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E Borda

Publications and source records attributed to E Borda.

At least 37 records · Page 2Linked to original sources
PubMed1999

Protein kinase C regulates NO-cGMP pathway in muscarinic receptor activation by HIV+-IgA.

In this work we demostrate that IgA purified from HIV infected patients recognizes a band with a molecular weight corresponding to radiolabelled ileal muscarinic acethylcholine receptors (mAChR) by immunoblotting. HIV+-IgA triggers the signals that are the consequence of mAChR stimulation in the intestine, regulating protein kinase C (PKC) and nitric oxide synthase (NOS) activity as well as 3',5'-cyclic guanosine monophosphate (cGMP) formation. On the one hand PKC activation by HIV+-IgA induces NOS inhibition and as a consequence, low amounts of NO that could improve local immunosuppression in the intestine; on the other hand HIV+-IgA stimulates cGMP production which could potentiate ileal motility and loss of water/electrolytes involved in intestinal damage in AIDS.

Animals↗
PubMed1999

Overview of molecular mechanisms in chagasic cardioneuromyopathy and achalasia.

Evidence accumulated by our investigations over the years give adequate proof for the existence of circulating antibodies in Chagas disease which bind to beta adrenergic and muscarinic cholinergic receptor of myocardium. The interaction of agonist-like antibodies with neurotransmitter receptors, triggers in the cells intracellular signal transductions that alter the physiological behaviour of the target organs. These events convert the normal cells into pathologically active cells. The interaction of antibodies with heart beta adrenergic and cholinergic receptors triggers physiologic, morphologic, enzymatic and molecular alterations, leading to tissue damage. The analysis of the prevalence and distribution of these antibodies reveals a strong association with cardiac and esophageal autonomic dysfunction in seropositive patients in comparison with those without alteration of the heart and esophagus autonomic disorders: therefore, the presence of these antibodies may partially explain the cardiomyoneurophathy and achalasia of Chagas disease, in which the sympathetic and parasympathetic systems are affected. The deposit of autoantibodies behaving like an agonist on neurotransmitter receptors, induceds desensitization and/or down regulation of the receptors. This in turn, could lead to a progressive blockade of neurotransmitter receptors, with sympathetic and parasympathetic dennervation, a phenomenon that has been described during the course of Chagas cardioneuropathy and achalasia. The clinical relevance of these findings is the demonstration, using biomolecules, of a strong association between the existence of circulating autoantibodies against peptides corresponding to the second extracellular loop of the human heart beta, adrenoceptor and M2 cholinoceptor in chagasic patients, and the presence of dysautonomic symptoms, making these autoantibodies a proper early marker of heart and digestive autonomic dysfunction.

Antibodies, Protozoan↗
PubMed1998

Nitric oxide synthase in experimental autoimmune myocarditis dysfunction.

This study reports the expression of inducible nitric oxide synthase (NOS) in heart from autoimmune myocarditis mice associated with an alteration in their contractile behavior. By mean of the production of [U-14C]citrulline from [U-14C]arginine and immunoblot assay, the expression of iNOS was demonstrated in autoimmune atria that was normally absent. The iNOS activity decreased with administration of dexamethasone and in mice treated with monoclonal anti-interferon-gamma antibody (anti-IFN-gamma mAb). The inhibitors of protein kinase C activity (staurosporine) but not calcium/calmodulin (trifluoperazine) attenuated the iNOS activity. Moreover, autoimmune atria presented contractile alterations (lower values of dF/dt than control). The in vivo treatment with inhibitors of NOS activity or anti-IFN-gamma mAb or dexamethasone improved the contractile activity of autoimmune atria with no change in the contractility of normal atria. The results suggest that the infiltrative cells in myocarditis heart have a potential role in cardiac dysfunction by production of IFN-gamma and subsequent expression of iNOS, that in turn alter the contractile behavior of the heart. The data indicate that cytokines induced activation of L-arginine nitric oxide pathway in myocarditis atria leading to contractile dysfunction.

Animals↗
PubMed1998

Role of nitric oxide in cardiac beta-adrenoceptor-inotropic response.

