Mast Cell Depletion Research Articles

Octacalcium phosphate crystals induce inflammation in vivo through interleukin‐1 but independent of the NLRP3 inflammasome in mice

To determine the mechanisms involved in inflammatory responses to octacalcium phosphate (OCP) crystals in vivo. OCP crystal-induced inflammation was monitored using a peritoneal model of inflammation in mice with different deficiencies affecting interleukin-1 (IL-1) secretion (IL-1α(-/-) , IL-1β(-/-) , ASC(-/-) , and NLRP3(-/-) mice) or in mice pretreated with IL-1 inhibitors (anakinra [recombinant IL-1 receptor antagonist] and anti-IL-1β). The production of IL-1α, IL-1β, and myeloid-related protein 8 (MRP-8)-MRP-14 complex was determined by enzyme-linked immunosorbent assay. Peritoneal neutrophil recruitment and cell viability were determined by flow cytometry. Depletion of mast cells or resident macrophages was performed by pretreatment with compound 48/80 or clodronate liposomes, respectively. OCP crystals induced peritoneal inflammation, as demonstrated by neutrophil recruitment and up-modulation of IL-1α, IL-1β, and MRP-8-MRP-14 complex, to levels comparable with those induced by monosodium urate monohydrate crystals. This OCP crystal-induced inflammation was both IL-1α- and IL-1β-dependent, as shown by the inhibitory effects of anakinra and anti-IL-1β antibody treatment. Accordingly, OCP crystal stimulation resulted in milder inflammation in IL-1α(-/-) and IL-1β(-/-) mice. Interestingly, ASC(-/-) and NLRP3(-/-) mice did not show any alteration in their inflammation status in response to OCP crystals. Depletion of the resident macrophage population resulted in a significant decrease in crystal-induced neutrophil infiltration and proinflammatory cytokine production in vivo, whereas mast cell depletion had no effect. Finally, OCP crystals induced apoptosis/necrosis of peritoneal cells in vivo. These data indicate that macrophages, rather than mast cells, are important for initiating and driving OCP crystal-induced inflammation. Additionally, OCP crystals induce IL-1-dependent peritoneal inflammation without requiring the NLRP3 inflammasome.

Mast cell repopulation of the peritoneal cavity: contribution of mast cell progenitors versus bone marrow derived committed mast cell precursors

BackgroundMast cells have recently gained new importance as immunoregulatory cells that are involved in numerous pathological processes. One result of these processes is an increase in mast cell numbers at peripheral sites. This study was undertaken to determine the mast cell response in the peritoneal cavity and bone marrow during repopulation of the peritoneal cavity in rats.ResultsTwo mast cell specific antibodies, mAb AA4 and mAb BGD6, were used to distinguish the committed mast cell precursor from more mature mast cells. The peritoneal cavity was depleted of mast cells using distilled water. Twelve hours after distilled water injection, very immature mast cells could be isolated from the blood and by 48 hours were present in the peritoneal cavity. At this same time the percentage of mast cells in mitosis increased fourfold. Mast cell depletion of the peritoneal cavity also reduced the total number of mast cells in the bone marrow, but increased the number of mast cell committed precursors.ConclusionsIn response to mast cell depletion of the peritoneal cavity, a mast cell progenitor is released into the circulation and participates in repopulation of the peritoneal cavity, while the committed mast cell precursor is retained in the bone marrow.

Alopecia in IL‐10‐deficient mouse pups is c‐kit‐dependent and can be triggered by iron deficiency

