Intraneuronal substance P contributes to the severity of experimental arthritis

Evaluation of PD 154075, a tachykinin NK1 receptor antagonist, in a rat model of postoperative pain

PD 154075 ([(2-benzofuran)-CH2OCO]-(R)-alpha-MeTrp-(S)-NHCH(CH3) Ph) is a selective tachykinin NK1 receptor antagonist. Its effect on development and maintenance of thermal and mechanical hypersensitivity was examined in a rat model of surgical pain. When administered 30 min before surgery, PD 154075 dose-dependently (3-100 mg/kg, s.c.) prevented the development of thermal and mechanical hypersensitivity with respective minimum effective doses of 10 and 30 mg/kg. These antihypersensitivity effects lasted for 72 h. In contrast, the administration of PD 154075 (30 mg/kg, s.c.) after surgery had little or no effect on these nociceptive responses. PD 154075 antagonised thermal hypersensitivity induced by intrathecal administration of substance P, over the same dose range that blocked surgical hypersensitivity. However, it only partially blocked the thermal hypersensitivity induced by the selective NK2 receptor agonist [betaAla8]neurokinin A-(4-10). Morphine dose-dependently (1-6 mg/kg, s.c.) lengthened isoflurane and pentobarbitone-induced sleeping time in the rat. In contrast, PD 154075 (3-100 mg/kg, s.c.) did not interact with these anaesthetics. It is suggested that tachykinin NK1 receptor antagonists, such as PD 154075, may possess therapeutic potential as pre-emptive antihypersensitive agents.

The tachykinin NK1 receptor. Part II: Distribution and pathophysiological roles

The tachykinin NK1 receptor is widely distributed in both the central and peripheral nervous system. In the CNS, NK1 receptors have been implicated in various behavioural responses and in regulating neuronal survival and degeneration. Moreover, central NK1 receptors regulate cardiovascular and respiratory function and are involved in activating the emetic reflex. At the spinal cord level, NK1 receptors are activated during the synaptic transmission, especially in response to noxious stimuli applied at the receptive field of primary afferent neurons. Both neurophysiological and behavioural evidences support a role of spinal NK1 receptors in pain transmission. Spinal NK1 receptors also modulate autonomic reflexes, including the micturition reflex. In the peripheral nervous system, tachykinin NK1 receptors are widely expressed in the respiratory, genitourinary and gastrointestinal tracts and are also expressed by several types of inflammatory and immune cells. In the cardiovascular system, NK1 receptors mediate endothelium-dependent vasodilation and plasma protein extravasation. At respiratory level, NK1 receptors mediate neurogenic inflammation which is especially evident upon exposure of the airways to irritants. In the carotid body, NK1 receptors mediate the ventilatory response to hypoxia. In the gastrointestinal system, NK1 receptors mediate smooth muscle contraction, regulate water and ion secretion and mediate neuro-neuronal communication. In the genitourinary tract, NK1 receptors are widely distributed in the renal pelvis, ureter, urinary bladder and urethra and mediate smooth muscle contraction and inflammation in response to noxious stimuli. Based on the knowledge of distribution and pathophysiological roles of NK1 receptors, it has been anticipated that NK1 receptor antagonists may have several therapeutic applications at central and peripheral level. At central level, it is speculated that NK1 receptor antagonists could be used to produce analgesia, as antiemetics and for treatment of certain forms of urinary incontinence due to detrusor hyperreflexia. In the peripheral nervous system, tachykinin NK1 receptor antagonists could be used in several inflammatory diseases including arthritis, inflammatory bowel diseases and cystitis. Several potent tachykinin NK1 receptor antagonists are now under evaluation in the clinical setting, and more information on their usefulness in treatment of human diseases will be available in the next few years.

Substance P diminishes lipopolysaccharide and interferon-gamma-induced TGF-beta 1 production by cultured murine macrophages

Recent evidence has demonstrated the importance of substance P and its receptor in macrophage-mediated inflammatory responses. While previous studies have shown that substance P can augment proinflammatory monokine production, little is known about the effects of this neuropeptide on the production of monokines that might limit inflammation. In the present study we have investigated the effect of substance P treatment on the production of transforming growth factor-beta 1 (TGF-beta 1) in cultured murine macrophages. We report that, while substance P agonist alone elicited increases in TGF-beta 1 mRNA expression and modest increases in TGF-beta 1 secretion, substance P dramatically diminished LPS- or IFN-gamma-induced TGF-beta 1 production. These results suggest a previously unrecognized mechanism where substance P may act as a proinflammatory mediator by limiting the production of excessive levels of TGF-beta 1 by LPS- or IFN-gamma-activated macrophages.

Sensory neuropeptides: their role in inflammation and wound healing

Vasoactive neuropeptides including substance P and calcitonin gene-related peptide (CGRP) are localised in sensory nerves which innervate blood vessels. These are the major vasoactive neuropeptides released from sensory nerve endings and both have been suggested to have roles in inflammatory and cardiovascular disease. The neuropeptides have potent effects on microvascular tone and permeability, which are seen soon after release from perivascular nerves. There is also evidence that neuropeptides can affect various activities of inflammatory cells and that sensory nerves play a role in the recovery of the healthy microcirculation during wound healing phases. This review concentrates on evidence that the neuropeptides substance P, acting via tachykinin NK1 and NK2 receptors, and CGRP, acting via CGRP1 receptors, play a pro-inflammatory role in disease and a beneficial role in wound healing. In addition, results from clinical trials of recently developed neuropeptide antagonists are discussed.

Dental innervation: functions and plasticity after peripheral injury

Oral tissues including the periodontal ligament, gingiva, and tooth pulp have a relatively dense sensory innervation and a rich vascular supply. Teeth and supporting tissues are susceptible to tissue injury and inflammation, partly due to lack of collateral blood and nerve supply and to their low compliance. This review focuses on dental nerve functions and adaptive changes in the trigeminal ganglion and tooth pulp after peripheral injuries. An overview of the peptidergic innervation of oral tissues is presented, followed by a discussion of plasticity in neuropeptide expression in trigeminal peripheral neurons after local insults to teeth and peripheral nerve injuries. The functional implications of these adaptive changes are considered, with special reference to nerve regeneration, inflammation, and hemodynamic regulation.

Suppression of substance P biosynthesis in sensory neurons of dorsal root ganglion by prodrug esters of potent peptidylglycine alpha-amidating monooxygenase inhibitors

Substance P as well as many other neuropeptides are synthesized as glycine-extended precursors and converted to the biologically active C-terminal amides by posttranslational modification. The final step of posttranslational processing is catalyzed by peptidylglycine alpha-amidating monooxygenase (PAM). In a previous study, N-substituted homocysteine analogs were found to be potent inhibitors of PAM partially purified from conditioned medium of cultured rat medullary thyroid carcinoma CA-77 cells. These compounds, however, were only modest inhibitors of substance P production in cultured dorsal root ganglion cells, possibly because of poor cell penetration. Several ester derivatives of hydrocinnamoyl-phenylalanyl-homocysteine, one of the most potent PAM inhibitors, were prepared to increase the intracellular accessibility of these compounds. Hydrocinnamoyl-phenylalanyl-(S-benzoyl-homocysteine) benzyl ester was identified as the most potent compound, inhibiting substance P biosynthesis in dorsal root ganglion cells with an IC50 of 2 microM. Inhibition of PAM resulted in a concomitant increase in the glycine-extended substance p (substance P-Gly) precursor peptide. In the presence of 3 microM benzyl ester derivative, the intracellular substance P-Gly level was 2.4-fold higher while the substance P level was 2.1-fold lower than the corresponding peptides in control cells. These results suggest that PAM inhibition represents an effective method for suppression of substance P biosynthesis and, therefore, may have therapeutic utility in conditions associated with elevated substance P levels. Furthermore, PAM inhibition may also prove useful in decreasing other amidated peptides.

