Are noscapine and raloxifene ligands of the bradykinin B2 receptor? An assessment based on the human umbilical vein contractility assay.

The centrally acting antitussive opiate derivative, noscapine, has been claimed to be a non-competitive bradykinin B2 receptor antagonist. Raloxifene, a selective estrogen receptor modulator, was predicted to bind the bradykinin B2 receptor and to exert a partial agonist activity. These intriguing claims suggest that new molecular scaffolds ("chemotypes") may be identified for small molecule ligands of kinin receptors and that some off-target effects of noscapine or raloxifene may be mediated by bradykinin B2 receptors. An established contractile bioassay for ligands of the bradykinin B2 receptor, the isolated human umbilical vein, was exploited to characterize the inhibitory effect of noscapine and raloxifene on the B2 receptor-mediated contractile response to bradykinin. Observed effects were compared with those of the peptide antagonist icatibant, a potent, selective and competitive B2 receptor antagonist. Our results indicate that neither noscapine (2.5 µM) nor raloxifene (20 µM) behave as B2 receptor antagonists in concentrations that vastly exceeded an effective concentration of the control antagonist, icatibant; further, none of these drugs had direct contractile effects. It is suggested that the previously reported B2 receptor inhibitory effect of noscapine, a putative sigma-receptor agonist, might result from an indirect physiological antagonism, while raloxifene did not appear to have any significant affinity for the B2 receptors.

Bifunctional ligands of the bradykinin B2 and B1 receptors: An exercise in peptide hormone plasticity.

Kinins are the small and fragile hydrophilic peptides related to bradykinin (BK) and derived from circulating kininogens via the action of kallikreins. Kinins bind to the preformed and widely distributed B2 receptor (B2R) and to the inducible B1 receptor (B1R). B2Rs and B1Rs are related G protein coupled receptors that possess natural agonist ligands of nanomolar affinity (BK and Lys BK for B2Rs, Lys-des-Arg9-BK for B1R). Decades of structure-activity exploration have resulted in the production of peptide analogs that are antagonists, one of which is clinically used (the B2R antagonist icatibant), and also non-peptide ligands for both receptor subtypes. The modification of kinin receptor ligands has made them resistant to extracellular or endosomal peptidases and/or produced bifunctional ligands, defined as agonist or antagonist peptide ligands conjugated with a chemical fluorophore (emitting in the whole spectrum, from the infrared to the ultraviolet), a drug-like moiety, an epitope, an isotope chelator/carrier, a cleavable sequence (thus forming a pro-drug) and even a fused protein. Dual molecular targets for specific modified peptides may be a source of side effects or of medically exploitable benefits. Biotechnological protein ligands for either receptor subtype have been produced: they are enhanced green fluorescent protein or the engineered peroxidase APEX2 fused to an agonist kinin sequence at their C-terminal terminus. Antibodies endowed with pharmacological actions (agonist, antagonist) at B2R have been reported, though not monoclonal antibodies. These findings define classes of alternative ligands of the kinin receptor of potential therapeutic and diagnostic value.

S100A9 potentiates the activation of neutrophils by the etiological agent of gout, monosodium urate crystals.

Gout is one of the most painful types of arthritis that arises when the body mounts an acute inflammatory reaction against a crystallized form of uric acid known as monosodium urate crystals (MSUs). Although MSUs are known to activate neutrophils, the most abundant leukocyte in the synovial fluid of patients with gout, few studies have investigated the effect on neutrophils of the simultaneous stimulation with MSU and proinflammatory mediators in the inflamed joint. Herein, we focused on a protein that is highly expressed in the synovium in gout, S100A9. The predominant expression of S100A9 in and around blood vessels suggests it may prime neutrophils during their migration toward the inflamed joint. Using a combination of functional and signaling assays, we found that S100A9 enhances the production of radical oxygen species as well as IL-1 and IL-8 release by human neutrophils activated with MSU. Moreover, upstream and downstream signaling events activated by MSUs in human neutrophils were also potentiated by S100A9, including the mobilization of intracellular calcium stores, tyrosine phosphorylation, the serine phosphorylation of PKC substrates, Akt, and p38. We also show that S100A9 alone increases glycolysis in human neutrophils, which is suggestive of an additional mechanism through which neutrophils can be primed. Together, our observations indicate a novel way in which S100A9 may contribute to the pathogenesis of gout, by priming neutrophils to respond to MSUs.

