Pharmacological characterization of 1-(5-chloro-6-(trifluoromethoxy)-1H-benzoimidazol-2-yl)-1H-pyrazole-4-carboxylic acid (JNJ-42041935), a potent and selective hypoxia-inducible factor prolyl hydroxylase inhibitor.

The hypoxia-inducible factor (HIF) prolyl hydroxylase (PHD) enzymes represent novel targets for the treatment of anemia, ulcerative colitis, and ischemic and metabolic disease inter alia. We have identified a novel small-molecule inhibitor of PHD, 1-(5-chloro-6-(trifluoromethoxy)-1H-benzoimidazol-2-yl)-1H-pyrazole-4-carboxylic acid (JNJ-42041935), through structure-based drug design methods. The pharmacology of JNJ-42041935 was investigated in enzyme, cellular, and whole-animal systems and was compared with other compounds described in the literature as PHD inhibitors. JNJ-42041935, was a potent (pK(I) = 7.3-7.9), 2-oxoglutarate competitive, reversible, and selective inhibitor of PHD enzymes. In addition, JNJ-42041935 was used to compare the effect of selective inhibition of PHD to intermittent, high doses (50 µg/kg i.p.) of an exogenous erythropoietin receptor agonist in an inflammation-induced anemia model in rats. JNJ-42041935 (100 µmol/kg, once a day for 14 days) was effective in reversing inflammation-induced anemia, whereas erythropoietin had no effect. The results demonstrate that JNJ-42041935 is a new pharmacological tool, which can be used to investigate PHD inhibition and demonstrate that PHD inhibitors offer great promise for the treatment of inflammation-induced anemia.

Single-cell microarray analysis in hippocampus CA1: demonstration and validation of cellular heterogeneity.

Laser capture microdissection in combination with microarrays allows for the expression analysis of thousands of genes in selected cells. Here we describe single-cell gene expression profiling of CA1 neurons in the rat hippocampus using a combination of laser capture, T7 RNA amplification, and cDNA microarray analysis. Subsequent cluster analysis of the microarray data identified two different cell types: pyramidal neurons and an interneuron. Cluster analysis also revealed differences among the pyramidal neurons, indicating that even a single cell type in vivo is not a homogeneous population of cells at the gene expression level. Microarray data were confirmed by quantitative RT-PCR and in situ hybridization. We also report on the reproducibility and sensitivity of this combination of methods. Single-cell gene expression profiling offers a powerful tool to tackle the complexity of the mammalian brain.

Molecular and pharmacological characterization of serotonin 5-HT2A and 5-HT2B receptor subtypes in dog.

We report the cloning, molecular characterization, and pharmacological characterization of the canine 5-HT2A and 5-HT2B receptors. The canine and human 5-HT2A receptors share 93% amino acid homology. The canine and human 5-HT2B receptors are also highly conserved (87% homology) with the exception of the carboxyl termini where the canine protein is 62 amino acids shorter. Both the canine 5-HT2A and 5-HT2B receptors have high affinity for [3H]5-HT (KD=4.50+/-0.89 nM and 3.10+/-0.82 nM, respectively) and, in general, the pharmacology of these two receptors matches closely the pharmacology of their human homologs for the 19 serotonergic ligands tested. However, the functional response (Ca2+ mobilization) of the canine 5-HT2B receptor to several agonists was weaker compared to the human 5-HT2B receptor. Using quantitative reverse transcriptase polymerase chain reaction, a high expression level of canine 5-HT2A receptor mRNA was detected in the brain and lower levels in peripheral tissues, whereas the highest levels of canine 5-HT2B receptor mRNA were observed in lungs and smooth muscles. A significant level of canine 5-HT2B receptor mRNA was detected in brain tissue. The availability of the full sequence and pharmacology of the canine 5-HT2A and canine 5-HT2B receptors provides useful information for the interpretation of previous and future pharmacological studies of 5-HT2A/2B ligands in dog.

Prolyl hydroxylase inhibition corrects functional iron deficiency and inflammation-induced anaemia in rats.

BACKGROUND AND PURPOSE: Small-molecule inhibitors of prolyl hydroxylase (PHD) enzymes are a novel target for the treatment of anaemia and functional iron deficiency (FID). Other than being orally bioavailable, the differentiation of PHD inhibitors from recombinant human erythropoietin (rhEPO) has not been demonstrated. EXPERIMENTAL APPROACH: JNJ-42905343 was identified and characterized as a novel inhibitor of PHD and its action was compared with rhEPO in healthy rats and in a rat model of inflammation-induced anaemia and FID [peptidoglycan-polysaccharide (PGPS) model]. KEY RESULTS: Oral administration of JNJ-42905343 to healthy rats increased the gene expression of cytochrome b (DcytB) and divalent metal-ion transporter 1 (DMT1) in the duodenum, and increased plasma EPO. Repeated administration of JNJ-42905343 for 28 days increased blood haemoglobin, mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV). The serum iron concentration was increased with low doses (0.3 mg·kg(-1) ) but reduced at high doses (6 mg·kg(-1) ). In PGPS-treated rats, administration of JNJ-42905343 for 28 days corrected FID and anaemia, as reflected by increased blood haemoglobin, MCH and MCV. Increased expression of DcytB and DMT1 genes in the duodenum resulting in increased iron availability was defined as the mechanism for these effects. rhEPO did not affect DcytB and DMT1 and was not effective in PGPS-treated rats. CONCLUSIONS AND IMPLICATIONS: PHD inhibition has a beneficial effect on iron metabolism in addition to stimulating the release of EPO. Small-molecule inhibitors of PHD such as JNJ-42905343 represent a mechanism distinct from rhEPO to treat anaemia and FID.

