Isolation and characterization of neurokinin A, neurokinin A(3-10) and neurokinin A(4-10) from a neutral water extract of a metastatic ileal carcinoid tumour

Genome editing with CRISPR-Cas nucleases, base editors, transposases and prime editors

The development of new CRISPR-Cas genome editing tools continues to drive major advances in the life sciences. Four classes of CRISPR-Cas-derived genome editing agents-nucleases, base editors, transposases/recombinases and prime editors-are currently available for modifying genomes in experimental systems. Some of these agents have also moved rapidly into the clinic. Each tool comes with its own capabilities and limitations, and major efforts have broadened their editing capabilities, expanded their targeting scope and improved editing specificity. We analyze key considerations when choosing genome editing agents and identify opportunities for future improvements and applications in basic research and therapeutics.

Production and Regulation of Levels of Amidated Peptide Hormones

Peptide hormones with a C-terminal amide regulate numerous physiological processes and are associated with many disease states. Consequently, the key enzymes involved in their production, peptidylglycine α-amidating monooxygenase and carboxypeptidase E, have been studied intensively. This review surveys what is known about the enzymes themselves and their cofactors, as well as their substrates and competitive and mechanism-based inhibitors.

Nuclear factor-kappaB is central to the expression of truncated neurokinin-1 receptor in breast cancer: implication for breast cancer cell quiescence within bone marrow stroma

Breast cancer is a leading cause of mortality among women in the United States. Tac1 and neurokinin-1 (NK1) are involved in autocrine stimulation of breast cancer cells (BCCs). The single NK1 gene produces full-length (NK1-FL) and truncated (NK1-Tr) forms. NK1-Tr mediates malignancy in breast cells. We now report a critical role for nuclear factor-kappaB (NF-kappaB) in the expression of NK1-Tr, but not NK1-FL, in human BCCs. By Western and Northern blot analyses, NK1-FL and NK1-Tr were coexpressed in BCCs but were undetectable in nontumorigenic cells. Loss of repressive activity within the 5' flanking region of the NK1 partly accounts for constitutive expression of NK1 in BCCs but could not account for the presence of NK1-Tr. Transient transfections with dominant-negative and wild-type IkappaB show that activation of NF-kappaB is required for the expression of NK1-Tr. Tac1 gene was linked to the generation of NK1-Tr because its overexpression in BCCs led to the production of multiple cytokines that can activate NF-kappaB to mediate NK1-Tr expression. Studies with Tac1 knockdown BCCs and Tac1-expressing nontumorigenic breast cells verified a role for NF-kappaB in the expression of NK1-Tr. The quiescent phenotype of BCCs on contact with bone marrow stroma was partly explained by decreased NF-kappaB activation and undetectable NK1-Tr. In summary, this study shows a role for NF-kappaB in the expression of NK1-Tr in BCCs, which seems to be reversed by bone marrow stromal cells.

Characterization of the gene structures, precursor processing and pharmacology of the endokinin peptides

The endokinins represent several species-divergent and peripherally located mammalian tachykinins (hemokinin-1 in mouse and rat, endokinin-1 in rabbit and endokinins A and B in humans) and also the tachykinin gene-related peptides. These peptides are all encoded on the preprotachykinin 4 (TAC4) gene. Their complementary DNA sequences, gene structures and expression profiles have been determined from a number of different mammalian species. They are all flanked by adjacent upstream and downstream dibasic cleavage sites in their respective precursor proteins, except for human EKA/B that instead possesses a N-terminal monobasic cleavage site. Evidence for differential processing in the periphery at the N-terminal cleavage site of the tachykinins could explain why in humans the evolutionary pressure to maintain the N-terminal dibasic cleavage site of EKA/B has been lost. Furthermore, the TAC4 encoded tachykinins all exhibit a remarkable selectivity and potency for the highly species conserved tachykinin NK(1) receptor, similar to that of substance P. Particular consideration is also given to the potential interactions of the endokinins with the short NK(1) receptor isoform and to speculation of whether there could be an "endokinin-sensitive" NK(1) binding site.

