Enhanced urinary excretion of leukotriene E4 by patients with multiple trauma with or without adult respiratory distress syndrome

Metabolism of Glutathione S-Conjugates: Multiple Pathways

Many potentially toxic electrophilic xenobiotics and some endogenous compounds are detoxified by conversion to the corresponding glutathione S-conjugate, which is metabolized to the N-acetylcysteine S-conjugate (mercapturate) and excreted. Some mercapturate pathway components, however, are toxic. Bioactivation (toxification) may occur when the glutathione S-conjugate (or mercapturate) is converted to a cysteine S-conjugate that undergoes a β-lyase reaction. If the sulfhydryl-containing fragment produced in this reaction is reactive, toxicity may ensue. Some drugs and halogenated workplace/environmental contaminants are bioactivated by this mechanism. On the other hand, cysteine S-conjugate β-lyases occur in nature as a means of generating some biologically useful sulfhydryl-containing compounds.

Enzymes Involved in Processing Glutathione Conjugates

Many potentially toxic electrophiles react with glutathione to form glutathione S-conjugates in reactions catalyzed or enhanced by glutathione S-transferases. The glutathione S-conjugate is sequentially converted to the cysteinylglycine-, cysteine- and N-acetyl-cysteine S-conjugate (mercapturate). The mercapturate is generally more polar and water soluble than the parent electrophile and is readily excreted. Excretion of the mercapturate represents a detoxication mechanism. Some endogenous compounds, such as leukotrienes, prostaglandin (PG) A2, 15-deoxy-Δ^12,14-PGJ₂, and hydroxynonenal can also be metabolized to mercapturates and excreted. On occasion, however, formation of glutathione S- and cysteine S-conjugates are bioactivation events as the metabolites are mutagenic and/or cytotoxic. When the cysteine S-conjugate contains a strong electron-withdrawing group attached at the sulfur, it may be converted by cysteine S-conjugate β-lyases to pyruvate, ammonium and the original electrophile modified to contain an –SH group. If this modified electrophile is highly reactive then the enzymes of the mercapturate pathway together with the cysteine S-conjugate β-lyases constitute a bioactivation pathway. Some endogenous halogenated environmental contaminants and drugs are bioactivated by this mechanism. Recent studies suggest that coupling of enzymes of the mercapturate pathway to cysteine S-conjugate β-lyases may be more common in nature and more widespread in the metabolism of electrophilic xenobiotics than previously realized.

Temporal profiles of cerebrospinal fluid leukotrienes, brain edema and inflammatory response following experimental brain injury

The post-traumatic changes of leukotrienes LTC4, LTD4, LTE4, and LTB4 in cerebrospinal fluid of rats from 10 min to 7 days were investigated after controlled cortical impact in relation to brain edema and cellular inflammatory response. LTC4 increased five-fold at 4 h, normalized at 24 h, and showed another four-fold increase at 7 days. The same pattern was observed for LTD4 and LTE4. LTB4 however, behaved differently: concentrations were lower and levels peaked two-fold at 24 h. Edema in the injured hemisphere increased continuously up to 24 h without change contralaterally. Leukocyte infiltration, macrophage presence and microglia activation were most prominent at 24 h, 7 days and 24 h respectively. Leukotriene changes in CSF seem to reflect those in the affected tissue, with a time delay and in lower concentrations, and were not linearly correlated to brain edema. The initially high leukotriene levels are rather likely to contribute to the cytotoxic edema than to enhance a vasogenic edema component. The profile of LTB4 was parallel to the time course of leukocyte infiltration, indicating initiation of infiltration as well as prolonged production by leukocytes themselves. The second leukotriene peak at 7 days is likely to follow a different pathway and might be related to a production in macrophages or activated glia.

