Substance P stimulation of amylase release by isolated parotid cells and inhibition of substance P induction of salivation by vasoactive peptides

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.

Effect of substance P and receptor antagonists on secretion of lingual lipase and amylase from rat von Ebner's gland

Substance P (SP, 1 microM) when incubated with minced von Ebner's glands for 15, 30, and 60 min, stimulated secretion of lingual lipase (12.14% +/- 0.90) and amylase (8.30% +/- 0.42). Only 10 microM of the SP receptor antagonist CP-96,345 significantly inhibited SP-evoked secretion. D-Pro2-D-Phe7-D-Trp9-SP (Ia), D-Pro2-D-Trp7,9-SP (Ib), D-Arg1-D-Trp7,9-D-Leu11-SP (Ic), or 1 microM CP-96,345 were not effective, suggesting that the SP receptor of von Ebner's gland might be an isoform. Propranolol and timolol, beta 1/beta 2-adrenergic receptor antagonists were not effective and the cholinergic receptor antagonist, atropine, was effective in only slightly reducing amylase secretion but not lingual lipase. Differential secretion of the two enzymes was observed for basal and stimulated secretion. Thus, exocytosis may not be the only pathway involved in SP-evoked protein secretion.

Peptide-evoked release of amylase from isolated acini of the rat parotid gland

Investigations of the effects of the neuropeptides, substance P (SP), neurokinin A (NKA), neuropeptide K (NPK), gastrin releasing peptide (GRP), calcitonin gene related peptide (CGRP) and vasoactive intestinal peptide (VIP), and of acetylcholine on amylase secretion have been carried out on isolated acini of the rat parotid gland. Furthermore, the occurrence and location of the peptides in the gland was studied. Finally, binding of 125I-BH-SP to isolated acini were studied in order to characterize their tachykinin receptor(s) and their binding kinetics. Only SP, NKA, NPK and VIP stimulated amylase release. VIP, however, with a rather low potency (EC50 at 155 nmol/l). Simultaneous stimulation with two compounds elicited additive responses, except for VIP and acetylcholine which elicited an effect significantly above additive response. Only SP, NKA, VIP and CGRP could be identified in extracts of the gland. The immunoreactivity of these peptides could be located to varicose nerve fibers in the gland. Binding of labeled SP to the isolated acini exhibited the characteristics of a genuine agonist/receptor interaction, and the rank order of displacement potencies indicated the presence of NK1-receptors. Thus, the results of the present study support previous suggestions that the tachykinins and VIP are likely to be involved in amylase secretion in the rat parotid gland.

Immunohistochemical localisation of substance P in human parotid gland

Based on the clinical observation that pain is experienced during parotid gland surgery under local anaesthesia, the presence of the sensory neuropeptide substance P (SP) was sought. Using a polyclonal antibody, the presence of SP was demonstrated by an indirect immunofluorescence technique, with rat parotid gland and spinal cord serving as controls. SP-containing neuronal elements occurred around acini, blood vessels and ducts. It is suggested that some of the SP-immunoreactive elements are the unmyelinated and thinly myelinated small diameter (A delta and C) fibres, which are regarded as the peripheral receptors for nociceptive information.

Up-regulation of substance P binding sites in the vagus nerve projection area of the cat brainstem after nodosectomy. A quantitative autoradiographic study

Substance P (SP) regulates visceral functions in the nucleus of the solitary tract (NST) area. High affinity SP binding sites labelled with [3H]SP or [125I]SP show a heterogeneous distribution in the cat medulla with high densities in the rostral and dorso-caudal parts of both the median subnucleus of NST and the dorsal motor nucleus (DMN). We previously observed a significant loss of SP immunoreactivity in the vagal area of the cat after an ipsilateral nodosectomy. It was thus important to study the correlated plasticity of SP binding in the context of the regulation of receptor function. Whichever labelled ligand was used, a unilateral nodose excision was followed by an ipsilateral increase in SP binding in the NST (200%) and the DMN (300%) after 30 days of survival. This increase was region-specific and did not match exactly the decrease in SP immunoreactivity following nodosectomy. This SP receptor density up-regulation could be due to long-term deprivation of SP afferent fibres in the NST and partly in the DMN. In the latter the increase of SP receptors occurred in both the cytoplasm of large neurons and the neuropile and did not affect the glia. The up-regulation phenomenon seems to be specific for SP receptors in the cat (at least in the DMN) and may constitute a reactive mechanism against the injury of axotomy of DMN neurons.

