Functional characterization of neurokinin-1 receptors on human U373MG astrocytoma cells

The neuropeptide substance P/neurokinin-1 receptor system and diabetes: From mechanism to therapy

Diabetes is a significant public health issue known as the world's fastest-growing disease condition. It is characterized by persistent hyperglycemia and subsequent chronic complications leading to organ dysfunction and, ultimately, the failure of target organs. Substance P (SP) is an undecapeptide that belongs to the family of tachykinin (TK) peptides. The SP-mediated activation of the neurokinin 1 receptor (NK1R) regulates many pathophysiological processes in the body. There is also a relation between the SP/NK1R system and diabetic processes. Importantly, deregulated expression of SP has been reported in diabetes and diabetes-associated chronic complications. SP can induce both diabetogenic and antidiabetogenic effects and thus affect the pathology of diabetes destructively or protectively. Here, we review the current knowledge of the functional relevance of the SP/NK1R system in diabetes pathogenesis and its exploitation for diabetes therapy. A comprehensive understanding of the role of the SP/NK1R system in diabetes is expected to shed further light on developing new therapeutic possibilities for diabetes and its associated chronic conditions.

Carbohydrate-Based NK1R Antagonists with Broad-Spectrum Anticancer Activity

NK1R antagonists, investigated for the treatment of several pathologies, have shown encouraging results in the treatment of several cancers. In the present study, we report on the synthesis of carbohydrate-based NK1R antagonists and their evaluation as anticancer agents against a wide range of cancer cells. All of the prepared compounds, derived from either d-galactose or l-arabinose, have shown high affinity and NK1R antagonistic activity with a broad-spectrum anticancer activity and an important selectivity, comparable to Cisplatin. This strategy has allowed us to identify the galactosyl derivative 14α, as an interesting hit exhibiting significant NK1R antagonist effect (kinact 0.209 ± 0.103 μM) and high binding affinity for NK1R (IC50 = 50.4 nM, Ki = 22.4 nM by measuring the displacement of [125I] SP from NK1R). Interestingly, this galactosyl derivative has shown marked selective cytotoxic activity against 12 different types of cancer cell lines.

Mitigation of Oxidation in Therapeutic Antibody Formulations: a Biochemical Efficacy and Safety Evaluation of N-Acetyl-Tryptophan and L-Methionine

PURPOSE

Biotherapeutics can be susceptible to oxidation during manufacturing and storage. Free L-methionine is known to protect methionine residues in proteins from oxidation. Similarly, free tryptophan and other indole derivatives have been shown to protect tryptophan residues from oxidation. N-acetyl-DL-tryptophan was previously identified as a potentially superior antioxidant to tryptophan as it has a lower oxidation potential and produces less peroxide upon light exposure. This study sought to confirm the antioxidant efficacy and safety of N-acetyl-DL-tryptophan and L-methionine as formulation components for biotherapeutic drugs.

METHODS

Antibodies were subjected to AAPH and light exposure in the presence of N-acetyl-DL-tryptophan and L-methionine. Oxidation in relevant CDR and Fc residues was quantified by peptide map. In silico, in vitro, and in vivo studies were performed to evaluate the safety of N-acetyl-DL-tryptophan and L-methionine.

RESULTS

Peptide mapping demonstrated that N-acetyl-DL-tryptophan was effective at protecting tryptophans from AAPH stress, and that the combination of N-acetyl-DL-tryptophan and L-methionine protected both tryptophan and methionine from AAPH stress. The safety assessment suggested an acceptable safety profile for both excipients.

CONCLUSIONS

N-acetyl-tryptophan and L-methionine effectively reduce the oxidation of susceptible tryptophan and methionine residues in antibodies and are safe for use in parenteral biotherapeutic formulations.

G protein-coupled receptors as oncogenic signals in glioma: emerging therapeutic avenues

Gliomas are the most common malignant intracranial tumors. Newly developed targeted therapies for these cancers aim to inhibit oncogenic signals, many of which emanate from receptor tyrosine kinases, including the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor receptor (VEGFR). Unfortunately, the first-generation treatments targeting these oncogenic signals provide little survival benefit in both mouse xenograft models and human patients. The search for new treatment options has uncovered several G protein-coupled receptor (GPCR) candidates and generated a growing interest in this class of proteins as alternative therapeutic targets for the treatment of various cancers, including glioblastoma multiforme (GBM). GPCRs constitute a large family of membrane receptors that influence oncogenic pathways through canonical and non-canonical signaling. Accordingly, evidence indicates that GPCRs display a unique ability to crosstalk with receptor tyrosine kinases, making them important molecular components controlling tumorigenesis. This review summarizes the current research on GPCR functionality in gliomas and explores the potential of modulating these receptors to treat this devastating disease.

Pharmacophore modeling, virtual screening, and in vitro testing reveal haloperidol, eprazinone, and fenbutrazate as neurokinin receptors ligands

Neurokinin receptors (NKRs) have been shown to be involved in many physiological processes, rendering them promising novel drug targets, but also making them the possible cause for side effects of several drugs. Aiming to answer the question whether the binding to NKRs could have a share in the side effects or even the desired effects of already licensed drugs, we generated a set of ligand-based common feature pharmacophore models based on the structural information about subtype-selective and nonselective NKR antagonists and screened an in-house database mainly composed of licensed drugs. The prospective pharmacological investigations of the virtual hits haloperidol, eprazinone, and fenbutrazate confirmed them to be NKR ligands in vitro. By the identification of licensed drugs as so far unknown NKR ligands, this study contributes to establishing an activity profile of the investigated compounds and confirms the presented pharmacophore models as useful tools for this purpose.

Involvement of substance P and the NK-1 receptor in cancer progression

Many data suggest the deep involvement of the substance P (SP)/neurokinin (NK)-1 receptor system in cancer: (1) Tumor cells express SP, NK-1 receptors and mRNA for the tachykinin NK-1 receptor; (2) Several isoforms of the NK-1 receptor are expressed in tumor cells; (3) the NK-1 receptor is involved in the viability of tumor cells; (4) NK-1 receptors are overexpressed in tumor cells in comparison with normal ones and malignant tissues express more NK-1 receptors than benign tissues; (5) Tumor cells expressing the most malignant phenotypes show an increased percentage of NK-1 receptor expression; (6) The expression of preprotachykinin A is increased in tumor cells in comparison with the levels found in normal cells; (7) SP induces the proliferation and migration of tumor cells and stimulates angiogenesis by increasing the proliferation of endothelial cells; (8) NK-1 receptor antagonists elicit the inhibition of tumor cell growth; (9) The specific antitumor action of NK-1 receptor antagonists on tumor cells occurs through the NK-1 receptor; (10) Tumor cell death is due to apoptosis; (11) NK-1 receptor antagonists inhibit the migration of tumor cells and neoangiogenesis. The NK-1 receptor is a therapeutic target in cancer and NK-1 receptor antagonists could be considered as broad-spectrum antitumor drugs for the treatment of cancer. It seems that a common mechanism for cancer cell proliferation mediated by SP and the NK-1 receptor is triggered, as well as a common mechanism exerted by NK-1 receptor antagonists on tumor cells, i.e. apoptosis.

