Intraneuronal substance P contributes to the severity of experimental arthritis

Origin of sympathetic and sensory innervation of the elbow joint in the rat: a retrograde axonal tracing study with wheat germ agglutinin conjugated horseradish peroxidase

After injection of wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) into the elbow joint of adult rats, labeled neurons were found in the stellate and the T2-T4 ganglia of the ipsilateral sympathetic trunk, and also in dorsal root ganglia at the C4-T4 levels. Most labeled sympathetic cells, 90% or more, were located in the stellate ganglion. The sensory innervation to the joint originated mainly from the dorsal root ganglia at the levels of C7-T1.

The effect of gold, an antirheumatic therapy, on substance P levels in rat peripheral nerve

Intramuscular injections of gold sodium thiomalate in the rat produce a significant depletion of the proinflammatory neuropeptide substance P (SP) from the sciatic nerve. The greatest reduction in SP content occurred during the first two months of treatment. The level of SP in the nerve, however, remained low, throughout an eight month administration of gold. These results, coupled with previous findings that gold produces a selective decrease in the number of unmyelinated axons in peripheral nerve, are consistent with the hypothesis that the anti-inflammatory action of gold involves a neurotoxic effect on peptidergic afferents.

Desensitization to intrathecal substance P in mice: possible involvement of opioids

Intrathecal (i.t.) injection of substance P (SP) results in a behavioral syndrome characterized by caudally directed biting and scratching. The present results indicate that repeated injections of 10 ng of SP, administered at 60 sec intervals, result in the rapid development of tachyphylaxis to this SP-induced behavioral phenomenon. Three injections of SP produced a greatly attenuated behavioral response compared to that of a single injection of SP. Mice injected with Freund's adjuvant in the hind foot pads to produce an arthritic-like condition exhibited significantly less desensitization to SP after repeated i.t. injection compared to that in saline-injected control mice. While large doses of naloxone (5 mg/kg s.c. or 1 microgram i.t.) combined with each injection of SP completely blocked the desensitization to the effect of SP in naive mice, a smaller dose of naloxone (0.5 mg/kg administered s.c.) failed to alter the apparent tachyphylaxis to SP similar to that seen in saline-treated control mice. Pretreatment with 0.5 micrograms i.t. of beta-funaltrexamine (beta-FNA) also failed to alter the degree of apparent tachyphylaxis to SP. Co-administration of 1 microgram of fluoxetine, a serotonin reuptake inhibitor, or 1 microgram of phentolamine, an alpha-adrenergic antagonist, completely blocked the development of tachyphylaxis to i.t. SP. These results indicate that tachyphylaxis to SP appears to involve activation of the endogenous opioid system. Desensitization also appears to involve activation and inhibition of the descending adrenergic and serotonergic systems respectively.

Neuroendocrine modulation of the immune system. Possible implications for inflammatory bowel disease

Evidence for neuroendocrine regulation of the immune system is reviewed. This includes human clinical studies of the influence of psychological stress on immune function, direct experimentation in animals, including classical Pavlovian conditioning of the immune response, modulation of immune function in vitro by chemical messengers such as neuropeptides, the finding of receptors for neuropeptides on immunocytes, and the demonstration that lymphoid tissue is directly innervated. Secretory products of the immune system, which include interleukins and neuropeptides, may also influence the neuroendocrine system. Communication between the two systems is therefore bidirectional. The potential importance of the neuropeptide-immunocyte interaction within the intestinal mucosal immune system is emphasized, and its possible relevance in inflammatory disorders is discussed. This aspect of the "gut-brain" interaction deserves further study.

Role of inflammatory mediators in colonic smooth muscle function in ulcerative colitis

Patients with ulcerative colitis have a decrease in colonic motility which may increase their diarrheal symptoms. Studies in patients with ulcerative colitis showed that the postprandial spike response was slightly decreased and the intraluminal pressure response was absent. In vitro studies showed that the circular smooth muscle, obtained from patients with ulcerative colitis or from a rabbit model of experimental colitis, generated decreased force compared to muscle not associated with mucosal inflammation. The decrease in muscle contraction was observed with bethanechol stimulation or electrical field stimulation. Since the response to an increased extracellular concentration of potassium [( K+]0) was also diminished, the decreased response appears to be caused by an abnormality in the intrinsic contractile mechanism of colonic smooth muscle. Further studies are necessary to determine if metabolic abnormalities are present in the colonic muscle in patients with colitis.

