Neural influences on synovial mast cell density in rat

Identification of novel immune cell signature in gastroesophageal reflux disease: altered mucosal mast cells and dendritic cell profile

Introduction

Heartburn pathogenesis in GERD remains incompletely understood. We aimed to identify differences in the immune cell signature and sensory mucosal markers between reflux phenotypes and healthy asymptomatic subjects.

Methods

Thirty-seven patients with heartburn symptoms were phenotyped endoscopically and with objective reflux studies into erosive reflux disease (ERD) (N=10), nonerosive reflux disease (NERD) (N=9), functional heartburn (FH) (N=9), and Barrett's esophagus (BO) (N=9). Bulk mRNA-sequencing(RNA-seq) was conducted on RNA extracted from endoscopic biopsies, and immune cell deconvolution analysis was performed using CIBERSORT. RNA-seq findings were validated by immunofluorescent staining for CD1a, nerve growth factor (NGF), and mast cell tryptase in corresponding patient biopsies.

Results

Transcriptomic analysis detected higher mast cell abundance in BO, ERD, and NERD compared to healthy controls (p<0.05), with decreased dendritic cell infiltration in BO, ERD, and NERD patients compared to healthy controls and FH patients. CD1a-positive dendritic cell infiltration was significantly higher in the healthy esophageal mucosa at protein level compared to BO (p=0.0005), ERD (p=0.0004), and FH patients (p=0.0096). Moreover, NGF co-expression on mast cells in GERD patients was significantly higher than in healthy controls (p=0.0094).

Discussion

The mucosa in patients with GERD had a significant increase in NGF expression on mast cells, suggesting an upregulation of signalling for neuronal sprouting in GERD. Moreover, decreased dendritic cell abundance in GERD esophageal mucosa may play a role in reduced oral tolerance and development of subsequent immune responses which may participate in esophageal sensitivity.

Origins of antidromic activity in sensory afferent fibers and neurogenic inflammation

Neurogenic inflammation results from the release of biologically active agents from the peripheral primary afferent terminal. This release reflects the presence of releasable pools of active product and depolarization-exocytotic coupling mechanisms in the distal afferent terminal and serves to alter the physiologic function of innervated organ systems ranging from the skin and meninges to muscle, bone, and viscera. Aside from direct stimulation, this biologically important release from the peripheral afferent terminal can be initiated by antidromic activity arising from five anatomically distinct points of origin: (i) afferent collaterals at the peripheral-target organ level, (ii) afferent collaterals arising proximal to the target organ, (iii) from mid-axon where afferents lacking myelin sheaths (C fibers and others following demyelinating injuries) may display crosstalk and respond to local irritation, (iv) the dorsal root ganglion itself, and (v) the central terminals of the afferent in the dorsal horn where local circuits and bulbospinal projections can initiate the so-called dorsal root reflexes, i.e., antidromic traffic in the sensory afferent.

Purinergic signalling and immune cells

This review article provides a historical perspective on the role of purinergic signalling in the regulation of various subsets of immune cells from early discoveries to current understanding. It is now recognised that adenosine 5'-triphosphate (ATP) and other nucleotides are released from cells following stress or injury. They can act on virtually all subsets of immune cells through a spectrum of P2X ligand-gated ion channels and G protein-coupled P2Y receptors. Furthermore, ATP is rapidly degraded into adenosine by ectonucleotidases such as CD39 and CD73, and adenosine exerts additional regulatory effects through its own receptors. The resulting effect ranges from stimulation to tolerance depending on the amount and time courses of nucleotides released, and the balance between ATP and adenosine. This review identifies the various receptors involved in the different subsets of immune cells and their effects on the function of these cells.

