Biomedical subjects

M M Teixeira

Publications and source records attributed to M M Teixeira.

At least 73 records · Page 4Linked to original sources

PubMed1999

Loss of bone mineral in patients with cachexia due to chronic heart failure.

We studied body composition and cytokine levels in 58 patients with heart failure and 16 control patients using dual-energy x-ray absorptiometry. Bone mineral content and density, and lean and fat tissue content, were reduced in cachectic compared with noncachectic patients and control subjects, with negative relations between indexes of bone composition and tumor necrosis factor and tumor necrosis factor receptor 1.

Absorptiometry, Photon↗

PubMed1999

Trypanosomatidae: Phytomonas detection in plants and phytophagous insects by PCR amplification of a genus-specific sequence of the spliced leader gene.

In this paper we describe a method for the detection of Phytomonas spp. from plants and phytophagous insects using the PCR technique by targeting a genus-specific sequence of the spliced leader (SL) gene. PCR amplification of DNA from 48 plant and insect isolates previously classified as Phytomonas by morphological, biochemical, and molecular criteria resulted in all cases in a 100-bp fragment that hybridized with the Phytomonas-specific spliced leader-derived probe SL3'. Moreover, this Phytomonas-specific PCR could also detect Phytomonas spp. in crude preparations of naturally infected plants and insects. This method shows no reaction with any other trypanosomatid genera or with plant and insect host DNA, revealing it to be able to detect Phytomonas spp. from fruit, latex, or phloem of various host plants as well as from salivary glands and digestive tubes of several species of insect hosts. Results demonstrated that SLPCR is a simple, fast, specific, and sensitive method that can be applied to the diagnosis of Phytomonas among cultured trypanosomatids and directly in plants and putative vector insects. Therefore, the method was shown to be a very specific and sensitive tool for diagnosis of Phytomonas without the need for isolation, culture, and DNA extraction of flagellates, a feature that is very convenient for practical and epidemiological purposes.

Animals↗

PubMed1999

The taxonomic position and evolutionary relationships of Trypanosoma rangeli.

This paper presents a re-evaluation of the taxonomic position and evolutionary relationships of Trypanosoma (Herpetosoma) rangeli based on the phylogenetic analysis of ssrRNA sequences of 64 Trypanosoma species and comparison of mini-exon sequences. All five isolates of T. rangeli grouped together in a clade containing Trypanosoma (Schizotrypanum) cruzi and a range of closely related trypanosome species from bats [Trypanosoma (Schizotrypanum) dionisii, Trypanosoma (Schizotrypanum) vespertilionis] and other South American mammals [Trypanosoma (Herpetosoma) leeuwenhoeki, Trypanosoma (Megatrypanum) minasense, Trypanosoma (Megatrypanum) conorhini] and an as yet unidentified species of trypanosome from an Australian kangaroo. Significantly T. rangeli failed to group with (a) species of subgenus Herpetosoma, other than those which are probably synonyms of T. rangeli, or (b) species transmitted via the salivarian route, although either of these outcomes would have been more consistent with the current taxonomic and biological status of T. rangeli. We propose that use of the names Herpetosoma and Megatrypanum should be discontinued, since these subgenera are clearly polyphyletic and lack evolutionary and taxonomic relevance. We hypothesise that T. rangeli and T. cruzi represent a group of mammalian trypanosomes which completed their early evolution and diversification in South America.

Animals↗

PubMed1999

A comparison of the inhibitory activity of PDE4 inhibitors on leukocyte PDE4 activity in vitro and eosinophil trafficking in vivo.

1. Phosphodiesterase (PDE) 4 inhibitors have been shown to inhibit eosinophil PDE4 activity in vitro and accumulation of eosinophils in experimental airways inflammation. However, direct effects on eosinophil trafficking have not been studied in detail and it is not known if activity in vitro translates into efficacy in vivo. In the present study, we compared the activity of five PDE4 inhibitors in vitro and against trafficking of (111)In-eosinophils in cutaneous inflammation in the guinea-pig. 2. The rank order of potency for inhibition of PDE4 activity in guinea-pig eosinophil, neutrophil and macrophage, and human neutrophil lysates was RP73401 > SB207499 >CDP840 > rolipram > LAS31025. On TNFalpha production by human PBMC, all inhibitors with the exception of rolipram showed potency similar to their effect on neutrophil lysates. 3. In a brain cerebellum binding assay, the rank order of potency at displacing [3H]-rolipram was RP73401 > rolipram > SB207499 > CDP840 > LAS30125. 4. Trafficking of (111)In-eosinophils to skin sites injected with PAF, ZAP or antigen in sensitized sites was inhibited by oral administration of all PDE4 inhibitors. The rank order of potency was RP73401 = rolipram > LAS31025 > SB207499 > CDP840. 5. With the exception was RP73401, which was the most potent compound in all assays, there was no clear relationship between activity of PDE4 inhibitors in vitro and capacity to inhibit eosinophil trafficking in vivo. Thus, we conclude that in vitro activity of PDE4 inhibitors does not predict in vivo efficacy in an experimental model of eosinophil trafficking.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

