Effect of a leukotriene B4 antagonist on substance P-induced granulocyte infiltration in mouse skin]

Substance P causes granulocyte (neutrophil and eosinophil) infiltration in mouse skin by inducing mast cell degranulation. However, the mediator responsible for this granulocyte infiltration has not been determined. In this study, we examined the effect of a leukotriene B4 (LTB4) antagonist ONO-4057 on substance P-induced granulocyte infiltration in the skin of BALB/c mice. Pretreatment with the LTB4 antagonist decreased substance P-induced neutrophil and eosinophil infiltrations in mouse skin at 6 h to the same extent that an inhibitor of mast cell degranulation disodium cromoglycate decreased those responses. The LTB4 antagonist also decreased substance P-induced neutrophil, but not eosinophil, infiltration in mouse skin at 24 h. We conclude that LTB4 is a major mast cell-derived chemotactic mediator for initiating substance P-induced neutrophil and eosinophil infiltrations in mouse skin.     

Induction of inflammatory cell infiltration and necrosis in normal mouse skin by the combined treatment of tumor necrosis factor and lithium chloride.

Previously we reported that lithium chloride (LiCl) potentiates tumor necrosis factor (TNF)-mediated cytotoxicity in vitro and in vivo. Here, using a murine normal skin model, it is shown that a subcutaneous injection of TNF plus LiCl induces acute dermal and subcutaneous inflammation and necrosis. Histology showed a marked initial dermal and subcutaneous neutrophil infiltrate by approximately 2 hours, followed by a predominantly mononuclear infiltrate by 24 hours, which remained present for several days. Tumor necrosis factor or LiCl alone induced negligible inflammation, disappearing after 6 hours; furthermore there was never necrosis or ulceration of the overlying skin in case of single-agent application. In vitro studies showed that the combination of TNF and LiCl, but not either agent alone, was directly cytotoxic to fibroblastic cells of murine skin. No inflammatory infiltration was visible in tumors treated intratumorally or perilesionally with TNF plus LiCl, although the latter treatment resulted in a perilesional leukocyte infiltration. Furthermore the combination of TNF and LiCl had no effect on macrophage cytotoxicity to L929 tumors.     

Inhibition of leukotriene B4 in neutrophils by lipoxins A4 and B4

Lipoxins are derived from the oxygenation products of arachidonic acid in human leukocytes. They have exhibited selective biological effects different from those of other eicosanoids. We have examined the effect of lipoxin A₄ and B₄ (LXA₄, LXB₄) on the production of leukotriene B₄ (LTB₄) in human neutrophils. Cultured human polymorphonuclear leukocytes were preincubated with LXA and B and their ability to inhibit LTB₄ generation was assessed after incubation with calcium ionophore A23187. We found that the pretreatment of neutrophils with lipoxins inhibit the release of LTB₄ by A23187 stimulated PMNs. Our data suggests that LXA₄ and B₄ can contribute to immunosuppression in an inflammatory state via the inhibition of LTB₄ synthesis.     

Plasma leukotriene B4 and C4 levels in patients with familial mediterranean fever

Department of Pharmacology, Erevan Medical Institute. Laboratory of Biochemical Pharmacology, Diagnostika Research and Production Combine, Ministry of Health of the Armenian SSR, Erevan. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 110, No. 9, pp. 296–297, September, 1990.     

Phagocytosis and bactericidal action of mouse peritoneal macrophages treated with leukotriene B4

The effects of exogenous leukotriene B4 (LTB4) on the resistance of mouse peritoneal macrophages against Salmonella (S.) typhimurium and Pseudomonas (P.) aeruginosa infections were studied. In vitro, LTB4 added to macrophage monolayers at final concentrations of 10(-12)-10(-8) M, enhanced their phagocytosis of S. typhimurium to 2.3 times the control level and that of P. aeruginosa to 1.8 times the control level. The intracellular killing rates were also elevated by the addition of LTB4: for S. typhimurium, 83.3% (LTB4) vs 59.1% (control) and for P. aeruginosa, 46.5% (LTB4) vs 9.2% (control). In vivo, intraperitoneally injected LTB4 (5 ng) enhanced the clearance at 24 h of intraperitoneally injected S. typhimurium from the mouse peritoneal cavity (2.38 x 10(3) +/- 0.94 x 10(3) cells [LTB4] vs 5.73 x 10(5) +/- 1.90 x 10(5) [control]) and spleen (5.00 x 10(2) +/- 0.94 x 10(2) [LTB4] vs 2.47 x 10(4) +/- 0.84 x 10(4) [control]), but this effect disappeared by 48 h. In contrast, in beige mice, an experimental model of the Chédiak-Higashi syndrome that is characterized by susceptibility to bacterial infection, there was no induction of the eliminating effect by intraperitoneal injection of LTB4. Activation of macrophages by exogenous LTB4 seemed to have contributed to such an augmented resistance of macrophages to bacterial infection. This study suggested a possible use of LTB4 in bacterial infectious diseases whereby phagocytes are able to play a key role in host defense.     

