Characterization of the human cysteinyl leukotriene 2 receptor

The contractile and inflammatory actions of the cysteinyl leukotrienes (CysLTs), LTC(4), LTD(4), and LTE(4), are thought to be mediated through at least two distinct but related CysLT G protein-coupled receptors. The human CysLT(1) receptor has been recently cloned and characterized. We describe here the cloning and characterization of the second cysteinyl leukotriene receptor, CysLT(2), a 346-amino acid protein with 38% amino acid identity to the CysLT(1) receptor. The recombinant human CysLT(2) receptor was expressed in Xenopus oocytes and HEK293T cells and shown to couple to elevation of intracellular calcium when activated by LTC(4), LTD(4), or LTE(4). Analyses of radiolabeled LTD(4) binding to the recombinant CysLT(2) receptor demonstrated high affinity binding and a rank order of potency for competition of LTC(4) = LTD(4) LTE(4). In contrast to the dual CysLT(1)/CysLT(2) antagonist, BAY u9773, the CysLT(1) receptor-selective antagonists MK-571, montelukast (Singulair(TM)), zafirlukast (Accolate(TM)), and pranlukast (Onon(TM)) exhibited low potency in competition for LTD(4) binding and as antagonists of CysLT(2) receptor signaling. CysLT(2) receptor mRNA was detected in lung macrophages and airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, and brain, and the receptor gene was mapped to chromosome 13q14, a region linked to atopic asthma.     

Functional characteristics of cysteinyl-leukotriene receptor subtypes

Cysteinyl-leukotrienes, i.e. leukotriene (LT) C4, D4 and E4, are inflammatory mediators and potent airway- and vasoconstrictors. Two different cysteinyl-leukotriene receptors, CysLT1 and CysLT2, have been cloned and functionally characterised using potent CysLT1 receptor antagonists and the dual CysLT1/CysLT2 receptor antagonist BAY u9773. However, the rank order of potency of the cysteinyl-leukotrienes at the CysLT receptors differs between tissues and studies, and a CysLT receptor classification based on agonist selectivity has not been established. In addition, the existence of more than two receptor subtypes for cysteinyl-leukotrienes has been suggested.     

In situ 2D fluorometry and chemometric monitoring of mammalian cell cultures

The main objective of the present study was to investigate the use of in situ 2D fluorometry for monitoring key bioprocess variables in mammalian cell cultures, namely the concentration of viable cells and the concentration of recombinant proteins. All studies were conducted using a recombinant Baby Hamster Kidney (BHK) cell line expressing a fusion glycoprotein IgG1-IL2 cultured in batch and fed-batch modes. It was observed that the intensity of fluorescence signals in the excitation/emission wavelength range of amino acids, vitamins and NAD(P)H changed along culture time, although the dynamics of single fluorophors could not be correlated with the dynamics of the target state variables. Therefore, multivariate chemometric modeling was adopted as a calibration methodology. 2D fluorometry produced large volumes of redundant spectral data, which were first filtered by principal components analysis (PCA). Then, a partial least squares (PLS) regression was applied to correlate the reduced fluorescence maps with the target state variables. Two validation strategies were used to evaluate the predictive capacity of the developed PLS models. Accurate estimations of viable cells density (r(2) = 0.95; 99.2% of variance captured in the training set; r(2) = 0.91; 97.7% of variance captured in the validation set) and of glycoprotein concentration (r(2) = 0.99 and 99.7% of variance captured in the training set; r(2) = 0.99 and 99.3% of variance captured in the validation set) were obtained over a wide range of reactor operation conditions. The results presented herein confirm that 2D fluorometry constitutes a reliable methodology for on-line monitoring of viable cells and recombinant protein concentrations in mammalian cell cultures.     