The neurokinin A receptor activates calcium and cAMP responses through distinct conformational states

G protein-coupled receptors are thought to mediate agonist-evoked signal transduction by interconverting between discrete conformational states endowed with different pharmacological and functional properties. In order to address the question of multiple receptor states, we monitored rapid kinetics of fluorescent neurokinin A (NKA) binding to tachykinin NK2 receptors, in parallel with intracellular calcium, using rapid mixing equipment connected to real time fluorescence detection. Cyclic AMP accumulation responses were also monitored. The naturally truncated version of neurokinin A (NKA-(4-10)) binds to the receptor with a single rapid phase and evokes only calcium responses. In contrast, full-length NKA binding exhibits both a rapid phase that correlates with calcium responses and a slow phase that correlates with cAMP accumulation. Furthermore, activators (phorbol esters and forskolin) and inhibitors (Ro 31-8220 and H89) of protein kinase C or A, respectively, exhibit differential effects on NKA binding and associated responses; activated protein kinase C facilitates a switch between calcium and cAMP responses, whereas activation of protein kinase A diminishes cAMP responses. NK2 receptors thus adopt multiple activatable, active, and desensitized conformations with low, intermediate, or high affinities and with distinct signaling specificities.

Synaptic control of motoneuronal excitability

Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K(+) current, cationic inward current, hyperpolarization-activated inward current, Ca(2+) channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior.

Increased expression of preprotachykinin-I and neurokinin receptors in human breast cancer cells: implications for bone marrow metastasis

Neuropeptides are implicated in many tumors, breast cancer (BC) included. Preprotachykinin-I (PPT-I) encodes multiple neuropeptides with pleiotropic functions such as neurotransmission, immune/hematopoietic modulation, angiogenesis, and mitogenesis. PPT-I is constitutively expressed in some tumors. In this study, we investigated a role for PPT-I and its receptors, neurokinin-1 (NK-1) and NK-2, in BC by using quantitative reverse transcription-PCR, ELISA, and in situ hybridization. Compared with normal mammary epithelial cells (n = 2) and benign breast biopsies (n = 21), BC cell lines (n = 7) and malignant breast biopsies (n = 25) showed increased expression of PPT-I and NK-1. NK-2 levels were high in normal and malignant cells. Specific NK-1 and NK-2 antagonists inhibited BC cell proliferation, suggesting autocrine and/or intercrine stimulation of BC cells by PPT-I peptides. NK-2 showed no effect on the proliferation of normal cells but mediated the proliferation of BC cells. Cytosolic extracts from malignant BC cells enhanced PPT-I translation whereas extracts from normal mammary epithelial cells caused no change. These enhancing effects may be protein-specific because a similar increase was observed for IL-6 translation and no effect was observed for IL-1alpha and stem cell factor. The data suggest that PPT-I peptides and their receptors may be important in BC development. Considering that PPT-I peptides are hematopoietic modulators, these results could be extended to understand early integration of BC cells in the bone marrow, a preferred site of metastasis. Molecular signaling transduced by PPT-I peptides and the mechanism that enhances translation of PPT-I mRNA could lead to innovative strategies for BC treatments and metastasis.

Substance P and related peptides in porcine cortex: whole tissue and nuclear localization

A large portion of the knowledge that has been gathered on the distribution of neuropeptides in neural tissues is based on findings obtained with immunocytochemistry and radioimmunoassay. However, these methods give limited structural information about the peptides being studied. Using porcine cortex as a model tissue, we combined immunoaffinity chromatography with reversed-phase high-performance liquid chromatography, radioimmunoassay, and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS). We determined the molecular nature of the peptides contributing to the substance P-like immunoreactivity measured in extracts of whole tissue and cell nuclei. In addition to substance P(1-11), other peptides were extracted using this protocol. The presence of SP(1-11) was confirmed through post-source decay analysis. These results illustrate the usefulness of MALDI-TOF-MS in the characterization of neuropeptides from biological tissues.