Substance P containing nerve fibers in rectal mucosa of ulcerative colitis

BACKGROUND AND PURPOSE

The intestine is rich in peptidergic innervation, which modulates mucosal immune responses. Among neuropeptides, substance P (SubP) has received considerable attention for stimulatory effects on various immunocytes in inflammatory diseases. In our prior study, we demonstrated increased innervation of SubP containing nerve fibers (SubP fibers) in ulcerative colitis (UC) surgically resected colonic specimens. In the present study, we examined the alterations of SubP fibers among various subgroups of UC, divided according to clinicopathologic features.

METHODS

Distribution of SubP fibers were examined immunohistochemically in the rectal biopsy specimens of UC. The UC group was further divided into subgroups according to six clinicopathologic parameters. The linear density of SubP fibers was measured by digitalized morphometry for quantitative analysis.

RESULTS

Multivariate analysis revealed significant correlations between linear density of SubP fibers vs. activity of diseases and total dose of prednisolone. Linear density was significantly increased in active cases of UC (active UC, 22.6 +/- 1.6 microm/1,000 microm2; vs. inactive UC, 12.2 +/- 0.8 microm/1,000 microm2; P < 0.01). Furthermore, the increase was pronounced in cases that showed persistent inflammation and, accordingly, needed a high dose or continuous administration of prednisolone.

CONCLUSION

Alterations in SubP fibers appear to play an important role in the pathogenesis of UC.

Number, distribution and neuropeptide content of rat knee joint afferents

Retrograde tracing with Fluoro-Gold was used to identify the complete population of knee joint afferents in the lumbar dorsal root ganglia of adult female Wistar rats. There was an average of 581 +/- 31 (mean +/- S.D.) afferents supplying each joint. These were found distributed from L1 to L5 with the great majority localised in the L3 and L4 ganglia. Electron microscopy of the posterior articular nerve of the knee revealed an average of 103 +/- 15 (mean +/- S.D.) myelinated and 513 +/- 39 unmyelinated axonal profiles. Since about 50-60% of the unmyelinated profiles would be expected to be sympathetic efferents, these numbers are consistent with the numbers of afferents found by Fluoro-Gold retrograde tracing and suggest that the posterior articular nerve contains about 50% of the total number of knee joint afferents in the rat. Immunohistochemistry revealed that an average of 10% of identified joint afferents expressed substance P-like immunoreactivity and that 33% expressed calcitonin gene-related peptide-like immunoreactivity.

Differential roles of neurokinin 1 and neurokinin 2 receptors in the development and maintenance of heat hyperalgesia induced by acute inflammation

1. Following induction of acute inflammation by intraarticular injection of kaolin and carrageenan into the knee joint in rats, there was a significant decrease in the withdrawal latency to radiant heat applied to the paw (i.e. heat hyperalgesia), an increased joint circumference and increased joint temperature. 2. A neurokinin1 (NK1) receptor antagonist (CP-99,994, 10 mM) had no effect on the paw withdrawal latency when it was administered spinally through a microdialysis fibre before the induction of inflammation. Pretreatment with a NK2 receptor antagonist (SR48968, 1 mM) administered spinally through the microdialysis fibre prevented the heat hyperalgesia from developing in the early stages of the inflammation. 3. Post-treatment through the microdialysis fibre with the NK1 receptor antagonist (0.01-10 mM) was effective in reversing the heat hyperalgesia. In contrast, post-treatment spinally with the NK2 receptor antagonist (0.01-1 mM) had no effect on the heat hyperalgesia. The inactive stereoisomers of the NK1 receptor antagonist, CP100,263, or the NK2 receptor antagonist, SR48965, administered at the same doses, had no effect on the joint inflammation or the heat hyperalgesia. 4. Pretreatment systemically with the NK1 receptor antagonist (30 mg kg-1) had no effect on the heat hyperalgesia or pain-related behaviour ratings where 0 is none and 5 is non weight bearing and complete avoidance of limb contact. Pretreatment with a NK2 receptor antagonist (10 mg kg-1) systemically prevented the heat hyperalgesia and pain-related behaviour ratings from developing in the early stages of the inflammation. The inactive stereoisomers of NK1 receptor antagonist, CP100,263, or the NK2 receptor antagonist, SR48965, administered at the same doses, had no effect on the joint inflammation or the heat hyperalgesia. 5. Post-treatment systemically with either the NK1 (0.1-30 mg kg-1) or the NK2 (0.1-10 mg kg-1) receptor antagonist resulted in a dose-dependent reversal of the heat hyperalgesia. Pain-related behaviour ratings were reduced by post-treatment only with the NK1 receptor antagonist. The inactive stereoisomers of the NK1 receptor antagonist, CP100,263, or the NK2 receptor antagonist, SR48965, administered at the same doses, had no effect on the behavioural responses. 6. Direct pretreatment of the knee joint with either the NK1 (30 mg) or the NK2 (10 mg) receptor antagonist prevented the heat hyperalgesia from developing without affecting joint swelling. The inactive stereoisomers of the NK1 receptor antagonist, CP100,263, or the NK2 receptor antagonist, SR48965, administered at the same doses, had no effect on the joint inflammation or the heat hyperalgesia. 7. There appears to be a differential role for the spinal tachykinin receptors in the development and maintenance of the heat hyperalgesia associated with acute joint inflammation. The NK2 receptors appear to be activated early in the development of the heat hyperalgesia and NK1 receptors are involved in the maintenance of the heat hyperalgesia. 8. Peripherally, both NK1 and NK2 receptors are involved in the development of heat hyperalgesia and pain-related behaviour ratings induced by acute inflammation.

Tribological evaluation of oxidized zirconium using an articular cartilage counterface: a novel material for potential use in hemiarthroplasty

Problems with total joint replacement that have surfaced in recent years have made reconsideration of more conservative hip reconstructive procedures compelling. Moreover, procedures such as hemiarthroplasty might benefit from newly developed materials that could provide more favourable tribological performance when employed as a counterface for articulation with articular cartilage. The objective of this study was to evaluate the tribology of a new biomaterial, oxidized zirconium, with articular cartilage in a laboratory test apparatus. Oxidized zirconium components are produced by oxidizing the zirconium alloy to form a relatively thick (7 microns), adherent, abrasion-resistant ceramic surface. We found that the coefficient of friction of bovine articular cartilage rubbed against oxidized zirconium was lower than with cobalt-chromium alloy control surfaces, and that there was a trend toward less wear with oxidized zirconium. A defined layer of degraded tissue was found on the surface of the articular cartilage specimens, providing some indication of the mechanism of wear. Results of this study warrant further investigation of oxidized zirconium as the bearing surface for hemiarthroplasty.

Involvement of calcium-activated potassium channels in the inhibitory prejunctional effect of morphine on peripheral sensory nerves

We examined the contribution of potassium channels to the inhibitory effect of morphine on the increase in substance P release and cutaneous blood flow evoked by antidromic stimulation of the sectioned sciatic nerve. Cutaneous blood flow in the instep of the rat hind paw was measured by the non-invasive technique of laser Doppler flowmetry. Antidromic stimulation of the sectioned sciatic nerve caused a biphasic flow response, an initial transient decrease followed by an increase and an increase in substance P release into the subcutaneous perfusate of the instep of the rat hind paw. Both the increases of substance P release and cutaneous blood flow evoked by antidromic stimulation of the sectioned sciatic nerve were significantly inhibited by intra-arterial (i.a.) infusion of morphine (30 mumol/kg). This inhibitory effect of morphine was antagonized by pretreatment with naloxone (2 mg/kg, i.p.) or potassium channels blockers such as tetraethylammonium (40 mg/kg, i.v.). apamin (0.5 mg/kg, i.v.) and charybdotoxin (0.12 mg/kg. i.v.) but not with cesium chloride (85 mg/kg, i.v.) and glibenclamide (25 mg/kg, i.v.). These results suggest that the calcium-activated potassium channels may be involved in the prejunctional inhibitory effects of morphine in the hind instep of rats.

