Resolvin D2 promotes host defense in a 2 - hit model of sepsis with secondary lung infection

In the development of sepsis, there is early, massive inflammation which can lead to multiple organ failure. Later there is an immunosuppressed phase where the host is susceptible to secondary infections or is unable to clear existing infection. Specialized Pro-resolving Mediators (SPMs) are endogenously produced lipids which resolve infection by decreasing bacteria load and reducing systemic inflammatory response. There has been little work studying if SPMs given late, can promote host defense. We examined if an SPM, Resolvin D2 (RvD2) could promote host defense in a 2-hit mouse model of cecal ligation and puncture (CLP) sepsis and secondary Pseudomonas aeruginosa lung infection. RvD2 given 48 h after mild CLP (1st hit), increased gene expression of Toll-like receptor-2 (TLR-2) and alveolar macrophage/monocyte phagocytic ability compared to CLP mice given saline vehicle. In this model, RvD2 did not affect plasma IL-6 or IL-10. These effects induced by RvD2, lowered lung bacterial load and decreased mortality after the secondary infection of Pseudomonas aeruginosa (2nd hit). Splenic T-cell numbers were also increased in RvD2 treated mice compared to saline vehicle treated animals. The results suggest that RvD2 promoted mechanisms of host defense in a 2-hit model sepsis and secondary lung infection.

Lipoxin A4 promotes reduction and antibiotic efficacy against Pseudomonas aeruginosa biofilm

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic bacterium commonly found in wound infections and airways of cystic fibrosis patients. P. aeruginosa readily forms biofilms which can reduce the efficacy of antibiotics used to eradicate the pathogen. We have previously shown that a Specialized Pro-resolving Mediator (SPM), Lipoxin A4 (LxA₄) is a quorum sensing inhibitor which can reduce P. aeruginosa virulence. In this study, we examined the direct actions of LxA₄ and RvD₂ on P. aeruginosa biofilm formation and virulence gene expression. The influence of LxA₄ on antibiotic efficacy and the combined effects on biofilm formation were also investigated. LxA₄ and RvD₂ reduced P. aeruginosa biofilm formation and virulence gene expression. LxA₄ increased ciprofloxacin inhibition on biofilm formation but did not affect ciprofloxacin's action on non-adherent bacteria. On the other hand, LxA₄ increased bacterial killing action of imipenem but did not affect imipenem's action on biofilm. We also found that LxA₄ can increase ciprofloxacin's bacterial killing ability in established biofilm. Together these results suggest that LxA₄ has direct effects on P. aeruginosa biofilm formation and can increase antibiotic efficacy directly.

Sign of lipid peroxidation as measured in the urine of patients with probable Alzheimer's disease

Free radical-induced oxidative damage may be involved in the neurodegenerative process associated with Alzheimer's disease (AD). 8-Isoprostaglandin F(2alpha) (iPF(2alpha)-III) is an isoprostane derived from free radical-induced non-enzymatic oxidation of arachidonic acid. It is formed in vivo and is an indicator of lipid peroxidation. Measurements were made of iPF(2alpha)-III in the urine of patients with mild to moderate dementia associated with probable AD and compared to those in the urine of non-demented subjects, who were similar in age and gender. 2,3-Dinor thromboxane B(2) (dinor TXB(2)), a urinary metabolite of TXB(2) was also measured, and served as an indicator of the enzymatic transformation of a product of arachidonic acid. Enzyme linked immunoassays were used to measure iPF(2alpha)-III and dinor TXB(2) in the urine. The concentration of iPF(2alpha)-III was significantly elevated in urine of patients assessed to have mild to moderate dementia as compared to non-demented patients. The concentration of urinary dinor TXB(2) was also significantly elevated in the patients with dementia and probable AD as compared to the non-demented subjects. There was considerable overlap of values obtained for demented and non-demented patients for iPF(2alpha)-III and dinor TXB(2), respectively. The observed elevation of iPF(2alpha)-III suggests that patients with mild to moderate dementia associated with probable AD are experiencing significant oxidative stress. This finding is consistent with current data suggesting that oxidative stress may be occurring in patients with dementia and probable AD. The increase of dinor TXB(2) may indicate that enzymatic processes related to the metabolism of arachidonic acid-derived products are also increased in demented patients with probable AD.

The percutaneous penetration of prostaglandin E1 and its alkyl esters

The percutaneous delivery of PGE1 and its alkyl esters in alcoholic saline solution through hairless mouse skin was compared. The quantification of alkyl esters was based on the same principle as that for PGE1, which was converted to PGB1 to enhance the sensitivity and minimize the interference. Results showed that it was PGE1 that appeared in the receiver compartment for all alkyl esters examined. The flux of all alkyl esters of PGE1 in the same concentration was higher than PGE1 itself at most of saline vehicle with various fractions of alcohol. The maximal flux for a fixed concentration of each alkyl ester appeared at different fractions of alcohol. When the fractions of alcohol was kept constant, the alkyl ester that showed the maximal flux at this concentration appeared to have a longer chain length with increasing the fraction of alcohol. But isopropyl ester deviated from this order. It was concluded that the alkyl ester derivatives promoted the penetration of PGE1 mainly as a result of enhancing the drug partitioning into the stratum corneum. The alcohol fraction that needed to achieve the maximal flux at the same concentration increased with the increase of alkyl chain length, which resulted in the decrease of solubility parameter. It is necessary to optimize the fraction of alcohol in the saline solution in order to achieve the maximal flux at a fixed concentration for these alkyl esters with different alkyl chain length.

Comparison between oral and vaginal administration of misoprostol on uterine contractility

OBJECTIVE

To compare the degree of absorption and the effect on uterine contractility of the prostaglandin E1 analogue misoprostol after vaginal and oral administration.

METHODS

Thirty women with a normal intrauterine pregnancy between 8 and 11 weeks' gestation who requested termination of pregnancy were given either 0.2 mg (orally n = 5; vaginally n = 6) or 0.4 mg (orally n = 10; vaginally n = 9) of misoprostol. Intrauterine pressure was recorded using a Grass polygraph connected to a pressure transducer 30 minutes before misoprostol was given and for 4 hours thereafter. At the end of the recording, suction curettage was performed. Blood samples were obtained at 0, 0.5, 1, 2, 4, and 6 hours for measurement of misoprostol, which was assayed by high-pressure liquid chromatography-mass spectrometry.

RESULTS

In all patients, the first effect was an increase in uterine tonus. After 0.4 mg of misoprostol administered orally, uterine tonus started to increase after a mean (+/- standard deviation) time of 7.8+/-3.0 minutes and reached its maximum after 25.5+/-5.0 minutes. The corresponding times after vaginal administration were 20.9+/-5.3 minutes and 46.3+/-20.7 minutes, respectively. The initial increase in tonus was also more pronounced after oral than after vaginal administration. After vaginal administration, all patients developed uterine contractions; the activity, measured in Montevideo units, increased continuously during the observation period. This was not the case after oral administration. Plasma levels of misoprostol were measured in 18 patients. The highest levels were found 30 minutes after oral treatment and 1-2 hours after vaginal administration.