The localization of sensory nerve fibers and receptor binding sites for sensory neuropeptides in canine mesenteric lymph nodes

Previous work has established that the central nervous system can modulate the immune response. Direct routes through which this regulation may occur are the sympathetic and sensory innervation of lymphoid organs. We investigated the innervation of canine mesenteric lymph nodes using immunohistochemistry and the expression of binding sites for sensory neuropeptides using quantitative receptor autoradiography. The sympathetic innervation of lymph nodes was examined by immunohistochemical methods using an antiserum directed against tyrosine hydroxylase (TOH), the rate limiting enzyme in catecholamine synthesis. TOH-containing fibers were associated with 90% of the blood vessels (arteries, veins, arterioles and venules) in the hilus, medullary and internodular regions of lymph nodes and in trabeculae with no obvious relationship to blood vessels. The sensory innervation of lymph nodes was investigated using antisera directed against the putative sensory neurotransmitters calcitonin gene-related peptide (CGRP) and substance P (SP). CGRP- and SP-containing fibers were detected in the hilus, the medullary region, and the internodular region of lymph nodes usually in association with arterioles and venules. About 50% of the arterioles and venules exhibited a CGRP innervation and a smaller fraction (5-10%) were innervated by SP-containing fibers. Few if any TOH, CGRP, and SP nerve fibers were detected in the germinal centers of lymph nodes. Using quantitative receptor autoradiography we studied the distribution of receptor binding sites for the sensory neuropeptides CGRP, SP, substance K (SK), vasoactive intestinal peptide (VIP), somatostatin (SOM), and bombesin. Specific CGRP binding sites were expressed throughout lymph nodes by trabeculae, arterioles, venules and 25% of the germinal centers. SP receptor binding sites were localized to arterioles and venules in the T cell regions and 25-30% of the germinal centers. VIP binding sites were localized to the internodular and T cell regions, to medullary cords, and to 10-20% of germinal centers. SK, SOM, and bombesin binding sites were not detected in the lymph nodes, although receptor binding sites for these peptides were detected with high specific/nonspecific binding ratios in other canine peripheral tissues. Taken together with previous results these findings suggest that the sympathetic and sensory innervation of mesenteric lymph nodes appears to be involved with the regulation of their blood and lymph flow. The neuropeptide receptor binding sites in lymph node germinal centers may be expressed by lymphocytes upon activation by antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Substance-P-like levels in inflammatory exudates

Levels of SP-like immunoreactivity were assessed by enzyme immunoassay in exudates induced in the rat by intrapleural injection of either calcium pyrophosphate (CaPP) or carrageenan. SP-like levels increased during the first hour, up to approximately 2 ng/ml, and remained significantly higher than control values from 1 to 6 h after the induction of pleurisy by CaPP. With carrageenan as the irritant, SP-like levels rose during the first 4 h, up to 3 ng/ml, and remained significantly higher than control values from 4 to 24 h. In terms of the total volume of exudate induced by carrageenan, total amounts increased up to 8 ng/rat at 16 h after the beginning of the reaction. Our data demonstrate a detectable release of SP-like material in these pleural exudates and suggest its involvement in the inflammatory response, either directly, or through other mediators, or simply by acting on nociceptive fibers and inducing vascular changes.

The sensory-efferent function of capsaicin-sensitive sensory neurons

Capsaicin-sensitive sensory neurons convey to the central nervous system signals (chemical and physical) arising from viscera and the skin which activate a variety of visceromotor and neuroendocrine reflexes integrated at various levels (intramurally in peripheral organs, at level of prevertebral ganglia, spinal and supraspinal level). Much evidence is now available that peripheral terminals of certain sensory neurons, widely distributed in skin and viscera have the ability to release, upon adequate stimulation, their transmitter content. In addition to the well-known "axon reflex" arrangement, the capsaicin-sensitive sensory neurons have the ability to release the stored transmitter also from the same terminal which is excited by the environmental stimulus. The efferent function of these sensory neurons is realized through the direct and indirect (i.e. mediated by activation of other cells) effects of released mediators. The action of released transmitters on postjunctional elements covers a wide range of effects which may have a physiological or pathological relevance. Development of drugs capable of controlling the sensory-efferent functions of the capsaicin-sensitive sensory neurons represent a new and very promising area of research for pharmacological treatment of various human diseases.

