Peptide immunoreactivities in the ganglionated plexuses and nerve fibers innervating the human gallbladder

Innervation of the extrahepatic biliary tract

The extrahepatic biliary tract is innervated by dense networks of extrinsic and intrinsic nerves that regulates smooth muscle tone and epithelial cell function of extrahepatic biliary tree. Although these ganglia are derived from the same set of precursor neural crest cells that colonize the gut, they exhibit structural, neurochemical, and physiological characteristics that are distinct from the neurons of the enteric nervous system. Gallbladder neurons are relatively inexcitable, and their output is driven by vagal inputs and modulated by hormones, peptides released from sensory fibers, and inflammatory mediators. Gallbladder neurons are cholinergic and they can express a number of other neural active compounds, including substance P, galanin, nitric oxide, and vasoactive intestinal peptide. Sphincter of Oddi (SO) ganglia, which are connected to ganglia of the duodenum, appear to be comprised of distinct populations of excitatory and inhibitory neurons, based on their expression of choline acetyltransferase and substance P or nitric oxide synthase, respectively. While SO neurons likely receive vagal input and their activity is modulated by release of neuropeptides from sensory fibers, a significant source of excitatory synaptic input to these cells arise from the duodenum. This duodenum-SO circuit is likely to play an important role in the coordination of SO tone with gallbladder motility in the process of gallbladder emptying. Now that we have gained a relatively thorough understanding of the innervation of the biliary tree under healthy conditions, the way is paved for future studies of altered neural function in biliary disease.

Painful cystic duct remnant diagnosed by endoscopic ultrasound

Postcholecystectomy pain may remain unexplained and difficult to treat. This report describes three patients with constant postcholecystectomy abdominal pain that may have arisen from the cystic duct remnant or a neuroma of the cystic duct stump. In each case pain was exacerbated by pushing on cystic duct surgical clips with an EUS-guided needle, and temporarily abolished by an EUS-guided injection of bupivicaine and triamcinolone. Two patients underwent surgical resection of the cystic duct remnant and the third did not require further treatment. Two of the three patients had long-term improvement. EUS is a novel modality for assessing the cystic duct remnant and performing a therapeutic trial.

Characterization of the intrinsic and extrinsic innervation of the gall bladder epithelium in the Australian Brush-tailed possum (Trichosurus vulpecula)

Intrinsic neurones of the gall bladder modulate its function. Nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) are present in gall bladder neurones and nitric oxide and VIP modulate its epithelial functions. As an extensive extrinsic innervation of the gall bladder is also present, the source of the epithelial innervation is unclear. In this study the source of the gall bladder epithelial innervation is defined. Immunoreactivity for VIP, NOS, substance P (SP), calcitonin gene related peptide (CGRP) and tyrosine hydroxylase (TH) in organotypic cultured and freshly fixed gall bladder were compared. Retrograde tracing in vitro from the epithelium was used to identify putative intrinsic secretomotor neurones, which were then characterized by immunohistochemistry. Abundant spinal afferent and sympathetic innervation of the gall bladder epithelium was demonstrated by CGRP/SP and TH immunohistochemistry, respectively. The intrinsic secretomotor innervation of the epithelium is derived exclusively from neurones of the subepithelial plexus. A majority of these neurones were immunoreactive for NOS. Some of the NOS-immunoreactive neurones of the subepithelial plexus also contained VIP and/or SP. Gall bladder subepithelial plexus neurones, containing NOS and/or VIP/SP, innervate the epithelium, as do extrinsic neurones.

Immune-mediated neural dysfunction in a murine model of chronic Helicobacter pylori infection

BACKGROUND & AIMS

Neuromuscular changes producing dysmotility and hyperalgesia may underlie symptom generation in functional gastrointestinal disorders. We investigated whether chronic Helicobacter pylori-induced gastritis causes neuromuscular dysfunction.