Suppressive effect of distinct bradykinin B2 receptor antagonist on allergen-evoked exudation and leukocyte infiltration in sensitized rats.

1. Bradykinin is suggested to play a role in the pathophysiology of several acute and chronic diseases, including allergic disorders such as asthma. In the present study, we have investigated the importance of bradykinin in mediating allergic inflammation in rats. 2. To this end we have tested the effects of the B2 receptor antagonists Hoe 140, FR173657 or FR172357 on the pleural inflammatory response triggered by intrapleural (i.pl.) injection of allergen (ovalbumin, 12 microg cavity(-1)) in 14 day-actively sensitized Wistar rats. Analysis of the pleural fluid effluent revealed a sequence of mast cell-dependent inflammatory events, including early protein exudation and neutrophilia and late pleural eosinophil influx. 3. Local treatment with Hoe 140 (0.1 and 1 microg cavity(-1)), FR173657 (1 and 10 microg cavity(-1)) or FR172357 (1 and 10 microg cavity(-1)) inhibited dose-dependently allergen-induced mast cell activation with impairment of pleural plasma leakage, neutrophil accumulation and late eosinophil influx. 4. Moreover, the B2 receptor antagonists also dose-dependently inhibited the allergic like inflammatory pleurisy triggered by bradykinin (50 microg cavity(-1)), which is characterized by acute mast cell degranulation, protein leakage and pleural eosinophil infiltration. 5. Taken together, our findings provide substantial evidence to suggest that bradykinin acting on its B2 receptors play a critical role in mediating allergic mast cell-dependent inflammation in rats, and suggest that B2 receptor antagonists may be useful therapeutically to control allergic dysfunction.

Allergens↗

PubMed1999

Pharmacological modulation of secondary mediator systems--cyclic AMP and cyclic GMP--on inflammatory hyperalgesia.

1. The objective of the present paper was to evaluate the relevance of neuronal balance of cyclic AMP and cyclic GMP concentration for functional regulation of nociceptor sensitivity during inflammation. 2. Injection of PGE2 (10-100 ng paw-1) evoked a dose-dependent hyperalgesic effect which was mediated via a cyclic AMP-activated protein kinase (PKA) inasmuch as hyperalgesia was blocked by the PKA inhibitor H89. 3. The PDE4 inhibitor rolipram and RP73401, but not PDE3 and PDE5 inhibitors potentiated the hyperalgesic effects of PGE2. The hyperalgesic effect of dopamine was also enhanced by rolipram. Moreover, rolipram significantly potentiated hyperalgesia induced by carrageenan, bradykinin, TNF alpha, IL-1 beta, IL-6 and IL-8. This suggests that neuronal cyclic AMP mediates the prostanoid and sympathetic components of mechanical hyperalgesia. Moreover, in the neuron cyclic AMP is mainly metabolized by PDE4. 4. To examine the role of the NO/cyclic GMP pathway in modulating mechanical hyperalgesia, we tested the effects of the soluble guanylate cyclase inhibitor, ODQ. This substance counteracts the inhibitory effects of the NO donor, SNAP, on the hyperalgesia induced by PGE2. 5. The ODQ potentiated hyperalgesia induced by carrageenan, bradykinin, TNF alpha, IL-1 beta, IL-6 and IL-8. In contrast, ODQ had no significant effect on the hyperalgesia induced by PGE2 and dopamine. This indicates that the hyperalgesic cytokines may activate soluble guanylate cyclase, which down-regulate the ability of these substances to cause hyperalgesia. This event appears not to be mediated by prostaglandin or dopamine. 6. In conclusion, the results presented in this paper confirm an association between (i) hyperalgesia and elevated levels of cyclic AMP as well as (ii) antinociception and elevated levels of cyclic GMP. The intracellular levels of cyclic AMP that enhance hyperalgesia are controlled by the PDE4 isoform and appear to result in activation of protein kinase A whereas the intracellular levels of cyclic GMP results from activation of a soluble guanylate cyclase.

