Enhanced synthesis of cysteinyl leukotrienes in psoriasis

Alterations of the Skin and Gut Microbiome in Psoriasis and Psoriatic Arthritis

Numerous scientific studies in recent years have shown significant skin and gut dysbiosis among patients with psoriasis. A significant decrease in microbiome alpha-diversity (abundance of different bacterial taxa measured in one sample) as well as beta-diversity (microbial diversity in different samples) was noted in psoriasis skin. It has been proven that the representation of Cutibacterium, Burkholderia spp., and Lactobacilli is decreased and Corynebacterium kroppenstedii, Corynebacterium simulans, Neisseria spp., and Finegoldia spp. increased in the psoriasis skin in comparison to healthy skin. Alterations in the gut microbiome in psoriasis are similar to those observed in patients with inflammatory bowel disease. In those two diseases, the F. prausnitzii, Bifidobacterium spp., Lactobacillus spp., Parabacteroides and Coprobacillus were underrepresented, while the abundance of Salmonella sp., Campylobacter sp., Helicobacter sp., Escherichia coli, Alcaligenes sp., and Mycobacterium sp. was increased. Several research studies provided evidence for the significant influence of psoriasis treatments on the skin and gut microbiome and a positive influence of orally administered probiotics on the course of this dermatosis. Further research is needed to determine the influence of the microbiome on the development of inflammatory skin diseases. The changes in microbiome under psoriasis treatment can serve as a potential biomarker of positive response to the administered therapy.

[Influence of nutrition, common autoimmune diseases and smoking on the incidence of foot mycoses]

BACKGROUND

Foot mycoses, including onychomycoses, are worldwide infectious diseases. As part of a regional survey using randomly selected residents of in Mecklenburg-Western Pomerania, we investigated the impact of dietary habits, the presence of most frequent autoimmune diseases and current smoking on fungal skin infections in order to reveal potential new risk factors to elucidate potential preventive interventions.

OBJECTIVES

The identification of potential new factors that influence the development of mycosis was performed in order to derive possible preventive measures.

METHODS

In the Study of Health in Pomerania (SHIP) in Mecklengburg-Western Pomerania, 2523 inhabitants were examined for mycotic lesions and asked about nutritional habits, the presence of atopic dermatitis, allergic rhinitis, psoriasis and smoking habits.

RESULTS

In all, 8% of probands were diagnosed with mycosis, 6.5% onychomycosis, 3.7% tinea pedis and 0.2% tinea corporis. Psoriasis, allergic rhinitis and atopic dermatitis and frequent consumption of cooked potatoes, oatmeal and corn flakes, cereals, pasta and rice were significantly associated with tinea pedis. Onychomycosis was positively associated with consumption of cooked potatoes. Cigarette consumption proved protective for tinea pedis and dermatophyte colonization.

CONCLUSIONS

The autoimmune disorders psoriasis and atopic dermatitis and allergic rhinitis seem to predispose to foot mycosis. Recalcitrant mycosis should raise the question of diets high in carbohydrates. Nicotine abuse seems to protect against skin mycosis and colonization.

Dysbiosis of Skin Microbiota in Psoriatic Patients: Co-occurrence of Fungal and Bacterial Communities