METHODS

In vitro muscle contractility and acetylcholine release were evaluated in mice before and after H. pylori eradication. H. pylori colonization and gastritis were graded histologically. Substance P (SP)-, vasoactive intestinal polypeptide (VIP)-, and calcitonin gene-related peptide (CGRP) immunoreactivity (IR) and macrophages were studied by immunohistochemistry.

RESULTS

In Balb/c mice, chronic H. pylori infection did not affect muscle function but augmented antral relaxation after nerve electric field stimulation. Infected mice had lower acetylcholine release by electric field stimulation and had higher density of SP-, CGRP-, and VIP-IR nerves in the stomach and of SP- and CGRP-IR in the spinal cord. Cholinergic nerve dysfunction worsened progressively and was associated with increasing macrophage and mononuclear but not polymorphonuclear infiltrate or bacterial colonization. SCID mice had unchanged acetylcholine release despite high H. pylori colonization and macrophage infiltration. Eradication of H. pylori normalized functional and morphologic abnormalities except for increased density of gastric SP- and CGRP-IR nerves.

CONCLUSIONS

H. pylori infection induces functional and morphologic changes in the gastric neural circuitry that are progressive and lymphocyte dependent, and some persist after H. pylori eradication. The data have direct implications regarding the role of H. pylori infection in functional dyspepsia.

Role of immunologic factors and cyclooxygenase 2 in persistent postinfective enteric muscle dysfunction in mice

BACKGROUND & AIMS

Chronic abdominal symptoms develop in some patients after acute enteric infection. This study examined mechanisms underlying smooth muscle hypercontractility that persists after acute infection in mice.

METHODS

Euthymic and athymic National Institutes of Health (NIH) Swiss mice were infected with Trichinella spiralis and studied 4 weeks postinfection (PI). Isometric tension was assessed in longitudinal muscle. Cytokine and cyclooxygenase (COX)-2 messenger RNA was determined in the muscularis externa by reverse-transcription polymerase chain reaction. COX-2 protein was identified by immunohistochemistry and prostaglandin E(2) was measured by enzymatic immunoassay. Studies were performed in euthymic and athymic NIH Swiss mice 28 days PI and in the presence or absence of treatment with corticosteroid or COX inhibitors.

RESULTS

Muscle hypercontractility was evident in euthymic mice but was attenuated in athymic mice or in steroid-treated euthymic mice 28 days PI. Expression of Th2 cytokines interleukins 4, 5, and 13 was increased during the acute infection but not thereafter. COX-2 was localized to muscle and its enzymatic activity remained significantly increased in the muscle on day 28 PI. Selective COX-2 inhibition in vitro reduced the sustained increase in tension generation.

CONCLUSIONS

These findings show that COX-2 activation in resident cells of the muscularis externa contributes to the muscle hypercontractility that persists after infection.

Chemical coding of intrinsic and extrinsic nerves in the guinea pig gallbladder: distributions of PACAP and orphanin FQ

The complexity of the neural regulation of the gallbladder is reflected by the variety of neuroactive compounds that are found in the intrinsic and extrinsic nerves of the guinea pig gallbladder. The studies reported here used antisera to test for the presence of gallbladder nerves that are immunoreactive for the neuroactive peptides, pituitary adenylyl activating polypeptide (PACAP), and/or orphanin FQ (OFQ, also known as nociceptin). PACAP immunoreactivity was observed in nerve fibers of the paravascular plexus that were also immunoreactive for calcitonin gene-related peptide. These nerve fibers, which are also immunoreactive for substance P, could be followed into the ganglionated plexus. Within the ganglia, a small proportion of neurons was found to be immunoreactive for PACAP; these neurons were also immunoreactive for vasoactive intestinal peptide and nitric oxide synthase. Immunoreactivity for OFQ was observed in the perivascular plexus in nerve fibers that were also immunoreactive for tyrosine hydroxylase. These nerves were previously shown to be immunoreactive for neuropeptide Y. In the ganglionated plexus, immunoreactivity was observed in all gallbladder neurons, as demonstrated by double staining with antiserum directed against the neuron-specific RNA binding protein, Hu. OFQ immunoreactivity was also present in the small catecholaminergic neurons that are observed in a subset of the ganglia. These results further demonstrate the neurotransmitter diversity of the nerves of the gallbladder, and they provide an incentive for studies of the actions of these compounds in the gallbladder wall.

