Pharmacological profile of the novel mammalian tachykinin, hemokinin 1

Regional differences of tachykinin effects on smooth muscle and pacemaker potentials of the stomach, duodenum, ileum and colon of an emetic model, the house musk shrews

BACKGROUND AND AIMS

The contractile effects of tachykinins on the gastrointestinal tract are well-known, but how they modulate slow-waves, particularly in species capable of emesis, remains largely unknown. We aimed to elucidate the effects of tachykinins on myoelectric and contractile activity of isolated gastrointestinal tissues of the Suncus murinus.

METHODS

The effects of substance P (SP), neurokinin (NK)A, NKB and selective NK₁ (CP122,721, CP99,994), NK₂ (SR48,968, GR159,897) and NK₃ (SB218,795, SB222,200) receptor antagonists on isolated stomach, duodenum, ileum and colon segments were studied. Mechanical contractile activity was recorded using isometric force displacement transducers. Electrical pacemaker activity was recorded using a microelectrode array.

RESULTS

Compared with NKA, SP induced larger contractions in stomach tissue and smaller contractions in intestinal segments, where oscillation magnitudes increased in intestinal segments, but not the stomach. CP122,721 and GR159,897 inhibited electrical field stimulation-induced contractions of the stomach, ileum and colon. NKB and NK₃ had minor effects on contractile activity. The inhibitory potencies of SP and NKA on the peristaltic frequency of the colon and ileum, respectively, were correlated with those on electrical pacemaker frequency. SP, NKA and NKB inhibited pacemaker activity of the duodenum and ileum, but increased that of the stomach and colon. SP elicited a dose-dependent contradictive pacemaker frequency response in the colon.

CONCLUSION

This study revealed distinct effects of tachykinins on the mechanical and electrical properties of the stomach and colon vs. the proximal intestine, providing a unique aspect on neuromuscular correlation in terms of the effects of tachykinin on peristaltic and pacemaker activity in gastrointestinal-related symptoms.

Novel Pituitary Actions of TAC4 Gene Products in Teleost

Tachykinin 4 (TAC4) is the latest member of the tachykinin family involved in several physiological functions in mammals. However, little information is available about TAC4 in teleost. In the present study, we firstly isolated TAC4 and six neurokinin receptors (NKRs) from grass carp brain and pituitary. Sequence analysis showed that grass carp TAC4 could encode two mature peptides (namely hemokinin 1 (HK1) and hemokinin 2 (HK2)), in which HK2 retained the typical FXGLM motif in C-terminal of tachyinin, while HK1 contained a mutant VFGLM motif. The ligand-receptor selectivity showed that HK2 could activate all 6 NKRs but with the highest activity for the neurokinin receptor 2 (NK2R). Interestingly, HK1 displayed a very weak activation for each NKR isoform. In grass carp pituitary cells, HK2 could induce prolactin (PRL), somatolactin α (SLα), urotensin 1 (UTS1), neuromedin-B 1 (NMB1), cocaine- and amphetamine-regulated transcript 2 (CART2) mRNA expression mediated by NK2R and neurokinin receptor 3 (NK3R) via activation cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA), phospholipase C (PLC)/inositol 1,4,5-triphosphate (IP3)/protein kinase C (PKC) and calcium²⁺ (Ca²⁺)/calmodulin (CaM)/calmodulin kinase-II (CaMK II) cascades. However, the corresponding stimulatory effects triggered by HK1 were found to be notably weaker. Furthermore, based on the structural base for HK1, our data suggested that a phenylalanine (F) to valine (V) substitution in the signature motif of HK1 might have contributed to its weak agonistic actions on NKRs and pituitary genes regulation.

Mast Cell-Specific MRGPRX2: a Key Modulator of Neuro-Immune Interaction in Allergic Diseases

PURPOSE OF REVIEW

Atopic dermatitis (AD) and allergic asthma are complex disorders with significant public health burden. This review provides an overview of the recent developments on Mas-related G protein-coupled receptor-X2 (MRGPRX2; mouse counterpart MrgprB2) as a potential candidate to target neuro-immune interaction in AD and allergic asthma.

RECENT FINDINGS

Domestic allergens directly activate sensory neurons to release substance P (SP), which induces mast cell degranulation via MrgprB2 and drives type 2 skin inflammation in AD. MRGPRX2 expression is upregulated in human lung mast cells and serum of asthmatic patients. Both SP and hemokinin-1 (HK-1 generated from macrophages, bronchial cells, and mast cells) cause degranulation of human mast cells via MRGPRX2. MrgprB2 contributes to mast cell-nerve interaction in the pathogenesis of AD. Furthermore, asthma severity is associated with increased MRGPRX2 expression in mast cells. Thus, MRGPRX2 could serve as a novel target for modulating AD and asthma.

Advances in Understanding the Initial Steps of Pruritoceptive Itch: How the Itch Hits the Switch

Pruritoceptive (dermal) itch was long considered an accompanying symptom of diseases, a side effect of drug applications, or a temporary sensation induced by invading pruritogens, as produced by the stinging nettle. Due to extensive research in recent years, it was possible to provide detailed insights into the mechanism of itch mediation and modulation. Hence, it became apparent that pruritus is a complex symptom or disease in itself, which requires particular attention to improve patients’ health. Here, we summarize recent findings in pruritoceptive itch, including how this sensation is triggered and modulated by diverse endogenous and exogenous pruritogens and their receptors. A differentiation between mediating pruritogen and modulating pruritogen seems to be of great advantage to understand and decipher the molecular mechanism of itch perception. Only a comprehensive view on itch sensation will provide a solid basis for targeting this long-neglected adverse sensation accompanying numerous diseases and many drug side effects. Finally, we identify critical aspects of itch perception that require future investigation.

Efficient synthesis of cyclic amidine-based fluorophores via 6π-electrocyclic ring closure

Novel 10π-electron cyclic amidines with excellent fluorescence properties were synthesized by a general and efficient 6π-electrocyclic ring closure of ketenimine and imine starting from N-sulfonyl triazoles and arylamines. The photophysical properties of cyclic amidine fluorophores have been studied in detail and have shown good properties of a large Stokes shift, pH insensitivity, low cytotoxicity and higher photostability, which have great potential for biological imaging. Furthermore, this novel fluorophore was successfully applied to the localization of the NK-1 receptor in living systems.

Novel 10π-electron cyclic amidines with excellent fluorescence properties were synthesized by a general and efficient 6π-electrocyclic ring closure of ketenimine and imine starting from N-sulfonyl triazoles and arylamines.

[18F]SPA-RQ/PET Study of NK1 receptors in the Whole Body of Guinea Pig and Rat

There is a substantial interest in the development of NK1 substance P antagonists as potential treatments for various neuropsychiatric and somatic disorders. The aim of this study was to determine whether [¹⁸F]SPA-RQ can be utilized as a tool for studying the whole body distribution and function of NK1 receptors in preclinical settings. The compound was injected into guinea pigs with or without premedication with a NK1 receptor antagonist (NK1A-2). For comparison, we included two rats in the study, as the affinity of antagonists for NK1 receptors is known to vary between species. The whole body biodistribution of the tracer was determined at several time points. The tracer showed specific binding in organs compatible with the known location of NK1-receptors. Premedication with a NK1 antagonist led to an inhibited uptake of [¹⁸F]SPA-RQ in several organs of guinea pigs, notably intestine, pancreas, urinary bladder, uterus, skin and lung. Specific binding was also seen in both cortex and striatum. In contrast, negligible specific binding was observed in the rat brain with [¹⁸F]SPA-RQ, whereas the tracer uptake in peripheral tissues was similar to that seen in guinea pigs. We conclude that [¹⁸F]SPA-RQ/PET is a useful tool to study the distribution and function of peripherally located NK1 receptors e.g. in different disease models.

