Role Of Neurokinin Research Articles

The role of neurokinin B in the pathophysiological mechanisms of vasomotor symptoms and sleep disorders in postmenopausal women

Problem statement. Menopausal vasomotor symptoms (VS) and sleep disorders are a significant socio-economic and medical problem occurring in almost 65% postmenopausal women. Research of the pathophysiology of VS is vital for the development of target therapy.

A role for neurokinin 1 receptor expressing neurons in the paratrigeminal nucleus in bradykinin-evoked cough in guinea-pigs.

Airway projecting sensory neurons arising from the jugular vagal ganglia terminate centrally in the brainstem paratrigeminal nucleus, synapsing upon neurons expressing the neurokinin 1 receptor. This study aimed to assess the involvement of paratrigeminal neurokinin 1 receptor neurons in the regulation of cough, breathing and airway defensive responses. Lesioning neurokinin 1 receptor expressing paratrigeminal neurons significantly reduced cough evoked by inhaled bradykinin but not inhaled ATP or tracheal mechanical stimulation. The reduction in bradykinin-evoked cough was not accompanied by changes in baseline or evoked respiratory variables (e.g. frequency, volume or timing), animal avoidance behaviours or the laryngeal apnoea reflex. These findings warrant further investigations into targeting the jugular ganglia and paratrigeminal nucleus as a therapy for treating cough in disease. Jugular vagal ganglia sensory neurons innervate the large airways and are thought to mediate cough and associated perceptions of airway irritations to a range of chemical irritants. The central terminals of jugular sensory neurons lie within the brainstem paratrigeminal nucleus, where postsynaptic neurons can be differentiated based on the absence or presence of the neurokinin 1 (NK1) receptor. Therefore, in the present study, we set out to test the hypothesis that NK1 receptor expressing paratrigeminal neurons play a role in cough evoked by inhaled chemical irritants. To test this, we performed selective neurotoxin lesions of NK1 receptor expressing neurons in the paratrigeminal nucleus in guinea-pigs using substance P conjugated to saporin (SSP-SAP). Sham lesion control or SSP-SAP lesion guinea-pigs received nebulised challenges, with the pan-nociceptor stimulant bradykinin or the nodose ganglia specific stimulant adenosine 5'-triphosphate (ATP), in conscious whole-body plethysmography to study cough and associated behaviours. Laryngeal apnoea reflexes and cough evoked by mechanical stimulation of the trachea were additionally investigated in anaesthetised guinea-pigs. SSP-SAP significantly and selectively reduced the number of NK1 receptor expressing neurons in the paratrigeminal nucleus. This was associated with a significant reduction in bradykinin-evoked cough, but not ATP-evoked cough, mechanical cough or laryngeal apnoeic responses. These data provide further evidence for a role of jugular vagal pathways in cough, and additionally suggest an involvement of NK1 receptor expressing neurons in the paratrigeminal nucleus. Therefore, this neural pathway may provide novel therapeutic opportunities to treat conditions of chronic cough.

The role of neurokinin A and its receptor in the regulation of prolactin secretion by the anterior pituitary of cyclic pigs.

In pigs, plasma prolactin concentration markedly changes during the oestrous cycle and the regulation of its secretion is very complex. The contribution of neurokinins in this process has not been sufficiently delineated. The aim of the study was to examine the effects of neurokinin A (NKA) on prolactin synthesis and secretion in cyclic gilts. The expression of NKA precursor (Ppta) and receptor (Tacr2) genes as well as NKA and TACR proteins content in the porcine pituitaries (days 2-3, 9-10, 12-13, 15-16 and 19-20 of the cycle) was determined. Furthermore, the in vitro influence of NKA on the expression of prolactin (Prl), dopamine receptor (D2r), TRH receptor (Trhr) genes and prolactin secretion by the porcine pituitary cells (days 9-10, 15-16 and 19-20 of the cycle) was assessed. The expression of Ppta and Tacr2 as well as NKA and TACR proteins in the pituitary tissue has been changing throughout the oestrous cycle. NKA affected in vitro the expression of studied genes and prolactin secretion depending on the stage of the cycle, dose of NKA and/or duration of the cell incubation. Altogether, the study indicates that NKA is engaged in the modulation of prolactin secretion in the pig during the oestrous cycle.

