Effects of leukotriene B4 on permeability, prostacyclin and thromboxane release by normal and oxygen-preexposed isolated, perfused rat lungs

This study assessed the hemodynamic and permeability effects of exogenous, synthetic leukotriene B4 (LTB4) on normal rat lungs and lungs from rats preexposed to oxygen for 48 h, which were isolated and perfused at constant flow in vitro. Adult, Sprague-Dawley rats were exposed to air or greater than 97% O2 for 48 h. After exposure, their lungs were removed from the thorax, ventilated with normoxic gas, and perfused at 12 ml/min with Krebs-Ringer bicarbonate buffer which contained 5 mM glucose and 3 mg/ml albumin. A total of 5.55 micrograms of synthetic LTB4 was infused in three separate boluses over 15 minutes. Perfusion and airway pressures were monitored, and the lungs release of 6-ketoprostaglandin F1 alpha and thromboxane B2 (TXB2) into the effluent from the pulmonary vasculature was measured by radioimmunoassay. The LTB4 had no measureable effects on pulmonary vascular pressures. LTB4 infusion caused a pronounced increase in permeability, indicated by increased albumin concentrations in alveolar lavage fluid from O2-preexposed lungs. Release of TXB2 from both air- and O2-preexposed lungs was increased after LTB4 infusion, while the change in 6-ketoprostaglandin F1 alpha release was not statistically significant. Both the increase in permeability enhanced TXB2 released after LTB4 infusion were inhibited by 10 microM indomethacin in the perfusate. These data indicate that exogenous LTB4 increases microvascular permeability in O2-exposed lungs in association with increased release of TXB2 into the pulmonary vascular effluent.     

Reduction of eicosanoid production by essential fatty acid depletion does not attenuate the inflammatory response induced by Pseudomonas aeruginosa pneumonia in rat lung.

Sipid mediators of inflammation have been implicated in the pathogenesis of Pseudomonas aeruginosa (PA) related pulmonary damage in patients with cystic fibrosis. We studied the role of these mediators in a rat model of PA endobronchitis using essential fatty acid deficient (EFAD) animals. Whole blood from EFAD animals produced significantly less leukotriene B4 (LTB4) and hydroxyheptadecatrienoic acid when stimulated ex vivo than did whole blood from control animals (p less than 0.005). Similarly, lung lavage fluid from EFAD animals infected with PA contained less LTB4 and thromboxane B2 (TXB2) than that from control animals. Despite these differences, cellular infiltration of airways in response to PA infection was virtually identical in animals from the regular diet and the EFAD groups. Both EFAD and control animals had a significant increase in white blood cells (WBC) in lung lavage fluid at 1, 3 and 6 days following infection with PA when compared to animals receiving sterile beads. Localized areas of consolidation and nodularity were grossly evident in the lungs of all PA infected animals irrespective of their ability to generate the lipid inflammatory mediators. Microscopic examination of lung sections demonstrated similar changes in all infected animals. We conclude that LTB4 and TXB2 production occurs early in the course of PA pulmonary infection in rats. This early rise in lipid mediators is temporally associated with an influx of WBC into the airways. However, attenuation of eicosanoid production by use of an EFAD diet does not lead to a reduction in the inflammatory response to PA infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Are lipid mediators implicated in the production of pro- and anti-inflammatory cytokines during cardiopulmonary bypass graft with extracorporeal circulation?

In this study the authors assessed the sequential release of lipid mediators (TXB2, PGE2, 6-keto-PGF1alpha, LTB4, LTC4, PAF), pro-inflammatory cytokines (IL-6, IL-8, TNF-alpha) and anti-inflammatory cytokines (IL-4, IL-10) in 17 patients undergoing coronary artery bypass graft (CABG) with extracorporeal circulation (ECC). Time course of appearance of inflammatory mediators revealed the early and transient increase in lipid mediator plasma concentrations (6-keto-PGF1alpha, LTB4, LTC4, PAF) whereas cytokines (IL-6, IL-8, IL-10) were involved only in late pre- and post-operative periods. No variation of TXB2, PGE2, IL-4 and TNF-alpha levels were found. No correlation was documented between the levels of lipid mediators and pro- or anti-inflammatory cytokines suggesting that lipidic compounds are not implicated in the genesis of cytokines which appear much later involved. Despite the common use of high doses of aprotinin (a non-specific enzyme inhibitor) in hope to abrogate the inflammatory response to cardiopulmonary bypass procedure, this study reports the persistent release of several inflammatory compounds that might be involved in the post-CABG multiple organ failure syndromes.     

