Neuroimmune/Hematopoietic Axis with Distinct Regulation by the High-Mobility Group Box 1 in Association with Tachykinin Peptides.

Hematopoiesis is tightly regulated by the bone marrow (BM) niche. The niche is robust, allowing for the return of hematopoietic homeostasis after insults such as infection. Hematopoiesis is partly regulated by soluble factors, such as neuropeptides, substance P (SP), and neurokinin A (NK-A), which mediate hematopoietic stimulation and inhibition, respectively. SP and NK-A are derived from the Tac1 gene that is alternately spliced into four variants. The hematopoietic effects of SP and NK-A are mostly mediated via BM stroma. Array analyses with 2400 genes indicated distinct changes in SP-stimulated BM stroma. Computational analyses indicated networks of genes with hematopoietic regulation. Included among these networks is the high-mobility group box 1 gene (HMGB1), a nonhistone chromatin-associated protein. Validation studies indicated that NK-A could reverse SP-mediated HMGB1 decrease. Long-term culture-initiating cell assay, with or without NK-A receptor antagonist (NK2), showed a suppressive effect of HMGB1 on hematopoietic progenitors and increase in long-term culture-initiating cell assay cells (primitive hematopoietic cells). These effects occurred partly through NK-A. NSG mice with human hematopoietic system injected with the HMGB1 antagonist glycyrrhizin verified the in vitro effects of HMGB1. Although the effects on myeloid lineage were suppressed, the results suggested a more complex effect on the lymphoid lineage. Clonogenic assay for CFU- granulocyte-monocyte suggested that HMGB1 may be required to prevent hematopoietic stem cell exhaustion to ensure immune homeostasis. In summary, this study showed how HMGB1 is linked to SP and NK-A to protect the most primitive hematopoietic cell and also to maintain immune/hematopoietic homeostasis.

ACS chemical neuroscience molecule spotlight on Saredutant.

Saredutant (SR48968), a potentially novel treatment option for major depressive disorders (MDD) and generalized anxiety disorder (GAD), is a drug from Sanofi-Aventis currently in phase III clinical trials. MDD is a common mental disorder that affects 121 million people worldwide, nearly 4% of the adult population (www.who.int/mental_health/management/depression/definition/en/). MDD continues to be one of the leading causes of disability with more than three quarters of the diagnosed cases having effective treatments available (www.who.int/mental_health/management/depression/definition/en/). However, even though MDD affects a large portion of the population, effective treatment options with low incidence of adverse events remain a major concern for the pharmaceutical industry. Adverse events (GI side effects1, weight gain, somnolence/insomnia, etc. (Demyttenaere K. (2003) Risk factors and predictors of compliance in depressionEur. Neuropshychopharm.13S69-S75)) from the typical treatments remain the major reason for premature stopping or poor compliance of treatment. New treatments to the market must bear in mind these adverse events, and the pharmaceutical industry is currently looking for drugs with new mechanisms of action and those that are better tolerated.

Novel triple neurokinin receptor antagonist CS-003 strongly inhibits neurokinin related responses.

Neurokinins are known to induce neurogenic inflammation related to respiratory diseases, though there is little information on triple neurokinin receptor antagonists. The pharmacological properties of the novel triple neurokinin 1, 2 and 3 receptor antagonist [1-(2-[(2R)-(3,4-dichlorophenyl)-4-(3,4,5-trimethoxybenzoyl)morpholin-2-yl]ethyl)spiro[benzo[c]thiophene-1(3H),4'-piperidine]-(2S)-oxide hydrochloride] (CS-003) were evaluated in this study. The binding affinities of CS-003 were evaluated with human and guinea pig neurokinin receptors. As well, the in vivo antagonism of CS-003 against exogenous neurokinins and effects on capsaicin-induced and citric acid-induced responses were investigated in guinea pigs. CS-003 exhibited high affinities for human neurokinin 1, neurokinin 2 and neurokinin 3 receptors with Ki values (mean+/-S.E.M.) of 2.3+/-0.52, 0.54+/-0.11 and 0.74+/-0.17 nM, respectively, and for the guinea pig receptors with Ki values of 5.2+/-1.4, 0.47+/-0.075 and 0.71+/-0.27 nM, respectively. Competitive antagonism was indicated in a Schild analysis of substance P-, neurokinin A- and neurokinin B-induced inositol phosphate formation with pA2 values of 8.7, 9.4 and 9.5, respectively. CS-003 inhibited substance P-induced tracheal vascular hyperpermeability, neurokinin A- and neurokinin B-induced bronchoconstriction with ID50 values of 0.13, 0.040 and 0.063 mg/kg (i.v.), respectively. CS-003 also inhibited capsaicin-induced bronchoconstriction (ID50: 0.27 mg/kg, i.v.), which is caused by endogenous neurokinins. CS-003 significantly inhibited citric acid-induced coughs and the effect was greater than those of other selective neurokinin receptor antagonists. CS-003 is a potent antagonist of triple neurokinin receptors and may achieve the best therapeutic efficacy on respiratory diseases associated with neurokinins compared to selective neurokinin receptor antagonists.