CONCLUSION

The long-lasting and continuously increasing uterine contractility after vaginal administration can be explained only in part by a direct effect of misoprostol. The longer period of elevated plasma levels of misoprostol may also have initiated the prolonged events leading to increased uterine contractility.

Investigation of the percutaneous penetration of prostaglandin E1 and its ethyl ester

The optimization of percutaneous delivery of PGE1 and its ethyl ester in alcoholic buffer solution through hairless mouse skin was investigated. A reversed-phase HPLC system with a photodiode array detector was used to differentiate the UV spectra of the penetration products. By comparison of the UV spectrum for each chromatographic peak, the conversion of PGE1 ethyl ester to PGE1 by enzymatic hydrolysis was found to be the predominant degradation pathway during the in vitro penetration. The quantification of ethyl ester was developed based on the same principle as that for PGE1. It was then applied to monitor the penetration of prostaglandins through hairless mouse skin from the vehicles containing various fractions of alcohol. Results demonstrated that the alkyl group promoted the penetration mainly as a result of enhancing the drug partitioning into the stratum corneum at its maximal thermodynamic activity. The alcohol fraction around 20% seemed to be optimal for the percutaneous delivery of the ethyl ester. The use of collagen gel to carry PGE1 ethyl ester for percutaneous application was included for comparison. The effect of adding alcohol in the collagen gel on the penetration of PGE1 ethyl ester was found to be slightly lower than that from the same vehicle without collagen.

Stimulation of protein kinase C redistribution and inhibition of leukotriene B4-induced inositol 1,4,5-trisphosphate generation in human neutrophils by lipoxin A4

1. To test the hypothesis that protein kinase C (PKC) is involved in the inhibitory actions of lipoxin A4 (LXA4) on second messenger generation, we studied the effects of LXA4 on PKC in human neutrophils and on leukotriene B4 (LTB4)-stimulated inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) generation. 2. LXA4, 1 microM, caused a fall in cytosolic PKC-dependent histone phosphorylating activity to 23.5% of basal levels. 3. LXA4, caused an increase in particulate PKC-dependent histone phosphorylating activity with a bell-shaped dose-response fashion; maximal stimulation was observed at 10 nM LXA4. 4. Western blot analysis with affinity-purified antibodies to alpha- and beta-PKC showed that only the beta-PKC isotype was translocated by LXA4. 5. LXA4 inhibited LTB4-stimulated Ins(1,4,5)P3 generation in a bell-shaped fashion with maximal inhibition at 1 nM LXA4. The observed inhibition was dose-dependently removed by pre-incubation with a PKC inhibitor (Ro-31-8220). 6. These results show that LXA4 activates PKC in whole cells and supports a role for PKC activation in the inhibitory action of LXA4 on LTB4-induced Ins(1,4,5)P3 generation. 7. LXA4 (1-1000 nM) pre-incubation did not affect specific binding of [3H]-LTB4 to neutrophils. Thus, the inhibitory effect of LXA4 on LTB4-stimulated Ins(1,4,5)P3 generation could not be attributed to an effect on LTB4 receptors.

Antithrombotic effects of peroxynitrite: inhibition and reversal of aggregation in human platelets

The inhibition of platelet aggregation by peroxynitrite, a reactive oxygen species derived from the interaction of nitric oxide (NO) and superoxide, was examined in platelet-rich plasma. In this report, we have used a preparation of peroxynitrite that was free of H2O2 and MnO2. As such, peroxynitrite dose-dependently (50-200 microM) inhibited aggregation of human platelets stimulated by ADP (5 microM), collagen (0.5 microgram), thrombin (0.5U/microL) and U46619 (1 microM). In addition, peroxynitrite reversed platelet aggregation induced by collagen, ADP, and thrombin. Peroxynitrite, preincubated with platelet-poor plasma or albumin (7%) for 30 min, did not alter the inhibition of platelet aggregation. This suggested that the inhibitory action of peroxynitrite may be due to nitrosylation of proteins, which by themselves possess activity, rather than conversion to NO or NO donors. Furthermore, we show that peroxynitrite increased the cGMP level only at 200 microM concentrations, further suggesting that the action of peroxynitrite was not completely due to its conversion to NO or NO donors.

Effects of lipoxin A4 on chemotaxis and degranulation of human eosinophils stimulated by platelet-activating factor and N-formyl-L-methionyl-L-leucyl-L-phenylalanine

Lipoxins are trihydroxytetraene metabolites derived through a double lipoxygenation of arachidonic acid. Lipoxin A4 (LXA4) was prepared by total chemical synthesis, and its capacity to modulate eosinophil migration has been evaluated. LXA4 is a weak and partial chemotactic agent; at 10(-6) M, it achieved about 20% of the response of 10(-6) M platelet-activating factor (PAF). Preincubation of eosinophils with increasing doses of LXA4 (10(-10)-10(-5) M) resulted in a concentration-dependent inhibition of cell migration induced by 10(-6) M formyl-methionyl-leucyl-phenylalanine (FMLP) and 10(-6) M PAF. The concentration of LXA4 which produced 50% inhibition (IC50) of eosinophil migration was approximately 10(-6) M. LXA4 (10(-10)-10(-6) M) did not elicit ECP release or modulate ECP release induced by 10(-6) M FMLP. LXA4 may have antiallergic properties in preventing eosinophilic migration.

Structure/activity relationship of leukotriene B4 and its structural analogues in chemotactic, lysosomal-enzyme release and receptor-binding assays

The biological activities of chemically synthesized leukotriene B4 and eight structural analogues have been studied using chemotaxis, lysosomal-enzyme release and receptor-binding assays on human neutrophils. The results show that increasing the number of double bonds between C14 and C20, having triple bonds at C6 or C14, substitution of the primary carboxyl group at C1, changing the geometry of the double bond at C6 from the cis to trans configuration and changing the chirality of the hydroxyl group at C12 from the R to the S configuration result in substantial loss of both biological activity and the capacity to bind to the LTB4 recognition site in parallel. We suggest that the functional epitopes of 5S,12R-dihydroxy-6,14-cis-8,10-trans-icosatetraenoic acid (LTB4) are either the same, or reside in the same domain as the binding site for the LTB4 receptor. Development of LTB4 antagonists to the high-affinity LTB4 receptor, based on the structure of LTB4, is unlikely to be successful.