Hair loss (alopecia) can result from a variety of metabolic, endocrine, immunologic, and environmental causes. This investigation was undertaken to determine the mechanisms underlying the sporadic development of alopecia in litters from C57BL/6 interleukin-10-deficient (Il10(-/-)) mice. All pups in affected litters demonstrated alopecia by postnatal days 17-19, with hair loss from their trunks but not from their head, base of tail, or feet. Histopathology revealed distorted hair follicles containing broken hair shafts and prominent dermal infiltrates containing increased numbers of activated mast cells. Hair re-growth began soon after weaning, suggesting that the alopecia was triggered by factors transmitted during lactation. Milk from Il10(-/-) dams induced macrophage secretion of pro-inflammatory cytokines in vitro regardless of whether or not their pups developed alopecia. Feeding dams a diet containing 3-6 ppm iron increased the percentage of litters with alopecia to 100% for pups with mast cells, with 0% alopecia in mast cell-deficient pups. When dams were fed a diet containing 131 ppm iron, significantly lower haemoglobin and hematocrit values were observed in pups from litters with alopecia (71%; 5 of 7 litters) compared to litters without alopecia. Genetic or pharmacologic inhibition of c-kit that resulted in depletion of mast cells in pups prevented hair loss in at-risk litters. These studies demonstrate that maternal iron-restricted diets enhance the incidence of alopecia in IL-10-deficient mouse pups and suggest mast cells as potential effector cells. Further studies are indicated to further explore the mechanisms involved and to determine how mast cells may contribute to alopecia in humans.

The Lectin ArtinM Induces Recruitment of Rat Mast Cells from the Bone Marrow to the Peritoneal Cavity

BackgroundThe D-mannose binding lectin ArtinM is known to recruit neutrophils, to degranulate mast cells and may have potential therapeutic applications. However, the effect of ArtinM on mast cell recruitment has not been investigated.MethodologyMale Wistar rats were injected i.p. with ArtinM or ConA (control). The ability of the lectin to degranulate peritoneal and mesenteric mast cells was examined. Recruitment of mast cells to the peritoneal cavity and mesentery after ArtinM injection was examined with or without depletion of peritoneal mast cells by distilled water.ResultsArtinM degranulated both peritoneal and mesentery mast cells in vitro. Three days after i.p. injection of the lectin there were reduced numbers of mast cells in the peritoneal lavage, while at 7 days post injection of ArtinM, the number of peritoneal mast cells was close to control values. Since immature mast cells are recruited from the bone marrow, the effect of the lectin on bone marrow mast cells was examined. Injection of ArtinM resulted in an increased number of mast cells in the bone marrow. To determine if degranulation of mast cells in the peritoneal cavity was required for the increase in bone marrow mast cells, the peritoneal cavity was depleted of mast cells with ultrapure water. Exposure to ArtinM increased the number of mast cells in the bone marrow of rats depleted of peritoneal mast cells.ConclusionsThe ArtinM induced recruitment of mast cells from the bone marrow to the peritoneal cavity may partially explain the therapeutic actions of ArtinM.

Serine proteases and protease-activated receptor 2-dependent allodynia: A novel cancer pain pathway

Mediators involved in the generation of pain in patients with cancer are poorly understood. Using a combined molecular, pharmacologic, behavioral, and genetic approach, we have identified a novel mechanism of cancer-dependent allodynia induced by protease-activated receptor 2 (PAR2). Here we show that human head and neck carcinoma cells have increased levels of proteolytic activity compared to normal human cell controls. Supernatant from human carcinoma cells, but not controls, caused marked and prolonged mechanical allodynia in mice, when administered into the hindpaw. This nociceptive effect was abolished by serine protease inhibition, diminished by mast cell depletion and absent in PAR2-deficient mice. In addition, non-contact co-culture of trigeminal ganglion neurons with human head and neck carcinoma cells increased the proportion of neurons that exhibited PAR2-immunoreactivity. Our results point to a direct role for serine proteases and their receptor in the pathogenesis of cancer pain. This previously unrecognized cancer pain pathway has important therapeutic implications wherein serine protease inhibitors and PAR2 antagonists may be useful for the treatment of cancer pain.

Connective tissue mast cells are the target of formaldehyde to induce tracheal hyperresponsiveness in rats: Putative role of leukotriene B 4 and nitric oxide

