Live-cell three-dimensional single-molecule tracking reveals modulation of enhancer dynamics by NuRD

To understand how the nucleosome remodeling and deacetylase (NuRD) complex regulates enhancers and enhancer-promoter interactions, we have developed an approach to segment and extract key biophysical parameters from live-cell three-dimensional single-molecule trajectories. Unexpectedly, this has revealed that NuRD binds to chromatin for minutes, decompacts chromatin structure and increases enhancer dynamics. We also uncovered a rare fast-diffusing state of enhancers and found that NuRD restricts the time spent in this state. Hi-C and Cut&Run experiments revealed that NuRD modulates enhancer-promoter interactions in active chromatin, allowing them to contact each other over longer distances. Furthermore, NuRD leads to a marked redistribution of CTCF and, in particular, cohesin. We propose that NuRD promotes a decondensed chromatin environment, where enhancers and promoters can contact each other over longer distances, and where the resetting of enhancer-promoter interactions brought about by the fast decondensed chromatin motions is reduced, leading to more stable, long-lived enhancer-promoter relationships.

Progesterone Inhibits Mast Cell Secretion

Mast cells are involved in allergic reactions, where they secrete numerous vasoactive, inflammatory and nociceptive mediators in response to immunoglobulin E (IgE) and antigen. However, they have also been implicated in inflammatory conditions, such as painful bladder syndrome/interstitial cystitis (PBS/IC), irritable bowel syndrome (IBS) and migraines, all of which occur more often in women and are exacerbated during ovulation, but are suppressed during pregnancy. Mast cells express high affinity estrogen receptors and estradiol augments their secretion, while tamoxifen inhibits it. Here we report that progesterone (100 nM), but not the structurally related cholesterol, inhibits histamine secretion from purified rat peritoneal mast cells stimulated immunologically or by substance P (SP), an effect also documented by electron microscopy. These results suggest that mast cell secretion may be regulated by progesterone and may explain the reduced symptoms of certain inflammatory conditions during pregnancy.

Luteolin inhibits myelin basic protein-induced human mast cell activation and mast cell-dependent stimulation of Jurkat T cells

BACKGROUND AND PURPOSE

Allergic inflammation and autoimmune diseases, such as atopic dermatitis, psoriasis and multiple sclerosis (MS), involve both mast cell and T-cell activation. However, possible interactions between the two and the mechanism of such activations are largely unknown.

EXPERIMENTAL APPROACH

Human umbilical cord blood-derived cultured mast cells (hCBMCs) and Jurkat T cells were incubated separately or together, following activation with myelin basic protein (MBP), as well as with or without pretreatment with the flavonoid luteolin for 15 min. The supernatant fluid was assayed for inflammatory mediators released from mast cells and interleukin (IL)-2 release from Jurkat cells.

KEY RESULTS

MBP (10 microM) stimulates hCBMCs to release IL-6, IL-8, transforming growth factor (TGF)-beta1, tumour necrosis factor-alpha (TNF-alpha), vascular endothelial growth factor (VEGF), histamine and tryptase (n=6, P<0.05). Addition of mast cells to Jurkat cells activated by anti-CD3/anti-CD28 increases IL-2 release by 30-fold (n=3, P<0.05). MBP-stimulated mast cells and their supernatant fluid further increase Jurkat cell IL-2 release (n=3, P<0.05). Separation of mast cells and activated Jurkat cells by a Transwell permeable membrane inhibits Jurkat cell stimulation by 60%. Pretreatment of Jurkat cells with a TNF-neutralizing antibody reduces IL-2 release by another 40%. Luteolin pretreatment inhibits mast cell activation (n=3-6, P<0.05), Jurkat cell activation and mast cell-dependent Jurkat cell stimulation (n=3, P<0.05).

CONCLUSIONS AND IMPLICATIONS

Mast cells can stimulate activated Jurkat cells. This interaction is inhibited by luteolin, suggesting that this flavonoid may be useful in the treatment of autoimmune diseases.

The flavonoid luteolin inhibits niacin-induced flush

BACKGROUND AND PURPOSE

Sustained release niacin effectively lowers serum cholesterol, LDL and triglycerides, while raising HDL. However, 75% of patients experience cutaneous warmth and itching known as flush, leading to discontinuation. Acetylsalicylic acid (aspirin) reduces this flush only by about 30%, presumably through decreasing prostaglandin D2 (PGD2). We investigated whether niacin-induced flush in a rat model involves PGD2 and 5-HT, and the effect of certain flavonoids.

EXPERIMENTAL APPROACH

Three skin temperature measurements from each ear were recorded with an infrared pyrometer for each time point immediately before i.p. injection with either niacin or a flavonoid. The temperature was then measured every 10 min for 60 min.

KEY RESULTS

Niacin (7.5 mg per rat, equivalent to a human dose of 1750 mg per 80 kg) maximally increased ear temperature to 1.9+/-0.2 degrees C at 45 min. Quercetin and luteolin (4.3 mg per rat; 1000 mg per human), administered i.p. 45 min prior to niacin, inhibited the niacin effect by 96 and 88%, respectively. Aspirin (1.22 mg per rat; 325 mg per human) inhibited the niacin effect by only 30%. Niacin almost doubled plasma PGD2 and 5-HT, but aspirin reduced only PGD2 by 86%. In contrast, luteolin inhibited both plasma PGD2 and 5-HT levels by 100 and 67%, respectively. CONCLUSIONS AND IMPLICATIONS. Niacin-induced skin temperature increase is associated with PGD2 and 5-HT elevations in rats; luteolin may be a better inhibitor of niacin-induced flush because it blocks the rise in both mediators.

Anti-chemokine therapy for inflammatory diseases

Chemokines are inflammatory proteins acting via G-protein coupled chemokine receptors that trigger different signaling pathways. Monocyte chemoattractant protein-1 (CCL2/MCP-1) and regulated on activation, normal T expressed and secreted (CCL5/RANTES) are the two major members of the CC chemokine beta subfamily. The roles of RANTES and MCP-1 are emerging in regulating the recruitment of inflammatory cells into tissue during inflammation. The inhibition of MCP-1 and RANTES with corresponding antibodies or other inhibitors may provide benefits in different clinical scenarios including cancer, inflammation, CNS disorders, parasitic disease, autoimmune and heart diseases. RANTES and MCP-1 may represent targets for diagnostic procedures and therapeutic intervention, and may be useful as a prognostic factor in the above diseases.

Intravesical Suplatast Tosilate (IPD-1151T) Inhibits Experimental Bladder Inflammation

PURPOSE

Interstitial cystitis is a painful bladder disease characterized by urgency, frequency and variable inflammation but there is no curative therapy. Suplatast tosilate (IPD-1151T) is an immunoregulatory compound that decreases interstitial cystitis symptoms but to our knowledge its mechanism of action is unknown. We investigated the effect of intravesical IPD-1151T on mediator release from bladder explants in experimental cystitis.