Anti-substance P anti-idiotypic antibodies modulate the secretory process in the rat parotid gland in vitro

Anti-idiotypic antibodies (anti-Id) obtained in rabbits in response to immunization with polyclonal anti-substance P antibodies (anti-SP) were shown to bind specifically and with high affinity to membranes from rat parotid gland cells. Whereas substance P (SP) was unable to displace anti-Id from membrane binding sites, anti-Id partly inhibited the binding of radiolabelled substance P. Like substance P, anti-Id were able to trigger protein secretion by parotid cells i.e. to behave as physiological agonists of the neuropeptide. Under our experimental conditions, the biological effects of both ligands appear to be additive. Unlike substance P, however, anti-Id did not potentiate the secretory response induced by a beta-adrenoceptor agonist. Taken together, the present results might indicate that anti-Id interact with epitope(s) at or/and near the peptide-combining site on the substance P receptor. These data demonstrate further the possibility of raising pharmacologically active anti-receptor antibodies through the immunological anti-idiotypic approach.

Substance P modulates single-channel properties of neuronal nicotinic acetylcholine receptors

Substance P (SP) is present in avian sympathetic ganglia and accelerates the decay rate of acetylcholine (ACh)-evoked macroscopic currents in sympathetic neurons. We demonstrate here that SP modulates ACh-elicited single channels in a manner consistent with an enhancement of ACh receptor (AChR) desensitization. Furthermore, since AChR channel function was monitored in cell-attached patches with SP applied to the extra-patch membrane, the peptide must act via a second messenger mechanism. SP specifically decreases the net ACh-activated single-channel current across the patch membrane by decreasing both channel opening frequency and mean open time kinetics. These experiments demonstrate that a peptide can modulate neuronal AChR function by a second messenger mechanism.

Substance P-induced reduction in the initial accumulation of cytosolic myo-[3H]inositol in rat parotid acinar cells mediated by the NK1 tachykinin receptor

Stimulation of rat parotid acinar cells by the tachykinin neurokinin (NK) 1 receptor agonist substance P (SP) resulted in a significant reduction in the initial accumulation of cytosolic myo-[3H]inositol. This effect was rapid, because a reduction of approximately 15% could be seen already at 30 s. with the maximal effect (approximately 45%) being observed at 15 min. The response to SP stimulation was temperature dependent, because at 4 degrees C no reduction was found. In addition, at 4 degrees C, cytosolic myo-[3H]inositol represented only 10% of the labeled inositol accumulated at 37 degrees C. The SP-induced reduction in cytosolic myo-[3H]inositol accumulation was concentration dependent; the EC50 obtained for SP was 5.8 +/- 2.5 nM. Spantide [D-Arg1, D-Trp7.9, Leu11]SP), a SP antagonist, used at a concentration of 10(-5) M, gave a competitive shift of the dose-response curve to SP. Various tachykinins and their analogs were evaluated for their ability to reduce cytosolic myo-[3H]inositol. [L-Pro9]SP and SP methyl ester, two highly selective agonists of NK1 receptors, reduced the initial accumulation of myo-[3H]inositol with EC50 values of 2.3 and 67.0 nM, respectively. Long SP C-terminal fragments were more potent than shorter ones. SP N-terminal fragments and SP free acid were without effect. [Pro7]NKB, a selective NKB analog, had no effect. The rank order of potency of mammalian tachykinins was SP greater than NKA greater than NKB. These findings and the close correlation between EC50 values and IC50 values obtained in binding studies implicate the NK1 receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Degradation of substance P by membrane peptidases in the rat substantia nigra: effect of selective inhibitors