Animals↗

PubMed1999

Differential inhibitory mechanism of cyclic AMP on TNF-alpha and IL-12 synthesis by macrophages exposed to microbial stimuli.

Microbial stimuli such as bacterial lipopolysaccharide (LPS) or glycosylphosphatidylinositol-mucins derived from Trypanosoma cruzi trypomastigotes (tGPI-mucins) are effective stimulators of the synthesis of cytokines by macrophages. Here, we evaluated the ability of cyclic AMP mimetic or elevating agents to modulate TNF-alpha and IL-12 synthesis by murine inflammatory macrophages. Cholera Toxin (ChTx) inhibited tGPI-mucins (2.5 nM) or LPS (100 ng ml(-1)) induced TNF-alpha and IL-12(p40) synthesis in a concentration-dependent manner. Similarly, the cyclic AMP mimetics, 8-bromo cyclic AMP or dibutyryl cyclic AMP, or prostaglandin (PG) E2 inhibited the synthesis of both cytokines by macrophages exposed to microbial stimuli. The protein kinase A inhibitor H-89 partially reversed the inhibitory effects of dibutyryl cyclic AMP and PGE2 on both IL-12(p40) and TNF-alpha synthesis. Pretreatment of macrophages with dibutyryl cyclic AMP or ChTx augmented the synthesis of IL-10 triggered by microbial products. Elevation of cyclic AMP inhibited the synthesis of TNF-alpha, but not IL-12(p40), by inflammatory macrophages from IL-10 knockout mice. Kinetic studies showed that synthesis of both TNF-alpha and IL-10 peaked at 8 h and IL-12 at 24 h after stimulation with microbial stimuli. Together, our findings favour the hypothesis that the cyclic AMP inhibitory activity on IL-12(p40) but not on TNF-alpha synthesis is dependent on de novo protein synthesis, most likely involving IL-10, by macrophages stimulated with microbial products. Accordingly, dibutyryl cyclic AMP inhibited IL-12(p40) synthesis only when added before or at the same time of the stimuli. In contrast, the effect of this cyclic AMP analogue on TNF-alpha synthesis was protracted and observed even 2 h after the addition of the stimuli.

Animals↗

PubMed1999

Cytokines and neurohormones relating to body composition alterations in the wasting syndrome of chronic heart failure.

BACKGROUND: Chronic heart failure is one of a number of disorders associated with the development of a wasting syndrome. The precise mechanisms of this remain unknown, but previous studies have suggested a role for immune and neurohormonal factors. METHODS: We aimed to investigate in detail the differences in body composition (dual X-ray absorptiometry) and the relationship to candidate biochemical factors of the immune, neurohormonal and metabolic systems in 15 healthy controls, 36 stable non-cachectic and 18 cachectic patients with chronic heart failure. RESULTS: Non-cachectic patients showed reduced leg lean tissue (-9.1%, P<0.01) compared to controls. Cachectic patients had significantly reduced lean (-21.0% vs controls, -19.9% vs non-cachectics), fat (-33.0% vs controls, -37. 0% vs non-cachectics) and bone tissue (-17.5% vs controls, -15.9% vs non-cachectics) (all P<0.0001). Cachectic patients showed a significantly increased cortisol/dehydroepiandrosterone ratio (+203% vs controls, P<0.0001; +89% vs non-cachectics, P=0.0011) and increased cytokine levels (TNF-alpha, soluble TNF-receptor 1, interleukin-6). The levels of catabolic hormones and cytokines correlated significantly with reduced muscle and fat tissue content and reduced bone mass. CONCLUSION: Peripheral loss of muscle tissue is a general finding in chronic heart failure. The wasting in cardiac cachexia affects all tissue compartments and is significantly related to neurohormonal and immunological abnormalities.

Adult↗

PubMed1999

Platelet-activating factor induces nitric oxide synthesis in Trypanosoma cruzi-infected macrophages and mediates resistance to parasite infection in mice.