Роль нейрокинина В в патофизиологических механизмах вазомоторных симптомов и нарушений сна у женщин в постменопаузе

Роль нейрокинина В в патофизиологических механизмах вазомоторных симптомов и нарушений сна у женщин в постменопаузе

Neurokinin A augments SynCAM expression and IL-10 release from mast cells

Abstract Cutaneous mast cells (MCs) initiate innate and adaptive immune responses. In the skin, MCs reside proximal to peripheral nerve fibers, forming a functional synapse mediated, in part, by Synaptic Cell Adhesion Molecule (SynCAM). Within the synapse, MC function is likely affected by the release of soluble neuropeptides. We and others have demonstrated that the immune functions of MCs are affected by the neuropeptides from the tachykinin family. Substance P promotes MC-inflammatory functions, whereas the role of neurokinin A (NKA) in MC biology is hereto unknown. In this study, the capacity for NKA to regulate MC stasis and IgE-initiated MC activation was evaluated. In bone marrow derived (BM) MCs, NKA increased expression of SynCAM, but not expression of other cell adhesion molecules, such as ICAM or NCAM. In IgE-activated MCs, NKA did not affect SynCAM expression. However, NKA promoted IL-10 secretion resulting in the inhibition of IgE-initiated STAT5 phosphorylation and nuclear localization, leading to the inhibition of type 2 cytokine release. STAT5 phosphorylation was restored in NKA treated BMMCs by neutralizing IL-10. In vivo, intradermal administration of NKA increased the density of MCs in the skin. In spite of this increase in MCs, NKA reduced IgE-initiated passive cutaneous anaphylaxis. Our data indicates that NKA strengthens the formation of the MC-neuron synapse and down-regulates MC pro-inflammatory functions.

Role of Neurokinin 3 Receptor Signaling in Oral Squamous Cell Carcinoma.

The neurokinin 3 receptor (NK-3R) is differentially expressed in the central nervous system including cases of human oral squamous cell carcinoma. However, the role of NK-3R signaling in oral squamous cell carcinoma is not well known. NK-3R expression in surgically resected oral squamous cell carcinoma was examined immunohistochemically and the strength of the expression was quantified. We evaluated the function of NK-3R signaling using NK-3R antagonist in human oral squamous cell carcinoma bone invasion mouse model. NK-3R was significantly expressed in tumor cells that had invaded the bone matrix compared to the oral side tumor cells. SB222200, a selective antagonist of NK-3R, significantly suppressed the radiographic osteolytic lesion and tumorigenesis. NK-3R signaling is a potential target for the treatment of oral squamous cell carcinoma in cases of bone destruction.

