Measurement of prostaglandin E2 and leukotriene B4 in the gingival crevicular fluid

The arachidonic acid metabolites prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) are inflammatory mediators which are likely to be involved in the pathogenesis of periodontal disease. PGE2 mediates vasodilatation, increases vascular permeability, enhances pain perception by bradykinin and histamine, alters connective tissue metabolism and enhances osteoclastic bone resorption. LTB4 causes the accumulation of inflammatory cells in the inflamed sites, and degranulation of polymorphonuclear leukocytes.

OBJECTIVE

To measure gingival crevicular fluid (GCF) levels of PGE2, LTB4 and periodontal health.

METHODS

The periodontal condition of 24 subjects was evaluated on the basis of plaque index, gingival index, probing depth, and attachment level. GCF samples were collected from one or two site(s) of each sextant per subject and the volume was measured using Periotron 6000. Samples were then assayed for PGE2 and LTB4 using a competitive enzyme immunoassay. Mean PGE2 and LTB4 levels were determined for each subject and group means compared.

RESULTS

Significant differences in the levels of PGE2 and LTB4 were found between patients with periodontitis, and non-periodontitis individuals (P < 0.001). The PGE2/LTB4 levels were positively correlated with the clinical parameters (P < 0.01) and reduced markedly after phase 1 of the periodontal treatment (P < 0.01). The total amount and concentration (ng ml-1) of LTB4 was positively correlated with the gingival index (P < 0.01).

CONCLUSIONS

These results indicate that the levels of PGE2 correlated with the severity of the periodontal status, and the levels of LTB4 correlated with gingival inflammation. Thus, our data suggest that the total amounts of PGE2/LTB4 may be good indicators for periodontal inflammation.

The chemotactic activity of sputum from patients with bronchiectasis

Persistent polymorphonuclear neutrophil (PMN) recruitment to airway is thought to be an important component of continuing inflammation and progression of chronic destructive lung diseases. Although chemoattractants are required for the PMN to migrate, the nature of the chemoattractants in the airways has not yet been clarified. We therefore investigated the contribution of interleukin-8 (IL-8) and leukotriene-B4 (LTB4) to the chemotactic activity of lung secretions by inhibiting their activity using a monoclonal antibody to IL-8 and an LTB4 receptor antagonist (LY293111 sodium). Fifty-nine sputum samples obtained from 19 patients with bronchiectasis were studied. In preliminary studies the chemotactic responses to IL-8 and LTB4 were found to be additive, and we were able to remove their contribution independently with the appropriate antibody and antagonist. The chemotactic activity of the secretions was related to the macroscopic appearance (mucoid, mucopurulent, and purulent), and this appeared to be related to an increase in IL-8 contribution. Chemotactic activity was reduced by antibiotic therapy and again that seemed to relate to a reduction in the IL-8 contribution. The contributions of LTB4 were similar among the three types of sputum in varying clinical states. These data suggest that LTB4 and IL-8 are important chemotactic factors in lung secretions from such patients, although IL-8 appears to play a more important role during acute exacerbations. These results may be useful in determining therapeutic strategies for chronic destructive lung diseases in the future.

Role of leukotriene B4 in bronchial hyperresponsiveness induced by interleukin-8

Repeated intranasal administration of interleukin 8 (IL-8) induces bronchial hyperresponsiveness (BHR) accompanied by lower airway neutrophil accumulation (ANA) in guinea-pigs. Leukotriene B4 (LTB4) is a chemotactic factor for neutrophils. To elucidate whether LTB4 and neutrophil elastase are involved in the IL-8-induced BHR and ANA, the effects of a LTB4 antagonist (ONO-4057) and a neutrophil elastase inhibitor (ONO-5046) on the responses were examined. IL-8 (5 microg x kg[-1]) was administered intranasally to guinea-pigs twice weekly for 3 weeks. One day after the last administration, animals were anaesthetized and artificially ventilated through tracheal cannulae, and lateral pressure at the tracheal cannula (Pao) was measured as an overall index of airway responses to inhaled histamine. ONO-4057 (2 or 20 mg x kg[-1]) or ONO-5046 (30 or 300 mg x kg[-1]) was administered intraperitoneally 24 and 1 h before anaesthesia. ONO-4057, but not ONO-5046, significantly inhibited the IL8-induced BHR and ANA, assessed by bronchoalveolar lavage, in a dose-dependent manner. These findings suggest that interleukin 8 causes bronchial hyperresponsiveness and airway neutrophil accumulation in guinea-pigs in vivo. In part this appears to be due to release of leukotriene B4, whereas it may not be mediated by neutrophil elastase.