Lysosomotropic cationic drugs induce cytostatic and cytotoxic effects: Role of liposolubility and autophagic flux and antagonism by cholesterol ablation.

Cation trapping in acidic cell compartments determines an antiproliferative effect that has a potential interest in oncology, as shown by clinical data and trials involving chloroquine and hydroxychloroquine. To further characterize the mechanism of this effect, we studied a series of 6 substituted triethylamine (s-Et3N) drugs that encompasses a wide range of liposolubility (amiodarone, quinacrine, chloroquine, hydroxychloroquine, lidocaine, and procainamide). Three tumor cell lines and primary human endothelial cells were exploited in proliferation assays (48h, cell counts). Accumulation of the autophagic effector LC3 II and the apoptotic marker cleaved PARP1 (immunoblots), cytotoxicity, cell cycle analysis and endocytic function were further tested in the p53-null histiocytic lymphoma U937 line. A profound and desynchronized antiproliferative effect was observed in response to all s-Et3Ns with essentially no cell type specificity. Predictors of s-Et3N potency were liposolubility and the acute accumulation of the autophagic effector LC3 II (6h-treatments). For each s-Et3N, there was an antiproliferative concentration range where cytotoxicity and apoptosis were not triggered in U937 cells (24-48h-treatments). Quinacrine was the most potent cytostatic drug (1-5µM). Co-treatment of cells with inhibitors of cholesterol, ß-cyclodextrin or lovastatin, partially reversed the antiproliferative effect of each s-Et3N. The cytopathology induced by cationic drug accumulation includes a cytostatic effect. Its intensity is cell type- and p53-independent, but predicted by the inhibition of autophagic flux and by the liposolubility of individual drugs and alleviated by cholesterol ablation. The superiority of quinacrine, biomarker value of LC3 II and antagonism by a statin may be clinically relevant.

Biotechnological Fluorescent Ligands of the Bradykinin B1 Receptor: Protein Ligands for a Peptide Receptor.

The bradykinin (BK) B1 receptor (B1R) is a peculiar G protein coupled receptor that is strongly regulated to the point of being inducible in immunopathology. Limited clinical evidence suggests that its expression in peripheral blood mononuclear cells is a biomarker of active inflammatory states. In an effort to develop a novel imaging/diagnostic tool, we report the rational design and testing of a fusion protein that is a ligand of the human B1R but not likely to label peptidases. This ligand is composed of a fluorescent protein (FP) (enhanced green FP [EGFP] or mCherry) prolonged at its N-terminus by a spacer peptide and a classical peptide agonist or antagonist (des-Arg9-BK, [Leu8]des-Arg9-BK, respectively). The design of the spacer-ligand joint peptide was validated by a competition assay for [3H]Lys-des-Arg9-BK binding to the human B1R applied to 4 synthetic peptides of 18 or 19 residues. The labeling of B1R-expressing cells with EGFP or mCherry fused with 7 of such peptides was performed in parallel (microscopy). Both assays indicated that the best design was FP-(Asn-Gly)n-Lys-des-Arg9-BK; n = 15 was superior to n = 5, suggesting benefits from minimizing steric hindrance between the FP and the receptor. Cell labeling concerned mostly plasma membranes and was inhibited by a B1R antagonist. EGFP-(Asn-Gly)15-Lys-des-Arg9-BK competed for the binding of [3H]Lys-des-Arg9-BK to human recombinant B1R, being only 10-fold less potent than the unlabeled form of Lys-des-Arg9-BK to do so. The fusion protein did not label HEK 293a cells expressing recombinant human BK B2 receptors or angiotensin converting enzyme. This study identifies a modular C-terminal sequence that can be adapted to protein cargoes, conferring high affinity for the BK B1R, with possible applications in diagnostic cytofluorometry, histology and drug delivery (e.g., in oncology).

Pharmacological profile of a bifunctional ligand of the formyl peptide receptor1 fused to the myc epitope.