磷脂酶A2活力与急性缺氧性肺动脉高压关系的探讨

通过动物实验探讨磷脂酶Ａ２及相关炎性介质在急性缺氧性肺动脉高压形成中的作用。３０只ＳＤ大鼠随机分为三组;正常对照组,缺氧组及缺氧加地塞米松组。均测定肺动脉压;缺氧３０ｍｉｎ后,取静脉血肺组织测定ＰＬＡ２活力,血小板活化因子,前列腺素Ｅ２,血栓素Ｂ２。     

Immunologically induced generation of tetraene and pentaene leukotrienes in the peritoneal cavities of menhaden-fed rats

The generation of sulfidopeptide leukotrienes and leukotriene B (LTB) in response to an IgG-mediated immune complex reaction in the peritoneal cavities of rats fed either a menhaden oil-supplemented diet or a beef tallow-supplemented diet for 9 to 10 wk was determined with the combined techniques of radioimmunoassay (RIA) and reverse-phase high performance liquid chromatography. Rats on the fish fat diet (FFD) incorporated eicosapentaenoic acid (EPA) into pulmonary and splenic tissues with an EPA:arachidonic acid ratio of approximately 2:1, whereas rats on the beef fat diet (BFD) showed no detectable EPA. The estimated total quantities of immunoreactive sulfidopeptide leukotrienes generated by each group of rats were similar, ranging from 70 to 99 ng/ rat in the FFD groups and 65 to 109 ng/rat in the BFD groups; for rats on the FFD this total included the pentaene products LTC5, LTD5, and LTE5 in quantities ranging from 24 to 39 ng/rat. The total quantities of immunoreactive LTB generated in the two groups of rats were similar, being 6 to 29 ng LTB4/rat for the BFD groups and the sum of LTB4 and LTB5 of 8 to 36 ng/rat for the FFD groups. There was a two- to seven-fold preferential generation of immunoreactive LTB5 over LTB4 in the FFD rats. LTC5 was equipotent with LTC4 in contracting guinea pig pulmonary parenchymal strips and ileal tissues. In contrast, LTB5 was 1/30 to 1/60 as potent and did not reach the same maximum as LTB4 in eliciting neutrophil chemotaxis. The finding that FFD favors the immunologic generation of LTB5, which has attenuated biologic activity when compared to LTB4, suggests that EPA-enriched tissues may produce less pro-inflammatory activity than tissues that are EPA-poor.     

Contribution of macrophages to immediate hypersensitivity reaction

The interaction of mast cells with other leukocytes during immediate hypersensitivity reactions was tested by in vivo and in vitro experiments. Intraperitoneal challenge of passively sensitized rats with antigen caused the production of peptidoleukotrienes, leukotriene (LT)B4, thromboxane (TX)B2, and 6-keto-prostaglandin (PG) F1 alpha in the peritoneal cavity. Pretreatment of the rats with thioglycollate i.p. markedly changed the amount of eicosanoids formed. When polymorphonuclear leukocytes were the predominant cell type in the peritoneal exudate, both LTC4 and 6-keto-PGF1 alpha were decreased by 75% each and TXB2 by 50%. When elicited macrophages were predominant, there was an additional reduction in LTC4 by 68% as compared with 18 hr after thioglycollate treatment, but no additional change in the other arachidonic acid metabolites. In vitro antigen challenge of passively sensitized mouse bone marrow-derived mast cells caused the release of LTC4, LTB4, 6-trans-LTB4, 5-hydroxyeicosatetraenoic (5-HETE), and TXB2. Exposure to antigen of these mast cells in the presence of resident peritoneal macrophages markedly altered eicosanoid formation. Early in the time course (2 to 15 min), macrophages markedly enhanced all 5-lipoxygenase products. However, later in the time course (30 to 120 min), these products were decreased. This decrease was reversed by catalase and superoxide dismutase, which suggests the involvement of oxygen radicals. These active oxygen species also seemed to be generated by mast cells, because these enzymes caused an increase in 5-lipoxygenase products when mast cells were challenged alone. RIA of cyclooxygenase products showed that mast cells released only TXB2 when stimulated with antigen. When they were stimulated in the presence of macrophages, TXB2 and also PGE2 and 6-keto-PGF1 alpha were synthesized. Therefore, macrophages probably contribute the PGE2 and 6-keto-PGF1 alpha. Because the same amount of TXB2 was generated whether macrophages were present or not, the mast cells seem to be the major source of this compound. These data indicate that macrophages and possibly polymorphonuclear leukocytes participate in immediate hypersensitivity reactions.     