Formaldehyde (FA) exposure induces upper airways irritation and respiratory abnormalities, but its mechanisms are not understood. Since mast cells are widely distributed in the airways, we hypothesized that FA might modify the airways reactivity by mechanism involving their activation. Tracheal rings of rats were incubated with Dulbecco's modified medium culture containing FA (0.1 ppm) in 96-well plastic microplates in a humid atmosphere. After 30 min, 6 h, and 24–72 h, the rings were suspended in an organ bath and dose–response curve to methacholine (MCh) were determined. Incubation with FA caused a transient tracheal hyperresponsiveness to MCh that was independent from tracheal epithelium integrity. Connective tissue mast cell depletion caused by compound 48/80 or mast cell activation by the allergic reaction, before exposure of tracheal rings to FA prevented the increased responsiveness to MCh. LTB 4 concentrations were increased in the culture medium of tracheas incubated with FA for 48 h, whereas the LTB 4-receptor antagonist MK886 (1 μM) added before FA exposure rendered the tracheal rings normoreactive to MCh. In addition, FA exposure did not cause hyperresponsiveness in tracheal segments incubated with l-arginine (1 μM). We suggest that airway connective tissue mast cells constitute the target and may provide the increased LTB 4 generation as well as an elevated consumption of NO leading to tracheal hyperresponsiveness to MCh.

Millimeter wave effects on electrical responses of the sural nerve in vivo

Millimeter wave (MMW, 42.25 GHz)-induced changes in electrical activity of the murine sural nerve were studied in vivo using external electrode recordings. MMW were applied to the receptive field of the sural nerve in the hind paw. We found two types of responses of the sural nerve to MMW exposure. First, MMW exposure at the incident power density >/=45 mW/cm(2) inhibited the spontaneous electrical activity. Exposure with lower intensities (10-30 mW/cm(2)) produced no detectable changes in the firing rate. Second, the nerve responded to the cessation of MMW exposure with a transient increase in the firing rate. The effect lasted 20-40 s. The threshold intensity for this effect was 160 mW/cm(2). Radiant heat exposure reproduced only the inhibitory effect of MMW but not the transient excitatory response. Depletion of mast cells by compound 48/80 eliminated the transient response of the nerve. It was suggested that the cold sensitive fibers were responsible for the inhibitory effect of MMW and radiant heat exposures. However, the receptors and mechanisms involved in inducing the transient response to MMW exposure are not clear. The hypothesis of mast cell involvement was discussed.

The effect of c-Kit inhibition on mast cells in skin, colon, and lung (39.46)

Abstract Stem Cell Factor (SCF) signaling via its receptor tyrosine kinase, c-Kit, is vital for mast cell development, function and survival. The effect of inhibition of c-Kit function using subcutaneous administration of a specific blocking monoclonal antibody weekly for up to 28 days was examined in African Green monkeys (Cercopithecus aethiops sabaeus). Treatment-related effects on mast cell populations were evaluated in tissue samples collected from wounded skin and colon biopsies on days 0, 7, 14, 21, and 28 (colon only) and skin, lung, and gastrointestinal tract collected at necropsy on day 28. Mast cells were visualized by Astra blue staining and immunohistochemistry for CD117, tryptase, and/or chymase. Specific c-Kit inhibition resulted in depletion of mast cells in unchallenged skin, colon, and lung after 28 days. Additionally, c-Kit antibody treatment inhibited the injury-induced expansion of dermal mast cells adjacent to wounded skin. Mast cells have been implicated as important mediators in a wide range of inflammatory diseases including asthma, rheumatoid arthritis, inflammatory bowel disease, and fibrosis. This is the first report of use of an antibody to deplete tissue mast cells in relevant organs in non-human primates.

Reduced expression of IL‐3 mediates intestinal mast cell depletion in diabetic rats: role of insulin and glucocorticoid hormones

Rats turned diabetic by alloxan treatment are refractory to systemic anaphylactic shock, in a direct association with reduced intestinal haemorrhage and tissue response to antigen challenge. As diabetic rats show reduction in mast cell numbers in different body compartments, this study was undertaken to investigate the influence of alloxan diabetes on mast cell population as well as the expression of the mast cell growth factor interleukin (IL)-3 in the small intestine of rats. We also analysed the putative involvement of endogenous insulin and glucocorticoid hormones in this phenomenon. There was a significant decrease in the number of mast cells present in the small intestine (ileum segment) of diabetic rats. Likewise, the immunohistochemical analysis revealed that IL-3 labelling was markedly attenuated in diabetic rats, as compared with normal animals, a phenomenon which paralleled with a decreased mRNA expression as attested by Reverse transcriptase-polymerase chain reaction technique. Treatment with insulin and with the steroid receptor antagonist RU 486 restored basal mast cell numbers, normal levels of IL-3 labelling and mRNA expression for IL-3 in the ileum of diabetic rats. In conclusion, our findings show that there is a causative relationship between down-regulation of mast cell numbers and the expression of IL-3 associated with diabetic state. In addition, as both parameters were suppressed by administration of insulin and RU 486, it indicates that an imbalance between the systemic levels of insulin and glucocorticoid hormones seems to be implicated in the reduction in intestinal mast cell population and refractoriness to antigen provocation in alloxan diabetes.

