Evidence that endogenous interleukin-1 is involved in leukocyte migration in acute experimental inflammation in rats and mice

Development of a Sensitive Bioluminogenic Probe for Imaging Highly Reactive Oxygen Species in Living Rats

A sensitive bioluminogenic probe for highly reactive oxygen species (hROS), SO3 H-APL, was developed based on the concept of dual control of bioluminescence emission by means of bioluminescent enzyme-induced electron transfer (BioLeT) and modulation of cell-membrane permeability. This probe enables non-invasive visualization of physiologically relevant amounts of hROS generated deep inside the body of living rats for the first time. It is expected to serve as a practical analytical tool for investigating a wide range of biological functions of hROS in vivo. The design concept should be applicable to other in vivo bioluminogenic probes.

Definition of a Novel Pathway Centered on Lysophosphatidic Acid To Recruit Monocytes during the Resolution Phase of Tissue Inflammation

Blood-derived monocytes remove apoptotic cells and terminate inflammation in settings as diverse as atherosclerosis and Alzheimer’s disease. They express high levels of the proresolving receptor ALX/FPR2, which is activated by the protein annexin A1 (ANXA1), found in high abundance in inflammatory exudates. Using primary human blood monocytes from healthy donors, we identified ANXA1 as a potent CD14⁺CD16⁻ monocyte chemoattractant, acting via ALX/FPR2. Downstream signaling pathway analysis revealed the p38 MAPK-mediated activation of a calcium independent phospholipase A₂ with resultant synthesis of lysophosphatidic acid (LPA) driving chemotaxis through LPA receptor 2 and actin cytoskeletal mobilization. In vivo experiments confirmed ANXA1 as an independent phospholipase A₂–dependent monocyte recruiter; congruently, monocyte recruitment was significantly impaired during ongoing zymosan-induced inflammation in AnxA1^−/− or alx/fpr2/3^−/− mice. Using a dorsal air-pouch model, passive transfer of apoptotic neutrophils between AnxA1^−/− and wild-type mice identified effete neutrophils as the primary source of soluble ANXA1 in inflammatory resolution. Together, these data elucidate a novel proresolving network centered on ANXA1 and LPA generation and identify previously unappreciated determinants of ANXA1 and ALX/FPR2 signaling in monocytes.

Nonredundant protective properties of FPR2/ALX in polymicrobial murine sepsis

Sepsis is characterized by overlapping phases of excessive inflammation temporally aligned with an immunosuppressed state, defining a complex clinical scenario that explains the lack of successful therapeutic options. Here we tested whether the formyl-peptide receptor 2/3 (Fpr2/3)--ortholog to human FPR2/ALX (receptor for lipoxin A4)--exerted regulatory and organ-protective functions in experimental sepsis. Coecal ligature and puncture was performed to obtain nonlethal polymicrobial sepsis, with animals receiving antibiotics and analgesics. Clinical symptoms, temperature, and heart function were monitored up to 24 h. Peritoneal lavage and plasma samples were analyzed for proinflammatory and proresolving markers of inflammation and organ dysfunction. Compared with wild-type mice, Fpr2/3(-/-) animals exhibited exacerbation of disease severity, including hypothermia and cardiac dysfunction. This scenario was paralleled by higher levels of cytokines [CXCL1 (CXC receptor ligand 1), CCL2 (CC receptor ligand 2), and TNFα] as quantified in cell-free biological fluids. Reduced monocyte recruitment in peritoneal lavages of Fpr2/3(-/-) animals was reflected by a higher granulocyte/monocyte ratio. Monitoring Fpr2/3(-/-) gene promoter activity with a GFP proxy marker revealed an over threefold increase in granulocyte and monocyte signals at 24 h post-coecal ligature and puncture, a response mediated by TNFα. Treatment with a receptor peptido-agonist conferred protection against myocardial dysfunction in wild-type, but not Fpr2/3(-/-), animals. Therefore, coordinated physio-pharmacological analyses indicate nonredundant modulatory functions for Fpr2/3 in experimental sepsis, opening new opportunities to manipulate the host response for therapeutic development.

Interleukin-1β and interleukin-1 receptor antagonist appear in grey matter additionally to white matter lesions during experimental multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) has been mainly attributed to white matter (WM) pathology. However, recent evidence indicated the presence of grey matter (GM) lesions. One of the principal mediators of inflammatory processes is interleukin-1β (IL-1β), which is known to play a role in MS pathogenesis. It is unknown whether IL-1β is solely present in WM or also in GM lesions. Using an experimental MS model, we questioned whether IL-1β and the IL-1 receptor antagonist (IL-1ra) are present in GM in addition to affected WM regions.

METHODS

The expression of IL-1β and IL-1ra in chronic-relapsing EAE (cr-EAE) rats was examined using in situ hybridization, immunohistochemistry and real-time PCR. Rats were sacrificed at the peak of the first disease phase, the trough of the remission phase, and at the peak of the relapse. Histopathological characteristics of CNS lesions were studied using immunohistochemistry for PLP, CD68 and CD3 and Oil-Red O histochemistry.

RESULTS

IL-1β and IL-ra expression appears to a similar extent in affected GM and WM regions in the brain and spinal cord of cr-EAE rats, particularly in perivascular and periventricular locations. IL-1β and IL-1ra expression was dedicated to macrophages and/or activated microglial cells, at sites of starting demyelination. The time-dependent expression of IL-1β and IL-1ra revealed that within the spinal cord IL-1β and IL-1ra mRNA remained present throughout the disease, whereas in the brain their expression disappeared during the relapse.

CONCLUSIONS

The appearance of IL-1β expressing cells in GM within the CNS during cr-EAE may explain the occurrence of several clinical deficits present in EAE and MS which cannot be attributed solely to the presence of IL-1β in WM. Endogenously produced IL-1ra seems not capable to counteract IL-1β-induced effects. We put forward that IL-1β may behold promise as a target to address GM, in addition to WM, related pathology in MS.

Changes in Mobility of the Golden Hamster with Induction of an IL-1-Induced Arthritis

Many studies in animals have examined biochemical, immune and histological changes during arthritis; however, the study of the effects of arthritis on mobility has been largely neglected. Interleukin-1, administered by the intraarticular route into hamster knee joints, resulted in inhibition of spontaneous wheel running activity; however, the effect was transient, lasting only through the evening following IL-1 administration. A further injection of IL-1 2 days later showed still greater inhibition of running. The effect again did not extend beyond the first evening after injection. IL-1alpha and IL-1beta showed equivalent effects on mobility, and no evidence was seen for cooperative interaction between them. A 50% inhibition of running occurred at a dose of approximately 10 ng/knee of IL-1alpha. The effect appeared not to be systemic since intraperitoneal injection required microgram amounts of IL-1 for an equivalent inhibition. At the time mobility had been restored to normal, histological examination showed the continued presence of inflammatory cells, soft tissue swelling and cartilage proteoglycan loss. These results suggest a lack of correlation between inhibition of mobility and histopathological changes in cartilage and soft tissue.