Neuroimmunomodulation via limbic structures--the neuroanatomy of psychoimmunology

During the last 20 years, mutual communications between the immune, the endocrine and the nervous systems have been defined on the basis of physiological, cellular, and molecular data. Nevertheless, a major problem in the new discipline "Psychoneuroimmunology" is that controversial data and differences in the interpretation of the results make it difficult to obtain a comprehensive overview of the implications of immunoneuroendocrine interactions in the maintenance of physiological homeostasis, as well as in the initiation and the course of pathological conditions within these systems. In this article, we will first discuss the afferent pathways by which immune cells may affect CNS functions and, conversely, how neural tissues can influence the peripheral immune response. We will then review recent data, which emphasize the (patho)physiological roles of hippocampal-amygdala structures and the nucleus accumbens in neuroimmunomodulation. Neuronal activity within the hippocampal formation, the amygdaloid body, and the ventral parts of the basal ganglia has been examined most thoroughly in studies on neuroendocrine, autonomic and cognitive functions, or at the level of emotional and psychomotor behaviors. The interplay of these limbic structures with components of the immune system and vice versa, however, is still less defined. We will attempt to review and discuss this area of research taking into account recent evidences for neuroendocrine immunoregulation via limbic neuronal systems, as well as the influence of cytokines on synaptic transmission, neuronal growth and survival in these brain regions. Finally, the role of limbic structures in stress responses and conditioning of immune reactivity will be commented. Based on these data, we propose new directions of future research.

Neurohumoral mechanisms in rheumatoid arthritis

The observation that following stroke or peripheral nerve injuries the development of rheumatoid arthritis is either prevented or ameliorated in the affected limb was the first observation of the involvement of the neurological system in the pathogenesis of the disease. Much subsequent work has established that there are intimate and intricate associations between the central nervous system, the endocrine system and immuno-inflammatory mechanisms. The predominant interaction is through the hypothalamic-pituitary adrenal axis which mediates the secretion of corticotrophin releasing hormone which then stimulates the pituitary to release ACTH. A subsequent stimulation of the adrenal cortex leads to glucocorticoid release with their known potent anti-inflammatory effects. Many factors can interact within the central nervous system to modify this pathway. Of particular relevance is the observation that the hypothalamic-pituitary adrenal axis may be defective in rheumatoid arthritis. This has implications not only in terms of pathogenesis but also in the way in which glucocorticoids are used for the treatment of rheumatoid arthritis.

Peripheral beta-endorphin in rheumatoid arthritis. A correlation with the disease activity

Beta-endorphin is a neuroendocrine peptide, with morphine-like effects, produced by anterior pituitary, cells of the immune system, and synovial cells. The clinical significance of Plasma Beta-endorphin was investigated in a well characterized cohort of 20 RA patients and 10 healthy controls. Beta-endorphin extraction and concentration were carried out according to Wardlaw. Plasma Beta-endorphin assay was measured as described by Naber. Plasma Beta-endorphin levels in severe RA patients were significantly lower (16.1 +/- 6.2 pg/ml) than in mild RA patients (45.4 +/- 2.8 pg/ml), P < 0.0001. The mean serum levels of Beta-endorphin were also significantly lower in both RA groups than those in normal controls (62.1 +/- 5.7 pg/ml), P < 0.001. The results indicate that there is an inverse correlation with the plasma Beta-endorphin levels, the rheumatoid disease activity score, and the duration of RA. The depressed plasma Beta-endorphin in patients with RA may be used as an indicator of the disease activity.

Effects of substance P on human T cell function and the modulatory role of peptidase inhibitors

Evidence has been presented for a modulatory role of surface peptidases on substance P-mediated immune responses. In this study, we first characterized the effects of substance P and its carboxy- and amino-terminal fragments on human lymphocyte proliferative responses to investigate whether peptidase inhibitors influence the effects of the neuropeptide. Substance P at 10(-7) M and the carboxy-terminal fragment SP(4-11) slightly enhanced the lymphocyte responses to phytohemagglutinin and concanavalin A. In contrast, the amino-terminal fragment SP(1-4) failed to have any positive effect. However, in the presence of dipeptidylpeptidase IV/CD26 and neutral endopeptidase/CD10 inhibitors (diprotin A and thiorphan, respectively), the effect of substance P on mitogen-induced proliferation was significantly increased. These data support the hypothesis that lymphocyte surface peptidases play a modulatory role in the effects of substance P on T cell function.

Psychoneuroimmunology: animal models of disease

OBJECTIVE

Psychoneuroimmunology, which investigates the bidirectional communication between the central nervous system and the immune system, has been greatly advanced by the use of animal models. The objective of this paper is to describe animal models of disease that can or might be utilized to elucidate neural-immune interactions that alter pathogenesis.

METHODS

This paper reviews animal studies that have demonstrated a link among the brain, behavior, immunity, and disease, highlighting models in which the potential contribution of CNS-immune interactions has not yet been explored.

RESULTS

Animal studies allow for careful control of environmental stimuli, genetic background, and immunological challenge. As such, they are an important component of psychoneuroimmunology research. Models in which one might study the role of psychosocial factors in immunologically mediated disease processes, as in the case of other pathophysiologic processes, profit from an ability to manipulate both stressful events and the magnitude of the challenge to the immune system.

CONCLUSIONS

Animal studies in psychoneuroimmunology highlight the complexity of the interactions among behavior, the brain, the immune system, and pathogen. The genetic background of the animal (both in terms of central nervous and immune system responses), its previous history, the nature of the stressor, the nature of the pathogen and the type of immune response generated are some of the interacting factors that determine the magnitude and direction of stress-induced changes in disease outcome.

Intra-articular tenoxicam relieves post-arthroscopy pain

BACKGROUND

Nonsteroidal anti-inflammatory drugs have been documented to be effective in the treatment of postoperative pain. The aim of this study was to evaluate the analgesic effect of local intra-articular injection of tenoxicam compared with intravenous injection on postoperative pain after arthroscopy.

METHODS

After day-case arthroscopy, 60 patients were randomized to receive either tenoxicam 20 mg in 20 ml of normal saline intra-articularly and 2 ml of normal saline i.v., or 20 ml of normal saline intra-articularly and 2 ml tenoxicam 20 mg i.v. Postoperative pain was assessed using a visual analogue scale and measuring analgesic requirements.

RESULTS

Pain scores were significantly lower in the intra-articular group at rest and during active flexion of the knee at 1, 2 and 4 hours postoperatively and during walking at 6 hours postoperatively (P < 0.05). Significantly more patients in the intravenous group required supplemental opioid analgesia within the first 4 hours postoperatively (P < 0.05).

CONCLUSION

Intra-articular tenoxicam 20 mg provided better analgesia and decreased the requirements for postoperative analgesic compared with i.v. tenoxicam 20 mg.

[Projections and fiber characteristics of sensory afferents of the anterior cruciate ligament in an animal experiment]

The sensory innervation of the rabbit anterior cruciate ligament was studied by retrograde tracing technique using wheat-germ-agglutinin-horseradish-peroxidase (WGA-HRP) and Fast Blue as neuronal tracers. Injection of the tracer into the ligament was followed by histo- and immunohistochemical investigation of labelled nerve cell bodies located in the dorsal root ganglia. In 4 animals we injected the tracer into the joint cavity to label general joint afferents. The segmental distribution of retrogradely labelled neurons following injection into the anterior cruciate ligament (L6, L7, S1) is significantly different from the distribution pattern after injection into the knee joint (L4-S2). Retrogradely labelled nerve cells innervating the anterior cruciate ligament were further investigated using immunohistochemical and morphometric analysis. The sensory innervation of the anterior cruciate ligament is therefore comprised of at least 2 different qualities of sensory afferent nerves: 1. Small neurones immunoreactive to the inflammatory peptide substance P most likely transmitting nociceptive information centrally (44%). 2. Large, presumably fast conducting A-fibre-afferents characterized by neurofilament proteins transmitting proprioceptive information from corpuscular mechanoreceptors (43%). The results of this study put further weight to the importance of the sensory role of the anterior cruciate ligament using neuroanatomical and immunohistochemical techniques.