Tachykinins in the gut. Part II. Roles in neural excitation, secretion and inflammation

The preprotachykinin-A gene-derived peptides substance (substance P; SP) and neurokinin (NK) A are expressed in intrinsic enteric neurons, which supply all layers of the gut, and extrinsic primary afferent nerve fibers, which innervate primarily the arterial vascular system. The actions of tachykinins on the digestive effector systems are mediated by three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Within the enteric nervous system, SP and NKA are likely to mediate, or comediate, slow synaptic transmission and to modulate neuronal excitability via stimulation of NK3 and NK1 receptors. In the intestinal mucosa, tachykinins cause net secretion of fluid and electrolytes, and it appears as if SP and NKA play a messenger role in intramural secretory reflex pathways. Secretory processes in the salivary glands and pancreas are likewise influenced by tachykinins. The gastrointestinal arterial system may be dilated or constricted by tachykinins, whereas constriction and an increase in the vascular permeability are the only effects seen in the venous system. Various gastrointestinal disorders are associated with distinct changes in the tachykinin system, and there is increasing evidence that tachykinins participate in the hypersecretory, vascular and immunological disturbances associated with infection and inflammatory bowel disease. In a therapeutic perspective, it would seem conceivable that tachykinin antagonists could be exploited as antidiarrheal, antiinflammatory and antinociceptive drugs.

Multiple molecular forms of tachykinins in rat spinal cord: a study comparing different extraction methods

Various procedures for extraction at acid, neutral and alkaline pH were compared with regard to the yield of different tachykinins and tachykinin-like substances from rat spinal cord. Reverse phase high performance liquid chromatography (RP-HPLC) and radioimmunoassay with various C-terminally directed tachykinin antisera and a newly developed N-terminally directed substance P (SP)-antiserum (SPN 1) were used. Antiserum SPN 1 fully reacts with SP-analogues modified at the C-terminal end (SP free acid and SP-Gly-Lys) and also (77%) with SP(1-9) but not with C-terminal SP-fragments lacking 2 or more N-terminal amino acids. The highest levels of SP-like immunoreactivity (LI) and neurokinin A (NKA)-LI were measured after combined water and acetic acid extraction procedures. Also when measuring cholecystokinin-like immunoreactivity the highest level was obtained following this extraction procedure. RP-HPLC revealed a major component of SP-LI at the position of synthetic SP irrespectively of the extraction method and if the C- or N-terminally directed antiserum was used. Neutral water extracts contained a late eluting component detected with the C-terminally, but not with the N-terminally, directed antiserum. Acid and alkaline extracts, in contrast, contained components which could be detected with the N-terminally, but not with the C-terminally, directed SP-antiserum. Immunoreactive components eluting at the position of NKA and NKB were found in all types of extracts with NKA-, kassinin- and eledoisin-antisera. The NKB- and neuropeptide K (NPK)-components were more prominent in acid than in neutral and alkaline extracts. In conclusion, the present results indicate that rat spinal cord may contain molecular forms of tachykinin-like immunoreactivity in addition to those previously described and illustrate the importance of the choice of extraction method in immunochemical studies. Combined extraction in water and acetic acid appears to be a suitable method when the content of peptides with different chemical properties are to be measured in a tissue sample.

Localization of neurokinin A and chromogranin A immunoreactivity in the developing porcine adrenal medulla

The presence of neurokinin A immunoreactivity was studied in the chromaffin cells of the porcine adrenal medulla and in the nerve fibres innervating the adrenal gland during ontogenic development. For comparison, chromogranin A immunoreactivity was used as a marker for chromaffin cells. Whereas chromogranin A was found in chromaffin cells through all steps in embryonic development, three developmental stages of neurokinin A immunoreactivity could be distinguished. In the first and second trimester of gestation, neurokinin A was observed in some groups of chromaffin cells, but no neurokinin-immunoreactive nerve fibres could be detected. In the last trimester of gestation, neurokinin A-reactive chromaffin cells and nerve fibres were both found in adrenal glands. However, in adrenal glands of neonatal piglets, neurokinin A was found only in nerve fibres and not in chromaffin cells. From these results a hypothesis is proposed that neurokinin A might act as a neurotrophic factor in the early stages of the developing porcine chromaffin cells. Biochemical studies are being performed in order to confirm these morphological results and to study the possible role of neurokinin A as a neurotrophic factor in the adrenal gland.