Humoral markers of severity and prognosis of critical illness

Despite the considerable advances made in understanding the pathophysiology of systemic inflammation during critical illness, clinical progress has been elusive as it remains a very deadly condition. Cortisol and thyroid hormone levels can be as predictive of outcome as the commonly used severity parameters (i.e. APACHE). Indeed, levels of endocrine humoral substances such as arachidonic acids, nitric oxide, endothelin, calcitonin precursors, leptin and adenosine correlate with the severity and outcome of critical illness. Furthermore, calcitonin precursors represent a potentially new hormokine paradigm, being transcriptionally activated in all cells in response to infection. The cytokines are immune markers that often correlate with severity and outcome, but their release is transient. In contrast, the so-called acute phase proteins, such as C-reactive protein and serum amyloid A, are highly sensitive to inflammatory activity and can be important markers of severity and outcome. Leukocyte esterase, adhesion molecules, platelet activating factor and activated protein C are additional humoral immune markers; the replacement of the latter has been shown to be a promising therapeutic option. Natriuretic peptides are neurocrine humoral markers that have important cardiovascular implications. The level of macrophage migrating inhibitory factor, released by the pituitary, is elevated in sepsis and counteracts glucocorticoid action. Cellular markers to severe stress include the enhanced expression of protective substances in the form of heat shock proteins. High mobility group-1 is a DNA-binding protein and a late mediator of the inflammatory response. Apoptotic markers such as the soluble fas ligand are also elevated in inflammation. In summary, during critical illness, the endocrine, immune and nervous systems elaborate a multitude of humoral markers, the roles of which merit further scrutiny in order to improve therapeutic outcome.

Correlating functional staging to effective treatment of acute surgical illness

BACKGROUND

Proinflammatory and anti-inflammatory events may eventually trigger host response, which acting via a broad spectrum of complex biological processes and molecular interactions may either enhance or resolve the symptoms of acute surgical illness (ASI). Staging the sequence of biological events that take place at the cellular level during the development of ASI may provide leads to effective stage-specific treatments. In line with the hypothesis that proper timing of therapeutic intervention may be crucial to the management of the disease, we have attempted in this review to correlate functional staging to effective treatment of ASI.

DATA SOURCE

The present report proposes a conceptual synthesis on the biogenesis and treatment of ASI that is based on known molecular and cellular aspects of human inflammatory sequence and patient data from clinical trials. It also introduces proper timing of therapeutic intervention as a potentially important determinant for the successful outcome of the disease process.

CONCLUSIONS

Progress in understanding the biogenesis of ASI did not result in successful therapeutic developments as yet. The challenge ahead should be a better understanding of the dynamics of the various processes and regulators in appropriate animal and clinical models of ASI, in order to properly intervene and direct effective therapies for the benefit of critically ill patients.

Application of gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry to assess in vivo synthesis of prostaglandins, thromboxane, leukotrienes, isoprostanes and related compounds in humans

Prostaglandins, thromboxane, leukotrienes, isoprostanes and other arachidonic acid metabolites are structurally closely related, potent, biologically active compounds. One of the most challenging tasks in eicosanoids research has been to define the role of the various eicosanoids in human health and disease, and to monitor the effects of drugs on the in vivo synthesis of these lipid mediators in man. Great advances in instrumentation and ionization techniques, in particular the development of tandem mass spectrometry and negative-ion chemical ionization (NICI), in gas chromatography and also advances in methodologies for solid-phase extraction and sample purification by thin-layer chromatography and high-performance liquid chromatography have been made. Now gas chromatography-mass spectrometry (GC-MS) and GC-tandem MS in the NICI mode are currently indispensable analytical tools for reliable routine quantitation of eicosanoid formation in vivo in humans. In this article analytical methods for eicosanoids based on GC-MS and GC-tandem MS are reviewed emphasizing the quantitative measurement of specific index metabolites in human urine and its importance in clinical studies in man. Aspects of method validation and quality control are also discussed.