Leukotriene B4

Leukotriene B4 is a pro-inflammatory mediator synthesised in myeloid cells from arachidonic acid. Synthesis is catalysed by 5-lipoxygenase and leukotriene A4 hydrolase and is increased by inflammatory mediators including endotoxin, complement fragments, tumor necrosis factor and interleukins. A nuclear membrane protein, 5-lipoxygenase activating protein, is an essential co-factor for 5-lipoxygenase. Leukotriene B4 induces recruitment and activation of neutrophils, monocytes and eosinophils. It also stimulates the production of a number of proinflammatory cytokines and mediators indicating an ability to augment and prolong tissue inflammation. Elevated levels of leukotriene B4 have been found in a number of inflammatory diseases and levels are related to disease activity in some of these. Initial data from pharmacological inhibition studies support a role for leukotriene B4 in the pathogenesis of neutrophil mediated tissue damage, and treatments which reduce its production or block its effects may prove beneficial in neutrophil mediated inflammatory diseases.

Effect of cigarette smoke on ethanol-induced gastric mucosal lesions: the role of nitric oxide and neutrophils

The roles of neutrophil aggregation, inducible nitric oxide synthase activation and chemoattractant, leukotriene B4, in potentiation of the cigarette smoke effect on ethanol-induced gastric mucosal damage were studied. Smoke exposure markedly increased gastric lesion formation following ethanol administration and this was accompanied by substantial increase in gastric mucosal leukotriene B4 concentration, myeloperoxidase and inducible nitric oxide synthase activities. Antineutrophil serum or aminoguanidine pretreatment significantly attenuated both gastric mucosal lesion formation and inducible nitric oxide synthase activity. The increased myeloperoxidase activity was abolished by antineutrophil serum but not by aminoguanidine. These data indicated that both neutrophil mobilization and inducible nitric oxide synthase activation in the gastric mucosa play an important role in the potentiating action of cigarette smoke on ethanol-induced gastric mucosal lesion formation. Increased synthesis of nitric oxide from inducible nitric oxide synthase during gastric damage may be secondary to neutrophil infiltration in the gastric mucosa. Chemoattractant leukotriene B4 could also contribute to neutrophil recruitment in the tissue.

Leukotriene B4 is the functional ligand binding to and activating the cloned chemoattractant receptor, CMKRL1

We recently described a novel chemoattractant receptor, provisionally named CMKRL1, which has turned out to be the first cloned leukotriene (LT) receptor. Present binding assays using tritiated LTB4 and isolated membranes from COS-7 cells, transiently transfected with cDNA encoding this receptor, yielded a linear Scatchard plot showing expression of only a single, high-affinity receptor population with a mean Kd of 2.1 nM and Bmax of 17.0 pmoles/mg protein. Sham-transfected cells exhibited no specific binding. LTB4 elicited concentration-dependent increases in intracellular calcium measured with Fura-2 in individual CHO cells stably expressing CMKRL1. No response was seen with sham-transfected control cells, or in calcium-free medium which suggests that calcium mainly originates from extracellular sources. The LTB4-induced cellular calcium increment was blocked in the presence of a monoclonal antibody, raised against a synthetic peptide corresponding to the extracellular tail of CMKRL1 and capable of visualizing the receptor by fluorescence immunocytochemistry. Taken together the analyses show that LTB4 is the endogenous ligand for CMKRL1 which is, thus, identical to the LTB4 receptor, designated BLTR according to the NC-IUPHAR nomenclature.

Epicutaneous application of leukotriene B4 induces patterns of tenascin and a heparan sulfate proteoglycan epitope that are typical for psoriatic lesions

Application of leukotriene B4 (LTB4) to normal human skin induces changes similar to those found in psoriatic skin, and it has proved to be a useful model for studying the pathogenesis and treatment of psoriasis. We studied the expression patterns of molecules that have recently been shown to be altered in lesional psoriatic skin, including the extracellular matrix protein tenascin (TN) and the basement membrane and cell surface-associated heparan sulfate proteoglycans (HSPGs). During 72-h the expression of these markers was studied immunohistochemically and the expression of TN was correlated with epidermal proliferation and influx of inflammatory cells. Following the peak influx of polymorphonuclear leukocytes, a marked increase in TN expression was noted in the papillary dermis 72 h after LTB4 application. The expression patterns of basal membrane-associated epitopes of HSPG remained unaltered, whereas the expression of cell surface-associated HSPG disappeared 72 h after LTB4 application. A significant correlation was found between dermal TN expression and epidermal hyperproliferation, and between TN expression and the presence of dermal T cells. These findings indicate that the model of LTB4-induced acute cutaneous inflammation displays many characteristics of early psoriatic lesions and could serve as a model to study some of the cell biological changes in this disease.