MATERIALS AND METHODS

A catheter was inserted into the bladder of female mice. After urine was emptied normal saline, carbachol (100 nM) or lipopolysaccharide (10 mg/ml) was introduced with or without 10-minute pretreatment with IPD-1151T. Urine was removed after 45 minutes for histamine and tumor necrosis factor-alpha assays. The bladder was removed after 4 hours, minced into 1 mm2 pieces and cultured with or without triggers overnight for mediator release. The effect of IPD-1151T was also tested on rat skin vascular permeability as well as on purified rat peritoneal mast cells and human cord blood derived mast cells.

RESULTS

Carbachol significantly increased histamine release in urine (61.3% in 8 preparations, p<0.05) but not in explant medium. IPD-1151T inhibited this effect by 77%. Lipopolysaccharide induced a 350% urine histamine increase in 9 preparations (p<0.05) and a 300% tumor necrosis factor-alpha increase in explant medium. IPD-1151T inhibited the lipopolysaccharide induced medium tumor necrosis factor-alpha increase by 95% in 5 preparations (p<0.05). IPD-1151T did not inhibit rat skin vascular permeability or purified rat peritoneal mast cell activation by compound 48/80 or human cord blood derived mast cells by anti-IgE.

CONCLUSIONS

IPD-1151T inhibits bladder release of histamine and tumor necrosis factor-alpha through a mechanism that does not appear to involve direct mast cell inhibition. These findings may justify a beneficial effect of IPD-1151T in interstitial cystitis.

IL-15 an immunoregulatory and anti-cancer cytokine. Recent advances

Interleukins are mediators of inflammation, immunity and cancer. IL-15 is a cytokine produced by several leukocytes including phagocytes in response to infections and other signals that trigger innate immunity. IL-15 has many homologies to interleukin-2 (IL-2) and like IL-2, stimulates NK cells. This cytokine acts also on memory CD8+ T-cell. IL-15, therefore acts, probably through selective inhibition of tumor promoting molecules, as a new compound for the adjuvant treatment of solid tumors. In this review we propose a newly revised mechanism of interleukin 15 in inflammation and cancer.

Immunological activation of human umbilical cord blood mast cells induces tryptase secretion and interleukin-6, and histidine decarboxilase mRNA gene expression

Allergy is the result of a complex immune cascade leading to the disregulated production of Th2 cytokines, the generation of allergen-specific IgE-producing B cells and the subsequent activation and degranulation of mast cells upon allergen challenge. Mast cell effector function significantly influences the quantity, duration and magnitude of most allergic reactions. Here, using isolated human umbilical cord blood mast cells (HUCBMC) from CD34+ cells, activated with anti-IgE (10 microg/ml) in culture, we found an augmented release of IL-6, tryptase and histamine (p < 0.01 compared with control). In addition, in these cells anti-IgE (10 microg/ml) activated the expression of histidine decarboxylase (HDC) and IL-6. In these studies we describe a new biological activity of anti-IgE in inducing histidine decarboxylase and IL-6, suggesting that this cytokine may have an important effect on allergic and inflammatory diseases mediated by mast cells. Moreover, with these data we confirm the immunoregulatory and inflammatory function of mast cells.

Acute Stress and Intravesical Corticotropin-Releasing Hormone Induces Mast Cell Dependent Vascular Endothelial Growth Factor Release From Mouse Bladder Explants

PURPOSE

Corticotropin-releasing hormone is typically released from the hypothalamus but it has proinflammatory effects outside of the brain, possibly through the activation of mast cells. These cells express corticotropin-releasing hormone receptors with selective secretion of vascular endothelial growth factor, which may be involved in the pathogenesis of painful bladder syndrome/interstitial cystitis. This condition is characterized by bladder inflammation and worsened by stress. We investigated the effect of intravesical corticotropin-releasing hormone and acute restraint stress on vascular endothelial growth factor release from mouse bladder explants and the role of mast cells.

MATERIALS AND METHODS

The bladder of C57BL/6 mast cell deficient (W/W(v)) and normal congenic (+/+) female mice (Jackson Laboratories, Bar Harbor, Maine) at ages 10 to 12 weeks was catheterized using anesthesia. After emptying urine 1) normal saline or corticotropin-releasing hormone was introduced for 45 minutes, urine was collected and the mice were allowed to recover for 4 hours before sacrifice or 2) the mice were stressed by placing them in a restrainer for 4 hours before sacrifice and urine was collected 2 hours after stress. The bladder was removed 4 hours after stress and processed for corticotropin-releasing hormone immunohistochemical staining. In other experiments the bladder was removed, minced into 1 mm(2) pieces and cultured with or without corticotropin-releasing hormone overnight. Urine and medium were frozen for histamine, interleukin-6, tumor necrosis factor-alpha and vascular endothelial growth factor assay.

RESULTS

Corticotropin-releasing hormone (100 nM) or acute restraint stress (4 hours) increased histamine release in urine and vascular endothelial growth factor release in medium without increasing interleukin-6 or tumor necrosis factor-alpha in the bladder explants of C57BL/6 or +/+ but not W/W(v) mice. No vascular endothelial growth factor, interleukin-6 or tumor necrosis factor-alpha was detected in urine before or after stimulation. Corticotropin-releasing hormone immunoreactivity was present in control bladders but it increased dramatically in the bladder of stressed mice.

CONCLUSIONS

Intravesical corticotropin-releasing hormone and acute restraint stress induced mast cell dependent vascular endothelial growth factor release from bladder explants. These findings suggest that stress, corticotropin-releasing hormone, mast cells and vascular endothelial growth factor might participate in the pathogenesis of painful bladder syndrome/interstitial cystitis, which is worsened by stress, and provide for new therapeutic targets.

Theophylline as "add-on" therapy in patients with delayed pressure urticaria: a prospective self-controlled study

Delayed pressure urticaria (DPU) is a skin condition that involves the gradual development of wheals and edema at sites of physical pressure. Its pathogenesis is not clear and histamine-1 receptor (H-1R) antagonists provide only partial relief. In this prospective, clinical study, we investigated the effect of theophylline, which has a long history of benefit in allergic asthma, added to cetirizine in patients with DPU. Twenty three patients received during period 1 cetirizine (10 mg po QD) and theophylline (200 mg po BID) for 6 months, followed by period 2 of 1 month washout with only rescue medication as needed, and then by period 3 with cetirizine (10 mg QD plus placebo (BID) for 5 more months. The addition of theophylline resulted in statistically significant improvement over cetirizine alone by 2 months and continued for the duration of treatment. Treatment of cultured human mast cells with theophylline (10 microM) did not inhibit allergic histamine release, but the in vivo beneficial effect of theophylline may require significant pretreatment period to manifest itself, or may involve inhibition of other mast cell dependent mediators. A double-blind study, accompanied by serum histamine and tryptase levels, should be in order.