Induction of leukotriene production by bleomycin and asparaginase in mast cells in vitro and in patients in vivo

Bleomycin and asparaginase are widely used antineoplastic agents which may induce allergic or inflammatory side-effects. Mast cells are implicated as effector cells in allergic and inflammatory responses. The aim of this study was to establish whether bleomycin or asparaginase modulate leukotriene production in vitro and in vivo. Leukotriene C4 (LTC4) production by murine bone marrow-derived mast cells (BMMC) was determined by radioimmunoassay (RIA). Leukotriene production in patients was assessed by determining leukotriene E4 and N-acetyl-leukotriene E4 in urine by means of combined HPLC and RIA. Bleomycin induced an up to 2.1-fold increase in LTC4 production both in unstimulated and in calcium ionophore-stimulated mast cells. In 3 of 7 patients treated with bleomycin, a greater than 2-fold increase in endogenous leukotriene production was observed. This effect was associated with febrile responses and was most pronounced in a patient who developed an Adult Respiratory Distress Syndrome (ARDS). Asparaginase increased leukotriene production up to 10-fold in stimulated but not in unstimulated BMMC. In a patient who developed an anaphylactic reaction after treatment with asparaginase, a pronounced increase in urinary leukotriene concentration was observed. In contrast to bleomycin or asparaginase, a number of other cytostatic agents did not significantly change leukotriene production by BMMC. Our data indicate that some of the inflammatory and allergic side-effects of bleomycin and asparaginase could be mediated by leukotrienes, a possible source of which may be mast cells.

Immunofiltration purification for urinary leukotriene E4 quantitation

Leukotriene E4 (LTE4) is a major leukotriene metabolite in urine. Urinary LTE4 concentration is often utilized as an index of total leukotriene synthesis. A novel method employing immunofiltration for the purification of urinary LTE4 was developed. This immunofiltration method is based upon the addition of excess anti-LTE4 antibody to urine which binds LTE4. Separation of bound LTE4 (high M(r)) from high levels of unbound contaminants (low M(r)) is then accomplished by filtration through a 10,000 M(r) cut-off filter. The LTE4-antibody complex is separated by precipitation of the antibody with methanol which is subsequently removed by centrifugation. Following evaporation of the methanol, enzyme immunoassay is utilized for quantitation. This methodology was validated by determining the recovery of tritiated and unlabeled LTE4 added to urine and buffer and by comparison of results obtained with urine samples measured after HPLC purification (correlation r2 = 0.72). Reproducibility of the assay was assessed by analyzing the same sample on two different days (standard deviation of 18%). The mean urinary LTE4 levels in healthy subjects and asthmatics measured utilizing this method were found to be identical to levels determined by HPLC/immunoassay. The ease and accuracy of this assay make it amenable for the analysis of large numbers of samples.

Diurnal variation of urinary leukotriene E4 and histamine excretion rates in normal subjects and patients with mild-to-moderate asthma

BACKGROUND

Leukotriene E4 (LTE4) and histamine excreted into the urine reflect the in vivo synthesis and release of cysteinyl leukotrienes and histamine, respectively. We examined the diurnal variation of the excretion rate of these mediators over 4 consecutive days in normal subjects (n = 5) and patients with stable mild-to-moderate asthma (n = 8).

METHODS

Sixteen consecutive 6-hour urine samples were collected over 4 days. Urinary LTE4 concentrations were determined by reverse-phase high-pressure liquid chromatography, followed by ELISA. Urinary histamine concentrations were measured by ELISA. The excretion rates of these compounds were normalized relative to urinary creatinine content.

RESULTS

The mean urinary LTE4 excretion rate was 83.8 +/- 38.2 pg/mg creatinine (mean +/- SD) in normal subjects; in patients with asthma, the urinary LTE4 excretion rate (110.0 +/- 59.2 pg/mg creatinine) was significantly higher than that in normal subjects (p < 0.05). The urinary histamine excretion rate was not different between normal subjects (24.0 +/- 12.5 ng/mg creatinine) and patients with asthma (31.5 +/- 25.8 ng/mg creatinine). A robust and systematic within-day variation (p < 0.01), but no day-to-day variation, was observed in histamine excretion rate. Although the magnitude of variation in LTE4 excretion within a day was significantly greater in patients with asthma than in normal subjects (p < 0.05), we could not identify any specific diurnal variation pattern in either the normal or the asthma group. No significant correlation was observed between urinary LTE4 and histamine excretion rate within any subject.