Ischemia-reperfusion injury in myocutaneous flaps: role of leukocytes and leukotrienes

Leukotriene B4 is a potent inflammatory mediator that is derived from the 5-lipoxygenase pathway of arachidonic acid metabolism and that has been implicated in the pathophysiology of polymorphonuclear leukocyte-dependent reperfusion injury in a variety of organ systems. The objectives of these investigations were to determine whether inhibition of leukotriene B4 attenuates postischemic polymorphonuclear leukocyte infiltration and subsequent injury in myocutaneous flaps. Anesthetized female Yorkshire pigs were randomized to receive normal saline (n = 8), the 5-lipoxygenase inhibitor diethylcarbamazine (n = 7), or the leukotriene B4 receptor antagonist SC-41930 (n = 7). All animals underwent 6 hours of rectus abdominis myocutaneous flap ischemia followed by 4 hours of reperfusion. In saline-treated controls, flap ischemia was associated with massive polymorphonuclear leukocyte infiltration at 1 and 4 hours of reperfusion (252 +/- 70 and 619 +/- 137 polymorphonuclear leukocytes per 25 high-power fields, respectively). Skeletal muscle neutrophil content was significantly attenuated by pretreatment with diethylcarbamazine (72 +/- 29 and 229 +/- 63 polymorphonuclear leukocytes per 25 high-power fields; p < 0.05) or SC-41930 (25 +/- 3 and 193 +/- 25 polymorphonuclear leukocytes per 25 high-power fields; p < 0.05). Wet-to-dry weight ratios of full-thickness flap biopsies were lower in the diethylcarbamazine and SC-41930 groups (2.98 +/- 0.15 and 2.90 +/- 0.26, respectively) than in the control group (4.13 +/- 0.23; p < 0.01), and mean muscle infarct size, as determined by nitroblue tetrazolium staining, diminished from 47.6 +/- 11.3 percent in controls to 25.1 +/- 6.5 percent in diethylcarbamazine-treated animals and 7.3 +/- 4.8 percent in SC41930-treated animals (p < 0.05). These data indicate that leukotriene B4 plays a critical role in mediating neutrophil-dependent injury in postischemic skeletal muscle flaps.

Eosinophil chemotaxis inhibited by 5-lipoxygenase blockade and leukotriene receptor antagonism

We studied the effects of the 5-lipoxygenase inhibition and sulfidopeptidyl leukotriene receptor antagonism on lumenal chemotaxis of eosinophils in 124 guinea pig tracheal explant preparations from 62 animals. Cell migration was assessed histologically and by differential cell count, and airway narrowing was measured by calibrated micrometry. Intralumenal instillation of the chemotaxin, formyl-met-leu-phe (FMLP) caused migration of 163,509 +/- 18,103 eosinophils/cm segment (eos/cm) versus 15,443 +/- 3,557 eos/cm for segments receiving vehicle only (p < 0.001). Coincubation of FMLP with zileuton, a selective inhibitor of 5-lipoxygenase, caused a concentration-related inhibition of eosinophil migration. At 10(-10) M zileuton, cell migration caused by FMLP was decreased by 57% and nearly complete reduction to 17,200 +/- 3,620 eos/cm resulted after 10(-6) M zileuton (p < 0.001 versus FMLP). Lumenal narrowing caused by FMLP (15.3 +/- 3.4%) was attenuated maximally to 1.15 +/- 2.51% after 10(-8) M zileuton (p < 0.02). In 36 preparations, concentration of leukotriene B4 (LTB4) was measured in treated tracheal perfusate. LTB4 secretion caused by FMLP was 6.4 +/- 0.48 pg/ml versus 3.32 +/- 0.89 pg/ml for buffer control at 5 min (p < 0.02) and was undetectable 120 min after activation with FMLP. Blockade of LTB4-receptor with the selective antagonist, LTB4 dimethyl amide, caused > 90% inhibition of eosinophil migration (p < 0.001). Comparable results were obtained with zafirlukast, an LTD4-receptor antagonist. Our data demonstrate that both LTB4 and LTD4 facilitate eosinophil migration from lamina propria to lumen caused by the chemotaxin, FMLP, and that LTB4-induced eosinophil migration is accompanied by initial lumenal secretion of LTB4.