Eicosanoid synthesis by alveolar macrophages in rats with malignant mammary tumors: differences in rats treated with and without carrageenan implants

Eicosanoid synthesis by alveolar macrophages (AM), harvested from tumor bearing animals, was measured after tumor inoculation in rats treated with or without carrageenan (carra), an immunomodulating agent. After incubation of the cells with [14]C-arachidonic acid and the Ca-ionophore A23187, samples were measured by high pressure liquid chromatography (HPLC). From the HPLC profiles the lypoxygenase products, 12-hydroxyeicosatetraenoic acid (12-HETE), 15-HETE, and leukotriene-B4 (LTB4) were determined as well as the cyclooxygenase products, prostaglandin (PG)E2, PGF2 alpha and TXB2. After tumor inoculation AM-synthesis of lipoxygenase products tended to increase to values twice those of the base line values, whereas cyclooxygenase products showed subnormal values. In the non treated animals, 10 days after tumor inoculation, statistically significant increases in 12- and 15-HETE, LTB4 and PGE2 were observed when compared with carra treated animals. Later measurements did not show these differences in AM metabolism. AM metabolism was (negatively) correlated with the number of macrophages, which was particularly evident in the correlation with 12-HETE synthesis.     

Prostaglandin E2 attenuation of sheep lung responses to endotoxin

Prostaglandin (PG) E2 can inhibit inflammatory responses of neutrophils and lymphocytes, including eicosanoid release. Diffuse lung injury after endotoxemia in sheep is accompanied by sequestration of neutrophils and lymphocytes in the lungs, and eicosanoids mediate some of the pathophysiology of the response. To determine whether exogenous PGE2 could prevent the endotoxin response, we measured pulmonary hemodynamics, gas exchange, and lung lymph responses to infusion of Escherichia coli endotoxin (0.5 micrograms/kg iv over 30 min) in unanesthetized sheep in the presence and absence of PGE2 (0.5 micrograms.kg-1.min-1) infused intravenously for 4 h beginning 0.5 h before endotoxin infusion. We also measured lung lymph concentrations of thromboxane B2 (TxB2) and prostacyclin metabolite, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), by radioimmunoassay and leukotriene B4 (LTB4) by gas chromatography-mass spectrometry. PGE2 decreased endotoxin-induced pulmonary hypertension and hypoxemia and markedly attenuated the lymph flow and lymph protein clearance responses. PGE2 also attenuated endotoxin-induced increases in lung lymph TxB2 and 6-keto-PGF1 alpha and decreased lymph LTB4 flow after endotoxin without decreasing lymph LTB4 concentrations. We conclude that PGE2 infusion attenuates lung dysfunction caused by endotoxemia, possibly by preventing endogenous release of other eicosanoids.     

Inflammation and pain sensitivity: effects of leukotrienes D4, B4 and prostaglandin E1 in the rat paw

Leukotrienes (LT's) and prostaglandins (PG's) have been proposed as mediators of vascular permeability changes in inflammatory reactions. Also, prostaglandins, especially of the E-type, have been shown to enhance pain responses. In the present studies in rats, the effects of LTB4 and LTD4 on edema and pain thresholds were examined in combination with PGE1 and/or brewer's yeast. Subplantar injections of LTD4 or LTB4 induced small increases in paw thickness which were potentiated by the co-administration of PGE1. LTD4 alone had no significant effect on the development of the yeast paw edema. LTB4 was found to reduce significantly the yeast edema and this reduction could be reversed by administration PGE1. A small but significant decrease in pain threshold was caused by PGE1 and this was significantly enhanced in the presence of LTD4. LTB4, like PGE1, was found to cause slight hyperalgesia but no synergy between the two agents was observed. LTD4 was found to have no effect on the initial hypoalgesia or subsequent development of hyperalgesia caused by brewer's yeast. Both LTB4 and PGE1, however, prevented the initial hypoalgesia and significantly reduced the latency for development of yeast induced hyperalgesia. These effects of LTB4 are discussed in terms of possible release of cyclooxygenase products.     

