cyclic-gmp and Chagas-Disease

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.

Topics: Animals; Antigens, Protozoan; Atropine; Cell Division; Chagas Disease; Chronic Disease; Concanavalin A; Cyclic GMP; Cyclooxygenase Inhibitors; Dinoprostone; Down-Regulation; Indomethacin; Mice; Mice, Inbred BALB C; Muscarinic Antagonists; Receptors, Muscarinic; T-Lymphocytes; Trypanosoma cruzi

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.

Topics: Adult; Aged; Animals; Antibodies, Protozoan; Blotting, Western; Chagas Disease; Cyclic GMP; Humans; Immunoglobulin G; Inositol Phosphates; Middle Aged; Myocardial Contraction; Nitric Oxide; Nitric Oxide Synthase; Rats; Receptors, Muscarinic; Signal Transduction

In this paper we analyse the interaction of IgG from T. cruzi infected patients with cardiac muscarinic acetylcholine receptors (mAChRs). Human chagasic IgG, activating M2 mAChR simulated the agonist actions excerting negative inotropic effect and stimulation of nitric oxide synthase (NOS). Inhibitors of phospholipase C, protein kinase C, calcium/calmodulin, NOS and guanylate cyclase activities prevented the chagasic effects upon contractility and NOS activity.

Topics: Animals; Carbachol; Chagas Disease; Cyclic GMP; Depression, Chemical; Enzyme Inhibitors; Heart Atria; Humans; Immunoglobulin G; Male; Muscarinic Agonists; Myocardial Contraction; Nitric Oxide; Nitric Oxide Synthase; Rats; Rats, Wistar; Receptors, Muscarinic

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.

Topics: Adult; Autoantibodies; Autonomic Nervous System Diseases; Biomarkers; Chagas Disease; Cyclic AMP; Cyclic GMP; Humans; Middle Aged; Myocardial Contraction; Peptides; Receptors, Muscarinic

It is demonstrated that human IgG in Chagas' disease and the corresponding F(ab)'2 fragment attach to lymphoid cells by specific interaction with beta-adrenergic and muscarinic cholinergic receptors. This interaction resulted in the transduction of signals that increased intracellular levels of cAMP in enriched T helper cell preparations and cGMP in enriched T suppressor cell preparations. The stimulation of Ts cell muscarinic cholinergic receptors by Chagas IgG or the corresponding F(ab)'2 fraction triggers the release of the immunomodulatory substance PGE2. These results are unified in a theory of immunoregulation and could contribute to the chronic course of Chagas' disease.

Topics: Binding, Competitive; Chagas Disease; Cyclic AMP; Cyclic GMP; Dinoprostone; Humans; Immunoglobulin G; Receptors, Adrenergic, beta; Receptors, Muscarinic; Signal Transduction; T-Lymphocytes; T-Lymphocytes, Helper-Inducer; T-Lymphocytes, Regulatory

It is demonstrated that murine chagasic IgG and the corresponding F(ab')2 fragments interfere with beta adrenergic and muscarinic cholinergic specific ligand occupancy on T cell-enriched population. From the interaction between chagasic IgG or F(ab')2 with Lyt-1+ cells, an increase in cAMP levels occurs as a consequence of beta adrenergic receptor activation. On the contrary, chagasic IgG or F(ab')2 interactions with Lyt-2+ cells induce an activation of muscarinic cholinergic receptor, leading to an increment in cGMP. Muscarinic cholinergic and beta adrenergic stimulation trigger the release of PGE2 and TXB2, respectively. Lyt-2+ cells treated with chagasic IgG or F(ab')2 are able to decrease the contractility of mouse atria. The same negative inotropic effect is elicited with Lyt-2+ cells from Trypanosoma cruzi-infected mice susceptible to developed myocarditis. The implications of these results in the pathogenesis of Chagas' myocarditis are discussed.

Topics: Animals; Atrial Function; Chagas Disease; Cyclic AMP; Cyclic GMP; Dinoprostone; Immunoglobulin Fab Fragments; Immunoglobulin G; Lymphocytes; Mice; Mice, Inbred BALB C; Myocardial Contraction; Protein Binding; Receptors, Adrenergic, beta; Receptors, Cholinergic; T-Lymphocytes; Thromboxane B2

The effects of agents that elevate intracellular levels of cGMP on macrophage internalization of the unicellular parasite Trypanosoma cruzi and latex particles were examined in an attempt to define characteristics of the infective process. Presence of imidazole, a drug that prevents degradation of the cGMP by inhibiting cGMP phosphodiesterase activity, during macrophage-T. cruzi interaction resulted in a marked increase in the number of parasites associated with the cells and the percentage of infected cells. Similar results were obtained when sodium nitroprusside (SNP), which increases cGMP levels by an as yet undefined mechanism, dibutyryl-cGMP, or both imidazole and dibutyryl-cGMP were added to the system. In contrast, the presence of imidazole, SNP, or dibutyryl-cGMP had no significant consequence on latex particle uptake by the macrophages. Whereas pretreatment of macrophages with imidazole plus dibutyryl-cGMP readily increased T. cruzi infection, pretreatment of the parasite with these drugs had no significant effect on the interaction. Furthermore, results of radioimmunoassays showed that imidazole and SNP indeed elevated cGMP levels in the macrophages but not in the parasites. Taken together, these results indicate that cGMP plays a facilitating role in macrophage infection by T. cruzi that contrasts with the lack of effect on the uptake of inert latex particles and the previously reported inhibitory effect of cAMP in the same system. Thus, cyclic nucleotides appear to play a role in modulating internalization of the parasite but not in the uptake of an inert particle by macrophages.

Topics: Animals; Chagas Disease; Cyclic GMP; Disease Susceptibility; Female; Imidazoles; Macrophages; Mice; Mice, Inbred ICR; Nitroprusside; Phagocytosis; Trypanosoma cruzi