[Role of leukotriene B4 in monocrotaline-induced pulmonary hypertension]

Monocrotaline (MCT) causes lung inflammation and chronic pulmonary hypertension associated with lung vascular thickening in rats. We hypothesized that leukotriene B4 (LTB4) and LTB4-induced accumulation of leukocytes in the lung play a role in MCT-induced lung disease, and therefore measured LTB4 and myeloperoxidase (MPO) levels in lung tissue of MCT-treated rats. Next, we examined the effect of an orally active LTB4 receptor antagonist (ONO4057) on MPO levels in lung tissue, on pulmonary hypertension, and on pulmonary vascular remodeling induced by MCT. Lung LTB4 and MPO levels had increased by 3 days after MCT injection. In the ONO4057-treated MCT rats, lung MPO levels were significantly lower than in the rats given MCT but not ONO4057. By the third week after injection. MCT had caused increases in mean pulmonary arterial pressure, in the ratio of right ventricular weight to left ventricle+septum weight (RV/[VS + S]), and in media wall thickness of the muscular arteries of the lung. Treatment with ONO4057, either for 3 weeks or during the first week after MCT injection, significantly reduced pulmonary hypertension, right ventricular hypertrophy, and lung vascular thickening induced by MCT. These results indicate that ONO4057 reduces both the accumulation of leukocytes in lung tissue and the chronic pulmonary hypertension induced by MCT, and they suggest a role for LTB4 in the inflammatory process that contributes to pulmonary hypertension and lung vascular remodeling induced by MCT in rats.

Leukotriene-deficient mice manifest enhanced lethality from Klebsiella pneumonia in association with decreased alveolar macrophage phagocytic and bactericidal activities

Leukotrienes (LTs) are potent mediators of inflammation derived from the 5-lipoxygenase pathway of arachidonic acid metabolism. Although they are known to enhance leukocyte recruitment and function, their role in antimicrobial host defense has not been established. To determine the role of endogenous LTs in the host response to pulmonary infection, wild-type mice and mice rendered LT-deficient by targeted disruption of the 5-lipoxygenase gene (knockout mice) were studied following intratracheal challenge with Klebsiella pneumoniae. Wild-type mice demonstrated a marked increase in lung LT levels and neutrophil numbers following bacterial challenge. As compared with wild-type animals, knockout animals manifested a greater degree of lethality as well as bacteremia following challenge. Interestingly, they displayed no defect in neutrophil recruitment to the lung. However, alveolar macrophages from knockout animals exhibited impairments in bacterial phagocytosis and killing, and these defects were overcome by in vitro addition of exogenous LTB4. We conclude that endogenous LTs play a critical role in the defense against bacterial pneumonia in this murine model.

Role of leukotriene B4 and interleukin-8 in acute bacterial and viral otitis media

In order to evaluate the role of polymorphonuclear leukocytes (PMNs) in acute otitis media (AOM), levels of leukotriene B4 (LTB4), a potent inflammatory product of PMNs, and interleukin-8 (IL-8), a PMN chemotactic cytokine, were measured in 271 middle ear fluid (MEF) samples from 106 children with AOM. Forty-two percent of the patients had evidence of respiratory viral infection. At the time of diagnosis, levels of both LTB4 and IL-8 were higher in the MEFs from patients with AOM associated with bacterial or bacterial and viral infection than those MEFs containing no pathogen (p < .05). Antibiotic treatment was not associated with a significant change in levels of LTB4 or IL-8 in the MEFs obtained 2 to 5 days into treatment, compared to those obtained at diagnosis. Bacteriologic failure after 2 to 5 days of treatment was associated with high LTB4 levels in the initial MEFs (p = .05). Recurrence of AOM within 1 month was associated with high IL-8 levels in the initial MEF (p = .04). Our findings suggest that LTB4 and IL-8 are produced during acute infection of the middle ear, and these PMN-related inflammatory substances may play an important role in delaying recovery or in recurrence of AOM. Effective treatment of AOM may require eradication of bacteria by antibiotics, as well as pharmacologic agents that modulate PMN functions.