Biosynthesis of leukotriene B4

Leukotriene B₄ (LTB₄) is a lipid mediator derived from arachidonic acid (AA) by the sequential action of 5-lipoxygenase (5-LOX), 5-lipoxygenase-activating protein (FLAP) and LTA₄ hydrolase (LTA₄H). It was initially recognized for its involvement in the recruitment of neutrophils and is one of the most potent chemotactic agents known to date. A large body of data has indicated that LTB₄ plays a significant role in many chronic inflammatory diseases, such as arthritis, chronic obstructive pulmonary disease (COPD), cardiovascular disease, cancer and more recently, metabolic disorder. In this review, we focus on the biosynthesis of LTB₄ and its biological effects. In particular, we will describe a basic biochemical understanding integrated with recent developments in the field of structural biology of the three key enzymes (5-LOX, FLAP and LTA₄H) in LTB₄ biosynthesis, and also summarize the most outstanding work on in vivo biological and pathogenic roles of these enzymes and the development of enzyme inhibitors.     

Priming effects of leukotriene B4 on endothelial cell injury induced by tpa-activated leukocytes

Among arachidonic acid metabolites, leukotriene B₄ (LTB₄) plays an important role in inflammation, such as in the activation, adhesion, chemotaxis, and invasion of leukocytes. In this paper, we examined the effect of LTB₄ on endothelial cell injury induced by polymorphonuclear leukocytes (PMNLs).⁵¹Crrelease, a marker of cellular injury, was elicited from prelabeled endothelial cells when the cells were cocultured with PMNLs activated by phorbol ester (TPA, 12-0-tetradecanoyl-phorbol-13-acetate). Under this condition, pretreatment of PMNLs with LTB₄ enhanced their injury in a dose-dependent manner (0.2–2 M). However, LTB₄ alone at any dose could not induce any cellular injury. We also determined the amount of active oxygen species produced by PMNLs in response to TPA. The intensity of luminoldependent chemiluminescence, a marker of active oxygen production, in PMNLs was also increased by pretreatment with 1 M LTB₄. These data suggest that LTB₄ enhances endothelial cell injury by the priming effect on active oxygen production in activated PMNLs.     

Biological activities of leukotriene B4

Leukotriene B₄ isomer III is released from polymorphonuclear leucocytes, monocytes, eosinophils and macrophagesin vitro and has been detected and measured in human synovial fluidin vivo. Its most prominent biological activities are to induce the aggregation of and to stimulate the movement (chemokinesis and chemotaxis) of leucocytesin vitro and it acts as a cytotaxinin vivo. In addition, it increases vascular permeabilityin vivo when administered together with the vasodilator, PGE₂.     

Effect of a leukotriene B4 receptor antagonist on leukotriene B4-induced neutrophil chemotaxis in cavine dermis

Leukotriene B₄ (LTB₄) is a proinflammatory product of arachidonic acid metabolism that has been implicated as a mediator in a number of inflammatory diseases. When injected intradermally into the cavine, LTB₄ elicits a dose-dependent immigration (chemotaxis) of neutrophils (PMNs) into the injection sites as assessed by the presence of a neutrophil marker enzyme myeloperoxidase. SC-41930 {7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]-3,4-dihydro-8-propyl-2H-l-benzopyran-2-carboxylic acid, a potent LTB₄ receptor antagonist inhibited the chemotactic actions of LTB₄ when coadministered into the dermal site and when given intravenously or orally with ED₅₀ values of 200 ng, 0.5 mg/kg, and 0.6 mg/ kg respectively. This compound may well have application in disease states, such as inflammatory bowel disease and psoriasis, where LTB₄ is implicated as a proinflammatory mediator.     

Metabolism of leukotriene B4 by activated human polymorphonuclear granulocytes

Human polymorphonuclear granulocytes (PMNs) synthesize leukotriene B4 (LTB4) as a response of cell activation. Inactivation of the potent inflammatory mediator proceeds via omega-oxidation, resulting in the formation of 20-hydroxy- and 20-carboxy-LTB4. The main metabolite after stimulation with the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) is 20-carboxy-LTB4, and after stimulation with the calcium ionophore A23187 is 20-hydroxy-LTB4. Differences in the LTB4 inactivation pathway were also observed when the catabolism of exogenously added LTB4 was analysed. In contrast to resting cells or cells preactivated with FMLP, prestimulation with the ionophore or with phorbol esters resulted in the inhibition of 20-carboxy-LTB4-generation. This decrease correlated with the reduction in specific [3H] LTB4-receptor expression. Studies with the non-penetrating diazonium salt of sulphanilic acid, which is known to interact with ectoenzymes, revealed that LTB4 is metabolized via receptor-mediated uptake. Our data suggest that the reduction in the amount of LTB4-receptor sites inhibits the conversion of 20-OH-LTB4 into 20-COOH-LTB4.     