Conceivable difference in the anti-inflammatory mechanisms of lipocortins 1 and 5

Human recombinant lipocortins (LCT) 1 and 5 have been expressed in a yeast secretion vector and purified by ion exchange chromatography. The action of the proteins has been investigated in two models of experimental acute inflammation in the rat: carrageenin induced paw oedema and zymosan induced pleurisy. The effects of the proteins on PGE(2) release in vitro by rat macrophages stimulated with zymosan and on rat neutrophil chemotaxis induced by FMLP have also been assessed. LCT-1 significantly inhibited both paw swelling in carrageenin oedema and leukocyte migration in zymosan pleurisy. Moreover it showed a dose dependent, inhibitory effect on PGE(2) release. Neutrophil chemotaxis was only weakly affected by LCT-1. Conversely LCT-5 did not reduce carrageenin oedema and slightly inhibited PGE(2) release, but showed profound, dose dependent inhibitory activity on leukocyte migration in zymosan pleurisy and on neutrophil chemotaxis. These data suggest that LCT-1 acts mainly by interfering with arachidonic acid metabolism via the inhibition of phospholipase A(2). The anti-inflammatory activity of LCT-5, at variance with LCT-1, may be due to a direct effect on cell motility in addition to the interference with arachidonic acid metabolism.

Glucocorticoids as cytokine inhibitors: role in neuroendocrine control and therapy of inflammatory diseases

Glucocorticoids are potent inhibitors of inflammation and endotoxic shock. This probably occurs through an inhibition of the synthesis of pro-inflammatory cytokines as well as of many of their toxic activities. Therefore, endogenous glucocorticoids (GC) might represent a major mechanism in the control of cytokine mediated pathologies. GC inhibit the synthesis of cytokines in various experimental models. Adrenalectomy or GC antagonists potentiate TNF, IL-1 and IL-6 production in LPS treated mice. GC inhibit the formation of arachidonic acid metabolites and the induction of NO synthase. They also inhibit various activities of cytokines including toxicity, haemodynamic shock and fever. Adrenalectomy sensitizes to the toxic effects of LPS, TNF and IL-1. On the other hand, GC potentiate the synthesis of several cytokine induced APP by the liver. Since many of these proteins have anti-toxic activities (antioxidant, antiprotease etc.) or bind cytokines, this might well represent a GC mediated protective feedback mechanism involving the liver. Not only do GC inhibit cytokines, but in vivo LPS and various cytokines (TNF, IL-1, IL-6) increase blood GC levels through a central mechanism involving the activation of the HPA. Thus, this neuroendocrine response to cytokines constitutes an important immunoregulatory feedback involving the brain.

Kinetics of proinflammatory cytokines after intraperitoneal injection of tribromoethanol and a tribromoethanol/xylazine combination in ICR mice

Tribromoethanol (2,2,2-tribromoethanol, TBE) is a popular injectable anesthetic agent used in mice in Korea. Our goal was to assess the risks associated with side effects (lesions) in the abdominal cavity, especially at high doses. To understand the underlying pathophysiological changes, we examined levels of cytokines through ELISA of abdominal lavage fluid and spleen collected from mice treated with low and high-dose TBE. ICR mice were anesthetized using one of the following protocols: a combination of TBE 200 mg/kg (1.25%) and xylazine 10 mg/kg; TBE 400 mg/kg (1.25%); and TBE 400 mg/kg (2.5%). Administration of high-dose TBE (400 mg/kg) increased the interleukin-1β and interleukin-6 levels in the peritoneal cavity over the short term (<1 day) compared with sham controls and low-dose TBE (200 mg/kg) groups. Cytokine expression in the low-dose TBE group was similar to the control group, whereas in the high-dose TBE group cytokine levels were higher in abdominal lavage fluid and spleen over the long term (10 days post-injection). We conclude that a combination of TBE 200 mg/kg (1.25%) and xylazine (10 mg/kg) is a safe and effective anesthetic for use in animals.

Anti-inflammatory role of the murine formyl-peptide receptor 2: ligand-specific effects on leukocyte responses and experimental inflammation

The human formyl-peptide receptor (FPR)-2 is a G protein-coupled receptor that transduces signals from lipoxin A(4), annexin A1, and serum amyloid A (SAA) to regulate inflammation. In this study, we report the creation of a novel mouse colony in which the murine FprL1 FPR2 homologue, Fpr2, has been deleted and describe its use to explore the biology of this receptor. Deletion of murine fpr2 was verified by Southern blot analysis and PCR, and the functional absence of the G protein-coupled receptor was confirmed by radioligand binding assays. In vitro, Fpr2(-/-) macrophages had a diminished response to formyl-Met-Leu-Phe itself and did not respond to SAA-induced chemotaxis. ERK phosphorylation triggered by SAA was unchanged, but that induced by the annexin A1-derived peptide Ac2-26 or other Fpr2 ligands, such as W-peptide and compound 43, was attenuated markedly. In vivo, the antimigratory properties of compound 43, lipoxin A(4), annexin A1, and dexamethasone were reduced notably in Fpr2(-/-) mice compared with those in wild-type littermates. In contrast, SAA stimulated neutrophil recruitment, but the promigratory effect was lost following Fpr2 deletion. Inflammation was more marked in Fpr2(-/-) mice, with a pronounced increase in cell adherence and emigration in the mesenteric microcirculation after an ischemia-reperfusion insult and an augmented acute response to carrageenan-induced paw edema, compared with that in wild-type controls. Finally, Fpr2(-/-) mice exhibited higher sensitivity to arthrogenic serum and were completely unable to resolve this chronic pathology. We conclude that Fpr2 is an anti-inflammatory receptor that serves varied regulatory functions during the host defense response. These data support the development of Fpr2 agonists as novel anti-inflammatory therapeutics.

Neutrophil migration induced by IL-1beta depends upon LTB4 released by macrophages and upon TNF-alpha and IL-1beta 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.