Tachykinin receptors: a radioligand binding perspective

The last decade has witnessed major breakthroughs in the study of tachykinin receptors. The currently described NK-1, NK-2, and NK-3 receptors have been sequenced and cloned from various mammalian sources. A far greater variety of tachykinin analogues are now available for use as selective agonists and antagonists. Importantly, potent nonpeptide antagonists highly selective for the NK-1 and NK-2 receptors have been developed recently. These improved tools for tachykinin receptor characterization have enabled us to describe at least three distinct receptor types. Furthermore, novel antagonists have yielded radioligand binding and functional data strongly favoring the existence of putative subtypes of NK-1 and especially NK-2 receptors. Whether these subtypes are species variants or true within-species subtypes awaits further evidence. As yet undiscovered mammalian tachykinins, or bioactive fragments, may have superior potency at a specific receptor class. The common C terminus of tachykinins permits varying degrees of interaction at essentially all tachykinin receptors. Although the exact physiological significance of this inherent capacity for receptor "cross talk" remains unknown, one implication is for multiple endogenous ligands at a single receptor. For example, NP gamma and NPK appear to be the preferred agonists and binding competitors at some NK-2 receptors, previously thought of as exclusively "NKA-preferring." Current evidence suggests that tachykinin coexistence and expression of multiple receptors may also occur with postulated NK-2 and NK-1 receptor subtypes. Other "tachykinin" receptors may recognize preprotachykinins and the N terminus of SP. In light of these recent developments, the convenient working hypothesis of three endogenous ligands (SP, NKA, and NKB) for three basic receptor types (NK-1, NK-2, and NK-3) may be too simplistic and in need of amendment as future developments occur (Burcher et al., 1991b). In retrospect, the 1980s contributed greatly to our understanding of the structure, function, and regulation of tachykinins and their various receptors. The development of improved, receptor subtype-selective antagonists and radioligands, in addition to recent advances in molecular biological techniques, may lead to a more conclusive pharmacological and biochemical characterization of tachykinin receptors. The 1990s may prove to be the decade of application, where a better understanding of the roles played by endogenous tachykinins (at various receptor subtypes) under pathophysiological conditions will no doubt hasten the realization of clinically useful therapeutic agents.

Selective inhibition by dactinomycin of NANC sensory bronchoconstriction and [125I]NKA binding due to NK-2 receptor antagonism

In the present study, dactinomycin (10(-5) M) inhibited the non-adrenergic, non-cholinergic bronchoconstriction upon antidromic vagal nerve stimulation (1 Hz for 1 min) in the isolated perfused guinea-pig lung by 84%. The release of calcitonin gene-related peptide was unchanged, however, suggesting a postjunctional action. Dactinomycin (10(-5), 5 x 10(-5) M) also reduced non-adrenergic non-cholinergic bronchial contractions (maximally by 75%) induced by electrical field stimulation or capsaicin, while the cholinergic component and non-adrenergic non-cholinergic relaxation remained intact. The neurokinin-2 receptor antagonist L-659,877 (10(-6) M) had a similar effect as dactinomycin, inhibiting the non-adrenergic non-cholinergic bronchial contractions by 69%, while the neurokinin-1 receptor antagonist CP-96,345 (10(-6) M) had no effect. The bronchoconstriction evoked by neurokinin A, the selective neurokinin-2 receptor agonist Nle10neurokinin A (4-10) and capsaicin was markedly inhibited by dactinomycin while the contraction induced by substance P (SP), the selective neurokinin-1 receptor agonist Sar9Met(O2)11SP, endothelin-1 and acetylcholine was not affected. In autoradiographic experiments on guinea-pig lung, [125I]neurokinin A-labelled sections showed dense binding in the bronchial smooth muscle layer. Dactinomycin inhibited the specific binding of [125I]neurokinin A in a concentration-dependent manner (IC50 = 6.3 x 10(-6) M) and 66% of [125I]neurokinin A total binding was inhibited by 10(-4) M dactinomycin. In the rat colon, [125I]neurokinin A binding to neurokinin-2 sites on circular smooth muscle was inhibited by dactinomycin with an IC50 value of 7.9 x 10(-6) M. Dactinomycin failed to reduce increased nerve-evoked contractions or those caused by Nle10neurokinin A (4-10) per se in the rat vas deferens, which are considered to be mediated by neurokinin-2 receptor activation. In the rat portal vein, dactinomycin did not influence the contractions caused by the neurokinin-3 selective agonist Pro7neurokinin B. In conclusion, dactinomycin selectively inhibited neurokinin-2 receptor activation in guinea-pig lung and rat colon, but not in rat vas deferens, which may depend on the existence of different neurokinin-2 receptor subtypes. Neurokinin A is most likely the main endogenous excitatory non-adrenergic non-cholinergic transmitter in guinea-pig bronchi.