Sensory nerve supply in the human subacromial bursa

The subacromial bursa is the major component of the subacromial gliding mechanism. The neural elements of the subacromial bursa obtained from specimens that underwent autopsy and surgery were investigated by the silver impregnation and immunohistochemical methods with antisera to substance P and calcitonin gene-related peptide; which are considered to be involved in nociceptive transmission, and protein gene product 9.5. Free nerve endings, Ruffini endings, Pacinian corpuscles, and two kinds of unclassified nerve endings were observed. Most of these receptors were observed of the roof side of the coracoacromial arch, which is exposed to stress because of the impingement. A delta and C fibers, thought to be nerve fibers of free nerve endings, were immunoreactive to substance P and calcitonin gene-related peptide. On the other hand, thick fibers thought to originate in encapsulated mechanoreceptors were not immunoreactive to substance P. The subacromial bursa receives nociceptive stimuli and proprioception and seems to regulate appropriate shoulder movement.

Suppression of adjuvant arthritis by kappa-opioid receptor agonist: effect of route of administration and strain differences

It is well established that kappa-opioid receptor agonists exert antiinflammatory and antihyperalgesic effects during nonspecific inflammation as well as suppressive effects on the development of humoral and cell-mediated immune responses to foreign antigens. The aim of this study was to investigate the ability of the kappa-opioid receptor agonist MR 2034 to modulate adjuvant arthritis in the rat. In the first series of experiments, treatments of Wistar rats were performed using several routes of drug administration: intraperitoneal (ip), intracaudal (ic), intracerebroventricular (icv) and intraplantar (ipl). MR 2034 significantly suppressed joint swelling after ip and ic treatment, slightly reduced inflammation after ipl treatment, and did not produce any effect after icv treatment. In the second series of experiments, the suppressive effect of ip injected MR 2034 was investigated using Wistar, Dark August (DA) and Lewis rats. In Wistar rats, MR 2034 significantly decreased the incidence of adjuvant arthritis, and suppressed mean joint score and aggregate joint score. Similarly, in DA rats treated with MR 2034, mean arthritic score was significantly suppressed, but other clinical parameters were not affected. In Lewis rats, however, ip treatment with MR 2034 failed to produce any suppressive effect on joint disease and even potentiated the initial development of arthritis. These data suggest that immunosuppressive and antiinflammatory action of MR 2034 markedly depend on the route of drug administration and strain susceptibility to opioids.

A model for experimental induction of acute temporomandibular joint inflammation in rats: effects of substance P(SP) on neuropeptide-like immunoreactivity

This is a study of neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)- like immunoreactivity(-LI) in the cerebrospinal fluid (CSF), plasma and perfusates (PF) from the temporomandibular joints (TMJs) of the rat during acute inflammation. Substance P (10(-5) M, 0.01 ml) was injected into the right TMJ of the rat. The TMJs of the control rats, were injected with 0.01 ml saline. CSF, plasma and PF from TMJs were taken at 2, 6 and 24 hrs following injection. The neuropeptide-LI level was analysed by specific radioimmunoassays and compared with control values. Unilateral injection of SP into the rat TMJ resulted in a general increase in the concentration of NKA-, CGRP- and NPY-LI in the TMJ PF at 2, 6 and 24 hrs following injection. In the CSF NKA- and CGRP-LI was increased leaving the NPY-LI unaffected. In general no changes in peptide concentrations were seen in plasma. The results indicate that SP directly or indirectly induces a local release of peptides through an action at sensory and sympathetic neurons.

Substance P and capsaicin-induced mechanical hyperalgesia in the rat knee joint; the involvement of bradykinin B1 and B2 receptors

1. Substance P (SP) and capsaicin induced a mechanical hyperalgesia when injected into rat knee joints. 2. The NK1 receptor antagonists CP 99994 (10-100 nmol) and RP 67580 (0.1-1 nmol) blocked the development of, and also reversed, SP-induced hyperalgesia. Capsaicin (10 nmol)-induced hyperalgesia was blocked by capsazepine (0.5-5 nmol). 3. Capsaicin-induced hyperalgesia was prevented and reversed by the NK1 receptor antagonists CP 99994 (100 nmol) and RP 67580 (1 nmol). 4. The bradykinin B2 receptor antagonist icatibant (5 pmol) blocked the development of both SP and capsaicin-induced hyperalgesia. Icatibant (100 pmol kg-1, i.v.) also reversed an established SP and capsaicin-induced hyperalgesia. 5. Both low dose SP (1 nmol) and capsaicin (1 nmol)-induced hyperalgesia were potentiated by the kininase II inhibitor captopril (100 micrograms). 6. The B1 receptor antagonists desArg9Leu8-bradykinin (BK) (0.5-5 nmol) and desArg10[Hoe 140] (5-50 pmol) only blocked the development of SP-induced hyperalgesia for 30 min after administration. desArg9Leu8-BK (10 nmol kg-1 i.v.) did not reverse an established SP-induced hyperalgesia. 7. Capsaicin-induced hyperalgesia was blocked by desArg9Leu8-BK (0.5 nmol) and this antagonist also reversed an established capsaicin-induced hyperalgesia. 8. Interleukin-1 receptor antagonist (IL-1ra 0.1 microgram) reduced the development of SP-induced hyperalgesia up to 4 h after administration, but did not reverse an established hyperalgesia. IL-1ra (0.1 microgram) also blocked the development of and reversed an established capsaicin-induced hyperalgesia. 9. Indomethacin pretreatment (1 mg kg-1, s.c.) did not reduce the development of either SP- or capsaicin-induced hyperalgesia but following indomethacin-pretreatment desArg9Leu8-BK (10 nmol kg-1, i.v.) failed to reverse a capsaicin-induced hyperalgesia. 10. In conclusion, both SP and capsaicin can induce behavioural hyperalgesia when injected into the knee joint of rats. In addition, blockade of NK1, bradykinin B1, B2 and IL-1 beta receptors can substantially modulate this hyperalgesia.

Approach to the management of nonmalignant pain

Pain is a universal, subjective, unpleasant sensation. It results from a noxious stimulus that causes the body to perceive existing or potential damage to its organs. The biochemical mechanism of pain is based on peripheral nociceptors that preferentially receive noxious stimuli and thereafter cause the primary afferent nociceptor fibers to release endogenous chemicals such as bradykinin, histamine, prostaglandins, serotonin, norepinephrine, and substance P. Additionally, substance P may stimulate prostaglandin and collagenase production, thus providing an explanation for the effectiveness of anti-inflammatory drugs in relieving pain. The interpretation of pain is highly individualized and embodies the entire personality. Thus, no two patients with pain can be treated in the same way. Pain is assessed through medical history, physical examination, and a variety of pain scales. General principles in managing pain call for the physician to (1) respect pain; (2) recognize the psychologic components of pain; and (3) treat the underlying disorder in a timely fashion. Modern management of pain evokes a multidisciplinary approach that includes patient education, pharmacologic intervention, physical medicine, minimally invasive procedures, psychologic counseling, behavioral modification and, in some instances, surgery or a variety of other nonpharmacologic modalities.