IL-10 subfamily members: IL-19, IL-20, IL-22, IL-24 and IL-26

It has been reported that the CD4+ T cell is a very important source of interleukin 10 (IL-10), while CD8+ cells produce low amounts. IL-10 exerts several immune stimulating, as well as inhibitory effects. There are at least five novel human IL-10 family-related molecules: IL-19, IL-20, IL-22, IL-24, and IL-26. Activated T cells produce IL-19, IL-22 and IL-26, while IL-24 is produced by activated monocytes and T-cells. IL-20 induces cheratin proliferation and Stat-3 signal transduction pathway, while IL-22 induces acute-phase production by hepatocytes and neonatal lethality with skin abnormalities reminiscent of psoriasic lesions in humans. In addition, IL-22 mediates inflammation and binds class II cytokine receptor heterodimers IL-22 RA1/CRF2-4. This cytokine is also involved in immuno-regulatory responses. IL-26 (AK155) is a novel cytokine generated by memory cells and is involved in the transformed phenotype of human T cells after infection by herpes virus. All these new IL-10 subfamily member cytokines are strongly involved in immune regulation and inflammatory responses.

Inhibitory effect of retinoic acid on proliferation, maturation and tryptase level in human leukemic mast cells (HMC-1)

Mast cells play important role in allergic inflammation by releasing histamine, tryptase and several inflammatory cytokines. Human leukemic mast cells (HMC-1) have been used to study mast cell mediator and their role in inflammatory mechanisms. HMC-1 contain and release several inflammatory mediators, of which the proteolytic enzyme tryptase is most characteristic. Retinoids, including retinoic acid, are naturally occurring and synthetic derivatives of vitamin A. All-trans-retinoic (ATRA) acid had been previously reported to inhibit cell proliferation, differentiation and apoptosis. In the present study, we investigated the effect of ATRA on the proliferation and secretion of tryptase in HMC-1. HMC-1 were treated with ATRA at 10(-4M), 10(-5M) or 10(-6M) for 3, 4 or 5 days in culture. Control HMC-1 were treated with equal amount of culture medium only. ATRA decreased the number of HMC-1 as compared to the control group. The same treatment for 3, 4 or 5 days also decreased intracellular tryptase levels. These results indicate that ATRA significantly inhibits both proliferation and growth as shown by the decreased intracellular tryptase levels in HMC-1. ATRA may be a useful agent in the treatment of mast cell proliferative disorders.

Pentosanpolysulfate inhibits mast cell histamine secretion and intracellular calcium ion levels: an alternative explanation of its beneficial effect in interstitial cystitis

PURPOSE

Mast cells are ubiquitous cells derived from the bone marrow and are responsible for allergic reactions as they release numerous vasodilatory, nociceptive and pro-inflammatory molecules in response to immunoglobulin E (IgE) and specific antigen. Mast cell secretion is also triggered by a number of peptides, such as bradykinin and substance P, and may also be involved in the development of inflammatory responses. An example is interstitial cystitis, which is a sterile painful bladder disorder that has been associated with a defective glycosaminoglycan bladder mucosal layer and an increased number of activated mast cells. Pentosanpolysulfate is a synthetic, sulfated polysaccharide that has been approved for the treatment of interstitial cystitis on the premise that it may replenish the defective glycosaminoglycan layer. We hypothesize that pentosanpolysulfate may also have an additional or alternate action on bladder mast cells. We report that pentosanpolysulfate has a powerful dose dependent inhibitory effect on mast cell release of histamine induced by the mast cell secretagogue compound 48/80.

MATERIALS AND METHODS

Inhibition of mast cell secretion was documented by light and electron microscopy and extended to stimulation by substance P or IgE and antigen.

RESULTS

The inhibition was more potent than that seen with the clinically available mast cell stabilizer disodium cromoglycate (cromolyn). Maximal inhibition by pentosanpolysulfate was apparent within 1 minute, was unaffected by the length of pre-incubation and persisted after the drug was washed off. In contrast, the effect of cromolyn was limited by rapid tachyphylaxis. In addition, while cromolyn has no effect on mucosal or rat basophilic leukemia cells, pentosanpolysulfate inhibited histamine secretion from both. Confocal microscopy using a calcium indicator dye showed that pentosanpolysulfate decreased intracellular calcium ion levels.

CONCLUSIONS

Pentosanpolysulfate appears to be a potent inhibitor of allergic and nonimmune mast cell stimulation, which is an alternative explanation of its benefit in interstitial cystitis.

Chondroitin sulphate inhibits connective tissue mast cells

1. Mast cells derive from the bone marrow and are responsible for the development of allergic and possibly inflammatory reactions. Mast cells are stimulated by immunoglobulin E (IgE) and specific antigen, but also by a number of neuropeptides such as neurotensin (NT), somatostatin or substance P (SP), to secrete numerous pro-inflammatory molecules that include histamine, cytokines and proteolytic enzymes. 2. Chondroitin sulphate, a major constituent of connective tissues and of mast cell secretory granules, had a dose-dependent inhibitory effect on rat peritoneal mast cell release of histamine induced by the mast cell secretagogue compound 48/80 (48/80). This inhibition was stronger than that of the clinically available mast cell 'stabilizer' disodium cromoglycate (cromolyn). Inhibition by chondroitin sulphate increased with the length of preincubation and persisted after the drug was washed off, while the effect of cromolyn was limited by rapid tachyphylaxis. 3. Immunologic stimulation of histamine secretion from rat connective tissue mast cells (CTMC) was also inhibited, but this effect was weaker in umbilical cord-derived human mast cells and was absent in rat basophilic leukemia (RBL) cells which are considered homologous to mucosal mast cells (MMC). Oligo- and monosaccharides were not as effective as the polysaccharides. 4. Inhibition, documented by light and electron microscopy, involved a decrease of intracellular calcium ion levels shown by confocal microscopy and image analysis. Autoradiography at the ultrastructural level showed that chondroitin sulphate was mostly associated with plasma and perigranular membranes. 5. Chondroitin sulphate appears to be a potent mast cell inhibitor of allergic and nonimmune stimulation with potential clinical implications.

Dual effect of spermine on mast cell secretion exhibits different calcium and temperature requirements

Mast cells release many biologically active molecules upon stimulation by a variety of molecules such as immunoglobulin E (IgE) and specific antigen, anaphylatoxins, as well as a number of cationic compounds which include drugs, kinins and neuropeptides. The effect of the naturally occurring polyamine spermine was studied because, even though it is polycationic, it has been implicated in the modulation of secretory processes in a variety of cells. In particular, it was previously shown that oxidation products of spermine inhibit mast cell secretion. High concentrations of spermine (5 x 10(-3) M) added at 37 degrees C induced mast cell secretion that had similar characteristics with that triggered by compound 48/80 (48/80). However, spermine inhibited mast cell secretion in a dose-dependent manner as long as it was added at 4-10 degrees C for at least 10 min in the absence of Ca++ before warming the cells to 37 degrees C and triggering them with 48/80. These findings were true both for purified rat peritoneal mast cells and for rat skin mast cells in situ. Addition of calcium after the cells had been warmed to 37 degrees C could not reverse this inhibition. The inhibition seen when spermine was added at 4 degrees C was, however, overcome if phorbol myristate acetate (PMA) or NaF, which activate PKC and G proteins respectively, were added to mast cells at 37 degrees C together with Ca++. These results indicate that polyamines could be important modulators of the activation state of mast cells and might help further define the biochemical events involved in mast cell secretion.