Diagnosis of peritonitis using near-infrared optical imaging of in vivo labeled monocytes-macrophages

Peritonitis is an inflammatory process characterized by massive monocytes-macrophages infiltration. Since early diagnosis is important for a successful therapeutic outcome, the feasibility for a selective labeling and imaging of macrophages for highly sensitive optical imaging was assessed. After in vitro incubation of mouse macrophages J774A.1 with the far-red/near-infrared fluorochrome DY-676, distinct fluorescence intensities (1026+/-142 a.u.) were detected as compared to controls (552+/-54 a.u.) using a whole-body small animal near-infrared fluorescence (NIRF) imaging system. Macrophage labeling was confirmed by confocal laser scanning microscopy (CLSM) and fluorescence-activated cell sorting, (FACS). The fluorochrome was also found to be predominantly distributed within compartments in the cytoplasm. Additionally, peritonitis was induced in mice by intraperitoneal injection of zymosanA. After intravenous injection of fluorochrome (55 nmol/kg) and using whole-body fluorescence imaging, higher fluorescence intensities (869+/-151 a.u.) were detected in the peritoneal area of diseased mice as compared to controls (188+/-41 a.u.). Furthermore, cells isolated from peritoneal lavage revealed the presence of labeled monocytes-macrophages. The results indicate that in vivo diagnosis of peritonitis by near-infrared optical imaging of labeled monocytes-macrophages is feasible. Possibly, early stages of other inflammatory diseases could also be detected by the proposed diagnostic method in the long term.

Spatial and temporal profiles for anti-inflammatory gene expression in leukocytes during a resolving model of peritonitis

The recent appreciation of the role played by endogenous counterregulatory mechanisms in controlling the outcome of the host inflammatory response requires specific analysis of their spatial and temporal profiles. In this study, we have focused on the glucocorticoid-regulated anti-inflammatory mediator annexin 1. Induction of peritonitis in wild-type mice rapidly (4 h) produced the expected signs of inflammation, including marked activation of resident cells (e.g., mast cells), migration of blood-borne leukocytes, mirrored by blood neutrophilia. These changes subsided after 48-96 h. In annexin 1(null) mice, the peritonitis response was exaggerated ( approximately 40% at 4 h), with increased granulocyte migration and cytokine production. In blood leukocytes, annexin 1 gene expression was activated at 4, but not 24, h postzymosan, whereas protein levels were increased at both time points. Locally, endothelial and mast cell annexin 1 gene expression was not detectable in basal conditions, whereas it was switched on during the inflammatory response. The significance of annexin 1 system plasticity in the anti-inflammatory properties of dexamethasone was assessed. Clear induction of annexin 1 gene in response to dexamethasone treatment was evident in the circulating and migrated leukocytes, and in connective tissue mast cells; this was associated with the steroid failure to inhibit leukocyte trafficking, cytokine synthesis, and mast cell degranulation in the annexin 1(null) mouse. In conclusion, understanding how inflammation is brought under control will help clarify the complex interplay between pro- and anti-inflammatory pathways operating during the host response to injury and infection.

Beneficial effects of troglitazone on neutrophil dysfunction in multiple low-dose streptozotocin-induced diabetic mice

Patients with poorly controlled diabetes are at high risk of acquiring bacterial infections. However, conflicting results have been reported on neutrophil function in diabetes. We periodically evaluated neutrophil dysfunction in multiple low-dose streptozotocin (STZ)-induced diabetic mice, and then evaluated the effects of troglitazone and other thiazolidinediones (TZDs) on the decline of neutrophil function. Zymosan was injected intraperitoneally and neutrophil infiltration and phagocytosis were evaluated. While phagocytosis of zymosan by peritoneal neutrophils was consistently reduced in diabetic mice, neutrophil infiltration was decreased on day 30, but increased on day 40 after STZ injection. The in vitro chemotactic and phagocytic activities of blood neutrophils in mice that did not receive zymosan were consistently reduced in diabetic mice. Phorbol myristate acetate (PMA)-stimulated superoxide production by zymosan-induced peritoneal neutrophils and the levels of zymosan-induced tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta in peritoneal exudate fluids were also reduced in the diabetic mice. Treatment of the diabetic mice with troglitazone beginning 2 weeks after STZ injection did not improve hyperglycaemia but did prevent the decline of zymosan-induced neutrophil infiltration on day 30, and additionally promoted the increased infiltration on day 40. Troglitazone also promoted the chemotactic activity of blood neutrophils isolated from normal mice in vitro. Rosiglitazone but not pioglitazone induced a similar effect. Neutrophil phagocytosis was not enhanced by troglitazone either in vivo or in vitro. Taken together, neutrophil function is impaired by STZ-induced diabetes, but inflammatory infiltration does not always vary with the chemotactic disability or cytokine levels. Furthermore, troglitazone and rosiglitazone were suggested to improve at least neutrophil chemotactic activity in these animals.

Neutrophil elastase (NE)-deficient mice demonstrate a nonredundant role for NE in neutrophil migration, generation of proinflammatory mediators, and phagocytosis in response to zymosan particles in vivo

Neutrophil elastase (NE) remains a controversial player in the process of leukocyte transmigration and much of this controversy stems from conflicting reports on the effects of NE inhibitors. The availability of NE-deficient mice (NE(-/-)) provides a clean and elegant tool for the study of leukocyte migration in vivo. In this study, NE(-/-) mice were used to investigate the role of NE in leukocyte migration through cremasteric venules, as observed by intravital microscopy, induced by locally administered cytokines IL-1beta and TNF-alpha and the particulate stimulus, zymosan. Although no defects in leukocyte responses induced by the cytokines were observed, zymosan-induced leukocyte firm adhesion and transmigration was suppressed in NE(-/-) mice. These responses were also inhibited in wild-type mice when zymosan was coinjected with a specific NE inhibitor. Quantification of inflammatory mediator levels in homogenates of zymosan-stimulated tissues indicated reductions in levels of IL-1beta, KC, and macrophage inflammatory protein-1alpha in NE(-/-) mice. Furthermore, phagocytosis of fluorescent zymosan particles, as observed by intravital microscopy, was diminished in NE-deficient animals. Collectively, the findings of this study indicate a nonredundant role for NE in zymosan-induced leukocyte firm adhesion and transmigration, and that this defect is associated with impaired generation of proinflammatory mediators as well as phagocytosis of zymosan particles in vivo.

Effect of FK506 (tacrolimus) in animal models of inflammation

Inflammation is the response of living tissue to damage. Cytokines play an important role in inflammatory processes. FK506 (tacrolimus), an immunosuppressant, is known to reduce the activation of microglia in vitro and affect the expression of various cytokines like interleukin-1, interleukin-6 and tumor necrosis factor. With this background the present study was designed to explore the effect of FK506 in animal models of acute inflammation and experimental pleurisy. Acute inflammation in rats was induced by intraplantar injection of carrageenan (1%, w/v). Experimental pleurisy was induced in rats by intrapleural injection of carrageenan (2%, w/v). Pretreatment with FK506 (0.5-3 mg/kg p.o.) significantly and dose-dependently reduced carrageenan-induced increase in paw volume, as well as carrageenan-induced inflammatory nociception. FK506 (1 and 3 mg/kg p.o.) inhibits exudate formation and migration of polymorhonuclear leukocytes and monocytes in carrageenan-induced experimental pleurisy. The myeloperoxidase enzyme level was significantly increased in carrageenan-treated animals, which was significantly reversed by FK506 treatment. The results of the present study suggest the potential anti-inflammatory properties of FK506 against carrageenan-induced acute inflammation and experimental pleurisy.