Mechanisms underlying the nociceptive responses induced by platelet-activating factor (PAF) in the rat paw

Platelet-activating factor (PAF) is an inflammatory mediator widely known to exert relevant pathophysiological functions. However, the relevance of PAF in nociception has received much less attention. Herein, we have investigated the mechanisms underlying PAF-induced spontaneous nociception and mechanical hypersensitivity in the rat paw. PAF injection (1–30 nmol/paw) resulted in a dose-related overt nociception, whilst only the dose of 10 nmol/paw produced a significant and time-related mechanical hypersensitivity. Local coinjection of PAF antagonist WEB2086 significantly inhibited both spontaneous nociception and mechanical hypersensitivity. Moreover, the coinjection of the natural IL-1β receptor antagonist (IRA) notably prevented both PAF-induced nociceptive responses, whilst these responses were not altered by anti-TNFα coinjection. Interestingly, pretreatment with the ultrapotent vaniloid agonist resiniferotoxin, coinjection of the TRPV1 receptor antagonist SB366791, or mast cell depletion with compound 48/80 markedly prevented PAF-induced spontaneous nociception. Conversely, PAF-elicited mechanical hypersensitivity was strikingly susceptible to distinct antineutrophil-related strategies, namely the antineutrophil antibody, the selectin blocker fucoidin, the chemokine CXCR2 receptor antagonist SB225002, and the C5a receptor antibody anti-CD88. Notably, the same antineutrophil migration strategies significantly prevented the increase of myeloperoxidase activity induced by PAF. The mechanical hypersensitivity caused by PAF was also prevented by the cyclooxygenase inhibitors indomethacin or celecoxib, and by the selective β 1 adrenergic receptor antagonist atenolol. Collectively, the present results provide consistent evidence indicating that distinct mechanisms are involved in the spontaneous nociception and mechanical hypersensitivity caused by PAF. They also support the concept that selective PAF receptor antagonists might constitute interesting targets for the development of new analgesic drugs.

Vascular permeability, neutrophil migration and edematogenic effects induced by the latex of Cryptostegia grandiflora

Inflammatory responses have been described as occurring after exposure to some latex materials. In this study pro-inflammatory activity in the latex of Cryptostegia grandiflora was investigated. The soluble proteins of the latex (CgLP) were isolated from the whole latex and evaluated by in vivo assays. CgLP induced strong inflammatory activity mediated by neutrophil migration, enlarging vascular permeability and increasing myeloperoxidase activity locally in rats. CgLP-induced inflammation was observed in peritonitis, paw edema and air push models. In addition, CgLP caused hyperemia in a healing model. The peritonitis effect was lost when CgLP was previously boiled suggesting the involvement of pro-inflammatory proteins. Thioglycollate increased the neutrophil migration induced by CgLP, but not by fMLP. Mast cell depletion provoked by 40/80 compound did not modify the course of inflammation triggered by CgLP, being similar to fMLP, which suggested that neutrophil migration was induced by direct mechanism mediated by macrophages. Neutrophil migration stimulated by CgLP was strongly inhibited by Dexamethasone and to a lesser extent by Thalidomide, indicating the involvement of cytokines in mediating neutrophil infiltration. Celecoxib and Indomethacin were inhibitory suggesting the involvement of prostaglandins. Cimetidine was effective only in the initial phase of edema. PCA 4248 was ineffective. It is concluded that the latex of C. grandiflora is a potent inflammatory fluid, and also that laticifer proteins may be implicated in this process.