We examined some of the signalling events in the negative modulation of isoproterenol-induced stimulation of contractility in rat isolated atria. Isoproterenol-mediated positive inotropic response is accompanied by the stimulation of nitric oxide synthase (NOS) and an increase in the production of cyclic GMP (cGMP). Inhibition of NOS and guanylate cyclase increased the dose-response curve of isoproterenol on contractility. Inhibitors of calcium flux or calcium calmodulin, but not of protein kinase C, abrogated these mechanisms. The existence of a modulatory negative inotropic-cyclic GMP-mediated mechanism limiting the effect of beta-adrenergic stimulation in myocardium is discussed.

Animals↗
PubMed1998

Autoantibodies against lacrimal gland M3 muscarinic acetylcholine receptors in patients with primary Sjögren's syndrome.

PURPOSE: The authors demonstrated that immunoglobulin G, present in the sera of patients with primary Sjögren syndrome (pSS), could recognize and activate muscarinic acetylcholine receptors (mAChRs) of rat exorbital acrimal gland. METHODS: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and radioligand binding and biologic assays were used to demonstrate autoantibodies against mAChRs. RESULTS: These autoantibodies recognized by means of SDS-PAGE and immunoblotting assay a band of approximately 70 kDa expressed on lacrimal gland membranes that comigrated with the peak of labeled mAChRs. Moreover, pSS IgG were able to inhibit, in an irreversible manner, the binding of [3H]quinuclidinyl benzilate to mAChRs of rat exorbital lacrimal glands and to simulate the biologic effect of mAChR agonists, because they trigger the activation of phosphoinositide turnover. Atropine and 4-diphenylacetoxy-N-methylpiperidine methiodide blocked the effect and carbachol mimicked it, confirming that the M3 subtype mAChRs mediated pSS IgG action. As control, IgG from sera of women without pSS gave negative results on immunoblotting, binding, and biologic assays, thus demonstrating the specificity of the reaction. CONCLUSIONS: Autoantibodies against mAChRs may be considered among the serum factors implicated in the pathophysiology of the development of pSS dry eyes.

Adult↗
PubMed1998

Trypanosoma cruzi antigens down-regulate T lymphocyte proliferation by muscarinic cholinergic receptor-dependent release of PGE2.

Here we demonstrate that T. cruzi antigen molecule SAPA (shed acute phase antigen) with neuraminidase-trans sialidase activity triggers down-regulation of T lymphocyte proliferation by interacting with T lymphocyte muscarinic acetylcholine receptors (mAChR). SAPA attachment to mAChR from Lyt 2.2+ T cells resulted in synthesis of cyclic GMP (cGMP) and secretion of PGE2, an immunoregulator effector substance. These T suppressor cell signals were blunted by atropine and by indomethacin. Cell sorter analysis showed that the interaction of SAPA with purified T cells, affected the ratio of L3T4+/Lyt 2.2+ T cells increasing the percentage of Lyt 2.2+ T cells, effect that was inhibited by the mAChR antagonist, atropine. The interaction between SAPA and mAChR from Lyt 2.2+ T cells may result, therefore, in the down-regulation of the host immune response as consequence of T suppressor/cytotoxic cells activation and PGE2 release as they were observed. These results support the theory of an immunosuppressive state that contribute to the chronic course of Chagas' disease.

Animals↗
PubMed1997

Participation of nitric oxide signaling system in the cardiac muscarinic cholinergic effect of human chagasic IgG.