In human peripheral blood neutrophils or in myeloid PLB-985 cells differentiated towards a neutrophil-like phenotype, the peptide N-formyl-L-norleucyl-L-leucyl-L-phenylalanyl-L-norleucyl-L-tyrosyl-L-leucyl-fluorescein isothiocyanate (f-Nle-Leu-Phe-Nle-Tyr-Lys-FITC) binds to and activates formyl peptide receptor1 (FPR1) and is submitted to receptor-mediated endocytosis (microscopy, cytofluorometry). This peptide may be considered a C-terminally extended version of f-Met-Leu-Phe which carries a fluorescent cargo into cells. By analogy to other peptide hormones for which we have evaluated epitope-tagged agonists as carriers of antibody cargoes, we have designed and evaluated f-Nle-Leu-Phe-Nle-Tyr-Lys-myc, C-terminally extended with the 10-residue myc tag. This peptide is as potent as f-Met-Leu-Phe to compete for f-Nle-Leu-Phe-Nle-Tyr-Lys-FITC uptake by PLB-985 cells, but did not mediate (10-1000nM) the internalization of the fluorescent anti-myc monoclonal antibody 4A6 added to the extracellular fluid at ~7nM (microscopy). The nonfluorescent version of the antibody (28nM) acts as a pre-receptor antagonist of f-Nle-Leu-Phe-Nle-Tyr-Lys-myc, but not of f-Met-Leu-Phe (superoxide release assay in differentiated PLB-985 cells). A further prolonged analog, f-Nle-Leu-Phe-Nle-Tyr-Lys-(Asn-Gly)5-myc, designed to decrease the possible steric hindrance between FPR1 and the bound anti-myc antibody, has little affinity for the receptor, precluding a direct assessment of this issue. Thus, the relatively low-affinity anti-myc antibody used at a high concentration functionally behaves as a selective pre-receptor antagonist of the agonist f-Nle-Leu-Phe-Nle-Tyr-Lys-myc.

A tagged parathyroid hormone derivative as a carrier of antibody cargoes transported by the G protein coupled PTH1 receptor.

Based on the known fact that the parathyroid hormone (PTH) might be extended at its C-terminus with biotechnological protein cargoes, a vector directing the secretion of PTH1-84 C-terminally fused with the antigenic epitope myc (PTH-myc) was exploited. The functional properties and potential of this analog for imaging PTH1R-expressing cells were examined. The PTH-myc construct was recombinantly produced as a conditioned medium (CM) of transfected HEK 293a cells (typical concentrations of 187nM estimated with ELISAs for PTH). PTH-myc CM induced cyclic AMP formations (10min), with a minor loss of potency relative to authentic PTH1-84, and c-Fos expression (1-3h). Treatment of recipient HEK 293a cells transiently expressing PTH1R with PTH-myc CM (supplemented with a fluorescent monoclonal anti-myc tag antibody, either 4A6 or 9E10) allowed the labeling of endosomal structures positive for Rab5 and/or for ß-arrestin1 (microscopy, cytofluorometry). Authentic PTH was inactive in this respect, ruling out a non-specific form of endocytosis like pinocytosis. Using a horseradish peroxidase-conjugated secondary antibody, the endocytosis of the PTH-myc-based antibody complex by endogenous PTH1R was evidenced in MG-63 osteoblastoid cells. The secreted construct PTH-myc represents a bona fide agonist that supports the feasibility of transporting cargoes of considerable molecular weight inside cells using arrestin and Rab5-mediated PTH1R endocytosis. PTH-myc is also transported into cells that express PTH1R at a physiological level. Such tagged peptide hormones may be part of a cancer chemotherapy scheme exploiting a modular cytotoxic secondary antibody and the receptor repertoire expressed in a given tumor.

C-C chemokine receptor-7 mediated endocytosis of antibody cargoes into intact cells.