Occurrence, release, and effects of multiple tachykinins in cat colonic tissues and nerves

Neurokinin A (NKA)-immunoreactivities and substance P (SP)-immunoreactivities were found in picomolar amounts in colonic tissues and almost an order of magnitude higher amounts in vagal, pelvic, splanchnic, and lumbar colonic nerves of the cat. Continuous electric stimulation of the pelvic nerve at 4 Hz or intermittent electric burst stimulation of the pelvic nerve at 40 Hz during 1 second with 10-second rest periods produced a marked release of NKA-like immunoreactivity (NKA-LI) and SP-LI from the colon to blood (P less than 0.001). Reflex activation of the pelvic nerve by mechanical stimulation of the anus or rectal distension produced a less pronounced release of NKA-LI and SP-LI from the colon to blood (P less than 0.01). There was a simultaneous colonic contraction and vasodilation during each nerve stimulation. Reverse-phase high performance liquid chromatography showed presence of NKA, NKA oxide, NKA (3-10)/NKA (4-10), and neuropeptide K (NPK) in colonic tissues and release of all these molecular forms except NPK on nerve stimulation. Substance P and SP oxide were present both in colonic tissue extracts and in released material. Close intraarterial infusions of NKA, neurokinin B, SP, NPK, eledoisin, and physalaemin at doses of 0.1-100 pmol/min induced dose-dependent contractions of the proximal and distal colon (P less than 0.001) and vasodilatation (P less than 0.001), NKA being the most potent. The effects of the tachykinins were reduced after tetrodotoxin (P less than 0.05) and atropine (P less than 0.05) but unchanged after treatment with hexamethonium. Our findings indicate that tachykinins are released from the pelvic nerve to induce a nonadrenergic noncholinergic contraction and vasodilatation of the colon in the cat.

Characterization of the C-terminal flanking peptide of human beta-preprotachykinin

The nucleotide sequence of cDNA encoding the common biosynthetic precursor of substance P, neurokinin A and neuropeptide K (beta-preprotachykinin) predicts that, in the human, the precursor contains a C-terminal flanking peptide of 19 amino acid residues [beta-preprotachykinin(111-129)-peptide]. Using an antiserum raised against synthetic human beta-preprotachykinin(117-126)-peptide in radioimmunoassay, we have demonstrated that an extract of a human neuroendocrine tumor of the adrenal medulla contained approximately equimolar concentrations of C-terminal preprotachykinin immunoreactivity (C-PPT-IR), substance P and neurokinin A. The C-terminal preprotachykinin flanking peptide was purified to homogeneity and its primary structure was determined. The amino acid sequence of the peptide, Ala-Leu-Asn-Ser-Val-Ala-Tyr-Glu-Arg-Ser-Ala-Met-Gln-Asn-Tyr-Glu, indicates identity with beta-preprotachykinin(111-126)-peptide. The data suggest that the C-terminal flanking peptide, like the tachykinins, is packed into secretory storage vesicles but the Arg127-Arg128-Arg129 residues in human beta-preprotachykinin are removed from the peptide by the action of endogenous processing enzyme(s).