Substance P modulates bone remodeling properties of murine osteoblasts and osteoclasts

Clinical observations suggest neuronal control of bone remodeling. Sensory nerve fibers innervating bone, bone marrow and periosteum signal via neurotransmitters including substance P (SP). In previous studies we observed impaired biomechanical and structural bone parameters in tachykinin (Tac) 1-deficient mice lacking SP. Here, we aim to specify effects of SP on metabolic parameters of bone marrow macrophage (BMM)/osteoclast cultures and osteoblasts isolated from Tac1-deficient and wildtype (WT) mice. We demonstrated endogenous SP production and secretion in WT bone cells. Absence of SP reduced bone resorption rate, as we found reduced numbers of precursor cells (BMM) and multinucleated osteoclasts and measured reduced cathepsin K activity in Tac1-/- BMM/osteoclast cultures. However, this might partly be compensated by reduced apoptosis rate and increased fusion potential of Tac1-/- precursor cells to enlarged "super" osteoclasts. Contrarily, increased ALP enzyme activity and apoptosis rate during early osteoblast differentiation accelerated osteogenesis and cell death in the absence of SP together with reduced ALP activity of Tac1-/- osteoblasts during late osteogenic differentiation resulting in reduced bone formation at later stages. Therefore, we suggest that absence of SP presumably results in a slight reduction of bone resorption rate but concomitantly in a critical reduction of bone formation and mineralization rate.

Mouse Hemokinin-1 Decapeptide Subjected to a Brain-specific Post-translational Modification

BACKGROUND/AIM

The tachykinin mouse hemokinin-1, expressed by the mouse Tac4 gene, produces either analgesia or nociception, interacting with the neurokinin 1 receptor. TAC4 precursor processing is not identical to the processing of the TAC1 precursor, for the release of substance P (amidated undecapeptide). The characterization of the mouse hemokinin-1 sequence was required.

MATERIALS AND METHODS

We developed anti-tachykinin-specific antibodies for the immunoaffinity purification of tachykinins.

RESULTS

Using MALDI-ToF, we identified mouse hemokinin-1 as an amidated decapeptide expressed in murine brain and periphery. Furthermore, we interestingly observed an additional mass peak corresponding to acetylated mouse hemokinin-1 and this post-translational modification is brain-specific, not detected in the periphery.

CONCLUSION

We suggest that the N-terminal acetylation of the peptide provides greater potency for ligand-receptor interactions during neural cell signaling.

Role of hemokinin-1 in health and disease

Hemokinin-1 (HK-1), the newest tachykinin encoded by the Tac4 gene was discovered in 2000. Its name differs from that of the other members of this peptide family due to its first demonstration in B lymphocytes. Since tachykinins are classically found in the nervous system, the significant expression of HK-1 in blood cells is a unique feature of this peptide. Due to its widespread distribution in the whole body, HK-1 is involved in different physiological and pathophysiological functions involving pain inflammation modulation, immune regulation, respiratory and endocrine functions, as well as tumor genesis. Furthermore, despite the great structural and immunological similarities to substance P (SP), the functions of HK-1 are often different or the opposite. They both have the highest affinity to the tachykinin NK1 receptor, but HK-1 is likely to have a distinct binding site and signalling pathways. Moreover, several actions of HK-1 different from SP have been suggested to be mediated via a presently not identified own receptor/target molecule. Therefore, it is very important to explore its effects at different levels and compare its characteristics with SP to get a deeper insight in the different cellular mechanisms. Since HK-1 has recently been in the focus of intensive research, in the present review we summarize the few clinical data and experimental results regarding HK-1 expression and function in different model systems obtained throughout the 16years of its history. Synthesizing these findings help to understand the complexity of HK-1 actions and determine its biomarker values and/or drug development potentials.

The effect of intra-articular botulinum toxin A on substance P, prostaglandin E2, and tumor necrosis factor alpha in the canine osteoarthritic joint

Background

Recently, intra-articular botulinum toxin A (IA BoNT A) has been shown to reduce joint pain in osteoarthritic dogs. Similar results have been reported in human patients with arthritis. However, the mechanism of the antinociceptive action of IA BoNT A is currently not known. The aim of this study was to explore this mechanism of action by investigating the effect of IA BoNT A on synovial fluid (SF) and serum substance P (SP), prostaglandin E₂ (PGE₂), and tumor necrosis factor alpha (TNF-α) in osteoarthritic dogs. Additionally, the aim was to compare SF SP and PGE₂ between osteoarthritic and non-osteoarthritic joints, and investigate associations between SP, PGE₂, osteoarthritic pain, and the signalment of dogs. Thirty-five dogs with chronic naturally occurring osteoarthritis and 13 non-osteoarthritic control dogs were included in the study. Osteoarthritic dogs received either IA BoNT A (n = 19) or IA placebo (n = 16). Serum and SF samples were collected and osteoarthritic pain was evaluated before (baseline) and 2 and 8 weeks after treatment. Osteoarthritic pain was assessed with force platform, Helsinki Chronic Pain Index, and joint palpation. Synovial fluid samples were obtained from control dogs after euthanasia. The change from baseline in SP and PGE₂ concentration was compared between the IA BoNT A and placebo groups. The synovial fluid SP and PGE₂ concentration was compared between osteoarthritic and control joints. Associations between SP, PGE₂, osteoarthritic pain, and the signalment of dogs were evaluated.

Results

There was no significant change from baseline in SP or PGE₂ after IA BoNT A. Synovial fluid PGE₂ was significantly higher in osteoarthritic compared to control joints. Synovial fluid PGE₂ correlated with osteoarthritic pain. No associations were found between SP or PGE₂ and the signalment of dogs. The concentration of TNF-α remained under the detection limit of the assay in all samples.

Conclusions

The results suggest that the antinociceptive effect of IA BoNT A in the joint might not be related to the inhibition of SP nor PGE₂. Synovial fluid PGE₂, but not SP, could be a marker for chronic osteoarthritis and pain in dogs.

Neurokinin-1 receptor mediated breast cancer cell migration by increased expression of MMP-2 and MMP-14

Breast cancer (BC) is a common reason of cancer-associated death in female. To develop novel strategy of therapeutics, it is crucial to comprehensively understand the receptor status of BC cells on the surface and inner, because chemical messengers can bind the receptors and promote tumorigenesis. Compared with normal and benign samples, BC cell lines and malignant biopsies showed higher expression of neurokinin-1 receptor (NK1). In current work, we examined the role and mechanism of NK1 receptor signaling in BC cell migration. Human hemokinin-1 (hHK-1) was the peripheral agonist of NK1 receptor. Our results showed that by activating NK1 receptor, hHK-1 promoted the migration of BC cells. Gelatin zymography and WB experiment showed that hHK-1 enhanced the levels of MMP-2 and MMP-14; inhibition of these two MMPs blocked hHK-1-induced cell migration. We further explored the underlying mechanism. hHK-1 incuced the phosphorylation of ERK1/2, JNK and Akt through PKC or PKA pathway. The phosphorylation of these kinases further regulated the activation of transcriptional factor AP-1 and NF-κB. Inhibition of AP-1 and NF-κB reduced the up-regulation of MMP-2 and MMP-14 by hHK-1. Taken together, we showed NK1 receptor was an important regulator of human BC cell migration and a potential target for BC treatment.