CONCLUSIONS

Patients with asthma excrete LTE4 in the urine at a greater rate than normal subjects. Although no systematic variation in urinary LTE4 excretion rates over the course of a day was observed in either normal subjects or patients with stable asthma, the presence of a systematic diurnal variation of urinary histamine excretion exists in both groups.

Chemical synthesis of dioxygen-18 labelled omega-/beta-oxidized cysteinyl leukotrienes: analysis by gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry

Cysteinyl leukotrienes (LT) C4, LTD4 and LTE4 are potent mediators of anaphylaxis and inflammation. LTE4 is extensively metabolized in man mainly by omega-oxidation followed by subsequent beta-oxidation to more polar and biologically inactive metabolites. This paper describes a method for the synthesis of [1,20-18O2]-carboxy-LTE4, [1,18-18O2]-carboxy-dinor-LTE4, and [1,16-18O2]-carboxy-14,15-dihydro-tetranor-LTE4 starting from the unlabelled dimethyl esters of 20-carboxy-LTA4, 18-carboxy-dinor-LTA4 and 16-carboxy-14,15-dihydro-tetranor-LTA4, respectively, by separate chemical conjugation with cysteine hydrochloride in H2-18O-methanol followed by alkaline hydrolysis with Li18OH. The isotopic purity of the isolated reaction products was 94% at 18O for all three preparations while only 0.3% remained unlabelled as confirmed by negative-ion chemical-ionization gas chromatography-mass spectrometry (GC-NICI-MS) after their catalytical reduction/desulphurization and derivatization. The 18O2-labelled compounds are demonstrated to be suitable internal standards for quantification by GC-NICI-MS and GC-NICI-tandem MS. We found by GC-NICI-tandem MS that the excretion rate of 20-carboxy-LTE4 is comparable to that of LTE4 (both in nmol/mol creatinine, mean +/- S.E.) in healthy children (26.7 +/- 4.7 vs. 32.0 +/- 6.0, n = 9) and adults (13.9 +/- 1.1 vs. 27.2 +/- 5.4, n = 3).

Modifying the host response to injury. The future of trauma care

It is beyond the scope of this article to describe all of the contributions of molecular biology to increasing our understanding of the pathophysiology of inflammation and the response to injury. This review focuses on those aspects that are clinically relevant. In addition to providing quantities of recombinant proteins, recent advances in molecular and cellular biology have provided other tools to help differentiate the pathophysiology of the host response to injury and infection. Hybridoma technology has facilitated the development of specific antibodies that are used to block the activity of a specific factor or toxin. Receptor and signal transduction biology has provided further insight into the activity and function of various factors and mediators. Studies at the level of the gene have shed light on the phylogenic relationship among various factors. Transgenic animals can be used to determine the effects of excess factor production; conversely, genetic "knockouts" are useful in determining the pathophysiology associated with the absence of a particular factor. It is clear that as our understanding of the complex interactions leading to inflammation increases, we will be able to take advantage of this knowledge to more effectively treat patients.

Enhanced synthesis of cysteinyl leukotrienes in juvenile rheumatoid arthritis

OBJECTIVE

Endogenous synthesis of cysteinyl leukotrienes in juvenile rheumatoid arthritis (JRA) was investigated.

METHODS

Cysteinyl leukotriene synthesis was assessed by measuring the excretion of leukotriene E4 (LTE4) in urine by radioimmunoassay. The identity of urinary LTE4 was investigated by gas chromatography-mass spectrometry (GC-MS), and 2,3-dinor-thromboxane B2 was measured with GC-MS.

RESULTS

Excretion of LTE4 into urine was significantly (P < 0.05) enhanced in children with JRA compared with that in healthy children (n = 10). Aspirin, in a dosage of 2.5 gm/day, had no effect on urinary LTE4 levels, but it reduced urinary 2,3-dinorthromboxane B2 levels by more than 85% in healthy adults. There was a positive correlation between LTE4 excretion and the number of affected joints.

CONCLUSION

This study demonstrates a markedly enhanced cysteinyl leukotriene synthesis and a positive correlation between LTE4 excretion and the number of affected joints in children with JRA.