Effects of experimental diabetes on spontaneous contractions, on the output of prostaglandins and on the metabolism of labelled arachidonic acid, in uteri isolated from ovariectomized rats. Influences of estradiol

Spontaneous changes in isometric developed tension (IDT) as a function of time after isolation (contractile constancy) in uteri from control-castrated and castrated chronic streptozotocin-diabetic rats, were explored. The effects of injecting 17-beta estradiol (Eo) were also studied. No differences in the minor changes of contractile constancy, between control and diabetic preparations, during a period of 60 min, were detected, whereas uteri from non-diabetic Eo injected animals (0.5 + 1.0 ug, prior to sacrifice), exhibited a profound reduction of IDT, significantly greater than in tissues obtained from Eo injected-diabetic rats. Moreover, basal generation and outputs into the suspending solution of prostaglandins (PGs) E1, E2 and F2 alpha, were explored in the same groups, at 60 min following tissue isolation. The basal outputs of these three PGs were similar in castrated control rats, but preparations from castrated-diabetics released significantly more PGE1. The administration of Eo to castrated-diabetics, failed to alter the releases of the three PGs explored. In addition, the metabolism of labelled arachidonic acid (AA) into different prostanoids (6-keto-PGF1, PGF2, PGE2 and thromboxane B2-TXB2), was also investigated. The non-diabetic spayed rat uterus converted AA into these four prostanoids, the transformation into 6-keto-PGF1 alpha (as an index of PGI2 formation) being the most prominent. In preparations from diabetic rats the formation) being the most prominent. In preparations from diabetic rats the formation of 6-keto-PGF1 alpha, PGF2 alpha and PGE2, was significantly smaller than in controls, whereas a greater % of TXB2 formation (as an index of TXA2), was detected. On the other hand uterine preparations from non-diabetic spayed rats injected with Eo formed less 6-keto-PGF1 alpha and PGE2 and similar amounts of PGF2 alpha or of TXB2 from AA, than Eo injected controls, whereas uteri from castrated diabetic animals injected with Eo, formed a similar % of 6-keto-PGF1 alpha, PGF2 alpha and PGE2 from AA, than tissue preparations from non-estrogenized controls. However, the enhanced transformation of the labelled fatty acid precursor (AA) into TXB2 in the diabetic group, was significantly reduced by the steroid. The role of the augmented generation and release of PGE1 in uteri from diabetic rats is discussed in terms of precedents indicating the relevance of PGs type E supporting rat uterine motility. In addition the influence of Eo is attractive, because its reducing effect on TX production, in diabetes, a disease known to be accompanied by enhanced synthesis of vasoconstrictor and platelet aggregation TXA2, and by frequent obstructive circulat     

Alveolar macrophage function in rats with severe protein calorie malnutrition. Arachidonic acid metabolism, cytokine release, and antimicrobial activity

To investigate the effects of protein calorie malnutrition (PCM) on alveolar macrophage function, we measured antimicrobial activity, IL-1 and TNF production, and arachidonic acid metabolism in alveolar macrophages of infant rats with moderate and severe PCM. Groups of weanling male rats were fed a diet containing 0.8% protein (PCM) or 24% protein (control). A third group (pair fed) was fed limited amounts of the control diet that matched the mean daily dietary intake of the PCM group. After 4 wk on the diets, alveolar macrophages from all three groups functioned similarly with respect to surface adherence, phagocytosis and killing of Listeria monocytogenes, release of hydrogen peroxide and superoxide anion, and production of IL-1 and TNF. In contrast, Listeria-stimulated alveolar macrophages from the PCM group exhibited a marked shift in arachidonic acid metabolism, with impaired production of leukotriene B4 and enhanced release of thromboxane B2 and PGE2. The membrane arachidonic acid content and the uptake of [3H]arachidonate by alveolar macrophages did not differ among the three groups. The shift toward the cyclooxygenase pathway was not seen after 2 wk of dietary restriction and was reversed if PCM animals were fed the control diet for 1 wk. Thus, PCM does not affect the antimicrobial activity or cytokine production of alveolar macrophages, but causes alterations in arachidonic acid metabolism that may interfere with the modulatory functions of alveolar macrophages.     