The hydrolysis of substance P by membrane peptidases prepared from the rat substantia nigra was studied in the presence of selective inhibitors. Substance P degradation by synaptic and mitochondrial membranes was completely inhibited by 1,10-phenanthroline (1 mM), a non-specific metallopeptidase inhibitor. Captopril and bestatine, selective inhibitors of angiotensin converting enzyme and aminopeptidases respectively, were without effects. However, phosphoramidon (1 microM), a putative 'enkephalinase' inhibitor, selectively inhibited substance P degradation by synaptic membranes. These results suggest that a phosphoramidon-sensitive endopeptidase may be the principal enzyme responsible for substance P degradation in substantia nigra.

Monoclonal antibodies to substance P: production, characterization of their fine specificities, and use in immunocytochemistry

Five hybrid clones secreting antibodies to the neuropeptide substance P have been obtained by somatic cell fusion of mouse myeloma cells with splenocytes from immunized mice of the Biozzi strain. To perform rapid and sensitive screening tests as well as to study the fine specificities of each monoclonal antibody, we developed a new enzyme immunoassay of substance P using acetylcholinesterase as label. All five monoclonal antibodies were directed to the C-terminal pentapeptide of substance P, especially to the Phe7 residue. They cross-reacted with neurokinin A and to some extent with neurokinin B but not with other nontachykinin mammalian peptides. One monoclonal antibody (SP 14) was used for immunocytochemical experiments in the rat spinal cord and spinal ganglion, both at the light and electron microscopic levels. A strong specific neurokinin-like immunoreactivity was observed in cell bodies, nerve fibers, and terminals, with a very low background staining. Finally, the affinities of several analogues of substance P for SP 14 monoclonal antibody were shown to be correlated with their biological activities, as measured by their hypotensive effects in vivo. These findings suggested a strong structural resemblance between the combining site of the antibody and that of the physiological substance P receptor.

Homologous desensitization of substance-P-induced inositol polyphosphate formation in rat parotid acinar cells

Maximal concentrations of substance P and methacholine induced a rapid increase in [3H]inositol trisphosphate ([3H]IP3) formation. After about 1 min, the [3H]IP3 in the substance-P-treated cells ceased to increase further, whereas in the methacholine-treated cells [3H]IP3 continued to increase. Addition of methacholine to the substance-P-treated cells caused a rapid increase in [3H]IP3, whereas a second addition of a 10-fold excess of substance P had no effect. Pretreatment of cells with substance P, followed by removal of the substance P by washing, resulted in a decreased response to a second application of substance P. A similar protocol involving pretreatment with methacholine had no effect on subsequent responsiveness to substance P. Analysis of [3H]substance P binding to substance-P-treated cells indicated that the number of receptors for substance P was decreased, but the affinity of the receptors for substance P was unaffected. After substance P pretreatment, a prolonged incubation (2 h) restored responsiveness of the cells to substance P, measured as [3H]IP3 formation, and restored the number of binding sites to control values. These findings indicate that, in the rat parotid gland, substance P induces a homologous desensitization of its receptor, which involves a slowly reversible down-regulation or sequestration of substance-P-binding sites.