Present and future approaches to screening of G-protein-coupled receptors

As G-protein-coupled receptors (GPCRs) mediate a multitude of cellular signal transduction events, affecting more or less all human disease areas, it is, therefore, no surprise that they comprise the largest family of current drug targets. Screening of compounds interacting with GPCRs has developed during the past decade from receptor binding assays, to various functional determination of coupling to G-proteins, and, more recently, G-protein-independent signal transduction events. Additional opportunities have been presented in drug discovery through novel pharmacological properties obtained for receptor dimers and by identification of ligands for orphan GPCRs. Furthermore, high-throughput formats and automation has substantially facilitated and accelerated the screening process providing powerful tools in improving modern drug discovery.

NK1 receptor antagonists and dexamethasone as anticancer agents in vitro and in a model of brain tumours secondary to breast cancer

Emend, an NK1 antagonist, and dexamethasone are used to treat complications associated with metastatic brain tumours and their treatment. It has been suggested that these agents exert anticancer effects apart from their current use. The effects of the NK1 antagonists, Emend and N-acetyl-L-tryptophan, and dexamethasone on tumour growth were investigated in vitro and in vivo at clinically relevant doses. For animal experiments, a stereotaxic injection model of Walker 256 rat breast carcinoma cells into the striatum of Wistar rats was used. Emend treatment led to a decrease in tumour cell viability in vitro, although this effect was not replicated by N-acetyl-L-tryptophan. Dexamethasone did not decrease tumour cell viability in vitro but decreased tumour volume in vivo, likely to be through a reduction in tumour oedema, as indicated by the increase in tumour cell density. None of the agents investigated altered tumour cell replication or apoptosis in vivo. Inoculated animals showed increased glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 immunoreactivity indicative of astrocytes and microglia in the peritumoral area, whereas treatment with Emend and dexamethasone reduced the labelling for both glial cells. These results do not support the hypothesis that NK1 antagonists or dexamethasone exert a cytotoxic action on tumour cells, although these conclusions may be specific to this model and cell line.

Neurokinin-1 receptor directly mediates glioma cell migration by up-regulation of matrix metalloproteinase-2 (MMP-2) and membrane type 1-matrix metalloproteinase (MT1-MMP)

Neurokinin-1 receptor (NK1R) occurs naturally on human glioblastomas. Its activation mediates glioma cell proliferation. However, it is unknown whether NK1R is directly involved in tumor cell migration. In this study, we found human hemokinin-1 (hHK-1), via NK1R, dose-dependently promoted the migration of U-251 and U-87 cells. In addition, we showed that hHK-1 enhanced the activity of MMP-2 and the expression of MMP-2 and MT1-matrix metalloproteinase (MMP), which were responsible for cell migration, because neutralizing the MMPs with antibodies decreased cell migration. The involved mechanisms were then investigated. In U-251, hHK-1 induced significant calcium efflux; phospholipase C inhibitor U-73122 reduced the calcium mobilization, the up-regulation of MMP-2 and MT1-MMP, and the cell migration induced by hHK-1, which meant the migration effect of NK1R was mainly mediated through the G(q)-PLC pathway. We further demonstrated that hHK-1 boosted rapid phosphorylation of ERK, JNK, and Akt; inhibition of ERK and Akt effectively reduced MMP-2 induction by hHK-1. Meanwhile, inhibition of ERK, JNK, and Akt reduced the MT1-MMP induction. hHK-1 stimulated significant phosphorylation of p65 and c-JUN in U-251. Reporter gene assays indicated hHK-1 enhanced both AP-1 and NF-κB activity; inhibition of ERK, JNK, and Akt dose-dependently suppressed the NF-κB activity; only the inhibition of ERK significantly suppressed the AP-1 activity. Treatment with specific inhibitors for AP-1 or NF-κB strongly blocked the MMP up-regulation by hHK-1. Taken together, our data suggested NK1R was a potential regulator of human glioma cell migration by the up-regulation of MMP-2 and MT1-MMP.

Glioblastoma cells express functional cell membrane receptors activated by daily used medical drugs

PURPOSE

Calcium ions are highly versatile spacial and temporal intracellular signals of non-excitable cells and have an important impact on nearly every aspect of cellular life controlling cell growth, metabolism, fluid secretion, information processing, transcription, apoptosis, and motility. Neurons and glia respond to stimuli, including neurotransmitters, neuromodulators, and hormones, which increase the intracellular calcium concentration. The function of intracellular calcium in gliomas is unknown. Lots of daily used drugs may act via receptors that can be linked to the intracellular calcium system and therefore could influence glioma biology.

METHODS

Glioma cells were loaded with the calcium ion sensitive dye Fura 2-AM. Subsequently, cells were stimulated with 25 different medical drugs for 30 s. The increase of free intracellular calcium ions was measured and calculated by a microscope-camera-computer-unit.

RESULTS

Except for the buffer solution HEPES that served as negative control and for the cortisol derivative dexamethasone, all other 24 tested drugs induced a rise of intracellular calcium ions. The cellular calcium responses were classified into seven functional groups. The tested substances activated several types of calcium channels and receptors.

CONCLUSIONS

Our study impressively demonstrates that medical drugs are potent inducers of intracellular calcium signals. Totally unexpected, the results show a high amount of functional cellular receptors and channels on glioma cells, which could be responsible for certain biological effects like migration and cell growth. This calcium imaging study proves the usability of the calcium imaging as a screening system for functional receptors on human glioma cells.

Substance P receptor in U373 MG human astrocytoma cells activates mitogen-activated protein kinases ERK1/2 through Src

Substance P (SP) acting through substance P receptor (SPR) increases the proliferation of glioblastoma cells. At the molecular level, stimulation of SPR in human U373 MG glioblastoma cells results in phosphorylation of mitogen-activated protein kinases ERK1/2. Examination of the underlying mechanism reveals that SPR mediates ERK1/2 phosphorylation in a calcium-dependent manner. Surprisingly, blockade of epidermal growth factor receptor (EGFR), which is transactivated by SPR, has a minimal effect on SPR-mediated ERK1/2 phosphorylation. However, SPR-mediated ERK1/2 phosphorylation is significantly reduced by the Src kinase inhibitor PP2. Interestingly, ERK1/2 in U373 MG cells is also activated by several other mitogenic G protein-coupled receptors (GPCRs) including alpha(1B)-adrenergic, M(3)-muscarinic, and H(1)-histaminergic in an Src-dependent manner. We conclude that c-Src is a mediator of SP-stimulated ERK1/2 phosphorylation in human U373 MG glioblastoma cells.