Airway responsiveness to leukotriene C4 (LTC4), leukotriene E4 (LTE4) and histamine in aspirin-sensitive asthmatic subjects

We wanted to determine whether the airway response to inhaled leukotriene C4 (LTC4) is similar to inhaled leukotriene E4 (LTE4) in aspirin-sensitive asthma and, therefore, determined airway responsiveness to histamine, LTC4 and LTE4 in seven aspirin-sensitive subjects and 13 control asthmatic subjects, who were tolerant of aspirin. The concentration of inhaled lysine-aspirin which produced a 15% fall in forced expiratory volume in one second (FEV1) (PC15) was determined in aspirin-sensitive asthmatic subjects. The dose of histamine, LTC4 and LTE4 which produced a 35% fall in specific airways conductance (PD35sGaw) was determined by linear interpolation from the log dose response curve. There was no correlation between the PC15 for lysine-aspirin and the airway reactivity to inhaled LTC4 or LTE4. There was no difference in airway response to histamine and LTC4 between any of the groups of asthmatic subjects. There was a rank order of potency LTC4 > LTE4 > histamine in both groups, with LTC4 approximately 1,000 fold more potent than histamine in both groups. Aspirin-sensitive asthmatic subjects were significantly more responsive to LTE4 (p = 0.02) than aspirin-tolerant asthmatic subjects. The relative responsiveness of LTE4 to histamine (PD35 histamine/PD35 LTE4) was significantly greater in aspirin-sensitive asthmatic subjects compared to aspirin-tolerant asthmatic subjects (p = 0.05). There was no difference in relative responsiveness of LTC4 to histamine between aspirin-sensitive or aspirin-tolerant asthmatic subjects. We conclude that the airways of aspirin-sensitive asthmatic subjects demonstrate a selective hyperresponsiveness to LTE4, which is not observed for LTC4.

Airway responsiveness to leukotriene C4 (LTC4), leukotriene E4 (LTE4) and histamine in aspirin-sensitive asthmatic subjects

We wanted to determine whether the airway response to inhaled leukotriene C4 (LTC4) is similar to inhaled leukotriene E4 (LTE4) in aspirin-sensitive asthma and, therefore, determined airway responsiveness to histamine, LTC4 and LTE4 in seven aspirin-sensitive subjects and 13 control asthmatic subjects, who were tolerant of aspirin. The concentration of inhaled lysine-aspirin which produced a 15% fall in forced expiratory volume in one second (FEV1) (PC15) was determined in aspirin-sensitive asthmatic subjects. The dose of histamine, LTC4 and LTE4 which produced a 35% fall in specific airways conductance (PD35sGaw) was determined by linear interpolation from the log dose response curve. There was no correlation between the PC15 for lysine-aspirin and the airway reactivity to inhaled LTC4 or LTE4. There was no difference in airway response to histamine and LTC4 between any of the groups of asthmatic subjects. There was a rank order of potency LTC4 > LTE4 > histamine in both groups, with LTC4 approximately 1,000 fold more potent than histamine in both groups. Aspirin-sensitive asthmatic subjects were significantly more responsive to LTE4 (p = 0.02) than aspirin-tolerant asthmatic subjects. The relative responsiveness of LTE4 to histamine (PD35 histamine/PD35 LTE4) was significantly greater in aspirin-sensitive asthmatic subjects compared to aspirin-tolerant asthmatic subjects (p = 0.05). There was no difference in relative responsiveness of LTC4 to histamine between aspirin-sensitive or aspirin-tolerant asthmatic subjects. We conclude that the airways of aspirin-sensitive asthmatic subjects demonstrate a selective hyperresponsiveness to LTE4, which is not observed for LTC4.

Leukotriene E4 and granulocytic infiltration into asthmatic airways

Sulphidopeptide leukotrienes are potent bronchoconstrictors and increase bronchial hyperreactivity, one of the hallmarks of asthma. We have demonstrated that leukotriene LTE4, the most stable of the sulphidopeptide leukotrienes, elicited an increase in the numbers of eosinophils and neutrophils in the lamina propria of the airway mucosa 4 h after inhalation in 4 asthmatic subjects. The numbers of eosinophils were, on average, 10-fold greater than those of neutrophils. There was no significant change in numbers of lymphocytes, plasma cells, mast cells, or macrophages. Since LTE4 recruits granulocytes, the potential of antisulphidopeptide leukotriene drugs as anti-inflammatory and "steroid-sparing" agents should be tested.

Effect of indomethacin on leukotriene4-induced histamine hyperresponsiveness in asthmatic subjects

The effect of indomethacin on the capacity of LTE4 to enhance airway histamine responsiveness was evaluated in eight mild asthmatic subjects. Subjects attended the laboratory on three separate pairs of study days when inhalation challenges with methacholine or LTE4 were performed and the airway responses to histamine were measured 4 and 7 h later. An open pair of study days was followed by a pair of study days during ingestion of either placebo or indomethacin capsules. The dose of agonist that produced a 35% fall in specific airways conductance (PD35 SGaw) was obtained by linear interpolation from the logarithmic dose-response curve. Indomethacin treatment did not affect baseline SGaw or methacholine airway responsiveness. However, indomethacin significantly inhibited LTE4-induced histamine hyperresponsiveness. Maximum enhancement of histamine responsiveness by LTE4 on the open and placebo study days was 4.1 +/- 0.9- (mean +/- SEM) and 5.7 +/- 1.2-fold, respectively (p = 0.36). Maximal enhancement on the indomethacin day was 1.68 +/- 0.46, and this was significantly decreased compared with that on the placebo day (p = 0.02). This suggests that LTE4-induced enhanced responsiveness to histamine is mediated in part by cyclooxygenase pathway-derived products.

The effect of epithelium removal on leukotriene E4-induced histamine hyperresponsiveness in guinea-pig tracheal smooth muscle

1. Removal of the epithelium resulted in a threefold increase in guinea-pig tracheal sensitivity to histamine without increasing the maximal response. 2. Preincubation of epithelially-denuded guinea-pig tracheal smooth muscle with leukotriene E4 (LTE4) in vitro increased the subsequent maximal response of the tissues to histamine. The sensitivity of the tissues to histamine was unaffected by LTE4 pretreatment. 3. Pretreatment of the epithelially-denuded tissues with the LTE4-analogue, 20-COOH LTE4, did not affect the maximal response to histamine. 4. LTE4 pretreatment increased the maximal response of the epithelially-denuded tissues to substance P (SP) but did not affect the maximal response to carbachol, KCl nor to the beta-adrenoceptor agonist, isoprenaline. 5. LTE4-induced airway histamine hyperresponsiveness was blocked by indomethacin (5 microM), GR32191 (3 microM) and atropine (1 microM). 6. Both LTE4 and U46619 pretreatment increased the contractile response of tracheal smooth muscle to electrical field stimulation. 7. It is proposed that LTE4 induces an increased maximal response of epithelially-denuded guinea-pig airway smooth muscle to both histamine and substance P via a facilitation of cholinergic neurotransmission, which is dependent upon the secondary generation of prostanoid mediator(s) acting on TP-receptors situated on cholinergic nerve terminals. Further, it is suggested that the increased maximal response of the epithelially-intact tissues to both histamine and substance P, after LTE4 pretreatment, may be suppressed by an epithelially-derived factor.