The molecular characterization and tissue distribution of the human cysteinyl leukotriene CysLT(2) receptor

Cysteinyl leukotrienes (CysLTs), slow-reacting substances of anaphylaxis, are lipid mediators known to possess potent proinflammatory action. Pharmacological studies using CysLTs indicate that at least two classes of G protein-coupled receptors (GPCRs), named CysLT(1) and CysLT(2), exist; the former is sensitive and the latter is resistant to the CysLT(1) antagonists currently used to treat asthma. Although the CysLT(1) receptor gene has been recently cloned, the molecular identity of the CysLT(2) receptor has remained elusive. Here we show that the pharmacological profile of an orphan GPCR (PSEC0146) is consistent with that of the CysLT(2) receptor. In human embryonic kidney 293 cells that express the PSEC0146 cDNA, leukotriene C(4) (LTC(4)) and leukotriene D(4) (LTD(4)) induce equal increases in intracellular calcium mobilization; these increases are not affected by CysLT(1) antagonists. Additionally, [(3)H]LTC(4) specifically binds to membranes from COS-1 cells transiently transfected with PSEC0146. Large amounts of the PSEC0146 mRNA are found in human heart, placenta, spleen, and peripheral blood leukocytes but not in the lung and the trachea. Pharmacological feature and expression studies will eventually lead to a better understanding of the classification of CysLT receptors, possibly leading to a reconsideration of the pathological and physiological role of CysLTs.     

Robust discriminant analysis and its application to identify protein coding regions of rice genes

Identification of protein coding regions is fundamentally a statistical pattern recognition problem. Discriminant analysis is a statistical technique for classifying a set of observations into predefined classes and it is useful to solve such problems. It is well known that outliers are present in virtually every data set in any application domain, and classical discriminant analysis methods (including linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA)) do not work well if the data set has outliers. In order to overcome the difficulty, the robust statistical method is used in this paper. We choose four different coding characters as discriminant variables and an approving result is presented by the method of robust discriminant analysis.     

An innovative chemometric method for processing direct introduction high resolution mass spectrometry metabolomic data: independent component–discriminant analysis (IC–DA)

Introduction

To perform large scale metabolomic analyses, high throughput approaches are required. The direct introduction mass spectrometry (DIMS) approach appears to be very attractive to achieve this goal. However, processing DIMS data is still very challenging due to the large number of samples and the intrinsic complexity of the mass spectra.

Objectives

The objective of this study is to develop a computational procedure, based on an innovative chemometric method, i.e. Independent component–discriminant analysis (IC–DA), for processing DIMS data.

Method

Metabolomic fingerprints were obtained by direct introduction high resolution mass spectrometry (DI-HRMS) analysis of urine samples of subjects that had been professionally exposed to pesticides. Spectral data were processed using the developed IC–DA procedure. Results obtained from this method were compared to those obtained by the conventional Partial least squares–discriminant analysis (PLS–DA). For both the IC–DA and PLS–DA methods, a validation was performed based on a permutation test.

Result

IC–DA results enabled a good detection of discriminant variables and a clear discrimination of control samples and exposure classes whereas a less striking discrimination was obtained with PLS–DA. Putative annotation of these variables was performed using metabolomic databases. Targeted correlation analysis was used for the detection of ions associated with the most discriminant variables, consolidating their identity assignment.

Conclusion

This study demonstrated the efficiency of IC–DA to discriminate the different exposure groups. As well the improvement of high throughput metabolomic studies was provided by combining DI–HRMS with this new chemometric tool.

     

Validation of chemometric models for the determination of deoxynivalenol on maize by mid-infrared spectroscopy