Stress-induced rat intestinal mast cell intragranular activation and inhibitory effect of sulfated proteoglycans

Cyclic vomiting syndrome is characterized by sudden episodes of vomiting and abdominal pain. It occurs primarily in children, is exacerbated by stress, and is often considered a migraine equivalent. Migraines have been linked to mast cells, which are often found close to neurons where they are activated by neuropeptides. We investigated the ultrastructural appearance of rat ileal brush border and mast cells following acute stress by immobilization. The effect of sulfated proteoglycans heparin and chondroitin sulfate was also tested on mast cell histamine secretion. Ileal brush border appeared intact in control animals, but was shorter and exhibited intercellular gaps after 30 min of acute immobilization stress. Mast cell activation in control rats was minimal, while stress induced obvious signs of activation as judged from disappearance of secretory granule electron dense contents. However, these intragranular changes were not accompanied by typical degranulation through exocytosis. Treatment of purified homogeneic rat peritoneal mast cells with 10(-4) M heparin or chondroitin sulfate 30 min prior to stimulation with 0.5 microg/ml compound 48/80 decreased histamine release by over 70% and 50% (P < 0.05), respectively. These results suggest the possible usefulness of chondroitin sulfate in conditions such as cyclic vomiting syndrome.

Differential effect of flavonoids on inhibition of secretion and accumulation of secretory granules in rat basophilic leukemia cells

Rat basophilic leukemia (RBL) cells resemble mucosal mast cells (MMC) and develop few secretory granules under normal culture conditions. RBL cells have been used for the study of secretion and for the possible involvement of MMC in food allergies and irritable bowel syndrome (IBS). The flavonoid quercetin is one of very few molecules that inhibit RBL cell proliferation and constitutive histamine release; it also induces synthesis of rat mast cell protease (RMCP) II and accumulation of secretory granules. Even though quercetin is available as a food supplement over the counter, some early studies had indicated it may be carcinogenic. We, therefore, compared the effect of quercetin to that of other flavonoids with similar structure. Flavone, kaempferol, myricetin and morin were investigated for their action on RBL cell secretion of beta-hexosaminidase stimulated by anti-DNP serum and DNP-BSA, as well as on secretory granule development. Quercetin, myricetin and kaempferol inhibited RBL cell secretion significantly only at 10(-4) M. Flavone inhibited secretion at 10(-4), 10(-5) and 10(-6) M; it also maximally induced secretory granule accumulation as evidenced by light and electron microscopy. In contrast, morin which differs structurally only by one extra hydroxyl group had minimal effect. These results indicate that flavone is capable of inhibiting stimulated secretion and inducing secretory granule development at reasonable concentrations.

Neurotensin mediates rat bladder mast cell degranulation triggered by acute psychological stress

OBJECTIVES

An increased number of activated mast cells have been documented in interstitial cystitis (IC), a painful bladder disorder occurring primarily in women and exacerbated by stress. Mast cells in the bladder and in the intestine are often found in juxtaposition to neurons, where they are activated by neuropeptides and neurotransmitters as well as by acute psychological stress. This work was undertaken to investigate whether the neuropeptide neurotensin (NT) is involved in the activation of bladder mast cells by acute psychological stress.

METHODS

Male 300-g Sprague-Dawley rats were either kept on the bench in a quiet procedure room or stressed by confining them one at a time for 30 minutes in a clear Plexiglas immobilizer and then killed with carbon dioxide. The bladder was removed and fixed with 4% paraformaldehyde. Frozen sections were either stained with acidified toluidine blue or processed for NT immunocytochemical analysis. An immunosorbent assay was used to also measure NT in bladder homogenate before and after stress.

RESULTS

Bladder mast cell activation in control rats was 37.3 +/- 1.4%, as judged by extrusion of granule contents. Degranulation in stressed animals increased to 75.3 +/- 5.5% (P = 0.0003). Treatment of the animals neonatally with capsaicin decreased mast cell degranulation to 48.9 +/- 7.5% (P = 0.008), a 35.1% inhibition. Intraperitoneal administration of the nonpeptide NT receptor antagonist SR48692 sixty minutes before stress decreased bladder mast cell degranulation to 25.2 +/- 3.6% (P = 0.00007), a 66.5% inhibition. This value is 32.5% below control levels, indicating that NT is involved in basal mast cell degranulation. Stress also reduced the total bladder NT content.

CONCLUSIONS

The present results indicate that NT mediates the effect of acute, nontraumatic psychological stress on bladder mast cell degranulation. They further suggest that NT receptor antagonists may be useful in subpopulations of patients with IC in whom symptoms worsen under stress.

Potent mast cell degranulation and vascular permeability triggered by urocortin through activation of corticotropin-releasing hormone receptors

Urocortin (Ucn) is related to corticotropin-releasing hormone (CRH), and both are released in the brain under stress where they stimulate CRH 1 and 2 receptors (CRHR). Outside the brain, they may have proinflammatory actions through activation of mast cells, which are located perivascularly close to nerve endings and degranulate in response to acute psychological stress. Here, we report that a concentration of intradermal Ucn as low as 10 nM induced dose-dependent rat skin mast cell degranulation and increased vascular permeability. This effect appeared to be equipotent to that of calcitonin gene-related peptide and neurotensin. Ucn-induced skin vasodilation was inhibited by pretreatment with the mast cell stabilizer disodium cromoglycate (cromolyn) and was absent in the mast cell-deficient W/Wv mice. The selective nonpeptide CRH receptor 1 antagonist, antalarmin and the nonselective peptide antagonist astressin both reduced vascular permeability triggered by Ucn but not that by Substance P or histamine. In contrast, the peptide antagonist alpha-helical CRH-(9-41) reduced the effect of all three. The vasodilatory effect of Ucn was largely inhibited by pretreatment with H1 receptor antagonists, suggesting that histamine is the major mediator involved in vitro. Neuropeptide depletion of sensory neurons, treatment with the ganglionic blocker hexamethonium, or in situ skin infiltration with the local anesthetic lidocaine did not affect Ucn-induced vascular permeability, indicating that its in situ effect was not mediated through the peripheral nervous system. These results indicate that Ucn is one of the most potent triggers of rat mast cell degranulation and skin vascular permeability. This effect of Ucn may explain stress-induced disorders, such as atopic dermatitis or psoriasis, and may lead to new forms of treatment.