Participation of interleukin-5 and interleukin-8 in the eosinophil migration induced by a large volume of saline

Recently we demonstrated that the eosinophil migration into rat peritoneal cavities induced by a large volume of saline is mediated by LTB4 released by the resident macrophages and mast cells. In the present study, we have investigated the involvement of IL-5 and IL-8 in this process. We observed that saline-stimulated mast cells released the eosinophil chemotactic cytokines IL-5 and IL-8, while macrophages released only IL-8. These observations were confirmed by the ability of antibodies against IL-5 and IL-8 block the eosinophil chemotactic activity of the mast cell supernatants while the chemotactic activity of the macrophage supernatants was inhibited only by the antibody to IL-8. Recombinant forms of IL-5 and IL-8, when injected intraperitoneally, induced a dose-dependent eosinophil accumulation in naïve rats. The mechanism by which these cytokines induce eosinophil migration seems to be dependent on the resident cell population since depleting the peritoneal cavities of the latter renders the animals unresponsive to the eosinophil recruitment when challenged with IL-5, IL-8 or the supernatants of saline-treated mast cells or macrophages. Dexamethasone and MK 886 blocked the eosinophil migration induced by both the supernatants of saline-stimulated mast cells or macrophages and by IL-5 or IL-8. The IL-5-induced eosinophil migration was also blocked by BW A4C, another lipoxygenase inhibitor. Together, these results suggest LTB4 to be the lipoxygenase metabolite involved in the eosinophil recruitment induced by IL-5 and IL-8. Our results indicate that the eosinophil migration induced by saline is a complex phenomenon which is dependent on the resident mast cells and macrophages and is mediated by LTB4, IL-5 and IL-8. Mast cells release LTB4, IL-5 and IL-8, whereas macrophages release mainly LTB4 and IL-8. The inhibition of one of these mediators (IL-5, IL-8 or LTB4) completely blocked the eosinophil migration induced by saline, suggesting that they act synergistically.

Cerebrospinal fluid concentrations of leukotriene B4 in bacterial meningitis

We investigated whether leukotriene B4 (LTB4), a granulocyte inflammatory mediator, is detectable in cerebrospinal fluid using a high performance liquid chromatographic method. In non-pleocytotic cerebrospinal fluid (n = 5) and in cerebrospinal fluid from children with aseptic meningitis (n = 8), LTB4 concentrations were below the detection limit (< 0.2 ng ml-1). In the range 0-20 ng ml-1, the recovery rate of LTB4 that had been added to non-pleocytotic cerebrospinal fluid was > 90%. In cerebrospinal fluid with a polymorphonuclear leucocyte (PMN) count higher than 1,000/ml, LTB4 was detectable in six out of seven specimens with a concentration of 0.35-3.3 ng ml-1. LTB4 concentration was significantly correlated with PMN number. These results, together with observations in animal models, are discussed with regard to a pathophysiological role of LTB4 in bacterial meningitis.

Distribution and anti-inflammatory effect of mesalazine on carrageenan-induced colitis in the rabbit

1. A controlled-release preparation of mesalazine microgranules (PentasaR; Ferring AS, Vanlose, Denmark) releases the active ingredient over a wide area from the small intestine to the rectum and is consequently expected to bring about therapeutic benefits to patients with ulcerative colitis and Crohn's disease. 2. Mesalazine microgranules (50 or 150 mg/kg per day) were administered orally to each rabbit with carrageenan-induced colitis for six weeks. Its inhibitory effect on colonic mucosal damage was assessed in terms of the microscopic damage scores, leukotriene B4 concentrations and concentrations of mesalazine derivatives. 3. At the end of the experiment, the mesalazine 150 mg group had gained a significantly greater bodyweight than the control group. Microscopic damage was significantly lower in the 150 mg group than in the untreated control group. Tissue concentrations of 5-aminosalicylic acid and acetyl-5-amino-salicylic acid in the small and large intestine were higher in the 150 mg group than in the 50 mg group. Mucosal leukotriene B4 levels tended to be lower in rabbits receiving the larger dose of mesalazine. 4. The present study indicates that slow release 5-amino-salicylic acid at the larger dose reaches the large bowel in sufficiently high concentrations following oral administration and significantly reduces carrageenan-induced colitis in the rabbit.