Ultrastructural localization and afferent sources of substance P in the rat parabrachial region

The ultrastructural morphology and afferent sources of terminals containing substance P-like immunoreactivity were examined in the rat parabrachial region. In the first portion of the study, a polyclonal antiserum to substance P was localized in the ventrolateral parabrachial region using the peroxidase-antiperoxidase labeling technique combined with electron microscopy. The antiserum was tested for cross-reaction with substance P, physalaemin, substance K and neuromedins B, C and K. Cross-reactivity was most intense with substance P. However, substance K, neuromedin K and physalaemin also exhibited limited cross-reactions with the antiserum. In the ventrolateral parabrachial region of untreated adult animals, substance P-like immunoreactivity was localized in axon terminals containing numerous small (40-60 nm) clear vesicle and 1-3 large (90-120 nm) dense-core vesicles. At least 54% of the labeled terminals formed asymmetric synapses with unlabeled dendrites; and at least 30% of the recipient dendrites received more than one labeled axon terminal. In addition, the labeled terminals were associated less frequently with other unlabeled soma, axon terminals and blood vessels. In the second part of the study, we examined whether or not perikarya in various extrinsic regions contributed to the substance P-like immunoreactivity in axon terminals in the parabrachial region. Wheat-germ agglutinin conjugated horseradish peroxidase was injected unilaterally into the parabrachial region of adult rats two days prior to being killed and one day prior to intraventricular injection of colchicine (100 micrograms in 7.5 microliter saline) which enhanced the detection of immunoreactivity in perikarya. Sections were first processed by a tetramethylbenzidine reaction stabilized with cobalt-diaminobenzidine for demonstration of the transported peroxidase then were immunocytochemically labeled for substance P. Perikarya containing both the black granular retrograde labeling and brown peroxidase-immunoreactivity were found in the nuclei of the solitary tracts, the caudal ventrolateral reticular formation, the lateral dorsal tegmental nucleus and the paraventricular, dorsomedial and lateral hypothalamic nuclei. The projections were largely, but not exclusively, from perikarya located on the same side as the parabrachial injection. We conclude that substance P, or a closely related tachykinin, is a putative transmitter or modulator within a number of pathways to the parabrachial region and that these afferents act primarily through axodendritic synapses with intrinsic neurons.

Immunohistochemical demonstration of substance P-containing nerve fibres in glomus tumours

Substance P (SP), S-100 protein, methionine-enkephalin, serotonin and myelin basic protein were studied in two solitary glomus tumours of the skin by peroxidase-antiperoxidase immunohistochemistry. Multiple SP-containing nerve fibres were distributed in the parenchyma of the tumour among proliferating glomus cells, and in the oedematous stroma of the tumour. Positive staining for myelin basic protein was detected in nerve fascicles in the capsule of the tumour, but not within the glomus tumour. S-100 protein immunoreactivity was found in nerve fascicles in the capsule of the tumour, and in addition, a few cells positive for S-100 protein were scattered throughout the stroma of the tumour. No positive staining for methionine-enkephalin and serotonin was found. The present finding may explain the clinical experience that the tumour is tender and can cause severe paroxysmal pain, because SP is known to be a primary sensory afferent neurotransmitter for mediating nociception. A possible role of SP for vasodilation in the glomus tumour is also discussed.

Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine or substance P in rat submandibular gland slices

Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine (ACh) or substance P (SP) were investigated in rat submandibular gland slices. The oxygen uptake induced by ACh or SP was significantly inhibited by removing Ca2+ from the medium and the slices. The oxygen uptake by ACh in the Ca2+-deficient slices was almost completely recovered by the addition of 3.0 and 5.0 mM Ca2+, whereas that by SP was not recovered by the addition of 3.0 mM Ca2+, but recovered by 5.0 mM Ca2+. Ca2+ antagonists, diltiazem, verapamil and La3+, significantly inhibited the ACh-induced oxygen uptake. On the other hand, the SP-induced oxygen uptake was inhibited by diltiazem and La3+, but not by verapamil. Calmodulin antagonists, trifluoperazine, chlorpromazine and W-7, had no inhibitory effects on the ACh-induced oxygen uptake. The SP-induced oxygen uptake was not affected by trifluoperazine, chlorpromazine and low concentrations of W-7, but was inhibited by high concentrations of W-7. These results suggest that the ACh- or SP-induced oxygen uptake is dependent on the presence and permeability of Ca2+ with a subtle difference between the ACh and the SP mechanisms and that the oxygen uptake is independent of calmodulin.

