Leukotriene B4 Levels Research Articles

Tepoxalin inhibits inflammation and microvascular dysfunction induced by abdominal irradiation in rats.

Inflammatory cells contribute to the acute and sub-acute sequelae of radiation therapy. Tepoxalin, an inhibitor of cyclooxygenase and 5-lipoxygenase that suppresses NF-kappaB activation, has potent anti-inflammatory activity. To assess the effects of tepoxalin on radiation-induced inflammatory damage, and determine its mechanisms of action. Leucocyte rolling, adhesion and emigration, and albumin leakage were determined by intra-vital microscopy in rat mesenteric venules. NF-kappaB activation was measured by electrophoretic mobility shift assays, and endothelial intercellular adhesion molecule-1 expression by the radiolabelled antibody technique. Groups of irradiated rats were treated with tepoxalin, N-acetyl-L-cysteine, zileuton (lipoxygenase inhibitor), or vehicle. Irradiated animals had a marked increase in the number of rolling, adherent and emigrated leucocytes in mesenteric venules, and in microvascular permeability. Tepoxalin prevented leucocyte adhesion and the increase in permeability after radiation. Tepoxalin did not inhibit radiation-induced NF-kappaB activation or intercellular adhesion molecule-1 up-regulation, while N-acetyl-L-cysteine, which attenuated NF-kappaB activation, had no effect on leucocyte recruitment. In contrast, tepoxalin inhibited the increase in leukotriene B4 levels after radiation, and the anti-inflammatory effects of the drug were mimicked by zileuton. Tepoxalin affords significant protection against radiation-induced inflammation and microvascular dysfunction in splanchnic organs through a mechanism dependent on leukotriene synthesis inhibition.

Exacerbation of pustulosis palmaris et plantaris after topical application of metals accompanied by elevated levels of leukotriene B4 in pustules

<h2>Abstract</h2> <b>Background:</b> Pustulosis palmaris et plantaris (PPP) is a chronic inflammatory disease consisting of polymorphonuclear leukocyte infiltration, and is often exacerbated by focal infections such as tonsillitis. In some cases, metal allergy has been reported. <b>Objective:</b> The purpose of this study was to evaluate (1) the significance of metal allergy in the formation of pustules, and (2) the participation of leukotriene (LT) B₄ in the formation of pustules of PPP. <b>Methods:</b> Patch tests with metals were performed on 7 patients with PPP, and both pustular and plasma levels of LTB₄ were measured in these 7 patients before and 48 hours after metal patch tests. <b>Results:</b> Palmoplantar pustules were exacerbated after the metal patch tests in all 7 patients. The mean levels of LTB₄ in plasma and pustules of the volar surface at 48 hours after the metal patch tests were significantly higher than those before the metal patch tests. <b>Conclusion:</b> Metals can be important in the pathogenesis of PPP by contributing to the induction of high LTB₄ concentration in the pustules. (J Am Acad Dermatol 2000;42:1021–5.)

Exacerbation of pustulosis palmaris et plantaris after topical application of metals accompanied by elevated levels of leukotriene B4 in pustules

Background: Pustulosis palmaris et plantaris (PPP) is a chronic inflammatory disease consisting of polymorphonuclear leukocyte infiltration, and is often exacerbated by focal infections such as tonsillitis. In some cases, metal allergy has been reported. Objective: The purpose of this study was to evaluate (1) the significance of metal allergy in the formation of pustules, and (2) the participation of leukotriene (LT) B4 in the formation of pustules of PPP. Methods: Patch tests with metals were performed on 7 patients with PPP, and both pustular and plasma levels of LTB4 were measured in these 7 patients before and 48 hours after metal patch tests. Results: Palmoplantar pustules were exacerbated after the metal patch tests in all 7 patients. The mean levels of LTB4 in plasma and pustules of the volar surface at 48 hours after the metal patch tests were significantly higher than those before the metal patch tests. Conclusion: Metals can be important in the pathogenesis of PPP by contributing to the induction of high LTB4 concentration in the pustules. (J Am Acad Dermatol 2000;42:1021–5.)

Stem cell factor plays a major role in the recruitment of eosinophils in allergic pleurisy in mice via the production of leukotriene B4.

