and IP, may provide more effective anti-inflammatory activity than global suppression of prostanoid synthesis or highly selective prostanoid receptor blockade. These investigations demonstrate the first working example of prostanoid receptor polypharmacology for potentially safer and more effective anti-inflammatory therapeutics by blocking multiple proinflammatory receptors while sparing those with anti-inflammatory activity.-Wang, J. W., Woodward, D. F., Martos, J. L., Cornell, C. L., Carling, R. W., Kingsley, P. J., Marnett, L. J. Multitargeting of selected prostanoid receptors provides agents with enhanced anti-inflammatory activity in macrophages.
No preview · Article · Sep 2015 · The FASEB Journal
[Show abstract][Hide abstract] ABSTRACT: Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid (AA) and its ester analog, 2-arachidonoylglycerol (2-AG), to prostaglandins (PGs) and prostaglandin glyceryl esters (PG-Gs), respectively. Although the efficiency of oxygenation of these substrates by COX-2 in vitro is similar, cellular biosynthesis of PGs far exceeds that of PG-Gs. Evidence that the COX enzymes are functional heterodimers suggests that competitive interaction of AA and 2-AG at the allosteric site of COX-2 might result in differential regulation of the oxygenation of the two substrates when both are present. Modulation of AA levels in RAW264.7 macrophages uncovered an inverse correlation between cellular AA levels and PG-G biosynthesis. In vitro kinetic analysis using purified protein demonstrated that the inhibition of 2-AG oxygenation by high concentrations of AA far exceeded the inhibition of AA oxygenation by high concentrations of 2-AG. An unbiased systems-based mechanistic model of the kinetic data revealed that binding of AA or 2-AG at the allosteric site of COX-2 results in a decreased catalytic efficiency of the enzyme toward 2-AG, whereas 2-AG binding at the allosteric site increases COX-2's efficiency toward AA. The results suggest that substrates interact with COX-2 via multiple potential complexes involving binding to both the catalytic and allosteric sites. Competition between AA and 2-AG for these sites, combined with differential allosteric modulation, gives rise to a complex interplay between the substrates, leading to preferential oxygenation of AA.
No preview · Article · Sep 2015 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Background: In aggregate, livers donated after circulatory death (DCD) provide lower rates of graft and patient survival compared to brain dead donors (DBD). A method to identify DCD livers likely to perform well would lead to better decision-making regarding which livers to use and which to discard and is an important unmet clinical need. We hypothesized that the ischemic time between extubation and cold perfusion in the donor leads to immediate and unique biochemical and molecular changes that could be used to predict subsequent function. Methods: Biopsies from normal perfused liver, immediately after cold perfusion during DCD or DBD liver procurement, and during subsequent cold storage were analyzed and compared. Biochemical analysis included adenosine triphosphate (ATP), adenosine diphosphate, adenosine monophosphate, hypoxanthine, xanthine, inosine, nicotinamide adenine dinucleotide, and flavin adenine dinucleotide. Levels of these metabolites were compared to peak posttransplant aspartate aminotransferase as a marker of ischemic injury. Molecular analysis was performed by transcriptional profiling using high throughput sequencing. Results: Immediately after cold perfusion in the donor, biochemical analysis revealed lower levels of ATP and adenosine diphosphate in DCD versus DBD liver samples (P < 0.01 in both cases). The ATP levels showed high negative correlation with peak aspartate aminotransferase levels in recipients (P = 0.029). Four hundred seventy genes showed differential expression in DCD but not DBD samples immediately after cold perfusion compared with normal liver samples. Upregulated genes function in inflammation and immunity, whereas downregulated genes function in translation. During cold storage, samples were transcriptionally inactive with no consistent changes in messenger RNA expression. Conclusion: The ATP content of liver samples taken immediately postperfusion correlates with ischemic injury. Transcriptional profiling identifies biological process that may be relevant for enhancing function in DCD liver transplantation. Transcriptional inactivity of cold stored samples suggests messenger RNA levels over time are unlikely to provide prognostic data.
[Show abstract][Hide abstract] ABSTRACT: Cyclooxygenase-2 (COX-2) is a promising target for the imaging of cancer in a range of diagnostic and therapeutic settings. We report a near-infrared COX-2-targeted probe, fluorocoxib C (FC), for visualization of solid tumors by optical imaging. FC exhibits selective and potent COX-2 inhibition in both purified protein and human cancercell lines. In vivo optical imaging shows selective accumulation of FC in COX-2-overexpressing human tumor xenografts [1483 head and neck squamous cell carcinoma (HNSCC)] implanted in nude mice, while minimal uptake is detectable in COX-2-negative tumor xenografts (HCT116)or 1483 HNSCC xenografts preblocked with the COX-2-selective inhibitor celecoxib. Time course imaging studies conducted from 3 h to 7-day post-FC injection revealed a marked reduction in nonspecific fluorescent signals with retention of fluorescence in 1483 HNSCC tumors. Thus, use of FC in a delayed imaging protocol offers an approach to improve imaging signal-to-noise that should improve cancer detection in multiple preclinical and clinical settings.
No preview · Article · May 2015 · Journal of Biomedical Optics
[Show abstract][Hide abstract] ABSTRACT: Cyclooxygenase-1 (COX-1) is implicated in ovarian cancer. However, patterns of COX expression and function have been unclear and controversial. In this report, patterns of COX-1 and COX-2 gene expression were obtained from RNA-seq data through The Cancer Genome Atlas. Our analysis revealed markedly higher COX-1 mRNA expression than COX-2 in high-grade serous ovarian cancers (HGSOC) and higher COX-1 expression in HGSOC tumors than 10 other tumor types. High microarray. In contrast, lower or similar expression of COX-1 compared to COX-2 was observed in endometrioid, mucinous and clear cell tumors. Stable COX-1 knockdown in HGSOC-representative OVCAR-3 ovarian cancer cells reduced gene expression in multiple pro-tumorigenic pathways. Functional cell viability, clonogenicity, and migration/invasion assays were consistent with transcriptomic changes. These effects were reversed by stable over-expression of COX-1 in SKOV-3 cells. Our results demonstrate a distinct pattern of COX-1 over-expression in HGSOC tumors and strong association of COX-1 with multiple pro-tumorigenic pathways in ovarian cancer cells. cancer and support further development of methods to selectively target COX-1 in the management of HGSOC tumors.
[Show abstract][Hide abstract] ABSTRACT: We report the design and synthesis of an activatable molecular imaging probe to detect hypoxia in mouse models of retinal vascular diseases. Hypoxia of the retina has been associated with the initiation and progression of blinding retinal vascular diseases including age-related macular degeneration, diabetic retinopathy, and retinopathy of prematurity. In vivo retinal imaging of hypoxia may be useful for early detection and timely treatment of retinal diseases. To achieve this goal, we synthesized HYPOX-3, a near-infrared (NIR) imaging agent coupled to a dark quencher, Black Hole Quencher 3 (BHQ3), which has been previously reported to contain a hypoxia-sensitive cleavable azo-bond. HYPOX-3 was cleaved in hypoxic retinal cell culture and animal models, enabling detection of hypoxia with high signal-to-noise ratios without acute toxicity. HYPOX-3 fluorescences in hypoxic cells and tissues and was undetectable under normoxia. These imaging agents are promising candidates for imaging retinal hypoxia in preclinical disease models and patients.