The effect of the leukotriene receptor antagonist zafirlukast on neurokinin A-induced bronchoconstriction in patients with asthma--A comparison with leukotriene D4 induced broncoconstriction.

The bronchoconstriction caused by inhaled neurokinin A (NKA) in patients with asthma is indirect. The mediators involved in NKA-induced bronchoconstriction are unknown. Studies with various H1 receptor antagonists were negative, making an important contribution of histamine unlikely. To study the role of cysteinyl leukotrienes in neurokinin A-induced bronchoconstriction, we performed a randomised, double-blind, cross-over, placebo controlled trial in 12 patients with mild to moderate asthma. Zafirlukast and matching placebo were given orally, 40 mg the evening before and 40 mg the morning of assessment. In one period NKA was administered, in the other period leukotriene D4 (LTD4). Increasing concentrations of NKA and LTD4 were inhaled from a 30 L bag, after nebulization via a Mallinckrodt nebuliser. The difference between log10PC20LTD4 after treatment with placebo or zafirlukast was highly significant (p<0.0001). A trend was observed towards a difference between log10PC20 neurokinin A after treatment with placebo or zafirlukast (p=0.0741). The dose ratio for the neurokinin A provocation was 4.4 and for the LTD4 provocation 67.7. In conclusion, zafirlukast had a large inhibitory effect on LTD4-induced bronchoconstriction, but offered only limited protective effect against neurokinin A-induced bronchoconstriction. We suggest that leukotrienes play a limited role in the bronchoconstrictor effect of neurokinin A in patients with asthma.

Estrogen determines sex differences in airway responsiveness after allergen exposure.

The female hormone estrogen is an important factor in the regulation of airway function and inflammation, and sex differences in the prevalence of asthma are well described. Using an animal model, we determined how sex differences may underlie the development of altered airway function in response to allergen exposure. We compared sex differences in the development of airway hyperresponsiveness (AHR) after allergen exposure exclusively via the airways. Ovalbumin (OVA) was administered by nebulization on 10 consecutive days in BALB/c mice. After methacholine challenge, significant AHR developed in male mice but not in female mice. Ovariectomized female mice showed significant AHR after 10-day OVA inhalation. ICI182,780, an estrogen antagonist, similarly enhanced airway responsiveness even when administered 1 hour before assay. In contrast, 17beta-estradiol dose-dependently suppressed AHR in male mice. In all cases, airway responsiveness was inhibited by the administration of a neurokinin 1 receptor antagonist. These results demonstrate that sex differences in 10-day OVA-induced AHR are due to endogenous estrogen, which negatively regulates airway responsiveness in female mice. Cumulatively, the results suggest that endogenous estrogen may regulate the neurokinin 1-dependent prejunctional activation of airway smooth muscle in allergen-exposed mice.

Depressed contractile responses to neurokinin A in idiopathic but not neurogenic overactive human detrusor muscle.