506 Probiotic technology modulates cytokines related to skin sensitization

503 Prebiotical effect of natural ingredients used in topical formulation DD Rodriguez, LM Vasquez-Pinto, VT Goncalves and C Porto 1 Natura Innovation and Product Technology, Cajamar, Brazil, 2 Biocenter Microbiologica, Sao Paulo, Brazil and 3 Maringa State University, Maringa, Brazil Prebiotics are substances with well spread use as functional food, which selectively induce the growth or activity of microorganisms that live in a microbiome, conferring benefits upon host well-being and health. Skin microbiome has an important role as host guardian, taking part in several physiological functions including skin turnover, reaction patterns in the immune system and disposition for inflammation-mediated diseases. Several studies have shown the effect of ingestion of prebiotics in improving skin health. However, little is known about the effect of several ingredients used topically in skin microbiome. In this study, we evaluated 4 natural ingredients commonly used in topical formulations for their prebiotic effect towards skin microorganisms. Results showed that Orbignya phalerata polissacarides and a-D-glucopyranosil stimulate S. epidermidis, S. xylosus and S. warneri proliferation in vitro. Besides, Carapa guianensis, Bertholletia excelsa and Mauritia flexuosa vegetal oils also increased S. xylosus and S. epidermidis proliferation in vitro. Finally, Caesaria sylvestris extract also increased S. epidermidis and S. xylosus population in vitro. Understanding the effect of topical formulations on skin microbiome can lead to novel breakthroughs in skin treatment. 504 Neurokinin A: A neuropeptide with the potential to inhibit the effector function of cutaneous mast cells TL Sumpter, O Tkacheva, L Falo and AT Larregina Dermatology, University of Pittsburgh, Pittsburgh, PA Mast cells (MCs) are potent effectors in atopic skin disorders. In the course of IgE-mediated skin allergy, MC activation is initiated by interactions between the FceRI and IgE-Ag complexes. IgE-initiated MC activation is bimodal, resulting in early release of inflammatory granules and late release of type 2 and pro-inflammatory cytokines. In the skin, dermal mast cells reside proximal to sensory fibers. MCs and sensory fibers have evolved common mechanisms for responding to noxious stimuli, including responsiveness to neuropeptides from the tachykinin family. We have previously shown that the tachykinin family member, hemokinin-1, which signals through the neurokinin 1 receptor (NK1R) promotes MC inflammatory functions. However the role of neurokinin A (NKA), a tachykinin which signals through the NK2R is not known in MCs. Limited information is available regarding the NKA/ NK2R in immune cells, but NK2R signaling is anti-inflammatory in a murine contact hypersensitivity model. Therefore, we hypothesized that NKAwould inhibit MC activation, with implications for MCs residing in the skin. In vitro, bone marrow (BM) derived MCs expressed low NK2R which increased with FceRI signaling. NKA downregulated surface expression of FceRIa and c-Kit on BMMCs. NKA alone had no affect on either granule or cytokine release. But, in response to IgE+Ag, NKA increased the percentage of MCs releasing granules while decreasing secretion of IL-4, IL-13 and IL-6. In an IgE-dependent murine model of passive cutaneous anaphylaxis, intradermal administration of NKA inhibited edema and reduced ear thickness, indicative of diminished MC inflammatory functions in the skin. Collectively, our data indicated that NKA down-regulated the intensity of IgE-initiated MC activation, an effect with potential for clinical application in the treatment of atopic dermatitis.

503 Prebiotical effect of natural ingredients used in topical formulation

503 Prebiotical effect of natural ingredients used in topical formulation DD Rodriguez, LM Vasquez-Pinto, VT Goncalves and C Porto 1 Natura Innovation and Product Technology, Cajamar, Brazil, 2 Biocenter Microbiologica, Sao Paulo, Brazil and 3 Maringa State University, Maringa, Brazil Prebiotics are substances with well spread use as functional food, which selectively induce the growth or activity of microorganisms that live in a microbiome, conferring benefits upon host well-being and health. Skin microbiome has an important role as host guardian, taking part in several physiological functions including skin turnover, reaction patterns in the immune system and disposition for inflammation-mediated diseases. Several studies have shown the effect of ingestion of prebiotics in improving skin health. However, little is known about the effect of several ingredients used topically in skin microbiome. In this study, we evaluated 4 natural ingredients commonly used in topical formulations for their prebiotic effect towards skin microorganisms. Results showed that Orbignya phalerata polissacarides and a-D-glucopyranosil stimulate S. epidermidis, S. xylosus and S. warneri proliferation in vitro. Besides, Carapa guianensis, Bertholletia excelsa and Mauritia flexuosa vegetal oils also increased S. xylosus and S. epidermidis proliferation in vitro. Finally, Caesaria sylvestris extract also increased S. epidermidis and S. xylosus population in vitro. Understanding the effect of topical formulations on skin microbiome can lead to novel breakthroughs in skin treatment. 504 Neurokinin A: A neuropeptide with the potential to inhibit the effector function of cutaneous mast cells TL Sumpter, O Tkacheva, L Falo and AT Larregina Dermatology, University of Pittsburgh, Pittsburgh, PA Mast cells (MCs) are potent effectors in atopic skin disorders. In the course of IgE-mediated skin allergy, MC activation is initiated by interactions between the FceRI and IgE-Ag complexes. IgE-initiated MC activation is bimodal, resulting in early release of inflammatory granules and late release of type 2 and pro-inflammatory cytokines. In the skin, dermal mast cells reside proximal to sensory fibers. MCs and sensory fibers have evolved common mechanisms for responding to noxious stimuli, including responsiveness to neuropeptides from the tachykinin family. We have previously shown that the tachykinin family member, hemokinin-1, which signals through the neurokinin 1 receptor (NK1R) promotes MC inflammatory functions. However the role of neurokinin A (NKA), a tachykinin which signals through the NK2R is not known in MCs. Limited information is available regarding the NKA/ NK2R in immune cells, but NK2R signaling is anti-inflammatory in a murine contact hypersensitivity model. Therefore, we hypothesized that NKAwould inhibit MC activation, with implications for MCs residing in the skin. In vitro, bone marrow (BM) derived MCs expressed low NK2R which increased with FceRI signaling. NKA downregulated surface expression of FceRIa and c-Kit on BMMCs. NKA alone had no affect on either granule or cytokine release. But, in response to IgE+Ag, NKA increased the percentage of MCs releasing granules while decreasing secretion of IL-4, IL-13 and IL-6. In an IgE-dependent murine model of passive cutaneous anaphylaxis, intradermal administration of NKA inhibited edema and reduced ear thickness, indicative of diminished MC inflammatory functions in the skin. Collectively, our data indicated that NKA down-regulated the intensity of IgE-initiated MC activation, an effect with potential for clinical application in the treatment of atopic dermatitis.