The understanding of the mechanisms underlying eosinophil migration into tissue is an essential step in the development of novel therapies aimed at treating allergic diseases where eosinophil recruitment and activation are thought to play an essential role. In this study, we have examined the effects of the in vivo administration of stem cell factor (SCF) on eosinophil recruitment and tested whether endogenous SCF was involved in mediating eosinophil recruitment in response to Ag challenge in sensitized mice. The intrapleural injection of SCF induced a time- and concentration-dependent recruitment of eosinophils in mice. In allergic mice, SCF message was expressed early after Ag challenge and returned to baseline levels after 8 h. In agreement with the ability of SCF to induce eosinophil recruitment and its expression in the allergic reaction, an anti-SCF polyclonal Ab abrogated eosinophil recruitment when given before Ag challenge. SCF increased the levels of leukotriene B4 (LTB4) in the pleural cavity of mice and an LTB4 receptor antagonist, CP105,696, abrogated the effects of SCF on eosinophil recruitment. Similarly, recruitment of eosinophils in the allergic reaction was virtually abolished by CP105,696. Together, our data favor the hypothesis that the local release of SCF following Ag challenge may activate and/or prime mast cells for IgE-mediated release of inflammatory mediators, especially LTB4. The mediators released in turn drive the recruitment of eosinophils. Inhibition of the function of SCF in vivo may reduce the migration of eosinophils to sites of allergic inflammation and may, thus, be a relevant principle in the treatment of allergic diseases.

Bronchial inflammation in acute bacterial exacerbations of chronic bronchitis: the role of leukotriene B4.

Neutrophils recruited to the airways in chronic obstructive pulmonary disease (COPD) are thought to mediate tissue destruction. Neutrophil recruitment is increased during bacterial exacerbations. The inflammatory process was studied in patients with an acute exacerbation of COPD in order to ascertain the role of leukotriene B4 (LTB4). The sputum of eight subjects with a bacterial exacerbation of COPD was analysed for neutrophil products (myeloperoxidase, elastase) and chemoattractants (interleukin-8 (IL-8) and LTB4). The contribution of LTB4 to the chemotactic activity of the sputum sol phase was determined using the LTB4 receptor antagonist LY293111. The concentrations of the serum acute phase proteins alpha1-proteinase inhibitor, alpha1-antichymotrypsin and C-reactive protein were measured. All patients received appropriate broad-spectrum antibiotic treatment for 7-14 days. Initially, the sputum myeloperoxidase activity was high, indicating neutrophil influx; this was associated with high levels of IL-8 and LTB4. All these concentrations fell with treatment (p<0.01). The chemotactic activity of the sputum was raised on presentation and fell with treatment (p<0.01). LTB4 contributed approximately 30% of the total chemotactic activity on presentation; this diminished with therapy. All acute phase proteins were raised on presentation and fell with therapy (p<0.01). These findings suggest that leukotriene B4 contributes to neutrophil influx into the airway in chronic obstructive pulmonary disease and may influence disease progression.

Levels of Leukotriene B4 and Platelet Activating Factor in Gingival Crevicular Fluid in Renal Transplant Patients Receiving Cyclosporine A

Cyclosporine A (CsA) is a potent immunosuppressant effectively used to prevent organ transplant rejection and also to treat several systemic diseases. CsA-induced gingival overgrowth (CsA GO) is the most widely seen side effect of this drug; its pathogenesis is not completely understood. The aim of the present study was to identify the role of leukotriene B4 (LTB4) and platelet activating factor (PAF) in the pathogenesis of CsA GO. LTB4 and PAF levels were detected in gingival crevicular fluid (GCF) samples from renal transplant patients receiving CsA therapy and exhibiting CsA GO, from patients with gingivitis and from periodontally healthy subjects. Plaque index, papilla bleeding index, and hyperplastic index were recorded at each study site. GCF samples and clinical data were obtained from: 2 sites exhibiting CsA GO (CsA GO+) and 2 sites not exhibiting CsA GO (CsA GO-) in each CsA-treated patient; 2 diseased sites in each patient with gingivitis; and 2 healthy sites in each subject with clinically healthy periodontium. LTB4 was extracted from the samples by solid-phase method using C18 cartridge and purified by high-performance liquid chromatographic (HPLC) method and analyzed by radioimmunoassay (RIA). PAF was extracted from GCF samples passing through amberlit resin columns, purified by HPLC, and analyzed by RIA. Total amounts of LTB4 and PAF in GCF were higher in CsA GO+ sites compared to the healthy sites from healthy controls. However, the amount of LTB4 and PAF elevation in CsA GO+ sites was not significantly higher than those in diseased sites. Clinical degrees of gingival inflammation were also similar between CsA GO+ and diseased sites. LTB4 and PAF total amounts in GCF were higher in CsA GO+ sites compared to CsA GO- sites in the same subjects, but this difference just failed to reach significance. Similar findings were obtained with concentration data. The results of this study indicate that CsA therapy does not have a significant effect on GCF LTB4 and PAF levels and that gingival inflammation seems to be the main reason for their elevation. In CsA-treated patients, alterations in LTB4 and PAF levels might play a role in CsA GO through some asyet unknown mechanism. To our knowledge, this is the first report describing the levels of lipid mediators in GCF of CsA-treated patients. We assume that further studies will contribute to the understanding of the pathogenesis of CsA-induced gingival overgrowth.

