P6297Genetic mutation of galectin-3 altered the temporal evolution of macrophage polarization and healing affecting the post myocardial infarct remodeling in mice

Background

Myocardial infarction (MI) is a dynamic process that leads to ventricular remodeling (VR) and largely to heart failure (HF). Previous studies established that Galectin-3 (Gal-3) is highly increased in the infarct zone from the beginning of MI and also that it is a prognostic marker of HF.

Purpose

We aimed to study the effects of genetic deletion of Gal-3 on macrophage (MΦ) infiltration, cytokines expression, fibrosis and MMP-2 activity as well as VR and function after MI in mice.

Methods

Male C57BL/6J and Gal-3 KO mice were subjected to permanent coronary ligature or sham. At 1 week post-MI LV function and VR were studied by echocardiography. We also studied in the infarct zone: 1) F4/80+ MΦ infiltration by flow cytometry; 2) M2 macrophage polarization by detection of mannose receptor (MR) and chitinase-3-like protein-3 (YM1) phenotype markers by rt-qPCR; 3) mRNA expression of TNF-α, IL-6, IL-10 and TGF-β; 4) MMP-2 activity by zymography and 5) fibrosis by histology.

Results

Results are expressed as X±SEM; *p<0.05 C57 MI vs Gal-3 KO MI. After 1 week post-MI, the pulmonary congestion assessed by the lung weight/body weight ratio (mg/g) was 9±0.4, 8±0.5 and 9±0.4 in C57 sham, Gal-3 KO sham and C57 MI, respectively, nevertheless it was severely increased to 15±1.2* in infarcted Gal-3 KO mice. MΦ infiltration, cytokine expression and MMP-2 activity in the infarct zone are shown in the table.

Table 1 Groups F4/80+ MR YM1 TNF-α IL-6 IL-10 TGF-β MMP-2 MΦ (%) (A.U.) (A.U.) (A.U.) (A.U.) (A.U.) (A.U.) (A.U.) C57 MI 5.6±0.9 (8) 0.5±0.2 (3) 1.7±0.4 (3) 26±0.3 (3) 1.7±0.5 (3) 0.7±0.03 (3) 1.8±0.5 (3) 1±0.1 (5) Gal-3 KO MI 2.6±0.4* (8) 1.8±0.4*(8) 4.2±0.4* (8) 0.4±0.5* (8) 6.7±0.9 * (8) 2.8±0.3 * (8) 0.5±0.2 * (8) 2±0.4* (6) A.U.: Arbitrary units. In MR, YM1, TNF-α, IL-6, IL-10 and TGF-β represent mRNA expression. In MMP-2 represent gelatinolytic activity. Number of samples is shown between parentheses.

After 1 week post-MI, LV end diastolic dimension was increased from 4.4±0.1 to 4.8±0.2* at the same time that ejection fraction (%) was significantly reduced from 47±2 to 38±3* in C57+MI (13) and Gal-3 KO+MI (16) respectively. Collagen concentration in the infarct zone was significantly reduced from 30±1.2% (6) to 17±0.5* % (8) in C57 and Gal-3 KO respectively.

Conclusion(s)

Gal-3 is an essential regulatory factor for the early wound healing since it regulates the dynamics of the reparative process through the phenotypic profile of MΦ, the pro- and anti-inflammatory cytokines expression and fibrosis along the temporal evolution of MI in mice. The deficit of Gal-3 diminished the infiltration of MΦ altering its phenotypic polarization and consequently, the dynamics of the wound healing as well as aggravating the functional and structural evolution of cardiac remodeling.