Vitamin D deficiency leads to sensory and sympathetic denervation of the rat synovium

Vitamin D deficiency is associated with increased susceptibility to inflammatory arthritis. Sensory and sympathetic synovial nerves are critical to the development of inflammatory arthritis and spontaneously degenerate in the early phases of disease. These nerves contain vitamin D receptors and vitamin D influences nerve growth and neurotrophin expression. We therefore examined the density of synovial nerves and neurotrophin-containing cells in vitamin D-deficient rats. Seven-week-old Sprague-Dawley rats were fed either control or vitamin D-deficient diets for 4weeks. Knee synovium sections extending from the patella to the meniscus were immunostained for total nerves, myelinated and unmyelinated nerves, sympathetic nerves, peptidergic and non-peptidergic sensory nerves, and neurotrophins and immune cell markers. In control rats, intimal innervation by unmyelinated sensory fibers was denser than subintimal innervation. In contrast, sympathetic innervation was confined to the subintima. Many sensory axons contained markers for both peptidergic and non-peptidergic nerves. Nerve growth factor (NGF) was primarily expressed by intimal CD163-negative type B synoviocytes, while neurturin, a ligand selective for non-peptidergic sensory neurons, was expressed by synovial mast cells. In vitamin D-deficient rats, there were significant reductions in sensory nerves in the intima and sympathetic nerves in the subintima. While there was no significant change in NGF-immunoreactivity, the number of neurturin-expressing mast cells was significantly reduced in the intima, suggesting that intimal reductions in sensory nerves may be related to reductions in neurturin. Vitamin D deficiency therefore may increase susceptibility to inflammatory arthritis by depleting sensory and sympathetic synovial nerves as a result of reduced synovial neurotrophin content.

Physiology and pathophysiology of purinergic neurotransmission

This review is focused on purinergic neurotransmission, i.e., ATP released from nerves as a transmitter or cotransmitter to act as an extracellular signaling molecule on both pre- and postjunctional membranes at neuroeffector junctions and synapses, as well as acting as a trophic factor during development and regeneration. Emphasis is placed on the physiology and pathophysiology of ATP, but extracellular roles of its breakdown product, adenosine, are also considered because of their intimate interactions. The early history of the involvement of ATP in autonomic and skeletal neuromuscular transmission and in activities in the central nervous system and ganglia is reviewed. Brief background information is given about the identification of receptor subtypes for purines and pyrimidines and about ATP storage, release, and ectoenzymatic breakdown. Evidence that ATP is a cotransmitter in most, if not all, peripheral and central neurons is presented, as well as full accounts of neurotransmission and neuromodulation in autonomic and sensory ganglia and in the brain and spinal cord. There is coverage of neuron-glia interactions and of purinergic neuroeffector transmission to nonmuscular cells. To establish the primitive and widespread nature of purinergic neurotransmission, both the ontogeny and phylogeny of purinergic signaling are considered. Finally, the pathophysiology of purinergic neurotransmission in both peripheral and central nervous systems is reviewed, and speculations are made about future developments.

Non-synaptic transmission at autonomic neuroeffector junctions

Non-synaptic transmission is characteristic of autonomic neuroeffector junctions. The structure of the autonomic neuromuscular junction is described. The essential features are that: the terminal portions of autonomic nerve fibers are varicose and mobile, transmitters being released 'en passage' from varying distances from the effector cells; while there is no structural post-junctional specialization on effector cells, receptors for neurotransmitters accumulate on cell membranes at close junctions; muscle effectors are bundles rather than single smooth muscle cells, that are connected by gap junctions which allow electrotonic spread of activity between cells. A multiplicity of transmitters are utilized by autonomic nerves, and cotransmission occurs often involving synergistic actions of the cotransmitters, although pre- and post-junctional neuromodulation of neurotransmitter release also take place. It is suggested that autonomic neural control of immune, epithelial and endothelial cells also involves non-synaptic transmission.

The role of joint nerves and mast cells in the alteration of vasoactive intestinal peptide (VIP) sensitivity during inflammation progression in rats