Neurotrophin-3 and neurotrophin receptor immunoreactivity in peptidergic enteric neurons

In the rat small intestine, neurotrophin-3 immunoreactivity was identified in ganglion cells and in processes mostly innervating the mucosa and occasionally the muscle layer and vasculature. The vast majority of neurotrophin-3 immunoreactive neurons contained vasoactive intestinal polypeptide (VIP), but not substance P or related tachykinin (SP/TK). Neurotrophin receptors visualized by pan-trk immunoreactivity were found in numerous ganglion cells of both plexuses and in nerve processes in the intestinal wall. Pan-trk submucosal neurons contained VIP (36%) or SP/TK-IR (47%). Pan-trk myenteric neurons contained VIP-IR (57%) or SP/TK (27%). Our data suggest that neurotrophin-3 and neurotrophin receptors may be involved in the maintenance of enteric neuronal circuits, transmission and phenotypic expression.

Evidence that tachykinins are the main NANC excitatory neurotransmitters in the guinea-pig common bile duct

Application of electrical field stimulation (EFS; trains of 10 Hz, 0.25 ms pulse width, supramaximal voltage for 60 s) to the guinea-pig isolated common bile duct pretreated with atropine (1 microM), produced a slowly-developing contraction ('on' response) followed by a quick phasic 'off' contraction ('off peak' response) and a tonic response ('off late' response), averaging 16+/-2, 73+/-3 and 20+/-4% of the maximal contraction to KCl (80 mM), n=20 each, respectively. Tetrodotoxin (1 microM; 15 min before) abolished the overall response to EFS (n 8). Neither in vitro capsaicin pretreatment (10 microM for 15 min), nor guanethidine (3 microM, 60 min before) affected the excitatory response to EFS (n 5 each), showing that neither primary sensory neurons, nor sympathetic nerves were involved. Nomega-nitro-L-arginine (L-NOARG, 100 microM, 60 min before) or naloxone (10 microM, 30 min before) significantly enhanced the 'on' response (294+/-56 and 205+/-25% increase, respectively; n=6-8, P<0.01) to EFS. The combined administration of L-NOARG and naloxone produced additive enhancing effects (655+/-90% increase of the 'on' component, n = 6, P<0.05). The tachykinin NK2 receptor-selective antagonist MEN 11420 (1 microM) almost abolished both the 'on' and 'off late' responses (P<0.01: n=5 each) to EFS, and reduced the 'off-peak' contraction by 55+/-8% (n=5, P<0.01). The subsequent administration of the tachykinin NK1 receptor-selective antagonist GR 82334 (1 microM) and of the tachykinin NK3 receptor-selective antagonist SR 142801 (30 nM), in the presence of MEN 11420 (1 microM), did not produce any further inhibition of the response to EFS (P>0.05; n=5 each). At 3 microM, GR 82334 significantly reduced (by 68+/-9%, P<0.05, n=6) the 'on' response to EFS. The contractile 'off peak' response to EFS observed in the presence of both MEN 11420 and GR 82334 (3 microM each) was abolished (P<0.01; n=6) by the administration of the P2 purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 30 microM). PPADS (30 microM) selectively blocked (75+/-9 and 50+/-7% inhibition, n = 4 each) the contractile responses produced by 100 and 300 microM ATP. Tachykinin-containing nerve fibres were detected by using immunohistochemical techniques in all parts of the bile duct, being distributed to the muscle layer and lamina propria of mucosa. In the terminal part of the duct (ampulla) some labelled ganglion cells were observed. In conclusion, this study shows that in the guinea-pig terminal biliary tract tachykinins, released from intrinsic neuronal elements, are the main NANC excitatory neurotransmitters, which act by stimulating tachykinin NK2 (and possibly NK1) receptors. ATP is also involved as excitatory neurotransmitter. Nitric oxide and opioids act as inhibitory mediators/modulators in this preparation.