Altered lymphocyte proliferation of immunized rats after neurological manipulation with capsaicin

The neurotoxic agent capsaicin was used for depletion of the content of neuropeptides in c-fibers of the sensory nerve system in rats. The effect of the capsaicin treatment on the immune response was assessed as lymphocyte proliferation of spleen cells, stimulated with Con A. Treatment of 2 day old rat pups and adult rats did not alter the lymphocyte proliferative response to Con A in nonimmunized rats. Spleen cells from capsaicin-treated and subcutaneously immunized rats showed a decreased proliferation response to Con A. Capsaicin treatment of aerosol immunized rats did not affect the proliferation level of the spleen cells to the same extent. The results indicate that abolishment of the content of neuropeptides in the c-fibers of sensory nerves with capsaicin, affects the immune response.

Neuropeptide regulation of immediate and delayed hypersensitivity

Peptide mediators of sensory nerves that are released in tissues by noxious stimuli or inflammatory reactions rapidly elicit local and systemic responses similar to those of immediate hypersensitivity. These sensory neuropeptides affect functions of smooth muscles, blood vessels, leukocytes, and epithelial glands both directly and indirectly, through the actions of mediators released from mast cells stimulated by the peptides. Stereospecific receptors transduce the effects of neuropeptides of the peripheral nervous system (PNS) and central nervous system (CNS) on diverse functions of human, murine and guinea pig mononuclear and polymorphonuclear leukocytes, mast cells, and basophils in vitro and in vivo. Stimulatory and inhibitory effects of neuropeptides on leukocytes are attained in vitro at concentrations which are similar to those in the circulation and in tissues. The dissociation constant (KD) for the binding of a neuropeptide to its leukocyte receptor is within the range of concentrations that evoke cellular responses critical to immunity and hypersensitivity. Neuropeptides exhibit both cellular and stimulus specificities, as exemplified by the greater potency of substance P in activating mucosal than connective tissue mast cells and the capacity of somatostatin to inhibit the release of mediators from basophils challenged by IgE-dependent mechanisms, but not by basic peptides or ionophores. The selective release of distinct neuropeptides from different subsets of sensory nerve endings, the specificity of neuropeptide recognition by mast cells, basophils, lymphocytes, and other target cells, and the diversity of relevant activities of the neuropeptides suggest that the nervous system may initiate and modulate immediate and delayed hypersensitivity by unique mechanisms.

Neuropeptide modulation of the immune response in gut associated lymphoid tissue

The neuropeptides vasoactive intestinal peptide (VIP), substance P, and somatostatin are found in high concentrations in both the central nervous system and the gastrointestinal tract. Specific high affinity receptors for VIP, substance P and somatostatin have been identified on both human and murine lymphocytes, suggesting a role for each of these neuropeptides in a neuroimmune axis. These peptides may be important modulators of mucosal immunity regulating lymphocyte proliferation and trafficking in gut associated lymphoid tissue, synthesis of IgA, and histamine release. Somatostatin antagonism of both VIP and substance P effects has been observed in the immune system. Though the mechanisms by which these neuropeptides modulate immune function have not been completely delineated, current evidence supports the hypothesis that VIP modulates immune function via cAMP dependent pathways while substance P regulation of the immune response involves phospholipid metabolism. Somatostatin inhibition of both cAMP dependent and phospholipid dependent effects has been documented in endocrine tissues. Delineation of the role of these peptide-peptide interactions in modulation of the immune response promises to be a fruitful area for further investigation.

Mechanisms of persistent synovitis

Rheumatoid arthritis is characterised by persistent and symmetrical synovitis. In this article we propose two linked hypotheses to explain these observations. A mechanism to explain symmetry of synovitis is described whereby fine afferent nerve fibres from joints become bilaterally sensitized to movement with resultant release of neuropeptides promoting an inflammatory response. Clinical and experimental evidence is reviewed and shows that movement and resulting hypoxic reperfusion injury leads to a persistent synovitis.