The present study examined the peripheral effects of vasoactive intestinal peptide (VIP) on rat knee joint blood flow during acute and chronic inflammation. The involvement of joint nerves and synovial mast cells on these effects was also investigated. Prior to blood flow assessment, animals were deeply anaesthetised with ethyl carbamate (urethane; 2 mg kg(-1) i.p.). Local application of VIP (10(-13)-10(-9) mol) onto the capsular surface of normal rat knee joints caused a dose-dependent increase in synovial perfusion with an ED50 of 1.2 x 10(-11) mol. The dilator effect of the peptide was transient with the maximal response occurring approximately 1 min after drug administration. VIP-induced vasodilatation was blocked by co-administration of the VIP receptor antagonist VIP(6-28) (10(-9) mol). The inhibitory effect of the antagonist was consistent across the entire VIP dose range (P=0.01). The vasoresponsiveness to VIP was significantly attenuated in acutely inflamed joints; however, surgical denervation of acutely inflamed knees re-established the vasodilator effect of the neuropeptide. Topical application of VIP to 1- and 3-week adjuvant monoarthritic knees produced a hyperaemic response, which was not significantly different from normal (P=0.06 and 0.73 for 1- and 3-week adjuvant treated joints, respectively). Stabilisation of synovial mast cells by disodium cromoglycate (cromolyn) pretreatment did not alter the vasoresponsiveness to VIP in acute or chronically inflamed joints. The vasodilatatory effect of VIP is lost during acute knee joint inflammation and this abrogated effect is neurally dependent. In the chronic phase of knee joint inflammation, VIP-mediated hyperaemia recovers to normal levels. Synovial mast cells do not influence the vasomotor effects of exogenously applied VIP in inflamed knee joints.

Biomechanics of musculoskeletal pain: dynamics of the neuromatrix

Pain, due to mechanical stimuli, is a normal, indeed healthy, response of animals to potential or actual damage to tissues. Mammals in general, and humans in particular, have evolved a highly sophisticated system of pain perception, which is characterized in humans by complementary but distinct neural processing of the intensity and location of a noxious stimulus, and a motivational/emotional or affective response to the stimulus. The peripheral and central neurons that comprise this system, which has been called the 'neuromatrix', dynamically (temporally) respond and adapt to noxious biomechanical stimuli. However, phenotypic variability of the neuromatrix can be large, which can result in a host of musculoskeletal conditions that are characterized by altered pain perception, which can and often does alter the course of the condition. This neural plasticity has been well recognized in the central nervous system, but it has only more recently become known that peripheral nociceptors also adapt to their altered extracellular matrix environment. This work reviews the biomechanics of pain focusing on the relevant stimulus that initiates responses by nociceptors to the cognitive perception of pain.

Substance P and calcitonin gene-related peptide expression at the extensor carpi radialis brevis muscle origin: implications for the etiology of tennis elbow

With use of immunohistochemistry and antibodies to substance P and calcitonin gene-related peptide, nerve fibers showing substance P-like and calcitonin gene-related peptide-like immunoreactivity were demonstrated at the origin of the extensor carpi radialis brevis muscle in patients with tennis elbow (n = 6) and in healthy controls (n = 6). The nerve fibers were distributed in association with a subpopulation of small blood vessels and in nerve bundles but were not distributed in the tunica media-adventitia junction of the arterioles. There were no inflammatory-cell infiltrates and few solitary mast cells. The present study gives further evidence to previous suggestions that tennis elbow is not an inflammatory process in the sense of involving inflammatory cells. Frequent mechanical involvement affects sensory innervation, and substance P and calcitonin gene-related peptide may have various important efferent effects, including microvascular leakage and local edema formation; therefore, the observations from this study constitute a morphological substrate for possible effects of substance P and calcitonin gene-related peptide at the origin of the extensor carpi radialis brevis muscle.

Neurotrophins, nociceptors, and pain

It is now well established that neurotrophins play a crucial role in the development of the nervous system. However, there is increasing evidence that the function of neurotrophins persists throughout adulthood. The broad scope of neurotrophin action is well documented in the case of nerve growth factor (NGF) and its effect on nociceptors and nociception. Here, we review the evidence for these multiple roles for NGF. Two manipulations influencing NGF levels are discussed in detail. The first involves the use of transgenic mice that overexpress or underexpress neurotrophins. A second strategy involves administration of NGF or its antibody in vivo to increase or decrease its level. During prenatal development, NGF is required for survival of nociceptors. In the early postnatal period, NGF is required for expression of the appropriate nociceptor phenotype. In adults, NGF acts as an important intermediate in inflammatory pain, contributing to both peripheral and central sensitization. The sensitization of peripheral nociceptors can be very rapid and can involve non-neural cells such as mast cells, neutrophils, fibroblasts, and macrophages. Recent evidence indicates that other neurotrophins also play key supporting roles in the development of nociceptors (e.g., NT-3) and in inflammatory pain (e.g., BDNF, NT-4/5). Furthermore, molecules from other superfamilies (e.g., GDNF) also are required to assure survival of certain classes of nociceptors. The diverse effects of neurotrophins on nociceptive processing emphasize their broad importance in the development and function of the nervous system.

