Air Pollution's Impact on Cardiac Remodeling in an Experimental Model of Chagas Cardiomyopathy

Abstract

Background: Chagas disease is characterized by intense myocardial fibrosis stimulated by the exacerbated production of inflammatory cytokines, oxidative stress, and apoptosis. Air pollution is a serious public health problem and also follows this same path. Therefore, air pollution might amplify the inflammatory response of Chagas disease and increase myocardial fibrosis.

Methods: We studied groups of Trypanosoma cruzi infected Sirius hamsters (Chagas=CH and Chagas exposed to pollution=CH+P) and 2 control groups (control healthy animals=CT and control exposed to pollution=CT+P). We evaluated acute phase (60 days post infection) and chronic phase (10 months). Echocardiograms were performed to assess left ventricular systolic and diastolic diameter, in addition to ejection fraction. Interstitial collagen was measured by morphometry in picrosirius red staining tissue. The evaluation of inflammation was performed by gene and protein expression of cytokines IL10, IFN-γ, and TNF; oxidative stress was quantified by gene expression of NOX1, MnSOD, and iNOS and by analysis of reactive oxygen species; and apoptosis was performed by gene expression of BCL2 and Capsase3, in addition to TUNEL analysis.

Results: Chagas groups had increased collagen deposition mainly in the acute phase, but air pollution did not increase this deposition. Also, Chagas groups had lower ejection fraction in the acute phase (p = 0.002) and again air pollution did not worsen ventricular function or dilation. The analysis of the inflammation and oxidative stress pathways were also not amplified by air pollution. Apoptosis analysis showed increased expression of BCL2 and Caspase3 genes in chagasic groups in the acute phase, with a marginal p of 0.054 in BCL2 expression among infected groups, and TUNEL technique showed amplified of apoptotic cells by pollution among infected groups.

Conclusions: A possible modulation of the apoptotic pathway was observed, inferring interference from air pollution in this pathway. However, it was not enough to promote a greater collagen deposition, or worsening ventricular function or dilation caused by air pollution in this model of Chagas cardiomyopathy.

Keywords: Chagas disease; air pollution; cardiomyopathy; myocardial fibrosis; remodeling.

Figure 1

Photomicrograph of the myocardium stained with picrosirius red (in red the collagen marking), and graphic of Interstitial Collagen Volume Fraction (ICVF). (A) Collagen deposition in the acute phase (n=51); (B) collagen deposition in the chronic phase (n=40). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 2

Left Ventricular diastolic diameter (LVDD), left ventricular systolic diameter (LVSD) and left ventricular ejection fraction (EF). (A) LVDD in the acute phase (n=62); (B) LVDD in the chronic phase (n=33). (C) LVSD in the acute phase (n=62); (D) LVSD in the chronic phase (n=33), (E) EF in the acute phase (n=62); (F) EF in the chronic phase (n=33). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 3

Absolute gene expression of inflammatory cytokines. (A) IL10 gene expression in the acute phase (n=49); (B) IL10 gene expression in the chronic phase (n=38). (C) IFN gene expression in the acute phase (n=49); (D) IFN gene expression in the chronic phase (n=38), (E) TNF gene expression in the acute phase (n=49); (F) TNF in the chronic phase (n=38). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 4

Gene expression of oxidative stress genes. (A) NOX1 gene expression in the acute phase (n=49); (B) NOX1 gene expression in the chronic phase (n=38). (C) MnSOD gene expression in the acute phase (n=49); (D) MnSOD gene expression in the chronic phase (n=38), (E) iNOS gene expression in the acute phase (n=49); (F) iNOS in the chronic phase (n=38). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 5

Gene expression of apoptosis genes. (A) BCL2 gene expression in the acute phase (n=49); (B) BCL2 gene expression in the chronic phase (n=38). (C) CASP3 gene expression in the acute phase (n=49); (D) CASP3 gene expression in the chronic phase (n=38). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 6

Protein expression of inflammatory cytokines. (A) IL10 protein expression in the acute phase (n=5); (B) IL10 protein expression in the chronic phase (n=5). (C) IFN protein expression in the acute phase (n=5); (D) IFN protein expression in the chronic phase (n=5), (E) TNF protein expression in the acute phase (n=5); (F) TNF protein expression (n=5). in the chronic phase. CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 7

Photomicrograph with apoptotic nuclear in brown color of the myocardium for detection of DNA fragmentation using the TUNEL technique, and graph of the quantification of apoptosis. (A) Apoptosis (TUNEL) in the acute phase (n=51); (B) Apoptosis (TUNEL) in the chronic phase (n=40). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 8

Photomicrograph of the myocardium for detection of reactive oxygen species (ROS) and graph of ROS quantification. (A) ROS in the acute phase (n=5); (B) ROS in the chronic phase (n=5). CT - control group, CT+P – control group exposed to pollution, CH – chagasic group, CH+P – chagasic group exposed to pollution.

Figure 9

Graph of animal survival at 10 months compared to study groups. CT - control group (n=25), CT+P – control group exposed to pollution (n=25), CH – chagasic group (n=25), CH+P – chagasic group exposed to pollution (n=25).