OBJECTIVE: The role of tachykinins such as neurokinin A in regulating bladder function is unclear, but NK2 receptors seem to mediate contraction in the human bladder and it has been suggested that these peptides may have a role in the pathophysiology of bladder dysfunction. The present study investigates neurokinin receptor-mediated contractility of detrusor muscle in the idiopathic overactive and neurogenic overactive bladder and investigates the neurokinin receptor subtypes involved. METHODS: Human bladder was obtained from patients undergoing cystectomy (normal) or clam cystoplasty (idiopathic overactive) and from patients with spinal injuries (neurogenic overactive). Strips of isolated detrusor muscle were mounted in physiological Krebs-bicarbonate solution and cumulative concentration-response curves to 1 nM to 300 microM neurokinin A (NKA) were obtained in the absence and presence of neurokinin receptor antagonists, either the NK2 receptor-selective antagonist SR 48968 or the NK3 receptor-selective antagonist SB 223412. RESULTS: NKA evoked concentration-dependent contraction of normal, idiopathic, and neurogenic overactive detrusor strips. In idiopathic overactive detrusor muscle, NKA-induced contraction was significantly reduced relative to normal detrusor (0.031 +/- 0.005 mg/g, n = 11 versus 0.193 +/- 0.039 mg/g, n = 7). Sensitivity to the peptide was also significantly (p < 0.01) reduced in idiopathic overactive detrusor, with mean pEC50 values (concentration producing 50% maximal response) of 6.62+/-0.16 (n = 11) compared to 7.47+/-0.19 (n = 7) in normal detrusor. In contrast, NKA-induced responses of neurogenic overactive detrusor were similar to those in normal detrusor, with a mean maximum contraction of 0.199 +/- 0.036 mg/g (n = 10) and mean pEC50 value of 7.85+/-0.16 (n = 10). NKA curves in all groups were shifted to the right by the NK2 receptor-selective antagonist SR 48968 with high affinity, pK(B) values being similar in normal, idiopathic, and neurogenic overactive detrusor (8.85 + 0.08, n = 14; 8.97 +/- 0.13, n = 12; 8.73 +/- 0.12, n = 8, respectively). In contrast the NK3 receptor-selective antagonist SB 223412 had a minimal effect on NKA responses and affinity values were low (pK(B) 5.81 +/- 0.11, n = 12 in normal; 5.75 +/- 0.08, n = 12 in idiopathic overactive, and 5.77 +/- 0.13, n = 11 in neurogenic overactive). CONCLUSION: These data indicate that NKA-induced responses are impaired in detrusor muscle from idiopathic overactive human bladder, but not in detrusor muscle from neurogenic overactive bladder. The NK2 receptor subtype appears to mediate NKA responses in the normal, idiopathic overactive, and neurogenic overactive detrusor. This is important evidence suggesting a difference between the bladder pathophysiology observed in idiopathic versus neurogenic overactive detrusor.

The triple neurokinin-receptor antagonist CS-003 inhibits neurokinin A-induced bronchoconstriction in patients with asthma.

Neurokinin A (NKA) causes bronchoconstriction in asthmatic patients. In vitro both NK1 and NK2 receptors can mediate airway contraction. Moreover in guinea pigs, NK3 receptors facilitate cholinergic neurotransmission. Dual tachykinin NK1/NK2 receptor antagonism results in prevention of NKA-induced bronchoconstriction. We have now examined the effect of a single dose of the triple tachykinin receptor antagonist CS-003 on NKA-induced bronchoconstriction in asthmatics. A double blind, crossover, placebo-controlled trial in 16 mild asthmatics was performed. One single dose of CS-003 (200 mg, solution in distilled water) or matched placebo was given orally on the assessment days. NKA-provocation tests were performed pre-dose and 1, 8 and 24 h after dosing. There was a significant shift to the right of the dose-response curve at 1 and 8 h after intake of CS-003. PC20 was not reached in 12/16 patients at 1h post-dose and in 5/16 patients at 8 h post-dose. This did not occur under placebo treatment. A single dose of 200 mg CS-003 protected significantly against NKA-induced bronchoconstriction at 1 and 8h post-dose in mild asthmatics.

Role of NK-1 and NK-2 tachykinin receptor antagonism on the growth of human breast carcinoma cell line MDA-MB-231.

We demonstrate that neurokinin A (NKA) and substance P (SP) play a role in the proliferation of the estrogen receptor-negative (ER-) cell line MDA-MB-231, a human breast carcinoma expressing both NK-1 and NK-2 receptors. In vitro experiments showed that the specific receptor antagonists MEN 11,467 (NK-1) and nepadutant (MEN 11,420; NK-2) inhibited tumor cell proliferation, and blocked the stimulatory effect of SP and NKA. Anti-tumoral activity of NK-1 and NK-2 receptor antagonists was demonstrated in nude mice, measuring growth inhibition of MDA-MB-231 tumor cells xenografted s.c. and by using the hollow-fiber assay. In both systems a significant inhibition was found when compounds were administered at 5 mg/kg i.v. every day for 2 weeks. Results obtained from both these models suggest that the in vivo activity of NK-1 and NK-2 antagonists may be a result of a cytostatic effect rather than a cytotoxic effect. Our results suggest that the control of breast carcinoma (ER-) growth by tachykinin receptor antagonists may become a new form of targeted therapy for these human tumors.