Validation methods for chemometric models are presented, which are a necessity for the evaluation of model performance and prediction ability. Reference methods with known performance can be employed for comparison studies. Other validation methods include test set and cross validation, where some samples are set aside for testing purposes. The choice of the testing method mainly depends on the size of the original dataset. Test set validation is suitable for large datasets (>50), whereas cross validation is the best method for medium to small datasets (<50). In this study the K-nearest neighbour algorithm (KNN) was used as a reference method for the classification of contaminated and blank corn samples. A Partial least squares (PLS) regression model was evaluated using full cross validation. Mid-Infrared spectra were collected using the attenuated total reflection (ATR) technique and the fingerprint range (800–1800 cm⁻¹) of 21 maize samples that were contaminated with 300 – 2600 μg/kg deoxynivalenol (DON) was investigated. Separation efficiency after principal component analysis/cluster analysis (PCA/CA) classification was 100%. Cross validation of the PLS model revealed a correlation coefficient of r=0.9926 with a root mean square error of calibration (RMSEC) of 95.01. Validation results gave an r=0.8111 and a root mean square error of cross validation (RMSECV) of 494.5 was calculated. No outliers were reported. Presented at the 25^th Mykotoxin Workshop in Giessen, Germany, May 19–21, 2003     

G protein-coupled receptor crosstalk and signaling in hematopoietic stem and progenitor cells

A variety of G protein-coupled receptors (GPCRs) is expressed in hematopoietic stem and progenitor cells (HPCs), including the chemokine receptor CXCR4, the leukotriene receptor CysLT1, the sphingosine 1-phosphate receptor S1P1, the cannabinoid receptor CB2, and the complement receptor C3aR. While the role of CXCR4 in stem cell homing is largely established, the function of the other GPCRs expressed in HPCs is only partially understood. CXCR4 and CysLT1 inhibit their own activation after ligand binding (homologous desensitization). Stimulation of S1P1 or C3aR has been shown to activate CXCR4 in HPCs that may sensitize CXCR4-dependent stem cell homing. In contrast, activation of CXCR4 results in a loss of CysLT1 function, which is most likely mediated by protein kinase C (PKC) signaling (heterologous desensitization) and could explain the ineffectiveness of CysLT1 antagonists to mobilize HPCs in vivo. Further characterization of GPCR crosstalk will allow a better understanding of HPC trafficking.     

Antiasthmatic drugs targeting the cysteinyl leukotriene receptor 1 alleviate central nervous system inflammatory cell infiltration and pathogenesis of experimental autoimmune encephalomyelitis

Cysteinyl leukotrienes (CysLTs) are potent proinflammatory mediators and are considered to play a key role in inflammatory diseases such as asthma. Antagonists targeting the receptor of CysLTs (CysLT1) are currently used as antiasthmatic drugs. CysLTs have also been implicated in other inflammatory reactions. In this study, we report that in experimental autoimmune encephalomyelitis animals, CysLT1 is upregulated in immune tissue and the spinal cord, and CysLT levels in the blood and cerebrospinal fluid are also higher than in normal mice. Two clinically used antiasthma drugs, montelukast and zafirlukast, both targeting CysLT1, effectively block the CNS infiltration of inflammatory cells and thus reduce the incidence, peak severity, and cumulative clinical scores. Further study indicated that CysLT1 signaling does not affect the differentiation of pathogenic T helper cells. It might affect the pathogenesis of experimental autoimmune encephalomyelitis by increasing the secretion of IL-17 from myelin oligodendrocyte glycoprotein-specific T cells, increasing the permeability of the blood-brain barrier and inducing chemotaxis of T cells. These effects can be blocked by CysLT1 antagonists. Our findings indicate that the antiasthmatic drugs against CysLT1 can also be used to treat multiple sclerosis.     

Distinct roles of CysLT1 and CysLT2 receptors in oxygen glucose deprivation-induced PC12 cell death