The effects of compound 45/80, morphine, and mast cell depletion on electroshock seizure in mice

The effects of compound 48/80 (C48/80), morphine, and mast cell depletion on maximal electroshock seizure (MES) were studied in Swiss albino mice. An electrical current (60Hz, 0.2 msec) inducing convulsions in 50% of the animals (CC50) was assessed as 46 mA. Compound 48/80 (5 mg/kg) and morphine (100mg/kg) were administered subcutaneously. CC50 was applied separately to electroshock-unexposed animal groups at 15, 30, 60, 120, and 240 min after the onset of the experiment. In untreated controls, the percent of seizure induced by CC50 and percent of death among mice having convulsions were 50 and 20, respectively. After C48/80, a significant increase in rates of seizure at 60th and 120th min and death beyond 60th min (p < .0001) indicates a pro-convulsive action of the drug, probably caused by a reduction in MES threshold. In contrast, rate of seizure tended to decrease following mast-cell depletion, which was readily reversed by C48/80 at the 60th min (p < .0001). Mast-cell depletion, alone or plus morphine, significantly increased the death percentage of convulsions. Morphine alone reduced the percentage of seizure induced by the application of CC50 in the mast-cell depleted animals (anticonvulsive action) but increased the percent of dying animals by as much as 100% at the 30th and 60th min (p < .0001). Combined morphine + C48/80 not only augmented the anticonvulsive effect of morphine at the 30th min but also nullified the rate of death among mice having convulsions. We concluded that compound 48/80 (1) penetrates into the central nervous system to produce a central effect; (2) acts as pro-convulsive, and (3) paradoxically augments the anticonvulsive action of morphine, likely caused by the ability of the compound to increase the permeability of blood-brain barrier for morphine or by the release of histamine from mast cells in the brain, acting as anticonvulsant through the stimulation of H1 receptors or both. The precise mechanism of the increased death rate by C48/80 or morphine in intact and in mast-cell-depleted mice appears to involve pro-convulsive effects, cardiovascular impairment, and respiratory depression. The nullification of morphine-induced lethal toxicity by C48/80 could be due to the antagonistic interaction of the drug with opiate receptors in the brain.

Modulation of Meningeal Nociceptors Mechanosensitivity by Peripheral Proteinase-Activated Receptor-2: The Role of Mast Cells

Inflammatory-related activation and sensitization of meningeal nociceptors is believed to play a key role in promoting the intracranial throbbing pain of migraine. We have shown recently that mast cell activation and various mast cell-derived inflammatory mediators can promote activation and sensitization of meningeal nociceptors. Mast cell tryptase has also been proposed to promote pain hypersensitivity by activating the proteinase-activated receptor 2 (PAR2) that is expressed on nociceptive neurons. In this study using in vivo single-unit recording in the trigeminal ganglion of anaesthetized rats, we found that local meningeal activation of PAR2 using the specific agonist SLIGRL-NH2 promoted sensitization of the threshold response while provoking desensitization of the suprathreshold responses. SLIGRL-NH2 also excited a subpopulation of meningeal nociceptors. Chronic mast cell depletion enhanced the sensitizing effects of PAR2 activation while curbing its desensitizing effects. Mast cell depletion did not change the PAR2-mediated excitatory effect. We propose that by enhancing the mechanical sensitivity of meningeal nociceptors local PAR2 activation could play a role in promoting the throbbing pain of migraine and that local mast cell degranulation may modulate such an effect.

Mast cells are an essential hematopoietic component for polyp development

It is generally agreed that most colon cancers develop from adenomatous polyps, and it is this fact on which screening strategies are based. Although there is overwhelming evidence to link intrinsic genetic lesions with the formation of these preneoplastic lesions, recent data suggest that the tumor stromal environment also plays an essential role in this disease. In particular, it has been suggested that CD34(+) immature myeloid precursor cells are required for tumor development and invasion. Here we have used mice conditional for the stabilization of beta-catenin or defective for the adenomatous polyposis coli (APC) gene to reinvestigated the identity and importance of tumor-infiltrating hematopoietic cells in polyposis. We show that, from the onset, polyps are infiltrated with proinflammatory mast cells (MC) and their precursors. Depletion of MC either pharmacologically or through the generation of chimeric mice with genetic lesions in MC development leads to a profound remission of existing polyps. Our data suggest that MC are an essential hematopoietic component for preneoplastic polyp development and are a novel target for therapeutic intervention.