The effects of lipoxin A4 on airway responses in asthmatic subjects

This study was performed to determine whether lipoxin A4 (LXA4) inhalation in asthmatic subjects has an effect on airways response. Eight subjects (six asthmatic, two normal) attended for bronchial inhalation challenge with LXA4. In three of these subjects (two asthmatics, one normal) blood pressure, pulse, and symptoms before and after challenge were recorded. Subsequently five male patients with mild asthma (22 to 34 yr of age) reattended for bronchial inhalation challenge with either leukotriene C4 (LTC4) or the combination of LTC4 and 1 x 10(-4) M LXA4. After inhalation of each dose of agonist SGaw and V25 were measured. Airway responsiveness was determined by the concentration of agonist in the nebulizer required to induce a 35% fall in SGaw (PC35). There was no effect of LXA4 inhalation on SGaw, V25, blood pressure, pulse, or symptoms. There was a significant shift of the SGaw and V25 dose-response curve to the right after inhalation challenge with LTC4 combined with 1 x 10(-4) M LXA4 as compared with that after inhalation challenge with LTC4 alone (p less than 0.01 and p less than 0.025, respectively). Thus, LXA4 may modulate LTC4-induced airway obstruction and may act as an endogenous sulfidopeptide leukotriene receptor antagonist.

The mechanism of LTE4-induced histamine hyperresponsiveness in guinea-pig tracheal and human bronchial smooth muscle, in vitro

1. Preincubation of guinea-pig tracheal smooth muscle with leukotriene E4 (LTE4) in vitro increased its subsequent responsiveness to histamine. 2. LTE4 pretreatment of guinea-pig tracheal strips did not affect the subsequent responsiveness to either the contractile agents, carbachol and KCl, or to the relaxant beta-adrenoceptor agonist, isoprenaline. 3. LTE4-induced airway histamine hyperresponsiveness was blocked by indomethacin (5 microM), GR32191 (3 microM), atropine (1 microM) and tetrodotoxin (1 microM). 4. U46619, a stable thromboxane A2-analogue, at a non-contractile concentration of 4 nM, increased tracheal smooth muscle sensitivity to histamine. 5. Both LTE4 and U46619 pretreatment increased the contractile response of tracheal smooth muscle to electrical field stimulation. 6. Preincubation of human bronchial spirals with LTE4 in vitro increased its subsequent responsiveness to histamine. 7. LTE4-induced histamine hyperresponsiveness of human bronchus was inhibited by GR32191 (3 microM) and atropine (1 microM). 8. It is proposed that LTE4 induces guinea-pig airway smooth muscle hyperresponsiveness to histamine via a facilitation of cholinergic neurotransmission, which is dependent upon the secondary generation of prostanoid mediator(s) acting on TP-receptors situated on cholinergic nerve terminals. In addition, it is suggested that LTE4 may induce histamine hyperresponsiveness of human bronchus in vitro by a similar mechanism as to that seen in guinea-pig central airway smooth muscle.

Inhibition of leukotriene B4-induced neutrophil migration by lipoxin A4: structure-function relationships

Lipoxins are trihydroxytetraene metabolites which are derived from arachidonic acid through an interaction between different lipoxygenase pathways. Previous work has shown that lipoxin A4 (LXA4) inhibits the chemotactic responsiveness of neutrophils (PMN) to leukotriene B4. We have now assessed the structural determinants of the lipoxin A4 molecule which are necessary for its inhibitory activity, using structural analogs of LXA4 prepared by chemical synthesis. Our results indicate the importance of two adjacent free hydroxyl groups in either the R or the S configuration; one hydroxyl group has to be in the C-6 position, but the other hydroxyl group can be in either the C-5 or the C-7 position for the conferment of inhibitory activity.

Leukotrienes C4, D4, and E4 enhance histamine responsiveness in asthmatic airways

The effects of prior inhalation of each of the sulfidopeptide leukotrienes (LT), LTC4, LTD4, and LTE4 on airway responsiveness to histamine have been compared in seven asthmatic and six normal subjects. Each subject underwent histamine inhalation challenge at 1, 4, and 7 h after inhalation of phosphate-buffered saline and bronchoconstricting doses of LTC4, LTD4, LTE4, and methacholine, which produced a greater than 30% fall in specific airway conductance. In asthmatic subjects, prior inhalation of LTC4, LTD4, and LTE4 enhanced airway responsiveness to histamine when compared with saline inhalation, on average by a maximum of 3.9-, 2.8-, and 3.1-fold, respectively, at 4 h after inhalation. Methacholine inhalation did not significantly after histamine responsiveness throughout the time course studied. In normal subjects, inhalation of LTC4, LTD4, LTE4, and methacholine did not change airway responsiveness to histamine. Thus, LTC4 and LTD4 were similar to LTE4 in their capacity to enhance airway responsiveness to histamine in asthmatic subjects, and, in common with LTE4, they failed to elicit a change in airway responsiveness to histamine in normal subjects.

Effects of dietary fish oil lipids on allergic and inflammatory diseases

Fish oil is rich in the polyunsaturated N-3 fatty acids, eicosapentaenoic (EPA) and docosahexaenoic acids (DCHA). EPA competes with arachidonic acid (AA) for metabolism by the cyclooxygenase and lipoxygenase pathways. Selective metabolites derived from EPA have reduced biological activities as compared with the AA-derived counterparts. Dietary supplementation with EPA led to incorporation of EPA into membrane phospholipids, an inhibition of 5-lipoxygenase pathway activity, and a reduction of the elaboration of platelet-activating factor. Neutrophil chemotaxis and the capacity of these cells to adhere to endothelial cells are substantially attenuated. This suggests that EPA has anti-inflammatory potential. Clinical trials in rheumatoid arthritis, psoriasis, atopic dermatitis, and bronchial asthma have shown beneficial effects. Whether the benefit obtained clinically is sufficient to replace or significantly reduce any clinical condition remains to be answered.