Role of neurokinin 1 receptors in dextran sulfate-induced colitis: studies with gene-deleted mice and the selective receptor antagonist netupitant

The function of the neurokinin 1 (NK1) receptor was investigated in the DSS-induced mouse colitis model using NK1 receptor-deficient mice and the selective antagonist netupitant. Colitis was induced by oral administration of 20 mg/ml DSS solution for 7 days in C57BL/6 and Tacr1 KO animals (n = 5-7). During the induction, one-half of the C57BL/6 and Tacr1 KO group received one daily dose of 6 mg/kg netupitant, administered intraperitoneally, the other half of the group received saline, respectively. Disease activity index (DAI), on the basis of stool consistency, blood and weight loss, was determined over 7 days. Histological evaluation, myeloperoxidase (MPO) measurement, cytokine concentrations and receptor expression analysis were performed on the colon samples. NK1 receptors are up-regulated in the colon in response to DSS treatment. DSS increased DAI, histopathological scores, BLC, sICAM-1, IFN-γ, IL-16 and JE in wildtype mice, which were significantly reduced in NK1 receptor-deficient ones. NK1 receptor antagonism with netupitant significantly diminished DAI, inflammatory histopathological alterations, BLC, IFN-γ, IL-13 and IL-16 in wildtype mice, but not in the NK1-deficient ones. MPO was similarly elevated and netupitant significantly decreased its activity in both groups. NK1 receptor antagonism could be beneficial for colitis via inhibiting different inflammatory mechanisms.

The Tachykinin Peptide Neurokinin B Binds Copper Forming an Unusual [CuII(NKB)2] Complex and Inhibits Copper Uptake into 1321N1 Astrocytoma Cells

Neurokinin B (NKB) is a member of the tachykinin family of neuropeptides that have neuroinflammatory, neuroimmunological, and neuroprotective functions. In a neuroprotective role, tachykinins can help protect cells against the neurotoxic processes observed in Alzheimer's disease. A change in copper homeostasis is a clear feature of Alzheimer's disease, and the dysregulation may be a contributory factor in toxicity. Copper has recently been shown to interact with neurokinin A and neuropeptide γ and can lead to generation of reactive oxygen species and peptide degradation, which suggests that copper may have a place in tachykinin function and potentially misfunction. To explore this, we have utilized a range of spectroscopic techniques to show that NKB, but not substance P, can bind Cu(II) in an unusual [Cu(II)(NKB)2] neutral complex that utilizes two N-terminal amine and two imidazole nitrogen ligands (from each molecule of NKB) and the binding substantially alters the structure of the peptide. Using 1321N1 astrocytoma cells, we show that copper can enter the cells and subsequently open plasma membrane calcium channels but when bound to neurokinin B copper ion uptake is inhibited. This data suggests a novel role for neurokinin B in protecting cells against copper-induced calcium changes and implicates the peptide in synaptic copper homeostasis.