The C-C chemokine receptor-7 (CCR7) is a G protein coupled receptor that has a role in leukocyte homing, but that is also expressed in aggressive tumor cells. Preclinical research supports that CCR7 is a valid target in oncology. In view of the increasing availability of therapeutic monoclonal antibodies that carry cytotoxic cargoes, we studied the feasibility of forcing intact cells to internalize known monoclonal antibodies by exploiting the cycle of endocytosis and recycling triggered by the CCR7 agonist CCL19. Firstly, an anti-CCR7 antibody (CD197; clone 150503) labeled surface recombinant CCR7 expressed in intact HEK 293a cells and the fluorescent antibody was internalized following CCL19 treatment. Secondly, a recombinant myc-tagged CCL19 construction was exploited along the anti-myc monoclonal antibody 4A6. The myc-tagged ligand was produced as a conditioned medium of transfected HEK 293a cells that contained the equivalent of 430 ng/ml of immunoreactive CCL19 (average value, ELISA determination). CCL19-myc, but not authentic CCL19, carried the fluorophore-labeled antibody 4A6 into other recipient cells that expressed recombinant CCR7 (microscopy, cytofluorometry). The immune complexes were apparent in endosomal structures, co-localized well with the small GTPase Rab5 and progressed toward Rab7-positive endosomes. A dominant negative form of Rab5 (GDP-locked) inhibited this endocytosis. Further, endosomes in CCL19-myc- or CCL19-stimulated cells were positive for ß-arrestin2, but rarely for ß-arrestin1. Following treatment with CCL19-myc and the 4A6 antibody, the melanoma cell line A375 that expresses endogenous CCR7 was specifically stained using a secondary peroxidase-conjugated antibody. Agonist-stimulated CCR7 can transport antibody-based cargoes, with possible therapeutic applications in oncology.

Vasopeptidase-activated latent ligands of the histamine receptor-1.

Whether peptidases present in vascular cells can activate prodrugs active on vascular cells has been tested with 2 potential latent ligands of the histamine H1 receptor (H1R). First, a peptide consisting of the antihistamine cetirizine (CTZ) condensed at the N-terminus of ε-aminocaproyl-bradykinin (εACA-BK) was evaluated for an antihistamine activity that could be revealed by degradation of the peptide part of the molecule. CTZ-εACA-BK had a submicromolar affinity for the BK B2 receptor (B2R; IC50 of 590 nM, [(3)H]BK binding competition), but a non-negligible affinity for the human H1 receptor (H1R; IC50 of 11 µM for [(3)H]pyrilamine binding). In the human isolated umbilical vein, a system where both endogenous B2R and H1R mediate strong contractions, CTZ-εACA-BK exerted mild antagonist effects on histamine-induced contraction that were not modified by omapatrilat or by a B2R antagonist that prevents endocytosis of the BK conjugate. Cells expressing recombinant ACE or B2R incubated with CTZ-εACA-BK did not release a competitor of [(3)H]pyrilamine binding to H1Rs. Thus, there is no evidence that CTZ-εACA-BK can release free cetirizine in biological environments. The second prodrug was a blocked agonist, L-alanyl-histamine, potentially activated by aminopeptidase N (APN). This compound did not compete for [(3)H]pyrilamine binding to H1Rs. The human umbilical vein contractility assay responded to L-alanyl-histamine (EC50 54.7 µM), but the APN inhibitor amastatin massively (17-fold) reduced its apparent potency. Amastatin did not influence the potency of histamine as a contractile agent. One of the 2 tested latent H1R ligands, L-alanyl-histamine, supported the feasibility of pro-drug activation by vascular ectopeptidases.

Bifunctional epitope-agonist ligands of the bradykinin B(2) receptor.

Two bradykinin (BK) B(2) receptor agonists N-terminally extended with the myc epitope were synthesized and evaluated: myc-KPG-BK and myc-KGP-B-9972. The latter was modeled on the inactivation-resistant agonist B-9972 (D-Arg(0), Hyp(3), Igl(5), Oic(7), Igl(8)-BK) and is also resistant to endosomal inactivation. Despite a large loss of affinity relative to the parent peptide, the tagged analogs are conventional agonists in the umbilical vein contractility assay and compete for [(3)H]BK binding at the rabbit B(2) receptor. Endocytosed myc-KGP-B-9972 most effectively carried AlexaFluor-488-conjugated anti-myc monoclonal antibodies into intact cells expressing the B(2) receptor. Results support the prospects of functionally-active cargoes entering cells in a pharmacologically controlled manner.

An in vitro reconstitution system to address the mechanism of the vascular expression of the bradykinin B1 receptor in response to angiotensin converting enzyme inhibition.