Endogenous substance P mediates cold water stress-induced increase in interleukin-6 secretion from peritoneal macrophages

Previous studies from this laboratory had shown that exposure of mice to cold water stress leads to an increase in the secretion of interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF alpha) from their peritoneal macrophages. We now report that the secretion of IL-6 from peritoneal macrophages is also increased after cold water stress and that the peptide substance P (SP) participates in this stress-induced response. The stress paradigm involved subjecting male C57BL/6J mice to 5 min swim tests in 10 +/- 2 degrees C water twice daily for 4 d. Cold water stress augments the lipopolysaccharide-induced IL-6 secretion from peritoneal macrophages, elevates immunoreactive SP (iSP) in the peritoneal wash fluid, and reduces iSP in certain peritoneum-containing tissues or organs (i.e., diaphragm, abdominal wall, ileum, and rectum). The 10 d stress time studies indicate that increased IL-6 secretion is positively related to elevated iSP in the peritoneal wash fluid and inversely related to reduced iSP in certain peritoneum-containing tissues. Pretreatment with capsaicin, which depletes SP in the sensory nerve endings, eliminates stress-control differences in the peritoneal wash fluid and in certain peritoneal tissues. Moreover, RP67,580, a specific SP antagonist, eliminates the cold water stress-induced augmentation of IL-6 secretion from peritoneal macrophages. These results suggest that cold water stress promotes the release of SP from peritoneal tissues into the peritoneal cavity, where it participates in the cold water stress-induced macrophage functional alterations.

Effects of adjuvant on neuropeptide-like immunoreactivity in experimentally induced temporomandibular arthritis in rats

Substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivities (-LI) were examined in cerebrospinal fluid (CSF), plasma and temporomandibular joint (TMJ) perfusates in rats 1 and 12 h after inoculation at the base of the tail (0.05 ml) or injection into the right TMJ (0.01 ml) of heat-killed Mycobacterium butyricum in paraffin oil. In the rats inoculated at the base of the tail (polyarthritic rats), there was a significant increase of CGRP-LI and NKA-LI. The changes in neuropeptide-LI were not as marked in the CSF of rats injected with adjuvant in one TMJ (monoarthritic rats) as in the polyarthritic group. Instead, the most significant changes in the monoarthritic rats were seen in the perfusates of both TMJs. The increases in SP-, NKA-, CGRP- and NPY-LI were significant for both TMJs and more pronounced than in the polyarthritic rats. The results show that inoculation of adjuvant at the base of the tail induces significant changes of neuropeptide-LI predominantly in CSF, whilst an intra-articular injection induces bilateral changes in neuropeptide-LI in joint perfusate. Therefore, two different neural mechanisms may be involved early in adjuvant-induced poly- and monoarthritis.

Increased substance P receptor expression by blood vessels and lymphoid aggregates in Clostridium difficile-induced pseudomembranous colitis

Pseudomembranous colitis is most often caused by toxins secreted by Clostridium difficile following bowel flora overgrowth after antibiotic use. The secretory and inflammatory effects observed in C. difficile toxin A-induced enterocolitis in the rat ileum are inhibited by CP-96,345, a substance P (SP) receptor antagonist. To determine if SP plays a role in the pathogenesis of human pseudomembranous colitis, SP receptor distribution was examined in a toxin A-positive specimen of bowel. Quantitative receptor autoradiography was used to examine SP receptors in tissue from a patient who tested positive for C. Difficile toxin. SP receptors were massively increased in small blood vessels and lymphoid aggregates in the pseudomembranous colitis bowel in comparison to control specimens. The SP binding was saturable and exhibited similar affinities for SP and CP-96,345. SP may contribute to the inflammatory response in pseudomembranous colitis via a massive increase in SP receptor antagonists may offer a novel therapeutic intervention for pseudomembranous colitis.

The effect of intra-articular capsaicin on nerve fibres within the synovium of the rat knee joint

The aim of this study was to establish the effects of intra-articular capsaicin (pelargonic acid vallinylamide) on synovial innervation of the rat knee. Rats were sacrificed 1, 2, 4 and 7 days after intra-articular injection of capsaicin and joint tissues stained with either conventional haematoxylin and eosin (H and E) or with specific antibodies to the calcitonin gene-related peptide (CGRP), substance P (both of which are markers for primary afferent fibres), the C-flanking peptide of neuropeptide Y (CPON) (localised in postganglionic sympathetic fibres), or protein gene product 9.5 (a pan-neuronal marker). At lower concentrations (0.1% and 0.25%), capsaicin produced no change in peptide staining pattern or histological appearance. At 0.5% capsaicin, there was complete loss of nerve fibres showing positive staining for CGRP and substance P at all time points. Staining for CPON and protein gene product 9.5 was still present, but decreased, 1 and 2 days after treatment and virtually absent at 4 and 7 days. These findings provide evidence for partially selective denervation induced by 0.5% capsaicin, in contrast to 1% capsaicin which abolished staining for all peptide markers, indicating a total ablation of nerve fibres. A consistent but unexpected finding was the presence of a severe inflammatory response in joints treated with 0.5% and 1% capsaicin. An influx of polymorphonuclear leucocytes was found to occur within 4 h of injection, with progressive appearance of mononuclear cells after this time. We conclude that it is difficult to specifically deplete sensory nerve fibres from the synovium by means of local capsaicin injection. Although selective loss of staining for sensory nerve fibres could be achieved by injection of 0.5% capsaicin, there was progressive non-specific loss of post-ganglionic autonomic fibres which may be related to the severe inflammatory response provoked by the higher doses of capsaicin.

Application of 6-hydroxydopamine into the fatpads surrounding the draining lymph nodes exacerbates adjuvant-induced arthritis

Adjuvant-induced arthritis (AA) was examined in Lewis rats following local injection of 6-hydroxydopamine (6-OHDA) into the fatpads of the popliteal and inguinal lymph nodes which drain the hindlimbs (DLN). This method of 6-OHDA treatment resulted in noradrenergic (NA) denervation of DLN, spleen, and other organs in the peritoneal cavity, while sparing NA nerve fibers in the hindlimbs. Sympathectomy exacerbated the inflammation and osteopathic destruction of arthritic joints. Significant increases in dorsoplantar width in arthritic rats following denervation were observed by day 27 following immunization compared to nondenervated arthritic animals. Radiographic evaluation on day 27 after immunization confirmed the inflammation of soft tissue and revealed deterioration of bones of the ankle joint in both AA groups compared with the control groups; more extensive joint damage was apparent in arthritic rats following denervation compared to nondenervated arthritic rats. These findings suggest that the NA innervation of DLN and spleen (and possibly other organs of the peritoneal cavity) plays a regulatory role in the expression of AA. These data supports the hypothesis that absence of NA innervation in lymphoid organs during initiation, onset, and progression of the disease results in exacerbation of AA.