Anti-allergic effects of sinomenine by inhibition of prostaglandin D2 and leukotriene C4 in mouse bone marrow-derived mast cells

Sinomenine is an alkaloid compound and a prominent anti-allergic agent found in the root of the climbing plant Sinomenium acutum. However, its effects on the bone marrow-derived mast cell (BMMC) mediated allergy and inflammation mechanism remain unknown. In this study, the biological effects of sinomenine were evaluated while focusing on its effects on the allergic mediator in PMA plus A23187-stimulated BMMCs. An investigation was also conducted to determine its effects on the production of several allergic mediators including interleukin-6 (IL-6), prostaglandin D₂ (PGD₂), leukotriene C₄ (LTC₄), β-Hexosaminidase (β-Hex), and cyclooxygenase-2 (COX-2) protein. The results revealed that sinomenine inhibited the PMA plus A23187-induced production of IL-6, PGD₂, LTC₄, β-Hex, and COX-2 protein. Taken together, these findings indicate that sinomenine has the potential for use in the treatment of allergy.     

Increased monocyte chemotaxis towards leukotriene B4 and platelet activating factor in patients with inflammatory dermatoses.

In vitro monocyte chemotaxis towards leukotriene B4(LTB4) and platelet activating factor (PAF) was studied with cells from 51 patients with various inflammatory dermatoses and 12 normal volunteers. Monocytes from normal subjects responded poorly to LTB4 (10(-8)-10(-12) M) and PAF (10(-6)-10(-10) M), and cells from patients with urticaria pigmentosa and vericella were even less responsive, while monocytes from patients with severe psoriasis and atopic eczema exhibited markedly enhanced chemotaxis. These changes persisted during high dose therapy with oral steroids, but returned to normal with healing of the skin lesions. Pre-incubation of monocytes with histamine, LTB4, PAF, lymphokines or sera from patients and normal controls did not result in enhanced chemotaxis of the cells. The chemotactic activity of monocytes did not correlate with that of neutrophils in the same patients (r = 0.08). Altered monocyte chemotaxis in patients with inflammatory dermatoses is therefore a reversible process that is related to the severity of the cutaneous inflammation but is not limited to a specific disease.     

Phlogistic activity of leukotriene D4 in the mouse

An investigation of the phlogistic activity of LTD₄ in the mouse was accomplished by examination of its ability to cause increased capillary permeability and edema formation following subcutaneous administration. It was observed that nanogram quantities of LTD₄ caused edema and increased capillary permeability in a dose-related manner. The increase in capillary permeability was not inhibited by pretreatment with indomethacin and thus was unrelated to the production of cyclooxygenase products. These data suggest that LTD₄ can mediate the edematous phase of the inflammatory response in the mouse and illustrate the sensitivity of this species to LTD₄.     

IgG4-positive plasma cell infiltration in the diagnosis of autoimmune pancreatitis.

Autoimmune pancreatitis typically produces an enlarged pancreas with narrowing of the pancreatic duct, and can mimic carcinoma. Autoimmune pancreatitis usually responds to corticosteroid treatment, making it important to differentiate from pancreatic ductal adenocarcinoma. Affected patients often have an elevated serum IgG4. It has been proposed that increased numbers of IgG4-positive plasma cells in tissue might be a marker for the condition. We investigated the role of IgG4 staining in the diagnosis of autoimmune pancreatitis, first in resected pancreas specimens (29 autoimmune pancreatitis, nine chronic alcoholic pancreatitis and 25 pancreatic cancer), then in pancreatic needle biopsies. Immunohistochemical stains for IgG4 were scored as none, mild, moderate or marked, according to published criteria. Moderate to marked numbers of IgG4-positive plasma cells were seen in 21/29 autoimmune pancreatitis patients, and were distributed in and around ducts, in interlobular fibrous tissue and in peripancreatic fat. In contrast, eight of nine examples of chronic alcoholic pancreatitis and 22/25 ductal adenocarcinomas had scores of none or mild. When we subdivided autoimmune pancreatitis into the histologic subtypes lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-destructive pancreatitis, 16/17 lymphoplasmacytic sclerosing pancreatitis had moderate to marked staining, compared to five to 12 idiopathic duct-destructive pancreatitis. Needle biopsies from nine patients suspected of having autoimmune pancreatitis had increased numbers of IgG4 cells. We conclude that pancreatic tissue from patients with autoimmune pancreatitis often shows moderate or marked infiltration by IgG4-positive plasma cells (>10/HPF). This is particularly so in the subtype we have designated lymphoplasmacytic sclerosing pancreatitis. We rarely see IgG4 staining in patients with chronic alcoholic pancreatitis and pancreatic ductal adenocarcinoma. IgG4-positive plasma cells are a useful marker for the tissue diagnosis of autoimmune pancreatitis.