Neurokinin 1 Receptor Antagonists: Correlation between in Vitro Receptor Interaction and in Vivo Efficacy

We compared the neurokinin 1 receptor (NK(1)R) antagonists aprepitant, CP-99994 [(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine], and ZD6021 [3-cyano-N-((2S)-2-(3,4-dichlorophenyl)-4-[4-[2-(methyl-(S)-sulfinyl)phenyl]piperidino]butyl)-N-methyl]napthamide]] with respect to receptor interactions and duration of efficacy in vivo. In Ca(2+) mobilization assays (fluorometric imaging plate reader), antagonists were applied to human U373MG cells simultaneously with or 2.5 min before substance P (SP). In reversibility studies, antagonists were present for 30 min before washing, and responses to SP were repeatedly measured afterward. The compounds were administered i.p. to gerbils, and the gerbil foot tap (GFT) response was monitored at various time points. The NK(1)R receptor occupancy for aprepitant was determined in striatal regions. Levels of compound in brain and plasma were measured. Antagonists were equipotent at human NK(1)R and acted competitively with SP. After preincubation, aprepitant and ZD6021 attenuated the maximal responses, whereas CP-99994 only shifted the SP concentration-response curve to the right. The inhibitory effect of CP-99994 was over within 30 min, whereas for ZD6021, 50% inhibition still persisted after 60 min. Aprepitant produced maximal inhibition lasting at least 60 min. CP-99994 (3 micromol/kg) inhibited GFT by 100% 15 min after administration, but the effect declined rapidly together with brain levels thereafter. The efficacy of ZD6021 (10 micromol/kg) lasted 4 h and correlated well with brain levels. Aprepitant (3 micromol/kg) inhibited GFT and occupied striatal NK(1)R by 100% for >48 h despite that brain levels of compound were below the limit of detection after 24 h. Slow functional reversibility is associated with long-lasting in vivo efficacy of NK(1)R antagonists, whereas the efficacy of compounds with rapid reversibility is reflected by their pharmacokinetics.

A role for substance P in cancer promotion and progression: a mechanism to counteract intracellular death signals following oncogene activation or DNA damage

In the present review we discuss a central role for substance P (SP) in carcinogenesis. We suggest that one mechanism to induce mitogenesis of tumor cells is the activation of neurokinin-1 receptor (NK1R) through SP, linking cancer promotion and progression to a neurokinin-mediated environment. After reviewing the role of both SP and its receptor NK1R in normal and neoplastic cells we propose the use of neurokinin-1 receptor antagonists as a novel and promising approach for treating patients with cancer.

The NK1 receptor is involved in the antitumoural action of L-733,060 and in the mitogenic action of substance P on neuroblastoma and glioma cell lines

We have carried out an in vitro study to investigate the ability of substance P to activate cell growth and the NK1 receptor antagonist L-733,060 to inhibit cell growth in the SKN-BE(2) neuroblastoma and GAMG glioma cell lines. A coulter counter was used to determine viable cell numbers, followed by application of the tetrazolium compound [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)2-(4-sulfophenyl)-2H-tetrazolium], inner salt, colorimetric method to evaluate cell viability in this cytotoxicity assay. Nanomolar concentrations of substance P increased, and micromolar concentrations of L-733,060 inhibited the growth of both cell lines studied, with and without previous administration of substance P. In addition, we have demonstrated by immunoblot analysis that NK1 receptors are present in both cancer cell lines studied here. Thus, this study demonstrates that substance P acts as a mitogen in the SKN-BE(2) neuroblastoma and GAMG glioma cell lines, and that the antitumoural action of L-733,060 on both human cell lines occurs through the NK1 receptor. This action suggests that the NK1 receptor is a new and promising target in the treatment of human neuroblastoma and glioma.

Expression of the NK-1 receptor on islet cells and invading immune cells in the non-obese diabetic mouse

The underlying mechanistic causes of immune cell infiltration in the islets of Langerhans and beta cell failure in the non-obese diabetic (NOD) mouse is still to be completely revealed. Substance P (SP) is a substance known to have pro-inflammatory, endocrine, neuromodulatory and trophic effects, and its preferred receptor, the neurokinin receptor 1 (NK-1 R), is reported to be involved in extravasation of granulocytes and in inflammation and tissue derangement. Therefore, we have investigated the expression of NK-1 R during development of insulitis in the NOD mouse. We show that the magnitude of immunoreactivity scoring NK-1 R expression in the islets was increased in the 12-week-old NOD mouse. Expression of NK-1 R co-localized with expression of glucagon. In line with this expression pattern, we did not detect any effect of SP on glucose-induced insulin release. NK-1 R expression was particularly observed in islet cells in association with the clusters of immune cells. Expression of NK-1 R was also demonstrated in a fraction of the infiltrating B and T lymphocytes, as well as on infiltrating macrophages and dendritic cells. The observations show that the level of NK-1 R expression is increased in 12-week-old NOD mice, being correlated with the occurrence of islet mononuclear infiltration. Our data suggest that SP may act as a chemoattractant, contributing to the pathogenic mononuclear infiltration process in the NOD mouse. On the whole, the observations suggest that SP and the NK-1 R to certain extents are involved in the changes that occur during the development of insulitis in the NOD mouse.

Inositol 1,4,5-trisphosphate and ryanodine receptors mobilize calcium from a common functional pool in human U373 MG cells

This investigation concentrates on the change in Ca(2+) concentration ([Ca(2+)]) caused by ryanodine in U373 MG cells. This cell type from a human astrocytoma is a unique cellular model because it only expresses the type 3 ryanodine receptor (RyR3), which is generally the least abundant isoform. In the presence of physiological [Ca(2+)] in the extracellular medium, U373 MG cells are caffeine-insensitive, even after forskolin treatment, and ryanodine-sensitive only when an unusually high concentration (30 microM) is applied. Xestospongin C behaves like thapsigargin and therefore cannot be used as a selective antagonist of inositol 1,4,5-trisphosphate receptors (InsP(3)Rs). After ryanodine challenge, addition of an analog of Substance P (SP), which should deplete InsP(3)-sensitive stores, has no effect on [Ca(2+)](i). After thapsigargin treatment, which unmasks the calcium leak from intracellular stores, neither ryanodine nor SP change [Ca(2+)](i), suggesting that thapsigargin completely depletes the ryanodine-sensitive and the InsP(3)-sensitive stores of U373 MG cells. Finally, in experiments monitoring the [Ca(2+)] in intracellular stores, InsP(3) stimulation of permeabilized cells causes a decrease in [Ca(2+)] that is not affected by subsequent ryanodine treatment. Our results support the conclusion that U373 MG cells express both InsP(3)Rs and RyRs that can individually or in combination mobilize only one functional Ca(2+) pool.

Expression of functional neurokinin-1 receptors in regenerative glands during gastric wound healing in rodents

BACKGROUND & AIMS

Although functions of the neurokinin-1 receptor have been well explored in neurogenic inflammation and immunoinflammatory responses, little is known about neurokinin-1 receptors during gastric wound healing. The aim of this study was to assess whether neurokinin-1 receptors play a role in gastric wound healing.

METHODS

In vitro neurokinin-1 receptor autoradiography and immunohistochemistry were performed to identify, locate, and quantify neurokinin-1 receptors during wound healing in rodents with cryoulcers in the gastric corpus and antrum. Moreover, to assess the functionality of these receptors, the effect of the neurokinin-1 receptor antagonist NKP608 on gastric wound healing was quantified in vivo in wild-type and cyclooxygenase-2(-/-) mice.