Lipid mediators in the rat retina: light exposure and trauma elicit leukotriene B4 release in vitro

Light exposure not only elicits a visual response but may also alter functional and structural characteristics of the retina. Furthermore, light exposure can lead to reversible or irreversible lesions of photoreceptors and pigment epithelium. Previous studies in our laboratory have shown that light liberates arachidonic acid from retinal membrane phospholipids mainly by activating the phospholipase A2. In this study we show that light and trauma elicit the synthesis of leukotriene B4 in the isolated rat retina in vitro. Male albino rats were dark adapted for 36 h, isolated retinae were taken, incubated and exposed a) either to darkness or to 5,000 lux of cool white fluorescent light for 5, 10 or 15 min at 37 degrees C, b) either to darkness or to 5,000 lux of cool white fluorescent light for 15 min at 0 degrees C or c) either to darkness or to 5,000 lux of cool white fluorescent light for 15 min at 37 degrees C with a 5-lipoxygenase inhibitor (zileuton). Eicosanoids were extracted and leukotriene B4 levels were determined by radioimmunoassay. Removal of retinae and incubation in darkness caused a significant rise in leukotriene B4 levels with increasing incubation time. This rise was further augmented significantly after light exposure. The leukotriene B4 levels obtained when incubating the retinae either at 0 degree C or with the lipoxygenase inhibitor zileuton as well as the high specificity of the radioimmunoassay indicate that the light- and trauma-elicited synthesis of leukotriene B4 is mediated by activating the 5-lipoxygenase. Leukotriene B4 may be involved, at least in part, in the pathogenesis of retinal diseases including light damage. Curr. Eye Res. 14: 1001-1008, 1995.

Ethanol affects leukotriene generation and leukotriene-induced functional responses in human polymorphonuclear granulocytes

Since ethanol has been shown to inhibit the inflammatory response, we evaluated whether ethanol affected generation of leukotrienes in polymorphonuclear granulocytes (PMN) in vitro. Using the calcium ionophore A23187 as stimulus, the leukotriene B4 (LTB4) and leukotriene C4 (LTC4) generation were dose-dependently impaired by ethanol. No significant difference in the levels of the omega-oxidized metabolites was observed. However, the total LTB4 production (LTB4 plus omega-oxidized metabolites) was significantly decreased in the samples treated with ethanol. Furthermore, ethanol also modulated LTB4-induced functional responses. PMN aggregation, oxidative metabolism and elastase release were all inhibited in the presence of 1% ethanol (to 74 +/- 15%, 50 +/- 4% and 57 +/- 3% of controls, respectively). However, ethanol had no effect on intracellular calcium mobilization or on the change of the PMN membrane potential induced by either LTB4 or A23187. Thus, a possible mechanism for the reduced functional PMN responses in the presence of ethanol might be impaired generation of leukotrienes, but it is conceivable that ethanol impairs also other steps of the stimulus response coupling since the LTB4-induced functional responses were inhibited.

Oxygen-induced lung injury in the pre-term guinea pig: the role of leukotriene B4

Leukotriene B4 (LTB4) has been reported to promote the formation of lung oedema when infused into the pulmonary circulation of adult animals. The present study evaluated the hypothesis that LTB4 was responsible, in part, for the oedema that develops during oxidative injury of the immature lung. Significant increases were found in LTB4 concentration in bronchoalveolar lavage fluid obtained from pre-term guinea pig pups maintained in 95% oxygen for 48 h (P < 0.05) and 72 h (P < 0.05) compared to pups maintained in 21% oxygen. Cellular analysis of lavage fluid revealed a concurrent influx of neutrophils into the hyperoxic-injured lung at these times. The protein concentration of lavage fluid was also increased by 48-h hyperoxia exposure indicating elevated pulmonary microvascular permeability. In a second series of experiments, pups exposed to 95% oxygen (and 21% oxygen controls) were treated with a specific LTB4 antagonist (U-75302), at either 0.5, 1.5 or 3.0 mg 100 g body wt to ascertain if LTB4 played a role in either neutrophil recruitment or oedema formation in the immature lung. The number of neutrophils recovered in bronchoalveolar lavage fluid was significantly reduced, compared to vehicle-treated pups, in pups treated with U-75302, at both 1.5 and 3.0 mg/100 g body wt but not 0.5 mg/100 g body wt. Histopathological analysis of pups treated with 1.5 mg U-75302/100 g body wt revealed fewer neutrophils in the pulmonary interstitium (198 vs. 218 mm-2, P < 0.05). The extent of lung microvascular permeability, elevated by hyperoxic exposure, was modulated by increasing concentrations of U-75302. Specifically, treatment with 0.5, 1.5 and 3.0 mg U-75302/100 g body wt reduced microvascular permeability by 17, 67 and 98%, respectively. In conclusion, LTB4 plays an important role in oedema formation in acute oxidative injury of the immature lung and this is mediated, in part, through neutrophils.