The role of neurokinin B and its receptor in hypothalamic-pituitary-gonad axis

Kisspoptin signaling plays an essential role in the onset of puberty and reproductive development.Recently studies implicate that steroid-responsive NKB,kisspeptin,NK3 R,and estrogen receptor α (ERα) coexpress in arcuate nucleus of hypothalamus of variety of mammalian species and regulate the secretion of gonadotrophic hormone.The function of neurons in the hypothalamus is to regulate the estrogen negative feedback on gonadotropin-releasing hormone (GnRH) secretion.Loss of function of neurokinin B (NKB) or its receptor,the neurokinin-3 receptor produces idiopathic hypogonadotropic hypogonadism.These studies demonstrate NKB and neurokinin-3 receptor as the essential elements of the human reproductive axis. Key words: Neurokinin B; Kisspeptin; Gonadotrophic hormone; Estrogen receptor α; Hypogonadotropic hypogonadism

Prevention of chemotherapy-induced nausea and vomiting and the role of neurokinin 1 inhibitors

A significant proportion of cancer patients experience nausea or vomiting during the course of their disease, either because of the cancer itself or because of the treatment received. Highly or moderately emetogenic drugs are part of the standard chemotherapy regimens frequently used in patients with lung cancer, breast cancer, ovarian cancer, and several other common solid tumors. In this review, we describe the impact of nausea and vomiting in patients receiving chemotherapy, and the main progress achieved in the prophylaxis of chemotherapy-induced nausea and vomiting with the introduction of neurokinin 1 inhibitors. The adherence to existing guidelines is particularly important to avoid suboptimal prophylaxis and maximize patients' outcome. This review is focused on lung, breast, ovarian, and colorectal cancer, which are among the solid tumors characterized by a numeric and clinical relevance of the chemotherapy-induced nausea and vomiting issue because of the wide use of highly and/or moderately emetogenic chemotherapy regimens.

Role of Neurokinin B in the Control of Female Puberty and Its Modulation by Metabolic Status

Human genetic studies have revealed that neurokinin B (NKB) and its receptor, neurokinin-3 receptor (NK3R), are essential elements for normal reproduction; however, the precise role of NKB-NK3R signaling in the initiation of puberty remains unknown. We investigated here the regulation of Tac2 and Tacr3 mRNAs (encoding NKB and NK3R, respectively) in female rats and demonstrated that their hypothalamic expression is increased along postnatal maturation. At puberty, both genes were widely expressed throughout the brain, including the lateral hypothalamic area and the arcuate nucleus (ARC)/medial basal hypothalamus, where the expression of Tacr3 increased across pubertal transition. We showed that central administration of senktide (NK3R agonist) induced luteinizing hormone (LH) secretion in prepubertal and peripubertal females. Conversely, chronic infusion of an NK3R antagonist during puberty moderately delayed the timing of vaginal opening (VO) and tended to decrease LH levels. The expression of NKB and its receptor was sensitive to changes in metabolic status during puberty, as reflected by a reduction in Tacr3 (and, to a lesser extent, Tac2) expression in the ARC after a 48 h fast. Yet, acute LH responses to senktide in pubertal females were preserved, if not augmented, under fasting conditions, suggesting sensitization of the NKB-NK3R-gonadotropin-releasing hormone signaling pathway under metabolic distress. Moreover, repeated administration of senktide to female rats with pubertal arrest due to chronic undernutrition rescued VO (in ∼50% of animals) and potently elicited LH release. Altogether, our observations suggest that NKB-NK3R signaling plays a role in pubertal maturation and that its alterations may contribute to pubertal disorders linked to metabolic stress and negative energy balance.