Trypanosoma cruzi replicates in nucleated cells and is susceptible to being killed by gamma interferon-activated macrophages through a mechanism dependent upon NO biosynthesis. In the present study, the role of platelet-activating factor (PAF) in the induction of NO synthesis and in the activation of the trypanocidal activity of macrophages was investigated. In vitro, PAF induced NO secretion by T. cruzi-infected macrophages and the secreted NO inhibited intracellular parasite growth. The addition of a PAF antagonist, WEB 2170, inhibited both NO biosynthesis and trypanocidal activity. The inducible NO synthase/L-arginine pathway mediated trypanocidal activity, since it was inhibited by treatment with L-N-monomethyl arginine (L-NMMA), an L-arginine analog. PAF-mediated NO production in infected macrophages appears to be dependent on tumor necrosis alpha (TNF-alpha) production, since the addition of a neutralizing anti-TNF-alpha monoclonal antibody mAb inhibited NO synthesis. To test the role of PAF in mediating resistance or susceptibility to T. cruzi infection, infected mice were treated with WEB 2170, a PAF antagonist. These animals had higher parasitemia and earlier mortality than did vehicle-treated mice. Taken together, our results suggest that PAF belongs to a group of mediators that coordinate the mechanisms of resistance to infections with intracellular parasites.

Animals↗

PubMed1999

beta-Chemokines enhance parasite uptake and promote nitric oxide-dependent microbiostatic activity in murine inflammatory macrophages infected with Trypanosoma cruzi.

In the present study, we describe the ability of Trypanosoma cruzi trypomastigotes to stimulate the synthesis of beta-chemokines by macrophages. In vivo infection with T. cruzi led to MIP-1alpha, RANTES, and JE/MCP1 mRNA expression by cells from peritoneal inflammatory exudate. In addition, in vitro infection with T. cruzi resulted in expression of beta-chemokine MIP-1alpha, MIP-1beta, RANTES, and JE mRNA by macrophages. The expression of the beta-chemokine MIP-1alpha, MIP-1beta, RANTES, and JE proteins by murine macrophages cultured with trypomastigote forms of T. cruzi was confirmed by immunocytochemistry. Interestingly, macrophage infection with T. cruzi also resulted in NO production, which we found to be mediated mainly by beta-chemokines. Hence, treatment with anti-beta-chemokine-specific neutralizing antibodies partially inhibited NO release by macrophages incubated with T. cruzi parasites. Further, the addition of the exogenous beta-chemokines MIP-1alpha, MIP-1beta, RANTES, and JE/MCP-1 induced an increased T. cruzi uptake, leading to enhanced NO production and control of parasite replication in a dose-dependent manner. L-NMMA, a specific inhibitor of the L-arginine-NO pathway, caused a decrease in NO production and parasite killing when added to cultures of macrophages stimulated with beta-chemokines. Among the beta-chemokines tested, JE was more potent in inhibiting parasite growth, although it was much less efficient than gamma interferon (IFN-gamma). Nevertheless, JE potentiates parasite killing by macrophages incubated with low doses of IFN-gamma. Together, these results suggest that in addition to their chemotactic activity, murine beta-chemokines may also contribute to enhancing parasite uptake and promoting control of parasite replication in macrophages and may play a role in resistance to T. cruzi infection.

Animals↗

PubMed1999

alpha4 integrin-dependent eotaxin induction of bronchial hyperresponsiveness and eosinophil migration in interleukin-5 transgenic mice.

We investigated the roles of eosinophil infiltration and activation induced by the eosinophil-selective chemokine eotaxin, and of the expression of eosinophil alpha4 and beta2 integrins in causing bronchial hyperresponsiveness (BHR) in interleukin (IL)-5 CBA/Ca transgenic mice. These mice did not show BHR, despite the presence of some eosinophils in the lungs. Intratracheal mouse recombinant eotaxin (3 micrograms) did not induce BHR in wild-type mice. In IL-5 transgenic mice, eotaxin (3 and 5 micrograms) increased responsiveness at 24 h and increased eosinophils in bronchoalveolar lavage (BAL) fluid by 9.4- and 14-fold by 24 h, respectively, together with augmentation of eosinophil peroxidase activity and eosinophil infiltration in the airway submucosa. Using flow cytometry, the expression of alpha4, CD11b, and CD18 was upregulated in BAL, but not in blood, eosinophils. A rat anti-alpha4 antibody inhibited eotaxin-induced BHR and eosinophil migration and activation, but an anti-CD11b antibody had no significant effects on BHR. A combination of both antibodies was more effective. IL-5 and eotaxin synergize in the induction of BHR and airway eosinophilia, effects that are dependent on the induction of eosinophil alpha4 integrin. Expression of BHR depends on the recruitment and activation of eosinophils.