RESULTS

Regenerative glands of the mucosal ulcer margin of rat cryoulcers of the gastric corpus showed strong expression of neurokinin-1 receptors in binding studies between days 3 and 22, with little expression on days 29-84. In addition, strong immunoreactivity for neurokinin-1 receptors was detected on the cell membrane of these regenerative glands. Expression of neurokinin-1 receptors in regenerative glands was confirmed in the rat antrum and the mouse gastric corpus. Moreover, in vivo functional tests during gastric ulcer healing showed that cell proliferation in the regenerative epithelia of the ulcer margin was significantly decreased by NKP608 compared with placebo; furthermore, gastric ulcer healing was significantly delayed by NKP608 both in wild-type and cyclooxygenase-2(-/-) mice.

CONCLUSIONS

This report shows the time-limited overexpression of neurokinin-1 receptors in the mucosal repair tissue of the corpus and antrum. Our in vitro and in vivo data suggest that neurokinin-1 receptors are involved in gastric wound healing.

Valproic acid inhibits substance P-induced activation of protein kinase C epsilon and expression of the substance P receptor

The neuropeptide substance P (SP) has been hypothesized to be involved in the etiopathology of affective disorders. This hypothesis is based on the findings that neurokinin-1-receptor antagonists have antidepressant effects in depressed patients and that SP may worsen mood. In this study, we investigated the effect of the mood-stabilizing agents valproic acid (VPA), carbamazepine, and lithium on SP-induced gene expression. As a model system, we used primary rat astrocytes and human astrocytoma cells, which both express functional SP-receptors and, upon stimulation with SP, synthesize interleukin-6 (IL-6), a cytokine which has been shown to be elevated during the acute depressive state. We found that VPA dose-dependently inhibited SP-induced IL-6 synthesis which was seen with pre-incubation periods of 30 min, 3, 7 and 14 days, whereas carbamazepine and lithium showed no inhibitory effect. The inhibitory effect of VPA was not mediated by inhibition of the stress-regulated kinases p38 and p42/44 (Erk1/2) but by inhibition of protein kinase C epsilon activation. Furthermore, VPA down-regulated the expression of the substance P receptor (neurokinin(NK)-1-receptor) as assessed by real-time PCR. Whether both mechanisms contribute to the mood-stabilizing properties of VPA has to be evaluated in further studies.

Substance P induced biosynthesis of the zinc finger transcription factor Egr-1 in human glioma cells requires activation of the epidermal growth factor receptor and of extracellular signal-regulated protein kinase

Substance P is a member of the tachykinin family of neuropeptides that plays an important role in pain transmission, neurogenic inflammatory diseases and the adaptive response to stress. Substance P exerts its biological activities via binding to a G-protein coupled receptor of the neurokinin (NK) receptor family. Here, we show by Western blot experiments that substance P induced a transient synthesis of the zinc finger transcriptional regulator Egr-1 in human glioma cells. Substance P-induced stimulation of Egr-1 biosynthesis was completely inhibited by the mitogen-activated protein kinase kinase inhibitor PD98059 and by AG1487, an epidermal growth factor (EGF) receptor-specific tyrosine kinase inhibitor. These results indicate that transactivation of the EGF receptor as well as stimulation of the mitogen activated/extracellular signal-regulated protein kinase (ERK) are essential for substance P/NK-1 receptor-induced activation of Egr-1 biosynthesis. Moreover, we show that the signaling cascade initiated by substance P or EGF are indistinguishable, including the activation of the EGF receptor, the activation of ERK, and the final stimulation of Egr-1 biosynthesis. The synthesis of Egr-1 in glioma cells as a result of substance P stimulation suggests that substance P exerts long-term effects in glioma cells via Egr-1-mediated gene transcription.

NK-1 receptor gene expression is related to pain in chronic pancreatitis

Recent theories of pathogenesis of pain in chronic pancreatitis (CP) are neuroimmune interactions of intrapancreatic nerves and inflammatory cells and increase in levels of pain neurotransmitters such as substance P (SP). This study analyzed the expression and localization of neurokinin 1 receptor (NK-1R), which binds SP, and its association with pain and inflammation in CP. Pancreatic tissues from 31 patients (22 males, nine females; mean age 45.9+/-9.4 years) with CP were evaluated. Nine normal pancreases (five males, four females; mean age 42.9+/-9.5 years) served as controls. Quantitative PCR was used to determine the NK-1R mRNA expression levels and in situ hybridization and immunohistochemistry were used to localize expression sites of NK-1R mRNA and protein, respectively. We also analyzed whether an association exists between NK-1R mRNA expression and pain and inflammation. In CP samples, in situ hybridization and immunohistochemistry localized NK-1R mRNA expression and protein mainly in the nerves, ganglia, blood vessels, inflammatory cells and occasionally in fibroblasts. In patients with mild to moderate and strong intensity of pain, NK-1R mRNA levels were increased 14- and 30-fold over controls, respectively. There was a significant relationship between NK-1R mRNA levels and intensity of pain (r=0.46, P=0.03), NK-1R mRNA and the frequency of pain (r=0.51, P=0.04), and NK-1 mRNA and duration of pain (r=0.46, P=0.01) in CP patients, but not with the degree of tissue inflammation. NK-1R signaling may be involved in the pain syndrome of CP. The expression of NK-1R in inflammatory cells and blood vessels also points to an interaction of immunoreactive substance P nerves, inflammatory cells and blood vessels, and further supports the existence of a neuroimmune interaction that probably influences the pain syndrome and chronic inflammatory changes so characteristic of CP.

The neuropeptide substance P activates p38 mitogen-activated protein kinase resulting in IL-6 expression independently from NF-kappa B

Substance P (SP), a member of the tachykinin peptide family, is a major mediator of neuroimmunomodulatory activities and neurogenic inflammation within the central and peripheral nervous system. SP has been shown to induce the expression of proinflammatory cytokines such as IL-6, which might be implicated in the etiopathology of several human brain disorders. We showed in a previous study that nanomolar concentrations of SP triggered activation of NF-kappaB, a transcription factor involved in the control of cytokine expression. However, activation of NF-kappaB was not involved in SP-induced expression of IL-6. Here, we describe p38 mitogen-activated protein kinase (p38 MAPK) as a signal transduction component that operates independently from NF-kappaB activation and that mediates SP-induced IL-6 expression in the human astrocytoma cell line U373 MG. SP induced the phosphorylation of p38 MAPK within 10 min, and this activation persisted up to 30 min and was independent from p42/44 MAPKs and protein kinase C activation, which all are induced after stimulation with SP. As shown by EMSA, p38 MAPK was not involved in SP-induced activation of NF-kappaB. p38 MAPK, however, mediated SP-induced IL-6 expression as shown by the use of specific inhibitors of this kinase. Our results suggest that activation of p38 MAPK is an important component controlling neurogenic inflammation within the CNS independently from NF-kappaB. Drugs targeting this MAPK may therefore interfere with SP-correlated neuropsychiatric disorders and may represent a therapeutic approach in these disorders.