The expression of the bradykinin (BK) B1 receptor (B1R), lacking in normal vascular tissues, is induced following innate immune system activation and chronic blockade of angiotensin converting enzyme (ACE). To identify cytokine-dependent or -independent mechanisms for the latter phenomenon, the ACE inhibitor enalaprilat and several peptides potentiated in vivo by ACE blockade were applied either directly to human umbilical artery smooth muscle cells (hUA-SMCs) or to differentiated monoblastoid U937 cells to produce a conditioned medium (CM) that was later transferred to hUA-SMCs. A phagocyte stimulant, lipopolysaccharide, did not upregulate B1R, measured using [³H]Lys-des-Arg9-BK binding, or translocate NF-κB to the nuclei if applied directly to the hUA-SMCs. However, the CM of lipopolysaccharide-stimulated U937 cells was active in these respects (effects inhibited by etanercept and correlated to TNF-α presence in the CM). A peptidase-resistant B1R agonist had no significant direct or indirect acute effect (4h) on B1R expression, but repeated hUA-SMC stimulations over 40 h were stimulatory in the absence of NF-κB activation. Other peptides regulated by ACE or enalaprilat did not directly or indirectly stimulate B1R expression. The reconstitution system supports the rapid cytokine-dependent vascular induction of B1Rs and a slow "autoregulatory" one potentially relevant for the ACE blockade effect.

Prolonged signalling and trafficking of the bradykinin B2 receptor stimulated with the amphibian peptide maximakinin: insight into the endosomal inactivation of kinins.

Maximakinin, a 19-residue peptide from the amphibian Bombina maxima, incorporates the full sequence of bradykinin (BK) at its C-terminus with a hydrophilic 10-residue N-terminal extension. As a putative venom component, it may stimulate BK B(2) receptors (B(2)Rs) in a distinct manner relative to the fragile mammalian agonist BK. Maximakinin affinity for B(2)Rs and angiotensin converting enzyme (ACE) and its pharmacological profile have been compared to those of BK. Maximakinin is an agonist of the human and rabbit B(2)R with a 8-12 fold lesser potency, but a prolonged duration of action relative to BK (ERK MAP kinase activation, c-Fos induction in HEK 293 cells). Maximakinin had a moderately inferior affinity (∼6-fold vs. BK) for recombinant ACE based on [(3)H]enalaprilat binding displacement. Unlike BK, maximakinin induced the internalization of the fusion protein B(2)R-green fluorescent protein (GFP) and the downregulation of this construction over a 12-h stimulation period, reproducing the effect of inactivation-resistant B(2)R agonists. Alternate homologues of BK extended at the N-terminus showed intermediate behaviours between BK and maximakinin in the B(2)R-GFP downregulation assay. The recycling of B(2)R-GFP at the cell surface after a 3-h BK treatment was notably inhibited by cotreatment with E-64 or bafilomycin A1, supporting that an endosomal cysteine protease degrades kinins in a process that determines the cycling and fate of the B(2)R. Maximakinin is the first known natural kinin sequence that elicits a prolonged cellular signalling, thus suggesting a possible basis for a venomous action and a naturally selected one for the design of B(2)R-transported biotechnological cargoes.

Met-Lys-bradykinin-Ser-Ser, a peptide produced by the neutrophil from kininogen, is metabolically activated by angiotensin converting enzyme in vascular tissue.