A novel radioimmunoassay for neuromedin K. I. Absence of neuromedin K-like immunoreactivity in guinea pig ileum and urinary bladder. II. Heterogeneity of tachykinins in guinea pig tissues

A novel and highly specific radioimmunoassay for the tachykinin peptide neuromedin K (NMK, also known as neurokinin beta, neurokinin B) has been developed and used to determine the distribution of this peptide in extracts of guinea pig tissues. In addition to immunoreactive components coeluting with the 3 mammalian tachykinins, substance P (SP), substance K (SK) and NMK, analyses using reverse-phase HPLC revealed immunoreactive peaks coeluting with the C-terminal octapeptide of SK (SK-(3-10], an N-terminally extended form of SK (gamma-preprotachykinin-(72-92)amide), and a yet unidentified peak eluting before NMK in the extracts of guinea pig brain and spinal cord. In contrast to the other tachykinins, SP and SK, which were present in high concentrations in extracts of all peripheral and central tissues examined, NMK-like immunoreactivity was detected only in extracts of central tissues. NMK-like immunoreactivity was not detected in extracts of terminal ileum and urinary bladder.

Neurokinin A, neurokinin B and neuropeptide K in the rabbit iris: a study comparing different extraction methods

Neurogenic inflammation in the rabbit eye is thought to be partly mediated by tachykinins released from trigeminal sensory nerve fibres. In the present study we have investigated the occurrence of neurokinin A (NKA), neurokinin B (NKB), neuropeptide K (NPK) and related immunoreactive components in the rabbit iris-ciliary complex using neutral and different types of acidic media for extraction, reverse phase high performance liquid chromatography (RP-HPLC) and radioimmunoassay (RIA). The immunoreactive material detected with an antiserum reacting almost equally well with NKA, NKB and NPK consisted mainly of NKA, and small amounts of NPK but almost no NKB. Acidic media seemed to be more effective than neutral media for extraction of NKA and NPK. Acid extraction yielded also an NKA-immunoreactive component which eluted immediately before NKA while neutral extracts, on the other hand, contained a component which appeared behind NKA, i.e. in the position of NKA-(3-10) and NKA-(4-10). The present results indicate that NKA but not NKB may play a role in neurogenic inflammation in the rabbit eye.

Neurokinin B in a human pheochromocytoma measured with a specific radioimmunoassay

An N-terminally directed antiserum to neurokinin B was raised in rabbits using an immunogen prepared by coupling the free-SH group of neurokinin B extended from its C-terminus by a cysteine residue (NKB-Cys) to an -NH2 group on human serum albumin using a heterobifunctional cross-linking reagent. In radioimmunoassay with 125I-Bolton-Hunter-labelled NKB-Cys as tracer, the antiserum showed no cross-reactivity with other tachykinins. An extract of a human pheochromocytoma, previously shown to contain peptides derived from preprotachykinin A, contained NKB-LI (13 pmol/g wet weight). The retention time of tumor neurokinin on reversed-phase HPLC was the same as that of synthetic neurokinin B. Peptides with the retention times of substance P, neurokinin A, neurokinin A (3-10)-peptide and neuropeptide K were also identified in the tumor extract. NKB-LI was not detected in extracts of a further nine pheochromocytomas or in five carcinoid tumors that expressed the preprotachykinin A gene.

The polyprotein nature of substance P precursors

Substance P and related tachykinin peptides probably act as neurotransmitters or modulators of neurotransmission, and regulate biological processes as diverse as salivary secretion and transmission of pain signals. Substance P peptide sequences are expressed in three distinct mRNAs that are generated from one gene by differential RNA splicing. In addition to substance P, as many as three other tachykinin peptides can be generated from the polyprotein precursors by differential posttranslational processing. Three tachykinin receptor subtypes have been extensively characterized which differentially interact with the naturally occurring tachykinin peptides. Therefore, the generation of diversity of tachykinin peptides results from differential precursor RNA splicing and differential posttranslational processing. The specificity of peptide responses is the result of selective receptor subtype expression.

Heterogeneity of tachykinin-like immunoreactive peptides in rat spinal cord and dorsal root ganglia

The concentrations of tachykinins in rat spinal cord and dorsal root ganglia (DRGs) were measured using a combination of high performance liquid chromatography (HPLC) and radioimmunoassays (RIAs). Substance P-like immunoreactivity (SPLI) was found to be significantly higher than either substance K-like immunoreactivity (SKLI) or neuromedin K-like immunoreactivity (NMKLI) in both tissues. In the spinal cord, the concentration of SKLI was comparable to that of NMKLI. In DRGs, NMKLI is present at concentrations much lower than those of SKLI or SPLI. In addition to immunoreactive components co-eluting with the three mammalian tachykinins SP, SK and NMK, analyses using reverse-phase HPLC revealed an immunoreactive peak co-eluting with the C-terminal octapeptide of SK (SK3-10), and a yet to be identified peak eluting before SK. This study also demonstrates the use of a novel and highly specific RIA for NMK to measure NMKLI without the need of reverse-phase HPLC.