A neurotensin receptor antagonist inhibits acute immobilization stress-induced cardiac mast cell degranulation, a corticotropin-releasing hormone-dependent process

Stress worsens certain disorders such as migraines or asthma, and has also been implicated in sudden myocardial arrest. It was previously shown that acute psychological stress by immobilization results in dura mast cell degranulation, an effect blocked by pretreatment with antiserum against corticotropin-releasing hormone (CRH). Moreover, CRH was recently shown to induce skin mast cell degranulation. The effect of psychological stress was investigated on rat cardiac mast cells, because their release of coronary constrictive and proinflammatory molecules contributes to myocardial ischemia and possibly arrhythmias. Immobilization of rats for 30 min induced maximal cardiac mast cell degranulation as evidenced by light and electron microscopy. This effect was inhibited by pretreatment with the "antiallergic" drug sodium cromoglycate (cromolyn), which is thought to act primarily through mast cell stabilization. Mast cell degranulation was also blocked by preincubation with antiserum against CRH and was partially inhibited by a CRH type-1 receptor selective antagonist. Sensory neuropeptides did not appear to influence this effect, but a nonpeptide neurotensin receptor antagonist blocked stress-induced cardiac mast cell degranulation. This finding supports the involvement of neuropeptide neurotensin which is present in the heart and is known to trigger mast cell degranulation. These results indicate acute stress could result in local CRH and nonpeptide neurotensin release which could contribute to myocardial pathophysiology through direct or indirect release of cardiac mast cell mediators.

Corticotropin-releasing hormone induces skin mast cell degranulation and increased vascular permeability, a possible explanation for its proinflammatory effects

Mast cells are involved in atopic disorders, often exacerbated by stress, and are located perivascularly close to sympathetic and sensory nerve endings. Mast cells are activated by electrical nerve stimulation and millimolar concentrations of neuropeptides, such as substance P (SP). Moreover, acute psychological stress induces CRH-dependent mast cell degranulation. Intradermal administration of rat/human CRH (0.1-10 microM) in the rat induced mast cell degranulation and increased capillary permeability in a dose-dependent fashion. The effect of CRH on Evans blue extravasation was stronger than equimolar concentrations of the mast cell secretagogue compound 48/80 or SP. The free acid analog of CRH, which does not interact with its receptors (CRHR), had no biological activity. Moreover, systemic administration of antalarmin, a nonpeptide CRHR1 antagonist, prevented vascular permeability only by CRH and not by compound 48/80 or SP. CRHR1 was also identified in cultured leukemic human mast cells using RT-PCR. The stimulatory effect of CRH, like that of compound 48/80 on skin vasodilation, could not be elicited in the mast cell deficient W/Wv mice but was present in their +/+ controls, as well as in C57BL/6J mice; histamine could still induce vasodilation in the W/Wv mice. Treatment of rats neonatally with capsaicin had no effect on either Evans blue extravasation or mast cell degranulation, indicating that the effect of exogenous CRH in the skin was not secondary to or dependent on the release of neuropeptides from sensory nerve endings. The effect of CRH on Evans blue extravasation and mast cell degranulation was inhibited by the mast cell stabilizer disodium cromoglycate (cromolyn), but not by the antisecretory molecule somatostatin. To investigate which vasodilatory molecules might be involved in the increase in vascular permeability, the CRH injection site was pretreated with the H1-receptor antagonist diphenhydramine, which largely inhibited the CRH effect, suggesting that histamine was involved in the CRH-induced vasodilation. The possibility that nitric oxide might also be involved was tested using pretreatment with a nitric oxide synthase inhibitor that, however, increased the effect of CRH. These findings indicate that CRH activates skin mast cells at least via a CRHR1-dependent mechanism leading to vasodilation and increased vascular permeability. The present results have implications for the pathophysiology and possible therapy of skin disorders, such as atopic dermatitis, eczema, psoriasis, and urticaria, which are exacerbated or precipitated by stress.

RANTES is a pro-inflammatory chemokine and chemoattracts basophil cells to extravascular sites

RANTES (regulated upon activation normal T expressed and secreted) is another member of the intercrine beta subfamily which acts as a selective chemoattractant for human monocytes and CD4-positive lymphocytes and increases the adherence of monocytes to endothelial cells. In this work, the effect of RANTES was studied on rat skin injection sites. Rats were intradermally injected with 50 microliters of RANTES, at different concentrations, fMet-Leu-Phe (FMLP), or LPS (positive controls) or PBS vehicle (negative control). The animals were then injected with 0.6 ml of Evans' blue in the tail vein in order to obtain a blue colour in the areas where the compounds were injected. After 4 h the rats were killed and the maximum diameter of the blue extravasation area was measured. The coloured areas were then excised and optical and electron microscopic studies were performed. In addition, in some of the excised tissue, a Northern blot analysis for histidine decarboxylase (HDC) mRNA was performed along with an estimation of the amount of histamine generated in the tissue injection sites. In these studies it was found that intradermal injections of 5, 2.5, and 1.25 x 10(-5) M RANTES produced a strong inflammatory response with the accumulation of a great number of basophil cells compared with the PBS (50 microliters) negative control, or FMLP (10(-6) M/50 microliters) or LPS (10 ng/50 microliters) positive control, after 4 h. Moreover, 5, 2.5, 1.25 x 10(-5) M RANTES produced a dose-response stimulation of HDC mRNA in the tissues of skin injection sites. The increasing number of basophils in the RANTES inflamed tissues led to augmentation of histamine content, compared with the PBS control. In conclusion, the pro-inflammatory chemokine RANTES stimulates the generation of HDC mRNA in skin injection sites.

Monocyte chemotactic protein-1 is a proinflammatory chemokine in rat skin injection sites and chemoattracts basophilic granular cells

Chemokines may control mast cell infiltrates found in many inflammatory diseases. These cells act through at least two main functions: migration and degranulation. Here we show that human recombinant monocyte chemotactic protein (MCP)-1 (10 ng/50 microliters) induces, after 4 h, an inflammatory vascular permeability and cellular extravasation reaction, determined by Evan's blue dye (1% in saline) injected into the tail vein of the rat, when injected intradermally in the rat skin. The blue color accumulating at the sites of injection provides evidence of vascular permeability and cellular extravasation. The colored areas of the skin were then enucleated and immersed in a fixative solution. Slides were prepared with sections of tissue colored with toluldine blue and analyzed under an optical microscope. A significant number of basophilic cells migrated to the injected area where MCP-1 (10 ng/50 microliters) was used compared to the control PBS treatment. Cell recruitment was slightly less than N-formyl-methionine-leucyl-phenylalanine (used at 10(-6) M/50 microliters). Electron microscopy studies confirmed the presence of basophilic granular cells where MCP-1 was intradermally injected. After preparation of a histidine decarboxylase (HDC) probe, a Northern blot analysis was determined for HDC mRNA in the enucleated tissue injected with MCP-1 (10 ng/50 microliters). Steady-state levels of HDC mRNA levels were induced after 4 h. These results were confirmed by the higher amount of histamine release, compared to the control PBS, in the enucleated tissue from the MCP-1 injection sites. Our results suggest that MCP-1 could play a significant role in diseases characterized by basophilic cell accumulation and migration to sites of tissue damage. Moreover, we show for the first time that MCP-1 is a pro-inflammatory chemokine that induces basophilic cell migration in rat skin injection sites.