Substance P- and CGRP-immunoreactive nerves in bone

The present study demonstrates the occurrence of substance P (SP)- and calcitonin gene related peptide (CGRP)-immunoreactive nerve fibres in bone, bone marrow, periosteum, synovial membrane and soft tissues adjacent to the bone. The distribution pattern of the two types of nerves was similar, although the CGRP-positive fibres generally were more numerous. Both types of nerves were particularly abundant near the epiphyseal plate, in the bone marrow of patella and epiphyses, and in the periosteum. Many SP- and CGRP-immunoreactive fibres were also observed around blood vessels.

Immunoaffinity purification of membrane protein constituents of the IM-9 lymphoblast receptor for substance P

Substance P (SP) is an undecapeptide neuromediator that stimulates human T-lymphocyte function by binding to stereospecific membrane receptors. Human IM-9 cultured B-lymphoblasts express approximately 20,000 receptors per cell for [125I]SP with a Kd of 0.3 nM. [125I]SP was specifically crosslinked by disuccinimidyl suberate to IM-9 cell membrane proteins of 78, 58, and 33 kDa. An indirect immunoaffinity purification procedure has now been developed based on immunoabsorption of detergent-solubilized [125I]SP-labeled IM-9 cell membrane proteins to anti-SP antibody that was bound to an epoxide ultraffinity high-performance liquid chromatography column, followed by elution in acidic 8 M urea. The 58- and 33-kDa SP-receptor complexes were purified to apparent homogeneity by immunoaffinity chromatography and identified by autoradiography and silver staining of sodium dodecyl sulfate-polyacryl-amide gels.

Substance P activation of rheumatoid synoviocytes: neural pathway in pathogenesis of arthritis

Several clinical features are consistent with nervous system involvement in the pathogenesis of rheumatoid arthritis. The neuropeptide substance P is one possible mediator of this interaction, since it can be released into joint tissues from primary sensory nerve fibers. The potential effects of the peptide on rheumatoid synoviocytes were examined. The results show that substance P stimulates prostaglandin E2 and collagenase release from synoviocytes. Furthermore, synoviocyte proliferation was increased in the presence of the neuropeptide. Similar effects were observed with a truncated form of substance P. Synoviocytes were sensitive to very small doses of the neuropeptide (10(-9) M), and its effects were inhibited by a specific antagonist. Thus, the specific stimulation of synoviocytes by the neuropeptide substance P represents a pathway by which the nervous system might be directly involved in the pathogenesis of rheumatoid arthritis.

Purification of the 33,000-dalton ligand binding-protein constituent of the lymphoblast substance P receptor

Substance P (SP) acts as an immunoregulator by binding to specific functional cell surface receptors on a subpopulation of human T-helper lymphocytes. Receptors with similar properties have also been characterized on the human IM-9 B-lymphoblast cell line. Four distinct proteins of molecular weight (MW) 33,000, 58,000, 78,000, and 116,000 can be specifically affinity labeled using [125I]-SP Bolton-Hunter reagent and disuccinymidyl suberate (DSS). Peptide-mapping studies of these individually purified affinity labeled proteins have shown that the 33,000 MW membrane protein is present in the higher molecular weight cross-linked proteins. In the present studies, the 33,000 MW affinity-labeled protein was purified using semipreparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) followed by high-performance hydroxylapatite chromatography. Starting with 800 mg of affinity-labeled protein, the final yield was 39.0 micrograms of 33,000 MW affinity-labeled protein. Based on an estimate of 53 mg receptor per 800 mg membrane protein, this represents an overall yield of greater than 70%. Peptide mapping was done by digesting 20 micrograms of the receptor protein with bovine trypsin. The proteolytic fragments were separated by reverse-phase high-performance liquid chromatography, and the amino acid content of 13 distinct peptides was determined. With this procedure, sufficient receptor can now be purified so that partial amino acid sequences can be obtained for further structural studies.