Effect of streptozotocin-diabetes on knee joint inflammation-induced changes in substance P and nerve growth factor in the rat

Given the involvement of the sensory nervous system in the aetiology of neurogenic inflammation, we have investigated the effect of experimental diabetes and any associated sensory nerve dysfunction on the development of complete Freund's adjuvant-induced inflammation in the rat knee. Twenty-four hours after induction of inflammation in non-diabetic rats, gamma-preprotachykinin mRNA expression was increased in the L4/L5 dorsal root ganglia. Substance P levels were increased in dorsal root ganglia and sciatic nerve whilst synovial levels of substance P were significantly decreased. Nerve growth factor, which regulates expression of gamma-preprotachykinin mRNA, was significantly increased in synovium and sciatic nerve after induction of inflammation. After 24 weeks of streptozotocin-diabetes, there was a non-significant reduction in gamma-preprotachykinin mRNA expression whilst substance P levels in dorsal root ganglia, sciatic nerve and synovium and nerve growth factor levels in the sciatic nerve were significantly decreased. Conversely, synovial levels of nerve growth factor were significantly increased. Injection of complete Freund's adjuvant into the knee of diabetic rats produced diminished joint swelling compared to that observed in non-diabetic rats. Substance P levels were unaltered compared to non-arthritic diabetic rats whilst nerve growth factor levels were significantly increased in synovium and sciatic nerve suggesting an uncoupling of substance P from nerve growth factor control in the inflammatory response in diabetic rats. The results show a significant reduction in the inflammatory response in rats with chronic streptozotocin-diabetes. Deficits in gamma-preprotachykinin mRNA expression and substance P and the altered levels of nerve growth factor indicate sensory neuronal dysfunction may play a major role in this abnormal response.

Vulvar vestibulitis subjects undergoing surgical intervention: a descriptive analysis and histopathological correlates

OBJECTIVE

We describe here a series of selected patients from an established vaginitis research clinic diagnosed with vulvovestibulitis (VV) who underwent surgical intervention for focal disease. Long-term results of surgical correction are reported and characteristic histopathology findings associated with vulvar vestibulitis are emphasized.

STUDY DESIGN

A retrospective chart review was carried out to extract relevant clinical, histologic, and outcome data. Tissue blocks of resected specimens were re-examined for specific inflammatory response.

RESULTS

Complete data and long-term follow up were available in 16 patients who underwent surgical intervention. All were cared for by the same practitioner (CM). The mean (+/- S.D.) age and gravidity on presentation were 26.9 +/- 5.3 years and 0.9 +/- 1.5, respectively. All but one was caucasian, and 70% were nulliparous. Symptoms included entry dyspareunia (100%), discharge (70%), burning (66%), itching (20%) and other (30%). All patients had focal tenderness; other findings were erythema (50%), acetowhite staining (80%), edema (20%), micropapules (20%) and condyloma (10%). After diagnosis, initial duration of conservative management was 9.4 +/- 6.9 months (1-26 months). No patients received interferon therapy. Because of persistent symptoms the 16 subjects underwent targeted partial perineoplasties. Initial histopathology results revealed chronic inflammation, parakeratosis, hyperkeratosis, edema, koilocytosis and acanthosis. When tissue blocks were cut and stained with Giemsa, large numbers of mast cells were identified. Mean postoperative follow up was 42.0 +/- 22.4 months (10-70 months). Follow up after surgery showed an overall improvement in 15/16 patients (93.8%).

CONCLUSIONS

VV affects primarily white, nulliparous women. In the carefully selected subject, surgical intervention has a high success rate, even on long-term follow up. Although the exact etiology for this condition has yet to be elucidated, the presence of mast cells supports an association with other genitourinary inflammatory syndromes such as interstitial cystitis; and allows for speculation about a possible role played by mast cell activation in the etiology of VV.