Involvement of leukotriene B4 in zymosan-induced rat pleurisy: inhibition of leukocyte infiltration by the 5-lipoxygenase inhibitor T-0757

The role of leukotriene B4 (LTB4) in leukocyte infiltration in zymosan-induced rat pleurisy was investigated by studying the effects of 5-lipoxygenase inhibitors, T-0757 and AA-861, and a cyclooxygenase inhibitor, indomethacin, on leukocyte infiltration and LTB4 levels in the inflammatory exudate of rat pleurisy induced by intrapleural injection of zymosan (20 mg/rat). T-0757 and AA-861 inhibited the infiltration of leukocytes, mainly neutrophils, 3 h after injection of zymosan at a dose of 100 mg/kg, p.o., but indomethacin did not do so at a dose of 5 mg/kg, p.o. LTB4 was detected in the exudate 1 h after zymosan injection, and its level peaked at 3 h (45.4 +/- 8.6 ng/rat) and decreased thereafter. These LTB4 levels were depressed by T-0757 and AA-861 in a dose-dependent manner. T-0757 completely prevented LTB4 production at a dose of 100 mg/kg. These observations suggest that the inhibition of leukocyte infiltration is mediated by the inhibition of LTB4 production, and that LTB4 is one of the main chemical mediators of leukocyte infiltration in zymosan-induced rat pleurisy.

Role of xanthine oxidase and eicosanoids in development of pancreatic ischemia-reperfusion injury

The implication of different eicosanoids and oxygen free radicals in the development of pancreatic injury after an ischemia-reperfusion process has been evaluated. For this purpose we have compared the effect of allopurinol and indomethacin administration on the pancreatic levels of eicosanoids in a rat model of pancreatic ischemia-reperfusion. After 60 min of pancreatic ischemia and 2 h of reperfusion, significant increases in 6-keto-PGF1 alpha, PGE2, and LTB4 in pancreas tissue were detected. Allopurinol before the ischemic period reduced 6-keto-PGF1 alpha, PGE2, and LTB4 levels to the range of basal values, while prior indomethacin treatment significantly reduced 6-keto-PGF1 alpha and PGE2 levels, with LTB4 remaining unmodified. Increased postischemic plasma lipases were also significantly reduced by allopurinol to the range of sham-operated animals whereas indomethacin did not modify these levels. The data suggest a role for lipoxygenase metabolites in the development of pancreatic injury and the importance of the enzyme xanthine oxidase as an inductor of eicosanoid biosynthesis.

Eicosanoids and asthma: an update

There have been significant advances in our understanding of the role of eicosanoids as mediators in inflammation since their discovery over 50 years ago. Our more recent understanding of asthma as an inflammatory disease has led to the appreciation of eicosanoids potentially being pivotal mediators in promoting some of the changes in asthma. Of particular importance are the cysteinyl LTs in producing bronchospasm and bronchial hyperresponsivenss, and PGE2 in modulating the bronchospastic and inflammatory response. Evidence from clinical studies suggests that other eicosanoids may also contribute, but their importance is secondary and their relative contributions vary between individuals. The development of new drugs based on our partial understanding of the role that eicosanoid mediators may play in asthma promises new approaches to the treatment of this common chronic inflammatory condition.

Leukotriene B4 receptor levels and intracellular calcium signalling in polymorphonuclear leukocytes from patients with Crohn's disease

OBJECTIVE

To investigate the leukotriene B4 (LTB4) signal transducing mechanism in polymorphonuclear neutrophils (PMNs) from patients with Crohn's disease.

METHODS

Cytosolic free calcium ([Ca2+]i), inositol (1,4,5)-trisphosphate [(1,4,5)-IP3] chemotaxis, LTB4 receptor number and affinity were investigated in peripheral PMNs from 11 patients with Crohn's disease and 11 healthy controls.