The effect of inhalation of the leukotriene receptor antagonist, SK&F 104353, on leukotriene C4- and leukotriene E4-induced bronchoconstriction in subjects with asthma

The effect of prior inhalation of the sulfidopeptide leukotriene receptor antagonist, SK&F 104353 (963 +/- 43.7 micrograms; mean +/- SEM), on (LTC4)- and leukotriene E4 (LTE4)-induced bronchoconstriction has been studied in six subjects with asthma (six male subjects, aged 24 to 36 years). Inhalation challenges with either synthetic LTC4 or LTE4 were performed after prior inhalation of aerosolized SK&F 104353 or placebo in a double-blind, randomized fashion. Airway responsiveness to each agonist was determined by the cumulative dose of agonist required to induce a 35% fall in specific airway conductance (PD35) as determined by linear interpolation of the log dose-response curve. There was no change in baseline specific airway conductance after inhalation of either placebo or SK&F 104353. LTC4- and LTE4-induced bronchoconstrictions were significantly inhibited by aerosolized inhalation of SK&F 104353 30 minutes before challenge. The geometric mean (GM) PD35 of LTC4 on the open-therapy and placebo-therapy days was 0.043 nmol (range, 0.01 to 0.1 nmol) and 0.036 nmol (range, 0.01 to 0.1 nmol), respectively. On the treatment day with SK&F 104353, it was not possible to obtain a GM PD35 LTC4 up to a maximum concentration of 0.52 nmol LTC4 (p less than 0.01). The GM PD35 of LTE4 on the open-therapy and placebo-therapy days was 0.30 nmol (range, 0.13 to 0.76 nmol) and 0.39 nmol (range, 0.14 to 0.9 nmol), respectively. On the treatment day with SK&F 104353, it was not possible to obtain a GM PD35 LTE4 up to a maximum concentration of 5 nmol LTE4 (p less than 0.005). Thus, LTC4- and LTE4-induced bronchoconstrictions are both inhibited by SK&F 104353.

Skin responses to intradermal histamine and leukotrienes C4, D4, and E4 in patients with chronic idiopathic urticaria and in normal subjects

Mast cell inflammatory mediators, such as histamine, and newly formed compounds, such as the leukotrienes, cause wheal and flare when they are injected intradermally into normal subjects and may therefore play a role in the formation of urticaria. The effects of intradermal injections (50 microliters) of six different concentrations of histamine (range, 3.3 x 10(-4) to 3.3 x 10(-9) mol/L) and the leukotrienes C4, D4, and E4 (range, 2 x 10(-4) to 2 x 10(-9) mol/L) have been compared in 10 normal subjects and in 10 patients with chronic idiopathic urticaria. Wheal-and-flare sizes were measured at timed intervals up to 4 hours, and area under the curve for each response over time was calculated. There were no significant differences in leukotriene-induced responses between groups. Maximum sizes of histamine-induced wheal and flare were similar in each group of subjects. There were, however, significant increases in mean areas under the response curve of histamine wheal and flare in the patients with urticaria (wheal, p less than 0.001; flare, p less than 0.001; analysis of variance). These findings demonstrate a prolongation of skin responses to histamine in patients with urticaria and suggest an impaired clearance of histamine (or other vasoactive agents released by histamine) from the skin of these patients.

Asthmatic airways have a disproportionate hyperresponsiveness to LTE4, as compared with normal airways, but not to LTC4, LTD4, methacholine, and histamine

Airways responsiveness to leukotriene (LT) C4, LTD4, LTE4, histamine, and methacholine have been studied in eight asthmatic and six normal subjects. Airways responsiveness to each bronchoconstrictor agonist was assessed by constructing cumulative dose-response curves, and the dose that produced a 35% decrease in specific airways conductance (PD35) was obtained by linear interpolation. Airways of subjects with asthma were approximately 14-, 15-, 6-, 9-, and 219-fold more responsive to histamine, methacholine, LTC4, LTD4, and LTE4, respectively, than were normal subjects. Thus, there was a substantially augmented level of hyperresponsiveness to LTE4 in bronchial asthma, which was not observed for the other bronchoconstrictor agents, when compared to normal subjects. In contrast to LTC4 and LTD4, as histamine and methacholine responsiveness increase, the dose ratio of histamine to LTE4 (PD35 histamine/PD35 LTE4) and the dose ratio of methacholine to LTE4 also tended to increase. This suggests that as the nonspecific airways responsiveness increases, the relative potency of LTE4 also increases, whereas potency of LTC4 and LTD4 decrease. These results suggest that the mechanism of the bronchoconstriction induced by LTE4 may be distinct from that produced by LTC4 or LTD4 in subjects with asthma. This may reflect leukotriene subtype receptor heterogeneity in asthmatic airways.

Identification of lipoxin A4 and its relationship to the sulfidopeptide leukotrienes C4, D4, and E4 in the bronchoalveolar lavage fluids obtained from patients with selected pulmonary diseases

Lipoxins are biologically active trihydroxytetraene containing products derived from arachidonic acid that are formed by interactions between lipoxygenases. Although the lipoxins have been generated from mixed cell suspensions in vitro, it has not been established whether these products are synthesized in vivo. We have performed bronchoalveolar lavage (BAL) in 12 patients with lung disease (sarcoid, six; pneumonia, two; asthma, two; carcinoma, one; alveolitis of unknown cause, one) and in six normal control subjects. The BAL fluid was analyzed for lipoxin A4 (LXA4) using gas chromatography mass spectrometry with selective ion monitoring, and the levels of the sulfidopeptide leukotrienes were determined using reverse-phase high-performance liquid chromatography and radioimmunoassay. LXA4 was detected in BAL fluid from nine of the 12 patients studied. The levels of LXA4 ranged from 0.4 to 2.8 ng/ml. LXA4 was not detected in any of the six normal subjects. Sulfidopeptide leukotrienes were detected in all the BAL samples, ranging from 0.04 to 0.7 ng/ml, and there was no significant difference between the patients and the normal subjects. In patients with detectable LXA4 in BAL fluid, the ratio of the concentrations of LXA4 to those of the sulfidopeptide leukotrienes ranged from 1.9 to 62 (mean, 19.0). This is the first demonstration of the presence of LXA4 in disease.

Lipoxin A4 inhibits phosphoinositide hydrolysis in human neutrophils

Lipoxins (LX) are trihydroxytetraene metabolites derived from arachidonic acid via an interaction between the 5- and 15-lipoxygenases. Preincubation of [3H] myo-inositol labeled PMN with 10-7M and 10-5M LXA4 for 1 minute at 37 degrees C resulted in a concentration dependent inhibition of the generation of [3H] IP3 and [3H] IP in cells subsequently stimulated by increasing doses of LTB4 or FMLP for 1 minute at 37 degrees C. Preincubation of PMN with LXA4 did not inhibit specific binding of [3H] LTB4 to PMN. These results indicate that LXA4 inhibits chemotactic factor-induced phosphoinositide hydrolysis at a post-receptor level.