[Mechanism of spinal pain transmission and its regulation]

Morphine has been widely used for the treatment of acute, chronic, and cancer pain and is considered the strongest analgesic in clinical care. Conversely, morphine-induced analgesia may be accompanied by several side effects. Animal studies have demonstrated that low doses of morphine administered intrathecally can produce reliable analgesia for thermal, mechanical, and chemical nociceptive stimulation. On the other hand, high doses of morphine administered intrathecally may induce spontaneous nociceptive responses such as scratching, biting, and licking in mice as well as agitation and vocalization in rats. In addition, similar nociceptive responses including hyperalgesia, allodynia, and myoclonus have been observed in humans following intrathecal or systemic administration of high-dose morphine. It has been suggested that the spontaneous nociceptive behaviors evoked by high-dose morphine may be mediated by a non-opioid mechanism that is not yet fully understood. This review describes the mechanisms of spontaneous nociceptive behaviors evoked by high-dose morphine focusing on the neurotransmitters/neuromodulators released from primary afferent fibers.

Hemokinin-1 is an important mediator of endotoxin-induced acute airway inflammation in the mouse

OBJECTIVE

Hemokinin-1, the newest tachykinin encoded by the preprotachykinin C (Tac4) gene, is predominatly produced by immune cells. Similarly to substance P, it has the greatest affinity to the tachykinin NK1 receptor, but has different binding site and signaling mechanisms. Furthermore, several recent data indicate the existence of a not yet identified own receptor and divergent non-NK1-mediated actions. Since there is no information on its functions in the airways, we investigated its role in endotoxin-induced pulmonary inflammation.

METHODS

Acute pneumonitis was induced in Tac4 gene-deleted (Tac4(-/-)) mice compared to C57Bl/6 wildtypes by intranasal E. coli lipopolysaccharide (LPS). Airway responsiveness to inhaled carbachol was measured with unrestrained whole body plethysmography 24h later. Semiquantitative histopathological scoring was performed; reactive oxygen species (ROS) production was measured with luminol bioluminescence, myeloperoxidase activity with spectrophotometry, and inflammatory cytokines with Luminex.

RESULTS

All inflammatory parameters, such as histopathological alterations (perivascular edema, neutrophil/macrophage accumulation, goblet cell hyperplasia), myeloperoxidase activity, ROS production, as well as interleukin-1beta, interleukin-6, tumor necrosis factor alpha, monocyte chemoattractant protein-1 and keratinocyte chemoattractant concentrations were significantly diminished in the lung of Tac4(-/-) mice. However, bronchial hyperreactivity similarly developed in both groups. Interestingly, in LPS-treated Tac4(-/-) mouse lungs, bronchus-associated, large, follicle-like lymphoid structures developed.

CONCLUSIONS

We provide the first evidence that hemokinin-1 plays a crucial pro-inflammatory role in the lung by increasing inflammatory cell activities, and might also be a specific regulator of lymphocyte functions.

A two-step strategy to enhance activity of low potency peptides

Novel strategies are needed to expedite the generation and optimization of peptide probes targeting G protein-coupled receptors (GPCRs). We have previously shown that membrane tethered ligands (MTLs), recombinant proteins comprised of a membrane anchor, an extracellular linker, and a peptide ligand can be used to identify targeted receptor modulators. Although MTLs provide a useful tool to identify and/or modify functionally active peptides, a major limitation of this strategy is the reliance on recombinant protein expression. We now report the generation and pharmacological characterization of prototype peptide-linker-lipid conjugates, synthetic membrane anchored ligands (SMALs), which are designed as mimics of corresponding MTLs. In this study, we systematically compare the activity of selected peptides as MTLs versus SMALs. As prototypes, we focused on the precursor proteins of mature Substance P (SubP) and Cholecystokinin 4 (CCK4), specifically non-amidated SubP (SubP-COOH) and glycine extended CCK4 (CCK4-Gly-COOH). As low affinity soluble peptides these ligands each presented a challenging test case for assessment of MTL/SMAL technology. For each ligand, MTLs and corresponding SMALs showed agonist activity and comparable subtype selectivity. In addition, our results illustrate that membrane anchoring increases ligand potency. Furthermore, both MTL and SMAL induced signaling can be blocked by specific non-peptide antagonists suggesting that the anchored constructs may be orthosteric agonists. In conclusion, MTLs offer a streamlined approach for identifying low activity peptides which can be readily converted to higher potency SMALs. The ability to recapitulate MTL activity with SMALs extends the utility of anchored peptides as probes of GPCR function.

Development of a membrane-anchored chemerin receptor agonist as a novel modulator of allergic airway inflammation and neuropathic pain

The chemerin receptor (CMKLR1) is a G protein-coupled receptor found on select immune, epithelial, and dorsal root ganglion/spinal cord neuronal cells. CMKLR1 is primarily coupled to the inhibitory G protein, Gαi, and has been shown to modulate the resolution of inflammation and neuropathic pain. CMKLR1 is activated by both lipid and peptide agonists, resolvin E1 and chemerin, respectively. Notably, these ligands have short half-lives. To expedite the development of long acting, stable chemerin analogs as candidate therapeutics, we used membrane-tethered ligand technology. Membrane-tethered ligands are recombinant proteins comprised of an extracellular peptide ligand, a linker sequence, and an anchoring transmembrane domain. Using this technology, we established that a 9-amino acid-tethered chemerin fragment (amino acids 149-157) activates both mouse and human CMKLR1 with efficacy exceeding that of the full-length peptide (amino acids 21-157). To enable in vivo delivery of a corresponding soluble membrane anchored ligand, we generated lipidated analogs of the 9-amino acid fragment. Pharmacological assessment revealed high potency and wash resistance (an index of membrane anchoring). When tested in vivo, a chemerin SMAL decreased allergic airway inflammation and attenuated neuropathic pain in mice. This compound provides a prototype membrane-anchored peptide for the treatment of inflammatory disease. A parallel approach may be applied to developing therapeutics targeting other peptide hormone G protein-coupled receptors.

Hemokinin-1(4-11)-induced analgesia selectively up-regulates δ-opioid receptor expression in mice

Our previous studies have shown that an active fragment of human tachykinins (hHK-1(4-11)) produced an opioid-independent analgesia after intracerebroventricular (i.c.v.) injection in mice, which has been markedly enhanced by a δ OR antagonist, naltrindole hydrochloride (NTI). In this study, we have further characterized the in vivo analgesia after i.c.v. injection of hHK-1(4-11) in mouse model. Our qRT-PCR results showed that the mRNA levels of several ligands and receptors (e.g. PPT-A, PPT-C, KOR, PDYN and PENK) have not changed significantly. Furthermore, neither transcription nor expression of NK₁ receptor, MOR and POMC have changed noticeably. In contrast, both mRNA and protein levels of DOR have been up-regulated significantly, indicating that the enhanced expression of δ opioid receptor negatively modulates the analgesia induced by i.c.v. injection of hHK-1(4-11). Additionally, the combinatorial data from our previous and present experiments strongly suggest that the discriminable distribution sites in the central nervous system between hHK-1(4-11) and r/mHK-1 may be attributed to their discriminable analgesic effects. Altogether, our findings will not only contribute to the understanding of the complicated mechanisms regarding the nociceptive modulation of hemokinin-1 as well as its active fragments at supraspinal level, but may also lead to novel pharmacological interventions.

The Concise Guide to PHARMACOLOGY 2013/14: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. G protein-coupled receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.

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.