Acknowledgement/Funding

Argentine Agency for Promotion of Science and Technology (PICT 2014-2320), University of Buenos Aires (UBACyT 20020170100619BA)

Detection of mRNA encoding H(1) receptor and iNOS by RT-PCR in autoimmune myocarditis with special reference to changes in heart contractility

Cardiac tissue from autoimmune myocarditis mice was studied to evaluate the expression and biological activity of mRNA encoding H(1) receptor and iNOS. BALB/c inbred mice were immunized with heart protein and sacrificed at 20, 45 and 50 days post immunization. Heart contractility studies and RT-PCR assays were performed. Heart from autoimmune myocarditis mice show mRNA iNOS-related dysfunction with a decrease in heart contractility. This effect was accompanied with an increase production of cyclic GMP and was improved by treating autoimmune mice with an inhibitor of iNOS activity. In addition, autoimmune myocardium expressed an active histamine H(1) receptor mRNA coupled to phospholipase C. The activation of H(1) receptor by ThEA stimulated both phosphoinositide hydrolysis and heart contractility. Normal myocardium did not expressed neither iNOS mRNA nor H(1) receptor mRNA. In conclusions: the development of autoimmune cardiac dysfunction was associated with the expression of iNOS mRNA, cyclic GMP accumulation and the expression of an active histamine H(1) receptor mRNA with increase production of inositol phosphates. These protein emergence during the course of autoimmune myocarditis may be involved a distinct compensatory mechanism operating in this disease.

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase expression in rat brain during development

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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.

Guaianolides from tanacetum argenteum subsp. canum var. canum

The aerial parts of Tanacetum argenteum subsp. canum var. canum (Compositae) afforded six guaianolides, five of them (2-6) being new: flabellin (1), epoxyflabellin (2), Delta3(4)-15-oxo-flabellin (3), Delta3(4)-15-hydroxydihydroflabellin (4), 11alpha-dihydroflabellin (5), and 11beta-dihydroflabellin (6). The structures of the compounds were elucidated by spectral methods including NMR (1H NMR, COSY, APT, HETCOR, NOE) and X-ray diffraction, as well as by some chemical reactions.

Myocardial dysfunction in an experimental model of autoimmune myocarditis: role of IFN-gamma

Experimental autoimmune myocarditis obtained in mice by immunization with heart antigens is characterized by the presence of lymphomononuclear infiltrates in atria and ventricles. Here we show the ability of soluble factors released by immune cells from mice immunized with heart antigens to decrease heart contractility in a similar way to a muscarinic agonist. These effects appear to be mediated by IFN-gamma since all of them could be blocked by an anti-IFN-gamma monoclonal antibody. Moreover, the negative inotropic effect induced by immune cell-conditioned media was blocked by atropine, confirming previous findings that IFN acts as a muscarinic agonist on isolated atria. The role of locally released cytokines and especially of IFN-gamma was also evaluated in infiltrated autoimmune myocarditis hearts; thus, the addition of monoclonal anti-IFN-gamma antibody reversed the decreased contractility characteristics of this model. We conclude that IFN released both systemically and locally by autoreactive T cells may contribute to the impaired cardiac function in this experimental model of autoimmune myocarditis.

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.

Increases in cyclic AMP levels couple to H1 receptors in atria from autoimmune myocarditis mice

We have previously shown that myocardium from experimental autoimmune myocarditis expresses H1 receptors not present in normal mice heart. ThEA acting via H1 receptors, augments cyclic AMP production in atria from autoimmune myocarditis mice without any effect on atria from control mice. Addition of mepyramine before ThEA caused cyclic AMP levels to fall to a level similar to basal, confirming the H1 receptor participation. Histamine at low concentrations mimicked the ThEA action on H1 receptor-stimulation of cyclic AMP production by autoimmune myocardium. The fact that the inhibition of phospholipase C blocked the cyclic AMP stimulation by ThEA, supports the assumption that this action is secondary to receptor-mediated hydrolysis of phosphoinositides, generating some oxidative metabolites (IP3-DAG), which in turn may be responsible for the cyclic AMP effect. So, the inhibition of protein kinase C and calcium/calmodulin partially prevented the stimulatory action of ThEA on cyclic AMP levels in autoimmune myocardium, suggesting that both pathways are implicated in this effect. Data shows that the stimulation of H1 receptors by specific agonist in atria from autoimmune myocarditis mice, augments the cyclic AMP, requiring the hydrolysis of phosphoinositide cycle. The role of this cyclic AMP augmentation in myocardium from autoimmune myocarditis mice, will provide a basis to assess the role of this second messenger as an important factor in the regulation and/or modulation of the physiological behaviour of the heart in the course of autoimmune myocarditis.