Epidermal growth factor receptor transactivation mediates substance P-induced mitogenic responses in U-373 MG cells

Ligand-induced activation of G protein-coupled receptors is emerging as an important pathway leading to the activation of certain receptors with intrinsic tyrosine kinase activity, such as the epidermal growth factor receptor (EGFR). Substance P (SP) exerts many effects via activation of its G protein-coupled receptor (neurokinin-1, NK-1). SP participates in acute inflammation and activates key proteins involved in mitogenic pathways, such mitogen-activated protein kinases (MAPKs), stimulating DNA synthesis. We tested the hypothesis that SP-induced MAPK activation and DNA synthesis require activation of the EGFR. In U-373 MG cells, which express functional NK-1, SP induced tyrosine phosphorylation of several proteins including EGFR. SP induced formation of an activated EGFR complex containing the adapter proteins SHC and Grb2, but not c-Src. SP activated the MAPK pathway as shown by increased Erk2 kinase activity. SP induced Erk2 activation, and DNA synthesis was inhibited in cells transfected with a dominant negative EGFR plasmid lacking kinase activity, as well as in cells treated with a specific EGFR inhibitor. In addition, pertussis toxin, an inhibitor of Galpha(iota) protein subunits, prevented SP-induced EGFR transactivation and subsequent DNA synthesis. Our results implicate EGFR as an essential regulator in SP/NK-1-induced activation of the MAPK pathway and cell proliferation in U-373 MG cells, and these events are mediated by a pertussis toxin-sensitive Galpha protein. We suggest that this mechanism by which SP controls cell proliferation is an important pathway in tissue restoration and healing.

Characteristics of the Ca(2+)-dependent inhibition of cyclic AMP accumulation by histamine and thapsigargin in human U373 MG astrocytoma cells

1. Histamine, acting on H(1)-receptors, caused a Ca(2+)-dependent inhibition of forskolin- and isoprenaline-induced cyclic AMP accumulation in monolayers of human U373 MG cells (IC(50) 1.3+/-0.3 microM, maximum inhibition 66+/-3%). The inhibition was not reversed by the protein kinase inhibitor K-252A. 2. Thapsigargin also inhibited cyclic AMP accumulation (IC(50) 6.0+/-0.3 nM, maximum inhibition 72+/-1%). In the absence of extracellular Ca(2+) 5 microM thapsigargin caused only a 12+/-2% inhibition of cyclic AMP accumulation. 3. The inhibitory effect of 100 nM thapsigargin on forskolin-stimulated cyclic AMP accumulation was blocked by La(3+) (best-fit maximum inhibition 81+/-4%, IC(50) 125+/-8 nM). In contrast, the inhibitory action of 10 microM histamine was much less sensitive to reversal by 1 microM La(3+) (33+/-5% reversal, compared with 78+/-6% reversal of the inhibition by thapsigargin measured concurrently). However, in the presence of both thapsigargin and histamine the inhibition of cyclic AMP accumulation was reversed by 1 microM La(3+) to the same extent as the inhibition by thapsigargin alone. 4.++Thapsigargin (5 microM)+1 microM La(3+) caused only a 20+/-1% inhibition of histamine-stimulated phosphoinositide hydrolysis. 5. There was no indication from measurement of intracellular Ca(2+) of any persistent La(3+)-insensitive Ca(2+) entry component activated by histamine. 6. The results provide evidence that Ca(2+) entry is required for the inhibition by histamine and thapsigargin of drug-induced cyclic AMP accumulation in U373 MG astrocytoma cells. The differential sensitivity of the inhibitory action of the two agents to block by La(3+) suggests that more than one pathway of Ca(2+) entry is involved.

Substance P activates responses correlated with tumour growth in human glioma cell lines bearing tachykinin NK1 receptors

The neuropeptide substance P (SP), by stimulating tachykinin NK1 receptors (NK1R), triggers a number of biological responses in human glioma cells which are potentially relevant for tumour growth. First, radioligand binding studies demonstrated the presence of tachykinin NK1R on SNB-19, DBTRG-05 MG and U373 MG, but not on U138 MG and MOG-G-GCM human glioma cell lines. Second, application of SP or neurokinin A (NKA) to NK1R+ glioma cell lines increased the secretion of interleukin 6 (IL-6) and potentiated IL-6 secretion induced by IL-1beta. SP also up-regulated the release of transforming growth factor beta1 (TGF-beta1) by the U373 MG glioma cell line. Third, SP induced new DNA synthesis and enhanced the proliferation rate of NK1R+, but not of NK1R- glioma cell lines. Also, NKA stimulated the proliferation and cytokine secretion in NK1R+ glioma cell lines. All the stimulant effects of SP/NKA on NK1R+ glioma cell lines were completely blocked by a specific tachykinin NK1R antagonist, MEN 11467. These data support the potential use of tachykinin NK1R antagonist for controlling the proliferative rate of human gliomas.

Inducible and constitutive transcription factors in the mammalian nervous system: control of gene expression by Jun, Fos and Krox, and CREB/ATF proteins

This article reviews findings up to the end of 1997 about the inducible transcription factors (ITFs) c-Jun, JunB, JunD, c-Fos, FosB, Fra-1, Fra-2, Krox-20 (Egr-2) and Krox-24 (NGFI-A, Egr-1, Zif268); and the constitutive transcription factors (CTFs) CREB, CREM, ATF-2 and SRF as they pertain to gene expression in the mammalian nervous system. In the first part we consider basic facts about the expression and activity of these transcription factors: the organization of the encoding genes and their promoters, the second messenger cascades converging on their regulatory promoter sites, the control of their transcription, the binding to dimeric partners and to specific DNA sequences, their trans-activation potential, and their posttranslational modifications. In the second part we describe the expression and possible roles of these transcription factors in neural tissue: in the quiescent brain, during pre- and postnatal development, following sensory stimulation, nerve transection (axotomy), neurodegeneration and apoptosis, hypoxia-ischemia, generalized and limbic seizures, long-term potentiation and learning, drug dependence and withdrawal, and following stimulation by neurotransmitters, hormones and neurotrophins. We also describe their expression and possible roles in glial cells. Finally, we discuss the relevance of their expression for nervous system functioning under normal and patho-physiological conditions.

Substance P enhances cytokine-induced vascular cell adhesion molecule-1 (VCAM-1) expression on cultured rheumatoid fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation of the synovial membrane of multiple joints. This inflammatory microenvironment allows fibroblast-like synoviocytes (FLS) to express or enhance several adhesion or costimulatory molecules. This phenotypic shift, under proinflammatory cytokines, seems to be related to functional consequences for antigen presentation to T cells. The sensory neuropeptide substance P (SP), present at high levels, is able to act on FLS proliferation and enzyme secretion. These data led us to investigate whether SP could also provoke a phenotypic change of FLS. Using flow cytometry and a three-step cellular ELISA method, we determined whether SP has an influence on the expression of MHC class II, intercellular adhesion molecule-1 (ICAM-1), VCAM-1, LFA-3, CD40, B7.1 or B7.2 molecules on RA FLS incubated with interferon-gamma (IFN-gamma) or IL-1beta or tumour necrosis factor-alpha (TNF-alpha) with or without SP. Our results indicate that SP potentiates the effect of proinflammatory cytokines on the expression of VCAM-1 on RA FLS. We verified the presence of specific SP (NK1) receptor mRNA. Using reverse transcription-polymerase chain reaction, we showed that RA FLS of patients express NK1 receptor mRNA. These results suggest that SP increase of cytokine-induced VCAM-1 expression acts via this specific SP receptor. Thus, during chronic inflammation RA FLS are at the interface between the immune and the nervous systems.