Hemokinin-1 competitively inhibits substance P-induced stimulation of osteoclast formation and function

Hemokinin-1 (HK-1) is a novel member of the tachykinin family that is encoded by preprotachykinin 4 (TAC4) and shares the neurokinin-1 receptor (NK1-R) with substance P (SP). Although HK-1 is thought to be an endogenous peripheral SP-like endocrine or paracrine molecule in locations where SP is not expressed, neither the distribution of HK-1 in the maxillofacial area nor the role HK-1 in bone tissue have been examined. In this study, we investigated the distribution of HK-1 in trigeminal ganglion (TG) and maxillary bone, and assessed the expression of HK-1 during osteoclast differentiation. In vivo, rat molars were loaded for 5 days using the Waldo method. In vitro, rat osteoclast-like cells were induced from bone marrow cells. HK-1 distribution and expression were examined by immunofluorescence staining and reverse transcription polymerase chain reaction (RT-PCR). In vivo, HK-1 was localized in rat TG neurons; however, the number of HK-1-positive neurons was less than that of SP-positive neurons. In the maxillary bone, nerve fibers, blood vessels, and osteocytes were immunopositive for HK-1. Furthermore, HK-1-positive immunoreactivity was found in osteoclasts on the pressure side. In vitro, PCR showed that TAC4 and NK1-R mRNA was expressed in osteoclasts as well as in bone marrow cells. Although SP (10⁻⁷ M) treatment led to an increased number of osteoclasts, HK-1 (10⁻⁷ M) treatment did not. The numbers of biotin-labeled HK-1 peptides bound osteoclasts significantly decreased upon incubation with unlabeled SP and biotin-labeled HK-1 compared with biotin-labeled HK-1 alone. These results suggest that HK-1 may not stimulate the differentiation and function of osteoclasts. SP-stimulated osteoclast formation is competitively regulated by peripheral HK-1 through NK1-Rs.

Study on the distribution sites and the molecular mechanism of analgesia after intracerebroventricular injection of rat/mouse hemokinin-1 in mice

Hemokinin-1 is a peptide encoded by Pptc, which belongs to the family of mammalian tachykinins. Our previous results showed that rat/mouse hemokinin-1 (r/m HK-1) produced striking analgesia after intracerebroventricular (i.c.v.) injection in mice, and the analgesia could be blocked by the NK1 receptor antagonist and the opioid receptor antagonist, respectively. However, the precise distribution sites and the molecular mechanism involved in the analgesic effect after i.c.v. administration of r/m HK-1 are needed to be further investigated deeply. Using the fluorescence labeling method, our present results directly showed that r/m HK-1 peptides were mainly distributed at the ventricular walls and several juxta-ventricular structures for the first time. Our results showed that the mRNA expressions of NK1 receptor, PPT-A, PPT-C, KOR, PDYN, DOR and PENK were not changed markedly, as well as the protein expression of NK1 receptor was hardly changed. However, both the transcripts and proteins of MOR and POMC were up-regulated significantly, indicating that the analgesic effect induced by i.c.v. administration of r/m HK-1 is related to the activation of NK1 receptor first, then it is related to the release of endogenous proopiomelanocortin, as well as the increased expression level of μ opioid receptor. These results should facilitate further the analysis of the analgesia of r/m HK-1 in the central nerval system in acute pain and may open novel pharmacological interventions.

Hemokinins modulate endothelium function and promote angiogenesis through neurokinin-1 receptor

Substance P as a member of tachykinin family plays an important role in angiogenesis. Hemokinins (HKs) have been identified as new members of substance P-like peptides of tachykinin family. However, the effects of HKs on endothelial cells and angiogenesis have not been studied. For the first time, here we demonstrated that r/mHK-1, hHK-1 and hHK(4-11) dose-dependently stimulated the proliferation, migration, adhesion and tube formation of freshly isolated human umbilical vein endothelial cells (HUVECs), and further exhibited in vivo angiogenic effects in chick embryo chorioallantoic membrane model. The angiogenic effects of HKs were inhibited by the selective antagonist of neurokinin-1 rather than neurokinin-2 receptor. Mechanistically, HKs activated ERK1/2 phosphorylation, stimulated nitric oxide production, and upregulated the expression of endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) in HUVECs. Taken together, our data suggest that HKs emerge as pivotal endogenous regulators of angiogenesis and represent potential targets for the intervention of angiogenesis in different pathological conditions given their specific peripheral distribution.

The role of neurokinin-1 receptor in the microenvironment of inflammation and cancer

The recent years have witnessed an exponential increase in cancer research, leading to a considerable investment in the field. However, with few exceptions, this effort has not yet translated into a better overall prognosis for patients with cancer, and the search for new drug targets continues. After binding to the specific neurokinin-1 (NK-1) receptor, the peptide substance P (SP), which is widely distributed in both the central and peripheral nervous systems, triggers a wide variety of functions. Antagonists against the NK-1 receptor are safe clinical drugs that are known to have anti-inflammatory, analgesic, anxiolytic, antidepressant, and antiemetic effects. Recently, it has become apparent that SP can induce tumor cell proliferation, angiogenesis, and migration via the NK-1 receptor, and that the SP/NK-1 receptor complex is an integral part of the microenvironment of inflammation and cancer. Therefore, the use of NK-1 receptor antagonists as a novel and promising approach for treating patients with cancer is currently under intense investigation. In this paper, we evaluate the recent scientific developments regarding this receptor system, its role in the microenvironment of inflammation and cancer, and its potentials and pitfalls for the usage as part of modern anticancer strategies.

Truncated neurokinin-1 receptor is increased in colonic epithelial cells from patients with colitis-associated cancer

Patients with chronic ulcerative colitis (UC) are at high risk for developing colorectal cancer. In this study, archival formalin-fixed paraffin-embedded colonic tissue from patients with UC who developed carcinoma (CA) or high-grade dysplasia (HGD) was examined for changes in expression of the proinflammatory and mitogenic neurokinin-1 receptor (NK-1R). Laser capture microscopy was used to microdissect epithelia from areas of colons that showed histologic evidence of CA, HGD, and epithelia that were not dysplastic or cancerous but did contain evidence of prior inflammation (quiescent colitis). mRNA was extracted from the dissected tissue, and PCR array analysis was performed on extracted mRNA. Two antibodies were necessary to separately estimate the protein levels of the truncated (tr-NK-1R) and full-length (fl-NK-1R) receptors by immunohistochemistry. mRNA expression of tr-NK-1R increased 14-fold (P = 0.02) when comparing the HGD and CA groups. In contrast, the fl-NK-1R transcript showed no significant differences among groups. The protein levels of the total NK-1R increased by 40% (P = 0.02) in HGD and 80% (P = 0.0007) in CA compared with quiescent colitis. There were no significant changes in protein levels of the fl-NK-1R. We conclude that the increase in total NK-1R protein in HGD and CA is attributable to an increase in tr-NK-1R, suggesting there may be a functional role for tr-NK-1R in malignant transformation in colitis-associated cancer. The tr-NK-1R could prove useful as a diagnostic marker to identify patients at risk for neoplasia and may serve as a useful therapeutic target in the treatment of colitis-associated cancer.

Hemokinin-1 stimulates prostaglandin E₂ production in human colon through activation of cyclooxygenase-2 and inhibition of 15-hydroxyprostaglandin dehydrogenase

Hemokinin-1 (HK-1) is a newly identified tachykinin, originating from the immune system rather than neurons, and may participate in the immune and inflammatory response. In colonic mucosa of patients with inflammatory bowel disease (IBD), up-regulation of the TAC4 gene encoding HK-1 and increased production of prostaglandin E₂ (PGE₂) occur. Our aim was to examine the mechanistic link between human HK-1 and PGE₂ production in normal human colon. Exogenous HK-1 (0.1 μM) for 4 h evoked an increased PGE₂ release from colonic mucosal and muscle explants by 10- and 3.5-fold, respectively, compared with unstimulated time controls. The HK-1-stimulated PGE₂ release was inhibited by the tachykinin receptor antagonists (S)1-2-[3-(3,4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)piperidin-3-yl]ethyl-4-phenyl-l azonia-bicyclo[2.2.2]octane (SR140333) [neurokinin-1 (NK₁)] and N-[(2S)-4-(4-acetamido-4-phenylpiperidin-1-yl)-2-(3,4-dichlorophenyl)butyl]-N-methylbenzamide (SR48968) [neurokinin-2 (NK₂)] and was also inhibited by the cyclooxygenase (COX)-2 inhibitor N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide) (NS-398) but not by the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560). A parallel study with substance P showed similar results. Molecular studies with HK-1-treated explants demonstrated a stimulatory effect on COX-2 expression at both transcription and protein levels. It is noteworthy that this was coupled with HK-1-induced down-regulation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) mRNA and protein expression. Immunoreactivity for 15-PGDH occurred on inflammatory cells, epithelial cells, platelets, and ganglia. This finding provides an additional mechanism for HK-1-evoked PGE₂ increase, in which HK-1 may interfere with the downstream metabolism of PGE₂ by suppressing 15-PGDH expression. In conclusion, our results uncover a novel inflammatory role for HK-1, which signals via NK₁ and NK₂ receptors to regulate PGE₂ release from human colonic tissue, and may further explain a pathological role for HK-1 in IBD when abnormal levels of PGE₂ occur.