The regeneration of substance P-containing nerve fibers in the process of burn wound healing in the guinea pig skin

The regeneration of substance P (SP)-containing nerve fibers in the process of burn wound healing in the guinea pig skin has been studied by immunohistochemistry. SP-like immunoreactivity, which was specifically localized in neural elements of intact skin, was found to disappear in the burn wound including its margin on day 2 post burn. The SP-containing nerve fibers were first detected in periods later than day 2 post burn, and the regeneration seemed to occur in association with regeneration of blood vessels at the wound margins. These nerve fibers gradually increased in number and acquired maximum density on day 14 post burn. In addition, such renewed fibers showed sprouting to form a dense network, which has never been observed in intact skin, in the upper granulation tissue just beneath the regrowing epidermis. Following that peak period, the density of the fibers gradually decreased to less than that of controls. The characteristic process of regeneration of SP-containing nerve fibers, having a peak period of fiber density at least in burn wound healing, appeared similar to that of the regeneration of sympathetic catecholaminergic nerve fibers reported previously.

Characteristics of 3H-substance P binding sites in rat brain membranes

Binding characteristics of 3H-Substance P (SP) were studied with rat brain membranes using a method applied to peripheral tissues by Lee and Snyder [15]. This method was well applicable to central nervous system (CNS) tissues. The results in the present study indicate that specific 3H-SP binding reaches a plateau only after 20 minutes of incubation, and the binding sites are saturable at a relatively low concentration of 3H-SP. Scatchard analysis of specific binding data reveals a single class of binding sites with a high affinity (Kd = 0.30 nM) and a low density (Bmax = 27.7 fmol/mg protein) in rat brain membranes. A Hill plot of the displacement curve of 3H-SP with unlabelled SP showed no indication for cooperativity (nH = 0.83). The relative potencies of binding of various SP fragments at 3H-SP binding sites were fairly parallel to the length of the C-terminal fragments. Neurotransmitters not structurally related to SP produced no effect on 3H-SP binding even when used at micromolar concentrations.

Two-dimensional electrophoretic analysis of secretory-granule, granule-membrane, and plasma-membrane proteins of rat parotid cells

Secretory granules and plasma membranes were isolated from rat parotid cells and characterized enzymatically and by electron microscopy. The proteins of the secretory granule membranes, the secretory granules and the plasma membranes were characterized by two-dimensional polyacrylamide gel electrophoresis and visualized by silver staining. The granule membrane contains 166 polypeptides of which only 26 are also present in the granule contents. The membrane proteins have isoelectric points between 4.75 and 6.45 and apparent molecular weights of 17 000 to 190 000 Daltons. The granule content proteins are surprisingly complex and contain 122 polypeptides with molecular weights of 11 000 to 138 000 and isoelectric points of 4.8 to 6.55. Thirteen of these peptides are present as major species. The plasma membrane contains 172 polypeptide species with molecular weights from 17 000 to 200 000 Daltons and isoelectric points of 5.0 to 6.8. Thirty-five of the plasma membrane proteins are also present in the secretory granule membranes indicating that the two membranes have some enzymatic or structural properties in common. Thus, secretory granule membranes and plasma membranes from parotid cells have a more complex polypeptide composition than has previously been shown for membranes of this type. The systems developed are suitable for the analysis of regulatory events such as protein phosphorylation, proteolytic processing, and other types of post-translational modifications that may be important to the secretory mechanism.