In vitro and in vivo responses of murine granulocytes to human complement-derived, haemolytically inactive C5b67 (iC5b67)

Haemolytically inactive C5b67 (iC5b67), which was made from purified human components and decayed to a haemolytically inactive form, was evaluated as an agonist for murine leucocytes both in vitro and in vivo. In an in vitro assay, iC5b67 stimulated chemotaxis for both neutrophils purified from mouse bone marrow and splenic eosinophils of IL-5 transgenic mice. The stimulation was dose-dependent, with high dose inhibition. As with human neutrophils, iC5b67 also failed to up-regulate CR3 (CD11b/CD18) expression and to stimulate superoxide generation in murine bone marrow neutrophils, in vitro. In vivo, iC5b67 elicited an inflammatory response in a mouse model of pleuritis. A marked infiltration of neutrophils, which peaked at 4 h, was followed by an infiltration of eosinophils and mononuclear leucocytes. This inflammatory response was dose- and time-dependent. However, the protein concentration in the pleural wash fluid did not increase, indicating that iC5b67 did not induce a capillary leak. Although the infiltration of neutrophils could not be reproduced by pure C7 or human serum albumin (HSA), C5b6 did induce an influx of neutrophils. We were able to document the existence of C7, both antigenically and functionally, in pleural washes of normal mice, making it likely that the activity of C5b6 resulted from the in situ formation of C5b67 and iC5b67. The mouse model of pleuritis promises to be a useful in vivo system in which to evaluate the pro- and anti-inflammatory effects of iC5b67 that have been noted in vitro.

Inhibition of poly (ADP-ribose) synthetase attenuates neutrophil recruitment and exerts antiinflammatory effects

A cytotoxic cycle triggered by DNA single-strand breakage and poly (ADP-ribose) synthetase activation has been shown to contribute to the cellular injury during various forms of oxidant stress in vitro. The aim of this study was to investigate the role of poly (ADP-ribose) synthetase (PARS) in the process of neutrophil recruitment and in development of local and systemic inflammation. In pharmacological studies, PARS was inhibited by 3-aminobenzamide (10-20 mg/kg) in rats and mice. In other sets of studies, inflammatory responses in PARS-/- mice were compared with the responses in corresponding wild-type controls. Inhibition of PARS reduced neutrophil recruitment and reduced the extent of edema in zymosan- and carrageenan-triggered models of local inflammation. Moreover, inhibition of PARS prevented neutrophil recruitment, and reduced organ injury in rodent models of inflammation and multiple organ failure elicited by intraperitoneal injection of zymosan. Inhibition of PARS also reduced the extent of neutrophil emigration across murine mesenteric postcapillary venules. This reduction was due to an increased rate of adherent neutrophil detachment from the endothelium, promoting their reentry into the circulation. Taken together, our results demonstrate that PARS inhibition reduces local and systemic inflammation. Part of the antiinflammatory effects of PARS inhibition is due to reduced neutrophil recruitment, which may be related to maintained endothelial integrity.

Nitric oxide synthase and cyclo-oxygenase pathways in the inflammatory response induced by zymosan in the rat air pouch

1. We have studied the participation of nitric oxide (NO) in an animal model of inflammation, the rat air pouch stimulated with zymosan. 2. Saline or zymosan was injected into 6-day rat air pouches at different time points and measurements were made of cell migration, levels of nitrite/nitrate (NO2/NO3-), prostaglandin E2 (PGE2), leukotriene B4 (L.TB4) and secretory phospholipase A2 (sPLA2) in exudates. Nitric oxide synthase (NOS) activity was determined in high speed supernatants from cells present in pouch exudates. Western blot analysis was also performed on these samples. 3. Zymosan injection induced a time-dependent increase in leukocyte infiltration, NO2/NO3- levels and cellular NOS activity that reached a peak by 8 h. Western blot analysis showed the same time course for induction of NOS protein. Colchicine administration to rats inhibited cellular infiltration and decreased the levels of NO metabolites and cellular NOS activity zymosan-injected air pouch at 8 h. NOS activity was present in polymorphonuclear leukocytes (PMNs) and monocytes, but not in the lymphocytes present in exudates. This enzyme is calcium-independent and needs NADPH for activity. PGE2 levels in exudates showed a time course inverse to that of NOS activity and NO metabolites, with maximum levels of PGE2 observed at 4 h after zymosan injection. 4. Administration of NG-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine to rats significantly reduced cellular NOS activity, NO2/NO3- levels and chemiluminescence, whereas they were without effect on cell migration and degranulation, eicosanoid levels and sPLA2 activity. 5. Treatment of animals with dexamethasone inhibited cellular NOS activity, NO2/NO3- levels, chemiluminescence and the increase in the levels of PGE2 and LTB4, with only a weak effect on elastase release. 6. Administration of the selective cyclo-oxygenase-2 (COX-2) inhibitor NS398 to rats strongly reduced PGE2 levels in exudates without affecting NO metabolites or NOS activity at 4 h after zymosan injection. 7. Our data indicate that NOS is induced in the zymosan-stimulated rat air pouch model of inflammation. This enzyme is expressed in the cells migrating into the air pouch and caused an increased production of NO metabolites in exudates. The results also suggest the presence of an earlier phase in which eicosanoids play the main role, with participation of COX-2 activity, and a later phase mediated by NO. The endogenous release of NO does not modify prostaglandin biosynthesis in this in vivo model.

Inhibition of neutrophil and monocyte recruitment by endogenous and exogenous lipocortin 1