Effects of fish oil on glomerular function in rats with diabetes mellitus

The mechanisms responsible for hyperfiltration in diabetes mellitus (DM) as well as for the initiation and progression of diabetic nephropathy are not fully elucidated. Enhanced prostaglandin E2 (PGE2) production has been invoked in the former and thromboxane (TXB2) and hyperlipidemia in the latter. Fish oil (FO)-enriched diets can favorably alter eicosanoid synthesis and serum lipid profiles. We therefore examined the effects of a FO-enriched diet on glomerular filtration (GFR), proteinuria, glomerular eicosanoid production, and serum lipids in rats with streptozotocin-induced DM (STZ-DM). Groups of 5-8 rats with STZ-DM were maintained on low insulin and then pair-fed with isocaloric diets enriched with either FO (20% w/w) or beef tallow (BT; 20% w/w). GFR was determined in the same animals at onset of diet and after 8 and 20 weeks on the respective diets by [14C]inulin clearance using implanted osmotic minipumps each time. Significant hyperfiltration was present initially and GFR did not change on either diet for 20 weeks, in spite of a significant and greater than 50% decrease in all prostaglandins (PGE2, TXB2, PGF2 alpha, 6-keto, PGF1 alpha) produced by glomeruli isolated from DM/FO as compared to DM/BT or control rats. FO diet completely corrected the hypertriglyceridemia of diabetes and significantly reduced the mild and early proteinuria of DM. The decrease in proteinuria and the correction of hyperlipidemia of DM by a FO-enriched diet may be beneficial in the long term not only for the development of diabetic glomerulopathy, but also for the accelerated atherosclerosis of DM.     

Effect of leukotriene B4, prostaglandin E2 and arachidonic acid on cytosolic-free calcium in human neutrophils

Changes in cytosolic free calcium [Ca2+]i and release of beta-glucuronidase in response to leukotriene B4 (LTB4) were measured in intact neutrophils loaded with the fluorescent Ca2+ indicator, quin 2. LTB4 (10(-10) M or higher) caused a rapid rise in [Ca2+]i due to influx from the extracellular medium and release from intracellular pools as well as enzyme release. PGE2 (3 microM) did not alter [Ca2+]i whereas arachidonic acid (10 microM) raised [Ca2+]i. Pretreatment of cells with the chemotactic peptide FMLP inhibited the subsequent rise of [Ca2+]i induced by LTB4. Since chemotactic peptides activate the lipoxygenase pathway of arachidonic acid metabolism, it may be speculated that endogenous LTB4 generation is involved in neutrophil activation.     

Leukotriene F4 and the release of arachidonic acid metabolites from perfused guinea pig lungs in vitro

Radioimmunoassay and bioassay techniques have been used to investigate the ability of leukotriene (LT)F4 to release products of arachidonic acid metabolism from guinea pig isolated lungs perfused via the pulmonary artery. Also, the abilities of LTC4, LTD4, LTE4 and LTF4 to contract guinea pig ileal smooth muscle (GPISM) was studied. Each of the LT's contracted GPISM. The rank order of potency was LTD4 greater than LTC4 greater than LTE4 much greater than LTF4 in a ratio of 1:7:170:280 respectively. Bioassay of pulmonary effluents indicated the passage of LTF4 through the lungs caused a contraction of rabbit aorta as well as an FPL-55712 sensitive contraction of GPISM. The contractions of rabbit aorta were inhibited by pretreatment of the lungs with Indomethacin but not with the thromboxane synthetase inhibitor Dazoxiben. Radioimmunoassay of the lung effluents indicated LTF4 to cause a 70-fold increase in thromboxane B2 (TXB2), 4-fold increase in prostaglandin (PG)E2 and a 16-fold increase in 6-keto PGF1 alpha levels. The LTF4-induced increments of these immunoreactive metabolites was inhibited by pretreatment of the lungs with Indomethacin. Pretreatment of lungs with Dazoxiben inhibited the LTF4-induced increment in TXB2 and enhanced the effluent levels of PGE2 24-fold (compared with untreated lungs). There were no detectable differences in either immunoreactive LTC4 or immunoreactive LTB4 levels. It is concluded LTF4 is a relatively weak agonist on GPISM and can induce the release of cyclooxygenase products of arachidonic acid metabolism from guinea pig perfused lung.     