Animals↗

PubMed1998

Contribution of endothelial selectins and alpha 4 integrins to eosinophil trafficking in allergic and nonallergic inflammatory reactions in skin.

The role of endothelial selectins in mediating eosinophil recruitment was assessed using the trafficking of 111In-labeled blood eosinophils in mouse skin. An intradermal injection of chemoattractants (leukotriene B4, macrophage inflammatory protein-l alpha, and eotaxin) resulted in a rapid accumulation of 111In eosinophils that was reduced 49 to 91% by anti-P-selectin mAb. An anti-E-selectin mAb was ineffective, although a combined E- and P-selectin blockade resulted in >95% inhibition of all responses. The accumulation of a pulse of 111In eosinophils at sites of active cutaneous anaphylaxis (ACA) at 4 to 8 h and at 20 to 24 h after Ag challenge was completely dependent upon E- and P-selectin in combination, but not in isolation. In contrast, at 20 to 24 h after Ag challenge in a delayed-type hypersensitivity (DTH) reaction in skin, 111In eosinophil accumulation was largely independent of endothelial selectins, even when L-selectin was also blocked. An anti-alpha 4 integrin mAb significantly reduced 111In eosinophil trafficking in both allergic reactions but was slightly more effective in the DTH reaction compared with the ACA reaction. These results show that P-selectin and to a lesser extent E-selectin mediate eosinophil recruitment in skin in acute inflammatory reactions. In allergic, late-onset inflammatory reactions, neither P- nor E-selectin alone are sufficient to mediate eosinophil accumulation; when combined, they are essential for trafficking in ACA but are less important in the DTH reaction. Whether alpha 4 integrin-based strategies will be more effective than selectin-based strategies at inhibiting eosinophil recruitment in human disease remains to be determined.

Anaphylaxis↗

PubMed1998

Role of the mitogen-activated protein kinases and tyrosine kinases during leukotriene B4-induced eosinophil activation.

Exposure of guinea-pig eosinophils to leukotriene B4 (LTB4; 1 microM) resulted in a rapid generation of H2O2 (index of NADPH oxidase activation), stimulated [3H]arachidonic acid (AA) release (index of phospholipase A2 activity), and promoted CD18-dependent homotypic aggregation. Under similar conditions, LTB4 (1 microM) induced a rapid activation of extracellular-regulated kinases-1 and 2 (ERK-1/2) but not c-jun N-terminal kinases 46 and 54 (JNK-46/54) or p38 mitogen-activated protein kinase (p38 MAP kinase). To examine the role of ERK-1/2 in the mechanism of eosinophil activation, a selective inhibitor of MAP kinase kinase-1/2 (MEK-1/2), PD098059, was employed. However, PD 098059 at concentrations that attenuated ERK-1/2 activation had no significant affect on eosinophil activation. In contrast, a role for tyrosine kinases in LTB4-induced eosinophil activation was suggested by studies with the tyrosine kinase inhibitors, herbimycin A and lavendustin A. However, the results of those experiments implied divergent pathways for the control of eosinophil responses because the inhibitors were more effective at attenuating H2O2 generation than [3H]AA release, and had little effect on homotypic aggregation.

Animals↗

PubMed1998

The role of lipocortin-1 in the inhibitory action of dexamethasone on eosinophil trafficking in cutaneous inflammatory reactions in the mouse.