Cysteinyl leukotrienes are involved in ischemic brain injury, and their receptors (CysLT(1) and CysLT(2)) have been cloned. To clarify which subtype mediates the ischemic neuronal injury, we performed permanent transfection to increase CysLT(1) and CysLT(2) receptor expressions in PC12 cells. Oxygen glucose deprivation (OGD)-induced cell death was detected by Hoechst 33258 and propidium iodide fluorescent staining as well as by flow cytometry. OGD induced late phase apoptosis mainly and necrosis minimally. Over-expression of CysLT(1) receptor decreased and over-expression of CysLT(2) receptor increased OGD-induced cell death. An agonist LTD(4) (10(-7)M) also induced apoptosis, especially in CysLT(2) receptor over-expressing cells. A selective CysLT(1) receptor antagonist montelukast did not affect OGD-induced apoptosis; while non-selective CysLT receptor antagonist Bay u9773 inhibited OGD-induced apoptosis, especially in CysLT(2) receptor over-expressing cells. Thus, CysLT(1) and CysLT(2) receptors play distinct roles in OGD-induced PC12 cell death; CysLT(1) attenuates while CysLT(2) facilitates the cell death.     

Cysteinyl leukotrienes are autocrine and paracrine regulators of fibrocyte function

Pulmonary fibrosis is characterized by the accumulation of fibroblasts and myofibroblasts. These cells may accumulate from three potential sources: the expansion of resident lung fibroblasts, the process of epithelial-mesenchymal transition, or the recruitment and differentiation of circulating mesenchymal precursors known as fibrocytes. We have previously demonstrated that fibrocytes participate in lung fibrogenesis following administration of FITC to mice. We now demonstrate that leukotriene-deficient 5-LO(-/-) mice are protected from FITC-induced fibrosis. Both murine and human fibrocytes express both cysteinyl leukotriene receptor (CysLT) 1 and CysLT2. In addition, fibrocytes are capable of producing CysLTs and can be regulated via the autocrine or paracrine secretion of these lipid mediators. Exogenous administration of leukotriene (LT) D(4), but not LTC(4) induces proliferation of both murine and human fibrocytes in a dose-dependent manner. Consistent with this result, CysLT1 receptor antagonists are able to block the mitogenic effects of exogenous LTD(4) on fibrocytes. Endogenous production of CysLTs contributes to basal fibrocyte proliferation, but does not alter fibrocyte responses to basic fibroblast growth factor. Although CysLTs can induce the migration of fibrocytes in vitro, they do not appear to be essential for fibrocyte recruitment to the lung in vivo, possibly due to compensatory chemokine-mediated recruitment signals. However, CysLTs do appear to regulate the proliferation of fibrocytes once they are recruited to the lung. These data provide mechanistic insight into the therapeutic benefit of leukotriene synthesis inhibitors and CysLT1 receptor antagonists in animal models of fibrosis.     

Analysis of chemometric models applied to Raman spectroscopy for monitoring key metabolites of cell culture

The Food and Drug Administration (FDA) initiative of Process Analytical Technology (PAT) encourages the monitoring of biopharmaceutical manufacturing processes by innovative solutions. Raman spectroscopy and the chemometric modeling tool partial least squares (PLS) have been applied to this aim for monitoring cell culture process variables. This study compares the chemometric modeling methods of Support Vector Machine radial (SVMr), Random Forests (RF), and Cubist to the commonly used linear PLS model for predicting cell culture components—glucose, lactate, and ammonia. This research is performed to assess whether the use of PLS as standard practice is justified for chemometric modeling of Raman spectroscopy and cell culture data. Model development data from five small-scale bioreactors (2 × 1 L and 3 × 5 L) using two Chinese hamster ovary (CHO) cell lines were used to predict against a manufacturing scale bioreactor (2,000 L). Analysis demonstrated that Cubist predictive models were better for average performance over PLS, SVMr, and RF for glucose, lactate, and ammonia. The root mean square error of prediction (RMSEP) of Cubist modeling was acceptable for the process concentration ranges of glucose (1.437 mM), lactate (2.0 mM), and ammonia (0.819 mM). Interpretation of variable importance (VI) results theorizes the potential advantages of Cubist modeling in avoiding interference of Raman spectral peaks. Predictors/Raman wavenumbers (cm⁻¹) of interest for individual variables are X1139–X1141 for glucose, X846–X849 for lactate, and X2941–X2943 for ammonia. These results demonstrate that other beneficial chemometric models are available for use in monitoring cell culture with Raman spectroscopy.     