Characterization of receptors for two Xenopus gastrointestinal tachykinin peptides in their species of origin.

Two tachykinin peptides, bufokinin and Xenopus neurokinin A (X-NKA) were recently isolated from Xenopus laevis. In this study we investigated the tachykinin receptors in the Xenopus gastrointestinal tract. In functional studies using stomach circular muscle strips, all peptides had similar potencies (EC50 values 1-7 nM). The rank order of potency to contract the intestine was physalaemin (EC50 1 nM)> or =bufokinin (EC50 3 nM)>substance P (SP)> or =cod SP>NKA>>X-NKA (EC50 1,900 nM). No maximum response could be obtained for [Sar9,Met(O2)11]SP, eledoisin and kassinin. In stomach strips, the mammalian tachykinin receptor antagonists RP 67580 (NK1) and MEN 10376 (NK2) had agonistic effects but did not antagonize bufokinin or X-NKA. In intestinal strips, RP 67580 (1 microM) reduced the maximal response to X-NKA but not bufokinin, while MEN 10376 was ineffective. [125I]BH-bufokinin bound with high affinity to a single class of sites, of KD 213+/-35 (stomach) and 172+/-9.3 pM (intestine). Specific binding of [125I]BH-bufokinin was displaced by bufokinin> or =SP>NKA> or =eledoisin approximately kassinin>X-NKA, indicating binding to a tachykinin NK1-like receptor. Selective tachykinin receptor antagonists were weak or ineffective. Other iodinated tachykinins ([125I]NKA and [125I]BH-eledoisin) displayed biphasic competition profiles, with the majority of sites preferring bufokinin rather than X-NKA. In conclusion, there is evidence for two different tachykinin receptors in Xenopus gastrointestinal tract. Both receptors may exist in stomach, whereas the bufokinin-preferring NK1-like receptor predominates in longitudinal muscle of the small intestine. Antagonists appear to interact differently with amphibian receptors, compared with mammalian receptors.

Pemirolast potently attenuates paclitaxel hypersensitivity reactions through inhibition of the release of sensory neuropeptides in rats.

The effects of anti-allergic agents on the hypersensitivity reactions to paclitaxel, an anti-cancer agent, were examined in rats. Intravenous injection of paclitaxel (15 mg/kg) caused a marked extravasation of plasma protein in lungs and a transient decrease in arterial partial oxygen pressure (PaO(2)). The paclitaxel-induced protein extravasation was inhibited by low doses (0.1-1 mg/kg) of pemirolast or high doses (30-100 mg/kg) of cromoglycate. However, ketotifen was not effective. The decrease in PaO(2) induced by paclitaxel was also significantly reversed by pemirolast. On the other hand, the paclitaxel-induced plasma extravasation was not attenuated by a histamine H(1) blocker diphenhydramine or an H(2) blocker famotidine, but was significantly reduced by a neurokinin NK(1) antagonist LY303870 (0.5 mg/kg) and an NK(2) antagonist SR48968 (1 mg/kg). The concentrations of proteins and sensory peptides such as substance P, neurokinin A and calcitonin gene-related peptide but not histamine in the rat bronchoalveolar lavage fluid were elevated by paclitaxel injection. Both cromoglycate and pemirolast reduced the paclitaxel-induced rise in proteins and sensory peptides. Therefore, we demonstrated for the first time that sensory nerve peptides are involved in paclitaxel hypersensitivity and that an anti-allergic agent pemirolast attenuates the paclitaxel response by inhibiting the release of sensory nerve peptides.

Effects of neuropeptides on the sumatriptan-disturbed circulation in the optic nerve head of rabbits.