Neutrophil Migration Induced by IL-1β Depends upon LTB4 Released by Macrophages and upon TNF-α and IL-1β Released by Mast Cells

In the present study, we investigate whether mast cells and macrophages are involved in the control of IL-1beta-induced neutrophil migration, as well as the participation of chemotactic mediators. IL-1beta induced a dose-dependent neutrophil migration to the peritoneal cavity of rats which depends on LTB(4), PAF and cytokines, since the animal treatment with inhibitors of these mediators (MK 886, PCA 4248 and dexamethasone respectively) inhibited IL-1beta-induced neutrophil migration. The neutrophil migration induced by IL-1beta is dependent on mast cells and macrophages, since depletion of mast cells reduced the process whereas the increase of macrophage population enhanced the migration. Moreover, mast cells or macrophages stimulated with IL-1beta released a neutrophil chemotactic factor, which mimicked the neutrophil migration induced by IL-1beta. The chemotactic activity of the supernatant of IL-1beta-stimulated macrophages is due to the presence of LTB(4), since MK 886 inhibited its release. Moreover, the chemotactic activity of IL-1beta-stimulated mast cells supernatant is due to the presence of IL-1beta and TNF-alpha, since antibodies against these cytokines inhibited its activity. Furthermore, significant amounts of these cytokines were detected in the supernatant. In conclusion, our results suggest that neutrophil migration induced by IL-1beta depends upon LTB(4) released by macrophages and upon IL-1beta and TNFalpha released by mast cells.

Resident peritoneal leukocytes are important sources of MMP-9 during zymosan peritonitis: Superior contribution of macrophages over mast cells

Metalloproteinase 9 (MMP-9) is crucial for normal neutrophil infiltration into zymosan-inflamed peritoneum. During the course of zymosan peritonitis MMP-9 is produced in a biphasic-manner as its presence is detectable as early as 30 min post zymosan and then between 2 and 8 h of inflammation. As inflammatory leukocytes were shown to produce MMP-9 we asked if also resident leukocytes, mast cells and macrophages, contribute to its production. And furthermore, if their contribution is limited only to the early phase of inflammation or extends to the later stages. For this purpose some mice were depleted of either resident macrophages or functional mast cells and expression of MMP-9 in peritoneal leukocytes and its release to the exudate were monitored. It turned out that depletion of peritoneal macrophages decreased both MMP-9 content in the leukocytes and its release to the inflammatory exudate at 30 min and 6 h of peritonitis. The functional depletion of mast cells also caused a significant decrease in the production/release of MMP-9 that was especially apparent at the early time point (30 min). Moreover, the study shows concomitant kinetics of MMP-9 expression in leukocytes and its release to the exudatory fluid. The findings indicate that resident tissue leukocytes, and among them especially macrophages, constitute an important source of MMP-9 during acute peritoneal inflammation. Overall, the study shows that resident tissue leukocytes, mostly macrophages, constitute an important cellular source(s) of inflammation-related factors and should be regarded as possible targets of anti-inflammatory treatment.

Development of mast cells

Mast cells are progeny of the multipotential hematopoietic stem cell (MHSC). Mast cell-committed progenitors (MCPs) leave hematopoietic tissues, migrate in peripheral blood, invade to connective or mucosal tissue, proliferate and differentiate to morphologically identifiable mast cells. Phenotype of mast cells (connective tissue-type or mucosal type) is determined by the site of lodgment of MCPs. Most progeny of the multipotential hematopoietic stem cell lose proliferation potential after maturation, but connective tissue-type mast cells (CTMCs) possess appreciable proliferation potential after maturation. Even after functioning by degranulation, CTMCs proliferate and restore the original morphology. The most important cytokine for development and survival of mast cells is KIT ligand, and the KIT receptor tyrosine kinase is expressed through the whole developmental process of mast cells from MHSC to mature mast cells. The loss-of-function mutation of KIT gene results in depletion of mast cells, whereas its gain-of-function mutation causes mast cell tumors. Since mast cells are involved in various disease processes, intervention in development of mast cells might be beneficial to the treatment.