Impact of Rantes and MCP-1 chemokines on in vivo basophilic cell recruitment in rat skin injection model and their role in modifying the protein and mRNA levels for histidine decarboxylase

RANTES and related molecules, constitute the C-C class of chemokine supergene family and a group of cytokines produced by hematopoietic cells constitute the MCP-1 or C-X-C class. The roles of most of these chemokines are not well known, although members of the C-X-C family are inflammatory agents. Here, we report that intradermal injection of RANTES 10 ng/50 microL subcutaneously in the abdominal skin produced a strong inflammatory reaction, as evidenced by Evans blue dye, greater than FMLP (10(-6) mol/L) (approximately 57%); while MCP-1, 10 ng/50 microL was less effective than FMLP (10(-6) mol/L) (approximately 54%). Moreover, the histologic analysis of the cells stained with Toluidine blue (0.1%) were analyzed at a magnification of x40). RANTES 10 ng/50 microL and LPS produced higher numbers (142 +/- 11 and 193 +/- 21 of cells/200 mm2, respectively) of basophilic cell accumulation in the skin injection sites compared with FMLP (10(-6) mol/L) (127 +/- 14/200 mm2), while MCP-1 10 ng/50 microL was less effective (88 +/- 10/200 mm2). Electron microscopy (x13,800) studies of skin injection sites revealed that RANTES was chemoattractant for mast cells. In a Northern blot analysis from homogeneous tissue biopsy from the intradermal injection sites, RANTES was more potent than MCP-1 in increasing histidine decarboxylase (HDC) mRNA, the sole enzyme responsible for the production of histamine from histidine. Since PGD2 is formed by mast cells on cell activation, we also studied the effect of RANTES and MCP-1 on PGD2 production in inflamed tissue in vivo. RANTES (20, 10, and 5 ng) and MCP-1 (20, 10, and 5 ng) strongly stimulated PGD2, in a dose-dependent manner, with a potency rank order of RANTES (10 ng/mL) approximately two times greater than MCP-1 (10 ng/mL).

Mast cell and substance P-positive nerve involvement in a patient with both irritable bowel syndrome and interstitial cystitis

Many patients with interstitial cystitis (IC) also have irritable bowel syndrome (IBS), both of which occur overwhelmingly in women, are characterized by pain, and worsen under stress. Bladder and colon biopsies of a female patient with both IC and IBS were evaluated immunohistochemically. There were 40 +/- 10 mast cells (MC)/mm2 (normal, less than 10) in the bladder, which were degranulated. The colon contained 148 +/- 11 MC/mm2 (normal, less than 50), mostly close to numerous substance P (SP)-positive nerves. Histamine, methylhistamine, and the unique MC enzyme tryptase were evaluated in 24-hour urine during two flare-ups. These results may help explain the concurrent presentation and the painful nature of these syndromes.

Monocyte chemotactic protein-1 provokes mast cell aggregation and [3H]5HT release

Monocyte chemotactic protein-1 (MCP-1) and MCP-3, the most active and representative compounds of the CC chemokine family, are proinflammatory cytokines that attract and activate specific types of leucocytes. We have used highly purified isolated rat peritoneal mast cells (RPMC) cultured for different lengths of time with and without MCP-1 (200, 100, 50 and 25 nM). Our data clearly show that MCP-1 (200 nM) causes a marked release of [3H]serotonin ([3H]5HT and histamine, which reach a peak at 40 min of incubation (56.6 +/- 5.3 and 34.7 +/- 6 above the control, respectively). In dose-response experiments, MCP-1 (200, 100, 50, 25, 12.5, 6.25 and 3.12 nM) provoked a dose-dependent release of [3H]5HT and histamine from RPMC, which was maximum at 200 nM. After preparation of the histidine decarboxylase (HDC) probe, a Northern blot analysis was determined for HDC mRNA. After 4 hr, steady-state levels of HDC mRNA were induced in a dose-dependent manner by MCP-1 (200-25 nM), compared to the controls. However, MCP-1 failed to prime RPMC in [3H]5HT and histamine release when C48/80 (0.05 micrograms/ml) or anti-IgE was used. In contrast, murine interleukin-3 (IL-3) in combination with MCP-1 (200 and 100 nM) provoked a greater release of histamine and [3H]5HT than the compounds alone. Moreover, RPMC treated with MCP-1 (200 nM) showed, under light microscopy (20x), greater clump formation, a phenomenon absent in the controls (untreated cells). The electron microscope studies revealed that treatment with MCP-1 (200 nM) promoted binding of RPMC and clearly demonstrated a communication between the cytoplasms of adjacent mast cells. Our report describes additional biological activities for MCP-1, suggesting for the first time that this human monocyte chemoattractant plays a fundamental role in histamine and serotonin release and cell aggregation in rat peritoneal mast cells.

Elevated mast cell tryptase in the urine of patients with interstitial cystitis

OBJECTIVE

To investigate the number of tryptase positive bladder mast cells and the level of urine tryptase in interstitial cystitis (IC), a bladder disorder which occurs mostly in women and is characterized by suprapubic pain, frequency and nocturia.

PATIENTS AND METHODS

Bladder biopsies from 37 women with IC and 15 control women with other bladder conditions (age range 18-63 years) were obtained during diagnostic bladder distension and frozen immediately. Mast cells positive for tryptase were identified by immunohistochemistry and evaluated by light microscopy. Tryptase was measured by solid phase radioimmunoassay in urine samples, collected immediately (spot) and during a period of 24 h, obtained from normal women volunteers, controls and patients with IC. To adequately quantify tryptase, the physiologically active tetramer was dissociated to inactive monomers with supersaturated NaCl (6.0 M), and then dialysed.

RESULTS

The patients' spot urine sample tryptase levels were indistinguishable from those of controls, which included the normal women volunteers. However, the tryptase levels in 24 h urine samples were greatly elevated only in patients with IC, both before (P < 0.005), and especially after NaCl treatment and dialysis (P < 0.001).

CONCLUSION

These results indicate that the tryptase levels of 24 h urine samples, combined with methylhistamine levels and the clinical criteria presently used, may possibly help to better identify IC.

Increased urine histamine and methylhistamine in interstitial cystitis

Interstitial cystitis is a painful bladder disorder occurring mostly in women, and is presently diagnosed by clinical presentation, as well as the presence of mucosal glomerulations and inflammation on bladder distention. An increased number of bladder mast cells have been implicated in the pathophysiology of interstitial cystitis but previous reports of spot urine histamine have not confirmed bladder mast cell activation. The availability of easily measurable objective criteria could make the diagnosis easier. Histamine and its major metabolite, methylhistamine, were measured in spot and 24-hour urine specimens from a number of normal female volunteers, control patients and interstitial cystitis patients. In interstitial cystitis patients the histamine levels were only slightly increased in the spot (p < 0.01) and 24-hour urine (p < 0.03) collections. Methylhistamine, on the other hand, was greatly elevated in spot (p < 10(-10)) and 24-hour (p < 0.0008) urine samples. These results indicate that methylhistamine levels could serve as useful diagnostic end points for interstitial cystitis.