The purpose of this work was to study 'in vivo' the vascular responses of retinal vessels of New Zealand white rabbits to substance P (SP), neurokinin A (NKA), neurokinin B (NKB), senktide, capsaicin (CAPS), and calcitonin gene related peptide (CGRP) before and after selective antagonist administration. We examined the effects of these neuropeptides on the normal circulation in the optic nerve head of the rabbit. Drugs were injected via pars plana through a micropipette system. Ten minutes before perivascular injection of 10 nmol/l sumatriptan (to contract the vessel), a selective antagonist or its solvent was administered. Then, cumulative injection of the agonist was performed. The other eye was used as control. Direct measurement of retinal arteriole diameters was performed using digital angiography. The quantification of the relaxing effect is expressed as percentage related to the precontracted vascular diameter. Microinjection of SP (NK1 receptor agonist) up to 10 nmol/l induced a dose-dependent arteriolar dilating effect [E(max) (mean +/- SEM) 21.3 +/- 2.3%]. After the perivascular preinjection of 1 nmol/l L-668,169 or 1 nmol/l L-733,060 (NK1 receptor antagonists), the SP dose-response curve was shifted to the right. The same results were obtained with NKA (NK2 receptor agonist) which induced the most potent effect of all neuropeptides (E(max) 53.3+/-2.5%). The NK2 receptor antagonists L-659,877 and GR 159897 (1 nmol/l) strongly inhibited this arteriolar vasodilation. As for CGRP, doses up to 10 nmol/l induced a marked vasodilation (E(max) 41.1+/-0.4%) which decreased after microinjection of the selective antagonist CGRP8-37. The NK3 receptor agonists (senktide and NKB) showed a minor vasodilating effect (E(max) 5.1+/-1.2 and 8.0+/-0.9%, respectively). On the contrary, CAPS showed a marked dose-dependent vasodilating effect (E(max) 43.2+/-2.9%), antagonized by the tachykinin receptor antagonists and CGRP8-37. These results suggest, for the first time, the presence of NK1, NK2, and CGRP receptors on the retinal arteriolar wall of the rabbit.

Pharmacological properties of peptides derived from an antibody against the tachykinin NK1 receptor for the neuropeptide substance P.

Two peptides were derived from the structural analysis of a previously described monoclonal antibody [Mol. Immunol. 37 (2000) 423] against the tachykinin NK(1) receptor for the neuropeptide substance P. Here we show that these two peptides were able to inhibit the inositol phosphate transduction pathway triggered both by substance P and neurokinin A, another high-affinity endogenous ligand for the tachykinin NK(1) receptor. They also reduced the cAMP production induced by substance P. By contrast, only one antagonist peptide was able to prevent substance P and neurokinin A from binding the receptor, as revealed both by biochemical and autoradiographic studies. First, these results illustrate the generality of the antibody-based strategy for developing new bioactive peptides. Second, they indicate that antagonists, even exhibiting very close amino acid composition, can interact with the tachykinin NK(1) receptor at different contact sites, some of them clearly distinct from the contact domains for endogenous agonists.

Inhibitory effect of a leukotriene receptor antagonist (montelukast) on neurokinin A-induced bronchoconstriction.

BACKGROUND: Tachykinins are potent contractors of human airways producing a dose-related bronchoconstriction when administered by means of inhalation to asthmatic subjects. OBJECTIVE: The aim of this study was to examine the effective role played by leukotrienes (LTs) in neurokinin A (NKA)-induced bronchoconstriction in asthmatic patients. METHODS: To address this question, we investigated the protective effect of a selective cysteinyl LT receptor antagonist, montelukast, against inhaled NKA and determined LTE(4) excretion in the urine. RESULTS: Inhaled NKA in the absence of any drug treatment produced a concentration-related bronchospasm with a geometric mean provocative concentration required to produce a 15% decrease in FEV(1) from the postsaline baseline value (PC(15)) value of 290.9 microg/mL (+SE, 407.1 microg/mL; -SE, 207.84 microg/mL). Montelukast pretreatment significantly increased (P <.01) the PC(15) NKA value (708.8 microg/mL; +SE, 890.47 microg/mL; -SE, 564.15 microg/mL) in comparison with placebo (394.4 microg/mL; +SE, 491.88 microg/mL; -SE, 248.16 microg/mL) and produced a shift of the NKA concentration-response curve to the right in all the subjects studied. When compared with placebo, montelukast did not have a significant protective effect against methacholine challenge; the geometric mean PC(15) values obtained were 0.87 and 0.96 mg/mL with placebo and montelukast, respectively. Although we have not observed any increase in urinary LTE(4) excretion after NKA inhalation, we have shown that pretreatment of asthmatic subjects with montelukast elicits a significant protection against NKA-induced bronchoconstriction. CONCLUSION: In asthmatic subjects NKA-induced bronchoconstriction is indirectly caused by the release of LTs, and this mechanism could explain some of the antiasthmatic and anti-inflammatory effects of LT antagonists.