1. The ability of glucocorticosteroids to inhibit tissue eosinophilia may be an important feature of their anti-inflammatory action in allergic diseases. Our previous work showed that an effect of dexamethasone on the release of eosinophils from the bone marrow could explain its inhibitory action on eosinophil accumulation in a mouse air-pouch model. Thus, it was unclear from that study whether dexamethasone could interfere with the process of eosinophil trafficking. In the present study, therefore, we used a newly developed mouse model to evaluate the effects of systemic treatment with dexamethasone on the recruitment of (111)In-labelled blood eosinophils to sites of cutaneous inflammation in the mouse and whether lipocortin-1 (LC-1) was involved. 2. The i.d. injection of ovalbumin (OVA) in sensitized mice induced a dose-dependent recruitment of (111)In-labelled blood eosinophils which peaked at 4 to 8 h after antigen challenge. Systemic treatment with dexamethasone (50 microg per mouse, 3 h after antigen) effectively inhibited (111)In-eosinophil recruitment in this reaction by 70 to 85%. Similarly, a 1 h pretreatment with dexamethasone significantly suppressed (111)In-eosinophil induced by platelet-activating factor (PAF), leukotriene B4(LTB4) and the chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) by 40 to 70%. 3. Two experimental approaches were used to evaluate the role of LC-1: treatment with LC-1 fragment Ac2-26 and use of an anti-LC-1 antiserum. LC-1 fragment Ac2-26 (100 microg per mouse) failed to affect (111)In-eosinophil recruitment. Moreover, pretreatment of animals with an anti-LC-1 antiserum failed to reverse the inhibitory effects of dexamethasone on (111)In-eosinophil recruitment induced by MIP-1alpha and by antigen in sensitized mice. 4. In contrast, the LC-1 fragment significantly inhibited glycogen-induced neutrophil recruitment into the peritoneal cavity of mice. Furthermore, the anti-LC-1 antiserum reversed the inhibitory effects of dexamethasone on the glycogen-induced neutrophil recruitment. 5. Thus, our results suggest that dexamethasone can inhibit the recruitment of eosinophils in mouse skin independent of an action on the bone marrow. However, by use of two different approaches, we showed that LC-1 does not play a role in mediating the inhibitory action of dexamethasone on eosinophil migration into cutaneous inflammatory reactions in the mouse. These data add further support to a LC-1-independent action of dexamethasone on eosinophils in vivo.

Animals↗

PubMed1998

Effect of PDE4 inhibitors on zymosan-induced IL-8 release from human neutrophils: synergism with prostanoids and salbutamol.

1. The activation of neutrophils with particulate stimuli such as zymosan induces the generation of the C-X-C chemokine interleukin (IL)-8. There is evidence that neutrophil derived IL-8 plays an important role in human diseases such as the adult respiratory distress syndrome. In the present study, we examined the effects of cyclic AMP elevating agents on the ability of human neutrophils to generate IL-8 in response to zymosan particles. 2. The PDE4 inhibitor rolipram had limited effect on zymosan-induced IL-8 generation. In contrast, the PDE4 inhibitors RP 73401 and SB 207499 concentration-dependently suppressed IL-8 generation. The potency of these inhibitors was RP 73401 > SB 207499 > rolipram which is correlated with their rank order of potency at inhibiting the catalytic site of purified neutrophil PDE4. Pretreatment of neutrophils with the PDE3 inhibitor ORG 9935 or the PDE5 inhibitor zaprinast had no effect on IL-8 generation. 3. The prostanoids prostaglandin E1 (PGE1) and PGE2 inhibited zymosan-induced IL-8 release from neutrophils in a dose-dependent manner, in response to 10(-5) M PGE1 and PGE2 inhibiting IL-8 generation by 89% and 75%, respectively. Similarly, the beta2-adrenoceptor agonist salbutamol also inhibited IL-8 generation, but it was less effective than the prostanoids. 4. Significant synergism between prostanoids or salbutamol and the PDE4 inhibitors to inhibit IL-8 generation was observed. In contrast, there was no significant synergism between PGE2 and the PDE3 inhibitor ORG 9935 or the PDE5 inhibitor zaprinast. 5. In order to evaluate the potential role of protein kinase A in mediating the inhibitory effects of cyclic AMP-elevating agents, we used the protein kinase A inhibitors, H 89 and KT 5720. Pretreatment of neutrophils with these drugs completely reversed the inhibitory effects of a combination treatment with rolipram and PGE2 on zymosan-induced IL-8 release. 6. Microscopic examination revealed that most neutrophils contained one or more zymosan particles and that combination treatment with rolipram and PGE2 noticeably reduced the number of ingested particles. Moreover, there was a significant reduction in the percentage of neutrophils which ingested three or more zymosan particles. 7. Thus, our results demonstrate that cyclic AMP-elevating agents modulate the ability of neutrophils to generate IL-8 in response to a particulate stimulus. However, these agents also modulate the ability of neutrophils to phagocytose zymosan particles. Whether this effect will translate into inhibition of the ability of neutrophils to deal with infectious agents needs to be investigated further.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1998

Priming and induction of eosinophil trafficking in guinea-pig cutaneous inflammation by tumour necrosis factor alpha.