Substance P and stress-induced changes in macrophages

The present paper further links nervous-endocrine-immune systems by describing influences of SP on the immune system, and more specifically, on macrophage function. We have discussed how macrophages are important to immune responses in that much of cellular and humoral responses depend on macrophage function. Macrophages are sensitive to stress in that cold-water stress causes increased cytokine production, either spontaneously (IL-1), or after induction with LPS (IL-6, TNF alpha). Increased cytokine levels (IL-1, IL-6) may induce acute phase reactants in the liver, which is presumably the mechanism operative in the studies indicating increases in acute phase reactants after certain stressors in animals. SP is a likely candidate to affect immune function. Previous data show that macrophages from various species have receptors for and respond to SP in vitro. SP stimulates phagocytic and chemotactic capacity, as well as increased cytokine, PGE2, and thromboxane B2 production. SP is also involved in neurogenic inflammation and is likely to be involved in the pathogenesis of several inflammatory diseases. Present data indicate SP's involvement in macrophage responses to stress. We have shown that stress induced differential SP receptor binding to peritoneal macrophages, although the precise nature of binding differences has not yet been clearly elucidated. Stress also induces more immunoreactive SP in the peritoneal fluid that bathes the peritoneal macrophages. We hypothesize that the two events, altered SP binding and concomitant increased ligand, are causally related. In addition to other correlational data showing concomitant increased SP binding plus ligand concentrations, there is more direct evidence that SP ligand may induce SP receptor expression since the SP antagonist, CP-96,345, prevents the induction of SP receptor mRNA in the staphylococcal toxin A-induced gastroenteritis (C. Pothoulakis and S. E. Leeman, personal communication). Further supporting our notion for a causal relationship we have found the elimination of SP in vivo (via capsaicin pretreatment) reduced SP binding, as has been previously reported. We have also examined the role of SP on stress-induced altered macrophage function in vitro. SP greatly enhanced the LPS-induced macrophage TNF alpha production from stressed animals; in contrast, it produced relatively little effect on macrophages from control animals. Capsaicin pretreatment diminished the enhanced cytokine production in response to stress, such that levels of TNF alpha and IL-6 approximated those of control mice. Taken together, past and present data suggest that (1) stress may initiate, or at least contribute to, an inflammatory response, and that (2) SP is involved in the macrophage stress response. SP has long been known to be involved in inflammatory processes; our data further suggest its role in mediating stress-induced cytokine alterations.

The effect of a unilateral inflammation at the rat's ankle joint on the expression of preprotachykinin-A mRNA and preprosomatostatin mRNA in dorsal root ganglion cells--a study using non-radioactive in situ hybridization

In rats with an acute (2 days) and chronic (20 days) unilateral ankle joint inflammation (induced by Freund's complete adjuvant), the proportion of dorsal root ganglion cells containing preprotachykinin-A mRNA or preprosomatostatin mRNA was determined using non-radioactive in situ hybridization. At the acute stage of inflammation, the proportion of neurons containing preprotachykinin-A mRNA was similar to that in control rats. At the chronic stage, the proportion of neurons expressing preprotachykinin-A mRNA was significantly higher on the inflamed side than on the contralateral side. The proportion of dorsal root ganglion cells containing preprosomatostatin mRNA did not change. These data suggest that inflammation influences the synthesis of substance P but not of somatostatin in afferent neurons.

Plasma and synovial fluid interleukin-1, interleukin-6 and substance P concentrations in rheumatoid arthritis patients: effect of the nonsteroidal anti inflammatory drugs indomethacin, diclofenac and naproxen

We performed an open, between patients, placebo controlled study in order to evaluate the effect of the treatment with the non steroidal anti inflammatory drugs indomethacin, diclofenac and naproxen on the concentrations of the cytokines IL-1 beta and IL-6 and of the neuropeptide substance P in plasma and synovial fluid of 24 rheumatoid arthritis patients. All patients had high synovial fluid cytokine and substance P levels, and high plasma cytokine levels at the beginning of the study. The treatment with the non steroidal anti inflammatory drugs significantly decreased both plasma and synovial fluid IL-6 and synovial fluid substance P in comparison to placebo, but did not affect IL-1 beta concentrations. This effect can participate in the therapeutic effect of non steroidal anti inflammatory drugs in rheumatoid arthritis.

Effects of the neuropeptide, substance P, on lymphocyte proliferation in rheumatoid arthritis

There is evidence supporting the involvement of the neuropeptide, substance P, in the pathogenesis of rheumatoid arthritis. In view of the suggested role of T-cells in this disease, we have investigated the effects of substance P on mitogen-induced lymphocyte proliferation in rheumatoid arthritis patients. The peripheral blood mononuclear cells from 20 patients with rheumatoid arthritis and 25 controls were cultured in the presence or absence of substance P (10(-10) M to 10(-6) M) and stimulated with phytohaemagglutinin or concanavalin A. After 3 days of culture the proliferative responses were determined by measuring [3H]thymidine incorporation into the cells. Substance P enhanced, in a dose-dependent manner, the lymphocyte proliferative responses both in rheumatoid arthritis patients and in controls. Although there was a trend towards a greater enhancing effect in the rheumatoid arthritis patients, this was not statistically significant. Some individual patients with rheumatoid arthritis showed enhancements of lymphocyte proliferation with substance P that were clearly outside the range seen in healthy controls. The possibility that substance P has a role in the pathogenesis of rheumatoid arthritis through the up-regulation of lymphocyte activation should be considered in further studies of the immunomodulatory properties of substance P in arthritis.

Projections of ankle joint afferents to the spinal cord and brainstem of the chicken (Gallus g. domesticus)

The projections of the ankle joint capsule afferents were studied by transganglionic transport of horseradish peroxidase injected directly into the ankle joint. The number and size of the labelled dorsal root ganglion cells were measured from synsacral nerves 2-9. In the dorsal root ganglia, all sizes of sensory neurones were labelled, and the largest number of labelled cells was in ganglia 5-7. The extensive sympathetic innervation of the ankle joint was identified by the large number of cell bodies labelled in the sympathetic ganglia of the paravertebral chain. Labelled afferent fibres projected to the spinal cord from the 2nd to the 8th synsacral nerves, with the rostral projection mainly via Lissauer's tract and the dorsal funiculus. Terminal labelling in the dorsal horn was identified in laminae I-III and VI, with a slight projection to V. Two areas of dense labelling, which did not correspond with the largest number of labelled dorsal root ganglion cells, were identified. A rostral area with the highest density of label was observed at the level of synsacral nerves 3-4 and a second slightly less dense area between synsacral nerves 7-8. In the caudal medulla, diffuse terminal labelling was observed in the nucleus gracilis et cuneatus, nucleus of the tractus solitarius, and the nucleus cuneatus externus. These results are discussed in a comparative context to identify similarities and differences between different primary afferent projections in birds and mammals and to highlight the possible functional significance of the avian articular afferent projection.

Endogenous substance P inhibits the expression of corticotropin-releasing hormone during a chronic inflammatory stress

We have investigated the effects of a chronic inflammatory stress on substance P (SP) levels in the hypothalami of rats given adjuvant-induced arthritis (AA). Fourteen days after injection of Mycobacterium butyricum, substance P concentrations in the paraventricular nucleus (PVN) and median eminence/arcuate nucleus were significantly increased. In AA rats injected intraperitoneally with the specific neurokinin-1 receptor antagonist RP67580, plasma ACTH and corticosterone concentrations were significantly elevated, and corticotropin-releasing hormone (CRH) mRNA in the PVN was increased compared to the AA group which received saline alone. The increases in hypothalamic SP in AA, together with the data demonstrating that HPA axis activity is enhanced in AA following injection of a SP antagonist, are consistent with the hypothesis that SP is acting as an inhibitor of CRH expression in this model of chronic inflammatory stress.

Synthesis and biological evaluation of novel NK-1 tachykinin receptor antagonists: the use of cycloalkyl amino acids as a template

In the course of a program aimed at synthesizing novel, potent NK-1 tachykinin receptor antagonists, we developed upon a bioactive model by comparing the low energy structures of a series of peptide and nonpeptide Substance P antagonists. The comparison was based on the superimposition of the aromatic rings, assuming that the rest of the molecule behaves predominantly as a template to arrange the key aromatic groups in the right spatial position. A series of 2-aminocyclohexane carboxylic acid analogues were then selected as the best templates for reproducing the postulated bioactive structure, leading to several pseudo-peptides with interesting biological activity. According to the molecular modeling, these compounds exhibit a neat parallel facing of the indolyl and naphthyl groups at about 3 A distance. Ultraviolet absorption and steady state fluorescence measurements support this conclusion, showing a linear correlation between the spectral properties and the binding affinity of these analogues. Stacking of the indole ring with naphthalene gives rise to a complex characterized by a well-defined molar extinction coefficient. Consistently, steady state and lifetime fluorescence measurements suggest that the quenching process is ascribable to ground-state interactions between the chromophores. Implications of the pi stacking propensity of aromatic groups in the biological activity of the compounds examined are briefly discussed.