Transcriptional regulation of 15-lipoxygenase in human coloretal carcinoma cells by histone deacetylase inhibitors

Anti-inflammatory effects of the 15-lipoxygenase (15-LO) derivatives lipoxin A4 (LXA4) and 15-S-hydroxyeicosatetraenoic acid (15-S-HETE) have been documented in many experimental models of acute inflammation. However, the expression levels of 15-LO and its products in human renal diseases remain unknown. This study investigated the expression levels of LXA4, leukotriene B4 (LTB4), and 15-LO in leukocytes and glomeruli obtained from 22 children with acute poststreptococcal glomerulonephritis (APSGN), and determined the modulatory effects of both 15-S-HETE and LXA4 on LTB4 synthesis in leukocytes and LTB4-evoked chemotaxis of polymorphonuclear leukocytes (PMNs) obtained from children during the first 3 days after onset of APSGN. Expression levels of both LXA4 and 15-LO in leukocytes and glomeruli were up-regulated during the acute phase of disease, further peaking between days 10 and 14, and remained increased after 6 to 8 weeks of APSGN onset. In contrast, blood and urinary levels of LTB4 as well as the number of glomerular PMNs peaked during the acute phase of disease and then decreased during the resolution phase. Administration of both 15-S-HETE and LXA4 in vitro inhibited LTB4-induced chemotaxis of PMNs and production of LTB4 from leukocytes obtained from patients with APSGN. The current study provides further support for an anti-inflammatory role for 15-LO products in human nephritis through both antagonism and inhibition of leukotriene synthesis and its biological activity.

Is administration n-3 fatty acids by enema mucosal protective against trinitrobenzene-induced colitis in rats?

We investigated the protective role of fish oil (FO-source of n-3 FA) enriched diet (in the first protocol) in 20 rats and FO administration intrarectally (in the second protocol) in 40 rats with trinitrobennzene (TNB) colitis. All colonic specimens were pathologically evaluated, myeloperoxidase enzyme activities were measured, leukotriene B4 (LTB4) and LTC4levels were determined by radioimmunoassay. In the first protocol 10 rats (group A1) were fed with 8% sunflower and cotton oil enriched diet and (group A2) with 8% FO enriched diet for 6 weeks. At the end of this period, TNB (30 mg in 0.25 ml of 30% ethanol) were intrarectally administered. After 2 weeks, rats were sacrificed. MPO activities (2.47 versus 30.17), LTB4 (34.5 versus 903.3) and LTC4 (77.7 versus 456.0) levels were significantly reduced in group A2 compared with group A1 (P<0.005). There was also a significant difference in pathologic scores (1.55 versus 2.12, P<0.002) between two groups. In the first part of the second protocol, 20 male rats were randomized into two equal groups (B1 and B2) and TNB colitis was induced. After 1 day, 1 ml of saline (group B1) or n-3 FA enemas (group B2) were administered every day for 2 weeks. At the end of this period, rats were sacrificed and evaluated as done for previous groups. Although there was no significant difference between the two groups in comparison with MPO enzyme activities and pathologic scores, the LTB4(130.1 versus 971.0) and LTC4(126.0 versus 532.0) levels of FO group were significantly reduced (P<0.005). In the second part of the second protocol, 20 male rats were randomized into two groups. One millilitre of saline (group B3) or FO enemas (group B4) were administered to rats every day for 3 days. At the fourth day, TNB-colitis was induced and after 24 h rats were sacrificed. We could not find any significant difference in MPO activities, pathologic scores, LTB4and LTC4levels between groups B3 and B4. In conclusion; FO enriched diet decreased both pathologic damage and tissue LT levels. The second protocol of our study revealed that the long-term FO enemas decreased the LTB4and LTC4levels; however, did not have any beneficial effect on the tissue lesions. Short periods of FO enemas did not have a protective role in the occurrence of experimental colitis. The present study showed that FO enemas significantly decreased LT levels. The protective effect of FO (oral and enema) in TNB colitis may open a new insight into the treatment of inflammatory bowel disease.