Quercetin-induced expression of rat mast cell protease II and accumulation of secretory granules in rat basophilic leukemia cells

Rat basophilic leukemia (RBL) cells are considered to be similar to bone-marrow derived mast cells and to mucosal mast cells (MMC), the latter of which may be involved in inflammatory bowel diseases. RBL cells are not able to accumulate histamine and secretory granules under regular growing conditions. Here we show that the flavonoid quercetin, which inhibits mast cell secretion of histamine, also inhibited RBL cell proliferation and constitutive histamine release while it induced synthesis of rat mast cell protease (RMCP) II and triggered processes leading to accumulation of secretory granules. Cell viability was also retained in the presence of quercetin, whereas untreated cells did not survive past 6 days of growth. Quercetin did not affect the expression of mRNA for alpha-subunit of immunoglobulin E (IgE) receptor, but led to increased expression of mRNA for, and synthesis of RMCP II, which is a marker protein for MMC. Many of these granules showed metachromasia with toluidine blue after 3 days of growth, stained red with alcian blue counterstained with safranin after 8 days of growth, and contained electron dense material. Our results suggest that RBL cells have the capacity to progress to a more mature state and may lend themselves to further analysis of a growth regulator(s) with action similar to that of quercetin.

Synergistic action of estradiol and myelin basic protein on mast cell secretion and brain myelin changes resembling early stages of demyelination

Mast cells are known for their participation in immediate and, more recently, delayed hypersensitivity reactions. They have been found in the meninges and certain brain areas where they are strictly perivascular, in close apposition to neurons, and they are activated by direct nerve stimulation or by neuropeptides. Intracranial mast cells contain many vasoactive substances which can increase the permeability of the blood-brain barrier, proteolytic enzymes which can degrade myelin in vitro, as well as chemotactic molecules which can attract inflammatory molecules in vivo. Connective tissue mast cells, with which intracranial mast cells share many characteristics, contain cytokines which can cause inflammation directly. Multiple sclerosis is a human demyelinating disease of unknown etiology, with a high prevalence in women which results in penetration of blood-borne immune cells within the brain parenchyma and subsequent destruction of myelin. Here, we report that 17 beta-estradiol and myelin basic protein, a major suspected immunogen in multiple sclerosis, had a synergistic action on inducing mast cell secretion. This effect was more pronounced in Lewis rats, which are susceptible to the development of experimental allergic encephalomyelitis, an animal model for multiple sclerosis, than in Sprague-Dawley rats, which are fairly resistant. Moreover, 18 h incubation of purified peritoneal mast cells with homogeneic slices of brain white matter in the presence of 17 beta-estradiol and myelin basic protein resulted in myelin changes resembling early stages of brain demyelination, which were also more evident in Lewis rats than in Sprague-Dawley rats. These results support the notion that mast cells could participate in the pathophysiology of demyelinating diseases.

Stimulated rat mast cells generate histamine-releasing peptide from albumin

Media conditioned by compound 48/80-stimulated rat mast cells generated immunoreactive histamine-releasing peptide (HRP) when incubated at physiological pH with bovine serum albumin and the carboxypeptidase inhibitor, O-phenanthroline. The generation of immunoreactive HRP (IR-HRP) was time (after 3 h the concentration of IR-HRP was 20 nM), temperature, and pH dependent and was prevented by omitting albumin, by using media conditioned by nonstimulated mast cells, or by pretreatment of mast cells with disodium cromoglycate, an inhibitor of mast cell secretion. The amount of IR-HRP generated increased linearly with the number of mast cells stimulated and varied directly with the concentration of conditioned media. After removal of the media from stimulated mast cells, the remaining cell pellet retained its ability to generate IR-HRP for up to 8 h. Stimulation of mast cells by either neurotensin or substance P, or of sensitized cells by anti-IgE serum, also produced conditioned media that generated IR-HRP. The amount of IR-HRP formed by various conditioned media or by stimulated cell pellets was dependent upon the concentration of O-phenanthroline used. Including the chymase inhibitor, chymostatin, prevented the formation of IR-HRP in a dose-dependent manner. HPLC analysis showed four peaks of IR-HRP. The major one coeluted with synthetic HRP. These results indicate that the peptide, HRP, can be generated by stimulated mast cells incubated in the presence of albumin. They suggest that a chymase-like enzyme secreted by the mast cell is able to cleave albumin to yield HRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Dermatitis characterized by mastocytosis at immunization sites in mast-cell-deficient W/Wv mice

W/Wv mice have been extensively used as an important model to study the maturation/differentiation and pathophysiology of mast cells. These albino mice have been shown to have less than 1% of the mast cells found in the skin of their +/+ controls or other normal mice. Moreover, no mast cells are detected in other organs even though they apparently have an adequate number of mast cell precursors. Presumably, these precursors do not respond appropriately to microenvironmental growth factors, while 'normal' precursors from the +/+ controls of S1/S1d-deficient mice mature appropriately in the tissue microenvironment of the W/Wv mice. Female W/Wv mice and +/+ controls were immunized with allogeneic spinal cord homogenate in complete Freund's adjuvant and Mycobacterium tuberculosis in order to induce experimental allergic encephalomyelitis. All W/Wv mice developed extensive dermatitis with mastocytosis at the injection sites about 4 months after inoculation. Mast cells were identified by light microscopy following staining with toluidine blue and berberine sulfate as well as electron microscopy. They were also found to be functional since they secreted serotonin and histamine in response to either compound 48/80 or carbachol. The majority of these mast cells were, therefore, considered to be mature, connective tissue like, but many of them were in different stages of granule maturation as seen with electron microscopy. These findings imply that W/Wv mice may not always be appropriate as models of mast cell deficiency. Moreover, these results suggest that the 'defect' in W/Wv mast cell precursors can be overcome by factors produced during immunization and/or development of dermatitis. These findings may, therefore, help elucidate what regulates mast cell maturation/differentiation as well as their pathophysiology.

