Carrageenan-induced suppression of T-lymphocyte proliferation in the rat: abrogation of suppressor factor production by the prostaglandin synthesis inhibitors, indomethacin and ETYA

Morphological and biochemical characterization of macrophages activated by carrageenan and lipopolysaccharide in vivo

Macrophages are able to recognize, internalize and destroy a large number of pathogens, thus restricting the infection until adaptive immunity is initiated. In this work our aim was to analyze the surface charge of cells activated by carrageenan (CAR) and lipopolysaccharide (LPS) through light and electron microscopy approaches as well as the release of inflammatory mediators in vitro. The ultrastuctural analysis and the light microscopy data showed that in vivo administration of CAR represents a potent inflammatory stimulation for macrophages leading to a high degree of spreading, an increase in their size, in the number of the intracellular vacuoles and membrane projections as compared to the macrophages collected from untreated animals as well as mice submitted to LPS. Our data demonstrated that CAR stimulated-macrophages displayed a remarkable increase in nitric oxide production and PGE2 release as compared to the cells collected from non-stimulated and stimulated mice with LPS in vivo. On the other hand, non-stimulated macrophages as well as macrophages stimulated by LPS produce almost the same quantities of TNF-alpha, while in vivo stimulation by CAR leads to a 30-40% increase of cytokine release in vitro compared to the other groups. In conclusion, our morphological and biochemical data clearly showed that in vivo stimulation with CAR induces a potent inflammatory response in macrophages representing an interesting model to analyze inflammatory responses.

Risks versus Benefits of NSAIDs Including Aspirin in Myocarditis

NSAIDs, including aspirin (acetylsalicylic acid), are frequently used and effective in a broad variety of inflammatory diseases, i.e. rheumatic carditis and pericarditis. Myocarditis may constitute another suitable indication for NSAIDs in order to relieve the symptoms of the presumed viral infection or because pericardial effusion is often associated with this condition. However, concerns have been raised about their indiscriminate use in myocarditis. To clarify this issue, we conducted a systematic review of the literature concerning myocarditis, aspirin and NSAIDs. We examined five animal studies of NSAIDs (indomethacin and ibuprofen) and aspirin in coxsackievirus B3- and B4-induced myocarditis. These studies indicated a deleterious effect of NSAIDs and aspirin in this setting, demonstrating a 2- to 3-fold increase in inflammation, myocytes necrosis and even mortality when compared with placebo. This possible deleterious effect was more predominant when NSAIDs or aspirin were administered during the acute and subacute phases of myocarditis; however, it was still noted when NSAIDs were administered during the late phase of the disease (the effect of aspirin was not evaluated in late phase studies). According to these animal studies, such effect might be attributed to decreased viral clearance (possibly via interferon inhibition) and/or exaggerated cytotoxic response (via interleukin-2 or inhibition of suppressor cells factors) and/or coronary artery spasm. We found one animal study looking at autoimmune myocarditis and it did not demonstrate any beneficial or detrimental effect of aspirin. Moreover, recent data suggest that aspirin and NSAIDs may counteract part of the efficacy of ACE inhibitors and be deleterious in chronic heart failure. Taken together, these studies point to a possible deleterious effect of aspirin and NSAIDs in human myocarditis. In view of these animal studies and in the absence of controlled studies of aspirin or NSAIDs in human myocarditis, we do not recommend indiscriminate treatment with NSAIDs or high-dose aspirin in patients with myocarditis where there is no or minimal associated pericarditis.

Changes in Eicosanoid and Tumour Necrosis Factor-alpha Production by Rat Peritoneal Macrophages During Carrageenin-Induced Peritonitis

Changes and correlations in cytokine and eicosanoid production by blood monocytes, non-purified and purified peritoneal cells during a carrageenin-induced peritonitis were investigated for a period of ten days. The cells were isolated and stimulated in vitro. Cytokine and eicosanoid production of the non-purified fraction increased steadily during peritonitis. During the whole episode of peritonitis the production capacity of granulocytes was very low and hardly any effect on the production capacity of macrophages (Mϕ) was observed. Cytokine and eicosanoid production of the non-purified fraction was mainly due to the presence of Mϕ. The production capacity of the peripheral blood monocytes was not similar to that of the peritoneal Mϕ.

Inhibition of tumor metastasis by carrageenan-induced granulomas

At -1, 0, +1 weeks from tumor inoculation, carrageenan-impregnated cotton sponges were subcutaneously implanted. Tumor BN472, a malignant adenocarcinoma, was transplanted in syngeneic Brown Norway female rats, either subcutaneously or intravenously. Plasma eicosanoid values (prostaglandin-E2, thromboxane-B2 and 6-keto-prostaglandin-F1 alpha) were determined as well as the cellular immune response (natural killer activity, concanavalin-A and phytohemagglutinin stimulation of spleen lymphocytes). Primary tumor growth and the number of tumor foci in the lungs were measured as parameters of tumor growth and dissemination. No statistically significant differences were observed in primary tumor growth. However, the number of metastatic foci in the lungs of rats in which the tumor was implanted subcutaneously, as well as those in which the tumor was inoculated intravenously, was significantly reduced in those that had carrageenan implanted one week after tumor inoculation. In all other carrageenan-treated groups only slightly reduced numbers of metastatic foci were seen. In those rats with a decreased number of tumor metastatic foci in the lungs, no correlation could be shown with either altered plasma prostaglandin levels, or cellular immune response.

Adjuvant properties of polysaccharides: effect of iota-carrageenan, pectic acid, pectin, dextran and dextran sulphate on the humoral immune response in the rat

Iota-carrageenan can both enhance agglutinating antibody responses and trigger reaginic antibody production against a protein associated antigen in rats. The present study investigates the strain specificity of this phenomenon and compares the adjuvanticity of high and low molecular weight iota-carrageenan with a series of structurally distinct polysaccharides (pectin, pectic acid, dextran and dextran sulphate). Using ovalbumin as the test antigen, high molecular weight iota-carrageenan induced a potent ovalbumin specific reaginic antibody response in PVG and Hooded Lister strain rats, an intermediate response in Sprague Dawley rats and a weak response in DA, AO and F344 strain rats. Further studies in PVG rats revealed that the nature and magnitude of the antibody response induced was influenced by the type of polysaccharide carrier used. Thus, whereas, high molecular weight carrageenan enhanced the agglutinating antibody (agglutinin) response and simultaneously elicited de novo reaginic antibody production to co-administered ovalbumin, low molecular weight carrageenan facilitated reaginic antibody production but had no effect on the agglutinin response. Pectin and dextran had no effect on the agglutinin response and failed to elicit reaginic antibody production. Conversely, pectic acid and dextran sulphate enhanced the agglutinin response and elicited a transient reaginic anti-ovalbumin response.