Modulation of acute inflammation by a chitin-binding lectin from Araucaria angustifolia seeds via mast cells

The effects of a lectin (AaL) from seeds of Araucaria angustifolia were investigated in the model of rat paw edema. In vivo anti-and pro-inflammatory activities, role of sugar residues, inflammatory mediators and systemic toxicity were assessed. Intravenous injection of AaL (0.1-1 mg/kg) dose-dependently inhibited the dextran-induced increase in edema and vascular permeability, which were prevented by association of the lectin with its binding sugar N-acetyl-glucosamine (Glyc-Nac). AaL also significantly inhibited edema induced by serotonin (18%) and compound 48/80 (33%), but not edema induced by histamine. In contrast, when applied by the s.c. route, AaL evoked a paw edema that peaked 1 h later and was partially prevented by association with Glyc-Nac (59%) or by prior i.v. administration of the lectin itself (38.8%). This AaL edematogenic activity was significantly inhibited by pentoxifylline (44.4%) or dexamethasone (51%) and also by depletion of rat paw mast cells (45.6%), but not by L-N-nitro-arginine methyl ester or indomethacin, excluding involvement of nitric oxide and prostaglandins. Treatment of animals with a single anti-inflammatory dose of AaL (1 mg/kg, i.v.) for 7 days did not affect rat corporal mass, liver, kidney, spleen or stomach wet weight, blood leukocyte count, and urea, creatinine or serum transaminase activity. Systemic toxicity was apparent only at much higher doses (LD50=88.3 mg/kg) than those required for the anti-inflammatory effect. Summarizing, AaL exerts anti-and pro-edematogenic actions via interaction with its specific lectin domain. These actions may share a common pathway involving either activation or inhibition of inflammatory mediators from resident mast cells.

Aldose reductase inhibitor zopolrestat restores allergic hyporesponsiveness in alloxan-diabetic rats

This study was undertaken to investigate the role of the aldose reductase in the refractoriness of diabetic rats to allergic inflammation. Wistar rats were actively sensitized with a mixture of Al(OH) 3 plus ovalbumin and intrapleurally challenged with ovalbumin, 14 days later. Diabetes was induced by intravenous injection of alloxan into fasted rats, 7 days before sensitization, and the aldose reductase inhibitor zopolrestat was administered after 3 days of diabetes induction, once a day during 18 consecutive days. The treatment with zopolrestat restored antigen-induced protein extravazation and mast cell degranulation in the pleural cavity of diabetic sensitized rats. Zopolrestat also significantly reversed the suppression in the increase of total and specific levels of serum immunoglobulin E (IgE) noted in sensitized animals under conditions of diabetes. In addition, we noted that the drop in the pleural mast cell numbers as well as the increase in serum corticosterone levels in diabetic rats were inhibited by the drug. Our findings show that zopolrestat restored the hyporesponsiveness of diabetic rats to antigen provocation, in parallel with impairment of alloxan-induced mast cell depletion and hypercorticolism, indicating that polyol pathway activity seems to play an important role in these phenomena.

Neurokinin-1 receptor in peripheral nerve terminals mediates thermal hyperalgesia

Neurokinin-1 receptor (NK-1) plays an important role in nociception. The present study was to explore whether activation of peripheral NK-1 receptor, especially expressed on primary sensory afferents, could induce hyperalgesia and sensitize C-type sensory afferents. (1) Intraplantar administration of NK-1 agonist [Sar 9, Met(O 2) 11]SP (Sar-SP, 0.2, 1 nmol, 20 μl) produced significant thermal hyperalgesia and edema, which was blocked by co-injection of NK-1 antagonist WIN51,708 (10 nmol). But in the rats with compound 48/80 treatment for mast cell depletion, the Sar-SP-induced edema, but not hyperalgesia, was attenuated. (2) Close-arterial injection of Sar-SP (1 nmol, 0.1 ml) excited and sensitized sensory C afferents of the sural nerve to heat stimuli. The results suggest involvement of NK-1 receptors expressed on the peripheral afferent terminals in thermal hyperalgesia mediated by directly sensitizing C-type sensory afferents.