Comparison of the generation of platelet-activating factor and leukotriene C4 in human eosinophils stimulated by unopsonized zymosan and by the calcium ionophore A23187: the effects of nedocromil sodium

The generation of platelet-activating factor (PAF) and leukotriene C4 (LTC4) from normodense human eosinophils (EOSs), stimulated with unopsonized zymosan or calcium ionophore A23187, has been studied. There was a zymosan time- and dose-dependent increase in both PAF and LTC4 production. A plateau of 0.11 +/- 0.04 ng of PAF per 10(6) EOSs (mean +/- SEM; n = 7) and of 1.38 +/- 0.58 ng of LTC4 per 10(6) EOSs (n = 5) was reached at 5 x 10(8) zymosan particles at 37 degrees C for 30 minutes. Under optimal conditions, 91 +/- 1% of the PAF and 66 +/- 13% of the LTC4 remained cell associated. Calcium ionophore A23187 induced a time- and dose-dependent increase in the quantities of PAF and of LTC4 generated by EOSs. A plateau of 31 +/- 13 ng of LTC4 per 10(6) EOSs (n = 5) was reached at 1 mumol/L of calcium ionophore A23187 at 37 degrees C for 15 minutes. The dose response for PAF generation reached 4.2 +/- 0.8 ng/10(6) EOSs (n = 8) at 10 mumols/L of calcium ionophore A23187 at 37 degrees C for 15 minutes and had not plateaued; 90 +/- 5% of the generated PAF was cell associated. In vitro preincubation of EOSs with 10(-8) to 10(-4) mol/L of nedocromil sodium for 15 minutes did not change the subsequent generation or cellular distribution of PAF or LTC4 in EOSs optimally stimulated with either zymosan or calcium ionophore A23187.

Lipoxin A4 and lipoxin B4 inhibit chemotactic responses of human neutrophils stimulated by leukotriene B4 and N-formyl-L-methionyl-L-leucyl-L-phenylalanine

1. Lipoxin A4 (LXA4) and lipoxin B4 (LXB4) have been evaluated for their capacities to modulate neutrophil (PMN) migration and endothelial cell adherence using compounds prepared by total chemical synthesis. 2. Increased PMN migration was seen with concentrations of LXA4 from 10(-9) mol/l to 10(-7) mol/l. LXA4 was 100-fold less potent than leukotriene B4 (LTB4) and it elicited only one-half of the maximal response of LTB4. 3. The (5S,6S,15S)-isomer of LXA4 induced only a weak migratory response and LXB4 was inactive, suggesting that the activity of LXA4 was stereospecific. 4. Modified chequerboard analysis indicated that LXA4 was a chemokinetic agent. 5. Preincubation of PMN with increasing concentrations of LXA4 induced a very similar dose- and time-dependent inhibition of the subsequent response to 10(-7) mol/l LTB4 or 10(-7) mol/l N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP). The inhibition was observed at 10(-10) mol/l LXA4; the concentration which produced 50% inhibition was 10(-8) mol/l and 100% inhibition of PMN locomotion occurred at 10(-6) mol/l LXA4. 6. The (5S,6S,15S)-isomers of LXA4 and LXB4 were 5- and 100-fold less potent than LXA4, respectively, in suppressing LTB4- or FMLP-induced PMN migration. 7. Preincubation of PMN with LXA4 led to a suppression of calcium mobilization, as assessed by Quin2-AM fluorescence, when the cells were subsequently stimulated under optimal conditions by LTB4 or FMLP. 8. These results suggest that the inhibitory activity of lipoxins may be related to the capacity of these molecules to regulate calcium ion mobilization.

Airway responsiveness to histamine and leukotriene E4 in subjects with aspirin-induced asthma

Airway responsiveness to histamine and leukotriene E4 (LTE4) has been compared between five subjects with aspirin-induced asthma (AIA) and 15 asthmatic subjects without aspirin sensitivity (non-AIA). In the AIA group, the geometric mean doses of histamine and LTE4 causing a 35% fall in specific airway conductance (PD35) were 0.31 mumol and 0.17 nmol, respectively, and LTE4 was 1,870 times more potent than histamine. In the non-AIA group, the histamine and LTE4 PD35 doses were 0.40 mumol (non-AIA versus AIA, NS) and 2.8 nmol (non-AIA versus AIA, p = 0.002), respectively, and LTE4 was 145 times more potent than histamine in eliciting bronchoconstriction (non-AIA versus AIA, p = 0.001). After desensitization to aspirin the geometric mean histamine and LTE4 PD 35 in the AIA group changed to 0.19 mumol (NS) and 3.3 nmol (p = 0.007), respectively, and there was an average 33-fold reduction in the responsiveness of the airways to LTE4 relative to histamine (p less than 0.001). In five non-AIA subjects. Ingestion of 600 mg of aspirin daily did not lead to any significant change in airway responsiveness to histamine or to LTE4. These results demonstrate a selective and marked increase in airway responsiveness to LTE4 in subjects with AIA. The efficacy of desensitization may relate in part to a selective down-regulation of LTE4 receptors within the airways.

The effects of dietary supplementation with fish oil lipids on the airways response to inhaled allergen in bronchial asthma

The effects of dietary supplementation with fish oil lipids on the airways responses to allergen and neutrophil biochemistry and function have been studied in 17 atopic asthmatic subjects. Nine subjects received 18 capsules of Max-EPA (3.2 g eicosapentaenoic acid and 2.2 g docosahexaenoic acid) a day and eight subjects received identical capsules containing olive oil, for 10 wk in a double-blind fashion. There were no differences between prediet values and those observed after dietary supplementation with Max-EPA or placebo in the dose of allergen causing an acute asthmatic response as assessed by a 35% fall in specific airways conductance (PD35), the extinction dose of allergen on skin prick testing, the histamine PD35, or the total serum IgE concentrations. Twelve of the 17 subjects developed late asthmatic responses after allergen challenge prediet. Six of these subjects received Max-EPA, and six received placebo capsules. As compared to prediet values, the magnitude of the allergen-induced late asthmatic response was significantly attenuated from 2 to 7 h after allergen challenge following dietary supplementation with Max-EPA (p less than 0.005) but not with placebo. The attenuation of the late response was not accompanied by any significant change in the clinical severity of disease as assessed by diurnal peak expiratory flow rates, symptom scores, or bronchodilator drug usage.(ABSTRACT TRUNCATED AT 250 WORDS)

The relative responsiveness to inhaled leukotriene E4, methacholine and histamine in normal and asthmatic subjects

The relative bronchoconstricting potencies of leukotriene E4 (LTE4) methacholine and histamine have been compared in asthmatic and normal subjects. LTE4 responsiveness in asthmatic subjects, as measured by the dose which produced a 35% fall in specific airways conductance (PD35), ranged from 0.06-24.4 nmol (geom mean 4.1 nmol, n = 20). This was significantly less than the PD35 in normal subjects (range 39.0-370 nmol, geom mean 105 nmol, n= 6; p less than 0.001). There was a correlation between LTE4 and methacholine responsiveness (r = 0.84, p less than 0.001) and between LTE4 and histamine responsiveness (r = 0.79, p less than 0.001). LTE4 was 73 times more potent than methacholine and 112 times more potent than histamine in asthmatic subjects. LTE4 was 20 times more potent than methacholine and 58 times more potent than histamine in normal subjects. LTE4 is a potent bronchoconstrictor agent, and LTE4 responsiveness correlates with both histamine and methacholine responsiveness.