Medium-chain triglycerides modulate ileitis induced by trinitrobenzene sulfonic acid.

It is important to develop an appropriate animal model for further investigation into inflammatory bowel disease (IBD). We therefore investigated a trinitrobenzene sulfonic acid (TNBS) ileitis model. Dietary fat in Crohn's disease is still a controversial risk factor for IBD. We therefore also studied the effects of medium-chain triglycerides (MCT) and long-chain triglycerides (LCT) on TNBS ileitis. An intraileal injection of TNBS induced ulceration and inflammation with thickening of the intestinal wall, which were characterized histologically by infiltration of polymorphic nuclear leucocytes and by granuloma formation. The mucosal damage score and serum sialic acid levels reached their highest 7 days after the TNBS injection and then gradually decreased. The mucosal damage series in the MCT group was significantly lower than in the LCT group, and levels of tumour necrosis factor-alpha (TNF-alpha) and leukotriene B4 (LTB4) tended to be lower in the MCT group. These results suggested that TNBS enteritis might be useful as an IBD animal model and that MCT modulates intestinal inflammation and is less damaging than LCT.

Endogenous Monocyte Chemoattractant Protein-1 (MCP-1) Protects Mice in a Model of Acute Septic Peritonitis: Cross-Talk Between MCP-1 and Leukotriene B4

We investigated the involvement of monocyte chemoattractant protein (MCP)-1 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that CLP induced a dramatic increase in MCP-1 production in the peritoneum, followed by an increase in the recruitment of leukocytes. MCP-1 blockade with anti-MCP-1 antiserum significantly decreased the survival rate following CLP, which was accompanied by an enhanced recovery of viable bacteria from the peritoneum. This was likely due to the reduction in the recruitment and activation of both macrophages and neutrophils. To understand the mechanisms whereby MCP-1 may influence neutrophil infiltration, levels of chemokines known to attract neutrophils were monitored, which showed that peritoneal levels of macrophage-inflammatory protein (MIP)-2, KC, and MIP-1alpha were not altered with anti-MCP-1 Abs. However, anti-MCP-1 Abs reduced the peritoneal levels of leukotriene B4 (LTB4) by 59%. The i.p. injection of MCP-1 into normal mice resulted in elevated levels of LTB4 in the peritoneum. In vitro, MCP-1 stimulated the production of LTB4 from peritoneal macrophages, in a dose-dependent manner. A specific LTB4 receptor antagonist (CP-105, 696) inhibited CLP-induced recruitment of both neutrophils and macrophages, which was accompanied by a reduced level of MCP-1 in the peritoneum. Finally, administration of CP-105,696 was extremely detrimental to the survival of mice following CLP. These experiments demonstrate that endogenous MCP-1 serves as an indirect mediator to attract neutrophils via the production of LTB4, and suggest the cross-talk can occur between MCP-1 and the lipid mediator LTB4 during septic peritonitis.

Zinc sulphate solution enema decreases inflammation in experimental colitis in rats.

It has been reported that zinc sulphate contributes an anti-inflammatory action in many animal models; however, the impact of zinc in colitis remains unclear. The aim of the present study was to examine the role of zinc sulphate in experimental colitis. Colitis was induced by 2,4,6-trinitrobenzenesulphonic acid (TNB) in rats. Beginning at the first day of TNB colitis, the rats were treated with a zinc sulphate enema once daily for 6 days. The rats were examined 8 days later. The TNB induced severe colitis as evidenced by increased mucosal lesion area, mucosal myeloperoxidase (MPO) activity and prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels. Six days after the application of the zinc sulphate enema, the mucosal lesion area, MPO activity, PGE2 and LTB4 levels all decreased significantly. Mucosal superoxide dismutase activity remained unchanged after zinc treatments. Our data suggest that zinc sulphate enemas have an anti-inflammatory action on experimental colitis.