1. The role played by endogenous lipocortin 1 in the anti-migratory action exerted by dexamethasone (Dex) on monocyte recruitment in an in vivo model of acute inflammation was investigated by use of several neutralizing polyclonal antibodies raised against lipocortin 1 or a lipocortin 1-derived N-terminus peptide (peptide Ac2-26). The efficacy of peptide Ac2-26 in inhibiting monocyte and polymorphonuclear leucocyte (PMN) recruitment was also tested. 2. Intraperitoneal (i.p.) injection of zymosan A (1 mg) produced a time-dependent cell accumulation into mouse peritoneal cavities which followed a typical profile of acute inflammation: PMN influx was maximal at 4 h post-zymosan (between 15 and 20 x 10(6) cells per mouse), and this was followed by an accumulation of monocytes which peaked at the 24 h time-point (between 10 and 15 x 10(6) cells per mouse). 3. Dex administration to mice reduced zymosan-induced 4 h PMN infiltration and 24 h monocyte accumulation with similar efficacy: approximately 50% of inhibition of recruitment of both cell types was achieved at the dose of 30 micrograms per mouse (approximately 1 mg kg-1, subcutaneously (s.c.)). Maximal inhibitions of 64% and 67% on PMN and monocyte recruitment, respectively, were measured after a dose of 100 micrograms per mouse (approximately 3 mg kg-1, s.c.). 4. Dex (30 micrograms s.c.) inhibited monocyte (53%) and PMN (69%) accumulation in response to zymosan application in mice which had been treated with a non-immune sheep serum (50 microliters s.c.). In contrast, the steroid was no longer active in reducing cell accumulation in mice which had been passively immunized against full length human recombinant lipocortin 1 (serum LCS3), or against lipocortin 1 N-terminus peptide. 5. Treatment of mice with vinblastine (1 mg kg-1, intravenously (i.v.)) produced a remarkable leucopenia as assessed 24 h after administration. This was accompanied by a 60% reduction in 4 h-PMN influx, and by a 27% reduction in 24 h-monocyte accumulation, measured after zymosan administration. The inhibitory effect of Dex on monocyte recruitment was not significantly modified in vinblastine-treated mice, with 36% and 57% of inhibition calculated at the dose of 30 micrograms Dex, and 70% and 60% of inhibition at 100 micrograms Dex, in vehicle- and vinblastine-treated mice, respectively. 6. Treatment of mice with peptide Ac2-26 dose-dependently attenuated PMN influx at 4 h post-zymosan with a significant effect at 100 micrograms per mouse (45% of inhibition, n-9, P < 0.05) and a maximal effect of 61% inhibition at the highest dose tested of 200 micrograms s.c. (n = 14, P < 0.05). No effect of peptide Ac2-26 (200 micrograms s.c.) was seen on zymosan-induced 24 h monocyte recruitment. In contrast, administration of 200 micrograms peptide Ac2-26 every 6 h was effective in reducing the number of monocytes harvested from the inflamed peritoneal cavities at 24 h post-zymosan: 9.40 +/- 0.58 x 10(6) monocytes per mouse (n = 13) and 5.74 +/- 0.34 monocytes per mouse (n = 14) in vehicle- and peptide Ac2-26-treated mice, respectively (P < 0.05). 7. Finally, peptide Ac2-26 produced a concentration-dependent inhibition of the rate of phagocytosis of mouse resident peritoneal macrophages as measured by flow cytometry, with a maximal reduction of 34% at the highest concentration tested of 100 micrograms ml-1 (n = 8 experiments performed in duplicate; P < 0.05). 8. In conclusion, this study suggests that in vivo monocyte recruitment during acute inflammation is, at least in part, under the negative modulatory control of endogenous lipocortin 1 (as seen after administration of Dex by using the specific antisera) and exogenous lipocortin 1 mimetics (as observed with peptide Ac2-26. In addition to the neutrophil, we can now propose that the monocyte also can be a target for the in vivo anti-inflammatory action of lipocortin 1.

Mobilizing lipocortin 1 in adherent human leukocytes downregulates their transmigration

Polymorphonuclear leukocyte (PMN) migration into sites of inflammation is fundamental to the host defense response. Activation of endothelial cells and PMNs increases the expression or activation of adhesion molecules, culminating in rolling and subsequent adherence of these cells to the vascular wall. Further activation of adherent PMNs, possibly by endothelial cell ligands, leads, within a few minutes, to extravasation itself. This process is not clearly understood, but adhesion molecules or related proteins, as well as endogenous chemokines, may play an important role. The anti-inflammatory glucocorticoids delay extravasation, which implies that an inhibitory regulatory system exists. Resting PMNs contain abundant cytoplasmic lipocortin 1 (LC1, also called annexin I)', and the activity profile of this protein suggests that it could reduce PMN responsiveness. To investigate this we have assessed neutrophil transmigration both in vivo and in vitro and examined the content and subcellular distribution of LC1 in PMNs by fluorescence-activated cell-sorting (FACS) analysis, western blotting and confocal microscopy. We report that LC1 is mobilized and externalized following PMN adhesion to endothelial monolayers in vitro or to venular endothelium in vivo and that the end point of this process is a negative regulation of PMN transendothelial passage.

Propentofylline inhibits polymorphonuclear leukocyte recruitment in vivo by a mechanism involving adenosine A2A receptors

Propentofylline is an atypical xanthine derivative that blocks adenosine uptake and has been shown to protect against ischemia-induced cerebral damage. We have studied the effect of propentofylline on recruitment of polymorphonuclear leukocytes during acute peritonitis induced by zymosan in mice. Following i.p. injection of zymosan, recruitment of polymorphonuclear leukocytes, reflected by myeloperoxidase activity in the peritoneal cavity, increased from 2 h onwards, peaked at 4 h and then decreased gradually. Propentofylline antagonized the zymosan-induced peritoneal myeloperoxidase accumulation in a concentration-dependent manner. This effect of propentofylline was counteracted by the non-selective adenosine receptor antagonist theophylline (50 mg/kg), and by the selective adenosine A2A receptor antagonists, 4-amino-8-chloro-1-phenyl-[1,2,4]-triazolo[4,3-a]quinoxaline (CP 66713) and 1,3-dipropyl-8-[3,4-dimethoxystyryl]-7-methylxanthine (KF 17387) (both at 2 mg/kg). The results indicate that propentofylline can reduce polymorphonuclear leukocyte recruitment in vivo and that this effect is related to an action on adenosine A2A receptors.

Intracolonic zymosan produces visceral hyperalgesia in the rat that is mediated by spinal NMDA and non-NMDA receptors

The present study examined the effects of colonic inflammation on reflex responses to colorectal distension (CRD) in awake rats. Visceromotor responses (VMR) to CRD were recorded in rats that received either no treatment or intracolonic saline or zymosan. Three hours following zymosan treatment (25 mg/ml; 1 ml) VMR response magnitudes were significantly increased at all intensities of CRD tested (10-80 mmHg). The enhanced responses to CRD were attenuated in a dose-dependent fashion by intrathecal administration of the non-competitive N-methyl-D-aspartate (NMDA) receptor channel blocker MK-801 to 60% of control and by the non-NMDA receptor antagonist DNQX to less than 20% of control. The metabotropic receptor antagonist AP-3 was without effect. Signs of multi-focal colonic inflammation were clearly present 3 h after zymosan treatment, characterized by an ingress of inflammatory cells and damaged crypts in and around these foci. Taken together these findings suggest that tissue inflammation increases the sensitivity of the colon to mechanical stimuli, leading to enhanced responses to CRD. This enhancement involves the activation of spinal NMDA as well as non-NMDA receptors, but not metabotropic receptors.