Distinct differences in tachykinin gene expression in ulcerative colitis, Crohn's disease and diverticular disease: a role for hemokinin-1?

BACKGROUND

In the intestine, the tachykinins substance P (SP) and neurokinin A (NKA) are found in neurons and have key roles in motility, secretion, and immune functions. A new tachykinin, hemokinin (HK-1), has been identified in non-neuronal cells in recent years and its role in intestinal inflammation is unclear. We aimed to examine the expression of genes encoding tachykinin peptides and receptors in colon from patients with ulcerative colitis (UC), Crohn's disease (CD), and acute diverticular disease (DD).

METHODS

Human colon segments were dissected into mucosa and muscle, and evaluated for tachykinin and tachykinin receptor gene expression by real-time PCR.

KEY RESULTS

In UC mucosa, the TAC4 gene (encoding HK-1) was 10-fold more abundant than in control mucosa (P < 0.01). Similarly, TAC1 (encoding SP and NKA) and TACR1 (encoding NK1 receptor) displayed 6-fold and 12-fold upregulation, respectively, in UC mucosa, but no change occurred in UC muscle. In contrast to UC, no difference was observed for any tachykinin genes in CD mucosa. In CD muscle, expression of TAC1 (P < 0.01), TAC4 and TACR1 (both P < 0.05) were moderately upregulated. In DD, there was a decrease in TACR1 (P < 0.05), and TACR2 (encoding NK2 receptor, P < 0.0001) in muscle compared with control. Histological staining showed increased collagen fibers between muscle bundles in DD smooth muscle.

CONCLUSIONS & INFERENCES

We provide evidence for the first time that HK-1, like SP, may be involved in the pathophysiology of inflammatory bowel disease. Distinctly different expression patterns of tachykinin-related genes occur in UC, CD and DD.

Expression and proliferative effect of hemokinin-1 in human B-cells

Tachykinins are a family of structurally related peptides, including substance P (SP), hemokinin-1 (HK-1), neurokinin A (NKA), and neurokinin B. SP and NKA have been shown to modulate hematopoiesis and rat/mouse HK-1 has been found to be involved in the survival and differentiation of mouse B-cells. This study was designed to assess the expression of tachykinins with a focus on human HK-1 (hHK-1) in human B lymphocytes and the role of these peptides in cell differentiation, apoptosis and proliferation. Expression of tachykinin and tachykinin receptor mRNA was determined quantitatively in human B lymphoproliferative malignancies and compared to normal B-cells. Expression of hHK-1 and NK(1) receptor, but not SP, was detected in human B-lymphocytes, and was up-regulated in B-lymphocytes from chronic lymphocytic leukemia and non-Hodgkin's lymphoma, while it was down-regulated in acute lymphoblastic leukemia. Moreover, hHK-1, in contrast to SP, was able to induce proliferation of human pre-B lymphocytes through a NK(1) receptor-independent mechanism. These data suggest a role for hHK-1 in normal and pathological B lymphopoiesis, and open the door to a better understanding of the physiopathological mechanisms leading to lymphoproliferative malignancies.

The N-terminal domain of human hemokinin-1 influences functional selectivity property for tachykinin receptor neurokinin-1

Human hemokinin-1 (hHK-1) is a substance P-like tachykinin peptide preferentially expressed in non-neuronal tissues. It is involved in multiple physiological functions such as inflammation, hematopoietic cells development and vasodilatation via the interaction with tachykinin receptor neurokinin-1 (NK1). To further understand the intracellular signal transduction mechanism under such functional multiplicity, current study was focused on the differential activation of Gs and Gq pathways by hHK-1 and its C-terminal fragments, which is termed as functional selectivity. We demonstrated these hHK-1 and related peptide fragments can independently activate Gs and Gq pathways, showing a relative bias toward Gq over Gs pathway. The T1, K3 and Q6 of hHK-1 might play roles in the activation of adenylate cyclase mediated by Gs, while having negligible effect on Gq mediated intracellular calcium release. The stepwise truncation of N-terminal amino acid of hHK-1 caused gradual decrease in ERK1/2 phosphorylation level and NF-κB activity. However, it had little influence on the induction of NK1 receptor desensitization and internalization. Taken together these data support that hHK-1 and its C-terminal fragments are human NK1 receptor agonists with different functional selectivity properties and that such functional selectivity leads to differential activation of downstream signaling and receptor trafficking.

Expression and function of human hemokinin-1 in human and guinea pig airways

Background

Human hemokinin-1 (hHK-1) and endokinins are peptides of the tachykinin family encoded by the TAC4 gene. TAC4 and hHK-1 expression as well as effects of hHK-1 in the lung and airways remain however unknown and were explored in this study.

Methods

RT-PCR analysis was performed on human bronchi to assess expression of tachykinin and tachykinin receptors genes. Enzyme immunoassay was used to quantify hHK-1, and effects of hHK-1 and endokinins on contraction of human and guinea pig airways were then evaluated, as well as the role of hHK-1 on cytokines production by human lung parenchyma or bronchi explants and by lung macrophages.

Results

In human bronchi, expression of the genes that encode for hHK-1, tachykinin NK₁-and NK₂-receptors was demonstrated. hHK-1 protein was found in supernatants from explants of human bronchi, lung parenchyma and lung macrophages. Exogenous hHK-1 caused a contractile response in human bronchi mainly through the activation of NK₂-receptors, which blockade unmasked a NK₁-receptor involvement, subject to a rapid desensitization. In the guinea pig trachea, hHK-1 caused a concentration-dependant contraction mainly mediated through the activation of NK₁-receptors. Endokinin A/B exerted similar effects to hHK-1 on both human bronchi and guinea pig trachea, whereas endokinins C and D were inactive. hHK-1 had no impact on the production of cytokines by explants of human bronchi or lung parenchyma, or by human lung macrophages.

Conclusions

We demonstrate endogenous expression of TAC4 in human bronchi, the encoded peptide hHK-1 being expressed and involved in contraction of human and guinea pig airways.