Role of Neurokinin B and Dynorphin A in pituitary gonadotroph and somatolactotroph cell lines

The role of Neurokinin B (NKB) and Dynorphin A (Dyn) in the regulation of the hypothalamic pituitary axis is an important area of recent investigation. These peptides are critical for the rhythmic release of GnRH, which subsequently stimulates the secretion of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The present study utilized the gonadotroph cell line LβT2 and the somatolactotroph GH3 cell line to examine the possible role of these peptides in pituitary hormone secretion. The NKB receptor (NK3R) and the Dyn receptor (the κ-opiate receptor (KOR)) were both detected in LβT2 cells and GH3 cells. NKB, by itself, failed to increase gonadotropin LHβ and FSHβ promoter activities and did not modulate the effects of GnRH on gonadotropin promoter activity. In GH3 cells, NKB significantly increased TRH-induced PRL promoter activity although NKB alone did not have an effect on basal PRL promoter activity. Dyn had no effect on gonadotropin promoters alone or in combination with GnRH stimulation. PRL promoters stimulated by TRH were not significantly changed by Dyn. TRH-induced PRL promoter activity was further increased in the presence of higher concentrations of NKB, whereas Dyn did not have a significant effect on the PRL promoter even at a high concentration. In addition, TRH-induced ERK (Extracelluar signal-regulated kinase) activation was enhanced in the presence of NKB. Our current study demonstrated that NKB had a stimulatory effect on PRL expression in a PRL-producing cell, but had no effect on gonadotropin secretion from a gonadotroph cell line.

The Role of Neurokinin 1 Receptors in the Maintenance of Visceral Hyperalgesia Induced by Repeated Stress in Rats

The neurokinin 1 receptors (NK(1)Rs) and substance P (SP) have been implicated in the stress and/or pain pathways involved in chronic pain conditions. Here we examined the participation of NK(1)Rs in sustained visceral hyperalgesia observed in rats exposed to chronic psychological stress. Male Wistar rats were exposed to daily 1-hour water avoidance stress (WA) or sham WA for 10 consecutive days. We tested intraperitoneal or intrathecal injection of the NK(1)R antagonist SR140333 on the visceromotor reflex to colorectal distention in both groups at day 11. Real-time reverse-transcription polymerase chain reaction, Western blot, and immunohistochemistry were used to assess the expression of NK(1)Rs and/or SP in samples of colon, spinal cord, and dorsal root ganglia. Both intraperitoneal and intrathecal SR140333 injection diminished the enhanced visceromotor reflex to colorectal distention at day 11 in stressed rats but did not affect the response in control animals. Real-time polymerase chain reaction and Western blotting demonstrated stress-induced up-regulation of spinal NK(1)Rs. Immunohistochemistry showed an increased number of NK(1)R-expressing neurons in the laminae I of the dorsal horn in stressed rats. The expression of NK(1)Rs was decreased in colon from stressed rats compared with control. The expression of SP gene precursor in dorsal root ganglia was unchanged in stressed rats compared with controls. Stress-induced increased NK(1)R expression on spinal neurons and the inhibitory effect of intrathecal NK(1)R antagonist on visceral hyperalgesia support the key contribution of spinal NK(1)Rs in the molecular pathways involved in the maintenance of visceral hyperalgesia observed after chronic WA.

Modulation of Stress- and Inflammation induced Visceral Hypersensitivity by peripheral Neurokinin 1 Receptors