Substance P stimulates sphincter of Oddi motility and inhibits trans-sphincteric flow in the Australian brush-tailed possum

Substance P containing nerves are widely distributed throughout the gastrointestinal tract. The aims of this study were to determine the distribution of substance P containing nerves in the extrahepatic biliary tree of the Australian brush-tailed possum and to characterize the effect of exogenous substance P on the sphincter of Oddi (SO) motility and transphincteric flow in vivo. Immunohistochemical staining of fixed specimens (n = 8) found moderate numbers of substance P containing nerve cell bodies and fibres throughout the neural plexuses of the SO, in particular in the serosal and intraluminal nerve trunks of the SO and gallbladder. Synthetic porcine substance P (1-2000 ng kg-1), administered by close intra-arterial injection (i.a.; n = 7), produced a dose-dependent elevation in basal pressure [P < 0.01] and an associated dose-dependent reduction in trans-sphincteric flow [P < 0.0001]. Substance P had no significant dose-dependent effect on SO phasic contraction amplitude or frequency. Tetrodotoxin (9 micrograms kg-1, i.a.) did not inhibit the effect of substance P on SO motility and trans-sphincteric flow (n = 5). In conclusion, substance P containing nerves are found throughout the possum extrahepatic biliary tree. Exogenous substance P stimulates SO motility and reduces trans-sphincteric flow in vivo by acting directly on the sphincter smooth muscle.

Detection of substance P immunoreactivity in human peripheral leukocytes

The neuropeptide substance P (SP) has a marked proinflammatory effect and modulates the immune response. In this study, we tested the hypothesis that human peripheral leukocytes contain SP. Resting peripheral leukocytes collected from healthy volunteers (n = 20) were studied by applying a SP rabbit polyclonal antiserum to both flow cytometry and immunohistochemistry. To identify possible changes in Sp expression, we also analyzed both activated T-lymphocytes (cell cultures; n = 5 normal subjects) and neoplastic hematologic samples of different types of leukemias. Flow cytometry showed that normal granulocytes and monocytes contained SP, whereas lymphocytes were generally negative (or weakly positive) with the exception of a few (10-20%) positive subsets. In comparison, activated T-lymphocytes were markedly immunolabeled by SP as well as samples from neoplastic patients demonstrated strong SP immunoreactivity in all cell lineages. This pattern was confirmed by immunohistochemistry on cytospins. Our results support a potential role for SP-mediated immunomodulatory mechanisms both in normal and pathological conditions.

NK1 receptor expression in the interstitial cells of Cajal and neurons and tachykinins distribution in rat ileum during development

The origin and function of the interstitial cells of Cajal (ICCs) that are located at the level of the deep muscular plexus (DMP) have not been completely identified. It has been recently reported that these cells express neurokinin-1 (NK1) receptors to which substance P (SP) shows the highest affinity. Studies during pre- and postnatal life have demonstrated that ICCs are identifiable in the rat ileum soon after birth and already show adult features at 7 days of postnatal life. Several neurotransmitters have been identified at the DMP which appear at specific times during development. We have studied the expression of NK1 receptors by ICCs and enteric neurons and the timing of the appearance of SP in the DMP, myenteric plexus (MP) and submucous plexus (SMP) of rat ileum during development. Rats, aged from 18 days of fetal life to adulthood, were used. NK1 receptors and SP were identified by using NK1 polyclonal antibodies and tachykinin (SP/TK) polyclonal antibodies, respectively. NK1-immunoreactivity (IR) was detected in the ICCs immediately after birth and reached maximal intensity at 7 days. From birth, SP/TK-IR fibers originated from short excitatory neurons at the MP and reached the DMP at 1 week of postnatal life. NK1- and SP/TK-IR appeared in the MP neurons in the fetus and in the SMP neurons at weaning. The present study demonstrates that by the first days of postnatal life, the NK1-IR might be used as a marker of the ICCs at the DMP and suggests that these cells may participate in the actions exerted by tachykinins on muscle cells.