Measurement of lipocortin 1 levels in murine peripheral blood leukocytes by flow cytometry: modulation by glucocorticoids and inflammation

1. Lipocortin 1 (LC1) immunoreactivity in murine peripheral blood leukocytes was quantified by use of a flow cytometric technique associated with a permeabilisation protocol with saponin. Using specific antisera raised against the whole protein or against its N-terminus peptide, cell-associated LC1-like immunoreactivity was easily detected in circulating neutrophils and monocytes, whereas very low levels were found in lymphocytes. Of the total protein measured 17.6% and 36% were associated with the external plasma membrane in neutrophils and monocytes, as assessed in the absence of cell permeabilisation, whereas no signal was detected on lymphocyte plasma membrane. 2. Treatment of mice with dexamethasone (Dex; 0.5-5 micrograms per mouse corresponding to approximately 0.015-1.5 mg kg-1) increased LC1 levels in neutrophils and monocytes. The 2-3 fold increase in LC1 levels was time-dependent with a peak at 2 h. Treatment of mice with the steroid antagonist, RU486 (two doses of 20 mg kg-1 orally) decreased LC1-like immunoreactivity in all three types of circulating leukocytes by > or = 50%. 3. Extravasation of blood neutrophils into inflamed tissue sites resulted in a consistent reduction (> or = 50%) in LC1 levels compared with circulating neutrophils. A high LC1-like immunoreactivity was also measured in resident macrophages, of which approximately one third was membrane-associated. Induction of an acute inflammatory response in the murine peritoneal cavity did not modify total LC1 levels measured in macrophages, but reduced membrane-associated LC1 to a significant extent, i.e. up to 70%. 4. In conclusion, flow cytometric analysis is a rapid and convenient method for detecting and measuring LC1 in murine leukocytes. We confirmed that LC1 protein expression is controlled by exogenous and endogenous glucocorticoids. Amongst other factor(s) influencing protein concentrations, extravasation was found to be associated with a reduced LC1 expression in the emigrated cells.

Acute inflammatory response in the mouse: exacerbation by immunoneutralization of lipocortin 1

1. An immuno-neutralization strategy was employed to investigate the role of endogenous lipocortin 1 (LC1) in acute inflammation in the mouse. 2. Mice were treated subcutaneously with phosphate-buffered solution (PBS), non-immune sheep serum (NSS) or with one of two sheep antisera raised against LC1 (LCS3), or its N-terminal peptide (LCPS1), three times over a period of seven days. Twenty four hours after the last injection several parameters of acute inflammation were measured including zymosan-induced inflammation in 6-day-old air-pouches, zymosan-activated serum (ZAS)-induced oedema in the skin, platelet-activating factor (PAF)-induced neutrophilia and interleukin-1 beta (IL-1 beta)-induced corticosterone (CCS) release. 3. At the 4 h time-point of the zymosan inflamed air-pouch model, treatment with LCS3 did not modify the number of polymorphonuclear leucocytes (PMN) recruited: 7.84 +/- 1.01 and 7.00 +/- 0.77 x 10(6) PMN per mouse for NSS- and LCS3 group, n = 7. However, several other parameters of cell activation including myeloperoxidase (MPO) and elastase activities were increased (2.2 fold, P < 0.05, and 6.5 fold, P < 0.05, respectively) in the lavage fluids of these mice. Similarly, a significant increase in the amount of immunoreactive prostaglandin E2 (PGE2; 1.81 fold, P < 0.05) and IL-1 alpha (2.75 fold, P < 0.05), but not tumour necrosis factor-alpha (TNF-alpha), was also observed in LCS3-treated mice. 4. The recruitment of PMN into the zymosan inflamed air-pouches by 24 h had declined substantially (4.13 +/- 0.61 x 10(6) PMN per mouse, n = 12) in the NSS-treated mice, whereas high values were still measured in those treated with LCS3 (9.35 +/- 1.20 x 10(6) PMN per mouse, n = 12, P < 0.05). A similar effect was also found following sub-chronic treatment of mice with LCPS1: 6.48 +/- 0.10 x 10(6) PMN per mouse, vs. 2.77 +/- 1.20 and 2.64 +/- 0.49 x 10(6) PMN per mouse for PBS- and NSS-treated groups (n = 7, P < 0.05). Most markers of inflammation were also increased in the lavage fluids of LCS3-treated mice: MPO and elastase showed a 2.47 fold and 17 fold increase, respectively (P < 0.05 in both cases); TNF-alpha showed a 11.1 fold increase (P < 0.05) whereas the IL-1 alpha levels were not significantly modified. PGE2 was still detectable in most (5 out of 7) of the mice treated with LCS3 but only in 2 out of 7 of the NSS-treated mice. 5. Intradermal injection of 50% ZAS caused a significant increase in the 2 hoedema formation in the skin of LCS3-treated mice in comparison to PBS- and NSS-treated animals: 16.7 +/- 1.5 microliters vs. 10.8 +/- 1.2 microliters and 10.2 +/- 1.0 microliters, respectively (n = 14 mice per group, P < 0.05). ZAS-induced oedema had subsided by 24 h in control animals but a residual significant amount of extravasation was still detectable in LCS3-treated mice: 4.4 +/- 0.8 microliters (P < 0.05). 6. A recently described model driven by endogenous glucocorticoids is the blood neutrophilia observed following administration of PAF. In our experimental conditions, a single bolus of PAF (100 ng, i.v.) provoked a marked neutrophilia at 2 h (2.43 and 2.01 fold) in NSS- and PBS-treated mice (n = 11), respectively, which was significantly attenuated in the animals treated with LCS3: 1.26 fold increase in circulating PMN (n = 11, P < 0.01 vs. NSS- and PBS-groups). 7. Intraperitoneal injection of IL-1 beta (5 micrograms kg-1) caused a marked increase in circulating plasma CCS by 2 h, to a similar extent in all experimental groups. In contrast, measurement of CCS levels in the plasma of mice bearing air-pouches inflamed with zymosan revealed significant differences between LCS3 and NSS-treated mice at the 4 h time-point: 198 +/- 26 ng ml-1 vs. 110 +/- 31 ng ml-1 (n = 8, P < 0.05). 8. In conclusion, we found a remarkable exacerbation of the inflammatory process with respect to both humoral and cellular components in mice passively immunised agains

Effect of rolipram in a murine model of acute inflammation: comparison with the corticoid dexamethasone

Treatment of mice with rolipram, a phosphodiesterase type 4 inhibitor, selectively modified the acute inflammatory reaction elicited by zymosan administration in 6-day-old mouse air-pouches. Rolipram (1-10 mg kg-1, i.p.) prevented the rise of endogenous tumor necrosis factor-alpha (TNF-alpha) in the lavage fluids (approximately 60% inhibition) induced by zymosan, with no effect upon interleukin-1 alpha levels. This action was not accompanied by changes in neutrophil accumulation, but the amount of elastase released in the lavage fluids was significantly reduced (approximately 50%). Dexamethasone (1.5 mg kg-1, i.v.), used for comparative purposes, significantly reduced the release of TNF-alpha (> 50%), interleukin-1 alpha (> 70%) and cellular infiltration (approximately 50%), but had only a marginal effect on the release of elastase activity. In conclusion, in this murine model of acute inflammation induced by zymosan, rolipram inhibited the endogenous TNF-alpha production at a local site of inflammation, such as the subcutaneous air-pouch, and prevented the full activation of migrated cells.