The possible role of altered humoral immune response in the pathogenesis of the chronic chagasic cardioneuromyopathy was examined by analyzing the interaction of IgG from T. cruzi infected patients with cardiac muscarinic acetylcholine receptors (mAChR). Human chagasic IgG by activating cardiac M2 mAChR, simulated the agonist actions triggering negative inotropic effect, inositol phosphate accumulation, nitric oxide synthase stimulation and increased production of cyclic GMP. Inhibitors of phospholipase C, protein kinase C, calcium/calmodulin, nitric oxide synthase and guanylate cyclase activities; prevented chagasic IgG effects on signaling pathways involved in M2 mAChR activation. In addition, sodium nitroprusside or 8-bromo cyclic GMP, mimicked the chagasic IgG effect associated with cholinergic-mediated cellular transmembrane signals. Moreover, these chagasic IgG immunoprecipitated the mAChRs solubilized from cardiac membranes. By means of SDS-PAGE and immunoblotting analysis, chagasic sera recognized a band of 70-75 kDa. The major protein recognized by chagasic IgG had an Rf coincident with the peak of [3H] propylbenzilylcholine mustard with an apparent molecular weight similar to that of mAChRs, which disappeared in the presence of atropine. The specificity of this interaction was checked by immunoprecipitation of rat cardiac mAChR and immunoblotting of pure human M2 mAChRs. Chronic interaction of chagasic IgG with myocardial mAChRs, behaving as a muscarinic agonist, might lead to cell dysfunction or tissue damage. Also, these antibodies could produce desensitization, internalization or degradation of mAChRs; explaining the progressive blockade of mAChRs in myocardium with parasympathetic denervation, a phenomenon that has been described in the course of Chagas' cardioneuromyopathy.

Adult↗
PubMed1997

Interaction of human chagasic IgG with the second extracellular loop of the human heart muscarinic acetylcholine receptor: functional and pathological implications.

Circulating antibodies from human and murine chagasic sera are able to interact with myocardium-activating neurotransmitter receptors. Here we reported the presence of autoantibodies against the second extracellular loop of the human heart muscarinic acetylcholine receptors (mAChR) in patients with Chagas' disease by using a synthetic 24-mer peptide in immunoblotting and enzyme immunoassay. Affinity-purified antipeptide IgG from chagasic patients, similar to monoclonal antihuman M2 mAChR, recognized bands with a molecular weight corresponding to the cardiac mAChR. The binding was inhibited by the peptide, assessing the specificity of the interaction. The antipeptide autoantibody also displayed an "agonist-like" activity modifying the intracellular events associated with mAChR activation, i.e., decreased contractility, increased cGMP, and decreased cAMP production. All of these effects on rat atria by chagasic antipeptide autoantibodies resemble the effects of the authentic agonist and those of the total polyclonal chagasic IgG, being selectively blunted by atropine and neutralized by the synthetic peptide corresponding in aminoacid sequence to the second extracellular loop of the human M2 mAChR. A clinical relevance of these findings is demonstrated by a strong association between the existence of circulating antipeptide autoantibodies in chagasic patients and the presence of dysautonomic symptoms, making these autoantibodies a proper early marker of heart autonomic dysfunction.

Acetylcholine↗
PubMed1997

IgA from HIV+ haemophilic patients triggers intracellular signals coupled to the cholinergic system of the intestine.

IgA was obtained from HIV-infected haemophilic patients and the intracellular signals triggered by its reaction with isolated rat intestinal strips were studied. HIV+ IgA stained intestinal microvilli with a granular immunofluorescence pattern and bound to the muscarinic acetylcholine receptor (mAChR), displacing the specific muscarinic cholinergic antagonist QNB in a non-competitive manner. It triggered the signals that are the consequence of mAChR stimulation in the intestine. Thus, it decreased cAMP synthesis and increased guanosine 3':5'-cyclic monophosphate (cGMP) formation and phosphoinositide (PI) turnover of the intestine. In addition, it stimulated prostaglandin E2(PGE2) synthesis by intestinal strips. Through its effect on PGE2 synthesis, HIV+ IgA could have a dual action. On the one hand, it could enhance immunosuppression at a local level, favouring pathogen growth and subsequent intestinal dysfunction. On the other hand, PGE2 could directly increase intestinal motility and electrolyte/fluid loss. Both effects could be involved in intestinal damage in AIDS.

Animals↗
PubMed1996

Lymphocyte muscarinic cholinergic activity and PGE2 involvement in experimental Trypanosoma cruzi infection.