Neuropeptides and gastrointestinal immunity

Several peptides originally described as neurotransmitters or gut hormones have recently been shown to modulate the immune response. Three of these peptides, vasoactive intestinal peptide, substance P, and somatostatin, regulate the function of immune effector cells in gut-associated lymphoid tissue. Vasoactive intestinal peptide modulates lymphocyte migration and natural killer cell activity by a cyclic adenosine monophosphate (cAMP)-dependent mechanism, whereas substance P induces mediator release by a cAMP-independent mechanism. Somatostatin antagonizes the effects of both vasoactive intestinal peptide and substance P by a mechanism that appears to involve inhibitory guanine nucleotide binding proteins. Neuropeptide regulation of immune cells in gut-associated lymphoid tissue may thus play an important role in gastrointestinal physiology.

Extravasation in the knee induced by antidromic stimulation of articular C fibre afferents of the anaesthetized cat

Electrical stimulation of the cut distal end of the posterior articular nerve (p.a.n.) of the cat knee joint resulted in significant extravasation of plasma proteins and erythrocytes into the synovial cavity of the knee. This effect was mediated by group IV afferents (C fibres) since stimulation of p.a.n. suprathreshold for group II or III afferents but subthreshold for group IV afferents did not produce extravasation. Unmyelinated sympathetic efferent fibres in the joint nerve did not contribute to the extravasation and were responsible for a diminution of this response as shown by the enhanced extravasation occurring after adrenergic blockade. Plasma and erythrocyte extravasation was mediated by afferents containing substance P (SP), as demonstrated by the reversible abolition of extravasation when the substance P antagonist (D-Pro4,D-Trp7,9,10)-SP (4-11) was injected into the synovial cavity. In some animals it was observed that electrical stimulation of the cut distal end of p.a.n. in one limb resulted in extravasation in the contralateral knee joint. It is suggested that articular C fibre afferents could make a significant neurogenic contribution to the initiation or maintenance of inflammatory joint disease.

Neuropeptides degranulate serous cells of ferret tracheal glands

To determine whether serous or mucous cells in tracheal submucosal glands respond to the neuropeptides substance P (SP) and vasoactive intestinal peptide (VIP), we studied the peptide-induced changes in gland cell morphology accompanying release of 35SO4-labeled macromolecules from tracheal explants of ferrets. Explants were labeled for 1 h in medium containing 35SO4 and washed for 3.5 additional hours. Base-line secretion in the absence of drugs declined between 1.5 and 3.5 h after the pulse. Between 2.5 and 3.5 h, the average percent change in counts per minute recovered per sample period was not significantly different from zero (P greater than 0.3; n = 6). Substance P (10(-5) M) and VIP (2 X 10(-6) M) added 4 h after labeling each increased greatly the release of 35SO4-labeled macromolecules (SP, 219%; VIP, 180%) above base line. Bethanechol, a muscarinic-cholinergic agonist (10(-5) M), increased secretion by an average of 142% above base line (each effect, P less than 0.05; n = 6 each). Light and electron microscopy of the control tissues showed glands with narrow lumens and numerous secretory granules. Glands treated with SP or VIP had enlarged lumens and the serous cells were markedly degranulated. These phenomena were documented by morphometry and suggest that SP and VIP cause secretion from glands at least partially by stimulating exocytosis from serous cells.

The neurotoxic effect of gold sodium thiomalate on the peripheral nerves of the rat. Insights into the antiinflammatory actions of gold therapy

Although gold is one of the few therapeutic agents that has been proven effective in producing remission in patients with rheumatoid arthritis, its mechanism of action is unknown. Since nociceptive afferent and sympathetic efferent fibers of the peripheral nervous system contribute to the pathophysiology of inflammation, and since a known side effect of gold therapy is a polyneuropathy, we tested the hypothesis that gold is toxic to small-diameter peripheral nerve fibers in the rat. We found that prolonged treatment with gold, at the same dosage reported to be effective against adjuvant-induced arthritis in the rat, produced a significant decrease in the numbers of unmyelinated, but not of myelinated, axons. Gold treatment also elevated nociceptive thresholds in both articular and nonarticular structures. These results suggest that gold produces an antiinflammatory effect on arthritis by a neurotoxic effect on the peripheral nerves involved in neurogenic inflammation.