Estradiol augments while tamoxifen inhibits rat mast cell secretion

Mast cells have been studied extensively for their involvement in allergic reactions, where they secrete numerous powerful mediators in response to immunoglobulin E and specific antigens. However, they are also triggered by neuropeptides, they have been found in close contact with neurons, and they are activated in diseases such as angioedema, interstitial cystitis and irritable bowel disease, the prevalence of which is much higher in women. When tested on purified rat peritoneal mast cells, 17 beta-estradiol augmented secretion of histamine and serotonin, starting at 1 microM and in a dose-dependent manner, whether stimulated by the mast cell secretagogue compound 48/80 or the neuropeptide substance P. However, 17 beta-estradiol did not augment mast cell secretion stimulated by immunoglobulin E and specific antiserum indicating that immunologic stimulation is under different regulation. Testosterone inhibited secretion induced by compound 48/80. Tamoxifen, an estrogen receptor antagonist used in the treatment of breast cancer, inhibited serotonin and histamine release from purified rat peritoneal mast cells triggered by compound 48/80 or substance P. Tamoxifen also inhibited the increase in intracellular free Ca2+ originating from an influx of extracellular Ca2+ in response to compound 48/80. Moreover, tamoxifen antagonized the synergistic effect of phorbol myristate and the cation ionophore A23187 on mast cell secretion, suggesting that tamoxifen's inhibition may be due to regulation of protein kinase C activity. Tamoxifen may, therefore, have a beneficial effect in other neuroimmunoendocrine disorders both through estrogen receptor blockade and inhibition of mast cell secretion.

Formation of histamine-releasing activity from albumin by medium conditioned by endotoxin-stimulated rat peritoneal macrophages

Incubation of bovine serum albumin (BSA), rat serum albumin or rat plasma with medium conditioned by endotoxin stimulated rat peritoneal macrophages produced an activity that released histamine from isolated rat serosal mast cells. The amount of histamine-releasing activity (HRA) produced increased with the length of the incubation period, with the concentration of albumin, with the number of macrophages stimulated, and with the duration of exposure of the macrophages to endotoxin. Moreover, the formation of the HRA showed a dependency on the pH of the incubation medium with an optimum at pH 4.5. Boiling the medium conditioned by stimulated macrophages before its incubation with albumin or including the acid protease inhibitor, pepstatin with the conditioned medium prevented the formation of HRA. The generation of HRA was not inhibited by pretreatment of the macrophages with the inhibitor of protein synthesis, cycloheximide. Media from macrophages not stimulated with endotoxin failed to generate HRA. Histamine release from mast cells in response to the HRA was inhibited by pretreatment of the cells with antimycin A and deoxyglucose or by preincubation in Ca-free Locke's solution containing a calcium chelating agent. When injected intradermally into anesthetized Evan's Blue treated rats, the generated HRA produced a change in vascular permeability that was prevented by the H1 antagonist, diphenhydramine. Treatment of the HRA with carboxypeptidase A reduced its ability to stimulate histamine release from mast cells. Histamine-Releasing Peptide (HRP), a neurotensin-related octapeptide, shown previously by us to be formed by the action of cathepsin D or pepsin on albumin, was identified by radioimmunoassay in acid:acetone extracts of the histamine-releasing activity. It is concluded that the formation of HRA is due to the actions of enzymes released from macrophages acting on albumin. It is suggested that such histamine-releasing activity could be formed during the later stages of the inflammatory response and that HRP is one of the peptides present.

Rapid degradation of neurotensin by stimulated rat mast cells

A RIA towards neurotensin (NT) using C-terminal- and N-terminal-specific antisera was used to study degradation of this tridecapeptide by isolated rat mast cells. Incubation of NT (10 microM) with peritoneal or pleural mast cells resulted in a rapid loss of NT immunoreactivity (iNT), as measured by C-terminal-directed antiserum, with little effect on N-terminal iNT. The rate of the reaction was faster with pleural cells (T1/2, 30 s) than with peritoneal cells (T1/2, 180 s) and was greater than 10-fold slower in the presence of metabolic poisons. The enzyme(s) involved is most likely released from the cells during secretion, as NT was degraded by media conditioned by compound 48/80-stimulated mast cells 40-60 times faster than by media from unstimulated cells. This degradation by conditioned media was concentration dependent, pH dependent, and temperature sensitive. HPLC analyses indicated a near stoichiometric conversion of NT to NT(1-12) (66%) and NT(1-11) (34%) after incubation for 10-30 s with conditioned media. By 30 min only NT(1-11) and NT(1-10) were present. Phenanthroline (1 mM), an inhibitor of carboxypeptidase, prevented the loss of C-terminal iNT and the generation of NT(1-12) and NT(1-11). While NT(1-12) was effective in releasing histamine from mast cells in vitro and increasing vascular permeability in vivo, NT(1-11) was not. These results suggest that carboxypeptidase-like enzyme(s) could modulate the level and form of NT-related peptides in various states involving activation of mast cells.

Generation of xenopsin-related peptides from tissue precursors by media conditioned by endotoxin-stimulated rat peritoneal macrophages

Incubation of media conditioned by endotoxin-stimulated rat peritoneal macrophages generates immunoreactive xenopsin (iXP) when incubated with acid extracts of various tissues of the rat. The generation of iXP, as measured by specific radioimmunoassay and confirmed by HPLC analysis, increased as the length of the incubation period increased and was inhibited by pepstatin, prior boiling of the conditioned media, or by omitting either the tissue extract or the conditioned media. The pH optimum for the generation of iXP was 3.0. The generated iXP showed biological activity in that stimulated histamine secretion from isolated rat mast cells and this secretory response was prevented by metabolically poisoning the cells. In addition, the generated iXP stimulated contraction of the isolated guinea pig ileum. In this regard, it was similar to neurotensin (NT). Tissue precursor levels for iXP, as measured by this system of generation, were highest in kidney, liver, and skin and lowest in skeletal muscle and plasma. These results suggest to us that during the inflammatory response, the NT-related peptide, xenopsin, can be generated from tissue precursor(s) by enzymes secreted by invading macrophages. The generated XP may then affect the participating cells of inflammation.

Neurotensin elevates hematocrit and plasma levels of the leukotrienes, LTB4, LTC4, LTD4 and LTE4, in anesthetized rats

The IV injection of neurotensin (NT) into anesthetized rats produced a marked increase in hematocrit, labored breathing and peripheral blood stasis with cyanosis. This effect could also be produced by the NT-related peptides, neuromedin-N and xenopsin; however, it was not observed when nine other biologically active peptides, including bradykinin and substance P, were tested. Associated with these responses were increases in the plasma levels of histamine (measured radioenzymatically) and the leukotrienes, LTB4, LTC4, LTD4, and LTE4 (measured by RIA and HPLC). The increment in hematocrit after varying doses of NT correlated to the increase in plasma levels of LTC4. Histamine and LTC4 were both capable of elevating hematocrit when given IV; however, LTC4 was approximately 1000 times more potent than histamine and active doses of histamine elevated LTC4 levels. Furthermore, the effects of NT on plasma LTC4 and hematocrit were reduced by pretreating animals with antagonists to histamine and serotonin. Pretreatment with the specific mast cell degranulating agent, compound 48/80, also blocked NT's ability to elevate plasma levels of histamine, LTB4 and LTC4 and prevented the increased hematocrit and cyanosis. These results indicate that NT-related peptides are very potent and specific stimulators of leukotriene release and that this action is mediated by mast cells and associated with loss of plasma volume and blood stasis. A working hypothesis is that histamine, released from mast cells in response to NT, stimulates LTC4 production by other cells.