Psoriasis is a chronic inflammatory skin disease, whose pathogenesis involves dysregulated interplay among immune cells, keratinocytes and environmental triggers, including microbiota. Bacterial and fungal dysbiosis has been recently associated with several chronic immune-mediated diseases including psoriasis. In this comprehensive study, we investigated how different sampling sites and methods reflect the uncovered skin microbiota composition. After establishing the most suitable approach, we further examined correlations between bacteria and fungi on the psoriatic skin. We compared microbiota composition determined in the same sample by sequencing two distinct hypervariable regions of the 16S rRNA gene. We showed that using the V3V4 region led to higher species richness and evenness than using the V1V2 region. In particular, genera, such as Staphylococcus and Micrococcus were more abundant when using the V3V4 region, while Planococcaceae, on the other hand, were detected only by the V1V2 region. We performed a detailed analysis of skin microbiota composition of psoriatic lesions, unaffected psoriatic skin, and healthy control skin from the back and elbow. Only a few discriminative features were uncovered, mostly specific for the sampling site or method (swab, scraping, or biopsy). Swabs from psoriatic lesions on the back and the elbow were associated with increased abundance of Brevibacterium and Kocuria palustris and Gordonia, respectively. In the same samples from psoriatic lesions, we found a significantly higher abundance of the fungus Malassezia restricta on the back, while Malassezia sympodialis dominated the elbow mycobiota. In psoriatic elbow skin, we found significant correlation between occurrence of Kocuria, Lactobacillus, and Streptococcus with Saccharomyces, which was not observed in healthy skin. For the first time, we showed here a psoriasis-specific correlation between fungal and bacterial species, suggesting a link between competition for niche occupancy and psoriasis. However, it still remains to be elucidated whether observed microbial shift and specific inter-kingdom relationship pattern are of primary etiological significance or secondary to the disease.

5-Lipoxygenase-derived lipid mediators are not required for the development of NSAID-induced inflammatory bowel disease in IL-10-/- mice

Leukotrienes are potent lipid mediators derived from the metabolism of arachidonic acid by the enzyme 5-lipoxygenase (5-LO). Elevated levels of the proinflammatory leukotriene LTB(4) have been found in preclinical models of inflammatory bowel disease (IBD) as well as in colon tissue from individuals with IBD. We therefore determined the extent to which absence of 5-LO-derived lipid mediators would alter the colitis in IL-10(-/-) mice, a model of human IBD. IL-10(-/-)/5-LO(-/-) mice were generated and were healthy. Absence of 5-LO did not alter the development of spontaneous colitis in IL-10-deficient mice. We then evaluated the extent to which absence of 5-LO would alter the development of NSAID-induced colitis in IL-10(-/-) mice. Absence of 5-LO did not delay the onset or alter the severity of inflammation in NSAID-treated IL-10(-/-) mice. At an early time point, 3 days after NSAID treatment was initiated, a qualitative increase in the number of dendritic cells and CD4(+) T cells was noted in the colons of IL-10(-/-)/5-LO(-/-); however, this difference was no longer present after 14 days of NSAID treatment. Absence of 5-LO did not alter the degree of neutrophil infiltration into the in this model. Absence of 5-LO does not alter the development of IFN-gamma producing Th1-type CD4(+) T cells or IL-17 producing CD4(+) T cells. Absence of 5-LO-derived mediators did not alter the expression of the adhesion molecules ICAM-1 and P-selectin. Development of colitis in IL-10(-/-) mice was associated with increased levels of the 5-LO-derived anti-inflammatory lipoxin LXA(4). These studies demonstrate that 5-LO-derived leukotrienes are not required for the development or maintenance of spontaneous or NSAID-induced colonic inflammation in IL-10(-/-) mice.

5-Lipoxygenase knockout mice exhibit a resistance to pleurisy and lung injury caused by carrageenan

In the present study, by comparing the responses in wild-type (WT) mice and mice lacking [knockout (KO)] the 5-lipoxygenase (5-LO), we investigated the role played by 5-LO in the development of acute inflammation. When compared with carragenan-treated 5-LOWT mice, 5-LOKO mice, which had received carrageenan, exhibited a reduced degree of pleural exudation, polymorphonuclear cell migration. Lung myeloperoxidase activity, an index of neutrophil infiltration, was significantly reduced in 5-LOKO mice in comparison with 5-LOWT. Lung-tissue sections from carrageenan-treated 5-LOWT mice showed positive staining for intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), P-selectin, and E-selectin, which were mainly localized around vessels. The intensity and degree of ICAM-1, VCAM-1, P-selectin, and E-selectin were markedly reduced in tissue section from carrageenan-5-LOKO mice, which also improved the histological status of the inflamed lungs. Taken together, our results clearly demonstrate that 5-LO modulates neutrophil infiltration in the acute lung inflammation.