Gastrin, gastric acid secretion, and gastric microflora in patients with rheumatoid arthritis

The relation between the basal and stimulated gastric acid secretion, plasma gastrin, and the gastric microflora was examined in 45 patients with rheumatoid arthritis. Sixteen patients (36%) had basal achlorhydria, and of these, 10 (22%) had achlorhydria or hypochlorhydria after stimulation with pentagastrin. The peak acid output and acidity showed inverse correlation with the disease duration but were not associated with age or with the degree of physical disability. Hypergastrinaemia was found in nine patients (20%), of whom 6 (13%) had significant titres of parietal cell antibody. The acidity of the peak acid output showed negative correlation with plasma gastrin. It was confirmed that the gastric secretory state is a determinant of plasma gastrin levels and in addition influences the growth of micro-organisms in the gastric lumen. The type of microflora in the non-acid stomach was similar to that found in the saliva. A subgroup of eight females was identified who showed low gastric acid secretion rates, positive bacterial cultures, and atlantoaxial subluxation. Gastrin- and insulin-like immunoreactivities were found in joint fluid. The concentrations reflected their plasma levels, suggesting that the peptides are not released at the inflammatory site, but rather that they reach synovial fluid from circulating blood.

Distribution of substance P-like immunoreactive nerve fibers in temporomandibular joint soft tissues of monkey

The distribution of substance P-immunoreactive and silver impregnated nerve fibers in the temporomandibular joint soft tissues of the Macaca fascicularis monkey was investigated in frozen sections. The pattern of substance P-immunoreactive structures in the soft tissues and periosteum of the temporomandibular joint was compared with the distribution of silver impregnated nerve fibers within these tissues. Presence of substance P-immunoreactive fibers was demonstrated in the temporomandibular joint capsule, disc attachments, fascia, adjacent periosteum and within the interfascicular connective tissue of the lateral pterygoid muscle. The overall distribution corresponded to that of silver impregnated nerve fibers. Substance P-immunoreactive nerve fibers were found in the adventitia of arteries in all vascularized temporomandibular joint soft tissues but could not be found in the adventitia of veins. No substance P-immunoreactive or silver impregnated nerve fibers were seen in the dense collagenous tissue forming the disc. Substance P is suggested to influence the major features of inflammation and to play a role in acute and chronic pain conditions.

Neurogenic inflammation caused by wool fabric in the rat; possible mediation by substance P

We have measured plasma extravasation in response to stimulation of the rat hind footpad with wool fabric. The stimulus was delivered using a constantly weighted disc of wool rotating at 4 revolutions per minute for 30 min on the base of blisters induced by vacuum. The protein content of prestimulated blister base perfusate was 38 +/- 2 micrograms/ml in a 30-min collection. With stimulation this increased to 80 +/- 10 micrograms/ml (P less than 0.001; Student's paired t-test). No increase in plasma extravasation was observed in adult animals pretreated as neonates with capsaicin indicating that the plasma extravasation observed was neurogenically mediated. Plasma extravasation was also observed with substance P added to the perfusate. The threshold for substance P-induced plasma extravasation was 2 X 10(-11) mol/30 min. These results suggest that neurogenic inflammation induced by the mechanical stimulus of wool fabric may be mediated by substance P. This reaction may be involved in wool-induced prickle and itch noted in some individuals.

Gastrointestinal regulatory peptides modulate in vitro immune reactions of mouse lymphoid cells

The effects of six gastrointestinal regulatory peptides (beta-endorphin, substance P, metenkephalin, vasoactive intestinal peptide, bombesin, and somatostatin) on mouse lymphocytes stimulated with concanavalin A, lipopolysaccharide, phytohemagglutinin, or alloantigens were evaluated. Lymphocytes were stimulated in vitro and the influences of exogenously adding varying concentrations of neuropeptides (10(-6)-10(-11) M) on the incorporation of [methyl-3H-]thymidine were determined. The roles of cell density and antigen concentration on neuropeptide induced immunomodulation were also assessed. We observed that vasoactive intestinal peptide (VIP) would significantly inhibit the response of B10 lymphocytes to concanavalin A (54%) and phytohemagglutinin (56%) but not to lipopolysaccharide (16%). The VIP-induced inhibition was progressively diminished as the neuropeptide concentration was reduced to 10(-11) M. By 24 hr after stimulation the lymph node cells were refractory to the inhibitory effects of VIP. In addition, VIP would not inhibit B10 lymph node cells from responding to B10. K spleen cells in mixed, one-way lymphocyte cultures. The other five peptides did not influence the in vitro responses. The potential role of neuropeptides in the pathophysiology of immunologic-based disorders is discussed.