Bradykinin (BK) is a vasoactive nonapeptide cleaved from circulating kininogens and that is degraded by angiotensin converting enzyme (ACE). It has been reported that the PR3 protease from human neutrophil releases an alternate peptide of 13 amino acids, Met-Lys-BK-Ser-Ser, from high molecular weight kininogen. We have studied vascular actions of this kinin. Its affinity for recombinant B1 and B2 receptors is very low, as assessed by the binding competition of [³H]Lys-des-Arg9-BK and [³H]BK, respectively, but Met-Lys-BK-Ser-Ser effectively displaced a fraction of [³H]enalaprilat binding to recombinant ACE. Mutant recombinant ACE constructions revealed that affinity gap between BK and Met-Lys-BK-Ser-Ser is larger for the N-terminal catalytic site than for the C-terminal one, based on competition for the substrate Abz-Phe-Arg-Lys(Dnp)-Pro-OH in an enzymatic assay. Met-Lys-BK-Ser-Ser is a low potency stimulant of the rabbit aorta (bioassay for B1 receptors), but the human isolated umbilical vein, a contractile bioassay for the B2 receptors, responded to Met-Lys-BK-Ser-Ser more than expected from the radioligand binding assay, this agonist being ∼30-fold less potent than BK in the vein. Venous tissue treatment with the ACE inhibitor enalaprilat reduced the apparent potency of Met-Lys-BK-Ser-Ser by 15-fold, while not affecting that of BK. In the rabbit isolated jugular vein, Met-Lys-BK-Ser-Ser is nearly as potent as BK as a contractile stimulant of endogenous B2 receptors (EC50 values of 16.3 and 10.5 nM, respectively), but enalaprilat reduced the potency of Met-Lys-BK-Ser-Ser 13-fold while increasing that of BK 5.3-fold. In vascular tissue, ACE assumes a paradoxical activating role for Met-Lys-BK-Ser-Ser.

Bradykinin B2 receptor-mediated transport into intact cells: anti-receptor antibody-based cargoes.

Endocytosis of the bradykinin-stimulated B(2) receptors is parallel to the transport and subsequent degradation of the ligand. To implement biotechnological applications based on receptor-mediated transport, one strategy is to conjugate the agonist ligand to a cargo. Alternatively, we studied whether the B(2) receptor can transport large antibody-based cargoes into intact cells and characterized the ensuing endosomal routing. Myc-tagged B(2) receptors (coded by the vector myc-B(2)R) and a truncated construction devoid of the Ser-Thr phosphorylation domain (myc-B(2)R(trunc) vector) were coupled to anti-myc monoclonal antibodies that did not impair bradykinin binding or elicit calcium signaling in intact cells. Anti-myc antibodies, conjugated or not with secondary antibodies optionally coupled to Qdot nanomaterials, were transported into early endosome autoantigen 1-, and ß-arrestin-positive vesicles in bradykinin-stimulated intact cells expressing receptors encoded by myc-B(2)R. Antibody-conjugated cargoes progressed into late-endosomes-lysosomes within 3h without evidence of autophagy. Receptors encoded by myc-B(2)R(trunc) did not support the ligand-controlled endocytosis of anti-myc antibodies. Aside from small ligand-conjugated cargoes, very large antibody-based cargoes can be transported by agonist-stimulated B(2) receptors into intact cells. The latter type of cargo requires a receptor competent for interaction with ß-arrestins, enters the degradation pathway separately from the receptor as a function of time and has the potential to confer a qualitatively novel function to a receptor.

Vascular smooth muscle contractility assays for inflammatory and immunological mediators.

The blood vessels are one of the important target tissues for the mediators of inflammation and allergy; further cytokines affect them in a number of ways. We review the use of the isolated blood vessel mounted in organ baths as an important source of pharmacological information. While its use in the bioassay of vasoactive substances tends to be replaced with modern analytical techniques, contractility assays are effective to evaluate novel synthetic drugs, generating robust potency and selectivity data about agonists, partial agonists and competitive or insurmountable antagonists. For instance, the human umbilical vein has been used extensively to characterize ligands of the bradykinin B(2) receptors. Isolated vascular segments are live tissues that are intensely reactive, notably with the regulated expression of gene products relevant for inflammation (e.g., the kinin B(1) receptor and inducible nitric oxide synthase). Further, isolated vessels can be adapted as assays of unconventional proteins (cytokines such as interleukin-1, proteases of physiopathological importance, complement-derived anaphylatoxins and recombinant hemoglobin) and to the gene knockout technology. The well known cross-talks between different cell types, e.g., endothelium-muscle and nerve terminal-muscle, can be extended (smooth muscle cell interaction with resident or infiltrating leukocytes and tumor cells). Drug metabolism and distribution problems can be modeled in a useful manner using the organ bath technology, which, for all these reasons, opens a window on an intermediate level of complexity relative to cellular and molecular pharmacology on one hand, and in vivo studies on the other.

Effect of interferon-γ on inflammatory cytokine-induced bradykinin B1 receptor expression in human vascular cells.