Nitric oxide synthase in neurons of the human gall-bladder and its colocalization with neuropeptides

The distributions of nerve cells and fibres that are immunoreactive for nitric oxide synthase (NOS) have been investigated in the human gall-bladder. In addition, the colocalization of NOS immunoreactivity (IR) with neuropeptide Y (NPY), pituitary adenylyl cyclase activating peptide (PACAP), somatostatin (SOM), substance P (SP), tyrosine hydroxylase (TH) and vasoactive intestinal peptide (VIP)-IR was determined. Nitric oxide synthase-IR nerve cell bodies comprised 13 and 30% of nerve cells in ganglia of the fibromuscular and subepithelial layers, respectively. To determine these percentages, neuron-specific enolase-IR was used as a marker for all nerve cells. Although SOM- and VIP-IR nerve cell bodies were found in both ganglia, they rarely contained NOS-IR. In the fibromuscular layer, NOS-IR nerve fibres were abundant and most PACAP-, SOM- and VIP-IR fibres and many NPY-IR fibres were also NOS positive. No colocalization was observed between NOS- and SP- or TH-IR. In the mucosal layer, moderate numbers of NOS-IR fibres were found and the degree of colocalization of NOS-IR with each of NPY-, PACAP-, SOM-, SP- and VIP-IR were as follows: PACAP and NPY > VIP > SOM and SP. Nitric oxide synthase and TH were not colocalized in mucosal fibres. These results suggest that nerve fibres in the fibromuscular layer in the human gall-bladder with the chemical coding NOS/NPY/PACAP/SOM/VIP are axons of inhibitory motor neurons. Nitric oxide synthase-IR fibres in the mucosal layer that contained NPY, PACAP, SOM, SP and VIP with various degrees of colocalization probably contribute to the control of epithelial secretion or absorption.

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.

Tachykinins in the gut. Part I. Expression, release and motor function

The preprotachykinin-A gene-derived peptides substance P and neurokinin (NK) A are expressed in distinct neural pathways of the mammalian gut. When released from intrinsic enteric or extrinsic primary afferent neurons, tachykinins have the potential to influence both nerve and muscle by way of interaction with three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Most prominent among the effects of tachykinins is their excitatory action on gastrointestinal motor activity, which is seen in virtually all regions and layers of the mammalian gut. This action depends not only on a direct activation of the muscle through NK1 and/or NK2 receptors, but also on stimulation of excitatory enteric motor pathways through NK3 and/or NK1 receptors. In addition, tachykinins can inhibit motor activity by stimulating either inhibitory neuronal pathways or interrupting excitatory relays. A synopsis of the available data indicates that endogenous substance P and NKA interact with other enteric transmitters in the physiological control of gastrointestinal motor activity. Derangement of the regulatory roles of tachykinins may be a factor in the gastrointestinal dysmotility associated with infection, inflammation, stress and pain. In a therapeutic perspective, it would seem conceivable, therefore, that tachykinin agonists and antagonists are adjuncts to the treatment of motor disorders that involve pathological disturbances of the gastrointestinal tachykinin system.