Measurement and drug induced modulation of interleukin-1 level during zymosan peritonitis in mice

The time-course and pharmacological modulation of interleukin-1 (IL-1) production were investigated during zymosan induced peritonitis in mice. IL-1 alpha liberation was assessed by specific immunoassay (ELISA) and the IL-1 like bioactivity (sensitive to both alpha- and beta-forms of IL-1) was measured by a sensitive bioassay (D10G4.1 costimulation). I.p. injection of zymosan induced significant IL-1 release into the peritoneal exudate. The level peaked at 4 h and by 24 h dropped below the detection limit in both assays. The effects of the prototypical antiinflammatory drugs indomethacin (IND) and dexamethasone (DEX) and that of IX 207-887, a compound which has been reported to interfere primarily with IL-1 production, were also tested. DEX and IX 207-887 dose-dependently decreased the immunoassayable IL-1 alpha level and the IL-1 like bioactivity as well. However, IND had no suppressant effect. Thus, the data obtained by immunoassay and bioassay correlated well proving the suitability of zymosan peritonitis model for the examination of IL-1 production in experimental inflammation.

Zymosan-induced arthritis in rats. II. Effects of anti-inflammatory drugs

As zymosan-induced arthritis in rats combines dual activation of early prostaglandin-dependent processes (edema, fever, pain) and IL-1 related effects on cartilage metabolism, we compared the respective influences of indomethacin (IMT) and dexamethasone (DEX) on its course. Different parameters were assessed: knee swelling, febrile response, loss of activity, cartilage metabolism and histology. DEX improved all these parameters, while IMT exerted only light beneficial effects on fever and knee swelling without obvious beneficial influence on cartilage metabolism and histological lesions. These results suggest that anti-inflammatory activities of DEX and IMT are due to interferences with different pathways during zymosan-induced arthritis in rats.

Tumor necrosis factor mediates zymosan-induced increase in glucose flux and insulin resistance

Intraperitoneal injection of sterile zymosan produces an inflammatory response ultimately resulting in multiple-organ failure. The purpose of the present study was to characterize the hormonal and metabolic alterations produced as a result of this nonbacterial nonendotoxic inflammatory agent and to determine whether these changes were mediated by enhanced production of tumor necrosis factor (TNF). Rats were injected intraperitoneally with either zymosan or saline and studied 18 h later. Under basal conditions, zymosan-injected rats were euglycemic but showed a 43% increase in hepatic glucose production and peripheral glucose uptake. The enhanced glucose flux in zymosan-treated rats was associated with elevations in plasma insulin (45%), glucagon (5-fold), corticosterone (2-fold), epinephrine (34%), and norepinephrine (115%). In vivo studies using 2-deoxyglucose (2-DG) demonstrated that the zymosan-induced increase in whole body glucose disposal resulted from an enhanced uptake by skeletal muscle (68%), diaphragm (3.7-fold), liver (144%), spleen (52%), and fat (133%). Under euglycemic hyperinsulinemic conditions, zymosan-treated rats exhibited both hepatic and peripheral insulin resistance, with the latter resulting from a decreased insulin-mediated glucose uptake by skeletal muscle, heart and diaphragm. Arterial TNF levels were increased by 1 h and remained elevated throughout the experimental protocol. Pretreatment of rats with a neutralizing anti-TNF antibody before zymosan prevented the elevation in basal glucose flux and attenuated the insulin resistance. We conclude that the inflammatory state induced by zymosan enhances basal glucose turnover and impairs insulin action and that these changes appear to be largely due to the enhanced endogenous production of TNF.

4-substituted-5-acetyl-2-methyl-6-phenyl-3(2H)pyridazinones as PGE2 and IL-1 release inhibitors from mouse adherent macrophages

A series of 4,5-functionalized 3(2H)-pyridazinones were evaluated as prostaglandin E2 (PGE2) and interleukin-1 (IL-1) release inhibitors from mouse adherent macrophages. Among the tested compounds only 2b was found to be devoid of activity in both the PGE2 and IL-1 tests, whereas the other compounds, showed a significant dose-dependent activity. Compounds 2a, 3 and 4 were able to inhibit PGE2 better than IL-1 release from stimulated macrophages. Compound 4, which showed an IC50 = 5.5 microM in the IL-1 test, appears to be a promising agent in this cell inflammation model. Structure-activity relationship (SAR) studies demonstrated the importance of the presence of a substituent characterized by a positive sigma constant at position 4 of the pyridazine system.

Characterization of zymosan-induced arthritis in the rat: effects on joint inflammation and cartilage metabolism

A single intra-articular (ia) injection of 2 mg zymosan on D0 led to the production of acute periarticular edema followed by subacute erosive synovitis. The development of the zymosan-induced arthritis was associated with an initial loss of running activity and with an initial decrease of proteoglycan synthesis. Febrile response was present only on D1. In addition, on D20 synovial pannus led to a marked depletion of the proteoglycan content in the articular cartilage. When injected ia, IL1 beta (1 microgram) provoked similar fever and similar changes in cartilage anabolism, but did not affect cartilage proteoglycan content (D20). These results suggest that zymosan-induced synovitis in the rat combines early prostaglandin-dependent processes (edema, pain, fever) with IL1-related effects on cartilage metabolism, thus allowing evaluation of chondroprotective drugs.

Serum corticosterone, interleukin-1 and tumour necrosis factor in rat experimental endotoxaemia: comparison between Lewis and Wistar strains

1. Circulating corticosterone, interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF alpha) activities in serum of Lewis and Wistar rats were measured following injection of lipopolysaccharide (LPS). IL-1 was measured as 'lymphocyte activation factor' (LAF) activity following precipitation of inhibitory activity with polyethylene glycol. TNF alpha activity was measured as cytotoxic activity. 2. Compared to the Wistar, the Lewis rat had higher circulating LAF and TNF activities following LPS, and release of both cytokines was prolonged in this strain. 3. Corticosterone increases in response to LPS were less in the Lewis than in the Wistar rat following the initial peak at 1 h; basal corticosterone was lower in the Lewis rat. 4. Adrenalectomized Lewis rats had even greater amounts of circulating LAF and TNF activities following LPS than did intact animals; the effect of adrenalectomy was not however mimicked by acute treatment with the steroid receptor antagonist, RU486, suggesting that endogenous corticosteroids did not acutely control cytokine release. 5. Although in vivo administration of anti-murine IL-1 alpha antiserum significantly lowered LAF activity of serum, circulating corticosterone in response to LPS was not affected. Similarly, treatment with anti-murine TNF alpha monoclonal antibody (mAb) abrogated TNF activity without affecting corticosterone, suggesting that other mediators may be responsible for corticosterone release following LPS. 6. This 'overproduction' of inflammatory cytokines together with lower circulating corticosterone may contribute to the susceptibility of the Lewis rat to diseases such as adjuvant arthritis or experimental allergic encephalomyelitis.