Synergistic antiallergic activity of combined histamine H1- and cysteinyl leukotriene1-receptor blockade in human bronchus.

Mast cell histamine (HA) and cysteinyl leukotrienes (CysLT) account for most of the early phase bronchospasm in asthma. However, activation of the smooth muscle CysLT1-receptor plays a major role in asthmatic bronchospasms. CysLT-receptor antagonists or CysLT-synthesis inhibitors are efficacious in asthma but do not completely abolish asthmatic bronchospasms. A recent clinical study showed that combined antagonists loratadine (H1) and zafirlukast (CysLT1) were more effective against allergic bronchospasms than either drug alone. We examined the combined efficacy of H1- and CysLT1-receptor antagonists in allergic human bronchus. The H1- and CysLT1-receptor antagonists chlorpheniramine (CTM; 1 microM) and MK-571 (0.03 microM), were tested alone and in combination, against anti-human IgE antibody (Ab)-induced contractions of passively sensitized isolated human bronchus. Ab-induced allergic contractions were reduced 15% and 36% by CTM (1 microM) and MK-571 (0.03 microM), respectively. Combined CTM (1 microM) and MK-571 (0.03 microM) significantly inhibited the Ab response by 87%. Mechanistic investigations in isolated human bronchus and cultured human cord blood mast cells suggest that H1- and CysLT-receptor interactions likely occur at the airway smooth muscle level. CTM and MK-571 synergistically inhibited human allergic bronchospasm in the present in vitro model. The mechanism underlying this synergistic activity requires further investigation.     

Pharmacotherapy of diseases mediated by 5-lipoxygenase pathway eicosanoids

Inflammatory eicosanoids generated by the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism are now known to have at least 6 receptors: OXE, which recognizes 5-HETE and 5-oxo-ETE; a putative receptor recognizing a potent 5-oxo-ETE metabolite, FOG(7); the LTB(4) receptors, BLT1 and BLT2; the cysteinyl leukotriene receptors, CysLT(1) and CysLT(2), which recognize leukotrienes LTC(4), LTD(4), LTE(4) and LTF(4). The 5-LO pathway is activated in many diseases and invokes inflammatory responses not affected by glucocorticoids, but therapy with selective BLT1 or CysLT(1) antagonists in asthma has met with variable success. Studies show that 5-LO pathway eicosanoids are not primary mediators in all cases of asthma, but may be especially important in severe persistent asthma, aspirin- and exercise-induced asthma, allergic rhinitis, COPD, idiopathic pulmonary fibrosis, atherosclerosis, atopic dermatitis, acne and ischemia-related organ injury. These disorders appear to involve multiple 5-LO pathway eicosanoids and receptor subtypes, suggesting that inhibition of the pathway at the level of 5-LO may be necessary for maximal efficacy.     

The application of a 3D-QSAR (autoMEP/PLS) approach as an efficient pharmacodynamic-driven filtering method for small-sized virtual library: application to a lead optimization of a human A3 adenosine receptor antagonist

We have recently reported that the combination of molecular electrostatic potential (MEP) surface properties (autocorrelation vectors) with the conventional partial least squares (PLS) analysis can be used to produce a robust ligand-based 3D structure-activity relationship (autoMEP/PLS) for the prediction of the human A3 receptor antagonist activities. Here, we present the application of the 3D-QSAR (autoMEP/PLS) approach as an efficient and alternative pharmacodynamic filtering method for small-sized virtual library. For this purpose, a small-sized combinatorial library (841 compounds) was derived from the scaffold of the known human A3 antagonist pyrazolo-triazolo-pyrimidines. The most interesting analogues were further prioritized for synthesis and pharmacological characterization. Remarkably, we have found that all the newly synthetized compounds are correctly predicted as potent human A3 antagonists. In particular, two of them are correctly predicted as sub-nanomolar inhibitors of the human A3 receptor.