Effect of modified ultrafiltration on plasma thromboxane B2, leukotriene B4, and endothelin-1 in infants undergoing cardiopulmonary bypass

Background. Plasma thromboxane B2 (TXB2), leukotriene B4 (LTB4), and endothelin-1 (ET-1) levels increase on cardiopulmonary bypass (CPB). Elevated levels of TXB2 and ET-1 have been correlated with postoperative pulmonary hypertension in infants undergoing repair of congenital heart defects. LTB4 is a potent chemotactic cytokine whose levels correlate with leukocyte-mediated injury. Modified ultrafiltration (MUF) has been associated with improved hemodynamics and pulmonary function, in addition to its beneficial effects on fluid balance and blood conservation. Recent investigations have suggested that removal of cytokines may be the cause of the improved cardiopulmonary function seen with MUF. Methods. Plasma TXB2, ET-1, and LTB4 levels were measured in 34 infants undergoing CPB: 22 underwent MUF (group 1), and 12 did not (group 2). Samples were obtained at various time points. All patients underwent conventional ultrafiltration during the rewarming phase of cardiopulmonary bypass. Results. In group 1, mean end-CPB TXB2 level was 101.2 pg/mL versus 46.9 pg/mL post-MUF ( p < 0.05). The mean TXB2 level 1 hour post-CPB (54.1 pg/mL) was not significantly different from the post-MUF level. In group 2, the mean end-CPB TXB2 level was 123.6 pg/mL versus 53.2 pg/mL 1 hour post-CPB. Hence, TXB2 levels decreased by similar amounts and to similar levels by 1 hour post-CPB in both groups. ET-1 levels increased after CPB and were unaffected by MUF: 1.45, 1.80, 2.55 pg/mL at end-CPB, post-MUF, and 1 hour post-CPB, respectively, in group 1; and 1.51, and 2.73 pg/mL at end-CPB and 1 hour post-CPB in group 2. LTB4 levels post-MUF were 119% of pre-MUF values, and were similar at 1 hour post-CPB in both groups. Conclusions. Despite reduction in TXB2 by MUF, values were similar and approached baseline 1 hour post-CPB in both groups. LTB4 levels increased slightly with MUF. ET-1 levels increased during and post-CPB and were unaffected by MUF. MUF does not appear to have a significant effect on post-CPB levels of TXB2, ET-1, and LTB4. Therefore, the improved hemodynamics observed with MUF do not appear to be related to removal of these cytokines.

The relationship between glycated hemoglobin and polymorphonuclear leukocyte leukotriene B4 release in people with diabetes mellitus

In order to evaluate polymorphonuclear leukocyte (PMN) activity in diabetes mellitus, leukotriene B4 (LTB 4) levels were measured in sixty patients, 31 affected with Type 1 diabetes mellitus and 29 affected with Type 2 diabetes mellitus. The LTB 4 levels (12.1+0.2 pg/100 μl) in diabetic patients were higher compared to those of the control group (7.9+0.1 pg/100 μl) ( P<0.001), and remained significantly higher ( P<0.001) (12.8+0.2 pg/100 μl) than in the control group (11.0+0.2 pg/100 μ1) after stimulation with calcium ionophore. A significant and positive correlation between glycated hemoglobin and LTB 4 was demonstrated ( P<0.001, r=0.80). This study demonstrates that in diabetic patients there is a PMN activation and that this activation is correlated to glycated hemoglobin level.

Activation of 5-lipoxygenase and related cell membrane lipoperoxidation in hemodialysis patients.

Lipid peroxidation was shown at the membrane level in peripheral blood cells of patients hemodialyzed on cuprophan dialyzers, and was mainly attributable to the generation of conjugated hydroperoxides in the lipid bilayer. The oxidative index (i.e., the A234/205 ratio) of membrane lipids was 3.2-fold higher in hemodialysis patients than in healthy control subjects, and also the level of leukotriene B4 was significantly increased (up to 1.7-fold over control). Both membrane peroxidation and release of leukotriene B4 were linked to upregulation of 5-lipoxygenase activity (up to 2.4-fold over control) and expression at the protein level (up to 1.9-fold). Vitamin E, the most important lipophilic antioxidant, prevented both membrane peroxidation and release of leukotriene B4 by inhibiting 5-lipoxygenase activity without affecting enzyme expression. Similar results were observed in patients hemodialyzed on polymethylmetacrylate membranes, but in this case the activation of 5-lipoxygenase was less pronounced. The use of a purified 5-lipoxygenase demonstrated that vitamin E was a reversible inhibitor of enzyme activity (IC50 = 35 +/- 4 microM), further characterized as noncompetitive (Ki = 30 +/- 3 microM). Taken together, the results reported here shed some light on the mechanism responsible for the oxidative damage in hemodialysis. Moreover, the beneficial effect of vitamin E described here may have relevance for the therapy of patients with kidney disease.