Structure-activity relationship in the mast cell degranulating capacity of neurotensin fragments

The mast cell degranulating capacity of neurotensin and three of its fragments was examined. In Tyrode solution (137 mM NaCl, 2.7 mM KCl, 0.4 mM NaH2PO4, 1.4 mM CaCl2, 1 mM MgCl2, 10 mM Hepes, 5.6 mM glucose, pH 7.4), neither intact neurotensin nor its C-terminal tripeptide (Tyr-Ile-Leu) caused any release of histamine. Concentrations of neurotensin exceeding 10(-4)M did cause histamine release but through lysis of the cells. The C-terminal hexa- and octapeptides of neurotensin (Arg-Arg-Pro-Tyr-Ile-Leu and Lys-Pro-Arg-Arg-Pro-Tyr-Ile-Leu, respectively) induced a non-cytolytic release of histamine with the latter peptide being more active (ED50 = 90 microM for the hexapeptide and 13 microM for the octapeptide). This release was not affected by the C-terminal tripeptide. It was found to be calcium-dependent and was inhibited by the anti-allergic drug, disodium cromoglycate. Phosphatidylserine did not enhance release of histamine and saturation of the immunoglobulin E (IgE) receptors did not inhibit it.

Relative secretory contributions of the three major salivary glands of the rat in response to substance P and super-sensitivity

In vivo salivation in the rat in response to a range of intravenous doses of substance P was studied. The ducts of the parotid, submandibular and sublingual glands were cannulated. The secretory threshold dose of substance P, in microgram/kg, was 0.05-0.1 in the submandibular glands, 0.2 in the parotid glands and 0.2-0.5 in the sublingual glands. The maximal secretory response in all three types of glands was obtained at a dose level of 5-10 micrograms/kg. The total amount of saliva secreted at this dose level from the three pairs of glands was calculated to about 300 mg; the submandibular glands were responsible for 65 per cent, the parotid glands for 32 per cent and the sublingual glands for 3 per cent. Parasympathetic decentralization but not sympathetic denervation caused the sublingual glands to develop a super-sensitivity to substance P. The secretory effect of substance P was not exerted via cholinergic, alpha-adrenergic or beta-adrenergic receptors.

Concentration of substance P-like immunoreactivity (SPLI) in tissues of dog, rat and mouse

The distribution of SPLI in various tissues from dog, rat and mouse was determined by radioimmunoassay. The gastrointestinal, urogenital and tracheobronchial tracts were found to contain SPLI with marked differences in levels in different parts of these tracts. Glandular tissues, such as salivary glands and pancreas, was well as eye, tongue and skin also contain SPLI. Species differences were encountered both in absolute amounts and the distribution of SPLI. The highest concentrations of SPLI were generally found in mouse followed by dog and rat. The present results are in agreement with those of previous studies in which SP was demonstrated by bioassay technique, but due to the greater sensitivity of the radioimmunoassay it was possible to show a much wider distribution of SP. Virtually all organs in which an effect of SP has been demonstrated also contain SPLI.

The effects of substance P and related peptides on alpha-amylase release from rat parotid gland slices

1 The effects of substance P and related peptides on amylase release from rat parotid gland slices have been investigated. 2 Supramaximal concentrations (1 microM) of substance P caused enhancement of amylase release over the basal level within 1 min; this lasted for at least 40 min at 30 degrees C. 3 Substance P-stimulated amylase release was partially dependent on extracellular calcium and could be inhibited by 50% upon removal of extracellular calcium. 4 Substance P stimulated amylase release in a dose-dependent manner with an ED50 of 18 nM. 5 All C-terminal fragments of substance P were less potent than substance P in stimulating amylase release. The C-terminal hexapeptide of substance P was the minimum structure for potent activity in this system, having 1/3 to 1/8 the potency of substance P. There was a dramatic drop in potency for the C-terminal pentapeptide of substance P or substance P free acid. Physalaemin was more potent than substance P (ED50 = 7 nM), eledoisin was about equipotent with substance P (ED50 = 17 nM), and kassinin less potent that substance P (ED50 = 150 nM). 6 The structure-activity profile observed is very similar to that for stimulation of salivation in vivo, indicating that the same receptors are involved in mediating these responses. 7 All the fragments of substance P tested were capable of eliciting a full amylase release response. This indicates that the apparent partial agonist action of the C-terminal nonapeptide fragment on in vivo salivation is not explicable at the receptor level.