Analysis of leukotrienes, prostaglandins, and other oxygenated metabolites of arachidonic acid by high-performance liquid chromatography

High-performance liquid chromatography procedures were developed which separate leukotrienes (LTs), hydroxy-fatty acids (HETEs), prostaglandins (PGs), the stable metabolite of prostacyclin (6-keto-PGF1 alpha), the stable metabolite of thromboxane A2 (TXB2), 12-hydroxyheptadecatrienoic acid (HHT), and arachidonic acid (AA). Two methods employing reverse-phase columns are described. One method uses a radial compression system, the other a conventional steel column. Both systems employ methanol and buffered water as solvents. The radial compression system requires 60 min for separation of the AA metabolites, while the conventional system requires 100 min. Both methods provide good separation and recovery of 6-keto-PGF1 alpha, TXB2, PGE2, PGF2 alpha, PGD2, LTC4, LTB4, LTD4, LTE4, HHT, 15-, 12-, and 5-HETE; and AA. The 5S,12S-dihydroxy-6-trans, 8-cis, 10-trans, 14-cis-eicosatetraenoic acid (5S,12S-diHETE), a stereoisomer of LTB4, coelutes with LTB4. To determine the applicability of the methods to biologic systems, AA metabolism was studied in two models, guinea pig lung microsomes and rat alveolar macrophages. Both HPLC systems demonstrated good recovery and resolution of eicosanoids from the two biological systems. A simple evaporation technique for HPLC sample preparation, which avoids the use of chromatographic and other time-consuming methodology, is also described.     

Receptor-mediated effects of glucocorticoids on inflammation: enhancement of the inflammatory response with a glucocorticoid antagonist

Glucocorticoids suppress the inflammatory response by altering leukocyte traffic and function, cytokine secretion and action, and phospholipid metabolism. We employed the glucocorticoid receptor antagonist RU 486, to examine whether glucocorticoids suppress the inflammatory response through a receptor-mediated mechanism and whether basal glucocorticoid secretion exerts antiinflammatory effects in the resting (non-stress) state. To test these hypotheses we evaluated the effects of increasing doses of dexamethasone, RU 486, or dexamethasone plus RU 486 on the exudate volume and concentrations of leukocytes, prostaglandin E2, (PGE2) and leukotriene B4 (LTB4) in intact rats that received subcutaneous carrageenin. Exudate volume, leukocyte concentration and LTB4 and PGE2 levels were all suppressed by dexamethasone in a dose-dependent fashion (P less than 0.005). RU 486 was able to antagonize fully the suppressive effects of dexamethasone on the inflammatory response (P less than 0.001) and to cause increases of exudate volume and leukocyte, PGE2 and LTB4 concentrations when given alone (P less than 0.05). These increases ranged between 30 and 100% above the basal inflammatory response. We conclude that glucocorticoids most likely suppress the inflammatory response by a glucocorticoid receptor-mediated mechanism and under basal conditions exert tonic antiinflammatory effects.     

cAMP and human neutrophil chemotaxis. Elevation of cAMP differentially affects chemotactic responsiveness.

Neutrophils (PMN) treated with cAMP elevating agents were evaluated for their chemotactic responsiveness to FMLP and leukotriene B4 (LTB4). PGE1 and isoproterenol, increased PMN cyclic AMP production and inhibited chemotaxis to both FMLP and LTB4. In contrast, forskolin, which activates adenylate cyclase directly, inhibited chemotaxis to FMLP but not to LTB4. The phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), was required for inhibition of PMN chemotaxis to FMLP by forskolin, PGE1, and isoproterenol. Isoproterenol and PGE1 inhibited PMN chemotaxis to LTB4 in the absence of IBMX and chemotaxis was further inhibited in the presence of IBMX. PMN cAMP levels were stimulated 2- to 3-fold with isoproterenol, 6- to 10-fold with PGE1, and 5- to 7-fold with forskolin over basal levels in the presence of IBMX. These observations demonstrate that total cellular cAMP concentration is not correlated with inhibition of PMN chemotaxis to all stimuli; forskolin, which increased cyclic AMP 5- to 7-fold over basal levels, did not inhibit chemotaxis to LTB4, whereas isoproterenol, which increased cyclic AMP only 2- to 3-fold over basal levels, inhibited chemotaxis to LTB4. PMN cAMP extrusion was determined under basal conditions and in the presence of PGE1, isoproterenol, or forskolin. PMN extruded cAMP under all conditions examined.     