Intrathecal histamine induces spinally mediated behavioral responses through tachykinin NK1 receptors.

Intrathecal injection of histamine elicited a behavioral response consisting of scratching, biting and licking in conscious mice. Here, we have examined the involvement of substance P (SP) by using intrathecal injection of tachykinin neurokinin (NK)(1) receptor antagonists and SP antiserum. Histamine-induced behavioral response was evoked significantly 5-10 min after intrathecal injection and reached a maximum at 10-15 min. Dose-dependency of the induced response showed a bell-shaped pattern from 200 to 3200 pmol, and maximum effect was observed at 800-1000 pmol. The H(1) receptor antagonist, d-chlorpheniramine and pyrilamine but not the H(2) receptor antagonists, ranitidine and zolantidine, inhibited histamine-induced behavioral response. The NK(1) receptor antagonists, CP-99,994, RP-67580 and sendide, inhibited histamine-induced behavioral response in a dose-dependent manner. A significant antagonistic effect of [D-Phe(7), D-His(9)]SP (6-11), a selective antagonist for SP receptors, was observed against histamine-induced response. The NK(2) receptor antagonist, MEN-10376, had no effect on the response elicited by histamine. Pretreatment with SP antiserum resulted in a significant reduction of the response to histamine. No significant reduction of histamine-induced response was detected in mice pretreated with NK A antiserum. The present results suggest that elicitation of scratching, biting and licking behavior induced by intrathecal injection of histamine may be largely mediated by NK(1) receptors via H(1) receptors in the spinal cord.

Effect of monensin on the levels of tachykinins and their processing enzyme activity in rat dorsal root ganglia.

Th effect of monensin, which inhibits trans-Golgi function, on the levels of tachykinins and their processing enzyme activity was examined in organ-cultured rat dorsal root ganglia (DRG). Using an enzyme immunoassay method, we measured neurokinin A and substance P immunoreactivity in the DRG cultured for 72 h with and without 0.1 microM monensin. Both tachykinins were reduced in the DRG treated with monensin. Treatment with monensin also reduced the activity of carboxypeptidase E, which is one of the proteolytic processing enzymes of neuropeptides. These data suggest that proteolytic processing enzymes may in part modulate the biological activity of neuropeptides within a trans-Golgi apparatus.

Tachykinin-stimulated small bowel myoelectric pattern: sensitization by NO inhibition, reversal by neurokinin receptor blockade.

UNLABELLED: Tachykinins stimulate motility whereas NO inhibits motility in the gastrointestinal tract. AIM: To investigate if inhibition of NO production sensitizes myoelectric activity to subthreshold doses of tachykinins in the small intestine of awake rats. METHODS: Rats were supplied with a venous catheter and bipolar electrodes at 5, 15 and 25 cm distal to pylorus for electromyography of small intestine. The motor responses were evaluated using pattern recognition. Substance P and neurokinin A dose-dependently stimulated gut motility, with neurokinin A being more potent than substance P. Therefore, neurokinin A was chosen and administered under baseline conditions and 45-60 min after N(omega)-nitro-L-arginine (L-NNA) 1 mg kg(-1), with or without pretreatment with L-arginine 300 mg kg(-1). In addition, myoelectric activity effects of neurokinin A in conjunction with L-NNA were studied before and after administration of the tachykinin receptor antagonists, SR140333 (NK1), SR48968 (NK2) and SR142801 (NK3), each at 2.5 mg kg(-1). RESULTS: Dose-finding studies verified 10 pmol kg(-1) min(-1) to be the threshold dose at which NKA caused phase II-like activity in a low percentage of experiments (12%, n=41). This dose was therefore used in combination with L-NNA for sensitization experiments of gut myoelectric activity. In experiments where NKA-induced no response, pretreatment with L-NNA led to phase II-like activity in 9 of 18 (50%, p<0.05) experiments. Co-administration of SR140333 and SR48968 abolished this effect. CONCLUSION: NO counteracts the stimulatory effect of tachykinins on small bowel myoelectric activity in the rat. Inhibition of the L-arginine/NO pathway sensitizes the gut to tachykinin-stimulated motor activity.