Modern diets and diseases: NO–zinc balance

Thanks to progress in zinc research, it is now possible to describe in more detail how zinc ions (Zn++) and nitrogen monoxide (NO), together with glutathione (GSH) and its oxidized form, GSSG, help to regulate immune responses to antigens. NO appears to be able to liberate Zn++ from metallothionein (MT), an intracellular storage molecule for metal ions such as zinc (Zn++) and copper (Cu++). Both Zn++ and Cu++ show a concentration-dependent inactivation of a protease essential for the proliferation of the AIDS virus HIV-1, while zinc can help prevent diabetes complications through its intracellular activation of the enzyme sorbitol dehydrogenase (SDH). A Zn++ deficiency can lead to a premature transition from efficient Th1-dependent cellular antiviral immune functions to Th2-dependent humoral immune functions. Deficiencies of Zn++, NO and/or GSH shift the Th1/Th2 balance towards Th2, as do deficiencies of any of the essential nutrients (ENs)– a group that includes methionine, cysteine, arginine, vitamins A, B, C and E, zinc and selenium (Se) – because these are necessary for the synthesis and maintenance of sufficient amounts of GSH, MT and NO.Via the Th1/Th2 balance, Zn++, NO, MT and GSH collectively determine the progress and outcome of many diseases. Disregulation of the Th1/Th2 balance is responsible for autoimmune disorders such as diabetes mellitus.Under Th2, levels of interleukin-4 (Il-4), Il-6, Il-10, leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) are raised, while levels of Il-2, Zn++, NO and other substances are lowered. This makes things easier for viruses like HIV-1 which multiply in Th2 cells but rarely, if ever, in Th1 cells. AIDS viruses (HIVs) enter immune cells with the aid of the CD4 cell surface receptor in combination with a number of co-receptors which include CCR3, CCR5 and CXCR4. Remarkably, the cell surface receptor for LTB4 (BLTR) also seems to act as a co-receptor for CD4, which helps HIVs to infect immune cells. The Th2 cytokine Il-4 increases the number of CXCR4 and BLTR co-receptors, as a result of which, under Th2, the HIV strains that infect immune cells are precisely those that are best able to accelerate the AIDS disease process. The Il-4 released under Th2 therefore not only promotes the production of more HIVs and the rate at which they infect immune cells, it also stimulates selection for the more virulent strains.Zn++ inhibit LTB4 production and numbers of LTB4 receptors (BLTRs) in a concentration-dependent way. Zn++ help cells to keep their LTB4 'doors' shut against the more virulent strains of HIV. Moreover, a sufficiency of Zn++ and NO prevents a shift of the Th1/Th2 balance towards Th2 and thereby slows the proliferation of HIV, which it also does by inactivating the HIV protease.Research makes it look likely that deficiencies of ENs such as zinc promote the proliferation of Th2 cells at the expense of Th1 cells.Zinc deficiency also promotes cancer. Under the influence of Th1 cells, zinc inhibits the growth of tumours by activating the endogenous tumour-suppressor endostatin, which inhibits angiogenesis.The modern Western diet, with its excess of refined products such as sugar, alcohol and fats, often contains, per calorie, a deficiency of ENs such as zinc, selenium and vitamins A, B, C and E, which results in disturbed immune functions, a shifted Th1/Th2 balance, chronic (viral) infections, obesity, atherosclerosis, autoimmunity, allergies and cancer. In view of this, an optimization of dietary composition would seem to give the best chance of beating (viral) epidemics and common (chronic) diseases at a realistic price.