In this paper, we demonstrated that the production of PGE2 by CD8+ T lymphocytes through muscarinic cholinergic receptor (mAChR) activation of lymphocytes from mice acutely infected with nonlethal Trypanosoma cruzi CA-1 strain could enhance resistance to infection. Treatment in vivo with either atropine or cyclooxygenase inhibitors enhanced mortality rates and parasitemia of mice infected with T. cruzi CA-1 strain. The mechanism by which CD8+ T lymphocytes released PGE2 appears to involve the activation of the cells by circulating IgG present in mice infected with T. cruzi CA-1 strain. Binding of these antibodies to mAChR on CD8+ T lymphocytes triggered the release of large amounts of PGE2. The results point to a role of serum antibodies against mAChR in the protection of T. cruzi infection. The prostanoid acting as an immunomodulator contributed to the maintenance of the chronic course of experimental Chagas disease.

Adjuvants, Immunologic↗
PubMed1996

Induction of ileum muscarinic cholinoceptor signal transduction pathways by rat interferon-gamma.

We have recently shown that rat interferon-gamma (IFN gamma) can trigger a cholinergic muscarinic response upon interaction with isolated rat atria, decreasing both the contractile tension and cAMP synthesis, and increasing cGMP production. Because the intestine is rich in cholinergic muscarinic receptors, and IFN gamma-producing cells are normal components of the mucosal immune system, we investigated whether IFN gamma could also modulate the muscarinic cholinergic activity of the intestine. Our results indicate that IFN gamma may interact with ileum cholinergic muscarinic receptors by inhibiting binding of the radiolabelled antagonist quinuclidinyl benzylate (3H-QNB), decreasing cAMP formation and increasing cGMP synthesis. These effects are associated with increased mechanical activity of the isolated ileum strips, and can be blunted by pretreatment of the tissue with atropine.

Animals↗
PubMed1996

Circulating antibodies against rat parotid gland M3 muscarinic receptors in primary Sjögren's syndrome.

In this study we demonstrate that IgG present in the sera of patients with primary Sjögren's syndrome (PSS) could bind and activate muscarinic acetylcholine receptors (mAChRs) of rat parotid gland. These antibodies were able to inhibit in a non-competitive manner the binding of 3H-quinuclidinyl benzilate (QNB) to mAChRs of purified rat parotid gland membranes. Moreover, IgG from PSS could modify biological effects mediated by mAChR activation; i.e. decrease cAMP, increase phosphoinositide turnover without affecting cGMP. Atropine and 4-DAMP blocked all of these effects, and carbachol mimicked them, confirming the M3 subtype mAChRs mediated PSS IgG action. Neither binding nor biological effect were obtained with IgG from sera of normal women. The prevalence of cholinergic antibody was 100% in PSS, and was independent of Ro/SS-A and La/SS-B antibodies. It could be concluded that antibody against mAChRs may be another serum factor to be considered in the pathophysiology of the development of PSS.

Adolescent↗
PubMed1996

"In vivo" and "in vitro" antitumoral action of Larrea divaricata Cav.

We previously reported that aqueous extract of Larrea divaricata Cav. had an antiproliferative activity upon tumoral lymphoid cells (BW 5147), without affecting normal immunity. To determine the probable mechanism of the inhibitory action of the extract upon cell growth, the participation of intracellular signals involved in the inhibition of cell proliferation, namely the activation of adenylate cyclase system was studied. The production of cyclic 3', 5 adenosine monophosphate (cAMP) in presence and absence of extract was analized. The extract increased the cAMP levels, but neither the cAMP production nor the inhibitory effect of the extract on proliferation were blocked by a beta adrenergic receptor antagonist (propranolol) or by histaminergic receptor antagonists (cimetidine and mepyramine). So, we concluded that the antiproliferative activity of the extract of BW 5147 cells would be mediated by an increase in cAMP intracellular levels no related to the activation of the membrane receptors here studied. In parallel, the extract was administered to a pregnant rat with a spontaneous mammarian carcinoma and "in vivo" antitumoral activity was found.

Analysis of Variance↗
PubMed1996

[Interaction of chagasic autoantibodies with the third extracellular domain of the human heart muscarinic receptor. Functional and pathological implications].