Functional, biochemical and anatomical changes in the rat urinary bladder induced by perigangliar injection of colchicine

The aim of this study was to assess the effect of blocking the axonal transport of sensory neuropeptides, by local injection of colchicine at pelvic ganglia level, on the sensory and efferent functions mediated by capsaicin-sensitive primary afferent neurons innervating the rat urinary bladder. Bilateral injection of colchicine in the prostatic tissue underneath the pelvic ganglia of male rats induced a time-dependent reduction (maximal at 72 h, 100% reduction) of the in vitro contraction of the bladder strips induced by capsaicin (1 microM). The response to electrical field stimulation was also reduced, although to a lesser extent. The direct contractions induced by substance P (100 nM) or KCl (80 mM) were not affected by colchicine pretreatment. In vivo, perigangliar injection of colchicine (72 h before) greatly increased bladder capacity, and reduced the amplitude of micturition contractions and micturition frequency. Capsaicin-induced plasma protein extravasation was abolished in the urinary bladder and reduced in the distal, but not the proximal ureter of colchicine-treated rats. Topical application of capsaicin onto the urinary bladder or onto the stomach induced a cardiovascular pressor reflex in urethane-anaesthetized, spinalized rats. Colchicine pretreatment reduced (by about 50%) the pressor response elicited by chemonociceptive stimulation of the bladder but not that arising from the stomach. Colchicine pretreatment did not produce overt changes of nerve profiles immunoreactive for calcitonin gene-related peptide- or tachykinin-like material in the rat urinary bladder. A more intense staining of nerve fibres positive for calcitonin-gene related peptide-like immunoreactivity and tachykinin-like immunoreactivity was observed in pelvic ganglia of colchicine-pretreated rats. No changes were detected in the dorsal horns of spinal cord segments where pelvic bladder afferents project (L6-S1). Colchicine pretreatment reduced, but did not abolish, bladder levels of substance P-, neurokinin A-, calcitonin gene-related peptide- and neuropeptide Y-like immunoreactivity. However, vasoactive intestinal peptide-like immunoreactivity levels were not changed. The capsaicin-evoked (1 microM) release of calcitonin gene-related peptide was abolished in capsaicin as well as in colchicine-pretreated animals. The present findings demonstrate that local treatment of pelvic ganglia with colchicine totally eliminates the "efferent" functions of capsaicin-sensitive afferent nerves in the urinary bladder. Although reduced, tissue levels of sensory neuropeptides are not completely depleted, thus indicating the existence of a releasable versus non-releasable pool. The chemically induced blockade of axoplasmic transport also induces a limited impairment of the sensory function of capsaicin-sensitive afferents, and of the parasympathetic efferent system.

Calcitonin gene-related peptide innervation of the rat hepatobiliary system

The digestive system is densely innervated by calcitonin gene-related peptide (CGRP)-immunoreactive neurons. The present study investigated a) the distribution and origin of CGRP-immunoreactive fibers in the rat hepatobiliary tract, and b) their relation with substance P/tachykinin (SP/TK) immunoreactivity using immunohistochemical and radioimmunoassay techniques. CGRP-containing fibers form dense networks in the fibromuscular layer of the biliary tree and surrounding the portal vein. Thin, varicose fibers are present at the base of the mucosa of the ducts. In the liver, labeled fibers are restricted to the portal areas and the stromal compartment. Neonatal treatment with capsaicin, a neurotoxin for primary afferent neurons, or celiac/superior mesenteric ganglionectomy depletes CGRP-containing fibers in the biliary tract, and reduces those associated with the portal vein. In contrast, subdiaphragmatic vagotomy does not appreciably modify the density of these fibers. Radioimmunoassay studies show a reduction of CGRP-immunoreactive contents in the biliary tract and portal vein by 84% and 65%, respectively, following capsaicin treatment, and by 80% and 66%, respectively, following ganglionectomy. By contrast, CGRP concentrations in vagotomized animals are comparable to those of controls. Most CGRP-positive fibers appear to contain SP/TK immunoreactivity, as indicated by double-label studies. These results demonstrate that the rat hepatobiliary tract is prominently innervated by CGRP- and CGRP/SP/TK-immunoreactive fibers, which are likely to originate from spinal afferent neurons. The abundance of these fibers and their association with a variety of targets are in line with the involvement of these peptidergic visceral afferents in regulating hepatobiliary activities, including hemodynamic functions of the hepatic vasculature.