Stress, symmetry, and psoriasis: possible role of neuropeptides

The role of stress as a triggering factor in the exacerbation of psoriasis and the clinically symmetric distribution of psoriatic plaques suggested a possible role for neuropeptides in the etiopathogenesis of psoriasis. Several observations by other investigators involving substance P suggested to us a possible role for substance P as a modulator of the inflammatory response in psoriasis. A hypothesis for the role of substance P that would account for the temporal onset with stress, the clinical symmetry of lesions, and the histopathologic features of psoriasis is presented.

Primary afferent fibers conduct impulses in both directions under physiological stimulus conditions

In electric fish of the family Mormyridae some primary afferent fibers conduct impulses not only from electroreceptors to the brain but also from the brain to the receptors. The efferent impulses may be elicited by electrical stimulation which is within the physiological range, i.e., by stimulation which is similar in amplitude and duration to the stimulation that is caused by the fish's own electric organ discharge. Afferent and efferent impulses in the same afferent fiber were identified by: simultaneously recording from a fiber at two different points, at the receptor and at the nerve trunk (Figs. 2C-H; 3B-D); by cutting the afferent fiber between the brain and the recording site as well as between the recording site and the periphery; and by intra-axonal recording from the afferent fiber near its entry into the brain (Fig. 4). The efferent impulses result from the central integration of a corollary discharge of the electric organ motor command with excitatory and inhibitory input from several different receptors near the one from which afferent impulses originate (Fig. 4). The centrally originating impulse may be capable of modifying the effect of signals originating in the periphery.

Psychic distress and the immune response

This minireview surveys recent progress in the field of immunoregulation by the central nervous system. Representative findings from human and animal studies show evidence for significant immunosuppression in states of psychic distress. Mechanisms of immunomodulation are discussed in light of data implicating neuroendocrine, genetic, neuroanatomical, and learning factors. Evidence for reciprocal modulation of immune and nervous systems is considered. A simple hierarchical model proposes traits that are acted on by environment and experience to produce chronic states of mental health vs. psychic distress; these states determine baseline immunocompetence and response to afferent signals during acute immune challenge. Multidisciplinary interest in psychoneuroimmunology has accelerated the rate of inquiry into the mechanistic details of immunoregulation and has generated new appreciation for the pervasive effects of mental status on physiologic homeostasis.

Substance P receptor-mediated chemotaxis of human monocytes

The undecapeptide substance P (SP) was tested for its ability to promote human monocyte chemotaxis in a modified Boyden chamber assay. Substance P was found to be active in this assay system with an ED50 for chemotactic effect of approximately 10(-13) M. This response was shown to be chemotactic in nature since a concentration gradient of attractant was required for maximal effect. Other substance P analogs tested showed a rank order of potency of substance P greater than or equal to SP(3-11) greater than SP(8-11) approximately equal to SP(9-11) much greater than SP(1-9), SP, free acid. These results suggest that chemotactic responsiveness is largely encoded in the C-terminus of the molecule. The relative potency order for SP and its analogs in promoting monocyte chemotaxis correlates well with their potencies in displacing labeled SP when binding sites are directly measured in other tissues, such as rat brain or human lymphocytes. Additionally, the chemotactic effects of SP could be partially reversed by the weak antagonist [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-SP. The N-formyl peptide receptor antagonist, t-Boc-Phe-Leu-Phe-Leu-Phe, did not block SP-mediated chemotaxis, further indicating the specificity of these effects. These results suggest the existence of a specific substance P receptor on human monocytes which directs this chemotactic response. The ability of monocytes to respond chemotactically to SP may be relevant to the enhancing effects of SP in arthritis or other inflammatory diseases.