The expression of the bradykinin B(1) receptor is strongly regulated in vascular tissue following injury, with little or no expression in healthy tissues. The present work aimed to verify whether primary human vascular cells (umbilical vein endothelial cells, umbilical artery smooth muscle cells) respond to tumor necrosis factor (TNF)-α and interferon (IFN)-γ by an upregulation of B(1) receptors and whether these pathways interact. B(1) receptor expression was quantified using a [(3)H]Lys-des-Arg(9)-bradykinin binding assay (cell surface protein) and RT-PCR (mRNA). A pharmacological approach exploiting several inhibitory drugs related to cytokine signaling was applied. The combined treatment with TNF-α and IFN-γ had a synergistic effect on B(1) receptor expression in both cell types, increasing primarily receptor abundance in both cell types (16 h) and mRNA concentration (4h) in endothelial cells. The synergistic effect of the IFN-γ-TNF-α combination was abated by drugs targeted at the signaling of either cytokine (for TNF-α: etanercept or the IκB kinase 2 inhibitor TPCA-1; for IFN-γ: neutralizing antibodies to IFN-γ, a pan-Jak inhibitor but not the Jak2 inhibitor AG490). Thus, Jak2 signaling may not be recruited by the IFN-γ receptors in vascular cells; however, Stat1 phosphorylation was correlated as expected to the effect of IFN-γ on B(1) receptor expression. Random migration was inhibited by the B(1) receptor agonist Lys-des-Arg(9)-bradykinin only in smooth muscle cells pretreated with the cytokine combination. The amplificatory effect of IFN-γ on TNF-α-induced bradykinin B(1) receptor expression is relevant to vasculopathies associated with T helper 1 cytokines.

A ligand-based approach to investigate the expression and function of angiotensin converting enzyme in intact human umbilical vein endothelial cells.

Angiotensin converting enzyme (ACE) is a drug target and an effective bradykinin (BK)-inactivating ectopeptidase. We exploited a recently described [(3)H]enalaprilat binding assay to quantify the full dynamic range of ACE expression in intact human umbilical vein endothelial cells (HUVECs) stimulated with known or novel modulators of ACE expression. Further, the affinities for ACE of a set of physiological substrates were determined using the same assay. BK has the highest affinity (K(i) 525 nM) among known substrates to displace [(3)H]enalaprilat binding from ACE. Tumor necrosis factor (TNF)-alpha repressed the expression of ACE in HUVECs while phorbol 12-myristate 13-acetate (PMA) upregulated it in 24h (approximately 12-fold dynamic range by [(3)H]enalaprilat binding, corroborated by ACE immunoblotting). Intermediate levels of ACE expression were seen in cells stimulated with both PMA and a cytokine. In contrast, high glucose, insulin or EGF failed to affect ACE expression. The effect of TNF-alpha was abated by etanercept, the IKK2 inhibitor TPCA-1, or a p38 inhibitor while that of PMA was reduced by inhibitors of PKC isoforms sensitive to phorbol esters and calcium. The short-term PKC- and MEK1-dependent increase of c-Fos expression was best correlated to PMA-induced ACE upregulation. The [(3)H]enalaprilat binding assay applied to HUVECs supports that ACE is a particularly active kininase and that endothelial ACE expression is dynamically and specifically regulated. This has potential importance in inflammatory diseases and diabetes.

Vacuolar ATPase-mediated sequestration of local anesthetics in swollen macroautophagosomes.