Pathophysiological role of leukotrienes in dermatological diseases: potential therapeutic implications

In vitro and in vivo data have demonstrated that leukotrienes play a key role not only in allergic airway diseases but also in inflammatory reactions of the skin. Antileukotriene drugs, i.e. leukotriene receptor antagonists and synthesis inhibitors, are a new class of anti-inflammatory drugs that have shown clinical efficacy in the management of asthma, allergic rhinitis and inflammatory bowel disease. To address the question of the validity and applicability of published evidence of the use of antileukotriene drugs in dermatological diseases, we reviewed data concerning the pathophysiological effect of leukotrienes in the skin and in skin diseases, and the experience with antileukotriene treatment that has been published. In vivo and in vitro data suggest that antileukotriene treatment may have efficacy in atopic dermatitis, different types of urticaria or psoriasis and other skin diseases such as bullous skin diseases, collagenoses, Sjogren-Larsson syndrome or Kawasaki disease. Nevertheless, published evidence is very limited and before any conclusions can be drawn, additional basic research needs to be performed with regard to the role of different leukotrienes and leukotriene receptors in skin diseases. On the basis of these data, randomised and placebo-controlled clinical trials with leukotriene antagonists and synthesis inhibitors should be performed. Moreover, future studies investigating the additive benefit of antileukotriene drugs are warranted, e.g. in combination with antihistamines, corticosteroids or other anti-inflammatory drugs.

Psoriasis and the arachidonic acid cascade

Arachidonic acid (5.8,11,14-eicosatetraenoic acid C20:4, n-6) is released from the cell membrane by the action of phospholipases on membrane phospholipids. Metabolites of arachidonic acid, which are generically termed eicosanoids, including prostaglandins, thromboxane, leukotrienes and hydroxyeicosatetraenoic acids, have been implicated as mediators or modulators of a number of physiological functions and pathological conditions in both normal and diseased human skin. Particularly, eicosanoids have been suspected to play an important role in the pathogenesis of psoriasis, because a number of phenomena observed in psoriasis can be explained, at least in part, by the action of eicosanoids. This review will focus on recent progress regarding the significance of eicosanoids in the pathogenesis of psoriasis. Recent developments in the molecular biology in the eicosanoids have renewed interest in the role of eicosanoids in psoriasis. New understanding of the etiology of psoriasis and advances in its treatment due to recent progress in eicosanoid biology will also be presented.

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.

Leukotriene D4 and cystinyl-bis-glycine metabolism in membrane-bound dipeptidase-deficient mice

We have developed mice deficient in membrane-bound dipeptidase (MBD, EC 3.4.13.19), the enzyme believed to be responsible for the conversion of leukotriene D4 (LTD4) to leukotriene E4 (LTE4). The MBD mutation generated by us was demonstrated to be a null mutation by Northern blot analysis and the absence of beta-lactamase activity in lung, kidney, small intestine, and heart. MBD gene deletion had no effect on viability or fertility. The mutant mice retain partial ability to convert LTD4 to LTE4, ranging from 80-90% of the wild-type values in small intestine and liver to 16% in kidney and 40% in lung, heart, and pancreas. MBD is also believed to function consecutively after gamma-glutamyl transpeptidase to cleave cystinyl-bis-glycine (cys-bis-gly) generated from glutathione cleavage. Our data indicate that kidney homogenates from MBD-deficient mice retain approximately 40% of their ability to cleave cys-bis-gly, consistent with only modest elevations (3-5-fold) of cys-bis-gly in urine from MBD-deficient mice. These observations demonstrate that the conversion of LTD4 to LTE4 and the degradation of cys-bis-gly are catalyzed by at least two alternative pathways (one of which is MBD) that complement each other to varying extents in different tissues.