Human substance P receptor expressed in Chinese hamster ovary cells directly activates G(alpha q/11), G(alpha s), G(alpha o)

Substance P receptor (SPR) stably expressed in Chinese hamster ovary (CHO) cells stimulates at least three second messenger systems including phosphoinositide hydrolysis, cyclic AMP (cAMP) formation, and arachidonic acid release. Whether these second messenger systems are activated via single or multiple G proteins is not known. Therefore, in the present study we examined whether human SPR (hSPR) stably expressed in CHO cells activates multiple G proteins. This was achieved by photoaffinity labeling of G(alpha)-subunits with [32P]azidoanilido-GTP ([32P]AA-GTP) upon hSPR stimulation in CHO-hSPR membranes followed by immunoprecipitation of the labeled G(alpha)-subunits with antibodies specific for various G(alpha)-subunits. These experiments reveal that hSPR directly activates G(alpha q/11), G(alpha s) and G(alpha o). While hSPR is known to couple G(alpha q/11), the present study provides the first evidence that hSPR can also activate G(alpha s) and G(alpha o) in a mammalian system.

Glial calcium: homeostasis and signaling function

Glial cells respond to various electrical, mechanical, and chemical stimuli, including neurotransmitters, neuromodulators, and hormones, with an increase in intracellular Ca2+ concentration ([Ca2+]i). The increases exhibit a variety of temporal and spatial patterns. These [Ca2+]i responses result from the coordinated activity of a number of molecular cascades responsible for Ca2+ movement into or out of the cytoplasm either by way of the extracellular space or intracellular stores. Transplasmalemmal Ca2+ movements may be controlled by several types of voltage- and ligand-gated Ca(2+)-permeable channels as well as Ca2+ pumps and a Na+/Ca2+ exchanger. In addition, glial cells express various metabotropic receptors coupled to intracellular Ca2+ stores through the intracellular messenger inositol 1,4,5-triphosphate. The interplay of different molecular cascades enables the development of agonist-specific patterns of Ca2+ responses. Such agonist specificity may provide a means for intracellular and intercellular information coding. Calcium signals can traverse gap junctions between glial cells without decrement. These waves can serve as a substrate for integration of glial activity. By controlling gap junction conductance, Ca2+ waves may define the limits of functional glial networks. Neuronal activity can trigger [Ca2+]i signals in apposed glial cells, and moreover, there is some evidence that glial [Ca2+]i waves can affect neurons. Glial Ca2+ signaling can be regarded as a form of glial excitability.

Functional characterization of substance P receptors on cultured human spinal cord astrocytes: synergism of substance P with cytokines in inducing interleukin-6 and prostaglandin E2 production

Following brain injury, astrocytes express receptors for cytokines and neuropeptides and secrete several regulatory mediators that have a well established role in inflammation, immunity, and tissue development or repair. To elucidate the role of substance P (SP), a neurotransmitter peptide of the tachykinin family, in inducing astrocyte secretory activities, we have examined the expression of SP receptors and the functional consequences of their activation in cultured astrocytes from the human embryonic brain or spinal cord. Radioligand binding studies revealed that only one type of SP receptors, the high affinity NK-1 receptor, was present on human astrocytes and that spinal cord astrocytes expressed about 6 times as many SP binding sites as brain astrocytes. Following SP treatment, a substantial inositol phosphate formation was observed in spinal cord astrocytes only. Stimulation of spinal cord astrocytes with SP alone did not induce secretion of cytokines [interleukin-6 (IL-6), granulocyte-macrophage-CSF, macrophage chemoattractant protein-1 or leukemia inhibitory factor] or prostaglandin E2 (PGE2). Interestingly, however, SP selectively potentiated the inducing effect of IL-1beta on IL-6 and PGE2 secretion by spinal cord astrocytes without affecting the IL-1-beta-evoked secretion of other cytokines. SP also enhanced the small inducing effect of tumor necrosis factor-alpha (TNF-alpha) on IL-6 and PGE2 secretion and that of transforming growth factor-beta on PGE2 secretion. These results suggest that SP can enhance immunoregulatory and neurotrophic astroglial functions mediated by IL-6 and PGE2 by acting in concert with a set of cytokines whose cerebral expression has been reported during development and in a variety of diseases.

Expression of ligand-gated ion channels with the Semliki Forest virus expression system

Two types of ligand-gated ion channels were expressed with the Semliki Forest virus (SFV) expression system. The cDNAs for mouse serotonin 5-HT3 receptor and rat and human purinoreceptor P2x subtypes were introduced into the pSFV1 vector. In vitro transcribed RNAs were coelectroporated with pSFV-Helper2 RNA into BHK cells, where in vivo packaging resulted in high titer SFV-5-HT3 and SFV-P2x virus stocks. Infection of BHK, CHO and RIN cells resulted in high-level expression of recombinant receptors. Saturation binding analysis indicated the presence of more than 3 x 10(6) 5-HT3 receptors per cell. Binding studies on isolated membranes yielded from 10 to 60 pmol of either 5-HT3 or P2x receptor per mg protein. Functional responses to the P2x receptors were demonstrated in SFV-infected CHO cells by Ca2+ mobilization or by 45Ca2+ influx. High amplitude electrophysiological responses were also detected for both SFV-5-HT3 and SFV-P2x infected CHO cells in whole-cell patch clamp recordings. To facilitate the purification procedure of SFV-expressed recombinant receptors a histidine tag was introduced at the C-terminus of the 5-HT3 receptor. This 5-HT3His receptor showed high levels of expression, specific binding and high amplitude electrophysiological responses. For large scale expression the BHK cells were adapted to suspension culture and were efficiently infected in a 11.5 liter fermentor culture with SFV-5-HT3His resulting in high-level expression, 52 pmol receptor per mg protein corresponding to 3.2 x 10(6) receptors per cell.