Tissue eosinophilia is a hallmark of allergic and parasitic diseases. Priming mechanisms may play an important role in mediating the process of eosinophil accumulation in these conditions. We have previously shown that blockade of tumour necrosis factor alpha (TNFalpha) inhibited the capacity of lipopolysaccharide to prime skin sites for chemoattractant-induced eosinophil recruitment. The present study was carried out to investigate the capacity of TNFalpha to prime an inflammatory site for enhanced eosinophil accumulation. Initial experiments investigated the capacity of TNFalpha itself to induce eosinophil accumulation. Intradermal injection of murine TNFalpha (10-300 ng per site) in the guinea-pig induced significant accumulation of 111In-eosinophils. Kinetic studies showed the response to be delayed in onset and inhibited by cycloheximide, consistent with a dependency on protein synthesis. Trafficking of 111In-eosinophils to sites treated for 2 h with TNFalpha (10-100 ng per site) was inhibited by monoclonal antibodies (mAbs) against beta2 or alpha4 integrins. Intradermal injection of a low dose (3 ng) of TNFalpha (which by itself had no significant effect on eosinophil trafficking) prior to chemoattractants or antigen in sensitized skin sites, induced significant priming of eosinophil accumulation. Recruitment of both 111In-eosinophils and endogenous eosinophils was enhanced. Trafficking to TNFalpha-primed responses was dependent on protein synthesis and beta2 integrins. In contrast, the alpha4 integrin mAb failed to inhibit the TNFalpha primed response. Thus, TNFalpha can induce and also prime eosinophil recruitment in guinea-pig skin. Our results provide further evidence that this cytokine may be an important mediator of allergic- or parasite-induced eosinophilic inflammation.

Animals↗

PubMed1998

Suppression of acute lung injury in mice by an inhibitor of phosphodiesterase type 4.

The present study has investigated the therapeutic potential of a type 4 phosphodiesterase (PDE) inhibitor, rolipram, in experimental lung injury. Acute lung injury was induced in the mouse by combined treatment with lipopolysaccharide (LPS; 10 mg/kg, i.v.) and zymosan (3 mg/kg, i.v.), and assessed using extravascular albumin accumulation; neutrophil sequestration in pulmonary capillaries was also measured. The results show that pretreatment with rolipram (5 mg/kg, i.p.) was protective against the induction of lung injury by combined LPS and zymosan; extravascular albumin accumulation was reduced by 89% and neutrophil sequestration in lung tissue, as assessed by lung myeloperoxidase (MPO) activity was reduced by 75%. Pretreatment with rolipram also attenuated increases in serum tumor necrosis factor alpha (TNFalpha) levels induced by LPS and zymosan treatment, measured after 2.5 h. The role of endogenous TNFalpha in the induction of lung injury was therefore assessed. Blockade of endogenous TNFalpha by treatment with the soluble receptor p55-IgG fusion protein or an anti-murine TNFalpha monoclonal antibody, TN3. 19.12, had no protective effect against LPS and zymosan-induced lung injury. This suggests that there is a disassociation between TNFalpha production and the induction of injury in this model. Administration of rolipram after LPS and before zymosan treatment obliterated the increase in pulmonary vascular permeability, but its effect on sequestration of neutrophils in pulmonary microvessels, as measured by MPO, was less marked. The results of the present study suggest that use of agents such as rolipram that inhibit PDE4 may have a therapeutic role in treatment of acute lung injury, since we have shown that it is effective in attenuation of neutrophil activation even after sequestration. However, its effect appears to be independent of TNFalpha inhibition.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1998

Eosinophil-active chemokines: assessment of in vivo activity.

The selective recruitment of eosinophils in tissue is a striking feature of allergic diseases. Recently, a family of chemoattractant molecules, namely chemokines, has been described which potently activates eosinophil function in vitro. We have developed a murine model of eosinophil recruitment to compare the relative potency and efficacy of chemokines in vivo. Of the chemokines tested, only eotaxin and MIP-1 alpha induced significant accumulation of eosinophils in vivo, but eotaxin was more effective than MIP-1 alpha. Chemokines, especially eotaxin acting via the CCR-3 receptor, may have a fundamental role in determining selective eosinophil recruitment in vivo.

Animals↗