PURPOSE: Local anesthetics in their therapeutic concentration range cause a vacuolar cytopathology that has been observed in vivo and in various types of mammalian cells. We examined whether active concentration ranges of drugs and the kinetics of the vacuolar response are clinically relevant and whether this phenomenon is associated with cytotoxicity, autophagy, and cell stress signalling. METHODS: We compared procaine and lidocaine for morphological, functional, and signalling responses in a previously exploited non-neuronal system, primary smooth muscle cells. Several markers conjugated to fluorescent proteins allowed morphological and functional analysis of vacuolar cells. Signalling related to autophagy and cell stress was addressed (immunoblotting of cell lysates). RESULTS: Within 2-4 hr, lidocaine and procaine (> or = 1 mM) induced massive cell vacuolization, a response abated by the V-ATPase inhibitor, bafilomycin A1, and activated macroautophagic signalling (LC3 II formation) but not other stress signalling (p38, ERK1/2, p53, no influence on serum-controlled Akt phosphorylation). Novel aspects of the morphological analysis include reduced LC3 labelling of the large vacuoles in cells treated with 3-methyl-adenine, inhibition of CD63 labelling of these vacuoles by co-expression of dominant negative Rab7, retention of secretory green fluorescent protein (GFP) possessing a signal sequence in vacuolar cells, and partial vacuole labelling with lysosomal-associated membrane protein 1 (LAMP1). Lidocaine (2.5-5 mM) was not overtly cytotoxic but arrested cell division over 48 hr. CONCLUSIONS: V-ATPase-mediated sequestration of clinically relevant concentrations of local anesthetics sequentially involves vacuolization, macroautophagic signalling, and lysosome fusion to large vacuoles. Disruption of the secretory pathway and mitotic arrest were also observed over several hours without major cytotoxicity.

Altered cardiac bradykinin metabolism in experimental diabetes caused by the variations of angiotensin-converting enzyme and other peptidases.

The peptidases angiotensin-converting enzyme (ACE) and neutral endopeptidase 24.11 (NEP) mediate most of the kinin catabolism in normal cardiac tissue and are the molecular targets of inhibitory drugs that favorably influence diabetic complications. We studied the variations of those kininases in the myocardium of rats in experimental diabetes. ACE and NEP activities were significantly decreased in heart membranes 4-8weeks post-streptozotocin (STZ) injection. However, insulin-dependent diabetes did not modify significantly bradykinin (BK) half-life (t(1/2)) while the effect of both ACE (enalaprilat) and ACE and NEP (omapatrilat) inhibitors on BK degradation progressively decreased, which may be explained by the upregulation of other unidentified metallopeptidase(s). In vivo insulin treatment restored the activities of both ACE and NEP. ACE and NEP activities were significantly higher in hearts of young Zucker rats than in those of Sprague-Dawley rats. BK t(1/2) and the effects of peptidase inhibitors on t(1/2) varied accordingly. It is concluded that kininase activities are subjected to large and opposite variations in rat cardiac tissue in type I and II diabetes models. A number of tissue or molecular factors may determine these variations, such as remodeling of cardiac tissue, ectoenzyme shedding to the extracellular fluid and the pathologic regulation of peptidase gene expression.

NTPDase1 (CD39) controls nucleotide-dependent vasoconstriction in mouse.

AIMS: Extracellular nucleotides are vasoactive molecules. The concentrations of these molecules are regulated by ectonucleotidases. In this study, we investigated the role of the blood vessel ectonucleotidase NTPDase1, in the vasoconstrictor effect of nucleotides using Entpd1(-/-) mice. METHODS AND RESULTS: Immunofluorescence, enzyme histochemistry, and HPLC analysis were used to evaluate both NTPDase expression and activity in arteries and isolated vascular smooth muscle cells (VSMCs). Vascular reactivity was evaluated in vitro and mean arterial blood pressure was recorded in anesthetized mice after nucleotide i.v. infusion. Expression of nucleotide receptors in VSMCs was determined by RT-PCR. Entpd1(-/-) mice displayed a dramatic deficit of nucleotidase activity in blood vessel wall in situ and in VSMCs in comparison to control mice. In aortic rings from Entpd1(-/-) mice, UDP and UTP induced a potent and long-lasting constriction contrasting with the weak response obtained in wild-type rings. This constriction occurred through activation of P2Y(6) receptor and was independent of other uracil nucleotide-responding receptors (P2Y(2) and P2Y(4)). UDP infusion in vivo increased blood pressure and this effect was potentiated in Entpd1(-/-) mice. In addition, pressurized mesenteric arteries from Entpd1(-/-) mice displayed an enhanced myogenic response, consistent with higher local concentrations of endogenously released nucleotides. This effect was inhibited by the P2 receptor antagonist RB-2. CONCLUSION: NTPDase1 is the major enzyme regulating nucleotide metabolism at the surface of VSMCs and thus contributes to the local regulation of vascular tone by nucleotides.