Histamine H1 receptor activation stimulates [3H]GABA release from human astrocytoma U373 MG cells

In U373 MG cells, a line derived from a human astrocytoma, histamine stimulated the release of [3H]gamma-aminobutyric acid ([3H]GABA) in a concentration-dependent manner (286 +/- 23% of basal release at 1 mM histamine). Neither Ca2+ removal nor Cd2+ (100 microM) affected [3H]GABA release evoked by 100 microM histamine but the response was significantly reduced by 10 microM U-73122 ({1-[6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)-amino)-hexyl]-1 H-pyrrole-2,5-dione}), an inhibitor of phospholipase C activation (79 +/- 8% inhibition) and by 10 microM dimethylbenzamil, a selective blocker of plasma membrane Na+/Ca2+ exchange (58 +/- 6% inhibition). In [3H]inositol-labelled cells histamine stimulated [3H]inositol phosphate accumulation (EC50, 17 +/- 2 microM; maximum effect, 203 +/- 4% of basal). Histamine-evoked Ca2+ mobilisation yielded an EC50 of 12 +/- 2 microM and maximum delta[Ca2+]i of 337 +/- 23 nM. Thapsigargin (1 nM) increased [Ca2+]i (delta[Ca2+]i 164 +/- 12 nM) and prevented any further increase by histamine (100 microM). The effects of histamine on [3H]GABA release, [3H]inositol phosphate accumulation and Ca2+ mobilisation were blocked by the selective histamine H1 receptor antagonist mepyramine. Taken together, these results indicate that histamine stimulates [3H]GABA release by increasing [Ca2+]i. The mechanism of release may be related to changes in transmembranal Na+ gradients and reversal of GABA carrier transport due to stimulation of plasma membrane Na+/Ca2+ exchange.

Substance-P receptors in human primary neoplasms: tumoral and vascular localization

Primary human neoplasms were examined for the presence of substance-P receptors by receptor autoradiography with 125I-labelled Bolton-Hunter substance P. Substance-P receptors were localized and characterized in the neoplastic cells of 9/12 astrocytomas, 10/10 glioblastomas, 10/12 medullary thyroid carcinomas, 8/16 breast carcinomas and 4/5 ganglioneuroblastomas. Conversely, substance-P receptors were not or only rarely identified on non-small-cell carcinomas of the lung (1/16), neuroblastomas (0/8), adenocarcinomas of the colon (1/21) or the pancreas (1/9), or on malignant lymphomas (3/18). However, in the great majority of the investigated tumours, substance-P receptors were found on intra- and peritumoral blood vessels. All substance-P receptors detected had the pharmacological characteristics of the neurokinin-I receptor sub-type. In addition, the expression of somatostatin receptors was examined in all the neoplastic tissues mentioned above. Both substance-P and somatostatin receptors were present in astrocytomas and in ganglioneuroblastomas, whereas little or no receptor was found in pancreatic and non-small-cell lung carcinomas. The extent of somatostatin-receptor expression was inversely correlated to that of the substance-P receptors in glioblastomas, neuroblastomas and non-Hodgkin's lymphomas. The tumoral and vascular localization of substance-P receptors in tumours may have clinical implications. The use of radiolabelled substance P for in vivo scintigraphy may supplement the current set of diagnostic tools. Substance-P antagonists might be used in the treatment of tumours, as their binding to vascular receptors may decrease tumoral blood supply and drainage.

High-level expression of G protein-coupled receptors with the aid of the Semliki Forest virus expression system

The expression of two G protein-coupled receptors was studied in several cell lines using the Semliki Forest virus expression system. Human neurokinin-2 and dopamine D3 receptor cDNAs were introduced into the pSFV1 vector. In vitro transcribed RNAs were coelectroporated with pSFV-Helper RNA into BHK cells resulting in in vivo packaging of high titer SFV-NK-2 and SFV-D3 virus stocks, respectively. Infection of BHK, HOS and CHO cells with the recombinant NK-2 virus resulted in high levels of receptor expression as detected by metabolic labelling with [35S]-methionine. The expression of the NK-2 receptors in the cell membrane was demonstrated by Flow cytometry experiments on infected BHK and CHO cells with fluoresceinyl-NKA as the ligand. Saturation binding assays on membranes prepared from SFV-NK-2 infected CHO cells with [3H] GR100679 showed maximum receptor densities of 6.5 pmol receptor/mg protein. Additionally, the expressed NK-2 receptors were able to stimulate Ca2+ mobilization in CHO cells indicating functional coupling to G proteins. CHO cells infected with SFV-D3 also produced high levels of receptor as evidenced by both [35S]methionine labelling and [3H]spiperone binding.

High-level expression of the human neurokinin-1 receptor in mammalian cell lines using the Semliki Forest virus expression system

Human neurokinin-1 receptor cDNA was introduced into the pSFV1 Semliki Forest virus (SFV) vector and the in vitro transcribed RNA was electroporated into BHK cells with pSFV-Helper RNA. This procedure resulted in the packaging of a high-titer SFV-NK-1 virus stock containing approximately 5 x 10(9) infective units/ml. Infection of baby hamster kidney, COS-7, Chinese hamster ovary and human osteosarcoma cells yielded high levels of human neurokinin-1 receptor expression as assessed by [3H]substance P binding. The maximal receptor expression level obtained was 4 x 10(6) receptors/cell and studies of the post-infection time indicated that a high level of receptor expression was observed 10-24 h post-infection. The human neurokinin-1 receptor expressed in infected baby hamster kidney, COS-7 and Chinese hamster ovary cells was able to stimulate Ca2+ mobilization indicating functional coupling to guanine-nucleotide-binding proteins. The application of the Semliki Forest virus expression system will permit the rapid and efficient production of large quantities of receptor protein for both pharmacological and structural studies.

Mobilization of intracellular calcium by substance P in a human astrocytoma cell line (U-373 MG)

Variations in intracellular free calcium concentration (delta[Ca2+]i) were measured in intact and isolated human astrocytoma cells (U373 MG) loaded with fura-2 acetoxymethylester. Microperfusion of 50 nM substance P (SP), applied for 1 s, increased [Ca2+]i by 351 nM from a stable basal level of [Ca2+]i of 26 nM. The peak delta[Ca2+]i induced by SP was dose dependent with a threshold of 10(-3) nM, an ED50 of 1.3 nM and a maximal effect for concentrations of SP greater than 100 nM. The NK1 receptor agonist, [Sar9Met(O2)11]SP, mimicked the effect of SP, while the NK2 and NK3 selective receptor agonists, [N1(10)]NKA(4-10) and senktide, respectively, had no effect. The delta[Ca2+]i induced by SP was unaffected by 100 microM cadmium or by removal of extracellular calcium ions. Caffeine up to 30 mM had no effect on [Ca2+]i. In contrast, thapsigargin increased resting [Ca2+]i by 92 nM and reduced the delta[Ca2+]i induced by SP. A pertussis treatment (500 ng/ml-24 h) did not modify the delta[Ca2+]i induced by SP. We conclude that SP, acting on a NK1 receptor, mobilizes cytosolic calcium from an intracellular calcium pool which can be partially depleted by thapsigargin.