Herein we demonstrate by ELISA and immunoblotting the presence in the sera of chagasic patients of circulating autoantibodies against the third extracellular domain of human muscarinic acetylcholine receptors by using a synthetic peptide corresponding to the sequence 169-192 of the receptor. Immunoaffinity purified antipeptide antibodies displayed cardiac muscarinic activity as decreased contractility and cAMP production and increased cGMP levels. These effects were specifically blocked by the synthetic peptide and by atropine. A strong association between the existence of circulating autoantibodies and the presence of dysautonomia was shown, making these autoantibodies an appropriate marker of heart autonomic dysfunction.

Adult↗
PubMed1995

PGE2 involvement in experimental infection with Trypanosoma cruzi subpopulations.

PGE2 involvement in experimental Trypanosoma cruzi infection depends on the lethal capacity of the parasite subpopulation used. Mice acutely infected with non-lethal K98 displayed an enhancement in PGE2 serum levels during the acute period, while those infected with lethal T. cruzi subpopulations (RA or K98-2) showed levels not different from normal mice. The enhancement detected in K98 group could be related both to an increased number of CD8+ T cell number and to enhanced PGE2 release per cell by CD8+; values of PGE2 release by adherent cells were not altered in this group. Treatment with cyclooxygenase inhibitors enhanced mortality rates of mice infected with K98, and administration of 16,16-dimethyl PGE2 (dPGE) reversed this effect. However, mice infected with RA did not reduce their mortality rates by administration of diverse doses of dPGE. These findings suggest that PGE2 could play a role in resistance in mice infected with K98.

16,16-Dimethylprostaglandin E2↗
PubMed1995

Pharmacological evidence for the existence of different subtypes of muscarinic acetylcholine receptors for phosphoinositide hydrolysis in neonatal versus adult rat atria.

The negative inotropic effect of carbachol, as well as phosphoinositide hydrolysis, was measured in atria from neonatal and adult rats. Carbachol increased phosphoinositide hydrolysis and decreased dF/dt of both neonatal and adult atria; however, the neonatal atria showed hypereactivity to carbachol as compared with adult atria. Inhibition of phospholipase C reduced the supersensitivity to carbachol upon contractility in neonatal atria producing values similar to those of the adult atria, suggesting that muscarinic acetylcholine receptor (mAchR) stimulation is secondary to receptor-mediated hydrolysis of phosphoinositides. Pharmacological analysis with mAchR antagonists tends to support the idea that m1 and m2 subtypes are the most important mediators of the response to carbachol in neonatal atria. In adult atria, the effect of carbachol is coupled only to mAchR m2 subtypes.

Animals↗
PubMed1995

Endogenous nitric oxide signalling system and the cardiac muscarinic acetylcholine receptor-inotropic response.

1. In this paper we have determined the different signalling pathways involved in muscarinic acetylcholine receptor (AChR)-dependent inhibition of contractility in rat isolated atria. 2. Carbachol stimulation of M2 muscarinic AChRs exerts a negative inotropic response, activation of phosphoinositide turnover, stimulation of nitric oxide synthase and increased production of cyclic GMP. 3. Inhibitors of phospholipase C, protein kinase C, calcium/calmodulin, nitric oxide synthase and guanylate cyclase, shifted the dose-response curve of carbachol on contractility to the right. These inhibitors also attenuated the muscarinic receptor-dependent increase in cyclic GMP and activation of nitric oxide synthase. In addition, sodium nitroprusside, isosorbide, or 8-bromo cyclic GMP, induced a negative inotropic effect, increased cyclic GMP and activated nitric oxide synthase. 4. These results suggest that carbachol activation of M2 AChRs, exerts a negative inotropic effect associated with increased production of nitric oxide and cyclic GMP. The mechanism appears to occur secondarily to stimulation of phosphoinositides turnover via phospholipase C activation. This in turn, triggers cascade reactions involving calcium/calmodulin and protein kinase C, leading to activation of nitric oxide synthase and soluble guanylate cyclase.

Analysis of Variance↗