Effects of rat/mouse hemokinin-1, human hemokinin-1 and human hemokinin-1(4-11), mammalian tachykinin peptides, on rate and perfusion pressure in the isolated guinea pig heart

Rat/mouse hemokinin-1 (r/m HK-1), human hemokinin-1 (h HK-1) and human hemokinin-1(4-11) (h HK-1(4-11)) are members of the tachykinin family. In the present study, the coronary vascular activities and cardiac functions of r/m HK-1, h HK-1 and h HK-1(4-11) were investigated in isolated, spontaneously beating guinea pig hearts. Bolus injections of r/m HK-1 caused decrease in perfusion pressure indicative of coronary vasodilation, which was primarily due to the action on tachykinin NK1 receptors on vascular endothelial cells, causing the release of nitric oxide that relaxed the coronary vessels. H HK-1 caused biphasic perfusion pressure changes that were coronary vasodilation followed by coronary vasoconstriction. The mechanisms involved in the vasodilation induced by h HK-1 were similar to that of r/m HK-1 while the mechanisms for coronary vasoconstriction were mediated through the activation of tachykinin NK2 receptors on coronary sympathetic neurons to release catecholamines. H HK-1(4-11) only produced coronary vasoconstriction and the mechanisms involved in this effect were similar to that of h HK-1 in vasoconstriction. Moreover, r/m HK-1 and h HK-1 produced similar decreases in heart rate indicative of negative chronotropic responses and the decreases were mainly mediated through the activation of tachykinin NK1 receptors to release ACh acting on muscarinic receptors. H HK-1(4-11) also produced negative chronotropic response, which was mainly mediated through tachykinin NK2 receptors and muscarinic receptors. Our present results provide evidence that all of the three tachykinins could influence cardiac function and coronary vascular activity in the isolated guinea pig heart.

Characterization of intrathecally administered hemokinin-1-induced nociceptive behaviors in mice

Hemokinin-1 is a novel mammalian tachykinin cloned from mouse bone marrow. At present, pharmacological profile and physiological role of hemokinin-1 are still unclear. In the present study, we found that intrathecal (i.t.) administration of hemokinin-1 (0.00625-1.6 nmol) induced nociceptive responses consisting of scratching, biting and licking, which resemble substance P-induced behavioral responses in mice. The behaviors evoked by low-dose of hemokinin-1 (0.0125 nmol) were dose-dependently inhibited by i.t. co-administration of CP-99,994, a non-peptidic tachykinin NK(1) receptor antagonist, whereas high-dose of hemokinin-1 (0.1 nmol)-induced behaviors were not affected. Moreover, sendide, a peptidic tachykinin NK(1) receptor antagonist, failed to reduce the behavioral responses of both low- and high-dose of hemokinin-1. In contrast, substance P-induced behaviors were completely suppressed by both CP-99,994 and sendide. These results suggest that hemokinin-1 plays an important role in pain transmission at spinal cord. Moreover, the mechanism of hemokinin-1-induced nociceptive behaviors may be dose-dependent, and distinct from substance P-induced nociceptive behaviors.

Targeted deletion of the tachykinin 4 gene (TAC4-/-) influences the early stages of B lymphocyte development

Hemokinin-1 (HK-1), encoded by the TAC4 gene, is a tachykinin peptide that is predominantly expressed in non-neuronal cells, such as immune cells. We have disrupted the mouse TAC4 gene to obtain a better understanding of the actions of HK-1 during hematopoiesis. We demonstrate here that TAC4(-/-) mice exhibit an increase of CD19(+)CD117(+)HSA(+)BP.1(-) "fraction B" pro-B cells in the bone marrow, whereas pre-B, immature, and mature B cells are within the normal range. We show that in vitro cultures derived from TAC4(-/-) bone marrow, sorted "fraction B" pro-B cells or purified long-term reconstituting stem cells, contain significantly higher numbers of pro-B cells compared with controls, suggesting an inhibitory role for HK-1 on developing B cells. Supporting this idea, we show that addition of HK-1 to cultures established from long-term reconstituting stem cells and the newly described intermediate-term reconstituting stem cells leads to a significant decrease of de novo generated pro-B cells. Based on our studies, we postulate that HK-1 plays an inhibitory role in hematopoiesis, and we hypothesize that it may be part of the bone marrow microenvironment that supports and regulates the proliferation and differentiation of hematopoietic cells.

Hemokinin-1 activates the MAPK pathway and enhances B cell proliferation and antibody production

Hemokinin 1 (HK-1) is a substance P-like tachykinin peptide predominantly expressed in non-neuronal tissues. In addition to a prominent function in lymphoid development, recent studies indicate a potential role for HK-1 in immunoregulation. The current study was focused on its action on mature B cells. Despite the negligible effect on its own, HK-1 exhibited a profound influence on B cell activation elicited by several classical signals, including LPS stimulation, BCR cross-linking, and CD40 ligation. Cells therefore showed enhanced proliferation, survival, and CD80/86 expression, and produced more IgM with a higher frequency of Ab-forming cells. Biochemical analysis revealed that HK-1 alone was sufficient to induce the activation of MAPKs and the expression of Blimp-1 and Xbp-1 in B cells. Nevertheless, costimulation with a known B cell activator resulted in much enhanced phosphorylation of MAPKs and transcriptional activation of Blimp-1 and Xbp-1. Overall, these data support that HK-1 provides an important costimulatory signal for B cell activation, possibly through synergistic activation of the MAPK pathway and induction of transcription factors critical for plasmacytic differentiation.

Tachykinin receptor assays

Described in this unit are methods for obtaining, preparing, and testing smooth muscle preparations bearing tachykinin receptors to study the agonist or antagonist properties of test compounds. Concentration-response curves to agonists are constructed to measure their ability to produce smooth muscle contractions and thus evaluate the potency and efficacy of the agonists. Antagonists are tested for their ability to shift the agonist concentration-response curve and to calculate their potency. Two different protocols are described for each of the three tachykinin receptors (NK(1), NK(2), and NK(3)). The NK(1) receptor assays use guinea pig ileum longitudinal muscle myenteric plexus (GPI) and rat urinary bladder (RUB), the NK(2) receptor assays use isolated endothelium-deprived rabbit pulmonary artery (RPA) and hamster trachea (HT), and the NK(3) receptor assays use GPI and rat portal vein (RPV).

Human hemokinin-1 and human hemokinin-1(4-11), mammalian tachykinin peptides, suppress proliferation and induce differentiation in HL-60 cells

Human hemokinin-1 (h HK-1) and its truncated form h HK-1(4-11) are mammalian tachykinin peptides encoded by the TAC4 gene identified in human, and the biological functions of these peptides have not been well investigated. The tachykinins have shown immuno-regulatory activities in humans. In the present study, we investigated the effects of h HK-1 and h HK-1(4-11) on the proliferation and differentiation of a human promyelocyte leukemia cell line, HL-60. It is noteworthy that h HK-1 (1-300muM) displayed inhibitory effects on the proliferation of HL-60 cells in a dose- and time-dependent manner. The effect of suppressing proliferation induced by these peptides was accompanied by an accumulation of cell cycle in the S phase. Moreover, this peptide induced differentiation of HL-60 cells by significantly increasing the NBT-reduction activity. The effects induced by h HK-1(4-11) on HL-60 cells were similar to that of h HK-1, indicating that it is the active fragment of h HK-1. However these effects induced by h HK-1 or h HK-1(4-11) were not antagonized by the NK(1) receptor antagonist SR140333 or the NK(2) receptor antagonist SR48968. All the results indicated that h HK-1 and h HK-1(4-11) were able to significantly inhibit proliferation and induce differentiation and S phase arrest of a human promyelocyte leukemia cell line HL-60, which may not be mediated through the activation of classical tachykinin NK(1) receptors and tachykinin NK(2) receptors. Our observations also implied that h HK-1 and h HK-1(4-11) could act as immunomodulatory factors in cancer chemotherapy.