Different susceptibility to neurokinin 1 receptor antagonists of substance P and septide-induced interleukin-6 release from U373 MG human astrocytoma cell line

In a human astrocytoma cell line U373 MG, the activation of the neurokinin 1 (NK1) receptor by substance P (SP) increase, in a concentration-related manner (1 nM to 10 microM), the basal release of interleukin-6 (IL-6) as assayed by an ELISA method, in cell supernatants after 18 h of incubation. Septide, a selective NK1 receptor agonist, is equipotent to SP in inducing the IL-6 release showing similar Emax (2644 +/- 285 and 2830 +/- 271 pg/ml) and EC50 (15.6 +/- 3.6 and 13.8 +/- 3.2 nM). However, in binding assays on intact cells, septide was an about 50-fold weaker displacer of the binding of [3H][Sar9,Met(O2)11]SP than SP (Ki's were 0.28 +/- 0.1 nM and 14.2 +/- 5.0 nM for SP and septide, respectively). NK2- and NK3-selective agonists (up to 1 microM) had no binding or functional effect. Highly selective non-peptide (CP96,345) or peptide (GR82,334) NK1 receptor antagonists were more effective in antagonizing septide-(IC50's 0.2 +/- 0.06 nM and 70 +/- 18 nM) than SP-(IC50's 6.7 +/- 1.3 nM and 1.95 +/- 0.4 microM) induced IL-6 secretion. These data support the existence, also in human U373 MG cells, of a septide-sensitive NK1 receptor subtype(s) and/or epitope(s) blocked with high affinity by NK1 antagonist.

SR 140333, a novel, selective, and potent nonpeptide antagonist of the NK1 tachykinin receptor: characterization on the U373MG cell line

The effects of a novel nonpeptide NK1 tachykinin receptor antagonist, SR 140333, on the functional consequences of NK1 receptor activation in a human astrocytoma cell line, U373MG, were investigated. Radioligand binding conducted with 125I-Bolton-Hunter substance P revealed a competitive inhibition by SR 140333 and its R enantiomer SR 140603 with Ki values of 0.74 and 7.40 nM, respectively. The NK1-selective agonist, [Sar9,Met(O2)11]-substance P, stimulated the formation of inositol phosphates with an EC50 of 3.8 x 10(-9) M. SR 140333 blocked the stimulatory effect of this agonist (10(-7) M) with an IC50 of 1.6 x 10(-9) M, whereas the effect of another NK1 agonist, septide (EC50 = 1.5 x 10(-8) M) was antagonized with an IC50 of 2.1 x 10(-10) M. Enhancement of [3H]taurine release by [Sar9,Met(O2)11]-substance P (EC50 = 7.4 x 10(-9) M) was also inhibited by SR 140333 with an IC50 of 1.8 x 10(-9) M. SR 140603 was 10-fold less potent than SR 140333 in inhibiting inositol monophosphate formation and [3H]taurine release. The calcium mobilization induced by [Sar9,Met(O2)11]-substance P (10(-8) M) was totally prevented by 10(-8) M SR 140333. Patch-clamp experiments showed that SR 140333 depressed the outward current evoked by 5 x 10(-8) M [Sar9, Met(O2)11]-substance P with an IC50 of 1.3 x 10(-9) M. The expression of c-fos was stimulated by [Sar9,Met(O2)11]substance P with an EC50 of 2.5 x 10(-10) M, an effect that was also inhibited by SR 140333 with an IC50 of 1.1 x 10(-9) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P receptors on human astrocytoma cells are linked to glycogen breakdown

In this study we report that substance P stimulated [3H]glycogen breakdown and elevation of intracellular Ca2+ concentration in the human astrocytoma cell line UC-11MG. Both effects were dose dependent, and completely blocked by CP-96,345 suggesting the involvement of an NK1 receptor. Our previous studies indicated that norepinephrine and histamine stimulate glycogenolysis via cAMP and Ca2+ respectively. Combined stimulation with substance P and norepinephrine or histamine resulted in additive effects suggesting that there is no interaction between these neurotransmitters in regulating glycogenolysis in these cells. These results confirm that UC-11MG cells are a useful model system to investigate the functional role of neurotransmitter receptors in astroglial cells.

In vitro and in vivo biological activities of SR140333, a novel potent non-peptide tachykinin NK1 receptor antagonist

(S)1-(2-[3-(3,4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)pip eridin-3- yl]ethyl)-4-phenyl-1-azoniabicyclo[2.2.2]octane chloride (SR140333) is a new non-peptide antagonist of tachykinin NK1 receptors. SR140333 potently, selectively and competitively inhibited substance P binding to NK1 receptors from various animal species, including humans. In vitro, it was a potent antagonist in functional assays for NK1 receptors such as [Sar9,Met(O2)11]substance P-induced endothelium-dependent relaxation of rabbit pulmonary artery and contraction of guinea-pig ileum. Up to 1 microM, it had no effect in bioassays for NK2 ([beta Ala8]neurokinin A-induced contraction of endothelium-deprived rabbit pulmonary artery) and NK3 ([MePhe7]neurokinin B-induced contraction of rat portal vein) receptors. The antagonism exerted by SR140333 toward NK1 receptors was apparently non-competitive, with pD2' values (antagonism potency evaluated by the negative logarithm of the molar concentration of antagonist that produces a 50% reduction of the maximal response to the agonist) between 9.65 and 10.16 in the different assays. SR140333 also blocked in vitro [Sar9,Met(O2)11]substance P-induced release of acetylcholine from rat striatum. In vivo, SR140333 exerted highly potent antagonism toward [Sar9,Met(O2)11]substance P-induced hypotension in dogs (ED50 = 3 micrograms/kg i.v.), bronchoconstriction in guinea-pig (ED50 = 42 micrograms/kg i.v.) and plasma extravasation in rats (ED50 = 7 micrograms/kg i.v.). Finally, it also blocked the activation of rat thalamic neurons after nociceptive stimulation (ED50 = 0.2 micrograms/kg i.v.).

Substance P-evoked calcium mobilization and ionic current activation in the human astrocytoma cell line U 373 MG: pharmacological characterization

In the human astrocytoma cell line U 373 MG, application of substance P (SP) leads to a transient increase in cytosolic calcium concentration and to a biphasic current response in voltage-clamped cells. Using these two functional assays we have characterized pharmacologically the SP response in U 373 MG cells. SP and [L-Pro9]SP displayed high potencies in both assays with EC50 values of 2.5 x 10(-9) M and 1 x 10(-9) M on calcium responses and 1 x 10(-9) M and 5 x 10(-9) M on ion current responses, respectively. The high potency of SP and [L-Pro9]SP as well as the low potency of [Lys5,MeLeu9,N-Leu10]neurokinin A(4-10) and the inactivity of senktide demonstrate the NK1-type pharmacology of these responses. Furthermore, the NK1 antagonists (+/-)-CP 96,345, its chloro analogue, (+/-)-cis-3-(2-chlorobenzylamino)-2-benzhydrylquinuclidine, and RP 67580 were potent antagonists of both SP responses. For the calcium mobilization induced by SP (10(-7) M), the IC50 values for the three antagonists were 4 x 10(-10) M, 4 x 10(-9) M, and 9 x 10(-9) M, respectively, whereas on the current response evoked by SP (10(-8) M), the IC50 values were 8 x 10(-9) M, 2.4 x 10(-8) M, and 1.2 x 10(-7) M, respectively. Despite differences in the absolute IC50 values obtained with both techniques, the relative potencies of the three antagonists correlate fairly well.(ABSTRACT TRUNCATED AT 250 WORDS)