2-Aryl indole NK(1) antagonists: optimisation of the amide substituent.

The in vivo properties of a series of 2-arylindole NK(1) antagonists have been improved, by modification of the amide substituent. The 1-(2-methoxyphenyl)piperazine amide was identified as a major area of metabolism in the lead compound 1. Replacement of this amine moiety by a 4-benzyl-4-hydroxypiperidine resulted in a compound 18 with reduced clearance and improved central duration of action.

Human colonic anti-secretory activity of the potent NK(1) antagonist, SR140333: assessment of potential anti-diarrhoeal activity in food allergy and inflammatory bowel disease.

1. This in vitro study was designed to determine the potential use of the NK(1) antagonist, SR140333 as an anti-diarrhoeal treatment for food allergy or inflammatory bowel disease. The effect of various immune and neuronal stimuli on human colonic substance P (SP) release and the effect of SR140333 on subsequently stimulated mucosal ion transport was investigated. 2. Submucosal and sensory nerve fibre stimulation using electrical field stimulation (1 ms/7 Hz/7 V) and capsaicin (50 microM) respectively, mast cell activation by anti-IgE (1/250 dilution) and granulocyte stimulation using fMLP (50 microM) each released SP and evoked a secretory response. 3. SP and the NK(1) selective agonist, Sar-SP (0.1 - 1000 nM) stimulated an increase in colonic secretion which was antagonized by SR140333 (pD'(2)=6.7 and 7.25 versus SP and Sar-SP respectively). 4. SR140333, at a concentration that blocked NK(1)-mediated secretion (500 nM), also reduced the secretory response to both alphaIgE and capsaicin. This suggests a pathophysiologic role for NK(1) receptors. 5. Capsaicin evoked SP release was increased in tissue taken from Crohn's disease but not ulcerative colitis patients. The response to SP was however reduced by 70 and 89% respectively. 6. Mast cells and sensory afferents contribute to allergic diarrhoea. Since SR140333 reduced the secretory response to mast cell and afferent stimulation this compound may be particularly useful in reducing the symptoms of food allergy.

Differential role of neurokinin receptors in human lymphocyte and monocyte chemotaxis.

The precise nature of neurokin receptor involvement in human immune cell chemotaxis is unclear. This study therefore sought to directly compare the chemotactic effects of neurokinins on human T lymphocytes and monocytes. Substance P was found to have a similar dose-dependent chemotactic action on T lymphocyte and monocyte populations. In contrast, T lymphocytes were found to be more responsive than monocytes both to the highly selective NK-1 agonist, [Sar(9)Met O(2)(11)]-substance P, and also to the NK-2 selective agonist, beta-alanine neurokinin A((4-10)). Consistent with these findings, substance P-induced chemotaxis of both T lymphocyte and monocytes was attenuated by the selective NK-1 antagonist LY303870. However, the selective NK-2 antagonist MEN 10,376 was only effective in inhibiting the T lymphocyte response. The study confirms that neurokinins have chemotactic actions on immune cells and indicates important functional differences between human T lymphocyte and monocyte responses. This provides a potential mechanism by which the nervous system can selectively influence cellular recruitment in inflammatory disease.

Role of tachykinins in asthma.

The sensory neuropeptides substance P (SP) and neurokinin A (NKA) are localized to sensory airway nerves, from which they can be released by a variety of stimuli, including allergen, ozone, or inflammatory mediators. Sensory nerves containing these peptides are relatively scarce in human airways, but it is becoming increasingly evident that inflammatory cells such as eosinophils, macrophages, lymphocytes, and dendritic cells can produce the tachykinins SP and NKA. Moreover, immune stimuli can boost the production and secretion of SP and NKA. SP and NKA have potent effects on bronchomotor tone, airway secretions, and bronchial circulation (vasodilation and microvascular leakage) and on inflammatory and immune cells. Following their release, tachykinins are degraded by neutral endopeptidase (NEP) and angiotensin-converting enzyme. The airway effects of the tachykinins are largely mediated by tachykinin NK1 and NK2 receptors. Tachykinins contract smooth muscle mainly by interaction with NK2 receptors, while the vascular and proinflammatory effects are mediated by the NK1 receptor. In view of their potent effects on the airways, tachykinins have been put forward as possible mediators of asthma, and tachykinin receptor antagonists are a potential new class of antiasthmatic medication.