Substance P gene expression in acute experimental colitis

We have previously shown (Gastroenterology, 101 (1991) 1211-1219), that substance P (SP) decreases early in the colon muscle layer after induction of colitis in rabbits. Since the SP content in the colonic muscle layer was unchanged by sensory denervation with capsaicin, we assume that SP is located predominantly in intrinsic neurons of the colon, and that the decrease of SP during inflammation reflects changes in intrinsic SP content. However, damage of SP neurons by inflammation would be another likely explanation for the decrease in SP content. The aim of this study was to determine SP gene expression in intrinsic (colonic muscle layer) and extrinsic (dorsal root ganglia, DRG) neurons to prove that SP transcription is preserved during colitis as an indicator of neuronal integrity. Colitis was induced in adult white New Zealand rabbits by formalin enemas (4 ml of 0.4% formalin) followed by 0.85 ml immune complex i.v. 2 h later. The animals were sacrificed 48 h after induction of colitis, and SP content and gene expression were determined by radioimmunoassay (RIA) and Northern blot analysis, respectively. Immunoreactive SP was reduced by 40% in the colon muscle layer and by 60% in the dorsal root ganglia (L4-S4) in the animals with colitis compared to controls without colitis. In contrast to the protein data, SP gene expression was not significantly altered in the colon muscle layer and the dorsal root ganglia 48 h after induction of inflammation compared to the control tissue. The preserved SP gene expression suggests that the intrinsic and extrinsic SP neurons are viable in this inflammatory model. The decreases of immunoreactive SP in the colonic extracts and the DRG after induction of colitis suggest that SP is released from extrinsic and intrinsic neurons during inflammation.

Differential expression of substance P receptors in patients with Crohn's disease and ulcerative colitis

BACKGROUND & AIMS

Although clinical and pathological differences exist between Crohn's disease (CD) and ulcerative colitis (UC), distinguishing features are often absent, making diagnosis and treatment problematic. This study evaluated the differences in the expression of substance P (SP) receptors in patients with CD or UC.

METHODS

Tissue samples from patients with inflammatory bowel disease or control patients were obtained at surgery, processed for 125I-SP binding, and analyzed by quantitative autoradiography.

RESULTS

Patients with CD showed a massive increase in SP receptors in lymphoid aggregates, small blood vessels, and enteric neurons of the small and large bowel relative to controls. Six of 16 CD specimens had no pathological evidence of CD yet continued to express high concentrations of SP receptors. Pathologically positive patients with UC showed high concentrations of SP receptors on colonic lymphoid aggregates and small blood vessels but not enteric neurons. No increased SP binding was evident in clinically and pathologically quiescent UC colons and normal UC ileostomy samples.

CONCLUSIONS

The increased expression of SP receptors on the enteric neurons of patients with CD distinguishes CD from UC. The persistent increased SP binding in pathologically normal CD tissue may indicate a subclinical disease state. SP receptor expression may have important diagnostic, etiologic, and therapeutic usefulness in inflammatory bowel disease.

Determination of temporomandibular joint fluid concentrations using vitamin B12 as an internal standard

The aim of the investigation was to test the reproducibility and accuracy of a new method to measure temporomandibular joint (TMJ) fluid concentrations of various substances by saline washing, using exogenous B12 as a marker. An in vitro test was first performed with glucose as a test substance. The difference between a B12-calculated and known standard concentration of glucose was very small. Saline washing of the TMJ was performed on 13 patients having signs of TMJ arthritis, and the aspirates obtained were analyzed for neuropeptide Y-like immunoreactivity (NPY-LI) and interleukin-1 beta (IL-1 beta). Vitamin B12 was mixed with the saline immediately before injection, and a sample of the aspirate was later compared photometrically with the injection solution. There were positive correlations between saline aspirate and joint fluid concentrations for NPY-LI and IL-1 beta, and the correlations were stronger for saline aspirates with high joint fluid content. This study shows that the method is reliable for measurement of joint fluid concentrations of various substances, such as NPY-LI and IL-1 beta.

Neuropeptide gene expression and capsaicin-sensitive primary afferents: maintenance and spread of adjuvant arthritis in the rat

1. Many experimental and clinical arthritides are characterized by their bilateral nature. There is strong evidence to suggest that this bilateral spread may be mediated by a neuronal mechanism. We have previously shown early and sustained induction of mRNAs encoding preprotachykinin (PPT) and calcitonin gene-related peptide (CGRP) in dorsal root ganglion (DRG) neurons innervating an inflamed, arthritic joint. We have now investigated the involvement of capsaicin-sensitive primary afferents and the expression of neuropeptide mRNAs in the maintenance and bilateral spread of mild adjuvant-induced arthritis in the rat. 2. Capsaicin was applied perineurally to either the left (Cap-L) or right (Cap-R) sciatic nerve of halothane-anaesthetized male Han Wistar rats. Two weeks after capsaicin lesioning, arthritis was induced by injection of Freund's complete adjuvant (FCA) around the left ankle at a dose that caused inflammation of the left ankle joint, and a delayed (14 days) contralateral (right) ankle arthritis. Arthritis was monitored for 15 days after injection, when animals were killed and the lumbar DRG dissected. PPT, CGRP, somatostatin (SS), and vasoactive intestinal polypeptide (VIP) mRNA expression was determined in L5 DRG using in situ hybridization. 3. Spread of inflammation/arthritis to the right limb was associated with bilateral rises in PPT and CGRP mRNA expression in L5 DRG. SS mRNA expression in right DRG was unaffected by spread of inflammation. FCA-L+Cap-L reduced left joint swelling and prevented spread of arthritis to the right joint when assessed by joint swelling. This inhibition of spread of arthritis was associated with significant reductions in all left L5 DRG neuropeptide mRNAs compared with controls, and the rise in right L5 DRG PPT mRNA expression seen in FCA-L-alone animals was blocked. FCA-L+Cap-R also reduced left joint swelling and prevented the spread of inflammation to the right ankle. This lesion prevented the rise in PPT and CGRP mRNA expression seen in right DRG with FCA-L alone. 4. These findings suggest a role for capsaicin-sensitive primary afferents and the primary afferent neuropeptides encoded by PPT and CGRP mRNA in the maintenance and spread of arthritis.

A topographical and ultrastructural study of sensory trigeminal nerve endings in the rat temporomandibular joint as demonstrated by anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP)

To extend our previous light microscopic observations concerning the distribution of trigeminal sensory nerves in the synovium of the rat temporomandibular joint, we investigated the detailed distribution and fine structure of sensory nerve endings at the light and electron microscopic level by the anterograde transport method using wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injected into the trigeminal ganglion. At the light microscopic level, HRP-labeled nerve fibers were observed in the joint capsule and peripheral portion of the disc. The anterior portion of the disc was more densely innervated than the posterior portion, while no nerves were found in the central portion. At the electron microscopic level, HRP reaction products were observed intra-axonally in the thinly myelinated (A delta) and unmyelinated (C) axons in the anterior portion of the joint capsule, and were also localized in the extracellular space surrounding the unmyelinated fibers and terminals. In the subsynovial layer of the synovial membrane, the majority of labeled axons located near blood vessels or among the collagenous fibrils were covered by Schwann cell sheaths, although some naked axon terminals without sheaths were also found. These unsheathed terminals contained mitochondria, small clear vesicles, and large granular vesicles, and were close to the synovial A and/or B cells near the joint cavity. The minimum distance between the terminals and synovial cells was 75 nm. This is the first demonstration of trigeminal sensory nerve terminals close to synovial lining cells or joint cavity and suggests that neuropeptides such as substance P may be released close to the synovial lining cells or joint cavity.