RESULTS

There was a slight reduction (P = 0.31) in the number of LTB4 receptor sites per cell expressed on PMNs (mean Bmax 931) from nine of the 11 patients studied compared with the healthy controls (mean Bmax 1095). LTB4-mediated (1,4,5)-IP3 formation and the increase in [Ca2+]i were markedly decreased in PMNs from the 11 patients with Crohn's disease [(1,4,5)-IP3, mean +/- SEM 12 +/- 0.84 and 27.4 +/- 1.4 pmol/l/tube for patients and controls, respectively; [Ca2+]i, mean +/- SEM 295 +/- 2.75 and 598 +/- 4.7 nmol/l for patients and controls, respectively]. The decrease in calcium might be related to the decrease in Bmax (P < 0.05). Ionomycin, a calcium ionophore which bypasses the initial steps of LTB4 receptor activation, showed only a minor difference in peak [Ca2+]i between PMNs from patients and controls. LTB4-directed chemotaxis showed that the sensitivity to suboptimal concentrations of LTB4 (1.0 nmol/l) was significantly depressed in PMNs from patients (P < 0.05).

CONCLUSION

Peripheral PMNs from patients with Crohn's disease had a small deficit in the expression of LTB4 receptors. This deficiency was paralleled by marked alterations in cellular signalling. Whether these results are specific to Crohn's disease or simply result from the exposure of circulating PMNs to elevated levels of LTB4 remains to be established.

Acute lung injury in endotoxemic pigs: role of leukotriene B4

The role of leukotriene B4 (LTB4) in the pathogenesis of acute lung injury was examined in endotoxemic pigs. In a preliminary study, the activity and specificity of an LTB4-receptor antagonist, LY-306669, were evaluated. In vitro, LY-306669 completely blocked the functional upregulation of phagocyte opsonin receptors induced by LTB4 but had a much smaller effect on opsonin receptor upregulation induced by platelet-activating factor. In pigs treatment with LY-306669 prevented leukopenia induced by injection of authentic LTB4 but had no effect on the hematologic or hemodynamic effects of PAF or U-48816, a thromboxane-A2 mimetic. In a second study, pigs received an intravenous priming dose of lipopolysaccharide (LPS) at time (t) = -18 h and were randomized to receive 1) no further treatment (n = 5), 2) LPS (250 micrograms/kg over 1 h beginning at t = 0 h) and LY-306669 (10 mg/kg bolus and 3 mg.kg-1.h-1 infusion beginning at t = -15 min) (n = 7), or 3) LPS and vehicle (n = 6). Treatment with LY-306669 significantly ameliorated LPS-induced hypoxemia, pulmonary edema, and alveolitis. These data suggest that LTB4 is an important mediator of pulmonary dysfunction and transendothelial migration of neutrophils in LPS-induced acute lung injury.

IL-1 is a potent inducer of eosinophil accumulation in rat skin. Inhibition of response by a platelet-activating factor antagonist and an anti-human IL-8 antibody

The aim of the present study was to investigate directly and characterize the ability of IL-1 beta in inducing eosinophil accumulation in vivo. For this purpose, we studied the recruitment of 111In-labeled eosinophils in rat skin in response to intradermally injected rat rIL-1 beta. Rat rIL-1 induced a dose-dependent accumulation of 111In-labeled eosinophils, with the maximal response being detected at 5 x 10(-13) mol/site. This response was slow in onset, progressively increasing over the 4-h period investigated. Rat rIL-1 also induced a small level of edema, as measured by the local accumulation of i.v. 125I-labeled albumin, which developed with a time course similar to that of 111In-labeled eosinophil accumulation. Co-administration of the cytokine with the IL-1R antagonist, IL-1ra, or actinomycin D, significantly inhibited the 111In-labeled eosinophil accumulation, and reduced the edema formation, induced by rat rIL-1. In addition, the 111In-labeled eosinophil accumulation was significantly suppressed in animals treated with the PAF antagonist UK-74,505 or an anti-human IL-8 mAb DM/C7. These observations demonstrate for the first time that IL-1 beta is a potent inducer of eosinophil accumulation in vivo. Moreover, the results reveal that this activity of IL-1 beta is receptor mediated and dependent on the induction of proteins that may be involved in the local generation of secondary inflammatory mediators including PAF and an IL-8-like molecule. These findings are consistent with the view that endogenously generated IL-1 may play an important role in the recruitment of eosinophils at sites of allergic inflammation.