Gas chromatographic-mass spectrometric determination of leukotriene E4 in human urine using deuterium-labelled leukotriene E4 standards

The utility of two deuterium-labelled leukotriene (LT) E4 analogs, e.g. [20,20,20-2H3]LTE4 and [14,15,17,17,18,18-2H6]LTE4, as internal standards for the determination of LTE4 in human urine by gas chromatography-mass spectrometry (GC-MS) was investigated. 2H-Exchange during hydrogenation occurred both in [20,20,20-2H3]LTE4 and [14,15,17,17,18,18-2H6]LTE4 in an extent of 9.4 +/- 0.5% and 67.3 +/- 0.6% (mean +/- S.D., n = 6), respectively. The lower extent of 2H-exchange in [20,20,20-2H3]LTE4 allowed a more accurate quantitation than the use of [14,15,17,17,18,18-2H6]LTE4. Applying [20,20,20-2H3]LTE4 as internal standard the coefficients of variation for the intra- and inter-assay determination of LTE4 in human urine were 5.7% and 6.2% (n = 4), respectively. The inter-assay coefficient of variation for [14,15,17,17,18,18-2H6]LTE4 was 15%. Using [20,20,20-2H3]LTE4 as internal standard and GC-MS, healthy volunteers were found to excrete 17 +/- 10 nmol LTE4 per mol creatinine (mean +/- S.D., n = 11). Similar excretion rates for LTE4 in urine of healthy volunteers were found using GC-tandem MS with [1,1-18O2]LTE4 as internal standard. Our results demonstrate that [20,20,20(-2)H3]LTE4 is a suitable internal standard for the GC-MS determination of urinary LTE4.

Increased excretion of endogenous urinary leukotriene E4 in extrahepatic cholestasis

The cysteinyl leukotrienes LTC4, LTD4 and LTE4 are potent lipid mediators eliminated from the blood circulation mainly due to uptake by the liver and the kidneys. In man hepatobiliary elimination of cysteinyl leukotrienes predominates over renal excretion. In the present study, the urine from patients with extrahepatic cholestasis (n = 25) and age- and sex-matched healthy control subjects (n = 25) was analyzed for endogenous LTE4, the predominant metabolite of LTC4 excreted into urine. LTE4 was separated by reversed-phase high-performance liquid chromatography and subsequently quantified by enzyme immunoassay. Healthy subjects excreted a median concentration of 14 nmol LTE4/mol creatinine (range 5-24 nmol/mol creatinine). Its median concentration increased significantly to more than 5-fold higher levels to 74 nmol LTE4/mol creatinine (range 52-93 nmol/mol creatinine) in patients with extrahepatic cholestasis (P < 0.01). These results indicate that extrahepatic cholestasis leads to a compensatory diversion of cysteinyl leukotriene elimination to the kidney with subsequent increased excretion of LTE4 into urine.

Enhanced synthesis of cysteinyl leukotrienes in atopic dermatitis

Synthesis of cysteinyl leukotrienes was assessed in patients with atopic dermatitis (AD; n = 8) and healthy volunteers (n = 8) by measuring urinary excretion of leukotriene E4 (LTE4), the main index metabolite of cysteinyl leukotrienes in man. Using this non-invasive method we demonstrated a significant (P < 0.05) 4.5-fold increase in excretion of LTE4 compared with healthy volunteers. The identity of LTE4 was unequivocally demonstrated by gas chromatography-mass spectrometry/mass spectrometry (GC-MS/MS). LTE4 was routinely measured by radioimmunoassay (RIA), and quantitative measurement of LTE4 by RIA was validated by GC-MS/MS. There was a linear correlation between LTE4 measured by RIA and by GC-MS/MS (r = 0.994). In representative samples, LTE4 was also quantitatively assessed by GC-MS/MS. In these samples, LTE4 values obtained by GC-MS/MS differed < 10% from those obtained by RIA. The present findings suggest that cysteinyl leukotrienes play a role in AD.