The relative responsiveness to inhaled leukotriene E4, methacholine and histamine in normal and asthmatic subjects

The relative bronchoconstricting potencies of leukotriene E4 (LTE4) methacholine and histamine have been compared in asthmatic and normal subjects. LTE4 responsiveness in asthmatic subjects, as measured by the dose which produced a 35% fall in specific airways conductance (PD35), ranged from 0.06-24.4 nmol (geom mean 4.1 nmol, n = 20). This was significantly less than the PD35 in normal subjects (range 39.0-370 nmol, geom mean 105 nmol, n= 6; p less than 0.001). There was a correlation between LTE4 and methacholine responsiveness (r = 0.84, p less than 0.001) and between LTE4 and histamine responsiveness (r = 0.79, p less than 0.001). LTE4 was 73 times more potent than methacholine and 112 times more potent than histamine in asthmatic subjects. LTE4 was 20 times more potent than methacholine and 58 times more potent than histamine in normal subjects. LTE4 is a potent bronchoconstrictor agent, and LTE4 responsiveness correlates with both histamine and methacholine responsiveness.

The contractile activities of lipoxin A4 and lipoxin B4 for guinea-pig airway tissues

1. The isometric contractile activities of lipoxin A4 (LxA4) and lipoxin B4 (LxB4) were evaluated on guinea-pig lung tissue over the concentration range, 10(-8) to 10(-5) M. 2. LxA4 contracted guinea-pig lung parenchymal strips; the concentration eliciting 50% maximum histamine response was 3 x 10(-6) M. LxA4 did not contract tracheal spirals. 3. The LxA4 dose-response curve was parallel to that of leukotriene D4 (LTD4) with LxA4 being approximately 10,000 fold less potent than LTD4. 4. The time course of the contraction elicited by LxA4 was similar to that of LTD4 and it was slow in onset and did not plateau for 20 min. 5. Pre-incubation of parenchymal strips with leukotriene receptor antagonists at a concentration of 1 x 10(-6) M to 3 x 10(-5) M FPL 55712 or 3 x 10(-5) M L 649923 inhibited LxA4 activity. 6. Pre-incubation of tissues with 1 x 10(-5) M L 651392, a 5-lipoxygenase inhibitor, or 1 x 10(-5) M indomethacin, a cyclo-oxygenase inhibitor, did not affect the contractile activity of LxA4. 7. LxB4 did not constrict parenchymal strips or tracheal spirals.

The effects of inhaled leukotriene E4 on the airway responsiveness to histamine in subjects with asthma and normal subjects

Eight subjects with asthma inhaled on separate occasions leukotriene E4 (LTE4) (6.1 nmol, geometric mean), methacholine, and diluent, which produced an average 41.0%, 37.0%, and 3.3% decrease in specific airway conductance (SGaw), respectively. When the SGaw had recovered to baseline levels at 60 minutes after challenge, the provocative dose of inhaled histamine that produced a 35% decrease in SGaw (PD35) was determined. The histamine PD35 observed after inhalation of LTE4 was 0.46 mumol, and this was significantly less than the histamine PD35 observed after inhalation of methacholine (0.88 mumol; p less than 10(-4) and diluent (0.97 mumol; p less than 10(-5). Histamine responsiveness was also enhanced by a fiftyfold lower dose of LTE4 (p = 0.005), and the enhancement was less than that elicited by the higher dose of LTE4 in the same individuals (p = 0.02). The changes in histamine PD35 during a 1-week period after LTE4 and methacholine challenges were compared in four subjects with asthma. There was a time-dependent enhancement in histamine responsiveness that reached a maximal of 3.5-fold at 7 hours after LTE4. The enhancement had disappeared by 1 week. Similar changes were not observed after methacholine challenge, which elicited the same degree of bronchoconstriction as LTE4. Inhalation of LTE4 in five normal subjects that produced a mean 37.6% decrease in SGaw did not change histamine responsiveness for up to 7 hours. These findings suggest that LTE4 may play a role in the perpetuation of nonspecific airway hyperresponsiveness in bronchial asthma.

Enhanced generation of leukotriene B4 by neutrophils stimulated by unopsonized zymosan and by calcium ionophore after exercise-induced asthma

The generation of LTB4 by peripheral blood neutrophils (PMN) isolated before and for as long as 6 h after exercise-induced asthma (EIA) has been analyzed. Three and 6 h after the development of EIA, PMN isolated from 10 asthmatic subjects and stimulated in vitro by 2 x 10(8) and 4 x 10(8) zymosan particles per 2 x 10(6) PMN demonstrated a 12- and 4-fold enhancement, respectively, in the production of immunoreactive LTB4 as compared with PMN isolated before exercise. At 6 h after EIA, there was a redistribution of generated LTB4 such that 30 to 40% of LTB4 produced by zymosan-activated PMN was released extracellularly as compared with 10% before exercise. There was no significant enhancement in the generation of LTB4 by unstimulated PMN at any time point after exercise. Resolution by reverse-phase high performance liquid chromatography (HPLC) of products from [3H]arachidonic-acid-labeled and zymosan-activated PMN demonstrated that, in addition to LTB4, there was enhanced metabolism to 6-trans-LTB4, omega-oxidation metabolites of LTB4 and 5-HETE. Stimulation of PMN with 10 microM A23187 revealed a 2-, 6-, and 5-fold enhancement in the production of LTB4, 6-trans-LTB4, and 5-HETE, respectively, at 6 h after EIA, as measured by integrated ultraviolet absorbance after HPLC. There was no significant enhancement in LTB4 generation by PMN in 6 asthmatic subjects after methacholine-induced bronchospasm, and after exercise in 6 subjects who did not develop asthma. The augmentation of PMN LTB4 generation in EIA correlated with the extent of the early decrease in SGaw.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of leukotriene B3: comparison of its biological activities with leukotriene B4 and leukotriene B5 in complement receptor enhancement, lysozyme release and chemotaxis of human neutrophils

1. Leukotriene (LT) B3 was prepared by total chemical synthesis and its identity was confirmed by nuclear magnetic resonance analysis and proton homonuclear plot of connectivities and chemical shift assignments. The effects of LTB3 on complement receptor enhancement, chemotaxis and lysozyme release in human neutrophils (PMN) were compared with those of LTB4 and LTB5. 2. LTB3 and LTB4 elicited a virtually identical dose- and time-dependent enhancement in complement receptors type 1 (CR1) and type 3 (CR3) and release of lysozyme. LTB5 was approximately 100 times less potent than LTB4 in enhancing CR1 and CR3, whereas it was 10,000 times less potent than LTB4 in releasing lysozyme from human PMN. 3. LTB3 and LTB5 were respectively 5- and 100-fold less potent than LTB4 in eliciting chemotaxis. 4. These findings indicate that the pro-inflammatory potential of LTB3 and LTB4 are similar, whereas LTB5 is substantially less potent as an inflammatory mediator. 5. The finding that LTB5 is a weak and partial agonist relative to LTB3 and LTB4 could be due to the rigidity of the C-17-C-18 double bond in LTB5. This may interfere with the active site specificity of LTB5 to a substantial extent. 6. One approach to the development of antagonists to the LTB4 receptor may be to establish a rigid structure in the C-17-C-18 region of the LTB4 molecule.