Characterization and pharmacological modulation of antigen-induced peritonitis in actively sensitized mice

1. The intraperitoneal (i.p.) injection of 1 or 10 micrograms ovalbumin to sensitized Balb/c mice led to an acute histamine release, firstly evidenced 1 min after the challenge and returning to basal levels 30 min thereafter. This phenomenon was unaccompanied by protein extravasation. A dose-dependent increase in the amounts of immunoreactive leukotriene (LT) C4 and LTB4 was observed in the peritoneal washing from sensitized mice 6 h after 1 or 10 micrograms ovalbumin administration. In separate experiments, the i.p. administration of 1 mg activated zymosan to non-immunized mice was followed by a marked protein extravasation, and by immunoreactive LTC4 and LTB4, but not histamine, release in mouse peritoneum 1 h after its injection. 2. Mediator release in the mice peritoneal cavity was concomitant with a transient neutrophil infiltration, which peaked at 6 h and returned to basal levels therefore. An intense eosinophil accumulation starting at 24 h, peaking at 48 h and returning to basal values at 164 h, was also observed. 3. Ovalbumin (1 microgram)-induced eosinophilia, observed at 24 h, was reduced by the pretreatment of the animals with dexamethasone (1 mg kg-1, s.c.) or with the 5-lipoxygenase inhibitor, BWA4C (20 mg kg-1, s.c.), whereas indomethacin (2 mg kg-1, s.c.) and the platelet-activating factor (PAF)-antagonist SR 27417 (10 mg kg-1, s.c.) were ineffective. These results indicate that metabolites of arachidonic acid of lipoxygenase pathway, but not cyclo-oxygenase derivatives or PAF, mediate antigen-induced eosinophil accumulation in the mouse peritoneum. 4. The histamine HI receptor antagonist drug, cetirizine (15-30 mg kg-1, s.c.) markedly reduced ovalbumin-induced eosinophil accumulation under conditions where terfenadine was ineffective, suggesting that the effect of cetirizine was not related to the inhibition of the H1 receptor effects of histamine.5. The immunosuppressive agent, FK-506 (1-2 mg kg-1, s.c.) and the protein synthesis inhibitor,cylcoheximide, when administered either in situ (0.06 ng/cavity) or systemically (5 mg kg-1, s.c.),prevented antigen-induced eosinophil accumulation in the mouse peritoneum, contributing to the concept that substances (probably cytokines) originating from lymphocytes may be involved in the modulation of the eosinophilotactic response in this model.6. The results of the present study indicate that the i.p. administration of ovalbumin to actively sensitized mice induced late eosinophil accumulation in the peritoneal cavity. This phenomenon, which may be in part mediated by the release of lipoxygenase metabolites and/or by newly generated factors,such as T-lymphocytes-derived eosinophilotactic cytokines, offers an interesting tool to investigate the mechanism of action of anti-allergic and anti-inflammatory drugs.

Copper and zinc body levels in inflammation: an overview of the data obtained from animal and human studies

The development of acute and chronic inflammatory processes induces, in the laboratory animal, a net accumulation of both copper and zinc in many body compartments, the inflamed area included. In rheumatoid arthritis, as well as in animal models, only plasma zinc concentration seems to be significantly correlated with disease severity, while the increase in total plasma copper could be described as an "all or nothing" phenomenon. Moreover, in rheumatoid arthritis, it appears that the disease develops and progresses without being linked to either copper or zinc deficiency conditions. Thus, it seems reasonable to suggest that a rationale for the use of copper and/or zinc in the treatment of inflammatory disorders can only be drawn from the intrinsic pharmacological properties of such trace elements, rather than from the need for their repletion.

A new assay for antiphlogistic activity: zymosan-induced mouse ear inflammation

A new model of local inflammation has been developed: intradermal zymosan-induced mouse ear edema. The symptoms of inflammation induced by injecting zymosan into one of the ears were followed up for 72 h. The ear edema and the local accumulation of polymorphonuclear leukocytes' (PMN) marker enzyme, myeloperoxidase (MPO), were determined. Edema peaked at 4-6 h, while MPO activity peaked at 24 h after zymosan application. The correlation between inflammatory response and concentration of zymosan was also tested. Of the various concentrations tested, 1% suspension has been found optimal. Anti-inflammatory drugs and mediator antagonists were examined in order to establish the selectivity and sensitivity of the assay. A glucocorticoid (dexamethasone), two cyclooxygenase inhibitors (indomethacin, piroxicam) and an interleukin-1 (IL-1) release inhibitor (IX 207-887, Sandoz) all reduced edema and MPO activity as well. However, a lipoxygenase inhibitor (phenidone), a serotonin receptor antagonist (methysergide) and H1 and H2 receptor antagonists (clemastine and cimetidine, respectively) all failed to inhibit the reaction.

Effect of treatment with interleukin-1 receptor antagonist on the development of carrageenan-induced pleurisy in the rat

Pretreatment of rats with the human interleukin-1 receptor antagonist (IL-1ra) by the subcutaneous route at -0.5 h, relative to the intrapleural injection of carrageenan (CG), suppressed the infiltration of cells into the pleural cavity of intact and adrenalectomized rats at 5 h (28 and 74% reduction in intact animals at 0.3 and 10 mg/kg, respectively). Exudate volume at 5 h was also suppressed at dosages of IL-1ra > or = 3 mg/kg. IL-1ra was still effective as an antiinflammatory agent in the 5-h pleurisy model when administered 1 or 2 h, but not 3 h, after CG. The addition of IL-1ra to a maximally effective antiinflammatory dosage of indomethacin (5 mg/kg) resulted in further reductions of cell number and exudate volume, suggesting that the antiinflammatory effects of IL-1ra in the 5-h model were not due solely to inhibition of IL-1-induced prostaglandin biosynthesis. The antiinflammatory effects of suboptimal dosages of IL-1ra and dexamethasone, administered in combination, were essentially additive. In 24-h pleurisy, IL-1ra reduced exudate volume and PMN number after a single dosage of 10 mg/kg, subcutaneously at -0.5 h and after dosages of 3 mg/kg at -0.5 and 5 h. Additional dosages of IL-1ra (3 mg/kg) at 10 and 15 h did not further inhibit PMN accumulation. Treatment with IL-1ra did not affect macrophage accumulation in 24-h CG-induced pleurisy. IL-1ra was not active as an antiinflammatory agent in the 24-h pleurisy model after three dosages of IL-1ra (3 mg/kg) at 5, 10 and 15 h.