Single-cell laser-capture microdissection and RNA amplification.

Generating gene-expression profiles from laser-captured cells requires the successful combination of laser-capture microdissection, RNA extraction, RNA amplification, and microarray analysis. To permit single-cell gene-expression profiling, the RNA amplification method has to be sufficiently powerful to bridge the gap between the amount of RNA available from a single cell to what is required by the microarray, a gap that spans 5 to 6 orders of magnitude. This chapter focuses on the amplification of RNA using a two-round T7 RNA amplification method. The protocols described are adapted for laser-captured material and have been used to generate gene expression profiles from single laser-captured cells.

Chimeric, mutant orexin receptors show key interactions between orexin receptors, peptides and antagonists.

Orexin receptor antagonists are being investigated as therapeutic agents for insomnia and addictive disorders. In this study the interactions between the orexin receptors (orexin 1 receptor and orexin 2 receptor), orexin peptides, and small molecule orexin antagonists were explored. To study these phenomena, a variety of mutant orexin receptors was made and tested using receptor binding and functional assays. Domains of the two orexin receptors were exchanged to show the critical ligand binding domains for orexin peptides and representative selective orexin receptor antagonists. Results from domain exchanges between the orexin receptors suggest that transmembrane domain 3 is crucially important for receptor interactions with small molecule antagonists. These data also suggest that the orexin peptides occupy a larger footprint, interacting with transmembrane domain 1, the amino terminus and transmembrane domain 5 as well as transmembrane domain 3. Transmembrane domain 3 has been shown to be an important part of the small molecule binding pocket common to rhodopsin and ß2-adrenergic receptors. Additional orexin receptor 2 point mutations were made based on the common arrangement of receptor transmembrane domains shown in the G-protein coupled receptor crystal structure literature and the impact of orexin 2 receptor residue threonine 135 on the ligand selectivity of the 2 orexin receptors. These data support a model of the orexin receptor binding pocket in which transmembrane domains 3 and 5 are prominent contributors to ligand binding and functional activity. The data also illustrate key contact points for ligand interactions in the consensus small molecule pocket of these receptors.

A novel form of neurotensin post-translationally modified by arginylation.

A novel bioactive form of neurotensin post-translationally modified at a Glu residue was isolated from porcine intestine. Purification of the peptide was guided by detection of intracellular Ca2+ release in SK-N-SH neuroblastoma cells. Using high resolution accurate mass analysis on an ion trap Fourier transform mass spectrometer, the post-translational modification was identified as arginine linked to the gamma-carboxyl of Glu via an isopeptide bond, and we named the newly identified peptide "arginylated neurotensin" (R-NT, N-(neurotensin-C5-4-yl)arginine). Although arginylation is a known modification of N-terminal amino groups in proteins, its presence at a Glu side chain is unique. The finding places neurotensin among the few physiologically active peptides that occur both in post-translationally modified and unmodified forms. Pharmacologically, we characterized R-NT for its ligand activity on three known neurotensin receptors, NTR1, -2, and -3, and found that R-NT has similar pharmacological properties to those of neurotensin, however, with a slightly higher affinity to all three receptors. We expressed the intracellular receptor NTR3 as a soluble protein secreted into the cell culture medium, which allowed characterization of its R-NT and neurotensin binding properties. The creation of soluble NTR3 also provides a potential tool for neutralizing neurotensin action in vivo and in vitro. We have shown that SK-N-SH neuroblastoma cells express NTR1 and NTR3 but not NTR2, suggesting that the Ca2+ mobilization elicited by R-NT is via NTR1.

INSL5 is a high affinity specific agonist for GPCR142 (GPR100).

Insulin-like peptide 5 (INSL5) is a peptide that belongs to the relaxin/insulin family, and its receptor has not been identified. In this report, we demonstrate that INSL5 is a specific agonist for GPCR142. Human INSL5 displaces the binding of (125)I-relaxin-3 to GPCR142 with a high affinity (K(i) = 1.5 nM). In a saturation binding assay, (125)I-INSL5 binds GPCR142 with a K(d) value of 2.5 nM. In functional guanosine (gamma-thio)-triphosphate binding and cAMP accumulation assays, INSL5 potently activates GPCR142 with EC(50) values of 1.3 and 1.2 nM, respectively. In addition, INSL5 stimulates Ca(2+) mobilization in HEK293 cells expressing GPCR142 and G alpha(16). Overall, INSL5 behaves as an agonist for GPCR142 similar to relaxin-3. However, unlike relaxin-3, which is also a potent agonist for GPCR135 and LGR7, INSL5 does not activate either GPCR135 or LGR7. INSL5 inhibits (125)I-relaxin-3 binding to GPCR135 with a low potency (K(i) = 500 nM). A functional assay shows that INSL5 (1 microm) is a weak antagonist for GPCR135. In addition, INSL5 (up to 1 microm) shows no affinity or activity at LGR7 or LGR8 either in a binding assay or a bio-functional assay. Previously, we have demonstrated that GPCR142 mRNA is expressed in peripheral tissues, particularly in the colon. Here we show that INSL5 mRNA is expressed in many peripheral tissues, similar to GPCR142. The high affinity interaction between INSL5 and GPCR142 coupled with their co-evolution and partially overlapping tissue expression patterns strongly suggest that INSL5 is an endogenous ligand for GPCR142.