Aims: Altered processing of visceral afferent information is believed to play a key role for the manifestation of symptoms in patients with functional gastrointestinal disorders. While it is well recognized that initiating events such as mucosal inflammation and stress precipitate the onset of symptoms the underlying mechanisms are poorly understood. Tachykinins and their receptors are known to modulate gastrointestinal function including motility, visceral sensitivity and inflammation. Aims: We aimed to study (1) the effect of mucosal inflammation, (2) a repeated standardized stressor and (3) the role of Neurokinin 1 receptors (NK1R) on visceral sensory function. Methods: In randomized order a total of 30 rats underwent intracolonic instillation of Trinitrobenzenesulphonic acid (TNB) or saline while additional 30 rats underwent seven days (1h/day) repetitive water avoidance stress (WAS) or Sham stress. Colorectal distensions (CRD) were performed with a barostat device (3min/40mmHg) and the visceromotor response (VMR) to CRD was quantified as abdominal electromyographic muscle activity (EMG). Measurements were performed 28 days after treatment initiation. After a baseline measurement (3x phasic 40mmHg CRD) either placebo or an NK1R antagonist (Sendide 5nmol) were administered intraperitoneally and a total of four CRD's 2, 5, 10 and 15 min after drug injection were performed. Results: Compared to controls (767±104μV), either TNB (908±144μV) and WAS (885±87μV) significantly (p<0.05) enhanced the VMR to CRD. The NK1R antagonist caused a significant decrease of VMR compared to baseline level in all study groups. The analgesic effect was significantly more potent, with a maximum after 10 min, in TNB (–66.7±4.1%) or WAS (–73±7.2%) treated rats compared to controls (–42.7±6.1). NK1R expression was significantly elevated in TNB (+33.2±4.5%) and WAS (+28.7±3.1%) treated rats compared to controls without any significant difference between those two treatment groups. Conclusions: Either stress or an acute mucosal inflammation have profound effects on visceral sensory function and peripheral NK1R function. The enhanced responsiveness to an NK1R antagonist in visceral hypersensitivity might be of therapeutic relevance

Excitatory convergence of periaqueductal gray and somatic afferents in the solitary tract nucleus: role for neurokinin 1 receptors.

Our previous studies (Boscan P, Kasparov S, and Paton JF. Eur J Neurosci 16: 907-920, 2002) showed that activation of somatic afferents attenuated the baroreceptor reflex via neurokinin type 1 (NK(1)) and GABA(A) receptors within the nucleus of the solitary tract (NTS). The periaqueductal gray matter (PAG) can also depress baroreceptor reflex function and project to the NTS. In the present study, we have tested the possibility that the dorsolateral (dl)-PAG projects to the NTS neurons that also respond to somatic afferent input. In an in situ, arterially perfused, unanesthetized decerebrate rat preparation, somatic afferents (brachial plexus), cervical spinal cord, and dl-PAG were stimulated electrically, whereas NTS neurons were recorded extracellularly. From 45 NTS neurons excited by either brachial plexus or dl-PAG stimulation, 41 received convergence excitatory inputs from both afferents. Onset latency and evoked peak discharge frequency from brachial plexus afferents were 39.4 +/- 4.7 ms and 10.7 +/- 1.1 Hz, whereas this was 43.9 +/- 6.4 ms and 7.9 +/- 1 Hz, respectively, following dl-PAG stimulation. As revealed by using a paired pulse stimulation protocol, monosynaptic connections were found in 9 of 36 neurons tested from both spinal cord and dl-PAG. We tested NK(1)-receptor sensitivity in 38 neurons that received convergent inputs from brachial plexus/PAG. Fifteen neurons were sensitive to selective antagonism of NK(1) receptors. CP-99994, the NK(1) antagonist, failed to alter ongoing firing activity but reduced the evoked peak discharge frequency following stimulation of both brachial plexus (from 12.3 +/- 1.8 to 7.2 +/- 1.3 Hz; P < 0.01) and PAG (from 7.8 +/- 1.5 to 4.5 +/- 1 Hz; P < 0.01). We conclude that 1) somatic brachial and PAG afferents can converge onto single NTS neurons; 2) this convergence occurs via either direct or indirect pathways; and 3) NK(1) receptors are activated by some of these inputs.