Role of the 5-lipoxygenase-activating protein (FLAP) in murine acute inflammatory responses

Leukotrienes are potent inflammatory mediators synthesized from arachidonic acid (AA) predominately by cells of myeloid origin. The synthesis of these lipids is believed to be dependent not only on the expression of the enzyme 5-lipoxygenase (5-LO), which catalyzes the first steps in the synthesis of leukotrienes, but also on expression of a nuclear membrane protein termed the 5-LO-activating protein (FLAP). To study the relationship of these two proteins in mediating the production of leukotrienes in vivo and to determine whether the membrane protein FLAP has additional functions in various inflammatory processes, we have generated a mouse line deficient in this protein. FLAP-deficient mice develop normally and are healthy. However, an array of assays comparing inflammatory reactions in FLAP-deficient mice and in normal controls revealed that FLAP plays a role in a subset of these reactions. Although examination of DTH and IgE-mediated passive anaphylaxis showed no difference between wild-type and FLAP-deficient animals, mice without FLAP possessed a blunted inflammatory response to topical AA and had increased resistance to platelet-activating factor-induced shock compared to controls. Also, edema associated with Zymosan A-induced peritonitis was markedly reduced in animals lacking FLAP. To determine whether these differences relate solely to a deficit in leukotriene production, or whether they reflect an additional role for FLAP in inflammation, we compared the FLAP-deficient mice to 5-LO-deficient animals. Evaluation of mice lacking FLAP and 5-LO indicated that production of leukotrienes during inflammatory responses is dependent upon the availability of FLAP and did not support additional functions for FLAP beyond its role in leukotriene production.

Leukotriene C4/D4 induces P-selectin and sialyl Lewis(x)-dependent alterations in leukocyte kinetics in vivo

The objective of this study was to assess the effect of leukotriene C4 (LTC4) on the flux of rolling leukocytes, leukocyte rolling velocity, and leukocyte adhesion in postcapillary venules in vivo and to study the underlying molecular mechanisms involved. LTC4 (20 nmol/L) induced a rapid and significant increase in leukocyte rolling flux that was inhibitable by an anti-P-selectin antibody and soluble sialyl Lewis(x) (sLe(x)). LTC4 also induced a significant reduction in leukocyte rolling velocity, an event that was independent of P-selectin but entirely dependent on sLe(x). This LTC4-induced reduction in leukocyte rolling velocity was independent of any hemodynamic alterations. Another P-selectin effector, histamine, did not affect leukocyte rolling velocity even at > 5000 times the concentration of LTC4. Treatment with an anti-L-selectin antibody had no effect on the LTC4-induced increase in leukocyte rolling or reduction in rolling velocity. Inhibition of LTC4 bioconversion to LTD4 by pretreatment with L-serine (100 mumol/L) prevented the LTC4-induced increase in leukocyte rolling flux and the LTC4-induced reduction in leukocyte rolling velocity. A subtle, yet significant, increase in leukocyte adhesion was also observed with LTC4. Pretreatment with a platelet-activating factor receptor antagonist returned the LTC4-induced leukocyte rolling velocity to baseline levels. The addition of a very low concentration of platelet-activating factor (1 nmol/L) induced significant leukocyte adhesion in the presence of LTC4 but not histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Expression of 5-lipoxygenase in differentiating human skin keratinocytes

We studied the expression of arachidonate 5-lipoxygenase (5-LO) in a cell line of human keratinocytes (HaCaT) and in normal human skin keratinocytes in tissue culture. In undifferentiated keratinocytes 5-LO gene expression was low or undetectable as determined by 5-LO mRNA, protein, cell-free enzyme activity, and leukotriene production in intact cells. However, after shift to culture conditions that promote conversion of prokeratinocytes into a more differentiated phenotype, 5-LO gene expression was markedly induced in HaCaT cells and, to a lesser extent, in normal keratinocytes. These results show that 5-LO gene expression is an intrinsic property of human skin keratinocytes.

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).

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.

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.