Serotonin-producing carcinoid tumour cells in long-term culture. Studies on serotonin release and morphological features

Tumour cells from a hepatic metastasis of a midgut carcinoid tumour were studied during 240 days of culture. A cell line could not be established, but the cells regularly formed large clusters and islets. The spontaneous release of serotonin (5-HT) and neuropeptide K-like immunoreactivity from cultures were followed. The amine and the peptide levels were unstable without evident covariation. The response to stimulation with noradrenaline and isoprenaline was studied during the culture period. The tumour cells released 5-HT selectively at stimulation with isoprenaline. This responsiveness also showed considerable variation with long periods of quiescence. Ultrastructurally the tumour cells showed a certain degree of polarization with apical microvilli and a supranuclear Golgi apparatus. When studied by confocal laser scanning the tumour cells were demonstrated to be cylindrical in shape with a cytoplasmic attachment to the matrix.

Carcinoid tumour cells in long-term culture: release of serotonin but not of tachykinins on stimulation with adrenoceptor agonists

Tumour cells from a lymph-node metastasis of a midgut carcinoid tumour, immunoreactive for serotonin and substance P, were isolated and kept in culture for 2 months. The formation of large clusters or islets of tumour cells was paralleled by an increase in immunoreactive tachykinins (neuropeptide K and substance P) in the culture medium. The concentration of tachykinins declined subsequently despite good viability of the cells. Spontaneous release of serotonin into the culture medium was much greater than that of tachykinins, and remained stable throughout the study. These findings indicate different turnover rates and/or different storage sites for the peptides and the amine. In stimulation experiments, a dose-dependent release of serotonin, but not of tachykinins, was induced by a beta-adrenoceptor agonist (isoprenaline), while stimulation of alpha-adrenoceptors (noradrenaline) was not effective in releasing any of the substances. Pretreatment of the cultures with a beta-adrenoceptor antagonist (propranolol) or stimulations after calcium deprivation did not influence the isoprenaline-induced release of serotonin. These findings may indicate a modification of genuine beta-adrenoceptors during culture.

Capsaicin-sensitive tachykinin-like immunoreactivity in the thymus of rats and guinea-pigs

Capsaicin-sensitive, substance P-like immunoreactivity (SP-LI) has been detected recently in rat thymus. Other tachykinins are frequently present with SP. In the present study, tachykinin-like immunoreactivity (TK-LI) was measured in guinea-pig, rat, mouse and hamster thymus with the amount detectable being greatest in guinea-pig, less in rat and least in mouse; it was not detectable in hamsters. In guinea-pig and rat thymus, but not in mouse, TK-LI was markedly reduced by pretreatment with capsaicin. TK-LI levels correlated significantly with those of SP-LI in both guinea-pig and rat thymus. High-performance liquid chromatography (HPLC) fractions considered to represent neurokinin A, eledoisin and neuropeptide K were present in guinea-pig thymus but only the first two were present in rat thymus.

Neurokinin A-(4-10): a potent bronchospastic agent virtually devoid of sialologic properties in anaesthetized guinea-pigs

The ability of substance P, neurokinin A and its C-terminal fragment, neurokinin A-(4-10), to elicit NK-1 (salivation) and NK-2 (bronchospasm) receptor-mediated responses was investigated in anaesthetized guinea-pigs. Neurokinin A-(4-10) produced a dose-related increase in tracheal insufflation pressure and its maximal effect was similar to that elicited by neurokinin A and significantly greater than that of substance P. On the other hand substance P induced a potent dose-dependent increase of salivation while neurokinin A was significantly less potent. Neurokinin A-(4-10) did not exert any sialologic effect even at the dose of 100 nM/kg. These findings indicate that neurokinin A-(4-10) might be a valuable pharmacological tool for characterizing the involvement of NK-1 and NK-2 receptors in physiological responses in vivo.