Immune activation: the role of pro-inflammatory cytokines in inflammation, illness responses and pathological pain states

It has recently become accepted that the activated immune system communicates to brain via release of pro-inflammatory cytokines. This review examines the possibility that pro-inflammatory cytokines (interleukins and/or tumor necrosis factor) mediate a variety of commonly studied hyperalgesic states. We will first briefly review basic immune responses and inflammation. We will then develop the concept of illness responses and provide evidence for their existence and for the dramatic changes in neural functioning that they cause. Lastly, we will examine the potential roles that both pro-inflammatory cytokines and the neural circuits that they activate may play in the hyperalgesic states produced by irritants, inflammatory agents, and nerve damage. The possibility is raised that apparently diverse hyperalgesic states may converge in the central nervous system and activate similar or identical neural circuitry.

Depression scales in rheumatoid arthritis: criterion contamination in interpretation of patient responses

Self-report depression scales include items concerning somatic symptoms, such as fatigue, pain, and inability to work, which may be symptoms of depression in individuals who do not have a chronic disease. However, in patients with somatic diseases such as rheumatoid arthritis, these symptoms may reflect disease rather than depression. Interpretation of responses to these items in patients with chronic disease as indicating depression is known as "criterion contamination". Criterion contamination has been described in responses of patients with rheumatoid arthritis on many widely-used depression scales, including the Minnesota Multiphasic Personality Inventory (MMPI), the Beck Depression Inventory, and the Center for Epidemiologic Studies Depression Index (CES-D). Evidence for criterion contamination in responses of patients with rheumatoid arthritis on these depression scales is summarized in this essay.

Interstitial cystitis: correlation with nerve fibres, mast cells and histamine

Interstitial cystitis (IC) is a painful condition in the urinary bladder of unknown aetiology and pathogenesis. To assess the contribution of the nervous system to IC a biopsy was taken from 6 patients with IC and from a control group of 6 patients with non-ulcerative IC. Mast cells were counted and histamine measured in bladder washings from all patients. There were significantly more nerve fibres within the sub-urothelium and detrusor muscle in chronic IC than there were in non-ulcerative IC. The bladder washings from all patients with IC contained mast cells and histamine, while only occasional mast cells and traces of histamine were found in washings from patients with non-ulcerative IC. There was a good correlation between the number of nerve fibres and number of mast cells as well as between the number of nerve fibres and the amount of histamine.

Interactions of mast cells with the nervous system ?Recent advances

This article reviews recent advances in the understanding of mast cell-nervous system interactions. It is drawn largely from work published within the last ten years, and discusses the anatomical and biochemical evidence of a functional connection between mast cells and the nervous system, and the implications that such a relationship may have for normal and abnormal physiological functioning. Mast cells are found at varying levels of association with the nervous system; in CNS parenchyma (mainly thalamus), in connective tissue coverings (e.g. meninges, endoneurium), and in close apposition to peripheral nerve endings in a variety of tissues. There is, as yet, no clearly defined role for mast cells in nervous system function, or vice-versa, and it seems most likely that their interactions fulfil mutually modulatory roles. By extension, pathological situations where one of the partners in this relationship is overly stimulated may lead to a dysregulation of the other, and contribute to disease symptomatology.

Interstitial cystitis: increased sympathetic innervation and related neuropeptide synthesis

To investigate the possibility of a neural deterioration of the bladder wall in interstitial cystitis, bladder tissue from 10 patients with interstitial cystitis was compared with that from 10 control subjects by means of immunohistochemistry. An enhanced innervation of the bladder in the submucosa and detrusor muscle was found to represent an increase of sympathetic but not cholinergic neurons. In interstitial cystitis the number of neurons positive for vasoactive intestinal polypeptide and neuropeptide Y was higher and carried a larger number of axonal varicosities, whereas the number of neurons positive for substance P and calcitonin-gene-related peptide was not significantly different in both groups. We conclude that interstitial cystitis is associated with increased sympathetic outflow into the bladder and altered metabolism of vasoactive intestinal polypeptide and neuropeptide Y. Since similar changes have been observed in other inflammatory diseases of a presumably autoimmune nature, such as rheumatoid arthritis, Crohn's disease and colitis ulcerosa, the pathophysiology of interstitial cystitis may share common pathways with the latter. Experience in these diseases may facilitate a better understanding of the pathophysiology of interstitial cystitis and suggest new therapeutic concepts.