Neuropeptide Y- and vasoactive intestinal polypeptide-like immunoreactivity in adjuvant arthritis: effects of capsaicin treatment

The occurrence of the neuropeptides vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) in ankle joints and dorsal root ganglia (L2-L6) was analyzed in normal and arthritic Lewis rats. In addition the effect of capsaicin pretreatment was investigated. The study included 92 rats consisting of 4 groups, 23 rats in each; normal rats, normal rats given capsaicin, arthritic rats and arthritic rats pretreated with capsaicin. The localization of the neuropeptides was assessed by immunohistochemistry and the tissue concentrations were determined by radioimmunoassay (RIA). In the arthritic rats, there was a slight increase in NPY immunoreactive nerve fibres in the ankle joint synovium and bone marrow, as compared to normal rats. Notably, there was an intense fluorescence and significant increase (p < 0.01, 41%) in the number of NPY-positive megakaryocytes in the tibial bone marrow of arthritic rats. RIA showed that the concentration of NPY-like immunoreactivity (LI) was increased by 50% in the ankle joint. Pretreatment with capsaicin did not affect the increased level of NPY-LI in the ankle joint of arthritic rats. The concentration of NPY-LI in the dorsal root ganglia was not altered in arthritic rats, nor was it affected by the capsaicin treatment. No NPY immunoreactive cells could be detected in the dorsal root ganglia. The number of VIP immunoreactive nerve fibres observed in ankle joints of arthritic and normal rats did not differ. However, RIA measurements showed an 11% increase in the VIP concentration in arthritic rats, which was unaffected by capsaicin treatment. In dorsal root ganglia, RIA disclosed a 21% increase in VIP-LI, although no VIP-positive cells could be detected. Capsaicin treatment did not affect the increased concentration of VIP-LI in the dorsal root ganglia.

Anti-inflammatory effects of kappa-opioids in adjuvant arthritis

Current therapies for arthritis are unsatisfactory and cause serious side effects and morbidity. It has been postulated that opioid drugs may block inflammatory mediators and attenuate the joint damage in adjuvant arthritis. However, the importance of opioid receptor subtypes involved in inflammation remains to be determined because data are conflicting in this regard. The present investigation was designed to test the effects of both a kappa-agonist, (+/-)U50488H and a kappa-antagonist, MR2266 on the progression of experimental arthritis. To produce adjuvant arthritis, male Lewis rats were inoculated subcutaneously (s.c.) with 0.05 ml of Freund's complete adjuvant (10 mg/ml) into the right hind paw. The kappa-opioid agonist, (+/-)U50488H (20 mg/kg/d s.c.) and the kappa-opioid antagonist, MR2266 (20 mg/kg/d s.c.) were administered for 3 days during the primary inflammatory phase of adjuvant arthritis. There were four treatment groups; group I were non-arthritic controls and received paraffin oil vehicle and opioid injections; group II were arthritic controls and received adjuvant and saline injections; group III received adjuvant and agonist and group IV received adjuvant and antagonist. The progression of adjuvant arthritis from day 0 to 24 was monitored by body weight change, hind limb size (ipsilateral and contralateral) and a total severity score for each clinical observation of gait, coat and limb condition. On day 24 histology and radiography of the contralateral limb was performed. There was less soft-tissue swelling, as judged by time-averaged % change in the volume of the contralateral limb, in both agonist (mean +/- se: 82 +/- 5) and antagonist (77 +/- 4) treated rats compared to untreated arthritic controls (99 +/- 5, p < 0.05). Other clinical measures of severity were not different between untreated and opioid-treated arthritic rats. However, the joint damage as judged by radiography was lower in kappa agonist treated rats (2.6 +/- 0.5, p < 0.05) compared to untreated controls (4.1 +/- 0.5) and antagonist treatment (4.4 +/- 0.5). Microscopic pathological scores were also significantly lower in agonist (2.8 +/- 0.3, p < 0.05) compared to both antagonist treated rats (4.2 +/- 0.1) and vehicle-treated controls (3.6 +/- 0.2). The results of this study show that kappa-opioid receptor agonists but not antagonists attenuate the progression of experimental arthritis. These observations have important implications for the evaluation and use of kappa-opioid agents in the management of arthritis.

Sympathetic and sensory innervation of the rat shoulder joint: a WGA-HRP tracing and CGRP immunohistochemical study

The innervation of the shoulder joint of the rat was investigated. Nerve origin was assessed by injection of a neuronal tracer (WGA-HRP) into the shoulder joint cavity and calcitonin gene-related peptide (CGRP), which is known to be present in some sensory neurons, was detected immunohistochemically with an anti-CGRP antibody. In the ipsilateral sympathetic and dorsal root ganglia, 133-312 and 12-55 nerve cell bodies were respectively labeled by injection of the tracer. In the sympathetic ganglia, 83% of all labeled cells were found in the stellate ganglion and 17% in the superior cervical ganglion. In the dorsal root ganglia, 75% of the labeled cells were found in C4 and the neighboring ganglia (C4-C5), while the rest were observed in C6-8 and T3. This suggested that the origin of sensory innervation for the shoulder joint was mainly in the mid-cervical cord. CGRP-immunoreactive fibers were found in the synovial capsule of the shoulder joint. These fibers were fine and resembled type 4 axons as classified by Brodal, i.e., nerve related to pain sensation. These findings indicate that sensory nerves from the mid-cervical cord and sympathetic nerves from the cervical ganglion are distributed to the shoulder joint. It is possible that these nerves are related to symptoms such as pain in patients with "frozen" shoulder or other diseases.

Increased levels of substance P and calcitonin gene-related peptide in rat adjuvant arthritis. A combined immunohistochemical and radioimmunoassay analysis

OBJECTIVE

To analyze the occurrence of substance P (SP) and calcitonin gene-related peptide (CGRP) in ankle joints and corresponding dorsal root ganglia (L2-L6) of rats with adjuvant arthritis.

METHODS

Arthritis was induced by inoculation with heat-killed mycobacteria. The morphologic distribution of SP and CGRP was assessed by immunohistochemical analysis. Tissue concentrations of the neuropeptides were determined by radioimmunoassay.

RESULTS

Neuronal CGRP-like immunoreactivity was clearly increased in the synovium and the dorsal root ganglia, whereas the increase in SP-positive structures was less pronounced. The tissue concentrations of SP and CGRP were significantly increased both in ankle joints and in dorsal root ganglia.

CONCLUSION

Levels of sensory neuropeptides are increased under conditions of joint inflammation.

Changes in preprotachykinin mRNA expression and substance P levels in dorsal root ganglia of monoarthritic rats: comparison with changes in synovial substance P levels

We have measured changes in the expression of gamma-preprotachykinin mRNA and levels of the neuropeptide substance P in the lumbar 4 and 5 dorsal root ganglia at various time points following the induction of an antigenic monoarthritis in the rat knee. The results were compared with changes in substances P levels in the knee joint synovium during acute and chronic phases of the disease. On day 3 post-induction, there was a significant increase in the expression of gamma-preprotachykinin mRNA in the dorsal root ganglia. Concomitant with this increase in message was a rise in the levels of substance P in the dorsal root ganglia. On days 7, 10 and 21, mRNA expression had returned to control values whereas ganglion peptide levels were significantly below controls. In contrast there was little change in the total substance P levels in the synovium on days 1 and 3 despite the observed changes in the ganglia. By day 10, however, synovial levels had risen significantly above control values and remained elevated thereafter. Our results show a transitory increase in substance P synthesis after induction of an antigenic monoarthritis. This response is not mirrored in the periphery where there is no initial change in total substance P levels perhaps reflecting increased degradation be enzymes known to be present within inflamed tissue. Paradoxically synovial substance P levels are increased in the latter phases of the model which may serve to modify the inflammatory response.