Eicosanoid production by adult Fasciola hepatica and plasma eicosanoid patterns during fasciolosis in sheep

Fasciola hepatica infection in sheep is known to cause anaemia, fever and elevated levels of liver enzymes. It was hypothesised that eicosanoids play a role in these pathophysiological changes, so the pattern of plasma eicosanoids during the course of acute and chronic fasciolosis was studied in sheep infected with a single dose of 800 F. hepatica metacercariae. Blood plasma was collected weekly until week 17 p.i. from infected sheep, and from uninfected controls. Adult F. hepatica were then recovered from bile ducts and incubated for production of ES products. Eicosanoids were determined by enzyme immuno-assay in blood plasma, fluke homogenates and ES products after chromatographic purification of the samples. Fever and anaemia were seen from 3 to 12 weeks p.i. and from 8 to 17 weeks p.i., respectively. Onset of fever was accompanied by elevated liver enzyme activities (aspartate amino transferase and gamma glutamyl transferase) in the plasma. In general, the plasma levels of prostaglandin E2 (PGE2), prostaglandin I2 (PGI2) and leukotriene B4 (LTB4) were reduced during the acute and chronic stages of the infection, whereas thromboxane B2 (TXB2) was reduced only at 8 weeks p.i. The TXB2/PGI2 ratio was increased in favour of TXB2 at 3 and 11 weeks p.i. Additionally, TXB2, PGI2, PGE2 and LTB4 were detected both in ES products and in homogenates of F. hepatica. It was concluded that eicosanoid depletion in the plasma is caused by parasite-induced liver damage. The changes in eicosanoid levels are highly correlated to the clinical signs of the disease. Changes in the pattern of host plasma eicosanoids during fasciolosis, as well as parasite-derived eicosanoids, may reflect or contribute to the pathology of the disease.

Alpha-tocopherol decreases interleukin-1 beta release from activated human monocytes by inhibition of 5-lipoxygenase.

Cardiovascular disease is the leading cause of morbidity and mortality in westernized populations. Low levels of alpha-tocopherol (AT) are associated with increased incidence of atherosclerosis and increased intakes appear to be protective. Recently, we showed that supplementation with AT resulted in significant decreases in monocyte superoxide anion release, lipid oxidation, interleukin-1 beta (IL-1 beta) release, and adhesion to endothelium. The reduction in superoxide and lipid oxidation by AT seemed to be mediated by inhibition of protein kinase C. The aim of this study was to investigate the mechanism(s) by which AT inhibits IL-1 beta release. Potential mechanisms examined included its effect as an antioxidant and its inhibitory effects on protein kinase C and the cyclooxygenase-lipoxygenase pathways. Although AT decreased superoxide release from activated monocytes, superoxide dismutase and catalase had no effect on IL-1 beta release. Also, a similar antioxidant, beta-tocopherol, had no effect on IL-1 beta release. The protein kinase C inhibitor, bisindolylmaleimide, did not inhibit IL-1 beta release from activated monocytes, in spite of AT decreasing protein kinase C activity. Leukotriene B4, a major product of 5-lipoxygenase, has been shown to augment IL-1beta release. In the presence of AT, a significant reduction in leukotriene B4 and IL-1 beta levels was observed, which was reversed by the addition of leukotriene B4. Similar observations were seen with specific inhibitors of 5-lipoxygenase. The product of cyclooxygenase, prostaglandin E2, has been shown to inhibit IL-1 beta activity in some systems. However, AT had no significant effect on prostaglandin E2 levels in activated monocytes. In the presence of indomethacin, a cyclooxygenase inhibitor, AT inhibited IL-1 beta activity. Also, AT had no effect on IL-1 beta mRNA levels or stability, suggesting a posttranscriptional effect. Thus, in activated human monocytes, AT exerts a novel biological effect of inhibiting the release of the proinflammatory cytokine, IL-1 beta, via inhibition of the 5-lipoxygenase pathway.

Role of eicosanoids in the pathogenesis of murine cerebral malaria.

Because microvascular damage is a common feature of cerebral malaria, we have examined the role eicosanoid metabolites (prostaglandins and leukotrienes) in experimental cerebral malaria. Eighty ICR mice were infected with Plasmodium berghei ANKA, with 40 uninfected mice as controls. Half of the infected mice were treated on days 4 and 5 with aspirin, a prostaglandin synthesis inhibitor. Infected mice started to die of cerebral malaria on day 6, and by day 17, all infected mice died. In contrast, all infected mice treated with aspirin died by day 12. Infected mice had increased phospholipase A2 mRNA expression in the spleen and cyclooxygenase 1 (COX1) and COX2 expression in the brain. At the peak of cerebral malaria, infected mice had higher serum leukotriene B4 levels than control mice, and aspirin-treated infected mice had higher serum leukotriene B4 levels than untreated infected mice. These results suggest that prostaglandins are protective whereas leukotrienes are detrimental in cerebral malaria.