In vitro characterization of the effects of rat/mouse hemokinin-1 on mouse colonic contractile activity: a comparison with substance P

Rat/mouse hemokinin-1 (r/m HK-1) has been identified as a member of the tachykinin family and its effect in colonic contractile activity remains unknown. We investigated the effects and mechanisms of actions of r/m HK-1 on the mouse colonic contractile activity in vitro by comparing it with that of substance P (SP). R/m HK-1 induced substantial contractions on the circular muscle of mouse colon. The maximal contractile responses to r/m HK-1 varied significantly among proximal-, mid- and distal-colon, suggesting that the action of r/m HK-1 was region-specific in mouse colon. The contractile response induced by r/m HK-1 is primarily via activation of tachykinin NK(1) receptors leading to activation of cholinergic excitatory pathways and with a minor contribution of NK(2) receptors, which may be on the smooth muscle itself. A direct action on colonic smooth muscles may be also involved. In contrast, SP induced biphasic colonic responses (contractile and relaxant responses) on the circular muscle, in which the contractile action of SP was equieffective with r/m HK-1. SP exerted its contractile effect predominantly through neural and muscular tachykinin NK(1) receptors, but unlike r/m HK-1 did not appear to act via NK(2) receptors. The relaxation induced by SP was largely due to release of nitric oxide (NO) produced via an action on neural NK(1) receptors. These results indicate that the receptors and the activation properties involved in r/m HK-1-induced mouse colonic contractile activity are different from those of SP.

Functional characterisation of hemokinin-1 in mouse uterus

The preprotachykinin gene Tac4 expressed in murine uterus and placenta is thought to encode a peptide RSRTRQFYGLM-NH(2), mouse hemokinin 1. We have examined the uterotonic effects of mouse hemokinin 1 and its N-terminally truncated analogue, mouse hemokinin 1(2-11) on mouse uterus. Mouse hemokinin 1(2-11) was equieffective with but slightly less potent than substance P in tissues from non-pregnant Swiss mice. On myometrium from Balb C mice primed with oestrogen the positions of concentration-response curves to substance P and the mouse hemokinins were similar to those of neurokinin A, but the maximum responses were lower. The tachykinin NK(1) receptor antagonist, 1-{2-(3, 4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl) piperidin-3-yl]ethyl}-4phenyl-1-azonia-bicyclo[2.2.2]octane (SR 140333), reduced the effects of the agonists in tissues from both groups of mice. In myometria from late pregnant (Days 17-18) Balb C mice the responses to mouse hemokinin 1(2-11) were less potent than in those from oestrogen-primed mice. Human hemokinin 1, the human orthologue of mouse hemokinin 1, was more effective than mouse hemokinin 1(2-11), while endokinin D was inactive. Mouse hemokinin 1 effects were blocked by SR 140333 alone and in combination with ((S)-N-methyl-N[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide (SR 48968) but not by SR 48968 alone. Thus the mouse hemokinins are tachykinin NK(1) receptor-preferring uterotonic agonists in non-pregnant mice but lack action at the myometrial tachykinin NK(2) receptors present in late pregnant mice.

In vivo characterization of the effects of human hemokinin-1 and human hemokinin-1(4-11), mammalian tachykinin peptides, on the modulation of pain in mice

Human hemokinin-1 (h HK-1) and its truncated form h HK-1(4-11) are mammalian tachykinin peptides encoded by the recently identified TAC4 gene in human, and the biological functions of these peptides have not been well investigated. In the present study, an attempt has been made to investigate the effects and mechanisms of action of h HK-1 and h HK-1(4-11) in pain modulation at the supraspinal level in mice using the tail immersion test. Intracerebroventricular (i.c.v.) administration of h HK-1 (0.3, 1, 3 and 6 nmol/mouse) produced a dose- and time-related antinociceptive effect. This effect was significantly antagonized by the NK(1) receptor antagonist SR140333, but not by the NK(2) receptor antagonist SR48968, indicating that the analgesic effect induced by i.c.v. h HK-1 is mediated through the activation of NK(1) receptors. Interestingly, naloxone, beta-funaltrexamine and naloxonazine, but not naltrindole and nor-binaltorphimine, could also block the analgesic effect markedly, suggesting that this effect is related to descending mu opioidergic neurons (primary mu(1) subtype). Human HK-1(4-11) could also induce a dose- and time-dependent analgesic effect after i.c.v. administration, however, the potency of analgesia was less than h HK-1. Surprisingly, SR140333 could not modify this analgesic effect, suggesting that this effect is not mediated through the NK(1) receptors like h HK-1. SR48968 could modestly enhance the analgesic effect induced by h HK-1(4-11), indicating that a small amount of h HK-1(4-11) may bind to NK(2) receptors. Furthermore, none of the opioid receptor (OR) antagonists could markedly block the analgesia of h HK-1(4-11), suggesting that the analgesic effect is not mediated through the descending opioidergic neurons. Blocking of delta ORs significantly enhanced the analgesia, indicating that delta OR is a negatively modulatory factor in the analgesic effect of h HK-1(4-11). It is striking that bicuculline (a competitive antagonist at GABA(A) receptors) effectively blocked the analgesia induced by h HK-1(4-11), suggesting that this analgesic effect is mediated through the descending inhibitory GABAergic neurons. The novel mechanism involved in the analgesic effect of h HK-1(4-11), which is different from that of h HK-1, may pave the way for a new strategy for the investigation and control of pain.

Cardiovascular responses to intravenous administration of human hemokinin-1 and its truncated form hemokinin-1(4-11) in anesthetized rats

Human hemokinin-1 and its carboxy-terminal fragment human hemokinin-1(4-11) have been recently identified as the members of the tachykinin family. The peripheral cardiovascular effects of these two tachykinin peptides were investigated in anesthetized rats. Lower doses of human hemokinin-1 (0.1-3 nmol/kg) injected intravenously (i.v.) induced depressor response, whereas higher doses (10 and 30 nmol/kg) caused biphasic (depressor and pressor) responses. The depressor response is primarily due to the action on endothelial tachykinin NK(1) receptor to release endothelium-derived relaxing factor (NO) and vagal reflex was absent in this modulation. The pressor response is mediated through the activation of tachykinin NK(1) receptor to release catecholamines from sympathetic ganglia and adrenal medulla. Moreover, human hemokinin-1 injected i.v. produced a dose-dependent tachycardia response along with blood pressure responses and the activation of sympathetic ganglia and adrenal medulla are involved in the tachycardia response. Human hemokinin-1(4-11) only lowered mean arterial pressure dose-dependently (0.1-30 nmol/kg) and the mechanisms involved in the depressor response are similar to that of human hemokinin-1. Additionally, human hemokinin-1(4-11) could also produce tachycardia response dose-dependently and the mechanisms involved in the tachycardia response are similar to that of human hemokinin-1 except that bilateral adrenalectomy could not affect the tachycardia markedly, indicating that the tachycardia induced by human hemokinin-1(4-11) is primarily due to the stimulation of sympathetic ganglia. In a word, to a certain extent, human hemokinin-1(4-11) is the active fragment of human hemokinin-1, however, the differences between human hemokinin-1 and hemokinin-1(4-11) involved in the effects of cardiovascular system suggest that the divergent amino acid residues at the N-terminus of human hemokinin-1 produced different activation properties for tachykinin NK(1) receptor.

Neurokinins robustly activate the majority of septohippocampal cholinergic neurons

In the brain, tachykinins acting via the three cloned neurokinin (NK) receptors are implicated in stress-related affective disorders. Hemokinin-1 is a novel tachykinin that reportedly prefers NK1 to NK2 or NK3 receptors. Although NK1 and NK3 receptors are abundantly expressed in the brain, NK2-receptor-mediated electrophysiological effects have rarely been described as NK2 receptors are expressed only in a few brain regions such as the nucleus of the medial septum/diagonal band. Medial septal/diagonal band neurons that control hippocampal mnemonic functions also colocalize NK1 and NK3 receptors. Functionally, intraseptal activation of all three NK receptors increases hippocampal acetylcholine release and NK2 receptors have specifically been implicated in stress-induced hippocampal acetylcholine release. Electrophysiological studies on the effects of NKs on septohippocampal cholinergic neurons are lacking and electrophysiological effects of hemokinin-1 have thus far not been reported in brain neurons. In the present study we examined the electrophysiological and pharmacological effects of multiple NKs on fluorescently tagged septohippocampal cholinergic neurons using whole-cell patch-clamp recordings in a rat brain slice preparation. We demonstrate that a vast majority of septohippocampal cholinergic cells are activated by NK1, NK2 and NK3 receptor agonists as well as by hemokinin-1 via direct post-synaptic mechanisms. Pharmacologically, hemokinin-1 recruits not only NK1 but also NK2 and NK3 receptors to activate septohippocampal cholinergic neurons that are the primary source of acetylcholine for the hippocampus.

