Macrophage activation reduces mobilization of arachidonic acid by guinea-pig and rat peritoneal macrophages in vitro

Nitrite is produced by elicited but not by circulating neutrophils

The generation of nitrite (NO(2) (-)) was used as an index of the production of nitric oxide by human and rat polymorphonuclear leukocytes (PMN) and rat peritoneal macrophages. Human peripheral blood PMN did not produce significant levels of NO(2) (-). Attempts to induce NO(2) (-) generation in human PMN by incubation with GM-CSF (1 nM), TNFalpha (0.3 nM), endotoxin (1 mug/ml) or formyl-Met-Leu-Phe (100 nM) for up to 16 h were not successful. Addition of human PMN primed by GM-CSF (1 nM) to rabbit aortic ring preparations precontracted with phenylephrine had no effect on tone. In contrast to these observations, PMN, isolated from the peritoneum of oyster glycogen treated rats, generated NO(2) (-) via a pathway sensitive to inhibition by the nitric oxide synthase inhibitor, N(G)-monomethyl L-arginine. However, peripheral blood rat PMN obtained from the same animals did not produce NO(2) (-), even during prolonged incubation for periods of up to 16 h. It is suggested that detectable NO production by PMN requires NO synthase activity to be induced either by the process of PMN migration or by exposure to certain cytokines produced locally at the site of inflammation.

Thrombin-stimulated DNA synthesis in human cultured airway smooth muscle occurs independently of products of cyclo-oxygenase or 5-lipoxygenase

Arachidonic acid (AA) liberation and metabolism via cyclo-oxygenase or lipoxygenases may be an important regulatory pathway for mitogenic signalling in human cultured airway smooth muscle (ASM) cells. In cytokine-treated cells, thrombin markedly enhances production of the anti-mitogenic arachidonic acid metabolite, PGE(2). In this study, in the absence of cytokines, we examined the role of endogenous AA metabolism in thrombin-stimulated ASM DNA synthesis. Selective inhibitors of cyclo-oxygenase of 5-lipoxygenase metabolism had no significant effect on 0.3 U/ml thrombin-stimulated DNA synthesis. However, the non-selective, redox-active lipoxygenase inhibitors NDGA and BWA4C inhibited thrombin-stimulated DNA synthesis. Under basal conditions, and following stimulation by thrombin, the levels of the AA metabolites PGE(2), TxA(2), and LTC(4), remained below assay detection limits. Exogenous addition of AA, LTD(4), or 5-, 12-, and 15-HETE and HpETE metabolites had no consistent or substantial stimulatory effect on either basal or thrombin-stimulated DNA synthesis. These data suggest that the non-selective lipoxygenase inhibitors influence DNA synthesis via effects unrelated to lipoxygenase inhibition. The lack of detection of AA metabolites, the lack of influence of selective antagonists/inhibitors of the AA pathway, and the failure of selected AA metabolites to either enhance or directly stimulate DNA synthesis suggest that in the absence of cytokines, cyclo-oxygenase and lipoxygenase metabolism has little role in signalling of human ASM DNA synthesis by thrombin.

Synthesis of novel derivatives of aroylaminoalcohols and 3-amino-substituted 1-phenylpropanols with potential anti-inflammatory and immunomodulating activities

The synthesis of aroylaminoalcohols and 3-amino-substituted 1-phenylpropanols is described. These novel basic compounds have potent anti-inflammatory activity, significantly inhibiting rat paw oedema induced by a variety of phlogistic agents as a result of the release of inflammatory mediators such as histamine, 5-hydroxytryptamine, kinins, prostaglandins or leukotrienes. The biological activity of a selected, representative number of these compounds was examined on adjuvant-induced arthritis, a good animal model for rheumatoid arthritis in man. The results show that 3-(1-hydroxymethylpropylamino)-1-phenylpropan-1-one hydrochloride (2) and 3-(3-hydroxypiperidin-1-yl)-1-phenylpropan-1-one hydrochloride (4) effectively suppress the secondary lesions of adjuvant arthritis. 2-(3-Hydroxy-3-phenylpropylamino)-butan-1-ol hydrochloride (6) had no preventive activity in this animal model. In addition, several of the compounds suppressed the mitogenic responses of T-lymphocytes to concanavalin A, suggesting direct or indirect action on lymphocytes and therefore possible immunosuppressive properties. Finally, we investigated the in-vitro effects of compounds 2 and 4 on production of interleukins 1 and 2 (IL-1 and IL-2). We found that compound 4 suppressed the in-vitro production or action of IL-2 and IL-1. In contrast, compound 2 significantly increased the IL-1 activity of arthritic macrophages while reducing the ability of normal and arthritic splenocytes to produce or release IL-2. Our data suggest that compounds 2 and 4 have immunomodulatory properties that influence T lymphocyte functions.

Human monocytes maintained in culture acquire functional responsiveness to platelet-activating factor that is independent of increases in protein tyrosine phosphorylation

1. Acute (day 0) stimulation with platelet-activating factor (PAF) did not elicit superoxide anion (O2-) generation from adherent monocytes. However, by day 2 of culture, PAF induced an increase in O2- generation that was inhibited by pretreatment with the PAF receptor antagonist WEB 2086. 2. The lack of effect of PAF on O2- generation was not due to the absence of receptors, as PAF stimulated an increase in tyrosine phosphorylation and intracellular calcium ([Ca2+]i) on both days 0 and 2 of culture. 3. Pretreatment with the protein tyrosine kinase inhibitor methyl 2,5-dihydroxycinnamate inhibited PAF-induced tyrosine phosphorylation; however, this inhibitor failed to inhibit PAF-induced O2- generation. In contrast, pretreatment with the protein kinase C inhibitor staurosporine had no effect on PAF-induced tyrosine phosphorylation, but did inhibit PAF-induced O2- generation. 4. These results indicate that monocytes maintained in culture acquire a functional response to PAF through a mechanism that appears to be independent of PAF receptor expression, coupling to increases in [Ca2+]i or tyrosine phosphorylation.