Regulation of interleukin 1 production by mouse peritoneal macrophages. Effects of arachidonic acid metabolites, cyclic nucleotides, and interferons

The effects of prostaglandin E2 (PGE2), cyclic nucleotides, leukotriene B4 (LTB4), and interferons on interleukin 1 (IL 1) production by lipopolysaccharide (LPS)-stimulated C3H/HeNCrl mouse peritoneal macrophages were studied. IL 1 production was inhibited by PGE2, the adenosine 3':5'-monophosphate analog dibutyryl cAMP, the cAMP agonist isoproterenol, and the phosphodiesterase inhibitor isobutylmethylxanthine. These agents were more inhibitory when added early in the latent phase of IL 1 synthesis following stimulation with LPS rather than just prior to release of IL 1 into the medium. Production of both the intracellular and extracellular forms of IL 1 was blocked by PGE2 and cAMP. Suppression of LPS-induced IL 1 production by PGE2 was prevented by leukocyte alpha-interferon. Moreover, alpha-interferon augmented LPS-induced IL 1 production but did not stimulate IL 1 production in the absence of LPS. Immune gamma-interferon markedly inhibited LPS-stimulated IL 1 production. The lipoxygenase inhibitor eicosa-5,8,11,14-tetraynoic acid suppressed, whereas 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline augmented, LPS-induced IL 1 production. The opposing effects of these agents suggested that lipoxygenase metabolites do not act as inducers of IL 1 production. Purified LTB4 did not stimulate base-line or augment LPS-induced IL 1 production (both intracellular and extracellular forms). Moreover, calcium ionophore A23187 (a lipoxygenase activator) did not stimulate IL 1 production, alone or in combination with LTB4. Thus, net IL 1 production by macrophages may be regulated by a balance between the effects of PGE2, cAMP, alpha-interferon, and gamma-interferon, but not LTB4.     

Oxidative stress and lipid mediators induced in alveolar macrophages by ultrafine particles

In ambient aerosols, ultrafine particles (UFP) and their agglomerates are considered to be major factors contributing to adverse health effects. Reactivity of agglomerated UFP of elemental carbon (EC), Printex 90, Printex G, and diesel exhaust particles (DEP) was evaluated by the capacity of particles to oxidize methionine in a cell-free in vitro system for determination of their innate oxidative potential and by alveolar macrophages (AMs) to determine production of arachidonic acid (AA), including formation of prostaglandin E2 (PGE2), leukotriene B4 (LTB4), reactive oxygen species (ROS), and oxidative stress marker 8-isoprostane. EC exhibiting high oxidative potential induced generation of AA, PGE2, LTB4, and 8-isoprostane in canine and human AMs. Printex 90, Printex G, and DEP, showing low oxidative capacity, still induced formation of AA and PGE2, but not that of LTB4 or 8-isoprostane. Aging of EC lowered oxidative potential while still inducing production of AA and PGE2 but not that of LTB4 and 8-isoprostane. Cellular ROS production was stimulated by all particles independent of oxidative potential. Particle-induced formation of AA metabolites and ROS was dependent on mitogen-activated protein kinase kinase 1 activation of cytosolic phospholipase A2 (cPLA2) as shown by inhibitor studies. In conclusion, cPLA2, PGE2, and ROS formation was activated by all particle types, whereas LTB4 production and 8-isoprostane were strongly dependent on particles' oxidative potential. Physical and chemical parameters of particle surface correlated with oxidative potential and stimulation of AM PGE2 and 8-isoprostane production.     

Effects of dietary selenium and tocopherol on glutathione peroxidase and superoxide dismutase activities in rat phagocytes

Glutathione peroxidase activities (GSH-Px) of peritoneal exudate polymorphonuclear neutrophils, pulmonary alveolar macrophages, and peritoneal exudate macrophages of rats depleted of dietary selenium for four to six weeks were markedly lower than the corresponding activities in rats fed the same diet supplemented with 0.5 ppm selenium as sodium selenite. GSH-Px in phagocytes from selenium-supplemented rats adequate or deficient in tocopherol status did not differ significantly. In selenium deficient animals, the residual GSH-Px of polymorphonuclear neutrophils and peritoneal macrophages, but not of alveolar macrophages were slightly higher in tocopherol-deficient rats than in tocopherol-supplemented animals. Superoxide dismutase activities of each cell type were comparable and were not significantly affected by dietary selenium or tocopherol.