The Role of the Na+/Ca2+ Exchanger in Aberrant Intracellular Ca2+ in Cardiomyocytes of Chagas-Infected Rodents

Abstract

Chagas disease is produced by the parasite Trypanosoma cruzi (T. cruzi), which is the leading cause of death and morbidity in Latin America. We have shown that in patients with Chagas cardiomyopathy, there is a chronic elevation of diastolic Ca2+ concentration ([Ca2+]d), associated with deterioration to further address this issue, we explored the role Na+/Ca2+ exchanger (NCX). Experiments were carried out in noninfected C57BL/6 mice and infected with blood-derived trypomastigotes of the T. cruzi Y strain. Anesthetized mice were sacrificed and the cardiomyocytes were enzymatically dissociated. Diastolic [Ca2+] ([Ca2+]d) was measured using Ca2+ selective microelectrodes in cardiomyocytes from control mice (CONT) and cardiomyocytes from T. cruzi infected mice in the early acute phase (EAP) at 20 dpi, in the acute phase (AP) at 40 dpi, and in the chronic phase (CP) at 120 dpi. [Ca2+]d was 1.5-times higher in EAP, 2.6-times in AP, and 3.4-times in CP compared to CONT. Exploring the reverse mode activity of NCX, we replaced extracellular Na+ in equivalent amounts with N-methyl-D-glucamine. Reduction of [Na+]e to 65 mM caused an increase in [Ca2+]d of 1.7 times in cardiomyocytes from CONT mice, 2 times in EAP infected mice, 2.4 times in AP infected mice and 2.8 in CP infected mice. The Na+ free solution caused a further elevation of [Ca2+]d of 2.5 times in cardiomyocytes from CONT, 2.8 times in EAP infected mice, 3.1 times in AP infected mice, and 3.3 times in CP infected mice. Extracellular Ca2+ withdrawal reduced [Ca2+]d in both CONT and cardiomyocytes from Chagas-infected mice and prevented the increase in [Ca2+]d induced by Na+ depletion. Preincubation with 10µM KB-R7943 or in 1µM YM-244769 reduced [Ca2+]d in cardiomyocytes from infected mice, but not control mice. Furthermore, both NCX blockers prevented the increase in [Ca2+]d associated with exposure to a solution without Na+. These results suggest that Ca2+ entry through the reverse NCX mode plays a significant role in the observed [Ca2+]d dyshomeostasis in Chagas infected cardiomyocytes. Additionally, NCX inhibitors may be a viable therapeutic approach for treating patients with Chagas cardiomyopathy.

α7 nicotinic receptors play a role in regulation of cardiac hemodynamics

“…During depolarization, NCX enables Ca 2+ influx and during depolarization, it facilitates Ca 2+ efflux, while its mode depends on the prevailing electrochemical driving forces for Ca 2+ and Na + (Bers, 2000; Matsuda et al, 1997). Incubation of cardiomyocytes in a Ca 2+ ‐free medium leads to reduced intracellular Ca 2+ levels and also prevents elevated intracellular Ca 2+ levels following Na + depletion (Lopez et al, 2022). Inhibition of the NCX has a beneficial effect in models of long QT syndrome (Milberg et al, 2008).…”

Unraveling the role of miRNAs as biomarkers in Chagas cardiomyopathy: Insights into molecular pathophysiology

“…Our in silico analyses ( Fig 4 ) demonstrated a significant relationship ( p = 0.009) between miR-145-5p and its regulation of calcium transport (GO: 0097553). Lopez and colleagues [ 37 ] observed an aberrant increase in the Na+/Ca2+ Exchanger pathway in infected C57BL/6 mice when compared to the control group. The same pathway shows an experimental relationship with changes in ventricular depolarization in a study conducted by Santos-Miranda and colleagues [ 38 ].…”