The generation and cellular distribution of leukotriene C4 in human eosinophils stimulated by unopsonized zymosan and glucan particles

Human eosinophils (EOSs) stimulated under optimal conditions with 5 X 10(8) unopsonized zymosan particles at 37 degrees C for 30 minutes produced an average total immunoreactive leukotriene (LT) C4 of 1.6 ng per 10(6) EOSs, and 30% to 60% of the generated product remained cell associated. The dose-response characteristics of zymosan-induced LTC4 generation were different from those of phagocytosis, suggesting that the two events were independent. Pretreatment of EOSs with 10(-8) mol/L of formyl-methionyl-leucyl-phenylalanine for 30 minutes led to a twofold to fivefold augmentation of LTC4 generation by cells subsequently activated by unopsonized zymosan. Optimal EOS activation with 1 mumol/L of the calcium ionophore A23187 at 37 degrees C for 15 minutes produced more than 100 times greater quantities of LTC4 than with zymosan. The amount of immunoreactive LTC4 that remained cell associated after calcium ionophore A23187 stimulation reached a maximum after 5 minutes and then declined. Of the relatively small amount generated in the first minute, 71% was cell associated, but this figure declined to 9% after 15 minutes, by which time there had been a redistribution of the LTC4 to the supernatant. Inflammatory leukocytes may respond to zymosan because the cells recognize either one or both of its major polysaccharide components, glucan and mannan. Glucan, but not mannan, stimulated EOSs to generate LTC4 in a dose- and time-dependent manner. Under optimal conditions, there was no significant difference in the total quantities of LTC4 elaborated by EOSs stimulated by glucan and by unopsonized zymosan. This suggests that zymosan may induce leukotriene generation in the human EOS through a glucan recognition mechanism.

Effect of dietary supplementation with fish oil lipids on mild asthma

Recruitment of inflammatory leucocytes to the airways may play a part in the pathogenesis of asthma. As dietary enrichment with fish oil lipids can suppress leucocyte function, the effect of these lipids on asthma control and neutrophil function was studied in 20 subjects with mild asthma. Twelve subjects received capsules containing 3.2 g of eicosapentaenoic acid and 2.2 g of docosahexaenoic acid daily and eight subjects received placebo capsules containing olive oil for 10 weeks in a double blind fashion. Baseline specific airways conductance, airways responsiveness to histamine and exercise, diurnal peak expiratory flow, symptom scores, and bronchodilator use were measured. Neutrophil fatty acid composition was evaluated by gas chromatography, calcium ionophore induced neutrophil leukotriene (LT)B4 and LTB5 generation were measured by reverse phase high performance liquid chromatography and radioimmunoassay, and neutrophil chemotactic responses to formyl-methionyl-leucyl-phenylalanine (FMLP) and LTB4 were assessed by a microchemotaxis technique. Although the fish oil supplemented diet produced a greater than 10 fold increase in the eicosapentaenoic acid content of neutrophil phospholipids, there was no significant change in airways responsiveness to histamine or any change in any of the clinical measurements. After dietary supplementation with fish oil there was a 50% inhibition of total LTB (LTB4 + LTB5) generation by ionophore stimulated neutrophils and neutrophil chemotaxis was substantially suppressed. Neutrophil function remained unchanged in the placebo group. It is concluded that in subjects with mild asthma a fish oil enriched diet attenuates neutrophil function without changing the severity of asthma.

Effects of dietary supplementation with marine fish oil on leukocyte lipid mediator generation and function in rheumatoid arthritis

Twelve patients with active rheumatoid arthritis supplemented their usual diet with 20 gm of Max-EPA fish oil, daily, for 6 weeks. Following this supplementation, the ratio of arachidonic acid to eicosapentaenoic acid in the patients' neutrophil cellular lipids decreased from 81:1 to 2.7:1, and the mean generation of leukotriene B4 (with calcium ionophore stimulation) significantly declined by 33%. The mean neutrophil chemotaxis to both leukotriene B4 and FMLP significantly increased toward the normal range at week 6. The generation of 5-lipoxygenase products by calcium ionophore-stimulated monocytes was not significantly suppressed, but a significant decline (37%) in platelet-activating factor generation was noted at week 6. The modulation of these measures of leukocyte inflammatory potential suggests that fish oil supplementation may have an antiinflammatory effect.

Effect of dietary enrichment with eicosapentaenoic and docosahexaenoic acids on in vitro neutrophil and monocyte leukotriene generation and neutrophil function

The effects of dietary fish-oil fatty acids on the function of the 5-lipoxygenase pathway of peripheral-blood polymorphonuclear leukocytes and monocytes were determined in seven normal subjects who supplemented their usual diet for six weeks with daily doses of triglycerides containing 3.2 g of eicosapentaenoic acid and 2.2 g of docosahexaenoic acid. The diet increased the eicosapentaenoic acid content in neutrophils and monocytes more than sevenfold, without changing the quantities of arachidonic acid and docosahexaenoic acid. When the neutrophils were activated, the release of [3H]arachidonic acid and its labeled metabolites was reduced by a mean of 37 per cent, and the maximum generation of three products of the 5-lipoxygenase pathway was reduced by more than 48 per cent. The ionophore-induced release of [3H]arachidonic acid and its labeled metabolites from monocytes in monolayers was reduced by a mean of 39 per cent, and the generation of leukotriene B4 by 58 per cent. The adherence of neutrophils to bovine endothelial-cell monolayers pretreated with leukotriene B4 was inhibited completely, and their average chemotactic response to leukotriene B4 was inhibited by 70 per cent, as compared with values determined before the diet was begun and six weeks after its discontinuation. We conclude that diets enriched with fish-oil-derived fatty acids may have antiinflammatory effects by inhibiting the 5-lipoxygenase pathway in neutrophils and monocytes and inhibiting the leukotriene B4-mediated functions of neutrophils.