The effects of phosphodiesterase type 4 inhibitors on tumour necrosis factor-alpha and leukotriene B4 in a novel human whole blood assay.

1. The aim of this study was to assess the inhibitory activities of phosphodiesterase type 4 (PDE4) inhibitors on tumour necrosis factor-alpha (TNF-alpha) and leukotriene B4 (LTB4) production in a novel human whole blood assay. 2. Lipopolysaccharide (LPS) stimulation of human whole blood caused a time dependent increase in TNF-alpha and prostaglandin E2 (PGE2) plasma levels. Inhibition of LPS-induced TNF-alpha by the selective PDE4 inhibitor RP73401 was proportionally enhanced with endogenous PGE2 (maximal after 24 h). In contrast, blocking endogenous PGE2 production with indomethacin in blood stimulated with LPS for 24 h decreased the potency of RP73401 to that observed with a 4 h LPS incubation. 3. Non-selective and selective PDE4 inhibitors showed greater inhibition of LPS-induced TNF-alpha after 24 h compared to 4 h. Stereoselectivity was only achieved in the 24 h method. 4. LPS-stimulation of whole blood for either 30 min or 24 h followed by N-formyl-Met-Leu-Phe (fMLP) activation resulted in low plasma LTB4 levels. Combination of both treatments resulted in a greater than 7 fold increase in plasma LTB4 levels. Inhibition of the double LPS and fMLP-activated LTB4 production was observed with non-selective and PDE4-selective inhibitors. Their LTB4 inhibitory potencies were similar to that observed in the 24 h LPS-induced TNF-alpha assay. Thus, stimulation of human whole blood with two LPS stimulations followed by fMLP gives rise to both TNF-alpha and LTB4 and their inhibition by various compounds can be assessed in the same blood sample. 5. Calcium ionophore (A23187) stimulation of whole blood resulted in plasma LTB4 levels similar to the double LPS and fMLP method. Inhibition of A23187-induced LTB4 biosynthesis was also achieved by PDE4-selective inhibitors as well as the direct 5-lipoxygenase (5-LO) inhibitor L-739,010. 6. These results confirm the anti-inflammatory properties of PDE4 inhibitors. Thus, this novel human whole blood can be used to assess the biochemical efficacy of PDE4 inhibitors in human subjects.

Effect of an antibacterial dental varnish on the levels of prostanoids, leukotriene B4, and interleukin-1β in gingival crevicular fluid

The aim of this study was to investigate the effects of a chlorhexidine/thymol-containing dental varnish on the levels of prostaglandin E2 (PGE2), prostaglandin I2 (PGI2), leukotriene B4 (LTB4), and interleukin-1β (IL-1β) in gingival crevicular fluid (GCF). The material consisted of 15 adolescents undergoing treatment with fixed orthodontic appliances. Four buccal sites adjacent to bands or brackets and exhibiting a mild chronic gingival inflammation were selected in the upper quadrants of each patient. According to a splitmouth technique, the first and second quadrants were randomly treated with either a varnish (Cervitec®) containing 1% chlorhexidine diacetate and thymol (CHX/thymol) or a placebo varnish without active ingredients. The varnishes were applied immediately after the baseline registration, and follow-up examinations were carried out after 3, 8, and 30 days. GCF was sampled with the aid of a paper strip and the volume was determined using a Periotron® 8000. The concentrations of PGE2, PGI2, LTB4, and IL-1β in GCF were assessed using radioimmunoassay and ELISA techniques. The results unveiled statistically significant reductions of PGE2, PGI2, and LTB4 levels in GCF following the active varnish treatment when compared to baseline values. A slight drop in IL-1β levels was registered after both active and placebo varnish applications, but the differences were not significant. The results suggest that treatment with an antibacterial varnish decreases the levels of inflammatory mediators PGE2, PGI2, and LTB4 in gingival crevicular fluid and further support the concept that topical application of a CHX/thymol-containing varnish is beneficial in patients with chronic gingival inflammation.