Impaired degradation of leukotrienes in patients with peroxisome deficiency disorders

The degradation of leukotrienes by beta-oxidation from the omega-end proceeds in peroxisomes (Jedlitschky et al. J. Biol. Chem. 1991. 266:24763-24772). Peroxisomal degradation of leukotrienes was studied in humans by analyses of endogenous leukotrienes in urines from eight patients with biochemically established peroxisome deficiency disorder and eight age- and sex-matched healthy infant controls. Leukotriene metabolites were separated by high-performance liquid chromatography, quantified by radioimmunoassays, and identified as well as quantified by gas chromatography-mass spectrometry. Urinary leukotriene E4 (LTE4) and N-acetyl-LTE4 excretions, relative to creatinine, were increased > 10-fold in the patients in comparison to healthy infants. The beta-oxidation product omega-carboxy-tetranor-LTE3 averaged 0.05 mumol/mol creatinine in the controls but was not detectable in the patients. However, omega-carboxy-LTE4 (median 13.6 mumol/mol creatinine) was significantly increased in the patients' urine, whereas LTB4 (median 0.07 mumol/mol creatinine) and omega-carboxy-LTB4 were detected exclusively in the urines of the patients. These data indicate an impairment of the inactivation and degradation of both LTE4 and LTB4 in patients with peroxisomal deficiency. The increased levels of the biologically active, proinflammatory mediators LTE4 and LTB4 might be of pathophysiological significance in peroxisome deficiency disorders. This is the first and so far only condition with a pronounced urinary excretion of omega-carboxy-LTE4, omega-carboxy-LTB4, and LTB4. This impaired catabolism of leukotrienes and the altered pattern of metabolites may be of diagnostic value. These findings underline the essential role of peroxisomes in the catabolism of leukotrienes in humans.

Enhanced synthesis of cysteinyl leukotrienes in psoriasis

Cysteinyl leukotriene synthesis was investigated in patients with psoriasis. A non-invasive test requiring no stimulation was employed by measuring the major index metabolite of LTC4, which appears in urine. The presence of this metabolite, LTE4, was shown unequivocally by gas chromatography-mass spectrometry. Routinely LTE4 was quantitated by specific radio immunoassay after its isolation by reversed-phase high-performance liquid chromatography. Furthermore, in representative samples amounts of LTE4 obtained by radioimmunoassay were validated by gas chromatography-mass spectrometry. We demonstrate a significant (p less than 0.01) more than fourfold increase of urinary LTE4 in psoriasis compared to healthy volunteers. Urinary LTE4 was log normally distributed with geometric mean values (95% confidence intervals) of 11 (9-14) nmol LTE4/mol creatinine in healthy volunteers (n = 11) and 51 (28-95) nmol LTE4/mol creatinine in psoriasis (n = 9). The present study shows that cysteinyl leukotriene synthesis is enhanced in patients with psoriasis and that measurement of urinary LTE4 is a useful parameter to monitor its rate of synthesis.

Enzymic preparation of dioxygen-18 labelled leukotriene E4 and its use in quantitative gas chromatography-mass spectrometry

A simple and rapid method is described for the preparation of a stable isotope oxygen-18 labelled leukotriene E4 (LTE4). Oxygen-18 labelling of LTE4 methyl ester in oxygen-18 water catalysed by a pig liver esterase resulted in the incorporation of two oxygen-18 atoms in the carboxylic group of LTE4 to the extent of 89.8% ([18O2]LTE4) and one oxygen-18 atom to the extent of 9.4% ([16O18O]LTE4), with only 0.7% remaining unchanged ([16O2]LTE4). [18O2]LTE4 was found not to back-exchange following incubation in acidified urine (pH 4.0) at 4 degrees C for up to 20 h. [18O2]LTE4 was demonstrated to be a useful internal standard in a method for the quantitative determination of LTE4 in human urine involving high-performance liquid chromatography and gas chromatography with negative-ion chemical ionization tandem mass spectrometry: the concentration of LTE4 in a 24-h urine sample of a healthy subject was determined to be 68.1 pg/ml.