Expression of neurokinin a receptor mRNA in human nasal mucosa

In airway tissues, it has been suggested that tachykinins act as the transmitter for afferent sensory nerves which respond to various irritants and may be involved in airway allergic reactions. Three classes of tachykinin receptor have been recognized, denoted NK1, NK2 and NK3, which exhibit preferential affinity for substance P, neurokinin A and neurokinin B, respectively. We used molecular probes to study the gene expression and distribution of NK2 receptor in human nasal mucosa. Total RNA was isolated from human nasal mucosa and NK2 receptor mRNA was detected in these tissues using reverse transcriptase polymerase chain reaction (RT-PCR). For an in situ hybridization study of human nasal mucosa, we utilized the PCR directly to incorporate a T7 RNA polymerase promoter sequence onto the NK2 receptor cDNA, and these PCR products were used as the DNA template for producing digoxigenin-labeled antisense and sense RNA probes. These studies revealed that NK2 receptor mRNA was expressed in blood vessels. The results suggest a primary role for neurokinin A in the form of vascular responses in the upper respiratory tract.

Mustard oil induces a transient receptor potential vanilloid 1 receptor-independent neurogenic inflammation and a non-neurogenic cellular inflammatory component in mice

A neurogenic component has been suggested to play a pivotal role in a range of inflammatory/immune diseases. Mustard oil (allyl-isothiocyanate) has been used in studies of inflammation to mediate neurogenic vasodilatation and oedema in rodent skin. The aim of the present study was to analyse mustard oil-induced oedema and neutrophil accumulation in the mouse ear focussing on the roles of neurokinin 1 (NK 1) and vanilloid (TRPV1) receptors using normal (BALB/c, C57BL/6) as well as NK 1 and TRPV1 receptor knockout mice. A single or double treatment of 1% mustard oil on the BALB/c mouse ear induced ear oedema with responses diminished by 6 h. However a 25–30% increase in ear thickness was maintained by the hourly reapplication of mustard oil. Desensitisation of sensory nerves with capsaicin, or the NK 1 receptor antagonist SR140333, inhibited oedema but only in the first 3 h. Neutrophil accumulation in response to mustard oil was inhibited neither by SR140333 nor capsaicin pre-treatment. An activating dose of capsaicin (2.5%) induced a large oedema in C57BL/6 wild-type mice that was minimal in TRPV1 receptor knockout mice. By comparison, mustard oil generated ear swelling was inhibited by SR140333 in wild-type and TRPV1 knockout mice. Repeated administration of mustard oil maintained 35% oedema in TRPV1 knockout animals and the lack of TRPV1 receptors did not alter the leukocyte accumulation. In contrast repeated treatment caused about 20% ear oedema in Sv129+C57BL/6 wild-type mice but the absence of NK 1 receptors significantly decreased the response. Neutrophil accumulation showed similar values in both groups. This study has revealed that mustard oil can act via both neurogenic and non-neurogenic mechanisms to mediate inflammation in the mouse ear. Importantly, the activation of the sensory nerves was still observed in TRPV1 knockout mice indicating that the neurogenic inflammatory component occurs via a TRPV1 receptor independent process.

NK(1) receptor and its interaction with NMDA receptor in spinal c-fos expression after lower urinary tract irritation.

The role of neurokinin 1 (NK(1)) receptor and possible interaction between NK(1) and N-methyl-D-aspartic acid (NMDA) glutamatergic receptors were investigated on spinal c-fos expression after lower urinary tract irritation with acetic acid infusion in rats. At both levels of the first (L(1)) and sixth lumbar (L(6)) spinal cord, where most of hypogastric nerve and pelvic nerve afferent terminals project, respectively, the selective NK(1) receptor antagonist CP-99,994 dose dependently reduced the total number of c-fos protein (Fos)-positive cells. However, CP-100,263, the enantiomer of CP-99,994 with a very low affinity for NK(1) receptor, did not have any effect on the total number of Fos-positive cells. Coadministration of a low dose (1 mg/kg) of CP-99,994 and NMDA receptor antagonist (MK-801), either of which alone did not affect c-fos expression, significantly inhibited c-fos expression at both levels of the spinal cord. Regarding regional differences, the number of Fos-positive cells decreased significantly at all regions of the L(6) level, but only at the dorsal horn of the L(1) level. These results indicate that NK(1) receptor is involved in spinal c-fos expression after lower urinary tract irritation and that NK(1) and NMDA receptors have a synergistic interaction in the spinal processing of nociceptive input from the lower urinary tract.