Studies on the contribution of PPAR Gamma to tuberculosis physiopathology

Introduction

Tuberculosis (TB) is a major health problem characterized by an immuno-endocrine imbalance: elevated plasma levels of cortisol and pro- and anti-inflammatory mediators, as well as reduced levels of dehydroepiandrosterone. The etiological agent, Mycobacterium tuberculosis (Mtb), is captured by pulmonary macrophages (Mf), whose activation is necessary to cope with the control of Mtb, however, excessive activation of the inflammatory response also leads to tissue damage. Glucocorticoids (GC) are critical elements to counteract the immunoinflammatory reaction, and peroxisome proliferator-activated receptors (PPARs) are also involved in this regard. The primary forms of these receptors are PPARϒ, PPARα, and PPARβ/δ, the former being the most involved in anti-inflammatory responses. In this work, we seek to gain some insight into the contribution of PPARϒ in immuno-endocrine-metabolic interactions by focusing on clinical studies in pulmonary TB patients and in vitro experiments on a Mf cell line.

Methods and results

We found that TB patients, at the time of diagnosis, showed increased expression of the PPARϒ transcript in their peripheral blood mononuclear cells, positively associated with circulating cortisol and related to disease severity. Given this background, we investigated the expression of PPARϒ (RT-qPCR) in radiation-killed Mtb-stimulated human Mf. The Mtb stimulation of Mf derived from the human line THP1 significantly increased the expression of PPARϒ, while the activation of this receptor by a specific agonist decreased the expression of pro- and anti-inflammatory cytokines (IL-1β and IL-10). As expected, the addition of GC to stimulated cultures reduced IL-1β production, while cortisol treatment together with the PPARϒ agonist lowered the levels of this proinflammatory cytokine in stimulated cultures. The addition of RU486, a glucocorticoid receptor antagonist, only reversed the inhibition produced by the addition of GC.

Conclusion

The current results provide a stimulating background for further analysis of the interconnection between PPARs and steroid hormones in the context of Mtb infection.

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)

PPARγ ligand treatment inhibits cardiac inflammatory mediators induced by infection with different lethality strains of Trypanosoma cruzi

Trypanosoma cruzi (T. cruzi), the etiological agent of Chagas' disease, causes cardiac alterations in the host. Although the main clinical manifestations arise during the chronic stage, the mechanisms leading to heart damage develop early during infection. In fact, an intense inflammatory response is observed from acute stage of infection. Recently, peroxisome proliferator-activated receptors (PPARs) have attracted research interest due to their participation in the modulation of inflammation. In this work we addressed the role of 15-Deoxy-∆(12,14) ProstaglandinJ2 (15dPGJ2), a PPARγ natural ligand in the regulation of inflammatory mediators, in acute and chronic experimental mouse models of Chagas' disease with the RA and K98 T. cruzi strains, respectively. This work demonstrates that 15dPGJ2 treatment inhibits the expression and activity of inducible nitric oxide synthase (NOS2) as well as TNF-α and IL-6 mRNA levels. Also, expression and activity of metalloproteinases 2 (MMP-2) and 9 (MMP9) were inhibited by 15dPGJ2. Moreover GW9662, a specific PPARγ antagonist, revealed the participation of other signaling pathways since, in GW9662 presence, 15dPJG2 had a partial effect on the inhibition of inflammatory parameters in the acute model of infection. Accordingly, NF-κB activation was demonstrated, assessing p65 nuclear translocation in the hearts of infected mice with both T. cruzi strains. Such effect was inhibited after 15dPGJ2 treatment. Our findings support the concept that in vivo PPARγ and NF-κB pathways are implicated in the inhibitory effects of 15dPGJ2 on inflammatory mediators at different times depending on whether the infection is caused by the lethal or non-lethal T. cruzi strain.