Effects of rat/mouse hemokinin-1, a mammalian tachykinin peptide, on the antinociceptive activity of pethidine administered at the peripheral and supraspinal level

We have recently reported that rat/mouse hemokinin-1 (r/m HK-1), a mammalian tachykinin, produced dose- and time-related antinociceptive effects at the supraspinal level via activating NK(1) receptors. Moreover, r/m HK-1 remarkably enhanced both the antinociceptive extent and duration of morphine administered at the peripheral and supraspinal level through a convergence of pharmacological effects of opioid-responsive neurons. Pethidine hydrochloride is an important narcotic analgesic, which acts as an opiate agonist and has pharmacological effects similar to morphine. To improve our knowledge of the pharmacology of pethidine, the aim of the present study was to investigate the relationship between the nociception of r/m HK and pethidine by comparing it with that of r/m HK-1 and morphine. Our data showed that r/m HK-1 remarkably enhanced the antinociceptive extent of pethidine administered at the peripheral level, but not at the supraspinal level. These antinociceptive effects were blocked by prior treatment with the classical opioid receptor antagonist naloxone, indicating that the potentiated analgesic effect is mediated by opioid-responsive neurons. Differences in the antinociceptive activity of pethidine and morphine in combination with r/m HK-1, arise because there are differences in the physicochemical and pharmacokinetic properties of pethidine and morphine, particularly their lipophilicity. Our results may pave the way for a new strategy for the control of pain and may provide a clinical strategy to enable selection of either opioid as a priority.

Pathophysiological mechanisms of angiogenesis

The growth of new blood vessels may be either beneficial or harmful. The angiogenic process may be measured by a variety of techniques, although it may often be the quality rather than quantity of resulting blood vessels that determines function. Endothelial cells play a key role in the initiation of angiogenesis, and vascular endothelial growth factor (VEGF) may be viewed as a prototypical direct-acting angiogenic factor. VEGF acts through multiple cell surface receptors and signaling pathways to stimulate endothelial cell proliferation, survival, and migration. By inducing other growth factor expression, VEGF stimulates a cascade of angiogenic activity. Different tissues may utilize various angiogenic pathways that are modulated by diverse host tissue responses. Furthermore, a single tissue may progress through a sequence of angiogenic pathways, for example, as acute injury progresses to chronic inflammation. The phenotype of the resulting neovasculature is critically dependent on the context in which it is formed. Biomarkers of angiogenesis are being developed as an aid to assessing human disease. Histological assessment of vascular density and angiogenic factor expression, in vivo imaging, Doppler ultrasound, and biofluid assays each may have clinical utility. Therapeutic targeting of angiogenesis will depend both on the generation of acceptable pharmacological agents and on the identification of patients who may and do gain benefit from such treatments.

In vivo signaling through the neurokinin 1 receptor favors transgene expression by Langerhans cells and promotes the generation of Th1- and Tc1-biased immune responses

The proinflammatory capacities of the skin and the presence of high numbers of resident dendritic cells (DCs) constitute an ideal microenvironment for successful immunizations. Regardless of the ability of DCs to respond to local inflammatory signals in an immunostimulatory fashion, the immune functions of skin-resident DCs remain controversial, and epidermal Langerhans cells (LCs) have been referred to recently as anti-inflammatory/protolerogenic APCs. Substance P (SP), released by skin nerve fibers, is a potent proinflammatory neuropeptide that favors development of skin-associated cellular immunity. SP exerts its proinflammatory functions by binding with high affinity to the neurokinin 1 receptor (NK1R). In this study, we tested whether signaling skin cells via the NK1R promotes humoral and cellular immunity during skin genetic immunizations. We used the gene gun to deliver transgenic (tg) Ag to the skin of C57BL/6 mice and the selective NK1R agonist [Sar(9)Met (O(2)) (11)]-SP as a potential proinflammatory Th1-biasing adjuvant. Our strategy expressed tg Ag exclusively in the epidermis and induced a preferential migration of activated LCs to skin-draining lymph nodes. Local administration of the NK1R agonist during skin genetic immunizations increased significantly the expression of tg Ag by a mechanism involving the translocation of NF-kappaB into the nuclei of cutaneous DCs homing to skin-draining lymph nodes. Importantly, our immunization approach resulted in Th1 and T cytotoxic (CTL)-1 bias of effector T cells that supported cellular and Ab-mediated immune responses. We demonstrate that signaling skin cells via the NK1R provides the adjuvant effect which favors the immunostimulatory functions of LCs.

Co-regulated decrease of Neurokinin-1 receptor and Hemokinin-1 gene expression in monocytes and macrophages after activation with pro-inflammatory cytokines

Hemokinin-1 (HK-1), a potent ligand for the Neurokinin-1 receptor (NK-1) is thought to play a role in the immune system. To investigate the regulation of this receptor-ligand pair, we examined the effects of pro-inflammatory cytokines on their expression in the monocyte/macrophage cell lines Wehi-3 and RAW264.7. We demonstrate co-expression of NK-1 and HK-1 mRNA in both lines, as well as functional NK-1 receptor protein in Wehi-3 cells. Stimulation with IFN-gamma, IL-1beta and TNF-alpha markedly decreased NK-1 and HK-1 mRNA as well as NK-1 receptor protein, which coincided with monocytic differentiation. A co-regulated decrease could also be observed in differentiating primary bone marrow macrophages, suggesting that this receptor-ligand pair may be controlled by cytokine networks and may serve a developmental role in the immune system.

Cardiovascular responses to rat/mouse hemokinin-1, a mammalian tachykinin peptide: systemic study in anesthetized rats

Rat/mouse hemokinin-1 is a mammalian tachykinin peptide whose biological functions have not been well characterized. In the present study, an attempt has been made to investigate the effect and mechanism of action of rat/mouse hemokinin-1 on systemic arterial pressure after intravenous (i.v.) injections in anesthetized rats by comparing it with that of substance P. Our data showed that injection of rat/mouse hemokinin-1 (0.1, 0.3, 1, 3 and 10 nmol/kg) lowered systemic arterial pressure dose-dependently. This effect was significantly blocked by pretreatment with SR140333 (a selective tachykinin NK1 receptor antagonist) and the NO synthase inhibitor L-NAME (Nomega-nitro-L-arginine methyl ester hydrochloride), respectively, but was not affected by bilateral vagotomy or the muscarinic receptor blocker atropine. Compared to rat/mouse hemokinin-1, a dose of 3 nmol/kg of substance P caused biphasic changes in systemic arterial pressure (depressor and pressor responses). The results suggest that the mechanism of the depressor response caused by substance P was similar to rat/mouse hemokinin-1 in that it was inhibited by SR140333 and L-NAME, respectively, but that there was a component of the cardiovascular change induced by rat/mouse hemokinin-1 (but not substance P) that was attenuated by SR48968 (a selective tachykinin NK2 receptor antagonist). The depressor response induced by rat/mouse hemokinin-1 (i.v.) might be explained primarily by the action on endothelial tachykinin NK1 receptors to release endothelium-derived relaxing factor (NO) and this effect was not affected by vagal components. In addition, rat/mouse hemokinin-1 could not induce the pressor response through stimulation of sympathetic ganglion like substance P in anesthetized rats.