Alterations in cardiac muscarinic acetylcholine receptors in mice with autoimmune myocarditis and association with circulating muscarinic receptor-related autoantibodies

Hearts from mice hyperimmunized with cardiac tissue were studied to evaluate the expression and biological activity of muscarinic cholinergic receptors and immunoglobulin G deposits along the immunization period. Mice were sacrificed at 10 day intervals from the first injection up to day 100. Simultaneously, the activity of autoantibodies against muscarinic receptors on normal hearts was also examined in sera. Hearts with autoimmune myocarditis showed a muscarinic receptor-related dysfunction, with an impaired response to exogenous muscarinic agonists and a significant reduction in muscarinic binding sites, both effects being maximum at 40-50 days post-immunization. In addition, serum or immunoglobulin G from mice with myocarditis were able to interact with muscarinic acetylcholine receptors displaying a partial agonist effect. Autoimmune sera and immunoglobulin G reduced heart contractility while inhibited 3H-QNB binding to cardiac acetylcholine receptors in a concentration dependent manner showing the highest effects at days 40-50 and decreased progressively thereafter. The development of muscarinic receptor-related cardiac dysfunction may be associated with the presence of circulating antibodies having muscarinic receptor activity. These studies are of relevance to clinical conditions such as Chagas' disease, where immunological processes involving the cholinergic system are considered to cause cardiomyopathy.

Effect of histamine in autoimmune myocarditis mice

The contractile effect of histamine, as well as the H1 receptor population and H2 receptor-mediated cAMP production, were measured in cardiac tissue from control normal and autoimmune myocarditis mice. Histamine triggered positive chronotropy and negative inotropy at high concentrations in both control and autoimmune auricles, H2 receptors being the most important mediator of these responses. In contrast, in atria from autoimmune myocarditis mice, histamine at lower concentrations caused positive inotropy and negative chronotropy. These effects, not verified in the normal control atria, are mediated by H1 receptors. The expression of H2 and H1 receptors mediating the cardiac response to histamine was evaluated through histamine-stimulated cAMP level and binding of [3H] mephyramine, respectively. Both control and autoimmune myocardium were able to increase cAMP levels, an effect that was inhibited by H2 antagonist drug. The amount of cAMP was significantly higher in control myocardium than in those from autoimmune ones. Saturable binding of [3H] mephyramine occurs in autoimmune myocardium, with distinct high and low affinity binding sites. In control myocardium non-saturable binding was detected. These results suggest that H1 and H2 receptors coexist in heart from autoimmune myocarditis mice, whereas only H2 receptors are present in myocardium from control mice. The presence of H1 receptors in autoimmune myocardium could be an important factor in the regulation of its physiological behaviour.

Expression of histamine H1 receptors in autoimmune myocarditis mice

Two populations of histaminergic H1 receptors with distinct high and low affinity binding sites were characterized by the specific H1 receptor antagonist [3H]mepyramine in autoimmune myocardium. No saturable binding of the radiolabelled H1 antagonist was observed in normal myocardium. Reaction of autoimmune myocardium with specific H1 agonist (2-thiazolylethylamine (ThEA)) triggered positive inotropy and negative chronotropy, which were inhibited by mepyramine. Inhibitors of phospholipase C and protein kinase C attenuated both the inotropic and chronotropic effects of ThEA, suggesting the participation of phosphoinositide hydrolysis in this phenomenon. The latter was verified by measurement of polyphosphoinositide hydrolysis in autoimmune myocardium following the reaction of ThEA with histaminergic H1 receptors. We conclude that functional H1 histaminergic receptors could involve a distinctive mechanism operating in autoimmune myocardium as a result of cardiac antigen immunization.